A comparative study on the Late Quaternary stratigraphic architecture and formation of megadeltas in East and South Asia

Based on the researches on the evolution of megadeltas in East and South Asia since last deglaciation, we carried out a comparative study on the Late Quaternary stratigraphic architecture, sedimentary systems and the initiation time of megadeltas at large river mouths of the region. Major control factors on deltaic evolution are revealed and discussed. Our data suggests that all the river mouths in the region seem having experienced similar evolutionary history, including the infilling of incised palaeo-valleys and estuaries in Early Holocene, and deltaic progradation in Middle to Late Holocene, controlled by the sea-level change. However, there are some differences in the stratigraphic architecture and sedimentary history from river to river. The most remarkable difference is the time of delta initiation, which is related to the geomorphology and geology of the drainage basin and the sedimentary basin at river mouths. Those rivers having short flow paths and erosive bedrocks in the drainage basin, such as the Ganges-Brahmaputra, usually produce a huge amount of sediment load. As a result, the time of the delta initiation was obviously earlier than other rivers. The Pearl River delta is another example. It has a semi-closed shallow sedimentary basin which is beneficial to the formation of delta in the Middle Holocene.