QUANTITATIVE ESTIMATION AND DISTRIBUTION OF DETRITAL CLAY MINERALS IN THE SURFACE SEDIMENTS OF SOUTH YATSUSHIRO KAI, JAPAN

Quantitative estimation of clay minerals in the clay fractions of the surface sediment samples from South Yatsushiro Kai is obtained from the X-ray diffraction patterns of the clay mineral suite that contains illite, chlorite, kaolinite, smectite and 10A halloysite. Among the clay species, illite and chlorite are exceptionally abundant and they comprise more than 60% of the total clay minerals present in most sediments. Relative amounts of other clay minerals varies markedly with locality particularly kaolinite and 10A halloysite and they tend to concentrate only near the point source except smectite which has a more unique behavior of transport and settling characteristics than other minerals. The relatively high supply of land-derived materials from various rock lithology surrounding South Yatsushiro Kai is the dominant contributing factor in outlining the trend of clay mineral distribution. Most, if not all, clay minerals are believed to be current-transported which shows that bottom water flow and shallow water currents are significant agents responsible for the distribution of various clay minerals.