The Precambrian basement underlying the Paleozoic rocks of the Western Canada Sedimentary Basin was studied by combining potential field (gravity and aeromagnetic) analysis with lithological and isotopic studies of crystalline basement samples. The 93 samples, mostly core, retrieved from hydrocarbon exploration wells, are described in this paper. The U-Pb zircon geochronology and systematics of 50 of the samples that were analyzed at the Geological Survey of Canada, are presented and interpreted. Monazite and titanite, with their lower closure temperatures, help delineate post-crystallization, regional thermal events. Sm-Nd data from 35 of the cores are presented and used to test and delineate models for the tectonic evolution of the region. The basement in southern Alberta is Archean, although an early Proterozoic titanite age in the Vulcan Low, when combined with the geophysical signature of the region suggests the presence of a Proterozoic collisional orogeny. Central Alberta is dominated by the formation of 2.3-1.8 Ga domains around the Snowbird Tectonic Zone. Northern Alberta contains a large, complex 2.4-2.0 Ga domain which is flanked by 1.95-1.85 Ga magmatic arc domains. The 1.9 Ga monazite and titanite ages on 2.0-2.4 Ga rocks show the regional effect of the magmatism at the domain margins. Sm-Nd data indicate that most of the Proterozoic domains of the Alberta basement contain a large component of remobilized Archean crustal material.

Results of U-Pb zircon dating are presented for crystalline clasts (stranger stones) in diamictites from the Rapitan and Misinchinka groups, which represent two glacial intervals during Neoproterozoic Windermere Supergroup sedimentation in the northern and central Canadian Cordillera. A leucogranite dropstone in the lowermost Sayunei Formation gives an age of 755 ± 18 Ma and provides a maximum depositional age for the Rapitan Group. Gabbro and syenogranite clasts yield nearly concordant ages of 1857 ± 3 Ma and 1860 ± 1Ma, respectively. The association of ca. 1860 Ma and 755 Ma plutonic rocks suggest an intra-Cordilleran source. Six felsic plutonic and volcanic boulders from the Vreeland Formation (lower Misinchinka Group) yields one discordant age of 1842+16/-14 Ma and the remaining ages in the narrow range of 1865-1862 Ma. The composition and restricted suite of ages for the Vreeland Formation suggest possible derivation from the Fort Simpson High or (less likely) Great Bear Magmatic Zone.

No abstract

The Windermere Supergroup is a regionally widespread succession of predominantly deep marine sedimentary rocks deposited on the continental margin of western Canada following its separation from Australia ca. 700 Ma. A vertical succession from sand-rich basin plain turbidites ta mud-rich slope facies occurs over a ca. 7 km thick stratigraphie interval and records the progradation of the continental margin attendant with diminished rates of thermally-driven subsidence. Although unfossiliferous and deformed in the Mesozoic, careful stratigraphie mapping, utilizing a lithologically distinct condensed interval (SHEET 2) and two carbonate-rich lowstand intervals have established regional continuity of this depositional system over ca. 4° of latitude. The continuity of the depositional system has also been established using geochronology of detrital zircons which reveals a uniform provenance throughout the southeastern Canadian Cordillera (SHEET 2). Taken in concert with facies patterns and paleocurrent data, the Windermere grits are interpreted as a longitudinal turbidite system that flowed west

Detrital zircons analyzed from coarse grits within the eastern Dorsey Terrane of the Thirtymile Range, southern Yukon Territory, yield Proterozoic and Archean 207Pb/206Pb ages that range from ca. 1777 Ma to 2600 Ma, similar to the range of crystallization ages of basement in the Peace River Arch area of northern Alberta and northeastern British Columbia. This suggests that the source of these grits was crystalline basement of western Canada, thus confirming a North American affinity for these sedimentary rocks and their correlation with the Cassiar Terrane of northern British Columbia. The western Canadian provenance documented in the detrital zircons is consistent with models that suggest approximately 450 km of right-lateral displacement along the Tintina-Northern Rocky Mountain Trench fault, rather than recent suggestions of a western Montana provenance for the Cassiar Terrane that require greater than 2000 km displacement.