| Computer Code: |
STSK |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Sinemurian Age (JS)
— Pliensbachian Age (JE) |
| Lithological Description: |
The Stack Skerry Formation is made up of white to grey, firm to hard, very fine- to occasionally coarse-grained, well-sorted, subangular to subrounded, carbonate- and kaolinite-cemented, micromicaceous, slightly carbonaceous sandstones with interbedded grey, firm, blocky to subfissile, calcareous, micromicaceous, microcarbonaceous, slightly silty mudstones and grey to black, calcareous, micromicaceous, microcarbonaceous, slightly sandy siltstones. |
| Definition of Lower Boundary: |
The base of the Stack Skerry Formation is not defined as no wells have penetrated it. |
| Definition of Upper Boundary: |
The top of the Stack Skerry Formation is marked by a downward change from Sule Skerry Formation mudstones to an interbedded succession of sandstones, mudstones and siltstones. This transition is represented on wireline logs by a downward decrease in gamma-ray log values and an increase in velocity. |
| Thickness: |
It attains an unbottomed thickness of 513 m. |
| Geographical Limits: |
The Stack Skerry Formation has been encountered only in well 202/3a-3 within the North Rona Basin. Lower Jurassic arenaceous sediments have been penetrated in British Geological Survey shallow boreholes to the south of this in the North Minch Basin (Stoker et al., 1993). These sediments may belong to the Stack 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: 2041-2554 m TD (6696-8379 ft) (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 |
