Geogaceta -- Nº 42, (2007)
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Item type: Item , Zona de transferencia en el sector occidental del Pirineo Central, ejemplo de la falla de Oroz-Betelu-Unzué. Zona surpirenaica. Navarra(2007) Pueyo Anchuela, Óscar; Millán Garrido, H.; Pocoví Juan, Andrés; Gil Imaz, AndrésBased on structural, stratigraphic and gravimetric data, a regional scale N 020-040 E blind-fault, named the Oroz-Betelu- Unzue fault, extending from the western part of the Oroz-Betelu massif to the Sierra de Alaiz thrust front, is inferred. This fault would have acted as a transfer extensional structure during Early Cretaceous times and later, during the Alpine compression, the different stratigraphic and structural characteristics of the fault-blocks would have favoured the formation of major differences between the contractional structures occurring in the blocks of the Oroz-Betelu-Unzúe fault-zone. The Alaiz thrust sheet and adjacent areas represents a good example of the structural changes related to the Tertiary evolution of Oroz-Betelu-Unzué transfer zoneItem type: Item , Using multiple geochemical proxies to trace origin of gypsum (Gulf of Carpentaria, Australia, -70ka)(2007) Playà, Elisabet; Cendón, Dioni I.; Travé i Herrero, Anna; Chivas, A. R.; García, AdrianaLos cambios en el nivel del mar y las asociadas fluctuaciones climáticas provocaron cambios cíclicos y extremos en los ambientes deposicionales en la región del Golfo de Carpentaria (N, Australia). La desconexión con el mar dio lugar al «Lago Carpentaria». En este ambiente, las condiciones evaporíticas alrededor de los 70 ka originaron una alternancia repetitiva de laminas evaporíticas y micríticas de espesores mm a mm con una apariencia de varvas. Estas láminas son interpretadas como precipitados primarios, depositadas en un lago somero que retuvo una cantidad limitada de agua en su centro (sondeo MD-32). Los datos de geoquímica elemental e isotópica de las láminas de yeso y micrita sugieren un ambiente evaporítico complejo donde las aguas marinas iniciales se evaporaron y la entrada de aguas continentales compensaron las pérdidas por evaporación. El contenido en estroncio del yeso varía entre 691 y 1353 ppm, el valor del d34S y del d18O del yeso varía entre +21.8 y +22.5 ‰ y entre +14.1 y +16.5 ‰; la relación 87Sr/86Sr oscila entre 0.7093 y 0.7098. Mientras que los contenidos en Sr y los valores de isótopos de azufre indican una contribución esencialmente marina, los valores isotópicos de estroncio y los de oxígeno en los sulfatos sugieren aportes continentales y otros procesos tales como el reciclado de evaporitas precipitadas anteriormente, la sulfatoreducción y efecto reservorio. Se analizaron elementos menores y traza, REE (<0.45 mm filtrado) en yesos con el objetivo de establecer la procedencia de las aguas continentales que llegan al Lago Carpentaria y se compararon con los valores de ríos actuales del área. Las tendencias normalizadas en elementos REE para muestras de yesos son comparables a las de los ríos del área norte de Cape York, lo que restringe los potenciales aportes continentales a un área geográfica limitada. La aproximación realizada en este estudio evidencia la importancia del uso de múltiples indicadores geoquímicos en las reconstrucciones paleoambientales de medios complejos, tales como las cuencas evaporíticasItem type: Item , Una vértebra de un pequeño ornitópodo (Dinosauria: Ornithischia) del Kimmeridgiense (Formación Lastres) de Tazones (Villaviciosa, Asturias)(2007) Ruiz Omeñaca, José Ignacio; Piñuela, Laura; García Ramos, José CarlosA small dinosaur vertebra from the Late Jurassic of the Principality of Asturias (north Spain) is described. It comes from an outcrop of the Lastres Formation (Kimmeridgian) at Tazones harbour (Villaviciosa) and it is identified as a dorsal vertebral centrum of a juvenile ornithopod. After a revision of the European record of Late Jurassic ornithopod, we conclude that the Tazones vertebra could pertain both to a «hypsilophodontid» or a dryosaurid. It represents the oldest ornithopod bony remain in Spain, and the first one of undoubted Late Jurassic ageItem