2008 Joint Annual Meeting (5-9 Oct. 2008): Smithian-Spathian Boundary: The Biggest Crisis in Triassic Conodont History
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318-3 Smithian-Spathian Boundary: The Biggest Crisis in Triassic Conodont History



Wednesday, 8 October 2008: 2:00 PM
George R. Brown Convention Center, 320DE
Nicolas Goudemand1, Mike Orchard2, Hugo Bucher3, Arnaud Brayard4, Thomas Brühwiler1, Thomas Galfetti1, Peter A. Hochuli3, Elke Hermann1 and David Ware1, (1)Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, Zurich, 8006, Switzerland
(2)Geological Survey of Canada, Vancouver, BC V6B5J3, Canada
(3)Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, Department of Earth Sciences, ETH Zürich, Zurich, 8006, Switzerland
(4)LMTG, UMR 5563 CNRS, Université Toulouse IRD, Observatoire Midi-Pyrénées, 14 Avenue Edouard Belin, Toulouse, 31400, France
Ongoing work in California, S-China, Tibet, Pakistan and Oman has led to a refined biochronologic subdivision of the late Early Triassic and allows reconstructing a high resolution diversity time series, partly constrained by new U-Pb ages from S-China [1-2].

Conodonts crossed the PTB without major changes [3]. In the Early Triassic the first major conodont faunal turnover occurred during the late Griesbachian - early Dienerian, with the disappearance of Anchignathodontids (Hindeodus-Isarcicella group), which were replaced by the emergent Neospathodus and Borinella? species.

In the earliest Smithian, conodonts experienced a dramatic radiation, which ended in a major extinction during the late Smithian. This extinction was the most severe of the entire Triassic in terms of generic diversity and multi-element apparatuses. In the early Spathian conodonts radiated again explosively and gradually declined during late Spathian times.

These global diversity patterns coincide with large perturbations of the global carbon cycle [4-7]. As indicated by changes in the latitudinal gradient of generic richness of ammonoids [8], the boreal palynological record [6], and a prominent positive δ13C-isotope shift, the late Smithian - early Spathian boundary interval is marked by a severe climatic change.

[1] Galfetti, T. et al. 2007a: EPSL 258.

[2] Ovtcharova, M. et al. 2006: EPSL 243.

[3] Orchard, M. 2007: PPP 252.

[4] Brühwiler, T. et al. 2007b: SGM Geneva.

[5] Galfetti, T. et al. 2007b: PPP 243.

[6] Galfetti, T. et al. 2007c: Geology 35.

[7] Payne, J. et al. 2004: Science 5683.

[8] Brayard, A. et al. 2006: PPP 239.

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