Calibration of a Neogene magnetostratigraphy by 40Ar-39Ar geochronology: the foreland basin strata of northern Mendoza Province, Argentina

Abstract

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.

The Pampean flat-slab of the Central Andes

“…This rapid increase of deformation marks a change in the propagation rate of the thrust front from 2.5 to 13.1 mm/a at about 9 Ma. Furthermore, an increase in subsidence in the foreland basin, as detected at this critical time by Irigoyen (1997) and Irigoyen et al (1998), is remarkable. Accumulation rates show an increase from 0.33 to 0.77 and 0.95 mm/a at this time, indicating a rapid eastward migration of the thrust front.…”

Provenance of the Miocene Alto Tunuyán Basin (33°40′S, Argentina) and its implications for the evolution of the Andean Range: Insights from petrography and U–Pb LA–ICPMS zircon ages

“…Nevertheless, on the eastern side of the Frontal Cordillera, at the same studied latitude (50 km from the Cordón del Portillo, Fig. 1c), a sandy volcanic deposit with a geochemistry and age similar to the Ignimbrita Arroyo Chileno (9.16 ± 0.5 Ma, average Ar-Ar ages; Irigoyen et al, 1999Irigoyen et al, , 2000 is represented by the Tobas Angostura lithology, which could represent reworked material from the same volcanic centre (on the axis of the Cordón del Portillo, Fig. 1c).…”

Crustal wedging triggering recent deformation in the Andean thrust front between 31°S and 33°S: Sierras Pampeanas‐Precordillera interaction

“…In the south, a $1700-m-thick Neogene succession outcrops around the la Pilona anticline and was deposited from 15.7 to 8.4 Ma (see location to the SW of Mendoza in Figure 1) [Irigoyen et al, 2000]. The Tobas de Angostura Formation outcrops in the upper part of the succession and the volcanic ashes there have been dated as 8.64 ± 0.17 Ma [Irigoyen et al, 1999]. In the Albarracín basin, to the west of San Juan, the youngest volcanic ashes are 8.3 ± 0.5Ma [Vergés et al, 2001].…”