BASIN-WIDE RECONSTRUCTION OF GLACIAL LAKE IROQUOIS USING LIDAR

During the retreat of the Laurentide Ice Sheet from the Last Glacial Maximum, glacial Lake Iroquois flooded a large portion of New York State and surrounding Lake Ontario basin leaving behind shore features including deltas, fans, and strandlines. Where available, high resolution lidar elevation data were used to extract elevation of these shore features and used to model the lake extent across the Lake Ontario basin. Modeling the shore of glacial Lake Iroquois required creating a surface to best fit the shore features. Using current data from research conducted in Cayuga County by the New York State Geological Survey, shoreline features from lidar data sets and previous works, 135 data points were used to generate a surface representing the former lake. The locations of the features were plotted using ArcMap 10.2 with the elevations noted. These elevations (ranging from 110m to 330m) were contoured then subsequently converted to a triangulated irregular network to create a grid that represents the surface that intersects each point. This grid was then subtracted from the modern digital elevation model to recreate the depressed landscape at the time of glacial Lake Iroquois prior to glacial rebound. This corrected elevation model can then be used to approximate the extent of glacial Lake Iroquois in the Lake Ontario basin with the outlet through Rome, NY at 134m and dammed at the northern edge of the state near Covey Hill in Ontario, Canada. A line perpendicular to the isobase lines trends N13°E. The best fit trendline is a curve defined by y=370e^-0.004x with an R² value of 0.9797. The isobase lines are not straight across the area but are curved to the south which indicates non-uniform isostatic depression across the area, notably in central New York, likely the result of influences from an ice lobe. The enhanced resolution of lidar data allows for delineation of glacial lakes at an unprecedented level by being able to include subtle nuances of the landscape previously missed. Glacial lake reconstruction at this scale can help anthropologist and paleontologist with accurate reconstructions of the paleoenvironments to facilitate studies of habitation and migration.