The Mid-Continent Rift System – It's a Whopper
Randy Keller, Jonathon Bueing, Miguel Merino, Seth Stein, and Carol Stein
The Mid-Continent rift system is a globally significant example of intracontinental rifting. At a minimum, it stretches from Central Kansas to its greatest expression in the Lake Superior region, through the remainder of the Great Lakes, to eastern Ohio. The amount of magmatic modification of the crust in the Lake Superior region is so great that at best, 25% of the pre-rift crust is still in recognizable. Other volcanic rocks of it's ~1.1 Ga age are found both to the south in Texas and New Mexico (the Central Basin Platform is cored by a mafic intrusion of the same age). Based on geophysical evidence, this rift has been inferred to be present in Oklahoma, southern Ohio, Kentucky, and Tennessee. It is easily comparable in several respects to the East African rift. These comparisons include degree of magmatic modification of the crust, structural style, geographical extent, and syn-rift basin formation. It is reasonable to infer that the Nemaha structures in southern Kansas and central and northern Oklahoma represent rift structures reactivated as transpressive structures during Pennsylvanian intraplate deformation. Given the search for "sweet spots" in plays such as the Mississippi Lime, the possibility of deep structural control is worth considering. In Ohio, the interaction of this rift system and the Grenville orogeny is an open question that is under investigation by our group.
AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013