Pollenstratigraphic Studies of Japanese Cenozoic Formations (IV) The Nishiyama Oil Field, Niigata Prefecture and the Ningyotoge Uranium Mine, Chugoku District.

1) The Cenozoic sediments in the Nishiyama Oil Field, Niigata Prefecture are divided in ascending order as follows: (1) Shichitani formation (Miocene), (2)Teradomari formation(Miocene), (3) Shiiya formation (Miocene or Pliocene), (4) Nishiyama formation (Pliocene), (5) Haizume formation (Pliocene) and (6) Uonuma Group (Pleistocene). The pollen-analytical results of the shale, mudstone and siltstonc from these formations are shown in Text. Fig.1. The Teradomari formation is characterized by a dominace of vesculate pollen and Tsuga. In the Shiiya formation, Abies and Tsuga are relatively rare, although Alnus and Liquidambar are abundant in some cases. In the Nishiyama formation, Pinus and Taxodiaceous pollen are dominat, and its pollen flora differs from the former fromations. The mudstone and siltstone of'the Haizume formation from the Niitzu Oil Field characterized by abundant occurence of Abies. The Uonuma group is dominated by non-arboreal pollen, such as Trapa, Persicaria, and Artemisa, together with fern-spore and Alnus. The pollen flora of this group differs from the former formations. 2) The Ningyotoge formation, well known as uranium bearing deposit, develops at the crest of the Ningyotoge on the border of Okayama and Tottori Prefectures, consits of conglomerate, sandstone, and siltstone. The siltsone contains abundant leave-remains, spore and pollen. The pollen-analytical results are shown in table 2. Chlonological character of the pollen flora seems to be younger than those of the Kobe Group (Miocene) and the Nizyo Group in Kinki district, and older than the Akashi Group and lower part of the Osaka Group (Upper Pliocene)