Side-looking airborne radar image map showing cross-strike structural discontinuities and lineaments of the central Appalachians

Abstract

Seven cross-strike structural discontinuities (CSD's), 100 lineaments, and 8 allochthonous-block and crustaHblock boundaries, recognized by various workers in the Central and Southern Appalachians, are compiled on a side looking airborne radar (SLAR) image mosaic of twelve I°x2° quadrangles to better understand their relationship to the regional structural framework.CSD's are broad zones of structural disruption that may contain many lineaments of varying size and orientation. Geologic and geophysical data suggest that some Appalachian CSD's and lineaments are the surficial expression of allochthonous-block and crustaHblock boundaries. The high-resolution, synoptic view and detailed expression of surficial morphology on XHband SLAR images provide a preliminary means of mapping CSD's and lineaments on the basis of alignment or disruption of structural and geomorphic patterns.Of the seven CSD's, two appear to involve basement, three appear to involve lateral ramps in cover rocks above basement (zones where a thrust fault transfers to a higher stratigraphic level along regional strike), and two may involve both basement and cover rocks. Of the 100 lineaments, 14 appear to involve basement, 78 are restricted to the allochthon cover rocks, and 8 may involve both basement and cover rocks. Thirty-two percent of all lineaments are attributed to the surficial expression of lateral ramps while 48 percent are attributed to interruptions in strike, such as regional-scale plunging fold noses and geomorphic gaps.CSD's and lineaments are an exploration target for natural gas because they are areas where fracture permeability is enhanced. The spatial relationship of CSD's and lineaments to gas fields in the Valley and Ridge province suggests structural closure of anticlinal traps due to differential movement associated with lateral ramps.