Le formidable succès évolutif des dinosaures, apparus au Trias il y a probablement plus de 240 millions d’années, pose toujours question. Dernière hypothèse en date : ils devraient leur domination à l’extermination de leurs concurrents, due aux gaz libérés par les grandes éruptions volcaniques qu'a provoquées la fracture de la Pangée.
Plus d'infos.
Une explication à la domination des dinosaures
Modérateurs : Eric, jerome, Travis, Charlotte, marie.m, Magda Dorner, Bull
Abstract de PNAS ci-dessous :
Proc Natl Acad Sci U S A. 2010 Mar 22. [Epub ahead of print]
Compound-specific carbon isotopes from Earth's largest flood basalt eruptions directly linked to the end-Triassic mass extinction.
Whiteside JH, Olsen PE, Eglinton T, Brookfield ME, Sambrotto RN.
Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912.
A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO(2). The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie's Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO(2) super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.