Palynostratigraphy and climatic implications of Neogene deposits in the Himi area of Toyama Prefecture, Central Japan

Abstract

A palynological study on the well-outcropped sections in the Himi area of Central Japan yields new evidence of Neogene floral and climatic changes. Five palynostratigraphical zones recognized from the strata show changes in palynofloras from the Middle Miocene to the Pliocene. Major changes in the palynofloras are indicated by the fluctuating occurrence of some elements such as Taxodiaceae, Tsuga, Picea, evergreen Quercus and now-extinct Tertiary types in Japan, reflecting a general trend of climate deterioration from before 13 to 2 Ma. This trend is punctuated by the re-expansion of warm-temperate types in the late Middle Miocene (13–9.2 Ma), and in part of the Early Pliocene (5.5–4 Ma). Our results are largely comparable to pollen data derived from the neighboring areas. The inferred climate is largely consistent with the pattern of Neogene climatic change revealed in marine sediment records of the Ocean Drilling Program and the Deep Sea Drilling Project, implying that the evolution of the Neogene climate in Japan has been primarily consistent with worldwide climatic change since the opening of the Sea of Japan.