| Computer Code: |
BACT |
Preferred Map Code: |
Bac |
| Status Code: |
Full |
| Age range: |
Early Triassic Epoch (TE)
— Early Triassic Epoch (TE) |
| Lithological Description: |
Comprises a lower unit of red, red-brown and grey mudstones (Bunter Shale Formation), and an upper unit of red, orange and white dolomitic sandstones interbedded with red and grey mudstone (Bunter Sandstone Formation). |
| Definition of Lower Boundary: |
Slightly unconformable, at an abrupt upward transition from the evaporites or dolomitic limestones of the upper part of the underlying Zechstein Group to the red or red-brown mudstones of the lower part of the Bacton Group. |
| Definition of Upper Boundary: |
Slightly unconformable, at abrupt upward change from sandstone of the Bacton Group to red-brown dolomitic mudstone with evaporites of the overlying Haisborough Group. |
| Thickness: |
Up to 600 m (Johnson et al., 1994). |
| Geographical Limits: |
Offshore UK, southern North Sea. Equivalent to the combined Roxby Formation and Sherwood Sandstone Group of onshore nomenclature, northeast England (Johnson et al., 1994). |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Conoco Group Well 49/21-2, central part of the Southern North Sea Basin, at 53 degrees 19' 00" N, 02 degrees 05' 45" E, between 1375.5 m and 2011.0 m depth (Rhys, 1974; definition modified by Johnson et al., 1974). |
| Reference(s): |
| Johnson, H, Warrington, G and Stoker, S J. 1994. 6. Permian and Triassic of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. |
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. |
| Rhys, G H. 1974. A proposed standard lithostratigraphic nomenclature for the southern North Sea and an outline structural nomenclature for the whole of the (UK) North Sea. Report of the Institute of Geological Sciences, 74/8. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
