Newly available seismic reflection data are applied to an interpretation of the Cibao basin of Hispaniola. The data include multichannel seismic reflection profiles from Samana Bay and the central part of the Cibao Valley, and single-channel seismic profiles from the western offshore extension of the Cibao Valley and the Windward Passage. A single track of GLORIA imagery through the Windward Passage is also used. The data in Samana Bay reveal a major, active, easterly oriented normal fault (transcurrent?) and a significant increase in sedimentation from the north, which probably began during Miocene to Pliocene time. A seismic reflection line in the central part of Cibao Valley demonstrates that the sedimentary material in the valley is at least 5 km thick, with the thickest section in the north adjacent to the Septentrional fault. The southern margin of the Cibao Valley appears to be the locus of a hingeline, although minor faults may be present. The oldest sedimentary basin fill overlying Cretaceous basement is probably of middle Miocene age based on outcrops of rock. At the western end of the Cibao Valley, the Septentrional fault curves northwesterly before going offshore. In addition, the Tortue fault, which extends offshore along the north coast of Haiti, is an extension of either the Guayubin-Hispaniola fault zones or is a southwestern branch of the Septentrional fault. It can be identified on the sidescan sonar images in Windward Passage.

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.