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The Burdwood Bank is a rocky platform emerging from the abyssal plain to depths of 50-100 m between the South Atlantic Ocean and the Drake Passage. Regarding its geological affinity, it has a composition similar to the Staten Island (Isla de los Estados), therefore aligned to the Andes-Darwin Cordillera. This bank is crossed from south to north by the Antarctic Bottom Water; very cold and rich in nutrients. Rocks dredged from the shallower portions at its western portion are composed of carbonatic blocks. The analyses indicate fossil specimens of Desmophyllum sp. (Order Scleractinia) and Gorgonacea palmatum (Order Gorgonacea), genera living today in the region. In this sense, sectors of this western portion should be considered as an ancient reef composed mostly of cold-water corals. The major implications are assigned to oceanographic and climatic issues. During the Upper-Pleistocene lowstand, sunlight was more available at shallower depths and therefore corals were very frequent at wave-dominated areas. Sea-level variations have therefore strong influence on cold-water coral growths in the sense that nutrient availability by currents can significantly changed between glacial and interglacial periods.

Tourism in the southern sandy temperate barriers has historically been one of the drivers of coastal development in Buenos Aires, Argentina. This process, which has been accompanied by dune fixation and a subsequent urbanization, began in the 1930s and occurred in the absence of coastal management policies causing several environmental problems. This work aims to analyze the historical development of two dune afforestation projects with the objective of characterizing their main environmental issues. These projects, which started almost simultaneously, are currently at completely different levels of development. For this purpose, a literature and relevant legislation review was carried out, allowing us to characterize them and generate comparisons. At the same time, it is intended to propose new strategies for dune fixation. One of the peculiarities of these afforestation projects is that two brothers carried them out: Carlos and Ernesto Gesell. Carlos initiated an afforestation that led to the sprawl of Villa Gesell. This city reached historical records of urban growth and it is actually one of the most popular bathing resorts of Argentina. Ernesto founded Dunamar on a more restricted dune field and it is currently at a significantly lower stage of development than Villa Gesell. Coastal erosion, surface runoff increase, decrease of foredune areas and replacement of native dune vegetation are some of the reported problems. Currently, there are projects for the expansion of the urban area of these villages under different strategies for dune stabilization. Although their effects have been extensively documented, they propose fixations with fast-growing exotic species. This work proposes the revegetation by means of native species corresponding to the original landscape of the dunes of about a century ago. To this end, certain aspects must be taken into account within the framework of integrated coastal management.

The Inner Río de la Plata Estuary is a sedimentary depositional system that resulted from fluvial-deltaic activity. Gentle Pliocene–Pleistocene slopes make-up the northern side of the estuary whereas small cliffs of the same age constitute the southern side. A long coastal estuarine barrier developed at about 6000 years BP when the maximum flooding surface occurred. Attached to this barrier, and at a lower elevation, is a large strandplain (covering an area of about 2400 km2) which displays more than 220 beach ridges. In different areas, the dating indicates a periodicity of 13.4–13.7 years for the development of each beach ridge. These data are like the periodicity of the ENSO effects, which could be associated with the variability of Sunspots. These ridges were formed shortly after the maximum flooding surface, which was followed by a gradual fall in sea-level that contributed significantly to the Inner Río de la Plata Estuary sedimentary infill. In addition, ENSO activities were probably instrumental in the distribution of the main geoforms in the Inner Rio de la Plata Estuary. Small deltas, which were generated by other rivers and creeks such as the Nogoyá Arroyo and the Gualeguay River, developed coevally with the coastal estuarine barrier. The Ibicuy Delta grew in the middle of the inner Río de la Plata Estuary when the former Paraná River flowed northwards during the sea-level fall. The upper part of the delta front was reworked, giving rise to a large dunefield. Thereafter, a chenier plain developed along with tidal flats. The current Paraná Delta continues to prograde at a rate of about 56–64 m/year (m year−1). The sedimentary infill of the Inner Río de la Plata Estuary occurred along the Holocene.

Holocene diatoms of the Colorado River Delta, Argentina. A paleoenvironmental approach from the study of “small fragilarioids”. Diatom assemblages of a sedimentary succession in the deltaic plain of the Colorado River (Argentina) were studied in order to reconstruct the paleoenvironmental conditions of the delta in response to Holocene sea-level changes. A 191 cm depth core was extracted by vibracoring from Las Isletas (LI), located 22 km from the coast (39°43’5.7”S, 62°20’49.7”W). A cluster analysis – CONISS of 35 subsamples defined three diatom zones (DZ). The sedimentary succession is dominated by small fragilarioids, being Punctastriata glubokoensis Williams, Chudaev & Gololobova the most abundant species; the accompanying flora included fresh-brackish and allochthonousmarine-coastal taxa. At the base, subzone DZIA (191–163 cm, 7,315±64 14C yr BP) included sandy lithological units and presented abundant marine-coastal species. The overlying subzone DZIB (163–96 cm) has low abundance of allochthonous marine species. The uppermost zone, DZII (96 cm from the top) integrate the silt-sandy lithological units, and it was deposited ca. 2,218±29 14C yr BP. DZII lacked marine species. The LI sequence represents the infilling of a river-estuarine channel with tidal influence ca. 7,300 14C yr BP that gradually evolved into a fresh-brackish river channel, similar to the current river, ca. 2,200 14C yr BP. During the Middle Holocene transgression, the greatest marine influence would have transported coastal marine species upstream to the LI site; the increase of fluvial influence associated with the progradation of the delta lobe would have favored the ubiquity and persistence of the small fragilarioids in the fluvial-delta assemblages of the Colorado River during the last ca. 7,000 14C yr BP. Keywords: Fragilariaceae, delta, sea level, Holocene, Patagonia. As associacoes de diatomaceas, de uma sucessao sedimentar da planicie deltaica do Rio Colorado (Argentina), foram estudadas com o objetivo de reconstruir as condicoes paleoambientais do delta, em resposta as flutuacoes do nivel do mar no Holoceno. Um testemunho de 191 cm de profundidade foi extraido usando um vibracoring no sitio Las Isletas (LI), localizado a 22 km da costa atual (39°43’5,7”S, 62°20’49,7”O). A analise diatomologica de 35 sub-amostras permitiu definir tres zonas de diatomaceas (DZ) por meio de uma analise de agrupamento – CONISS. O testemunho foi dominado por pequenos fragilarioides, sendo Punctastriata glubokoensis Williams, Chudaev & Gololobova a especie mais abundante. A flora acompanhante apresentou especies de agua salobra-duciaquicolas e taxons marinho-costeiros aloctones. A subzona basal DZIA (191–163 cm, 7.315 ± 64 anos 14C AP) incluiu unidades litologicas arenosas e apresentou abundantes diatomaceas marinhas costeiras aloctone. A subzona sobrejacente (DZIB: 163–96 cm) exibiu poucos taxons marinhos. A zona DZII (96 cm no topo) integrou unidades litologicas de areia-siltosa, formadas ca. 2.218 ± 29 anos 14C AP. DZII e nao apresentou especies marinhas costeiras. A sequencia LI representa o assoreamento de um canal fluvial-estuarino com influencia de mares ca. 7.300 anos 14C AP que evoluiu gradualmente para um canal fluvial de aguas salobra-dulciaquicolas, semelhante ao rio atual ca. 2.200 anos 14C AP. Durante a transgressao do Meso-holoceno, o aumento da influencia marinha teria transportado especies costeiras-marinhas a montante do sitio LI. O aumento da influencia fluvial associada a progradacao do lobo deltaico teria favorecido a onipresenca e a persistencia de pequenos fragilarioides nas associacoes fluvio-deltaica do Rio Colorado durante os ultimos ca. 7.000 anos 14C AP. Palavras-chave: Fragilariaceae, delta, nivel do mar, Holoceno, Patagonia.

Isla F.I. and Espinosa M., 2021. The gravels of the Rio De La Plata: The Holocene beaches of Bella Vista, Uruguay. Journal of Coastal Research, 37(5), 987–992. Coconut Creek (Florida), ISSN 0749-0208. The Rio de la Plata has a ria-type estuary, with a coastal plain dominated by fine to very-fine sands to the south and a tectonic coast to the north dominated by fine to coarse sand. Although the headlands of the river were dominated by fluvial processes related to the deltaic lobes of the Parana River, the Parana Guazu, and Parana de las Palmas, the outer estuary is subject to wave action that increased significantly during storms from the SE. Wave statistics confirmed a littoral drift responsible for the spits at the outlets of affluent rivers deflected to the west (Solis Grande, Solis Chico). At the northern Uruguayan coast the interval between Bella Vista and Las Flores is composed of gravel that is described here. Bella Vista beach has two berms; the upper berm is partially covered by eolian sands. Las Flores beach consists of a single berm where gravels segregate upward and sand moves toward the river coastline. The storm berm of Bella Vista includes finer gravels (3–6 cm) whereas the gravels from the tidal berms (both beaches) are coarser, from 6 to 15 cm. According to the Zingg diagram, oblate and tabular gravels abraded by the wave action dominate. Considering old photographs, these gravel berms are stable and relicts from the highstand of the Middle Holocene. They were, therefore, derived by waves from submerged deposits originally derived from the Complex Sierra de las Animas.

Coastal erosion is a critical problem that affects several countries around the World that would increase concerning the anthropogenic sea-level rise. Gravel beaches have proved to be more stable facing coastal erosion. The mixture of sand and gravel has been used to replenish beaches as a soft mechanism that increases beach stability. Most of the Buenos Aires coastline is composed of sand, although some beaches are composed of mixed sand and gravel. These beaches vary spatially and temporally in the sand-gravel proportion; the gravel fraction is mainly composed of volcanic lithics derived from Patagonia, with caliche and bioclasts of local contribution. Six mixed sand and gravel beaches (MSGB) with diverse grain size and sand-gravel rates were monitored to evaluate the morphodynamic changes and grain-size variability in cross-shore profiles throughout a year (May 2016—April 2017). Also, the wave conditions were analyzed to identify high-energy wave events using ERA5 dataset. A general behaviour of the six beaches was discerned, where the gravel fraction increases significantly in the seasons with more high-energy wave events (autumn and spring), especially in the upper-foreshore. In these periods, the gravel-runs formation and the sediment armouring were described. In summer times, an increment in the accretion of the cross-shore profiles and sand fraction proportion were recorded. The increase of gravel proportion, gravel runs development and armouring processes are some responses of MSGB to high energy conditions that cause greater stability.

The goal of this work was to infer the spatio-temporal patterns of bottom circulation of San José Gulf (SJG), Patagonia, Argentina. The SJG is mainly affected by tidal circulation and presents two hydrographic domains. The Western Hydrographic Domain (WHD) presents vertically mixed waters year-round contrary to the seasonal stratified Eastern Hydrographic Domain (EHD), resulting in the formation of a thermal front between domains. Samples of sediments were collected in spring 2016 and summer 2017 at several locations to analyze the grain-size composition by means of laser diffractometry. A conceptual model of bottom hydrodynamics was inferred based on sediment's grain-size trends. Asymmetric dominant tidal currents affect bottom sediment distribution. A general northward sediment transport is dominant at the WHD, while at the EHD there is a seasonal shift in the transport direction. There, a net northward transport with a counterclockwise gyre dominates bottom hydrodynamics at the end of the thermal front formation, conditioned by residual currents. In contrast, a net southward circulation likely driven by strong westerly winds throughout autumn and winter prevails at the beginning of the water column stratification. The inferred sediment transport suggests a net loss of material that has to be recovered by tidal currents entering through the mouth and coastal sources as runoff, mudslides, and/or aeolian dust. Fil: Hernández Moresino, Rodrigo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Crespi Abril, Augusto Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Soria, Rodrigo Gaspar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Sánchez, Alberto. Centro Interdisciplinario de Ciencias Marinas; México Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina

The area involved by the triple junction between the South American, Nazca and Antarctic plates activity was affected by Quaternary glaciations. Before 12,800 yrs BP an extended ice field occupied the top of the Patagonian Andes, irradiating glaciers towards the east and the west dominantly. Towards the east, the ice melted in piedmont lakes; towards the west, fjords melted into the Pacific Ocean. The Upper-Pleistocene climate amelioration caused the recession of those glaciers. Some piedmont lakes reversed their Atlantic outflow towards to the Pacific Ocean. The glaciers retreat caused the fluvial reactivations along crustal former faults that were located below the ice. The Patagonian ice field became therefore split into present Northern and Southern fields. At the second largest lake of South America, the Buenos Aires-General Carrera Lake, the water level dropped from about 500 m over present mean sea level to 230 m. Several glaciolacustrine deposits from this area are indicating significant variations caused by climatic changes, volcanism and tectonics, differing in spatial and temporal magnitudes. The triple junction activity involved subduction of the Chile Ridge below the continental South American plate, volcanic activity and faulting. During the glacier melting the Baker River captured three eastern-moving glacial systems towards the southwest, towards the Pacific Ocean. This rapid event is thought to occur 12,800 yrs BP. The lowering of these glaciolacustrine systems should be also interpreted in terms of the tectonic activity in the region and considering other processes operating in the lakes and within the watersheds. Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

The Scotia Plate is interacting between the South American and the Antarctic plates. The original plate has been subdivided in relation to new studies that recognized an active oceanic ridge that separate it from the Sandwich Plate. At the same time, the Shackleton Fracture Zone separates it into two other small plates: the Drake and the South Shetland plates. All these plates are mostly of oceanic composition with a small portion of continental crust emerging at the northwestern corner, at the south of the Fuegian Archipelago. Most of the emergent areas of these plates have been repeatedly glaciated during the Quaternary, although the last glaciation was not so extended as in the Northern Hemisphere. In order to get light about rock provenance, beach and coastal sands were collected and analyzed in their mineral composition, assuming that they are indicating the geotectonic setting. Quartz, lithic fragments and plagioclases are dominant at the Atlantic coast of the Isla Grande de Tierra del Fuego. These sediments have been transported by piedmont glaciers from the Darwin Cordillera. On the other hand, and due to their volcanic origin, opaque minerals are dominant at the beaches of the South Shetland Islands, and less common at the Antarctic Peninsula. To the north and south of the Scotia Plate, there is an important contribution of metamorphic minerals (garnets). These contributions are related to the Patagonian Batholith at Beagle Channel, and to those rocks outcropping at the South Orkney Islands and the Antarctic Peninsula.

