Geochemistry and stable isotope record of black shales and inoceramids from the Demerara Rise ...

• Main Authors: Jiménez Berrocosco, Álvaro, MacLeod, Kenneth G, Calvert, Stephen E, Elorza, Javier
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA 2008
• Subjects: Ocean Drilling Program ODP; North Atlantic
• Online Access: https://dx.doi.org/10.1594/pangaea.832152; https://doi.pangaea.de/10.1594/PANGAEA.832152

The bulk rock geochemistry and inoceramid isotopic composition from Cenomanian to Santonian, finely laminated, organic-rich black shales, recovered during Ocean Drilling Program Leg 207 on Demerara Rise (western tropical North Atlantic), suggest persistent anoxic (free H2S) conditions within the sediments and short-term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a ~15 Ma time interval. In addition to being organic-rich, the 50-90 m thick sections examined exhibit substantial bulk rock enrichments of Si, P, Ba, Cu, Mo, Ni, and Zn relative to World Average Shale. These observations point to high organic burial fluxes, likely driven by high primary production rates, which led to the establishment of intensely sulfidic pore waters and possibly bottom waters, as well as to the enrichments of Cr, Mo, U, and V in the sediments. At the same time, the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not ... : Supplement to: Jiménez Berrocosco, Álvaro; MacLeod, Kenneth G; Calvert, Stephen E; Elorza, Javier (2008): Bottom water anoxia, inoceramid colonization, and benthopelagic coupling during black shale deposition on Demerara Rise (Late Cretaceous western tropical North Atlantic). Paleoceanography, 23(3), PA3212 ...