Desarrollo de modelos numéricos de flexión litosférica: aplicación a fosas oceánicas y cuencas de antepaís

La flexión de la Litosfera es un proceso observado en distintos contextos tectónicos y su estudio tiene especial relevancia para la comprensión de los procesos de formación de cuencas de antepaís y fosas oceánicas. Dicha flexión es consecuencia de la aplicación de cargas superficiales (p. e., apilamiento de mantos de corrimiento) y/o cargas intemas de origen incierto (p.e., deformación intema de la litosfera). Por tanto, la evolución de la deflexión y la consiguiente geometría del relleno sedimentario están relacionados con la evolución de la carga. El objetivo del trabajo que se presenta en esta Memoria es el desarrollo de modelos numéricos de flexión litosférica y su aplicación a la formación de fosas oceánicas y cuencas de antepaís. En la primera parte de la Memoria se describen los modelos conceptuales que relacionan los procesos de carga con la deflexión del basamento y la geometría sedimentaria resultante. Esta relación está basicamente determinada por el comportamiento reológico de la Litosfera y los procesos superficiales de erosión/sedimentación. En la segunda parte, se desarrollan los algoritmos de cálculo de la deflexión que están basados en el modelo de placa delgada y permiten incorporar distintas reologías: elástica, viscoelástica y elastoplástica. Una de las aportaciones de este trabajo es la integración en el modelo de flexión de la cinemática en 2D y 3D del proceso de carga, permitiendo una simulación más rigurosa del emplazamiento de láminas cabalgantes. El tratamiento de los procesos de erosión y sedimentación es distinto en los modelos 2D y 3D. En el primer caso se han considerado los modelos simples de tasa constante y transporte difusivo, mientras que en el segundo caso se ha incorporado el transporte advectivo a través de la red de drenaje. Ambos modelos consideran el efecto de las variaciones eustáticas del nivel del mar y de la paleobatimetría. La versatilidad con que se han diseñado los algoritmos de cálculo ha permitido su aplicación a dos contextos geodinámicos distintos. En primer lugar, el modelo de flexión de placa con diferentes reologías se ha aplicado a las fosas oceánicas de Tonga y Kermadec, permitiendo acotar la estructura de la litosfera en la Placa Pacífica y la magnitud de las fuerzas que actúan sobre la misma. En segundo lugar, el mismo modelo de flexión, conjuntamente con las aproximaciones adoptadas para la formación de la carga y el transporte de sedimentos en 2D y 3D, se ha aplicado a la cuenca de antepaís del Guadalquivir, permitiendo relacionar el movimiento de las Zonas Béticas Externas con la geometría de las unidades sedimentarias. El modelo de placa elástica homogenea no permite reproducir el conjunto de observables (deflexión, arquitectura de la cuenca, etc.) y predice una distribución de esfuerzos en el interior de la placa que es incompatible con el comportarniento reológico de la litosfera. Por el contrario, el modelo de placa viscoelástica permite reproducir geometrías complejas del relleno sedimentario, mientras que el modelo de placa elastoplástica no homogénea predice, además, una distribución mas realista de los esfuerzos generados en el interior de la placa De la aplicación de los modelos a las fosas del Tonga y Kermadec se deduce que es necesario imponer una fuerza horizontal extensiva para ajustar correctamente la deflexión del basamento. Ello implica que el mecanismo preponderante en la subducción de la Placa Pacífica es la contribución gravitatoria del slab que subduce (slab pull), y no el arrastre del manto astenosférico. De acuerdo a los parámetros reológicos escogidos, los resultados obtenidos favorecen el modelo termico de Stein & Stein (1992) frente al de Parsons & Sclater (1977). No obstante, la validez de este resultado debe tomarse con precaución dado el alto grado de incertidumbre en Ia deterrninación de los parámetros reológicos. Del estudio realizado en la Cuenca del Guadalquivir se deduce que la influencia de la carga asociada a las Zonas Béticas Internas es despreciable en el proceso de formación de la Cuenca. La subsidencia de la Cuenca precisa de la concurrencia de la carga topográfica, la carga asociada a la paleobatimetría, la contribución de la deformación cortical y la presencia de una carga de origen subcortical que, de acuerdo con las anomalías