CHEMICAL ANALYSIS OF SOILS DEVELOPED ON THE HENRYVILLE MEMBER OF THE DEVONIAN NEW ALBANY SHALE: THE EFFECT OF DEVELOPMENT TIME ON SOIL CHEMISTRY

The metals and sulfur, which are a significant component of the New Albany Shale, weather readily as metal and sulfur oxides. Consequently, the resulting soil is shallow, acidic and infertile, making it difficult to establish groundcover along roads and areas of new construction adjacent to this rock unit, which can lead to erosion. Another environmental consequence that has not been studied, is the possibility that black shales and their overlying soils may be natural non-point source "pollutants." Previous studies indicate that high metal (Cd, Cu, Mo, Ni, Pb, V, and Zn) and sulfur oxides leach out of the shale when weathered by meteoric water, which impacts the local water chemistry and soil formation. With these environmental implications in mind, this research explores how the metal and sulfur composition of the soil changes with varying lengths of exposure time (10-10,000 years) for the overlying parent rock. Samples from the three Henryville Member black shales and three comparable Borden Formation gray shales with varying exposure times for soil development were examined. Analysis of the parent rock, soil, and surface water samples were conducted, including methods such as sequential extraction for isotopic analysis for sulfur compounds and X-ray fluorescence for metals. Results show the Henryville Member of the New Albany Shale to have 0.8% total sulfur and the Borden gray shale to have 0.05% total sulfur. Sulfate concentration from seeps in the outcrops of the Henryville bed range from 0.06 to 1.36 mg/L. As the length of exposure time for the parent rock increases, so does the concentration of sulfur and metal oxides in the soil. With the better understanding of the soil development and composition, the development of soil supplements will warrant further research.