The BGS Lexicon of Named Rock Units — Result Details

Great Arc Sandstone

Computer Code: GAS Preferred Map Code: notEntered
Status Code: Full
Age range: Langsettian Substage (CA) — Langsettian Substage (CA)
Lithological Description: Sandstone, buff-grey, fine-to medium-grained, micaceous, thickly-to thinly-bedded, cross-bedded and ripple-laminated.
Definition of Lower Boundary: The lower boundary is taken at the base of the first sandstone of a sandstone-dominated unit above the Lower Mountain Coal.
Definition of Upper Boundary: The upper boundary is taken at the base of a mudstone-dominated succession overlying the sandstone of the Great Arc Sandstone; often coincident with the base of the seatearth underlying the Upper Foot Coal.
Thickness: 20 m maximum thickness.
Geographical Limits: Wigan (SD 5805), Manchester (SJ 8398) and Rochdale (SD 8913) areas.
Parent Unit: Pennine Lower Coal Measures Formation (PLCM)
Previous Name(s): Bullion Mine Rock [Obsolete Name And Code: Use GAS] (BR)
Alternative Name(s): none recorded or not applicable
Type Section  Stream section east of Clough Bottom Reservoir, in Warmden Clough (no further details available). Wright et al. 1927. 
Reference Section  Laund Clough, waterfall section, which exposes the base of the unit. (no further details available). Wright et al. 1927. 
Wright, W B, Sherlock, R L, Wray, D A, Lloyd, W and Tonks, L H, 1927. The Geology of the Rossendale Anticline. Memoir of the Geological Survey, England. England and Wales Sheet 76. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E084 E085 E076