Neogene Structures in Jamaica and the Tectonic Style of the Northern Caribbean Plate Boundary Zone

Abstract

Late Miocene and younger structures in and around Jamaica are dominated by east-west left-lateral strike-slip faults, on which we have identified cumulative offsets of about 40 km indicating a displacement rate which is equivalent to 10% to 20% of the contemporary rate of displacement between the North American and Caribbean plates. This movement is the cause of NE-SW shortening and NW-SE extension (much as in simple shear experiments) in a plate boundary zone (PBZ) that reaches 200 km into the Caribbean plate. Extensional structures are mainly depressions and lie offshore, whereas compressional structures are mainly elevations on the island. Minor alkalic basalt occurrences are associated with extensional structures. A similar tectonic style can be recognized elsewhere along the northern border of the Caribbean and its mirror image occupies the southern border of the plate. Detailed studies of neotectonics in PBZ's are becoming important as attempts begin to directly measure movements between plates. These studies may also complement seismic network results in helping to pinpoint areas of seismic hazard.