RELIC APPALACHIAN UPLANDS: LANDSCAPES THAT MAY HAVE EVOLVED FROM THE FRONT- AND BACK-SIDES OF RIFTING

Relic Appalachian Uplands mostly occur in three locations: 1) stretches of Eastern Continental Divide where drainage-divides separate major river systems along/east of Mississippi River (Tennessee-Cumberland; Kanawha-New River; Ohio-Alleghany-Monongahela) from Atlantic coastal river systems (e.g., Delaware; Susquehanna; Potomac; James; Roanoke; Pee Dee; Savannah) and Gulf of Mexico (Chattahoochee); 2) stretches of drainage-divides of major Atlantic coastal river systems (e.g., in Blue Ridge along James/Potomac systems); and 3) stretches of upper Mississippi systems drainage-divides (e.g., upper New River/upper Tennessee systems). Only along the oldest relic parts of these divides do elevated, low-gradient drainages exist in the Appalachian region above escarpments dominated by erosion of competing mass-wasting processes. Examples of these oldest landscapes (referred to by relic streams/nearby peaks) are: Long Hope Ck.-Elk Knob, NC; upper Little Stony Ck.-Butt Mtn., VA; Stony Ck.-Devils Knob, VA; Chimney Rock, NC. Some (like Long Hope Ck.-Elk Knob, west/above an asymmetric ~200-300m-high E-facing escarpment incised by upper New River, NC) indicate retreat of ancient escarpments. Others reflect Appalachian structural landscapes (upper Little Stony Ck.-Butt Mtn., VA; Lookout Point, GA). Some with multiple periods of incision, possibly reflect uplift (Stony Ck.-Devils Knob, VA; Chimney Rock, NC). Residual, lithological-controlled components dominate other areas (Cumberland Plateau, TN; Blue Knob region, PA). Once competing mass-wasting processes along a divide capture relic upland streams, then that divide is non-reversibly lowered as a diminishing linear ridge. Larger relic uplands with streams are preferentially preserved due to lithology/structural setting.