Five-fold expansion of the Caspian Sea in the late Pliocene: New and revised magnetostratigraphic and 40Ar/39Ar age constraints on the Akchagylian Stage

S. Lazarev*, K. F. Kuiper, O. Oms, M. Bukhsianidze, D. Vasilyan, E. L. Jorissen, M. J. Bouwmeester, V. Aghayeva, A. J. van Amerongen, J. Agustí, D. Lordkipanidze, W. Krijgsman

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The Global climate reorganisation in the late Pliocene linked to enhancement of the Atlantic Ocean Thermohaline Circulation (AOTC), instigated a transition to glacial-interglacial cyclicity in the Quaternary. Enhancement of the AOTC amplified atmospheric precipitation over the Eurasian interior strengthening Northern Hemisphere Glaciation. Increased rainfall on the vast Russian Plain drained into the endorheic Caspian Sea, which makes the Caspian geological record highly potential for tracing atmospheric precipitation changes. Two major palaeohydrological events in the Caspian Sea, the Akchagylian transgression and the Akchagylian marine incursion, led to a five-fold enlargement of the Caspian Sea surface area and transformed the basin palaeoecology, enabling active interregional faunal dispersals. The Akchagylian Stage still lacks an unequivocal age model with two age constraints – the “long Akchagylian” (3.6–1.8 Ma) and the “short Akchagylian” (2.7–2.1 Ma) standing on magnetostratigraphic studies of geological records in Turkmenistan and the Kura Basin, respectively. The age discrepancies also exist within the Kura Basin, where the fossil mammal-bearing Kvabebi locality with Akchagylian marine fauna was magnetostratigraphically dated at 3.2 Ma. In this paper, we try to resolve the age contradictions for the Akchagylian Stage. We revisit the Kvabebi (Georgia) and Kushkuna (Azerbaijan) sections of the western Kura Basin and provide new magnetostratigraphic and 40Ar/39Ar age constraints on these marginal Akchagylian deposits. Moreover, we revise the magnetostratigraphy of 25 geological records from Turkmenistan and the Kura Basin and propose a new unified age model for the Akchagylian Stage: 1. Intrabasinal Akchagylian freshwater-mesohaline transgression at 2.95 ± 0.02 Ma; 2. Akchagylian marine incursion through establishment of a Caspian-Arctic connection (2.75–2.45 Ma); 3. Akchagylian–Apsheronian boundary highlighting a Caspian-Black Sea connection at 2.13 Ma. The sudden expansion of the Caspian Sea at 2.95 ± 0.02 Ma potentially correlates to the interglacial intensification of the AOTC between 2.95 and 2.82 Ma. The new ages constrain a much shorter (2.95–2.1 Ma) Akchagylian than in previously mentioned regional geological time scales (3.6–1.8 Ma) and strongly appeal to reconsider the ages of numerous archaeological and mammalian sites in the Caspian region.

Original languageEnglish
Article number103624
Pages (from-to)1-19
Number of pages19
JournalGlobal and Planetary Change
Volume206
Early online date28 Aug 2021
DOIs
Publication statusPublished - Nov 2021

Bibliographical note

Funding Information:
We would like to thank Dr. Thomas Hoyle for scientific discussion on the topic of this manuscript. We are also thankful to Qucho and Maia Navrozashvili for amazing Georgian hospitality during our fieldwork. We are also very thankful to two anonymous reviewers whose critical reviews helped to improve the manuscript. At this historical time, we would also like to give our words of support to all people fighting against the COVID pandemic. This research is a part of the PRIDE project (Pontocaspian RIse and DEmise), which is funded by the European Union's Horizon 2020 Research and Innovation Program, under the Marie Sk?odowska-Curie Action (grant agreement ? 642973).

Funding Information:
We would like to thank Dr. Thomas Hoyle for scientific discussion on the topic of this manuscript. We are also thankful to Qucho and Maia Navrozashvili for amazing Georgian hospitality during our fieldwork. We are also very thankful to two anonymous reviewers whose critical reviews helped to improve the manuscript. At this historical time, we would also like to give our words of support to all people fighting against the COVID pandemic. This research is a part of the PRIDE project (Pontocaspian RIse and DEmise), which is funded by the European Union's Horizon 2020 Research and Innovation Program , under the Marie Skłodowska-Curie Action (grant agreement № 642973 ).

Publisher Copyright:
© 2021 The Authors

Keywords

  • Ar/Ar chronology
  • Akchagylian
  • Caspian Basin
  • Kushkuna
  • Kvabebi
  • Magnetostratigraphy
  • Plio–Pleistocene

Fingerprint

Dive into the research topics of 'Five-fold expansion of the Caspian Sea in the late Pliocene: New and revised magnetostratigraphic and <sup>40</sup>Ar/<sup>39</sup>Ar age constraints on the Akchagylian Stage'. Together they form a unique fingerprint.

Cite this