Modern sedimentary environments and dynamic depositional systems in the southern Yellow Sea

Based on analyses of more than 600 surfacesediment samples together with large amounts of previoussedimentologic and hydrologic data, the characteristics ofmodern sedimentary environments and dynamic deposi-tional systems in the southern Yellow Sea (SYS) are ex-pounded, and the controversial formation mechanism ofmuddy sediments is also discussed. The southern Yellow Seashelf can be divided into low-energy sedimentary environ-ment and high-energy sedimentary environment; the low-energy sedimentary environment can he further divided intocyclonic and antieyclonic ones, and the high-energy envi-ronment is subdivided into high-energy depositional anderoded environments. In the shelf low-energy environments,there developed muddy depositional system. In the centralpart of the southern Yellow Sea, there deposited the coldeddy sediments under the actions of a meso-scale cycloniceddy (cold eddy), and in the southeast of the southern YellowSea, an anticyclonic eddy muddy depositional system (warmeddy sediment) was formed. These two types of sedimentsshowed evident differences in grain size, sedimentation rate,sediment thickness and mineralogical characteristics. Thehigh-energy environments were covered with sandy sedi-ments on seabed; they appeared mainly in the west, southand northeast of the southern Yellow Sea. In the high-energyeroded environment, large amounts of sandstone gravelswere distributed on seabed. In the high-energy depositionalenvironment, the originally deposited fine materials (includ-ing clay and fine silt) were gradually re-suspended and thentransported to a low-energy area to deposit again. In thispaper, the sedimentation model of cyclonic and anticyclonictypes of muddy sediments is established, and a systematicinterpretation for the formation cause of muddy depositionalsystems in the southern Yellow Sea is given.