Geogaceta -- Nº 39, (2005)

Permanent URI for this collectionhttps://hdl.handle.net/10272/8619

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Variaciones de espesor y de contenido en CaCO3 en los pares marga-caliza del Maastrichtiense inferior en Sopelana (Arco Vasco)
(Sociedad Geológica de España, 2005) Baguer, A.; Martínez López de Sabando, M.; Múgica, J.; Pérez García, J. R.; Unanue, L.; Elorza, Javier; Álvarez Llano, Irantzu
The Sopelana sea-cliff section exposes, in very good conditions, a continuous marl-limestone alternation from the Lower Maastrichtian in the deep Basque Arc domain. The 55 rhythms studied represent ~1100 ka and correspond to ~60cm/20ka. The marls are thicker than limestone layers and the Fischer diagram detects several shifts of high sedimentation and a well-marked minimum. The spectral analysis of the (%) CaCO3 content of the 30 selected rhythms (179 analysis, 18.74 m), confirms the rhythm with two frequency peaks, which correspond to the precession and eccentricity periods. The high-resolution analysis of four rhythms (<2cm/sample; 117 analysis, 2.04 m) shows a lack of symmetry and a different behaviour among them. The weathering surfaces point out an (%, CaCO3 ) enrichment tendency
Transferencia de Tierras Raras entre la fase disuelta y la particulada en el agua de un estuario afectado por drenaje ácido (SO de España)
(Sociedad Geológica de España, 2005) Carro Flores, Berta; Borrego Flores, José; López González, Nieves; Lozano Soria, O.
The Odiel river estuary shows a strong longitudinal gradient in pH and Conductivity values of the water, in agreement with the acid neutralization processes and salt-induced mixing that occur in the middle and the upper sectors of the estuarine system. The Odiel river supplies high REE dissolved (128.8 μg·l-1) that diminishing progressively until the middle zone of system (1.2 μg·l-1). In the particulate phase the REE concentration ranges between 237.8 and 48.1 mg·l-1, displaying the greater concentrations in the middle zone of the estuary. The middle and high dissolved REE are the first transferred to the particulate phase, causing a light REE depletion in the upper sectors of the mixing zone (pH between 4.2 and 5.7). The light REE transference takes place at the end of the acid neutralization processes (pH > 7), concluding in the marine zone of the estuary
Superposición de fallas y paleoesfuerzos en el Corredor del Almanzora desde el Tortoniense a la actualidad (Cordilleras Béticas)
(Sociedad Geológica de España, 2005) Pedrera Parias, Antonio; Galindo Zaldívar, Jesús; Sanz de Galdeano, Carlos; López Garrido, Ángel Carlos
The Almanzora Corridor in the Betic Cordilleras is affected by brittle deformations since the Tortonian. The analysis of fault overprinting shows a first group formed by a set of E-W dextral strike-slip faults, N-S leftlateral strike-slip faults and NW-SE normal faults compatible with a NW-SE shortening and an associated NE-SW extension. A second group corresponds to younger NW-SE normal faults, formed during NE-SW oblique extension to the Corridor, with an oblate stress ellipsoid that also reactivates, in some cases, previous faults. A more recent stress ellipsoid indicates extension, that is locally pluridirectional and reactivate previous fault surfaces, although horizontal striations have been overprinted in the Somontín fault, associated to a NW-SE recent shortening that is only locally registered
Respuesta de los Cocolitofóridos a los cambios atmosféricos y oceanográficos durante el Periodo Húmedo Africano del Holoceno en el Atlántico
(Sociedad Geológica de España, 2005) Mejía Molina, Alejandra; Flores, José Abel; Bárcena, María Ángeles; Sierro, Francisco Javier; Grousset, F.
Core MD03 2705 was recovered at 18ºN-21ºW at a water depth of 3100 m off Mauritania-Senegal (NW Africa) during the Marion Dufresne II Cruise PICABIA. Qualitative analyses carried out in coccolithophores and wind-transported microfossils from continental NW African areas (phytholiths and fresh-water diatoms), allow us to interpret variations in the direction and intensity of winds and their relationship with surface water dynamics during the Holocene African Humid Period (AHP) (9-5.5 ka). The terrigenous record exhibits a well-defined period of low influx associated with the AHP, when the Sahara was near completely vegetated and covered by perennial lakes. Variations in the production of coccolithophores, showing high productivity during the wet conditions, were monitored. A rapid shift to arid conditions at the end of the AHP coincides with higher abundance in fresh-water diatoms and phytholiths, as well as a positive pulse in the Ti/Al ratio, suggesting intensification in the wind regime. At this time, coccolithophores show a dramatic decreasing of the cool-water species Gephyrocapsa muellerae, interpreted as a return to warmer conditions
Procesos de Mezcla de un estuario afectado por drenaje de aguas ácidas (Ría de Huelva, España)
(Sociedad Geológica de España, 2005) Carro Flores, Berta; Borrego Flores, José; López González, Nieves; Lozano Soria, O.
It has studied mixing processes in a estuary affected by AMD during a biannual sampling corresponding to 2003-2004. The mixture between fresh masses waters to pH 2 with marine waters to pH 8 introduces in the system a mixing process salty induced and a mixing process pH induced. A space displacement of the processes in the interior of the estuary has been demonstrated. Thus during dry stations the mixing processes take place in the most internal zones of the estuary, whereas in wet stations, these processes take place towards sectors more outward
Procesos de silicificación y tipos de cuarzos en rocas volcánicas (Área volcánica del Cabo de Gata)
(Sociedad Geológica de España, 2005) Aparicio, Alfredo; Bustillo Revuelta, María Ángeles; Fernández, P.; García, R.
The original mineralogical and geochemical compositions of andesitic volcanic rocks from SE of Spain have been modified by different processes, under hydrothermal environment. In particular, silicification process increases the initial silica concentration of the volcanic rock from 69 % to 97%. One of the characteristics of this alteration is the breakdown of mafics minerals and feldspars with supply of Al, Fe, Mg…etc to the interstitial fluids which can be later introduce as traces in the new quartz formed. The silica rocks created in the process are mainly constituted by quartz with different crystal sizes and textures. The spectral analysis of the cathodoluminiscence (CL) emission in combination with the Scanning Electron microscopy observations show that the igneous quartz crystals of the volcanic rock are characterized by a dominant band at 2,95 eV (420 nm) while the quartz crystals formed by silicification have a dominant band at 2,54 eV (~ 500 nm). Although it is difficult to identify the causes of these spectral differences, it is considered that the 420 nm emission band is due to native defects of the igneous quartz and the ~ 500 nm emission band is due to the substitutional incorporations of impurity ions in the hydrothermal quartz crystals. The SEM-CL imagines show a non uniform luminescent emission. This is interpreted in terms of either microsilicifications affecting the quartz crystals and the groundmass of the volcanic rocks or as consequence of the pseudomorphic replacements by quartz of the primary minerals. The hydrothermal silicification is an early process that increase the amount of silica of the initial andesitic rock making other petrological and geochemical types of volcanic rocks
Principales características de las aguas termales en acuíferos carbonatados en el Principado de Asturias
(Sociedad Geológica de España, 2005) Meléndez Asensio, Mónica; Nuño Ortea, C.
There are nine thermal springs, with temperatures between 16 ºC and 31ºC, associated with carbonated carboniferous rocks. The hydrogeochemical study as well as tectonic situation has permitted establish the principal characteristics of their hydrodynamic behaviour, which will be the beginning of posterior investigations
Primeras icnitas de dinosaurio en Murcia (Albiense de Yecla)
(Sociedad Geológica de España, 2005) Pérez Lorente, Félix; Guillén Mondéjar, F.; Ramo, A. del
The first found tracks of dinosaur in Murcia are described. They are in the formation Utrillas of Yecla and come from herds of sauropod dinosaur. In spite of the bad conservation, they have importance by the shortage of tracks in Spain of Albian and because they open the possibility for future campaigns of surface survey
Pliegues magmáticos en el plutón trondhjemítico de La Fronda, Sierras Pampeanas de Córdoba, Argentina
(Sociedad Geológica de España, 2005) D’Eramo, Fernando J.; Vegas, Néstor; Pinotti, Lucio P.; Tubía, José María; Coniglio, Jorge E.
From structural and magnetic fabric patterns, this work reports a complex folded structure in the La Fronda pluton, a small trondhjemite massif located in the Sierras de Córdoba which form the eastern part of the Sierras Pampeanas in Argentina. Isoclinal folds with no thickening at the hinge zones deform the compositional banding of these igneous rocks. Both the orientation of axial surfaces and fold axes vary from place to place and do not concur with the orientation of folds from the metamorphic country rocks. Microstructural data point to a fabric formed by grain-supported flow in a crystal-rich magma during the imprint of a vanishing regional stress field
Monitorización de la subsidencia del terreno en la Vega Media del río Segura mediante Interferometría SAR diferencial (DInSAR)
(Sociedad Geológica de España, 2005) Tomás, Roberto; Márquez, Yolanda; López Sánchez, Juan Manuel; Delgado, José; Blanco, P.; Mallorquí, J. J.; Martínez, M.; Herrera, G.; Mulas de la Peña, J.
