A 50 km long by 11 km wide ridge rises above the Cibao Valley along the southern edge of the eastern Cordillera Septentrional in northeastern Hispaniola. This seismically active feature, the San Francisco Ridge, is interpreted to be a “push-up” because it is a compressed and elevated ridge intimately associated with strike-slip faulting. Deformed and uplifted Middle Miocene to Recent sedimentary units in the ridge provide a stratigraphic window into the later depositional history of the Cibao basin. The depositional environments, paleobathymetry, ages of unconformities, and structural development of the San Francisco Ridge indicate Neogene to recent transpression related to uplift and slip of the eastern Cordillera Septentrional against the eastern Cibao basin.

From the city of San Francisco de Macoris eastward, the ridge consists of six to eight west-northwest-trending left oblique-slip faults associated with northwest-trending asymmetric to overturned kink folds. Northeast-striking right-slip faults divide the ridge into domains with contrasting lithologies and structures.