Título / Autor(es)Página(s)
 Origen de las simas de Partagat (Sierra de Aitana, Alicante) /
 Caracterización geológica de los afloramientos de El Pimpollar, extremo nororiental de la Zona Surportuguesa /
[R]Plegamiento recumbente en las Serra do Galiñeiro (Pontevedra, NO España) / Díez Fernández, R. / Martínez Catalán, J.R. / Abati, J.
Three main deformation phases(D1, D2 and D3), has been made with the down-plunge method, for the folds related to each phase. In order to apply this technique, the fold axis orientation has been calculated from the structural data collected. The results of this research prove the existence of recumbent folds in the southern part of the Malpica-Tui Unit, and the presence of a stretching lineation related to the main foliation and the recumbent folds, and clearly oblique to their axes.
 Historia del levantamiento tectónico de la Sierra de Cameros (Cordillera Ibérica, España): restricciones en base a cronología mediante huellas de fisión y (U-Th)/He en apatitos / Río, P. Del / Barbero, L. / Stuart, F.7-10
[R]Tensor actual de esfuerzos y fallas potencialmente activas en el Domo del Tormes (NO de Iberia) / Antón, L. / Vicente, G. De
Located in the NW of the Iberian Peninsula, the Domo del Tormes is an intra-plate granitic domain made up of a Hercynian megastructure and traditionally considered of very low or null seismicity. The geology of the area makes difficult to determine the recent deformations and the characterization of neotectonic activity. The data compilation and further discussion of seismic activity in the area provide inforamtion on present day stress tensor orientation and the match of gravimetry, geological and structural data revealed a series of main anomalies related to faulting on a regional scales, faulting some potentially active structures in the area.
[R]Secuencia de cabalgamientos en la Zona Sub-Atlásica y cuenca de Ouarzazate; borde sur del Alto Atlas (Marruecos) / Tesón, E. / Teixell, A.
The Sub-Atlas thrust belt and Ouarzazate basin constitutes the best and almost the unique synorogenic record of the Atlas mountain building. During the Eocene and Oligocene the deformation migrated foreleandwards when complex thrust sequences created the Sub-Atlas foreland fold and thrust belt. Thrusting took place up to Pliocense times entraining the synorogenic sedimentary roks, locally-sourded terrigenous and lacustrine deposits.
[R]Caracterización sísmica del Anticlinorio del Bajo Segura (Alicante): Fallas del Bajo Segura, Torrevieja y San Miguel de Salinas / García-Mayodormo, J. / Martínez-Díaz, J.J.
This paper presents a seismic characterization of the most important faults of the Lower Segura Anticlinorium. Available evidence of quaternary faulting, as well as the characteristics of the seismic record in the area, are analized in order to perform an estimation of the maximun magnitude earthquake and mena recurrence period for each of the faults. These results can be used in probabilistics seismic azar calculations.
[R]Neotectónica en el norte de Galicia: Fallas inversas de actividad cuaternaria en la cuenca fluvial del alveolo de Alfoz, Lugo / Rodríguez García, A. / Quintana, L. / González Menéndez, L. / Suárez Rodríguez, A.
In the weathered depression developed on the A Toxiza variscan granite (northern Galicia) two high angle reverse faults have been located putting the granitic basement over pleistocene fluvial deposits. Several inferred folds are probably related to these NW-SE faults. The location of another reverse fault affecting the granite basement further to the NW allow us to correlate all these faults wth a major fault system of NW-SE strike known for its recent seismogenic activity in the cantabrian domain. Our results on the anlysis of the faults establish an important reverse component in contrast with the normal component calculated for the NW-Se faults of nothern Galicia from seismic data and fault population analysis in previous works.
[R]Estudio geométrico comparativo de pliegues asociados a la propagación y terminación lateral de cabalgamientos / Mantero, E.M. / Fernández, C. / Alonso-Chaves, F.M.
This work examines the geometry of two examples of fault-propagation folds related to the lateral termination of thrusts. Inspite of thier differences in age (Variscan and Alpine) and composition of the involved rocks (metamorphic or sedimentary), the geometry of the resulting folds is quite similar, indicating that are universal the mechanisms responsible for these structures.
[R]Desarrollo simultáneo de pliegues, esquistosidad y cabalgamientos en el Eoceno inferior de Isaba (Valle del Roncal, Pirineo navarro) / Gil, A. / Simón, J.L. / Pueyo, O. / Millán, H. / Pocoví, A. / Andrés, J.A.
Geometric and kinematic analysis of Pyrenean folds, cleavage and thrusts is carried out in several exceptional outcrops of the Eocene flysch at Isaba (Navarra, Spain). Distribution, orientation and cross-cut relationships between these structures suggest that they are roughly coeval and co-genetic, the total deformation being distributed into different ductile and brittle mechanisms. The footwall of the Sierra de Arrigorrieta thrust shows a set of harmonic folds with axial-plane cleavage; an overall flattening Ö l2/Ö l1 =0, 7-0, 85 has been estimated from their profile-section geometry. The structural position and the presence of some cuspatelobate folds (mullions) in turbidite levels suggest an early deformation even previous to the Larra thrust system.
[R]La transversal de Gavarnie-Guara. Estructura y edad de los mantos de Barnie, Guarga (Pirineo centro-occidental / Millán Garrido, H. / Oliva Urcia, B. / Pocoví Juan, A.
The estructure of the eastern extreme of the Jaca Basin is defined by the Gavarnie, Guara-Gèdre and Guarga thrust sheets. The Guara-Gèdre thrust was active during mid Luttetian-earliest Chattian and the Gavarnie thrust, that results from the inversion of a normal fault, developed at least from early Bartonian to mid Rupelin. During the latter, the southward translation of the cover rocks occurred along parallel detachment horizons located at Lower Eocene and Triassic incompetent levels. The movement of the Guarga thrust gave rise to both the reactivation of old structures in the External Sierras, previously originated by the Guara-Gèdre thrust, and the formation of new ones. Along the studied transect the Guarga thrust sheet evolved from early Chattian to Aquitanian times, consumed ~ 5 km of horizontal shortening, and in the Jaca Basin produced a tectonic uplift not smaller than o km. The latter is interpreted to be partially related with a significant amount of Alpine ductile shortening of the basement allochthonous units. Comparison of the translation values of the Guara-Gèdre and the Guarga thrusts betwen the Ansó and Gavarnie-Guara transects indicate that the tranlation related to the Guara-Gédre thrust decreases westward whereas the one associated to the Guarga thrust decreases eastward.
[R]Propuesta de clasificación geotécnica del "Efecto Sitio" (Amplificación Sísmica) de las formaciones geológicas de la Región de Murcia / Tsige, M / García Flórez, I
In this paper a geotechnical-siesmic amplification classification based on geological data is proposed for the Murcia region, (SE Spain). The structural damages caused during earthquake are controlled by local geological condition specially surface geology condiitions and topography. The presence of some kind of soil type cold produce increase in the intensity as a consequence of seimsic wave amplification. The factor of amplification which can duplicate or triplicate the seismic waves is directly related to the geotechnical (dynamic) properties of geological materials. Regarding this fact, we have carried out geotecnical classification of the geological materials, in order to see their possible contribution to this local ground amplification. Acccording to his classification the amplification effect in the earthquake area varies from nil, where bedrock is exosed to high where Plio-Quaternary fluvial an alluvial sediments are present.
[R]Clasificación geomecánica de macizos pizarrosoo en el sinclinal de Truchas / Rodríguez Sastre, M.A.
Rock mass characterization and classification are significant in geological investigations involving enginering works and in the field of applied geology. Discontinuities characterization and rock properties determination are essential within the intended engineering work type. An outcrop of the metamorphic rocks from Casio Formation at The Truchas Syncline has been the target of this investigation. The most widely used rock mass classification systems are the Rock Mass Quality Index (Q system) and the Geomechanics Classification (RMR) and amore recently the SRC system and those were applied in this site of investigation. Fair rock with a III RMR class has been described for this outcrop under investigation while Q rock mass clasification is set between very poor and poor in that site. In addition the SRC classification provide a class V rock mass.
[R]Influencia de la orientación de la anisotropía en el desarrollo de shear bands: estudio experimental / Gómez-Rivas, E. / Griera, A. / Carreras, J. / Druguet, E.
