The impact of the South-American plate motion and the Nazca Ridge subduction on the flat subduction below South Peru

During evolution of the South Sandwich subduction zone, which has consumed South American plate oceanic lithosphere, somehow continental crust of both the South American and Antarctic plates have become incorporated into its upper plate. Continental fragments of both plates are currently separated by small oceanic basins in the upper plate above the South Sandwich subduction zone, in the Scotia Sea region, but how fragments of both continents became incorporated in the same upper plate remains enigmatic. Here we present an updated kinematic reconstruction of the Scotia Sea region using the latest published marine magnetic anomaly constraints, and place this in a South America-Africa-Antarctica plate circuit in which we take intracontinental deformation into account. We show that a change in fracture zone orientation in the Weddell Sea requires that previously inferred initiation of subduction of South American oceanic crust of the northern Weddell below the eastern margin of South Orkney Islands continental crust, then still attached to the Antarctic Peninsula, already occurred around 80 Ma. We propose that subsequently, between ~71-50 Ma, the trench propagated northwards into South America by delamination of South American lithosphere: this resulted in the transfer of delaminated South American continental crust to the overriding plate of the South Sandwich subduction zone. We show continental delamination may have been facilitated by absolute southward motion of South America that was resisted by South Sandwich slab dragging. Pre-drift extension preceding the oceanic Scotia Sea basins led around 50 Ma to opening of the Drake Passage, preconditioning the southern ocean for the Antarctic Circumpolar Current. This 50 Ma extension was concurrent with a strong change in absolute plate motion of the South American Plate that changed from S to WNW, leading to upper plate retreat relative to the more or less mantle stationary South Sandwich Trench that did not partake in the absolute plate motion change. While subduction continued, this mantle-stationary trench setting lasted until ~30 Ma, after which rollback started to contribute to back-arc extension. We find that roll-back and upper plate retreat have contributed more or less equally to the total amount of ~2000 km of extension accommodated in the Scotia Sea basins. We highlight that viewing tectonic motions in a context of absolute plate motion is key for identifying slab motion (e.g. rollback, trench-parallel slab dragging) and consequently mantle-forcing of geological processes.

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Recurrence of megathrust events: Impact on hazard and risk in South America

10.5194/egusphere-egu21-7112 ◽

2021 ◽

Author(s):

Jochen Woessner ◽

Jessica Velasquez ◽

Marleen Nyst ◽

Delphine Fitzenz ◽

Laura Eads

Keyword(s):

Risk Management ◽

South America ◽

Seismic Hazard ◽

Disaster Risk ◽

South American ◽

The South ◽

South American Plate ◽

Megathrust Earthquakes ◽

Hazard And Risk ◽

The Impact

Megathrust earthquakes along the South American subduction zone where the Nazca plate slips below the South American plate rapidly subducts below the South American plate contribute significantly to the seismic hazard in Chile, Peru, Ecuador and Colombia. Estimating recurrence of the megathrust events is of prime interest not only for securing effective counter measures for engineering purposes, but also for assessing seismic hazard and risk for appropriate disaster risk management solutions in the insurance sector.We present an evaluation and interpretation of recent research on the recurrence of megathrust earthquakes along the South America subduction zone. The modelling approach is conceptually founded in the asperity model and in this spirit evidence for documented earthquakes is assembled. We utilize time-independent and time-dependent recurrence models to understand the range and likelihood of recurrence times given the incomplete picture of the seismic history and the impact from uncertain event dates based on paleo-seismic / paleo-tsunami studies. In addition, we illustrate the sensitivity of recurrence rates for the largest earthquakes due to assumptions on seismic coupling and the size of potential ruptures.Downstream from the recurrence rate analysis, the results are used to estimate the impact of the subduction interface model seismicity on a select set of exposure subject to earthquake shaking due to those events. These examples highlight the potential range of seismic hazard and risk and set the basis to further constrain disaster risk management solutions.&#160;

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Impact of enriched analyses on regional numerical forecasts over southeastern South America during SALLJEX

Revista Brasileira de Meteorologia ◽

10.1590/0102-778620100248 ◽

2014 ◽

Vol 29 (3) ◽

pp. 315-330

Author(s):

Yanina García Skabar ◽

Matilde Nicolini

Keyword(s):

