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ADVENTDALEN GP
GROUP
Adventdalen Group

Name
The group is named after a major valley in central Spitsbergen.
Type area
The type area is Central Spitsbergen.
Thickness
Thickness on Svalbard: ca. 750-1600 m, known thickness on the Barents Sea Shelf: ca. 1000-1750 m.
Lithology
The Adventdalen Group comprises shales, siltstones and sandstones of Late Jurassic to Early Cretaceous age in Svalbard and throughout the Barents Sea Shelf.
Distribution
The group is widely exposed along the margins of the Central Tertiary Basin on Spitsbergen, as well as in eastern Spitsbergen (Sabine Land) and on Kong Karls Land. It continues across the Barents Sea Shelf to the Bjarmeland Platform, around the Loppa High and into the Hammerfest and Nordkapp basins. The Adventdalen Group was eroded down to varying levels during the late Cretaceous uplift. On the southem Barents Sea Shelf, this hiatus comprises only the Cenomanian and part of the Turonian, while the entire Upper Cretaceous is lacking on Svalbard.
Age
Late Jurassic - Early Cretaceous.
Depositional environment
The group is dominated by dark marine mudstones, but includes also deltaic and shelf sandstones as well as thin, condensed carbonate beds. Important hydrocarbon source rocks occur in the Upper Jurassic succession, both in Svalbard and in the Barents Sea (Agardhfjellet, Fuglen and Hekkingen formations). A Barremian sandstone unit, (Helvetiafjellet Formation) in Svalbard is the result of local uplift and deltaic progradation, while a coeval, condensed limestone interval in the Barents Sea ( Klippfisk Formation ) grades into marls and calcareous mudstones in the basins. A hiatus occurs around the Jurassic - Cretaceous boundary.
Subdivision
Six formations are defined within the group on the Barents Sea Shelf: the Fuglen , Hekkingen , Klippfisk , Knurr , Kolje and Kolmule formations.
Compiled from
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp. hans
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Groups&nav3=1
1
AGAT FM
FORMATION
CROMER KNOLL GP
Agat Formation

Name
Named after the gas-condensate Agat Discovery in Norwegian block 35/3.
Well type section
Norwegian well 35/3-4 from 3589 m to 3345 m, coordinates N 61°51'54.54", E 03°52'26.99" (Fig 5.19) , 95 m of cores, mainly from the lower half of the formation.
Well reference section
Norwegian well 35/3-5 from 3620 m to 3219 m, coordinates N 61°47'46.71",E 03°54'44.01" (Fig 5.20) . 65 m of cores from the upper part of the formation.
Thickness
In the type well the gross thickness of the formation is 244 m, and in the reference well 401 m. The gross thickness varies in that range in the wells in block 35/3.
Lithology
In the type well the formation consists of white to light grey, fine- to medium-grained, moderately to well-sorted sandstones alternating with grey claystones. The sandstones are usually micaceous and glauconitic and sometimes contain small amounts of pyrite. The sandstones in the type well are carbonate- and silica-cemented in zones. In the reference well, the upper part of the formation consists of medium- and coarse-grained to pebbly sandstones and conglomerates alternating with dark grey claystones. The conglomerates are both matrix- and grain-supported. The claystones are often found as 0.5-5 m thick layers between the sandstones. They are dark grey, usually calcareous and contain varying amounts of siltstone. They may occasionally pass into light grey, micaceous, calcareous and glauconitic siltstones.
Basal stratotype
The lower boundary is defined where sandstones become the dominant lithology and is placed at the base of the first marked coarsening-upwards sandstone unit or distinct sand body. On logs it shows as an upward reduction in gamma-ray response (Fig 5.19) and (Fig 5.20) and most often an increase in velocity (Fig 5.20) .
Characteristics of the upper boundary
The upper boundary is placed at the top of the upper sandstone layer. This boundary is especially distinct on the gamma-ray log since the overlying sediments are dominated by calcareous shales with a low sandstone content. The overlying sediments are represented either by the Rødby Formation (well 35/3-1 and 35/3-2 ), or by the Svarte Formation (well 35/3-4 and 35/3-5 ), (Fig 5.19) . (Fig 5.20) .
Distribution
The formation is encountered in the area around the Måløy Fault Blocks in Norwegian blocks 35/3-36/1 (Fig 5.21) and is expected to be present along the western boundary of the Fennoscandian Shield. It is assumed to pass into shales towards the west (Fig 5.21) .
Age
Aptian-Albian (possibly Early Cenomanian).
Depositional environment
Marine environment influenced by gravity flows of sediment.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=2
2
23
AKKAR MBR
MEMBER
FRUHOLMEN FM
Akkar Member

Origin of name
Norwegian for “squid”.
Well type section
Norwegian well 7121/5-1 coordinates 71° 35'54.88"N, 21° 24'21.78"E (Fig 4.46) .
Well reference section
Norwegian well 7120/12-1 coordinates 71°6'48.71"N, 20° 45'20.13"E (Fig 4.47) .
Thickness
The gross thickness of the member is 55 m in the type well, and 38 m in the reference well.
Lithology
Grey to dark grey shales, interbedded sandstones, coal.
Lower boundary definition
The base of the Akkar Member (and the Fruholmen Formation ) is defined by a marked increase in gamma ray and neutron porosity logs, but often more moderate increases in interval transit time and bulk density readings.
Age
Norian (based on palynology).
Depositional environment
Open marine.
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Members&nav3=3
3
46
ALGE MBR
MEMBER
HEKKINGEN FM
Alge Member

Name
Norwegian for “alga”.
Well type section
Norwegian well 7119/12-1 coordinates N 71°6'08.00'' E 19°47'40.29''.
Reference well section
Norwegian well 7120/12-1 coordinates N 71°6'48.71'' E 20°45'20.13''.
Thickness
35 m in the type well and 50 m in the reference well.
Lithology
The Alge Member forms the lower high gamma intensity part of the Hekkingen Formation and consists of black paper shales rich in organic material.
Lower boundary definition
The base is defined by the transition from carbonate cemented and pyritic mudstones to poorly consolidated shales, producing a sudden increase in interval transit time and an abrupt decrease in bulk density values.
Age
Late Oxfordian – Kimmeridgian, based on ammonites and palynology.
Depositional environment
The member was deposited in restricted shelf environments.
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Members&nav3=202
202
63
ALKE FM
FORMATION
HEGRE GP
Alke Formation
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=211
211
61
AMUNDSEN FM
FORMATION
DUNLIN GP
Amundsen Formation

Name
Named by Deegan & Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2993m to 3051m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2838 m to 2923m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) , 31/2-1 (Shell) from 2272.5 m to 2292.5 m and from 2134 m to 2176 m, coord N 60°46'19,16", E 03°33'15.87" (Fig 3.13) . and 30/6-7 (Norsk Hydro) from 3023 m to 3151.5 m, coord N 60°38'39.49", E 02°45'21.74" (Fig 3.12) .
Thickness
58 m in the type well, 85 m in well 33/9-1 , 128.5 m in well 30/6-7 and 62 m in well 31/2-1 , where the formation is split by the Johansen Formation , forming an upper (42 m) and a lower (20 m) unit.
Lithology
In the well type section the formation consists of light to dark grey, firm, non-calcareous siltstones and shales, in part carbonaceous and pyritic. Thin, fine to coarse grained, grey calcareous and glauconitic sandstone beds are present in the marginal areas of the basin. In the Norwegian sector the formation is more calcareous, especially in the lower part.
Boundaries
The base of the formation is the base of the Dunlin Group (defined above). The top is marked by the change to the more regular gamma ray and sonic log response of the overlying Burton Formation . Where the Burton Formation is missing (on the Horda Platform), the upper boundary is the base of the Cook Formation .
Distribution
The formation is widely distributed in the East Shetland Basin and Viking Graben north of 59°N. Towards the northwest the formation appears to overstep the Statfjord Formation and rests on the Hegre Group .
Age
Probably Hettangian to Sinemurian or Early Pliensbachian.
Depositional environment
The formation contains exclusively marine sediments, representing deposition on a shallow marine shelf.
Source
Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=4
4
29
ANDREW FM
FORMATION
ROGALAND GP
Andrew Formation

Name
Named by Deegan & Scull (1977) after the Andrew Field in UK blocks 18/27 and 16/28.
Well type section
UK well 14/25-1 from 2199 m to 1897 m, coordinates N58°01'11.40", E 00°00'56.40". No cores.
Well reference section
UK well 21/10-1 from 2464 to 2370 m, coordinates N 57°43'50.37", E 00°58'29.19" (Fig 5.44) . No cores.
Thickness
The Andrew Formation is 302 m thick in the type well and 94 m in the reference well, which represents the general thinning southwards from the East Shetland Platform. Close to the Fladen Ground Spur, the formation reaches thicknesses of approximately 1200 m.
Lithology
The Andrew Formation consists of sandstones with claystone interbeds. The sandstones are generally very fine to medium grained and are composed of subangular to subrounded, clear to orange-stained quartz and feldspar grains. The sandstones are poorly sorted and often have a calcareous cement. Thin stringers of limestone occur.
Basal stratotype
The Andrew Formation overlies the shales, marls and limestone interbeds of the Våle Formation , reflected by a higher gamma-ray level in the Andrew Formation. It may also rest on the Maureen Formation , and in that case the boundary is still seen as an increase in gamma-ray readings upwards into the less calcareous Andrew Formation (Fig 5.44) .
Characteristics of the upper boundary
The Lista Formation usually overlies the Andrew Formation, and the boundary is characterized by higher gamma-ray readings and lower velocity upwards into the Lista Formation . Where the Forties Formation directly overlies the Andrew Formation, the boundary may be difficult to define, but the Forties Formation generally has a lower velocity than the Andrew Formation (Fig 5.44) . This boundary is very difficult to determine in the Norwegian sector.
Distribution
The Andrew Formation was deposited as an elongated lobe trending southeastwards from the western part of the Fladen Ground Spur into the Central Trough. The formation is not well developed in the Norwegian sector, even though the distal parts of the lobe may be expected to occur. Its approximate distribution is shown in (Fig 5.47) .
Age
Paleocene.
Depositional environment
The Andrew Formation was deposited as submarine fans.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=5
5
131
BALDER FM
FORMATION
ROGALAND GP
Balder Formation

Name
Named by Deegan & Scull (1977) from the Balder Field in Norwegian blocks 25/10 and 25/11. Balder was a son of Odin, and one of the most famous gods in Norse mythology.
Well type section
Norwegian well 25/11-1 from 1780 m to 1705 m, coordinates N 59°10'57.39", E 02°24'28.18" (Fig 5.57) . Cores.
Well reference sections
Norwegian well 30/2-1 from 1993 m to 1917 m, coordinates N 60°52'05.42", E 02°38'49.16". Cores. Norwegian well 15/9-17 from 2253 to 2204 m, coordinates N 58°26'44.19", E 01°56'53.58" (Fig 5.58) . No cores.
Thickness
The Balder Formation is 75 m thick in the type well. Generally its thickness varies from less than 20 m to more than 100 m. Normally it is between 40 and 60 m.
Lithology
The Balder Formation is composed of laminated varicoloured, fissile shales with interbedded grey, green and buff, often pyritic, sandy tuffs and occasional stringers of limestone, dolomite and siderite. Sandstones are locally present, as shown in the type well (Fig 5.57) .
Basal stratotype
The lower boundary to the Sele or Lista formations is generally identified on logs as an upward decrease in gamma-ray response and an increase in velocity (Fig 5.56) (Fig 5.58) . This probably reflects the increase in the tuffaceous component of the Balder Formation.
Characteristics of the upper boundary
The upper boundary is defined at the transition from the laminated shales of the Balder Formation to the non-laminated, often glauconitic, occasionally reddish, overlying sediments. On logs this can normally be seen as an upward reduction in gamma-ray response and a decrease in velocity (Fig 5.56) . When the Balder Formation is overlain by the Frigg Formation the boundary is seen as a decrease in gamma-ray response and an increase in velocity into the Frigg Formation (Fig 5.62) . The log response of the Balder Formation is often described as bell-shaped (Fig 5.58) .
Distribution
The Balder Formation is distributed over most of the North Sea, and may correspond in part to the Mo Clay Formation in Denmark.
Age
Paleocene - Early Eocene.
Depositional environment
The Balder Formation was deposited in a deep marine setting, mainly as hemipelagic sediments. Some turbiditic sands occur locally. There was probably more than one volcanic source.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=6
6
131
BASEMENT
GROUP
Basement

On the Norwegian Continental Shelf bedrock of pre-Devonian age are regarded as basement in a petroleumgeological context. More than 50 wells in the North Sea, Norwegian Sea and Barents Sea have penetrated pre-Devonian rocks. Most of these wells were drilled on structural highs with depth to top basement quite evenly distributed between 1200 and 4000m.
The thicknesses drilled have generally been in the order of a few meters. 5 wells have drilled more than 100m of basement rock:
2/6-3 (142m),
16/1-4 (146m),
16/1-5 (195m),
35/3-2 (233m),
6306/10-1 (207m).
Some of the pre-Devonian rocks have been dated by the K/Ar-, Ar/Ar- or Rb/Sr-methods, indicating pre-Middle Devonian metamorphic ages. The age of formation of the rocks are ranging from the Precambrian to the Early Paleozoic.
The pre-Devonian rocks normally encountered include diverse rocks of low to high metamorphic grade, including metamorphosed igneous rocks such as granitic gneiss, and metasedimentary rocks such as mica schist, greenschist, quartzite and marble. The existing data indicate that these rocks are highly fractured and record a history of polyphase deformation from at least late Proterozoic times onward. In some wells weathered rock material forms an intermediate zone between basement and overlying sediments.
In more than 30 of the wells basement rocks were cored. The cores were taken to confirm that the wells had reached basement, and coring was therefore usually carried out below any weathering. All wells have information from cuttings and logs.
Gas condensate was tested from fractured crystalline basement in well 16/1-4 . Minor shows in basement fractures are recorded in various wells. Highly fractured and/or weathered basement rocks can have some potential as conduits for hydrocarbon migration or as reservoirs.
Compiled from
  • Basset, M. G. Sub-Devonian geology. 61 – 63 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
  • and NPD-observations.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Groups&nav3=10
10
BILLEFJORDEN GP
GROUP
Billefjorden Group

Name
Cutbill & Challinor (1965) introduced the term “Billefjorden Group” for a suite of nonmarine sediments now recognised to be of late Devonian to early Carboniferous age. The type area is in the environs of Billefjorden in central Spitsbergen. The Billefjorden Group is a well-established lithostratigraphic unit and its overall facies development and depositional evolution is well known (e.g. Gjelberg 1981; Steel & Worsley 1984). Lower Carboniferous units in the southern Norwegian Barents Sea are herein also assigned to the group. The offshore development of the group resembles that described from onshore with one major exception: the upper part of the group includes some shallow marine deposits in the southeastern Finnmark Platform. As yet enigmatic red-bed sequences on the Loppa High are also tentatively assigned to the group, but need further investigation (see below).
Offshore reference areas
The Barents Sea subsurface reference area is located on the eastern Finnmark Platform (Fig 9.1 , 9.2 , 9.7) , where the Billefjorden Group has been penetrated in its entirety in wells 7128/4-1 from 2503 to 2058 m (Fig 9.8) . and 7128/6-1 from 2533.5 m to 2150 m (Fig 9.9) . Southwards, towards the Norwegian mainland, the Upper Palaeozoic succession subcrops against the Pliocene/Pleistocene unconformity and the IKU shallow cores 7127/10-U-02, 7127/10-U-03 and 7029/03-U-01 penetrated different intervals of the group (Bugge et al.1995). Present seismic coverage and quality provides reasonable control on the seismic-scale lateral development of the group on the Finnmark Platform.
Thickness
Thicknesses of 445 m and 384 m in wells 7128/4-1 and 7128/6-1 respectively should be compared to cumulative thicknesses of up to 2500 m in the type area of Billefjorden and of 590 m on Bjørnøya (Dallmann et al. 1999; Worsley et al. 2001). As elsewhere, the group’s sediments were deposited in the early phase of a period with active rifting, and both wells are located over the crests of structural highs in the southern part of the Finnmark Platform; seismic data indicate that the group is more than 600 m thick in the adjacent halfgrabens. Well 7120/2-1 on the Loppa High penetrated an 847 m thick succession of sediments tentatively assigned herein to the Billefjorden Group; the succession was encountered from 2624 m to 3471 m, before the well was terminated in a possible dolerite (Fig 9.10) , see also discussion in next section).
Lithology
On the Finnmark Platform, medium- to coarse-grained, occasionally conglomeratic, sandstones and minor siltstones and coals dominate the basal part of the succession represented by the Soldogg Formation . These are overlain by a succession of stacked metre-scale fining-upward cycles of sandstone, siltstone, claystone and coal assigned to the Tettegras Formation . The upper part of the group, represented by the Blærerot Formation , is characterised by a basal unit of fossiliferous limestones, overlain by marine shales and fine- to medium-grained, fluvial and shallow marine sandstones. Sediments tentatively assigned to the group are very differently developed on the Loppa High where well 7120/2-1 penetrated 847 m of varicoloured arkosic breccias, conglomerates, ignimbrites and other types of volcanoclastic deposits (Fig 9.10) . The basal 115 m are dominated by brownish siltstone and mudstone. The red nature of these sediments, together with their high content of volcanoclastics, makes them anomalous representatives of the Billefjorden Group in this area, although palynomorphs indicate an early Carboniferous age (Viséan PU to VF Miospore zones from 3467 to 2682 m and early Serpukhovian TK Zone from 2645 to 2630 m) (Lindström, in press). The only other arctic areas where lower Carboniferous red beds have been found are in the northern part of eastern Greenland (Stemmerik et al. 1993), but even there the change to red beds appears to have occurred in the late Tournaisian – i.e. older than the earliest datings on the Loppa High. The Loppa sequence’s overall lithology and tectonic setting seems rather to suggest closer affinities to the lowermost clastics of the overlying mid-Carboniferous Gipsdalen Group . More work is clearly needed on this problem, especially in view of this representing the only occurrence of volcanoclastics in the Upper Palaeozoic of the Barents Shelf; we note that dolerite dykes of probable mid- to late Carboniferous age have been reported by Lippard & Prestvik (1997) on Magerøy in Finnmark and mid-Carboniferous volcanics have also been identified on the adjacent Kola peninsula in northern Russia (Ulmishek 1982). In view of these uncertainties, this sequence has not yet been defined as a formational unit, and its assignment to the Billefjorden Group is still tentative.
Lateral extent and variation
The group is generally difficult to map outside the Finnmark Platform and little is known about its regional distribution and variation, although the overall impression is that the Billefjorden Group represents thick siliciclastic-dominated wedges that fill developing Carboniferous half-grabens in the southwestern Barents Sea. On the Finnmark Platform itself seismic mapping of the group suggests pronounced lateral variations in thickness due to infill of local half grabens resulting from Viséan–Serpukhovian rifting. Most of the thickening and probably most of the lateral facies changes are in the uppermost part of the group. The rift event appears to be less pronounced east of approximately 29º 30' on the Finnmark Platform where the base of the group is poorly defined seismically. A possibly pre-Viséan sedimentary succession is present locally in this eastern part of the platform. The group’s representatives also seem to infill local half-grabens on the Loppa High and the Norsel High (central Bjarmeland Platform), and deeply buried half-graben systems appear to be also present further to the east on the Bjarmeland Platform. Thick wedge-shaped units corresponding to the Billefjorden Group are observed on seismic lines along the margins of the Nordkapp Basin, suggesting that the basin already formed a major depocentre at that time.
Sediments assigned to the Billefjorden Group are generally separated from the underlying strata by an angular unconformity, as seen in wells
7128/6-1 , 7128/4-1 and core 7029/03-U-01. In 7128/6-1 , the group rests on Precambrian metasandstones (Røe & Roberts, 1992) at 2533.5 m RKB, with a 45 m thick transitional zone of conglomeratic sandstones interpreted as weathered and reworked basement rocks. These sediments are included in the Billefjorden Group (see definition of Soldogg Formation ). Upwards, they pass into more mature sandstones with rare siltstone and coal beds defined by a sharp upward decrease in bulk density and sonic velocity at 2488.5 m.
Age
The Billefjorden Group has been assigned to the Famennian to Viséan in the onshore areas of Bjørnøya and Spitsbergen (Dallmann et al. 1999; Worsley et al. 2001). The offshore development has been dated to the Viséan to early Serpukhovian. On the Finnmark Platform, palynomorphs suggest that the basal part of the group is of middle to late Viséan age (Bugge et al. 1995), i.e. significantly younger than the Famennian to Tournaisian age recorded for the basal sediments onshore. The upper part of the group is apparently of late Viséan to early Serpukhovian age (Bugge et al. 1995; Simon-Robertson 1992 and Geochem Group 1994). As noted above - the succession on the Loppa High has been dated to the Viséan to early Serpukhovian (Lindström, in press).
Depositional environments
The Billefjorden Group is characterised by an overall transition from continental fluvially dominated deposits of the Soldogg and Tettegras formations into transitional continental to marginal marine deposits of the Blærerot Formation on the eastern Finnmark Platform. The presence of coal indicates deposition in overall humid climatic conditions in contrast to the overlying Gipsdalen Group that is characterised by sediments deposited in more arid climates.
Shallow core data from 7029/03-U-01 suggest that the lower parts of the
Soldogg Formation represent basement wash and braided river deposits. These pass upwards into delta/coastal plain sandstones, siltstones, claystones and coals of the Tettegras Formation , and are overlain by marine and transitional continental to marginal marine deposits of the Blærerot Formation in well 7128/6-1 . The transitional nature of this upper part is demonstrated by rare coal beds in the lowermost part of the formation at well 7128/6-1 . The Blærerot Formation appears to be missing in 7128/4-1 either as the result of local uplift and erosion or because the marine transgression never reached the high on which the well was drilled. This depositional area was separated by a major fault southwest of well 7128/4-1 from the provenance areas of basement rocks and metasediments towards the Finnmark coast (Gabrielsen et al. 1990). Shallow cores 7127/10-U-02 and 7127/10-U-03 were taken in a proximal position, 2-3 km away from this main fault and record a thick development of Viséan syn-rift fluvial deposits (Bugge et al. 1995).
The succession on the Loppa High apparently represents deposition in alluvial fans and proximal braided river systems in a rapidly subsiding sub-basin. Local volcanic activity is suggested on the basis of the large amount of volcanoclastic material in well
7120/2-1 . The depositional environments recorded from the Finnmark Platform generally resemble those recognised in the onshore areas of Spitsbergen and Bjørnøya. The most important difference is the evidence of marine flooding of the eastern Finnmark Platform, perhaps suggesting more prevalent marine conditions in the contemporaneous Nordkapp Basin, with transgression from the east. The lithofacies and depositional environments of the Billefjorden Group on Spitsbergen and Bjørnøya are summarised by Gjelberg (1981), Steel & Worsley (1984) and Harland (1997), all emphasising the considerable facies variations related to local variations in tectonic regime. The reservoir potential of the group’s sandstones has been noted by several authors (Grønlie et al. 1980, Steel & Worsley 1984, Worsley et al. 2001).
Formations assigned to the group
The Billefjorden Group is represented by three formations on the Finnmark Platform and these are formally defined and described herein. Formational names are selected from land plants found in northern Norway that utilise nourishment from insects that stick to their leaves. The succession in well 7120/2-1 on the Loppa High is not yet given any formal formational status.
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Groups&nav3=11
11
BJARMELAND GP
GROUP
Bjarmeland Group

Name
Bjarmeland was used by the Vikings to describe the area immediately south of the Barents Sea. The area was visited and described by the Norwegian Viking, Ottar, in the 9th century. The name was more recently used to name a structural element on the Barents Shelf: the Bjarmeland Platform (Gabrielsen et al. 1990). The group was introduced and briefly reviewed by Dallmann et al. (1999) in the knowledge of the ongoing more detailed work presented herein.
Type area
The Bjarmeland Platform in the southern Norwegian Barents Sea is here defined as type area for the group since the offshore successions are best displayed in wells from this area, including the eastern flanks of the Loppa High (Fig 9.38) . Three wells show typical developments of the group: 7124/3-1 (4271 m to 3900 m), 7226/11-1 (4334 m to 4103 m) and 7121/1-1 R (3990 m to 3502 m): the base of the group is defined by the basal stratotype of the biohermal Polarrev Formation in well 7229/11-1 on the northern Finnmark Platform.
Reference areas
Well 7228/9-1 S (4361 m to 4065 m) (Fig 9.38) . located on the Finnmark Platform’s northern margins towards the Nordkapp Basin illustrates the group’s development in a deeper water basinal setting. The Finnmark Platform itself is an important reference area since the group has been drilled in a variety of settings from the outer platform areas to the north ( 7229/11-1 , 4282 m to 3970 m, (Fig 9.38) . across the central platform ( 7128/4-1 , 1820 m to 1704 m) and 7128/6-1 , 1835 m to 1745 m) to the southern updip areas represented by core 7128/12-U-01, 569.2 m to 557.5 m). The succession assigned to the group in 7128/4-1 and 7128/6-1 corresponds to lithological unit L-8 of Ehrenberg et al. (1998a). Hambergfjellet on the southern mountain massif of Bjørnøya is designated as an onshore reference area. Hambergfjellet is the type area of the Hambergfjellet Formation, the only onshore unit to be assigned to the Bjarmeland Group at the present time.
Thickness
The group attains a maximum thickness of 488 m in well 7121/1-1 R at the eastern flank of the Loppa High. It is thinner, 233-371 m, in wells 7226/11-1 and 7124/3-1 on the Bjarmeland Platform (Fig 9.38) . On the Finnmark Platform the group thins from 312 m in well 7229/11-1 to 116-89 m in wells 7128/4-1 and 7128/6-1 central on the platform and less than 50 m in the IKU cores further updip. The Hambergfjellet Formation on the southern cliffs of Bjørnøya shows a similar thickness of up to 60 m, but this unit wedges out and disappears northwards on the island.
Lithology
The group is dominated by white to light grey bioclastic limestones containing a typical cool-water fauna of crinoids, bryozoans, brachiopods and siliceous sponges. Silty, dark grey to black, locally bituminous limestones characterise the deeper-water succession. Minor cherts occur, especially in the uppermost part. Siliciclastics are rare, except on the Polheim Subplatform where the group is unusually developed and dominated by fine-grained siliciclastics and marls (well 7120/1-1 R2 ). The Hambergfjellet Formation on Bjørnøya consists of basal sandstones which onlap all older units from basement to Gipsdalen Group , passing up into sandy bioclastic limestones with a fauna dominated by crinoids, bryozoans and brachiopods (Worsley et al. 2001).
Lateral extent and variation
The group is most thickly developed at the eastern flanks of the Loppa High and eastward across the Bjarmeland Platform. The thickest development is in outer platform settings north and south of the Nordkapp Basin where thick bryozoan-dominated buildups occur as isolated mounds or merge to form elongated complexes (Gerard & Buhrig 1990; Nilsen et al. 1993). Intermound and basinal areas are dominated by more fine-grained and thinly bedded limestones, which in well 7120/1-1 R2 are interbedded with siliciclastic shales. The platform areas of the eastern Finnmark Platform are characterised by relatively uniform successions of bedded crinoid- and bryozoan-dominated packstones and grainstones.
The group is seen to onlap palaeohighs and the margins of the depositional basin such as the eastern flank and crestal areas of the Loppa High and the southern parts of the Finnmark Platform. It is missing in wells
7120/12-2 and 7120/12-4 from the southern Hammerfest Basin – western Finnmark Platform and onshore it is only known from the Hambergfjellet Formation on Bjørnøya, - although future work may well demonstrate that the uppermost Gipsfjorden Formation and the Vøringen Member (Kapp Starostin Formation) of the Tempelfjorden Group both age- and facies-wise represent lateral equivalents of parts of the group on Spitsbergen.
Age
Fusulinids suggest a mid-Sakmarian to late Artinskian age in 7128/6-1 (Ehrenberg et al. 2000). The base of the group is thought to be highly diachronous, oldest in the more distal settings and youngest on the platforms (Fig 9.4) . The Hambergfjellet Formation on Bjørnøya is dated as late Artinskian based on fusulinids and conodonts (Nakrem 1991; Nakrem et al. 1992). Fusulinids indicate a similar age in cores 7128/12-U-01 and 7129/10-U-01 (Bugge et al. 1995; Ehrenberg et al. 2000).
Correlation
The lower, Sakmarian to early Artinskian, part of the group may correlate to the uppermost Gipsfjorden Formation of Spitsbergen. The upper, late Artinskian, part - including the Hambergfjellet Formation of Bjørnøya - perhaps should be correlated to the transgressive Vøringen Member of the Kapp Starostin Formation on Spitsbergen (Dallmann et al. 1999; Worsley et al. 2001).
Depositional environments
The group is characterised by deposition of carbonates dominated by crinoids, bryozoans, brachiopods and siliceous sponges. The fauna is markedly different from the foraminifer-dominated warm-water fauna of the underlying Gipsdalen Group and is believed to reflect deposition in more temperate cool-water environments (Stemmerik 1997). Deposition took place in a variety of cool-water carbonate environments and deposits range from shallow inner shelf bioclastic grainstones to outer shelf bryozoan-dominated buildups and thinly bedded bioclastic wackestones and packstones. Siliciclastic input to the basin was limited - except locally in the west where deeper water shales are interbedded with resedimented carbonates in 7120/1-1 R2 ; sand input was also significant on Bjørnøya, immediately adjacent to the subaerially exposed parts of the Stappen High. The bryozoan-dominated carbonate buildups formed along the margins of the Nordkapp Basin on the outer part of the platforms. They are often located above older buildups. Distally to the trend of build-ups more marly sediments have been recorded in well 7228/9-1 S .
Formations assigned to the group
The Bjarmeland Group is represented by three formations in the offshore areas of the southern Norwegian Barents Sea. The formations are formally described herein and named after predators common to Arctic Norway. The Polarrev and Ulv formations show an interfingering of the carbonate buildups of the former and the inter-buildup lithofacies of the latter formation. The Ulv Formation was also developed in the outer platform and basinal areas throughout deposition of the group, while the uppermost Isbjørn Formation in inner shelf areas overlies earlier buildups but does not extend into deeper waters characteristic of the Ulv Formation . The Hambergfjellet Formation of Bjørnøya, defined by Worsley & Edwards (1976) is included in the group, as it appears to represent a lithologically similar but highly condensed (<60 m thick) development of the Isbjørn Formation .
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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12
BLODØKS FM
FORMATION
SHETLAND GP
Blodøks Formation

Name
Named after Eirik Haraldson Blodøks, a Norwegian king who reigned in Norway (A.D. 930-934) and in Northumberland (A.D. -954).
Well type section
Norwegian well 25/1-1 from 3807 m to 3790 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig 5.33) . No cores.
Well reference sections
Norwegian well 35/3-2 from 3207 m to 3190 m, coordinates N 61°51'05.98", E 03°46'28.22" (Fig 5.34) . No cores. Norwegian well 1/3-1 from 4371 m to 4343 m, coordinates N 56°51'21.00", E 02°51'05.00" (Fig 5.24) . No cores. Danish well BO-1 from 2220 m to 2213 m, coordinates N 55°48'02.22", E 04°34'18.66" (Fig 5.27) . Cored throughout.
Thickness
The formation is 17 m thick in the type well ( 25/1-1 ), 17 m in well 35/3-2 , 28 m in well 1/3-1 and 7 m in well BO-1. It rarely exceeds 20 m in thickness.
Lithology
The formation consists of red, green, grey and black shales and mudstones which are non-calcareous to moderately calcareous. In the central North Sea the formation may show a varied influx of marls, limestones and chalky limestones.
Basal stratotype
The lower boundary is generally characterized by a distinct log break with an upward increase in gamma-ray intensity and a distinct decrease in velocity from the Svarte Formation (Fig 5.33) . or Hidra Formation (Fig 5.24) . into the Blodøks Formation. This is due to the lower content of carbonate in the Blodøks Formation.
Characteristics of the upper boundary
The upper boundary shows a decrease in gamma-ray intensity and an increase in velocity from the Blodøks Formation upwards into the more calcareous Tryggvason Formation (Fig 5.34) . or the chalky Hod Formation (Fig 5.24) .
Distribution
The formation is present throughout the North Sea, lacking only on local highs such as the Sørvestlandet High, the Utsira, Mandal, Jæren and Sele highs and the Grensen Ridge as well as above many salt diapirs.
Age
Latest Cenomanian to early Turonian.
Depositional environment
The formation was deposited during a period characterised by anoxic bottom conditions (e.g. Hart & Leary 1989). Presence of carbonates may indicate periods of more oxic conditions or supply of allochthonous limestones and chalks (e.g. Norwegian wells 1/3-1 and 2/5-1 ).
Remarks
The Blodøks Formation is equivalent to the former Plenus Marl Formation and the informal “formation B” of Deegan and Scull (1977) (Fig 5.6) . A black shale of early Turonian age is also widespread outside the North Sea, e.g. the Yorkshire Black Band in England (Jeffries 1963) and similar facies on Helgoland and in northwestern Germany (Schmidt and Späth 1980).
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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13
143
BLÆREROT FM
FORMATION
BILLEFJORDEN GP
Blærerot Formation

