Geogaceta -- Nº 30, (2001)

Permanent URI for this collectionhttps://hdl.handle.net/10272/9509

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Estructura de Ios mantos superior e inferior del Pedraforca (Pirineos orientales)
(Sociedad Geológica de España, 2001) Martinez, A.; Berástegui, X.; Losantos, M.; Schöllhorn, Elmar
The Pedraforca nappe is one of the allochtonous structural units in which the Cover Upper thrust sheets of the southern Pyrenees are organised. Its is internally constituted by two thrust sheets, namely Upper Pedraforca thrust sheet and Lower Pedraforca thrust sheet. As a whole, they were emplaced in a piggyback thrusting sequence. But in the detail, a new, minor structural unit, here named "Intermediate unit", has been found in between them. This newly identified thrust sheet mainly consists of a carbonate breccia series, derived from the Lower Cretaceous sediments forming the Upper Pedraforca thrust sheet, showing an "inverted mountain" internal arrangement of elements. Restoration of a detailed cross-section allows us to interpret the Upper Pedraforca thrust sheet as the result of tectonic inversion of a Lower Cretaceous extensional basin occurred during late Cretaceous times. The sediments forming the Intermediate Unit are syntectonic materials, because they generated synchronously to the tectonic transportation of the Upper Pedraforca thrust sheet (Santonian to Maastrichtian). Further emplacement of the Intermediate unit included piggy back transportation of the Upper Pedraforca thrust sheet, until both structural units were definitively emplaced, and their frontal parts were covered by late Cretaceous to Palaeogene continental redbeds
Variaciones del estilo deposicional en el grupo aluvial Scala Dei, Cuenca del Ebro (Provincias de Tarragona y Lleida): Características y significado sedimentológico
(Sociedad Geológica de España, 2001) Pérez Lacunza, E.; Colombo Piñol, Ferrán
The Scala Dei Croup, which is composed mainly of conglomerates, is located in the SE sector of the Ebro Basin. Many alluvial fans were developed in this area during the Eocene-Oligocene time span. The clastic materials were transported and accumulated by hydraulic currents in braided-style rivers. However, there is a conglomeratic lithosome with a characteristic medium angle cross bedding continuous from the basal scar up to the medial part of the body. This is interpreted as a deposited in a sinuous channel with characteristics of coarse-grained meandering, and represents an important variation in depositional style. These variations can be associated with the a real shifting of the technically active basin border
Un dinosaurio saurópodo (Titanosauria) en el Cretácico superior de Cubilla, Soria (España)
(Sociedad Geológica de España, 2001) Pereda Suberbiola, Xabier; Ruiz Omeñaca, José Ignacio
An isolated sauropod vertebra from the Late Cretaceous of Cubilla (Soria, Spain), described originally in 1957 by Lapparent and collaborators, has recently been rediscovered in the collections of the Museum National d'Histoire Naturelle of Paris. The specimen was recovered from fluviatile clays of the „Carumnian fades" (Santibanez del Val Formation sensu Floquet, Maastrichtian in age). It is a posterior caudal vertebra characterised by a subrectangular centrum that has nearly flat ventral and lateral surfaces. The presence of a neural arch situated on the anterior part of the centrum is a synapomorphy of Titanosauriformes. The Cubilla vertebra is roughly similar to those of basal titanosaurians in having an amphicoelous centrum, in contrast to the procoelous caudals of the Titanosauridae. It is here referred to Titanosauria indet
The Northeast Alentejo Neoproterozoic-Lower Cambrian succession (Portugal): Implications for regional correlations in the Ossa-Morena Zone (Iberian Massif)
(Sociedad Geológica de España, 2001) Francisco Pereira, M.; Brandáo Silva, J.
The Neoproterozoic-Lower Cambrian succession of the Northeast Alentejo (Portugal) is revised from a stratigraphic perspective in order to propose regional correlations with similar Ossa-Morena Zone domains in Spain. This revision now allows a better characterization of one of the most illustrative Neoproterozoic-Lower Cambrian stratigraphic sections of the Iberian Massif. The Serie Negra Group that is represented in Portugal by the Mosteiros Formation and Besteiros Amphibolites can be correlated with the Tentudia Formation and probably to part of the Montemolin Succession. The Neoproterozoic?- Cambrian transition unit known as the Volcano-Sedimentary Complexes of Nave de Crou-Azeiteiros and Freixo-Segóvia in Portugal are correlationable with the Malcocinado Formation widely distributed within the Ossa Morena Zone in Spain. The uppermost units, attributed to the Lower Cambrian and recognized as the Detritic-Carbonate Complexes of Ouguela and Assumar in the Northeast Alentejo can be correlated with the terrigenous Torreárboles Formation and the carbonate Alconera Formation described in Spain. In the context of the orogenic cycles in Iberia, the concept of Cadomian basement should be enlarged to the Cambrian period
Tectonic and environmental controls on platform geometry and facies architecture: The late Aptian-early Albian carbonate episode of the Castro Urdíales platform margin (Cantabria, northern Spain)
(Sociedad Geológica de España, 2001) Rosales, Idoia
El episodio carbonatado Aptiense superior-Albiense inferior (Zonas jacobi-tardefurcata) del margen de plataforma de Castro Urdíales registra un aumento gradual del stress paleoambiental acompañado por cambios en el estilo y geometría de la plataforma carbonatada, que precedieron a un episodio de rifting que tuvo lugar durante el Albiense inferior. Este estudio sugiere que los cambios en la geometría de la platforma carbonatada respondieron principalmente a cambios en factores paleoceanográficos y niveles tróficos que acompañaron a una etapa de hundimento general de la cuenca y aceleración de la subsidencia justo antes del episodio de rift
Señales geoquímicas y micropaleontológicas como marcadores de eventos paleoceanográficos en el Santoniense del Arco Vasco
(Sociedad Geológica de España, 2001) Jiménez Berrocoso, A.; Pascual, Ana; Elorza, Javier
Comparative study of micropalaeontologic (planktonic and benthic foraminifers) and isotopic (8,80 and 5'3C values from inoceramids and whole rock) data from the Santonian of the Barrika section (Basque Arc, northern Spain) shows the existence of four events, each one with different biotic and geochemical signals. Diagenetic alteration of isotopic profiles (5,eO and 8I3C) have not been so severe to delete completely the geochemical signals from inoceramids and whole rock. As a consequence, events 1st, 2nd and 3rd show a 5lsO positive excursion (cooling) and sea level falls; however the 4th event marks a global regression at 85 m.y., that could have caused strong local alteration of the planktonic and benthic foraminifer assemblages. In this case, the eustatic fall shows a S'0O negative excursion, that could be related to meteoric cementation, due to sea level lowstand
Sedimentologia de la Formación Chenque (Oligoceno-Mioceno) en Comodoro Rivadavia. Argentina
(Sociedad Geológica de España, 2001) Paredes, J.; Colombo Piñol, Ferrán
The Oligocene-Miocene marine rocks of the San Jorge Basin (Argentine Patagonia) were studied in the proximity ofComodoro Rivadavia. The basal transgression deposited a residual lag composed ofshoreface sediments on the Sarmiento Formation (Eocene-Oligocene). Shelf sediments above the basal transgression have bioclastic lenses suggesting strong currents and transport of sediment under the fair-weather base level. A progradational complex was formed showing coarsening-upward cycles in shoreface-inner foreshore setting, which include some channels with bioclastic and clastic in-fill, and little evidence of tidal action. The presence of carbonaceous concretions, hardground and glauconitic mineral deposits on the top of this section suggests the abandonment of the,system. A new transgressive cycle accumulates shelf clay and siltstone intercalated with bioclastic material. This progradational system was covered with shoreface and foreshore facies, showing tidal and wave action. Bioclastic and clastic materials, accumulated on a major discontinuity surface by meandering tidal channels show progradacional pattern stacking and fining upwards successions. These materials grades, by means of medium sandstone with bioclastic lenses, to mudstone deposited in a estuarine bay (or lagoon) with very little bioturbation. Some bioclastic and clastic materials intercalated with the mudstones, represent storm deposits in a restricted area. The unit may be interpreted as having been deposited in a clastic shelf with tidal and wave influence
Rodingitización y formación de pectolita en diques graníticos de las Peridotitas de Ronda (Cordilleras Béticas, España)
(Sociedad Geológica de España, 2001) Esteban, José Julián; Cuevas, Julia; Tubía, José María; Yusta, Iñaki
This work reports the local occurrence of rodingites formed from granitic dykes intrusive in the Ronda Peridotites. Representative mineral assemblages include chlorite, hydrogrossular, and prehnite but also pectolite, and xonotlite uncommon mineral in rodingites. In addition, some granitic dykes are characterized by the albitization of plagioclases. The development oflizardite in the adjacent serpentinites suggests that rodingitization was a low-temperature metasomatic process, which affects the granitic dykes in contact with peridotites during serpentinization
Resultados de SEM/EDX en morteros de restauración aplicados a areniscas del Eoceno de Gipuzkoa utilizadas en la construcción de edificios
(Sociedad Geológica de España, 2001) García Garmilla, Francisco; Cano, M.; Yusta, Iñaki; Ibáñez Gómez, J. A.; Rodríguez Maribona, I.; Beraza, K.; Garin, S.
The restoration of buildings made of sandstones is a critical problem in the Basque Country, because the wide use of Eocene sandstones that appear as a constructing material very frequently affected by weathering processes. The impossibility to recuperate the original material sometimes leads to complete or even replace the masonry stones with mortars which should have the same physical properties and visual appearance than the original stones. Our research is focused to find the better mortars for the Eocene sandstones, and even to synthesize a mortar having the same resistance to weathering than the original sandstone. In order to improve the research, the first step was to accurately know the intimate textures of several types of mortars for furtherly test their physical behaviour under different experimental techniques in the laboratory. We have compared the textures of three commercial mortars (A, B and C) and a fourth one synthesized by Teusa. The mortar A is an amorphous arid-free alite-mortar, whereas the B and C are composed by quartz, alite and calcite. From all the four studied mortars, the A seems to be the most appropriate to rejoin the Igueldo sandstone masonry stones, without exclude its use for completion. The B and C mortars are suitable for completion because their composition and texture is very similar to that of Eocene sandstones. Finally, the uncommercialized Teusa mortar is thought to have by the moment an excessively resistant behaviour when compared to Eocene sandstones. Being relatively-close the textures of all the four studied mortars, we think that both organic additives or catalysts together with the ratio high-Ca-lime/white-cement should play an important role in the final properties of the mortars
Restos de elefante (Proboscidea, Mammalia) en el Pleístoceno de Obón (Cordillera Ibérica, Teruel)
(Sociedad Geológica de España, 2001) Barco, J. L.; Cuenca Bescós, G.; Gutiérrez Santolalla, F.; Rubio, C.; Rubio Dobón, J. C.
An elephant tusk has been found in a fluvial terrace of a small creek affluent of the Martin river. The tooth is slightly curved, almost round in section and becomes increasingly smaller towards the tip. The specimens measurements and morphology lead us to propose it as a task of the "wood elephant" of the Pleistocene of Europe: Paleoloxodon antiquus, probably of an adult male
Reconstrucción paleoambiental del tránsito Cretácico-Terciario en La Lajilla (México) con foraminíferos
(Sociedad Geológica de España, 2001) Alegret, Laia; Arenillas, J. I.; Arz, José Antonio; Meléndez Hevia, Alfonso
Upper Maastrichtian and lower Danian sediments belonging to the Méndez and the Velasco formations, respectively, contain abundant foraminifera at La Lajilla section (northeastern México). Foraminifera! turnover across the K/T boundary indicate a catastrophic mass extinction of planktic foraminifera, whereas benthic foraminiferal extinction do not exceed 25%. The most important change in benthic foraminifera across the KIT boundary consists of a reorganisation of their communities: infaunal morphogroups were more affected than the epifaunal ones. Most of the infaunal species became extinct or temporally disappeared, due to the lack of nutrient supply toward the sea bottom floor. Infaunal percentages increased after the boundary, and indicate primary productivity recovery at La Lajilla during the lower Danian
Rasgos estructurales de la formación granulítica de alta presión de la Bacariza (Cabo Ortegal, NO España)
(Sociedad Geológica de España, 2001) Puelles, Pablo; Ábalos, Benito; Gil Ibarguchi, José Ignacio
Heterogeneous ductile deformation occurred in the Bacariza formation coeval with hercynian high-pressure granulite facies metamorphism. Eye and anvil fold structures in YZ structural sections have been identified in several outcrops as well as on the map scale. They are interpreted as lineation-perpendicular sections of sheath folds. The mapped foliation trajectory closures produce a variety of geometries defining dome, saddle, basin and inverted saddle configurations, likely related to culminations and depressions of secondary sheath folds within a major one. These sheath-like folded structures might be considered as natural examples of heterogeneous shear in deep subduction/collision channels
Problemática de la Formación Las Médulas y sus implicaciones morfotectónicas (El Bierzo y SE de Galicia)
(Sociedad Española de Geología, 2001) Pagés Valcarlos, J. L.; Hacar, M.; Alonso, Ángela
The usual ideas about the Cenozoic stratigraphy of El Bierzo Basin are reconsidered in this article, putting up a new chronoestratigraphic interpretation of Las Médulas Formation. The Unit is considered as fluvial in origin and Palaeogene in age, and, according to that estimated age, the géomorphologie evolution of El Bierzo Basin during the Cenozoic is also outlined
Presencia de una anfibolita derivada de un MORB en el dominio Continental de la banda metamorfica de Aracena (Macizo Ibérico meridional)
(Sociedad Española de Geología, 2001) Díaz Azpiroz, Manuel; Castro Dorado, Antonio; Fernández Rodríguez, Carlos
The La Corte Amphibolites are a part of the medium grade metamorphic series of the continental domain of the Aracena metamorphic belt (AMB). These amphibolites are rich in iron, as it is deduced from the abundance ofFe-rich amphiboles, includinggrunerites, and metallic minerals as well. Acording to different characteristics concerning structure, mineral chemistry and whole rock geochemistry, we can suggest that the La Corte amphibolites were not formed from the same protoUth that generated the Acebuches amphibolites, in the oceanic domain of the AMB. Multielemental and REE spidergrams allow as to conclude that the La Corte amphibolites formed from an oceanic crust whose characteristics are typical of those of a transitional oceanic basalt (T-MORB)
Pliegues eocenos de dirección N-S en el Pirineo occidental
(Sociedad Española de Geología, 2001) Payros, Aitor; Pujalte, Victoriano; Tosquella Angrill, Josep; Orue Etxebarria, Xabier
Several N-S trending folds have been identified in the Eocene strata of the western Pyrenees. Stratigraphical and sedimentological lines of evidence show that they formed from late Ypresian to middle Lutetian times. These new data agree with previous works considering this time interval as a period of increasing tectonic activity. The N-S orientation of the folds is anomalous in the the pyrenean domain, where most tectonic structures are SE-NW elongated. Therefore, the N-S folds might have formed in response to local strains. They could represent «en echelon» folds related to the shear-stress produced by the dextral movement along the SW-NE trending Pamplona fault
Ostracofauna y Foraminíferos: implicaciones cronoestratigráficas y paleoambientales durante el Neógeno superior en el área del Oued Arjat (Cuenca de Bou Regreg, Marruecos)
(Sociedad Española de Geología, 2001) Civis-Llovera, Jorge; González Lucas, C.; Alonso Gavilán, G.; González Delgado, José Ángel
In this work we analyze the Ostracofauna and Foraminifers from the Upper Neogene of the Oued Arjat area (Bou Regreg basin, N of Morocco). There is a significative change in paleobathymetry between the lower and the upper levels, separated by an unconformity. As showed by Ostracofauna, benthic Foraminifera and Mollusks, the communities of the lower levels are interpreted as originated in paleoenvironments of external marine platform, whereas those of the upper levels are typical of circalittoral conditions of an inner platform. The levels overlying the unconformity are atributed to the Globorotalia puncticulata biozone (Upper Zanclean), wereas those under them, are discussed as Upper Messinian-Lowermost Pliocene age
Nuevos datos bio-cronoestratigráficos para el sector suroccidental de la cuenca del Guadalquivir (Área de Lepe-Ayamonte, Huelva, España)
(Sociedad Española de Geología, 2001) Muñiz Guinea, Fernando; Mayoral Alfaro, Eduardo; Cáceres Puro, Luis Miguel; Cachão, Mário
The paleontological data of the marine neogene sediments in the Lepe-Ayamonte area, Huelva (SW of the Guadalquivir basin) allow to establish a relative chronology from the presence of calcareous nannoplancton and malacofaunes. These data are congruent with the previous radiometric age
Nuevos datos mineralógicos y texturales de los granates y fases asociadas del Cerro El Hoyazo (Almería)
(Sociedad Española de Geología, 2001) Muñoz Espadas, M. J.; Martínez Frías, J.; Lunar Hernández, Rosario
New data from the Cerro El Hoyazo Neogene volcanic complex (Níjar, Almería province, SE Spain) are given, stressing the mineralogical assemblages and textures of garnets and their associate phases. In addition, the characteristics of garhet, biotite, sillimanite, plagioclase, cordierite and quartz from both the dacite lava and metamorphic xenoliths are compared
Nuevos datos microestructu rales sobre la existencia de deformaciones precámbricas en la Sierra de la Demanda (Cordillera Ibérica)
(Sociedad Española de Geología, 2001) Ábalos, Benito
Microstructural surveying of pebbles of the early Cambrian «Anguiano Conglomerates» permits to recognize a variety of microstructures and textures that resulted from syn-metamorphic (up to 400°C, low-temperature greenschists facies) ductile deformations. The source area of the conglomerates was likely a Neoproterozoic basement that recorded the imprint of the Cadomian orogeny and that contained penetratively deformed metamorphic rocks in addition to the arc-related ingeous suites that have been detected or inferred so far in other realms of the northern Iberian Massif
Nuevas icnitas de dinosaurios terópodos y saurópodos en Galve y Miravete de la Sierra (Teruel. España)
(Sociedad Española de Geología, 2001) Pérez Lorente, Félix; Romero Molina, M. M.
Five new Theropod and Sauropod dinosaur footprint associations (RB, 1.1MV, 1.2MV, 2.1MV, 2.2MV), from three new sites (RB, 1MB, 2MB) in the Teru4l province, have been studied. The Theropod dinosaur footprints from the RB site are the oldest and there are the first plantigrade trackway that has been ever quoted in this province. The Sauropod dinosaur footprints have the general characteristics of the prints left by herds of these animals, which could mean these group of dinosaur were relatively abundant in those lands

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