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

摘要OPP-9807066 Davis Steg这是本特利学院以及佛蒙特州和科罗拉多州大学的科学家们共同研究的巴芬岛南部坎伯兰湾威斯康星州冰川历史，以更好地了解劳伦蒂德冰盖。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，但仍然存在重大的地质年代学不确定性。从蓬尼东山口和峡湾沿线的冰雹和基岩表面采集的139个样品的宇宙成因核素暴露年龄表明，冰川在2500-1000万年前(Ka)从坎伯兰半岛内部推进，然后迅速后退10-7ka，接近今天的冰缘。这些年龄似乎与威斯康星州晚期之前的湖底沉积物的放射性碳年龄相冲突。有限数量样本的初步宇宙成因核素数据表明坎伯兰海湾外部冰川的时间相似，但似乎与海洋沉积物岩心的较年轻放射性碳结果相冲突。将对以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，目的是改进坎伯兰海湾地区的冰川年代学。Pangnirtung Fjord周围高地地区26个Al/10Be暴露年龄的不一致表明，这些地区有漫长而复杂的埋藏和暴露历史，在威斯康星州晚期，高地上可能存在冷基冰，而暖基冰则充满了Pangnirtung Fjord和坎伯兰海湾。对这些额外样本的分析将更准确地确定威斯康星州晚期在庞尼尔通峡湾地区的垂直范围，并测试东南方向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.