As from some time back, various structural characteristics identified in the Llanos Orientales and Barinas-Apure basins known as arcs are found to be aproximately perpendicular to the Eastern Cordillera of Colombia and the Venezuelan Andes. Such arcs were identified by means of magnetic and seismic data as well as stratigraphic data from the various oil wells drilled. Recently, as a result of the pooling of data from different sources and disciplines, the presence of deep-seated ancestral (Proterozoic?) Northwest-Southeast trending fractures was determined. These fractures have been reactivated in different epochs, are referred to as lineaments of which eleven are known in the Eastern Cordillera of Colombia in the Girardot-Cucuta sector and four in the Merida andes. These lineaments have lengths that vary between 400 and 1,200 km being spaced every 40 to 50 km in Colombia and multiples of this in Venezuela. The observed lineaments represent the surficial traces of the edges of crustal blocks whose differential displacements have defined the tectonic and sedimentological development of the Andean Cordillera as well as the sub-andean basins. In these last basins, the aforementioned blocks roughly coincide with the recognized and accepted position and orientation of the so-called arcs. It is believed that there is a direct connection between the fractures present in the Guayanan Craton and those structures that appear in the Andean chain as well as the series of uplifted or downthrown blocks (horsts and grabens) of Northwest-Southeast trend in the Colombian and Venezuelan subandean basins. It is then proposed that the so-called arcs are none others than the edges of the uplifted blocks defined by the NW-SE lineaments. This proposal would then become an important tool for hydrocarbon prospection.