Ground subsidence caused by aquifer exploitation is a geotechnical hazard that affects wide areas, causing important economic damages. This phenomenon is due to soil consolidation produced by the increase of effective stress caused by piezometric depletion. In this work a Remote Sensing Technique called Coherent Pixel (CPT) is applied to monitor subsidence in the Vega Media of the Segura River during a period of eleven years
Modelo de desarrollo y formación de concreciones carbonáticas en los sedimentos lutíticos anóxicos (Coniaciense-Campaniense), de la Formación La Luna en Venezuela Occidental
(Sociedad Geológica de España, 2005) Zapata, Eglee; Soto González, Gilberto; Kertznus, V.
The carbonate concretions that characterize the anoxic-dysoxic calcareous shales deposits of Late Cretaceous La Luna Formation in Western Venezuela, represent a non-conventional model of growth and development of carbonate concretions. Its evolutionary pattern is closer to that of the geodes. A hard outer layer cone in cone cement protects the nucleus consisting of friable and humid carbonate mud associated with fenestral structures composed of Mg-calcite and framboidal pyrite. The migration of fluids determines the characteristics of the textural facies as well as their typical internally laminated structure. The size and shape of the concretions vary within the stratigraphic sequence, following a pattern that seemed to be linked to the oxygen variation in the basin. The evaluation and the modelling proposed respond to a systematic and detailed petrographic evaluation (SEM-BSEM) and isotopic analyses (oxygen and carbon isotopes)
Microestructura y cementos en Crassostrea sp. del Albiense superior-Cenomaniense inferior (Playa de Somocuevas, Cantabria): Perfiles geoquímicos y luminiscencia
(Sociedad Geológica de España, 2005) Higuera Ruiz, R.; Elorza, Javier
The shells of the oyster Crassostrea sp. of the Somocuevas beach preserve EsMT patterns in the hinge region that can be used to establish paleoambiental conclusions, like the presence of periods of annual transit in the, so called, Zonas de Transición (ZT). The interaction of diagenetical fluids with the shell through the ZT was favoured by the existence of a microporosity that was developed in zones rich in organic matter, related to periods of low rate or cease of the shell growth, giving rise to an enrichment in diagenetic elements: Mg, Fe and Mn in the cements that filled up this microporosity. The cements that filled the cameras, originally empty, are enriched in Fe, Mn and Mg, with respect to the regular foliated calcite of the shell, which indicates that a diagenesis in reducing conditions, with mixing-water contributions, has taken place
Magnitud y rango de transmisividades en las unidades acuíferas carbonatadas UH7 y UH2 del Sistema Mancha Oriental (SMO). SE Español
(Sociedad Geológica de España, 2005) Sanz Mangas, David; Castaño Fernández, Santiago; Gómez Alday, Juan José; Martínez Alfaro, P.E.
The hydrogeologic units UH7 (mid-Jurassic) and UH2 (mid-Miocene) mainly support the whole of the groundwater abstractions in the Mancha Oriental System (SMO). In both units, the empirical relationship among transmissivity and specific yield data has been determined on a prediction interval equal to 90%. Once the values of transmissivity have been estimated from the linear relatonship between log-T and logq, it has been determined the most representative interval of transmissivity values. In this sense, the highest transmissivity values belong to the UH7 and are found in the SE block of the «Multiple Fracturation Line (MFL)». On the other hand, the lowest ones are found in the carbonte deposits of the UH2
Las rocas volcánicas del Edificio Submarino de la isla de La Gomera: características composicionales
(Sociedad Geológica de España, 2005) Herrera, Raquel; Ancochea, Eumenio; Huertas, María José
The Submarine Edifice rocks are the oldest rocks in La Gomera. This edifice is made up of submarine lava and breccias, with marine sediments associated, all of which is transverse by a very dense network of diques. This essay shows the first geochemical and mineralogical submarine volcanic rocks data. These rocks are intensely altered and have an alkaline chemical affinity. Compositions vary between alkaline basalts and trachyandesites, and all of them show typical Within Plate and Ocean Island basalts immobile elements contents. The latter Subaerial Edifice volcanic rocks are similar in composition, although they are slightly less alkaline and they have less evolved types
Interpretación sismotectónica de la serie sísmica de Gérgal (2002, Mw 4.8) mediante datos sismológicos y de interferometría de RADAR (INSAR)
(Sociedad Geológica de España, 2005) Bejar, M.; Herráiz, E.; Martínez Díaz, J. J.; López, C.; Capote, Ramón; Tsige, Meaza
This work analyzes the geological source of the Mw 4.8 February 4 2002, Gérgal earthquake. The interpretation of local geological data, the relocation of the aftershocks sequence using a local velocity model, the focal mechanism calculation and the interferometric study of the area using RADAR images give evidences that support a tensional stress source with a rupture plane oriented NW-SE to NNE-SSW
Influencia de los eventos de recarga en la hidrogeoquímica del acuífero del Ventós-Castellar (Alicante)
(Sociedad Geológica de España, 2005) Andreu Rodes, José Miguel; García Sánchez, Ernesto; Carratalá, A.; Sanz, M. José; Pulido Bosch, Antonio; Bellot, Juan; Villacampa, L.
The Ventós-Castellar aquifer is a small karstic system situated in Alicante province in the Southeast of Spain. Nowdays this aquifer is exploted by just one well which water is carried to supply a small town. In the last years, this aquifer has been monitored for several parameters, including chemical composition, in order to establish its hydrogeochemistry and also the influence of recharge events on it. The hydrogeochemistry results have shown that calcium and bicarbonates are the main ions, but sulphates and chlorides are high as well. Some rainfall events lead to significant recharge in the aquifer which make a dilution. Dilution is proportional to the entrances in the aquifer. The hydrogeochemical data could be useful in defining of the infiltration rate, the water reseves, the hydrodinamic functioning and, basically, the conceptual model of this aquifer
Indicadores estructurales y morfológicos de deformaciones postmiocenas en el sector occidental de la Falla de Crevillente (Cordillera Bética)
(Sociedad Geológica de España, 2005) Canora Catalán, C.; Martínez Díaz, J. J.
According to the NNW-SSE regional shortening direction active in the Eastern Betic Cordillera since the Upper Miocene, the ENE-WSW Crevillente Fault should be either blocked or locally reverse. However, dextral, sinestral or reverse movements have been reported along the fault zone. In this work, new observations on the post-Miocene deformations of the Crevillente Fault are described. A block-tectonics model active on different scales is proposed to explain the kinematics variability of the fault
Identificación de Tractos Sedimentarios en sedimentos pelágicos mediante métodos geoquímicos. Formación La Luna, Occidente de Venezuela
(Sociedad Geológica de España, 2005) Soto González, Gilberto; Zapata, Eglee; Kertznus, V.
An integrated study of the geochemistry, sedimentology and biostratigraphy of two outcrop sections of the La Luna Formation in Western Venezuela was carried out to determine the eustatic changes that influenced the deposition and preservation of anoxic sediments in the Late Cretaceous. Five (5) depositional sequences within the La Luna Formation were identified in the studied outcrop sections (Las Hernández and San Miguel) by shifts in 13C stable isotopes, as well as in CaCO3, Si, and Ti elemental content (normalized to Al). Transgressive system tracts (TST) are characterized by heavier values in 13C isotopes, lower CaCO3, and higher content of TOC. During these periods the values of Si/Al and Ti/Al show an increasing trend and reach their highest peaks at the maximum flooding surfaces (MFS). Highstand system tracts (HST) are characterized by high contents of CaCO3, and a shift towards lighter values of 13C isotopes. The sequence boundaries (SB) are evidenced by a rapid shift in the 13C isotopes (from lighter to heavier values) and by the geochemical contrast between the HST and the TST. The identified systems tracts (Turonian-Campanian), clearly correspond with the Haq et al (1988) global sea-level change curve
Geometría y Cinemática de un Sistema Imbricado deCabalgamientos en la Faja Pirítica Ibérica (Zona Sudportuguesa)
(Sociedad Geológica de España, 2005) Mantero Romero, Elena María; Alonso Chaves, Francisco Manuel; Azor, A.
The Puebla de Guzmán and Valverde del Camino Anticlines consist of fault-propagation folds linked to a frontal thrust system striking N110ºE. In the Puebla de Guzmán Anticline, the thrust system has a fan imbricated geometry and represents a ~40 km-long and 4-5 km-wide frontal ramp; its internal structure results from the tectonic stacking of thrust sheets with normal stratigraphic polarities. Some thrusts show relay geometries, as for example the Valdecascajos and the Sierra de la Estrella Thrusts. An antiform-sinform system is developed in the intervening thrust sheet. Fault-propagation folds are very conspicuous in the hanging wall of most internal thrusts, where a rather continuous reverse limb is present. Both thrust system and fault-propagation folds, as well as a locally developed crenulation cleavage, were generated in a second tectonic phase
Geología de la isla de Branco (Cabo Verde)
(Sociedad Geológica de España, 2005) Ancochea, Eumenio; Brändle, José Luis; Hernán, Francisco; Huertas, María José
The morphological, structural and volcanological aspects of Branco, an island of the Cape Verde Archipelago, are described and interpreted in this work. The isle consists of a 700 m thick pile of basalt lava flows and scarce pyroclastics crossed by several families of dikes. The structure of the island could correspond to the remaining fragment of a primitive large shield volcano. The main hypothetical emission centre could once be situated between the present islands of Santa Luzia and Branco

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