T17 From the Caspian to Mediterranean: Environmental Change and Human Response during the Quaternary (INQUA IFG POCAS, IGCP 610) I

Sunday, 10 October 2021
8:00 AM - 12:00 PM
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LATE QUATERNARY REGRESSIONS IN THE CASPIAN SEA

Paper number: T17-5
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM

Authors

Abstract

The main characteristic of the Caspian Sea in the Quaternary is its transgressions and regressions. The most important events in the Caspian Late Quaternary history are the Atelian and the Mangyshlak regressions. Our paleogeographic reonstructions are based on an analysis of cores obtained from boreholes on areas of oil-gas researches. The laboratory studies included lithological analysis, pollen-spores and faunal studies of the organic remains, the isotope analysis and radiocarbon dating.

In the depositional series of the Northern Caspian the regressive intervals are represented by paleodepressions and erosional landforms distinctly seen in the seismic stratigraphic profiles. As follows from the composition of organic remains, there existed lakes with fresh water and wetlands. The oxygen isotope analysis lends support to the opinion that the Volga inflow influence on the Caspian area increased.

The Atelian pollen assemblages are indicative of rather diversified landscapes north of the Caspian Sea – from forests dominated by conifers to periglacial forest-steppe and tundra-forest-steppe. The age of final phase of the regression was determined as 44–42 ka BP (first half of the MIS 3). Well-developed cryogenic wedges found at the base of Atelian series and deeply penetrating into the underlying deposits (dated to MIS 5) suggest the accumulation of the subaerial Atelian deposits to begin at the cold (glacial) epoch MIS 4.

The Mangyshlak deposits were formed during arid conditions. The saturation of water with carbonates during the accumulation of sapropel led to the deposition of chemogenic carbonates. The Mangyshlak deposits contain few faunal remains compared to the overlying and underlying transgressive sequence but include freshwater and terestrial molluscs. The absence of the Didacna genus is its characteristic feature. Dating defines the age of the regression to be between 11,9 and 10,5 ka BP (the beginning of MIS 1).

The work is in the fram of RFBR Project 20-39-70020. Isotope analysis executed on the RFBR Project 20-35-90020.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-364725

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