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  1. Evolution of Parinacota volcano, Central Andes, Northern Chile

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    Jorge E. Clavero R.

    2004-12-01

    Full Text Available Parinacota is an active composite stratovolcano located in the Central Andes of Northern Chile (18°S. During its earlier stage (Parinacota 1 unit, Late Pleistocene, 300-70? ka rhyolitic to andesitic magmas were erupted, forming a voluminous lava-dome complex with its associated pyroclastic fans (mainly block-and-ash flow deposits, essentially deposited towards the Upper Lauca basin (West. It later evolved to a steep-sided composite stratocone (Parinacota 2 unit, Late Pleistocene-Holocene, 70?-8 ka, mainly formed by andesitic lava flows and scoria tephra fallout deposits.Around 8 ka ago the ancestral Parinacota volcano, built during Parinacota 1 and 2, partially collapsed towards the west, in a single and catastrophic event generating the outstanding Parinacota Debris Avalanche deposit.Soon after the collapse a new stratocone started to build with the emission of andesitic lava flows and pyroclastic flows, and their associated fallout deposits (Parinacota 3 unit, Holocene, La evolución del volcán Parinacota, Andes Centrales, norte de Chile. El volcán Parinacota es un estratovolcán activo ubicado en los Andes Centrales del norte de Chile (18°S. Durante su primera etapa de evolución (Unidad Parinacota 1, Pleistoceno Superior, 300-70? ka emitió magmas de composición riolítica a andesítica, formando un voluminoso complejo de lavas-domo con abanicos piroclásticos asociados (esencialmente depósitos de bloques y ceniza, distribuidos principalmente hacia la parte superior de la cuenca del río Lauca (oeste. Posteriormente, evolucionó a un estratocono compuesto, de fuertes pendientes (Unidad Parinacota 2, Pleistoceno-Holoceno, 70?-8 ka, formado principalmente por lavas y depósitos de caída andesíticos. Aproximadamente hace 8 ka el volcán Parinacota ancestral, construido durante las unidades Parinacota 1 y 2, colapsó parcialmente hacia el oeste, en un evento único y catastrófico generando el Depósito de Avalancha de Parinacota. Poco

  2. Revisiting mountain-building in the Andes of Central Chile: constraints from structural geology and thermochronology.

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    Riesner, M.; Lacassin, R.; Simoes, M.; Armijo, R.; Carrizo, D.

    2015-12-01

    The Andes, one of the most significant reliefs on Earth, is the case example of a subduction-type mountain belt. In central Chile and western Argentina, the particular east-vergent structure of the Aconcagua fold-and-thrust belt (AFTB) is found atop a huge basement high with elevations > 4000 m, the Frontal Cordillera. Classical conceptual models consider the Andes as an east-vergent orogen, opposite to the Nazca subduction, and describe the exhumation of the Frontal Cordillera as an eastward in-sequence event that occurred late in the andean deformation (by ~10My). An alternative model recently challenged this view by proposing that the Andes have mainly a primary westward vergence. Within this scheme, the exhumation of the Frontal Cordillera would have begun earlier, by ~25My, synchronous with formation of the AFTB on the western side of the basement high. Here we test these two models by revisiting structural cross-sections of the Andes at the latitude of Santiago de Chile and of the Aconcagua (~33°S). We provide thermochronological constraints on the timing of exhumation of the Frontal Cordillera by (U-Th)/He dating on apatites retrieved from paleozoic granitoids along a 2,3km high nearly vertical section in the core of the basement high. Preliminary results suggest that the Frontal Cordillera exhumation was not a late event and likely began around 25 Ma. Therefore it appears to be synchronous with deformation within the AFTB and the westernmost fold-and-thrust belt at this latitude. We discuss these results and their implications while building a crustal-scale cross section of the range at the latitude of Santiago de Chile.

  3. Classification of debris-covered glaciers and rock glaciers in the Andes of central Chile

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    Janke, Jason R.; Bellisario, Antonio C.; Ferrando, Francisco A.

    2015-07-01

    In the Dry Andes of Chile (17 to 35° S), debris-covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover, thickness of surface debris, and ice content. Internal ice is preserved by an insulating cover of thick debris, which acts as a storage reservoir to release water during the summer and early fall. These landforms are more numerous than glaciers in the central Andes; however, the existing legislation only recognizes uncovered or semicovered glaciers as a water resource. Glaciers, debris-covered glaciers, and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains. In addition, agricultural expansion and population growth in this region have placed additional demands on water resources. In a warmer climate, as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season, rock glaciers and debris-covered glaciers contribute a larger component of base flow to rivers and streams. As a result, identifying and locating these features to implement sustainable regional planning for water resources is important. The objective of this study is to develop a classification system to identify debris-covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs. The classification system is linked to field observations and measurements of ice content. Debris-covered glaciers have three subclasses: surface coverage of semi (class 1) and fully covered (class 2) glaciers differentiates the first two forms, whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris. Based on field observations, the amount of ice decreases from more than 85%, to 65-85%, to 45-65% for semi, fully, and buried debris-covered glaciers, respectively. Rock glaciers are characterized by three stages. Class 4 rock glaciers have pronounced

  4. Reconstruction of cryospheric changes in the Maipo and Juncal river basins, central Andes of Chile: an integrative geomorphological approach

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    Nussbaumer, Samuel U.; García, Juan L.; Gómez, Gabriel; Vega, Rodrigo M.; Gärtner-Roer, Isabelle; Salzmann, Nadine

    2016-04-01

    Water in the central Andes (32-38° S), a semi-arid mountainous area with elevations over 6000 m asl., is of great importance and a critical resource especially in the dry summer months. Ice bodies, such as glaciers and rock glaciers (permafrost) in the high mountains, provide a substantial part of the fresh-water resources but also for intensive economical use for the lowlands including Santiago metropolitan region, Chile. However the evolution of these ice bodies since the last deglaciation (i.e., Holocene, last ˜12,000 years), and in particular during historical times, and their feedback with climate is fairly unknown. In view of projected climate change, this is striking because it is also unknown whether these natural resources could be used as sustainable fresh-water source in the future. Within the presented project, we develop and apply an integrative geomorphologic approach to study glaciers and their long-term evolution in the central Andes of Chile. Apart from glaciers (with variable debris-coverage), rock glaciers have evolved over time as striking geomorphological landforms in this area. We combine geomorphologic mapping using remote-sensing and in-situ data with an innovative surface exposure dating technique to determine the ages of distinct moraine ridges at three study sites in watersheds of the Santiago region: Juncal Norte, Loma Larga and Nieves Negras glaciers. First results of the project are presented, including a detailed geomorphological mapping and first analysis of the landform dynamics. At all three sites, we distinguished at least three moraine systems of a Holocene putative age. These prominent moraine belts show that glaciers were at least 5 km longer than at present. Deglaciation from these ice marginal positions was gradual and complex in response to the detrital cover on the glaciers. Differences in ice thickness of the main glaciers in the respective valleys amount to about 100 m. Due to the partial, extensive debris coverage, the

  5. Altitudinal vegetation belts in the high-Andes of central Chile (33°S Pisos altitudinales de vegetación en los Andes de Chile central (33°S

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    Lohengrin A. Cavieres

    2000-06-01

    Full Text Available The limits of alpine vegetation belts have been established mainly based on physiognomic criteria. However, a more objective approach for fixing limits of vegetation belts are methods based on species composition and relative abundance of each species. While these methods are more time consuming, they are more detailed and permit the detection of physical factors affecting the limits of vegetation belts. In this paper we: 1 describe the altitudinal changes of vegetation above timberline, 2 compare vegetation belts defined with physiognomy and two floristic methods (a qualitative one based on altitudinal changes in species composition, and a quantitative one based on changes in dominant species; and 3 detect some environmental factors responsible for the altitudinal distribution of alpine vegetation between 2100 and 3700 masl in the Andes of Santiago, central Chile (33°S. There was a complete agreement between the different methods in delimiting the subalpine belt. However, in the lower alpine belt (the cushion's belt floristic methods subdivided it in 2-3 sub-belts. In the floristic methods, elevations 3500-3700 that formed the higher alpine belt segregated in separate ways because they have no species in common. Physiognomic descriptions lose relevant information about species distribution, especially at higher elevations. Mean annual temperature and nitrogen content of soil are the main environmental factors affecting the altitudinal limits of vegetation belts in the central Chilean AndesLa delimitación de los pisos altitudinales de vegetación andina se ha basado principalmente en criterios fisionómicos. Sin embargo, un criterio más objetivo para la delimitación es usar métodos basados en la composición y abundancia relativa de las especies presentes. Mientras estos métodos requieren de un mayor esfuerzo de muestreo, son más detallados y permiten detectar factores físicos involucrados en la delimitación altitudinal de la vegetaci

  6. A study of the energy balance and melt regime on Juncal Norte Glacier, semi-arid Andes of central Chile, using melt models of different complexity

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    Pellicciotti, Francesca; Helbing, Jakob; Rivera, Andrés; Favier, Vincent; Corripio, Javier; Araos, José; Sicart, Jean-Emmanuel; Carenzo, Marco

    2008-01-01

    We use meteorological data from two automatic weather stations (AWS) on Juncal Norte Glacier, central Chile, to investigate the glacier-climate interaction and to test ablation models of different complexity. The semi-arid Central Andes are characterized by dry summers, with precipitation close to zero, low relative humidity and intense solar radiation. We show that katabatic forcing is dominant both on the glacier tongue and in the fore field, and that low humidity and absence of clouds caus...

  7. Pluri-decadal (1955–2014) evolution of glacier–rock glacier transitional landforms in the central Andes of Chile (30–33° S)

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    Monnier, S.; C. Kinnard

    2016-01-01

    This study deals with relationships between debris-covered glaciers and rock glaciers in the central Andes of Chile. Three glacier–rock glacier transitional landforms are investigated over the last decades in order to highlight and question the significance of their landscape evolution and dynamics. We use series of historical air photos and Geoeye satellite images together with common remote sensing operations including imagery orthorectification, digital elevation model generation, an...

  8. Photosynthetic performance of Colobanthus quitensis (Kunth Bartl. (Caryophyllaceae in a high-elevation site of the Andes of central Chile Desempeño fotosintético de Colobanthus quitensis (Kunth Bartl. (Caryophyllaceae en los Andes de Chile central

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    M. ANGÉLICA CASANOVA-KATNY

    2006-03-01

    Full Text Available Photosynthesis of Colobanthus quitensis and mesoclimatic conditions of air temperature and light intensity during the growing season were investigated at 2,650 m in the central Chilean Andes. On three typical days of the growing period (January, March and May, CO2 exchange and chlorophyll fluorescence were measured. In addition, a series of fluorescence response curves with increasing light intensity at different temperatures were performed to estimate the propensity of Andean C. quitensis populations to be photoinhibited. Net Photosynthesis (Pn was low (ca. 2.0 mmol CO2 m-2s-1 during the morning and noon in days with high photosynthetic active radiation (PAR, above 1,800 mmol photons m-2s-1. Pn increased in the afternoon (3.5-4.8 mmol CO2 m-2s-1 when PAR decreased to ca. 1,400 mmol photons m-2s-1 and leaf temperature were ca. 20 °C. Fv/Fm in the diurnal periods was between 0.7-0.75 without evidence of photoinhibition. Leaves at 15 and 22 °C exhibited a slow decrease of F PSII with the increase in actinic light intensity, although the fraction of reaction centers open (expressed by qP remained higher at 22 °C. NPQ was saturated at light intensities close to 500 mmol photons m-2s-1 in leaves at 22 °C and at higher intensities at 15 °C, suggesting that NPQ could be a mechanism of energy dissipation at high light intensity and high leaf temperature in the field. Our results indicated that C. quitensis is not photodamaged during the diurnal cycle and that the low Pn registered during some diurnal periods are likely to be related with photorespiration, which has been suggested as an efficient protective mechanism for photoinhibition in alpine plants. Our results are also compared with the photosynthetic performance of C. quitensis populations from the maritime AntarcticSe estudió la fotosíntesis de Colobanthus quitensis y las condiciones mesoclimáticas de temperatura del aire e intensidad lumínica a 2.650 m en los Andes de Chile central. Se

  9. Parasite loads and altitudinal distribution of Liolaemus lizards in the central Chilean Andes Cargas parasitarias y distribución de lagartijas Liolaemus en los Andes de Chile central

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    JOHN H. CAROTHERS

    2001-09-01

    Full Text Available This study compared the distributions of ten species of Liolaemus lizards in the central Chilean Andes to the distributions of four types of parasites: malaria-causing Plasmodium, gut nematodes, ticks, and mites. We wanted to see if parasite numbers might be a factor in determining distributional limits of the lizards. We found that there was no evidence of malarial infestation of the lizards, that ticks were almost absent, that more often than not mite numbers decreased at the distributional limits of the lizards, and that gut nematodes confined to the herbivorous lizards in our sample may well be beneficial rather than detrimental. Rather than parasitism, other biotic interactions (e.g., predation or competition are more likely candidates as factors influencing lizard elevational distributions, as are abiotic characteristics such as microhabitat availabilities and thermal factorsEste estudio compara las distribuciones de diez especies de lagartijas Liolaemus en los Andes de Chile central, con las distribuciones de cuatro tipos de parásitos: Plasmodium causantes de malaria, nemátodos intestinales, garrapatas y ácaros. Quisimos verificar si los números de parásitos pudieran ser un factor determinante de los límites de distribución de las lagartijas. Encontramos que no había evidencia de infestación por malaria en las lagartijas; que las garrapatas estaban casi ausentes; que los números de ácaros más a menudo decrecían que aumentaban en los límites distribucionales de las lagartijas; y que los nemátodos intestinales confinados a las lagartijas herbívoras en nuestra muestra bien podían ser beneficiosos antes que dañinos. Más bien que parasitismo, otras interacciones bióticas (e.g., depredación o competencia son candidatos más probables como factores que influyen las distribuciones altitudinales de las lagartijas, además de características abióticas tales como la disponibilidad de microhábitats y los factores térmicos

  10. Estimating glacier and snowmelt contributions to stream flow in a Central Andes catchment in Chile using natural tracers

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    M. Rodriguez

    2014-07-01

    Full Text Available This paper presents a methodology for hydrograph separation in high elevation watersheds, which aims at identifying individual flow sources such as snow- and ice melt, rainfall and soil water. Daily summer and bi-daily spring water samples from the outlet of the Juncal River were analyzed for all major ions as well as stable water isotopes, δ18O and δ2H. Additionally, various water sources such as rain, springs, snow- and glacial melt were sampled throughout the catchment. A principal component analysis (PCA was performed in order to reduce the dimensionality of the problem. Potential sources were identified in a two-component U space that explains 77% of variability. Hydrograph separation (HS was performed through three models: (i Isotopic model, (ii Mixing–PCA model, and (iii Informative–Bayesian model, with very similar results in each case. At the Juncal River outlet, summer flows were composed by at least 50% of water originating in highly glaciarized headwaters in 2011–2012 (a dry period in the Central Andes. Autumn and winter flows were highly influenced by soil water and affect total annual discharge. Before the high flow season, snow melt accounted for approximately 25% of streamflow, However during summer, when streamflow was highest, snowmelt contribution was minimal, while glacier melt and soil water were the most important sources.

  11. Tectonic styles and crustal shortening of the Central Andes "Pampean" flat-slab segment in northern Chile (27-29°S)

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    Martínez, Fernando; Arriagada, César; Peña, Matías; Deckart, Katja; Charrier, Reynaldo

    2016-01-01

    The Andean orogenic belt, located in the Central Andes "Pampean flat-slab" segment in northern Chile (27-29°S), is composed of two major tectonic regions: the Coastal Cordillera and the Frontal Cordillera. To understand their internal tectonic styles, history of growth and the shortening absorbed by the upper crustal structure of this segment, we combined regional geological mapping data, new ages obtained from radiometric U-Pb dating, and a semibalanced and restored cross-section 225.18 km in length. The results as shown in the previous Mesozoic extensional fault systems, established in northern Chile by the Gondwana breakup, have played a fundamental role in the orogenic buildup. The central structure is characterized by an asymmetric basin (Upper Cretaceous-Paleocene) confined by a doubly vergent fault system composed of inverted faults related to the edges of the Mesozoic Chañarcillo and Lautaro Basins. The U-Pb geochronological data obtained from synorogenic volcano-sedimentary deposits and the angular unconformities recorded between the Cenozoic geological units have revealed that the compressive deformation in this segment started at around ~ 80 Ma by tectonic inversion in the eastern Coastal Cordillera and western Frontal Cordillera, however, the presence of Paleocene and Miocene synorogenic successions at the footwall of the basement reverse faults of the Frontal Cordillera suggests a migration of Andean deformation from the west to the east during the Paleocene-Miocene by propagation of ramps involving inherited basement highs. The pre-compression restoration makes it possible to estimate 40.94 km of minimum shortening, concentrated by inversion anticlines and fault-controlled basement highs across the Frontal Cordillera.

  12. Arc-oblique fault systems: their role in the Cenozoic structural evolution and metallogenesis of the Andes of central Chile

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    Piquer, Jose; Berry, Ron F.; Scott, Robert J.; Cooke, David R.

    2016-08-01

    The evolution of the Main Cordillera of Central Chile is characterized by the formation and subsequent inversion of an intra-arc volcano-tectonic basin. The world's largest porphyry Cu-Mo deposits were emplaced during basin inversion. Statistically, the area is dominated by NE- and NW-striking faults, oblique to the N-striking inverted basin-margin faults and to the axis of Cenozoic magmatism. This structural pattern is interpreted to reflect the architecture of the pre-Andean basement. Stratigraphic correlations, syn-extensional deposits and kinematic criteria on fault surfaces show several arc-oblique structures were active as normal faults at different stages of basin evolution. The geometry of syn-tectonic hydrothermal mineral fibers, in turn, demonstrates that most of these structures were reactivated as strike-slip ± reverse faults during the middle Miocene - early Pliocene. Fault reactivation age is constrained by 40Ar/39Ar dating of hydrothermal minerals deposited during fault slip. The abundance and distribution of these minerals indicates fault-controlled hydrothermal fluid flow was widespread during basin inversion. Fault reactivation occurred under a transpressive regime with E- to ENE-directed shortening, and was concentrated around major plutons and hydrothermal centers. At the margins of the former intra-arc basin, deformation was largely accommodated by reverse faulting, whereas in its central part strike-slip faulting was predominant.

  13. Positive interactions between alpine plant species and the nurse cushion plant Laretia acaulis do not increase with elevation in the Andes of central Chile.

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    Cavieres, Lohengrin A; Badano, Ernesto I; Sierra-Almeida, Angela; Gómez-González, Susana; Molina-Montenegro, Marco A

    2006-01-01

    In alpine habitats, positive interactions among plants tend to increase with elevation as a result of altitudinal increase in environmental harshness. However, in mountains located in arid zones, lower elevations are also stressful because of scarce availability of water, suggesting that positive interactions may not necessarily increase with elevation. Here we analysed the spatial association of plant species with the nurse cushion plant Laretia acaulis at two contrasting elevations, and monitored the survival of seedlings of two species experimentally planted within and outside cushions in the semiarid Andes of central Chile. Positive spatial associations with cushions were more frequent at lower elevations. Species growing at the two elevations changed the nature of their association with cushions from neutral or negative at higher elevations to positive at lower elevations. Survival of seedlings was higher within cushions, particularly at lower elevations. The increased facilitation by cushions at lower elevations seems to be related to provision of moisture. This result suggests that cushion plants play a critical role in structuring alpine plant communities at lower elevations, and that climatic changes in rainfall could be very relevant for persistence of plant communities. PMID:16390419

  14. Depositación atmosférica de nitrógeno en un transecto valle longitudinal-cordillera de Los Andes, centro-sur de Chile Atmospheric deposition of nitrogen in a transect from the Central Valley to Cordillera de Los Andes, south-central Chile

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    CARLOS E. OYARZÚN

    2002-03-01

    Full Text Available El aumento de las actividades agrícolas y ganaderas en el centro-sur de Chile puede producir elevadas emisiones de nitrógeno hacia la atmósfera (mayormente NH3. El amoniaco es transportado por corrientes de aire y depositado en el suelo y vegetación. El presente estudio evalúa la depositación atmosférica de compuestos nitrogenados (NO3- y NH4+ en la química de las precipitaciones en un transecto altitudinal de 66 km, desde los alrededores de la ciudad de Osorno (40º 35' S, 72º 57' O, 55 m de altitud hasta la cordillera de Los Andes, Parque Nacional Puyehue (40º 46' S, 72º 11' O, 1.120 m de altitud. En siete sitios, durante el período anual junio-1999 hasta mayo-2000, se registró la precipitación y mensualmente se colectaron muestras de agua para determinar: pH, conductividad y las concentraciones de NO3- y NH4+. La precipitación anual se incrementó desde 1.103 mm en la zona de Osorno hasta 6.799 mm en el sector Antillanca, Parque Nacional Puyehue. Los valores promedio anual del pH registraron escasa variación desde 6,3 en el valle central hasta 5,8 en la cordillera de Los Andes. La conductividad presentó los máximos valores en la proximidad de Osorno (22,9 myS cm-1 para descender a través del transecto en zonas intermedias y alcanzar en la Cordillera de los Andes un valor de 11,3 myS cm-1. Las concentraciones promedio de NO3-Nen la lluvia fluctuaron entre 52,3 myg L-1 en la zona agrícola-ganadera y 6,9 myg L-1 en los bosques del Parque Nacional Puyehue. Las concentraciones de NH4-N variaron entre 699,4 myg L-1 en el sector de Osorno y 37,8 myL-1 en la cordillera de Los Andes. Los valores de N-inorgánico poseen una marcada tendencia estacional en el sector agrícola, con valores máximos en primavera-verano y los mínimos en invierno. Las tasas anuales de depositación atmosférica de NO3-N fluctuaron entre 0,53 y 0,57 kg ha-1 año-1 y las de NH4-N fueron entre 6,4 y 2,8 kg ha-1 año-1 para los sitios agrícola-ganaderos de

  15. Parasite loads and altitudinal distribution of Liolaemus lizards in the central Chilean Andes Cargas parasitarias y distribución de lagartijas Liolaemus en los Andes de Chile central

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    JOHN H. CAROTHERS; Jaksic, Fabián M

    2001-01-01

    This study compared the distributions of ten species of Liolaemus lizards in the central Chilean Andes to the distributions of four types of parasites: malaria-causing Plasmodium, gut nematodes, ticks, and mites. We wanted to see if parasite numbers might be a factor in determining distributional limits of the lizards. We found that there was no evidence of malarial infestation of the lizards, that ticks were almost absent, that more often than not mite numbers decreased at the distributional...

  16. Reconstructing glacier mass balances in the Central Andes of Chile and Argentina using local and regional hydro-climatic data

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    M. H. Masiokas

    2015-09-01

    Full Text Available Despite the great number and variety of glaciers in southern South America, in situ glacier mass balance records are extremely scarce and glacier–climate relationships are still poorly understood in this region. Here we use the longest (> 35 years and most complete in situ mass balance record, available for glaciar Echaurren Norte in the Andes at ~34° S, to develop a minimal glacier surface mass balance model that relies on nearby monthly precipitation and air temperature data as forcing. This basic model is able to explain 78 % of the variance in the annual glacier mass balance record over the 1978–2013 calibration period. An attribution assessment indicates that precipitation variability constitutes the most important forcing modulating annual glacier mass balances at this site. A regionally-averaged series of mean annual streamflow records from both sides of the Andes is then used to estimate, through simple linear regression, this glacier's annual mass balance variations since 1909. The reconstruction model captures 68 % of the observed glacier mass balance variability and shows three periods of sustained positive mass balances embedded in an overall negative trend totaling almost −42 m w.eq. over the past 105 years. The three periods of sustained positive mass balances (centered in the 1920s–1930s, in the 1980s and in the first decade of the 21st century coincide with several documented glacier advances in this region. Similar trends observed in other shorter glacier mass balance series suggest the glaciar Echaurren Norte reconstruction is representative of larger-scale conditions and could be useful for more detailed glaciological, hydrological and climatological assessments in this portion of the Andes.

  17. A new species of Phymaturus of the P. mallimaccii Group from the Andes of central Chile (Iguania: Liolaemidae

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    Jaime Troncoso-Palacios

    2014-08-01

    Full Text Available A new species of Phymaturus from the Provincia Mountain in the San Ramón Mountains in the Metropolitan Region of Chile is described. It is a member of the P. palluma Group and the P. mallimaccii subgroup. The new species can be distinguished from other members of the P. mallimaccii subgroup by having a highly fragmented subocular scale (4 or 5, a preocular scale that is smaller than the canthal, males having a olive dorsum with a diffuse pattern of light bands on the paravertebral fields and a light triangle between the shoulders, which has the apex of the triangle oriented toward the snout. The distribution of new species lies south of that of other members of the P. mallimaccii subgroup, from which it is completely isolated. The low abundance of the new species is noteworthy. Information about the natural history of the lizard is provided and some aspects of unnamed populations of Chilean Phymaturus are discussed.

  18. Modelling the hydrological response of debris-free and debris-covered glaciers to present climatic conditions in the semiarid Andes of central Chile

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    Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Vivero, Sebastián; Campos, Cristián; Egli, Pascal

    2016-04-01

    We investigate the main contributors to runoff of a 62 km2 glacierized catchment in the semiarid Andes of central Chile, where both debris-free and debris-covered glaciers are present, combining an extensive set of field measurements, remote sensing products and an advanced glacio-hydrological model (TOPKAPI-ETH). The catchment contains two debris-free glaciers reaching down to 3900 m asl (Bello and Yeso Glaciers) and one debris-covered avalanche-fed glacier reaching to 3200 m asl (Piramide Glacier). A unique dataset of field measurements collected in the ablation seasons 2013-14 and 2014-15 included four automatic weather stations, manual measurements of snow depth and debris cover thickness, discharge measurements at glaciers outlets, photographic monitoring of surface albedo as well as ablation stakes measurements and snow pits. TOPKAPI-ETH combines physically-oriented parameterizations of snow and ice ablation, gravitational distribution of snow, snow albedo evolution, glacier dynamics, runoff routing and the ablation of debris-covered ice.We obtained the first detailed estimation of mass balance and runoff contribution of debris-covered glaciers in this mountainous region. Results show that while the mass balance of Bello and Yeso Glaciers is mostly controlled by air temperature lapse rates, the mass balance of Piramide Glacier is governed by debris thickness and avalanches. In fact, gravitational distribution by avalanching on wet years plays a key role and modulates the mass balance gradient of all glaciers in the catchment and can turn local mass balance from negative to positive. This is especially the case for Piramide Glacier, which shows large amounts of snow accumulation below the steep walls surrounding its upper area. Despite the thermal insulation effect of the debris cover, the contribution to runoff from debris-free and debris-covered glaciers is similar, mainly due to elevation differences. At the catchment scale, snowmelt represents more than 60

  19. Estudio hidrogeoquímico en la cuenca altiplánica de Pampa Lirima, Andes Centrales (Chile)

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    Achurra, Luciano; Custodio Gimena, Emilio; Aguirre, Igor; Arcos, Rodrigo; Clavero, Jorge

    2011-01-01

    La cuenca de Pampa Lirima se ubica en el límite occidental del Altiplano. Las cumbres y zonas elevadas (4200-5800 msnm) de la cuenca se componen de rocas volcánicas del Oligoceno a Plioceno, donde localmente se desarrollan acuíferos colgados y acuitardos en los sectores afectados por alteración hidrotermal. En la zona central más deprimida (4000-4200 msnm) la cuenca está rellena de depósitos aluviales y pluvioglaciales, que forman un acuífero intergranular libre y artesiano en sectores pun...

  20. Floristic changes in alpine plant communities induced by the cushion plant Azorella madreporica (Apiaceae in the Andes of central Chile Cambios florísticos en comunidades de plantas alpinas inducidos por la planta en cojín Azorella madrepórica (Apiaceae en los Andes de Chile central

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    CONSTANZA L QUIROZ

    2009-06-01

    Full Text Available It is well known that the number of plant species associated with nurse plants increases with elevation. However, studies conducted so far have largely ignored the effect of nurse plants on other community attributes, such as the species abundances, diversity and evenness. Moreover, changes in these community attributes along environmental gradients have also been seldom examined. The present study evaluates the effect of the cushion plant Azorella madrepórica (Apiaceae on species richness, species abundance, diversity and evenness of vascular plants at two elevations in the Andes of central Chile. Theoretically, the impact of this nurse cushion plant on these community attributes should be grater at a higher elevation. Results showed that the proportion of plant species associated with cushion plants increases with elevation, and the abundance of some species is also greater within cushions than on bare ground. Although the proportion of species growing within cushions increased with elevation, diversity and evenness were higher on bare ground. This is due to some few species that attained very high densities within cushions, generating assemblages highly dominated by some few species. Ordination analyses indicated differences in species assemblages within and outside A. madrepórica at the higher elevation. Therefore, the influence of cushion plants on community structure changes with elevation. Accordingly, we suggest that attributes other than species richness must be included in future studies in order to analyze the impact of nurse species on community structure along environmental gradients.Se sabe que el número de especies asociado a plantas nodrizas aumenta con la altitud. Sin embargo, el efecto de plantas nodrizas sobre otros atributos de las comunidades, como la abundancia de especies, diversidad y equidad, ha sido largamente ignorado. Más aún, cambios en estos atributos en gradientes ambientales han sido pocas veces examinados

  1. Nurse effect in seedling establishment: facilitation and tolerance to damage in the Andes of central Chile Efecto nodriza en el establecimiento de plántulas: facilitación y tolerancia al daño en los Andes de Chile central

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    IAN S ACUÑA-RODRÍGUEZ

    2006-09-01

    Full Text Available Nurse effects, which occur when one plant species enhances the survival or growth of another plant species, are predicted to be most relevant in stressful environments. These effects are particulary important during seedling establishment due to their vulnerability to both biotic and abiotic factors, such as herbivory and drought. Tolerance to herbivory reflects the degree to which plants are able to regrow and reproduce after damage, and should vary with resource availability. In the high Andes of central Chile, the cushion plant Laretia acaulis (Apiaceae acts as a buffer against environmental stress, enhancing survival of several associated plant species. We hypothesized that tolerance to herbivory of seedlings growing inside the canopy of L. acaulis should be greater than that of seedlings growing outside the cushion plant. We conducted a field experiment to test this hypothesis for two native perennial species in the high Andes of central Chile: Hordeum comosum (Poaceae and Haplopappus anthylloides (Asteraceae. Seedlings of each species were planted inside and outside L. acaulis cushions and half of them received manual damage (50 % foliar tissue removed. Seedlings growing inside the nurse species showed high survival independent of the damage treatment. Whereas position (inside or outside the cushion plant did not affect tolerance of Haplopappus anthylloides, it significantly affected tolerance of Hordeum comosum. Thus, we found similar survival of damaged and control seedlings of H. comosum inside the cushions, but survival of damaged seedlings in the bare ground was lower than that of control seedlings. We verified the occurrence of nurse effects of Laretia acaulis on the establishment of both species, and detected enhancement of tolerance to damage in Hordeum comosum in this stressful habitatSe ha sugerido que el efecto nodriza, el cual se evidencia cuando una especie vegetal incrementa la supervivencia o el crecimiento de otra, es m

  2. Recent temperature trends in the South Central Andes reconstructed from sedimentary chrysophyte stomatocysts in Laguna Escondida (1742 m a.s.l., 38°28 S, Chile)

    Science.gov (United States)

    De Jong, R.; Schneider, T.; Hernández-Almeida, I.; Grosjean, M.

    2016-02-01

    In this study we present a quantitative, high resolution reconstruction of past austral winter length in the Chilean Andes at 38°S from AD 1920 to 2009. For Laguna Escondida, a nearly pristine lake situated on the flanks of the Andes at 1740 m above sea level, past variability in the duration of the winter season (Days T4 °C) was reconstructed. Because high elevation meteorological stations are absent in this region, the reconstruction provides novel insights into recent temperature trends in the central-southern Andes. As a cold-season temperature proxy, we used chrysophyte stomatocysts. This novel proxy for cold season temperature was so far applied successfully in the European Alps and Pyrenees but has not yet been tested in the Southern Hemisphere. The reconstruction in this study was based on a newly developed Transfer Function to estimate Days T4 °C (number of consecutive days with surface water temperatures at or below 4 °C) from sedimentary stomatocyst assemblages (R2boot = 0.8, RMSEPboot = 28.7 days (= half the standard deviation)). To develop a high quality TF model, sediment traps and thermistors were placed in thirty remote lakes along an altitude gradient (420-2040 m a.s.l.). Complete materials and data were collected in 24 lakes after one year. Detailed statistical analyses indicate that modern stomatocysts primarily respond to the length of the cold season. The TF model was then applied to the sedimentary stomatocysts from a 210Pb-dated short core of L. Escondida. Comparison to independent reanalysis data showed that reconstructed changes in Days T4°C provides detailed information on winter-spring temperature variability since AD 1920. The reconstruction shows that recent warming (onset in AD 1980) in the southern Chilean Andes was not exceptional in the context of the past century. This is in strong contrast to studies from the Northern Hemisphere. The finding is also in contrast to the cooling temperature trends which were detected using

  3. Importance of water quality on plant abundance and diversity in high-alpine meadows of the Yerba Loca Natural Sanctuary at the Andes of north-central Chile Importancia de la calidad del agua sobre la abundancia y diversidad vegetal en vegas altoandinas del Santuario Natural Yerba Loca en los Andes de Chile centro-norte

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    ROSANNA GINOCCHIO

    2008-12-01

    Full Text Available Porphyry Cu-Mo deposits have influenced surface water quality in high-Andes of north-central Chile since the Miocene. Water anomalies may reduce species abundance and diversity in alpine meadows as acidic and metal-rich waters are highly toxic to plants The study assessed the importance of surface water quality on plant abundance and diversity in high-alpine meadows at the Yerba Loca Natural Santuary (YLNS, central Chile (33°15' S, 70°18' W. Hydrochemical and plant prospecting were carried out on Piedra Carvajal, Chorrillos del Plomo and La Lata meadows the growing seasons of 2006 and 2007. Direct gradient analysis was performed through canonical correspondence analysis (CCA to look for relationships among water chemistry and plant factors. High variability in water chemistry was found inside and among meadows, particularly for pH, sulphate, electric conductivity, hardness, and total dissolved Cu, Zn, Cd, Pb and Fe. Data on species abundance and water chemical factors suggests that pH and total dissolved Cu are very important factor determining changes in plant abundance and diversity in study meadows. For instance, Festuca purpurascens, Colobanthus quitensis, and Arenaria rivularis are abundant in habitals with Cu-rich waters while Festuca magellanica, Patosia clandestina, Plantago barbata, Werneria pygmea, and Erigeron andícola are abundant in habitals with dilute waters.Los megadepósitos de pórfidos de Cu-Mo han influido sobre la calidad de las aguas superficiales en las zonas altoandinas del centro-norte de Chile desde el Mioceno. Estas alteraciones en la calidad de las aguas podrían afectar negativamente a la vegetación presente en las vegas altoandinas, ya que las aguas acidas y ricas en metales son altamente tóxicas para las plantas. En este estudio se evaluó el efecto de la calidad de las aguas en la abundancia y diversidad florística de las vegas altoandinas del Santuario de la Naturaleza Yerba Loca (SNYL, en Chile central (33

  4. Incomplete trimorphic incompatibility expression in Oxalis compacta Gill. ex Hook. et Arn. subsp. compacta in the central Chilean Andes Expresión incompleta de incompatibilidad trimórfica en Oxalis compacta Gill. ex Hook. et Arn. subsp. compacta en los Andes de Chile central

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    MARY T. K ARROYO

    2012-01-01

    Full Text Available The expression of trimorphic incompatibility was investigated in a high altitude population of Oxalis compacta subsp. compacta distributed in the upper alpine belt (3100-3470 m of the central Chile Andes. Stigma-anther reciprocity (2 populations, morph representation (7 populations, unassisted selfing capacity and open-pollination fruit set (6 populations were determined. O. compacta ssp. compacta es highly dependent on external pollinators. Although it has typical tristylous flowers, considerable seed set is possible following illegitimate intermorph and intramorph cross pollination. Open pollination fruit set varied from 9-83% and on average was lower in the higher-elevation populations. The possibility of seed set following two kinds of illegitimate cross pollination is seen as a means of enhancing reproductive output by enabling more effective use of the limited pollinator resource in the high alpine environment, where fruit set shows high inter-annual variability and there is some evidence for pollination limitation in Oxalis compacta subsp. compacta.Se investigó la expresión de incompatibilidad trimórfica en una población de Oxalis compacta subsp. compacta distribuida en la zona alpina superior de los Andes de Chile central. Se determinó la reciprocidad de los estigmas y anteras (dos poblaciones, representación de morfos florales (7 poblaciones, capacidad para autofecundación no asistida y polinización abierta (6 poblaciones. O. compacta subsp. compacta es altamente dependiente de polinizadores externos. No obstante la presencia de flores tristilicas, las dos categorías ilegítimas de polinización dieron semillas. La producción de frutos mediante polinización abierta fluctuó entre 9-83% y en promedio fue menor en las poblaciones de mayor elevación. Se plantea que la capacidad de formar semillas mediante polinización ilegítima permitirá el uso más eficaz del recurso limitado de polinización en la zona andina superior

  5. Combining point and distributed snowpack data with landscape-based discretization for hydrologic modeling of the snow-dominated Maipo River Basin, in the semi-arid Andes central Chile

    Science.gov (United States)

    Videla Giering, Y. A., III; McPhee, J. P.

    2015-12-01

    Snow hydrology in mountain environments plays an important role in the availability of hydrological resources in warm climate areas and height effects, since the magnitude of snowpack, its spatial and temporal distribution is very important to determine the availability of water in the snowmelt season and take forward different productive activities This investigation models and assess the main phenomena hydrological cycle of snow using the software Cold Region Hydrological Model (Pomeroy et al., 2007). The software is a physically based model developed by the centre for hydrology, University of Saskatchewan. The aim of this model is to have a better understanding of hydrological processes involved in cold environments, which are particular in the sense that a host of specific phenomena such as snow and ice accumulation, transport and melt, infiltration through frozen soils, and the like, control the hydrograph timing) The analysis involved the development of a hydrologic model for the Upper Maipo River Basin, with elevations between 800 and 6500 meters above sea level and 5000-km^2 watershed in the Andes of Central Chile which supplies water resources to the capital city of Santiago (7 million inhabitants), to a thriving agricultural region, as well as to hydropower and large mining activities. The paper concludes that there is a differential distribution of snow cover in the study area, determined mainly by steep terrain geomorphology. These factors have been considered in the parameterization of the model, showing considerable variation in storage time, redistributions by blowing snow, melting intervals, infiltration rates and drainage basin. The fictional scenarios modeled demonstrate noticeable changes in the hydrograph, showing the fragile climate and hydrological condition of this basin of Central Chile.

  6. Geochronology (40Ar/39Ar, K-Ar and He-exposure ages of Cenozoic magmatic rocks from Northern Chile (18-22°S: implications for magmatism and tectonic evolution of the central Andes

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    Gerhard Wörner

    2000-12-01

    Full Text Available K-Ar and Ar/Ar ages from magmatic rocks of northern Chile (18-22°S describe duration and extent of the Tertiary and Quaternary magmatic evolution and date major tectonic events in northernmost Chile. This paper summarizes new K-Ar and Ar-Ar mineral and whole rock ages for intrusive rocks from the Precordillera, Tertiary ignimbrites and andesitic stratovolcanoes from the Western Andean Escarpment at 18°S (WARP and the volcanic front. Intrusive rocks of the Precordillera (Quebrada Paguana, Quebrada Blanca, Quebrada Choja, Quebrada Guatacondo, Cerro Chandacolla represent the Cretaceous to Eocene magmatic arc system and gave ages between 45 and 35 Ma. Younger ages on intrusive rocks are invariably caused by deuteric alteration. Ignimbrites of the Putani and Oxaya formations gave Ar-Ar sanidine ages around 24.2 to 24.8 Ma and 22.8 to 19.4 Ma, respectively. Andesitic stratovolcanoes, which directly overlie Oxaya ignimbrites east of the Western Cordillera gave ages of 20.3 Ma (Cordon Quevilque to 9.0 Ma (Cerro Margarita. Samples from the Miocene to Pleistocene arc system on the Chilean Altiplano underlying the volcanoes of the active volcanic front have been dated between 10.5 to ~3 Ma. A widespread ignimbrite can be correlated from the Lauca basin to the Pacific coast and to the east to occurrences of near Pérez. Repeated Ar-Ar sanidine dating of the Lauca-Pérez-ignimbrite resulted in highly concordant ages of 2.71±0.25 Ma, 2.72 Ma±0.01 Ma, and 2.73±0.11 Ma. Rocks from the active chain (Volcanic Cordillera gave ages younger than 0.9 Ma (Volcán Irruputuncu, Volcán Olca, Volcán Aucanquilcha, Volcán Ollagüe, Volcán Poruñita. These new data are used to constrain Miocene stratigraphy and tectonic movements as well as the timing of uplift and sedimentary response at the Western Andean Escarpment within the framework of the tectonic evolution of the Central AndesGeocronología (49Ar/39Ar, K-Ar y edades He de exposición de rocas cenozoicas del

  7. Geometry of the inverted Cretaceous Chañarcillo Basin based on 2-D gravity and field data. An approach to the structure of the western Central Andes of northern Chile

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    F. Martínez

    2015-08-01

    Full Text Available This paper discusses an integrated approach that provides new ideas about the structural geometry of the NNE-striking, Cretaceous Chañarcillo Basin located along the eastern Coastal Cordillera in the western Central Andes of northern Chile (27–28° S. The results obtained from the integration of two transverse (E–W gravity profiles with previous geological information, show that the architecture of this basin is defined by a large NNE–SSE-trending and east-vergent anticline ("Tierra Amarilla Anticlinorium", which is related to the positive reactivation of a former Cretaceous normal fault (Elisa de Bordos Master Fault. Moreover, intercalations of high and low gravity anomalies and steep gravity gradients reveal a set of buried, west-tilted half-grabens associated with a synthetic normal fault pattern. These results, together with the uplift and folding style of the Cretaceous syn-rift recognized within the basin, suggest that their complete structural geometry could be explained by an inverted fault system linked to the shortening of pre-existing Cretaceous normal fault systems. Ages of the synorogenic deposits exposed unconformably over the frontal limb of the Tierra Amarilla Anticlinorium confirm a Late Cretaceous age for the Andean deformation and tectonic inversion of the basin.

  8. Síndrome pulmonar por hantavirus Andes en Chile CARDIOPULMONARY SYNDROME DUE TO ANDES VIRUS IN CHILE

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    CONSTANZA CASTILLO H.

    2002-01-01

    Full Text Available Desde 1993 han ocurrido 204 casos de Síndrome Cardiopulmonar por Hantavirus (SCPH en Chile. Los brotes epidémicos comenzaron en el sur y avanzan hacia el norte del país. Los más afectados son varones jóvenes, obreros agrícolas o forestales. En Chile, el SCPH es causado por el virus Andes, cuyo reservorio es el Oligorizomys longicaudatus (ratón de cola larga, que se distribuye desde la III Región al sur. El cuadro clínico es similar al descrito en EE.UU., caracterizado por una fase prodrómica que simula un estado gripal o cuadro gastrointestinal febril y que agrava por la aparición de edema pulmonar agudo e inestabilidad hemodinámica (fase cardiopulmonar. Sin embargo, cursa con mayores alteraciones hemorragí-paras y compromiso renal. La mortalidad inicial fue sobre 50% y actualmente es de alrededor del 33,3%. La presente revisión incluye: historia de la enfermedad, reservorio, modos de transmisión, patogenia, cuadro clínico, diagnóstico, tratamiento y medidas de prevenciónSince 1993, 204 cases of Hantavirus cardiopulmonary syndrome (HCPS occurred in Chile. Epidemic began in the south and moved thereafter to the northern regions. The disease affected predominantly young males, who worked in agricultural labours or as timber workers. The HCPS in Chile is caused by the Andes virus. The reservoir is the wild rat Oligoryzomis longicaudatus distributed from the III to the XII Region. The clinical features are similar to those described for Sin Nombre Virus. The disease has a prodromal stage characterised by fever, muscular pain, with or without gastrointestinal manifestations, followed by the rapid onset of respiratory insufficiency and haemodynamic unstability. Andes virus courses more often with haemorrhagic disorders and overt renal failure, than Sin Nombre Virus. The initial mortality was over 50% and declined to 33,3% in the last year. History of hantavirus-diseases, reservoir, and mode of contagion, pathogenesis, clinical

  9. Evolución tectónica, paleogeográfica y metalogénica durante el Cenozoico en los Andes de Chile norte y central e implicaciones para las regiones adyacentes de Bolivia y Argentina Tectonic, paleogeographic, and metallogenic evolution during the Cenozoic in the Andes of Central and Northern Chile and implication for the adjacent regions of Bolivia and Argentina

    OpenAIRE

    Reynaldo Charrier; Marcelo Farías; Víctor Maksaev

    2009-01-01

    La orogenia incaica dio origen a un importante relieve en el Eoceno Medio, el que se concentró en el ámbito del arco magmático precedente, la Cordillera Incaica. Este relieve positivo de orientación NNE se extendió desde el sur de Perú hasta la región central de Chile y separó dos dominios paleogeográficos que tuvieron evoluciones diferentes durante el resto del Cenozoico. El dominio occidental se caracterizó por el predominio de procesos de erosión y sedimentación. En el dominio oriental tam...

  10. LANDSAT imagery of the Central Andes

    Science.gov (United States)

    Komer, C. A.; Morgan, P.

    1986-01-01

    The central Andes of South America extend from approximately 14 deg. S to 28 deg. S as an unbroken chain of mountains and volcanoes over 2000 km long. It is here that the Nazca plate dives under the South American plate at angles varying from 10 deg to 30 deg. Very little is known about the volcanoes comprising this classic, subduction-type plate margin. A catalogue of the volcanoes in the central Andes is being prepared by Dr. P.W. Francis and Dr. C.A. Wood at the NASA Lunar and Planetary Institute. At present, more than 800 volcanoes of Cenozoic age have been recognized in the chain, with an estimated 75-80 major, active Quarternary volcanoes. Approximately one hundred 1536 x 1536 pixel color composite Optronics positives were produced from six full LANDSAT Thermatic Mapper scenes and three partial TM scenes. These positives cover a large portion of the central Andes. The positives were produced from LANDSAT data using the VAX imaging package, LIPS. The scenes were first transferred from magnetic tape to disk. The LIPS package was then used to select volcanically interesting areas which were then electronically enhanced. Finally, the selected areas were transferred back to tape and printed on the Optronics equipment. The pictures are color composites using LANDSAT TM bands 7,4, and 2 in the red, green, and blue filters, respectively.

  11. Evolución tectónica, paleogeográfica y metalogénica durante el Cenozoico en los Andes de Chile norte y central e implicaciones para las regiones adyacentes de Bolivia y Argentina Tectonic, paleogeographic, and metallogenic evolution during the Cenozoic in the Andes of Central and Northern Chile and implication for the adjacent regions of Bolivia and Argentina

    Directory of Open Access Journals (Sweden)

    Reynaldo Charrier

    2009-10-01

    Full Text Available La orogenia incaica dio origen a un importante relieve en el Eoceno Medio, el que se concentró en el ámbito del arco magmático precedente, la Cordillera Incaica. Este relieve positivo de orientación NNE se extendió desde el sur de Perú hasta la región central de Chile y separó dos dominios paleogeográficos que tuvieron evoluciones diferentes durante el resto del Cenozoico. El dominio occidental se caracterizó por el predominio de procesos de erosión y sedimentación. En el dominio oriental también existieron importantes episodios de erosión que originaron depósitos que se encuentran en la vertiente oriental de la cadena en la actualidad y presentan una cronología comparable con la de los depósitos del dominio occidental. Sin embargo, la evolución se caracterizó por presentar, a partir del Eoceno Tardío, diferencias al norte y sur de los ~27ºS. Al norte de esa latitud, en el ámbito del Altiplano-Puna, el arco magmático se mantuvo aproximadamente en la misma posición, coincidente con la del arco actual, y estuvo bordeado por una cuenca de antepaís de retroarco; mientras que, al sur de ~27ºS, se desarrollaron sucesivos arcos magmáticos con una marcada migración hacia el este. El arco magmático del Eoceno Tardío al Oligoceno Tardío - Mioceno Temprano se caracterizó por el desarrollo de una amplia cuenca extensional de intra-arco, la cuenca de Abanico. En esta cuenca se acumularon hasta 3.000 m de rocas volcánicas, volcaniclásticas y, subordinadamente, sedimentarias. A partir del límite oligoceno-mioceno, tuvo lugar un nuevo evento compresivo a lo largo de todo el orógeno que rejuveneció el núcleo de la Cordillera Incaica e invirtió la cuenca de Abanico permitiendo la generación de abundantes depósitos sintectónicos a ambos lados de los nuevos relieves. El inicio de este evento coincide con la orogenia pehuenche, los pulsos compresivos se mantuvieron hasta el Plioceno Temprano. En el Mioceno Temprano a Medio

  12. Late Mesozoic to Paleogene stratigraphy of the Salar de Atacama Basin, Antofagasta, Northern Chile: Implications for the tectonic evolution of the Central Andes

    Science.gov (United States)

    Mpodozis, Constantino; Arriagada, César; Basso, Matilde; Roperch, Pierrick; Cobbold, Peter; Reich, Martin

    2005-04-01

    The Salar de Atacama basin, the largest "pre-Andean" basin in Northern Chile, was formed in the early Late Cretaceous as a consequence of the tectonic closure and inversion of the Jurassic-Early Cretaceous Tarapacá back arc basin. Inversion led to uplift of the Cordillera de Domeyko (CD), a thick-skinned basement range bounded by a system of reverse faults and blind thrusts with alternating vergence along strike. The almost 6000-m-thick, upper Cretaceous to lower Paleocene sequences (Purilactis Group) infilling the Salar de Atacama basin reflects rapid local subsidence to the east of the CD. Its oldest outcropping unit (Tonel Formation) comprises more than 1000 m of continental red sandstones and evaporites, which began to accumulate as syntectonic growth strata during the initial stages of CD uplift. Tonel strata are capped by almost 3000 m of sandstones and conglomerates of western provenance, representing the sedimentary response to renewed pulses of tectonic shortening, which were deposited in alluvial fan, fluvial and eolian settings together with minor lacustrine mudstone (Purilactis Formation). These are covered by 500 m of coarse, proximal alluvial fan conglomerates (Barros Arana Formation). The top of the Purilactis Group consists of Maastrichtian-Danian alkaline lava and minor welded tuffs and red beds (Cerro Totola Formation: 70-64 Ma K/Ar) deposited during an interval of tectonic quiescence when the El Molino-Yacoraite Late Cretaceous sea covered large tracts of the nearby Altiplano-Puna domain. Limestones interbedded with the Totola volcanics indicate that this marine incursion advanced westwards to reach the eastern CD slope. CD shortening in the Late Cretaceous was accompanied by volcanism and continental sedimentation in fault bounded basins associated to strike slip along the north Chilean magmatic arc to the west of the CD domain, indicating that oblique plate convergence prevailed during the Late Cretaceous. Oblique convergence seems to have

  13. Long-term denudation rates from the Central Andes (Chile) estimated from a digital elevation model using the black top hat function and inverse distance weighting : implications for the neogene climate of the Atacama Desert

    OpenAIRE

    Riquelme, R.; Darrozes, J; Maire, E.; Hérail, Gérard; J. C. Soula

    2008-01-01

    A methodology for determining long-term denudation rates from morphologic markers in a Digital Elevation Model (DEM) is checked by a comparative study of two drainage basins in the Precordillera of the Central Andes. In both cases the initial configuration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH) function and the Inverse Distance Weighting (IDW) interpolation. Where vertical incision and hillslope erosion are recorded, the 1DW ap...

  14. A Regional GIS of the Central Andes, South America - Integration of Satellite and Geophysical Data Sets

    OpenAIRE

    Hofmann, K; F. K. List;  

    1996-01-01

    The Central Andes of northern Chile, southwestern Bolivia and northwestern Argentina are studied by a research project supported by the Deutsche Forschungsgemeinschaft (SFB 267). The main topics of these geological and geophysical investigations are the orogeny of the Andean mountains and the crustal development at an active continental margin. The "Andean GIS" is designed as a tool for data collection, management, overview, analysis and mapping. The integration of different data supports the...

  15. An InSAR-based survey of volcanic deformation in the central Andes

    OpenAIRE

    M. E. Pritchard; Simons, M.

    2004-01-01

    We extend an earlier interferometric synthetic aperture radar (InSAR) survey covering about 900 remote volcanos of the central Andes (14°–27°S) between the years 1992 and 2002. Our survey reveals broad (10s of km), roughly axisymmetric deformation at 4 volcanic centers: two stratovolcanoes are inflating (Uturuncu, Bolivia, and Hualca Hualca, Peru); another source of inflation on the border between Chile and Argentina is not obviously associated with a volcanic edifice (here called Lazufre); a...

  16. Depositación atmosférica de nitrógeno en un transecto valle longitudinal-cordillera de Los Andes, centro-sur de Chile Atmospheric deposition of nitrogen in a transect from the Central Valley to Cordillera de Los Andes, south-central Chile

    OpenAIRE

    Oyarzún, Carlos E; ROBERTO GODOY; SERGIO LEIVA

    2002-01-01

    El aumento de las actividades agrícolas y ganaderas en el centro-sur de Chile puede producir elevadas emisiones de nitrógeno hacia la atmósfera (mayormente NH3). El amoniaco es transportado por corrientes de aire y depositado en el suelo y vegetación. El presente estudio evalúa la depositación atmosférica de compuestos nitrogenados (NO3- y NH4+) en la química de las precipitaciones en un transecto altitudinal de 66 km, desde los alrededores de la ciudad de Osorno (40º 35' S, 72º 57' O, 55 m d...

  17. Evolución tectónica, paleogeográfica y metalogénica durante el Cenozoico en los Andes de Chile norte y central e implicaciones para las regiones adyacentes de Bolivia y Argentina

    OpenAIRE

    2009-01-01

    La orogenia incaica dio origen a un importante relieve en el Eoceno Medio, el que se concentró en el ámbito del arco magmático precedente, la Cordillera Incaica. Este relieve positivo de orientación NNE se extendió desde el sur de Perú hasta la región central de Chile y separó dos dominios paleogeográficos que tuvieron evoluciones diferentes durante el resto del Cenozoico. El dominio occidental se caracterizó por el predominio de procesos de erosión y sedimentación. En el dominio oriental tam...

  18. Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile

    OpenAIRE

    Gascoin, S.; C. Kinnard; R. Ponce; S. Lhermitte; MacDonell, S; A. Rabatel

    2010-01-01

    Quantitative assessment of glacier contribution to present-day streamflow is a prerequisite to the anticipation of climate change impact on water resources in the Dry Andes. In this paper we focus on two glaciated headwater catchments of the Huasco Basin (Chile, 29° S). The combination of glacier monitoring data for five glaciers (Toro 1, Toro 2, Esperanza, Guanaco, Estrecho and Ortigas) with five automatic streamflow records at sites with glacier coverage of 0.4 to 11% allows the estimation ...

  19. Salar de Atacama basin: A record of compressional tectonics in the central Andes since the mid-Cretaceous

    Science.gov (United States)

    Arriagada, Cesar; Cobbold, Peter R.; Roperch, Pierrick

    2006-02-01

    The Salar de Atacama basin lies in the inner fore arc of northern Chile. Topographically and structurally, it is a first-order feature of the central Andes. The sedimentary fill of the basin constrains the timing and extent of crustal deformation since the mid-Cretaceous. We have studied good exposures along the western edge of the basin and have correlated them with seismic reflection sections and data from an exploration well. Throughout most of its history, the basin developed in a foreland setting, during periods of thin-skinned and thick-skinned thrusting. Growth strata provide evidence for coeval sedimentation and thrust motions during mid-Cretaceous, Paleogene, and Neogene times. Pre-Neogene deformation was significant in the basin and in surounding areas of the early central Andes. Models that attempt to explain the current thickness of the central Andes should consider Late Cretaceous and Paleogene shortening, as well as the more obvious Neogene and Quaternary shortening.

  20. On the generation of coastal lows in central Chile

    International Nuclear Information System (INIS)

    Previous studies of the coastal-low occurrences in central Chile have been aimed at the formulation of a conceptual model to explain observed features in connection with applied studies. The most prominent weather pattern associated with CL occurrences, (type A), coincides with the onset of a warm, middle-troposphere ridge over central Chile, and a surface high over northern Argentina. The synoptic forcing of the low is related to weak frontal disturbances that travel equatorwards. They result in a thickening of the marine layer that becomes blocked by the coastal escarpment, at the time of the onset of the ridge aloft. The blocking of the stable air above the subsidence inversion by the Andes is also hypothesized. The analysis of the subsidence inversion, the geometry of the coastal and Andes mountain ranges, and a scale analysis of the non-dimensional governing equations for the generation of the coastal lows, following the approach of Reason and Steyn (1990); leads to the conclusion that both blocking actions are strong and persistent in central Chile. An interactive mechanism between the upper and lower blocking effects is postulated to explain the cyclonic vorticity and the initial steering of the coastal lows. The scale analysis of the governing equations for the propagation stage of the low suggests that, departing for the South African case, non-linearity is important here, and that solitary Kelvin waves could be expected. Theoretical phase propagation speeds and Rossby radii are found to range between 8 and 15 m s-1 and 100-250 km, respectively. The importance of strong southerly winds ahead of the low and weak winds at its trailing edge is also stressed, as another major departure from the coastal-low behaviour elsewhere. (author). 17 refs, 4 figs, 4 tabs

  1. Magnetotelluric study of Parincota and Lascer volcanoes, central Andes

    International Nuclear Information System (INIS)

    Complete text of publication follows. This investigation considers two regions of interest, the first one includes the zone around Parinacota (6350 m, 18 deg09'S, 69 deg08'W), a subduction related stratovolcano situated in the limit of Bolivia and Chile, which had its biggest eruptive episodes around 8000 years ago. The second zone is more to the south, around Lascar volcano (5592 m, 23 deg22'S, 67 deg41'W), located on the eastern side of the Salar de Atacama basin in northern Chile, it has been one of the most active volcanoes of the central Andes in the last years. Between September and November 2007, magnetotelluric and audio magnetotelluric sites were built in the area close to Lascar and Parinacota volcanoes. AMT sites were installed in the proximities of the volcanoes, for a more shallow view, and the MT sites, which can reach longer periods and larger depths, were installed on a profile south of Lascar, which goes from the volcanic arc, crossing the Salar de Atacama basin, and as an outer ring in the Parinacota region. Remote reference and robust techniques were used in the data processing. Induction arrows, phase tensor ellipses and strike direction of the conductivity distribution have been calculated for the AMT sites, showing some 3-D behavior for the shallower depths, with induction vectors at the closest sites to the volcanoes pointing away from them, influenced by the topography. For the higher periods, the behavior is more 2-D in both regions, with a more stable strike direction which is coherent with the induction vectors and the largest semi axis of the phase tensor ellipses. All these parameters show a strong influence in the higher periods which seem to be due to a large conductive anomaly in the backarc, according with other studies in the zone, under the Bolivian altiplano. From a first analysis, deep large conductive bodies are not present in these zones around the volcanoes. Topographic corrections have been developed as well as sensitivity

  2. Contrasting response of glacierized catchments in the Central Himalaya and the Central Andes to climate change

    Science.gov (United States)

    Ragettli, Silvan; Pellicciotti, Francesca; Immerzeel, Walter

    2015-04-01

    The Andes of South America and the Himalaya in high-mountain Asia are two regions where advanced simulation models are of vital importance to anticipate the impacts of climate change on water resources. The two mountain systems hold the largest ice masses outside the polar regions. Major rivers originate here and downstream regions are densely populated. In the long run, glacier recession generates concerns about the sustainability of summer runoff. This study benefits from recent efforts of carefully planned short-term field experiments in two headwater catchments in the Central Andes of Chile and in the Central Himalaya in Nepal. The two study catchments contrast in terms of their climate and in the characteristics of their glaciers. A systematic approach is developed, built upon the available local data, to reduce the predictive uncertainty of a state-of-the-art glacio-hydrological model used for the projection of 21st century glacier changes and catchment runoff. The in-situ data are used for model development and step-wise, multivariate parameter calibration. Catchment runoff and remotely sensed MODIS and Landsat snow cover are used for model validation. The glacio-hydrological model simulates the water cycle with a high temporal (hourly time steps) and spatial (100 m grid cells) resolution and accounts for processes typical of both regions like glacier melt under debris cover or mass redistribution through avalanching. Future projections are based on the outputs of twelve stochastically downscaled global climate models for two emission scenarios (RCP 4.5 and RCP 8.5). This is one of the first truly intercomparative modeling studies at the catchment scale across mountain regions of the world to assess and compare future changes in glaciers and snow cover and associated impacts on streamflow production. Both catchments will experience significant glacier mass loss throughout the twenty-first century. However, the trajectories of simulated future runoff and

  3. Miocene-Quaternary structural evolution of the Uyuni-Atacama region, Andes of Chile and Bolivia

    OpenAIRE

    Tibaldi, A.; Università degli Studi di Milano-Bicocca; Corazzato, C.; Università degli Studi di Milano-Bicocca; Rovida, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia

    2008-01-01

    We describe the Miocene-Quaternary geological-structural evolution of the region between the Salar de Uyuni and de Atacama, Andes of Chile and Bolivia. We recognised four main tectonic events based on fold geometry, fault kinematics and stratigraphic data. The oldest event, of Miocene age, is characterized by folding and reverse faulting of the sedimentary successions with an E-W direction of shortening in the northern part of the studied area and a WNW-ESE shortening in the southern part. Th...

  4. Surface control on contrasts in deformation between eastern and western margins of the Central Andes

    Science.gov (United States)

    Schlunegger, F.; Norton, K. P.

    2012-04-01

    enhanced orographic rainfall, which promotes thrusting and internal shortening. A fault-scale coupled erosion-deformation model also shows that low erosion rates and steep topographic angles would have forced a migration of deformation from the Western Escarpment to the eastern side. These findings illustrate the strong control of orographic precipitation on the deformation of the Central Andes. Kober, F. et al. Denudation rates and topography-driven rainfall threshold in northern Chile: multiple cosmogenic nuclide data and sediment budgets. Geomorphology 83, 97-120 (2007). Norton, K. & Schlunegger, F. Migrating deformation in the Central Andes from enhanced orographic rainfall. Nat. Commun. 2, 584 (2011). Safran, E. B et al. Erosion rates driven by channel network incision in the Bolivian Andes. Earth Surf. Process Landforms 30, 1007-1024 (2005).

  5. Evolución tectónica, paleogeográfica y metalogénica durante el Cenozoico en los Andes de Chile norte y central e implicaciones para las regiones adyacentes de Bolivia y Argentina

    Directory of Open Access Journals (Sweden)

    Reynaldo Charrier

    2009-10-01

    Full Text Available La orogenia incaica dio origen a un importante relieve en el Eoceno Medio, el que se concentró en el ámbito del arco magmático precedente, la Cordillera Incaica. Este relieve positivo de orientación NNE se extendió desde el sur de Perú hasta la región central de Chile y separó dos dominios paleogeográficos que tuvieron evoluciones diferentes durante el resto del Cenozoico. El dominio occidental se caracterizó por el predominio de procesos de erosión y sedimentación. En el dominio oriental también existieron importantes episodios de erosión que originaron depósitos que se encuentran en la vertiente oriental de la cadena en la actualidad y presentan una cronología comparable con la de los depósitos del dominio occidental. Sin embargo, la evolución se caracterizó por presentar, a partir del Eoceno Tardío, diferencias al norte y sur de los ~27ºS. Al norte de esa latitud, en el ámbito del Altiplano-Puna, el arco magmático se mantuvo aproximadamente en la misma posición, coincidente con la del arco actual, y estuvo bordeado por una cuenca de antepaís de retroarco; mientras que, al sur de ~27ºS, se desarrollaron sucesivos arcos magmáticos con una marcada migración hacia el este. El arco magmático del Eoceno Tardío al Oligoceno Tardío - Mioceno Temprano se caracterizó por el desarrollo de una amplia cuenca extensional de intra-arco, la cuenca de Abanico. En esta cuenca se acumularon hasta 3.000 m de rocas volcánicas, volcaniclásticas y, subordinadamente, sedimentarias. A partir del límite oligoceno-mioceno, tuvo lugar un nuevo evento compresivo a lo largo de todo el orógeno que rejuveneció el núcleo de la Cordillera Incaica e invirtió la cuenca de Abanico permitiendo la generación de abundantes depósitos sintectónicos a ambos lados de los nuevos relieves. El inicio de este evento coincide con la orogenia pehuenche, los pulsos compresivos se mantuvieron hasta el Plioceno Temprano. En el Mioceno Temprano a Medio

  6. Moho topography in the central Andes and its geodynamic implications

    OpenAIRE

    Xiaohui Yuan; S. V. Sobolev; Rainer Kind

    2002-01-01

    P-to-S converted waves at the continental Moho together with waves multiply reflected between the Earth's surface and the Moho have been used to estimate the Moho depth and average crustal Vp/Vs variations in the central Andes. Our analysis confirms and significantly complements the Moho depth estimates previously obtained from wide-angle seismic studies and receiver functions. The resulting crustal thickness varies from about 35 km in the forearc region to more than 70 km beneath the plateau...

  7. Geodetic observations of megathrust earthquakes and backarc wedge deformation across the central Andes

    Science.gov (United States)

    Weiss, J. R.; Brooks, B. A.; Foster, J. H.; Bevis, M. G.; Echalar, A.; Caccamise, D.; Heck, J. M.

    2014-12-01

    High-precision Global Positioning System (GPS) data offer an opportunity to investigate active orogenic wedges yet surface velocity fields are available for only a few examples worldwide. More observations are needed to link deformation processes across multiple timescales and to better understand strain accumulation and release in active wedge settings. Here we present a new GPS velocity field for the central Andes and the backarc orogenic wedge comprising the southern Subandes of Bolivia (SSA), a region previously thought to be mostly isolated from the plate boundary earthquake cycle. The time span of our observations (2000 to mid-2014) includes two megathrust earthquakes along the Chile trench that affected the SSA. The 2007 Mw 7.7 Tocopilla, Chile earthquake resulted in a regional postseismic decrease in the eastward component of horizontal surface velocities. Preliminary analysis of the deformation field from the April 01 2014 Mw 8.2 Pisagua, Chile earthquake also indicates a postseismic signal extending into the SSA. We create an interseismic velocity field for the SSA by correcting campaign GPS site velocities for the seasonal cycles estimated from continuous GPS site time series. We remove the effects of both megathrust events by estimating coseismic steps and fitting linear and logarithmic functions to the postseismic GPS site motions. The velocity estimates at most locations increase after correcting for the transients. This finding suggests that forces leading to shortening and earthquakes in the backarc wedge are not as temporally consistent as previously considered.

  8. 3D density model of the Central Andes

    Science.gov (United States)

    Prezzi, Claudia B.; Götze, Hans-Jürgen; Schmidt, Sabine

    2009-12-01

    We developed a 3D density model of the continental crust, the subducted plate and the upper mantle of the Central Andes between 20-29°S and 74-61°W through the forward modelling of Bouguer anomaly. The goal of this contribution is to gain insight on the lithospheric structure integrating the available information (geophysical, geologic, petrologic, and geochemical) in a single model. The geometry of our model is defined and constrained by hypocentre location, reflection and refraction on and offshore seismic lines, travel time and attenuation tomography, receiver function analysis, magnetotelluric studies, thermal models and balanced structural cross-sections. The densities allocated to the different bodies are calculated considering petrologic and geochemical data and pressure and temperature conditions. The model consists of 31 parallel E-W vertical planes, where the continental crust comprises distinct bodies, which represent the different morphotectonic units of the Central Andes. We include a partial melting zone at midcrustal depths under the Altiplano-Puna (low-velocity zone) and consider the presence of a rheologically strong block beneath the Salar de Atacama basin, according to recent seismic studies. Contour maps of the depth of the continental Moho, the thickness of the lower crust and the depth to the bottom of the lithosphere below South America are produced. The possible percentage of partial melt in the Central Andes low-velocity zone is estimated. The residual anomaly is calculated by subtracting from the Bouguer anomaly the gravimetric effect of the modelled subducted slab and of the modelled Moho. Isostatic anomalies are calculated from regional and local isostatic Mohos calculated with and without internal loads, derived from our gravity model, which are then compared to the modelled continental Moho. This study contributes to a more detailed knowledge of the lithospheric structure of this region of the Andes and provides an integrated 3D

  9. The largest holocene eruption of the Central Andes found

    OpenAIRE

    Fernandez-Turiel, J. L.; J. Saavedra; Perez-Torrado, J. F.; Rodriguez-Gonzalez, A.; Carracedo, Juan Carlos; Osterrieth, M.; Carrizo, J. I.; Esteban, G.

    2013-01-01

    We present new data and interpretation about a major eruption -spreading 110 km3 ashes over 440.000 km2- long thought to have occurred around 4200 years ago in the Cerro Blanco Volcanic Complex (CBVC) in NW Argentina. This eruption may be the biggest during the past five millennia in the Central Volcanic Zone of the Andes, and possibly one of the largest Holocene eruptions in the world. The environmental effects of this voluminous eruption are still noticeable, as evidenced by the high conte...

  10. Giant evaporite belts of the Neogene central Andes

    Science.gov (United States)

    Alonso, Ricardo N.; Jordan, Teresa E.; Tabbutt, Kenneth T.; Vandervoort, Dirk S.

