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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.

The central Cordillera Septentrional straddles the presently active strike-slip plate boundary faults separating the North American and Caribbean plates. Major and minor faults and folds in Paleocene to lower Pliocene marine sedimentary rocks indicate three distinct folding events that progressively uplifted the present-day mountains of the Cordillera Septentrional. The first folding event is marked by an angular unconformity that separates locally folded Paleocene to middle Eocene pelagic carbonates from a tilted upper Eocene basal conglomerate. We correlate this late middle or early late Eocene folding and erosion event with a better studied middle Eocene folding and erosion event of the same age in Cuba that has been interpreted by previous workers as the result of a collision between the northeast-facing Greater Antilles arc and the Bahamas Platform. A second folding event is marked by a slight angular unconformity separating broadly folded upper Eocene to lower Miocene deep-marine clastic rocks from upper Miocene to lower Pliocene shallow-marine carbonate rocks. We interpret this middle Miocene folding event as initial Miocene transpressional deformation at a strike-slip restraining bend along the Septentrional fault zone. The axis of a large fold formed during this event is transected by a left-lateral strike-slip fault. A third folding event is marked by a broad anticline developed in upper Miocene to lower Pliocene shallow-marine carbonate rocks and is interpreted as continued late Pliocene to present transpression at the restraining bend along the Septentrional fault zone.

High-resolution single-channel seismic reflection profiles, bathymetry and sides-can sonar imagery from the Puerto Rico trench document the present-day and post-collisional effects of the obliquely subducting southeastern extension of the Bahama Province and the Main Ridge fracture zone on the northern Puerto Rico–Virgin Islands margin. In contrast to an orthogonal system, where it is unlikely that two high-standing ridges will impact the same section of margin, along the Puerto Rico trench convergence is highly oblique and the deformational effects of the two ridges are superimposed and often difficult to isolate. A middle–upper Miocene margin-wide unconformity in the Oligocene–lower Pliocene shallow-water carbonate platform of the Virgin Islands, Puerto Rico, and eastern Hispaniola provides an excellent horizontal reference frame for the timing and impact of the high-standing ridges on the margin. During the past 10 m.y., trenchward tilting (4–6°) of the carbonate platform including the margin-wide erosional surface to >5000 m water depths provides evidence that the margin has experienced significant subsidence. In this paper we present a model of accelerated subduction erosion and diachronous margin subsidence triggered by the ridges sweeping from east to west beneath the Puerto Rico forearc. Evidence for ongoing and past subduction erosion include zones of enhanced seismicity, oversteepening and mass wasting of the forearc slope, and landward migration of the inner trench-slope break. We document over 3 km of Neogene subsidence presumed to be the result of rapid crustal thinning associated with the tunneling of the buoyant, thick (∼20-km-thick crustal/sediment section) southeastern Bahama Province beneath the forearc. During the past 3.5–5 m.y., the volume of material eroded from the overriding plate is estimated to be ∼210 km 3 /km of margin, equivalent to an erosion rate of 42–60 km 3 /m.y./km of margin. A significant reduction in the rate of margin subsidence in the eastern part of the survey area suggests that the Main Ridge fracture zone has had a relatively small erosional impact on the margin, and that under normal conditions, this highly oblique convergent boundary is characterized by relatively slow rates of subduction erosion. Three strike-slip fault zones are imaged in the forearc: the East Septentrional fault zone, the Bunce fault zone, and the Bowin fault zone. The Bunce and Bowin fault zones trend N80°–90°E, subparallel to the predicted North America–Caribbean relative plate motion vector (N70°E) determined by global positioning system (GPS) studies. Seismic reflection profiles across the Puerto Rico trench in the western section of the survey area, where the Bunce fault zone is <10 km from the deformation front, reveal thick (0.75–1.5 km) accumulations of relatively undeformed trench sediment fill. This lack of shortening deformation suggests that convergence approaches pure strike-slip and that strain within the forearc is largely accommodated by the strike-slip fault zones. Strike-slip faulting appears to be progressively partitioned to the east where deformation in the trench is more clearly contractional. Although not a typical plow mark, the Bowin fault zone appears to represent the long-term (∼10 m.y.) track of the underthrusting and colliding southeastern Bahama Province across the forearc area that is consistent with the convergence direction exhibited by GPS results.