HR: 09:30h
AN: B31E-07    [Abstracts]
TI: Stable Isotopic Results Across the Permian /Triassic Boundary in the Karoo of South Africa: Evidence for both Gradual and Abrupt Extinctions
AU: * Ward, P D
EM: argo@u.washington.edu
AF: University of Washington, Department of Earth and Space Sciences, Seattle, 98195
AU: Garrison, G
EM: Garrison@ESS.Washington.edu
AF: University of Washington, Department of Earth and Space Sciences, Seattle, 98195
AB: We have sampled for stable isotopes from paleontologically constrained stratigraphic sections in the southern and central Karoo basin of South Africa, which contains the most abundantly fossiliferous succession of late Permian to middle Triassic terrestrial vertebrates yet described. Over a narrow stratigraphic interval at the end of the Permian in this region, we have found a light carbon isotope anomaly (Ccarb) and succession of negative anomalies (Corg) coincident with, and right after an enhanced pulse of extinction among terrestrial vertebrates. While it is clear that a short interval of intense environmental change occurred over our sampled interval, there is no evidence of impact debris or characteristic boundary sedimentology equivalent to that observed in similar terrestrial facies at numerous Cretaceous/Paleogene boundaries. Our isotopic and paleontological data also show marked dissimilarity to similar data from terrestrial K/P sites. The Permian/Triassic succession in South Africa is thus inconsistent with the K/P model of single-impact mass extinction, and to date shows no evidence of impact of any size.
DE: 6006 Atmospheres--evolution
DE: 1040 Isotopic composition/chemistry
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting