A continental-weathering control on orbitally driven redox-nutrient cycling during Cretaceous Oceanic Anoxic Event 2.

Poulton, Simon W., Henkel, Susann, März, Christian, Urquhart, Hannah, Flögel, Sascha, Kasten, Sabine, Sinninghe Damsté, Jaap S. and Wagner, Thomas (2015) A continental-weathering control on orbitally driven redox-nutrient cycling during Cretaceous Oceanic Anoxic Event 2. Open Access Geology, 43 (11). pp. 963-966. DOI 10.1130/G36837.1.

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The Cretaceous period (similar to 145-65 m.y. ago) was characterized by intervals of enhanced organic carbon burial associated with increased primary production under greenhouse conditions. The global consequences of these perturbations, oceanic anoxic events (OAEs), lasted up to 1 m.y., but short-term nutrient and climatic controls on widespread anoxia are poorly understood. Here, we present a high-resolution reconstruction of oceanic redox and nutrient cycling as recorded in subtropical shelf sediments from Tarfaya, Morocco, spanning the initiation of OAE2. Iron-sulfur systematics and biomarker evidence demonstrate previously undescribed redox cyclicity on orbital time scales, from sulfidic to anoxic ferruginous (Fe-rich) water-column conditions. Bulk geochemical data and sulfur isotope modeling suggest that ferruginous conditions were not a consequence of nutrient or sulfate limitation, despite overall low sulfate concentrations in the proto-North Atlantic. Instead, fluctuations in the weathering influxes of sulfur and reactive iron, linked to a dynamic hydrological cycle, likely drove the redox cyclicity. Despite the potential for elevated phosphorus burial in association with Fe oxides under ferruginous conditions on the Tarfaya shelf, porewater sulfide generation drove extensive phosphorus recycling back to the water column, thus maintaining widespread open-ocean anoxia.

Document Type: Article
Additional Information: WOS:000364057700009 - GSA Data Repository item 2015320, methods and data, including geologic setting, model parameters and mineralogical analyses, is available online at www.geosociety.org/pubs/ft2015.htm, or on request from editing@geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
Keywords: Cretaceous, weathering, nutrient, hydrological cycle
Research affiliation: OceanRep > SFB 754 > A7
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > SFB 754
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1130/G36837.1
ISSN: 0091-7613
Projects: SFB754
Date Deposited: 27 Nov 2015 09:36
Last Modified: 23 Sep 2019 17:38
URI: http://oceanrep.geomar.de/id/eprint/30379

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