Author : Nilotpal Ghosh
Release : 2015
Genre :
Kind : eBook
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Book Synopsis Evidence of Catastrophe in the Permian-Triassic Tethyan Ocean by : Nilotpal Ghosh
Download or read book Evidence of Catastrophe in the Permian-Triassic Tethyan Ocean written by Nilotpal Ghosh. This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt: "Interpreting global consequences of the Permian-Triassic (P-Tr) extinction event at ~252 million years (Ma) before present requires geological examination across paleogeographic sites of Pangaea, including Panthalassic Ocean, Paleotethys, Neotethys, Laurasia and Gondwanaland. Despite numerous studies on Tethyan and Boreal sediments extending from China and Europe to Canada, Neo-Tethyan sediments spanning this geological boundary have received much lesser attention. This thesis provides a detailed geological, geochemical and isotopic characterization of the P-Tr boundary in Spiti Valley of India that is a remnant of the peri-Gondwana continental shelf along Neo-Tethys Ocean. New sedimentological observations and high-resolution trace element and carbon, oxygen, lead isotope data across the P-Tr boundary in Spiti are reported and documented for the first time. Discovery of framboidal pyrites, fossil assemblages and laminated lithology of the Late Permian shales indicate deeper anoxic depositional environment while carbon isotope excursions in Atargu and Guling outcrops, respectively, identify the P-Tr transition across a clayey, partly gypsiferous ferruginous layer. Sedimentological similarities of this layer to other Neo-Tethyan sections from Transcaucasia and Iran indicate subaqueous oxidation of shallow marine sediments on a regional scale. Light Rare Earth Element - enriched Late Permian shales with Ce - Eu anomalies reflect their source as Panjal Trap basalt (ca. 289 Ma) of Kashmir while Nb-Ta and Zr-Hf anomalies at and above the P-Tr boundary indicate increased erosion in oxidizing conditions. The [delta]13Corg, trace element and Pb isotope record from Spiti indicate catastrophic changes in sediment sources and facies, with effects on global carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing, also observed elsewhere along northern Gondwanaland. In contrast, the Raman spectroscopic and lead isotope investigation of a P-Tr boundary Tethyan section in Vietnam shows large scale deposition of black carbon soot into the Paleo-Tethys, a likely cause of marine anoxia. We propose that a chain of catastrophic processes, primarily triggered by Siberian flood volcanic eruption and bolide impact in the Parana basin of Brazil and possibly elsewhere, in combination, left catastrophic local to regional imprints on sea level, climate, marine anoxia and tectonic instability that connected the P-Tr crisis across the terrestrial and marine realms of Pangaea"--Page vii-viii.
