Late Cretaceous uplift in the Malargüe fold-and-thrust belt (35°S), Southern Central Andes of Argentina and Chile

MESCUA, J., GIAMBIAGI, L.B. Y RAMOS, V.A.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Lugar: Santiago de Chile; Año: 2013 vol. 40 p. 102 - 116

0718-7092

The Cordillera de los Andes is one of the most important mountain ranges in the world, extending for more than 8.000 km along the western margin of South America. It is the result of the subduction of the oceanic Nazca plate below continental South America, being the typical example of a subduction-related orogen (Dewey and Bird, 1970; James, 1971). The present configuration of the range is the result of Cenozoic deformation and uplift (Jordan et al., 1983; Mégard, 1984; Ramos and Alemán, 2000; Vicente, 2005; and many others). However, in many sectors of the Andes, the first stage of Andean uplift took place in the Late Cretaceous. This deformation stage is known as the Peruvian Phase, since it is more clearly recognized in the Peruvian Andes (Steinmann, 1929; Aubouin et al., 1973; Vicente et al., 1979; Mégard, 1984) where the deformation has been recently dated as starting in mid-Turonian times (Jaillard et al., 2005). Cretaceous compressional deformation has also been recognized in other sectors of the Andes such as the Northern Andes of Ecuador, Colombia and Venezuela (Aspden et al., 1992; Jaimes and de Freitas, 2006; Martin-Gombojav and Winkler, 2008), the Central Andes in Bolivia (Sempere, 1995), and the Patagonian Andes (Fildani et al., 2003). In the Southern Central Andes, south of 36ºS, deposits of the Late Cretaceous Neuquén Group have recently been interpreted as syn-orogenic strata corresponding to a Cretaceous foreland basin (Cobbold and Rossello, 2003; Ramos and Folguera, 2005). Cobbold and Rossello (2003) have also presented evidences of Late Cretaceous activity for many structures in the same area. Based on detrital zircon ages, Tunik et al. (2010) have dated the beginning of deposition of syn-orogenic strata as taking place in the early Cenomanian. At the latitude of 33ºS, Orts and Ramos (2006) have described syn-tectonic angular unconformities in beds of the Neuquén Group. In this contribution, we will present evidences of a Cretaceous age for the beginning of Andean uplift and deformation at 35ºS.