During the last glacial maximum the Cordilleran and Laurentide ice sheets coalesced east of the Rocky Mountains and geomorphological evidence indicates ice flowed over the main ridge of the Rocky Mountains between ~54–56°N. However, this ice flow has thus far remained unconstrained in time. Here we use in situ produced cosmogenic 10Be dating to determine when Cordilleran ice stopped flowing over the mountain range. We dated eight samples from two sites: one on the western side (Mount Morfee) and one on the eastern side (Mount Spieker) of the Rocky Mountains. At Mount Spieker, one sample is rejected as an outlier and the remaining three give an apparent weighted mean exposure age of 15.6 ± 0.6 ka. The four samples at Mount Morfee are well clustered in time and give an apparent weighted mean exposure age of 12.2 ± 0.4 ka. These ages indicate that Mount Spieker became ice free before the Bølling warming and that the western front of the Rocky Mountains (Mount Morfee) remained in contact with the Cordilleran Ice Sheet until the Younger Dryas.

中文翻译：

---

使用 10Be 约会确定科迪勒拉冰盖何时停止流过加拿大落基山脉

在最后一次冰期最大值期间，Cordilleran 和 Laurentide 冰盖在落基山脉以东合并，地貌证据表明冰在 ~54-56°N 之间流过落基山脉的主要山脊。然而，到目前为止，这种冰流在时间上仍然不受限制。在这里我们使用原位产生的宇宙10约会以确定科迪勒拉冰何时停止流过山脉。我们对来自两个地点的八个样本进行了约会：一个在落基山脉的西侧（莫菲山），一个在东侧（斯皮克山）。在斯皮克山，一个样本作为异常值被拒绝，其余三个给出的表观加权平均暴露年龄为 15.6 ± 0.6 ka。Mount Morfee 的四个样品在时间上聚集得很好，表观加权平均暴露年龄为 12.2 ± 0.4 ka。这些年龄表明，斯皮克山在伯林变暖之前已经无冰，落基山脉的西部前部（莫菲山）一直与科迪勒拉冰盖接触，直到年轻的仙女木。