Testing Alternative Models of Laurentide Icesheet Dynamics Using Cosmogenic Nuclide Exposure Dating, Cumberland Sound Area, Southern Baffin Island, Arctic Canada

这是佛蒙特州和科罗拉多的本特利学院和大学的科学家们对巴芬岛南部坎伯兰海峡的威斯康星冰川历史进行的一项合作研究，目的是更好地了解劳伦泰德冰盖。 对坎伯兰海峡气候和冰川历史的科学认识目前正在进行重大修订，但仍存在重大的地质年代学不确定性。 从冰碛和基岩表面取样沿着庞纳通山口和峡湾的139个样品的宇宙成因核素暴露年龄表明，冰川从坎伯兰半岛内部前进25-10万年前（ka），然后迅速撤退10-7 ka到今天的冰缘附近。 这些日期似乎是在冲突与前晚威斯康星州的放射性碳年龄从基底湖泊沉积物。 有限数量的样本的初步宇宙成因核素数据表明，类似的时间冰川的外部部分的坎伯兰声音，但似乎与年轻的海洋沉积物芯的放射性碳结果冲突。 将对先前收集的其他宇宙成因核素样本进行处理和分析，以进一步调查这些差异，目的是改善坎伯兰海峡地区的冰川年表。 不一致的26铝/10铍暴露年龄从周围的Pangnirtung峡湾高地地区，表明这些地区有一个漫长而复杂的埋藏和暴露的历史，可能存在的冷基冰的高地，而温暖的冰填充Pangnirtung峡湾和坎伯兰声音在威斯康星晚期。 对这些额外样本的分析将更精确地确定Pangnirtung峡湾地区晚期威斯康星的垂直范围，并测试东南部是否存在类似的冰川条件。

ABSTRACT OPP-9807066Davis SteigThis is a collaborative study is by scientists at Bentley College and Universities of Vermont and Colorado on the Wisconsinan glacial history of Cumberland Sound on southern Baffin Island to gain a better understanding of the Laurentide ice sheet. Scientific understanding of the Climatic and glacial history of the Cumberland Sound is currently undergoing a major revision but significant geochronological uncertainties still remain. Cosmogenic nuclide exposure ages for 139 samples from moraines and bedrock surfaces sampled along the Pangnirtung Pass and Fjord suggest that the glacier advanced from the interior of Cumberland Peninsula between 25-10 million years ago (ka) and then rapidly retreated 10-7 ka to near present-day ice margins. These date appear to be in conflict with pre-late Wisconsinan radiocarbon ages from basal lake sediments. Preliminary cosmogenic nuclide data for a limited number of samples suggest similar timing for glaciation of the outer part of Cumberland Sound, but appear to conflict with younger radiocarbon results from marine sediment cores. Additional previously collected cosmogenic nuclide samples will be processed and analyzed to further investigate these discrepancies, with the goal of improving the chronology of glaciation in the Cumberland Sound region. Discordant 26 Al/10Be exposure ages from upland areas surrounding the Pangnirtung Fjord, indicate these areas have a long and complex burial and exposure history, with the likely presence of cold-based ice on the uplands while warm-based ice filled the Pangnirtung Fjord and Cumberland Sound during the late Wisconsinan. Analyses of these additional samples will more precisely determine the vertical extent of the late Wisconsinan in the Pangnirtung Fjord area and test whether similar glaciological conditions existed further to the southeast.