| Computer Code: |
SHHI |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Early Triassic Epoch (TE)
— Early Triassic Epoch (TE) |
| Lithological Description: |
The Shoal High Formation comprises a succession of sandstones, siltstones and mudstones. The sandstones are brown to red, fine grained to very fine grained, subangular to subrounded, moderately to well sorted, sometimes micaceous, slightly calcareous, argillaceous and arkosic. The mudstones are red to light brown or brown to grey or green, variably calcareous and micaceous, and occasionally silty or dolomitic, whereas the siltstones are red to brown or dark brown, very micaceous and slightly calcareous. Overall, the succession shows evidence of varying degrees of cementation, with a noticeable decrease downwards from about 1457 m. |
| Definition of Lower Boundary: |
The base of the Shoal High Formation is marked by a downward change from interbedded mudstones, sandstones and siltstones to interbedded sandstones, mudstones, anhydrites and halites of the West Orkney Evaporite Formation. On wireline logs, this transition is represented by a downward decrease in gamma-ray log values and a marked increase in velocity. |
| Definition of Upper Boundary: |
The top of the Shoal High Formation is represented by a downward transition from Foula Formation sandstones, to sandstones and mudstones. On wireline logs, this change is marked by a downward increase in gamma-ray log values and a slight increase in velocity. |
| Thickness: |
It attains a thickness of 598 m. |
| Geographical Limits: |
The Shoal High Formation only occurs in well 202/19-1 within the West Orkney Basin. |
| Parent Unit: |
Papa Group (PAPA)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 202/19- 1: 1159-1757 m (3802-5764 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.) |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
