The Swansea Valley Fault, Wales

The Swansea Valley Fault, Wales SIR-The recent letter from Dr Tunbridge (Geol. Mag. 117 (5), pp. 497-8) concerning a possible Devonian movement along the Swansea Valley Fault presented evidence on the sub-Old Red Sandstone geology of the area. He described conglomerates within the Brownstones containing angular clasts of acid volcanics, lithic arenites and vein quartz and indicated a likely local easterly derivation. The source of the exotic clasts was problematic, though they might, he suggested, be from the local lower Palaeozoic rocks.