Resumen
Crustal thickening by horizontal shortening and associated deformation have been broadly considered as
prime mechanisms for mountain building in the Central Andes of western South America. However, timing and structural
style of Andean orogeny in northernmost Chile remains to be fully understood. By means of this contribution we attempt
to unravel the Cenozoic tectonostratigraphy and structural architecture of a narrow segment within the Western Cordillera
(western flank of the Altiplano plateau), based on detailed structural mapping, available and new geochronological data
gathered from the Aquine region (~19°15? S). The geology of this area indicates that compressive tectonics dominated for
~21 Myr, between 27 Ma and 6 Ma, and that onset of deformation probably occurred in the middle Eocene (after ca. 49 Ma).
According to angular unconformities registered throughout the region, three principal compressive episodes have been
determined: (1) middle Eocene-late Oligocene (ca. 49-27 Ma); (2) late Oligocene-middle Miocene (ca. 27-14 Ma);
and (3) middle-latest Miocene, 14-6 Ma. Paleogene and Neogene structural development within the Aquine region was
concomitant to activity on the bordering West and East Vergent Thrust Systems (WTS and ETS), which controlled uplift
of the western Altiplano since the late Oligocene-early Miocene, located at the foot of the Precordillera and within the
eastern part of the Western Cordillera, respectively. Major structures in the western segment of the region are high-angle,
east-vergent, substratum-involving thrusts that affect late Mesozoic and Cenozoic volcanic and sedimentary intra-arc
deposits. Unalike, a west-vergent fold-and-thrust belt is developed in the southeastern segment of the region, involving
only Miocene deposits. These contrasting structural styles and opposite vergences indicate a combination of thin- and
thick-skinned tectonics in a ?pop-up? like structural array. Growth strata and sedimentological features in alluvial and
fluvial sandstones and conglomerates of the upper Miocene Mauque Formation suggest the occurrence of syntectonic
deposition. In addition, gentle angular unconformities within upper Oligocene-upper Miocene arc deposits suggest that
sedimentation and volcanism developed synchronic to compressive tectonics throughout the Miocene and coeval to
deposition in the active bordering thrust systems (WTS and ETS). The interpreted tectonostratigraphic development
of the study area is similar to but slightly diachronic with the Cenozoic evolution in the Belén region (18°-19° S) of
northernmost Chile. We interpret that east- and west-vergent thrusts within the Western Cordillera, are deeply rooted
in a crustal-scale ?pop-up? structure that accommodated Cenozoic deformation on the western flank of the Altiplano.
Uplift as a consequence of contraction along the Western Cordillera was coeval to late Paleogene block exhumation and
subsequent Neogene development of fold-and-thrust belts on the eastern border of the Altiplano. The main structural
characteristics within the Aquine region suggest that inversion of an Upper Cretaceous intra-arc basin was of major
relevance for the Cenozoic structural development of the Western Cordillera.