The control of Mesozoic extensional structures on the Andean deformation in the northern sector of the Malargüe fold and thrust belt

BECHIS, GIAMBIAGI, YAGUPSKY, CRISTALLINI, GARCÍA, MESCUA

Niza, Francia

Simposio; VII International Symposium on Andean Geodynamics; 2008

IRD

The study area is located in the northern sector of the Malargüe fold and thrust belt, in the Southern Central Andes of central-western Argentina (fig. 1). In this sector of the belt, Andean deformation inverted a Late Triassic to Early Jurassic extensional depocentre of the Neuquén basin (Kozlowski et al., 1993; Manceda and Figueroa, 1995; Giambiagi et al., in press). A Late Triassic to Early Jurassic extensional pulse marked the beginning of the history[L1]  of the Neuquén basin in west-central Argentina. The synrift sequences are restricted to isolated depocentres limited by normal faults, showing considerable lateral thickness and facies variations. The extensional structure of the Neuquén basin in its western sector has been subsequently overprinted by the Andean deformation, and part of the synrift infill has been deformed and uplifted, being actually exposed in the Andean fold and thrust belts. Several basement-involved reverse faults have been interpreted as the result of inversion of Mesozoic normal faults in the Agrio and Malargüe fold and thrust belts (Kozlowski et al., 1993; Manceda and Figueroa, 1995; Zapata et al., 1999; Zamora Valcarce et al., 2006; Giambiagi et al., in press; among others) and even further north, in the southern sector of the Aconcagua fold and thrust belt (Giambiagi et al., 2003). The main goal of this contribution was to identify the principal controls of extensional structures on the Andean deformation in the northern sector of the Malargüe fold and thrust belt[L2] . Our study was mainly based on data obtained from detailed structural and geological field mapping, integrated with information from subsurface data. The orientation, timing and structural style of the Andean structures were compared with the extensional architecture of the Atuel depocentre, previously addressed by Manceda and Figueroa (1995), Lanés (2002, 2005) and Giambiagi et al. (2005a, 2005b). On the other hand, the compressive structures were compared with the results obtained from analogue models of inversion of obliquely oriented half-grabens during the evolution of a fold and thrust belt (Yagupsky et al., submitted to the Journal of Structural Geology) In the study case there is a feedback between the study of Andean structures and the identification of the Mesozoic normal faults, because the Cenozoic deformation was controlled by preexisting structures, while identification of the rift structures is helped by their control in the Andean structures. Hence, an integrated approach is needed to carry out these studies.     [L1]Opening no queda major???  [L2]Lo simplifiqué un poco