The geology of the Panama-Chocó arc

Abstract

The Panama-Chocó Arc is a composite volcano-plutonic island arc of Late Cretaceous to Miocene age developed on ocean crust of the Caribbean large igneous province (CLIP) on the western or trailing edge of the Caribbean Plate. An early arc of Late Cretaceous to Eocene age developed by northerly or north-easterly subduction of the Farallon Plate to form the volcano-plutonic rocks of the Chagres, Mamoní, San Blas, Atrato and Mandé Mountains. Arc shutdown in the middle Eocene was coincident with a change from compressional to extensional tectonics, with graben development in the fore-arc to form the Chuqunaque-Tuira-Atrato Basins; the opening of the Panama Canal Basin in a radial rift basin; and block rotations and displacements. This extension and arc break-up may be explained by steepening of the subducting Farallon Plate by slab rollback and ultimately break-off, and/or initial oblique collision of the eastern part of the Panama-Chocó Arc with South America in the Istmina area as a result of consumption of the proto-Caribbean Plate beneath South America. Following the break-up of the Farallon Plate at 25–23 Ma (late Oligocene), a short-lived later arc, related to the NE-dipping subduction of the Nazca Plate, was formed to the south of the early arc and fore-arc basins in the Majé-Baudó Mountains and the Pearl Islands. Oblique collision of the Chocó Block of Colombia was complete by about the Early Miocene. Panama started to collide against South America in the Middle Miocene, a process which is still ongoing. The Nazca Plate convergence with Panama changed to left-lateral strike-slip, resulting in the cessation of subduction and arc shutdown, formation of the east Panama deformed belt by left-lateral transpression, basin closure and uplift of the isthmus to create the land bridge with South America.