Palynological Characteristics of Miocene Deposits from the Submarine Yamato Rise (Sea of Japan)

Abstract

Four heterochronous spore and pollen complexes (SPC) have been identified in the deposits of the submarine Yamato Rise: SPC-1 (Early Miocene), SPC-2 (the end of Early and the beginning of the Middle Miocene), SPC-3 (Middle–Late Miocene), and SPC-4 (Late Miocene). Pollen of various woody plants dominates in SPC-1; the families of gymnosperms (Pinaceae) also prevail in this complex. The climate was moderate and humid because of the proximity to the water area. The complex SPC-2 differs from SPC-1 in the highly increased role of thermophile angiosperms due to the impact of the climatic optimum between the Early and Middle Miocene. The complex SPC-3 is distinguished by the diversity and predominance of broad-leaved woody plants. Gymnosperms are mainly represented by pine families. The composition of palynoflora points to a dissected relief and the burial of pollen not far from the places of its growth. Gymnosperms with a predominance of the Taxodiaceae family are characteristic of SPC-4. The SPC-4 composition is indicative of humid habitat conditions, marshy shoreland, and pollen burial in places of plants growth. The climate was moderate and humid. Palynological investigation suggests the existence of a dry land in the area of the current Yamato Rise throughout the Miocene. The relief was highly dissected and mountainous in the Early and early Middle Miocene; then, the relief roughness and firm-land area reduced dramatically.