YOUNG SCIENTIST AWARD (DONATH MEDAL): DECIPHERING INTRACONTINENTAL DEFORMATION THROUGH FIELD-BASED INVESTIGATIONS

Plate tectonic theory does not adequately describe intracontinental deformation because the buoyant, weak, and compositionally/mechanically heterogenous continental crust readily decouples from the mantle, thus leading to distributed zones of deformation that stretch far into plate interiors. This is exemplified by the >2,000-km-wide Himalayan-Tibetan orogen, >1,500-km-wide Laramide orogen, >1,000-km-wide San Andreas-Basin and Range transtensional system. The style and extent of intra-plate deformation is controlled by the thermal state and mechanical strength of the continental lithosphere. Here I discuss some examples of how holistic investigations of intra-plate deformation based around field observations integrated with geophysical and analytical data improves our understanding of continental tectonics. First, study of the unique geometry of the Cenozoic Himalayan-Tibetan shows that it reflects plate convergence across a heterogenous lithosphere that was preconditioned via protracted orogeny over the past ~1 Gyr with preceding subduction-collision and mantle plume events. Although the development of the Tibetan plateau is considered the archetypical result of continent-continent collision, its geologic history is the culmination of unique geologic events and thus, its evolution may not be readily transferrable nor necessarily scalable to other collisional orogens. Second, in the North American Cordillera, reconstruction of dissected exposures of the mid-upper crust constrains the thermal state and rheology of the Cordilleran hinterland crust, which was exceptionally hot in the Late Cretaceous. These observations imply a weak and mobile lower crust that decoupled from the mantle, which explains the lack of Laramide-aged crustal deformation in the hinterland and demonstrates the influence of basal traction to drive Laramide deformation far within the plate interior. I dedicate this talk to An Yin, a larger-than-life mentor who had an incredible influence on so many in the field of continental tectonics.