SHELF STORM BEDS ON THE SOUTHERN MARGIN OF THE WELSH BASIN - THE WENLOCK OF THE TORTWORTH INLIER, ENGLAND

The Brinkmarsh Beds (Wenlock, Silurian) of the Tortworth Inlier, near Bristol, SW England were deposited in shallow marine water on the sout hern margin of the Welsh Basin. Occasional sandstone units are interpr eted as storm-induced deposits that periodically overwhelmed the quiet -water deposition of siltstones and mudstones. Evidence for storm-bed deposition is the episodic nature of the sandstone units, their erosiv e bases, hummocky cross-stratification in some, and suspended coquinit es in others. There are two types of shell bed within the sequence: in situ units within the siltstones containing shallow-water brachiopods , corals, and crinoids, and transported faunas in the sandstones exclu sively of large brachiopods. Palaeontological and sedimentological evi dence suggests that deposition took place in a protected embayment on the shallow shelf.