The BGS Lexicon of Named Rock Units — Result Details

OXFORD CLAY FORMATION
Computer Code: OXC  Status Code: FORMAL, NATIONAL 
Preferred Map Code: OxC 
Age or Age Range: [ JC ] CALLOVIAN  to [ JO ] OXFORDIAN 
Lithological Description:
Silicate-mudstone, grey, generally smooth to slightly silty, with sporadic beds of argillaceous limestone nodules. Over most of the outcrop (except the Cleveland Basin, where only the upper part is present) it comprises a tripartite succession: lower part (Peterborough Member) silicate-mudstone, mainly brownish-grey, fissile, organic-rich ("bituminous"), with subordinate beds of pale to medium grey, blocky mudstone; middle part (Stewartby Member) silicate-mudstone, mainly pale to medium grey, smooth to slightly silty, blocky, with subordinate beds of silty shell-debris-rich mudstone; upper part (Weymouth Member) mudstone, mainly pale grey, calcareous, smooth, blocky. For more detail see Peterborough, Stewartby and Weymouth members. 
Definition of Lower Boundary:
Generally a fairly sharp but generally conformable junction with silicate-sandstone or sandy mudstone of the underlying Kellaways Formation or, in the Cleveland Basin, sandstone of the underlying Osgodby Formation, overlain by silicate-mudstone. In thicker, expanded successions (Wessex Basin) arbitary boundary drawn at the top of highest substantial silicate-sandstone or sandy mudstone above which the succession is predominantly silicate-mudstone. 
Definition of Upper Boundary:
Upward transition from silicate-mudstone to silty mudstone of the overlying West Walton Formation (Oxford to Market Weighton) or sandy mudstones and calcareous sediments (Dorset to Oxford, and Yorkshire, north of Market Weighton) of the Corallian Group. In Market Weighton area, sharp disconformable contact with chalk (Chalk Group, Hunstanton Formation). In the Westbury to Longleat area, Wiltshire, sharp disconformable contact with sandy micaceous mudstone (Cretaceous, Gault Formation). 
Thickness:
To 185m (perhaps in south Dorest); typically 50 to 70m over much of the East Midlands Shelf. 
Geographical Limits:
Dorset coast (Weymouth area) to North Yorkshire coast. Extensive in onshore subcrop, though absent above the interior of the London Platform. 
Parent Unit: Parent Unit Code:
ANCHOLME GROUP  AMG
Previous Name(s): Previous Code(s):
FEN CLAY FORMATION [PART]   
CLUNCH CLAY   
CLUNCH CLAY AND SHALE   
FEN CLAY   
FOREST CLAY   
Alternative Name(s):
none recorded or not applicable
Stratotypes:
Reference Section  BGS Chalgrove Borehole (SU69NE/20). 2.0km eastsoutheast of Chalgrove, near Oxford. 
Type Area  Oxford area, including brickpits in and around the city of Oxford. 
Reference(s):
Arkell, W J. 1933. The Jurassic System in Great Britain. [Oxford: Clarendon Press.] 
Smith, W. 1817. Strata identified by organized fossils, Part 3. [London.] 
Gallois, R W and Cox, B M. 1977. The stratigraphy of the Middle and Upper Oxfordian sediments of Fenland. Proceedings of the Geologists' Association, Vol.88, 207-228. 
Phillips, W, 1818. A selection of facts from the best authorities, arranged so as to form an outline of the geology of England and Wales. (London: W Phillips). 
Cox, B M, Hudson, J D and Martill, D M, 1992. Lithostratigraphic nomenclature of the Oxford Clay (Jurassic). Proceedings of the Geologists' Association, Vol.103, p.343-345. 
Arkell, W J. 1947. The Geology of Oxford. [Oxford: Clarendon Press.] 
Gaunt, G D, Fletcher, T P amd Wood, C J. 1992. Geology of the country around Kingston upon Hull and Brigg. Memoir of the British Geological Survey, sheets 80 and 89 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  281
E  310
E  341
E  144
E  173
E  342
E  312
E  54
E  204
E  236
E  266
E  328
E  43
E  114
E  171
E  297
E  327
E  202
E  265
E  158
E  186
E  252
E  313
E  143
E  218
E  63
E  53
E  188
E  254
E  127
E  237
E  42
E  187
E  220
E  253
E  52
E  145
E  157
E  235
E  128
E  72
E  64
E  129
E  159
E  81
E  102
E  282
E  115
E  172
E  251
E  268
E  189
E  203
E  343

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