Erosion rates and mechanisms of knickzone retreat inferred from 10 Be measured across strong climate gradients on the northern and central Andes Western Escarpment
Erosion rates and mechanisms of knickzone retreat inferred from 10 Be measured across strong climate gradients on the northern and central Andes Western Escarpment
复制标题
根据 10 中安第斯山脉西部悬崖北部和中部的强气候梯度进行测量，推断出危险带退缩的侵蚀率和机制
DOI：
10.1002/esp.2164
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发表时间：
2011
影响因子：
3.3
通讯作者：
Abbühl L
中科院分区：
文献类型：
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作者：
Abbühl L
陡峭的悬崖边缘、深深的峡谷和河流剖面中明显的断层带是安第斯山脉西斜坡在南纬5° ~18°之间（秘鲁北方至智利北方）的地貌特征。利用强南北和东西降水梯度，以确定气候如何影响剥蚀率在三个流域，否则相对统一的地质和地貌环境。晚中新世构造抬升了Meseta/Altiplano高原（海拔约3000米），其下是一系列第三纪火山岩在这个高原上的河流仍然是渐变到晚中新世基准面。在梅塞塔边缘以下，河流通过一系列陡峭的、向前后退的、逐渐变平到太平洋所定义的现今基准面的断结带，深深地切入断裂的中生代岩石，从而对这种斜坡隆起做出了反应。这有助于陡崖边缘和上结带尖端的平行后退。10里约皮乌拉（5°S）的Be导出集水剥蚀率，在Meseta/Altiplano上，Rio皮斯科（13°S）和Rio Lluta（18°S）的平均剥蚀率约为10 mm ky− 1，与降水率无关;而在悬崖边缘的下游，剥蚀率范围为10 mm ky− 1至250 mm ky− 1，与降水率呈正相关，但与山坡角度或河道陡度没有很强的相关性。这些关系可以用盖层的存在和气候驱动的河流切割来解释，这种切割使山坡变陡，达到接近门槛的条件。由于悬崖退缩和降水模式至少在中新世就已确立，因此推测在过去的几百万年里，随着结带向前扩展到高原，现今的形态和剥蚀率分布可能基本保持不变。版权所有© 2011约翰威利父子有限公司.
A steep escarpment edge, deep gorges and distinct knickzones in river profiles characterize the landscape on the Western Escarpment of the Andes between ~5°S and ~18°S (northern Peru to northern Chile). Strong north–south and east–west precipitation gradients are exploited in order to determine how climate affects denudation rates in three river basins spanning an otherwise relatively uniform geologic and geomorphologic setting. Late Miocene tectonics uplifted the Meseta/Altiplano plateau (~3000 m a.s.l.), which is underlain by a series of Tertiary volcanic‐volcanoclastic rocks. Streams on this plateau remain graded to the Late Miocene base level. Below the rim of the Meseta, streams have responded to this ramp uplift by incising deeply into fractured Mesozoic rocks via a series of steep, headward retreating knickzones that grade to the present‐day base level defined by the Pacific Ocean.It is found that the Tertiary units on the plateau function as cap‐rocks, which aid in the parallel retreat of the sharp escarpment edge and upper knickzone tips.10Be‐derived catchment denudation rates of the Rio Piura (5°S), Rio Pisco (13°S) and Rio Lluta (18°S) average ~10 mm ky−1on the Meseta/Altiplano, irrespective of precipitation rates; whereas, downstream of the escarpment edge, denudation rates range from 10 mm ky−1to 250 mm ky−1and correlate positively with precipitation rates, but show no strong correlation with hillslope angles or channel steepness. These relationships are explained by the presence of a cap‐rock and climate‐driven fluvial incision that steepens hillslopes to near‐threshold conditions.Since escarpment retreat and the precipitation pattern were established at least in the Miocene, it is speculated that the present‐day distribution of morphology and denudation rates has probably remained largely unchanged during the past several millions of years as the knickzones have propagated headward into the plateau. Copyright © 2011 John Wiley & Sons, Ltd.