Shear bands are geologic structures widely used as kinematic indicators. Despite the large amount of studies about these structures, their mechanical development is not yet well known. This work presents an experimental study of shear band localization and evolution under coaxial deformation. Particular attention is given to the influence of the obliquity of anisotropy planes on the orientation of shear bands. During deformation, two conjugate sets of shear bands develop symmetrically for models with layers parallel to the extension axis, while for oblique orientations one set dominates. Anisotropy planes have a strong influence on the local stress field around conjugate fracture systems, which deviates from the applied boundary conditions.
[R]Resultados y experiencias de aplicación del métodos de Refracción por Microtremor (Sísmica Pasiva) para la investigación geofísica de las nuevas líneas de metro en Madrid (España) / Muñoz Martín, A. / Carbó Gorosabel, A.
Geophysical exploration with seismic methods in urban zones presents several disadvantages: the presence of numerous sources of seismic noise, the scanty penetration when the seismic source is a hammer and the disability to detect buried low-velocity beds. Recently (Louie, 2001) a new method of seismic investigation has been developed, which allows vertical modeling of Raleygh waves from spectral analysis (Vphase/frequency) using the seismic signal registered with conventional seismographs and geophones. This method allows to detect low-velocity buried beds, of great interest in tunneling, and to reach depths below 50 meters. In this work we discuss the conditions of application and experiences obtained during the 2005 geophysical surveys carried out in Madrid before the excavation of the new subway tunnels.
[R]Mapa de esfuerzos de Europa a partir de Mecanismos Focales calculados desde el Tensor de Momento Sísmico / Olaiz, A. / De Vicente, G. / Muñoz Martín, A. / Vegas, R.
This work shows a new stress map for Europe obtained from the inversion of earthquakes focal mechanisms calculated with the centroid tensor method (Dzieownski et al., 1982). An amount of 1608 focal mechanisms have been selected with several quality criteria from different catalogues (CMT Harvard, ETH, Med-Net, I.G.N. And I.A.G.) from 1973 to present-day. Values for the maximum horizontal stress and the shape factor of the ellipsoid (horizontal/vertical stress) have been calculated following the Reches (1983) and De Vicente (1988) slip model. The local results have been interpolated to a 1ºx1º regular grid in which the relation between tectonic horizontal stress and vertical load has been taken into account. The final map shows a good correlation with the primary tectonic forces generated in the plate boundaries and the local perturbations related with main crustal heterogeneities as suggested by Gölke and Coblentz (1996).
[R]Estado actual de esfuerzos en Béticas y Alborán a partir del análisis de "breakuts" / Fernández-Ibáñez, F. / Soto, J.i. / Zoback, M.D.
Logging data from several onshore and offshore deep wells located at the South-Iberian Margin were selected to perform breakout anlysis. Every data used to determine the orientation of breakouts come from magnetically oriented four-arm caliper which is part of the dipmeter logging tool. Most of the wells were drilled through Plio-Quaternary and late Miocene sediments, in cases reaching the metamorphic basement. Breakouts zones have been recognized in 6 wells; in depths up to 3000 m. Mean orientation and standard deviation of breakouts at each well have been used to assess the borehole quality following ranking criteria of the World Stress Map (WSM). From the well data set anlyzed, three wells are considered as reliable stress indicators to characterize the present-day stress field throughout the margin (Andalucía A-1, Andalucía G-1, and Bética 18-1). The rest must be interpreted with caution because of the sparse number of breakotus. Stress inversion performed in these wells evidences that maximum horizontal stress (S Hmax tend to parallel coast strike, resulting in a roughly E-W orientation along the northern margin of the Alboran Sea.
[R]Valores de subsidencia reciente (Pioceno-Cuaternario) en el Mar de Alborán mediante análisis de "bakstripping" / Martínez-García, P. / Soto, J.I.
A backstripping analysis is presented for the different scientific ODP wells in the Alboran sea (Leg 161, Holes 976B, 978A, and 979A). The study has been performed for the complete Pliocene-to-Quaternary sedimentary sequence, based on the detailed paleontological dataset available in these wells. Logging data together with in-situ determinations of porosity and density have been fitted to obtain robust subsidence pattern shows a remarkable coincidence in all the wells (Y0310-355 m) equivalent to a subsidence rate of 0, 06-0.07 mm/y for the last 5.1 Ma. In regions where a significant intra-Pliocenen hiatus (2.2-5.0 Ma) ocurred, like the Site 976-basement high in the West Alboran Basin or the Alboran Ridge, we infer the existence of a major tectonic pulse wiht high subsidence rates (2.2-5.0mm/) that diminished towards the Quaternaty (0.07-0.11 mm/y). According to these results, the stimated stretching factor (b; )for this basin is 1.35-1.42.
[R]Un protocolo de tratamiento estadístico para muestras polifásicas de lineaciones de disolución / Simón Gómez, J.L.
Accurate analysis of orientations of linear elements from polyphase populations involves computing statistics (mean, standard deviation) of each sub-population, which needs previous identification of the polymodal character and separation of sub-samples. The procedure here proposed for a regional study involves: (a) distinguishing polyphase from monophase samples; (b) characterizing mean and deviation of clearly monophase populations; (c) separating poliphase samples into sub-samples using density diagrams in equal-area projection and standard deviation values; (d) applying a correpondence test based upon the 95% confidence cone, as well as an equality F-test for directional samples, by comparison with monophase reference samples. An example of application of this procedure to pressure-solution lineations in carbonate pebbles of the Aliaga Tertiary basin (Teruel, Iberian Chain) is shown.
[R]Caracterización morfo-estructural del Borde occidental de Sierra De Gádor (Cordillera Bética) / Fernández-Ibáñez, F. / Pérez Peña, J.V. / Azañón, J.M. / González-Lodeiro, F.
An integrated geomorphic and structural study has been performed along the western border of Sierra de Gádor (Betic Cordillera, SE spain). To do this, we have calculated some of the most reliable geomorphic indexes for tectonic activity (mountain-front sinuosity, Smf; asymmetry factor, AF; and stream-length index, SL) combined with a slope analysis. Field observations evidence that most of the topographic scarps that characterize the western termination of Sierra de Gádor match with a NW-SE trending normal fault system. These normal faults dip to the West and, in cases, affect Quaternaty alluvial deposits. Values of SL ad AF indexes applied to the Cástal stream catchment are suggest a westwards tilting of this side of Sierra de Gádor. Thus, estructural and geomorphologic data coincide and suggest that western Sierrra de Gádor orography is mainly influenced by NW-SE high-angle normal fauls with very recent activity.
[R]Procesos neotectónicos en los depósitos de rasa de la zona de Canero (Occidente de Asturias) / Gutiérrez Claverol, M. / López Fernández, C. / Alonso, J.L.
The Pleistocene sediments deposited on the emerged marine abrasion platform near Canero village (Valdés, Asturias) are truncated by reverse faults which are parallel to basement bedding. These structures imply a neotectonic activity with a NW-SE maximum compressive stress, consistent with recent fault population analysis and current seismicity studies. The described deformation corresponds to a reactivation of folds in the Palaeozoic basement through a flexural slip mechanism, with the subsequent accommodation of the unconformable Pleistocene cover.
[R]Primeros resultados de huellas de fisión en apatito en el sector Lugo-Ancares (Noroeste de la Península Ibérica) / Martín-González, F. / Capote, R. / Barbero, L. / Insua, J.M. / Martínez-Díaz, J.J.
The Northwest of the Iberian Peninsula is characterised by the absence of Mesozoic sedimentary deposits, the Cenozoic sediments being scarce. Due to that, the chronology of the geological events in the area is difficult to establish. Nevertheless, in the absence of deposits during a certain time span, the thermal history a particular are during that time-elapse could have been recorded in previous materials. Modelling of the apatite fission-track (AFT)data is a powerful tool to infer geological information in this kind of regions. The tectonothermal history observed in the AFT models beging with the intrusion of the late Variscan granitic plutons and their cooling in the upper crustal levels. After this initial event, three main episodes have been identified. The first involves and important heating during the Upper Jurassic and Earlier Cretaceous, which can be related to the evolution of the Atlantic passive margin. The second heating episode can be connected to the begining of the Europe-Africa collision during the Upper Cretaceous and the Earlier Palaeogene. Finally, a cooling episode is observed during the Paleogene, which can reflect exuhumation processes according with the tectonic structures and the development of the present day topography.
