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Bogotá, Colombia

Jimenez G.,Third University of Rome | Jimenez G.,Italian National Institute of Geophysics and Volcanology | Speranza F.,Italian National Institute of Geophysics and Volcanology | Faccenna C.,Third University of Rome | And 2 more authors.
Tectonics | Year: 2014

We report the paleomagnetic and magnetic fabric results of 58 sites from Cretaceous-Miocene marine and continental strata from the Eastern Cordillera (EC) and the Cucuta zone, at the junction between the Santander Massif and the Merida Andes of Colombia. The EC is an intracontinental doubly vergent range inverting a Triassic to Early Cretaceous rift zone. Twenty-three sites reveal nonsystematic tectonic rotations, including unrotated areas of the EC range with respect to stable South America. Our data show that the EC inverted a NNE oriented rift zone and that the orientation of the Mesozoic rift and the mountain chain roughly correspond. Interestingly, magnetic lineations from anisotropy of magnetic susceptibility analysis do not trend parallel to the chain but rather are oblique to the main orogenic trend. By also considering GPS evidence of a ∼1 cm/yr ENE displacement of central western Colombia accommodated by the EC, we suggest that the Miocene-Recent deformation event of this belt arises from ENE oblique convergence reactivating a NNE oriented rift zone. Oblique shortening was likely partitioned into pure dip-slip shear characterizing thick-skinned frontal thrust sheets (well known along both chain fronts) and by range-parallel right-lateral strike-slip faults, which have not been identified yet, but likely exist in the axial part of the EC. Finally, the 35° ± 9° clockwise rotation observed in four post-Miocene magnetically overprinted sites from the Cucuta zone re flects late Cenozoic and ongoing right-lateral strike-slip displacement occurring along faults parallel to the Boconó fault system, possibly connected with the right-lateral faults inferred to exist along the axial part of the EC. ©2014. American Geophysical Union. All Rights Reserved. Source

Montes C.,Smithsonian Tropical Research Institute | Guzman G.,Invemar | Bayona G.,Corporacion Geologica Ares | Cardona A.,Smithsonian Tropical Research Institute | And 2 more authors.
Journal of South American Earth Sciences | Year: 2010

A moderate amount of vertical-axis clockwise rotation of the Santa Marta massif (30°) explains as much as 115. km of extension (stretching of 1.75) along its trailing edge (Plato-San Jorge basin) and up to 56. km of simultaneous shortening with an angular shear of 0.57 along its leading edge (Perijá range). Extensional deformation is recorded in the 260. km-wide, fan-shaped Plato-San Jorge basin by a 2-8. km thick, shallowing-upward and almost entirely fine-grained, upper Eocene and younger sedimentary sequence. The simultaneous initiation of shortening in the Cesar-Ranchería basin is documented by Mesozoic strata placed on to lower Eocene syntectonic strata (Tabaco Formation and equivalents) along the northwest-verging, shallow dipping (9-12° to the southeast) and discrete Cerrejón thrust. First-order subsidence analysis in the Plato-San Jorge basin is consistent with crustal stretching values between 1.5 and 2, also predicted by the rigid-body rotation of the Santa Marta massif. The model predicts about 100. km of right-lateral displacement along the Oca fault and 45. km of left-lateral displacement along the Santa Marta-Bucaramanga fault. Clockwise rotation of a rigid Santa Marta massif, and simultaneous Paleogene opening of the Plato-San Jorge basin and emplacement of the Cerrejón thrust sheet would have resulted in the fragmentation of the Cordillera Central-Santa Marta massif province. New U/Pb ages (241 ± 3. Ma) on granitoid rocks from industry boreholes in the Plato-San Jorge basin confirm the presence of fragments of a now segmented, Late Permian to Early Triassic age, two-mica, granitic province that once spanned the Santa Marta massif to the northernmost Cordillera Central. © 2009 Elsevier Ltd. Source

Montes C.,Smithsonian Tropical Research Institute | Montes C.,University of Los Andes, Colombia | Cardona A.,Smithsonian Tropical Research Institute | Cardona A.,National University of Colombia | And 14 more authors.
Bulletin of the Geological Society of America | Year: 2012

