Abstract

The Pliocene Pleshet Formation was deposited in moderately high energy, nearshore environments dominated by upper shoreface and foreshore sediments, characterized by concentrations of heavy minerals and shell fragments, beach rock, shoreline conglomerates, and organic burrowing. The Pliocene marine transgression which prevailed during the deposition of the Pleshet Formation was offset by progradation related to infilling of the shallow marine basins by influxes of sand from both Negev and Mediterranean source areas. The sands are multi-component systems which contain up to 7 populations. The statistical parameters of the grain-size frequency distributions are directly related to the way in which these populations are mixed. The abrupt change in these parameters at the tops of the depositional sand units coincides with surfaces of erosion and suggests that one of the 2 source areas became a more active supplier of sand, thus changing the modal composition. Nearshore beach sedimentation ranging from current dominated to shallow water shoals with prevailing wave action is indicated by bivariate plots of grain-size parameters and the bimodality of the central parts of the frequency distributions. An upward improvement of sorting in several of the units reflects a shallowing of the environment with more influence of wave action.

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