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

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