Crustal Structure of the Mérida Andes - Venezuela

Abstract

Between 2012 and 2015, field investigations were carried out in the northwestern region of Venezuela, within the framework of the Integrated Geoscience of the Mérida Andes (GIAME) project to estimate the depth of the basement and the thickness of sediments; determine the lithospheric structure and study its tectonic evolution, with the main objective of refining the proposed geodynamic models and improving the calculation of the seismic hazard. The models generated from this research along the Andes South profile support the floating orogen model, in which the Mérida Andes are an asymmetric mountain chain and whose orogen has a positive flower shape. This orogen delimits the Maracaibo Block to the east in response to the low-angle subduction of the Caribbean Plate under the South American continent. The Andean root along the Andes South profile varies between 45 and 55 km in depth and is displaced ∼ 35 km towards the Northwest with respect to the topographic expression of the orogen. There is a type B-subduction of the Caribbean Plate below the South American Plate from Santa Marta (Colombia) in a NW-SE direction with a dip of ∼ 25°. The integrated crustal model of the Andes South profile suggests a regional compensation system, in which the bending of the South American Plate is produced by the orogenic load of the Mérida Andes and the Barinas-Apure Basin, while the bending of the Maracaibo Block can be attributed both, to the great sedimentary load, and a response to the type A-subduction of the South American Plate.