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El Valle de Tulum está ubicado en la provincia de San Juan, en el Centro-Oeste de Argentina y tiene una población de 629.530 habitantes. Se encuentra en una zona de la Diagonal Árida Sudamericana. Sus habitantes han convertido el territorio en un oasis de riego, aprovechando las aguas superficiales del río San Juan a través de tres grandes obras como son los embalses de Ullúm, Punta Negra y Caracoles, más uno aún en construcción; y las aguas subterráneas de su amplio abanico aluvial.Algunas prácticas antrópicas que en épocas pasadas contribuyeron al desarrollo de la región, como el drenaje de humedales, que amplían la frontera agrícola, hoy son el origen de suelos con severos problemas para habitar. En el siglo XIX, el valle se caracterizó por la presencia de cuerpos hidromórficos que lo ocuparon en su parte central, cerca del río San Juan. Este paleoambiente del Holoceno estaba formado por extensos humedales con agua permanente y un gran número de canales intercomunicados, así como por cauces de ríos abandonados. Los humedales desaparecieron por acciones de drenaje. Los nuevos suelos han permitido ampliar la frontera agrícola y proporcionar suelos orgánicos para la producción de alimentos.In recent years, the region has experienced a serious water deficit, due to decreasing snow fall and high temperatures in the Andes Mountains, where the basins that supply water to the river, are located. (Pucheta, 2021). This condition unfavorably affected the agricultural soils caused by the action of anthropic drainage, which caused a large part of them to remain available for the real estate market.In this new context, numerous problems have been detected and have been increasing with the water crisis due to climate change. For example, deformations and subsidence of the soil due to lower water tables, constructions on the river's paleochannels that are not visible to the naked eye because of anthropogenic changes in the landscape, which are evidenced through undulations and cracks in the streets and houses that can be detected by indirect geophysic consumption. As a result, there are dry vegetation areas and peat associated with old wetlands which are burnt during the summer, as well as salinization of the soil, among others. These problems have consequences, both for the environment, because it will not recover its original condition, and for the socio-economic dimension of the inhabitants, since the scarcity of irrigation water leads to the loss of agricultural and livestock production. Eventually, future scenarios that show serious difficulties in obtaining water for human consumption.

Unravelling the orogenic structure of the Sierra Grande de San Luis (Argentina) is essential to understand the geological evolution of the Famatinian orogen and the western margin of Gondwana. However, its structural organization is still poorly known and widely debated. In this contribution, a new interpretation of the complex geological structures in the southern sector of the Sierra Grande de San Luis is presented. This work is based on a litho-constrained joint inversion of gravity and magnetic datasets combining lithological, structural and rock properties information. Results are consistent with a large-scale doubly-vergent structure caused by a compressional tectonic setting as a consequence of the collision between an allochthonous terrane (Cuyania/Precordillera) and the proto margin of Western Gondwana. A convex morphology of the indenter is proposed to be responsible for producing a significant clockwise rotation of the horizontal deviatoric stresses. This stress field caused a small sinistral component of movement and gave rise to the doubly-vergent transpressive mega-structure. Fil: Christiansen, Rodolfo Omar. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Morosini, Augusto Francisco. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina Fil: Enriquez, Eliel. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina Fil: Muñoz, Brian Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Martínez, Myriam Patricia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Ortiz Suarez, Ariel Emilio. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina Fil: Kostadinoff, Jose. Universidad Nacional del Sur. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

A magnetotelluric survey comprising 18 broadband stations disposed along a 450 km-long profile was carried out at the transition between the Chaco-Parana (CPB) and the Parana (PB) intracratonic basins in northeastern Argentina. Three-dimensional inversions of the responses show that the CPB and southern PB lithospheres are resistive (~103 Ω m) down to 120 km, but with distinct crustal and upper mantle electrical properties. Also, Bouguer gravity and density anomalies are positive at CPB, whereas they are negative at PB. We associate the CPB lithosphere with the Paleoproterozoic Rio Tebicuary craton and the southern PB lithosphere with an ancient and buried piece of craton, the Southern Parana craton. Geochemical data of mantle xenoliths from the Cenozoic alkaline/carbonatitic province within the Rio Tebicuary craton suggest a subcontinental lithospheric mantle affected by metasomatic processes, which explains its lower resistivity (reaching values as low as 300 Ω m) and higher density (#Mg = 0.87). In contrast, the Southern Parana craton is more resistive (>103 Ω m) and less dense, suggesting a de-hydrated, depleted, and thicker craton. These cratons are separated by a crustal conductor (15 to 20 km depth; 1–10 Ω m) that we interpret as a southward continuation of a linear anomaly (Parana Axial Anomaly) defined in former induction studies within the PB in Brazil. Hence, we redefined the trace of this conductive lineament: instead of bending towards the Torres Syncline, it continues inside the CPB. We propose the lineament to be an Early Neoproterozoic suture zone that controlled the location of maximum subsidence in the intracratonic basins during the Paleozoic. In the Early Cretaceous, the Parana Axial Anomaly was the site of maximum extrusion and deposition of Serra Geral basalts. This anomaly separates compositionally distinct cratonic lithospheres along its path. Melting of this heterogeneous and enriched mantle created the Parana igneous province.

