PREDICTING PALEOSTRESS ORIENTATIONS FROM FRACTURE PATTERNS IN THE CHRISTMAS MOUNTAINS

The Christmas Mountains caldera complex developed approximately 42 Ma ago. The complex preserves a unique variety of geologic features due to different tectonic and volcanic activities: Ouachita Orogeny, Laramide Orogeny, Tertiary Volcanism, and Basin and Range tectonics, and Rio Grande rifting. Pre-field observations show eighty-two fractures oriented with a mean vector of 347.5 ˚ ± 18.5˚, five faults were oriented with a mean vector of 348˚ ± 60.8˚, and two dikes ≈1.6 km long are oriented ≈020˚.

The goal of this research is to study the complex variations of lineaments, classify as dikes, fractures, and faults using remote sensing, GIS, and aerial photography. The methods used in the classification of features combined remote sensing mapping using Google Earth Pro, and ESRI ArcMap. Faults were determined based on the presence of visible offset using 3D map view in Google Earth Pro.

We predict that the patterns of structures present within this local study area may contribute to further define the paleostress associated with the tectonic history of the Trans-Pecos region. Based upon observation of satellite imagery, we predict some fractures are limited to lithology, however, some are observed to cut through different domains. The most common visual pattern within fractures shows an orientation of ≈310˚-320˚with perpendicular fractures oriented ≈050˚ suggesting two different tectonic events. The lineaments predicted to be faults cut and offset units. The offset across faults averaged ~40 meters and were examined in ArcMap using a digital elevation model to corroborate offset units. Dikes were determined based on their long-range linear trend and weathering discoloration.

The objective of this study is to utilize the patterns of fractures and orientations of faults and dikes to predict the paleostresses that contributed to the broader deformation of the region. Field mapping of structures and lithologies will ground truth remote sensing interpretations. A geodatabase will compile the interpretations and field data to assist in a regional study of the Christmas Mountains.