Cauca-Patía Basin is a 440 km long intermountain depression, elongated in direction N24°E. It separates the Colombian Central and Western Cordilleras between 1°20’ and 5°5’ north latitude. In the Popayán area, a basement high divides this basin into two sub-basins: Cauca at the north and Patía at the south. The Cauca sub-basin is covered mostly with Quaternary alluvial deposits; only in the southwestern margin out crops a sequence of Paleogene sedimentary folded rocks. By contrast, in the Patía sub-basin mainly folded and faulted Paleogene and Neogene rocks are observed in surface. It is suggested that the Cauca-Patía Basin resulted from the collision and accretion of an oceanic terrain located in the western margin of the South American Plate, during Mesozoic and Cenozoic times. Fluvial, volcaniclastic, locally lacustrine and marine sedimentation, took place during the Cenozoic. For most of the part, the margins of the Cauca- Patía Basin show regional inverse and strike slip faults. The Cauca- Romeral Fault System represents the boundary between the central Cenozoic sedimentary fill and the lateral complexes constituted by Paleozoic metamorphic rocks and Cretaceous rocks of oceanic affinity (Figure 2).