The BGS Lexicon of Named Rock Units — Result Details

Fornham Member

Computer Code: FHAM Preferred Map Code: notEntered
Status Code: Full
Age range: Quaternary Period (Q) — Quaternary Period (Q)
Lithological Description: Sand and gravel with beds of clayey, sandy and pebbly silt. A borehole at TL 8504 6747 (BGS Registered No. TL86NE/101) proved 5.6m of the member including 2.1m of clayey, sandy, pebbly silt. Mean grading figures show 23 per cent fines, 71 per cent sand and 6 per cent gravel.
Definition of Lower Boundary: Generally unconformably overlies Chalk bedrock,but locally for example in the vicinity of Kentford they overlie glacial silt.
Definition of Upper Boundary: At surface.
Thickness: Generally up to about 4m but a borehole at [TL 8504 6747] proved 5.6m. BGS Borehole Registration No.TL86NE/101.
Geographical Limits: Within the Kennett valley (tributary of the Lark) around Kentford and Fornham and upstream as far as Moulton.
Parent Unit: Lark Valley Formation (LKVY)
Previous Name(s): 4th Terrace Of River Lark (Clayton 1983) (-247)
Alternative Name(s): 4th Terrace Of River Lark (Bristow,1990)
Type Area  The stratotype is an area adjacent to the River Kennett around Kentford, Suffolk which has been largely worked out. Bristow, 1990 
Clayton, A R. 1983. The sand and gravel resources of the country between Maidenhall and Barrow, Suffolk: description of 1:25000 Sheets TL76, TL77 and part of TL87. Mineral Assessment Report, 123, Institute of Geological Sciences, London. 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Bristow, C R. 1990. Geology of the country around Bury St Edmunds. Memoir of the British Geological Survey, Sheet 189 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used: