Ancient offshore tidal deposits

Abstract

Powerful tidal currents, winnowing shelly gravels and transporting sands and other grades along well defined paths, are a major feature of many partially enclosed continental shelf seas bordering large oceans. Clearly similar environments must have existed in the geological past, but the geologist must not be tempted merely to identify tidal deposits; there is other vital information to be gained. Studies of modern continental shelf tidal currents and sediments have yielded data concerning the lithology and geometry of deposits and the directions and rates of sediment transport, as discussed in earlier chapters. There are, however, two aspects about which relatively little is known, namely, the process of bedform preservation and the nature of the sedimentary sequences eventually produced by tidal currents operating in different continental shelf settings. The recognition of ancient offshore tidal current deposits is important because such discoveries offer the opportunity to seek information on these aspects.