OROGENY ALONG THE RIFTED MARGINS OF LAURENTIA AND BALTICA: A COMPARASION OF THE OUACHITA AND VARISCAN OROGENIES

Southwestern North America and Central Europe share many aspects of their Neoproterozoic and Phanerozoic tectonic evolution. In particular, the break-up of the Rodinian supercontinent created the continental blocks called Laurentia and Baltica. Passive margins developed after the rifting that formed these continents, and these margins were deformed by late Paleozoic orogenies (Appalachian-Ouachita; Caledonian-Variscan respectively). Our group has studied the Ouachita orogeny that affected southern Laurentia for many years and has recently had the opportunity to study Central Europe by participating in several large seismic experiments. The most recent was CELEBRATION 2000 (Central European Lithospheric Experiment Based on Refraction, 2000), an extremely large active source seismic experiment that was undertaken by a large consortium of institutions (28 in all) from Europe and North America. This experiment 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 southwestern portion of the East European craton, the Carpathian Mountains, the Pannonian basin, and the Bohemian massif. In the TESZ region, we observed a complicated wave field in the area of the Polish basin, Holy Cross Mountains and Upper Silesia block. This result and that of the POLONAISE’ 97 experiment have delineated the rifted margin of Baltica, and it is quite similar to crustal models we have developed for the Ouachita margin. In addition, the Holy Cross Mountains exposed a crustal block that is similar to the Devil’s River uplift in west Texas. The Polish basin contains a thick pre-Permian section similar to that observed along the Ouachita orogenic belt that is overlain by a Permian and younger sequence that is analogous to the Gulf Coast sequence. Both 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.