The BGS Lexicon of Named Rock Units — Result Details

Oakley Member

Computer Code: OKLY Preferred Map Code: Oa
Status Code: Full
Age range: Oxfordian Age (JO) — Oxfordian Age (JO)
Lithological Description: Interbedded pale grey marls, silty, argillaceous micritic limestones, siltstones and silty to sandy mudstones, commonly containing scattered ferruginous ooids, and locally rich in Nanogyra nana and serpulids.
Definition of Lower Boundary: A marked, and generally sharp, non-sequential, lithological change from sand or sandstone of the Beckley Sand or Arngrove Spiculite members of the Kingston Formation, or silty mudstones of the West Walton Formation.
Definition of Upper Boundary: An upward change to mudstones of the West Walton Formation or Ampthill Clay Formation.
Thickness: Up to about 5 m thick.
Geographical Limits: Around Wheatley to Westcott, north-east of Oxford, restricted to 1:50 000 sheet 237 (see inset map for south-west limit). Similar facies which occur at the same horizon farther north-east; e.g. sheets 219, 220 and 203 are not Oakley Member, but should be treated as part of the West Walton Formation.
Parent Unit: Stanford Formation (STFD)
Previous Name(s): Exogyra Nana Beds (-1741)
Exogyra Nana Clay (-1742)
Exogyra Nana Zone (-1743)
Oakley Clay (-2352)
Oakley Beds (-1526)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Primary reference: Brill No. 1 Birehole (SP61SE/10) 102.58 to 106.06. 
Type Area  Oakley, near Brill, Bucks. 
Reference Section  Railway cutting between Dorton and Ashendon Junction. Davies. In: Arkell, 1927. 
Reference(s):
Arkell, W J. 1947. The Geology of Oxford. 267pp. [Oxford: Clarendon Press.] 
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Arkell, W J, 1927. The Corallian rocks of Oxford, Berkshire and north Wiltshire. Philosophical Transactions of the Royal Society of London, Vol.B216, 67-181. 
Wright, J K and Cope, J C W. In press. Oxfordian - Kimmeridgian Correlation Chart. In: A correlation of Jurassic rocks in the British Isles: Middle and Upper Jurassic. Cope, J C W (editor). Special Report of the Geological Society of London. 
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). 
Buckman, S S, 1927. Type Ammonites, Vol.6. (London: S S Buckman) 
Davies, A M. 1907b. Excursion to Dorton, Brill and Arngrove. Proceedings of the Geologists' Association, Vol. 20, 183-186. 
Cox, B M and Wright, J K, 2001. British Upper Jurassic stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series, No. 21. (Peterborough: Joint Nature Conservation Committee.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E237