LONG-TERM TECTONIC DEFORMATION OF THE SOUTHERN RIO GRANDE RIFT

The goal of this research is to measure the long-term uplift of ranges along the Southern Río Grande Rift. In most settings, extensional ranges are flanked with alluvial fans and bajadas that create an irregular mountain front. In the southern Río Grande Rift, the sediment from the river buried the alluvial fans and juxtaposed horizontal playas and low-gradient floodplains with the bedrock of the mountains. This presents an opportunity to document long-term deformation of these low-relief surfaces. We compare the flanks of the Franklin Mountains with the slope of the plain on the western side of the Río Grande valley. The terraces reflect modern range topography, being highest in the center of the range and with offset decreasing toward the flanks. The terraces also reflect the westward tilt of the range with the eastern terraces uplifted higher than the western terraces.