Shear tardihercynian zones in the Central part of the Gredos Sierra (Spanish Central Range)

[Resumen] En este trabajo, se exponen las principales conclusiones alcanzadas en nuestra Tesis Doctoral (DOBLAS, M., 1989), en cuanto a la historia deformativa del sector central de la Sierra de Gredos para tiempos tardihercínicos, distinguiéndose tres episodios tectónicos dentro de un marco geotectónico global, durante los cuales se generan diferentes familias de zonas de cizalla: 1) Un primer episodio caracterizado por un regimen extensional con un eje de esfuerzos a 1 subvertical, que denominamos «Episodio Dúctil Extensional Tardihercínico» (DETH); 2) Un segundo episodio, caracterizado por un régimen transcurrente dúctil, con un eje de esfuerzos a 1 de direcci6n EW, que denominamos «Episodio Dúctil Transcurrente Tardihercínico» (D1TH); y, 3) Un tercer y último evento, bajo un régimen transcurrente frágil, con un eje de esfuerzos a 1 según NS, que denominamos Episodio Frágil Transcurrente Tardihercínico» (FfTH).[Abstract] This paper presents the main conclusions reached in our Doctoral Thesis (DOBLAS, M., 1989), regarding the deformational history of the central part of the Gredos Sierra for the tardihercynian time-span, during which three tectonics events, might be distinguished within a generalizated geotectonic frame, with different sets of shear zones: 1) A first extensional event with a subvenical a 1 stress axis, termed «Ductile Extensional Tardihercynian Event» (DETH); 2) A second episode characterized by transcurrent tectonics within a ductile regime, with an EW-oriented a 1 stress axis, termed «Ductile Transcurrent Tardihercynian Event» (D1TH); and, 3) A last event with brittle transcurrent faults, with a NS-oriented a 1 axis, termed «Brittle Transcurrent Tardihercynian Event» (FfTH)

Caledonian and late Caledonian Europe: a working hypothesis involving two contrasted compressional/extensional scenarios

The tectonomagmatic and metamorphic structuration of the European Caledonian realm suggests that two mutually perpendicular compressional/extensional scenarios developed during the Ordovician-Devonian time-span. As a result of the mid Ordovician Grampian compressional scheme (Caledonian s.s.), a major extensional province developed further east from the Caledonian foldbelt in continental Europe. This scenario ended by early/mid Devonian, with the complete locking of North America, Baltica and Gondwana into a Pangaea supercontinent, thus triggering a contrasted tectonic environment which might be termedLa estructuración tectonomagmática y metamórfica del dominio caledónico europeo sugiere que dos escenarios, compresional y extensional, mutuamente perpendiculares, se desarrollaron durante el Ordovícico-Devónico. Como resultado del esquema compresional del Ordovícico medio (Grampian, caledónico s.s.), en el O de Europa continental se desarrolló una provincia extensional localizada al E de la faja de plegamiento caledónica. Esta situación finalizó hacia el Devónico inferior/medio, cuando la convergencia de América del Norte, Báltica y Gondwana dió origen al supercontinente Pangea. Esta colisión generó un ambiente tectónico caracterizado por: 1. plegamiento y plutonismo en Europa continental occidental, y 2. extensión y volcanismo en la parte N de la faja de plegamiento caledónica (Escocia, SO de Noruega y E de Groenlandia). Este evento puede ser tentativamente denominado «Tardicaledónico». En términos globales, la evolución del dominio caledónico puede ser explicada en términos de «tectónica de inversión» (s.l.), esto es, períodos de adelgazamiento cortical (extensionales) seguidos por períodos de engrosamiento cortical (compresionales) y vicevers

Late hercynian dike sets in Central Iberia as a result of progressive deformation within a megacontinental dextral shear zone

[Resumen] En este trabajo se analiza el contexto geotectónico global de los sistemas filonianos intruidos en el centro peninsular durante tiempos tardihercínicos. Estos sistemas forman tres familias diferenciadas, con el siguiente orden de intrusión: 1) Diques EW de pórfido y aplita; 2) Filones de baritina, de direcciones N65 °E a N120oE; y 3) Diques NS de cuarzo, diabasa y lamprófido. La intrusión de estas tres familias de diques puede asociarse con los tres episodios tectónicos tardihercínicos: Uno primer extensional, uno segundo transcurrente dúctil, y un último transcurrente frágil. Tanto estos episodios tectónicos, como los sistemas filonianos, pueden explicarse dentro de un esquema de deformación progresiva en una zona de cizalla transcurrente dextral de escala megacontinental (paniendo del clásico esquema para la provincia tardihercínica europea de ARTHAUD, F. YMATIE, Ph., 1977).[Abstract] In this work we analize the global geotectonic context characterizing the intrusion of different dike sets in central Iberia during late Hercynian times. Three main dike sets might be distinguished, with the following order of intrusion: 1) EW porphyry and aplitic dikes; 2) N65°E to N1200E barite veins; and, 3) NS dikes of quartz, diabase, and lamprophyre. The intrusion of these three dike sets might be associated with the three late Hercynian tectonic events: A first one extensional, a second one ductile-transcurrent, and a last one brittle-transcurrent. Both these dike sets, and the tectonic events which triggered them, might be understand within a scheme involving progressive deformation within a megaconúnental dextral shear zone (fol1owing theclassical scenario for the late Hercynian european province of ARTHAUD, F. and MArrE, Ph., 1977)

