Abstract—

This work presents the results of integrated micropaleontological and lithogeochemical analysis of Upper Oligocene continental deposits of the Turtas Formation from the Zyryanskaya-1 borehole (southwestern part of the Tyumen Region, Western Siberia). The predominance of freshwater planktonic diatoms at the subordinate significance of benthic species, as well as the presence of gemmuloscleres of sponges, indicates the coastal sedimentation conditions in a freshwater basin varying in depth from 3 to 50 m. The studied palynocomplex is similar to the spore-and-pollen spectra of the Turtas Formation of the Lower Ob Region, but differs from palynocomplexes of the same formation spread over the southern regions of Western Siberia in a low amount of Taxodiaceae/Cupressaceae and Betulaceae pollen, as well as the absence of Fagaceae pollen and Pseudokomewuia freshwater dinocysts. The revealed differences can be explained both by facies features and by variations in the volume of the Turtas Formation in the currently known localities. The data on the microelemental composition of samples, as well as geochemical and petrogeochemical modules, indicate that the accumulation of the Turtas Formation occurred in the coastal areas of a low-mineralized basin under relatively warm humid climatic conditions.

中文翻译：

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西西伯利亚Turtas组（上渐新世）的微古生物学和岩石地球化学特征

摘要—

这项工作提出了从Zyryanskaya-1井眼（西伯利亚州秋明州西南部）Turtas组上渐新世大陆上沉积的综合微古生物学和岩相化学分析的结果。淡水浮游硅藻在底栖物种的次要意义上占主导地位，以及海绵的宝石核的存在，表明淡水盆地的沿海沉积条件在3至50 m范围内变化。所研究的古植物络合物与下奥布地区图尔塔斯组的孢子和花粉光谱相似，但与西伯利亚西部南部地区分布相同的古植物络合物不同，紫杉科/柏科和桦木花粉较少，以及没有流苏科花粉和假单胞菌淡水藻囊。所揭示的差异可以通过相特征或当前已知地区的图尔塔斯组的体积变化来解释。关于样品的微量元素组成以及地球化学和岩石化学模块的数据表明，Turtas组的堆积发生在相对温暖潮湿的气候条件下的低矿化盆地的沿海地区。