The BGS Lexicon of Named Rock Units — Result Details

Bacton Group

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 600m (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 1375.5m and 2011.0m depth. Rhys, 1974. Definition modified by Johnson et al., 1974. 
Reference(s):
Johnson, H, Warrington, G and Stoker, S J. 1994. Permian and Triassic of the Southern North Sea. In Knox, R W O'B and Cordey, W G (editors), Lithostratigraphic nomenclature of the UK North Sea. [Nottingham: British Geological Survey.] 
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