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The BGS Lexicon of Named Rock Units — Result Details

Aston Limestone Formation

Computer Code: ASLS Preferred Map Code: AsL
Status Code: Full
Age range: Bajocian Age (JB) — Bajocian Age (JB)
Lithological Description: Grey and brown variously shelly, ooidal, sandy, shell-detrital and bioturbated limestones; rubbly in parts, with a median peloidal ooid-grainstone unit (Notgrove Member) well developed in places, and minor sandy and shell-detrital calcareous mudstone beds. The formation includes a bored hardground on top of the Notgrove Member.
Definition of Lower Boundary: Disconformity: upward change from ooidal and peloidal limestone (Scottsquar Member: Birdlip Limestone Formation) or sand, mudstone and sandy limestone (Harford Member: Birdlip Limestone Formation) – the Bajocian Unconformity, into grey and brown variously shelly, ooidal, sandy, shell-detrital and bioturbated limestones. The basal beds commonly contain pebbles derived from the underlying rocks. Generally a hardground.
Definition of Upper Boundary: Disconformity, generally a hardground: grey and brown variously shelly, ooidal, sandy, shell-detrital and bioturbated limestones overlain by members of the Salperton Limestone Formation, i.e. very shelly and coarsely shell-detrital ooidal grainstone and packstone (Upper Trigonia Grit Member, where present) or rubbly, fine- to coarse-grained ooidal, peloidal and finely shell-detrital packstone to grainstone (Clypeus Grit Member) – the Vesulian Unconformity.
Thickness: Type section up to about 6.45m. Maximum c.22m (Cleeve Hill area).
Geographical Limits: North and mid-Cotswolds: west of Northleach, Cold Aston and Blockley, and northeast of Stroud, Gloucestershire. Present locally outside this area to the south of Cold Aston, and absent between Birdlip and Cirencester ('Birdlip Anticline') due to overstepping relationships resulting from differential subsidence (Barron et al., 1997, fig. 4; Sumbler et al., 2000).
Parent Unit: Inferior Oolite Group (INO)
Previous Name(s): Middle Inferior Oolite [Obsolete Name And Code: Use ASLS] (MINO)
Hartley Hill Formation (-1958)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Cleeve Hill, Gloucestershire. Buckman, J, 1897; Richardson, L, 1929; Barron, A J M, 1999. 
Type Section  Harford railway cutting SSSI. Buckman, J, 1887, sections 3 and 4; Richardson, L, 1929; Parsons, C F, 1976; British Geological Survey files [BA 91]; Cox, B M, and Sumbler, M G. 2002. 
Reference Section  'Tumulus' railway cutting, Chedworth Woods, Gloucestershire. Buckman, J, 1895; Richardson, L, 1933, pp.27-28; Sumbler, M G and Barron, A J M, 1995, appendix 1, locality A. For further reference sections see Barron, A J M, et al, 1997. 
Reference(s):
Barron, A J M, 1999. Geology of the Bishop's Cleeve area (1:10 000 Sheet SO92NE). British Geological Survey Technical Report WA/99/01. 
Richardson, L. 1933. The Country around Cirencester. Memoir of the Geological Survey of Great Britain, Sheet 235 (England and Wales). 
Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
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. 
Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. 
Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217 (England and Wales). 
Buckman, S S, 1905. A monograph of the ammonites of the Inferior Oolite Series, Pt.13, Supplement pp.clxix-ccix. 
Barron, A J M, Sumbler, M G and Morigi, A N, 1997. A revised lithostratigraphy for the Inferior Oolite Group (Middle Jurassic) of the Cotswolds, England. Proceedings of the Geologists' Association, Vol.108, 269-285. 
Buckman, S S, 1887. The Inferior ooilte between Andoversford and Bourton-on-the-Water. Proceedings of the Cotteswold Naturalists' Field Club, Vol.9, 108-135. 
Buckman, S S, 1895. The Bajocian of the mid-Cotswolds. Quarterly Journal of the Geological Society of London, Vol.51, 388-445; 458-462. 
Buckman, S S, 1897. Deposits of the Bajocian age in the northern Cotswolds: the Cleeve Hill Plateau. Quarterly Journal of the Geological Society of London, Vol.53, 607-629. 
Buckman, S S, 1901. Bajocian and contiguous deposits in the north Cotswolds: the main hill-mass. Quarterly Journal of the Geological Society of London, Vol.57, 126-155. 
Parsons, C F, 1976. Ammonite evidence for dating some Inferior Oolite sections in the North Cotswolds. Proceedings of the Geologists' Association, 87, 45-63. 
Parsons, C F, 1980. Aspects of the statigraphy and ammonite faunas of the Aaenian-Bajocian stages in Great Britain. Unpublished PhD thesis, University of Keele. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E234 E235 E217