New Early Triassic ammonoid faunas from the Dienerian/Smithian boundary beds at the Induan/Olenekian GSSP candidate at Mud (Spiti,Northern India) |
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| Institution: | 1. State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. School of Geosciences, Yangtze University, Wuhan 430100, China;1. Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan;2. The Center for Academic Resources and Archives Tohoku University Museum, Tohoku University, Aramaki Aza Aoba 6-3, Aoba-ku, Sendai 980-8578, Japan;3. Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba 305-0005, Japan;4. Vietnam Institute of Geosciences and Mineral Resources (VIGMR), Hanoi, Viet Nam;5. Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8567, Japan;6. Vietnam National Museum of Nature (VNMN), Hanoi, Viet Nam;7. Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan;1. Dipartimento di Geoscienze, Università degli Studi di Padova, via Gradenigo 6, 35131 Padova, Italy;2. Istituto di Geoscienze e Georisorse CNR, via Gradenigo 6, 35131 Padova, Italy;3. Museo di Scienze Naturali dell''Alto Adige, via Bottai 1, 39100 Bolzano, Italy;4. Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität und Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Straße 10, 80333 München, Germany;5. Dipartimento di Fisica e Scienze della Terra, via Saragat 1, 44100 Ferrara, Italy |
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| Abstract: | New collections at the Induan/Olenekian boundary GSSP candidate at Mud (Himachal Pradesh, Northern India) lead to the recognition of several well preserved ammonoid faunas that significantly improve the biostratigraphic resolution in the beds underlying the proposed GSSP level. In ascending order, the new biostratigraphical sequence comprises: the Ambites lilangense beds, the Fuchsites markhami beds, the Kingites lens beds, the Prionolobus rotundatus beds, the Flemingites bhargavai beds, the Kashmiritidae gen. nov. A beds and the Vercherites cf. pulchrum beds. The faunas from Bed 10, located about 1 m below the proposed GSSP level, contain certain ammonoids with typical early Smithian affinity (Flemingitidae, Kashmiritidae) and thus reflect the beginning of the early Smithian evolutionary radiation. Seen from an evolutionary point of view, the Dienerian/Smithian boundary can therefore be placed just below Bed 10. Ideally, the stage boundary should also be intercalibrated with other biological, chemical or physical proxies as additional tools for world-wide correlations.Four new species (Flemingites bhargavai, Kingites korni, ?Kingites parkashi and Xenodiscoides variocostatus) and two new genera (Mudiceras, Vercherites) are described. |
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