STRUCTURE AND SEDIMENTARY ENVIRONMENT FOR SUBMARINE DUNE RIDGES IN THE EAST CHINA SEA
YANG Wen-da (1st Brigade of Marine Geology,Shanghai Marine Petroleum Bureau,Shanghai 201208,China)
In the south of the East China Sea,are widely distributed ridge-trough landforms,which have attracted great attention,and in some documents,they are called Holocene transgressive tidal ridges,but the inner structure,sedimentary succession and movements of the ridges are not yet established.Studies on stratigraphic structures,sedimentary environment and sedimentation history of submarine dune ridges in the East China Sea have indicated the following results. (1) Inner structure and sedimentary succession of the dune ridges are typical of regressive delta on the basis of shallow stratigraphic profile and drilling. (2) Micro-paleontologic and sporopollen data from layerset Ⅱ of the seafloor dune are similar to those of deltaic succession in sedimentary environment. (3) Inner structure of the dune ridges is not consistent with structure and environmental characteristics of tidal dunes.Ridge bodies are not located at the same tidal erosion level.Each body cannot be an independent sedimentary trap and it becomes one successive system together with the underlying strata,surrounding strata and trough strata,and thus cannot be called tidal dunes. (4) After the formation of the submarine dunes,the surficial layers were once reworked by marine dynamic processes,but there are no evidences for their migration and movement.
【CateGory Index】： P736.21