Análisis de procedencia del registro sin-orogénico Maastrichtiano de la Formación Cimarrona, flanco occidental de la Cordillera Oriental colombiana
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Boletin de Geologia
abstract
The Maastrichtian clastic record of the Cimarrona Formation on the western flank of the Colombian Eastern Cordillera documents the erosion of a generated topography and is associated with the beginning of the Andean orogeny during the Late Cretaceous-Paleocene. Sedimentary provenance analyzes (conglomerate clast count, sandstone petrography, heavy minerals and U-Pb detrital geochronology) in conjunction with previously published paleocurrent data allow us to reconstruct the history of the source areas. Detrital zircons with ages primarily from the Upper Cretaceous, including a maximum accumulation of ~66 Ma, as well as more limited ages from the Permian (276 Ma), Triassic (246 Ma), and Jurassic (153 Ma), suggest that sedimentation was associated to contemporary volcanism and to the erosion of older crystalline and sedimentary rocks. The high quartz content of the sandstones, together with the lithic association suggest that source rocks included clastic sedimentary rocks, low grade metamorphic rocks and felsic to intermediate volcanic rocks. The source area was characterized by a Cretaceous volcano-sedimentary cover sequence deposited on top of Jurassic and Permian-Triassic basement rocks; this source area configuration resembles the present-day lithostratigraphic domains of the Central Cordillera. The discontinuous character of the coarse clastic record of the Cimarrona Formation suggests that the source areas were discontinuous uplifted blocks with valleys in between, these blocks likely extended eastwards and are now buried beneath the basin fill of the Magdalena Valley. The Central Cordillera segment that is most compatible with these characteristics is currently located north of the basin, suggesting that strike-slip tectonics was responsible for the northward displacement of the source areas after the Maastrichtian.
