Miocene freshwater diatoms from the eastern slope of the submarine Ulleung Plateau (Krishtofovich Rise) in the Sea of Japan

Resumo

The freshwater diatom flora from the tuffogenous sedimentary rocks of the submarine Ulleung Plateau of the southern Sea of Japan is studied and its complete taxonomic composition (96 species and varieties belonging to 33 genera) is revealed. It is characterized by species diversity and abundance of representatives of the freshwater genus Aulacoseira. The predominance of Aulacoseira is characteristic of the Miocene lacustrine deposits of the Sea of Japan and other regions, but the presence of ellipsoid species of narrow stratigraphic distribution allows the age of the recognized diatom flora to be limited to the Early Miocene. The species diversity and abundance of diatoms in the deposits of the Ulleung Plateau indicate the presence in the Early Miocene of a large freshwater lake in this region. Such lakes also existed on other large submarine rises of the Sea of Japan and its periphery before the onset of the tectonic activation which led to the descent of vast fragments of the continent and expansion of the Sea of Japan.