A new limit for the NW Río de la Plata Craton Border at about 24°S (Argentina) detected by Magnetotellurics

Old South American structures constitute a puzzle where the Río de la Plata Craton is the most important clue in the assembly of SW Gondwana. The present study is aimed at characterizing the western border of the Río de la Plata Craton on the basis of magnetotelluric studies. Magnetotelluric (MT) data were acquired along an approximately NW-SE 750km profile at about 24ºS, from the Sub-Andean Ranges in the province of Salta (NW) to the Formosa Province frontier (SE) next to Paraguay River. Distortion and structure dimensionality analysis indicates that MT responses are two-dimensional with a NS strike orientation, consistent with the regional geological strike. A 2-D inversion of the data provided a model showing a lateral discontinuity, possibly associated with cratonic structures. The high resistivity observed (>5000ohm·m), from about the middle of the profile toward its eastern end, may be interpreted as the terranes accreted to the Río de la Plata Craton during Neoproterozoic to Cambrian times, or as the Río de la Plata Craton itself. Along the profile from the surface to a depth of about 10km the resistivity model shows a significant resistivity variation in the structure. The resistive block identified at the western end of the profile represents the Sub-Andean system. The markedly enhanced low-resistivity structure (~1 to 10ohm·m) corresponds to a sedimentary pile whose thickness decreases from NW to SE.Fil: Favetto, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Rocha, Veronica. Universidad Nacional de Salta. Facultad de Cs.naturales. Escuela de Geología; ArgentinaFil: Pomposiello, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Garcia, Rodolfo Fernando. Universidad Nacional de Salta. Facultad de Cs.naturales. Escuela de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barcelona, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentin

Implementation of a web application firewall for a high availability front end

Nowadays, thanks to globalisation, companies and their bussines are growing fast, making their main objectives to keep up with market demands to satisfy user needs. Since market demands are not static, high availability is a requirement that a company infastructure must meet. If any company wants to stay competitive in these circumstances, it must be able to change what it is doing to fill the needs and wants that customers have. Therefore, companies experience growth in its resources, services and data while still having to provide the efficiency and the quality of service of the offered services. This study aims to determine how companies should protect their services and how they could scale them by analysing, designing, implementing and testing a high availability web application firewall in order to avoid security threats and, as the company's systems grows, to continue meeting market demands efficiently and securely.Avui en dia, gràcies a la globalització, les empreses i els seus negocis creixen ràpidament, cosa que fa que els seus objectius principals siguin seguir les exigències del mercat per satisfer les necessitats dels usuaris. Com les exigències del mercat no són estàtiques, l'alta disponibilitat és un requisit que ha d'acomplir la infastructura d'una empresa. Si alguna empresa vol mantenir la competència en aquestes circumstàncies ha de ser capaç de canviar el que està fent per cobrir les necessitats i els desitjos dels clients. Per tant, les empreses experimenten un creixement en els seus recursos, serveis i dades tot i que han de proporcionar l'eficiència i la qualitat del servei dels serveis oferts. Aquest estudi pretén determinar com les empreses han de protegir els seus serveis i com poden escalar-los analitzant, dissenyant, implementant i provant un web application firewall d'alta disponibilitat per tal d'evitar amenaces de seguretat i, a mesura que creixin els sistemes de l'empresa, per continuar acomplint les demandes del mercat de manera eficient i segura.Actualmente, gracias a la globalización, las empresas y sus negocios están creciendo rápidamente, lo que hace que sus objetivos principales sean satisfacer las demandas del mercado y satisfacer las necesidades de los usuarios. Dado que las exigencias del mercado no son estáticas, la alta disponibilidad es un requisito que deben cumplir las infraestructuras de la empresa. Si alguna empresa quiere mantenerse competitiva en estas circunstancias debe ser capaz de cambiar el enfoque de lo que está haciendo para satisfacer las necesidades y las necesidades que los clientes tienen al momento. Debido a ello, las empresas deben proporcionar la eficiencia y la calidad de los servicios, aunque experimenten un crecimiento en sus recursos, servicios y datos. Este estudio tiene como objetivo determinar cómo las empresas deben proteger sus servicios y cómo pueden escalarlos analizando, diseñando, implementando y probando un web application firewall de alta disponibilidad para evitar amenazas de seguridad y, a medida que crezcan los sistemas de la empresa, poder continuar satisfaciendo las exigencias del mercado de manera eficiente y de forma segura

Understanding the Caviahue-Copahue volcanic complex through kinematic solutions, paleotensors and analogue modelling

This work aims to study the interaction between two of the most representative structural systems controlling the Caviahue-Copahue volcanic complex. To achieve this objective, a structural analysis based on outcrop-scale fault-slip data field surveys and analogue models were carried out. The deformation regime acting on the studied area was characterized, and the associated paleostresses were obtained from the kinematic data inversion. The performed analysis in Caviahue-Copahue volcanic complex allowed to define two main sets of faults controlling the deformation of the area: NE-SW to ENE-WSW, and WNW-ESE to NW-SE, respectively. The first group comprises high-angle normal faults, resulting in a horst-and-graben setting with along-strike lengths up to 2 km. The second group shows strike-slip kinematics with a minor normal component. These NW-SE faults are related to the Miocene-Pliocene fissure-related volcanism and define the major caldera axis direction. In the geothermal area, the obtained paleostress orientation shows a consistent vertical σ1, denoting a local extensional regime. Regarding the geothermal field, the NE-SW extensional fault system is proposed as the main circulation pathways for hydrothermal fluids rising to the surface. The major NW-SE faults would act as barriers for this circulation. The set of analogous experiments was used to contrast the obtained local structural kinematic results. Two non-coaxial extensional events were established to achieve a local scale approach to the structural configuration observed in the area. Simulations aimed to understand the structural behavior of the superposition of non-coaxial extensive events; they allowed us to assess the role of the different fault sets surveyed in the field within the system. Particularly, our findings support that the NW-SE-oriented structures compartmentalize the subsequent NE-SW-oriented faults, acting on occasions as transfer zones.Fil: Vigide, Nicolás Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Servicio Geologico Minero Argentino. Instituto de Geologia y Recursos Minerales. Observatorio Argentino de Vigilancia Volcanica.; ArgentinaFil: Yagupsky, Daniel Leonardo. 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"; ArgentinaFil: Barcelona, Hernan. 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"; ArgentinaFil: Agusto, Mariano Roberto. 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"; ArgentinaFil: Caselli, Alberto Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; Argentin

Geothermal system of Despoblados by magnetotelluric data, Valle del Cura, San Juan

El Valle del Cura se emplaza dentro de un sistema de corrimientos N-S en la alta cordillera de San Juan. Este valle presenta manifestaciones geotermales variadas destacándose los manantiales hipertermales de Despoblados. El objetivo de este trabajo fue estudiar el fenómeno geotermal mediante magnetotelúrica de alta resolución para resolver la geometría del sistema en profundidad. Se midió alta frecuencia (1000 - 10 Hz) en 47 sitios y banda ancha (10 - 0,03 Hz) en 18 sitios. Se efectuó un procesamiento robusto de la señal y un análisis estándar de sus propiedades. Inversiones 2-D permitieron caracterizar la distribución de la resistividad eléctrica del subsuelo mediante 5 modelos luego integrados en uno pseudo 3-D. Los modelos definen dos anomalías conductivas, una de ellas directamente vinculada con los manantiales calientes y la otra sin expresión superficial. Ambas evidencian un fuerte control estructural y una circulación profunda de fluidos geotermales. El modelo del sistema geotermal propuesto para Despoblados implica zonas de surgencia tipo plumas canalizadas por las fallas que controlan la geometría del valle y zonas de recarga asociadas a los corrimientos principales, por donde se infiltra agua meteórica. No existe evidencia de un nivel estratigráfico somero que conforme el reservorio, aunque no se descarta la existencia de uno más profundo. La circulación profunda de fluidos bajo un gradiente geotérmico normal favorecería la convección, aunque no se descarta que esté localmente controlada por una anomalía térmica remanente del volcanismo del Cerro de Vidrio (1,5Ma). Finalmente, se abren interrogantes sobre la existencia de un sistema geotermal mayor que integre todas las manifestaciones de Valle del Cura.Valle delCura develops within a N-S thrust system in the high cordillera of San Juan. This valley has various geothermal manifestations, where the hot springs of Despoblados are highlighted. The aim of the work was to study the geothermal phenomenon by magnetotellurics, in order to obtain the geometry of the system in depth. High frecuency (1000 - 10 Hz) and broad band (10 - 0.03 Hz) were recorded in 47 and 18 sites. Robust signal processing and standard parameters analysis were performed. 2-D inversion of the data was carried out to obtain the electrical resistivity distribution through five models and a single pseudo 3-D model. The models defined two conductive anomalies, one directly linked with the hot springs and the other one without superficial manifestation. Both anomalies show structural control and a deep circulation of geothermal fluids. The proposed Despoblados geothermal system has plumes like upwelling zones channeled by faults that surround the valley and downwelling zones linked to the main thrusts, were the meteoric water leaks. Although there is no evidence of shallow lithostratigraphic level as reservoir, is not discarded the existence of one bellow 4000 m depth. The geothermal fluid circulation could be by normal geothermal gradient convection or favored by a remnant thermal anomaly from the Cerro de Vidrio volcanic event (1.5 Ma). Finally, some questions remains about the existence of a main geothermal systems that groups the apparent isolated manifestations on Valle del Cura.Fil: Barcelona, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Favetto, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Peri, Verónica Gisel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Pomposiello, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Ostera, Hector Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentin

Crustal structure of the Lazufre volcanic complex and the Southern Puna from 3-D inversion of magnetotelluric data: Implications for surface uplift and evidence for melt storage and hydrothermal fluids

The Central Andes are unique in the global system of subduction zones in that a significant, high-altitude plateau has formed above a subduction zone. In this region, both subduction and the associated magmatism have been shown to vary in both space and time. Geophysical data have been invaluable in determining the subsurface structure of this region. Extensive seismic studies have determined the regional-scale distribution of partial melt in the crust and upper mantle. Magnetotelluric studies have been effective in providing independent constraints on the quantity and composition of partial melt in the crust and upper mantle. Geodetic studies have shown that a small number of volcanic centers exhibit persistent, long-term uplift that may indicate the formation of plutons or future eruptions. This paper describes a detailed study of the Southern Puna using magnetotelluric (MT) data. This region is located at the southern limit of the Central Andes in a region where a recent transition from flat-slab subduction to normal subduction has caused an increase in magmatism, in addition to hypothesized lithospheric delamination. It is also a region where an extensive zone adjacent to the volcanic arc is undergoing surface uplift, located near Volcán Lastarria and Cordon del Azufre (collectively called Lazufre). The main goals of the work are to define the crustal structure and to investigate processes that may cause surface uplift of relatively large regions not associated with active volcanism. As part of the PLUTONS project, MT data were collected on an east-west transect (approximately along 25°S) that extended across the Southern Puna, from Lazufre to north of Cerro Galan. The data were combined with previously collected MT data around Lazufre and inverted to give a 3-D resistivity model of the crust. The low resistivity of the crust resulted in limited sensitivity to mantle structure. A number of major crustal conductors were detected and included (1) a mid-crustal conductor extending eastward from the volcanic arc as far as the Salar de Antofalla; (2) an upper- to mid-crustal conductor located north of Cerro Galan; and (3) a conductor that rises westward from (1) and terminates directly beneath the region of surface uplift at Lazufre. These conductors are broadly coincident with the location of crustal lowshear-wave anomalies. The conductive features were interpreted to be due to zones of partial melt stored in the crust, and petrological data were used to estimate melt fractions. Below Lazufre, it is likely that aqueous fluids contribute to the high conductivity, which is observed within the depth range of the inflation source, giving evidence that the surface uplift may be associated with both magmatic and hydrothermal processes

Structural control on carbon dioxide diffuse degassing at the Caviahue – Copahue Volcanic Complex, Argentina

The Caviahue – Copahue Volcanic Complex (CCVC) is located within the Andean Cordillera, in the Neuquén province, Argentina. This tectono-magmatic system lies within the northern termination of the Liquiñe – Ofqui fault zone, a 1,200-km-long intraarc strike-slip fault system. Fluid emissions at this active volcanic complex are fed by a hydrothermal reservoir located at 800 m depth, mostly recharged by meteoric water. The reservoir is heated by a magmatic chamber located at 5 km depth, which also provides the system with magmatic gases. Fluid emissions at the CCVC release over 200 tons per day of soil diffuse CO2. The aim of this study is to evaluate the control that the local structural architecture exerts on CO2 flow, from the hydrothermal reservoir to the surface.Fil: Lamberti, María Clara Isabel. 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"; ArgentinaFil: Vigide, Nicolás Carlos. 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"; ArgentinaFil: Venturi, Stefanía. Consiglio Nazionale delle Ricerche; ItaliaFil: Agusto, Mariano Roberto. 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"; ArgentinaFil: Yagupsky, Daniel Leonardo. 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"; ArgentinaFil: Winocur, Diego Alejandro. 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"; ArgentinaFil: Barcelona, Hernan. 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"; ArgentinaFil: Velez, Maria Laura. 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"; ArgentinaFil: Tassi, Franco. Università degli Studi di Firenze; ItaliaEGU General Assembly 2019VienaAustriaEuropean Geosciences Unio

