Displacement transfer from fault-bend to fault-propagation fold geometry: An example from the Himalayan thrust front
Displacement transfer from fault-bend to fault-propagation fold geometry: An example from the Himalayan thrust front
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DOI：
10.1016/j.jsg.2014.10.010
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发表时间：
2015-08
影响因子：
3.1
通讯作者：
M. Qayyum;D. Spratt;J. M. Dixon;R. D. Lawrence
中科院分区：
文献类型：
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作者：
M. Qayyum;D. Spratt;J. M. Dixon;R. D. Lawrence
巴基斯坦东北东向喜马拉雅冲断前锋的前缘表现为沿走向的变形样式变化，从断层弯曲到断层传播褶皱。尽管构造几何学在整个盐岭都有轻微的变形，但向东逐渐变得更加复杂，因为新出现的盐岭逆冲的前沿变得盲目。地表地质学、地震反射、油井和年代地层数据被综合起来，产生了一个三维运动学模型，该模型协调了喜马拉雅逆冲前缘这一部分不同的构造几何形状。我们提出了一个模型，即通过新发现的侧向斜坡，位移从西部的断层弯曲褶皱转移到东部的断层传播褶皱，而类似的缩短由两种根本不同的机制同步调节：平移和伸缩。然而，在这些构造反差较大的区段内，截然不同的缩短分布模式需要撕裂断层，该断层后来被重新激活为逆冲断层。这种S形位移传递带的现今形态是北西-南东向挤压侧向顶壁和伴生的撕裂断裂的综合结果，以及由于下伏韧性盐的活动而随后的改造。
The leading edge of the ENE-trending Himalayan thrust front in Pakistan exhibits along-strike changes in deformational style, ranging from fault-bend to fault-propagation folds. Although the structural geometry is very gently deformed throughout the Salt Range, it becomes progressively more complex to the east as the leading edge of the emergent Salt Range Thrust becomes blind. Surface geology, seismic reflection, petroleum well, and chronostratigraphic data are synthesized to produce a 3-D kinematic model that reconciles the contrasting structural geometries along this part of the Himalayan thrust front. We propose a model whereby displacement was transferred, across a newly-identified lateral ramp, from a fault-bend fold in the west to fault-propagation folds in the east and comparable shortening was synchronously accommodated by two fundamentally different mechanisms: translation vs. telescoping. However, substantially different shortening distribution patterns within these structurally contrasting segments require a tear fault, which later is reactivated as a thrust fault. The present geometry of this S-shaped displacement transfer zone is a combined result of the NW–SE compression of the lateral culmination wall and associated tear fault, and their subsequent modification due to mobilization of underlying ductile salt.