Geogaceta -- Nº 33, (2002)

Permanent URI for this collectionhttps://hdl.handle.net/10272/9029

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Water solubility in monzogranite melts: experimental and calculated water contents at 6 kbar
(Sociedad Geológica de España, 2002) García Moreno, Olga; Castro Dorado, Antonio; Corretgé Castañón, Luis Guillermo
Several piston-cylinder crystallisation experiments have been performed with a synthetic monzogranitic glass with different initial water contents at 6 kbar. Comparison with calculated water contents shows: 1) some differences of the order of 10% of XH2Q; 2) "non-linear" behaviour in XH2C/T curves; and 3) similar pattern in the XH2JT curves in both measured and calculated data. Resumen Se han realizado varios experimentos de cristalización en aparatos "piston-cylinder" a 6 kbar, usando como material de partida vidrios monzograníticos con diferentes contenidos de agua inicial. La comparación con los contenidos de agua calculada han puesto de manifiesto que: 1) existen diferencias del orden del 10% de XH20; 2) las curvas XH2C/T muestran comportamiento no linear; y 3) la forma de las curvas XH1JT calculadas y medidas son similares
Variaciones de salinidad en Las Albuferas de Adra (Almería)
(Sociedad Geológica de España, 2002) Benavente Herrera, José; El Amrani Paaza, N.; Rodríguez Rodríguez, Miguel
Water level and water salinity (expressed as electrical conductivity, EC) of the two Adra lagoons -"Honda" and "Nueva"- have been periodically recorded during the years 7999 and 2000. EC was also measured in a number of open wells and shallow piezometers around the lagoons. Data obtained have been compared with previous EC measures, dating back to 1 984. Salinity evolution in the lagoons is mainly conditioned by evaporation and rain-induced dillution effects. Evaporative concentration is comparatively less intense in the Nueva lagoon, due to its higher water storage. Dillution is more effective in the Honda lagoon because of the Incidence of esporadic runoff which doesn't affect to the Nueva. Then, the range in EC variations is higher in the Honda than in the Nueva, and the seasonal evolution can show different trends during the normal hydroperiod. As an average, the salinity in both lagoons is fairly similar to that of the shallow groundwater in the sector of the aquifer where the lakes are located (mean values of 3-7 mS/cm of EC). A trend has been Identified of increasing salinity with the vicinity of the sea shore. This is in agreement with geophysical data which suggest the existence of brackish connate waters in recent littoral sediments below the lagoons
Tasas de sedimentación reciente en la Ría de Huelva
(Sociedad Geológica de España, 2002) Morales González, Juan Antonio; Gutiérrez de San Miguel Herrera, Enrique; Borrego Flores, José
The Ria of Huelva is located at the central sector of the Huelva Coast. It Is a mesotidal estuary supplied by two rivers (Tinto and Odiel). Tinto and Odiel rivers have small mean discharges (100.48 Hm3 and 429.40 Hm3) but they are strongly seasonal. The mean tidal range is two meters. Sedimentation is controlled by the water mixing model, which is well mixed in both cases. Water usually has high concentrations of suspended matter, so the sediment is mainly muddy in the central basin. The fluvial estuarine channels may accumulate fluvial sandy bars during winter discharges. The outer estuary displays sandy facies of marine origin. The results of accumulation rates t210Pb y UC) supplied by this paper suggest a direct relation between the agradation rate, the depositional subenvironment and the lithology. These rates oscillate between 1 and 4 mm/year for subtidal and intertidal unvegetated muddy environments and grow to about 6 mm/year for sandy subtidal environments and more than 1 cm/year in vegetated marshes
Sistemas fluviales efímeros del Jurásico Superior en la cuenca Neuquina, República Argentina
(Sociedad Geológica de España, 2002) Spalletti, L.; Colombo Piñol, Ferrán
