Caribbean Plate Research Articles

Morphology, structure, and tectonic evolution of the Mona canyon (northern Mona passage) from multibeam bathymetry, side-scan sonar, and seismic reflection profiles

[1] The submarine Mona Canyon is a rift between Puerto Rico and Hispaniola of the Greater Antilles. An integrated marine geophysical data set, including multibeam bathymetry, side-scan sonar imagery, single channel and multichannel seismic reflection profiles is used to evaluate the morphology, structure, and tectonic evolution of the Mona Canyon. A structural restoration of the central Mona canyon indicates that extension in the rift initiated in the Middle Oligocene, approximately 30 Ma. A minimum total extension of 6.1 km and a minimum longitudinal strain of 11.4% across the central Mona canyon are calculated. The overall extension is proposed to have occurred over two phases. Phase I occurred from the Middle Oligocene to Late Miocene, and was a slow (0.09 mm/yr) stage of at least 1.7 km of opening. Phase II was most likely controlled by the impact of the subducted southeast portion of the Bahamas platform beneath the northeastern Caribbean plate margin. Phase II was a more rapid (0.4 mm/yr) stage of extension of at least 4.4 km that occurred from the Late Pliocene to the Recent as the SE Bahamas collision warped the middle and upper slope of the northern Puerto Rico margin along its advancing path and slowed the eastward movement of Hispaniola relative to Puerto Rico. The upper reaches of the Mona canyon form the trailing edge of the Puerto Rico–Virgin Islands block as it pulls away from a pinned Hispaniola. The Mona reentrant marks the trailing edge of a northern Hispaniola forearc sliver that forms due to increased coupling between the subducting North America plate and the overriding plate.

Constraints on upper plate deformation in the Nicaraguan subduction zone from earthquake relocation and directivity analysis

In the Nicaraguan segment of the Central American subduction zone, bookshelf faulting has been proposed as the dominant style of Caribbean plate deformation in response to oblique subduction of the Cocos plate. A key element of this model is left‐lateral motion on arc‐normal strike‐slip faults. On 3 August 2005, a Mw 6.3 earthquake and its extensive foreshock and aftershock sequence occurred near Ometepe Island in Lake Nicaragua. To determine the fault plane that ruptured in the main shock, we relocated main shock, foreshock, and aftershock hypocenters and analyzed main shock source directivity using waveforms from the TUCAN Broadband Seismic Experiment. The relocation analysis was carried out by applying the hypoDD double‐difference method to P and S onset times and differential traveltimes for event pairs determined by waveform cross correlation. The relocated hypocenters define a roughly vertical plane of seismicity with an N60°E strike. This plane aligns with one of the two nodal planes of the main shock source mechanism. The directivity analysis was based on waveforms from 16 TUCAN stations and indicates that rupture on the N60°E striking main shock nodal plane provides the best fit to the data. The relocation and directivity analyses identify the N60°E vertical nodal plane as the main shock fault plane, consistent with the style of faulting required by the bookshelf model. Relocated hypocenters also define a second fault plane that lies to the south of the main shock fault plane with a strike of N350°E–N355°E. This fault plane became seismically active 5 h after the main shock, suggesting the influence of stresses transferred from the main shock fault plane. The August 2005 earthquake sequence was preceded by a small eruption of a nearby volcano, Concepción, on 28 July 2005. However, the local seismicity does not provide evidence for earthquake triggering of the eruption or eruption triggering of the main shock through crustal stress transfer.

Tectonics, basin subsidence mechanisms, and paleogeography of the Caribbean-South American plate boundary zone

Using a mega-regional dataset that includes over 20,000 km of on- and offshore 2D seismic lines and 12 wells, we illustrate three different stages of fault formation and basin evolution in the Caribbean arc-South American continent collisional zone. Transpressional deformation associated with oblique collision of the Caribbean arc migrates diachronously over a distance of ∼1500 km from western Venezuela in Paleogene time (∼57 Ma) to a zone of active deformation in the eastern offshore Trinidad area. Each diachronous stage of pre-, syn-, and post-collisional basin formation is accompanied by distinct patterns of fault families. We use subsidence histories from wells to link patterns of long-term basinal subsidence to periods of activity of the fault families. Stage one of arc-continent collision Initial collision is characterized by overthrusting of the south- and southeastward-facing Caribbean arc and forearc terranes onto the northward-subducting Mesozoic passive margin of northern South America. Northward flexure of the South American craton produces a foreland basin between the thrust front and the downward-flexed continental crust that is initially filled by clastic sediments shed both from the colliding arc and cratonic areas to the south. As the collision extends eastward towards Trinidad, this same process continues with progressively younger foreland basins formed to the east. On the overthrusting Caribbean arc and forearc terranes, north-south rifting adjacent to the collision zone initiates and is controlled by forward momentum of southward-thrusting arc terranes combined with slab pull of the underlying and subducting, north-dipping South American slab. Uplift of fold-thrust belts arc-continent suture induces rerouting of large continental drainages parallel to the collisional zone and to the axis of the foreland basins. Stage two This late stage of arc-continent collision is characterized by termination of deformation in one segment of the fold-thrust belt as convergent deformation shifts eastward. Rebound of the collisional belt is produced as the north-dipping subducted oceanic crust breaks off from the passive margin, inducing inversion of preexisting normal faults as arc-continent convergence reaches a maximum. Strain partitioning also begins to play an important role as oblique convergence continues, accommodating deformation by the formation of parallel, strike-slip fault zones and backthrusting (southward subduction of the Caribbean plate beneath the South Caribbean deformed belt). As subsidence slows in the foreland basins, sedimentation transitions from a marine underfilled basin to an overfilled continental basin. Offshore, sedimentation is mostly marine, sourced by the collided Caribbean terranes, localized islands and carbonate deposition. Stage three This final stage of arc-continent collision is characterized by: 1) complete slab breakoff of the northward-dipping South American slab; 2) east-west extension of the Caribbean arc as it elongates parallel to its strike forming oblique normal faults that produce deep rift and half-grabens; 3) continued strain partitioning (strike-slip faulting and folding). The subsidence pattern in the Caribbean basins is more complex than interpreted before, showing a succession of extensional and inversion events. The three tectonic stages closely control the structural styles and traps, source rock distribution, and stratigraphic traps for the abundant hydrocarbon resources of the on- and offshore areas of Venezuela and Trinidad.

Regional provenance study of Eocene clastic sedimentary rocks within the South America–Caribbean plate boundary zone using detrital zircon geochronology

Previous on- and offshore studies have postulated that the Caribbean plate has translated hundreds of kilometers eastward during the Cenozoic along strike-slip and oblique thrust faults bounding the northern margin of the continental South America plate. Two previously proposed tectonic-sedimentary models to explain the complex linkages between plate motions and sedimentation within the broad plate boundary zone include: 1) eastward bulldozing by the Caribbean plate of a single, large point source, thick Eocene proto-Maracaibo deltaic system of northwestern South America, over 1000 km to the east and incorporation of these continentally derived sediments into the ∼ 12-km-thick Barbados accretionary prism along the leading edge of the Caribbean plate; and 2) eastward bulldozing by less than 300 km of smaller point and line sources of Eocene and younger clastic sediments derived from erosion of the Guyana shield located in north-central and northeastern South America. We test both models by sampling eight Eocene localities that span a 1200-km-length of the plate boundary zone from the proto-Maracaibo delta in western Venezuela to Barbados Island in the subaerial part of the large accretionary prism bounding the eastern margin of the Caribbean plate. Ages of 972 single grains from samples at these eight localities support the multiple-source model, in which the Barbados prism was partly constructed from the bulldozing and incorporation of smaller point and line sources derived from older-than 1500 Ma crustal provinces of the Precambrian Guyana shield in central and northeastern South America. Eocene clastic sediments of the proto-Maracaibo delta derived from Paleozoic and Precambrian crustal provinces in northwestern South America are distinct in their ranges of detrital zircon ages from the ranges of the Guyana shield sources to the east.

A New Look at Evidence for a Wadati-Benioff Zone and Active Convergence at the North Panama Deformed Belt

The nature of the northern boundary of the Panama microplate, often referred to as the north Panama deformed belt (NPDB), has been the subject of much speculation. Previous studies have used a variety of data, including teleseismic, gravity, bathymetric, marine magnetic, and field studies of uplift and tsunami deposits, as well as modified Mercalli intensity distributions from historic earthquakes to reveal the nature of the NPDB. Data have been collected for over 30 yrs and yet the character of the NPDB remains unclear. Current analyses and interpretation provide a number of mutually exclusive options and much controversy. In this article we examine local and regional seismicity combined with teleseismic observations and historic earthquake data to present an alternative analysis for the NPDB. Using small earthquakes recorded by a local network we image a well-defined Wadati–Benioff zone dipping southward beneath the Panama microplate. These data provide new evidence regarding the nature of Panama microplate–Caribbean plate boundary kinematics and demonstrate the existence of an active subduction zone. A more complete understanding of the nature of the seismicity and plate interactions along the NPDB offshore Panama, including a subduction zone capable of producing earthquakes of M >7, should be included in future earthquake hazard assessments.

U/Pb detrital zircon provenance from late cretaceous metamorphic units of the Guajira Peninsula, Colombia: Tectonic implications on the collision between the Caribbean arc and the South American margin

Abstract Mesozoic metamorphic units exposed along the northern margin of the South American plate record the different stages of subduction evolution or arc-continent collision between the margins of the Caribbean plate and the South American continent. U–Pb detrital zircon geochronology for provenance analysis was carried out on meta-sedimentary rocks of the Etpana formation and metamorphic boulders found within a nearby Tertiary conglomerate, including high-pressure rocks in the Colombian Caribbean. All samples have similar age populations, suggesting that they share a relatively common source and paleogeography. Prominent age peaks include Meso and Paleoproterozoic ages of ca. 1624 Ma and 1315 Ma, Cambrian to Neoproterozoic ages of ca. 630 Ma, 580 Ma and 547 Ma, and less abundant Jurassic and Permian ages of ca. 270 Ma and 160 Ma, which indicate that the South American margin is a major source for the sedimentary protoliths. There are also remnants of younger Cretaceous allocthonous Caribbean arc input at ca. 90–70 Ma. The deposition and metamorphism of these units records the ongoing Late Cretaceous continental subduction of the South American margin within the Caribbean intra-oceanic arc-subduction zone. This gave way to an arc-continent collision between the Caribbean and the South American plates, and sediments with continental signatures were incorporated into the subduction channel and the accretionary wedge. As convergence continued, sediments derived from a mix of South American and arc sources were deposited and included in the collisional wedge up until

Seismicity and Crustal Structure of the Polochic-Motagua Fault System Area (Guatemala)

Research Article| November 01, 2009 Seismicity and Crustal Structure of the Polochic-Motagua Fault System Area (Guatemala) A. Franco; A. Franco Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 1Laboratoire de Géologie, Ecole Normale Supérieure, Centre National de la Recherche Scientifique (CNRS), Paris, France Search for other works by this author on: GSW Google Scholar E. Molina; E. Molina Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 2Instituto Nacional de Sismología, Vulcanología, Meterología e hidrología, Guatemala Ciudad, Guatemala Search for other works by this author on: GSW Google Scholar H. Lyon-Caen; H. Lyon-Caen Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 1Laboratoire de Géologie, Ecole Normale Supérieure, Centre National de la Recherche Scientifique (CNRS), Paris, France Search for other works by this author on: GSW Google Scholar J. Vergne; J. Vergne Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 1Laboratoire de Géologie, Ecole Normale Supérieure, Centre National de la Recherche Scientifique (CNRS), Paris, France 3Institut de Physique du Globe de Strasbourg, CNRS, Strasbourg, France Search for other works by this author on: GSW Google Scholar T. Monfret; T. Monfret Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 4Geosciences Azur, University of Nice, Sophia Antipolis, CNRS, Institut de Recherche pour le Developpement, Nice, France Search for other works by this author on: GSW Google Scholar A. Nercessian; A. Nercessian Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 5Institut de Physique du Globe de Paris, CNRS, France Search for other works by this author on: GSW Google Scholar S. Cortez; S. Cortez Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 6Universidad de Coban, Coban, Guatemala Search for other works by this author on: GSW Google Scholar O. Flores; O. Flores Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 7Centro de Estudios Superiores de Energí a y Minas-Universidad de San Carlos de Guatemala, Guatemala Ciudad, Guatemala Search for other works by this author on: GSW Google Scholar D. Monterosso; D. Monterosso Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 8Coordinadora Nacional para la Reducción de Desastres, Guatemala Ciudad, Guatemala Search for other works by this author on: GSW Google Scholar J. Requenna J. Requenna Laboratoire de Géologie Ecole Normale Supérieure de Paris 24, rue Lhomond 75231 Paris cedex 05 France franco@geologie.ens.fr (A. F.) 6Universidad de Coban, Coban, Guatemala Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2009) 80 (6): 977–984. https://doi.org/10.1785/gssrl.80.6.977 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation A. Franco, E. Molina, H. Lyon-Caen, J. Vergne, T. Monfret, A. Nercessian, S. Cortez, O. Flores, D. Monterosso, J. Requenna; Seismicity and Crustal Structure of the Polochic-Motagua Fault System Area (Guatemala). Seismological Research Letters 2009;; 80 (6): 977–984. doi: https://doi.org/10.1785/gssrl.80.6.977 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search We report results from a six-month seismological experiment in the area of the eastern Polochic-Motagua fault system (Guatemala) designed to both characterize the present seismicity and bring some constraints on the lithospheric structure. The seismic activity occurs in the upper 15 km of the crust, on the Polochic and the Motagua faults as well as in a NS-trending graben south of the Motagua fault and within the active folds north of the Polochic fault. From receiver function analysis the Moho discontinuity is found at about 35 km depth north of the Polochic fault and south of the Motagua fault, while... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Thermal constraints on the frictional conditions of the nucleation and rupture area of the 1992 Nicaragua tsunami earthquake

