Thermo-Kinematic Appraisal of the SE Canadian Cordilleran Foreland Belt , the Restoration of a Severely Denudated Orogenic Wedge

The SE Canadian orogenic belt forms a prolific case-area to scrutinize the progressive development of an orogenic wedge, focussing on fault block thermo-kinematics and burial-exhumation histories. This study aims to elucidate the denudation history that have not only affected the deformed Canadian Foreland Belt on the small wavelength of individual thrust sheets and severe tectonic unroofing in the Cordillera interior, but also on an extended scale involving the undeformed distal foreland. The southern Canadian Foreland Fold and Thrust Belt forms a northeastward tapering contractional belt comprising an thick piloted Mesoproterozoic continental margin sequence that has overridden an strongly imbricated Paleozoic carbonate sequence and Mesozoic to lower Tertiary foredeep sequences that record an upper Cretaceous to Paleocene compressional history. Contraction is accommodated by a few major thrusts (a.o. Lewis thrust; ~115-125 km of shortening estimated), and accompanied by the development of a presumably thick, currently eroded syntectonic foredeep wedge and followed by Late Eocene-Oligocene extension. Along 3 east-west trending regional cross-sections, classical structural restoration together with 1D and 2D forward thermo-kinematic modelling allowed for the appraisal (i.e. timing, amplitude and wavelength) of the combined sedimentary and tectonic burial, and subsequent exhumation. With the aid of organic maturity ranks providing a dense regional coverage and FT inferences for necessary constraints on timing, the severely denudated orogenic wedge could be deciphered. So far, two alternative burial-exhumation history scenarios hold valid; overburden and peak temperatures are achieved by (1) pure sedimentary burial prior to thrusting or alternatively (2) in combination with a strong tectonic loading component. 2D thermo-kinematic modelling examinates the thermal implications of foreland belt kinematics (i.e. basement flexures, tectonic and sedimentary burial and denudation) especially by tracing the vertical movements and thermal history of a set of synthetic samples. This integrated data-analytical and modeling study reveal a short-wavelength syn-orogenic exhumation (~4-6 km) signal limited to the deformed Foreland Belt effected by upper Cretaceous lower Palaecene thrustsheet, followed by upper Palaeocene-Eocene large wavelength exhumation involving the entire former foredeep (2-4 km). Finally the, inherited structural bearing on the denudation and thermal history has been appraised with additional application to petroleum systems.