New data on the Pleistocene history of the Aral Sea-Lake

Abstract

A 23.5 m deep borehole was drilled on the dried bed of the Aral Sea 9 km south of the former Barsakelmes Island. At a depth of 21.3 m, the borehole penetrated Paleogene bedrock. In the interval 21.3 - 15.2 m the conditions of a shallow freshwater reservoir at a considerable distance from the flowing rivers (deltaic channels of the Syr Darya River) - the first phase of filling of the Aral Basin with river water - were reconstructed. It has been preliminary attributed by three 14C AMS dates to the time about 23-25 thousand years BP. Above 15.2 m of the section the conditions become even more shallow, starting from 12.0 m of the section - brackish-water. The upper 10.5 m of the section correlates with the sediments of the modern geological phase of the Aral Sea development studied in detail in the same area by Burr et al. (2019), the beginning of which was estimated at 17.6 thousand BP. The new data obtained indicate an earlier appearance of the modern Aral Sea, which originated as a shallow freshwater body.