Claudia Prezzi - Academia.edu (original) (raw)
Papers by Claudia Prezzi
Lithospheric structure of the Central Andes based on a 3D gravimetric model. We developed a 3D de... more Lithospheric structure of the Central Andes based on a 3D gravimetric model. We developed a 3D density model of the conti nental crust, the subducted plate and the upper mantle of the Central Andes between 20-29°S and 74-61°W through the forward modelling of Bouguer anomaly. The goal of this contribution is to gain insight on the lithospheric structure of the area, integrating the available information (geophysical, geologic, petrologic, and geochemical) in a single model. The geometry of our model is defined and constrained by hypocenters location, reflection and refraction seismic lines, travel time and attenuation tomography, receiver function analysis, magnetotelluric studies, thermal models and structural cross sections. The densities allocated to the different bodies were calculated considering petrologic and geochemical data and pressure and temperature conditions. The model consists of 31 parallel E-W vertical planes, where the continental crust comprises distinct bodies, which represent the different morphotectonic units of the Central Andes. Contour maps of the depth to the top of the subducted plate, the depth of the continental Moho and the depth to the top of the asthenosphere below South America were produced. The residual anomaly was calculated by subtracting from the Bouguer anomaly the gravimetric effect of the modelled subducted slab and of the modelled Moho. This study demonstrates how 3D gravity modelling, integrating geophysical, geologic and petrologic information, can help to reveal the lithospheric structure of the Central Andes.
Journal of South American Earth Sciences
Tectonophysics, 2018
Evolution of the paleozoic claromecó basin (Argentina) and geodynamic implications for the southw... more Evolution of the paleozoic claromecó basin (Argentina) and geodynamic implications for the southwestern margin of Gondwana: Insights from isostatic, gravimetric and magnetometric models. Tecto (2017),
Tectonophysics, 2019
et al., 3D data-derived lithospheric structure of the Central Andes and its implications for defo... more et al., 3D data-derived lithospheric structure of the Central Andes and its implications for deformation: Insights from gravity and geodynamic modelling, Tectonophysics,
Journal of African Earth Sciences, 2014
Africa, without whose support we could not have successfully pursued our investigations of confir... more Africa, without whose support we could not have successfully pursued our investigations of confirmed and possible African impact structures.
Journal of Geophysical Research: Solid Earth, 2021
We present three‐dimensional (3D) models of the present‐day steady‐state conductive thermal field... more We present three‐dimensional (3D) models of the present‐day steady‐state conductive thermal field and strength distribution in the lithosphere beneath the Central Andes. Our primary objective was to investigate the influence that the structure of the Central Andean lithosphere has on its thermal and rheological state, and the relationship between the latter and the active deformation in the region. We used our previous data‐driven and gravity‐constrained 3D density model as starting point for the calculations. We first assigned lithology‐derived thermal and rheological properties to the different divisions of the density model and defined temperature boundary conditions. We then calculated the 3D steady‐state conductive thermal field and the maximum differential stresses for both brittle and ductile behaviors. We find that the thickness and composition of the crust are the main factors affecting the modeled thermal field, and consequently also the strength distribution. The orogen i...
DOAJ (DOAJ: Directory of Open Access Journals), May 1, 2012
ABSTRACT Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagn... more ABSTRACT Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (~19°S) and clockwise to the south. Different hypothe-sis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the CARP is a subject of ongoing debate. Recently, the quantity, quality, and geographic distribution of paleomagnetic data have expanded greatly. Such expansion has been accompanied by an increase in the knowledge of the deformation periods in the Andes, allowing a more detailed analysis of the temporal and spatial distribution of the detected rotations. We compiled and analyzed the available Cenozoic paleomagnetic data for the region extending between 19° and 27.5°S. The results suggest the possible existence of different rotational domains with distinct characteristics. We propose that in the Southern Central Andes, a close correlation would exist between the style and the temporal and spatial pattern of deformation and the amount of recorded vertical axis rotations. However, in order to further investigate such relationship, new paleomagnetic studies are necessary, particularly in the Eastern Cordillera domain, in Paleogene rocks cropping out in the Altiplano-Puna and in Neogene rocks of the forearc. RESUMEN. Rotaciones tectónicas según ejes verticales en los Andes Centrales del Sur: relaciones con el patrón de deformación. En los Andes Centrales se ha identificado un patrón de rotaciones tectónicas según ejes verticales a través de estudios paleomagnéticos. Dichas rotaciones son en sentido antihorario al norte del codo de Arica (~19°S) y en sentido horario hacia el sur. Distintos autores han propuesto diferentes hipótesis y modelos para tratar de explicar el Patrón de Rotaciones de los Andes Centrales (PRAC). Sin embargo, el PRAC sigue siendo objeto de debate. Reciente-mente, la cantidad, calidad y la distribución geográfica de los datos paleomagnéticos ha aumentado de manera notable. Dicho incremento ha sido acompañado por un importante progreso del conocimiento de los períodos de deformación en los Andes, permitiendo un análisis más detallado de la distribución espacial y temporal de las rotaciones detectadas. En este trabajo se recopilan y analizan los datos paleomagnéticos cenozoicos disponibles para la región que se extiende entre los 19° y los 27,5°S. Los resultados obtenidos sugieren la posible existencia de distintos dominios rotacionales con diferentes características. Aparentemente existe una estrecha correlación entre el estilo y el patrón espacial y temporal de deformación y la magnitud de las rotaciones según ejes verticales. Sin embargo, para investigar de manera más detallada dicha relación, es necesario disponer de un mayor número de datos paleomagnéticos. Especialmente, deberían llevarse a cabo nuevos estudios paleomagnéticos de rocas paleógenas del Altiplano-Puna, de rocas paleógenas y neógenas de la Cordillera Oriental y de rocas neógenas del norte de Chile. Palabras clave: Andes Centrales del Sur, Datos paleomagnéticos, Deformación, Dominios rotacionales, Cenozoico.
Journal of Geodynamics, Aug 1, 2014
Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identifie... more Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (∼19 • S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the origin of the CARP is a subject of ongoing debate. Recently, different authors have proposed the possible existence of a close correlation between the time-space distribution of deformation and the amount of registered vertical axis rotations in the Southern Central Andes. In order to further investigate such relationship, new paleomagnetic studies were carried out in Upper Oligocene-Lower Miocene rocks of the Northern Argentine Puna and the Southern Bolivian Altiplano. Our results indicate that while one of the sampled localities did not undergo significant vertical axis rotations, the other two recorded clockwise vertical axis rotations larger than 30 •. These results suggest the occurrence of small-block rotations in the Southern Bolivian Altiplano-Northern Argentine Puna prior to 15 Ma, which would correspond to the local accommodation of the regional deformation field.
International Journal of Earth Sciences, Sep 9, 2012
From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid... more From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid supercontinent called Pangea. The first palaeomagnetic data of South America indicated that the continent remained stationary in similar present-day latitudes during most of the Mesozoic and even the Palaeozoic. However, new palaeomagnetic data suggest that such a scenario is not likely, at least for the Jurassic. In order to test the stationary versus the dynamic-continent model, we studied the Jurassic apparent polar wander paths of the major continents, that is, Eurasia, Africa and North America that all in all show the same shape and chronology of the tracks with respect to those from South America. We thus present a master path that could be useful for the Jurassic Pangea. One of the most remarkable features observed in the path is the change in pole positions at ~197 Ma (Early Jurassic), which denotes the cessation of the counter-clockwise rotation of Pangea and commencement of a clockwise rotation that brought about changes in palaeolatitude and orientation until the end of the Early Jurassic (185 Ma). Here, we analyse a number of phenomena that could have triggered the polar shift between 197 and 185 Ma and conclude that true polar wander is the most likely. In order to do this, we used Morgan’s (Tectonophysics 94:123–139, 1983) grid of hotspots and performed “absolute” palaeogeographical reconstructions of Pangea for the Late Triassic and Jurassic. The palaeolatitudes changes that we observe from our palaeomagnetic data are very well sustained by diverse palaeoclimatic proxies derived from geological and palaeoecological data at this time of both the southern and northern hemispheres.
Surveys in Geophysics, Dec 15, 2022
Physics of the Earth and Planetary Interiors, Dec 1, 2014
The most remarkable feature of the Central Andes is the Altiplano-Puna plateau. This plateau is c... more The most remarkable feature of the Central Andes is the Altiplano-Puna plateau. This plateau is characterized by 3.5 km average elevation, approximately 70 km crustal thickness and very high heat flow. The upper mantle structure changes along strike below the plateau. The upper mantle below the Puna becomes hotter, and the lithosphere becomes thinner and weaker. These features suggest that thermal isostasy could play a role in the compensation of the Altiplano-Puna. Thermal isostasy is the geodynamic process whereby regional variations in the lithospheric thermal regime cause changes in elevation. Elevation changes result from variations in rock density in response to thermal expansion. The aim of this study is to estimate the thermal and geodynamic contributions to the elevation. While the thermal component of the Altiplano elevation would be of 1 km, the thermal contribution to the southern Puna elevation would be of 1.5 km. However, in the case of the southern Puna a portion of the actual topography ($20%) cannot be explained considering only compositional and thermal effects, suggesting additional geodynamical support. The obtained results suggest that the thermal state of the lithosphere would play a significant role in the elevation of the Central Andes, and may be responsible of some of the geological differences displayed by the Altiplano and the Puna.
Tectonophysics, Jul 1, 2014
The Chaco-Parana Basin was initiated during the late Oligocene as a result of shortening in respo... more The Chaco-Parana Basin was initiated during the late Oligocene as a result of shortening in response to Nazca-South America plate convergence, which produced a fold and thrust belt in the backarc region of the Central Andes. Foreland basins are the result of the flexural isostatic response of an elastic plate to orogenic and/or thrust sheet loading. We carried out flexural modeling along a W-E profile (22.5 degrees S) to determine flexural, crustal, and Chaco-Parana foreland basin development using available information on ages, elastic and sedimentary thicknesses, topographic and structural histories. We also developed a 3D flexural model, considering present day topography and elastic thickness values, in order to assess the possible existence of major differences with 2D models. It is possible to reproduce present day elevation, gravity anomaly, Moho depth, elastic thicknesses, foreland sedimentary thicknesses and the basin geometry. The 2D modeling also permits to reproduce foreland sedimentary thicknesses documented at 10 Ma and 12 Ma. The new results indicate that any decrease of the elastic thickness beneath the Eastern Puna-Eastern Cordillera would have occurred during the 14-12/10 Ma interval, suggesting a major change in the thermal state of the lithosphere during such time span. Coincidently, other authors determined the occurrence of a rapid elevation increase of the Southern Altiplano/Eastern Cordillera at 13-9 Ma, possibly related to piecemeal removal of lower lithosphere. In spite of the numerous limitations and simplifications mentioned above, our flexural model has shown to be a useful tool for the better understanding of the relationships between the development of the Chaco-Parana foreland basin and the spatiotemporal evolution of the Andean orogen.
The region north of Villarrica Volcano and the rupture zone of the 1960 Valdivia earthquake have ... more The region north of Villarrica Volcano and the rupture zone of the 1960 Valdivia earthquake have been studied extensively. However, previous work focused on the parts of the plate interface adjacent to the epicentre and did not cover the area of maximum slip (39–42°S). This region has been considered a seismic gap due to the scarcity of local earthquakes registered in this region; this is consistent with a locked plate interface upon which significant strain can accumulate. To investigate this part of the Chilean margin, the seismology subproject deployed 55 seismic stations between 39° and 40°S, covering the area from the coast to the back-arc in Argentina. The network was installed in November 2008 and operated for one year, consisting of 40 short-period and 15 broadband seismometers. The local seismicity is significantly higher than expected, with more than 1000 events out of which about 300 were localized in the area covered by the network. The plate interface where the 1960 slip occurred is free of seismicity. At greater depths, the Wadati-Benioff-Zone can be observed down to 160 km with a dip angle of 30°; some indication for a double Benioff-zone at shallower depths is found. In the continental crust, seismicity is observed related to local fault structures. Some clusters of seismicity occur offshore, associated with the trench and fault structures in the incoming oceanic plate. In addition to the seismicity, we present focal mechanisms and first results from local earthquake tomography.
International Journal of Earth Sciences, May 25, 2022
We present 3D thermal and rheological models of a key intra-plate locality of South America: the ... more We present 3D thermal and rheological models of a key intra-plate locality of South America: the southernmost limit of the Río de la Plata Craton area (which encompasses the Claromecó Basin, the Sierras Australes, and the Colorado Basin). Both models were calculated on the basis of a previously published 3D lithospheric scale density model, after the population of the different units with thermal and rheological properties. Firstly, the steady-state conductive thermal field was modelled using different thermal properties in accordance with the assumed lithological composition of the units. Moving forward, the strength distribution was calculated considering the resulting thermal field and published rheological properties for common rock types as input for the different layers that compose the 3D density configuration of the area. Our main results suggest that the thickness and composition of the crust exert a first-order control on the present-day thermal field of the area and, subsequently, on the lithospheric strength. Particularly, we identified a rheologically weak lithospheric zone that coincides with previously proposed inherited Paleozoic structures of Gondwana. This inherited lithospheric fabric could have controlled the opening of the Colorado Rift Basin during the early Late Jurassic. In that sense, the present day high strength of the Rio Negro and Colorado transfer zones associated with the mafic infill of Colorado rifting in the Mesozoic suggests that the weak zones should have necessarily been developed during (at least) Paleozoic to early Mesozoic times. This supports the hypothesis that the reactivation and interaction of the latter with the Gondwanic weak lithospheric zone could have deformed and uplifted the Sierras Australes during the Gondwanides Orogeny.
Andean Geology, May 30, 2012
Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically ... more Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (~19°S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the CARP is a subject of ongoing debate. Recently, the quantity, quality, and geographic distribution of paleomagnetic data have expanded greatly. Such expansion has been accompanied by an increase in the knowledge of the deformation periods in the Andes, allowing a more detailed analysis of the temporal and spatial distribution of the detected rotations. We compiled and analyzed the available Cenozoic paleomagnetic data for the region extending between 19° and 27.5°S. The results suggest the possible existence of different rotational domains with distinct characteristics. We propose that in the Southern Central Andes, a close correlation would exist between the style and the temporal and spatial pattern of deformation and the amount of recorded vertical axis rotations. However, in order to further investigate such relationship, new paleomagnetic studies are necessary, particularly in the Eastern Cordillera domain, in Paleogene rocks cropping out in the Altiplano-Puna and in Neogene rocks of the forearc.
Tectonophysics, Jun 1, 1998
... This vec tor would have produced components perpendicular and parallel to previous structural... more ... This vec tor would have produced components perpendicular and parallel to previous structural features, where the tangential components would be rightlateral to the south and leftlateral to the north of Arica, ex plaining the sense of the observed ... Elsevier, Amsterdam, pp. 562. ...
Journal of South American Earth Sciences
Geosphere, October 2017, v. 13, p. 1541-1554, doi:10.1130/GES01444.1, Supplemental Material. Pale... more Geosphere, October 2017, v. 13, p. 1541-1554, doi:10.1130/GES01444.1, Supplemental Material. Paleomagnetic analysis and paleoreconstructions of Pangea for three consecutive timespans.
Lithospheric structure of the Central Andes based on a 3D gravimetric model. We developed a 3D de... more Lithospheric structure of the Central Andes based on a 3D gravimetric model. We developed a 3D density model of the conti nental crust, the subducted plate and the upper mantle of the Central Andes between 20-29°S and 74-61°W through the forward modelling of Bouguer anomaly. The goal of this contribution is to gain insight on the lithospheric structure of the area, integrating the available information (geophysical, geologic, petrologic, and geochemical) in a single model. The geometry of our model is defined and constrained by hypocenters location, reflection and refraction seismic lines, travel time and attenuation tomography, receiver function analysis, magnetotelluric studies, thermal models and structural cross sections. The densities allocated to the different bodies were calculated considering petrologic and geochemical data and pressure and temperature conditions. The model consists of 31 parallel E-W vertical planes, where the continental crust comprises distinct bodies, which represent the different morphotectonic units of the Central Andes. Contour maps of the depth to the top of the subducted plate, the depth of the continental Moho and the depth to the top of the asthenosphere below South America were produced. The residual anomaly was calculated by subtracting from the Bouguer anomaly the gravimetric effect of the modelled subducted slab and of the modelled Moho. This study demonstrates how 3D gravity modelling, integrating geophysical, geologic and petrologic information, can help to reveal the lithospheric structure of the Central Andes.
Journal of South American Earth Sciences
Tectonophysics, 2018
Evolution of the paleozoic claromecó basin (Argentina) and geodynamic implications for the southw... more Evolution of the paleozoic claromecó basin (Argentina) and geodynamic implications for the southwestern margin of Gondwana: Insights from isostatic, gravimetric and magnetometric models. Tecto (2017),
Tectonophysics, 2019
et al., 3D data-derived lithospheric structure of the Central Andes and its implications for defo... more et al., 3D data-derived lithospheric structure of the Central Andes and its implications for deformation: Insights from gravity and geodynamic modelling, Tectonophysics,
Journal of African Earth Sciences, 2014
Africa, without whose support we could not have successfully pursued our investigations of confir... more Africa, without whose support we could not have successfully pursued our investigations of confirmed and possible African impact structures.
Journal of Geophysical Research: Solid Earth, 2021
We present three‐dimensional (3D) models of the present‐day steady‐state conductive thermal field... more We present three‐dimensional (3D) models of the present‐day steady‐state conductive thermal field and strength distribution in the lithosphere beneath the Central Andes. Our primary objective was to investigate the influence that the structure of the Central Andean lithosphere has on its thermal and rheological state, and the relationship between the latter and the active deformation in the region. We used our previous data‐driven and gravity‐constrained 3D density model as starting point for the calculations. We first assigned lithology‐derived thermal and rheological properties to the different divisions of the density model and defined temperature boundary conditions. We then calculated the 3D steady‐state conductive thermal field and the maximum differential stresses for both brittle and ductile behaviors. We find that the thickness and composition of the crust are the main factors affecting the modeled thermal field, and consequently also the strength distribution. The orogen i...