type: Item , Sobre la calidad del agua del futuro embalse de Alcolea (Cuenca del río Odiel, Huelva)(2007) Olías Álvarez, Manuel; Nieto Liñán, José Miguel; Galván González, Laura; Miguel Sarmiento, Aguasanta; Ruiz Cánovas, CarlosThe Odiel River drains the central part of the Iberian Pyrite Belt, an area with many polymetallic massive sulphide mines that have been worked since prehistoric times. As a consequence of the oxidative dissolution of the sulphides exposed in the surface associated to mining activities, acid mine drainage pollution is an important processes in the Odiel basin that lower considerably the water quality of the river. In fact, near its mouth, the Odiel river has a very low pH and high concentrations of metals and metalloids in solution. Two reservoirs are planned in the Odiel river within the National Hydrologic Plan: Alcolea and Coronada. The construction of the Alcolea dam is suppose to start this year, with a total planned investment of 200.000.000 . After the study and analysis of the water quality in the watershed of the Alcolea dam, and the study of the chemical evolution with time in others water dams in the Odiel basin, the inferred longterm quality for the water in the Alcolea dam will not allow its direct use for agriculture or industrial uses. Therefore, taking into account the important investment planned and the poor quality of the water expected, it is necessary an important re-evaluation of the original project that takes into account, in a more rigorous way, the final quality of the water accumulated in the damItem type: Item , Preliminary data on oil and aqueous fluid inclusions of the fracture-fill in the Corones and Armàncies Fms, Eocene, SE Pyrenees(2007) Caja, Miguel Ángel; Permanyer, Albert; Munz, Ingrid A.; Johansen, H.Las calizas del Eoceno del Pirineo sur-oriental están afectadas por fracturas con direcciones N-NE, buzamientos subverticales (55-72º), espesores centimétricos y longitudes de varios metros. En ocasiones también se observan cavidades vacuolares. Tanto las fracturas como las cavidades vacuolares están rellenas por cementos carbonáticos que no ocluyen totalmente la porosidad. Además, la presencia de indicios de petróleo es muy abundante en las fracturas que afectan a la parte alta de la Fm Armàncies (Cuisiense, Eoceno) y son menos abundantes, pero están también presentes, en la Fm Corones (Cuisiense inferior). El objetivo principal de este trabajo es caracterizar los tipos de inclusiones fluidas (IF) en los cementos carbonáticos que rellenan fracturas como primera aproximación a la historia de migración del petróleo. El estudio detallado de petrografía, fluorescencia y microtermometría ha revelado que en la Fm Corones aparecen tres tipos de inclusiones con dos fases (líquido y vapor): i) IF de petróleo con fluorescencia amarilla; ii) IF de petróleo con fluorescencia amarilla y color marrón en luz transmitida; ambos tipos de IF aparecen como trazas de pequeña longitud que afectan sólo a uno o dos cristales de calcita, lo cual sugiere un origen secundario; iii) IF acuosas de tamaños muy pequeño (5-10 μm) que aparecen en los bordes de los cristales indicando un origen primario. En la Fm Armàncies aparecen cuatro tipos de inclusiones con dos fases (líquido y vapor): i) IF de petróleo con fluorescencia amarilla; ii) IF de petróleo con fluorescencia amarilla y color marrón en luz transmitida; iii) IF petróleo con fluorescencia azul y azul intenso, que son las más abundantes; todas las IF de petróleo aparecen como trazas de gran continuidad, paralelas a los márgenes de las fracturas, lo cual sugiere un origen primario; iv) IF acuosas que son muy escasas y aparecen como trazas. En resumen, los datos preliminares del estudio de inclusiones fluidas sugieren que el petróleo en la Fm Armàncies migró a través de fracturas de forma coetánea con la precipitación de los cementos carbonáticos. Por el contrario, el petróleo fue atrapado en el cemento carbonático de las fracturas de la Fm Corones, pero no durante su precipitación, sino posteriormenteItem type: Item , Precisiones sobre la edad, mediante ammonoideos y nautiloideos, de la Fm. Margas del Forcall en la subcuenca de Oliete (Cadena Ibérica, España)(2007) Moreno, J. A.; Company, M.; Delanoy, G.; Grauges, A.; Martínez, G.; Salas, RamónAmmonoids and nautiloids from Margas del Forcall Formation, located in the Oliete sub-basin (Iberian Chain), were studied. Taphonomic, sedimentologic and biostratigraphic analyses were carried out. The fossil record of cephalopods is especially abundant in a layer made up of reddish limestone with elongated nodules that are usually covered by a ferruginous-manganese crust. These nodules are embedded in a micritc matrix where infaunal tiering is largely preserved. The biostratigraphic study has allowed recognizing Hambrovi Subzone and proposing a new bioestratigraphic position for this stratigraphic intervalItem type: Item , Nuevas aportaciones a la biogeografía de cocolitóforos en el Pacífico ecuatorial y suroriental(2007) Saavedra Pellitero, Mariem; Flores, José Abel; Sierro, Francisco JavierFor this proposal 114 surface sediment samples from the Equatorial and Southwestern Pacific were analysed, recovered during three cruises: Génesis III-RR9702A, NEMO-Me0005A and PUCK: Valparaiso-Talcahuano. A total of 19 different species (or groups in some cases) were identified using petrographic microscope. Five biogeographic coccolithophore zones have been established taking into account the distribution patterns of the taxa and some physical parameters such as temperature and salinity. These zones are: -Tropical North, characterized by an assemblage mainly composed of Gephyrocapsa oceanica, Florisphaera profunda, «small» Gephyrocapsa and Gephyrocapsa muellerae. - Equatorial, basically dominated by placoliths. -Tropical South, where F.profunda, G.oceanica, «small» Gephyrocapsa, Calcidiscus leptoporus, Emiliania huxleyi and G.muellerae are dominant. Characteristic taxa are Umbilicosphaera sp., Calcisosolenia sp., Oolithotus sp., Syracosphaera spp. and Rhabdosphaera clavigera. -Subtropical South, with an assemblage dominated by gephyrocapsids, F.profunda, C.leptoporus and Helicosphaera carteri. -Transitional-Subpolar, where «small» Gephyrocapsa is the most abundant taxa, although E.huxleyi, G.muellerae, C.leptoporus, G.oceanica, F.profunda, C.pelagicus (very abundant in this zone) and H.carteri are also well representedItem type: Item , Nuevas aportaciones al registro paleoicnológico en Cabezón de Cameros (La Rioja. España)(2007) Díaz Martínez, Ignacio; García-Ortiz de Landaluce, E.; Ibisate, Ruth; Pérez Lorente, FélixCabezon de Cameros is a well known place for paleoichnological workers because one of the first described iguanodontid cuadrupedal trakways was found there. Up to now, this was the only site known in this place. In this paper we describe five new sites found near the one mentioned above. They not only widen the paleoichnological record of the region, but also give new interesting data about the kind and distribution of dinosaurs and the ichnological record of Cameros Basin lithoestratigraphical groupsItem type: Item , Nuevas aportaciones al estudio del «siderolítico» (Fm. Areniscas de Salamanca). Borde Oeste de la cuenca del Duero (Zamora)(2007) Molina Ballesteros, Eloy; Alonso Gavilán, G.; García Talegón, JacintaThe Areniscas de Salamanca Formation, located in the western border of the Duero basin, has been studied by means of the polarized light microscope and the SEM. The study has brought out some interesting remarks: 1) important processes of redistribution of matter within the sediments displaying many bioturbation features (collapses, tubules, cutans, etc) all of them being previous to lithification; 2) presence of spicules of sponges (megascleras) appearing in the intermediate member of this Formation; 3) progressive enrichment in silica upwards with an increase in the contrasts of hues of the sediment due to Fe oxyhydroxides segregations. Although the dominant forms of silica are lepispheres, cavities filled up by idiomorphic crystals of tridimite, fibrous forms, microquartzs and isotropic opal are frequents. The presence of sponge spicules, both isolated or grouped, open the possibility (¿?) that this Formation had been related in some