Together with colleagues at Western, we are developing an inclusive, accessible alternative to field-based geoscience capstone courses that we’re calling Lab Camp. The project seeks to increase diversity and inclusion in the Geosciences by creating a more accessible alternative to the traditional Field Camp model and it will provide students with opportunities to develop high-impact lab-based research skills that are increasingly valuable in Geoscience professions.
The annual GSA Cordilleran Section meeting is taking place in Portland, OR next week. A number of students from the group will be presenting their work and I’ll be giving a talk. A list and link to our presentations is given below. Hope to see you there!
Student Authored Presentations
- Andra Nordin (B.S.) et al (11-4) Timing of oblique motion of the La Puntilla – La Falda shear zone in northwest Argentina from monazite U-Pb geochronology.
- Wes Johns (B.S.) et al (11-5) Timing and kinematics of intra-arc deformation in the middle crust of the Famatina arc.
- Peter Baker (M.S.) et al (21-7) Age of metamorphism in the Cascades Crystalline Core from garnet Lu-Hf and Sm-Nd geochronology
- Nyle Weldon (M.S.) et al (21-8) Tectonic significance of ductile structures in the Chelan Mountains Terrane, North Cascades, WA.
Non-Student Authored Presentations
- Sean Mulcahy et al (18-8) Flare-up and cessation of the Famatina arc linked to changes in oblique convergence and translation on the Gondwana margin.
Between a Rock and a Hard Plate: How to Save Your Metamorphic Sole
Graduate student Katie Lang describes her research for the general public in Western today! “My research is focused on understanding how metamorphic soles, or the first little slivers of rock that are pulled down between two tectonic plates, are created and ultimately preserved”
Recent Western M.S. graduate, Jeremy Cordova, published the results of his thesis research in the journal Lithosphere. In the paper, titled Subduction initiation and early evolution of the Easton metamorphic suite,northwest Cascades,Washington, Jeremy combined Ar/Ar geochronology with thermometry and detailed microstructural analyses to reconstruct the temperature-time-deformation history of a newly formed subduction zone over ~40 million years. The study documents an impressive history of progressive cooling following subduction initiation via accretion and underplating of distinct litho-tectonic units.
We just published a new paper in Tectonics titled, Early onset of Franciscan subduction. Our study focused on the Franciscan complex of California, which is considered a type example of an ancient subduction zone. The timing of Franciscan subduction initiation, however, has long been debated, resulting in conflicting models for the tectonic history of western North America. The study was unique because we dated the mineral zircon preserved as inclusions within garnet formed during the early stages of subduction. We also dated zircon outside of garnet formed during a younger event within the subduction history. The zircon inclusions within garnet yielded an age of ~176 Ma, whereas the zircon outside the garnet had a younger age of ~160 Ma. These ages require that Franciscan subduction began by 180 Ma, significantly older than commonly believed and constrain models for the tectonic evolution of the western North American margin. Data used in the paper and supplemental material, as well as, python code to construct some plots within the paper are available on Github and Zenodo.
GSA in Seattle is drawing near and I’m excited to take part in a number of student authored paper this year. I’m also chairing a session on the tectonic evolution of convergent margins view through the lens of the Andean margin. I’m looking for students for the upcoming 2018-2019 academic year to work on the structural and metamorphic evolution of subduction zone and arc processes. If you’re interested please come and find me at any of the below presentations or send me an email to arrange a time to meet.
Student authored presentations
- Cordova et al. (Sun, 57-6), Initiation and early evolution of a subduction zone: T-t-D history of the Easton Metamorphic Suite, northwest Washington State.
- Webber et al. (Tues, 213-11), U/Pb of the Sierra de Maz: Implications for the timing of terrane accretion and translation along the western margin of Gondwana.
- Tholt et al. (Tues, 291-7), Metamorphic evolution of the Sierra de Maz: Implications for the timing of terrane accretion along the western margin of Gondwana.
- Houlihan et al. (Tues, 291-8), 40Ar/30Ar geochronology and kinematic analysis of the Sierra de Maz: Implications for the timing and orientation of deformation on the Paleozoic margin of western Gondwana.
Non-student authored presentations
- McClelland et al. (Tues, 291-6), Detrital zircon characterization of metasedimentary units of the Sierra de Maz, Western Sierras Pampeanas, Argentina.
- Roeske et al. (Tues, 213-12), The link between Ordovician-Early Devonian terrane accretion and translation and the sudden arc flare-up and cessation of the Famatina arc.
- Mulcahy et al. (Tues, 213 and 291), Understanding the interplay of structural, metamorphic, and magmatic processes in the evolution of convergent margins: Lessons from the Proterozoic to present-day Andean margin. Invited speakers include:
We just published a new paper in American Mineralogist, by lead author Marie Jackson. The paper, Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete, explored seawater interaction with zeolite minerals to produce Al-tobermoreite, a zeolite mineral that significantly increases the durability of ancient Roman cement compared to modern day materials. The paper received considerable press with articles by the Gaurdian, Nature News, and the Washington Post, among others. My contribution came from electron probe microanalysis (EPMA) of phillipsite and Al-tobermorite and an analysis of published compositions. The paper is open access and all of the data are available in the supplemental material. In addition, the EPMA data and code to generate related figures are available on Github and archived on Zenodo.
Next week is AGU and I’m excited to take part in two student presentations. Shaina Myers, an undergraduate student at Western, is presenting the results of her senior research on lawsonite stability and REE chemistry from the Franciscan subduction zone. Michael Kenney, a recent M.S. graduate at UC Davis, is presenting his thesis research using U-Pb dating of titanite to try and understand a protracted metamorphic history in a collisional orogen of northwest Argentina.
Shaina Myers’ poster is on Wed from 08:00-12:20
T31E-2962: Retrograde lawsonite formation in the Franciscan subduction complex
Michael Kenney’s poster is on Monday from 13:40-18:00
V13D-2888: Differentiating metamorphic events in a polymetamorphic terrane using Zr-in-Ttn thermometry and titanite U-Pb geochronology
Andy Tholt is starting at Western this fall. He and I are headed to Argentina in August to test models for the metamorphic evolution of the Famatina margin. Andy earned his B.S. degree from U.C. Berkeley and then spent a year working at the Berkeley Geochronology Center. I’m really excited to have Andy join on as my first graduate student.
Western graduate student Jeremy Cordova was awarded and EarthScope AGeS Program grant. Jeremy is working with Liz Schermer and I to date the initiation and duration of subduction metamorphism in the Northwest Cascades. Jeremy will be working with Laura Webb in UVM Noble Gas Lab to date high pressure mineral assemblages associated with subduction.