Sources of sediment to the Ionian Sea and western Levantine basin of the Eastern Mediterranean during S-1 sapropel times

摘要

The provenance of sediments to the Ionian Sea andwestern Levantine basin during S-1 sapropel times was studiedusing 87Sr/86Sr isotopic ratios together with major elements.Measurements were made on sediment profiles from 5 box coresin the Eastern Mediterranean, on Saharan dust and on a core fromthe Nile delta which included sediment deposited during S-1sapropel times. In the sediment profiles, there was a decrease in87Sr/86Sr ratio, 1/Sr, Ti/Al, Mg/Al and Si/Al ratio starting at theupper Mn peak and finishing at the base of the organic-rich layer.This showed that there was a major change in the nature of thedetrital input during S-1 sapropel times. The timing of the changein detrital input was similar to the change in surface salinity asmeasured by δ18O. There was linear relationship between87Sr/86Sr and 1/Srand for 87Sr/86Sr and Ti/Al for all the sedimentsamples. The favoured interpretation of this pattern was that thedetrital input was a mixture of Saharan dust, similar to that beingdeposited today on Corsica, and a local riverine sediment source.The data were imcompatible with the riverine source to the IonianSea and western Levantine basin, bein from the river Nile. Theminor variations in Sr isotopes, and metal/Al ratios in the Niledelta core was interpreted as due to changes in the proportion ofBlue Nile to White Nile inputs brought about by climaticvariations. It was calculated that the change in detrital input duringS-1 time was caused by a simultaneous increase in riverine inputand decreas in Saharan dust input.