The parent materials of three heavy clays formed on the terraces in Northern Hokkaido were clarified from the particlesize distribution by a laser scattering method, the ESR-signal intensities of quartz, and the clay-mineral contents by a X-ray diffraction method and a thermogravimetry in each soil horizon with the cores of boring survey. The results summarized as follows: The measurement of 3-20μm particle by the laser scattering method and the ESR-signal intensities of oxygen vacancy in quartz suggested that the dominant parent materials of soil horizons above 320 to 375 cm in depth were mainly eolian dust brought from the Precambrian area of Asia Continent by the winds, and those of lower ones were mainly autochthonous terrace deposits consisted of fluvial materials from the Mesozoic to the Tertiary in underlain horizons. Namely, the contents of fine particles were high, and ESR-signals of fine quartz below 20μm presented relatively high values, in eolian-dust dominant horizons. On the other hand, the fine particles were low, and ESR-signals of quartz showed low values, in the autochthonous horizons. The contents of vermiculite and kaolin minerals were high compared with that of mica minerals and smectite in the eolian-dust dominant horizons as reported in the previous paper. The contents of mica and kaolin minerals were relatively high in the underlain autochthonous horizons, and the clay mineral composition was different between them. Especially in eolian-dust dominant horizons, mica minerals and chlorite decreased, and vermiculite and smectite contrarily increased as the soil horizon deepened. This phenomenon should result in the release of K and Al ions from interlayer position of 2:1-type minerals brought by the eolian dust through the soil weathering.
