抄録
In the eastern and middle San-in districts, on the southern coast of the Western Japan Sea, the following floral change is recognized since the middle Pleistocene.
There were three types of flora during the middle Pleistocene. First was the interglacial flora composed of cool temperate forest elements such as Fagus crenata, Quercus sp., Cryptomeria japonica, etc., and a pollen assemblage which is predominated by Fagus or represented by Fagus and Cyptomeria. Second is the glacial flora composed of subarctic elements as Picea jezoensis, Tsuga diversifolia, Menyanthes trifoliata, etc., and pollen assemblage represented by Pinus Subgen Haploxylon and Picea. Third is the interstadial flora composed of pollen assemblages represented by Picea and Cyptomeria.
During the late Pleistocene, a fourth type of flora appeared, composed of warm temperate forest elements with pollen assemblages containing Cyclobalanopsis. Moreover, some species occur in each type of flora: Pinus koraiensis occurs in glacial flora, Lagerstroemia pollen in interglacial and Buxus microphylla var. japonica and Pseudotsuga japonica in interstadial. By means of pollen analysis, the latest Pleistocene and Holocene pollen zones are clearly identified as follows.
Quercus and Alnus PZ: before about 10, 000y.B.P.
Quercus and Aphananthe-Celtic PZ: about 10, 000 to 9, 000y.B.P.
Fagus and Tsuga PZ: about 9, 000 to 7, 000y.B.P.
Pinus and Abies PZ: about 7, 000 to 5, 500y.B.P.
Cyclobalanopsis and Castanopsis PZ: about 5, 500 to 2, 400y.B.P.
Gramineae PZ: about 2, 400y.B.P. to present
Cryptomeria Subzone: about 2, 400y.B.P. to about A. D. 700
Typical Subzone: about A. D. 700 to 1, 500
Pinus Subzone: about A. D. 1, 500 to later than 1, 900
Pinus and Cyptomeria Subzone: later than A. D. 1, 900 to present.
