Deformation of the northeastern Venezuelan Andes. Relationships with the Caribbean overthrusts

Abstract

The Merida Andes (Venezuela) formed in the middle Miocene due to oblique convergence between the South American plate and the Maracaibo block [Audemard et al., 2002] (figs. 1A and 1B). The study area corresponds to the so-called "Barbacoas platform" [Renz, 1960], which constitutes the northeastern termination of the belt, NE of Valera (fig. 2). It is located in the northeastern part of Trujillo block [Hervouet et al., 2001], considered as an independent block separated from the main Maracaibo block along the Valera fault. According to Stephan [1982], the N170°E-trending Caribbean compression developed in this area from late Cretaceous to Eocene. It was followed by a N105°E-trending compression older than middle Miocene, and finally by the NW-SE Andean compressional stage that lasted till now in most of the chain. However, east of El Empedrado fault, a NNE-SSW compression presently occurs that is oblique to the classical Andean stage. The tectonic evolution of the Andean stage is not well understood. The Merida Andes are mainly composed of Precambrian and Paleozoic rocks. The northern part of the belt only comprises a complete and continuous Jurassic to Paleogene cover. This lithologic pattern is probably a consequence of the tectonic escape of the Maracaibo block, and more particularly of the smaller Trujillo block. The Merida and Carribean belts being close to each other, the influence of the Andean deformation on the Caribbean allochthonous must be taken into account. In order to make a structural analysis at regional scale, we privileged the use of remote sensing data (Landsat, Spot and Radar images) and aerial photographs. This was complemented by structural data obtained in the field, allowing the study of geometric and chronological relationships between the tectonic structures.