[en] Full text: At the southernmost extension of the Pre cordillera fold-and-thrust belt, 33 S latitude, about 4000 m of Cenozoic foreland-basin strata record the eastern migration of the Andean thrust from since the Neogene. These deposits accumulated in response to exhumation and deformation of the western Principal and Frontal cordilleras. The detrial clastic strata cropping out in the La Pilona-Tupungato region, comprise five formation units that record fluvial, eolian and alluvial deposition in an arid setting. To link the sequence of deformational events in the western mountain belts with the sedimentary record, all units except the youngest have been dated using magnetic polarity stratigraphy calibrated with ⁴⁰Ar - ³⁹Ar dates on inter bedded tephras. A precise chronology of these deposits in conjunction with a multiple data set that include rates of sedimentation in the foreland, a provenance study on these rocks, and facies and textural patterns, provide the basis for documenting details of tectonic activity, volcanism and deposition. The oldest Marinio Fm., whose deposition spans ∼15.7-12.2 Ma, is interpreted to record two phases of thrusting in the Principal Cordillera (Irigoyen 1997). The earlier phase is tied to deformation of the Mesozoic andesitic volcanic complex cropping out in the western part of the Aconcagua fold-and-thrust belt. The second phase of thrusting is linked with deformation of the Mesozoic marine sequences of the central part of the Aconcagua fold-and-thrust belt. The overlying La Pilona Fm., whose deposition spans ∼11.7-9.0 Ma, is thought to record the initiation of exhumation of the Frontal Cordillera. Provenance and paleocurrent data are consistent with clast derivation from northwestern highland sources (i.e., cordon and cuchillas del Tigre) which provided volcanic detritus from the Choiyoi Group and low-grade metamorphic and sedimentary rocks of lower Paleozoic age. Exhumation and displacement of the Frontal Cordillera overlapped in time with deformation in the Principal Cordillera in which the latest phase of deformation is known to occur at ∼8.0 Ma (e.g., Ramos 1996). The extensive ash-rich unit, the 8.9-8.7 Ma Tobas Angostura Fm., is correlated with the latest extrusive episode that included pyroclastic eruptions in the Principal Cordillera. An unconformity separates the Rio de los Pozos Fm., probably at least as young as ∼7.2 Ma, from the youngest Mogotes Fm. This unit, whose deposition spans ∼3.1 Ma, includes the large boulder conglomerates that today lie at the foot of the cordon del Plata immediately to the west of the study site. Therefore, deposition of this unit is linked with deformation in the flanking Frontal Cordillera. Neogene strata are deformed into fault-propagation folds and emergent east-verging thrusts which, in some cases, also display a sinistral strike-slip component. The timing of deformation of the Tertiary sequence is constrained by an ash-tuff layer un conformably overlying these deposits and dated at 0.39 ± 0.03 Ma. (author)