A STUDY OF ALEXANDER CAVERNS (MIFFLIN COUNTY, PA): WATER CHEMISTRY AND STRUCTURAL GEOLOGY

Honey Creek emerges from Alexander Caverns and flows through the Benner and Loysburg Limestone Formations near Milroy (Mifflin County), Pennsylvania. The water chemistry of the creek was tested both within and just downstream of the cavern. In-situ analyses of pH, conductivity, and dissolved oxygen were taken at ten sampling sites. Alkalinity and acidity analysis were conducted on filtered samples within a few hours of collection, and turbidity was determined on non-filtered samples prior to filtering for each of the ten sites. Samples were also tested for eleven different metals (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) using ICP-OES. Analysis of anions and Group I and II cations was performed using ion chromatography. Water samples were taken from the cave stream on three dates: May 19, July 21, and November 17, 2012, in order to determine if there are any changes in water chemistry related to discharge. Drip samples from the cave ceiling were also analyzed and were consistently much higher in pH, conductivity, alkalinity, and dissolved potassium, calcium, magnesium, barium, and arsenic, although the concentrations of these dissolved species did vary over time. We performed rock-water interaction experiments to test for a direct correlation between rock type and water chemistry. Joint and fracture orientations of the limestone were measured both inside the cavern and in two nearby quarries located within the Benner and Loysburg Limestone Formations. Vertical to nearly vertical orthogonal joint sets were oriented at 045-225 and 135-315.