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Detrital U–Pb Provenance, Mineralogy, and Geochemistry of the Cretaceous Colombian Back–Arc Basin
By Javier GUERRERO, Alejandra MEJÍA–MOLINA and José OSORNO
The geology of the Cretaceous Colombian back–arc basin is reviewed taking into consideration detrital U–Pb provenance ages, mineralogy, and geochemistry, of samples collected from outcrop sections and wells at several localities in the core of the Eastern Cordillera, Middle Magdalena Valley (MMV) and Catatumbo areas. The data set supports previous studies indicating a basin which main grabens were located in the present day Eastern Cordillera, between the Guaicáramo/Pajarito and Bituima/Salina border faults, which during the Cretaceous were normal faults. Limestones are common on the western and northern sides of the basin, whereas terrigenous strata predominate on the eastern and southern side of it. After the Berriasian grabens of the basin were connected by marine flooding during the Valanginian, two main source areas with distinct element and mineral content can be documented, one in the Central Cordillera magmatic arc, and another in the Guiana Shield. Some elements present in Lower Cretaceous shales, including scandium, vanadium and beryllium, are not related to the sediment supply areas of the basin, but are instead linked to the hydrothermal activity and dykes of gabbro, diorite, and tonalite, emplaced in the strata during the Berriasian to Cenomanian main extension of the basin.
Keywords: Cretaceous, back–arc, Colombia, U–Pb provenance, geochemistry.