In the San-in district the Plio-Pleistocene deposits widely distribute in the area facing to the Japan Sea. They are called the Tsunozu group in Shimane Prefecture. The Tsunozu group typically distributed in the hilly-land neighbouring Gotsu and Tsunozu (the stratotype) , and partly in the hills around Mt. Oe-takayama. The Tsunozu group, according to Imamura (1964) , is composed of marine and non-marine sediments and is correlated to the lower part of the Osaka group of Kinki district. In the Tsunozu group, Stegodon sp. and plant fossils, such as Pseudolarix, Glyptostrobus, Sequoia, Cunninghamia, Metasequoia, Nyssa, and Paleodavidia, were discovered (Imamura, 1964 ; Miki, 1950 etc.) . It is very characteristic that Stegodon and some elements of Pinus trifolia flora, as mentioned above, have coexisted at certain time of the geologic past. This coexistence shows that the deposition of the Tsunozu group began with the Pliocene age.
In this paper the writer describes the results of the pollen analysis of the Tsunozu group and will verify the floral changes in the Plio-Pleistocene age in Shimane Prefecture.