Forward Stratigraphic Modelling of the Depositional Process and Evolution of Shallow Water Deltas in the Poyang Lake, Southern China

Large-scale shallow-water deltas in lacustrine basins have recently been identified as important reservoir plains in the world. The Poyang Lake, the largest fresh water lake of China, develops a series of modern shallow-water deltas, hence provides a good modern analogue for understanding various key depositional processes that control deltaic development and evolution. This paper uses Sedsim, a three-dimensional stratigraphic forward modelling program, to simulate the development and evolution of the shallow-water deltas in the Poyang Lake by considering a number of key processes and parameters affecting the deltaic deposition over 1200 years. According to our simulation results, the construction of the shallow-water deltas in the Poyang Lake is primarily controlled by the lake level fluctuations, the discharge rate of sediment, and the pre-existing topography/bathymetry. It shows that the sand bodies in the delta front are basically sand sheets, which are mainly distributed near the lake open circulation area due to the shallow water depth of the lake, the gentle slope of the depositional basement and the high frequency of lake-level fluctuations. In addition, the frequency of relative lake level oscillation appears to be a significant controlling factor on the development and divarication of river channels on the upper delta plain. A lower rate of the lake level rise and a faster rate of the lake level fall would cause enhanced river channel development and divarication. This study not only enables us to quantitatively understand the dynamic processes of shallow-water delta systems and the key factors controlling the deltaic development and evolution but also provides a reference model for similar ancient depositional systems in sedimentary basins, where active hydrocarbon exploration is currently being undertaken.