Lateral Ramps in the Folded Appalachians and in Overthrust Belts Worldwide: A211 Fundamental Element of Thrust-Belt Architecture

摘要

Lateral ramps are zones where decollements change stratigraphic level along211u001estrike; they differ from frontal ramps, which are zones where decollements change 211u001estratigraphic level perpendicular to strike. In the Appalachian Mountains, the 211u001esurface criteria for recognizing the subsurface presents of lateral ramps include 211u001e(1) an abrupt change in wavelength or a termination of folds along strike, (2) a 211u001econspicuous change in the frequency of mapped faults or disturbed zones 211u001e(extrememly disrupted duplexes) at the surface, (3) long, straight river trends 211u001eemerging onto the coastal plain or into the Appalachian Plateaus province, (4) 211u001emajor geomorphic discontinuities in the trend of the Blue Ridge province, (5) 211u001einterruption of Mesozoic basins by cross-strike border faults, and (6) zones of 211u001emodern and probable ancient seismic activity. Additional features related to 211u001elateral ramps include tectonic windows, cross-strike igneous instructions, areas 211u001eof giant landslides, and abrupt changes in Paleozoic sedimentation along strike.