Forward stratigraphic modelling of the shallow-water delta system in the Poyang Lake, southern China

摘要

Large-scale shallow-water deltas in lacustrine basins have recently been identified as important reservoir plays worldwide. The Poyang Lake, the largest fresh water lake in China, develops a series of modern shallow-water deltas, hence provides an excellent modern analogue for understanding various key depositional processes that control deltaic development and evolution. This paper uses SEDSIM, a three-dimensional strati-graphic forward modelling programme, 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. The simulations show that the shallow water deltas have some unique characteristics. The delta plain is dominated by distributary channel sandbodies and thins towards the lake centre, whereas the delta front thickens lake-centre-wards. The major delta has very gentle delta slope less than 0.06°. The frequency of lake level oscillations appears to be a significant controlling factor in determining the deltaic architecture within the deltaic systems. The simulation indicates that the "Gilbert-type" deltas would not commonly develop in shallow-water basins even if the basin margin may be steeply sloped. The study has demonstrated that the process-based modelling approach can be effectively used to simulate complex geological processes and environments and quantify key controlling factors that otherwise cannot be easily acquired due to physical constraints.