The BGS Lexicon of Named Rock Units — Result Details

Nar Valley Formation

Computer Code: NARC Preferred Map Code: notEntered
Status Code: Full
Age range: Mid Pleistocene Epoch (QPM) — Holocene Epoch (QH)
Lithological Description: The Nar Valley Formation encompasses the fluvial, lacustrine, organic and marine deposits of the Nar River and its tributaries. Floodplain alluvium comprises soft clay, silts and fine sands, with bodies of peat, overlying sands and gravels. River terrace deposits (Wormegay Member, Pentney Member and Marham Member of Lewis, 1999) comprise sands, gravelly sands and gravels, with the pebbles dominantly of angular to sub-rounded flint, and Chalk. Marine deposits ("Nar Valley Clay") comprise blue-grey finely laminated shelly silty clays; the underlying Nar Valley Freshwater Bed comprises grey fine-grained silty sands and silts and a compressed wood peat.
Definition of Lower Boundary: Unconformable on Mid Pleistocene glacial deposits, and on bedrock.
Definition of Upper Boundary: Surface.
Thickness: To c.5m
Geographical Limits: The entire catchment of the Nar River and tributaries, in Norfolk.
Parent Unit: Ouse-Nene Catchments Subgroup (ONCA)
Previous Name(s): Nar Valley Clay [Obsolete Code: Use NARC] (NV)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The valley of the Nar River, Norfolk. Ventris, 1986. 
Reference(s):
Ventris, P A. 1986. The Nar Valley. 7-55 in West, R G and Whiteman, C A (editors), The Nar Valley and North Norfolk Field Guide. [Coventry: Quaternary Research Association.] 
Lewis, S G. 1999. Eastern England. 10-27 in Bowen D Q (editor), A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, 23. [London: Geological Society.] 
Ventris, P A. 1985. Pleistocene environmental history of the Nar Valley, Norfolk. PhD, University of Cambridge. 
Gallois, R W, 1994. The geology of the country around King's Lynn and The Wash. Memoir of the British Geological Survey, Sheet 145 and part of 129 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E160 E146 E145 E129 E159