The BGS Lexicon of Named Rock Units — Result Details

Traligill Till Member

Computer Code: TRTI Preferred Map Code: TRT
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Orange-brown to dull grey, poorly sorted, sandy, clay-rich, matrix-supported diamicton with boulders. The till shows some evidence of subglacial deposition; namely edge-rounded, striated clasts and high consolidation. Clasts are lithologically diverse; but typically include Eriboll Formation sandstone (Cambrian quartzite), An-t Sron Formation sandstone and mudstone, Moine Supergroup rocks and/or various minor igneous rocks to greater or lesser degrees. Clasts of Durness Group limestone are rare but may exist near the till-bedrock boundary. Much of the clay-rich matrix is probably derived from local muddy dolostones and mudstones. Sporadic clasts of Torridon Group sandstone and Lewisian gneiss may also be present, particularly in the River Traligill catchment. The till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older.
Definition of Lower Boundary: Unconformable on bedrock, predominantly on Durness Group limestone and An-t Sron Formation, sandstone and mudstones.
Definition of Upper Boundary: Overlain locally by Holocene (Flandrian) deposits, typically peat or (glacio)fluvial gravel.
Thickness: Variable; 0.2 to 8m. (maximum observed thickness).
Geographical Limits: Patchy, discontinuous extent across the outcrop of the Moine Thrust Belt, between Ullapool and Eriboll. Occurs exclusively to the west of the Moine Thrust (except on north edge of Cromalt Hills [NC 20], and predominantly on Durness Group limestone.
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  Large cutting on track to Glen Bain cottage, 500m east of Inchnadamph Lodge, Traligill Valley, Assynt, Sutherland. 
Reference(s):
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable