What drove hinterland uplift and exhumation in the southern central Andes (29−34°S)?

The elevated Andean hinterland at 29−34°S overlies a modern spatial transition from normal to flat-slab subduction. Development of this zone of high topography has been attributed to crustal thickening driven by internal (hinterland) shortening, underthrusting during shortening in external fold-thrust belts, or deeper processes associated with increased buoyancy forces and/or plate coupling above the flat slab. We integrate geologic and geo/thermochronological data to resolve the timing and magnitude of rock uplift, exhumation, and cooling necessary to evaluate possible mechanisms of hinterland construction. New and published apatite (U-Th)/He, apatite fission track, and zircon (U-Th)/He data and allied thermal history models from hinterland samples spanning >400 km along strike define protracted low-temperature residence of most samples since the late Mesozoic, followed by rapid Neogene cooling after ca. 20−15 Ma. Multi-sample models and other datasets demonstrate the influence of shortening-induced exhumation, with considerable spatial variations identified for different orogen-perpendicular (E-W) transects. At 29−31°S, ∼10° east-down tilting recorded hinterland development via continental underthrusting linked to external (eastern) fold-thrust belt shortening. In contrast, at 31−33°S, underthrusting was overprinted by internal (hinterland) shortening. At 33−34°S, reverse faults within the hinterland principally drove rock uplift and exhumation. These latitudinal variations in the kinematics and style of hinterland deformation coincide with along-strike changes in structural/stratigraphic inheritance, arc magmatism, and subduction geometry. Our findings underscore the range of processes governing orogenic construction above a modern type-example of flat-slab subduction, while demonstrating the enhanced capabilities of multi-sample thermal history modeling to test structural and geodynamic hypotheses.