地质学报2017，Vol.91Issue(9)：2047-2064,18.
曲流河浅水三角洲沉积过程与沉积模式探讨——沉积过程数值模拟与现代沉积分析的启示
Depositional Process and Sedimentary Model of Meandering-River Shallow Delta:Insights from Numerical Simulation and Modern Deposition
摘要
Abstract
Meandering-river shallow water delta is a hotspot in the study of sedimentology and an objective in oil and gas exploration.Scholars home and abroad have carried out a lot of studies based on the subsurface reservoir, outcrop and modern deposits.Regarding the depositional process and mode of meandering-river shallow water delta, there has been no consensus because of lacking the observation and analysis of deposition process and evolution features.Based on this account, this study selected a typical meandering-river shallow water delta in Poyang lake, Ganjiang delta, as an example.Combined with hydrodynamic force, water depth and sediments, the growth and evolution process of the Ganjiang delta was reproduced using the sediment hydrodynamic principle-based software (Delft 3D) and the sedimentary mode of meandering-river shallow water delta was established in comparison with modern shallow water delta.Research shows that: (Ⅰ) In the shallow water environment, meandering river delta grows lakeward rapidly.Delta front extends forward and transforms to delta plain rapidly and is characterized by the wide plain and the relatively narrow front.Although the vertical thickness of sediment is thin, the ternary structure consisting of bottom set, forward set and top set is integrated.(Ⅱ) Several active high-sinuosity distributary channels were developed simultaneously in delta plain and lateral migration occurred frequently in the proximal part to distal part of distributary channels.Previous delta front and prodelta underwent avulsion reformation, resulting in the formation of moniliform point bar.Long-term lateral migration formed a wide compound channel belts.Long-term reformation of distributary channels to the previous deposition body produced a positive rhythm in most thick sand bodies, resulting in poor preservation of the previous channel dams.In the distal part of delta plain, unstable levee causes distributary channels avulsing and rechanneling frequently.The abandoned channel was filled with argillaceous sediment, and multiple abandoned channels can construct a channel network filled with argillaceous sediment.(Ⅲ) In front delta, underwater distributary channel is regarded as the extension of meandering channels of delta plain, with a length up to 300m.Shallow water resulted in that estuarine current has a strong ability to erode, and the sediments carried by water deposited at the channel side edge, and finally grew into a finger bar.Controlled by the lateral migration and avulsion of distributary channel, subsurface distributary channel happened avulsion or lateral migration.Multiple repeating formed a multiple branched complex while the underwater channels were filled with argillaceous sediment after abandonment.(ⅣV) Controlled by the distributary channels' avulsion in the distal part of delta plain, the branched mouth bar complexes migrated laterally along the shoreline, finally forming a large sand body with approximately equal thickness in delta front.关键词
曲流河浅水三角洲/沉积过程数值模拟/沉积特征/演化过程/沉积模式Key words
meandering-river shallow water delta/numerical simulation of depositional process/sedimentary characteristics/evolution features/sedimentary model引用本文复制引用
冯文杰,吴胜和,张可,赵文凯,贾风娟..曲流河浅水三角洲沉积过程与沉积模式探讨——沉积过程数值模拟与现代沉积分析的启示[J].地质学报,2017,91(9):2047-2064,18.基金项目
本文为国家自然科学基金项目(编号41372116)、国家重大科技专项(编号2011ZX05009-003)联合资助成果. （编号41372116）
