Abstract

The concentration of heavy-minerals by storm wave erosion of dune/beach ridges and of light minerals from wind-winnowing the beach surface were observed on the beach of Sapelo Island, Georgia from fall 1971 through the spring of 1973. The observations support earlier proposals of others that such processes are largely responsible for extensive heavy-mineral concentrations found on both modern and ancient strandlines throughout the world. In addition serial observations along with sample data indicate that the period of most efficient heavy-mineral concentration on the Sapelo Island beach occurs during moderate surf energy levels attending storm wane. High velocity eolian winnowing during low tide periods is all important complementary effect. The processes of heavy-mineral concentration in the backshore of Sapelo Island during the recent cycle of shoreline retrogradation may be related to those affective in the development of some southeast U.S. heavy-mineral ore-bodies. Similarities include evidence of a predominantly progradational barrier construction with cyclic periods of retrogradation.

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