A postulated post-Hercynian rift valley system in southern Britain

Abstract

It is suggested that post-(Hercynian)orogenic tensional forces may have initiated a major rift valley system in the Palaeozoic rocks of southern Britain. Large graben structures may underlie the Bristol Channel, the Severn Basin and the Weald Jurassic trough. Smaller graben structures are present in Devon and are associated with extrusive, potassium-rich lavas. The bounding faults of the larger postulated grabens may have been active during early Mesozoic times and may have fundamentally controlled sedimentation in local sags. A model is proposed which ascribes the development of fault-bounded Permo-Triassic basins and Jurassic axes of uplift to fracturing in the Palaeozoic basement.