A Comparison of Limestone Hardness on Weathered and Fresh Surfaces

Abstract

In this study we investigated the hardness of naturally-exposed weathered dip surfaces and freshly exposed dip surfaces in Conococheague Formation near Shepherdstown, WV. The Conococheague Formation is a thick, Cambrian aged limestone with interbedded dolostone. We identified four different variations of limestone in the formation, with ribbon rock being the most common. Using a type N Schmidt Hammer we tested the hardness of the rock at 28 field sites. Fresh surfaces were exposed using a sledge hammer and chisel. We also collected measurements of outcrop exposure, outcrop orientation, and formation strike and dip. A T-test was used to determine if there is a significant difference between the weathered and fresh surface. The T-test revealed a significant difference in hardness does exist between the two surfaces. ANOVA was used to determine if a statistically significant difference exists in hardness between the different lithologies, exposures, dip angles, and orientations. We rejected the null hypothesis for the different lithologies, dip angles, and orientations, suggesting a statistical difference in hardness exists in those characteristics. No significant difference was determined in the different types of exposure.