Oxford Clay

Middle Jurassic (Callovian)

Lithology
Silicate-mudstone, mainly brownish-grey, fissile, organic-rich ("bituminous"), with subordinate beds of pale to medium grey, blocky mudstone.

Upper Boundary
In Gloucestershire, there is no solid geology present above the Oxford Clay. Deposits overlying therefore date from the Quaternary and are generally unconsolidated deposits of head, sands and gravels and alluvium.

Lower Boundary
Generally a fairly sharp but generally conformable junction with silicate-sandstone or sandy mudstone of the underlying Kellaways Formation

Representative Sites
South Cerney Railway Cutting

Information on lithology and boundaries taken from the British Geological Survey Lexicon of Named Rock Units