HR: 0800h
AN: PP51F-1375    [Abstracts]
TI: the Pliocene Evolution of E-Pacific and Caribbean SST Reveals the Final Phase of the Closure of the Panamanian Gateway.
AU: * Groeneveld, J
EM: jgroeneveld@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischofstrasse 1-3, Kiel, 24148 Germany
AU: Steph, S
EM: ssteph@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischofstrasse 1-3, Kiel, 24148 Germany
AU: Tiedemann, R
EM: rtiedemann@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischofstrasse 1-3, Kiel, 24148 Germany
AU: Nuernberg, D
EM: dnuernberg@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischofstrasse 1-3, Kiel, 24148 Germany
AB: We used samples from ODP Sites 999 ($12\deg$44N, $78\deg$44W, 2828m waterdepth) and 1241($5\deg$50N, $86\deg$26W, 2027m waterdepth) to investigate the development of the sea surface temperature (SST) gradient between the East-Pacific and the Caribbean for the Pliocene interval 2.2-4.8 Ma. For Site 1241 we constructed new benthic and planktonic $\delta$$^{18}$O-records. The benthic $\delta$$^{18}$O-record was used to construct an orbitally tuned age model to which the age model of Site 999 was tuned. SST was determined by applying Mg/Ca-analyses on the planktic foraminifer Globigerinoides sacculifer. The spatial resolution for the SST-records averages 5 kyr, for the $\delta$$^{18}$O-records 3 kyr. An open gateway, permitting the throughflow of water from the Pacific into the Caribbean, leads to equal SSTs on both sides of the Isthmus. When the gateway reached the final phase of the closure, the Caribbean started to warm up and the E-Pacific cooled down, resulting in an increasing SST-gradient (E-Pacific-Caribbean SST difference). Before 4.6 Ma the Caribbean was slightly warmer than the E-Pacific by about $1\deg$C, suggesting the inflow of Pacific water into the Caribbean. After 4.6 Ma, average SST at Site 999 decreased by about $2\deg$C, while at Site 1241 average SST remained the same. This implies that no longer the same watermass is bathing both Sites, suggesting a cooler watermass, probably originating from the Peru-Chile Current, to penetrate into the Caribbean. The final phase of the closure is indicated by a change in Caribbean-Pacific SST relationships. Positively correlated SST fluctuations persisted from 4.8Ma until about 3.2Ma, before larger-scale sea level fluctuations became important in response to the amplification of the northern hemisphere glaciation. After about 3.2Ma, glacial stages (indicative of sea level low-stand) are associated with Pacific minima in SST (Site 1241) and maxima in Caribbean SST (Site 999). Thus, the cessation of the throughflow during glacials terminated the imprint of cooler Pacific surface waters in the Caribbean and allowed Caribbean temperatures to increase. This documents the final phase of the closure of the Central American Isthmus, when sea level fluctuations on the order of 50-70 m start to control the Pacific water inflow into the Caribbean.
DE: 9355 Pacific Ocean
DE: 9360 South America
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1520 Magnetostratigraphy
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting