Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA
Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA
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美国俄勒冈州喀斯喀特山脉玄武岩景观的水文和地形协同演化
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
S. Lancaster
中科院分区：
文献类型：
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作者：
A. Jefferson;G. Grant;S. Lewis;S. Lancaster
年轻的玄武岩地形提供了一个特殊的机会，研究景观和水文演变随着时间的推移，因为景观本身的年龄可以通过测定熔岩流。这些构造地形也具有高渗透性，允许人们检查地貌演变的时间尺度和过程，因为它们与地表和地下水流之间的水文流路划分有关。美国俄勒冈州喀斯喀特山脉的西坡是由一个从全新世到渐新世的厚厚的熔岩流序列组成的，该景观每年接收2000至3500 mm的丰富降水。在全新世和晚更新世熔岩景观中，地下水系统将大部分补给输送到具有非常稳定的水文线的大泉（≥0·85 m3 s−1）。在超过100万年的流域中，没有泉水，由浅层地下暴雨流补给的发达排水网络产生了闪光的水文线。在这片玄武岩景观中，排水密度随着时间的推移而缓慢增加，需要100万年才能使密度增加一倍。在这一时间尺度上，还发生了渐进的山坡变陡和河流下切。泉水和地下水补给的河流几乎不输送沉积物，因此在切割河谷方面基本上是无效的，因此河流景观解剖似乎只有在泉水被浅层地下暴雨流取代为主要的径流生成机制之后才会发生。有人提出，玄武岩地形中的景观演变受到渗透性充分降低以使地表水流取代地下水流所需时间的限制。版权所有© 2010约翰威利父子有限公司.
Young basalt terrains offer an exceptional opportunity to study landscape and hydrologic evolution through time, since the age of the landscape itself can be determined by dating lava flows. These constructional terrains are also highly permeable, allowing one to examine timescales and process of geomorphic evolution as they relate to the partitioning of hydrologic flowpaths between surface and sub‐surface flow. The western slopes of the Cascade Range in Oregon, USA are composed of a thick sequence of lava flows ranging from Holocene to Oligocene in age, and the landscape receives abundant precipitation of between 2000 and 3500 mm per year. On Holocene and late Pleistocene lava landscapes, groundwater systems transmit most of the recharge to large springs (≥0·85 m3 s−1) with very steady hydrographs. In watersheds >1 million years old, springs are absent, and well‐developed drainage networks fed by shallow subsurface stormflow produce flashy hydrographs. Drainage density slowly increases with time in this basalt landscape, requiring a million years to double in density. Progressive hillslope steepening and fluvial incision also occur on this timescale. Springs and groundwater‐fed streams transport little sediment and hence are largely ineffective in incising river valleys, so fluvial landscape dissection appears to occur only after springs are replaced by shallow subsurface stormflow as the dominant streamflow generation mechanism. It is proposed that landscape evolution in basalt terrains is constrained by the time required for permeability to be reduced sufficiently for surface flow to replace groundwater flow. Copyright © 2010 John Wiley & Sons, Ltd.