Estudio clínico, observacional, de una nueva modalidad ventilatoria; Ventilación Asistida Proporcional. Hospital de la Santa Creu i Sant Pau, Barcelona, 2010

La ventilació assistida proporcional és una modalitat en la que el respirador genera una assistència proporcional a l'esforç muscular del pacient. En aquest estudi s'han inclòs vuit malalts en "weaning" de la ventilació mecànica. Es descriu la tolerància clínica i es quantifica l'esforç muscular dels pacients. L'esforç muscular va estar sempre dintre de límits predefinits de confort. Concloem que la ventilació assistida proporcional dóna una ventilació mecànica similar a altres modalitats i és probablement més fisiològica.La Ventilación Asistida Proporcional es una modalidad en la que el respirador genera una asistencia proporcional al esfuerzo muscular del paciente. En el estudio se incluyeron ocho pacientes en "weaning" de ventilación mecánica. Se describe la tolerancia clínica y analiza el esfuerzo muscular que los pacientes realizan. El esfuerzo muscular se mantuvo dentro de los niveles predefinidos de confort durante toda la ventilación. Concluimos que la ventilación asistida proporcional brinda una ventilación mecánica similar a otras modalidades ventilatorias y probablemente más fisiológica

The layered model of the Copahue geothermal reservoir, Argentina

Abstract An exhaustive review of the available data related to the reservoir of the volcano-hosted Copahue geothermal system is presented. Reservoir interpretation to date suggests a vapor-dominated nature. However, the review provided reveals the limitations of this model, regarding the transition from shallow argillic to deep propylitic alteration zones, gas geothermometers calibrated to near-neutral pH environment, production tests, and low recharge of the feed zone, among the other features. We propose that a layered model with a shallow vapor zone above a fluid pressurized reservoir better accounts for the known features of the geothermal reservoir. Temperature profiles define the 800-m-thick upper thermal boundary that includes the impermeable clay cap. An argillic alteration layer (smectite + chlorite + illite + kaolinite) with low electric resistivity response, consistent with the presence of smectite, composes the clay cap. A shallow steam cap develops immediately below the impermeable layer. This vapor zone has 200–215 °C, low seismic activity, and high electrical resistivity, and is highlighted by the isothermal segment of the well logs. The bottom part of the reservoir is subjected to controversy because of the lack of direct measurements. The deep liquid-dominated reservoir has a temperature of ~ 280 °C, develops below 1500 m depth under near-neutral pH condition, and probably has a pervasive propylitic alteration, and wairakite + laumontite + chlorite + epidote + prehnite + actinolite is the likely mineral assemblage. Pressure collapse might trigger the development of the shallow steam cap during deflation–inflation volcanic cycles or Pleistocene-to-recent tectonic deformation. This work points out the main weak points of the previous conceptual model, providing an alternative one based on the first comprehensive compilation of data of the Copahue reservoir. Further research, including a deep exploration drilling stage, is required to establish the physicochemical reservoir state precisely and to validate the proposed layered model

