Browsing by Author "Charrier, Reynaldo"

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    Late Cenozoic geomorphologic signal of Andean forearc deformation and tilting associated with the uplift and climate changes of the Southern Atacama Desert (26°S-28°S)
    (2007) Riquelme, Rodrigo; Herail, Gerard; Martinod, Joseph; Charrier, Reynaldo; Darrozes, Jose
    We analyze remarkable examples of the large (similar to 10,000 km(2)) and local-scale (similar to 100 km(2)) landscape forms related to Late Cenozoic geomorphologic evolution of the Andean forearc region in the Southern Atacama Desert. We also consider the continental sedimentary deposits, so-called "Atacama Gravels", which are related to the degradation of the landscape during the Neogene. Our analysis integrates 1:50,000 field cartography, Landsat TM images observations, similar to 1:1000 sedimentary logging data, and 50 m horizontal resolution topographic data to reconstruct the Late Cenozoic geomorphologic evolution of this region and discuss the factors that control it, i.e., Miocene aridification of the climate and Neogene Central Andean uplift. We determine that the Precordillera was already formed in the Oligocene and most of the present-day altitude of the Precordillera was reached before that time. Afterward, five episodes of geomorphologic evolution can be differentiated: (1) the development of an Oligocene deep incised drainage system cutting the uplifted Precordillera (up to 2000 m of vertical incision) and connecting it to the Ocean; followed by (2) the infilling of deep incised valleys by up to 400 m of Atacama Gravels. This infill started in the Early Miocene with the development of fluvial deposition and finished in the Middle Miocene with playa and playa lake depositions. We propose that playa-related deposition occurs in an endorheic context related to tectonic activity of the Atacama Fault System and Coastal Cordillera uplift. However, the upward sedimentologic variation in the Atacama Gravels evidences a progressive aridification of the climate. Subsequently, we have identified the effects of the Middle-Upper Miocene slow tectonic deformation: the Neogene Andean uplift is accommodated by a tilting or flexuring of the inner-foreare (Central Depression and Precordillera) related to some hundreds of meters of uplift in the Precordillera. This tilting or flexuring results in (3) the Middle Miocene re-opening of the valley network to the Pacific Ocean. Upper Miocene aridification, from and to hyperarid, induces alluvial fans backfilling in the Central Depression (4) resulting in up to 50 m of Atacama Gravel deposition. Finally, in response to an increase in the rate of tilting, a new phase of vertical incision (Lip to 800 in in the Precordillera) allows the development of the canyon that crosses the forearc (5). (c) 2006 Elsevier B.V. All rights reserved.
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    Unravelling geological controls on groundwater flow and surface water-groundwater interaction in mountain systems: A multi-disciplinary approach
    (ELSEVIER, 2023) Marti, Etienne Bernard Christian; Leray, Sarah Tiphaine Lucile; Villela, Daniela; Maringue Canales, José Ignacio; Yañez Morroni, Gonzalo José; Salazar, Esteban; Poblete, Fernando; Jiménez, Jose; Reyes, Gabriela; Poblete Farias, Guillermo Hernán; Huaman Sevilla, Zeidy Lisseth; Figueroa González, Ronny Javier; Araya Vargas, Jaime Andrés; Sanhueza, Jorge; Muñoz, Marjorie; Charrier, Reynaldo; Fernández, Gabriel
    Mountain water resources are considered to be the world's water towers. Still, despite their importance for downstream societies and ecosystems and their vulnerability to climate change, they remain poorly understood - It is the case in particular of mountain groundwater systems. Their complexity makes them difficult to conceptualize, while their remoteness makes them difficult to study, both observationally and instrumentally. Understanding mountain hydrogeological systems is mostly limited by the lack of characterization of the subsurface geologic framework and by the limited understanding of the role of geological structures on groundwater flow and on surface water-groundwater interaction. Removing methodological barriers is therefore a necessary step for improving the understanding of mountain hydrogeological systems. To tackle this problem, we develop a comprehensive multi-disciplinary approach to gain insights into the hydrogeological role of geological structures in ungauged mountain catchments. The methodology consists of several complementary methods: (1) geological mapping at multiple scales; (2) a geophysical study including on ground Electrical Resistivity Tomography (ERT) and, gravimetry transects, and a UAV-based magnetic survey; (3) hydraulic data, including a 9 km long transect of streamflow measurements in the recession period, the longterm Normalized Difference Vegetation Index (NDVI), and varied hydric markers (e.g., a thermal spring and a puddle). The methodology is tested in the Parque Nacional del Rio Clarillo, an ungauged catchment in the Andes Mountains (& AP;130 km2) that is illustrative of the complexity of mountain hydrosystems featuring fault zones, weathered zones, intrusive rocks, and volcano-sedimentary successions.An increase of approximately 50% in the streamflow is observed over a short distance of 1 km. Such a localized and significant increase in the baseflow is not related to any superficial supply and can only be explained by groundwater exfiltration. Based on the multiscale geological mapping and geophysical survey, a regional N-S fault and a secondary set of E-W local faults are identified in the vicinity of the resurgence area, which conjointly are likely to export groundwater from a neighbouring subcatchment up to the resurgence area. Downstream of the resurgence area, no significant change in the baseflow is observed, corresponding to the presence of an impermeable granitic pluton identified by the geological and geophysical mapping. Finally, a fractured zone in the Andean foothills is identified in the volcanic unit, which coincides with a perennial thermal spring, indicating upwelling flow and hydrogeological connectivity between the mountain block and the alluvial basin.The results strongly support the ability of the proposed methodology to identify geological structures that substantially impact the evolution of the baseflow through the catchment. The complementary multi-disciplinary methods are used innovatively to infer the link between geological and hydrogeological structures. The methodology does not aim to fully characterize the geological framework of the catchment but pragmatically focuses on hydrogeologically pertinent structures that may impact baseflow and consequently catchment management.