The BGS Lexicon of Named Rock Units — Result Details

Eggardon Grit Member

Computer Code: ECG Preferred Map Code: notEntered
Status Code: Full
Age range: Albian Age (KA) — Albian Age (KA)
Lithological Description: The lower part of the member is a white or grey, soft, friable calcite-cemented sandstone, rich in shell fragments. The quartz grains are subangular to moderately well-rounded. The upper part of the member is less bioclastic and includes very coarse-grained sandstone formed of polished rounded quartz grains in a matrix of finer sand, with calcite cement. Scattered glauconite occurs in the upper part, but is usually insufficient to colour the rock. Locally, lumps of chert occur in the member (e.g. Thorncombe, Dorset). The top of the member is a phosphatised hardground (possibly equivalent to the Small Cove Hardground). Records of Cenomanian ammonites (Kennedy, 1970) might be from burrow infills at the base of the overlying Grey Chalk Subgroup.
Definition of Lower Boundary: The lower boundary is a sharp contact between cemented calcareous shelly sandstone of the member with the underlying glauconitic fine- to medium-grained sand of the Boyne Hollow Chert Member (Upper Greensand Formation).
Definition of Upper Boundary: The upper boundary occurs at the top of the phosphatised Small Cove Hardground at the junction with the overlying glauconitic, calcarenite of the Glauconitic Marl Member of the Grey Chalk Subgroup.
Thickness: Up to 3m.
Geographical Limits: In Dorset on the Bridport (327) Sheet.
Parent Unit: Upper Greensand Formation (UGS)
Previous Name(s): Calcareous Grit (-883)
Eggardon Grit (*880)
Alternative Name(s): none recorded or not applicable
Type Area  Eggardon Hill, Dorset Numerous exposures around the hill demonstrating parts of the succession. Wilson et al. (1958, 152-164) 
Wilson, V, Welch, F B A, Robbie, J A, and Green, G W. 1958. Geology of the country around Bridport and Yeovil. Memoir of the Geological Survey of Great Britain, Sheets 327 and 312 (England and Wales). 
Kennedy, W J. 1970. A correlation of the uppermost Albian and the Cenomanian of South-West England. Proceedings of the Geologists' Association, Vol.81, 613-677. 
Jukes-Browne, A J and Hill, W. 1900. The Cretaceous Rocks of Britain. 1. Gault and Upper Greensand. Memoir of the Geological Survey of Great Britain. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E327 E341 E342 E343