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After the last bird had settled to rest, a ghost crab came out of his burrow in the loose white sand above the high-water mark. He sped along the beach, running swiftly on the tips of his eight legs. He paused at a mass of sea wrack left by the night tide not a dozen paces from the spot where Silverbar stood on the edge of the sanderling flock. The crab was a creamy tan, matching the sand so closely that he was all but invisible when he stood still. Only his eyes, like two black shoe buttons on stalks, showed color.
Rachel Carson (Under the Sea Wind, 1941)

Abstract

Marginal marine zones comprise a multitude of depositional environments, including salt marshes, tidal flats, washover fans, lagoons, bays, estuaries, tidal deltas and tidal inlets and channels. The facies of many of these environments are intimately related and may differ from one another only in subtle ways. Considerable work has been accomplished on the physical and biogenic characteristics of such facies along modern coastlines, particularly the coasts of Georgia (Howard and Frey, 1980a, 1980b, 1980c; Frey and Howard, 1980, California (Warme, 1967,1971; Ronan, Miller and Farmer, 1981 and Germany (Schafer, 1962; Reineck and Singh, 1973.

From a biological standpoint marginal marine zones are environmentally very stressful, because they are subject to extreme short-term variations in temperature, salinity, subaerial exposure, energy level and food supply. For these reasons they are inhabited only by organisms that are well-suited to withstand such rigors. Trace-making organisms constitute an integral part of the assemblage, and the distribution of their traces aids in recognizing marginal marine environments in the rock record.

Washover fans are formed from wind-generated storm surges that cross over or cut through barrier islands. Such deposits generally range in thickness from a few centimeters to several meters, and they consist of lobate to sheet-like sand bodies, which extend into the marsh or back-barrier lagoon (Andrews, 1970; Schwartz, 1975). Under transgressive conditions, the development of washover fans constitutes an important mechanism for the landward migration of barrier island complexes (Reinson, 1979). Their recognition in the rock record, therefore, may be critical in interpreting marginal marine

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