The BGS Lexicon of Named Rock Units — Result Details

Sule Skerry Formation

Computer Code: SUSK Preferred Map Code: notEntered
Status Code: Full
Age range: Pliensbachian Age (JE) — Pliensbachian Age (JE)
Lithological Description: The Sule Skerry Formation is made up of dark grey to black, hard, brittle, subfissile, calcareous, carbonaceous, pyritic mudstones with very thin interbedded grey to brown, soft to hard, calcareous, micaceous, siltstones and brown to grey, hard to friable, fine-grained silty, carbonaceous limestones.
Definition of Lower Boundary: The base of the Sule Skerry Formation is represented by a downward change from mudstones, to sandstones, mudstones and siltstones of the Stack Skerry Formation. On wireline logs this transition is marked by a downward decrease in gamma-ray log response and an increase in velocity.
Definition of Upper Boundary: The top of the Sule Skerry Formation is marked by an unconformity, and a downward change from Rona Formation sandstones, to mudstones. This transition is represented on wireline logs by a downward increase in gamma-ray log values and a decrease in velocity.
Thickness: It attains a thickness of 257 m.
Geographical Limits: The Sule Skerry Formation has been encountered only in well 202/3a-3 within the North Rona Basin. Lower Jurassic argillaceous sediments have been penetrated in a number of British Geological Survey shallow boreholes to the south of this in the North Lewis Basin and North Minch Basin (Stoker et al., 1993). These strata may belong to the Sule Skerry Formation.
Parent Unit: Skerry Group (SKRY)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 202/03a- 3: 1784-2041m (5853-6696ft) (Ritchie et al., 1996). 
Reference(s):
Ritchie, J D, Gatliff, R W and Riding, J, 1996. 1. Pre - Tertiary lithostratigraphy. In: Stratigraphic Nomenclature of the UK North West Margin. British Geological Survey, Nottingham. 
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
Morton, N, Smith, R M, Golden, M, and James, A V. 1987. Comparative stratigraphic study of Triassic-Jurassic sedimentation and basin evolution in the northern North Sea and north-west of the British Isles. In: Brooks, J, and Glennie, K W (eds.) Petroleum geology of North-West Europe, (London: Graham and Trotman), 751-763. 
Stoker, M S, Hitchen, K, and Graham, C C. 1993. United Kingdom offshore regional report: the geology of the Hebrides and West Shetland shelves and adjacent deep-water areas. (London: HMSO for the British Geological Survey.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable