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The BGS Lexicon of Named Rock Units — Result Details

Chipping Norton Limestone Formation

Computer Code: CNL Preferred Map Code: CNL
Status Code: Full
Age range: Bathonian Age (JN) — Bathonian Age (JN)
Lithological Description: Limestone, off-white to pale brown fine- to medium-grained ooidal and coated peloidal grainstone, with common fine burrows, medium- to coarse-grained shell debris and flakes of greenish grey mudstone and dark lignite and minor amounts of fine-grained sand. Thick-bedded and cross-bedded or massive, weathering to flaggy or platy. Thin shell-detrital and ooidal marl and mudstone intercalations in places. Becoming very sandy eastward ("Swerford Beds" facies). Locally a mudstone bed ("Roundhill Clay" of Richardson, L, 1929) up to c.1m thick occurs at the base.
Definition of Lower Boundary: Conformable/non-sequential on fine- to coarse-grained ooidal and peloidal limestone, locally ironshot, of Clypeus Grit Member. Oversteps northeastwards to rest non-conformably on Grantham Formation, Northampton Sand Formation and Whitby Mudstone Formation.
Definition of Upper Boundary: Rapid passage upwards into mudstone-dominated Fuller's Earth Formation or Sharp's Hill Formation.
Thickness: 0 to 12m
Geographical Limits: North Gloucestershire to north Oxfordshire, where it passes northeastwards(on BGS 1:50 000 sheet 218) into the Horsehay Sand Formation (shown on 1968 edition of sheet 218 as the 'Lower Estuarine Series', now known as the Grantham Formation, but now thought to be generally absent south of Kettering).
Parent Unit: Great Oolite Group (GOG)
Previous Name(s): Chipping Norton Formation (-151)
Chipping Norton Limestone (-800)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Ditchley Road (or Town) Quarry, Charlbury. Sellwood, B W and McKerrow, W S, 1974; Horton, A, et al, 1987; Cox, B M, and Sumbler, M G. 2002. For other reference sections see Horton, A, et al, 1987. 
Type Section  Oxfordshire County Council Quarry, Chipping Norton. Horton, A, et al, 1987, p.71. 
Type Area  The Chipping Norton area of north Oxfordshire. 
Reference(s):
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217 (England and Wales). 
Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D. 1987. Geology of the country around Chipping Norton. Memoir of the British Geological Survey, Sheet 218 (England and Wales). 
Sellwood, B W and Mc Kerrow, W S. 1974. Depositional environments in the lower part of the Great Oolite Group of Oxfordshire and north Gloucestershire. Proceedings of the Geologists' Association, Vol.85, 189-210. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E201 E217 E218 E235 E236 E237