EARLY CENOZOIC SHIFT IN CARIBBEAN PLATE DIRECTION INFERRED FROM PALEOSTRESS MEASUREMENTS FROM STRIATED FAULT PLANES IN THE CIRCUM-CARIBBEAN REGION

Paleostress analysis is based on the assumption that slickenside lineations indicate both the direction and sense of maximum resolved shear stress on that fault plane. In this study we have compiled previously published fault measurements and their calculated paleostresses from 40 published studies collected at 417 outcrops over an along-strike distance of approximately 8,000 km in Mexico, Cuba, Haiti, Dominican Republic, Puerto Rico, Vieques, Trinidad, Aruba, Bonaire, Curacao, Venezuela, and Colombia. Our goal is to compare rock deformation at the outcrop scale to plate tectonic models compiled from data sources at all scales. Rocks of Late Cretaceous and to Eocene ages yield greater spread in derived paleostress directions as these rocks have steeper dips, more pervasive faulting, and were likely affected by large rotations as inferred from previous studies of Caribbean plate margins. Despite more scatter in measurements from older rock units, two major major events are recognizable from the data compilation in Mexico and the northern Caribbean: 1) prior to the Eocene and Paleocene in areas of southern Mexico, the direction of maximum paleo-compression is north-south or northeast-southwest and is inferred to reflect the northward or northeastward-directed terminal convergence of the Caribbean plate first into the southern margin of the Yucatan peninsula and later into the Bahamas carbonate platform; 2) younger rock units of post-Eocene age show a dominance of extensional deformation commonly oriented east-west or northeast-southwest. These extensional structures and their more complexly and locally changing paleostress directions are inferred to represent the development of the left-lateral strike-slip boundary superimposed on the former suture zone between the leading edge of the Caribbean plate and the Yucatan Peninsula-Bahama platform. In the 900-km-long area of Cuba, gradual shifts in the direction of maximum compression support the gradual shift in Caribbean plate direction from northeastward to eastward. In northern South America a similar shift in paleostress directions is seen with east-southeast paleo-compression propagating from the late Cretaceous in Colombia to the Middle Miocene in Trinidad that is superimposed by a more complex pattern of extensional and strike-slip deformation.