Thin thrust sheet formation of the Kapuskasing structural zone revealed by Lithoprobe seismic reflection data

Regional and high-resolution seismic reflection data across the Kapuskasing structural zone in Ontario, Canada, image at least three significant thrust faults that are low angle, merge into a flat detachment on the west, and together were responsible for the uplift of amphibolite and granulite facies rocks. Their geometry resembles a ramp-and-flat style of deformation that results in a thin upper plate above the 10-12 km (about 4.0 s) detachment. Northwest-southeast horizontal shortening is estimated to be at least 55 km. This large amount of shortening implies that much of the Superior province was detached during the formation of the Kapuskasing structural zone.