Changes in the ostracodes of the Mediterranean with the Messinian salinity crisis

Abstract

The likelihood of an environmental “crisis” in the evolution of the Tethys Ocean-Sea to the Mediterranean Ocean-Sea during Late Miocene is examined and tested against the present knowledge of the ostracode fossil record in Italy, Sicily, Crete, northern Tunisia, southern Spain and from some of the DSDP cores of the deep regions of the Mediterranean, especially in the Balearic Basin. It is concluded that there has been a substantial evolutionary and ecological change in the ostracode fauna that occurred at the time of the crisis. At the present time the best explanation available is that of isolation of deep basins from the World Ocean accompanied by extreme environmental change. The sudden oceanic “normalization” th that followed the “crisis” was perhaps just as extreme, but because of the buffering effects of the re-establishment of marine conditions in the newly formed Mediterranean, the shallower ostracode faunas coming from the Atlantic were not greatly different from those of westernmost Tethys.