Data Assimilation ◽

South America ◽

Atmospheric Modeling ◽

South American ◽

The South ◽

Low Level ◽

Positive Effects ◽

Accumulated Rainfall ◽

Low Level Jet ◽

The Impact

During the warm season 2002-2003, the South American Low-Level Jet Experiment (SALLJEX) was carried out in southeastern South America. Taking advantage of the unique database collected in the region, a set of analyses is generated for the SALLJEX period assimilating all available data. The spatial and temporal resolution of this new set of analyses is higher than that of analyses available up to present for southeastern South America. The aim of this paper is to determine the impact of assimilating data into initial fields on mesoscale forecasts in the region, using the Brazilian Regional Atmospheric Modeling System (BRAMS) with particular emphasis on the South American Low-Level Jet (SALLJ) structure and on rainfall forecasts. For most variables, using analyses with data assimilated as initial fields has positive effects on short term forecast. Such effect is greater in wind variables, but not significant in forecasts longer than 24 hours. In particular, data assimilation does not improve forecasts of 24-hour accumulated rainfall, but it has slight positive effects on accumulated rainfall between 6 and 12 forecast hours. As the main focus is on the representation of the SALLJ, the effect of data assimilation in its forecast was explored. Results show that SALLJ is fairly predictable however assimilating additional observation data has small impact on the forecast of SALLJ timing and intensity. The strength of the SALLJ is underestimated independently of data assimilation. However, Root mean square error (RMSE) and BIAS values reveal the positive effect of data assimilation up to 18-hours forecasts with a greater impact near higher topography.

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ENSO impact on simulated South American hydro-climatology

Advances in Geosciences ◽

10.5194/adgeo-6-227-2006 ◽

2006 ◽

Vol 6 ◽

pp. 227-236 ◽

Cited By ~ 4

Author(s):

J. Stuck ◽

A. Güntner ◽

B. Merz

Keyword(s):

Climate Model ◽

Initial Conditions ◽

Circulation Model ◽

Empirical Orthogonal Functions ◽

South American ◽

The South ◽

Time Space ◽

The Pacific ◽

Hydro Climatology ◽

The Impact

Abstract. The variability of the simulated hydro-climatology of the WaterGAP Global Hydrology Model (WGHM) is analysed. Main object of this study is the ENSO-driven variability of the water storage of South America. The horizontal model resolution amounts to 0.5 degree and it is forced with monthly climate variables for 1961-1995 of the Tyndall Centre Climate Research Unit dataset (CRU TS 2.0) as a representation of the observed climate state. Secondly, the model is also forced by the model output of a global circulation model, the ECHAM4-T42 GCM. This model itself is driven by observed monthly means of the global Sea Surface Temperatures (SST) and the sea ice coverage for the period of 1903 to 1994 (GISST). Thus, the climate model and the hydrological model represent a realistic simulated realisation of the hydro-climatologic state of the last century. Since four simulations of the ECHAM4 model with the same forcing, but with different initial conditions are carried out, an analysis of variance (ANOVA) gives an impression of the impact of the varying SST on the hydro-climatology, because the variance can be separated into a SST-explained and a model internal variability (noise). Also regional multivariate analyses, like Empirical Orthogonal Functions (EOF) and Canonical Correlation Analysis (CCA) provide information of the complex time-space variability. In particular the Amazon region and the South of Brazil are significantly influenced by the ENSO-variability, but also the Pacific coastal areas of Ecuador and Peru are affected. Additionally, different ENSO-indices, based on SST anomalies (e.g. NINO3.4, NINO1+2), and its influence on the South American hydro-climatology are analysed. Especially, the Pacific coast regions of Ecuador, Peru and Chile show a very different behaviour dependant on those indices.