Geoteetonie models of the E-W trending dikes in the Spanish Central System

[Resumen] En este trabajo se efectúa una revisión de los modelos geotectónicos actualmente existentes para explicar el emplazamiento de los haces de diques ácidos, que con dirección E-W afloran en el Sistema Central Español. Clásicamente, se han propuesto dos tipos de modelos distintos: uno de origen ligado a la intrusión de los batolitos graníticos que los contienen, y otro de origen ligado a procesos tectónicos posteriores a la intrusión de dichos batolitos. Sin embargo, recientemente ha sido sugerido un modelo mixto (DOBLAS, M., 1987) que invoca a la vez la participación de procesos tectónicos y magmáticos, dentro de un esquema de «detachments» extensionales tardi-hercínicos. En nuestra opinión, este último modelo parece ser el que mejor explica el conjunto de las características de estos haces de diques, y por tanto es el que desarrollamos, más ampliamente, en este trabajo.[Abstract] In this paper we revise different geotectonic models which have been proposed till now, to explain the emplacement of the EW trending acid dike swarrns in the Spanish Central System. Two types of models have been suggested: one of them invokes an origin related to the emplacement of the granitic batholiths, and the other proposes an origin related to tectonic processes happening after the emplacement of these batholiths. However, recently, a combined model has been suggested (DOBLAS, M., 1987), in which both magmatic and tectonic processes playa role, within a latehercynian extensional detachment scheme. We think that this hypothesis is the most adequate to explain the different characteristics of the dike swarms, and in this paper we will develop further this idea

ENSEMBLES: a new multi-model ensemble for seasonal-to-annual predictions: Skill and progress beyond DEMETER in forecasting tropical Pacific SSTs

A new 46-year hindcast dataset for seasonal-to-annual ensemble predictions has been created using a multi-model ensemble of 5 state-of-the-art coupled atmosphere-ocean circulation models. The multi-model outperforms any of the single-models in forecasting tropical Pacific SSTs because of reduced RMS errors and enhanced ensemble dispersion at all lead-times. Systematic errors are considerably reduced over the previous generation (DEMETER). Probabilistic skill scores show higher skill for the new multi-model ensemble than for DEMETER in the 4–6 month forecast range. However, substantially improved models would be required to achieve strongly statistical significant skill increases. The combination of ENSEMBLES and DEMETER into a grand multi-model ensemble does not improve the forecast skill further. Annual-range hindcasts show anomaly correlation skill of ∼0.5 up to 14 months ahead. A wide range of output from the multi-model simulations is becoming publicly available and the international community is invited to explore the full scientific potential of these data

Full-field and anomaly initialization using a low-order climate model: a comparison and proposals for advanced formulations

Initialization techniques for seasonal-to-decadal climate predictions fall into two main categories; namely full-field initialization (FFI) and anomaly initialization (AI). In the FFI case the initial model state is replaced by the best possible available estimate of the real state. By doing so the initial error is efficiently reduced but, due to the unavoidable presence of model deficiencies, once the model is let free to run a prediction, its trajectory drifts away from the observations no matter how small the initial error is. This problem is partly overcome with AI where the aim is to forecast future anomalies by assimilating observed anomalies on an estimate of the model climate. The large variety of experimental setups, models and observational networks adopted worldwide make it difficult to draw firm conclusions on the respective advantages and drawbacks of FFI and AI, or to identify distinctive lines for improvement. The lack of a unified mathematical framework adds an additional difficulty toward the design of adequate initialization strategies that fit the desired forecast horizon, observational network and model at hand. Here we compare FFI and AI using a low-order climate model of nine ordinary differential equations and use the notation and concepts of data assimilation theory to highlight their error scaling properties. This analysis suggests better performances using FFI when a good observational network is available and reveals the direct relation of its skill with the observational accuracy. The skill of AI appears, however, mostly related to the model quality and clear increases of skill can only be expected in coincidence with model upgrades. We have compared FFI and AI in experiments in which either the full system or the atmosphere and ocean were independently initialized. In the former case FFI shows better and longer-lasting improvements, with skillful predictions until month 30. In the initialization of single compartments, the best performance is obtained when the stabler component of the model (the ocean) is initialized, but with FFI it is possible to have some predictive skill even when the most unstable compartment (the extratropical atmosphere) is observed. Two advanced formulations, least-square initialization (LSI) and exploring parameter uncertainty (EPU), are introduced. Using LSI the initialization makes use of model statistics to propagate information from observation locations to the entire model domain. Numerical results show that LSI improves the performance of FFI in all the situations when only a portion of the system's state is observed. EPU is an online drift correction method in which the drift caused by the parametric error is estimated using a short-time evolution law and is then removed during the forecast run. Its implementation in conjunction with FFI allows us to improve the prediction skill within the first forecast year. Finally, the application of these results in the context of realistic climate models is discussed