[R]Magma flow directions in Azores basaltic dykes from AMS data: preliminary results from Corvo island / Pueyo Anchuela, Ó. / Gil, A. / Lago, M. / França, Z. / Galé, C.
Se presenta el estudio preliminar de flujo ígneo en diques basálticos de la isla de Corvo, (Azores), usando la técnica de la Anisotroía de la Susceptibilidad Magnética (ASM). Las muestras proceden de un total de 5 diques con unaorientación varaible N-S a NE-SO. Uno de los diques se localiza en la zona central ce la cladera volcánica y el resto en la sector meridional de la isla. Todos los diques muestran una fábrica magnética normal determinada por la orientación preferente de cristales de mangetita y caracterizada por una foliación magnética paralela a las paredes. Para el dique localizado en la caldera volcánica, la lineación magnética, en posición vertical, contrasta con la lineación horizontal obtenida en el resto de las estaciones. Esto resultados son compatilbes con un modulo de emplazamiento caracterizado por un flujo vertical del magma en la zona central del complejo volcáncio que gradualmente se horizontaliza en las zonas distales del complejo.
[R]Geochemistry of alkaline basals of Corvo Island (Azores, Portugal): preliminary data / França, Z. / Lago, M. / Nunes, J.C. / Galé, C. / Forjaz, V.H. / Pueyo, O. / Arranz, E.
El vulcanismo de la isla de Corvo (Azores Occidentales, Portugal) comprende diversos episodios eruptivos, desde 1.5 a 1.0 Ma. Los líquidos son mayoritariamente basaltos con una composición modal de olivino, Ti-augita, plagioclasa y Ti-magnetita, existiendo una variedad de litotipos petrográficos según la proporción modal de las fases mayoritarias. La composición geoquímica corresponde a magmas de tipo OIAB, con una fuente mantélica enriquecida próxima a HIMU de origen astenosférico.
[R]Composición y evolución de las lavas de la isla de Branco (Cabo Verde) / Brändle, J.L. / Hernán, F. / Huertas, M.J. / Ancochea, E.
The first data about the composition of lava flows from Branco Island (Cabo Verde) are presented in this work. Most lava flows in the sequence are alkali basalts (Fo84-76 olivine, En44-36 diopside, An83-31plagioclase) showing geochemical affinity of typical ocean island basalts. The scarce most evolved members are mugearites (olivine absent, En41-31 clinopyroxene, An51-26 plagioclase, and kaersutite). The compositional variations between both the types are explained by crystal fractionation and extraction of pyroxene (up to 29%) and lesser proportions of olivien and FE and Ti oxides (Cpx: 75; Ol: 21; OxFe Ti: 4). The transition to mugearites from the most evolved basalts would mainly be due to extraction of pryoxene (24%) and Fe and Ti oxides (Cpx: 68; Ol: 3; Plag: 5; OxFeTi: 30).
[R]El edificio Antiguo de la isla de San Vicente (Cabo Verde): características del sector occidental / Huertas, M.J. / Hernán, F. / Ancochea, E. / Brändle
A more than 1000m thick pile of basaltic lava flows and pyroclasts dipping seawards rises on the western sector of San Vicente. Several systems of dikes cut across the succession that is composed of two different sequences. The lower sequence (Lazareto Formation), about 400 m thick, is formed mainly by pahoe-hoe, frequently ankaramitic, basalt lavas and some breccias intercalated. This sequence is exposed in small hill and low rounded ridges of gentle slopes. The upper sequence (Monte Cara Formation), some 700 m thick, consisting in individually thicker basaltick lava flows with typical scoria levels is well exposed in high scarps. Numerous subvertical dikes cross the enire succession. The dikes vary increasingly their strike from south to north. Frequent sills (one every 3-5 m) also intrude the lower sequence. The distribution of the lava flow dip stikes as well as the dike srikes suggests that the succession as a whole was part of a central volcanic edifice, 16-20 km in diameter and 1600-2000m high, would have extended off the present coast. According to the radiometric ages obtained the volcano built up between 6, 1 Ma and 4, 6 Ma with maximum activity concentrated between 5, 5 and 5 Ma.
[R]Aplicaciones geotermobarométricas de los contenidos en elementos trazas de minerales granulíticos: Zr en rutilo y HREE en granate de los xenolitos félsicos de la corteza inferior del Sistema Central Español / Villaseca, C. / Orejana, D.
Geothermobarometric estimations based on the trace element concentration of minerals from lower crustal peraluminous felsic granulite xenoliths from the Spanish Central System (SCS) have been performed. Zr in rutile thermometry (Zack et al., 2004) gives a main range of 970 to 1100ºC whereas HREE in garnet barometry (Bea et al., 1997) yieldsa pressure range of 7.2 to 9.3 kbar. These new thermobarometric data overlap previous P-T estimates based on conventional metamorphic phase equilibria. Nevertheless, the slightly higher temperature range obtained with rutile trermometry force to future revision of granulite mineral equilibria of the SCS lower crustal xenoliths.
[R]Los diques alcalinos de pórfidos monzo-sieníticos del Sistema Central Español: relación con los diques lamprofídicos acompañantes / Orejana, D. / Villaseca, C.
The alkaline monzo-syenitic porphyries from the Spanish Central System (SCS) show a heterogeneous composition ranging from basic to acid terms which give rise to major and trace element compositional trends in accordance with fractional crystallization of amphibole, plagioclase, biotite, alkaline feldspar, Timagnetite and apatite. The whole-rock geochemistry of the basic porphyries shows clear similarities with respect to the SCS isotopically enriched alkaline lamprophyres, indicating that a genetic link between both groups of dykes might exist. This relationship would problably represent an origin of the monzo-syenitic prophyries after differentiation of parental lamprophyric, magmas due to fractional crystallization.
[R]Petrología y mineralogía de los xenolitos mantélicos del volcán la Banya del Boc (Girona) / Oliveras, V. / Galán, G.
Type I mantle xenoliths enclosed in alkaline mafic lavas and pyroclastic materials from La Banya del Boc volcano are studied in order to assess the nature of the subcontinental lithospheric mantle in the Catalan area. Anhydrous spinel lherzolites and harzburgites are the dominant lithologies, but pyroxenites are also found. Amphibole as accessory mineral is occasionally observed in peridotites. Protogranular is the most characteristic texture, but peridotites also show porphyroclastic and equigranular textures. All major mineral and spinel compositions indicate depletion by partial melting in peridotites, but metasomatism is also inferred. Decreasing of jadeite component in clinopyroxene with the degree of melting suggests that this could be related to decompression and upwelling of the mantle. The pyroxenites do not follow the melting trend.
[R]Ultramilonitas de apariencia fluidad, pseudotaquilitas o algo intermedio? (Formación Bacariza, Cabo Ortegal) / Pueblles, P. / Ábalos, B. / Gil Ibarguchi, J.I.
Ocurrence of tectonites with features characteristic of both pseudotachylytes and ultramylonites formed under high-pressure granulite-facies conditions is reported in the Cabo Ortegal Complex of NW Spain. We interpret that these rocks were originated due to a seismic event at great depth (1.4 GPa) under high temperatures (740 ºC). Shear heating would have affected the still hot and mechanically rigid granulites and provoked melt formation. Ambient hight P and T would have led to subsequent recrystallization of the previously formed melt giving rise to a weak planar fabric.
[R]Secuencia de emplazameinto, alteración hidrotermal y metamorsifmo en el Complejo instrusivo de Jorn, distrito minero de Skellefte, norte de Suecia / González Roldán, M.J. / Allen, R.L. / Donaire, T. / Pascual, E
The Skellefte district is one of the most important mining districts in Sweden, located in an early Proterozoic (1.90-1.87Ga) volcanic arc province in the Baltic Shield, northern Sweden. The district consits of a complex vocanosedimentary succession formed by submarine, mainly felsic, volcanic rocks named Slellefte Group, overlain by a subaerial, felsic volcanic succession named Arvidsjaur Group and shallow- to deep-marine sedimentary rocks known as Vargfors Group (Allen et al., 1996). The Jörn Granitoid Complex (jGC) crops out at the northern boundary of the Skellefte district, and is constituted by several intrusions ranging incomposition from gabbro to granite. Some features of the JGC suggest that it is comagmatic with the volcanic rocks of the Skellefte and Arvidsjaur Group. Our recent study has revealed that earlier intrusives in the complex (GI) have significant geochemical differences with the rest of plutonic rocks in the complex (GII to GIV). Crystallization of GI was followed by intense hydrothermal alteration and late, regional contact metamorphism that do not affect the later GII to GIV facies. This sequence intime, together with the chemical contrasts between the successive Jörn facies, suggests that a significant time gap lasted between the emplacement of GI and the later plutonic rocks in the Jörn facies, suggests that a significant time gap lasted between the emplacement of GI and the later plutonic rocks in the Jörn complex. This is probably relevant to the geological history and ore research in the district, in that a major change occurred beteen GI and the rest of the JGC facies, involving changes in the geochemical character of magmatism and coeval thermal activity.
