Nordland Group

The extensive exploration activities on the Norwegian Shelf the past 15 years have significantly increased our knowledge of the Cenozoic succession, and a revision of the existing formal lithostratigraphy is appropriate and needed. New and high-resolution stratigraphic data from exploration wells, seismic well ties, and new data from regional seismic 2D and 3D surveys assists the revision of the previous published Norwegian Cenozoic lithostratigraphies published by Deegan & Scull (1977), Dalland et al. (1988) and Isaksen & Tonstad (1989). Improved seismic-, well log- and biostratigraphy, including restudies of the Cenozoic formations type wells have led to a better understanding of the regional and temporal distribution of these units. An illustrative example concerns the Utsira and Skade formations of Isaksen & Tonstad (1989), which where thought to span the Middle-Late Miocene and Late Oligocene time intervals, respectively. New age-determinations have proved that the Utsira unit is of Late Miocene to Early Pliocene age, while the Skade unit has been reassigned from its previously Paleogene position, to belong in the Miocene. In addition, we now have a better understanding of the presence and extent of the ?mid-Miocene hiatus? between the Skade and Utsira units. The stratigraphic gap between the units increase rapidly northward from a minimal time gap in the south Viking Graben to 15-20 m.y. in the northernmost North Sea. The hiatus marks the boundary between the uppermost Hordaland Group (Oligocene and Lower Miocene) and the overlying lowermost Nordland Group (Middle Miocene to Lower Pliocene).

In addition to provide the new age information, we here further propose that both units are given Member status; the Utsira Member being assigned to the Kai Formation and the Skade Member to the Lark Formation. The Kai Formation has consequently been extended from the original type area in the Norwegian Sea to embrace the lithological similar Middle Miocene-Early Pliocene deposits of the Northern North Sea. This extension is a consequence of the obvious need for unifying the formal lithostratigraphy as the gaps between the established (and previously separated) are being filled. Originally Deegan & Scull (1977) subdivided the Middle Miocene to Recent strata of the central and northern North Sea into the Nordland Group. Subsequently, Dalland et al. (1988) defined the Nordland Group to also to cover the Miocene to Recent strata Off Mid-Norway and on the Barents shelf.

In the North Sea the Nordland Group incorporates the Utsira Member, and in the Norwegian Sea the group is subdivided into the Kai Formation, with the Molo Member, and the overlying Naust Formation.

No regional formational subdivision has been presented for the Nordland Group in the Barents Sea. Several Quaternary and Holocene units have been defined by Vorren et al. (1978), Hald and Vorren (1984). Informal lithostratigraphic units have been described in the Bjørnøya West area by Sættem et al. (1994).


English / Norwegian

Nordland Group / Nordlandgruppen

Derivatio nominis

Named by Deegan & Scull (1977) after Norwegian name Nordland, the land of the North.

Original definition

Deegan, C. E. & Scull, B. J. 1977. A standard lithologic nomenclature for the Central and Northern North Sea. Institute of Geological Sciences Report 77/25. NPD Bulletin no. 1, 33 pp.


In the North Sea area the Nordland Group is dominated by marine claystones. These are grey, sometimes greenish-grey and grey-brown, soft, and locally silty and micaceous (Deegan & Scull 1977) In the Viking Graben area the lower part of the Nordland Group comprise sandstones assigned to the Utsira Member. The upper part of the group consists of unconsolidated clays and sands, and contains occasional with larger ice-rafted detritus. The content with glacial deposits increase in the uppermost part of the group.

In the Norwegian Sea the group consists of alternating claystone, siltstone and sandstone of the Kai Formation (Worsley et al. 1988), and thick sandstones with pebbles comprising the Molo Member (Gustavson & Bugge 1995, Eidvin et al. in press).

In the Barents Sea the group consists of sands and clays which 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 green, soft to firm, blocky, noncalcareous, and in parts silty (Worsley et al. 1998).

