Oligocene to Recent Geodynamic Reconstruction of the Northern Nazca Subduction

The subduction kinematics of the northern Nazca and southwestern Caribbean plates beneath South America cannot be simplified as the independent subduction of two oceanic crusts. Indeed, the interaction between these subducting plates has significant tectonic implications on the overriding South American plate. Although there is ambiguity on the present-day geometry of these plates, we present an updated interpretation of the Nazca and Caribbean slabs based on an integral approach between seismological-tomography data and a three-dimensional geodynamic reconstruction after the break-up of the Farallon plate. The first fact that needs to be considered is that the oceanic crust that makes up the Nazca plate north of 3°S is different from its counterpart in southern latitudes. Convergence of this young and warm crust derived from the Galapagos hotspot - spreading center since the late Oligocene implies a more buoyant subduction in the northernmost Nazca plate. Additionally, several jumps in this spreading center resulted in a changing convergence kinematics. Another crucial factor is the nature of convergence at the triple junction, which is not a static element in time, but its position has migrated to the north with the Caribbean plate. As this junction migrated to the north, the angle between the Panamanian and Colombian trenches became orthogonal, leading to mechanically tight subduction. Some consequences of this complex geodynamics are multiple episodes of flattening, slab fragmentation, tearing and trench retreat locking. This setting keeps a close relationship with the magmatic history and migration of the orogenic front in the northern Andes.