Three-dimensional approach to understanding the relationship between the Plio-Quaternary stress field and tectonic inversion in the Triassic Cuyo Basin, Argentina.

GIAMBIAGI L.B.; SPAGNOTTO S.; MOREIRAS S.M.; GÓMEZ, G.; STAHLSCHMIDT, E.; MESCUA, J.

Solid Earth

EGU

Año: 2015 vol. 7 p. 459 - 494

1869-9510

In the Southern Central Andes of Chile and Argentina, basin inversion of Mesozoic or early Cenozoic extensional basins has always been assigned to compressive stress states during the growth of the orogen (i.e. Uliana et al., 1995; Godoy et al., 1999; Jordan et al., 2001; Charrier et al., 2002; Giambiagi et al., 2003; Mescua and Giambiagi, 2012; Mescua et al., 2014). Across west-central Argentina, inversion of half-grabens has received great attention because of the important economic role played by inversion structures in petroleum trapping (Uliana et al., 1995; Zencich et al., 2008). The oil-bearing Triassic Cuyo basin (Fig. 1A), located in the foreland region of the Andes between 30° and 34°S, has been traditionally described as a classical example of Mesozoic rift basins subsequently inverted during the Cretaceous-Quaternary Andean orogeny (Ramos and Kay, 1991; Legarreta et al., 1992; Ávila et al., 2005; Zencich et al., 2008). This basin is mainly a sub-surface feature (Rolleri and Criado Roque, 1968), buried under more than 3,000 m of Cenozoic synorogenic sedimentary cover. It 30 is composed by NW to NNW31 oriented fault-bounded narrow and elongated sub-basins, filled with siliciclastic continental deposits. One of the largest fault-bounded troughs, the Cacheuta sub-basin (Fig. 1B), was extensively studied, due to its abundant oil accumulations (Rolleri and Fernández Garrasino, 1979; Kokogian and Mancilla, 1989). The great majority of the Cuyo basin oils were sourced from this sub-basin kitchen to feed the other reservoirs (Zencich et al., 2008). Although the majority of oil-bearing structures have been attributed to inversion of extensional faults (Dellapé and Hegedus, 1995), there is no general agreement on the inversion of the sub-basin. Paleozoic inherited weaknesses have been proposed to control the structural However, it is unclear to which extent these pre-existing planes of weakness contribute to inversion tectonics.In this paper we argue that a three-dimensional approach is needed to characterize the structural style and amount of rift inversion under a particular stress field pattern. The goals of this article are threefold: (1) characterize the three-dimensional structure of the Cacheuta sub-basin, by integrating surface and subsurface data, (2) provide a dynamic model for the Andean thrust front, identifying spatial variations in Plio-Quaternary stress fields that could explain the N-S change in the tectonic reactivation styles, and (3) investigate the control of the Plio-Quaternary stress field over the inversion of the Triassic rift basin. The moderate inversion, the good preservation of rift-related and syn-orogenic strata and the excellent surface and sub-surface geological and geophysical data set make this basin a good candidate to investigate these themes. Our results suggest a direct relationship between the southward gradual change in the foreland stress regime from compression (Svvertical stress=σ3) to strike-slip (Sv=σ2) and the degree of tectonic inversion of the basin.