The Guacha Corral shear zone (GCSZ) is represented by mylonites that were developed under amphibolites facies conditions from migmatitic protoliths. In this contribution, geophysical, petrological and structural data were combined to determine the 3D geometry of the GCSZ. New gravimetric, magnetometric and structural studies, along an E-W profile, were integrated with existing magnetotelluric and seismological data from a representative regional database of the Eastern Sierras Pampeanas. The zonation of different fabrics across the GCSZ suggests that the pre-existing heterogeneities of the protoliths played a key role in governing the degree of metamorphism of different regions. The low gravity anomalies observed in the GCSZ suggest a transitional boundary zone between the migmatitic and mylonitic domains, where highly deformed shear bands are interspersed with undeformed rocks, presenting gradual contacts. The mylonites in this shear zone show a considerably reduced density when compared to the migmatite protoliths. The density of the rocks gradually increases with depth until it reaches that of the protolith. These changes in the gravity values in response to density changes allowed us to infer a listric geometry at depth of the GCSZ. Low gravity anomalies in the profiles, in regions where high density rocks (migmatites) outcrop at the surface, modeled as buried granitic plutons.

A high-resolution superficial geophysical study was carried out in an area of the retroarc region of the Andes mountains, located in the southwest of San Juan Province (31°45′ S, 68°50′ W), Central Precordillera of Argentina. The main objectives of this study were to confirm the presence of blind neotectonic structures and characterize them by observing variations in magnetic susceptibility, density and p-wave velocities. Geological evidence demonstrates the existence of a neotectonic fault scarps affecting Quaternary alluvial deposits in eastern piedmont of de Las Osamentas range, in addition to direct observation of the cinematic of this feature in several natural exposures. The Maradona valley is characterized by the imbricated eastern-vergence Maradona Fault System that uplifts Neogene sedimentary rocks (Albarracín Formation) over Quaternary (Late Pleistocene-Holocene) alluvial deposits. The combined application of different geophysical methods has allowed the characterization of a blind fault geometry also identified on a natural exposure. The magnetic data added to the gravimetric model, and its integration with a seismic profile clearly shows the existence of an anomalous zone, interpreted as uplifted blocks of Miocene sedimentary rocks of Formation Albarracín displaced over Quaternary deposits. The application and development of different geophysical methods, together with geological studies allow to significantly improving the knowledge of an area affected by Quaternary tectonic activity. Finally, this multidisciplinary study, applied in active blind structures is very relevant for future seismic hazard analysis on areas located very close to populated centers. Fil: Lara Ferrero, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Perucca, Laura Patricia A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina Fil: Rojo, Guillermo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina Fil: Vargas, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina Fil: Leiva, Flavia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina

Combined models from satellite gravity measurements and terrestrial observations provide a model of Earth’s gravity field with high spatial resolution and accuracy. In this work, we used the combined EIGEN-6C4 model and satellite-only GOCE data, both corrected for topography, to study the crustal structure of the transition zone between the Southern Central Andes and Patagonian Andes, adjacent foreland zone and Atlantic passive margin. We calculated gravity anomalies and vertical gravity gradients for mapping crustal density heterogeneities with the aim of validating and discussing previously proposed crustal models. This work provides additional geophysical constraints for several crustal structures that were discussed and proposed on the basis of geological evidence, such as the Pampean-Pan-African boundary that borders the western edge of the Rio de la Plata craton or the Famatinian paleogeographic boundary that juxtaposes the Laurentia-derived Cuyania and Pampean basement blocks. However, other gravimetric contrasts need to be further evaluated in relation to their tectonic significance, including the Malvinas Fault Zone through the Atlantic passive margin and the internal structure of the North Patagonian Massif. In this work, we highlight that new gravity field models are useful for identifying and mapping with high-precision crustal-order features, providing an innovative tool in geophysical exploration and development of tectonic and paleogeographic models.

This research is based on a joint geological and geophysical study performed in the South Central Andes region. We acquired and processed terrestrial and satellite gravity data, as well as terrestrial and aeromagnetic data. Balanced geological cross-sections were constrained by physical properties of rocks (densities and magnetic susceptibilities obtained from field samples and well log). This study was performed in order to interpret a complex region that is still under debate: the location of Famatinian magmatic arc and its boundary with the Cuyania terrain. By means of gravity anomaly we developed direct and inverse models constrained by field data. The existence of a major high-density geological structure was evidenced from these models, located below the Vinchina basin and to the east of Cerro Rajado respectively. The existence of such gravity high could be linked to the boundary between the Famatinian magmatic arc and the accreted Cuyania wedge.

The Iglesia basin hosts a key sedimentary archive of the evolution of the southern Central Andes. This basin is classically interpreted as recording the transition from an outer- to an inner-wedge-top (piggyback basin) depozone in the early Bermejo foreland basin system. In this study, we reevaluate the tectonic evolution of the Iglesia basin based on the interpretation of 2D seismic reflection data, structural geology, zircon U Pb geochronology, and provenance analysis. We report an extensional event that initiated the basin opening. Our results indicate normal faulting development and synextensional deposition from the latest Oligocene (?)-earliest Miocene to middle Miocene. Since the middle Miocene, extensional activity experienced a progressive decrease in changing to shortening and basin inversion between the middle-late Miocene. The latter stage coincided with the full development of Pampean flat-slab subduction indicating maximum plate coupling at that time. Our findings challenge the idea of uninterrupted Paleogene to Neogene flexural subsidence related to the Andean orogenic-load in the backarc area. Therefore, the results of this study have important consequences for the early evolution of the Bermejo foreland basin and ultimately, for the growth of the southern Central Andes.

Deformation along the 3,500 km subduction Pacific margin of the Peru-Chile trench is partially controlled by ocean bathymetric heterogeneities and sediments. Oceanic highs (e.g. ridges, fracture zones, plateaus) influence deformation in the fore-arc zone where collision occurs, and control turbiditic flow dispersal and consequently the amount of sediments accreted at the frontal accretionary prism and subduction channel, compartmentalizing the trench into segments linked to seismic segmentation. Recent satellite missions (CHAMP, GRACE and GOCE) have introduced an extraordinary improvement in the reconstruction of the global gravity field. Earth gravity field models, mainly derived from satellite measurements, reflect mass inhomogeneities of the earth. This chapter focuses on the determination of mass heterogeneities over the oceanic plate and their relation to general distribution of sediments over the Peru-Chilean margin, seismic segmentation along the margin, and the relationship between trench sediment thickness and the variable Andean orogenic volume, by means of a gravimetric analysis. Using the gravity potential model EGM2008 and satellite GOCE data we calculated two functionals of the geopotential: the Bouguer anomaly and the vertical gravity gradient, both corrected for the topographic effect. The vertical gravity gradient field is of special interest as it highlights main geological features, and allows unraveling unknown structures that are concealed by sediments. From these, different features can be clearly depicted such as the contact between the Pacific oceanic crust and the South American plate, the Nazca Ridge, the Juan Fernandez Ridge and the Chile Rise, among others. The segmentation between a filled trench south of Juan Fernandez Ridge, a partially filled trench to the north up to the Copiapo Ridge, and a completely starved trench north of this latitude is depicted. Finally, the relationship between gravity derived fields, high oceanic features and seismic segmentation is discussed for the last megathrust earthquakes that affected this subductive plate boundary. Fil: Alvarez Pontoriero, Orlando. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Braitenberg, Carla. Universita di Trieste; Italia

Global studies have assessed the importance of elastic thickness (Te) on orogenic evolution, showing that the style and nature of upper crustal shortening are influenced by the inherited lithospheric strength. Thus, pioneer works have identified that the upper crustal deformation style in the easternmost sector of the Central Andes in South America are related to the elastic thickness (Te). There, the thick-skinned and pure-shear style of Santa Bárbara system was initially related to the existence of low Te values. In contrast, the thin-skinned and simple-shear style of deformation in the Subandean system involves high Te values. However, more recent Te studies in the Central Andes present conflicting results which lead to question this straightforward relation. Results from these studies show a strong dependence on the applied methodology hampering the general understanding of the lithospheric thermo-mechanical state of the Central Andes. To contribute to this issue, we perform a high-resolution Te map, using forward modeling by solving flexural equation of infinite plate model in two dimensions. To achieve this, the crust-mantle interface was calculated using a high-resolution gravity anomaly dataset which combines satellite and terrestrial data, and an average density contrast. Additionally, the gravity anomaly and the foreland basin depth in the Central Andes were best predicted by considering that lower crustal rocks fill the space deflected downward in the plate model. The obtained Te values show an inverse correlation with previous heat flow studies, and a strong spatial correlation with the styles and mechanisms of deformation in the easternmost sector of the Central Andes. In the Santa Bárbara system Te values less than 10 km predominate, whereas in the Subandean system high Te values were observed. Such high values correlate with the orogenic curvature and with an shallower gravity Moho zone, which breaks the regional trend of the Central Andes. This shallower gravity Moho is linked to a high-gravity anomaly located in the east part of the Eastern Cordillera and Subandean system. These results are also correlated with a high-velocity zone in the upper mantle previously found by receiver functions studies. This correlation could indicate changes in the properties of the lower crustal rocks that justify the shallower gravity Moho zone and explain in part the highest Te values. Fil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lupari, Marianela Nadia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sanchez, Marcos Ariel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soler, Santiago Rubén. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Flat subduction segments are generally related to cold lithospheric zones, which suggest low Heat flow values and therefore a deeper Curie isotherm. In this study we perform a geophysical analysis by using high - resolution magnetic data, obtaining shallower Curie point depths through the Chilean-Pampean flat-slab zone. Then using temperatures from borehole data and Curie Point Depths, we performed a Heat Flow map which indicates the existence of mean to high thermal anomalies across the Chilean - Pampean flat-slab. These results were contrasted with Elastic Thickness map (Te) obtained from the Eigen-6C4 gravity model. Low Te values acquired indicate zones with weak mechanical behavior in correspondence to thermal anomalous zones. This spatial correlation suggests that the local high thermal anomalies are conditioning the mechanical behavior of the lithosphere in the study area and the locations of geothermal sources. Overall, our results indicate that the thermal structure of the flat-slab segment is more heterogeneous than previously thought. This has implications for evolution, maturity and fluid circulation in foreland basins of the Main and Frontal cordilleras and the Precordillera thrust belts. Finally, further studies will allow improving our database as well as extending our understanding of the thermal structure of the Chilean-Pampean flat-slab. Fil: Sanchez, Marcos Ariel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Ariza, Juan Pablo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gianni, Guido Martin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Weidmann, María Cecilia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martínez, Myriam Patricia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We present a new gravity map between 45°?70° W and 5°?40° S integrating open source terrestrial gravity data of Argentina with the South American Gravity Model 2004 (SAGM04), a 5 min-arc resolution gravity model. The Bouguer anomaly map reveals a 2000 km long linear gravity feature from 15° S to 30° S at longitude 55° W, with a steep horizontal gradient separating two gravity domains. The eastern domain is the Paraná basin, with NE-SW trending Bouguer anomalies of −80 mGal in average. The western domain comprises the Chaco-Paraná, Chaco-Tarija and Pantanal basins, with circular positive anomalies of up to 20 mGal in amplitude. Previous seismic studies mapped a thinner crust of less than 35 km in the western domain and the present gravity models indicate a 10?20 kg/m3 denser crust. On the other hand, the eastern domain has a thicker crust of more than 40 km. Seismic tomography models also show P- and S-wave velocity reduction in the western domain whereas high-velocity characterises the Paraná basin. These geophysical data indicate that the gravity gradient marks a transition between two distinct lithospheres. The gravity gradient is associated with a tectonic feature referred to as the Western Paraná suture/shear zone. Granites of 530?570 Ma ages, located parallel or over the gravity gradient, suggest a Neoproterozoic to Early Cambrian age suture/shear zone, thus approximately synchronous and parallel to the Pampean belt. Sediment corrected residual gravity map and its vertical derivative allow us to define the limits of the Rio Apa, Rio de la Plata and Rio Tebicuary cratons. Their eastern and western limits are the Western Paraná suture and the Pampean belt, respectively. This study unravels Precambrian tectonic elements concealed by the Phanerozoic sedimentary basins adding new constraints for the amalgamation history of SW Gondwana. Fil: Dragone, Gabriel Negrucci. Universidade de Sao Paulo; Brasil Fil: Ussami, Naomi. Universidade de Sao Paulo; Brasil Fil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Chaves, Carlos Alberto Moreno. Universidade de Sao Paulo; Brasil

