In southern Kyushu, there are distributed Late Cenozoic formations which were deposited from the Early Miocene to the Latest Pleistocene period. The formations consist mainly of lava, tuff breccia, tuff and occasionally intercalate beds composed of siltstone or claystone deposited in the lacustrine and shallow marine. Among them, siltstone and claystone bads commonly include macro and micro plant fossils.
In the present paper the writers have examined the plant fossil bearing beds on the basis of stratigraphy and fossil evidence. As a result of the investigation, five major pollen assemblage zones can be distinguished in ascending chronological order. They are as follows;
1)
Metasequoia zone. Most of the pollen grains shown as Taxodiaceae in Figs. 3 and 4 are regarded as
Metasequoia because of the abundance of fossil leaves of the
Metasequoia sp. in the Nagano Formation and the Daiwa Member of the Koriyama Formation. The Arcto-Tertiary element such as
Metasequoia is characteristic of this zone. The age may be assigned to the period from the Late Pliocene to the Early Pleistocene.
2)
Fagus zone. Cool-temperate deciduous broad leaved trees and conifers such as
Fagus, Ulmus and/or
Zelkova, Pinus, Abies and
Tsuga are characteristic of this zone. The age may be considered to be the Early-Middle Pleistocene.
3)
Cryptomeria-Sciadopitys-Alnus zone. Temperate coniferous forests, coexisting with
Alnus, Juglans and
Corylus, dominated and
Cryptomeria increased later. This zone occupies a relatively warm period in the Middle-Late Pleistocene.
4)
Cryptomeria zone. This is characterized by a predominance of temperate conifers such as
Cryptomeria and
Abies suggesting a cool and damp climate. The age is considered to be the Late Pleistocene.
5) Pinaceae zone. This is yielding of such sub-arctic or cool-temperate coniferous taxa as
Picea, Pinus and
Tsuga. This may indicate a cold and dry climate during the Latest glaciation period.
View full abstract