New Data on the Neogene Volcano-sedimentary Complex of the Icha Depression: The Tyrkachyn Section (West Kamchatka)

IF 0.9 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY Russian Journal of Pacific Geology Pub Date : 2024-02-04 DOI:10.1134/s1819714023080092

T. V. Oreshkina, M. M. Pevzner, V. V. Petrova, T. D. Karimov

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Abstract

In the 90-m river bank of the middle reaches of the Icha River, thick strata of volcano-sedimentary deposits represented by pyroclastic rocks and siliceous tuffites with layers of diatomites were studied. Representative diatom assemblages assigned to the Middle Miocene Denticulopsis hyalina Zone (14.9–13.1 Ma) indicate relatively deep-water conditions of the marine basin. Comparison with the data on diatom assemblages from reference sections of West Kamchatka indicates that the deposits of the Tyrkachyn section belong to the upper part of the Kakert Formation. The petrographic composition and lithological structure of volcanogenic formations (members 1, 2, and 4) suggest that they are the product of pyroclastic flows associated with volcanic activity in central Kamchatka. It is supposed that members 1 and 2 were formed in subaerial conditions, as indicated by the complete absence of marine microfossils, signs of primary volcanic stratification, and the absence of layering. The sediments of member 4 with eroded contacts and pronounced layering apparently accumulated in a subaqueous setting.

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伊恰凹陷新近纪火山沉积岩群的新数据：蒂尔卡钦地段（西堪察加半岛）

摘要在伊察河中游 90 米河岸，研究了以火成岩和硅质凝灰岩为代表的火山沉积物厚地层以及硅藻土层。具有代表性的硅藻群被归入中新世 Denticulopsis hyalina 区（14.9-13.1Ma），表明该海盆处于相对较深的水域条件下。与西堪察加参考剖面的硅藻组合数据比较表明，蒂尔卡钦剖面的沉积物属于卡克尔特地层的上部。火山成因地层（1、2 和 4 号岩层）的岩相组成和岩性结构表明，它们是堪察加半岛中部火山活动相关火成碎屑流的产物。根据完全没有海洋微化石、原生火山分层迹象以及没有分层的情况来看，1 号和 2 号岩层应该是在亚大气层条件下形成的。岩层 4 的沉积物具有侵蚀接触和明显的层理，显然是在水下环境中堆积而成。

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来源期刊

Russian Journal of Pacific Geology 地学-地球科学综合

CiteScore

1.30

自引率

37.50%

发文量

审稿时长

>12 weeks

期刊介绍： Russian Journal of Pacific Geology publishes the results of research on the Earth crust and mantle composition and provides articles on the geological structure and patterns of distribution of mineral deposits in the Pacific Ocean, marginal seas and continental margins. It discusses the topics of stratigraphy, sedimentology, magmatic activity, and seismicity. The journal deals with the problems of lithosphere plates tectonics, and offers the results of neotectonic, geomorphological, geodesic, environmental and mining studies in the Pacific region. The journal accepts theoretical, methodical and philosophical articles covering general issues of geology, geophysics, geochemistry, geoecology and mining. The journal also publishes critical notes and comments, and reviews.