| Computer Code: |
UPTI |
Preferred Map Code: |
LGT |
| Status Code: |
Full |
| Age range: |
Devensian Stage (QD)
— Devensian Stage (QD) |
| Lithological Description: |
[Obsolete: use ASGL]
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: |
none recorded or not applicable
|
| 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): |
| McMillan, A A, Hamblin, R J O, and Merritt, J W. 2011. A lithostratigraphical framework for onshore Quaternary and Neogene (Tertiary) superficial deposits of Great Britain and the Isle of Man. British Geological Survey Research Report, RR/10/03. 343pp. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
