In northern Dominican Republic, Cretaceous and Lower Cenozoic rocks are exposed in a 250-km 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.

Chaotic, allochthonous, submarine gravity slide deposits (olistostromes) have been reported with increasing frequency during the past 15 yrs in stratigraphic columns throughout the world. One such unit, estimated to be several hundred meters thick, is distributed over 90 sq km in the Puerto Plata area of north-central Dominican Republic. The gray, clay-sized, structureless matrix of this unit behaves as a quick-clay under shock, and is composed of kaolinite, quartz, montmorillonite, and illite. Pelagic Foraminifera date the matrix as Paleocene(?) or early Eocene(?). Exotic blocks within the olistostrome include limestone, serpentinite, andesite, pillow volcanics, and tuffaceous rocks. The longest dimensions of the blocks range from 1 cm to 1.5 km, and the known ages range from pre-Paleocene to middle Eocene. Thus, the exotic blocks are older, the same age as, and younger than their enclosing matrix. The matrix probably was once a marine tuffaceous unit of Paleocene-early Eocene age which was deposited rapidly and retained enough water to liquify spontaneously and to begin moving rapidly down a gentle submarine basin slope following an earthquake shock during the late-middle Eocene. Younger more competent overlying rocks were ruptured and incorporated into the moving mass, while older rocks were torn loose from the submarine slope. The entire unit was emplaced essentially instantaneously into a marine sedimentary sequence. Although olistostromes record catastrophic events in the geologic record, they do not necessarily imply a major orogeny. However, most described olistostromes were formed during times of tectonic activity. The middle Eocene was such a time in the Puerto Plata area.

The Rio San Juan complex includes the largest exposed area of Cretaceous basement rocks exposed in the North Coast Zone of Hispaniola. The northern area of the complex consists of: (1) the Imbert Formation, a Paleocene to lower Eocene series of interbedded sandstone, conglomerate, white tuff, and sedimentary serpentinite; (2) Hicotea schists, pervasively fractured, mafic greenschists with patchily developed glaucophane and lawsonite; (3) Puerca Gorda schists, dominantly mafic, foliated greenschists, also with patchily developed glaucophane and lawsonite; (4) El Guineal schists, fine-grained, dominantly felsic schists; (5) Jagua Clara melange, retrograde eclogite, and garnet blueschist blocks in a highly metasomatically altered and hydrated ultramafic matrix; (6) Arroyo Sabana melange, fine-grained blueschist, marble, altered volcanic and mica-plagioclase blocks in a serpentinite matrix; and (7) Gaspar Hernandez serpentinites. The southern area of the complex is structurally simpler and consists of: (8) Cuaba amphibolites, mafic to felsic gneisses intruded by (9) the Rio Boba Intrusive Suite, gabbros, diorites, and ultramafic cumulates. We suggest that the Hicotea, Puerca Gorda, and El Guineal schists were metamorphosed in a Late Cretaceous subduction zone where they were protruded at depth Fust by the Jagua Clara melange and later by the Arroyo Sabana melange. Serpentinite protrusion also occurred during the Paleocene-Lower Eocene, and when some of these protrusions breached the surface, they were the source of clasts for conglomerate beds in the Imbert Formation. The southern part of the complex was formed either in the Hispaniola magmatic arc or by intrusion of fore-arc gabbroic magmas (the Rio Boba Suite) into fore-arc basement represented by the Cuaba amphibolites. The southern area was juxtaposed against the northern area before the Paleocene, but the mechanism by which this was achieved is unclear. Exposure of the assembled complex had occurred by the Eocene, but the complex was probably covered by clastic sediments during Late Eocene to Miocene times. Both the Cretaceous subduction complex and the mid-Tertiary clastic cover were disrupted and deformed by Neogene, east-west-trending, sinistral, transcurrent movements. Major fault displacements of tens to hundreds of kilometers separated the Puerto Plata area from the Rio San Juan complex, and both areas from southeastern Cuba. Minor displacements occurred within the Rio San Juan complex on sinistral oblique and strike-slip faults. Serpentinite protrusions were probably also reactivated at this time. Transcurrent faulting continues to the present and has resulted in eastward tilting of the Rio San Juan complex and the establishment of its present drainage systems.

Abstract The analysis of mid-scale distributive fluvial systems (DFS) provides an opportunity to study fluvial depositional patterns in sedimentary basins in a manner similar to megafans, but under the more homogeneous external conditions that control small alluvial fans from the source area to the depositional area. Four mid-scale Quaternary DFS and the areas of their drainage basins were analysed with the aim of understanding and predicting the mechanism and magnitude of fluvial fan deposition. These DFS were located in the Gastre Basin, Argentina, an endorheic basin that has evolved during the Quaternary under relatively uniform climatic and tectonic conditions. Using a geomorphological and sedimentological approach, the measured areas of the DFS were compared with the calculated areas using different regression equations for variables such as the drainage basin area and the drainage basin slope. The results suggest a moderate to high percentage of deviation in all cases, indicating that at an intermediate scale the size of the DFS is not solely a function of the size of the drainage basin. Adjacent DFS with similar depositional areas and catchment bedrock lithologies were linked with very different drainage basin areas and vice versa. This study suggests that the horizontal accommodation space, determined by the incision and distribution of previous deposits, and the drainage basin slope may also influence the size of mid-scale DFS.