利根川沖積低地下に埋没した小松古墳の基盤について

土壌学的手法による解明

抄録

The old burial mound“Komatsu Kofun, ”which has been buried under the River Tone alluvial soil, was discovered at Hanyu City in Saitama Prefecture. The bottom of the chamber is situated 3 meters below the surface. It is considered that the mound was sunk by the Kanto Basin-forming movement, and has been buried by river sediments.
In this study, the location of Kofun ground was defined by pedological analyses of soil just under the chamber. The following conclusions can be drawn by making a comparison between these data and the characteristics of nearby Kanto loam terraces.
1) The basement of the burial mound is Tachikawa loam formation (tephra layer), which was formed in the Late Pleistocene, and Kofun was constructed on Kanto loam terrace. The formation is tephra in situ, not banked.
2) As there is no soil horizon A (Kuroboku soil) at the bottom of the chamber, it is estimated that the chamber was set on Tachikawa loam formation, which acquires bearing capacity by stripping coarse structural Kuroboku soil.
3) Tachikawa loam formation of the Kofun ground is air-borne and air-laid tephra, and non-tephra particles are also included in it. This mixed-particle tephra is not so extensive as to change the pedological characteristics of the Tachikawa loam formation.