Late Cenozoic Glaciation of the Northern Nenana Valley
Late Cenozoic Glaciation of the Northern Nenana Valley
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北尼纳纳山谷晚新生代冰川作用
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发表时间：
1986
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通讯作者：
R. Thorson
中科院分区：
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作者：
R. Thorson
摘要北方内纳纳河流域至少有五个，可能多达七个不同的冰川事件，早于威斯康星州晚期的莱利溪冰川。最古老的冰川期，在内纳纳砾石中以杂岩和不稳定的巨石为代表，其年龄为第三纪晚期;莱利溪之前最年轻的冰前进（希利冰川期）可能是年龄为早期的威斯康星州。三个新的漂移的中间年龄的描述和非正式名称Teklanika河，熊溪，褐煤溪和使用的预先存在的术语布朗冰川作用被保留。先前描述的干溪冰川作用的证据还不足以证明它是一个独立的主要冰川事件。北方Nenana河谷的冰川记录被描述为三个区域，这些区域由于侵蚀或断层作用而在物理上相互分离：外山麓、八里湖地区和Nenana峡谷。每个地区之间的漂移的相关性，主要是基于重建的冰梯度和山谷内的地形位置，提供了一个一致的框架来解释该地区的晚新生代历史。基于冰碛物表面特征的相对年龄标准被认为是有限的价值相关的目的。然而，冰碛的整体形态表现，它们在山谷中的垂直位置，以及它们的相对范围是区域相关性的有用标准。
Abstract The northern Nenana River valley contains evidence for a minimum of five and probably as many as seven distinct glacial episodes that predate the Riley Creek glaciation of late Wisconsin age. The oldest glacial episode, represented in the Nenana Gravel by diamictons and erratic boulders, is late Tertiary in age; the youngest pre-Riley Creek ice advance (the Healy glaciation) is probably early Wisconsin in age. Three new drifts of intermediate age are described and given informal names—Teklanika River, Bear Creek, and Lignite Creek—and use of the preexisting term Browne glaciation is retained. Evidence for the previously described Dry Creek glaciation is not strong enough to justify its designation as a separate major glacial episode. The glacial record in the northern Nenana River valley is described for three areas that have been physically separated from each other by erosion or by faulting: the outer foothills, the Eight Mile Lake area, and the Nenana canyon. Correlations of drifts between each area, based largely on reconstructed ice gradients and on topographic position within the valley, provide a consistent framework for interpreting the region’s late Cenozoic history. Relative-age criteria based on moraine surface characteristics were found to be of limited value for correlation purposes. However, the overall morphologic expression of moraines, their vertical position in the valley, and their relative extents are useful criteria for regional correlations.