The BGS Lexicon of Named Rock Units — Result Details

COALBROOKDALE FORMATION
Computer Code: CBRD  Status Code: FORMAL ENTRY 
Preferred Map Code: Cbrd 
Age or Age Range: [ SS ] SHEINWOODIAN  to [ SH ] HOMERIAN 
Lithological Description:
Compact, well-bedded, olive grey to dark blue-grey silty mudstones with some calcareous siltstones, nodular calcareous beds and bentonites. 
Definition of Lower Boundary:
Transitional through 3m to 9m with the underlying Buildwas Formation in type area; similar transition with the underlying Woolhope Limestone in the Woolhope-Malverns area; base placed immediately above the highest nodular horizon of the Buildwas Formation or Woolhope Limestone. 
Definition of Upper Boundary:
Transitional, but in practice placed at base of lowest, regularly bedded limestone of the Much Wenlock Limestone. 
Thickness:
192 - 265m in type area (excluding 10m of Farley Member). 
Geographical Limits:
Welsh Borderland and South Wales. 
Parent Unit: Parent Unit Code:
NO IMMEDIATE PARENT [HIERARCHY CODE: NO PARENT OF THE NEXT HIGHER RANK IS IDENTIFIED]  NOPAR
Previous Name(s): Previous Code(s):
WENLOCK SHALE  WEN 
Alternative Name(s):
none recorded or not applicable
Stratotypes:
Reference Section  BGS Lower Farm Borehole, from 1.83 to 194.4m depth. See Bassett, and others, (1975) and Bassett (1989) for other sections; original exposures described in Coalbrookdale railway cutting are inadequate. 
Type Section  Stream section running north west from near Rowley, 40m from its junction with Harley Brook. 
Reference(s):
Davidson, T and Maw, G, 1881. Notes on the physical character and thickness of the Upper Silurian rocks of Shropshire with the Brachiopoda they contain grouped in Geological Horizons. Geological Magazine, (2) Vol.8, p.104. 
Pocock, R W and others, 1938. The Shrewsbury District including the Hanwood Coalfield. Memoir of the Geological Survey of Great Britain, p.101, 113. 
Bassett, M G, Cocks, L R M, Holland, C H, Rickards, R B and Warren, P T. 1975. The type Wenlock Series. Institute of Geological Science, Report No.75/13, p.19. 
Bassett, M G, 1989. The Wenlock Series in the Wenlock area. 51-73 in "A global standard for the Silurian System". Holland, C H and Bassett, M G, (editors). National Museum of Wales, Gelogical series No.9, Cardiff. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  199
E  154
E  181
E  167
E  281

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