ANALYZING THE GEOMAGNETISM OF THE THREE SISTERS OUTCROP LOCATED IN EL PASO, TEXAS

The purpose of this study was to gain an understanding of the underlying rock composition of the Three Sisters outcrop located in El Paso, Texas by conducting magnetic tests. Using a Proton Precession Magnetometer, magnetic readings were taken along multiple 100 meter lines at one meter intervals in order to find the contact between the andesitic pluton and the Cretaceous strata that the pluton once intruded. During the process of data interpretation, the magnetic readings across a portion of the hills that were previously mapped as andesite were not consistent with expectations. Possible explanations for these trends in data could be mineralogic changes across the andesite, variations in the thickness of the andesite intrusion, or outcrops of completely different rock units that were previously incorrectly mapped as andesite. To gain more insight, other geophysical and geological studies were incorporated into this project, such as conductivity measurements to compare against the magnetic readings and mineralogic analysis of andesite samples. Four andesite samples were collected from what we assumed to be exposed outcrops among the three hills to conduct mineralogic analyses in order to obtain magnetite percentages within the various andesite samples. The collected data supports the conclusion that the andesite pluton of the North Hill is smaller than previously mapped to be, the relative magnetic high readings indicating andesite were influenced by large pieces of andesitic drift rather than outcrops.