Geochemical environment of the Coniacian-Santonian western tropical Atlantic at Demerara Rise

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doi: 10.1016/j.palaeo.2008.05.004
Author(s): März, C.; Beckmann, B.; Franke, C.; Vogt, Christoph; Wagner, T.; Kasten, S.
Author Affiliation(s): Primary:
University of Bremen, Department of Geosciences, Bremen, Federal Republic of Germany
Universita di Modena e Reggio Emilia, Italy
Newcastle University, United Kingdom
University of Michigan, United States
University of Cologne, Federal Republic of Germany
Alfred Wegener Institute for Polar and Marine Research, Federal Republic of Germany
Volume Title: Organic-carbon-rich sediments through the Phanerozoic; processes, progress, and perspectives
Volume Author(s): Negri, Alessandra, editor; Ferretti, A.; Wagner, T.; Meyers, P. A.
Source: Organic-carbon-rich sediments through the Phanerozoic; processes, progress, and perspectives, edited by Alessandra Negri, A. Ferretti, T. Wagner and P. A. Meyers. Palaeogeography, Palaeoclimatology, Palaeoecology, 273(3-4), p.286-301. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 107 refs.; illus., incl. 2 tables, sketch map
Summary: Organic carbon-rich shales deposited during the Coniacian-Santonian Oceanic Anoxic Event 3 were drilled during ODP Leg 207 at Demerara Rise. We present integrated high-resolution geochemical records of core intervals from ODP Sites 1259 and 1261 both from nannofossil biozone CC14. Our results reveal systematic variations in marine and detrital sediment contribution, depositional processes, and bottom water redox conditions during black shale formation at two locations on Demerara Rise in different paleo-water depths. A combination of redox proxies (Fe/S, P/Al, C/P, redox-sensitive/sulfide-forming trace metals Mn, Cd, Mo, Ni, V, Zn) and other analytical approaches (bulk sediment composition, P speciation, electron microscopy, X-ray diffraction) evidence anoxic to sulfidic bottom water and sediment conditions throughout the deposition of black shale. These extreme redox conditions persisted and were periodically punctuated by short-termed periods with less reducing bottom waters irrespective of paleo-water depth. Sediment supply at both sites was generally dominated by marine material (carbonate, organic matter, opal) although relationships of detrital proxies as well as glauconitic horizons support some influence of turbidites, winnowing bottom currents and/or variable detritus sources, along with less reducing bottom water at the proposed shallower location (ODP Site 1259). At Site 1261, located at greater paleo-depth, redox fluctuations were more regular, and steady hemipelagic sedimentation sustained the development of mostly undisturbed lamination in the sedimentary record. Strong similarities of the studied deposits exist with the stratigraphic older Cenomanian-Turonian OAE2 black shale sections at Demerara Rise, suggesting that the primary mechanisms controlling continental supply and ocean redox state were time-invariant and kept the western equatorial Atlantic margin widely anoxic over millions of years. Abstract Copyright (2009) Elsevier, B.V.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Anaerobic environment; Atlantic Ocean; Black shale; Cadmium; Clastic rocks; Coniacian; Correlation; Cretaceous; Demerara Rise; Detritus; Eh; Enrichment; Equatorial Atlantic; Experimental studies; Geochemistry; High-resolution methods; Iron; Laminations; Leg 207; Manganese; Marine environment; Mesozoic; Metals; Molybdenum; Nickel; North Atlantic; Northwest Atlantic; OAE 3; ODP Site 1259; ODP Site 1261; Ocean Drilling Program; Oceanic anoxic events; Organic compounds; Paleo-oceanography; Phosphorus; Planar bedding structures; SEM data; Santonian; Sediment supply; Sedimentary rocks; Sedimentary structures; Senonian; Sequential extraction; Terrigenous materials; Time factor; Total organic carbon; Trace elements; Trace metals; Tropical environment; Turbidite; Upper Cretaceous; Vanadium; West Atlantic; X-ray diffraction data; Zinc
Coordinates: N090300 N090300 W0541900 W0541900
N091800 N091800 W0541200 W0541200
Record ID: 2009046705
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands