17. PALEOGENE OXYGEN ISOTOPE RECORD FOR DEEP SEA DRILLING SITES 511 AND 512, SUBANTARCTIC SOUTH ATLANTIC OCEAN: PALEOTEMPERATURES, PALEOCEANOGRAPHIC CHANGES, AND THE EOCENE/OLIGOCENE

• Main Author: Boundary Event
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ewing; Falkland Plateau; Maurice; Maurice Ewing Bank; Southern Ocean; South Atlantic Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.568.2385; http://www.deepseadrilling.org/71/volume/dsdp71pt1_17.pdf

An Eocene-Oligocene oxygen and carbon isotope history based on planktonic and benthic foraminifers from Deep Sea Drilling Project Leg 71 cores has been constructed for the Maurice Ewing Bank of the eastern Falkland Plateau, Southwest Atlantic Ocean. Specifically, the cores cover portions of the middle Eocene, upper Eocene, and lower Oligo-cene. Surface water isotopic temperatures postulated for the middle Eocene at Site 512 fluctuated within about four degrees but generally averaged about 9°C. Bottom isotopic temperatures at Site 512 (water depth, 1846 m) were gener-ally a degree lower than surface water temperatures. Surface water isotopic temperatures at Site 511 initially averaged about 11 °C during the late Eocene, but dropped to an average of 7°C in the early Oligocene. Bottom isotopic temperatures at Site 511 (water depth, 2589 m) generally rec-ord temperatures between 12.5°C and 8°C, similar to the range in the surface water isotopic temperatures. During the early Oligocene, bottom isotopic temperatures dropped sharply and averaged about 2°C (very close to present-day val-ues). Surface water temperature values also decreased to an average of about 7°C, therefore leading to a significant di-vergence between surface and bottom water isotopic temperatures during the early Oligocene. Comparisons among Southern Ocean DSDP Sites 511,512, and 277, and between these and other DSDP sites from central and northern lati-