FLUVIOKARST CONDUIT ENLARGEMENT POTENTIAL DUE TO SEDIMENT AND CHEMISTRY FLUCTUATIONS DURING STORM EVENTS AT SMULLTON SINKS, CENTRE COUNTY, PA

Most research on karst development (speleogenesis) has focused primarily on dissolution, assuming that abrasion and mechanical erosion have either very little or no impact on conduit growth. Although the extent to which abrasion affects the growth of a conduit is unknown, the potential for abrasion by transported sediment begins when the conduit reaches 1 cm in diameter and flow becomes turbulent.

To examine the potential for abrasion, we collected suspended and bedload sediment, water level, and chemical parameters across storm events in a fluviokarst setting in Centre County, Pennsylvania. Smullton Sinks is a series of karst windows in Ordovician limestone in anticlinal Brush Valley in the Appalachian Valley and Ridge of central Pennsylvania. Continuous and grab sampling at one and two hour intervals, during two storms, focused on the physical and chemical agents of erosion and revealed fluctuations in chemistry and sediment load on the rising limb of the hydrograph. Sediment samples and turbidity data indicate a flushing of sediment through the system in response to the storm event, with the most sediment entrained near the beginning of the storm with maximum potential for wall retreat occurring at that time. The composition of the bedload sediment was mostly quartz sand and silt, likely derived from the clastics upstream, with a high potential for limestone abrasion and erosion during times of high sediment flux. The detailed sampling regime allows us to compare the potential for chemical and physical processes through the rising limb of the hydrograph at Smullton.