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Abstract <p>For the first time, the results of potassium–argon (K–Ar) dating of Neogene–Quaternary volcanic rocks that make up Onekotan and Shiashkotan islands (Northern Kuril Islands) are presented. Earlier, ideas about the age of the rocks that make up these islands were based solely on their lithological similarity to paleontologically characterized sections of neighboring (best-studied) Paramushir Island. For rocks of the Okruglovsky volcanic complex (VC) of Onekotan Island, three age determinations were obtained in the range from 6.1 to 3.1 Ma (isotope analyses (K–Ar method) were performed in the laboratory of isotope geochemistry and geochronology of the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences (Moscow); the content of radiogenic argon was determined by the isotope dilution method using the single isotope ³⁸Ar as a tracer). Two age datings were obtained from the sections of Shiashkotan Island: one for rocks of the Okruglovsky VC (2.6 Ma) and one for the rocks of the Levashovsky VC (1.06 Ma). The obtained isotope-geochronological data indicate that the most ancient formations on these islands are hydroexplosive and volcanosedimentary rocks of the late Miocene–Gelasian Okruglovsky VC. In addition, these data indicate the absence of Oligocene–Lower Miocene rocks of the “green tuff” complex in the section of these islands. Isotope dating of subaerial volcanics, which unconformably overlie rocks of the Okruglovsky VC, allowed them to be attributed to Gelasian–Early Neopleistocene formations of the Levashovsky VC. The stratigraphic hiatus between the Okruglovsky and Levashovsky complexes marks an important milestone in the geological history of the Kuril Islands, associated with a change in the volcanic regime and a new stage in the tectonic reorganization of the Greater Kuril Arc.</p>

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New Data on the Geological Structure of Onekotan and Shiashkotan Islands (Greater Kuril Ridge) Based on Isotope Dating Results

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • A. V. Rybin,
  • A. V. Degterev,
  • P. Y. Kovtunovich,
  • V. A. Lebedev,
  • M. V. Chibisova

摘要

Abstract

For the first time, the results of potassium–argon (K–Ar) dating of Neogene–Quaternary volcanic rocks that make up Onekotan and Shiashkotan islands (Northern Kuril Islands) are presented. Earlier, ideas about the age of the rocks that make up these islands were based solely on their lithological similarity to paleontologically characterized sections of neighboring (best-studied) Paramushir Island. For rocks of the Okruglovsky volcanic complex (VC) of Onekotan Island, three age determinations were obtained in the range from 6.1 to 3.1 Ma (isotope analyses (K–Ar method) were performed in the laboratory of isotope geochemistry and geochronology of the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences (Moscow); the content of radiogenic argon was determined by the isotope dilution method using the single isotope ³⁸Ar as a tracer). Two age datings were obtained from the sections of Shiashkotan Island: one for rocks of the Okruglovsky VC (2.6 Ma) and one for the rocks of the Levashovsky VC (1.06 Ma). The obtained isotope-geochronological data indicate that the most ancient formations on these islands are hydroexplosive and volcanosedimentary rocks of the late Miocene–Gelasian Okruglovsky VC. In addition, these data indicate the absence of Oligocene–Lower Miocene rocks of the “green tuff” complex in the section of these islands. Isotope dating of subaerial volcanics, which unconformably overlie rocks of the Okruglovsky VC, allowed them to be attributed to Gelasian–Early Neopleistocene formations of the Levashovsky VC. The stratigraphic hiatus between the Okruglovsky and Levashovsky complexes marks an important milestone in the geological history of the Kuril Islands, associated with a change in the volcanic regime and a new stage in the tectonic reorganization of the Greater Kuril Arc.