scholarly journals Basement composition and basin geometry controls on upper-crustal deformation in the Southern Central Andes (30–36°S)

2016 ◽  
Vol 153 (5-6) ◽  
pp. 945-961 ◽  
Author(s):  
JOSÉ F. MESCUA ◽  
LAURA GIAMBIAGI ◽  
MATÍAS BARRIONUEVO ◽  
ANDRÉS TASSARA ◽  
DIEGO MARDONEZ ◽  
...  
Keyword(s):  
Central Andes ◽  
Nazca Plate ◽  
The Andes ◽  
Structural Style ◽  
Thrust Belts ◽  
Southern Central ◽  
History Of ◽  
Basin Geometry ◽  
Subduction System ◽  
Different Parts

AbstractDeformation and uplift in the Andes are a result of the subduction of the Nazca plate below South America. The deformation shows variations in structural style and shortening along and across the strike of the orogen, as a result of the dynamics of the subduction system and the features of the upper plate. In this work, we analyse the development of thin-skinned and thick-skinned fold and thrust belts in the Southern Central Andes (30–36°S). The pre-Andean history of the area determined the formation of different basement domains with distinct lithological compositions, as a result of terrane accretions during Palaeozoic time, the development of a widespread Permo-Triassic magmatic province and long-lasting arc activity. Basin development during Palaeozoic and Mesozoic times produced thick sedimentary successions in different parts of the study area. Based on estimations of strength for the different basement and sedimentary rocks, calculated using geophysical estimates of rock physical properties, we propose that the contrast in strength between basement and cover is the main control on structural style (thin- v. thick-skinned) and across-strike localization of shortening in the study area.

The nature of the North-South change of the magnitude of tectonic shortening in Central Andes at Altiplano-Puna latitudes: a thermomechanical modeling approach.

2020 ◽  
Author(s):  
Michaël Pons ◽  
Stephan Sobolev
Keyword(s):  
Cross Sections ◽  
Pure Shear ◽  
Foreland Basin ◽  
Central Andes ◽  
South American ◽  
Nazca Plate ◽  
South American Plate ◽  
The Andes ◽  
Subduction System ◽  
Roll Back

<p><span>The Andean orogeny is a subduction-type orogeny, the oceanic Nazca Plate sinks under the continental South American Plate. While the subduction has been active since ~180 Ma, the shortening of the Andes initiated at ~50 Ma or less.</span></p><p><span>In a oceanic-continental subduction system, the absolute velocity of the overriding-plate (OP) largely controls the style of subduction (stable, advancing, retreating), the geometry of the slab (dipping angle, curvature) and the style of deformation (shortening or spreading) within the OP. In the case of the Central Peru-Chile subduction, the South American plate is advancing westwards whereas the Nazca plate is anchored into the transition zone (~660 km). As a consequence, the trench is forced to retreat and the Nazca plate to roll-back. The dip of the slab decreases meanwhile the Andes experienced a maximum shortening of ~300 km at ~19-21°S latitudes.</span></p><p><span>Previous study have shown that the strain localizes within areas of low strength and low gravitational potential of energy. In central Andes, weakening mechanisms of the OP such as lithospheric delamination have intensified the magnitude of tectonic shortening and contributed to formation of the Altiplano-Puna plateau. The deformation between the plateau and the foreland occurs in the form of pure shear or simple shear and is expressed in terms of different tectonic styles in the foreland basin, thick-skinned (e.g the Puna) and thin-skinned (e.g the Altiplano), respectively. Nevertheless, the influence of the strength variations of the OP on the subduction dynamics in the case of the central Andes has been </span><span>poorly</span><span> explored so far. Our hypothesis is that lateral variations of OP strength result in variable rates of trench roll-back. To test it, we have built 2D high-resolution E-W cross sections along the Altiplano and Puna latitudes (12-27°S) including the subduction of the Nazca plate. For that purpose, we used the FEM geodynamic code ASPECT. Our model includes visco-plastic rheology in addition to gabbro-eclogite phase transition. These preliminary results contribute to the discussion on the nature of the magnitude of shortening in a subduction system. They are also a first step to derive a 3D model of the entire region and to consider additional surface processes such as erosion, transportation and sedimentation. </span></p>

Lithospheric density structure of the Southern Central Andes and their forelands constrained by 3D gravity modelling

2020 ◽  
Author(s):  
Constanza Rodriguez Piceda ◽  
Magdalena Scheck-Wenderoth ◽  
Maria Laura Gómez Dacal ◽  
Judith Bott ◽  
Claudia Prezzi ◽  
...  
Keyword(s):  
Central Andes ◽  
Crustal Thickening ◽  
Velocity Variation ◽  
Mountain Range ◽  
South American ◽  
The South ◽  
Complex Deformation ◽  
Nazca Plate ◽  
Southern Central ◽  
The Relationship

<p>The Andean orogeny is a ~7000 km long N-S trending mountain range developed along the South American western margin. The formation of this mountain range is driven by the subduction of the oceanic Nazca plate beneath the continental South American plate, being the only known present-day case of subduction-type orogeny. In this tectonic setting, the intrinsic physical properties of the overriding plate govern the formation of zones of crustal strength and weakness and control the localization and the style of deformation. Furthermore, the dynamics of the subducting oceanic lithosphere is strongly conditioned by the properties of the continental counterpart. The southern segment of the Central Andes (29°S-39°S) is a suitable scenario to investigate the relationship between the two plates for several reasons. It is characterized by a complex deformation pattern with variations in horizontal shortening, crustal thickening and mean topographic elevation. In addition, the subduction angle changes at 33°S-35°S latitude from flat in the North to normal in the South. To gain insight into this geodynamic system, a detailed characterization of the lithosphere is needed. Therefore, we constructed a 3D model of the entire segment of the Southern Central Andes that is consistent with the available geological, seismic and gravity data in order to assess the geometry and density variation within the lithosphere. The derived configuration shows a spatial correlation between density domains and known tectonic features. It is also consistent with other independent observations such as S wave velocity variation and surface deformation. The generated structural model allows us to reach the first conclusions about the relationship between the characteristics of the overriding plate and the crustal deformation and dynamics of the subduction system. It is also useful to constrain thermomechanical experiments and therefore contributes to discussions about the crustal thermal and rheological fields within the region.</p>

Thrust belts of the southern Central Andes: Along-strike variations in shortening, topography, crustal geometry, and denudation

2012 ◽  
Vol 124 (7-8) ◽  
pp. 1339-1351 ◽  
Author(s):  
L. Giambiagi ◽  
J. Mescua ◽  
F. Bechis ◽  
A. Tassara ◽  
G. Hoke
Keyword(s):  
Central Andes ◽  
Thrust Belts ◽  
Southern Central

Early exhumation of the Frontal Cordillera (southern Central Andes at ~33.5°S) and implications for Andean mountain-building

2020 ◽  
Author(s):  
Robin Lacassin ◽  
Magali Riesner ◽  
Martine Simoes ◽  
Tania Habel ◽  
Audrey Margirier ◽  
...  
Keyword(s):  
Central Andes ◽  
Crustal Thickening ◽  
Mountain Range ◽  
Mountain Building ◽  
Ongoing Debate ◽  
First Order ◽  
The Andes ◽  
Minimum Age ◽  
Southern Central ◽  
Basement Structures

