湖平面变化对扇三角洲发育影响的模拟试验

通过水槽试验模拟扇三角洲的形成过程,考察湖平面变化对扇三角洲发育的影响.试验结果表明:湖平面上升期扇面以片流沉积为主,分流河道不明显;湖平面稳定期扇面分流河道侧向侵蚀作用较强,改道频繁,底砾层在剖面上呈倾斜的月牙状杂乱分布;湖平面下降期扇面分流河道数量少且发育稳定,下切作用明显,剖面上底砾层为平行下凹的月牙形;随着湖平面由上升至稳定再至下降,扇三角洲垂向加积程度减弱、侧向进积程度增强,扇体厚度减薄、范围扩大,扇缘由圆滑弧形变为不规则弧形,扇面粒度分布差异性亦明显减小.

Simulation experiment for effects of lake level change on fan delta development

The formation of fan delta was simulated by flume experiment, and the effects of lake level change on fan delta development were investigated. The experimental results show that in the period of lake level ascending, sheet deposits develop on fan surface and the distributary channels are indistinct. When the lake level is immobile, the fan-surface channels laterally erode strong and changed the routes frequently. Basal debris beds distribute in a jumble with the shape of angled crescents in profile. In the period of lake level descending, the fan-surface channels develop steadily with obvious vertical erosion. And the basal debris beds develop like parallel and concave crescents in profile. And also, with lake level from ascending to immobile, then to descending, the vertical accretion of fan delta is reduced, but the lateral progradation is intensified. The thickness of fan delta decreases, but the range extends. The boundary of fan delta changes from smoothing arc-like to irregular arc-like. The difference of grain distribution on fan surface decreases.