9. 西八木層出土木材の樹種(前篇 発掘調査の成果 / 第Ⅱ部 古環境の復元)

Abstract

The Nishiyagi Formation is distributed at Akashi district of Hyogo Prefecture, and it is regarded as deposits of the last interglacial epoch, the Shimosueyoshi age. 146 specimens of fossil wood were excavated from a cliff of the lower two members of the Nishiyagi Formation in 1985, and were identified in the present paper. Furthermore, specimens which has been excavated from the comparable strata with the Nishiyagi Formation near the cliff in 1948 and preliminary identified by Watari Shunji are also reidentified here. Some of the specimens excavated in 1948, however, are sometimes regarded as those were not derived from the Nishiyagi Formation but from an older stratum of the Lower Pleistocene.Totally 306 specimens were identified into 33 taxa of 18 families as shown in Table 8. Ecological habitats of those taxa are quite wide in range from the subarctic to the subtropical climate, and it is considered the fossil wood does not indicate a single vegetation but indicates several vegetations of a single age or of several ages. Although most of the identified taxa are still now distributed in Japan, some trees which has been already extinct from Japan or Honshu Island, for example, Metasequoia, Cudrania and Lagerstroemia, are included. The extinction of the latter two taxa in the last glacial age is presumed here, while it is generally considered that Metasequoia has been already extincted in Japan before the last interglacial age

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