Geogaceta -- Nº 11, (1991)

Permanent URI for this collectionhttps://hdl.handle.net/10272/14917

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Una zona de cizalla sinmetamórfica de importancia regional al SW de Sierra Albarrana (zona de Ossa Morena)
(Sociedad Geológica de España, 1991) Azor, A.; González Lodeiro, Francisco; Simancas Cabrera, J. F.
A subvertical syn-metamorphic shear zone with dextral sense of movement is described. This shear sone is slightly obligue to the metamorphic zonation and the lithological contacts. The south eastern end of the Sierra Albarrana Quartzites is explained by the superposition of the shear zone to the previous folds in the Quartzites
The Aitzgorrigain platform-margin paleokarst: general characteristics and origin (Lower Albian, N Spain)
(Sociedad Geológica de España, 1991) Gómez Pérez, I.; Fernández Mendiola, Pedro Ángel; García Mondéjar, Joaquín
El paleokarst de Aitzgorrigain se encuentra en el margen de plataforma carbonatada de ltxina (Gorbea, Vizcaya). Es de tipo localizado, con una gran cavidad de disolución de 10 a 30 m. de anchura y 40 de profundidad, con morfologías ramificadas; fuera de esta cavidad apenas hay reflejo de disolución a gran escala. El relleno presenta calcarenitas laminadas con bioclastos recristalizados, alternando con micritas y ocasionales clastos de caliza encajante y dolomía. Tanto en el frente de la plataforma como detrás del margen el paleokarst se correlaciona con megabrechas calizas de resedimentación en masa. Se invoca una caída del nivel del mar de un máximo de 60 m. para explicar su origen; dicha caída provocó disolución localizada en grietas, resedimentación en masa y dolomitización superficial. El relleno de la cavidad principal se produjo durante la subida posterior del nivel de/ mar, mediante una sedimentación restringida de aguas tranquilas (micritas) y agitadas (calcarenitas).
Tectónica pliocena en la Fosa de Daroca (prov. de Zaragoza)
(Sociedad Geológica de España, 1991) Gracia Prieto, Francisco Javier
The Daroca Graben was generated in Pliocene times, being filled by detritic sediments of Pliocene s.l. age. These deposits are afected by normal faults and by the renewed movement of the main fau/t that limits the NE border of the graben. Such dislocations are fossilized by plioquaternary alluvial fans, which permit us define a distensive tectonic episode at the fina/ Pliocene (Darocian Phase). The distensive tectonic activity has continued during quaternary times, although with a lesser intensity
Significado de la composición isotópica (ò 13 C y ò 18 0) en paleosuelos carbonatados. Mioceno de la Cuenca de Madrid
(Sociedad Geológica de España, 1991) Wright, V. P.; Alonso Zarza, Ana María
Carbon and oxygen isotope analyses from pedogenic carbonates of the N and NE areas of the Madrid Basin show ranges of ô 13C from —10 to —5.5 and 8 80 from —9.2 to —3.5 in the N area and ô13C from —8.2 to —5.5 and ô180 from —8 to —4 in the NE one. Differences between calcretes and shaIlow lake carbonates in the N area are related to differences in the evaporation rate, possible vegetation type and ground-water influence of the adjacent lake system. In the NE area a pedogenetic trend is observed and lighter values are indicative of a higher degree of pedogenetic alteration. Differences between the studied areas may indicate distinct vegetation types or a slight contamination by marine carbonates. In this paper we try to show how the interpretation of the isotopic composition of calcretes is particularly difficult in view of the large number of factors which may such values
Paleokarst jurásico en la Unidad del Ventisquero (Subbético Externo, Cordilleras Béticas)
(Sociedad Geológica de España, 1991) Molina, José Miguel; Nieto, Luis M.; Ruiz Ortiz, Pedro Alejandro
The importance of Jurassic karstification at the top of the Gavilan Fm. (Lower Jurassic) in the Ventisquero Unit (southern External Subbetic) is stated. We have recognized and analysed a significant subaeria/ exposure surface with paleokarst morphologies and calcrete. The different sediments and paleokarst fossilization phases are characterized and interpreted in the context of the Mesozoic South-lberian margin
Observaciones sobre las fracturas de las diaclasas plumosas
(Sociedad Geológica de España, 1991) Pocoví Juan, Andrés; Arlegui, L. E.; Simón Gómez, José Luis
Many joint surfaces show en échelon arrays of microfractures (F-joints) along one or both fringes of hackle marks. Our field observations indícate that, where both sets are present, they are stepped in oposite senses. So the F-joints can not be used as shear criteria for discontinuities. Good examples of hackle marks with F-joints have been reproduced in the laboratory by submitting silicone putty to tensile tests when these include sorne rotational component. Rotation induces shear in different senses if observed from an external point of view; so it can explain the development of two sets of Riedel fractures showing opposite stepping. In geological conditions, this rotation occurs around the tips of fractures undergoing vertical displacement. Thus, from this model, hackle marks and F-joints could be used for detecting the sense of small dip-slip movements on joints
Nuevos datos sobre la edad del inicio de la sedimentación continental en la Cuenca de Guadix. Cordillera Bética
(Sociedad Geológica de España, 1991) Soria, Jesús M.; Ruiz Bustos, A.
A new microvertebrate site named Salinas is found in the north edge of Guadix Basin. lt is date as Upper Turolian: MN 12, and permit approximate us to starting age of the continental sedimentation in the basin
Nuevos datos biostratigráficos de los materiales continentales del sector suroriental de la Cuenca de Guadix-Baza. El yacimiento de Caniles
(Sociedad Geológica de España, 1991) Guerra Merchán, Antonio; Ruiz Bustos, A.
The presence of the Mimomys (Villanyia) savini (Hinton, 1910) in the Caniles site allow us to assign a Lower-Middle Pleistocene age for Caniles Materials and permits to arrange in a temporary order this lithologica/ unit within the continental fil/ of the Southeastern sector of Guadix-Baza Basin
Nota preliminar sobre la presencia de turmalinitas estratiformes en el Ordovícico Inferior de Latedo (NO de Zamora)
(Sociedad Geológica de España, 1991) Fernández Fernández, A.; Moro Benito, M. C.
In this paper, the geological, texto-structural, mineralogical and chemical features of the stratiforme tourmalinites from the Lower Ordovician volcano-sedimentary Cabeza de las Viñas Formation (Alcañices Synforme), are given. According to these data, it is suggested that these tourmalinites has been originated by regional metamorphisme of the B-rich pelitic beds. The B were probably trought to the sediment by the hidrothermal solutions related with the underlayžng metabasaltic rocks existing in the studied area
Modelos gravimétricos para la corteza superior en el borde SE del Sistema Central Español
(Sociedad Geológica de España, 1991) Babín, Rosa; Bergamín, J. F.; Fernández Rodríguez, Carlos; González Casado, J. M.; Hernández Enrile, J. L.; Rivas, A.; Tejero López, Rosa; Vicente, Gerardo de
A gravity research was carried out in the SE of the Spanish Centra/ System. The upper crust has been modelled in 2 1/2 D along three profiles. The gravity models suggest that the faults affecting both the Mesozoic-Cenozoic cover and the Hercynian basement are main/y high angle inverse fau/ts. Sorne of them bound permian bassins and they are basement faults, reactivated during the alpine deformations. Key words: Gravity models, Upper Crust, Spanish Central System
Mejoras en la separación de minerales pesados usando politungstato sódico
(Sociedad Geológica de España, 1991) Pérez Mazarío, F.; Rincón, R.; Hernando, S.
Sodium polytungstate is a new product that can be used for purposes of separation of heavy minerals. The solution is nontoxic and it is recomended as a substitute for tetrabromoetane (TBE) and bromoform, considered as hazardous substances to handle in laboratory. In this paper we point out the advantages and missadvantages observed in its use as well as the laboratory procedures for its management. We also present advances that al/ow us to avoid the problems coming from the slow filtration rates ofsodium polytungstate
Magnetoestratigrafía y origen de la remanencia del Triásico en la Cordillera Ibérica
(Sociedad Geológica de España, 1991) Rey, Daniel; Turner, P.; Ramos, A.
Detailed palaeomagnetic sampling has been made of two units of the Middle Triassic in the western Cordillera Ibérica in Central Spain. Thermal demagnetization reveals the preservation of characteristic Triassic remanence. A recent overprint is also present, but it is almost completely removed after 5000 C. A magnetostratigraphic section was constructed based upon the isolated stab/e components related to the higher unblocking temperature
Magmatismo postorogénico y anorogénico en el Sistema Central Español
(Sociedad Geológica de España, 1991) Villaseca, Carlos; Huertas, María José; Nuez, J. de la
This work is a summary of the last magmatism in the Spanish Central System, which range in age from Permian to Jurassic times. During Permian the magmas change from peraluminous and calcalkaline to shoshonitic affinities, essentially as small plutons and later dike intrusions. This postorogenic magmatism could be related to latehercynian shear faults. At Iower Mesozoic age there are some dike intrusions ofalka/ine to tholeitic magmas in an anorogenic environnement related to Pangea transform zones of pre-At/antic opening
Los granates de rocas metapelíticas de la Región Central Española: implicaciones en el origen de granates en granitoides
(Sociedad Geológica de España, 1991) Villaseca, Carlos; Barbero, Luis
The differences in garnet composition of three grade-metamorphic zones of Central Hercynian Belt, can be used to estimate the thermobaric conditions of the rocks. The unusual garnet composition in granulite xenoliths ofalkaline dikes suggest a younger granulite episode linked with the latehercynian granite generation. The restitic origin of garnets in some granitoids of this region is also argued
Los Esciurópteros del Mioceno de la cuenca del Vallès-Penedès (Cataluña, España)
(Sociedad Geológica de España, 1991) Atdana Carrasco, E. J.
In this paper the Sciuropteres from the Miocene of Vallès-Penedès basin are described. Two genera and four species were recognised. The distribution of Miocene Sciuropteres remains in Cata[uña is compared with that of Other Spanish localities, obtaining interesting paleoecological conclusions
Las mineralizaciones estratoides de Zn-Pb de la serie de Vegadeo en la zona de Ponferrada (zona Astur Occidental Leonesa, NO de España)
(Sociedad Geológica de España, 1991) Ribera, F.; Tornos, Fernando; Locutura, J.
In relationship with the Cambrian limestones of the Ponferrada area three kinds of stratabound Zn-Pb ore deposits are formed in different epochs and conditions. They include diagenetic mineralizations in undisturbed limestones, probably late-diagenetic ones in relationship with a silicification of limestones in contact with shales and, fina/ly, breccias interpretated as their possible hercynian remobilization
Las discontinuidades estratigráficas del Buntsandstein en el borde occidental de la cuenca triásica y su implicación en las correlaciones
(Sociedad Geológica de España, 1991) Sánchez Moya, Yolanda; Muñoz, A.; Ramos, A.; Sopeña, Alfonso
The correlation among the diverse areas where the Triassic sediments have been described in the western Cordillera Ibérica and the border area of the Sistema Central has proved to show great difficulties. A very detailed field work, carried out here, have resulted in the elaboration ofa geological map where the various lithological units and the existing unconformities have been recognized A correlation chart has been elaborated where is clearly displayed how the main changes are related to the beginning of triassic where the major changes in thickness and facies took place, as a result of different subsidence areas
Isopiezas y direcciones del flujo regional en el acuífero carbonatado mesozoico del margen Ibérico de la Depresión del Ebro
(Sociedad Geológica de España, 1991) Sánchez Navarro, José Ángel; San Román, J.; Miguel, J. L. de; Pérez Muñoz, Antonio; Martínez Gil, F. J.
Groundwater discharge from the Iberian Chain into the Ebro tertiary basin takes place through the mesozoic carbonated rocks. These rocks extend from La Rioja to the Mediterranean sea. In this work, it is shown the Jurassic aquifer equipotential levels map as well as the groundwater flow directions. The recharge and discharge areas, the aquifer-river relationship, and the hydrogeological limits of the aquifer are also shown
Incised valley fills at a Iower Albian sequence boundary (Western basque-cantabrian basin, North Spain)
(Sociedad Geológica de España, 1991) García Mondéjar, Joaquín; Fernández Mendiola, Pedro Ángel
El límite de secuencia Albiense inferior basal del Complejo Urgoniano Vasco-cantábrico pre senta un paleorelieve con valles excavados en la parte oeste de la cuenca. El relleno de estos valles fue de conglomerados fluviales en zona proximal (Polientes), areniscas y conglomerados fluviales en zona intermedia (Santa Gadea), y deltas conglomeráticos y areniscosos de tipo Gilbert en zona distal (Cotero-Lunada). E/ origen de las excavaciones se atribuye a una caída relativa importante del nivel del mar que siguió a un pulso tectónico regional. Los valles tuvieron polaridades N y NW, y se dis pusieron en sinclinales y fosas siguiendo directrices tectónicas de bloques de zócalo o alineaciones diapíricas
High pressure mineral assemblages in the Trevenque Unit (Central Alpujarrides, Andalucía)
(Sociedad Geológica de España, 1991) Azañón, José Miguel; García Dueñas, V.; Goffé, B.
The Trevenque Unit is located in the Alpujarride Complex. In this unit, the Fe-Mg carpholite, cloritoid, chlorite, kyanite aragonite assemblages show metamorphic evolution at HP-LT conditions The metamorphic peal< is estimated to have been at 400-4500 C and at least 10 Kb. The pressure conditions in the Alpujarride Complex are similar to those observed in the underlying Nevado-Filabrides Complex

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