Erosion and sedimentation associated with the last sea level rise offshore Hong Kong, South China Sea

Abstract

Abstract High-resolution seismic data reveals an extensive planar, seaward-dipping reflector offshore south of Hong Kong. This is interpreted as a ravinement surface created during the last transgression and is associated with ca. 2.5 m of shoreface sand, which is overlain by a 6–15 m thick sheet of prodelta-marine shelf sediments. On seismic profiles, the shoreface sand is characterised by a chaotic reflector pattern and the sheet by low-amplitude, parallel, flat or low-angle, continuous reflectors. Particle size data reveal a westward-coarsening and decrease in sorting, which reflects increasing proximity to the Pearl River. Foraminiferal and diatom assemblages demonstrate the same overall westward-shallowing trend, with increase in inner shelf foraminifera and brackish planktonic diatom species. A phase of early Holocene shoreface sand and intertidal silt deposition in eastern and central areas culminated in a brief period of subaerial exposure. This was succeeded by an extensive period of shelf and inner shelf deposition, brought about by variation in balance between the rate of sea-level rise and accommodation, and the discharge and sediment supply from the Pearl River.