The BGS Lexicon of Named Rock Units — Result Details

Upper Grinstead Clay

Computer Code: UGRC Preferred Map Code: UGrC
Status Code: Index Level
Age range: Valanginian Age (KV) — Valanginian Age (KV)
Lithological Description: The unit comprises soft grey mudstones and silty mudstones the top of which commonly weathers to a red colour. In some areas the Cuckfield Stone Bed occurs at the base.
Definition of Lower Boundary: The lower boundary is an up-section change from fine-grained, silty, cross-bedded, buff sandstone with local thin mudstones and limestones (Cuckfield Stone Member) up into mudstones (Upper Grinstead Clay unit) that commonly have a marked basal pebble bed (Cuckfield Pebble Bed).
Definition of Upper Boundary: The upper boundary is placed at the up-section conformable change from mudstones (Upper Grinstead Clay unit) up into the silt and sand rhythms of the upper unit of the Tunbridge Wells Sand Formation. The top of the Grinstead Clay unit is commonly red stained, which helps to emphasise the contact.
Thickness: Up to 12.2m proved.
Geographical Limits: The Upper Grinstead Clay unit is recognised at a number of localities on the eastern part of the Horsham district (sheet 302) from the Scaynes Hill area, east to the Cuckfield-Handcross-Balcombe area and then northeast to East Grinstead. On the Tunbridge Wells sheet (287), it is present between East Grinstead and Royal Tunbridge Wells, with a further small outcrop near Danehill. On the Sevenoaks sheet (287) the unit is restricted to a small area near Finch Green and it is again present along the northeastern margin of the Brighton and Worthing Sheet (318/333), where it is found in a small area north of the Lunce's Common Fault, north of Burgess Hill. See also the Lexicon entry for Grinstead Clay Member (GRC).
Parent Unit: Grinstead Clay Member (GRC)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Pit at Hillhouse Farm. Gallois and Worssam, 1993. 
Reference Section  Hammond's Farm. Gallois & Worssam, 1993. 
Reference Section  Cuckfield Borehole TQ22NE2 between 166.04 and 178.27m depth. Gallois & Worssam, 1993 
Reference Section  Pit at Great Bently. Gallois & Worssam, 1993 
Reference Section  Haywards Heat Road, Ardingley. Gallois and Worssam, 1993. 
Reference Section  Old quarries 275m south of the west end of Lyewood Railway Tunnel. Gallois & Worssam, 1993. 
Reference Section  Freshfield Lane Brickworks. Gallois and Worssam, 1993. 
Reference Section  Whitemans Green. Gallois & Worssam, 1993 
Reference(s):
Young, B and Lake, R D. 1988. Geology of the country around Brighton and Worthing. Memoir of the British Geological Survey, Sheet 318 and 333 (England and Wales). 
Bristow, C R and Bazley, R A. 1972. Geology of the country around Royal Tunbridge Wells. Memoir of the Geological Survey of Great Britain, sheet 303 (England and Wales). 
Gallois, R W and Worssam, B C. 1993. Geology of the country around Horsham. Memoir of the British Geological Survey, Sheet 302 (England and Wales). 130pp. 
Dines, H G, Buchan, S and Bristow, C R. 1969. Geology of the country around Sevenoaks and Tonbridge. Memoir of the Geological Survey of Great Britain, Sheet 287 (England and Wales), 183pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E287 E302 E303 E318 E333