Diachronous uplift and recycling of sedimentary basins during Cenozoic tectonic transpression, northeastern Caribbean plate margin

Abstract

Four marine sedimentary sequences of Late Cretaceous to Pleistocene age crop out in the 320 km long, 1 to 30 km wide Peralta-Rio Ocoa belt of Hispaniola (Haiti and Dominican Republic). The four sedimentary sequences are dominated by marine turbiditic rocks ranging up to 11.5 km in apparent thickness and exhibit mainly northwest to southeast, belt-parallel paleocurrents. The three younger sequences are generally in fault or unconformable contact with the underlying sequence. From northwest to southeast, the four belts become progressively wider, younger, less metamorphosed, less folded and faulted, and lower in topographic elevation. We interpret the three younger sequences as a syn-tectonic stratigraphic record of diachronous, northwest to southeast transpressional closure of a Coniacian-Danian back-arc basin represented by the oldest exposed sedimentary sequence at the northwest end of the belt and inferred at depth beneath the three younger sequences. Using the stratigraphic record, we infer the following three stages in the closure of the back-arc basin and the overlying younger basins. Stage One: latest Cretaceous to early Late Eocene closure. A minimum of 11 km of Paleocene turbidites and limestone in the Padre las Casas area and a minimum of 11.5 km of Early Eocene to early Late Eocene pelagic limestone, mudstone, sandstone, and siltstone in the Peralta and Sierra El Numero areas was deposited in an elongate basin derived from the first stage of latest Cretaceous-early Late Eocene closure and erosion of the Coniacian-Danian back-arc basin to the northwest. Paleocene-Eocene turbidites in both areas contain large amounts of reworked Campanian-Paleocene microfauna and exhibit northwest to southeast belt-parallel paleocurrents. Syn-deformational features in Eocene sedimentary rocks in the Peralta and Sierra El Numero area indicate that convergent deformation accompanied sedimentation (Witschard and Dolan, 1990). Stage Two: Middle Eocene to Early Miocene closure. Up to 8.6 km of Middle Eocene to Early Miocene turbidites, debris flows, and olistostromes of the Rio Ocoa Group of the Dominican Republic were deposited in an elongate basin derived from Middle Eocene to Early Miocene closure, uplift, and erosion of the Peralta Group to the west and northwest. Turbidites contain reworked Eocene faunas and lithologies similar to those in the underlying Peralta Group and exhibit northwest to southeast, belt-parallel paleocurrents. Erosion of Late Cretaceous island arc and overlying Paleogene carbonate rocks of the Cordillera Central provided additional belt-perpendicular sources of coarser-grained conglomerate and olistostromes. Following deposition of the Rio Ocoa Group, both the Peralta and the Rio Ocoa Group were deformed in a southwest-verging fold-and-thrust belt during the Early Miocene. Stage Three: Middle Miocene to Recent closure. Up to 1.5 km of Middle Miocene to Pleistocene sandstone, conglomerate, and reefal limestone of the Ingenio Caei Group of the Dominican Republic were deposited in an elongate basin above a pronounced angular unconformity developed on the older, deformed rocks of the Rio Ocoa Group. Sediments of the Ingenio Caei Group were derived from Middle Miocene to Recent closure, uplift, and erosion of the Rio Ocoa and Peralta Groups to the northwest. Onshore exposures of the Ingenio Caei Group can be correlated with submerged strata seen on seismic reflection profiles across the offshore San Pedro basin. Recent submarine clastic sedimentation in the San Pedro basin is dominated by northwest to southeast influx of clastic turbidites derived from active erosion of onshore exposures of the Rio Ocoa and Ingenio Caei Groups. Middle Miocene (?) to Recent sediments of the San Pedro basin are being actively shortened by northward to northeastward-directed underthrusting along the Muertos trench. Underthrusting at the Muertos trench is suggested to represent ongoing closure of the back-arc basin thought to be deeply buried beneath the San Pedro basin. Tectonic transpression along the closing back-arc basin marks one edge of an actively deforming microplate within the North America-Caribbean strike-slip plate boundary zone.