Faults in the Purbeck—Isle of Wight monocline

Abstract

Faults at Arish Meli and Corfe Castle in Dorset, and at Freshwater Bay and Shide, Newport, on the Isle of Wight cut the Purbeck-Isle of Wight monocline. Evidence for these hitherto unrecognized faults is based on outcrop displacements and differences in: (a) outcrop widths either side of the faults; (b) strike and dip of the strata; and (c) the direction of the axis of the monocline. The faults developed above offsets in large normal faults beneath the subsequent monocline and were active growth faults during deposition of the Chalk. During the later Alpine tectonic episode which formed the Purbeck-Isle of Wight monocline these faults were reactivated, so displacing the boundary between the Chalk and the Reading Beds. The faults locally weakened the chalk ridge and allowed south to north drainage to develop through the ridge.