Examinando por Materia "fission track dating"
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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 Fission-track datings and geomorphic evidences for long-term stability in the Central Cordillera highlands, Colombia(Gebruder Borntraeger Verlagsbuchhandlung, 2006-01-01) Toro, G.; Hermelin, M.; Schwabe, E.; Posada, B.O.; Silva, D.; Poupeau, G.; Toro, G.; Hermelin, M.; Schwabe, E.; Posada, B.O.; Silva, D.; Poupeau, G.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaAge of weathered andesitic volcanic ash layers, which cover most of the landscape in the Central Cordillera northern massif plateaus in Colombia, were determined through the use of fission track counting in volcanic zircon crystals. A stoneline, exposed in many outcrops, which corresponds to the lower limit of younger tephras, gave ages between 350 ka and 440 ka. Andosols lying above the stoneline could not be dated. Paleolake deposits in the study area and surroundings were dated at about 2 Ma; older ashes deposited on the Rio Negro erosion surface (SII) below the stoneline level gave ages between 3.4 and 5.4 Ma. The study area is located about 150 km from the volcanic center. The ash layers decrease in thickness only slightly with distance, as perceived from profiles sampled in flat areas. We conclude that the only noticeable erosional event in the region was the emplacement of the stone-line. This erosion event which was relatively short and mild in intensity, as part of the underlying soil derived from quartzdiorite was preserved. This soil formed above a saprolite with a thickness which may reach 150 m, a fact which supports the inference that the plateaus have been stable for millions of years, in contrast to the high erosion rates observed in the surrounding steep slopes and canyons. © 2006 Gebrüder Borntraeger.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...