Abstract
AbstractMarked along‐strike changes in stratigraphy, mountain belt morphology, basement exhumation, and deformation styles characterize the Andean retroarc; these changes have previously been related to spatiotemporal variations in the subduction angle. We modeled new apatite fission track and apatite (U‐Th‐Sm)/He data from nine ranges located between 26°S and 28°S. Using new and previously published data, we constructed a Cretaceous to Pliocene paleogeographic model that delineates a four‐stage tectonic evolution: extensional tectonics during the Cretaceous (120–75 Ma), the formation of a broken foreland basin between 55 and 30 Ma, reheating due to burial beneath sedimentary rocks (18–13 Ma), and deformation, exhumation, and surface uplift during the Late Miocene and the Pliocene (13–3 Ma). Our model highlights how preexisting upper plate structures control the deformation patterns of broken foreland basins. Because retroarc deformation predates flat‐slab subduction, we propose that slab anchoring may have been the precursor of Eocene–Oligocene compression in the Andean retroarc. Our model challenges models which consider broken foreland basins and retroarc deformation in the NW Argentinian Andes to be directly related to Miocene flat subduction.
Highlights
Cordilleran orogens, such as the Andes, are characterized by subduction of an oceanic plate beneath continental lithosphere (DeCelles et al, 2009)
The Andes are characterized by spatial and temporal variations in the deformation patterns that are responsible for changes in mountain belt morphology, magnitude of shortening, and foreland basin geometry (Figure 1a) (e.g., Jordan et al, 1983; Pearson et al, 2012)
During the early Miocene, burial beneath more than 2 km of sediments caused reheating of several basement blocks. This contribution documents the controls exerted by preexisting basement structures on basin geometry, the amount of basement exhumation, and deformation patterns during the Cenozoic deformation phases
Summary
Cordilleran orogens, such as the Andes, are characterized by subduction of an oceanic plate beneath continental lithosphere (DeCelles et al, 2009). Several authors proposed different conditions such as flat subduction, interactions between the slab and the mantle, and upper plate inherited structures to be the main precursor of these spatiotemporal variations along the Andes (e.g., Chen et al, 2019; Horton, 2018b; Martinod et al, 2020; Pearson et al, 2013). Diachronic flat‐slab subduction along the Andean continental margin has been suggested to be the main precursor of thick‐skin retroarc deformation and may be responsible for variations in foreland basin geometries, deformation patterns, and mountain belt morphology (e.g., Horton, 2018b; Jordan et al, 1983; Martinod et al, 2020; Ramos, 2009). We aim to better understand the evolution of the Andean retroarc by documenting
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