Abstract: High resolution shallow seismic exploration with dense grids,line intervals of mostly 120 m and 200 m, was carried out in tidal ridges and troughs area west of Taiyangshan Ridge in the South Yellow Sea. The maximum sediment penetration was about 80~90 m. Two seismic sequences(SQ1 and SQ2) were identified and further divided into five sub-sequences (U1~U5). The underlain Sequence 1(U1) consisted of land sediments of Late Pleistocene, while the upper Sequence 2(U2~U5) was mainly formed by marine sediments of Holocene. Sedimentary environments of each sub-sequence were studied based on seismic facies characteristics. Since the later period of Late Pleistocene, the study area has been mainly undergone sedimentary environment evolution of delta distributaries—river incision—paleo-river channel fill—estuary offshore—delta offshore-shallow sea —present tidal ridges and troughs. A tidal sand ridge in narrow river mouth was developed during the middle Early Holocene in the study area, but afterwards were buried due to fast sea level rise. Present tidal sand ridges were formed after the last high sea level. They did not have any inherited relationship with paleo-tidal sand ridges, nor with paleo-topography of Late Pleistocene, but were controlled by tidal current system.

Key words: seismic sequences, Late Quaternary, tidal sand ridges, sedimentary environment evolution, South Yellow Sea