Imaging of Fault and Fracture Controls in the Arbuckle-Simpson Aquifer, Southern Oklahoma, USA, through Electrical Resistivity Sounding and Tomography Methods
Arbuckle-Simpson aquifer in southern Oklahoma, USA, is a major source of water for industrial and municipal use. It is also a major source for spring-fed streams in the area. As part of an ongoing study to map and characterize the Arbuckle-Simpson aquifer, an electrical resistivity tomography (ERT) study and electrical resistivity sounding studies were conducted in Johnston County, Oklahoma, USA, to map the subsurface of a small area of the carbonate aquifer. The main aim of the study was to obtain constraints on the location of near surface faults and fractures and how they control groundwater flow in the study area. The interpreted resistivity section along an N-S profile indicates that the water table in the region is deepening to the south and probably bounded in the north by a south dipping fault. Inverse modeling of 2D electrical resistivity tomography (ERT) data acquired at two adjacent locations within the study area indicate shallow, fractured Arbuckle group rocks saturated with water adjacent to dry rocks. From electrical resistivity mapping results, it is inferred that the Mill Creek block in the Arbuckle-Simpson aquifer is an isolated system, interacting with the northern segment of a silicate-based aquifer through dissolution faults and fractures. 1. Introduction The Arbuckle-Simpson aquifer located near Pilot Springs and the town of Mill Creek, Johnston County, Oklahoma, USA (Figure 1), is a highly fractured carbonate aquifer. This aquifer serves as a primary water source for around 39,000 residents of the surrounding areas. Figure 1: (a) Geographic location of the study area in Oklahoma. (b) Fault structure map of the Mill Creek block, Arbuckle-Simpson aquifer (From [ 13]). Line A-B represents the N-S sounding profile. CD and EF represent the electrical resistivity tomography profile locations. Red dots indicate the locations where electrical resistivity sounding data were collected. Faults F1 and F2 are imaged in the subsurface using electrical resistivity method to understand how they control ground water flow in the region. Well locations from which depth to groundwater level were obtained are shown by blue dots along with well numbers. Blue square indicates the location of Pilot Springs. Conservation of the Arbuckle-Simpson aquifer in south-central Oklahoma has been a recent concern. Citizens for the Protection of the Arbuckle-Simpson Aquifer (CPASA) have made efforts to protect against the depletion of the aquifer and its natural springs and waterways as well as protection against pollution and waste. CPASA has concerns about a
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