<departmental bulletin paper>
Pollen Stratigraphical Study of the Pleistocene Series in Oita City, Central Kyushu, Japan
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Abstract | Neogene and Quaternary deposits are widely distributed around Oita City, and they have been regarded as a standard of the Upper Cenozoic stratigraphy in West Japan (SHUTO, 1953, 1962, 1970; SHUTO et a...l., 1966, 1971). Especially, the Quaternary deposits in the Nyu and Tsurusaki Hills show a nearly complete succession ranging from the Early Pleistocene to the Late Pleistocene. Therefore, they are considered to provide a very suitable basis for revealing the successive change of pollen assemblages through the Quaternary in the Oita district. ONISHI (1965) outlined the succession of pollen assemblages in the Upper Cenozoic in this area. However, his samples were taken so sporadically through the strata that the result seems to be insufficient to clarify the succession of vegetation, and climatic change. It is also insufficient for the correlation of the deposits with other districts. In the present paper, the writer carried out the pollen analysis of the Pleistocene Oita Group and the Kuju Group on the basis of the systematically collected samples and could go into the consideration of the vegetational changes, palaeoclimatic succession and correlation. The results are summarized as follows: 1) By the pollen assemblages, the Oita Group and the Kuju Group are divided into three major pollen assemblage zones in which five subzones are distinguished. These are as follows in ascending order i) Taxodiaceae zone ii) Pinaceae zone a. Pinaceae-Alnus subzone b. Pinaceae-Fagus subzone iii) Fagus zon a. Fagus-Cyclobalanopsis subzone b. Lower Fagus-Quercus-Ulmus subzone c. Upper Fagus-Quercus-Ulmus subzone 2) On the basis of the pollen assemblages in each zone, successive changes of vegetation and palaeoclimate are clarified. 3) The lower part of the Katashima sand and gravel member corresponds to the Osaka Group below Ma 2 bed. 4) The upper part of the Takajo alternation member is correlated with the Kamikurata Formation in Yokohama City and with the Am 1 bed in the Ama Formation in the Nobi Plain 5) Liquidambar is detected in Jhe Late Pleistocene Oka mud member. The fact suggests that Liquidambar still survived into the Late Pleistocene in Oita district, although NISHIMURA (1980) asserts that the genus survived till the Middle Pleistocene in the Pacific coastal region of Southwest Japan.show more |
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Created Date | 2021.10.27 |
Modified Date | 2022.06.20 |