The BGS Lexicon of Named Rock Units — Result Details

Cotham Member

Computer Code: CTM Preferred Map Code: Ctm
Status Code: Full
Age range: Rhaetian Age (TR) — Rhaetian Age (TR)
Lithological Description: Grey and grey-green calcareous mudstones and shales and laminated and lenticular calcareous siltstones with beds of coarse-grained oolitic sandstone.
Definition of Lower Boundary: Placed at sharp, commonly channelled base, resting on underlying Westbury Formation.
Definition of Upper Boundary: Placed at base of porcellanous limestones of overlying Langport Member.
Thickness: 1-2m
Geographical Limits: Present throughout England.
Parent Unit: Lilstock Formation (LTK)
Previous Name(s): Cotham Beds (-2131)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Lilstock, west Somerset. 
Type Area  West Somerset and South Glamorgan. 
Reference Section  Immediately north of Lavernock Point, South Glamorgan. 
Reference(s):
Warrington, G, Audley-Charles, M G, Elliott, R E, Evans, W B, Ivimey-Cook, H C, Kent, P E, Robinson, P L, Shotton, F W and Taylor, F M. 1980. A correlation of the Triassic rocks in the British Isles. Special Report of the Geological Society of London, No.13. 
Waters, R A and Lawrence, D J D. 1987. Geology of the South Wales Coalfield - Part III: the country around Cardiff. Memoir of the British Geological Survey, Sheet 263. (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E183 E199 E127 E202 E142 E141 E279