Abstract The Kosika locality is situated on the lowest terrace of the Enotayevka River (right channel of the Volga River) near Kosika village, in the Astrakhan region of the Russian Federation. This locality includes several sections, named Kosika 1–4 and Borehole 2 Kosika that are described in detail for the first time. Drilling, sediment descriptions, and sampling were performed during the 2008–2015 field seasons. Application of complex biostratigraphical methods and optically stimulated luminescence (OSL) dates were used to reconstruct the Neopleistocene (Middle-Late Pleistocene) palaeoenvironment in the Lower Volga area. During the Tyurkyan Period (at the early beginning of the Neopleistocene), regression of the Apsheronian Sea began. Lithological features and the presence of freshwater molluscs demonstrate that deposits accumulated in rivers and lakes under humid climatic conditions. Molluscs, ostracods, and dinoflagellates inhabited the Baku Sea. Climate was arid at the beginning of this period and humid during a later phase. Several changes affecting the marine and fluvial environments characterise the Early Khazar period. In particular, the climate oscillated from humid conditions at the beginning to an arid state, then returned to a more humid setting at the end of this period. These changes are indicated by palynological and malacological data. Regression of the Early Khazar Sea occurred during Singil time, when rivers, lakes, and limans (lagoons) existed. Large mammals inhabited plains that were covered by extensive vegetation. The climate during this period was humid and slightly cooler than the present day climate. Late Khazar and Khvalyn transgressions occurred during the Late Neopleistocene. When the Late Khazar Sea retreated from the territory, river valleys became the dominant landscape feature. Floodplains of Late Khazar rivers became sites of deposition of loamy and sandy material emplaced during flood events. At the end of this regressive period, the climate was arid and dry enough to allow for accumulation of anhydrite sediment in shallow lagoons and lakes. Afterwards, the Khvalyn transgression began, as indicated by the occurrence of specific key mollusc species. Fluvial-marine deposits formed geological bodies representative of an undersea delta, which in relief form the Baer Knolls. The modern Volga valley was formed during the Holocene.

中文翻译：

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生物地层学调查作为俄罗斯下伏尔加河 Kosika 新更新世（中上更新世）古环境重建的工具

摘要 科西卡地区位于俄罗斯联邦阿斯特拉罕地区科西卡村附近的 Enotayevka 河（伏尔加河右航道）最低阶地。该地点包括多个部分，命名为 Kosika 1-4 和 Borehole 2 Kosika，它们是首次详细描述。在 2008-2015 年的野外季节期间进行了钻探、沉积物描述和采样。应用复杂的生物地层学方法和光激发光 (OSL) 数据重建了伏尔加河下游地区的新更新世（中-晚更新世）古环境。在秋尔金时期（新更新世初期），阿普谢罗尼亚海开始回归。岩性特征和淡水软体动物的存在表明，在潮湿气候条件下，河流和湖泊中积累了沉积物。软体动物、介形动物和甲藻栖息在巴库海。这一时期初期气候干旱，后期气候潮湿。影响海洋和河流环境的一些变化是早期可萨时期的特征。特别是，气候从开始时的潮湿条件摆动到干旱状态，然后在这一时期结束时恢复到更加潮湿的环境。这些变化由孢粉学和马拉色菌学数据表明。早期可萨海的回归发生在辛吉尔时期，当时存在河流、湖泊和泻湖。大型哺乳动物居住在被茂密植被覆盖的平原上。这一时期的气候潮湿，比现在的气候稍凉。Khazar 和 Khvalyn 海侵发生在新更新世晚期。当晚可萨海从领土撤退时，河谷成为主要的景观特征。晚哈扎尔河的漫滩变成了在洪水事件中出现的壤土和沙质物质的沉积点。在这个回归期结束时，气候干旱干燥，足以使浅水泻湖和湖泊中的硬石膏沉积物堆积。之后，Khvalyn 海侵开始，具体的关键软体动物物种的出现表明了这一点。河流-海相沉积物形成了代表海底三角洲的地质体，这些三角洲形成了贝尔丘陵（Baer Knolls）。现代伏尔加河谷形成于全新世。