The BGS Lexicon of Named Rock Units — Result Details

Hotwells Limestone Formation [Obsolete Name And Code: Use OHL]

Computer Code: HL Preferred Map Code: notEntered
Status Code: Index Level
Age range: Asbian Substage (CR) — Brigantian Substage (CX)
Lithological Description: Hard dark grey crinoidal oolitic bioclastic limestone with interbedded dark grey shales and mudstones.
Definition of Lower Boundary: Boundary is marked by the incoming of more massive oolitic and crinoidal rocks above the relatively unfossiliferous calcite-mudstones of the Clifton Down Group or, where present, the Middle Cromhall Sandstone.
Definition of Upper Boundary: Change to predominantly arenaceous sandstone facies of the Upper Cromhall Sandstone or at the Sub-Namurian unconformity.
Thickness: 54m
Geographical Limits: Bristol and north Somerset area. Lateral facies change to west South Wales and Forest of Dean.
Parent Unit: Hotwells Group [Obsolete Name And Code: Within PEMB] (HOG)
Previous Name(s): Vaughans D1 Zone (-4708)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Avon Gorge, Bristol, between the Suspension Bridge and Hotwells. 
Reference(s):
Green, G W and Welch F B A, 1965. The geology of the country around Wells and Chedder. Memoir of the Geological Survey of England and Wales, Sheet 280. 
Kellaway, G A and Welch, F B A, 1993. Geology of the Bristol district. Memoir of the British Geological Survey Special Sheet [England and Wales]. 
Kellaway, G A and Welch, F B A, 1955. The Upper Old Red Sandstone and Lower Carboniferous rocks of the Bristol and the Mendips compared with those of Chepstow and the Forest of Dean. Bulletin of the Geological Survey of Great Britain, No.9, p.1-21. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E264 E265 E279 E280 E281 E250 E251