Shipboard analysis was carried out on the free biomarker fraction of total lipid extracts of 10 Cretaceous black shale samples from Sites 1257 and 1258. The principal aim of the investigation was to study the primary biological sources and the thermal maturity of the organic matter in the core samples as well as the conditions of its preservation. The samples have total organic carbon contents of 4.5–28 wt%. Molecular analysis of biomarkers focused on n-alkane, sterane, and pentacyclic triterpane biomarkers. The organic matter in the black shales is thermally immature and dominantly derived from algal and microbial sources with varying contributions of higher plant material. Sulfur incorporation into organic matter is evident from the abundance of hopanoid thiophenes and isorenieratane thianes. High yields of lycopane relative to n-C35 indicate that the preservation of organic matter is excellent, which is consistent with deposition under oxygen-depleted conditions in the background of low sedimentation rates.
1Forster, A., Sturt, H., Meyers, P.A., and the Leg 207 Shipboard Scientific Party, 2004. Molecular biogeochemistry of Cretaceous black shales from the Demerara Rise: preliminary shipboard results from Sites 1257 and 1258, Leg 207. In Erbacher, J., Mosher, D.C., Malone, M.J., et al., Proc. ODP, Init. Repts., 207 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/207_IR/chap_10/chap_10.htm>. [Cited
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2Department of Marine Geobiological and Environmental Chemistry, Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands.
forster@nioz.nl
3Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Mail #22, Woods Hole MA 02543, USA.
4Department of Geological Sciences, University of Michigan, 2534 C.C. Little Building, Ann Arbor MI 48109-1063, USA.
5Shipboard
Scientific Party addresses can be found under "Shipboard
Scientific Party" in the preliminary pages of the volume.
Ms 207IR-110