High-resolution seismic reflection studies of late quaternary sediments in the eastern yellow sea

Abstract

The post-glacial sedimentation in the eastern Yellow Sea is addressed through echo type analysis of high-resolution subbottom profiles (Chirp, 2-7 kHz) aided by sediment cores. A total of eleven echo types are identified based on the seafloor morphology and acoustic characteristics. Distribution and development of echo types suggest that post-glacial sedimentation was controlled by the rate of sea-level rise, variations in sediment supply, and hydrodynamic conditions. During the trans- gressive period (about 11.5-8 ka), rapid retreat of shoreface and tidal processes formed transgressive lag deposits (echo type 1-1) and tidal ridges (echo types 2-1, 2-2, and 2-3) in the inner-shelf area. A transgressive sediment sheet (echo type 1- 3a), largely composed of bioturbated silty mud (unit 2), extensively covers the transgressive surface of erosion in the central Yellow Sea. The seafloor in the northern Yellow Sea was sculptured by strong tidal currents, resulting in channels and valley-like depressions (echo types 3-1 and 3-2). As the inner-shelf area offshore the Jiangsu coast was flooded, a seaward prograding wedge (echo type 2-5) formed in the distal part of the paleo-Huanghe delta. During the late transgressive to high- stand period (since 8 ka), two distinctive mud deposits, i.e., Huanghe-derived mud belt (echo type l-3b; unit 1) and elongated mud bank (echo type 2-4) formed in the central part and the southeastern nearshore area, respectively. Transgressive ridges and large-scale dunes (echo types 1-4, 2-2, and 2-3) have been modified by strong tidal currents and waves in the eastern nearshore area. © 2004 by the American Geophysical Union.