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.
