The BGS Lexicon of Named Rock Units — Result Details

Annat Bay Formation

Computer Code: ATBA Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Dark grey (5Y 4/1)-dark greenish grey (GLEY 1 4/1), poorly sorted, homogeneous, soft, silty clay, with sporadic bivalve fragments, rare gastropod shells, and rare thin sand beds.
Definition of Lower Boundary: Unconformable boundary with Assynt Glacigenic Formation below.
Definition of Upper Boundary: Unconformable, commonly erosional, boundary with Summer Isles Formation above.
Thickness: Up to 25 m.
Geographical Limits: The present, glacially overdeepened, deep-water basins landward of the Summer Isles, i.e. Tanera, Coigach, North Annat, South Annat, Skerries and South Priest basins, as well as inner Little Loch Broom, but excluding Loch Broom and outer Little Loch Broom.
Parent Unit: Eilean Siar Glacigenic Group (EISR)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  57.9471 deg N, 05.2696 deg W. BGS vibrocore 57-06/277, which penetrated 4.24 m into the uppermost part of the formation in the North Annat Basin (0.4-4.64 m below sea bed). Stoker, M S and Bradwell, T. In press. Quaternary geology of the Summer Isles region - a brief explanation of the marine environment map. Sheet Explanation of the British Geological Survey. 1:50 000 Special Sheet Summer Isles (Scotland). 
Reference(s):
Stoker, M S and Bradwell, T. In press. Quaternary geology of the Summer Isles region - a brief explanation of the marine environment map. Sheet Explanation of the British Geological Survey. 1:50 000 Special Sheet Summer Isles (Scotland). 
Stoker, M S, Bradwell, T, Howe, J A, Wilkinson, I P & McIntyre, K. 2009. Lateglacial ice-cap dynamics in NW Scotland: evidence from the fjords of the Summer Isles region. Quaternary Science Reviews, 28, 3161-3184. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable