Late Cenozoic brittle deformation in the Southern Patagonian Andes: Record of plate coupling/decoupling during variable subduction?

Abstract

The Andes of southern Patagonia experienced a Miocene shift towards faster and higher angle subduction followed by the approach and collision of the Chile oceanic ridge. We present a kinematic study characterizing palaeostress fields computed from brittle tectonics to better constrain upper crustal deformation during this complex scenario. Although previous studies already suggested variable kinematics, it is striking that in a long-lasting subduction environment, the computed palaeostress tensors are mostly strike-slip (55%), while 35% are extensional, and only 10% compressive which are concentrated along a main frontal thrust. Cross-cutting relationships and synsedimentary deformation indicate that a long-lived strike-slip regime was punctuated by a lower Miocene extensional event in the foreland before the main compressional event. The results are discussed in contrasting geodynamic models of plate coupling/decoupling versus direction and rate of convergence of the subducting plate, to explain the main mechanisms that control back-arc deformation.

Tectonic segmentation across Patagonia controlled by the subduction of oceanic fracture zones

“…In the vicinity of the CTJ shear wave splitting studies show ENE trends related to the upper mantle flow from west to east through the slab window (Russo et al, 2010). From this ongoing process, the upper plate crustal structure south of the CTJ registered the subduction of different segments of the former Chile Ridge at these latitudes (Lagabrielle et al, 2007;Scalabrino et al, 2009;Barberón et al, 2018Barberón et al, , 2019. The Andean front at the northern part of the Austral Basin (Fig.…”

“…The Andean front at the northern part of the Austral Basin (Fig. 12) have experienced differential growth of eastward advancing thrust systems in Miocene times controlled by enhanced plate coupling driven by the approaching ridge segments (Lagabrielle et al, 2007;Scalabrino et al, 2009;Barberón et al, 2018Barberón et al, , 2019. Following the Chile Ridge subduction and subsequent opening of the slab window, a extensional or transtensional tectonic event occurred after 5 Ma, reactivating ENE and NNW-trending lineaments (Lagabrielle et al, 2007;Scalabrino et al, 2009).…”

GRACE Data Explore Moho Change Characteristics Beneath the South America Continent near the Chile Triple Junction

“…At present, many studies have explored the external and internal geoscience issues of the SAC, such as the impact of the subduction of the NZ on the lithospheric erosion of the SAC, the changes of horizontal and vertical surface displacement, the distribution of stress and strain fields in Patagonia and the crustal thickness and Moho depth of the SAC, all of which have obtained satisfactory results. [15][16][17][18][19][20][21][22][23].…”