Review of the general geology and solid-phase geochemical studies in the vicinity of the Central Oklahoma aquifer

Abstract

The Central Oklahoma aquifer is the principal source of ground water for municipal, industrial, and rural use in central Oklahoma. Ground water in the aquifer is contained in consolidated sedimentary rocks consisting of the Admire, Council Grove, and Chase Groups, Wellington Formation, and Garber Sandstone and in the unconsolidated Quaternary alluvium and terrace deposits that occur along the major stream systems in the study area. The Garber Sandstone and the Wellington Formation comprise the main flow system and, as such, the aquifer is often referred to as the 'Garber-Wellington aquifer.' The consolidated sedimentary rocks consist of interbedded lenticular sandstone, shale, and siltstone beds deposited in similar deltaic environments in early Permian time. Arsenic, chromium, and selenium are found in the ground water of the Central Oklahoma aquifer in concentrations that, in places, exceed the primary drinking-water standards of the Environmental Protection Agency. Gross-alpha concentrations also exceed the primary standards in some wells, and uranium concentrations are uncommonly high in places. As a prerequisite to a surface and subsurface solid-phase geochemical study, this report summarizes the general geology of the Central Oklahoma study area. Summaries of results from certain previously reported solid-phase geochemical studies that relate to the vicinity of the Central Oklahoma aquifer are also given; including a summary of the analytical results and distribution plots for arsenic, selenium, chromium, thorium, uranium, copper, and barium from the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) Program.