Thick-skinned thrusting in the northern Tien Shan foreland, Kazakhstan: structural inheritance and polyphase deformation
Thick-skinned thrusting in the northern Tien Shan foreland, Kazakhstan: structural inheritance and polyphase deformation
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DOI：
10.1144/sp377.7
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发表时间：
2013-04
期刊：
影响因子：
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通讯作者：
M. Kober;N. Seib;J. Kley;T. Voigt
中科院分区：
文献类型：
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作者：
M. Kober;N. Seib;J. Kley;T. Voigt
哈萨克斯坦新生代天山北方前缘由东向-北东向逆冲基底隆起组成。其中一些是开放的、不对称的背斜，而另一些则是有断层的块体。在出露和暴露的地方，边界断层陡倾45-70°。新生代盖层中的大波长张开褶皱也覆盖在基底构造之上。火山岩、（Meta）沉积岩和花岗岩的古生代基底包含更古老的构造，如褶皱、板状劈理、断层和岩墙。一些新生代断层截断了所有早期构造，正如一些新生代褶皱与下伏层状基底岩石的产状无关一样。对新生代构造的最强控制是由陡峭的NW向基底断裂引起的，这些断裂导致一些基底脊的沿走向分段和侧向终止。在褶皱和逆冲作用之前的新生代东西向伸展阶段，这些基底断层中的一些已经作为正断层被重新激活。一些正断层在收缩阶段表现为右旋走滑断层的复活，这些断层至今仍然活跃。由于北东向的主基底山脉没有明显的前兆构造，我们解释厚皮构造基本上反映了现代缩短方向，调制，但不受先存的基底断裂。局部运动学随时间的变化可能是由于各向异性基底的应变分配，而不是改变远场应力。陡倾滑逆断层的发生显然与再活化无关，这与某些低角度正断层类似，是一个尚未解决的力学悖论。
Abstract The northern front of the Cenozoic Tien Shan mountains in Kazakhstan comprises east- to NE-trending thrust-related basement uplifts. Some of these are open, asymmetric anticlines, whereas others are fault-bounded blocks. Where emergent and exposed, the bounding faults dip steeply at 45–70°. Large-wavelength open folds in the Cenozoic cover also overlie basement structures. The Palaeozoic basement of volcanic, (meta-) sedimentary and granitic rocks contains older structures such as folds, slaty cleavage, faults and dykes. Some Cenozoic faults truncate all earlier structures, just as some Cenozoic folds are independent of the attitudes of underlying stratified basement rocks. The strongest control on the Cenozoic structure is exerted by steep, NW-striking basement faults that induce along-strike segmentation and lateral terminations of some basement ridges. A few of these basement faults had already been reactivated as normal faults during a Cenozoic phase of east–west extension that preceded folding and thrusting. Some normal faults show reactivation as dextral strike-slip faults during the contractional phase, which is still active today. Since the NE to east trend of the main basement ranges has no obvious precursor structures, we interpret the thick-skinned structures to essentially reflect the modern shortening direction, modulated but not dominated by pre-existing basement faults. Variations in local kinematics over time are probably due to strain partitioning in the anisotropic basement, not to changing far-field stresses. The occurrence of steep dip-slip reverse faults apparently unrelated to reactivation presents an unsolved mechanical paradox similar to some low-angle normal faults.