A gravimetric analysis over the Tulum Valley was made. This data was used to reveal the structuralsetting of the Tulum Fault System situated in the southeastern part of San Juan province in the aridwestern part of Argentina. This system is the boundary between two geological provinces, the easternPrecordillera Oriental and the Sierras Pampeanas Occidentales. Gravity data was processed using upwardcontinuation and vertical derivative filters and all the results were compared with the geomorphologicaland the drainage systems maps of the area. Our assessment confirms the presence of two structures inthe Pampeano basement with positive anomalies similar to those found in Valdivia and Barboza hills,two important depocenters with low gravimetric gradients separated by a zone with higher gravityanomalies than the depocenters to the east and west. In view of this, a structural map is proposed for thearea. This system is important not only because it is the boundary between two geological provinces andhas significance regarding regional tectonic issues but also because it controls the surface drainage, soilsdistribution and groundwater flow of the Tulum basin conditioning the land use distribution. Fil: Rodríguez, Aixa Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Christiansen, Rodolfo Omar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Suvires, Graciela Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto de Geologia "Dr. Emiliano Aparicio"; Argentina Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Martínez, Myriam Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina

A high-resolution geophysical study was carried out in a region of the retroarc of the Patagonian Andes located on the western slope of the Sierra de El Maitén. This structure is characterized by an imbricated west-vergent fault system developed in the orogenic front area of the North Patagonian Andes that has uplifted. Oligocene volcanic rocks (Ventana Formation) affect Miocene to Quaternary sediments. Even though neotectonic fault scarps are affecting Quaternary deposits in the foothills of this range, no direct observation of slip in Quaternary strata was determined. The main objective of this study is to determine geometry of recognized neotectonic structures, characterizing them by variations in magnetic susceptibility, density, and p-wave velocities. The combined application of different geophysical methods has allowed the characterization of the bedrock geometry and the determination of neotectonic displacements along faults. The potential field model and its integration with a seismic profile show the accurate geometry of this tectonic zone, which is crucial for seismogenic hazard analysis, in the area of northern Patagonia, a highly significant economic zone due to tourism with several towns (El Maitén, Esquel, and San Carlos de Bariloche) dispersed throughout the area of young tectonic activity. Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Orts, Darío Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos ; Argentina Fil: Gimenez, Mario Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos ; Argentina Fil: Martinez, Patricia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina

The La Rioja Valley is a sedimentary basin in the Pampean Ranges, a region of basement uplifts and broad valleys in the Andean foreland. The present study advances understanding of the genesis of the basin by providing subsurface data on its geometry and characteristics. Gravity and topographic data, including a newly completed gravity survey, were integrated to create a complete Bouguer anomaly map. Euler and Werner deconvolution techniques sum with traditional potential-fields methods and sparse independent data from seismic and magnetotelluric methods to test and constrain the subsurface geophysical characterization of the La Rioja Valley Basin. The residual anomaly, obtained through upward continuation, was inverted to obtain the best 3D gravity model of the La Rioja Valley Basin, which shows the first-order geometry of the basin. This reveals that the basin is asymmetric, with up to [Formula: see text] of low-density basin fill in a depocenter located in the west-central sector of the valley. Second-order features of the basin include a southeast-trending basement high, likely a fault zone that subdivides the basin, which has been revealed by a suite of analytical methods (3D model of depth to basement, a 2D inverse model, and Werner deconvolution solutions).

GOCE satellite data and EGM2008 model are used to calculate the gravity anomaly and the vertical gravity gradient, both corrected by the topographic effect, in order to delineate main tectonic features related to density variations. In particular, using the Bouguer anomaly from GOCE, we calculated the crust–mantle discontinuity obtaining elastic thicknesses in the frame of the isostatic lithospheric flexure model applying the convolution method approach. Results show substantial variations in the density, compositional and thermal structure, and isostatic and flexural behavior of the continental lithosphere along the Southern Andes and adjacent foreland region.

