Tectonics of the Continental Interior in the United States

The continental interior of the United States encompasses the region between the Rocky Mountain front and the Appalachia-Ouachita front. It is a region of cratonic platform that represents the southern third of the North American craton. Crust of the continental interior consists of Precambrian basement (formed mostly during Proterozoic accretionary orogeny) overlain, at the Great Unconformity (which formed due to late Proterozoic exhumation), by a relatively thin cover of Phanerozoic stratigraphic sequences that were deposited during transgressions and regressions of shallow seas. Nearer the margins of the interior, clastic wedges derived from bordering orogens spread out onto the craton. The continental interior has not undergone orogenic deformation for about 1 billion years, so it does not display the consequences of penetrative deformation or dynamothermal metamorphism, but it does display the consequences of tectonic activity. This Phanerozoic activity produced several epeirogenic domes, basins, and arches, as well as numerous midcontinent fault-and-fold zones. The fault-and-fold zones likely represent transpressional and transtensional reactivation of Proterozoic rift-related normal faults. The timing of Phanerozoic tectonism in the continental interior of the United States corresponds with the timing of orogenic activity in the continent's marginal orogens, suggesting that stress transmitted into the interior of the continent during orogeny caused continental-interior tectonism. Uplifts related to tectonic events also drove groundwater flow that produced distinct pulses of diagenesis. Though the topography of the continental interior is not as dramatic as occurs in orogenic belts, the region nevertheless contains a rich record of lithospheric evolution through the Phanerozoic.