Subduction, Buoyant Braking, Flipping, and Strike-Slip Faulting in the Northern Caribbean

Abstract

The distribution of metamorphic rocks and their division into continental and oceanic types, the distribution of ophiolites and alpine ultramafic rocks, and the distribution and age of volcanic rocks in the Greater Antilles indicates that a northward-dipping subduction zone may have been the first orogenic event in the northern Caribbean. Buoyant continental crust entering the zone from the south stopped that subduction in Late Jurassic or Early Cretaceous time (120-130 m.y.b.p.), as evidenced by lithologic types and metamorphic rock ages in Cuba, Dominican Republic, and Puerto Rico. Continued compression resulted in a new, "flipped" subduction zone dipping southward on the north side of the old island arc. The second episode of subduction began about 110 m.y. ago and formed most of the exposed island arc. Two alternative models are proposed: 1) continuous subduction on a variably-dipping plane such that the western segment dipped too gently to permit volcanism after 85 m.y.b.p.; 2) subduction converted about 85 m.y.b.p. into strike-slip motion with anatectic volcanism. In both models, intense deformation ended at 45 m.y.b.p., volcanism ended in the west at 85 m.y.b.p. and in the east at 45 m.y.b.p. Still-continued compression of the Caribbean microplate since 45 m.y.b.p. has resolved itself into an eastward transform motion which continues to the present.