Cooling Cycles Linked to Carbon Isotopic Shifts During the Early Aptian Oceanic Anoxic Event

HR: 0800h
AN: PP51B-0598 [Abstracts]
TI: Cooling Cycles Linked to Carbon Isotopic Shifts During the Early Aptian Oceanic Anoxic Event
AU: * Dumitrescu, M
EM: mdumitre@indiana.edu
AF: Biogeochemical Laboratories, Department of Geological Sciences, Indiana University, 1001 E 10th Street, Bloomington, IN 47405 United States
AU: Brassell, S C
EM: simon@indiana.edu
AF: Biogeochemical Laboratories, Department of Geological Sciences, Indiana University, 1001 E 10th Street, Bloomington, IN 47405 United States
AU: Schouten, S
EM: schouten@nioz.nl
AF: Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, PO Box 59, Den Burg, Texel, 1790 AB Netherlands
AU: Hopmans, E C
EM: hopmans@nioz.nl
AF: Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, PO Box 59, Den Burg, Texel, 1790 AB Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, PO Box 59, Den Burg, Texel, 1790 AB Netherlands
AB: `Greenhouse' conditions in the Cretaceous were fueled by elevated atmospheric CO₂ and accompanied by perturbations of the global carbon cycle described as `oceanic anoxic events' (OAE). Geological and geochemical evidence from high latitudes suggests that cooler intervals occurred during the Early Cretaceous, but their duration and influence at low latitudes is unknown. Here tropical sea surface temperatures varying between 30 and 36°C are recorded by the TEX₈₆ paleothermometer in a sequence of organic-rich, Lower Aptian sediments deposited in the tropical Pacific during the first Cretaceous OAE (OAE 1a). The lower values occur within discrete cooler intervals that coincide with positive excursions in δ¹³C of organic matter reflecting changes in carbon cycling induced by enhanced carbon burial. Stratigraphic constraints suggest that the cooler intervals occur on cycles of ~83-135 kyr, timescales that are consistent with orbital forcing. Temperatures during the Early Aptian cooling interludes are comparable with those in the modern equatorial Pacific sustained by polar ice, suggesting that glaciation episodes and concomitant changes in deep-water circulation and ocean productivity may all be integral to OAE 1a.
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4926 Glacial
DE: 4946 Milankovitch theory
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005