scholarly journals The role of arc migration in the development of the Lesser Antilles: A new tectonic model for the Cenozoic evolution of the eastern Caribbean

Geology ◽  
2019 ◽  
Vol 47 (9) ◽  
pp. 891-895 ◽  
Author(s):  
R.W. Allen ◽  
J.S. Collier ◽  
A.G. Stewart ◽  
T. Henstock ◽  
S. Goes ◽  
...  
Keyword(s):  
Large Scale ◽  
Lesser Antilles ◽  
Caribbean Region ◽  
Tectonic Model ◽  
Continental Arc ◽  
Show Evidence ◽  
Geochemical Variations ◽  
Eastern Caribbean ◽  
Two Phases ◽  
Subduction System

Abstract Continental arc systems often show evidence of large-scale migration both toward and away from the incoming plate. In oceanic arc systems, however, while slab roll-back and the associated processes of backarc spreading and arc migration toward the incoming plate are commonplace, arc migration away from the incoming plate is rarely observed. We present a new compilation of marine magnetic anomaly and seismic data in order to propose a new tectonic model for the eastern Caribbean region that includes arc migration in both directions. We synthesized new evidence to show two phases of backarc spreading and eastward arc migration toward the incoming Atlantic. A third and final phase of arc migration to the west subdivided the earlier backarc basin on either side of the present-day Lesser Antilles arc. This is the first example of regional multidirectional arc migration in an intra-oceanic setting, and it has implications for along-arc structural and geochemical variations. The back and forth arc migrations were probably due to the constraints imposed by the neighboring American plates on this isolated subduction system, rather than variations in subducting slab buoyancy.

Assessing the geodynamics of strongly arcuate subduction zones in the eastern Caribbean subduction setting

2020 ◽  
Author(s):  
Menno Fraters ◽  
Wim Spakman ◽  
Cedric Thieulot ◽  
Douwe Van Hinsbergen
Keyword(s):  
Stress Field ◽  
Subduction Zones ◽  
Focal Mechanisms ◽  
North American Plate ◽  
Plate Motion ◽  
Caribbean Region ◽  
The North ◽  
Eastern Caribbean ◽  
Subduction Setting ◽  
Subduction System

<p>The eastern Caribbean Lesser-Antilles subduction system is a strongly arcuate subduction system. We have investigated the dynamics of this system through numerical modelling, demonstrating the developed capabilities and computational feasibility for assessing the 3D complexity and geodynamics of natural subductionsystems and applied this to the eastern Caribbean region. We show the geodynamic feasibility of westward directed trench-parallel slab transport through the mantle, i.e. slab dragging, on the northern segment of the slab, while the eastern segment of the slab is subducting by a mantle-stationary trench. The resistance of the mantle against slab dragging by the North American plate motion, as well as the deformation associated with the arcuate geometry of the slab, creates a complex 3D stress field in the slab that deviates strongly from the classical view of slab-dip aligned orientation of slab stress. More generally this means that the process of slab dragging may reveal itself in the focal mechanisms of intermediate and deep earthquakes. The characteristics of the arcuate subduction such as slab dragging and a complex 3D stress field as studied in the Caribbean region can be more generically applied to other arcuate subduction systems as well, such as the Izu-Bonin-Marianas or the Aleutians-Alaskasystems, where anomalous focal mechanisms of slabs are observed.</p>

scholarly journals New radiolarian assemblages from La Désirade Island basement complex (Guadeloupe, Lesser Antilles arc) and Caribbean tectonic implications

2009 ◽  
Vol 180 (5) ◽  
pp. 399-409 ◽  
Author(s):  
Fabrice Cordey ◽  
Jean-Jacques Cornée
Keyword(s):  
Spatial Association ◽  
Lesser Antilles ◽  
Caribbean Region ◽  
Geodynamic Setting ◽  
Basement Complex ◽  
Tectonic Model ◽  
Geological Unit ◽  
Early Late ◽  
Lesser Antilles Arc ◽  
Radiolarian Assemblages

Abstract New radiolarian assemblages of Late Jurassic age were extracted from seven chert localities of the basement complex of La Désirade Island (Guadeloupe), the oldest geological unit of the Lesser Antilles arc and the eastern Caribbean region. These fauna range in age from Kimmeridgian or early Tithonian to early or early late Tithonian, showing that La Désirade cherts are not all coeval, contrary to what was established by previous studies. Furthermore, the close spatial association of cherts and volcanic elements composed of basaltic flows and volcaniclastics suggests a mixed setting of hydrothermal siliceous deposits and biogenous sedimentation consistent with an arc-related oceanic setting rather than an ophiolite-type oceanic crust. As the youngest age is obtained to the northwest of the basement complex whereas older data are found to the southeast, it also suggests that La Désirade basement complex may have undergone some structural stacking consistent with an accretion-type geodynamic setting. Our biochronological data provide a preliminary tectonic model of an eastward subduction zone for Lesser Antilles arc basement emplacement during the Mesozoic.