    1991-04-01

    Large volumes of continental evaporites accumulated within the central Andes during Neogene uplift of the Altiplano-Puna plateau and development of the Andean volcanic arc. Halite and gypsum are dominant minerals, along with local and economically important borates. Playa conditions have existed since ca. 15 Ma; halite and borate deposition has occurred for the past 7 to 8 m.y. Evaporites formed in salar environments (e.g., playa lakes) and are characterized by complex mineral assemblages, occurrence, zonation, and geochemistry. Evaporite deposition was controlled by volcanism, geothermal activity, closed drainage, and climate. These Andean deposits, and their controls, differ from evaporites in other continental and marine environments.

  11. The Largest Holocene Eruption of the Central Andes Found

    Science.gov (United States)

    Fernandez-Turiel, J.; Rodriguez-Gonzalez, A.; Saavedra, J.; Perez-Torrado, F.; Carracedo, J.; Osterrieth, M.; Carrizo, J.; Esteban, G.

    2013-12-01

    We present new data and interpretation about a major eruption -spreading ˜110 km3 ashes over 440.000 km2- long thought to have occurred around 4200 years ago in the Cerro Blanco Volcanic Complex (CBVC) in NW Argentina. This eruption may be the biggest during the past five millennia in the Central Volcanic Zone of the Andes, and possibly one of the largest Holocene eruptions in the world. The environmental effects of this voluminous eruption are still noticeable, as evidenced by the high content of arsenic and other trace elements in the groundwaters of the Chacopampean Plain. The recognition of this significant volcanic event may shed new light on interpretations of critical changes observed in the mid-Holocene paleontological and archaeological records, and offers researchers an excellent, extensive regional chronostratigraphic marker for reconstructing mid-Holocene geological history over a wide geographical area of South America. More than 100 ashes were sampled in Argentina, Chile and Uruguay during different field campaigns. Ash samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), grain size distributions laser diffraction, and geochemically by electron microprobe (EMPA) and laser ablation-HR-ICP-MS. New and published 14C ages were calibrated to calendar years BP. The age of the most recent CBVC eruption is 4407-4093 cal y BP, indirectly dated by 14C of associated organic sediment within the lower part of a proximal fall deposit of this event (26°53'16.05"S-67°44'48.68"W). This is the youngest record of a major volcanic event in the Southern Puna. This age is consistent with other radiocarbon dates of organic matter in palaeosols underlying or overlying distal ash fall deposits. Based on their products, all of rhyolitic composition, we have distinguished 8 main episodes during the evolution of the most recent CBVC eruption: 1) the eruption began with a white rhyolite lava dome extrusion; 2) followed by a Plinian

  12. Heinrich I and Younger Dryas Glaciation in the Central Andes

    Science.gov (United States)

    Zech, J.; Zech, R.; May, J.; Kubik, P. W.; Veit, H.

    2009-12-01

    Short term climate reversals, such as Heinrich I (H-I) and the Younger Dryas (YD), are well documented in the Northern Hemisphere. However, the respective response of the climate system in the Southern Hemisphere during these events remains enigmatic. Here we present 10Be surface exposure ages from the Wara Wara Valley (17°S, 66°W), Cordillera Cochabamba, that reveal glacial advances in the Central Andes before 14.3 ka and 11.9 ka. These advances correlate with H-I and YD and coincide with the lake transgression phases Tauca (18-14 ka) and Coipasa (13-11 ka) on the Altiplano. They corroborate the precipitation sensitivity of glacier mass balances in the semi-arid Central Andes. We suggest that sufficient moisture for glacial advances can be explained by enhanced upper tropospheric easterlies as a response to an intensified tropical circulation and sustained la Niña like patterns in the eastern Pacific. This redistribution of the ocean and atmospheric circulation was caused by a southward shift of the ITCZ due to northern hemispheric cooling. At 10.8 ka glacier advanced again attributed to increased moisture supply by enhanced polar advection and SE trade winds during the Early Holocene. Final deglaciation started only at 9.2 ka induced by a change to drier conditions.

  13. The Bolivian and Maipo Oroclines: Two first scale structural features of the Central Andes

    Science.gov (United States)

    Arriagada, C. A.

    2013-05-01

    Two remarkable curvatures of the orogenic system of the Central Andes are the Bolivian and the Maipo Oroclines. While the former has been widely studied, the latter in central Chile, where few, geographically restricted, paleomagnetic studies have been carried out, knowledge about vertical-axis rotations is scarce. Here we show the results of the paleomagnetic studies carried out in the last years along the Central Andes within the Bolivian and Maipo Oroclines. Along-strike variations in horizontal shortening in the back- arc provided an efficient mechanism to explain the Bolivian Orocline and block rotations of the forearc region in northern Chile and southern Peru. As a first approximation, it appears reasonable that the arcuate shape of the Maipo Orocline could be accompanied by a significant pattern of rotations about a vertical axis in the forearc region and by a progressive decrease of crustal shortening and the resulting topography from north to south in the back-arc region. Furthermore, although the Maipo Orocline is located more than 1000 km south of the axial zone of the Central Andes, south of 30, clockwise rotations of up to 20 could have occurred during the evolution of the Bolivian Orocline. While the northern segment of the Maipo orocline corresponds with the ongoing subduction of the Pampean flat slab segment which proceeds nearly horizontally beneath the South American lithosphere, the southern segment coincides with the normal subduction segment developed to the south of 33S. The Maipo Orocline is thought to be result of collision of the Challenger Fracture Zone and Juan Fernández Ridge with the continent since 25 Ma. The southern flank of the Maipo Orocline can be traced along strike to around 38S. North of 33S, previous studies show no evidence for significant tectonic rotations. In contrary, south of 33S, both in the Coastal Cordillera and High Andes, clockwise block rotations have been observed and attributed to in situ block rotations in

  14. Meteorological drivers of ablation processes on a cold glacier in the semiarid Andes of Chile

    Directory of Open Access Journals (Sweden)

    S. MacDonell

    2013-04-01

    Full Text Available Meteorological and surface change measurements collected during a 2.5 yr period are used to calculate surface mass and energy balances at 5324 m a.s.l. on Guanaco Glacier, a cold-based glacier in the semi-arid Andes of Chile. Meteorological conditions are marked by extremely low vapour pressures (annual mean of 1.1 hPa, strong winds (annual mean of 10 m s−1, high shortwave radiation receipt (mean annual 295 W m−2 and low precipitation rates (mean annual 45 mm w.e.. Net shortwave radiation provides the greatest source of energy to the glacier surface, and net longwave radiation dominates energy losses. The turbulent latent heat flux is always negative, which means that the surface is always losing mass via sublimation, which is the main form of ablation at the site. Sublimation rates are most strongly correlated with net shortwave radiation, incoming shortwave radiation, albedo and vapour pressure. Low glacier surface temperatures restrict melting for much of the period, however episodic melting occurs during the austral summer, when warm, humid, calm and high pressure conditions restrict sublimation and make more energy available for melting. Low accumulation (131 mm w.e. over the period and relatively high ablation (1435 mm w.e. means that mass change over the period was negative (−1304 mm w.e., which continued the negative trend recorded in the region over the last few decades.

  15. Parameterisation of incoming longwave radiation over glacier surfaces in the semiarid Andes of Chile

    Science.gov (United States)

    MacDonell, Shelley; Nicholson, Lindsey; Kinnard, Christophe

    2013-02-01

    A good understanding of radiation fluxes is important for calculating energy, and hence, mass exchange at glacier surfaces. This study evaluates incoming longwave radiation measured at two nearby glacier stations in the high Andes of the Norte Chico region of Chile. These data are the first published records of atmospheric longwave radiation measurements in this region. Nine previously published optimised parameterisations for clear sky emissivity all produced results with a root mean square error (RMSE) ~20 W m-2 and bias within ±5 W m-2, which is inline with findings from other regions. Six optimised parameterisations for incoming longwave in all sky conditions were trialled for application to this site, five of which performed comparably well with RMSE on daytime data <18 W m-2 and bias within ±6 W m-2 when applied to the optimisation site and RMSE <20 W m-2 and bias within ±10 W m-2 when applied to the validation site. The parameterisation proposed by Mölg et al. (J Glaciol 55:292-302, 2009) was selected for use in this region. Incorporating the proposed elevation modification into the equation reduced the bias in the modelled incoming longwave radiation for the validation site. It was found that applying the parameterisation optimised in the original work at Kilimanjaro produced good results at both the primary and validation site in this study, suggesting that this formulation may be robust for different high mountain regions.

  16. Constraints on sediment transfer from the Andes to the coast of northern Chile

    Science.gov (United States)

    Binnie, Steven; Liermann, Ariane; Dunai, Tibor; Dewald, Alfred; Heinze, Stefan

    2013-04-01

    While rates of denudation have been suggested as having the potential to link tectonic processes with climate in many settings, the roles that sediment transport must also play have been largely neglected. It is the transport, or not, of eroded material, not necessarily the rate at which that material is produced which is the critical factor in many models of tectonic-climatic interactions. The notable lack of sediment in sections of the Peru-Chile trench has been implicated as a key control of subduction zone processes and consequently Andean mountain building, but little empirical data on sediment transport in the region exists. Here, we present the initial results of a study aiming to constrain the westward transfer of sediment from the Andes Mountains to the Pacific Coast of northern Chile by using in situ-produced cosmogenic nuclides. Fluvial sediments were collected at the mouths of several large catchments between 19° S and 26° S, where they drain into the Pacific, and also from upstream locations within each catchment. Sample sites were selected in order to investigate the cosmogenic nuclide derived basin-averaged denudation rates of the western flank of the Andes, and to compare this with the cosmogenic nuclide concentrations of fluvial sediments further downstream where the catchments exit to the coast. A simplistic interpretation of the cosmogenic 10Be concentrations as denudation rates gives results varying between ~10 and 300 m/Myr. We would expect the most rapid erosion to occur on the steeper, wetter western Andean flank and for slower erosion to be recorded from the more gentle sloping, hyperarid/arid regions between the foothills of the Andes and the Pacific coast. This pattern is observed in some basins but in others the nuclide concentrations imply the opposite, with several-fold higher erosion rates measured for the large catchments sampled at the coast in comparison to their mountainous Andean headwaters. One explanation for this unusual

  17. Intraseasonal variability of organized convective systems in the Central Andes: Relationship to Regional Dynamical Features

    Science.gov (United States)

    Mohr, K. I.; Slayback, D. A.; Nicholls, S.; Yager, K.

    2013-12-01

    The Andes extend from the west coast of Colombia (10N) to the southern tip of Chile (53S). In southern Peru and Bolivia, the Central Andes is split into separate eastern and western cordilleras, with a high plateau (≥ 3000 m), the Altiplano, between them. Because 90% of the Earth's tropical mountain glaciers are located in the Central Andes, our study focuses on this region, defining its zonal extent as 7S-21S and the meridional extent as the terrain 1000 m and greater. Although intense convection occurs during the wet season in the Altiplano, it is not included in the lists of regions with frequent or the most intense convection. The scarcity of in-situ observations with sufficient density and temporal resolution to resolve individual storms or even mesoscale-organized cloud systems and documented biases in microwave-based rainfall products in poorly gauged mountainous regions have impeded the development of an extensive literature on convection and convective systems in this region. With the tropical glaciers receding at unprecedented rates, leaving seasonal precipitation as an increasingly important input to the water balance in alpine valley ecosystems and streams, understanding the nature and characteristics of the seasonal precipitation becomes increasingly important for the rural economies in this region. Previous work in analyzing precipitation in the Central Andes has emphasized interannual variability with respect to ENSO, this is the first study to focus on shorter scale variability with respect to organized convection. The present study took advantage of the University of Utah's Precipitation Features database compiled from 14 years of TRMM observations (1998-2012), supplemented by field observations of rainfall and streamflow, historical gauge data, and long-term WRF-simulations, to analyze the intraseasonal variability of precipitating systems and their relationship regional dynamical features such as the Bolivian High. Through time series and

  18. Late Pleistocene glaciations of the arid subtropical Andes and new results from the Chajnantor Plateau, northern Chile

    Science.gov (United States)

    Ward, Dylan J.; Cesta, Jason M.; Galewsky, Joseph; Sagredo, Esteban

    2015-11-01

    The spatiotemporal pattern of glaciation along the Andes Mountains is an important proxy record reflecting the varying influence of global and regional circulation features on South American climate. However, the timing and extent of glaciation in key parts of the orogen, particularly the deglaciated arid Andes, are poorly constrained. We present new cosmogenic 10Be and 36Cl exposure ages for glacial features on and near the Chajnantor Plateau (23 °S). The new dates, although scattered due to cosmogenic inheritance, imply that the most recent extensive glacial occupation ended before or during the global Last Glacial Maximum (LGM). We discuss this new record in the context of published glacial chronologies from glacial features in Peru, Bolivia, and northern Chile rescaled using the latest cosmogenic 10Be production rate calibration for the tropical Andes. The results imply regionally synchronous moraine stabilization ca. 25-40 ka, 15-17 ka, and 12-14 ka, with the youngest of these moraines absent in records south of ˜20 °S, including in our new Chajnantor area chronology. This spatial pattern implicates easterly moisture in generating sufficient snowfall to glaciate the driest parts of the Andes, while allowing a role for westerly moisture, possibly modulated by the migration of the Southern Westerly Wind belt, in the regions near and south of the Atacama Desert.

  19. Interseismic coupling and seismic potential along the Central Andes subduction zone

    Science.gov (United States)

    Chlieh, Mohamed; Perfettini, Hugo; Tavera, Hernando; Avouac, Jean-Philippe; Remy, Dominique; Nocquet, Jean-Mathieu; Rolandone, FréDéRique; Bondoux, Francis; Gabalda, Germinal; Bonvalot, Sylvain

    2011-12-01

    We use about two decades of geodetic measurements to characterize interseismic strain build up along the Central Andes subduction zone from Lima, Peru, to Antofagasta, Chile. These measurements are modeled assuming a 3-plate model (Nazca, Andean sliver and South America Craton) and spatially varying interseismic coupling (ISC) on the Nazca megathrust interface. We also determine slip models of the 1996 Mw = 7.7 Nazca, the 2001 Mw = 8.4 Arequipa, the 2007 Mw = 8.0 Pisco and the Mw = 7.7 Tocopilla earthquakes. We find that the data require a highly heterogeneous ISC pattern and that, overall, areas with large seismic slip coincide with areas which remain locked in the interseismic period (with high ISC). Offshore Lima where the ISC is high, a Mw˜8.6-8.8 earthquake occurred in 1746. This area ruptured again in a sequence of four Mw˜8.0 earthquakes in 1940, 1966, 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a Mw > 8.5 earthquake. The region where the Nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period (low ISC) and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years. In southern Peru, ISC is relatively high and the deficit of moment accumulated since the Mw˜8.8 earthquake of 1868 is equivalent to a magnitude Mw˜8.4 earthquake. Two asperities separated by a subtle aseismic creeping patch are revealed there. This aseismic patch may arrest some rupture as happened during the 2001 Arequipa earthquake, but the larger earthquakes of 1604 and 1868 were able to rupture through it. In northern Chile, ISC is very high and the rupture of the 2007 Tocopilla earthquake has released only 4% of the elastic strain that has accumulated since 1877. The deficit of moment which has accumulated there is equivalent to a magnitude Mw˜8.7 earthquake. This study thus

  20. Moho topography in the central Andes and its geodynamic implications

    Science.gov (United States)

    Yuan, X.; Sobolev, S. V.; Kind, R.

    2002-06-01

    P-to-S converted waves at the continental Moho together with waves multiply reflected between the Earth's surface and the Moho have been used to estimate the Moho depth and average crustal Vp/ Vs variations in the central Andes. Our analysis confirms and significantly complements the Moho depth estimates previously obtained from wide-angle seismic studies and receiver functions. The resulting crustal thickness varies from about 35 km in the forearc region to more than 70 km beneath the plateau and thins (30 km) further to the east in the Chaco plains. Beneath the Andean plateau, the Moho is deeper in the north (Altiplano) and shallower in the south (Puna), where the plateau attains its maximum elevation. A non-linear relation exists between crustal thickness and elevation (and Bouguer gravity), suggesting that the crust shallower than 50-55 km is predominately felsic in contrast to a predominately mafic crust below. Such a relation also implies a 100 km thick thermal lithosphere beneath the Altiplano and with a lithospheric thinning of a few tens of kilometers beneath the Puna. Absence of expected increase in lithospheric thickness in regions of almost doubled crust strongly suggests partial removal of the mantle lithosphere beneath the entire plateau. In the Subandean ranges at 19-20°S, the relation between altitude and crustal thickness indicates a thick lithosphere (up to 130-150 km) and lithospheric flexure. Beneath a relative topographic low at the Salar de Atacama, a thick crust (67 km) suggests that the lithosphere in this region is abnormally cold and dynamically subsided, possibly due to coupling with the subducting plate. This may be related to the strongest (Ms=8.0) known intra-slab earthquake in the central Andes that happened very close to this region in 1950. The average crustal Vp/ Vs ratio is about 1.77 for the Altiplano-Puna and it reaches the highest values (1.80-1.85) beneath the volcanic arc, indicating high ambient crustal temperatures and

  1. Stable isotope evidence for multiple pulses of rapid surface uplift in the Central Andes, Bolivia

    OpenAIRE

    Leier, Andrew; McQuarrie, Nadine; Garzione, Carmala; Eiler, John

    2013-01-01

    Paleoelevation histories from mountain belts like the Central Andes of Bolivia provide important constraints on the timing and geodynamic mechanisms associated with surface uplift. We present new oxygen and carbon isotope data (δ^(18)O, δ^(13)C, and Δ_(47)) from Oligocene–Miocene strata exposed in the Eastern Cordillera of the Bolivian Central Andes in order to reconstruct both the deformation and paleoelevation history of the region prior to late Miocene time. Paleosol carbonate in strata >2...

  2. Miocene-Quaternary structural evolution of the Uyuni-Atacama region, Andes of Chile and Bolivia

    Science.gov (United States)

    Tibaldi, A.; Corazzato, C.; Rovida, A.

    2009-06-01

    We describe the Miocene-Quaternary geological-structural evolution of the region between the Salar de Uyuni and de Atacama, Andes of Chile and Bolivia. We recognized four main tectonic events based on fold geometry, fault kinematics and stratigraphic data. The oldest event, of Miocene age, is characterized by folding and reverse faulting of the sedimentary successions with an E-W direction of shortening in the northern part of the studied area and a WNW-ESE shortening in the southern part. The following two events, of Pliocene age, are characterized by lower shortening amounts; they occurred first by reverse faulting with a NW-SE-trending greatest principal stress ( σ1, computed with striated fault planes) and a vertical least principal stress ( σ3), followed by pervasive strike-slip faulting with the same NW-SE-trending σ1 and a horizontal NE-SW σ3. The fourth event, dating to the late Pliocene-Quaternary is characterized by normal faulting: the σ3 still trends NE-SW, whereas the intermediate principal stress σ2 exchanged with σ1. Volcanism accompanied both the contractional, transcurrent and extensional tectonic phases. The Mio-Pliocene compression appears directly linked to a rapid convergence and an apparently important coupling between the continental and oceanic plates. The E-W to WNW-ESE direction of shortening of the Miocene structures and the NW-SE σ1 of the Pliocene structures seem to be more linked to an intra-Andean re-orientation of structures following the WNW-directed absolute motion of the South-American Plate. The extensional deformations can be interpreted as related to gravity forces affecting the highest parts of the volcanic belt in a sort of asymmetrical (SW-ward) collapse of the belt.

  3. A satellite geodetic survey of large-scale deformation of volcanic centres in the central Andes

    Science.gov (United States)

    Pritchard, Matthew E.; Simons, Mark

    2002-07-01

    Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Stratovolcanoes tend to exhibit a complex relationship between deformation and eruptive behaviour. The characteristically long time spans between such eruptions requires a long time series of observations to determine whether deformation without an eruption is common at a given edifice. Such studies, however, are logistically difficult to carry out in most volcanic arcs, as these tend to be remote regions with large numbers of volcanoes (hundreds to even thousands). Here we present a satellite-based interferometric synthetic aperture radar (InSAR) survey of the remote central Andes volcanic arc, a region formed by subduction of the Nazca oceanic plate beneath continental South America. Spanning the years 1992 to 2000, our survey reveals the background level of activity of about 900 volcanoes, 50 of which have been classified as potentially active. We find four centres of broad (tens of kilometres wide), roughly axisymmetric surface deformation. None of these centres are at volcanoes currently classified as potentially active, although two lie within about 10km of volcanoes with known activity. Source depths inferred from the patterns of deformation lie between 5 and 17km. In contrast to the four new sources found, we do not observe any deformation associated with recent eruptions of Lascar, Chile.

  4. A satellite geodetic survey of large-scale deformation of volcanic centres in the central Andes.

    Science.gov (United States)

    Pritchard, Matthew E; Simons, Mark

    2002-07-11

    Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Stratovolcanoes tend to exhibit a complex relationship between deformation and eruptive behaviour. The characteristically long time spans between such eruptions requires a long time series of observations to determine whether deformation without an eruption is common at a given edifice. Such studies, however, are logistically difficult to carry out in most volcanic arcs, as these tend to be remote regions with large numbers of volcanoes (hundreds to even thousands). Here we present a satellite-based interferometric synthetic aperture radar (InSAR) survey of the remote central Andes volcanic arc, a region formed by subduction of the Nazca oceanic plate beneath continental South America. Spanning the years 1992 to 2000, our survey reveals the background level of activity of about 900 volcanoes, 50 of which have been classified as potentially active. We find four centres of broad (tens of kilometres wide), roughly axisymmetric surface deformation. None of these centres are at volcanoes currently classified as potentially active, although two lie within about 10 km of volcanoes with known activity. Source depths inferred from the patterns of deformation lie between 5 and 17 km. In contrast to the four new sources found, we do not observe any deformation associated with recent eruptions of Lascar, Chile. PMID:12110886

  5. Genesis of adakite-like lavas of Licancabur volcano (Chile—Bolivia, Central Andes)

    Science.gov (United States)

    Figueroa, Oscar; Déruelle, Bernard; Demaiffe, Daniel

    2009-04-01

    The Licancabur volcano is located on the Bolivia—Chile Altiplano (Central Andes). The lavas are andesites and dacites. Numerous mineralogic features attest that magma mixing occurred. Andesites have concave (spoon-shaped) REE patterns whereas dacites have steep slopes. A spectacular crossover of patterns occurs with increasing SiO 2. Most geochemical discrimination criteria of adakites are satisfied by Licancabur dacites, except their high Sr-isotope compositions (> 0.7075). For the genesis of the Licancabur adakite-like lavas, a four-step model is proposed: (1) partial melting (5 to 10 wt %) of a subducted altered oceanic crust; (2) hybridation (< 10 wt %) of the magmas with melts derived from the overlying lithospheric mantle; (3) contamination (≈ 1 wt %) of these hybrid magmas by TTG-type granodiorites of the Archean lower continental crust (with present-day Sr-isotope ratios ≈ 0.820); (4) evolution and differentiation by crystal fractionation (< 6 wt %) and magma mixing at upper crustal levels.

  6. Tectonic control on denudation rates in the central Bolivian Andes

    Science.gov (United States)

    Zeilinger, Gerold; Kober, Florian; Hippe, Kristina; Lendzioch, Theodora; Grischott, Reto; Pillco Zolá, Ramiro; Christl, Markus

    2013-04-01

    Effects of a positive feedback loop between erosion and tectonics have been shown by analogue and numerical models and have been inferred from field observations at the scale of mountain ranges. We present new data from the Bolivian Andes supporting these observations, although common geomorphic parameters do not indicate a simple correlation. The upper Rio Grande segment, located between Cochabamba, Santa Cruz and Sucre, drains a major catchment in the central Bolivian Cordillera, from the Eastern Cordillera (EC) in the W, through the Interandean Zone (IAZ) and the Subandes (SA) in the E. The catchment covers an area of 58939 km² with an altitude range from 400 to 5150 m above sea level. Geologically, the Bolivian Andes comprise (from W to E) the Altiplano, the EC, the IAZ and the SA fold and thrust belts. The Altiplano represents an almost perfectly closed basin with distinct barriers defined by the Western Cordillera and Eastern Cordillera. The Rio Grande does not reach the Altiplano (unlike Rio La Paz and Rio Consata) but has its western drainage divide along the high peaks of the EC that experienced a period of intense shortening between Late Oligocene and Miocene. Near Cochabamba, the EC comprises metasedimentary siliciclastic rocks of Ordovician age. These rocks are overlain by Cretaceous to Paleocene and / or Neogene sediments with an angular unconformity. The IAZ and SA form an east-vergent fold and thrust belt and comprise Paleozoic and Mesozoic units. Farther east, the structures of the SA progressively include Neogene foreland strata of the Chaco foreland basin. The Chaco basin rests on the Brazilian shield east of the Subandean Belt and forms the modern foreland basin, where the lower Rio Grande catchment is sited. We obtained 58 cosmogenic 10Be catchment wide denudation rates for the Rio Grande catchments upstream of Abapó. They range from 7 mm/kyr to 1550 mm/kyr thus integrating at maximum over the last 10.000 years, with a mean of 262 mm/kyr. In

  7. Late Pleistocene deglaciation histories in the central Mérida Andes (Venezuela)

    OpenAIRE

    Angel Ceballos, Isandra Fortuna

    2016-01-01

    The central Mérida Andes (Venezuela) landscape is characterized by the presence of well-preserved glacial landforms located between 2400 and 4978 m a.s.l. Geomorphological studies of these glacial landforms significantly contribute to the Venezuelan Andes glaciations reconstructions. However, Last Glaciation (locally called Mérida Glaciation) was poorly reconstructed because of limited chronological data. This dissertation attempts to contribute to the Last Glaciation reconstruction and paleo...

  8. Characteristics of Precipitation Features and Annual Rainfall during the TRMM Era in the Central Andes

    Science.gov (United States)

    Mohr, Karen I.; Slayback, Daniel; Yager, Karina

    2014-01-01

    The central Andes extends from 7 deg to 21 deg S, with its eastern boundary defined by elevation (1000m and greater) and its western boundary by the coastline. The authors used a combination of surface observations, reanalysis, and the University of Utah Tropical Rainfall Measuring Mission (TRMM) precipitation features (PF) database to understand the characteristics of convective systems and associated rainfall in the central Andes during the TRMM era, 1998-2012. Compared to other dry (West Africa), mountainous (Himalayas), and dynamically linked (Amazon) regions in the tropics, the central Andes PF population was distinct from these other regions, with small and weak PFs dominating its cumulative distribution functions and annual rainfall totals. No more than 10% of PFs in the central Andes met any of the thresholds used to identify and define deep convection (minimum IR cloud-top temperatures, minimum 85-GHz brightness temperature, maximum height of the 40-dBZ echo). For most of the PFs, available moisture was limited (less than 35mm) and instability low (less than 500 J kg(exp -1)). The central Andes represents a largely stable, dry to arid environment, limiting system development and organization. Hence, primarily short-duration events (less than 60 min) characterized by shallow convection and light to light-moderate rainfall rates (0.5-4.0 mm h(exp -1)) were found.

  9. Phylogenetic relationships between telmatobiinids (Anura, Ceratophryidae, Telmatobiinae) of central Andes based on morphology of larval and adult stages

    OpenAIRE

    César Aguilar; Niels Valencia

    2011-01-01

    Batrachophrynus and Telmatobius are the two genus of Telmatobiinae from the central Andes. Both genera have species with adaptations for life at high altitude in the Andes, with aquatic or semi-aquatic habits in creeks, lagoons and lakes. The objective of this study is to evaluate the phylogenetic relationships between Batrachophrynus and 13 species of Telmatobius from the central Andes using larval and adult morphology including diagnostic characters for Batrachophrynus and Telmatobius, and ...

  10. Evolution of crustal thickening in the central Andes, Bolivia

    Science.gov (United States)

    Eichelberger, Nathan; McQuarrie, Nadine; Ryan, Jamie; Karimi, Bobak; Beck, Susan; Zandt, George

    2015-09-01

    Paleoelevation histories from the central Andes in Bolivia have suggested that the geodynamic evolution of the region has been punctuated by periods of large-scale lithospheric removal that drive rapid increases in elevation at the surface. Here, we evaluate viable times and locations of material loss using a map-view reconstruction of the Bolivian orocline displacement field to forward-model predicted crustal thicknesses. Two volumetric models are presented that test assumed pre-deformation crustal thicknesses of 35 km and 40 km. Both models predict that modern crustal thicknesses were achieved first in the northern Eastern Cordillera (EC) by 30-20 Ma but remained below modern in the southern EC until ≤10 Ma. The Altiplano is predicted to have achieved modern crustal thickness after 10 Ma but only with a pre-deformation thickness of 50 km, including 10 km of sediment. At the final stage, the models predict 8-25% regional excess crustal volume compared to modern thickness, largely concentrated in the northern EC. The excess predicted volume from 20 to 0 Ma can be accounted for by: 1) crustal flow to the WC and/or Peru, 2) localized removal of the lower crust, or 3) a combination of the two. Only models with initial crustal thicknesses >35 km predict excess volumes sufficient to account for potential crustal thickness deficits in Peru and allow for lower crustal loss. However, both initial thickness models predict that modern crustal thicknesses were achieved over the same time periods that paleoelevation histories indicate the development of modern elevations. Localized removal of lower crust is only necessary in the northern EC where crustal thickness exceeds modern by 20 Ma, prior to paleoelevation estimates of modern elevations by 15 Ma. In the Altiplano, crustal thicknesses match modern values at 10 Ma and can only exceed modern values by 5 Ma, post-dating when modern elevations were thought to have been established. Collectively, these models predict that

  11. Chile.

    Science.gov (United States)

    1988-09-01

    Chile is a long (2650 miles), narrow (250 miles at widest point) country sandwiched between the Andes mountains and the Pacific. The northern desert is rich in copper and nitrates; the temperate middle region is agricultural and supports the major cities, including Santiago, the capital, and the port of Valparaiso; and the southern region is a cold and damp area of forests, grasslands, lakes, and fjords. The country is divided into 12 administrative regions. Chile's population of 12.5 million are mainly of Spanish or Indian descent or mestizos. Literacy is 92.3%, and the national language is Spanish. Infant mortality is 18.1/1000, and life expectancy is 68.2 years. 82% of the people are urban, and most are Roman Catholics. Chile was settled by the Spanish in 1541 and attached to the Viceroyalty of Peru. Independence was won in 1818 under the leadership of Bernardo O'Higgins. In the 1880s Chile extended its sovereignty over the Strait of Magellan in the south and areas of southern Peru and Bolivia in the north. An officially parliamentary government, elected by universal suffrage, drifted into oligarchy and finally into a military dictatorship under Carlos Ibanez in 1924. Constitutional government was restored in 1932. The Christian Democratic government of Eduardo Frei (1964-70) inaugurated major reforms, including land redistribution, education, and far-reaching social and economic policies. A Marxist government under Salvador Allende lasted from 1970 to 1973 when the present military government of General Pinochet Ugarte took power, overthrew Allende, abolished the Congress, and banned political parties. It has moved the country in the direction of a free market economy but at the cost of systematic violations of human rights. A new constitution was promulgated in 1981, and congressional elections have been scheduled for October, 1989. A "National Accord for Transition to Full Democracy" was mediated by the Catholic Church in 1985. The social reforms of the

  12. Comparative phylogeography of co-distributed Phrygilus species (Aves, Thraupidae) from the Central Andes.

    Science.gov (United States)

    Álvarez-Varas, R; González-Acuña, D; Vianna, J A

    2015-09-01

    The Neotropical ecoregion has been an important place of avian diversification where dispersal and allopatric events coupled with periods of active orogeny and climate change (Late Pliocene-Pleistocene) have shaped the biogeography of the region. In the Neotropics, avian population structure has been sculpted not only by geographical barriers, but also by non-allopatric factors such as natural selection and local adaptation. We analyzed the genetic variation of six co-distributed Phrygilus species from the Central Andes, based on mitochondrial and nuclear markers in conjunction with morphological differentiation. We examined if Phrygilus species share patterns of population structure and historical demography, and reviewed the intraspecific taxonomy in part of their geographic range. Our results showed different phylogeographic patterns between species, even among those belonging to the same phylogenetic clade. P. alaudinus, P. atriceps, and P. unicolor showed genetic differentiation mediated by allopatric mechanisms in response to specific geographic barriers; P. gayi showed sympatric lineages in northern Chile, while P. plebejus and P. fruticeti showed a single genetic group. We found no relationship between geographic range size and genetic structure. Additionally, a signature of expansion was found in three species related to the expansion of paleolakes in the Altiplano region and the drying phase of the Atacama Desert. Morphological analysis showed congruence with molecular data and intraspecific taxonomy in most species. While we detected genetic and phenotypic patterns that could be related to natural selection and local adaptation, our results indicate that allopatric events acted as a major factor in the population differentiation of Phrygilus species. PMID:25987531

  13. An InSAR-based survey of volcanic deformation in the central Andes

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2004-02-01

    We extend an earlier interferometric synthetic aperture radar (InSAR) survey covering about 900 remote volcanos of the central Andes (14°-27°S) between the years 1992 and 2002. Our survey reveals broad (10s of km), roughly axisymmetric deformation at 4 volcanic centers: two stratovolcanoes are inflating (Uturuncu, Bolivia, and Hualca Hualca, Peru); another source of inflation on the border between Chile and Argentina is not obviously associated with a volcanic edifice (here called Lazufre); and a caldera (Cerro Blanco, also called Robledo) in northwest Argentina is subsiding. We explore the range of source depths and volumes allowed by our observations, using spherical, ellipsoidal and crack-like source geometries. We further examine the effects of local topography upon the deformation field and invert for a spherical point-source in both elastic half-space and layered-space crustal models. We use a global search algorithm, with gradient search methods used to further constrain best-fitting models. Inferred source depths are model-dependent, with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure. Source depths relative to sea level are: 8-18 km at Hualca Hualca; 12-25 km for Uturuncu; 5-13 km for Lazufre, and 5-10 km at Cerro Blanco. Deformation at all four volcanoes seems to be time-dependent, and only Uturuncu and Cerro Blanco were deforming during the entire time period of observation. Inflation at Hualca Hualca stopped in 1997, perhaps related to a large eruption of nearby Sabancaya volcano in May 1997, although there is no obvious relation between the rate of deformation and the eruptions of Sabancaya. We do not observe any deformation associated with eruptions of Lascar, Chile, at 16 other volcanoes that had recent small eruptions or fumarolic activity, or associated with a short-lived thermal anomaly at Chiliques volcano. We posit a hydrothermal system at Cerro Blanco to explain the

  14. Ophiolites in the Eastern Cordillera of the central Peruvian Andes

    OpenAIRE

    Castroviejo Bolibar, Ricardo; Rodrigues, Feliciano; Tassinari, Colombo G.; Pereira, Eurico; Acosta, Jorge

    2010-01-01

    A discoutinuous NNW-SSE trending belt of scattered ultraiuafic (UM) and subordínate mafic (M) rocks ís exposed alona some 250 km in the Eastern Cordillera of the peruvian Andes (Junin and Huanuco Departnients. -°"-12° S). New data questiou tlieír pieviousty assuuned [1.2] intrusive origin. Work, in progress shows tLat the essential geologic and tecronk featiires are comnion to most of them, as will t e shown on the southeniniost occurrences: Tapo and Acobaniba (Tarraa proviuce). The Tapo mass...

  15. Long-term denudation rates from the Central Andes (Chile estimated from a Digital Elevation Model using the Black Top Hat function and Inverse Distance Weighting: implications for the Neogene climate of the Atacama Desert Tasas de denudación de largo tiempo en los Andes Centrales, Chile, estimadas a partir de un modelo digital de elevación usando la función 'Top Hat' por cierre y la interpolación ponderada por el inverso de la distancia: implicancias del clima Neógeno del Desierto de Atacama

    Directory of Open Access Journals (Sweden)

    Rodrigo Riquelme

    2008-01-01

    Full Text Available A methodology for determining long-term denudation rates from morphologic markers in a Digital Elevation Model (DEM is checked by a comparative study of two drainage basins in the PrecordiUera of the Central Andes. In both cases the initial configuration of an incised pediment surface has been restored by using two different methods: the Black Top Hat (BTH function and the Inverse Distance Weighting (IDW interpolation. Where vertical incision and hillslope erosion are recorded, the IDW appears to be the most adequate to reconstitute the pediment surfaces. Conversely, where only vertical incision is observed, the BTH describes more precisely the former pediment surfaces and it is easier to solve. By subtracting the DEM from the reconstructed marker we calculated an eroded volume, and estimated its uncertainty by considering Root Mean Square Error (RMSE and DEM grid error. For the last ~10 Myr we obtained long-term denudation rates of 7.33±1.6 m/Myr in the San Andrés drainage basin and 13.59±1.9 m/Myr in the El Salado drainage basin. These estimations are largely in agreement with other reported estimates of long-term denudation rates in the Atacama Desert. Comparison with long-term denudation rates reported in a wide range of climatic regimes suggests that our estimates cannot be explained by the current rainfall in the PrecordiUera. However they could be explained by a rainfall similar to that reported 40 km to the east in the Puna. This suggests that during the time span concerned the geomorphologic evolution of the study area, this evolution is dominated by an orographically controlled rainfall pattern. The preserved pediment surface and the small long term denudation rates determined in this study also indicate that the PrecordiUera was never reached by humid tropical air masses and precipitation as currently observed in the Altiplano during the summer monthsUna metodología para determinar tasas de denudación de largo tiempo a partir de

  16. Erratic pollination, high selfing levels and their correlates and consequences in an altitudinally widespread above-tree-line species in the high Andes of Chile

    Science.gov (United States)

    Arroyo, Mary T. K.; Muñoz, María S.; Henríquez, Carolina; Till-Bottraud, Irène; Pérez, Fernánda

    2006-09-01

    Unfavorable temperatures and weather conditions for biotic pollination in above-tree-line alpine habitats predict self-compatibility, high levels of autogamy and small flower size ("autogamy reproductive assurance hypothesis"), or alternatively, compensatory measures such as greater flower longevity and larger display size so as to capture scarce visits and maintain outcrossing ("increased pollination probability hypothesis"). We assess these possibilities in a fine-tuned study of Chaetanthera euphrasioides (Asteraceae) populations located above-tree-line in the Andes of central Chile, where prior, independently obtained information on community flower visitation rates is available. Visitation by flies and Andrenid bees was highly erratic in all populations and among years, and the rates well below the community averages. We found evidence for high levels of self-compatibility, equally high autogamous potential, low genetic diversity and high and similar F IS in all populations studied, associated with no clear trends in floral morphology. Strong decoupling of C. euphrasioides reproductive biology with community-level pollinator availability in the alpine fails to support either of the above-mentioned hypotheses and suggests early acquisition of autogamy with present-day pollinator conditions being adequate to maintain low visitation rates at all elevations. Our study provides the only instance where alternative hypotheses on alpine breeding systems have been tested with prior access to independently quantified community-level flower visitation rates.

  17. Asynchronous Glacial Chronologies in the Central Andes (15-40°S) and Paleoclimatic Implications

    Science.gov (United States)

    Zech, R.; Kull, C.; Kubik, P. W.; Veit, H.

    2006-12-01

    We have established glacial chronologies along a N-S transect over the Central Andes using 10Be surface exposure dating. Our results show that maximum glacial advances occurred asynchronously and reflect the varying influence and shifts of the major atmospheric circulation systems during the Late Quaternary: the tropical circulation in the north and the westerlies in the south. In Bolivia (three research areas in the Cordillera Real and the Cordillera Cochabamba, ~15°S) glacial advances could be dated to ~20 and 12 ka BP. This is in good agreement with published exposure age data from moraines in Bolivia and Peru (provided that all ages are calculated following the same scaling system). Accordingly, the maximum glaciation there probably occurred roughly synchronous to the temperature minimum of the global Last Glacial Maximum (LGM) and the lateglacial cold reversals. Strict correlation with neither the Younger Dryas in the northern hemisphere, nor the Antarctic Cold Reversal is possible due to the current systematic exposure age uncertainties (~10%). Glacier-Climate-Modelling corroborates the sensitivity of the reconstructed glaciers to temperature changes, rather than precipitation. On the contrary, there is good evidence for the dominant role of precipitation changes on the glacial chronologies in the lee of the Cordillera Occidental, i.e. on the Altiplano and further south. The pronounced lateglacial wet phase, which is well documented in lake transgression phases as far south as 28°S (-> tropical moisture source), seems to have caused glacial advances even at ~30°S. In two research areas in Chile at that latitude, we were able to date several lateglacial moraines. Besides, the maximum datable glaciation there occurred at ~30 ka BP. That is significantly earlier than the LGM (sensu strictu) and points to favourable climate conditions for glaciation at that time (particularly increased precipitation). We conclude that the westerlies were more intensive or

  18. Morphologic evolution of the Central Andes of Peru

    Science.gov (United States)

    Gonzalez, Laura; Pfiffner, O. Adrian

    2012-01-01

    In this paper, we analyze the morphology of the Andes of Peru and its evolution based on the geometry of river channels, their bedrock profiles, stream gradient indices and the relation between thrust faults and morphology. The rivers of the Pacific Basin incised Mesozoic sediments of the Marañon thrust belt, Cenozoic volcanics and the granitic rocks of the Coastal Batholith. They are mainly bedrock channels with convex upward shapes and show signs of active ongoing incision. The changes in lithology do not correlate with breaks in slope of the channels (or knick points) such that the high gradient indices (K) with values between 2,000-3,000 and higher than 3,000 suggest that incision is controlled by tectonic activity. Our analysis reveals that many of the ranges of the Western Cordillera were uplifted to the actual elevations where peaks reach to 6,000 m above sea level by thrusting along steeply dipping faults. We correlate this uplift with the Quechua Phase of Neogene age documented for the Subandean thrust belt. The rivers of the Amazonas Basin have steep slopes and high gradient indices of 2,000-3,000 and locally more than 3,000 in those segments where the rivers flow over the crystalline basement of the Eastern Cordillera affected by vertical faulting. Gradient indices decrease to 1,000-2,000 within the east-vergent thrust belt of the Subandean Zone. Here a correlation between breaks in river channel slopes and location of thrust faults can be established, suggesting that the young, Quechua Phase thrust faults of the Subandean thrust belt, which involve Neogene sediments, influenced the channel geometry. In the eastern lowlands, these rivers become meandering and flow parallel to anticlines that formed in the hanging wall of Quechua Phase thrust faults, suggesting that the river courses were actively displaced outward into the foreland.

  19. Two new species of Siphocampylus (Campanulaceae, Lobelioideae) from the Central Andes.

    Science.gov (United States)

    Lagomarsino, Laura P; Santamaría-Aguilar, Daniel

    2016-01-01

    Two species of Siphocampylus (Campanulaceae: Lobelioideae) from the Central Andes of Peru and Bolivia are described, illustrated, and discussed with reference to related species. One species, Siphocampylus antonellii, is endemic to high elevation grasslands of Calca, Peru, while the second, Siphocampylus siberiensis, is endemic to cloud forests of Cochabamba, Bolivia. Both species are robust shrubs that produce tubular pink flowers that are likely pollinated by hummingbirds. PMID:26884710

  20. Eighty Years of History of the Central Bank of Chile

    OpenAIRE

    Vittorio Corbo; Leonardo Hernández

    2005-01-01

    The Central Bank of Chile was founded in 1925, to provide the country with an institution that could stabilize the currency, regulate interest and discount rates, and avoid disruptions in the country’s financial, industrial and economic development (Decree Law Nº486, August 22, 1925). But a weak institutional framework meant that the Bank, far from ameliorating these problems, aggravated them, leading to decades of high and persistent inflation. Inflation became under control only during the ...

  1. Active orogeny of the south-central Andes studied with GPS geodesy

    Directory of Open Access Journals (Sweden)

    E. Kendrick

    2006-12-01

    Full Text Available We present GPS measurements of the crustal velocity field in the southern Central Andes between the Santa Cruz corner and the Malargüe fold and thrust belt, and model this interseismic velocity field as the combination of an ephemeral, elastic signal associated with locking of the main plate boundary, and a steady and non-reversing component of displacement associated with localized backarc convergence and growth of the mountain belt. We find that this second component, i.e. the ongoing and permanent displacement of the forearc and the high Andes relative to the craton, can be modeled very well as a steady clockwise rotation of an Andean microplate about a pole located in southern Argentina. Near the Malargüe Basin, this microplate (or block is moving nearly parallel to the strike of the orogen, transporting material towards the bend in the central Andes. Farther north, in the southern limb of the Central Andes, the motion of this same crustal block is directed nearly perpendicular to the strike of the mountain belt. Our results suggest that permanent deformation rates in the backarc range from a maximum of ~ 6-7 mm/yr in the Bolivian Subandes to less than ~ 3 mm/yr in the Argentine Precordillera and Malargue fold and thrust belt. It is likely that most active backarc deformation is accruing in a narrow zone (~ 50 km wide associated with the backarc boundary (usually defined as the thrust front though at this stage it is impossible to distinguish whether specific backarc structures are actively accruing strain.

  2. River runoff and regional climate of a small glaciated catchment area in the Andes in southernmost Patagonia, Chile

    Science.gov (United States)

    Schneider, C.; Moritz, M.; Kilian, R.

    2003-04-01

    The river runoff from a small partly glaciated catchment area in southernmost Patagonian Andes in Chile is measured to analyse the influence of regional precipitation and climate dependent glacier ablation on runoff. The first data from March to September 2002 were compared to climate data recorded at an automatic weather station in the area. The poster presents the first detailed hydrometeorological investigation from this part of the Andes. The investigation area is located at 53°S in southernmost South America exactly east of the main divide of the mountain range of the Andes at 72.5°W. The catchment area of about 15 km2 comprises parts of the Gran Campo Nevado Ice Cap reaching up to 1500 m asl, and the outlet glacier Glaciar Lengua which ends at a proglacial lake at 100 m asl. The Gran Campo Nevado Ice Cap is the major ice mass between the Southern Patagonian Ice field in the north and the Strait of Magallan to the South. Climate in the area is characterised by whole-year round cool and super-humid conditions with a mean annual air temperature of 5,6°C at sea level and an annual precipitation sum of approximately 7,000 mm. The Río Lengua itself meets approximately 3.5 km downstreams from the proglacial lake into the fjord system of Canal Garjado which is a branch of Seno Skyring. A continuous hourly record of water levels in the river was obtained from two digital water depth sensors. Runoff was calibrated against river level by measuring runoff at different times with the tracer method of salt dilution and with velocity measurements employing a hydrometric vane. Mean runoff was computed to about 3 m3/s with peak flows exceeding 10 m3/s. Ablation on the glacier was estimated using the degree-day method with a degree-day factor that has been calibrated previously using data from a temporal energy balance weather station on Glacíar Lengua. The correlation between runoff and air temperature and precipitation returned significant correlation coefficients of rt

  3. Meteorological drivers of ablation processes on a cold glacier in the semi-arid Andes of Chile

    Directory of Open Access Journals (Sweden)

    S. MacDonell

    2013-09-01

    Full Text Available Meteorological and surface change measurements collected during a 2.5 yr period are used to calculate surface mass and energy balances at 5324 m a.s.l. on Guanaco Glacier, a cold-based glacier in the semi-arid Andes of Chile. Meteorological conditions are marked by extremely low vapour pressures (annual mean of 1.1 hPa, strong winds (annual mean of 10 m s−1, shortwave radiation receipt persistently close to the theoretical site maximum during cloud-free days (mean annual 295 W m−2; summer hourly maximum 1354 W m−2 and low precipitation rates (mean annual 45 mm w.e.. Snowfall occurs sporadically throughout the year and is related to frontal events in the winter and convective storms during the summer months. Net shortwave radiation provides the greatest source of energy to the glacier surface, and net longwave radiation dominates energy losses. The turbulent latent heat flux is always negative, which means that the surface is always losing mass via sublimation, which is the main form of ablation at the site. Sublimation rates are most strongly correlated with net shortwave radiation, incoming shortwave radiation, albedo and vapour pressure. Low glacier surface temperatures restrict melting for much of the period, however episodic melting occurs during the austral summer, when warm, humid, calm and high pressure conditions restrict sublimation and make more energy available for melting. Low accumulation (131 mm w.e. over the period and relatively high ablation (1435 mm w.e. means that mass change over the period was negative (−1304 mm w.e., which continued the negative trend recorded in the region over the last few decades.

  4. Summer energy balance and ablation of high elevation glaciers in the central Chilean Andes

    Science.gov (United States)

    Brock, Benjamin; Rivera, Andres; Burger, Flavia; Bravo, Claudio

    2014-05-01

    Glaciers of the semi-arid central Chilean Andes are an important freshwater source for the populous Central Valley region of Chile, but have been shrinking in recent decades. The surface energy balance of these glaciers is of high scientific interest as summer ablation occurs through both sublimation and melt. During the 2012-13 Austral Summer a glacio-meteorological monitoring programme was established on Olivares Alfa (3.9 km2, 4130-4800 m elevation) and Beta (8.3 km2, 3620-4850 m elevation) Glaciers and their forelands in the Upper Olivares Valley, 33°00'-33°11' S, 70°05'-70°15' W, approximately 50 km north-east of Santiago. This included complete automatic weather stations (AWSs) with sonic rangers to record surface ablation on the ablation zones of the two glaciers, and one AWS in the proglacial area of Olivares Alfa Glacier including precipitation gauge. To complement these point data, daily images of the glaciers were captured with fixed cameras in order to calculate snow cover and albedo distributions. To calculate the surface energy balance and rates of melt and sublimation, a model was developed which uses direct AWS measurements of the radiative fluxes and calculates the turbulent fluxes of sensible and latent heat using the bulk aerodynamic approach. The model also calculates the subsurface heat flux and includes a simple scheme to estimate refreezing of melt water within surface snow or ice. Meteorological data and model results for the December to May period will be presented in this paper. Model calculations match closely the cumulative ablation curve of the sonic ranger at Olivares Alfa, with a slight overestimation, and overestimate cumulative ablation recorded by the sonic ranger at Olivares Beta, possibly due, at least in part, to uncertain snow density values. Modelled cumulative ablation in the December-April period is 2.2 m water equivalent (w.e.) at Olivares Alfa (0.10 m sublimation, 2.10 m melt) and 2.34 m w.e. at Olivares Beta (0.18 m

  5. Late Pleistocene to Holocene tephrostratigraphy of the Lonquimay Volcano, South Central Chile

    Science.gov (United States)

    Gilbert, D.; Freundt, A.; Kutterolf, S.; Burkert, C.

    2010-12-01

    The Lonquimay Volcanic Complex (LVC) in South Central Chile (38.38°S, 71.58°W) is part of the Southern Volcanic Zone of the Andes, which formed in response to the subduction of the Nazca Plate beneath the South American Plate. During the course of its magmatic evolution, the LVC produced explosive eruptions documented in the succession of widespread tephra deposits, as well as large lava flows that originated from the main edifice and several adjacent minor eruptive centers. The last eruptive phase in Lonquimays volcanic evolution occurred from 1988-1990. It led to the formation of the Navidad cinder cone with its associated 10.2 km long lava flow, and a widely distributed tephra blanket of andesitic composition (Moreno and Gardeweg, 1989). During recent field work we reinvestigated and complemented the LVC tephrostratigraphy as originally established by Polanco (1998)by detailed logging of 22 outcrops and collecting 126 stratigraphically controlled samples that were analyzed for their matrix glass, mineral and bulk rock compositions. This data set allows us to verify and extend the field-based correlations, and to establish a tephrostratigraphy for the LVC that comprises 15 stratigraphic units (LQA-LQO) and provides a framework for ongoing investigations of the petrogenetic evolution of the LVC. The stratigraphic record identifies at least 13 explosive eruptions of VEI > 3 that occurred since the last glaciation period (17150 a BP, McCulloch et al. 2000). Magmatic compositions of the tephra deposits range from basaltic scoriae (51wt% SiO2) to evolved dacitic pumice lapilli layers (67wt% SiO2), and thus have a wider compositional range than the chemically distinct andesitic lavas (57-63wt%) of the LVC. The vertical succession of tephra compositions reflects four periods of progressive magmatic differentiation, each successively tapped by several eruptions. The maximum degree of fractionation reached during these periods increases to younger ages. The

  6. Prediction of extreme floods in the Central Andes by means of Complex Networks

    Science.gov (United States)

    Boers, Niklas; Bookhagen, Bodo; Barbosa, Henrique; Marwan, Norbert; Kurths, Jürgen; Marengo, Jose

    2014-05-01

    Based on a non-linear synchronisation measure and complex network theory, we present a novel framework for the prediction of extreme events of spatially embedded, interrelated time series. This method is general in the sense that it can be applied to any type of spatially sampled time series with significant interrelations, ranging from climate observables to biological or stock market data. In this presentation, we apply our method to extreme rainfall in South America and show how this leads to the prediction of more than 60% (90% during El Niño conditions) of extreme rainfall events in the eastern Central Andes of Bolivia and northern Argentina, with only 1% false alarms. From paleoclimatic to decadal time scales, the Central Andes continue to be subject to pronounced changes in climatic conditions. In particular, our and past work shows that frequency as well as magnitudes of extreme rainfall events have increased significantly during past decades, calling for a better understanding of the involved climatic mechanisms. Due to their large spatial extend and occurrence at high elevations, these extreme events often lead to severe floods and landslides with disastrous socioeconomic impacts. They regularly affect tens of thousands of people and produce estimated costs of the order of several hundred million USD. Alongside with the societal value of predicting natural hazards, our study provides insights into the responsible climatic features and suggests interactions between Rossby waves in polar regions and large scale (sub-)tropical moisture transport as a driver of subseasonal variability of the South American monsoon system. Predictable extreme events result from the propagation of extreme rainfall from the region of Buenos Aires towards the Central Andes given characteristic atmospheric conditions. Our results indicate that the role of frontal systems originating from Rossby waves in polar latitudes is much more dominant for controlling extreme rainfall in

  7. On the uplift anomaly of the Arica Bend, Western Central Andes

    Science.gov (United States)

    Madella, Andrea; Delunel, Romain; Szidat, Sönke; Schlunegger, Fritz

    2015-04-01

    The architecture of the Western Andes is remarkably constant between southern Peru and northern Chile. An exception, however, is present near Arica at 18°S, where the Andes change their strike direction by ca. 50° and the Coastal Cordillera is absent over a lateral width of 50 km. Here, we propose a large-scale model to explain the Ma-long low-uplift rate of the Arica Bend in connection with interplate coupling and continental wedge-top basin evolution. We complement new geomorphic and sedimentological observations with structural, stratigraphic and seismic data compiled from the literature. We additionally present a new set of 14C ages to infer the Holocene uplift pattern of the region, which we support with stream profile analysis. Results show that the absence of a sediment barrier and the amphitheater-shaped topography at the Arica Bend has conditioned a relatively high sediment discharge to the corresponding trench segment since 2.7 Ma and possibly earlier. However, the 14C ages and the river profile analyses yield contradicting high coastal uplift rates for the past 10 ka. It appears that, at the large scale, higher sediment supply likely reduced the friction at the interplate boundary, keeping the uplift push at lower levels and the Coastal Cordillera submerged below Arica, thereby explaining the lower frequency of large subduction earthquakes in the area. Nonetheless, at a smaller scale, Quaternary sea-level fluctuations repeatedly shifted the water-load on the accretionary wedge, thereby inducing short-term elastic buckling, which has perturbed the trunk stream's profile.

  8. Active orogeny of the south-central Andes studied with GPS geodesy Orogenia activa de los Andes centro-australes estudiada mediante geodesia de GPS

    Directory of Open Access Journals (Sweden)

    E. Kendrick

    2006-12-01

    Full Text Available We present GPS measurements of the crustal velocity field in the southern Central Andes between the Santa Cruz corner and the Malargüe fold and thrust belt, and model this interseismic velocity field as the combination of an ephemeral, elastic signal associated with locking of the main plate boundary, and a steady and non-reversing component of displacement associated with localized backarc convergence and growth of the mountain belt. We find that this second component, i.e. the ongoing and permanent displacement of the forearc and the high Andes relative to the craton, can be modeled very well as a steady clockwise rotation of an Andean microplate about a pole located in southern Argentina. Near the Malargüe Basin, this microplate (or block is moving nearly parallel to the strike of the orogen, transporting material towards the bend in the central Andes. Farther north, in the southern limb of the Central Andes, the motion of this same crustal block is directed nearly perpendicular to the strike of the mountain belt. Our results suggest that permanent deformation rates in the backarc range from a maximum of ~ 6-7 mm/yr in the Bolivian Subandes to less than ~ 3 mm/yr in the Argentine Precordillera and Malargue fold and thrust belt. It is likely that most active backarc deformation is accruing in a narrow zone (~ 50 km wide associated with the backarc boundary (usually defined as the thrust front though at this stage it is impossible to distinguish whether specific backarc structures are actively accruing strain.Se presentan mediciones GPS del campo de velocidad en los Andes centro-australes entre el extremo norte de Santa Cruz y la faja plegada de Malargüe. Se modela el campo de velocidad intersísmico como la combinación de una señal elástico/efímera asociada con el anclaje del límite principal de placas, y una componente constante, no reversible de desplazamiento asociada con una convergencia localizada en el retroarco y crecimiento del

  9. Structural Evolution of the Central Venezuelan Andes: Changes From Compression to Strike-slip and Extension

    Science.gov (United States)

    Hervouet, Y.; Dhont, D.; Backe, G.

    2006-12-01

    The Venezuelan Andes form a N50°E-trending belt extending from the colombian border in the SW to the Caribbean sea in the NE. The belt is 100 km wide and its highest summits reach 5000 m in its central part. Uplift of the belt is a consequence of the relative convergence between the triangular-shaped Maracaibo crustal block on the west and the Guyana shield belonging to South America. The Maracaibo block is cut by a series of strike-slip faults separating several crustal units. Among these, the easternmost Trujillo triangular block is limited on the west by the N-S left-lateral Valera fault and on the south-east by the NE-trending right-lateral Bocono fault. Our methodology, based on the analysis of radar satellite and digital elevation model imagery and implemented by structural field work and the compilation of seismotectonic data, presents a new understanding of the tectonic evolution of the Venezuelan Andes during the Neogene-Quaternary. We have characterized three stages of deformation. The first, Mio-Pliocene in age, corresponds to the NW-SE Andean compression responsible for the uplift of the Venezuelan Andes. The second tectonic stage is consitent with a strike-slip regime of deformation marked by shearing along the Bocono and Valera faults and hence individualizing the Trujillo block, which has been cut into two smaller triangular wedges. This strike-slip faulting- dominated compressional-extensional tectonic regime started at some point between the Pliocene and the Quaternary and allowed the Trujillo crustal block to move towards the NE. The third stage of deformation corresponds to extension in the Trujillo block and is still active today. The present-day distribution of the deformation in the Venezuelan Andes is consistent with strain partitioning. While compression is restricted on both flanks of the belt, strike-slip and extension occurs in the central part of the mountain range. Extension is associated with the motion of crustal blocks moving

  10. Geometric evolution of the Horcones Inferior Glacier (Mount Aconcagua, Central Andes) during the 2002-2006 surge

    Science.gov (United States)

    Pitte, Pierre; Berthier, Etienne; Masiokas, Mariano H.; Cabot, Vincent; Ruiz, Lucas; Ferri Hidalgo, Lidia; Gargantini, Hernán.; Zalazar, Laura

    2016-01-01

    The Central Andes of Chile and Argentina (31-35°S) contain a large number and variety of ice masses, but only two surging glaciers have been studied in this region. We analyzed the 2002-2006 surge of the Horcones Inferior Glacier, Mount Aconcagua, Argentina, based on medium spatial resolution (15-30 m) satellite images and digital elevation models. During the buildup phase the glacier was stagnant, with velocities lower than 0.1 m/d. In the active-phase velocities reached 14 m/d and the glacier front advanced 3.1 km. At the peak of the active phase (2003-2004), the area-averaged elevation change was -42 m in the reservoir zone (2.53 km2) and +30 m in the receiving zone (3.31 km2). The estimated ice flux through a cross section located at 4175 meter above sea level was 108 m3 during a period of 391 days, a flux that suggests a mean glacier thickness at this location of ~90 m. The depletion phase showed a recovery of the reservoir zone elevation, the down wasting of the receiving zone (-17 m, 2007-2014), and a return to quiescent velocities. The short active phase, the abrupt change in the velocities, and the high level of the proglacial stream indicate a hydrological switch (Alaska type) trigger. The 2002-2006 and 1984-1990 surges of Horcones Inferior were synchronous with the surges of nearby Grande del Nevado Glacier. These events occurred after periods of positive mass balance, so we hypothesize a climate driver.

  11. Caracterización y procedencia de obsidianas de sitios arqueológicos del Centro Oeste de Argentina y Centro de Chile con metodología no destructiva por fluorescencia de Rayos X (XRF Non-destructive x-ray fluorescence (XRF characterization and sourcing of obsidian from archaeological sites in Central West Argentina and Central Chile

    Directory of Open Access Journals (Sweden)

    Víctor Durán

    2012-11-01

    Full Text Available Se presentan los resultados de 101 análisis químicos por fluorescencia de Rayos X efectuados sobre artefactos de obsidiana provenientes de sitios arqueológicos del Centro Oeste Argentino y Chile Central. También se hace una caracterización química de seis fuentes y subfuentes de obsidiana ubicadas en ambientes cordilleranos y extracordilleranos del sur de Mendoza, Neuquén y Chile Central. Con esa información se discuten propuestas referidas a la movilidad y sistemas de intercambio de las sociedades humanas que ocuparon las dos vertientes de la cordillera de Los Andes durante el Holoceno medio y tardío. Los resultados obtenidos confirman que el método no destructivo por XRF es una herramienta válida para determinar el origen y dispersión de las obsidianas arqueológicas.The results of chemical analysis by X-ray Fluorescence (XRF performed on 101 obsidian artifacts from archaeological sites of Central western Argentina and Central Chile are presented. A chemical characterization of six obsidian sources and subsources located in both Andean and extra-Andean environments of Southern Mendoza, Northern Neuquén and Central Chile, is also performed. Based on this information, different proposals related to mobility patterns and exchange systems of human societies that occupied the two slopes of the Andes during the middle and late Holocene are discussed. The results confirm that non-destructive X-ray Fluorescence is a valid tool to determine the origin and dispersal of archaeological obsidian artifacts.

  12. Phylogenetic relationships between telmatobiinids (Anura, Ceratophryidae, Telmatobiinae of central Andes based on morphology of larval and adult stages

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    César Aguilar

    2011-07-01

    Full Text Available Batrachophrynus and Telmatobius are the two genus of Telmatobiinae from the central Andes. Both genera have species with adaptations for life at high altitude in the Andes, with aquatic or semi-aquatic habits in creeks, lagoons and lakes. The objective of this study is to evaluate the phylogenetic relationships between Batrachophrynus and 13 species of Telmatobius from the central Andes using larval and adult morphology including diagnostic characters for Batrachophrynus and Telmatobius, and putative sinapomorphies for Telmatobius. The phylogenetic analysis showed 20 parsimonious trees with 56 steps length. The results of this study hypothesize that the species assigned to Batrachophrynus form a monophyletic group nested within Telmatobius. In this study, most of the synapomorphies that support Telmatobius (including Batrachophrynus come from larval morphology and these sinapomorphies will probably support the whole genus.

  13. What controls millennial-scale denudation rates across the Central Andes?

    Science.gov (United States)

    Zeilinger, Gerold; Korup, Oliver; Schlunegger, Fritz; Kober, Florian

    2015-04-01

    Sustainable planning of erosion control measures in the Central Andes requires robust knowledge about natural denudation rates. We explore a large dataset combining new and published 10Be (and 26Al) catchment-wide denudation rates from a swath at 17 to 19° S spanning the Western Cordillera that rises from sea level to 5500 m elevation; the Altiplano at ~4000 m; the Eastern Cordillera with elevations up to 6500 m; the Interandean Zone; the Subandean Zone; and the Chaco Plain at 300 m. The selected catchments span a large spread regarding morphometric and climate properties where mean slope angles range from 1 to 31°, and mean precipitation from 100 to 3900 mm/a. The denudation rates (0.0036 to 1.93 mm/a) are averaged over millennia, and reveal two to three magnitudes difference across the Central Andes. The regional distribution of denudation rates clearly demonstrates a more complex interaction of geomorphological, geological and meteorological parameters with the dominant geomorphological processes. In order to elucidate the key controls on denudation, we use multivariate statistics such as principal component analysis in order to remove potentially redundant predictors of denudation in the studied catchments. These predictors include catchment elevation, topographic relief, hillslope inclination, mean precipitation, tree cover, specific stream power, channel steepness indices, sinuosity, drainage density and hypsometric index that we derived from the SRTM 90 m Digital Elevation Database, the Tropical Rainfall Measuring Mission (TRMM) data, and the Terra MODIS Vegetation Continuous Fields dataset. Additionally, the rock strength index (PLI) was estimated based on geological units. Preliminary results allow distinguishing five different longitudinal domains of denudation on the basis of climatic regime, hillslope steepness, and the degree of accumulated crustal deformation. We find that the pattern of 10Be catchment-wide denudation rates in the Central Andes

  14. The High Andean Cordillera of central Argentina and Chile along the Piuquenes Pass-Cordon del Portillo transect: Darwin's pioneering observations compared with modern geology La Alta Cordillera de los Andes del centro de Argentina y Chile a lo largo de la transecta del Paso Piuquenes-Cordón del Portillo: Las observaciones pioneras de Darwin comparadas con la geología moderna

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    Laura Giambiagi

    2009-04-01

    Full Text Available The geological observations made by Darwin in 1835 during his crossing of the Andes from Santiago to Mendoza via the Piuquenes Pass and Cordón del Portillo are compared with the present geological knowledge of the Cordillera Principal and Cordillera Frontal at 33°-34°S. The analysis of the complex stratigraphy of the Cordillera Principal, the imbricated structure of the Aconcagua fold and thrust belt, as well as the stratigraphy and structure of the inter mountain foreland Tunuyán Basin, allows to assess the pioneer observations of Darwin. He recognized the old metamorphic basement and the granitoids and volcanic sequences of late Paleozoic to Triassic age of the Cordillera Frontal, established the Cretaceous age of the marine successions cropping out along the eastern Cordillera Principal and studied the conglomeratic deposits associated with the uplift of the Cordillera in the Alto Tunuyán Basin. Based on the study of clast provenance of the synorogenic deposits of the Alto Tunuyán Basin, Darwin recognized that the Cordillera Frontal was uplifted later than the Cordillera Principal. The present knowledge of this sector of the Andean Cordillera confirms his pioneer observations and show that Darwin was one of the first scientists ever in realizing that in an orogenic system the sequence of uplift and deformation proceeds from hinterland towards foreland, according to a process that is exceptionally well-illustrated along the Piuquenes-Cordón del Portillo transect.Las observaciones geológicas efectuadas por Darwin en 1935 durante su cruce de la Cordillera de Los Andes entre Santiago y Mendoza realizado en 1835 a través de los pasos del Portillo y Piuquenes son examinadas y comparadas con el conocimiento actual existente de las Cordilleras Principal y Frontal entre los 33°-34°S. El análisis de la compleja estratigrafía de la Cordillera Principal, la estructura de las diferentes láminas imbricadas de la faja plegada y corrida del

  15. Late Pleistocene glaciation in the Central Andes: Temperature versus humidity control — A case study from the eastern Bolivian Andes (17°S) and regional synthesis

    Science.gov (United States)

    Kull, C.; Imhof, S.; Grosjean, M.; Zech, R.; Veit, H.

    2008-01-01

    A glacier-climate model was used to calculate climatic conditions in a test site on the east Andean slope around Cochabamba (17°S, Bolivia) for the time of the maximum Late Pleistocene glaciation. Results suggest a massive temperature reduction of about - 6.4 °C (+ 1.4/- 1.3 °C), combined with annual precipitation rates of about 1100 mm (+ 570 mm/- 280 mm). This implies no major change in annual precipitation compared with today. Summer precipitation was the source for the humidity in the past, as is the case today. This climate scenario argues for a maximum advance of the paleo-glaciers in the eastern cordillera during the global Last Glacial Maximum (LGM, 20 ka BP), which is confirmed by exposure age dates. In a synthesized view over the central Andes, the results point to an increased summer precipitation-driven Late Glacial (15-10 ka BP) maximum advance in the western part of the Altiplano (18°S-23°S), a temperature-driven maximum advance during full glacial times (LGM) in the eastern cordillera, and a pre- and post-LGM (32 ka BP/14 ka BP) maximum advance around 30°S related to increased precipitation and reduced temperature on the western slope of the Andes. The results indicate the importance of understanding the seasonality and details of the mass balance-climate interaction in order to disentangle drivers for the observed regionally asynchronous past glaciations in the central Andes.

  16. Contenidos de uranio de lavas recientes en el sector sur de los Andes centrales

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    Guerra, N.

    1984-12-01

    Full Text Available We have studied the distribution of U in modern lava -flows of the southern part from the Central Andes (16°-28° S. For a given SiO2, content of the rocks, U abundance increases from west to east in a transects to the Andean Belt, while the depth of the subduction zone increases and the thickness of the continental curst decreases. Besides, U content tends to inerease steadly with the latitude, while the thick of the continental crust and the depth of the seismic zone decreases southward. Thus, on the basis of the available data, we are in a position to suggest that the U behavior in the studied lavas depends on the alkalanity and magmatic history of each volcanic center.

    Se presenta un estudio de distribución de U en lavas modernas del sector sur de los Andes centrales (16°-28° S. Para rocas de contenidos similares en SiO2 la abundancia de U crece de oeste a este en un perfil transversal al cordón andino, mientras que aumenta la profundidad de subducción, y disminuye la potencia de la corteza continental. Además, mientras la potencia de la corteza continental y la profundidad de la zona sísmica de Benioff disminuyen hacia el sur, U tiende a aumentar con la latitud. Así, y basado en los datos disponibles, estamos en posición de sugerir que el comportamiento de U en las rocas estudiadas, depende de la alcalinidad y de la historia magmática de cada centro volcánico.

  17. Subduction and collision processes in the Central Andes constrained by converted seismic phases.

    Science.gov (United States)

    Yuan, X; Sobolev, S V; Kind, R; Oncken, O; Bock, G; Asch, G; Schurr, B; Graeber, F; Rudloff, A; Hanka, W; Wylegalla, K; Tibi, R; Haberland, C; Rietbrock, A; Giese, P; Wigger, P; Röwer, P; Zandt, G; Beck, S; Wallace, T; Pardo, M; Comte, D

    The Central Andes are the Earth's highest mountain belt formed by ocean-continent collision. Most of this uplift is thought to have occurred in the past 20 Myr, owing mainly to thickening of the continental crust, dominated by tectonic shortening. Here we use P-to-S (compressional-to-shear) converted teleseismic waves observed on several temporary networks in the Central Andes to image the deep structure associated with these tectonic processes. We find that the Moho (the Mohorovicić discontinuity--generally thought to separate crust from mantle) ranges from a depth of 75 km under the Altiplano plateau to 50 km beneath the 4-km-high Puna plateau. This relatively thin crust below such a high-elevation region indicates that thinning of the lithospheric mantle may have contributed to the uplift of the Puna plateau. We have also imaged the subducted crust of the Nazca oceanic plate down to 120 km depth, where it becomes invisible to converted teleseismic waves, probably owing to completion of the gabbro-eclogite transformation; this is direct evidence for the presence of kinetically delayed metamorphic reactions in subducting plates. Most of the intermediate-depth seismicity in the subducting plate stops at 120 km depth as well, suggesting a relation with this transformation. We see an intracrustal low-velocity zone, 10-20 km thick, below the entire Altiplano and Puna plateaux, which we interpret as a zone of continuing metamorphism and partial melting that decouples upper-crustal imbrication from lower-crustal thickening. PMID:11140679

  18. Neotectónica de los Andes entre 1°N y 47°S (Ecuador, Bolivia y Chile: una revisión

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    A. Lavenu

    2006-12-01

    Full Text Available En los Andes, el estudio del estado de deformación instantánea pleistocena permite reconocer diferentes tipos de comportamientos de la placa continental de Sudamérica a lo largo del margen activo. En Ecuador, el bloque costero está empujado hacia el norte. La costa es afectada por una extensión de dirección N-S, resultado del levantamiento del borde del continente por la subducción de la dorsal asísmica de Carnegie. Por otra parte, la cadena principal sufre una deformación compresiva de dirección E-W. Los altos Andes de Bolivia han sido afectados por una deformación pleistocena extensional de dirección N-S. En el centro y sur de Chile, se observa una partición de la deformación: la zona de antearco ha sido afectada por una compresión N-S y la zona de intraarco por transpresión de dirección NE-SW.

  19. Late cenozoic tectonic and geomorphic evolution of the Patagonian Andes between 42oS and 52oS, southern Chile assessed using fission-track thermochronology

    International Nuclear Information System (INIS)

    Fission-track (FT) analysis has been applied in the Patagonian Andes of southern Chile to assess the late Cenozoic geomorphic and tectonic response of the overriding plate to subduction of the Chile rise active oceanic spreading centre (Thomson et al., 2001). The timing and nature of tectonic uplift and denudation along the southern parts of the major transpression intra-arc Liquine-Ofqui fault (LOF) system have also been investigated (Thomson, 2001, submitted). Results from 130 FT ages (72 zircon and 58 apatite ages) and 39 apatite track length measurements reveal initiation of rapid cooling and denudation at ca. 30 Ma at the western margin of southern continental South America. This was followed by a ca. 200km eastward migration of the locus of maximum denudation to the position of the present day topographic divide between ca. 30 Ma and ca. 12 to 10 Ma. East of the Andean divide less than 3 km of denudation has occurred since the Late Cretaceous. Enhanced denudation is interpreted to be the result of increased tectonic uplift driven by a large increase in convergence rates at ca. 28 to 26 Ma that triggered orographically enhanced precipitation on the west-side of the Patagonian Andes allowing increased erosion by fluvial incision and mass transport processes. The eastward migration of the locus of maximum denudation can be related to either coeval eastward migration of the retro-arc deformation front, the effects of subduction erosion in the overriding plate at the Peru-Chile trench or shallowing of the angle of subduction. Away from the influence of the LOF the process of spreading centre subduction and collision itself coincides with an overall slow-down in denudation rates in the overriding plate most likely caused by a major reduction in the main tectonic force driving tectonic uplift in the upper plate to subduction. In contrast to the Andes south of ca. 46oS, increased cooling and denudation related to transpression induced rock uplift and erosion along

  20. Paleoenvironmental change in central Chile as inferred from OSL dating of ancient coastal sand dunes

    Science.gov (United States)

    Andrade, Belisario; Garcia, Juan L.; Lüthgens, Christopher; Fiebig, Markus

    2013-04-01

    To present day, the climatic and geographic expression of glacials and interglacials in the semiarid coast of central Chile remains unclear. The lack of well dated paleoclimatic records has up to now precluded firm conclusions whether maximum glacials evident in the Andes mountain range probably coincide with wetter (e.g., pluvials) or drier conditions at the coast. The natural region locally known as "Norte Chico" represents a transitional semiarid area between the extreme Atacama Desert to the North and the wetter, Mediterranean-like type of climate, to the South. In this semiarid region of Chile several generations of eolian sand dunes, some of them separated by paleosoils, have been preserved. In addition to the occurrence of paleosoils, thick debris flow deposits in some places overly ancient dune bodies, likely indicating significant environmental changes during the formation of these archives. However, the exact timing of these processes within the mid to late Pleistocene and Holocene is still unclear. A key aspect is that some of the ancient dunes are recently hanging above rocky coastlines, where no supply of sand exists today, likely implying their formation during a lower than present, probably glacio-eustatically induced sea level. The location of the research area in a key mid-latitude region of the eastern Pacific in combination with the preserved landform record offers a chance to reconstruct climatic shifts during the Quaternary by studying the variability of morphogenetic conditions throughout time, in order to promote knowledge about possible forcing factors driving climatic variability. Within this pilot study, samples for optically stimulated luminescence (OSL) dating were taken from three different stratigraphic sections that denote a complex environmental variability as indicated by paleosoils and debris flow units intercalated in ancient sand dunes. First dating results inferred from OSL measurements using a post-IR IRSL (pIRIR) protocol for

  1. Evidence of proterozoic crust under the coastal Cordillera of Central Chile: Grenville age xenocrystic zircons in cretaceous volcanic rocks

    International Nuclear Information System (INIS)

    In the central Andes, Proterozoic basement rocks outcrop in isolated areas from beneath a Mesozoic and Cenozoic cover in southern Peru, northernmost Chile, Bolivia, and in northwestern Argentina. Their role in Andean magmatism and metallogenesis is well documented. In the southern Central Andes, Proterozoic rocks are so far known to outcrop in Argentina, east of the continental divide. In the course of U-Pb dating of the bimodal volcanic and sub-volcanic host rocks for Mesozoic manto-type copper deposits, we have encountered xenocrystic zircon with Proterozoic and Paleozoic ages. In the Punta del Cobre Cu-Fe (Au) District (27o30' S / 70o15' W) 22 km south of Copiapo xenocrystic zircon in the Lower Cretaceous host dacite yields ca. 1 Ga ages. In the El Soldado Cu District, (32o38' S /71o04' W), 120 km northwest of Santiago, scarce and strongly resorbed zircon crystals in the Lower Cretaceous host rhyodacite yield ages of 0.5 to 1.3 Ga. The early Cretaceous bimodal volcanic and subvolcanic rocks, which consists of primitive calc-alkaline basalts and rhyodacites, display geochemical evidence of crustal contamination. Our results suggest that, during their formation and ascent, the felsic magmas picked up zircons in the Proterozoic and Paleozoic crystalline basement of the Coastal Cordillera. The presence of Proterozoic (Grenville age) basement underlying localities as close as 30 km from the Pacific coast has implications for the extent and age of the Chilenia Terrane and gives further credence to correlation models that juxtapose eastern North America (Laurentia) and southwestern South America (Gondwana) during the Late Proterozoic (au)

  2. Tectonic and lithological controls on denudation rates in the central Bolivian Andes

    Science.gov (United States)

    Kober, F.; Zeilinger, G.; Hippe, K.; Marc, O.; Lendzioch, T.; Grischott, R.; Christl, M.; Kubik, P. W.; Zola, R.

    2015-08-01

    The topographic signature of a mountain belt depends on the interplay of tectonic, climatic and erosional processes, whose relative importance changes over times, while quantifying these processes and their rates at specific times remains a challenge. The eastern Andes of central Bolivia offer a natural laboratory in which such interplay has been debated. Here, we investigate the Rio Grande catchment which crosses orthogonally the eastern Andes orogen from the Eastern Cordillera into the Subandean Zone, exhibiting a catchment relief of up to 5000 m. Despite an enhanced tectonic activity in the Subandes, local relief, mean and modal slopes and channel steepness indices are largely similar compared to the Eastern Cordillera and the intervening Interandean Zone. Nevertheless, a dataset of 57 new cosmogenic 10Be and 26Al catchment wide denudation rates from the Rio Grande catchment reveals up to one order of magnitude higher denudation rates in the Subandean Zone (mean 0.8 mm/yr) compared to the upstream physiographic regions. We infer that tectonic activity in the thrusting dominated Subandean belt causes higher denudation rates based on cumulative rock uplift investigations and due to the absence of a pronounced climate gradient. Furthermore, the lower rock strength of the Subandean sedimentary units correlates with mean slopes similar to the ones of the Eastern Cordillera and Interandean Zone, highlighting the fact, that lithology and rock strength can control high denudation rates at low slopes. Low denudation rates measured at the outlet of the Rio Grande catchment (Abapo) are interpreted to be a result of a biased cosmogenic nuclide mixing that is dominated by headwater signals from the Eastern Cordillera and the Interandean zone and limited catchment sediment connectivity in the lower river reaches. Therefore, comparisons of short- (i.e., sediment yield) and millennial denudation rates require caution when postulating tectonic and/or climatic forcing without

  3. Nitrogen fixation in four dryland tree species in central Chile

    International Nuclear Information System (INIS)

    Results are presented from a 5-year experiment using 15N-enriched fertilizer to determine N2 fixation in four tree species on degraded soils in a Mediterranean-climate region of central Chile in which there are 5 months of drought. Species tested included three slow-growing but long-lived savannah trees native to southers South America, (acacia caven, Prosopic alba and P. chilensis; Mimosoideae), and Tagasaste (Chamaecytisus proliferus ssp. palmensis; Papilonoideae), a fast-growing but medium-lived tree from the Canary Islands. Tagasaste produced four- to twenty-fold more biomass than the other species, but showed declining N2 fixation and biomass accumulation during the 5th year, corresponding to the juvenile-to-adult developmental transition. Nitrogen content was significantly higher in Tagasaste and Acacia caven than in the other species. The data revealed inter-specific differences in resource allocation and phenology of N2 fixation rarely detailed for woody plants in dryland regions. (author)

  4. The Continental Distillery: Building Thick Continental Crust in the Central Andes (Invited)

    Science.gov (United States)

    Wagner, L. S.; Beck, S. L.; Zandt, G.; Long, M. D.; Tavera, H.; Minaya, E.; Biryol, C. B.; Bishop, B.; Eakin, C. M.; Franca, G.; Knezevic Antonijevic, S.; Kumar, A.; Ryan, J. C.; Scire, A. C.; Ward, K. M.; Young, B. E.

    2013-12-01

    The formation of stable continental crust and the associated development and destruction of mantle lithospheric roots is central to our understanding of plate tectonics, both at its inception and as an ongoing process today. Subduction zones play an important role in the creation and refinement of continental crust, and also serve as a possible mechanism for the removal of residual mantle material. The central Andes provide an intriguing laboratory for the study of these processes. Up to 400 km wide, 1500 km long, and with an average elevation of 4 km, the Altiplano Plateau is the largest orogen on earth associated with an ocean-continent subduction zone. This is much larger than adjacent 'normal' sections of the Andes, raising the question of why this portion of South American crust became so much more substantial than surrounding areas. Over the past several years, new seismic data have made it possible for us to develop a more complete picture of the lithospheric and asthenospheric processes involved in the development of the Altiplano Plateau and the adjacent narrower orogen further to the north. The 'Central Andean Uplift and the Geodynamics of High Topography' (CAUGHT) comprises in part a broadband deployment of 50 stations across the northern flank of the Altiplano Plateau in southern Peru and northern Bolivia. The adjacent 'PerU Lithosphere and Slab Experiment' (PULSE) includes 40 broadband stations that cover the region directly north of the CAUGHT deployment, encompassing the northern edge of the Altiplano, the transition to 'normal' width orogen, and the transition in slab geometry from normal to flat from south to north across the study area. Uplift of the Altiplano Plateau is likely due to some combination shortening, isostasy due to lithospheric destruction or changes in crustal density, magmatic addition to the crust, and/or flow within the thickened crust. Our studies indicate pervasive low velocities across the Altiplano consistent with a

  5. A survey of volcano deformation in the central Andes using InSAR: Evidence for deep, slow inflation

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2001-12-01

    We use interferometric synthetic aperture radar (InSAR) to survey about 50 volcanos of the central Andes (15-27o S) for deformation during the 1992-2000 time interval. Because of the remote location of these volcanos, the activity of most are poorly constrained. Using the ERS-1/2 C-band radars (5.6 cm), we observe good interferometric correlation south of about 21o S, but poor correlation north of that latitude, especially in southern Peru. This variation is presumably related to regional climate variations. Our survey reveals broad (10's of km), roughly axisymmetric deformation at 2 volcanic centers with no previously documented deformation. At Uturuncu volcano, in southwestern Bolivia, the deformation rate can be constrained with radar data from several satellite tracks and is about 1 cm/year between 1992 and 2000. We find a second source of volcanic deformation located between Lastarria and Cordon del Azufre volcanos near the Chile/Argentina border. There is less radar data to constrain the deformation in this area, but the rate is also about 1 cm/yr between 1996 and 2000. While the spatial character of the deformation field appears to be affected by atmosphere at both locations, we do not think that the entire signal is atmospheric, because the signal is observed in several interferograms and nearby edifices do not show similar patterns. The deformation signal appears to be time-variable, although it is difficult to determine whether this is due to real variations in the deformation source or atmospheric effects. We model the deformation with both a uniform point-source source of inflation, and a tri-axial point-source ellipsoid, and compare both elastic half-space and layered-space models. We also explore the effects of local topography upon the deformation field using the method of Williams and Wadge (1998). We invert for source parameters using the global search Neighborhood Algorithm of Sambridge (1998). Preliminary results indicate that the sources at both

  6. EL ESTADO ACTUAL DEL HUEMUL (HIPPOCAMELUS BISULCUS EN CHILE CENTRAL CURRENT STATUS OF THE HUEMUL (HIPPOCAMELUS BISULCUS IN CENTRAL CHILE

    Directory of Open Access Journals (Sweden)

    Anthony Povilitis

    2002-01-01

    Full Text Available La única población sobreviviente del huemul en Chile central (Los Nevados de Chillán se encuentra en un descenso clásico hacia la extinción. Se utilizan los datos de prospecciones en terreno por el período entre 1975 a 2002 para estimar el tamaño, la estructura espacial y la tendencia de la población. Un análisis de la población en 1997 arrojó un mínimo de 60 huemules en 12 sitios, y una declinación de un 58% en la población durante un período de dos décadas. Prospecciones recientes entre 1998-2002 indican que la población de huemules ha continuado disminuyendo a 40 individuos en 11 sitios, lo que representa un descenso adicional de un 33%. Desde el año 1987, los huemules han desaparecido de 5, y posiblemente 8, sitios de hábitat primario. Solamente un sitio, el del Río Niblinto que es protegido, muestra un grupo del huemul más o menos estable. Las amenazas al huemul y a su hábitat, tal como los impactos del ganado doméstico, la urbanización, el desarrollo recreativo, la presencia de perros domésticos y las actividades industriales siguen sin disminución en la gran mayoría de los 26 sitios de hábitat primario necesario para la recuperación del huemul. Los datos actuales muestran claramente que una compaña de conservación más amplia es necesaria para resguardar y recuperar la especie en Chile central. Se requieren proteger los sitios de hábitat primario y los corredores conectantes de hábitat del huemul. Para realizar tal objetivo, se necesitan un fuerte compromiso e inversión financiera del gobierno y del sector privado. La creación de un nuevo parque nacional o gran reserva para el huemul y la biodiversidad en el sector de Los Nevados de Chillán, con beneficios relacionados al turismo, la educación pública, e investigaciones científicas, podría ayudar a atraer los recursos financieros que se necesitan para un programa exitoso de conservaciónABSTRACT The only surviving population of huemul in central

  7. Surface uplift and convective rainfall along the southern Central Andes (Angastaco Basin, NW Argentina)

    Science.gov (United States)

    Pingel, Heiko; Mulch, Andreas; Alonso, Ricardo N.; Cottle, John; Hynek, Scott A.; Poletti, Jacob; Rohrmann, Alexander; Schmitt, Axel K.; Stockli, Daniel F.; Strecker, Manfred R.

    2016-04-01

    Stable-isotopic and sedimentary records from the orogenic Puna Plateau of NW Argentina and adjacent intermontane basins to the east furnish a unique late Cenozoic record of range uplift and ensuing paleoenvironmental change in the south-central Andes. Today, focused precipitation in this region occurs along the eastern, windward flanks of the Eastern Cordillera and Sierras Pampeanas ranges, while the orogen interior constitutes high-elevation regions with increasingly arid conditions in a westward direction. As in many mountain belts, such hydrologic and topographic gradients are commonly mirrored by a systematic relationship between the oxygen and hydrogen stable isotope ratios of meteoric water and elevation. The glass fraction of isotopically datable volcanic ash intercalated in sedimentary sequences constitutes an environmental proxy that retains a signal of the hydrogen-isotopic composition of ancient precipitation. This isotopic composition thus helps to elucidate the combined climatic and tectonic processes associated with topographic growth, which ultimately controls the spatial patterns of precipitation in mountain belts. However, between 25.5 and 27°S present-day river-based hydrogen-isotope lapse rates are very low, possibly due to deep-convective seasonal storms that dominate runoff. If not accounted for, the effects of such conditions on moisture availability in the past may lead to misinterpretations of proxy-records of rainfall. Here, we present hydrogen-isotope data of volcanic glass (δDg), extracted from 34 volcanic ash layers in different sedimentary basins of the Eastern Cordillera and the Sierras Pampeanas. Combined with previously published δDg records and our refined U-Pb and (U-Th)/He zircon geochronology on 17 tuff samples, we demonstrate hydrogen-isotope variations associated with paleoenvironmental change in the Angastaco Basin, which evolved from a contiguous foreland to a fault-bounded intermontane basin during the late Mio

  8. Seismic imaging of a convergent continental margin and plateau in the central Andes (Andean Continental Research Project 1996 (ANCORP'96))

    OpenAIRE

    Onno Oncken; Stephan V. Sobolev; Manfred Stiller; Günter Asch; Christian Haberland; James Mechie; Xiaohui Yuan; E. Lüchen; P. Giese; P. Wigger; Stefan Lüth; E. Scheuber; H.-J. Götze; H. Brasse; S. Buske

    2003-01-01

    A 400-km-long seismic reflection profile (Andean Continental Research Project 1996 (ANCORP'96)) and integrated geophysical experiments (wide-angle seismology, passive seismology, gravity, and magnetotelluric depth sounding) across the central Andes (21°S) observed subduction of the Nazca plate under the South American continent. An east dipping reflector (Nazca Reflector) is linked to the down going oceanic crust and shows increasing downdip intensity before gradual breakdown below 80 km. We ...

  9. A glaciological baseline for the upper Olivares basin, Chilean Central Andes

    Science.gov (United States)

    Loriaux, T.; Bown, F.; Burger, F.; Cisternas, S.; Gacitúa, G.; Hernández, J.; Malmros, J.; Muñoz, C.; Oberreuter, J.; Rivera, A.; Silva, R.

    2013-12-01

    Santiago de Chile, with near 6.7 million of inhabitants, is located at the foot of the Andes, in the Maipo river basin, where there are approximately 424 km2 of ice, being the biggest glaciers, those located at the upper Olivares basin. Very little has been researched in recent years about the ongoing changes taking place in the area or about the glacier meltwater contribution or about the human impact on the glaciers. In order to tackle this deficiency, we began a research program in 2012, aiming to complete a glaciological baseline for this area, including glacier mass, energy and hydrological studies. For this purpose, we have established a detailed monitoring program on two glaciers where we installed 3 automatic weather stations, two arrays of stakes for mass balance studies, two automatic photographic cameras for monitoring albedo changes and two runoff stations, among several other instruments. Also, we have surveyed 5 glaciers with our airborne radar and lidar systems, allowing mapping their surface topographies at different seasons and the bedrocks underneath the ice. Analysis of satellite images shows generalized glacier area shrinkage, with a mean area lost of 25.5% since 1967 (total of 68.6 km2 in 1967 among 6 studied glaciers). The collected radar ice thickness data (maximum ice thickness of 223 m), allowed calculating a total volume of water equivalent of 3 km3 storage in 5 main glaciers of the basin. The GPS surveys of several stakes resulted in surface ice velocities between 1 and 5 m/yr. The mass balance studies showed high summer ablation rates, with an important role of sublimation, expressed as penitentes with heights of up to 1.5 m. Runoff contributed by Olivares Alfa glacier averaged 461 l/s between January and April 2013 with peaks of up to 2000 l/s, confirming the importance of glacier meltwater for the basin during summer months (January-March). The above numbers are some of the results obtained in the area, illustrating the importance of

  10. Miocene Vetigastropoda and Neritimorpha (Mollusca, Gastropoda) of central Chile

    Science.gov (United States)

    Nielsen, Sven N.; Frassinetti, Daniel; Bandel, Klaus

    2004-09-01

    Species of Vetigastropoda (Fissurellidae, Turbinidae, Trochidae) and one species of Neritimorpha (Neritidae) from the Navidad area, south of Valparaı´so, and the Arauco Peninsula, south of Concepción, are described. Among these, the Fissurellidae comprise Diodora fragilis n. sp., Diodora pupuyana n. sp., two additional unnamed species of Diodora, and a species resembling Fissurellidea. Turbinidae are represented by Cantrainea sp., and Trochidae include Tegula (Chlorostoma) austropacifica n. sp., Tegula (Chlorostoma) chilena n. sp., Tegula (Chlorostoma) matanzensis n. sp., Tegula (Agathistoma) antiqua n. sp., Bathybembix mcleani n. sp., Gibbula poeppigii [Philippi, 1887] n. comb., Diloma miocenica n. sp., Fagnastesia venefica [Philippi, 1887] n. gen. n. comb., Fagnastesia matanzana n. gen. n. sp., Calliostoma mapucherum n. sp., Calliostoma kleppi n. sp., Calliostoma covacevichi n. sp., Astele laevis [Sowerby, 1846] n. comb., and Monilea riorapelensis n. sp. The Neritidae are represented by Nerita (Heminerita) chilensis [Philippi, 1887]. The new genus Fagnastesia is introduced to represent low-spired trochoideans with a sculpture of nodes below the suture, angulated whorls, and a wide umbilicus. This Miocene Chilean fauna includes genera that have lived at the coast and in shallow, relatively warm water or deeper, much cooler water. This composition therefore suggests that many of the Miocene formations along the central Chilean coast consist of displaced sediments. A comparison with different fossil and Recent faunas from around the Pacific and South America indicates that the vetigastropod and neritid fauna from the Miocene of Chile has only minor affinities with taxa living near New Zealand, Argentina, and the tropical eastern Pacific at that time.

  11. Selenium concentration in compartments of aquatic ecosystems in Central Chile

    Energy Technology Data Exchange (ETDEWEB)

    Pinochet, H.; Gregori, I. de; Cavieres, M.F. [Catholic University of Valparaiso, Valparaiso (Chile). Chemical Institute

    2002-07-01

    A study was conducted during 1995-96 to evaluate Se concentration in water, sediment, and plants from aquatic ecosystems of central Chile, an area particularly affected by mining activities. Samples were collected from Panquehue, Chagres, and Ocoa along the Acongua River (presumably receives discharges from a copper refinery and a copper mine). Samples were also collected from one site on the Puchuncavi Stream (directly contaminated by both a coal power plant and a copper refinery). In addition, samples were also collected from one site on the Limache Stream (an urban area with no Se-contaminating sources). The sediment and plant samples collected in Puchuncavi had higher Se levels, which were statistically different to the concentration in samples from other sites. Sediments from Puchuncavi and Ocoa had the highest levels of Se (520 plus or minus 46 and 440 plus or minus 10 {mu} g/kg, respectively) while the plant (Jussiaea repens (Ludwigia repens)) collected in Puchuncavi had an Se concentration 6.5 times higher than the sample collected in Panquehue (116 plus or minus 154 and 182 plus or minus 54 {mu} g/kg, respectively). Puchuncavi water had more acidic pH than water from the other sites thus decreasing Se solubility. Se concentrations in sediment and water collected in Chagres were lower than the concentration determined in sediment and water from either Ocoa or Panquehue. Plant/water and plant/sediment accumulation factors and a sediment/water distribution factor were similar for all sampling sites, except Puchuncavi (accumulation and distribution factors are higher than at the other sites). Hydrocotyle ranunculoides had practically the same plant/sediment accumulation factor at all sites while the accumulation factor for J. repens varied according to site. The samples collected in the Limache stream had Se at equal or even higher concentration than the other samples collected from presumably contaminated sites (except Puchuncavi). 19 refs.

  12. Chile.

    Science.gov (United States)

    1992-05-01

    The background notes on Chile provide a statistical summary of the population, geography, government, and the economy, and more descriptive text on the history, population, government, economy, defense, and foreign relations. In brief, Chile has 13.3 million Spanish Indian (Mestizos), European, and Indian inhabitants and an annual growth rate of 1.6%. 96% are literate. Infant mortality is 18/1000. 34% of the population are involved in industry and commerce, 30% in services, 19% in agriculture and forestry and fishing, 7% in construction, and 2% in mining. The major city is Santiago. The government, which gained independence in 1810, is a republic with executive, legislative, and judicial branches. There are 12 regions. There are 6 major political parties. Suffrage is universal at 18 years. Gross domestic product (GDP) is $29.2 billion. The annual growth rate is 5% and inflation is 19%. Copper, timber, fish, iron ore, nitrates, precious metals, and molybdenum are its natural resources. Agricultural products are 9% of GDP and include wheat, potatoes, corn, sugar beets, onions, beans, fruits, and livestock. Industry is 21% of GDP and includes mineral refining, metal manufacturing, food and fish processing, paper and wood products, and finished textiles. $8.3 billion is the value of exports and $7 billion of imports. Export markets are in Japan, the US, Germany, Brazil, and the United Kingdom. Chile received $3.5 billion in economic aid between 1949-85, but little in recent years. 83% live in urban centers, principally around Santiago. Congressional representation is made on the basis of elections by a unique binomial majority system. Principal government officials are identified. Chile has a diversified free market economy and is almost self-sufficient in food production. The US is a primary trading partner. 49% of Chile's exports are minerals. Chile maintains diplomatic relations with 70 countries, however, relations are strained with Argentina and Bolivia. Relations

  13. Future runoff from glacierized catchments in the Central Andes could substantially decrease

    Science.gov (United States)

    Kronenberg, Marlene; Schauwecker, Simone; Huggel, Christian; Salzmann, Nadine; Drenkhan, Fabian; Frey, Holger; Giráldez, Claudia; Gurgiser, Wolfgang; Kaser, Georg; Suarez, Wilson; García Hernández, Javier; Fluixá-Sanmartín, Javier; Ayros, Edwin; Rohrer, Mario

    2016-04-01

    In Peru, about 50% of the energy is produced from hydropower plants. An important amount of this energy is produced with water from glaciated catchments. In these catchments river streamflow is furthermore needed for other socio-economic activities such as agriculture. However, the amount and seasonality of water from glacial melt is expected to undergo strong changes. As glaciers are projected to further decline with continued warming, runoff will become more and more sensitive to possible changes in precipitation patterns. Moreover, as stated by a recent study (Neukom et al., 2015), wet season precipitation sums in the Central Andes could decrease up to 19-33 % by the end of the 21st century compared to present-day conditions. Here, we investigate future runoff availability for selected glacierized catchments in the Peruvian Andes. In a first step, we apply a simplified energy balance and runoff model (ITGG-2.0-R) for current conditions. Thereafter, we model future runoff for different climate scenarios, including the possibility of strongly reduced precipitation. Preliminary findings indicate (i) changes in the seasonal distribution of runoff and (ii) significant reductions of the annual runoff in future for the mentioned scenario with significant precipitation decreases. During early phases of glacier recession, melt leads to increased runoff - respectively compensates for the precipitation reduction in the corresponding scenario - depending on the fraction of catchment glaciation. Glaciers are acting as natural water reservoirs and may buffer the decreasing precipitation in glacierized catchments for a limited period. However, strongly reduced precipitation will have noticeable consequences on runoff, particularly when glacier melt contribution gets smaller and finally is completely missing. This will have consequences on the water availability for hydropower production, agriculture, mining and other water uses. Critical conditions may emerge in particular

  14. Use of time series of optical and SAR images in the estimation of snow cover for the optimization of water use in the Andes of Argentina and Chile

    Science.gov (United States)

    Salinas de Salmuni, Graciela; Cabezas Cartes, Ricardo; Menicocci, Felix

    2014-05-01

    This paper describes the progress in the bilateral cooperation project between academic and water resources management institutions from the Andes region of Argentina and Chile. The study zone is located in fragile ecosystems and mountain areas of the Andes (limit zone between the Province of San Juan, Argentina, and the IV Region of Coquimbo, Chile), with arid climate, where snow precipitates in the headwaters of watershed feed the rivers of the region by melting, which are the only source of water for human use, productive and energetic activities, as well as the native flora and fauna. CONAE, the Argentine Space Agency, participates in the Project through the provision of satellite data to the users and by this it contributes to ensuring the continuity of the results of the project. Also, it provides training in digital image processing. The project also includes the participation of water resource management institutions like Secretaria de Recursos Hidricos of Argentina and the Centro de Información de Recursos Naturales de Chile (CIREN), and of academic institution like the University of San Juan (Argentina) and University of La Serena (Chile). These institutions benefit from the incorporation of new methodologies advanced digital image processing and training of staff (researcher, lecturers, PhD Students and technical). Objectives: 1-Improve water distribution incorporating space technology for application in the prediction models of the stream flow. 2- Conduct an inventory of glaciers as well as studies in selected watersheds in the Andean region, aiming to know the water resource, its availability and potential risks to communities in the region. 3. Contribute to vulnerability studies in biodiversity Andean watersheds. Results: For estimation Snow cover Area, the MODIS images are appropriate due their high temporal resolution and allows for monitoring large areas (greater than 10 km) The proposed methodology (Use of snow index, NSDI) is appropriate for

  15. The paradigm of paraglacial megafans of the San Juan river basin, Central Andes, Argentina

    Science.gov (United States)

    Suvires, Graciela M.

    2014-11-01

    The spatial distribution and several morphometric characteristics of the Quaternary alluvial fans of the San Juan River, in the province of San Juan, at the Central and Western part of Argentina, have been studied to classify them as paraglacial megafans, as well to ratify its depositional environmental conditions. The high sedimentary load exported by San Juan river from the Central Andes to the foreland depressions is estimated about 3,682,200 hm3. The large alluvial fans of Ullum-Zonda and Tulum valleys were deposited into deep tectonic depressions, during the Upper Pleistocene deglaciation stages. The outcome of collecting remotely sensed data, map and DEM data, geophysical data and much fieldwork gave access to morphometric, morphographic and morphogenetic data of these alluvial fans. The main drainage network was mapped on processed images using QGis (vers.2.0.1). Several fan morphometric parameters were measured, such as the size, the shape, the thickness, the surface areas and the sedimentary volume of exported load. The analyzed fans were accumulated in deep tectonic depressions, where the alluvium fill reaches 700 to 1200 m thick. Such fans do not reach the large size that other world megafans have, and this is due to tectonic obstacles, although the sedimentary fill average volume surpasses 514,000 hm3. The author proposes to consider Ullum-Zonda and Tulum alluvial fans as paraglacial megafans. According to the stratigraphic relationships of the tropical South American Rivers, the author considers that the San Juan paraglacial megafans would have occurred in the period before 24 ka BP , possibly corresponding to Middle Pleniglacial (ca 65-24ka BP). They record colder and more humid conditions compared with the present arid and dry conditions.

  16. VariaciOn morfolOgica de Phacelia secunda J.F. Gmel. (Hydrophyllaceae a lo largo de un gradiente a ltitudinal en Chile central Morphological variation of Phacelia secunda J.F. Gmel. (Hydrophyllaceae along an altitudinal gradient in central Chile

    Directory of Open Access Journals (Sweden)

    Lohengrin A. Cavieres

    2000-01-01

    Full Text Available Phacelia secunda J.F. Gmel. (Hydrophyllaceae es una hierba perenne que en Chile, y también en Argentina, presenta una amplia distribución, habitando desde Parinacota (18°S hasta Tierra del Fuego (54°S, y desde el nivel del mar hasta la alta cordillera. En este estudio se documentan algunas variaciones morfológicas que presenta esta especie a lo largo de un gradiente altitudinal desde los 1.600 m a los 3.400 m en los Andes de Chile central (33°S. Se encontró que el diámetro de las rosetas aumenta significativamente con la altitud, al igual que el número de inflorescencias por individuo y la longitud de la pubescencia. Por el contrario, la altura de las inflorescencias disminuye con la altitud. La tendencia a privilegiar el crecimiento vertical a bajas altitudes y el crecimiento horizontal en altitudes mayores sería una respuesta adaptativa a las frías condiciones de los ambientes de alta montaña. Del mismo modo, el aumento en la longitud de la pubescencia con la altitud sería una adaptación para mantener un balance térmico positivo y evitar los excesos de radiación en dichos ambientesPhacelia secunda J.F. Gmel. (Hydrophyllaceae is a perennial herb that both, in Chile and Argentina, shows a wide distributional range, inhabiting from Parinacota (18°S to Tierra del Fuego (54°S, and from the sea level up to the high Andes. In this study some morphological variations along an altitudinal gradient from 1600 to 3400 m in Andes of central Chile (33°S are reported. The diameter of the rosettes significantly increased with elevation, as well as the number of inflorescences per individual and the longitude of pubescence. In contrast, the height of inflorescences decreased with elevation. Tendencies for privileging vertical growth at lower elevations and horizontal growth at higher elevations would be adaptations to the cold and harsh climate of high mountain habitats. In a similar vein, the increase in the longitude of pubescence with

  17. Preliminary Results From the CAUGHT Experiment: Investigation of the North Central Andes Subsurface Using Receiver Functions and Ambient Noise Tomography

    Science.gov (United States)

    Ryan, J. C.; Ward, K. M.; Porter, R. C.; Beck, S. L.; Zandt, G.; Wagner, L. S.; Minaya, E.; Tavera, H.

    2011-12-01

    Jamie Ryan, Kevin M. Ward, Ryan Porter, Susan Beck, George Zandt, Lara Wagner, Estela Minaya, and Hernando Tavera The University of Arizona The University of North Carolina San Calixto Observatorio, La Paz, Bolivia IGP, Lima, Peru In order to investigate the interplay between crustal shortening, lithospheric removal, and surface uplift we have deployed 50 broadband seismometers in northwestern Bolivia and southern Peru as part of the interdisciplinary Central Andean Uplift and Geodynamics of High Topography (CAUGHT) project. The morphotectonic units of the central Andes from west to east, consist of the Western Cordillera, the active volcanic arc, the Altiplano, an internally drained basin (~4 km elevation), the Eastern Cordillera, the high peaks (~6 km elevation) of an older fold and thrust belt, the Subandean zone, the lower elevation active fold and thrust belt, and the foreland Beni basin. Between northwestern Bolivia and southern Peru, the Altiplano pinches out north of Lake Titicaca as the Andes narrow northward. The CAUGHT seismic instruments were deployed between 13° to 18° S latitudes to investigate the crust and mantle lithosphere of the central Andes in this transitional zone. In northwest Bolivia, perpendicular to the strike of the Andes, there is a total of 275 km of documented upper crustal shortening (15° to 17°S) (McQuarrie et al, 2008). Associated with the shortening is crustal thickening and possibly lithospheric removal as the thickening lithospheric root becomes unstable. An important first order study is to compare upper crustal shortening estimates with present day crustal thickness. To estimate crustal thickness, we have calculated receiver functions using an iterative deconvolution method and used common conversion point stacking along the same profile as the geologically based shortening estimates. In our preliminary results, we observed a strong P to S conversion corresponding to the Moho at approximately 60-65 km depth underneath the

  18. Ten new species from the Patagonian Andes (Argentina and Chile), mostly belonging to a newly designated Stigmella purpurimaculae group (Lepidoptera: Nepticulidae).

    Science.gov (United States)

    Stonis, Jonas R; Remeikis, Andrius; Davis, Donald R

    2014-01-01

    Ten new Stigmella Schrank species are described: Stigmella purpurimaculae Remeikis & Stonis, sp. nov., S. cana Remeikis & Stonis, sp. nov., S. truncata Remeikis & Stonis, sp. nov., S. sceptra Remeikis & Stonis, sp. nov., S. concreta Remeikis & Stonis, sp. nov., S. pseudoconcreta Remeikis & Stonis, sp. nov., S. quadrata Remeikis & Stonis, sp. nov. (all belonging to the newly designated S. purpurimaculae group), and S. semilactea Remeikis & Stonis, sp. nov., S. brutea Remeikis & Stonis, sp. nov., S. pseudodigitata Remeikis & Stonis, sp. nov. (not attributed to a species group) are described from the Andes (Patagonia: Argentina and Chile). For the species of the purpurimaculae group, a partial reduction of phallus, dentate cornuti, and strong development of utriculus (which can be equal or longer of the corpus bursae) are characteristic. Some of the species of the purpurimaculae group were collected near Nothofagus pumilio (Poepp. & Endl.) Krasser, Nothofagaceae, but there is still no confirmation that Nothofagus is a host-plant. All new Stigmella species are illustrated with photographs and drawings of the adults and genitalia. PMID:25543936

  19. Chile.

    Science.gov (United States)

    1986-04-01

    In 1985, Chile's population stood at 12 million, with an annual growth rate of 1.7%. 1984's infant mortality rate was 20/1000 live births and life expectancy was 67 years. The literacy rate was 94%. Of the work force of 3,841,000 in 1985, 15.9% were engaged in agriculture, forestry, and fishing; 31.3% were employed in industry and commerce; 38.6% were in the service sector; 8.7% worked in mining; and 4.4% were employed in construction. Chile's military junta is scheduled to be replaced by an elected legislature in 1990. The GDP was US $19.2 billion in 1984, with an annual real growth rate of 6.3%, and per capita GDP stood at US$1590. Inflation averages 23%. Industry comprises 21% of the GDP. Longterm prospects for the Chilean economy are influenced by a high debt service ratio, very low domestic savings and investment, the prospect of little or no increase in copper prices, and continuing problems in the domestic financial sector. In 1985-88, under the International Monetary Fund macroeconomic program, Chile will strive for moderate economic growth while managing its external debt servicing burden. PMID:12178144

  20. Pucarilla-Cerro Tipillas volcanic complex: the oldest recognized caldera in the southeastern portion of central volcanic zone of Central Andes?

    International Nuclear Information System (INIS)

    We recognize the most eastern and oldest collapse caldera structure in the southern portion of the Central Volcanic Zone of the Andes. A description of Middle-Upper Miocene successions related to explosive- effusive events is presented. The location of this centre close to Cerro Galn Caldera attests a recurrence in the volcanism between 12 and 2 Ma in this portion of the Altiplano - Puna Plateau.

  1. Pucarilla-Cerro Tipillas volcanic complex: the oldest recognized caldera in the southeastern portion of central volcanic zone of Central Andes?

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, Silvina; Petrinovic, Ivan [CONICET -IBIGEO. Museo de Cs. Naturales, Universidad de Salta, Mendoza 2 (4400), Salta (Argentina)], E-mail: guzmansilvina@gmail.com

    2008-10-01

    We recognize the most eastern and oldest collapse caldera structure in the southern portion of the Central Volcanic Zone of the Andes. A description of Middle-Upper Miocene successions related to explosive- effusive events is presented. The location of this centre close to Cerro Galn Caldera attests a recurrence in the volcanism between 12 and 2 Ma in this portion of the Altiplano - Puna Plateau.

  2. Drought increases the freezing resistance of high-elevation plants of the Central Chilean Andes.

    Science.gov (United States)

    Sierra-Almeida, Angela; Reyes-Bahamonde, Claudia; Cavieres, Lohengrin A

    2016-08-01

    Freezing temperatures and summer droughts shape plant life in Mediterranean high-elevation habitats. Thus, the impacts of climate change on plant survival for these species could be quite different to those from mesic mountains. We exposed 12 alpine species to experimental irrigation and warming in the Central Chilean Andes to assess whether irrigation decreases freezing resistance, irrigation influences freezing resistance when plants are exposed to warming, and to assess the relative importance of irrigation and temperature in controlling plant freezing resistance. Freezing resistance was determined as the freezing temperature that produced 50 % photoinactivation [lethal temperature (LT50)] and the freezing point (FP). In seven out of 12 high-Andean species, LT50 of drought-exposed plants was on average 3.5 K lower than that of irrigated plants. In contrast, most species did not show differences in FP. Warming changed the effect of irrigation on LT50. Depending on species, warming was found to have (1) no effect, (2) to increase, or (3) to decrease the irrigation effect on LT50. However, the effect size of irrigation on LT50 was greater than that of warming for almost all species. The effect of irrigation on FP was slightly changed by warming and was sometimes in disagreement with LT50 responses. Our data show that drought increases the freezing resistance of high-Andean plant species as a general plant response. Although freezing resistance increases depended on species-specific traits, our results show that warmer and moister growing seasons due to climate change will seriously threaten plant survival and persistence of these and other alpine species in dry mountains. PMID:27053321

  3. Giant magmatic water reservoir beneath Uturuncu volcano and Altiplano-Puna region (Central Andes)

    Science.gov (United States)

    Laumonier, Mickael; Gaillard, Fabrice; Muir, Duncan; Blundy, Jon; Unsworth, Martyn

    2016-04-01

    Volcanism at continental arcs is the surface manifestation of long-lived crustal magmatic processes whereby mantle-derived hydrous basalt magma differentiates to more silica-rich magmas by a combination of crystallization and crustal melting. What erupts is just a fraction of the total volume of magma produced by these processes; the unerupted, plutonic residues solidify and are inaccessible to direct study until millions of years of uplift and erosion bring them to the surface. In contrast, geophysical surveys, using electromagnetic and seismic waves, can provide real-time images of subduction zone magmatic systems. Several such studies have revealed that arc volcanoes are underlain by large partially molten regions at depths of >10 km, the largest known example being the Altiplano-Puna magma body (APMB) in central Andes. Interpreting such geophysical images in terms of amount, composition and distribution of partial melts is limited by our lack of knowledge of the physical properties of silicate melts at elevated pressures and temperatures. Here we present high-pressure, in situ experimental data showing that the electrical conductivity of andesitic melts is primarily controlled by their dissolved water contents. Linking our new measurements to petrological constraints from andesites erupted on the Altiplano, we show that the APMB is composed of 10-20% of an andesitic melt containing 8-10 wt% dissolved water. This implies that the APMB is a giant water anomaly in the global subduction system, with a total mass of dissolved magmatic water about half of the water contained within the Adriatic Sea. In addition to the controls on the physical properties of the melts, the abundance of dissolved water governs the structural levels of magma ponding, equivalent to the depth of water saturation, where degassing and crystallisation promote partial melting and weakening of the upper crust. Unexpectedly, very high concentrations of water in andesite magmas shall impede their

  4. A paleolimnological perspective on industrial-era metal pollution in the central Andes, Peru.

    Science.gov (United States)

    Cooke, Colin A; Abbott, Mark B

    2008-04-15

    To date, few studies have investigated the environmental legacy associated with industrialization in the South American Andes. Here, we present an environmental archive of industrial pollution from (210)Pb-dated lake cores recovered from Laguna Chipian, located near the Cerro de Pasco metallurgical region and Laguna Pirhuacocha, located near the Morococha mining region and the La Oroya smelting complex. At Laguna Chipian, trace metal concentrations increase beginning ~1900 AD, coincident with the construction of the central Peruvian railway, and the rapid industrial development of the Cerro de Pasco region. Trace metal concentrations and fluxes peak during the 1950s before subsequently declining up-core (though remaining well above background levels). While Colonial mining and smelting operations are known to have occurred at Cerro de Pasco since at least 1630 AD, our sediment record preserves no associated metal deposition. Based on our (14)C and (210)Pb data, we suggest that this is due to a depositional hiatus, rather than a lack of regional Colonial pollution. At Laguna Pirhuacocha, industrial trace metal deposition first begins ~1925 AD, rapidly increasing after ~1950 AD and peaking during either the 1970s or 1990s. Trace metal concentrations from these lakes are comparable to some of the most polluted lakes in North America and Europe. There appears to be little diagenetic alteration of the trace metal record at either lake, the exception being arsenic (As) accumulation at Laguna Pirhuacocha. There, a correlation between As and the redox-sensitive element manganese (Mn) suggests that the sedimentary As burden is undergoing diagenetic migration towards the sediment-water interface. This mobility has contributed to surface sediment As concentrations in excess of 1100 microg g(-1). The results presented here chronicle a rapidly changing Andean environment, and highlight a need for future research in the rate and magnitude of atmospheric metal pollution. PMID

  5. A paleolimnological perspective on industrial-era metal pollution in the central Andes, Peru

    International Nuclear Information System (INIS)

    To date, few studies have investigated the environmental legacy associated with industrialization in the South American Andes. Here, we present an environmental archive of industrial pollution from 210Pb-dated lake cores recovered from Laguna Chipian, located near the Cerro de Pasco metallurgical region and Laguna Pirhuacocha, located near the Morococha mining region and the La Oroya smelting complex. At Laguna Chipian, trace metal concentrations increase beginning ∼ 1900 AD, coincident with the construction of the central Peruvian railway, and the rapid industrial development of the Cerro de Pasco region. Trace metal concentrations and fluxes peak during the 1950s before subsequently declining up-core (though remaining well above background levels). While Colonial mining and smelting operations are known to have occurred at Cerro de Pasco since at least 1630 AD, our sediment record preserves no associated metal deposition. Based on our 14C and 210Pb data, we suggest that this is due to a depositional hiatus, rather than a lack of regional Colonial pollution. At Laguna Pirhuacocha, industrial trace metal deposition first begins ∼ 1925 AD, rapidly increasing after ∼ 1950 AD and peaking during either the 1970s or 1990s. Trace metal concentrations from these lakes are comparable to some of the most polluted lakes in North America and Europe. There appears to be little diagenetic alteration of the trace metal record at either lake, the exception being arsenic (As) accumulation at Laguna Pirhuacocha. There, a correlation between As and the redox-sensitive element manganese (Mn) suggests that the sedimentary As burden is undergoing diagenetic migration towards the sediment-water interface. This mobility has contributed to surface sediment As concentrations in excess of 1100 μg g-1. The results presented here chronicle a rapidly changing Andean environment, and highlight a need for future research in the rate and magnitude of atmospheric metal pollution

  6. A paleolimnological perspective on industrial-era metal pollution in the central Andes, Peru

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, Colin A. [Department of Geology, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, T6G 2E3 (Canada)], E-mail: cacooke@ualberta.ca; Abbott, Mark B. [Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, T6G 2E3 (Canada); Section of Anthropology, Carnegie Museum of Natural History, Pittsburgh, PA 15206 (United States)

    2008-04-15

    To date, few studies have investigated the environmental legacy associated with industrialization in the South American Andes. Here, we present an environmental archive of industrial pollution from {sup 210}Pb-dated lake cores recovered from Laguna Chipian, located near the Cerro de Pasco metallurgical region and Laguna Pirhuacocha, located near the Morococha mining region and the La Oroya smelting complex. At Laguna Chipian, trace metal concentrations increase beginning {approx} 1900 AD, coincident with the construction of the central Peruvian railway, and the rapid industrial development of the Cerro de Pasco region. Trace metal concentrations and fluxes peak during the 1950s before subsequently declining up-core (though remaining well above background levels). While Colonial mining and smelting operations are known to have occurred at Cerro de Pasco since at least 1630 AD, our sediment record preserves no associated metal deposition. Based on our {sup 14}C and {sup 210}Pb data, we suggest that this is due to a depositional hiatus, rather than a lack of regional Colonial pollution. At Laguna Pirhuacocha, industrial trace metal deposition first begins {approx} 1925 AD, rapidly increasing after {approx} 1950 AD and peaking during either the 1970s or 1990s. Trace metal concentrations from these lakes are comparable to some of the most polluted lakes in North America and Europe. There appears to be little diagenetic alteration of the trace metal record at either lake, the exception being arsenic (As) accumulation at Laguna Pirhuacocha. There, a correlation between As and the redox-sensitive element manganese (Mn) suggests that the sedimentary As burden is undergoing diagenetic migration towards the sediment-water interface. This mobility has contributed to surface sediment As concentrations in excess of 1100 {mu}g g{sup -1}. The results presented here chronicle a rapidly changing Andean environment, and highlight a need for future research in the rate and magnitude

  7. Estructura litosférica de los Andes centrales a partirde un modelo gravimétrico 3D Lithosphericstructure of the Central Andes based ona 3D gravimetric model

    Directory of Open Access Journals (Sweden)

    Claudia B. Prezzi

    2009-10-01

    Full Text Available A través del modelado directode la anomalía de Bouguer se desarrolló un modelo de densidades en 3D de lacorteza continental, la placa subducida y el manto superior, para los AndesCentrales entre los 20-29°S y los 74-61°O. El objetivo de este trabajo escontribuir a un mejor conocimiento de la estructura litosférica, integrando lainformación disponible (geofísica, geológica, petrológica y geoquímica en unúnico modelo. La geometría del modelo está definida y limitada por la ubicaciónde hipocentros, líneas sísmicas de reflexión y refracción, tomografías deatenuación y de tiempos de arribo, estudios magnetotelúricos, modelos térmicosy secciones estructurales balanceadas. Las densidades asignadas a losdiferentes cuerpos fueron calculadas a partir de datos petrológicos ygeoquímicos, estimando las condiciones de presión y temperatura. El modeloconsiste de 31 planos verticales E-O paralelos, donde la corteza continentalestá compuesta por distintos cuerpos que representan a las diferentes unidadesmorfotectónicas de los Andes Centrales. Se generaron mapas isocóricos del techode la placa subducida, del Moho continental y del techo de la astenósferadebajo de Sudamérica. Se calculó la anomalía residual mediante la sustracciónde los efectos gravimétricos de la placa subducida modelada y del Moho modeladode la anomalía de Bouguer. Este estudio demuestra como el modelado gravimétrico3D, integrando información geofísica, geológica y petrológica, puede contribuiral mejor conocimiento de la estructura litosférica de los Andes Centrales.We developed a 3Ddensity model of the conti nental crust, the subducted plate and the uppermantle of the Central Andes between 20-29°S and 74-61°W through theforward modelling of Bouguer anomaly. The goal of this contribution is to gaininsight on the lithospheric structure of the area, integrating the availableinformation (geophysical, geologic, petrologic, and geochemical in a singlemodel

  8. The age and constitution of Cerro Campanario, a mafic stratovolcano in the Andes of central Chile

    Science.gov (United States)

    Hildreth, W.; Singer, B.; Godoy, E.; Munizaga, F.

    1998-01-01

    Cerro Campanario, a towering landmark on the continental divide near Paso Pehuenche, is a glacially eroded remnant of a mafic stratovolcano that is much younger than previously supposed. Consisting of fairly uniform basaltic andesite, rich in olivine and plagioclase, the 10-15 km3 edifice grew rapidly near the end of the middle Pleistocene, about 150-160 ka, as indicated by 40Ar/39Ar and unspiked K-Ar analyses of its lavas.

  9. The age and constitution of Cerro Campanario, a mafic stratovolcano in the Andes of Central Chile

    OpenAIRE

    Wes Hildreth; Brad Singer; Estanislao Godoy; Francisco Munizaga

    1998-01-01

    ABSTRACT Cerro Campanario, a towering landmark on the continental divide near Paso Pehuenche, is a glacially eroded remnant of a mafic stratovolcano that is much younger than previously supposed. Consisting of fairly uniform basaltic andesite, rich in olivine and plagioclase, the 10-15 km³ edifice grew rapidly near the end of the middle Pleistocene, about 150-160 ka, as indicated by 40Ar/39Ar and unspiked K-Ar analyses of its lavas.La edad y formación del cerro Campanario, un estratovolcán má...

  10. Crustal contributions to arc magmatism in the Andes of Central Chile

    Science.gov (United States)

    Hildreth, W.; Moorbath, S.

    1988-01-01

    Fifteen andesite-dacite stratovolcanoes on the volcanic front of a single segment of the Andean arc show along-arc changes in isotopic and elemental ratios that demonstrate large crustal contributions to magma genesis. All 15 centers lie 90 km above the Benioff zone and 280??20 km from the trench axis. Rate and geometry of subduction and composition and age of subducted sediments and seafloor are nearly constant along the segment. Nonetheless, from S to N along the volcanic front (at 57.5% SiO2) K2O rises from 1.1 to 2.4 wt %, Ba from 300 to 600 ppm, and Ce from 25 to 50 ppm, whereas FeO*/MgO declines from >2.5 to 1.4. Ce/Yb and Hf/Lu triple northward, in part reflecting suppression of HREE enrichment by deep-crustal garnet. Rb, Cs, Th, and U contents all rise markedly from S to N, but Rb/Cs values double northward - opposite to prediction were the regional alkali enrichment controlled by sediment subduction. K/Rb drops steeply and scatters greatly within many (biotite-free) andesitic suites. Wide diversity in Zr/Hf, Zr/Rb, Ba/Ta, and Ba/La within and among neighboring suites (which lack zircon and alkali feldspar) largely reflects local variability of intracrustal (not slab or mantle) contributions. Pb-isotope data define a limited range that straddles the Stacey-Kramers line, is bracketed by values of local basement rocks, in part plots above the field of Nazca plate sediment, and shows no indication of a steep (mantle+sedimentary) Pb mixing trend. 87Sr/86Sr values rise northward from 0.7036 to 0.7057, and 143Nd/144Nd values drop from 0.5129 to 0.5125. A northward climb in basal elevation of volcanic-front edifices from 1350 m to 4500 m elevation coincides with a Bougueranomaly gradient from -95 to -295 mgal, interpreted to indicate thickening of the crust from 30-35 km to 50-60 km. Complementary to the thickening crust, the mantle wedge beneath the front thins northward from about 60 km to 30-40 km (as slab depth is constant). The thick northern crust contains an abundance of Paleozoic and Triassic rocks, whereas the proportion of younger arc-intrusive basement increases southward. Primitive basalts are unknown anywhere along the arc. Base-level isotopic and chemical values for each volcano are established by blending of subcrustal and deep-crustal magmas in zones of melting, assimilation, storage and homogenization (MASH) at the mantle-crust transition. Scavenging of mid-to upper-crustal silicic-alkalic melts and intracrustal AFC (prominent at the largest center) can subsequently modify ascending magmas, but the base-level geochemical signature at each center reflects the depth of its MASH zone and the age, composition, and proportional contribution of the lowermost crust. ?? 1988 Springer-Verlag.

  11. Introducción a la Geología de los Andes Centrales Meridionales: El Noroeste Argentino

    OpenAIRE

    Colombo Piñol, Ferrán; Queralt Mitjans, Ignacio; I.A. Petrinovic

    1999-01-01

    Bajo el título genérico de "Geología de los Andes Centrales Meridionales: El Noroeste Argentino" se recopilan un conjunto de trabajos realizados en los últimos años en sectores del Noroeste Argentino. Las investigaciones realizadas se localizan en la región andina de la provincia de Salta y territorios adyacentes. Este volumen monográfico reúne trabajos que constituyen el esfuerzo conjunto de veinticinco autores de diferentes países,europeos y suramericanos,trabajando en proyectos de colabora...

  12. Neoproterozoic ultramafic and mafic magmatism in the Eastern Cordillera of the central peruvian Andes: the Tapo Massif

    OpenAIRE

    Tassinari, Colombo G.; Castroviejo Bolibar, Ricardo; Rodrigues, Jose F.; Acosta, Jorge; Pereira, Eurico

    2010-01-01

    A highly dismembered assemblage of ultramafic and mafic rocks is exposed in the Eastern Cordillera of the Central Peruvian Andes, extending along a discontinuous NW-SE belt over some 250 km between 12° and 9° S of latitude. One of the most important occurrences is the Tapo Mafic-Ultramafic Complex, which occurs at 3750 to 4200 m above sea level, 2 km to the west of Tapo locality, in the Tarma province, about 200 Km west of Lima. The Tapo complex is a lens-shaped body, 5 km long and 1-2...

  13. Reverse Faulting as a Crucial Mechanism for Magma Ascent in Compressional Volcanic Arcs: Field Examples from the Central Andes

    Science.gov (United States)

    Aron, F. A.; Gonzalez, G.; Cembrano, J. M.; Veloso, E. E.

    2010-12-01

    The nature of crustal deformation in active arcs and the feedback mechanisms between tectonics and magma transport constitute fundamental problems in the understanding of volcanic systems. Additionally, for geothermal energy exploration, a better understanding of how crustal architecture and stress field controls fluid ascent and heat transfer from deep levels to the surface is crucial. The Central Andes volcanic belt is an excellent, modern example of such systems but, the scarcity of good outcrops has limited our ability to define the relations between structure and volcanism. In the Salar de Atacama Basin of northern Chile, there are good exposures of folded and faulted Neogene units (continental sediments, volcanic rocks and ignimbrites) and reverse faults spatially and temporally related to volcanic edifices. The subsurface of the study area has been interpreted by previous authors as a thin-skinned, 6-8 km-deep, east-vergent compressional belt. We carried out structural mapping, Digital Elevation Models (DEMs) analyses, strain tensor analyses and fault-related fold kinematic modelling to assess the causal relationship between compressional deformation and magmatism in this region. Field observations indicate that the structures deformed progressively Oligocene-Miocene continental sedimentary units, the upper sedimentary infill of the Salar de Atacama basin (Pliocene-Present), and Pliocene-Pleistocene Ignimbrites. The topographic expression of the compressional belt corresponds to a set of subparallel, asymmetric, fault-related-folds, which can be seen in the field as prominent NS-trending ridges with heights ranging between 50 and 400 m. Furthermore, we found evidence of a ~100 km-long structure along the active magmatic arc, so-called Miscanti Fault. This fault represents the easternmost expression of the above mentioned compressional belt. Pleistocene-Holocene monogenetic cones and strato-volcanoes are located either at the hinge zone of fault

  14. A NEW LOCALITY OF THE HOODED ANTPITTA (GRALLARICULA CUCULLATA: GRALLARIDAE FOR THE COLOMBIAN CENTRAL ANDES

    Directory of Open Access Journals (Sweden)

    OSCAR HUMBERTO MARÍN GÓMEZ

    2014-05-01

    Full Text Available We report a new locality record of the Hooded Anpitta (Grallariculla cucullata, a threatened species inhabiting montane cloud forests of the Colombian and Venezuelan Andes. This is the first record for Quindío department. We present capture-rate data at this site that suggests a resident, relatively large population. 

  15. Comparison of Airborne LiDAR and Satellite Hyperspectral Remote Sensing to Estimate Vascular Plant Richness in Deciduous Mediterranean Forests of Central Chile

    Directory of Open Access Journals (Sweden)

    Andrés Ceballos

    2015-03-01

    Full Text Available The Andes foothills of central Chile are characterized by high levels of floristic diversity in a scenario, which offers little protection by public protected areas. Knowledge of the spatial distribution of this diversity must be gained in order to aid in conservation management. Heterogeneous environmental conditions involve an important number of niches closely related to species richness. Remote sensing information derived from satellite hyperspectral and airborne Light Detection and Ranging (LiDAR data can be used as proxies to generate a spatial prediction of vascular plant richness. This study aimed to estimate the spatial distribution of plant species richness using remote sensing in the Andes foothills of the Maule Region, Chile. This region has a secondary deciduous forest dominated by Nothofagus obliqua mixed with sclerophyll species. Floristic measurements were performed using a nested plot design with 60 plots of 225 m2 each. Multiple predictors were evaluated: 30 topographical and vegetation structure indexes from LiDAR data, and 32 spectral indexes and band transformations from the EO1-Hyperion sensor. A random forest algorithm was used to identify relevant variables in richness prediction, and these variables were used in turn to obtain a final multiple linear regression predictive model (Adjusted R2 = 0.651; RSE = 3.69. An independent validation survey was performed with significant results (Adjusted R2 = 0.571, RMSE = 5.05. Selected variables were statistically significant: catchment slope, altitude, standard deviation of slope, average slope, Multiresolution Ridge Top Flatness index (MrRTF and Digital Crown Height Model (DCM. The information provided by LiDAR delivered the best predictors, whereas hyperspectral data were discarded due to their low predictive power.

  16. Chanco formation, a potential Cretaceous reservoir, central Chile

    Energy Technology Data Exchange (ETDEWEB)

    Cecione, G.

    1983-07-01

    The Chanco embayment lies 300 km SSW of Santiago, Chile. The sequence within this basin above the metamorphic basement is: Chanco Formation (very clean sandstone), Quiriquina Formation (glauconitic sandstone, rich in organic matter), and Navidad Group (a very good caprock). This section thus contains reservoir, source and caprocks, and is therefore very promising for petroleum investigations. The offshore C-1 well yielded salt-water with gas shows, and two wells drilled onshore yielded shows of gas. The C-1 well lies on a gently-dipping EW-striking anticlinal structure, the presence of which makes the area very prospective.

  17. Precipitation intensity and vegetation controls on geomorphology of the central Andes

    Science.gov (United States)

    Jeffery, M. L.; Poulsen, C. J.; Ehlers, T. A.; Yanites, B. J.

    2012-12-01

    Field observations and landscape evolution models indicate that landscape processes in active mountain belts are strongly dependent on vegetation and climate. In fluvial landscapes, erosional efficiency is commonly thought to depend on the intensity, frequency, and duration of precipitation events. We use Tropical Rainfall Measuring Mission (TRMM) observations to test the importance of precipitation intensity in determining geomorphology at the mountain belt scale. Precipitation metrics, including mean annual precipitation, and the mean intensity, duration, and frequency of precipitation events, are derived from the TRMM 3B42v7 product. The new precipitation datasets are then compared with different topographic metrics of the central Andes. Statistical analyses, including multiple linear regression, are used to quantify the importance of different precipitation metrics in controlling the regional topographic characteristics. In addition to climate properties, spatial variations in tectonic regime, bedrock lithology, and the amount and type of vegetation cover are accounted for in the statistical analyses. Our analysis indicates that in regions with high vegetation cover (>80%), mean precipitation intensity and mean interval correlate most strongly with mean hillslope (r = -0.51 and r = -0.66 respectively). In these regions, mean hillslope decreases from ~25° to ~ 10° with increasing mean event precipitation intensity (from 10 to 40 mm/day). In contrast, in sparsely vegetated (control on critical erosion thresholds at the landscape scale. Furthermore, the property of precipitation that governs surface processes is dependent on the amount and type of vegetation cover. Both grass and trees effectively increase erosion thresholds and act to stabilize the landscape. Only precipitation events that are capable of exceeding the erosion threshold set by the vegetation can do geomorphic work. High mean slopes (15 - 33°) develop where the mean precipitation intensity is

  18. Andes 1997 Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Central Andes gravity data (6,151 records) were compiled by Professor Gotze and the MIGRA Group. This data base was received in April, 1997. Principal gravity...

  19. Physical, chemical and mineralogical evolution of the Tolhuaca geothermal system, southern Andes, Chile: Insights into the interplay between hydrothermal alteration and brittle deformation

    Science.gov (United States)

    Sanchez-Alfaro, Pablo; Reich, Martin; Arancibia, Gloria; Pérez-Flores, Pamela; Cembrano, José; Driesner, Thomas; Lizama, Martin; Rowland, Julie; Morata, Diego; Heinrich, Christoph A.; Tardani, Daniele; Campos, Eduardo

    2016-09-01

    In this study, we unravel the physical, chemical and mineralogical evolution of the active Tolhuaca geothermal system in the Andes of southern Chile. We used temperature measurements in the deep wells and geochemical analyses of borehole fluid samples to constrain present-day fluid conditions. In addition, we reconstructed the paleo-fluid temperatures and chemistry from microthermometry and LA-ICP-MS analysis of fluid inclusions taken from well-constrained parageneses in vein samples retrieved from a ~ 1000 m borehole core. Based on core logging, mineralogical observations and fluid inclusions data we identify four stages (S1-S4) of progressive hydrothermal alteration. An early heating event (S1) was followed by the formation of a clay-rich cap in the upper zone (inhibited. In contrast, in the deep upflow zone the less pervasive formation of clay mineral assemblages has allowed retention of rock strength and dilatant behavior during slip, sustaining high permeability conditions. Numerical simulations of heat and fluid flows support our observations and suggest that the presence of a low permeability clay cap has helped increase the duration of high-enthalpy conditions by a factor of three in the deep upflow zone at Tolhuaca geothermal system, when compared with an evolutionary scenario where a clay cap was not developed. Furthermore, our data demonstrate that the dynamic interplay between fluid flow, crack-seal processes and hydrothermal alteration are key factors in the evolution of the hydrothermal system, leading to the development of a high enthalpy reservoir at the flank of the dormant Tolhuaca volcano.

  20. Expanding Geophysical and Geochemical Investigation of Causes of Extraordinary Unrest at the Laguna del Maule (Rhyolitic) Volcanic Field, Southern Andes, Chile

    Science.gov (United States)

    Singer, B. S.

    2014-12-01

    The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007 the crust here has been inflating at an astonishing rate of 25 cm/yr. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ~20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. Swarms of volcano-tectonic and long period earthquakes, mostly of M Nanyang Technological University-Singapore, SERNAGEOMIN, OVDAS, USGS, and SEGEMAR-Argentina. Team members will be introduced in this presentation. Our approach includes augmenting the OVDAS array of 6 permanent seisic stations with 40 additional instruments to conduct tomographic, receiver function and ambient noise studies. We continue to collect 4-D gravity data from 37 stations. Surface deformation is monitored via cGPS at 5 permanent receivers and InSAR data. A magnetotelluric survey across the Andes at 36o S is planned. Geochemical studies include mineral zoning and U-Th disequilibrium of zircons to constrain the timing of magma intrusion and mixing events prior to the current unrest. The overall aim is to integrate these observations and to construct numerical models of system dynamics. We are developing communications protocols and a web site to facilitate sharing of findings among the team members and with the public.

  1. Physical, chemical and mineralogical evolution of the Tolhuaca geothermal system, southern Andes, Chile: Insights into the interplay between hydrothermal alteration and brittle deformation

    Science.gov (United States)

    Sanchez-Alfaro, Pablo; Reich, Martin; Arancibia, Gloria; Pérez-Flores, Pamela; Cembrano, José; Driesner, Thomas; Lizama, Martin; Rowland, Julie; Morata, Diego; Heinrich, Christoph A.; Tardani, Daniele; Campos, Eduardo

    2016-09-01

    In this study, we unravel the physical, chemical and mineralogical evolution of the active Tolhuaca geothermal system in the Andes of southern Chile. We used temperature measurements in the deep wells and geochemical analyses of borehole fluid samples to constrain present-day fluid conditions. In addition, we reconstructed the paleo-fluid temperatures and chemistry from microthermometry and LA-ICP-MS analysis of fluid inclusions taken from well-constrained parageneses in vein samples retrieved from a ~ 1000 m borehole core. Based on core logging, mineralogical observations and fluid inclusions data we identify four stages (S1-S4) of progressive hydrothermal alteration. An early heating event (S1) was followed by the formation of a clay-rich cap in the upper zone (creation or reactivation of highly permeable extensional fractures is inhibited. In contrast, in the deep upflow zone the less pervasive formation of clay mineral assemblages has allowed retention of rock strength and dilatant behavior during slip, sustaining high permeability conditions. Numerical simulations of heat and fluid flows support our observations and suggest that the presence of a low permeability clay cap has helped increase the duration of high-enthalpy conditions by a factor of three in the deep upflow zone at Tolhuaca geothermal system, when compared with an evolutionary scenario where a clay cap was not developed. Furthermore, our data demonstrate that the dynamic interplay between fluid flow, crack-seal processes and hydrothermal alteration are key factors in the evolution of the hydrothermal system, leading to the development of a high enthalpy reservoir at the flank of the dormant Tolhuaca volcano.

  2. New estimated Holocene denudation rates for non-glaciated areas in the southernmost Patagonian Andes (53°S), Chile

    Science.gov (United States)

    Breuer, Sonja; Kilian, Rolf; Baeza, Oscar; Arz, Helge

    2010-05-01

    Cenozoic denudation rates are sparsely known for the southernmost Patagonian Andes. One of the scientific approaches is to calculate long-term denudation rates based on fission track analyses. Though, these average rates comprise a long period with distinct climate conditions and very different extend of glaciation. These integrated denudation rates include extensive surface areas with different morphological, glacial and vegetational properties. In contrast, our approach is restricted to relative short Holocene periods and small catchment areas, for which the denudation and its controlling surface characteristics could be defined more precisely. Thus a more precise evaluation of the influencing parameters like climate, morphology and vegetation cover was possible. We concentrated on three restricted and nearly closed areas of denudation and accumulation. In those catchments we determined the sediment masses of lakes, based on sediment drilling, echosounding and computer based interpolation of the siliciclastic sediment masses. These masses were transferred to the denudation areas which have been characterised and measured by remote sensing. The westernmost Tamar Lake is located on the Tamar Island in the western part of the Magellan Strait, where the annual precipitation is about 4,000 mm. The catchment area has a dense vegetation cover. The lake surrounding slopes reach an elevation of 400 m a.s.l and they are up to 60° steep. The calculated denudation rate for this catchment is about 2.56 mm/ka, which represents a minimum value, because the postglacial weathering horizon is only partly removed into the lake. The highest elevated lake Muy Profundo (500 m a.s.l.) possesses a denudation area with a nearly vegetation-free zone up to 750 m a.s.l. within the Patagonian Batholith. The catchment area of this lake is characterised by a roche moutonnée landform with steep slopes and active fracture zones. The precipitation varies between 5,000 and 8,000 mm/a. The

  3. Estimation of slip scenarios of mega-thrust earthquakes and strong motion simulations for Central Andes, Peru

    Science.gov (United States)

    Pulido, N.; Tavera, H.; Aguilar, Z.; Chlieh, M.; Calderon, D.; Sekiguchi, T.; Nakai, S.; Yamazaki, F.

    2012-12-01

    We have developed a methodology for the estimation of slip scenarios for megathrust earthquakes based on a model of interseismic coupling (ISC) distribution in subduction margins obtained from geodetic data, as well as information of recurrence of historical earthquakes. This geodetic slip model (GSM) delineates the long wavelength asperities within the megathrust. For the simulation of strong ground motion it becomes necessary to introduce short wavelength heterogeneities to the source slip to be able to efficiently simulate high frequency ground motions. To achieve this purpose we elaborate "broadband" source models constructed by combining the GSM with several short wavelength slip distributions obtained from a Von Karman PSD function with random phases. Our application of the method to Central Andes in Peru, show that this region has presently the potential of generating an earthquake with moment magnitude of 8.9, with a peak slip of 17 m and a source area of approximately 500 km along strike and 165 km along dip. For the strong motion simulations we constructed 12 broadband slip models, and consider 9 possible hypocenter locations for each model. We performed strong motion simulations for the whole central Andes region (Peru), spanning an area from the Nazca ridge (16^o S) to the Mendana fracture (9^o S). For this purpose we use the hybrid strong motion simulation method of Pulido et al. (2004), improved to handle a general slip distribution. Our simulated PGA and PGV distributions indicate that a region of at least 500 km along the coast of central Andes is subjected to a MMI intensity of approximately 8, for the slip model that yielded the largest ground motions among the 12 slip models considered, averaged for all assumed hypocenter locations. This result is in agreement with the macroseismic intensity distribution estimated for the great 1746 earthquake (M~9) in central Andes (Dorbath et al. 1990). Our results indicate that the simulated PGA and PGV for

  4. Boron isotope composition of geothermal fluids and borate minerals from salar deposits (central Andes/NW Argentina)

    Science.gov (United States)

    Kasemann, Simone A.; Meixner, Anette; Erzinger, Jörg; Viramonte, José G.; Alonso, Ricardo N.; Franz, Gerhard

    2004-06-01

    We have measured the boron concentration and isotope composition of regionally expansive borate deposits and geothermal fluids from the Cenozoic geothermal system of the Argentine Puna Plateau in the central Andes. The borate minerals borax, colemanite, hydroboracite, inderite, inyoite, kernite, teruggite, tincalconite, and ulexite span a wide range of δ11B values from -29.5 to -0.3‰, whereas fluids cover a range from -18.3 to 0.7‰. The data from recent coexisting borate minerals and fluids allow for the calculation of the isotope composition of the ancient mineralizing fluids and thus for the constraint of the isotope composition of the source rocks sampled by the fluids. The boron isotope composition of ancient mineralizing fluids appears uniform throughout the section of precipitates at a given locality and similar to values obtained from recent thermal fluids. These findings support models that suggest uniform and stable climatic, magmatic, and tectonic conditions during the past 8 million years in this part of the central Andes. Boron in fluids is derived from different sources, depending on the drainage system and local country rocks. One significant boron source is the Paleozoic basement, which has a whole-rock isotopic composition of δ11B=-8.9±2.2‰ (1 SD); another important boron contribution comes from Neogene-Pleistocene ignimbrites ( δ11B=-3.8±2.8‰, 1 SD). Cenozoic andesites and Mesozoic limestones ( δ11B≤+8‰) provide a potential third boron source.

  5. An InSAR survey of the central Andes: Constraints on magma chamber geometry and mass balance in a volcanic arc

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2002-12-01

    The central Andes (14-28o S) has a high density of volcanoes, but a sparse human population, such that the activity of most volcanoes is poorly constrained. We use InSAR to conduct the first systematic observations of deformation at nearly 900 volcanoes (about 50 of which are classified ``potentially active'') during the 1992-2002 time interval. We find volcanic deformation in four locations. Subsidence is seen at Robledo (or Cerro Blanco) caldera, Argentina. We observe inflation at the stratovolcano Uturuncu, Bolivia, near stratovolcano Hualca Hualca, Peru, and in a region not associated with any known edifice on the border between Chile and Argentina that we call ``Lazufre'' because it lies between volcanoes Lastarria and Cordon del Azufre. The deformation pattern can be well explained by a uniform point-source source of inflation or deflation, but we compare these model results with those from a tri-axial point-source ellipsoid to test the robustness of estimated source depth and source strength (inferred here to be volume change). We further explore the sensitivity of these parameters to elastic half-space and layered-space models of crustal structure, and the influence of local topography. Because only one satellite look direction is available for most time periods, a variety of models are consistent with our observations. If we assume that inflation is due solely to magmatic intrusion, we can compare the rate of magma intrusion to volcanic extrusion during the decade for which data is available and the longer-term geologic rate. For the last decade, the ratio of volume intruded to extruded is between about 1-10, which agrees with previous geologic estimates in this and other volcanic arcs. The combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate.

  6. Climatic and paleoclimatic forcing of erosion in the southern Central Andes and the northwestern Himalaya (Invited)

    Science.gov (United States)

    Bookhagen, B.; Strecker, M. R.

    2013-12-01

    The windward flanks of the tectonically active southern Central Andes and the NW Himalaya are characterized by steep climatic, tectonic, and topographic gradients. The first windward topographic rise of these mountain ranges constitutes a significant orographic barrier resulting in high orographic rainfall causing some of the wettest places on Earth. However, the higher-elevation areas of the windward flanks of both regions become progressively drier, until arid conditions are attained in the orogen interiors (i.e., the Altiplano-Puna and Tibet plateaus). Both areas have experienced significant paleoclimatic changes with deeper penetration of moisture into the orogen and thus an orogenward shift of the climate gradient. Some of the world's largest rivers with high sediment loads emerge from these mountain belts, and understanding the relation between climate and erosion is key in predicting mass fluxes, assessing the impacts of climate variability, and long-term climate forcing of erosion on landscape evolution. Here, we quantify the impact of the climatic gradients and their spatial shifts during the late Pleistocene and Holocene. We rely on sedimentary archives, digital topography, and cosmogenic inventories of river sands (10Be) and bedrock-erosion rates (10Be and 26Al) from the Puna Plateau in NW Argentina and the interior of the western Himalaya in NW India. We make three key observations that underline the importance of present-day climatic parameters and paleoclimatic changes on the effiency of surface processes in both areas: (1) First-order spatial erosion patterns follow the climatic gradient and catchment-mean erosion rates vary by three orders of magnitude from the wet mountain fronts to the dry orogen interior. In NW Argentina, our measurements represent the fluvial transport rates and indicate very low fluvial activity in the interior of the Puna Plateau during the Late Pleistocene; (2) the spatial distribution of erosion rates can be explained by a

  7. The evolution of seabirds in the Humboldt Current: new clues from the Pliocene of Central Chile.

    Directory of Open Access Journals (Sweden)

    Martín Chávez Hoffmeister

    Full Text Available BACKGROUND: During the last decade, new Neogene fossil assemblages from South America have revealed important clues about the evolution of seabird faunas in one of the major upwelling systems of the world: the Humboldt Current. However, most of this record comes from arid Northern Chile and Southern Peru and, in consequence, our knowledge of the evolutionary history of seabirds in the temperate transitional zone is negligible. A new Late Pliocene assemblage of fossil birds from the coastal locality of Horcon in Central Chile offers a unique opportunity to fill this gap. PRINCIPAL FINDINGS: Isolated bones of a medium-sized penguin are the most abundant bird remains. Morphological and cladistic analyses reveal that these specimens represent a new species of crested penguin, Eudyptes calauina sp. nov. Eudyptes is a penguin genus that inhabit temperate and subantarctic regions and currently absent in central Chile. Additionally, a partial skeleton of a small species of cormorant and a partial tarsometatarsus of a sooty shearwater have been identified. CONCLUSION/SIGNIFICANCE: The Horcon fossils suggest the existence of a mixed avifauna in central Chile during the Pliocene in concordance with the latitudinal thermal gradient. This resembles the current assemblages from the transitional zone, with the presence of species shared with Northern Chile and Southern Peru and a previously unrecorded penguin currently absent from the Humboldt System but present in the Magellanic region. Comparison of Pliocene seabird diversity across the Pacific coast of South America shows that the Horcon avifauna represents a distinctive assemblage linking the living faunas with the Late Miocene ones. A comparison with the fossil record near the Benguela Current (west coast of southern Africa suggests that the thermic gradient could play an important role in the preservation of a higher diversity of cold/temperate seabirds in the Humboldt Current.

  8. The Evolution of Seabirds in the Humboldt Current: New Clues from the Pliocene of Central Chile

    Science.gov (United States)

    Chávez Hoffmeister, Martín; Carrillo Briceño, Jorge D.; Nielsen, Sven N.

    2014-01-01

    Background During the last decade, new Neogene fossil assemblages from South America have revealed important clues about the evolution of seabird faunas in one of the major upwelling systems of the world: the Humboldt Current. However, most of this record comes from arid Northern Chile and Southern Peru and, in consequence, our knowledge of the evolutionary history of seabirds in the temperate transitional zone is negligible. A new Late Pliocene assemblage of fossil birds from the coastal locality of Horcon in Central Chile offers a unique opportunity to fill this gap. Principal Findings Isolated bones of a medium-sized penguin are the most abundant bird remains. Morphological and cladistic analyses reveal that these specimens represent a new species of crested penguin, Eudyptes calauina sp. nov. Eudyptes is a penguin genus that inhabit temperate and subantarctic regions and currently absent in central Chile. Additionally, a partial skeleton of a small species of cormorant and a partial tarsometatarsus of a sooty shearwater have been identified. Conclusion/Significance The Horcon fossils suggest the existence of a mixed avifauna in central Chile during the Pliocene in concordance with the latitudinal thermal gradient. This resembles the current assemblages from the transitional zone, with the presence of species shared with Northern Chile and Southern Peru and a previously unrecorded penguin currently absent from the Humboldt System but present in the Magellanic region. Comparison of Pliocene seabird diversity across the Pacific coast of South America shows that the Horcon avifauna represents a distinctive assemblage linking the living faunas with the Late Miocene ones. A comparison with the fossil record near the Benguela Current (west coast of southern Africa) suggests that the thermic gradient could play an important role in the preservation of a higher diversity of cold/temperate seabirds in the Humboldt Current. PMID:24621560

  9. VIOLENCIA POLÍTICA, ASISTENCIA MILITAR DE ESTADOS UNIDOS Y PRODUCCIÓN DE COCA EN LOS ANDES CENTRALES

    Directory of Open Access Journals (Sweden)

    Moisés Arce

    2006-01-01

    Full Text Available ¿Tiene la violencia política un impacto significativo sobre la producción de drogas en los Andes Centrales? ¿Disminuye la ayuda militar estadounidense la oferta de drogas ilícitas que se origina en los Andes Centrales? ¿Qué otros factores ayudan a explicar dicha producción? ¿Tiene la lucha estadounidense contra el narcotráfico las mismas consecuencias en cada país? Este trabajo evalúa de manera empírica los efectos de la violencia política y la ayuda exterior de Estados Unidos (EE.UU. en los tres países productores de droga más prolíficos de América Latina: Colombia, Bolivia y Perú. Los resultados guardan relación directa con la literatura existente que recalca los obstáculos que los gobiernos enfrentan cuando pretenden regular los mercados de bienes de contrabando. Un análisis comparativo de la política antidrogas de EE.UU. aclara los éxitos y las limitaciones de la estrategia que actualmente se lleva a cabo, particularmente en Colombia, donde la violencia política ha facilitado el fortalecimiento del narcotráfico a nivel internacionalWhat is the effect of political violence on the production of coca in the Central Andes? Does U.S. military aid reduce the amount of drugs that originate from this region? What other factors help explain the production of coca? Are the effects of U.S. military aid the same across the Andean nations? This paper tests the effects of political violence and U.S. military aid in the drug producing nations of Colombia, Bolivia and Peru. Our results are consistent with existing literature that emphasizes the obstacles that governments face as they attempt to suppress markets for prohibited goods. Our comparative analysis sheds new light on the limitations of the current U.S. policy, particularly in Colombia, where political violence has strengthened the global drug trade

  10. Estructura litosférica de los Andes centrales a partirde un modelo gravimétrico 3D

    Directory of Open Access Journals (Sweden)

    Claudia B. Prezzi

    2009-10-01

    Full Text Available A través del modelado directode la anomalía de Bouguer se desarrolló un modelo de densidades en 3D de lacorteza continental, la placa subducida y el manto superior, para los AndesCentrales entre los 20-29°S y los 74-61°O. El objetivo de este trabajo escontribuir a un mejor conocimiento de la estructura litosférica, integrando lainformación disponible (geofísica, geológica, petrológica y geoquímica en unúnico modelo. La geometría del modelo está definida y limitada por la ubicaciónde hipocentros, líneas sísmicas de reflexión y refracción, tomografías deatenuación y de tiempos de arribo, estudios magnetotelúricos, modelos térmicosy secciones estructurales balanceadas. Las densidades asignadas a losdiferentes cuerpos fueron calculadas a partir de datos petrológicos ygeoquímicos, estimando las condiciones de presión y temperatura. El modeloconsiste de 31 planos verticales E-O paralelos, donde la corteza continentalestá compuesta por distintos cuerpos que representan a las diferentes unidadesmorfotectónicas de los Andes Centrales. Se generaron mapas isocóricos del techode la placa subducida, del Moho continental y del techo de la astenósferadebajo de Sudamérica. Se calculó la anomalía residual mediante la sustracciónde los efectos gravimétricos de la placa subducida modelada y del Moho modeladode la anomalía de Bouguer. Este estudio demuestra como el modelado gravimétrico3D, integrando información geofísica, geológica y petrológica, puede contribuiral mejor conocimiento de la estructura litosférica de los Andes Centrales.

  11. Surface Uplift History of the Central Andes: Implications for the Growth of Orogenic Plateaus

    Science.gov (United States)

    Garzione, C. N.; Hoke, G. D.; Libarkin, J. C.; MacFadden, B. J.; Withers, S.

    2007-05-01

    Sedimentation, paleoelevation, and incision histories provide important constraints on the timing and magnitude of regional surface uplift of mountain belts that point to specific processes that led to surface uplift. The sedimentary record and stable isotopic compositions of carbonates are used to reconstruct the late Miocene subsidence history, paleoenvironment, and paleoelevation of the northern Altiplano basin. Multiple paleoelevation proxies, including paleoleaf physiognomy, δ18O paleoaltimetry, and Δ47 paleothermometry, suggest that the Altiplano rose by 2.5±0.5 km to 3.5±0.5 km to its current elevation between ~10 and 7 Ma. Geomorphic evidence from widespread, low-relief paleosurfaces on both the eastern and western flanks of the Andes also shows that the onset of rapid incision of paleosurfaces occurred between ~10 and 6.5 Ma over the entire width of the mountain belt and over at least 5° latitude. Stream profile analysis of the drainage systems that incise these paleosurfaces has been inferred to reflect ~1 to 2 km of surface uplift of the flanks of the Andes. Combining geomorphic evidence with paleoelevation constraints, the paleotopographic evolution of the Andes is reconstructed over the late Miocene. Late Miocene regional surface uplift requires the removal of mantle lithosphere as the dominant geodynamic mechanism for raising the plateau during this time. However, crustal thickening and redistribution of crust by erosion/sedimentation and/or lower crustal flow set the limit of surface uplift. Regional surface uplift of the Andean plateau in the late Miocene predicts a decrease in the horizontal deviatoric stress in the plateau that is consistent with observations of upper crustal shortening, sedimentation rates, and magmatism in the plateau. Shortening ceased across the plateau between 10 and 7 Ma, coincident with widespread ignimbrite eruptions and an abrupt decrease in sedimentation rates. The combination of geodynamic processes that appear to

  12. Personajes fuera de lugar: antropomorfos tardíos en el arte rupestre del norte semiárido de Chile Images out of place: late period antropomorphous figures in the rock art of central Chile

    Directory of Open Access Journals (Sweden)

    Andrés Troncoso

    2011-07-01

    Full Text Available Los personajes con vestimenta son una de las representaciones rupestres más conocidas del noroeste argentino y el norte de Chile, y su presencia en ambas áreas es un indicador de la importante dinámica de interacción ocurrida durante el período Tardío entre ambos espacios. Una variedad de estos personajes son los antropomorfos con cuerpos de lados cóncavos (sensu Montt 2005, los que en ocasiones se representan asociados a escutiformes santamarianos. Si bien se ha planteado que su distribución meridional por la vertiente andina occidental no traspasa el área de San Pedro de Atacama (Montt 2005, en este trabajo presentamos tres diseños antropomorfos con cuerpo de lados cóncavos reconocidos en el arte rupestre del valle de Illapel (30° LS, Provincia del Choapa, Norte Semiárido de Chile. En particular, se establece un análisis formal de estos diseños y se los compara con aquellos reconocidos en zonas más septentrionales, para luego discutir su cronología y evaluar las implicancias de su presencia en espacios tan alejados a su área de distribución original, registro que se asocia, en la región, a la circulación de diseños establecida por el Tawantinsuyu.Anthropomorphous figures with clothing stand out among the most frequent representations in the rock art of Northwestern Argentina and Northern Chile. Their ubiquity in both areas has been considered as an indicator of the dynamics of interregional interaction during late prehistory. Antropomorphous with concave sides (sensu Montt 2005 are but one expression of these popular type of representations, and at least in some cases are associated with "shield-man" of the Santa María style. Even though it has been stated previously that for the western Cordillera de los Andes the southernmost dispersion of this type of anthropomorphous figure is the San Pedro de Atacama area (Montt 2005, in this paper we present three such figures recently recorded in the rock art of the Illapel valley

  13. Monitoring land cover change of the dryland forest landscape of Central Chile (1975–2008)

    OpenAIRE

    Rey Benayas, José María; Schulz, Jennifer J.; Cayuela Delgado, Luis; Echeverría, Cristian; Salas Rey, Francisco Javier

    2010-01-01

    Las figuras que contiene el documento se localizan al final del mismo. Land cover and its configuration in the landscape are crucial components in the provision of biodiversity and ecosystem services. In Mediterranean regions, natural landscapes mostly covered by evergreen vegetation have been to a large extent transformed into cultural landscapes since long time ago. We investigated land cover changes in Central Chile using multi-temporal satellite imagery taken in 1975, 1985, 1999 and 20...

  14. Polygenetic development and paleoenvironmental implications of a Pleistocene calcrete at Tongoy, central northern Chile.

    OpenAIRE

    M. Pfeiffer; J. Le Roux; H. Kemnitz

    2011-01-01

    The Norte Chico Region, in central northern Chile, is a particularly sensitive area to Quaternary climate changes because of its extreme climatic gradients. However, very little has been done to determine the late Pleistocene climatic conditions of the area. Calcretes are known to be important repositories of information on past ecosystems and environments. In the Tongoy paleobay, a series of four marine beach terraces have developed over a Mio-Pliocene calcareous formation since MIS 11 to th...

  15. Direct measurement and prediction of bulk density on alluvial soils of central Chile

    OpenAIRE

    Manuel Casanova; Elizabeth Tapia; Oscar Seguel; Osvaldo Salazar

    2016-01-01

    The significance of soil bulk density (ρ) as a key indicator of soil quality was examined in this study. Bulk density values obtained by direct methods (clod, cylinder, and excavation) with three sample sizes (small, medium, and large) were compared with those obtained by 10 published pedotransfer functions (PTFs) for two alluvial soils (a massive fine-textured Fluventic Haploxeroll and an aggregated, coarse-textured Fluventic Haploxerept) of central Chile. With the exception of small cylinde...

  16. Provenance variations in the Late Paleozoic accretionary complex of central Chile as indicated by detrital zircons

    OpenAIRE

    Hervé, F.; Calderón, M.; Fanning, C. M.; Pankhurst, R.J.; Godoy, E.

    2013-01-01

    We present detrital zircon UPb SHRIMP age patterns for the central segment (34–42°S) of an extensive accretionary complex along coastal Chile together with ages for some relevant igneous rocks. The complex consists of a basally accreted high pressure/low temperature Western Series outboard of a frontally accreted Eastern Series that was overprinted by high temperature/low pressure metamorphism. Eleven new SHRIMP detrital zircon age patterns have been obtained for meta-turbidites from the cent...

  17. Coastal, valley, and oasis interaction: impact on the evolution of ancient populations in the South Central Andes.

    Science.gov (United States)

    Varela, Héctor H; Cocilovo, Jose A; Fuchs, María L; O'Brien, Tyler G

    2014-12-01

    The existing biocultural links are analyzed among ancient inhabitants of the Cochabamba valleys (Bolivia) from the Formative and Tiwanaku periods, coastal and inland Azapa region (Chile) from the Late Archaic to the Late periods, and the Atacama Desert oases (Chile) from the Formative period to the time of European contact. Craniometric information obtained from a sample of 565 individuals from different sites of the studied regions was evaluated using methods derived from quantitative genetics and multivariate statistical analysis techniques. It is shown that during the Formative and Tiwanaku periods inhabitants of the Cochabamba valleys maintained contact with the population of northern Chile. This contact was more fluid with the people from the interior valley of Azapa than it was with the settlers of San Pedro Atacama (SPA). An important biological affinity in the Late Period between the inhabitants of the Azapa valley and the late SPA groups is also examined. The Late-Inca Catarpe SPA sample shows a broad genetic variability shared with the majority of the groups studied. The results reaffirm the differences between the coastal and interior Azapa valley groups and strengthen the hypothesis of two pathways to populating the south central Andean area. The divergence observed among subpopulations can be explained by the spatiotemporal dispersion between them, genetic drift dispersion compensated by the action of gene flow, and cultural norms that regulate within group mating. PMID:25234247

  18. Tectonique Cénozoïque du Haut Plateau de la Puna, Nord Ouest Argentin, Andes Centrales.

    OpenAIRE

    Coutand, Isabelle

    1999-01-01

    Mémoires de Géosciences Rennes, n° 92, 381 p., ISBN: 2-905532-91-2 Les Andes Centrales sont l'exemple type d'une chaîne se développant le long d'une marge active en contexte non collisionel et résultent de la subduction légèrement oblique (-N75°E) de la plaque océanique Nazca sous le continent sud-américain. Elles sont caractérisées par la présence du haut plateau de l'Altiplano-Puna s'étendant depuis le Pérou au Nord jusqu'en Argentine au Sud et présentant une altitude moyenne avoisinant ...

  19. Early last glacial maximum in the Southern Central Andes reveals northward shift of the westerlies at ~39 ka

    Directory of Open Access Journals (Sweden)

    R. Zech

    2010-10-01

    Full Text Available The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka, resulting in reduced deep ocean ventilation, accumulation of "old dissolved carbon", and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the Southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

  20. Early last glacial maximum in the southern Central Andes reveals northward shift of the westerlies at ~39 ka

    Directory of Open Access Journals (Sweden)

    R. Zech

    2011-01-01

    Full Text Available The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka, resulting in reduced deep ocean ventilation, accumulation of old dissolved carbon, and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

  1. Investigating links between climate and orography in the central Andes: Coupling erosion and precipitation using a physical-statistical model

    Science.gov (United States)

    Lowman, Lauren E. L.; Barros, Ana P.

    2014-06-01

    Prior studies evaluated the interplay between climate and orography by investigating the sensitivity of relief to precipitation using the stream power erosion law (SPEL) for specified erosion rates. Here we address the inverse problem, inferring realistic spatial distributions of erosion rates for present-day topography and contemporaneous climate forcing. In the central Andes, similarities in the altitudinal distribution and density of first-order stream outlets and precipitation suggest a direct link between climate and fluvial erosion. Erosion rates are estimated with a Bayesian physical-statistical model based on the SPEL applied at spatial scales that capture joint hydrogeomorphic and hydrometeorological patterns within five river basins and one intermontane basin in Peru and Bolivia. Topographic slope and area data were generated from a high-resolution (˜90 m) digital elevation map, and mean annual precipitation was derived from 14 years of Tropical Rainfall Measuring Mission 3B42v.7 product and adjusted with rain gauge data. Estimated decadal-scale erosion rates vary between 0.68 and 11.59 mm/yr, with basin averages of 2.1-8.5 mm/yr. Even accounting for uncertainty in precipitation and simplifying assumptions, these values are 1-2 orders of magnitude larger than most millennial and million year timescale estimates in the central Andes, using various geological dating techniques (e.g., thermochronology and cosmogenic nuclides), but they are consistent with other decadal-scale estimates using landslide mapping and sediment flux observations. The results also reveal a pattern of spatially dependent erosion consistent with basin hypsometry. The modeling framework provides a means of remotely estimating erosion rates and associated uncertainties under current climate conditions over large regions. 2014. American Geophysical Union. All Rights Reserved.

  2. Non-explosive magma water interaction in a continental setting: Miocene examples from the Eastern Cordillera (central Andes; NW Argentina)

    Science.gov (United States)

    Vezzoli, Luigina; Matteini, Massimo; Hauser, Natalia; Omarini, Ricardo; Mazzuoli, Roberto; Acocella, Valerio

    2009-07-01

    The Middle-Upper Miocene Las Burras Almagro-El Toro (BAT) igneous complex within the Eastern Cordillera of the central Andes (˜24°S; NW Argentina) has revealed evidence of non-explosive interaction of andesitic magma with water or wet clastic sediments in a continental setting, including peperite generation. We describe and interpret lithofacies and emplacement mechanisms in three case studies. The Las Cuevas member (11.8 Ma) comprises facies related to: (i) andesite extruded in a subaqueous setting and generating lobe-hyaloclastite lava; and (ii) marginal parts of subaerial andesite lava dome(s) in contact with surface water, comprising fluidal lava lobes, hyaloclastite, and juvenile clasts with glassy rims. The Lampazar member (7.8 Ma) is represented by a syn-volcanic andesite intrusion and related peperite that formed within unconsolidated, water-saturated, coarse-grained volcaniclastic conglomerate and breccia. The andesite intrusion is finger-shaped and grades into intrusive pillows. Pillows are up to 2 m wide, tightly packed near the intrusion fingers, and gradually become dispersed in the host sediment ≥50 m from the parent intrusion. The Almagro A member (7.2 Ma) shows evidence of mingling between water-saturated, coarse-grained, volcaniclastic alluvial breccia and intruding andesite magma. The resulting intrusive pillows are characterized by ellipsoidal and tubular shape and concentric structure. The high-level penetration of magma in this coarse sediment was unconfined and irregular. Magma was detached in apophyses and lobes with sharp contacts and fluidal shapes, and without quench fragmentation and formation of a hyaloclastite envelope. The presence of peperite and magma water contact facies in the BAT volcanic sequence indicates the possible availability of water in the system between 11 7 Ma and suggests a depositional setting in this part of the foreland basin of the central Andes characterized by an overall topographically low coastal floodplain

  3. Carbonatite diversity in the Central Andes: the Ayopaya alkaline province, Bolivia

    Science.gov (United States)

    Schultz, Frank; Lehmann, Bernd; Tawackoli, Sohrab; Rössling, Reinhard; Belyatsky, Boris; Dulski, Peter

    2004-12-01

    The Ayopaya province in the eastern Andes of Bolivia, 100 km NW of Cochabamba, hosts a Cretaceous alkaline rock series within a Palaeozoic sedimentary sequence. The alkaline rock association comprises nepheline-syenitic/foyaitic to ijolitic intrusions, carbonatite, kimberlite, melilititic, nephelinitic to basanitic dykes and diatremes, and a variety of alkaline dykes. The carbonatites display a wide petrographic and geochemical spectrum. The Cerro Sapo area hosts a small calciocarbonatite intrusion and a multitude of ferrocarbonatitic dykes and lenses in association with a nepheline-syenitic stock. The stock is crosscut by a spectacular REE-Sr-Th-rich sodalite-ankerite-baryte dyke system. The nearby Chiaracke complex represents a magnesiocarbonatite intrusion with no evidence for a relationship to igneous silicate rocks. The magnesiocarbonatite (Σ REE up to 1.3 wt%) shows strong HREE depletion, i.e. unusually high La/Yb ratios (520 1,500). Calciocarbonatites (Σ REE up to 0.5 wt%) have a flatter REE distribution pattern (La/Yb 95 160) and higher Nb and Zr contents. The sodalite-ankerite-baryte dyke system shows geochemical enrichment features, particularly in Na, Ba, Cl, Sr, REE, which are similar to the unusual natrocarbonatitic lavas of the recent volcano of Oldoinyo Lengai, Tanzania. The Cerro Sapo complex may be regarded as an intrusive equivalent of natrocarbonatitic volcanism, and provides an example for carbonatite genesis by late-stage crystal fractionation and liquid immiscibility. The magnesiocarbonatite intrusion of Chiaracke, on the other hand, appears to result from a primary carbonatitic mantle melt. Deep seated mantle magmatism/metasomatism is also expressed by the occurrence of a kimberlite dyke. Neodymium and strontium isotope data (ɛNd 1.4 5.4, 87Sr/86 Sr

  4. Impact of Intrathermocline eddies on seamount and oceanic island off Central Chile: Observation and modeling

    Science.gov (United States)

    Hormazabal, Samuel; Morales, Carmen; Cornejo, Marcela; Bento, Joaquim; Valencia, Luis; Auger, Pierre; Rodriguez, Angel; Correa, Marco; Anabalón, Valeria; Silva, Nelson

    2016-04-01

    In the Southeast Pacific, oceanographic processes that sustain the biological production necessary to maintain the ecosystems associated to seamounts and oceanic islands are still poorly understood. Recent studies suggest that the interaction of mesoscale and submesoescale eddies with oceanic islands and seamounts could be playing an important role in the time-space variability of primary production. In this work, research cruises, satellite data and Regional Ocean Modeling System (ROMS) results have been used to describe the main characteristics of intrathermocline eddies (ITE) and their impact on the Juan Fernández archipelago (JFA), off central Chile. The JFA is located off the coast of central Chile (33°S), and is composed of three main islands: Robinson Crusoe (RC), Alejandro Selkirk (AS) and Santa Clara (SC). Between the RC and AS are located the westernmost seamounts (JF6 and JF5) of the Juan Fernández archipelago. Satellite altimetry data (sea surface height from AVISO) were used to detect and track mesoscale eddies through eddy-tracking algorithm. Physical, chemical and biological parameters as temperature, salinity, dissolved oxygen and fluorescence were measured in the water column at JF5 and JF6, and along the coast off central Chile (30-40°S). Results from the research cruise exhibit the interaction between an ITE and the seamount JF6. Eddy-tracking results showed that the ITE observed at the JF6 was formed at the coast off central-southern Chile, traveled ~900 km seaward and after ~9 months reached the JF5 and JF6 region. Observations along the Chilean coast confirmed that the coast corresponds to the formation area of the observed ITE. In this region, ITEs are represented by subsurface lenses (~100 km diameter; 400 m thickness) of homogeneous salinity, nutrient rich and oxygen-poor equatorial subsurface water mass (ESSW) which is transported poleward by the Peru-Chile undercurrent in the coastal band and seaward by ITEs. The effect of ITEs on the

  5. Seismic imaging of a convergent continental margin and plateau in the central Andes (Andean Continental Research Project 1996 (ANCORP'96))

    Science.gov (United States)

    Oncken, O.; Asch, G.; Haberland, C.; Metchie, J.; Sobolev, S.; Stiller, M.; Yuan, X.; Brasse, H.; Buske, S.; Giese, P.; GöRze, H.-J.; Lueth, S.; Scheuber, E.; Shapiro, S.; Wigger, P.; Yoon, M.-K.; Bravo, P.; Vieytes, H.; Chong, G.; Gonzales, G.; Wilke, H.-G.; Lüschen, E.; Martinez, E.; RöSsling, R.; Ricaldi, E.; Rietbrock, A.

    2003-07-01

    A 400-km-long seismic reflection profile (Andean Continental Research Project 1996 (ANCORP'96)) and integrated geophysical experiments (wide-angle seismology, passive seismology, gravity, and magnetotelluric depth sounding) across the central Andes (21°S) observed subduction of the Nazca plate under the South American continent. An east dipping reflector (Nazca Reflector) is linked to the down going oceanic crust and shows increasing downdip intensity before gradual breakdown below 80 km. We interpret parts of the Nazca Reflector as a fluid trap located at the front of recent hydration and shearing of the mantle, the fluids being supplied by dehydration of the oceanic plate. Patches of bright (Quebrada Blanca Bright Spot) to more diffuse reflectivity underlie the plateau domain at 15-30 km depth. This reflectivity is associated with a low-velocity zone, P to S wave conversions, the upper limits of high conductivity and high Vp/Vs ratios, and to the occurrence of Neogene volcanic rocks at surface. We interpret this feature as evidence of widespread partial melting of the plateau crust causing decoupling of the upper and lower crust during Neogene shortening and plateau growth. The imaging properties of the continental Moho beneath the Andes indicate a broad transitional character of the crust-mantle boundary owing to active processes like hydration of mantle rocks (in the cooler parts of the plate margin system), magmatic underplating and intraplating under and into the lowermost crust, mechanical instability at Moho, etc. Hence all first-order features appear to be related to fluid-assisted processes in a subduction setting.

  6. A glassy lava flow from Toconce volcano and its relation with the Altiplano-Puna Magma Body in Central Andes

    Science.gov (United States)

    Godoy, B.; Rodriguez, I.; Aguilera, F.

    2012-12-01

    Toconce is a composite stratovolcano located at the San Pedro - Linzor volcanic chain (SPLVC). This volcanic chain distributes within the Altiplano-Puna region (Central Andes) which is characterized by extensive rhyodacitic-to-rhyolitic ignimbritic fields, and voluminous domes of dacitic-to-rhyolitic composition (de Silva, 1989). The felsic melts that gave origin to ignimbrites and domes at this area were generated by mixing of mantle-derived magmas and anatectic melts assimilated during their ascent through the thick crust. Thus, partially molten layers exist in the upper crust below the APVC (de Silva et al., 2006). Evidence of large volumes of such melts has been also proposed by geophysical methods (i.e. the Altiplano-Puna Magma Body; Chmielowsky et al., 1999) In this work, petrography and whole rock, mineralogical and melt inclusions geochemistry of a glassy lava flow of Toconce volcano are presented. Petrographically, this lava flow shows a porphyric texture, with euhdral to subhedral plagioclase, ortho- and clino-pyroxene phenocrysts immersed in a glassy groundmass. Geochemically, the lava flow has 64.7% wt. SiO2. The glassy groundmass (~70% wt. SiO2) is more felsic than all the lavas in the volcanic chain (47-68% wt., Godoy et al., 2011). Analyzed orthopyroxene-hosted melt inclusions show an even higher SiO2 content (72-75% wt.), and a decreasing on Al2O3, Na2O, and CaO content with differentiation. Crystallization pressures of this lava flow, obtained using Putirka's two-pyroxene and clinopyroxene-liquid models (Putirka, 2008), range between 6 and 9 kbar. According to crystallization pressures, and major element composition, a felsic source located at shallow crustal pressures - where plagioclase is a stable mineralogical phase - originated the inclusions. This could be related to the presence of the Altiplano-Puna Magma Body (APMB) located below SPLVC. On the other hand, glassy groundmass, and disequilibrium textures in minerals of this lava flow could

  7. Modelling the seasonal dynamics of the Peru-Chile Undercurrent off Central Chile (30-40°S)

    Science.gov (United States)

    Vergara, Odette A.; Echevín, Vincent; Sepúlveda, Héctor H.; Colas, Francois; Quiñones, Renato A.

    2016-07-01

    The seasonal variability of the hydrology and the poleward subsurface Peru-Chile Undercurrent (PCUC) off the central Chilean coast (29-41°S) were examined using a high-resolution regional model. The model realistically reproduced observed sea level variability, such as intense anticyclonic eddies, the offshore intensification of the poleward flow and the reduced nearshore equatorward flow during autumn, as well as the equatorward intensification of nearshore meandering flow during spring. Values for geostrophic eddy kinetic energy were high along the coast between 30° and 37°S, and lower south of this area. The modelled poleward undercurrent showed latitudinal variability in velocity and transport. The maximum average transport reported was 0.8 Sv near 30°S, consistent with previous modelling studies and estimations derived from in situ observations. The poleward reduction in undercurrent strength was shown to be partly generated by the poleward decrease in wind stress curl and by the formation of a westward jet near 35°S associated with westward-propagating eddies. A Lagrangian analysis of the modelled water parcels transported by the undercurrent shows that only 14-20% of the subsurface floats transported by the undercurrent upwelled into the surface layer within the subsequent six months after their release. The floats remaining within the subsurface layer were likely transported further south by the current, offshore by westward-propagating eddies or equatorward by the deeper part of the surface coastal current.

  8. Characterization of the hydrothermal system of the Tinguiririca Volcanic Complex, Central Chile, using structural geology and passive seismic tomography

    Science.gov (United States)

    Pavez, C.; Tapia, F.; Comte, D.; Gutiérrez, F.; Lira, E.; Charrier, R.; Benavente, O.

    2016-01-01

    A structural characterization of the hydrothermal-volcanic field associated with the Tinguiririca Volcanic Complex had been performed by combining passive seismic tomography and structural geology. This complex corresponds to a 20 km long succession of N25°E oriented of eruptive centers, currently showing several thermal manifestations distributed throughout the area. The structural behavior of this zone is controlled by the El Fierro-El Diablo fault system, corresponding to a high angle reverse faults of Oligocene-Miocene age. In this area, a temporary seismic network with 16 short-period stations was setup from January to April of 2010, in the context of the MSc thesis of Lira (2010), covering an area of 200 km2 that corresponds with the hydrothermal field of Tinguiririca Volcanic Complex (TVC), Central Chile, Southern Central Andes. Using P- and S- wave arrival times, a 3D seismic velocity tomography was performed. The preliminary locations of 2270 earthquakes have first been determined using an a priori 1D velocity model. Afterwards, a joint inversion of both, the 3D velocity model and final locations have been obtained. High Vp/Vs ratios are interpreted as zones with high hot fluid content and high fracturing. Meanwhile, low Vp/Vs anomalies could represent the magmatic reservoir and the conduit network associated to the fluid mobility. Based on structural information and thermal manifestations, these anomalies have been interpreted. In order to visualize the relation between local geology and the velocity model, the volume associated with the magma reservoir and the fluid circulation network has been delimited using an iso-value contour of Vp/Vs equal to 1.70. The most prominent observed feature in the obtained model is a large "V" shaped low-velocity anomaly extending along the entire study region and having the same vergency and orientation as the existing high-angle inverse faults, which corroborates that El Fierro-El Diablo fault system represents the

  9. August-September 2003 small vulcanian eruption at the Nevados de Chillán Volcanic Complex (36°50'S, Southern Andes (Chile

    Directory of Open Access Journals (Sweden)

    José A. Naranjo

    2004-12-01

    Full Text Available During the winter months of August-September 2003 a small (VEI=0-1 eruption took place at the 9 km long fissure-like Nevados de Chillán Volcanic Complex (36°50'S, that includes Nuevo (formed between 1906 and 1945 and Arrau (formed in the 1973-1986 period volcanoes. Only the local inhabitants and tourists of the ski resort located at the foothills noted the eruption. From August 29 to September 4, 2003, low-magnitude explosive events occurred and brown-greyish to white gas and ash columns reached up to 400 to 500 m above the crater, rising at periods that lasted for 20 to 25 minutes. After the first week, explosions became more sporadic and occurred at two-three day intervals. Strong prevailing winds from the north dispersed the low-altitude plume to the SSE until the eruption finally stopped by the middle of September. A new compound crater is now present in the saddle between Nuevo and Arrau volcanoes. This 64 m fissure-like double crater is surrounded by an area of intense fumaroles near to Nuevo volcano suggesting the renewal of activity in the complexPequeña erupción vulcaniana de agosto-septiembre en el Complejo Volcánco Nevados de Chillán (36°50'S, Andes del sur (Chile. Durante los meses invernales de agosto y septiembre de 2003 ocurrió una pequeña erupción (IEV=0-1 en la fisura de 9 km de largo del Complejo Volcánico Nevados de Chillán (36°50'S, que incluye a los volcanes Nuevo (formado entre 1906 y 1945 y Arrau (formado entre 1973 y 1986. La erupción fue advertida únicamente por los lugareños y los visitantes del centro invernal situado a los pies del volcán. La semana del 20 al 27 de agosto 2003 se produjeron eventos explosivos de baja magnitud con columnas de gas y ceniza de color pardo-grisáceo y blanco que alcanzaron alturas de 400 a 500 m con períodos de 20 a 25 minutos. Después de la primera semana las explosiones se hicieron más esporádicas ocurriendo a intervalos de 2 a 3 días. Los fuertes vientos

  10. Snakes of an urban-rural landscape in the central Andes of Colombia: species composition, distribution, and natural history

    Directory of Open Access Journals (Sweden)

    Julián Andrés Rojas-Morales

    2012-12-01

    Full Text Available From 2005 to 2011, I studied the composition, distribution and natural history of an Andean urban-rural snake assemblage at the Cordillera Central of Colombia, based on three data sources: (1 examination of specimens in the MHN-UC [Museo de Historia Natural, Universidad de Caldas], (2 incidental encounters by author, and (3 collection of data by other researchers. Additionally, I provide natural history notes for the species involved. A total of 14 species, including two subspecies of snakes, belonging to 12 genera and four families, have been found in the studied area (municipality of Manizales, Caldas. Taking into account this total, 10 had atleast one record in the urban area, 13 in the rural area and 14 in forested areas. Only Liophis epinephelus bimaculatus was found exclusively in forest environment. Three species (21.4% are apparently endemic to the region, six species (42.8% correspond to afauna representative of the Tropical–Andean range of South America, four species (28.5% are distributed from Central America to the tropical Andes, and only one species is widely distributed in the whole continent. The snake assemblage in Manizales is mostly terrestrial, and in general, the species tend to be more active in the rainy periods of the year (mainly from October–December, and most of them may occasionally be found in urban areas, mainly close to areas of vegetation such as crops and pastures.

  11. Sediment yield along the Andes: continental budget, regional variations, and comparisons with other basins from orogenic mountain belts

    Science.gov (United States)

    Latrubesse, Edgardo M.; Restrepo, Juan D.

    2014-07-01

    We assess the sediment yield at 119 gauging stations distributed from Colombia to Patagonia, covering the different morphotectonic and morphoclimatic settings of the Andes. The most productive areas are the Meta River basin within the northern Andes and the Bolivian and northern Argentina-Chaco systems, which produce an average of 3345, 4909 and 2654 t km2 y- 1 of sediment, respectively. The rivers of the northern and central Andes (excluding the Pacific watersheds of Peru, northern Chile, and central Argentina) have a weighted mean sediment yield of 2045 t km- 2 y- 1 and produce 2.25 GTy- 1 of total sediment. A major constraint estimating the Andean continental budget of sediment yield lies in the lack of gauging data for the Peruvian region. Using the available gauge stations, the regional sediment yield appears underestimated. Assuming a higher value of sediment yield for the Peruvian Andes, the total budget for the whole central Andes could range between 2.57 GT y- 1 and 3.44 GT y- 1. A minimum of ~ 0.55 GT y- 1 and a probable maximum of ~ 1.74 GT y- 1 of sediment are deposited in the intramontane and surrounding proximal sedimentary basins. The magnitude of sediment yield in the Andes is comparable to other rivers draining orogenic belts around the world.

  12. Las comunidades relictas de Gomortega keule (Gomortegaceae, Magnoliopsida en Chile central

    Directory of Open Access Journals (Sweden)

    Sánchez Álvarez, Ana

    1999-12-01

    Full Text Available Some inventories were made in fourteen localities of Chilean températe forest with presence of Gomortega keule. All of them are situated on the west side of the Coastal Range in Central Chile. This species, the only member of the Gomortegaceae and an endemic to this área of Chile, is endangered because of habitat occupation by plantations of exotic species. In this paper, the floristic composition and ecology of these communities are described. The information about the distribution of this species is also updated.Se caracterizan florísticamente las comunidades de Gomortega keule existentes en la ladera occidental de la Cordillera de la Costa de Chile central. La riqueza florística de estas comunidades es muy elevada, con un total de 106 especies para las 14 localidades inventariadas, distribuidas en 56 familias y 83 géneros. La clara dominancia de fanerófitos (78,3%, y dentro de éstos la distribución de las distintas formas de crecimiento (17% de trepadoras y 3,8% de epífitos, condiciona tanto estructural como fisionómicamente a estas comunidades. El grupo de especies propias del bosque valdiviano es el más abundante, 42,5% de las especies, seguido de las de carácter esclerófilo típicas del Valle Central (14,2%. La conservación de G. keule, única especie de la familia Gomortegaceae, está completamente ligada al mantenimiento de estas comunidades, que en la actualidad están siendo sustituidas sistemáticamente por plantaciones forestales de especies exóticas en toda su área de distribución.

  13. A new species of Phymaturus (Iguania: Liolaemidae) of the palluma group from Central Chile

    OpenAIRE

    Troncoso-Palacios, Jaime; Lobo, Fernando

    2012-01-01

    We examined specimens of Phymaturus from four locations in central Chile, between 34º50´S and 36º00´S (from Termas del Flaco and from Lircay and its surroundings), where the only recognized species is P. maulense. We found several differences in the scalation and in the color pattern among them. The samples from Lircay and its surroundings correspond to topotypes of P. maulense and two more populations assignable to this species (Termas del Campanario and Laguna del Maule, new records), but t...

  14. Cloud forest restoration for erosion control in a Kichwa community of the Ecuadorian central Andes Mountains

    Science.gov (United States)

    Backus, L.; Giordanengo, J.; Sacatoro, I.

    2013-12-01

    The Denver Professional Chapter of Engineers Without Borders (EWB) has begun conducting erosion control projects in the Kichwa communities of Malingua Pamba in the Andes Mountains south of Quito, Ecuador. In many high elevation areas in this region, erosion of volcanic soils on steep hillsides (i.e., erosion sites, the multidisciplinary Erosion Control team traveled to Malingua Pamba in October 2012 to conduct final design and project implementation at 5 sites. In partnership with the local communities, we installed woody cloud forest species, grass (sig-sig) contour hedges, erosion matting, and rock structures (toe walls, plunge pools, bank armoring, cross vanes, contour infiltration ditches, etc.) to reduce incision rates and risk of slump failures, facilitate aggradation, and hasten revegetation. In keeping with the EWB goal of project sustainability, we used primarily locally available resources. High school students of the community grew 5000 native trees and some naturalized shrubs in a nursery started by the school principal, hand weavers produced jute erosion mats, and rocks were provided by a nearby quarry. Where possible, local rock was harvested from landslide areas and other local erosion features. Based on follow up reports and photographs from the community and EWB travelers, the approach of using locally available materials installed by the community is successful; plants are growing well and erosion control structures have remained in place throughout the November to April rainy season. The community has continued planting native vegetation at several additional erosion sites. Formal monitoring will be conducted in October 2013, followed by analysis of data to determine if induced meandering and other low-maintenance erosion control techniques are working as planned. For comparison of techniques, we will consider installing check dams in comparable gullies. The October 2013 project will also focus on training the community how to conduct erosion

  15. A multi-institutional and interdisciplinary approach to the assessment of vulnerability and adaptation to climate change in the Peruvian Central Andes: problems and prospects

    Directory of Open Access Journals (Sweden)

    A. G. Martínez

    2008-04-01

    Full Text Available A local integrated assessment of the vulnerability and adaptation to climate change in the Mantaro River Basin, located in Peruvian Central Andes, was developed between years 2003 to 2005. In this paper we present some lessons learned during the development of this study, emphasizing the multi-institutional and interdisciplinary efforts, briefly showing the methodological aspects, and pointing out the main problems found.

  16. 40Ar/39Ar ages from blueschists of the Jambaló region, Central Cordillera of Colombia : implications on the styles of accretion in the Northern Andes

    OpenAIRE

    Bustamante, A.; Juliani, C.; C. M. Hall; Essene, E. J.

    2011-01-01

    This paper presents the first argon dating of blueschists from the Jambaló area (Cauca Department) in the Central Cordillera of the Colombian Andes. Step-heating 40Ar/39Ar spectra were obtained for mica from several lenses of blueschists including greenschist facies rocks. The blueschists are mainly constituted of preserved lenticular cores in strongly mylonitic rocks, which resulted from retrometamorphic processes that affected the high pressure rocks during their exhumation. The majority of...

  17. Evolucion paleogeografica del Paleozoico medio y superior de los Andes centrales (14°-18°S) en Bolivia : evidencia del desplazamiento latitudinal de la cuenca de antepais

    OpenAIRE

    Isaacson, P.E.; Diaz Martinez, Enrique

    1994-01-01

    El estudio estratigrafico, sedimentologico y paleontologico de la secuencia del Devonico a Permico del oeste de Bolivia permite la reconstruccion de la paleogeografia de una parte de los Andes Centrales (14 a 18oS), cuya historia sedimentaria puede dividirse en cuatro fases: 1) Sedimentacion siliciclastica en una cuenca marina somera durante la mayor parte del Devonico (Lochkoviano a Frasniano), con un aumento de la sedimentacion durante el Emsiano y Eifeliano, y aparentes interrupciones dura...

  18. Improved 3D density modelling of the Central Andes from combining terrestrial datasets with satellite based datasets

    Science.gov (United States)

    Schaller, Theresa; Sobiesiak, Monika; Götze, Hans-Jürgen; Ebbing, Jörg

    2015-04-01

    As horizontal gravity gradients are proxies for large stresses, the uniquely high gravity gradients of the South American continental margin seem to be indicative for the frequently occurring large earthquakes at this plate boundary. It has been observed that these earthquakes can break repeatedly the same respective segment but can also combine to form M>9 earthquakes at the end of longer seismic cycles. A large seismic gap left behind by the 1877 M~9 earthquake existed in the northernmost part of Chile. This gap has partially been ruptured in the Mw 7.7 2007 Tocopilla earthquake and the Mw 8.2 2014 Pisagua earthquake. The nature of this seismological segmentation and the distribution of energy release in an earthquake is part of ongoing research. It can be assumed that both features are related to thickness variations of high density bodies located in the continental crust of the coastal area. These batholiths produce a clear maximum in the gravity signal. Those maxima also show a good spatial correlation with seismic asperity structures and seismological segment boundaries. Understanding of the tectonic situation can be improved through 3D forward density modelling of the gravity field. Problems arise in areas with less ground measurements. Especially in the high Andes severe gaps exist due to the inaccessibility of some regions. Also the transition zone between on and offshore date data displays significant problems, particularly since this is the area that is most interesting in terms of seismic hazard. We modelled the continental and oceanic crust and upper mantle using different gravity datasets. The first one includes terrestrial data measured at a station spacing of 5 km or less along all passable roads combined with satellite altimetry data offshore. The second data set is the newly released EIGEN-6C4 which combines the latest satellite data with ground measurements. The spherical harmonics maximum degree of EIGEN-6C4 is 2190 which corresponds to a

  19. Constraining the magma flow record based on magmatic and magnetic data in La Gloria Pluton, central Chile

    Science.gov (United States)

    Gutierrez, F. J.; Payacán, I.; Gelman, S. E.; Bachmann, O.; Creative Physical Petrology Team

    2013-05-01

    The magmatic origin of the anisotropy of magnetic susceptibility (AMS) is examined in comparison with magmatic anisotropy data in a small, shallow, silicic magma reservoir in the upper crust. La Gloria Pluton (LGP) is a 10 Ma granodiorite/quartz monzonite of about 250 km3 located in the southern Andes, central Chile. LGP represents a particularly simple case of a silicic intrusion that was assembled in only a few pulses and cooled over a short time interval. Hornblende, biotite and minor magnetite are ubiquitous mafic phases. The AMS tensor indicates that magnetic fabric has an oblate shape (i.e. magnetic foliation is higher than magnetic lineation). Lineations are weak (values up to 1.05), have a N-NW trend with a nearly horizontal dip and are interpreted to represent axisymmetric convection parallel to the main pluton elongation. Foliations are more pronounced (values up to 1.14), having NW trends and dips that vary gradually from vertical at the walls, to horizontal at the center and near the roof of the chamber. We selected 12 samples from AMS sites to obtain petrographic data (well-distributed throughout the pluton, containing samples from the walls, the center and the roof of LGP), and then, determine the magmatic fabric (anisotropy, lineation, foliation). We made 3 oriented thin sections per sample oriented with the AMS. Magmatic anisotropy data were obtained by measuring mineral length, width and orientation in photomicrographs of the three main planes of the AMS tensor, producing 3-D mineral data which were collected for plagioclase and amphibole + bitotite independently. For each site, a Bingham distribution with 95% of confidence is used to determine the mean mineral orientations and their angle difference with the AMS axes. Magmatic anisotropy tensor and rotations with respect to the AMS tensor are determined using both eigenvalues and minimization algorithms. Preliminary results indicate that crystals are coherently oriented in both mineral groups, and

  20. A Terrestrial Reference Frame (TRF, coordinates and velocities for South American stations: contributions to Central Andes geodynamics

    Directory of Open Access Journals (Sweden)

    M. V. Mackern

    2009-12-01

    Full Text Available Satellite positioning systems allow the fixing of the location of a point on the Earth's surface with very good precision and accuracy. To do this, however, it is necessary to determine the point coordinates taking account the reference system and the movements that affect them because of tectonic plate movements. These reference systems are materialized by a significant number of continuous measurement stations in South America. In SIRGAS (Sistema de Referencia Geocéntrico para las Américas, there are four Analysis Centers that process the data collected from satellites of the Global Navigation Satellite Systems (GNSS, with the primary purpose to maintain the international terrestrial reference frame through calculation of the coordinates and velocities of the continuous GNSS stations of the SIRGAS-CON Network.

    In this work, we demonstrate the quality of the solutions from CIMA, one of the SIRGAS official processing centers operating in Mendoza, Argentina, in comparison with other South American processing centers. The importance of precise calculations of coordinates and velocities in a global frame is also shown. Finally, we give estimations of velocities from stations located within deformation zones in the Central Andes.

  1. Reduction of firewood consumption by households in south-central Chile associated with energy efficiency programs

    International Nuclear Information System (INIS)

    Cities in the central-southern area of Chile face serious environmental pollution due to extensive use of firewood for heating. Low energy efficiency of constructions and cold climate increase the problem, which also affects native forests. The aims of this study are to characterize energy consumption in dwellings of this region, investigate the reduction potential, and study social and environmental consequences of high consumption of firewood. Actual energy consumption is studied with information from surveys, potential for reduction is modeled with software and other consequences are analyzed from previous studies. Results for the city of Valdivia show high firewood consumption per household, with a media bulk volume near 12 m3/year. Thermal regulations are softer compared with other countries. Moreover, around 85% of buildings were built before enforcing codes in 2007, and has almost no thermal protection. The reduction potential due to thermal improvements is found to be very high (62%) if buildings are refurbished to comply with the present Chilean Norm of 2007, but it reaches a 77% reduction if refurbished according to stricter foreign regulations. Therefore, an energy efficiency program strongly addressing existing buildings has the largest potential for reducing firewood use, and therefore mitigate environmental and health impacts. - Highlights: • High firewood consumption and environmental pollution in cities of south-central Chile. • High use of firewood due to inefficient constructions and soft thermal regulations. • Potential reduction of energy consumption up to 77% with more demanding regulations. • Policies should address building stock before thermal regulation, corresponding to 85%

  2. Growth of Stone pine (Pinus pinea L. European provenances in central Chile

    Directory of Open Access Journals (Sweden)

    Loewe_Muñoz V

    2016-08-01

    Full Text Available Pinus pinea is characterized by phenotypic plasticity, tolerance to harsh soils and climates, but low differentiation in growth parameters and low genetic variability. Growth and cone production of six European stone pine provenances (two from Italy, three from Spain and one from Slovenia were analyzed in a field trial experiment established in central Chile. The study evaluated height, diameter at breast height (DBH and crown diameter growth of 147 nineteen-year-old trees per provenance, as well as fruiting variables (i.e., number of cones per tree and cone weight. Survival over the first 7 years was also evaluated. Provenances significantly differed in cone number per tree, cone weight, height and DBH growth, and crown diameter growth. Provenances were grouped according to growth and production variables: one group included the Italian and Slovenian provenances, the second group Andalucía and Sierra Morena (Spain, and the third included Meseta Castellana (Spain. Individual cone production was positively correlated with cone weight and other growth variables. Meseta Castellana provenance showed the highest growth and productivity. Our results provide useful information for the selection of P. pinea provenances to be used in new plantations in central Chile.

  3. Diet in pottery-making societies from Central Chile: The contribution of stable isotope analyses

    International Nuclear Information System (INIS)

    This is the first time that stable carbon, nitrogen and oxygen isotope analyses of human bones and teeth have been used to reconstruct subsistence and settlement patterns of prehispanic ceramic societies from Central Chile. Isotope analyses, unlike the evidence from botanical, faunal and artifactual remains from archaeological sites, and from dental and skeletal pathologies, gave information of which resources were really eaten by each individual during the last years of their life. The human data were evaluated against isotopic values of marine and terrestrial resources from central Chile. These results were interpreted taking into consideration different lines of paleodiet evidence. The main contributions are: empirical evidence of dietary differences according to cultural groups; low dependence on marine foods for most people living on the coast; indirect evidence of mobility strategies that show differences between Early and Late Intermediate societies; increased dependence on maize with time, especially among the Aconcagua people; gender differences in maize consumption for the same Aconcagua groups, men showing the greatest levels of maize intake. The results support some hypotheses, such as the difference in dietary patterns between contemporary Bato and Lolleo groups, contradict others, such as the supposed importance of marine diet for coastal inhabitants, and open new research questions for the future

  4. Phylogeny and biogeography of the New World siskins and goldfinches: rapid, recent diversification in the Central Andes.

    Science.gov (United States)

    Beckman, Elizabeth J; Witt, Christopher C

    2015-06-01

    Time-calibrated molecular phylogenies can help us to understand the origins of the diverse and unique Andean avifauna. Previous studies have shown that the tempo of diversification differed between the Andes and adjacent lowland regions of South America. Andean taxa were found to have speciated more recently and to have avoided the decelerated diversification that is typical of Neotropical lowland clades. The South American siskins, a Pleistocene finch radiation, may typify this Andean pattern. We investigated the phylogenetic biogeography of all the New World siskins and goldfinches in new detail. To understand the specific role of the Andes in siskin diversification, we asked: (1) Was diversification faster in Andean siskin lineages relative to non-Andean ones? (2) Did siskin lineages move into and out of the Andes at different rates? We found that siskin lineages in the Andes had higher diversification rates and higher outward dispersal rates than siskin lineages outside the Andes. We conclude that páramo expansion and contraction in response to Pleistocene climatic cycles caused accelerated diversification and outward dispersal in Andean siskins. The younger average age of bird species in the Andes compared to lowland South America may be attributable to bursts of recent diversification in siskins and several other vagile, open-habitat clades. PMID:25796324

  5. Geodynamic controls on the contamination of Cenozoic arc magmas in the southern Central Andes: Insights from the O and Hf isotopic composition of zircon

    Science.gov (United States)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Dhuime, Bruno; Elliott, Tim; Litvak, Vanesa D.; Alonso, Ricardo; Hinton, Richard

    2015-09-01

    Subduction zones, such as the Andean convergent margin of South America, are sites of active continental growth and crustal recycling. The composition of arc magmas, and therefore new continental crust, reflects variable contributions from mantle, crustal and subducted reservoirs. Temporal (Ma) and spatial (km) variations in these contributions to southern Central Andean arc magmas are investigated in relation to the changing plate geometry and geodynamic setting of the southern Central Andes (28-32° S) during the Cenozoic. The in-situ analysis of O and Hf isotopes in zircon, from both intrusive (granitoids) and extrusive (basaltic andesites to rhyolites) Late Cretaceous - Late Miocene arc magmatic rocks, combined with high resolution U-Pb dating, demonstrates distinct across-arc variations. Mantle-like δ18O(zircon) values (+5.4‰ to +5.7‰ (±0.4 (2σ))) and juvenile initial εHf(zircon) values (+8.3 (±0.8 (2σ)) to +10.0 (±0.9 (2σ))), combined with a lack of zircon inheritance suggests that the Late Cretaceous (∼73 Ma) to Eocene (∼39 Ma) granitoids emplaced in the Principal Cordillera of Chile formed from mantle-derived melts with very limited interaction with continental crustal material, therefore representing a sustained period of upper crustal growth. Late Eocene (∼36 Ma) to Early Miocene (∼17 Ma) volcanic arc rocks present in the Frontal Cordillera have 'mantle-like' δ18O(zircon) values (+4.8‰ (±0.2 (2σ) to +5.8‰ (±0.5 (2σ))), but less radiogenic initial εHf(zircon) values (+1.0 (±1.1 (2σ)) to +4.0 (±0.6 (2σ))) providing evidence for mixing of mantle-derived melts with the Late Paleozoic - Early Mesozoic basement (up to ∼20%). The assimilation of both Late Paleozoic - Early Mesozoic Andean crust and a Grenville-aged basement is required to produce the higher than 'mantle-like' δ18O(zircon) values (+5.5‰ (±0.6 (2σ) to +7.2‰ (±0.4 (2σ))) and unradiogenic, initial εHf(zircon) values (-3.9 (±1.0 (2σ)) to +1.6 (±4.4 (2

  6. Ages and geochemistry of Mesozoic-Eocene back-arc volcanic rocks in the Aysén region of the Patagonian Andes, Chile

    Directory of Open Access Journals (Sweden)

    Miguel A. Parada

    2001-07-01

    Full Text Available Eighteen new radiometric ages (fourteen 40Ar-39Ar, four K-Ar, combined with previously published ages, confirm the existence of three main extensional back-arc volcanic events, previously defined by stratigraphic relationships, in Chilean Patagonia (Aysén region. These three events developed during the Middle Jurassic -Early Cretaceous (160-130 Ma. Cretaceous (114-75 Ma, and Eocene (55-46 Ma. Based on distinct geochemical data and Sr-Nd isotopic characteristics of the back-arc volcanic rocks collected north and south of 46°30'S, two Mesozoic-Eocene magmatic domains are recognized: Northern Magmatic Domain (NMD and Southern Magmatic Domain (SMD. Most analyzed basalts and intermediate volcanic rocks of the NMD have alkaline affinities and depleted to slightly depleted Sr-Nd isotopic values similar to those derived from an asthenosphere-dominated source. The SMD mafic volcanic rocks have a subalkaline character and more enriched Sr-Nd isotopic signatures, comparable to those derived from a lithospheric source. The felsic volcanic rocks of the SMD have lower eNd values and slightly higher initial 87Sr/86Sr ratios than the NMD felsic rocks, suggesting a larger crustal contribution in the magma sources. The geochemical and isotopic distinction between NMD and SMD felsic rocks could be influenced by the presence of Paleozoic metamorphic rocks as basement of the volcanic rocks of the SMD. Moreover, the compositional distinction between basalts of both domains may correspond to differences in magnitude of extension, the NMD being the one where the extension would have been greater and, consequently, the lithosphere thinnerEdades y geoquímica de las rocas volcánicas del trasarco del Mesozoico-Eoceno en la región de Aysén de los Andes patagónicos, Chile. Diez y ocho nuevas edades radiométricas (catorce 40Ar-39Ar, cuatro K-Ar junto con las ya publicadas confirman la existencia de tres eventos volcánicos (previamente definidos por relaciones

  7. Paleowetlands and regional climate change in the central Atacama Desert, northern Chile

    Science.gov (United States)

    Quade, Jay; Rech, Jason A.; Betancourt, Julio L.; Latorre, Claudio; Quade, Barbra; Rylander, Kate Aasen; Fisher, Timothy

    2008-05-01

    Widespread, organic-rich diatomaceous deposits are evidence for formerly wetter times along the margins of the central Atacama Desert, one of the driest places on Earth today. We mapped and dated these paleowetland deposits at three presently waterless locations near Salar de Punta Negra (24.5°S) on the western slope of the Andes. Elevated groundwater levels supported phreatic discharge into wetlands during two periods: 15,900 to ~ 13,800 and 12,700 to ~ 9700 cal yr BP. Dense concentrations of lithic artifacts testify to the presence of paleoindians around the wetlands late in the second wet phase (11,000?-9700 cal yr BP). Water tables dropped below the surface before 15,900 and since 8100 cal yr BP, and briefly between ~ 13,800 and 12,700 cal yr BP. This temporal pattern is repeated, with some slight differences, in rodent middens from the study area, in both paleowetland and rodent midden deposits north and south of the study area, and in lake level fluctuations on the adjacent Bolivian Altiplano. The regional synchroneity of these changes points to a strengthening of the South American Monsoon — which we term the "Central Andean Pluvial Event" — in two distinct intervals (15,900-13,800 and 12,700-9700 cal yr BP), probably induced by steepened SST gradients across the tropical Pacific (i.e., La Niña-like conditions).

  8. Paleowetlands and regional climate change in the central Atacama Desert, northern Chile

    Science.gov (United States)

    Quade, Jay; Rech, Jason A.; Betancourt, Julio L.; Latorre, Claudio; Quade, Barbra; Rylander, Kate Aasen; Fisher, Timothy

    2008-01-01

    Widespread, organic-rich diatomaceous deposits are evidence for formerly wetter times along the margins of the central Atacama Desert, one of the driest places on Earth today. We mapped and dated these paleowetland deposits at three presently waterless locations near Salar de Punta Negra (24.5°S) on the western slope of the Andes. Elevated groundwater levels supported phreatic discharge into wetlands during two periods: 15,900 to ~ 13,800 and 12,700 to ~ 9700 cal yr BP. Dense concentrations of lithic artifacts testify to the presence of paleoindians around the wetlands late in the second wet phase (11,000?–9700 cal yr BP). Water tables dropped below the surface before 15,900 and since 8100 cal yr BP, and briefly between ~ 13,800 and 12,700 cal yr BP. This temporal pattern is repeated, with some slight differences, in rodent middens from the study area, in both paleowetland and rodent midden deposits north and south of the study area, and in lake level fluctuations on the adjacent Bolivian Altiplano. The regional synchroneity of these changes points to a strengthening of the South American Monsoon — which we term the "Central Andean Pluvial Event" — in two distinct intervals (15,900–13,800 and 12,700–9700 cal yr BP), probably induced by steepened SST gradients across the tropical Pacific (i.e., La Niña-like conditions).

  9. Identificación de Hantavirus Andes en Rattus norvegicus Identification of Andes Hantavirus in Rattus norvegicus

    Directory of Open Access Journals (Sweden)

    J Fernández

    2008-01-01

    Full Text Available En Chile y Argentina la especie Oligoryzomys longicaudatus ha sido identificada como el principal reservorio para Virus Andes (ANDV. El objetivo de este trabajo es reportar la presencia del virus Andes en Rattus norvergicus, roedor urbano recolectado de un muestreo en San Diego del Cristo, comuna de Melipilla, Región Metropolitana. La presencia del virus Andes en Rattus norvegicus podría indicar la importancia de otros roedores como eventuales vectores virales.In Chile and Argentina Oligoryzomys longicaudatus has been identified as the main reservoir for Hantavirus Andes. The aim of this work was to report the presence of Hantavirus Andes in Rattus norvegicus, an urban rodent collected during sampling in San Diego del Cristo, Melipilla, Metropolitan Region. The existence of Hantavirus Andes in Rattus norvegicus could indicate the importance of other rodents as possible viral vectors.

  10. Southern Hemisphere circulation signals in connection with winter rainfall forecasting in central Chile

    International Nuclear Information System (INIS)

    The possibility of detecting easterly propagating low frequency signals in the Southern Hemispheric circulation is explored in connection with the assessment of a possible seasonal rainfall forecast in central Chile. The analysis has focused on the seasonal variability associated with the biennial component of the Southern Oscillation (SO) and on the one resulting from superimposed intraseasonal oscillations, in relation with winter precipitation and individual rainfall events, respectively. Based on a previous work, relating wet winters to frequent blocks to the SW of South America during warm events of the SO, time-longitude cross sections of a 5-day average blocking index (BI) calculated from ECMWF 200 hPa daily hemispheric analyses for the period 1980-1987 are presented. A general eastward displacement of western and central Pacific positive BI areas seems to characterize the developing phase of warm SO events and vice versa, while intraseasonal variability patterns appear to be related to single rainstorms, either when the positive BI phase of the wave amplifies while crossing the western Pacific or when it reaches the far southeastern Pacific, frequently with a double block structure. It is concluded that the behaviour of both sources of variability is consistent with previously described teleconnection patterns for ENSO events in the southern winter, and that a primary prospect for winter precipitation and for the occurrence of relatively large individual rainstorms in central Chile could be obtained following the filtered BI and 500 hPa height anomalies in both time scales during the fall season. (author). 28 refs, 12 figs

  11. Comparative Study Of Focal Mechanisms In South Central Chile Before And After The 2010 Maule Earthquake

    Science.gov (United States)

    Agurto, H.; Rietbrock, A.; Ryder, I. M.; Haberland, C. A.

