Northeastern Caribbean Research Articles

Spatial distribution of settlement of Diadema antillarum around Saba, Dutch Caribbean.

The mass mortality event of the herbivorous sea urchin Diadema antillarum in 1983-1984 has been a major contributor to the diminished resilience of coral reefs throughout the Caribbean. The reduction in grazing pressure resulted in algae proliferation, which inhibited coral recruitment after disturbances such as disease, hurricanes, pollution and climatic change induced marine heat waves. Natural recovery of D. antillarum after the 1983-1984 die-off has been slow. However, the few locations with recovered populations exhibit signs of improvement in coral reef health, prompting interest in D. antillarum restoration. Current restoration strategies include translocation of wild individuals, the restocking of juveniles that are either cultured from gametes or collected as settlers and head-started in a nursery, and assisted natural recovery by providing suitable settlement substrate. Both the collection of wild settlers and assisted natural recovery necessitate an understanding of the local, spatiotemporal trends in settlement. In this study, which was carried out on the Dutch Caribbean Island of Saba, artificial turf settlement collectors were deployed at nine locations around the island and monitored from June 2019 till July 2020 (13 months). The primary objective was to identify trends in larval settlement in space and time, to be able to optimize restoration efforts. Additionally, the small size of Saba allowed us to deploy settlement collectors around the island and compare D. antillarum settlement between windward and leeward sides. Our study showed that on Saba, D. antillarum settlement peaked in June and July, following similar seasonal trends observed around other islands in the Northeastern Caribbean. By far the most settlement occurred at the leeward side of the island, suggesting that hydrodynamic forces entrained D. antillarum larvae in the lee of Saba and/or calmer waters facilitated settlement. Limited settlement occurred on the more exposed windward locations. The identified high settlement locations are candidates for settler collection and restoration attempts. Continued monitoring of D. antillarum settlement, especially in light of the 2022 D. antillarum die-off, holds significance as it can provide insights into the potential of natural recovery.

Northeastern Caribbean Rainfall Variability Linked to Solar and Volcanic Forcing

AbstractWe present a 500‐year precipitation‐sensitive record based on co‐varying speleothem δ18O values and Mg/Ca ratios from Larga cave in Puerto Rico. This multi‐proxy record shows that the evolution of rainfall in the northeastern Caribbean was characterized by alternating centennial dry and wet phases corresponding to reduced versus enhanced convective activity. These phases occurred synchronous with relatively cool and warm tropical Atlantic sea‐surface temperatures (SSTs), respectively. While the observed pattern suggests a close link of northeastern Caribbean rainfall to the Atlantic Multidecadal Variability, a regional comparison reveals intermittent regional heterogeneity especially on decadal timescales, which may be related to a superimposing influence of the Pacific and Atlantic basins. Furthermore, the speleothem‐based hydroclimate reconstruction indicates a significant volcanic impact during the past two centuries, and further reveals a potential solar signal in the preceding three centuries. We posit that the forcing likely shifted from solar to volcanic during the eighteenth century in being an important source of multidecadal to centennial Caribbean rainfall variability. The link between convective rainfall and natural forcing may be explained through a modulation of SST variations in the tropical Atlantic and Pacific oceans.

Stronger Hurricanes and Climate Change in the Caribbean Sea: Threats to the Sustainability of Endangered Coral Species

An increasing sea surface temperature as a result of climate change has led to a higher frequency and strengthening of hurricanes across the northeastern Caribbean in recent decades, with increasing risks of impacts to endangered corals and to the sustainability of coral reefs. Category five Hurricanes Irma and María during 2017 caused unprecedented damage to coral reef ecosystems across northeastern Puerto Rico, including mechanical destruction, localized sediment bedload (horizontal sediment transport and abrasion), and burial by hurricane-generated rubble fields. Hurricanes inflicted significant site-, depth-, and life history trait-specific impacts to endangered corals, with substantial and widespread mechanical damage to branching species, moderate mechanical damage to foliose species, and moderate to high localized damage to small-sized encrusting and massive morphotypes due to sediment bedload and burial by rubble. There was a mean 35% decline in Acropora palmata live cover, 79% in A. cervicornis, 12% in Orbicella annularis, 7% in O. faveolata, 12% in O. franksi, and 96% in Dendrogyra cylindrus. Hurricane disturbances resulted in a major regime shift favoring dominance by macroalgae, algal turf, and cyanobacteria. Recovery from coral recruitment or fragment reattachment in A. palmata was significantly higher on more distant coral reefs, but there was none for massive endangered species. Stronger hurricanes under projected climate change may represent a major threat to the conservation of endangered coral species and reef sustainability which will require enhancing coral propagation and restoration strategies, and the integration of adaptive, ecosystem-based management approaches. Recommendations are discussed to enhance redundancy, rapid restoration responses, and conservation-oriented strategies.

