Holocene stable oxygen isotope record from the North Caspian Rybachya core
DOI:
https://doi.org/10.31951/2658-3518-2024-A-4-712Keywords:
Caspian Sea, Neocaspian transgression, Mangyshlak regression, stable oxygen analysis, paleovalley, OstracodaAbstract
The first results of 22 δ18Oost measurements on ostracod shells from the Rybachya core in the North Caspian Sea are presented. The stable oxygen isotope record here confirms previous studies of Upper Quaternary and Holocene sediments of the Rybachya core area, where it was suggested that a paleovalley was formed during the Mangyshlak regressive stage and then gradually filled during the Holocene transgressive stage. We recorded three local isotopic stages, each characterized by δ18Oost values. The hydrological variability and sea level changes associated with the transgressive-regressive rhythm of the Caspian Basin and the climatic changes in the Northern Hemisphere led to the δ18Oost changes obtained in this work. Relatively depleted δ18Oost values from sediments filling the paleovalley allowed to interpret the isotope record in terms of freshwater influx. The average δ18O enrichment of ostracod shells is taken as evidence for the isolation of the paleovalley during the Caspian Sea level retreat. However, the higher δ18Oost values obtained for the last (modern) stage of Caspian history are under the strong control of host water salinity, which is higher than during the paleovalley filling episode.
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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
This work is distributed under the Creative Commons Attribution-NonCommercial 4.0 International License.