Boettcher, Michael E.; Hetzel, Almut; Brumsack, Hans-Juergen; Schipper, Andrea (2007): Sulfur-iron-carbon geochemistry in sediments of the Demerara Rise. Texas A&M University, Ocean Drilling Program, College Station, TX, United States, In: Mosher, David C., Erbacher, Jochen, Malone, Mitchell J., Berti, Debora, Bice, Karen L., Bostock, Helen, Brumsack, Hans-Juergen, Danelian, Taniel, Forster, Astrid, Glatz, Christine, Heidersdorf, Felix, Henderiks, Jorijntje, Janecek, Thomas R., Junium, Christopher, Le Callonnec, Laurence, MacLeod, Kenneth G., Meyers, Philip A., Mutterlose, H. Joerg, Nishi, Hiroshi, Norris, Richard D., Ogg, James G., O'Regan, A. Matthew, Rea, Brice, Sexton, Philip, Sturt, Helen, Suganuma, Yusuke, Thurow, Juergen W., Wilson, Paul A., Wise, Sherwood W., Jr., Proceedings of the Ocean Drilling Program; scientific results; Demerara Rise; equatorial Cretaceous and Paleogene paleoceanographic transect, western Atlantic; covering Leg 207 of the cruises of the Drilling Vessel JOIDES Resolution; Bridgetown, Barbados, to Rio de Janeiro, Brazil; sites 1257-1261; 11 January-6 March 2003, 207, georefid:2007-087728

Abstract:
The geochemical composition of sediments (squeeze cake samples) from five drill sites (Ocean Drilling Program Sites 1257-1261) on the Demerara Rise in the tropical Atlantic was determined, with special regard to a sequence of Cretaceous black shales. Sediments were analyzed for different iron (total, pyrite, Na dithionite, and HCl leachable) and sulfur (total, pyrite, acid volatile, and organic bound) fractions, in addition to total organic carbon (TOC) and total inorganic carbon. The relative abundance of highly reactive iron (Fe (sub HR) /Fe (sub T) ) in the investigated black shale samples indicates that pyrite was formed both in the water column and the sediment. This corresponds to euxinic paleoenvironmental conditions, a situation similar to the modern deep Black Sea. This geochemical approach is independent of a possible minor contribution from ongoing sulfate reduction which is triggered by anaerobic methane oxidation above the black shale sequence. Pyrite sulfur in black shales makes up between 30% and 100% of total sulfur. In addition to fixation of sulfide with iron, organic matter (OM) acted as an important sulfur trap during early diagenesis, with organic sulfur composing between 5 and 10 atom% of TOC. The relative importance of OM sulfurization is increasing with its content.
Coverage:
West: -54.4400 East: -54.1100 North: 9.2800 South: 9.0200
Relations:
Expedition: 207
Site: 207-1257
Site: 207-1258
Site: 207-1259
Site: 207-1260
Site: 207-1261
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.207.109.2006 (c.f. for more detailed metadata)
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