Sedimentary processes from the shelf edge to the Okinawa Trough in the East China Sea based on the coccolith assemblages

The seasonal succession of coccolith in the Okinawa Trough was investigated through a time series sediment trap experiment from March 1993 to February 1994, and compared with coccolith thanatocoenoses in the underlying surface sediments. The coccolith flux was low in the shallow trap (water depth 600m) and markedly high in the middle (water depth 800m) and deep (water depth 1020m) traps. Coccolith assemblages of the three traps were similar to each other, except that the assemblages of the shallow trap differed from those of the middle trap during summer. On the other hand, the coccolith species composition of surface sediments shows considerable differences among the inner-middle shelf, shelf edge and the Okinawa Trough areas. These observation, together with comparison of coccolith species composition between trap and surface sediments, indicate the lateral transport of particulate matters from adjacent shelf edge and shelf slope of the Okinawa Trough to the central area of the Okinawa Trough.