Sample records for ANAQUEL CONTINENTAL SALIDA (outer continental shelf)
from WorldWideScience.org

Sample records 1 - 15 shown.



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

Subduction-related structures in the North Iberian Margin

Alvarez-Marrón, Joaquina; Rubio, Luis Eduardo; Torné, Montserrat
1997-10-10

Digital.CSIC (Spain)

3

Storm-driven shelf-to-canyon suspended sediment transport at the southwestern Gulf of Lions

Palanques, Albert; Guillén, Jorge; Puig, Pere; Durrieu de Madron, Xavier
2008-08-30

Digital.CSIC (Spain)

4

Morphosedimentary features and recent depositional architectural model of the Cantabrian continental margin

Ercilla, Gemma; Casas, David; Estrada, Ferrán; Vázquez, Juan T.; Iglesias, Jorge; García, M.; Gómez, M.; Acosta, Juan; Gallart, Josep
2008-01-10

Digital.CSIC (Spain)

6

GEOMORFOLOGÍA Y FORMACIONES ARRECIFALES RECIENTES DE ISLA FUERTE Y BAJO BUSHNELL, PLATAFORMA CONTINENTAL DEL CARIBE COLOMBIANO/ GEOMORPHOLOGY AND RECENT REEF STRUCTURES OF ISLA FUERTE AND BAJO BUSHNELL, COLOMBIAN CARIBBEAN CONTINENTAL SHELF

Díaz, Juan M.; Sánchez, Juan A.; Díaz-Pulido, Guillermo
1996-12-01

Resumen en español Con base en observaciones directas en el campo e interpretación de fotografías aéreas y de perfiles efectuados con ecosonda se hace una descripción general de los rasgos geomorfológicos y de las formaciones coralinas de Isla Fuerte y Bajo Bushnell, dos áreas arrecifales localizadas frente a la costa sur-central del Caribe colombiano. Isla Fuerte es un complejo arrecifal holocénico parcialmente emergido. La plataforma insular ocupa un área de unos 13 km² y, ademá (mas) s de una porción emergida, posee diversas estructuras arrecifales, tales como barrera franjeante a barlovento, cinturón arrecifal periférico en el borde de la plataforma y arrecifes de parche someros, además de amplias praderas de fanerógamas a sotavento. De otro lado, Bajo Bushnell es un banco coralino de unos 1300 m de diámetro, en forma de domo, próximo al borde de la plataforma, con una profundidad mínima de 12 m. Aunque las comunidades del fondo son relativamente homogéneas y los límites entre éstas son poco discretos, se distinguen en Bushnell al menos cuatro unidades de paisaje bentónico con base en la presencia/dominancia de la biota sésil más conspicua. La zona de mayor cobertura de coral vivo corresponde a la más somera, en el borde de sotavento del bajo. Se incluye una lista de los corales observados en ambas áreas. Al igual que otros bancos coralinos e islas situados frente a la costa central del Caribe colombiano, el origen de estos alto-relieves en la plataforma continental parece estar asociado a diapirismo y tectonismo, y subsecuente colonización por organismos hermatípicos desde el Holoceno. Resumen en inglés Based on field surveys and interpretation of aerial photography and echosounder profiles, a general description of the geomorphological features and a characterization of the coralline structures of two reefal areas off the southern-central Colombian Caribbean coast, Isla Fuerte and Bajo Bushnell, are presented. Isla Fuerte is a partially emerged Holocenic reef-complex. The insular shelf occupies an area of about 13 km² and, besides a highstanding island, it has diverse (mas) geomorphological features such as a seaward fringing barrier reef, a peripherical reef-belt at the outer shelf margin, and shallow patch reefs, as well as large seagrass meadows on its leeward side. On the other hand, Bushnell is a dome-shaped coral bank, about 1300 m in diameter, with a minimum depth of 12 m, located near the shelf-edge. Despite the bottom communities being relatively homogeneous and their boundaries are ill-defined, at least four ecological bottom units could be distinguished at Bushnell on the basis of the presence/dominance of conspicuous sessile organisms. The zone of greater living coral coverage corresponds to the shallowest, seaward part of the shoal. A list of coral species observed in both areas is included. Like other coral banks and islands off the central part of the Colombian Caribbean coast, the origin of these high-reliefs on the continental shelf seems to be related to diapiric and tectonic activity, and subsequent colonization by hermatipic organisms since Holocene times.

Scientific Electronic Library Online (Spanish)

7

Flushing submarine canyons

Canals, Miquel; Puig, Pere; Durrieu de Madron, Xavier; Heussner, Serge; Palanques, Albert; Fabrés, Joan
2006-11-16

Digital.CSIC (Spain)

8

Evolución paleoambiental y paleogeográfica de la cuenca cámbrica de la Precordillera argentina/ Paleoambiental and paleogeographic evolution of the cambrian basin of the Argentine Precordillera

