HR: 0800h
AN: PP51B-0586    [Abstracts]
TI: Geochemical Support for Insolation Linked Nannofossil Productivity Changes During the Mid-Pliocene
AU: * Waite, A J
EM: awaite@rsmas.miami.edu
AF: University of Delaware, College of Marine Studies, 700 Pilottown Road, Lewes, DE 19958 United States
AU: Diester-Haass, L
EM: l.haass@mx.uni-saarland.de
AF: Universitaet des Saarlandes, Zentrum fur Umweltforschung, Saarbruecken, 66041 Germany
AU: Gibbs, S J
EM: sxg@noc.soton.ac.uk
AF: National Oceanographic Centre, University of Southampton, Southampton, SO14 3ZH United Kingdom
AU: Rickaby, R
EM: Rosalind.Rickaby@earth.ox.ac.uk
AF: Oxford University, Department of Earth Sciences, Parks Road, Oxford, OX1 3PR United Kingdom
AU: Billups, K
EM: kbillups@udel.edu
AF: University of Delaware, College of Marine Studies, 700 Pilottown Road, Lewes, DE 19958 United States
AB: Recent studies have linked the ratio of strontium to calcium (Sr/Ca) in coccolith carbonate to the growth rate and productivity of the coccolithophorid marine algae, though not all of the factors controlling the geochemical signature in this nannofossil carbonate are well defined. We set out to investigate species effects on nannofossil Sr/Ca by constructing Sr/Ca records from size fractioned nannofossils which parallel mid-Pliocene abundance counts from sediments at Ceara Rise ODP Site 926 (Gibbs et al., 2004). Our results show that coarse fraction (8.0 to 20.0 microns) nannofossil Sr/Ca varies in a manner similar to Northern Hemisphere insolation. Specifically, Sr/Ca is high when insolation is high and vice versa. Gibbs et al. (2004) found that abundances of the nannofossil genera, Discoaster, Sphenolithus and Florisphaera, also varied with Northern Hemisphere insolation suggesting an environmental (precession related) control on their productivity. Assuming that Sr/Ca in our coarse fraction is predominantly driven by variability in these genera, and in particular Discoaster which is typically larger than 8.0 microns and abundant throughout the interval, the coincidence of Sr/Ca maxima with maximum abundance would be consistent with studies that have shown an increase in nannofossil Sr/Ca with growth and calcification rates. This idea is being tested by the comparison of nannofossil abundances in the size-fractionated samples used for geochemical analyses with bulk carbonate nannofossil abundances from Gibbs et al. (2004).
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 3030 Micropaleontology (0459, 4944)
DE: 4825 Geochemistry
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4934 Insolation forcing
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005