Composition of the rocks of the Kotikovo Group and the main stages in the Late Cretaceous-Paleogene evolution of the Terpeniya Peninsula, Sakhalin Island

Abstract

This paper reports and discusses the composition of the rocks of the Kotikovo Group (the Uchir, Zaslonovskaya, Turovskay, and Ol’don formations) of the Terpeniya Peninsula (East Sakhalin). It is suggested that the Cenozoic deposits unconformably overlay the Maastrichtian-Danian rocks with basal conglomerates at the base. Two main stages were distinguished in the Late Cretaceous-Paleogene evolution of this area on the basis of our study. The first stage was responsible for the formation of the Maastrichtian-Danian volcaniclastic and volcanogenic-sedimentary rocks of the Uchir Group, while the second stage produced the Paleocene-Eocene sedimentary rocks of the Zaslonovskaya, Turovskaya, and Ol’don formations. The end of the first stage (at the boundary of the Uchir and Zaslonovskaya formations) was marked by a change in the tectonic regime. This was expressed in the weakening of the volcanic activity, the uplift of the territory, and the exposure of new provenances to erosion. During the second, Early Paleogene stage, the area of the East Sakhalin Mountains, the Terpeniya Peninsula, and the submarine Terpeniya Ridge represented a shallow-water marine sedimentary basin representing the western flank of the Cenozoic Pogranichnyi Basin. The formation of the anticlinal East Sakhalin Mountains-Terpeniya Peninsula-submarine Terpeniya Ridge structure occurred during the Late Cenozoic period of the East Sakhalin evolution.