Modern sedimentation in the Yellow Sea: Application to geologic models of epicontinental-shelf and macrotidal-mudflat environments

The distribution of sediment accumulation rate, grain size, and sedimentary structure is studied along the Huanghe dispersal system in the Yellow Sea and in the muddy tidal flats of west Korea to develop interpretive geologic models of ancient epicontinental-shelf and muddy-intertidal environments.; Modern sediment accumulation in the Yellow Sea (established by Pb-210 geochronology) takes the form of a subaqueous delta (extending south from the Shandong Peninsula) with gently dipping topset deposits (rates 1-2 mm/y), steeply dipping foreset deposits (rates 3-9 mm/y), and gently dipping bottomset deposits (rates 0.3-3 mm/y). C-14 age dates indicate that the Shandong subaqueous delta predominantly formed between 4060-6200 y B.P. (at an average rate of at least 20 mm/y). A sediment budget demonstrates that 9-15% of the annual Huanghe discharge is presently accumulating in the Yellow Sea: two-thirds of the total in the topset and foreset deposits of the subaqueous delta and the remaining third as extensive bottomset deposits. The development of extensive bottomset deposits may be restricted to epicontinental-shelf environments and may be diagnostic of sedimentation in this type of setting. Sedimentary structure reveals a trend from laminated, to mottled, to homogenous structure, and grain size fines, southward along the Huanghe dispersal system. Unimodal grain-size distributions are observed in proximal portions of the dispersal system; polymodal grain size distributions are typical of areas where Huanghe sediments border the transgressive deposit.; Pb-210 accumulation rates in the muddy Korean tidal flats are highest on the mid-tidal flat (5-9 mm/y) and decrease both seaward and landward (1-2 mm/y); this distribution is reflected in the greater amount of preserved physical stratification (mm-scale, parallel-bedded to lenticular laminae) in mid-tidal-flat sediments. Sediments coarsen seaward (from 8.8 phi to 4.6 phi) and downcore, indicating that the tidal flats are actively prograding seaward. Sediments are derived dominantly from the Korean peninsula; the modern Huanghe dispersal system is not a dominant source of sediment to the tidal flats.; The characteristics of stratigraphic sequences representing a muddy clinoform deposit prograding over a coarse basal layer and representing a prograding, muddy tidal flat are presented.