Publication Date:
2024-01-09
Description:
Sapropels -organic-matter rich layers- are common in Neogene sediments of the eastern Mediterranean Sea. The formation of these layers has been attributed to climate-related increases in organic-matter production (Calvert et al., 1992, doi:10.1038/359223a0; Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X) and increased organic-matter preservation due to oxygen depletion in more stagnant bottom waters (Rossignol-Strick et al., 1982, doi:10.1038/295105a0; Rohling, 1994, doi:10.1016/0025-3227(94)90202-X). Here we report that eastern Mediterranean Pliocene sapropels (Emeis et al., 1996, doi:10.2973/odp.proc.ir.160.102.1996) contain molecular fossils of a compound (isorenieratene) known to be synthesized by photosynthetic green sulphur bacteria, suggesting that sulphidic (euxinic) -and therefore anoxic- conditions prevailed in the photic zone of the water column. These sapropels also have a high trace-metal content, which is probably due to the efficient scavenging of these metals by precipitating sulphides in a euxinic water column. The abundance and sulphur-isotope composition of pyrite are consistent with iron sulphide formation in the water column. We conclude that basin-wide water-column euxinia occurred over substantial periods during Pliocene sapropel formation in the eastern Mediterranean Sea, and that the ultimate degradation of the increased organic-matter production was strongly influential in generating and sustaining the euxinic conditions.
Keywords:
160-964D; 160-964E; 160-966C; 160-967C; 160-969E; Accumulation rate, total organic carbon; AGE; Barium; Cadmium; Carbon, organic, total; Code; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Eastern Basin; Enrichment factor; Event label; Isorenieratene derivative; Joides Resolution; Leg160; Molybdenum; Nickel; Ocean Drilling Program; ODP; Sample code/label; Selenium; Sulfur of pyrite; Vanadium; δ34S, pyrite
Type:
Dataset
Format:
text/tab-separated-values, 145 data points
Permalink
