Provenance of lithogenic surface sediments and pathways of riverine suspended matter in the Eastern Mediterranean Sea: evidence from 143Nd/ 144Nd and 87Sr/ 86Sr ratios

Abstract

In order to characterize the provenance of lithogenic surface sediments from the Eastern Mediterranean Sea (EMS), residual (leached) fraction of 34 surface samples have been analysed for their 143Nd/ 144Nd and 87Sr/ 86Sr isotope ratios. The sample locations bracket all important entrances of riverine suspended matter into the EMS as well as all sub-basins of the EMS. The combined analyses of these two isotope ratios provide a precise characterization of the lithogenic fraction of surface sediments and record their dilution towards the central sub-basins. We reconstruct provenance and possible pathways of riverine dispersal and current redistribution, assuming more or less homogenous isotopic signatures and flux rates of the eolian fraction over the EMS. Lithogenic sediments entering the Ionian Sea from the Calabrian Arc and the Adriatic Sea are characterized by high 87Sr/ 86Sr isotope ratios and low ε Nd(0) values (average 87Sr/ 86Sr=0.718005 and ε Nd(0)=−11.06, n=5). Aegean Sea terrigenous sediments show an average ratio of 87Sr/ 86Sr=0.713089 ( n=5) and values of ε Nd(0)=−7.89 ( n=5). The Aegean isotopic signature is traceable up to the southwest, south, and southeast of Crete. The sediment loads entering the EMS via the Aegean Sea are low and spread out mainly through the Strait of Casos (east of Crete). Surface sediments from the eastern Levantine Basin are marked by the highest ε Nd(0) values (−3.3, n=6) and lowest 87Sr/ 86Sr isotope ratios (average 0.709541, n=6), reflecting the predominant input of the Nile sediment. The influence of the Nile sediment is traceable up to the NE-trending, eastern flank of the Mediterranean Ridge. The characterization of the modern riverine dispersal and eolian flux, based on isotope data, may serve as a tool to reconstruct climate-coupled variations of lithogenic sediment input into the EMS.