gravimétricas y geoidales, debe localizarse en la base de la litosfera. Por otro lado, el retroceso que se observa en los depósitos del Tortoniense y el avance subsiguiente de los depósitos del Mesiniense se han reproducido satisfactoriamente considerando el modelo de placa elastoplástica no homogénea y el modelo de placa viscoelástica. Por tanto, el retroceso de la unidad Tortoniense puede atribuirse a un efecto combinado de variaciones del nivel del mar, relajación viscosa de los esfuerzos y estratificación de la resistencia litosférica. Por último, el modelo elastoplástico permite, además, explicar la existencia de fallas extensionales en el basamento coetáneas al proceso de carga.Flexure of the lithosphere is a widely observed process in different tectonic settings. Its study is particularly relevant to understand the formation of foreland basins and oceanic trenches. The lithosphere bends in response to external loads (e.g., thrusts) and/or hidden Loads (e.g., lithospheric deformation). Thereby, the evolution of the deflection and the basin infill geometry are directly related to loading processes. The main goal of this work is to develop numerical models of lithospheric flexure and their application to the study of oceanic trenches and foreland basin formation. The first part of this Thesis deals with the conceptual models that link loading processes to basement deflection and basin infill geometry. This relationship is mainly controlled by the rheological behavior of the litosphere and by surface processes such as erosion and sedimentation. The second part includes the development of thin plate model based algorithms with different rheologies: elastic, viscoelastic, and elastoplastic. A relevant contribution of this work is the integration in the flexural model of a 2D and 3D fully kinematic approach which realistically simulates thrust emplacement. Erosion and sedimentation processes are treated distinctly in the 2D and 3D approaches. The 2D approach considers either a constant erosion/sedimentation rate or a diffusive model, whereas the 3D can also incorporate advection through a drainage network. Both approaches include eustatic sea level variations and paleobathymetry. Elastic and homogeneous elastoplastic plate models do not account for the observed deflection and basin architecture. Moreover, these models predict an unrealistic lithospheric stress distribution. In contrast, the viscoelastic plate model permits to reproduce complex infill geometries, whereas the non-homogeneous elastoplastic plate model predicts, in addition, a more realistic stress distribution. The application of the 2D algorithms to the Tonga and Kennadec trenches has allowed to constrain the lithospheric structure of the Pacific Plate and the magnitude of the forces acting on the subducting slab. The most outstanding result is the necessity to impose a horizontal extensional force to fit the deflection of the basement. This implies that the driving mechanism is mainly governed by slab pull rather than mantle drag. Results also favour the half plate cooling model proposed by Stein & Stein (1992) instead of that proposed by Parsons & Sclater (1977), although the uncertainties on the rheological parameters do not allow for firm conclusions. The application of the 2D and 3D algorithms to Southern Spain reveals that the Internal Betics play a negligible role in the formation of the Guadalquivir foreland basin. The basement deflection can only be explained considering the topography and paleobathymetry loads, the Load associated with crustal deformation, and a hidden or extra load seated at subcrustal levels. The analysis of gravity and geoid anomalies suggests that the hidden load is likely related to lithospheric thickening beneath the Betics. The complex stratigraphy of the Guadalquivir basin, particularly during Tortonian and Messinian times, is successfully reproduced by the viscoelastic and the non-homogeneous elastoplastic plate models suggesting that the basin infill resulted from the combination of eustatic sea-level variations, viscous stress relaxation, and layered lithospheric strength. Furthermore, the non-homogeneous elastoplastic plate model accounts for the presence of basement extensional faults that developed during thrusting

Desarrollo de modelos numéricos de flexión litosférica: aplicación a fosas oceánicas y cuencas de antepaís

[spa] La flexión de la Litosfera es un proceso observado en distintos contextos tectónicos y su estudio tiene especial relevancia para la comprensión de los procesos de formación de cuencas de antepaís y fosas oceánicas. Dicha flexión es consecuencia de la aplicación de cargas superficiales (p. e., apilamiento de mantos de corrimiento) y/o cargas intemas de origen incierto (p.e., deformación intema de la litosfera). Por tanto, la evolución de la deflexión y la consiguiente geometría del relleno sedimentario están relacionados con la evolución de la carga. El objetivo del trabajo que se presenta en esta Memoria es el desarrollo de modelos numéricos de flexión litosférica y su aplicación a la formación de fosas oceánicas y cuencas de antepaís. En la primera parte de la Memoria se describen los modelos conceptuales que relacionan los procesos de carga con la deflexión del basamento y la geometría sedimentaria resultante. Esta relación está basicamente determinada por el comportamiento reológico de la Litosfera y los procesos superficiales de erosión/sedimentación. En la segunda parte, se desarrollan los algoritmos de cálculo de la deflexión que están basados en el modelo de placa delgada y permiten incorporar distintas reologías: elástica, viscoelástica y elastoplástica. Una de las aportaciones de este trabajo es la integración en el modelo de flexión de la cinemática en 2D y 3D del proceso de carga, permitiendo una simulación más rigurosa del emplazamiento de láminas cabalgantes. El tratamiento de los procesos de erosión y sedimentación es distinto en los modelos 2D y 3D. En el primer caso se han considerado los modelos simples de tasa constante y transporte difusivo, mientras que en el segundo caso se ha incorporado el transporte advectivo a través de la red de drenaje. Ambos modelos consideran el efecto de las variaciones eustáticas del nivel del mar y de la paleobatimetría. La versatilidad con que se han diseñado los algoritmos de cálculo ha permitido su aplicación a dos contextos geodinámicos distintos. En primer lugar, el modelo de flexión de placa con diferentes reologías se ha aplicado a las fosas oceánicas de Tonga y Kermadec, permitiendo acotar la estructura de la litosfera en la Placa Pacífica y la magnitud de las fuerzas que actúan sobre la misma. En segundo lugar, el mismo modelo de flexión, conjuntamente con las aproximaciones adoptadas para la formación de la carga y el transporte de sedimentos en 2D y 3D, se ha aplicado a la cuenca de antepaís del Guadalquivir, permitiendo relacionar el movimiento de las Zonas Béticas Externas con la geometría de las unidades sedimentarias. El modelo de placa elástica homogenea no permite reproducir el conjunto de observables (deflexión, arquitectura de la cuenca, etc.) y predice una distribución de esfuerzos en el interior de la placa que es incompatible con el comportarniento reológico de la litosfera. Por el contrario, el modelo de placa viscoelástica permite reproducir geometrías complejas del relleno sedimentario, mientras que el modelo de placa elastoplástica no homogénea predice, además, una distribución mas realista de los esfuerzos generados en el interior de la placa De la aplicación de los modelos a las fosas del Tonga y Kermadec se deduce que es necesario imponer una fuerza horizontal extensiva para ajustar correctamente la deflexión del basamento. Ello implica que el mecanismo preponderante en la subducción de la Placa Pacífica es la contribución gravitatoria del slab que subduce (slab pull), y no el arrastre del manto astenosférico. De acuerdo a los parámetros reológicos escogidos, los resultados obtenidos favorecen el modelo termico de Stein & Stein (1992) frente al de Parsons & Sclater (1977). No obstante, la validez de este resultado debe tomarse con precaución dado el alto grado de incertidumbre en Ia deterrninación de los parámetros reológicos. Del estudio realizado en la Cuenca del Guadalquivir se deduce que la influencia de la carga asociada a las Zonas Béticas Internas es despreciable en el proceso de formación de la Cuenca. La subsidencia de la Cuenca precisa de la concurrencia de la carga topográfica, la carga asociada a la paleobatimetría, la contribución de la deformación cortical y la presencia de una carga de origen subcortical que, de acuerdo con las anomalías gravimétricas y geoidales, debe localizarse en la base de la litosfera. Por otro lado, el retroceso que se observa en los depósitos del Tortoniense y el avance subsiguiente de los depósitos del Mesiniense se han reproducido satisfactoriamente considerando el modelo de placa elastoplástica no homogénea y el modelo de placa viscoelástica. Por tanto, el retroceso de la unidad Tortoniense puede atribuirse a un efecto combinado de variaciones del nivel del mar, relajación viscosa de los esfuerzos y estratificación de la resistencia litosférica. Por último, el modelo elastoplástico permite, además, explicar la existencia de fallas extensionales en el basamento coetáneas al proceso de carga.[eng] Flexure of the lithosphere is a widely observed process in different tectonic settings. Its study is particularly relevant to understand the formation of foreland basins and oceanic trenches. The lithosphere bends in response to external loads (e.g., thrusts) and/or hidden Loads (e.g., lithospheric deformation). Thereby, the evolution of the deflection and the basin infill geometry are directly related to loading processes. The main goal of this work is to develop numerical models of lithospheric flexure and their application to the study of oceanic trenches and foreland basin formation. The first part of this Thesis deals with the conceptual models that link loading processes to basement deflection and basin infill geometry. This relationship is mainly controlled by the rheological behavior of the litosphere and by surface processes such as erosion and sedimentation. The second part includes the development of thin plate model based algorithms with different rheologies: elastic, viscoelastic, and elastoplastic. A relevant contribution of this work is the integration in the flexural model of a 2D and 3D fully kinematic approach which realistically simulates thrust emplacement. Erosion and sedimentation processes are treated distinctly in the 2D and 3D approaches. The 2D approach considers either a constant erosion/sedimentation rate or a diffusive model, whereas the 3D can also incorporate advection through a drainage network. Both approaches include eustatic sea level variations and paleobathymetry. Elastic and homogeneous elastoplastic plate models do not account for the observed deflection and basin architecture. Moreover, these models predict an unrealistic lithospheric stress distribution. In contrast, the viscoelastic plate model permits to reproduce complex infill geometries, whereas the non-homogeneous elastoplastic plate model predicts, in addition, a more realistic stress distribution. The application of the 2D algorithms to the Tonga and Kennadec trenches has allowed to constrain the lithospheric structure of the Pacific Plate and the magnitude of the forces acting on the subducting slab. The most outstanding result is the necessity to impose a horizontal extensional force to fit the deflection of the basement. This implies that the driving mechanism is mainly governed by slab pull rather than mantle drag. Results also favour the half plate cooling model proposed by Stein & Stein (1992) instead of that proposed by Parsons & Sclater (1977), although the uncertainties on the rheological parameters do not allow for firm conclusions. The application of the 2D and 3D algorithms to Southern Spain reveals that the Internal Betics play a negligible role in the formation of the Guadalquivir foreland basin. The basement deflection can only be explained considering the topography and paleobathymetry loads, the Load associated with crustal deformation, and a hidden or extra load seated at subcrustal levels. The analysis of gravity and geoid anomalies suggests that the hidden load is likely related to lithospheric thickening beneath the Betics. The complex stratigraphy of the Guadalquivir basin, particularly during Tortonian and Messinian times, is successfully reproduced by the viscoelastic and the non-homogeneous elastoplastic plate models suggesting that the basin infill resulted from the combination of eustatic sea-level variations, viscous stress relaxation, and layered lithospheric strength. Furthermore, the non-homogeneous elastoplastic plate model accounts for the presence of basement extensional faults that developed during thrusting

Сравнительный анализ дедуктивных средств различных логических теорий (на примере времéнных и алетических логик)

The buoyancy of the lithospheric mantle relative to the asthenospheric mantle is the driving force of plate subduction and mantle delamination (the peeling off of the lithospheric mantle from the crust and its detachment and sinking into the asthenospheric mantle). Both mechanisms are often invoked for the evolution of collision zones, yet there are still open questions about the conditions under which they take place. The higher density of the lithosphere relative to the asthenosphere is thought to lead to subduction or delamination as it sinks. However, it is true only when the densities are temperature dependent. We adopt a mineral physics viewpoint where the density depends on temperature, pressure, and composition such that lithospheric mantle can be less dense than that of the underlying asthenosphere, posing a severe problem for the initiation of delamination. The density and its pressure-temperature dependence, in the lithosphere and asthenosphere are calculated from stable mineral assemblages computed using major oxides composition based on mantle xenoliths/garnet peridotites in the (CFMAS) framework. We present a parametric study on the relationship between slab buoyancy and convergence rate using a simple 2D kinematic numerical model, incorporating thermal advection and diffusion. We consider different types of the lithospheric mantle (e.g. Archon, Tecton, Proton, and Oceanic), subducting with different convergence rate and constant angle, into the asthenosphere. Our results suggest that Oceanic, Tecton and Proton lithospheres are always negatively buoyant and maximum negative buoyancy increases with the convergence velocity whereas Archons are always positively buoyant. In case of oceanic lithosphere maximum negative buoyancy also increases with its age for a given velocity. This is a SUBITOP (674899-SUBITOP-H2020-MSCA-ITN-2015) and MITE (CGL2014-59516) contribution.Peer Reviewe

3-D lithospheric structure and regional/residual Bouguer anomalies in the Arabia-Eurasia collision (Iran)

The aim of this work is to propose a first-order estimate of the crustal and lithospheric mantle geometry of the Arabia-Eurasia collision zone and to separate the measured Bouguer anomaly into its regional and local components. The crustal and lithospheric mantle structure is calculated from the geoid height and elevation data combined with thermal analysis. Our results show that Moho depth varies from ~42 km at the Mesopotamian-Persian Gulf foreland basin to ~60 km below the High Zagros. The lithosphere is thicker beneath the foreland basin (~200 km) and thinner underneath the High Zagros and Central Iran (~140 km). Most of this lithospheric mantle thinning is accommodated under the Zagros mountain belt coinciding with the suture between two different mantle domains on the Sanandaj-Sirjan Zone. The regional gravity field is obtained by calculating the gravimetric response of the 3-D crustal and lithospheric mantle structure obtained by combining elevation and geoid data. The calculated regional Bouguer anomaly differs noticeably from those obtained by filtering or just isostatic methods. The residual gravity anomaly, obtained by subtraction of the regional components to the measured field, is analyzed in terms of the dominating upper crustal structures. Deep basins and areas with salt deposits are characterized by negative values (~-20 mGal), whereas the positive values are related to igneous and ophiolite complexes and shallow basement depths (~20 mGal). © 2012 The Authors Geophysical Journal International © 2012 RAS.This research has been partly funded by ProjectsATIZA (CGL2009-09662-BTE) and TECLA (CGL2011–26670) and consolider-Ingenio 2010 Topo-Iberia (CSD2006-00041).Peer Reviewe

Computational Fluid Dynamics simulations of the Late Pleistocene Lake Bonneville Flood

