In the marine confining units (Tertiary) of the Atlantic Coastal Plain, analysis of the mechanically-extracted pore waters from cores indicate elevated concentrations of sulfate (maximum value, 2200 mg/L). This project proposes to determine (a) the source of the elevated sulfate concentrations, and (b) the impact the sulfate concentrations have on water quality in the confined aquifers. The principal investigator and 3 independently-funded collaborators propose to evaluate sulfate transformations and pathways in deep confining beds. Sediments from deep marine (unweathered) confining units will be retrieved as core samples in cooperation with a Continental Dynamics Program drilling project during March through the Fall of 1993. Twenty core samples from one confining unit will be analyzed over the following 18 months. Major analyses include the determination of pore-water chemistry, mineralogy, sulfur and strontium isotopes in solid and aqueous phases, and microbiology. These results will be used to constrain a coupled flow and transport model to assess the relative impact that various processes have on sulfate transport through marine confining units. This proposal reviews the nature and implications of the elevated sulfate concentration issue, describes the rationale for the chosen analytic activity, and outlines the field procedures and logistics. Successful analysis will provide important understanding of sulfate hydrogeochemistry and valuable insight into confining unit effects on aquifer water quality.
