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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi-arid, arroyo-dominated landscape, Rio Puerco Basin, New Mexico
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Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi-arid, arroyo-dominated landscape, Rio Puerco Basin, New Mexico

机译：在新墨西哥州里奥普尔科盆地的一个半干旱，阿罗约占主导的景观中，使用宇宙成因核素来对比侵蚀和沉积物产生的速率

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摘要

Analysis of in-situ-produced Be-10 and Al-26 in 52 fluvial sediment samples shows that millennial-scale rates of erosion vary widely (7 to 366 m Ma(-1)) through the lithologically and topographically complex Rio Puerco Basin of northern New Mexico. Using isotopic analysis of both headwater and downstream samples, we determined that the semi-arid, Rio Puerco Basin is eroding, on average, about 100 m Ma(-1). This rapid rate of erosion is consistent with estimates made using other techniques and is likely to result from a combination of easily eroded lithologies, sparse vegetation, and monsoon-dominated rainfall. Data from 331 stream water samples collected by the US Geological Survey between 1960 and 1995 are consistent with basin-wide, average chemical denudation rates of only about 1.4 m Ma(-1); thus, the erosion rates we calculate may be considered rates of sediment generation because physical weathering accounts for almost 99 per cent of mass loss.The isotopic data reveal that sediment is generally well mixed downstream with the area-weighted average sediment generation rate for 16 headwater samples (234 ton km(-2) a(-1) for basin area 170 to 1169 km(2)) matching well that estimated from a single sample collected far downstream (238 ton km(-2) a(-1), basin area = 14 225 km(2)). A series of 15 samples, collected from an arroyo wall and representing deposition through the late Holocene, indicates that Be-10 concentration in sediment delivered by the fluvial system has not changed appreciably over the last 1200 years despite at least two cycles of arroyo cutting and filling. Other samples (n = 21) were collected along the drainage network.Rio Puerco erosion rates scale directly with a variety of metrics describing vegetation, precipitation, and rock erodibility. Using the headwater basins for calibration, the erosion rates for both the downstream samples and also the data set as a whole, are best modelled by considering a combination of relief and vegetation metrics, both of which co-vary with precipitation and erodibility as inferred from lithology. On average, contemporary sediment yields, determined by monitoring suspended-sediment discharge, exceed cosmogenically determined millennial-scale erosion rates by nearly a factor of two. This discrepancy, between short-term rates of sediment yield and long-term rates of erosion, suggests that more sediment is currently being exported from the basin than is being produced. Because the failure of incised channel walls and the head cutting of arroyo complexes appear to be the main sources of channel sediment today, this incongruence between rates of sediment supply and sediment yield is likely to be transitory, reflecting the current status of the arroyo cycle and perhaps the influence of current or past land-use patterns. Copyright (c) 2005 John Wiley & Sons, Ltd.
机译：对52个河流沉积物样品中原位生成的Be-10和Al-26的分析表明，在整个加利福尼亚州的岩性和地形复杂的里约普尔科盆地，千年尺度的侵蚀率变化很大（7至366 m Ma（-1））。新墨西哥州北部。通过对源头和下游样品的同位素分析，我们确定半干旱的里约普尔科盆地正在平均侵蚀约100 m Ma（-1）。这种快速的侵蚀速度与使用其他技术得出的估计值一致，并且很可能是由容易侵蚀的岩性，稀疏的植被和季风为主的降雨共同造成的。 1960年至1995年间，美国地质调查局收集的331个溪流水样的数据与全流域平均化学剥蚀率只有1.4 m Ma（-1）一致。因此，我们计算出的侵蚀速率可以认为是沉积物的生成速率，因为物理风化几乎占质量损失的99％。同位素数据显示，沉积物通常在下游与16个源头的区域加权平均沉积物生成速率充分混合流域面积为170至1169 km（2）的样本（234 ton km（-2）a（-1））与根据下游采集的单个样本（238 ton km（-2）a（-1）估计的采样值相匹配流域面积= 14225 km（2））。从Arroyo壁收集的一系列15个样品代表了整个全新世晚期的沉积，这表明尽管至少有两个Arroyo切割和循环周期，但在过去1200年中，河流系统输送的沉积物中Be-10的浓度并未发生明显变化。填充。沿排水网络收集了其他样本（n = 21）。里奥·普埃尔科（Rio Puerco）侵蚀速率直接通过各种描述植被，降水和岩石易蚀性的指标进行缩放。使用上游水源进行标定，可以通过考虑浮雕和植被指标的组合来对下游样品和整个数据集的侵蚀率进行最佳建模，这两者都与降水和侵蚀性共同变化岩性。平均而言，通过监测悬浮泥沙的排放量确定的当代沉积物产量，比宇宙成因确定的千年尺度侵蚀速率高出将近两倍。短期沉积物产率与长期侵蚀率之间的这种差异表明，目前从流域输出的沉积物要多于产生的沉积物。由于切开的河道壁的破坏和arroyo配合物的头部切割似乎是当今河道沉积物的主要来源，因此，沉积物供应速率和沉积物产量之间的这种不一致可能很短暂，反映了arroyo循环和也许是当前或过去土地利用方式的影响。版权所有（c）2005 John Wiley＆Sons，Ltd.

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