The trace element budget of the eastern Mediterranean during Pliocene sapropel formation

Abstract

Geochemical data are presented from an organic-carbon-rich Pliocene sapropel (i-282) from three different Leg 160 sites (Sites 964, 967, and 969). The geochemical characteristics of this sapropelare comparable to those of previous studies, except for the very high organic carbon and trace element contents. The high organic carbon is explained by both increased productivity and improved preservation. Estimates of the trace element budget during formation of this sapropel suggest that a marine trace element source must have been most important. Other sources that contributed are river input and diagenesis; eolian input and hydrothermal activity can be disregarded. Most trace elements that weresupplied to the Eastern Mediterranean during the formation of this sapropel probably ended up in the sediment. Thus, an effective mechanism of transfer of these elements from seawater to sediment was operative. This mechanism is thought to be scavenging by organic matter and sulfides under widespread anoxic conditions. Results of analyses of Sapropel i-292 from Sites 964, 966, and 967 were similar, thus these characteristics are not unique to the i-282 sapropel.