Biodiversity mapping in urban areas is imperative for their conservation. Remote sensors produce environmental information, such as the Normalized Difference Vegetation Index (NDVI), an indicator of vegetation cover in urban areas. NDVI can be used to predict the taxonomic, functional and phylogenetic bird diversity in urban areas. Moreover, a predictive model constructed in one city can be used to predict the bird diversity in other cities. The objectives of this study were: 1) to construct and evaluate predictive models between NDVI and taxonomic, functional and phylogenetic diversity of birds in Mar del Plata city, Argentina; and 2) to extrapolate these models to two other cities in the region: Balcarce and Miramar. Generalized additive models were applied to relate bird diversity variations to NDVI. In Mar del Plata, the taxonomic and functional diversity increased with increasing NDVI values, and the predictive models explained 64–81% of the taxonomic and functional diversity variation. The models correctly predicted taxonomic and functional diversity values in additional transects not included in the models, although they had a low predictive power of phylogenetic diversity. The models constructed in Mar del Plata adequately predicted the spatial variation of species diversity (Shannon index) in Balcarce and Miramar, the spatial variation of species richness in Balcarce, and the variation of functional diversity in Miramar. Our analysis revealed that a predictive model of bird diversity based on NDVI patterns created in one city can also depict the expected species diversity in other cities, being a time-saving and cost-effective method to create a tool for urban biodiversity conservation. Fil: Leveau, Lucas Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Bellocq, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

Coastal cities have particular spatial urbanization trends conditioned by the dominant activities, meaning tourism, fishing or commerce. Notwithstanding that, there are other issues or restrictions that also conditioned the growing pattern of these villages or cities that can change during their development. In this sense, monocentric patterns (harbor cities) may evolve into a radial model related to main accessing routes. Touristic cities emplaced on barrier systems extended alongshore while their service areas installed at opposite directions where lots are cheaper. Some coastal villages grew exponentially in the last century in Argentina although they had original restrictions in the freshwater availability. Today, they are also conditioned to the recreational qualities of their beaches, or the disposal availability of residential sewages. Coastal cities have particular spatial urbanization trends conditioned by the dominant activities, meaning tourism, fishing or commerce. Notwithstanding that, there are other issues or restrictions that also conditioned the growing pattern of these villages or cities that can change during their development. In this sense, monocentric patterns (harbor cities) may evolve into a radial model related to main accessing routes. Touristic cities emplaced on barrier systems extended alongshore while their service areas installed at opposite directions where lots are cheaper. Some coastal villages grew exponentially in the last century in Argentina although they had original restrictions in the freshwater availability. Today, they are also conditioned to the recreational qualities of their beaches, or the disposal availability of residential sewages. Fil: Isla, Federico Ignacio. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Isla, Maria del Pilar. Universidad Nacional de Mar del Plata. Facultad de Arquitectura, Urbanismo y Diseño; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina

The Chubut River is a Patagonian river that flows from the Andes to the Atlantic Ocean, and is interrupted by a dam built at the middle valley. To investigate the sedimentary history of the lower river basin, a sediment core was collected from the floodplain. Fossil diatom assemblages contained within the core obtained at Gaiman village have been applied to a diatom-based inference model of conductivity. Two phases in the evolution of the Chubut River lower basin were identified through diatomological and sedimentological analyses, in which multivariate analysis were included, assisted by radiocarbon dating. Phase 1 representing natural conductivity and depth changes during the Early Holocene and Phase 2 the infilling of the lotic environment in recent times influenced by the anthropogenic effects, nutrients input and dam construction. Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Vélez Agudelo, Camilo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina

The Tirúa-Mocha Island area (38.2°-38.4° S) in southern Chile has been affected by two megaearthquakes in only 50 years: the 1960 Mw=9.5 Valdivia earthquake and 2010 Mw=8.8 Maule earthquake. We studied in the field the vertical ground movements occurred during the interseismic period between both earthquakes and the coseismic period of 2010 Maule earthquake and 2011 Mw=7.1 Araucanía earthquake. During the 1960 earthquake, vertical coseismic ground movements are typical of subduction related earthquakes with Mocha Island, located close to the trench, experienced bigger ground uplift (150 cm) than that occurred in Tirúa (-20 cm), place located in the continental margin at the latitude of Mocha Island. Then during the 1960-2010 interseismic period, the 1960 coseismic uplift remained at Mocha Island unlike the normal interseismic subsidence that occurred northward at Arauco Peninsula and Santa María Island. Also Tirúa experienced the biggest interseismic uplift (180 cm) in all the area affected later by 2010 Maule earthquake. Then during the 2010 Mw=8.8 Maule earthquake an anomalous vertical coseismic ground uplift occurred in the study area, opposite to that of 1960 since Mocha Island experienced lower (25 cm) ground uplift than Tirúa (90 cm). Subsequently, during the Araucanía 2011 earthquake a ground uplift in Mocha Island (50 cm) and subsidence at Tirúa (20 cm) occurred. These unexpected vertical ground movements can be explained by the existence of an upper plate splay fault located below the sea bottom between Tirúa and Mocha Island: the Tirúa-Mocha splay fault. Considering the last seismic cycle, the activity of this fault would have started after the 1960 Valdivia earthquake. During 2010 Maule earthquake, the main slip occurred at Tirúa Mocha splay fault. Finally during 2011 Araucanía earthquake, the slip occurred mainly at the updip of Wadati-Benioff plane with probable normal activity of Tirúa-Mocha splay fault. Simple elastic dislocation models considering the Wadati-Benioff plane and the Tirúa-Mocha splay fault activity, can account for all the vertical ground movements observed during 1960 earthquake, the 1960-2010 interseismic period, the 2010 Maule earthquake and the 2011 Araucanía earthquake. El área de Tirúa-Isla Mocha (38,2° S-38,4° S) ubicada en el sur de Chile ha sido afectada por dos megaterremotos en solo 50 años: el terremoto de Valdivia Mw=9,5 de 1960 y el terremoto del Maule Mw=8,8 de 2010. Se estudiaron en el campo los movimientos verticales del terreno asociados al período intersísmico entre estos terremotos y los cosísmicos relacionados con los terremotos del Maule 2010 y Araucanía 2011 Mw=7,1. Durante el terremoto de 1960, los movimientos cosísmicos verticales del terreno fueron los esperados, ya que la isla Mocha, localizada cerca de la fosa experimentó mayor alzamiento (150 cm) que Tirúa (-20 cm), localidad situada en el margen continental frente a esta isla. Luego, durante el período intersísmico (1960-2010), el alzamiento cosísmico de 1960 permaneció en la isla Mocha a diferencia de la subsidencia intersísmica normal que ocurrió más al norte en la península de Arauco e isla Santa María. Además, Tirúa experimentó la mayor tasa de alzamiento intersísmico (180 cm) en el área afectada posteriormente por el terremoto de Maule de 2010. Después en el terremoto del Maule Mw=8,8 de 2010, ocurrió un alzamiento cosísmico vertical anómalo opuesto al de 1960, donde la isla Mocha experimentó menor alzamiento (25 cm) que Tirúa (90 cm). Más tarde durante el terremoto de Araucanía del año 2011, ocurrió un alzamiento del terreno en isla Mocha (50 cm) y subsidencia en Tirúa (20 cm). Estas anomalías pueden ser explicadas por la existencia de una falla subsidiaria en la placa superior, localizada bajo el piso oceánico entre Tirúa y la Isla Mocha: la falla subsidiaria Tirúa-Mocha. Considerando el último ciclo sísmico, la actividad de esta falla habría comenzado después del terremoto de Valdivia de 1960. Durante el terremoto de Maule de 2010, el deslizamiento principal ocurrió en la falla subsidiaria Tirúa-Mocha. Finalmente durante el terremoto de Araucanía de 2011, el deslizamiento ocurrió principalmente en la parte superior del plano de Wadati-Benioff con probable actividad normal de la falla subsidiaria Tirúa-Mocha. Modelos de dislocación elástica simples, considerando el plano de Wadati-Benioff y la falla subsidiaria de Tirúa-Mocha y su actividad, explican todos los movimientos verticales del período intersísmico 1960-2010, y los cosísmicos de los terremotos del Maule del 2010 y Araucanía del 2011. Fil: Quezada, Jorge. Universidad de Concepción; Chile Fil: Jaque, Edilia. Universidad de Concepción; Chile Fil: Catalán, Nicole. Universidad de Concepción; Chile Fil: Belmonte, Arturo. Universidad de Concepción; Chile Fil: Fernández, Alfonso. Universidad de Concepción; Chile Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

As the Buenos Aires Province coastline is dominated by a longshore transport from south to north, obstructions performed at the beginning of the 20th century originated the width reduction of some beaches. Fields of groins were constructed without a master plan; therefore, more obstructions caused a dramatic decrease in the longshore sand supply. These defense alternatives were only applied in the counties of the southeast of the province (General Pueyrredon, General Alvarado, Mar Chiquita), close to the quarries, and with resistant abrasion platforms. Northern beaches (Villa Gesell, Pinamar and Partido de la Costa), on the other hand, are natural with a dissipative morphodynamics. Where the coastal route is close to active cliffs, riprap structures were constructed parallel to the coastline. Today, the southeastern coast remains with the higher erosion rates of the Buenos Aires coastline. With the aim of aerial and satellite photographs, and images, erosion rates were calculated. In order to analyze the success of coastal defenses, comparisons were established according to two intervals: 1960–1980, and 1980–2008. Defense structures have contributed to the decrease in the erosion rates in some areas; in other areas, the rates have increased due to the drift obstruction. In some critic areas, and considering present erosion rates, future positions of the coastline were simulated for the next 20–30 years. At the same time, there are new unexpected problems derived from a project to construct detached breakwaters that were not completed, and considering jetties that were constructed without a previous impact-assessment analysis. Fil: Isla, Federico Ignacio. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Cortizo, Luis. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Merlotto, Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Bertola, German Ricardo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Pontrelli Albisetti, Melisa. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Finocchietti, Cecilia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina

The increasing urbanization within cities correlates with the loss of green cover, affecting the distribution of bird species. Therefore, to foresee possible effects induced by green cover loss, it is essential to have spatial data of species occurrence. Remote sensors produce spatial data of green cover, such as the Normalized Difference Vegetation Index (NDVI), which can be used to model bird species occurrence within and between cities. The objectives of this study were: 1) to construct and evaluate predictive models between NDVI and bird species distribution in Mar del Plata city, Argentina; and 2) to extrapolate these models to two other cities of the region, Balcarce and Miramar. Most of the 21 species analyzed showed positive associations with NDVI. However, the minimum NDVI values at which species started to be present were dissimilar, showing different habitat requirements. The models of nine species had r-squared values ≥ 0.40, and eight of these species showed an adequate prediction of occurrence in additional areas of Mar del Plata. However, only the occurrence of the Tropical Kingbird (Tyrannus melancholicus) was adequately extrapolated to Miramar and Balcarce. Results showed that NDVI is successful to predict bird species occurrence within a city, but the extrapolation to other cities is not totally adequate. Thus, bird-habitat suitabilities for urban species are considered to be specific for each city.

The Colorado River has significantly diminished its drainage area and annual discharge. Today it flows across several provinces of Argentina (Neuquen, Mendoza, La Pampa, Rio Negro and Buenos Aires) although during the Upper Pleistocene this watershed area was more extended. Its discharge also diminished significantly during documented times although floods occurred episodically during anomalous ENSO years. The delta plain is composed of several lobes of different ages. Four distributary arms were operating during the Mid-Holocene highstand. At the northernmost distributary arm, Tagelus plebeius remains of 350 ± 50 14C years BP were collected living in position on the supratidal flat. Close to this modern channel several foredune ridges were recognised. A blocking of the river occurred in 1906, and originated a conic lobe located 36 km from the present shoreline. Due to a flood caused by a sudden scabland of the Cari Lauquen Lake in 1914, the blockage opened. Another blockage was achieved between 1924 and 1925, but another flood in 1931 originated a new arm: the Colorado Nuevo. The ENSO-triggered flood of 1983 signified the last connection of the Desaguadero-Curaco River system. Man-made alterations are responsible for the increase in salinity along the lower floodplain and increasing the risk of onion crops. These particular processes of desertification with floods should be monitored in relation to climate-change previsions.

