The Nastapoka arc is a geological feature located on the southeastern shore of Hudson Bay

Hudson Bay

Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It is a near-perfectly circular arc

Arc (geometry)

In geometry, an arc is a closed segment of a differentiable curve in the two-dimensional plane; for example, a circular arc is a segment of the circumference of a circle...

, 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

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

. In August 1972, Dr. Robert S. Deitz and J. Paul Barringer conducted extensive search of much of the Nastapoka arc by Indian and Eskimo 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

Suevite

Suevite is a rock consisting partly of melted material, typically forming a breccia containing glass and crystal or lithic fragments, formed during an impact event...

-type or other unusual melt rocks, pseudotachylite

Pseudotachylite

Pseudotachylite is a fault rock that has the appearance of the basaltic glass, tachylyte. It is dark in color and has a glassy appearance. However, the glass has normally been completely devitrified into very fine-grained material with radial and concentric clusters of crystals...

 or mylonite

Mylonite

Mylonite is a fine-grained, compact rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. It is classified as a metamorphic rock...

, radial faults or fractures, unusual injection breccia

Breccia

Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....

s, or any other evidence of shock metamorphism. More commonly, it is regarded to be an arcuate

Arcuate

Arcuate can refer to:* Arcuate delta, a type of river delta* Arcuate fasciculus* Arcuate line * Arcuate artery* Arcuate nucleus* Arcuate nucleus * Internal arcuate fibers of the brain...

 boundary, which was created during the Trans-Hudson orogeny

Trans-Hudson orogeny

The Trans-Hudson orogeny, Trans-Hudsonian orogeny, Trans-Hudson orogen , or Trans-Hudson Orogen Transect , , was the major mountain building event that formed the Precambrian Canadian Shield, the North American craton , and the...

, of tectonic origin between the Belcher Fold Belt and granitic rocks of the Superior Craton.