Global Eustasy or Tectonic Subsidence? Investigating Controls on Basin Evolution During Cenozoic Plate Reorganization, Magallanes Basin, Patagonia

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Tectonic activity and climate interact to control the growth of mountains, erosion of steepened topography, and fluctuations between marine and terrestrial conditions along low-lying continental margins. Continents located in complex tectonic plate settings undergoing continental separation are especially sensitive to changes in tectonic deformation and sea level, which together modulate biogeographic pathways between major landmasses and global ocean/atmosphere circulation between ocean basins. This project uses stratigraphy, geochronology, basin modeling, structural geology, and paleobiology in the Cenozoic Magallanes-Austral region of South America (Chile and Argentina) to investigate how tectonic deformation, sea level, and climate affect coastal depositional patterns and paleogeography during an important time interval for global climate. The project advances the role of science in our society by 1) engaging the general public and college students enrolled in general education courses by developing a field-based learning module on plate tectonics, global climate, and paleogeography, 2) promoting increased participation of women in science and technology, 3) supporting international research and training opportunities for graduate and undergraduate students, and 4) stimulating new international collaborations between U.S. and Chilean academic institutions and regional parkland organizations. The NSF Office of International Science and Engineering is providing support for international activities associated with this project. The primary research objective of this project is to evaluate the controlling factors on marine transgressions and continental sediment dispersal patterns in the Magallanes-Austral region of South America during an important time interval for global climate. This work aims to test the hypothesis that the middle Cenozoic Atlantic transgressions in Patagonia were caused by tectonic loading and deepening of sedimentary environments during Andean deformation and opening of the Drake Passage. This project also investigates how the intercalated coarse-grained progradational deposits are linked to thrusting history and physiographic changes in upland sediment source areas. Stratigraphy, basin modeling, structural mapping, and sedimentary provenance tools (detrital zircon geochronology, sandstone petrography, and mudstone geochemistry) will be combined to evaluate how tectonic and climatic changes in upland source areas affect sedimentation style, grain size, accumulation rate, and basin paleogeography during Eocene through middle Miocene time. Erosion rates derived from detrital apatite thermochronology will further resolve potential influences from thrust-belt deformation and climatic events. This project promotes scientific progress on understanding the deformation of the continental lithosphere by: 1) evaluating along-strike differences in retroarc foreland basin evolution during a major phase of Andean orogenesis, 2) contributing an improved chronostratigraphic framework for the diverse middle Cenozoic Patagonian fossil assemblages, 3) investigating relationships between orogenic paleogeography, transgressions, sediment pulses, and biotic events, and 4) integrating new datasets for improved numerical models of lithospheric deformation and climatic processes in orogenic systems.