Palynological studies from the upper Pliocene-lower Pleistocene hemipelagic sediments of the Eastern South Korea Plateau, East Sea: paleoclimate and paleoceanographic implications

Palynofloral analysis from Site U1430 Core drilled at the Eastern South Korea Plateau of the East Sea by IODP Expedition 346 was carried out to interpret paleoclimate and paleoceanography during the late Pliocene to early Pleistocene climate transition period. East Sea is controlled by climatic and oceanographic conditions, especially East Asian monsoon (EAM) and Tsushima Warm Current (TWC). Site U1430 provides a good opportunity to monitor paleoclimate and oceanographic changes by intensity of EAM and TWC. According to results of the palynofloral analysis, two pollen and dinocysts zones were established and their zone boundary was recognized at ca. 2.93 Ma on the basis of assemblages and some critical taxa. Paleoclimate and paleoceanography prior to ca. 2.93 Ma (P-I, D-I) are considered to have been unstable long term East Asia Winter monsoon (EAWM) indicated by fluctuation between cold-dry and cool-wet climatic pollen taxa. In addition, an abundance of warm water species such as Tuberculodinium vancampoae and Lingulodinium sp. in this section may indicate warm marine conditions influnced by inflowing of the TWC into the East Sea. After ca. 2.93 Ma (P-II, D-II), the pollen assemblage was characterized by not only increased cold-dry climatic conifer pollen (Abies, Picea and Pinus-Haploxylon) and xerophytic grass pollen (Artemisia), but also decreased cool temperate conifer pollen (Tsuga), which indicates enhanced EAWM with stable cold-dry conditions. High abundance cold-dry climatic conifer pollen and cold water species dinocysts (Spiniferites elongatus and Operculodinium centrocarpum) after ca. 2.75 Ma may indicate more intensified EAWM and cold-dry conditions.