In the central Andes of South America, a combination of crustal shortening and thickening, lithospheric densification and delamination, and surficial and climate interactions have resulted in development of the 3-5 km- high central Andean plateau and flanking 6-7 km peaks of the Eastern and Western cordilleras. Questions remain concerning the timing and rate of surface uplift and the relative roles of these mechanisms in producing and supporting these extreme elevations. End-member models attempting to answer these questions propose either a large-magnitude, rapid late Miocene uplift event, or rather slow and steady topographic growth initiating in the late Oligocene-early Miocene. The former model is based primarily on climate- and temperature-sensitive stable isotope analysis of carbonate material as a paleo-elevation proxy and is consistent with an uplift mechanism involving large-scale delamination and foundering of negatively buoyant lower crust and mantle lithosphere. The latter model is consistent with surface uplift driven directly by crustal shortening and is supported by climate simulations that suggest a nonlinear climate response to topographic uplift, indicating instead that there are threshold changes in temperature and isotopic composition of precipitation with rising topography, and highlighting that the use of such proxies may overestimate uplift rate and magnitude. The majority of research focusing on the mechanism(s) driving uplift, deformation, and support of the central Andean plateau has taken place in Bolivia. However, to the north, Cenozoic intermontane basins in southern Peru present an opportunity to test predictions of the end-member models. Multiple hinterland basins have been targeted that have had little (e.g., Ayacucho, Ayaviri, Crucero, Macusani, Putina, Ene,) to no (e.g., Huaccochullo) investigation involving paleo-elevation, analysis (Fig. 1). To determine the uplift and deformation history of the central Andean plateau we use a novel approach to constrain paleo-elevation by conducting stable isotopic analysis of deuterium from hydrated volcanic glass sampled from interbedded tuffs. This paleo-elevation proxy provides a snapshot of the isotopic composition of surface water at the time of tuff deposition, and is temperatureinsensitive, thus circumventing several of the caveats highlighted by climate simulation models. Here, we present preliminary results that suggest delamination and rapid surface uplift the northeastern central Andean plateau may initiate in the late Miocene. When compared with published estimates for paleo-elevation, results are consistent with a rapid surface uplift model, but one that is spatially and temporally variable, as there appears to be a broad trend of younger rapid uplift parallel to the direction of the northeast-directed subducting Nazca plate.
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