SLIP HISTORY OF THE DIXIE VALLEY FAULT SYSTEM (NV, USA) BASED ON INTEGRATION OF GEOMORPHOLOGIC, STRATIGRAPHIC, AND STRUCTURAL DATA

Knowledge of last reactivation age of faults in the western Basin and Range Province is key to understanding the recent evolution of the Pacific-North America plate boundary. The Dixie Valley fault system (DVFS) is an important and still active normal fault in this region, but its slip history is not well known. Our goal is to determine the history of vertical displacement along the fault at the million-year time scale.

We used well data from the Dixie Valley geothermal field and existing geologic maps to calculate offsets of geologic units. Tectonic events and their ages were determined from analysis of knickpoint migration in the Stillwater Range. We then combined basin data and knickpoint migration to obtain a detailed vertical displacement history.

Our analysis shows that the age of faulting initiation on the modern DVFS is most likely between 13 and 7 Ma. The total vertical displacement of the geologic units is between 3 and 3.5 km. If we assume an average erosion rate of 0.04 – 0.05 m/ka, the maximum vertical displacement rate (between 0.8 and 1.5 mm/a) occurred between 0.5 and 2 Ma and resulted in about 1 km of vertical displacement. Finally, the age vs. distance profile of the Stillwater Range crest is tapered at both ends, as expected for a propagating range-bounding normal fault, but it also has two maxima that match the deepest parts of the Dixie Valley sedimentary basin. This indicates that the present-day DVFS likely started out as two separate strands that connected within 2 - 3 million years of inception.