2:45 PM - 3:00 PM
[HGM03-05] Isolating lithologic controls on landscape morphology in the Guadalupe Mountains, Texas, USA
Keywords:Geomorphology, Channel Steepness, Lithology, Digital Elevation Model, Topographic Relief, Rock Erodibility
We first compared the datasets using the Kruskal-Wallis method for hypothesis testing and found that significant differences exist between the lithologic groups, suggesting potential correlation among channel steepness and lithology. To better evaluate the different rock units, we used published unit descriptions to develop a simple and a semi-quantitative ranking of relative rock erodibility. This ranking system assumes units with evaporates are softer and units limestone and dolomite are harder, with other units, including sandstone and shale in between. This ranking system also accounts for other factors such as relative bed thicknesses, as well as spatial heterogeneity and variety of rock type within a given unit. These objective ranks were correlated with average steepness indices for each of the 23 lithologic units, giving an R2 value of approximately 0.44, suggesting that steepness provides some predictive ability in determining rock properties. Finally, we show that some of the variability in the relation between steepness and relative erodibility can be explained by effects of stratigraphic order.