The stratigraphy and geological setting of the Oxfordian Corallian Group around Steeple Ashton and Westbury, Wiltshire, U.K.

Abstract

Study of a number of new exposures of strata belonging to the Oxfordian Corallian Group in the area around Steeple Ashton, Wiltshire, combined with geological mapping, has enabled the production of the first full synthesis of Oxfordian sedimentation in the area. Situated on the north-western margin of the Wessex Basin, the area experienced intermittent sedimentation, with episodes of subsidence leading to the accumulation of shallow marine shelf sediments, interspersed with episodes of uplift and erosion, with pebble beds and erosion surfaces. One of the most celebrated stratal units in the area is the Steeple Ashton Coral Bed. The extent of the outcrop of the Coral Bed has been established here for the first time. Apart from the very localised Ringstead Coral Bed of Dorset, this is the only coralliferous development in the Upper Oxfordian of Britain, and is remarkable for the wide variety of coral species present. Corals only developed substantially for one short period, during which there was the most varied and prolific coral growth. This study sets the Steeple Ashton Coral Bed into the context of Oxfordian sedimentation in Wiltshire, and of Late Oxfordian sedimentation in N. W. Europe.