Climate and topography control the size and flux of sediment produced on steep mountain slopes
Climate and topography control the size and flux of sediment produced on steep mountain slopes
复制标题
气候和地形控制陡峭山坡上产生的沉积物的大小和通量
DOI：
10.1073/pnas.1503567112
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
D. Shuster
中科院分区：
文献类型：
--
作者：
C. Riebe;L. Sklar;C. Lukens;D. Shuster
重要河流利用下伏基岩的生物、化学和物理风化作用在山坡上产生的沉积物来雕刻景观。泥沙的大小和供应速率都影响河流切割和地貌演变的速度，但由于难以量化坡面提供的泥沙的粒度分布，因此两者之间的联系仍然知之甚少。这项研究结合了现有的沉积物追踪技术，以一种以前未被确定的方法来量化加利福尼亚州High Sierra的一个高山集水区的沉积物产量。结果表明，越冷、越陡、植被越少的斜坡产生的泥沙越粗，侵蚀进入河网的速度就越快。这些结果表明，沉积物示踪方法可以用来量化气候、地形和侵蚀之间的反馈。山坡上的风化作用将岩石转化为沉积物，侵蚀成沟渠，从而为溪流提供了切割基岩的工具。坡面泥沙的大小和流量都会影响河道切割，使泥沙的产生和侵蚀成为气候和构造在景观演变中相互作用的中心。虽然侵蚀速率通常使用宇宙源核素来测量，但还没有补充的方法来量化沉积物产生的斜坡上沉积物大小的变化。在这里，我们展示了如何使用在不同大小的水系沉积物中测量的磷灰石氦年龄和宇宙成因核素的组合来克服这一限制。我们将这种方法应用于加利福尼亚州高塞拉山脉东侧花岗闪长岩基岩下的集水区。我们的结果表明，海拔更高的斜坡更陡峭、更寒冷、植被更少，正在产生更粗糙的沉积物，侵蚀到河网的速度更快。这表明，从斜坡到渠道的泥沙的大小和流量都受到气候、植被和集水区地形的海拔变化的影响。通过量化风化产生的沉积物大小的空间变化，这种分析使人们能够对气候、构造和山脉景观演变之间的反馈作用中的沉积物供应有新的理解。
Significance Rivers carve through landscapes using sediment produced on hillslopes by biological, chemical, and physical weathering of underlying bedrock. Both the size and supply rate of sediment influence the pace of river incision and landscape evolution, but the connections remain poorly understood, because the size distributions of sediment supplied from slopes have been difficult to quantify. This study combined existing sediment-tracing techniques in a previously unidentified approach to quantify sediment production across an alpine catchment in the High Sierra, California. Results show that colder, steeper, and less vegetated slopes produce coarser sediment that erodes faster into the channel network. These results demonstrate that the sediment-tracing approach can be used to quantify feedbacks between climate, topography, and erosion. Weathering on mountain slopes converts rock to sediment that erodes into channels and thus provides streams with tools for incision into bedrock. Both the size and flux of sediment from slopes can influence channel incision, making sediment production and erosion central to the interplay of climate and tectonics in landscape evolution. Although erosion rates are commonly measured using cosmogenic nuclides, there has been no complementary way to quantify how sediment size varies across slopes where the sediment is produced. Here we show how this limitation can be overcome using a combination of apatite helium ages and cosmogenic nuclides measured in multiple sizes of stream sediment. We applied the approach to a catchment underlain by granodiorite bedrock on the eastern flanks of the High Sierra, in California. Our results show that higher-elevation slopes, which are steeper, colder, and less vegetated, are producing coarser sediment that erodes faster into the channel network. This suggests that both the size and flux of sediment from slopes to channels are governed by altitudinal variations in climate, vegetation, and topography across the catchment. By quantifying spatial variations in the sizes of sediment produced by weathering, this analysis enables new understanding of sediment supply in feedbacks between climate, tectonics, and mountain landscape evolution.
影响因子：
5
作者：
K. Norton;F. Blanckenburg
通讯作者：
K. Norton;F. Blanckenburg