2020-05-01 – 2023-04-30
Lead Principal Investigator:
Recent tectonic models of the southwestern US Cordillera suggest that a flattening slab, coupled with the subduction of an oceanic plateau (the conjugate Shatsky Rise: CSR) in Late Cretaceous ? Eocene time (90-40 Ma) led to subduction erosion, extension and associated paleogeographic change. This 3-year research project will test the hypothesis that extension and gravitational collapse was widespread across southern California during this time and led to the development of supra-detachment basins and exhumation of a relict subduction complex (PORC schist). This study targets the Goler and Maniobra Formations located east of the San Andreas Fault in the Mojave Desert area of southern California. Strata consist of terrigenous and marine rocks uniquely located along the northern and southern margins of the Mojave Desert, where ocean plateau subduction is interpreted to have occurred. We hypothesize that the Goler and Maniobra Formations were deposited in supra-detachment basins formed just after the proposed plateau subduction. To test this hypothesis, we propose new mapping of stratigraphic and structural relationships within these Formations combined with detrital zircon analysis and magnetostratigraphy to define the onset of basin formation and test the compatibility of these strata with deposition in extensional basins related to exhumation of the PORC schist subduction complex. The results will refute or support models for tectonic collapse of the southwestern Cordillera in the wake of CSR subduction and provide precise age-control for these broad tectonic changes. Moreover, this project will provide unique opportunities for the participation, training and education of ~50 undergraduates from under-represented groups in active STEM research. This project will form the basis for 15 undergraduate theses and will provide financial support for 2 MS students at CSUN. Another ~45 students will participate in field research related to this project as part of an annually-taught Sedimentology & Stratigraphy course required of majors. Data products from this study (e.g. measured sections, paleocurrents, magnetostratigraphy, zircon U-Pb-Hf data), together with a 3D photo library, will be used to create a Google Earth?based virtual field trip module with associated student assignments. The module will be made available as a teaching tool to the geoscience community via the online public access Science Education Resource Center (SERC). Detrital zircon data will be archived in the online Geochron database and paleomagnetic data will be archived in the MagIC database. Field data will be collected using the Strabo app and made publicly available at the end of the project.