The BGS Lexicon of Named Rock Units — Result Details

Westbury Formation
Computer Code: WBY Preferred Map Code: Wby
Status Code: Full
Age range: Rhaetian Age (TR) — Rhaetian Age (TR)
Lithological Description: Dark grey mudstones or shales with subordinate thin limestones, sandstones and fossiferous arenaceous units ('bone beds').
Definition of Lower Boundary: Usually non-sequential with underlying Blue Anchor Formation, locally transitional.
Definition of Upper Boundary: Placed at locally transitional junction with overlying Cotham Member of the Lilstock Formation.
Thickness: 5-10m
Geographical Limits: Present throughout United Kingdom outcrop area.
Parent Unit: Penarth Group (PNG)
Previous Name(s): Westbury Beds (-601)
Contorta Shales (-1910)
Lower Rhaetic (-2374)
Black Shales (-4390)
Rhaetic, Lower [Obsolete Name And Code: Use WBY Or PNG] (LRRH)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Coastal section north of Lavernock Point, south Glamorgan. 
Type Area  Village of Westbury-on-Severn, Gloucestershire. 
Reference Section  Coastal section, St Mary's Well Bay, Penarth, 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 E072 E127 E202 E142 E141
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