The BGS Lexicon of Named Rock Units — Result Details

Ness Formation

Computer Code: NESS Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Bajocian Age (JB) — Bajocian Age (JB)
Lithological Description: Interbedded sandstones, siltstones, mudstones and coals. Sandstones are variable, those interbedded with siltstones and mudstones are thinly bedded, parallel laminated, ripple laminated or hummocky cross-laminated, especially in the lower part of the formation. They may be bioturbated and often micaceous. Thin carbonaceous, flaser-bedded sandstones also occur. Thicker beds are up to 5 m thick, have a sharp base and may show upward fining; more or less micaceous and carbonaceous; and cross-bedded, ripple laminated or parallel laminated. Siltstones and mudstones are grey, often lenticular bedded and bioturbated. Plants are present in places, with coal seams developed, particularly in the lower part. An informal tripartite division has been recognised (e.g. Richards, 1992; Richards et al., 1993) with a 'lower interbedded unit', a middle 'mudstone unit' ('Mid Nes Shale') and an 'upper sandstone unit'. These were considered members by Cannon et al. (1992) named, respectively Enrick, Oich and Foyers members.
Definition of Lower Boundary: The Ness/Etive formational boundary is drawn at the base of the lowest significant mudstone or coal bed over most of the East Shetland Basin. It coincides with a significant down-section decrease in gamma values. In some areas, however, where the distinctive argillaceous interval is not present in the basal Ness Formation, the boundary is difficult to identify on wire-line logs.
Definition of Upper Boundary: The boundary over much of the East Shetlands Basin is marked by a sharp down-section change from micaceous and/or bioturbated sandstones (Tarbert Formation) to thinly bedded, heterolithic sediments. A sharp down-section change to more erratic gamma-ray values takes place at the boundary. In some areas, where Tarbert sandstones are thin, the Tarbert/Ness formational boundary is difficult to differentiate on wire-line logs. Similar difficulties exist in areas where both formations are sandstones or where minor coals and mudstones are interbedded with Tarbert sandstones. In many cored sections, the boundary can be recognised by a coarse-grained lag deposit. Locally the boundary is recognised by the downward change from siltstones and minor limestones (Heather Formation) to an interbedded sequence of sandstone, mudstone and coal; and a sharp down-section decrease in gamma values.
Thickness: Up to 180 m.
Geographical Limits: East Shetland Basin eastwards into the Viking Graben. North Sea quadrants 2, 3, 210, and 211.
Parent Unit: Brent Group (BRNT)
Previous Name(s): Middle Brent Sand Member (-5196)
Ness Sub-Unit (-5197)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea Well 211/29-3 between 2633.5 and 2772 m below KB (Deegan and Scull, 1977). 
Reference Section  North Sea Well 210/24-2 between 2147 and 2178 m (Richards et al., 1993). 
Reference Section  North Sea Well 211/16a-5 between 2775.5 and 2793.5 m (Richards et al., 1993). 
Reference Section  North Sea Well 211/27-10 between 3516 and 3583 m (Richards et al., 1993). 
Reference Section  North Sea Well 3/3-3 between 3124 and 3198 m below KB (Richards et al., 1993). 
Reference(s):
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. 
Bowen, J M. 1975. The Brent Oil-Field. In: Woodland, A W (ed.) Petroleum and the contineental shelf of North-West Europe, 353-361. [Heyden & Son, London] 
Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G (eds.). Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham] viii + 219 pp. 
Cannon, S J C, Miles, M R, Whitaker, M F, Please, P M and Martin, S V. 1992. A regional assessment of the Brent Group, UK Sector, North Sea. In: Morton, A C, Haszeldine, R S, Giles, M R and Brown, S (eds.) Geology of the Brent Group. Special Publication of the Geological Society, London, No.61, 81-107. 
Brown, S, Richards, P C and Thomson, A R. 1987. Patterns in the deposition of the Brent Group (Middle Jurassic) UK North Sea. In: Brooks, J and Glennie, K W (eds.) Petroleum Geology of North West Europe, 899-913. [Graham & Trotman, London] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable