A history of N-S faulting in the Wessex Basin including new evidence from the Clay Vale

Recent remapping of the Sidmouth and Wellington areas by the British Geological Survey has clearly shown a large number of faults orientated in a North-South direction. In the Sidmouth area these faults complicate the pattern of Jurassic and Triassic strata beneath the Cretaceous. The pattern of faulting continues onto the Wellington sheet to the North, where the faults appear to terminate against the prominent WNW-ESE faults such as the Hatch fault. The N-S faulting is thought to be driven by regional E-W extension of the Wessex Basin, causing subsidence from the mid Triassic into the Jurassic. The Clay Vale is an area around Ilchester, dominantly underlain by clays of Jurassic age, belonging to the Blue Lias Formation and the Charmouth Mudstone Formation. The area lies to the East of Wellington on the junction of the Yeovil and Glastonbury geological map sheets. Few faults are currently shown within these formations on the published Geological Survey maps. New evidence of abundant small scale N-S faulting is presented from the Clay Vale, demonstrating the continuation of the same structural regime in this area.