Name
From the Norwegian name for Bladderwort (Utriculária vulgáris).
Definition
The basal stratotype is defined at 501.8 m in IKU core 7029/03-U-01 on the Finnmark Platform (Fig 9.12) , (Fig 9.17) ; Table 9.1). Increased sonic velocities, imaging the contrast between the underlying porous sandstones and overlying tight carbonates, define the transition from the Tettegras Formation into the basal beds of the Blærerot Formation. Bedrock is overlain by glacial drift at 436 m in the core so that the formation’s upper part and total thickness is unknown in the type section (Fig 9.12) . Bugge et al. (1995) noted that the upper 15 m of the core, dated by them to the Serpukhovian, appear to show facies characteristic for both the Billefjorden and Gipsdalen groups, “reflecting a probable gradual transition between the two groups” in this area.
Reference section
A reference section is defined in the interval from 2202 m to 2150 m in well 7128/6-1 (Fig 9.9) ; Table 9.1). No cores were cut in this well, but logs show the same pattern as in the type section.
Thickness
The preserved thickness is 65.8 m in the type well and the total thickness 52 m in the reference well.
Lithology
The lowermost five metres of the Blærerot Formation consist of intensely bioturbated grey to yellowish brown limestone and sandy dolomites in core 7029/03-U-01. Bugge et al. (1995) described these as partially dolomitised mudstones and wackestones containing gastropods, brachiopods, bivalves, trilobites, foraminifers and crinoids. Large, laminated irregular nodules, interpreted as oncoids, are present in the lower part. The carbonates are overlain by a 23 m thick coarsening-upward succession of dark grey silty shale with a total organic carbon (TOC) content of 3-4% in the lower part. The shale becomes more bioturbated and less organic-rich upwards. It contains much of the same marine fossils as in the underlying carbonate unit, but in addition abundant terrestrial plant remains are present. There is sharp transition towards the overlying 22 m thick sandstone dominated unit, which consists of two coarsening-upwards cycles with basal dark grey siltstones. The sandstones are fine- to medium-grained and contain low-angle trough cross lamination and wave ripples (Fig 9.17) . Yellowish-brown silty shales with some coal abruptly overlie the apparently shallow marine succession of the lower Blærerot Formation and these are interpreted as coastal plain deposits (Fig 9.18) . Log correlation suggests that the same overall lithologies are present in the reference well 7128/6-1 . Cuttings from the basal carbonate bed in this well include a fauna very similar to that described from the type section.
Lateral extent and variation
The formation is only known from 7029/03-U-01 and 7128/6-1 . It is thinnest in 7128/6-1 , which is located over the crest of a rotated fault block. The formation is missing from 7128/4-1 on the crest of an adjacent uplifted block. Available biostratigraphic data suggest that the Blærerot Formation interfingers laterally with the Tettegras Formation towards the south (see Bugge et al. 1995).
Age
Palynomorphs in the type section indicate a late Viséan – early Serpukhovian age in the type section (Bugge et al. 1995). A similar age range is indicated for the formation in well 7128/6-1 (Simon-Robertson 1992).
Depositional environments
The carbonate beds at the base of the formation record the first marine flooding of the Finnmark Platform. Initial deposition of shallow marine platform carbonates was followed by deposition of shale in lower shoreface environments. The sandstones in the top of the type section are of upper shoreface to possibly fluvial origin (Bugge et al. 1995). The entire formation represents deltaic or shoreface progradation as the depositional response to a rapid marine transgression and its development resembles that of the classical Yoredale cycles of the UK (see e.g. Elliott 1975).
Correlation
Marine sediments are not known from the Billefjorden Group onshore Spitsbergen and Bjørnøya. Age-equivalent, non-marine sediments are widespread in the region and lacustrine organic-rich shales have been reported from the Sverdrup Basin (Goodarzi et al.1987; Davies & Nassichuk 1988). However, this unit probably represents the farthest extent of a marine transgression, presumably from the Timan-Pechora Basin to the east (c.f. Alsgaard 1993; Johansen et al. 1993) and correlative marine sequences should be expected to be present at depth in the Nordkapp Basin.
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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14
11
BOKNFJORD GP
GROUP
Boknfjord Group

Name
From the main fjord in Rogaland, Norway.
Type area
The Fiskebank and Egersund Sub-Basins comprise the type area. The group is illustrated in the Norwegian well 9/4-3 (Conoco), (Fig 3.36) .
Thickness
In the type area wells show thicknesses of up to 500 m. In well 9/4-3 the thickness of the group is 290 m. Towards the basin margins the section thins considerably.
Lithology
The sediments of the group are dominated by shales. Varying amounts of siltstone, sandstone, limestone stringers and differences in organic content make it possible, however, to subdivide the group into formations (Olsen and Strass, 1982).
Boundaries
The lower boundary is characterized by a distinct log break with the underlying sandstones of the Vestland Group . The upper boundary is usually characterized by abrupt changes in log response to lower gamma ray and interval transit times in the overlaying Valhall Formation1). In the Egersund Sub-Basin this boundary may be difficult to identify due to a large supply of clastic material.
Distribution
The group is confined to the Fiskebank and Egersund Sub-Basins although the upper two formations extend further westwards than those lying below.
Age
The group ranges in age from Callovian to Ryazanian.
Subdivisions
The group can be subdivided into four formations, the Egersund (base), Tau , Sauda and Flekkefjord formations (top).
Remarks
The term "Bream Formation" was first used by Deegan and Scull (1977) to describe a Callovian-Portlandian (Volgian) sequence, mainly clay-stones and siltstones, distributed throughout the Norwegian-Danish Basin. The formation comprised the Egersund Member, Børglum Member and Fredrikshavn Member. The Bream Formation was adopted with some modification by Michelsen (1978) for the Danish Sub-Basin where it comprises the Børglum and Fredrikshavn Members. Recent correlation work in the Egersund and Fiskebank Sub-Basin (e.g. Olsen and Strass, 1982) shows the existence of four argillaceous units, ranging in age from Callovian-Ryazanian, which are considered stratigraphically useful. They are widespread enough to deserve formation status and different enough from the Danish deposits to merit separate nomenclature. These units are the Egersund , Tau , Sauda and Flekkefjord formations. The formal definitions of the unit in this volume outline their relationship to the Egersund/Børglum/Fredrikshavn Members of Deegan and Scull (1977). Note that the Flekkefjord Formation was formerly part of the early Cretaceous Vallhall Formation, also defined by Deegan and Scull.
The four formations fall naturally into a single "claystone" group. It is not however considered proper to elevate the former Bream Formation to a "Bream Group" which would encompass these units, since it may still desirable to retain the formation status of the Bream Formation and the member status of the Børglum/Fredrikshavn Members in the Danish sector.
It is therefore proposed that the term "Bream Formation" should be abandoned for the Fiske-bank and Egersund Sub-Basins, and replaced by the Boknfjord Group, which is defined above.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
Footnotes
  • 1) Åsgard Formation according to Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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15
BRENT GP
GROUP
Brent Group

Name
Named by Deegan and Scull (1977). According to Norwegian usage, the unit earlier had formation status and the type well was UK well 211/29-3 (Shell). In this report the unit is given group status, also in the Norwegian sector.
Type area
The type area is the East Shetland Basin. The following wells are used to illustrate the Brent Group: UK well 211/29-3 (Shell), Norwegian wells 33/9-1 (Mobil), 30/6-7 (Norsk Hydro) and 31/4-4 (Norsk Hydro).
Thickness
The thickness of the group varies considerably. In UK well 211/29-3 (Brent Field) it is 226.5 m, while the Norwegian well 33/9-1 in the Statfjord Field has 204 m of Brent Group sediments. Wells used to illustrate the group on and around the Horda Platform have thicknesses between 159 m ( 30/6-7 ) and 78 m ( 31/4-4 ). Thicknesses of 200 m or more are present to the north in quadrant 35.
Lithology
The group consists of grey to brown sandstones, siltstones and shales with subordinate coal beds and conglomerates.
Boundaries
In the Brent-Statfjord area the group normally rests with a minor disconformity on the predominantly argillaceous Dunlin Group. To the west and in the southern Viking Graben it cuts down onto lower levels within the Dunlin Group . On the Horda Platform the lower boundary is either picked at the base of a "coarsening upward" log motif, with underlying marine shales, or at the base of a homogenous sandstone with a "blocky" log appearance. The upper boundary of the Brent Group may vary in nature due to post-middle Jurassic tectonism and erosion. Variable amounts of the group may be missing, particulary, towards the crests of tilted fault blocks, but the contact is nevertheless easy to pick where the sandy Brent Group is overlain by Heather Formation shales.
Distribution
The Brent Group is recognizable over most of the East Shetland Basin and the northern part of the Horda Platform. It passes southwards into the Vestland Group south of the Frigg Field area. The absence of the basal marine sandstones is considered to be the distinguishing feature of the Vestland Group . Northwards, the Brent Group shales out within the East Shetland Basin between 61°30' N and 62°N.
Age
Mainly Bajocian to Early Bathonian but including Late Toarcian to the east.
Subdivision
The group is divided into five formations. These are: the Broom (base), Rannoch , Etive , Ness and Tarbert (top) formations.1) According to Norwegian usage, the units earlier had a member status (Deegan and Scull, 1977). In this report it is proposed to give the units formation status also in the Norwegian sector. All formations are recognizable in the Brent-Statfjord area. However, difficulties are met when moving away from the type area. On the Horda Platform the Broom Formation appears to be absent, and the presence of the Rannoch Formation is under debate.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
Footnotes
  • 1): In addition the javascript:void(window.open('https://factpages.npd.no/factpages/Default.aspx?nav1=strat&nav2=PageView%7CLitho%7CFormations&nav3=123&menu=No','popup','width=700,height=800,resizable=yes,scrollbars=yes')) Oseberg Formation has been defined at the base of the Brent Group in the Oseberg Field and neighbouring fields in Graue et al. (1987).
Reference
  • Graue, E., Helland-Hansen, W., Johnsen, J., Lømo, L., Nøttvedt, A., Rønning, K., Ryseth and A., Steel, R. Advance and retreat of Brent Delta system, Norwegian North Sea. 915 - 937 in: Brooks, J. and Glennie, K. (eds.) 1987: Petroleum Geology of North West Europe.
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16
BROOM FM
FORMATION
BRENT GP
Broom Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2818 m to 2829 m, coord N 61°08'06", E 01'43'36.5" (Fig 3.10) .
Well reference section
Norwegian well 33/9-1 (Mobil) from 2664 m to 2668 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) .
Thickness
11 m in the type well and 4 m in 33/9-1 . In the Brent-Statfjord area it varies from a few meters to about fifteen meters in thickness.
Lithology
In the type well it is a pale grey to brown, coarse-grained poorly sorted conglomeratic sandstone containing shale clasts.
Boundaries
The Broom Formation is distinguished from the underlying Dunlin Group and the overlying Rannoch Formation by its irregular, but generally lower, gamma ray readings.
Distribution
The Broom Formation is easily identified in the Brent - Statfjord area. In parts of the East Shetland Basin a thin distal equivalent of the Broom Formation is present within the shales of the Drake Formation .
Age
Late Toarcian to Bajocian.
Depositional environment
The Broom Formation is a shallow marine deposit, and is a precursor of the regression which characterizes the overlying Rannoch Formation .
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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17
16
BRYGGE FM
FORMATION
HORDALAND GP
Brygge Formation

Name
From the Norwegian name for wharf or quay. The formation corresponds to the informally used Narvik Formation (H6-1).
Well type section
Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 2212.5 m to 1762.5 m (Fig 4.37) . No cores.
Thickness
450 m in the type well.
Lithology
Mainly claystone with stringers of sandstone, siltstone, limestone and marl. Pyrite, glauconite and shell fragments are seen in the sandstones.
Basal Stratotype
The base is defined by a decrease in interval transit time shown on the sonic log and by an increase in the density log readings.
Lateral extent and variation
The Brygge Formation is ubiquitous across Haltenbanken, but it is absent on the crest of the Nordland Ridge. A sand-dominated succession of Oligocene age, termed the Røyrvik formation, has been mapped (but not formally defined) off the Møre-Trøndelag coast (Askvik and Rokoengen, 1985). The Rørvik formation probably interfingers with the fine grained Brygge Formation to the west.
Age
Early Eocene to Early Miocene.
Depositional environment
The sediments were deposited in marine environments.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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18
67
BRYNE FM
FORMATION
VESTLAND GP
Bryne Formation

Name
From a town in the south-western part of Norway. This new formation represents the lower part of the Haldager Formation as described by Deegan and Scull (1977).
Well type section
Norwegian well 9/4-3 (Conoco) from 2507.5 m to 2613 m, coord N 57°36'54.5", E 04°18'57.7" (Fig 3.29) .
Well reference section
Norwegian well 8/12-1 (Conoco) from 2710.5 m to 2813 m, coord N 57°13'18.6", E 03°46'45.13" (Fig 3.30) .
Thickness
The formation is 105.5 m thick in the type well and 102.5 m in the reference well. It shows local variations in thickness which probably reflect both Middle Jurassic syndepositional structuring and later erosion.
Lithology
The Bryne Formation comprises interbedded sandstones, siltstones, shales and coals. The sandstones are white to grey, very fine to coarse grained, poorly sorted, friable to hard and occasionally kaolinitic. The shales are generally grey to brown, micaceous, occasionally silty, non-calcareous and often carbonaceous.
Boundaries
The base of the Bryne Formation is unconformable and represents the contact with the partly eroded shales of the Fjerritslev Formation or with arenaceous Triassic rocks. The boundary with the Fjerritslev Formation is usually clearly defined on both gamma ray and sonic logs, whereas the boundary with the Lower Jurassic/ Triassic sandy sequences ( Gassum and Skagerrak formations) often gives no appreciable log breaks. However, on most logs the appearance of these sediments is marked by an overall sonic log shift to higher interval velocities. Where the formation is overlain by the shales of the Boknfjord or Tyne groups, clear breaks can be observed both on gamma ray and sonic logs. However, where the formation is overlain by the Sandnes or Ula formations the boundary is not so easily defined due to internal facies changes within these two formations (see description of the Sandnes and Ula formations).
Distribution
The Bryne Formation is present in the Norwegian-Danish Basin and in the Central Graben. Two main Middle Jurassic depocentres are recognized; one in the Danish Sub-Basin and another in the Fiskebank Sub-Basin (Hamar et al., 1982). The Bryne Formation is equivalent to the Haldager Sand Member of the Haldager Formation as described in Denmark (Larsen, 1966; Michelsen, 1978).
Age
Mainly Bajocian to Bathonian, but may locally be older in the Norwegian-Danish Basin.
Depositional environment
The Bryne Formation represents deposition in a fluvial/deltaic environment.
Remarks
The Bryne Formation as described above is ap proximately equivalent in age and lithofacies to the Sleipner Formation of the Southern Viking Graben. So far it is not possible to demonstrate a connection between the two deposits, and this constitutes the reason for use of separate nomenclature. The Bryne Formation represents the lower part of the Haldager Formation, extended into the Norwegian sector from the Danish sector by Deegan and Scull (1977). Having defined exten-sive marine sands worthy of formation status ( Ula , Sandnes formations) comprising the upper part of Deegan and Scull's Haldager Forma tion, workers on this project saw the need for a separate formation, defining the lower non-marine sands. The term "Haldager Formation" could not be used since it essentially equates to the Haldager Sand Member, the lower part of the Haldager Formation in the Danish sector (Michelsen, 1978). (The upper part of the Danish Haldager Formation is the Flyvberg Member, a marine sandstone/siltstone unit approximately time-equivalent to the Sandnes Formation of the Norwegian-Danish Basin). When a previously established formation is sub divided into new units which are formally given formation status, the original formation with its original name should be either raised to group rank or abandoned; the old name should not be retained for any of the divisions of the original unit (Hedberg, 1976). It was therefore thought expedient to abandon the name "Haldager Formation" in the Norwegian sector. It is recognised, however, that there is probably complete lithological continuity between the new Bryne Formation of the Norwegian sector and the Haldager Sand Member of the Danish Haldager Formation.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=19
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186
BURTON FM
FORMATION
DUNLIN GP
Burton Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2950.5 m to 2993 m, coord N 61°08'06", E 01°43'36.5", (Fig 3.10) .
Well reference section
Norwegian well 33/9-1 (Mobil) from 2801 m to 2838 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) .
Thickness
42.5 m in the type well and 37 m in the reference well.
Lithology
In the type well it consists of a uniform development of dark grey to reddish-grey, soft non-calcareous claystone and shale, which may be in part slightly carbonaceous.
Boundaries
The formation is normally represented on both gamma ray and sonic logs by smooth linear almost constant readings, reflecting the lithological uniformity. The upper and lower contacts are identified where this log character changes.
Distribution
Although the log character changes slightly away from the type section, the formation can be recognised over a wide area of the northern North Sea. The formation has not been identified on the Horda Platform. It represents essentially a basinal facies and passes laterally into the Amundsen Formation in marginal areas.
Age
Sinemurian to Pliensbachian.
Depositional environment
The formation is believed to represent open marine basinal deposits.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=20
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29
BØRGLUM UNIT
FORMATION
BOKNFJORD GP
Børglum unit

This unit was first described by Larsen (1966) as the Børglum Formation. Later it was amended several times, the latest being by Michelsen (1978) who redefined it and reduced it to member status. It has been informally redesignated a formation by Hamar et al. (1982).
In the type area in Jutland, Denmark, the formation is of Kimmeridgian-Volgian age and consists of homogeneous shaly claystones, olive grey to blackish grey, slightly calcareous to non-calcareous, with mica, pyrite, shell fragments and lignite. This description is generally valid also in the eastern and southern parts of the Fiskebank Sub-Basin, as illustrated by the Norwegian well
10/5-1 (Conoco) from 1396 m to 1472.5 m, (Fig 3.39) . Further to the west a gradual change in lithology can be observed. The amount of carbonaceous material in the upper claystones increases, Norwegian well 9/12-1 (Shell), from 2011 m to 2038 m (Olsen, 1980) resulting in the transition to the Tau Formation in the Fiskebank Sub-Basin and in the Egersund Sub-Basin. The lower part of the Børglum unit as observed in the eastern areas is probably equivalent to the silty Egersund Formation in the north-west.
It is therefore recommended that the Danish nomenclature (the Børglum Member) should be applied in the south-eastern Norwegian Danish Basin and that the Norwegian nomenclature should be applied in the north-western area.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=21
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15
BÅT GP
GROUP
Båt Group

Name
Norwegian name for boat. The Båt Group comprises the lower and middle parts of the earlier used informal Halten Group (H1).
Type area
The transition from the Halten Terrace to the Trøndelag Platform in Blocks 6507/11 and 6507/12.
The group's development is illustrated by the type section of its basal unit in well
6507/12-1 (Saga Petroleum), coordinates 65°07'01.62"N, 07°42'42.61"E from 2920 m to 2213 m (Fig 4.7) . and in the reference well 6407/1-2 (Statoil), coordinates 64°47'50.61"N, 07°02'23.76"E from 4548 m to 3907 m (Fig 4.8) .
Thickness
707 m in well 6507/12-1 and 641 m in well 6407/1-2 .
Lithology
The Båt Group consists of alternating sandstone and shale/siltstone units, with sandstone as the dominant lithology.
Basal Stratotype
The base of the Båt Group is defined by the base of the Åre Formation as described herein.
Lateral extent and variation
The Båt Group is present in most of the wells drilled on Haltenbanken and Trænabanken, with maximum thicknesses in excess of 700 m. The upper part of the succession is progressively truncated towards the crestal part of the Nordland Ridge and the whole group is absent on the highest parts of the ridge. Shallow boreholes off the Trøndelag coast (Bugge et al. 1984) indicate that the Åre Formation may be absent and younger strata within the Båt Group onlap directly on Precambrian basement.
Age
Rhaetian to Toarcian.
Depositional environment
Shallow marine to deltaic environments dominated during deposition of the group.
Correlation
The group corresponds to the mid- Fruholmen to mid- Stø Formation sequence in the Realgrunnen Group1) of the Hammerfest Basin. The group is also partially equivalent to the Statfjord Formation and the Dunlin Group of the North Sea.
Subdivision
The group comprises four formations (Fig 4.7 , 4.8) 4.8) all of which are defined herein.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
Footnotes
  • 1) Kapp Toscana Group according to Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
Footnotes
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COOK FM
FORMATION
DUNLIN GP
Cook Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2887 m to 2950.5 m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2715 m to 2801 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) . 30/6-7 (Norsk Hydro) from 2975 m to 3023 m, coord N 60°38'39.49'' E 02°45'21.74" (Fig 3.12) . 31/2-1 (Shell) from 2093 m to 2134 m, coord N 60°46'19.16'' E 03°33'15.87" (Fig 3.13) . and 30/7-7 (Norsk Hydro) from 4735 m to 4801 m, coord N 60°16'19.30" E 02°16'07.30" (Fig 3.14) .
Thickness
63.5 m in the type well, 86 m in 33/9-1 , 66 m in 30/7-7 , 48 m in 30/6-7 and 41 m in 31/2-1 .
Lithology
In the type well section the formation is dominantly a marine siltstone with minor grey, silty claystone intercalations. The siltstones and claystones may contain sandy streaks, becoming more prominent away from the type well, especially in Norwegian waters. On the Horda Platform and along its western margin, sandstones are the dominant lithology in the formation. The sands are white to greyish brown, very fine to fine grained, subangular to subrounded and well sorted. Occasionally thin layers of medium to coarse grained sandstones are found. The sandstones are hard to friable. Silica is the most common cement. Mica, glauconite, carbonaceous material and calcareous cement may be present.
Boundaries
The formation can be distinguished from the more uniform and more argillaceous sediments above and below by a decrease in gamma ray response and an increase in velocity.
Distribution
The formation appears to be present throughout the East Shetland Basin and on the northern part of the Horda Platform.
Age
Pliensbachian to Toarcian.
Depositional environment
The sandstones can be divided into three types, related to depositional environment and basin geometry. In the Statfjord Field area the sandstones are believed to represent marine shoal sands (e.g. ref. well 33/9-1 ). On the Horda Platform and along its western margin the sandstones represent prograding shelf sands and several cycles can be identified within the formation (ref. 31/2-1 and 30/6-1 ). In the graben area the sands are thinner bedded, and the shale intercalations show no gradations into the sands (ref. 30/7-7 ). These sandstones are believed to represent redeposited sands from the edge of the shelf (the Horda Platform and East Shetland Basin west of the graben area).
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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29
CROMER KNOLL GP
GROUP
Cromer Knoll Group

Name
From the Cromer Knoll buoy in the southern North Sea. Named by Rhys (1974) in the southern North Sea and extended in use to the northern North Sea by Deegan and Scull (1977). The group as now used off mid-Norway corresponds to the informal Finnvær Group (H3).
Type area
The type area is in the southern North Sea. Rhys (1974) used UK well 48/22-2 to illustrate a typical section of the group, and Deegan & Scull (1977) used UK wells 29/25-1, 22/1-2A and 3/29-1, and Norwegian well 2/11-1 . In the North Sea the following Norwegian wells have been used to illustrate local developments of the group: 2/6-2 , 2/7-15 , 2/11-1 , 7/3-1 , 17/11-2 , 34/10-18 , 35/3-4 , 35/3-5 , 31/6-3 , 24/12-2 and 17/4-1 ; the Danish well DK1-1 has also been used.

In the Norwegian Sea the following wells are used to illustrate the local development of the group:
6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 3855 m to 3132.5 m and 6506/12-1 (Statoil) coordinates 65°10'07.58"N, 06°43'44.07"E, from 3835 m to 3175 m (Fig 4.25 , 4.26) The base of the Lyr Formation marks the lower boundary of the Cromer Knoll Group on Halten Terrace. In basinal areas to the west the Lange Formation is expected to rest directly on shales of the Viking Group (Fig 4.5) (Fig 4.6) .
Thickness
The thickness of the group varies considerably since the sediments were deposited in response to an active Late Jurassic tectonic phase. In the Viking Graben, the Åsta Graben and locally in the Central Trough the thickness is often more than 600 m, gradually thinning towards the basin margins. The group is 667 m thick in Norwegian well 2/11-1 and 643 m thick in Norwegian well 17/11-1 . Seismic data indicate that the group is thickest in the Sogn Graben, where it probably reaches up to 1400 m. In the Norwegian Sea 722.5 m are recorded in well 6506/12-4 and 660 m in well 6506/12-1 .
Lithology
The Cromer Knoll Group consists mainly of fine-grained, argillaceous, marine sediments with a varying content of calcareous material. Calcareous claystones, siltstones and marlstones dominate, but subordinate layers of limestone and sandstone occur. The claystones are generally light to dark grey, olive-grey, greenish and brownish, often becoming light grey, light greenish-grey and light olive-grey marlstones. Mica, pyrite and glauconite are common. Generally, marlstones become the more dominant lithology in both the upper and lower parts of the group. On Haltenbanken, the group consists of calcareous and non-calcareous claystones inter-bedded with marls and stringers of carbonates and sandstones. Sandstones are more common in the upper part of the group.
Basal stratotype
The lower boundary is usually well defined and is recognised by a distinct decrease in gamma-ray response and an increase in velocity when passing upward from the generally more organic-rich shales of the underlying Upper Jurassic formations (Fig 5.12, 5.13 , 5.14 and 5.22)
Characteristics of the upper boundary
South of approximately 59° N (Fig 5.32ab) , the upper boundary is the base of the chalk facies of the Shetland Group , defined by the onset of a decrease in gamma-ray response and an increase in velocity into the overlying carbonates (Fig 5.12 , 5.13 ,5.14 ,5.15 and 5.22 , 5.23 , 5.24 , 5.25 , 5.26 , 5.27 , 5.28) . The uppermost Rødby Formation of the Cromer Knoll Group often appears on logs as a transition between the overlying carbonates of the Shetland Group and the more argillaceous parts of the Cromer Knoll Group (Fig 5.12 , 5.22). Further north, the upper boundary is the base of the siliclastic facies of the Shetland Group (Fig 5.32ab) . This boundary is normally also shown by a decrease in gamma-ray response and an increase in velocity when passing into the overlying, generally more calcareous, Svarte Formation of the Shetland Group (Fig 5.33 , 5.36) However, the opposite log response at the boundary is also observed (Fig 5.37) .
Distribution
The group is widely distributed in the Norwegian sector of the North Sea. It is absent from the highest parts of the Mandal High, Jæren High, Utsira High and Lomre Terrace in the Troll area and locally from the Tampen Spur (Fig 5.7 , 5.8 , 5.9 , 5.10 , 5.11) . The group's representatives are found throughout the Halten Terrace and in basinal areas to the west. There is little lateral variation apart from a gradual increase in sandstone content to the north. The sequence is generally several hundred metres thick on the Halten Terrace and within the Helgoland Basin, but it is much thinner and locally absent on the Trøndelag Platform. The group is not preserved on parts of the Nordland Ridge nor on local highs along the western flank of the Trøndelag Platform.
Age
Ryazanian (usually late) to Albian/Early Cenomanian (Noth Sea). Ryazanian to Turonian (Norwegian Sea).
Depositional environment
Open marine, with generally low energy (North Sea). The sediments were deposited in shallow to deep marine environments (Norwegian Sea).
Subdivision
Six formations are defined within the group in the Norwegian sector of the North Sea (Fig 5.7 , 5.8 , 5.9 , 5.10 , 5.11) : the Åsgard , Tuxen (Jensen et al. 1986), Mime , Sola (Hamar & Hesjedal 1983; Jensen et al. 1986), Rødby and Agat formations. In addition we recognise a need to introduce the Ran sandstone units (Fig 5.7 , 5.8 , 5.9 , 5.10 , 5.11). Fig 5.4 shows an idealised development of the Cromer Knoll Group in the northern and central North Sea. In the Norwegian Sea the Cromer Knoll Group comprises three formations in the area (Fig 4.25 , 4.26) : Lyr , Lange and Lysing formations.
Remarks
The group was erected by Rhys (1974) to embrace three marine, arenaceous, argillaceous to marly formations of mainly Early Cretaceous age recognisable onshore and offshore. Deegan & Scull (1977) formally defined the group to include the sediments between the underlying Humber Group and Bream Formation and the overlying Shetland and Chalk groups. Vollset & Doré (1984) replaced the Humber Group of the northern North Sea by the Viking Group , and the Bream Formation in the Central Trough and the Norwegian-Danish Basin by the Tyne and Boknfjorden groups, respectively. The tops of the Draupne Formation of the Viking Group , the Mandal Formation of the Tyne Group and the Flekkefjord Formation of the Boknfjorden Group define the base of the Cromer Knoll Group. The Cromer Knoll Group is partly equivalent to the Rijnland Group of the Dutch sector (NAM & RGD 1980, Crittenden 1982) and the Speeton Clay Formation together with the Red Chalk Formation of the UK sector (Rhys 1974). The subdivision in this paper can be used for the Danish sector (see also Jensen et al. 1986).
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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DELFIN FM (INFORMAL)
FORMATION
SHETLAND GP
Delfin Formation (informal)

The Delfin Formation has been encountered in several wells in the northern Vøring Basin. It comprises sandstones of Early Campanian and Late Santonian age and is interpreted as a basin floor fan intercalated into shales of the Nise Formation . Wells show thicknesses of up to more than 1000 metres of good sandstone. The development of the Delfin Formation is illustrated by well 6707/10-1 . Well 6704/12-1 is situated in a partly different sub-basin. The sandstones encountered in this well are derived from a slightly different source area.
The Delfin Formation is named informally, no well type nor well reference sections have been established.
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143
DRAKE FM
FORMATION
DUNLIN GP
Drake Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2829 m to 2887 m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2668 m to 2715 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) . 30/6-7 (Norsk Hydro) from 2786 m to 2975 m, coord N 60°38' 39.49'', E 02°45'21.74" (Fig 3.12) . 31/2-1 (Shell) from 1985 m to 2093 m, coord N 60°46'19.16", E 03°33'15.87" (Fig 3.13) . 25/2-4 (Elf) from 3876 m to 3895 m, coord N 59°58'44.09", E 02°22'58.88" (Fig 3.15) .
Thickness
58 m in the type well, 47 m in 33/9-1 , 189 m in 30/6-7 , 108 m in 31/2-1 and 19 m in 25/2-4 .
Lithology
In the type well the lower part of the formation consists of medium grey, slightly sandy, calcareous claystone. The upper part is dark grey to black, fissile, micaceous shale containing calcareous nodules. On the Horda Platform and along its western margin white to grey, fine to coarse sandstones are found within the formation. The sandstones are often hard and calcite cemented. They also show and "upward coarsening" on the gamma ray log. The claystone is often silty.
Boundaries
In the basinal areas, where the sandstones are not present, the formation has more regular gamma ray and sonic log responses than that of the underlying formation, the gamma ray response being uniformly higher and the velocity lower. The lower velocity is also apparent where sandstone beds are present. The upper boundary is marked by the presence of arenaceous sediments of the overlying Brent Group , and the upper boundary is placed at the base of the upward coarsening sequence of the Rannoch Formation of the Brent Group . The Brent Group shows a more erratic sonic log pattern than the Drake Formation. In the south the top of the formation is marked by an unconformity (e.g. well 25/2-4 , (Fig 3.15) . In the northernmost area where the Brent Group is not recognised, the Dunlin Group is often unconformably overlain by the Viking Group .
Distribution
The formation is widely distributed throughout the East Shetland Basin and northern Horda Platform. It thins towards the west and south, where it may be absent due to erosion. The sand developments within the formation seem to be a function of marginal position within of the basin.
Age
Toarcian to Bajocian.
Depositional environment
The Drake Formation is generally considered to have been deposited in prodelta and delta front environments.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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29
DRAUPNE FM
FORMATION
VIKING GP
Draupne Formation

