LITHOSPHERIC STRUCTURE ACROSS THE OUACHITA OROGENIC BELT AND COMPARISONS WITH THE VARISCIDES

We have complied a wide variety of data to produce a series of crustal scale transects that cross the Ouachita orogenic belt. The main transect is based on the PASSCAL wide-angle reflection/refraction data that show a thick mass of Ouachita sedimentary rocks above transitional or oceanic crust outboard of the rifted margin of Precambrian crust. Our integrated models and geologic constraints show that the Applachian and Ouachita orogenic belts were formed during assembly of supercontinent Pangea (by ~270 Ma), and were driven onto the Iapetan rifted margin by collisions with arcs, exotic terranes, and other continents. They also show that the sinuous curves of the Appalachian-Ouachita orogen mimic the shape of the Iapetan rifted margin and subsequent passive-margin shelf edge. Our results show that all around the Ouachita thrust belt, imbricated continental-slope facies (in an accretionary prism at the leading edge of an arc complex) were thrust onto the continental shelf. Southern North America and Central Europe share many aspects of their Neoproterozoic and Phanerozoic tectonic evolution. Thanks to a series of large seismic experiments in Europe and the southern U. S., we have been conducting comparative analyses of major structures in Laurentia and Baltica. The efforts in Europe primarily targeted the structure and evolution of the complex collage of major tectonic features in the Trans- European suture zone (TESZ) region, as well as, the Carpathian Mountains and the Eastern Alps, the Pannonian basin, and the Bohemian massif. In the TESZ region, these efforts have delineated the rifted margin of Baltica, and it is quite similar to crustal models we have developed for the Ouachita margin. Our integrated seismic and gravity modeling efforts indicate that the Variscan orogeny in Central Europe and the Ouachita orogeny appear to be the result of soft collisions that have left the pre-orogenic rifted margins largely in tact.