DOAJ (DOAJ: Directory of Open Access Journals), May 1, 2012
ABSTRACT Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagn... more ABSTRACT Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (~19°S) and clockwise to the south. Different hypothe-sis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the CARP is a subject of ongoing debate. Recently, the quantity, quality, and geographic distribution of paleomagnetic data have expanded greatly. Such expansion has been accompanied by an increase in the knowledge of the deformation periods in the Andes, allowing a more detailed analysis of the temporal and spatial distribution of the detected rotations. We compiled and analyzed the available Cenozoic paleomagnetic data for the region extending between 19° and 27.5°S. The results suggest the possible existence of different rotational domains with distinct characteristics. We propose that in the Southern Central Andes, a close correlation would exist between the style and the temporal and spatial pattern of deformation and the amount of recorded vertical axis rotations. However, in order to further investigate such relationship, new paleomagnetic studies are necessary, particularly in the Eastern Cordillera domain, in Paleogene rocks cropping out in the Altiplano-Puna and in Neogene rocks of the forearc. RESUMEN. Rotaciones tectónicas según ejes verticales en los Andes Centrales del Sur: relaciones con el patrón de deformación. En los Andes Centrales se ha identificado un patrón de rotaciones tectónicas según ejes verticales a través de estudios paleomagnéticos. Dichas rotaciones son en sentido antihorario al norte del codo de Arica (~19°S) y en sentido horario hacia el sur. Distintos autores han propuesto diferentes hipótesis y modelos para tratar de explicar el Patrón de Rotaciones de los Andes Centrales (PRAC). Sin embargo, el PRAC sigue siendo objeto de debate. Reciente-mente, la cantidad, calidad y la distribución geográfica de los datos paleomagnéticos ha aumentado de manera notable. Dicho incremento ha sido acompañado por un importante progreso del conocimiento de los períodos de deformación en los Andes, permitiendo un análisis más detallado de la distribución espacial y temporal de las rotaciones detectadas. En este trabajo se recopilan y analizan los datos paleomagnéticos cenozoicos disponibles para la región que se extiende entre los 19° y los 27,5°S. Los resultados obtenidos sugieren la posible existencia de distintos dominios rotacionales con diferentes características. Aparentemente existe una estrecha correlación entre el estilo y el patrón espacial y temporal de deformación y la magnitud de las rotaciones según ejes verticales. Sin embargo, para investigar de manera más detallada dicha relación, es necesario disponer de un mayor número de datos paleomagnéticos. Especialmente, deberían llevarse a cabo nuevos estudios paleomagnéticos de rocas paleógenas del Altiplano-Puna, de rocas paleógenas y neógenas de la Cordillera Oriental y de rocas neógenas del norte de Chile. Palabras clave: Andes Centrales del Sur, Datos paleomagnéticos, Deformación, Dominios rotacionales, Cenozoico.
Journal of Geodynamics, Aug 1, 2014
Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identifie... more Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (∼19 • S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the origin of the CARP is a subject of ongoing debate. Recently, different authors have proposed the possible existence of a close correlation between the time-space distribution of deformation and the amount of registered vertical axis rotations in the Southern Central Andes. In order to further investigate such relationship, new paleomagnetic studies were carried out in Upper Oligocene-Lower Miocene rocks of the Northern Argentine Puna and the Southern Bolivian Altiplano. Our results indicate that while one of the sampled localities did not undergo significant vertical axis rotations, the other two recorded clockwise vertical axis rotations larger than 30 •. These results suggest the occurrence of small-block rotations in the Southern Bolivian Altiplano-Northern Argentine Puna prior to 15 Ma, which would correspond to the local accommodation of the regional deformation field.
International Journal of Earth Sciences, Sep 9, 2012
From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid... more From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid supercontinent called Pangea. The first palaeomagnetic data of South America indicated that the continent remained stationary in similar present-day latitudes during most of the Mesozoic and even the Palaeozoic. However, new palaeomagnetic data suggest that such a scenario is not likely, at least for the Jurassic. In order to test the stationary versus the dynamic-continent model, we studied the Jurassic apparent polar wander paths of the major continents, that is, Eurasia, Africa and North America that all in all show the same shape and chronology of the tracks with respect to those from South America. We thus present a master path that could be useful for the Jurassic Pangea. One of the most remarkable features observed in the path is the change in pole positions at ~197 Ma (Early Jurassic), which denotes the cessation of the counter-clockwise rotation of Pangea and commencement of a clockwise rotation that brought about changes in palaeolatitude and orientation until the end of the Early Jurassic (185 Ma). Here, we analyse a number of phenomena that could have triggered the polar shift between 197 and 185 Ma and conclude that true polar wander is the most likely. In order to do this, we used Morgan’s (Tectonophysics 94:123–139, 1983) grid of hotspots and performed “absolute” palaeogeographical reconstructions of Pangea for the Late Triassic and Jurassic. The palaeolatitudes changes that we observe from our palaeomagnetic data are very well sustained by diverse palaeoclimatic proxies derived from geological and palaeoecological data at this time of both the southern and northern hemispheres.
