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.
| Original language | English |
|---|---|
| Pages (from-to) | S82-S91 |
| Number of pages | 10 |
| Journal | Russian Journal of Pacific Geology |
| Volume | 17 |
| Issue number | SUPPL 2 |
| DOIs | |
| Publication status | Published - Dec 2023 |
Funding
The authors are grateful to G.N. Aleksandrova for assistance in laboratory processing of samples and to N.V. Gorkova for microfossil investigation in a scanning microscope and microprobe analysis of minerals. This work was carried out within the framework of the state assignment for the Geological Institute of the Russian Academy of Sciences (nos. FMMG2021-0003 and FMMG-2022-0002) and with the financial support of the Russian Foundation for Basic Research (no. 20-05-00085).