The BGS Lexicon of Named Rock Units — Result Details

Unapool Till Member

Computer Code: UPTI Preferred Map Code: LGT
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Grey-brown to dark grey, very poorly sorted, sandy, clast-rich diamicton with boulders. The till has a silty sand matrix with a low clay content. The till shows some evidence of subglacial deposition; with edge rounding and lodged clasts. Clasts are predominantly of Lewisian gneiss, but may also include sporadic Torridon Group sandstone, Eriboll Formation sandstone (quartzite) and Moine Supergroup clasts. The till is typically autochthonous, being derived from the local gneissose bedrock. However, the till may also contain reworked glaciofluvial and/or morainic deposits of Devensian age or older. Local lithological variations within the Lewisian complex are reflected by till clast lithogies (eg. Laxford granite sheets; Scourie dykes; ultramafic zones, etc.).
Definition of Lower Boundary: Unconformable on bedrock, predominantly Lewisian gneiss.
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).
Geographical Limits: Patchy, discontinuous extent across much of western Assynt and northwest Sutherland; almost exclusively occurs on Lewisian gneiss bedrock.
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 roadside cutting (A984), 0.4km north of Unapool House, Loch Glencoul, 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