Distal mud deposits associated with the Pearl River over the northwestern continental shelf of the South China Sea

Continental shelf mud deposits represent an important archive of the Holocene earth history. Such deposits are usually associated with large rivers that transport a large quantity of suspended sediment. The Pearl River has formed a distal, shore-parallel Holocene mud deposit on the northwestern continental shelf of the South China Sea; investigations into its spatial distribution and evolutionary history are necessary for an improved understanding of such sedimentary systems. Seabed sediment sampling, in situ tidal cycle measurements, seismic survey and the associated data analyses reveal that the distal mud deposit associated with the Pearl River occupies an area of approximately 8.87×10³km², with a modern deposition rate of 1.27 to 5.66mmyr^-1. Evidence from sediment balance, environmentally sensitive components, sediment transport processes and regional shelf circulation patterns indicates that the Pearl River is a major sediment source for the mud deposit. This distal mud deposit represents an initial stage of its development. The fining upward pattern and the negative skewness values in the layer are indicative of the Pearl River influence, and the ²¹⁰Pb age is younger than 10²yr. The main body of the Holocene deposit of the region is not related directly to the modern Pearl River sediment. For most of the Holocene periods the Pearl River has been trapping the sediment to fill its extensive estuarine waters and, therefore, the formation of the distal mud is a recent event. A regional characteristic is that the timing of the formation of distal muds associated with large rivers depends on the estuarine morphological evolution and the quantity of sediment discharge.