DEGLACIATION OF THE FORT MCMURRAY, ALBERTA, AREA: IS IT LATER THAN WE THINK?

New radiocarbon ages from the Fort McMurray, Alberta area allows for a later deglaciation that was originally supposed. Deglaciation maps of Dyke et al, suggest a regional southwest to northeast retreat of the ice sheet parallel to the Cree Lake Moraine (lying some 100 km east of Ft. McMurray). The 11 ka isochron lies midway between Fort McMurray and the Cree Lake Moraine and the 10 ka isochron lies on the Cree Lake Moraine. However, preliminary investigation of DEM data suggest that moraines in the uplands south of Fort McMurray and lowlands north of Fort McMurray have an east-west orientation, and moraines in the uplands north of Fort McMurray have a north-south orientation, Such ice margin geometries would block drainage in both the Athabasca and Clearwater pathways and any other regional waters from draining toward the north. Provisional chronology is assigned to these moraines from a network of 19 core sites from small lakes associated with moraines in the region. Although a portion of the sites yielded Holocene ages, key sites in the Gregoire Hills south of Fort McMurray suggest that moraines in that area formed about 9730 ± 65 14C yr BP. The same analysis on the Cree Lake Moraine suggests that it formed prior to 8975±60 14C yr BP. Since some of the younger ages appear to be coeval with the age of peat bog formation observed elsewhere in the northern prairie provinces, a full assessment of this young chronology awaits further dating and stratigraphic analysis.