SUMMARY The 1992 Nicaragua earthquake was a ‘tsunami earthquake’, which generated tsunamis disproportionately large for its surface wave magnitude Ms = 7.2. Seismological studies and tsunami simulation indicated that the event was a slow earthquake, which occurred on the plate boundary between the subducting Cocos plate and the overriding Caribbean plate. We present a finite element model that enables us to estimate for the first time the temperature and inferred frictional conditions in the rupture area of a tsunami earthquake. Direct and indirect observations are used to constrain all model parameters, and surface heat-flux measurements provide independent information to verify the model results. Furthermore, we used a genetic algorithm to perform a sensitivity analysis of all model parameters and to define the spatial range of thermally defined updip limit of the seismogenic zone. The earthquake nucleated in the seismogenic zone at temperatures of ∼150 ◦ C and propagated updip towards the trench axis. The centroid or centre of mass of moment release was located in a region characterized by temperatures of ∼50 ◦ C. Thus, the rupture propagated through a region where plate motion is normally accommodated by aseismic creep. Our observations support a model in which tsunami earthquakes nucleate in the seismogenic zone near its updip limit. However, in such an environment coupled asperities are perhaps too small to cause large earthquakes. Seamounts, however, are abundant on the incoming Cocos plate. Therefore, in addition to temperature-dependent metamorphic induration of sediments, increased normal stress by seamount subduction may contribute to accumulate stress sufficiently large to release enough energy near the updip limit of the seismogenic zone to promote dynamic slip along a )

Jura, Alps and the boundary of the Adria subplate

The thin-skinned Jura fold/thrust belt is the frontal part of a thick-skinned late Miocene Alpine nappe. Important late Miocene structures in the Alps that help define this nappe are the External Massifs in the north, the Orobic thrusts and the Piemontese Southern Alps in the south, the Giudicarie–Brenner Line in the east and, more vaguely, the south end of the Belledonne Massif in the west. A bottom boundary compatible with the data is the Brittle–Ductile Transition (BDT). This Jura nappe is separated from the (latest Oligocene)–early Miocene Helvetic nappe system most obviously by the late Miocene Orobic–Giudicarie–Brenner fault complex. In contrast, the distinctive boundary of the early Miocene thick-skinned Helvetic nappe was the Iorio–Tonale Line (IT) in the south, merging into the Piemontese Southern Alps at what may be termed the “Locarno Singularity”–the point of minimum width of the thick-skinned Alps; the northern boundary passed through the Gotthard–and Montblanc Massifs. Motion along the southern boundary was dextrally transpressive, associated with complex strain partitioning patterns. One part of these patterns is the confusing entity comprising the Piemontese Southern Alps and the Lepontine “dome”. The slivers composing the Piemontese Southern Alps are dragged dextrally by the Iorio–Tonale strike–slip at the “Locarno Singularity” and thereby exhibit an important characteristic trait of “exotic terranes” — crustal slivers dragged along strike–slip faults. The Lepontine “dome” around the Locarno Singularity on the north side of the Iorio–Tonale Line displays the characteristics of a backstop in thrust systems as modeled in sandbox experiments. The special boundary functioning as a backstop, compatible with the transpressive kinematics, was the Ivrea body, a strong mafic–ultramafic–granulitic complex which in the early Miocene migrated dextrally along the Iorio–Tonale Line, forcing detachment to descend into the hot middle crust and producing an upsurge of the hot masses. In the late Miocene Jura phase this particular impediment had moved to the west, enabling décollement at the Brittle–Ductile Transition to propagate across the Insubric Line into the Lombardic domain. Large-scale strain partitioning manifestations resemble those of the equally dextrally transpressive southern boundary of the Caribbean plate, in spite of a difference in scales. The foremost of these manifestations are regional right-slip faults slicing through a broad band of contraction, accompanied by collapse basins.

Corundum-bearing garnet peridotite from northern Dominican Republic: A metamorphic product of an arc cumulate in the Caribbean subduction zone

Garnet peridotite in oceanic subduction complexes has been reported only in two locations in the world. One of these examples occurs in the late Cretaceous to early Tertiary subduction complex in northern Dominican Republic. The garnet peridotite (wehrlite and olivine-bearing clinopyroxenite) occurs as large (≤ 4 m) boulders together with boulders of eclogites and serpentinites along a narrow (< 10 m) stream of the Rio Cuavas in the southern part of the Rio San Juan Complex. The peridotite is composed of garnet, diopsidic clinopyroxene (partially altered to magnesiohornblende), olivine (extensively altered to serpentine), Al-spinel and minor corundum; the latter two are mostly enclosed in garnet. Coarse-grained garnet also encloses small grains of early-formed garnet that contain Ca- and Al-rich cores and Mg-rich rims. The garnet peridotite contains low Cr, Ni, and Ir-group platinum group elements in bulk rock compared to primitive mantle values, low Mg (Mg#; 0.74–0.83) and NiO (< 0.1 wt.%) in olivine, and elevated concentrations of fluid-mobile elements (Sr, Pb and U) in clinopyroxene and bulk rock. Combined with the rare earth element data of bulk rocks and clinopyroxene, these data suggest that the peridotite originally solidified as a plagioclase-bearing cumulate of an arc melt at a shallow depth, < 35 km, in the mantle wedge. The cumulate was later dragged by mantle flow from the subarc mantle towards the subduction plane. Subsequent downward movement along the subduction plane resulted in the crystallization of corundum and Ca- and Al-rich garnet at the expense of plagioclase, at a depth of ~ 50 km. The garnet peridotite continued to be subducted to a depth of ~ 120 km, causing a progressive increase in pressure and temperature that resulted in the crystallization of Mg-rich garnet. The garnet periodotite was then exhumed in the serpentinite subduction channel. These events likely took place during the very early stages of the subduction system, where a strong mantle corner flow was likely produced by poor lubrication along the interface between the subducting plate and the overlying Caribbean Plate.

