Displacement rates on the Toroweap and Hurricane faults: implications for Quaternary downcutting in the Grand Canyon, Arizona
Displacement rates on the Toroweap and Hurricane faults: implications for Quaternary downcutting in the Grand Canyon, Arizona
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托罗维普断层和飓风断层的位移率：对亚利桑那州大峡谷第四纪下切的影响
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
R. Poreda
中科院分区：
文献类型：
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作者：
C. Fenton;R. Webb;P. Pearthree;T. Cerling;R. Poreda
被认为是亚利桑那州最活跃的Toroweap断层和飓风断层穿过西部大峡谷的Uinkaret火山场。这些正常的断层向西倾倒，科罗拉多河在大峡谷向西流动时穿过这些断层。利用玄武岩流和相关地貌的宇宙成因3He(3Hec)年龄计算了这些断裂的垂直位移速率。这两条断层横跨3ka(Toroweap)和8ka(飓风)的未破裂冲积扇，以及其他10个年龄在30到400 ka之间的地貌发生了位移。第四纪中期和晚第四纪，Toroweap断层和飓风断层的位移速率分别为70-180和70-170米/英里。根据这些速率，这些断层上580米的总位移可能发生在过去3到5英里内。这3个He-Ar年龄都比现有的K-Ar年龄年轻，与新的40Ar/39Ar年龄和现有的玄武岩流动热释光(TL)年龄一致。这些不同的测年技术可以结合在一起来分析位移速率。科罗拉多河在大峡谷东部的下降率(400米/英里)断层以西的下切速度(70-160米/英里)至少是下切速度的两倍。在第四纪晚期，相对于西部大峡谷的下切，断层作用可能增加了大峡谷东部的下切。
The Toroweap and Hurricane faults, considered to be the most active in Arizona, cross the Uinkaret volcanic field in the western Grand Canyon. These normal faults are downthrown to the west, and the Colorado River crosses these faults as it flows west in the Grand Canyon. Cosmogenic 3 He ( 3 He c ) dates on basalt flows and related landforms are used to calculate vertical displacement rates for these faults. The two faults cross unruptured alluvial fans dated as 3 ka (Toroweap) and 8 ka (Hurricane), and 10 other landforms that range in age from 30 to 400 ka are displaced. Middle and late Quaternary displacement rates of the Toroweap and Hurricane faults are 70–180 and 70–170 m/m.y., respectively. On the basis of these rates, the combined displacement of 580 m on these faults could have occurred in the past 3 to 5 m.y. All 3 He c dates are younger than existing K- Ar dates and are consistent with new 40 Ar/ 39 Ar dates and existing thermoluminescence (TL) dates on basalt flows. These different dating techniques may be combined in an analysis of displacement rates. Downcutting rates for the Colorado River in the eastern Grand Canyon (400 m/m.y.) are at least double the downcutting rates west of the faults (70–160 m/m.y.). Faulting probably increased downcutting in the eastern Grand Canyon relative to downcutting in the western Grand Canyon during the late Quaternary.