ANALYZING AND CORRELATING CRETACEOUS-ERA STRATA IN THE EL PASO, TEXAS AREA

Numerous Cretaceous sedimentary deposits exists in the El Paso, Texas area that have been deformed by thrusting and intruded by Eocene andesite. Light gray to nearly black shales occur commonly near the Campus Andesite and the Cristo Rey andesite plutons, while “mystery” strata identified at Three Sisters, Thunderbird, Crazy Cat Mountain, and Coronado outcrops are yellow to light brown in color, at least when weathered. Shales at the Campus Andesite and Cristo Rey plutons have been identified as late to early Cretaceous, while lighter strata at Three Sisters and Crazy Cat have been identified as possibly part of the Late Cretaceous Boquillas formation. The purpose of this project is to obtain a mineralogical “fingerprint” of strata from each of these sites in order to correlate the yellow-colored shales from Three Sisters, Crazy Cat Mountain, Coronado, and Thunderbird to a specific geological formation. I will be using X-ray powder diffraction (XRD) using a PANalytical Empyrean Series 2 XRD at 5-90 degrees 2-theta to determine the mineral composition of strata from several different sites. The strata from the Campus Andesite and Cristo Rey pluton will be used as “reference” strata, especially those from Cristo Rey. I am hoping the “mystery strata” samples will have a similar mineral composition to one or more of the reference samples, so I can definitively tie the unknown strata to a specific geological formation from the El Paso area. Identifying the formation name of the “mystery” strata by correlating it with known strata will aid in the overall understanding of the structural and stratigraphic setting of the andesite intrusions that followed the deposition of the interbedded shale and limestone formations.