The Midcontinent Rift System: An Overview

Abstract

Combined geophysical/geological studies in the North American craton testify to the widespread development of continental rifts in this region during Proterozoic time. The most prominent of these rifts in terms of extent and effect upon the crust is the Midcontinent Rift system (MCR) which extends in a series of generally linear segments in an arcuate pattern for a distance of over 2000 km from southern Kansas to the Lake Superior basin and then south across Michigan. The rift may also extend southerly from the western limb of the arc into Oklahoma and Texas and into Ohio, Kentucky, and Tennessee along the eastern limb, although these extensions have not yet been proven. Nearly flat-lying Phanerozoic sedimentary strata overlie the feature except in the Lake Superior basin region; therefore, its location and attributes are for the most part known from its profound geophysical signature and limited, poorly distributed deep drill holes. Except for the East African Rift System, this rift is unparalleled in its extent and impact upon the nature of the entire crust.