<p>The Andes are the modern active example of a Cordilleran-type orogen, with mountain-building
 and crustal thickening within the upper plate of a subduction zone. Despite numerous studies of
 this emblematic mountain range, several primary traits of this orogeny remain unresolved or poorly documented. The timing of uplift and deformation of the Frontal Cordillera basement culmination of
 the Southern Central Andes is such an example, even though this structural unit appears as a first-order topographic and geological feature. Constraining this timing and in particular the onset of uplift is a key point in the ongoing debate about the initial vergence of the crustal-scale thrusts at the start of the Cenozoic Andean orogeny. To solve for this, new apatite and zircon (U-Th)/He ages from granitoids of the Frontal Cordillera at ~33.5°S are provided here. These data, interpreted as an age-elevation thermochronological profile, imply continuous exhumation initiating well before ~12–14 Ma, and at most by ~22 Ma when considering the youngest zircon grain from the lowermost sample (Riesner et al. 2019). The inverse modeling of the thermochronological data using QTQt software confirms these conclusions and point to a continuous cooling rate since onset of cooling. The minimum age of exhumation onset is then refined to ~20 Ma by combining these results with data on sedimentary provenance from the nearby basins. Such continuous exhumation since ~20 Ma needs to have been sustained by tectonic uplift on an underlying crustal-scale thrust ramp. Such early exhumation and associated uplift of the Frontal Cordillera question the classically proposed east-vergent models of the Andes at this latitude. Additionally, this study provides further support to recent views on Andean mountain-building proposing that the Andes-Altiplano orogenic system grew firstly over west-vergent basement structures before shifting to dominantly east-vergent thrusts. <br>Riesner M. et al. 2019, Scientific Reports, DOI: 10.1038/s41598-019-44320-1</p>

Unravelling the thermal state of the southern Central Andes and its controlling factors

2021 ◽  
Author(s):  
Constanza Rodriguez Piceda ◽  
Magdalena Scheck-Wenderoth ◽  
Judith Bott ◽  
Maria Laura Gomez Dacal ◽  
Michaël Pons ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Thermal Field ◽  
Thermal State ◽  
Plate Boundary ◽  
Central Andes ◽  
Tectonic Deformation ◽  
S Wave ◽  
Nazca Plate ◽  
The North ◽  
The Andes

<p>The Andes represent the modern type area for orogeny at a non-collisional, ocean-continent convergent margin. Subduction geometry, tectonic deformation, and seismicity at this plate boundary are closely related to lithospheric temperature distribution in the upper plate. Despite recent advances in the assessment of the thermal state of the Andean lithosphere and adjacent regions derived from geophysical and geochemical studies, several unknowns remain concerning the 3D temperature configuration at lithospheric scale. In particular, it is not clear how both, the configuration of the continental overriding plate (i.e., its thickness and composition) and the variations of the subduction angle of the oceanic Nazca plate influence thermal processes and deformation in the upper plate. To address this issue, we focus on the southern segment of the Central Andes (SCA, 29°S-39°S), where the Nazca plate changes its subduction angle between 33°S and 35°S from the Chilean-Pampean flat-slab zone (< 5° dip, 27-33°S) in the north to a steeper sector south of 33°S (~30° dip). Additionally, the overriding plate exhibits variations in the crustal geometry and density distribution along- and across-strike of the subduction zone. We derived the 3D lithospheric temperature distribution and the surface heat flow of the SCA from the inversion of S-wave velocity to temperatures and calculations of the steady-state conductive thermal field. The configuration of the region – concerning both, the heterogeneity of the lithosphere and the slab dip – was accounted for by incorporating a 3D data-constrained structural and density model of the SCA into the workflow. We conclude that the generated thermal model allows us to evaluate how mantle thermal anomalies and first-order structural and lithological heterogeneities in the lithosphere, observed across and along-strike of Andean orogen, affect the thermal field of the SCA and thus the propensity of the South American lithosphere to specific styles in deformation. In addition, our results are useful to constrain thermo-mechanical simulations in geodynamic modelling and therefore, contribute to a better understanding of the present-day rheological state of the Andes and adjacent regions.</p>

Eruptive history of Incahuasi, Falso Azufre and El Cóndor Quaternary composite volcanoes, southern Central Andes

2018 ◽  
Vol 80 (5) ◽  
Author(s):  
Pablo Grosse ◽  
Yuji Orihashi ◽  
Silvina R. Guzmán ◽  
Hirochika Sumino ◽  
Keisuke Nagao
Keyword(s):  
Central Andes ◽  
Eruptive History ◽  
Southern Central ◽  
History Of

scholarly journals Lithospheric density structure of the southern Central Andes constrained by 3D data-integrative gravity modelling

