An assessment of the minimum timing of ice free conditions of the western Laurentide Ice Sheet
An assessment of the minimum timing of ice free conditions of the western Laurentide Ice Sheet
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DOI：
10.1016/j.quascirev.2013.06.001
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发表时间：
2013-09-01
影响因子：
4
通讯作者：
Gowan, Evan J.
中科院分区：
文献类型：
--
作者：
Gowan, Evan J.
这项研究对威斯康星州冰川期间覆盖加拿大部分地区和美国北部的西部劳伦蒂德冰盖的最小退缩时间进行了调查。由于指示无冰条件的年代学数据的空间分辨率较低，冰盖的撤退受到的限制很差。放射性碳测年和发光测年方法的一个局限性是，只能确定某个区域没有冰的时间，这可能与冰缘消退的真实日期有很大不同。无冰条件的最小时间是使用冰盖退缩模型来确定的，该模型是从冰川晚期形成的地形推断出来的，并外推了相反方向的年代学数据的校准概率分布。这项分析排除了放射性碳样本，这些样本来自已被证明会造成人为老化的材料，如散装沉积物。分析结果确定了对模型影响最大的55个日期。洛伦蒂德西部冰盖的退缩至少开始于15000卡尔·BP，而劳伦蒂冰盖和科迪勒拉之间无冰条件的最小时间是在11000卡尔·BP之后。由于缺乏Keewatin区段的数据，无法确定Laurentide冰盖最后残迹的无冰条件的准确时间。该模型提供了一个指南，说明在哪里增加样本可以改善对冰缘位置的年代学控制。(C)2013爱思唯尔有限公司。保留所有权利。
This study presents an investigation of the minimum timing of retreat of the western Laurentide Ice Sheet, which covered parts of Canada and the northern United States during the Wisconsin glaciation. The retreat of the ice sheet is poorly constrained due to low spatial resolution of chronological data that indicate ice free conditions. A limitation of radiocarbon and luminescence dating methods is that it is only possible to determine the time when it is certain that ice is absent from a region, which may differ substantially from the true date of ice margin retreat. The minimum timing of ice free conditions is determined using a model of ice sheet retreat, inferred from landforms that formed during the late stages of glaciation, and extrapolating the calibrated probability distribution of chronological data in the opposite direction. The analysis excludes radiocarbon samples from materials that have been shown to give artificially old ages, such as bulk sediments. The results of the analysis identify 55 dates that have the most impact on the model. The retreat of the western Laurentide Ice Sheet commenced by at least 15 000 cal yr BP, while the minimum timing of ice free conditions between the Laurentide Ice Sheet and the Cordillera is after 11 000 cal yr BP. A lack of data in the Keewatin sector prevents the determination of a precise timing of ice free conditions in the last vestiges of the Laurentide Ice Sheet. The model provides a guide to where additional samples could improve chronological control on ice margin location. (c) 2013 Elsevier Ltd. All rights reserved.