The BGS Lexicon of Named Rock Units — Result Details

Nar Clay Formation

Computer Code: NACL Preferred Map Code: notEntered
Status Code: Full
Age range: Hoxnian Stage (QX) — Hoxnian Stage (QX)
Lithological Description: The Nar Clay Formation consists of finely laminated marine clays, silts and silty clays, and peat of the Nar Valley Freshwater Peat Beds. Brickpits have yielded a rich fauna of well preserved bivalves and gastropods, foraminiferida, ostracods and diatoms. The clay has also yielded the bones and teeth of mammals.
Definition of Lower Boundary: Clays of the Nar Clay Formation overlie freshwater peat of the Nar Valley Freshwater Beds (NVFB) (which are included in the formation), and oversteps onto a variety of older rocks with marked unconformity. At East Winch the base of the clays is marked by a shell bed composed almost entirely of the oyster Ostrea edulis.
Definition of Upper Boundary: The Nar Clay Formation is present at surface. It is locally overlain unconformably by the Tottenhill Sand and Gravel Formation (Briton's Lane Formation)
Thickness: Up to 10m
Geographical Limits: The Nar Clay Formation is restricted to the Nar Valley, Norfolk
Parent Unit: British Coastal Deposits Group (COAS)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  BGS Nar Valley Borehole, Setch, registered No. TF61SE25, 5.6 -17.5 m Gallois, 1976 
Reference Section  Tottenhill Gravel Pit Gallois, 1979 
Reference(s):
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Gallois, R W. 1976. Nar Valley Borehole. p 11 in IGS Boreholes 1975. Report of the Institute of Geological Sciences No. 76/10. 
Lord, A R and Robinson, J E. 1978. Marine Ostracoda from the Quaternary Nar Valley Clay, West Norfolk. Bulletin of the Geological Society of Norfolk, 30. 
Lord, A R, Horne, D J and Robinson, J E. 1988. An introductory guide to the Neogene and Quaternary of East Anglia for ostracod workers. British Micropalaeontological Society Field Guide, Vol. No.5, 10pp. 
Mitlehner, A G. 1992. Palaeoenvironments of the Hoxnian Nar Valley clay, Norfolk, England; evidence from an integrated study of diatoms and ostracods. Journal of Quaternary Science, Vol. 7, No.4, 335-341. 
Stevens, L A. 1960. The interglacial of the Nar Valley, Norfolk. Quarterly Journal of the Geological Society of London, Vol. 115, 291-315. 
Ventris, P A. 1985. Pleistocene environmental history of the Nar Valley, Norfolk. PhD, University of Cambridge. 
Ventris, P A. 1996. Hoxnian interglacial freshwater and marine deposits in northwest Norfolk, England and their implications for sea-level reconstruction. Quaternary Science Reviews, Vol. 15, No. 5-6,437-450. 
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.] 
Whitaker, W, Skertchley, S B J and Jukes-Browne, A J. 1893. The geology of south-western Norfolk and of northern Cambridgeshire. Memoir of the Geological Survey of England and Wales. 
Athersuch, J, Horne, D J and Whittaker, J E. 1985. G. S. Brady's Pleistocene ostracods from the Brickearth of the Nar Valley, Norfolk, UK Journal of Micropalaeontology, Vol. 4, No.2, 153-158. 
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). 
Gallois, R W. 1978. The Pleistocene history of West Norfolk. Bulletin of the Geological Society of Norfolk, Vol.30, 3-38. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E145