Abstract
In subduction zones, vertical and horizontal motion of the upper plate induce rapid paleogeographic changes influencing in turn the migration, adaptation, and speciation of the biosphere. In the Caribbean region, paleontological studies have demonstrated Cenozoic (~35 Ma) migrations of South American terrestrial faunas toward the Greater Antilles, suggesting the existence of a now disappeared terrestrial pathway. The most widespread hypothesis (GAARlandia) suggests the presence of a land bridge during the late Eocene located on the Aves ridge. However, recent studies have proved the existence of mid-late Eocene and middle Miocene emerged areas in the north-east Caribbean (GrANoLA land). This region also exposes the extinct branch of the Lesser Antilles arc, whose phase of activity, although partially constrained, corresponds to the period of migration of South American species. These results suggest that the Lesser Antilles could represent an alternative pathway, connected to the Greater Antilles and/or to the Aves ridge. Nevertheless, the northeastern Caribbean plate is structured by crustal faults that bound tectonic blocks whose kinematic evolution remains debated, leading to uncertainty in paleogeographic reconstructions of the region.This thesis aims to constrain the magmatic, stratigraphic, and tectonic evolution of the extinct branch of the Lesser Antilles arc and to quantify and reconstruct the evolution of the intra-plate deformation of the northeastern Caribbean plate, from the Eocene to present-day. In that perspective, I precise the activity of the extinct branch of the Lesser Antilles arc from the middle Eocene to the upper Oligocene using a combined geochronological, biostratigraphic and fault kinematic study of the island of Antigua. My results indicates that magmatism may have contributed to land emersion froming terrestrial pathways in the Northern Lesser Antilles. I also propose that the cessation of magmatic activity is related to a flattening and progressive curvature of the downgoing plate.Then, I quantified the Cenozoic intraplate deformation of the northeastern Caribbean region with a paleomagnetic study conducted on the island of Martinique, Antigua, St. Martin, Anguilla, Puerto Rico, and the British Virgin Islands. I estimate ~45° of counterclockwise rotations of the Puerto Rico-Virgin Islands (PRVI) and Northern Lesser Antilles (NoLA) blocks from the late Eocene to the Miocene and an absence of rotation of the Southern Lesser Antilles block. Two tectonic end-member scenarios are proposed to explain these rotations: an oroclinal bending related to the curvature of the subduction trench or fore-arc sliver motion along an already curved subduction. These scenarios are tested with a regional kinematic reconstruction, developed on Gplates. The results indicates that most of the PRVI and NoLA blocks rotation are underwent with ~ 600 km of displacement by fore-arc sliver motion, accommodated by left-lateral motion along the Muertos and Monserrat-Harvers faults. These movements restore the NoLA block in front of the Grenada-Tobago basin, in contact with the South American continent. This reconstruction, the presence of an Eocene to Oligocene magmatic phase and of Eocene and Miocene regional emerged lands defines the Northern Lesser Antilles as a potential pathway for South American fauna. The kinematic reconstruction also suggests that the accretion of the Bahamas Bank and its westward motion, acquired following an Eocene regional plate motion change, could influence the evolution of the Lesser Antilles arc and trigger the PRVI and NoLA block rotations and fore-arc sliver motion.