The frequent ice-rafted material found in the Nordland Group consists of both sedimentary rocks typical for the Barents Shelf and crystalline rock fragments (Eidvin et al. 1993). A core from the Bjørnøya West area has recovered more than 150 m of Upper Pliocene gravity flow sandstone and siltstone with basaltic ash and lapilli (Mørk & Duncan 1993; Sættem et al. 1994).

The base of the group coincides with the Oligocene/Miocene unconformity. 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 (Worsley et al 1988).

The group is often drilled with return to seabed only (seabed 30" casing) (Worsley et al. 1988; Eidvin et al. 1993; Ryseth et al. 2003). 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 (Worsley et al. 1988).


The Nordland Group is 1514 m in the North Sea type well 2/2-1 and appears to exceed 1700 m in the Central Through. The group is approximately 1000 m thick in the Viking Graben area (Isaksen & Tonstad 1989).

In the Norwegian Sea well 6407/2-1 the Nordland Group is 1288 m (Worsley et al. 1988), and the group

In the Barents Sea the group thins from approximately 250 m in the 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 (Worsley et al. 1988), while seismic data suggest that the Upper Pliocene and younger deposits in the central part of the wedge exceed 3 km in thickness (Eidvin et al. 1994, Eidvin et al. 2000). Similar thicknesses are seen in the Sørvestsnaget Basin and in the Bjørnøya West area (Sættem et al. 1994; Ryseth et al. 2003).

Geographical distribution

The Nordland Group extends from the southern North Sea up to the western Barents Sea.

The Nordland Group is present throughout the Mid-Norwegian shelf, but the lower part is not present on the crest of the Nordland Ridge (Worsley et al. 1988). The sand content may vary locally, but there is no significant regional variation.

On the western Barents Shelf the Nordland Group is represented over the whole of Tromsøflaket (Worsley et al. 1988) and along the western margin of the Barents Shelf. The most continuous sequence is recovered over and to the west of the Senja Ridge (Eidvin et al. 1993), in the Sørvestsnaget Basin (Ryseth et al. 2003) and in the Bjørnøya West area (Sættem et al. 1994; Eidvin et al. 1998).

Type well

Well name



WGS84 coordinates: 57°47'15.69''N, 3°38'15.62''E
UTM coordinates: 6294075.10N, 538959.15E
UTM zone: 31

Drilling operator name

Saga Petroleum ASA

Completion date




Interval of type section (m)

In the type well the type section of the Nordland Group extends from 1600 m to 86 m (see Isaksen & Tonstad 1989, fig. 60).

Thickness in type well (m)

The type section occupies 1514 m in the type well 2/2-1.

Reference well (new)

Well name



WGS84 coordinates: 58°22'25.96"N, 02°02'02.97"E
UTM coordinates: xx
UTM zone: xx

Drilling operator name


Completion date

Interval of reference section (m)

In the reference well the Nordland Group extends from 1064 m to the sea bed.

Norwegian Sea reference section

Well 6407/1-2 , coordinates 64°47'50.61"N, 07°02'23.76"E, from 1690 m to the sea bed (Worsley et al. 1988).

Barents Sea reference section

Well 7119/12-1 , coordinates 71°06'08.00"N, 19°47'40.29"E, from 465 m to the sea bed (Worsley et al. 1988).


Lower boundary (basal stratotype)

The lower boundary of the group corresponds to the transition 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 where Lower to Middle Miocene strata are missing. In the type well 2/2-1 in the Central Trough, where the lower boundary is placed at the base of a claystone, this break is marked by an increase in gamma readings.

Upper boundary (characteristics)

The top of the group corresponds to the sea bed (Isaksen & Tonstad 1989).

Upper and lower boundaries in reference well sections

In the Central Trough the lower boundary of the Nordland Group is placed at the base of a claystone with high gamma readings. In the Viking Graben the lower boundary is normally at the base of the Utsira Member (see type well 16/1-1 ), and the lower boundary is marked by a decrease in gamma log readings from the claystones of the underlying Hordaland Group to the sandstones of the Utsira Member. 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 from brown to grey.

