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

Abstract

The provenance of sediments to the Ionian Sea and western Levantine basin during S-1 sapropel times was studied using 87 Sr/ 86 Sr isotopic ratios together with major elements. Measurements were made on sediment profiles from 5 box cores in the Eastern Mediterranean, on Saharan dust and on a core from the Nile delta which included sediment deposited during S-1 sapropel times. In the sediment profiles, there was a decrease in 87 Sr/ 86 Sr ratio, 1/Sr, Ti/Al, Mg/Al and Si/Al ratio starting at the upper Mn peak and finishing at the base of the organic-rich layer. This showed that there was a major change in the nature of the detrital input during S-1 sapropel times. The timing of the change in detrital input was similar to the change in surface salinity as measured by δ 18 O . There was linear relationship between 87 Sr/ 86 Sr and 1/Sr and for 87 Sr/ 86 Sr and Ti/Al for all the sediment samples. The favoured interpretation of this pattern was that the detrital input was a mixture of Saharan dust, similar to that being deposited today on Corsica, and a local riverine sediment source. The data were incompatible with the riverine source to the Ionian Sea and western Levantine basin, being from the river Nile. The minor variations in Sr isotopes, and metal/Al ratios in the Nile delta core was interpreted as due to changes in the proportion of Blue Nile to White Nile inputs brought about by climatic variations. It was calculated that the change in detrital input during S-1 time was caused by a simultaneous increase in riverine input and decrease in Saharan dust input.