Stratigraphy and geological history of the Puerto Plata area, northern Dominican Republic

In northern Dominican Republic, Cretaceous and Lower Cenozoic rocks are exposed in a 250-km (super 2) area near Puerta Plata (Puerto Plata Inlier), defined by the sea to the north, the Camu fault and Cenozoic sediments to the south, and Late Neogene carbonate rocks to the east and west. Cretaceous(?) basement rocks, herein called the Puerto Plata Basement Complex (PPBC), consist of an association mostly of dismembered, variably sheared masses of rock ranging from tens to hundreds(?) of cubic kilometers in size, of serpentinite, tectonized harzburgite, cumulate gabbro rock, and mafic to intermediate volcanic rock, the latter of which is pillowed with red interpillow cherts in at least one area. The PPBC is interpreted as the remnants of an ophiolite suite. The PPBC is overlain by two units of apparently similar faunal age, neither of which was observed to overlie the other, and hence their age relations are unclear. One is the Paleocene-Early Eocene Imbert Formation consisting mostly of off-white crystal tuffs, vari-colored cherts, and sandy to pebbly turbiditic sedimentary rocks. Coarse clastic beds are more common low in the formation, and contain sand and pebbles of serpentinite, volcanic and metamorphic rock, and limestone. The second unit overlying the PPBC consists of sedimentary serpentinite conglomerates and algal-limestone buildups or patch reefs of the early(?) Paleogene shallow-water La Isla Formation. La Isla limestone build-ups and serpentinite conglomerates contain fragments of one another, and corals were observed in growth attachment to serpentinite cobbles, indicating coeval, shallow-water deposition of the conglomerate and limestone. The Imbert Formation is believed to be older than La Isla based on two arguments: First, the Imbert appears to be more deformed than La Isla, although actual bedding is difficult to decipher in the latter; and second, deposition of the Imbert occurred in deeper water than deposition of La Isla, suggesting that Imbert deformation was accompanied by regional uplift that led to the relatively shallow-water conditions in which La Isla and subsequent units were deposited. The period during which La Isla was deposited and probably longer was a time of local erosion across much of the inlier, leading to the angular unconformity between the Imbert and younger units. The Eocene uplift and erosional hiatus probably records arc (Greater Antilles) collision with the Bahamas Bank. In the Late Eocene through Oligocene, a marine transgression and inner shelf(?) deposition is indicated by basal conglomerates and terrigenous sands and shales of the Luperon Formation. Tectonism during this period was apparently minor. Deformation and erosion (emergence?) occurred again in the Early to Medial Miocene, but deposition was renewed in the Medial to Late Miocene with the carbonate rocks (terrigenous input greatly reduced) of the Villa Trina Formation. The Miocene uplift, deformation, and change in sedimentation is interpreted as the onset of sinistral strike-slip motion and separation of northern Hispaniola from Cuba along the still-active Oriente Transform fault. Major regional uplift and erosion have occurred again since the Early Pliocene, elevating the Villa Trina Formation to several hundred meters throughout northern Hispaniola, and exposing Pleistocene(?) reefal limestones and beachrock along coastal areas as much as 10 to 20 m in elevation. This uplift is the result of oblique convergence of Hispaniola with the easternmost tip of the Bahamas Bank by motion along the Oriente fault. Finally, since Medial Miocene time, and probably associated with the Pliocene-Recent uplift, a sheared mud unit carrying 0.001 to 100-m size blocks of all the above-mentioned lithologies (and others) has diapirically intruded the inlier from beneath and flowed horizontally across areas of the Imbert, Luperon, and Villa Trina Formations. The intrusion of this mobile unit (and the serpentinites of the PPBC) is responsible for the morphologic development of the Puerto Plata Inlier, and is interpreted to be related to upper crustal extension or pull-apart basin development north of the Camu fault during oblique convergence with the Bahamas Bank.