HR: 0800h
AN: PP51B-1333    [Abstracts]
TI: The Late Miocene Carbon Isotope Shift and Marine Biological Productivity.
AU: * Diester-Haass, L
EM: l.haass@mx.uni-saarland.de
AF: Universitaet des Saarlandes, Zentrum fuer Uweltforschung, Saarbruecken, 66041 Germany
AU: Billups, K
EM: kbillups@UDel.Edu
AF: University of Delaware, 700 Pilottown Road, Lewes, DE 19958 United States
AU: Emeis, K C
EM: emeis@geowiss.uni-hamburg.de
AF: Universitaet Hamburg, Institut fuer Biogeochemie und Meereschemie, Hamburg, 20146 Germany
AB: The late Miocene global carbon isotope shift of approximately 1 per mil is not well understood. Is it linked to ocean-related processes such as the AŸA›A›ƒ_sAªA.ƒ_oBiologic BloomAŸA›A›ƒ_sAª \(Farrell et al., 1995\), or to changes in type \(C3/C4 plants\) or cover of terrestrial vegetation? Here we examine the evolution of marine biological productivity during the isotope shift at ODP Site 846 \(Pacific equatorial upwelling, where the AŸA›A›ƒ_sAªA.ƒ_oBiologic BloomAŸA›A›ƒ_sAª has been first described, Farrell al, 1995\) and at Indian Ocean Site 721 \(monsoon-driven upwelling\), and compare their productivity history with non upwelling locations in the Atlantic Ocean. The onset of the carbon isotope shift is accompanied at all locations by an increase in paleoproductivity derived from benthic foraminiferal accumulation rates \(expressed as gC/cm2 * ky; Huerguera, 2000\) and increased abundance of Uvigerina spp.. At the equatorial upwelling sites the increase is comparable to half present-day values to present-day values; in the Atlantic Ocean paleoproductivity increases from present-day up to 3 times present-day values. But the productivity maxima are not concurrent. The carbon isotope shift is accompanied by severe carbonate dissolution and reduced ventilation of bottom waters, as reflected in the occurrence of pyrite and good preservation of cartilageous fish debris. Carbonate preservation is good since about 6 Ma despite high productivity. We discuss changing deep water circulation patterns, increased weathering and continental nutrient delivery, as well as erosion of terrestrial vegetation as possible factors to explain our findings.
DE: 9604 Cenozoic
DE: 4267 Paleoceanography
DE: 4279 Upwelling and convergences
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting