Chapter 3

Abstract

A continuous, long-lived sedimentary record contains important evidence bearing on the geologic evolution of the Eastern Cordillera in the northern Andes of Colombia. Today, this largely isolated NNE-trending mountain range forms a ca. 1-3 km high topographic barrier separating the Magdalena Valley hinterland basin from the Llanos foreland basin. A Mesozoic -Cenozoic history of marine and nonmarine sedimentation affected the Eastern Cordillera and flanking Magdalena and Llanos provinces during contrasting tectonic regimes. (i) Jurassic to earliest Cretaceous extension led to the development and linkage of extensional sub-basins (commonly half graben features governed by normal faults) in selected regions. (ii) A subsequent phase of postextensional thermal subsidence generated a thermal sag basin across a broader region. (iii) In latest Cretaceous to Paleocene time, initial crustal shortening in the Central Cordillera created a regional flexural basin that was successively broken by the Paleocene -Oligocene emergence of thrust/reverse-fault related uplifts within the Eastern Cordillera partitioning the original regional basin into the Magdalena hinterland basin and Llanos foreland basin. (iv) Major Neogene uplift and establishment of an effective topographic barrier occurred as continued shortening became focused along the bivergent eastern and western flanks of the fold-thrust belt comprising the Eastern Cordillera. Shortening commonly involved contractional reactivation of preexisting normal faults and inversion of pre-foreland basin elements. This geologic history is largely expressed in the clastic sedimentary archives of the Eastern Cordillera, Magdalena Valley Basin, and Llanos Basin. Growth strata and cross-cutting relationships among fold-thrust structures and basin fill provide essential timing constraints for individual structures, particularly when integrated with thermochronological data. Regional stratigraphic correlations and sediment accumulation histories help identify shared and divergent stratigraphic histories during progressive basin compartmentalization. Substantial shifts in sediment provenance, identified through U-Pb geochronology, demonstrate the changes in sediment source regions and paleodrainage patterns during several changes in tectonic conditions.

Chapter 4

“…Detrital zircon U-Pb ages (e.g., Ibañez-Mejia et al 2015 and references therein) have the technical advantage of efficiently dating hundreds of zircon crystals from sedimentary rocks (Figure 3b). In identifying major zircon age populations in the northern Andes, multiple studies have been able to more precisely suggest when particular sediment sources in the northern Andes shed sediments to adjacent basins (e.g., Bande et al, 2012;Caballero et al, 2013aCaballero et al, , 2013bHorton, 2018a;Horton et al, 2010aHorton et al, , 2010bHorton et al, , 2015Horton et al, , 2020Nie et al, 2010Nie et al, , 2012Silva et al, 2013;). In addressing the timing of terrane accretion, other works have applied this technique to reveal that basement rocks of the Panamá-Chocó Terrane have a dominant Eocene age signature (ca.…”

Coal petrology analysis and implications in depositional environments from upper Cretaceous to Miocene: a study case in the Eastern Cordillera of Colombia

“…The low oxidation and good preservation of the macerals are corroborated by deposition that occurs in extensional basins with half-graben geometry (post-rift). The accommodation space generated the subsequent deposition of marine facies and the beginning of a transgressive event (Guerrero and Sarmiento 1996;Horton et al 2020).…”

“…16), along an open lagoon with tidal and wave processes active, possibly. In the regional geological framework, the oxidation periods are related to the initial pulse of the Colombian Andes uplift (Central Cordillera), with the first great crust shortening and the foreland basin formation as the evidence (Horton et al 2020). For this reason, tectonics controlled the sedimentation, the accommodation space decreased, and shallow coastal marine environments developed (Villamil 1999).…”

Coal petrology analysis and implications in depositional environments from Upper Cretaceous to Miocene: a study case in the Eastern Cordillera of Colombia

“…of a transgressive event(Guerrero and Sarmiento 1996;Horton et al 2020). The Palmichal Group (Early Campanian-Maastrichtian).The coals of this unit show a medium degree of oxidation with a moderate concentration of the vitrinitic, inertinitic, and liptinitic micro-lithotypes.…”

“…16), along an open lagoon with tidal and wave processes active, possibly. In the regional geological framework, the oxidation periods are related to the initial pulse of the Colombian Andes uplift (Central Cordillera), with the rst great crust shortening and the foreland basin formation as the evidence(Horton et al 2020). For this reason, tectonics controlled the sedimentation, the accommodation space decreased, and shallow coastal marine environments developed (Villamil 1999).Arcillas del Limbo Formation-Late Paleocene.…”