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The Legacy of European Colonialism

The Physical Geography of South America ◽

10.1093/oso/9780195313413.003.0026 ◽

2007 ◽

Author(s):

Gregory Knapp

Keyword(s):

Eighteenth Century ◽

Fifteenth Century ◽

New Technologies ◽

Colonial Period ◽

Resource Extraction ◽

South American ◽

The South ◽

European Colonialism ◽

The Impact ◽

The Guianas

South America was first “encountered” by Europeans during Columbus’ third voyage in 1498. This marked the end of the pre-Columbian period of the continent, and the beginning of the colonial period that lasted until the end of the wars of independence in the early nineteenth century. Total liberation of the continent from Spain was finally achieved at the Battle of Ayacucho in 1824. Brazilian independence from Portugal was achieved more peacefully in 1822, when Dom Pedro became constitutional emperor. The Guianas remained colonies far longer; indeed Guyane (French Guiana) is still an overseas department of France, while Suriname (Dutch Guiana) became independent in 1975, and Guyana (originally a Dutch colony, later British) became independent in 1966. It could be suggested that dependency remained after the end of formal colonial rule, owing to the continued influence of global economic powers on the continent. However, for the purposes of this chapter, the colonial period can be considered as lasting for 326 years from 1498 to 1824. If recent research has tended to enhance our appreciation of the impact of pre-Columbian peoples on the South American environment, it has also corrected some stereotypes concerning European colonial impacts. Europeans were not the first to substantially impact the South American environment. The colonial period was generally marked by depopulation and agricultural disintensification, with the result that many environments were more “pristine” at the end of the eighteenth century than at the end of the fifteenth century. Migrations, cultural hybridities, and new local, regional, and global economic linkages led to changes in demands on agriculture and resource extraction. New technologies, crops, and social structures also had an impact. These impacts were not always as negative as sometimes portrayed, and local populations often had a substantial say in the outcome. Many of the most noticeable impacts resulting from the encounter with Europeans did not become widespread until after independence (McAlister, 1984; Bethell, 1987; Hoberman, 1996; Hoberman et al., 1996; Mörner, 1985; Newson, 1995; Robinson, 1990; Butzer and Butzer, 1995).

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Lithosphere Structure of the South American Plate From Dispersion of Surface Waves

10.3997/2214-4609-pdb.313.320 ◽

1995 ◽

Author(s):

M.A. Carvalho

Keyword(s):

Surface Waves ◽

South American ◽

The South ◽

South American Plate ◽

Lithosphere Structure

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The impact of the subtropical South Atlantic SST on South American precipitation

Annales Geophysicae ◽

10.5194/angeo-26-3457-2008 ◽

2008 ◽

Vol 26 (11) ◽

pp. 3457-3476 ◽

Cited By ~ 24

Author(s):

A. S. Taschetto ◽

I. Wainer

Keyword(s):

South America ◽

Southern Oscillation ◽

South Atlantic ◽

Empirical Orthogonal Functions ◽

Convergence Zone ◽

South American ◽

The South ◽

Inter Tropical Convergence Zone ◽

The Impact ◽

Sst Anomalies

Abstract. The Community Climate Model (CCM3) from the National Center for Atmospheric Research (NCAR) is used to investigate the effect of the South Atlantic sea surface temperature (SST) anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed. A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF) is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM) and spring (SON) precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF) and winter (JJA) rainfall. While the Inter-tropical Convergence Zone (ITCZ) region is dominated by external variance, the South Atlantic Convergence Zone (SACZ) over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent. An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño – Southern Oscillation (ENSO). Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic branch during MAM. Both local and remote influences, however, are confounded by the large internal variance in the region. During MAM and JJA, the South Atlantic SST anomalies affect the magnitude and the meridional displacement of the ITCZ. In JJA, the ENSO has relatively little influence on the interannual variability of the simulated rainfall. During SON, however, the ENSO seems to counteract the effect of the subtropical South Atlantic SST variations on convection over South America.

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Lithospheric magnetic property contrasts within the South American plate derived from damped least-squares inversion of satellite magnetic data

Tectonophysics ◽

10.1016/0040-1951(91)90254-p ◽

1991 ◽

Vol 192 (1-2) ◽

pp. 159-168 ◽

Cited By ~ 6

Author(s):

D.N. Ravat ◽

W.J. Hinze ◽

R.R.B. von Frese

Keyword(s):

Magnetic Property ◽

Least Squares ◽

Magnetic Data ◽

South American ◽

The South ◽

South American Plate ◽

Damped Least Squares

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Metamorphic evolution of Raspas complex (Ecuador) and its relation with a J-K belt of melanges in NW of the South American plate.

