JURASSIC MICROPLATE MOVEMENTS AND BRACHIOPOD MIGRATIONS IN THE WESTERN PART OF THE TETHYS

The paleobiogeography of the Jurassic brachiopods of the Alpine-Carpathian region and adjacent areas is discussed on the basis of the distribution of ''distinctive taxa''. The Jurassic microplates of the western part of Tethys and the present-day ''terranes'' of the Alpine-Carpathian region are outlined and their relationships are discussed. The migration possibilities of the brachiopods in the Jurassic Tethys were controlled mainly by plate/microplate movements and by changes in the oceanic current system. The Mediterranean microcontinent, isolated from the European and African shelves by oceanic/deep-sea belts, was the homeland of the Mediterranean brachiopod province. In the course of the Jurassic, the Mediterranean microcontinent moved, as part of the African plate, away from Europe, the widening Alboran-Ligurian-Penninic oceanic belt became a barrier preventing migration of brachiopods. By the end of the Middle Jurassic the Tisza microplate detached from Europe and formed a ''stepping stone'' for brachiopod dispersal. At about the same time, the ''Hesperian Strait'' opened between the basins of the Tethys and the Central Atlantic. The opening of this strait resulted in a reorganization of the Tethyan current system. The westward flowing equatorial currents which made a turn in the western corner of Tethys in the first half of the Mesozoic, now ran to the west through the Hesperian Strait via the Central Atlantic to the Pacific. This change produced a new pattern in brachiopod distribution: the Mediterranean fauna successfully invaded the European shelf, at the same time the Mediterranean province became impoverished.