410 / 2024-09-16 15:24:14

Mouth bars’ development along the West Pearl River main course, China

river mouth bar,Pearl River Delta,geomorphologic evolution,Holocene

River mouth bars’ formation is a key process of the delta development and river bifurcation, but details of the long-term developmental history of mouth bars and their role in the delta evolution are substantially less well documented. To characterize deltaic mouth bars’ development, this study investigated the Sixianjiao, Jun’an, Da’aosha and Denglongsha mouth bars formed successively along the main course of the West Pearl River. The detailed lithological analyses of 8 sediment cores obtained from these mouth bars indicate that the mouth bar sediment is characterized by its sandy nature with laminations and sand/mud pockets. Secondly, the mouth bar sedimentation may begin from about 15m water depth. The Sixianjiao and Jun’an mouth bars initiated at shallower water (8.5m and 10.5m, respectively) due to the restrictions of higher basement landforms. In an area where water is deeper, the mouth bar development would begin only with the site being elevated up to about 15m water depth, such as a case in Denglongsha. Thirdly, all four mouth bars ended their upward growth when they reached an elevation very close to local low tide level. Fourthly, the duration between their onset and end of vertical growth varies between 2000 and 2800 years. Finally, the ages of these four mouth bars show a chronological order from land to sea, reflecting seaward delta progradation. Our reconstruction of the West River mouth bars’ developmental history provides a new insight into the morphological evolution of the Pearl River delta, a special delta developed within a complex estuarine bay.