Resource assessment of the Copahue geothermal field

This paper assesses the electrical generating capacity of the Copahue geothermal field. Because it plays a critical role in driving financial support, we discuss these results in terms of its geothermal project. We performed a set of estimates, including the volumetric method and wellhead output calculations. The former was supported by a 3D-geological model that allowed us to subdivide the reservoir into blocks to constraint the parameters to each zone better. The probability models estimate that the proved resource can produce more than 10.2 MWe and 13.5 MWe at 90 % and 50 % confidence level, respectively. The wellhead power output calculations were supported by long- and short- period discharge test performed at three production wells and one slim hole and by the analysis of its decline paths. We estimate 10 MWe in the most optimistic prediction ruling out the identified power plant decline, above 5 % per year. Regardless of the method, our results support less than half of the previously calculated proven power output (i.e., 30 MWe) used to scale the offered tenders to develop a power plant. Overestimation cases worldwide invite us to be even more restricted over our power capacity estimations. Moreover, a tighter characterization of the reservoir volume (e.g., Chilean ranking) could redefine it from proven to probable, increasing the uncertainty over the resource. Throughout its 50 years of history the Copahue Geothermal Project reached significant milestones (first power plant on South America, a district –heating system, and four drilled wells). However, an in-depth review of the project history revealed several setbacks (closure of the power generation and direct use projects because of technical issues, developer retreatments, inadequate tenders) that partially explain its current on-hold status. We concluded that more work is needed before advancing towards the development stage of the project. The vast heat storage at Copahue is beyond doubt, but it is mandatory to improve the estimations of the steam supply, enhance the success rate of wells by a new drilling exploration stage, resize the projected power plant and perform a more accurate feasibility report. New attempts to attract investors and future developers should consider these goals and the project history to avoid new setbacks.Fil: Barcelona, Hernan. 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"; ArgentinaFil: Senger, Martin. Universidad de Ginebra; SuizaFil: Yagupsky, Daniel Leonardo. 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"; Argentin

Shallow geophysical evaluation of the transition zone between the Guaraní and Yrendá-Toba-Tarijeño aquifer systems (Argentine Gran Chaco)

The shallow geology and local hydrogeological systems of the Argentine Gran Chaco are poorly known. This area is part of the Chaco-Pampean Plain in the Andean foreland and is predominantly known by the subsurface data. Otumpa hills constitute a gentle topography located in the study area (26°- 28° S; 63°- 61° W) with N-S orientation. This morphology represents a transition zone between the western and eastern limits of the Guaraní and Yrendá-Toba-Tarijeño aquifer systems, respectively. Here, we report the results of two west-east profiles across Otumpa hills (northern profile at 26º40? S; southern profile at 27º S) consisting in vertical electrical soundings and audiomagnetotelluric soundings. We utilized 1-D and 2-D inversion techniques to obtain resistivity models from the measured data. The models defined several geoelectric layers, which were very consistent in both methods and in both profiles. We identified the upper geoelectric layer UL (> 20 Ω m), the semi-conductive geoelectric layers SC, SC2 and SC3 (6-20 Ω m), the conductive geoelectric layers C and C2 (4-8 Ω m) and the highly conductive geoelectric layers HC and HC2 (< 5 Ω m). SC and SC2 showed the best hydrogeological possibilities of presenting freshwater. These layers lie on very porous aeolian sandstone and very silty loess. This is because they are hosted in the Pampa formation northward, in the Chaco formation southwestward, and in the Chaco or Tacuarembó formations eastward, which are laterally uplifted. The shallowest SC is 10 meters thick while SC2 is 100 meters thick. Northward, SC2 provides continuity to an analogous geoelectric layer identified eastward. Several boreholes corroborate the presence of freshwater at both levels. HC and C in the audiomagnetotelluric profiles and C2 in the vertical electrical soundings profile suggest the presence of high-saline water (< 8 Ω m). This 100-meter-thick hydrogeological level is the most exploited in the area and is hosted by the Pampa and Chaco formations. However, the saturated zone for all layers is unknown. HC2, the deepest hydrogeological level (between 250 and 350 meters), is hosted by the Chaco and Tacuarembó formations and could be related to the thermal high-saline water found southeastward at a depth of 350 meters depth. We correlated the shallowest levels (SC, SC2, HC, C and C2) with the Toba aquifer system that may pass eastward the Guaraní aquifer system because the Tacuarembó Formation is the host there and the deepest level HC2 could also be related to the Guaraní aquifer system. The results provide a new shallow geological-geophysical model of the Otumpa hills area that reveals aquifers more associated with lithology and topography than with stratigraphy. A slight ductile deformation is evidenced by the geometric shapes of HC2 and SC2 and by the gentle tilts that accompany the slopes (SC2, HC and SC). Finally, the relevance of this work resides in the local aquifers identification and providing information to improve its usually poor management in this region. Moreover, further studies are likely to provide new insights into the hydrological interaction between the Guaraní and Yrendá-Toba-Tarijeño aquifer systems of the South American region.Fil: Peri, Verónica Gisel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; ArgentinaFil: Barcelona, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; ArgentinaFil: Pomposiello, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; ArgentinaFil: Rossello, Eduardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Favetto, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; Argentin