Age and conditions of formation of sedimentary cover of the Ulleung Plateau of the Sea of Japan according to micropaleontological data

The paper reports on the micropaleontologcal (diatoms, silicoflagellates, radiolarians, and pollen flora) data substantiating the age and conditions of sedimentary cover formation of the submarine Ulleung Plateau (Krishtofovich Rise) in the Sea of Japan. Five rock complexes with different age and origin were distinguished on the basis of micropaleontological and petrographic data. Complex 1 (tuffites, tuffogenous siltstones) with numerous freshwater diatoms and pollen flora that prove the lacustrine genesis and the Early Miocene age occurs at the base of the sedimentary cover. Complexes 2–5 are composed of marine tuffogenous sedimentary deposits of end of Early Miocene–Pleistocene age. Stratigraphic unconformity between continental and marine deposits involves a short-time interval in the end of the Early Miocene and points to rather fast tectonic submersion of the Ulleung Plateau. Marine sedimentation in bathyal conditions dominated from the end of the Early Miocene. In the Late Miocene, in the northern part of the plateau, the region of the large rise was characterized by shallow-water conditions, indicating supposed existence of an island territory in this place.