Geological mapping and multiscalar fracture analysis of some Tepuisof the Gran Sabana (Venezuela) by using remote sensing techniques

The Gran Sabana Region (Venezuela) is characterized by the presence of some of the most impressive mountain in the world, called Tepuis. These unique flat-top mountains are carved in the Mataui Formation, a massive quartzitic sandstone representing the youngest deposit of the Proterozoic Roraima Group. This formation has been intruded by Proterozoic and Mesozoic Diabase dikes and sills, associated to hydrothermal alteration, which strongly affects the morphology of the Tepuis. In the first part of this work the various lithologies have been mapped using some advanced remote sensing techniques, resulting in a 1:25 000 geological map of the studied area. The study area is deformed by large amplitude folds with WNW/ESE and NNE/SSW axis. In addition, the Tepuis are affected by a network of high-angle fractures. The analysis of the fracture systems on the Auyan and Chimantà tepuis reveals the existence of four main joint sets, the most prominent of which has N 30° direction, while two sets of conjugate joints are are arranged simmetrically to the main set. These fractures are interpreted in relation to the folding event with NNE/SSW axis. Accordingly, a main compressive stress oriented NW/SE has been inferred. At the meso-scale additional fracture systems have been found analyzing a point cloud of a rock wall belonging to the Auyan Tepui. The comparison of structural data collected in the same area at the local and regional scales shows that the orientation of these groups of fracture planes does not match with the two sets found on the Auyan Tepui surface.