Indicators of the sense of intrusion in dikes

[Resumen] En este trabajo se establecen una serie de criterios que permite deducir el sentido de la inyección en los diques. Estos criterios son de dos tipos: A) Criterios basados en indicadores cinemáticos de la deformación, que se observan a meso y microescala en los contactos dique-roca de caja, y B) Criterios basados en la observaci6n cartográfica de ciertas variaciones geométricas, texturales, composicionales y de la deformación a lo largo de la dirección de flujo dentro del dique. A su vez, los primeros se subdividen en: 1) EStructuras de flujo magmático. 2) EStructuras miloníticas dúctiles a dúctiles-frágiles. 3) EStructuras frágiles. La deducci6n del sentido de la intrusi6n en los diques tiene gran importancia, tanto para los los esquemas tectónicos regionales, como para el estudio de los flujos magmáticos.[Abstract] In this paper we study sorne criteria that are useful as indicators of the sense of intrusion in dikes. There are two types of criteria: A) Criteria based on kinematic indicators, which are observable on the meso and microscale, on the dike/host-rock interfaces; B) Criteria based on the cartographical observation of certain geometrical, textural, compositional, and deformational variations along the direction of intrusion of the dikes. The meso and microscale indicators might be subdivided into three main types of structures: 1) Structures of magmatic flow; 2) Ductile to ductile-brittle mylonitic structures); 3) Brittle structures. The deduction of the sense of intrusion in dikes is very important, both for the establishment of regional tectonic schemes, and for the study of magmatic flow patterns

Criterios del sentido de movimiento en espejos de fricción: clasificación y aplicación a los granitos cizallados de la Sierra de San Vicente (Sierra de Gredos)

In this paper, we first classify the different shearing sense criteria on slickensided surfaces, obtaining thus a practical guide both for the field, and the laboratory. We then apply some of these criteria to the C shearing planes present in the San Vicente deformed granites. These planar structures in granites, which have not been used yet for the study of slickensided surfaces, seem ideal for verifying and/or proposing criteria, as their shearing senses are already known from previous studies (Doblas et al., 1983, Doblas 1985). Some of these features are investigated here under the scanning electron microscope. Apart from indicative of the shearing senses, these structures also reveal interesting characteristics of formation of the C planes.En este trabajo establecemos primeramente una clasificación de los diferentes criterios para la deducción del sentido de movimiento en espejos de fricción, obteniendo así una guía práctica de utilización en el campo o en el laboratorio, inexistente hasta ahora. En segundo lugar, aplicamos algunos de estos criterios a los planos de cizallamiento C de los granitos deformados de la Sierra de San Vicente. Estas estructuras planares en granitos, que hasta ahora no se habían empleado en estudios de espejos de fricción, resultan muy útiles para comprobar y/o proponer criterios, ya que sus sentidos de movimiento se conocen en nuestra zona por investigaciones anteriores (Doblas et al., 1983, Doblas 1985). Una innovación que aportamos aquí, es la utilización del microscopio electrónico de barrido para el estudio de estas estructuras. Las estructuras observadas en los planos C, además de indicarnos el sentido del movimiento, revelan también interesantes características genéticas de los mismos

El empresario y los negocios en las pantallas

LA IMAGEN DE LOS NEGOCIOS Y LAS FINANZAS EN EL CINE Y LA TELEVISIÓN NO TRANSMITE LAS VIRTUDES DEL EMPRESARIO, SINO MÁS BIEN ALGUNOS VICIOS ESTEREOTIPADOS DEL CAPITALIST