Implied basement-tectonic control on deposition of Lower Carboniferous carbonate ramp, southern Cordillera, Canada

Abstract

cambrian (Kanasevich et al., 1969) and preThe Mount Head embayment is a regional downwarp along the west coast of Lower Middle Devonian (Norris and Price, 1966; Carboniferous western Canada that developed by differential subsidence, which we recog- Benvenuto and Price, 1979). nize from lithostratigraphic and biostratigraphic patterns. Palinspastic restoration of the Mount Head embayment illustrates that subsidence domains are geometrically coincident with previously identified tectonic elements of the autochthonous basement. Thus, it ap- METHODS pears that basement-tectonic elements controlled sediment accommodation and accumu- Geologic observations were recorded on lation within the Mount Head embayment. The overall shape of this embayment is probably palinspastically restored maps and cross setinherited from the arcuate shape of the Late Proterozoic cratonic rift margin. Within the tions and to basement-tectonic Mount Head embayment, several northeast-southwest-trending Archean and Proterozoic domains defined on aeromagnetic and gravbasement-tectonic elements intersect the autochthonous cratonic margin at high angles. ity maps (Brandley, 1993). The palinspastic Carboniferous piano-key-like structural reactivation of these tectonic elements produced base map is modified from Gibson,s (1985) oriented trends of differential subsidence that partitioned the Mount Head embayment into map of displacement vectors for Jurassic two subbasins (Crowsnest and Kananaskis depocenters) separated by a more positive area rocks. The magnitudes of the vectors were (Highwood high). Moreover, our data imply that Precambrian basement structure noted by others under the Plains and Rocky Mountain fold and thrust belt continued across the altered to reflect displacements at the MisRocky Mountain trench to the west, and that tectonic control on sedimentation noted by sissippian level documented by Bally et al. others for Precambrian and pre-Middle Devonian rocks extends clearly into overlying (1966), Price (1981), and Price and Fermor Carboniferous deposits. (1985), university theses, and Geological Survey of Canada maps and sections across