Comparison of changes in ocean chemistry in the early triassic with trends in diversity and ecology

Abstract

The end-Permian mass extinction resulted in the demise of ∼90% of marine genera. Recent work on the Early Triassic using carbon isotopes, ammonoids, conodonts, and some benthic fauna shows that this supposed recovery period was almost as turbulent as the extinction itself. Carbon isotope records from China, India, and Italy portray a global signal with major perturbations at stage boundaries in the Early Triassic most likely as a result of fluctuating environmental conditions. Comparison of global cycles of extinction and radiation of ammonoids and conodonts to the global carbon signal suggests that the two are related. In order to investigate the ubiquity of the connection between the carbon signal and biological changes, the benthic diversity and ecological structure of the western USA was examined. Instead of the fluctuating patterns that were expected, evidence for gradual increases in both taxonomic and guild diversity was found. The lack of evenness in the recovery suggests ecological stagnation; dominance of a few genera and a few life habits. The prolonged benthic recovery, and trends of pelagic boom and bust, both point to environmental instability in the Early Triassic as the probable cause for the protraction of the biotic crisis.

Keywords

Early Triassic / carbon isotope / benthic / volcanism / ammonoid / conodont

References

[1] Bottjer D. J., Clapham M. E., Fraiser M. L., . Understanding Mechanisms for the End-Permian Mass Extinction and the Protracted Early Triassic Aftermath and Recovery. GSA Today, 2008, 18(9): 4-10.

[2] Brayard A., Escarguel G., Bucher H., . Good Genes and Good Luck: Ammonoid Diversity and the End-Permian Mass Extinction. Science, 2009, 325: 1118-1121.

[3] Brühwiler T., Bucher H., Brayard A., . Smithian Ammonoids: The First Diversity Peak in Ammonoid Recovery Following the Permian-Triassic Mass Extinction. Geological Society of America, Abstracts with Programs, 2008, 40 507

[4] Galfetti T., Bucher H., Ovtcharova M., . Timing of the Early Triassic Carbon Cycle Perturbations Inferred from New U-Pb Ages and Ammonoid Biochronozones. Earth and Planetary Science Letters, 2007, 258: 593-604.

[5] Korte C., Kozur H., Bruckschen P., . Strontium Isotope Evolution of Late Permian and Triassic Seawater. Geochimica et Cosmochimica Acta, 2003, 67(1): 47-62.

[6] Payne J. L., Kump L. R.. Evidence for Recurrent Early Triassic Massive Volcanism from Quantitative Interpretation of Carbon Isotope Fluctuations. Earth and Planetary Science Letters, 2007, 256: 264-277.

[7] Payne J. L., Lehrmann D. J., Wei J., . Large Perturbations of the Carbon Cycle during Recovery from the End-Permian Extinction. Science, 2004, 305: 506-509.

[8] Posenato R.. Global Correlations of Mid-Early Triassic Events: The Induan/Olenekian Boundary in the Dolomites (Italy). Earth-Science Reviews, 2008, 91: 93-105.

[9] Pruss S. B., Bottjer D. J., Corsetti F. A., . A Global Marine Sedimentary Response to the End-Permian Mass Extinction: Examples from Southern Turkey and the Western United States. Earth-Science Reviews, 2006, 78: 193-206.

[10] Schubert J. K., Bottjer D. J.. Aftermath of the Permian-Triassic Mass Extinction Event: Paleoecology of Lower Triassic Carbonates in the Western USA. Palaeogeography, Palaeoclimatology, Palaeoecology, 1995, 116: 1-39.

[11] Stanley S. M.. Evidence from Ammonoids and Conodonts for Multiple Early Triassic Mass Extinctions. Proceedings of the National Academy of Sciences, 2009, 106(36): 15256-15259.

[12] Tong J. N., Zuo J. X., Chen Z. Q.. Early Triassic Carbon Isotope Excursions from South China: Proxies for Devastation and Restoration of Marine Ecosystems Following the End-Permian Mass Extinction. Geological Journal, 2007, 42: 371-389.