At approximately 18.0 ka, pluvial Lake Bonneville reached its maximum level. At its northeastern extent it was impounded by alluvium of the Marsh Creek Fan, which breached at some point north of Red Rock Pass (Idaho), leading to one of the largest floods on Earth. About 5320 km3 of water was discharged into the Snake River drainage and ultimately into the Columbia River. We use a 0D model and a 2D non-linear depth-averaged hydrodynamic model to aid understanding of outflow dynamics, specifically evaluating controls on the amount of water exiting the Lake Bonneville basin exerted by the Red Rock Pass outlet lithology and geometry as well as those imposed by the internal lake geometry of the Bonneville basin. These models are based on field evidence of prominent lake levels, hypsometry and terrain elevations corrected for post-flood isostatic deformation of the lake basin, as well as reconstructions of the topography at the outlet for both the initial and final stages of the flood. Internal flow dynamics in the northern Lake Bonneville basin during the flood were affected by the narrow passages separating the Cache Valley from the main body of Lake Bonneville. This constriction imposed a water-level drop of up to 2.7 m at the time of peak-flow conditions and likely reduced the peak discharge at the lake outlet by about 6%. The modeled peak outlet flow is 0.85·106 m3 s−1. Energy balance calculations give an estimate for the erodibility coefficient for the alluvial Marsh Creek divide of ∼0.005 m y−1 Pa−1.5, at least two orders of magnitude greater than for the underlying bedrock at the outlet. Computing quasi steady-state water flows, water elevations, water currents and shear stresses as a function of the water-level drop in the lake and for the sequential stages of erosion in the outlet gives estimates of the incision rates and an estimate of the outflow hydrograph during the Bonneville Flood: About 18 days would have been required for the outflow to grow from 10% to 100% of its peak value. At the time of peak flow, about 10% of the lake volume would have already exited; eroding about 1 km3 of alluvium from the outlet, and the lake level would have dropped by about 10.6 m

Crustal-scale cross-sections across the NW Zagros belt: Implications for the Arabian margin reconstruction

Quantified balanced and restored crustal cross-sections across the NW Zagros Mountains are presented in this work integrating geological and geophysical local and global datasets. The balanced crustal cross-section reproduces the surficial folding and thrusting of the thick cover succession, including the near top of the Sarvak Formation (∼90 Ma) that forms the top of the restored crustal cross-section. The base of the Arabian crust in the balanced cross-section is constrained by recently published seismic receiver function results showing a deepening of the Moho from 42 ± 2 km in the undeformed foreland basin to 56 ± 2 km beneath the High Zagros. The internal parts of the deformed crustal cross-section are constrained by new seismic tomographic sections imaging a ∼50° NE-dipping sharp contact between the Arabian and Iranian crusts. These surfaces bound an area of 10800 km2 that should be kept constant during the Zagros orogeny. The Arabian crustal cross-section is restored using six different tectonosedimentary domains according to their sedimentary facies and palaeobathymetries, and assuming Airy isostasy and area conservation. While the two southwestern domains were directly determined from well-constrained surface data, the reconstruction of the distal domains to the NE was made using the recent margin model of Wrobel-Daveau et al. (2010) and fitting the total area calculated in the balanced cross-section. The Arabian continental-oceanic boundary, at the time corresponding to the near top of the Sarvak Formation, is located 169 km to the NE of the trace of the Main Recent Fault. Shortening is estimated at ∼180 km for the cover rocks and ∼149 km for the Arabian basement, including all compressional events from Late Cretaceous to Recent time, with an average shortening rate of ∼2 mm yr-1 for the last 90 Ma. © 2011 Cambridge University Press.We thank the following projects for their additional support: DARIUS Programme and its sponsors, TopoMed CGL2008– 03474-E/BTE, ESF-Eurocores 07-TOPOEUROPE-FP006, TopoAtlas (CGL2006–05493/BTE), ATIZA (CGL2009– 09662-BTE) and Consolider-Ingenio 2010 Topo-Iberia (CSD2006–00041).Peer Reviewe