[R]Sucesión de secuencias volcánicas félsicas en el Complejo Vulcanosedimentario de la Faja Pirítica Ibérica: discriminación entre modelos volcanánicos y subvolcánicos / Donaire, T. / Pascual, E. / Valenzuela, A. / González Roldán, M.J. / Toscano, M.
A field study is presented on two selected areas in the Volcano-Sedimentary Complex (VSC) of the Iberian Pyrite Belt (IPB); the Odiel River section and the Paymogo Volcanic lineament. Field evidence has allowed to distinguish two major groups of felsic rocks, which successiviely appear in the stratigraphic column. Probably, this conclusion can be extended to other areas in the IPB. In addition, field, petrographic and geochemical evidence shows that at least the felsic rhyolitic succesión in the Odiel River (and probably also in Paymogo) formed in a volcanic, environment, favouring a volcanic-pile model in the VSC.
[R]Caracterización geológica de los afloramientos de El Pimpollar, extremo nororiental de las Zona Surportuguesa / Díez Montes, A. / Bellido, F. / Cózar, P. / Monteserín, V.
Two volcanic units can be distinguised in the "El Pimpollar" outcrop (eastern South-Portuguese Zone). The Lower Unit is composed mainly of submarine dacites and andesites, with some subordinated basalts and trachyandesites. The Upper Unit is composed of massive rhyolites, with volcano-sedimentary and volcanoclastic deposits towards the base. Radiolaritic sediments interbeded with the andesits and dacites show that these volcanic rocks extruded in a relatively deep maritne basin. The upper part and top of the Lower Volcanit Unit includes some diamictic layers related with masstransport processes. Some of these diamictic layers contain limestone pebbles and blocks with middle Visean microfossils. These sedimentary deposits mark possibly the beginning of a tectonic event that was reponsible for the destruction of a carbonate platform, and for severe changes in the tecto-sedimentary environment.
[R]Estudio petrológico y geoquímico de las bulcanitas de los afloramientos de El Pimpolar, extremo nororiental de la Zona Surportuguesa / Bellido, F. / Díez Montes, A. / Ortiz, G.
The Lower Unit of "El Pimpollar" volcanic outcrop (South-Portuguese Zone) is mainly composed of submarine dacites and andesites, with some subordinate basalts and trachyandesites. All these volcanic materials have intraplate affinities. The more basic rocks have alkaline character and show some differences with the equivalent vulcanites of the Iberian Pyrine Belt. The rhyolites of the Upper Unit are very rich in K and have geochemical characteristics intermediate between the silica rich ingenous rocks related with volcanic arcs or collisional orogens. These rhyolitic rocks are different from other volanic rocks with similar SiO2 content of the Iberian Pyrite Belt. The volanic suit has a post-Middle-Visean age and its two units extruded in differnt tectono-sedimentary environments.
[R]Estructura interna del Batolito granítico de Nisa-Alburquerque / González Menéndez, L. / Azor, A.
The late Variscan Nisa-Alburqueque batholith (SW-Iberian Peninsula) is located close to the boundary between two major geologic domains of the Iberian Massif: the Central Iberian Zone and the Ossa-Morena Zone. This baholith is made up of S-type granitic rocks with minor l-type ones. The main facies displays frequent magmatic orientations defined by the k-feldspar ± plagioclase phenocrysts. We have made six schematic cross sections perpendicular to the internal structure and to the elongated shape of the batholith. These sections show the internal structue of the batholih and the relationships between the different granitic facies. The cross-cutting relationships indicate that the general orientation was developed during the emplacement of the main granitic magma and prior to the differentiation/intrusion of the remainig between the western and central-eastern domains of th batholith: sharp contacts and fabric tightening in western domains versus sinuous contacts, magma mixing and re-intrusion of different magmas, in central-eastern domains.
[R]Modelo gravimétrico tridimensional del "stock" de Aguablanca (Badajoz) / Romeo, I. / Tejero, R. / Capote, R. / Lunar, R. / Martínez, Q,
The Aguablanca stock is located in the NE zone of the Snata Olalla Igneous Complex, in the Ossa-Morena Zone. Paleozoic rocks of the Bodonal-Cala Complex and Santa Olalla tonalites bound this gabbronorite stock. This rock hosts a Ni-Cu-EGP ore deposit. A gravity survey, Bouguer anomaly map production and 3D gravity modelling have been carried out in the area in order to investigate de Aguablanca stock geometry. The residual gravity map exhibits a gravity high related to the gabbronorite of Aguablanca, a denser rock than the surroundings, as well as to the semi-massive sulphides outcrops. As featured in the 3D density model, the Aguablanca stock has a tabular geometry subparallel to its northern limit, deeping to 1850 m. In its upper part the igneous body spreads and adopts a circular shape. The Aguablanca stock emplacement is related to a variscan ductile shear zone.
[R]Contribución del estudio estructural del enjambre de diques básicos del Precámbrico del Anti-Atlas al conocimiento de su significación geotectónica en la orogenia panafricana / Carreras, J. / Druguet, E. / Rahimi, A. / Castaño, L.M. / Griera, A. / Gómez-Rivas, E.
The Precambrian inliers in the Anti-Atlas of Morocco are extensively intruded by swarms of dolerite dykes. On the basis of detail analysis of foliation patterns around dyke from Kerdous and Zenaga inliers it is inferred that dyke emplacement wa syntectonic with the main Panafrican collisional event.
[R]Morofología de circones vs. Filiación geoquímica de rocas metavolcánicas en el Antiforme del Narcea (N de España) / Rubio-Ordónñez, A. / Cuesta, A. / Gallastegui, G. / Suárez, O. / Pupin, J.P. / Corretgé, L.G.
In the Narcea Antiform, both Ediacaran upper volcanic series and volcanic clasts in the overlying Cambrian micro-conglomerates, show geochemistry between those of calc-alkaline and alkaine series in the TAS diagram, and a mainly calc-alkaline trend in the Zr/TiO2-Nb/Y diagram. However, zircons reveal a common high temperature nature of the crystals and have overall characteristics typical of alkaline magmas. Such an apparent contradiction can be interprted as a result of a change in the tectonic conditions. This would account for the mixed characteristics of rocks having a calc-alakaline geochemical signature but with an account for the mixed characteristics of rocks having a clac-alkaline geochemical signature but with and alkaline mineal assemblage. Moreover, zircon morphology has turned out to be an interesting clue to resolve the petrographical an geochemical discrimination in low-grade metamorphosed paleovolcanic rocks.
[R]Las albititas del Paleozoico Inferior del occidente de Asturias: ¿posible fuente de leucogranitos? / García-Arias, M. / Corretgé, L.G. / Castro, A.
In the West Asturian-Leonese Zone there are some albititic beds of volcanoclastic origin interlayered in the lower part of the Serie de los Cabos, deposited in a graben-type basin during the Middle Cambrian. The serpentine cryptocrystaline masses. Melting experiments at 850ºC, 6 kbar and added 10% water conditions produce very silicic melts, with different rates of melting according to quartz percentage, but the fertility of these rocks as sources of leucogranites is very low.
[R]Estructura del granito de Beariz (Ourense, Galicia) / González Cuadra, P. / Díaz García, F. / Cuesta Fernández, A.
The geological map, cross-sections and structural analysis of the Beariz granite are presented. The Geometric and structural characteristics of this intrusive body are in good agreement with a sinkynematic emplacement within a srike-slip shear zone.
[R]Geoquímica de las micas blancas detríticas de las rocas ediacarenses y cámbricas del Antiforme del Narcea (NO España) / Abad, I. / Gutiérrez-Alonso, G. / Nieto, F. / Fernández-Suárez, J.
Detrital minerals provenance studies have become a common tool to decipher paleogeographic scenarios in many orogenic belts. Together with the geochronological single mineral dating, the geochemistry of detrital minerals can provide insights on the source rocks of the studied detrital minerals. In this paper we study the chemistry of the detrital micas from two samples of Ediacaran and Cambrian age. The obtained results provide an almost identical chemical signature for the studied detrital white micas in both samples. The fengitic vector conditions the Fe + Mg proportion with some influence of the ferrimuscovitic vector mainly in the cambrian sample. The results point towards an origin of the sediments from LP igneous or metamorphic source rocks.
[R]Primeras icnitas de dinosaurio en sur del Alto Atlas Central. Carixiense (Formación de Arhbalou. Goulmina. Marruecos / Pérez-Lorente, F. / Hadri, M. / Boutakiout, M.
The first found tracks of dinosaur in the North of the Goulmina-Tinerhir line (Inner Haut Atlas Central, Morocco) are described. They are located in the Arhbalou Formation and come from isolated and grouped prints mainly of theropod dinosaur. They have importance by the enlargement of the geographical are with dinosaur paleochnological sites and by they constitue the first dated Carixian dinosaur footprints founds in Morocco.
[R]Estudio osteométrico preliminar de los restos de ciervo (Cervus elaphus) del yacimiento paleontológico del Pleistoceno Superior de Kiputz IX (Mutriku, Gipuzkoa) / Castaños, J. / Castaños, P. / Murelada, X.
This work provide the first news about the recovered fauna from the Late Pleistocene site of Kiputz IX (Mutriku, Gipuzkoa). It describes the site stratigraphy as well as the preliminary listing of the identifed fauna furthemore of the geographic and geologic cave context. It also describes the anatomic distribution of red deer remains and its relation with the taphonomic origin, offering the osteometric description of red deer. For this purpose statistical values of the main bones are gathered to emphasize its interst as a representative pattern of this species in the Late Pleistocene.
[R]Biometría de Strombus bubonius Lamark 1791 del yacimiento de Cerro Largo (Roquetas de Mar, Almería) / Tores, T. / Ortiz, J.E. / Puche, O. / Vega de la, R. / Arribas, I.
This paper deals with a comparative metrical study of the mesogastropods Strombus busbonius and Strombus latus. The former from the raised marine deposits of Cerro Largo (Roquetas de Mar, Almería) of Middle Pleistocene age, and the second still living in the Gulf o Guinea and Cabo Verde Islands. The high correlation between length and maximum width reveals a positive allometrical relationship in fossil an living species. There is a good metrical coincidence between Cerro Largo S. Bubonius representatives and S. Latus form Cabo Verde, while S. Latus representatives form Guinea and Senegal reach larger sizes. It is postulated that a partially developed sexual dimorphism explains the co-occurrence at the same beds of small and big sized S. Bubonius shells.
[R]Nueva localidad fosilífera en el Mioceno Inferior de Bargota (Navarra) (Cuenca del Ebro, Península Ibérica) / Murelaga, X. / Almar, Y. / Beamud, B. / Larrasoaña, J.C. / Garcés, M.
In this study we report a new fossil locality found in the continental sediments of the Haro Formation. This formation is composed of palustrine, lacustrine and distal alluvial facies that represent the sedimentary filling of the west-central sector of the Ebro basin during the lower Miocene. In this paper we describe the vertebrate remains (fishes, laceritans, crocodiles, Turtles, glirids, cricetids and eomiids) found in the site of Bargota (Navarra). Based on the micromammals teeth sutdy, the new fossil locality can be planed within the Agenian biozone Y.
[R]Análisis bioestratigráfico del Eoceno Inferior de la sección de Barinatxe (Pirineos Occidentales) mediante nanofósiles calcáreos / Bernaola, G. / Nuño-Arana, Y. / Payros, A.
The Barinatxe section (Western Pyrenees) contains one of the most complete and expanded deep-water succession of the early Eocene so far described. The succession, cropped out continuously along sea cliffs, is rich in well preserved calcareous nannofossil. The calcareous nannofossil species have been identified, has allowed us to identify Zones NP10, NP11, NP12 and NP13. Furthermore, we have precisely pinpointd the succession of calcareous nannofossil biohorizons and their relative position within the planktic foraminifer zones. The calcareous nannofossil and planktic foraminifer intercalibration scheme resulted from this study does not agree with the current standard biomagnetochronologic correlations scheme. In order to corroborate or contradict our observations similar studies in sections of a wide range of latitudes and depositional environments are needed.
[R]Hallazgo de un fósil silúrico en los depósitos auríferos cenozoicos de la mina romana de Las Médulas (León, NO de España) / Gutiérrez-Marco, J.C.
A Silurian fossil has been collected from sandstone pebbles in the red Cenozoic depositis of the famous Roman gold-mine of Las Médulas. It consists on an articulated shell of the cardiolid bivalve Cardiola gibbosa Barrande, of basal Gorstian age (ludlow). This species is considered as an exotic element to the neighboring Paleozoic outcrops, being most probably reworked from an unknown area souther of the Ollo de Sapo anticlinorium. This hypothesis agrees with the recent geological reinterpretation of the gold beating units as a system of Paleogene fluvial terraces. The fossiliferous pebble is attributed to the third terrace scoured by an ancient river flowing to the NE, being progressively entrenched during the initial stages of the Alpine convergence which ends with the formation of the compressive El Bierzo Cenozoic basin.
[R]Situación medioambiental de la marisma Joyel (Cantabria): datos aportados por los foraminíferos bentónicos / Pascual, A. / Elorza Remón, M. / Martín-Rubio, M. / Rodríguez-Lázaro, J.
A total of sixty nine species of benthic foraminifiers have been identified in the Joyel-Ria of Quejo marsh (Cantabria, N Spain). Fifty six of those species had living individuals in the time of sampling. Main foraminifer assemblages change from the mouth to the head of the estuary. Thus, in the silty channels of the marsh area, the most abundant species is Ammonia tepida, while in the vegetated middle marsh area is composed by Ammonia tepida, Cribroelphidium williamsoni, Haynesina germanica and Lobatula lobatula. The last one, besides Rosalina globularis are dominat at the mouth and with Quinqueloculina seminula, now occupied by an old sewage point, confirms the recovering of this area thanks to the environmental policy of the last years. Finally, the occurrence of live speciments of Ammonia tepida and Haynesina germanica inside the lagoon of Joyel indicates the influence of brackish water.
[R]Distribución areal y ecología de las asociaciones de ostrácodos recientes en la marisma Joyel (Cantabria) / Martín-Rubio, M. / Elorza-Remón, M. / Rodríguez-Lázaro, J. / Pascual, A.
Recent ostracod assemblages of the Joyel marsh (Cantabria, N Spain) are described. Eigteen species are living in this marsh. The strongly eurihaline especies Loxoconcha elliptica dominates the assemblages in the most of samples, which is indicative of the estuarine character of the area. Taking into account the ecology of these species, known from the literature, a zonal sketch of the different sub-environments is proposed for this transitional area. Fresh to oligohaline waters are detected by the occurrence of continental species as Eucypris virens and Cypridopsis vidua. The estuarine influence is evidenced by the eurihaline character of more diversified of species such L. Elliiptica na Cyprideis torosa. A coastal marien zone is characterised by the occurrence of more diversified assemblage with Leptocyther castanea, Aurila convexa, Aurila woutersi, Heterocytheries albomaculata, Pontocythere elongata and Urocytheris oblonga, among others. Finally, the marine inner albomaculata, Pontocythere elongata and Urocytheris oblogna, among other. Finally, the marine inner shelf influence is denoted by the presence of Semicytherura sella, Basslerits sp. And Caudites calceolatus.
[R]Alteración diagenética en conchas de rudistas Monopleúridos del Complejo Urgoniano de Ereño (Aptiense-Albiense Inferior, Bizkaia) / Damas Mollá, L. / Arnburu Artano, A. / García Garmilla, f.
Cathodoluminescence and microprobe analysis in monopleurid shells from Aptian - Lower Albian limestones in Ereño (Bizkaia) has allowed to us to realize that different rudist shells show different diagenetic responses in front of a similar degree of diagenetic alteration. Monopleurid shells show a relatively high diagenetic degree when compared to that of requienids. Early neomorphism processes were dissimilar for different shells. The relatively thin monopleurid prisms could allow a diagenetic alteration in a higher degree than that affected requienid shells.
