QUATERNARY SEA-LEVEL CHANGE ON THE CONTINENTAL-SHELF OF HONG-KONG

High-resolution seismic reflection profiles and continuously sampled b oreholes have been used to investigate the Quaternary offshore sequenc e that overlies weathered bedrock in Hong Kong. Four formations have b een recognized: the lowermost Chek Lap Kok Formation comprises dominan tly fluvial sand and mud, much of which probably accumulated prior to 130 000 years BP, during sea-level lowstands of Middle Pleistocene (Ox ygen Isotope Stage 6) age and earlier. The upper surface of the Chek L ap Kok Formation is defined by a fluvial/tidal entrenchment surface th at is overlain by transgressive, fine-grained, marine sediments of the Sham Wat Formation. These were deposited during the Eemian interglaci al (Stage 5e) at a time when sea level was similar to that of today. I n southeastern Hong Kong waters, a late Weichselian (Stage 5c) ravinem ent surface is overlain by submerged shoreface sands, succeeded by a b ack-stepping wedge of marine sediments that comprise the Waglan Format ion. Fluvial/tidal entrenchment of the top of this formation occurred prior to the deposition of the uppermost dominantly marine Hang Hau Fo rmation, deposited during the Late Weichselian to Holocene transgressi on, the main phase of which is represented by a ravinement surface.