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.

上新世晚期的全球气候重组与大西洋温盐环流 (AOTC) 的增强有关，促使第四纪向冰期-间冰期周期性转变。AOTC 的增强放大了欧亚大陆内部的大气降水，加强了北半球冰川作用。广阔的俄罗斯平原降雨量增加，流入内陆里海，这使得里海地质记录具有追踪大气降水变化的潜力。里海的两个主要古水文事件，即阿克恰吉利亚海侵和阿克恰吉利亚海洋入侵，导致里海表面积扩大了 5 倍，并改变了盆地古生态，使区域间动物群的扩散活跃。根据土库曼斯坦和库拉盆地地质记录的磁地层研究，阿克恰吉连阶仍然缺乏具有两个年龄限制的明确年龄模型——“长阿克恰吉连”（3.6-1.8 Ma）和“短阿克恰吉连”（2.7-2.1 Ma） ， 分别。库拉盆地内也存在年龄差异，那里的化石哺乳动物 Kvabebi 地区与 Akchagylian 海洋动物群的磁地层学年代为 3.2 Ma。在本文中，我们试图解决 Akchagylian 阶段的年龄矛盾。我们重新考察了库拉盆地西部的 Kvabebi（格鲁吉亚）和 Kushkuna（阿塞拜疆）部分，并提供了新的磁地层和 1 Ma) 分别站在土库曼斯坦和库拉盆地地质记录的磁地层研究上。库拉盆地内也存在年龄差异，那里的化石哺乳动物 Kvabebi 地区与 Akchagylian 海洋动物群的磁地层学年代为 3.2 Ma。在本文中，我们试图解决 Akchagylian 阶段的年龄矛盾。我们重新考察了库拉盆地西部的 Kvabebi（格鲁吉亚）和 Kushkuna（阿塞拜疆）部分，并提供了新的磁地层和 1 Ma) 分别站在土库曼斯坦和库拉盆地地质记录的磁地层研究上。库拉盆地内也存在年龄差异，那里的化石哺乳动物 Kvabebi 地区与 Akchagylian 海洋动物群的磁地层学年代为 3.2 Ma。在本文中，我们试图解决 Akchagylian 阶段的年龄矛盾。我们重新考察了库拉盆地西部的 Kvabebi（格鲁吉亚）和 Kushkuna（阿塞拜疆）部分，并提供了新的磁地层和⁴⁰氩/ ³⁹这些边际 Akchagylian 矿床的 Ar 年龄限制。此外，我们修正了土库曼斯坦和库拉盆地 25 个地质记录的磁地层学，并提出了阿克恰吉阶新的统一时代模型：1. 2.95±0.02 Ma 的盆地内阿克恰吉里淡水-中盐海侵；2. 通过建立里海-北极连接（2.75-2.45 Ma）的阿克恰吉利亚海洋入侵；3. Akchagylian-Apsheronian 边界突出了 2.13 Ma 的里海-黑海连接。里海在 2.95 ± 0.02 Ma 的突然扩张可能与 AOTC 在 2.95 到 2.82 Ma 之间的间冰期强化有关。与前面提到的区域地质时间尺度（3.6-1.1.2.95-2.1 Ma）相比，新时代限制了更短的（2.95-2.1 Ma）阿克恰吉连。