The Foothills erratics train of Alberta was carried into place during
coalescence between montane glaciers and the Laurentide ice sheet. Its
age has been controversial: Late Wisconsinan and pre-Wisconsinan ages
have been assigned to it. Cosmogenic Cl-36 exposure dating was carrie
d out on erratics over a 130 km segment of the erratics train. Seven o
f eight age determinations support emplacement during the late Wiscons
inan glaciation. These ages eliminate the possibility of an ice-free c
orridor during the last glacial maximum. They are also consistent with
the hypothesis that the Laurentide ice sheet was the most extensive o
f all Pleistocene continental ice sheets in western Canada.