The BGS Lexicon of Named Rock Units — Result Details

Cromer Forest Bed Formation

Computer Code: CRF Preferred Map Code: notEntered
Status Code: Full
Age range: Pre-Pastonian/Baventian Stage (QV) — Cromerian Stage (QC)
Lithological Description: The formation encompasses the fluvial, lacustrine and organic deposits of the postulated "Ancaster River", which is believed to have flowed from the Pennines to the North Sea along a line corresponding approximately to the present north coast of Norfolk. Four members are recognised in north Norfolk coastal sections. The Sheringham Member (lowest member) comprises freshwater organic mud, clay and sand. The Runton Member includes laminated freshwater silty clay. The West Runton Member comprises layers of alluvial clay and organic freshwater mud. The Bacton Member (highest Member) comprises clay and organic mud.
Definition of Lower Boundary: Rests disconformably on Chalk or on Wroxham Crag Formation, and interdigitates with Wroxham Crag Formation. The interdigitated succession is as follows, from top down: Bacton Member (Cromer Forest-bed Formation); Mundesley Member (Wroxham Crag Formation); Runton Member (upper part, Woman Hithe Gravel of Reid, 1882; Wroxham Crag Formation); Runton Member (lower part, Woman Hithe Clay of Reid, 1882; Cromer Forest-bed Formation); Paston Member (Wroxham Crag Formation); Sheringham Member (Cromer Forest-bed Formation); Sidestrand Member (Wroxham Crag Formation).
Definition of Upper Boundary: Overlain by Middle Pleistocene glacial deposits (Happisburgh, Lowestoft, Sheringham Cliffs and Briton's Lane formations).
Thickness: c.6m
Geographical Limits: The formation is restricted to North Norfolk. If further deposits of the Ancaster River were discovered farther west, ie west of the Wash, they would constitute a new formation.
Parent Unit: Dunwich Group (DUNW)
Previous Name(s): West Runton Freshwater Bed (-2722)
Woman Hithe Clay (-2115)
Lower Freshwater Bed of Reid, 1882 (-819)
Arctic Freshwater Bed (-163)
Forest Bed (-164)
Upper Freshwater Bed (-2114)
Alternative Name(s): West Runton Member
Sheringham Member
Bacton Member
Runton Member
Stratotypes:
Type Area  The coast of North Norfolk from Weybourne to Happisburgh. Moorlock et al., 2002b. 
Reference(s):
Moorlock, B S P, Hamblin, R J O, Booth, S J and Woods, M A. 2002. Geology of the Mundesley and North Walsham district - a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Series Sheets 132 and 148 Mundesley and North Walsham (England and Wales). 
Funnell, B M and West, R G. 1977. Preglacial Pleistocene deposits of East Anglia. 247-265 in Shotton, F W (Editor), British Quaternary studies: recent advances. [Oxford: Clarendon Press.] 
Reid, C. 1882. The geology of the country around Cromer. Memoir of the Geological Survey of Great Britain. 
West, R G. 1980. The Pre-Glacial Pleistocene of the Norfolk and Suffolk coasts. [Cambridge: Cambridge University Press.] 
Moorlock, B S P, Hamblin, R J O, Booth, S J, Kessler, H, Woods, M A and Hobbs, P R N. 2002. Geology of the Cromer district - a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Sheet 131 Cromer (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E132 E148 E176 E131