A review about the mechanisms associated with active deformation, regional uplift and subsidence in southern South America

doi:10.1016/j.jsames.2015.07.007

Journal of South American Earth Sciences

Volume 64, Part 2, December 2015, Pages 511-529

https://doi.org/10.1016/j.jsames.2015.07.007 Get rights and content

Highlights

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A broad range of processes acted simultaneously during the Quaternary producing relief in the Andes and adjacent foreland.
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Orogenic processes are dominant north of 35°S, while to the south dynamic forces predominate.
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A slab tearing south of 38°S is associated with retroarc extensional subsidence Between 35° and 38°S an asthenospheric anomaly is coincident with sites of neotectonic deformation South of 45°S predominate dynamic effects linked to a slab window.

Abstract

A broad range of processes acted simultaneously during the Quaternary producing relief in the Andes and adjacent foreland, from the Chilean coast, where the Pacific Ocean floor is being subducted beneath South American, to the Brazilian and the Argentinean Atlantic platform area. This picture shows to be complex and responds to a variety of processes. The Geoid exemplifies this spectrum of uplift mechanisms, since it reflects an important change at 35°S along the Andes and the foreland that could be indicating the presence of dynamic forces modeling the topography with varying intensity through the subduction margin. On the other hand, mountains uplifted in the Atlantic margin, along a vast sector of the Brazilian Atlantic coast and inland regions seem to be created at the area where the passive margin has been hyper-extended and consequently mechanically debilitated and the forearc region shifts eastwardly at a similar rate than the westward advancing continent. Therefore the forearc at the Arica latitudes can be considered as relatively stationary and dynamically sustained by a perpendicular-to-the-margin asthenospheric flow that inhibits trench roll back, determining a highly active orogenic setting at the eastern Andes in the Subandean region. To the south, the Pampean flat subduction zone creates particular conditions for deformation and rapid propagation of the orogenic front producing a high-amplitude orogen. In the southern Central and Patagonian Andes, mountain (orogenic) building processes are attenuated, becoming dominant other mechanisms of exhumation such as the i) impact of mantle plumes originated in the 660 km mantle transition, ii) the ice-masse retreat from the Andes after the Pleistocene producing an isostatic rebound, iii) the dynamic topography associated with the opening of an asthenospheric window during the subduction of the Chile ridge and slab tearing processes, iv) the subduction of oceanic swells linked to transform zones and v) the accretion of oceanic materials beneath the forearc region. Additionally and after last geodetic studies, vi) exhumation due to co- and post-seismic lithospheric stretching associated with large earthquakes along the subduction zone, also shows to be a factor associated with regional uplift that needs to be further considered as an additional mechanism from the Chilean coast to the western retroarc area. Finally, this revision constitutes a general picture about the different mechanisms of uplift and active deformation along the Southern Andes, in which orogenic processes become dominant north of 35°S, while south of these latitudes dynamic forces seem to predominate all over the Patagonian platform.

Introduction

Active uplift in the Andes has been generally associated with contraction imposed by the convergence between the oceanic Nazca and Antarctic subducted plates and the South American plate (Ramos et al., 2004, Costa et al., 2006, Oncken et al., 2006, Schellart et al., 2011). However, in the last years multiple mechanisms have been recognized along the Andes that produce, together with orogenic forces, regional to local uplift and eventually exhumation of the upper crust. These additional mechanisms involve isostatic readjustments due to crustal stretching interrupting Andean constructional stages and delamination, to co-seismic extension, lower crustal flow, accretion of underplated materials associated with tectonic erosion, and even deep mantle dynamics. Additionally, segments where exhumation seems to be governed by thrusting are not clearly delimited and their associated mechanisms are not totally understood.

In general terms a narrow band of thrusts has been described bordering the eastern Altiplano and Pampean regions from southern Perú and Bolivia to northern and central Argentina between 10° and 33°S (Fig. 1). This segment coincides with a broad and high mountain chain associated with important amounts of intracrustal earthquakes that denote active mountain building processes (see Costa et al., 2006 for a review). South of 33°S, crustal seismicity on the eastern Andes diminishes sensibly, becoming mountain morphology narrower and lower. Even though orogenic mechanisms are described for this southern sector of the Andes at least discontinuously, other factors have been linked to regional and local uplift in the last years, in particular for the Patagonian region.

This review outlines the main processes that are associated with uplift and exhumation of vast sectors of the Southern Andes and their foreland area. These processes, mainly recognized in the last years since technological innovations, have allowed i) recognizing centimeter to millimeter fluctuations of the landscape, ii) illuminating the thermal structure of the lower crust and upper mantle, and iii) analyzing variations in the gravity field through time, from the Altiplano region to Patagonia passing through the foreland area and even the passive margin where no subduction of oceanic lithosphere exists.

Section snippets

Central and Patagonian Andes tectonic setting

The Andes are formed over a subduction system consisting of three oceanic plates, Cocos, Nazca and Antarctica, subducting beneath the South American plate. This configuration shows a noticeable symmetry with an orogenic plateau at its mid sector flanked by two flat subduction systems, the Peruvian in the north and the Pampean in the south (Fig. 1) (Gephart, 1994). Topography is higher at the mid sector and diminishes steadily towards both edges of the subduction system, where narrow mountain

Regional uplift in the Central Andes and Atlantic passive margin

An anomalously high topography is developed north and south of the Arica bend region around the Altiplano (Fig. 1). This topography is correlated with an unusually high crustal thickening in the order of 70–75 km, estimated by geophysical methods, that can't be fully explained by shortening in the retroarc zone (Baby et al., 1997). However, these shortening estimates can be considered as conservative according to other studies (see McQuarrie et al., 2005). This lack in correlation between

The geoid and the lack of isostatic equilibrium in the Southern Andes

The geoid is sensitive to a broad range of perturbing masses from the topography developed above sea level to deep masses uplifted and sank by asthenospheric dynamics. Since the potential of the gravity depends inversely on distance, in contrast to gravity that depends on square distance, long wavelengths of the geoid become sensitive to asthenospheric dynamics, where conventional gravimetry is not able to detect density variations. Thus, the longest undulations of the geoid are found to have a

Uplift in the Southern Central Andes

Exhumation between 27 and 36°S along the Andes foreland region is associated with orogenic mechanisms determined by the Pampean flat subduction zone (27–33°S) and a segment to the south where the Nazca plate changes its dip angle smoothly from flat to 30° (Pesicek et al., 2012) (Fig. 2). This flat to shallow subduction system determines a high-amplitude orogen where the foreland area is fragmented in a series of basement blocks such as the Sierras Pampeanas in the Pampean flat subduction system

Uplift at the transition zone between the Southern Central Andes and Northern Patagonia

The area interposed between 36 and 38°S shows transitional characteristics in the mechanisms responsible for uplift and exhumation between the Southern Central Andes and the Patagonian Andes. Structures affecting Quaternary strata that accommodate contraction are present at the Tromen volcanic plateau in the retroarc zone (Fig. 4) (Galland et al., 2007, Sagripanti et al., 2014). Evidences of young deformation are found in volcanic products of less than 2 Ma, where morphometric analyses

Regional uplift in Northern Patagonia (38–44°S)

To the south, between 38 and 39°S, a Pliocene to Quaternary slab tear has been visualized from seismic tomographies after the 27/2/2010 Maule earthquake (Fig. 8) (Pesicek et al., 2012). This slab tear determines a discrete transition between a shallower slab in the north (∼30°E) and a steeper subducted slab south of 38°S (Fig. 8) through a W-NW direction that coincides with the northern development of the Loncopué trough (Fig. 8b-to the left) and an attenuation of the Moho (Fig. 8b-to the

Regional uplift and subsidence in southern Patagonia (44–52°S)

The Southern Patagonian region shows particular mechanisms during the last 5 My that explain active regional uplift (Fig. 13). Young and buoyant oceanic crust subducted obliquely at the South American Pacific margin decouples a forearc sliver through the Liquiñe-Ofqui fault zone (LOFZ) (Lavenu and Cembrano, 1999, Vargas et al., 2013). This fault zone runs through more than 1000 km through the arc front accommodating strike-slip to reverse dip-slip displacements along the North Patagonian Andes (

Discussion

Mechanisms associated with active uplift along the Southern Andes in the last 2 Ma show to be highly contrasting through the different analyzed sectors. While in the Central Andes predominate contraction mainly associated with thrust activity concentrated in the eastern Andean slope, and isostatic rebound in areas of over-thickened crust suffering delamination of the lower crust, to the south in the Southern Central and Patagonian Andes asthenospheric dynamics due to tearing processes, a slab

Concluding remarks

Uplift and exhumation at the Central Andes are mainly governed by thrusting that accommodates horizontal displacement of the South American craton at the zones of i) stationary trench in the Arica region, both in the eastern Andes, as well as more limitedly over the Atlantic coast where the passive margin has been hyper-extended and consequently mechanically debilitated, and ii) the Pampean-Chilean flat subduction zone. Delamination of the lower lithosphere, coupled with crustal thickening

Acknowledgments

We acknowledge constructive reviews made by Eduardo Contreras-Reyes and Laura Giambiagi. This work was financed by PIP 11220110100506, UBACYT 20020110100019, PICT-2012-1490. This is the XX contribution of the Instituto de Estudios Andinos “Don Pablo Groeber”.

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Citation Excerpt :
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A review about the mechanisms associated with active deformation, regional uplift and subsidence in southern South America

Highlights

Abstract

Introduction

Section snippets

Central and Patagonian Andes tectonic setting

Regional uplift in the Central Andes and Atlantic passive margin

The geoid and the lack of isostatic equilibrium in the Southern Andes

Uplift in the Southern Central Andes

Uplift at the transition zone between the Southern Central Andes and Northern Patagonia

Regional uplift in Northern Patagonia (38–44°S)

Regional uplift and subsidence in southern Patagonia (44–52°S)

Discussion

Concluding remarks

Acknowledgments

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Tectonophysics

Tectonophysics

Tectonophysics

J. Volcanol. Geotherm. Res.

J. Geodyn.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Tectonophysics

Tectonophysics

J. Struct. Geol.

Earth Planet. Sci. Lett.

Tectonophysics

J. Geodyn.

Geomorphology

Tectonophysics

J. Volcanol. Geotherm. Res.

Geomorphology

Geomorphology

Tectonophysics

Tectonophysics

J. South Am. Earth Sci.

Phys. Earth Planet. Inter.

Permanent fore-arc extension and seismic segmentation: Insights from the 2010 Maule earthquake, Chile

J. Geophys. Res. Solid Earth

The west andean thrust, the san Ramón fault, and the seismic hazard for Santiago, Chile

Tectonics

Seismological studies of the Central and Southern Andes

Neogene shortening contribution to crustal thickening in the back arc of the Central Andes

Geology

Peligro sísmico y neotectónica. 12° Congreso Geológico Argentino y 2º Congreso de Exploración de Hidrocarburos

Review of seismicity and Neogene tectonics in northeastern Brazil

Rev. Asoc. Geológica Argent.

Crustal motion in the Southern Andes (26°–36°S): do the Andes behave like a microplate?

Geochem. Geophys. Geosystems

Orogenic-wedge deformation and potential for great earthquakes in the central Andean backarc

Nat. Geosci.

Megathrust seismic Events, post seismic deformation and mountain building: andean deformation and the maule earthquake

Rift migration explains continental margin asymmetry and crustal hyper-extension

Nat. Commun.

Three-dimensional electrical conductivity in the mantle beneath the Matru Volcanic Field in the Andean back-arc of Argentina Pay un near 36. 5 S: Decapitation of a mantle plume by resurgent upper mantle shear during slab steepening?

Geophys. J. Int.

Seismicity and shape of the subducted Nazca plate

J. Geophys. Res.

Velocity structure beneath the southern Puna plateau: evidence for delamination

Geochem. Geophys. Geosystems

Late Cenozoic tectonics of the Southern Chile trench

J. Geophys. Res.

Tectono-stratigraphic evolution of the andean orogen Chile

Cuaternario y dinámica costera

Post-breakup tectonics in southeast Brazil from thermochronological data and combined inverse-forward thermal history modeling

J. Geophys. Res.

Seismic structure of the north-central Chile convergent margin: subduction erosion of a paleomagmatic arc

Geophys. Res. Lett.

Fallas cuaternarias oblicuas al frente montañoso en la cordillera Frontal de Mendoza (34-34°30′S)

Rev. Cuaternario Ciencias Ambient.

Late Holocene faulting in the southeast Sierras Pampeanas of Argentina

Geology

An overview of the main Quaternary deformation of South America

Rev. la Asoc. Geológica Argent.