Sulphidic Mediterranean surface waters during Pliocene sapropel formation

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 and increased organic-matter preservation due to oxygen depletion in more stagnant bottom...

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Bibliographic Details
Published in:Nature (London) 1999-01, Vol.397 (6715), p.146-149
Main Authors: Passier, Hilde F, Bosch, Hendrik-Jan, Nijenhuis, Ivar A, Lourens, Lucas J, Böttcher, Michael E, Leenders, Anke, Damsté, Jaap S. Sinninghe, de Lange, Gert J, Leeuw, Jan W
Format: Article
Language:English
Subjects:
Bacteria
Climate
Earth sciences
Earth, ocean, space
Exact sciences and technology
Humanities and Social Sciences
Isotope geochemistry
Isotope geochemistry. Geochronology
letter
Marine
Marine geology
multidisciplinary
Neogene
Oceans
Organic chemistry
Oxygen depletion
Pliocene
Sapropels
Science
Science (multidisciplinary)
Sediments
Sulfur
Surface water
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Summary: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 and increased organic-matter preservation due to oxygen depletion in more stagnant bottom waters,. Here we report that eastern Mediterranean Pliocene sapropels 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.
ISSN:0028-0836
1476-4687
DOI:10.1038/16441