Collaborative Research: Punctuated versus gradual topographic evolution of Cordilleran-style orogenic belts

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Researchers have long debated how large Cordilleran orogens such as the Sierra Nevada, Cascades and Patagonian Andes develop through time. In particular, two dominant theories have emerged that explain how mountain belts evolve in response to subduction of oceanic crust beneath continental crust. These theories argue for either protracted mountain building, or an episodic model in which topography repeatedly rises and falls due to crustal shortening and removal of lithosphere beneath a subducting arc. The southern Patagonian Andes provides a natural laboratory for evaluating the drivers of long-term topographic change in a classic Cordilleran Orogen. This study aims to quantify the elevation history of the Southern Patagonia Andes for the last 100 million years to test these competing theories for Cordilleran mountain building. Results will improve understanding about how subduction processes shape the Earth's surface and will have broad implications for understanding current and past seismic activity, hazards, and resources. In addition, insight into changes in the ancient environment will shed light on how evolution of large mountain belts influences plants and animals over millions of years. A new Augmented Reality exhibit at the Yale University Peabody Museum will enable countless visitors to virtually explore how mountains influence precipitation and illustrate important concepts in atmospheric processes and geomorphology. Other important societal outcomes include providing support for an early career faculty researcher and broadening participation in an important STEM discipline through graduate and undergraduate recruiting.There has been a long debate about punctuated versus steady orogeny. In particular, two opposing ideas argue for either protracted orogenesis or an episodic "Cordilleran cycle" in which topography repeatedly rises and falls due to crustal shortening and convective removal of sub-arc lithosphere. The large Cordilleran orogens (e.g. Sierra Nevada, Cascades, Southern Andes) all host massive granitic batholiths that formed from the partial melting of the sub-arc mantle and the migration of silicic melts through the upper crust. This project explores the idea that emplacement of granitic batholiths was the primary driver of topography in the Patagonian Andes and other Cordilleran orogens. The proposed work will reconstruct the Cretaceous to recent stable isotopic composition of paleoprecipitation on the windward and leeward side of the Patagonian Andes to test competing hypotheses for the formation of Cordilleran-style orogens. Volcanic glasses, soil carbonates and sedimentary leaf waxes from several well-dated Cretaceous to recent sedimentary basins will be sampled to reconstruct precipitation deltaD and delta18O. Isotope data will be coupled with a numerical atmospheric physics model with high-resolution water isotope fields to constrain the timing and spatial heterogeneity of topographic change in the Patagonian Andes. The isotope-enabled numerical model deals with observed complexities in the behavior of airflow and produces realistic representation of modern distribution of precipitation isotopes on the scale of an orogen. This approach enables separation of climatic and topographic effects on precipitation isotopes and more accurate reconstructions of topographic change.