Seismic stratigraphic reconstruction of late Pleistocene lowstand wedges on the shelf margin and trough region of the Korea Strait: a review

Abstract

This paper is a review of stratigraphic architectures and evolution history of late Pleistocene lowstand deposits on the outer shelf of Korea Strait. Located between the southeastern tip of the Korean Peninsula and the Tsushima Island, the Korea Strait is a seaway connecting the East Sea with the East China Sea. Detailed analysis of high-resolution seismic profiles and sediment data give a good evidence for the existence of three superimposed wedge-shaped sedimentary units that thicken seaward. The individual sedimentary wedges are characterized by seaward dipping and complex sigmoid-oblique prograding reflection configurations with some chaotic or hummocky reflectors. On the basis of distribution and external geometry, these sedimentary wedges are interpreted as a “shelf-margin or shelf-edge delta”, mainly related to falling and lowstand sea level. Occurrence of this delta type is a common constitute of the Quaternary shelf in the Korea Strait. Although the entire units have not been fully dated, it is believed that these wedges were deposited during late Pleistocene sea-level lowstands. Repeated falls and lowstands of sea level (isotopic stages 8, 6 and 2/4) resulted in the formation of lowstand prograding wedges along the present shelf margin and trough region, having been separated from the inner shelf deposits. During subsequent episodes of sea-level rise (isotopic stages 8/7, 6/5, and 2/1), the upper part of sedimentary wedges was eroded, and thin covered by thin transgressive sands. Consequently, the late Pleistocene sequences on the shelf margin and trough region in this area mainly consist of a succession of stacked lowstand prograding wedges formed during the regression and lowstand of sea level.