Surveys in Geophysics, Dec 15, 2022
Physics of the Earth and Planetary Interiors, Dec 1, 2014
The most remarkable feature of the Central Andes is the Altiplano-Puna plateau. This plateau is c... more The most remarkable feature of the Central Andes is the Altiplano-Puna plateau. This plateau is characterized by 3.5 km average elevation, approximately 70 km crustal thickness and very high heat flow. The upper mantle structure changes along strike below the plateau. The upper mantle below the Puna becomes hotter, and the lithosphere becomes thinner and weaker. These features suggest that thermal isostasy could play a role in the compensation of the Altiplano-Puna. Thermal isostasy is the geodynamic process whereby regional variations in the lithospheric thermal regime cause changes in elevation. Elevation changes result from variations in rock density in response to thermal expansion. The aim of this study is to estimate the thermal and geodynamic contributions to the elevation. While the thermal component of the Altiplano elevation would be of 1 km, the thermal contribution to the southern Puna elevation would be of 1.5 km. However, in the case of the southern Puna a portion of the actual topography ($20%) cannot be explained considering only compositional and thermal effects, suggesting additional geodynamical support. The obtained results suggest that the thermal state of the lithosphere would play a significant role in the elevation of the Central Andes, and may be responsible of some of the geological differences displayed by the Altiplano and the Puna.
Tectonophysics, Jul 1, 2014
The Chaco-Parana Basin was initiated during the late Oligocene as a result of shortening in respo... more The Chaco-Parana Basin was initiated during the late Oligocene as a result of shortening in response to Nazca-South America plate convergence, which produced a fold and thrust belt in the backarc region of the Central Andes. Foreland basins are the result of the flexural isostatic response of an elastic plate to orogenic and/or thrust sheet loading. We carried out flexural modeling along a W-E profile (22.5 degrees S) to determine flexural, crustal, and Chaco-Parana foreland basin development using available information on ages, elastic and sedimentary thicknesses, topographic and structural histories. We also developed a 3D flexural model, considering present day topography and elastic thickness values, in order to assess the possible existence of major differences with 2D models. It is possible to reproduce present day elevation, gravity anomaly, Moho depth, elastic thicknesses, foreland sedimentary thicknesses and the basin geometry. The 2D modeling also permits to reproduce foreland sedimentary thicknesses documented at 10 Ma and 12 Ma. The new results indicate that any decrease of the elastic thickness beneath the Eastern Puna-Eastern Cordillera would have occurred during the 14-12/10 Ma interval, suggesting a major change in the thermal state of the lithosphere during such time span. Coincidently, other authors determined the occurrence of a rapid elevation increase of the Southern Altiplano/Eastern Cordillera at 13-9 Ma, possibly related to piecemeal removal of lower lithosphere. In spite of the numerous limitations and simplifications mentioned above, our flexural model has shown to be a useful tool for the better understanding of the relationships between the development of the Chaco-Parana foreland basin and the spatiotemporal evolution of the Andean orogen.
