THE PERMIAN EXTINCTION AND THE SHAPE OF THE PALAEO-TETHYS

The Permian extinction was not universal as at least some sections in Japan, New Zealand and the US Cordillera show continuous faunal records and no anoxia. By contrast, evidence for Capitanian and Changsingian extinctions in and around the Palaeo-Tethys is ubiquitous. This has led to the suggestion that the major Permian extinctions were confined to the Palaeo-Tethys and to the areas influenced by it. This makes the shape of the Palaeo-Tethys and the circum-Tethyan regions important to know. The main question now is the shape of the Pangaea during the times of extinction. We have looked at the structure and evolution of the Hercynian/Appalachian orogenic belt to see whether any evidence is recoverable for the relative motion of Gondwana-Land with respect to Laurasia during the Permian. It seems clear that the eastern part of the Hercynides from the southern Carpathians and the Tisza Block to Turkey remained as an active, Gondwania-bound, Andean arc throughout the Permian. I.e., there is no evidence for a Laurasia-Gondwania ‘Hercynian’ collision in these regions. Farther west, the Bohemian Massif has rotated close to 90° in a clockwise direction while major, east-west orientated dextral shear systems were active in southern eand eastern Europe. The Rheic Ocean had already closed during the medial Carboniferous. In Central and Northern Europe there were also numerous dextral shear systems beginning in the east with the Tornquist-Teisseyre fault zone. Some of these shears ended in the transtensional rift of the North German Basin and the extensional North Sea rifts, while others hooked up with the west Iberian/Greenland/Norwegian rifts. At the same time, the Pyrenees and the Montaigne Noir and the Mouthoumet massifs were functioning as large dextral strike-slip related metamorphic core complexes. All of these shear systems, making up a large keirogen in the site of the Hercynides, accumulated at least 2500 km dextral shear bsetween Gondwana-Land and Laurasia. This indicates that in the earliest Permian the Pangaea had a Pangaea B shape which was transformed into the Pangaea A shape during the late Permian. The Palaeo-Tethys thus progressively gained volume during the Permian. This might be an explanation for the greater Magnitude (M) of the terminal Permian extinction.