Abstract Permafrost is considered to be one of the important sources of additional water for the vast Late Quaternary Caspian Sea transgressions. The insufficiency of proxy evidence on landscape and climate dynamics during the long Atelian regression (MIS-4 – MIS-3) complicates the analysis of changes in the Caspian water balance. Traces of Late Pleistocene cryogenesis structures were catalogued in the alluvial and loess-soil deposits of the Srednyaya Akhtuba reference section. Four stages of permafrost development were described for the first time in the Lower Volga region. Under conditions of seasonal and longer-term freezing in the Late Pleistocene, cryogenic transformation of the deposits took place; this determined the composition, structure and properties of the loess-paleosol complex at the site. Cryolithological, micromorphological analyzes and particle size distribution of mineral matter were carried out for each horizon, and traces of cryogenic processes were described in order to evaluate the regional paleoclimatic conditions that prevailed during their formation. Optically stimulated luminescence dating was used to establish a chronological framework for the main phases of the development of cryogenic modification in the Lower Volga region. The fourth stage of formation involved deep cracking of the substrate, which occurred during freezing in MIS-4, coincident with the Atelian regression of the Caspian Sea. The third stage is expressed as large wedge-shaped structures (pseudomorphs) on the border of loess and alluvial packages, with their formation known to be associated with the degradation of ice wedges. During the second and first stages of freezing, plastic deformation of deposits occurred.

中文翻译：

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俄罗斯伏尔加河下游 Srednyaya Akhtuba 参考剖面黄土-古土壤层序的晚更新世低温特征

摘要 多年冻土被认为是晚第四纪里海海侵的重要补充水源之一。在长期的 Atelian 回归 (MIS-4 – MIS-3) 期间，景观和气候动态的代理证据不足，这使里海水平衡变化的分析变得复杂。在 Srednyaya Akhtuba 参考部分的冲积和黄土土壤沉积物中编目了晚更新世低温结构的痕迹。在伏尔加河下游地区首次描述了永久冻土发展的四个阶段。在晚更新世季节性和长期冻结条件下，沉积物发生低温转化；这决定了现场黄土-古土壤复合体的组成、结构和特性。冰晶，对每个层位进行了矿物的微形态分析和粒度分布，并描述了低温过程的痕迹，以评估其形成过程中的区域古气候条件。光激发光测年被用来为下伏尔加地区低温改造发展的主要阶段建立一个时间框架。形成的第四阶段涉及基底的深裂，发生在 MIS-4 冻结期间，与里海的 Atelian 回归同时发生。第三阶段表现为黄土和冲积层边界上的大型楔形结构（伪地貌），它们的形成与冰楔的退化有关。