Orbital and suborbital variability in Coccolithophore assemblages in the eastern tropical and equatorial Pacific Ocean (7冷 to17刨) for the last 500 ka (ODP Leg 202)

HR: 0800h
AN: PP51F-1377 [Abstracts]
TI: Orbital and suborbital variability in Coccolithophore assemblages in the eastern tropical and equatorial Pacific Ocean (7冷 to17刨) for the last 500 ka (ODP Leg 202)
AU: * Flores, J
EM: flores@usal.es
AF: Universidad de Salamanca, Departamento de Geolog｛, Salamanca, 37008 Spain
AU: Alvarez, M
AF: Universidad de Salamanca, Departamento de Geolog｛, Salamanca, 37008 Spain
AU: Lopez-Otalvaro, G E
AF: Universidad de Salamanca, Departamento de Geolog｛, Salamanca, 37008 Spain
AU: Sierro, F J
AF: Universidad de Salamanca, Departamento de Geolog｛, Salamanca, 37008 Spain
AU: Shipboard Scientific Party, O
AF: ODP, ODP, x, x United States
AB: Ocean Drilling Program Leg 202 covered a South-North transect in the eastern Pacific Ocean, providing excellent material to reconstruct variations in surface and subsurface water dynamics in selected time-slices. The main goal here is to investigate the evolution of coastal and equatorial upwelling systems and their relationship to global and/or regional climate processes such as El Nino or related features. Based on a preliminary age-model using calcareous nannofossil-calibrated datums, a quantitative analysis in the Coccolithophore assemblages was carried out to investigate orbital variations in surface water dynamics during the last 500 kys. Here we present data from four ODP sites: Site 1237 situated in the west South America upwelling system; Sites 1240 and 1241 in the equatorial Pacific upwelling system, and Site 1242 close to the Costa Rica margin. The ratio between the shallow and deep coccolithophore dwellers is used to reconstruct fluctuations in the nutricline/thermocline position, and consequently, monitor variations in the upwelled waters. Our preliminary results show a orbital periodicity (ca. 100, ca. 40 and ca. 20 ka periodicity), together with an obvious millennial signal in the above mentioned proxy. Moreover, other well-defined patterns are overprinted in all sites, allowing us to differentiate three intervals without a clear orbital relationship. Periods of well defined upwelling alternate with other intervals where surface and subsurface waters appear better stratified. This model seems to respond to regional and almost synchronous variations linked to variations in like-El Nino-La Nina periods of orbital range.
DE: 3344 Paleoclimatology
DE: 3030 Micropaleontology
DE: 1635 Oceans (4203)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting