Synorogenic extension and extrusion in southern Taiwan
Synorogenic extension and extrusion in southern Taiwan
复制标题
DOI：
10.1016/j.tecto.2022.229562
复制
发表时间：
2022-09
期刊：
影响因子：
2.9
通讯作者：
W. Hsu;T. Byrne;Jonathan C. Lewis;Yue‐Gau Chen;P. Yeh
中科院分区：
文献类型：
--
作者：
W. Hsu;T. Byrne;Jonathan C. Lewis;Yue‐Gau Chen;P. Yeh
台湾中部山脉南部东翼141条露头断层的古应力反演显示，该断层的水准和GPS资料显示，岩石隆升速率的陡峭梯度产生了两个主要的运动变形阶段。第一期由93条正断层组成，一般向东北偏北倾斜；第二期由48条走滑断层组成，一般向西北偏西倾斜。两相均有北东向亚水平伸展，但主缩短方向不同；在第一阶段，主缩短轴几乎是垂直的，而在第二阶段，它缓慢地向中等东南方向倾斜。东北向伸展与GPS和震源机制得到的伸展方向一致。然而，这些当代变形指标也揭示了沿山脉东、西两翼和山脉西南深部地壳的更复杂的应力状态。我们将这些更复杂的应力状态解释为反映了中央山脉南部的“强力挤压”，在那里，下地壳被以沛康高地和吕宋弧为代表的更坚硬的地壳块挤压。在这种背景下，在露头中观察到的从走滑到正断层的时间进展可能反映了岩石从低到高的结构水平的平流。东北伸展正断层可以解释为容纳了中部山脉南部地壳的横向和垂直运动。根据热年代学资料和台湾西南部晚更新世的挤压开始时间，我们推测这次西南挤压过程可能更晚于0.5 Ma。
Paleostress inversion of 141 outcrop-scale faults across the eastern flank of the southern Central Range of Taiwan where leveling and GPS data suggest a steep gradient in rock uplift rates yields two main kinematic phases of deformation. Phase 1 consists of 93 normal faults that generally dip moderately northeast whereas phase 2 consists of 48 strike-slip faults that generally dip steeply west-northwest. Both phases record NE-trending sub-horizontal extension but different orientations of principal shortening; in phase 1, the principal shortening axis is nearly vertical whereas in phase 2 it plunges gently to moderately southeast. The northeast extension is consistent with extension directions obtained from GPS and earthquake focal mechanisms in the central part of the southern Central Range. However, these indicators of contemporary deformation also reveal more complicated states of stress along the eastern and western flanks of the range and in the deep crust southwest of the range. We interpret these more complicated stress states as reflecting “forceful extrusion” of the southern Central Range where the lower crust is being pinched between more rigid crustal blocks represented by the Peikang High and the Luzon Arc. In this context, the temporal progress from strike-slip to normal faulting observed in outcrops may reflect the advection of the rocks from lower to higher structural levels. The northeast extension normal faults can be interpreted that accommodating the lateral and vertical movement of the crust in the southern Central Range. Based on thermochronological data and the onset of extrusion in southwest Taiwan in the late Pleistocene, we infer that this SW extrusion process may be younger the 0.5 Ma.