Delineation and description of the regional aquifers of Tennessee; basal sandstone aquifer west of the Valley and Ridge Province

Abstract

The basal sandstone aquifer is believed to underlie most of Tennessee west of the Valley and Ridge Province. It is a Cambrian sandstone that overlies the granites of the Precambrian basement complex. The basal sandstone is a poorly known resource defined only by 14 data points (wells) for the entire state of Tennessee. Because the aquifer occurs at depths of more than 5 ,500 feet below land surface, and is overlain by about 1,000 feet of low permeability Paleozoic carbonates and shales. Consequently vertical recharge to the aquifer is probably very small per unit area. Data from two sampling sites indicate that the basal sandstone aquifer has low porosity and permeability. The concentrations of dissolved solids in water from the basal sandstone aquifer range from less than 10,000 mg/L to more than 200,000 mg/L. It is believed that some of the values above 50 ,000 mg/L are due to contaminants from nearby disposal wells. This aquifer is not being used as a source of drinking water because of its great depth, the presence of shallower sources, suspected low yields, and possible concentrations of more than 10,000 mg/L dissolved solids. (USGS)