A Geophysical Overview of the Structure and Evolution of the Crust of the Mid-Continent Region of North America

Abstract:

A variety of geophysical data, including newly released 3-D seismic reflection data, show us that the crustal structure of the Mid-Continent region of North America is very complex. The dimensions of many of the crustal structures is very large by global standards, and thus, they are a tectonic puzzle because of their size, structural complexity, and distance from active plate margins that usually create the driving mechanisms for intraplate deformation evident. The crust of the Mid-Continent region formed during a period of continental growth that extended from about 1.8 to 0.9 Ga. The impressive Mid-Continent rift system (MCRS) tried to interrupt this period of continental growth at about 1.1 Ga but it its western arm failed even though it modified the crust massively. However, the supercontinent resulting from this growth did not survive long and began to break up by ~700 Ma. This period of rifting established the structural framework of the southern Mid-Continent region, subsequent Early Paleozoic basin development, and at least partly, the formation of the Ancestral Rocky Mountains in the late Paleozoic. The Southern Oklahoma aulacogen (SOA) is an impressive example of this rifting event. The deformation that formed the Ancestral Rocky Mountains resulted in massive inversion of SOA rift structures and is due to a plate collision in the late Paleozoic whose origin is under debate. There has been increased emphasis on the use of gravity, magnetic, seismic, drilling, and remote sensing data in studies of the Mid-Continent region. For example, the MCRS is traditionally viewed as ending in central Kansas and the SOA can be interpreted as ending in the Texas panhandle. However, we used enhancement of gravity and magnetic data, seismic data, geologic mapping, and deep-drilling data to study its southern extent, and it appears that the MCRS could extend further southward beneath the much younger Anadarko basin of Oklahoma to abut the SOA.