Richard F. Madole P. Kubik Richard R. McDonald Larry Benson 2007 <p><span>Surface-exposure (</span>¹⁰<span>Be) ages have been obtained on boulders from three post-Pinedale&nbsp;<a title="Learn more about Glacial Drift from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/glacial-drift" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/glacial-drift">end-moraine</a>&nbsp;complexes in the Front Range, Colorado. Boulder rounding appears related to the cirque-to-moraine transport distance at each site with subrounded boulders being typical of the 2-km-long Chicago Lakes Glacier, subangular boulders being typical of the 1-km-long Butler Gulch Glacier, and angular boulders being typical of the few-hundred-m-long Isabelle Glacier. Surface-exposure ages of angular boulders from the Isabelle Glacier moraine, which formed during the&nbsp;<a title="Learn more about Little Ice Age from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/little-ice-age" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/little-ice-age">Little Ice Age</a>&nbsp;(LIA) according to previous lichenometric dating, indicate cosmogenic inheritance values ranging from 0 to ∼3.0&nbsp;</span>¹⁰<span>Be</span><span>&nbsp;</span><span>ka.</span><a class="workspace-trigger" name="bfn1" href="https://www.sciencedirect.com/science/article/pii/S0277379107000650?via%3Dihub#fn1" data-mce-href="https://www.sciencedirect.com/science/article/pii/S0277379107000650?via%3Dihub#fn1">¹</a><span>&nbsp;Subangular boulders from the Butler Gulch end moraine yielded surface-exposure ages ranging from 5 to 10.2&nbsp;</span>¹⁰<span>Be</span><span>&nbsp;</span><span>ka. We suggest that this moraine was deposited during the 8.2</span><span>&nbsp;</span><span>cal</span><span>&nbsp;</span><span>ka event, which has been associated with&nbsp;<a title="Learn more about Outburst from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/outburst" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/outburst">outburst</a>&nbsp;floods from Lake Agassiz and Lake Ojibway, and that the large age range associated with the Butler Gulch end moraine is caused by cosmogenic shielding of and(or)&nbsp;<a title="Learn more about Spalling from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/spalling" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/spalling">spalling</a>&nbsp;from boulders that have ages in the younger part of the range and by cosmogenic inheritance in boulders that have ages in the older part of the range. The surface-exposure ages of eight of nine subrounded boulders from the Chicago Lakes area fall within the 13.0–11.7&nbsp;</span>¹⁰<span>Be</span><span>&nbsp;</span><span>ka age range, and appear to have been deposited during the&nbsp;<a title="Learn more about Younger Dryas from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/younger-dryas" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/younger-dryas">Younger Dryas</a>&nbsp;interval. The general lack of inheritance in the eight samples probably stems from the fact that only a few thousand years intervened between the retreat of the Pinedale glacier and the advance of the Chicago Lakes glacier; in addition,&nbsp;<a title="Learn more about Bedrock from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/bedrock" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/bedrock">bedrock</a>&nbsp;in the Chicago Lakes&nbsp;<a title="Learn more about Cirque from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cirque" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cirque">cirque</a>&nbsp;area may have remained covered with snow and ice during that interval, thus partially shielding the bedrock from cosmogenic radiation.</span></p> application/pdf 10.1016/j.quascirev.2007.02.015 en Elsevier Surface-exposure ages of Front Range moraines that may have formed during the Younger Dryas, 8.2 cal ka, and Little Ice Age events article