Geogaceta -- Nº 20-2, (1996)

Permanent URI for this collectionhttps://hdl.handle.net/10272/11789

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Variabilidad sedimentaria en la playa de Las Canteras (Gran Canaria)
(Sociedad Geológica de España, 1996) Alonso, I.; Vilas, Federico
The sedimentary dynamic at Las Canteras beach is characterised by means of beach profiles data. A very strong seasonal pattern has been shown, consisting on succesive erosions and accretions coupled with an important volume of sediments transported all along the beach. On a shorter temporal scale, the quantification of the amount of transported sediments induced by a certain storm has proved a similar longshore transport pattern and very quick beach recovery
Turbiditas calcáreas y otros fenómenos de resedimentación/ erosión en el Jurásico superior-Cretácico inferior de la unidad de Huelma (Jaén). Zonas Externas de las cordilleras Béticas
(Sociedad Geológica de España, 1996) Ruiz Ortiz, Pedro Alejandro; Molina, José Miguel; Nieto, Luis M.
Carbonate turbidites made up by conglomerates and calcarenites are interpreted as a base-of-slope apron. The slope was, probably, the transition between the trough of the Intermediate domain and the External Subbetic swell. This slope was a place of erosion and resedimentation during the Late Jurassic and Early Cretaceous, in relation with two main tectonic events which resulted in the erosion of the platform margin and turbidite deposition
The submarine "El Golfo" debris avalanche and the Canary debris flow, West Hierro lsland:The last major slides in the Canary archipelago
(Sociedad Geológica de España, 1996) Urgelés, R.; Canals, M.; Baraza, J.; Alonso, Belén
Swath bathymetry and geophysical data of the island of Hierro show that the western flank of the island is affected, at least, by two major catastrophic slope failures. One of the two, called the El Golfo debris avalanche, led to the deposition of a sedimentary body of about 150 km3 of volcanic rock debris on the upper rise. The second major instability event, named the Canary debris flow, originated at the base-of-slope of the island of Hierro, and involved a larger amount of remobilized material. New evidences suggest that the Canary debris flow is the oldest in age. As a consequence of the Canary slide event, oversteeping and undermining of the lower island flanks occurred and subsequently triggered the El Golfo debris avalanche, whose deposits covered and obliterated the source area of the Canary debris flow. The triggering of El Colfo debris avalanche seems to be related also to the rift zones in the island of Hierro. From the establishment of the complex relationships between both slides, the El Golfo debris avalanche has been dated between 12.000 and 6.000 yBP
Tempestitas en el Subbético medio (Fm. Milanos, Jurásico superior). Sus características y facies relacionadas
(Sociedad Geológica de España, 1996) Molina, José Miguel; Vera, J. A.
We have recognized and analysed tempestites, made up by calcisiltites and calcarenites with chert and hummocky cross-stratification (HCS), in the Milanos Fm (Upper Jurassic) of the Middle Subbetic (Betic Cordillera). The most characteristic calcareous tempestite levels are packstone and grainstone (more rarely wackestone) with peloids and bioclasts. They have a thickness between 25 to 75 cm and a distinctive elemental sequence. The presence of these tempestite levels is a fundamental new argument to interpret these deposits as characteristics of the deeper parts of a platform or carbonate outer ramp, less than 200 m in depth
Significado geodinàmico de las vergencias al norte en el NE de la Provincia de Sevilla (Zona de Ossa-Morena)
(Sociedad Geológica de España, 1996) Apraiz, A.; Eguiluz, Luis
The area s tu d ie d is characterized by the occurrence o f structures w h ich associate a N te c to n ic vergence. These are the results of deformational features varying from localized mylonite generation in highly strained granitic parent rocks to rough-cleavage development in the less deformed ones of the metasedimentary succession. In the context of the Ossa-Morena Zone, where most often structures associate a dominant S vergence, the structures described here would reflect, in turn, the existence of upper Paleozoic shear zones whose orientation is antithetic with respect to that of Hercynian subduction and obduction of the South-Portuguese Zone below the Ossa-Morena
Sedimentología de los materiales paleocenos de Zamora
(Sociedad Geológica de España, 1996) Delgado, J.; Alonso Gavilán, G.
Palaeocene materials surrounding Zamora city are studied. From a sedimentologie point of view, they are the sedimentary record of active chanels coming from a western metamorohic area and shallow channels of gravels braided rivers in which the main bedforms are megaripples
Sedimentologia, paleoalteraciones y diagénesis en la unidad Carbonática de Cihuela (Eoceno superior de la Cuenca de Almazán, Soria)
(Sociedad Geológica de España, 1996) Armenteros, Ildefonso; Bustillo Revuelta, María Ángeles
The Cihuela Carbonate u n it consists o f up ward-growing carbonate sequences 0.5 to 2 m thick, and intercalated clayey marly levels 5 to 8 m thick. Dolostones predominate in the lower 40 m of the unit and limestones in the remaining of the section. The main postdepositional features are represented by ubiquitous and numerous calcite pseudomorphs after interstitial micro/meso lenticular gypsum, penecontemporaneous dolomitization and later silicification and gypsum calcitization. The abundance of crumb and clotted microstructures related with recurrent dessication processes and the above diagenetic characteristics indicate an ephemeral lacustrine system in a dry warm climate
Resultados Preliminares de la primera campaña en la Zona Económica Exclusiva Española en el Golfo de Valencia y mar Balear. ZEE-95
(Sociedad Geológica de España, 1996) Herraz, P.; Acosta, J.; Muñoz, A.; Palomo, C.; Carbó Gorosabel, A.; Pardo de Donlebum, M.; Sanz, J. L.; Uchupi, E.
In this paper w e present th e general objetives and scope o f the Spanish Exclusive Econom ic Zone program and the preliminary results of the first cruise carried out by Hydrographic Institute of the Navy (IHM) and the Spanish Oceanographic Institute (IEO) in the continental margin off Valencia - Balearic Islands. The 2 2 0 geophysic al p ro file s to ta liz e s 9 2 0 4 km . o f g ra vim e try, magnetic s , sin gle beam echosounder, sub-bottom profiler and multibeam echosounder, covering 12.000 Km2. Morphologically, the first processed area, the Valencia slope, shows a striking pattern of channels with low sinuosity index and deeply incised in the slope that flow in NW-SE direction to the Valencia Deep.This area also shows a general cover of unconsolidated sediments in different slumped degrees
Relaciones entre la evolución sedimentaria del Grupo de Arén y el Cabalgamiento de Boixols (Campaniense terminalMaastrichtiense del Pirineo Meridional -Central)
(Sociedad Geológica de España, 1996) Arbués, Pelayo; Pi, E.; Berástegui, X.
The Arén Croup was deposited synchronously to the growth of the Boixols thrust. Sedimentation took place in siliciclastic marine and alluvial environments. The growth of a footwall syncline affected the geometry of the basin fill by adding drowning and uplifting movements. Such a mechanism might be common to those settings where fault propagation folds develop. In the Arén Croup, this differential subsidence mechanism was not able to overprint the identified sedimentary cycles
Quantification of neogene and quaternary sediment input to the Madeira Abyssal Plain
(Sociedad Geológica de España, 1996) Alibés, B.; Canals, M.; Alonso, Belén; Lebreiro, S. M.; Weaver, P. P. E.
Cruises Tydeman 80, Tyro 82 and ODP Leg 157 provided 7000 km of single-channel seismic profiles and three d rillin g sites w ith a to ta l o f 11 58 m o f core in the Madeira Abyssal Plain. Merging o f the lithological records and conventional logs into the seismic units and subunits defined, allowed their 3D mapping and calculation of both the sediment volume and approximate accumulation rates in the Great Meteor East area (central subbasin of the Madeira Abyssal Plain) since the Middle Miocene. The total volum e is arou nd 1 9 3 2 7 km3and the accum ulation rates are 2 2 .6 6 m /m y r fo r the U p p er-M id d le Miocene, 68.78 m/myr for the Lower Pliocene, 49.23 m/myr for the Upper Pliocene and 54.93 m/myr for the Quaternary
Physical properties of sediments from Madeira Abyssal plain : results from ODP Leg 157
(Sociedad Geológica de España, 1996) Baraza, J.; ODP Leg 157 Shipboard Scientific Party
Physical properties measured on cores from d rill Sites o f O D P Leg 157 reveal th a t the d iffe re n t turbidites of Madeira Abyssal Plain have a distinct physical signal. Major differences result from the compositional variations among the three main types of turbidites (volcanic, organic-rich, and calcareous), and from changes in the carbonate content in the pelagic Intervals
Perfiles sísmicos en el Margen Insular de Tenerife:Proyecto Teide. Resultados preliminares
(Sociedad Geológica de España, 1996) Acosta, J.; Herraz, P.; Muñoz, A.; Palomo, C.; Sanz, J. L.; Uchupi, E.
Continous seismic reflection profiles from north and south slopes of Tenerife, Canary Islands, indicate tha t the slopes o f this island are d o m in ate d by g ra v ita tio n a l structures includin g slumps, catastrophic avalanches, debris flows and turbid ites. O n the n o rth slope th e p ro x im a l ends o f th e tw o massive avalanches display a ridge-valley morphology and the distal ends by overlapping fans. Included with the fans is a extensive fie ld o f exotic blocks . The ridge and valley m o rp h o lo g y is the results o f lo n g itu d in a l shears created by diferentia l movements. The south slope is made up o f tw o terrains, a n o rth one whose morphology is due to a massive avalanche modified by volcanic processes, and a south terrain whose morphology is the result of massive slumpping of a thick sequence of structurally weak volcanic ash and pyroclastic rocks. Both of these terrains are modified on their distal ends by reworking by southerly flowing Atlantic Deep water
Paleokarstificación en facies yesíferas e implicaciones sedimentarias. Ejemplos del Mioceno de la Cuenca de Madrid
(Sociedad Geológica de España, 1996) Rodríguez Aranda, J. Pablo; Calvo, J. Pedro; Sanz Montero, María Esther
Paleokarst surfaces developed in gypsum deposits are present in two distinct situations within the Miocene evaporite formations of the Madrid Basin: 1) paleokarst surfaces related to major sedimentary breaks and 2) incipient paleokarsts at the tops of the evaporite sedimentary sequences (sedimentary diastems). The karstification features are varied and include small dolines, networks of chimneys and fissures as well as collapse frameworks. Emphasis is placed on the role of bush vegetation in promoting dissolutional features of the gypsum karst, which is clearly evidenced within the sedimentary diastems
Morfologia del Basamento en el Noroeste del Mar de Alboran
(Sociedad Geológica de España, 1996) Linde, J. de la; Comas, M. C.; Soto, Juan I.
A detailed basement depth contour map of the NW Alboran Sea basin is performed from multichannel seismic p ro file data. The map shows a NE-SW trendin g trough as being the north e rn branch o f the West Alboran Basin. The trough opens and deeps to the SW, and is filled of lower-Mlocene to Recent sediments up to 6 seconds (twtt) in thickness. The trough corresponds to a complex half-graben with a gently dipping northern slope and a sharper southern flank which bounds the basement horst drilled at DSDP Site 121 and ODP Site 976: The northern slope mainly corresponds to low-angle normal faults crosscutted by NW-SE trending high-angle normal and strike-slip faults. The basement horst resulted form interference between several faults, NW dipping low-angle normal faults, SW-NE■ directed high-angle faults; and top of rollover structures related to the low-angle faulting. Both trough and horst axes are tilted towards the SW, probably as a result of post-Messinian subsidence
Morfologfa comparada de un monte submarino en el Mar Balear.Sistemas Batimetricos Monohaz Vs. Multihaz
(Sociedad Geológica de España, 1996) Polglase, R. B.; Acosta, J.; Pardo de Donlebum, M.; Muñoz, A.; Herraz, P.; Palomo, C.; Sanz, J. L.; Uchupi, E.
The applications of multibeam systems with their high resolutions and capability to eliminate "blind zones" between track lines, characteristic of single beam systems, had led to a major development in the investigation of submarine geomorphology. In this study we compare the results obtained with single and m u ltib e a m echosounders survey o f a sea m ou nt east o f Ibiza, Balearic islands. As illu s tra te d by these date sets the multibeam system is better able than the single-beam system to define the configuration of this high. Multibeam systems also led themshelves to the creation of computer generated physiographic diagrams displaying the information provided by the Simrad multibeam system available on the R/V Hesperides, and makes it possible for the investigator to infer the geologic processes that have molded the seamount
Mass physical, granulometric and mineralogical Characterisation of the glaciomarine sediments of the Bransfield Basin ( NW Antarctic Peninsula)
(Sociedad Geológica de España, 1996) Fabrés, J.; Calafat, A. M.; Canals, M.; Francés, Guillermo; Flores, José Abel
The textural analysis of two gravity cores reveals that the sediments in the Central and Eastern Bransfield subbasins are mainly clayey silts with some coarser levels of sandy silts. While a turbidity origin can be attributed to the coarser levels, other processes should control the deposition of the fine fractions, e.g. settling of suspended particles, ice-rafting and ash airfall Chlorite, smectite and illite are the dominant clay minerals. While a detritic origin can be attributed to chlorite and illite the diagenetic alteration of volcanic glass origin is the most likely origin for smectite even though a minor detritic contribution cannot be completely enied Higher sand and smectite contents, and more abundant ash laminated facies suggest that the volcanic influence is higher in the Eastern Bransfield core than in the Central Bransfield core
Los campos de ondas de arena en la Plataforma Continental del Golfo de Cádiz entre Chipiona y Zahara de los Atunes
(Sociedad Geológica de España, 1996) Lobo, Francisco J.; Hernández Molina, F. Javier; Maldonado, Andrés; Rodero, J.
The analysis o f the seafloor g éom orpholo gie features In the c o n tin e n ta l s h e lf o f the C u lf o f Cadiz with high resolution seismic profiles reveals a well defined distribution pattern of bedforms controlled by the morphology and the hidrodynamic of the area. Three zones are differentiated according to the bedform types and the hidrodynamic processes: a) a northern, shallow submarine zone at 30 m depth situated between ConiI and Barbate (Barbate ridge), where sand waves migrate towards the SE; b) a southern zone southward of the Barbate ridge, where sand waves migrate towards the NW, and c) the infralittoral-inner shelf between Coni! and Cadiz Bay, where sand waves migrate towards the SE and also are influenced by the waves action
Las perforaciones del ODP=leg 161 en el Mediterráneo Occidental
(Sociedad Geológica de España, 1996) Comas, M. C.; Zahn, R.; Klaus, A.; ODP Leg 161 Scientific Party
Leg 767 drilled a transect of six sites in the Western Mediterranean. Sites 974 (Tyrrhenian Basin) and 975 (Menorca Rise, South-Balearic Basin) were dedicated to paleoceanography and Sites 976, 977, 978, 979 (Alboran Basin) focused on tectonic goals but also involved paleoceanographic studies. A total length of 3.9 km of sediment and rock cores were collected from nearly 7 kilometer below the sea floor. One of the most Intriguing paleoceanographic results of Leg 767 was the discovery of sapropels in the Western Mediterranean. Pleistocene sapropels were recovered at Site 974 and Site 975, and Pleistocene organic-rich layers at Sites 976, 977, and 979. Site 976 cored 258.97 m of high-grade metamorphic rocks down into the basement, and demonstrates that the basement beneath the Alboran Sea is formed by rocks of continental origin that have undergone exhumation and decompression. Sites 977, 978 and 979 cored through a zone of structures within the sedimentary sequence, yielded information on the compressive post-Messinian tectonic reorganization of the Alboran basin
Las facies palustres y fluviales del Paleógeno de Rossell (Baix Maestrat, Castellón)
(Sociedad Geológica de España, 1996) Arasa Tuliesa, A.; Colombo Piñol, Ferrán
The study of several stratigraphic sections of the Rossell paleogene sediments allows us to differentiate facies and facies associations. From the study of these facies we Can deduce a theoretical depositional model composed of the following depositional environments: fluviatile, mud flats and palustrine. We discuss the depositional significance of the development of these depositional environments
La depresión periférica y el lomo contourítico de Menorca: evidencias de la actividad de corrientes de fondo al N del Talud Balear
(Sociedad Geológica de España, 1996) Velasco, J. P. B.; Baraza, J.; Canals, M.; Balón, J.
A peripheral depression with a sediment drift on its N flank develop N and E of Minorca Island. Both are interpreted to result from the activity of bottom currents circulating parallel to the base of the island slope since the Pliocene. Evidences of the contouriric activity are: the presence of a depression with an erosive character, a sedimentary ridge with the typical characteristics of contourite drifts, and large sediment waves. The depression has a maximum width of 5 km, and a depth of 150-200 m, whereas the contourite drift reaches up to 150 km in length, is 25 km wide, and 100 m high. The sediment waves developed on the inner flank of the contourite drift reach up to 5 km in length and 40 m in height. The genesis of all these structures is related to the circulation of the Mediterranean Deep Water ( MDW) in the area. The steep island slope, devoided of sediment and deeply gullied, is considered as the potential source area for the sediments reworked by the currents. Further seaward, the contourite deposits are in lateral continuity with the deposits of the North-Balearic Basin and the Valencia Fan

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