The rise of the Isthmus of Panama, linked to a number of climatic, paleoceanographic, and biological events, has been studied mostly from indirect, often distal, geochemical and biotic evidence. We have upgraded existing geologic mapping in central Panama with more than 2000 field stations, over 40 petrographic analyses, and more than 30 new geochronological and thermo chrono logical analy ses. This data set suggests that the isthmus was an uninterrupted chain above sea level from late Eocene until at least late Miocene times. The basement complex of central Panama is a folded-faulted, ~3-km-thick arc sequence, intruded by granitoid bodies and onlapped by mildly deformed upper Eocene and Oligocene strata. Six U/Pb zircon ages in the granitoids-along with published geochronological data-reveal intense late Paleocene to middle Eocene magmatism (58-39 Ma), a temporary cessa tion of magmatic activity between 38 and 27 Ma, and renewed magmatism between 25 and 15 Ma in a position ~75 km south of the former magmatic axis. Thermochronological analyses in zircon (eight U-Th/He ages), and in apatite crystals (four U-Th/He ages and nine fission-track ages) obtained from a subset of 58-54 Ma granitoid bodies record a concordant Lutetian-age (47-42 Ma) cooling from ~200 °C to ~70 °C in ~5 m.y., and cooling below ~40 °C between 12 and 9 Ma. Cooling is linked to exhumation by an angular unconformity that separates the deformed basement complex below from mildly deformed, upper Eocene to Oligocene terrestrial to shallowmarine strata above. Exhumation and erosion of the basement complex are independently confirmed by lower Miocene strata that have a detrital zircon signature that closely follows the central Panama basement complex age distribution. These results greatly restrict the width and depth of the strait separating southern Central America from South America, and challenge the widely accepted notion that the Central American Seaway closed in late Pliocene time, when the ice age began. © 2012 Geological Society of America. Source

Emmerton S.,Imperial College London | Muxworthy A.R.,Imperial College London | Sephton M.A.,Imperial College London | Aldana M.,Simon Bolivar University of Venezuela | And 3 more authors.
Geochimica et Cosmochimica Acta | Year: 2013

A relationship between hydrocarbons and their magnetic signatures has previously been alluded to but this is the first study to combine extensive geochemical and magnetic data of hydrocarbon-associated samples. We report a detailed study that identifies a connection between magnetic mineralogy and oil biodegradation within oil-bearing sedimentary units from Colombia, Canada Indonesia and the UK.Geochemical data reveal that all the oil samples are derived from mature type-II kerogens deposited in oxygen-poor environments. Biodegradation is evident to some extent in all samples and leads to a decrease in oil quality through the bacterially mediated conversion of aliphatic hydrocarbons to polar constituents. The percentage of oil components and the biodegradation state of the samples were compared to the magnetic susceptibility and magnetic mineralogy. A distinct decrease in magnetic susceptibility is correlated to decreasing oil quality and the amount of extractable organic matter present. Further magnetic characterization revealed that the high quality oils are dominated by pseudo-single domain grains of magnetite and the lower quality oils by larger pseudo-single domain to multidomain grains of magnetite and hematite. Hence, with decreasing oil quality there is a progressive dominance of multidomain magnetite as well as the appearance of hematite. It is concluded that biodegradation is a dual process, firstly, aliphatic hydrocarbons are removed thereby reducing oil quality and secondly, magnetic signatures are both created and destroyed. This complex relationship may explain why controversy has plagued previous attempts to resolve the connection between magnetics and hydrocarbon deposits.These findings reinforce the importance of bacteria within petroleum systems as well as providing a platform for the use of magnetization as a possible exploration tool to identify subsurface reservoirs and a novel proxy of hydrocarbon migration. © 2013 Elsevier Ltd. Source

Cardona A.,Smithsonian Tropical Research Institute | Cardona A.,Instituto Colombiano del Petroleo | Valencia V.A.,Washington State University | Bayona G.,Corporacion Geologica Ares | And 7 more authors.
Terra Nova | Year: 2011

The timing of orogeny in the northern Andes and the mechanism driving it are still debated. We have studied the age, composition and provenance of granitoids and sandstones of the Santa Marta Massif and Rancheria Basin, northern Colombia, to relate deep-seated and surface tectonic processes attending the Late Cretaceous-Palaeogene history of the northern Andes. Our results indicate the development of five tectonic episodes: (1) collision of northwestern South America with a 92-80 Ma Caribbean arc (70 Ma); (2) late-collisional to early-subduction metamorphism and magmatism (65 Ma); (3) distal accumulation of a thick siliciclastic sequence (60-58 Ma); (4) renewed arc magmatism (58-50 Ma); and (5) magmatic quiescence and block uplift (post-50 Ma). The first episodes are related to the onset of subduction, and the last episode is related to shallow subduction and oblique convergence. Similar events in Colombia and Ecuador reveal that the Late Cretaceous-Eocene orogeny of the northern Andes was influenced by the collision and subduction of the Caribbean oceanic plate. © 2010 Blackwell Publishing Ltd. Source

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