The BGS Lexicon of Named Rock Units — Result Details

Bothkennar Gravel Member

Computer Code: BKGR Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Fine- to coarse-grained gravel, cobbles and boulders (one recorded to be at least 1.8m across in an old excavation at Bo'ness), subangular to rounded with some striated, locally in a matrix that varies from loose sand to firm clayey sandy silt. Clasts of mainly locally-derived Carboniferous and Devonian lithogies. The deposit is poorly sorted. It is considered to have been deposited by ice-rafting of materials during the Loch Lomond Stadial.
Definition of Lower Boundary: Markedly erosive base cut into the various members of the Forth Clay Formation, Wilderness Till Formation and bedrock.
Definition of Upper Boundary: Overlain unconformably by the early Holocene transgressive estuarine sand, silt and clay of the Letham Silt Member and also younger units including the Carse of Stirling Clay Member and later Claret Clay Member (Carse Clay Formation).
Thickness: Veneer to at least 3.5m
Geographical Limits: Lower Forth valley, Forth estuary and Firth of Forth, concealed below younger estuarine and marine deposits.
Parent Unit: Forth Clay Formation (FOCL)
Previous Name(s): Bothkennar Gravel Formation (-4468)
Bothkennar Gravel (-1358)
Alternative Name(s): Buried Gravel Layer
Stratotypes:
Type Section  Bothkennar IGS No.1 Borehole, BGS Ref NS98NW/205, from 13.9m to 17.3m depth. 
Reference(s):
Sissons, J B. 1969. Drift stratigraphy and buried morphological features in the Grangemouth-Falkirk-Airth areas, Central Scotland. Transactions of the Institute of British Geographers, Vol.48, 19-50 
Peacock, J D. 1998. The Bothkennar Gravel Formation ("buried gravel layer") of the Forth Estuary. Scottish Journal of Geology, Vol.34, 1-5 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S039 S039 S040 S040 S031 S032 S032