The BGS Lexicon of Named Rock Units — Result Details

Loch Lurgainn Till Member

Computer Code: LLNN Preferred Map Code: TST
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Orange-brown, red-brown or dull brown poorly sorted, sandy, matrix-rich diamicton with boulders. Clay content is usually very low. The till shows evidence of subglacial deposition; namely edge-rounded, striated, clasts and high consolidation. Clasts are predominantly Torridon Group sandstone, but may also include Lewisian gneiss. Eriboll Formation sandstone (quartzite), Moine Supergroup rocks and/or various igneous rocks to greater or lesser degrees. However, in certain areas the till is autochthonous and is comprised entirely of Torridon Group sandstone that has undergone little transportation. The till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Definition of Lower Boundary: Unconformable on bedrock, predominantly Torridon Group sandstone.
Definition of Upper Boundary: Overlain locally by Holocene (Flandrian) deposits, typically peat or (glacio)fluvial gravel.
Thickness: Variable; 0.5 to 6m (maximum observed thickness); possibly up to 10m.
Geographical Limits: Patchy, discontinuous extent across Coigach, Stoer headland, Handa Island and between Kinlochbervie and Cape Wrath, northwest Sutherland. Occurs predominantly on Torridon Group sandstone.
Parent Unit: Assynt Till Formation (ASTI)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Road cutting on Achiltibuie road, 100m north of Loch Lurgainn, Coigach, Wester Ross. Bradwell, T. 2003. BGS Internal Report IR/03/120. 
Reference(s):
Bradwell, T. 2003. The Quaternary deposits and glacial history of the area around Inchnadamph, Sutherland. BGS Internal Report IR/03/120. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable