| The outer shelf of the East China Sea-Continental slope-Okinawa Trough is a key target area for studying the modern sedimentary characteristics of continental margin sediments and the interaction between land and sea.In this paper,the surface particle size,element,detrital minerals and clay minerals of the surface sediment samples obtained from the sea area were analyzed,the composition characteristics of surface sediments were described.The sediment sources of coarse and fine surface sediments in different sedimentary units,sedimentary environment,provenance,transport mechanism and path were discussed.The surface sediments in the study area are mainly composed of sand,silty sand,sandy silt and silt.They have obvious zoning characteristics: sand and silty sand are widely distributed in the outer shelf of the East China Sea.The Continental slope area consists of silt and sand grade components.The Okinawa Trough is mainly composed of silt sand.The overall granularity feature is that the grain size of the surface sediments gradually becomes finer from the outer shelf to the Okinawa Trough.The distribution of elements in most surface sediments of the study area is consistent with the elemental “granularity control law”,that is,the content of elements in the Okinawa Trough area dominated by fine particles is relatively high,and the content in the outer shelf area where coarse particles concentrate is significantly reduced.The R-factor analysis showed that the distribution of surface sediments in the study area was mainly controlled by terrigenous clastic sedimentation and was less affected by marine sedimentation and chemical deposition.The detrital mineral combination in the outer shelf of the East China Sea area is mainly potassium feldspar-amphibole-epidote-ilmenite-garnet.Light minerals dominate,with content ranging from 88.60% to 98.14%,and their high value area is located in the middle of the outer shelf.The heavy mineral content is much lower than that of light minerals,and the content ranges from 1.17% to 11.16%.Hydrodynamic separation is an important factor affecting the distribution of detrital minerals in the study area.The clay mineral assemblages of the continental slope-Okinawa Trough can be divided into three types: the clay mineral assemblages of Class I and Class II are illite-chlorite-kaolinite-smectite,and their contents are different,mainly distributed in the continental slope area.Class III clay mineral assemblages are kaolinite-illite-chlorite-smectite,mainly distributed in the Okinawa Trough.The flow field in the sediment area of the continental shelf of the East China Sea is very complex,experiencing multi-stage transgression during the deglaciation and Holocene.The characteristics of heavy mineral assemblages show that the coarse clastic sediments come from the Paleo-Yangtze River.The sedimentary characteristics of gravity flow in the slope depositional area are obvious,which is influenced by Kuroshio and shelf tidal current.The sedimentary area of the Okinawa Trough reflects both turbidite sedimentary characteristics and bathyal-abysmal deposition characteristics.Clay mineral assemblages reveal that fine particles in the continental slope and Okinawa Trough mainly originates from Taiwan Island,the mainland Yangtze River,the rivers along Zhejiang and Fujian coasts and the continental shelf of the East China Sea.The surface sediments in the study area are mainly terrigenous,and sediment transport depends on the joint action of river input to the sea(mainland China,Taiwan),near-bottom transport of continental shelf suspension,Kuroshio transport and residual sediment re-transport(block collapse,turbidity flow,traction flow). |
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