Age verification of the Lake Gribben forest bed and the Younger Dryas Advance of the Laurentide Ice Sheet

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Lowell, Thomas V, Larson, Graham J, Hughes, John D, Denton, George H
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1999
• Subjects: North Bay; Ice Sheet
• Online Access: http://dx.doi.org/10.1139/e98-095; http://www.nrcresearchpress.com/doi/pdf/10.1139/e98-095

Analysis of nine wood samples from the Lake Gribben forest bed near Lake Gribben, Michigan, yielded a combined age of 10 025 ± 100 14 C years BP, which confirms and refines prior age estimates for the bed. The stratigraphic position of these samples below a prograding ice-contact fan indicates the time that a glacial margin reached the southern edge of the Lake Superior basin. Geomorphic tracing and correlation of associated deposits indicate that a contemporaneous margin extended almost 1000 km from Duluth, Minnesota, across the Lake Superior basin to North Bay, Ontario. Along the southern shore of Lake Superior ice-margin expansion began during and ended at the close of the Younger Dryas. A surging glacier system would not produce a nearly linear moraine system across both a major basin (Lake Superior) and a major upland (Abitibi Upland). Therefore, we attribute this advance of the Laurentide Ice Sheet to climatic forcing of the Younger Dryas event.