The BGS Lexicon of Named Rock Units — Result Details

Fen Farm Limestones Bed

Computer Code: FFML Preferred Map Code: FF
Status Code: Full
Age range: Sinemurian Age (JS) — Sinemurian Age (JS)
Lithological Description: Group of about three thin (0.1 to 0.3m) limestone beds, separated by up to 0.5m of calcareous mudstone beds. Limestones are bioclastic packstone/grainstone, shelly, grey, weathering pale orange brown. Fauna includes bivalves, echinoderms, ammonites, corals and the trace fossil Kulindrichnus. Whole Gryphaea shells and crinoid (Pentacrinus) debis abundant on the outcrop. Forms a strong feature with a broad dip slope.
Definition of Lower Boundary: Change up from grey, calcareous mudstone of the undifferentiated Granby Member; at 58.14m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Definition of Upper Boundary: Change up into bluish grey, shaly mudstone of the undifferentiated Buckingham Member; at 56.75m depth in type section Fulbeck Airfield Borehole F/B5 (SK95SW/17).
Thickness: 1.39m in type section; up to 2m in Leicestershire.
Geographical Limits: East Midlands; north Leicestershire to Lincolnshire. Not recognised in north Lincolnshire, or south Leicestershire, where it passes south into part of the more argillaceous and less bioclastic Rugby Limestone Member of the Blue Lias Formation (Ambrose, 2001).
Parent Unit: Granby Member (GRBL)
Previous Name(s): Fen Farm Limestone (-4647)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Fulbeck Airfield Borehole F/B5 (SK95SW/17). 
Reference(s):
Brandon, A, Sumbler, M G and Ivimey-Cook, H C, 1990. A revised lithostratigraphy for the Lower and Middle Lias (Lower Jurassic) east of Nottingham, England. Proceedings of the Yorkshire Geological Society, Vol.48, 121-141. 
Carney, J N, Ambrose. K and Brandon A, 2002. Geology of the Melton Mowbray district - a brief explanation of the geological map. British Geological Survey Sheet Explanation, Sheet 142 (England and Wales). 
Ambrose, K, 2001. The lithostratigraphy of the Blue Lias Formation (Late Rhaetian-Early Sinemurian) in the southern part of the English Midlands. Proceedings of the Geologists' Association, Vol.112, 97-110. 
Berridge, N G, Pattison, J, Samuel, M D A, Brandon, A, Howard, A S, Pharaoh, T C and Riley, N J. 1999. Geology of the Grantham district. Memoir of the British Geological Survey, sheet 127 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E127 E142 E126