The BGS Lexicon of Named Rock Units — Result Details

Western Isles Glacigenic Subgroup

Computer Code: WISG Preferred Map Code: WIG
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: A suite of glacial, glaciofluvial and glaciolacustrine deposits that contain clasts derived predominantly from Lewisian rocks of the Western Isles, including sandy diamictons (till), sand, gravel, silt and clay. Deposited by ice that mainly radiated outwards from an ice divide positioned along the western seaboard of the Western Isles archipelago.
Definition of Lower Boundary: Sharp, unconformable contact with bedrock or planar unconformity with units of the Western Isles (Albion) Glacigenic Subgroup.
Definition of Upper Boundary: Ground surface or unconformable contact with various Flandrian deposits, predominantly peat.
Thickness: To 20m
Geographical Limits: The Western Isles archipelago.
Parent Unit: Caledonia Glacigenic Group (CALI)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  The Western Isles archipelago. Bowen 1999. See also the stratotypes of constituent informal formations documented in Bowen (1999). 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
McMillan, A A, Hamblin, R J O and Merritt, J W. 2005. An overview of the lithostratigraphical framework for the Quarternary and Neogene deposits of Great Britain (onshore). British Geological Survey Research Report RR/04/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable