Erosion and Burial of Granite Rocky Shores in the Recent and Late Pleistocene of the Seychelles Islands: Physical and Biological Perspectives

Abstract Modern and abandoned Pleistocene rocky shores are described for several of the Seychelles Islands in order to examine the range of erosional features typical of granite shores in a tropical setting and to gauge the prospects for their preservation at unconformities in the rock record. The proportion of sandy beaches to rocky shores is estimated for each of the various islands under consideration, including Mahé, Praslin, Ronde, La Digue, Grande Sœur, and Cocos. Aspects of physical geography related to the position of reefs and the variable width of lagoons that surround and buffer the islands is considered with respect to the regional pattern of prevailing winds and oceanic circulation. Literature on the erosion of granite landforms is reviewed and applied to the Seychelles Inner Islands and the Seychelles Bank on which they sit. Outcrops of Pleistocene limestone closely associated with granite surfaces were searched for body fossils that represent an intertidal rocky-shore biota. Coralline red algae and vermetid gastropods are the primary components of laminated limestone attached directly to granite surfaces as protective bioconstructions. Cemented limestone rubble includes the body fossils of a dozen different kinds of invertebrates also found extant on modern granite shores in the Seychelles. Among them are gastropods that represent a range of different life styles, as well as corals.

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