EVALUATING RELATIONSHIPS BETWEEN ROCK STRENGTH AND LANDSCAPE EVOLUTION IN THE SOUTHERN GUADALUPE MOUNTAINS, TEXAS

The geomorphology of longitudinal bedrock rivers may supplement speleological research that aims to constrain Miocene to Pliocene tectonic and climatic histories of the Guadalupe Mountains. Anomalous hillslope gradients were identified within these mountains and are speculated to have formed due to differential rock strength, tectonics, or local faulting. These speculations are unsupported, however, and require further investigation to confidently justify which mechanisms likely control the local geomorphology. Resampled 10m DEMs were constructed to model the Guadalupe Mountain landscape and perform topographic analyses that identify spatial distributions of erosional and other geologic features such as rock-type and faulting. Twenty-four locations were sampled in McKittrick and Pine Springs Canyons for Schmidt hammer rebound values and rock mass strength (RMS) analyses. Bedrock channel and hillslope gradients will be coupled with rock strength analyses to locate and disseminate how, where, and to what degree geologic units control erosion and landscape evolution.

Statistical T-tests will be performed to correlate bedrock channel gradients and other landforms with rock-strength values from Schmidt hammer and RMS analyses. Anomalous convexities in longitudinal river profiles associated with statistically different rock-strengths are considered features related to differential rock-strengths and reflect quasi-equilibrium conditions. Conversely, anomalous convexities in bedrock river channels that do not correlate with statistically significant changes in rock-strength may have formed due to other processes independent of rock strength. These processes include tectonic uplift or subsidence, local faulting, global or local climate change, and random landscape processes. Each of these processes are related to some form of disequilibrium and reflect regional transient landscape evolution. Understanding which forces are driving landscape evolution in these mountains will determine if the American southwest is currently recording Miocene to Pliocene tectonic and climatic history and aid in directing further research.