Coastal dry tropical forests in Florida and the Caribbean in peril: A review

AbstractCoastal dry tropical forests (CDTFs) are important yet vulnerable ecosystems. In this paper, we highlight the special conservation issues facing CDTFs by focusing on one variant of the type, those that occupy limestone substrate in the northeastern Caribbean. Our analysis draws largely from the coastal terrestrial broadleaf forests of the northern Bahamas, the Florida Keys, and southwestern Puerto Rico. Based on the surveys of storm surge recorded during major hurricanes during the last 50 years, we define CDTFs as coastal terrestrial broadleaf forests on ground surfaces elevated up to 5 m above sea level and occurring within 5 km of the coast. These forests are not only threatened by land‐use change from urbanization but also climate‐driven sea level rise (SLR) and hurricanes, which have degraded them and reduced their extent. CDTFs are distinguished from other dry tropical forests by the occasional influence of marine water incursion during periodic storms, requiring species common to these forests to have some level of salt tolerance despite experiencing well‐drained, fresh water conditions during most of their life span. With precipitation being the sole freshwater source for most CDTFs, SLR and the resulting salinization in the rooting zone subjects these forests to increasingly stressful conditions. Hence, even a modest rise in sea level can push numerous imperiled and endangered species and coastal terrestrial broadleaf communities to the edge of their tolerance, causing a decline in extent or their complete disappearance. Outside of protected areas, rapid urbanization has fragmented these forests and reduced their extent, which in turn have modified the interaction between rising seas and forest function. This work emphasizes the need for refined risk assessments to be completed and for conservation measures to be enforced so that resources can be directed appropriately to prevent further loss of CDTFs.Abstract in Spanish is available with online material.

A sequence of abrupt climatic fluctuations in the north-eastern Caribbean related to the 8.2 ka event

A speleothem collected from Palco Cave (Puerto Rico) spans the 8.2 ka event, a time interval associated with fluctuations of Atlantic Ocean circulation and possible drying in the Caribbean region. While stalagmite δ18O, δ13C, and Mg/Ca data do not show a sustained change in mean state over the 8.2 ka event, the proxies provide robust evidence for three abrupt fluctuations toward drier conditions in rapid succession, each lasting less than two decades, occurring at 8.20, 8.14, and 8.02 ka BP. A cave monitoring program at Palco Cave supports the interpretation of the speleothem proxy records. Because changes in the position of the Intertropical Convergence Zone (ITCZ) are directly coupled to sea-surface temperature variations in the North Atlantic, we hypothesize that cold events in the North Atlantic temporarily limited the northward migration of the ITCZ and tropical rain belt in boreal summer during these abrupt drying periods. The speleothem record suggests that the 8.2 ka event was associated with rapid rainfall fluctuations in the northern Caribbean followed by a comparably warm and wet phase after the 8.2 ka event. This enhanced variability during the transitional period of the deglaciation appears to be linked to a fast coupling between interacting oceanic and atmospheric processes. This involves, in particular, the Atlantic Meridional Overturning Circulation in modulating interhemispheric heat transport.

