The BGS Lexicon of Named Rock Units — Result Details

Grimley Andesite

Computer Code: GYA Preferred Map Code: GyA
Status Code: Full
Age range: Ediacaran Period (AD) — Ediacaran Period (AD)
Lithological Description: Grey to green, massive to autobrecciated, sparsely porphyritic high-silica andesite or dacite. Locally grades to monomictic (andesite-clast) block-breccia in Bardon Quarry.
Definition of Lower Boundary: All boundaries seen are faulted, except where one small sheet is chilled against the Peldar Dacite Breccia in Whitwick Quarry.
Definition of Upper Boundary: All boundaries seen are faulted, except where one small sheet is chilled against the Peldar Dacite Breccia in Whitwick Quarry.
Thickness: 0-500m
Geographical Limits: Extends from Whitwick Quarry northwards into Whitwick and Thringstone villages, and eastwards to Hob's Hole. To the south, it is last seen in Bardon Quarry.
Parent Unit: Whitwick Volcanic Complex (WVO)
Previous Name(s): Bardon 'Good Rock' (-2225)
Grimley-Type Porphyroid (-1580)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Bardon Quarry. 
Type Section  Crags to east of Cademan Street, Whitwick. 
Reference Section  Grimley Rock to Whitwick Quarry. 
Reference(s):
Carney, J N, 1994. Geology of the Thringstone, Shepshed and Loughborough districts (SK41NW, SK41NE and SK51NW). British Geological Survey Technical Report WA/94/08. 
Watts, W W, 1947. Geology of the ancient rocks of Charnwood Forest, Leicestershire. Leicester: Leicester Literary and Philosophical Society. 
Moseley, J and Ford, T D, 1985. A stratigraphic revision of the Late Precambrian rocks of Charnwood Forest, Leicestershire. Mercian Geologist, Vol.10(I), 1-18. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E141