Pliocene sediments of Shikotan Island (Lesser Kuril Ridge) |
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| Authors: | E P Terekhov I B Tsoy A V Mozherovskii N K Vagina |
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| Institution: | 1. V.I. Il’ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences, ul. Baltiiskaya 43, Vladivostok, 690041, Russia
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| Abstract: | Shikotan Island of the Lesser Kuril Ridge forms, together with the Vityaz Ridge, the outer arc of the Kuril island-arc system. Marine Pliocene sediments first registered on the island contain diatoms and palynomorphs, which allow their dating. The thin Pliocene semiconsolidated sediments constitute the upper part of sections in the coastal and central areas of the island. They rest with the erosional surface and stratigraphic hiatus upon the Upper Cretaceous-Lower Paleogene (Campanian-Danian) Malokuril’sk Formation. The Pliocene sediments were deposited in relatively shallow-water environments of open sea near the shore, with a forest-free landscape and freshwater basins. The occurrence of reworked marine Oligocene and Miocene diatoms in these sedimentary rocks indicates their development in the Lesser Kuril Ridge area and contribution of their eroded material to the formation of Pliocene sequences. Wide development of Pliocene Marine sediments on Shikotan Island is evidence for ascending movements in the region during the post-Pliocene period, which is also characteristic of the Greater Kuril Ridge islands. The composition and formation conditions of the Pliocene sediments in the outer arc of the Kuril island-arc system suggest that the southwestern (Lesser Kuril Ridge) and northeastern (Vityaz Ridge) segments of this single anticlinal structure evolved under different tectonic regimes through the Pliocene. |
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