Geophysical interpretation of the Fort Simpson Basin, southwest Northwest Territories

The Fort Simpson Basin is imaged along Lithoprobe Slave - Northern Cordillera Lithospheric Evolution transect (SNORCLE) lines 1 and 2b in southwest Northwest Territories and northern British Columbia. It is buried beneath Phanerozoic rocks of the Western Canada Sedimentary basin and is interpreted to represent up to 16 km of westward thickening metasedimentary strata formed after 1.845 Ga. Strata within the Fort Simpson basin were identified by drill hole intersection, seismic stratigraphy, and correlation with the Proterozoic Muskwa assemblage by a gravity tie and a synthetic seismogram created from Proterozoic outcrop. Correlating the Muskwa assemblage to the reflections within the Fort Simpson basin implies these thick Proterozoic metasedimentary sequences are extensive in the subsurface. The reflections within the Fort Simpson basin have been divided into 8 reflective units based on seismic character and geometry. Two are Phanerozoic in age. Three are most likely Proterozoic strata, possibly meta-sediments younger then 1.845 Ga, and the three lower most units are most likely basement rocks. There are four major unconformities observed that separate reflection "packages" with distinctive geometry and character. Geometric relationships between the reflections and unconformities are interpreted to represent major variations in sea level.