3. THE SAPROPEL THEME OF LEG 1601Kay-Christian Emeis2 and Tatsuhiko Sakamoto3 |
ABSTRACTResearch on sediments recovered during Ocean Drilling Program Leg 160 has concentrated on two issues: 1) the stratigraphy of sapropel formation, and 2) the clarification of specific processes that explain sapropel origin. Progress has been made in the construction of stratigraphic composites out of sedimentary sequences from individual holes at each of the paleoceanographic sites. On the composites, initial work has resulted in the establishment of high-resolution and intermediate-resolution stratigraphies for three sites (Sites 963, 964, 967); correlation of sedimentary cycles to astronomical (insolation) cycles extends the stratigraphies to Sites 969 and 966. The sapropel occurrences in the marine and land sequences over the entire Eastern Mediterranean are correlatable; with the resolution that can be obtained from isotope studies, groups of sapropels occurred simultaneously over the entire basin. In detail, however, the temporal and facies patterns of sapropel sequences differ between individual sites and depositional basins. The differences may be related to effects of water depth, diagenesis, and postdepositional tectonic attenuation of sequences. Studies on the geochemistry and facies of sapropels agree that anoxic conditions favored preservation of organic matter in sapropels, caused the enrichment of trace metals associated with sapropels, and helped preserve primary sedimentary structures. All evidence is consistent with elevated flux of organic matter and associated elements during sapropel events. |
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