Cenozoic Orogenic Growth of the North Andes Revealed Through Basin Analysis and Low Temperature Thermochronology in the Eastern Cordillera of Colombia

Mauricio Parra¹, Andrés Mora², Edward R. Sobel¹, Carlos Jaramillo³, Manfred R. Strecker¹, Paul B. O’Sullivan⁴, and Román González^5
1Instutut für Geowissenschaften, Universität Potsdam, Potsdam, Germany
²Ecopetrol, Instituto Colombiano del Petróleo, Bucaramanga, Colombia
³Center for Tropical Paleoecology and Archeology, Smithsonian Tropical Research Institute, Panama, Panama
⁴Apatite to Zircon, Inc., Viola, ID
⁵Hocol S.A, Bogotá, Colombia

Cenozoic to Recent oblique subduction and tectonic accretion of oceanic terranes in the NW corner of South America have resulted in orogenesis and foreland basin formation in the Colombian Andes. Basin analysis and apatite and zircon fission-track data from west of the modern volcanic arc of the Central Cordillera reveal a Cenozoic history of tectonic inversion and orogenic propagation. Late Cretaceous to Paleocene uplift of the Central Cordillera resulted in initial foreland basin development. Subsequent bivergent tectonic inversion of the Eastern Cordillera subdivided a formerly continuous basin into the present-day Magdalena Valley basin to the west and the Llanos basin to the east. Growth strata and episodes of rapid accumulation documented by the Cenozoic foreland record of these basins, as well as the present structural configuration of the mountain range, suggest eastward transferal of the tectonic load through an initial pop-up uplift of the Eastern Cordillera during the late Eocene-early Oligocene. Limited eastward migration of the leading edge of deformation since then seems to have resulted from contractional and transpressional deformation being accommodated along pre-existing anisotropies. Furthermore, variable thickness of the pre-orogenic stratigraphy may have prevented eastward orogenic migration by modifying critical taper angles. Denudation inferred from bedrock thermochronology and gravel petrography in palynologically dated foreland deposits at the eastern margin suggest moderate exhumation rates (~0.3 mm/yr) during the late Oligocene-Miocene, followed by rapid exhumation (1-2 mm/yr) in the Pliocene. We attribute this Pliocene acceleration in exhumation to focused denudation on the windward side of the orogen, where moisture-laden winds caused an effective erosional regime, resulting in a positive feedback with tectonic processes.

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