Surface sediments and macrofaunas of the crati submarine fan (ionian sea, Italy)

Abstract

Five dredge samples, 8 grab samples and 18 light-gravity cores from the fan-delta fed Crati submarine fan indicate that the surface cover of the fan is mud-dominated, comprising muddy turbidites, thin-bedded silty-sandy turbidites and prodelta muds. This high mud content does not reflect an abandonment phase of the fan, but is the product both of the composition of the sediment load discharged by the Crati River and of the littoral processes affecting the constline of the Crati fan delta. A predominantly northward longshore drift catches most of the coarse bed load and redistributes it along the actively prograding beaches of the fan delta. The whole mud reaches the submarine basin via turbidity currents and surficial turbid plumes. The biogenic fraction, represented by Mollusca and benthic Foraminifera, is scarce because of the high terrigenous input. In situ mollusc assemblages, which occur only outside the channellized areas, vary significantly in composition between the different depositional environments of the fan. There is a much higher proportion of filter-feeding species in depositional areas more affected by the flow of turbidity currents (lobes, levees).