Contributors: State Key Laboratory of Geological Processes and Mineral Resources Wuhan (GPMR); China University of Geosciences Wuhan (CUG); Department of Geology; University of Cincinnati (UC); Geological Survey of Canada Sidney - Vancouver (GSC Pacific); Geological Survey of Canada - Office (GSC); Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan); Biogéosciences UMR 6282 (BGS); Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS); State Key Laboratory of Biogeology and Environmental Geology; Study supported by NSFC grants (No. 41673011, 41473006, 41272025, 41803011 and 41821001), by Natural Science Foundation of Hubei Province (No. 2018CFB263), by China Postdoctoral Science Foundation (2018M642945) and by the Fundamental Research Funds for the Central Universities, China University of Geosciences-Wuhan (No. CUGQYZX1728 and CUGCJ1815, CUG170683).; ANR-13-JS06-0001,AFTER,Après la fin : la reconstruction des communautés marines durant la rediversification du Trias inférieur.(2013); ANR-15-IDEX-0003,BFC,ISITE " BFC(2015)
نبذة مختصرة : 30 pages ; International audience ; The transition from the Smithian substage to the Spathian substage of the Olenekian stage of the late Early Triassic was a critical time marked by a series of biological and environmental changes during the multimillion-year recovery interval following the end-Permian mass extinction. However, the Smithian/Spathian boundary (SSB) does not yet have an agreed definition, a shortcoming that complicates high-resolution analysis of events during the Smithian-Spathian transition. Here, we review key biostratigraphic (i.e., ammonoid and conodont) studies of the Smithian and Spathian substages in historically important regions (e.g., the Canadian Arctic for the Boreal realm, western North America for the eastern Panthalassic Ocean) and more recently re-studied locations (e.g., Pakistan and India in the southern Tethys, South China in the eastern Tethys) as well as the carbon isotope chemostratigraphy of 29 major Smithian-Spathian sections globally. Key ammonoid genera (e.g., Wasatchites, Anasibirites, Glyptophiceras and Xenoceltites of the late Smithian, and Bajarunia, Tirolites and Columbites of the early Spathian), conodont species (e.g., Scythogondolella milleri, Novispathodus waageni, and Borinella buurensis of the late Smithian, and ‘Triassospathodus’ hungaricus, Neogondolella aff. sweeti, and Icriospathodus spp. of the early Spathian), and carbonate carbon isotope excursions provide appropriate markers for constraining the SSB. Use of the first occurrence of the conodont Novispathodus pingdingshanensis as a potential marker of the SSB is also discussed. Based on correlations of biostratigraphic and carbon isotope data globally, we propose to revise previous placements of the SSB transition in some sections. Finally, we show that the Smithian Thermal Maximum (STM; herein named) was middle Smithian in age and not correlative with the SSB, as inferred in some earlier studies, and that the SSB coincided with a subsequent major global cooling event.
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