Localization and characterization of an active fault in an urbanized area in central Guatemala by means of geoelectrical imaging

The Polochic and Motagua faults define the active plate boundary between the North American and Caribbean plates in central Guatemala. A splay of the Polochic Fault traverses the rapidly growing city of San Miguel Uspantán that is periodically affected by destructive earthquakes. This fault splay was located using a 2D electrical resistivity tomography (ERT) survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built. ERT images show the fault as a ~50 m wide, near-vertical low-resistivity anomaly, bounded within a few meters by high resistivity anomalies. Forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location, geometry, and internal structure of the fault zone as well as the affected lithologies. Our results indicate that the city is constructed on a ~20 m thick surficial layer consisting of poorly consolidated, highly porous, water-logged pumice. This soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking. The electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might, at least in part, be fed by water rising along the fault. Therefore, the potential threat posed by this fault splay may not be limited to its seismic activity per se, but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments. The results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of San Miguel Uspantán and illustrate the potential of ERT surveying for paleoseismic studies.

Regional structure and tectonic history of the obliquely colliding Columbus foreland basin, offshore Trinidad and Venezuela

Cenozoic eastward migration of the Caribbean plate relative to the South American plate is recorded by an 1100-km-long Venezuela-Trinidad foreland basin which is oldest in western Venezuela (65–55 Ma), of intermediate age in eastern Venezuela (34–20 Ma) and youngest beneath the shelf and slope area of eastern offshore Trinidad (submarine Columbus basin, 15.0 Ma-Recent). In this study of the regional structure, fault families, and chronology of faulting and tectonic events affecting the hydrocarbon-rich Columbus foreland basin of eastern offshore Trinidad, we have integrated approximately 775 km of deep-penetration 2D seismic lines acquired by the 2004 Broadband Ocean-Land Investigations of Venezuela and the Antilles arc Region (BOLIVAR) survey, 325 km of vintage GULFREX seismic data collected by Gulf Oil Company in 1974, and published industry well data that can be tied to some of the seismic reflection lines. Top Cretaceous depth structure maps in the Columbus basin made from integration of all available seismic and well data define for the first time the elongate subsurface geometry of the 11–15 km thick and highly asymmetrical middle Miocene-Recent depocenter of the Columbus basin. The main depocenter located 150–200 km east of Trinidad and now the object of deepwater hydrocarbon exploration is completely filled by shelf and deepwater sediments derived mainly from the Orinoco delta. The submarine Darien ridge exhibits moderate (20–140 m) seafloor relief, forms the steep (12°–24°), northern structural boundary of the Columbus basin, and is known from industry wells to be composed of 0.5–4.5 km thick, folded and thrust-imbricated, hydrocarbon-bearing section of Cretaceous and early Tertiary limestones and clastic rocks. The eastern and southern boundaries of the basin are formed by the gently (1.7°–4.5°), northward-dipping Cretaceous–Paleogene passive margin of South America that is in turn underlain by Precambrian rocks of the Guyana shield. Interpretation of seismic sections tied to wells reveals the following fault chronology: (1) middle Miocene thrusting along the Darien ridge related to highly oblique convergence between the Caribbean plate and the passive margin of northern South America; continuing thrusting and transpression in an oblique foreland basin setting through the early Pleistocene; (2) early Pliocene-recent low-angle normal faults along the top of the Cretaceous passive margin; these faults were triggered by oversteepening related to formation of the downdip, structurally and bathymetrically deeper, and more seaward Columbus basin; large transfer faults with dominantly strike-slip displacements connect gravity-driven normal faults that cluster near the modern shelf-slope break and trend in the downslope direction; to the south no normal faults are present because the top Cretaceous horizon has not been oversteepened as it is adjacent to the foreland basin; (3) early Pliocene–Recent strike-slip faults parallel the trend of the Darien ridge and accommodate present-day plate motions.