    2011-12-01

    On 27 February 2010, a Mw=8.8 earthquake occurred off the coast of south central Chile rupturing nearly 500 km of the subduction zone plate interface. The earthquake also generated a tsunami and caused more than 500 fatalities. The largest earthquakes recorded have taken place along subduction margins (e.g. Chile 1960, 2010, Andaman-Sumatra 2004, Japan 2011) and understanding their rupture mechanisms and deformation regimes is therefore of vital importance. From November 2004 to October 2005, the TIPTEQ project ("From The Incoming Plate to megaThrust EarthQuake"; Rietbrock et al., 2007; Haberland et al., 2009) maintained a network of 120 seismic stations inland and 10 stations at sea between 37 and 39° lat. S., continuously-recording and monitoring the seismicity occurring in the area before the 2010 Maule earthquake. By using first motion polarities and moment tensor inversion we have computed and analyzed focal mechanisms for a subset of data from these records. We found thrust faulting along the subduction interface down to a depth of ~30 km, followed by a gap in the seismicity and then deeper earthquakes showing diverse faulting mechanisms more sparsely distributed within the subducting plate. We also see strike-slip crustal faulting occurring down to ~12 km depth within the area of the Lanalhue fault. The most striking observation is the presence of deep (40 km) normal faulting seismicity in the fore-arc, close to the trench. We have now started to analyze the International Maule Aftershocks Dataset (IMAD) of the 2010 earthquake in the southern rupture region. Again we observe thrust faulting in the subduction interface and a seismic gap between an upper and lower zone of seismicity along the interface. By comparison of the pre- and post-earthquake datasets we are investigating whether the Maule earthquake caused any changes in the style of deformation in this part of Chile. References Haberland, C., A. Rietbrock, D. Lange, K. Bataille, and T. Dahm (2009

  12. Structural inheritance and selective reactivation in the central Andes: Cenozoic deformation guided by pre-Andean structures in southern Peru

    Science.gov (United States)

    Perez, Nicholas D.; Horton, Brian K.; Carlotto, Victor

    2016-03-01

    Structural, stratigraphic, and geochronologic constraints from the Eastern Cordillera in the central Andean plateau of southern Peru (14-15°S) demonstrate the existence and position of major pre-Andean structures that controlled the accumulation of Triassic synrift fill and guided subsequent Cenozoic deformation. The timing of initial clastic deposition of the Triassic Mitu Group is here constrained to ~ 242-233 Ma on the basis of detrital and volcanic zircon U-Pb geochronology. Regionally distinct provenance variations, as provided by U-Pb age populations from localized synrift accumulations, demonstrate Triassic erosion of multiple diagnostic sources from diverse rift-flank uplifts. Stratigraphic correlations suggest synchronous initiation of extensional basins containing the Mitu Group, in contrast with previous interpretations of southward rift propagation. Triassic motion along the NE-dipping San Anton normal fault accommodated up to 7 km of throw and hanging-wall deposition of a synrift Mitu succession > 2.5 km thick. The contrasting orientation of a non-reactivated Triassic normal fault suggests selective inversion of individual structures in the Eastern Cordillera was dependent on fault dip and strike. Selective preservation of a ~ 4 km thick succession of Carboniferous-Permian strata in the down-dropped San Anton hanging wall, beneath the synrift Mitu Group, suggests large-scale erosional removal in the uplifted footwall. Field and map observations identify additional pre-Andean thrust faults and folds attributed to poorly understood Paleozoic orogenic events preserved in the San Anton hanging wall. Selective thrust reactivation of normal and reverse faults during later compression largely guided Cenozoic deformation in the Eastern Cordillera. The resulting structural compartmentalization and across-strike variations in kinematics and deformation style highlight the influence of inherited Paleozoic structures and Triassic normal faults on the long

  13. Summer freezing resistance decreased in high-elevation plants exposed to experimental warming in the central Chilean Andes.

    Science.gov (United States)

    Sierra-Almeida, Angela; Cavieres, Lohengrin A

    2010-05-01

    Alpine habitats have been proposed as particularly sensitive to climate change. Shorter snow cover could expose high-elevation plants to very low temperatures, increasing their risk of suffering damage by freezing, hence decreasing their population viability. In addition, a longer and warmer growing season could affect the hardening process on these species. Thus, understanding the ability of these species to withstand freezing events under warmer conditions is essential for predicting how alpine species may respond to future climate changes. Here we assessed the freezing resistance of 11 species from the central Chilean Andes by determining their low temperature damage (LT(50)) and freezing point (FP) after experimental warming in the field. Plants were exposed during two growing seasons to a passive increase in the air temperature using open top chambers (OTCs). OTCs increased by ca. 3 K the mean air and soil daytime temperatures, but had smaller effects on freezing temperatures. Leaf temperature of the different species was on average 5.5 K warmer inside OTCs at midday. While LT(50) of control plants ranged from -9.9 to -22.4, that of warmed plants ranged from -7.4 to -17.3 degrees C. Overall, high-Andean species growing inside OTCs increased their LT(50) ca. 4 K, indicating that warming decreased their ability to survive severe freezing events. Moreover, plants inside OTCs increased the FP ca. 2 K in some studied species, indicating that warming altered processes of ice crystal formation. Resistance of very low temperatures is a key feature of high-elevation species; our results suggest that current climate warming trends will seriously threaten the survival of high-elevation plants by decreasing their ability to withstand severe freezing events. PMID:20237942

  14. Erosion and Sediment Transport Across and Along Pronounced Topographic and Climatic Gradients: Examples from the Central Andes and Himalaya

    Science.gov (United States)

    Bookhagen, Bodo; Strecker, Manfred; Olen, Stephanie

    2016-04-01

    Moisture impinging on high topographic barriers results in effective orographic barriers. For example, the interaction of the Indian Monsoon with the southern Himalaya and the South American Monsoon System with the eastern central Andes result in some of the most efficient orographic barriers on Earth. The steep topographic gradients, the impact of focused rainfall along the southern and eastern flanks of the range, and the northward and westward shifts of rainfall during frequent intensified storm systems are responsible for an efficient erosional regime, with some of the highest known erosion rates. The spatiotemporal correlation between various topographic, tectonic, climatic, and exhumational phenomena in these regions has resulted in the formulation of models of possible long-term erosional and tectonic feedback processes that drive the lateral expansion and vertical growth of mountain belts. However, despite an increase in thermochronologic, cosmogenic radionuclide, and sedimentological datasets that help explain some underlying mechanisms, the true nature of these relationships is still unclear and controversies particularly exist concerning the importance of the different forcing factors that drive sediment transport on different time scales. Here, we synthesize and assess these controversies with observations from studies conducted perpendicular to and along strike of the orogens, and combine them with new basin-wide erosion-rate data from the Sutlej Valley in the NW Himalaya and from the southern central Andean Plateau (Puna) in NW Argentina. At first order and across strike, erosion rates based on cosmogenic nuclide inventories on river sands suggest a correlation with rainfall rates. But along-strike rainfall gradients in the Himalaya indicate additional moderating factors, such as vegetation. Leeward of the orographic barrier, fluvial erosion variability increases and erosion processes become more stochastic. Further leeward in the high-elevation and

  15. Biogeochemistry of sulfur and iron in Thioploca-colonized surface sediments in the upwelling area off central Chile

    DEFF Research Database (Denmark)

    Zopfi, Jakob; Michael E., Böttcher; Jørgensen, Bo Barker

    2008-01-01

    The biogeochemistry of sedimentary sulfur was investigated on the continental shelf off central Chile at water depths between 24 and 88 m under partial influence of an oxygen minimum zone. Dissolved and solid iron and sulfur species, including the sulfur intermediates sulfite, thiosulfate, and el...

  16. Environmental management in Chile: The power plants case; Gestion ambiental en Chile: Caso de las centrales termoelectricas

    Energy Technology Data Exchange (ETDEWEB)

    Jadrijevic, Maritza [Comision Nacional del Medio Ambiente, (Chile)

    1996-12-31

    In this paper are presented the general aspects of the historic evolution o the legal norms on environmental matters in Chile; general aspects of the electric generation system and the instruments of environmental management currently applied in the fossil fueled power plants, such as: the assessment system of the environmental impact; compliance of the air quality and emissions Standards and plans for decontamination [Espanol] En este trabajo se dan a conocer aspectos generales de la evolucion historica de las normas juridicas en materia ambiental en Chile; aspectos generales del sistema de generacion electrica y los instrumentos de gestion ambiental que actualmente se aplican a las plantas de generacion termoelectricas, tales como: el sistema de evaluacion de impacto ambiental; cumplimiento de normas de la calidad de aire y de emision y, planes de descontaminacion

  17. Sustainable extraction tripeperro (Philodendron longirrhizum M. Mora and Croat, Araceae) in the central Andes of Colombia

    International Nuclear Information System (INIS)

    The tripeperro (Philodendron longirrhizum) is a widely distributed hemiepiphyte along the Andean region of Colombia. The aerial roots of this species have been employed as a source of fiber for the production of baskets and other handicrafts in the Eje Cafetero region (Cordillera Central). This activity is concentrated in the town of Filandia, in the Quindio state, where a decrease in the availability of appropriate roots for craftsmanship has been detected over the last years. In order to propose sustainable harvest alternatives, we evaluated the natural stock and product demand of tripeperro. Root production and life cycle, distribution of the harvested areas, harvest time and costs, and product demand were studied. It was found that tripeperro natural stock can only supply the demand for improve the economic benefits for artisans.

  18. Proposals to enhance thermal efficiency programs and air pollution control in south-central Chile

    International Nuclear Information System (INIS)

    Major cities in South-central Chile suffer high levels of particulate matter PM10 and PM2.5 due to combustion of solid fuels for heating. Exposure to these air pollutants is recognized as a major contribution to ill health in the region. Here we discuss new strategies to reduce air pollution. Regulations and subsidies focusing on improved combustion by providing drier wood fuel and better stoves have been in effect since 2007. However, air pollution due to combustion of wood fuel has been steadily rising, along with reports on health consequences. The paper analyzes a survey of 2025 households in the city of Valdivia, which found that wood fuel quality, stove renewal, and awareness of programs are strongly affected by income level, and that higher consumption of wood fuel is found in households already having better stoves and drier wood fuel. The analysis suggests that regulations intended to improve combustion are influenced by user's behavior and have limited potential for lowering pollution. We conclude that thermal refurbishment has a larger potential for improvement, not yet been implemented as an energy policy for the majority. Here we propose improvements and additions to current programs to enhance effectiveness and cover the whole social spectrum. - Highlights: • High levels of PM2.5 from wood combustion affect cities of south-central Chile. • Current programs on dry wood fuel and stoves renewal have not reduced air pollution. • Real operation of wood stoves strongly depends on user's behavior. • Buildings' energy efficiency has greater potential for reducing emissions. • Retrofit prevents degradation of native forest and improves indoor temperature

  19. Sr-Nd isotope changes of late cretaceous to early miocene volcanic rocks in central Chile (33oS)

    International Nuclear Information System (INIS)

    A longitudinal depression, the Central Valley, separates the Coast Range from the Andean Cordillera in central Chile. It contains volcanic and volcaniclastic rocks of Late Cretaceous to Tertiary age deposited in a continental environment, and partly eroded Tertiary volcanic complexes. The age of the rocks at the northern end of the Central Valley and their grouping in formations have been a long-standing controversy in Chilean geology (Thomas, 1958; Aguirre, 1960; Drake et al., 1976; Vergara and Drake, 1979; Thiele, 1980; Moscoso et al., 1982; Gana and Wall, 1997; Lopez-Escobar and Vergara, 1997; Selles, 1999). Here, we report new 40Ar/39Ar data and Sr-Nd isotope ratios for lavas, pyroclastic flows and associated subvolcanic rocks from this part of central Chile (au)

  20. The tomato borer, Tuta absoluta, invading the Mediterranean Basin, originates from a single introduction from Central Chile.

    Science.gov (United States)

    Guillemaud, Thomas; Blin, Aurélie; Le Goff, Isabelle; Desneux, Nicolas; Reyes, Maritza; Tabone, Elisabeth; Tsagkarakou, Anastasia; Niño, Laura; Lombaert, Eric

    2015-01-01

    The Lepidopteran pest of tomato, Tuta absoluta, is native to South America and is invasive in the Mediterranean basin. The species' routes of invasion were investigated. The genetic variability of samples collected in South America, Europe, Africa and Middle East was analyzed using microsatellite markers to infer precisely the source of the invasive populations and to test the hypothesis of a single versus multiple introductions into the old world continents. This analysis provides strong evidence that the origin of the invading populations was unique and was close to or in Chile, and probably in Central Chile near the town of Talca in the district of Maule. PMID:25667134

  1. Soil n-alkane δD and Branched GDGTs Distributions Track Elevation-induced Precipitation and Temperature Changes along the South Central Andes (Argentina)

    Science.gov (United States)

    Nieto-Moreno, V.; Rohrmann, A.; van der Meer, M.; S Sinninghe Damsté, J.; Sachse, D.; Tofelde, S.; Niedermeyer, E. M.; Strecker, M. R.; Mulch, A.

    2015-12-01

    Orogenic surface uplift and topographic evolution of tectonically active mountain belts exert a strong impact on climatic teleconnections and Earth surface processes, including changes in global atmospheric circulation patterns, erosion rates, distribution of biomes, and precipitation patterns. Hence, quantifying the driving processes shaping the evolution of topography in ancient and active orogens is required in order to disentangle the dynamic interactions and feedbacks among surface uplift, climate, erosion and sedimentation. The south central Andes of Argentina provide a particularly suitable setting to study the interplay between the tectonic and climatic evolution of an actively subduction orogen over short and long time-scales. We present δD values of soil-derived n-alkane and brGDGTs distributions to assess their suitability for paleoelevation reconstructions in the southern central Andes. We collected soil samples from two different environmental and hydrological gradients, across the hillslope (26-28°S) and along a river-valley (22-24°S) of two individual mountain ranges. δD n-alkane and brGDGTs distributions are both linearly related with elevation and may be used for paleoaltimetry studies along the windward flanks of the south central Andes. δD n-alkane and brGDGT-derived temperature lapse rates broadly follow regional lapse rates along steep orographic fronts. The observed lapse rates are lower than the annual mean values of satellite-derived temperatures but approach those of temperature loggers along each transect. Instead, δD n-alkane lapse rates are in line with regional stream-water data. These linear relationships along the windward slopes break down when entering the internally drained part of the Puna plateau. Our data document that δD n-alkane and brGDGTs distributions can be used over time scales relevant for paleoclimate/-altimetry reconstructions but also stress that such reconstructions require knowledge of the depositional

  2. Riparian leaf litter processing by benthic macroinvertebrates in a woodland stream of central Chile Procesamiento de detritus ripariano por macroinvertebrados bentónicos en un estero boscoso de Chile central

    Directory of Open Access Journals (Sweden)

    CLAUDIO VALDOVINOS

    2001-06-01

    Full Text Available Leaf litter input from riparian landscapes has been identified as both a major energy flow to stream ecosystems and as a food source for stream macroinvertebrates. In riparian landscapes of woodland streams of central Chile, the native deciduous hardwoods are being artificially replaced by exotic coniferous trees at a large spatial scale. It is suggested that this process has a significant impact on the stream communities of central Chile. Today, exotic plantations occur throughout central Chile, with Pinus radiata (D. Don (Monterrey pine accounting for about 80 % of the more than 1,800,000 ha of exotic forests. The objective of this paper was to analyze the effect of the litter beds of a dominant native species (Nothofagus pumilio and an exotic species (P. radiata on the detritus processing carried out by benthic macroinvertebrates, in an experimental catchment of central Chile (Rucúe Creek; 36° 26'00" S, 71° 35'40" W. Results revealed that processing rates of native leaf packs are higher than rates of coniferous leaf packs, suggesting that the replacement of the native hardwoods by exotic coniferous riparian flora has an important impact on the stream energy flow in central Chile. The decay rate coefficients (k were 0.0072 for N. pumilio, and 0.0027 for P. radiata. The greater abundance and biomass of shredders per gram of leaf pack of native Nothofagus would explain the differences in leaf processing rates, especially through the activity of two Plecoptera Gripopterygidae, Limnoperla jaffueli and Antarctoperla michaelseniLa entrada de detritus foliar procedente de áreas riparianas ha sido reconocido como un componente importante en la energética de ecosistemas fluviales y como fuente de alimento de macroinvertebrados acuáticos. En áreas riparianas de esteros boscosos de Chile central los componentes nativos caducifolios están siendo artificialmente reemplazados a gran escala por coníferas exóticas, sugiriendo que este proceso tiene

  3. Composition and processes in the lithosphere-asthenosphere system beneath the Central Andes constrained by P- and S-local source tomography

    OpenAIRE

    I. Koulakov; Stephan V. Sobolev; Günter Asch;  

    2004-01-01

    We use about 50000 of P and S arrival times from more than 1500 deep and crustal earthquakes to image lithosphere-asthenosphere system in Central Andes. Based on available a-priori information the entire region is subdivided into three domains: (1) slab, with upper boundary defined as intraslab seismicity envelope, (2) continental crust, with Moho topography defined by receiver-function Moho, and (3) mantle wedge. A reference velocity distribution in each of 3 domains was set from a-priori in...

  4. Monumento Natural El Morado (Andes Centrales Chilenos). Análisis del medio biofísico, paisaje y propuesta de actuación, El

    OpenAIRE

    Infante Fabres, Nelson Osvaldo

    2009-01-01

    [spa] Esta tesis doctoral centra su interés en el estudio geográfico de la cuenca hidrográfica del estero Morales, afluente del río Volcán, en los Andes centrales chilenos. Para ello analiza el medio biofísico, describe, analiza y clasifica el paisaje, realiza una serie de propuestas para su mejor y adecuada gestión. Se trata de una investigación de base que aporta datos de interés relativo al funcionamiento del sistema natural del valle, catalogado como figura de protección por parte del Gob...

  5. Influencia humana y conservación de la riqueza de especies en un paisaje fragmentado de los Andes centrales de Colombia

    OpenAIRE

    Aubad Echeverri, Jorge

    2009-01-01

    Esta tesis doctoral tiene como fin evaluar los efectos que sobre la riqueza de especies tienen tanto la influencia humana directa, estimada mediante la tala ilegal como fuente complementaria de combustible, la accesibilidad humana a los fragmentos de bosque y la caza ilegal de aves, como la estructura del paisaje en un área propuesta como parque regional natural en los Andes centrales de Colombia. Los resultados de esta tesis se encuentran divididos en dos grupos según sus objetivos. En el pr...

  6. Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47°S), Chile

    Science.gov (United States)

    Georgieva, Viktoria; Melnick, Daniel; Schildgen, Taylor F.; Ehlers, Todd A.; Lagabrielle, Yves; Enkelmann, Eva; Strecker, Manfred R.

    2016-06-01

    The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at ~47°S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an ~140 km long fore-arc sliver -- the NPI block -- results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquiñe-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape.

  7. Unraveling an antique subduction process from metamorphic basement around Medellín city, Central Cordillera of Colombian Andes

    Science.gov (United States)

    Bustamante, Andres; Juliani, Caetano

    2011-10-01

    varies between 400 and 555 °C at pressures of 5-6 kbar in the retrograde metamorphic path. The El Retiro rocks evidence strong decompression with narrow variation in temperature, showing pressure values between 8.7 and 2.7 kbar at temperatures of 740-633 °C. These metamorphic fragments of the basement in the Central Cordillera of the Colombian Andes could represent a close relationship with an antique subduction zone.

  8. Estimating glacier and snowmelt contributions to stream flow in a Central Andes catchment in Chile using natural tracers

    OpenAIRE

    Rodriguez, M.; N. Ohlanders; McPhee, J

    2014-01-01

    This paper presents a methodology for hydrograph separation in high elevation watersheds, which aims at identifying individual flow sources such as snow- and ice melt, rainfall and soil water. Daily summer and bi-daily spring water samples from the outlet of the Juncal River were analyzed for all major ions as well as stable water isotopes, δ18O and δ2H. Additionally, various water sources such as rain, springs, snow- and glacial melt were sampled thr...

  9. Sr-Nd-Pb isotope compositions of felsic intrusions in the El Teniente and Laguna La Huifa areas, Central Chile

    International Nuclear Information System (INIS)

    The giant El Teniente porphyry Cu-Mo deposit is located in the Andes foothills of Central Chile (34oS). In simplistic terms, the igneous rocks at the mine can be grouped in two major units: a felsic suite of silicic intrusives (the porphyries; SiO2≥56wt%) with subvertical stock-like to dyke shapes, and a mafic volcanic to subvolcanic sequence (the Farellones formation; SiO2<≤56wt%) with a sub-horizontal nature. The felsic rocks intrude the volcanogenic Farellones formation, which is known at the mine site as 'Andesitas de la mina'. The major felsic intrusives are locally known as the 'Diorita Sewell' and 'Porfido Teniente' bodies, plus a series of minor plugs, apophyses and dikes. According to Cuadra (1986), the age of the main intrusive units spans from Late Miocene ('Diorita Sewell'; 7-8Ma) to Early Pliocene ('Porfido Teniente'; ∼4-5Ma). These felsic intrusives are closely related to copper mineralization ( ∼4-5Ma; Cuadra, 1986), particularly the younger 'Porfido Teniente' (Camus, 1975). Additionally, Skewes and Stern (1996) have suggested the existence of an even slightly younger porphyry pluton, not exposed at surface, but still linked to the ore genesis. Similar felsic intrusive bodies are also present in the Laguna La Huifa area (Reich, 2001), located less than 3 km to the NE from the main El Teniente body. The copper mineralization here, is interpreted to be almost contemporaneous with the El Teniente mineralization (Cuadra, 1986). Based on petrographic and geochemical information on the silicic intrusive suite, Rabbia et al. (2000) suggested that this magmatism could be considered as a Phanerozoic equivalent of an Archean high-Al TTG. Furthermore it may be classified as a modified (Na-rich) 'I' type granitoid, in the sense of Atherton and Petford (1993) and Petford and Atherton (1996). According to these authors, the younger (and hotter) lower Andean crust would be a better candidate than the older (and colder) subducted Nazca plate basalts (NPB

  10. Mycotrophy in Gilliesieae, a threatened and poorly known tribe of Alliaceae from central Chile Micotrofía en Gilliesieae, una tribu amenazada y poco conocida de Alliaceae de Chile central

    OpenAIRE

    GUSTAVO A TORRES-MELLADO; INELIA ESCOBAR; GOTZ PALFNER; M. ANGÉLICA CASANOVA-KATNY

    2012-01-01

    The five known genera of Gilliesieae have their diversity center in the Mediterranean zone of central Chile, where many of their habitats are threatened by urban expansion, industrial and agroforestry activities, as well as other anthropogenic impacts. Very little is known about the biology of these particular geophytes, the majority of which currently have either vulnerable or endangered status, mainly due to their dispersed and small populations generally associated to remnants of native ve...

  11. Lavas Las Pataguas: volcanismo alcalino en el antearco andino del Mioceno Inferior, Chile central Lavas Las Pataguas: alkaline volcanism in the Early Miocene Andean forearc of central Chile

    Directory of Open Access Journals (Sweden)

    Renate M Wall

    2001-12-01

    Full Text Available La presencia de rocas volcánicas del Mioceno Inferior en la cordillera de la Costa de Chile central constituye una singularidad ya que los afloramientos más occidentales del arco volcánico oligo-mioceno se encuentran 80 km al este. Lavas Las Pataguas (LLP; 33,8°S, se expone en 1,15 km², sin vestigios de un edificio volcánico ni conductos alimentadores. La presencia de túmulos del tipo `flow lobe tumuli', alineados y elongados en dirección este-oeste, indica un flujo local desde el oeste sobre una superficie de muy baja pendiente. Estos antecedentes sugieren un ciclo eruptivo de tipo fisural. La edad de LLP de ca. 18 Ma resulta intermedia entre las formaciones Abanico (34-20 Ma y Farellones (20-10 Ma y coetánea a facies litorales de la Formación Navidad, expuestas 20 km al oeste. LLP presenta contenidos de sílice de 52,8-54,5%, en el rango de las traquiandesitas basálticas, y su alto contenido de álcalis (6,21-6,26% de K2O+Na2O las sitúa en la serie alcalina de diferenciación. Destaca la clara diferencia con los productos toleíticos de la Formación Abanico, y los típicamente calcoalcalinos de la Formación Farellones. Estas lavas están significativamente enriquecidas en tierras raras livianas, con una razón La/Sm de 3,4 y un patrón plano de tierras raras pesadas. Tanto el contenido de sílice como de MgO, indican un estado de diferenciación avanzado dominado por cristalización fraccionada de olivino, clinopiroxeno y magnetita. El contenido de Ba y Nb señalaría una contribución significativa del manto litosférico. El Th, y la anomalía de Ta-Nb indicarían, también, un sello cortical. Su particular petrogénesis, así como su posición occidental y aislada en el antearco, podría explicarse como respuesta a la desaceleración de la convergencia con que culmina el ciclo extensional vigente hasta el Mioceno Inferior alto y que acompañó al volcanismo representado por la Formación Abanico. De este modo, las lavas

  12. A new species of Phymaturus (Iguania: Liolaemidae of the palluma group from Central Chile

    Directory of Open Access Journals (Sweden)

    Troncoso-Palacios, Jaime

    2012-07-01

    Full Text Available We examined specimens of Phymaturus from four locations in central Chile, between 34º50´S and 36º00´S (from Termas del Flaco and from Lircay and its surroundings, where the only recognized species is P. maulense. We found several differences in the scalation and in the color pattern among them. The samples from Lircay and its surroundings correspond to topotypes of P. maulense and two more populations assignable to this species (Termas del Campanario and Laguna del Maule, new records, but the specimens from Termas del Flaco are a new species: P. damasense. It is characterized by: dorsal pattern of the male formed by a thin reticulation over greenish background color with yellowish-brown tail, subocular scale fragmented in three or four scales, scales in the anterior border of the auditory meatus are projected posteriorly, females have dark bars on the flanks (formed by small spots, enlarged scales in the center of the gular fold and may have precloacar pores. Also, we call attention to some Chilean populations of the genus Phymaturus referred in the literature which need to be assigned. Examinamos especimenes de Phymaturus procedentes de cuatro localidades de Chile central, entre los 34º50'S y 36º00'S (Termas del Flaco y los alrededores de Lircay, donde la única especie reconocida es P. maulense. Estas poblaciones muestran diferencias en la escamación y en el diseño de coloración. Las muestras de la cuenca del Maule corresponden a topotipos de P. maulense y dos poblaciones más asignables a esta especie (Termas del Campanario y Laguna del Maule, nuevos registros, mientras que las poblaciones del río Las Damas constituyen una nueva especie caracterizada por: diseño dorsal del macho formado por una reticulación oscura sobre un fondo verde con cola café-amarillenta, escama subocular fragmentada en tres o cuatro, escamas agrandadas en el borde anterior del meato auditivo (proyectadas posteriormente, hembras con escamas agrandadas en el

  13. Pre-collisional extensional tectonics in convergent continental margins: the cretaceous evolution of the central cordillera of the Colombian Andes

    OpenAIRE

    Zapata Henao, Sebastian

    2015-01-01

    Abstract: The Cretaceous tectonic evolution of the Northern Andes continental margin is characterized by continuous convergence that allowed the formation of continental volcanic arcs, back arc basins, extensional divergent tectonics and accretion of exotic terranes. Such a record, particularly the extensional phases, is commonly hidden by the overimposition of deformational events associated with evolution of the subduction configuration, collision of exotic terranes and strike slip fragment...

  14. The Under-side of the Andes: Using Receiver Functions to Map the North Central Andean Subsurface

    Science.gov (United States)

    Ryan, J. C.; Beck, S. L.; Zandt, G.; Wagner, L. S.; Minaya, E.; Tavera, H.

    2012-12-01

    The Central Andean Uplift and Geodynamics of High Topography (CAUGHT) project is an interdisciplinary project to investigate connections between lithospheric removal, crustal shortening and surface uplift in the northern Bolivia and southern Peru region of the South American Andean orogen. The central Andes are defined by six major tectonomorphic provinces; the forearc, the volcanically active Western Cordillera (WC, ~6 km elevation), the internally drained Altiplano (~4 km elevation), an inactive fold and thrust belt in the Eastern Cordillera (EC, ~6 km elevation), a lower elevation active fold and thrust belt in the Subandean (SA) zone and the Beni, a foreland basin. Forty seismic stations installed for the CAUGHT project were deployed between 13° and 18° S latitude, covering the transition zone where the Altiplano region pinches out in southern Peru, in an effort to better constrain the changing character of the crust and mantle lithosphere. Geologic studies across the northern Bolivian portion of the eastern Andean margin (15-17° S) have documented a total of 275 km of upper crustal shortening (McQuarrie et al, Tectonics, v27, 2008), which may be associated with crustal thickening and/or the removal of lithospheric material as a thickened lithosphere root becomes unstable. For this receiver function (converted wave) study, we have little coverage in the forearc and foreland, ~75 km spacing in most of the array, and a relatively dense ~20 km spaced profile along the Charaña-La Paz-Yucumo transect, the eastern portion of which is nearly coincident with the balanced cross-section of McQuarrie et al. (2008). Using the first year of available data, more than 1200 receiver functions have been calculated using an iterative deconvolution method, and stacked using the common conversion point (CCP) method, along profiles parallel to and nearly coincident to those used for the geologic shortening estimates. We identified arrivals for the Moho and generated a 3D map of

  15. Metallurgical traditions under Inka rule: a technological study of metals and technical ceramics from the Aconcagua Valley, Central Chile

    OpenAIRE

    Plaza, M.T.; Martinón-Torres, M.

    2015-01-01

    The spread of the Inka state in the Aconcagua Valley (Central Chile) is thought to have been culturally mediated, avoiding military coercion, and thus leading to different forms of cultural acceptance, resistance or hybridisation. However, there has been no previous attempt to investigate the extent to which these interactions are reflected in the use of metals and metallurgical technologies. Here we present analytical work on metallic artefacts and technical ceramics from Cerro La Cruz and L...

  16. Methane in shallow cold seeps at Mocha Island off central Chile

    Science.gov (United States)

    Jessen, Gerdhard L.; Pantoja, Silvio; Gutiérrez, Marcelo A.; Quiñones, Renato A.; González, Rodrigo R.; Sellanes, Javier; Kellermann, Matthias Y.; Hinrichs, Kai-Uwe

    2011-04-01

    We studied for the first time the intertidal and subtidal gas seepage system in Mocha Island off Central Chile. Four main seepage sites were investigated (of which one site included about 150 bubbling points) that release from 150 to 240 tonnes CH 4 into the atmosphere per year. The total amount of methane emitted into the atmosphere is estimated in the order of 800 tonnes per year. The gases emanated from the seeps contain 70% methane, and the stable carbon isotopic composition of methane, δ 13C-CH 4 averaged -44.4±1.4‰ which indicates a major contribution of thermogenic gas. Adjacent to one of the subtidal seeps, rocky substrates support a diverse community of microbial filaments, macroalgae, and benthic organisms. While stable carbon isotopic compositions of marine benthic organisms indicate a dominant photosynthesis-based food web, those of some hard-substrate invertebrates were in the range -48.8‰ to -36.8‰, suggesting assimilation of methane-derived carbon by some selected taxa. This work highlights the potential subsidy of the trophic web by CH 4-C, and that its emission to the atmosphere justifies the need of evaluating the use of methane to support the energy requirements of the local community.

  17. Landsat image and sample design for water reservoirs (Rapel dam Central Chile).

    Science.gov (United States)

    Lavanderos, L; Pozo, M E; Pattillo, C; Miranda, H

    1990-01-01

    Spatial heterogeneity of the Rapel reservoir surface waters is analyzed through Landsat images. The image digital counts are used with the aim or developing an aprioristic quantitative sample design.Natural horizontal stratification of the Rapel Reservoir (Central Chile) is produced mainly by suspended solids. The spatial heterogeneity conditions of the reservoir for the Spring 86-Summer 87 period were determined by qualitative analysis and image processing of the MSS Landsat, bands 1 and 3. The space-time variations of the different observed strata obtained with multitemporal image analysis.A random stratified sample design (r.s.s.d) was developed, based on the digital counts statistical analysis. Strata population size as well as the average, variance and sampling size of the digital counts were obtained by the r.s.s.d method.Stratification determined by analysis of satellite images were later correlated with ground data. Though the stratification of the reservoir is constant over time, the shape and size of the strata varys. PMID:24243254

  18. Effects of maize cultivation on nitrogen and phosphorus loadings to drainage channels in Central Chile.

    Science.gov (United States)

    Corradini, Fabio; Nájera, Francisco; Casanova, Manuel; Tapia, Yasna; Singh, Ranvir; do Salazar, Osval

    2015-11-01

    There are concerns about the impact of maize cultivation with high applications of nitrogen (N) and phosphorus (P) on water quality in surface waters in Mediterranean Central Chile. This study estimated the contribution of N and P from maize fields to nearby drainage channels and evaluated the effects in water quality. An N and P budget was drawn up for three fields managed with a maize-fallow system, El Maitén (20.7 ha), El Naranjal (14.9 ha) and El Caleuche (4.2 ha), and water quality variables (pH, EC, dissolved oxygen, total solids, turbidity, NO3-N, NH4-N, PO4(3-), COD, total N, total P and sulphate) were monitored in nearby drainage channels. The N and P balances for the three fields indicated a high risk of N and P non-point source pollution, with fertiliser management, soil texture and climate factors determining the temporal variations in water quality parameters. Elevated levels of NH4-N and PO4(3-) in the drainage channels were usually observed during the winter period, while NO3- concentrations did not show a clear tendency. The results suggest that excessive slurry application during winter represents a very high risk of N and P runoff to drainage channels. Overall, great emphasis must be placed on good agronomic management of fields neighbouring drainage channels, including accurately calculating N and P fertiliser rates and establishing mitigation measures. PMID:26490735

  19. Marine protected areas facilitate parasite populations among four fished host species of central Chile.

    Science.gov (United States)

    Wood, Chelsea L; Micheli, Fiorenza; Fernández, Miriam; Gelcich, Stefan; Castilla, Juan Carlos; Carvajal, Juan

    2013-11-01

    1. Parasites comprise a substantial proportion of global biodiversity and exert important ecological influences on hosts, communities and ecosystems, but our knowledge of how parasite populations respond to human impacts is in its infancy. 2. Here, we present the results of a natural experiment in which we used a system of highly successful marine protected areas and matched open-access areas in central Chile to assess the influence of fishing-driven biodiversity loss on parasites of exploited fish and invertebrate hosts. We measured the burden of gill parasites for two reef fishes (Cheilodactylus variegatus and Aplodactylus punctatus), trematode parasites for a keyhole limpet (Fissurella latimarginata), and pinnotherid pea crab parasites for a sea urchin (Loxechinus albus). We also measured host density for all four hosts. 3. We found that nearly all parasite species exhibited substantially greater density (# parasites m(-2)) in protected than in open-access areas, but only one parasite species (a gill monogenean of C. variegatus) was more abundant within hosts collected from protected relative to open-access areas. 4. These data indicate that fishing can drive declines in parasite abundance at the parasite population level by reducing the availability of habitat and resources for parasites, but less commonly affects the abundance of parasites at the infrapopulation level (within individual hosts). 5. Considering the substantial ecological role that many parasites play in marine communities, fishing and other human impacts could exert cryptic but important effects on marine community structure and ecosystem functioning via reductions in parasite abundance. PMID:23855822

  20. Modelling the day to day wind variability offshore central Chile at about 30 deg. south

    International Nuclear Information System (INIS)

    Cycles of strengthening and relaxation of the winds offshore 30 degrees S at central Chile, are related to the propagation of coastal-lows, a year-round phenomenon occurring with periodicities of about one in five days. Simple physical modelling of the day to day variability of the alongshore wind component at a coastal strip extending offshore up to the Rossby deformation radius of these wave perturbations, is presented in terms of the relevant horizontal pressure gradients and the ageostrophic components arising from the coastal-low propagation. The results of 5-day composites of 8 wind-events each, at the winter and summer halves of the annual cycle, respectively; lead to a good agreement between the observed phase-lag of the winds with respect to the pressure forcing field, stressing the importance of the ageostrophic wind components at the extremes of the pressure wave perturbation associated with the passage of coastal-lows over the Point Lengua de Vaca (30 15 S) area. A possible contribution of the upwelling-favorable wind enhancement at the time of the pressure rise and subsequent fall, ahead of the coastal-low, is postulated through an upwelling-front low-level jet, that would be carried onshore and closer to the surface by the combination of the enhanced coastal upwelling, the coastal depression of the subsidence inversion base and the coastal ageostrophic wind components during the passage of the leading edge of the coastal lows. (author). 26 refs, 5 figs, 1 tab

  1. Soundscape of a management and exploitation area of benthic resources in central Chile

    Directory of Open Access Journals (Sweden)

    Alfredo Borie

    2015-11-01

    Full Text Available Acoustic ecology is an emerging and poorly known field of research. Soundscape has been used to infer the behavior of several species in different environments and can serve as a reliable indicator of the habitat type and quality; also, it is believed that it is an important factor for larvae orientation in settlement areas. We used the passive acoustic method to evaluate the soundscape of a management and exploitation area of benthic resources, a rocky reef area in central Chile. It was possible to hear a continuous cracking sound during recording and underwater observations. We detected two distinct frequency bands with similar parameters during the night and day, a band between 90 and 300 Hz, which corresponded to the effects of sea waves (geophony, and a frequency band with a range of 1,500 to 2,700 Hz (biophony, with a fundamental frequency of 2,070 Hz. Both bands had similar energy (~88.0 dB re: 1V/µPa. These results show the relevant acoustic activity in the area, which may have important ecological implications for the recruitment of commercially important benthic resources.

  2. Analyzing Food-Related Life Satisfaction and other Predictors of Life Satisfaction in Central Chile.

    Science.gov (United States)

    Schnettler, Berta; Lobos, Germán; Orellana, Ligia; Grunert, Klaus; Sepúlveda, José; Mora, Marcos; Denegri, Marianela; Miranda, Horacio

    2015-01-01

    This study aimed to assess the effect of satisfaction with food-related life on life satisfaction among inhabitants of the main municipalities of central Chile. A survey was applied to a sample of 1,277 people, distributed proportionally by municipality. The questionnaire included the following scales: SWLS (Satisfaction with Life Scale), SWFL (Satisfaction with Food-related Life) and the Health-Related Quality of Life Index (HRQOL). Questions were asked regarding eating habits inside and outside the home, time available for meals at home, the assessment of five sources of happiness and the demographic characteristics of those surveyed. An ordered logit model was proposed, in which the dependent variable was satisfaction with life. Satisfaction with life was significantly related to the respondent's socioeconomic status, self-perception of health, degree of satisfaction with food-related life, monthly food expenditure, time available for supper with the family (p consumption in fast food outlets (p < .10). Satisfaction with life in the study sample is related to aspects associated with health, family and eating, and the family interaction associated with eating may play an important role in overall satisfaction with life. PMID:26083311

  3. A Centralized Auction Mechanism for the Disability and Survivors Insurance in Chile

    Science.gov (United States)

    Reyes H., Gonzalo

    As part of the pension reform recently approved in Chile, the government introduced a centralized auction mechanism to provide the Disability and Survivors (D&S) Insurance that covers recent contributors among the more than 8 million participants in the mandatory private pension system. This paper is intended as a case study presenting the main distortions found in the decentralized operation of the system that led to this reform and the challenges faced when designing a competitive auction mechanism to be implemented jointly by the Pension Fund Managers (AFP). In a typical bilateral contract the AFP retained much of the risk and the Insurance Company acted in practice as a reinsurer. The process to hire this contract was not competitive and colligated companies ended up providing the service. Several distortions affected competition in the market through incentives to cream-skim members by AFPs (since they bear most of the risk) or efforts to block disability claims. Since the price of this insurance is hidden in the fees charged by AFPs for the administration of individual accounts and pension funds there was lack of price transparency. Since new AFPs have no history of members’ disability and mortality profile the insurance contract acted as a barrier to entry in the market of AFP services, especially when D&S insurance costs reached 50% of total costs. Cross-subsidies between members of the same AFP, inefficient risk pooling (due to pooling occurring at the AFP rather than at the system level) and regulatory arbitrage, since AFPs provided insurance not being regulated as an insurance company, were also present. A centralized auction mechanism solves these market failures, but also gives raise to new challenges, such as how to design a competitive auction that attracts participation and deters collusion. Design features that were incorporated in the regulation to tackle these issues, such as dividing coverage into predefined percentage blocks, are presented

  4. Antibacterial Activity, Antioxidant Effect and Chemical Composition of Propolis from the Región del Maule, Central Chile

    Directory of Open Access Journals (Sweden)

    Nélida Nina

    2015-10-01

    Full Text Available Propolis is commercialized in Chile as an antimicrobial agent. It is obtained mainly from central and southern Chile, but is used for the same purposes regardless of its origin. To compare the antimicrobial effect, the total phenolic (TP, the total flavonoid (TF content and the phenolic composition, 19 samples were collected in the main production centers in the Región del Maule, Chile. Samples were extracted with MeOH and assessed for antimicrobial activity against Gram (+ and Gram (− bacteria. TP and TF content, antioxidant activity by the DPPH, FRAP and TEAC methods were also determined. Sample composition was assessed by HPLD-DAD-ESI-MS/MS. Differential compounds in the samples were isolated and characterized. The antimicrobial effect of the samples showed MICs ranging from 31.5 to > 1000 µg/mL. Propolis from the central valley was more effective as antibacterial than those from the coastal area or Andean slopes. The samples considered of interest (MIC ≤ 62.5 µg/mL showed effect on Escherichia coli, Pseudomonas sp., Yersinia enterocolitica and Salmonella enteritidis. Two new diarylheptanoids, a diterpene, the flavonoids pinocembrin and chrysin were isolated and elucidated by spectroscopic and spectrometric means. Some 29 compounds were dereplicated by HPLC-MS and tentatively identified, including nine flavones/flavonol derivatives, one flavanone, eight dihydroflavonols and nine phenyl-propanoids. Propolis from the Región del Maule showed large variation in antimicrobial effect, antioxidant activity and composition. So far the presence of diarylheptanoids in samples from the coastal area of central Chile can be considered as a marker of a new type of propolis.

  5. Constuccion social de comuninad y migración en Usibamba : un estudio sobre el impacto de los procesos de globalización en los Andes centrales del Perú

    NARCIS (Netherlands)

    Gilvonio Perez, J.M.

    2009-01-01

    The research for the thesis was conducted in the village of Usibamba, located in a high-Andean area called Alto Cunas east from the Mantaro Valley in the Peruvian Central Andes. Special attention was paid to the institutional context and the everyday life conditions in which the social construction

  6. "Un devorador de su propia especie". Violencia, justicia y cultura popular en Santa Rosa de los Andes: las formas de la autoridad a los ojos de un peón de oficio matador, Chile 1805

    Directory of Open Access Journals (Sweden)

    Daniel Moreno Bazaes

    2016-01-01

    Full Text Available A través del análisis microhistórico del proceso judicial seguido por las autoridades de la villa de Santa Rosa de Los Andes e intervenido por la Real Audiencia de Santiago contra Juan Francisco Varas, “peón-gañan” de la hacienda de Llay-Llay, responsable de a lo menos seis homicidios y otros tantos crímenes que atentaron contra el orden local y el gobierno civil, se pretende dar cuenta de los pormenores de la organización social en el Valle del Aconcagua a fines del siglo XVIII y durante los primeros años del siglo XIX. De modo que a través de la observación de las tensiones generadas por el uso indiscriminado de la violencia, el desacato y la desobediencia a la autoridad local, se desea mostrar uno de los rostros más violentos que presentaron los procesos de campesinización en Chile durante el periodo colonial, indagando en las formas en que los contemporáneos, la administración y autoridades locales reaccionaron frente a este tipo de prácticas consideradas como intolerables y excesivas. Por supuesto, se pretende dar cuenta delos mecanismos desplegados por controlar ese tipo de conductas y desde ahí profundizar en los horizontes que adoptaron lo justo y la autoridad frente a una cultura popular que se configuró al margen de la “civilidad”.

  7. Karyotypic polymorphism and evolution within and between the Liolaemus monticola (Iguanidae "northern 2n = 38-40" chromosome race populations in central Chile Polimorfismo cromosómico y evolución intra e inter poblacional de la raza cromosómica "Norte 2n = 28-40" de Liolaemus monticola (Iguanidae en Chile Central

    Directory of Open Access Journals (Sweden)

    MADELEINE LAMBOROT

    2001-03-01

    como genotipos mendelianos y resumidos en varios algoritmos de agrupaciones y de genética de poblaciones. La diferenciación espacial y temporal fue pesquisada por las frecuencias cromosómicas, la diversidad cromosómica y la heterocigocidad. Si bien en la raza "Norte 2n = 38-40" no encontramos diferenciación para la diversidad cromosómica, las frecuencias y la heterocigosidad cromosómicas muestran una significativa diferenciación espacial, permite distinguir las poblaciones procedentes de la cordillera de La Costa, cordillera de Los Andes y cordón transversal. La muestra Cuesta de Chacabuco (Transversal podría corresponder a una zona de hibridación entre los restantes rangos. La comparación entre las razas cromosómicas en relación al origen de los rearreglos cromosómicos, a la citogenética poblacional y a los patrones de recombinación genética resultantes de la heterocigosidad, permiten expandir el área de estudio y discutir la evolución de este complejo en Chile, destacando la importancia de algunas barreras biogeográficas como los ríos de Chile Central

  8. Post-earthquake coastal evolution and recovery of an embayed beach in central-southern Chile

    Science.gov (United States)

    Martínez, Carolina; Rojas, Daniel; Quezada, Matías; Quezada, Jorge; Oliva, Ricardo

    2015-12-01

    Earthquakes and tsunamis are significant factors for change along active margin shores, and influence coastal evolution. The Chilean coast was affected in 2010 by a subduction earthquake with a magnitude of Mw 8.8 and also by a trans-Pacific tsunami, which generated violent geomorphologic changes and damaged homes. Following these events, the magnitude of the changes which affect Chile's central-southern coast (37°S) and the role of subduction earthquakes in coastal evolution on a historical scale were investigated. At Lebu bay (an embayed beach) data were generated for variations in time and space along the shoreline, topographical and bathymetric changes in the bay, and for morphodynamic littoral processes. Logarithmic and parabolic models were applied to the shoreline along with map overlays in order to determine changes. The shoreline processes were analyzed based on statistics for waves, tides and sediment transport for pre- and post-tsunami conditions. An average accretion rate of 2.80 m/year (1984-2010) was established for the shoreline, with a strong trend towards accretion in the last 30 years. A parabolic function best represented the general form of the shoreline, although the presence of a river in the concave zone affected the fit in this sector. Two factors controlled historical changes on the beach: one of anthropic origin in addition to the earthquake and tsunami on February 27th, 2010. The post-earthquake recovery was fast, and currently the beach is in a stable condition despite the inter-seismic subsidence process previous to the event. This coastal system showed a high resilience in the face of coastal geomorphological changes induced by high-impact natural disturbances. However, the opposite occurred in relation to changes induced by anthropogenic disturbances.

  9. Assessing the benefits and costs of dryland forest restoration in central Chile.

    Science.gov (United States)

    Schiappacasse, Ignacio; Nahuelhual, Laura; Vásquez, Felipe; Echeverría, Cristian

    2012-04-30

    Investment in natural capital restoration is increasing as a response to the widespread ecological degradation of dryland forests. However, finding efficient mechanisms to promote restoration among private landowners is a significant challenge for policy makers with limited financial resources. Furthermore, few attempts have been made to evaluate the costs and benefits of restoration interventions even though this information is relevant to orient decision making. Hence, our goal was to estimate the benefits and costs of dryland forest restoration by means of reforestation with native trees in a study area in central Chile. To determine benefits we applied a Contingent Valuation questionnaire that allowed for the calculation of willingness to pay measures. Restoration costs were calculated based on market prices following existing technical recommendations developed for the study area. The results showed that the restoration project had a negative NPV irrespective of the discount rate applied in the analysis. Thus, the NPV varied between -US$71,000 and -US$258,000. The NPV attained positive results only for negative discount rates (US$15,039 for -2%) and only when the national subsidy available for forest restoration was taken into account. This shows that landowners in Colliguay do not have incentives for carrying out restoration interventions due to a classic market failure: that in which ecosystems are mismanaged because many of their benefits are externalities from the perspective of landowners. Overall, these results stress the need for developing new compensation mechanisms and enhancing those in existence, with the aim of making restoration competitive with other land uses. PMID:22325581

  10. Climate change adaptation in a highly urbanized snowmelt dominated basin in Central Chile

    Science.gov (United States)

    Vicuna, S.; Bustos, E.; Merino, P.; Henriquez Dole, L. E.; Jansen, S.; Gil, M.; Ocampo, A.; Poblete, D.; Tosoni, D.; Meza, F. J.; Donoso, G.; Melo, O.

    2015-12-01

    The Maipo river basin holds 40% of Chile's total population and produces almost half of the country's Gross Domestic Product. The basin is located in the semiarid and snowmelt dominated central region of the country and, aside from the typical pressures of growth in developing country basins, the Maipo river basin faces climate change impacts associated with a reduction in total runoff and changes in its seasonality. Surface water is the main water source for human settlements, natural ecosystems, and economic activities including agriculture, mining and hydropower production. In 2012 a research project, called MAPA (Maipo Plan de Adaptacion), began with the objective of articulating a climate variability and climate change adaptation plan for the Maipo river basin. The project engaged at the beginning a group of relevant water and land use stakeholders which allowed for a good representation of critical aspects of an adaptation plan such as the definition of objectives and performance indicators, future land use scenarios, modeling of the different components of the system and design of adaptation strategies. The presentation will highlight the main results of the research project with a special focus on the upper catchments of the basin. These results include the assessment of impacts associated with future climate and land use scenarios on key components of the hydrologic cycle including snowmelt and glacier contribution to runoff and subsequent impacts on water availability for the operation of hydropower facilities, satisfaction of instream (recreation and aquatic ecosystem) uses and provision of water for the city of Santiago (7 million people) and to irrigate more than 100,000 hectares of high value crops. The integrative approach followed in this project including different perspectives on the use of water in the basin provides a good opportunity to test the varying degree of impacts that could be associated with a given future scenario and also understand

  11. Evaluation of TRMM Multi-satellite Precipitation Analysis (TMPA) performance in the Central Andes region and its dependency on spatial and temporal resolution

    Science.gov (United States)

    Scheel, M. L. M.; Rohrer, M.; Huggel, Ch.; Santos Villar, D.; Silvestre, E.; Huffman, G. J.

    2011-08-01

    Climate time series are of major importance for base line studies for climate change impact and adaptation projects. However, for instance, in mountain regions and in developing countries there exist significant gaps in ground based climate records in space and time. Specifically, in the Peruvian Andes spatially and temporally coherent precipitation information is a prerequisite for ongoing climate change adaptation projects in the fields of water resources, disasters and food security. The present work aims at evaluating the ability of Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) to estimate precipitation rates at daily 0.25° × 0.25° scale in the Central Andes and the dependency of the estimate performance on changing spatial and temporal resolution. Comparison of the TMPA product with gauge measurements in the regions of Cuzco, Peru and La Paz, Bolivia were carried out and analysed statistically. Large biases are identified in both investigation areas in the estimation of daily precipitation amounts. The occurrence of strong precipitation events was well assessed, but their intensities were underestimated. TMPA estimates for La Paz show high false alarm ratio. The dependency of the TMPA estimate quality with changing resolution was analysed by comparisons of 1-, 7-, 15- and 30-day sums for Cuzco, Peru. The correlation of TMPA estimates with ground data increases strongly and almost linearly with temporal aggregation. The spatial aggregation to 0.5°, 0.75° and 1° grid box averaged precipitation and its comparison to gauge data of the same areas revealed no significant change in correlation coefficients and estimate performance. In order to profit from the TMPA combination product on a daily basis, a procedure to blend it with daily precipitation gauge measurements is proposed. Different sources of errors and uncertainties introduced by the sensors, sensor-specific algorithm aspects and the TMPA processing scheme

  12. Evaluation of TRMM Multi-satellite Precipitation Analysis (TMPA performance in the Central Andes region and its dependency on spatial and temporal resolution

    Directory of Open Access Journals (Sweden)

    M. L. M. Scheel

    2010-10-01

    Full Text Available Climate time series are of major importance for base line studies for climate change impact and adaptation projects. However, in mountain regions and in developing countries there exist significant gaps in ground based climate records in space and time. Specifically, in the Peruvian Andes spatially and temporally coherent precipitation information is a prerequisite for ongoing climate change adaptation projects in the fields of water resources, disasters and food security. The present work aims at evaluating the ability of Tropical Rainfall Measurement Mission (TRMM Multi-satellite Precipitation Analysis (TMPA to estimate precipitation rates at daily 0.25° × 0.25° scale in the Central Andes and the dependency of the estimate performance on changing spatial and temporal resolution. Comparison of the TMPA product with gauge measurements in the regions of Cuzco, Peru and La Paz, Bolivia were carried out and analysed statistically. Large biases are identified in both investigation areas in the estimation of daily precipitation amounts. The occurrence of strong precipitation events was well assessed, but their intensities were underestimated. TMPA estimates for La Paz show high false alarm ratio.

    The dependency of the TMPA estimate quality with changing resolution was analysed by comparisons of 1-, 7-, 15- and 30-day sums for Cuzco, Peru. The correlation of TMPA estimates with ground data increases strongly and almost linearly with temporal aggregation. The spatial aggregation to 0.5°, 0.75° and 1° grid box averaged precipitation and its comparison to gauge data of the same areas revealed no significant change in correlation coefficients and estimate performance.

    In order to profit from the TMPA combination product on a daily basis, a procedure to blend it with daily precipitation gauge measurements is proposed.

    Different sources of errors and uncertainties introduced by the sensors, sensor-specific algorithm aspects

  13. Evaluation of TRMM Multi-satellite Precipitation Analysis (TMPA performance in the Central Andes region and its dependency on spatial and temporal resolution

    Directory of Open Access Journals (Sweden)

    M. L. M. Scheel

    2011-08-01

    Full Text Available Climate time series are of major importance for base line studies for climate change impact and adaptation projects. However, for instance, in mountain regions and in developing countries there exist significant gaps in ground based climate records in space and time. Specifically, in the Peruvian Andes spatially and temporally coherent precipitation information is a prerequisite for ongoing climate change adaptation projects in the fields of water resources, disasters and food security. The present work aims at evaluating the ability of Tropical Rainfall Measurement Mission (TRMM Multi-satellite Precipitation Analysis (TMPA to estimate precipitation rates at daily 0.25° × 0.25° scale in the Central Andes and the dependency of the estimate performance on changing spatial and temporal resolution. Comparison of the TMPA product with gauge measurements in the regions of Cuzco, Peru and La Paz, Bolivia were carried out and analysed statistically. Large biases are identified in both investigation areas in the estimation of daily precipitation amounts. The occurrence of strong precipitation events was well assessed, but their intensities were underestimated. TMPA estimates for La Paz show high false alarm ratio.

    The dependency of the TMPA estimate quality with changing resolution was analysed by comparisons of 1-, 7-, 15- and 30-day sums for Cuzco, Peru. The correlation of TMPA estimates with ground data increases strongly and almost linearly with temporal aggregation. The spatial aggregation to 0.5°, 0.75° and 1° grid box averaged precipitation and its comparison to gauge data of the same areas revealed no significant change in correlation coefficients and estimate performance.

    In order to profit from the TMPA combination product on a daily basis, a procedure to blend it with daily precipitation gauge measurements is proposed.

    Different sources of errors and uncertainties introduced by the sensors, sensor

  14. The ANDES Deep Underground Laboratory

    CERN Document Server

    Bertou, X

    2013-01-01

    ANDES (Agua Negra Deep Experiment Site) is a unique opportunity to build a deep underground laboratory in the southern hemisphere. It will be built in the Agua Negra tunnel planned between Argentina and Chile, and operated by the CLES, a Latin American consortium. With 1750m of rock overburden, and no close- by nuclear power plant, it will provide an extremely radiation quiet environment for neutrino and dark matter experiments. In particular, its location in the southern hemisphere should play a major role in understanding dark matter modulation signals.

  15. Cenozoic tholeiitic volcanism in the Colbún area, Linares Precordillera, central Chile (35º35'-36ºS

    Directory of Open Access Journals (Sweden)

    Mario Vergara

    1999-07-01

    Full Text Available RESUMEN Volcanismo toleítico Terciario en el área de Colbún, Precordillera de Linares, Chile central (35º-35º36'S. En la Precordillera de Linares, Chile central (35º5'-36ºS, afloran rocas volcánicas, cuyas edades varían del Eoceno Superior al Mioceno Medio. Sobre la base de criterios estratigráficos y dataciones K-Ar y Ar-Ar, se han diferenciado dos unidades: 1- una Unidad Inferior (Eoceno Superior a Oligoceno Superior, con predominio de rocas volcánicas silíceas en la base y básicas en el nivel superior y 2- una Unidad superior (Mioceno Inferior a Medio, con basaltos afíricos y tobas soldadas riolíticas. Las características geoquímicas de las rocas volcánicas de Colbún, tales como bajos contenidos en K2O, razones MgO/FeO altas, patrones de REE planos, abundancia normalizada con respecto al MORB cercana a la unidad para los elementos Nb a Sc, razones isotópicas iniciales de Sr relativamente bajas (0.703575-0.704028 y relativamente altas de Nd (0.512919-0.513003, son consistentes con una afinidad toleítica y con un grado de contaminación cortical bajo en la evolución de los magmas parentales. Las relaciones isotópicas de Pb y el enriquecimiento en algunos elementos incompatibles, tales como K, Rb, Sr y Ba, sugieren un reciclamiento de material subductado de la placa de Nazca, el cual estuvo acompañado por un adelgazamiento cortical y el desarrollo de estructuras tipo calderas. Isotópicamente, las rocas de Colbún son las más primitivas de los Andes chilenos. Relaciones geoquímicas sugieren que estas rocas se emplazaron en un ambiente geotectónico de trasarco, intracontinental, postorogénico y extensional. Los magmas de Colbún evolucionaron, principalmente, por cristalización fraccional a partir de magmas primarios generados en el manto. Las semejanzas químicas e isotópicas presentadas por estas rocas emplazadas entre el Eoceno Superior y el Mioceno Medio sugieren que las fuentes y procesos, involucrados en su g

  16. Receiver Function Migration of Broadband Seismograms recorded by the International Maule Aftershock Deployment (IMAD) in Central Chile

    Science.gov (United States)

    Morell, M.; Beck, S. L.; Roecker, S. W.; Meltzer, A.; Russo, R. M.

    2011-12-01

    The Mw=8.8 Maule earthquake that occurred off the coast of Chile on February 27, 2010 is one of the largest megathrust earthquakes ever to be recorded and ruptured ~600 km of the plate boundary. This segment of the Nazca-South America plate boundary is an ideal region to investigate the processes related to the structure of the down-dip edge of the seismogenic zone, forearc wedge and subducting slab. Immediately after the Maule earthquake, international teams from France, Germany, Great Britain and the United States joined Chilean seismologists to install an array of seismic stations between 33°-38.5°S, from the coast to the foothills of the Andes to produce the International Maule Aftershock Deployment (IMAD) data set. These arrays were deployed from mid-March until the end of December 2010 in order to capture and study the aftershocks in and around the rupture zone, and to better understand crustal and mantle wedge structure. We calculated receiver functions (RFs) from P and PP phases and made Common Conversion Point stacks to image the structures in the slab and forearc wedge down to a depth of 100 km. We have identified the oceanic slab Moho on several E-W and N-S profiles at 40 to 60 km depth beneath the array and several discontinuities above the slab in the forearc. These profiles also show a large low-velocity zone beneath the northern half of the array in the forearc. In addition, we are using a 2.5D finite difference teleseismic waveform tomography technique described in Roecker et al. (2010) to image the crust and upper mantle beneath that part of the Chilean Andes occupied by the IMAD array and the earlier TIPTEQ deployment of Rietbrock et al. (2005). While the technique does not require any kind of formal source deconvolution, in sparse deployments we can apply this technique in an RF type migration by normalizing medium sensitivities. Both these techniques will improve our imaging of the down-dip limit of the seismogenic zone, forearc wedge and

  17. Dieta del pez espada Xiphias gladius Linnaeus, 1758, en aguas oceánicas de Chile central en invierno de 2003 Diet of the swordfish Xiphias gladius Linnaeus, 1758 in oceanic waters off central Chile in winter 2003

    OpenAIRE

    Christian M Ibáñez; Carlos González; Luis Cubillos

    2004-01-01

    Se analiza la dieta del pez espada en tres zonas de pesca en aguas oceánicas de Chile central durante el invierno de 2003, considerando como hipótesis que el tamaño de las presas se incrementa significativamente con el tamaño del depredador, conjuntamente con una disminución del número de presas. El estudio se realizó sobre la base de 48 estómagos de Xiphias gladius con contenido estomacal. Para su análisis se utilizó los descriptores cuantitativos de frecuencia de ocurrencia y método numéric...

  18. Application of the 137Cs technique to quantify soil redistribution rates in paleohumults from Central-South Chile

    International Nuclear Information System (INIS)

    The objective of the present study was to evaluate the applicability of the 137Cs technique in obtaining spatial distributed information on mean soil redistribution rates in Central-South Chile. For this purpose four fields of Palehumult soil and contrasting land use and management were selected in the Coastal Mountain Range of the 9th Region: Crop fields under subsistence and commercial management and non-permanent prairies under subsistence and commercial management. The spatial distribution of the soil redistribution rates obtained by the 137Cs method was similar to the one obtained by pedological observations. Also, annual sediment fluxes measured at experimental plots were similar to the erosion rates determined by the 137Cs method at adjacent points. The 137Cs technique is seen as an efficient method to obtain long-term soil redistribution rates under the climatic conditions and the soil type selected in Chile. In the future, it is necessary to study the applicability of the method under other climatic conditions and soil types occurring in Chile in which erosion is not so evident, and to adjust the method to optimise costs and benefits. (author)

  19. El aprecio por el paisaje y su utilidad en la conservación de los paisajes de Chile Central

    OpenAIRE

    Gonzalo de la Fuente de Val; José A. Atauri Mezquida; José V. de Lucio Fernández

    2004-01-01

    La transformación del paisaje mediterráneo de Chile Central comienza a plantearse en la sociedad como una prioridad en todas sus dimensiones y funcione. Se consideran no sólo sus factores ecológicos, sociales, económicos sino también culturales, escénicos y afectivos. Se ha sugerido la percepción del paisaje como una pieza significativa para emprender nuevas formas de relación con el entorno. Este trabajo ilustra los resultados generales de un amplio estudio de preferencias paisajísticas y me...

  20. Palaeoenvironment reconstruction, volcanic evolution and geochronology of the Cerro Blanco subcomplex, Nevados de Chillan volcanic complex, Central Chile

    OpenAIRE

    Mee, Katy; Gilbert, Jennie S.; McGarvie, David W.; Naranjo, Jose A.; Pringle, Malcolm S.

    2009-01-01

    Nevados de Chillán Volcanic Complex, central Chile, has been active for at least 640 ka—a period spanning a number of glacial and interglacial periods. Geologic mapping, radiometric dating and geochemical analysis have identified six new volcanic units and produced four new 40Ar/39Ar ages for Cerro Blanco, the northern subcomplex of Nevados de Chillán volcano. Compositions range from dacite to basaltic-andesite and a new geologic map is presented. Examination of lava fracture structures on bo...

  1. Syntectonic emplacement of the Middle Jurassic Concon Mafic Dike Swarm, Coastal Range, central Chile (33 degrees S)

    OpenAIRE

    C. Creixell; M.A. Parada; Roperch, Pierrick; D. Morata; Arriagada, C; Arce, C.P. de

    2006-01-01

    The Concon Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Palcozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (512 in) and a late group of thin dikes (0.5-3 m). Two new amphibole Ar-40/Ar-39 dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field obser...

  2. A new species of Phymaturus (Iguania: Liolaemidae) of the palluma group from Central Chile

    OpenAIRE

    Troncoso-Palacios, Jaime; Lobo, Fernando

    2012-01-01

    We examined specimens of Phymaturus from four locations in central Chile, between 34º50´S and 36º00´S (from Termas del Flaco and from Lircay and its surroundings), where the only recognized species is P. maulense. We found several differences in the scalation and in the color pattern among them. The samples from Lircay and its surroundings correspond to topotypes of P. maulense and two more populations assignable to this species (Termas del Campanario and Laguna del Maule, new records), but t...

  3. Glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland: The case of the Tapado glacier, dry Andes of Chile (30°S)

    Science.gov (United States)

    Pourrier, J.; Jourde, H.; Kinnard, C.; Gascoin, S.; Monnier, S.

    2014-11-01

    The Tapado catchment is located in the upper Elqui river basin (4000-5550 m) in northern Chile. It comprises the Tapado glacial complex, which is an assemblage of the Tapado glacier and the glacial foreland (debris-covered glacier, rock glacier, and moraines). Although the hydrological functioning of this catchment is poorly known, it is assumed to actively supply water to the lower semi-arid areas of the Elqui river basin. To improve our knowledge of the interactions and water transfers between the cryospheric compartment (glacier, debris-covered glacier, and rock glacier) and the hydrological compartment (aquifers, streams), the results of monitoring of meteorological conditions, as well as discharge, conductivity and temperature of streams and springs located in the Tapado catchment were analyzed. The hydrological results are compared to results inferred from a ground penetrating radar (GPR) survey of the underground structure of the glacial foreland. Water production from the Tapado glacier was shown to be highly correlated with daily and monthly weather conditions, particularly solar radiation and temperature. The resulting daily and monthly streamflow cycles were buffered by the glacial foreland, where underground transfers took place through complex flow paths. However, the development of a thermokarst drainage network in a portion of the glacial foreland enabled rapid concentrated water transfers that reduced the buffer effect. The glacial foreland was shown to act as a reservoir, storing water during high melt periods and supplying water to downstream compartments during low melt periods. GPR observations revealed the heterogeneity of the internal structure of the glacial foreland, which is composed of a mixture of ice and rock debris mixture, with variable spatial ice content, including massive ice lenses. This heterogeneity may explain the abovementioned hydrological behaviors. Finally, calculation of a partial hydrological budget confirmed the

  4. The origin of the Loncopué Trough in the retroarc of the Southern Central Andes from field, geophysical and geochemical data

    Science.gov (United States)

    Rojas Vera, E. A.; Sellés, D.; Folguera, A.; Gímenez, M.; Ruíz, F.; Orts, D.; Zamora Valcarce, G.; Martínez, P.; Bechis, F.; Ramos, V. A.

    2014-12-01

    This work analyzes through field, geophysical, geochemical and geochronological data, a particular setting of the Southern Andes in which an extensional system is flanking the mountain front. This setting is represented by the Loncopué Trough, whose origin is discussed for this part of the Andes. This work reconstructs 3-dimensionally the structure of this basin and its evolution through time, since Jurassic times as a series of isolated depocenters, to Late Cretaceous-Eocene times with the construction of a positive relief that subsequently was relaxed through two extensional stages during the late Oligocene-early Miocene and the Pliocene-Quaternary respectively. The last episode of extension is characterized by an initial stage with a series of caldera-collapses in the latest Pliocene-early Quaternary. This passed to a stage of development of a broad basaltic plateau in pre- and inter-glacial times, circumscribed with new radiometric data to the Pleistocene. Quaternary products in northern and central Loncopué Trough have chemical relations that are intermediate between the arc front and the southern Loncopué Trough volcanic rocks studied in previous works. Thus, retroarc eruptions would be part of an extended arc configuration that goes from typical arc series in the northern part of the trough to within-plate series in the south. Low elastic thicknesses computed from gravity data in this work correlate with the area of retroarc volcanic activity. Magnetic data have allowed determining the Curie isotherm, showing two areas of relatively abnormal heat flow, one along the Loncopué Trough itself and the other in the foreland zone. This scenario is discussed through three main hypotheses: an occurrence linked to a slab-steepening after a shallow subduction in the area; co-seismic crustal stretching linked to giant earthquakes in the subduction zone; and, finally slab-tearing associated with asthenospheric upwelling.

  5. Suspended sediments and organic matter in mountain headwaters of the Amazon River: Results from a 1-year time series study in the central Peruvian Andes

    Science.gov (United States)

    Townsend-Small, Amy; McClain, Michael E.; Hall, Bonnie; Noguera, Jorge L.; Llerena, Carlos A.; Brandes, Jay A.

    2008-02-01

    Few studies have examined the dynamics of sediments and suspended organic matter and their export from headwater basins in the Andes Mountains to the Amazon River, despite the fact that the Andes are the primary source of sediments to the lower Amazon basin. We measured river discharge as well as the concentration, δ 15N, δ 13C, %N, and %OC of coarse and fine suspended sediments (CSS and FSS) in the Chorobamba River, located in the central Andean Amazon of Peru. Samples were taken at least weekly over an entire year (July 2004-July 2005), with additional sampling during storms. Concentrations of particulate organic matter (POM) were generally low in the study river, with concentrations increasing by up to several orders of magnitude during episodic rain events. Because both overall flow volumes and POM concentrations increased under stormflow conditions, the export of POM was enhanced multiplicatively during these events. We estimated that a minimum of 80% of annual suspended sediment transfer occurred during only about 10 days of the year, also accounting for 74% of particulate organic carbon and 64% of particulate organic nitrogen transport. Significant differences occurred between seasons (wet and dry) for δ 13C of coarse and fine POM in the Chorobamba River, reflecting seasonal changes in organic matter sources. The time series data indicate that this Andean river exports approximately equal amounts of fine and coarse POM to the lower Amazon. The observation that the vast majority of sediments and associated OM exported from Andean rivers is mobilized during short, infrequent storm events and landslides has important implications for our understanding of Amazon geochemistry, especially in the face of incipient global change.

