PRINCIPAL STAGES IN THE PERMIAN EVOLUTION OF ASIAN MARINE BASINS AND BRACHIOPOD FAUNA |
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| Abstract: | In consequence of Hercynian folding, the Asian marine basin outlines repeatedly and essentially changed throughout the Permian. At the opening of the Sakmarian age the communication between the Arctic and Tethys marine basins was realized through the Caspian Sea region. In the middle of the Sakmarian age this channel was closed and the Arctic and Tethys seas were isolated from each other resulting in the development of various brachiopod faunas in both basins. Such an environment continued up to the beginning of the Upper Permian when a transgression of the boreal sea far to the south into the Mongolian geosyncline area and farther on into India and Burma took place. The Upper Permian marine basins of these regions became, therefore, inhabited by fauna of the Arctic type. Meanwhile the tropical forms of brachiopods did not migrate from the Tethys into the Arctic. At the beginning of the Kazanian age the sea retreated from Mongolia and the Arctic and Tethys basins became almost isolated again, their fauna growing essentially different towards the close of the Permian. In consequence of the fact that the tropical forms common in the Tethys couldn't exist through out the Permian within the present area of the Arctic, it might be assumed that the climate was most severe at the time, i.e. the region was located in the nearest proximity to the pole. At the same time the region adjacent to Japan where the North Pole moved to during the Permian (according to the opinion of most advocates of the polar migration theory) is found to be inhabited by tropical fauna. Thus analysis of the distribution of Permian fauna doesn't confirm the theory of a considerable migration of the earth's poles.—Auth. English summ. |
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