The South American Arid Diagonal extends in Argentina from Puna to Patagonia regions. Several dune fields are scattered between the Andes and Pampas ranges, covering plains and plateaus. One of the northernmost dune fields is occupying the tectonic valley known as Bolsón de Fiambalá (27°S; 67°W) White transverse dunes extend from west to east, climbing to the Fiambalá Range. Some outcrops from the surrounding area allow to understand the evolution of this dune field. At the Chaschuil valley, a profile composed of 4 m of stratified sands and gravels were sampled at Las Lozas site. Epiphytes and benthic diatom assemblages suggest a shallow lake located at 3700 m altitude. Many of these brackish/freshwater aerophilous taxa tolerate desiccation periods and salt concentration. The assemblages were dominated by Nitzschia frustulum, Nitzschia linearis, Achnanthes thermalis var. rumrichorum, Epithemia adnata, Pinnularia viridis y Nitzschia capitellata. Limestones from this outcrop were dated on 32,000 ± 520 and 29,380 ± 410 1 4C years BP (Garleff et al., 1993), suggesting the Marine Isotopic Stage 3. The Holocene Interglacial is recorded either at the Chaschuil and Abaucán rivers valleys. Lake deposits at 3000 m altitude gave ages between 6175 ± 70 and 2990 ± 70 14C years BP (Garleff et al., 1993). The sand of this dune field at the northern part of the Bolsón de Fiambalá was supplied by the fanglomerates located to the west, at Medanitos. There is also a significant supply of pumicite, derived from the Cerro Blanco volcanic dome. An aridity increase have been previously recorded from archaeological data and confirmed by the discharge records of the Abaucán River during the 1919–1957 interval. Although these sand dunes with a high content in volcanic glass clearly derived from the Andes, other sand dunes of central Argentina derived from the deactivation of the Desaguadero-Curacó system. Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina

Diatom assemblage composition and distribution from surface sediment samples of the Colorado River, Patagonia were analysed in relation to environmental variables using multivariate techniques. The aim of this study was to determine the ecological preferences of the taxa and provide analogues for paleoenvironmental reconstructions in estuarine and fluvial environments of southern South America. Cluster analysis identified two main diatom assemblages, one grouping sites with a marine influence, and another group influenced by typical riverine conditions. Canonical correspondence analysis indicated that major ion concentrations contribute significantly to explain the variation in the composition of diatom assemblages. A total of 208 taxa belonging to 56 genera were recorded. In estuarine sites, the assemblages were characterized by marine-brackish tychoplankton, such as Cymatosira belgica, Rhaphoneis amphiceros, Delphineis minutissima, Paralia sulcata and Paralia sulcata var. coronota. Diatom communities in riverine sites were dominated by freshwater taxa such as Staurosira venter, Pseudostaurosira brevistriata, Punctastriata glubokoensis and Punctastriata lancettula. Two Punctastriata species that were difficult to distinguish with LM were examined in detail with SEM, and the value of detailed LM and SEM analysis for distinguishing Punctastriata spp. and other small fragilarioids is discussed. Based on their autoecological affinities, it is likely that the dominance of small fragilarioids is related to the increase in ionic concentration in the basin, as a consequence of both precipitation decrease, and an increase in urban, industrial and agricultural activities. The construction of a flood-control structure in the northern branch of the delta modified the diatom community so that marine taxa were replaced by brackish-freshwater taxa in response to changes in salinity, substrata and water depth. Fil: Vélez Agudelo, Camilo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Fayó, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

The genus Megatherium includes nearly ten species that are distributed along the Pleistocene of South America. In contrast with the abundant and geographically widespread Pleistocene record, remains of Pliocene Megatherium are restricted to a single and poorly known species from the highlands of Peru. The aim of the present contribution is to describe a skull referable to the genus Megatherium coming from Late Pliocene beds at the San Eduardo del Mar locality, Buenos Aires Province, Argentina. This constitutes the first undoubted record of Megatherium from the Pliocene of Argentina, and one of the oldest records for the genus. This finding blurs previous biogeographical proposals sustaining that the genus originated in the High Andes and later dispersed to the lowlands. On the contrary, present finding, together with the record of coeval Megatherium species in the Pleistocene of the Argentine Pampas, suggests a more complex palaeobiogeographical scenario and indicates that the diversity of lowland Pliocene megatheriines is still underrepresented.

The urban growth of the southern neighborhoods of Mar del Plata City provoked significant changes in the groundwater balance of the loessic sequences. These regional loessic levels with a significant portion of volcanic ash layers were reported subject to fluoride and nitrate concentrations. Residential houses pump from sands located 70 m depth and withdraw the sewages to depths less than 5 m. These effects cause significant local and seasonal (summer) increments of the water table outcropping via springs at certain unconformities of the coastal cliffs. A mathematical model was applied to analyze the water level lowering at the productive levels, while there is a decrease in the quality of the upper levels subject to waste discharges. Much of this groundwater flow is concentrated in unconformities between different types of sediments. Human activities have affected the aquifer dynamics increasing the groundwater pumping rates and the return velocity of the sewages. This should be considered in the management strategies of coastal hydric resources. Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Quiroz Londoño, Orlando Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Cortizo, Luis Camilo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Diatom assemblages recovered from a Colorado River delta core in northern Patagonia, Argentina were analyzed in order to assess past environmental conditions. A total of 35 samples were selected from a 172-cm core extracted 37 km from the mouth (39°36′19.6″S; 62°29′26.1″W). One-hundred and thirty-eight taxa were recognized and grouped according to life forms. Two diatom zones were identified by cluster analysis. At the base of the sequence, the Diatom Zone I (DZI; 4132 ± 35 − 2919 ± 27 14C yr BP), consisted of clays, and was characterized by assemblages dominated by aerophilous and benthic taxa and chrysophyte stomatocysts, which led to inferences of a sedimentary environment corresponding to a pond experiencing dry periods. The upper section (DZII) was dominated by fine sands and silts encompassing the last ~ 150 yr with abundant planktonic and tychoplanktonic diatoms. Benthic diatoms were abruptly replaced by planktonic forms in this zone indicating a shift to deeper waters. These results characterize the meandering dynamics of a deltaic system. During the Mid-Holocene, more arid periods would have favored the deactivation of meanders and the formation of riverine and oxbow wetlands. In Late-Holocene and historical times, more humid conditions and the hydrological system across the floodplain reactivated the paleochannel. Today, the dominant diatom species are brackish/freshwater fragilaroids. A non-multidimensional scaling analysis showed a lack of analogy between fossil and modern samples. The change in diatom floras in recent historical times was attributed to anthropogenic disturbances, a consequence of the regulation of the river flow. This regulation is evidenced by less discharge, morphological modifications in the floodplain and increased salinity in the last decade. Fil: Fayó, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Vélez Agudelo, Camilo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Pan, Jeronimo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

The normalized difference vegetation index (NDVI) is a strong and widely used proxy for bird species richness in urban environments. However, its potential to predict composition and seasonal dynamics of bird communities in urban areas remains unexplored. Our main objective was to analyze the power of NDVI to predict the seasonal dynamics of bird communities along urbanization gradients. Birds were surveyed in the breeding and non-breeding seasons. Bird species richness was estimated using COMDYN, and bird community composition was summarized in two axes using Non-metric Multidimensional Scaling (NMDS). For each of the breeding and non-breeding seasons, bird richness and the NMDS axis scores were related to both the mean NDVI of the season and the annual seasonal variation of NDVI (mean NDVI of the breeding season - mean NDVI of the non-breeding seasons). Results showed that NDVI decreased towards the most urbanized areas, with the highest seasonal variation occurring in agricultural areas. Single-family houses surrounded by yards held a high NDVI in both seasons and the lowest seasonal variation. Bird richness increased at intermediate levels of NDVI and was negatively related to the seasonal variations of the NDVI. Seasonal variation in bird community composition increased with annual mean and seasonal variation of the NDVI predicting higher seasonal stability of assemblage composition in urban than in non-urban areas. The results suggest that urbanization alters ecosystem functioning by reducing seasonal dynamics and the amount of primary productivity, which in turn promotes seasonal homogenization of urban avifauna relative to non-urban areas. Fil: Leveau, Lucas Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Bellocq, Maria Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina

The Chubut River flows from the Andes to the Atlantic Ocean, and is interrupted by a single dam built at the middle valley. The lower valley is dominated by the aggradation of an alluvial plain induced by a complex of spits that enclosed the inlet in the last 5000years. The river has reduced its flow because the blocking of the upper basin by terminal moraines during the Upper Pleistocene. At least the last two marine transgressions have flooded this estuary, and contributed to the aggradation during regressions. The area is of particular interest in regard to irrigation channels practiced since the XIX century. Today, the mean monthly flow is less than 10m3/s although peaks of 95m3/s have been recorded in Gaiman in July 2001. The dynamics of the estuary is dominated by waves (wave-dominated estuary) as tidal effects attenuate in less than 5km. Three vibracores were collected within this floodplain: (a) at Gaiman, an area without any effect of the sea (35km from the coast); (b) at Trelew, at the former avulsion plain of the river (18km from the coast); and (c) at Playa Magagna, a saltmarsh located 0.4km from the beach.(a)At the Gaiman core (1.54m long) fresh-water epiphytic diatoms dominate (Epithemia sorex, Cocconeis placentula, Ulnaria ulna) suggesting the aggradation of an alluvial plain.(b)The Trelew core (2.19m long) was collected from a deltaic plain. It was composed by fine sand with organic matter at the base that evolved into silty layers to the top. Several unconformities and laminae with heavy minerals were detected by their geochemical composition analysed by micro X-ray fluorescence (Itrax XRF core scanner). Fine-sand laminated layers were perfectly detected by their high content in S and Cl. On the other hand, mud layers presented lower content in Mg and Al with increments in Ca and V.(c)The core from the marsh area (1.67m long) was analysed in terms of the diatom evolution in order to detect Holocene sea-level and salinity effects. The sand flats from the bottom of the core were dominated by Nitzchia navicularis (mesohalobous and benthic taxa) and evolved into mixed flats, mudflats and marshes to the top. Sharp contacts have been detected between these facies, with wavy and lenticular bedding characterising the mixed flat deposits. The middle of the sequence is dominated by a coastal marine diatom (Paralia sulcata) while the top was dominated by Pinnularia borealis, an aerophilous and brackish/freshwater taxa. Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Espinosa, Marcela Alcira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Rubio, Belén. Universidad de Vigo; España Fil: Escandell, Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Gerpe, Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Miglioranza, Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Rey, Daniel. Universidad de Vigo; España Fil: Vilas, Federico. Universidad de Vigo; España

Barriers, barrier islands and spits characterise low-lying coasts. However, they can grow along erosive coasts where there is a constant supply of sand, gravel, or both. At the Argentine coast, sandy barriers characterise the template coast of Buenos Aires. The availability of gravel at the Patagonian and Tierra del Fuego coasts induces the formation beach-ridge plains that can derived into coarse-grained spits. The morphology of these spits obeys to the basin depth and the availability of sediment. Recurved spits signify that the beach drift is locally modified by the action of waves or sediment-supply shortages. Some spits are today subject to local erosion (cannibalisation) that compensates these sediment deficits. Barriers and spits are ideal to locate harbours, marinas or touristic (resort) villages. However, the freshwater volumes inside their bodies are limited, even in areas where rain-fed aquifers have plenty of capacity. In this sense, resort villages are limited in their urban sprawl and planners should foresee these resource-based limitations.

Marine Isotopic Stage 3 (MIS 3) was a period of rapid climatic changes and sea level fluctuations. Regarding these fluctuations some doubts were based on the limit of the radiocarbon dating method (about 50,000 years B.P.). However, the modelling of the isotopic oxygen ratios is also indicating sea level fluctuations. In this sense, only at certain depths it is possible to accept these ages at stable coasts, and taking note about the taphonomic conditions within the sequence. Shells located at depths higher than 60 m on stable and wide continental shelves as that of the Northern Patagonia have been analyzed here in that sense.

Espinosa, M.A., Hassan, G.S. & Isla, F.I., September 2012. Diatom-inferred salinity changes in relation to Holocene sea-level fluctuations in estuarine environments of Argentina. Alcheringa 36, 377–391. ISSN 0311-5518. The analysis of diatoms from three sedimentary sequences in the Quequen Grande River basin (Buenos Aires province, Argentina) has allowed the reconstruction of local and regional palaeosalinity changes in relation to Holocene sea level fluctuations. An established diatom-based salinity transfer function is used in combination with autecological methods to reveal a maximum sea level between ca 7000 and 6000 14C years BP. This marine influence was recorded in deposits exposed 2 km and 12 km upstream, but not 32 km from the mouth. The fossil diatom assemblages are characteristic of an estuarine lagoon with maximum inferred salinities of 15‰. When the Holocene transgression began to flood the former valley (ca 7000 14C years BP), brackish lagoons evolved into estuarine settings in the lower val...

ISLA, F. I.; QUEZADA, J. F.; MARTINEZ, C.; FERNANDEZ, A.; and JAQUE, E. 2012. The evolution of the Bio Bio delta and the coastal plains of the Arauco Gulf, Bio Bio region: The Holocene sea-level curve of Chile. Mid-Holocene highstands are characteristic of the Southern Hemisphere. The Chilean coast extends from 17°S to 56°S in a dominant microtidal regime; thus, it is an ideal place to test ages and altitudes of this highstand with minimal errors. However, coseismic events, the dynamic phenomena they triggered (tsunamis), and the behaviour of land in relation to the overriding of the South American Plate over the oceanic Nazca Plate, make it necessary to distinguish these effects from purely eustatic changes. To the south, the glacioisostatic uplift has been approximately measured. At 37°S, the Coronel coastal plain extends several kilometres inland. Its sediment availability has been related to the supplies of the Bio Bio River. From this beach-ridge plain, shell remains gave a radiocarbon age o...

Diatom and sedimentological analyses of two cores from San Blas Bay and the analysis of historical charts provide information about the environmental evolution of this estuarine complex during the last 5000 yr BP. The Holocene sea-level regression is recorded in San Blas Bay by infilling of a tidal channel. Two sediment cores were drilled at Arroyo Jabali (San Blas Bridge) and at the former inlet of Arroyo Walker and Arroyo Jabali (Paso Seco). The diatom record of the San Blas Bridge sequence is dominated by marine and brackish/freshwater plankton and tychoplankton and composed by fine to very fine sand and mud characterizing the infilling of a tidal channel. The Paso Seco sequence is more abundant in sand. Textural and diatom facies are interpreted as the infilling of a tidal channel very similar to the one at San Blas Bridge, that evolved towards the top into a sandflat characterized by the dominance of marine and marine-brackish epipsammon accompanied by marine tychoplankton. Arroyo Walker an...