Bordonaro, OL
2003-09-01

Resumen en español El análisis espacial y temporal de las rocas cámbricas de la Precordillera argentina ha permitido elaborar una nueva interpretación del margen continental precordillerano. La litoestratigrafía y la bioestratigrafía son ensambladas en un modelo paleogeográfico no palinspástico coincidente con la actual distribución del basamento precámbrico expuesto en las Sierras Pampeanas Occidentales. La asociación de biofacies y litofacies reconocidas en toda la cuenca cámbr (mas) ica precordillerana permiten interpretar una plataforma con margen y es posible distinguir tres grandes áreas que corresponden a una plataforma interna, una plataforma externa y una zona donde las dos anteriores se interdigitan con un talud superior y con una barrera marginal. Durante el Cámbrico inferior tardío se inició una etapa de rifting con sedimentación siliciclástica y evaporítca dentro de un graben intracontinental que evolucionó hacia una plataforma abierta. Se detecta un hiatus faunístico en el límite Cámbrico inferior-Cámbrico medio correlacionable con el evento regresivo Hawke Bay de Los Apalaches. En el Cámbrico medio tardío se instaló una plataforma restringida con lagoon, barreras internas, terrígenos internos y sabkha costero desarrollados en el E de la Precordillera, mientras que barreras marginales y una plataforma externa se desarrollaban en el O de la Precordillera. Durante el Cámbrico superior una amplia plataforma perimareal progradaba hacia el O limitada por barreras marginales en el S de la cuenca, mientras que en el N se manifestaba con una menor restricción. Cerca del límite Cámbrico-Ordovícico una nueva plataforma con margen retrogradaba hacia el E como consecuencia de un evento de inundación de la cuenca. Durante el Cámbrico superior comenzaba a manifestarse un colapso tectónico distensivo en el S de la cuenca que luego se generalizaría en toda la Precordillera durante el Ordovícico. Resumen en inglés The Cambrian rocks of the Argentine Precordillera are analyzed in space and time to arrive at new interpretation of the precordilleran continental margin. The lithostratigraphy and biostratigraphy are incorporated into a nonpalinspastic paleogeographic model that accords with the structural distribution of the Precambrian basement, now exposed in the western Sierras Pampeanas.The lithofacies and biofacies assemblages recognized in all the precordilleran cambrian basins pr (mas) ovide evidence to interpretate a rimmed platform. It is posible to distinguish three large areas corresponding to an inner platform, an outer platform and a mixed zone where both platforms interfinger with a rim and talus. In the later Early Cambrian, a mixed open platform was developed above underlying, localized rifting stage with siliciclastics and evaporites of the intracontinental graben system. A faunistic hiatus near the Lower-Middle Cambrian boundary is present in the all Precordillera wich appears to correlate with the Hawke Bay regressive event in the Appalachian area of North America. In the later Middle Cambrian a rimmed platform with lagoon, inner barriers, terrigenous and coastal sabkha facies developed at the eastern, and shoals or barriers were built at the western margin of the shelf, evolving seaward with an open subtidal platform. During the Late Cambrian, a broad peritidal platform prograded to the west, bounded by sand barriers mainly in the southern areas, meantime the northern areas remaining less restricted. Around the Cambrian-Ordovician boundary interval, a new rimmed platform was established but the platform margin retreated to the east as part of a flooding event. A distensive tectonic collapse of the carbonate platform began in the latest Cambrian in the southern areas.

Scientific Electronic Library Online (Spanish)

9

El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

Arntz, Wolf E.; Gallardo, V. A.; Gutiérrez, D.; Isla, Enrique; Levin, L. A.; Mendo, J.; Neira, C.; Rowe, G. T.
2006-01-01

Digital.CSIC (Spain)

10

Contrasting styles of the Holocene highstand sedimentation and sediment dispersal systems in the northern shelf of the Gulf of Cadiz

Lobo, F. J.; Sánchez, R.; González-Álvarez, R.; Dias, J. M. A.; Hernández-Molina, F. Javier; Fernández-Salas, L. M.; Díaz del Río, V.
2004-03-01

Digital.CSIC (Spain)

13

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)

15

Altos estructurales costa afuera en la región de Valparaíso, Chile central/ Offshore structural highs at Valparaíso region, central Chile

Vergara, Hernán P; Astudillo, René
2008-12-01

Resumen en español Mediante altimetría satelital 3-D se detectó y describió un lineamiento submarino de 40 km ubicado en el quiebre de pendiente plataforma-talud continental, entre los 32° y 33°S, 27 km costa afuera de la región de Valparaíso. El alineamiento consiste en tres cumbres a 200, 733 y 880 m de profundidad orientadas al N10ºW, con relieves de 1230, 1350 y 1545 m respectivamente desde la base a la cima. Se propone designarlos como Los Molles, Horcón y Zapallar en su orien (mas) tación hacia el norte, de acuerdo a la normativa internacional para los relieves submarinos. El patrón morfológico sugiere un dislocamiento holocénico de un bloque no confinado del borde externo de la plataforma, con relación al borde superficial del talud superior, posiblemente vinculado a mecanismos tensionales y la sismicidad generada por la subducción de la aspereza Papudo bajo el talud medio Resumen en inglés By means of satellite 3-D altimetry, a 40 km submarine alignment sited at 32º-33º south latitude on the shelf break in slope, 27 km offshore Valparaíso region, was detected and described. The alignment consists of three peaks at 200, 733 and 880 m below sea level bearing N10ºW and showing 1230, 1350 and 1545 m relief relative to the surface of the upper slope. According to the international standards for undersea features, the names of Los Molles, Horcón and Zapallar (mas) are proposed for them in a northward trend. The whole morphological pattern suggests a non confined block displacement of the outer shelf relative to the surface of the upper slope border implying a Holocene subsidence displacement possibly related to the stresses and seismicity generated by the subduction of the Papudo asperity below the middle slope

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