Spatially Variable Increase in Rock Uplift in the Northern U.S. Cordillera Recorded in the Distribution of River Knickpoints and Incision Depths
Spatially Variable Increase in Rock Uplift in the Northern U.S. Cordillera Recorded in the Distribution of River Knickpoints and Incision Depths
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DOI：
10.1029/2018jf004880
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
N. Mitchell;B. Yanites
中科院分区：
文献类型：
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作者：
N. Mitchell;B. Yanites
景观演化是由构造和气候等因素驱动的，解开这些因素可以揭示景观形态中记录的历史。美国北方科迪勒拉山脉有许多潜在的驱动因素，如黄石火山柱，一个大火成岩省的挤压，以及大型湖泊的排水。在这一复杂的地质历史中，爱达荷州中部清水河和鲑鱼流域的瞬时切割的驱动因素还没有得到很好的理解。为了约束区域切割的模式，我们分析了80个独立的支流下的单一岩性的形态。从北到南，在我们的研究区域，缺口点海拔从800米增加到2,200米，切口深度从300米增加到1,200米。我们使用数值和分析模型来证明，这样的梯度可以代表岩石隆起的空间变化。这些研究结果表明，瞬态是由岩石隆起的空间变化增加所驱动的，这种增加破坏了低起伏的古地貌，而主要排水系统的高陡度值表明，高岩石隆起率仍然保持到现在。岩石隆起的变化可能与黄石羽流和岩石圈之间的相互作用有关，尽管从爱达荷州的排水系统到原蛇河的基准面下降可能叠加在岩石隆起的这些模式上。我们表明，对地质复杂地区的河流剖面进行仔细的定量分析，可以区分岩石隆起和远场基准面变化的影响。
Landscape evolution is driven by factors like tectonics and climate, and unraveling such factors can reveal the history recorded in landscape morphology. The northern U.S. Cordillera features many potential drivers, such as the Yellowstone plume, the extrusion of a large igneous province, and the drainage of large lakes. Among this complex geologic history, the drivers of transient incision in the Clearwater and Salmon watersheds of central Idaho are not well understood. To constrain the pattern of regional incision, we analyze the morphologies of 80 individual tributaries underlain by single lithologies. From north to south across our study area, knickpoint elevations increase from about 800 to 2,200 m, and incision depths increase from about 300 to 1,200 m. We use both numerical and analytical models to demonstrate that such a gradient could represent spatial variations in rock uplift. These findings suggest that transience is driven by a spatially variable increase in rock uplift that has disrupted a low‐relief paleolandscape, and the high steepness values of main drainages suggest that high rock‐uplift rates are still maintained to the present. Changes in rock uplift may be related to interactions between the Yellowstone plume and the lithosphere, although base level fall from the drainage of the Lake Idaho down the proto‐Snake River may be superimposed over these patterns in rock uplift. We show that careful, quantitative analyses of river profiles in geologically complex regions can differentiate between the influences of rock uplift and far‐field base level changes.