Sample records for INVESTIGACION GEOLOGICA (geological surveys)
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1

Las Secuencias Depositacionales del Plioceno-Cuaternario en la Plataforma Submarina adyacente al Litoral del Este Bonaerense/ Pliocene-Quaternary depositional sequences of the continental shelf adjacent to eastern Buenos Aires Province, Argentina

Parker, Gerardo; Violante, Roberto A; Paterlini, C. Marcelo; Costa, Irundo P; Marcolini, Susana I; Cavallotto, José L
2008-12-01

Resumen en español Se describen las características sismoestratigráficas, sedimentológicas y morfológicas del sector de plataforma submarina adyacente al este bonaerense. El trabajo se basa en los resultados obtenidos durante el desarrollo de sucesivos proyectos destinados al estudio de la cubierta sedimentaria del Plioceno-Cuaternario y reciente, utilizando metodologías de relevamiento sísmico de reflexión de media a alta resolución y muestreos de sedimentos. El sector de plataform (mas) a estudiado constituye una típica plataforma submarina silicoclástica de margen pasivo, de gran extensión y suave relieve. Su configuración morfológica está caracterizada por relieves aterrazados con una cobertura sedimentaria de depósitos arenosos relicto a palimpsestos que resultaron del retrabajamiento de sistemas costeros de playas, barreras y lagunas litorales durante el retroceso de la línea de costa como consecuencia del ascenso del nivel del mar durante la transgresión postglacial, con una etapa final de remodelado parcial durante el descenso del nivel del mar del Holoceno superior. Se diferencian dos ámbitos, la plataforma interior ("Terraza Rioplatense", entre la línea de costa y los 30/40 m de profundidad) con geoformas ajustadas a la hidrodinámica actual, y la plataforma exterior (entre la isobata de 70 m y el borde exterior de la plataforma en transición al talud), con sedimentos relicto de poca movilidad; en ambas se hallan relieves pre-transgresivos labrados en depósitos marinos y continentales del Plio-Pleistoceno que afloran bajo la cubierta sedimentaria reciente. Un escalón abrupto de 30/40 m de desnivel separa ambas plataformas. La secuencia estratigráfica estudiada está constituida por seis Secuencias Depositacionales (SD 1 a SD 6 de techo a base) que representan paquetes sedimentarios separados por discordancias. La SD 6 constituye la base de la secuencia, y corresponde a depósitos marinos del Mioceno correlacionables con las unidades costeras conocida como "Paranense-Entrerriense-Chapadmalense". La SD 5 son depósitos marinos en transición a continentales equivalentes a la Fm Barranca de los Lobos del litoral marplatense y a la unidad conocida como "Fm Puelches Equivalente" del Plioceno. La SD 4 está caracterizada por sedimentos marinos correspondientes al denominado "Interensenadense" en el litoral bonaerense, de edad aproximada a los 2,41 Ma (Plioceno superior), y se reconocen en ella diversas sismofacies de ambientes marinos, costeros y continentales con una secuencia litológica granodecreciente hacia arriba. La SD 3, marina, tiene la particularidad de tener una distribución saltuaria, a diferencia de las restantes que se extienden de manera uniforme en toda la región, lo que demuestra la ocurrencia, con posterioridad a su depositación, de importantes procesos erosivos probablemente asociados a tectónica y/o glacioeustatismo. La SD 2 representa a los depósitos marinos-costeros formados durante el estadío isotópico 5e (120 ka), que en las llanuras costeras vecinas se lo conoce como "Belgranense", y está constituida por diversas facies entre las que se destacan barreras-lagunas litorales, playas y estuarios. La SD 1 es la cobertura superficial formada durante la transgresión postglacial en ambientes de barreras-lagunas costeras-estuarios. La secuencia integrada por las SD 5 a 1 representa a las transgresiones glacioeustáticas del Plioceno- Cuaternario, con diferentes grados de preservación en la plataforma y el Río de la Plata en virtud de variantes tectónicas y morfológicas. Existe la posibilidad de que no todas las transgresiones marinas ocurridas en la región hayan quedado preservadas en el registro geológico. Resumen en inglés The Argentina Continental Shelf (ACS) is one of the largest and smoothest silicoclastic shelves in the world, condition that resulted from its geotectonic setting in a passive margin adjacent to a continental region with very extended and low-lying coastal plains. As a consequence, Pliocene-Quaternary glacio-eustatic sea-level fluctuations have been very important in its modelling and sedimentary characteristics. The study area is located between 35 and 39º S, the wester (mas) n boundary is the coastline and the eastern boundary in around 55º W that includes the outer shelf border (Fig. 1). The research is based on middle to high-resolution seismic reflection surveys and bottom/ subbottom sampling (piston cores), carried out in the context of several projects that are part of the Framework Project "Reconocimiento Geológico Geofísico del Margen Continental". The information obtained during these projects, as well as the results coming from previous projects and bibliographic compilation, allowed to gather around 4.000 km of seismic lines, 1.200 bottom samples and 92 piston cores (Fig. 2). Morphology: The ACS shows two major features (Figs. 1 and 3): inner shelf (corresponds to Terrace I, Parker et al., 1997, 1999; Violante, 2005) and outer shelf (northern part of Terrace II, Parker et al., 1997; Violante, 2005). The inner shelf extends from the coastline (or the prodelta front in the de la Plata River outlet) to the 30/40 m isobath, and includes the "Rioplatense Terrace" (RT) which represents the surface that has been modelled during the postglacial transgression but not covered by the late Holocene coastal wedge that constitutes the coastal plains. Several lower-order features modelled by the postglacial transgressive and regressive events developed on the RT surface, as the de la Plata river delta, the linear shoals systems and the La Plata Bank (Fig. 1). On the other hand, relict features composed of semiconsolidated plio-pleistocene sediments as Punta Piedras-Alto Marítimo and Restinga de los Pescadores, are significant elements in the inner shelf morphology. The outer shelf is separated from the inner shelf by a high-gradient step between 40-80 m depth (outer border of RT), which becomes, south and southeast Mar del Plata, of lower relief with a rough surface cut by transverse channels and depressions. Further east from the 80 m contourline, the outer shelf can be subdivided in two sectors: north of Querandí lighthouse it is uniformly dipping towards the shelf border, whereas in the southern part it shows a western depression (90 m depth) closer to the outer border of RT, and a eastern shoal-like elevation (75/80 m depth) near the shelf-slope transition (Fig. 3). Sedimentology: The ACS is a silicoclastic shelf where sediment characteristics and distribution are the result of dynamic, oceanographic and climatic factors. The shelf surface is covered by a relict to palimpsestic terrigenous sandy mantle which is the remnant of reworking of the deposits that constituted ancient coastal environments (barriers, coastal lagoons, estuaries) during the coastline retreat that occurred as a result of the postglacial transgressive event as well as during the sediment redistribution during the late Holocene regressive event (Urien and Ewing, 1974; Parker and Violante, 1982; Parker et al., 1999; Violante and Parker, 2000, 2004). The sandy mantle constitutes in the inner shelf a "shoal retreat massif" (in the sense of Swift, 1976) partially reworked in linear shoals systems; outcrops of the underlying plio-pleistocene substratum - partially covered by a discontinuous sheet of pebbles composed of rock fragments and caliche, beach rocks (coquinas) and sand- are common in some parts of the inner shelf. On the other hand, the outer shelf is mainly characterized by outcrops of the same substratum with minor patches of post-transgressive relict sands with a shoal-like morphology (Fig. 4). Sediment dynamic: Coastal dynamic that influenced Holocene and recent sedimentation is the result of three main sediment transport pathways: a) from the south and southeast as a consequence of the dominant oceanic circulation, that brings the relict sands stored on the shelf surface towards the coastal system, b) the regional northwards littoral transport (coastal currents) parallel to the coastline, although local inversions in the general circulation (littoral cells) are evident in the geological record, as in the Mar Chiquita Lagoon area; this transport redistributes along the coast both the shelf sands and the products of coastal erosion, c) The southwards transport of fine (muddy) sediments from the de la Plata River. Stratigraphy: The Neogene stratigraphy was defined by the application of the seismic stratigraphic method following de concepts of Mitchum et al. (1977). Six Depositional Sequences (named SD 1 to 6 from top to bottom) bounded by major seismic reflectors identified by their seismic attributes (amplitude, frequency and continuity) were recognized (Figs. 4 and 5). SD 6 (base of the sequence): corresponds to marine deposits correlated with the Miocene-Pliocene sediments known as "Paranense-Entrerriense-Chapadmalense" in the adjacent coastal areas (Parker et al., 1994, 2005). SD 5: it has seismic and sedimentological characteristics that indicate marine facies at sea changing to nearshore and fluvial facies towards the coast, and is correlated with the upper Pliocene Barranca de los Lobos Fm as well as with the Puelches Equivalente Fm defined by Yrigoyen (1975) and Parker et al. (1994). SD 4: this unit is broadly extended on the shelf with diverse seismic and litho-facies of marine, nearshore, sublittoral, low-energy coastal and continental environments, with an upwards decreasing grain-size sequence; SD 4 is equivalent to the unit known as "Interensenadense" in the adjacent coastal plains and has an upper Pliocene (2.41 Ma) age. SD 3: it is also marine/littoral and has a unique characteristic given by its discontinuous distribution in the nearshore and coastal regions as well as in some places of the shelf (Figs. 4 and 6) as a consequence of deep post-depositional erosive processes probably produced by intensification of tectonic and/ or glacioisostatic adjustments. SD 2: this unit has again a broad regional distribution, and shows different facies that represent diverse nearshore, coastal and continental environments with the particular characteristic of having been deposited as extensive barriers-coastal lagoon systems (Parker et al., 1999; Violante, 2003); it is correlated with the unit known as "Belgranense" in the adjacent coastal areas, and corresponds to the isotopic stage 5e (120 ka). SD 1: represents the uppermost sedimentary sequence formed during the last postglacial transgressive event; it is constituted by a lower transgressive system tract with different environments such as barriers/lagoons systems and estuaries, and an upper highstand system tract with regressive coastal plains, deltas and a mantle of palimpsestic and relict sands formed by reworking of the previous transgressive deposits; in most of the inner shelf surface their deposits are adjusted to the present hydrodynamic conditions (Urien and Ewing, 1974; Parker et al., 1982). Conclusive remarks: The following conclusions can be highlighted: 1) Major geomorphological features are the inner and outer shelf, which correspond to two topographically and sedimentologically different terraces separated by a step. The upper terrace (inner shelf) is a significant feature in the region which is named "Rioplatense Terrace". 2) From the sedimentological point of view, the shelf is silicoclastic; surface deposits resulted from the postglacial transgressive-regressive event. The main difference between the inner and outer shelf is given by the predominance of palimpsestic deposits in the first one and relict deposits with outcrops of the underlying Pliocene-Pleistocene substratum in the second one. 3) The Neogene stratigraphy is defined by seismicstratigraphic units representing Depositional Sequences (SD), which have been characterized on the basis of their seismic and lithological aspects and correlated with geological units known in the adjacent coastal regions. In this way it was described an uppermost, postglacial unit, followed below by a sequence of three transgressiveregressive units equivalent to the "Pampean" (Plio-Pleistocene) deposits, then a underlying unit corresponding to the "Puelches" (upper Pliocene) sands and finally the basal unit correlated with the "Paranense-Entrerriense- Chapadmalense" (Miocene-Pliocene) sequence. 4) Each SD shows a vertical sequence grading from marine (in the base) to continental (in the top) deposits in an upward decreasing grain-size distribution, therefore representing an individual and complete transgressive-regressive event. 5) The different degree of preservation of the SD in the shelf and the de la Plata River not only indicates different tectonic-glacioisostatic behaviours between both regions, but also determines the possibility that other transgressive events than those preserved in the shelf could have occurred but later completely eroded without leaving any record of their deposition.

Scientific Electronic Library Online (Spanish)

2

Un modelo gravimétrico 3D de la profunda cuenca sedimentaria de Ischigualasto-Villa Unión (San Juan y La Rioja)-Argentina/ A 3D gravity model of the sedimentary deep basin of Ischigualasto-Villa Unión (San Juan and La Rioja), Argentina

Ruiz, F.; Introcaso, A.
1999-03-01

Resumen en español Se efectuaron relevamientos gravimétricos areales que cubren la profunda cuenca intermontana de Ischigualasto-Villa Unión y que abarcan el norte de la Precordillera Andina y una importante porción de las Sierras Pampeanas Occidentales. A partir de los datos observados se prepararon cartas de anomalías de Bouguer (AB) y de anomalías de Bouguer afectadas por corrección geológica (ABcg). La cuenca se ubica en un ambiente tectónico complejo que contamina fuertemente e (mas) l campo gravimétrico. El presente estudio apunta a interpretar la geometría 3D de la cuenca sedimentaria mediante análisis de los datos gravimétricos. La separación del efecto gravimétrico del depósito sedimentario es una tarea compleja que se resolvió empleando: i- el método de suavizado gráfico sobre la AB y ii- filtrados numéricos sobre la ABcg (AB corregida por los efectos sedimentarios de cuencas vecinas a la estudiada). Este análisis permite inferir que en el centro y norte de la cubeta las anomalías gravimétricas se deben, principalmente, al efecto del paquete sedimentario, mientras que en el sur de la misma, prevalecen efectos positivos en corteza debidos, muy probablemente, a intrusiones de rocas máficas. Por inversión gravimétrica de la anomalía residual se preparó un modelo gravimétrico, apoyado en datos sísmicos, que proporciona potencias sedimentarias de hasta 9 km en la región central de la cuenca. Resumen en inglés Areal gravimetric surveys were carried out in the Ischigualasto-Villa Unión intermontane deep basin, the north of the Andean Precordillera, and in a wide portion of the western Sierras Pampeanas. Maps of Bouguer anomalies (AB) and Bouguer anomalies "affected by geological reduction" (ABcg) were derived from the observed data. The basin is located in a complex tectonic setting that strongly contaminates the gravity field. The present study aims to interpret the 3D geometr (mas) y of the sedimentary basin through gravity data analysis. The separation of the gravimetric effect of the sedimentary filling is a complex task presently solved by employing: i- a graphical smoothing method from AB; and ii- numerical filterings from ABcg (AB corrected by the sedimentary filling effect of neighboring basins). This analysis permits to deduce that in the center and north of the basin the gravity anomalies should be mainly the result of the sedimentary filling effect, whereas in the south of the basin positive effects in the crust prevail due most likely to mafic intrusive rocks. A gravity model supported by seismic data that provides sedimentary thicknesses of up to 9 km in the central region of the basin was formulated by using gravimetric inversion of the residual anomaly.

