Paleoclimate and paleoceanography over the past 20,000 yr in the Mediterranean Sea Basins as indicated by sediment elemental proxies

Marine sediments record paleoenvironmental changes over time through variations in major and trace element concentrations. The main objective of this paper is to review such changes in the Mediterranean Sea basins over the last 20 ka, using the inorganic chemistry and mineralogy of marine sediment records. Elemental ratio proxies that are mostly used are discussed, and the uncertainties involved in using them for paleoclimate and paleoceanographic reconstructions are evaluated. The focus on the Mediterranean region is based on the sensitivity of this region to global climate changes due to its semi-enclosed nature. The elemental ratios that have been particularly useful for reconstructing terrigenous inputs into the Mediterranean have been Ti/Al and Zr/Al ratios as proxies for eolian dust input, and Mg/Al, K/Al and Rb/Al ratios as proxies for fluvial input. Redox sensitive elements (e.g., U, Mo, V, Co, Ni, Cr) have provided reliable reconstructions of oxygen conditions at the time of deposition. Some of these elements are also particularly susceptible to post-depositional remobilization and record diagenetic processes instead of the original environmental signatures. Regarding productivity fluctuations, most of the paleoproductivity reconstructions are based on the abundance of barite and Ba excess algorithms. The biogeochemistry of Ba is, however, not fully understood and mechanisms for barite precipitation in the water column are not yet known. Two case studies are presented: the eastern Mediterranean sapropel Si (deposited between 10.8 and 6.1 cal ka BP) and the westernmost Mediterranean paleoclimate record over the last 20 ka. (C) 2014 Elsevier Ltd. All rights reserved.