The BGS Lexicon of Named Rock Units — Result Details

Nordland Group

Computer Code: NORD Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Miocene Epoch (NM) — Miocene Epoch (NM)
Lithological Description: The Nordland Group is dominated by grey to brown-grey, locally green-grey, poorly bedded, soft, silty mudstones and siltstones. Sandstones are mostly limited to marginal areas in the Miocene and Pliocene sections, but they occur more extensively in Pleistocene and Recent successions, with glacial deposits also occurring in the former. The upper boundary of the group is the sea bed. In mudstone and siltstone dominated sections, the lower boundary is marked by a sharp downward decrease in gamma-ray values and often corresponds to the base of a broad high-gamma peak. The high-gamma values reflect the presence of glauconite, which is abundant in the sandy siltstones of marginal areas. The base of the Nordland Group was similarly defined by Isaksen & Tonstad (1989), although Bjørslev-Nielsen et al. (1986) had proposed that it should be drawn at a lower level, corresponding to the base of the Miocene. Much of the Nordland Group is characterized on seismic profiles by large-scale, westerly dipping clinoforms. The base of the group is regarded as unconformable (Deegan & Scull 1977). A basal sandstone unit, the Utsira Formation, was recognized by Deegan & Scull (1977) and Isaksen & Tonstad (1989) in Northern North Sea sections. The sandstones were described as fine to coarse grained and glauconitic, with common bioclastic debris. They are thus very similar to sandstones included here in the Skade Formation (Westray Group), and it is not clear whether they constitute a separate stratigraphic unit.
Definition of Lower Boundary: The base of the group is regarded as unconformable (Deegan & Scull 1977). The base of the Nordland Group is marked by a downward change from dominantly grey and silty mudstones to brownish mudstones of the underlying Westray Group.
Definition of Upper Boundary: The Nordland Group was established by Deegan & Scull (1977) for the entire succession lying between the top of the Hordaland Group (equivalent to the top of the Westray Group of Knox & Holloway 1992) and the present-day sea bed.
Thickness: 1500 m+
Geographical Limits: The Nordland Group extends throughout the North Sea Basin. Knox et al. (1997) noted that the Nordland Group sediments extend onto the Shetland Platform and are in direct continuity with sediments of equivalent age in the West of Shetland area. Consequently they extended the geographical range of the Nordland Group to include the west of Shetland area. Lott and Knox (1994) extended the geographical range of the Nordland Group to the UK Southern North Sea. Stoker (1999) divided the Nordland Group on the West Shetland margin into three informal units: upper, middle and lower Nordland units. Recent, unpublished work in the Rockall-Hebrides region (Stoker et al. 2007) has proposed that the status of the Neogene-Quaternary succession along the Atlantic margin be revised, with the development of a new lithostratigraphic scheme for the Upper Cenozoic succession to replace the somewhat generalised UKOOA framework. Stoker et al. (2007) proposed a new group nomenclature for the Cenozoic of the Rockall-Hebrides region. Stoker et al. (in prep.) propose a rationalisation of Quaternary stratigraphy of the UKCS with the delineation and definition of a series of groups.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Isaksen, D and Tonstad, K. 1989. A revised Cretaceous and Tertiary lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No.5 
Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. 
Stoker, M S, McInroy, D and Hitchen, K. 2007. A preliminary lithostratigraphic scheme for the Cenozoic of the Rockall-Hebrides region. British Geological Survey Commissioned Report, CR/07/019, 23pp. 
Knox, R W O'B, Holloway, S, Kirby, G A and Baily, H E. 1997. Stratigraphic nomenclature of the UK North West Margin. 2. Early Paleogene lithostratigraphy and sequence stratigraphy. British Geological Survey, Nottingham. 
Stoker, M S. 1999. Stratigraphic nomenclature of the UK North West Margin. 3. Mid- to Late Cenozoic Stratigraphy. BGS, Nottingham. 
Stoker, M S, Balson, P S, Long, D, and Tappin, D R. 2011. An overview of the lithostratigraphical framework for the Quaternary deposits on the United Kingdom continental shelf. British Geological Survey Research Report, RR/11/03. 48pp. 
Bjorslev-Nielsen, O, Sorensen, S, Thiede, J, and Skarbo, O. 1986. Cenozoic differential subsidence of the North Sea. American Association of Petroleum Geologists Bulletin 70, 276-298. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable