The sapropel record of the eastern Mediterranean Sea - results of Ocean Drilling Program Leg 160

Research on sediments recovered during Ocean Drilling Leg 160 has concentra ted on two issues: the first concerned the stratigraphy of sapropel formati on, the second was oriented to clarify specific processes that explain sapr opel origin. Progress has been made in the construction of stratigraphic co mposites out of sedimentary sequences from individual holes at each of the palaeoceanographic sites. On the composites, initial work has resulted in t he establishment of high-resolution and intermediate-resolution stratigraph ies for three sites (963, 964, 967); correlation of sedimentary cycles to a stronomical (insolation) cycles extends the stratigraphies to Sites 969 and 966. The sapropel occurrences in the marine and land sequences over the en tire Eastern Mediterranean are correlated: with the resolution that call be obtained from isotope studies, groups of sapropels occurred simultaneously over the entire basin. In detail, however, the temporal and facies pattern s of sapropel sequences differ between individual sites and depositional ba sins. The differences may be related to effects of water depth, diagenesis, and post-depositional tectonic attenuation of sequences. Studies on the ge ochemistry and facies of sapropels agree that anoxic conditions favoured pr eservation of organic matter in sapropels. caused the enrichment of trace m etals associated with sapropels, and helped to preserve primary sedimentary structures. Besides, all evidence is consistent with elevated fluxes of or ganic matter and associated elements during sapropel events. (C) 2000 Elsev ier Science B.V. All rights reserved.