Collaborative Research: Quantifying Paleotopography and Paleoclimate to Test Geodynamic Models in the Peruvian Andes

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Although plate tectonics provides a first-order explanation of the origin of mountain belts, the tectonic processes that drive surface the uplift and exhumation of mountain belts are not well understood. Even less well understood are the interactions of between uplift, erosional processes, and climate that shape the mountain landscape. This project uses state-of-the art to examine the interaction of tectonics, erosion, and climate in the Peruvian Andes to test new and controversial ideas concerning the uplift of the Andes. The project advances desired societal outcomes through: (1) full participation of women and underrepresented minorities in STEM through support of an female researchers and students plus outreach programs to high school and undergraduate students from underrepresented minorities; (2) increased public scientific literacy and public engagement with STEM through participation of outreach programs that provide research experiences for high school and undergraduate students from underrepresented minorities ; (3) development of a diverse, globally competitive STEM workforce through undergraduate and graduate student training and support of several early career researchers; and (4) increased partnerships through international collaboration. The Division of Earth Sciences Tectonics and Geomorphology & Land Use Dynamics Programs and the NSF Office of International Science and Engineering supported this project.Earth's surface topography responds directly to mantle processes and plate tectonics, controls surface drainage and sediment transport patterns, and influences atmospheric circulation and climate. As the type example of ocean-continent subduction-generated high topography, the Central Andes are critical to evaluating geodynamic models of orogenesis. Although previous studies of the structural history, past elevations, and incision record have provided important insights on surface uplift, these studies also suggest a disparate range of uplift histories and associated tectonic drivers. Current geodynamic models for Andean orogenesis include: (1) continuous late Cenozoic crustal thickening and shortening, resulting in gradual surface uplift and canyon incision; (2) late Cenozoic delamination of South American lithosphere, resulting in rapid surface uplift and a late Miocene pulse of incision; and (3) early Cenozoic contraction-driven crustal thickening, resulting in near modern elevations in the west by late Eocene and propagating deformation eastward through the Cenozoic. To distinguish between models, this project uses: (1) stable isotope analyses of volcanic glasses and soil carbonates to provide quantitative estimates of paleoelevations over time, coupled with geochronology to constrain timing; (2) isotope-enabled general circulation modeling to determine how changing elevations affected climate and to quantitatively interpret stable isotope data, constrained by modern elevation-isotope and climate-isotope relationships; (3) data-validated fluvial erosion modeling to predict the erosional response to different models; and (4) fluvial and lacustrine sedimentology and sediment provenance to identify changes in drainage system extent and basin development. By synthesizing these data, the research team will quantify surface topography and erosion during orogenic evolution and distinguish between proposed tectonic and climatic controls.