The BGS Lexicon of Named Rock Units — Result Details

Cuckfield Stone Bed

Computer Code: CKST Preferred Map Code: CkSt
Status Code: Full
Age range: Valanginian Age (KV) — Valanginian Age (KV)
Lithological Description: Sandstone, fine-grained, calcareous in part, pale yellow brown, fissile and flaggy (Tilgate Stone) with some parts showing trough cross-bedding ("festoon-bedding"), load casts and flute casts. Thin mudstone containing carbonaceous plant debris partings. Rare peletal and ferruginous shelly limestones developed in places towards base of unit.
Definition of Lower Boundary: The lower boundary is at a minor erosional contact between the grey mudstones of the informally named Lower Grinstead Clay below and the yellow brown fine-grained sandstones of the Cuckfield Stone Bed. This boundary can be marked locally by a thin bed of peletal or ferruginous limestone. The upper part of the Lower Grinstead Clay mudstone is commonly reddened.
Definition of Upper Boundary: The upper boundary is an erosional contact with sandstones of the Cuckfield Stone Bed sharply overlain by the grey mudstones of the basal informally named Upper Grinstead Clay grey mudstones. In places the basal bed of the Upper Grinstead Clay is informally called the Cuckfield Pebble Bed, variously described as: pebbly sand with quartz and phosphatic pebbles; an iron cemented pellet bed of rolled sandstone and mudstone pebbles with plant debris and bones; or simply as a coarse pebble bed.
Thickness: From 1.5 to 4.4m at outcrop but up to 8.3m in the Cuckfield No.1 Borehole.
Geographical Limits: The Cuckfield Stone Bed occurs in much of Horsham, including around Cuckfield, Drewitts and Ardingley. It disappears northwest of an arc from Handcross to Turners Hill and to the south of East Grinstead (Gallois and Worssam, 1993). It can also be traced into the Royal Tunbridge Wells district from Turner's Green to the area east of Greenhurst (east of Maresfield) and between East Grinstead to Royal Tunbridge Wells. The member has also been identified in a small area in the northeastern corner of sheet 318, north of Burgess Hill.
Parent Unit: Grinstead Clay Member (GRC)
Previous Name(s): Cuckfield Stone (-4542)
Cuckfield Stone Member (-4543)
Tilgate Stone (-1437)
Alternative Name(s): none recorded or not applicable
Reference Section  660m west of Rocks Farm, Handcross-Balcombe area. Exposure in a stream bed shows 1.58m of the lower part of the bed. Gallois and Worssam (1993, p.46). 
Reference Section  Paxhill Park small quarry on north side. About 1.75 of the bed exposed above the lower Grinstead Clay. Gallois and Worssam (1993, p 48). 
Reference Section  Cuckfield No.1 Borehole TQ22NE/2. 178.27 to 186.54m depth. 
Reference Section  Coney Gill, Handcross-Balcombe area. 4.5 m of full succession exposed in an old quarry. Gallois and Worssam (1993 p 46). 
Reference Section  Quarry 685m west-north-west of Balcombe Place, Balcombe. Small quarry exposes 2.25 of the lower part of the bed. Gallois and Worssam (1993, p. 46). 
Reference Section  Philpots Quarry near West Hoathly. The lower 1.5 m of the bed is exposed above the lower Grinstead Clay. Gallois and Worssam (1993. p 47). 
Type Area  There is no designated type section but extensive pits in the Whiteman's Green area near Cuckfield [around TQ 300 255] were famous for the dinosaur finds of Mantell; most of these pits are now backfilled and landscaped. The whole of the Cuckfield Stone Bed is exposed from time to time on the access road to Freshfield Lane Brickworks [TQ 383 265] and in the absence of an original designated site this provides the best complete paratype section. There are old quarries [TQ 2417 2467] southeast of Drewitts. There are many small exposures around Balcombe, Ardingley, West Hoathley and Cuckfield area of the Horsham Geological Sheet 302. The bed is also known from the Sevenoaks, Tunbridge Wells and Brighton sheet areas. 
Reference Section  Hillhouse Farm, near Ardingley. A deep pit exposes the upper boundary with the upper Grinstead Clay. Gallois and Worssam (1993, p. 47). 
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, Holmes, S C A and Bristow, C R. 1969. Geology of the country around Sevenoaks and Tonbridge. Second edition. Memoir of the Institute of Geological Sciences, Sheet 287 (England and Wales). 
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). 
Gallois, R W. 1963. In Summary of Progress of the Geological Survey of Great Britain for 1962, p.37. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E287 E302 E303 E318