龙门山褶皱冲断带沿走向差异剥蚀作用——砂箱物理模型的启示

褶皱冲断带- 前陆盆地系统普遍存在浅表构造剥蚀- 沉积作用及其相关耦合机制，从而具有复杂的三维空间构造变形特征与演化过程。本文基于青藏高原东缘龙门山褶皱冲断带- 前陆盆地系统，通过沿走向变化的剥蚀- 沉积作用砂箱物理模拟实验和野外地质调查等研究，揭示其沿走向变化的剥蚀- 沉积作用，导致了褶皱冲断带大规模抬升剥蚀、断层多期活化与无序变形；断层与冲起构造沿走向合并生长、形成斜向断层；尤其是冲断带三维空间上差异性抬升剥蚀，常常形成与构造剥蚀作用相关的反转构造。剥蚀作用越强、〖JP〗断层翻转越明显（形成视正断层）。龙门山褶皱冲断带广泛出露的拉张构造变形样式，可能受控于晚中生代—新生代沿走向变化的剥蚀- 沉积作用过程。上述沿走向变化的剥蚀- 沉积作用，可能导致川西南前陆盆地系统中低角度断层多期活化与无序冲断变形。研究表明，晚三叠世以来的构造缩短与浅表作用，对青藏高原东缘龙门山独特地貌构造特征具有重要的控制作用。

Along- strike erosion processes at the Longmenshan fold- and- thrust belt, evidence from analogue experiments

Tectonic- erosion- sedimentation interaction and their coupled relationships control the evolution of fold- and- thrust belts and foreland basin systems at different time and space scales. In this study, we use analog experiments to investigate the influence of erosion and sedimentation of fold- and- thrust belt, in particular, the along- strike change of erosion- sedimentation in the Longmenshan fold- and- thrust belt. The along- strike change of surface processes results in a strong erosion in wedge hinterland, reactivation of faults and out- of- sequence thrusting, some of faults join together along strike to form lateral faults (or transfer faults). Furthermore, along- strike change of erosion accommodates overturning of faults, even normal ones, in the wedge hinterland. Stronger the erosion, bigger the change for the faults in the hinterland. Extensional deformation is found across the Longmenshan fold- and- thrust belt, which could be accounted by the along- strike change of erosion that occurred in the Cretaceous to Cenozoic time. In particular, the along- strike change of erosion induces reactivation of low- angle faults, and out- of- sequence thrusting in the southwestern Sichuan basin. Thus, we argue that the tectonic shortening and surface processes have had a significant influence on the architecture of the Longmenshan.