HR: 0800h
AN: PP11B-0571    [Abstracts]
TI: Marine carbonate dissolution event across the Eocene/Oligocene boundary: the Walvis Ridge transect, South Atlantic (ODP Leg 208)
AU: * Liu, Z
EM: lzhifei@online.sh.cn
AF: Laboratory of Marine Geology, Tongji University, 1239 Siping Road, Shanghai, 200092 China
AU: Tuo, S
EM: tuosht@hotmail.com
AF: Laboratory of Marine Geology, Tongji University, 1239 Siping Road, Shanghai, 200092 China
AU: Zhao, Q
EM: qhzhaok@online.sh.cn
AF: Laboratory of Marine Geology, Tongji University, 1239 Siping Road, Shanghai, 200092 China
AU: Chen, X
EM: xrchengk@online.sh.cn
AF: Laboratory of Marine Geology, Tongji University, 1239 Siping Road, Shanghai, 200092 China
AB: Sediments recording the response of South Atlantic to global cooling and marine carbonate dissolution during the Eocene-Oligocene transition were recovered across a broad range of depths of five sites on the northeastern flank of Walvis Ridge during ODP Leg 208. Although the Eocene/Oligocene (E/O) boundary is not well preserved biostratigraphically, especially at two deepest sites (Sites 1262 and 1267), oxygen and carbon stable isotopes of benthic and/or planktonic foraminifers have determined the exact boundary position for most of sites. High-resolution carbonate content and foraminiferal grain size combined with coarse fraction and siliciclatic element geochemistry reveal that the strongest carbonate dissolution event occurred just above the E/O boundary, leading the global Earliest Oligocene Glacial Maximum (EOGM). This carbonate dissolution event may take up abundant atmospheric CO2 into the deep ocean by the calcium carbonate pump system, and then induces the global cooling during the earliest Oligocene. The recovery of the foraminiferal preservation does not appear to be immediate with rapid cooling; however, it lags behind about 500 kyr, implying that the shift in carbonate preservation was triggered by changes in climate. The carbonate dissolution event is associated with deepening of carbonate compensation depth (CCD) and falling of sea level. Moreover, the event has a close relationship with continental weathering rates indicated by element geochemistry, implying the possible carbon cycle-forced global cooling event across the E/O boundary.
DE: 4806 Carbon cycling
DE: 4835 Inorganic marine chemistry
DE: 4870 Stable isotopes
DE: 3022 Marine sediments--processes and transport
DE: 1635 Oceans (4203)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting