Late Paleozoic and Triassic bryozoans from the Tethys Himalaya (N India, Nepal and S Tibet) |
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Authors: | Sumio Sakagami Dario Sciunnach Eduardo Garzanti |
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Institution: | (1) Konakano 48, Akiruno-shi – Tokyo 190-0165, Japan;(2) Dipartimento di Scienze della Terra, Via Mangiagalli 34, 20134 Milano, Italy;(3) Ev-K2-CNR, Via Ampère 56, 20133 Milano, Italy;(4) Dipartimento di Scienze Geologiche e Geotecnologie, Piazza della Scienza 4, 20159 Milano, Italy;(5) Present address: Regione Lombardia, Infrastruttura per l’Informazione Territoriale, Via Sassetti 32/2, 20124 Milano, Italy |
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Abstract: | New findings of Late Paleozoic and Triassic bryozoans from the Tethys Himalaya are reported. Fifteen species, including three undetermined, were described, while determinations at order, family or genus level were obtained on fragmentary material. The studied bryozoans were framed in a solid lithostratigraphic scheme spanning across the Tethys Himalaya for over 1500 km, from NW India (Zanskar and Spiti) through Nepal (Dolpo and Manang) to South Tibet; they are concentrated in correlatable stratigraphic intervals corresponding to the Upper Devonian-Tournaisian, Bashkirian, Sakmarian, Midian and Lower Norian. This study allowed us to integrate bryozoan occurrences reported from the literature, mostly referring to the Tournaisian, Bashkirian and Early Norian, and to refine the available biostratigraphic dates. Bryozoan-rich intervals are interpreted as associated to long-term transgressions, in turn driven by major climatic and/or tectonic events. Cosmopolitan genera which prevail in the Paleozoic, are replaced by provincial forms after the Triassic crisis. |
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Keywords: | Bryozoans Tethys Himalaya Late Paleozoic Triassic Biostratigraphy Paleogeography |
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