Seismic reflection surveys in the southern part of the Eastern overthrust reveal that crystalline rocks of the Blue Ridge and Piedmont were thrust westward burying a large segment of sedimentary rocks of the Valley and Ridge. Surface and subsurface data suggest that the buried segment includes Cambrian and Lower Ordovician shallow-shelf clastic and carbonate rocks overlain by Middle Ordovician foredeep black shale. Because eastward-increasing regional thermal patterns existed prior to thrusting, westward movement of thrust sheets disrupted and telescoped that pattern by placing more thermally mature eastern rocks over less mature western rocks. The original thermal pattern can be reconstructed by restoring the thrust sheets to their prethrust position. The reconstruction emphasizes that rocks less metamorphosed than greenschist facies are contained in only two thrust sheets: all of the Saltville and part of the Pulaski. Because subgreenschist rocks of the Saltville and Pulaski thrust sheets appear to be confined to the subsurface of the Blue Ridge and westward, it is most likely that rocks with commercial gas potential will not be present in the subsurface of the Piedmont east of the Brevard fault. Nevertheless, the concealed area of the southern Eastern overthrust with possible gas potential is about as wide as its exposed part. Thus the combined surface and subsurface area for future exploration in the southern Appalachians is about doubled in size.