Gravel-capped benches above northern tributaries of the Escalante River, south-central Utah
Gravel-capped benches above northern tributaries of the Escalante River, south-central Utah
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犹他州中南部埃斯卡兰特河北部支流上方的砾石长凳
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发表时间：
2012
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影响因子：
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通讯作者：
T. Cerling
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作者：
David W. Marchetti;S. Hynek;T. Cerling
位于犹他州中南部的埃斯卡兰特河北部支流之上的沉积基岩上切割出的安山岩巨石沉积地幔槽。安山岩砾石矿床产于博尔德山南部断崖和宝瓶高原。这些沉积物的沉积学和地貌特征表明，它们是经过河流作用改造的泥流体运动形成的。安山岩巨石明显比当地的沉积基岩坚硬，并引起巨石盔甲和地形反转。安山岩巨石在穿越较弱基岩时也是河流切割的有效工具。4个不同矿床踏面上暴露的一些最大的巨石的He暴露年龄在303±48 ~ 1395±241 ka之间。暴露在矿床表面的最高的巨石往往会产生最古老的暴露年龄，这表明巨石侵蚀和沉积物侵蚀控制着暴露年龄的种群，并表明即使是给定矿床中最古老的暴露年龄也可能是最小年龄估计。利用各地表的最老暴露年龄，我们估计在0.6 ~ 1.4 Ma期间，埃斯卡兰特河北部支流的最大切口率为151 ~ 323 m Ma−1。
Andesitic boulder deposits mantle straths cut in sedimentary bedrock high above the northern tributaries of the Escalante River in south-central Utah. The andesitic gravel deposits are derived from the southern escarpments of Boulder Mountain and Aquarius Plateau. The sedimentology and geomorphic expression of these deposits suggest they are from slurry-flow mass movements that have been reworked by fluvial processes. The andesitic boulders are significantly tougher than the local sedimentary bedrock and cause boulder armoring and topographic inversion. The andesitic boulders are also effective tools for fluvial incision when transported across weaker bedrock. Cosmogenic 3 He exposure-age dating of some of the largest boulders exposed on the treads of four different deposits range from 303 ± 48 to 1395 ± 241 ka. The tallest boulders exposed on the deposit surfaces tend to yield the oldest exposure ages, suggesting that boulder erosion and deposit erosion are controlling the exposure-age populations and indicating that even the oldest exposure ages from a given deposit are likely minimum age estimates. Using the oldest exposure age from each surface, we estimate maximum Escalante River northern tributary incision rates of 151–323 m Ma −1 for the period since 0.6–1.4 Ma.