The BGS Lexicon of Named Rock Units — Result Details

Highworth Clay Member

Computer Code: HWCL Preferred Map Code: HwC
Status Code: Pending Upgrade
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Variably sandy grey to brown mudstone.
Definition of Lower Boundary: Basal contact may be erosional. In Wiltshire, sharp change up from yellow to grey fine to medium sand, sandstone and muddy sandstone (Hazelbury Bryan Formation) or in Oxfordshire change up from bedded shelly ooidal limestone (Highworth Limestone Member) or sandy ooidal limestone (Pusey Flags Member) into mudstone or sandy mudstone of the Highworth Clay Member. In reference section Faringdon Borehole (SU39SW/1), the base is at 6.71m.
Definition of Upper Boundary: Passage up from grey to brown mudstone or sandy mudstone into sand or sandstone with ooids (Highworth Grit Member) in Oxfordshire. Non-sequence overlain by shelly, shell detrital ooidal limestone of the Stanford Formation (Calne Freestone) in Wiltshire.
Thickness: 2 to 3m in type area, 1.2m at Lamb and Flag Quarry, c.3.7m at Wootton Bassett.
Geographical Limits: North Wiltshire to south-west Oxfordshire. Best developed in the area of Highworth and Hatford. May be represented at Spirt Hill, near Calne, Wilts (Arkell, 1951).
Parent Unit: Kingston Formation (KTON)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Faringdon Borehole (SU39SW/1). Cuttings only. Full thickness penetrated. 
Reference Section  Lamb and Flag Quarry, Kingston Bagpuize, Oxfordshire. Formerly exposed here. Wright in Wright and Cox, 2001. 
Reference(s):
Arkell, W J. 1951. The geology of the Corallian ridge between Wootton Bassett and Lyneham, Wiltshire. Wiltshire Archaeological and Natural History Magazine, Vol.54, 1-18. 
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. 1941a. Map of the Corallian Beds around Highworth, Wiltshire. Proceedings of the Geologists' Association, Vol.52, 79-109. 
Arkell, W J. 1939. Map of the Corallian Beds between Marcham and Faringdon, Berkshire. Proceedings of the Geologists' Association, Vol.50, 487-509. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E253