Abstract
(1) The soils derived from tertiary miocene series are distributed on the hills of Tsuyama basin in Okayama Prefecture. This series consists of two beds-viz. Uetsuki brackish water deposits and Tsuyama shallow sea deposits. Most of Uetsuki soils are sandy or loamy and Tsuyama soils are principally clayey or loamy. (Annual mean temperature 13℃, annual rainfall 1432 mm). (2) The profiles of Uetsuki soils have dark brown A horizons, brown or yellowish-brown B horizons, and yellow C horizons. (3) The clay minerals were determined by the author's colour reaction method, and it indicates that Uetsuki soils are halloysite-kaolinitic and Tsuyama soils are halloysite-montmorillonitic. (4) In Uetsuki soils the complex A_2 has the SiO_2/R_2O_3 ratio of 2,and this ratio of complex B also is about 2. In the upper horizons of Uetsuki profiles the complex A_2 increases and the complex B decreases. Complex A_2 was determined by the author's method. (5) In Uetsuki soils the amounts of free iron oxide correspond to 61〜78% of Fe_2O_3 soluble in hydrochloric acid. The free iron oxide was determined by the author's photochemical method. (6) Uetsuki soils are very poor in exchangeable bases and have strong acid reaction (pH 4.6〜4.9).
