NEW INTEGRATED GEOLOGICAL AND GEOPHYSICAL OBSERVATIONS CONCERNING INTRAPLATE DEFORMATION IN THE CENTRAL U. S

EarthScope’s USArray is rolling into the central U. S. and is focusing scientific interest on this region. A variety of geophysical data, including newly released 3-D seismic reflection data, show us that the basement structure of the central U. S. is very complex. The dimensions of many of these basement 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 make the driving mechanisms for intraplate deformation evident. The crust of the region formed during a period of continental growth that formed the cratonal core of North America (Laurentia). The impressive Mid-Continent rift system (MCRS) tried to interrupt this period of continental growth at about 1.1 Ga but failed even though it modified the crust massively. However, Laurentia was part of a supercontinent that did not survive long and began to break up by ~800 Ma. The Southern Oklahoma aulacogen (SOA) is an impressive example of the effects of the intraplate extension that accompanied this break-up. The deformation that formed the Ancestral Rocky Mountains resulted in massive inversion of SOA rift structures and extensive deformation in the central U. S. There has been increased emphasis on the use of gravity, magnetic and remote sensing data, and these data have been particularly effective when used in an integrated fashion with seismic and drilling data. 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, 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. Also, new geophysical and geological results in Southern Oklahoma and the Wet Mountains of Southern Colorado show that major SOA magmatism extended into Colorado and the tectonic inversion was extremely complex.