Abstract
Costa Rica and Panama form part of the Chorotega Block, a geologic province comprising oceanic basement of Mesozoic - Cenozoic age. The isthmus represents an intraoceanic island are which has developed since Upper Cretaceous.
The segment of the isthmus, comprised by eastern Costa Rica and northern Panama, is made up of a single tectonic unit limited by faults. The northern boundary corresponds to the North Panama Deformed Belt, which at the latitude of Port Limón changes into an east - west trending Transcurrent Fault System of a sinistral type. This fault system divides the isthmus of Costa Rica until it meets the Mesoamerican Trench which forms the southern boundary of the segment. The western limit conforms to a fault system, which roughly parallels the Panama Canal. The tectonic activity in the Mesoamerican Trench has produced a system of arc island basins, which in the backarc of the segment, correspond to the Limón and Bocas del Toro basins.
The Upper Tertiary - Quaternary evolution of these backarc basins have been controlled by the subduction in the Mesoamerican Trench and particularily, during the Quaternary by the shallow subduction of the Coco Asismic Ridge. Nevertheless, an additional source for the deformation in the basins is associated with a process of interplate convergence, corresponding to the North Panama Deformed Belt.