HR: 1340h
AN: B33C-0273    [Abstracts]
TI: Repeated Carbon-Cycle Disturbances at the Permian-Triassic Boundary Separate two Mass Extinctions
AU: Nicol, J A
EM: nicolj@mcmaster.ca
AF: University of Sydney, School of Geosciences, Sydney, NSW 2006 Australia
AU: Watson, L
EM: bibber@hotmail.com
AF: University of Sydney, School of Geosciences, Sydney, NSW 2006 Australia
AU: Claire, M
EM: mclaire@astro.washington.edu
AF: University of Washington, Dept. Astronomy, Seattle, WA 98195 United States
AU: * Buick, R
EM: buick@ess.washington.edu
AF: University of Washington, Dept. Earth & Space Science, Seattle, WA 98195-1310 United States
AU: Catling, D C
EM: davidc@atmos.washington.edu
AF: University of Washington, Dept. Atmospheric Sciences, Seattle, WA 98195 United States
AB: Non-marine organic matter in Permian-Triassic sediments from the Blue Mountains, eastern Australia shows seven negative δ13C excursions of up to 7%, terminating with a positive excursion of 4%. Fluctuations start at the late Permian Glossopteris floral extinction and continue until just above the palynological Permian-Triassic boundary, correlated with the peak of marine mass extinction. The isotopic fluctuations are not linked to changes in depositional setting, kerogen composition or plant community, so they evidently resulted from global perturbations in atmospheric δ13C and/or CO2. The pattern was not produced by a single catastrophe such as a meteorite impact, and carbon-cycle calculations indicate that gas release during flood-basalt volcanism was insufficient. Methane-hydrate melting can generate a single -7% shift, but cannot produce rapid multiple excursions without repeated reservoir regeneration and release. However, the data are consistent with repeated overturning of a stratified ocean, expelling toxic gases that promoted sequential mass extinctions in the terrestrial and marine realms.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting