The Pliocene-Pleistocene transition resulted in extensive global cooling and glaciation, but isolating this climate signal within erosion and exhumation responses in tectonically active regimes can be difficult. The Nenana Gravel is a foreland basin deposit in the northern foothills of the Alaska Range (USA) that has long been linked to unroofing of the Alaska Range starting ca. 6 Ma. Using 26Al/10Be cosmogenic nuclide burial dating, we determined the timing of deposition of the Nenana Gravel and an overlying remnant of the first glacial advance into the northern foothills. Our results indicate that initial deposition of the Nenana Gravel occurred at the onset of the Pleistocene ca. 2.34 Ma and continued until at least ca. 1.7 Ma. The timing of initial deposition is correlative with expansion of the Cordilleran ice sheet, suggesting that the deposit formed due to increased glacial erosion in the Alaska Range. Abandonment of Nenana Gravel deposition occurred prior to the first glaciation extending into the northern foothills. This glaciation was hypothesized to have occurred ca. 1.5 Ma, but we found that it occurred ca. 0.39 Ma. A Pleistocene age for the Nenana Gravel and marine oxygen isotope stage 10 age for the oldest glaciation of the foothills necessitate reanalysis of incision and tectonic rates in the northern foothills of the Alaska Range, in addition to a shift in perspective on how these deposits fit into the climatic and tectonic history of the region.

中文翻译：

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阿拉斯加山脉早更新世气候引起的侵蚀形成了 Nenana Gravel

上新世-更新世转变导致了广泛的全球变冷和冰川作用，但将这种气候信号与构造活跃地区的侵蚀和剥脱反应隔离开来可能很困难。Nenana Gravel 是位于阿拉斯加山脉（美国）北部山麓的前陆盆地沉积物，长期以来一直与阿拉斯加山脉的开顶有关。6 马。使用 26Al/10Be 宇宙成因核素埋藏年代测定法，我们确定了 Nenana Gravel 和第一次冰川推进到北部山麓的上覆残余物的沉积时间。我们的结果表明，Nenana Gravel 的初始沉积发生在更新世约​​开始时。2.34 Ma 并持续到至少大约。1.7 马。初始沉积的时间与科迪勒拉冰盖的扩张有关，表明沉积物是由于阿拉斯加山脉冰川侵蚀加剧而形成的。Nenana Gravel 沉积的废弃发生在第一次冰川作用延伸到北部山麓之前。这种冰川作用被假设发生在大约。1.5 Ma，但我们发现它发生了大约。0.39 毫安。Nenana Gravel 的更新世年龄和山麓最古老冰川的海洋氧同位素阶段 10 年龄需要重新分析阿拉斯加山脉北部山麓的切割和构造速率，此外还需要转变这些沉积物如何适应该地区的气候和构造历史。这种冰川作用被假设发生在大约。1.5 Ma，但我们发现它发生了大约。0.39 毫安。Nenana Gravel 的更新世年龄和山麓最古老冰川的海洋氧同位素阶段 10 年龄需要重新分析阿拉斯加山脉北部山麓的切割和构造速率，此外还需要转变这些沉积物如何适应该地区的气候和构造历史。这种冰川作用被假设发生在大约。1.5 Ma，但我们发现它发生了大约。0.39 毫安。Nenana Gravel 的更新世年龄和山麓最古老冰川的海洋氧同位素阶段 10 年龄需要重新分析阿拉斯加山脉北部山麓的切割和构造速率，此外还需要转变这些沉积物如何适应该地区的气候和构造历史。