Sequence stratigraphy and evolution history of the continental shelf of South Sea, Korea, since the Last Glacial Maximum (LGM)

Abstract

High-resolution seismic data (Chirp and Sparker profiles) were used to investigate the sequence stratigraphy and evolution of the continental shelf of the South Sea, Korea, since the Last Glacial Maximum (LGM). Approximately 1950 km of chirp and sparker profiles were acquired. Along with seismic profiling, 30 piston core samples were collected and two previous long drill cores (SSDP-103 and 104) were tied to the seismic data. Our data show nine types of seismic facies on the basis of seafloor morphology and sub-bottom acoustic characters. Based on the analysis of seismic profiles, shelf deposits of the South Sea accumulated after the onset of the LGM can be divided into five sedimentary units; S1 to S5, from top to bottom. Correlation between sediment cores and seismic data suggests that Unit S5 is an incised channel fill formed by fluvial or coastal sediments during the early transgressive stage, accompanied by backstepping of the shoreline. Unit S4 is a transgressive sand layer reflecting the deposition of coarse sediments due to the strong currents and tides, following the rapid retreat of the coastline. Unit S3 represents paleo channel- and basin-fill deposits formed in estuary or delta environments near the inner continental shelf. Unit S2 forms an inner shelf transgressive sand layer including sand ridges. Unit S1 is interpreted as the most recent mud formed during the sea level highstand stage when the sea-level rise ended. Our results show that the sedimentary evolution of the continental shelf of the South Sea, since the LGM, has been closely related to the sea-level changes. The distribution of paleo-channels is associated with the paleo-Seomjin River, local sediment supply, and continental shelf erosion.