Tectonic evolution of the Central Andean Plateau and implications for ore distribution

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In the entirety of the Andes, the Central Andean Plateau (CAP) is anomalously wide, with distances between the subduction zone in the west and the easternmost deformation front up to 600-800 km. The CAP also hosts 70 km thick crust: the thickest in South America. The CAP has experienced vertical-axis rotations resulting in formation of the Bolivian orocline and greater shortening than regions to the north or south. The CAP also hosts copper, tin, and silver in Eocene (~45-35 million years ago) deposits ringing the CAP. Some of these deposits are among the largest in the world and therefore understanding the geodynamic processes that drove Eocene basin formation also provides insight into the processes that form large ore deposits.Multiple hypotheses, including both upper and lower plate effects, have been advanced to explain the evolution of the CAP and its anomalous characteristics. The large scale implicated by many of these mechanisms requires equally large-scale observations. However, testing these hypotheses has been hampered by a lack of datable material, particularly in Paleogene clastic strata. The lack of datable material has hampered stratigraphic correlations across the CAP, and therefore evaluation of the rate of subsidence (downward crustal movement) which accommodated sediment accumulation. The timing and rate of subsidence are symptomatic of specific geodynamic mechanisms acting to cause vertical crustal displacement. This proposal seeks funding to develop a preliminary correlation among Paleogene strata in Bolivia. We will use U-Pb geochronology of detrital zircons in Paleogene strata to develop independent chronostratigraphies at multiple latitudes in Bolivia. This will be interpreted and correlated in the context of newly acquired seismic lines across the Altiplano. This proposal will enable a new collaboration and research visits between PI Saylor and collaborator Ramos and their students.