Cordilleran systems

Cerro Aconcagua (6,961 m/22,837 ft): The highest peak in the western hemisphere, as seen from a flight between Mendoza, AR and Santiago, CL

I work primarily in Cordilleran systems, in which subduction of an oceanic plate leads to mountain building in the overriding continent.

Beyond just creating topography that’s interesting to look at (and fun to climb), these systems control things like:
– atmospheric circulation and precipitation
– river drainage and sediment discharge
– biodiversity and biome development
– natural hazards, like earthquakes and volcanoes
– deposition of economic minerals and petroleum

If we can better understand how Cordilleran systems grow and evolve, we can better understand their influence on these things that matter to people.

The Andes are Earth’s best modern example of such a system. My Ph.D. and some ongoing work is part of the TransANdean Great Orogeny (TANGO) project, an internationally collaborative and multi-disciplinary project focused on studying processes responsible for variations in the modern crustal thickness and history of uplift of this mountain belt.

By integrating geophysics, structural geology, thermochronology, sedimentology/basin analysis, and other approaches, our overarching goal is to build and test a generalizable model of Cordilleran mountain building.

Tectonic insight from the geologic record

Sunset over a braided river system in the High Andes.

I believe that tectonic insight comes from starting at the outcrop and working up from the grain to the plate scale. My scientific approach is rooted in field geology but integrates diverse analytical methods—including geochemical and isotopic techniques applied to detrital minerals—to better understand the processes of mountain building on Earth.

My ongoing work applies geochemical and isotopic approaches including:

• Zircon U-Pb geochronology: My go-to tool for constraining the age of igneous rocks and provenance of sedimentary rocks.
• Unconventional U-Pb: We can (sometimes) date calcite, or even opal! I’m applying these methods to various types of paleosols to better constrain how foreland basins migrate and how climate changes through time.
• Zircon petrochronology: Trace elements in zircon have immense potential for reconstructing the crustal thickness evolution of magmatic arcs. These data can also enhance U-Pb provenance methods.
• Carbonate δ18O and volcanic glass δD: Applied to minerals formed or hydrated in-situ, these stable isotope techniques provide insight into the evolution of surface topography and climate.
• Thermochronology: Fission track and (U-Th-Sm)/He analysis of apatite and zircon track the pace of exhumation and sediment routing. These data can be inverted to model long-term thermal histories.

I’m actively involved in developing several of these techniques.

I’m working with Mihai Ducea (University of Arizona, USA) and Peter Luffi (University of Bucharest, Romania) to generate a global compilation of zircon T/REE data from Quaternary volcanoes. This will allow us to calibrate zircon geochemical ‘mohometers’ (sub-arc Moho depth sensors) against regions of known crustal thickness, improving our ability to reconstruct the crustal thickness evolution of ancient orogens.

I’m also working with Jason Kirk (University of Arizona, USA) to test applications of calcite and opal U-Pb in paleosols. This approach can facilitate greater temporal precision on the rate of flexural wave migration and climatic changes.