10.5194/egusphere-egu2020-12395 ◽

2020 ◽

Author(s):

Mayda Arrieta-Prieto ◽

Carlos Zuluaga-Castrillón ◽

Oscar Castellanos-Alarcón ◽

Carlos Ríos-Reyes

Keyword(s):

High Pressure ◽

Subduction Zones ◽

Mineral Chemistry ◽

White Mica ◽

Petrographic Analysis ◽

South American ◽

The South ◽

South American Plate ◽

Subduction Channel ◽

Southern Ecuador

High-pressure complexes along the Earth's surface provide evidence of the processes involved in both the crystallization of rocks in the subduction channel and its exhumation. Such processes are key to understand the dynamics and evolution of subduction zones and to try to reconstruct P-T trajectories for these complexes.Previous studies on the Raspas complex (southern Ecuador) agree to state that it is composed of metamorphic rocks, mainly blueschists and eclogites, containing the mineral assemblage: glaucophane + garnet + epidote + omphacite + white mica + rutile &#177; quartz &#177; apatite &#177; pyrite &#177; calcite; which stabilized in metamorphic conditions of high pressure and low temperature. Additionally, the Raspas Complex has been genetically related to accretion and subduction processes of seamounts, which occurred in South America during the Late Jurassic - Early Cretaceous interval; and the exhumation of the complex was related to subduction channels. However, the evidence presented in the existing literature makes little emphasis on the reconstruction of thermobarometric models for the rocks of this complex.By combining petrographic observations, whole-rock chemistry, and mineral chemistry in this work; it was possible to determine that pressure values of 10 &#177; 3 Kbar and temperature values of 630 &#177; 30 &#176; C, (obtained by simulations with THERMOCALC&#174;) correspond to an event of retrograde metamorphism, suffered by the complex during its exhumation. This theory is complemented by the specific textures (that suggest this retrograde process) observed during petrographic analysis, such as amphibole replacing pyroxene, garnet chloritization, plagioclase crystallization and rutile replacement by titanite.The results obtained, together with the thermobarometry data published for the Arqu&#237;a complex in Colombia, allow us to establish a P-T trajectory, that may suggest a genetic relationship between these two complexes as a result of the tectonic processes associated with an active subduction margin that affected the NW margin of the South American plate at the end of the Jurassic.&#160;

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Geodynamic study of the north of the Andes block (Colombia, Panama, Ecuador and Venezuela) through gnss-gps: models of displacements, models of deformation and definition of local and regional geodynamic structures.

10.5194/egusphere-egu2020-21362 ◽

2020 ◽

Author(s):

Berrocoso Manuel ◽

Del Valle Arroyo Pablo Emilio ◽

Colorado Jaramillo David Julián ◽

Gárate Jorge ◽

Fernández-Ros Alberto ◽

...

Keyword(s):

South America ◽

Seismic Activity ◽

Great Part ◽

Velocity Model ◽

South American ◽

The South ◽

South American Plate ◽

Northern Andes ◽

Velocity Models ◽

The North

The northwest of South America is conformed by the territories of Ecuador, Colombia and Venezuela. Great part of these territories make up the Northern Andes Block (BAN). The tectonic and volcanic activity in the northwest of South America is directly related to the interaction of the South American plate, and the Nazca and Caribbean plates, with the Maracaibo and Panama-Choc&#243; micro plates. The high seismic activity and the high magnitude of the recorded earthquakes make any study necessary to define this complex geodynamic region more precisely. This work presents the velocity models obtained through GNSS-GPS observations obtained in public continuous monitoring stations in the region. The observations of the Magna-eco network (Agust&#237;n Codazzi Geographic Institute) are integrated with models already obtained by other authors from the observations of the GEORED network (Colombian Geological Service). The observations have been processed using Bernese software v.52 using the PPP technique; obtaining topocentric time series. To obtain the speeds, a process of filtering and adjustment of the topocentric series has been carried out. Based on this velocity model, regional structures have been defined within the Northern Andes Block through a differentiation process based on the corresponding speeds of the South American, Nazca and Caribbean tectonic plates. Local geodynamic structures within the BAN itself have been established through cluster analysis based on both the direction and the magnitude of each of the vectors obtained. Finally, these structures have been correlated with the most significant geodynamic elements (fractures, faults, subduction processes, etc.) and with the associated seismic activity.

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