The region north of Villarrica Volcano and the rupture zone of the 1960 Valdivia earthquake have ... more The region north of Villarrica Volcano and the rupture zone of the 1960 Valdivia earthquake have been studied extensively. However, previous work focused on the parts of the plate interface adjacent to the epicentre and did not cover the area of maximum slip (39–42°S). This region has been considered a seismic gap due to the scarcity of local earthquakes registered in this region; this is consistent with a locked plate interface upon which significant strain can accumulate. To investigate this part of the Chilean margin, the seismology subproject deployed 55 seismic stations between 39° and 40°S, covering the area from the coast to the back-arc in Argentina. The network was installed in November 2008 and operated for one year, consisting of 40 short-period and 15 broadband seismometers. The local seismicity is significantly higher than expected, with more than 1000 events out of which about 300 were localized in the area covered by the network. The plate interface where the 1960 slip occurred is free of seismicity. At greater depths, the Wadati-Benioff-Zone can be observed down to 160 km with a dip angle of 30°; some indication for a double Benioff-zone at shallower depths is found. In the continental crust, seismicity is observed related to local fault structures. Some clusters of seismicity occur offshore, associated with the trench and fault structures in the incoming oceanic plate. In addition to the seismicity, we present focal mechanisms and first results from local earthquake tomography.
International Journal of Earth Sciences, May 25, 2022
We present 3D thermal and rheological models of a key intra-plate locality of South America: the ... more We present 3D thermal and rheological models of a key intra-plate locality of South America: the southernmost limit of the Río de la Plata Craton area (which encompasses the Claromecó Basin, the Sierras Australes, and the Colorado Basin). Both models were calculated on the basis of a previously published 3D lithospheric scale density model, after the population of the different units with thermal and rheological properties. Firstly, the steady-state conductive thermal field was modelled using different thermal properties in accordance with the assumed lithological composition of the units. Moving forward, the strength distribution was calculated considering the resulting thermal field and published rheological properties for common rock types as input for the different layers that compose the 3D density configuration of the area. Our main results suggest that the thickness and composition of the crust exert a first-order control on the present-day thermal field of the area and, subsequently, on the lithospheric strength. Particularly, we identified a rheologically weak lithospheric zone that coincides with previously proposed inherited Paleozoic structures of Gondwana. This inherited lithospheric fabric could have controlled the opening of the Colorado Rift Basin during the early Late Jurassic. In that sense, the present day high strength of the Rio Negro and Colorado transfer zones associated with the mafic infill of Colorado rifting in the Mesozoic suggests that the weak zones should have necessarily been developed during (at least) Paleozoic to early Mesozoic times. This supports the hypothesis that the reactivation and interaction of the latter with the Gondwanic weak lithospheric zone could have deformed and uplifted the Sierras Australes during the Gondwanides Orogeny.
Andean Geology, May 30, 2012
Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically ... more Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (~19°S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the CARP is a subject of ongoing debate. Recently, the quantity, quality, and geographic distribution of paleomagnetic data have expanded greatly. Such expansion has been accompanied by an increase in the knowledge of the deformation periods in the Andes, allowing a more detailed analysis of the temporal and spatial distribution of the detected rotations. We compiled and analyzed the available Cenozoic paleomagnetic data for the region extending between 19° and 27.5°S. The results suggest the possible existence of different rotational domains with distinct characteristics. We propose that in the Southern Central Andes, a close correlation would exist between the style and the temporal and spatial pattern of deformation and the amount of recorded vertical axis rotations. However, in order to further investigate such relationship, new paleomagnetic studies are necessary, particularly in the Eastern Cordillera domain, in Paleogene rocks cropping out in the Altiplano-Puna and in Neogene rocks of the forearc.
Tectonophysics, Jun 1, 1998
... This vec tor would have produced components perpendicular and parallel to previous structural... more ... This vec tor would have produced components perpendicular and parallel to previous structural features, where the tangential components would be rightlateral to the south and leftlateral to the north of Arica, ex plaining the sense of the observed ... Elsevier, Amsterdam, pp. 562. ...
Journal of South American Earth Sciences
Geosphere, October 2017, v. 13, p. 1541-1554, doi:10.1130/GES01444.1, Supplemental Material. Pale... more Geosphere, October 2017, v. 13, p. 1541-1554, doi:10.1130/GES01444.1, Supplemental Material. Paleomagnetic analysis and paleoreconstructions of Pangea for three consecutive timespans.