IIDYPCA   23948
INSTITUTO DE INVESTIGACIONES EN DIVERSIDAD CULTURAL Y PROCESOS DE CAMBIO
Unidad Ejecutora - UE
artículos
Título:
Thrust belts of the southern Central Andes: Along-strike variations in shortening, topography, crustal geometry, and denudation
Autor/es:
LAURA BEATRIZ GIAMBIAGI; JOSÉ FRANCISCO MESCUA; FLORENCIA BECHIS; ANDRÉS TASSARA; GREGORY HOKE
Revista:
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
Editorial:
GEOLOGICAL SOC AMER, INC
Referencias:
Lugar: Boulder; Año: 2012 vol. 124 p. 1339 - 1351
ISSN:
0016-7606
Resumen:
The Andean fold and thrust belts of west-central Argentina (33° and 36°S), above the normal subduction segment, present important along-strike variations in mean topographic uplift, structural elevation, amount and rate of shortening, and crustal thickness. To analyze the controlling factors of these latitudinal changes we compare these parameters and the chronology of deformation along eleven balanced crustal cross-sections across the thrust belts between 70° and 69°W, where the majority of the upper crustal deformation is concentrated, and reconstruct the Moho geometry along the transects. Our results indicate a synchronous onset of deformation along-strike at ca. 17-18 Ma, a progressive southward reduction of total amount of shortening from 55 to 10 km, shortening rates from 3.8 to 0.7 mm/a, and a small reduction in crustal thickness from 51 to 47 km. However, average topographic elevation does not vary gradually southward as the other parameters, with an abrupt step from 3,500 to 2,200 m between 34°40´ and 35°20´S. We propose two models of crustal deformation. A 33°40´S model, where the locus of upper-crustal shortening is aligned with respect to the maximum crustal thickness, and a 35°40´S model, where the upper-crustal shortening is uncoupled from the lower-crustal deformation and thickening. This degree of coupling between brittle upper crust and ductile lower crust deformation has strong influence on mean topographic elevation. In the northern sector of the study area, an initial thick and felsic crust favors the coupling model; while in the southern sector, a thin and mafic lower crust allows the uncoupling model. Our results indicate that interplate dynamics may control the overall pattern of tectonic shortening, however local variations in mean topographic elevation, deformation styles and crustal root geometry are not fully explained and are more likely to be due upper-plate lithospheric strength variations.