Rates of erosion and topographic evolution of the Sierra Nevada, California, inferred from cosmogenic 26Al and 10Be concentrations
Rates of erosion and topographic evolution of the Sierra Nevada, California, inferred from cosmogenic 26Al and 10Be concentrations
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根据宇宙成因 26Al 和 10Be 浓度推断的加利福尼亚州内华达山脉的侵蚀率和地形演化
DOI：
10.1002/esp.1258
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发表时间：
2005
影响因子：
3.3
通讯作者：
R. Finkel
中科院分区：
文献类型：
--
作者：
G. Stock;R. Anderson;R. Finkel
宇宙成因的26铝和10铍在洞穴沉积物和基岩表面的浓度，结合景观形态学的研究，阐明了在过去5马的地形历史的南部山脉内华达州。在埋藏的沉积物中的26 Al/10 Be测年的洞穴表明，在公元前20世纪至公元前20世纪之间，河流的切割速率是中等到缓慢的。5和3 Ma（≤ 0.07 mm a−1），在3和1.5 Ma之间加速（c. 0·3 mm a−1），然后变得慢得多（c。0·02 mm a−1）。虽然发病的加速切口在时间上与假设的上新世构造和明显的全球气候变化相吻合，我们认为，它主要代表了3和5马之间的离散构造事件的响应。测年的洞穴位置显示，在3 Ma之前，河流峡谷显示出高达1.6 km的局部地形，表明上新世岩石隆起抬高了先前存在的地形。从c开始重新切口。3 Ma加深了高达400米的峡谷，创造了狭窄的内部峡谷。支流表现出强烈的凸性，表明上新世隆起的瞬态侵蚀响应尚未传播到高地表面。裸露基岩中26 Al和10 Be的浓度表明高地表面正以缓慢的c. 0·01 mm a−1。过去C。3 Ma，高地表面侵蚀缓慢，而邻近的河流切割迅速，增加了当地的救济。虽然浮雕生产可能驱动至少适度的顶部隆起，相当大的上新世前浮雕和低空间平均侵蚀率表明，气候驱动的岩石隆起不足以解释所有隆起暗示倾斜的标志在西部边缘的范围。尽管最近的侵蚀脉冲，空间平均侵蚀率低，并可能采取行动，以保持广泛的地形形式的内华达州的大部分晚新生代。版权所有© 2005年约翰威利父子有限公司。
Concentrations of cosmogenic 26Al and 10Be in cave sediments and bedrock surfaces, combined with studies of landscape morphology, elucidate the topographic history of the southern Sierra Nevada over the past 5 Ma. Caves dated by 26Al/10Be in buried sediments reveal that river incision rates were moderate to slow between c. 5 and 3 Ma (≤0·07 mm a−1), accelerated between 3 and 1·5 Ma (c. 0·3 mm a−1), and then have subsequently become much slower (c. 0·02 mm a−1). Although the onset of accelerated incision coincides in time with both postulated Pliocene tectonism and pronounced global climate change, we argue that it primarily represents the response to a discrete tectonic event between 3 and 5 Ma. Dated cave positions reveal that, prior to 3 Ma, river canyons displayed up to 1·6 km of local relief, suggesting that Pliocene rock uplift elevated pre‐existing topography. Renewed incision beginning c. 3 Ma deepened canyons by up to 400 m, creating narrow inner gorges. Tributary streams exhibit strong convexities, indicating that the transient erosional response to Pliocene uplift has not yet propagated into upland surfaces. Concentrations of 26Al and 10Be in bare bedrock show that upland surfaces are eroding at slow rates of c. 0·01 mm a−1. Over the past c. 3 Ma, upland surfaces eroded slowly while adjacent rivers incised rapidly, increasing local relief. Although relief production probably drove at least modest crestal uplift, considerable pre‐Pliocene relief and low spatially averaged erosion rates suggest that climatically driven rock uplift is not sufficient to explain all uplift implied by tilted markers at the western edge of the range. Despite the recent pulse of erosion, spatially averaged erosion rates are low, and have probably acted to preserve the broad topographic form of the Sierra Nevada throughout much of the late Cenozoic. Copyright © 2005 John Wiley & Sons, Ltd.