Paleomagnetic Rotations in the Northeastern Caribbean Region Reveal Major Intraplate Deformation Since the Eocene

AbstractRelative Caribbean‐North American plate motion is partitioned over the trench and intra‐Caribbean plate faults that bound large scale tectonic blocks. Quantifying the kinematic evolution of this tectonic corridor is challenging because much of the region is submarine. We present an extensive regional paleomagnetic data set (1,330 cores from 136 sampling locations) from Eocene and younger rocks of the northern Lesser Antilles, the Virgin Islands, and Puerto Rico, and use a statistical bootstrapping approach to quantify vertical axis block rotations. Our results show that the Puerto Rico–Virgin Island (PRVI) block and the Northern Lesser Antilles (NoLA) block formed two coherently rotating domains that both underwent at least 45° counterclockwise rotation since the Eocene. The first ∼20° occurred in tandem in late Eocene and Oligocene time, after which the blocks were separated in the Miocene by the opening of the Anegada Passage. The last 25° of rotation of the PRVI block ended in the middle Miocene, whereas the NoLA block rotated slower, until the latest Miocene. The boundary between the NoLA block and a non‐rotated Southern Lesser Antilles was likely the Monserrat‐Harvers fault zone. These results require hundreds of kilometers of intra‐Caribbean motions with oroclinal bending of the trench or forearc sliver motion along the curved plate boundary as endmembers. These data invite a critical re‐evaluation of the kinematic reconstruction of Caribbean‐North American plate motion. The consequent changes in paleogeography may provide a new view on the enigmatic eastern Caribbean paleo‐biogeography and the Paleogene dispersal of South American mammals toward the Greater Antilles.

A comparison of claw removal methods on the survival and claw regeneration of stone crab (Menippe mercenaria)

Commercial and recreational stone crab (Menippe mercenaria) fisheries primarily occur along the Gulf of Mexico and Atlantic coasts of the southeastern United States and the northeastern Caribbean. The fishery is unique in that only the crabs claws are retained and the animal is returned to the water alive. While the fishery is often regarded as sustainable because it is believed to exploit the crabs natural ability to voluntarily drop (autotomize) and regenerate lost claws, the survival of de-clawed stone crabs is often low, especially when both claws are harvested. In this study, a controlled laboratory experiment was used to compare an induced-autotomy method of claw removal to the typical forced break method currently used in the fishery. For the two different claw removal methods, we compared crab survival and start time to claw regeneration as a function of one or both claws removed. Overall, we found a significant effect of the removal method and number of claws removed on crab survival, but these factors did not influence the time to start claw regeneration. Although the induced-autotomy method was several seconds slower in processing time than the typical forced break method, it resulted in a 29% increase in survival (up to 92% survival throughout the study) compared to the typical forced break method of claw removal (63% survival throughout the study). Overall, these results suggest that the induced-autotomy method of claw removal significantly increases survival of stone crabs.

Three Decades of Road and Trail Runoff and Erosion Work in the Northeastern Caribbean – a Research Program Perspective

HighlightsThe infiltration capacities of unsurfaced roadways are frequently exceeded by rain intensity, promoting overland flow.Erosion rates from unsurfaced roadways and cut slopes are 101 to 104 times greater than on undisturbed hillslopes.Roads in steep, subtropical wet terranes may increase landslide erosion by a factor of 5 relative to areas without roads.The hydro-geomorphic impact of roads is so prominent that they must be explicitly considered in watershed assessments. ABSTRACT. Erosion is a key environmental concern in the northeastern Caribbean because it can diminish soil productivity, damage infrastructure, and threaten human life. Additionally, sediment released by erosion can be delivered to streams where it can degrade water quality and aquatic habitat, reduce reservoir storage capacity, and threaten critical marine resources such as sea grass beds and coral reefs. Road erosion has been a concern in the region since the 1990s, and a considerable body of research has been conducted over the last ~30 years. This article reviews the key findings and identifies additional research needs. In some tropical dry coastal watersheds of the US Virgin Islands and Puerto Rico, unpaved roads and foot or off-road vehicle trails are the primary sediment sources. Watershed scale sediment production rates in these tropical dry settings are 0.3 to 3.7 Mg ha-1 yr-1, depending on unpaved road density, and these are 3 to 40 times greater than under undisturbed conditions. In wetter settings, like the forested and actively cultivated landscapes of highland Puerto Rico, sediment contributions include those from unpaved farm roads but also those from croplands, streambanks, and landslides. Watershed scale sediment production rates in actively cultivated tropical wet settings are 15 to 60 Mg ha-1 yr-1, with road-induced surface erosion and landslides accounting for 50% to 95% of total sediment production. Designing management alternatives will require additional research to improve our understanding of road-to-stream and road-to-coast connectivity, develop effectiveness metrics of applied management practices, and establish the specific causes of road-induced landslides. Keywords: Connectivity, Coral reefs, Landslides, Puerto Rico, Sedimentation, Surface erosion, Virgin Islands.

Historical Records of Loggerhead Sea Turtle (Caretta caretta) Nesting at Tortuguero, Costa Rica

Costa Rica is considered a hot spot for biodiversity and wildlife conservation in Central America, and sea turtles are a good example of this. Largely distributed along both the Caribbean and Pacific coast, adult females of five of the seven extant sea turtle species select beaches on both coasts as their breeding sites. Although Green Sea Turtles (Chelonia mydas), Leatherback Sea Turtles (Dermochelys coriacea), Hawksbill Sea Turtles (Eretmochelys imbricata), and Olive Ridley Sea Turtles (Lepidochelys olivacea) have been extensively studied in Costa Rica, little information regarding Loggerhead Sea Turtles (Caretta caretta) is available. Thus, we present an exhaustive data record of every Loggerhead encountered at Tortuguero beach (northeastern Caribbean coast of Costa Rica) over the past 60 yr. We collected Loggerhead nesting data between 1957 and 2021 through daytime and nocturnal monitoring activities. We documented 14 Loggerhead Sea Turtle nesting attempts between 1957 and 2021 at Tortuguero. Among them, seven nested successfully, four did not lay eggs, and one's fate is unknown. Additionally, two turtles were killed by jaguars. Mean minimum curve carapace length (CCLmin) measurements for Loggerheads was 98.2 ± 3.7 cm (range, 90.0–101.4 cm). Finally, we found that every encounter occurred between April and July, which coincides with the Loggerhead nesting season in the Northwest Atlantic. Our study is the first assessment of Loggerhead Sea Turtles nesting in Costa Rica, bringing to light new records for this species in the Caribbean Sea.

Assessing Effects of Sediment Delivery to Coral Reefs: A Caribbean Watershed Perspective

Coral reefs in the western Atlantic and Caribbean are deteriorating primarily from disease outbreaks, increasing seawater temperatures, and stress due to land-based sources of pollutants including sediments associated with land use and dredging. Sediments affect corals in numerous ways including smothering, abrasion, shading, and inhibition of coral recruitment. Sediment delivery resulting in deposition and water quality deterioration can cause degradation at the spatial scale of corals or entire reefs. We still lack rigorous long-term studies of coral cover and community composition before, during and after major sediment stress, and evidence of recovery after watershed management actions. Here we present an overview of the effects of terrestrial sediments on corals and coral reefs, with recent advances in approaches to watershed assessment relevant to the delivery of sediments to these ecosystems. We present case studies of northeastern Caribbean watersheds to illustrate challenges and possible solutions and to draw conclusions about the current state of knowledge of sediment effects on coral reefs. With a better understanding of erosion and the pathways of sediment discharge to nearshore reefs, there is the increased potential for management interventions.

Transtensional Rupture within a Diffuse Plate Boundary Zone during the 2020 Mw 6.4 Puerto Rico Earthquake

Abstract On 7 January 2020, an Mw 6.4 earthquake occurred in the northeastern Caribbean, a few kilometers offshore of the island of Puerto Rico. It was the mainshock of a complex seismic sequence, characterized by a large number of energetic earthquakes illuminating an east–west elongated area along the southwestern coast of Puerto Rico. Deformation fields constrained by Interferometric Synthetic Aperture Radar and Global Navigation Satellite System data indicate that the coseismic movements affected only the western part of the island. To assess the mainshock’s source fault parameters, we combined the geodetically derived coseismic deformation with teleseismic waveforms using Bayesian inference. The results indicate a roughly east–west oriented fault, dipping northward and accommodating ∼1.4 m of transtensional motion. Besides, the determined location and orientation parameters suggest an offshore continuation of the recently mapped North Boquerón Bay–Punta Montalva fault in southwest Puerto Rico. This highlights the existence of unmapped faults with moderate-to-large earthquake potential within the Puerto Rico region.

