Abstract

The results of integrated study of the Cretaceous/Paleogene transition in the northeastern Caucasus are reported. The lithological, geochemical and micropaleontological characteristics of the sediments from two sections (Okhli and Gubden, Mountainous Dagestan) accumulated in different parts of paleobasin are displayed. An analysis of nannofossil distribution at the Cretaceous/Paleogene transition allowed to define the stratigraphic position of the stage boundary and reveal the interval of sediments (1–2 m thick transitional zone) accumulated under stress conditions. The large-scale sea-level fall occurred at the onset of the Cretaceous/Paleogene boundary event is evidenced. It led to the erosion and redeposition of the Maastrichtian calcareous sediments. In Okhli section, the occurrence of palygorskite is detected in the clay mineral assemblage of the transitional zone. The local concentrations of coprolites (Decapoda?) and spherical nodules of different composition (more likely, concretions) are found in the clay layer onlapping the erosional surface at the top of Maastrichtian. There is no reliable evidence of the impact nature of these nodules. The lithological record at the Cretaceous/Paleogene transition of the studied sections is similar to those exposed in other areas of the NE Peri-Tethys (e.g., southern Turkmenistan and Mangyshlak Peninsula).

中文翻译：

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达格斯坦东北高加索地区白垩纪-古近界：沉积学，地球化学和生物群

摘要

报道了东北高加索地区白垩纪/古近纪过渡的综合研究结果。展示了古巴辛不同地区两段（奥赫利和古登，达吉斯坦山）沉积物的岩性，地球化学和微古生物学特征。对白垩纪/古近纪过渡期的纳米化石分布的分析可以确定阶段边界的地层位置，并揭示应力条件下沉积的沉积物（1-2 m厚过渡带）的间隔。有证据表明，大型海平面下降发生在白垩纪/古近纪边界事件的开始。它导致了马斯特里赫特钙质沉积物的侵蚀和再沉积。在Okhli部分，在过渡带的粘土矿物组合中发现了坡缕石的存在。在马斯特里赫特顶部的侵蚀面上覆盖的粘土层中发现了共浓缩的Proprolites（十足草）和球形结节（组成更可能是凝结物）。没有可靠证据证明这些结核的影响性质。所研究断面的白垩纪/古近纪过渡期的岩性记录与东北特提斯北部其他地区（例如，土库曼斯坦南部和Mangyshlak半岛）暴露的岩性记录相似。没有可靠证据证明这些结核的影响性质。所研究断面的白垩纪/古近纪过渡期的岩性记录与东北特提斯北部其他地区（例如，土库曼斯坦南部和Mangyshlak半岛）暴露的岩性记录相似。没有可靠证据证明这些结核的影响性质。所研究断面的白垩纪/古近纪过渡期的岩性记录与东北特提斯北部其他地区（例如，土库曼斯坦南部和Mangyshlak半岛）暴露的岩性记录相似。