In the Norwegian Sea the lower boundary of the Nordland Group corresponds to the transition from brownish claystones of the Brygge Formation to grey claystones of the Kai Formation, or from the Brygge Formation to overlying sandstones of the Molo Member. Comparable to what is found in the North Sea area this boundary usually corresponds to a stratigraphic break, where Lower-Middle Miocene strata are missing.

In the Sørvestsnaget Basin in the Barents Sea the lower boundary of the Nordland Group corresponds to the transition between Upper Oligocene brown to grey mudstone of the Sotbakken Group and overlying Middle Miocene silty mudstone of the Nordland Group (Ryseth et al. 2003). Eastwards on the Barents shelf the Nordland Group rest directly on Middle Eocene claystones of the Torsk Formation.

"Reference" seismic sections

Seismic section in Fig. 69 of Tonstad & Isaksen 1989


Middle Miocene to Recent based on micropaleontology, palynology, and Sr and Ar isotope ages (Worsley et al. 1988; Eidvin et al. in press).

Depositional environment

The Nordland Group was deposited in an open marine environment, with glacio-marine deposits in the upper part.


Worsley at al. (1988) suggested a Late Pliocene to Pleistocene/Holocene age in the Hammerfest Basin, extending back to the mid-Oligocene along the western shelf margins. Revised ages from the Senja Ridge (Eidvin et al. 1993), the Bjørnøya West area (Mørk & Duncan 1993, Sættem et al. 1994; Eidvin et al. 1998), and from the Sørvestsnaget Basin (Ryseth et al. 2003) give a Miocene to Recent age for the entire group (i.e. an age corresponding to the age of the group in the northern North Sea and in the Norwegian Sea).


Deegan, C.E. and Scull, B.J. 1977. A standard lithostratigraphic nomenclature for the central and northern North Sea, in Institute of Geological Sciences Report, NPD Bulletin 1. 35pp.

Eidvin, T., Jansen, E., Rundberg, Y., Brekke, H. & Grogan, P. 2000. The upper Cainozoic of the Norwegian continental shelf correlated with the deep sea record of the Norwegian Sea and the North Atlantic. Marine and Petroleum Geology 17, 579-600.

Gustavson, M. & Bugge, T. (1995). Geologisk kart over Norge, berggrunnskart VEGA, M 1:250 000. Norges Geologiske Undersøkelse.

Hald, M. & Vorren, T.O. 1984. Modern and Holocene foraminifera and sediments on the continental shelf off Troms, North Norway. Boreas 13, 133-154.

Isaksen, D. and Tonstad, K. 1989. A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD Bulletin 5, 59 pp.

Mørk, M.B.E. & Duncan, R.A. 1993. Late Pliocene basaltic volcanism on the Western Barents Shelf margin: implications from petrology and Ar-Ar dating of volcaniclastic debris from a shallow drill core. Norsk GeologiskTisskrift 73, 209-225.

Ryseth, A., Augustson, J.H., Charnock, M., Haugerud, O., Knutsen, S.-M., Midb?e, P.S., Opsal, J.G. & Sundsbø, G. 2003. Cenozoic stratigraphy and evolution of the Sørvestsnaget Basin, southwestern Barents Sea. Norwegian Journal of Geology 83, 107- 130.

Sættem, J., Bugge, T., Fanavoll, S., Goll, R.M., Mørk, A., Mørk, M.B.E., Smelror, M. & Verdenius, J.G. 1994. Cenozoic margian development and erosion of the Barents Sea: Core evidence from southwest of Bjørnøya. Marine Geology 118, 257-281.

Vorren, T.O., Strass, I.F. & Lind-Hansen, O.W. 1978. Late Quaternary sdiments and stratigraphy on the continental shelf off Troms and West Finnmark, northern Norway. Quaternary Research 10, 340-365.

Worsley, D., Johansen, R. & Kristensen, S.E. 1988. The Mesozoic and Cenozoic succession of Tromsøyflaket. In Dalland, A., Worsley, K. & Ofstad, K. (eds.): A lithostratigaphic scheme for the Mesozoic and Cenozoic succession offshore mid- and northern Norway. NPD Bulletin No. 42-61.

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