Retreat of the Western Cordilleran Ice Sheet Margin During the Last Deglaciation
Retreat of the Western Cordilleran Ice Sheet Margin During the Last Deglaciation
复制标题
DOI：
10.1029/2018gl079419
复制
发表时间：
2018-09-28
影响因子：
5.2
通讯作者：
Caffee, M. W.
中科院分区：
文献类型：
--
作者：
Darvill, C. M.;Menounos, B.;Caffee, M. W.
加拿大不列颠哥伦比亚省中部海岸科迪勒拉冰盖消融的时间为气候强迫和早期人类迁徙提供了信息。前冰盖西缘冰川不稳定和当地基岩的 32 个 Be-10 暴露年龄代表了科迪勒拉冰盖在末次冰消期的最早暴露年龄。这些数据显示，西部冰缘正在退缩 18.1 +/- 0.2 ka，与全球冰块损失记录一致。相比之下，南缘部分地区在大约 10 年前达到最大值。 17.6-16.6 ka，我们的数据证明了科迪勒拉冰盖在消冰过程中的历时响应。我们还表明，一个低海拔地点暴露了至少 17.7 +/- 0.3 ka，这意味着此时沿海边缘存在许多无冰区域，为第一批进入美洲的人类提供了一条可行的路线。 通俗语言摘要 在过去的数十万年里，为了响应传入太阳辐射的周期性变化，大冰盖已经前进和后退了多次。曾经覆盖加拿大西部大部分地区的科迪勒拉冰盖在上一个主要周期中被认为比其他冰盖前进和后退得晚。冰盖的消退也开辟了第一批人类进入美洲的路线。我们发现冰盖西缘的退缩比之前认为的要早。冰盖的其他边缘随后推进，随着时间的推移形成了一幅复杂的图景。西部冰缘的早期退缩暴露了许多岛屿，这些岛屿本可以被早期向南迁徙的人们所利用。
The timing of Cordilleran Ice Sheet deglaciation along the central coast of British Columbia, Canada, informs climate forcing and early human migration. Thirty-two Be-10 exposure ages from glacial erratics and local bedrock on the western margin of the former ice sheet represent the earliest exposure ages for the Cordilleran Ice Sheet during the last deglaciation. These data show the western ice margin was retreating by 18.1 +/- 0.2 ka, consistent with the global record of ice mass loss. In contrast, parts of the southern margin reached a maximum at ca. 17.6-16.6 ka, and our data demonstrate a diachronous response of the Cordilleran Ice Sheet during deglaciation. We also show that a low altitude site was exposed by at least 17.7 +/- 0.3 ka, implying that numerous ice-free areas existed along the coastal margin by this time, providing a viable route for the first humans entering the Americas.Plain Language Summary Large ice sheets have advanced and retreated multiple times over the last several hundred thousand years in response to cyclical changes in incoming solar radiation. The Cordilleran Ice Sheet, which once covered much of western Canada, was thought to have advanced and retreated later than others during its last major cycle. The retreat of this ice sheet also opened routes that allowed the first people to enter the Americas. We show that the western margin of the ice sheet retreated earlier than previously thought. Other margins of the ice sheet advanced later, creating a complex picture through time. The early retreat of the western ice margin exposed numerous islands that could have been used by early people migrating southward.