Ex-ante assessment of the cost-effectiveness of public policies to sequester carbon in soils

Soil organic carbon stocks have been declining for more than a century, mostly in the tropics. Maintaining soil organic matter is critical to tackling climate change and controlling soil health. One way to address this problem is to encourage farmers to improve soil carbon on their farms. We provide an ex-ante assessment of the cost-effectiveness of innovative Agri-Environmental Measures (AEM) that subsidize the use of compost. To do so, we ran a choice experiment in Guadeloupe, in the northeastern Caribbean, where there is an urgent need to preserve soil organic matter levels. The 305 farmers who participated were asked to choose one of several AEM that offer financial support in exchange for using compost in their farming activities, as well as free technical assistance, a collective financial bonus, and the possibility of combining chemical fertilisers with composts. We found that offering free technical assistance increases the participation rate by 30 percentage points and offering a collective bonus increases it by 14 percentage points. In contrast, including a requirement on the reduction of chemical fertilization would decrease the probability of participation by only two percentage points. We then estimated the amount of carbon that would be sequestered in the soil using compost as prescribed under each of the AEM proposed. We found that the most effective AEM would sequester up to 25,000 teqCO2 per year at the territory level and that the most cost-effective scheme would reach this target at a cost of about 500 euros per teqCO2. Finally, we find that the so-called 4 per 1000 target could be reached through AEM under a variety of scenarios.

“Transinsular” Music – Glissant’s Opacity

The author makes the case for “transinsularism” as a descriptive approach to address the complexities of Caribbean island identities. This approach accounts for the Caribbean islands’ condition of being simultaneously isolated and connected, mobile and insular, and constituted in processes of relations with other island spaces. In the article, the concept of transinsularism is related to Glissant’s reflections on the opacity of culture and the methodological implications of his approach. The author (Cubero) suggests an ethnographic contextualisation of Glissant’s ideas by presenting an account of musical politics on the Caribbean island of Culebra, which is located in the north-eastern Caribbean. He argues for a continuance of Glissant’s approach to identity as a performative act that finds expression in affective practices, rather than in predetermined structural markers of difference.

Paleogene V‐Shaped Basins and Neogene Subsidence of the Northern Lesser Antilles Forearc

AbstractOblique collision of buoyant provinces against subduction zones frequently results in individualizing and rotating regional‐scale blocks. In contrast, the collision of the Bahamas Bank against the Northeastern Caribbean Plate increased the margin convexity triggering forearc fragmentation into small‐scale blocks. This deformation results in a prominent sequence of V‐shaped basins that widens trenchward separated by elevated spurs, in the Northern Lesser Antilles (NLA, i.e., Guadeloupe to Virgin Island). In absence of deep structure imaging, various competing models were proposed to account for this Basins‐and‐Spurs System. However, high‐resolution bathymetric and deep multichannel seismic data acquired during cruises ANTITHESIS 1‐3, reveal a drastically different tectonic evolution of the NLA Forearc.During Eocene‐Oligocene time, the Caribbean Northeastern Boundary accommodated the Bahamas Bank collision and the subsequent margin convex bending by major left‐lateral strike‐slip faults systems in the Greater Antilles and by trench‐parallel extension along N40°–90°‐trending normal faults in the NLA. Block rotations, forearc fracturing, and V‐shaped valleys opening went along with this tectonic phase, which ends up with tectonic uplifts and an earliest‐middle Miocene regional emersion phase. Post middle Miocene regional subsidence and tectonic extension in the forearc are partly accommodated along the newly imaged N300°‐trending, 200‐km‐long normal Tintamarre Faults Zone. This drastic subsidence phase reveals vigorous margin basal erosion, which likely generated the synchronous westward migration of the volcanic arc. Thus, unlike widely accepted previous theoretical models, the NE‐SW faulting and the prominent V‐shaped valleys result from a past and sealed tectonic phase related to the margin bending and subsequent blocks rotation.

