--> Abstract: A Comparison of Orogenic Architecture and Foreland Basin Evolution in Colombia (Northern Andes) and Bolivia (Central Andes), by Brian K. Horton, Mauricio Parra, and Andrés Mora; #90078 (2008)

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A Comparison of Orogenic Architecture and Foreland Basin Evolution in Colombia (Northern Andes) and Bolivia (Central Andes)

Brian K. Horton1, Mauricio Parra2, and Andrés Mora3
1Institute for Geophysics and Department of Geological Sciences, University of Texas at Austin, Austin, TX
2Institut für Geowissenschaften, Universität Potsdam, Potsdam, Germany
3Ecopetrol, Instituto Colombiano del Petróleo, Bucaramanga, Colombia

A comparison of the Bolivian and Colombian Andes reveals the influence of pre-existing structure, inherited stratigraphy, erosion, and climate in shaping the histories of shortening, exhumation, and basin evolution in South America. In both systems, east-west shortening and construction of a broad (>250 km wide) fold-thrust belt within an eastward-tapering sedimentary wedge has dominated the Late Cretaceous-Cenozoic record and controlled the modern landscape. However, the magnitude of shortening and role of pre-existing structures are dramatically different. In Bolivia, >200-300 km of shortening occurred along first-generation structures in a region that underwent limited Mesozoic extension. In contrast, <100-150 km of shortening in Colombia was largely accommodated along basement-involved compressional or transpressional structures that reactivate Mesozoic extensional faults. Another key difference is the absence of an elevated hinterland plateau in Colombia. Nevertheless, the topography of a formerly closed intermontane region (Sabana de Bogotá) in the Eastern Cordillera of Colombia resembles the Altiplano plateau of Bolivia, albeit at a smaller scale. We attribute the lack of a large plateau in Colombia to long-term humid conditions and efficient external drainage rather than fundamental differences in structural or geodynamic processes. In terms of synorogenic sedimentation, both systems contain a major hinterland basin and foreland basin: the Magdalena Valley and Llanos basins of Colombia, and the Altiplano and Chaco/Beni basins of Bolivia. Variations in the eastward advance of the foreland basin may be tracked by identifying forebulge deposits and the onset of rapid accumulation in multiple locations. Preliminary syntheses of Late Cretaceous-Cenozoic sedimentation suggest a more continuous advance of the fold-thrust belt and basin in Bolivia than in Colombia.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas