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Paleogene Burial processes of Non-conventional and Conventional Cretaceous Resources in the Eastern Cordillera of Colombia: Testing the Foreland Basin and lithospheric Folding Hypotheses

Bayona, German1; Cardona, Agustin; Jaramillo, Carlos; Mora, Andrés; and Montes, Camilo
1[email protected]

The Eastern Cordillera of Colombia and adjacent basins include Cretaceous black shales and Paleogene coal-bearing strata. However, burial processes and thermal history of the basin need to be re-evaluated for exploration of nonconventional resources. Comprehensive tectono-stratigraphic analysis in Paleogene successions contributes to determine the temporal and spatial change of sedimentation rates of Paleogene units, and its comparison with sedimentation rates along different sections. Additionally, we report magmatic arc and intraplate during the Paleogene.

The new results consider three phases of deformation, or tectonostratigraphic intervals, during the Paleogene. In the first phase, of late Maastrichtian-early Eocene age, two major depocenters formed. The first along the western foothills with accumulation of coarse-grained deposits interbedded with sand- and mud rich intervals, and the second along the axial zone where dominated fine-grained deposition. A magmatic arc formed in the Central Cordillera by subduction of the Caribbean plate, as well as in intraplate volcanism as far as 400 kms of the magmatic arc. The second phase, of middle to late Eocene age, deformation affected coarse-grained deposition in the western foothills, whereas very-low accumulation rates took place along the axial zone and eastern foothills (accumulation of conventional reservoir deposits). Magmatism stopped in the Central Cordillera, but continued along the central and northern segments of the axial zone. The third phase, of late Eocene to Oligocene age, had the most important depocenter located along the axial zone of the Eastern Cordillera, where sandy and muddy deposition on alluvial to lacustrine environments dominated. Even though syn-orogenic clastic wedges formed in both foothills, they did not have sedimentation rates as high as the one reported along the axial zone. Magmatism stopped in the axial zone, and started in the latest Oligocene as result of onset of Nazca plate subduction.

Location of multiple depocenters and intraplate volcanism data do not support the hypothesis of a broken retroarc foreland basin. Lithospheric folding is an alternative model that supports the long-lived and non-migrated depocenter in the axial zone and intraplate volcanism. Geochemical analysis of conventional and non-conventional resources, as well as themochronological studies should consider this alternative model during definition of geothermal profiles.

 

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013