The BGS Lexicon of Named Rock Units — Result Details

Ringstead Clay Member

Computer Code: RWC Preferred Map Code: RiC
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Pale to dark grey mudstone, variably calcareous, with locally numerous, fine calcareous laminae. The upper part of the member is reddish silty mudstone with siltstone lenses and is characterised by red-weathering, lens-shaped sideritic concretions. Poorly fossiliferous, with echinoids, bivalves and rare ammonites.
Definition of Lower Boundary: A sharp, non-sequential boundary, marked by the upward change from ferruginous, bioturbated sandstone or sandy mudstone of the underlying Sandsfoot Grit, or ferruginous oolite of the Westbury Ironstone Member (Wilts), to grey, calcareous mudstone.
Definition of Upper Boundary: Either: Sharp change up from reddish mudstone with siderite nodules of Ringstead Clay into shelly, ferru-ooidal calcareous mudstone or limestone (Osmington Mills Ironstone Member, including Ringstead Coral Bed), or: Non sequence; overlain by dark grey mudstone (Kimmeridge Clay Formation), with basal bed of very dark grey shelly bioturbated mudstone with ferruginous ooids and phosphatic pebbles (Inconstans Bed).
Thickness: Dorset coast: 3.5-5m at outcrop, up to 18m in boreholes at Kimmeridge. Inland Dorset: up to 9m. Westbury, Wilts: 6.3m.
Geographical Limits: Dorset: Weymouth to Abbotsbury, Mappowder to Bourton. Wiltshire: Westbury and Steeple Ashton; northeast limit uncertain. NB: Because of poor exposure and landslipping, the Ringstead Clay Member has been included in the mapped outcrop of the Kimmeridge Clay Formation in Dorset.
Parent Unit: Sandsfoot Formation (SDT)
Previous Name(s): Ringstead Waxy Clay Member (-4869)
Ringstead Waxy Clays (-1156)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Ringstead Bay, Dorset. Full thickness exposed in cliffs. Arkell, 1936, pp.42-44. 
Reference Section  Cliffs between Black Head and Osmington Mills, Dorset. Wright and Cox, 2001, pp.18-20. 
Reference(s):
Wright, J K. 1986. A new look at the stratigraphy, sedimentology and ammonite fauna of the Corallian Group (Oxfordian) of south Dorset. Proceedings of the Geologists' Association, Vol. 97, 1-21. 
Wright, J K, and Cox, B M. 2001. British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series. No. 21. (Peterborough: Joint Nature Conservation Committee/Chapman and Hall.) 
Arkell W J. 1936. The Corallian Beds of Dorset, Part 1: The Coast. Proceedings of the Dorset Natural History and Archaeological Society, Vol.57, 59-93. 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M and Woods, M A. 1999. The Wincanton district - a concise account of the geology. Memoir of the British Geological Survey, Sheet 297 (England and Wales). 
Arkell, W J. 1947. Geology of the country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the British Geological Survey. Sheets 341, 342, 343 and small portions of sheets 327, 328 and 329 (England and Wales). 
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales). 
Birkelund, T, Callomon, J H, Clausen, C K, Nohr Hansen, H and Salinas, I. 1983. The Lower Kimmeridge Clay at Westbury, Wiltshire, England. Proceedings of the Geologists' Association, Vol.94, 289-309. 
Bristow, C R, Cox, B M, Woods, M A, Prudden, H C, Sole, D, Edmunds, M and Callomon, J H, 1992. The geology of the A303 trunk road between Wincanton, Somerset and Mere, Wiltshire. Proceedings of the Dorset Natural History and Archaeological Society, Vol.113, 139-143. 
Coe, A L. 1995. A comparison of the Oxfordian successions of Dorset, Oxfordshire and Yorkshire. 151-172 in Taylor, P D (Ed.) Field Geology of the British Jurassic. [Bath: The Geological Society.] 
Gallois, R. 1998. The stratigraphy of well and completion reports for the Swanworth Quarry No.1 and No.2 and Metherhills No.1 boreholes (RGGE) Project), Dorset. British Geological Survey Technical Report WA/97/91. 
Gallois, R. 2000. The stratigraphy of the Kimmeridge Clay Formation (Upper Jurassic) in the RGGE Project boreholes at Swanworth Quarry and Metherhills, south Dorset. Proceedings of the Geologists' Association, Vol.111, 265-280. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E327