Geochronological databases are powerful tools for characterizing the crustal evolution and the age spectra of a region and allow comparison with other areas at a regional scale. In this contribution, we present the Colombian Geochronological Database (CGD), which contains a curated compilation of ca. 67,406 individual published U-Th-Pb, K-Ar, Ar-Ar, Rb-Sr, Sm-Nd, Lu-Hf, Fission-track, U-Th-He, and Re-Os mineral and whole rock ages that are reported in the published literature. Each date includes geographic coordinates, geological setting, petrologic and chemical information extracted from the respective publications. The structure of the database provides a powerful interface for constructing queries and allows searching and extracting information on geographic domains, provinces, stratigraphic units, isotopic systems, date interpretations, references, etc. This information establishes a framework for regional and global geological interpretations with geochronological, stratigraphic, structural and palaeogeographic implications. With the present effort we present to the geoscience community a clear insight, from a regional perspective, to the geology and tectonics of Colombia since Precambrian times. The comparison of all (detrital and magmatic) single zircon U-Pb dates from the Colombian (Gondwana sourced) geochronological database with the Global and North American (Laurentia sourced) databases provides a temporal constraint on the evolution of the South American continent. U-Pb zircon ages in Colombia define 13 peak clusters centred at 1767, 1530, 1325, 1178, 1007, 605,540, 468, 271, 237, 182, 76 and 10 Ma but of those, only few have a good correlation in all three databases: 1007 (Grenvillian/Orinoquian/Putumayo Orogeny), 605 (Braziliano/Pan-African Orogeny), 468 (Famatinian/Taconic Orogeny), and 182 Ma (Break-up of Pangea) zircon peaks. This correlation suggests that some tectonic events in Colombia are global and might represent crustal production and preservation while the other peaks might just represent local arc magmatic events.
Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21-25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile element enrichments, a THI of 0.88, and a H2Ocalc of >3 wt. %. In contrast, the Miocene Pedro Miguel and Late Basalt Fm. exhibit reduced Nb-Ta anomalies, flattened REE curves, depleted fluid mobile elements, a THI of 1.45, a H2Ocalc of <1 wt. %, and plot in mid-ocean ridge/back-arc basin fields. Geochemical modeling of Miocene rocks indicates 0.5-0.1 kbar crystallization depths of hot (1100-1190°C) magmas in which most compositional diversity can be explained by fractional crystallization (F = 0.5). However, the most silicic lavas (Las Cascadas Fm.) require an additional mechanism, and assimilation-fractional-crystallization can reproduce observed compositions at reasonable melt fractions. The Canal volcanic rocks, therefore, change from hydrous basaltic pyroclastic deposits typical of mantle-wedge-derived magmas, to hot, dry bi-modal magmatism at the Oligocene-Miocene boundary. We suggest the primary reason for the change is onset of arc perpendicular extension localized to central Panama. High-resolution mapping along the Panama Canal has revealed a sequence of inward dipping maar-diatreme pyroclastic pipes, large basaltic sills, and bedded silicic ignimbrites and tuff deposits. These volcanic bodies intrude into the sedimentary Canal Basin and are cut by normal and subsequently strike-slip faults. Such pyroclastic pipes and basaltic sills are most common in extensional arc and large igneous province environments. Overall, the change in volcanic edifice form and geochemistry are related to onset of arc perpendicular extension, and are consistent with the idea that Panama arc crust fractured during collision with South America forming the observed Canal extensional zone.
Abstract We investigate how the mechanical properties of intra‐oceanic arcs affect the collision style and associated stress‐strain evolution with buoyancy‐driven models of subduction that accurately reproduce the dynamic interaction of the lithosphere and mantle. We performed a series of simulations only varying the effective arc thickness as it controls the buoyancy of intra‐oceanic arcs. Our simulations spontaneously evolve into two contrasting styles of collision that are controlled by a 3% density contrast between the arc and the continental plate. In simulations with less buoyant arcs (15–31 km; effective thickness), we observe arc‐transference to the overriding plate and slab‐anchoring and folding at the 660 km transition zone that result in fluctuations in the slab dip, strain‐stress regime, surface kinematics, and viscous dissipation. After slab‐folding occurs, the gravitational potential energy is dissipated in the form of lithospheric flow causing lithospheric extension in the overriding plate. Conversely, simulations with more buoyant arcs (32–35 km; effective thickness) do not lead to arc‐transference and result in slab break‐off, which causes an asymptotic trend in surface kinematics, viscous dissipation and strain‐stress regime, and lithospheric extension in the overriding plate. The results of our numerical modeling highlight the importance of slab‐anchoring and folding in the 660 km transition zone on increasing the mechanical coupling of the subduction system.