scholarly journals Large-scale variation in seismic anisotropy in the crust and upper mantle beneath Anatolia, Turkey

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Cédric P. Legendre ◽  
Li Zhao ◽  
Tai-Lin Tseng
Keyword(s):  
Upper Mantle ◽  
Large Scale ◽  
Seismic Anisotropy ◽  
Crust And Upper Mantle ◽  
Wave Splitting ◽  
Mantle Processes ◽  
Open Question ◽  
Subduction System ◽  
Anisotropic Phase ◽  
Regional Tectonics

AbstractThe average anisotropy beneath Anatolia is very strong and is well constrained by shear-wave splitting measurements. However, the vertical layering of anisotropy and the contribution of each layer to the overall pattern is still an open question. Here, we construct anisotropic phase-velocity maps of fundamental-mode Rayleigh waves for the Anatolia region using ambient noise seismology and records from several regional seismic stations. We find that the anisotropy patterns in the crust, lithosphere and asthenosphere beneath Anatolia have limited amplitudes and are generally consistent with regional tectonics and mantle processes dominated by the collision between Eurasia and Arabia and the Aegean/Anatolian subduction system. The anisotropy of these layers in the crust and upper mantle are, however, not consistent with the strong average anisotropy measured in this area. We therefore suggest that the main contribution to overall anisotropy likely originates from a deep and highly anisotropic region round the mantle transition zone.

scholarly journals Self-Adaptive K-Means Based on a Covering Algorithm

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Yiwen Zhang ◽  
Yuanyuan Zhou ◽  
Xing Guo ◽  
Jintao Wu ◽  
Qiang He ◽  
...  
Keyword(s):  
Large Scale ◽  
Clustering Algorithm ◽  
Real Data ◽  
Second Phase ◽  
Data Sets ◽  
Number Of Clusters ◽  
Large Scale Data ◽  
Long Time ◽  
Two Phases ◽  
Selection Of

The K-means algorithm is one of the ten classic algorithms in the area of data mining and has been studied by researchers in numerous fields for a long time. However, the value of the clustering number k in the K-means algorithm is not always easy to be determined, and the selection of the initial centers is vulnerable to outliers. This paper proposes an improved K-means clustering algorithm called the covering K-means algorithm (C-K-means). The C-K-means algorithm can not only acquire efficient and accurate clustering results but also self-adaptively provide a reasonable numbers of clusters based on the data features. It includes two phases: the initialization of the covering algorithm (CA) and the Lloyd iteration of the K-means. The first phase executes the CA. CA self-organizes and recognizes the number of clusters k based on the similarities in the data, and it requires neither the number of clusters to be prespecified nor the initial centers to be manually selected. Therefore, it has a “blind” feature, that is, k is not preselected. The second phase performs the Lloyd iteration based on the results of the first phase. The C-K-means algorithm combines the advantages of CA and K-means. Experiments are carried out on the Spark platform, and the results verify the good scalability of the C-K-means algorithm. This algorithm can effectively solve the problem of large-scale data clustering. Extensive experiments on real data sets show that the accuracy and efficiency of the C-K-means algorithm outperforms the existing algorithms under both sequential and parallel conditions.

scholarly journals K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B stars

2018 ◽  
Vol 616 ◽  
pp. A77 ◽  
Author(s):  
D. M. Bowman ◽  
B. Buysschaert ◽  
C. Neiner ◽  
P. I. Pápics ◽  
M. E. Oksala ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Intrinsic Variability ◽  
B Stars ◽  
Pulsating Stars ◽  
Chemically Peculiar ◽  
Large Scale Magnetic Field ◽  
Peculiar Stars ◽  
Show Evidence ◽  
Chemically Peculiar Stars

Context. The physics of magnetic hot stars and how a large-scale magnetic field affects their interior properties is largely unknown. Few studies have combined high-quality observations and modelling of magnetic pulsating stars, known as magneto-asteroseismology, primarily because of the dearth of detected pulsations in stars with a confirmed and well-characterised large-scale magnetic field. Aims. We aim to characterise observational signatures of rotation and pulsation in chemically peculiar candidate magnetic stars using photometry from the K2 space mission. Thus, we identify the best candidate targets for ground-based, optical spectropolarimetric follow-up observations to confirm the presence of a large-scale magnetic field. Methods. We employed customised reduction and detrending tools to process the K2 photometry into optimised light curves for a variability analysis. We searched for the periodic photometric signatures of rotational modulation caused by surface abundance inhomogeneities in 56 chemically peculiar A and B stars. Furthermore, we searched for intrinsic variability caused by pulsations (coherent or otherwise) in the amplitude spectra of these stars. Results. The rotation periods of 38 chemically peculiar stars are determined, 16 of which are the first determination of the rotation period in the literature. We confirm the discovery of high-overtone roAp pulsation modes in HD 177765 and find an additional 3 Ap and Bp stars that show evidence of high-overtone pressure modes found in roAp stars in the form of possible Nyquist alias frequencies in their amplitude spectra. Furthermore, we find 6 chemically peculiar stars that show evidence of intrinsic variability caused by gravity or pressure pulsation modes. Conclusions. The discovery of pulsations in a non-negligible fraction of chemically peculiar stars make these stars high-priority targets for spectropolarimetric campaigns to confirm the presence of their expected large-scale magnetic field. The ultimate goal is to perform magneto-asteroseismology and probe the interior physics of magnetic pulsating stars.

scholarly journals An Efficient Partition-Based Approach to Identify and Scatter Multiple Relevant Spreaders in Complex Networks

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1216
Author(s):  
Jedidiah Yanez-Sierra ◽  
Arturo Diaz-Perez ◽  
Victor Sosa-Sosa
Keyword(s):  
Complex Networks ◽  
Information Diffusion ◽  
Large Scale ◽  
Centrality Measures ◽  
Correct Identification ◽  
Graph Analysis ◽  
Relevant Role ◽  
Two Phases ◽  
Large Scale Networks ◽  
Spreading Processes

One of the main problems in graph analysis is the correct identification of relevant nodes for spreading processes. Spreaders are crucial for accelerating/hindering information diffusion, increasing product exposure, controlling diseases, rumors, and more. Correct identification of spreaders in graph analysis is a relevant task to optimally use the network structure and ensure a more efficient flow of information. Additionally, network topology has proven to play a relevant role in the spreading processes. In this sense, more of the existing methods based on local, global, or hybrid centrality measures only select relevant nodes based on their ranking values, but they do not intentionally focus on their distribution on the graph. In this paper, we propose a simple yet effective method that takes advantage of the underlying graph topology to guarantee that the selected nodes are not only relevant but also well-scattered. Our proposal also suggests how to define the number of spreaders to select. The approach is composed of two phases: first, graph partitioning; and second, identification and distribution of relevant nodes. We have tested our approach by applying the SIR spreading model over nine real complex networks. The experimental results showed more influential and scattered values for the set of relevant nodes identified by our approach than several reference algorithms, including degree, closeness, Betweenness, VoteRank, HybridRank, and IKS. The results further showed an improvement in the propagation influence value when combining our distribution strategy with classical metrics, such as degree, outperforming computationally more complex strategies. Moreover, our proposal shows a good computational complexity and can be applied to large-scale networks.

Advisory Opinion on the Environment and Human Rights

2018 ◽  
Vol 112 (3) ◽  
pp. 460-466
Author(s):  
Angeliki Papantoniou
Keyword(s):  
Human Rights ◽  
Large Scale ◽  
Environmental Law ◽  
Caribbean Region ◽  
Environmental Harm ◽  
Significant Finding ◽  
Advisory Opinion ◽  
Personal Integrity ◽  
Infrastructure Projects ◽  
Extraterritorial Jurisdiction

On November 15, 2017, the Inter-American Court of Human Rights (Court) rendered a historic advisory opinion (Advisory Opinion) on the relationship between human rights and the environment. The opinion was a response to a request from Colombia regarding extraterritorial jurisdiction of state parties to the American Convention, in particular their obligations under the rights to life and personal integrity, arising from the construction and operation of large-scale infrastructure projects in the Greater Caribbean region. Colombia's concern was that, due to their dimensions and permanence, such projects could cause significant environmental harm, that goes beyond national borders, and, as a consequence, adversely affect the inhabitants of the whole region and the enjoyment of their rights under the Convention (para. 2). One of the most important aspects of the Advisory Opinion is the Court's finding that in relation to large-scale transboundary infrastructure projects, state parties to the Convention can exercise extraterritorial jurisdiction under certain circumstances and thus be responsible for the human rights of the people in the affected area. Another significant finding of the Court is that Article 26 of the American Convention, which provides for the progressive realization of economic, social, and cultural rights, includes an autonomous right to a healthy environment—a right fundamental for the existence of humankind. Finally, the Court directly linked the rights to life and personal integrity with general principles of international environmental under a due diligence obligation. The Court's extensive use of international environmental law instruments, case law, and reasoning could pave the way for greater interconnection and integration between human rights and international environment law obligations.

