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Bernard Monod, University of Pau (France)
Damien Dhont, University of Pau (France)
Yves Hervouet, University of Pau (France)
Stephanie Klarica, University of the Andes (Venezuela)
Jaime Lafaille, University of the Andes (Venezuela)
Bertrand Niviere, University of Pau (France)
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The La Gonzalez basin constitutes one of the most well-expressed depression in the Venezuelan Andes that started to rise in the Late Miocene. It lies at an elevation of 800 m and is surrounded by a rugged topography with summits reaching 2500 m. It has been defined as lazy Z-shaped pull-apart basin (30 km 4.5 km in size, Schubert, 1980) that initiated in a E-W relay zone of the N65°E-trending right-lateral strike-slip Bocono fault. The Paleozoic substratum of the basin forms topographic heights unconformably overlain by Quaternary deposits. Based on geomorphological observations, microtectonic data and analysis of remote sensing images, a structural model is proposed to account for the tectonic evolution of the La Gonzalez basin during the Quaternary. On-going activity of the N80°-trending northern border fault is indicated by right-lateral offset of the river network. Complementary normal motion is also evidenced by progressive unconformities in the Quaternary sediments. This normal component is responsible for basin subsidence resulting from a down-to-the-northeast tilting of the Paleozoic substratum. Collapse is accompanied by the formation of N110°E-trending normal faults bounding domino-style fault blocks tilted to the north. Microtectonic data show a combination of both a strike-slip regime of deformation characterized by NNE-SSW extension and WNW-ESE compression and a multidirectional extension within the basin. These data are compatible with dextral shearing along the Bocono fault accompanied by subsidence in the basin. Formation of the La Gonzalez basin during the Quaternary implies recent right-lateral strike-slip motion along the Bocono fault, which therefore initiated later on the mountain building.
Schubert, C., 1980 - Late Cenozoic pull-apart basins, Boconó fault zone, Venezuelan Andes - Journal of Structural Geology, V. 2, pp. 283-292.
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