2008 Volume 115 Issue 2 Pages 64-79
Pollen data from the upper part of the Tanaka Formation in the Higashinada 1700-m drill core, obtained from Kobe City, southwest Japan, enable the construction of a pollen biostratigraphy and detailed record of paleoenvironmental change during the Middle Pleistocene.
In this study, 174 sediment samples were collected at ca. 2-m intervals from the upper part of the Tanaka Formation, which approximately corresponds to the upper Osaka Group. This formation, which is the hypostratotype for the Pleistocene stratigraphy in the Osaka sedimentary basin, consists mainly of fluvial and lacustrine sediments intercalated with 19 marine clay beds.
The fossil pollen assemblages in the marine clay beds are dominated by tree and shrub pollen belonging mainly to temperate and cool-temperate deciduous broad-leaved and temperate evergreen coniferous tree taxa, accompanied by pollen of warm-temperate deciduous coniferous and evergreen broad-leaved tree taxa. The pollen assemblages within non-marine sediments that immediately underlie each of the marine clay beds are dominated by herbaceous taxa and tree taxa such as Alnus; they also contain Pteridophyte spores.
The pollen biostratigraphy from Ma 2 to Ma 12 marine clay beds in the Higashinada core comprises 20 pollen assemblage zones and 5 superzones: the Quercus-Metasequoia, Fagus-Quercus, Cryptomeria-Fagus, Cyclobalanopsis-Sciadopitys, and Pinaceae-Cryptomeria, in ascending stratigraphic order.
At the time of the Quercus-Metasequoia Superzone, the paleovegetation consisted of warm-temperate deciduous broad-leaved forest. Subsequently, temperate evergreen conifers show a gradual increase in abundance. At the time of the Fagus-Quercus Superzone, the paleovegetation consisted of mixed warm-temperate deciduous broad-leaved and temperate evergreen conifer forest. The Cryptomeria-Fagus Superzone is characterized by alternating periods of temperate evergreen conifers and temperate deciduous broad-leaved trees. The Cyclobalanopsis-Sciadopitys Superzone is characterized by warm-temperate evergreen broad-leaved forest accompanied by temperate evergreen conifers in the hinterland, and the Pinaceae-Cryptomeria Superzone is dominated by temperate evergreen coniferous forest.