Name
From a gold ring owned by Odin (the mythologic Viking God) which "dripped" 7 new rings, of the same weight as the original, every 9th day. The name is considered particularly appropriate in view of the Draupne Formation's role as a prolific hydrocarbon source in the Northern North Sea. It replaces the name "Kimmeridge Clay Formation" as used by Deegan and Scull (1977) in the Northern North Sea (see remarks).
Well type section
Norwegian well 30/6-5 (Norsk Hydro) from 2452 m to 2615 m, coord N 60°41 '20.6", E 02°57'11.09", (Fig 3.22) .
Well reference sections
UK wells 211/21-1A (Shell) from 2729.5 m to 2810 m, coord N 61°11'09.6", E 01°06'45", (Fig 3.18) . and 210/30-1 (Arpet), from 3330 m to 3717.5 m, coord N 61°04'05.4", E 00°54'14.4'', (Fig 3.20) .
Norwegian wells
33/9-1 (Mobil) from 2443 m to 2450 m, coord N 61°15'07.5", E 01°50'25.8", (Fig 3.11) . 15/9-2 (Statoil) from 3397 m to 3478 m, coord. N 58°25'34.06", E 01°42'28.2", (Fig 3.26) . and 15/3-1 S (Elf) from 3947 m to 4754 m, coord N 58°50'57.00", E01°43'13.25", (Fig 3.19) .
Thickness
163 m in the type well, 80,5 m in 211/21-1A, 387,5 m in 210/30-1, 7 m in 33/9-1, 81 m in 15/9-2 and 807 m in 15/3-1 S .
Lithology
The formation consists of dark grey-brown to black, usually non-calcareous, carbonaceous, occasionally fissile claystone. It is characterized by very high radioactivity (often above 100 API units) which is a function of organic carbon content. It has anomalously low velocity, density and high resistivity. Minor limestone streaks and concretions occur throughout the formation. In addition interbedded sandstones and siltstones can cause a reduction in gamma ray response. The reference well 15/3-1 S is an atypical example of the Draupne Formation which has been chosen to illustrate these arenaceous intercalations.
An informal three-fold subdivision has been identified, and is best recognizable along the basin rim areas where a middle high gamma ray zone separates two zones of lower gamma ray response (e.g. 210/30-1).
Boundaries
These are marked by distinct log breaks due to the very high gamma ray response and low velocity shown by the Draupne Formation.
In basinal areas the formation generally has a diachronous contact with the
Heather Formation . On marginal highs the formation onlaps pre-Upper Jurassic rocks. On the northern Horda Platform, Upper Jurassic sandstones of the Sognefjord Formation mark the base of the Draupne Formation.
The upper boundary is often an unconformity or discontinuity, usually overlain by Cretaceous sediments which have a higher velocity and lower gamma ray response than the Draupne Formation. The importance and regional validity of this unconformity is under debate; see for example Rawson and Riley (1982).
Distribution
The formation is found in the East Shetland Basin, the Viking Graben and over the Horda Platform.
Age
The formation ranges from Oxfordian to Ryazanian in age.
Depositional environment
The Draupne Formation was deposited in a marine environment with restricted bottom circulation and often with anaerobic conditions. In places the formation may contain sandstones which are generally considered to be of turbiditic origin (De`Ath and Schuyleman, 1981; Harms et al, 1981).
Remarks
The Norwegian Lithostratigraphic Nomenclature Committee formally proposes abandonment of the name "Kimmeridge Clay Formation" for Upper Jurassic claystones encountered north of the Mid-North Sea High. The committee further recommends substitution of the names "Mandal Formation" (in the Central Graben area) and "Draupne Formation" (in the Northern North Sea) for intervals formerly termed Kimmeridge Clay Formation in those areas. The principal reasons for this revision are:
  1. distance from type area
  2. change in meaning of the term "Kimmeridge Clay Formation" from area to area
The type area for the Kimmeridge Clay Formation is Kimmeridge Bay in Dorset, southern England (e.g. Arkell 1947). There the unit consists of dark, organic-rich claystones of Kimme-ridgian to Volgian age (using Boreal stage terminology). The term was extended by Rhys (1974 and 1975) into the Southern North Sea to describe a unit of comparable age overlying Oxfordian limestones (Corallian Formation) in type well 47/15-1. Deegan and Scull (1977) further extended the Kimmeridge Clay into the Northern North Sea to denote a generally highly radioactive, generally low velocity claystone sequence. The age range of the formation was broadened to include part of the Oxfordian and Ryazanian. It was remarked that the sediments in the Southern North Sea were less radioactive (less than 60 A.P.I, units compared with 100-200 A.P.I, units in the north). However, the low seismic velocities shown by both units were considered sufficient grounds to justify a correlation.
Deegan and Scull did not specifically discuss the application of the term "Kimmeridge Clay" to the Central Graben region of the Central North Sea. Nevertheless, the name is in common usage there (e.g. Ofstad, 1983). It has, among other meanings, been taken to denote:
  1. all claystones of Upper Jurassic age regardless of log character, or more usually
  2. only the upper, most highly radioactive claystone unit of Volgian-Ryazanian age
To the northwest, in the Norwegian-Danish Basin, a similar deposit is present (the Tau Formation , described in this publication). This unit has never been referred to the Kimmeridge Clay Formation but is nevertheless a typical Upper Jurassic organic shale. It is of Kimmeridgian — Volgian age and occupies a lower relative position in the overall Upper Jurassic shale sequence than the Central Graben "hot shales". (Table 3.4). A connection between the two deposits across the Southern Vestland Arch is most unlikely.
In extending the Kimmeridge Clay Formation from the type area to the Northern North Sea (a distance of approximately 1300 km) the stratigraphic meaning of the name has varied considerably (Table 3.5). It is recognised that deposits of this type were laid down over a very wide area in intervals of the late Jurassic, the widespread deoxygenated bottom conditions reflecting the combined effect of paleo-geography with general sea level rise (e.g. Tyson et al., 1979; Ziegler 1982). However, acceptance of this overall regime should not alone be taken as a basis for lithostratigraphic classification. The nature and timing of the organic shales appears to have varied according to the evolution of individual basins. Use of the generic term Kimmeridge Clay Formation is a potential cause of mistaken correlation and does not further understanding of inter-basin relationships. Replacement of the name is a more palatable alternative to its continued extension northwards to the Arctic and Russia, where alternative nomenclature already exists.
It therefore seems appropriate to limit the "Kimmeridge Clay Formation" of the North Sea to to the area south of the Mid-North Sea High, as described by Rhys (1974). The Norwegian Lithostratigraphic Nomenclature Committee proposes substitution of the name "Draupne Formation" for the "Kimmeridge Clay Formation" of the Northern North Sea as defined by De-egan and Schull (1977). It is suggested that the name
"Mandal Formation" should be applied specifically to the "hot" shales of Volgian — Ryazanian age in the Central Graben region (Table 4), following the precedent set by Hamar et al., (1982).
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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188
DUNLIN GP
GROUP
Dunlin Group

Name
Named by Deegan and Scull (1977). According to earlier Norwegian usage the unit had formation status, and the type well was UK well 211/29-3. In this report the unit is given group status in Norwegian as well as UK usage.
Type area
The type area is the East Shetland Basin, in particular the region of the Brent Field. The group is illustrated in the following wells: UK well 211/29-3 (Shell), Norwegian wells 33/9-1 (Mobil), 30/6-7 (Norsk Hydro), 31/2-1 (Shell) and 25/2-4 (Elf).
Thickness
222 m in the UK well 211/29-3, 255 m, 365.5 m, 308 m and 204 m in Norwegian wells 33/9-1 (Mobil), 30/6-7 (Norsk Hydro), 31/2-1 (Shell) and 25/2-4 (Elf) respectively. The group is thickest in the northern Viking Graben area.
Lithology
The group consists mainly of dark to black argillaceous marine sediments, but in the marginal areas of the basin marine sandstones are well developed at several stratigraphic levels and can extend a considerable distance into the basin. The sandstones are white to light grey, very fine to medium grained and generally well sorted. The group tends to be more calcareous in the Norwegian sector, and in places limestone beds, some of which contain chamosite and siderite ooliths, are found.
Boundaries
The lower boundary with the Statfjord Group and the upper boundary with the Brent Group are clearly marked by gamma ray log breaks. The Dunlin Group generally has a more regular log character than the underlying and overlying sediments. In the northernmost area where the Brent Group is not recognised, the Dunlin Group is often unconformably overlain by the Viking Group .
Distribution
The group is more widespread than the underlying Statfjord Group and is thickest in the Viking Graben area, east of the Statfjord and Brent fields. It is recognizable over most of the East Shetland Basin and northern part of the Horda Platform. In places the Dunlin Group rests with an apparent unconformity on the Statfjord Group . In the western part of the basin higher formations within the group are thought to be transgressive onto pre- Statfjord Group sediments. Variation in thickness on tilted fault blocks probably reflects syndepositional movement.
Age
The group ranges from Hettangian to Bajocian in age.
Subdivisions
The Dunlin Group is divided into five formations. These are named the Amundsen (base), Johansen , Burton , Cook and Drake (top) formations and can be clearly differentiated on sonic and gamma ray logs. The Amundsen , Cook and Drake formations are found throughout the East Shetland Basin. The Burton Formation is found over most of the area but is not present on the Horda Platform. The Johansen Formation , on the other hand, has so far only been found on the Horda Platform. It should be stressed that the upper part of the calcareous sands in the Statfjord Group passes laterally into the lower part of the calcareous silts and shales of the Amundsen Formation in the central parts of the basin.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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29
EGERSUND FM
FORMATION
BOKNFJORD GP
Egersund Formation

Name
Named by Deegan and Scull (1977) who gave the unit member status.
Well type section
Norwegian well 9/4-1 (Amoseas) from 2251 m to 2288 m, coord N 57°35'02", E 04°01'13" (Fig 3.34) .
Well reference section
17/12-1 R (Phillips) from 2215 m to 2290 m, coord N 58° 11' 15.4'', E 03°56'22.2'' (Fig 3.35) .
Thickness
37 m in the type well and 75 m in the reference well.
Lithology
In the type well the formation consists of dark grey micromicaceous shales and siltstones with brownish, locally oolitic, microcrystalline carbonate beds and occasionally sandstone streaks. The latter become more important east and north-east of the type well.
Boundaries
The lower boundary is also the junction of the Boknfjord Group with the Vestland Group and is described above. At the base of the formation a more radioactive part is recognizable in several wells. The upper boundary is marked by the appearance of the dark grey to black organic-rich shales of the overlying Tau Formation . The shales of the Tau Formation have a high radioactivity and a low velocity, and therefore the upper boundary is marked by strong log breaks.
Distribution
The formation is distributed throughout Fiskebank and Egersund Sub-Basins.
Age
Callovian to Kimmeridgian.
Depositional environment
The Egersund Formation was deposited in an open marine, generally low energy basinal environment.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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15
EGGA FM (INFORMAL)
FORMATION
ROGALAND GP
Egga Formation (informal)

The Egga Formation (also referred to as Egga Member or Egga sandstone unit) has been encountered in a number of wells in the Møre Basin and Slørebotn Sub-basin. It comprises sandstones of Danian age and is interpreted as deepmarine massflow deposits. The development of the Egga Formation is illustrated by well 6305/7-1 . Wells on the Ormen Lange Field where it is the main reservoir unit have shown thicknesses of 40 to 80 m, while wells further east and south have encountered thicker sand-rich intervals. The Egga Formation is named informally, no well type nor well reference sections have been established.
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131
EIRIKSSON FM
FORMATION
STATFJORD GP
Eiriksson Formation

Name
Named after Leiv Eiriksson, the discoverer of North America in the year 1000, according to the Norse Sagas. He was the son of Eirik Raude.
Well type section
Norwegian well 33/12-2 (Mobil) (Fig 1.17-18) . from 2719 m to 2790 m below KB.
Well reference section
UK well 211/24-1 (Conoco/Gulf/NCB) (Fig .17-18) .
Thickness
71 m in the type well. In the reference well the formation is 157 m thick. The thickness is relatively constant over the area of the Statfjord Field but the formation thickens towards the south and west (Fig .17-18) . where sandstone characteristic of this formation occur at lower levels in the section.
Lithology
In the type well the formation is characterised by massive sandstone beds, generally correlatable between the wells, interbedded with hard grey shales. The sandstones are white to light grey, medium to very coarse grained with thin horizons of granules, pebbles, and lignite fragments, often concentrated in channels and along cross-bedding foresets. They contain slightly less kaolinite matrix, mica and rock fragments than the sandstones of the Raude Formation . The shales are slightly and commonly micaceous and carbonaceous. In the area of the Statfjord Field the sandstone beds average about 5 m in thickness and the shale beds average about 2.5 m. The sediments of this formation appear more mature than those of the Raude Formation , and marine fossils and glauconite are present near the top of the formation in the type well.
Boundaries
The originally Eiriksson Member of the Statfjord Formation was elevated to formation level by Lervik, 2006. There is usually a sharp upward transition from the Raude Formation reflecting a change to a more humid climate as well as a tectonic uplift of the hinterland. Sandstones are more abundant and thicker. The modified climate resulted in a change in the colour of the siltstones and mudstones from red to green and grey, and carbonate nodules and soils that formed in the previous evaporitic environment were replaced by coal- and carbonaceous-rich beds. The lower boundary is formed by the base of the lowest massive sandstone which can be well correlated. The upper boundary is marked by the base of the distinctive sandstones of the Nansen Formation which are frequently calcareous. The Eiriksson Formation has a characteristic blocky gamma ray and sonic log response but the boundaries may not always be marked by prominent log breaks.
Distribution
The formation is present over much of the northern North Sea, but not in the southern part of the East Shetland Basin.
Age
In the type well it is Hettangian, possibly extending into the early Sinemurian. However, to the west and south the base of the formation appears to be progressively older.
Depositional environment
Nystuen and Fält (1995) reported vertically stacked channel-sandstones forming multi-storey sandstone units up to 30-40 m thick. Cross-bedded sandstones with basal channel-lag conglomerates of coarse- to very coarse-grained sandstones with pebbles of quartz and gneiss (Nystuen and Fält, 1995) associated with coal facies are interpreted as having a fluvial origin (Røe and Steel, 1985). Røe and Steel (1985) discussed the sheet-like extent of the sand bodies, interpreting them as having formed in a relatively high-gradient, braided-alluvial setting. The Eiriksson Formation is interpreted as the more proximal braided-stream deposit of a fan-delta system associated with coastal to shallow marine elements. Deegan and Scull (1977) reported marine fossils and glauconite near the top of the fromation in well 33/12-2 , suggesting a marginal marine environment varying from coastal backswamp and river mouth situations to coastal barriers.
Compiled from
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25. The Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
  • Goldsmith, P. J., Hudson, G. and Van Veen, P. Triassic. 105 – 127 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
  • Lervik, K.-S. 2006: Triassic lithostratigraphy of the Northern North Sea Basin. Norwegian Journal of Geology, Vol. 86, pp. 93-116.
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157
EKOFISK FM
FORMATION
SHETLAND GP
Ekofisk Formation

Name
Named after the Ekofisk Field in Norwegian block 2/4 (Deegan & Scull 1977).
Well type section
Norwegian well 2/4-5 from 3164 m to 3037 m, coordinates N 56°34'29.77", E 03°12'13.03" (Fig 5.30) . No cores.
Well reference sections
Norwegian well 1/3-1 from 3354 m to 3258 m, coordinates N 56°51'21.00", E 02°51'05.00" (Fig 5.24) . No cores. UK well 22/1-2A from 2982.5 m to 2935 m, coordinates N 57°56'12.20", E 01°02'55.80" (Fig 5.25) . No cores. Norwegian well 2/5-1 from 3132 m to 3041 m, coordinates N 56°38'19.95", E 03°21'07.94" (Fig 5.31) . Cored through the upper 78 m.
Thickness
The formation is 127 m thick in the type-well, 96 m in 1/3-1 , 47.5 m in 22/1-2 A and 91 m in 2/5-1 . In the Norwegian sector, seismic interpretation indicates that a thickness of more than 150 m is found in the northwestern part of the Central Trough.
Lithology
In the type well, the formation comprises white, tan or beige, hard, dense, sometimes finely crystalline limestones, although softer chalky textures are also present. The formation usually consists of white to light grey, beige to brownish, mudstones or wackestones with occasional packstones/grainstones and pisolitic horizons, often alternating with argillaceous chalks, chalky limestones or limestones. Thin beds of grey, calcareous, often pyritic shales or clays are most common in the lower part while brownish-grey cherts occur rarely to abundantly throughout the formation.
Basal stratotype
The lower boundary is marked by a change in gamma-ray readings from a constant low level in the Tor Formation to a slightly lower level. The velocity may or may not show a corresponding increase. The lower boundary separates the Cretaceous and Tertiary chalks and may represent an unconformity (e.g. Norwegian well 1/9-1 , (Fig 5.29) .
Characteristics of the upper boundary
The upper boundary is defined where the gamma-ray response increases and the velocity decreases towards the marly beds of the Våle Formation . Where the marl is not present the change is more abrupt (e.g. Norwegian well 2/8-8 , (Fig 5.28) .
Distribution
The formation is widespread in the southern and central North Sea. In the Norwegian sector, it is missing from parts of the Sørvestlandet High and the Lindesnes Ridge.
Age
Danian.
Depositional environment
Open marine with deposition of calcareous debris flows, turbidites and autochthonous periodites (Skovbro 1983, d'Heur 1986, Hatton 1986).
Remarks
Two zones of the formation are readily correlatable within the Central Trough area (Hatton 1986, (Fig 5.24 , 5.29 , 5.30 , 5.31)
LOWER MEMBER OF THE EKOFISK FORMATION
The lowermost part consists of a low porosity to tight zone with a higher terrigenous clay content, and is informally termed the Ekofisk tight zone. The larger part consists of the informal Ekofisk reworked zone with mainly reworked Maastrichtian chalks ( Tor Formation ) deposited as various mass flows and periodite-facies chalks. This lower member is present in Norwegian wells 1/3-1 from 3354 m to 3307 m, 1/9-1 from 3104 m to 3072 m, 2/4-5 from 3164 m to 3106 m and 2/5-1 from 3132 m to 3099 m.
UPPER MEMBER OF THE EKOFISK FORMATION
This zone is composed of mainly homogenous chalks with a low clay content, debris flows of reworked Danian chalks and minor turbiditesc A lower tight to low porosity zone, informally termed the Tommeliten tight zone, is present in parts of the Central Trough. The zone is found in Norwegian wells 1/3-1 from 3311 m to 3258 m, 1/9-1 from 3072 m to 3036 m, 2/4-5 from 3102 m to 3037 m and 2/5-1 from 3094 m to 3041 m.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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143
ELDFISK FM
FORMATION
TYNE GP
Eldfisk Formation

Name
From the Eldfisk Field in Norwegian block 2/7.
Well type section
Norwegian well 2/7-3 (Phillips) from 3626 m to 3695m, coord N 56°23'02.9", E 03°14'45.9" (Fig 3.40) .
Well reference section
Norwegian well 1/9-3 R (Statoil) from 4359.5 m to 4386.5 m, coord N 56°24'56.2", E 02°54'15.15" (Fig 3.43) .
Thickness
69 m in the type well 2/7-3 and 27 m in the reference well.
Lithology
The Eldfisk Formation consists predominantly of sandstone but contains substantial interbeds of shale. In the type well the sandstone is dark yellowish brown, fine to coarse grained, poorly sorted and generally angular, while the shale is medium light grey to dark grey. Both the sandstone and the shale contain calcareous streaks which produce high amplitude peaks on the sonic log.
Boundaries
The sands of the Eldfisk Formation are entirely enclosed within the thick upper Jurassic shale sequence of the Central Graben. The Eldfisk Formation is therefore easily distinguished from the underlying Haugesund Formation and the overlying Farsund Formation by its lower gamma ray readings.
Distribution
As defined at present, the main development of the Eldfisk Formation is confined to the region of the Eldfisk Field , although thin time equivalent sands are present in other parts of the Central Graben.
Age
Kimmeridgian.
Depositional environment
The Eldfisk Formation represents an influx of sand into the axial portions of the Central Graben at a time of regression, and for this reason it is postulated that the formation is turbiditic in origin. However, no conventional cores have been taken in the sands and there is no definitive sedimentological evidence.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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177
ETIVE FM
FORMATION
BRENT GP
Etive Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2772 m to 2783 m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2575 m to 2602 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) . 30/6-7 (Norsk Hydro) from 2727 m to 2786 m 1), coord N 60°38'39.49", E 02°45'21.74" (Fig 3.16) . and 31/4-4 (Norsk Hydro) from 2721 m to 2758 m, coord N 60°40'01.12", E 03°06'54.12" (Fig 3.17) .
Thickness
11 m in the type well, 27 m in 33/9-1 , 59 m in 30/6-7 and 37 m in 31/4-4 .
Lithology
The formation consists of massive grey-brown to clear, fine to coarse, occasionally pebbly and cross-bedded sandstones. The mica-content is generally low. Calcite cemented stringers are also present, especially on the Horda Platform.
Boundaries
The formation is characterised by low gamma ray readings. This characteristic and the low mica content distinguish it from the underlying Rannoch Formation. The lower boundary may, however, be transitional in places. The formation is often found to cut into and occasionally through the underlying formations, thus giving a “blocky” gamma ray log character either above a truncated Rannoch Formation , or directly above marine shales of the Dunlin Group (ref. well 31/4-4 ). The upper boundary is taken at the first significant shale or coal in the overlying Ness Formation .
Distribution
The distribution of the Etive Formation is essentially the same as that of the Brent Group .
Age
Bajocian.
Depositional environment
The formation has been interpretated as upper shoreface, barrier bar, mouth bar and distributary channel deposits.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.

Footnotes

References
  • Graue, E., Helland-Hansen, W., Johnsen, J., Lømo, L., Nøttvedt, A., Rønning, K., Ryseth and A., Steel, R. Advance and retreat of Brent Delta system, Norwegian North Sea. 915 - 937 in: Brooks, J. and Glennie, K. (eds.) 1987: Petroleum Geology of North West Europe.
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16
FALK FM
FORMATION
GIPSDALEN GP
Falk Formation

Name
From the Norwegian name for a falcon (4 species, all belonging to the genus Falco, are found in northern Norway).
Definition
The type section is defined in the interval from 2221 m to 2024 m (log depth) in well 7120/2-1 , on the Loppa High (Fig 9.20) ; Table 9.1). The base corresponds to 2225, 7 m in core depth (Fig 9.24) . The formational base reflects an abrupt change from non-marine, reddish brown conglomerates of the Ugle Formation to dark grey, marine shales and marks the first marine transgression in the area; this gives a log response characterised by a change toward overall lower readings on the gamma ray log as a result of the transition into carbonates (Fig 9.20) . The formation otherwise shows a noisy log pattern, reflecting the intercalation of siliciclastics and carbonates.
Reference sections
Reference sections are found from 2150 m to 2050 m in well 7128/6-1 (Fig 9.25) . 2058 m to 1952 m in 7128/4-1 (Fig 9.26) . 498.6 m to 363.5 m in core 7029/03-U-02 (Fig 9.27) . and from TD at 481.7 m to 458 m in 7030/03-U-01 (Fig 9.28) . all located on the Finnmark Platform. In 7029/03-U-02 the base also represents an abrupt change in both colour and overall lithofacies from non-marine, red and green mottled silty shales to marine, greenish-grey, bioturbated silty shales. In wells 7128/4-1 and 7128/6-1 the formation corresponds to units L1 and L2 of Ehrenberg et al. (1998a).
Thickness
The formation is thickest in the type well (201.7 m); it is 135 m thick in 7029/03-U-02 on the southern Finnmark Platform and thins northwards to 100 m in well 7128/6-1 and 58 m in 7128/4-1 (Fig 9.19) . The formation is missing in 7226/11-1 where carbonates of the overlying Ørn Formation rest directly on basement, while wells 7124/3-1 , 7121/1-1 R , 7228/9-1 S and 7229/11-1 reached TD higher in the Gipsdalen Group .
Lithology
The formation consists of a mixture of shallow marine sandstones, marine siltstones and shallow marine carbonates. In 7120/2-1 , the lower 51 m consists of stacked, less than 5 m thick rhythms of coarse-grained pebbly sandstone with minor shale and dolomite (Fig 9.24) . Trough cross-bedding and horizontal lamination is common. This lower development is overlain by a 125 m thick unit of rhythmically interbedded shales, fossiliferous dolomitic mudstones to packstones (locally with anhydrite or chert nodules), and fine- to medium-grained sandstones with a few pebbly sandstone beds. Crinoids, brachiopods, fusulinids, small foraminifers and corals are the most abundant fossils, together with occasional phylloid algae and palaeoaplysinid plates. In the lower part of core 7029/03-U-02 and in 7030/03-U-01, the Falk Formation consists of 1 to 5 m thick fining upward units of light grey, medium- to coarse-grained, pebbly, trough cross-bedded to planar-laminated sandstones grading upwards into laminated greenish silty shales. Each unit has a sharp and erosive lower boundary. Marine fossils are limited to very rare brachiopods. The upper part of the formation in 7128/6-1 and 7029/03-U-02 consists of cycles of fine- to very fine-grained sandstone, green silty shale and carbonate wackestones to boundstones (Fig 9.25), (Fig 9.27), (Fig 9.29).
Lateral extent and variation
The base of the formation represents a major transgression of the platform areas as seen in 7120/2-1 from the Loppa High and in the Finnmark Platform wells 7128/4-1 7128/6-1 , and 7029/03-U-02, where marine siliciclastics overlie continental deposits or basement. The top of the Falk Formation is likely to be highly diachronous as it reflects the differing times when local siliciclastic source areas were drowned and the mixed siliciclastic-carbonate depositional system was replaced by carbonates. The formation is accordingly expected to be thickest in proximal platform areas and around tectonically active highs; thinnest developments are expected distally on the platforms, and either highly condensed or missing in the basins; these prognoses are supported by the gross wedge-shaped geometry of the formation seen on the Finnmark Platform. The formation is missing in areas that have been sheltered from siliciclastic supply, like the local high on the southern Bjarmeland Platform where well 7226/11-1 was drilled: in this location carbonates of the overlying Ørn Formation rest directly on basement .
Age
Stemmerik et al. (1995, 1998) suggested a late Bashkirian to early-middle Gzelian age based on fusulinid data. The formation is of late Bashkirian to Moscovian age in 7120/2-1 , where the lower part of the overlying Ørn Formation is dated as being of late Moscovian age (Stemmerik et al. 1998). The top of the formation in 7030/03-U-01 apparently coincides with the Kasimovian-Gzelian boundary whereas an even younger age is indicated in 7029/03-U-02 where the uppermost part of the formation extends into the early to middle Gzelian (Stemmerik et al. 1995; Bugge et al. 1995). In 7128/6-1 , the formation is of late Moscovian to early Gzelian age (Ehrenberg et al. 1998a).
Depositional environments
The Falk Formation is characterised by sediments deposited as a response to high frequency and high amplitude fluctuations in sea level (see e.g. Stemmerik et al. 1998; Stemmerik & Worsley 2000). Deposition also took place during an overall rise in relative sea level in shallow shelf environments ranging from offshore silt-dominated to shoreface sand-dominated lithofacies during deposition of the lower part of the formation. Sediments in the upper part of the formation suggest that the relative sea level rise had by then flooded most platform areas so that lithofacies there are characterised by more fine-grained siliciclastic input, deposited in offshore to lower shoreface environments, and by subtidal carbonates. The presence of caliche indicates periods of subaerial exposure of the carbonates, and during sea level lowstands the platform areas apparently formed vast lowlands.
Correlation
Mixed siliciclastics and shallow marine carbonates are common in the lower part of the Gipsdalen Group in the onshore areas of Svalbard. The formation correlates to the Kapp Kåre and Kapp Hanna formations on Bjørnøya (Worsley et al. 2001; Stemmerik & Worsley 2000), perhaps to the uppermost red-bed Hyrnefjellet Formation and lower Treskelodden Formation in Hornsund, the Tårnkanten/Schleteligfjellet and lower Wordiekamen formations of western Spitsbergen, and the Minkinfjellet, Malte Brunfjellet, Hårbardbreen and lowermost Wordiekammen formations of central to eastern Spitsbergen and Nordaustlandet (Dallmann et al. 1999: (Fig 9.6) . In contrast to the offshore and most onshore areas, both Bjørnøya and Hornsund were characterised by significant syndepositional tectonism at the time.
Possible members
No formal members are proposed herein, but the work of Ehrenberg et al. (1998a) and seismic mapping on the Finnmark Platform indicates that the formation in this area may comprise two distinctive units (“L-1” and “L-2”) separated by a hiatus spanning the lower Kasimovian in well 7128/6-1 . This corresponds to a period of tectonic activity on Bjørnøya (Worsley et al. 2001). On a seismic scale, however, these two informal units appear to be conformable on the Finnmark Platform.
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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51
FANGST GP
GROUP
Fangst Group

Name
Norwegian name for catch. Previous informal name was the Tomma Formation (H1-4).
Type area
The Halten Terrace. The group's development is illustrated by the type section of its basal unit in well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2536m to 2412 m (Fig 4.16) . Reference wells for the group are 6407/1-2 (Statoil), coordinates 64°47'50.61"N, 07°02'23.76"E, from 3907 m to 3658.5 m (Fig 4.17) and 6507/12-1 (Saga Petroleum), coordinates 65°07'01.62"N, 07°42'42.61"E, from 2213 m to 2094 m (Fig 4.18) .
Lithology
The Fangst Group typically comprises three lithological units: a lower fine to medium-grained sandstone with numerous shaly interbeds, a middle mudstone, and an upper relatively massive fine to coarse-grained sandstone. Each of these units are defined as formations herein.
Basal Stratotype
The base of the group is defined by the base of the Ile Formation as described below.
Lateral extent and variation
The Fangst Group is represented in most of the Trænabanken-Haltenbanken area except on the highest parts of the Nordland Ridge where its constituent units have been eroded. Time-equivalent sandstone-dominated sequences subcrop on the sea-floor along the inner part of the Trøndelag Platform (Bugge et al. 1984) and outliers of Middle Jurassic sediments are present east of the Froan islands and beneath Beitstadfjorden in Trøndelag. The latter probably represent a continental facies equivalent to the dominantly marine Fangst Group.
Along the southern margin of the Nordland Ridge (e.g. the
Heidrun Field ) the succession is much thinner than on Halten Terrace and the threefold lithologic division is not so obvious. Further north the Trænabanken wells show a lateral facies change to marine mudstone of the Viking Group and only the lower unit of the Fangst Group (the Ile Formation ) is recognized.
Age
Late Toarcian to Bathonian.
Depositional environment
Shallow marine to coastal/deltaic facies dominate sequences on the Halten Terrace. Increasing continental influence is inferred towards the Trøndelag Platform to the east, especially in the lower part of the group. Upper parts interfinger with marine shales to the northeast in the Trænabanken area.
Correlation
The Fangst Group corresponds generally to the Brent Group in the North Sea and to the Stø Formation on Tromsøflaket. However, the basal part of Stø Formation is older and the base of the Brent Group is slightly younger than the Fangst Group.
Subdivision
Although three formations are described herein it is clear that increasing knowledge will lead to the establishment of a more varied framework to reflect the lateral facies changes seen in the area.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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FARSUND FM
FORMATION
TYNE GP
Farsund Formation

Name
After the town of Farsund on the south-west coast of Norway.
Well type section
Norwegian well 2/7-3 (Phillips) from 3414 m to 3626 m, coord N 56°23'02.9", E 03°14'45.9" (Fig 3.40) .
Well reference sections
Norwegian well 7/12-2 (BP) from 3306 m to 3378.5 m, coord N 57°06'41.34", E 02°50'50.73" (Fig 3.32) and 2/8-3 (Amoco) from 3594m to 3761 m, coord N 56°18'31", E 03°26'54.1" (Fig 3.41) .
Thickness
200 m in the type well and 72.5 m ( 7/12-2 ) and 167 m ( 2/8-3 ) in the reference wells. The formation attains its maximum thickness in the axial part of the Central Graben and thins towards the flanking highs.
Lithology
The Farsund Formation consists predominantly of medium to dark grey shale. The shale is often well laminated and contains frequent calcareous streaks. Sandstone stringers are common in the type well 2/7-3 , particularly in the lowermost part of the sequence. In the reference well 7/12-2 , closer to the flank of the Southern Vestland Arch, a thinner Farsund Formation is present as a clear "coarsening upward cycle", becoming consistently less radioactive towards the top of the unit.
Boundaries
In the type well the base of the Farsund Formation occurs at the top of the sandy Eldfisk Formation and as a consequence is a pronounced gamma ray marker. Similarly, in the reference well the Farsund Formation overlies the sandy Ula Formation and is easily distinguished on logs. In several wells within the Central Graben, the Farsund Formation overlies the shaly Haugesund Formation with no intervening sand (e.g. reference well 2/8-3 . Here the base of the Farsund Formation is picked directly above the gamma ray minimum which forms the top of the Haugesund Formation .
The top of the Farsund Formation is marked by a further gamma ray minimum. Above this occurs the distinct log motif of the
Mandal Formation , with its high gamma ray and inter val transit time readings.
Distribution
The formation is present throughout the Central Graben but thin or absent over the Southern Vestland Arch and intra-basinal highs.
Age
Kimmeridgian to Volgian.
Depositional environment
The Farsund Formation shales were mainly deposited in a low-energy marine environment. The gamma ray log profile suggests that the formation represents an initial period of deepening followed by gradual shallowing. In parts of the Central Graben the occurence of thin sand stringers in the lower part of the formation probably represent minor turbidite influxes from the adjacent shelf, where time equivalent sands of the Ula Formation were being deposited.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=39
39
177
FENSFJORD FM
FORMATION
VIKING GP
Fensfjord Formation

Name
After a fjord on the west coast of Norway, adjacent to the type area in Quadrant 31.
Well type section
Norwegian well 31/2-1 (Shell) from 1594.5 m to 1741.5 m, coord N 60°46 '19.16", E 03°33' 15.87", (Fig 3.21) .
Well reference section
None at present.
Lithology
The formation consists of sandstones, grey-brown in colour, fine to medium grained, well sorted and moderately friable to consolidated. Calcite cemented sandstones occur in bands containing common bioclastic material. In the type well it is often carbonaceous and occasionally micaceous. Minor shale intercalations occur throughout. The formation has a "serrate" log character, composed of 3-5 m thick units arranged in several cycles.
Boundaries
The formation has an overall higher gamma ray intensity and larger FDC-CNL separation than the underlying Krossfjord Formation . The top of the Fensfjord Formation is characterized by a transition in the gamma ray log from a high intensity, serrate log shape to a high intensity but smooth outline in the overlying Heather Formation .
Distribution
The formation has only been clearly recognized in the Troll Field area.
Age
Callovian.
Depositional environment
The formation was deposited in a coastal shallow marine environment.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=40
40
188
FISKEBANK FM
FORMATION
ROGALAND GP
Fiskebank Formation

Name
From the Fiskebank (Fisher Bank), off the shore of southern Norway. Named by Deegan & Scull (1977).
Well type section
Norwegian well 9/11-1 from 1483 m to 1335 m, coordinates N 57°00'41.40", E 04°00'33.52" (Fig 5.54) . No cores.
Well reference section
Norwegian well 8/9-1 from 1399 m to 1307 m, coordinates N 57°26'27.28", E 03°51'03.48" (Fig 5.55) . No cores.
Thickness
The formation is 148 m thick in the type well and 92 m thick in the reference well.
Lithology
In the type section the major lithology is very fine grained, well sorted, slightly silty sandstone, which occasionally has calcareous cement.
Basal stratotype
The basal contact of the Fiskebank Formation is defined by the boundary between the shales of the Lista Formation and the coarser sediments of the Fiskebank Formation. The difference between the two formations is not well defined on the logs. The boundary is placed where the gamma-ray readings decrease and the velocity increases somewhat upwards into the Fiskebank Formation (Fig 5.54, 5.55)
Characteristics of the upper boundary
The Fiskebank Formation is overlain by the shales of the Balder Formation . The boundary is generally seen as an upward decrease in gamma-ray response and an increase in velocity (Fig 5.55) .
Distribution
The formation is encountered in the Norwegian-Danish Basin.
Age
Late Paleocene.
Depositional environment
The formation is probably a basin-margin deposit, and appears to be mostly time-equivalent with the Sele Formation .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=41
41
131
FJERRITSLEV FM
FORMATION
Fjerritslev Formation

