EXPLORING RELIC LANDSCAPES ON TOP OF SAND MOUNTAIN AND LOOKOUT MOUNTAIN TO UNDERSTAND LINKS BETWEEN UPPER-CRUSTAL ARCHITECTURE AND TECTONIC GEOMORPHOLOGY IN THE SOUTHERN APPALACHIAN FORELAND THRUST BELT AND PLATEAU

Relic landscapes are related to either the retreat of ancient escarpments, ancient structural landscapes, repeated uplift and incision events, or residual, lithologically-controlled components. Coupling modern technology (DEMs and LIDAR) with traditional balanced cross sections and field data provides the opportunity to examine the possible development of relic landscapes in the southern Appalachian foreland thrust belt and plateau. Sand Mountain and Lookout Mountain are NE-SW trending, broad topographic ridges in the southern Appalachians of Alabama, Georgia, and Tennessee. Sand Mountain is bound to the west by the Sequatchie thrust fault, which is the westernmost thrust fault in the southern Appalachians. The Will’s Valley Anticline separates Sand Mountain to the west and Lookout Mountain to the east. Both ridges exhibit ~ 150-300 m of relief from adjacent valleys and are synclines underlain by clastic Pennsylvanian (Pottsville Formation) strata. Adjacent to Sand Mountain and Lookout Mountain are valleys that consists of anticlines with Cambrian/Ordovician through Mississippian strata. This structure-lithology-topography defines a topographic inversion in the area. On top of Sand Mountain and Lookout Mountain are Quaternary unconsolidated clastic deposits of sandy-silt, decompositional shale residuum, and sandy-shale colluvium. Along the west and east slopes of Sand Mountain and Lookout Mountain are large-block colluvium deposits and chert-residuum colluvium. Therefore, we utilize upper-crustal architecture, Quaternary sedimentation, and digital elevation models to explore the establishment of a relic upland surface along Sand Mountain and Lookout Mountain. Near the junction of Alabama, Georgia, and Tennessee, where the Tennessee River deviates from a southwestern to northwestern direction, cutting across Lookout Mountain a relic landscape is proposed.