way to a seashore sedimentary environment in someone period of its geological historyItem type: Item , Morphosedimentary evidence of the Last Interglacial Maximum on the coast of Governor’s Beach, Gibraltar(2007) Rodríguez Vidal, Joaquín; Cáceres Puro, Luis Miguel; Abad de los Santos, Manuel; Ruiz Muñoz, Francisco; Martínez Aguirre, AranchaLos registros marinos, erosivo-sedimentarios, en la costa de Gibraltar son el resultado de episodios de elevaciones eustáticas, sobre los que se depositan secuencias continentales eólicas y gravitacionales de descenso eustático, en las que se intercalan paleosuelos. En la costa oriental de Governor’s Beach, se han reconocido dos altas paradas marinas durante OISs-5e. La primera transgresiva, a +5,0 m, con un amplio y marcado socave, cuevas, abrigos, cantiles y un cortejo bioerosivo de ascenso eustático; la segunda regresiva, a +1,5 m, con pequeñas rasas mareales y una secuencia sedimentaria de playa-duna-suelo rojo. Registros semejantes han sido reconocidos en otros lugares del Mediterráneo occidental a ~130 ka y ~120-110 ka. Todas estas evidencias fueron parcialmente cubiertas por episodios continentales posteriores de carácter eólico-kárstico-gravitacionalItem type: Item , Micritización de espeleotemas en ambiente meteórico vadoso (Cueva de Castañar de Ibor, Cáceres)(2007) Martín García, Rebeca; Alonso Zarza, Ana María; Martín Pérez, AndreaThe aragonite and calcite speleothems of the Castañar de Ibor Cave show white and matt coatings that formed by micritization and dissolution of the initial crystals. These processes are also recognised in the inner part of the speleothems. Either in the inner or outher parts the result is the lost of brightness and transparency of the speleothems. Petrographically these coatings are seen as lines of micrite liked to dissolution processes that probably occurred because of the circulation of undersaturated fluids within the cave. At the moment no organic structures have been recognised in relation to the micritizated areas, indicating very probably that the process was inorganically drivenItem type: Item , Los yacimientos de baritina de Bou Ouzzal (Macizo Central Hercínico, Marruecos)(2007) Benjouali, M.; Gonzalo, L.; El Hnot, H.; El Mahi, B.; López Andrés, S.; El Wartiti, M.; Zahraoui, M.The deposit of Bou Ouzzal’s barite is located in the eastern extreme of the Moroccan Hercynian Massif- Central, to approximately 7 km to the south of Khénifra. The mineralization occurs in the paleozoic schists and late Visean limestones. The barite appears in the shape of veins and karst associated with oxides and iron hydroxides. This deposit is distinguished by his great heterogeneity and the variability of his composition. In spite of the fact that the region has been an object of numbers mining works from 1922, date in which the deposit was discovered, the analytical studies are scarce and half-close to the mineralization. The aim of the present note is concentrated on the detailed description of the different generations of barite, his distribution and relation with the iron’s minerals. The samples have been studied by polarizing microscopy, SEM, XRD, XRF and EPMA. This work is the preliminary result of the collaboration established between the University Mohammed VAgdal and the University Complutense of Madrid within the framework of the Spanish-Moroccan Intervarsity Cooperation’s program of the Spanish Agency for International Cooperation «AECI»Item type: Item , La tomografía eléctrica: una herramienta para la detección de huecos mineros (concesión de Arrayanes, Linares-Jaén)(2007) Martínez López, Julián; Rey Arrans, Javier; Sandoval, S.; Rodríguez, M.Electrical resistivity tomography is well suited to find and map subsurface cavities because of its ability to detect resistive features and discriminating subtle resistivity variations. The Linares area (Jaén, Spain), where an important mining activity on metallic sulphides ores was developed, has been selected for this study. This activity has produced a large volume of mining voids. Electrical resistivity tomography is a geophysical tool well suited to the detection and mapping