[R]Resitencia a la alteración diagenética de conchas de Chondrodonta sp en las calizas rojas del Aptiense - Albiense inferior de Ereño (Bizkaia) / Damas Mollá, L. / Arnburu Artano, A. / García Garmilla, f.
Chondrodonta sp. Shells from Aptian - Lower Albian red limestones of Ereño (Bizkaia, northern Spain) have proved to be excellent indicators of a high resistance to the entrance of diagenetic fluids and further diagenetic alteration. Chondrodonta sp. Shells, when compared to their coeval rudist shells, show higher Sr+2 and Na+ contents, together with very dull or even null luminescence. For this reason they could be very appropriate for further C, O an Sr isotopic studies as a tool for reconstruction of palaeotemperatures and palaeoenvironmental conditions.
[R]Microestructura, luminiscencia geoquímica en Crassostrea sp. De la Formaicón Zufía, Navarra (Albiense superior-Cenomainiense inferior). Parte I / Higuera-Ruiz, R. / Elorza, J.
Shells of the oyster Crassostrea sp. From the Zufia Formation, deposited in a strongly subsiding basinat the ene d of the Albian, show the same micrisotructures than recent and fossil Crassostrea sp., deposited in other less subsiding areas; the best preserved microstructure is the regula foliated (RF), while the most altered one is the complex cross foliated (CCF); the external regular simple prismatic (RSP) microstructure, however, shows different degrees of alteration. Both daily-tidal (La) and seasonal (Lb) growth lines can be seen in the RF microstructure. The CCF and RSP ones show, in the vest preserved areas, daily-tidal growth lines. Our trace element analyses, carried out at a fine-scaled resolution along a sclerochronological transect in the condrophore area of the shell, indicate sinusoidal patterns for the Mg/Ca and Sr/Ca ratios. Interestingly, such patterns follow that of the growth line and, thus, they provide seasonal informaiton. Accordingly, an age of more than 3 years has been asssigned to a selected sample. The Na/Ca ratio porgressively decreases with a the life of the oyster. The FE/Ca and Mn/Ca ratios are both higher in the luminescent Lb seasonal growth lines.
[R]Perfiles geoquímicos y luminiscencia en las cámaras y concha de Crassostrea sp. De la Formación Zufía, Navarra (Albiense superio-Cenomaniense inferior). Part II / Higuera-Ruiz, R. / Elorza, J.
Shells of the oyster Crassostrea sp. From the Zufia formation show chambers filled with different diagenetic carbonates that record a complex diagenetic history. Evidences of "burial" diagnesis, represented by the formation of ferrous "saddle" dolomite, suggest high formation termperatures. However, the absence of dissolution/recrystallization features in the Regular Foliated microstructure (RF) indicates its remarkable resistance to diagenetic alteration. Avoiding the camouflage of diagenetic signals, such microstructure is therefore the propitious one to undertake geochemical studies when searching for environmental information. After the "burial" diagenensis stage, an "uplift" process was experience, characterized by the influence of more aggressive, meteoric fluids with lower Fe and Mn concentrations. As a consequence, pressure-solution textures were developed in the contact Ds and RF. Likewise, a dedolomitization process, progressing from the walls of the cameras to the center, originated the calcitic late digenetic stages C1, C2 and C3.
[R]Tafonomía cuantitativa del yacimiento de Cacela (Tortoniense superior; Algarve, Sur de Portugal) / Rico-García, A. / Aguirre, J. / Civis, J. / González Delgado, J.A. / Alonso-Gavilán, G.
A quantitative taphonomic analysis were performed in the fossil assemblages of the late Tortonian of the lower-mid part of the Cacela Formation (Cacela, Algarve, S Portugal). Taphonomic results, together with sedimentological analysis and the faunal assemblages, allow to inferring palaeoenvironmental changes. The upper Tortonian sedimentation started with fan-delta conglomerates that quickly changed to outerplatform silty marls deposited in a setting with a relatively low sedimentation rate as indicated by the concentatiton of glaucnotite. Higher up in the section, a progressive shalowing trend is inferred, and sediments of inner platform settings were formed.
[R]Presencia de Mammuthus sp. En Caravaca (Murcia) / Mancheño, M.A. / Romero, G. / Carlos Calero, J.A. / Ros Montoya, S. / Rodríguez Estrella, T. / Robles, F.
In Rambla del Pizcalejo(Caravaca, Murcia, Spain) new Proboscidea fossil remains were found. In this paper are described all postcranial bones belonging to a 2-4 years old Mammuthus. Stratigraphycal and mollusc data confirm the lacustrine paleoenvironment. The remains shouldn't have suffered a hard transport; neither should their time of exposure have been long. The date of the remains to the genus Mammuthus that allows to surmise a period about Plio-Pleistocene.
[R]Paleoambiente y procesos de formación de un depósito paleolítico al aire libre: El yacimiento arqueológico de Mendieta (Sopelana, Bizkaia) / Iriarte, E. / Cearreta, A. / Ríos, J. / Garate, D.
An urgent archaelogical excavation on the Mendieta area (Sopelana, Biscay province) has envidenced the presence of lithic industry within an original stratigraphic context of possible lower Palaeolithic age. The materials containing the lithic industry exhibit stratigraphic and sedimentary features derived from fluvio-alluvial and pedogenic processes. The formation procedures of this open-air site took place under warm and humid palaeoenvironmental climatic conditions. This characterizacition supplies an important information in order to understand the genesis and location of the scarce open-air archaelogical sites of lower Palaeolithic age present in the Cantabrian region.
[R]Estudio de paleotemperaturas en el Mar de Alboraán entre 250 y 150 ka ultizando la técnica de los análogos modernos / González-Mora, B. / Sierro, F.J. / Flores, J.A.
Planktonic foraminifers from core ODP site 977a have been studied to estimate sea surface temperatures (SST) in the Alboran Sea between 245 and 145 kyr. Similar studies have been performed in this basin but only for the last 150 kyr (Pérez-Folgado et al., 2004). SSTs in this basin are highly controlled by the atlantic superficial incoming flux through the Gibraltar Strait. In this study we estimate paleotemperatures with the modern analog technique which consists on a comparison between core and modern sample assemblages. This method assumes that similar planktonic foraminifer assemblages develop under the same ecological conditions and that foraminifer ecological preferences have not changed in time. This technique also provides a dissimilarity index (between 0 and 1) which depends on the liability of the estimation obtained. In this study we used Kallel et al. (1997) modern database which contains a total of 253 samples, 123 from the North Atlantic and 130 from the Mediterranean Sea. For the estimations we used PaleoAnalogs 2.0, computer program developed by the University of Salamanca (Theron et al., 2004). A small SST difference exists between substages 7.3, 7.2, and 7.1. Important millennial cyclicities (7.4, 5.6 and 4.6 kyr) occur during the whole studied period, both in warm and cold intervals, although changes seem to be broader during cold ones. Seasonality is higher during the warmer substages, 7.5 and 7.3, whereas it is smaller during the stron Northern Hemisphere summer insolation minimun in substage 7.4.
[R]Varianciones en las faunas de foraminífieros bentónicos del mar de Alborán durante el evento Heinrich 6 / Pérez-Martín, R. / Sierro, F.J. / Flores, J.A.
Heinrich events are cold periods during which icebergs discharge took place in the North Atlantic Ocean. Those cold events modified both the surface water temperature and the North Atlantic deep water formation, this influecing bottom water ventilation. The present study has been carried out in core ODP 977 from the Alboran Sea in order to analyze the variations in the deep sea water formation in the Western Mediterranean Sea during Heinrich Event 6. During non-Heinrich events benthic foraminifera Cibicidoides pachyderma and Globobulimina spp. Dominated the foraminifer association, but during Heinrich Events modification in the amount of the oxygen and organic matter in the environment ocurred, with the consequence of an uprise in the Cassidulina laevigata presence. Those observed changes during Heinrich Event 6 in Western Mediterranean Sea are similar to those previously described by other authors in North Atlantic sediments.
[R]Paleoambiente y usos del suelo durante el Holoceno reciente en la Tolla Collado de le Berrueco (Sierra de Guadarrama Madrid) / Ruiz Zapata, M.B. / Gómez Gonzáles, C. / López Sáez, J.A. / Dorado Valiño, M. / Valdeolmillos Rodríguez, A. / Gil García, M.J.
