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ABSTRACT

A model to account for the occurrence of heavy mineral concentrations as discrete lamina on beaches is presented. The model is based on the shoreward variation in the distribution of bottom fluid velocities due to shoaling, progressive, gravity, water waves. This variation causes certain portions of the sediment population to be transported shoreward at a faster rate than other portions. On moderate energy shorelines composed of sand-sized sediment the selectively transported portion may include the relatively hard-to-move heavy mineral fraction. Wave tank experiments with artificially prepared sediment populations provide empirical support for the proposed model. Under certain wave conditions it was found that the heavy mineral fraction of the sediment population moved shoreward at a faster rate than did the light mineral fraction.