Abstract

For the first time, sections of the Upper Miocene Ishim Formation in the south of Tyumen oblast near the villages of Pyatkovo, Masali and Bigila were thoroughly studied by the palynological method. A series of mineralogical analyses of these sediments and radiocarbon analysis of the Quaternary sediments overlying the Ishim Formation were carried out. Four palynological assemblages (PA) were established in the Ishim Formation: PA1 with Botryococcus; PA2 with Botryococcus and Sigmopollis; PA3 with Alnus, Polypodiaceae, Botryococcus, and Sigmopollis; PA4 with Betula, Alnus, and Corylus. The layers with PA1, PA2, and PA3 were observed in two sections near Masali and Bigila. PA4 was found in sands and aleuropelites in the outcrop near Pyatkovo; it contained a significant amount of diverse pollen of temperate thermophylic broad-leaved taxa and scarce elements typical of Miocene (Taxodiaceae, Nyssa, and Tsuga). PA3 and PA4 were compared to the known complexes of Neogene sediments in Western Siberia. PA5 with Betula, Herbae, and Fungi was discovered in the bedded silts overlying the Ishim Formation in Masali outcrop. Previously, these sediments were attributed to the Late Miocene Pavlodar Formation. The composition and the structure of PA5 suggested Quaternary age of the hosting sediments. Radiocarbon analysis of the organic substance occurring in the silts has shown that these sediments were accumulated in the Late Pleistocene (Sartan Ice Age). For the first time, the information about microphytoplankton (Botryococcus, Pediastrum, Zygnemataceae, Sigmopollis) and other non-pollen palynomorphs contained in the Ishim Formation (Upper Miocene) and in Pleistocene sediments is presented. Development stages of the Late Miocene Ishim Basin were distinguished, the vegetation surrounding this basin was described, and the depositional environment of Pleistocene sediments (Masali outcrop) was reconstructed using palynological data.

中文翻译：

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西西伯利亚Tobol-Ishim Interfluve的Ishim组（中新世）的孢粉剖面和沉积环境

摘要

第一次，通过孢粉学方法对秋明州南部南部的中新世Ishim组的断面进行了彻底研究，该村靠近Pyatkovo，Masali和Bigila村庄。对这些沉积物进行了一系列的矿物学分析，并对覆盖了伊希姆组的第四纪沉积物进行了放射性碳分析。在Ishim组中建立了四个孢粉组合：PA1和葡萄球菌；PA2与葡萄球菌和葡萄球菌; PA3与nu木，Poly科，葡萄球菌和乙藻; PA4与桦木，Al木和锦鸡儿。在Masali和Bigila附近的两个区域中观察到了具有PA1，PA2和PA3的层。在Pyatkovo附近的露头的沙子和钙铝矾石中发现了PA4。它包含大量不同的温带温带阔叶类群花粉和中新世典型的稀有元素（紫杉科，Nyssa和Tsuga）。将PA3和PA4与西西伯利亚新近纪沉积物的已知复合物进行了比较。PA5与桦木在Masali露头的Ishim组上覆的层状粉砂中发现了草科，Herbaae和真菌。以前，这些沉积物归因于中新世晚期Pavlodar组。PA5的组成和结构表明了沉积物的第四纪年龄。对淤泥中有机物的放射性碳分析表明，这些沉积物是在更新世晚期（萨坦冰期）积累的。首次，约microphytoplankton（信息葡萄藻，盘星，Zygnemataceae，Sigmopollis）以及伊希姆组（中新世）和更新世沉积物中所含的其他非花粉状古物。区分了中新世Ishim盆地的发育阶段，描述了该盆地周围的植被，并利用孢粉学数据重建了更新世沉积物（Masali露头）的沉积环境。