Cuenca De Llanos Orientales De Colombia

Abstract


Tectonic and subsidence history of the Llanos foreland basin of Colombia




Henry Miguel Campos, M.S. GeoSci
The University of Texas at Austin, 2011

Supervisor: Paul MannHidden text: The abstract may be included at the discretion of the supervisor.
The Llanos foreland basin of eastern Colombia shows a major episode of Middle Miocene subsidence at the onset ofthe formation of the foreland basin. This subsidence was in response to shallow subduction and collision events along the Pacific margin of northwestern South America. The collision of the Panama arcalong the Pacific margin of Colombia has caused east-west shortening that began in the Middle Miocene and continues today. These events created a major thrust salient, the Cordillera Oriental, thatoverrides the Llanos foreland basin, forming an arcuate thrust front that extends 40km basinward. For this thesis, we interpreted 1200km of 2D-seismic data arranged along 4 regional cross-sections. Asedimentary backstripping technique was applied to the observed structure maps to construct subsidence maps. Also, a 2D flexural modeling was performed to calculate the tectonic and sedimentarysubsidence. Subsidence maps show an increase in the tectonic subsidence rate in the salient area from the middle to late Miocene, coeval with the collision of the Panama arc with the northwestern SouthAmerica plate. The models developed also help predict the position of the basin edge as well as the position, height, and length of the forebulge, indicator parameters for hydrocarbon migration andaccumulation through time. Most known hydrocarbons in the thrust belt and foreland basin are located either south of the salient (Cusiana-Cupiagua, Rubiales oilfields) or north of the salient (Guafita-CanoLimon, Arauca oilfields) but surprisingly not within the salient where subsidence, source rock thicknesses, and fracturing may be most favorable according to the model of Macedo and Marshak (1999).