OSL AGE RESULTS FOR A TRANSECT ACROSS CAMPBELL SHORELINES AND SUB-CAMPBELL SPIT COMPLEXES OF LAKE AGASSIZ IN TRAILL COUNTY, NORTH DAKOTA

Lake Agassiz water levels are important to understanding the fluctuations in the southern margin of the Laurentide ice sheet and aspects of Pleistocene and early Holocene climate change. A leading hypothesis suggests that the rapid discharge of water from Lake Agassiz may have triggered the Younger Dryas climate cooling event. However, terrestrial evidence of the water routing and timing of the water release from Lake Agassiz is unresolved. Changes in shoreline position indicate significant volume changes in the lake, so understanding the ages of the shorelines helps determine when major drawdown events may have occurred. OSL dating of Lake Agassiz shorelines has thus far been focused mainly on the eastern edge of the lake basin in Minnesota, with the goal of setting ages for the Herman, Norcross, Tintah, and Campbell beach ridges. The current accepted dates for the Herman, Norcross, and Campbell ridges are 14.10.3 ka, 13.60.3 ka, and 10.50.3 ka, respectively. The age of the Tintah has yet to be confirmed, though prior age estimates range from ~11.5 to 16.2 ka. Diverging from the previous work of ChronoQuest groups, this study’s goal was to collect samples from beach ridges on the western side of Lake Agassiz in North Dakota and provide dates for previously undated beach ridges below the Campbell level. Spits within Traill County, North Dakota were targeted for sampling, because spits form directly at paleo-water level and sands deposited within spits have been shown successful for obtaining accurate OSL dates. Each sample site was chosen using LiDAR Satellite imagery, integrated soil survey data, and previously published digital beach ridge maps. We present here the first set of age results strategically sampled from sub-Campbell shorelines. Our results are from an approximate west-east transect from the Tintah through the Emerado shorelines, including upper and lower Campbell ridges.