Integration of several geologic lines of evidence reveals the prevalence of a lowland trans-Andean portal communicating western Amazonia and the westernmost Andes from at least middle Miocene until Pliocene times. Volcanism and crustal shortening built up relief in the southernmost Central and Eastern Cordilleras of Colombia, closing this lowland gap. Independent lines of evidence consist first, of field mapping in the Tatacoa Desert with a coverage area of ∼381 km 2 , 1,165 km of geological contact traces, 164 structural data points, and 3D aerial digital mapping models. This map documents the beginning of southward propagation of the southernmost tip of the Eastern Cordillera’s west-verging, fold-and-thrust belt between ∼12.2 and 13.7 Ma. Second, a compilation of new and published detrital zircon geochronology in middle Miocene strata of the Tatacoa Desert shows three distinctive age populations: middle Miocene, middle Eocene, and Jurassic; the first two sourced west of the Central Cordillera, the latter in the Magdalena Valley. Similar populations with the three distinctive peaks have now been recovered in western Amazonian middle Miocene strata. These observations, along with published molecular and fossil fish data, suggest that by Serravallian times (∼13 Ma), the Northern Andes were separated from the Central Andes at ∼3°N by a fluvial system that flowed into the Amazon Basin through the Tatacoa Desert. This paleogeographic configuration would be similar to a Western Andean, or Marañon Portal. Late Miocene flattening of the subducting Nazca slab caused the eastward migration of the Miocene volcanic arc, so that starting at ∼4 Ma, large composite volcanoes were built up along the axis of today's Central Cordillera, closing this lowland Andean portal and altering the drainage patterns to resemble a modern configuration.
Abstract A geological transect across the suture separating northwestern South America from the Panama Arc helps document the provenance and thermal history of both crustal domains and the suture zone. During middle Miocene, strata were being accumulated over the suture zone between the Panama Arc and the continental margin. Integrated provenance analyses of those middle Miocene strata show the presence of mixed sources that includes material derived from the two major crustal domains: the old northwestern South American orogens and the younger Panama Arc. Coeval moderately rapid exhumation of Upper Cretaceous to Paleogene sediments forming the reference continental margin is suggested from our inverse thermal modeling. Strata within the suture zone are intruded by ~12 Ma magmatic arc‐related plutons, marking the transition from a collisional orogen to a subduction‐related one. Renewed late Miocene to Pliocene acceleration of the exhumation rates is the consequence of a second tectonic pulse, which is likely to be triggered by the onset of a flat‐slab subduction of the Nazca plate underneath the northernmost Andes of Colombia, suggesting that late Miocene to Pliocene orogeny in the Northern Andes is controlled by at least two different tectonic mechanisms.
ABSTRACT ABSTRACT Isolated precloacal vertebrae from the early to middle Miocene Gaillard Cut of Panama represent the first Central American fossil record of the extant boine snake Boa and constrain dispersal of the genus into Central America from South America as no younger than approximately 19.3 Ma. Boa from the Las Cascadas fossil assemblage and the Centenario Fauna represent the oldest record of terrestrial southern vertebrate immigration into Central America, and demonstrate American interchange by the earliest Neogene. Interchange of snakes precedes contiguous terrestrial connection between Central and South America by approximately 17 Ma, necessitating dispersal across an approximately 100 km wide marine strait. The biogeographic history of snakes across the Neotropics is distinct from the mammalian record, and indicates a more complicated assembly of New World vertebrate faunas than previously recognized. ACKNOWLEDGMENTS This research was made possible through the collaboration and funding of the Autoridad del Canal de Panama (ACP), the Mark Tupper Fellowship, Ricardo Perez S.A., the National Science Foundation grants EAR 0824299 and OISE 0966884, and the National Geographic Society. We thank the paleontology/geology team at Smithsonian Tropical Research Institution and UF for help with fieldwork. Support for collection and curation of fossils was provided by US NSF grants OISE 0638538 and EAR 0642528 and University of Florida 2007 Research Opportunity Fund to B. J. MacFadden, PI/PD. J.J.H. was supported by a NSERC Discovery Grant. Handling editor: Paul Barrett
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