The Daaosha is located in the nearmouth section of the Xijiang estuarine of the Pearl River Delta. The boundary of tidal influence during flood season is near the top of the Daaosha. Two boreholes (PRD04 and PRD05) were drilled in the proximal and central parts of the Daaosha respectively. The core records show that the sedimentation rates and sediment grain size are quite different between PRD04 and PRD05 since the postglacial period. PRD04 exhibits lower sedimentation rates than PRD05 prior to 7630 aBP, but hihger since 7630 a BP. The sediments in PRD04 are poorlysorted, and the sediment grain size is coarser when the burial depth is below 12.28 m, but the sediments become finer and wellsorted above 12.28 m compared with PRD05. Analyses indicate that the sediments were transported by flood currents from south to north during 9000~4200 a BP. The flood currents eroded the previously deposited sediments. With a marked decrease in current velocity after the flood currents passed through the Modaomen channel, the coarsegrained muds and sands accumulated first, while the finegrained sediments were transported further towards the north. Since 3500a BP, the sediments in the north became coarser than those in the south, suggesting that the sediments were transported from the north to the south due to the change to river dominance. The formation of the Daaosha was closely related to the flood jet. The flood jet inlet, with a width about 2 200 m, was situated between the Shedi Hill and the hills along the right bank of the Xijiang River.