Groundwater Salinity within the Mt. Simon Sandstone in Illinois and Indiana

Borehole Mt. Simon

ISGS Circular 582 by E. Mehnert and P. Weberling

In the Cambrian-age Mt. Simon Sandstone, salinity varies widely from less than 1,000 mg/L in northern Illinois to more than 250,000 mg/L total dissolved solids (TDS) in southern Illinois.  Salinity is an important characteristic of groundwater and is quantified by measuring the total dissolved solids.  With recent interest in geologic carbon sequestration, new wells have been completed in the Mt. Simon and new TDS data have been collected.  These new TDS data, along with other available data from Illinois and Indiana wells, were compiled and plotted to generate an updated map of salinity in the Mt. Simon Sandstone (Figure 1).