SALINITY FLUCTUATIONS DURING THE HOLOCENE IN THE MAR CHIQUITA COASTAL LAGOON (BUENOS AIRES PROVINCE, ARGENTINA): A DIATOM-BASED QUANTITATIVE APPROXIMATION. Diatom assemblages recovered from a sediment core obtained from the north of Mar Chiquita coastal lagoon (Buenos Aires Province) were studied, in order to characterize the paleosalinity fluctuations during the Holocene. Data were analyzed quantitatively by means of the application of a paleosalinity transfer function available for estuaries of the southeastern Buenos Aires Province. Two main stages during the evolution of the lagoon were inferred. Between c. 8670 and 2500 yr 14C BP, marine planktonic and tychoplanktonic diatoms, such as Paralia sulcata (Ehr.) Cleve and Cymatosira belgica Grunow, indicate the presence of an environment subject to tidal action, with salinities ranging between 20 and 30‰. Towards c. 2500 years 14C BP the assemblages changed abruptly, being dominated by the tychoplankters Staurosira construens var. venter (Ehr.) ...

The marine terraces located on the atlantic coast of Tierra del Fuego (Argentina) were previously assigned to different sea-level highstands from the Middle Pleistocene to the Holocene. This study is focused on the analysis of the mollusc assemblages recovered from those terraces. When comparing Middle/Late Pleistocene mollusc assemblages with adjacent Holocene/modern ones, ecological changes in the fauna were recognized. The Pleistocene assemblages are less diverse and are dominated by infaunal bivalves, whereas Holocene and modern assemblages are more diverse and are dominated by epifaunal taxa, with a higher presence of gastropods. However, on a biogeographic scale, the fact that Pleistocene taxa (with the probable exception of Retrotapes sp.) are living today in the region is attributed to the location of the study sites, at the centre of the Magellan biogeographic unit, with species far away from the edges of their ranges of distribution. Regional faunistic changes and the local disappearance of Retrotapes in post-glacial benthic communities in the area are therefore interpreted on the basis of regional and local causes, most probably associated to substrate changes, and not on a global trend related to large-scale patterns.

The most complete record of a Hoplophorini (Xenarthra: Glyptodontidae) for the Chapadmalalan-Marplatan Stages (Late Pliocene-Early Pleistocene). The late Neogene (Chapadmalalan-Marplatan Stages; ca. 3.9-1.8 Ma) Glyptodontidae from southern South America are poorly known since most of the record are limited to remains of the dorsal and/or caudal armour. In this sense, the exceptions are represented by Paraglyptodon chapadmalensis (Ameghino in Rovereto), a fossil guide of the Upper Chapadmalalan Stage, and the Plohophorini Plohophorus figuratus Ameghino. On the other hand, the “Hoplophorinae” Hoplophorini are glyptodonts that have its first records during the Huayquerian (late Miocene) and “Araucanian” Stages (late Miocene-early Pliocene), but they are almost absents during the Chapadmalalan-Marplatan Stages (Pliocene-early Pleistocene). Later, the Hoplophorini (Neosclerocalyptus Paula Couto) are, together with Glyptodon Owen, the most common South American Pleistocene Glyptodontidae. In this contribution we report the first record of a Chapadmalalan Hoplophorini, assigned to the genus Eosclerocalyptus C. Ameghino (Eosclerocalyptus cf. E. lineatus), coming from the Mar del Plata locality, Buenos Aires province (Argentina). This new material, represented by a complete dorsal carapace, was exhumed from the upper section of the Chapadmalalan Formation. From a morphological perspective, this dorsal carapace shows an intermediate size between E. tapinocephalus Cabrera, E. proximus (Moreno & Mercerat) and Neosclerocalyptus Paula Couto. Together with cf. Paraglyptodon chapadmalensis and Plohophorus figuratus Ameghino those records represents the most entire Pliocene Glyptodontidae known and, in addition, it partially complete the stratigraphical distribution of the Glyptodontidae Hoplophorini.

The Negro River extends from the Andes to the Atlantic Ocean supplying water to several cities and to the most important fruit-bearing productive region of Patagonia. Floodplains from the Upper Valley are artificially irrigated with water delivered from the main channel. Pesticides are increasingly used without strict government control. Dams constructed at the tributary rivers retain sediment and therefore the clean water delivered becomes free of sediment and therefore is able to erode certain levees during high-discharge events. Bedload–transport fraction (sand dunes) increases at the Upper Valley and is fixed at the levees of the Lower Valley by riparian vegetation. This riparian vegetation is dominated by Salix humboldtiana and Schoenoplectus californicus while Spartina sp is abundant at the estuarine marsh area. Organochlorine compounds (OCCs) were measured by GC-ECD including dichloro-diphenyl-trichloroethane (DDT), dichlorophenyl-dichloroethylene (DDE) and dichloro-dyphenyl-dichloroethane (DDD) en...

Pesticide distribution in the soil profile depends on soil and pesticide properties as well as on the composition of irrigation water. Water containing surfactants, acids or solvents, may alter pesticide desorption from soil. The distribution of organochlorine pesticides (OCPs) in two Argentinean agricultural areas, Pampa and Patagonia, was evaluated. Furthermore, pesticide desorption from aged and freshly spiked soils was performed by the batch technique, using solutions of sodium oxalate and citrate, dissolved organic carbon (DOC), wastewater and surfactants. Patagonian soil showed the highest OCP levels (46.5-38.1 μg g(-1) OC) from 0 to 30 cm depth and the predominance of p,p'-DDE residues reflected an extensive and past use of DDT. Pampean soil with lower levels (0.039-0.07 μg g(-1) OC) was mainly polluted by the currently used insecticide endosulfan. Sodium citrate and oxalate, at levels usually exuded by plant roots, effectively enhanced desorption of p,p'-DDT, p,p'-DDE and α-cypermethrin, while no effects were observed for α-endosulfan and endosulfan sulfate. The non-ionic surfactant Tween 80 behaved similarly to the acids, whereas the anionic sodium dodecyl sulfate enhanced desorption of all pesticides. Increased desorption of the hydrophobic pesticides also occurred when DOC from humic acids but not from sewage sludge or wastewater were used. Soil profile distribution of pesticides was in accordance with results from desorption studies. Data suggest pesticide leaching in Pampean and Patagonian soils, with risk of endosulfan to reach groundwater and that some organic components of wastewaters may enhance the solubilisation and leaching of recalcitrant compounds such as p,p'-DDT and p,p'-DDE.

