Recent deformation across the Basin and Range: from kinematics to mechanics

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I request funds to investigate the growth of mountain ranges across the Basin and Range Province, Nevada. At isolated locations across this province there is evidence that activity on faults driving the uplift of these mountain ranges has increased within the last 3-4 million years, however it is unclear if this increased fault activity is widespread or localised. Understanding the nature of this activity will reveal the processes that are driving this increased activity. I plan to use two types of data to investigate these processes. First, I will use a "top-down" approach, based on topographic signatures of the landscape to identify when fault activity changed at individual mountain ranges. The principle behind this approach is that when fault activity increases, rivers steepen and cut down, and this incision can be measured using digital elevation models. Second, I will combine these observations with a "bottom-up" approach, based on geochemical methods that tell us about the thermal history of rocks as they approach Earth's surface through erosion. As rocks approach the Earth's surface due to erosion, they cool and this cooling is preserved in the concentration of helium atoms that are produced by radioactive decay. At high temperatures, helium is lost through diffusion, but as temperatures decrease, the rate of diffusion also decreases and helium is retained. We can measure the amount, and distribution of helium, within a single crystal of apatite and use this to infer the cooling history of a rock as it approaches the surface. By combining the "bottom-up" approach and "top-down" approach it is possible to estimate fault activity with increased accuracy, but also gain an insight into the processes of erosion. Furthermore, the abundance of digital elevation data allows us to tackle many ranges at the same time and therefore, measure the extent of increased fault activity. Finally, by synthesizing these datasets and observations using numerical models of how erosion and tectonic processes interact, we can understand the forces driving fault activity, and potentially predict fault activity in the future.