The BGS Lexicon of Named Rock Units — Result Details

Forth Clay Formation

Computer Code: FOCL Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Holocene Epoch (QH)
Lithological Description: Clay, silt and sand with sporadic dropstones. For details of lithologies see entries for constituent members.
Definition of Lower Boundary: Generally transitional, locally unconformable on the Errol Clay Formation or on glaciofluvial deposits; locally overlies bedrock.
Definition of Upper Boundary: Unconformable top related to marine transgression and regression and associated erosion, overlain by members of the Carse Clay Formation (the Carey Silt and Carse of Gowrie Clay members in the Tay area, the Letham Silt, Carse of Stirling Clay and Claret Clay members in the Forth area), or by the Flanders Moss Peat Formation (the sub-Carse Peat).
Thickness: Veneer to >38m
Geographical Limits: River Tay from just northwest of Perth and the Earn from Forgandenny eastwards, and adjacent to the Tay/Earn estuaries; some of the units might occur in the Eden and Montrose basins. Also the River Forth east of Aberfoyle, the Forth estuary and the Firth of Forth.
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  Powgavie B Borehole, BGS Ref.NO22NE/31 from 6.15m to 35.10m in depth; Carse of Gowrie west of Perth. 
Partial Type Section  Culfargie Borehole, BGS Ref.NO11NE/2, from 7.8m to 46.2m in depth; Lower Earn valley. 
Reference(s):
Armstrong, M, Paterson, I B and Browne, M A E, 1985. Geology of the Perth and Dundee district. Memoir of the British Geological Survey, Sheets 48W, 48E and 49 (Scotland). 108pp. 
Francis, E H, Forsyth, I H, Read, W A and Armstrong, M. 1970. The geology of the Stirling district. Memoir of the Geological Survey of Great Britain, Sheet 39 (Scotland). 
Browne, M A E, Graham, D K and Gregory, D M 1984. Quaternary estuarine deposits in the Grangemouth area, Scotland. Report of the Institute of Geological Sciences, No.16/3. 
Paterson, I B, Armstrong, M and Browne, M A E. 1981. Quaternary estuarine deposits in the Tay-Earn area, Scotland. Report of the Institute of Geological Sciences, No.81/7. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S048 S048 S038 S038 S039 S040 S040 S041 S031 S032