Bickerstaff encephalitis

Introducción: La encefalitis de Bickerstaff es una enfermedad neurológica aguda poco frecuente, que se caracteriza clínicamente por oftalmoplejía relativamente simétrica, ataxia, alteración del nivel de consciencia e hiperreflexia, perteneciendo a un espectro patológico continuo que incluye la oftalmoplejía aguda, síndrome de Miller Fisher y síndrome de Guillain-Barré. Caso clínico: Femenino de 26 años de edad. Inició con visión borrosa, cefalea holocraneana, mialgias generalizadas y fiebre de 38.5°C de 7 días de evolución. Se encontró con amnesia, disartria, ataxia e hiperreflexia generalizada, paresia facio-braquio-crural izquierda y ptosis palpebral izquierda. Ante deterioro del nivel de consciencia progresivo se inició manejo avanzado de la vía aérea. Tomografía computarizada (TC) de cráneo con edema cerebral severo y resonancia magnética (RM) de cráneo con disminución de calibre de vasos corticales posteriores. Punción lumbar con disociación albumino citológica Electroencefalograma con encefalopatía con actividad de base tetha reactivo a maniobras de activación y potenciales evocados visuales con neuropatía óptica bilateral de tipo desmielinizante. Anticuerpos IgG antigángliosido con Anti-GQ1b positivos. Se inició tratamiento con inmunoglobulina a dosis de 0.4 g/kg/día durante cinco días con posterior respuesta clínica satisfactoria. Conclusión: El caso ilustrado reúne múltiples características de las descritas por Bickerstaff en sus series iniciales, como lo son la oftalmoplejía, la hiperreflexia y la alteración del estado de conciencia. La controversia en cuanto a si la encefalitis de Bickerstaff y el síndrome de Guillain-Barré son entidades diferentes, ya está planteada, así como la hipótesis alterna de que puede tratarse de enfermedades dentro de un mismo espectro.Introduction: Bickerstaff encephalitis is a rare acute neurological disease, characterized clinically by relatively symmetric ophthalmoplegia, ataxia, altered level of consciousness and hyperreflexia, belonging to a continuous pathological spectrum that includes acute ophthalmoplegia, Miller Fisher syndrome and Guillain Barre syndrome. Case report: Female, 26 years old. He started with blurred vision, holocranean headache, generalized myalgias and a 38.5 ° C fever of 7 days of evolution. He found amnesia, dysarthria, ataxia and generalized hyperreflexia, left facio-brachio-crural paresis and left palpebral ptosis. Faced with the deterioration of the level of progressive consciousness, advanced airway management began. Computed tomography (CT) of the skull with severe cerebral edema and magnetic resonance imaging (MRI) of the skull with reduced caliber of posterior cortical vessels. Lumbar puncture with cytological albumine dissociation Electroencephalogram with encephalopathy with tetha-based activity reactive to activation maneuvers and visual evoked potentials with bilateral optic neuropathy of demyelinating type. IgG antigangglioside antibodies with Anti-GQ1b positive. Immunoglobulin treatment was started at a dose of 0.4 g / kg / day for five days with subsequent satisfactory clinical response. Conclussion: The illustrated case has multiple characteristics of those described by Bickerstaff in its initial series, such as ophthalmoplegia, hyperreflexia and altered state of consciousness. The controversy as to whether Bickerstaff’s encephalitis and Guillain-Barré syndrome are different entities, is already raised, as well as the alternative hypothesis that it can be diseases within the same spectrum

An evaluation of peri-implant marginal bone loss according to implant type, surgical technique and prosthetic rehabilitation: a retrospective multicentre and cross-sectional cohort study

