Preserved Through Hyperaridity, 150 Million Years of Exhumation and Strike‐Slip Deformation in the Atacama Coastal Cordillera

Abstract The Coastal Cordillera of northern Chile, in the forearc of the Andean subduction zone, provides an ideal site to evaluate exhumation above the oldest active subduction under extreme aridity. This range lies parallel to a sediment‐starved trench, has experienced hyperaridity since the Miocene, and is transected by the ∼1,000‐km‐long Atacama Fault System (AFS). Previous thermochronology documents regional cooling since the Late Jurassic, but away from major structures, limiting assessment of fault‐controlled exhumation. Using a targeted sampling strategy, we test whether faulting has driven localized erosion within the Atacama's hyperarid core. We present new apatite and zircon (U‐Th)/He and apatite fission‐track data from a 720‐m‐relief transect crossing the Salar Grande Fault (SGF), the northern termination of the AFS. Dates range from 150 Ma to 30 Ma and thermal modeling indicates a multistage cooling history: (a) post‐emplacement cooling from ∼150 to 110 Ma); (b) slower cooling from ∼110 to ∼55–45 Ma with prolonged residence near ∼100°C; (c) renewed cooling between ∼50 and 35 Ma; and (d) very slow to negligible exhumation after ∼35 Ma. The cooling intervals align grossly with Andean tectonic phases and can be related to regional, plate boundary‐wide events (cooling intervals 1–3) as well as local fault deformation (interval 3). Specifically, we relate the mid Cenozoic cooling to pull‐apart basin formation along the SGF. Our findings show the value of low‐temperature thermochronology in low‐erosion environments such as the Atacama, where uplift‐driven exhumation occurs, albeit more slowly, ultimately preserving a long record of cooling.