  6. Water Erosion Prediction Using the Revised Universal Soil Loss Equation (RUSLE) in a GIS Framework, Central Chile Estimación de la Erosión Hídrica Empleando la Ecuación Universal de Pérdida de Suelo Revisada (RUSLE) y SIG en Chile Central

    OpenAIRE

    Carlos A. Bonilla; Reyes, José L.; Antoni Magri

    2010-01-01

    Soil erosion is a growing problem in Central Chile, particularly in coastal dry lands, where it can significantly decrease the productivity of rainfed agriculture and forestry. In this study, the Revised Universal Soil Loss Equation (RUSLE) was integrated into a Geographic Information System (GIS), and used to evaluate the effects of different combinations of vegetative cover on soil erosion rates for Santo Domingo County in Central Chile. Implementing RUSLE in the GIS required a complete des...

  7. Estimation of real evapotranspiration and its variation in Mediterranean landscapes of central-southern Chile

    Science.gov (United States)

    Olivera-Guerra, L.; Mattar, C.; Galleguillos, M.

    2014-05-01

    Evapotranspiration (ETd) is a key controller in the ecohydrological processes of semi-arid landscapes. This is the case of the dry land in Chile's central-southern zone, where forestry, farming and livestock activities must adapt to precipitation with considerable year-on-year variations. In this study, the spatial distribution of ETd was estimated in relation to the land use map and physical parameters of the soil. The ETd was estimated through the Simplified Surface Energy Balance Index (S-SEBI) using data from weather stations and remote data provided by the ASTER and MODIS sensors for November 2004 and 2006, respectively. The spatial variability of ETd was compared among different plant types, soil textural classes and depths using non-parametric statistical tests. In this comparison, the highest rates of ETd were obtained in the forest covers with values of 7.3 ± 0.8 and 8.4 ± 0.8 mm d-1 for 2004 and 2006, respectively. The lowest values were estimated for pastures and shrublands with values of 3.5 ± 1.2 mm d-1 and for crops with rates of 4.4 ± 1.6 mm d-1. Comparison of the ETd of the native forest covers and plantations of exotic species showed statistically significant differences; however, no great variation was noted, at least in the study months. Additionally, the highest rates of ETd were found in the clay loam textures (6.0 ± 1.8 and 6.4 ± 2.0 mm d-1) and the lowest rates in the sandy loam soils (3.7 ± 1.6 and 3.9 ± 1.6 mm d-1) for 2004 and 2006, respectively. The results enable analysis of the spatial patterns of the landscape in terms of the relation between water consumption, ET and the biophysical characteristics of a Mediterranean ecosystem. These results form part of the creation of tools useful in the optimization of decision-making for the management and planning of water resources and soil use in territories with few measuring instruments.

  8. Latitudinal discontinuity in thermal conditions along the nearshore of central-northern Chile.

    Science.gov (United States)

    Tapia, Fabian J; Largier, John L; Castillo, Manuel; Wieters, Evie A; Navarrete, Sergio A

    2014-01-01

    Over the past decade, evidence of abrupt latitudinal changes in the dynamics, structure and genetic variability of intertidal and subtidal benthic communities along central-northern Chile has been found consistently at 30-32°S. Changes in the advective and thermal environment in nearshore waters have been inferred from ecological patterns, since analyses of in situ physical data have thus far been missing. Here we analyze a unique set of shoreline temperature data, gathered over 4-10 years at 15 sites between 28-35°S, and combine it with satellite-derived winds and sea surface temperatures to investigate the latitudinal transition in nearshore oceanographic conditions suggested by recent ecological studies. Our results show a marked transition in thermal conditions at 30-31°S, superimposed on a broad latitudinal trend, and small-scale structures associated with cape-and-bay topography. The seasonal cycle dominated temperature variability throughout the region, but its relative importance decreased abruptly south of 30-31°S, as variability at synoptic and intra-seasonal scales became more important. The response of shoreline temperatures to meridional wind stress also changed abruptly at the transition, leading to a sharp drop in the occurrence of low-temperature waters at northern sites, and a concurrent decrease in corticated algal biomass. Together, these results suggest a limitation of nitrate availability in nearshore waters north of the transition. The localized alongshore change results from the interaction of latitudinal trends (e.g., wind stress, surface warming, inertial period) with a major headland-bay system (Punta Lengua de Vaca at 30.25°S), which juxtaposes a southern stretch of coast characterized by upwelling with a northern stretch of coast characterized by warm surface waters and stratification. This transition likely generates a number of latitude-dependent controls on ecological processes in the nearshore that can explain species

  9. Is tourism damaging ecosystems in the Andes? Current knowledge and an agenda for future research

    OpenAIRE

    Barros, Agustina; Monz, Christopher; Pickering, Catherine

    2014-01-01

    Despite the popularity of tourism and recreation in the Andes in South America and the regions conservation value, there is limited research on the ecological impacts of these types of anthropogenic use. Using a systematic quantitative literature review method, we found 47 recreation ecology studies from the Andes, 25 of which used an experimental design. Most of these were from the Southern Andes in Argentina (13 studies) or Chile (eight studies) with only four studies from the Northern Ande...

  10. Strategies for improving thermal performance and visual comfort in office buildings of Central Chile

    OpenAIRE

    Bustamante Gómez, Waldo; Encinas Pino, Felipe; Pino, Alan; Otarola, Roberto; PLEA 2011 - 27th International Conference on Passive and Low Energy Architecture: Architecture & Sustainable Development

    2011-01-01

    Overheating, high cooling energy demand and glare are recurrent problems in office buildings in Santiago and Valparaíso, Chile. Santiago (33°S) presents a Mediterranean climate, with a high temperature oscillation between day and night during cooling period. Valparaiso (33°S), by the coast, shows lower temperature fluctuation compared with Santiago. In order to evaluate impact on thermal and lighting performance of office buildings of these cities, a sensitivity study has been made. Variation...

  11. The complete mitochondrial genome of the endemic and threatened killifish Orestias ascotanensis Parenti, 1984 (Cyprinodontiformes, Cyprinodontidae) from the High Andes.

    Science.gov (United States)

    Quezada-Romegialli, Claudio; Guerrero, Claudia Jimena; Véliz, David; Vila, Irma

    2016-07-01

    The killifish Orestias ascotanensis is endemic to the small isolated springs of Ascotán salt pan in the Central High Andes, Chile. Due to small populations, mining activity, and increasing aridity, this species is catalogued in danger of extinction. The complete mitochondrial genome of O. ascotanesis was assembled with an Ion Torrent sequencer (chip 318) that produced 2.61 million of reads. The 16 617 bp of the entire genome consisted of 22 transfer RNAs, 2 ribosomal RNAs, 13 protein-coding genes, and a control region, showing that the gene composition and arrangement match to that reported for most fishes. PMID:26152352

  12. Constuccion social de comuninad y migración en Usibamba : un estudio sobre el impacto de los procesos de globalización en los Andes centrales del Perú

    OpenAIRE

    Gilvonio Perez, J.M.

    2009-01-01

    The research for the thesis was conducted in the village of Usibamba, located in a high-Andean area called Alto Cunas east from the Mantaro Valley in the Peruvian Central Andes. Special attention was paid to the institutional context and the everyday life conditions in which the social construction of community takes place. The thesis focuses on ongoing changes in agrarian situations relating to processes of modernization, globalization and different kinds of migration experiences (both natio...

  13. Extensional Basins in a Convergent Margin: Oligocene-Early Miocene Salar de Atacama and Calama basins, Central Andes

    Science.gov (United States)

    Jordan, T. E.; Mpodozis, C.; Blanco, N.; Pananont, P.; Dávila, F.

    2004-12-01

    The Salar de Atacama Basin (SdAB) is the largest and most persistent sedimentary basin of northern Chile, accumulating nonmarine sediment from Cretaceous to modern times. Its northwestern neighbor, the Calama, was a Cenozoic basin. Although SdAB was in the backarc zone early in the Andean orogeny, both are now forearc basins. Others demonstrated that the basins overlie anomalously cold, strong, and dense crust and lithosphere. We focus on an extensional Oligocene basin stage. Interpretation of the basin-controlling faults is based on seismic reflection studies supported by field relations. The SdAB is limited to the west by the NNE-trending, steeply east-dipping, Paciencia Fault (PF). The PF experienced 5-7 km of down-to-the-east offset during the Oligocene-early Miocene. Syntectonic strata, an arid succession of siliciclastics and evaporites, are asymmetric, with thicknesses of 5000 m and abundant halite adjacent to the PF, and of 1000 m with fine detrital clastic strata 25 km farther east. Relations in conglomeratic growth strata that overlap the PF also demonstrate normal displacement during sediment accumulation. Seismic data reveal that a buried normal fault with 1-1.5 km down-to-the-east displacement limits the western margin of the Oligocene-Miocene Calama siliciclastic basin fill. Regionally, Oligocene-early Miocene margin-parallel strike-slip deformation dominated northwest of the basins, contributing sinistral offset (West Fissure Fault) to the northern segment of the long-lived Domeyko Fault System. The new SdAB and Calama data reveal that a 20,000 km2 domain of extensional basins existed within the dominantly strike-slip region. Even if PF and the fault in the Calama Basin were transtensional, the proportion of extension to strike-slip displacement is much greater in these basins than elsewhere in northern Chile. Further study is required to understand what combination of factors caused this kinematic distinction as well as delayed the onset of CVZ

  14. Composición, estructura y flujo energético del meiobentos frente a Chile central Composition, structure and energy flux of the meiobenthos off central Chile

    Directory of Open Access Journals (Sweden)

    JAVIER SELLANES

    2003-09-01

    Full Text Available Se estudió la estructura de la meiofauna metazoaria (a nivel de grandes grupos taxonómicos y su rol en el flujo de energía en el subsistema bentónico frente a Concepción (~3630' S. Las muestras se recolectaron en mayo y noviembre de 1997 y mayo de 1998 en cinco sitios correspondientes a: interior de la Bahía de Concepción (28 m, boca de la bahía (35 m, plataforma interior (64 m, plataforma intermedia (88 m y plataforma externa (120 m. El periodo de estudio coincidió con el evento El Niño 1997-1998 (EN. El meiobentos resultó ser poco diverso a nivel de grandes grupos, pero con abundancias y biomasas moderadas a altas, en comparación con los valores promedio reportados en la literatura para el sublitoral fangoso. Nematoda fue el grupo dominante, con más de un 95 % (10³­10(4 ind 10 cm­2 de la densidad total, seguidos por Copepoda y Polychaeta. Las mayores abundancias y biomasas totales se encontraron siempre en la boca de la bahía, seguida de su parte interior y de la plataforma interior, mientras que los menores valores se ubicaron en la plataforma intermedia y externa. Frente a Concepción el meiobentos juega un importante rol en el flujo de energía a través del subsistema bentónico. Se estimó que estos organismos podrían estar remineralizando y/o convirtiendo a biomasa hasta un 36 y 45 % del carbono orgánico que llega desde la columna de agua a los sedimentos en el centro y en la boca de la bahía, respectivamente.The general objective of this study was to determine the structure of metazoan meiofauna (at a high taxonomic level and to estimate its role in the energy flux of the benthic sub-system off Concepción, Chile (~3630' S. Samples were collected in May and November 1997 and May 1998 at five sites located at the: inner Bay of Concepción (28 m, bay-mouth (35 m, inner-shelf (64 m, mid-shelf (88 m and outer-shelf (120 m. The study period coincided with the El Niño 1997-1998 (EN event. The diversity of the meiobenthos

  15. Energy balance and temperature relations of Azorella compacta, a high-elevation cushion plant of the central Andes.

    Science.gov (United States)

    Kleier, C; Rundel, P

    2009-05-01

    The environmental relationships and ecophysiology of Azorella compacta, a giant cushion plant, were investigated in Parque Nacional Lauca, Chile (18 degrees 10'-18 degrees 25' S and 69 degrees 16' W, 4400 m asl). The diurnal temperature range can reach 42 degrees C on some days of the year. The surface temperature of A. compacta was 13 degrees C below that of the air temperature of -7 degrees C at dawn, but from midmorning to late afternoon, the plant surface temperature remained within a few degrees of the air temperature. Soil surface temperatures did not differ between north- and south-facing slopes, but a model showed an increase in radiation reception by north-facing slopes throughout most of the year. Gas exchange measurements of A. compacta measured at the onset of the wet season ranged from -0.6662 to 11.4 micromol.m(-2).s(-1), and maximum stomatal conductance (Gs) was 410 mmol.m(-2).s(-1). The estimated light compensation point was 89 micromol.m(-2).s(-1) and estimated light saturation occurred at about 1280 mumol.m(-2).s(-1). Diurnal water potential measurements for A. compacta ranged from -1.67 to -2.65 MPa. This is one of the first ecophysiological studies of a tropical alpine cushion plant. PMID:19470106

  16. Social and economic factors of chile de agua (Capsicum Annum L. in three municipalities of the Central Valley in Oaxaca

    Directory of Open Access Journals (Sweden)

    María de los Ángeles Rodríguez Mendoza

    2013-01-01

    Full Text Available This issue was carried out in the municipalities of San Pablo Huixtepec, San Sebastián Abasolo and Culiapan of Guerrero as part of the Central Valleys of Oaxaca, Mexico. We studied the production system of Agua Chile, using the technique of structured interview,information was obtained that allowed us to determine and meet the current models of socio-economic benefits in the form of productionof this vegetable. The importance of this study is that the chile de agua despite being a highly profitable crop has been little studied, so it is not known the extent that can have, there are markets that offer potentially greater benefits to farmers, therefore it is important to know the current situation of farmers in order to provide alternatives to improve their economic situation. The results indicate that according to the practices of peasant production and the low level of technology that includes the type of fertilizers, agrochemicals to combat pests and diseases and low use of agricultural machinery, yields of 3.97 t ha-1 allow total revenues are higher than the costs of production. Besides the existence of limited marketing networks (primarily in local markets and in the Oaxaca city, is a competitive crop in terms of profitability for finance of small production units and furthermore, it is growing factor relevant food security of farming families.

  17. Geographic variation in diversity of wave exposed rocky intertidal communities along central Chile Variación geográfica de la biodiversidad en hábitats intermareales rocosos de Chile central

    Directory of Open Access Journals (Sweden)

    BERNARDO R BROITMAN

    2011-03-01

    Full Text Available Along the coast of central Chile, geographic trends of diversity have been inferred from literature compilations and museum collections based on species range limits for some taxonomic groups. However, spatially-intensive field-based assessments of macrobenthic species richness are largely missing. Over the course of a multiyear study (1998-2005, we characterized latitudinal patterns of rocky intertidal diversity at 18 sites along the coast of central Chile (29-36° S. At each site, the number of sessile and mobile macrobenthic species was quantified in 0.25 m² quadrats. Two estimators of local (alpha diversity were used: observed local species richness, calculated from the asymptote of a species-rarefaction curve, and the Chao2 index, which takes into account the effect of rare species on estimates of local richness. We identified a total of 71 species belonging to 66 genera for a total of 86 taxa. The most diverse groups were herbivorous mollusks (27 taxa and macroalgae (43 taxa. Diversity showed a complex spatial pattern with areas of high species richness interspersed with areas of low richness. In accordance with previous work, we found no trend in the number of herbivorous mollusks and an inverse and significant latitudinal gradient in the number of algal species. Our results highlight the need for taxonomically diverse assessments of biodiversity of the dominant taxa that conform intertidal communities.A lo largo de la costa de Chile central, los patrones geográficos de diversidad han sido inferidos a partir de revisiones literarias y colecciones de museos para algunos grupos taxonómicos. Sin embargo, aun no contamos con una evaluación integral, y en terreno, de la riqueza de especies macrobentónicas intermareales. En un estudio de largo plazo conducido entre 1998 y 2005 caracterizamos los patrones latitudinales en la biodiversidad del intermareal rocoso en 18 sitios a lo largo de la costa de Chile central (29-36° S. En cada sitio

  18. Mycotrophy in Gilliesieae, a threatened and poorly known tribe of Alliaceae from central Chile Micotrofía en Gilliesieae, una tribu amenazada y poco conocida de Alliaceae de Chile central

    Directory of Open Access Journals (Sweden)

    GUSTAVO A TORRES-MELLADO

    2012-06-01

    Full Text Available The five known genera of Gilliesieae have their diversity center in the Mediterranean zone of central Chile, where many of their habitats are threatened by urban expansion, industrial and agroforestry activities, as well as other anthropogenic impacts. Very little is known about the biology of these particular geophytes, the majority of which currently have either vulnerable or endangered status, mainly due to their dispersed and small populations generally associated to remnants of native vegetation. As mycorrhizal associations are essential for soil resource acquisition and stress mitigation in most plants, our objective was to assess the hitherto unknown mycotrophic status of ten species of Gilliesieae from central Chile by qualitative and quantitative assessment of intraradical fungal structures. All sampled genera (Gethyum, Gilliesia, Miersia, Solaria, Speea showed regular presence of arbuscular mycorrhiza, while other mycorrhizal or putatively mutualistic associations, like dark septate endophytes, were practically absent. Mycorrhizal colonization of fine roots reached a mean of ca. 45 % across all examined taxa, with highly variable values ranging from 9 % to 82 % in Miersia tenuiseta and Gilliesia curicana, respectively. The high level of mycorrhization indicates that arbuscular mycorrhiza should be considered for conservation strategies of threatened species or biotechnological use in plant propagation. The main future task is the identification of the associated fungal taxa.Los cinco géneros conocidos de Gilliesieae tienen su centro de diversidad en la zona mediterránea de Chile central, donde muchos de sus hábitats están amenazados por la expansión urbana, actividades industriales y agroforestales, así como otros impactos antropogénicos. Se sabe muy poco sobre la biología de estas particulares geófitas, que en la actualidad tienen en su mayoría estatus de vulnerable o en peligro de extinción, debido a sus poblaciones

  19. Mapping South American Summer Monsoon Changes during Heinrich Event 1 and the LGM: Insights from New Paleolake Records from the Central Andes

    Science.gov (United States)

    Chen, C. Y.; McGee, D.; Quade, J.

    2015-12-01

    Cave stalagmite records show strong evidence of abrupt changes in summer monsoons during Heinrich events, but we lack rigorous constraints on the amount of wetting or drying occurring in monsoon regions. Studies on shoreline deposits of closed-basin lakes can establish quantitative bounds on water balance changes through mapping-based estimates of lake volume variations. We present new dating constraints on lake level variations in Agua Caliente I and Laguna Loyoques, two closed-basin, high-altitude paleolakes on the Altiplano-Puna plateau of the Central Andes (23.1°S, 67.4°W, 4250 masl). Because this area receives >70% of its total annual precipitation during austral summer, the region is ideally suited to capture a pure response to changes in the South American summer monsoon (SASM). The plateau is home to several small (modern. Hydrologic modeling constrained by paleotemperature estimates is used to provide bounds for these past precipitation changes. We also tentatively explore physical mechanisms linking Heinrich events and the regional hydroclimate by comparing freshwater hosing experiments and transient climate simulations. Our results in Agua Caliente I and Laguna Loyoques act as a proof of concept, and lend us confidence in expanding our U-Th work to other shoreline tufas in the surrounding region to produce a more detailed, spatiotemporal record of water balance changes in South America.

  20. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Chile

    International Nuclear Information System (INIS)

    Chile has an area of 740,760 square kilometers. The capital is Santiago. The country is 4,183 km. long and ranges from 22.5 to about 354 km. in width. Its chief topographic features para]lei each other - the Coastal Range, Andes Mountains and Central Valley. The Coastal Range rises to 2,130 meters in the north, but averages from 610 to 700 meters high generally. The range plunges into the Pacific Ocean far south of Valparaiso and reappears in the southern archipelagic islands. The Andes extend along nearly the entire length of Chile and contain 100 volcanoes. Andean peaks range mostly from 3,000 to 6,700 meters in elevation. In southern Chile the Andes are lower, and contain about a dozen major lakes. The mountains disappear in Chilean Patagonia, but reappear at Cape Horn. The Central Valley lies between the Coastal Range and the Andes, being best defined in the midland region as a 64 to 72 km sloping plain. It is the Chilean heartland with three-quarters of the country's population. Salt basins are found over much of northern Chile in the very arid desert, while the region south of the Gulf of Reloncavi consists of unpopulated islands, fjords, channels and heavily forested mountains. The Strait of Magellan, the Tierra del Fuego archipelago and a flat grassland area make up the extreme southern end of the country. Much of Chile is subject to flash floods, earthquakes, volcanic eruptions, landslides and avalanches. In September 1976 the Comision Chilena de Energia Nuclear (CCEN) was given exclusive rights to negotiate contracts with private companies for the exploration, development and mining of uranium and other radioactive minerals. The new law provides the CCEN with considerable flexibility in the terms of the contracts. Pre-964 owners of uranium deposits may reach agreements with foreign companies to mine the uranium, but since 1964 all uranium has belonged to the state. Uranium produced in the country can only be exported after Chile's needs have been met. The

  1. Latencia y banco de semillas en plantas de la región mediterránea de Chile central Seed bank and dormancy in plants of the Mediterranean region of central Chile

    Directory of Open Access Journals (Sweden)

    JAVIER A. FIGUEROA

    2004-03-01

    Full Text Available Los bancos de semillas en las regiones mediterráneas presentan rasgos particulares que los distinguen de bancos de otras regiones del mundo. El banco de semillas es concentración de propágulos viables enterrados en el suelo por períodos variables de tiempo. Los bancos de semillas del matorral de Chile central son principalmente transitorios y funcionalmente semejantes a los bancos presentes en otros ecosistemas mediterráneos no perturbados por fuego, a excepción de Australia. El banco transitorio es aquel formado por semillas que permanecen viables en los horizontes superiores del suelo por no más de 1 año después de la dispersión. En el matorral de Chile central, en los horizontes superiores del suelo, se encuentra una de las densidades de semillas de hierbas más altas de las regiones mediterráneas. Una gran proporción de esta reserva está constituida por semillas sin latencia, fácilmente germinables, especialmente pastos anuales que germinan en otoño. Con respecto a los mecanismos de latencia de las semillas del banco transitorio responsables del almacenamiento de las semillas en el suelo, nuestra revisión bibliográfica reveló los siguientes principales síndromes de germinación: (1 especies con semillas que deben ser estratificadas en frío debido a la presencia de latencia fisiológica (principalmente hierbas introducidas; (2 especies con semillas que deben ser escarificadas con ácidos o procedimientos mecánicos debido a la presencia de latencia física (principalmente especies leñosas nativas; (3 especies con latencia fisiológica que necesitan de estratificación cálida para activar la germinación (hierbas nativas e introducidas. Estos síndromes provocan que la época de germinación en Chile central esté situada entre otoño e inicio de la primavera. Además, no hay referencias sobre la presencia de algún síndrome esporádico de germinación para los componentes de un banco de semillas permanente. Proponemos

  2. Regional ceramic production and distribution systems during the late intermediate ceramic period in central Chile based on NAA

    International Nuclear Information System (INIS)

    This research focused on the pre-Hispanic ceramic production and distribution systems of the Maipo region in central Chile by means of determining the concentration of the chemical elements in pottery of the Aconcagua culture (900-1450 A.D.) with instrumental neutron activation analysis (INAA). Pottery fragments from eight archaeological sites and natural clays from the study region were included. The differences in chemical composition between subsets of the sample (sites, paste group and ceramic type) were interpreted as indicators of resource and ceramic production locations as well as the imprint of the geological background. These results contributed to the understanding of the Aconcagua ceramic assemblage and helped to test some hypotheses about the Aconcagua social organization. (author)

  3. Osseous skeletal material and fish scales in marine sediments under the oxygen minimum zone off northern and central Chile

    Science.gov (United States)

    Milessi, Andrés C.; Sellanes, Javier; Gallardo, Víctor A.; Lange, Carina B.

    2005-08-01

    The significance of whale falls for the study of the biogeography, evolution and biodiversity of deep-sea biota has been recently recognized by international programs since large carcasses are known to give rise to biogenic chemosynthetic ecosystems. However, the plain accumulation of smaller bone material in the shallower settings of the continental shelf and upper slope under the hypoxic conditions of the Oxygen Minimum Zone (OMZ), has received much less attention. Here we describe new findings of skeletal material and fish scales in marine sediments under the OMZ off northern and central Chile which, combined with previous reports for the study area, lead us to suggest the existence of a band in the benthos of accumulation of bones and scales extending at least twenty degrees in latitude (18-38° S). Future studies should focus on the characterization of biotic communities living upon these resources in order to elucidate their peculiarities and importance in the Eastern South Pacific.

  4. First radiometric age (U-Pb, LA-ICP-MS, on detrital zircons) from the Punta Topocalma Formation: insights on Late Cretaceous marine deposition in central Chile

    International Nuclear Information System (INIS)

    Upper Cretaceous marine rocks crop out along the Pacific coast of central and south-central Chile between 33o and 37oS. These strata constitute an important reference for the Upper Cretaceous of South America due to their diverse fossil fauna and flora. The type unit of these deposits is the Quiriquina Formation, near Concepcion. This unit is considered Maastrichtian in age based on ammonites. Upper Cretaceous marine strata from other localities of central and south-central Chile are largely unstudied and their biostratigraphic ages are not precisely known. We present the first radiometric dating (U-Pb on detrital zircons) for Upper Cretaceous marine strata of the Chilean forearc at Punta Topocalma that indicates a probable depositional age of 71.9+0.9 Ma (latest Campanian-earliest Maastrichtian). Provenance analysis indicates that the source of sediments of the Punta Topocalma Formation was plutonic and volcano-sedimentary rocks from the Coastal Cordillera and the Central Depression of central Chile. The Lo Valle Formation, a volcano-sedimentary unit in the Central Depression, recorded deposition of the Upper Cretaceous volcanic arc that was coeval with marine sedimentation in the Topocalma area

  5. Efectos de la planta en cojín Oreopolus glacialis (Rubiaceae sobre la riqueza y diversidad de especies en una comunidad alto-andina de Chile central Effects of the cushion plant Oreopolus glacialis (Rubiaceae on species richness and diversity in a high-Andean plant community of central Chile

    Directory of Open Access Journals (Sweden)

    ERNESTO I BADANO

    2002-12-01

    we analyzed the effect of Oreopolus glacialis -a cushion plant from the South American Andes- on the species richness, total and individual abundance, diversity and evenness of a plant community located in a high mountain environment at 1,900 m of altitude in central Chile. Species richness and abundance were determined both within and outside O. glacialis cushions. Results showed that, per area, species richness and individual abundance were higher within cushions. In contrast, diversity and evenness within O. glacialis cushions were lower than outside. This apparent incongruence was caused by some species being highly dominant within cushions. Analyses of the frequency and abundance of each species showed that not all the species were affected in the same way by the cushions, with only four species growing more frequently within cushions. This suggests that nurse effect of O. glacialis is a species-specific phenomenon

  6. Multiproxy approach revealing climate and cultural changes during the last 26kyrs in south-central Chile

    Science.gov (United States)

    Abarzua, Ana M.; Jarpa, Leonora; Martel, Alejandra; Vega, Rodrigo; Pino, Mario

    2010-05-01

    Multiproxy approach from Purén Lumaco Valley (38°S) describes the paleonvironmental history during the Last Maximum Glacial (LGM) in south-central Chile. Three sediment cores and severals AMS 14C dates were used to perform a complete pollen, diatoms, chironomids, and sedimentological records demonstrating the existence of a large and non profundal paleolake, between 25 and 20kyr BP. Some of these evidence are laminated silty-clay sediments (lacustrine rhythmites), associated with the presence of siderite mineral (FeCO3), besides biological proxies like Fragilaria construens and Stauroforma inermes (planctonic diatoms), and Dicrotendipes sp. and Tanytarsini tribe (littoral chironomids). The pollen ensemble reveals the first glacial refuge of Araucaria araucana forests in the low lands during the LGM. The lake was drained abruptly into a swamp/bog at 12kyr BP and colonized by Myrtaceae wet forest. This evidence suggest the dry/warm climate period of early Holocene in south-central Chile. Later, the sediments indicate variable lacustrine levels, and increase of charcoal particles, associated to current climatic conditions. The pollen spectrum dominated by Myrtaceae and Nothofagus contrasts with a strongly disturb current landscape. Actually, Purén-Lumaco valley constitutes a complex peat-bog system dominated by exotic grasses and forest species (Tritricum aestivum, Pinus radiata and Eucalyptus spp.). Some archaeological antecedents in the area document the human development at ca. 7yrs BP. The greatest archaeological characteristic present in the valley is the kuel, a Mapuche earth accumulation. The presence and extension of almost 300 kuel in the valley reflect the social/economic development, and partly explains why the region was the major resistance area for Spanish colonizer during XVI-XVII centuries. Also the archaeological findings reveal the presence of maize pollen (Zea mays) within their food consumption. The influence of climate and human impact in

  7. Freezing resistance varies within the growing season and with elevation in high-Andean species of central Chile.

    Science.gov (United States)

    Sierra-Almeida, Angela; Cavieres, Lohengrin A; Bravo, León A

    2009-01-01

    Predicted increases in the length of the growing season as a result of climate change may more frequently expose high-elevation plants to severe frosts. Understanding the ability of these species to resist frosts during the growing season is essential for predicting how species may respond to changes in temperature regimes. Here, we assessed the freezing resistance of 24 species from the central Chilean Andes by determining their low temperature damage (LT(50)), ice nucleation temperature (NT), freezing point (FP) and freezing resistance mechanism (i.e. avoidance or tolerance). The Andean species were found to resist frosts from -8.2 to -19.5 degrees C during the growing season, and freezing tolerance was the most common resistance mechanism. Freezing resistance (LT(50)) varied within the growing season, decreasing towards the end of this period in most of the studied species. However, the FP showed the opposite trend. LT(50) increased with elevation, whilst FP was lower in plants from lower elevations, especially late in the growing season. Andean species have the potential to withstand severe freezing conditions during the growing season, and the aridity of this high-elevation environment seems to play an important role in determining this high freezing resistance. PMID:19210722

  8. Petrology and mineralogy of the La Peña igneous complex, Mendoza, Argentina: An alkaline occurrence in the Miocene magmatism of the Southern Central Andes

    Science.gov (United States)

    Pagano, Diego Sebastián; Galliski, Miguel Ángel; Márquez-Zavalía, María Florencia; Colombo, Fernando

    2016-04-01

    The La Peña alkaline igneous complex (LPC) is located in the Precordillera (32°41‧34″ S - 68°59‧48″ W) of Mendoza province, Argentina, above the southern boundary of the present-day flat-slab segment. It is a 19 km2 and 5 km diameter subcircular massif emplaced during the Miocene (19 Ma) in the Silurian-Devonian Villavicencio Fm. The LPC is composed of several plutonic and subvolcanic intrusions represented by: a cumulate of clinopyroxenite intruded by mafic dikes and pegmatitic gabbroic dikes, isolated bodies of malignite, a central intrusive syenite that develops a wide magmatic breccia in the contact with clinopyroxenite, syenitic and trachytic porphyries, a system of radial and ring dikes of different compositions (trachyte, syenite, phonolite, alkaline lamprophyre, tephrite), and late mafic breccias. The main minerals that form the LPC, ordered according to their abundance, are: pyroxene (diopside, hedenbergite), calcium amphibole (pargasite, ferro-pargasite, potassic-ferro-pargasite, potassic-hastingsite, magnesio-hastingsite, hastingsite, potassic-ferro-ferri-sadanagaite), trioctahedral micas (annite-phlogopite series), plagioclase (bytownite to oligoclase), K-feldspar (sanidine and orthoclase), nepheline, sodalite, apatite group minerals (fluorapatite, hydroxylapatite), andradite, titanite, magnetite, spinel, ilmenite, and several Cu-Fe sulfides. Late hydrothermal minerals are represented by zeolites (scolecite, thomsonite-Ca), epidote, calcite and chlorite. The trace element patterns, coupled with published data on Sr-Nd-Pb isotopes, suggest that the primary magma of the LPC was generated in an initially depleted but later enriched lithospheric mantle formed mainly by a metasomatized spinel lherzolite, and that this magmatism has a subduction-related signature. The trace elements pattern of these alkaline rocks is similar to other Miocene calc-alkaline occurrences from the magmatic arc of the Southern Central Andes. Mineral and whole

  9. The lower cretaceous volcanism in the coastal range of Central Chile: Geochronology and isotopic geochemistry

    International Nuclear Information System (INIS)

    Major factors involved in subduction zone magmatism are related to the melting of the underlying mantle, which can contain a component of aqueous fluid and/or melts derived from the subducting plate (e.g. Peate et al., 1997). The Chilean Pacific margin is a subduction zone, active from Early Mesozoic to now, in which the magmatic arc emplaced on the Paleozoic basement progressively migrate to the east. The western part of this arc constitutes the Coastal Range. In this work, isotopic and radiometric data from four E-W profiles along c. 500 km of the Lower Cretaceous volcanic rocks in the Coastal Range of Chile are presented. The aim of this research is to obtain a model for the genesis of this Cretaceous volcanic arc based on their isotopic signature (au)

  10. Characterization of backyard poultry production systems and disease risk in the central zone of Chile.

    Science.gov (United States)

    Hamilton-West, C; Rojas, H; Pinto, J; Orozco, J; Hervé-Claude, L P; Urcelay, S

    2012-08-01

    Backyard poultry production systems (BPS) are an important and widespread form of poultry production. There is a common perception that biosecurity standards in BPS are generally poor and BPS are usually associated with animal diseases and zoonoses. In this study BPS were identified in the vicinity of six wetlands, having these a higher risk of presenting and introducing avian diseases such as HPAI and Newcastle disease, as defined by the national veterinary services, in to Chile's main poultry production area. BPS were characterized through a field questionnaire and the main areas covered by the survey were BPS structure, biosecurity and value chain. The BPS identified in this study share most characteristics on biosecurity, poultry management and product commercialization, but it was possible to identify a certain degree of variation within and among the study sites. BPS in Chile are similar to those in other regions, with a relatively small flock size (average 37 birds), a low level of biosecurity measures and lack of poultry disease management. Management findings include that most farmers used mixed/partial confinement, with low or no biosecurity and disease control measures in place. Eggs were the main output and were used mainly for home consumption or sale at local markets. Sick birds' treatment with drugs approved for other species or for human use could represent a risk to human health, owing to the possible presence of drug residues in poultry products. Despite the different structures of the poultry sector worldwide, BPS can play a major role in disease maintenance and spread because its management conditions characteristics and the lack of animal health services adapted to these production systems. This should be an alert message to the veterinary authorities to improve coverage of veterinary assistance and surveillance activities in backyard poultry production. PMID:21752410

  11. Vivid valleys, pallid peaks? Hypsometric variations and rural–urban land change in the Central Peruvian Andes

    OpenAIRE

    Haller, Andreas

    2012-01-01

    What happens to the land cover within the hinterland's altitudinal belts while Central Andean cities are undergoing globalization and urban restructuring? What conclusions can be drawn about changes in human land use? By incorporating a regional altitudinal zonation model, direct field observations and GIS analyses of remotely sensed long term data, the present study examines these questions using the example of Huancayo Metropolitano – an emerging Peruvian mountain city of 420,000 inhabitant...

  12. Trends and ENSO/AAO Driven Variability in NDVI Derived Productivity and Phenology alongside the Andes Mountains

    Directory of Open Access Journals (Sweden)

    Francisco J. Meza

    2013-03-01

    Full Text Available Increasing water use and droughts, along with climate variability and land use change, have seriously altered vegetation growth patterns and ecosystem response in several regions alongside the Andes Mountains. Thirty years of the new generation biweekly normalized difference vegetation index (NDVI3g time series data show significant land cover specific trends and variability in annual productivity and land surface phenological response. Productivity is represented by the growing season mean NDVI values (July to June. Arid and semi-arid and sub humid vegetation types (Atacama desert, Chaco and Patagonia across Argentina, northern Chile, northwest Uruguay and southeast Bolivia show negative trends in productivity, while some temperate forest and agricultural areas in Chile and sub humid and humid areas in Brazil, Bolivia and Peru show positive trends in productivity. The start (SOS and length (LOS of the growing season results show large variability and regional hot spots where later SOS often coincides with reduced productivity. A longer growing season is generally found for some locations in the south of Chile (sub-antarctic forest and Argentina (Patagonia steppe, while central Argentina (Pampa-mixed grasslands and agriculture has a shorter LOS. Some of the areas have significant shifts in SOS and LOS of one to several months. The seasonal Multivariate ENSO Indicator (MEI and the Antarctic Oscillation (AAO index have a significant impact on vegetation productivity and phenology in southeastern and northeastern Argentina (Patagonia and Pampa, central and southern Chile (mixed shrubland, temperate and sub-antarctic forest, and Paraguay (Chaco.

  13. Spatial-temporal evolution of topography of the central Andes and implications for deep tectonic processes (Invited)

    Science.gov (United States)

    Garzione, C. N.; Auerbach, D. J.; Bershaw, J. T.; Kar, N.; Smith, J. J.

    2013-12-01

    Resolving the spatial and temporal evolution of changes in the elevation of mountain belts provides constraints on the geodynamic mechanisms that caused surface uplift of these regions. Several recent studies in the Central Andean plateau (between 13°S and 28°S) have used multiple climate proxies to demonstrate punctuated (several myr) changes in the composition of meteoric water and surface temperature inferred to reflect significant (≥1000 m) surface uplift. These studies suggest that different regions experienced surface uplift at different times. In comparison with crustal thickening histories derived from reconstructions of crustal shortening, it is also clear that crustal thickening and surface uplift are temporally decoupled, with significant crustal thickening preceding punctuated surface uplift events by several tens of millions of years. Here we compile results from paleoclimate studies of the Central Andean plateau to infer regional patterns of surface uplift. Limited paleoclimate data and geologic evidence indicate that the Eastern Cordillera experienced an earlier pulse of surface uplift than the Altiplano zone, associated with an eastward sweep of magmatism that marks the current limits of the plateau. Within the Altiplano zone, the southern Altiplano appears to have risen beginning in middle Miocene time and continuing through late Miocene time. During this time, the north-central Altiplano remained low and experienced increasing rates of sedimentation. In late Miocene time, sedimentation rates slowed dramatically at the same time that climate proxy data suggest rapid surface uplift of the north-central Altiplano. The northernmost Altiplano of Peru experienced a pulse of surface uplift in middle Miocene to early Pliocene time, with the exact timing unconstrained as of yet. Crustal shortening reconstructions from the southern through the north-central plateau (between 17°S and 24°S) yield upper estimates that range between 300×20 km, sufficient

  14. Un modelo de la historia de la vegetación de la Cordillera de La Costa de Chile central-sur: la hipótesis glacial de Darwin A model for the history of vegetation of the Coastal Range of central-southern Chile: Darwin's glacial hypothesis

    Directory of Open Access Journals (Sweden)

    CAROLINA VILLAGRÁN

    2001-12-01

    . En contraste, los registros polínicos de los sitios de baja altitud de la Región de Los Lagos, muestran que las coníferas y las tundras magallánicas se localizaron en el Valle Longitudinal, durante el último Máximo Glacial, alrededor de 22.000 14C años AP. Numerosos perfiles de la Región de Los Lagos y de Los Canales documentan, durante el Tardiglacial, la rápida expansión hacia el sur del bosque norpatagónico con coníferas, siguiendo la deglaciación de estas áreas. Para el Holoceno de la Región de Los Lagos, se registra la colonización del bosque valdiviano, en el Valle Longitudinal; de las coníferas, en las cordilleras de Los Andes y de La Costa; y de las tundras magallánicas, en la Cordillera de La Costa. También durante el Holoceno se registran las tundras magallánicas, en el área continua que actualmente ocupan en la Región de los Canales, al sur de 46° S. En base a estos resultados, se propone un modelo de la dinámica histórica de la vegetación de Chile central-sur, durante el último ciclo glacial-postglacial, mostrando que los elementos más resistentes al frío (tundras magallánicas, Nothofagus, coníferas, habrían sobrevivido la última glaciación en sitios de baja altitud, dentro de la Región de Los Lagos, entre 40 y 43° S. Durante el Tardiglacial y Holoceno, se produjeron ascensos altitudinales y latitudinales de esta vegetación glacial, que culminaron con la recolonización de los sectores australes y de las de cimas de cerros de ambas cordilleras, en la Región de los Lagos. Sincrónicamente, se producían expansiones de las formaciones de bosques norpatagónico y valdiviano en los sitios bajos de esta misma región. Algunas inferencias del modelo, hacia otras formaciones aisladas en cimas de cerros de Chile central y centro-norte, nos permiten concluir que Chile constituye el escenario ideal para verificar este tipo de hipótesis biogeográficasIsolated communities of conifers and Magellanic moorlands, distributed along

  15. Trench investigation on the main strand of the Boconó fault in its central section, at Mesa del Caballo, Mérida Andes, Venezuela

    Science.gov (United States)

    Audemard M., Franck A.; Ollarves, Reinaldo; Bechtold, Michel; Díaz, Gustavo; Beck, Christian; Carrillo, Eduardo; Pantosti, Daniela; Diederix, Hans

    2008-11-01

    The Mesa del Caballo trench assessment confirms the Holocene activity of the main strand of the Boconó fault at the Apartaderos pull-apart basin. Fifteen earthquakes, of which fourteen have been radiocarbon dated, have been recognized, spanning the last 20,500 yr. Recurrence intervals of these ≥ 7 magnitude events are variable. The dominant mode of recurrence is 400-450 yr, and the second one is 900 yr. Eventually some events are 1400-1800 yr apart. We suspect that our seismic record may be incomplete. This could be easily justified by several conditions: most of the earthquake recognitions is based on open-crack filling and they superpose spatially (eventually masking or destroying older fills), trenching may miss some events because the fault is made of en echelon Riedel shears, and a short return period may lead to faint differences between paleosoils few hundreds years of age apart. This trench also images an older activity of the fault, as evidenced by plentiful earthquake-triggered liquefaction features, as well as slumping and rotational sliding. By comparing paleoseismic results between the Morro de Los Hoyos and Mesa del Caballo trenches, it appears that both fault strands bounding the Apartaderos pull-apart basin move simultaneously. Besides, the main strand also coseismically slips twice in between those common events. In other words, the seismic scenario could be that the northern strand recurs every 1200-1350 yr while the southern does every 400-450 yr. This is also in agreement with a respective slip share of 25 and 75% of the 9-10 mm/yr average slip of the Boconó fault in the Mérida Andes central sector.

  16. Geometry and kinematics of the Andean thick-skinned thrust systems: Insights from the Chilean Frontal Cordillera (28°-28.5°S), Central Andes

    Science.gov (United States)

    Martínez, F.; Arriagada, C.; Valdivia, R.; Deckart, K.; Peña, M.

    2015-12-01

    The structure of the Chilean Frontal Cordillera, located over the Central Andes flat-slab subduction segment (27°-28.5°S), is characterized by a thick-skinned deformation, affecting both the pre-rift basement and the Mesozoic and Cenozoic infill of the NNE-SSW Lautaro and Lagunillas Basins, which were developed during the Pangea-Gondwana break-up. The compressive deformation show a complex interaction between Mesozoic rift structures and thrust systems, affecting a suite of Permo-Triassic (258-245 Ma) granitic blocks. We used a combination of geological mapping, new structural data, balanced and restored cross sections and geochronological data to investigate the geometry and kinematics of the Andean thick-skinned thrust systems of the region. The thrust systems include double-vergent thick-skinned thrust faults, basement-cored anticlines and minor thin-skinned thrusts and folds. The presence of Triassic and Jurassic syn-rift successions along the hanging wall and footwall of the basement thrust faults are keys to suggest that the current structural framework of the region should be associated with the shortening of previous Mesozoic half grabens. Based on this interpretation, we propose a deformation mechanism characterized by the tectonic inversion of rift-related faults and the propagation of basement ramps that fold and cut both, the early normal faults and the basement highs. New U-Pb ages obtained from synorogenic deposits (Quebrada Seca and Doña Ana formations) indicate at least three important compressive pulses. A first pulse at ˜80 Ma (Late Cretaceous), a second pulse related to the K-T phase of Andean deformation and, finally, a third pulse that occurred during the lower Miocene.

  17. El tarwi o chocho: una de las principales fuentes de proteína vegetal de las comunidades indígenas de los Andes Centrales

    Directory of Open Access Journals (Sweden)

    Planchuelo, Ana M.

    2005-01-01

    Full Text Available El lupino andino (Lupinus mutabilis Sweet conocido también como tarwi o chocho, es una especie de leguminosa nativa de los Andes Centrales. Su domesticación se remonta a los principios de la cultura Nazca y desde ese entonces hasta la actualidad el cultivo está ampliamente difundido en las laderas montañosas y en los altos valles de Ecuador, Perú y Bolivia. La importancia del lupino para las comunidades andinas prehispánicas quedo documentada en pinturas de cerámicas y en tributos encontrados en tumbas de 100-150 años AC. Diversas técnicas de lavado y de mejoramiento vegetal fueron aplicadas desde la antigüedad para eliminar los alcaloides tóxicos que le confieren el sabor amargo a la planta y los granos. El tarwi, el maíz. los frijoles, los pseudocereales, quinoa y amaranto y la papa junto a otras raíces y tubérculos constituyen la comida básica de muchas culturas andinas. El objetivo de este trabajo fue determinar los componentes nutricionales de los granos del lupino andino para compararlos con los otros constituyentes de la dieta de las comunidades campesinas. Se analizaron por medio de técnicas fitoquímicas distintas variedades de tarwi. Se determinaron los contenidos de proteínas y grasas y los patrones de ácidos grasos. Los resultados muestran que la ingesta de lupinos, que provee un buen balance de proteínas y grasas en combinación con el maíz y los tubérculos, que aportan los hidratos de carbono, forman una dieta balanceada y de alto valor nutricional.

  18. Horizontal subduction zones, convergence velocity and the building of the Andes

    CERN Document Server

    Martinod, Joseph; Roperch, Pierrick; Guillaume, Benjamin; Espurt, Nicolas; 10.1016/j.epsl.2010.09.010

    2010-01-01

    We discuss the relationships between Andean shortening, plate velocities at the trench, and slab geometry beneath South America. Although some correlation exists between the convergence velocity and the westward motion of South America on the one hand, and the shortening of the continental plate on the other hand, plate kinematics neither gives a satisfactory explanation to the Andean segmentation in general, nor explains the development of the Bolivian orocline in Paleogene times. We discuss the Cenozoic history of horizontal slab segments below South America, arguing that they result from the subduction of oceanic plateaus whose effect is to switch the buoyancy of the young subducting plate to positive. We argue that the existence of horizontal slab segments, below the Central Andes during Eocene-Oligocene times, and below Peru and North-Central Chile since Pliocene, resulted (1) in the shortening of the continental plate interiors at a large distance from the trench, (2) in stronger interplate coupling and...

  19. Mineralog??a de alteraci??n en el pozo Pte-1, campo geotermal Tinguiririca, Chile

    OpenAIRE

    Droguett, B??rbara; Morata, Diego; Clavero, Jorge; Pineda, Germ??n; Morales-Ruano, Salvador; Carrillo-Ros??a, Javier

    2012-01-01

    Este trabajo presenta los avances en el estudio mediante petrograf??a ??ptica, DRX y SEM de la mineralog??a de alteraci??n presente en el pozo PTe-1, ubicado en el campo geot??rmico Tinguiririca (Chile central). Los 813,85m de rocas perforadas pertenecen al Complejo Volc??nico Tinguiririca (Pleistoceno-Holoceno) formado por lavas, tobas y brechas volc??nicas de composici??n andes??tica. Sobre la base de las asociaciones minerales se ha determinado dos zonas de alteraci??n principales. La de m...

  20. Conducta de forrajeo del gastrópodo Acanthina monodon Pallas, 1774 (Gastropoda: Muricidae en el intermareal rocoso de Chile central Foraging behavior of the gastropod Acanthina monodon Pallas, 1774 (Gastropoda: Muricidae in the intertidal rocky shores of central Chile

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    RUBÉN E. SOTO

    2004-03-01

    Full Text Available En el presente trabajo investigamos aspectos de la ecología y conducta de forrajeo de Acanthina monodon, un gastrópodo murícido que habita en el intermareal rocoso de Chile central. En terreno, estudiamos las variaciones temporales en su distribución, densidad y dieta. En el laboratorio, cuantificamos la tasa de consumo, las preferencias alimentarias, el tiempo de ingestión y la rentabilidad energética obtenida con distintos tipos de presas mediante experimentos y registros en video. Las mayores densidades de individuos de A. monodon fueron observadas en la franja intermareal cercana al nivel cero de marea. En terreno, A. monodon realiza sus actividades de forrajeo principalmente durante la noche y su dieta consistió principalmente de mitílidos (95 % y cirripedios (5 %. La composición de la dieta de A. monodon en terreno presentó variaciones temporales las cuales dependerían principalmente de cambios en la oferta de los distintos tipos de mitílidos presentes en terreno durante los dos años de muestreo. En el laboratorio, los individuos de Acanthina presentaron preferencias alimentarias significativas por el mitílido Semimytilus algosus. En general, A. monodon bajo condiciones de laboratorio presentó una conducta de forrajeo en la cual maximizó la ganancia neta de energía, mediante la selección de las especies y tamaños de presas que le retribuyen la mayor rentabilidad energéticaWe investigated the ecology and foraging behavior of Acanthina monodon, a muricid gastropod that inhabits in the intertidal rocky shores of central Chile. In the field, we studied temporal variation of their spatial distribution, density, and diet composition. While in the laboratory, we quantified the consumption rate, alimentary preferences, ingestion times and energy profitability obtained with different types of prey using experiments and video recording. High densities of A. monodon individuals were observed in the intertidal fringe near at the

  1. Presence of Arctotherium (Carnivora, Ursidae, Tremarctinae in a pre-cultural level of Baño Nuevo-1 cave (Central Patagonia, Chile

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    López Mendoza, P.

    2015-12-01

    Full Text Available The description of an I3 assigned to Arctotherium sp. obtained from the Baño Nuevo-1 site (Central Patagonia, Chile is presented. The finding was recovered from Layer 5 and it is associated to Macrauchenia sp., Lama guanicoe, Felidae, Camelidae, Equidae and Mylodontidae, within a sterile deposit of cultural material, dated between ca. 13.500 and 11.200 BP. Despite the fact that it is only a single specimen, such finding extends the known distribution for the genus in Chile.Se presenta la descripción de un I3 asignado a Arctotherium sp. proveniente del sitio Baño Nuevo-1 (Patagonia Central, Chile. El hallazgo fue realizado en la Capa 5 y está asociado a restos de Macrauchenia sp., Lama guanicoe, Felidae, Camelidae, Equidae y Mylodontidae dentro de un depósito estéril de material cultural, datado entre los ca. 13.500 y 11.200 años AP. Aunque se trata de un único espécimen, amplía el rango de distribución conocido para este género en Chile.

  2. The Donoso copper-rich, tourmaline-bearing breccia pipe in central Chile: petrologic, fluid inclusion and stable isotope evidence for an origin from magmatic fluids

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    Skewes, M. Alexandra; Holmgren, Carmen; Stern, Charles R.

    2003-01-01

    The copper-rich, tourmaline-bearing Donoso breccia pipe is one among more than 15 different mineralized breccias in the giant (>50 million metric tonnes of copper) Miocene and Pliocene Río Blanco-Los Bronces copper deposit in the high Andes of central Chile. This breccia pipe, bracketed in age between 5.2 and 4.9 Ma, has dimensions of 500 by 700 m at the current surface 3,670 m above sea level. Its roots have yet to be encountered, and it is >300 m in diameter at the depth of the deepest drill holes. The Donoso breccia is, for the most part, monolithic, containing clasts of the equigranular quartz monzonite pluton which hosts the pipe. It is matrix supported, with between 5 and 25% of the total rock volume consisting of breccia-matrix minerals, which include tourmaline, quartz, chalcopyrite, pyrite, specularite, and lesser amounts of bornite and anhydrite. An open pit mine, centered on this breccia pipe, has a current production of 50,000 tonnes of ore per day at an average grade of 1.2% copper, and copper grade in the breccia matrix is significantly higher. Measured δ18O for tourmaline and quartz from the matrix of the Donoso breccia at different levels of the pipe range from +6.9 to +12.0‰, and measured δD in tourmaline ranges from -73 to -95‰. Temperatures of crystallization of these minerals, as determined by the highest homogenization temperatures of highly saline fluid inclusions, range from 400 to >690°C. When corrected for these temperatures, the stable isotope data indicate that fluids from which these breccia-matrix minerals precipitated were magmatic, with δ18O between +5.6 to +9.1‰ and δD between -51 to -80‰. These isotopic data preclude participation of a significant amount of meteoric water in the formation of the Donoso breccia. They support a model in which brecciation is caused by expansion of magmatic fluids exsolved from a cooling pluton, and breccia-matrix minerals, including copper sulfides, precipitated from the same magmatic

  3. Consistent magmatic and magnetic anisotropy data in La Gloria Pluton, central Chile: Implications for the magma flow record in a shallow pluton

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    Payacan, I.; Gutierrez, F. J.; Bachmann, O.; Parada, M.

    2012-12-01

    The magmatic origin of the anisotropy of magnetic susceptibility (AMS) is examined in comparison with magmatic anisotropy data in a small, shallow, silicic magma reservoir in the upper crust. La Gloria Pluton (LGP) is a 10 Ma granodiorite/quartz monzonite of about 250 km3 located in the southern Andes, central Chile. LGP represents a particularly simple case of a silicic intrusion which was assembled in a few pulses and cooled over a short time interval. Hornblende, biotite and minor magnetite are ubiquitous mafic phases. The AMS tensor indicates that magnetic fabric has an oblate shape (i.e. magnetic foliation is higher than magnetic lineation). Lineations are weak (values up to 1.05), have a N-NW trend with a nearly horizontal dip and represent axisymmetric convection parallel to the main pluton elongation. Foliations are more pronounced (values up to 1.14), having NW trends and dips that vary gradually from vertical at the walls, to horizontal at the center and near the roof of the chamber. We interpret this to represent shear localization near the magma locking point along solidification fronts. Magmatic anisotropy data were obtained by measuring mineral length, width and orientation in the three main planes of the AMS tensor. We define the planes Pmax, Pint, and Pmin as orthogonal to the maximum, intermediate, and minimum axes of the AMS tensor, respectively. Mineral data were collected for plagioclase and amphibole + bitotite independently. For each site, the Bingham distribution with 95% of confidence is used to determine the mean mineral orientation and their angle difference with the AMS axes. Preliminary results indicate that mean crystal orientations are well defined for Pmax and Pint for all analyzed minerals, but Pmin is only well constrained for amphibole + bitotite and poorly constrained for plagioclase. Angle differences generally decrease with magnetic anisotropy but are independent of the size and aspect ratio of the crystals. Mean values of

  4. The effect of heat and smoke on the emergence of exotic and native seedlings in a Mediterranean fire-free matorral of central Chile Efecto del calor y el humo sobre la emergencia de plántulas exóticas y nativas en un matorral mediterráneo libre de fuego en Chile central

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    JAVIER A FIGUEROA

    2012-03-01

    Full Text Available We studied the effect of heat shock and wood-fueled smoke on the emergence of native and exotic plant species in soil samples obtained in an evergreen matorral of central Chile that has been free of fire for decades. It is located on the eastern foothills of the Andes Range in San Carlos de Apoquindo. Immediately after collection samples were dried and stored under laboratory conditions. For each two transect, ten samples were randomly chosen, and one of the following treatments was applied: (1 heat-shock treatment, (2 plant-produced smoke treatment, (3 combined heat-and-smoke treatment, and (4 control, corresponding to samples not subjected to treatment. Twenty-seven species, representing 13 families, emerged from the soil samples. The most abundant families were Asteraceae and Poaceae. All of the emerged species were herbaceous, and 18 species were exotic. Respect to general hypothesis, there is no evidence for the proposition that fire-free matorral has lower proportion of exotic and native species with fire-related cues than matorral with fires. Among the exotic and native, the mean number of species that emerged from soil samples did not change significantly with respect to the control for any of the treatments applied. Nevertheless, important species-specific responses were observed. Smoke and heat-smoke combination significantly increased the emergence of the exotic species Anthriscus caucalis. While smoke-related cues significantly increased the emergence of the exotic species Avena barbata, the emergence of the exotic Aphanes arvensis and the native Bromus berteroanus decreases. For several species our results showed inconsistent responses to fire-related cues compared to those reported in the literature. We suggest that these differences might be related with the fire-history in the populations, an important issue poorly acknowledge in the literature.Nosotros estudiamos el efecto del golpe de calor y del humo de la combustión de

  5. Vivid valleys, pallid peaks? Hypsometric variations and rural-urban land change in the Central Peruvian Andes.

    Science.gov (United States)

    Haller, Andreas

    2012-11-01

    What happens to the land cover within the hinterland's altitudinal belts while Central Andean cities are undergoing globalization and urban restructuring? What conclusions can be drawn about changes in human land use? By incorporating a regional altitudinal zonation model, direct field observations and GIS analyses of remotely sensed long term data, the present study examines these questions using the example of Huancayo Metropolitano - an emerging Peruvian mountain city of 420,000 inhabitants, situated at 3260 m asl in the Mantaro Valley. The study's results indicate that rapid urban growth during the late 1980s and early 1990s was followed by the agricultural intensification and peri-urban condominization at the valley floor (quechua) - since the beginning of Peru's neoliberal era. Moreover, regarding the adjoining steep slopes (suni) and subsequent grassland ecosystems (puna), the research output presents land cover change trajectories that clearly show an expansion of human land use, such as reforestation for wood production and range burning for livestock grazing, even at high altitudes - despite rural-urban migration trends and contrary to several results of extra-Andean studies. Consequently, rural-urban planners and policy makers are challenged to focus on the manifold impacts of globalization on human land use - at all altitudinal belts of the Andean city's hinterland: toward sustainable mountain development that bridges the social and physical gaps - from the bottom up. PMID:23564987

  6. An integrated framework to assess adaptation options to climate change impacts in an irrigated basin in Central North Chile

    Science.gov (United States)

    Vicuna, S.; Melo, O.; Meza, F. J.; Alvarez, P.; Maureira, F.; Sanchez, A.; Tapia, A.; Cortes, M.; Dale, L. L.

    2013-12-01

    Future climate conditions could potentially affect water supply and demand on water basins throughout the world but especially on snowmelt-driven agriculture oriented basins that can be found throughout central Chile. Increasing temperature and reducing precipitation will affect both the magnitude and timing of water supply this part of the world. Different adaptation strategies could be implemented to reduce the impacts of such scenarios. Some could be incorporated as planned policies decided at the basin or Water Use Organization levels. Examples include changing large scale irrigation infrastructure (reservoirs and main channels) either physically or its operation. Complementing these strategies it is reasonable to think that at a disaggregated level, farmers would also react (adapt) to these new conditions using a mix of options to either modify their patterns of consumption (irrigation efficiency, crop mix, crop area reduction), increase their ability to access new sources of water (groundwater, water markets) or finally compensate their expected losses (insurance). We present a modeling framework developed to represent these issues using as a case study the Limarí basin located in Central Chile. This basin is a renowned example of how the development of reservoirs and irrigation infrastructure can reduce climate vulnerabilities allowing the economic development of a basin. Farmers in this basin tackle climate variability by adopting different strategies that depend first on the reservoir water volume allocation rule, on the type and size of investment they have at their farms and finally their potential access to water markets and other water supplies options. The framework developed can be used to study these strategies under current and future climate scenarios. The cornerstone of the framework is an hydrology and water resources model developed on the WEAP platform. This model is able to reproduce the large scale hydrologic features of the basin such as

  7. Characterization of copper-resistant bacteria and bacterial communities from copper-polluted agricultural soils of central Chile

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    Altimira Fabiola

    2012-09-01

    Full Text Available Abstract Background Copper mining has led to Cu pollution in agricultural soils. In this report, the effects of Cu pollution on bacterial communities of agricultural soils from Valparaiso region, central Chile, were studied. Denaturing gradient gel electrophoresis (DGGE of the 16S rRNA genes was used for the characterization of bacterial communities from Cu-polluted and non-polluted soils. Cu-resistant bacterial strains were isolated from Cu-polluted soils and characterized. Results DGGE showed a similar high number of bands and banding pattern of the bacterial communities from Cu-polluted and non-polluted soils. The presence of copA genes encoding the multi-copper oxidase that confers Cu-resistance in bacteria was detected by PCR in metagenomic DNA from the three Cu-polluted soils, but not in the non-polluted soil. The number of Cu-tolerant heterotrophic cultivable bacteria was significantly higher in Cu-polluted soils than in the non-polluted soil. Ninety two Cu-resistant bacterial strains were isolated from three Cu-polluted agricultural soils. Five isolated strains showed high resistance to copper (MIC ranged from 3.1 to 4.7 mM and also resistance to other heavy metals. 16S rRNA gene sequence analyses indicate that these isolates belong to the genera Sphingomonas, Stenotrophomonas and Arthrobacter. The Sphingomonas sp. strains O12, A32 and A55 and Stenotrophomonas sp. C21 possess plasmids containing the Cu-resistance copA genes. Arthrobacter sp. O4 possesses the copA gene, but plasmids were not detected in this strain. The amino acid sequences of CopA from Sphingomonas isolates (O12, A32 and A55, Stenotrophomonas strain (C21 and Arthrobacter strain (O4 are closely related to CopA from Sphingomonas, Stenotrophomonas and Arthrobacter strains, respectively. Conclusions This study suggests that bacterial communities of agricultural soils from central Chile exposed to long-term Cu-pollution have been adapted by acquiring Cu genetic determinants

  8. PLAGUICIDAS ORGANOCLORADOS PERSISTENTES EN SEDIMENTOS DE TRES LAGOS COSTEROS Y UN LAGO ANDINO DE CHILE CENTRAL

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    RICARDO BARRAL

    2001-06-01

    Full Text Available Se evaluó la presencia y distribución de los compuestos orgánicos persistentes (COPs en núcleos de sedimentos de los lagos Chica y Grande de San Pedro, Lleu-Lleu e Icalma. Los compuestos fueron extraídos mediante sistema soxhlet con solvente n-hexano, la identificación y cuantificación, de estos, se realizó por cromatografía gaseosa con detector de captura de electrones de 63Ni. Se realizó un análisis estadístico de componentes principales (ACP y Correlación de Pearson. Los plaguicidas identificados en los sedimentos fueron: a-HCH, g-HCH, Heptacloro, Aldrin, Endrin, pp´-DDT, pp'-DDE y pp'-DDD. Los resultados indican variaciones en la distribución y concentración de los COPs, al comparar los lagos urbanos con los lagos prístinos. Destaca la presencia de pp'-DDE (rango: b.n.d- 1.68 ng g-1 peso seco y pp'-DDT (rango: b.n.d- 0.89 ng g-1 peso seco en tres de los cuatro cuerpos de agua analizados. El análisis estadístico identificó correlaciones significativas entre el pp'-DDE y pp'-DDD. No se detectaron correlaciones entre el pp'-DDT y sus metabolitos. El ACP permitió agrupar algunos compuestos orgánicos en función de sus concentraciones y degradación a través del tiempo. Se concluye que Laguna Chica de San Pedro presentó las concentraciones más altas de COPs, las cuales son bajas al ser comparadas con concentraciones detectadas en áreas limpias del Sur de ChileWe have measured concentrations and distribution of Persistent Organic Compounds (POC in sediment cores from four Chilean lakes: Laguna Chica de San Pedro, Laguna Grande de San Pedro, Lleu-lleu, and Icalma. The organochlorine compounds were extracted with n-hexane in a soxhlet system and then identified and quantified by gas chromatography using a 63 Ni Electron Capture Detector. Statistical analyses were performed using a Principal Components Analysis (PCA and the Pearson Correlation. The following pesticides were identified in the sediments: a-HCH, Lindane

  9. Adaptation and Genotype x Environment Interaction of Flaxseed (Linum usitatissimum L. Genotypes in South Central Chile Adaptación e Interacción Genotipo x Ambiente en Lino (Linum usitatissimum L. en la Zona Centro Sur de Chile

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    Marisol Berti

    2010-09-01

    Full Text Available Flaxseed (Linum usitatissimum L. is imported into Chile mostly for bread making and feed. Identification of genotypes best adapted for seed production in South Central Chile would facilitate producer’s decision. The objective of this study was to determine the adaptation and genotype x environment interaction of 16 flaxseed genotypes (including 10 from North American and six from Argentine sources grown at 11 environments (defined as location-year in Chile from 2003 to 2007. Genotype seed yield was above 5700 kg ha-1 for some environments indicating a high yield potential. According to the AMMI (Additive Main Effects and Multiplicative Interaction and SREG (Sites regression models the 11 environments were classified into four groups by the AMMI and three groups by the SREG models. Genotypes were classified into five groups by the SREG model with four of the groups as single genotypes. Overall mean seed yield was similar for all genotypes; however the genotype Nekoma was the most stable and higher yielding genotype across environments. The environment with the highest yield potential was Chillán 2003-2004, but this location had low yield stability across years. The environments with greatest seed yield potential, Chillán 2003-2004 and Los Ángeles 2004-2005, had irrigation during flowering and seed filling. Seed oil content fluctuated between 420 and 530 g kg-1. The climatic differences among environments did not influence oil composition as expected from previous research. Flaxseed appears adapted to South Central Chile with differences observed among genotypes for biomass and seed yield, harvest index, test weight, oil content, and composition.La semilla de lino (Linum usitatissimum L. se importa a Chile principalmente para panaderías y alimento animal. La identificación de genotipos altamente productivos en la zona Centro Sur de Chile facilitaría la decisión de los productores. El objetivo de este estudio fue determinar la adaptaci

  10. Food web and fish stock changes in central Chile: comparing the roles of jumbo squid (Dosidicus gigas) predation, the environment, and fisheries

    Science.gov (United States)

    Neira, Sergio; Arancibia, Hugo

    2013-10-01

    We analyzed recent food web and fish stock changes in the central Chile marine ecosystem, comparing the roles of jumbo squid (Dosidicus gigas) as predator, the environment, and fishing. To accomplish this we used food web modeling and the Ecopath with Ecosim software (EwE). The principal fish stocks have experienced wide decadal fluctuations in the past 30 years, including stock collapses of horse mackerel (Trachurus murphyi) and hake (Merluccius gayi), and there was a large influx of jumbo squid during the mid-2000s. We used two EwE models representing the food web off central Chile to test the hypothesis that predation by jumbo squid has been significant in explaining the dynamics of the main fishing resources and other species in the study area. Results indicate that predation by jumbo squid on fish stocks is lower than that of other predators (e.g. hake) and the fishery. Long-term fluctuations (1978-2004) in the biomass of the main fish stocks (as well as other components of the food web) seem to be related to fishing and to variation in primary production, rather than to predation by jumbo squid alone. Jumbo squid seems to play a role as predator rather than prey in the system, but its impacts are low when compared with the impacts of other predators and fishing. Therefore, we conclude that jumbo squid predation on its prey was not the primary force behind the collapse of important fish stocks off central Chile. Future efforts should be directed to better understanding factors that trigger sudden increases in jumbo squid abundance off central Chile, as well as modeling its trophic impacts.

  11. Community response of zooplankton to oceanographic changes (2002-2012) in the central/southern upwelling system of Chile

    Science.gov (United States)

    Medellín-Mora, Johanna; Escribano, Ruben; Schneider, Wolfgang

    2016-03-01

    A 10-year time series (2002-2012) at Station 18 off central/southern Chile allowed us to study variations in zooplankton along with interannual variability and trends in oceanographic conditions. We used an automated analysis program (ZooImage) to assess changes in the mesozooplankton size structure and the composition of the taxa throughout the entire community. Oceanographic conditions changed over the decade: the water column became less stratified, more saline, and colder; the mixed layer deepened; and the oxygen minimum zone became shallower during the second half of the time series (2008-2012) in comparison with the first period (2002-2007). Both the size structure and composition of the zooplankton were significantly associated with oceanographic changes. Taxonomic and size diversity of the zooplankton community increased to the more recent period. For the second period, small sized copepods (1.5 mm) and medium size copepods (1-1.5 mm), whereas euphausiids, decapod larvae, appendicularian and ostracods increased their abundance during the second period. These findings indicated that the zooplankton community structure in this eastern boundary ecosystem was strongly influenced by variability of the upwelling process. Thus, climate-induced forcing of upwelling trends can alter the zooplankton community in this highly productive region with potential consequences for the ecosystem food web.

  12. Heterogeneity of farms entering export supply chains: the case of fruit growers from central-south Chile

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    J. A. Barrena Ruiz

    2013-03-01

    Full Text Available The increasing stringency of world food markets requires farmers to adjust farm structure and commercial strategies to remain integrated in export supply chains. The goal of this study was to identify and characterize different types of fresh fruit farms with regard to farm structural and commercial strategies for a representative sample of fresh fruit growers from central-south Chile exporting to world markets. A typology of farms was constructed based on multivariate analysis, according to which five types of farms were differentiated from five distinct factors. Cluster I comprised the smallest and uncertified farms (14.3% of the sample. The remaining four clusters comprised certified farms, but with different farm structural and commercial characteristics. Cluster II (15.1% was composed of farms located further from market connections. Cluster III (23.9% comprised farms with the highest number of fruit species, and consequently, more diversified in fruit production. Cluster IV (8.8% was the smallest group, and comprised the largest firms. Finally, Cluster V (37.8% was composed of highly specialized fruit farms, with the highest proportion of hectares dedicated to the production of a single fruit species. The results show the heterogeneity among fresh fruit farms and support the need for differentiated incentives and technological transfer schemes from the public sector and fruit companies in order to successfully keep farmers within export supply chains.