Name
After the village of Fjerritslev, Jutland, Denmark, (Larsen, 1966)
Well type section
Fjerritslev No 2 well, Jutland, (Larsen 1966).
Well reference sections
In Norwegian waters wells 17/9-1 R (Esso) from 2835 m to 2992 m, coord N 58°28'27.26", E 03°50'16.18" (Fig 3.25) . and 7/9-1 (Conoco) from 2524 m to 2601 m, coord N 57°20'37.10", E02°51'21.4" (Fig 3.24) .
Thickness
In the Norwegian reference wells the thickness of the Fjerritslev Formation is 157 m ( 17/9-1 R ) and 77 m ( 7/9-1 ).
Lithology
The formation consists predominantly of grey to dark grey or greyish brown marine claystone. It is variably calcareous and pyritic. Silty intervals occur frequently, grading into grey or buff micaceous siltstone. In the Danish area the Fjerritslev Formation is divided into four members according to degree of siltiness (Michelsen, 1978). However, such a subdivision is not merited in the Norwegian sector.
Boundaries
The formation is distinguished from the underlying sandy deposits of the Gassum and Skagerrak formations, and from the overlying sands of the Vestland Group , by its higher gamma ray and lower sonic log velocity readings.
In reference well
17/9-1 R the Fjerritslev Formation is overlain by a sequence of interbedded lavas and sediments over 500 m thick which are probably of Lower-Middle Jurassic age. This sequence has only been identified in one well. The boundary between the Fjerritslev Formation and the volcanics is again made by an upward change to lower gamma ray readings and higher sonic log velocities, (Fig 3.25) .
Distribution
The Fjerritslev Formation is only patchily developed in the Norwegian sector. The developments which are present probably represent those remnants of a once more widely distributed deposit which survived the mid-Jurassic erosional episode. The formation has been penetrated in two distinct and separate areas; around the Southern Vestland Arch (e.g. blocks 7/9 and 7/12) and in the Egersund Sub-Basin (e.g. block 17/9).
Age
The formation ranges in age from Hettangian to Pliensbachian. It is approximately equivalent to the Lower Jurassic Dunlin Group of the Northern North Sea, although no direct connection between the two sequences is thought likely.
In reference well
17/9-1 R a dyke immediately below the Fjerritslev Formation has been dated as Pliensbachian (Fumes et al., 1982).
Depositional environment
The claystones of the Fjerritslev Formation are shallow marine sediments deposited during a widespread marine transgression.
Remarks
In block 17/12 (Bream area) a sequence of continental clastics has been dated as Pliensbachian to Toarcian (Olsen and Strass, 1982). They are therefore partially age-equivalent to the Fjerritslev Formation, but cannot on lithological grounds be referred to the latter, (Table 3.4). These deposits have not been named by the present nomenclature group.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=42
42
FLADEN GP
GROUP
Fladen Group

Name
From the Fladen Ground Spur, a structural feature.
Type area
The group is typically developed in the UK sector of the Central North Sea particularly in the area between the Piper and Forties oilfields.
Thickness
Within the volcanic province the thickest section penetrated so far is 1100 m and in this well the base of the volcanic was not reached. A considerable amount of thickness information was presented by Howitt and others (1975).
Lithology
The group embraces both volcanic and non-volcanic formations. Therefore the group contains a wide range of lithologies including basalts, tuff agglomerates, and normal continental to shallow water sediments.
Boundaries
The group normally rests on pre-Jurassic rocks, frequently Triassic sediments, and the lower boundary is marked either by the incoming of igneous rocks or the change from Triassic continental sediments to paralic sediments containing tuff horizons. The upper boundary is the contact with the marine sediments of the Humber Group. The Piper or Kimmeridge Clay formations may overlie the Fladen Group and in some sections the Heather Formation may be present but as noted earlier the complex interdigitations of the component formations of the Humber Group are not precisely known for this part of the Central North Sea.
Distribution
The group is largely restricted to the area of UK quadrants 14, 15, 16, and the more northerly parts of 21 and 22.
Age
Middle Jurassic.
Subdivision
As noted above the rocks of the Fladen Group are divided into two formations which are essentially end members of an interdigitating sequence. These are named the Rattray and Pentland formations. For present purpose if the encounters section contains more than half volcanic it is assigned to the Rattray Formation while if it contains more than half sedimentary rocks then it is placed in the Pentland Formation. As more data become available it will almost certainly be possible to subdivide the two formations further, and a proper understanding of the relationship between these end members may necessitate revision of the nomenclature in the future.
Source
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25; the Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Groups&nav3=205
205
FLEKKEFJORD FM
FORMATION
BOKNFJORD GP
Flekkefjord Formation

Name
From a town on the south-west coast of Norway. This formation was formerly included in the Valhall Formation of the Cromer Knoll Group (Deegan and Scull, 1977). The same unit was defined as the Flekkefjord Member by Rawson and Riley (1982), and is here elevated to formation status.
Well type section
Norwegian well 9/4-2 (Texaco) from 2155 m to 2208m, coord N 57°41'11.05", E 04°02'34.85" (Fig 3.38) .
Well reference section
Norwegian well 8/1-1 (Phillips) from 2379 m to 2425m, coord N 57°51'43.53", E 03° 12'27.64" (Fig 3.37) .
Thickness
In the type well it is 53 m, and in the reference well it is 46 m. This is also the approximate thickness in most wells within the Egersund Sub-Basin.
Lithology
The formation consists of dark grey shales which are variably carbonaceous, pyritic and may contain thin limestone stringers.
Boundaries
The lower boundary of the formation is clearly defined both on gamma and sonic logs by the contact with the more silty Sauda Formation . The upper boundary usually appears as a distinct log break, with higher radioactivity and higher interval transit times in the Flekkefjord Formation. In the Egersund Sub-Basin, which is situated closer to the source area, the boundary may be difficult to identify on logs.
Distribution
The formation is present in the Norwegian-Danish Basin. It is time-equivalent to the upper part of the Mandal Formation in the graben areas to the west and to the Fredrikshavn Unit C in the Danish sector to the east (Michelsen, 1978).
Age
Ryazanian.
Depositional envitronment
The Flekkefjord Formation was deposited in a marine, low-energy, basinal environment.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=43
43
15
FORTIES FM
FORMATION
ROGALAND GP
Forties Formation

Name
Named by Deegan & Scull (1977) from the Forties Field in UK block 21/10.
Well type section
UK well 21/10-1 from 2370 m to 2131 m, coordinates N 57°43'50.37", E 00°58'29.19" (Fig 5.44) . Cores.
Well reference section
Norwegian well 7/11-1 from 3069 m to 2904 m, coordinates N 57°04'15.60", E 02°26'24.40" (Fig 5.46) . No cores.
Thickness
The Forties Formation is 239 m thick in the type well and 165 m thick in the reference well. The thickness decreases eastwards and southwards into the Norwegian sector.
Lithology
The formation typically consists of interbedded sandstones, siltstones and claystones, becoming predominantly sandy higher in the section. The sand is fine to coarse grained, poorly to moderately sorted and contains minor amounts of lignite, pyrite, glauconite and mica. The sands encountered in the Norwegian sector were deposited distally in a lobe, and consist of very fine to fine, angular to subangular grains often with mica and a calcareous cement.
Basal stratotype
Where the Forties Formation rests on the Andrew Formation (Deegan & Scull 1977) its lower boundary is defined by a decrease in velocity into the sandstones of the Forties Formation (Fig 5.44) . This boundary may be difficult to define on logs. Eastwards the Forties Formation overlies the argillaceous Lista Formation , and the boundary is characterised by decreasing gamma-ray and increasing velocity readings into the Forties Formation.
Characteristics of the upper boundary
The upper boundary is defined as the break between the Forties sandstones and the shales of the more or less time-equivalent Sele Formation . The log response changes from low gamma-ray readings and high velocity to higher gammaray readings and lower velocity in the Sele Formation (Fig 5.44) . As the Forties Formation passes into shales eastwards it may be enveloped by the Sele Formation .
Distribution
The Forties Formation extends as a large lobe from the area south of the Halibut Horst to the northwestern part of the Central Trough. Its approximate distribution on the Norwegian continental shelf is shown in (Fig 5.47) .
Age
Late Paleocene.
Depositional environment
The Forties Formation was deposited as submarine fans.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=44
44
131
FRIGG FM
FORMATION
HORDALAND GP
Frigg Formation

Name
Named by Deegan & Scull (1977) after a Norse goddess, the wife of Odin.
Well type section
Norwegian well 25/1-1 from 2115 m to 1836 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig 5.62) . 42 m of cores (1868-1910 m).
Well reference section
Norwegian well 30/7-6 from 1923 m to 1783 m, coordinates N 60°29'29.82", E 02°03'26.14" (Fig 5.63) . No cores.
Thickness
The formation has a thickness of 279 m in the type well and 140 m in the reference well. A depocentre with a maximum thickness of approximately 300 m lies in Norwegian block 25/1.
Lithology
The formation consists of sandstones with some lenses and streaks of silty claystone. The sandstones are poorly consolidated, light brown to buff, micaceous and carbonaceous, and very fine to medium, occasionally coarse grained. Some layers have a calcareous cement. Traces of glauconite are present. The silty claystones are green to grey and carbonaceous.
Basal stratotype
The lower boundary normally shows a decrease in gamma-ray intensity and an increase in velocity from the Balder Formation into the Frigg Formation (Fig 5.62) .
Characteristics of the upper boundary
The top of the formation is placed where the sandstones give way to light grey to brown, occasionally green claystone of the Hordaland Group . The boundary is seen on logs as an increase in gamma-ray response and a decrease in velocity (Fig 5.62) .
Distribution
The Frigg Formation is found in the southwestern part of quadrant 30, the northwestern part of quadrant 25, and in adjacent areas in the UK sector. The Frigg sands of the Beryl and Brace Fields just extend into the Norwegian sector at about 59°30'N.
Age
Early Eocene.
Depositional environment
The Frigg Formation was deposited as submarine fans, by gravity flows. The mode of deposition led to the formation varying in thickness over short distances. The source was the East Shetland Platform to the west.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=45
45
67
FRUHOLMEN FM
FORMATION
REALGRUNNEN SUBGP
Fruholmen Formation

Name
From a lighthouse on a skerry north of Ingøy in Finnmark. The present formational concept embraces the two units T2-1 and T2-2 (Helgøy and Ytterøy formations) of earlier informal usage.
Well type section
Well 7121/5-1 (Statoil), coordinates 71°35'54.88"N, 21°24'21.78"E, from 2793 m to 2572m (Fig 4.46) .
Well reference section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 2535 m to 2337 m (Fig 4.47) .
Thickness
From 221 m in the type well to 198 m in 7120/12-1 .
Lithology
Basal grey to dark grey shales pass gradually upwards into interbedded sandstones, shales and coals. Sand dominates in the middle of the formation in several wells, while the upper part is more shaly, prompting a tripartite subdivision into (ascending order) the Akkar (Squid) Reke (Prawn) and Krabbe (Crab) members. The extent of these members in the type and reference wells are shown in (Fig 4.46 , 4.47).
Basal Stratotype
The base of the formation (and of the Akkar Member) is defined by a marked increase in gamma ray and neutron porosity logs, but often more moderate increases in interval transit time and bulk density readings.
The middle
Reke Member is characterized by a lower gamma ray response, but its base can be best defined by a carbonate bench above which the separation between density and porosity logs decreases markedly. This separation increases again at the base of the uppermost Krabbe Member . A characteristic feature of the Reke and Krabbe members are funnel-shaped gamma ray responses.
Lateral extent and variation
No marked trends in lateral variation are suggested by present data, although few wells have yet penetrated the entire formation; the thickest sequence (262 m) is seen in well 7120/9-2 . The unit may be represented in its entirety further to the north in the Hammerfest Basin by the more shaly marine lithofacties of the Akkar Member passing up into sands of the overlying Tubåen Formation .
Age
The base of the formation is early Norian. The top corresponds in general to the Triassic/ Jurassic transition, but available data indicate that it is somewhat diachronous.
Depositional environment
Open marine shales of the Akkar Member pass up into coastal and fluvial sandstone dominated sequences of the Reke Member . These represent northward fluviodeltaic pro-gradation with a depocentre to the south. As the main deltaic input shifted laterally, most of the central and southern parts of the basin became the site of flood-plain deposition, with more marine environments to the north.
Subdivision
Present information suggests subdivision into three members as described above.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=46
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128
FUGLEN FM
FORMATION
ADVENTDALEN GP
Fuglen Formation

Name
Fuglen lighthouse is situated on the western tip of Sørøy at 70°40'N and 21°55'E. The unit corresponds to T3-1 or Risfjord Formation of earlier informal schemes.
Well type section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 2047 m to 2019 m (Fig 4.50) . The lowermost 5 m and the contact with the underlying Stø Formation are cored in this well.
Well reference section
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 2658 to 2610 m (Fig 4.51) .
Thickness
28 m in the type well and 48 m in the reference well.
Lithology
Pyritic mudstones with interbedded thin limestones give characteristic gamma, sonic and density log responses. The shales are dark brown and the limestones white to brownish grey.
Basal Stratotype
The lower boundary is marked by sharp increases in gamma ray and density responses and by an accompanying decrease in interval transit time.
Lateral extent and variation
The formation is thickest in southwestern parts of the Hammerfest Basin, thinning to less than 10 m on the central highs in the basin; these areas are characterized by rare, thin limestones and by pyritic shales.
Age
Late Callovian to Oxfordian.
Depositional environment
The formation was deposited in marine environments during a highstand with ongoing tectonic movements. Coarse clastic sources were not emergent, but local block structures were the sites of low sedimentation rates.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=47
47
1
GARN FM
FORMATION
FANGST GP
Garn Formation

Name
From the Norwegian word for a net. The unit corresponds to the upper part of the Tomma Formation (H1-4) of informal usage, or “Tomma I”.
Well type section
Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3704 m to 3600 m (Fig 4.20) . The lower 84 m of the unit are cored, including the base.
Well reference section
Well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2457 m to 2412 m (Fig 4.16) . The lower 29 m of the unit are cored, including the base.
Thickness
104 m in the type well and 45 m in the reference well.
Lithology
The Garn Formation consists of medium to coarse-grained, moderately to well-sorted sandstones. Mica-rich zones are present. The sandstone is occasionally carbonate-cemented.
Basal Stratotype
The lower boundary is defined by a drop in gamma ray response. In the type well this coincides with an erosional contact at the base of a thin conglomerate.
Age
Bajocian to Bathonian.
Depositional environment
The Garn Formation may represent progradations of braided delta lobes. Delta top and delta front facies with active fluvial and wave-influenced processes are recognized.
Lateral extent and variation
The Garn Formation is encountered across most of Haltenbanken. It may be over 100 m thick on the Halten Terrace, but in structurally high positions the entire unit may be eroded. In the Trænabanken area shaly sediments are lateral equivalents of the Garn Formation sandstones.
Correlation
The Garn Formation is time equivalent to parts of the Brent Group in the North Sea, to the lower part of the Vardekløft Formation in East Greenland and to the upper part of the Stø Formation in the Hammerfest Basin.
Subdivision
The formation is not subdivided at present although two different units may be identified in the western part of Haltenbanken.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=48
48
38
GASSUM FM
FORMATION
Gassum Formation

Name
After the village of Gassum, Jutland, Denmark, (Larsen, 1966).
Well type section
Danish well Gassum No. 1 from 1613 m to 1643 m below ground (Ground evelation 53.3 m) (Bertelsen, 1978).
Well reference sections
In Norwegian waters wells 17/10-1 (Shell) from2682 m to 2825 m, coord N 58°01 '54", E 03°09'58" (Fig 3.23) . and 7/9-1 (Conoco) from 2601 m to 2609 m, coord N 57°20' 37.1", E 02°51'21.4" (Fig 3.24) . The section in well 17/10-1 was included by Deegan and Scull (1977) in the Skagerrak Formation .
Thickness
In the Norwegian reference wells the thickness of the Gassum Formation is 143 m ( 17/10-1 ) and 8 m ( 7/9-1 ).
Lithology
In the type well the formation consists of predominantly light grey to whitish, in places rather coarse-grained sandstones, with subordinate dark-coloured clay bands and coal lenses (Larsen, 1966). In Norwegian waters the formation is predominantly a white to light grey, mainly fine to medium grained sandstone, but frequently contains coarse sand and gravel. It is often calcite cemented and in some instances contains glauconite.
Boundaries
In the Norwegian sector the lower boundary may be characterized by a general lowering of the velocity when entering the underlying Skagerrak Formation . Often this boundary coincides with a distinct horizon with high gamma ray response (e.g. well 17/4-1 (Elf) and well 9/12-1 (Shell)).
The upper boundary of the Gassum Formation is easily picked where it is overlain by Lower Jurassic shales of the
Fjerritslev Formation or Upper Jurassic shales of the Boknfjord or Tyne groups. Where the Gassum Formation is overlain by the Middle Jurassic Bryne Formation (Norwegian sector), the boundary may only show a slight decrease in the gamma ray response and an overall decrease in velocity marking the appearance of the Bryne Formation .
In the reference well
17/10-1 , where the Fjerritslev and Bryne formations are missing, the Gassum Formation is overlain by the shales of the Boknfjord Group .
Distribution
In the Norwegian sector the Gassum Formation occurs throughout the Norwegian-Danish Basin, on the Southern Vestland Arch and along the northeastern margin of the Central Graben. Its distribution towards the axial part of the Central Graben is unknown. It is often completely or partially eroded as a result of mid-Jurassic earth movements.
Age
Rhaetian in the type well, but seems to become younger northwards (Bertelsen, 1978). Sparse dating in the Norwegian sector gives Rhaetian to Sinemurian ages.
Depositional environment
The sedimentology of the Gassum Formation in the Norwegian sector has not been much studied, but is assumed to represent fluvial to marginal marine deposits laid down during a transgressive phase at the Triassic/Jurassic transition.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=49
49
GIPSDALEN GP
GROUP
Gipsdalen Group

Name
Cutbill and Challinor (1965) introduced the term Gipsdalen Group for a suite of rocks of mid-Carboniferous to early Permian age. The group is widely exposed on Svalbard, with its type area in central Spitsbergen. The group’s overall geological development is well known onshore, both on Spitsbergen itself (e.g. Steel & Worsley 1984; Dallmann et al. 1999) and on Bjørnøya on the Stappen High (Worsley et al. 2001). The Gipsdalen Group is here extended to cover the offshore mid-Carboniferous to early Permian succession in the southern Norwegian Barents Sea and is there dominated by red-coloured siliciclastics and warm-water, often dolomitised carbonates – also with the significant presence of evaporites and the halite diapirs in the Nordkapp Basin. Wells 7121/1-1R , 7124/3-1 and 7226/11-1 from the margins of the Loppa High and the Bjarmeland Platform record deposition in deeper marine settings than seen onshore. The formational scheme proposed herein is relatively broad and reflects three, easily recognised, highly diachronous stages of development starting with red-bed sedimentation in isolated fault-controlled basins, followed by mixed siliciclastic-carbonate deposition and terminated by carbonate-dominated sedimentation on the platforms and carbonates and evaporites in the basins.
Offshore reference areas
In the Norwegian Barents Sea, 11 wells and 4 shallow cores have penetrated strata assigned to Gipsdalen Group. The subsurface reference area is located on the eastern Finnmark Platform where this succession has been penetrated by 7229/11-1 and 7228/9-1 S on the northern margin and 7128/6-1 and 7128/4-1 in a more central position on the platform (Fig 9.19) . Further toward the south, IKU drilled three cores (7029/03-U-02, 7030/03-U-01 and 7129/10-U-02) close to the Finnmark coast where the group’s sediments subcrop against the Pliocene/Pleistocene unconformity (Bugge et al. 1995). Additional information on the group’s development comes from well 7120/12-4 on the western Finnmark Platform.
The Loppa High also forms an important reference area with good seismic coverage, including a 3D survey, and three wells, viz.
7120/1-1R2 , 7120/2-1 and 7121/1-1R , that penetrate the succession in the southern Loppa High area (Fig 9.19 , 9.20) Further to the east, the group was encountered in wells 7124/3-1 and 7226/11-1 on the southern margins of the Bjarmeland Platform. A shallow core and several minicores have also been drilled on the Svalis Dome on the Bjarmeland Platform (Nilsson et al. 1996).
Thickness
The Finnmark and Bjarmeland platforms and the Loppa High formed low-angle ramps dipping toward the Nordkapp and eastern Hammerfest basins during deposition of the Gipsdalen Group. The thickest drilled succession is from the southern flanks of the Loppa High, where the group is more than 1000 m thick in well 7121/1-1R and seismic data suggest that a further 500 m is present below TD. This is comparable to the up to 1800 m thick successions recorded locally in marked half-graben structures such as Inner Hornsund and Billefjorden on Spitsbergen. In contrast the group’s sediments are totally absent on the crest of the Loppa High – as on southern Bjørnøya on the Stappen High – while well 7120/2-1 in a near-crestal position shows a 680 m thick development, similar to the 595 m thick development on northern Bjørnøya.
The group thins from approximately 315 m in well
7128/6-1 to 250 m in 7128/4-1 on the Finnmark Platform; IKU cores suggest comparable thicknesses (Bugge et al. 1995). Further to the west, well 7120/12-4 penetrated the upper 85 m of the group. Wells 7228/9-1 S and 7229/11-1 on the northern Finnmark Platform penetrated only the upper (Moscovian-Sakmarian) part of the group: this interval is 211 m and 333 m thick respectively in these wells - significantly thicker than the corresponding interval in 7128/4-1 and 7128/6-1 further to the south. The group thickens even more towards the northwest and seismic data from the Nordkapp Basin indicate thicknesses of several hundred metres. On the Bjarmeland Platform, the group is more than 800 m thick in well 7226/11-1 , where Bashkirian carbonates rest directly on basement. A total thickness of 1000 m is suggested by the 465 m penetrated in 7124/3-1 combined with seismic data from the underlying section. The group is 670 m thick in well 7120/1-1 R2 where it rests on garnet mica schists/gneisses of Caledonian age.
Lithology
The group is composed of metre-thick to rarely tens of metre-thick rhythmic units generally showing shallowing upward trends continental red bed sandstones, siltstones and conglomerates dominate the basal part of the succession. These are overlain by mixed carbonates and siliciclastics where the siliciclastics are grey-coloured marine sandstones, conglomerates and shales and the carbonates include a variety of shallow marine facies. The upper part of the group is dominated by rhythmically bedded limestones and dolomites with occasional small phylloid algal – Palaeoaplysina buildups, and minor evaporites on the platform areas. The biota is of chlorozoan composition and dominated by algae and foraminifers (c.f. Lees & Buller 1972). Seismic data suggest that the shelf carbonates pass into several hundred metre thick successions of stacked buildups in the deeper ramp areas (Elvebakk et al. 2002). These buildups have not been drilled and their internal composition and exact stratigraphic position is therefore unknown. However, similar relationships are described from age equivalent rocks in the Sverdrup Basin where the largest build-ups occur on the basin slope (Beauchamp 1993). Evaporites dominate in the basinal areas; anhydrite occurs interbedded with carbonates near platform margins whereas halite dominates in more distal settings.
Lateral extent and variation
The group’s sediments are found throughout the Norwegian Barents Sea. Thickest developments are seen in the Nordkapp Basin and other basinal areas where the succession is dominated by evaporites. The thickest carbonate-dominated successions are found on the distal parts of the platforms, such as the eastern flanks of the Loppa High and the northern margins of the Finnmark Platform. The group thins towards structural highs and mainland Norway: it shows a clearly onlapping development, so that the lower non-marine parts were deposited in isolated half-grabens, while platforms and highs only became part of the depositional basin later, when relative second order sea-level rise led to marine flooding of the entire circum-Arctic region (c.f. onland Spitsbergen, Steel & Worsley 1984). The group’s occurrence resting directly on basement in 7226/11-1 (see above) confirms this general pattern. The considerable variations in lithology, both laterally and vertically, reflect the ongoing sea level rise and resultant varying timing of drowning of different siliciclastic provenance areas. A larger proportion of shallow marine siliciclastics are expected updip on the platforms, while carbonate buildups are best developed on basinal margins. The Loppa and Stappen highs experienced several phases of tectonism during deposition of the group, in contrast to the vast bulk of offshore platforms and basins, and onshore exposures on Bjørnøya show interesting analogues for the development expected on the Loppa High (Worsley et al. 2001).
The boundary between the Gipsdalen Group and the underlying
Billefjorden Group is only known with certainty from wells 7128/4-1 and 7128/6-1 on the Finnmark Platform and from 7120/2-1 on the Loppa High. On the Finnmark Platform, the sharp contact between Lower Carboniferous grey fluvial siliciclastics with coals below and red bed facies with caliche above marks a boundary represented by a major regional unconformity in the circum-Arctic and is associated with a significant change in palaeoclimate from warm and humid to warm and arid to semi-arid (Steel & Worsley 1984; Stemmerik & Worsley 1989; Stemmerik 2000).
Age
The basal non-marine red-bed succession contains palynomorphs indicating a general Serpukhovian to Bashkirian age. Fusulinids suggest a late Bashkirian to Sakmarian age for the marine part of the group (Stemmerik et al. 1998; Ehrenberg et al. 1998a). In onshore areas of Svalbard, the group’s sediments have been dated to the late Serpukhovian to early Artinskian (Dallmann et al. 1999) (Fig 9.6)
Depositional environments
The basal non-marine red-bed succession of the Ugle Formation was deposited during active rifting in the ?late Serpukhovian to Bashkirian and cores from 7120/2-1 represent alluvial fan and braided river deposits. The overlying Falk Formation marks the transition into shallow marine deposition at a time when there still was siliciclastic supply from emergent highs. The Ørn Formation uppermost in the group was deposited in a variety of shallow to deeper marine carbonate environments during sea level highstands. The presence of extensive subaqueous anhydrite and halite deposits in the basins and sabkha evaporites on the platforms clearly suggests deposition took place in warm semi-arid to arid climates (Steel & Worsley 1984; Stemmerik 2000). The platform succession is characterised by stacked rhythmic shelf deposits often terminated by subaerial exposure surfaces, reflecting deposition during a time period characterised by high frequency and high amplitude fluctuations in sea level (e.g. Stemmerik & Worsley 1989; Pickard et al. 1996; Stemmerik et al. 1998; Ehrenberg et al. 1998a; Samuelsberg & Pickard 1999; Worsley et al. 2001). The depositional environments recorded from the platform areas generally resemble those recognised onshore Spitsbergen and Bjørnøya. The deeper marine, outer ramp and basinal deposits have no counterparts onshore.
Formations assigned to the group
Three formations are formally described below and these are named after birds of prey common to northern Norway. The still poorly known outer platform and basinal succession is provisionally included in the uppermost Ørn Formation .
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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51
GREY BEDS (INFORMAL)
GROUP
Grey Beds (informal)

Sediments of Triassic age beneath the Åre Formation have been encountered in a number of wells offshore mid-Norway. Based on their colour the Triassic section in the Norwegian Sea has been informally divided into “Grey Beds” and “Red Beds” . The “Grey Beds” sediments represent continental clastics of grey colour, deposited in a more humid climate compared to the “ “Red Beds” sediments. Thicknesses of more than 2500 meters have been drilled. No type well section has been established.
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52
GRID FM
FORMATION
HORDALAND GP
Grid Formation

Name
Named after a female giant in Norse mythology, who was one of the wives of Odin.
Well type section
Norwegian well 15/3-3 from 1840 m to 1470 m, coordinates N 58°52'31.25", E 01°46'46.24" (Fig 5.64) . No cores.
Well reference sections
Norwegian well 24/12-1 from 1660 m to 1502 m, coordinates N 59°02'29.80", E 01°52'57.93" (Fig 5.61) . No cores. Norwegian well 24/12-2 from 1397 m to 1282 m, coordinates N 59°12'00.75", E 01°52'53.34" (Fig 5.65) . No cores.
Thickness
In wells 24/12-1 and 24/12-2 it is 158 m and 115 m, respectively.
Lithology
The formation consists of sandstones with interbeds of claystone and siltstone. The sandstones often have a massive, "blocky", appearance as illustrated by type well 15/3-3 (Fig 5.64) . Individual sandstone beds show little, or no evidence of fining-upwards or coarsening- upwards. The sandstones are very fine to fine, sometimes medium to coarse. Sorting is generally moderate to good. Traces of mica, pyrite, glauconite and fossil fragments are common. A higher argillaceous content is found in distal areas. Well 24/12-1 illustrates the interfingering of thicker claystone units of the Hordaland Group with the Grid Formation (Fig 5.61) . Further subdivision may be possible in the future (see Remarks).
Basal stratotype
The lower boundary shows a decrease in gamma-ray response and an increase in velocity from the Hordaland Group into the sandstones of the Grid Formation (Fig 5.64) .
Characteristics of the upper boundary
The upper boundary is characterised by an increase in gamma-ray readings and a decrease in velocity from the sandstones of the Grid Formation into the clay-stones of the Hordaland Group (Fig 5.64) .
Distribution
The sandstones were probably derived from the East Shetland Platform and the formation is recognised in the Viking Graben area between 58°30'N and approximately 60°30'N (Fig 5.66) . A depocentre lies in Norwegian block 15/3 where the formation reaches a thickness of nearly 400 m. It thins eastwards and is not penetrated by wells on the Utsira High. It has been identified in some wells in the Oseberg area. In the Viking Graben north of 61° N, several sandstone bodies occur in the Hordaland Group at the same level, but it is uncertain whether they belong to the Grid Formation.
Age
Middle to Late Eocene, but wells 25/6-1 and 24/12-2 have given an Early Oligocene age.
Depositional environment
The formation is thought to have been deposited in an open marine environment during a regressive period. An eustatic fall in sea level in the Late Eocene is indicated by Haq et al. (1987).
Remarks
The formation comprises a series of sand bodies which interfinger with claystones. There is a considerable increase in thickness from less than 200 m north of 59° N (e.g. wells 24/12-1 and 24/12-2 ) to nearly 400 m south of 59° N (e.g. well 15/3-3 ). This is not due to a general increase in thickness, but rather to sand deposition having started earlier in the south. This could give grounds for erecting two formal units, a lower one confined to the area south of 59° N and probably of Middle Eocene age, and an upper one. In some areas the lower unit is separated from the upper one by a sequence of claystones which is referred to informally as the Belton member in the UK sector. However, lithological uniformity renders such subdivision impractical at present.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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67
HARDRÅDE FM
FORMATION
SHETLAND GP
Hardråde Formation

Name
Named after Harald "Hardråde" Sigurdsson, a Norwegian king (A.D. 1046-1066).
Well type section
Norwegian well 30/11-3 from 2892 m to 2601 m, coordinates N 60°02'38.59", E 02°32'15.47" (Fig 5.36) . No cores.
Well reference section
Norwegian well 31/6-2 from 978 m to 968 m, coordinates N 60°34'58.24", E 03°54'55.76" (Fig 5.37) . No cores.
Thickness
The formation is 291 m thick in the type well ( 30/11-3 ) and 10 m in well 31/6-2 . It is absent on tilted fault blocks in the Troll area (e.g. well 31/2-9 ).
Lithology
The formation consists generally of interbedded limestones and mudstones, except in the Troll area where it is thin and consists of a single limestone bed. The limestones are white or pale, moderately hard to very hard. The mudstones are medium to light grey, often silty and calcareous.
Basal stratotype
The lower boundary is towards the Kyrre Formation or an unconformity above older rocks. The boundary towards the Kyrre Formation is identified by the absence of relatively thick limestone beds in this formation and a lower content of calcareous material in the mudstone. This results in a decrease in gamma-ray intensity and an increase in velocity from the Kyrre Formation into the Hardråde Formation (Fig 5.36) . The formation has an unconformable lower boundary in the Troll area.
Characteristics of the upper boundary
The upper boundary is towards the Rogaland Group . When it is towards the Lista Formation it is characterized by an upward increase in gamma-ray intensity and a distinct drop in velocity due to a transition from limestones to mudstones (Fig 5.36) . An upper boundary towards the Våle Formation lacks the distinct drop in velocity. This is due to the presence of limestones and a more marly facies in the Våle Formation . An upper boundary towards the Ty Formation is shown by a change to sandstone.
Distribution
The formation is present on the Horda Platform (Fig 5.32ab) .
Age
Late Campanian to Maastrichtian.
Depositional environment
Open marine.
Remarks
The Hardråde Formation is time-equivalent with the Jorsalfare and Tor formations of the Shetland Group (Fig 5.6) .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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143
HAUGESUND FM
FORMATION
TYNE GP
Haugesund Formation

Name
After the town of Haugesund on the west coast of Norway.
Well type section
Norwegian well 2/7-3 (Phillips) from 3695 to 4191 m, coord N 56°23'02.9", E 03°15'45.9'7, (Fig 3.40) .
See “remarks” for qualification of this well type section.
Well reference sections
Norwegian well 3/5-2 (Gulf) from 3182.5 to 3345 m, coord N 56°32', 56°32'34.46", E 04°23 '11.1", (Fig 3.42) . and 2/8-3 (Amoco) from 3761 m to 4115 m (TD.), coord N 56°18'31", E03°26'54.1", (Fig 3.41) .
Thickness
496 m in the type well, 162.5 m in 3/5-2 , and 354 m in 2/8-3 . The formation is thickest in the axis of the Central Graben and thins towards the flanking highs, where it passes partially or entirely into the sandy lithology of the Ula Formation .
Lithology
The Haugesund Formation consists predominantly of shale ranging in colour from light grey to brownish black. The shale is often carbonaceous and calcareous, and contains frequent thin sandstone interbeds. In general the upper part of the formation represents an overall "coarsening-upward cycle", becoming sandier and siltier upwards.
Boundaries
In the type well, 2/7-3 , the Haugesund Formation overlies Zechstein salt and the base of the formation is therefore obvious from both logs and cuttings. However, the Zechstein salt is almost certainly penetrative at this location and does not therefore provide a true stratigraphic base for Haugesund Formation (see “remarks”). In the reference well 2/8-3 and elsewhere in the Central Graben the base of the Haugesund Formation is often found overlying the Vestland Group . This is shown in the reference well 3/5-2 where the upward change from the sandy Bryne Formation to the shales of the Haugesund Formation produces the expected gamma ray/sonic log break (see (Fig 3.42) .
The top of the Haugesund Formation in the type well is the contact with the sandy
Eldfisk Formation . In areas of the Central Graben where the Eldfisk Formation is absent, the top of the Haugesund Formation is picked at a clearly correlatable gamma ray minimum, above which the gamma ray increases to the higher values of the basal Farsund Formation (e.g. well 2/8-3 ).
Distribution
The formation is ubiquitous in the Central Graben and widely distributed around the flanks of the basin and intra-basinal highs. It is absent in the Ula Field where it is entirely replaced by time-equivalent sands of the Ula Formation , and is also absent on the crest of the Southern Vestland Arch and intra-basinal highs.
Age
Callovian to Early Kimmeridgian. In neither the type nor the reference wells have pre-late Oxfordian ages been proven but Callovian mudstones assignable to the Haugesund Formation occur in the vicinity of the reference well 3/5-2 .
Depositional environment
The bulk of the shales of the Haugesund Formation were deposited in a marine, low energy, basinal environment. The common thin sand interbeds may represent sporadic turbidite influxes emanating from the adjacent shelf where coarser elastics (i.e. the Ula Formation ) were being deposited. The "coarsening-upward" nature of the sequence represents an overall regression which was terminated by a further transgression and the deposition of the Farsund Formation shales.
Remarks
The type well 2/7-3 penetrated a thick development of the Haugesund Formation, considered to be typical of the formation as it is commonly encountered in the Central Graben. However, the inadequately defined base of the formation makes 2/7-3 ultimately unsatisfactory as a type well. None of the other Central Graben wells available to this study establish a base for this formation, and penetrations on the flanks of the basin (such as the reference well 3/5-2 are fewer, atypical and potentially controversial stratigraphically. Penetration of a well-defined base for the Haugesund Formation by a future well in the Central Graben would perhaps provide a rare instance in which replacement of a type well might be justified.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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177
HAVERT FM
FORMATION
SASSENDALEN GP
Havert Formation

