Middle and Upper Miocene Deposits and Facies of Northern Ustyurt (Western Kazakhstan)

Abstract

Abstract —We present data on the most complete Neogene sections and wells of northern Ustyurt and the Cis-Aral area. Miocene deposits in the northern chinks and the North Ustyurt depression are composed of sediments of the Tarkhanian, Chokrakian, Karaganian, Konkian, and Sarmatian regional stages of the Eastern Paratethys, which are overlapped by lower Pontian beds. The distribution of thickness and facies shows that the North Ustyurt depression remained the main synclinal structure of the region, along which the waters of all Miocene transgressions were spread. Sandy material was brought by the rivers from the north: A sandy lens of Chokrakian age is traced along the Shomishtykol Sor almost to the axial part of the depression. Transgressions were pulsating, and the lower and middle Sarmatian deposits were most widespread. These data are presented as a geological profile near Beineu Village and as schematic maps of facies for the middle Miocene regional stages.