Discussion on the Quaternary initial sedimentary age and sedimentary evolution in the Pearl River Delta

The characteristics and the age of the Quaternary sediments of the Pearl River Delta are important to understand the evolution in fluvial-delta sedimentation, fluctuations in sea level change, climate, and geography of the area as well as the South China. The optical stimulated luminescence (OSL) of the bottom sediment from the estuaries of the Pearl River Delta was studied and the age was determined to be 102.52±6.14 ka, indicating that the Quaternary deposition started in the late Pleistocene. In addition, AMS ¹⁴C dateing was conducted. Combining the OSL results and precious studies, we believe that the Pearl River Delta experienced at least two major transgressions and one regression since the late Pleistocene to Holocene. The first large-scale transgression began in the early Late Pleistocene (MIS5 stage), followed by regression in the late MIS2 stage, and transgressed again in the early Holocene (about 11 kaBP, MIS1 stage), forming at least three layers of weathered clay. During the late Pleistocene transgression, sea level fluctuated significantly. Sea level dropped notably at about 40 kaBP (MIS3 stage), forming the lower weathered clay layer; rose at about 30 kaBP, during which the delta received sediments until the late MIS2; and then the sea level went down again apparently, forming the middle and upper weathered clay layers.