Suture-zone geometry along an irregular Paleoproterozoic margin; the Superior boundary zone, Manitoba, Canada

Lithoprobe acquired a 190-km-long deep seismic reflection profile across the Superior boundary zone at the eastern margin of the Paleoproterozoic Trans-Hudson orogen. The profile is located approximately 250 km south of a major promontory along the ancient margin of the Superior craton and complements earlier profiles closer to the promontory. The new data image the remnants of a craton-verging thrust belt, younger than 1864 Ma, within the Superior boundary zone extending to a maximum depth of 15 km above a shallowly west dipping basal decollement. Across the surface suture zone, a dip reversal to east-dipping reflections occurs within the adjacent Reindeer zone, where a crustal-scale imbricate stack is imaged. Reindeer zone lower crust and upper mantle extend eastward beneath the Superior craton margin for 40-100 km. Preservation of a foreland thrust belt within the Superior boundary zone is explained as a result of reduced collisional convergence and subsequent exhumation within a reentrant flanking the Thompson promontory.