The Permian Extinction and the Tethys: An Exercise in Global Geology
A.M. Celâl Şengör, Saniye Atayman, 2009. "The Permian Extinction and the Tethys: An Exercise in Global Geology", The Permian Extinction and the Tethys: An Exercise in Global Geology, A.M. Celâl Şengör, Saniye Atayman
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The Tethyan realm stretches across the Old World from the Atlantic to the Pacific Oceans along the Alpine-Himalayan mountain ranges and extends into their fore- and hinterlands as far as the old continental margins of the now-vanished Tethyan oceans reached. It contains the Tethyside superorogenic complex, including the orogenic complexes of the Cimmerides and the Alpides, the products of the closure of the Paleo- and the Neo-Tethyan oceans, respectively. Paleo-Tethys was the oceanic realm that originated when the late Paleozoic Pangea was assembled by the final Uralide–Scythide–Hercynide–Great-Appalachide collisions. It was a composite ocean, i.e., not one formed by the rifting of its opposing margins, and its floor was already being consumed along both Laurasia- and Gondwana-Land–flanking subduction zones when it first appeared. The Gondwana-Land-flanking subduction systems, in particular, created mostly extensional arc families that successively led to various Paleo-Tethyan marginal basins, the last group of which was the oceans that united to form the Neo-Tethys.
The Paleo-Tethys may have become an entirely continent-locked ocean through the construction, to the east of it, of a Cathaysian bridge uniting various elements of China and Indochina into an isthmian link between Laurasia and Gondwana-Land during the latest Permian, inhibiting any deep-sea connection between the Paleo-Tethys and the Panthalassa. That land bridge may have been responsible for the peculiarities in the distribution of the latest Permian-early Triassic Dicynodonts and possibly some brachiopods, benthic marine microorganisms, and land plants.
The existence of the Cathaysian bridge seems to have helped the formation of anoxic conditions in the Paleo-Tethys. In fact, it seems that the major Permian extinctions began in the Paleo-Tethys and were really mainly felt in it and in areas influenced by it. This isolated setting of the Paleo-Tethys we refer to as a Ptolemaic condition, in reference to the isolated oceans Claudius Ptolemy had depicted on a geocratic Earth in his world map in the second century AD. Ptolemaic conditions are not uncommon in the history of Earth. Today, such a condition is represented by the Mediterranean and its smaller dependencies such as the Black Sea and the South Caspian Ocean. Para-Tethys in the Neogene had a similar but even more isolated setting.
As we see in all these late Cenozoic cases, such Ptolemaic oceans have a major influence on the evolution of the biosphere. The Paleo-Tethys seems to have had a much larger impact than any of its successors owing to its immense size and may have been the key player in the so-called “end-Permian” extinction, which, in reality, was a mid to late Permian affair, with some late phases even in the earliest Triassic. The Permian extinction happened in at least two main phases, one in the Guadalupian and the other near the end of the Lopingian, and in each phase different animal and plant groups became extinct diachronously, phasing out according to the degree they were influenced by the developing anoxia within the Paleo-Tethys.
What these conclusions suggest is that when investigating the causes of past events, regional geology must always form the foundation of all other considerations. Many speculations concerning the Permian extinction events cannot be adequately assessed without placing their implications into the geography of the times to which they are relevant. A purely “process-orientated” research that downplays or ignores regional geology and attempts to ape physics and chemistry, as is now prevalent in the United States and in western Europe and regrettably encouraged by the funding organizations, is doomed to failure.