Pulsed Mesozoic Deformation in the Cordilleran Hinterland and Evolution of the Nevadaplano: Insights from the Pequop Mountains, NE Nevada
Pulsed Mesozoic Deformation in the Cordilleran Hinterland and Evolution of the Nevadaplano: Insights from the Pequop Mountains, NE Nevada
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DOI：
10.2113/2020/8850336
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发表时间：
2020-06
期刊：
影响因子：
2.4
通讯作者：
A. Zuza;C. Thorman;C. Henry;D. Levy;Seth M. Dee;S. Long;C. Sandberg;E. Soignard
中科院分区：
文献类型：
--
作者：
A. Zuza;C. Thorman;C. Henry;D. Levy;Seth M. Dee;S. Long;C. Sandberg;E. Soignard
北美科迪勒拉山系内陆的中生代地壳缩短与内华达造山高原的形成有关。科迪勒拉山系核杂岩的岩石学和地球化学指标表明，在高原形成过程中，晚白垩世地壳显著增厚。在内华达州东部，来自蛇岭以及鲁比山 - 东洪堡岭 - 伍德山 - 佩库普山（REWP）核杂岩的地质压力测量表明，厚约10 - 12千米的新元古代 - 三叠纪被动边缘层序在中生代缩短过程中被深埋至很大深度（>30千米），后来又通过新生代大规模伸展被抬升至地表。深部区域埋藏通常与涉及隐伏逆冲断层的构造模型相契合，比如在REWP中假设的温德米尔逆冲断层。我们通过研究佩库普山REWP中变形最小的部分来检验深部逆冲断层埋藏的可行性。观测结果包括对新的和已发表的跨越新元古代 - 三叠纪地层的峰值温度估计值（n = 60）的汇总、对限制变形样式和时间的关键野外关系的记录以及新的40Ar/39Ar年龄。这些证据反驳了深部区域逆冲断层埋藏的模型，包括（1）认识到佩库普山的大多数收缩构造形成于侏罗纪，而非白垩纪；（2）峰值温度限制和野外关系与深埋不一致。这里记录的侏罗纪变形与从内华达州西部到犹他州中部的同时代构造相关，这突出表明中 - 晚侏罗世缩短在科迪勒拉山系内陆具有重要意义。这些观测结果对REWP和科迪勒拉山系内陆中生代 - 新生代早期演化的普遍观点提出了挑战，包括收缩应变的时间、高原生长的时间演化以及新生代大规模伸展的初始条件。内华达核杂岩中峰值压力估计值和野外关系之间长期存在的差异可能反映了构造超压。
Mesozoic crustal shortening in the North American Cordillera’s hinterland was related to the construction of the Nevadaplano orogenic plateau. Petrologic and geochemical proxies in Cordilleran core complexes suggest substantial Late Cretaceous crustal thickening during plateau construction. In eastern Nevada, geobarometry from the Snake Range and Ruby Mountains-East Humboldt Range-Wood Hills-Pequop Mountains (REWP) core complexes suggests that the ~10–12 km thick Neoproterozoic-Triassic passive-margin sequence was buried to great depths (>30 km) during Mesozoic shortening and was later exhumed to the surface via high-magnitude Cenozoic extension. Deep regional burial is commonly reconciled with structural models involving cryptic thrust sheets, such as the hypothesized Windermere thrust in the REWP. We test the viability of deep thrust burial by examining the least-deformed part of the REWP in the Pequop Mountains. Observations include a compilation of new and published peak temperature estimates (n=60) spanning the Neoproterozoic-Triassic strata, documentation of critical field relationships that constrain deformation style and timing, and new 40Ar/39Ar ages. This evidence refutes models of deep regional thrust burial, including (1) recognition that most contractional structures in the Pequop Mountains formed in the Jurassic, not Cretaceous, and (2) peak temperature constraints and field relationships are inconsistent with deep burial. Jurassic deformation recorded here correlates with coeval structures spanning western Nevada to central Utah, which highlights that Middle-Late Jurassic shortening was significant in the Cordilleran hinterland. These observations challenge commonly held views for the Mesozoic-early Cenozoic evolution of the REWP and Cordilleran hinterland, including the timing of contractional strain, temporal evolution of plateau growth, and initial conditions for high-magnitude Cenozoic extension. The long-standing differences between peak-pressure estimates and field relationships in Nevadan core complexes may reflect tectonic overpressure.