走滑断层相关源-汇体系演化的砂箱物理模拟实验

Sandbox modeling on development of source-to-sink system along strike-slip fault

以走滑断层为边界的隆升剥蚀区和山前沉积区组合是盆山体系的重要类型之一。由于走滑断层两盘不断发生相对滑动,因此走滑断层两侧的源区和沉积区之间的空间关系随走滑运动不断发生变化。走滑断层两侧的源-汇系统之间的耦合机制是一个有待研究的问题。针对这一问题,本文设计了一个简化的构造地貌砂箱实验,用来揭示源区特定母岩的沉积物分布特征以及两者之间的时空关系。实验结果表明,特定母岩在沉积区的沉积信号分布范围受包括山前洪积扇形态、岩体在流域内的分布等多种因素影响。由于洪积扇向沉积区呈扇状展开的形态特征,沉积信号在离走滑断层更远的位置分布范围更宽。当一个岩体分布在不同流域内时,其沉积物分布在两个洪积扇内,从而使其沉积信号分布范围更宽。相反,规模较小的洪积扇会被相邻较大的洪积扇限制形态从而使得沉积范围变窄。由于上述原因,在利用沉积信号和岩体之间的错开距离计算获得的走滑速率,可能会低估或者高估真实的走滑速率。本文的实验为研究以走滑断层为边界的盆山耦合系统及其源-汇体系提供了重要的模型参考。

The combination of uplift denudation area and piedmont depositional area bounded by strike-slip fault is one of the important types of basin-mountain system.Due to the continuous relative slip between the two plates of the strike-slip fault,the spatial relationship between the source and sedimentary area on both sides of the strike-slip fault constantly changes as the fault slips.The coupling mechanism between source and sedimentary systems on both sides of the strike-slip fault needs to be investigated.Towards this end,a simplified geomorphic sandbox experiment was designed to reveal the distribution of sediment eroded from the intrusive bodies in the source area.The experimental results showed that the distribution area of the sedimentary signal of the intrusive bodies in the sedimentary area was affected by many factors,including the shape of the piedmont alluvial fan and the distribution of the intrusive bodies in different drainages.Due to the fan-shaped development of the alluvial sediment,the sedimentary signals were distributed in a wider range further away from the strike-slip fault.When the same intrusive bodies were distributed in different drainage basins,its sediment was distributed in two alluvial fans,which makes its sedimentary signal distribution range wider.Conversely,the sedimentary area of an alluvial fan became narrower when restricted by larger adjacent fans.Due to the above relationships,the calculated strike-slip rate might be underestimated or overestimated using the offset amount between the strata with sedimentary signal and the source intrusive body.The experiment in this paper provide an important model for studying the source-to-sink system bounded by strike-slip faults.