Cordillera Septentrional Research Articles

Geodynamics and Neotectonics of the Cordillera Septentrional and Samaná Peninsula, Dominican Republic: implications for seismotectonics and seismic hazard assessment

The Dominican Republic is exposed to a high seismic hazard due to its geodynamic location between two active margins of oblique convergence. New geodynamic, neotectonic and seismotectonic data of the Cordillera Septentrional and Samaná Peninsula, and also the onshore area of the northern microplate, have allowed the location of the main seismotectonic fault zones. Structural, stratigraphic and morphotectonic information obtained from the fault zones at several scales has allowed us to interpret their kinematics and consistency with the obtained regional stress tensor deduced from dynamic inverse methods. This information complemented by the record of historical seismicity, displacement velocity and seismic parameters of the fault zones has allowed us to evaluate the seismic hazard of the studied area.The method used for the evaluation of the seismic hazard is probabilistic and considers three types of seismic sources: the subduction zone, the main strike-slip fault zones and the areas located between them. This method allows us to calculate the iso-lines of peak ground acceleration (PGA) with a resolution of 0.05º for an exceedance probability of 10% (50 years) and a return period of 475 years. Resulting PGA bands are arranged sub-parallel to the North Hispaniola, Septentrional and Camú Fault Zones, as well as the main ONO-ESE-trending faults systems, detecting a maximum of PGA towards the SE of the modelled area. Consequently, the cities with the lowest seismic hazard are those located towards the NW of the maximum PGA zone.

Quaternary deformation and uplift of coral reef terraces produced by oblique subduction and underthrusting of the Bahama Platform below the northern Hispaniola forearc

Active tectonics linked to the rise of the Hispaniola forearc explain the morphological characteristics, spatial distribution and U-Th geochronological ages of the uplifted coral reef terraces of the La Isabela Formation in both the eastern Cordillera Septentrional and the Samaná Peninsula of northeastern Dominican Republic. Depositional coral reef terraces of MIS 5e (TII), 7e (TIII) and 9 (TIV) stages occur respectively at maximum heights of about 25 m, 80 m and 120 m above the current sea level. The development of heterogeneous brittle deformation structures in the coral limestone at all scales document active tectonics and include small faults, shear fractures, extensional joints and calcite veins. Their geometric and kinematic characteristics, as well as the stress tensors calculated from fault-slip and fracture orientation data, are all compatible with ENE to NE-trending regional shortening, and indicate that a left-lateral transpressive regime is deforming the forearc during the Quaternary.Along the northern Hispaniola coastline, the tectonic uplift mimics the distribution of the bathymetric features on the subducting Bahamas Platform, outboard the Hispaniola-Puerto Rico Trench. The highest calculated uplift rates in the eastern Cordillera Septentrional and Samaná Peninsula correspond to the collision zone of the Silver Spur and Navidad Bank (≥0.4 m/ka), respectively. Uplift rates decrease towards the west (≤0.2 m/ka), where the oblique collision of carbonate ridges and related forearc deformation would not have been recorded since at least the Early Pleistocene. Oblique subduction and underthrusting of the Bahamas Platform followed by basal erosion at the subduction channel explain the observed time-transgressive pattern of uplift and subsidence in the northern Hispaniola forearc and the change from accretionary to erosive processes in the convergent margin.

A Study on the Formation Environment of the La Cumbre Amber Deposit, from Santiago Province, the Northwestern Part of the Dominican Republic

The amber-bearing coaly shale from the La Cumbre deposit (Cordillera Septentrional, Dominican Republic) contains a large quantity of altered, coalified plant detritus. The coals in these shales are in the transition stage from meta-lignite to subbituminous coals. They are composed mainly of inertinite macerals such as fusinite, semifusinite, macrinite and secretinite. Fossil resin found in the deposit occurs in two forms: detrital grains up to several centimetres in size (type I) and very fine authigenic grains, of a few micrometers in size, inside the humic laminae (type II, resinite). The detrital fossil resins are transparent, with few mineral and organic inclusions. In their composition they contain sulfides, which may come from sulfate reduction, inclusions of plants and/or insects or be caused by volcanic activity developed in surrounding coal series. The resinites are strongly saturated with various inclusions and spatially associated with framboidal pyrite aggregates. Both fossil resin types were probably deposited in a shallow coastal lake environment in the zone bordering the floodplain of the river, with periodic floods. The marine environment conditions, which were progressively changing from oxidizing to reducing, are likely associated with the formation of the fossil resin.

