Abstract The Caspian Sea is the world's largest lake noted for a unique history of its evolution in the past. One of most important events in the Caspian history is the Atelian regression. The purpose of this work is to specify the extent, the time, and environments of the Atelian regression, as well as its correlation with events in the adjacent regions, on the basis of multidisciplinary studies of the Atelian deposits penetrated by engineering boreholes in the Northern Caspian. Processing of two-frequency seismoacoustic profiles permitted to stratify the sequence and to perform a spatial correlation between the determined boundaries of the sedimentary series. The laboratory studies included lithological and geotechnical analysis of the cores, floristic and faunal studies of the organic remains extracted from the cores, as well as analyses of pollen and spores, the isotope and radiocarbon (14C) analysis. In the seismic-acoustic profiles Atelian regression is represented by erosional landforms (incisions) under the reflecting horizon at the base of Khvalynian sediments. The regressive series is noted for inhomogeneous lithology. In depressions they are represented by interlayered clays and clay loams. The elevations between the depressions are composed of loamy sands in association with loams. Plant detritus occur as separate inclusions, or forms layered concentrations; there are also shells of freshwater and terrestrial mollusks. The paleontological material suggests aquatic or wetland environments with freshwater or freshened brackish-water shallow water bodies. The palynological materials provide evidence of diversified landscapes in the northern Caspian Lowland at the time of the Atelian regression – from forests dominated by conifers to periglacial forest-steppe and tundra-forest-steppe, mostly resulting from the climate fluctuations. The redeposited pollen is present in abundance, often well-preserved, indicative of highly active erosion at the time of regression. The Atelian regression maximum and the erosional processes on the northern Caspian Lowland correspond to the maximum cooling of the Kalinin (MIS 4) glacial time. The final stages of the regression fell on the initial phases of the MIS 3 interstadial. As follows from materials obtained by seismic-acoustic profiling and drilling, the Caspian level dropped to −100 m. We attribute the sea level lowering to the Caspian (Hyrcanian) water discharge through the Manych into the Pontian basin and to the specific glacial environment during the Valday (MIS 4) time. The Atelian regression maximum is correlatable with the maximum of the post-Karangatian regression of the Black Sea. It was at the same time that the lacustrine Burtass (Gudilo) series were deposited in the Manych depression. In the stratigraphic scheme of the Caspian Sea the Atelian regressive horizon (as a stratigraphic unit) is positioned between Hyrcanian and the base of Lower Khvalynian deposits. In the Northern Caspian the continental Atelian formation spans a greater chronological interval and should be considered as a suite (or formation) in the regional stratigraphic scheme. A comparison between the position of Atelian deposits in the Pleistocene sequence within the sea basin and on the dry land supports the assumption that the geological records exposed in the coastal zone are incomplete. Only a thorough analysis of the materials obtained from the offshore drilling and from the sequences studied in exposures on land can give a comprehensive picture of the history of regional environments and present them correctly in a stratigraphic scheme.

中文翻译：

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里海Atelian回归的古地理（基于钻探数据）

摘要 里海是世界上最大的湖泊，以其过去独特的演变历史而闻名。里海历史上最重要的事件之一是 Atelian 回归。这项工作的目的是在对北部工程钻孔穿透的 Atelian 矿床进行多学科研究的基础上，确定 Atelian 回归的范围、时间和环境，以及它与邻近地区事件的相关性。里海。双频地震声剖面的处理允许对序列进行分层并在沉积系列的确定边界之间进行空间相关。实验室研究包括对岩心进行岩性和岩土工程分析，对从岩心中提取的有机遗骸进行植物区系和动物区系研究，以及花粉和孢子分析、同位素和放射性碳 (14C) 分析。在地震声学剖面中，Atelian 回归由 Khvalynian 沉积物底部反射层下的侵蚀地貌（切口）表示。回归系列以非均质岩性着称。在洼地，它们以夹层粘土和粘壤土为代表。洼地之间的高地由壤土和壤土组成。植物碎屑以单独的夹杂物形式出现，或形成分层集中；还有淡水和陆生软体动物的贝壳。古生物学材料表明具有淡水或经过净化的咸水浅水体的水生或湿地环境。孢粉学材料提供了 Atelian 回归时里海低地北部多样化景观的证据——从以针叶树为主的森林到冰缘森林草原和苔原森林草原，主要是由气候波动造成的。重新沉积的花粉大量存在，通常保存完好，表明退化时侵蚀非常活跃。Atelian 回归最大值和里海低地北部的侵蚀过程对应于加里宁 (MIS 4) 冰川时期的最大冷却。回归的最后阶段落在了 MIS 3 间质的初始阶段。根据通过地震声学剖面和钻孔获得的材料，里海水平下降到-100 m。我们将海平面下降归因于里海 (Hyrcanian) 水通过曼尼奇河排放到笨珍盆地以及瓦尔代 (MIS 4) 时期的特定冰川环境。Atelian 回归最大值与黑海的后卡朗加特回归的最大值相关。与此同时，湖相Burtass (Gudilo)系列沉积于Manych凹陷。在里海的地层方案中，Atelian 回归层位（作为地层单位）位于 Hyrcanian 和下 Khvalynian 矿床的底部之间。在里海北部，大陆 Atelian 地层跨越更大的年代间隔，应被视为区域地层方案中的一个套件（或地层）。Atelian 沉积物在海盆和旱地上更新世序列中的位置之间的比较支持了海岸带暴露的地质记录不完整的假设。只有对从海上钻井获得的材料和从陆地暴露研究的序列中获得的材料进行彻底分析，才能全面了解区域环境的历史，并在地层方案中正确地呈现它们。