Name
From the seal species Halichoerus grypus: The unit corresponds to unit T1-1 or the Svolvær Formation of earlier informal usage.
Well type section
Well 7120/12-2 (Norsk Hydro), coordinates 70°7'30.03"N, 20°48'19.00"E, from 3657 m to 3552 m (Fig 4.42) .
Well reference section
Well 7120/9-2 (Norsk Hydro), coordinates 71°29'40.81"N, 20°42'05.38"E, from 4956 m to 4806 m (Fig 4.43) .
Thickness
105 m in the type well and 150 m in the reference well.
Lithology
In the type well the formation consists of medium to dark grey shales with minor inter-bedded pale grey siltstones and sandstones comprising two generally coarsening upwards sequences. The reference section further north in the Hammerfest Basin shows a more monotonous silty shale sequence with only a very weak upwards coarsening trend.
Basal Stratotype
The base is defined by increasing gamma ray and decreasing density responses above underlying mixed clastic and carbonate sequences. In the reference well the base is also easily recognised as basal silty shales directly overlie a 6 m thick limestone bed.
Lateral extent and variation
Present information suggests a fining trend from the southern margins of the Hammerfest Basin northwards. Thicknesses are moderate and show no marked trends.
Age
Palynomorphs suggest a Griesbachian to Dienerian age.
Depositional environment
The formation was deposited in marginal marine to open marine settings with coastal environments to the south and southeast.
Correlation
Palynofloras and sequence development show similarities to the Vardebukta Formation of western Spitsbergen.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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140
HEATHER FM
FORMATION
VIKING GP
Heather Formation

Name
Named by Deegan and Scull (1977).
Well type section
UK well 211/21-1A (Shell) from 2810 m to 2840 m, coord N 61°11'9.6", E 01°06'5.7", (Fig 3.18) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2450 m to 2464m, coord N 61 °15°07.5", E 01°50'25.8", (Fig 3.11) . 31/2-1 (Shell) from 1531.5 m to 1594.5 m, coord N 60°46'19.16'°, E 03°33'15.87", (Fig 3.21) . and 15/3-1S (Elf) from 4754 m to 4986 m, coord N 58°50' 57.0'', E 01°43'13.25", (Fig 3.19) .
Thickness
30 m in the type well, but attains thicknesses in the order of a thousand metres in graben areas. In the reference wells the thicknesses are
Lithology
The formation consists of mainly of grey silty claystone with thin streaks of limestone. A further subdivision of the formation is possible (Fig 3.18) . although no formal status is proposed for this subdivision. Two divisions are commonly recognized. The lower division is light to dark grey, hard, silty claystone, often micaceous and calcareous. The upper division is separated into two further units by an unconformity detected by dipmeter data or biostratigraphical gaps, but no distinct lithological difference is noted. The lithology is dark grey silty claystone, carbonaceous in part with limestone streaks. (For further discussion see Deegan and Scull (1977) p. 18). On the Horda Platform where the Heather Formation interdigitates with sandstones of the Krossfjord , Fensfjord and Sognefjord formations, it becomes in places highly micaceous and may grade into a sandy siltstone.
Boundaries
The lower boundary is the contact with the arenaceous Brent Group . The upper boundary is the contact with the Draupne Formation , which has an anomalously high gamma ray response and low velocity. Both boundaries are therefore marked by log breaks.
Distribution
The formation can be recognized over most of the northern North Sea north of 58°N and east of the East Shetland Platform boundary faults.
Age
Bathonian to Kimmeridgian.
Depositional environment
The silty claystones of the Heather Formation were deposited in an open marine environment, brought about by the marine transgression which initially deposited the youngest formation of the Brent Group .
Remarks
Use of the Heather Formation is here restricted to the part of the North Sea north of approximately 58°N. Deegan and Scull (1977) indicated the presence of the formation in the Central Graben, but did not describe the area in any detail. Recent work (e.g. Ofstad 1983, and this report) suggests a subdivision of the Middle Jurassic-earliest Cretaceous claystones of this region into three new formations. None of these can alone be referred to the northern Heather Formation, and the name has therefore not been used in the southern area.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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188
HEGRE GP
GROUP
Hegre Group

Name
From the bird (English: heron) of the same name. The pre-Rhaetian Triassic rocks of the Northern North Sea were earlier designated the Cormorant Formation by Deegan and Scull (1977), having UK well 211/21-1A (Shell) as a type well section. In this report this Triassic Unit is given group status, while the Cormorant Formation is only applied to certain areas where a subdivision of the Triassic is impossible. We suggest that the Cormorant Formation should refer to attenuated sequences confined to structural highs in the UK sector.
Type area
The type area is the East Shetland Basin, west of the Viking Graben. The group is illustrated by UK well 211/29-5 (Shell), and Norwegian wells 33/5-1 (Norsk Hydro), 33/12-2 and 33/12-5 (Mobil).
Thickness
No well has penetrated a complete Triassic succession. The maximum drilled sequence is 1839 m in well 33/12-5 .
Lithology
The Hegre Group consists of intervals of interbedded sandstones, claystones and shales associated with sequences of dominantly sand or shale/claystone. Shales and claystones usually have reddish colours whereas the sandstones show a range in colour from white, light grey, orange to brick red. The grain size varies from very fine to very coarse and the sediments are in parts of a pebbly nature. The Hegre Group also has subordinate white limestone, anhydrite and brownishred marl.
Boundaries
The Hegre Group is directly overlain by Cretaceous strata on some of the structural highs. Where Jurassic is present, the top of the Hegre Group is normally placed at the change from interbedded sandstones and shales of the Hegre Group to the relatively massive clean sandstones of the Statfjord Formation . This is normally represented by a change from an irregular sonic log response in the Hegre Group to a more regular or blocky one in the Statfjord Formation . In addition the upper boundary of the Hegre Group is often close to the top of abundant red beds in the section - see also the description of the Statfjord Formation . The base of the Triassic rocks is only penetrated on structural highs and close to the margins of the sedimentary basin. In these sections only late Triassic seems to be present, and hence the nature of the lower boundary of the Hegre Group is not yet established. It is realized that the Hegre Group cannot be given full formal definition until its base has been adequately defined, but we nevertheless offer the term for interim use.
Distribution
The Hegre Group is apparently present in the whole Northern North Sea area. Its relationship to the Triassic units defined further south by Deegan and Scull (1977) is unclear. We therefore recommend that the term Hegre Group should only be used in the area north of 60°N. It is terminated to the west by major faults along the east flank of the East Shetland Platform and to the east by the Øygarden Fault Zone (Hamar et al., 1980). In the northeastern part of the North Sea area, where Precambrian/ Caledonian basement dips gently to the west, progressively younger Triassic sediments onlap basement in an easterly direction. In the east, on the Måløy Fault Blocks, Triassic strata are probably missing, but may have been preserved from erosion in N-S elongated basins to the east of the structural highs. Alternatively Triassic sediments might not have been deposited in this area. The thickness of the Hegre Group within the East Shetland Basin shows a general increase from the western flank toward the central part of the depositional basin. On the eastern flank thick Triassic deposits are found just west of the Øygarden Fault Zone, which may indicate that the Triassic sediments were deposited in an asymmetric basin.
Age
The Triassic sections penetrated in the Northern North Sea show ages from Late Triassic (early Rhaetian) to possibly Early Triassic (?Scythian).
Subdivision
The Hegre Group is divided into three formations: the (basal) Teist Formation, the Lomvi Formation and the Lunde Formation (top). The subdivision suggested here for the Triassic of the Northern North Sea is based on information from areas to the west of the Viking Graben. However, available data from the Horda Platform indicate that a subdivision is also possible in that area.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Groups&nav3=61
61
HEIMDAL FM
FORMATION
ROGALAND GP
Heimdal Formation

Name
Named by Deegan & Scull (1977) after the Heimdal Field on the Norwegian continental shelf. Heimdal was a son of the Norse god Odin, and one of the principal gods in Norse mythology.
Well type section
Norwegian well 25/4-1 from 2423 m to 2067 m, coordinates N 59°34'27.30", E 02°13'22.60" (Fig 5.52) . 36 m of cores from the upper part of the formation, and 6.5 m from the lower part.
Well reference section
Norwegian well 15/9-5 from 2684 m to 2448 m, coordinates N 58°24'12.47", E 01°42'29.20" (Fig 5.42) . No cores.
Thickness
The Heimdal Formation is 356 m thick in the type well and 236 m thick in the reference well. It thins rapidly east of these wells and south of well 15/9-5 .
Lithology
The formation is dominated by thick units of poorly sorted, fine to coarse grained, poorly cemented sandstones with variable amounts of mica, glauconite and detrital lignite. The sandstone units are interbedded with grey and black shales, limestones and sandy limestones. There is a wide range in number and thickness of interbedded lithologies. In general, the amount of carbonate increases towards the base of the formation.
Basal stratotype
The lower boundary of the Heimdal Formation is usually marked by a transition from the Lista Formation into the interbedded sandstones of the Heimdal Formation. The log response is characterised by lower gamma-ray readings and higher velocities when entering the overlying Heimdal Formation (Fig 5.52) . The Heimdal Formation locally overlies the cleaner sandstones of the Ty Formation . In that case, the lower boundary is placed where clean sandstones give way to the interbedded sandstones of the Heimdal Formation. These formations are normally separated by the Lista Formation .
Characteristics of the upper boundary
The upper boundary is usually defined by a transition into the Lista Formation shales and is then characterized by higher radioactivity and lower velocity (Fig 5.52) . Locally, the Heimdal Formation is overlain by the Hermod Formation , the upper boundary therefore being defined by a change into clean, "blocky" sand.
Distribution
The sandstones of the Heimdal Formation are distributed in a broadly lobate pattern eastwards from the western margin of the Viking Graben. Their approximate distribution on the Norwegian continental shelf is shown in (Fig 5.47) .
Age
Paleocene.
Depositional environment
In the westernmost areas (East Shetland Platform/Fladen Ground Spur), the Heimdal Formation was deposited on a shallow-marine shelf under high-energy conditions. In the Viking Graben, the formation was deposited as submarine fans derived from sand accumulations on the shallow shelf to the west. The shale layers consist partly of the fine fraction of the turbidity currents and of hemipelagic mud.
Remarks
In a narrow belt extending from the eastern part of quadrant 15 (Fig 5.47) , the Heimdal Formation is developed as a clean sandstone without interbedded shales. This is described as the Meile member .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=62
62
131
HEKKINGEN FM
FORMATION
ADVENTDALEN GP
Hekkingen Formation

Name
The formation name is taken from Hekkingen Lighthouse at 69°30'N and 17°40'E on the northern tip of Senja. The formation corresponds to T3-2 or Olderfjord Formation of earlier usage.
Well type section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 2019 m to 1660 m (Fig 4.50) . Two short cores have been taken between 1661 and 1668 m and between 1702.6 and 1707.6 m.
Well reference section
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 2610 to 2497 m (Fig 4.51) .
Thickness
359 m in the type well and 113 m in the reference well.
Lithology
The formation consists of brownish-grey to very dark grey shale and claystone with occasional thin interbeds of limestone, dolomite, siltstone and sandstone. These minor clastic components are most common towards basinal margins. Lower parts of the formation show especially high gamma ray readings. This is used to differentiate the lower Alge from the upper Krill Member in the formation (Fig 4.50, 4.51)
Basal Stratotype
The base is defined by the transition from carbonate cemented and pyritic mudstones to poorly consolidated shales, producing a sudden increase in interval transit time and an abrupt decrease in bulk density values.
Lateral extent and variation
The formation is thickest in its type well. It thins northwards to less than 100 m towards the axis of the Hammerfest Basin. This pattern reflects the development of semigrabens along basin margins while doming was active along the basin axis.
Age
Palynomorphs suggest an age span of late Oxfordian/early Kimmeridgian to Ryazanian. There are local breaks in deposition at the base and top, probably most developed near the basinal axis.
Depositional environment
Marine, deep water with anoxic conditions resulted from the formation of local barriers to circulation by Kimmerian movements.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=63
63
1
HERMOD FM
FORMATION
ROGALAND GP
Hermod Formation

Name
Hermod was a son of Odin, and was known as "the quick one".
Well type section
Norwegian well 25/2-6 from 2361 m to 2221 m, coordinates N 59°45'33.55", E 02°33'05.96" (Fig 5.56) . No cores.
Well reference section
UK well 10/1-1A from 2212 m to 2127 m, coordinates N 59°50'10.50", E 02°00'33.60" (Fig 5.48) . No cores.
Thickness
The Hermod Formation is 140 m thick in the type well and 85 m thick in the reference well. It thickens towards the centre of its distribution area (Fig 5.47) .
Lithology
The Hermod Formation consists of clean sandstones which are very fine to fine grained and clear to grey. The formation is to a limited extent interbedded with dark shales.
Basal stratotype
The lower boundary of the Hermod Formation is identified by a transition from the shales of the Lista Formation . This boundary essentially represents the boundary between the Lista and Sele formations, and the Hermod Formation may rest on shales of the Sele Formation . The log response in both cases is a sharp transition from the high gamma-ray readings and low velocity of the shales to the low and regular gamma-ray readings and higher velocity of the Hermod Formation sandstones (Fig 5.56) . Where the Hermod Formation rests directly on the Heimdal Formation the boundary may be indistinct, but the log response changes from an erratic pattern in the Heimdal Formation to a smoother one, reflecting the more homogeneous sandstones of the Hermod Formation.
Characteristics of the upper boundary
The Hermod Formation is overlain by the time-equivalent Sele Formation , and the boundary is an abrupt change from sandstones to dark shales. The gamma-ray response changes from low readings in the sandstones to significantly higher ones in the Sele Formation , and the velocity is lower in the Sele Formation (Fig 5.56) .
Distribution
The Hermod Formation is found in the South Viking Graben, in the northwestern part of quadrant 25. It may also be found in other parts of the South Viking Graben. The main distribution area is outlined in (Fig 5.47) .
Age
Late Paleocene.
Depositional environment
The Hermod Formation was deposited in submarine fan systems connected with the deltaic Moray Group in the west.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=64
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131
HIDRA FM
FORMATION
SHETLAND GP
Hidra Formation

Name
Named by Deegan & Scull (1977) after the Hidra High in Norwegian blocks 1/3 and 2/1. The name Hidra is after the island of Hidra on the southern coast of Norway.
Well type section
Norwegian well 1/3-1 from 4441 m to 4371 m, coordinates N 56°51'21.00", E 02°51'05.00" (Fig 5.24) . No cores.
Well reference sections
UK well 22/1-2A from 3783 m to 3738 m, coordinates N 57°56'12.20", E 01°02'55.80" (Fig 5.25) . No cores. UK well 29/25-1 from 2258.5 m to 2228 m, coordinates N 56°18'10.00", E 01°51'48.80" (Fig 5.26) . No cores. Danish well BO-1 from 2275.5 m to 2220 m, coordinates N 55°48'8.22", E 04°34'18.66" (Fig 5.27) . Cored through the upper 35 m.
Thickness
The formation is 70 m thick in the type well, 45 m in 22/1-2 A, 30.5 m in 29/25-1 and 55.5 m in BO-1. Seismic interpretation suggests that the formation reaches a maximum thickness of about 150 m in the northwestern part of the Central Trough in the Norwegian sector.
Lithology
In the type well the formation consists of white to light grey, hard chalks with thin interbeds of grey to black shale in the lower part of the formation. Locally the formation is more marly with interbedded marly chalk and marl. The chalks are occasionally softer with abundant glauconite and pyrite. The colour may be white, grey, green, brown or pink. At the base of the formation in UK well 22/1-2 A, hard, black, carbonaceous and argillaceous limestones are present. Traces of pink waxy tuff occur in places. The formation is generally highly bioturbated.
Basal stratotype
The formation usually shows a gamma-ray response that has constant low values and high velocities. These contrast sharply at the lower boundary with the higher gamma-ray response and lower velocity of the Åsgard and Sola formations. The lower boundary is more gradational when the carbonate-rich facies of the Rødby Formation is present beneath the Hidra Formation.
Characteristics of the upper boundary
The upper boundary is defined by the stratotype of the Blodøks Formation . The boundary is characterised by a change from the chalk lithology to mainly mudstone. This is seen as an abrupt change to higher gamma-ray response and a decrease in velocity in the Blodøks Formation . The boundary shows as a glauconitised hardground in the core from Danish well BO-1.
Distribution
The formation is found in the central and southern North Sea. In the Norwegian sector, it is missing above highs such as the Sørvestlandet, Mandal, Jæren, Utsira and Sele highs, the Grensen Ridge, as well as many of the salt diapirs.
Age
Cenomanian.
Depositional environment
Open marine with a perioditic or turbiditic origin for the sediments.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=65
65
143
HOD FM
FORMATION
SHETLAND GP
Hod Formation

Name
Named by Deegan & Scull (1977) from the Hod Field in Norwegian block 2/11. The name Hod derives from one of the twelve principal gods in Norse mythology. Hod was a son of Odin.
Well type section
Norwegian well 1/3-1 from 4343 m to 3828 m, coordinates N 56°51'21.00", E 01°51'05.00" (Fig 5.24) . No cores.
Well reference sections
UK well 29/25-1 from 2225 m to 2012 m, coordinates N 56°18'10.00", E 01°51'48.80" (Fig 5.26) . No cores.
Norwegian well
2/8-8 from 2601 m to 2494 m, coordinates N 56°16'50.28", E 03°24'15.93" (Fig 5.28) . 36 m of cores discontinuously through the upper 78 m and lowermost 6 m of the formation.
Thickness
The formation is 515 m thick in the type well, 213 m in UK well 29/25-1 and 107 m in Norwegian well 2/8-8 . In the Norwegian sector, seismic interpretation indicates that the formation may reach a thickness of more than 700 m in the northwestern part of the Central Trough.
Lithology
In the type well the formation consists of hard, white to light grey, crypto- to microcrystalline limestones which may become argillaceous or chalky in places. White, light grey to light brown, soft to hard chalk facies may dominate the formation or alternate with limestones. The limestones may be pink or pale orange. Thin, silty, white, light grey to green or brown, and soft, grey to black, calcareous clay/shale laminae are occasionally present. Pyrite and glauconite may occur throughout the formation and the latter may be common in the lower part.
Basal stratotype
The lower boundary is usually marked by a distinct log break to a lower gamma-ray response and higher velocity from the Blodøks Formation to the Hod Formation (Fig 5.24) . The boundary may be less distinct when the Blodøks Formation is more calcareous (Fig 5.31) .
Characteristics of the upper boundary
The upper boundary towards the Tor Formation is generally marked by a change in gamma-ray readings to a more constant and slightly lower level, and also by higher velocity, (Fig 5.24, 5.31) . The upper boundary may represent an unconformity in the Ekofisk area (e.g. Norwegian well 2/8-8 , (Fig 5.28) .
Distribution
The formation is widely distributed in central and eastern parts of the central North Sea, passing laterally into sediments of the Herring and Flounder Formations to the west and the Tryggvason and Kyrre formations to the northwest.
Age
Turonian to Campanian.
Depositional environment
Open marine with deposition of cyclic pelagic carbonates (periodites) and distal turbidites (Skovbro 1983 and d'Heur 1986).
Remarks
An informal, tripartite subdivision of the Hod Formation into lower, middle and upper members is often possible in the southern part of the Central Trough in the Norwegian sector. The subdivision is based on the frequent presence of a higher clay content in the middle of the Hod Formation (Fig 5.24, 5.28, 5.29).
Lower member of the HOD Formation
This unit constitutes the largest part of the Hod Formation and is a sequence of bioturbated laminated chalks with a low clay content. It occurs in Norwegian wells 1/3-1 from 4343 m to 4066 m, 2/8-8 from 2601 m to 2538 m and 1/9-1 from 3648 m to 3353 m.
Middle member of the HOD Formation
This is a sequence consisting mainly of periodites, which generally have a greyish colour reflecting a marked increase in terrigenous clay. It is shown on well logs as an increase in gamma-ray readings. It occurs in Norwegian wells 1/3-1 from 4066 m to 4009 m, 2/8-8 from 2538 m to 2518 m and 1/9-1 from 3353 m to 3344m.
Upper member of the HOD Formation
This unit constitutes another sequence dominated by periodites with minor allochthonous intercalations, but with a return to a low clay content. It occurs in Norwegian wells 1/3-1 from 4009 m to 3828 m, 2/8-8 from 2518 m to 2494 m and 1/9-1 from 3344 m to 3312 m.
The Herring Formation of Deegan & Scull (1977) includes a similar lithology and was deposited at the same time as the Hod Formation. It is regarded here as the lower part of the Hod Formation. The Hod Formation is also equivalent in age to the Tryggvason and Kyrre formations (Fig 5.6) .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
Footnotes
  • 1) Fritsen and Riis (unpublished) propose a subdivision of the original Hod Formation into three new formations: Narve, Thud and Magne formations.
References
  • Fritsen, A. and Riis, F. (unpublished): A revised chalk lithostratigraphic nomenclature.
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143
HORDALAND GP
GROUP
Hordaland Group

Name
The group was named by Deegan and Scull (1977) after the county of Hordaland in Norway. In the Norwegian Sea the group's local develoment corresponds to the lower part of the informal Sklinna Group (H6).
Type area
The type area is the North Sea Tertiary Basin. Typical sections through the group are shown in Norwegian wells 2/2-1 (Fig 5.60) . and 24/12-1 (Fig 5.61) . (Fig 5.69) , shows a seismic section through the group in the Central Trough area. The lithostratigraphy is shown in (Fig 5.40) .
In the Norwegian Sea, well
6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°53'47"E, from 2212.5 m to 1762.5 m, is used to illustrate the local development of the group (Fig 4.37) . No cores.
Thickness
The group has a thickness of 1060 m in well 2/2-1 and 1365 m in well 24/12-1 . Its average thickness is around 1100-1200 m in the central and southern part of the Viking Graben, but in the northern Viking Graben the group only reaches a thickness of a few hundred metres. Maximum thicknesses in the central and southern part of the Viking Graben are approximately 1300 m and 1400 m, respectively. The thickness decreases towards the basin margins. The group is 450 m thick in well 6407/1-3 .
Lithology
The group consists of marine claystones with minor sandstones. The claystones are normally light grey to brown, fissile and fossiliferous. Red and green claystones sometimes occur at the base. Thin limestones and streaks of dolomite are present. Sandstones are developed at various levels in the group. These are generally very fine to medium grained, and are often interbedded with claystones.
In Haltenbanken the Hordaland Group consists of claystones and minor sandstones, assigned to the
Brygge Formation . The sandstone content increases to the east.
Basal stratotype
In the North Sea the lower boundary shows an increase in gamma-ray intensity and a decrease in velocity from the laminated tuffs of the Balder Formation into the claystones of the Hordaland Group (Fig 5.56) . Where the Frigg Formation is present at the base of the Hordaland Group the lower boundary normally shows a decrease in gamma-ray response and an increase in velocity from the Balder Formation into the Frigg Formation (Fig 5.62) .
In the Norwegian Sea the base is defined by a decrease in interval transit time shown on the sonic log and by an increase in the density log readings.
Characteristics of the upper boundary
In the North Sea the upper boundary is placed at the contact with undifferentiated grey to grey-brown claystones of the Nordland Group or sandstones of the Utsira Formation . It represents an unconformity of Early to Middle Miocene age, which may be difficult to identify in some wells.
In the Central Trough, a zone occurs which has high gamma-ray readings and usually a slightly lower velocity than the underlying and overlying claystones. The upper boundary of the Hordaland Group is placed at the base of this zone
(Fig 5.60) . On seismic sections, the sediments below this horizon normally have a distorted signature whilst those above it have a smoother one. The boundary shows a very small angular unconformity; it is not clear whether a small hiatus is present. In the Viking Graben, the upper boundary is normally the base of the sandy Utsira Formation 1). The contact is then marked by an upward decrease in gamma-ray intensity (Fig 5.70) . Where the basal part of the Nordland Group is developed as claystone the boundary is placed at log breaks associated with a change in claystone colour.
In the Norwegian Sea the top of the group is defined by a decrease in interval transit time on the sonic log and an increase in the density log readings.
Distribution
The group is distributed over most of the North Sea Tertiary Basin. It is incomplete at the basin margins, owing to erosion or non-deposition.
The Hordaland Group occurs throughout Haltenbanken. It thins eastwards and is eroded on the Nordland Ridge. Close to the coastline the group comprises a sandy sequence informally termed the Røyrvik Formation (Askvik and Rokoengen, 1985).
Age
The group is of Eocene to Early Miocene age both in the North Sea2) and the Norwegian Sea. Datings in wells 2/2-1 , 2/2-2 and 2/2-3 indicate that the uppermost part of the group may be of Middle Miocene age in the Central Trough.
Depositional environment
The sediments are marine, mainly deposited in deep water.
Subdivision
In the North Sea the Frigg Formation was formally erected by Deegan & Scull (1977). Three additional sandstone formations are now recognised in the Hordaland Group, and are described here. Claystone intervals between the sandstones are not defined as formations and remain as unnamed units of the Hordaland Group. The Grid and Skade formations are widely distributed in the Viking Graben area, whereas the Vade Formation, which is found in the Central Trough, has a limited distribution. Other sandstones, which cannot be assigned to the formations described here, are found in the Norwegian part of the North Sea Basin. Subregional work and further information from wells may enable more units to be formally erected in the future.
On Haltenbanken the Hordaland Group comprises the
Brygge Formation . Lateral facies changes and breaks in the sequence may form the basis for future subdivision.
Remarks
The boundary between the Hordaland and Nordland groups in the Central Trough area may be slightly different from the position selected in well 2/7-1 by Deegan & Scull (1977). The boundary is difficult to identify in that well, owing to the borehole being damaged directly below the casing which is placed at 1591m (5221 ft).
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
Footnotes
  • 1) Through most of the Viking Graben area a shale unit is usually developed between the Utsira Formation and the top of the Hordaland Group (mid Miocene unconformity). In the Tampen area the Utsira Formation rests directly on the Hordaland Group. See also Eidvin and Rundberg (2001, 2007).
  • 2) See also Eidvin and Rundberg (2007).
References
  • Eidvin, T. and Rundberg, Y. (2001): Late Cainozoic stratigraphy of the Tampen area (Snorre and Visund fields) in the northern North Sea, with emphasis on the chronology of early Neogene sands. Norsk Geologisk Tidsskrift, 81, 119–160.
  • Eidvin, T. and Rundberg, Y., 2007: Post-Eocene strata of the southern Viking Graben, northern North Sea; intergrated biostratigraphic, strontium isotopic and lithostratigraphic study. Norwegian Journal of Geology 87, 391-450.
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67
HUGIN FM
FORMATION
VESTLAND GP
Hugin Formation

Name
One of Odin's two ravens in Norse mythology.
Well type section
Norwegian well 15/9-2 (Statoil) from 3483 m to 3657 m, coord N 58°25' 34.06" , E 01 °42'28.2" (Fig 3.26) .
Well reference section
Norwegian well 15/6-5 (Esso) from 3627 m to 3679 m, coord N 58°30'29.67", E 01 °45' 50.4" (Fig 3.28) .
Thickness
The formation is 174 m thick in the type well and 52 m thick in the reference well.
Lithogy
The formation consists of light brown to yellow, very fine to medium grained sandstones. Occasional coarse grained layers are found. The sandstones have fair sorting, and the grains are subangular to subrounded. Shale and siltstone partings are common. Carbonaceous material and coal fragments are abundant. Occasional thin coal beds can be observed. The sandstones are often bioturbated, but cross bedding can sometimes be observed. The sandstones are often calcareous and glauconitic.
Boundaries
The lower boundary represents the transition from the coaly Sleipner Formation . The upper boundary represents the transition into the shales of the Viking Group , giving clear breaks both on sonic and gamma ray logs.
Distribution
The formation is found in the southern Viking Graben, north of the Jæren High.
Age
Early Bathonian to Early Oxfordian.
Depositional environment
The formation represents near shore, shallow marine sandstones with the occasional influence of continental fluviodeltaic conditions.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=69
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186
ILE FM
FORMATION
FANGST GP
Ile Formation

Name
From the Norwegian word for a stone sinker or a drag. The unit corresponds to the lower part of the informal Tomma Formation (H1-4) or “Tomma III”.
Well type section
Well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2536 m to 2471.5 m (Fig 4.16) . The entire formation is cored except for the basal 2 m.
Well reference section
Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3813 m to 3741 m (Fig 4.19) . One core (10 m recovery), from the upper part of the unit.
Thickness
64.5 m in the type well and 72 m in the reference well.
Lithology
Fine to medium and occasionally coarse-grained sandstones with varying sorting are interbedded with thinly laminated siltstones and shales. Mica-rich intervals are common. Thin carbonate-cemented stringers occur, particularly in the lower parts of the unit.
Basal Stratotype
The lower boundary is defined at the base of a generally upwards coarsening sequence visible on the gamma ray log. In wells where this coarsening trend is not evident on logs, the base of the formation may be picked where the overall lithology changes from siltstone to sandstone. Often this transition is associated of one or more carbonate-rich beds.
Age
Late Toarcian to Aalenian.
Depositional environment
The formation represents various tidal-influenced delta or coastline settings.
Lateral extent and variation
The Ile Formation generally varies from 50 m to 100 m over most of Haltenbanken, with a general thickening to the west and a marked thinning to the northeast. It is also encountered in wells on Trænabanken. Sandstone-dominated successions of similar age have been located by sea bottom sampling and shallow drilling on the eastern part of the Trøndelag Platform (Bugge et al. 1984).
Correlation
No distinct comparable time equivalent formations are known from the North Sea area. In the Hammerfest Basin the middle part of the Stø Formation may be correlated to the Ile Formation.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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38
INTRA BALDER FM SS
FORMATION
ROGALAND GP
Intra Balder Formation sandstones (informal)

Intra Balder Formation sandstones have been encountered in a number of wells in the Viking Graben and adjacent areas. They are described as part of the Balder Formation and illustrated in the type well 25/11-1 .
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7
131
INTRA DRAUPNE FM SS
FORMATION
VIKING GP
Intra Draupne Formation SS (informal)

Intra Draupne Formation sandstones have been encountered in a number of wells in the Tampen and Oseberg areas and along the flanks of the Utsira and Jæren highs. The sandstones are generally considered to be of turbiditic origin (De`Ath and Schuyleman, 1981; Harms et al., 1981) and are described as part of the Draupne Formation . Well 15/3-1 S illustrates these arenaceous intercalations.
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26
188
INTRA HEATHER FM SS
FORMATION
VIKING GP
Intra Heather Formation SS (informal)

Intra Heather Formation sandstones have been encountered in a number of wells in the Sleipner, Oseberg, Tampen and Måløy/Sogn areas as well as along the flanks of the Utsira High. On the Horda Platform, sandy interdigitations of the Heather Formation have been formalized as the Krossfjord , Fensfjord and Sognefjord formations.
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188
INTRA MELKE FM SS
FORMATION
VIKING GP
Intra Melke Formation sandstones (informal)

Intra Melke Formation sandstones have been encountered in a number of wells in block 6608/10 on the Rødøy High. The sandstones are intercalated with the Melke Formation .
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188
INTRA ÅSGARD FM SS
FORMATION
CROMER KNOLL GP
Intra Åsgard Formation sandstones (informal)

Intra Åsgard Formation sandstones have been encountered in a few wells on the Utsira High. The sandstones are intercalated with the Åsgard Formation .
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210
23
ISBJØRN FM
FORMATION
BJARMELAND GP
Isbjørn Formation

