The BGS Lexicon of Named Rock Units — Result Details

Coombe deposits

Computer Code: COD Preferred Map Code: notEntered
Status Code: Full
Age range: Quaternary Period (Q) — Quaternary Period (Q)
Lithological Description: Superficial deposit of chalk dry valleys, composed of fine-grained weathered chalky silt and clay matrix with clasts of chalk and flint and some erratic pebbles. Coombe deposits are solifluction and gelifluction deposits (head) found in some valleys on chalk and other limestone bedrock (called coombe rock, where cemented).
Definition of Lower Boundary: Variable lithology. Scree and solifluction deposits in some chalk valleys ('Coombe Rock' where cemented). [Generic description: 'TMOS' Procedures].
Definition of Upper Boundary: Upper surface, or may be overlain by more-recent superficial deposits.
Thickness: Typically 1 to 2 m.
Geographical Limits: The Chalk outcrop of England from Flamborough Head (Yorkshire) to East Anglia, Chilterns and Dorset, and across to the North and South Downs. Not everywhere mapped where present.
Parent Unit: Head (HEAD)
Previous Name(s): Combe deposits [Obsolete Name and Code: Use COD] (-4561)
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Hopson, P M, Aldiss, D T and Smith, A. 1996. The geology of the country around Hitchin. Memoir of the British Geological Survey, Sheet 221 (England and Wales). 
Shepard-Thorn, E R, Moorlock, B S P, Cox, B M, Allsop, J M and Wood, C J. 1994. Geology of the country around Leighton Buzzard. Memoir of the British Geological Survey, Sheet 220 (England and Wales). 
McMillan, A A and Powell, J H. 1999. The classification of artificial (man made) ground and natural superficial deposits. British Geological Survey Research Report, RR/99/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E220 E221