Scientific Electronic Library Online (Spanish)

3

Two more Bohemian trilobites from the Ordovician of Portugal and Morocco

Rábano, I.; Sá, Artur A.; Gutiérrez-Marco, J. C.; García-Bellido, Diego
2010-01-01

Digital.CSIC (Spain)

4

The Baraza Slide: Defining its dynamic (Northern Alboran Sea)

Ercilla, Gemma; Estrada, Ferrán; Yenes, Mariano; Casas, David; Alonso, Belén; Farrán, Marcel-li; [SAGAS Team]
2009-05-01

Digital.CSIC (Spain)

5

Tectonic hydrogeological survey of the Rio Tinto Mars analog: Implications for Mars underground water fluxes

Gómez-Ortiz, David; Fernández Remolar, David; Prieto Ballesteros, Olga; Gómez Gómez, Felipe
2007-07-01

Digital.CSIC (Spain)

6

Synthetic Aperture Radar Interferometry (InSAR): Application to ground deformation studies for volcano and seismic monitoring

Romero, R.; Fernández Torres, José; Rodríguez Velasco, Gema; Araña, V.; Aparicio, Alfredo; Carrasco, D.; Luzón, Francisco; Moreno, V.; Martínez, A.
2002-01-01

Digital.CSIC (Spain)

8

Structural results for La Palma island using 3-D gravity inversion

Camacho, A. G.; Fernández Torres, José; González Méndez, Pablo José; Rundle, J. B.; Prieto, Juan Francisco; Arjona, Alicia
2009-01-01

Digital.CSIC (Spain)

9

Structural characterization of kerogen in 3.4 Ga Archaean cherts from the Pilbara Craton, Western Australia

Marshall, Craig P.; Love, Gordon D.; Snape, Colin E.; Hill, Andrew C.; Allwood, Abigail C.; Walter, Malcolm R.; Van Kranendonk, Martin J.; Bowden, Stephen A.; Sylva, Sean P.; Summons, Roger E.
2007-05-05

Digital.CSIC (Spain)

11

Seismic reflection imaging over the South Portuguese Zone fold-and-thrust belt, SW Iberia

Schmelzbach, C.; Simancas, José Fernando; Juhlin, C.; Carbonell, Ramón
2008-08-01

Digital.CSIC (Spain)

12

Rupture lengths and temporal history of significant earthquakes on the offshore and north coast segments of the Northern San Andreas Fault based on turbidite stratigraphy

Goldfinger, Chris; E. Morey, Ann; Hans Nelson, C.; Gutiérrez-Pastor, Julia; E. Johnson, Joel; Karabanov, Eugene; Chaytor, Jason D.; Ericsson, Andrew; Scientific Party, Shipboard
2007-02-15

Digital.CSIC (Spain)

13

Remote Sensing in BOREAS: Lessons learned

Gamon, J. A.; Huemmrich, K. F.; Peddle, D. R.; Chen, J.; Fuentes, D.; Hall, F. G.; Kimball, J. S.; Goetz, S.; Gu, J.; McDonald, K. C.; Miller, J. R.; Moghaddam, M.; Rahman, A. F.; Roujean, J. L.; Smith, E. A.; Walthall, C. L.; Zarco-Tejada, Pablo J.; Hu, B.; Fernandes, R.; Cihlar, J.
2004-01-01

Digital.CSIC (Spain)

14

Prospección geofísica del yacimiento Las Águilas, provincia de San Luis/ Geophysical prospecting of the Las Águilas deposit, San Luis Province, Argentina

Kostadinoff, Jose; Bjerg, Ernesto; Mogessie, Aberra; Raniolo, Ariel; Alvarez, Guillermina; Santiago, Emiliano
2004-03-01

Resumen en español El yacimiento de sulfuros Las Águilas se halla emplazado en el sector sur de las Sierras Grandes de San Luis. La exploración geofísica de este yacimiento presenta numerosos problemas debido a su estructura, al tipo de mineralización de las rocas ultramáficas y a su composición mineralógica. Los métodos de polarización inducida son eficientes en la ubicación de mineralizaciones de sulfuros polimetálicos, pero necesitan de la concurrencia de otras metodologías g (mas) eofísicas para resolver el problema que puede conllevar la existencia de grafito como elemento indeseable en la evaluación de este yacimiento. Esta investigación se basa en la comparación de los resultados de las prospecciones de polarización inducida (PI) y las magnéticas. El análisis de los resultados de los perfiles indica que en zonas donde de las rocas tienen alta susceptibilidad magnética ésta es debida a la presencia de sulfuros (pirrotina). La presencia del grafito es irrelevante para la prospección magnética debido a su naturaleza diamagnética. Esta situación se ve también reflejada al comparar las anomalías magnéticas con los parámetros de polarización inducida (resistividad, factor metálico y al porcentaje de la Variación de la Resistividad por Efecto de la Frecuencia (PVREF)), siendo posible deducir que la pirrotina es la causante de las anomalías de (PI), asumiendo que en el yacimiento no coexisten el grafito y los sulfuros y que la magnetita no se encuentre en altas concentraciones. Resumen en inglés The Las Águilas sulphide deposit is located in the southern part of the Sierra Grande of San Luis, Argentina. Geophysical exploration in this area is faced with several problems due to the geological structure and the varied mineral composition of the sulphides carried by mafic-ultramafic rocks. Induced polarization (IP) methods are very promising for the recognition of polymetalic disseminated sulphide mineralization, but they require the application of other geophysica (mas) l methods to establish the influence of graphite, which clearly is an undesired element in evaluating the potential of a sulphide deposit. This contribution focuses on the evaluation and comparison of results obtained with both induced polarization (IP) and magnetic surveys. Our results show that, in the areas where the rocks have high magnetic susceptibility, it is due to the presence of the sulphide pyrrhotite. Graphite is irrelevant to magnetism because of its diamagnetic nature. When magnetic anomalies (total component) are compared with the results of the induced polarization method (resistivity, metallic factor and % frequency effect (PFE)) it is usually possible to deduce that the pyrrhotite is responsible for the magnetic anomalies, and pyrrhotite together with other sulphides are causing the IP anomalies, provided one assumes that the graphite and sulphides do not co-exist and, that there are no larger concentrations of magnetite.

