The BGS Lexicon of Named Rock Units — Result Details

Coombe Deposits [Obsolete Name: Use HEAD]

Computer Code: COD Preferred Map Code: notEntered
Status Code: Index Level
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.
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 2m
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: Not Entered (?)
Previous Name(s): COMBE DEPOSITS
Alternative Name(s): HEAD
none recorded or not applicable
Shephard-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). 
Hopson, P M, Aldiss, D T and Smith, A, 1996. Geology of the country around Hitchin. Memoir of the British Geological Survey, Sheet 221 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E220 E221