LOCALIZED STRUCTURALLY-DERIVED TENSILE STRESS DEVELOPMENT OFPOLYGONAL CRACKED SURFACES ON POTTSVILLE SANDSTONES (LOWERPENNSYLVANIAN) ALONG THE PERIMETER OF THE CHANDLER MOUNTAIN ANDLOOKOUT MOUNTAIN PLATEAUS, NORTHEASTERN ALABAMA ANDNORTHWESTERN GEORGIA

摘要

Well-indurated Pottsville sandstones(lower Pennsylvanian) cap the ChandlerMountain and Lookout Mountain plateaus.These massive orthoquartzites have experi-enced varying levels of tensile and compres-sional stress and strain associated withfolding and warping during and followingthe Alleghanian Orogeny. This has resultedin the development of fractures, joints, andpolygonal cracks in some of the exposedPottsville sandstones. While these structuralfeatures are interrelated, they are not viewedas gradational. We interpret the polygonalcracks as the smallest of the three mac-roscale structural features. The best devel-oped polygonal cracks occur on weatheredsandstone surfaces along the perimeters ofboth plateaus in areas where localized struc-tural tensile stress has developed within thesandstone layers.