GSA Connects 2021 in Portland, Oregon

Paper No. 17-5
Presentation Time: 9:15 AM


TKACH, Nikolai, Lomonosov Moscow State University, Moscow, 119991, Russian Federation, SOROKIN, Valentin, Faculty of Geology, Moscow M.V. Lomonosov State University, 1 Leninskie Gory, Moscow, 119991, Russia and MAKSHAEV, Radik, Faculty of Geography, Moscow State University, Moscow, 119991, Russian Federation

During the Quaternary Caspian Sea level changed several times. Numerous researchers have been exploring the Caspian Sea for two centuries. However, there is still no consensus on the number of transgressive-regressive events, their scale, chronology, and causes. The most controversial question is about the chronology of paleogeographic events, since absolute dates were obtained only for the last two transgressions: the New-Caspian (the Holocene) and the Khvalynian (the late Pleistocene). The most interesting transgression is Khvalynian, which is complicated and consist of two stages (early and late separated by deep Enotaevian regression).

Estimated age of the last huge transgression (early Khvalynian; max. highstand +50 m a.s.l.) by different researchers varied from 70,000 years to 11,000 years, i.ะต. from the first half of the Wurm to the beginning of the Holocene. Estimated age are based on thermoluminescence dating, electron paramagnetic resonance spectroscopy (ESR), uranium-ionium, radiocarbon dating.

Late Khvalynian transgression (max. highstand 0 m a.s.l) dated uncertainly by different researchers and methods. Late Khvalynian dating results have nearly same ages as radiocarbon early Khvalynian dates. Most part of researchers estimate its age as 11,000 to 9,000 years.

The latest one โ€“ New-Caspian transgression โ€“ correlates with the last 8,000 years.

The most unstudied materials that could help to sort all paleogeographical questions out are cores from the Caspian basin. Our group focused on cores from the Northern Caspian. Their sedimentological record is much more full than onshore and contains less hiatuses.

Based on the geochemical and geophysical data, radiocarbon dates, biostratigraphy and clay minerology the sedimentological record was divided in four stages.

  1. Early Khvalynian transgression dates from 32,000 years (slow sea-level rise) to 13,000 years (rapid and brief sea-level rise).
  2. Late Khvalynian sea-level stabilization (appx. 0 m a.s.l.) during the regression, appx. 12,000-11,000.
  3. Deep Mangyshlakian regression (down to -100 m a.s.l.) that leaves many cuts in Northern Caspian relief.
  4. New Caspian transgression (first meters above modern sea-level) started about 8,000 years ago.

This work is supported by RSF โ„– 20-77-00068.