PALEOGEOGRAPHIC EVOLUTION OF THE ISSYK KUL LAKE DEPRESSION DURING THE NEO-PLEISTOCENE

Abstract

Paleogeographical reconstruction of major natural changes between the Pliocene and the Pleistocene is based on the complex analysis of recent lacustrine deposits of the Issyk Kul depression. Main stages of sedimentation in the coastal zone of the lake are described, as well as the evolution of the lake during the Late Pliocene. ThePaleo-IssykKulLakewas considerably larger during the Pliocene than the modern one. There were lakes in other mountain depressions too, but at the turn of the Pliocene to the Pleistocene most of them were emptied. At the same time the Issyk Kul became a deep-water lake. Several profound changes in the history of the lake evolution were identified. General trend of theIssykKulLakeevolution, i.e. the decrease in area and lowering of the water level, was analyzed using the data of deep wells and sections. The turn of the Pliocene to the Pleistocene was characterized by changes in the lake volume and oscillations of its level, as well as the profound transformation of surrounding landscapes. The mountain ridges became much higher, mountain glaciers were formed and the pattern of the river network changed considerably. Major transformation of the natural environment led to the formation of new Pleistocene landscapes quite different from the Pliocene ones.