Parent Materials of Holocene Volcanic Ash Soils on South Kanto District, Japan. Evaluation with primary mineral and element composition.

Volcanic ash soils occur widely on South Kanto district. The surface soil has black color and high humus content. The parent material is derived from Holocene volcanic ash. There are some buried humic horizons resulted from a succession of volcanic ash accumulation and plant residue supply leading to the accumulation of soil organic matter or humus. It has commonly been considered that Mt. Fuji supplied parent material of those soils.