INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Structural models of the Malargue fold-and-thrust belt at 35ºS: insights from the regional variation of shortening and crustal thickness
JOSÉ F. MESCUA, LAURA GIAMBIAGI, ANDRÉS TASSARA, AND VÍCTOR RAMOS
Congreso; GEOSUR; 2013
Different structural models have been used to construct balanced cross-sections of the Malargüe fold-and-thrust belt (FTB) at 35ºS. Consequently, shortenings estimated from each model are different. Kozlowski et al. (1993) estimated 35 km based on a model using low-angle Andean thrusts, only for the eastern part of the belt. Manceda and Figueroa (1995) estimated 27 km for the same sector, with a model in which faults have higher angles because of the control by pre-existing structures. Mescua (2011) built a cross-section including the inner part of the belt, using both inverted Mesozoic normal faults and Andean thrusts, obtaining a shortening of 26,2 km, of which 23,2 km correspond to the eastern sector. The regional trend of decrease in shortening towards the south in the Aconcagua and Malargüe FTBs has been noted by many researchers. In this contribution, we will compare the values estimated at 35ºS with the regional trend, and with estimates of crustal thickness and area derived from the Tassara and Echaurren (2012) crustal model. We will show that a shortening of 35 km for the eastern sector would constitute a positive anomaly in the regional trend. Estimates lower than 30 km seem more consistent with the regional shortening trend and with the variation with latitude of maximum crustal thickness and crustal root area. This indicates the importance of pre-existing structures during Andean deformation, which influenced the structural style either through tectonic inversion or controlling the dip of Andean thrusts.