Geogaceta -- Nº 10, (1991)

Permanent URI for this collectionhttps://hdl.handle.net/10272/14918

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Zonación magnética y caracterización del elipsoide de la susceptibilidad magnética en el plutón de Posets (Pirineos centrales)
(Sociedad Geológica de España, 1991) García Maiztegi, C.; Aranguren, A.; Tubía, José María
This work deals with the magnetic susceptibility and anisotropy of the Variscan Posets pluton in the Central Pyrenees. Magnetic susceptibility values provide a concentric zoning. The measurements of the magnetic anisotropy show the existence ofa N110º E trending band which can be interpreted as a magmatic fault
Un ejemplo de paleocaverna con relleno calizo brechoide (Punta Arenillas, Albiense inferior, Cantabria)
(Sociedad Geológica de España, 1991) Rosales, Idoia; Fernández Mendiola, Pedro Ángel; García Mondéjar, Joaquín
The Lower Albian pimacle platform of Arenillas in Castro-Urdiales (Cantabria, northern Spain) shows a paleocavern about 120 m long and 40 m high, whose base is 60 m below an unconformity. This vadose structure is infilled with breccia clasts up to 4 m long which have terrigenous matrix in the Iower part and carbonate matrix in the upper-central part. The paleo-cavern was formed during a phase of subaerial exposure, and was filled from local and external sources during the ensuing marine transgression
Una rampa carbonatada con fases de emersión y excavación de paleocañones (Calcarenitas de Peñalba, Albiense inferior, Bizkaia)
(Sociedad Geológica de España, 1991) Aranburu Artano, Arantza; Fernández Mendiola, Pedro Ángel; García Mondéjar, Joaquín
The architecture and vertical evolution of facies in the Peñalba Calcarenitic ramp (Bizkaia) suggest several phases of emersion. These were coeval with the formation of incised canyons which were later filled with mass-gravity deposits and autochthonous marls. Proximal ramp facies display paleokarst features, whereas distal ramp sediments are more terrigenous and show most of the incised erosions.
Tratamiento de Ias cimentaciones. Consideraciones alrededor de un ensayo de inyecciones. Presa de Las Portas. España
(Sociedad Geológica de España, 1991) Foyo, A.; Tomillo, C.
The difficulties to obtain the groutability of slate rocks in Large Dams foundations are shown through the grouting test realised in Las Portas Dam foundation. The use of high pressures, over the Critical Permeability Pressure, produces the cement absorption under Hydraulic Fracturing conditions.
Synchysita en las carbonatitas de la Pta. del Peñón Blanco, Fuerteventura, Islas Canarias
(Sociedad Geológica de España, 1991) Ahijado, A.; Palacios Medrano, Teodoro
Synchisite, a REE-fluorocarbonate, appears in a carbonatitic vein located in Pta del Peñon Blanco, Fuerteventura. This mineral is interpreted as the result of the action of carbonated water over REE-fluorapatite.
Superposición de estructuras hercinianas en el sector de Buitrago-Somosierra (Sierra del Guadarrama, Sistema Central)
(Sociedad Geológica de España, 1991) Azor, A.; González Lodeiro, Francisco; Martín Parra, L. M.; Villar Alonso, P.
The Preordovician rocks of the Buitrago-Somosierra area have undergone three penetrative phases of Hercynian deformation. The phases 1 & 2 are of tangential character, F1 probably generates a recumbent syncline Eastern vergence, whereas F2 generates a subhorizontal ductile shear zone of SE sense of movement. F3 is a tight backfolding. Subsequently, ductile-brittle fracturation and subvertical folding take place
Sobre la posición estratigráfica de Perisphinctes wartae Bukowski y el desarrollo de la Subbiozona Rotoides (Biozona Transversarium, Oxfordiense Medio) en la Cordillera Ibérica Nororiental
(Sociedad Geológica de España, 1991) Meléndez Hevia, Guillermo; Fontana, B.
The new, recently defined biostratigraphic unit Rotoides Subzone has been widely recognised throughout the Iberian Chain (E. Spain) and characterized by means of successive representatives of Oxfordian ammonite genus Perisphinctes. The classically misinterpreted species Perisphinctes wartae BUKOWSKI has been morphologically characterized and replaced at his right stratigraphic position, within this subzone. Another classically misplaced species, Perisphinctes rotoides Ronchadze is also localized, at the top of subzone. The possible subdivision of Rotoides Subzone into biohorizons is discussed.
