The Nastapoka arc is a geological feature located on the southeastern shore of Hudson Bay, Canada. It is a near-perfect circular arc, covering more than 160° of a 450 km diameter circle. Due to its shape, the arc has long been suspected as the remnant of an ancient impact crater.
In August 1972, Robert S. Dietz and J. Paul Barringer conducted extensive search of much of the Nastapoka arc by First Nations and Inuit canoes and fishing boat in an investigation of its impact origin. They examined the abundant and extensive rock exposures that occur within the region of the Nastapoka arc and found a complete lack of shatter cones, suevite-type or other unusual melt rocks, pseudotachylite or mylonite, radial faults or fractures, unusual injection breccias, or any other evidence of shock metamorphism. More commonly, it is regarded to be an arcuate boundary, which was created during the Trans-Hudson orogeny, of tectonic origin between the Belcher Fold Belt and granitic rocks of the Superior Craton.
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