2020 ◽  
Author(s):  
Constanza Rodriguez Piceda ◽  
Magdalena Scheck Wenderoth ◽  
Maria Laura Gomez Dacal ◽  
Judith Bott ◽  
Claudia Beatriz Prezzi ◽  
...  
Keyword(s):  
Density Distribution ◽  
Gravity Data ◽  
Spatial Relationship ◽  
Central Andes ◽  
Crustal Thickening ◽  
South American ◽  
Short Term ◽  
Nazca Plate ◽  
Southern Central

AbstractThe southern Central Andes (SCA) (between 27° S and 40° S) is bordered to the west by the convergent margin between the continental South American Plate and the oceanic Nazca Plate. The subduction angle along this margin is variable, as is the deformation of the upper plate. Between 33° S and 35° S, the subduction angle of the Nazca plate increases from sub-horizontal (< 5°) in the north to relatively steep (~ 30°) in the south. The SCA contain inherited lithological and structural heterogeneities within the crust that have been reactivated and overprinted since the onset of subduction and associated Cenozoic deformation within the Andean orogen. The distribution of the deformation within the SCA has often been attributed to the variations in the subduction angle and the reactivation of these inherited heterogeneities. However, the possible influence that the thickness and composition of the continental crust have had on both short-term and long-term deformation of the SCA is yet to be thoroughly investigated. For our investigations, we have derived density distributions and thicknesses for various layers that make up the lithosphere and evaluated their relationships with tectonic events that occurred over the history of the Andean orogeny and, in particular, investigated the short- and long-term nature of the present-day deformation processes. We established a 3D model of lithosphere beneath the orogen and its foreland (29° S–39° S) that is consistent with currently available geological and geophysical data, including the gravity data. The modelled crustal configuration and density distribution reveal spatial relationships with different tectonic domains: the crystalline crust in the orogen (the magmatic arc and the main orogenic wedge) is thicker (~ 55 km) and less dense (~ 2900 kg/m3) than in the forearc (~ 35 km, ~ 2975 kg/m3) and foreland (~ 30 km, ~ 3000 kg/m3). Crustal thickening in the orogen probably occurred as a result of stacking of low-density domains, while density and thickness variations beneath the forearc and foreland most likely reflect differences in the tectonic evolution of each area following crustal accretion. No clear spatial relationship exists between the density distribution within the lithosphere and previously proposed boundaries of crustal terranes accreted during the early Paleozoic. Areas with ongoing deformation show a spatial correlation with those areas that have the highest topographic gradients and where there are abrupt changes in the average crustal-density contrast. This suggests that the short-term deformation within the interior of the Andean orogen and its foreland is fundamentally influenced by the crustal composition and the relative thickness of different crustal layers. A thicker, denser, and potentially stronger lithosphere beneath the northern part of the SCA foreland is interpreted to have favoured a strong coupling between the Nazca and South American plates, facilitating the development of a sub-horizontal slab.

XXVII.—A Structural History of the Girvan District, S.W. Ayrshire

1959 ◽  
Vol 63 (3) ◽  
pp. 629-667 ◽  
Author(s):  
Alwyn Williams
Keyword(s):  
Maximum Stress ◽  
Second Order ◽  
Maximum Pressure ◽  
Reverse Fault ◽  
North West ◽  
North East ◽  
Structural Style ◽  
South West ◽  
Thrust Belts ◽  
History Of

