DETERMINATION OF STREAM-INCISION RATE IN THE APPALACHIAN PLATEAUS BY USING CAVE-SEDIMENT MAGNETOSTRATIGRAPHY

Paleomagnetic dating of elastic fluvial sediments contained in caves w ithin the walls of a steeply incised gorge allowed calculation of a ma ximum incision rate for the East Fork Obey River. The maximum incision rate for this major stream on the western margin of the Cumberland Pl ateau, north-central Tennessee, was found to be 0.06 m/ka. This rate w as determined on the basis of the paleohydraulic relation between the caves and the surface stream, the presence of a normal-to-reverse pola rity transition in elastic fluvial sediments deposited within the cave s, and the vertical distribution of polarity found in sediments throug hout the gorge. The dating results indicate that this highly developed fluviokarst, containing several of the longest known caves in the Uni ted States, developed wholly within the Pleistocene and Holocene.