The basal sandstone is a poorly sorted, well indurated sandstone, which lies below the Conasauga Group and above the Precambrian crystalline rocks. It is an unknown resource defined by limited data, with only 14 data points (wells) for the entire State of Tennessee. The basal sandstone is thought to occur throughout most of the State west of the Valley and Ridge province at depths of generally more than 5,500 feet below land surface. The basal sandstone probably does not receive significant vertical recharge because the sandstone is overlain by such a thick sequence of flat-lying, low-porosity lower Paleozoic carbonates and shales. Data from two sites indicate that the rocks of the basal sandstone have relatively low porosity and permeability.
The concentrations of dissolved solids in water from the basal sandstone range from less than 40,000 milligrams per liter to more than 200,000 milligrams per liter. The basal sandstone is not being used as a source of drinking water because of its great depth, the presence of shallower sources of drinking water, and possible concentrations of more than 10,000 milligrams per liter dissolved solids throughout its area of occurrence.