acase@tulane.edu / Geomorphic features such as fluvial channels and shorelines can act as tape recorders of accumulated tectonic deformation. Because these features can survive in a landscape for up to105 years, the deformation represents tectonic activity over timescales longer than earthquake cycles but shorter than geological timescales. Deformed landscape features can be used to understand the impact of changing tectonic rates on landscape evolution (given information on the tectonic processes involved). Conversely, we can take advantage of how a landscape is expected to evolve and utilize those deviations to explore details of tectonic processes that do not manifest over short timescales (i.e. single earthquakes). Fault slip rate is expected to increase within the overlapping region of two en echelon normal faults, but how increasing slip rate affects the landscape is poorly understood (as discussed in Chapter 1). Additionally, details of this tectonic process that occur over geomorphic timescales are not clearly understood. Chapter 2 of this dissertation explores the impact of fault slip rate increase on fluvial channels during normal fault interaction and linkage. Results of this work show that the landscape responds by increasing channel slope and decreasing channel width before fault segments link. Channel width only shows sustained decreases when a threshold channel slope of about 0.05 is exceeded. In Chapter 3 vertically deformed lacustrine shorelines are mapped along linked faults through the former overlap zones. These results show that despite the presence of linking structures between faults, portions of the former overlapping tips remain active post-linkage for 104 years. Chapter 4 investigates the effect of fault length, spacing, and overlap on the area of relay ramps that drains parallel to fault strike. Twenty-seven sites are examined and results show that for fault lengths below 15 km most of the relay ramp area drains parallel to fault strike, whereas fault lengths >15 km no particular drainage geometry is favored. Data on the overlap/spacing ratio are biased to <2 for faults above ~15 km length. This bias is an inherent characteristic because faults that define low overlap/spacing ratio relays do not link rapidly and are, therefore, preserved within the landscape along large mature fault systems. The results of this dissertation show that, while faults are mechanically interacting, relay ramps are dynamic features that have significant impacts on landscape evolution. Following complete linkage between segments, the relays do not behave as passive structures and can actively deform over significant (>104 years) timescales. Finally, the structural geometry of relay ramps impacts long-term morphodynamics and channel network topology, which directly influences basin sedimentary architecture in extensional basins. / 1 / Michael C. Hopkins

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The dune field at White Sands, New Mexico, shows a well-defined pattern of dunes and interdune areas, as well as spatial variations in this pattern. The purpose of this research is to determine which measured pattern parameters are most consistent across the dune field and to determine the cause of depositional spatial variability. This was accomplished using an airborne LiDAR generated digital-elevation model (DEM) collected in June 2007 and covering 39 km² of the dune field. Properties of the dune field are defined by measurements from three dune populations: 1) 110 randomly selected dunes, 2) 247 dunes along transects oriented in the net transport direction, and 3) 171 dunes from three zones within the field where differences in pattern are visible. Measurements of eight common dune parameters show that the lowest coefficients of variation occur with dune orientation and crestline sinuosity, which largely define the field pattern. Cross-plotting of parameters shows generally poor correlations, which is thought to reflect variation around field-scale means that are comparable to other dune fields globally. Removing the dunes from the LiDAR DEM reveals a depositional substrate with breaks in slope interpreted as three paleoshorelines associated with Pleistocene Lake Otero. The paleoshorelines are antecedent boundary conditions that exert the primary control on spatial variability within the dune pattern. / text