Field organizers: Madison Myers, Montana State University; Christine Regalla, Northern Arizona University; Cal Barnes, Texas Tech, Geoff Abers, Cornell

Education Leads: Samuel Cornelius Nyarko, Stuart Kenderes, Indiana Univ-Purdue Univ Indianapolis

Project team: Shubham Agrawal, U South Carolina; Marge Belcasto, Portland State University; Catalina Castro, Universidad de Concepción Chile, Alfredo Esquivel, Millennium Institute on Volcanic Risk; Cameron Essex, U Wisconsin-Milwauke; Lalo Guerro, Oregon Department of Geology and Mineral Industries; Hiroko Kitajima, Texas A&M U, Kelly Lascano, Universidad Central del Ecuador; Chloe Marks, U Michigan; Diana Mindaleva, Tohoku University (Japan), Jiale Mou, Rice U; Ekaterina Rojas Kolomiets, U South Carolina; Arnab Roy, U Idaho; Maria Tilman, Portland Community College. 

This past July, seventeen interdisciplinary geoscientists from around the world, selected from a competitive 144 person applicant pool, descended on Mount Ashland, located in southwestern Oregon. The aim: participate in a collaborative SZ4D community sample and data collection campaign. Despite challenges involving a cyberattack on the airlines, rampant wildfires, and questionable breakfast burritos, the participants were eager to take on the field and learn from one another. The field effort focused on the collection of integrated geologic and geophysical data from the Ashland Pluton, an exhumed, Jurassic, arc-related pluton that preserves magmatic and tectonic records that when understood, can serve as proxies for processes occurring beneath active volcanoes today. We spent five days formulating and executing an integrated field data collection plan.

But fear not - it wasn’t all work!  We also bookended the data campaign with road trips to explore the spectacular local geology including Giiwas (Crater Lake - Mount Mazama volcano), exhumed ophiolites (uplifted ocean floor), observed evidence for active deformation in river terraces (something to look for when you raft the Rogue!), the impacts of tsunami inundation in Crescent City, and the magic of large redwoods inhabited by Ewoks.

Under the guidance of our resident pluton expert Cal Barnes, our group of structural geologists, petrologists, and seismologists turned their eyes to the same pairs of outcrops. Our goal? Observe and question the geology, and over the course of several days, find ways to collect meaningful, interesting and interrelated datasets. We taught each other about our fields, the questions we found interesting, and discussed (frequently) how our fields might overlap; through this experience we achieved the goal of building a new kind of geo-experience involving integration and collaboration across multiple sub-disciplines. 

At the pluton, intense conversations over several days led to a realization that some very creative approaches could be taken at the outcrop-scale to ask cutting-edge research questions. We saw that magmatic foliations, a rock fabric marker of magma mush deformation under an applied stress field, varied greatly between outcrops, and we hypothesized that these fabrics could produce anisotropy in seismic wave speeds. We therefore designed a joint data collection campaign to test this idea. Geologists could document the intensity, and measure the orientation, of that fabric in outcrop exposures, as well as the number and orientation of stretched enclaves, joints and other hallmarks of rock deformation. Seismologists could measure seismic wave speed and anisotropy on top of the exact same outcrop  – taking traditional refraction gear and placing the geophones in a circle. And petrologists, structural geologists, and rock deformation specialists could sample the rocks to determine the physical properties that produce seismic anisotropy. 

After we developed our plan, it was hammer time! Rocks on the outcrop, and a metal plate on top, felt the brunt of impact as everyone attacked the field area. We had folks that had never experienced hitting a rock, or hitting a metal plate, exchanging places and exploring new lines of work. And best of all, it worked! In near-real time we found that strongly foliated rocks have 25-30% seismic anisotropy with a fast direction that exactly lined up with the geologic fabric measurements, whereas the site without strong foliations had more isotropic velocities.

Our field successes allowed us to craft an AGU abstract, accomplished in a record one day out of the field. Locals were so impressed during our Ashland library community talk that they even proposed a new national holiday, National Foliation Day. By the end, we were no longer just participants chosen to push interdisciplinary field research into a completely new direction, we were colleagues, co-mentors, and friends.

Our group is continuing this work via post-field analyses, involving seismic data processing, thin section petrography, and laboratory measurements of seismic anisotropy to evaluate what rock properties best explain this observed anisotropy. Until then, our team can take pride in the knowledge that their efforts provides proof-of-concept that near-surface seismic anisotropy may be an effective new tool to quantify pluton fabrics, and that when integrated with petrologic analysis, can be used to evaluate magma emplacement and deformation processes at depth. Want to learn more? We will see you at a conference near you (starting with AGU)!