DISTRIBUTION OF CLAY MINERAL ASSEMBLAGES IN THE RIVERS ENTERING YELLOW SEA AND EAST CHINA SEA AND THE MUDDY SHELVE DEPOSITS AND CONTROL FACTORS

Clay minerals,as the finest portion of the deposits in the marginal sea,recorded the weathering and denudation processes in the provenance,and the transportation,deposition and burial processes of the river sediments and eolian dust in the sea.In this regard,clay minerals are widely used as tracers to sediment provenance and paleoenvironmental changes.This study deals with the clay minerals from the sediments of the major rivers entering the Yellow Sea and East China Sea and the muddy deposits on shelves. The results reveal that there are obvious differences of clay mineral assemblages among different rivers.Illite and chlorite are the highest in the Taiwan rivers,but lowest in the Minjiang River.Kaolinite is relatively enriched in the Minjiang and other rivers in Fujian Province,but depleted in Taiwan rivers.Smectite is mainly concentrated in the modern and old Yellow River,and rarely observed in the Minjiang,Taiwan and Korean rivers.The differences of clay mineral assemblages in these rivers are mainly controlled by latitude and monsoon climate;the ratios of some clay minerals can be used as effective proxies to the weathering in provenance.The clay mineral compositions in the estuarine areas can be influenced by differential deposition and other factors.Although provenance discrimination diagrams based on clay minerals can in general distinguish the sources of the muddy deposits on the Yellow Sea and East China Sea shelves,the uncertainty of the method has to be considered carefully,and the integrated study with other approaches is recommended.