Abstract

The ophiolite complexes exposed along the Pacific coast of Costa Rica and western Panama evolved from Jurassic ocean floor to the island arc of the Tertiary to the present. We attribute Late Cretaceous volcanism to the Caribbean sill event that thickened the oceanic crust to form an oceanic plateau. Tectonostratigraphic units formed by Late Cretaceous nappe thrusting and block rotation. Rotated blocks, as revealed by paleomagnetic data, are covered by neoautochthonous sedimentary and volcanic rocks. Collision with the Cocos Ridge in the late Tertiary fragmented and rotated the ophiolite complexes south of the Costa Rica Fracture Zone.

The oceanic basement formed in the Jurassic Period in an equatorial position. Its latitudinal drift path as deduced from paleomagnetic inclination data matches that of the South American continent and differs from that of the Farallon/Phoenix plates. We favor formation of the ophiolite complexes in a Caribbean (inter-American) position as opposed to a distant origin in the Pacific region.

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