HR: 0800h
AN: PP51B-1340    [Abstracts]
TI: Top Down and Bottom up: A Comparison of Coccolith Sr/Ca Ratios and Benthic Foraminiferal Accumulation Rates as Indicators of Paleoproductivity
AU: * Waite, A
EM: awaite@udel.edu
AF: University of Delaware, College of Marine Studies 700 Pilottown Road, Lewes, DE 19958 United States
AU: Billups, K
EM: kbillups@udel.edu
AF: University of Delaware, College of Marine Studies 700 Pilottown Road, Lewes, DE 19958 United States
AU: Diester-Haass, L
EM: 0684167360-0001@t-online.de
AF: Universitaet des Saarlandes, Zentrum fur Umweltforschung, Saarbruecken, 66041 Germany
AU: Gibbs, S
EM: sgibbs@geosc.psu.edu
AF: Pennsylvania State University, Dept of Geosciences, University Park, PA 16802 United States
AU: Rickaby, R
EM: Rosalind.Rickaby@earth.ox.ac.uk
AF: Oxford University, Dept of Earth Sciences, Oxford, OX1 3PR United Kingdom
AU: Stoll, H
EM: Heather.M.Stoll@williams.edu
AF: Williams College, Dept of Geosciences, Williamstown, MA 01267 United States
AB: Recent studies have linked coccolith Sr/Ca ratios to the growth rate of the coccolithophorid algae (Stoll and Schrag, 2000). While this link implies a correlation between coccolith Sr/Ca ratios and primary productivity, application of this proxy has not yet been fully tested against other paleoproductivity indicators. Here we compare down-core measurements of coccolith Sr/Ca ratios to down-core changes in benthic foraminiferal accumulation rates (BFAR), a proxy for export production, from two Ocean Drilling Program sites in the Atlantic (western tropical Atlantic Site 925 and subpolar North Atlantic Site 982). The sediments used for this analysis span the late Miocene through early Pliocene (9-3 Ma), which was chosen for its significance as a period marked by a massive "biogenic bloom". Although not synchronous, increases in paleoproductivity are apparent in both BFAR records (Diester-Haass et al., submitted). Our preliminary Sr/Ca record from Site 982, which is based on a single coccolith size fraction, shows that the overall long-term trend is matched and that there are a number of synchronous maxima and minima. Statistical analysis confirms a significant correlation between coccolith Sr/Ca ratios and BFAR at this site. Our preliminary interpretations demonstrate that a relationship exists between coccolith Sr/Ca and BFAR, supporting our understanding of the proxies as paleoproductivity indicators. Further work includes a separation of discrete coccolith size fractions and down-core monitoring of species assemblages to better constrain the potential effects of nannofossil species assemblage changes on coccolith Sr/Ca ratios.
DE: 4825 Geochemistry
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting