Evaluating Fault Line Escarpment Exposure in the Guadalupe Mountains of West Texas and New Mexico

Abstract

The Permian stratigraphy of the Guadalupe Mountains is well-known due to the impeccable exposure of Permian strata along distinct escarpments that define the boundaries of the range. Even though the Permian strata have been closely examined to understand the associated petroleum reservoirs in the adjacent Delaware basin, little work has been done on the escarpments that expose the well-known rocks at the surface by way of tectonic and erosional processes. The development of escarpments are directly affected by multiple processes that create the landscape, and can be used as a tool to temporally and spatially constrain tectonic and erosional activity (Phillips et al., 2003). Distinct fault escarpments define the western margin of the range and provide an interesting location to study interactions between climatic, tectonic and erosional processes using bedrock exposure near the Rio Grande Rift. In-situ produced cosmogenic nuclides, 10 Be and 36 Cl, are used as tools to effectively measure the exposure of bedrock surfaces along western escarpments in the Guadalupe Mountains. In total, ten bedrock samples were collected from the top and bottom of five different mapped fault segments to measure exposure ages and erosion rates along the western boundary of the mountain range to learn about the geomorphic history of the region. The cosmogenic nuclide concentrations measured in these rock samples were used to calculate exposure ages, which resulted in Pleistocene exposure ages. Results also indicate the landscape achieved steady-state conditions, suggesting that the mechanisms driving erosion in this tectonic and climatic regime have remained similar over the timescale represented. Spatial comparison of the age results show a general increase in exposure age from south to north. Another trend observed in the data is a tendency for younger exposure ages at the top of the escarpment than at corresponding bottom locations. Furthermore, five out of ten samples exhibit exposure ages that correspond to the last glacial maximum, including four locations in the southern portion of the range, three of which are top samples. Local climate variation due to elevation change along the escarpment is a key component in erosional processes taking place because temperature decreases as elevation increases. The increase in elevation increases precipitation, wind velocity, and erosional processes, resulting in younger exposure ages at the top and backward migration of the escarpment. The greater number of faults in the southern portion of the range may contribute to younger exposure ages, however, the number and location of samples limit the information necessary to fully interpret and understand all the geomorphic conditions in the region. The Guadalupe Mountains prove to have an interesting history incorporating some components of climatic, tectonic, and erosional process interactions that shaped the landscape. Continued work on surface processes throughout the region is necessary to better constrain the geomorphic history of the Guadal...

Evaluating Relationships Between Rock Strength And Longitudinal Stream Profile Morphometry In The Southern Guadalupe Mountains, Texas

“…Pines Springs Canyon contains one major channel with several smaller tributaries. Faulting does occur near the lower portions of the main channel, but in association with quaternary alluvium (King, 1948 (Happel et al, 2017), likely due to arid or semi-arid climatic conditions. Therefore, active incision and sediment transport most likely occur in upper reaches of stream segments and during low-frequency flood events (Reid et al, 1998).…”