Name
From the Norwegian name for the Polar Bear (Ursus maritimus).
Definition
The type section is defined as the interval from 1834.7 m to 1745.4 m in well 7128/6-1 on the Finnmark Platform (Fig 9.48) , apparently concurring with informal unit L-8 of Ehrenberg et al. (1998a). Cores cover the entire section (Fig 9.49) . In this well the base of the formation is marked by a decrease in gamma ray response, reflecting the transition from silty warm water carbonates to clean cool-water carbonates.
Reference sections
A reference section is defined as the intervals from 3700 m to 3625 m and 3586 m to 3502 m in well 7121/1-1 R on the Loppa High, these intervals interfingering with Ulv Formation lithofacies (Fig 9.43) . A small core, 2.7 m long, exists from the uppermost part of the formation, between 3513.7 m and 3511.0 m. An additional reference section is designated in 7229/11-1 (4046 m to 3970 m), where the Isbjørn Formation rests directly on carbonate buildups of the Polarrev Formation . The uppermost part of the formation has been drilled in the southernmost part of the Finnmark Platform (cores 7128/12-U-01 from 569.2 m to 557.5 m and 7129/10-U-01 from 475.3 m to 464 m) (Bugge et al. 1995). The base is not easy to pick on logs in areas where the formation rests directly on the Polarrev Formation (e.g. 7229/11-1 ), as the boundary there represents a limestone-limestone contact (Fig 9.39) . It is recognised by a slight decrease in interval transit time and neutron porosity log values accompanied by an increase in bulk density in wells 7121/1-1 R and 7229/11-1 . However, over the buildups, the base of the formation is easily picked on seismic data. In 7121/1-1 R the transition from the interfingering Ulv Formation up into the Isbjørn Formation shows a marked decrease in gamma ray response, reflecting the transition from silty wackestones into cleaner packstones and grainstones (Fig 9.43) .
Thickness
The formation is approximately 75-90 m thick in the central and northern parts of the Finnmark Platform, thinning to 10 m in the IKU cores. It is slightly thinner in 7124/3-1 and absent from the outer shelf environments represented by the Ulv Formation in 7226/11-1 on the Bjarmeland Platform (Fig 9.38) . The formation is thickest in 7121/1-1 R on the southeastern flank of the Loppa High, where its two intercalations have a composite thickness of approximately 160 m (Fig 9.43) .
Lithology
Bedded, white to light grey bioclastic limestones with a fauna of mainly crinoids and bryozoans dominate the formation. The dominant facies are grainstones and packstones (Fig 9.50) . The formation has a characteristic low gamma ray response throughout, except for thin intervals of dark grey silty wackestone that represent temporary deeper water deposition related to flooding events. Chert nodules occur sporadically throughout the section. The dark grey silty limestone intervals are lithologically similar to the Ulv Formation , but are regarded as part of the Isbjørn Formation if they are of subordinate importance and less than 15-20 m thick. Thicker intervals such as that from 3625 m to 3586 m in well 7121/1-1 R are included in the Ulv Formation .
Lateral extent and variation
The formation represents deposition in inner shelf environments. Following a major transgression in the early Artinskian the formation developed over earlier carbonate build-ups and submerged structural highs and platforms. The formation is not known from either outer shelf regimes or from basinal areas.
Age
The base of the formation is apparently diachronous. In the type section in 7128/6-1 fusulinids suggest that the base is of mid-Sakmarian age and the top is late Artinskian (Ehrenberg et al. 1998a). In well 7229/11-1 the top of the underlying Polarrev Formation is dated as late Sakmarian, indicating a late Sakmarian or younger age for the formation in this well (Davydov 1998). The formation is apparently of late Artinskian age in IKU cores (Bugge et al. 1995).
Depositional environments
The bioclastic crinoid- and bryozoan- dominated grainstones and packstones of the Isbjørn Formation represent deposition in inner shelf environments on cool-water carbonate platforms (Stemmerik 1997). The more silty wackestone facies represent temporary flooding and deposition in slightly deeper environments below storm wave base.
Correlation
The upper part of the Isbjørn Formation correlates age- and facies-wise with the Hambergfjellet Formation on Bjørnøya and with the Vøringen Member of the Kapp Starostin Formation on Spitsbergen.
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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72
12
JOHANSEN FM
FORMATION
DUNLIN GP
Johansen Formation

Name
Named after Hjalmar Johansen, member of the Amundsen South Pole expedition.
Well type section
Norwegian well 31/2-1 (Shell) from 2176 m to 2272.5 m, coord N 60°46'19.16'', E 03°33'15.87" (Fig 3.13) .
Well reference section
None at present.
Thickness
95.5 m in the type well.
Lithology
In the type well the formation consists of a sequence of sandstones with thin calcite cemented streaks throughout. The lower part is medium to fine-grained, micaceous, well sorted sandstone which grades downwards into light grey silty micaceous claystone. The main section of the formation is composed of medium grained, friable sandstones, with well sorted quartz grains which are angular to subrounded. The uppermost part is composed of medium to fine grained, micaceous sandstones, which are moderately sorted, silty and argillaceous.
Boundaries
In the type well area the Johansen Formation splits the Amundsen Formation . It is distinguished by a low response, crescentic gamma ray profile.
Distribution
The formation is restricted to an area extending from the eastern part of the Horda Platform northwards to the Måløy Fault Blocks.
Age
Sinemurian to Pliensbachian.
Depositional environment
The formation was probably deposited on a high energy, shallow marine shelf.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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73
29
JORSALFARE FM
FORMATION
SHETLAND GP
Jorsalfare Formation

Name
Named after Sigurd "Jorsalfare" Magnusson, a Norwegian king (A.D. 1103-1130).
Well type section
Norwegian well 25/1-1 from 2997 m to 2711 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig 5.33) . One core (17 m) in the middle of the formation and another (4 m) at the base.
Well reference sections
Norwegian well 35/3-2 from 1665 m to 1520 m, coordinates N 61051'05.98", E 03°46'28.22" (Fig 5.34) . No cores. Norwegian well 24/9-1 from 3117 m to 2752 m, coordinates N 59°16'09.48", E 01°47'31.18" (Fig 5.35) . No cores.
Thickness
The formation is 286 m thick in the type well ( 25/1-1 ), 145 m in well 35/3-2 and 365 m in well 24/9-1 .
Lithology
The formation generally consists of mudstones interbedded with thin limestone beds. The mudstones are light to medium grey, often calcareous. The limestones are white to light grey, fine grained, occasionally sandy and dolomitic.
Basal stratotype
The lower boundary is defined by a decrease in gamma-ray intensity and an increase in velocity, reflecting an increase in calcareous content from the Kyrre Formation into the Jorsalfare Formation (Fig 5.33 , 5.34) . In the Tampen Spur area, however, the boundary may be difficult to identify due to small differences in calcareous content. The lower boundary may be unconformable above the Jurassic sequences (e.g. in the Gullfaks area).
Characteristics of the upper boundary
The upper boundary may be towards the Våle , Lista or Ty formations of the Rogaland Group . When the upper boundary is towards the shale of the Lista Formation it is usually characterised by an upward increase in gamma-ray intensity and a distinct drop in velocity (Fig 5.34) . When it is towards the Våle Formation it does not show the same distinct drop in velocity and increase in gamma-ray intensity, because the overlying lithology consists of limestones or calcareous mudstones (Fig 5.35) . Where the upper boundary is towards the Ty Formation it is identified as a change to sandstone (Fig 5.33) .
Distribution
The formation is present in the Viking Graben and on the Tampen Spur. Its boundaries towards the Jorsalfare Formation in the Viking Graben, the Hardråde Formation on the Horda Platform and the Tor Formation on the Utsira High are illustrated in (Fig 5.32ab) .
The main characteristics that can be used to distinguish the three formations are:
  1. The Jorsalfare Formation contains shales with thin limestone beds which are usually no thicker than 5 m.
  2. The Tor Formation is dominated by limestones, and has a negligible shale content,
  3. The Hardråde Formation contains thick limestone beds (10-60 m), as well as shales, except in the Troll area where it is thin and may consist of only a single bed of limestone or marly limestone.
Separation of these three formations may be difficult in transitional areas.
Age
Late Campanian to Maastrichtian.
Depositiohal environment
Open marine.
Remarks
The Jorsalfare Formation is time-equivalent with the Hardråde and Tor formations of the Shetland Group and also with the informal ”formation E” of Deegan & Scull (1977) (Fig 5.6) .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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74
143
KAI FM
FORMATION
NORDLAND GP
Kai Formation

Name
The Norwegian word for quay. The formation corresponds to the informal Korgen Formation (H6-2).
Well type section
Well 6407/1-2 (Statoil), coordinates 64°47'50.61"N, 07°02'23.76"E, from 1690 m to 1419 m (Fig 4.38) . No cores.
Thickness
271 m in the type well.
Lithology
Alternating claystone, siltstone and sandstone with limestone stringers. Glauconite, pyrite and shell fragments are common.
Basal Stratotype
The base is defined by a decrease in interval transit time on the sonic log and an increase in the density log readings.
Lateral extent and variation
The formation is present throughout the Haltenbanken area apart from the crest of the Nordland Ridge. The sand content varies locally.
Age
Early Miocene to Late Pliocene.1)
Depositional environment
The formation was deposited in marine environments with varying water depths.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
Footnotes
  • 1) Datings of the Kai Formation are also documented in: Eidvin, T., Bugge, T. & Smelror, M., 2007: The Molo Formation, deposited by coastal progradation on the inner Mid-Norwegian continental shelf, coeval with the Kai Formation to the west and the Utsira Formation in the North Sea. Norwegian Journal of Geology, Vol. 87, pp. 75-142.
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77
113
KAPP TOSCANA GP
GROUP
Kapp Toscana Group

Name
The group is named after a cape on the southern coast of Van Keulenfjorden.
Type area
Central eastern Spitsbergen.
Thickness
Up to >475 m in Svalbard, up to 2000 m (?) on the Barents Sea Shelf.
Lithology
The Kapp Toscana Group comprises shales, siltstones and sandstones of Late Triassic to Middle Jurassic (Bathonian) age in Svalbard and on the Barents Sea Shelf. The group starts with the grey shales of the Tschermakfjellet Formation which normally grade upward into the immature sandstones of the De Geerdalen Formation (Storfjorden Subgroup). This interval contains a number of coarsening-upward successions with increasing proportions of sandstone towards the SW, NE and E, while shales dominate in the central areas of Svalbard. On Svalbard, the upper part forms a condensed clastic sedimentary succession, only a few metres thick in southern and western Svalbard, which gradually is more completely developed towards the east (Wilhelmøya Subgroup). Equivalents on the Barents Sea Shelf show a comparatively thick development (Realgrunnen Subgroup; Worsley et al. 1988). Sandstones and shales also dominate the group in the Barents Sea.
Distribution
The group is exposed along the Tertiary fold-thrust belt on western Spitsbergen, in central and eastern Spitsbergen, as well as on Barentsøya, Edgeøya, Hopen, Kong Karls Land and Bjørnøya. It continues in the subsurface between these islands and southwards across the Barents Sea Shelf to the Bjarmeland Platform and the Hammerfest and Nordkapp basins.
Age
Ladinian to Bathonian.
Depositional environment
The Kapp Toscana Group has been deposited in a generally nearshore, deltaic environment and is characterised by shallow marine and coastal reworking of deltaic and fluviodeltaic sediments (Mørk et al. 1982).
Subdivision
Five formations are recognized within the group on the Barents Sea Shelf: the Snadd , Fruholmen , Tubåen , Nordmela and Stø formations.
Compiled from
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
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79
KLAPPMYSS FM
FORMATION
SASSENDALEN GP
Klappmyss Formation

Name
The formation's name is derived from the seal species Cystophora cristata. The formation corresponds to T1-2 and the lower parts of T1-3 (Andenes and lower Gimsøy formations) of earlier informal terminology.
Well type section
Well 7120/12-2 (Norsk Hydro), coordinates 71°7'30.03"N, 20°48'19.00"E, from 3552 m to 3095 m (Fig 4.42) .
Well reference section
Well 7120/9-2 (Norsk Hydro), coordinates 71°29'40.81"N, 20°42'05.38"E, from 4806 to 4245 m (Fig 4.43)
Thickness
457 m in the type well and 561 m in the reference well.
Lithology
Medium to dark grey shales pass upwards into interbedded shales, siltstones and sandstones in the type well. The reference well shows a similar trend, but with more shale throughout.
Basal Stratotype
The base is defined by clear log breaks, with increasing gamma ray, interval transit time and neutron porosity readings. This represents an important sequence boundary throughout the area, reflecting an early Smithian transgressive pulse.
Lateral extent and variation
The formation thickens and fines northwards from the southern margins of the Hammerfest Basin.
Age
Palynofloras suggest a Smithian to Spathian age.
Depositional environment
Marginal to open marine environments are indicated, with renewed northwards coastal progradation following the early Smithian transgression.
Correlation
The unit is equivalent to the Tvillingodden Formation of western Spitsbergen.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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80
140
KLIPPFISK FM
FORMATION
ADVENTDALEN GP
Klippfisk Formation

Name
Norwegian for “stockfish”, “dried cod”.
Well type section
Norwegian well 7430/10-U-01, coordinates N 74°12'47.79", E 30°14'44.22"
Well reference section
Norwegian well 7231/01-U-01 coordinates N 72°45'12.45" , E 31°07'30.21"
Thickness
In the type well the gross thickness of the formation is 8.9 m and in the reference well 4.5 m. 15 m on Kong Karls Land.
Lithology
Limestone, marl and calcareous sandstone.
Description
The Klippfisk Formation represents a condensed carbonate succession occurring in platform areas ( Kutling Member ), where it consists of limestones and marls, and is often glauconitic. The limestones may have a nodular appearance. Fossil debris, dominated by Inoceramus prisms may be abundant. The formation is strongly bioturbated.
In Kong Karls Land the coeval Tordenskjoldberget Member has a similar lithology and is assigned to the Klippfisk Formation.
The Klippfisk Formation is the carbonate platform time-equivalent of the
Knurr Formation (Hammerfest Basin) and the Rurikfjellet Formation (Svalbard). The unit has also been penetrated by shallow drilling and sampling in Hopendjupet and in the Olga Basin as well as farther south in the Barents Sea.
Lower boundary definition
The base is defined at the abrupt decrease in gamma ray intensity, where the dark mudstones of the underlying formation are replaced by marls.
Distribution
Offshore unit, known from the Bjarmeland Platform and Kong Karls Land.
Age
Late Berriasian to Hauterivian, based on palynology, nanofossils and bivalves.
Compiled from
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
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81
1
KNURR FM
FORMATION
ADVENTDALEN GP
Knurr Formation

Name
From the fish species Eutrigla gurnardus (grey gurnard). The formation corresponds to T4-1 or Slettnes Formation of earlier informal terminology.
Well type
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 2497 m to 2441 m (Fig 4.51) .
Well reference section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 1660 to 1375 m. A core was taken between 1535 and 1546 m in this well (Fig 4.50) .
Thickness
56 m in the type well and 285 m in the reference well.
Lithology
In the type well the formation consists of dark grey to greyish brown claystone with thin limestone and dolomite interbeds. Thin sandstones are also seen in the unit's lower parts, but these disappear laterally into the Hammerfest Basin. Red to yellow brown claystone generally occurs in the upper parts of the formation.
Basal Stratotype
The base is defined by decreasing gamma ray response and by the sonic log showing decreasing interval transit time. In the type well the density log response shows a slight decrease in an otherwise increasing trend across the boundary. However, the general pattern in most wells is an increase in the density log response accompanying the sonic log response. The base is marked by a thin sandy limestone in the reference well.
Lateral extent and variation
Present data suggest similar lithologies in all wells which penetrate the formation. The sand content is somewhat higher close to the Troms-Finnmark Fault Complex (e.g. well 7119/12-1 ). Most complete sequences are seen along basin margins.
Age
Dinoflagellates and foraminifera suggest a Ryazanian/Valanginian to early Barremian age.
Depositional environment
The formation was deposited in open and generally distal marine environments with local restricted bottom conditions.
Correlation
The formation is a lateral equivalent of the dark shale dominated Rurikfjellet Member of the Janusfjellet Formation on Svalbard.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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82
1
KOBBE FM
FORMATION
SASSENDALEN GP
Kobbe Formation

Name
From the Norwegian collective name for several seal species common in arctic waters. The unit corresponds to T1-3 or upper Grimsøy Formation of earlier usage.
Well type section
Well 7120/12-2 (Norsk Hydro), coordinates 71°7'30.03"N, 20°48'19.00"E, from 3095 to 2927 m (Fig 4.44) .
Well reference section
Well 7120/9-2 (Norsk Hydro), coordinates 71°29'40.81"N, 20°42'05.38"E, from 4245 m to 3962 m (Fig 4.45) .
Thickness
168 m in the type well and 283 m in the reference well.
Lithology
A basal 20 m thick shale unit passes up into interbedded shale, siltstone and carbonate cemented sandstone.
Basal Stratotype
The formation is defined by upwards increasing gamma ray, interval transit time and neutron porosity responses into the basal shale. Log responses show much more variation above this unit.
Lateral extent and variation
This unit shows a coarser proximal facies development, along the southern margin of the Hammerfest Basin and fines towards the basin axis. The formation thickens northwards from 140 m on the Troms - Finnmark Platform. Thicknesses vary more from platform to basin than in the underlying units.
Age
An Anisian age is suggested by palynomorphs, with a probable break in deposition in the early and/or late Anisian.
Depositional environment
A transgressive pulse marking the base of the unit was followed by renewed build-out of clastic marginal marine regimes from southern coastal areas.
Correlation
The base of the formation is a clear regional marker, which elsewhere (on Svalbard and in the Sverdrup Basin) marks the onset of deposition of phosphatic organic rich shales. This facies, well displayed by the Botneheia Member of the Barentsøya Formation in central and eastern Svalbard, has not yet been encountered in the Hammerfest Basin. The Kobbe Formation shows greater similarities to the Bravaisberget Formation of western Spitsbergen.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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83
140
KOLJE FM
FORMATION
ADVENTDALEN GP
Kolje Formation

Name
From the fish species Melanogrammus aeglefinus (haddock). The formation corresponds to T4-2 and T4-3, the Tamsøy and Anda formations of earlier informal terminology.
Well type section
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 2441 m to 2004 m (Fig 4.52) .
Well reference section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 1375 m to 1272 m (Fig .53) .
Thickness
437 m in the type well and 103 m in the reference well.
Lithology
Dark brown to dark grey shale and claystone dominate, with minor interbeds of pale limestone and dolomite. The upper part of the formation also has thin interbeds of light grey-brown siltstone and sandstone. The reference well displays similar lithologies.
Basal Stratotype
The base is marked by gradually decreasing gamma ray, decreasing interval transit time and increasing density log responses in the type well. However, in the central part of the Hammerfest Basin the density log response shows a decreasing trend at the formation base. A marker in the middle part of the formation (boundary between unit T4-2 and T4-3 of earlier informal terminology) shows an increase in density in parts of the Hammerfest Basin. An increasing gamma log response is associated with this log break westwards. The log breaks at the base and in the middle parts of the formation are thought to reflect condensed intervals providing important regional seismic markers.
Lateral extent and variation
The formation thickens westwards but thins towards the central part of the Hammerfest Basin. There are no marked regional variations in lithology.
Age
An early Barremian to late Barremian/early Aptian age is suggested.
Depositional environment
The formation was deposited in distal open marine conditions, with good water circulation, but also with periodic restricted environments.
Correlation
The formation is a lateral equivalent of the Helvetiafjellet Formation, a distinctive sand-dominated unit on the Svalbard Platform.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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84
1
KOLMULE FM
FORMATION
ADVENTDALEN GP
Kolmule Formation

Name
From the fish species Micromesistius poutassou (blue whiting). The formation corresponds to T4-4 (Torsvåg Formation) of earlier informal terminilogy.
Type well
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 2004 m to 1059 m (Fig 4.54) .
Reference well
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 1272 m to 742 m (Fig 4.53) .
Thickness
945 m in the type well and 530 m in the reference well.
Lithology
Dark grey to green claystone and shale, silty in parts with minor thin siltstone interbeds and limestone and dolomite stringers. Traces of glauconite and pyrite occur. The reference well has the same lithology.
Basal Stratotype
In the type well the base is defined by sharply increasing interval transit time and neutron porosity readings and a slight decrease in gamma log response. The reference well shows a similar sonic and neutron log trend, although with a gradually increasing gamma ray log response.
Lateral extent and variation
The formation thickens towards and into the Tromsø Basin and shows a slight increase in thickness eastwards in the Hammerfest Basin. Lithologies are laterally continuous.
Age
Aptian to mid-Cenomanian.
Depositional environment
Open marine environments are indicated.
Correlation
The lower parts of the formation correlate to the prodeltaic to open shelf deposits of the Carolinefjellet Formation on the Svalbard Platform. The base of the unit marks a regionally significant transgressive pulse; its top is eroded by the Cretaceous uplift of northern shelf margins. The youngest beds preserved onland Svalbard are of Albian age.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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85
1
KRABBE MBR
MEMBER
FRUHOLMEN FM
Krabbe Member

Name
Norwegian for “crab”.
Well type section
Norwegian well 7121/5-1 coordinates 71°35'54.88''N, 21°24'21.78''E (Fig 4.46) .
Well reference section
Norwegian well 7120/12-1 coordinates 71°6'48.71"N, 20° 45'20.13"E (Fig 4.47) .
Thickness
The gross thickness of the member is 87 m in the type well, and 76 m in the reference well.
Lithology
Shale.
Lower boundary definition
The lower boundary of the Krabbe Member is characterised by an increasing separation between density and porosity logs. The member shows funnel-shaped gamma ray responses.
Age
Rhaetian (based on palynology).
Depositional environment
Marine.
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Members&nav3=86
86
46
KRILL MBR
MEMBER
HEKKINGEN FM
Krill Member

Name
“Krill” in English and Norwegian is a small, marine shrimp-like crustacean, the main food source of many marine mammals and bird species.
Well type section
Norwegian well 7120/12-1 coordinates N 71°6'48.71" E 20° 45'20.13"
Well reference section
Norwegian well 7119/12-1 coordinates N 71°6'08.00" E 19°47'40.29"
Thickness
80 m in the type well and 310 m in the reference well.
Lithology
The Krill Member is dominated by brownish-grey to very dark grey shale and mudstone with occasional thin interbeds of limestone, dolomite, siltstone and sandstone.
Lower boundary definition
The base is defined at the abrupt reduction in gamma ray intensity.
Age
Kimmeridgian – Volgian.
Depositional environment
The unit was deposited in open to restricted shelf environments.
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203
63
KROSSFJORD FM
FORMATION
VIKING GP
Krossfjord Formation

Name
After a fjord on the west coast of Norway, adjacent to the type area in Quadrant 31.
Well type section
Norwegian well 31/2-1 (Shell) from 1741.5 m to 1880 m, coord N 60°46'19.16", E 03°33'15.87", (Fig 3.21) .
Well reference section
None at present.
Lithology
The formation consists of sandstones, light grey-brown in colour, medium to coarse grained, well sorted, and loose to very friable. Occasionally calcite cemented streaks occur. The lower portion of the Krossfjord Formation is slightly argillaceous and carbonaceous with minor shale intercalations.
Boundaries
In the type well the formation overlies the lower part of the Heather Formation . It has a "blocky" log character and is the first continuous thick sandstone unit above the Brent Group . The base of the formation is shown by the underlying reduction in gamma-ray intensity and FDC-CNL separation. The top is characterized by the change to the serrate gamma ray log motif of the overlying Fensfjord Formation and an overall upward increase in gamma ray intensity.
Distribution
The formation has only been clearly recognized in the Troll Field area.
Age
Bathonian.
Depositonal environment
The formation was deposited in a coastal shallow marine environment.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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87
188
KUPFERSCHIEFER FM
FORMATION
ZECHSTEIN GP
Kupferschiefer Formation

Name
An old German mining term meaning “Copper Shale”.
Well type section
UK well 49/26-4 (Shell/Esso) (see Rhys, 1974) from 2012 to 2013 m.
Well reference section
The formation is illustrated in the following wells which may be considered as reference sections. UK wells 30/16-1 (Shell/Esso) (Fig 1.5-8) . 21/11-1 (Shell/Esso) (Fig 1.5-8) and 15/26-1 (BP) (Fig 1.9-11) . Norwegian wells 7/3-1 (Amoco/Noco) (Fig 1.5-8) . and 17/4-1 (Petronord) (Fig 1.9-11) .
Thickness
1 m in the type well. In the reference wells it is 1 to 2 m thick and appears to be of the same order of thickness throughout the North Sea Basin. Although typically about 1 m or less in thickness, it can be overlain by additional shale to reach a combined thickness of 10 m; it then loses its sharp spike.
Lithology
Thin, grey-black, radioactive, locally calcareous organic-rich shale. In the type well it is a dark brown to black dolomitic shale. In the reference wells it is dark grey to black, carbonaceous and micaceous shale, usually laminated and fissile.
Boundaries
The formation is easily distinguished on wireline logs by a very high gamma ray response and low acoustic velocities. Since it normally occurs between the arenaceous sediments of the Rotliegend Group and the carbonates and evaporites of the Zechstein Group it forms a distinctive marker horizon.
Distribution
Despite the fact that the formation is very thin it is widely distributed over the Southern and Central North Sea. The Kupferschiefer Formation can be very thin or even absent over local highs and in marginal areas of local paleorelief. It is present on land in the UK and northern Europe.
Age
Late Permian.
Depositional environment
Marine, anoxic basinal environment.
Compiled from:
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25. The Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
  • Glennie, K. W., Higham, J. and Stemmerik, L. Permian. 91 – 103 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
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88
194
KUTLING MBR
MEMBER
KLIPPFISK FM
Kutling Member

Name
Norwegian for the fish family “goby” (Gobiidae).
Well type section
Norwegian well 7430/10-U-01 coordinates N 74°12'47.79", E 30°14'44.22".
Well reference section
Norwegian well 7231/01-U-01 coordinates N 72°45'12.45", E 31°07'30.21".
Thickness
8.9 m in the type well and 4.5 m in the reference well.
Lithology
The Kutling Member is a condensed carbonate succession consisting of limestones and marls and represents the entire Klippfisk Formation on the Bjarmeland Platform.
Lower boundary definition
The base is defined at the abrupt decrease in gamma ray intensity, where the dark mudstones of the underlying formation are replaced by marls.
Age
Late Berriasian – Hauterivian, based on palynology, nanofossils, bivalves.
Depositional environment
The member was deposited in a carbonate platform environment.
Compiled from
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
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201
81
KVEITE FM
FORMATION
NYGRUNNEN GP
Kveite Formation

Name
From the fish species Hippoglossus hippoglossus (halibut). The formation has not previously been differentiated.
Well type section
Well 7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 1059 m to 810 m (Fig 4.57) .
Well reference section
Well 7119/7-1 (Norsk Hydro), coordinates 71°23'42.40"N, 19°15'18.43"E, from 2529 m to 1331.5 m.
Thickness
Approximately 1200 m in the reference well, thinning eastwards to 249 m in the type well.
Lithology
Greenish-grey to grey shales and claystones show thin interbeds of limestone and siltstone. A tuffaceous and/or glauconitic component is reported from several wells.
Basal Stratotype
The formation is characterized by a lower gamma response and higher interval transit time than the underlying unit. A basal sand in the type well gives a marked break in both these logs. The boundary in this well is also marked by a sudden increase in bulk density readings above a generally decreasing trend, but the formation as a whole shows a highly variable and irregular density response.
Lateral extent and variation
The formation appears to be characteristically developed in the Tromsø Basin and across the Ringvassøya - Loppa Fault Complex into the Hammerfest Basin, thinning eastwards and passing into the sands and carbonates of the Kviting Formation .
Age
Total span appears to be late Cenomanian to early Maastrichtian.
Depositional environment
Deep open shelf with normal circulation.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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89
122
KVITING FM
FORMATION
NYGRUNNEN GP
Kviting Formation

Name
From the fish species Merlangius merlangus (whiting). The formation has not been differentiated previously.
Well type section
Well 7120/12-1 (Norsk Hydro), coordinates 71°06'48.7"N, 20°45'20.1"E, from 742 m to 725 m (Fig 4.55) .
Well reference section
Well 7121/5-1 (Statoil), coordinates 71°35'54.88"N, 21°24'21.78"E, from 1036 m to 1005 m (Fig 4.56) .
Thickness
17 m in the type well. 31 m in the reference well.
Lithology
The type section shows calcareous sandstones with interbedded sandy and glauconitic mudstones. Limestones in the reference well are interbedded with, and grade up into sandy claystones.
Basal Stratotype
The base is defined in the type well by log breaks showing a sharp fall in gamma response and interval transit time, and increasing density.
Lateral extent and variation
The unit is apparently restricted to central and eastern parts of the Hammerfest Basin.
Age
Campanian.
Depositional environment
Deep to shallow shelf environments with normal circulation are indicated.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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90
122
KVITNOS FM
FORMATION
SHETLAND GP
Kvitnos Formation

Name
From the whale species Lagenorhynchus albirostris.
Well type section
Well 6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 3132.5 m to 2600 m (Fig 4.31) . No cores.
Well reference section
Well 6506/12-1 (Statoil), coordinates 65°10'07.58"N, 06°43'44.07"E, from 3175 m to 2658 m (Fig 4.32) . No cores.
Thickness
532.5 m in the type well and 517 m in the reference well.
Lithology
Grey and greyish green calcareous claystones with carbonate and sandstone stringers.
Basal Stratotype
The base is defined by a marked increase in the gamma ray log, an increase in the interval transit time on the sonic log and a decrease in the resistivity log readings.
Lateral extent and variation
The formation is laterally continuous. It is missing on parts of the Nordland Ridge and on local highs along the western flank of the Trøndelag Platform; otherwise it is very thinly developed on the platform.
Age
Turonian to Santonian.
Depositional environment
Open marine.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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91
143
KYRRE FM
FORMATION
SHETLAND GP
Kyrre Formation

Name
Named after Olav "Kyrre" Haraldson, a Norwegian king (A.D. 1067-1093).
Well type section
Norwegian well 25/1-1 from 3582 m to 2997 m, coordinates N 59°53'17.40", E 02°04'42.70" (Fig 5.33) . Part of one core (0.5 m), including the upper boundary.
Well reference sections
Norwegian well 35/3-2 , from 2864 m to 1665 m, coordinates N 61°51'05.98", E 03°46'28.22" (Fig 5.34) . No cores. Norwegian well 24/9-1 from 3638 m to 3117 m, coordinates N 59°16'09.48", E 01°41'31.18" (Fig 5.35) . No cores. Norwegian well 30/11-3 from 3162 m to 2892 m, coordinates N 60°02'38.59", E 02°31'15.47" (Fig 5.36) . No cores.
Thickness
The formation is 585 m thick in the type well ( 25/1-1 ), 1199 m in well 35/3-2 , 521 m in well 24/9-1 and 270 m in well 30/11-3 .
Lithology
The formation consists of mudstones with occasional limestone beds. Some sandstone beds are found in parts of the Agat area. The mudstones are medium grey to grey, silty to calcareous, occasionally pyritic, glauconitic or micaceous. The sandstones are clear to white, and very fine to fine grained.
Basal stratotype
The lower boundary is defined by an increase in gamma-ray intensity and a decrease in velocity from the Tryggvason Formation into the Kyrre Formation (Fig 5.33) . due to changes in carbonate content. The boundary is unconformable on structural highs, usually above the Cromer Knoll Group .
Characteristics of the upper boundary
The upper boundary shows a decrease in gamma-ray intensity and an increase in velocity from the Kyrre Formation upwards into the Jorsalfare Formation (Fig 5.33 , 5.34) . This log change is also a result of the higher carbonate content and the presence of basal limestone beds in the Jorsalfare Formation .
Distribution
With the exception of the Gullfaks area, the formation is present in the Viking Graben, on the Tampen Spur and the western margin of the Horda Platform.
Age
Late Turonian to Campanian.
Depositional environment
Open marine.
Remarks
The Kyrre Formation is time-equivalent with the Flounder Formation in the western part of the central North Sea and the upper part of the Hod Formation in the eastern part (Deegan & Scull 1977). It is also equivalent with the informal "formation D" of Deegan & Scull (1977) (Fig 5.6) .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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92
143
LANGE FM
FORMATION
CROMER KNOLL GP
Lange Formation

Name
From the Norwegian name for the fish species Molva molva (ling).
Well type section
Well 6506/12-1 (Statoil), coordinates 65°10'07.58"N, 06°43'44.07"E, from 3812.5 m to 3190 m (Fig 4.26) . No cores.
Well reference section
Well 6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 3835 to 3150 m (Fig 4.25) . The uppermost 7 m are cored.
Thickness
622.5 m in the type well and 685 m in the reference well.
Lithology
Dominant light/medium grey to green and brown claystones contain stringers of carbonates and sandstones. Claystones in the Barremian-Aptian interval are often reddish-brown and are occasionally interbedded with tuffs.
Basal Stratotype
The base is generally marked by a distinct drop in gamma ray response and a decrease in interval transit time shown by the sonic log. In the type well and on Halten Terrace and Trøndelag Platform marls of the Lyr Formation underlie the Lange Formation. In this case the boundary is defined by a gradual decrease in the gamma ray response and a slight but sharp decrease in interval transit times. The boundary has been sampled in shallow cores from the eastern part of the Trøndelag Platform (Bugge et al. 1984), but logs and detailed descriptions of these are not yet available.
Lateral extent and variation
The formation is only absent from parts of the Nordland Ridge and on local highs along the western flank of the Trøndelag Platform. The early Cenomanian interval shows a sandstone-rich development in well 6507/7-1 . Sandstones are also expected along the western flank of the Nordland Ridge.
A thin sequence of claystones of Hauterivian to Barremian age subcrop along the eastern part of the Trøndelag Platform. Red-brown oxidized silty claystone found there is also commonly encountered in wells further offshore. Similar sequences are exposed on Andøya and on East Greenland.
Age
Ryazanian to Turonian.
Depositional environment
The formation was deposited in a marine environment, possibly shallower on the Halten Terrace area and deeper in the basins to the west.
Correlation
The lower part of the Lange Formation may be correlated with the Valhall Formation 1) defined in the central North Sea (Deegan and Scull, 1977).
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
Footnotes
  • 1) Åsgard Formation according to Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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94
23
LISTA FM
FORMATION
ROGALAND GP
Lista Formation

