Main Stratigraphic Boundaries in the Cenozoic of Primorye and Their Manifestation in Lithology and Paleofloras

Within the territory of Primorye, regional boundaries between the high-rank stratigraphic subdivisions were discussed, including the boundaries between the Cretaceous and Paleogene, Paleogene and Neogene, and Neogene and Quaternary systems, as well as the boundaries between series within the systems. The following boundaries can be considered as the most valid and suitable as stratotypes: the Eocene, Oligocene boundary, attributed to the transition from the coal-bearing Khasanskaya Formation to the coal-free tuff siltstone Fatashinskaya Formation (Khasan Basin); the Paleogene, Neogene boundary, marked by the change in the lithological type of rocks from coal-bearing Upper Oligocene sediments to tuff siltstones and tuffs that make up the base of the Miocene (Rakovka Basin). It is proposed that the Miocene, Pliocene boundary be drawn within the basaltic lava complex with sedimentary rock members forming the Shufan and Shkotov volcanic plateau at the base of the Kedrovskaya sequence. The proposed Pliocene, Quaternary boundary corresponds to the base of the red-colored “pudding” sequence (Spassk Basin). The Cretaceous, Paleogene and Paleocene, Eocene boundaries cannot be determined with acceptable accuracy due to the lack of corresponding sections in the region.