Sedimentary Environment and Sequence Stratigraphy of Late Quaternary Deposits in the East China Sea

Abstract

High-resolution (Chirp and Sparker system) seismic profiles were analyzed to investigate the sedimentary environment and sequence stratigraphy of the late Quaternary deposits in the East China Sea. Echo types in the study are divided into three major echo types which are classified as flat (transgressive sediment sheets, relict sands, and Holocene muds), mounded (tidal ridges), and irregular echoes (channels). Sequence analysis of high-resolution seismic profiles reveals that the shelf deposits form a succession of high-frequency (fifth-order) sequences consisting of three depositional sequences (DI, DII, and DIII) developed during the late Quaternary. The depositional sequence includes five sedimentary units, each with different seismic facies and geometry: (1) regressive estuarine/deltaic wedge (unit J1), (2) regressive deltaic/offshore deposits (unit J2), (3) low-stand deltaic wedge with incised-channel fill (unit J3), (4) transgressive estuarine/deltaic complex (unit J4-a) and sand ridges/sheet (unit J4-b), and (5) recent mud (unit J5). The results (correlation of echo types and depositional sequences, sedimentary features, and sequence stratigraphic interpretation etc.) of this study suggest that the late Quaternary deposits of the East China Sea were formed by complex sedimentary processes and systems under the influence of tidal action, sea-level change, and an enormous bulk of sediment inflow from adjacent rivers.