Distribution of Phanerozoic Faulting and Folding, Seismicity, and Ore Deposits in the Midcontinent Region, United States: A Reflection Widespread Proterozoic Rifting in the North American Craton?

Abstract

Most of the Midcontinent region in the United States is a continental interior platform, where Precambrian basement is almost completely covered by a veneer of Phanerozoic sedimentary strata. To structural geologists accustomed to working in orogens, continental-interior platforms appear, at first glance, to have been undeformed during the Phanerozoic. Yet on closer examination the Midcontinent does contain a fascinating history of Phanerozoic tectonism; this history is recorded by structural features that differ markedly in style from the more dramatic features of orogens. Structural features of the Midcontinent can be divided into two general categories: (1) epeirogenic features (basins, domes, and arches of regional extent) whose development, though affecting regional patterns of stratigraphic thickness and facies, has resulted only in regional bedding dips of less than a few degrees; and, (2) fault and fold zones, which are belts of relatively localized deformation in which faulting has displaced stratigraphic contacts and/or bedding has been significantly bent or tilted. In this paper, we speculate on the question of fault and fold zones originated.