Collaborative Research: RUI: Resolving the effects of lithospheric foundering on orogenesis: An example from the southern Puna plateau, Argentina

Purdue University, West Lafayette IN

Investigators

Abstract

Earth’s largest mountain belts and high plateaus are supported by thick, buoyant crust and an anomalous lack of dense lower crust and mantle lithosphere. This project investigates the processes by which the lower crust and mantle lithosphere are removed by detaching and sinking, known as foundering, and the imprint of such processes on the geologic record. This research focuses on the southern Puna plateau, NW Argentina, where multiple lithosphere removal events are hypothesized from geological, geophysical, and geochemical datasets. By generating new geological datasets and numerical modeling results, the project will test the geological evidence and physical feasibility of hypothesized modes of lithosphere removal. The project supports 2 PhD students and at least 7 undergraduate researchers, who will be recruited from underrepresented minority groups, as well as 2 postdoctoral researchers and 3 early-career PIs. The project builds connections between North American and Argentinian scientists via collaboration on the project, running a research field trip with multiple research groups working in the southern Puna plateau, and hosting a numerical modeling short course in Argentina. The themes of the project, including the effects of density on the evolution of mountain belts, serve as the basis for a new annual field trip and retreat to build belonging among students at Utah Tech University (UTU), which is a highly affordable, open-enrollment, undergraduate-serving institution. To test hypothesized foundering mechanisms, this study employs a combination of field and numerical modelling work focusing on the southern Puna plateau, NW Argentina, a case locality for building large mountain belts and plateaus. The Puna plateau preserves a unique sedimentary record of Cenozoic mountain-building, and Miocene lithospheric foundering has long been proposed from geophysical and geochemical datasets. Recent studies suggest foundering as an explanation for anomalous Miocene subsidence/shortening and uplift/extension of the Arizaro and Antofalla Basins, respectively, ~150 km apart. The opposite senses of deformation associated with these potential foundering events suggest that foundering may induce highly diverse modes of deformation in the overlying crust, potentially controlled by the thermal, compositional, or structural state of the crust. This multi-disciplinary project uses geologic mapping, measured stratigraphic sections, and geo- and thermochronology to better constrain the spatial-temporal distribution of deformation and subsidence in the southern Puna plateau, as well as cutting-edge numerical modeling to characterize controls on foundering style or other processes that may have driven deformation in the region. This integrated approach will allow rigorous testing of whether foundering is consistent with observations from the Antofalla and Arizaro Basins, and if so, what crustal parameters control the effects of foundering. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.