SynopsisAn analysis of the structural style of the Palæozoic rocks exposed around Girvan in S.W. Ayrshire suggests that it was fashioned by at least nine phases of deformation. Five of these phases were active when maximum pressures were horizontal and together constitute the local expression of the Caledonian orogeny. The oldest phase recognized, the Main fold phase, consisted of overfolding due to an over-riding maximum pressure from between 150° and 170° and was penecontemporaneous with thrusting generated by a modal maximum stress from 145° to 325°. Three important thrust belts resulted but there were considerable local swings in the azimuths of maximum stress, a variation which culminated in the propagation of the Ardwell fold and reverse fault phase by a maximum stress from 110°. Later Caledonian movements, presumably influenced by an increase in overburden due to folding and thrusting, were represented by two episodes of wrench faulting: an older Ardwell “cross-fold” phase due to a maximum stress from north-east to south-west and a younger Main wrench system with a maximum stress aligned at 160–340° which generated an intricate pattern of sinistrai and dextral shears together with second-order relatives. The three following phases, the first, second and third “normal” phases represented an episode in stress history when the relief of pressure was horizontal and aligned from approximately north to south, north-north-west to south-south-east and just north of west to south of east respectively. Maximum pressures tended to vacillate between the vertical and near horizontal and as a result much of the faulting was oblique-slip. All three phases were responsible for important faults and some evidence is put forward to suggest that all three are possibly Proto-Armorican or probably not later than Armorican, although the existence of a few mineral veins shows that reactivation certainly took place in Borcovician times. An analysis of the tensional joints recorded for the area indicates that, apart from the dominant Caledonian and less conspicuous Armorican sets, Tertiary joints were formed when there was a relief of pressure from north-east to south-west and this final phase of deformation was accompanied by the intrusion of dykes.The study also includes discussions on the methods and merits of the resolution by stereographic means of the stress fields responsible for oblique-slip faults and on the nature and origin of first- and second-order wrench faulting in the light of the abundant statistical data available.

The Origin of the Mystery

Anaconda ◽  
2020 ◽  
pp. 222-232
Author(s):  
Jesús A. Rivas
Keyword(s):  
Pacific Ocean ◽  
South America ◽  
Large River ◽  
Nazca Plate ◽  
Congo River ◽  
The Andes ◽  
The Pacific ◽  
Western Border ◽  
History Of ◽  
The Pacific Ocean

This chapter traces the paleo-history of South America to tackle evolutionary questions about anacondas. Going back in history 150 million years ago, the current continents of South America and Africa were joined in a single mega-continent that also included current Australia and Antarctic. In the northern part of this continent (current South America and Africa) was a large river that started roughly where the current Congo River starts and drained the continent out of what is currently western Ecuador. Approximately 110 million years ago, South America separated from Africa and drifted west. The continent was drained by the paleo-Amazon. As South America drifted west, it collided with the Nazca plate in the eastern Pacific. As the two landmasses moved against each other, the Nazca plate subsided under South America, pushing up the western border of the latter, giving rise to the Andes. The creation of the Andes would result in the eventual closing of the drainage of the paleo-Amazon into the Pacific Ocean. The chapter looks at the significance of this paleo-history to the evolution of anacondas. It seems like the conditions in the paleo-history of the continent of constant flooding were not all that different from the conditions that anacondas encounter currently in the llanos.

Christianity in the Twentieth Century

2019 ◽  
Author(s):  
Brian Stanley
Keyword(s):  
Latin America ◽  
Racial Identity ◽  
Sub Saharan Africa ◽  
Central Importance ◽  
Regional Survey ◽  
History Of Christianity ◽  
The World ◽  
History Of ◽  
Sub Saharan ◽  
Different Parts

This book charts the transformation of one of the world's great religions during an age marked by world wars, genocide, nationalism, decolonization, and powerful ideological currents, many of them hostile to Christianity. The book traces how Christianity evolved from a religion defined by the culture and politics of Europe to the expanding polycentric and multicultural faith it is today—one whose growing popular support is strongest in sub-Saharan Africa, Latin America, China, and other parts of Asia. The book sheds critical light on themes of central importance for understanding the global contours of modern Christianity, illustrating each one with contrasting case studies, usually taken from different parts of the world. Unlike other books on world Christianity, this one is not a regional survey or chronological narrative, nor does it focus on theology or ecclesiastical institutions. The book provides a history of Christianity as a popular faith experienced and lived by its adherents, telling a compelling and multifaceted story of Christendom's fortunes in Europe, North America, and across the rest of the globe. It demonstrates how Christianity has had less to fear from the onslaughts of secularism than from the readiness of Christians themselves to accommodate their faith to ideologies that privilege racial identity or radical individualism.

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