Scientific Electronic Library Online (Spanish)

15

Organic matter accumulation during the Holocene in the Guadalquivir marshlands (SW Spain)

Ortiz, José E.; Torres, Trinidad; López-Pamo, José E.; Soler, V.; LLamas, Juan F.; Barettino, Daniel; García, María J.
2007-07-17

Digital.CSIC (Spain)

16

Multibeam backscatter as a tool for sea-floor characterization and identification of oil spills in the Galicia Bank

Medialdea, Teresa; Somoza, Luis; León, Ricardo; Farrán, Marcel-li; Ercilla, Gemma
2008-03-11

Digital.CSIC (Spain)

17

Internal features, mineralogy and geochemistry of ferromanganese nodules from the Gulf of Cadiz: The role of the Mediterranean Outflow Water undercurrent

González, F. J.; Somoza, L.; Lunar, Rosario; Martínez-Frías, Jesús; Martín Rubí, J. A.; Torres, T.; Ortiz, J. E.; Díaz del Río, Víctor
2010-03-01

Digital.CSIC (Spain)

18

Hydrocarbon-derived ferromanganese nodules in carbonate-mud mounds from the Gulf of Cadiz: Mud-breccia sediments and clasts as nucleation sites

González, F. J.; Somoza, L.; Lunar, Rosario; Martínez-Frías, Jesús; Martín Rubí, J. A.; Torres, T.; Ortiz, J. E.; Díaz del Río, Víctor; Pinheiro, L. M.; Magalhães, V. H.
2009-06-01

Digital.CSIC (Spain)

20

Growth patterns of a proximal terrigenous margin offshore the Guadalfeo River, northern Alboran Sea (SW Mediterranean Sea): glacio-eustatic control and disturbing tectonic factors

Lobo, F. J.; Maldonado, Andrés; Hernández-Molina, F. Javier; Fernández-Salas, L. M.; Ercilla, Gemma; Alonso, Belén
2008-09-01

Digital.CSIC (Spain)

21

Geomorfología y sedimentología de la Cuenca Superior del Río Salado (Sur de Santa Fe y Noroeste de Buenos Aires, Argentina)/ Geomorphology and sedimentology of the upper basin of the Salado River (Southern Santa Fe and NW Buenos Aires provinces; Argentina)