Name
Named by Deegan & Scull (1977) after the Lista Spur structure (Lista Fault Block Complex on (Fig 5.3) . in the Norwegian-Danish Basin.
Well type section
Norwegian well 2/7-1 from 2918 m to 2873 m, coordinates N 56°25'44.68", E 03°12'14.21" (Fig 5.43) . No cores.
Well reference sections
Norwegian well 15/9-11 from 2386 m to 2308 m, coordinates N 58°24'02.53", E 01°53'41.79" (Fig 5.51) . 10 m of cores from the lowermost part of the formation.
Norwegian well
16/8-1 from 1749 to 1708 m, coordinates N 58°27'24.80", E 02°25'56.80". No cores.
Thickness
The Lista Formation is 45 m thick in the type well. In the Viking Graben its thickness varies between 100 and 200 m. There are two major depocentres, a northern one around the Beryl Field where thicknesses are up to 550 m, and a southern one at the northwestern edge of the Jæren High with a maximum thickness of approximately 350 m. Between these two depocentres the formation is thin (less than 50 m). The formation generally thins towards the highs where thicknesses are less than 50 m.
Lithology
The Lista Formation consists of brown to grey-brown shales, which are generally non-tuffaceous and poorly laminated. Occasionally it contains stringers of limestone, dolomite and pyrite. Thin sandstone layers are locally developed. They are less than 5 m thick, and are most common in the lower part of the formation.
Basal stratotype
In general, the lower boundary is marked by a transition into a lithology with higher gamma-ray and lower velocity readings than the underlying formations (Fig 5.41 , 5.48 , 5.50) .
Characteristics of the upper boundary
In areas where the Lista Formation is overlain by sandy Paleocene formations, the logs show the incoming of coarser elastics with a characteristic, blocky, gamma-ray and sonic log pattern (Fig 5.48 , 5.52) . Where the Sele Formation overlies the Lista Formation, the boundary is well defined on logs, without any distinct changes in lithology. The Sele Formation shows higher, and often smoother, gamma-ray readings and a very smooth, lower velocity pattern (Fig 5.51) . In some areas, both the Lista and Sele formations contain sandstone beds, resulting in a poorly defined boundary based on log character. Where the Lista Formation is overlain by the Balder Formation , the boundary is defined by lower gamma-ray readings and higher velocity in the Balder Formation . It is difficult to distinguish the Lista and Sele formations in the Frigg area.
Distribution
The Lista Formation is widespread in the Norwegian North Sea.
Age
Late Paleocene.
Depositional environment
The deposition of the Lista Formation shales took place in relatively deep water under low-energy conditions. Sandstone layers represent distal parts of sandy formations within the Rogaland Group .
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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95
131
LOMVI FM
FORMATION
HEGRE GP
Lomvi Formation

Name
From the bird (English: guillemot) of the same name.
Well type section
Norwegian well 33/12-5 (Mobil) from 3747m to 3867m, coord N 61°11'05.53", E 01°51'53.34" (Fig 3.2) .
Well reference section
Norwegian well 33/5-1 (Norsk Hydro) from 3220 m to 3298 m, coord N 61°44'46.10", E 01°34'47.40" (Fig 3.3) .
Thickness
120 m in the type well, 78 m in the reference well.
Lithology
The Lomvi Formation consists of fine to coarse-grained kaolinitic sandstone with subordinate and thin red marls and claystones. The sandstones, which are light brown, grey or white, are generally more coarse-grained in the reference well than in the type well.
Boundaries
The lower boundary represents the transition from interbedded sandstones and marls to the coarse-grained sandstones of the Lomvi Formation. The upper boundary, in the Statfjord Field area, is chosen at the base of the first thick argillaceous unit belonging to the Lunde Formation . Gamma ray log patterns are more regular in the Lomvi Formation than in the overlying and underlying formations.
Distribution
The Lomvi Formation is present in all deep wells between the Brent Field and the southern edge of the Møre Basin.
Age
Triassic; no more precise dating available.
Depositional environment
The Lomvi Formation most probably consists of fluvial deposits.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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96
61
LUNDE FM
FORMATION
HEGRE GP
Lunde Formation

Name
From the bird (English: puffin) of the same name.
Well type section
Norwegian well 33/12-2 (Mobil) from 2951 m to 4048 m, coord N 61°13'31.38", E 01°51'25.97", (Fig 3.4) .
Well reference section
UK well 211/29-5 (Shell) from 3003 m to 4055 m, coord N 61°04'43.0", E 01°45'46.5" (Fig 3.5) .
Thickness
1079 m in the type well, 1052 m in the reference well.
Lithology
The formation is an interbedded sequence of very fine to very coarse-grained sandstones (2 to 10 m thick), claystones, marls and shales.
The sandstones are mainly white, pink or grey and cemented to a variable degree with kaolinite, anhydrite and carbonate. Fine-grained sandstones from the upper portion of the formation (core data from UK well 211/13-1) display small scale ripple cross stratification, bioturbation and incorporated mud clasts and mud balls. This part of the formation may also have small fining upward sequences.
The interbedded argillaceous units are dominantly red-brown claystones, siltstones and shales with thin limestones (possibly caliche). Tuff horizons are present in the lower half of the formation in the
Statfjord Field area. The lowermost part of the Lunde Formation consists in the Statfjord Field area (and westward into UK waters), of a sequence which is very uniform both in lithology and thickness. It is around 300 thick and consists mainly of brick red to red brown calcareous claystones grading to marls which are normally soft, silty and micaceous. This lower sequence is easily recognisable and may eventually be separated out and assigned formation status.
Boundaries
The base of the formation is picked at the base of the first thick claystone unit. This boundary is marked by sonic and gamma ray log breaks. The alternating lithologies of the Lunde Formation result in an irregular gamma ray response. On structural highs the top of the formation is represented by a hiatus, with Jurassic or younger strata resting on the Triassic sequence. Where the Statfjord Formation is present, the upper boundary of the Lunde Formation is placed at the change to the relatively massive clean standstone of the overlying Statfjord Formation . In the Statfjord Field area, this transition often occurs via a coarsening upward unit, clearly defined on gamma ray and sonic logs. The base of this unit is the top of the Lunde Formation. (See also the description of the Statfjord Formation ).
Distribution
The formation is assumed to be present throughout the northern North Sea Area, although major parts may be missing on structural highs owing to erosion or non-deposition.
Age
Late Triassic, possibly Norian to early Rhaetian age.
Depositional environment
The Lunde Formation is dominantly of continental origin, deposited in lacustrine and fluvial environments.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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97
61
LYR FM
FORMATION
CROMER KNOLL GP
Lyr Formation

Name
From the fish species Pollachius pollachius (pollack).
Well type section
Well 6506/12-1 (Statoil), coordinates 65°10'07.58"N, 06°43'44.07"E, from 3836 m to 3812.5 m (Fig 4.27) . No cores.
Well reference section
Well 6407/1-2 (Statoil), coordinates 64°47'50.61"N, 07°02'23.76"E, from 3526 m to 3510 m (Fig 4.28) . No cores.
Thickness
23.5 m in the type well and 16 m in the reference well.
Lithology
The formation consists of light/medium grey to light greyish-green marls with interbedded carbonates.
Basal Stratotype
In the type well the base is defined by a decrease of interval transit times shown by the sonic log. The gamma ray and the resistivity responses also decrease.
The base has been sampled in shallow cores from the eastern part of the Trøndelag Platform (Bugge et al. 1984), but logs and detailed descriptions are not yet available.
Lateral extent and variation
The formation is encountered in all wells on Halten Terrace, but is absent on the Nordland Ridge and on structural highs on the Nordland Ridge and the Trøndelag Platform. The carbonate content is expected to decrease to the west in the Møre and Vøring Basins. The formation consists of very thin limestones with intraformational conglomerates on the eastern part of the Trøndelag Platform (Bugge et al. 1984).
Age
Valanginian to Early Aptian.
Depositional environment
The formation was deposited under open marine conditions.
Correlation
The Lyr Formation is comparable to the Valhall Formation11) (Deegan and Scull, 1977) in the central North Sea. It is also equivalent to the Leira Member on Andøya (Dalland, 1979).
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
Footnotes
  • 1) Åsgard Formation according to Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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98
23
LYSING FM
FORMATION
CROMER KNOLL GP
Lysing Formation

Name
From the fish species Merluccius merluccius (hake).
Well type section
Well 6507/7-1 (Conoco), coordinates 65°27'16.7"N, 07°12'52.6"E, from 3000 m to 2926 m (Fig 4.29) . No cores.
Well reference section
Well 6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 3150 m to 3132.5 m (Fig 4.30) . The lower 15 m of the formation are cored, including the base.
Thickness
74 m in the type well and 17.5 m in the reference well.
Lithology
Predominantly fine to medium, occasionally coarse grained, white-grey sandstones, partly carbonate-cemented and interbedded with shales.
Basal Stratotype
The base is defined by a gradual decrease in the gamma ray log response and by the onset of a more nervous pattern on the resistivity and sonic logs.
Lateral extent and variation
The formation is widely distributed over the Halten Terrace, but is absent on the Trøndelag Platform. It thins to the south and north of the type well.
Age
Late Cenomanian to Turonian/Coniacian.
Depositional environment
Interpretations vary from shallow to deep marine, possibly as submarine fan deposits.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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99
23
MANDAL FM
FORMATION
TYNE GP
Mandal Formation

Name
From a town on the south coast of Norway. It replaces the Kimmeridge Clay Formation as used by authors in the Central Graben area (e.g. Ofstad, 1983). The name was informally proposed by Hamar et. al., (1982).
Well type section
Norwegian well 7/12-3 A (BP) from 3514 m to 3552 m, coord N 57°06'24.54", E 02°48'41.56" (Fig 3.44) .
Well reference sections
Norwegian wells 2/1-2 (BP) from 3300 m to 3316m, coord N 56°57'30.76", E 03°12'32.07" (Fig 3.33) , and 1/9-3 R (Statoil) from 4265 m to 4319m, coord N 56°24'56.2", E 02°54'15.15" (Fig 3.43) .
Thickness
In the type well 38 m and in the reference wells 16m and 54 m. The thickness usually varies between 10 m and 70 m and generally thins over structural highs.
Lithology
The formation consists of a dark grey-brown to black, slightly to non-calcareous, carbonaceous claystone becoming fissile in places. It is characterized by a very high level of radioactivity which is a function of organic carbon content. In addition it has an anomalously low velocity, a high resistivity and a low density. It may contain thin stringers of limestone/dolomite and, in some areas, sandstone (e.g. 1/9-3 R ).
Boundaries
The contacts of the Mandal Formation with underlying and overlying sediments are easily recognized on logs due to its high gamma ray and resistivity readings and its low velocity and density.
Distribution
The Mandal Formation is found in the Central Graben, and on the margins of the Southern Vestland Arch. The northern limit is the Jæren High.
Age
Volgian to Ryazanian.
Depositional environment
The formation was deposited in an anaerobic marine environment with high organic productivity and restricted bottom water circulation.
Remarks
See Draupne Formation . Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=101
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177
MAUREEN FM
FORMATION
ROGALAND GP
Maureen Formation

Name
Named by Deegan & Scull (1977) from the Maureen Field in UK block 16/29.
Well type section
UK well 21/10-1 from 2524 m to 2464 m, coordinates N 57°43'50.37", E 00°58'29.19" (Fig 5.44) . No cores.
Well reference sections
UK well 16/29-4 from 2796 m to 2679 m, coordinates N 58°05'20.90", E 01°39'15.10" (Fig 5.45) . No cores.
Norwegian well
7/11-1 from 3173 m to 3069 m, coordinates N 57°04'15.60", E 02°26'24.40" (Fig 5.46) . No cores.
Thickness
The Maureen Formation is thickest in the Witch Ground Graben in the UK sector of the central North Sea where it consists of as much as 400 m of mainly sandstones. It thins westwards and southwards, and is poorly developed in Norwegian waters, the maximum thickness in a well is found 7/11-1 where there are 104 m of sandstones and carbonates.
Lithology
The Maureen Formation consists of sandstones that are slightly to very calcareous and often contain reworked limestones. The sandstones are interbedded with brown and dark grey shales, and are fine to medium grained, locally very coarse.
The type well established by Deegan & Scull (1977) represents a distal and somewhat atypical section. A more representative well from the Maureen Formation sandstones is UK well 16/29-4
(Fig 5.45) .
The formation pinches out distally and is replaced by the light grey marls and shales of the
Våle Formation .
Basal stratotype
The Maureen Formation rests on the Shetland Group .
Characteristics of the upper boundary
The upper boundary is defined by the change from sandstones containing reworked limestone fragments and limestone beds, to the shales of the Lista Formation . The boundary is characterised by an upward increasing gamma-ray response (Fig 5.45) . and an overall decreasing velocity. Where the Andrew Formation rests on the Maureen Formation the transition is seen as an increase in gamma-ray readings and decrease in velocity (Fig 5.44) .
Distribution
The coarse detrital facies of the Maureen Formation is developed in the central North Sea, in what is in general a lobe-shaped deposit trending from the East Shetland Platform southeast along the Central Trough. The formation thins towards the east and west, and grades into the Våle Formation . The Maureen Formation is not well developed in the Norwegian sector. Its approximate distribution on the Norwegian continental shelf is shown in (Fig 5.47) .
Age
Early Paleocene.
Depositional environment
The Maureen Formation was deposited in an open marine environment dominated by sand influx from the northwest, together with local erosion of Danian and Cretaceous rocks.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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131
MEILE MBR (INFORMAL)
MEMBER
HEIMDAL FM
Meile Member (informal)

Name
Meile was a son of the Norse god Odin. Little is told about him except that he was one of 3 messengers from the gods to save Balder from Hel (hell in Norse mythology).
Well reference section
Norwegian well 15/9-11 from 2526 m to 2386 m, coordinates N 58°24'02.53", E 01°53'41.79" (Fig 5.51) .
Thickness
The Meile Member is 140 m thick in the reference well. It has a relatively constant thickness.
Lithology
The Meile Member consists of clean, well-sorted sandstones, which are very fine to fine grained, friable to hard, and clear to white.
Basal stratotype
The lower boundary of the Meile Member is defined by the transition from the marly claystones of the Våle Formation . The gamma and sonic logs change from an erratic pattern in the Våle Formation to a smooth pattern with low gamma-ray readings when passing into the Meile Member (Fig 5.57) . Where the Våle Formation is absent the Meile Member rests directly on the calcareous deposits of the chalk facies of the Shetland Group . This boundary is characterised by upward increasing gamma-ray readings and decreasing velocity (Fig 5.51) .
Characteristics of the upper boundary
The upper boundary is identified by a transition from clean sandstones into the shales of the Lista Formation . On the logs the upper boundary is seen as an increase in gamma-ray values and a change to a more erratic log pattern on both gamma and sonic logs (Fig 5.51) .
Distribution
The Meile Member is found in a narrow belt extending north-northeastwards from the eastern part of quadrant 15. Its approximate distribution on the Norwegian continental shelf is shown in (Fig 5.47) .
Age
Paleocene.
Depositional environment
The clean sandstones of the Meile Member may have been derived by winnowing of the Heimdal Formation sands by submarine currents acting along highs. The formation can also be interpreted in terms of high-density turbidites which source from well-sorted shelf sand.
Remarks
The Meile Member has earlier informally been referred to as the “Gamma sand on Sleipner”. The Meile Member is defined informally.
Source
Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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62
MELKE FM
FORMATION
VIKING GP
Melke Formation

Name
The Norwegian word for milt or soft roe. This unit corresponds to the informal Engelvær Formation (H2-1).
Well type section
6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 3979.5 m to 3863 m (Fig 4.21) . One core, 8 m recovery, including formational base.
Well reference section
6407/2-2 (Saga Petroleum), coordinates 64°59'39.64"N, 07°31'53.08"E, from 2461 to 2417 m (Fig 4.23) . One core, 2 m recovery, including the base.
Thickness
116.5 m in the type well, 44 m in the reference well.
Lithology
Dominantly claystone, with siltstone and limestone interbeds and stringers of sandstone. The claystone is dark grey to dark brown and slightly calcareous.
Basal Stratotype
The base is defined by a sharply increasing gamma ray response at the contact between the underlying sandstones of the Garn Formation and the claystones of the Melke Formation .
Lateral extent and variation
The formation was deposited throughout the Haltenbanken-Trænabanken area and is locally absent on structural highs. The formation may attain thicknesses of several hundred metres in down-flank basinal situations. The formation also shows lateral variation in lithology, being more silty or having more frequent limestone beds in some areas. Deposition of the unit's mudstones commenced earlier on Trænabanken than elsewhere (Fig 4.6) .
The unit subcrops beneath the Quaternary on the eastern part of the Trøndelag Platform as evidenced by several shallow cores (Bugge et al. 1984).
Age
Bajocian to Oxfordian.
Depositional environment
The Melke Formation was deposited in an open marine environment.
Correlation
The Melke Formation is comparable to the Heather Formation of the North Sea. The upper parts of the Melke Formation are time equivalent to the Fuglen Formation in the Hammerfest Basin.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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188
MIME FM
FORMATION
CROMER KNOLL GP
Mime Formation

Name
Named after a god from Norse mythology who was considered to be very wise.
Well type section
Norwegian well 34/10-18 from 2351 m to 2340 m, coordinates N 61°14'22.48", E 02°03'18.83" (Fig 5.16) . Cores (lower half of the formation).
Well reference section
Norwegian well 17/4-1 from 2122 m to 2080 m, coordinates N 58°35'54.00", E 03°16'05.00" (Fig 5.17) . No cores.
Thickness
In the type well the Mime Formation is 11 m, and in the reference well it is 42 m thick. Usually, the thickness varies between 5 and 20 m.
Lithology
The formation is dominated by limestones and marls. It often contains impure carbonates that are reworked and mixed with smaller quantities of sand and silt. The formation is sometimes chalky. The matrix is usually very calcareous. Oolites are observed in some wells in the East Shetland Basin. The colour is usually white or light pink, but may vary slightly on account of the sand/silt mixture.
Basal stratotype
In those wells where the Mime Formation is present it defines the lower boundary of the Lower Cretaceous, lying on the Upper Jurassic sediments or older rocks. This boundary is always an unconformity and can most often be seen on the logs as a decrease in gamma-ray readings and an increase in velocity upwards from the underlying Jurassic sediments.
Characteristics of the upper boundary
The upper boundary is usually defined at the bottom of more or less calcareous shales in the Åsgard Formation . This boundary is reflected on the logs as an upward increase in gamma-ray readings and a reduction in velocity (Fig 5.17) . The upper boundary can also be defined by the overlying shales of the Sola or Rødby formations. The boundary will normally be reflected on logs as described above (Fig 5.16) .
Distribution
The formation is found only as narrow zones along structural highs. On the flanks of the Viking Graben it may be seen almost continuously from approximately 58° to 62° N. It is also found as a thin carpet over most of the East Shetland Basin and along the Fladen Ground Spur, the Utsira High-Lomre Terrace, the northwest side of the Sele High, and the Jæren High.
The formation is not encountered in the more central parts of the basins, and it is doubtful if it is present along the boundaries of the Fennoscandian Shield.
Age
The formation is time-transgressive, and is dated to Late Valanginian to Albian. It is oldest in the deeper parts along the basin margins and becomes younger up along the flanks. In most of the East Shetland Basin, along the Utsira, Bergen, Sele and Jæren highs, and along the flanks of the Viking Graben, it is usually of Barremian/Hauterivian age (Fig 5.4) .
Depositional environment
Palaeontological investigations together with the observation of oolites indicate a transgressive, shallow marine, depositional environment.
Remarks
Hesjedal & Hamar (1983) described the impure, reworked limestones resting directly on the Base Cretaceous unconformity over the structural highs, as the Utvik Formation. This formation is formally defined as the Mime Formation in this paper, since the name suggested was not in accordance with existing recommendations.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
https://factpages.npd.no/factpages/default.aspx?nav1=strat&nav2=PageView|Litho|Formations&nav3=106
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23
MOLO FM
FORMATION
NORDLAND GP
Molo Formation1)

Name
Molo is the Norwegian name for jetty.
Well type section
Well 6610/3-1 (Statoil) from approximately 349 m (the top is not sampled and logged in the well) to 555 m (Fig. A9) , in Eidvin et al. (2007)), coordinates 66°55’29.70’’N, 10°54’06.28’’E (Nordland Ridge, (Fig. A1) in Eidvin et al. (2007)).
Well reference section
Well 6407/9-5 (Shell) from 670 to 787 m ( (Fig. A1) coordinates 64°16’42.35’’N, 07°44’14.66’’E (Trøndelag Platform, (Fig. A1) in Eidvin et al. (2007)).
Thickness
A total thickness of 206 m in the type well is only sampled with five side wall cores (Fig. A9) . In the reference well a total thickness of 117 m is sampled with ditch cutting samples at ten meters interval (Fig. A1) . in Eidvin et al. (2007)). Some short vibro cores are sampled in the Nordland Ridge area (Fig. A1) . in Eidvin et al. (2007)). Close to its northern boundary (block 6610/2 and 6610/5) the unit increases to more than 500 m (Fig. A1) . in Eidvin et al., (2007)).
Distribution
The formation extends from the coast off Møre at approximately 63º30’N, along the inner Mid Norwegian shelf up to the Nordland Ridge and Lofoten area at approximately 67º40’ N (Fig. A1) . in Eidvin et al. (2007)).
Lithology
The lithology varies considerably throughout its distribution area. In most wells and boreholes from proximal parts, the unit consists mainly of red to yellow coloured sand. Some sections also contain well rounded, rust-tinted pebbles. In some wells glauconitic sand and mica-rich sand are recorded. In the Draugen Field (Trøndelag Platform), where the distal part has been investigated, the unit contains glauconitic sand, silt and clay.
Basal boundary
In the type well the lower boundary is recognized by an abrupt change from greyish claystone of the Brygge Formation to grey mica-rich sand of the Molo Formation. The boundary is marked by a strong negative spike at approximately 555 m on the gamma log (Fig. A9) . in Eidvin et al. (2007)). In the reference well the lower boundary is recognised by an abrupt change from greyish claystone of the Brygge Formation to dark (nearly black) glauconitic sand of the Molo Formation. The boundary is further marked by an increase in the gamma ray response and a decrease in velocity (Fig. A1) . in Eidvin et al. (2007)).
Characteristics of the upper boundary
The upper boundary is not sampled and logged in the type well and it is only recognised on seismic lines. In the reference well the upper boundary is recognised by a marked decrease in velocity and a slight decrease in the gamma ray response into the overlying glacio-marine diamicton (Fig. A1) . in Eidvin et al. (2007)).
Age
Late Miocene – Early Pliocene.
Depositional environment
The formation was deposited in a coastal shallow marine to prograding deltaic environment, probably formed in a wave-dominated environment with extensive long-shore drift.
Remarks
It is only in wells from the distal part, including the reference well, that it is possible to date the Molo Formation by means of biostratigraphical and strontium isotope analyses. In wells from the proximal part, including the type well, only reworked fossils are recorded. Most of the sediments in this part are probably reworked from other formations including the Brygge and Tare formations. The Molo Formation has previously informally been called the “Delta” by Bugge et al. (1976), IKU Bedrock Unit IX by Bugge et al. (1984) and Rokoengen et al. (1988, 1995), the “Frøyrygg formation” by Askvik & Rokoengen (1985) and informally introduced as the “Molo formation” by Gustavson & Bugge (1995).
Source
  • Eidvin, T., Bugge, T. & Smelror, M., 2007: The Molo Formation, deposited by coastal progradation on the inner Mid-Norwegian continental shelf, coeval with the Kai Formation to the west and the Utsira Formation in the North Sea. Norwegian Journal of Geology, Vol. 87, pp. 75-142. Available from the internet
Footnotes
  • 1) In the NPD-factpages the Molo Formation has only been used for the wells analysed by Eidvin et al. (2007).
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NANSEN FM
FORMATION
STATFJORD GP
Nansen Formation

Name
After the Norwegian polar scientist, explorer and statesman, Fridtjof Nansen.
Well type section
UK well 211/24-1 (Conoco/Gulf/NCB) (Fig 1.17-18) . 1.17) from 3112 m to 3159 m below KB.
Well reference section
Norwegian well 33/12-2 (Mobil) (Fig 1.17-18) .
Thickness
46 m in the type well and 19 m in the reference well.
Lithology
In the type well the formation consists of medium- to coarse-grained, fairly well-sorted, homogeneous, white sandstones with a calcite-cement and a subordinate kaolinite matrix. Occasional horizons with granules or pebbles are present. Carbonaceous material and mica are rare but glauconite is quite common. Thin shale beds containing marine fossils are present, most commonly in its upper part.
At the top of the formation, from 3112 m to 3135 m in the type well is a more prominent calcareous horizon defined informally as the calcareous sandstone bed. This may grade locally into a sandy limestone, for example in the Brent Field.
The Nansen Formation thins towards the east and passes laterally into calcareous siltstones and shales in the Norwegian sector
(Fig 1.17-18) . Although these siltstones and shales are lateral equivalents of the Nansen Formation they are placed in the overlaying Dunlin Group on lithological grounds.
Boundaries
The originally Nansen Member of the Statfjord Formation was elevated to formation level by Lervik, 2006. The lower boundary is marked by the change from the non-calcareous sandstones of the Eiriksson Formation to the cleaner, generally calcareous sandstones of the Nansen Formation. The upper boundary is marked by the change from calcareous sandstone to the argillaceous sediments of the Dunlin Group . Both boundaries are well marked on gamma ray and sonic logs particularly in the UK sector where the formation is best developed. The calcareous sandstone bed at the top of the formation is normally reflected by a distinctive sonic log response (Fig 1.17-18) . However, as this passes laterally into calcareous siltstones and shales the sonic log still responds to the calcareous nature of the sediments.
Distribution
The formation is widespread in the northern North Sea. Deegan and Scull (1977) describes the formation as well developed in the Brent Field area. The lower part of the formation overlaps westwards to the Cormorant Field area where it is probably the only representative of the Statfjord Group . The calcareous sandstone bed at the top does not extend as far west as the lower part of the formation.
Age
Probably Hettangian to Early Sinemurian.
Depositional environment
Subaerial depositional conditions are suggested for parts of the fine-grained units by the presence of calcrete, coals and root-traces. In contrast, delicate lenticular and flaser lamination, wave-ripple laminae and abundant bioturbation suggest that the other parts of the fine-grained units were deposited in standing water (Røe and Steel, 1985). Based on the stacking pattern of facies associations and the presence of marine fossils, the upper part of the sequence is interpreted to have been deposited in a marine environment.
Although the Nansen Formation in the Gullfaks and Statfjord area has been described as marine (Deegan and Scull, 1977; Røe and Steel, 1985), Nystuen and Fält (1995) interpret this formation as being a massive, rapidly deposited and dewatered fluvial sandstone with evidence of glauconite only near its top at Statfjord. Evidence for marine incursions at the
Snorre Field is equivocal, for they may be stratigraphically higher than the Nansen Formaion. Equally the sandstones interpreted as shallow marine in origin may be interpreted as the deposits of a fluvial environment, such as a laterally extensive braided stream or a sheetflood.
Compiled from
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25. The Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
  • Goldsmith, P. J., Hudson, G. and Van Veen, P. Triassic. 105 – 127 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
  • Lervik, K.-S. 2006: Triassic lithostratigraphy of the Northern North Sea Basin. Norwegian Journal of Geology, Vol. 86, pp. 93-116.
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157
NAUST FM
FORMATION
NORDLAND GP
Naust Formation

Name
From the Norwegian word for a boathouse. The formation corresponds to the informal Sula Group (H7).
Well type section
Well 6507/12-1 (Saga Petroleum) coordinates 65°07'01.62"N, 07°42'42.61"E, formational base at 1342 m (Fig4 .39) . No cores.
Thickness
The base of the overlying, dominantly glacio-marine deposits is not yet defined. Precise thicknesses are therefore unknown, but generally the Naust Formation is several hundred metres thick in the Haltenbanken-Trænabanken area.
Lithology
Interbedded claystone, siltstone and sand, occasionally with very coarse clastics in the upper part.
Basal Stratotype
The base is defined by a decrease in interval transit time and gamma ray response and an increase in the resistivity log readings.
Lateral extent and variation
The Naust Formation is laterally continuous across the Mid-Norwegian Shelf.
Age
Late Pliocene.
Depositional environment
The formation was deposited in a marine environment. A transition to glaciomarine environments occurs in the upper part, but this transition is poorly documented by the exploration wells.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
Footnotes
  • 1) In the NPD-factpages the Naust Formation also comprises Pleistocene deposits.
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NESS FM
FORMATION
BRENT GP
Ness Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2633.5 m to 2772 m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference sections
Norwegian wells 33/9-1 (Mobil) from 2509 m to 2575 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) . 30/6-7 (Norsk Hydro) from 2646 m to 2727 m, coord N 60°38' 39.49'', E 02°45'21.74" (Fig 3.16) . and 31/4-4 (Norsk Hydro) from 2695 m to 2721 m, coord N 60040'01.12", E 03°06'54.12" (Fig 3.17) .
Thickness
138.5 m in the type well, 66 m in 33/9-1 , 81 m in 30/6-7 and 26 m in 31/4-4 .
Lithology
The formation consists of an association of coals, shales, siltstones and very fine to medium grained sandstones. The formation is carbonaceous throughout and contains numerous rootlet horizons. Small scale cross-bedding and horizontal bedding are common. Synsedimentary deformation is frequently observed. The shales are silty, fissile and frequently pyritic. The formation occasionally shows some marine influence. Coarsening and fining upward sequences are common features. The varied lithology produces an irregular but distinctive gamma ray and sonic response.
Boundaries
The lower boundary defines the top of the Etive Formation (see above). The upper contact is marked by the change to the more massive cleaner sandstone of the overlying Tarbert Formation . This upper contact may be a minor disconformity.
Distribution
The distribution of the Ness Formation is essentially the same as that of the Brent Group .
Age
Bajocian.
Depositional environment
The formation is thought to represent delta plain or coastal plain deposition.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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NISE FM
FORMATION
SHETLAND GP
Nise Formation

Name
From the whale species Phocoena phocoena.
Well type section
Well 6506/12-4 (Statoil), coordinates 65°12'46.97"N, 06°43'30.37"E, from 2600 m to 2380 m (Fig 4.33) . No cores.
Well reference section
Well 6506/12-1 (Statoil), coordinates 65°10'07.58"N, 06°43'44.07"E, from 2658 m to 2446 m (Fig 4.34) . No cores.
Thickness
220 m in the type well and 212 m in the reference well.
Lithology
Dominant grey and greyish-green claystones interbedded with carbonate and sandstone stringers.
Basal Stratotype
The base is defined by a log break giving an increase in interval transit time and a weak decrease in resistivity from the calcareous claystones of the Kvitnos Formation into the less calcareous claystones of the Nise Formation.
Lateral extent and variation
The formation is regionally extensive but is absent on parts of the Nordland Ridge and on local highs along the western flanks of the Trøndelag Platform.
Age
Santonian to Campanian.
Depositional environment
Open marine.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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143
NO DATA
GROUP
No data

No data was available to assign the interval to a certain group or formation.
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NO FORMAL NAME
FORMATION
No formal name

“No formal name” is used for units that have not yet received a formal name, as for example shaly intervals in the Hordaland Group in the North Sea. Exceptionally, informal names have been used to assign reservoir intervals, for example Intra Balder Formation sandstone , Intra Draupne Formation sandstone and Intra Heather Formation sandstone .
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NO GROUP DEFINED
GROUP
No group defined

According to the current stratigraphic nomenclature no group is defined for this interval. Only formations may be formalised in this interval not belonging to any particular group.
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NORDLAND GP
GROUP
Nordland Group

