Identification and Colors of Wood Buried by a Sector Collapse at Mt. Chokai

In 2014, large numbers of specimens of buried wood were excavated at the construction site for Nihonkai-tohoku expressway in Nikaho, Akita prefecture, Japan. They had been buried by the Kisakata debris avalanche following a sector collapse at Mt. Chokai in 466 B.C. The aim of this study is to identify the species of the buried wood and to record its characteristics, including colors. Sections made by sliding microtome were observed under a light microscope and samples were identified on the basis of anatomical features. As a result, wood identification of 39 buried specimens, included : Castanea crenata, Quercus section Quercus, Zelkova serrata, Aesculus turbinate, Fagus, Ostrya japonica, and Cryptomeria japonica. The color of buried wood was different from that of wood from living specimens of the same species. Buried wood of C. crenata and Quercus species was black in color, of Z. serrata was dark green, of A. turbinate, Fagus, and O. japonica was brown, and of C. japonica ranged from green-gray to brown. These buried wood specimens are valuable, not only as a model sample to analyze the mechanism by which color and strength of wood change during prolonged burial, but also as a part of the cultural heritage of the area. Therefore, it is significant to know the characteristic properties and chemical composition of buried wood specimens. Our results should provide fundamental and practical information for future investigation.