Iriondo, Martín; Kröhling, Daniela
2007-07-01

Resumen en español El S de la provincia de Santa Fe y el NO de la provincia de Buenos Aires forman parte del Mar de Arena Pampeano (Sistema Eólico Pampeano), que ha sufrido una secuencia de episodios áridos y húmedos a lo largo de los últimos períodos del Pleistoceno. El paisaje actual resulta fundamentalmente de la influencia del período húmedo del Estadio Isotópico 3 (EIO 3; 64-36 ka) y de la actividad eólica durante un clima seco del Holoceno tardío (3,5-1,4 ka). La secuencia d (mas) e eventos sedimentológicos y geomorfológicos fue la siguiente: Durante el período húmedo del EIO 3 se desarrolló una red fluvial de llanura, que actualmente forma la alta cuenca del Río Salado de Buenos Aires, labrada sobre sedimentos de la Fm Carcarañá. Posteriormente se depositó la Formación Teodelina, por sedimentación eólica. Esta tiene 10 a 12 m de espesor típico y unos 5 m en áreas sometidas a erosión; está compuesta por limo grueso arenoso y arena fina limosa, con modas principales entre 125-250 y 53-62 μm, color 10YR 6/4 (marrón amarillento) y similares. La composición mineralógica de la fracción entre 53 y 62 μm está dominada por vidrio volcánico, con feldespato, cuarzo y alteritas como accesorios. La redondez y esfericidad de los granos varían entre bajas y moderadas, con dos poblaciones. En el Pleistoceno final ocurrió un episodio eólico predominantemente erosivo, dominado por vientos del oeste que labraron cientos de depresiones de miles de metros de extensión. Ocurrió una sedimentación discontinua de loess arenoso de hasta 2 m de espesor con granulometría bimodal. El período Hypsithermal del Holoceno Medio (8,5-3,5 ka) estuvo caracterizado por un clima cálido y húmedo con régimen údico, que generó un suelo en los terrenos loéssicos y produjo el ascenso del nivel del agua en las lagunas y pantanos. El Holoceno tardío, entre 3,5 y 1,4 ka, estuvo dominado por un clima seco, con formación de campos de dunas denominadas aquí Formación San Gregorio. Está formada por arena muy fina a fina, suelta, masiva, color marrón amarillento, y compuesta por trizas vítreas, alteritas y feldespatos como componentes principales y cuarzo como componente secundario; los minerales pesados son de procedencia serrana. La época actual está caracterizada por un exceso de agua en el paisaje; el proceso sedimentológico más relevante es la movilización de grandes volúmenes de sales disueltas, particularmente cloruros y sulfatos. Resumen en inglés The geomorphology, Late Quaternary stratigraphy, sedimentology and hydrology of the upper basin of the Salado River were investigated. The study area is located in S Santa Fe and NW Buenos Aires provinces (11.000 km²) and comprises the NE sector of the Pampean Sand Sea (defined by Iriondo and Kröhling, 1995; Figures 1 and 2). The methodology applied in this study produced conclusions of stratigraphic and paleoclimatic nature. Works were performed in photographic and ima (mas) ges cabinet, in the field and laboratory. In cabinet, the geological cartography produced by the first author in former projects was issued, particularly the geological map of Santa Fe province, in 1:500.000 scale (Iriondo, 1987; Figure 3), the map of the South American plains (Iriondo, 1990a; Petit Maire et al., 1999) and the map of the Pampean Sand Sea in scale 1:1.000.000 (Iriondo, 1992). That was complemented with satellite images and photomosaic analyses, integrated with classical topographic quadrangles of IGM. Field works made in the region covered a period of two decades. The first expedition was done in the year 1985, during a dry inter-annual period which favored the description of geological profiles and collection of fossils in the bottom of channels. Further expeditions were made in the 1990's, resulting in the elaboration of the regional stratigraphy (Figure 4; Kröhling, 1998; Iriondo and Kröhling, 1995). The last three field surveys, between the years 2001 and 2004 (during the present humid period), were focused on the studies of dune fields, with areal sampling (about 50 samples) and the recovering of sedimentary cores (41 m drilled). Four stratigraphic boreholes were made in the study area and a complementary one outside it, with recovering of undisturbed samples and complemented with geotechnical S.P.T. tests. The main boreholes were drilled in Teodelina (34°11´lat. S; 61°31´long.W; 88 m a.s.l.; Santa Fe; Figure 5) and in San Gregorio (34°17' lat. S y 61°55´ long. W; 102 m a.s.l, Santa Fe). Laboratory analises comprises grain size analysis by sieving at intervals of ¼ Φ between 125 and 37 μm. For mineralogical determinations were applied loose grain techniques (in the very fine sand fraction) and X-ray diffractometry (on total samples; Figure 6). Complementary, morphoscopic determinations were carried out in the 74 μm fraction. Two geological formations of eolian origins are widespread in the region, Teodelina Fm (Late Pleistocene) and San Gregorio Fm (Late Holocene), which are formally defined here. The Teodelina Fm has a typical thickness of 10 to 12 m and has been eroded up to 5 m in some areas; it is composed of sandy coarse silt and silty fine sand, with main modes at 125-250 μm and 53-62 μm; the colour is yellowish brown and similar ones. The mineral composition of the 53-62 μm fraction is dominated by volcanic glass, with feldspars, quartz and alterites as accessory minerals. Roundness and sphericity of the grains vary from low to moderate, with two populations. The San Gregorio Fm is more than 7 m thick. It is composed of loose, massive, yellowish brown in color, very fine to fine sand (Figures 7a and 7b). The mineral composition is dominated by vitreous shards, alterites and feldspars as its main components and quartz as a secondary component; main heavy minerals were originated in the Pampean Ranges. The geomorphology of the area and the present hydric dynamics are controlled by eolian geoforms generated during the Late Quaternary. The exception is the fluvial collector in S Santa Fe which is a paleochannel of the Tercero river, controlled by tectonics (Figure 8). The study area underwent a sequence of dry and humid episodes during the Late Quaternary. Basically, the present landscape is the result of the influence of a humid climate which took place in the Oxygen Isotopic Stage 3 (OIS 3; 64-36 ka) and the eolian activity produced by a dry climate in the Late Holocene (3.5- 1.4 ka). The sequence of sedimentary and geomorphic events deduced from the data of this research was the following: during the humid OIS 3, a fluvial net developed; it forms at present the upper basin of the Salado River of Buenos Aires, and is carved in the Carcarañá Formation (OIS 3; Kröhling, 1999). In a subsequent dry episode (Late Pleistocene), the Teodelina Formation was sedimented by eolian and associated processes. A largelly erosive eolian phase occurred after Teodelina Fm accumulation; it was characterized by Western winds that carved hundreds of large deflation hollows. A discontinuous sedimentation of a sandy loess up to 2 m thick with bimodal grain size distribution covered the minor accidents of the landscape. The humid period of the Middle Holocene (8.5-3.5 ka) was characterized by a warm and humid climate with an udic soil regime, which generated a soil profile on the loessic terrains and provoked the water level rising in lakes and swamps. The Late Holocene, from 3.5 to 1.4 ka BP, was characterized by a dry climate that produced the development of parabolic dune fields, named here as the San Gregorio Formation. An interesting geomorphological feature of the study area is represented by numerous shallow lakes occupying large deflation hollows generated by W winds. That indicates a shift of the Westerlies to the N up to 34° lat. S at the Upper Pleistocene-Lower Holocene interval (Figure 9). During the Little Ice Age the studied area underwent an arid climate with dominance of SW winds that produced a general mobilization of sand to the NE (Figure 10); the inherited shallow lakes were transformed in playas (Dangavs and Mormeneo, 2006). The present dynamics is dominated by an excess of water in the landscape as a consequence of the Present humid climate and the morphosedimentological control referred above. The significant sedimentological process is the mobilization of large volumes of dissolved salts, mainly chlorides and sulphates.