We present the results of palynologycal analyses carried out both in a core obtained from a deposit located in Sierra de Guadarrama (Madrid), and modern pollen data from one transect across Tolla Collado de El Berrueco-El Berrueco. The comparison between these data sets shows that the pollen spectra faithfully reflect the current taxa in the study area. In addition, these resuls have permitted to distinguish several phases of the vegetation dynamic and human acitivity from the Late Holocene in El Berrueco area, inferred from the development of anthropozoogenic taxa.
[R]Geología y estructura de la Mina de Río Tinto (Faja Pirítica Ibérica, España) / Mellado, D. / González Clavijo, E. / Tornos, F. / Conde, C.
The Rio Tinto mining district is regarded as the largest volcanogenic massive sulphide district worldwide, but its geologic and structural setting remains poorly disclosed. The mineralized sequence includes a lower unit o interbedded mafic volcanics, shale and conglomerate overlain by a felsi dome-sill complex. The massive suphides occur within the felsi rocks, either as exhalative deposits on the top or as replacive masses within the volcanicalstic rocks. The present review has a special aim on structural geology bearing up a genetic model update for the ore. Regional thin-skinned tectonic was clearly identified as the leading Variscan structural style in the district. Several stocked units bounded by thrust-faults display normal polarity on structural and sedimentary criteria basis. Reconstruction of the palaeogeography prior to the tectonic stacking reveals a very extensive mineralizing system.
[R]Mineralizaciones de magnetita asociadas a skarns y bandas de cizalla: La mina de Cala (Huelva) / Carriedo, J. / Tornos, F. / Velasco, F. / Terrón, A.
The Cala iron deposit has been traditionally regarded as a classic iron skarn developed on Cambrian limestone adjacent to a Variscan monzogranitic stock. Ongoing studies show that the geologic setting is more complex and the mineralization is replacive on marble and calcsilicate and pelitic hornfels and controlled by syntectonic hydrothermal activity with a pull-apart structure. The skarn only forms a part of the hydrothermal alteration. Most of the magnetite is related to an biotite-quartz-ankerite-chlorite assemblage, while the pyrite-chalcopyrite ore seems to be slightly younger, replacing magnetite along extensional structures, sharing many features with the IOCG style of mineralization.
[R]Sedimentos glaciomarinos del Ordovícico terminal en la Zona Cantábrica (NO de España) / Bernárdez, E. / Gutiérrez-Marco, J.C. / Hacar, M.
Preliminary studies of some stratigraphic sections spanning the Ordovician-Silurian boundary in the sourthern Cantabrian Zone (Iberian Massif, NW Spain) demonstrate the existence of a record of Himantian glaciomarine diamicites and shallow-water quartzites in at least three localities, situated in the Bodón nappe. These rocks, evidenced for the first time in the Cantabrian Zone, are probably related to the infilling of a paleorelief, scoured in the Barrios Formation during the Late Ordovician glaciation. The occurrence of an ubiquitous quartzite unit, generally related to the Ordovician-Silurian boundary in most parts of northern Gondwana, is now extended to the outcrops here analyzed. The Himantian quarzite probably occurs in additional areas of the Bodón and Correcilla nappes, where its loation and significance might be underestimated, and described as the uppermost part of the Barrios Formation (Middle Cambrian to Arenigian). The same quartzite is probably recognized in the areas with volcanic necks within the Barrios Formation, and also in its stratotype, in which a latest Ordovician/earliest Silurian quartzite overlies unconformably on Middle Ordovician shales.
[R]Estructura y paleografía de los materiales del Triásico en la terminación meridional del Arco de Cazorla (Jaén, Cordillera Bética): Implicaciones tectónicas / Pérez-Valera, F. / Sánchez -Gómez, M. / Pérez-López, A.
This study proposes a tectonic reinterpretation of the southwest end of the Cazorla Arc from two different points of view never used before in external zones of the Betic Cordillera: the paleogreographic study of the Triassic sedimentary sequences together with the structural analysis of the ductile fabrics developed in clay- and gypsum- bearing Triassic rocks. This new approach has allowed to distinguish two kinematically distinct tectonic episodes separated in the time: a first strike-slip E-W system of faults followed by a relatively recent strike-slip SE-NW system, both dextral. The study from these points of view of other similar regions could clarify the origin of the so-called Triassic chaotic complexes, at the same time that improve the knowledge of the tectonic evolution of the Cordillera.
[R]Sedimentología y caracterización paloambiental de la serie cretácida inferior de Antromero-Luanco (Asturias) / Alonso-García, M. / Bahamonde, J.R.
A paleoenvironmental study for a Lower Cretaceuos (Late Barremian-Aptian) succession (Antromero-Luanco section, Asturian coast) is showed in this work based on stratigraphic, sedimentological and paleontological data. The lower part of the succession shows terrigenous deposits (the Peñaferruz Fm) recording fluvial and fan-deltaic sedimentation, while the upper part is characterized by shallow-water carbonates (the Antromero Fm) covering a broad carbonate platform environments from restricted to open marine zones. Fossil associations had been very helpful in order to interpret the main environmental features.
[R]Registro del evento anóxico oceánico OAE1a (Aptiense inferior) en un contexto de paltaforma. Prebético (provincia de Alicante) / Castro, J.M.; Gea, G.A. De / Quijano, M.L.
The Early Aptian was a time of major global events, being probably the most notable the Oceanic Anoxic Event 1a. In this paper, we present the study of the record of the OAE1a in a platform setting, the Prebetic Zone of the Betic Cordillera, which represents the shallow platform environments of the Southern Iberian Palaeomargin during the Mesozoic. In this context, several events of global and regional character are recorded, whose timing and relationships are extremely interesting to be clarified. The correlation between the studied sections has permitted the establishment of the timing of the main sedimentary events. The transgressive general context raecorded in the studied units, linked to the tectonic subsidence, resulted in several retrogradational pulses, leading finally to the drowning of the shallow platform, which was postdated by the OAE1a event. The record of the OAE1a in a platform setting is explained as related to a local combination of factors, as a transgressive general context, strong local subsidence rate, and important imput of terrestrial organic matter in the platform, as has been supported by the data provided from the analysis of the organic matter contained in the sediments.
[R]Estructuras sedimentarias de deformación interpretadas como / Alfaro, P. / Galindo-Zaldívar, J. / Jabaloy, A. / López-Garrido, A.C. / Sanz de Galdeano, C.
We estudied various Upper Miocene (Turolian) layers of superimposed soft-sediment deformation structures induced by liquefaction in the Granada basin (Betic Cordillera). These are principally load structures: sagging and dome load casts, ball-and-pillow and drop structures. Based on analyses of their morphology and of the facies, these have been interpreted as being the result of liquefaction of non-cohesive sediments during earthquakes. The intense synsedimentary fracturing and the presene of seismites highlight the strongly influence of tectonic activity in the Granada basin during the Late Miocene, with earthquakes of moderate to high magnitude occurring which were capable of liquefying the sediment.
[R]La Unidad Inferior e Intermedia de la Cuenca de Madrid en el valle de Henares (Provincia de Guadalajara) / Najarro, M. / Montes, M. / López Olmedo, F.
The northeastern sector of the Madrid Basin shows a substancial succession of miocene material that culminate with the so-called "páramo limestones". The purpose of this study is the identification and characterization of the deposits that compose the Lower and Intermediate Units, aged Aragonian, in the left bank of Henares valley. In addition, the boundary of both units has been reviewed. The findings show that in the margin of the basin, this boundary is defined by an angular discordance between the Lower and the Intermediate Units, whereas along the valley it is recognized by disconformitites represented by a change in the sequence evolution.
[R]Cronoestratigrafía de los registros aluviales del tránsito Pleistoceno superior-Holoceno en la depresión de La Bardena Blanca (Navarra) / Muñoz, A. / Sancho, C. / Peña, J.L. / Benito, G. / Rhodes, E. / McDonald, E. / Longares, L.A.
In this work, preliminary chronostratigaphic features of the Upper Pleistocene-Holocene morphosedimentary alluvial unit covering the bottom of the Bardena Blanca depression are described. This unit is made up by 1) gravels and sands related to a braided channel system, 2) laminated sands and clays accumulated in distal flats of alluvial frans and 3) clays and gypsums corresponding to a playa-lake environment. According the first chronological data supplied by OSL and 14C the age of this sequence ranges between 18 and 5 ka. The prevailed paleoclimatic conditions were cold and humid during Last Glacial Maximum-Oldest Dryas and arid during Lower Holocene.
