Diagenetic variation in the Oregon Coast Range: Implications for rock strength, soil production, hillslope form, and landscape evolution
Diagenetic variation in the Oregon Coast Range: Implications for rock strength, soil production, hillslope form, and landscape evolution
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俄勒冈海岸山脉的成岩变化：对岩石强度、土壤产量、山坡形态和景观演化的影响
DOI：
10.1002/2013jf003004
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
J. Roering
中科院分区：
文献类型：
--
作者：
J. Marshall;J. Roering
岩性调制地貌过程的机制知之甚少。在俄勒冈州海岸山脉（OCR），始新世Tyee组的韵律层状砂岩位于陡峭的土壤覆盖山坡之下，山脊-山谷间距相对均匀。这些独特的地貌在成岩变化表现为抵抗悬崖的地方受到干扰。在这里，我们使用岩石学，岩石力学和激光雷达来表征岩石性质的粒度变化及其对岩石强度，山坡过程和两个相邻流域的景观形态的影响。岩相学分析表明，一套成岩产品的“耐”基岩帐户的抗拉强度增加2.5倍，相对于“典型的”Tyee基岩。我们的参考集水区表现出可忽略不计的阻力露头，一致的山坡坡度和纵向山谷剖面。相比之下，邻近的集水区充满了1至10米厚的不连续砂岩层，形成了悬挂的山谷，上游山坡平缓，山谷狭窄。机械和地形分析表明，低断裂密度特性，这些耐床可能使他们相对不受粉碎树根活动，占主导地位的OCR土壤生产机制。根据山坡坡度和山顶曲率侵蚀模型，我们估计，山坡上栖息的阻力床侵蚀的速度约为山坡不受下游缺口的一半。成岩作用的变化可能影响流域尺度的地形起伏。沉积位置和成岩过程似乎控制了抵抗层的出现，提供了一个框架来量化岩石性质中看似微妙的变化如何对景观形式和演化施加一级控制。
The mechanisms by which lithology modulates geomorphic processes are poorly known. In the Oregon Coast Range (OCR), rhythmically bedded sandstones of the Eocene Tyee Formation underlie steep, soil‐mantled hillslopes, with relatively uniform ridge‐valley spacing. These characteristic landforms are perturbed where diagenetic variations manifest as resistant cliffs. Here we use petrology, rock mechanics, and lidar to characterize grain‐scale variations in rock properties and their influence on rock strength, hillslope processes, and landscape morphology in two adjacent watersheds. Petrographic analyses suggest that a suite of diagenetic products in the “resistant” bedrock account for a 2.5 times increase in tensile strength relative to “typical” Tyee bedrock. Our reference catchment exhibits negligible resistant outcrops, and consistent hillslope gradients and longitudinal valley profiles. By contrast, the adjacent catchment teems with resistant, 1 to 10 m thick, noncontiguous sandstone beds that form hanging valleys with gentle upstream hillslopes and anomalously narrow valleys. Mechanical and topographic analyses suggest that the low fracture density characteristic of these resistant beds may render them relatively impervious to comminution by tree root activity, the dominant OCR soil production mechanism. Based on both hillslope gradient‐ and hilltop curvature‐erosion models, we estimate that hillslopes perched above resistant beds erode at approximately half the pace of hillslopes unencumbered by downstream knickpoints. The diagenetic variations likely influence relief at the watershed scale. Depositional position and diagenetic processes appear to control the occurrence of resistant beds, providing a framework to quantify how seemingly subtle variations in rock properties can impose first‐order controls on landscape form and evolution.
DOI：
10.1002/2013jf002981
发表时间：
2014-02
期刊：
Journal of Geophysical Research: Earth Surface
影响因子：
--
作者：
S. Mudd;Mikael Attal;D. Milodowski;S. Grieve;Declan A. Valters
通讯作者：
S. Mudd;Mikael Attal;D. Milodowski;S. Grieve;Declan A. Valters
影响因子：
3.9
作者：
Hurst, Martin D.;Mudd, Simon M.;Yoo, Kyungsoo
通讯作者：
Yoo, Kyungsoo