A sedimentary model for the Kimmerídgian Tordillo Formation of the Neuquén basin is proposed. Through the measurement of three strati graphic logs, an ephemeral fluvial system associated with continental mud flats is proposed. The proximal areas are characterised by gravelly and sandy-gravelly longitudinal bars formed in a traction-dominated braid-plain. Towards distal areas, sandy lobes composed of small 3D bars and aggrading current ripples formed during sudden non-channelised floods, alternate with mudflat deposits. This ephemeral fluvial system was developed under a generalised phase of arid to semiarid climate. The volcaniclastic nature of the Tordillo deposits and the palaeocurrent trends allow to suggest a positive land located to the south (Dorsal de Huincul). The uplift of this structure was intense and active at the time of deposition of the Tordillo Formation
Secuencia cronoestratigráfica del Pleistoceno Superior en Sierra Morena: la cueva de La Sima (Constantina, Sevilla)
(Sociedad Geológica de España, 2002) Rodríguez Vidal, Joaquín; Cáceres Puro, Luis Miguel; Álvarez, G.; Martínez Aguirre, Arancha; Alcaraz, J. M.; Riquelme Cantal, José Antonio; Recio Espejo, José Manuel
La Sima of Constantina, located at the northermost part of Seville province, is a karstic cave with a thick terrigenous and chemical (flowstone) record. These sedimentary formations are representative of the Late Quaternary palaeoenvironmental history about these mountains (Sierra Morena) of the Southwestern Iberian Peninsula. There are many evidences of vertebrate bone remains of alleged prays, coprolites and bones of spotted hyaena (Crocuta cf. crocuta), mainly at the lower sedimentary layers, dated c.a. 72.5 ky BR Upper detritic sediments show Calcolithic remains, with human bones, pottery and charcoal layers aged 4 600 ± 200 cal yr AMS
Relleno sedimentario y destrucción de una pequeña cuenca fluvio-lacustre en la Sierra Sur de Jaén (Cordilleras Béticas)
(Sociedad Geológica de España, 2002) García García, Fernando; Sánchez Gómez, Mario
The sedimentary infill of a small continental basin and the processes involved in its transformation into an erosionaI basin have been studied. The Otíñar basin is a fluvio-lacustrine basin developed during the Quaternary (?) on the Subbetic rocks at the south of Jaén city. Its sedimentary infill is made up of three stratigraphic units representing different stages as exorheic and endorheic basin. The destruction of the basin took place when the axial fluvial system base level occupied a relatively lower position and the fluvial system entrenched in the sedimentary infill leaving at least three terraces levels. Climatic and tectonic factors are discussed as controls of the sedimentary and erosional evolution of the Otíñar basin
Registros de conductividad y temperatura y flujos preferenciales en el campo de Dalias (Almería)
(Sociedad Geológica de España, 2002) Molina, Luis; Vallejos, Ángela; Pulido Bosch, Antonio; Sánchez Martos, Francisco
Groundwater temperature and electrical conductivity logs were applied to gain an understanding of the hydrogeological behaviour of a complex system. This system, compartmentalized by a large number of fractures, is that of the Campo de Dalias (Almería). In addition to this complexity one must consider the different levels with aquifer properties and their varying lithologies, which in some cases are in direct contact with the sea. The various logs allow lateral correlation and provide information on the existence of both ascending and descending vertical flows, and the inflow of seawater into the system
Paleoecología de los niveles lumaquélicos con Heterostegina en el Tortoniense del sector central de la Cuenca del Guadalquivir (SO España)
(Sociedad Geológica de España, 2002) Tosquella Angrill, Josep; Abad de los Santos, Manuel; González-Regalado Montero, María Luz; Ruiz Muñoz, Francisco; Pendón Martín, José Gabriel
The Iumaquellic levels with Heterostegina in a detritic-bioclastic succession (Km 98 section) located in the central sector of the Guadalquivir Basin has been studied. The sedimentological and micropaleontological analysis (larger foraminifera, benthic and planktic microforaminifera, and ostracoda) allows deduce an outer infralittoral environment of deposition for these levels. Larger foraminifera (Heterostegina) could dominate the more oligotrophic depositional conditions during intervals of sea level rise; ostracoda and small benthic foraminifera could dominate preferably the more eutrophic ones during intervals of continental clastic input
Nuevos datos sobre la actividad post-Neógena en la Isla de Mallorca
(Sociedad Geológica de España, 2002) Giménez, J.
During Neogene times Mallorca Island was subjected to an extensive regime characterized by NE-SW normal faults. On the other hand, geologic evidences indicate that this stress regime changed in Pliocene times. Thus géomorphologie evidences indicate the presence of compressive structures and Neogene and Quaternary materials are affected by compressive structures. Seismic activity of the area can be related to the former Neogene Faults. Focal mechanisms and geologic evidences indicate that the tectonic regime at present is characterized by a N-S compression together with a E-W extension
New data on evolutive trends of Third Magmatic Cycle (Post-Roque Nublo Group) volcanism in Gran Canaria (Canary Islands, Spain)
(Sociedad Geológica de España, 2002) Gimeno, Domingo; Pérez Torrado, Francisco J.; Aulinas, Maritxell; Hansen, A.; Carracedo, J. C.; Guillou, Herve
This note exposes preliminary data (petrography, TAS classification) obtained from a 44-samples study of lavas corresponding to the Third Magmatic Cycle of Gran Canaria island. These samples has been chosen from a 120 studied set, taking into account good preservation and specific geologic situation in order to obtain a new K/Ar systematic geochronology of recent volcanic rocks of the island. We can remark a good agreement with published available results (including older ones); in despite of this, the simultaneous knowledge of correct ages allows new interpretations of the recent geologic history of Gran Canaria island. The most prominent new evidence is that evolved rocks corresponding to the end of Roque Nublo Cycle are coeval during a relatively broad span of time (3.6-2.9 Ma) with the pristine (basanitic) terms of rift volcanism (initial volcanism of Third Magmatic Cycle)
Morfología de la pirita diagenética en sedimentos recientes del estuario del Río Odiel (SO de España)
(Sociedad Geológica de España, 2002) Borrego Flores, José; Monterde, J.; Morales González, Juan Antonio; Carro Flores, Berta; López González, Nieves
Diagenetic sulphurs have been observed in subsurficial sediments from Odiel River Estuary. These sulfurs display three distinct morphologies: microcrystal aggregates, framboidal aggregates and euhedral pyrite macrocrystals. The genesis of these pyrite morphologies occurs in non-strictly-anoxic environments with a continuous sulphate and iron support where the bacterial activity induces a fast nucléation and growth of microcrystals. These optimal environmental conditions present in the Odiel estuary allow an accelerated evolution from framboidal morphologies to euhedral macrocristals during early diagenetic stages
Modelizacion del transporte sedimentario longitudinal en playas de poca energía. Playa de Vistahermosa (Bahía de Cádiz)
(Sociedad Geológica de España, 2002) Gracia Prieto, Francisco Javier; Benavente, Javier
Theoretical and empirical estimations of the longshore sediment transport were applied to a beach in the northern Cádiz Bay. In the first case, several predictive models were applied by combining energetic, morphological and sedimentological characteristics of the beach. In the second case, a field experiment was been carried out by injecting tracers in the beachface, with a later sampling permitted to determine the displacement of the centre of mass. At the same time, remobilization depth was quantified by using rods and sticks. As a conclusion, it can be stated that the models give super-estimations of the real amount of transported sediment measured in the field. This contradiction confirms the limited applicability of these kind of predictive models in a low energy coast like this
La transgresión Aptiense en la Sierra de Segura (Zona Prebética, provincia de Jaén)
(Sociedad Geológica de España, 2002) García Hernández, M.; Castro Jiménez, José Manuel; Nieto, Luis M.
The cretaceous successions of the Prebetic; deposited on the Southern Iberian Continental Margin, record the later part of a rifting stage (Oxfordian to early Albian). The northern part of the sierra de Segura (jaén province, SE Spain) shows a stratigraphic record of the tectonosedimentary evolution of the early cretaceous time. Four sedimentary sequences have been defined for the Barremian - Early Albian interval, which are evidence for different transgressive pulses, coinciding with the extensional phases of the north atlantic rifting. The first transgressive episode took place in the early Barremian, with deposition of several marine carbonate beds within a lacustrine succession (sequence 04). In the late Bedoulian arose the maximum transgression, with deposition of litoral calcarenites in previously emerged areas of the margin (sequence Ci5). The concluding reactivation of the rifting phase occurred in the late Aptian, with deposition of rudist-bearing limestones in all the studied area (sequence 06). This last tectonic phase caused the migration of depocenters towards the continent. The deposition of sequence 07, with expansive continental and marine deposits marked the end of the rifting and de beginning of the post-rift phase
La cuenca terciaria continental del Diapiro de Murgia: la Formación Izarra (Oligoceno superior-Mioceno inferior, Cuenca Vasco-Cantábrica)
(Sociedad Geológica de España, 2002) López Horgue, Mikel A.; Hernández, José María
The tertiary continental Izarra Formation (Alava, Basque-Cantabrían Basin) is formally described for the first time. Its materials were deposited on a small basin originated in the central part of the Murgia diapir. Those materials are subdivided in four members which are: a) a basal unit of red marls and conglomerates formed in diapiric-fringe alluvial systems; b) the intermediate member consists of marls and limestones with paedogenic structures deposited in a temporary inundated outer alluvial plain; c) a top unit with calcareous lutites and fossiliferous limestone concretions (Konservat-Lagerstatten) of lacustrine origin; and d) a calcareous tufa unit overlying the basal member and originated next to hard-water springs whose stratigraphic correlation with the intermediate and top members is not clear. The chemical content of the waters was at least locally influenced by sulfates and carbonates derived from the diapir and surrounding cretaceous carbonates and ore deposits
Internal Structure of the Évora Massif: The Évora High-grade Terrains and the Montemor-o-Novo Shear Zone (Ossa-Morena Zone, Portugal)
(Sociedad Geológica de España, 2002) Francisco Pereira, M.; Brandáo Silva, J.; Chichorro, Martim
The Évora Massif is divided into two major tectonic units, in order to improve the general understanding of their internal complex structure: (1) the Évora High-grade Metamorphic Terrains and (2) the Montemor- o-Novo Shear Zone. Geological mapping based on stratigraphic, structural and metamorphism data of Neoproterozoic-Paleozoic rocks has shown great variations in style and Intensity of deformation and metamorphic processes on both tectonic units. A progressive deformation regime associated with slnistral transcurrent movements parallel to the orogen-strike is proposed to explain the overall structural pattern. Key words: Ossa-Morena Zone, Évora Massif, Évora High-grade Metamorphic Terrains, Montemor-o-Novo Shear Zone, Transcurrent movements
Inicio del vulcanismo en el sector de Calañas (Faja Pirítica Ibérica). Caracterización y datación
(Sociedad Geológica de España, 2002) Moreno Garrido, María Carmen; González Barrionuevo, Felipe; Sáez Ramos, Reinaldo; Sierra del Pino, Sonia
First volcanic rocks of the Calañas area, Central Sector of the Iberian Pyrite Belt, are felsic lavas that are included in a black shaly sequence at the bottom of the Volcano-Sedimentary Complex. This sequence is stratigraphically conformable with the underlying Phyllite-Quartzite Croup. Well-preserved palynomorph assemblages have been obtained from the shales. The miospore assemblages are assigned to the LN Biozone, indicating a latest Devonian age for the beginning of vulcanism. Palynological and isotopic results from Tharsis, Aználcollar and Neves-Corvo orebodies are similar, suggesting that the shaly sequence of Calañas area can be laterally correlated with the mineralized level. Presence/absence of sulphide ores could be explained by changes of facies related with basin paleogeography
Influencia de las burbujas en la viscosidad de magmas haplograníticos vesiculados
(Sociedad Geológica de España, 2002) López, S.; Fernández Rodríguez, Carlos; Donaire Romero, Teodosio; Castro Dorado, Antonio
The changes in the viscosity of bubble-bearing haplogranitic magmas with crystallinity are a prime function of the applied deformation rate. Under high deformation rates melt and magma viscosities are found to strongly increase with crystallinity. Low deformation rates promote, instead, a decrease in melt viscosity and a rather small increase in magma viscosity with crystallinity. These changes could explain some observed geological features in plutons
Evolución morfodinámica de la playa de Panxón (Galicia, NO de España)
(Sociedad Geológica de España, 2002) Álvarez Vázquez, R.; Bernabeu, Ana M.; Nombela, M. A.; Méndez, G.; Vilas, Federico
Panxón beach (Pontevedra, NW of Spain) was quarterly surveying from November 2000 to January 2002. Five beach profiles were monitored and four sediment samples were collected in each profile that were located at the beach face and along the intertidal zone. This work presents Panxón beach behavior during the monitoring time and develops the foundations to a morphodynamical model of this beach. Seasonal variations of the beach respond to changes in wave climate: the slope of the measured profiles decreases and grain size increases during winter and storm conditions. In fair-weather conditions, the profile recovers sediment increasing its slope and building the berm of the profile. This seasonal behavior shows differential response along the beach: the zone protected by a headland at the north end of the beach and the zone exposed to waves, located at the south end. In the exposed zone, the slope variation range is related to the wave height changes. Morphology' of the exposed zone is conditioned by wave characteristics. In the protected area, wave height variation is minimum (0.2-0.4 m) during the monitoring period whereas slope profile changes is similar to the exposed profiles. Morphology of the protected profiles is defined by wave climate in summer conditions. During energetic conditions (winter and storm) it is made clear the existence of a different mechanism controlling the morphology in this zone
Estudio preliminar de los sedimentos recientes de las lagunas de Villafáfila (Zamora)
(Sociedad Geológica de España, 2002) Santisteban, Juan Ignacio; García del Cura, María Angeles; Mediavilla López, Rosa; Dabrio, Cristino José
Recent sedimentation in the Lagunas de Villafafila is dominated by fine-grained sllicidastic deposits mainly composed of quartz, feldspar, muscovite, illite and kaolinite. Sediments are clay, clayey silts and clayey fine sands with sparse pedogenic carbonates and organic matter. The recentmost sediments contain diatoms and carbonates with bacterial features. Their structure is composed by parallel lamination, sometimes inclined by adaptation to bottom topography, and erosive surfaces. Rootlets are common to the top. Layering, textures and sedimentary structures reflect energy changes in the hydrological regime mainly related to water incomes from nearby areas. Although saline eflorescences are known to be generated since several millennia ago, saline layers and minerals are rare in the cores
Estructuras de escape de anémonas marinas (Conichnus indet. isp.) y sedimentación en depósitos litorales del Complejo Basal Transgresivo del sector central de la Cuenca del Guadalquivir (SO España)
(Sociedad Geológica de España, 2002) Abad de los Santos, Manuel; Ruiz Muñoz, Francisco; Pendón Martín, José Gabriel; Tosquella Angrill, Josep; González-Regalado Montero, María Luz
The study of faunistic associations, ichnology and sedimentology of coastal deposits, that crops out in the central sector of pasive margin of the Guadalquivir Basin, allows us to make an approached reconstruction of ambient features which dominated in this sector of the basin during Tortonian. High dimensions escape structures, interpreted like trace make by marine anemones (Conichnus indet. isp.), receive especial attention on this paper. Their presence shows arrives of an enormous amounts of sediment to the beach from nearer deltaic system

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