Structure and tectonic evolution of the South Patagonian fold and thrust belt: Coupling between subduction dynamics, climate and tectonic deformation

GHIGLIONE, MATÍAS C.; RONDA, GONZALO; SUÁREZ, RODRIGO J.; ARAMENDÍA, INÉS; BARBERÓN, VANESA; RAMOS, MIGUEL E.; TOBAL, JONATHAN; GARCÍA MORABITO, E.; MARTINOD, JOSEPH; SUE, CHRISTIAN

Andean tectonics

Elsevier

Año: 2019; p. 675 - 697

This work focuses on the geometry of the SPA (Southern Patagonian Andes), recognizing a thick-skinned basement domain, and hybrid thick- and thin-skinned tectonic systems in the FTB (fold and thrust belt). The distribution and width of structural domains, Andean shortening, and sedimentary thickness in the retroarc are compared with exhumation patterns from thermochronological studies to assess the influence of erosion on the internal dynamics of mountain building. The SPA measures 380km across in its northern segment, which is dominated by a broad basement domain up to 350km wide and is flanked by a narrow thin-skinned FTB, in agreement with focused glacial erosion in the hinterland leading to exhumation of deep structural levels. A southward increase in the width and shortening of the FTB along the southern segment coincides with a thicker sedimentary cover and erosion focused in retroarc zones. We found that erosion efficiency through climate (i.e., glaciations), and the relative rheology and thickness of foreland strata are the primary controls on north to south contrasts in width and exhumation of the SPA in the context of Neogene shortening. The northern segment endured enhanced glacial erosion in the hinterland, sustaining a subcritical wedge state with active uplift of the basement domain and an underdeveloped FTB. An abrupt and steady increase in the width and shortening of the FTB toward the southern segment coincides with reduced erosion in the basement, which favors a critical-wedge state and widening of the FTB.