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Paleozoic to early Cenozoic cooling and exhumation of the basement underlying the eastern Puna plateau margin prior to plateau growth

Constraining the pre‐Neogene history of the Puna plateau is crucial for establishing the initial conditions that attended the early stage evolution of the southern extent of the Andean plateau. We apply high‐ to low‐temperature thermochronology data from plutonic rocks in northwestern Argentina to quantify the Paleozoic, Mesozoic and early Tertiary cooling history of the Andean crust. U‐Pb crystallization ages of zircons indicate that pluton intrusion occurred during the early mid‐Ordovician (490–470 Ma) and the late Jurassic (160–150 Ma). Lower‐temperature cooling histories from40Ar/39Ar analyses of K‐feldspar vary substantially. Basement rocks underlying the western Puna resided at temperatures below 200°C (<6 km depth) since the Devonian (∼400 Ma). In contrast, basement rocks underlying the southeastern Puna were hotter (∼200–300°C) throughout the Paleozoic and Jurassic and cooled to temperatures of <200°C by ∼120 Ma. The southeastern Puna basement records a rapid cooling phase coeval with active extension of the Cretaceous Salta rift at ∼160–100 Ma that we associate with tectonic faulting and lithospheric thinning. The northeastern Puna experienced protracted cooling until the late Cretaceous with temperatures <200°C during the Paleocene. Higher cooling rates between 78 and 55 Ma are associated with thermal subsidence during the postrift stage of the Salta rift and/or shortening‐related flexural subsidence. Accelerated cooling and deformation during the Eocene was focused within a narrow zone along the eastern Puna/Eastern Cordillera transition that coincides with Paleozoic/Mesozoic structural and thermal boundaries. Our results constrain regional erosion‐induced cooling throughout the Cenozoic to have been less than ∼150°C, which implies total Cenozoic denudation of <6–4 km.