REGIONAL SHORTENING FABRICS IN EASTERN NORTH-AMERICA - FAR-FIELD STRESS TRANSMISSION FROM THE APPALACHIAN-OUACHITA OROGENIC BELT

Paleozoic carbonates of cratonic eastern North America comprise the footwall of the Appalachian-Ouachita fold-and-thrust belt and contain a layer-parallel shortening (lps) fabric that is preserved by mechanically twinned calcite. Shortening directions are generally parallel to the Appalachian-Ouachita thrust-transport direction in carbonates of the thrust belt proper (restored width approximately 400 km) and within carbonates up to 1700 km into the foreland, giving a pre-thrusting sedimentary prism approximately 2100 km wide through which compressive orogenic stresses were transmitted. The shortening strain magnitudes (<6%) and the inferred calcite twinning differential stress magnitudes (<90 MPa) decrease exponentially away from the orogenic front. Calcite twinning strain patterns in other adjacent tectonic provinces, such as the Grenville, Laramide, Keweenawan Rift, and Newark Basin, are distinct from the twinning strains preserved in the cratonic Paleozoic carbonates.