三角洲在坳陷盆地沉积中所占比例研究

在对全球现代三角洲体系统计分析的基础上,将坳陷盆地沉积体系简化为河流-三角洲-湖泊,建立沉积体系模型。后期沉积体系叠置在前期沉积体系之上,同时也对前期沉积体系进行改造。每期沉积体系体系均发育有河流-三角洲-湖泊,将其作为整体进行研究。假设盆地规模不变,沉积基准面下降-进积过程表现为河流沉积在盆地中所占比例增大,沉积基准面上升-退积过程表现为湖泊沉积在盆地中所占比例增大。变化过程中,三角洲在盆地中所占的比例变化较小;相对于沉积盆地,三角洲体系不占主体地位,而是处于一定的比例范围(三角洲总面积/盆地面积在0~10%之间)。因此三角洲的规模,取决于沉积盆地的规模,开展沉积相研究必须考虑宏观盆地尺度背景。

Porportions of deltas in downwarped basin deposits

In the light of statistics of the modern delta depositional systems in the world,the depositional systems of downwarped basin deposits are generalized as the fluvial-dalta-lake depositional systems. The paulopost depositional systems may overlie and modify the preceding depositional systems,all of which may contain fluvial-dalta-lake depositional systems. Assuming that the scales of sedimentary basins are constant,the sedimentary base-level falling-progradational processes may give rise to the increase of the proportions of the fluvial deposits in the sedimentary basins while the sedimentary base-level rising-retrogradational processes may bring about the increase of the proportions of the lake deposits in the sedimentary basins. However,the delta deposits may be less variable in proportion and less developed in the sedimentary basins. The total delta area /basin area ratios generally range between 0 and 10%. Therefore,the scales of the deltas tend to depend on those of sedimentary basins. The macroscopic scales of sedimentary basins should be considered in the sedimentary facies analysis.