Geochemical characteristics of the Río Verde Complex, Central Hispaniola: Implications for the paleotectonic reconstruction of the Lower Cretaceous Caribbean island-arc

New geochronological, trace element and Sr–Nd isotope data for metabasalts, dolerites and amphibolites from the Río Verde Complex, Central Hispaniola, are integrated with existing geochemical data for mafic volcanic rocks and metamorphic derivatives from the Los Ranchos, Amina and Maimón Formations, giving new insights into magma petrogenesis and paleotectonic reconstruction of the Lower Cretaceous Caribbean island-arc–back arc system. U–Pb and 40Ar/ 39Ar age data show that the Río Verde Complex protoliths were in part coeval with volcanic rocks of the Los Ranchos Formation (Upper Aptian to Lower Albian). The geochemical data establish the existence of gradients in trace element parameters (Nb/Yb, Th/Yb, Zr/Yb, Zr/Ba, and normalized Ti, Sm, Y and Yb abundances) and Nd isotope compositions from throughout Hispaniola, which reflect differences in the degree of mantle wedge depletion and contributions from the subducting slab. The Río Verde Complex mafic rocks and some mafic sills and dykes intruding in the Loma Caribe Peridotite, have a transitional IAT to N-MORB geochemistry and a weak subduction-related signature, and are interpreted to form in a rifted arc or evolving back-arc basin setting. The Los Ranchos, Amina and Maimón Formations volcanic rocks have arc-like characteristics and represent magmatism in the volcanic front. Trace element and Nd isotope modeling reproduce observed data trends from arc to back-arc and suggest that the variations in several geochemical parameters observed in a SW direction across the Caribbean subduction system can be explained from the progressively lower subduction flux into a progressively less depleted mantle source. The low Nb contents and high ( ε Nd) i values in both arc and back-arc mafic rocks imply, however, the absence of a significant Lower Cretaceous plume enriched component. In order to explain these observations, a model of proto-Caribbean oceanic lithosphere subducting to the SW at least in the 120–110 Ma interval, is proposed to cause the observed magmatic variations in the Lower Cretaceous Caribbean island-arc–back-arc system. In this context, arc rifting and initial sea-floor spreading to form the Río Verde Complex protoliths occurred in the back-arc setting of this primitive island-arc, built on the NE edge of the Caribbean plate.

Bivergent thrust wedges surrounding oceanic island arcs: Insight from observations and sandbox models of the northeastern Caribbean plate

At several localities around the world, thrust belts have developed on both sides of oceanic island arcs (e.g., Java-Timor, Panama, Vanuatu, and the northeastern Caribbean). In these localities, the overall vergence of the backarc thrust belt is opposite to that of the forearc thrust belt. For example, in the northeastern Caribbean, a north-verging accretionary prism lies to the north of the Eastern Greater Antilles arc (Hispaniola and Puerto Rico), whereas a south-verging thrust belt called the Muertos thrust belt lies to the south. Researchers have attributed such bivergent geometry to several processes, including: reversal of subduction polarity; subduction-driven mantle fl ow; stress transmission across the arc; gravitational spreading of the arc; and magmatic infl ation within the arc. New observations of deformational features in the Muertos thrust belt and of fault geometries produced in sandbox kinematic models, along with examination of published studies of island arcs, lead to the conclusion that the bivergence of thrusting in island arcs can develop without reversal of subduction polarity, without subarc mantle fl ow, and without magmatic infl ation. We suggest that the Eastern Greater Antilles arc and comparable arcs are simply crustalscale bivergent (or “doubly vergent”) thrust wedges formed during unidirectional subduction. Sandbox kinematic modeling suggests, in addition, that a broad retrowedge containing an imbricate fan of thrusts develops only where the arc behaves relatively rigidly. In such cases, the arc acts as a backstop that transmits compressive stress into the backarc region. Further, modeling shows that when arcs behave as rigid blocks, the strike-slip component of oblique convergence is accommodated entirely within the prowedge and the arc—the retrowedge hosts only dip-slip faulting (“frontal thrusting”). The existence of large retrowedges and the distribution of faulting in an island arc may, therefore, be evidence that the arc is relatively rigid. The rigidity of an island arc may arise from its mafi c composition and has implications for seismic-hazard analysis.

