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The BGS Lexicon of Named Rock Units — Result Details

Hampen Formation

Computer Code: HMB Preferred Map Code: Hm
Status Code: Full
Age range: Bathonian Age (JN) — Bathonian Age (JN)
Lithological Description: Limestone with subordinate interbedded calcareous mudstone ('marl'); limestone characteristically grey to brown, thinly bedded, fine- to very fine-grained, well-sorted, ooidal grainstone to packstone, commonly slightly sandy or silty, with small-scale cross-bedding.
Definition of Lower Boundary: Well bedded fine-grained limestone and calcareous mudstone, resting sharply on cross-bedded coarse-grained ooidal grainstone of the Taynton Limestone Formation or on mudstone/sandy limestone of the Fuller's Earth Formation.
Definition of Upper Boundary: More or less sharp boundary between interbedded fine-grained limestone and calcareous mudstone, overlain by purer, off-white or yellowish peloidal packstone, wackestone or grainstone of the White Limestone Formation.
Thickness: About 4-11m; 8.96m at type locality.
Geographical Limits: Frome Valley, west of Cirencester (where it passes into limestone beds in the upper part of the Fuller's Earth Formation) eastwards to Oxford-Brackley area (where it passes into the Rutland Formation).
Parent Unit: Great Oolite Group (GOG)
Previous Name(s): Hampen Marly Beds (-2243)
Marly Beds (-320)
Hampen Marly Formation (-3471)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Chedworth Station Railway Cutting, formerly exposed at least 9.1 m of the formation, overlain by the White Limestone Formation; the base not seen (Sumbler and Barron, 1995). 
Type Section  Hampen [Railway] Cutting SSSI, near Salperton, Gloucester, about 11km west of Bourton-on-the-Water (Sumbler and Barron, 1996). Exposes the full thickness of the formation comprising interbedded calcareous mudstone and fine-grained ooid-grainstone, the former dominating the upper part, the latter the lower, total 8.96 m thick, resting on the Taynton Limestone Formation and overlain by the White Limestone Formation. 
Reference Section  Daglingworth Quarry, exposes about 8 m of the upper part of the formation (Sumbler et al., 2000). 
Reference(s):
Arkell, W J. 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Richardson, L. 1911. On the sections of the Forest Marble and Great Oolite on the railway between Cirencester and Chedworth, Gloucestershire. Proceedings of the Geologists' Association, Vol.22, 95-115. 
Sumbler, M G, Barron, A J M and Morigi, A N, 2000. Geology of the Cirencester district. Memoir of the British Geological Survey, Sheet 235 (England and Wales). 
Cope, J C W (Editor) 1980b. A correlation of Jurassic rocks in the British Isles. Part Two: Middle and Upper Jurassic. Geological Society of London Special Report, No.15 
Palmer, T J, 1979. The Hampen Marly and White Limestone formations: Florida-type carbonate lagoons in the Jurassic of central England. Palaeontology, Vol.22, 189-228. 
Wyatt, R J. 2009. The status and local stratigraphical context of the Hampen Formation type section (Bathonian, Middle Jurassic). Proceedings of the Geologists' Association, Vol. 120, 126-132. 
Horton, A, Sumbler, M G, Cox, B M and Ambrose, K, 1995. Geology of the country around Thame. Memoir of the British Geological Survey, Sheet 237 (England and Wales). 
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. 
Barron, A J M, Lott, G K, and Riding, J B. 2012. Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report RR/11/06. 
Sumbler, M G and Barron, A J M, 1995. Geological notes and local details for 1: 10 000 Sheet SP01SE (Chedworth). British Geological Survey Technical Report, WA/95/73. 
Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
McKerrow, W S and Kennedy, W J. 1973. The Oxford district. Geologists' Association Guide No.3. 
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. 
Sumbler, M G and Barron, A J M, 1996. The type section of the Hampen Formation (Middle Jurassic, Great Oolite Group) at Hampen Cutting, Gloucestershire. Proceedings of the Cotteswold Naturalists' Field Club, Vol.40, 118-128. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E235 E236 E252 E217