| A vast area of the Precambrian craton of Laurentia lies buried beneath Phanerozoic rocks of the Western Canada Sedimentary Basin (WCSB). The lithospheric evolution of this crystalline basement and the stratigraphic architecture of the overlying sedimentary rocks have been investigated using geophysical techniques. A 1400-km reflection-seismic profile constructed from LITHOPROBE lines was used for regional investigation of basin structure and the nature of the basement-cover contact. Instantaneous attribute analysis of the top-of-basement reflection reveals domain-dependent properties. The seismic data also show that normal faulting in the basin, widely separated in both space and time, displays previously undocumented characteristics of extensional forced-folding.; Previous workers have used gravity and magnetic data as the basis for qualitative subdivision of the crystalline basement into tectonic domains. Here, crustal structure in the vicinity of 6 prominent gravity and magnetic anomalies were investigated in a quantitative fashion by numerical simulation. Independent constraints from seismic and magnetotelluric data were used to mitigate the inherent non-uniqueness of the potential-field interpretations. In the case of the Vulcan Structure, a Paleoproterozoic collision zone in southern Alberta, significant remanent magnetization was invoked to simplify the interpretation of paired positive-negative magnetic anomalies that had been interpreted previously as separate domains. If correct, this interpretation challenges the almost universally held assumption that remanent magnetization is negligible in Precambrian terranes. Elsewhere, numerical modelling shows that previous seismic interpretations of a 10-km offset in the Moho across a splay of the Snowbird tectonic zone is consistent with, but not required by, the gravity signature of this feature.; The Great Slave Lake shear zone is a conspicuous 1300-km linear potential-field anomaly that has been interpreted as type example of a subvertical crustal-scale transcurrent fault. Teleseismic receiver functions suggest that the fault extends through the crust but is not vertical, dipping toward the southeast at an average angle of ∼67°. On the basis of gravity modelling, mylonites within the shear zone appear to be more dense than the surrounding crust. The load produced by these rocks may account for the apparent inward dip of the Moho toward the axis of the shear zone. |
