PRECAMBRIAN RIFT SYSTEMS IN NORTH AMERICA COMPARED TO OTHER CONTINENTAL RIFTS AROUND THE WORLD

Continental rifts can evolve to seafloor spreading and be preserved in passive margins, or fail and remain as fossil features in continents. Rifts at different stages give insight into their evolutionary paths as either a failure because they did not form a new ocean or a success that resulted in a new oceanic basin. Insights into the structure and evolution of the Midcontinent Rift (MCR) that was formed by 1.1 Ga rifting of Amazonia from Laurentia, followed by the Cambrian opening of the Iapetus Ocean that formed the southern margin of North America, can be gained by comparisons to other well-studied rifts around the world. This presentation compares the MCR to the active East African, Rio Grande, and Baikal rifts, the failed Western and Central African rift systems, and the strongly inverted Southern Oklahoma and Dnieper Donets aulacogens. The MCR was highly magmatic and is associated with a pronounced, horseshoe-shaped gravity high. The amount of inversion along the rift varies, but is well studied in the Great Lakes area, and industry drilling and seismic data reveal prominent inversion in central Iowa. In other areas around the world, aulacogens have produced gravity highs largely due to structural inversion, and younger rifts have experienced varying amounts of magmatism but little compressive deformation. A variety of geological and geophysical data have been employed to provide insight into the deep structure and evolution of several diverse rift systems that are compared to the MCR.