The occurrence and chemical composition of smectite in hyaloclastite from the Toyohama rock fall site of Feb.10, 1996 and the Oshoro Bay area were examined by using optical microscopy, X-ray diffractometry, electron microprobe analysis and analytical transmission electron microscopy. Usually, smectite occurs as fillings and linings of pores in various aspects, and occasionally in replacement of volcanic glass in hyaloclastite. The analytical results show that the smectite is dioctahedral and Fe-rich type. Its composition varies extensively between montmorillonite and nontronite. Moreover, interlayer cations of smectite vary extensively in relation with the type of weathering in hyaloclastite. Na-dominant smectite occurs characteristically in discolored hyaloclastite affected by surficial weathering, whereas Ca-and Ksmectite occurs dominantly in hyaloclastite collected from the inner part of rockmass. These features of the smectite in hyaloclastite can be attributed to its formation and weathering environments.

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Core samples of the Quaternary sediments to the depth of 120 m were collected at a site in the north coast of Ariake Bay, Kyushu. Particle-size distribution and clay mineralogical composition in the clay fraction were determined for total 106 samples taken at about 1 m interval and correlated with depositional environment and weathering in the terrestrial condition. Depositional environment was assessed by the determination of total sulfur; the ratio of the acid-oxalate-soluble to the DCB-soluble Fe contents was used for the estimation of weathering intensity.
Repetition of marine and fluvial deposition was recognized. Marine sediments were dominated with clay and silt. Fluvial sediments had the high contents of fine and coarse sands, and domination with fine sand was ascribed to the deposition in the floodplain while domination with coarse sand to the deposition in the alluvial fan. Concerning the clay mineralogical composition, fluvial sediments were dominated with mica, vermiculite, kaolin minerals, and 2: 1 minerals-chlorite intergrades, derived from granitic rocks in the surrounding mountains. Composition of these minerals varied with the particle-size distribution of the sediments. Marine sediments were dominated with smectite in addition to the minerals originating from granitic rocks. Smectite content generally increased with transgression and decreased with regression, and the formation of smectite was suggested to be due to the chemical alteration of pyroclastic materials. In addition, transformation of mica to smectite was observed in the intensive weathering condition.

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Carbonaceous materials and clay minerals in the Triasic sedimentary rocks, Nariwa group, were studied in the Noda landslide area, central Chugoku, Japan by means of mainly X-ray diffractometry (XRD). The sliding surfaces were confirmed in excarvated wall of drainege wells. The specimens were obtained from the boring core as well as block sample. Carbonaceous materials were extracted from coaly mudstone.
Illite, chlorite, smectite, vermiculite and kaolin minerals are recognized in the samples. Smectite, vermiculite and kaolin minerals characterize the samples collected from relatively shallow depth. The amount of smectite increases with closing to the sliding surface. It is considered that smectite, vermiculite and kaolin minerals were formed through the weathering process whereas illite which occurred commonly with chlorite were representative constituent of the host sedimentary rocks.
The value of d (002) of carbonaceous materials is in the range of 3.40Å to 3.57Å. It is to be noted that the d (002) value near the sliding surface is smaller than those of the others. The fact indicates that the crystalization degree of the carbonaceous materials near the sliding surface is relatively high.

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