Abstracts of Symposium 55 and some papers from other related Symposia.

Interpretation of Holocene Paleosols Derived from Volcanic Ash Fall Deposits in Japan

Makiko WATANANBE, Chuo-Gakuin Univ., Abiko-shi, Chiba 270-11, Japan,
Kumiko AOKI, Institut fur Bodenkunde, Univ. Hamburg, Allende-Platz 2, Hamburg, Germany, &
Kan-ichi SAKAGAMI, Dept. of Agriculture, Tokyo Univ. of Agriculture and Technology, Saiwai-cho, Fuchu-shi, Tokyo 183, Japan

Andisol profiles develop according to the rate of volcanic ash supply and the rate of soil formation. In many parts of Japan, we can observe profiles consisting of buried soils which have common features of a high content of humus and clay. The forming age of these soils is approximately 5-6 ka, the period of Hypsithermal or the Holocene optimum (Wanatabe,1990). This fact suggests the response of extensive environmental changes preserved in the buried soils. In this paper, we will introduce a study on the buried soils of Andisols to discuss the concept of Holocene Paleosols.

The 10 m giant profile, located in Shizuoka Prefecture, Central Japan, consists of 6 Holocene buried soils, including Fuji Black Humic Ash (4.5-8.0 ka) after Machida(l968). Buried soils existing among Younger Fuji Tephra and Old Fuji Tephra, present high-resolution materials for examination of the pedological records of Holocene environmental changes. Sakagami et al.(1983) and Oakazaki et al. (1983) investigated inorganic and organic components of soil samples taken from this profile. The strength of pedogenetic weathering was clearly traced by the vertical distribution of zirconium. The concentration of zirconium was higher in buried soils. Sakagami (1988) calculated the estimated amount of past humus accumulation using the coefficient of mean humus decomposition (r) proposed by Wada (1967). The estimated amount of humus accumulation of FB (Fuji Black Humic Ash) was calculated to be 2 times as large as the existent humus amount The vertical distribution of humus content also harmonises with the. temperature variation of the Holocene supported by pollen analyses.

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