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Geochronological constraints on post-extinction recovery of the ammonoids and carbon cycle perturbations during the Early Jurassic

Guex, Jean
Schoene, Blair
Bartolini, Annachiara
Spangenberg, Jorge
O'Dogherty, Luis
Taylor, David
Bucher, Hugo
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Published in Palaeogeography, Palaeoclimatology, Palaeoecology. 2012, vol. 346-347, p. 1-11
Abstract This paper presents the first quantitative study of the Early Jurassic recovery of ammonoids after the end- Triassic mass extinction based on detailed U-Pb ID-TIMS (isotope dilution thermal ionization mass spectrometry) geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level. This study was triggered by the discovery of a rich Peruvian succession of ammonites, deposited concomitantly with an unusually large number of ash beds. Two major phases of rediversification are observed during the Psiloceras spelae and Angulaticeras zones that correspond to positive peaks in the δ13Corg curve, providing a possible link between biodiversity and the global carbon cycle. In the case of the post-extinction recovery, the development of the earliest Hettangian ammonites occurs within the genus Psiloceras,which begins with the occurrence of P. spelae and then explodes into worldwide development of smooth psiloceratids of the Psiloceras planorbis group s.l. This rapid biodiversification likely occurred less than 100 ka after the end-Triassic crisis; the genus Psiloceras occupied all the possible ecological niches worldwide, from the Pacific deep waters to the NW European shallow deposits and also in some rare Tethyan occurrences like at Germig in Tibet. This global dispersion allowed the differentiation of the group in several major phyla, the Schlotheimiidae, Discamphiceratinae, Arietitidae and Lytocerataceae, which were the roots of all other Jurassic and Cretaceous ammonites.
Keywords U-Pb datingCarbon isotope stratigraphyTriassic-Jurassic boundaryPeruMass extinctionPost extinction recoveryAmmonoids evolutionary rates
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Research group Isotope Geochemistry, Geochronology and Thermochronology
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GUEX, Jean et al. Geochronological constraints on post-extinction recovery of the ammonoids and carbon cycle perturbations during the Early Jurassic. In: Palaeogeography Palaeoclimatology Palaeoecology, 2012, vol. 346-347, p. 1-11. doi: 10.1016/j.palaeo.2012.04.030 https://archive-ouverte.unige.ch/unige:21977

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Deposited on : 2012-08-08

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