EAR-PF: Evaluating the forearc response to shallow subduction: a geo-/thermochronologic investigation of the world's type exhumed shallow subduction complex, southern California

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Dr. Alan D. Chapman has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at Stanford University. This work aims to quantify crustal fluxes associated with shallow subduction by applying modern geo-/thermochronologic techniques (e.g., U-Pb geochronology, (U-Th)/He thermochronology, and fission track analysis) to the best recognized exposure of an ancient shallow subduction system on Earth, located in southern California. The resulting dataset will be used to address: 1) regional issues pertinent to the North American Cordillera, most notably the relative importance of subduction erosion versus trench-linked transform faulting during the Late Cretaceous to early Tertiary Laramide orogeny and 2) global questions centered on processes by which crustal materials are recycled during shallow subduction (e.g., tectonic erosion, delamination, underplating, and magmatism).The proposed research will directly engage faculty, postdocs, researchers, and students of active geo-/thermochronology and subduction zone tectonics groups at Stanford. The results of this investigation will provide new insights into subduction dynamics, addressing questions of global importance regarding the life cycle of shallow subduction and the mechanisms of mass transfer between the crust and mantle. This project will deliver a wide range of data that address fundamental questions posed by the Subduction Cycles and Deformation initiative of the GeoPRISMS Program, the most pertinent of which concerns the origin and evolution of the continental crust. The proposed education plan involves: 1) teaching a seminar on the topic of shallow subduction followed by a field course to Big Sur, California; 2) mentoring a high school intern through the Stanford High School Internship Program; and 3) maintaining an active outreach program through the GeoKids cooperative with the U.S. Geological Survey.