Distribution and ontogenetic habitat shifts of reefassociated shark species in the northeastern Caribbean

Understanding how reef-associated sharks utilise coastal reef habitats throughout their ontogeny is essential for their effective management. In this study, we assessed the distribution of sharks in the northern Caribbean Netherlands (Saba, Saba Bank and St Eustatius) and ontogenetic shifts in habitat and depth use of the 2 most observed species: Caribbean reef shark Carcharhinus perezi and nurse shark Ginglymostoma cirratum. We used stereo baited remote underwater video (stereo-BRUV) surveys at 376 sites. A total of 126 shark sightings (6 species) were recorded, with C. perezi (n = 72) and G. cirratum (n = 42) most frequently observed. The probability of recording at least 1 shark per deployment ranged from 0.19 to 0.37 and is comparable with shark occurrences in the small number of other stereo-BRUV studies in the Wider Caribbean Region. Habitat type was the most important factor driving reef-associated shark occurrences, with the highest probability of observing C. perezi and G. cirratum in soft-coral habitat. Additionally, occurrences of C. perezi were significantly influenced by the management zone, with highest probabilities of occurrence in no-fishing zones. Almost all observed reef-associated sharks (95.6%) were juveniles, indicating that the study area may be a nursery area. Overall, both species were observed in deeper waters with increasing size, indicating ontogenetic shifts in depth use. Our findings imply that protected areas should not be limited to a single habitat or depth, but focus on protecting a large area with the range of habitats and depths necessary for reef-associated sharks to complete their life cycle.

The marine fishes of St Eustatius Island, northeastern Caribbean: an annotated, photographic catalog.

Sint Eustatius (Statia) is a 21 km2 island situated in the northeastern Caribbean Sea. The most recent published sources of information on that island’s marine fish fauna is in two non-governmental organization reports from 2015–17 related to the formation of a marine reserve. The species-list in the 2017 report was based on field research in 2013–15 using SCUBA diving surveys, shallow “baited underwater video surveys” (BRUVs), and data from fishery surveys and scientific collections over the preceding century. That checklist comprised 304 species of shallow (mostly) and deep-water fishes. In 2017 the Smithsonian Deep Reef Observation Project surveyed deep-reef fishes at Statia using the crewed submersible Curasub. That effort recorded 120 species, including 59 new occurrences records. In March-May 2020, two experienced citizen scientists completed 62 SCUBA dives there and recorded 244 shallow species, 40 of them new records for Statia. The 2017–2020 research effort increased the number of species known from the island by 33.6% to 406. Here we present an updated catalog of that marine fish fauna, including voucher photographs of 280 species recorded there in 2017 and 2020. The Statia reef-fish fauna likely is incompletely documented as it has few small, shallow, cryptobenthic species, which are a major component of the regional fauna. A lack of targeted sampling is probably the major factor explaining that deficit, although a limited range of benthic marine habitats may also be contributing.

A 1600 year-long sedimentary record of tsunamis and hurricanes in the Lesser Antilles (Scrub Island, Anguilla)

The Lesser Antilles are a densely populated region where local populations and industrial facilities are concentrated at the coastlines, and are therefore exposed to many rapid-onset hazards such as hurricanes and tsunamis. However, the historical catalog of these events is too short to allow risk assessment and return period estimations, and it needs to be completed with long-term records of washover deposits in coastal sedimentary environments such as lagoons. In this study, two sediment cores were taken in March 2018 in a small coastal lagoon on Scrub Island (northeastern Caribbean). Sedimentological, geochemical, microfaunal and chronological analyses enabled us to identify 25 sandy layers resulting from high-energy-marine floods. Two of these layers were interpreted as tsunami deposits based on sedimentological (rip-up clast of the underlying cohesive substrate and internal mud laminae), and geochemical evidence. The most recent deposit is associated with the transatlantic tsunami triggered by the 1755 CE Lisbon earthquake. The older one is the thickest sandy layer recorded in the lagoon, with an age range of 1364–1469 cal. CE, as determined using 14C dating. This event was recorded in sedimentary archives of both the northern and the southern part of the Caribbean, with its large spatial extent, supporting a distant tsunamigenic origin. The 23 remaining sandy layers were interpreted as storm deposits, based on sedimentological and chronological data, with the three most recent layers being correlated with historical hurricanes. This new 1600 year-long record displays similarities with that of the Bahamas, with the periods of intense hurricane activity being in antiphase with those of the north-eastern US coast. This regional comparison may provide evidence for a latitudinal forcing of hurricane tracks through time in relation to climate fluctuations.

