BENTONITES IN THE LOWER D BEDS (RYAZANIAN) OF THE SPEETON CLAY OF YORKSHIRE

Abstract
SUMMARY: Four volcanogenic mudstone beds totalling 50cm thickness occur in the lower D beds (Ryazanian) of the Speeton Clay in Filey Bay, Yorkshire. These structureless mudstones are composed essentially of smectite or kaolinite, with residual igneous grains suggesting that the clays have originated by alteration of a primary ash fall. Volcanoes of comparable age arc known at Zuidwal in the Netherlands and at the Wolf Rock off Cornwall but it is possible that the Speeton Clay ash was derived from an as yet undiscovered volcanic source.