Asteroid impacts are not the only possible cause for the Permian and Triassic extinctions. Some recent papers on one possible cause.
1. Saunders, A., and M. Reichow, 2009, The Siberian Traps and the End-Permian mass extinction: a critical review. Chinese Science Bulletin. vol. 54, no. 1, pp. 20-37. http://www.springerlink.com/content/1743222152769702/ “Compromise of the carbon sequestration systems (by curtailment of photosynthesis, destruction of biomass, and warming and acidification of the oceans) probably led to rapid atmospheric CO2 build-up, warming, and shallow-water anoxia, leading ultimately to mass extinction.” 2. Knoll, A. H., R. K. Bambach, J. L. Payne, S. Prussa and Woodward W. Fischer, 2007, Paleophysiology and end-Permian mass extinction. Earth and Planetary Science Letters. vol. 256, no. 3-4, pp. 295-313. http://dx.doi.org/10.1016/j.epsl.2007.02.018 “Global warming, anoxia, and toxic sulfide probably all contributed to end-Permian mass mortality, but hypercapnia (physiological effects of elevated PCO2) best accounts for the selective survival of marine invertebrates.” 3. Hautmann, M., 2004, Effect of End-Triassic CO2 maximum on carbonate sedimentation and marine mass extinction. Facies. vol. 50, pp. 257–261. http://www.springerlink.com/content/ajvptjvenfvte5ck/ “Besides the frequently cited climatic effect of enhanced carbon dioxide, lowering the saturation state of sea water with respect to calcium carbonate was an additional driving force of the end-Triassic mass extinction, which chiefly affected organisms with thick aragonitic or high-magnesium calcitic skeletons. Replacement of aragonite by calcite, as found in the shells of epifaunal bivalves, was an evolutionary response to this condition.” 4. Hautmann, M., M., J. Benton, and A. Tomasovych, 2008, Catastrophic ocean acidification at the Triassic–Jurassic boundary. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. vol. 249, pp. 119–127. "Using carbon isotopes as a geochemical marker, we found that the onset of the CO2 emissions coincided with an interruption of carbonate sedimentation in palaeogeographically distant regions, suggesting that hydrolysis of CO2 led to a short but substantial decrease of seawater pH that slowed down or inhibited precipitation of calcium carbonate minerals. The cessation of carbonate sedimentation correlates with a major marine extinction event, which especially affected organisms with aragonitic or high-Mg calcitic skeletons and little physiological control of biocalcification." 5. Ryan, D., and D. Lehrann, 2009, Petrographic evaluation of a Permian-Triassic erosion surface and implications for causes of the end-Permian mass extinction. Geological Society of America Abstracts with Programs, Vol 41, No. 4, p. 17 http://gsa.confex.com/gsa/2009NC/finalprogram/abstract_156104.htm “our results favor genesis as a submarine dissolution surface resulting from ocean acidification during the end-Permian extinction.” 6. Veron, J. E. N., 2008, Mass extinctions and ocean acidification: biological constraints on geological dilemmas. Coral Reefs. vol. 27, no. 3., pp. 459-472. http://www.springerlink.com/content/085g2151l3nlt871/ 7. Zhuravlev, A. Y.,* and R. A. Wood, 2009, Controls on carbonate skeletal mineralogy: Global CO2 evolution and mass extinctions. Geology. vol. 37, no. 12, pp. 1123-1126. http://geology.gsapubs.org/content/37/12/1123.abstract “Mass extinction events, many of which may be caused by rapid global changes in temperature and/or pCO2, represent major intervals of turnover.” Yours, Paul H. ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list