  13. Tropical/subtropical Upper Paleocene Lower Eocene fluvial deposits in eastern central Patagonia, Chile (46°45'S)

    Science.gov (United States)

    Suárez, M.; de la Cruz, R.; Troncoso, A.

    2000-11-01

    A succession of quartz-rich fluvial sandstones and siltstones derived from a mainly rhyolitic source and minor metamorphic rocks, located to the west, represent the first Upper Paleocene-Early Eocene deposits described in Chilean eastern central Patagonian Cordillera (46°45'S). This unit, exposed 25 km south of Chile Chico, south of lago General Carrera, is here defined as the Ligorio Márquez Formation. It overlies with an angular unconformity Lower Cretaceous shallow marine sedimentary rocks (Cerro Colorado Formation) and subaerial tuffs that have yielded K-Ar dates of 128, 125 and 123 Ma (Flamencos Tuffs, of the Divisadero Group). The Ligorio Márquez Formation includes flora indicative of a tropical/subtropical climate, and its deposition took place during the initial part of the Late Paleocene-Early Eocene Cenozoic optimum. The underlying Lower Cretaceous units exhibit folding and faulting, implying a pre-Paleocene-Lower Eocene contractional tectonism. Overlying Oligocene-Miocene marine and continental facies in the same area exhibit thrusts and normal faults indicative of post-Lower Miocene contractional tectonism.

  14. Interannual variations in the hatching pattern, larval growth and otolith size of a sand-dwelling fish from central Chile

    Science.gov (United States)

    Rodríguez-Valentino, Camilo; Landaeta, Mauricio F.; Castillo-Hidalgo, Gissella; Bustos, Claudia A.; Plaza, Guido; Ojeda, F. Patricio

    2015-09-01

    The interannual variation (2010-2013) of larval abundance, growth and hatching patterns of the Chilean sand stargazer Sindoscopus australis (Pisces: Dactyloscopidae) was investigated through otolith microstructure analysis from samples collected nearshore (<500 m from shore) during austral late winter-early spring off El Quisco bay, central Chile. In the studied period, the abundance of larval stages in the plankton samples varied from 2.2 to 259.3 ind. 1000 m-3; larval abundance was similar between 2010 and 2011, and between 2012 and 2013, but increased significantly from 2011 to 2012. The estimated growth rates increased twice, from 0.09 to 0.21 mm day-1, between 2011 and 2013. Additionally, otolith size (radius, perimeter and area), related to body length of larvae, significantly decreased from 2010 to 2012, but increases significantly in 2013. Although the mean values of microincrement widths of sagitta otoliths were similar between 2010 and 2011 (around 0.6-0.7 μm), the interindividual variability increases in 2011 and 2013, suggesting large environmental variability experienced by larvae during these years. Finally, the hatching pattern of S. australis changed significantly from semi-lunar to lunar cycle after 2012.

  15. Large scale hydrogen production from wind energy in the Magallanes area for consumption in the central zone of Chile

    International Nuclear Information System (INIS)

    The energy proposal of this research suggests the use of places with abundant wind resources for the production of H2 on a large scale to be transported and used in the central zone of Chile with the purpose of diversifying the country's energy matrix in order to decrease its dependence on fossil fuels, increase its autonomy, and cover the future increases in energy demand. This research showed that the load factor of the proposed wind park reaches a value of 54.5%, putting in evidence the excellent wind conditions of the zone. This implies that the cost of the electricity produced by the wind park located in the Chilean Patagonia would have a cost of 0.0213 US$ kWh-1 in the year 2030. The low prices of the electricity obtained from the park, thanks to the economy of scale and the huge wind potential, represent a very attractive scenario for the production of H2 in the future. The study concludes that by the year 2030 the cost of the H2 generated in Magallanes and transported to the port of Quinteros would be 18.36 US$ MBTU-1, while by that time the cost of oil would be about 17.241 US$ MBTU-1, a situation that places H2 in a very competitive position as a fuel. (author)

  16. P- and S- velocity images of the lithosphere-asthenosphere system in the Central Andes from local-source tomographic inversion

    Science.gov (United States)

    Koulakov, I.; Sobolev, S. V.; Asch, G.

    2003-04-01

    In this study we perform an iterative tomographic inversion of P- and S-travel times for the local sources in Central Andes with consequent relocalization of sources. The processing starts from a reference model constrained from various geophysical and mineral physics data. The entire 3-D tomographic-inversion region (600 x 600 x 250 km) is subdivided into three domains: (1) slab, with upper boundary defined as intraslab seismicity envelope, (2) continental crust, with Moho topography defined by receiver-function and wide-angle-reflection Moho, and (3) mantle wedge between the crust and the slab. A reference velocity distribution in each of 3 domains was set from information on average composition and temperature in the crust, slab and upper plate lithosphere. Iterative procedure consists of the following steps: (A) Relocation of sources using both P- and S-phases. A key feature of this step is a new precise and fast algorithm of two-points ray tracing in a 3-D velocity model containing seismic boundaries; (B) Parameterisation of the study volume. Each of three domains was parameterised by a mesh with the density of nodes proportional to the rays density; (C) Inversion that allows calculation of both velocity anomalies in nodes and station corrections; (D) Calculation of 3D field of smoothed velocity anomalies in a regular grid. Steps B-C-D are performed separately for P- and S- rays. As the results of inversion, after five iterations we achieved a RMS reduction of P- and S-residuals from 0.53 s to 0.23 s. We show that the similar variance reductions can be obtained with different starting models (for instance, for 1D model). This fact proves importance of use of available a-priory information to set the starting model. To check reliability of the obtained velocity anomalies, different tests were performed, in particular, reconstruction of synthetic anomalies and independent inversion of two subsets of data. The P and S- tomographic images contain many features

  17. Palaeoclimate reconstructions from lacustrine terraces and lake-balance modeling in the southern central Andes: New insights from Salar de Pocitos (Salta Province, Argentina)

    Science.gov (United States)

    Bekeschus, Benjamin; Bookhagen, Bodo; Strecker, Manfred R.; Freymark, Jessica; Eckelmann, Felix; Alonso, Ricardo

    2013-04-01

    The arid Puna Plateau in the southern central Andes of NW-Argentina constitutes the southern part of Earth's second largest orogenic plateau. Numerous internally drained basins are restricted by ranges that peak 5-6 km above sea level, creating a compressional basin and range morphology. The conspiring effects of this structurally controlled topography and the high degree of aridity have resulted in low stream power of the fluvial network and internally drained basins. A steep rainfall gradient exists across this area ranging from a humid Andean foreland (>1m/yr annual rainfall) to progressively drier areas westwards. At the present-day, the interior of the plateau is widely characterized by Salar de Pocitos (24.5°S, 67°W, 3650 m asl) records repeated former lake highstands. This intermontane basin has existed since the late Tertiary, constituting a 435 km² salt flat in the region of Salta, NW Argentina. Comparison with palaeoclimate records from the neighboring Salar de Atacama suggests that the terrace systems at Salar de Pocitos were formed during the Late Pleistocene and early Holocene. Here we report on our preliminary results of the extent of several terrace generations in this region. We mapped terraces in the field and on satellite images and determined their elevations during a high-resolution DGPS field survey. Our analysis reveals 3-4 distinct terrace levels associated with individual lake-level highstands. However, basin-wide correlation is difficult due to ongoing tectonism and differential tilting of the basin. The highest lake terrace, ca. 25 m above modern base level, locally comprises a calcrete horizon, which provided a 14C age of 40.180 (+1420/-1200) yr BP, which may coincide with a protracted highstand in other basins in the Puna and the Bolivian Altiplano. If the extent of this pronounced terrace is used for volumetric calculations, the corresponding former water body involved 8 km³. To reconstruct palaeoenvironmental conditions and the

  18. Breeding distribution and abundance of seabirds on islands off north-central Chile Distribución reproductiva y abundancia de aves marinas en islas del norte y centro de Chile

    OpenAIRE

    ALEJANDRO SIMEONE; GUILLERMO LARA-JORQUERA; MARIANO BERNAL; STEFAN GARTHE; FELIPE SEPÚLVEDA; ROBERTO VILLABLANCA; URSULA ELLENBERG; MACARENA CONTRERAS; JULIETA MUÑOZ; TAMARA PINCE

    2003-01-01

    Between 1999 and 2003 we collected information on the breeding distribution and abundance of 12 seabird species occurring on nine islands off the coasts of north and central Chile (27°-33°S). The Peruvian booby Sula variegata was the most abundant seabird with a breeding population of ca. 18,000 pairs concentrated in two islands, followed by the Humboldt penguin Spheniscus humboldti with ca. 9,000 pairs, the largest colony being at Chañaral Island with ca. 7,000 pairs. Kelp gulls Larus domini...

  19. El clima de la vertiente del Pacífico de los Andes Centrales y sus implicaciones geomorfológicas El clima de la vertiente del Pacífico de los Andes Centrales y sus implicaciones geomorfológicas

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    Jose Úbeda Palenque

    2008-12-01

    Full Text Available Climate studies are of main importance to explain the external geodynamics of the Pacific Basin of the Central Andes between 15°S and 19°S. This is because the processes by which the relief modeling or morphogenesis develop are controlled by pluviometric variables and phyto stabilization. Moreover, the internal geodynamic of the region is related to the climatic conditions that determine the amounts of sediments aported to the Ocean basin (Kulm et al. 1977, affecting the erosion rate by subduction in the plane of contact between the tectonic plates and the composition of the magazas formed below the Andean erogene.In this paper we analyze the climatic effects in the external geodynamics, within a theoric framework that considers a morphoclimatic system as a set formed by the morphogenetic agents and processes that work the relief modeling in a territory, in function of its bioclimatic characteristics; and a morphoclimatic dominion is the spatial environment where a specific morphoclimatic system develops.First, we present the clima of the Central Andes, the factors that control its mean configuration and its main characteristics with diagrams made from the pluviometric data collected in a series of stations regularly distributed in the region. Second, we differentiate two climatic dominions, one in the Altiplano, related to Amazonia precipitations and the other at the Pacific side, associated to the anticyclonic permanency in the western cordillera. Third, we propose a subdivision of the western façade of the cordillera in altitudinal intervals or bioclimatics sections using bioindicators such as the vegetation absence or presence with altitudinal change. Fourth, we give a new division in altitudinal intervals or morphoclimatic zones, using the existence of some geoindicators, such as the endemic geomorphic units of each morphoclimatic zone.El estudio del clima es imprescindible para explicar la geodinámica externa en la vertiente del Pac

  20. Adaptation to climate changes on a multipurpose hydrosystem in South-Central Chile with explicit regard of model uncertainty

    Science.gov (United States)

    Ayala; McPhee, J. P.

    2010-12-01

    Decision-making in the agricultural and hydropower sectors can benefit from water resources availability projections that take into account uncertainty in a meaningful way. In this work we use statistically downscaled projections of 12 general circulation models under 3 emissions scenarios to drive a hydrologic-operational model of the upper Laja river basin in south-central Chile. The Laja hydrosystem is characterized by a large natural reservoir of 5600 Hm3 that is used for agricultural purposes in the lower basin and as the cornerstone of hydroelectric supply for the entire central Chilean electric system. The upper Laja river basin is snowmelt driven so water resources are very sensitive to both precipitation and temperature. Using each future projected series as an independent observation, empirical probability distributions are calculated for hydro-meteorological and operational variables such as reservoir levels and energy production. By the end of the 21st century, the mean value of projections shows a temperature increase of 2C, a precipitation decrease of 20%, and a decrease close to 25% in runoff due to evapotranspiration effects. A runoff-precipitation-temperature relation shows that the evaporation is most important in wet conditions because of the higher levels of water availability on surface and superior layers of soil. Operational results show a decrease of reservoir levels coupled with diminishing energy output, which suggests that the current operational policy is inappropriate for ensuring adaptation to climate change. Differences among GCMs clearly increase trough the analysis period resulting in a greater uncertainty in the magnitude of changes by the end of the 21st century. Almost all models and scenarios agree about the general trends of the estimated variables. Nevertheless, for climate change applications, the considerable magnitude differences between projections suggest the use of many models instead of a particular one or, in lieu if

  1. Vertebrados terrestres de la Reserva Nacional Río Clarillo, Chile central: representatividad y conservación Terrestrial vertebrates of the Río Clarillo National Reserve, central Chile: representation and conservation

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    IVÁN A. DÍAZ

    2002-06-01

    Full Text Available Analizamos la representatividad, distribución y perspectivas de conservación de los vertebrados terrestres de la Reserva Nacional Río Clarillo, Chile central. Mediante recorridos periódicos realizados entre 1987 y 1996, determinamos la riqueza y distribución altitudinal de los vertebrados terrestres en esta Reserva. Registramos 127 especies (22 mamíferos, 85 aves, 15 reptiles y cinco anfibios, que representan el 69 % del total de especies que por su distribución geográfica y tipo de hábitat podrían habitar este lugar. De éstas, 32 especies (25 % están catalogadas con problemas de conservación. La riqueza de vertebrados decrece con la altitud, desde 101 especies a los 870 m hasta ocho especies a los 3.050 m. La riqueza de vertebrados se concentró bajo los 1.600 m, albergando 109 especies, 55 de las cuales no se registraron a mayor altitud. En cambio, sobre los 1.600 m se registraron 57 especies. Paradójicamente sólo el 31 % de la superficie de la Reserva está bajo los 1.600 m. Nuestros resultados sugieren que la superficie de la Reserva no es suficiente para albergar poblaciones viables de la mayoría de los vertebrados registrados. Alrededor de la Reserva existen propiedades privadas con grandes extensiones de bosques esclerófilos bajo los 1.600 m, los cuales podrían actuar como fuentes y la Reserva como sumidero de vertebrados. Por lo tanto, sugerimos desarrollar estrategias de conservación en estas áreas y realizar monitoreos para determinar si las poblaciones de vertebrados mas sensibles están aumentando o disminuyendo, tanto dentro como fuera de la ReservaWe analyzed the representation, distribution and conservation perspectives of terrestrial vertebrates in the Río Clarillo National Reserve, central Chile. During periodical surveys conducted between 1987 and 1996, we determined the composition and altitudinal distribution of the terrestrial vertebrates in this Reserve. We recorded 127 species (22 mammals, 85 birds, 15

  2. Supervivencia adulta y dinámica poblacional del lauchón orejudo Phyllotis darwini en Chile central Adult survival and population dynamics in the leaf-eared mouse Phyllotis darwini in central Chile

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    Laurent Crespin

    2006-09-01

    Full Text Available A nivel demográfico, los resultados clásicos de los modelos matriciales separan a las especies de tiempo generacional corto de las especies de tiempo generacional largo en cuanto a la importancia de la supervivencia adulta para la dinámica poblacional. Específicamente, la supervivencia adulta no debería contribuir de manera importante en la tasa de cambio poblacional de especies de tiempo generacional corto. Sin embargo, Yoccoz et al. (1998, Research Population Ecology 40: 107-121 propusieron que la supervivencia adulta sería el parámetro demográfico más importante para determinar la tasa de cambio poblacional en pequeños roedores cuando se toma en consideración una escala de tiempo mensual. Con el fin de poner a prueba esta hipótesis en este trabajo, utilizamos cinco años de datos de captura-marcaje-recaptura para estimar la supervivencia y la maduración de las hembras del lauchón orejudo, Phyllotis darwini, en una localidad de Chile central. El análisis mostró que las probabilidades de supervivencia disminuían con el promedio anual de la cantidad de lluvia y que las probabilidades de maduración disminuían con la densidad poblacional. Basados en las probabilidades de supervivencia y maduración, construimos un modelo matricial estacional para medir la importancia relativa de cada parámetro demográfico en el ciclo de vida de la especie a través de un análisis de perturbación. A fin de reflejar la variabilidad estacional del ambiente, dos estaciones fueron incorporadas en el modelo matricial: una estación de lluvia de cinco meses y una estación seca. Se observó que la supervivencia adulta era en efecto el parámetro demográfico con la elasticidad más fuerte. Por lo tanto, estos resultados apoyan la hipótesis de Yoccoz et al. (1998Classic results of matrix models predict that, in species with a long generation time, adult survival should be the demographic parameter driving population dynamics whereas, in species

  3. Hábitos tróficos de la reineta Brama australis (Pisces: Bramidae) durante el periodo estival frente a Chile central

    OpenAIRE

    Francisco Santa Cruz; Ciro Oyarzún; Gustavo Aedo; Patricio Gálvez

    2014-01-01

    La reineta Brama australis es un importante recurso pesquero artesanal en la zona central chilena, incorporado en los programas de seguimiento biológico, pero con escasas evaluaciones de sus aspectos tróficos. Para actualizar el estado del conocimiento, se analizó su dieta durante el verano austral época de mayor disponibilidad de este recurso en la zona central de Chile, mediante el análisis del contenido gástrico de 300 ejemplares capturados entre noviembre 2011 y marzo 2012. Se identificó ...

  4. The relation of the mid-Tertiary coastal magmatic belt in south-central Chile to the late Oligocene increase in plate convergence rate

    OpenAIRE

    Jorge Muñoz; Rosa Troncoso; Paul Duhart; Pedro Crignola; Lang Farmer; Charles R. Stern

    2000-01-01

    The mid-Tertiary Coastal Magmatic Belt in south-central Chile, which crops out both in the Central Valley and, south of 41°S, in the Coastal Cordillera as far west as the Pacific coast, formed when the locus of Andean magmatic activity expanded, both to the west and to the east relative to its previous and current location in the Main Cordillera. This expansion of the magmatic arc occurred in conjunction with a regionally widespread episode of late Oligocene to Miocene extension which thinned...

  5. Corrales de piedra-pirkas- un patrimonio cultural del paisaje rural de Chile central

    OpenAIRE

    Tomic Jakas, Tonci Stipe

    2016-01-01

    Quisiéramos partir con este soliloquio, quizás el más famoso del drama español; ocurre al final del primer acto, cuando Segismundo piensa en la vida y en su suerte. No es el fatalismo lo que interesa si no que desde el inicio explicitar que se trata de una reflexión que lleva a configurar un visión –algo que anida en la mente-- que su fin central radica es tratar de poner en valor sobre la base de la importancia histórica, cultural y patrimonial de los muros de piedra o pirkas; en particular ...

  6. Histoires de déglaciation pendant le Pléistocène Supérieur dans les Andes centrales de Mérida (Venezuela)

    OpenAIRE

    Angel Ceballos, Isandra Fortuna

    2016-01-01

    Les Andes de Mérida (Venezuela) est caractérisé par la présence de morphologie glaciaire bien préservée entre 2400-4978 m. Les études de ces morphologies glaciares font la contribution pour mieux comprendre et reconstruire la Dernière Glaciation aux Andes Vénézuéliennes. La reconstruction de la Dernière Glaciation (connue dans la région comme Glaciation Mérida) était limitée par la disponibilité de chronologie glaciaire. Cette thèse fait sa contribution à la reconstruction de la Dernière Glac...

  7. Volatile Compounds in Honey Produced in the Central Valley of Ñuble Province, Chile Compuestos Volatiles en Miel Producida en el Valle Central de la Provincia de Ñuble, Chile

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    María Pía Gianelli Barra

    2010-03-01

    Full Text Available Headspace solid-phase microextraction (SPME with an 85 µm Carboxen polydimethylsiloxane (CAR/PDMS fiber was used to extract volatile compounds, and a gas chromatograph equipped with a mass spectometry detector (GC-MS was used to identify the volatile compounds in honeys. Thirty-four different volatile compounds from the headspace of honey produced in the central valley of Ñuble Province, Chile, were extracted with fiber coating CAR/PDMS. The identified compounds were: 10 alcohols, 9 acids, 6 ketones, 3 aldehydes, 2 furans, 2 terpenes and 2 lactones. Only four of the volatile compounds had never been reported before as honey compounds; these being: 1,3-propanodiol, 2-methyl butanoic acid, 3,4-dimethyl-3-hexen-2-one, and 6-methyl-5-octen-2-one. These four compounds were found in three of the 10 analyzed samples. The compounds found in the highest percentage of area were ethanol, acetic acid, 1-hydroxy-2-propane, 3-hydroxy-2-butane, and furfural. However, the analyzed samples did not present a distinctive profile.La extracción de compuestos volátiles desde el espacio de cabeza de mieles se realiza mediante microextracción en fase sólida (SPME, utilizando una fibra de 85 µm de Carboxen polidimetilsiloxano (CAR/PDMS, el análisis de los compuestos volátiles se realiza mediante cromatografía de gases con detector de masa (GC-MS. Un total de 34 diferentes compuestos volátiles fueron extraídos desde el espacio de cabeza de mieles provenientes del valle central de la provincia de Ñuble con la fibra de CAR/PDMS. Los compuestos identificados fueron 10 alcoholes, 9 ácidos, 6 cetonas, 3 aldehídos, 2 furanos, 2 terpenos y 2 lactonas. De los compuestos volátiles sólo tres no han sido reportados con anterioridad en mieles, estos compuestos fueron: 1,3-propanodiol, ácido 2-metil butanoico, 3,4-dimetil-3-hexen-2-ona, 6-metil-5-octen-2-ona. Estos cuatro compuestos se encontraron en sólo tres de las 10 muestras analizadas. Los compuestos que se

  8. "Un devorador de su propia especie". Violencia, justicia y cultura popular en Santa Rosa de los Andes: las formas de la autoridad a los ojos de un peón de oficio matador, Chile 1805

    OpenAIRE

    Daniel Moreno Bazaes

    2016-01-01

    A través del análisis microhistórico del proceso judicial seguido por las autoridades de la villa de Santa Rosa de Los Andes e intervenido por la Real Audiencia de Santiago contra Juan Francisco Varas, “peón-gañan” de la hacienda de Llay-Llay, responsable de a lo menos seis homicidios y otros tantos crímenes que atentaron contra el orden local y el gobierno civil, se pretende dar cuenta de los pormenores de la organización social en el Valle del Aconcagua a fines del siglo XVIII y durante los...

  9. On the effect of operation of the hydropower plant on the water quality of Rapel reservoir, central Chile

    Science.gov (United States)

    Rossel, V.; De La Fuente, A.

    2013-12-01

    Eutrophication of lakes and reservoirs is a common problem in systems with high incoming loads of nutrients. The consequent algae bloom related to the eutrophication alters the water quality and generates an incompatibility with the tourist and recreational activities. This study is focused on Rapel reservoir: an old, dentritic and monomictic reservoir, located in central Chile (34°S, 71.6°W), that has experienced numerous algae bloom events in the past years produced by high loads of nutrients, sediments and metals. This reservoir was originally constructed in 1968 for hydropower generation without environmental restrictions on its operation. Rapel is part of Chile's Central Interconnected System (SIC), and is controlled by an independent system operator (ISO) that decides the optimal allocation of water by minimizing the SIC's operation cost. As a result of this framework, Rapel reservoir operates based on a hydropeaking scheme, thus producing energy few hours a day while zero outflows are observed the remaining hours, impacting on Rapel river located downstream the reservoir. However, previous research showed that this hydropeaking has important effects on the hydrodynamic of the reservoir as well. Particularly, it enhances vertical mixing nears the dam, and reduces horizontal dispersion. Furthermore, hydropeaking defines the outflows water temperature, and the temperature profile near the dam. As a consequence of this role of hydropeaking on the hydrodynamics and mixing of Rapel reservoir, it is expected to be a link between hydropeaking and water quality. The aim of the study is to evaluate the impact of the operation of hydropower plant on the water quality of Rapel reservoir, for which the reservoir system is modeled using the three dimensional hydrodynamic and water quality model ELCOM-CAEDYM. Field data to validate the results and to define boundary and initial conditions are available for the austral summer period of 2009-2010. Different scenarios of

  10. Pyruvate Oxidoreductases Involved in Glycolytic Anaerobic Metabolism of Polychaetes from the Continental Shelf off Central-South Chile

    Science.gov (United States)

    González, R. R.; Quiñones, R. A.

    2000-10-01

    The presence of low oxygen conditions in extensive areas of the continental shelf off central-south Chile has important effects on the biochemical adaptations of the organisms living in this ecosystem. Polychaetes assemblages cohabit on the shelf with an extensively distributed prokaryotic community made up of giant filamentous sulfur bacteria (mainly Thioploca sp.). The aim of this research was to characterize the pyruvate oxidoreductases enzymes involved in the biochemical adaptation of these benthic polychaetes. Nine polychaete species ( Paraprionospio pinnata, Nephtys ferruginea, Glycera americana, Haploscoloplos sp., Lumbrineris composita, Sigambra bassi, Aricidea pigmentata , Cossura chilensis, and Pectinaria chilensis) were assayed for lactic dehydrogenase (LDH), octopine dehydrogenase (OPDH), strombine dehydrogenase (STRDH) and alanopine dehydrogenase (ALPDH). Each species had a characteristic number of the pyruvate oxidoreductases assayed ranging from 4 in Paraprionospio pinnata to 1 in Pectinaria chilensis . The pyruvate saturation curves obtained for the enzymes from all species analysed, except L. composita, suggest that NADH can be oxidized at different rates depending on the amino acid used in the reaction with pyruvate. Our results indicate that organisms having more that one pyruvate oxidoreductase present a greater metabolic capacity to cope with functional and environmental hypoxia because these enzymes would better regulate the pyruvate consumption rate during the transition period. Thus, the dominance of Paraprionospio pinnata in the study area and its worldwide distribution is consistent with its higher number of pyruvate oxidoreductases with different pyruvate consumption rates involved in anaerobic metabolism. Finally, a positive allometric relationship was found between body size and the specific activity of ALPDH, STRDH, and maximum pyruvate oxidoreductase specific activity. This latter result suggests a positive scaling of the specific

  11. A time series of prokaryote secondary production in the oxygen minimum zone of the Humboldt current system, off central Chile

    Science.gov (United States)

    Levipan, H. A.; Quiñones, R. A.; Urrutia, H.

    2007-11-01

    Because the marine picoplanktonic communities are made up of phylogenetically different microbial groups, the re-evaluation of key processes such as bacterial secondary production (BSP) has become an important contemporary issue. The difficulty of differentiating the metabolic processes of Bacteria from the rest of the microorganisms in the water column (i.e., Archaea and Eukarya) has made it difficult to estimate in situ BSP. This work presents the seasonal variability of the prokaryote secondary production (PSP) measured by the incorporation of 14C-leucine in the oxygen minimum zone (OMZ) off central-southern Chile. The BSP and potential archaeal secondary production (PASP) were determined through the combined use of 14C-leucine and N1-guanyl-1, 7-diaminoheptane (GC 7), an efficient inhibitor of archaeal and eukaryote cell growth. BSP accounted for the majority of the PSP (total average, 59 ± 7.5%); maximum values were ∼600 μg C m -3 h -1 and, on several dates, BSP represented 100% of the PSP. Similarly, PASP was also an important fraction of the PSP (total average, 42.4 ± 8.5%), although with levels that ranged from not detectable (on given dates) to levels that represented up to ∼97% of PSP (winter 2003). Our results showed that both Bacteria and Archaea accounted for almost equal portions of the prokaryote heterotrophic metabolism in the OMZ, and that PASP is notoriously enhanced through temporal pulses of heterotrophy. This indicates that, at least in marine systems with high abundance of Archaea (e.g., mesopelagic realm), the secondary production obtained through methods measuring the uptake of radiolabeled substrates should be considered as PSP and not as BSP. If the latter is the target measurement, then the use of an inhibitor of both archaeal and eukaryote cell growth such as GC 7 is recommended.

  12. Degradation capability of the coastal environment adjacent to the Itata River in central Chile (36.5° S

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    P. Ampuero

    2011-08-01

    Full Text Available The response of the coastal ocean influenced by both river discharges and inputs of photosynthetically derived organic carbon product of upwelling, was evaluated by estimating rates of microbial hydrolysis of macromolecules with the goal of estimating the potential degradation capability of the coastal ecosystem off central Chile. Extracellular enzymatic activity (EEA in seawater was dominated by aminopeptidase activity on substrate L-leucine-4-methyl-7-coumarinylamide (MCA-leu (1.2 to 182 nmol l−1 h−1 followed by 4-methylumbelliferyl-ß-D-glucoside (MUF-glu (0.08–61 nmol l−1 h−1 and 4-methylumbelliferyl-ß-D-cellobiose (MUF-cel (0.15–7 nmol l−1 h−1, with the highest rates measured during spring-summer. In riverine waters, extracellular enzymatic hydrolysis remained within the range of 45 to 131 nmol l−1 h−1 for MCA-leu and ca. 20 nmol l−1 h−1 for glucosidic substrates, year-round. Contrary to the EEA observed for the marine water column, surface sediment extracellular enzymatic hydrolysis of MCA-leu (0.04 to 6.13 nmol g−1 dw h−1 was in the same order of magnitude as the rates observed for MUF-cel (0.004 to 5.1 nmol g−1 dw h−1 and MUF-glu (0.007 to 10.5 nmol g−1 dw h−1. Moreover, hydrolysis in sediments was characterized by higher rates during winter compared with spring-summer in the coastal and estuarine zone. The five years of data allowed us to evaluate the potential capability of microbial processing of organic carbon in the coastal area adjacent to the Itata river discharge where the increase in primary production in the productive seasons is accompanied by the increase in hydrolysis of macromolecules.

  13. Contribution of legumes to the availability of soil nitrogen and its uptake by wheat in Mediterranean environments of central Chile

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    Soledad Espinoza

    2015-03-01

    Full Text Available The absorption and partitioning of N is determined by its availability and demand during the various phenological stages of the crop. In two experiments conducted in rainfed areas of the Mediterranean climate region of central Chile, legume-wheat (Triticum aestivum L. rotations were compared to oat (Avena sativa L.-wheat systems (with and without applications of N fertilizer. The objective was to assess the contribution of legumes to the availability of soil N and N uptake by the wheat crop following grain legumes. N mineralization and uptake, N use efficiency (NUE, and N uptake efficiency (NUpE by wheat were evaluated at different phenological stages in 2010. Synchronization existed between accumulated soil N mineralization and N uptake by the wheat. N uptake by wheat was higher in Experiment II (Andean foothill than in Experiment I (interior dryland. Grain yields after legumes ranged 60-110% and 72-103% of yields in the fertilized cereal rotation (oat-wheat in Experiments I and II, respectively. There was high correlation between soil N availability vs. grain yield (R² = 0.84 and 0.64 and N uptake vs. grain yield (R² = 0.55 and 0.64 for Experiments I and II, respectively. Rotations with lupine (Lupinus spp. and field peas (Pisum sativum L. showed high NUE and NUpE in Experiment I, and Experiment II in pea. The lowest NUE was after oats with N fertilizers. It is concluded that wheat cultivated in both agro-ecological areas after grain legumes or green manure was more efficient in N uptake and use than cereal, especially when the latter was fertilized.

  14. Contrasting climate change impact on river flows from high-altitude catchments in the Himalayan and Andes Mountains.

    Science.gov (United States)

    Ragettli, Silvan; Immerzeel, Walter W; Pellicciotti, Francesca

    2016-08-16

    Mountain ranges are the world's natural water towers and provide water resources for millions of people. However, their hydrological balance and possible future changes in river flow remain poorly understood because of high meteorological variability, physical inaccessibility, and the complex interplay between climate, cryosphere, and hydrological processes. Here, we use a state-of-the art glacio-hydrological model informed by data from high-altitude observations and the latest climate change scenarios to quantify the climate change impact on water resources of two contrasting catchments vulnerable to changes in the cryosphere. The two study catchments are located in the Central Andes of Chile and in the Nepalese Himalaya in close vicinity of densely populated areas. Although both sites reveal a strong decrease in glacier area, they show a remarkably different hydrological response to projected climate change. In the Juncal catchment in Chile, runoff is likely to sharply decrease in the future and the runoff seasonality is sensitive to projected climatic changes. In the Langtang catchment in Nepal, future water availability is on the rise for decades to come with limited shifts between seasons. Owing to the high spatiotemporal resolution of the simulations and process complexity included in the modeling, the response times and the mechanisms underlying the variations in glacier area and river flow can be well constrained. The projections indicate that climate change adaptation in Central Chile should focus on dealing with a reduction in water availability, whereas in Nepal preparedness for flood extremes should be the policy priority. PMID:27482082

  15. ESTRUCTURA DE LA MACROFAUNA EN AMBIENTES OXICOS DE BAHIA COLIUMO, REGION DEL BIO-BIO, CHILE CENTRAL STRUCTURE OF MACROFAUNA IN OXIC ENVIRONMENTAL OFF BAY COLIUMO, BIO-BIO REGION, CENTRAL CHILE

    Directory of Open Access Journals (Sweden)

    Karina Neira

    2007-01-01

    Full Text Available Se analizó la densidad, biomasa, diversidad y riqueza de especies de la macrofauna bentónica (³500 mm en ambientes óxicos (> 0.5 ml L-1 en Bahía Coliumo (36º32`S, 72º57`W, Chile central. En un transecto de cinco estaciones, entre 3,6 y 22,5 m de profundidad, fueron recolectadas muestras de sedimento con una draga tipo Van veen de 0,051 m², a bordo de la embarcación científica L/C Kay-Kay. A partir de las muestras de sedimento se determinó, el porcentaje de materia orgánica total, el tamaño de grano, densidad y biomasa de la macrofauna. Adicionalmente, se tomaron muestras de agua para el análisis de oxígeno disuelto de fondo, temperatura y salinidad. Las densidades de la macrofauna total fluctuaron entre 1111 y 11183 ind m-2. En tanto, los valores de biomasa alcanzaron 9,9 y 252,86 g m-2. Del total de la macrofauna 29 especies fueron identificadas. Los valores más altos de diversidad (3,23 coinciden con los valores más bajos de dominancia y uniformidad. Los parámetros de diversidad no mostraron una relación lineal con la profundidad. Los poliquetos fueron el grupo dominante (51,8%, seguido de los crustáceos (41% y moluscos (6,8%. Adicionalmente, a través del análisis BIOENV, se observó que el porcentaje de arena y el contenido de materia orgánica fueron los principales factores ambientales que regulan la estructura de la macrofauna de Bahía Coliumo.The density, biomass, diversity and species richness of macrofaunal benthic (³500 mm in oxic environment (> 0.5 ml L-1 off Bay Coliumo (36º32`S, 72º57`W, Chile were analyzed. One transect of five stations between 3.6 and 22.5 m of depth were collected samples of sediments with a dredged Van veen of 0.051 m²a board R/V Kay-Kay in August (winter of 2004. From sediment sample the organic matter percent, size of grain, density and biomass of the macrofauna were determined. Additionally, were taken water column samples for analyses of dissolved oxygen of bottom, temperature and

  16. Mixed bird flocks: patterns of activity and species composition in a region of the Central Andes of Colombia Bandadas mixtas de aves: patrones de actividad y composición de especies en una región de la Cordillera Central de los Andes de Colombia

    Directory of Open Access Journals (Sweden)

    Enrique Arbeláez-Cortés

    2011-06-01

    Full Text Available Mixed bird flocks are groups of individuals from different species that travel and forage together. Such groups are common in several bird communities around the world. We present species composition and activity patterns of mixed bird flocks in a region of the Central Andes of Colombia. We compared the number of species per flock, as well as the number of flocks among 3 different habitats. We tested hypotheses concerning the flocks daily activity and the co-occurrences of species within them. We recorded 75 species, and the species number per flock varied from 4 to 21. Our data suggest that habitat affects the number of flocks but not their species number, and that the activity of flocks is similar throughout the day. In addition, the association of birds in flocks is affected by interspecific facilitation, with some species co-occurrences found more times than expected by chance. We hypothesize that some tanager species could have a role in flock cohesion. We witnessed 2 predator attacks upon flocks, a number of agonistic interactions among flock members, and squirrels following bird flocks. Our results meet some general patterns described for mixed bird flocks.Las bandadas mixtas de aves son grupos de individuos de diferentes especies que viajan y forrajean juntos, y son comunes en varias comunidades de aves alrededor del mundo. Presentamos la composición de especies y los patrones de actividad de las bandadas mixtas de aves en una región de la Cordillera Central de los Andes Colombianos. Comparamos el número de especies por bandada y el número de bandadas en 3 hábitats distintos. Evaluamos hipótesis relacionadas con la actividad de las bandadas durante el día y la presencia simultánea de especies en estos grupos. Observamos 75 especies, y el número de especies por bandada varió entre 4 y 21. Nuestros datos indican que el hábitat parece afectar el número de bandadas pero no su número de especies y que la actividad de las bandadas

  17. Is tourism damaging ecosystems in the Andes? Current knowledge and an agenda for future research.

    Science.gov (United States)

    Barros, Agustina; Monz, Christopher; Pickering, Catherine

    2015-03-01

    Despite the popularity of tourism and recreation in the Andes in South America and the regions conservation value, there is limited research on the ecological impacts of these types of anthropogenic use. Using a systematic quantitative literature review method, we found 47 recreation ecology studies from the Andes, 25 of which used an experimental design. Most of these were from the Southern Andes in Argentina (13 studies) or Chile (eight studies) with only four studies from the Northern Andes. These studies documented a range of impacts on vegetation, birds and mammals; including changes in plant species richness, composition and vegetation cover and the tolerance of wildlife of visitor use. There was little research on the impacts of visitors on soils and aquatic systems and for some ecoregions in the Andes. We identify research priorities across the region that will enhance management strategies to minimise visitor impacts in Andean ecosystems. PMID:25201299

  18. History of Lake Andes

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Information about the history and management of Lake Andes is compiled in this report. It is intended to help future refuge managers become acquainted with the...

  19. Present and future water resources supply and demand in the Central Andes of Peru: a comprehensive review with focus on the Cordillera Vilcanota

    Science.gov (United States)

    Drenkhan, Fabian; Huggel, Christian; Salzmann, Nadine; Giráldez, Claudia; Suarez, Wilson; Rohrer, Mario; Molina, Edwin; Montoya, Nilton; Miñan, Fiorella

    2014-05-01

    Glaciers have been an important element of Andean societies and livelihoods as direct freshwater supply for agriculture irrigation, hydropower generation and mining activities. Peru's mainly remotely living population in the Central Andes has to cope with a strong seasonal variation of precipitations and river runoff interannually superimposed by El Niño impacts. Direct glacier and lake water discharge thus constitute a vital continuous water supply and represent a regulating buffer as far as hydrological variability is concerned. This crucial buffer effect is gradually altered by accelerated glacier retreat which leads most likely to an increase of annual river runoff variability. Furthermore, a near-future crossing of the 'peak water' is expected, from where on prior enhanced streamflow decreases and levels out towards a new still unknown minimum discharge. Consequently, a sustainable future water supply especially during low-level runoff dry season might not be guaranteed whereas Peru's water demand increases significantly. Here we present a comprehensive review, the current conditions and perspectives for water resources in the Cusco area with focus on the Vilcanota River, Cordillera Vilcanota, Southern Peru. With 279 km2 the Cordillera Vilcanota represents the second largest glacierized mountain range of the tropics worldwide. Especially as of the second half of the 1980s, it has been strongly affected by massive ice loss with around 30% glacier area decline until present. Furthermore, glacier vanishing triggers the formation of new lakes and increase of lake levels and therefore constitutes determining hazardous drivers for mass movements related to deglaciation effects. The Vilcanota River still lacks more profound hydrological studies. It is likely that its peak water has already been or might be crossed in near-future. This has strong implications for the still at 0.9% (2.2%) annually growing population of the Cusco department (Cusco city). People mostly

  20. Reconstructing the annual mass balance of the Echaurren Norte glacier (Central Andes, 33.5° S) using local and regional hydroclimatic data

    Science.gov (United States)

    Masiokas, Mariano H.; Christie, Duncan A.; Le Quesne, Carlos; Pitte, Pierre; Ruiz, Lucas; Villalba, Ricardo; Luckman, Brian H.; Berthier, Etienne; Nussbaumer, Samuel U.; González-Reyes, Álvaro; McPhee, James; Barcaza, Gonzalo

    2016-04-01

    Despite the great number and variety of glaciers in southern South America, in situ glacier mass-balance records are extremely scarce and glacier-climate relationships are still poorly understood in this region. Here we use the longest (> 35 years) and most complete in situ mass-balance record, available for the Echaurren Norte glacier (ECH) in the Andes at ˜ 33.5° S, to develop a minimal glacier surface mass-balance model that relies on nearby monthly precipitation and air temperature data as forcing. This basic model is able to explain 78 % of the variance in the annual glacier mass-balance record over the 1978-2013 calibration period. An attribution assessment identified precipitation variability as the dominant forcing modulating annual mass balances at ECH, with temperature variations likely playing a secondary role. A regionally averaged series of mean annual streamflow records from both sides of the Andes between ˜ 30 and 37° S is then used to estimate, through simple linear regression, this glacier's annual mass-balance variations since 1909. The reconstruction model captures 68 % of the observed glacier mass-balance variability and shows three periods of sustained positive mass balances embedded in an overall negative trend over the past 105 years. The three periods of sustained positive mass balances (centered in the 1920s-1930s, in the 1980s and in the first decade of the 21st century) coincide with several documented glacier advances in this region. Similar trends observed in other shorter glacier mass-balance series suggest that the Echaurren Norte glacier reconstruction is representative of larger-scale conditions and could be useful for more detailed glaciological, hydrological and climatological assessments in this portion of the Andes.

  1. Water input and water release from the subducting Nazca Plate along southern Central Chile (33°S-46°S)

    Science.gov (United States)

    Völker, David; Stipp, Michael

    2015-06-01

    The age of the subducting Nazca Plate off Chile increases northward from 0 Ma at the Chile Triple Junction (46°S) to 37 Ma at the latitude of Valparaíso (32°S). Age-related variations in the thermal state of the subducting plate impact on (a) the water influx to the subduction zone, as well as on (b) the volumes of water that are released under the continental fore arc or, alternatively, carried beyond the arc. Southern Central Chile is an ideal setting to study this effect, because other factors for the subduction zone water budget appear constant. We determine the water influx by calculating the crustal water uptake and by modeling the upper mantle serpentinization at the outer rise of the Chile Trench. The water release under fore arc and arc is determined by coupling FEM thermal models of the subducting plate with stability fields of water-releasing mineral reactions for upper and lower crust and hydrated mantle. Results show that both the influx of water stored in, and the outflux of water released from upper crust, lower crust, and mantle vary drastically over segment boundaries. In particular, the oldest and coldest segments carry roughly twice as much water into the subduction zone as the youngest and hottest segments, but their release flux to the fore arc is only about one fourth of the latter. This high variability over a subduction zone of <1500 km length shows that it is insufficient to consider subduction zones as uniform entities in global estimates of subduction zone fluxes.

  2. Mid-cretaceous crustal shortening: evidence from a regional-scale ductile shear zone in the Coastal Range of central Chile (32° S)

    Science.gov (United States)

    Arancibia, Gloria

    2004-11-01

    In the Coastal Range of central Chile, widespread Early Cretaceous volcanism associated with extensional volcanosedimetary intra- or back-arc basins and subsequent basin closures, uplift, and increased erosion/exhumation rates during the mid-Cretaceous suggests a major change from a mainly extensional tectonic regime to a relatively contractional regime and resultant crustal shortening. The author documents the contractional Silla del Gobernador shear zone (SGSZ), which developed at the western boundary of the Coastal Range in central Chile (32° S). This structure corresponds to a high-strain ductile and cataclastic shear zone that developed under low-grade (greenschist facies) metamorphic and fluid-present conditions, which indicates EW-NWW crustal shortening in a compressional (transpressional) regime. UVLAMP 40Ar/ 39Ar laserprobe dating of neoformed white mica during mylonitic deformation suggests a maximum age for the reverse ductile shearing of 109±11 Ma. An inverse isochron age of 97.8±1.5 Ma from biotite samples of a mylonitized granodiorite suggests the minimum age of deformation. These ages constrain the ductile deformation age to approximately 100 Ma (mid-Cretaceous), coeval with high exhumation/erosion rates that appear to represent uplift of the Coastal Range. The uplift and crustal shortening of the Coastal Range of central Chile has been associated with high spreading rates from the SE Pacific and southern Atlantic convergence during a change from an extensional regime developed during the Early Cretaceous to a more compressional regime that started during the mid-Cretaceous. In this sense, the SGSZ records this tectonic regime change.

  3. Modelación y análisis probabilístico del balance hídrico superficial de un sistema de riego en Chile Central

    OpenAIRE

    Molina, José Manuel; Gurovich R., Luis A.; Varas, Eduardo

    2003-01-01

    El presente artículo presenta una propuesta de modelación de los elementos y procesos involucrados en la oferta superficial y demanda hídrica de un sistema de riego de la zona central de Chile, como metodología para el estudio del balance hídrico predial en la planificación de los recursos hídricos disponibles. El estudio contempló una descripción y evaluación general del sistema mediante visitas de terreno y recolección de información, teniendo en cuenta aspectos de suelos, cultivos, agua...

  4. Consideraciones biogeográficas y ecológicas de equinodermos arquibentónicos de Chile Central (com excepción de crinoidea

    Directory of Open Access Journals (Sweden)

    Héctor Andrade Vasquez

    1980-12-01

    Full Text Available 30 echinoderm species (the crinoias excepted have been recorded from the archibenthos off Central Chile. Samples were taken at 5 stations (from Los Vilos to Quíntero. 250-450 m depth range, every 15 days for one year. The concept of Region or Province, usually related to the intertital fauna from high latitudes are showed to be impractical using them with archibenthal echinoderms. The presence oj some species that had been registered as characteristic from the Antarctic Region and/or present in the Argentinian and Magellanic Province is related with the Antarctic Intermediate Water Mass, which is at the capture depth in the sampled area.

  5. The Jurassic-Cretaceous Boundary (Tithonian - Hauterivian) in the Andean Basin of Central Chile: Ammonites, Bio- and Sequence Stratigraphy and Palaeobiogeography

    OpenAIRE

    Salazar Soto, Christian Andrés

    2012-01-01

    Five sections of the Baños del Flaco and Lo Valdés formations in the High Andean Cordillera of Central Chile have been analyzed with regard to sediment, bio- and sequence stratigraphy, ammonite assemblages and palaeobiogeography, in order to reveal the age and depositional facies of the sediment sequence, and to evaluate the age and important bioevents across the Jurassic-Cretaceous boundary. The Baños del Flaco Formation was investigated at Rio Tinguiririca and in the Rio Maitenes valley,...

  6. Hábitos tróficos de la reineta Brama australis (Pisces: Bramidae durante el periodo estival frente a Chile central

    Directory of Open Access Journals (Sweden)

    Francisco Santa Cruz

    2014-11-01

    Full Text Available La reineta Brama australis es un importante recurso pesquero artesanal en la zona central chilena, incorporado en los programas de seguimiento biológico, pero con escasas evaluaciones de sus aspectos tróficos. Para actualizar el estado del conocimiento, se analizó su dieta durante el verano austral época de mayor disponibilidad de este recurso en la zona central de Chile, mediante el análisis del contenido gástrico de 300 ejemplares capturados entre noviembre 2011 y marzo 2012. Se identificó una dieta dominada por Euphausia mucronata (IIR = 92,33, aunque a escala mensual se identificó una dieta mixta de E. mucronata durante noviembre, diciembre 2011 y marzo 2012, además de Pterygosquilla armata y anfípodos hipéridos durante enero y marzo 2012. No se encontró diferencias significativas entre ambos sexos (P > 0,01. Estos resultados demuestran y corroboran que B. australis es un depredador pelágico con un reducido espectro trófico en el litoral de Chile central.

  7. Using fecal profiles of bile acids to assess habitat use by threatened carnivores in the Maulino forest of central Chile Empleo del perfil de ácidos biliares fecales para evaluar uso del hábitat por carnívoros amenazados en el bosque maulino de Chile central

    OpenAIRE

    CARLA GUERRERO; LUIS ESPINOZA; HERMANN M. NIEMEYER; JAVIER A SIMONETTI

    2006-01-01

    The distribution and habitat use by carnivores can be assessed by studying their tracks or feces. If these methods are to be used confidently, they should not only unequivocally discriminate among species, but should also render the same patterns of spatial distributions. We assessed the fulfillment of these requirements with five carnivores inhabiting the Maulino forest of central Chile: Galictis cuja, Oncifelis guigna, Pseudalopex culpaeus, Pseudalopex griseus, and Puma concolor. Fecal bile...

  8. Biología reproductiva del águila Geranoaetus melanoleucus (Aves: Accipitridae en Chile central Breeding biology of the black-chested eagle Geranoaetus melanoleucus (Aves: Accipitridae in central Chile

    Directory of Open Access Journals (Sweden)

    EDUARDO F. PAVEZ

    2001-09-01

    Full Text Available Durante dos años (julio 1987­enero 1989 se estudió la biología reproductiva del águila (Geranoaetus melanoleucus en San Carlos de Apoquindo, en Chile central. El inicio del período reproductivo se evidenció por un aumento del número de vuelos en pareja. Los cortejos incluyeron vuelos sincronizados de la pareja, capturas, transporte de material al nido y cópulas. Los traspasos de presas ocurrieron durante todo el año, aunque fuera del período reproductivo fueron escasos y forzados por la hembra. Se localizaron 4,7 nidos pareja-1, lo que está en el límite superior documentado para grandes águilas. Fuera del período reproductivo las águilas visitaron ocasionalmente los nidos. Antes de la postura el macho visitó el nido con mayor frecuencia y por menos tiempo que la hembra. En las tres parejas estudiadas se observó visitas a nidos alternativos, con aporte de material y presas. Se promedió 2,3 huevos postura-1 (DE = 0,5, n = 6, incubando macho y hembra, y eclosionando el 100 %. A los 25 días de edad comenzaron a emerger las plumas de vuelo de los pollos, a los 35 días comían solos las presas aportadas al nido y a los 59 días abandonaron el nido. Durante la crianza la hembra permaneció más tiempo en el nido que el macho, con una tendencia de los adultos a disminuir el tiempo de permanencia en el nido. El 79 % de los pollos sobrevivió a la crianza, lo que se puede considerar un éxito reproductivo elevado, y que se explicaría por la elevada disponibilidad de presas en el sitio de estudio, particularmente de conejos. Los pollos permanecieron en el territorio paterno 10 meses, lo que coincidió con la siguiente postura de huevos, disminuyendo gradualmente su presencia en el área y aumentando la intolerancia de los adultos hacia sus hijos. Los resultados presentados se corresponden con el patrón descrito en la literatura para otras águilasThe breeding biology of the black-chested eagle (Geranoaetus melanoleucus was studied

  9. Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile

    Science.gov (United States)

    Sellanes, Javier; Zapata-Hernández, Germán; Pantoja, Silvio; Jessen, Gerdhard L.

    2011-12-01

    We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release. At the control site, located 11 km away from the gas emanation, fauna exhibited moderate δ 13C values ranging from -16.2‰ (in a nereid polychaete) to -14.8‰ (in a cirolanid isopod), which were consistent with those of the potential photosynthetic food sources sampled at this site (-20.2 to -16.5‰). δ 13C values of the photosynthetic food sources at the seep site similarly ranged between -25.4 and -17.9‰. However, a portion of the animals at this site were consistently more 13C-depleted, with δ 13C values close to that of the seeping methane (-43.8‰) and the bacteria-like filaments (-39.2 ± 2.5‰) also collected at this site. Specific examples were the Marphysa sp. polychaetes (δ 13C = -44.7 ± 0.6‰), the Schistomeringos sp. dorvilleid polychaetes (δ 13C = -42.9‰), and the tanaid crustacean Zeuxo marmoratus (δ 13C = -37.3 ± 0.2‰). The significantly higher δ 13C values of the herbivorous gastropod Tegula atra at the seep site (-29.3 ± 3.1‰) than at the control site (-12.6 ± 0.3‰) also indicated differences among sites of the preferred carbon sources of this species. Mixing model estimates indicate that at the seep site bacteria-like filaments could be contributing up to ˜60% of the assimilated diet of selected invertebrates. Furthermore, several indicators of trophic structure, based in isotopic niche metrics, indicate a

  10. Persistent toxic substances in soils and waters along an altitudinal gradient in the Laja River Basin, Central Southern Chile.

    Science.gov (United States)

    Barra, Ricardo; Popp, Peter; Quiroz, Roberto; Bauer, Coretta; Cid, Hernan; von Tümpling, Wolf

    2005-02-01

    In this study the levels and distribution of some persistent toxic substances (PTS) were investigated in soils, superficial water, and snow along an altitudinal gradient in the Laja River Basin (South Central Chile). The principal objective was to establish the basin's contamination status. The working hypothesis was that PTS levels and distribution in the basin are dependent on the degree of anthropogenic intervention. Fifteen PAHs, seven PCBs congeners, and three organochlorine pesticides were studied in superficial soil and water samples obtained along the altitudinal gradient and from a coastal reference station (Lleu-Lleu River). Soil samples were extracted using accelerated solvent extraction with acetone/cyclohexane (1:1) for PAHs and organochlorine compounds. Contaminants were extracted from water and snow samples by liquid-liquid extraction (LLE). PAH and organochlorine compound quantification was carried out by HPLC with fluorescence detection and GC-MS, respectively. PCBs in soils presented four different profiles in the altitudinal gradient, mainly determined by their chlorination degree; these profiles were not observed for the chlorinated pesticides. In general, the detected levels for the analyzed compounds were low for soils when compared with soil data from other remote areas of the world. Higher summation operator PAHs levels in soils were found in the station located at 227 masl (4243 ng g-1 TOC), in a forestry area and near a timber industry, where detected levels were up to eight times higher than the other sampling sites. In general, PAH levels and distribution seems to be dependent on local conditions. No pesticides were detected in surface waters. However, congeners of PCBs were detected in almost all sampling stations with the highest levels being found in Laja Lake waters, where 1.1 ng/l were observed. This concentration is two times higher than values reported for polluted lakes in the Northern Hemisphere. The presence of organochlorine

  11. Combined impact of ocean acidification and corrosive waters in a river-influenced coastal upwelling area off Central Chile

    Science.gov (United States)

    Vargas, C.; De La Hoz, M.; San Martin, V.; Contreras, P.; Navarro, J. M.; Lagos, N. A.; Lardies, M.; Manríquez, P. H.; Torres, R.

    2012-12-01

    Elevated CO2 in the atmosphere promotes a cascade of physical and chemical changes affecting all levels of biological organization, and the evidence from local to global scales has shown that such anthropogenic climate change has triggered significant responses in the Earth's biota. The increased concentration of CO2 is likely to cause a corresponding increase in ocean acidification (OA). In addition, economically valuable shellfish species predominantly inhabit coastal regions both in natural stocks and/or in managed stocks and farming areas. Many coastal ecosystems may experience seawater pCO2 levels significantly higher than expected from equilibrium with the atmosphere, which in this case are strongly linked to biological processes and/or the impact of two important processes; river plumes and coastal upwelling events, which indeed interplay in a very dynamic way on continental shelves, resulting in both source or sink of CO2 to the atmosphere. Coastal ecosystems receive persistent acid inputs as a result of freshwater discharges from river basins into the coastal domain. In this context, since shellfish resources and shellfish aquaculture activities predominantly occur in nearshore areas, it is expected that shellfish species inhabiting river-influenced benthic ecosystems will be exposed persistently to acidic conditions that are suboptimal for its development. In a wider ecological context, little is also known about the potential impacts of acid waters on the performance of larvae and juveniles of almost all the marine species inhabiting this benthic ecosystem in Eastern Southern Pacific Ocean. We present here the main results of a research study aimed to investigate the environmental conditions to which economically valuable calcifiers shellfish species are exposed in a river-influenced continental shelf off Central Chile. By using isotopic measurements in the dissolved inorganic carbon (DIC) pool (d13C-DIC) we showed the effect of the remineralization of

  12. Etude paléomagnetique des formations crétacées et tertiaires des Andes centrales du Pérou. Rôle des rotations dans la formation des déflexions andines

    OpenAIRE

    Macedo Sanchez, Orlando

    1993-01-01

    La déflexion majeure d'Arica, située entre 19-22° S et qui dévie l'orientation générale des structures des Andes Centrales depuis une direction péruvienne N W-SE jusqu'à une direction chilienne presque NS, est une des caractéristiques importantes de la chaîne andine. Aussi à cette latitude la croûte sud-américaine atteint une épaisseur double de la normale (-70 km). Cet épaississement crustal est à l'origine du développement de l'Altiplano, vaste plateau situé à une altitude moyenne proche de...

  13. Cuando ya no se puede tomar trago ni chacchar coca. When alcohol can no longer be drunk or coca leaves chewed. the case of the “protestants” in the Peruvian central Andes

    Directory of Open Access Journals (Sweden)

    Caroline Magny

    2009-12-01

    Full Text Available Desde hace mucho tiempo el alcohol y la coca ocupan un lugar central en las comunidades andinas. Hasta ahora en el distrito de Churcampa (Huancavelica, Perú, los católicos, mayoritarios, siguen explicando al visitante lo siguiente: “acá no se puede hacer nada sin trago ni coca”. No obstante, durante las ultimas décadas, muchas personas en este distrito – así como en muchos otros distritos de los Andes peruanos – se han convertido y siguen convirtiéndose al “protestantismo” (termino genérico usado por los católicos para referirse en forma general a las Iglesias evangélicas. Esta conversión implica, entre otras cosas, dejar completamente de masticar hojas de coca y de beber cualquier tipo de bebidas alcohólicas. En esta exposición proponemos analizar hasta qué punto y bajo qué modalidades estas restricciones alimenticias afectan a los conversos (quienes siguen siendo minoritarios en el distrito en su vida social cotidiana.Alcohol and coca have played a central role in Andean communities for many centuries. Nowadays, in the district of Churcampa (Huancavelica, Peru, the Catholic people, who are the majority, still explain to visitors that “here you can’t do anything without trago [alcohol] and coca”. Yet, over the past decades, many men and women in this district - as well as in many other districts of the Peruvian Andes - have been converting to “Protestantism” (a generic term used by Catholics to refer to the Evangelical Churches. This conversion implies, among other things, completely giving up chewing of coca leaves and drinking of any type of alcoholic drink. The aim of this article is to analyze to what extent and how these restrictions in the dietary habits affect converted people in their everyday social life.alcohol, coca leaves, religion, conversion, evangelic Churches, Peru

  14. Future Temperatures and Precipitations in the Arid Northern-Central Chile: A Multi-Model Downscaling Approach

    Science.gov (United States)

    Souvignet, M.; Heinrich, J.

    2010-03-01

    Downscaling of global climate outputs is necessary to transfer projections of potential climate change scenarios to local levels. This is of special interest to dry mountainous areas, which are particularly vulnerable to climate change due to risks of reduced freshwater availability. These areas play a key role for hydrology since they usually receive the highest local precipitation rates stored in form of snow and glaciers. In the central-northern Chile (Norte Chico, 26-33ºS), where agriculture still serves as a backbone of the economy as well as ensures the well being of people, the knowledge of water resources availability is essential. The region is characterised by a semiarid climate with a mean annual precipitation inferior to 100mm. Moreover, the local climate is also highly influenced by the ENSO phenomenon, which accounts for the strong inter-annual variability in precipitation patterns. Although historical and spatially extensive precipitation data in the headwaters of the basins in this region are not readily available, records at coastal stations show worrisome trends. For instance, the average precipitation in La Serena, the most important city located in the Coquimbo Region, has decreased dramatically in the past 100 years. The 30-year monthly average has decreased from 170 mm in the early 20th century to values less than 80 mm nowadays. Climate Change is expected to strengthen this pattern in the region, and therefore strongly influence local hydrological patterns. The objectives of this study are i) to develop climate change scenarios (2046-2099) for the Norte Chico using multi-model predictions in terms of temperatures and precipitations, and ii) to compare the efficiency of two downscaling techniques in arid mountainous regions. In addition, this study aims at iii) providing decision makers with sound analysis of potential impact of Climate Change on streamflow in the region. For the present study, future local climate scenarios were developed

  15. Cambio del uso del suelo en el centro sur de Chile a fines del siglo XX: Entendiendo la dinámica espacial y temporal del paisaje Land use change in the south central Chile at the end of the 20th century: Understanding the spatio-temporal dynamics of the landscape

    Directory of Open Access Journals (Sweden)

    MAURICIO AGUAYO

    2009-01-01

    Full Text Available Los humanos han transformado gran parte de la superficie del planeta en los últimos 300 años. La tala de bosques, las prácticas agrícolas de subsistencia, la intensificación de la producción agrícola y la expansión de los centros urbanos han cambiado drásticamente el paisaje. En el centro y sur de Chile las transformaciones han estado asociadas, en un inicio, a la expansión de la frontera agropecuaria que permitió satisfacer tanto las necesidades internas como la creciente demanda externa por productos agrícolas. Posteriormente, un fuerte incentivo a la forestación, comandado por el Estado, generó un acelerado proceso de desarrollo forestal que explica, en gran medida, la actual configuración del paisaje en esta región. En este trabajo hemos analizados la dinámica espacial de los cambios en el uso del suelo ocurridos durante las últimas décadas en un área de 2.3 millones de hectáreas ubicada entre las regiones del Biobío y La Araucanía. Las coberturas del suelo fueron obtenidas a partir de dos imágenes Landsat correspondientes a los años 1979 y 2000. Los resultados confirman que las principales transformaciones del paisaje son consecuencia del desarrollo forestal, la mantención de los rubros agropecuarios y el crecimiento urbano e industrial. Asimismo, fue posible determinar que la pérdida del bosque nativo se debe, principalmente, a la expansión de las plantaciones forestales hacia los cordones montañosos andinos y costeros.Land use changes have transformed much of the Earth's surface in the last 300 years. Deforestation, intensification of agriculture, and urban sprawl have radically changed the preindustrial landscape. In south-central Chile, landscape change was initially related to the expansión of farming to address national needs and the growing international demand for agricultural products. Subsequently, prívate forestry, subsidized by the State, promoted the accelerated expansión of industrial

  16. A study of the relationship between degree of ethnocentrism and typologies of food purchase in supermarkets in central-southern Chile.

    Science.gov (United States)

    Schnettler, Berta; Miranda, Horacio; Lobos, Germán; Sepúlveda, José; Denegri, Marianela

    2011-06-01

    The objective of this study was to distinguish different types of consumers according to their level of ethnocentrism in relation to the consumption of foodstuffs in central-southern Chile. To do this a modification of the CETSCALE (Consumer Ethnocentric Tendencies Scale) was applied through direct survey of 800 habitual supermarket shoppers in two cities in central-southern Chile. The modified CETSCALE presented a sufficient level of internal consistency and there were three factors which included the 17 items of the scale. Five typologies of consumer with different degrees of ethnocentrism were distinguished by cluster analysis, based on the values of the factors and items in the CETSCALE. The composition of the typologies of consumers were related to the city and zone of residence, age, socioeconomic level, self-declared life-style, ethnic origin, knowledge of the origin of the foodstuffs purchased, frequency of purchase of imported foodstuffs and reasons for rejection in the case of a low purchase frequency. It may therefore be concluded that different levels of ethnocentrism exist in the consumption of foodstuffs, related with some socio-demographic characteristics of consumers and their attitudes to imported foodstuffs. PMID:21335039

  17. Cambios de largo plazo en el paisaje y los ensambles de micromamíferos y rapaces en Chile central Long-term changes in landscape and in small mammal and raptor assemblages in central Chile

    Directory of Open Access Journals (Sweden)

    EDUARDO F PAVEZ

    2010-03-01

    Full Text Available San Carlos de Apoquindo, en la precordillera de Chile central, es una localidad con estudios de larga data en vertebrados (ca. 30 años, situación favorable para el análisis de procesos de largo plazo que operan sobre dichos ensambles. En este contexto estudiamos la trayectoria del uso del suelo mediante imágenes satelitales LANDSAT, correspondientes a 1975, 1989 y 2003 y su presunto efecto sobre la vegetación, micromamíferos y aves rapaces. El análisis de las imágenes satelitales revela una expansión acelerada del área urbana en desmedro del suelo agrícola y matorrales naturales. Las especies de micromamíferos nativos de talla reducida y media no evidencian grandes variaciones de abundancia durante el período de estudio pero las de mayor tamaño redujeron sus poblaciones. El conejo europeo (Oryctolagus cuniculus es una de las especies más abundantes del área, y estaría siendo favorecido por la modificación del paisaje. En la dieta del águila (Geranoaetus melanoleucus y del peuco (Parabuteo unicinctus se observó una disminución sostenida de la principal presa nativa, el degú (Octodon degus y un aumento de la presa exótica, el conejo. Además se observó una tendencia a la disminución de la riqueza y abundancia de aves rapaces durante el período de estudio, la que se asociaría a la expansión urbana y al deterioro del matorral natural. Postulamos que la expansión urbana y la pérdida y fragmentación del matorral han producido una disminución de la población de degú, con su consecuente disminución en la dieta de águilas y peucos, lo que a su vez ha potenciado un incremento de depredación sobre conejo.San Carlos de Apoquindo, a piedemont area to the east of Santiago city, is a site with 30 years of data on vertebrates. Using LANDSAT satellite imagery for the years 1975, 1989 and 2003, we studied the spatio-temporal trajectory of land use and its putative effects on vegetation, small mammals and raptors. On the basis

  18. Craniofacial chronological microdifferentiation of human prehistoric populations of the Azapa valley, northern Chile Microdiferenciación cronológica craneofacial de poblaciones humanas prehistóricas del Valle de Azapa, norte de Chile

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    FRANCISCO ROTHHAMMER

    2002-03-01

    Full Text Available Archeological evidence suggest that the cultural developments occurred in the highlands around lake Titicaca in the Central Andes, exerted influence on the cultural elaborations of the human groups that peopled the valley of Azapa, close to the city of Arica, and the Pacific coast of northern Chile. In this communication we show by means of a distance analysis, that a craniofacial differentiation accompanied the process of cultural evolution in the valley. The biological influence of Tiwanaku is partially reflected in craniofacial morphology, providing preliminary evidence that cultural changes were associated to intermittent gene flow from the highlands, specially during the Alto Ramírez and San Miguel phasesLos desarrollos culturales ocurridos en el altiplano en el área circumtiticaca en los Andes centrales, ejercieron influencia sobre las elaboraciones culturales de los grupos humanos que poblaban el Valle de Azapa cercano a la ciudad de Arica y la costa del norte de Chile. En esta comunicación presentamos un análisis de distancias que demostró que una diferenciación craniofacial acompaño en el valle el proceso de evolución cultural. La influencia biológica de Tiwanaku se refleja parcialmente en la morfología craniofacial, proporcionando evidencia preliminar de que los cambios culturales en el valle se realizaron acompañados de flujo génico intermitente desde el altiplano, especialmente durante las fases Alto Ramírez y San Miguel

  19. The low-grade Canal de las Montañas Shear Zone and its role in the tectonic emplacement of the Sarmiento Ophiolitic Complex and Late Cretaceous Patagonian Andes orogeny, Chile

    Science.gov (United States)

    Calderón, M.; Fosdick, J. C.; Warren, C.; Massonne, H.-J.; Fanning, C. M.; Cury, L. Fadel; Schwanethal, J.; Fonseca, P. E.; Galaz, G.; Gaytán, D.; Hervé, F.

    2012-02-01

    The Canal de las Montañas Shear Zone (CMSZ), southern Patagonian Andes (51-52°S), is a low-grade mylonite belt generated from felsic ignimbritic, pelitic and basaltic protoliths of the Late Jurassic-Early Cretaceous Rocas Verdes basin. The different types of rock fabrics across the CMSZ are thought to be associated with relatively intermediate and high strain conditions, characterized by the development of a narrow western belt of S-Ć-type mylonites and phyllonites interpreted as the metamorphic sole thrust of the Sarmiento Ophiolitic Complex. Highly strained rocks of the CMSZ display a reverse, continent-ward tectonic transport, with a minor dextral component of shearing. Transitional pumpellyite-actinolite and upper greenschist facies metamorphic conditions at ca. 5-6 kbar and 230-260 °C indicate that the primary shearing event occurred in a subduction zone setting. In-situ 40Ar/39Ar laserprobe chronology yielded ages of ca. 85 Ma on syntectonic phengite which are interpreted as representing cooling synchronous with mica crystallization during the main compressive deformational event. The 78-81 Ma U-Pb zircon crystallization ages of cross-cutting plutonic and hypabyssal rocks and 40Ar/39Ar amphibole age of ca.79 Ma from lamprophyric dikes within the fold-thrust belt constrain an upper age limit of the ophiolite tectonic emplacement deformation.

  20. Infrastructure development and agricultural exposure to climate variability and change: lessons from the Limarí basin in Central Chile

    Science.gov (United States)

    Vicuna, S.; Alvarez, P.; Melo, O.; Dale, L. L.; Meza, F. J.

    2012-12-01

    The Limarí basin, located in Central Chile, is a world famous example of how the development of reservoirs and irrigation infrastructure can reduce climate vulnerabilities allowing the economic development of a basin. Before the infrastructure was developed low value crops such as cereals dominated land use acreage. Today high value crops such as vineyards, orchards and vegetables account for almost 50% of total land and cereals have almost disappear. Key to this evolution have been the reduction in water supply variability, access to international markets, increased irrigation efficiency, and the existence of water markets and other flexible and strong institutions that have helped moving the water from low to high value uses. These factors are related to each other sharing infrastructure development as a common root. The system of reservoirs in the Limarí basin was designed and has been operated since its construction with the premise that droughts in this basin do not last longer than 4 years. Until recently that had been the case and farmers have been able to withstand the impacts of droughts. When faced with water supply reductions farmers would select from a set of options to accommodate their needs including: water market participation, groundwater extraction and crop irrigation and crop acreage decisions. The use of these options has even allowed increasing total irrigated land mostly through the expansion of permanent water demand crops. In the past 9 years however, the basin has experienced a longer than usual drought, interrupting the reservoir refilling cycle that characterized climate variability in the region. This situation has led to dramatically low reservoir levels and continuous reductions in water supply. In addition, due to the already high levels of irrigation efficiency and large amount of acreage devoted to permanent water demand crops, the effectiveness of the portfolio of options available to farmers to accommodate to these stressing

  1. Active tectonics of the Andes

    Science.gov (United States)

    Dewey, J. F.; Lamb, S. H.

