Continental margin response to multiple arc-continent collisions: The northern Andes-Caribbean margin

Abstract

An integration of diverse strain markers into a palinspastic reconstruction of the northern Andes provides a first-order quantitative approximation to the response of a complex margin to two consecutive arc-continent collisions. A palinspastic reconstruction highlights margin-parallel displacements, with crustal blocks traveling ~400 to ~500 km northward, while the margin-normal shortening component—excluding subduction—is limited to ~100 km. The first arc-continent collision closed a ~500 km-wide ocean basin, where subduction of Atlantic lithosphere took place under an intra-oceanic arc ~90 to ~65 Ma old originally ~1100 km long, and currently stretched ~2200 km. Following collision, eastward-directed oblique subduction started at ~65 Ma, with ~800 km of proto-Caribbean lithosphere consumed under northwestern South America, igniting a short-lived magmatic arc along the post-collisional margin. Two molasse deposits track deformation, cooling, exhumation, and erosion of the margin. The first heralds the arrival of the first intra-oceanic arc to the southernmost northern Andes in late Campanian times, younging-northward as the collision propagated north. This latest Cretaceous molasse deposit records also the first altitudinal gain in the northern Andean orogen along the Central and Real cordilleras. The second molasse follows middle to late Eocene magmatic arc shut down, and regional exhumation and cooling of the margin. Formation, rise and docking of the intra-oceanic Panama arc closed a ~1200 km wide middle Eocene seaway, and renewed Miocene magmatism in the northern Andes, as the Nazca plate started subducting behind the docked arc.