The BGS Lexicon of Named Rock Units — Result Details

Minchinhampton Limestone Member

Computer Code: MHPL Preferred Map Code: ML
Status Code: Full
Age range: Bathonian Age (JN) — Bathonian Age (JN)
Lithological Description: Ooid-limestone, mainly grainstone, very fine- to coarse-grained, white, grey, yellow, cross-bedded and bedded, variably shell-detrital, pervasively burrowed in parts, with common whole shells in some beds, including rare ammonites.
Definition of Lower Boundary: Ooid-limestone, resting sharply on brown, fine-grained sandy limestone of Througham Member of Fuller's Earth Formation, or where that is absent, grey calcareous mudstone of Fuller's Earth Formation.
Definition of Upper Boundary: Ooid-limestone, sharply overlain by shell-detrital, fine-grained calcisiltite limestone of Dodington Ash Rock Member (Fuller's Earth Formation), where present, or very shelly calcareous mudstone (part of 'The Scroff') at the base of the Athelstan Oolite Formation at Minchinhampton Common.
Thickness: 5 to 9m at Minchinhampton Common, including Minchinhampton Borehole (SO80SE4), at least 4.4m at Bisley Borehole. Thins to zero to the south and west, probably passes east into the Taynton Limestone and Hampen formations.
Geographical Limits: Identified at outcrop only in Minchinhampton Common area, near Stroud, Gloucestershire, where also proved in Minchinhampton Borehole (SO80SE4). Also tentatively identified in Bisley Borehole (SO90SW1) [SO 9029 0491] 5km to NE, and possibly in IGS Charlton Borehole (ST98NE2) [ST9775 8947]. Probably passes east into the Taynton Limestone and Hampen formations.
Parent Unit: Taynton Limestone Formation (TY)
Previous Name(s): Minchinhampton Beds (-5070)
Shelly Beds And Weatherstones (-5071)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Crane Quarry, Minchinhampton Common, Stroud, Glos. Quarry now backfilled. NGR given is from Channon, 1950, but more accurately is thought to be SO 8562 0152. Quarry formerly exposed up to 6.4m of the Minchinhampton Limestone Member (Woodward, 1894, Beds 2 and 3), comprising 1.2 to 1.8m of cross-bedded white shelly ooid-limestone on 3.6 to 4.6m of cross-bedded shelly and shell-detrital ooid-limestone (='Shelly beds and Weatherstone'). These are reported to rest on Fuller's Earth clay/mudstone - fissile sandy limestone of the Througham Member may or may not be present. The overlying beds are attributed to the Athelstan Oolite Formation, including the beds called 'The Scroff' and 'Planking' (Woodward's Beds 4 and 5), probably still exposed in the nearby Gate Quarry [SO 8555 0165] (Wyatt and Sumbler, pp 151-153 in Cox and Sumbler, 2002). Woodward, 1894, pp 278-279; see also Channon, 1950, pp 251-252, Wyatt and Sumbler, pp 148-153 in Cox and Sumbler, 2002. 
Reference Section  IGS/BGS Minchinhampton (Old Common) Borehole (SO80SE4), 22.00 to 26.51m depth, penetrating full thickness of 4.51m of bedded very fine- to medium-grained ooid-limestone, with common shells (bivalves, brachiopods and gastropods) and large burrows at some levels; overlain by Dodington Ash Rock Member and underlain by Througham Member. Wyatt, 1996, fig. 6, p 311. 
Reference(s):
Wyatt, R J. 1996. A correlation of the Bathonian (Middle Jurassic) succession between Bath and Burford, and its relation to that near Oxford. Proceedings of the Geologists' Association, Vol. 107, 299-322. 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Channon, P J. 1950. New and enlarged Jurassic sections in the Cotswolds. Proceedings of the Geologists' Association, Vol. 61, 242-260. 
Sumbler, M G. 1999. Correlation of the Bathonian (Middle Jurassic) succession in the Minchinhampton-Burford district: a critique of Wyatt (1996). Proceedings of the Geologists' Association, Vol. 110, 53-64. 
Woodward, H B, 1894. The Jurassic Rocks of Britain, Vol.4. The Lower Oolitic Rocks of England (Yorkshire excepted). Memoir of the Geological Survey of the United Kingdom. 
Arkell, W J and Donovan, D T. 1952. The Fuller's Earth of the Cotswolds and its relation to the Great Oolite. Quarterly Journal of the Geological Society of London, Vol.107, 227-253. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable