Geogaceta -- Nº 29, (2000)

Permanent URI for this collectionhttps://hdl.handle.net/10272/9752

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Thermal evolution of the Miers Bluff Formation from apatite fission track (Livingston Island, Antarctic Peninsula region)
(Sociedad Geológica de España, 2000) Sell, I.; Poupeau, G.; González Casado, J. M.; López Martínez, Jerónimo
El análisis de las trazas de fisión en apatitos procedentes de los metasedimentos de bajo grado metamòrfico de la Formación Miers Bluff (Península Hurd, Isla Livingston, Islas Shetland del Sur) muestra que el enfriamiento posterior al pico metamòrfico comenzó hace unos 28 Ma. Este momento coincide con el fin de la actividad magmatica en este arco volcánico. Probablemente, el metamorfismo puede estar relacionado con la actividad magmàtica de este arco volcánico (140-30 Ma). La modelización de las trazas de fisión sugieren que la exhumación de la Península Hurd comenzó hace 13 Ma. La actividad volcánica reciente de la cuenca de Bransfield no está recogida en las huellas de fisión de los apatitos de la formación Miers Bluff
Sobre la composición isotópica del agua de lluvia en Sierra de Gádor (Almería)
(Sociedad Geológica de España, 2000) Vallejos, Ángela; Gisbert, Josep; Sánchez Martos, Francisco; Molina, Luis; Pulido Bosch, Antonio; Martín Rosales, Wenceslao
The stable isotopes of rainwater, measured in samples at locations with different altitude, show a distinctive altitudinal distribution. Analysis of the precipitation indicates the dominant source and direction of the air masses. The local meteoric water line that is established indicates a primarily Mediterranean origin for the precipitation recharging the aquifers
Sinistrai transcurrent transpression at the Ossa-Morena Zone / Central-lberian Zone boundary: the Portalegre-Esperanga shear zone (Portugal)
(Sociedad Geológica de España, 2000) Francisco Pereira, M.; Brandáo Silva, J.
En el borde sur del Macizo Ibérico, al NE del Alentejo (Portugal) se ha reconocido la zona de cizalla varíscica de Portalegre-Esperanga (PESZ). Esta zona incluye rocas del basamento de Ossa Morena del Proterozoico superior sobre las que reposa, discordante, una secuencia de rocas sedimentarías del Paleozoico Inferior de la Zona Centroibéríca. El análisis estructural de la PESZ revela una compleja arquitectura tridimensional caracterizada por una foliación milonitica muy vertical izad a, una lineación de estiramiento subhorizontal y simultánea una componente direccional (desgarre) y oblicua-direccional (inversa o normal) de sentido sinistrorso. Se ha interpretado como parte de un regimen de deformación transpresivo, en el que predomina una partición de la deformación y una dirección de transporte tectónico paralela al orógeno
Sedimentación pelágica jurásica sobre rocas volcánicas submarinas en Algarinejo (Provincia de Granada, Zona Subbética)
(Sociedad Geológica de España, 2000) Vera, J. A.; Molina, José Miguel
In the Median Subbetic (Algarinejo locality) submarine volcanic flows interbedded in pelagic Middle Jurassic sedimentary rocks have been previously described. Levels of caldsiltites with wave lamination and hummocky cross-stratification have been recently recognized in pelagic sedimentary rocks located directly on the Aalenian submarine volcanic rocks and below the Jarropa Radiolarite Formation. These sedimentary structures are an important argument in favour of a bathymetric interpretation of the pelagic sediments in which the depositional deep was moderate, permitting that the wave of the strongest storms could affect the sea floor
Sedimentación en plataforma somera durante el Neoproterozoico. Formación Boque-Serpins (Grupo de las Beiras) en Trevim (Sierra de Lousá, Portugal Central)
(Sociedad Geológica de España, 2000) Alonso Gavilán, G.; Sequeira, A. J.; Rodríguez Alonso, M. D.; Medina, J.
The metasediments of the Schist-Greywacke Complex (Durico-Beirao Supergroup) of late Neoproterozoic to lower Cambrian age are at present divided in Portugal into Beiras, Douro and Arda-Marofa Groups. In the Sierra de Lousa (western part of Central Portugal) there are outcrops of metasediments which belong to the Beiras Group, which comprises two formations known as Caneiro and Boque-Serpins. This work concentrates on the Boque-Serpins formation at Trevim, which is constituted by a dominant metapelitic succession that sporadically contains metagreywacke alternances. The great variety of sedimentary structures, most of them interpreted as wave generated helps define a set of facies associations which are arranged in several types of sequences reflecting a wide range of energy conditions that are explained as resulting from the interplay of storm and fear weather conditions. The sedimentolcgical characteristics recorded are consistent with a muddy shallow marine platform depositional environment on which longshore directed sandy bars were formed under the influence of storm events. On the other hand, the diversity of Quartz and Rock Fragments found in the greywackes has made it possible to identify several source areas (sedimentary, metamorphic, plutonic and volcanic) which, given their metaestable character and degree of preservation, would be located near the sedimentary basin
Reinterpretación paleoambiental de la Formación Rio Bonito (Pérmico de la Cuenca de Paraná) en el yacimiento de carbón de Iruí, Rio Grande do Sul, Brasil: Integración de análisis de facies, ¡enología y estratigrafía secuencial de alta resolución
(Sociedad Geológica de España, 2000) Buatois, L. A.; Netto, F. G.; Mángano, M. G.
The Permian Rio Bonito Formation of the Parana Basin, southern Brazil, has been traditionally interpreted in terms of a fluvio-dominated deltaic model. Integration of facies analysis, ichnology, and high-resolution sequence stratigraphy suggests that this unit represents deposition in a tide-dominated, fluvio-estuarine valley system. The overlying Palermo Formation records deposition in open-marine environments
Registro de isótopos estables -813C y 8180- en la sucesión miocena de la región suroriental de la Cuenca del Duero
(Sociedad Geológica de España, 2000) Armenteros, Ildefonso; Recio, Clemente; Corrochano, A.
The stable isotopic record for the carbonate rocks, mostly palustrine facies, making up the chemical facies of the Miocene (middle -Aragonian- and upper -Vallesian- Miocene) section in the southeastern region of the Duero Basin makes evident: i) S'JCPD8 and 8,sOP0B are respectively-6.41-7.9 and -5.11-7.1 for the Lower Unit, -6.61-7.9 and-6.M-6.7 for the Middle U., -5.71-8.1 and-5.21-6.7 for the Upper U.; ii) the cross-plot 8UC versus 8iaO indicates a different representation for the Upper and Lower Units and the Middle Unit plots at an intermediate position; Hi) only the U. Unit shows a moderate correlación (r = 0.69, n= 27); and iv) some carbonate sequences show an increasing 81sO trend at the same time as 813C values decrease. The range of 8wO and 8'3C values recorded is consistent with the pedogenetic effects observed on the limestones -palustrine facies-, with the 813C compositions (-5.7 to -8.1, somewhat heavier than an extreme C3 vegetation signature), suggesting the contribution of organic C. The recorded trends for 8,sO and 8UC values in some carbonate sequences point to an increasing exposure intensity at their tops. The slight increase in the 8,sO values for the Upper Unit could indicate that climatic conditions were somewhat warmer during the Vallesian
Reconocimiento geoeléctrico de paleovalles en la depresión terciaria de Ciudad Rodrigo
(Sociedad Geológica de España, 2000) Corrochano, A.; Andrés, M. F.; Barba, Pedro; Curiel, N.; Armenteros, Ildefonso
The V.E.S. (vertical electrical sounding) study undertaken in the Ciudad Rodrigo Craben unravels the structure and the lithology of the graben infill. The basement resistivity values (200-350 Qm) indicate the presence of NW-SE oriented paleovalleys which were responsible for the tertiary drainage. The resistivity values of the tertiary rocks show the presence of sandstones and conglomerates (40-70 Qm), sand and clay (20-30 ?m) and claystone (10-18 ?m). Each of these groups can be correlated to Paleogene and Neogene rocks according to surface observations
Reconocimiento geológico del entorno de las albuferas de Adra (Almería) a partir de datos geofísicos
(Sociedad Geológica de España, 2000) Benavente Herrera, José; Rodríguez, Mario
Geophysical techniques (Electrical Resistivity Profiles and Penetration Tests) have been used to identify the nature and geometry of the materials in which the Adra (Almería) lagoons are placed. Furthermore, a series of shallow piezometers (less than 3 meters depth) have been made in order to measure the watertable and to take soil samples. The obtained results show a substratum (metapelitic?) approximately at 70 m depth. Above this substratum there are sandy detritic materials saturated with waters of various salinity between fresh and saline. This fact indicates a thick transition zone due to the relatively low freshwater flow to the sea in this area. In the inmediate setting in which the lagoons are situated, there has been found alternating organic mud beddings and gravels into the sandy matrix. The sedimentary environment may correspond to several coastal bars with fluvial influence in a context of neotectonic activity
Paleoceanografía del Oceáno del Sur: nuevas aportaciones en el contexto del Ocean Drilling Program
(Sociedad Geológica de España, 2000) Flores, José Abel
Mineralogía de depósitos de tipo moonmilk en la Cueva de Nerja (Málaga, España)
(Sociedad Geológica de España, 2000) Casas, J.; Martín de Vidales, J. L.; Durán Valsero, Juan José
The mineralogical composition of moonmilk-type deposits located in Nerja Cave (southern Spain) has been studied. These deposits are composed only by carbonates, mainly huntite and dolomite. Magnesite and calcite are also present and occasionally aragonite. Depositional sequence proposed for the deposits in this cave is: calcite —> Mg-rich calcite —> aragonite —> dolomite —> huntite —> magnesite. Initial precipitation of calcium carbonates, progressive water evaporation and lost ofC02 give rise to the final precipitation of magnesium-rich terms
Low-K Tholeiitic Signatures in Calayan Island (Northern Luzon, Philippines)
(Sociedad Geológica de España, 2000) Pendón, R. R.; Corretgé Castañón, Luis Guillermo; Ordaz, Jorge
The Calayan island is a Tertiary (7-4 Ma) volcanic island situated in the northern portion of the Philippine archipelago, a part of Babuyan segment of the Luzon arc. It is a product of subduction of South China Sea oceanic crust underneath the Philippine terrane. Rock spectrum in the island ranges from basalt to rhyolite with andesite as the most predominating lava. Geochemical signatures are characterized by low concentrations of large-ion lithophile and flat behavior of rare-earth elements, a significant type of low-K tholeiitic series. The objective of this preliminary investigation is to determine the geochemical affinities of the island and its brief correlation to the nearby island of Camiguin de Babuyanes
Liesegang rings in pelagic limestones: genetic considerations
(Sociedad Geológica de España, 2000) Vera, J. A.; Molina, José Miguel
Liesegang rings have been recognized in Middle Jurassic pelagic marly limestones of the Subbetic, Southern Spain. The rings of these structures consist of iron hydroxide concentrations and/or small textural changes and are three-dimensionally distributed in the limestone and marly limestone beds. These structures have been previously described in siliceous rocks, in volcanic rocks and only rarely in limestones and marls. Liesegang rings are the result of geochemical and textural self-organization processes mainly produced by iron-rich fluids coming possibly from contemporaneous volcanic rocks. Chemical, mineralógica! and textural changes occurred prior to the lithification of the marly limestone beds, as is demonstrated by the presence of synsedimentary faults affecting these structures
Las pizarras negras del "Sinclinal de Las Herrerías", Faja Pirítica Ibérica
(Sociedad Geológica de España, 2000) González Barrionuevo, Felipe; Moreno Garrido, María Carmen; Rodríguez, R. M.; Sáez Ramos, Reinaldo
Black Shale Level of Las Herrerías Sindine is Tournaisian-Upper Visean (close to basal Namurian) in age and, it is stratigraphically equivalent to the Vulcano Sedimentary Complex in other places of the Iberian Pyrite Belt. Mapping features, including lateral pinch out of the volcanic levels, and palynological data point to a condensed sequence s.s. for this black shale level
La aureola de contacto de Porcía-Salave ( NO de Asturias): paragénesis y condiciones termobarométricas
(Sociedad Geológica de España, 2000) Rodríguez Vieítez, N.; Suárez Hernando, Oier
The Porcia-Salave contact aureole surround the igneous complex consisting of gabbros and granodiorites emplaced in a chlorite-zone metasedimentary rocks. Andalucite-cordierite-biotite assemblages are the most common at intermediate grade. Adjacent to the intrusive contact assemblages involving combinations of cordierite, andalusite, sillimanite and K felspar; spinel and corundum appears in quartz-absent rocks. The pressure contact metamorphism estimated on minerals equilibria is 2.6-3 kbar. Application of garnet-biotite and spinel-cordierite exchange thermometry gave T > 800 °C which are consistent with equibria involving Spl+Qtz=Crd.
Interaction between sedimentation and submarine volcanism (Jurassic, Subbetic, Southern Spain)
(Sociedad Geológica de España, 2000) Molina, José Miguel; Vera, J. A.
Se estudia la relación entre vulcanismo submarino y sedimentación carbonatada principalmente pelágica en el margen continental pasivo que actualmente aflora en el Subbético. Existen dos grupos principales de relación entre vulcanismo y sedimentación: 1) normal o gradual, y 2) catastrófica. En el grupo normal o gradual se presentan cinco tipos desde rocas volcánicas, compuestas sólo por lavas almohadilladas hasta la única sedimentación, incluyendo siete tipos en los que coexisten ambas rocas. La intensidad de la actividad volcánica controló especialmente el tipo y distribución de estas facies sedimentarias durante el Jurásico medio-superior del Subbético Medio, en esta parte de la cuenca
Información oceanógrafica suministrada por los Foraminíferos del Cuaternario terminal de la plataforma del Pacífico Colombiano
(Sociedad Geológica de España, 2000) Pascual, Ana; Pujos, Michel
The study of five Holocene sedimentary cores from the continental shelf of Colombia (Central East Pacific) allowed us to identify 89 species of benthic foraminifers. Two main foraminiferal assemblages have been distinguished. An assemblage, dominated by the cold-water species Brizalina subaenariensis, Uvigerina peregrina, Globocassidulina subgobosa, Bolivina alata and, Bulimina gibba is well developed between Curiche and Cupica Bay, in a water depth less than 60 m. This assemblage is characteristic of low oxygen and high organic carbon waters, possibly caused by upwelling. Southwards, from Baudo till Buenaventura locations, a second benthic foraminiferal assemblage occurs at 20 m depth, with the species Hanzawaia concéntrica and Nonionella atlantica, that appear only on core top samples of this area. The absence of microfauna, as well as the presence of abundant gypsum (desert rose) in the basal portion of these cores, suggest a change from open marine conditions to restricted lagoon paleoenvironment
Granates en las rocas intrusivas calcoalcalinas ricas en K de la Unidad Pisuerga-Carrión (Zona Cantábrica, Norte de España)
(Sociedad Geológica de España, 2000) Gallastegui, G.; Cuesta, Andrés; Suárez Hernando, Oier; Lobo Gallardo, Antonio
A small scale calcalkaline and late-orogenic intrusive assembly outcrops in the outermost part of the northern branch of Iberian Variscan Chain. Carnet is present as an accesory phase in the intermediate to acidic intrusive host rock (quartzdiorite to granodiorite) and associated metamorphic and igneous enclaves. Garnets are zoned and almandinic in composition; however, three types have been differentiated from compositional variations. Types 7 and 2 garnets are deep origin xenocrists rich in Ca and poor in Mn, whilst Mn rich and Ca poor Type 3 garnets are metamorphic restites. The presence of garnet xenocrists and other geochemical features evidence that melting processes involving stable garnet took place in the origin of the Pisuerga-Carridn intrusive rocks
Génesis y caracterización del cordón estuarino de Las Nuevas (P. N. de Doñana)
(Sociedad Geológica de España, 2000) Cáceres Puro, Luis Miguel; Rodríguez Ramírez, Antonio; Ruiz Fernández, Federico; González-Regalado Montero, María Luz; Muñiz Guinea, Fernando; Rodríguez Vidal, Joaquín; Abad de los Santos, Manuel; Carretero León, María Isabel
The georñorphological and palaeontological studies of the Las Nuevas estuaríne ridge indicates that these silty sands with abundant macrofaune were deposited over clayey marsh deposits during some erosive events at approximately 2000-1800 Cal UC years BP. >4 detailed analysis of the macro- and microfaune included in two drillings collected in this unit permits to delimitate two palaeogeographic sectors during this period: a) to the western, a lagoon with little to very little tidal renewal and; b) the main channel, introducing abundant marine microfaune toward the salt marshes during the tidal fluxes
Foraminíferos bentónicos actuales de la plataforma continental del norte del Golfo de Cádiz
(Sociedad Geológica de España, 2000) González-Regalado Montero, María Luz; Ruiz Fernández, Federico; Tosquella Angrill, Josep; Baceta, Juan Ignacio; Pendón Martín, José Gabriel; Abad de los Santos, Manuel; Hernández Molina, F. Javier; Somoza, L.; Díaz del Río, Víctor
The Benthic foraminifera of the superficial sediments of several cores from the continental shelf of the north Cádiz Cu If have been analized. The distribution of these organisms shows a clear dependency to the water depth, distinguishing therefore, two different associations: the first one, an inner shelf of around 30 m depth) and the second one, a middle shelf of around 30 and 100 m depth. The transition between both associations is gradual, however, the disappearance of representative species at middle depth in the inner shelf is observed

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