%0 Journal Article
%T Variable structural controls through time in the Southern Central Andes (~36¡ãS) Controles estructurales variables en el tiempo en los Andes Centrales Australes (~36¡ãS)
%A Dar¨ªo L Orts
%A Andr¨¦s Folguera
%A Mario Gim¨¦nez
%A V¨ªctor A Ramos
%J Andean Geology
%D 2012
%I Servicio Nacional de Geolog¨ªa y Miner¨ªa (SERNAGEOMIN)
%X The Southern Central Andes at 36¡ãS have been recognized as an orogenic belt where contraction, accommodated mainly by basement structures, is associated with the inversion of a Late Triassic-Early Jurassic extensional detachment. Based on a structural cross-section, constrained by field data, 2D seismic and bore-hole information, and the processing of Bouger anomalies, we propose a polyphasic tectonic evolution. In the westernmost sector, along the axis of the Cordillera, NW to NNW basement structures were inverted, being a first order control in the generation of frontal narrow N-trending thin-skinned belts. This slip transfer is controlled by the Late Jurassic main detachment. These structures have low gravity anomalies that cross obliquely the main Andean trend. East of this inversion domain, beneath the frontal thin-skinned belts, seismic information reveals that Late Triassic wedge-like depocenters did not experience substantial inversion. To the east double-vergent basement blocks define the Andean emergent orogenic front at these latitudes. These contractional structures truncate gravity anomalies defined by basement discontinuities, indicating that they are not related to tectonic inversion, in contraposition to the westernmost domain. Two contractional phases were distinguished. The oldest is Late Cretaceous in age, as inferred from onlap relations in Upper Cretaceous strata identified in seismic lines. These successions have a maximum age of 97 Ma as inferred by U-Pb in detrital zircons published in previous studies in the area. Contrastingly, the easternmost sector was mainly deformed in Late Miocene times as inferred from less than 18 Ma old synorogenic deposits. Moreover, contractional mechanisms varied through time for each specific sector. While Late Cretaceous contractional tectonics was generated by tectonic inversion and subordinate thin-skinned deformation, it is proposed that Late Miocene deformation was controlled mainly by brittle-ductile transitions at the upper crust with no major influence of previous structures. This fact can be explained by a higher thermal flux achieved in the retroarc area in the last 17 Ma due to the eastward arc expansion during a shallow subduction regime. Los Andes Centrales Australes a los 36¡ãS han sido reconocidos como una faja orog¨¦nica en donde la contracci¨®n, principalmente acomodada por estructuras de basamento, est¨¢ asociada a la inversi¨®n de un sistema extensional del Tri¨¢sico Tard¨ªo-Jur¨¢sico Temprano. Basados en una secci¨®n estructural, construida a partir de datos de campo, l¨ªneas s¨ªsmicas 2D, d
%K Andes Centrales
%K Faja plegada y corrida de Malarg¨¹e
%K Inversi¨®n tect¨®nica
%K Transiciones fr¨¢giles-d¨²ctiles
%K Frente orog¨¦nico
%K Cuenca de antepa¨ªs
%K Argentina
%K Central Andes
%K Malarg¨¹e fold and thrust belt
%K Tectonic inversion
%K Brittle-ductile transitions
%K Orogenic front
%K Foreland basin
%K Argentina
%U http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062012000200002