26Al and 10Be dating of late pleistocene and holocene fill terraces: a record of fluvial deposition and incision, Colorado front range
26Al and 10Be dating of late pleistocene and holocene fill terraces: a record of fluvial deposition and incision, Colorado front range
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晚更新世和全新世充填阶地的 26Al 和 10Be 测年：科罗拉多锋岭河流沉积和切割的记录
DOI：
10.1002/esp.352
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发表时间：
2002
影响因子：
3.3
通讯作者：
M. Caffee
中科院分区：
文献类型：
--
作者：
T. Schildgen;D. Dethier;P. Bierman;M. Caffee
科罗拉多前缘山脉陡峭峡谷中河流充填阶地的宇宙成因26Al、10Be和14C测年为分析幕式沉积和切割提供了一个时间框架。来自博尔德峡谷的研究结果表明，现代航道(等级)以上的阶地高度可划分为：(1)牛湖(≳100ka，海拔20-15m)；(2)松林(32-10ka，海拔15-4m)；(3)全新世(<；海拔4m)。Boulder Canyon沿线没有保存任何牛湖前沉积，仅有三个高于等级15米的小残留物记录了牛湖沉积。保存完好的松林时代的梯田表明，梯田高于地面的高度范围反映了河流剖面在河流负荷和功率快速变化期间的短期波动。网状河流切割明显发生在向间冰期过渡期间。土壤发育和地层位置以及有限的宇宙成因和14C测年表明，博尔德峡谷的∼130ka阶地与卢维耶冲积层相关，峡谷中的32~10ka填充物与邻近高平原的百老汇冲积层相关。巨石峡谷的晚更新世切割速率(∼·15m ka−1)超过了晚更新世之前的切割速率，也高于高平原的中晚更新世切割速率(∼0.04m ka−1)。这项研究提供了一个例子，说明现代地质年代学技术如何使我们能够更好地了解排干冰川集水区的河流。版权所有©2002 John Wiley&Sons，Ltd.
Cosmogenic 26Al, 10Be, and 14C dating of fluvial fill terraces in steep canyons of the Colorado Front Range provides a temporal framework for analysing episodic aggradation and incision. Results from Boulder Canyon show that terrace heights above the modern channel (grade) can be divided into: (1) Bull Lake (≳100 ka; 20–15 m above grade); (2) Pinedale (32–10 ka; 15–4 m above grade); and (3) Holocene age (<4 m above grade). No pre‐Bull Lake deposits are preserved along Boulder Canyon, and only three small remnants >15 m above grade record Bull Lake deposition. Well‐preserved terraces of Pinedale age suggest that the range of terrace height above grade reflects short‐term fluctuations in the river profile during periods of rapidly changing stream load and power. Net river incision apparently occurred during transitions to interglacial periods. Soil development and stratigraphic position, along with limited cosmogenic and 14C dating, suggest that ∼130 ka terraces in Boulder Canyon correlate with the Louviers Alluvium, and that 32 to 10 ka fills in the canyon correlate with the Broadway Alluvium on the adjacent High Plains. Late Pleistocene incision rates (∼0·15 m ka−1) along Boulder Canyon exceed pre‐late Pleistocene incision rates, and are higher than middle to late Pleistocene incision rates (∼0·04 m ka−1) on the High Plains. This study provides an example of how modern geochronologic techniques allow us to understand better rivers that drain glaciated catchments. Copyright © 2002 John Wiley & Sons, Ltd.