The BGS Lexicon of Named Rock Units — Result Details

Forse Till Member

Computer Code: FOTI Preferred Map Code: FT
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Diamicton, sandy, silty and clayey, typically dark grey to olive grey and grey brown, often weathered and mottled in the upper parts to orange, brown and yellow, cobble and boulder sized-clasts include Devonian flagstones, Jurassic and Lower Cretaceaous mudstones, siltstones, sandstones and shell fragments together with Moine metamorphic and Caledonian igneous rocks.
Definition of Lower Boundary: Unconformable on bedrock.
Definition of Upper Boundary: The base of the Ellanmore Lower Gelifluctate Member (Hall and Whittington, 1989), which although distinctive, is considered too thin at less than 1m thick, to be formalised as a separate unit.
Thickness: To 25m
Geographical Limits: Caithness and Sutherland, northeast of a line between Reay and Berridale (1:50 000 sheets 115E and W, 116 E and W and sheet 110)
Parent Unit: Reisgill Burn Till Formation (REDR)
Previous Name(s): Shelly Till (-4049)
Caithness Shelly Drift (-4653)
Lybster Till (-4654)
Shelly Boulder Clay (-258)
Alternative Name(s): Forse Till Member Of The Lybster Formation
Stratotypes:
Type Section  Stream section at Forse, south of Lybster on the east coast of Caithness. Hall and Whittington, 1989, 315-316. 
Reference Section  The river cliff on the eastern bank of Forss Water (note this is the correct spelling), 300m southeast of the confluence with the Burn of Brimside, between Reay and Thurso on the north coast of Caithness. 
Reference(s):
Hall, A M and Whittington, G. 1989. Late Devensian glaciation of southern Caithness. Scottish Journal of Geology, Vol.25, 307-324. 
Crampton, C B and Carruthers, R G, 1914. The geology of Caithness. Memoir of the Geological Survey, Scotland. Sheets 110 and 116 (Scotland). 
Sissons, J B. 1967. The evolution of Scotland's Scenery. (London: Oliver and Boyd.) 
Omand, D. 1973. The glaciation of Caithness. Unpublished MSc Thesis, University of Strathclyde. 
Johnston, G S and Mykura, W. 1989. British regional geology: the Northern Highlands (4th edition) (London: HMSO for the British Geological Survey.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S116 S110 S115 S116 S115 S116