A CLOSER LOOK AT THE DEPOSITIONAL AGES FOR THE UPPER AND LOWER CAMPBELL SHORELINE OF GLACIAL LAKE AGASSIZ IN NORTHWESTERN MINNESOTA

Glacial Lake Agassiz (GLA) formed at the close of the Pleistocene Epoch, existing between 14.2 ka and 8.2 ka, in mid-continental North America. Over this time frame, the lake covered portions of the United States including North and South Dakota, Minnesota, as well as Canadian provinces of Manitoba, Saskatchewan, and Ontario. GLA has been suggested as a potential trigger for the Younger Dryas climate cooling event circa 12.9 ka. Shoreline chronology within the Lake Agassiz basin is crucial to understand the timing of drawdown events that could have supplied the volume of water required to disrupt northern hemisphere climate. The shorelines represent stable water plains that would have existed immediately prior to large drawdown events. Four major strandline complexes (Norcross, Tintah, Herman, and Campbell) along with minor strandlines were deposited by GLA. Past work by student research groups at North Dakota State University have used optically stimulated luminescence (OSL) dating to detect several variations from the accepted chronology. This study focuses on the Campbell strandlines, currently recognized as having an upper and lower expression, in Northwestern Minnesota because they are well defined geomorphologically. Originally, the Upper and Lower Campbell were thought to be separated by the Moorhead Low water phase, however, studies have suggested that this phase happened after the deposition of the Tintah. Fours samples were collected and dated from each of the two Campbell shorelines along a 75 km transect; eight samples in total. The sampling strategy seeks to help resolve past age anomalies found in the Campbell shoreline deposits and to evaluate if the two expressions of the shoreline are significantly different in age. OSL equivalent dose data sets suggest that all deposits were well reset at the time of deposition and should produce reliable ages. Age results will be presented and implications for our growing understanding of GLA history with be discussed.