Revised chronology of northwest Laurentide ice-sheet deglaciation from 10Be exposure ages on boulder erratics
Revised chronology of northwest Laurentide ice-sheet deglaciation from 10Be exposure ages on boulder erratics
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DOI：
10.1016/j.quascirev.2021.107369
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发表时间：
2022-02
影响因子：
4
通讯作者：
A. Reyes;A. Carlson;G. Milne;L. Tarasov;J. R. Reimink;M. Caffee
中科院分区：
文献类型：
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作者：
A. Reyes;A. Carlson;G. Milne;L. Tarasov;J. R. Reimink;M. Caffee
我们通过基岩上的巨石提出了新的10be表面暴露年龄，通过加拿大西部盾的一大片地区，直接确定了西北劳伦泰德冰盖的冰川消融日期，这些地区以前没有可靠的冰缘退缩时间限制。在Slave克拉通西部边缘的一个地点，隆升校正的巨石表面暴露年龄为13.9±0.2 ka (n = 6)，在以东约110 km的冰面上的另一个地点，暴露年龄为12.4±0.2 ka （n = 5.1）。这些冰缘退缩的直接10be年龄分别比基于最低限制14c年的西北劳伦泰德冰盖的标准冰期年表要早~ 2.4 kyr和~ 1.6 kyr。我们推断这两个地点之间的冰缘退缩率为60-100 m yr - 1，跨越了从Allerød温暖期到新仙女木期寒冷期的过渡。这明显慢于从早期冰期去冰年代学推断出的西北劳伦泰德冰盖的快速退缩速度，后者被假设为新仙女木时期寒冷时期融水强迫的潜在来源。在这一数据贫乏的地区，这些关于消冰时空格局的第一个直接年龄表明，需要对消冰年表进行进一步的改进，以检验关于冰盖退缩、相关融水排放、气候突变和海平面快速上升之间关系的假设。
We present new10Be surface exposure ages from boulders on bedrock to directly date northwest Laurentide ice-sheet deglaciation through a wide swath of the western Canadian Shield that had no previous reliable temporal constraints on ice-margin retreat. Uplift-corrected boulder10Be surface exposure ages are 13.9 ± 0.2 ka (n = 6) at a site on the western edge of the Slave Craton and 12.4 ± 0.2 ka (n = 5, 1 outlier) at a second site ∼110 km up-ice to the east. These direct10Be ages for ice-margin retreat are ∼2.4 kyr and ∼1.6 kyr older, respectively, than the canonical deglacial chronology for the northwest Laurentide ice sheet that is based on minimum-limiting14C dates. We infer an ice-margin retreat rate of 60–100 m yr−1between the two sites over an interval spanning the transition from the Allerød warm period into the Younger Dryas cold period. This is significantly slower than the rapid >800 m yr−1retreat rate for the northwest Laurentide ice sheet inferred from earlier deglacial chronologies, which has been hypothesized as a potential source of meltwater forcing for the Younger Dryas cold period. These first direct ages on spatio-temporal patterns of deglaciation in this data-poor region suggest that additional refinement of the deglacial chronology is needed to test hypotheses on the relation between ice-sheet retreat, associated meltwater discharge, abrupt climate change, and rapid sea-level rise.