Neogene–Quaternary tectonic evolution of the Leeward Antilles islands (Aruba, Bonaire, Curaçao) from fault kinematic analysis

Aruba, Bonaire, and Curaçao are islands aligned along the crest of a 200-km-long segment of the east–west-trending Leeward Antilles ridge within the broad Caribbean–South America plate boundary zone presently characterized by east–west, right-lateral strike-slip motion. The crust of the Leeward Antilles ridge represents the western segment of the Cretaceous–early Cenozoic Great Arc of the Caribbean, which obliquely collided, with the continental margin of northern South America in early Cenozoic time. Following the collision, the ridge was affected by folding and was segmented by oblique, northwest-striking normal faults that have produced steep-sided, northwest-trending, elongate islands and narrow shelves separated by deepwater, sediment-filled and fault-controlled basins. In this paper, we present the first fault slip observations on the Neogene carbonate rocks that cover large areas of all three islands. Our main objective is to quantify the timing and nature of Neogene to Quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential. These data constrain three fault phases that have affected Aruba, Bonaire, and Curaçao and likely the adjacent offshore areas: 1) NW–SE-directed late Paleogene compression; 2) middle Miocene syndepositional NNW–SSE to NNE–SSW extension that produced deep rift basins transverse to the east–west-trending Leeward Antilles ridge; and 3) Pliocene–Quaternary NNE-trending compression that produced NW–SE-trending anticlines present on Aruba, Curaçao and Bonaire islands. Our new observations – that include detailed relationships between striated fault planes, paleostress tensors, and bedding planes – show that prominent bedding dips of Neogene limestone on Aruba, Bonaire and Curaçao were produced by regional tectonic shortening across the entire Leeward Antilles ridge rather than by localized, syndepositional effects as proposed by previous workers. We interpret Pliocene–Quaternary NNE-directed shortening effects on the Leeward Antilles ridge as the result of northeastward extrusion or “tectonic escape” of continental areas of western Venezuela combined with southeastward shallow subduction of the Caribbean plate beneath the ridge.

Crustal structure of the central Costa Rica subduction zone: implications for basal erosion from seismic wide-angle data

On the Pacific margin off central Costa Rica, an anomalous lens-shaped zone is located between the overriding plate and the subducting oceanic lithosphere approximately 25 km landward of the deformation front. This feature was previously recognized in reflection seismic data when it was termed 'megalens'. Its origin and seismic velocity structure, however, could not unambiguously be derived from earlier studies. Therefore during RV SONNE cruise SO163, seismic wide-angle data were acquired in 2002 using closely spaced ocean bottom hydrophones and seismometers along two parallel strike and two parallel dip lines above the 'megalens', intersecting on the middle slope. The P-wave velocities and structure of the subducting oceanic Cocos Plate and overriding Caribbean Plate were determined by modelling the wide-angle seismic data in combination with the analysis of coincident reflection seismic data and the use of synthetic seismograms. The margin wedge is defined by high seismic velocities (4.3-6.1 km s(-1)) identified within a wedge-shaped body covered by a slope sediment drape. It is divided into two layers with different velocity gradients. The lower margin wedge is clearly constrained by decreasing velocities trenchward and terminates beneath the middle slope at the location of the 'megalens'. Seismic velocities of the 'megalens' are lower (3.8-4.3 km s(-1)) relative to the margin wedge. We propose that the 'megalens' represents hybrid material composed of subducted sediment and eroded fragments from the base of the upper plate. Upward-migrating overpressured fluids weaken the base of the margin wedge through hydrofracturing, thus causing material transfer from the upper plate to the lower plate. Results from amplitude modelling support that the 'megalens' observed off central Costa Rica is bound by a low-velocity zone documenting fluid drainage from the plate boundary to the upper plate.

Metamorphic reworking of a high pressure–low temperature mélange along the Motagua fault, Guatemala: A record of Neocomian and Maastrichtian transpressional tectonics

The Guatemala suture zone is a major east–west left-lateral strike slip boundary that separates the North American and Caribbean plates in Guatemala. The Motagua fault, the central active strand of the suture zone, underwent two major collisional events within a system otherwise dominated by strike–slip motion. The first event is recorded by high-pressure/low temperature (HP/LT) eclogites and related rocks that occur within serpentinites both north and south of the Motagua fault. Lawsonite eclogites south of the fault are not significantly retrograded and give 40Ar/ 39Ar ages of 125–116 Ma and Sm–Nd mineral isochrons of 144–132 Ma. Eclogites north of the fault give similar Sm–Nd isochron ages (131–126 Ma) but otherwise differ in that they are strongly overprinted by a lower pressure assemblage and, along with associated HP/LT rocks, give much younger 40Ar/ 39Ar ages of 88–55 Ma indicating a later amphibolite facies metamorphic event. We propose therefore that all serpentinite hosted eclogites along the Motagua fault formed at essentially the same time in different parts of a laterally extensive Lower Cretaceous forearc subduction system, but subsequently underwent different histories. The southern assemblages were thrust southwards (present coordinates) immediately after HP metamorphism whereas the northern association was retrograded during a later collision that thrust it northward at ca. 70 Ma. They were subsequently juxtaposed opposite each other by major strike slip motion. This model implies that the HP rocks on opposing sides of the Motagua fault evolved along a plate boundary that underwent both dip slip and strike slip motion throughout the Late Cretaceous as a result of oblique convergence. The juxtaposition of a convergent and strike slip system means that HP/LT rocks within serpentinites can be found at depth along much of the modern Guatemala suture zone and its eastward extension into the northern Caribbean. Both sets of assemblages were exhumed relatively recently by the uplift of mountain ranges on both sides of the fault caused by movement along a restraining bend. Recent exhumation explains the apparently lack of offset of surface outcrops along a major strike slip fault.

Fore‐arc motion and Cocos Ridge collision in Central America

We present the first regional surface velocity field for Central America, showing crustal response to interaction of the Cocos and Caribbean plates. Elastic half‐space models for interseismic strain accumulation on the dipping subduction plate boundary fit the GPS data well and show strain accumulation offshore and beneath the Nicoya and Osa peninsulas in Costa Rica but not in Nicaragua. Since large subduction zone earthquakes occur in Nicaragua, we suggest that interseismic locking in Nicaragua and some other parts of Central America occurs but is mainly shallow, &lt;20 km depth, too far offshore to be detected by our on‐land GPS measurements. Our data also show significant trench‐parallel motion for most of the region, generally interpreted as due to oblique convergence and strong mechanical coupling between subducting and overriding plates. However, trench‐parallel motion is also observed in central Costa Rica, where plate convergence is normal to the trench, and in the Nicaraguan fore arc, where trench‐parallel motion is fast, up to 9 mm a−1, but mechanical coupling is low. A finite element model of collision (as opposed to subduction) involving the aseismic Cocos Ridge also fits the GPS surface velocity field, most significantly reproducing the pattern of trench‐parallel motion. We infer that buoyant, thickened CNS‐2‐Cocos Ridge crust resists normal subduction and instead acts as an indenter to the Caribbean plate, driving crustal shortening in southern Costa Rica and contributing to trench‐parallel fore‐arc motion in Costa Rica and perhaps Nicaragua as a type of tectonic escape.

Crustal structure of the South American–Caribbean plate boundary at 67°W from controlled source seismic data

We present the results of new seismic reflection and wide‐angle data across the SE Caribbean plate boundary. The 550 km long N–S profile crosses the structures involved in the active 55 Ma long continent‐arc oblique collision between the Caribbean (CAR) and the South American (SA) plate. From the north to the south these structures include the accretionary prism, the extinct volcanic arc (Leeward Antilles arc), the Tertiary Bonaire basin, the continental‐size dextral strike‐slip fault system (San Sebastián–El Pilar fault), the allochthonous exhumed terranes, and the authocthonous fold and thrust belt (Caribbean Mountain system) and foreland basin. The wide‐angle data show that these elements are characterized by different velocity structures and that they are separated by sharp lateral velocity variations. The Leeward Antilles arc exhibits a velocity structure similar to that of the Lesser Antilles active volcanic arc, indicating that the extinct arc has not been modified by the collision with the SA plate. The data show a ∼20 km change in crustal thickness across the San Sebastián fault, suggesting that the dextral strike‐slip fault is a crustal feature that likely continues in the mantle as a primary strand of the plate boundary between the South American and the Caribbean plates. South of the strike‐slip fault and beneath the exhumed eclogitic terranes, the data image a north dipping, high‐velocity (&gt;6.5 km/s) anomaly in the upper crust (3–11 km), indicating that high‐pressure/low‐temperature rocks are the likely lithologies responsible for the high seismic velocities and suggesting that exhumation of these assemblages is enabled by the strike‐slip fault.

Palaeomagnetism of the central Cuban Cretaceous Arc sequences and geodynamic implications

A detailed palaeomagnetic study of Cretaceous age volcanic and sedimentary arc rocks from central Cuba has been carried out. Samples from 32 sites (12 localities) were subjected to detailed demagnetisation experiments. Nineteen sites from the Los Paso, Mataguá, Provincial and Cabaiguán Formations yielded high unblocking temperature, dual polarity directions of magnetisation which pass the fold tests with confidence levels of 95% or more and are considered to be primary in origin. The palaeomagnetic inclinations are equivalent to palaeolatitudes of 9°N for the Aptian, 18°N for the Albian. A synfolding remanence identified in 5 sites from the younger Hilario Formation indicates a late Cretaceous remagnetisation at a palaeolatitude of 16°N. Our results are in good agreement with previous palaeogeographic models and provide the first high quality palaeomagnetic data demonstrating the gradual northward movement of the Cretaceous Volcanic Arc throughout the Cretaceous. The declination values obtained all indicate significant and similar amounts of anticlockwise rotation from the oldest sequences studied through to the late Cretaceous remagnetisation. This rotation is most likely related to collision of the arc with the North American plate and transpressional strike slip movement along the northern margin of the Caribbean plate as it progressed eastwards into the large Proto-Caribbean basin.