HR: 1340h
AN: T13A-1125    [Abstracts]
TI: The Cretaceous OAE1a-Submarine Plateau Link: Additional Geochemical Evidence from Marine Sedimentary Sections
AU: * Duncan, R A
EM: rduncan@coas.oregonstate.edu
AF: College of Oceanic and Atm Sciences, Oregon State University, Corvallis, OR 97331, United States
AU: Tiraboschi, D
EM: daniele.tiraboschi@unimi.it
AF: Dipartimento di Scienze della Terra, University of Milan, Milan, 08123, Italy
AU: Erba, E
EM: elisabetta.erba@unimi.it
AF: Dipartimento di Scienze della Terra, University of Milan, Milan, 08123, Italy
AU: Walczak, P
EM: pwalczak@coas.oregonstate.edu
AF: College of Oceanic and Atm Sciences, Oregon State University, Corvallis, OR 97331, United States
AU: Clarke, L J
EM: l.clarke@bangor.ac.uk
AF: School of Ocean Sciences, University of bangor, Bangor, LL5 5AB, United Kingdom
AB: We explore the proposed link between submarine plateau volcanism associated with construction of the Ontong Java-Manihiki-Hikurangi plateau (122 Ma) and early Aptian Ocean Anoxic Event 1a (OAE1a) through biostratigraphic data and trace metal abundance anomalies in marine sedimentary sections recovered in cores from DSDP Site 167 (Magellan Rise), ODP Sites 463 and 866 (Mid-Pacific Mountains), and at the Cismon and Piobbico on-land drillsites (Belluno and Umbria-Marche Basins, Italy). Sections were correlated using bio- and magneto-stratigraphic data, and the global d13C isotope anomaly associated with OAE1a. Bulk sediment samples that bracket the OAE1a interval at each site were analyzed by ICP-MS methods. After normalizing element concentrations to Zr to remove the variable contribution of terrigenous material to these sediments, we detected an interval of concentrated metal abundance anomalies that precedes the abrupt positive climb in the d13C isotope excursion, beginning near magnetic chron M0, continuing through the organic-rich interval of anoxic conditions. The metal abundance anomalies (e.g., Sc, Cu, Co, Sn, Cr, Ni, V, Cd, Ag, Bi, Se, W, Mo, Sb, Pb up to 100x background), variable in intensity and pattern of elements, indicate that intermittent hydrothermal activity, in the form of both water/rock exchange and magmatic degassing, introduced large concentrations of trace metals into the Cretaceous ocean at the same time that turnover in plankton communities and increases in isotopically light organic carbon burial occurred. The stratigraphic position of the intervals of trace metal anomalies matches events prior, during and after OAE1a and indicates that intermittent hydrothermal activity on a massive scale triggered abrupt changes in biota, carbon burial and deep ocean oxygen contents. Calcareous nannofossil abundance and composition display major changes in biogenic paleofluxes, temperature and fertility of surface waters, coeval with metal enrichments. Thus, hydrothermal activity during plateau construction seems vital for primary productivity as well as for biocalcification. The geographical variation in abundances and patterns of trace metals is consistent with a source in the south- central Pacific.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4924 Geochemical tracers
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: 2007 Fall Meeting