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Geodetic Control of the Present Tectonic Deformation of the Betic Cordillera (Spain)

Alfaro, P.; Estévez-Rubio, Antonio; Blázquez, E. B.; Borque Arancón, María Jesús; Garrido, M. S.; Gil, Alejandro J.; Lacy Pérez de los Cobos, M.ª Clara de; Ruiz, Antonio M.; Giménez, J.; Molina Palacios, S.; Rodríguez Caderot, Gracia; Ruiz-Morales, M.; Sanz de Galdeano, Carlos
2006-01-01

Digital.CSIC (Spain)

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Geodesia de precisión aplicada al control de movimientos y deformaciones en la Caldera del Teide

Vieira, Ricardo; Sevilla, Miguel J.; Camacho, A. G.; Toro y Llaca, Carmen de; Martín, M. D.
1986-01-01

Digital.CSIC (Spain)

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Fe-Mn nodules associated with hydrocarbon seeps: A new discovery in the Gulf of Cadiz (Eastern Central Atlantic)

González, F. J.; Somoza, L.; Lunar, Rosario; Martínez-Frías, Jesús; Martín Rubí, J. A.; Torres, T.; Ortiz, J. E.; Díaz del Río, V.
2007-09-01

Digital.CSIC (Spain)

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Descubrimiento y modelización de clavos mineralizados en vetas polimetálicas a partir de exploración geoeléctrica, proyecto Pingüino, macizo del Deseado/ Polymetallic ore-shoots discovery and modelization with geoelectric surveys: Pingüino project, Deseado Massif

Guido, Diego M; Jovic, Sebastián M; Echeveste, Horacio; Tessone, Mario O; Ramayo Cortes, Leduar; Schalamuk, Isidoro B
2009-06-01

Resumen en español El macizo del Deseado contiene numerosas mineralizaciones epitermales de oro y plata asociadas al evento magmático extensional jurásico medio a superior. En el proyecto Pingüino, en función de condiciones estructurales particulares, se exponen rocas magmáticas del Jurásico inferior, correpondientes al inicio del evento extensional. Esto condiciona la ubicación de una mineralización atípica, caracterizada por la superposición de menas polimetálicas (Zn, In, Pb, (mas) Ag, Au, Cu, con As, Cd, Sn, W, Bi) y argentíferas (Ag y Au, con Zn y Pb). El descubrimiento de esta mineralización ha sido llevado adelante desde 2004 por la empresa Argentex Mining Corporation, con participación del grupo de geólogos del Instituto de Recursos Minerales (INREMI) desde el 2005. De todas las metodologías empleadas, la geoeléctrica de polarización inducida representa el método más eficaz y confiable para la prospección de vetas polimetálicas en el área. Las anomalías de cargabilidad, debidamente controladas con tareas de campo, constituyen una herramienta adecuada de prospección. A modo de ejemplo, se ha considerado uno de los siete sectores relevados por el equipo geológico-geofísico del INREMI, donde se han determinado tres categorías de anomalías de cargabilidad: A, B y C en orden decreciente, en función de su magnitud, continuidad vertical y lateral, y relación espacial con mineralización aflorante. La anomalía de mayor jerarquía fue perforada y uno de los pozos (P200-08) resultó ser el tramo de mayor ley de metales base de todo el proyecto (12,49 metros con 2,25 gr/ton de Au equivalente, 13,44 % entre Zn y Pb y 31 gr/ton de In). Resumen en inglés The Deseado Massif has numerous gold and silver epithermal occurrences related to the middle to upper Jurassic magmatic event. The Pingüino project, according to particular structural conditions, exposes lower Jurassic magmatic rocks which belong to the beginning of the extensional event. This is conditioning the location of an atypical mineralization, characterized by the overlapping of polymetallic (Zn, In, Pb, Ag, Au, Cu, with As, Cd, Sn, W, Bi) and argentiferous ore (mas) (Ag and Au, with Zn and Pb). The discovery of this mineralization was carried our since 2004 by Argentex Mining Corporation, with participation of the geological group of the Instituto de Recursos Minerales (INREMI) since 2005. Considering all the exploration techniques, the induced polarization geoelectric survey is the most precise and trustable method to explore polymetallic veins in the area. The chargeability anomalies, controlled in the field, are an unequivocal exploration tool. As an example, one of the seven areas surveyed by the geological-geophysical team of the INREMI was considered. Three categories of chargeability anomalies were defined: A, B and C, in decreasing order of importance, according to intensity, vertical and lateral continuity, and spatial relationship with outcropping mineralization. The most important anomaly was drilled, and one of the holes (P200-08) becomes the most important base metal intersection of the entire project (12.49 meters with 2.25 gr/ton Au equivalent, 13.44 % between Zn and Pb and 31 gr/ton In).