Significado estratigráfico de dos alteraciones en el Mioceno superior de la Cuenca del Duero
(Sociedad Geológica de España, 1991) Armenteros, Ildefonso
Analysis was made of two alterations located within and on the top of the Late Miocene in the central-eastern region of the Duero Basin. Questions arising about their stratigraphic significance are also approached. The lower alteration affects the top of the marly-gypsiferous unit (U. 3) and is related to major paleogeographic change towards less evaporitic conditions. The upper alteration defines the upper boundary of Neogene record in the basin and is related to the extensive Plio-Pleistocene pediment, which bevels the Neogene serie from the borders to the centre of the basin
Secuencia estratigráfica y análisis de facies del Mioceno entre Elche y Crevillente (Cordilleras Béticas. Alicante)
(Sociedad Geológica de España, 1991) Domenech Morante, C.; Soria Juan, A.
The materials from Miocene age which appeared in this area are attributed to the so-ca/led «post-manto» materials. Those materials form a calcareous series with more detritical parts generated in the zone comprehended between the continent and the shallow platfform. Sub-environments are very well represented in a sequence which includes four tecto-sedimentary units
Regionalización de la precipitación en el País Vasco: Aplicación del modelo de análisis regional de lluvias
(Sociedad Geológica de España, 1991) García Muñiz, J.; Antiguedad Auzmendi, Iñaki; Llamas Siendones, J.
The heterogeneity of the rainfall in a region is known, which lets distinguish different zones by their rainfall characteristics. In the Basque Country two zones can be distinguished: the Cantabric and the Mediterranean versant. This work shows the rainfall regionalization applied to the Basque Country. lt has been made using the Rainfall Regional Analysis (Llamas, 1986). In order to do it we have grouped the rainfall in events. The importance of these events, in number and intensity, let establish homogeneous periods in the year, twelve, and different zones in a region, two zones: the Cantabric and the Mediterranean versant
Rasgos erosivos y deposicionales en la zona proximal de un «Slope-Apron» carbonatado del Paleoceno Inferior (Eibar, Cuenca vasca)
(Sociedad Geológica de España, 1991) Baceta, Juan Ignacio; Pujalte, Victoriano; Orue Etxebarria, Xabier
An 1.5 km wide section of the proximal part of a Paleocene carbonate slope-apron system has been reconstructed through the correlation of 10 columnar sections. lt is oriented perpendicular to the general paleocurrents and offers, therefore, a transversal view of the system. On this basis, the magnitude of the erosional surfaces bounding depositional sequences is demonstrated to be closely related to that of the levels falls that promoted them. However, the vertical and lateral arrangement of the constituent facies are controlled in many cases by autocyclic processes
Primeros datos sobre la fauna de roedores del yacimiento Pleistoceno de Plines-l (Cuenca de Granada, Cordilleras Béticas)
(Sociedad Geológica de España, 1991) Ruiz Bustos, A.
Contributions from the Plines-1 site aid in increasing what little information is available on lower Pleistocene small vertebrate fauna from the Granada Basin. A new species, Castillomys plinensis nov. sp. is defined
Pautas de distribución de Sr/Ca, Mg/Ca y Mn/Fe en carbonatos urgonianos del oeste de Vizcaya (España)
(Sociedad Geológica de España, 1991) Yusta, Iñaki; Herrero, J. M.; Velasco, Francisco
The distribution patterns of Ca, Si, Sr, Mn, Mg and Fe in Urgonian carbonate rocks from NW Biscay (Spain) reveals the differences between shallow-water (270 ppm Sr, 62 ppm Mn) and deepwater (820 ppm Sr, 116 ppm Mn) limestones. Freshwater diagenesis is responsible for the depletion in molar Sr/Ca ratios (0,034 x 10-2 in platform carbonates). Some facies show diagenetic-hydrothermal dolomitization and Zn-Pb enrichment. Ferroan and calcian dolomites have low Sr and Mn contents.
