EVALUATING FAULT LINE ESCARPMENT EXPOSURE IN THE GUADALUPE MOUNTAINS OF WEST TEXAS AND NEW MEXICO

The Guadalupe Mountains are well known for their Permian stratigraphy, but little work has been done on the timing of events that have brought the rocks to surface and shaped the current landscape. The purpose of this study is to fill the gap in geologic history in the Guadalupe Mountains by evaluating exposure ages of rocks along fault line escarpments associated with the extensional forces related to the Rio Grande Rift region. Sample pairs were collected along the western portion of the range where a series of normal fault line escarpments and adjacent sedimentary basins are linked together to form a feature known as the Rim. The sample pairs were taken from the top and bottom of the Rim at the center of five distinct fault segments. Exposure ages calculated from cosmogenic nuclide concentrations will also be computed into rates between sample pairs. Results will be spatially analyzed along the length of the Rim. Due to the proximity to the regional extensional tectonic setting, we expect two different distributions of ages. One outcome is that sample exposure ages young to the north because of the northward spreading of Rio Grande Rift suggested by other studies in the region. A different result related to the extensional setting is that the calculated rates will be greatest in the center of the range due to propagation typical of normal fault systems. Alternatively, if results are the same across the entire area, we would conclude that erosional forces are more effective than tectonic forces in shaping the current landscape. Overall the results of this study will give insight into the tectonic and erosional mechanisms that shaped the existing terrain.