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The Caribbean plate is an enclosed oceanic basin whose formation and evolution are controversial. In the most commonly accepted model, the Caribbean plate is mainly composed of the Caribbean Large Igneous Province (CLIP) and the buoyant characteristic of this oceanic plateau resisted subduction and allowed an eastward migration to its present position north of South America. In this study, we integrate a broad range of geophysical and geomorphological data to define structural elements and present‐day tectonics of the Caribbean plate and the surrounding region. We present a Bouguer gravity anomaly map and a new crustal thickness map that documents large areas of normal‐thickness oceanic crust within the Venezuela and Colombia basins of the Caribbean plate. Selected cross sections of seismicity and P‐wave anomalies from a seismic tomographic model depict the present‐day geometry of subducting oceanic plates within the Caribbean region. We observe that rather than resisting subduction, as expected for the thick crust of a buoyant large igneous province, the subduction of the Caribbean plate can be traced to a depth of 600 km beneath NW South America. This, together with the crustal thickness map, implies that a significant area of the Caribbean plate, including the subducted portion, is composed of normal‐thickness oceanic crust. As proposed by the Pacific origin model, the Caribbean plate likely migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism (CLIP). Plain Language Summary: The Caribbean plate and northern South America are studied using topography and multiple geophysical data sets, including gravity, magnetics, crustal thickness, seismicity, and seismic images of the upper mantle. These data sets were used to analyze crustal properties as well as the past and present interaction of tectonic plates in this region. Our results show large areas of ocean crust with normal thickness within the Caribbean plate. Seismicity in the circum‐Caribbean subduction zones rarely exceeds 200 km in depth, whereas seismic imaging shows subducting slabs reach a depth of 600 km or more. This implies that subduction has been long‐lived at these active margins. These results also show that the Caribbean plate is subducting beneath NW South America, something that would not be expected for the thick crust of a buoyant large igneous province. As proposed by the Pacific origin model, the Caribbean plate migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism. Key Points: A new crustal thickness map and gravity maps reveal large areas of normal‐thickness oceanic crust within the Caribbean plateP‐wave seismic tomography images show that the subducted Caribbean plate reaches 660 km depth, but slab seismicity terminates at 200 kmCombined seismicity, gravity, and magnetic maps reveal the active tectonics of the circum‐Caribbean accretionary and magmatic boundary [ABSTRACT FROM AUTHOR]

Abstract The Arabian Plate shows a strong asymmetry between its Shield and Platform, in terms of topography, seismic velocity and density structure of the upper mantle. This asymmetry also results in significant rheological differences between these blocks, as revealed by the effective elastic thickness (EET) estimates, obtained using a spectral gravity method. However, these estimates may be biased due to various factors. Therefore, other approaches based on a direct rheological modeling of the lithospheric structure should be employed to verify these results. In this study, we use a recent model of the lithosphere, based on an integrative interpretation of the gravity field and seismic tomography, to correct an initial thermal model obtained from the inversion of seismic velocity, assuming a uniform composition. The results are used together with the most recent crustal model of the Arabian Plate to construct two alternative models of strength and EET of the lithosphere. The first model (Model I) assumes a constant value of 10− 15 s− 1 for the strain rates. In the second model (Model II), we used the strain rates obtained from a global mantle flow model. Model I confirms the asymmetry in the rigidity of the Shield and Platform. In contrast, Model II shows that the influence of the variable strain rates causes a significant increase in the strength and EET of the central and eastern part of the Shield and in contrast to previous studies, reveals that most of the Arabian Plate is a long-term stable tectonic feature, predominantly characterized by large EET values (≥ 70 km). Highlights • Two alternative strength and EET models of the Arabian Plate are proposed. • Strain rates variations influence the rigidity of the Arabian Plate. • Most of the Arabian Plate is a long-term stable tectonic feature. [ABSTRACT FROM AUTHOR]

Abstract: Numerical models are presented that simulate mantle convection coupled with superimposed continents. The continents and main islands are modelled as thin rigid spherical caps with non-slip boundary conditions and continuity conditions for temperature and heat flux at their bottom. Additional repulsive forces prevent overlap of the continents in the case of their collision. The initial temperature distribution in the mantle is calculated based on seismic tomography data. The evolving mantle model implies 10% basal and 90% internal heating and uniform viscosity. Mechanical coupling leads to near horizontal convection currents under continents and consequently to a noticeable decrease of the mantle temperature under them in spite of the thermal blanket effect. The modelling results show that a long-term evolution of the free convection model and of the model with implemented continents leads to principally different structures. Several common stages of the continental evolution are revealed. Back-arc basins at the active continental margins are closed at the first stage. In the next stage of the modelled evolution the convection pattern is reorganized and the main downwellings start to move to the south pulling the continents, which tend to assemble a new super-continent around Antarctica. Due to the repulsive forces the continents rotate and adjust to each other. [Copyright &y& Elsevier]

