Paper No. 11
Presentation Time: 8:00 AM-12:05 PM
COMPARISON OF VIBRACORE RECORDS OF MASSIVE HUMAN-INDUCED EROSION AT PROVIDENCE CANYON STATE PARK IN SOUTHWEST GEORGIA
This study examines 5 vibracore samples collected within valley floors from a ~550 m longitudinal transect along a human-induced erosional gully at Providence Canyon State Park in southwest Georgia. Canyons at the park reveal in excess of 50 m of Cretaceous and younger poorly consolidated sandstone that was exposed by runaway erosion that followed deforestation at the time of European settlement. Sediments eroded from the canyon headlands are transported down valley by alluvial and colluvial processes, creating deposits that exceed 6 m in thickness at some sites. Stratigraphic interpretations of those cores are compared with previous studies of 14 cores collected from an adjacent canyon to better understand the spatial variability of sedimentary records of canyon development. Sediments indicate systematic down-valley trends related to three sedimentary units. Lowermost Unit I consists of in situ Cretaceous sediments that are unconformably overlain by modern floodplain (Unit II, at open-valley locations), and medium- to coarse-grained canyon-derived alluvium (Unit III, at all locations). Unit I, present in cores PC09-02 and PC09-03, consists of Cretaceous clay-rich marine muds which are bioturbated and weakly laminated. At up-valley locations, Unit I consists of cross-bedded medium sandstone of the Providence Formation. Unit II, present in cores PC09-01 and PC09-04, consists of a clay-rich, floodplain deposits which are only present at down-valley locations. All coring sites are capped by alluvial deposits (Unit III) consisting of medium- to coarse-grained sand with abundance of kaolin rip-up clasts, suggesting cut and fill deposition. Similar sediments occur in the adjacent canyon, although the new cores lack colluvium due to channel erosion.