Igneous activity in central-southern Italy: Is the subduction paradigm still valid?

2022 ◽  
Author(s):  
Michele Lustrino ◽  
Claudio Chiarabba ◽  
Eugenio Carminati
Keyword(s):  
Large Scale ◽  
Oceanic Lithosphere ◽  
Tyrrhenian Sea ◽  
Calc Alkaline ◽  
Quaternary Volcanism ◽  
High K ◽  
Igneous Activity ◽  
Lateral Extent ◽  
Subduction System ◽  
Sea Area

ABSTRACT The Pliocene–Quaternary igneous record of the Tyrrhenian Sea area features a surprisingly large range of compositions from subalkaline to ultra-alkaline and from ultrabasic to acid. These rocks, emplaced within the basin and along its margins, are characterized by strongly SiO2-undersaturated and CaO-rich to strongly SiO2-oversaturated and peraluminous compositions, with sodic to ultrapotassic alkaline and tholeiitic to calc-alkaline and high-K calc-alkaline affinities. We focused on the different models proposed to explain the famous Roman Comagmatic Region, part of the Quaternary volcanism that spreads along the eastern side of the Tyrrhenian area, in the stretched part of the Apennines thrust-and-fold belt. We reviewed data and hypotheses proposed in the literature that infer active to fossil subduction up to models that exclude subduction entirely. Many field geology observations sustain the interpretation that the evolution of the Tyrrhenian-Apennine system was related to subduction of the western margin of Adria continental lithosphere after minor recycling of oceanic lithosphere. However, the lateral extent of the subducting slab in the last millions of years, when magmatism flared up, remains debatable. The igneous activity that developed in the last millions of years along the Tyrrhenian margin is here explained as originating from a subduction-modified mantle, regardless of whether the large-scale subduction system is still active.

scholarly journals Impact of Model Resolution on Tropical Cyclone Simulation Using the HighResMIP–PRIMAVERA Multimodel Ensemble

2020 ◽  
Vol 33 (7) ◽  
pp. 2557-2583 ◽  
Author(s):  
Malcolm John Roberts ◽  
Joanne Camp ◽  
Jon Seddon ◽  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Northwestern Pacific ◽  
Model Resolution ◽  
Enhanced Resolution ◽  
Systematic Improvement ◽  
Ensemble Mean ◽  
Show Evidence ◽  
Storm Frequency ◽  
The Impact

AbstractA multimodel, multiresolution set of simulations over the period 1950–2014 using a common forcing protocol from CMIP6 HighResMIP have been completed by six modeling groups. Analysis of tropical cyclone performance using two different tracking algorithms suggests that enhanced resolution toward 25 km typically leads to more frequent and stronger tropical cyclones, together with improvements in spatial distribution and storm structure. Both of these factors reduce typical GCM biases seen at lower resolution. Using single ensemble members of each model, there is little evidence of systematic improvement in interannual variability in either storm frequency or accumulated cyclone energy as compared with observations when resolution is increased. Changes in the relationships between large-scale drivers of climate variability and tropical cyclone variability in the Atlantic Ocean are also not robust to model resolution. However, using a larger ensemble of simulations (of up to 14 members) with one model at different resolutions does show evidence of increased skill at higher resolution. The ensemble mean correlation of Atlantic interannual tropical cyclone variability increases from ~0.5 to ~0.65 when resolution increases from 250 to 100 km. In the northwestern Pacific Ocean the skill keeps increasing with 50-km resolution to 0.7. These calculations also suggest that more than six members are required to adequately distinguish the impact of resolution within the forced signal from the weather noise.

scholarly journals A GCM study of the response of the atmospheric water cycle of West Africa and the Atlantic to Saharan dust radiative forcing

2009 ◽  
Vol 27 (10) ◽  
pp. 4023-4037 ◽  
Author(s):  
K. M. Lau ◽  
K. M. Kim ◽  
Y. C. Sud ◽  
G. K. Walker
Keyword(s):  
West Africa ◽  
Radiative Forcing ◽  
Large Scale ◽  
Water Cycle ◽  
Deep Convection ◽  
Saharan Dust ◽  
Caribbean Region ◽  
Atmospheric Water ◽  
The West ◽  
Dust Layer

Abstract. The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerly flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer over the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher.

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