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

The Mount Head embayment is a regional downwarp along the west coast of Lower Carboniferous western Canada that developed by differential subsidence, which we recognize 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 appears that basement-tectonic elements controlled sediment accommodation and accumulation within the Mount Head embayment. The overall shape of this embayment is probably inherited from the arcuate shape of the Late Proterozoic cratonic rift margin. Within the Mount Head embayment, several northeast-southwest - trending Archean and Proterozoic basement-tectonic elements intersect the autochthonous cratonic margin at high angles. Carboniferous piano-key-like structural reactivation of these tectonic elements produced oriented trends of differential subsidence that partitioned the Mount Head embayment into two subbasins (Crowsnest and Kananaskis depocenters) separated by a more positive area (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 Rocky Mountain trench to the west, and that tectonic control on sedimentation noted by others for Precambrian and pre - Middle Devonian rocks extends clearly into overlying Carboniferous deposits. May 1996