Coloring mechanisms of ancient buried wood: Japanese cedar trees excavated from the foothills of Mt. Chokai

Abstract

Spectroscopic characterization of ancient buried Japanese cedar (Cryptomeria japonica) woods excavated from the foothills of Mt. Chokai was carried out to investigate the factors governing their color tones. X-ray fluorescence analysis confirmed primary metal elements in the Japanese cedar wood to be Ca and Fe. Infrared photoacoustic spectroscopy revealed that prolonged burial had not caused severe chemical decomposition of the ancient wood. 57Fe Mössbauer spectra of the ancient wood samples suggested that Fe in the Japanese cedar wood was present in the high-spin Fe3+ or low-spin Fe2+ state. Although the dark color tone of the ancient wood has been assumed to be due to the presence of multinuclear Fe complexes with multidentate ligands such as tannin, no positive correlation was observed between the color depth and Fe content of the ancient wood samples.