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Ítem Hydrogeochemical characteristics at Doña Juana Complex (SW Colombia): A new area for geothermal exploration in the Northern Andes region(Elsevier Ltd., 2020-01-01) Gómez Diaz E.; Marín Cerón M.I.; Gómez Diaz E.; Marín Cerón M.I.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaThe Doña Juana Volcanic Complex (DJVC) is an active volcanic zone located in southern Colombia, an area lacking geothermal exploration data. Using the results of hydrogeochemical analyses of hot springs, thermal waters were divided into two groups: Doña Juana System (DJS) and Las Animas System (AS). The DJS thermal waters are sulphate-bicarbonate and the AS dilute-chloride waters with relatively high concentrations of alkalis. The stable isotope and some element ratios suggested a mixing process between geothermal fluids and meteoric waters where AS is related to the upflow with a reservoir temperature around 180 °C estimated through solute geothermometers and mineral equilibrium geothermometry, showing a high temperature system in which the fault systems apparently play an important role in the flow of the geothermal fluids. © 2019 Elsevier LtdÍtem Tectonic and climate driven fluctuations in the stratigraphic base level of a Cenozoic continental coal basin, northwestern Andes(PERGAMON-ELSEVIER SCIENCE LTD, 2008-12-01) Tamayo, J. C. Silva; Sierra, G. M.; Correa, L. G.; Tamayo, J. C. Silva; Sierra, G. M.; Correa, L. G.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaChanges in the sedimentologic and stratigraphic characteristics of the coal-bearing middle Oligocene-late Miocene siliciclastic Amagá Formation, northwestern Colombia, reflect major fluctuations in the stratigraphic base level within the Amagá Basin, which paralleled three major stages of evolution of the middle Cenozoic Andean Orogeny. These stages, which are also traceable by the changes in the compositional modes of sandstones, controlled the occurrence of important coal deposits. The initial stage of evolution of the Amagá Basin was related to the initial uplift of the Central Cordillera of Colombia around 25 Ma, which promoted moderate subsidence rates and high rates of sediment supply into the basin. This allowed the development of aggradational braided rivers and widespread channel amalgamation resulting in poor preservation of both, low energy facies and geomorphic elements. The presence of poorly preserved Alfisols within the scarce flood plains and the absence of swamp deposits suggest arid climate during this stage. The compositional modes of sandstones suggest sediment supply from uplifted basement-cored blocks. The second stage of evolution was related to the late Oligocene eastward migration of the Pre-Andean tholeitic magmatic arc from the Western Cordillera towards the Cauca depression. This generated extensional movements along the Amagá Basin, enhancing the subsidence and increasing the accommodation space along the basin. As a result of the enhanced subsidence rates, meandering rivers developed, allowing the formation of extensive swamps deposits (currently coal beds). The excellent preservation of Entisols and Alfisols within the flood plain deposits suggests rapid channels migration and a humid climate during deposition. Moderate to highly mature channel sandstones support this contention, and point out the Central Cordillera of Colombia as the main source of sediment. Enhanced subsidence during this stage also prevented channels amalgamation and promoted both, high preservation of geomorphic elements and high diversity of sedimentary facies. This resulted in the most symmetric stratigraphic cycles of the entire Amagá Formation. The final stage of evolution of the Amagá Basin was related to the early stage of development of the late Miocene northwestern Andes tholeitic volcanism (from ~10 to ~8 Ma). The extensive thrusting and folding associated to this volcanism reduced the subsidence rates along the basin and thus the accommodation space. This permitted the development of highly aggradational braided rivers and promoted channels amalgamation. Little preservation of low energy facies, poor preservation of the geomorphic elements and a complete obliteration of important swamp deposits (coal beds) within the basin are reflected by the most asymmetric stratigraphic cycles of the whole formation. The presence of greenish/reddish flood plain deposits and Alfisols suggests a dry climate during this depositional stage. The presence of channel sandstones with high contents of volcanic rock fragments supports a dry climate, and suggests an incipient phase of the Combia tholeiitic magmatism present during deposition of the Amagá Formation. The subsequent eastward migration of the NW Andes magmatic arc (after ~8 Ma) may have produced basin inversion and suppressed deposition along the Amagá Basin. © 2008 Elsevier Ltd. All rights reserved.Ítem Timing of rifting in the southern Gulf of California and its conjugate margins: Insights from the plutonic record(Geological Society of America, 2015-05-01) Duque-Trujillo, J.F.; Duque-Trujillo, J.F.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaThe Gulf of California is a young example of crustal stretching and transtensional shearing leading to the birth of a new oceanic basin at a formerly convergent margin. Previous studies focused along the southwestern rifted margin in Baja California...