The Congo basin is one of the largest intracratonic basins in the World, locating within a cold lithospheric plate. The structure of the thick sedimentary layer is investigated by seismic studies only in limited places. Here, we present a map of sedimentary thickness for the whole Congo basin, based on the inversion of the decompensative gravity anomalies. Contrary to the conventional Bouguer or isostatic gravity anomalies, the effect of the isostatic compensation of sediments is reduced in the decompensative anomalies, which provides a possibility to recover the full effect of low-density sediments. The calculated decompensative correction reaches ±70 mGal and exceeds the amplitude of the isostatic anomalies, especially in the long wavelengths. The final decompensative anomalies are negative over the whole basin and their patterns well correspond to its tectonic fragmentation. By inverting these anomalies with the predefined density-depth relationship we have obtained the sedimentary thickness map for the whole Congo basin. The maximum basement depth exceeding 10 km is found in the Lokoro basin and basins in the South. In the Lomami basin, thickness of sediments reaches about 6.5 km. It is important to note, that these deep depressions, are not covered by seismic studies. Furthermore, we found a new deep basin adjacent to the Lokonia High (on the SW side) that we propose to name as the Salonga basin. • Decompensative gravity anomalies, which reflect density variations in the upper crust, are computed for the Congo basin. • A map of sedimentary thickness has been obtained for the first time for the whole Congo basin. • This map demonstrates a good fit to available seismic determinations. • We found several deep depressions, which were not previously covered by seismic studies. One of them is the Salonga basin. [ABSTRACT FROM AUTHOR]

The Alps is a part of the Alpine-Himalayan orogenic belt formed as a result of the collision of the African and Eurasian plates during the Cenozoic Era. This collision formed a compound tectonic structure characterized by complex geology. To better understand geology and tectonics of the Alps, additional knowledge on density distribution, stress state and rheology of the crust and upper mantle are essential. The mantle convection is actively involved in the plate tectonics and interacts with the lithosphere at its base, greatly affecting the stress distribution and deformation in the lithosphere. On the other hand, the basal traction forces caused by the mantle flow do not only affect the stress field in the lithosphere, they also induce geoid, dynamic topography and gravity anomalies.To understand how the mantle flow affects the deformation of the lithosphere in the Alpine region, a numerical geodynamic model on a continental or even global scale in 3D is required. However, the model setup needs in additional data such as distribution of the density, viscosity and temperature within the modeling domain. In our study we have developed a global mantle convection model based on the refined density model and viscosity distribution derived from tectonic, rheological and seismic data. The global density model of the upper mantle is refined for Europe based on the new high-resolution 3D model. This model, based on joint inversion of the residual gravity and topography, provides much better resolution of the 3D density structure compared to the global model based solely on seismic tomography. The refined density model and the viscosity distribution calculated using a homologous temperature approach provide an initial setup for further numerical calculations. The present-day snapshot of the mantle convection is computed using the numerical code ProSpher 3D, which takes into account strong lateral variations of viscosity (Petrunin et al., 2013). The setup includes weak plate boundaries, while the measured GPS velocities are used to constrain the solution.As a result of the modeling we present maps of density, viscosity and stress distribution. These results allowed us to more accurately locate subducted slabs in the upper mantle in the Alpine region and its surroundings. We also demonstrate a map of maximum principal stress orientation as a proxy for polarization of seismic waves and stress state (compressional or extensional environment) of the lithosphere that can be used for further geodynamic modeling. Petrunin, A. G.; Kaban, M. K.; Rogozhina, I., and Trubitsyn, V. (2013). Revising the spectral method as applied to modeling mantle dynamics. Geochemistry Geophysics Geosystems (G3), EDOC: 21048. [ABSTRACT FROM AUTHOR]

The southeastern Tibetan Plateau (SE Tibet), located between the Eastern Himalayan Syntaxis and Sichuan Basin, is a heterogeneous structure combining different tectonic regimes. It encompasses a gently sloping long-wavelength margin, and is characterized by intense deformation and active seismicity. Mechanical strength of the lithosphere is one of the parameters that controls deformation and evolution of any region. In particular, anisotropy of the strength is important for understanding the relation between tectonic processes and lithosphere deformation. As a proxy, the effective elastic thickness of the lithosphere (T e ) can be used to study both spatial distribution and anisotropy of the lithospheric strength. Here we use the fan wavelet coherence method to determine variations of T e and its anisotropy based on the topography and Bouguer gravity anomaly data. The coherence analysis shows that low T e (5–30 km) and high T e anisotropy are widespread in SE Tibet, indicating a weak and highly mechanical anisotropic lithosphere. This also implies that the style of lithospheric deformation is continuous, and may be dominated by lower crustal flow. Compared with the crustal stress and lithospheric strain indicators, we find that the T e anisotropy is predominantly governed by the present-day tectonic stress in SE Tibet. This may indicate a post-collision compression tectonics within the plateau due to the India–Eurasia plate convergence and a resistance by the rigid Sichuan Basin. However, the anisotropy reflects extension stresses in approximately WNW–ESE direction in Yunnan and northern Indochina off the plateau, which may relate to the Burma plate subduction processes. We infer that the present-day tectonic stresses and mantle processes associated with the India–Eurasia collision continuously modify and rework the mechanical structure, and both govern the lithospheric deformation in SE Tibet. [ABSTRACT FROM AUTHOR]