Grenville orogenic belt...been brought to the present surface on major thrusts from the mid-lower crust. A result of the terminal continental collision that occurred at about 1.1 billion years ago was the formation of the Midcontinent (or Keweenawan) rift system that extends southward for more than 2,000 km (about 1,240 miles) from Lake Superior.The Midcontinent Rift developed contemporaneously with northwest-directed crustal-scale thrusting in the Grenville orogenic belt. The belt is exposed principally along the southeastern margin of the Canadian Shield, but inliers occur in the Appalachians, the East Greenland Caledonides, Texas, and Mexico. It has been traced at depth across the eastern and southern fringes of the interior...
Midcontinent rift system
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