CORDILLERAN GLACIATIONS IN CANADA: THE MAGNETOSTRATIGRAPHIC RECORD
The most complete records are found at 4 localities in the Yukon and NWT: in the Tintina Trench, where multiple tills and paleosols record 7 polarity chrons and subchrons; in the Klondike area where loess, paleosols, and glacial gravel sequences record 8 polarity chrons and subchrons; along the Yukon River near Fort Selkirk, where volcanics and interbedded glacial/interglacial sediments record at least 7 polarity chrons and subchrons; and in the Mackenzie Mtns. where a record of 6 glaciations and paleosols are assigned to the Gauss, Matuyama and Brunhes Chrons.
Near Edziza, in northwest B.C. a record of at least 5 Brunhes and possibly as many as 6 late Matuyama glaciations occur, some of which may represent local ice extent only. Near Merritt, in southern B.C. as many as 2 Matuyama and 3 Brunhes age glaciations are recorded, and recently, a till beneath a 1.6 Ma basalt has been exposed near Kelowna. At Lillooet, in south-central B.C., at least 1 Matuyama, 2 Brunhes, and possibly 1 Gauss age glaciation occurs, while at Dog Creek, a possible late Gauss and Matuyama glaciation are recorded. Tuyas and other features of ice-contact volcanism in south-central and southern B.C. provide evidence for at least 2 Matuyama and 6 Brunhes age glaciations, some of which may represent local ice only.
Along the eastern slopes of the Rocky Mtns., in the Alberta-Montana border region, there is evidence for an early glaciation, possibly of Gauss age, as well as 4 Matuyama, and 2 Brunhes age glaciations. Finally, tills in northern Washington (Puget Lowlands and Olympic Mtns.), as well as glacial lake sediments of Cordilleran (B.C.) provenance provide a record of early and late Matuyama, as well as Brunhes age glaciations.
It is clear that the northern Canadian Cordillera was repeatedly glaciated from about 3.0 Ma onward. The extent of regional and local ice varied temporally and spatially. In B.C., the buildup of large (regional) Cordilleran ice sheets may have commenced somewhat later than in the Yukon and NWT, possibly not until the late Matuyama, or until the mid-Pleistocene revolution (about 1.0 Ma), which is also suggested for the Alps in Europe.