THE BEGINNING, DEVELOPMENT AND TERMINATION OF THE MIDDLE MIOCENE BADENIAN SALINITY CRISIS IN CENTRAL PARATETHYS

Abstract

Middle Miocene Badenian evaporites of the Carpathian region are underlain and overlain by deep-water deposits, the onset of evaporite deposition was sudden but not synchronous in all facies zones and the deposition of evaporites was controlled by the evolution of Carpathian orogen. In the Carpathian Foredeep (and most probably in other basins) the Badenian evaporites represent the lower part of the NN6 zone. Halite and associated deposits in the central part of the Badenian evaporite basin show the same facies successions and marker beds can be traced across and between individual basins. Characteristic marker beds made it possible to correlate various facies zones of the marginal Ca-sulfate platform. These marker beds seem to reflect events that may be related to sudden and widespread changes in water chemistry, which in turn imply major changes in basin hydrology. The onset of the evaporitic deposition in the Carpathian Foredeep was clearly diachronous and the evaporites deposited in the basin centre preceded the beginning of evaporite sedimentation in the marginal basin, however, depositional history in the marginal basin and the basin centre was the same. A general transgressive sequence of evaporites found in the Carpathian Foredeep resulted from the migration of facies zones induced by the nappe movement. Isotopic studies of Badenian foraminifers occurring below evaporites suggest that the interrupted communication of the Paratethys with the ocean was a consequence of eustatic sea-level fall, possibly related to climatic cooling, and it was coupled with a tectonic closure of connection with the Tethys. Thus both tectonics and eustacy have contributed to the origin of salinity crisis. Sedimentological and geochemical data indicate recycling of evaporites throughout most of the evaporite deposition. The recycling at the end of gypsum deposition in the marginal sulfate platform was accompanied by a change in the hydrology of the Central Paratethys that was tectonically-driven, and possibly related to the block tectonic phase manifested in the marginal part of the Carpathian Foredeep Basin. The change in hydrology implied the dilution of brines by inflowing marine water and this terminated the Middle Miocene Badenian salinity crisis. The onset of the Badenian salinity crisis shows great similarities to the onset of the Messinian salinity crisis and the terminations of both crises were different. © 2006 Elsevier B.V. All rights reserved.