Integrated coastal zone management techniques usually search the preferences of the owners of the coastal properties but without considering the beach users. Multipurpose artificial reefs are submerged structures built in order to diminish wave action, to modify breaker conditions, to protect the coast, and to increase marine biodiversity. Alternatives construction types are considered in relation to the surfing quality of the waves of Mar del Plata. Although detached emerged breakwaters and low-crested submerged structures have been successfully applied to protect beaches from breaking waves, the artificial surfing reefs can improve breaker conditions for recreational purposes. Both structures may increase sand accumulation at the beach if it is naturally available; if not the beaches should be artificially nourished. Based on knowledge of the littoral transport and the bottom composition of the Ensenada Mogotes, artificial submerged reefs, combined with nourishment efforts, are proposed to recover the beach called Los Acantilados. The surfing conditions can improve as a surplus to the stability of the rocky-sandy nearshore ecosystem. As técnicas de gestão integrada da zona costeira são normalmente direccionadas para a protecção dos interesses dos donos das propriedades costeiras e menosprezam, ou não consideram, os interesses dos utentes das praias. Os recifes artificiais multi-funcionais são estruturas submersas construídas para mitigar ou reduzir a acção das ondas, modificar/melhorar as condições de rebentação, proteger a zona costeira (em particular, campos dunares e praias) e aumentar a biodiversidade marinha. São abordadas construções alternativas relativamente à qualidade das ondas para a prática de surf em Mar del Plata. Embora construções clássicas como quebra-mares destacados e estruturas submersas tenham revelado sucesso na protecção da praia, os recifes artificiais multi-funcionais permitem melhorar as ondas para a prática de surf e outros fins recreativos. Ambos os tipos de estruturas promovem alguma acumulação de areia na praia, se esta estiver naturalmente disponível; não existindo, a praia deverá ser alimentada artificialmente. Com base no conhecimento do transporte litoral e na composição dos fundos da Mogotes Ensenada, é proposta uma solução de recifes artificiais submersos, eventualmente combinada com alimentação artificial, para recuperar a praia de Los Acantilados. As condições de surf deverão melhorar e espera-se uma contribuição positiva para a estabilidade do ecossistema arenoso existente. Fil: Isla, Federico Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Exhumed organic megastructures are analyzed in this paper. Large paleocaves (0.7–2.1 m width and 0.7–1.5 m height) are related to the digging of Xenarthra (Mammalia) that lived in the Pampas during the Pleistocene. Some of these burrows are completely filled by sediment, and others are found partially empty. They occur within the city of Mar del Plata and its surroundings, mostly restricted to the Miramar Formation. Three types of galleries have been identified. The larger caves (type I) are related to the digging activity of mylodontids (e.g. Glossotherium). Type II caves are related to smaller mylodontids (Scelidotherim leptocephalus). Other caves of similar size are attributed to the dasypodid Pampatherium (type III). The number of digits recognized in scratch marks on the cave walls helped to distinguish between mylodontid and dasypodid activities. The abundance of these caves has been interpreted in relation to water availability in the surroundings of the Tandilia Range, flooding potential, and shelter to avoid predation by carnivores. The paleobiologic and paleoecological significance of the structures assigned to ants or termites, and cave reoccupation by specimens of Arctotherium latidens (Ursidae, Tremarctinae), are also discussed.

article i nfo The relationship between benthic diatom assemblages and environmental variables was analyzed in 40 sites at three estuaries from the northeastern coast of Argentina by using multivariate analyses. Surface sediment samples were collected along the estuarine gradient and analyzed for diatoms, organic matter, water content and grain size. Water salinity, pH, turbidity and temperature were measured seasonally at every sampling site. Canonical Correspondence Analysis (CCA) was applied in order to recognize which environmental variables correlated most closely with the distributions of diatom taxa. Salinity and sediment properties were identified as the most important variables influencing diatom distribution in the studied estuaries. A two-component Weighted-Averaging Partial Least Squares (WA-PLS) calibration model was developed to infer salinity based on diatom assemblages. The reliability of the model was evaluated by the error of prediction (RMSEPjack-knifed=4.42‰) and the correlation (r 2 jack-knifed=0.75) between observed and diatom- inferred values. The transfer function was applied to fossil diatom assemblages recovered from a Holocene sequence from the Argentinean coast. The application of the model to the fossil record allowed quantitative inferences of salinity changes in southern South America, improving the quality of the inferences performed

Sea-level behavior can be analyzed from tidal records and as the response to oceanic forcings. However, tidal gauges are not uniformly distributed and some are located within estuaries. Eastern South America is particularly subject to ENSO-triggered floods, critical in the last years, and particularly causing severe impacts in some estuaries. Large estuaries, as the Rio de la Plata, and a small estuary as the Quequen Grande river, suffered these interannual effects. Tidal stations located within these estuaries are not exclusively recording the oceanic sea-level behavior; they are recording the effects of large volumes of water that seldom transfer from Western to Eastern South America. Some forecasts of sea-level rise based on annual MSL data are questioned in the sense that they can be biased by these interannual effects.

The main objective of this contribution is to evaluate the environmental fidelity of dead diatom assemblages along two microtidal estuarine systems from southeastern Buenos Aires Province (Argentina). Living communities (inferred from counting protoplasm-containing cells) were compared to dead diatom assemblages through several fidelity metrics. Gradient analysis (by canonical correspondence analysis) was applied in order to assess the quantitative relationship between diatom assemblages and the environmental gradient. The presence of allochthonous components in diatom assemblages was assessed by analyzing the distribution of the main ecological groups. Results indicated a good agreement between living communities and total assemblages in surface sediments, as well as between total surface and subsurface assemblages from both estuaries. A high percentage of the variance in diatom assemblage composition was explained by the environmental gradient, particularly by sediment composition and salinity, indicating that taphonomic alterations play a minor role in structuring these assemblages. The good preservation of diatom thanatocoenoses in estuarine sediments makes them accurate indicators of the environmental conditions at the point of deposition, providing useful information for paleosalinity reconstructions in coastal settings.

In the context of a main project that aims to recover modern data on diatom distribution applicable to paleosalinity reconstructions in coastal areas of Southern South America, the composition and distribution of dead diatom assemblages in the littoral zone of the Quequen Salado estuary (Argentina) were studied. Diatom zones were defined along the estuarine gradient by cluster analysis and related to the salinity range and sediment composition by Canonical Correspondence Analysis. Four diatom zones were identified. A mixture of marine, brackish and freshwater diatoms, probably allochthonous, characterized the inlet (zone I). Marine/brackish taxa, represented mainly by Paralia sulcata dominated zone II, characterized by polyhaline conditions and sandy sediments. Zone III was characterized by mesohaline conditions, muddy sediments and the dominance of the estuarine diatom Amphora helenensis. Brackish/freshwater and freshwater diatoms dominated the headwaters (zone IV), where salinity was always below 5‰. The comparison of Quequen Salado diatom assemblages with previous results from the Quequen Grande estuary showed a similar taxonomic composition between both estuaries. However, differences in the salinity ranges of the estuaries (related to differences in the degree of human impact and tidal range) lead to a displacement in their spatial distribution along the longitudinal estuarine axis. This paper contributes to the knowledge of the ecological requirements of South American estuarine diatoms and provides useful data for paleosalinity reconstructions in the region.