The Cenozoic tectonic evolution of the North Patagonian Andes is analyzed linking geological and geophysical data in order to decipher the deformational processes that acted through time and relate them to basin formation. Field observations and seismic reflection profiles reveal the shallow structure of the retroarc area where contractional structures, associated with Oligocene to early Miocene inverted extensional sections, are partially onlapped by early to late Miocene synorogenic deposits. From the construction of five structural cross sections along the retroarc area between 40° and 43° 30′S, constrained by surface, gravity, and seismic data, a shortening gradient is observed along Andean strike. The highest shortening of 18.7 km (15.34 %) is determined near to 41° 30′S where basement blocks were uplifted in the orogenic front area, and the deepest and broadest synorogenic depocenters were formed toward the foreland. Additionally, eastward shifting of Miocene calc-alkaline arc rocks occurred at these latitudes, which is interpreted as indicative of a significant change in the subduction parameters at this time. Deep crustal retroarc structure is evaluated through inversion of gravity models that made also possible to infer Moho attenuated zones. These coincide with the occurrence of younger than 5 Ma within-plate volcanics as well as with crustal thermal anomalies suggested by shallowing of the Curie isotherm calculated from magnetic data.

The Oligocene to present evolution of the North Patagonian Andes is analyzed linking geological and geophysical data in order to decipher the deformational processes that acted through time and relate them to basin formation processes. Seismic reflection profiles reveal the shallow structure of the retroarc area where contractional structures, associated with Oligocene to early Miocene inverted extensional depocenters, are partially onlapped by early to late Miocene synorogenic deposits. From the construction of five structural cross sections along the retroarc area between 40° and 43°30′ S, constrained by surface, gravity and seismic data, a shortening gradient is observed along Andean strike. The highest shortening of 18.7 km (15.34%) is determined near 41°30′ S coincidentally with maximum mean topographic values on the eastern Andean slope, where basement blocks were uplifted in the orogenic front area, and the deepest and broadest synorogenic depocenters were formed towards the foreland. Additionally, eastward shifting of Miocene calc-alkaline rocks occurred at these latitudes, which is interpreted as indicative of a change in the subduction parameters at this time. Deep crustal retroarc structure is evaluated through inversion of gravity models that made possible to infer Moho attenuated zones. These coincide with the occurrence of younger than 5 Ma within-plate volcanics as well as with crustal thermal anomalies suggested by shallowing of the Curie isotherm calculated from magnetic data. Younger volcanism and thermal anomalies are explained by slab steepening since early Pliocene, after a mild-shallow subduction setting in the middle to late Miocene, age of the main compressive event. Fil: Orts, Darío Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Ruiz, Francisco. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Rojas Vera, Emilio Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Gravity measurements and reinterpretations of previously released seismic lines were made, focusing on the provincial border between neighboring provinces San Juan and Mendoza. A Bouguer anomaly map was obtained after the processing of gravimetric data, which were previously filtered, to obtain the Bouguer residual anomalies used for studying the geologic structures located on the upper crust. The analysis of these Bouguer residual anomalies allowed identification of the Jocolí Basin in a foreland position within a triangle zone at the boundary of the Precordillera fold-and-thrust belt with the Sierras Pampeanas thick-skinned foreland province. The seismic images allowed interpretation of three horizons: Paleozoic, Triassic, and Tertiary-Quaternary ages. The authors have reinterpreted the seismic and well data and reconstructed gravity models for the area under study aiming at unraveling the deep structure of the region and identifying features with potential for oil and gas exploration. Fil: Martinez, Myriam Patricia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Gimenez, Mario Ernesto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Folguera Telichevsky, Andres. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geologicas. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; Argentina Fil: Lince Klinger, Federico Gustavo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina

En el presente trabajo, a partir de datos gravimétricos terrestres, se preparó una carta de anomalías de Bouguer, la cual fue adecuadamente filtrada a fin de separar efectos gravimétricos someros y profundos. Con base en un modelo de densidad, mediante de técnicas de inversión gravimétrica, se modeló la discontinuidad corteza-manto y el basamento cristalino, respectivamente. De forma posterior, se evaluó el espesor elástico equivalente considerando la información de la discontinuidad de la corteza-manto y la carga topográfica. Se encontraron valores altos de espesor elástico Te, al este de la precordillera Andina y al oeste de la sierra Pampeana de Velasco. Estos resultados son consistentes con los valores positivos de anomalía residual de Bouguer e isotáticos, lo que estaría indicando la presencia de rocas de alta densidad en corteza media a superior. Además, los análisis petrográficos y geoquímicos realizados en afloramientos en superficie indican un origen mantélico. Fil: Weidmann, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Spagnotto, Silvana Liz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina Fil: Gimenez, Mario Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina Fil: Martinez, Myriam Patricia. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales. Instituto Geofisico Sismologico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Alvarez Pontoriero, Orlando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Sanchez, Marcos Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina

We present the results of a gravimetric study carried out in the region of the General Levalle sedimentary basin, Cordoba province, Argentina. We obtained the geometry of the basement roof for the region where the basin is located and the surface of the crust-mantle interface. The latter resulted in a surface of mild slope that deepens to the west. The fact that the interface crust-mantle is rather plane indicate that the sedimentary column has no antiroot that isostatically balances it. Also, the gravimetric effect of the sediments was evaluated and subtracted from the Bouguer anomalies. In the basin area, a positive gravimetric effect was identified, which may be linked to inhomogeneities located in the intermediate crust. On the basis of the gravimetric results, their comparison with stratigraphic analysis and of basin studies of the region, we propose possible alternatives that consider the presence of thick masses in the intermediate crust: 1)Emplacement of alkaline magmas during the Cretaceous extension, 2) An anomaly in the geometry of the crust, whether by the effect of a thinned crust associated to Cretaceous rifting or to Cenozoic extension or 3) Due to the flexion of the upper crustal layer during the Andean compression.

Se presenta un estudio gravimétrico en el borde noreste del macizo Norpatagónico provincia de Río Negro, con el objeto de conocer la distribución en profundidad de las distintas unidades aflorantes en el área de estudio, como así también, la geometría del Complejo Plutónico Navarrete. Las anomalías negativas en el mapa residual de Bouguer reproducen el cambio lateral de densidad entre lo que sería el basamento de edad Cámbrica y las unidades litológicas de edad Mesozoica. Las soluciones de la señal analítica junto a las variaciones en la curva del gradiente horizontal de la gravedad, obtenidas a lo largo de un perfil transversal a los afloramientos del Complejo Plutónico Navarrete, evidencian contactos entre el cuerpo intrusivo y la roca de caja de diferente densidad. Sobre este perfil se obtiene un modelo de inversión gravimétrico 2D ajustado con datos de densidad de rocas en superficie. Sobre el afloramiento del Complejo Yaminué existe un máximo gravimétrico que no se corresponde con su densidad en superficie. Esto es una nueva evidencia de que el mismo es una serie de intrusiones y escamas tectónicas delgadas subhorizontales y que su espesor es probablemente de poca magnitud. Por otro lado el Plutón Navarrete muestra mayor desarrollo en su tamaño y profundidad haciael este del arroyo Treneta. We present a gravimetric study on the northeast edge of the North Patagonian massif in the province of Rio Negro, to ascertain the depth distribution of the different outcrop units in the study area, as well as the geometry of the Navarrete Plutonic Complex. The negative anomalies in the Bouguer residual map reproduce the lateral density contrast between what would be the bedrock of Cambrian age and the lithologic units of the Mesozoic age. The solutions of the analytical signal along with variations in the curve of the horizontal gradient of gravity, obtained along a profile across the outcrops of the Navarrete Plutonic Complex, show contacts between the intrusive body and the bedrock with different densities. Over this profile we obtained a 2D (dimensional) gravimetric forward model adjusted with the density data of the surface rocks. Above the outcrop of the Yaminué Complex there exists a gravimetric high which does not correspond to the density in this area. This is a new evidence that proves that it is a series of intrusions and thin subhorizontal tectonic slices and that its thickness is probably thin. On the other hand theNavarrete Pluton shows the greatest development in size and depth to the east of Treneta stream. Fil: Lince Klinger, Federico Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Martínez, Myriam Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Rapalini, Augusto Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentina Fil: Gimenez, Mario Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Luchi, Mónica G. López de. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina Fil: Croce, Flavia Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Ruiz, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina