Neotectonic provinces and joint orientations of northern South America

Abstract

The data on the stress field in northern South America are reviewed and complemented by new measurements. These data are based on the interpretation of orientations of joints, earthquake fault planes, and stylolites. The maximum tectonic pressure direction is constant throughout the mountain regions from the Colombia/Ecuador border to the Cordillera de la Costa in Venezuela. Its orientation is 130° to 151°, which is roughly normal to the strike of the eastern front of the Andes. This whole area ust therefore be considered as a single geotectonic province. In the anterior — i.e., from the Colombian Llanos to the Guayana Shield in Venezuela, again a consistent tectonic stress direction of 161° to 166°E is found; this, threfore, is a second tectonic province. Possibly, this direction represents the regular intraplate stress direction which is gradually rotated toward the Andes so as to become normal to its front. Finally, the maximum tectonic stress north directions north eof the Oca and ther Morón-El Pilar fault zones are quite varied, which may be an indication of the perturbations causedby the presence of the bondary between the South American and Caribbean tectonic plates.