Magnitude and significance of Miocene crustal extension in the central Mojave Desert, California
Magnitude and significance of Miocene crustal extension in the central Mojave Desert, California
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加利福尼亚州莫哈韦沙漠中部中新世地壳伸展的幅度和意义
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
J. Walker
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文献类型：
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作者：
A. Glazner;J. Bartley;J. Walker
加州州莫哈韦沙漠中部新发现的沃特曼山拆离断层（WHDF）意义重大，因为它首次明确地证明了莫哈韦沙漠中部存在大规模核杂岩式地壳伸展，而且它显著地重新排列了莫哈韦沙漠的前中新世古地理。WHDF在糜棱岩前第三纪基底上陡倾于倒转的中新世火山岩和沉积岩。糜棱岩明显形成于拉张过程中，主要为L型构造岩，表现为自上而下的北东向剪切。WHDF在莫哈韦沙漠中部的多米诺断裂范围和科罗拉多河槽的滑脱断层下向东北倾斜，形成了一个叠瓦状的早中新世滑脱断层系统。在莫哈韦沙漠中部的扩张停止后，科罗拉多河槽的扩张仍在继续。
对中生代侵入体的初步对比表明，WHDF有约40公里的滑动，其上盘携带优地斜古生代岩石，下盘携带克拉通/微地斜古生代岩石。恢复40 km的滑动（1）消除了优地斜相和双斜/缓地斜相之间边界的一个明显扭折，（2）使Victorville附近的双斜/缓地斜地层与更北的晚古生代大陆边缘更接近，（3）在结构上将双斜/缓地斜岩置于优地斜岩之下，这意味着这些相是通过逆冲作用叠加的，（4）使晚侏罗世独立岩墙群的西缘变直。
The newly recognized Waterman Hills detachment fault (WHDF) of the central Mojave Desert, California, is significant because it provides the first unambiguous evidence for large-scale core complex-style crustal extension in the central Mojave Desert, and because it has significantly rearranged the pre-Miocene paleogeography of the Mojave Desert. The WHDF places steeply dipping to overturned Miocene volcanic and sedimentary rocks upon mylonitic pre-Tertiary basement. The mylonites, which apparently formed during extension, are predominantly L-tectonites which manifest top-to-northeast shear. The WHDF dips to the northeast beneath dominofaulted ranges of the central Mojave Desert and detachment faults of the Colorado River trough, forming an imbricated early Miocene system of detachment faults. Extension continued in the Colorado River trough after extension had ceased in the central Mojave Desert.
Tentative correlations of Mesozoic intrusions suggest about 40 km of slip across the WHDF, which carries eugeoclinal Paleozoic rocks in its hanging wall and cratonal/miogeoclinal Paleozoic rocks in its footwall. Restoration of 40 km of slip (1) removes a prominent kink in the boundary between eugeoclinal and cratonal/miogeoclinal facies, (2) aligns cratonal/miogeoclinal strata near Victorville more closely with the late Paleozoic continental margin farther north, (3) places cratonal/miogeoclinal rocks structurally beneath eugeoclinal rocks, implying that the facies were stacked by thrusting, and (4) straightens the western margin of the Late Jurassic Independence dike swarm.