| Computer Code: |
AFTL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Devensian Stage (QD)
— Devensian Stage (QD) |
| Lithological Description: |
Stiff, calcareous, grey, silty clay with well dispersed small pebbles, shells, foraminiferids, ostracods and inclusions of diamicton, sand and gravel. The clay is generally massive although locally laminated with concentrations of dark minerals and/or organic material. The lenses of diamicton, sand and gravel are sparse and disrupted in deformation zones within a metre or so of the upper boundary.
The foraminiferal and dinoflagellate cyst associations present in the clay both indicate a cold but not fully glacial estuarine environment.Two samples of benthonic foramiferids from near the top of the sequence have yielded a Conventional Radiocarbon Age of 41002 +/- 803 years BP.The calculated Calendar age is 45,605+/-731 years BP (a minimum a Mid Devensian age).
The deposit is very likely to have been ice-rafted from an original position nearer to the coast to the west or from the Firth of Clyde. |
| Definition of Lower Boundary: |
Not observed, probably unconformable directly on bedrock, but possibly a gradational glacitectonic contact with underlying till. |
| Definition of Upper Boundary: |
Either a sharp, concavo-convex to planar boundary with overlying reddish brown sandy, silty, clay with scattered cobbles (Auchenwinsey Till Member of the Wilderness Till Formation), or a gradational, glacitectonic boundary involving intercalation and intermixing with the overlying till. |
| Thickness: |
>5m |
| Geographical Limits: |
South Ayrshire. |
| Parent Unit: |
British Coastal Deposits Group (COAS)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Partial Type Section |
Augerhole sunk into the bed of the Ladykirk Burn at the confluence with an un-named minor tributary joinng the main stream from the south 200m NNE of Afton Lodge, Ayrshire. Smith et al.in preparation |
| Partial Type Section |
Trial pit (no 2) excavated 200m SSE of Shawwood Farm, Ayrshire. Smith et al.in preparation |
| Reference(s): |
| Smith, R A.and others. In preparation. Glacial raft at Afton Lodge, Ayrshire, Scotland: evidence for onshore ice movement from the Firth of Clyde. |
| Gordon, J E.1993. Afton Lodge. 538-541 in Gordon, J E and Sutherland, D G.(editors) Quaternary of Scotland. The Geological Conservation Review Series 6, Joint Nature Conservation Committee. London: Chapman and Hall. |
| Smith, R A. 2002. A review of significant Quaternary Geology sites in the Western Midland Valley of Scotland: targets for the Quaternary methods and training programme. British Geological Survey Internal Report, IR/02/143. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