of known and unknown mining voids. The technique is capable of discriminating between the developing cavities, where the target is primarily conductive weathered material, and the empty voids comprising resistive air-filled cavities. Such cavities may be water-filled, in which case they are likely to yield conductive anomalies as the water would be significantly more conductive than the surrounding material (unweathered granite in this case). The survey results suggest that electrical resistivity tomography is an ideal geophysical tool to aid in the detection and monitoring of mining voids and other subsurface cavitiesItem type: Item , Incorporación de datos y criterios geológicos en el análisis de la peligrosidad sísmica en regiones de actividad moderada: II. Función de atenuación del movimiento del suelo y cálculo probabilístico(2007) García Mayordomo, JuliánThis paper constitutes the second part of a previous one where the importance of geological data and geologically based criteria in the first two steps of a seismic hazard analysis (SHA) were studied. This paper deals now with the last two steps in SHA: Strong ground motion attenuation function and probabilistic calculations. In the first one, geological knowledge is of great importance to identify and classify soil conditions and to effectively incorporate the effect of faulting mechanism in hazard calculations. In the second one, the interest of considering paleoseismological data –e.g., maximum geological magnitude, mean recurrence period, elapsed time since last event– in computing probabilities is reviewedItem type: Item , Huellas de dinosaurios conservadas en materiales del cortejo transgresivo en cauces encajados. Jurásico superior y Cretácico inferior de Alpuente, Valencia(2007) Santisteban, Carlos de; Vila, B.; Suñer, MaiteThe upper Jurassic and lower Cretaceous deposits of the Southwestern Iberian Basin at Alpuente (Valencia) contain abundant remains of dinosaurs, including several localities with footprints. In this area deltaic sediments deposited in fluvial, estuarine, beach and shallow-marine environments, controlled by eustatic sea-level changes outcrop extensively. In spite of the fluvial deposits dominance, most of dinosaur footprints sites found here are placed in beach sandstones. Beach sandstones were deposited in the basin during the low sea-level stand and transgressions. The study of four new ichnological sites shows that the footprints are preferently preserved in those beach deposits that built up the transgressive system tract, as the infill of incised valleysItem type: Item , Hecates Tholus, Marte: Inestabilidad del Edificio Volcánico(2007) Pablo, Miguel Ángel de; López, Iván; Martín González, Fidel; Márquez, ÁlvaroHecates Tholus is a volcano located at the Elysium volcanic province in the Martian lowlands (32ºN, 210ºW). In addition to several nested calderas, the volcano shows several geological and geomorphological features that could be indicative of a complex volcanic evolution: channels, depressions, pits, faults and ridges, and a complex volcano topography. The processes that can explain the structural evolution of the volcano, include: (1) volcanic spreading, (2) lateral volcanic activity, (3) development of large landslides, (4) hydrothermal activity, and (5) tectonic deformation. We discuss these hypotheses and their implications, in order to establish the most feasible volcanic history of Hecates TholusItem type: Item , Geoarchaeology of the Holocene slope processes in the cave of Torca l’Arroyu (Llanera, Asturias, Spain)(2007) Jordá Pardo, Jesús Francisco; Estrada García, Rogelio; Mestres Torres, J. S.; Yravedra Sainz de los Terreros, J.; Marín Suárez, C.Torca l’Arroyu fue descubierta durante la construcción de la nueva red de saneamiento de Llanera (Asturias, España). Es una pequeña cueva desarrollada en las calizas y margas del Cretácico superior rellena por sedimentos cuyo techo presenta una abertura tipo torca. El depósito tiene forma de cono cuyo vértice se encuentra bajo la torca y está formado por capas inclinadas depositadas a partir de los arrastres producidos en la ladera exterior. En estos