THE CARIBBEAN/PACIFIC SUBDUCTION UNDER THE SOUTH AMERICAN MARGIN AND ITS EFFECT ON THE CONFIGURATION OF SOUTHERN COLOMBIAN ANDES

The southern Colombian Andes splits into the Western, Central and Eastern Cordilleras which are respectively separated by the Cauca-Patía and Upper Magdalena Valley basins. In this poster, we present a new tectono-stratigraphic analysis of the low-lying onshore segment of the Tumaco forearc basin (Colombian Pacific) and we compare the results with the Late Cretaceous–Cenozoic stratigraphy of the inland basins in southern Colombia to determine their common tectonic signatures.

The proposed configuration at southern Colombia started since the Late Cretaceous when the collision and fragmentation of the Colombian Caribbean Oceanic Plateau against South America configured the Western Colombian Cordillera and the basements of the Tumaco forearc basin and the Patía sub-basin. The accretion setting prevailed until the Maastrichtian, which is the time of important deformation in the terranes of the Colombian and Ecuadorian Western Cordilleras, and other coeval deformation along the Andes to the south. The main cause of this continuity has been suggested to be related to the absolute motion of South America.

Since Paleocene, the convergence between the Farallón/Nazca and South American plates allowed the development of the Pacific forearc as well as shortening leading to the uplift of the Colombian Central Cordillera and formation of the eastern foreland basin system, which later was divided into the Upper Magdalena Valley broken foreland basin and the southern part of the Putumayo-Caguán foreland basin..

Since Miocene, events in addition to plate convergence as the collision of the Baudó-Panamá Arc and the subduction of Carnegie Ridge perturbed the subduction zone in southern Colombia, and it coincides with a a time of major and rapid mountain uplift in Colombia and throughout of South America. A shallow subduction zone with an angle <30° is proposed for southern Colombia to explain the occurrence of Miocene arc magmatic rocks from the Western Cordillera to the foothills of Putumayo-Caguán Basin.

The new data allow a margin scale comparison of the response to the Caribbean/Pacific subduction under the South American margin. And the integration of all of these tectonic events offers a new improved dynamic framework for the evolution of this region.