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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Evidence of transient topographic disequilibrium in a landward passive margin river system: Knickpoints and paleo-landscapes of the New River basin, southern Appalachians
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Evidence of transient topographic disequilibrium in a landward passive margin river system: Knickpoints and paleo-landscapes of the New River basin, southern Appalachians

机译：陆上被动边缘河系统中瞬时地形不平衡的证据：阿巴拉契亚南部新河盆地的拐点和古地貌

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摘要

The upper New River basin of the southern Appalachian Mountains, a major tributary of the modern Ohio River, represents the unglaciated headwaters of the Tertiary Teays River system of eastern North America. Dating of relict fluvial gravels have suggested that New River incision may be outpacing lowering of the surrounding uplands, but physical evidence of transient topographic disequilibrium has yet to be identified. We use focused topographic analysis of the upper New River basin to delineate a perched, low-relief paleo-landscape that is experiencing transgressive dissection due to incision by the New River and its tributaries. Accelerated incision has decoupled hillslopes from the drainage network, generating knickpoints which represent the boundary between remnants of the paleo-landscape and actively adjusting topography downstream. Steepening of hillslopes downstream of knickpoints suggests dynamic headward migration which, along with knickpoint occurrence throughout the drainage network, is inconsistent with the development of fixed stream profile convexities atop strike-extensive geologic contacts. In the absence of tectonic forcing, we favor a climatically-forced drop in external base level as driver of the incision pattern we observe. Plio-Pleistocene glacial damming and diversion of the Teays River to form the modern Ohio River lowered regional base level for the study area, potentially forcing the paleo-landscape developed during the Teays era to adjust to the modern drainage pattern. The upper New River may therefore represent the potential for glacially-driven drainage rearrangement to drive transient topographic evolution hundreds of kilometers away from the ice margin, long after the disappearance of ice sheets.
机译：阿巴拉契亚山脉南部的新河上游流域是现代俄亥俄河的主要支流，代表了北美东部蒂阿斯河系统的无冰河源头。遗迹河流砾石的年代已经表明，新河的切口可能超过了周围高地的下降，但是暂时的地形不平衡的物理证据尚未确定。我们使用新河上游流域的集中地形分析来描绘栖息，低浮雕的古地形，由于新河及其支流的切口，该海域正经历海侵性解剖。加速的切割使山坡与排水管网脱钩，产生了代表古土壤残余之间边界的拐点，并积极调整了下游的地形。拐点下游的山坡变陡表明动态的向前移动，连同在整个排水管网中出现的拐点，与在走向广泛的地质接触之上固定流剖面凸起的发展是不一致的。在没有构造强迫的情况下，我们倾向于将气候强迫的外部基础水平降低作为观察到的切口样式的驱动因素。 Teaios河的上新世冰川筑坝和改道，形成了现代俄亥俄河，降低了研究区域的区域基础水平，可能迫使Teays时代发展的古地貌适应现代排水模式。因此，上游新河可能代表着冰川驱动的排水系统重新布置的潜力，从而在冰盖消失后很长一段时间内驱使短暂的地形演变远离冰缘数百公里。

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