Stratigraphy and structure of regionally-isolated hydrocarbon occurrences in the Azua Basin, south-central Dominican Republic (Northeastern Caribbean)

Abstract Oil seeps and small-production oilfields in south-central Hispaniola are regionally isolated from much larger hydrocarbon provinces in the circum-Gulf of Mexico and northern South America. In this study, we evaluate the tectonic, stratigraphic and structural setting of these hydrocarbon occurrences. The zone of late Miocene to Recent oblique convergence includes the Bahamas Platform, Cretaceous and Paleogene arc rocks in Hispaniola, and the Cretaceous Caribbean oceanic plateau. Twentieth-century hydrocarbon exploration in Hispaniola has been concentrated on the elongate, NW- to WNW-trending, thrust- and strike-slip fault-bounded Cibao, San Juan–Azua and Enriquillo basins. Analyses of Cretaceous to Neogene rocks in the Dominican Republic have revealed that most rocks contain poor to marginal total organic carbon values. In the Azua Basin, a shallow marine, basin-edge facies of the middle Miocene Sombrerito Formation underlies the area of natural oil seeps and limited historical oil production and exhibits good to excellent total organic carbon values greater than 1%. Structural traps for oil at the Maleno and Higuerito oilfields of the Dominican Republic are large anticlines formed in post-late Miocene time. Reservoir rock for oil at the Maleno and Higuerito oilfields of the Dominican Republic is submarine fan-deposited sandstone of the late Miocene Trinchera Formation.

Regional hydrocarbon potential of the northeastern Caribbean based on integration of sediment thickness and source rock maturity data

AbstractOver 72 exploration wells have been drilled on the Caribbean islands of Hispaniola and Puerto Rico over the past century, but with no commercial success. A question is whether these Caribbean oceanic islands have experienced sufficient subsidence and burial for any potential source rocks to reach maturity and produce commercial hydrocarbons. Subsurface data from previous studies were compiled into a regional depth to basement and sediment thickness map for Hispaniola, Puerto Rico and their offshore areas. The thickest basins include the Enriquillo/Cul-de-Sac basin (6.3 km), San Juan/Plateau Central basin (5 km), Azua basin (2.8 km), Cibao basin (5 km), North Coast basin (2.5 km), South Coast basin (1.3 km), Haiti sub-basin (3.7 km), Hispaniola basin (3.5 km) and San Pedro basin (3 km). One-dimensional modelling for six onland basins shows that only the Azua basin of the south-central Dominican Republic has reached sufficient maturity to place potential source rocks into the oil window. Our study shows that commercial hydrocarbons are possible in the deeper basins – Azua basin, San Juan–Plateau Central basin and Cibao basin of Hispaniola – but unlikely in the shallower basins that lack sufficient overburden for organic maturity.

Eocene intra-plate shortening responsible for the rise of a faunal pathway in the northeastern Caribbean realm.

Intriguing latest Eocene land-faunal dispersals between South America and the Greater Antilles (northern Caribbean) has inspired the hypothesis of the GAARlandia (Greater Antilles Aves Ridge) land bridge. This landbridge, however, should have crossed the Caribbean oceanic plate, and the geological evolution of its rise and demise, or its geodynamic forcing, remain unknown. Here we present the results of a land-sea survey from the northeast Caribbean plate, combined with chronostratigraphic data, revealing a regional episode of mid to late Eocene, trench-normal, E-W shortening and crustal thickening by ∼25%. This shortening led to a regional late Eocene-early Oligocene hiatus in the sedimentary record revealing the location of an emerged land (the Greater Antilles-Northern Lesser Antilles, or GrANoLA, landmass), consistent with the GAARlandia hypothesis. Subsequent submergence is explained by combined trench-parallel extension and thermal relaxation following a shift of arc magmatism, expressed by a regional early Miocene transgression. We tentatively link the NE Caribbean intra-plate shortening to a well-known absolute and relative North American and Caribbean plate motion change, which may provide focus for the search of the remaining connection between 'GrANoLA' land and South America, through the Aves Ridge or Lesser Antilles island arc. Our study highlights the how regional geodynamic evolution may have driven paleogeographic change that is still reflected in current biology.