| Computer Code: |
BOBA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Guadalupian Epoch (PUG)
— Lopingian Epoch (PUL) |
| Lithological Description: |
The Bosies Bank Formation is largely composed of white and reddish brown sandstone and siltstone, and reddish brown, red, and greenish grey mudstone. Minor intercalations of limestone, dolomitic limestone and anhydrite have been recorded near the basinward limit of the formation. |
| Definition of Lower Boundary: |
The base of the Bosies Bank Formation is in most areas defined by the top of the highly radioactive shales of the Kupferschiefer Formation. In parts of the Inner Moray Firth, Upper Permian clastic sediments overstep the Kupferschiefer to rest on cleaner Lower Permian desert sandstones of the Findhorn Formation; the boundary is marked by a relatively sharp downhole decrease in gamma-ray values and velocity (e.g. 12/21-2). |
| Definition of Upper Boundary: |
The Bosies Bank Formation is overlain by coarser and cleaner sandstones of the Hopeman Sandstone Formation in the western Inner Moray Firth, and by the sandy Lossiehead or Cormorant formations in most other areas. The boundary is marked by a sharp downward change to more variable wirelinelog responses, commonly with an increase in gamma-ray values and velocity. Elsewhere, the Bosies Bank Formation is overlain by Triassic silty mudstones of the Smith Bank Formation, or, in some areas of deep Mesozoic erosion, subcrops post-Triassic sediments. |
| Thickness: |
The formation is generally between 40 and 170 m thick. Its maximum thickness encountered to date is 270 m in well 20/9-1, close to a fault zone in the South Halibut Basin. |
| Geographical Limits: |
The Bosies Bank Formation is most widespread in the Inner Moray Firth, but it has also been proved on the eastern flanks of the East Shetland Platform and Fladen Ground Spur and, locally, elsewhere. It encroaches close to the south coast of the Moray Firth, but the consensus is that equivalent sediments do not crop out there (Andrews et al., 1990). |
| Parent Unit: |
Zechstein Group (ZG)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North Sea well 12/29- 2: 849.5-994.5 m (2787-3263 ft) below KB (Cameron, 1993). |
| Reference Section |
North Sea well 12/21- 2: 2802.5-2862 m (9194-9389 ft) (Cameron, 1993). |
| Reference Section |
North Sea well 12/27- 1: 1621.5-1699.5 m (5320-5576 ft) (Cameron, 1993). |
| Reference Section |
North Sea well 13/17- 1: 1919-2038 m (6295-6686 ft) (Cameron, 1993). |
| 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. |
| Andrews, I J, Long, D, Richards, P C, Thomson, A R, Brown, S, Chesher, J A, and McCormac, M. 1990. The geology of the Moray Firth. (London: British Geological Survey.) |
| 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.) |
| Cameron, T D J. 1993. 4. Triassic, Permian and pre-Permian 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
