Collaborative Research: Elucidating the geologic record of Late Paleozoic subduction initiation along the southwestern margin of Laurentia, southern California and Sonora, Mexico

The principle aim of this project is to document the timing and response of the southwestern Laurentian margin to the initiation of subduction during late Paleozoic time. Although the recycling of lithosphere at subduction zones is a fundamental part of plate tectonic theory, the manner by which subduction zones initiate is a poorly constrained process, largely because there are few modern examples and ancient examples are largely not recognized or well preserved. Unique sequences of sedimentary and volcanic rocks exposed in southern California (El Paso Mountains region) and northern Mexico (Carborca Block) will be investigated in order to better understand how subduction inception is recorded in stratigraphic successions and how the paleogeography of continental margins evolves in response to the onset of plate convergence. We propose that continental margin successions recording subduction initiation will have predictable deepening and shallowing trends and distinct changes in sand composition and detrital zircon provenance through time reflecting the changing paleogeography of source regions. An additional geochemical and geochronologic investigation of volcanic sequences and coeval intrusions will be used to constrain the timing and petrogenesis of magmatic products, which we suggest will record conditions unique to cold, nascent continental arc settings. Results of this project may contribute significantly to global models of the birth and development of subduction zones. This project is a multi-disciplinary and collaborative effort between researchers at California State University - Northridge and Northern Arizona University, which are both minority-serving institutions. In addition to the science goals of the project, this research will provide training and mentorship for masters level and undergraduate students and promote the involvement of underrepresented groups in STEM research. Sample collections and study results will be used for the development of resources for teaching, community outreach, and further research.