Neotectonic structures and stress fields associated with oblique collision and forearc sliver formation in northern Hispaniola: Implications for the seismic hazard assessment

Active oblique collision between the Caribbean and North America plates has led to the formation of the Septentrional forearc sliver, which is a wedge-shaped crustal domain limited to the north by the North Hispaniola subduction thrust and to the south by the Septentrional Fault Zone (SFZ). In northern Hispaniola, oblique collision of the Bahamas Platform began in the uppermost Pliocene to Early Pleistocene and continues today. Collision-related tectono-stratigraphic processes include destruction of the shallow-water carbonate forearc platform, uplift and erosion of the Cordillera Septentrional and Samaná Peninsula, emergence of the Cibao Basin and syn-tectonic deposition of alluvial fan systems. The geometry and kinematics of neotectonics structures at all scales, together with stress field solutions obtained from late Cenozoic fault-slip data, show that the ENE-directed (far-) stress field associated with collision triggered the formation of the WNW-trending, left-lateral strike-slip SFZ. The SFZ thus represents the inland, concave master fault bounding the Septentrional forearc sliver. Subsidiary ENE to NE-trending left-lateral strike-slip faults (R-type) and NNE to NE-trending normal and oblique faults (T-type) controlled the internal deformation and subdivision into smaller tectonic blocks of the sliver. The highly oblique convergence and the increase in frictional plate coupling associated with the underthrusting of the Bahamas Platform are the likely causes of the formation of this forearc sliver. In the Western Cordillera Septentrional and Cibao Basin, an extensional regime is locally produced by the transfer of the left-lateral movement to a southern splay of the SFZ with the incorporation of a detached block to the Septentrional forearc sliver during the Middle Pleistocene-Holocene. The regional distribution of the modeled Peak Ground Acceleration values indicates that the SFZ is the greatest seismic hazard in northern Hispaniola.

Modeling spatial variation in winter abundance to direct conservation actions for a vulnerable migratory songbird, the Bicknell's Thrush (Catharus bicknelli)

ABSTRACT The winter range of the Bicknell's Thrush (Catharus bicknelli), a globally vulnerable Nearctic–Neotropical migratory songbird, is restricted to the Greater Antilles. Most birds occur on Hispaniola, where the species exhibits sexual habitat segregation, and where the loss of its preferred wet broadleaf habitats has been severe. Conservation of female-dominated habitats has been identified as a top priority for the species' preservation. During 2010, we conducted standardized field surveys for the Bicknell's Thrush in forests of the Dominican Republic's Cordillera Septentrional, an area of high importance for females. We combined occurrence data with environmental variables to create a model of thrush distribution and habitat selection in the region. Elevation (densities peaked at ∼600 m), aspect (northeastern slopes), the amount of forest cover within 1 km, and forest density best described thrush presence and abundance. As an example of how predictive models of abundance can inform conservation, ...

One new species, two new combinations and taxonomic notes on the All-spice genus Pimenta (Myrtaceae) from Hispaniola

One new species and two new combinations are here published as taxonomic updates on the all-spice genus Pimenta (Myrtaceae) for the flora of Hispaniola, Greater Antilles. Pimenta berciliae is a small tree, the type of which was found in the vicinity of the National Botanical Gardens in Santo Domingo. Natural populations of this species are restricted to a small area in Samaná and Cordillera Septentrional, and the preliminary assessment of its conservation status indicates an endangered species. Additionally, Eugenia yumana and Eugenia samanensis are here formally transferred to Pimenta after molecular and morphological analyses demonstrate that they belong to this latter genus. Two new combinations, Pimenta yumana and Pimenta samanensis are here provided. These three additions to the flora of Pimenta in Hispaniola increase the known diversity of the genus on the island and are important to better understand the diversity of the all-spice genus in the region.

Marine terraces of the Promontorio de Cabrera (Pleistocene, northern Dominican Republic)

Eleven marine terraces, locally faulted and southward-tilted, can be recognized in the Promontorio de Cabrera, at the eastern end of the Cordillera Septentrional in the northern Dominican Republic. The lower terraces (T1-T7) are reefal platforms belonging to the La Isabela Formation, whereas the upper ones (T8-T11) are abrasion platforms sculpted in the carbonates of the Los Haitises Formation. The terraces formed during Pleistocene uplift, initially as a series of erosional steps and later as staircase offlapping depositional terraces. According to available radiometric data, the lower terrace (T1) formed in the MIS 5e and its uplift rate can be estimated as 0.15-0.17 mm/year in the northern sector. This uplift rate suggests that T2 formed in the Middle Pleistocene, T3 in the Middle Pleistocene-Calabrian boundary, T4-T8 in the Calabrian, and T9-T11 in the Gelasian. The Promontorio de Cabrera has been built by the continuous uplift and emersion of successive terraces since the Early Pleistocene (Gelasian).

The San Marcos mélange, Cordillera Septentrional of the Dominican Republic. Nature, origin and age

Understanding the nature, origin, and age of a mélange is crucial to deciphering the evolution of certain orogenic belts. Located in the Cordillera Septentrional of the Dominican Republic, the San Marcos Mélange is characterized by a blocks-in-matrix internal structure. Apparently arranged chaotically, the blocks have centimeter to kilometer sizes, include exotic ophiolitic, volcaniclastic, and intrabasinal sedimentary lithologies, and are of Cretaceous to Miocene in age, all immersed in a scaly and variably sheared argillaceous matrix. In less-deformed coherent sections, the Mélange consists of alternating sandstones, siltstones, and clays, indicative of a distal turbiditic depositional environment. Syn-sedimentary deformation is pervasive and produces systems of conjugated extensional shear fractures, veins filled with calcite, cataclastic bands, and boudinage and pinch-and-swell, symmetrical and asymmetrical structures. They are consistent with a layer parallel extension, produced in a low-energy slope setting, and indicate a low-ductility contrast between few or no lithified lithologies. Paleostress analysis of fractures and veins establishes a NE-SW trend of sub-horizontal extension, suggesting an orientation of the basin along a WNW-ESE to NW-SE axis (current coordinates). The biochronological data of nannofossils present in the matrix gives a sedimentary age for the Mélange from, at least, the top of the lower Miocene to the base of the upper Miocene. The San Marcos Mélange has therefore an essentially gravitational origin. Its deformation was temporally syn-sedimentary and was produced by processes of gravitational sliding, probably triggered by both instability processes within the basin and tectonic (earthquake shaking) mechanisms. Blocks and megablocks of ophiolitic rocks derived from the underlying Puerto Plata complex and of well-lithified, volcaniclastic and sedimentary rocks of the Imbert Fm, represent "exotic" blocks caused by the gravitational collapse of the high topographically margins of the depositional basin, slide down, and emplaced into the unconsolidated slope and basin turbiditic deposits, at least in the lower and middle Miocene. The existence of a large-scale, syn-sedimentary shearing surface directed to-the-ONO at the basal contact suggests that the whole Mélange was displaced once or several times in that direction, contributing to the chaotic nature of the unit. The San Marcos Mélange is not a subduction-zone mélange, but was caused by the submarine landslide of turbiditic sediments in a syn-collisional, piggy-back basin, transported on top of a supra-subduction zone ophiolite of the Caribbean plate.

Beetles with Orchid Pollinaria in Dominican and Mexican Amber

Orchids are extraordinary plants that have evolved the strategy of dispersing their pollen in little sacs called pollinia. Pollinia are normally attached by supports (caudicles) to adhesive pads (viscidia) that stick to various body parts of the pollinator. The entire pollination unit is called a pollinarium. Since pollen dispensed in pollinia is not available as food to most insects (van der Cingel 1995), orchids supply nectar or have evolved ingenious patterns of mimicry and deceit to attract potential pollinators (Endress 1994). Beetle associations with orchids are diverse. Beetles may visit orchid flowers simply for nectar, or at the same time acquire pollinaria and serve as pollinators. Beetles can also feed and raise their brood on orchid floral and vegetative parts. Some orchids depend on various Coleoptera for pollination and have produced “cantharophilous” flowers especially attractive to beetles (Endress 1994, Kalshoven and van der Laan 1981). The present study provides the first fossil evidence of beetles serving as pollinators of orchids. The two examples consist of a cryptorhynchine weevil (Coleoptera: Curculionidae) in Dominican amber with an orchid pollinaria attached to its thorax and a ptilodactyline beetle (Coleoptera: Ptilodactylidae) in Mexican amber with a pollinarium adhering to its mouthparts. These pollinaria are described below and associations between beetles and orchids are reviewed. The Dominican amber specimen was obtained from mines located in the Cordillera Septentrional of the Dominican Republic. These mines are in the Altimira facies of the El Mamey formation, which is shale-sandstone interspersed with a conglomerate of well-rounded pebbles (Eberle et al. 1980). Ages range from 20–15 Ma (Iturralde-Vinent …

Mélanges and olistostromes in the Puerto Plata area (northern Dominican Republic) as a record of subduction and collisional processes between the Caribbean and North-American plates

The Cordillera Septentrional records the oblique subduction and collisional processes between the Caribbean and North American plates during Late Cretaceous to early Palaeogene times. The Puerto Plata basement complex of this range is considered to represent a fragment of the frontal part of the Great Arc of the Caribbean in Hispaniola that originated during thrusting of the Caribbean plate onto the North American shelf. This paper describes and interprets mélange-type formations spatially related to this basement complex and its associated sedimentary cover, the Imbert Fm. Such formations include the San Marcos olistostromic Fm and a unit of Serpentinic Breccias located at the base and interbedded in the lower section of the former. Both units are Eocene in age, have been mainly deposited by syntectonic subaqueous mass-transport processes and typically host a varied mixture of blocks of known and unknown origin, including high-P metamorphic rocks (knockers). Cartoon models of palaeotectonic reconstructions depicting the final stages of subduction and the onset of collisional process in Early and Middle Eocene times respectively, are proposed in order to show the original relationships among all geological units involved in the study area. The Serpentinic Breccias are interpreted as being the result of extensive sedimentary recycling of peridotite and serpentinite massive bodies or subduction related mélanges when exposed at the surface by return flow during early exhumation stages of the accretionary complex, coevally with the end of island-arc volcanism. This process is inferred to be the triggering mechanism for the feeding of originally deep-sited knockers, probably in combination with strike-slip tectonics and associated mud diapirism The slightly younger San Marcos Fm records the collision event and main exhumation stage, while displaying the typical features present in olistostromes and other mass-wasting, gravitationally-driven deposits recognized in extensive areas of forearc and accretionary complexes involved in arc-continent collisional processes.

Salcedoa gen. nov., a Biogeographic Enigma in the Caribbean Mutisieae (Asteraceae)

Abstract A new genus, Salcedoa, is described from the Cordillera Septentrional, northern Dominican Republic. The bilabiate florets, smooth style branches, caudate anthers, and pollen grains size and shape, exine structure and sculpture, and endoaperture shape place it close to the South American genera of the tribe Mutisieae (Asteraceae) centered in the Guayana Shield. Two morphology-based phylogenetic analyses, one using Gochnatia and the other using Chaetanthera as outgroups, and including Salcedoa and the 12 Guayanan genera were performed to determine the sister group relationships of Salcedoa. The results suggest that Salcedoa is sister to Gongylolepis. The unusual distributional pattern of Salcedoa and the Guayanan genera was explored through the dispersal-vicariance method. A trans-oceanic dispersal of fruits is postulated as a probable mechanism by which Salcedoa reached Hispaniola from a South American ancestor.

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

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.

New Technomyrmex in Dominican amber (Hymenoptera: Formicidae), with a reappraisal of Dolichoderinae phylogeny

AbstractA new species of Technomyrmex (T. caritatis sp. n.) is described based on workers and larvae from Dominican amber (Oligocene to Lower Miocene). These are preserved with eggs and pupae of the same species and with five other insects in one amber piece found in the Palo Quemado Mine, near Santiago and in two separate amber pieces collected in Carlos Diaz Mine. Both mines are in Cordillera Septentrional. Iridomyrmex hispaniolae Wilson is redescribed and transferred to Technomyrmex. Most Technomyrmex species occur from Africa, east through southern Asia, to Australia. One species transported by human activity is known in the New World and there is only one extant native Neotropical species recorded from Panama. Technomyrmex likely represents a case of an Old World ant genus undergoing extinction in the New World. We discuss the affinities of this genus with the extant Dolichoderinae and the phylogeny of the subfamily.

Taxonomic Studies in the Miconieae (Melastomataceae). II. Systematics of the Miconia subcompressa Complex of Hispaniola, Including the Description of Two New Species

TheMiconia subcompressa complex containsMiconia subcompressa, M. selleana, M. hypiodes, and two taxa described here:M. septentrionalis (collected mainly at Pico Diego de Ocampo, Cordillera Septentrional) andM. jimenezii (collected at high elevations in the Sierra de Neiba-Montagnes Noires). Members of the group are characterized by a shrubby or arborescent habit; leaves densely covered with ferrugineous, stellate hairs on the abaxial surface; large, actinomorphic flowers with white petals and stamens; and large, globose fruits turning from red to blue as they mature. The taxa comprising the group are compared and their phylogenetic relationships are analyzed. An identification key, along with species descriptions, specimen citations, and eco-geographical characterizations for each taxon, is presented.

The northern Caribbean Plate boundary in Hispaniola; tectonics and stratigraphy of the Dominican Cordillera septentrional, (Greater Antilles)

The northern Caribbean Plate boundary in Hispaniola; tectonics and stratigraphy of the Dominican Cordillera septentrional, (Greater Antilles)

Notes on the Moss Flora of Hispaniola

Twenty-three mosses are reported for the first time from Hispaniola. an island poorly studied bryologically in spite of its diverse flora. Ptilium ortho- thecium Ther. is placed in synonymy under Hypnum polypterum (Mitt.) Broth. The island of Hispaniola in the Greater Antilles includes peaks of the highest elevations in the Caribbean (Pico Duarte, formerly Pico Trujillo, 3175 m alt.), and its mountainous areas are covered with cloud forests, high to low elevation Pinus occidentalis forests, and sclerophyllous thickets. Thus, the island's flora is quite diverse (see Ciferri 1936; Moscoso 1943; Howard 1973). In spite of this diversity, Hispaniola has been relatively poorly col- lected. No bryophyte flora is available, although several papers dealing with Haitian or Dominican mosses have been published (i.e., Miiller 1898; Williams 1930; Theriot 1944; Crum & Steere 1958; Crum 1965). In 1976 the author made a small collection of bryophytes in the Dominican Republic and portions of this collection are listed alphabetically below. Twenty-three mosses are recorded for the first time in Hispaniola. Taxa not reported in any of the above cited lists of species (or not reported in recent revisionary work) are indicated by an asterisk. The author's collection numbers are given in italics, and the specimens are on deposit at either the Farlow Herbarium (FH) or the Herbarium of the University of Florida (FLAS). The various collection localities are indicated by Roman numeral notations given be- low. Locality I: Pico Diego de Ocampo (prov. Santiago). This, the highest peak (1249 m) in the Cordillera Septentrional, is the only one to support a lush cloud forest at its summit. Except where indicated otherwise, the collections from this locality were made from 1170 to 1249 m alt. Locality II: Loma de la Sal (prov. La Vega). This mountainous area is southeast of Jarabacoa. A rich cloud forest (dominated by Magnolia domingensis, Myrsine coriacea, Alsophila spp., various Melastomataceae) is present toward the summits of the highest peaks. Collections from this region were made between 1280 and 1340 m alt. Locality III: Cordillera Central (prov. La Vega). Collections in this region were made along the road that passes through Valle Nuevo from Constanza to La Nuez. The elevations vary from 1130 m (near Constanza) to ca. 2300 m at Valle Nuevo. These collections were made in low to high elevation forests of Pinus occidentalis. Common understory plants included: Baccharis myrsinites, Lobelia rotundifolia, Myrica cerifera, Garrya fadyenii, Cestrum coelophlebium, Citharexylum fruticosum, Gaultheria domingensis, Myrsine co- riacea, Pteridium aquilinum, Rhytidophyllum berteroanum, Miconia spp., Tetrazygia spp., Lyonia spp., Andropogon spp., and Danthonia domingensis. Locality IV: Monteada Nueva (prov. Barahona). This peak, which is east of Polo in the Sierra de Baoruco, has an interesting cloud forest at its summit (ca. 1300 m alt.). The cloud forest is dominated by Magnolia emarginata, M. hamori, Clusia grisebachiana, Ocotea leucoxylon, and many Melastomataceae and Rubiaceae. It is rapidly being destroyed by slash-and-burn agricul- tural methods. Locality V: El Rio (prov. La Vega). Collections were made in the vicinity