niveles se recogieron materiales arqueológicos, restos óseos y fragmentos carbonosos. Para situar los depósitos en el tiempo se dataron mediante 14C dos muestras óseas y varios carbones. Las fechas ofrecidas por las muestras óseas del nivel inferior son: UBAR-803 4.930±70 BP y UBAR-804 4.240±60 BP; las obtenidas de los carbones son: nivel inferior, UBAR-745 3.190±150 BP, y nivel superior UBAR-746 2.050±120 BP. Las dataciones de los huesos asociados a materiales arqueológicos nos indican la existencia en la ladera exterior de un asentamiento humano holoceno, cuyos materiales fueron arrastrados por la ladera y depositados en la cueva en una fecha posterior, como consecuencia del desarrollo de un incendio, proceso este que se repitió años después como atestigua la fecha más reciente. Las fechas 14C fueron sometidas a calibración dendrocronológica y comparadas con las de otros yacimientos cantábricos de similar cronologíaItem type: Item , Genesis of granitoids by interaction between mantle peridotites and hydrothermal fluids in oceanic spreading setting in the Oman Ophiolite(2007) Amri, I.; Ceuleneer, G.; Benoit, M.; Python, M.; Puga, Encarnación; Targuisti, K.Los granitos potásicos que afloran en las ofiolítas supra-subducción son atribuidos a la fusión de metasedimentos durante el inicio de la obducción o durante procesos petrogenéticos relacionados con la subducción. En este artículo, presentamos nuevos datos de campo, petrológicos y geoquímicos (elementos mayores, trazas e isótopos), que apoyan la opinión de que parte de estos granitoides pueden haber sido formados a partir de un manto empobrecido afectado por procesos hidrotermales de muy alta temperatura en un ambiente de expansión de litosfera oceánicaItem type: Item , Experiencia sobre la adaptación de la asignatura «Paleontología general y de invertebrados» al Espacio Europeo de Educación Superior(2007) Pascual, Ana; Murelaga, XabierMost of the text, including the Bolonia’s document, that define the European Higher Education Area, refers to the organization of the University curriculum following the rule called ECTS. The ECTS is a student centred system based on the student workload required to achieve the objectives of a programme, objectives preferably specified in terms of the learning outcomes and competences to be acquired. This work shows the teaching strategies, the competences, the learning activities, the student workload (shown in number of hours), the assessment and the learning outcomes for the subject «General and Invertebrate Paleontology» in the Geology degree (University of the Basque Country)Item type: Item , Estudio diagenético en conchas de braquiópodos de la cuenca del Guadiato (Mississippiense, SO del Macizo Ibérico)(2007) Armendáriz, M.; Rosales, Idoia; Quesada, C.Detailed petrographic and geochemical analyses of brachiopod shells from the Guadiato Carboniferous basin (Córdoba, SW Iberian Massif) has been carried out in order to evaluate their textural and geochemical preservation degree and their potential to be used as indicators of paleoenvironmental changes during the Carboniferous. The preservation degree of the shell´s microstructure has been evaluated by petrographic microscope, cathodoluminescence (CL) and scanning electron microscope (SEM). Under CL, ventral valves are mainly nonluminescent (NL) or nonluminescent with small slightly luminescent areas (NL-SL). In contrast, most of the dorsal valves are luminescent with moderate luminescent areas (ML-L). Under SEM, the samples show very well preserved lamellar and fibrous microstructures. The elemental contents (Ca, Mg, Sr, Mn and Fe) for the NL portions agree with elemental contents of modern brachiopods in equilibrium with ambient seawater and that have not undergone significant diagenetic modification. Therefore, our findings reveal a better microstructural preservation of the ventral valves of Gigantoproductids than the dorsal valves. The NL and NL-SL shell portions present the better microstructural and geochemical preservation and are interpreted to reflect the original isotopic and chemical composition of the marine water from which they precipitated