Name
The group was named by Deegan & Scull (1977) after the county of Nordland in Norway.
In the Norwegian Sea the group corresponds to the upper part of the informal Sklinna Group and to the Sula Group (H6 and H7).
The sequence in the Hammerfest Basin is believed to belong to this laterally continuous unit, although only the younger parts of the group are represented in this area. The unit corresponds to T7 or Egga Group of earlier usage.
Type area
The type area is the North Sea Tertiary Basin. Typical sections through the group are seen in Norwegian well 2/2-1 (Fig 5.60) . (Fig 5.69) . shows a seismic section through the group in the Central Trough area. The lithostratigraphy is shown in (Fig 5.40) .
In the Norwegian Sea well
6407/1-2 (Statoil), coordinates 64°47'50.61"N, 07°02'23.76"E, from 1690 m to 302 m, is used to illustrate the local development of the group (Fig 4.38) .
In the Barents Sea well
7119/12-1 (Statoil), coordinates 71°06'08.00"N, 19°47'40.29"E, from 465 m to 225m illustrates the development of the Nordland Group.
Thickness
The group is 1514 m thick in well 2/2-1 , but may exceed 1700 m in the Central Trough. It is approximately 1000 m thick in the Viking Graben area.
In well
6407/1-2 it is 1388 m thick.
The group thins from approximately 250 m in southern wells to less than 100 m in northernmost locations in the Hammerfest Basin. Westernmost wells drilled over the Senja Ridge in Block 7117/9 show thicknesses of over 700 m.
Lithology
In the North Sea the Nordland Group is dominated by marine claystones. These are grey, sometimes greenish-grey and grey-brown, soft, locally silty and micaceous. The sandy Utsira Formation occurs in the lower part of the group in the Viking Graben area. The uppermost part of the group consists of unconsolidated clays and sands with glacial deposits uppermost.
In the Norwegian Sea alternating the group consists of claystone, siltstone and sandstone.
In the Barents Sea sand and clays grade into sandstones and claystones, the sand content increasing upwards. Cobbles and boulders of quartzite, granite and different metamorphic rocks occur with clay in the upper parts of the group. The clay is grey to greyish greeen, soft to firm, blocky, non-calcareous, and in parts silty.
The base of the group coincides with the Oligocene unconformity1). In the reference well this is defined by a decrease in interval transit time and gamma ray readings, and a lithologic change from claystones in the underlying
Sotbakken Group to the basal sand/sandstones of this group. In wells where claystones are found above the base, the boundary is not easily identified by wireline logs. In such cases, minor lithological variations have to be relied upon; the claystones of the Nordland Group are generally softer and darker than those of the Sotbakken Group .
The group is often drilled with returns to seabed only (seabed - 30" casing). As a consequence, especially where there is no marked lithological variation, it is often difficult to pick the base of the group, particularly when it is thin and poorly developed. This is the case for most wells located north of 71°15'N and east of 20°20'E.
Basal stratotype
The base of the group occurs at the passage from the generally brown shales of the Hordaland Group into the more massive and blocky, generally grey, claystones of the Nordland Group. This contact is usually marked by a break on the logs which represents an unconformity of Early to Middle Miocene age. In the Central Trough the lower boundary is placed at the base of a claystone with high gamma-ray readings (Fig 5.60) . In the Viking Graben area the lower boundary is normally the base of the sandy Utsira Formation 2). In this case the contact is marked by a decrease in gamma-ray readings from the claystones of the Hordaland Group into the Utsira Formation . Where the basal part of the Nordland Group is developed as claystone the boundary is placed at log breaks associated with a change in claystone colour.
Characteristics of the upper boundary
The upper boundary is the sea bed.
Distribution
The group is distributed over most of the North Sea Tertiary Basin. It may be incomplete at the basin margins due to erosion or non-deposition.
The Nordland Group is present throughout the Mid-Norwegian shelf, but the lower part is not present on the crest of the Nordland Ridge. The sand content may vary locally, but there is no significant regional variation.
The sequence in the Hammerfest Basin is believed to belong to this laterally continuous unit, although only the younger parts of the group are represented in this area. The Nordland Group is represented over the whole of Tromsøflaket. The most continuous sequences should be found over and to the west of the Senja Ridge.
Sequences in the Hammerfest Basin itself are mainly of glacial and post-glacial origin.
Age
Middle Miocene to Recent (North Sea)3).
Early Miocene to Recent (Norwegian Sea)4).
Late Pliocene to Pleistocene/Holocene in the Hammerfest Basin, extending back to the mid-Oligocene along western shelf margins5).
Depositional environment
Open marine, with glacial deposits in the upper part in some areas (North Sea).
In the Norwegian Sea the Nordland Group was deposited in a marine environment in a rapidly subsiding basin characterised by major westerly prograding wedges. The upper part is of glacial to glacio-marine origin.
In the Barents Sea the depositional environment is characterised as bathyal to glacial marine.
Subdivision
The Utsira Formation is the only formation presently defined in the Nordland Group in the North Sea. Additional units may be defined in the future from subregional work and further well information.
In the Norwegian Sea the Nordland Group consists of the
Kai , Molo 6) and Naust formations.
In the Barents Sea no regional formational scheme has yet been presented, although several Quaternary and Holocene units have been defined (see e. g. Vorren et al. 1978 and Vorren 1984).
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
Footnotes
  • 1) Base Oligocene unconformity according to Gradstein et al. (1992)
  • 2) Through most of the Viking Graben area a shale unit is usually developed between the Utsira Formation and the top of the Hordaland Group (mid Miocene unconformity). In the Tampen area the Utsira Formation rests directly on the Hordaland Group. See also Eidvin and Rundberg (2001, 2007).
  • 3) See also Eidvin and Rundberg (2007).
  • 4) Middle Miocene to recent, see Eidvin et al. (2007).
  • 5) See also Eidvin and Riis (1988) and Eidvin et al. (1993, 1998).
  • 6) The Molo Formation has been proposed by Eidvin et al. (2007).
References
  • Eidvin, T. and Riis, F., 1989: Nye dateringer av de tre vestligste borehullene i Barentshavet. Resultater og konsekvenser for den Tertiære hevningen. NPD-Contribution 27, 44 pp.
  • Eidvin, T. and Rundberg, Y. (2001): Late Cainozoic stratigraphy of the Tampen area (Snorre and Visund fields) in the northern North Sea, with emphasis on the chronology of early Neogene sands. Norsk Geologisk Tidsskrift, 81, 119–160.
  • Eidvin, T. and Rundberg, Y., 2007: Post-Eocene strata of the southern Viking Graben, northern North Sea; intergrated biostratigraphic, strontium isotopic and lithostratigraphic study. Norwegian Journal of Geology 87, 391-450.
  • Eidvin, T., Bugge, T. & Smelror, M., 2007: The Molo Formation, deposited by coastal progradation on the inner Mid-Norwegian continental shelf, coeval with the Kai Formation to the west and the Utsira Formation in the North Sea. Norwegian Journal of Geology, Vol. 87, pp. 75-142.
  • Eidvin, T., Goll, R. M., Grogan, P., Smelror, M. and Ulleberg, K., 1998b: The Pleistocene to Middle Eocene stratigraphy and geological evolution of the western Barents Sea continental margin at well site 7316/5-1 (Bjørnøya West area). Norsk Geologisk Tidsskrift 78, 99-123.
  • Eidvin, T., Jansen, E. and Riis, F., 1993: Chronology of Tertiary fan deposits of the western Barents Sea: implications for the uplift and erosional history of the Barents Shelf. Marine Geology 112, 109-131.
  • Gradstein, F. M., Kristiansen, I. L., Loemo, L. and Kaminski, M. A. (1992). Cenozoic foraminiferal and dinoflagellate cyst biostratigraphy of the central North Sea. Micropaleontology 38, No. 2, 101-137.
  • Rundberg, Y. and Eidvin, T., 2005: Controls on depositional history and architecture of the Oligocene-Miocene succession, northern North Sea Basin. In B.T.G. Wandaas et al. (eds.): Onshore-Offshore Relationships on the North Atlantic Margin. NPF Special Publication 12, 207-239.
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113
NORDMELA FM
FORMATION
REALGRUNNEN SUBGP
Nordmela Formation

Name
Nordmela is a small community on the west coast of Andøya. Our use of the term corresponds to the description by Olaussen et al. (1984) and to the informal term T2-4.
Well type section
Well 7121/5-1 (Statoil), coordinates 71°35'54.88"N, 21°24'21.78"E, from 2507 to 2445m. The entire formation is cored in this well (Fig 4.48) .
Well reference section
Well 7119/12-2 (Statoil), coordinates 71°00'51.81"N, 19°58'20.81"E, from 1719 m to 1517 m. All but the basal 31 m are cored in this well (Fig 4.49) .
Thickness
62 m in the type well and 202 m in the reference well.
Lithology
The formation consists of interbedded siltstones, sandstones, shales and claystones with minor coals. Sandstones become more common towards the top.
Basal Stratotype
The base is defined by a sharp increase in gamma ray response to high, irregular, patterns in contrast to the cylindrical, blocky to bell-shaped pattern of the underlying unit. This shift is accompanied by an increase in bulk density readings.
Lateral extent and variation
Thickness variation between the type and reference wells clearly illustrates a southwest thickening wedge. This is in marked contrast to the underlying Tubåen Formation . Westwards thickening may be the result of early Kimmerian subsidence over the site of the Ringvassøy-Loppa Fault Complex.
Age
The formation extends from the Sinemurian to the late Pliensbachian in the reference area. Its top may be diachronous, younging eastwards into the Toarcian in the type section.
Depositional environment
The formation was deposited in tidal flat to flood plain environments. Individual sandstone sequences represent estuarine and tidal channels which dissected this low-lying area.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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128
NOT FM
FORMATION
FANGST GP
Not Formation

Name
From the Norwegian word for a sweep net. The unit corresponds to the middle part of the informal Tomma Formation (H1-4), or “Tomma II”.
Well type section
Well 6507/11-3 (Saga Petroleum), coordinates 65°01'59.8"N, 07°30'42.34"E, from 2471.5 m to 2457 m (Fig 4.16) . The entire unit is cored, including the base.
Well reference section
Well 6407/1-3 (Statoil), coordinates 64°52'25.48"N, 07°02'53.47"E, from 3741 m to 3704 m (Fig 4.20) . One core, 10 m recovery, including the top.
Thickness
14.5 m in the type well and 37 m in the reference well.
Lithology
Claystones with micronodular pyrite coarsen upwards into bioturbated fine-grained sandstones which are locally mica-rich and carbonate cemented.
Basal Stratotype
The lower boundary is defined by an abrupt increase to a steady high gamma ray response. In the type well this occurs immediately above a thin matrix-supported conglomerate.
Age
Aalenian to Bajocian.
Depositional environment
The basal part of the formation reflects a semi-regional transgression which led to the development of lagoons or sheltered bays. The upper part of the unit consists of prograding deltaic or coastal front sediments.
Lateral extent and variation
The formation is recognized over the entire Haltenbanken area, if not eroded. The thickest development (<50 m) is seen on the southwestern part of the Halten Terrace and the unit generally thins eastwards on the Trøndelag Platform. On Trænabanken a time equivalent succession dominated by mudstone is assigned to the Viking Group .
Correlation
In the Hammerfest Basin the middle part of the Stø Formation is thought to correlate with the Not Formation. No similar unit is recognized in the North Sea.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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38
NYGRUNNEN GP
GROUP
Nygrunnen Group

Name
The group is named after a fishing bank to the NW of Sørøya, around 71°N and 21°E. The unit corresponds to T5 or the Kvaløy Group of earlier usage.
Type area
The most complete sequence seen in the Hammerfest Basin is in Block 7119/12. Blocks 7121/5 and 7120/12 show a thinner development more typical of central and southeastern basin areas.
Thickness
The group thins eastwards in the Hammerfest Basin from approximately 250 m in the type area to less than 50 m in easternmost wells and in locations near the southern margins of the basin. The only well drilled to date in the Tromsø Basin penetrated a 1200 m thick development assigned to the group, while wells on the Senja Ridge show a thin sequence, reflecting late Cretaceous structuring of the area.
Lithology
Greenish grey to grey claystones with thin limestone intervals in the Tromsø Basin and western parts of the Hammerfest Basin pass eastwards and southeastwards into more calcareous ( 7121/5-1 ) or sandy ( 7120/12-1 ) condensed sequences. The claystones are here assigned to the Kveite Formation , the condensed sequences to the Kviting Formation . Central wells on Tromsøflaket, e.g. in the 7120/9 area, show a transitional development with a lower Kviting limestone passing up into a Kveite shale. Further exploration may show the need for differentiation between sandy and calcareous units, but there is insufficient data at present.
Age
The group appears to represent remnants of a depositional sequence with an age span from late Cenomanian to Maastrichtian. The Tromsø Basin was a depositional centre throughout most of this period. Areas further east were either only transgressed at times of maximum sea level and/or display only condensed sections of the original sequence. The Campanian seems to be the most widespread age represented in wells.
Depositional environment
Open marine, deep shelf environments in the west passed into shallower starved shelf regimes (uplifted at times) in the east.
Correlation
This unit is not represented on Svalbard. The equivalent Shetland Group in mid-Norway shows a more complete development, reflecting continuous subsidence over large areas.
Subdivision
Two formations are recognized within the group, the Kviting and Kveite Formations.
Source
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
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122
OSEBERG FM
FORMATION
BRENT GP
Oseberg Formation

Name
Named after the Oseberg Field in Norwegian blocks 30/6 and 30/9. Oseberg is the name of a Viking ship, discovered in a large burial mound at the Oseberg farm near Tønsberg in Vestfold county, Norway.
Well type section
Norwegian well 30/6-7 from 2739 m to 2786 m, coord N 60°38 '39.49", E 02°45' 21.74".
Well reference section
None at present.
Thickness
47 m in the type well.
Lithology
The name Oseberg Formation should be used for the relatively homogeneous, predominantly coarse-grained sandstone unit, 20-60 m thick, that is well documented from the base of the Brent Group in the Oseberg Field and neighbouring fields. The sandstone unit now defined as the Oseberg Formation has long been considered anomalous in the sense that it does not fit well into the “normal” Brent Group succession as is seen, for example, in well 34/10-8 . The basal unit`s (now Oseberg Formation) anomalous coarseness an homogeneity, its common, sharply defined base and “blocky” log pattern, and the indications of a Late Toarcian/Aalenian age for its lowermost parts in some wells have always been awkward aspects of Brent Group lithostratigraphy where the sand unit was interpreted as Etive Formation or as a combined Rannoch / Etive Formation.
The Oseberg Formation has a typical “blocky” log motif (gamma-ray and neutron/density logs), reflecting the homogeneous nature of the sand units compared to the underlying and intercalating mudstones. Occasional upwards-coarsening motifs occur in structurally high locations.
Five types of lithofacies sequences are identified within the formation:
  • bioturbated, micaceous mudstones and siltstones containing wave-generated ripple lamination,
  • bioturbated, flat-lying to low-angle inclined (or undulating), medium- to coarse-grained sandstones, with little internal lamination,
  • inclined sets (10-30o, unidirectional dips), of medium- to coarse-grained sandstones with common “floating” granules and small pebbles, rare bioturbation,
  • units of coarse to very coarse and pebbly sandstone, with internal erosion surfaces and a diffuse flat or irregular lamination
  • massive or low-angle laminated, well-sorted sandstones, occasionally interbedded with poorly sorted sandstones or bioturbated, micaceous mudstones
Boundaries
The base of the formation is defined by the first appearance of sandstones or siltstones/mudstones above the shales of the Dunlin Group . The log response is characterised by lower gamma-ray readings when entering the overlying Oseberg Formation. The formation`s top, easily recognised throughout the region, is defined by the aprupt vertical change from the formation`s massive or wispy laminated sandstones to the micaceous mudstones and well-laminated sandstones of the Rannoch Formation and is characterized by higher radioactivity.
Distribution
The formation has been clearly recognized in the Oseberg Field area (main reservoir unit) and can also be recognised in the neighbouring fields to the north-east ( Veslefrikk ) and east ( Brage , Troll ).
Age
Late Toarcian – Early Bajocian.
Depositional environment
The lower part of the formation was deposited in a shallow marine environment, and gravitational processes are suggested. For the upper part of the Oseberg Formation sheetflooding and/or shallow-braided streams in an alluvial environment are suggested. The uppermost part of the formation is interpreted as a wave-reworked “transgressive” sand unit deposited during a relative rise of sea level. The sandstones form a number of fan-shaped sand-bodies that originated from the eastern highlands.
Compiled from
  • Graue, E., Helland-Hansen, W., Johnsen, J., Lømo, L., Nøttvedt, A., Rønning, K., Ryseth and A., Steel, R. Advance and retreat of Brent Delta system, Norwegian North Sea. 915 - 937 in: Brooks, J. and Glennie, K. (eds.) 1987: Petroleum Geology of North West Europe.
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16
POLARREV FM
FORMATION
BJARMELAND GP
Polarrev Formation

Name
From the Norwegian name for the Polar Fox (Alopex lagopus).
Definition
The type section is defined as the interval from 4282 m to 4046 m in well 7229/11-1 on the northern margin of the Finnmark Platform (Fig 9.39) ; Table 9.1). Eight cores with a total recovery of approximately 180 m, including the base, exist (Fig 9.40) . The base of the formation is defined by an abrupt and sharp decrease in gamma ray log response and an accompanying decrease in interval transit time and neutron porosity log response, giving only a slight separation between the neutron and bulk density logs (Fig 9.39) . The cored base in the type well shows a sharp transition from underlying laminated silty to very fine-grained sandy carbonates to the overlying carbonate buildups typical of the Polarrev Formation (Fig 9.40) .
Reference sections
Reference sections have been defined in the intervals from 4334 m to 4182 m in well 7226/11-1 (Fig 9.41) . and 4271 m to 4000 m in 7124/3-1 (Fig 9.42) , both located on the southern Bjarmeland Platform, and the interval from 3990 m to 3700 m in 7121/1-1 R (Fig 9.43) . on the eastern flanks of the Loppa High. No cores exist from the reference wells.
Thickness
The formation is very locally developed and is absent from most areas as it represents isolated carbonate buildups and carbonate buildup complexes. It attains a maximum thickness of 290 m in well 7121/1-1 R on the eastern flank of the Loppa High and thins eastward along the margin of the Bjarmeland Platform, ranging from 271 m in well 7124/3-1 to 152 m in 7226/11-1 (Fig 9.38) . The formation is 236 m thick in the type well on the northern Finnmark Platform.
Lithology
The formation consists of a variety of facies that characterise carbonate buildups. The bulk of the formation consists of bryozoan- and bryozoan/Tubiphytes-dominated wackestones and cementstones with abundant early marine cement (Fig 9.44) . Wackestones dominate the bioherm encountered in the type well, where a sparse assemblage of fenestrate bryozoans, brachiopods and crinoids formed a loose framework that trapped the carbonate mud. The wackestones also display Stromatactis-like cavities, which form a complex interconnected pore system. The cavities are often partly supported by fenestrate bryozoans and brachiopods, and are often filled by geopetal internal sediments with a grainstone or packstone fabric. The geopetal fabrics indicate that deposition occurred on primary slopes of up to 45o (Blendinger et al. 1997). The limestone is massive to thickly bedded, white to light grey, locally pinkish grey and light brownish grey in colour. In the lower part of the formation more thin bedded and silty limestones are locally present. The formation has a characteristic (very) low gamma ray response throughout, except for the thin units of silty limestones in the lower part (Fig 9.39) .
Lateral extent and variation
Seismic data indicate that carbonate buildups belonging to the Polarrev Formation rim the shelf along the Loppa High and around the margins of the Nordkapp Basin (Gerard & Buhrig 1990; Nilsen et al. 1993). The buildups also form linear trends across central parts of the Finnmark Platform and across northern areas of the Bjarmeland Platform. Isolated buildup complexes occur in the Norvarg Dome-Mercurius High area and on a structural high on the northeastern Finnmark Platform. The distribution of the laterally extensive buildup complexes seems to be controlled by underlying tectonic elements and they are preferably localised to areas that experienced relatively high rates of subsidence. Therefore the best-developed buildup trends often coincide with pinch-out of salt in the underlying Gipsdalen Group . Isolated buildups have been seen to occur in the proximal parts of the basins where they form isolated patch reefs, apparently located on local palaeotopographic highs. Well data suggest that all drilled buildups have a very uniform composition although the buildups vary significantly in thickness.
The base of the formation may represent a subaerial exposure surface on structural highs, while it is a correlative conformity on the outer part of the platforms and along the margins of the depositional basin.
Age
Fusulinids suggest a mid-Sakmarian age for the basal part of the formation in wells 7229/11-1 and 7121/1-1 R and a late Sakmarian age near the top of the formation in the same wells (Davydov 1998, Davydov 2000). Comparisons with overlying units suggest that the formational top is of ?earliest Artinskian age.
Depositional environments
The formation represents deposition in a variety of subenvironments within a bryozoan-dominated bioherm complex. The bulk of the bioherm is composed of repeated graded units of mud-dominated to cement-dominated bryozoan facies believed to represent individual banks. Deposition started in relatively deep water, well below storm wave base. The presence of reworked bioclastic grain-/packstone with fragmented and abraded bioclasts and reworked early marine cement indicates periods of reworking as the bioherm grew upwards into shallower water - possibly near storm wave base. The fine-grained bioclastic limestones in the lower part of the type section (between 4257.5 and 4264.5 m) and other units with higher gamma ray readings were deposited on the distal part of a carbonate ramp below normal wave base.
Correlation
The formation is not known from the onshore areas.
Source
  • Larssen, G. B., Elvebakk, G., Henriksen, L. B., Kristensen, S. E., Nilsson, I., Samuelsberg, T. J., Svånå, T. A., Stemmerik, L. and Worsley, D. 2002: Upper Palaeozoic lithostratigraphy of the Southern Norwegian Barents Sea. NPD-Bulletin No. 9, 69 pp.
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12
RAN SANDSTONE UNITS
FORMATION
CROMER KNOLL GP
Ran sandstone units

Name
Ran was the wife of the sea god Gir in Norse mythology. She liked to drag sailors down to the depths with her net.
Well reference sections
Norwegian well 2/7-15 from 3498 m to 3450 m, coordinates N 56°23'46.82", E 03°18'54.63" (Fig 5.22) . 16 m of cores in the lowermost part of the formation. Norwegian well 7/3-1 from 2412 m to 2396 m, coordinates N 57°50'35.25", E 02°44'55.61" (Fig 5.23) . No cores. Norwegian well 17/11-2 from 1802 m to 1767 m, coordinates N 58°06'54.91", E 03°22'09.81" (Fig 5.13) . No cores.
Thickness
The gross sandstone thicknesses vary from a few metres up to approximately 100 m. The gross thicknesses in the reference wells are 48 m ( 2/7-15 ), 16 m ( 7/3-1 ) and 35 m ( 17/11-2 ). Up to 130 m (gross) of Aptian-Albian sandstone sequences are penetrated in block 16/27 in the UK sector (see Distribution).
Lithology
The colour of the sandstones ranges from white to light grey, green and brown to reddish-brown. The sandstones are generally argillaceous, sometimes calcareous and glauconitic, and usually do not represent potential reservoir rocks in these wells.
Basal stratotype
The various sandstone units may appear in contact with the Åsgard , Tuxen , Sola and Rødby formations (Fig 5.4 , 5.7 , 5.8 , 5.9). Their lower boundaries are generally defined as the base of an upward decrease in the gamma-ray response when passing into the sandstone units (Fig 5.22 , 5.23) . The gamma-ray readings in the calcareous marlstones and chalks of the Tuxen Formation , especially its upper part, and the Mime Formation may be similar to those in the sandstones. The velocity curve is often less suitable for defining the lower boundary.
Characteristics of the upper boundary
The upper boundary can usually be identified as an upward increase in the gamma-ray readings (Fig 5.22) , and generally by a slight decrease in the sonic velocity.
Distribution
The Ran sandstone units are encountered in only a few wells in the Norwegian sector (Fig 5.21) , and Remarks).
Age
Ryazanian-Albian.
Depositional environment
The sandstones that have been penetrated are described as shallow (Norwegian sector) and deep water (UK sector) submarine fans.
Remarks
Hesjedal & Hamar (1983) recognised several scattered sandstone sequences which they described as the Kopervik and Klepp Formations in the Central Trough and Norwegian-Danish Basin, and the Florø Formation in the Agat Discovery in blocks 35/3 and 36/1. The Kopervik and Klepp Formations are here described as the Ran sandstone units. Since they consisted of several isolated sandstone bodies they should not have been given formation status, and the names did not conform with the existing recommendations. The Florø Formation is formally defined as the Agat Formation in this paper (see also General lithostratigraphic notes for Cretaceous).
In the UK sector (the Andrew Field), just south of the Andrew Ridge and Fladen Ground Spur, Aptian-Albian sandstone sequences (the Bosun Member) are encountered in many wells, among others UK wells 16/27-1 and 16/27a-2 (100-130 m gross), 16/28-1 (50 m gross) and 16/28-6 (90 m gross). The palaeogeographical position of these sandstones, i.e. basinal areas close to the subaerially exposed major structural highs mentioned above, may be quite similar to the palaeogeographical situation along the western margin of the Maløy Fault Blocks. Here, up to 400 m (gross) thick sandstone sequences of Aptian-Early Cenomanian age were deposited in Norwegian blocks 35/3 and 36/1, and are defined as the
Agat Formation in this paper.
The Devil's Hole Formation (UK well 29/25-1) and the "Unnamed Formation" (UK well 14/20-5) in the UK sector are comparable to the Ran sandstone units.
Source
  • Isaksen, D. and Tonstad, K. (eds.) 1989: A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 5, 59 pp.
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23
RANNOCH FM
FORMATION
BRENT GP
Rannoch Formation

Name
Named by Deegan and Scull (1977) who gave it "sub-unit" status.
Well type section
UK well 211/29-3 (Shell) from 2783 m to 2818m, coord N 61°08'06", E 01°43'36.5" (Fig 3.10) .
Well reference section
Norwegian well 33/9-1 (Mobil) from 2602 m to 2664 m, coord N 61°15'07.5", E 01°50'25.8" (Fig 3.11) .
Thickness
35 m in the type well and 62 m in 33/9-1 .
Lithology
In the type well the formation is a light brown, fine grained, well sorted, friable, very micaceous sandstone. In the Brent Field area the lower part is more argillaceous with siltstones and thin shales.
Towards the top the formation tends to be coarser grained and less micaceous, often resulting in a distinctive gamma ray pattern suggesting a "coarsening upward" sequence. Some workers consider that the Rannoch Formation is occasionally represented on the Horda Platform by one or more such coarsening upward cycles. However, in the majority of cases these cannot be observed and the presence of the Rannoch Formation must be considered debatable.
Boundaries
The high mica content of the sandstone produces an anomalously high gamma ray log response and generally distinguishes the Rannoch Formation from the overlying and underlying sandstones. Where the Broom Formation is missing the lower boundary is gradational into the dark, silty shales of the Dunlin Group . The upper boundary is normally defined by the "blocky" gamma ray log of the overlying Etive Formation .
Distribution
The distribution of the Rannoch Formation is essentially the same as that of the Brent Group , except on the Horda Platform where the presence of the formation is under debate.
Age
Late Toarcian to Bajocian.
Depositional environment
The formation is generally interpreted as delta front sheet sands and/or prograding shoreface sands.
Source
  • Vollset, J. and Doré, A. G. (eds.) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No. 3, 53 pp.
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16
RATTRAY FM
FORMATION
FLADEN GP
Rattray Formation

Name
From Rattray Head on the coast of Scotland adjacent to the volcanic province.
Well type section
UK well 21/10-1 (BP) (Fig 1.23-26) ure from 2680 m (8792 ft) to 3422.3 m (11228 ft) below KB.
Well reference section
None at present but Howitt and others (1975, (Fig 1.1-2) . illustrate the nature of the formation in wells adjacent to the type well.
Thickness
742.3 m (2436 ft) in the type well but the base of the formation was not reached.
Lithology
In the type section and adjacent wells (BP 21/9-1 and Shell/Esso 22/6-1), the formation consists of a thick series of basaltic lava flows (1 to 9 m thick where cored), with interbedded agglomerates, tuffs and tuffaceous sediments. The lavas are grey or purplish, vesicular and often partially altered, and locally completely laterised. Large fresh pyroxene phenocrysts and smaller altered olivine phenocrysts are set in a groundmass of pyroxene and feldspar. Autobrecciation, late hydrothermal activity and deep weathering and oxidation are fairly common. The epiclastics, ranging from agglomerate to tuffs, comprise lava and phenocryst clasts, or primary pumice and ? lapilli fragments. Only minor pyroclastics have been recognised. Interbedded sediments are present towards the base of the type section, consisting of dominantly red to brown mudstone, which is soft to firm and locally calcareous. Minor amounts of red-brown or grey-green siltstone and fine grained, friable, brown sandstone are present. Lateral lithological and petrographical variations have been described by Howitt and others (1975).
Boundaries
The base of the formation generally rests on pre-Jurassic rocks and is marked by the incoming of igneous rocks. The upper boundary of the formation is normally a distinctive contact with Late Jurassic or Cretaceous rocks and is marked by clear changes of log character (Fig 1.23-26) ure.
Distribution
The volcanic province extends from approximately 0° to 1°40’E and from 57°40’ to 58°45’ in the UK sector. Scattered occurrences of thin volcanic have been reported from the Norwegian sector but no details are available. The province appears to be controlled by faults at the junction of the Viking and Central grabens and the Moray Firth Basin. Both the amount of volcanic detritus and the percentage of lava decrease sharply along the south-eastern and western margins, with a more gradual change towards the north and east. The thickest sections of lavas and volcanic detritus pass into an outermost zone dominated by volcanic clastics with much interbedded non-volcanic sediment.
Age
Present evidence indicates a Middle Jurassic age (Bajocian–Bathonian). In the southern part of the volcanic province the interbedded red-beds are barren, but sparsely fossiliferous grey beds in the north near the base and top of the formation yield Bajocian–Bathonian dates, based on floral dating and rare ostracods. Radiometric dating of whole-rock samples which are sheared, altered and often with secondary mineralization has provided a range of minimum ages from 165+/- 4 Ma (million years) to 109+/- 2 Ma. No systematic change in age has been recognized and the volcanic are assumed to be essentially the product of one synchronous episode.
Source
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25; the Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
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RAUDE FM
FORMATION
STATFJORD GP
Raude Formation

Name
The formation is named after Eirik Raude (Raude=Red), the Viking discoverer of Greenland.
Well type section
Norwegian well 33/12-2 (Mobil) (Fig 1.17) . from 2790 m to 2951 m below KB.
Well reference section
UK well 211/24-1 (Conoco/Gulf/NCB) (Fig 1.17) .
Thickness
In the type well the formation is 161 m thick and in 211/24-1 it is 119 m.
Lithology
In the type well the basal part of the formation consists of a coarsening upward sequence of grey, green, and red-brown silty claystones, grey arkosic sandstones and white, pink and grey-brown dolomitic limestones. This basal part of the section is often difficult to recognise away from the type well and is locally absent. Above 2905 m in the type well the formation consists of approximately equal amounts of sandstone and silty shale. These sandstones are fine to medium grained and poor to moderately sorted with subangular grains. They are generally micaceous and have a kaolinitic matrix. The silty shales are grey and light green or occasionally red-brown in colour, and micromicaceous. Carbonaceous debris, sometimes in thin laminae, is present but distinct lignite beds are absent. Away from the type well the sandstone percentage in the upper part of the formation may vary from about 15 to about 75. In the area of the Brent and Statfjord fields the average sandstone bed thickness is about 2.5 m and shale beds average about 4 m in thickness. Correlation of individual beds from well to well is virtually impossible.
In well
33/12-5 the Raude Formation consists of alternating, 5 to 10 m-thick, red claystones and sandstones, except for the lowermost 25 m of claystone, while in well 30/6-5 a similar pattern as in the type well is observed.
Boundaries
The originally Raude Member of the Statfjord Formation was elevated to formation level by Lervik, 2006. The base of the formation is the base of the Statfjord Group . The change from the underlying more argillaceous sediments to the more sandy Statfjord Group via the transitional coarsening-upward units is clearly defined on the gamma ray and sonic logs. The top of the formation is the base of the first massive sandstone of the overlying more arenaceous formation. This boundary is normally clearly marked by a change from irregular to a blockier log response, particularly in the gamma ray log. Individual sandstone beds in the overlying Eiriksson Formation are more laterally extensive. The base of the lowermost sandstone can be well correlated which will generally indicate the top of the Raude Formation.
Distribution
The formation can generally be recognized wherever the Statfjord Group is well developed. The basal coarsening upward unit is thought to have a more limited distribution but this cannot be defined as many wells terminated in or just above this basal unit.
Age
Rhaetian. The top of the formation may approximate to the Rhaetian – Lower Jurassic boundary in the type well but is probably older to the west (Fig 1.18) .
Depositional environment
The Raude Formation was interpreted as a braided-stream, based on the lithological content and sedimentary structures in the upper part of the formation, particularly large cross-bedding, scour and fill, Deegan and Scull (1977), Røe and Steel (1985) interpreted the few component sandstones within Raude Formation as distal alluvial-fan stream deposits in a flood-basin environment. Mudstones of reddish-brown or mottled colours with palaeosols may represent a subaerial, well-drained floodplain environment (Nystuen and Fält, 1995). Carbonate nodules, root structures and dessication cracks are abundant in the palaeosols.
Compiled from
  • Deegan, C. E. and Scull, B. J. (compilers) 1977: A standard lithostratigraphic nomenclature for the Central and Northern North Sea. UK Institute of Geological Sciences, Report 77/25. The Norwegian Petroleum Directorate, NPD-Bulletin No. 1, 36 pp.
  • Goldsmith, P. J., Hudson, G. and Van Veen, P. Triassic. 105 – 127 in: Evans, D., Graham, C., Armour, A. and Bathurst, P. (editors and coordinators) 2003: The Millennium Atlas: petroleum geology of the central and northern North Sea. The Geological Society of London, 389 pp.
  • Lervik, K.-S. 2006: Triassic lithostratigraphy of the Northern North Sea Basin. Norwegian Journal of Geology, Vol. 86, pp. 93-116.
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REALGRUNNEN SUBGP
SUBGROUP
KAPP TOSCANA GP
Realgrunnen Subgroup
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RED BEDS (INFORMAL)
GROUP
Red beds (informal)

Sediments of Triassic age beneath the Åre Formation have been encountered in a number of wells offshore mid-Norway. Based on their colour the Triassic section in the Norwegian Sea has been informally divided into “Grey Beds” and “Red Beds”. The “Red Beds” sediments represent continental clastics of red colour deposited in a more arid climate compared to the “Grey Beds” sediments. Thicknesses of more than 2500 meters have been drilled. No type well section has been established.
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REKE MBR
MEMBER
FRUHOLMEN FM
Reke Member

Name
Norwegian for “prawn” or “shrimp”.
Well type section
Norwegian well 7121/5-1 coordinates 71° 35'54.88''N, 21° 24'21.78''E (Fig 4.46) .
Well reference section
Norwegian well 7120/12-1 coordinates 71°6'48.71"N, 20° 45'20.13"E (Fig 4.47) .
Thickness
The gross thickness of the member is 77 m in the type well, and 84 m in the reference well.
Lithology
Sandstone.
Lower boundary definition
The lower boundary is defined by the base of a carbonate horizon, where the separation between density and porosity logs decreases markedly. The Reke Member is characterised by a lower, more funnel-shaped gamma ray response than the underlying Akkar Member .
Age
Norian - ?Rhaetian (based on palynology).
Depositional environment
Coastal and fluvial.
Compiled from
  • Dalland, A., Worsley, D. and Ofstad, K. (eds.) 1988: A lithostratigraphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD-Bulletin No. 4, 65 pp.
  • Dallmann, W. K. (ed.) 1999: Lithostratigraphic lexicon of Svalbard. Review and recommendations for nomenclature use. Upper Palaeozoic to Quaternary Bedrock. Norwegian Polar Institute, 318 pp.
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ROGALAND GP
GROUP
Rogaland Group

Name
The Rogaland Group was named by Deegan & Scull (1977) after the county of Rogaland in southwest Norway.
Use of the group off mid-Norway corresponds to the informal Skomvær Group (H5).
Type area
The group is developed in the northern and central North Sea. In this paper the Rogaland Group comprises all the formations allotted to the Montrose and Rogaland Groups by Deegan & Scull (1977). The division into the Montrose Group and the Rogaland Group is not retained. It was based on differences in proximal and distal parts of the same sedimentary system, and therefore caused numerous practical problems.
The Rogaland Group in the Norwegian sector consists generally of proximal sediments in the west which interfinger with more distal equivalents in the east. The proximal part is illustrated in UK wells 10/1-1 A and 21/10-1 from the northern and central North Sea, respectively. The corresponding distal part of the sedimentary system is illustrated in Norwegian wells
31/2-6 and