The BGS Lexicon of Named Rock Units — Result Details

Gartocharn Till Formation

Computer Code: GATI Preferred Map Code: GATI
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Consists of massive silty clay with isolated pebbles, gravel and boulders, and knots of sand. It is brown or dark brownish grey with many dark sulphide patches and marine shells. It is of stiff to hard consistenct and medium to high plasticity. It contains joints and low angle thrust surfaces, some of which are polished, striated and grooved. Locally rafts and more diffuse patches of bedded clay are present.
Definition of Lower Boundary: Unconformity or glacial deformation boundary on older Quaternary strata such as the Linwood Clay Member and the Wilderness Till Formation; also on bedrock. Complex relationships laterally with fluvioglacial and deltaic/lacustrine sediments (Drumbeg Sand and Gravel Formation and Blane Water Clay Formation) forming part of the Loch Lomond Stadial Terminal Moraine Complex in the Leven and Endrick valleys in the Loch Lomond Basin.
Definition of Upper Boundary: Unconformity below younger Quaternary strata or glacial deformation boundary. Where data are available the Gartocharn Till Formation is overlain by the Drumbeg Sand and Gravel Formation and by the Buchanan Clay Member of the Clydebank Clay Formation in the Loch Lomond area.
Thickness: Veneer to over 6m
Geographical Limits: West central Scotland, related to ice streams sourced in the Highlands during the Loch Lomond Stadial; Loch Lomond area including the Leven and Endrick valleys, sea lochs in the northern Firth of Clyde and the Stirling area to the northwest of Callander.
Parent Unit: Midland Valley Glacigenic Subgroup (MVG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Loch Lomond Basin within the limits of Loch Lomond Stadial ice sheet. 
Reference(s):
Browne, M A E, McMillan, A A and Hall, I H S. 1983. Blocks of marine clay in till near Helensburgh, Strathclyde. Scottish Journal of Geology, Vol.19, 321-325. 
Rose, J. 1981. Field Guide to the Quaternary of the southeastern part of the Loch Lomond Basin. Proceedings of the Geological Society of Glasgow, Sessions 122/123, 12-28. 
Browne, M A E and McMillan, A A. 1989b. Geology for land use planning: drift deposits of the Clyde valley Volume 1: Planning Report. British Geological Survey Technical Report, WA/89/78. 
Hall, I H S, Browne, M A E and Forsyth, I H. 1998. Geology of the Glasgow district. Memoir of the British Geological Survey, Sheet 30E (Scotland). 
Rose, J, 1989. Stadial type sections in the British Quaternary, 45-67 in Quaternary Type Sections: Imagination or Reality ? Rose, J and Schluchter (Editors). Balkema, Rotterdam. 
Browne, M A E and McMillan, A A. 1989a. Quaternary geology of the Clyde valley. British Geological Survey Research Report, SA/89/1. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable