Circum-Caribbean Tectonic and Igneous Activity and the Evolution of the Caribbean Plate: Reply
Convergence of the North and South American blocks and northeastward movement of the East Pacific-Caribbean plate during the Late Cretaceous and early Tertiary led to the Laramide tectonic and igneous activity that has been recorded in the geology of the circum-Caribbean region. Volcanism in Central America and the initiation of major transcurrent faulting along northern South America during the late Eocene suggest that the Caribbean decoupled from the East Pacific plate near the end of the Laramide Orogeny. Lack of post-Eocene structural activity in the Greater Antilles is consistent with the initiation of eastward movement of the Caribbean plate during the Eocene.

The evolution of the Cayman Trough and the history of orogenic activity in Cuba can be explained by assuming that Caribbean lithosphere was transferred to the Americas plate as the trough developed from west to east. As each new section was added to the eastward-growing trough, a new transform fault formed in the Caribbean lithosphere to connect the eastern end of the trough with the Cuban Trench. This west to east stepping of the plate boundary transferred “Caribbean” lithosphere to the Americas plate and allowed underthrusting and related tectonic activity to continue longer in eastern than in western Cuba. The presence of intermediate depth earthquakes and high seismicity along the Puerto Rico Trench suggest that the Atlantic lithosphere which underthrust Puerto Rico prior to the Oligocene is beginning to break away from the Americas plate. Fault displacements inferred along the Caribbean-Americas boundary in the Greater Antilles are equivalent to a constant post-Eocene eastward movement of 0.5 cm/yr for the Caribbean plate.