Paragénesis metamórficas de contacto en xenolitos de la granodiorita de Los Pedroches (Córdoba, España): evidencia de emplazamiento a alta temperatura
(Sociedad Geológica de España, 1991) Donaire Romero, Teodosio; Pascual Martínez, Emilio
Xenoliths in Los Pedroches granodiorite (Centra/ Iberian Zone, Iberian Massif, Spain) are described. From high-grade metamorphic assemblages containing spinel + corundum + cordierite ± simillimanite, an emplacement temperature of about 8000 C is suggested for granodiorite
Oxygen Isotopic data for the early and late diagenetic chert in carbonate turbidites (Upper Cretaceous), Northeast Bilbao, Spain
(Sociedad Geológica de España, 1991) Elorza, Javier; Fallick, A. E.
Se han obtenido los valores de ô18 0 (SMOW) de dos tipos de sílex (temprano y tardío) presentes en las turbiditas carbonatadas de la Formación Plencia (Cuenca Vasco Cantábrica). El sílex temprano tiene unos valores medios de 29.3 ± 0/45 0/00 mientras que el sflex tardío alcanza 28.3 ± 0/37 0/00 (n=5). A partir de la expresión de Kita et al. (7 985) sugerimos que el sflex temprano fue formado a una tQ entre 45-55Q C, según los valores ô18 0 (1-120) = 0± 1 0/00 , y que el tardío supera en unos 52 C tal temperatura, considerando semejante la composición de los fluidos intersticiales
Modelos y evolución espacio-temporal de las asociaciones de facies sedimentarias presentes en la Serie Westfaliense del borde meridional de la Cuenca Carbonífera Central de Asturias (Zona Cantábrica)
(Sociedad Geológica de España, 1991) Barba Regidor, E J.
The Sedimentary Facies Associations in the Meridional Border ofthe Central Coal Basin of Asturias (Cantabrian Zone, NW Spain) are characterized. Vertical and lateral distribution of these Facies Associations is also studied. The southward evolution of the sedimentary environments is stressed by the cuneiform character of the mixed (lutitic and carbonate) platform and by the fan-deltaic deposits
Mecanismos de evolución magmática en los diques microdioríticos de la sierra de Guadarrama
(Sociedad Geológica de España, 1991) Huertas, María José; Ancochea, Eumenio
In the Central System of Spain outcrop several dyke swarms of late-hercynian age. They are mainly composed by granitic porphyry and microdioritic dykes. The last one, when globaly considered, show scattering in the contents of most of the major and trace elements. When we study the individual microdioritic swarms, it can be observed that they exhibit more defined compositional and evolutionary trends. These trends are diferent from one microdioritic swarm to another. The variations can be justified by different crystal fractionation models and reflect heterogeneities in the source or differences on the melting process
Los primeros mamíferos ramblienses (Mioceno inferior) de la Cuenca de Almazán (Zaragoza)
(Sociedad Geológica de España, 1991) Cuenca Bescós, G.
One new locality in the continental deposits of Almazán Basin is studied. The Rodentia fauna: Eucricetodon aff. aquitanicus, Pseudodryomys simplicidens, Peridyromys murinus y Heteroxerus rubricati is characteristc of the Z local Zone of the Ramblian (Lower Miocene). Also several Lagomorpha, Lipotyphla and Artiodactyla indeterminados have been found
Los ciclos sedimentarios del Eoceno medio y superior en el sector NE de la depresión del Ebro (zona de Bergas-Vic). Caracterización de sus Iímites
(Sociedad Geológica de España, 1991) Mató, E.; Saula, E.
In the middle and upper Eocene strata of the South Pyrenean foreland basin, three sedimentary cicles have been distinguished. These cycles are bounded by angular uncorfirmities, each cycle being related to the development of a particular thrust system. The stiking of the thrust systems is recorded by rhe angular uncorformities that bound the cycles
Litoestratigrafía del Jurásico de Gipuzkoa y NW de Navarra
(Sociedad Geológica de España, 1991) Garmendia, J. M.; Robles, Sergio
Lithostratigraphic correlation of numerous sequences leads to the reconstruction of the mesoscale depositional geometries of the Jurassic succession of the eastern part of the Basque-Cantabrian Basin (Gipuzkoa and Navarra provinces). In all studied sections, the Lias shows similar thickness and limited facies changes; the Dogger-Malm succession reveals the initial development of swells and troughs triggered by differential subsidence, and a significant facies changes; both of these features are even more marked on the latest Jurassic-Neocomian succession. lt is concluded, therefore, that the Jurassic evolution of the area was controlled by tectonics of increasing intensity, in addition to eustatism

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