| Title: | Cyclic fluctuations in the composition of organic matter of OAE3 black shales (ODP Site 959, off Ivory Coast/Ghana) |
| Author: | Britta Beckmann |
| Date Submitted: | 04/30/2002 |
| Address: | Klagenfurter Strasse
Bremen
Germany
28359
|
| Phone: | +49 421 2188938 |
| Email: | bbeckman@uni-bremen.de |
| Co-Authors: | Wagner, Thomas, University of Bremen, wagner@uni-bremen.de; Hofmann, Peter, University of Cologne, adg03@uni-koeln.de; Scheeder, Georg, BGR, scheeder@bgr.de;Sinninghe Damsté, Jaap, S., NIOZ, damste@nioz.nl |
| Affiliation: | University of Bremen, Geosciences |
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| Abstract URL: | http://cis.whoi.edu/science/GG/ccod/viewAbstracts.cfm?RefNumber=19725542 |
| Keywords: | OAE3, black shale, ODP Site 959 |
| Abstract: | The importance of Cretaceous oceanic anoxic events as key mechanism for the development of large organic carbon sinks and its relationship to rapid climate changes is widely acknowledged. Our study focuses on organic and inorganic geochemical analysis of sediments accumulated during the final, Coniacian-Santonian OAE3, in the Ivory Coast basin at ODP Site 959 (off Ivory Coast/Ghana). The composition of organic matter throughout the sedimentary record at Site 959, timing of changes in its composition, and the identification of global or regional controls on the sedimentation are of special interest.
Two opposing depositional modes are supported by our data: a black shale mode with TOC content up to 16%, and a background mode with TOC concentrations of about 3%. Maceral analysis reveals an overall dominance of marine amorphous organic matter (AOM). Apart from AOM, particulate marine organic matter dominates in black shale samples resulting in oil-prone kerogen Type I. The temporal occurrence of Isorenieratane derivates, biomarkers indicative for photic zone anoxia, evidence extreme depositional conditions off Equatorial West-Africa. In contrast, sediments deposited during the background mode mainly consist of kerogen Type II/III organic matter with considerable contribution from terrigenous sources.
To identify global and/or local controls on the sedimentation at Site 959, analyses of d18O and d13C isotopes are shown and compared to carbon- and oxygen-isotope stratigraphies from England and Italy, as reported from the literature. |
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