Browsing by Author "Viguier, Benoit"

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    Changes in the conceptual model of the Pampa del Tamarugal Aquifer : Implications for Central Depression water resources
    (2019) Viguier, Benoit; Daniele, Linda; Jourde, H.; Léonardi, Véronique; Yáñez Carrizo, Gonzalo Alejandro
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    Groundwater resources and recharge processes in the Western Andean Front of Central Chile
    (ELSEVIER, 2020) Taucare, Matias; Daniele, Linda; Viguier, Benoit; Vallejos, Angela; Arancibia, Gloria
    In Central Chile, the increment of withdrawals together with drought conditions has exposed the poor understanding of the regional hydrogeological system. In this study, we addressed theWestern Andean Front hydrogeology by hydrogeochemical and water stable isotope analyses of 23 springs, 10 boreholes, 5 rain-collectors and 5 leaching-rocks samples at Aconcagua Basin. From the upstream to the downstream parts of the Western Andean Front, most groundwater is HCO3-Ca and results from the dissolution of anorthite, labradorite and other silicate minerals. The Hierarchical Cluster Analysis groups the samples according to its position along the Western Andean Front and supports a clear correlation between the increasing groundwater mineralization (31-1188 mu S/cm) and residence time. Through Factorial Analysis, we point that Cl, NO3, Sr and Ba concentrations are related to agriculture practices in the Central Depression. After defining the regional meteoric water line at 33 degrees S in Chile, water isotopes demonstrate the role of rain and snowmelt above similar to 2000 m asl in the recharge of groundwater. Finally, we propose an original conceptual model applicable to the entire Central Chile. During dry periods, water releases fromhigh-elevation areas infiltrate in mid-mountain gullies feeding groundwater circulation in the fractured rocks of Western Andean Front. To the downstream, mountain-block and -front processes recharge the alluvial aquifers. Irrigation canals, conducting water from Principal Cordillera, play a significant role in the recharge of Central Depression aquifers. While groundwater in the Western Andean Front has a high-quality according to different water uses, intensive agriculture practices in the Central Depression cause an increment of hazardous elements for human-health in groundwater. (C) 2020 Elsevier B.V. All rights reserved.
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    Integration of Near-Surface Complementary Geophysical Techniques for the Study of Ancient Archaeological Areas in the Atacama Desert (Pampa Iluga, Northern Chile)
    (2023) Gallegos-Poch, Fernanda; Viguier, Benoit; Menanno, Giovanni; Mandakovic, Valentina; Yanez, Gonzalo; Gutierrez, Sergio; Lizarde, Catalina; Araya, Jaime Vargas; Lopez-Contreras, Camila; Mendez-Quiros, Pablo; Maldonado, Antonio; Uribe, Mauricio
    Near-surface geophysical techniques are useful for the characterization of archaeological areas because of their ability to rapidly cover wide extensions and obtain high-resolution data to identify the location for archaeological excavations. However, in hyperarid environments usual geophysical techniques may fail to obtain the expected results due to the dry near surface. This study proposes an integration of ground penetrating radar (GPR) and electromagnetic induction (EMI) techniques, to elucidate the origin of thousands of aligned circular features located at the Iluga archaeological area emplaced on one of the driest places on Earth (Pampa del Tamarugal, Atacama Desert). The GPR was useful to recognize alluvial deposits, sandy aeolian filling in pre-existing holes and roots right underneath circular features. Magnetic susceptibility data derived from the EMI in-phase component, usually considered a complementary result, were useful to identify fireplaces in the vicinity of the alignments. These geophysical findings were verified with an archaeological excavation. It has been found that circular features resulted from an extensive deforestation process in the Pampa del Tamarugal, consisting in the extraction of both trunk and roots of algarrobos (Prosopis chilensis) or tamarugos (Prosopis tamarugo), likely for recent charcoal production. The proposed methodology delivers promising results for archaeological and shallow geological studies in hyperarid and dry environments.
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    Selective reactivation of inherited fault zones driven by stress field changes: Insights from structural and paleostress analysis of the Pocuro Fault Zone, Southern Central Andes (32.8 degrees S)
    (PERGAMON-ELSEVIER SCIENCE LTD, 2022) Taucare, Matias; Roquer, Tomas; Heuser, Gert; Perez-Estay, Nicolas; Arancibia, Gloria; Yanez, Gonzalo; Viguier, Benoit; Figueroa, Ronny; Morataa, Diego; Daniele, Linda
    This study aims to explain the selective reactivation of normal faults during the Andean orogeny at the Southern Central Andes western flank. We conducted a structural mapping and paleostress field reconstruction in the regional-scale Pocuro Fault Zone (PFZ) at 32.8 degrees S. Results reveal that the architecture of the PFZ results from at least two deformation phases, each revealing an individual progressive and gradual evolution. The earliest deformation phase is recorded by two similar to NS-striking normal faults involving a 5 km wide damage zone characterized by quartz-laumontite and calcite veins that were developed under an extensional regime with a WNW-ESE-trending sigma 3-axis. The latest deformation phase is recorded by one NS-striking reverse-dextral fault with goethite-hematite syn-tectonic precipitation and two NW-striking reverse-sinistral faults. Reverse faults were developed under a compressional/transpressional regime characterised by an ENE-WSW-trending sigma 1-axis with a sigma 2-/sigma 3-axis permutation. From a geophysical data reassessment, we inferred that observed faults in the surface within the PFZ are regional-scale deep-seated structures. Considering previous geochronological data, we correlated the earliest and latest phases with the Abanico Basin extension (middle Eocene-early Miocene) and its subsequent inversion (Miocene). Given the neotectonic evidence (geomorphic markers and deformation of unconsolidated deposits), the latter phase likely remains active. Quartz-laumontite cementation of the fault core's cataclastic material promotes mechanical strengthening leading to negative feedback for the reactivation of inherited normal faults as reverse ones. Conversely, the concentration of fractures in the damage zone between the normal faults promotes mechanical weakening resulting in a preferential area for the propagation of reverse fault during the compressive/transpressional phase.