October 2026 Meeting of the Chapter

Global seismic imaging models reveal the presence of seismically fast, relatively thick regions of lithosphere beneath the stable cores of continents, commonly referred to as cratons. These deep “cratonic keels” are thought to be cold, strong and highly viscous, properties that have allowed them to remain stable for billions of years. While global seismic models suggest that cratons are relatively homogeneous, other observables such as geologic mapping, thermochronological petrological studies, and regional geophysical studies, point to a much more complex history within individual cratons. These varied, and sometimes contradicting results, have made it difficult to reach a consensus on how cratons formed and evolved.

The Wyoming Craton provides an excellent natural laboratory for improving our understanding of craton formation and evolution. Numerous exposures of basement rocks, along with targeted geophysical studies, allow us to investigate subsurface structures not resolvable in global surveys. Temporary seismic arrays, including the CIELO experiment, were deployed to better understand the evolution of the Wyoming Craton and to better define its boundaries. While geophysically and geologically inferred boundaries agree in parts of the craton, the location and nature of the eastern boundary have proven difficult to determine because of significant sedimentary cover.

Using improved station coverage from CIELO, along data from other experiments, we have completed a suite of seismic analyses which allow us to characterize changes in the structure of the crust and upper mantle beneath Wyoming Craton. Our results reveal a well-defined change in seismic properties beneath the Powder River Basin. We hypothesize that this feature is the result of suturing that occurred prior to the Proterozoic and before the Wyoming Craton was fully cratonized. This hypothesis differs from previous suggestions that the seismically observable feature marks the eastern boundary of the craton. Instead, it is consistent with geological evidence suggesting that the Black Hills were already part of the Wyoming Craton prior to the Trans-Hudson Orogeny in the Proterozoic.

I am an Assistant Professor in the Department of Earth and Planetary Sciences at the University of California, Riverside. My research focuses on the tectonic and dynamic evolution of the Earth’s continents and interior. My research program at UCR focuses on using seismic waves generated by distant earthquakes to image deep into the Earth’s interior, a technique conceptually similar to medical CT scans. The seismic data are collected by seismometers that are either permanently installed or temporary deployed across a region of interest. The primary goal of my research efforts is to better understand how the continents initially formed, the physical and chemical properties that have allowed them to endure, and their relative strength over time.