Geogaceta -- Nº 01, (1986)
Permanent URI for this collectionhttps://hdl.handle.net/10272/18213
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Item type: Item , Tectónica alpina y morfogénesis en el Sistema Central español: Modelo de deformación intracontinental distribuida(Sociedad Geológica de España, 1996) Vegas, Ramón; Marcos, A.; Vázquez Garrido, Juan TomásThe formation of the Spanish Central System is a adscribed to an intracontinental shear zone whose activity implies rotation of blocks within areas of intense deformation. This model of distributed deformation explains the fragmented shape of the relief and can be referred to the intraplate deformation of IberiaItem type: Item , Situación estratigráfica de los yacimientos de vertebrados del borde oeste de la depresión de Guadix-Baza (zona de Huélago y Fonelas)(Sociedad Geológica de España, 1986) Alonso Diago, María A.The use of paleontologic and sedimentologic-morfologic arguments has allow us to identify four groups of sediments with diverse chronology: —Lower Unit (Upper Ruscinian, Ruscinian-VilIafranchian limit).—Upper Unit (Villafranchian).—lncrust Glacis Sistem (Upper Pleistocene).—Watershed deposits (Upper Pleistocene, Holocene). Their geometric distribution, litology, lateral changes and relations between them give information about some aspects of the Plio-Pleistocene history in the West edge of the Guadix-Baza DepressionItem type: Item , Petrogénesis de los basaltos alcalinos de La Garrotxa, región volcánica del NE de España(Sociedad Geológica de España, 1986) López Ruiz, José; Rodríguez Badiola, E.; Cebriá Gómez, J. M.Compositional trends and trace elements abundance in leucite-basanites, nepheline basanites and olivine basalts from La Garrotxa (NE Spain region), suggest that the parental magma were originated from an homogeneous lherzolite source, strongly enriched in incompatible elements (between x15-x4 the chondritic values for the highly incompatible elements and between x5-x2 for the moderately incompatible), in which neither kaersutite, phlogopite or apatite remained as residual phases. The leucite-basanite magmas were derived by lower degrees of melting (7-10%) than the basanite s.s. and the olivine basalt magmas (13-15%). Except some primary leucite-basanites, the lavas from La Garrotxa underwent a moderate fractionation (—20%) of 01 + cpx + mg, in proportion that range between 75-40%, 55-10% and 15-0%, respectivelyItem type: Item , Nuevos datos sobre la fase de deformación sárdica. Geometría de los pliegues pre-hercínicos del río Salor (Cáceres)(Sociedad Geológica de España, 1986) Roda Querol, J.A study made over some 50 pre-hercinian folds shows how the attitude of their axes are in the NE-SW quadrants, being similar to the attitude of those of the Sardic fase known up to now in the Zona Centroibérica. The exam of their morphology, density and scale suggest a stronger intensity of that fase in the studied areaItem type: Item , Nuevo yacimiento de moluscos fósiles en el Würm de Rubí (Barcelona, España)(Sociedad Geológica de España, 1986) Abad, A.; Puisségur, J, J.; Calzada, S.We describe a new outcrop of the continental molluscs which has been found in the terrace of 10 m in Riera de Rubí. After geographical setting this fauna belongs to Würm and points to a very cold environmentItem type: Item , Notas preliminares sobre la geomorfología glaciar del Valle de Rongbuk, vertiente norte del Qomolangma (Everest). Tíbet. R. P. China(Sociedad Geológica de España, 1986) Martínez de Pisón, E.; López Martínez, Jerónimo; Nicolás, P.Five major glacial episodes are diferenciated in Rongbuk Valley along the Upper Pleistocene and Holocene, till the Little Ice Age, with the frontal morraines at 5150, 5140, 5075, 4970 and 4.700 meters over sea levelItem type: Item , Modelos arrecifales neógenos de la depresión del río Almanzora (Almería)(Sociedad Geológica de España, 1986) Dabrio, Cristino José; Polo, María DoloresTwo models of reef growth are proposed for the Neogene reefs interbedded into the siliciclastic rocks of the narrow, fault-controlled Almanzora Basin: patch reefs on activelyprograding fan deltas (e.g. Purchena and Serón) and fringing reefs on top of erosional reliefs cut down into uplifted areas of alluvial fans and/or pre-Neogene substratum (e.g. Cantoria)Item type: Item , La zona de falla de Torres Cartas, conjunto de fallas normales de bajo ángulo entre Nevado-Filábrides y Alpujárrides (Sierra Alhamilla, Béticas Orientales)(Sociedad Geológica de España, 1986) García Dueñas, V.; Martínez Martínez, J. M.; Navarro Villa, F.The Torres Cartas Fault Zone is a large low-angle extensional structure, strongly thinning the Nevado-Filabride and Alpujarride nappes. These nappe complexes form the basement of the Alboran sea southwest Sierra Alhamilla. The fault zone, being already probably active in Burdigalian times, was folded during the Upper MioceneItem type: Item , La zona de cizalla del contacto entre el grupo de mantos del Mulhacén y la unidad del Veleta (Sierra Nevada y Sierra de los Filabres, Andalucía)(Sociedad Geológica de España, 1986) Campos, J.; García Dueñas, V.; González Lodeiro, Francisco; Orozco, MiguelThe existence of an important ductil shear-zone developed in relation with the emplacement of the Mulhacen nappes group on the Veleta Unit (Betic Cordilleras) is manifested. The overlaping in the ENE sense is over 200 km implying that most of the shortening in the Nevado Filabride occurred irrespectively of the convergence between Africa and EuropeItem type: Item , La estructuración diapírica del Sector Prebético(Sociedad Geológica de España, 1986) Martínez del Olmo, W.; Leret Verdú, G.; Suárez Alba, J.The main structural features of the external and internal Prebetic domains allow its subdividion into three great areas that exhibit an increasing diapiric activity from NNW to SSE. The amount of diapiric structurations points to a minimum final tectonic shortening and enable us to interpret the relationships between basement and its sedimentary cover over an extense area of the Betic chainItem type: Item , Grandes fallas de contracción y de extensión implicadas en el contacto entre los dominios de Alborán y Sudibérico en el arco de Gibraltar(Sociedad Geológica de España, 1986) Balanyá, Juan Carlos; García Dueñas, V.Constitutive units of Alboran and Sudiberic Domains near Gibraltar Arc are specified. The boundary between both domains results from a crustal scale westward transpressive thrust and superimposed Iow angle normal faults later developed. Thus most of the tectonic contacts presently observed are extensional in characterItem type: Item , Génesis y evolución de la fosa de la Cerdanya (Pirineos Orientales)(Sociedad Geológica de España, 1986) Roca, E.; Santanach, P.The Cerdanya basin is located at the SW end of the Tet fault, in its NW block. Its formation, during the Upper Miocene, was conditioned by dextral slip of this fault anf the normal slip of E-W trending faults that absorbed the movement of the formerItem type: Item , Forma y orientación de los enclaves negros en el Sistema Central español(Sociedad Geológica de España, 1986) Martín Escorza, CarlosOver 1453 black microgranular enclaves (EN) the spatial analysis about their axes orientations and lengths we have determined the existence of a predominant distribution: the minor axis (Z) is quasi vertical position; the greater axis (X) is subhorizontal and orientated near south. These promediate oblate EN can be made to correspond to a regional stress wich deformed the EN in plastic stateItem type: Item , Fábrica de cuarzo y cabalgamientos hacia el ENE en Sierra Nevada y Sierra de los Filabres (Cordilletas Béticas)(Sociedad Geológica de España, 1986) Orozco, MiguelFrom microstructures and quartz c-axis fabric analysis the characterization of the «Mulhacen/Veleta ductil shear zone» is made. The existence of important eastward directed thrustings predating the S-N movements is inferred. These eastward thrustings must be taken into account in any tectonic reconstruction of the Betic-Riffean OrogenItem type: Item , Evidencia de un fenómeno de autoinversión de la NMR en piroclastos de la erupción de 1985 del volcán Nevado del Ruiz (Colombia)(Sociedad Geológica de España, 1986) Carracedo, J. C.; Heller, F.; Soler, VicenteDuring the catastrophic 13 November 1985 eruption of the Nevado del Ruiz volcano (Colombia), that caused the death of 25000 people and damages assessed at US$ 300 million, several types of pyroclastics were emitted including incandescent fragments of andesitic pumice. Oriented samples collected by one of the authors (J.C.C.) from pumice fragments embedded in the ground due to the force of impact contradict one of the fundamental principles of palaeomagnetism that states that the direction of natural remanent magnetization (NRM) is acquired paralel to the applied field. Indeed, these pumice samples carry a stable NRM, but antiparallel to the present geomagnetic field. This fact has been shown to be due to a phenomenon of self-reversal that controls the process of NRM acquisition and is recorded for the first time on this occasion and reproduced in thermal experiments in the laboratoryItem type: Item , Estudio comparativo de los cuerpos intrusivos básicos asociados a los materiales de edad triásica de los dominios Subbético y Nevado-Filábride del sector Centro-Oriental de las cordilleras béticas(Sociedad Geológica de España, 1986) Muñoz, M.The basic intrusive bodies, from both Subbetic and Nevado-FiIábride domains, display analogous geological and petrographic features, as well as Ti, Zr, Y, Nb, trace elements content. All these aspects point to an alkaline intraplate magmatism, that can be related to a continental, tensional transcurrent zoneItem type: Item , Depositional sedimentary controls on sepiolite occurrence in Paracuellos de Jarama, Madrid basin(Sociedad Geológica de España, 1986) Calvo, J. Pedro; Alonso Zarza, Ana María; García del Cura, María AngelesLa presencia de sepiolita en los sedimentos neógenos (Aragoniense medio y superior) aparece ligada a paleoambientes de orla distal en abanicos aluviales. Dentro de ellos la formación de sepiolita tuvo lugar en charcas de carácter más o menos perenne próximas al borde de un lago salino, así como a cuerpos de agua desarrollados en la orla en momentos de retrogradación o estabilización relativa de Ios abanicos. Un último ambiente de formación de sepiolita son los perfiles de calcreta que aparecen ampliamente desarrollados en estas zonas distales del sistema aluvialItem type: Item , Caracterización de las arcillas por el método del azul de metileno(Sociedad Geológica de España, 1986) Fernández Calvo, C.; Martínez Bueno, G.; Páez Martínez, J.This is a simple method for caracterisation of clays in soils and its relation with consistency limits. It has been checked by X-ray diffraction analysisItem type: Item , Aplicación de técnicas paleomagnéticas de corto período a la datación del volcanismo subhistórico de la isla de Tenerife(Sociedad Geológica de España, 1986) Soler, Vicente; Carracedo, J. C.The use of short period palaeomagnetic techniques (secular variation and palaeointensities) in studying the recent volcanism of the Canary Islands has permitted us to date seven volcanic eruptions which happened in the last 2000 years in Tenerife. With these dates and the historical records we have been able to define three cycles of activity in the dorsal of Teno-Pico Viejo, clearly the most active of the island during this period