SEPARATING CHEMICAL AND PHYSICAL EROSION PROCESSES IN FLUVIOKARST: ABRASION MILL EXPERIMENTS WITH LIMESTONE

Dissolution and abrasion both play roles in eroding carbonate rocks during karst development. While the rates of calcite dissolution have been carefully measured, the importance of abrasion is almost universally neglected. The potential rates of abrasion by storm related siliciclastic sediment flux through karst terrains must be understood in order to both accurately estimate denudation and to properly model conduit system formation.

Abrasion mill experiments using 99.9% methanol to saltate silica sand over limestone disks indicate possible conduit abrasion rates in the absence of dissolution. The disks used are from the Ordovician Centre Hall limestone, a common cave-former in the Valley & Ridge Province. The abrasion mill used consists of a motorized stirrer moving liquid and sediment over a disk of rock placed in a cylindrical container. Higher erosion rates, similar to those observed in fluvial geomorphology studies, occur in water driven experiments. Methanol experiments indicate abrasion plays an important role in erosion of limestone.

Improved understanding of abrasion rates in carbonate rocks will allow for more accurate modeling of landscape evolution in karst terrains and cave development as influenced by sediment flux. To advance this work beyond the lab bench, sediment fluxes in karst must be measured with more frequency and in varying settings.