The mystery off the sapropels

摘要

The Mediterranean Sea has an almost overwhelming amount of history, as anyone can attest who has tackled Fer-nand Braudel's great opus. But even Braudel stopped short of describing the strange and wonderful geological history of the sea, which includes a sustained period of almost total desiccation during the latest Miocene, some 7-5 million years ago, and the puzzling occurrence of sapropels (Fig. 1). Sapropels are sediment layers with high concentrations of organic carbon, and for years there has been a simmering debate over the mechanism or mechanisms that could produce them. On page 57 of this issue, Kemp et al. bring together a variety of observations from modern studies and sapropel microstructure to produce a feasible scheme of events which reconciles the apparent contradictions in the debate.