Neogene Sedimentation and Tectonics in the Cibao Basin and Northern Hispaniola: An Example of Basin Evolution Near A Strike‐Slip‐Dominated Plate Boundary

Abstract

Sedimentologic analyses, subsidence history interpretation, and a new gravity survey are synthesized to interpret basin evolution in a region of large strike‐slip offsets and oblique crustal convergence within the northern Caribbean plate boundary zone. We investigate the mid‐Miocene to mid‐Pliocene Yaque Group, which accumulated in the western Cibao basin of northern Hispaniola. Asymmetric subsidence of the Cibao basin was accompanied by southward transgression and deposition of an upward‐fining succession from shallow‐marine or brackish water conglomerate through sub‐wavebase siltstone to deep‐water calcareous siltstone and uncommon interbedded sandstone; bioclastic limestone is locally present and in most cases accumulated in a forereef location. In early Pliocene time (ca. 4 Ma), fine‐grained sediment deposition was briefly interrupted by widespread conglomerate accumulation; however, basin subsidence was uninterrupted, and water depths continued to increase. At this time, basinal subsidence accelerated as the Cordillera Septentrional was uplifted along the Septentrional fault zone at the basin's northern flank. The across‐strike gravity profiles require a S‐vergent thrust component along most of the Septentrional fault zone. Gravity variations indicate that the Septentrional fault zone dips northward (∼50°) in the central part of the basin, adjacent to the Septentrional fault zone, where the basin is deepest, and steepens eastward and westward. Contrasts in sedimentation patterns between the Cibao basin and elsewhere in northern Hispaniola reveal a complex history of dominantly strike‐slip faulting modified by varying amounts of convergence.