[R]Tasas de erosion en la cuenca de Guadix-Baza durante el Pleistoceno superior-Holoceno / Pérez Peña, J.V. / Azañón, J.M. / González-Lodeiro, F.
Erosion rates in the Guadix-Baza basin have been calculated drawing on a volumetric estimation of sediment lost by hidric erosion in the entire basin. The resulting erosion rate is 6.57 m3ha-1yr1. Individual erosion rates for Guadix and Baza sub-basins (11.80 m3ha-1yr1 and 1.77 m3ha-1yr1 respectively) suggest differetn stages of drainage pattern evolution inboth sub-basins. We attribute the lower values obatined in the Baza sub-basin as related to the downthrowing of this sub-basin due to very recent activity along the Baza fault.
[R]Origen de las simas de Partagat (Sierra de Aitana, Alicante) / Alfaro, P. / Delgado, J. / Estévez, A. / García Tortosa, F.J. / Tomás, R. / Marco Molina, J.A.
The Partagat chasms, located at the highest part of the Sierra de Aitana (Province of Alicante), are large joints which have opened up in Eocene limestone. They measure up to 15-20 metres in width and dozens of metres in depth. These joints have originated from lateral-spreading, which have evolved with time into slides. They have formed here along the lines of pre-existing NW-SE and NE-SW fractures, due to the movement of large blocks of limsestone over an underlying layer of marls, both Eocene in age. Throughout the Quarteneray, these landslides caused the mountain front retreat of the Aitana fault, a normal E-W fault with a throw of several hundred metres.
[R]Modelos de abanicos aluviales en los materiales cantabrienses (Grupo Cea) del Manto del Esla, Cordillera Cantábrica / Llorens, T. / Colmenero, J.R. / Suárez-Ruíz, I.
The main aim of this paper is to describe two alluvial fan models that have been generated in the Esla Nappe of the Cantabrian Zone during the lower Stephanian. These models have been named Duerna alluvial fan and Peña Verde-Remolina system. The alluvial fans were generated by two different processes, mass-flow the first, and water-flow the last one. The differences between both depositional models were promoted by alocyclic agents. The most important of them is provenance of the sediments.
[R]Petrografía de los crbones cantabrienses (Carbonífero sup.) del Grupo Cea de la Cuenca Guardo-Valderrueda (León-Palencia) / Llorens, T. / Colmenero, J.R. / Suárez-Ruíz, I.
The petrographic analysis of the coals of Guardo-Valderrueda basin (Cantabrian Mountains) shows ranks varying from bituminous coals to meta-anthracite. Vitrinite Group dominates the maceral composition, with low Inertinite and scarce Liptinite contents. The presence of natural coke and pyrolytic carbon in many samples indicates and important thermal alteration, mainly due to Variscan tectonism and Permic igneous activity.
[R]Diagénesis y estratigrafía secuencial de la arenisca "U" de la Fm Napo del Oriente, Ecuador / Estupiñán, J. / Marfil, R. / Permanyer, A.
The Napo Formation of Cretaceous age in the Oriente basin, Ecuador, is an important sandstone reservoir. The "U" sandstone is one oil interval within the Napo Formation. It is buried at a depth of 1500 m in the eastern part of the basin and down to 3100 m in the western part. This sandstone display higher porosity values (av. 20%) than other reservoirs in the region. The sandstone was deposited in fluvial, transitional and marine environments, and their correlation with the sequence stratigraphy is related to HST, LST, TS. "U" sandstone is fine to medium grained quartzarenite and subordinate subarkose. The principal cements are carbonates, quartz overgrowth and kaolin, with scarce amounts of pyrite and chlorite. Carbonate cements include: Eogenetic siderite (S1), mesogenetic and post-compactional calcite, FE-dolomite, ankerite and siderite (S2). Early siderite helped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldspars and mesogenetic carbonate cements is the main mechanism for secondary porosity development during mesodiagenesis. The stable isotope composition of the S1 siderite are consistent with precipitation from meteoric waters. The anomalous low ä18O‰ values of some of these carbonate phases could reflect the replacement and recristalizaiton from S1 to S2 siderite at deep burial la hight temperature. However, due to this higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mg rich organic matter. The last carbonate cements to precipitate were dolomite/ankerite. The negative ä 18O‰ in these cements is related to the continued precipitation at higher temperature and burial depth.
[R]El deslizamiento de Güevéjar (provincia de Granada): un caso de inestabilidad de ladera inducida por sismos / Jiménez Pintor, J. / Azor, A.
Drawing on historical documents and a detailed field study, we have been able to characterize the Güevéjar landslide as a complex landmass movement with a dominant multi-rotational component. The landslide body is made up of very heterogeneous rocks, while the basal surface is located on lignite-bearing marls. The main triggering factor responsible for this landslide is thought to be the dynamic effect of high magnitude earthquakes with the focus located at very long distances (tens to hundreds of km) from Güevéjar. Some pieces of evidence poin to local-scale amplification of seismic waves (site effect)as causing reactivation of the landslide.
[R]Variación estacional de las características texturales en los sedimentos intermareales del estuario de los ríos Tinto y Odiel (SO España) / López-González, N. / Morales, J.A. / Borrego, J. / Carro, B.
The seasonal evolution in the sediment textural characteristics along the Tinto and Odiel river estuaries has been studied by means of 12 sediment traps. The fine-grained material is associated with flocculation and decantation processes that take place in the zones of saline mixing and acid neutralization of both estuaries. The bed load deposits are related with two different processes. In winter the are located in the confluence of the fluvial and tidal curents, while in spring and summer, they are redistributed by the tidal currents that deposit them in the central zones of the estuaries.
[R]Variación estacional de los contenidos en carbono orgánico, inorgánico y azufre en los sedimetnos del esturio de los ríos Tinto y Odiel (SO España) / López-González, N. / Morales, J.A. / Borrego, J. / Carro, B.
The estudy of 12 sediment traps located in the Tinto and Odiel river estuary show the influence of the acid contributions in the seasonal variation of the contents in organic carbon, inorganic carbon and sulfur. The sasonal relations between organic carbon and sulfur (C/S) have allowed determining environmental conditions of the estuarine system. Of this form, the winter conditions correspond to a normal marine environment, whereas rest of the year varies between euxinic and semi-euxinic conditions due to the high rate of evaporation that takes place in the intertidal zone that favors sulphate precipitation.
[R]El monasterio de Raíces (Castrilón, Asturias): Estudio Petrográfico de los materiales de construcción / Martos, E. / Alonso, F.J. / Jiménez-Sánchez, M. / Torres Alonso, M.
This work synthesizes the data collected in the analysis of the petreal materials used in construction of the Monastery of Santa María de Raíces in Asturias. The most probable area of origin of those is show with the purpose to identify the transport done during its construction. Macroscopic and microscopic petrologic analysis and bibliographic and field study allow to conclude that there exists a great litologic variability. Carbonated and siliciclastic materials are show, with ages ranging from Devonic to Jurasic. Possible supply areas are proposed, belonging in most cases to close surroundings inferior to 7 km.
[R]Estudio experimental de refuerzo de suelos con fibras sintéticas / Fernández Calvo, C.
This paper presents the results of a laboratory investigation of the mechanical behaviour of two cohesive soils, an expansive marl an a silty clay soil, reinforce with synthetic fibres. Results indicated that fiber reinforcement increases the shear strength better in the marl, and the increase lies with length of fibers.
[R]Comparación de métodos de interpolación para la realización de mapas de precipitación para el acuífero de Icod-Cañadas (Tenerife, Islas Canarias) / Izquierdo, T. / Márquez, A.
Groundwater is the main water resource in Tenerife (Canary Islands) where it represents almost 90% of the consumption. For the Insula Hydrological Plan the most important aquifer in the future will be the one located in Las Cañadas which belongs to the III Hydrogeological Zone. For exploitig this aquifer in a rational way in the future it is necessary to know and asses carefully the recharge estimates. It is for this reason, that the choice of the rainfall interpolation method is so important. In this study three different interpolation methods have been used to compare their results with the real data of the gauges and to obtain doing that, the best precipitation estimate in the area. The results show the ordinary kriging to be the best interpolation method in the study area and that the use of the relationship between elevation and precipitation do not increase the accuracy of the interpolation even though the climatic characteristics of the island have been taken into account.