ЭВОЛЮЦИЯ ПРИРОДНОЙ СРЕДЫ КАСПИЯ В УСЛОВИЯХ ГЛОБАЛЬНЫХ ИЗМЕНЕНИЙ КЛИМАТА

Abstract

Evolution of environment of the Caspian Sea in the conditions of global climate changes is considered for two multi-scale temporary periods: the last climatic macrocycle (marine isotope stages, MIS, 5-2) and the Holocene (MIS 1). Both of them are characterized by considerable climatic changes. The Caspian Sea reacted to climatic events of MIS 5 epoch by the development of two transgressive basins - the warm-water Late Khazarian and moderately warm-water Hyrcanian basins. The Atelian regression was answered to the MIS 4 glacial stage and initial phases of interstadial warming MIS 3. The climatic conditions of the second half of interstadial warming were reflected by development of the first stage of the Khvalynian transgression. The transgressive trend of level was interrupted during an epoch of the maximum cold and dryness of MIS 2 stage. During an epoch of glacial degradation the development of Khvalynian transgression was resumed. Climatic events of late glacial epoch, the warming phases Bolling and Allered, got a response in development of the transgressive stage of the Khvalynian basin. Phases of a considerable cold snap (Oldest, Older and Yanger Dryas) were reflected by regressive stages in the history of the Khvalynian basin. The most considerable of them answered to the Yanger Dryas. Development of the Mangyshlakian regression is a response of the Caspian Sea to the continentalization of climate of the Boreal period of the Holocene. In development of the New Caspian transgression, the three transgressive stages are established. They are closely connected with regional climate changes. The composition of mollusks of the Caspian Sea represents the result of evolutionary processes in the Pleistocene faunae occurring in the conditions of climatic changes and transgressive and regressive rhythmics of the basin. The New Caspian (Holocene) complexes reflect the change of biotic conditions of the basin - the invasion of the Black Sea species. The invasiv species and acclimatizin species made much more essential changes to structure of the biodiversity, than it is caused by natural factors. The natural ecosystems underwent the anthropogenous transformation, turning the unique ecosystems of the Caspian Sea created for its Pleistocene history into similarity of the Azov-Black Sea ecosystems.