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Pulsed Mesozoic Deformation in the Cordilleran Hinterland and Evolution of the Nevadaplano: Insights from the Pequop Mountains, NE Nevada
Lithosphere ( IF 1.8 ) Pub Date : 2020-08-25 , DOI: 10.2113/2020/8850336
Andrew V. Zuza 1 , Charles H. Thorman 2 , Christopher D. Henry 1 , Drew A. Levy 1 , Seth Dee 1 , Sean P. Long 3 , Charles A. Sandberg 2 , Emmanuel Soignard 4
Affiliation  

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 NeoproterozoicTriassic 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 Ar/Ar 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.

中文翻译:

Cordilleran 腹地的脉冲中生代变形和内华达普拉诺的演化:来自内华达州 Pequop 山脉的见解

北美科迪勒拉山脉腹地的中生代地壳缩短与内华达普拉诺造山高原的建造有关。科迪勒拉岩心复合体中的岩石学和地球化学指标表明,在高原建造过程中,晚白垩世地壳大量增厚。在内华达州东部,来自蛇山脉和红宝石山脉-东洪堡山脉-伍德山-佩阔普山脉 (REWP) 核心复合体的地理气压测量表明,约 10-12 公里厚的新元古代三叠纪被动边缘层序被埋藏到很深的地方(>30 公里) ) 在中生代缩短过程中,后来通过新生代的高强度伸展被挖掘到地表。深层区域埋藏通常与涉及隐秘逆冲层的结构模型相一致,例如 REWP 中假设的温德米尔逆冲。我们通过检查 Pequop 山脉 REWP 变形最小的部分来测试深冲埋埋藏的可行性。观测包括新元古代-三叠纪地层的新的和已发表的峰值温度估计值 (n = 60) 的汇编、限制变形方式和时间的关键场关系的文档,以及新的 Ar/Ar 年龄。这一证据驳斥了深部区域逆冲埋藏模型,包括 (1) 认识到 Pequop 山脉中的大多数收缩结构形成于侏罗纪,而不是白垩纪,以及 (2) 峰值温度限制和现场关系与深埋藏不一致。这里记录的侏罗纪变形与跨越内华达州西部到犹他州中部的同时代结构相关,这突出表明中晚期侏罗纪缩短在科迪勒拉腹地很重要。这些观察结果挑战了人们对 REWP 和 Cordilleran 腹地中生代早期演化的普遍看法,包括收缩应变的时间、高原生长的时间演化以及高强度新生代伸展的初始条件。内华达核心复合体中峰值压力估计值和现场关系之间的长期差异可能反映了构造超压。
更新日期:2020-08-25
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