Collaborative Research: Deglaciation Chronology of the Des Moines Lobe - implications for ice sheet dynamics and climate change

在最后一次冰川消融期间，劳伦泰德冰原的得梅因裂片占据了贯穿大陆中部的主要地形洼地，并将冰原的核心排干。要研究的问题是，得梅因地区的衰退与一系列不受时间限制的进步有关。在一次衰退期间，大石冰碛形成，随后形成了阿加西斯冰川湖的南部边缘。通过对冰碛上洼地的湖泊取芯，可以用放射性碳定年法确定冰碛的年龄，以提供对冰川消融速率的估计，并提供阿加西湖形成的年龄。这项研究的直接目标是确定大石碛的年龄。阿加西湖是覆盖北美的最大的前冰期湖泊，在末次冰期结束时，它与历史上各种突变的气候变化有关，但湖泊的开始年龄尚不清楚。这一合作提案以两种方式建立在过去和目前的研究基础上：首先，在通往加拿大的横断面上，研究比大石冰碛更年轻的地区的冰川消融模式获得了资金。这一支持将确定劳伦泰德冰原主要部分的消冰年代学。其次，在另外两个拟议的阿加西湖出口的研究已接近完成（安大略省的桑德湾和阿尔伯塔省的麦克默里堡）。在每个地区，冰川消融年代学确定了这些潜在的溢洪道可能在什么时候活跃起来。该提案将确定何时在剩余的出口开始排水，并允许整个系统的时间整合。这项工作的更广泛的影响是对地球系统主要地貌要素的冰盖动力学和气候变化历史的理解。

During the last deglaciation, the Des Moines lobe of the Laurentide Ice Sheet occupied a major topographic depression through the mid-continent and drained the core of the ice sheet. The problem to be studied is that recession of the Des Moines lobe has been implicated in a series of readvances not constrained in time. During one recession, the Big Stone Moraine formed and subsequently formed the southern edge of glacial Lake Agassiz. By coring lakes in depressions on the moraine, the age of the moraine can be determined using radiocarbon dating to provide estimates on deglaciation rates, as well as providing an age for the beginning of Lake Agassiz. The immediate goal of this research is to establish the age of the Big Stone Moraine. Lake Agassiz was the largest pro-glacial lake to cover North America, and it has been implicated in a variety of abrupt climate changes during its history at the end of the last glaciation, yet the beginning age of the lake is unknown. This collaborative proposal builds on past and current research in two ways: First, funding is secured to study deglaciation patterns in areas younger than the Big Stone Moraine along transects into Canada. This support will establish the deglaciation chronology of a major portion of the Laurentide Ice Sheet. Second, research at two other proposed outlets of Lake Agassiz is nearly complete (Thunder Bay, Ontario and Fort McMurray, Alberta). In each area the deglacial chronology defines when these potential spillways could have been active. This proposal will establish when drainage began in the remaining outlet, and allow temporal integration of the entire system. The broader impacts of this work are the ramifications for the understanding ice sheet dynamics and climate change history for a major geomorphic element of the earth system.