Examinando por Materia "pluton"
Mostrando 1 - 2 de 2
Resultados por página
Opciones de ordenación
Ítem Detrital zircon fission-track thermochronology and magnetic fabric of the Amagá Formation (Colombia): Intracontinental deformation and exhumation events in the northwestern Andes(ELSEVIER SCIENCE BV, 2017-07-01) Piedrahita, V.A.; Bernet, M.; Chadima, M.; Sierra, G.M.; Marín-Cerón, M.I.; Toro, G.E.; Piedrahita, V.A.; Bernet, M.; Chadima, M.; Sierra, G.M.; Marín-Cerón, M.I.; Toro, G.E.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaNew detrital zircon-fission track (ZFT) and magnetic fabric data are presented to constrain the time of deposition, provenance and deformation of the of Lower and Upper members of the Amagá Formation in the Amagá Basin. The Amagá Basin is located in the northern Andes, between the Western and Central Cordilleras of Colombia. The Amagá Formation was deposited in a transpressive geodynamic context and is allegedly synchronous with tectonic events such as the Andean orogeny and the Panama-Choco Block collision with the northwestern South American Plate. Detrital ZFT data confirm an Oligocene age for the Lower Member and a middle-Miocene age for the Upper Member of the Amagá Formation. In addition to constraining the depositional age, the ZFT data presented in this study also reflect Paleocene-Eocene, late to early Oligocene and late to middle Miocene cooling in sediment source areas mainly located in the Central and Western Cordilleras of Colombia. These ages can be associated with regional exhumation events in the central and northern Andes of South America. Collisional stages of the Panama-Choco Block against northwestern South America, subduction of the Farallon-Nazca Plate and strike-slip reactivation periods of the Cauca-Romeral fault system, caused NW-SE compression and NE-SW simple shear in the Amagá Basin. This deformational regime, identified by magnetic fabric data, induces syn- and post-depositional deformation over the Amagá Formation. © 2017 Elsevier B.V.Ítem Magnetic biomonitoring as a tool for assessment of air pollution patterns in a tropical valley using Tillandsia sp.(MDPI AG, 2018-07-01) Mejía-Echeverry, D.; Chaparro, M.A.E.; Duque-Trujillo, J.F.; Chaparro, M.A.E.; Miranda, A.G.C.; Mejía-Echeverry, D.; Chaparro, M.A.E.; Duque-Trujillo, J.F.; Chaparro, M.A.E.; Miranda, A.G.C.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaRecently, air pollution alerts were issued in the Metropolitan Area of Aburrá Valley (AVMA) due to the highest recorded levels of particulate matter (PM2.5 and PM10) ever measured. We propose a novel methodology based on magnetic parameters and an epiphytic biomonitor of air pollution in order to improve the air pollution monitoring network at low cost. This methodology relies on environmental magnetism along with chemical methods on 185 Tillandsia recurvata specimens collected along the valley (290 km2). The highest magnetic particle concentrations were found at the bottom of the valley, where most human activities are concentrated. Mass-specific magnetic susceptibility (?) reaches mean (and s.d.) values of 93.5 (81.0) and 100.8 (64.9) × 10-8 m3 kg-1 in areas with high vehicular traffic and industrial activity, while lower ? values of 27.3 (21.0) × 10-8 m3 kg-1 were found at residential areas. Most magnetite particles are breathable in size (0.2-5 µm), and can host potentially toxic elements. The calculated pollution load index (PLI, based on potentially toxic elements) shows significant correlations with the concentration-dependent magnetic parameters (R = 0.88-0.93; p < 0.01), allowing us to validate the magnetic biomonitoring methodology in high-precipitation tropical cities and identify the most polluted areas in the AVMA. © 2018 by the authors.