To evaluate implant loss (IL) and marginal bone loss (MBL); follow-up period of up to 10 years after prosthetic loading. Retrospective multi-centre cross-sectional cohort study. Double analysis: (1) all the implants (n = 456) were analysed; (2) to allow for possible cluster error, one implant per patient (n = 143) was selected randomly. Statistical analysis: Spearman's correlation coefficient; Kruskal-Wallis (post-hoc U-Mann-Whitney); Chi-square (post-hoc Haberman). (1) Analysing all the implants (456): IL was observed in patients with past periodontitis (6 vs. 2.2%, p < 0.05), short implants (12 vs. 2.8%, p < 0.001) and when using regenerative surgery (11.3 vs. 2.9%, p < 0.001); greater MBL was observed among smokers (0.39 ± 0.52 vs. 0.2 ± 0.29, p < 0.01), maxillary implants (0.28 ± 0.37 vs. 0.1 ± 0.17, p < 0.0001), anterior region implants (0.32 ± 0.36 vs. 0.21 ± 0.33, p < 0.001), external connection implants (0.2 ± 0.29 vs. 0.63 ± 0.59, p < 0.0001), and 2-3 years after loading (p < 0.0001). (2) analysing the cluster (143): IL was observed in smokers (18.8 vs. 3.5%, p < 0.05), splinted fixed crowns (12.9%, p < 0.01), short implants (22.2 vs. 4.0%, p < 0.01) and when using regenerative surgery (19.2 vs. 3.4%, p < 0.01); greater MBL was observed in maxillary implants (0.25 ± 0.35 vs. 0.11 ± 0.18, p < 0.05), in the anterior region (p < 0.05), in the first 3 years (p < 0.01), in external connection implants (0.72 ± 0.71 vs. 0.19 ± 0.26, p < 0.01) and in short implants (0.38 ± 0.31 vs. 0.2 ± 0.32, p < 0.05). There is greater risk in smokers, patients with past periodontal disease, external connection implants, the use of short implants and when regenerative techniques are used. To prevent MBL and IL, implantologists should be very meticulous in indicating implants in patients affected by these host factors

Influence of marginal bone loss on peri-implantitis : systematic review of literature

The marginal bone of dental implants is subjected to slight load modifications over time, conditioning implant survival. Objective: Perform a systematic review of the literature analyzing the factors that contribute to marginal bone loss (MBL) and the subsequent development of peri-implantitis. Bibliographic research in the databases PubMed, Medline and Scopus between 2010 and 2018 was performed. The inclusion criteria were articles published in the last 10 years and that were in English or Spanish, that were carried out on humans, that were cohort studies, that included cases and controls or that used randomized clinical trials. Exclusion criteria removed articles that contained clinical cases, case series or systematic reviews. A total of 90 articles were analyzed that examined all the factors reported in the literature, such as idiosyncratic factors, toxic habits, systemic drugs and implant characteristics (diameter, length, type surface, implant connection, implant design and type of platform at the moment of the prosthetic load). Discussion: Patient characteristics and associated pathologies must be taken into account when assessing MBL. MBL in all dental implants can be considered independent of the type of prosthetic rehabilitation and the moment of load; this was emphasized. The MBL is smaller in dental implants with rough surfaces, switch platforms and infracrestal localization, as they are of multifactorial origin. All the reviewed articles maintain a common criterion regarding the concept and measurement of the MBL and highlighting the importance of radiodiagnosis for quantification. Longterm prospective studies with unified criteria are needed to reduce bias by identifying the most relevant factors in MBL

Thermomechanical modelling of lithospheric slab tearing and its topographic response

Lithospheric slab tearing, the process by which a subducted lithospheric plate is torn apart and sinks into the Earth’s mantle, has been proposed as a cause for surface vertical motions in excess of 100 s of meters. However, little is known about the mechanisms that help initiate and control the propagation of slab tearing and the associated uplift. This study aims to explore these processes by means of 3D thermo-mechanical geodynamic modelling of a slab retreat oblique to a continental margin, using the Gibraltar Arc region (Betic Cordillera) as a scenario for inspiration. Our results suggest that the obliquity of the continental passive margin relative to the subduction trench leads to an asymmetric distribution of subduction forces and strength, facilitating the initiation of slab tearing. The model results predict a lateral migration of the tearing point at a velocity ranging between 38 and 68 cm/yr for a sublithospheric-mantle viscosity of up to 1e+22 Pa s. This fast slab tearing propagation yields uplift rates of 0.23–2.16 mm/yr above the areas where the subducted slab is torn apart, depending on mantle viscosity. Although a more detailed parametric exploration is needed, this range of uplift rates is compatible with the uplift rates required to overcome seaway erosion along the Atlantic-Mediterranean marine corridors during the Late Miocene, as proposed for the onset of the Messinian Salinity Crisis