The B.C. Rockies: an overview
Authors: McMechan M E , Price R A 
Published: January 2011

The B.C. Rockies are part of the Cordilleran foreland thrust and fold belt formed along the western edge of the Laurentian craton during the Jurassic and Tertiary as the Laurentian craton moved relatively westward into terranes now comprising the Intermontane
Belt. The B.C. Rockies comprise a series of thrust slices of mainly sedimentary strata carried northeastward above a basal detachment and crystalline basement. Over 250 km of shortening occurred by fault displacement, folding and cleavage formation. Most of the shortening occurred as large
displacements along a small number of large thrust faults. Thrust faults in the western part of the B.C. Rockies moved prior to the mid-Cretaceous (108 Ma), whereas the most eastern major thrust in the B.C. Rockies started to move at 72 Ma.

Four main tectonostratigraphic assemblages comprise the B.C. Rockies. 1) The MesoProterozoic Belt-Purcell assemblage (1500- 1400 Ma) accumulated in a deep (15-20 km) intercontinental rift basin. This basin forms one of the main metallogenic provinces in North America with numerous mines,
prospects, and showings. 2) The Neoproterozoic Windermere assemblage (750- 600 Ma) accumulated to thicknesses of a few kilometers in a rift-basin that truncated but also partially overlapped the Belt-Purcell basin. It has been interpreted as both an intracontinental rift and as the eastern margin
of the proto-Pacific ocean basin. In the B.C. Rockies it has little known economic potential. 3) Eocambrian to Middle Jurassic (600- 180 Ma) assemblage of the Cordilleran miogeocline and cratonic platform assemblage. Important paleogeographic elements developed during Cambrian rifting influenced
the thickness and facies of sedimentation and had an important effect on localizing mineralization in Cambrian and Devonian strata as well as the distribution of economically important Middle Devonian gypsum deposits. 4) The Late Jurassic to Upper Cretaceous Cordilleran foreland basin deposits
accumulated in front of the northeastward prograding deforming wedge, as the weight of the wedge caused the underlying continental lithosphere to subside. In the B.C. Rockies these strata were incorporated into the thrust and fold belt and cannibalized. Thick coal developed in the Early
Cretaceous form an important energy resource in the B.C. Rockies. Tectonic inheritance from the underlying Paleoproterozoic crystalline basement affected sedimentation and economic potential in most of the assemblages. Displacement above the basal detachment caused inversion of the original
sedimentary basins. Major broad regional structural culminations and depressions that are evident at the 1: 2,000,000 scale of the tectonoassemblage map of the Canadian Cordillera correspond to the restored positions of the rifted margins of the three older assemblages.

Intrusions form a small but important component of the B.C. Rockies. The Mississippian Ice River Complex, Paleozoic diatremes and Cretaceous intrusions have economic potential. Intrusions plugging faults show that deformation of the B.C. Rockies had reached the east side of the Rocky Mountain
Trench by the mid-Cretaceous.