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Configuración geofísica-geológica del sector norte de la provincia de Río Negro/ Geophysical and geological character of the northern sector of Río Negro Province

Kostadinoff, J.; Gregori, D.A.; Raniolo, A.
2005-06-01

Resumen en español En el sector norte de la provincia de Río Negro y sur de la de La Pampa se realizaron relevamientos gravimétricos y magnetométricos que permitieron establecer la existencia de siete sectores geológicamente diferenciables. Entre ellos, la cuenca neuquina que se extiende hasta Chelforó y su evidencia gravimétrica desaparece progresivamente hacia el este y noreste en dirección del Alto de Chimpay - Gobernador Duval, así como al sudeste hacia la zona de alto gradiente (mas) Bajo de Trapalcó-Chimpay. Varios depocentros expresados como mínimos gravimétricos asociados a la falla de Huincul se ubican en el tramo Chimpay-Chichinales. La cuenca de Estancia El Caldén, conformada por sedimentitas mesozoicas y cenozoicas y localizada al este de Choele Choel, podría estar relacionada con aquella estructura. Altos del basamento de edad pampeana como el alto de Río Colorado y neoproterozoica, correspondiente al cierre gravimétrico de Chimpay - Gobernador Duval, se prolongan hasta la falla de Huincul. Una configuración similar posee la cuenca de Carapacha y las rocas ácidas de la Formación Choique Mahuida o equivalentes, las cuales se extienden hasta la falla de Huincul. Esta falla cruza toda la provincia de Río Negro, hasta la longitud del río Colorado, manteniendo un comportamiento de tipo dextral a lo largo de su recorrido. Al sur de Río Negro, el alto de Choele Choel, conformado por rocas de edades pampeanas e ígneas del ciclo gondwánico, habrían sido desplazadas esporádicamente en direcciones este y noroeste entre el Neopaleozoico y el Cretácico medio-superior. Resumen en inglés In the north sector of Río Negro and southern La Pampa provinces, gravimetric and magnetometer surveys distinguish seven different geological areas. The Neuquén Basin extends as far as Chelforó and its gravimetric signature disappears progressively eastward and north-eastward toward the Chimpay-Governor Duval High, as well as south-eastward to the high-gradient Bajo de Trapalcó-Chimpay area. Several depocenters expressed as gravimetric minima, associated with the Huin (mas) cul Fault are located between Chimpay and Chichinales. The Estancia El Caldén Basin, formed of Mesozoic and Cenozoic sedimentary rocks and located east of Choele Choel, could be related to the Huincul Fault. Basement highs of Pampean and Neoproterozoic age (Río Colorado High and Chimpay-Governor Duval High) extend south, and are truncated by the Huincul Fault. A similar configuration occurs in the Carapacha Basin, and the acidic rocks of the Choique Mahuida Formation and equivalents, which also extend as far as the Huincul Fault. The Huincul Fault crosses the entire Río Negro Province to the longitude of Río Colorado, maintaining a dextral type behaviour along strike. South of the Río Negro, the Choele Choel High, formed by Pampean- and Gondwana age rocks, has been displaced sporadically in easterly and northwesterly directions between Late Palaeozoic and mid-Late Cretaceous times.

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Changes in surface CO2 and ocean PH in ICES shelf sea ecosystems

Barry, James; Bellerby, Richard; Blackford, Jerry; Børsheim, Knut; Dulvy, Nick; Gattuso, Jean-Pierre; Gazeau, Frederic; Hain, Stefan; Hardman-Mounford, Nicholas; Hydes, David; Kildow, Judith; Silke Kröger, Silke; Laing, Ian; Leonardos, Nikos; Marubini, Francesca; Pelejero, Carles; Pörtner, Hans; Studd, Shaun; Suggett, Dave; Widdicombe, Steve
2008-04-01

Digital.CSIC (Spain)

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Cenozoic ice sheet history from east Antarctic Wilkes Land continental margin sediments.

Escutia, Carlota; De Santis, L.; Donda, F.; Dunbar, R.B.; Cooper, A.K.; Brancolini, G.; Eittreim, S.L.
2005-02-01

Digital.CSIC (Spain)

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An Early Ordovician (Floian) Conodont Fauna from the Eastern Cordillera of Peru (Central Andean Basin)

Gutiérrez-Marco, J. C.; Albanesi, G. L.; Sarmiento, Graciela N.; Carlotto, Víctor
2008-01-01

Digital.CSIC (Spain)

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An Assessment of the BGS δDδI Vector Magnetometer

Marsal, Santiago; Torta, Joan Miquel; Riddick, John C.
2007-01-01

Digital.CSIC (Spain)