650-m Profiles of Self-potential, Contact Resistance, and Electric Resistance Tomography Measurements Adjacent to Hamilton Creek, Burnet County, Texas, July 2017 - January 2018

This data release consists of three different types of geoelectric data measured along three curvilinear profiles during two separate geophysical surveys completed on July 9, 2017 and January 9, 2018. The data sets include three self-potential (SP) profiles, two spatially-coincident electric contact-resistance (CR) profiles, and two spatially-coincident electric resistance tomography (ERT) tomograms. All profiles were oriented in a northeast-southwest alignment along 650 meters of a natural berm parallel to a surface-water reservoir to the west and Hamilton Creek to the east, in Burnet County, Texas. The profiles along the berm began at the northeastern end at latitude and longitude coordinates (30.716319o N, -98.229917o W) and terminated at latitude and longitude coordinates (30.712362o N, -98.232302o W) at the southwestern end. The resulting data sets contain (a) 265 SP measurements acquired along three separate profiles using a high resolution (1 µV) Agilent U1252 data-logging multi-meter (Agilent Technologies, Santa Clara, Calif.) and two non-polarizing Cu-CuSO4 electrodes, (b) 162 CR measurements along profiles that were spatially-coincident with two of the SP profiles, and (c) 11,328 electric resistance measurements acquired with an IRIS Syscal Pro Switch 96 instrument (Iris Instruments, Orléans, France) along profiles that were spatially-coincident with two of the SP profiles. Additionally, the data sets include global positioning system (GPS) coordinates of the SP, CR, and ERT measurement locations, which were measured with a hand-held Garmin GPSMAP 62s receiver (Garmin Ltd., Canton of Schaffhausen, Switzerland) with two-meter accuracy. The data were collectively interpreted in the companion journal article to (a) identify areas beneath the profiles where preferential groundwater seepage was occurring at the time the surveys were completed, and (b) image dissolution cavities within the subsurface geoelectric structure of the Tanyard and Gorman Formations and the San Saba Member of the Ellenburger –San Saba aquifer to depths of 100 meters (m). The ERT data were interpreted by inversion using the Res2dinv version 4.06 software (Geotomo Software, Kardinya, Australia). The SP data were interpreted by finite-element numerical modeling using COMSOL Multiphysics version 5.3 (COMSOL, Inc., Burlington, Massachusetts) to calculate the self-potential field at the surface of a simplified three-dimensional conceptual model of the field site from a prescribed distribution of electric resistivity determined from the ERT data. The Res2dinv version 4.06 and COMSOL Multiphysics version 5.3 files are included as a part of this data release.

Tags: burnet-county-texas, electric-contact-resistance, electric-resistance-tomography, ellenburger-group, ellenburger-san-saba-aquifer, geophysics, gorman-formation, hamilton-creek, hydrogeology, karst, numerical-modeling, san-saba-member, self-potential, tanyard-formation, usgs-5ab54a7fe4b081f61ab77fdd, wilberns-formation
Organization: Department of the Interior