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Neogene strata exposed in the southernmost part of the Precordillera fold-and-thrust belt, Mendoza Province, Argentina, record the eastward migration of the Andean deformation front since the middle Miocene. In order to link the sequence of deformational events occurring in the western thrust belts with the sedimentary record, the Neogene succession has been dated using magnetic polarity stratigraphy calibrated with 40Ar-39Ar isotopic dates. This paper reports on age determinations obtained by 40Ar-39Ar isotopic dating of six tuff beds interbedded in the Neogene sequence, which assist in tying the local magnetostratigraphy to the geomagnetic polarity time scale. In addition, the age results of two samples collected from air-fall tuff horizons interbedded in Quaternary deposits, which have been dated to provide temporal constraints on the age of the youngest Mogotes Formation and the timing of the formation of major structures in the region, are presented.