Quaternary Folding of the Tame Anticline, Llanos Basin, Colombian Andes: Impacts on Hydrocarbon Charge History
Veloza-Fajardo, Gabriel1; Taylor, Michael; and Mora, Andrés
Trap formation versus hydrocarbon charge are critical elements to understand the presence of hydrocarbons in structural traps. Here we conducted a neotectonic analysis to document the age and growth of the Tame anticline and the impacts on the petroleum systems. Active deformation in the Colombian Andes is thought to reflect the complex interaction between eastward flat slab subduction of the Nazca plate and the oblique southward subduction of the Caribbean plates; producing active faulting and shallow earthquake seismicity in the Eastern Cordillera foothills, uplifting and deforming the Quaternary deposits at the thrust front. Such activity is recorded at the northern part of the thrust front by the Tame anticline. The Tame anticline trends N15E, is 6 km wide by 14 km long that actively grows due to slip on the blind Tame fault system. The kinematic evolution of the fold geometry is modeled based on the analysis of a 300 km² seismic reflection cube and geochronological constrains are provided by using In situ terrestrial cosmogenic nuclide dating of warped and abandoned terraces, useful for deriving uplift and shortening rates. This approach provides the first estimates of Quaternary surface uplift and horizontal shortening along the foothills of the northeastern Colombian Andes at millennial time scales. The south to north variation in finite shortening from 624±28 m to 378±33 m is likely controlled by the geometry of preexisting Mesozoic extensional structures, and also by the along strike variation in folding style at depth. Our results reveal Quaternary surface shortening rates ranging from 1.7±0.2 to 2.4±0.5 mm/yr within the extent of the fold. Based on these rates the initiation of folding is estimated at 0.39±0.05 Ma. The presence of such a youthful structure at the thrust front, suggests that the orogen migrated eastward since the Pleistocene, probably due to topographic development and internal deformation leading to a supercritical thrust wedge. Our analysis provides evidence to explain the scarcity of hydrocarbons in an otherwise inversion-related structural trap, which is against the expected idea of old and fully charged inherited structures. Therefore the Tame anticline is an example of the relevance of having a detailed temporal framework for the petroleum systems and not traps geometries only.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013