    1992-04-01

    Nearly 90 mm a -1 of relative plate convergence is absorbed in the Andean plate-boundary zone. The pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved. Along any traverse across the plate-boundary zone, the sum of relative velocities between points must equal the relative plate motion. We have developed a kinematic synthesis of displacement and strain partitioning in the Andes from 47°S to 5°N relevant for the last 5 Ma based upon: (1) relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080; (2) moment tensor solutions for over 120 crustal earthquakes since 1960; (3) structural studies of deformed Plio-Pleistocene rocks; (4) topographic/geomorphic studies; (5) palaeomagnetic data; and (6) geodetic data. We recognize four neotectonic zones, with subzones and boundary transfer zones, that are partitioned in different ways. These zones are not coincident with the 'classic' zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form; the long-term segmentation and finite evolution of the Andes may not occur in constantly defined segments in space and time. In Segment 1 (47°-39°S), the slip vector is partitioned into roughly orthogonal Benioff Zone slip with large magnitude/large slip-surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50° and dextral slip in the curved Liquine-Ofqui Fault System giving 5°-10° of anticlockwise fore-arc rotation. In Segment 2 (39°-20°S), the slip vector is partitioned into Benioff Zone slip roughly parallel with the slip vector, Andean crustal shortening and a very small component of dextral slip, including that on the Atacama Fault System. Between 39° and 34°S, a cross-strike dextral transfer, which deflects

  2. Spatio-temporal variability in ontogenetic guild structure of an intertidal fish assemblage in central Chile Variabilidad espacio-temporal en la estructura de gremios ontogenéticos de un ensamble de peces intermareales de Chile central

    Directory of Open Access Journals (Sweden)

    PATRICIA A BERRÍOS

    2011-12-01

    variabilidad en las condiciones ambientales, especialmente en peces intermareales, los que alcanzan varios órdenes de magnitud en tamaño corporal. Sin embargo, la influencia de los cambios ontogenéticos en la membresía gremial sobre la estructura espacio-temporal de los ensambles de peces permanece virtualmente desconocida. En este trabajo estudiamos la variabilidad espacio-temporal en la estructura de los gremios alimenticios ontogenéticos (OFG de los ensambles de peces intermareales que ocurren en el intermareal rocoso de la costa de Chile central. Para esto realizamos an��lisis de componentes principales (PCA y pruebas de aleatorización (pruebas R de la composición relativa de las OFG de estos ensambles, obtenidos de muestreos estacionales en diez pozas intermareales ubicadas en dos alturas de mareas en la zona intermareal en tres localidades entre los 33° y 34° S. En general, los PCA y pruebas R sugieren que la variabilidad espacial domina sobre la variabilidad temporal en la estructura de las OFG, debido principalmente a la alta representatividad de las especies omnívoras en las pozas altas del intermareal en dos de las tres localidades muestreadas. Sin embargo, cambios relacionados a la fenología en la representación de las clases de tamaño de los peces (i.e. reclutamiento de carnívoros en primavera-verano junto con diferencias ontogenéticas en la selección de hábitat (e.g., selección por pozas del intermareal bajo por la OFG de carnívoros de gran tamaño contribuyeron a una diferenciación espacial y temporal de la estructura de la OFG. Finalmente, la representación relativa de cada OFG se correlacionó con la de sus especies dominantes, sin evidencia de una compensación por densidad. Esto sugiere bajos niveles de redundancia funcional entre las especies en cada OFG, lo cual denota la vulnerabilidad del funcionamiento de estos ensambles a perturbaciones sesgadas en tamaño corporal tales como la pesca.

  3. Palaeoindian occupation of the Atacama Desert, northern Chile

    Science.gov (United States)

    Grosjean, Martin; Núñez, Lautaro; Cartajena, Isabel

    2005-10-01

    Palaeoindian occupation of the Atacama Desert in northern Chile has been found between 12 600 and 10 200 cal. yr BP. The new site at Salar Punta Negra (24°28S/60°53W/2976 m) includes about 1000 classifiable, mostly unifacial artefacts and, uniquely, three different diagnostic types of early projectile points. Two of the Lateglacial/early Holocene projectile types have wide distribution and are known from different geographical areas in South America: the Palaeoindian Fell fish-tail point mainly from the southern cone of South America, and the triangular Tuina points typical of the Puna of the south-central Andes in northern Chile and northwestern Argentina. In addition, we found a third type, a stemmed point typical for the Salar Punta Negra. Filling a large geographical gap of Fell occupation, the site at Salar Punta Negra provides evidence for generally much higher mobility and diversity of early cultures, and supports an Andean-Pacific route for early human exploration of South America to the south through the desert at intermediate altitudes. Contemporaneous high-amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats, and to make Palaeoindian hunting-gathering occupation possible in the Atacama Desert.

  4. Fallout radionuclides 137Cs and 7Be as an important tool to evaluate effectiveness of no-tillage systems in Central-South Chile

    International Nuclear Information System (INIS)

    Since 1970 the process of agricultural intensification has drastically increased soil erosion and associated soil degradation in the coastal mountains of south-central Chile. Due to conventional tillage (with burning of crop residues), over 80% of the soils under agriculture show evidence of compaction below plough depth and erosion rates are described amongst the highest for any agricultural land in Chile. The current study developed a simplified method for using 137Cs depth distribution datasets to estimate soil loss or accumulation at a sampling point under conventional tillage and after the shift to a no-till system. Previous applications of 137Cs measurements had been limited to the estimation of erosion rates during the period extending from the beginning of fallout receipt to the time of sampling. The new procedure allows the change in erosion rates associated with a shift in land tillage practices to be estimated. It represents an innovative application of 137Cs measurements in soil erosion research. In an additional study to assess no-till systems with and without burning of crop residues after harvesting, 7Be was used to quantify the erosion that occurred within the same field area, as a result of burning and a period of extreme rainfall (400 mm in 27 days, May 2005)

  5. Satellite-measured interannual variability of turbid river plumes off central-southern Chile: Spatial patterns and the influence of climate variability

    Science.gov (United States)

    Saldías, Gonzalo S.; Largier, John L.; Mendes, Renato; Pérez-Santos, Iván; Vargas, Cristian A.; Sobarzo, Marcus

    2016-08-01

    Ocean color imagery from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the Aqua platform is used to characterize the interannual variability of turbid river plumes off central-southern Chile. Emphasis is placed on the influence of climate fluctuations, namely El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Antarctic Oscillation (AAO). Additional satellite data on wind, boat-based hydrographic profiles, and regional climate indices are used to identify the influence of climate variability on the generation of anomalous turbid river plumes. The evolution of salinity at a coastal station on the 90 m isobath between the Itata and Biobío Rivers shows a freshwater surface layer with salinity importance of long-term and high-resolution ocean color observations for studying the temporal evolution of river plumes.

  6. Talla de madurez y época de desove de la reineta (Brama australis Valenciennes, 1836) en la costa central de Chile Maturity size and spawning time of the Pacific pomfret (Brama australis Valenciennes, 1836) in the central coast of Chile

    OpenAIRE

    Elson Leal; Ciro Oyarzún

    2003-01-01

    La reineta (Brama australis) adquiere cada vez mayor importancia en los desembarques de la pesca artesanal, no obstante, es escasa la información que existe acerca de su biología básica, particularmente sobre su dinámica reproductiva. En este trabajo se determina la época principal de desove de B. australis en la costa central de Chile y la talla de madurez (TM), para lo cual se analizó un total de 1061 individuos capturados frente a Lebu (37º37'S-73º40'W), entre enero y septiembre de 2001. E...

  7. Botanical Composition of Alpaca (Lama pacos Linn.) Diet in a Central Mediterranean Range of Chile Composición Botánica de la Dieta de Alpaca (Lama pacos Linn.) en un Pastizal del Secano Mediterráneo de la Zona Central de Chile

    OpenAIRE

    G Castellaro; F Squella N; F León C; A Raggi S

    2008-01-01

    The re-introduction of domestic South American camelids (alpacas and llamas) in the central zone of Chile makes it necessary to study their behaviour and adaptability. Since it is fundamental to characterize the camelid’s diet, the present work had as an objective the determination of the plant species selected by the alpacas (Lama pacos Linn.) in different phenological stages (vegetative, reproductive and dry season). The study was carried out over three years in a paddock of 2.5 ha of spars...

  8. Shoreline changes in Concón and Algarrobo bays, central Chile, using an adjustment model Cambios en la línea litoral de las bahías de Algarrobo y Concón, Chile central, a través de un modelo de ajuste

    OpenAIRE

    Carolina Martinez

    2007-01-01

    Adjustment models for both Algarrobo and Concón bays, central Chile, are presented herein; the results show a nearly logarithmic spiral shape for the shore. Spatial-temporal variations in the shorelines of both bays were found based on aerial photographs from different years. The results indicate important variations in the relative position of the Concón Bay shoreline between 1945 and 2006, with extreme oscillations (-368 to 123.8 m) only occurring in the proximal zone, where the Aconcagua E...

  9. Productivity and Persistence of Yellow Serradela (Ornithopus compressus L. and Biserrula (Biserrula pelecinus L. in the Mediterranean Climate Region of Central Chile Productividad y Persistencia de Serradela Amarilla (Ornithopus compressus L. y Biserrula (Biserrula pelecinus L. en la Región Climática Mediterránea de Chile Central

    Directory of Open Access Journals (Sweden)

    Alejandro del Pozo

    2009-09-01

    Full Text Available The production and sustainability of non-irrigated pastures in the Mediterranean climate region of central Chile is currently limited by the low diversity of valuable species and cultivars of annual forage legumes, able to persist in zones with highly variable annual rainfall, and low fertility or poorly drained soils. In this work, DM production, seed yield, hardseededness and pasture persistence were evaluated for cultivars of yellow serradella (Ornithopus compressus L. and biserrula (Biserrula pelecinus L., in field experiments conducted in the subhumid portion of the Mediterranean climate region of Chile. Burr medic (Medicago polymorpha L. and sub clover (Trifolium subterraneum L. were used as a reference plants. A remarkable DM production and seed yield were observed in biserrula (cvs. Mor96 and Casbah, and in some cultivars of yellow serradella (e.g. Madeira, Santorini; biserrula produced by far the largest number of seeds per m². As was expected for species that produce very high levels of hard-seeds, the regeneration of biserrula and serradella was low in second growing season, but plant density and productivity were high in the third growing season. The use of biserrula and serradela in monoculture or in mixture with other annual legumes, either in pasture-crop rotation or permanent pasture, would contribute to the improvement of the prevailing productive systems in the Mediterranean climate region of central Chile.La producción y la sostenibilidad de las praderas de secano en la región de clima mediterráneo de Chile central están actualmente limitadas por la baja diversidad de especies valiosas y cultivares de leguminosas forrajeras anuales, capaces de persistir en zonas con precipitaciones anuales sumamente variables, y suelos de baja fertilidad o de mal drenaje. En este trabajo se evaluó la producción de fitomasa, producción de semilla, dureza seminal y la persistencia de cultivares de serradela amarilla (Ornithopus

  10. A new record of Equus (Mammalia: Equidae from the Late Pleistocene of central-south Chile Un nuevo registro de Equus (Mammalia: Equidae para el Pleistoceno Superior de Osorno, Chile

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    OMAR P RECABARREN

    2011-12-01

    Full Text Available Fourteen dental and bone parts of a horse excavated from the Pilauco paleontological site, Osorno (40°39' S-73°07' W are analysed and interpreted. This site was formed in association with a peat bog located on the banks of the old Damas River and has conserved abundant late Pleistocene mammalian fauna and flora materials. A date of 11457 ± 140 14C yrs B.P. was obtained from a molar and agrees with our stratigraphic age model. We have identified the fossils as pertaining to the species Equus (Amerhippus andium, which confirms its presence in central-south Chile. Furthermore, the recorded geographic location indicate that the metapodial adaptations of the specimens previously described agree with the reconstructed late Pleistocene landscape of Pilauco, dominated by soft volcanic soils and isolated forest patches over large extensions of grasslands.Se analizan e interpretan 14 fósiles correspondientes a dientes y huesos de caballo registrados en el sitio Pilauco, Osorno (40°39' S-73°07' W. El sitio se formó asociado a un pantano en un borde del antiguo río Damas; en él se ha conservado abundante material de mastofauna y flora pleistocénica. Una fecha radiocarbónica de 11457 ± 140 A.P obtenida de un molar, es concordante con el modelo de edad del sitio. La identificación taxonómica permite asociar a los fósiles a la especie Equus (Amerhippus andium, lo que confirma la presencia de la especie en el centro-sur de Chile. Por otra parte, la posición geográfica de los hallazgos y la reconstrucción del paisaje indicarían que se trata de ejemplares cuyas adaptaciones en los metapodios son concordantes para el paisaje pleistocénico de Pilauco dominado por suelos volcánicos blandos, con presencia de bosquetes dispersos en grandes extensiones de praderas de gramíneas.

  11. Seasonal changes in the photosynthetic performance of two evergreen Nothofagus species in south central Chile Cambios estacionales en el desempeño fotosintético de dos especies siempreverdes de Nothofagus en el centro sur de Chile

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    RAFAEL ZÚÑIGA

    2006-12-01

    Full Text Available The evergreen Nothofagus dombeyi and Nothofagus nitida are important members of the temperate Chilean rainforest. They seldom grow together in nature. Nothofagus nitida is more susceptible to excess light and drought than N. dombeyi. We postulate that the different properties of the photosynthetic apparatus under common garden conditions of these species could explain their contrasting habitat preferences. The two species growing in a common garden in south central Chile were studied. The optimal photochemical efficiency (Fv/Fm of both species remained within normal values (»0.8 with the exception of a decrease in N. dombeyi at midday in summer, suggesting reversible reduction in photochemical efficiency of photosystem II (PSII. During summer the effective photochemical efficiency (F PSII, photochemical quenching (qP, photosynthesis (Amax, stomatal conductance (gs and transpiration rates (E in N. dombeyi were higher than in N. nitida. The highest increments in photoprotective pigments (zeaxanthin + antheraxanthin and lutein contents between predawn and midday were obtained in summer in N. dombeyi. In N. nitida a nocturnal retention of dissipative pigments, without a decrease in Fv/Fm, was found in winter. The results suggest that N. dombeyi showed a better photosynthetic performance than N. nitida under high light, high temperature, and drier conditions. These data support are consistent with the pioneer character of N. dombeyi and the semi-tolerant shade properties and more restricted distribution of N. nitida. These photosynthetic characteristics, along with their freezing and flooding resistance differences, may result from their habitat separationLas siempreverdes, Nothofagus dombeyi y Nothofagus nitida, representantes importantes de los bosques lluviosos templados de Chile, raramente crecen juntos en forma natural. Nothofagus nitida es más sensible al exceso de luz y déficit de agua que N. dombeyi. Se postula que diferentes propiedades

  12. Three-dimensional models of P wave velocity and P-to-S velocity ratio in the southern central Andes by simultaneous inversion of local earthquake data

    Science.gov (United States)

    Graeber, Frank M.; Asch, Günter

    1999-09-01

    The PISCO'94 (Proyecto de Investigatión Sismológica de la Cordillera Occidental, 1994) seismological network of 31 digital broad band and short-period three-component seismometers was deployed in northern Chile between the Coastal Cordillera and the Western Cordillera. More than 5300 local seismic events were observed in a 100 day period. A subset of high-quality P and S arrival time data was used to invert simultaneously for hypocenters and velocity structure. Additional data from two other networks in the region could be included. The velocity models show a number of prominent anomalies, outlining an extremely thickened crust (about 70 km) beneath the forearc region, an anomalous crustal structure beneath the recent magmatic arc (Western Cordillera) characterized by very low velocities, and a high-velocity slab. A region of an increased Vp/Vs ratio has been found directly above the Wadati-Benioff zone, which might be caused by hydration processes. A zone of lower than average velocities and a high Vp/Vs ratio might correspond to the asthenospheric wedge. The upper edge of the Wadati-Benioff zone is sharply defined by intermediate depth hypocenters, while evidence for a double seismic zone can hardly be seen. Crustal events between the Precordillera and the Western Cordillera have been observed for the first time and are mainly located in the vicinity of the Salar de Atacama down to depths of about 40 km.

  13. Crustal and Upper Mantle Investigations Using Receiver Functions and Tomographic Inversion in the Southern Puna Plateau Region of the Central Andes

    Science.gov (United States)

    Heit, B.; Yuan, X.; Bianchi, M.; Jakovlev, A.; Kumar, P.; Kay, S. M.; Sandvol, E. A.; Alonso, R.; Coira, B.; Comte, D.; Brown, L. D.; Kind, R.

    2011-12-01

    We present here the results obtained using the data form our passive seismic array in the southern Puna plateau between 25°S to 28°S latitude in Argentina and Chile. In first instance we have been able to calculate P and S receiver functions in order to investigate the Moho thickness and other seismic discontinuities in the study area. The RF data shows that the northern Puna plateau has a thicker crust and that the Moho topography is more irregular along strike. The seismic structure and thickness of the continental crust and the lithospheric mantle beneath the southern Puna plateau reveals that the LAB is deeper to the north of the array suggesting lithospheric removal towards the south. Later we performed a joint inversion of teleseismic and regional tomographic data in order to study the distribution of velocity anomalies that could help us to better understand the evolution of the Andean elevated plateau and the role of lithosphere-asthenosphere interactions in this region. Low velocities are observed in correlation with young volcanic centers (e.g. Ojos del Salado, Cerro Blanco, Galan) and agree very well with the position of crustal lineaments in the region. This is suggesting a close relationship between magmatism and lithospheric structures at crustal scale coniciding with the presence of hot asthenospheric material at the base of the crust probably induced by lithospheric foundering.

  14. Crypsis in early benthic phases of Brachyuran Decapod Crustaceans in central Chile Cripsis en fases bentónicas tempranas de crustáceos decápodos braquiuros en Chile central

    Directory of Open Access Journals (Sweden)

    ÁLVARO T. PALMA

    2003-06-01

    Full Text Available Although common and in some cases of commercial value, little is known about the mechanisms and processes that affect the distribution and abundance of many species of decapod crustaceans, particularly in Chile. All of these species have planktonic larvae that must settle and recruit before becoming part of the adult segments of their populations. For several of these species we have detected the presence of a variety of color morphs in newly settled individuals. The existence of these morphs in Chilean species is comparable with those observed in other latitudes (e.g., coast of the Gulf of Maine. On the other hand, it is characteristic that the occurrence of these patterns only appears during the early juvenile stages and that after reaching a certain size it disappears, with adults being typically monochromatic. The expression of this pattern in the Chilean subtidal seems to be more pronounced in detritivorous species than in carnivorous ones. We propose that the existence of these kind of phenotypic attributes, apparently generalized in brachyuran decapods, could play an important role both from an ecological as well as evolutionary point of viewAunque comunes, y en algunos casos de valor comercial, poco es lo que se conoce acerca de los mecanismos y procesos que afectan la distribución y abundancia de muchas especies de crustáceos decápodos, particularmente en Chile. Todas estas especies poseen larvas planctónicas que deben asentarse y reclutar antes de pasar a formar parte de los segmentos adultos de sus poblaciones. En varias de estas especies hemos detectado la presencia de una variedad de morfos de coloración en individuos recién asentados. La existencia de dichos morfos en especies chilenas es comparable con aquellos observados en otras latitudes (e.g., costa del Golfo de Maine. Por otro lado, es característica la aparición de estos patrones solo durante los estadíos juveniles tempranos y, al alcanzar cierto tamaño, estos

  15. Presencia del tiburón martillo Sphyrna zygaena (Carchariniformes: Sphyrnidae y nuevo registro del tiburón espinudo Echinorhinus cookei (Squaliformes: Squalidae en San Antonio, Chile central Presence of the smooth hammerhead Sphyrna zygaena (Carchariniformes: Sphyrnidae and new records of prickly shark Echinorhinus cookei (Squaliformes: Squalidae in San Antonio, central Chile

    Directory of Open Access Journals (Sweden)

    José L. Brito

    2004-11-01

    Full Text Available Se documenta el registro de Sphyrna zygaena (Linnaeus, 1758, sobre la base de un ejemplar capturado en la bahía de San Antonio (33°35'S y un ejemplar de Echinorhinus cookei Pietschmann, 1928, capturado al oeste de Santo Domingo (33°37'S. En el primer caso, se amplía su distribución geográfica desde Arica hasta San Antonio, y en el segundo, se agrega un quinto registro para esa especie en aguas chilenasThe sighting of Sphyrna zygaena (Linnaeus, 1758 based on the capture of a specimen in the bay of San Antonio (33°35'S and a specimen of Echinorhinus cookei Pietschmann, 1928 captured to the west of the coast of Santo Domingo (33°35'S. The former case, the known geographic distribution is increased from region to the north to San Antonio, in central Chile and in the alter, a fifth sighting is noted for the species in Chilean waters, confirming its presence in the central region of Chile

  16. Use of 137Cs to estimate tillage- and water-induced soil redistribution rates on agricultural land under different use and management in central-south Chile

    International Nuclear Information System (INIS)

    The purpose of this research was to evaluate the applicability of conventional 137Cs sampling and a simplified approach, for estimating medium-term tillage- and water-induced soil erosion and sedimentation rates on agricultural land in Chile. For this purpose, four study sites under contrasting land use and management were selected in central-south Chile. First, a conventional 137Cs approach, based on grid sampling was applied, adapting a mass balance conversion model incorporating soil movement by tillage to the site specific conditions of the study region. Secondly, using the same conversion model, the feasibility of estimating soil redistribution rates from measurements of 137Cs inventories based on composite soil samples taken along contour lines was also tested at all four sites. The redistribution rates associated with tillage and water and the total rates estimated using both methods correlated strongly at all four sites. The conventional method provides more detailed information concerning the redistribution processes operating over the landscape. The simplified method is suitable for assessing soil loss and sediment accumulation in areas exhibiting simple topography and almost similar slopes along the contour lines. Under these conditions, this method permits faster estimation of soil redistribution rates, providing the possibility of estimating soil redistribution rates over larger areas in a shorter time. In order to optimise the costs and benefits of the methods, the sampling and inventory quantification strategy must be selected according to the resolution of the required information, and the scale and complexity of the landscape relief. Higher tillage- and water-induced erosion rates were observed in the annually ploughed cropland sites than in the semi-permanent grassland sites. Subsistence managed crop and grassland sites also show greater erosion effects than the commercially managed sites. The 137Cs methods used permit discrimination between

  17. Distribution of chemical elements in calc-alkaline igneous rocks, soils, sediments and tailings deposits in northern central Chile

    Science.gov (United States)

    Oyarzún, Jorge; Oyarzun, Roberto; Lillo, Javier; Higueras, Pablo; Maturana, Hugo; Oyarzún, Ricardo

    2016-08-01

    This study follows the paths of 32 chemical elements in the arid to semi-arid realm of the western Andes, between 27° and 33° S, a region hosting important ore deposits and mining operations. The study encompasses igneous rocks, soils, river and stream sediments, and tailings deposits. The chemical elements have been grouped according to the Goldschmidt classification, and their concentrations in each compartment are confronted with their expected contents for different rock types based on geochemical affinities and the geologic and metallogenic setting. Also, the element behavior during rock weathering and fluvial transport is here interpreted in terms of the ionic potentials and solubility products. The results highlight the similarity between the chemical composition of the andesites and that of the average Continental Crust, except for the higher V and Mn contents of the former, and their depletion in Mg, Ni, and Cr. The geochemical behavior of the elements in the different compartments (rocks, soils, sediments and tailings) is highly consistent with the mobility expected from their ionic potentials, their sulfates and carbonates solubility products, and their affinities for Fe and Mn hydroxides. From an environmental perspective, the low solubility of Cu, Zn, and Pb due to climatic, chemical, and mineralogical factors reduces the pollution risks related to their high to extremely high contents in source materials (e.g., rocks, altered zones, tailings). Besides, the complex oxyanions of arsenic get bound by colloidal particles of Fe-hydroxides and oxyhydroxides (e.g., goethite), thus becoming incorporated to the fine sediment fraction in the stream sediments.

  18. Air quality forecasting for winter-time PM2.5 episodes occurring in multiple cities in central and southern Chile

    Science.gov (United States)

    Saide, Pablo E.; Mena-Carrasco, Marcelo; Tolvett, Sebastian; Hernandez, Pablo; Carmichael, Gregory R.

    2016-01-01

    Episodic air quality degradation due to particles occurs in multiple cities in central and southern Chile during the austral winter reaching levels up to 300-800 µg/m3 hourly PM2.5, which can be associated with severe effects on human health. An air quality prediction system is developed to predict such events in near real time up to 3 days in advance for nine cities with regular air quality monitoring: Santiago, Rancagua, Curicó, Talca, Chillan, Los Ángeles, Temuco, Valdivia, and Osorno. The system uses the Weather Research and Forecasting with Chemistry model configured with a nested 2 km grid-spacing domain to predict weather and inert tracers. The tracers are converted to hourly PM2.5 concentrations using an observationally based calibration which is substantially less computationally intensive than a full chemistry model. The conversion takes into account processes occurring in these cities, including higher likelihood of episode occurrence during weekends and during colder days, the latter related to increased wood-burning-stove activity for heating. The system is calibrated and evaluated for April-August 2014 where it has an overall skill of 53-72% of episodes accurately forecasted (61-76% for the best initialization) which is better than persistence for most stations. Forecasts one, two, and three days in advance all have skill in forecasting events but often present large variability within them due to different meteorological initializations. The system is being implemented in Chile to assist authority decisions not only to warn the population but also to take contingency-based emission restrictions to try to avoid severe pollution events.

  19. Long-term responses of sandy beach crustaceans to the effects of coastal armouring after the 2010 Maule earthquake in South Central Chile

    Science.gov (United States)

    Rodil, Iván F.; Jaramillo, Eduardo; Acuña, Emilio; Manzano, Mario; Velasquez, Carlos

    2016-02-01

    Earthquakes and tsunamis are large physical disturbances frequently striking the coast of Chile with dramatic effects on intertidal habitats. Armouring structures built as societal responses to beach erosion and shoreline retreat are also responsible of coastal squeeze and habitat loss. The ecological implications of interactions between coastal armouring and earthquakes have recently started to be studied for beach ecosystems. How long interactive impacts persist is still unclear because monitoring after disturbance generally extends for a few months. During five years after the Maule earthquake (South Central Chile, February 27th 2010) we monitored the variability in population abundances of the most common crustacean inhabitants of different beach zones (i.e. upper, medium, and lower intertidal) at two armoured (one concrete seawall and one rocky revetment) and one unarmoured sites along the sandy beach of Llico. Beach morphology changed after the earthquake-mediated uplift, restoring upper- and mid-shore armoured levels that were rapidly colonized by typical crustacean species. However, post-earthquake increasing human activities affected the colonization process of sandy beach crustaceans in front of the seawall. Lower-shore crab Emerita analoga was the less affected by armouring structures, and it was the only crustacean species present at the three sites before and after the earthquake. This study shows that field sampling carried out promptly after major disturbances, and monitoring of the affected sites long after the disturbance is gone are effective approaches to increase the knowledge on the interactive effects of large-scale natural phenomena and artificial defences on beach ecology.

  20. Determination of trace elements in Pre-Hispanic ceramics from Chile's Central Zone using instrumental neutron activation analysis

    International Nuclear Information System (INIS)

    The determination of the element composition in archaeological ceramics is an often unexplored potential, that could provide a unique set of data to verify regional economic and socio-political hypotheses. By chemically defining the elements in these materials, their manufacturing and production centers may be identified, as well as the territorial and social organization of the peoples. Appropriate analytical methodologies for this type of research are limited since there are strict requirements with reference to precision, sensitivity and detection limits, all characteristics that the activation analysis technique provides. The Chilean Nuclear Energy Commission, the University of Chile, the Smithsonian Institution and the International Atomic Energy Agency developed together a cooperative interregional project to promote interdisciplinary research, to resolve archaeological problems and to develop a new application for a nuclear analytical technique. Until this work was undertaken, no systematic studies of trace elements in archaeological ceramics had been done in Chile using the technique of Instrumental Neutron Activation Analysis (INAA). This analytical technique was used in this research to chemically characterize archaeological pieces with the sensitivity, precision and accuracy needed to be able to work with mathematical models that can or cannot establish relationships between the different samples. Protocols were defined first for preparing the pottery samples in order to generate representative samples that could be analyzed by INAA. The homogeneity in preparing the samples used was defined using a group of elements that could be determined by INAA with a precision under 2%. A group of 18 elements was selected and an analytical test procedure was planned that included the type of packaging for the irradiation, the irradiation times, decline and count, the standards to be used and the type of monitor for correcting the neutron flow. The methodology used

  1. Polyphenol content and antioxidant activity of maqui (Aristotelia chilensis Molina Stuntz during fruit development and maturation in Central Chile Contenidos de polifenoles y actividad antioxidante de maqui (Aristotelia chilensis Molina Stuntz durante el desarrollo y maduración de frutos en Chile Central

    Directory of Open Access Journals (Sweden)

    Carolina Fredes

    2012-12-01

    Full Text Available Maqui (Aristotelia chilensis Molina Stuntz, Elaeocarpaceae is a Chilean native species which produces small berries that are mainly collected from the wild. The health benefits of maqui fruit are attributed to their high polyphenol content as well as their wide variety of anthocyanins and flavonols. One of the main factors that affect the polyphenol content in fruit is the maturity stage at harvest. The objective of this study was to determine total phenol and total anthocyanin content and antioxidant activity (by ferric reducing ability of plasma FRAP assay of maqui fruits harvested at different fruit maturity stages from two wild populations located in Central Chile. Each maturity stage was determined by days from fruit set, berry size, and soluble solids. Total phenol content declined while total anthocyanin content increased from the green to light red stage. Nevertheless, both total phenol and anthocyanin content increased from the light red to dark purple stage. The highest anthocyanin content and antioxidant activity was found in the late maturity stage (dark purple. The results show that ripening in maqui fruit can be expected with 1100 growing degree-days (91 d after fruit set in Central Chile. At this moment of harvest, fruits with 18-19 °Brix have the highest anthocyanin content and antioxidant activity (FRAP. This study constitutes the first advances in the understanding of maqui fruit ripening and corresponding antioxidant activity.El maqui (Aristotelia chilensis Molina Stuntz, Elaeocarpaceae es una especie nativa de Chile que produce unas bayas pequeñas que se recolectan principalmente de individuos silvestres. Los beneficios para la salud atribuidos a los frutos de maqui se deben a sus altos contenidos de polifenoles, así como a la gran variedad de antocianos y flavonoles. Uno de los principales factores que afectan el contenido de polifenoles en frutos es el estado de madurez a la cosecha. El objetivo de este estudio fue

  2. Estudio del comportamiento serológico de Actinobacillus pleuropneumoniae (App en planteles porcinos comerciales de la zona central de Chile Serological behaviour study of Actinobacillus pleuropneumoniae (App in commercial swine herds from the central region of Chile

    Directory of Open Access Journals (Sweden)

    D Muñoz

    2008-01-01

    Full Text Available En Chile se ha realizado sólo un estudio en Actinobacillus pleuropneumoniae (App. Este trabajo pretende determinar la duración de la inmunidad materna, la edad de seroconversión y la prevalencia aparente y verdadera en 7 planteles de cerdos comerciales. Se obtuvieron 60 muestras por plantel, divididas en 10 muestras de suero, de animales de 4, 6, 10, 14,18 y 21 semanas de edad, y analizadas a través de un kit ELISA® comercial. De las 420 muestras se detectaron 134 positivas, de las cuales 112 correspondían a cerdos menores de 10 semanas y sólo 22 provenían de animales mayores de 10 semanas, que seroconvirtieron probablemente debido a una infección de campo. La caída de la inmunidad materna fue alrededor de la 10ª semana de edad. En cuanto a la seroconversión, se observó que a partir de la 18* semana comenzaron a aparecer los animales con anticuerpos circulantes propios. Dos de los siete planteles no seroconvirtieron. Además, dos presentaron una seroconversión igual o superior al 50% a las 18 semanas. La seroprevalencia aparente de App fue de 10,48%, mientras que prevalencia verdadera, mediante dos métodos estadísticos, fue de 9,6% (IC: 7,6% y 11,7% y 10,67% respectivamente. En este trabajo se encontró que la prevalencia es similar a la observada en EE.UU., debido presumiblemente al sistema de producción y a los serotipos que están presentes en ambos países. Por otro lado, si bien la mayoría de los planteles seroconvierten luego de la caída de la inmunidad materna, se observaron diferentes patrones serológicos entre ellos.In Chile, there was only one existing study on App. This study was designed to determine the maternal immunity duration, the age of seroconversion and the apparent and true prevalence in animals from 7 swine commercial herds. 60 samples were taken per herd and divided into 10 serum samples from animals of 4, 6,10,14,18and21 weeks of age, which were analyzed by ELISA®. Out of the 420 samples, 134 were

  3. Breeding distribution and abundance of seabirds on islands off north-central Chile Distribución reproductiva y abundancia de aves marinas en islas del norte y centro de Chile

    Directory of Open Access Journals (Sweden)

    ALEJANDRO SIMEONE

    2003-06-01

    Full Text Available Between 1999 and 2003 we collected information on the breeding distribution and abundance of 12 seabird species occurring on nine islands off the coasts of north and central Chile (27°-33°S. The Peruvian booby Sula variegata was the most abundant seabird with a breeding population of ca. 18,000 pairs concentrated in two islands, followed by the Humboldt penguin Spheniscus humboldti with ca. 9,000 pairs, the largest colony being at Chañaral Island with ca. 7,000 pairs. Kelp gulls Larus dominicanus bred at all the surveyed sites in colonies of variable size, ranging from 40 to 2,000 pairs. Peruvian diving-petrels Pelecanoides garnotii and Peruvian pelicans Pelecanus occidentalis bred at restricted sites, but generally in large colonies. Magellanic penguins Spheniscus magellanicus, wedge-rumped storm-petrels Oceanodroma tethys, Neotropical cormorants Hypoleucos brasiliensis, guanay cormorants Leucocarbo bougainvillii, red-legged cormorants Stictocarbo gairmardi, band-tailed gulls Larus belcheri and Inca terns Larosterna inca nested at few sites forming small colonies (from a few to 150 pairs. Two new breeding sites are reported for the Peruvian diving-petrel and nesting of the wedge-rumped storm-petrel is confirmed on the Chilean coast for the first time. Despite protective status, most of the islands showed human disturbance, derived mainly from guano harvesting, egging and tourism. On at least five of these islands we were able to confirm introduced mammals including rats, rabbits and cats. These factors are likely to be detrimental to seabirds and thus demand detailed assessment. Further comprehensive ornithological surveys in other areas are needed so as to improve the scarce knowledge that we currently have on the seabird populations along the Chilean coast

  4. Fungal parasites infect marine diatoms in the upwelling ecosystem of the Humboldt current system off central Chile.

    Science.gov (United States)

    Gutiérrez, Marcelo H; Jara, Ana M; Pantoja, Silvio

    2016-05-01

    This is the first report of fungal parasitism of diatoms in a highly productive coastal upwelling ecosystem, based on a year-round time series of diatom and parasitic Chytridiomycota abundance in the Humboldt Current System off Chile (36°30.80'S-73°07.70'W). Our results show co-variation in the presence of Skeletonema, Thalassiosira and Chaetoceros diatoms with attached and detached chytrid sporangia. High abundance of attached sporangia was observed during the austral spring, coinciding with a predominance of Thalassiosira and Skeletonema under active upwelling conditions. Towards the end of austral spring, a decreasing proportion of attached sporangia was accompanied by a decline in abundance of Skeletonema and Thalassiosira and the predominance of Chaetoceros, suggesting specificity and host density dependence of chytrid infection. The new findings on fungal parasitism of diatoms provide further support for the inclusion of Fungi in the current model of the role played by the marine microbial community in the coastal ocean. We propose a conceptual model where Fungi contribute to controlling the dynamics of phytoplankton populations, as well as the release of organic matter and the transfer of organic carbon through the pelagic trophic web in coastal upwelling ecosystems. PMID:26914416

  5. Mujeres de los Andes

    OpenAIRE

    Arango, Luz Gabriela; Arizabaleta de García, María Teresa; Bejarano, Nilse; Borchart de Moreno, Christiana; Bucheli, Rocío Vaca; Cervantes, Elvira Llanos; Cisneros, Tatiana; Defossez, Anne-Claire; Fassin, Didier; Giraldo, Fernando Urrea; Li, Dina; Malaver, José; Montúfar, Verónica; Moscoso, Martha; Ortega, Diego Zapata

    2016-01-01

    El Seminario "Mujeres De Los Andes: Condiciones De Vida Y Salud" tuvo lugar en la ciudad de Quito, del 6 al 10 de junio de 1991. Reunió investigadores de distintas disciplinas académicas y actores de variados campos, de cuatro países del área andina-Bolivia, Colombia, Ecuador y Perú-, en los cuales está presente el Instituto Francés de Estudios Andinos, principal instigador del evento. Este libro, que reúne la mayor parte de las ponencias en él presentadas, se inscribe en la línea de las corr...

  6. Sedimentology, paleontology and age of the Ayacara and Lago Ranco formations (south-central Chile, 40°- 42°S). Tectonic implications.

    Science.gov (United States)

    Encinas, Alfonso; Zambrano, Patricio; Bernabe, Pablo; Finger, Kenneth; Buatois, Luis; Duhart, Paul; Valencia, Victor; Fanning, M.; Herve, Francisco

    2010-05-01

    Deep-marine, Mio-Pliocene strata correlative with the Navidad Formation crop out in different areas along the forearc of south-central Chile (~34°-41°) and have also been recognized in boreholes drilles on the continental shelf. However, at Lago Ranco (40°S) and Ayacara (42°) there are outcrops of marine strata whose age and correlation with these units remain uncertain. These deposits consist of rhythmic successions of sandstone and siltstone representing facies similar to those of the Navidad and correlative formations. These marine successions are known ase the Estratos de Lago Ranco and Ayacara formations. They both crop out in the western Andean Cordillera near the limit with the Intermediate Depression at Lago Ranco and the submerged equivalent of this physiographic unit at Ayacara. There are very few studies carried out on these units and most of them consist on internal reports and unpublished theses.In order to unravel the sedimentary enviroment, age and tectonic history of this area during the Neogene we carried out sedimentological, ichnological and micropaleontological studies. In addition, we carried out U-Pb dating in detrital zircons (LAICPMS and SHRIMP). Our studies show the presence of sedimentary features and ichnofacies typical of deposition in a deep-marine environment for these units..In agreement, benthic foraminifers (Ciclamina incisa and Siphonodosaria sangrinensis) indicate lower bathial depths (1500 m). U-Pb (LAICPMS and SHRIMP) indicate a maximum depositional age of around 20 Ma for these units. In agreement, the occurrence of the planktic foraminifer species Globorotalia siakensis (P22-N14), Globigerinoides quadrilobatus (N6-Recent) and Globigerinoides sikanus (N8-N9) in strata of the Ayacara Formation suggest an early-middle Miocene age for this unit. These data indicate that the area corresponding to the western Main Andean Cordillera in south central Chile, was subjeted to major subsidence during the early-middle Miocene. Major

  7. Estructura comunitaria de diatomeas presentes en los sedimentos superficiales de ocho lagos andinos de Chile central Diatoms community structure in superficial sediments of eight Andean lakes of central Chile

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    INGRID E ALVIAL

    2008-03-01

    Full Text Available En este trabajo se analizó la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontró un total de 99 taxa de diatomeas, distribuidos en 48 géneros. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepción de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que están descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composición florística de diatomeas. De esta manera, en los ensambles diatomológicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueño y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentónicas, típicas de aguas oligotróficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomológicos de los lagos Galletué, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctónicas, características de aguas alcalinas y mesotróficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibbaIn this research the taxonomic structure of diatoms in sediments of high mountain lakes was studied. These lakes are located in Chile between 32°49' and 38°48' S in the Andean Cordillera. A total of 99 diatom taxa distributed in 48 genera were identified and all this taxa are cosmopolitan excepting a Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis and Pinnularia acidicola, which are know only for the Southern Hemisphere. The assemblages of diatoms were different in the studied lakes. So the high mountain lakes Ocho, Huifa, Ensueño and Negra, dominated benthic diatoms which are typical of oligotrophic and acid waters as Achnanthidium

  8. Synchronous degassing patterns of the neighbouring volcanoes Llaima and Villarrica in south-central Chile: the influence of tidal forces

    Science.gov (United States)

    Bredemeyer, Stefan; Hansteen, Thor H.

    2014-10-01

    The neighbouring volcanoes Villarrica and Llaima are two of the most active volcanoes in Chile and both currently degas continuously. We present a semi-continuous time series of SO2 fluxes for Villarrica and Llaima volcanoes. The time series was obtained using five scanning Mini-Differential Optical Absorption Spectrometers (Mini-DOAS, UV spectrometers) over 6 months (13 February to 31 July 2010) and is based on 6,829 scans for Villarrica and 7,165 scans for Llaima. Statistical analyses of the SO2 flux time series reveal a periodicity of degassing maxima about every 7 days, and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes. Intra-day variations in SO2 fluxes also show a striking correlation between Villarrica and Llaima. All these patterns correlate well with the trend of the modelled solid Earth tide curves, where the 7-day degassing maxima correspond with both the fortnightly tidal maxima and minima. The intra-day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle, and further with semidiurnal minima in atmospheric pressure, a phenomenon we refer to as "the tidal pump". As there is little time lag between the tidal action and the changes in degassing rates, we infer that degassing at both volcanoes is controlled by conduit convection, involving physical separation between gas and magma at comparatively shallow levels. Variations in daily degassing rates were up to a factor of ca. 12 and 10 for Villarrica and Llaima, respectively, without any noticeable changes in the periodicity. We thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation.

  9. Valinia INIA, a New Early Storage Onion Variety for Central South Chile Valinia INIA, una Nueva Variedad de Cebolla de Guarda Precoz para la Zona Centro Sur de Chile

    Directory of Open Access Journals (Sweden)

    María Inés González A

    2012-03-01

    Full Text Available In Central South Chile, storage onion varieties (Allium cepa L. sold domestically usually begin the maturation process in March, which implies that a large proportion of bulbs do not mature adequately and do not resist prolonged storage. This situation led the Quilamapu vegetable program of the Instituto de Investigaciones Agropecuarias INIA to select an early maturing onion variety. This breeding method involved a recurrent selection with free plant crossing that began in 1994 on a population of 2000 plants of the 'Valenciana' commercial variety. Plants were first selected when they reached physiological maturity (tops down before 28 February, and then for shape, size, storage capacity, and single-centered bulbs. The result of the program was 'Valinia INIA', a type of Valenciana onion variety: early maturing, medium-sized bulb, spherical, yellow, and resistant to sprouting during storage. From the 2001-2002 to the 2008-2009 season, variety assays were carried out to compare 'Valinia INIA' with commercial cultivars, i.e., 'Sintética 14', 'Grano de Oro', and 'Valenciana Cobra'. 'Valinia INIA' precocity exceeded the other varieties in all seasons with a mean of 1.5 wk ahead of 'Sintética 14', which is the earliest commercial variety and more than 2 wk ahead of the other two. Its yield is similar to 'Valenciana Cobra' and higher than the other two varieties. Its storage capacity is similar to 'Grano de Oro' and 'Sintética 14', but greater than 'Valenciana Cobra'.En la zona centro sur de Chile es habitual que las variedades de cebolla (Allium cepa L. de guarda que se comercializan en el pais inicien el proceso de maduración preferentemente en marzo, lo que conlleva a que una gran proporción de bulbos no madure adecuadamente, no resistiendo el almacenaje por un tiempo prolongado. Esta situación llevó al programa de hortalizas del Instituto de Investigaciones Agropecuarias INIA Quilamapu a la selección de una variedad de cebolla de madurez

  10. Fecal Contamination of Groundwater in a Small Rural Dryland Watershed in Central Chile Contaminación Fecal en Agua Subterránea en una Pequeña Cuenca de Secano Rural en Chile Central

    Directory of Open Access Journals (Sweden)

    Mariela Valenzuela

    2009-06-01

    Full Text Available Research on microbiological groundwater quality was conducted in Chile in a rural watershed that has almost no other water source. Forty-two wells were randomly selected and levels of indicator bacteria - total coliforms (TC, fecal coliforms (FC, and fecal streptococci (FS - were repeatedly measured during the four seasons of 2005. The aim of this study was to characterize microbiological groundwater quality, relate indicator levels to certain watershed features and management characteristics which are likely to affect water quality. The dynamics of seasonal temporal contamination was determined with statistical analyses of indicator organism concentrations. Nonparametric tests were used to analyze relationships between bacterial indicators in well water and other variables. TC, FC, and FS were found in all samples indicating the wells had been contaminated with human and animal fecal material. The frequency distribution of microorganisms fitted a logistic distribution. The concentrations appeared to be temporal and levels varied between seasons with higher concentrations in winter. The cause of contamination could be linked to the easy access of domestic animals to the wells and to the permeable well casing material. Local precipitation runoff directly influenced the bacterial concentrations found in the wells.Se realizó una investigación de la calidad microbiológica de las aguas subterráneas en una cuenca rural chilena. En esta cuenca prácticamente no había otra fuente de agua disponible. En 42 pozos seleccionados al azar, se midieron niveles de bacterias indicadoras en cuatro temporadas distintas durante el año 2005. Las bacterias incluyeron coliformes totales (TC, coliformes fecales (FC y Estreptococos fecales (FS. El objetivo fue caracterizar la calidad microbiológica del agua subterránea y relacionar los indicadores con ciertas propiedades y el manejo de la cuenca que pueden afectar la calidad del agua. La dinámica temporal de la

  11. Reactivation episodes of the romeral fault system in the northwestern part of central andes, colombia, through 39ar-40ar and k-ar results

    OpenAIRE

    VINASCO VALLEJO, CESAR JAVIER; Cordani, Umberto

    2013-01-01

    Direct dating of reactivation of the San Jerónimo Fault (SJF), easternmost limit of the Romeral fault system (RFS), is presented through 39Ar-40Ar and K-Ar results in neo-formed micas and mylonitic bands of strongly hidrothermalized gabbros. Published cooling and crystallization ages from sin-tectonic magmatic rocks exposed in the western fl ank of the Central Cordillera have suggest that tectonic evolution of the paleo-fault system began since Triassic and Lower Jurassic before the installat...

  12. The relation of the mid-Tertiary coastal magmatic belt in south-central Chile to the late Oligocene increase in plate convergence rate

    Directory of Open Access Journals (Sweden)

    Jorge Muñoz

    2000-12-01

    Full Text Available The mid-Tertiary Coastal Magmatic Belt in south-central Chile, which crops out both in the Central Valley and, south of 41°S, in the Coastal Cordillera as far west as the Pacific coast, formed when the locus of Andean magmatic activity expanded, both to the west and to the east relative to its previous and current location in the Main Cordillera. This expansion of the magmatic arc occurred in conjunction with a regionally widespread episode of late Oligocene to Miocene extension which thinned the crust below the proto-Central Valley in south-central Chile and generated sedimentary basins west of, within, and east of the Main Cordillera. The extrusive rocks of the mid-Tertiary Coastal Magmatic Belt are interbedded with the late Oligocene to Miocene continental and marine sediments deposited in these basins, and forty-seven of the fifty new and previously published age determinations for these rocks are within the time period 29 Ma (late Oligocene to 18.8 Ma (early Miocene. The initiation of extension, basin formation and the westward migration of magmatic activity coincides closely to the beginning, in the late Oligocene, of the current period of both high convergence rate (>10 cm/yr and less oblique convergence, which together resulted in an approximately three-fold increase in trench-normal convergence rate between the Nazca and South American plates. Extension continued, along with a transient steepening of subduction angle as indicated by the westward migration of the volcanic front during the formation of the mid-Tertiary Coastal Magmatic Belt, during an approximately 10 million year period after the trench-normal convergence rate tripled across the Nazca and South American plate boundary. The mid-Tertiary Coastal Magmatic Belt includes igneous rocks chemically similar to modern Andean arc magmas, as well as rocks with ocean island basalt chemical affinities characterised by lower Ba/La (+5. The latter formed by melting of mantle

  13. Application of stable isotopes to evaluate groundwater recharge of a coastal aquifer in North-Central Chile and its role in vegetation dynamics

    International Nuclear Information System (INIS)

    The understanding of the water sources for plant growth is one of the key elements to evaluate the present and long term primary productivity in arid ecosystems. We use stable isotope tools to evaluate the recharge mechanisms in a coastal aquifer located in the arid zone of north-central Chile. The main water sources in the study area, fog, rain and groundwater, were isotopically characterized over a decade. The isotope data confirmed that fog does not play any role in groundwater recharge. The water table and isotope data showed that during low water conditions (dry periods), the aquifer is maintained primarily by water recharged in the higher part of the Romeral basin. During high water table conditions (wet periods), recharge associated with local precipitation becomes a significant source of groundwater recharge. The aquifer responded very fast to rains with amounts over the average level for precipitation (like El Nino conditions), while no recharge was detected with precipitation events lower than the average value for precipitation. The recharge pattern can also influence the behavior of plants characterized by a dimorphic root systems than can perform hydraulic redistribution. Part of the fast recharge of the aquifer could be related to this water redistribution. (author)

  14. Patrón de asentamiento durante el periodo Alfarero en la cuenca de Santiago, Chile Central: Una mirada a la escala local Settlement pattern during the early Ceramic period in the Santiago basin, Central Chile: A view at the local level

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    Luis Cornejo

    2012-11-01

    Full Text Available Se presentan y discuten la metodología y los resultados de prospecciones superficiales de alta intensidad realizadas en el extremo meridional de la cuenca de Santiago, poniendo énfasis en una escala de análisis hasta ahora no considerada en la arqueología de Chile Central, que es el estudio sistemático de la localidad. Los resultados muestran que el patrón de asentamiento denota una alta concentración de ocupaciones domésticas del periodo Alfarero temprano, continuadas más tardíamente pero con menor intensidad. Estas ocupaciones resultan estar vinculadas a la disponibilidad en esta localidad de recursos de aguas superficiales y reflejarían una forma de ocupar el espacio definida por unidades domésticas dispersas que en sus cercanías tendrían a otras unidades sociales no necesariamente vinculadas socialmente.This paper presents the methodology and results of intensive surface surveys carried out in the southern Santiago Basin, focused on the locality, a scale of analysis not previously undertaken in archeological studies of Central Chile. The settlement pattern point out to a high concentration of Early Ceramic Period domestic occupations, followed by less intense occupations during the Late Ceramic Period. These occupations were linked to the availability in this locality of surface water resources and reflect a way of occupying space defined by scattered domestic units , in whose vicinity were other domestic units, although not necessarily connected socially.

  15. Deformación frágil de los depósitos neógenos de la cuenca de Navidad (Cordillera de la Costa, 34°S, Chile central Brittle deformation of the Neogene deposits of the Navidad Basin (Coastal Cordillera, 34°S, central Chile

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    Alain Lavenu

    2005-07-01

    Full Text Available En la cuenca neógena de Navidad, situada en la Cordillera de la Costa de Chile central (~34°S, se identificaron una serie de deformaciones frágiles que fueron generadas durante el Mioceno Tardío y el Plioceno. A partir del análisis numérico de planos de microfallas y sus estrías, se determinaron las direcciones principales de los esfuerzos producidos por diversos eventos tectónicos extensionales y compresivos. Los resultados obtenidos en la cuenca de Navidad permiten concluir que durante el Mioceno Tardío-Plioceno Temprano se produjo una extensión con dirección desconocida. Posteriormente, una deformación extensional, de dirección aproximada este-oeste, afecta a esta zona durante todo el Plioceno. Durante esta época se produce un corto pulso tectónico compresivo de dirección este oeste. A pesar de este evento compresivo la cuenca marina de Navidad se desarrolló esencialmente en un ambiente tectónico extensional durante todo el NeógenoIn the Neogene Navidad Basin, located in the Coastal Range of central Chile (34°S, a series of brittle deformations generated during the Late Miocene and Pliocene, were observed. Based on the numerical analysis of microfault planes and their slickensides, the main stress directions, caused by various extensional and compressive tectonic events, were determined. Results obtained in the Navidad Basin indicate that an extension of unknown direction occurred during the Late Miocene-Early Pliocene. Thereafter, extensional deformation orientated approximately east-west, affected this zone during the whole of the Pliocene. During this epoch a short east-west compressive pulse occurred. In spite of this compressive event, the marine Navidad Basin developed essentially in an extensional tectonic regime during the entire Neogene

  16. Talla de madurez y época de desove de la reineta (Brama australis Valenciennes, 1836 en la costa central de Chile Maturity size and spawning time of the Pacific pomfret (Brama australis Valenciennes, 1836 in the central coast of Chile

    Directory of Open Access Journals (Sweden)

    Elson Leal

    2003-01-01

    Full Text Available La reineta (Brama australis adquiere cada vez mayor importancia en los desembarques de la pesca artesanal, no obstante, es escasa la información que existe acerca de su biología básica, particularmente sobre su dinámica reproductiva. En este trabajo se determina la época principal de desove de B. australis en la costa central de Chile y la talla de madurez (TM, para lo cual se analizó un total de 1061 individuos capturados frente a Lebu (37º37'S-73º40'W, entre enero y septiembre de 2001. El análisis macroscópico de los ovarios, mostró ejemplares sexualmente maduros durante todo el período de muestreo. El Indice Gonadosomático (IGS presentó fluctuaciones que indican un extenso período de desove, con un máximo invernal (junio-agosto. La TM se calculó a partir del método de longitud del 50% de hembras maduras a los 36,9 cm longitud horquilla (LH, con intervalo de confianza entre 35,3 y 37,8 cm y en 39 cm LH mediante el método del Incremento Relativo del IGS (IR.IGS. Debido a que las capturas ocurrieron principalmente en ejemplares sobre 39 cm LH, la flota estaría extrayendo mayoritariamente peces madurosLandings of Pacific pomfret (Brama australis is acquiring an increasing importance to the Chilean artisanal fishery. However, lack of information regarding its basic biology, in particular, reproductive dynamics, still persists. In this work we determine the spawning season of B. australis in the central coast of Chile and the length of maturity (LM. A total of 1061 individuals captured in the coastal zone of Lebu (37°37'S-73°40'W, Chile, between January and September 2001, were analyzed. Macroscopic analysis of ovaries, showed sexually mature individuals throughout the sampling period. Gonadosomatic Index (IGS showed fluctuations indicative of extensive spawning periods, with a maximum in the austral winter season (June-August. LM of females was estimated with the length at 50% maturity method, in 36.9 cm fork length (LH, with

  17. Effects of massive wind power integration on short-term water resource management in central Chile - a grid-wide study

    Science.gov (United States)

    Haas, J.; Olivares, M. A.; Palma, R.

    2013-12-01

    In central Chile, water from reservoirs and streams is mainly used for irrigation and power generation. Hydropower reservoirs operation is particularly challenging because: i) decisions at each plant impact the entire power system, and ii) the existence of large storage capacity implies inter-temporal ties. An Independent System Operator (ISO) decides the grid-wide optimal allocation of water for power generation, under irrigation-related constraints. To account for the long-term opportunity cost of water, a future cost function is determined and used in the short term planning. As population growth and green policies demand increasing levels of renewable energy in power systems, deployment of wind farms and solar plants is rising quickly. However, their power output is highly fluctuating on short time scales, affecting the operation of power plants, particularly those fast responding units as hydropower reservoirs. This study addresses these indirect consequences of massive introduction of green energy sources on reservoir operations. Short-term reservoir operation, under different wind penetration scenarios, is simulated using a replica of Chile's ISO's scheduling optimization tools. Furthermore, an ongoing study is exploring the potential to augment the capacity the existing hydro-power plants to better cope with the balancing needs due to a higher wind power share in the system. As reservoir releases determine to a great extent flows at downstream locations, hourly time series of turbined flows for 24-hour periods were computed for selected combinations between new wind farms and increased capacity of existing hydropower plants. These time series are compiled into subdaily hydrologic alteration (SDHA) indexes (Zimmerman et al, 2010). The resulting sample of indexes is then analyzed using duration curves. Results show a clear increase in the SDHA for every reservoir of the system as more fluctuating renewables are integrated into the system. High

  18. Hábitos alimentarios de Dosidicus gigas (D' Orbigny, 1835 (Cephalopoda: Teuthoidea frente a la costa centro-sur de Chile Feeding habits of Dosidicus gigas (D'Orbigny, 1835 (Cephalopoda: Teuthoidea in the central-south coast off Chile

    Directory of Open Access Journals (Sweden)

    PATRICIO ULLOA

    2006-12-01

    Full Text Available Se estudiaron los hábitos alimentarios del calamar rojo Dosidicus gigas (D'Orbigny, 1835 frente a la costa de Chile centro-sur, durante el invierno del año 2005. Se examinaron un total de 52 estómagos, en todos los cuales había contenido alimentario. Los ejemplares provenían de pescas efectuadas por la flota arrastrera industrial que opera entre 36°39' S y 38°55'S sobre la merluza común Merluccius gayi (Guichenot 1848 y a una profundidad media de 290 m sobre la plataforma continental. Para la descripción del espectro trófico, alimento principal y el establecimiento de las eventuales diferencias sexuales u ontogenéticas en la frecuencia de aparición de los ítemes presa, se utilizaron los métodos numérico, gravimétrico, de frecuencia de ocurrencia, índice de importancia relativa (IIR e índice de similitud porcentual (ISP. No se observaron diferencias sexuales ni ontogenéticas en la frecuencia de aparición de los ítemes presa. Los resultados muestran que D. gigas es un depredador oportunista, principalmente ictiófago, y secundariamente malacófago (incluye el canibalismo y carcinófago. Se discuten los eventuales motivos e implicancias de tal conductaA study on the feeding habits of the jumbo squid Dosidicus gigas (D'Orbigny, 1835 was carried out during the winter season 2005, in waters of the Chilean central and southern Pacific. A total of 52 jumbo squid stomachs from the fishing of the continental slope were collected and examined, in the Eighth and Ninth regions, between 36°40' S and 38°55'S, at an average depth of 290 m. To determine the trophic spectrum, the feeding preferences and the importance of the sex and ontogenetic condition in the diet, the numeric, gravimetric, frequency of occurrence methods, and the index of relative importance and dietary similarity were utilized. The frequency of the prey did not vary with relation to the sex and ontogenetic conditions, and was besides a hight trophic similarity in such

  19. Water Erosion Prediction Using the Revised Universal Soil Loss Equation (RUSLE in a GIS Framework, Central Chile Estimación de la Erosión Hídrica Empleando la Ecuación Universal de Pérdida de Suelo Revisada (RUSLE y SIG en Chile Central

    Directory of Open Access Journals (Sweden)

    Carlos A Bonilla

    2010-03-01

    Full Text Available Soil erosion is a growing problem in Central Chile, particularly in coastal dry lands, where it can significantly decrease the productivity of rainfed agriculture and forestry. In this study, the Revised Universal Soil Loss Equation (RUSLE was integrated into a Geographic Information System (GIS, and used to evaluate the effects of different combinations of vegetative cover on soil erosion rates for Santo Domingo County in Central Chile. Implementing RUSLE in the GIS required a complete description of the county’s soils, climate, topography and current land use/land cover. This information was compiled in rasters of 25 x 25 m cells. RUSLE parameter values were assigned to each cell and annual soil loss estimates were generated on a cell by cell basis. Soil losses were estimated for the current and for three alternate scenarios of vegetative cover. Under current conditions, 39.7% of the county is predicted to have low erosion rates ( 1.1 t ha-1 yr-1. The remainder of the surface (10.2% is not subject to erosion. Under the recommended alternate scenario, 89.3% of the county is predicted to have low erosion rates, and no areas are affected by high soil loss, reducing soil erosion to a level that will not affect long term productivity. This paper describes how RUSLE was implemented in the GIS, and the methodology and equations used to evaluate the effects of the land use/land cover changes.La erosión hídrica es un problema creciente en la Zona Central de Chile, especialmente en el Secano Costero, donde reduce la productividad de los suelos agrícolas y forestales. En este trabajo se empleó la Ecuación Universal de Pérdida de Suelo Revisada (RUSLE integrada a un Sistema de Información Geográfica (GIS para evaluar el efecto de distintas combinaciones de cubierta vegetal en las tasas de erosión en la comuna de Santo Domingo, Chile. La implementación de RUSLE en el GIS requirió la caracterización de suelos, clima, relieve y uso actual del

  20. Field study and three-dimensional reconstruction of thrusts and strike-slip faults in the Central Andes: implications for deep-seated geothermal circulation and ore deposits exploration

    Science.gov (United States)

    Norini, Gianluca; Groppelli, Gianluca; Giordano, Guido; Baez, Walter; Becchio, Raul; Viramonte, Jose; Arnosio, Marcelo

    2014-05-01

    The Puna plateau (NW Argentina), located in the back-arc of the Central Andes, is a plateau characterized by both orogen-parallel and orogen-oblique deformation styles, extensive magmatic and geothermal activity, and the broad occurrence of igneous and hydrothermal ore-forming minerals. In this area, like in other convergent margins, the behaviour of the magma-tectonics interplay can affect the circulation of hydrothermal fluids, so that the full comprehension of the tectonic control on the magmas and fluids paths in the continental crust is crucial to plan the geothermal and ore exploration. In this study, we present a structural analysis of the back-arc portion of the orogen-oblique Calama-Olacapato-El Toro fault system and the surrounding orogen-parallel thrust faults in the central-eastern Puna Plateau, comprising the Cerro Tuzgle-Tocomar geothermal volcanic area, with high geothermal potential, and silicic calderas and domes associated with epithermal ore deposits. We also focused on the tectonic and volcanotectonic structures of the Chimpa and Tuzgle stratovolcanoes, two of the most important polygenetic volcanic centres of the plateau. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the tectonic structures of the studied area. These data and the available stratigraphic and geophysical data have been integrated with the software MOVE and PETREL in a three-dimensional reconstruction of the main fault planes, showing their attitude and intersections at depth. As a result of our study, we show that despite different geometry and kinematics of the Calama-Olacapato-El Toro fault system and the thrust faults, they formed and evolved under the same progressive evolving dynamic state, forming a single tectonic system and accommodating crustal shortening of a thickened crust. In this frame, the crust underwent simultaneous deformation along both the low-angle thrust faults and the vertical transcurrent strike-slip faults

  1. K-Ar geochronologic evidence for a triassic metamorphic event in the main Chiloe Island, south-central Chile

    International Nuclear Information System (INIS)

    Pioneers geological reconnaissance studies in the Chiloe Archipelago recognised a Palaeozoic metamorphic basement (Saliot, 1969; Watters and Fleming, 1972; Valenzuela, 1982; Valdivia, 1986). Currently in progress geologic studies (Munoz et al., 1999, Duhart et al., 2000; Antinao et al., 2000) interpreted these rocks as part of the Bahia Mansa Metamorphic Complex (Duhart et al., 2000), well exposed to the north and equivalent to the 'Serie Occidental' (Aguirre et al., 1972). Geochronologic data set indicate that this complex evolved during Devonian to Triassic times. In the main Chiloe Island, this metamorphic complex is mainly conform by metasedimentary and metavolcanic rocks covered by Tertiary sedimentary and volcanic rocks and Quaternary glacial, fluvial, estuarine, beach, eolian and fluvial deposits. According to north-west and north-south lineament observed in satellite images, regional magnetic maps and topographic features, the main Chiloe island have been divide in northern, central and southern segments (Munoz et al., 1999). These lineaments are interpreted as regional faults but their ages and cinematic are not well constrained. The central segment was interpreted as an uplifted tectonic block and recent studies in the northern part of this segment have identified an intrusive body herein named as 'Metalqui Pluton'. Although the age of this pluton is unknown yet, Cretaceous intrusive rocks in the same tectonic setting of the Metalqui Pluton have been reported in the Valdivia area (Munizaga et al., 1988; Duhart et al., 1998). Previous U-Pb radiometric ages for detrital zircons from pelitic schists in the northern segment indicated a maximum sediment deposition age during Early to Middle Devonian (Duhart et al., 1999). Also, Triassic K-Ar and 40Ar/39Ar ages have been determined for the main metamorphic and tectonic event. This contribution report Triassic K-Ar ages for the central segment and discuss their regional significance (au)

  2. Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

    Science.gov (United States)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-08-01

    Powerful subduction zone earthquakes rupture thousands of square kilometres along continental margins but at certain locations earthquake rupture terminates. To date, detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 2015 September 16, the Mw 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here, we analyse the temporal and spatial pattern of the coseismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hr after the main shock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km hr-1. At the southern rupture boundary, aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area, aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic-aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

  3. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

    International Nuclear Information System (INIS)

    Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were undertaken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32o and 34oS. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Meson Alto massif), 10.3±0.2 Ma (La Gloria pluton), 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock) and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith). Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32oS, slightly younger mineralized porphyries at Rio Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758- 0.512882), plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf-data variation for the younger age group (10-12 Ma; 7.04-9.54) and show a more scattered range for the older one (14-15 Ma; 8.50-15.34); both sets plot between the DM and CHUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Rio Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening across the NE

  4. PETROGENESIS OF THE METACARBONATE AND RELATED ROCKS OF THE SILGARÁ FORMATION, CENTRAL SANTANDER MASSIF, COLOMBIAN ANDES: AN OVERVIEW OF A “REACTION CALCIC EXOSCARN”

    Directory of Open Access Journals (Sweden)

    Castellanos O.M

    2008-06-01

    Full Text Available Metacarbonate rocks (pure and impure marbles, carbonate-silicate rocks, calc-silicate rocks and carbonate-bearing silicate rocks form a very complex group within the metamorphic sequence of the Silgará Formation at the central Santander Massif (CSM. These rocks are interpreted as derived from a sedimentary sequence (including limestones and dolostones, carbonate-bearing mudstones,  sandstones, tuffaceous and evaporitic sediments and marlstones overprinted by near-isochemical regional metamorphism. They usually appear as scarce intercalations from millimeter up to meter scale, within the high-grade pelitic rocks, in the lower part of the metamorphic section, although the proportion of metacarbonate rocks can be higher and different marble layers are exploited. We report for the first time the occurrence of a "reaction calcic exoskarn", which corresponds to
    such metacarbonate rocks, taking into account that a skarn can be developed during regional metamorphism and by different metasomatic processes, adjacent to intrusive bodies, along faults and shear zones, and what defines these rocks as a skarn is its mineralogy, which includes a variety of calc-silicate and associated minerals, usually dominated by garnet and pyroxene. Therefore, this paper focus attention to the occurrence of metacarbonate and
    related rocks, which occurs as small scale reactions zones that show a gradational contact from garnet-bearing pelitic rocks to marbles or carbonate-silicate rocks, giving particular interest to the calc-silicate rocks, which are characterized by the presence of elongated grains of banded clinopyroxene (diopside and scapolite and massive
    or scattered garnet. Several reaction-zones occur in the contact between impure calcite marble and garnet-bearing metapelite and the sequence of mineral assemblages in these reaction zones is: biotite + plagioclase K-feldspar garnet (Zone I, biotite + plagioclase K-feldspar garnet staurolite epidote

  5. Estabilidad temporal de las infracomunidades de parásitos en la borrachilla Scartichthys viridis (Valenciennes, 1836 (Pisces : Blenniidae en la costa central de Chile Temporal stability in parasite infracommunities of the blenny Scartichthys viridis(Valenciennes, 1836 (Pisces: Blenniidae on the central coast of Chile

    Directory of Open Access Journals (Sweden)

    FREDDY DÍAZ

    2002-12-01

    Full Text Available Se comparan las infracomunidades de parásitos de la borrachilla Scartichthys viridis (Pisces: Blenniidae de tres muestras tomadas en un lapso de 17 meses, entre 1999 y 2001, desde pozas intermareales vecinas a Las Cruces (33°27' S, 71°37' O, Chile central. El objetivo es averiguar si la riqueza, diversidad, abundancia y composición de las infracomunidades de parásitos son persistentes o no en el tiempo ontogenético y cronológico. Se recolectaron 10 taxa parasitarios en cerca del 89 % de los 63 huéspedes examinados, de los cuales ocho eran metazoarios. La búsqueda de protozoos se realizó sólo en los últimos 2 años. El 75 % de los ocho taxa de metazoos ocurrieron en los tres años, uno no estuvo presente en un año, y otro fue encontrado solamente en un año. La mayoría de los huéspedes examinados albergaba protozoos parásitos. La prevalencia de los protozoos Cryptobia sp. fue alta para ambos años, y menor en Trichodina sp. La longitud total de los huéspedes era un predictor relevante de las variaciones en la riqueza, abundancia, diversidad y composición infracomunitaria en el conjunto de los tres años. En cambio, el año de muestreo no lo fue, en particular al comparar entre huéspedes de similar longitud total. Estos resultados son similares a los encontrados en infracomunidades de parásitos de otras especies de peces en Chile, en que hay baja variabilidad en las propiedades agregadas de las infracomunidades en el tiempo cronológico. Se discute acerca de la extensión relativa del tiempo ontogenético en contraste al tiempo cronológico al ser probablemente ambos de importancia en las características de las infracomunidades, y se propone que se explore la medida en la cual estos resultados constituyen un patrón.Parasite infracommunities of the blenny Scartichthys viridis (Pisces: Blenniidae are compared among three samples taken within a 17-month period during three consecutive years (1999-2001, from intertidal pools at

  6. Fission track thermochronology of Neogene plutons in the Principal Andean Cordillera of central Chile (33-35°S): Implications for tectonic evolution and porphyry Cu-Mo mineralization Termocronología mediante trazas de fision de plutones neógenos en la Cordillera Principal Andina de Chile central (33-35°S): Implicancias para la evolución tectónica y mineralización de pórfidos de Cu-Mo

    OpenAIRE

    Víctor Maksaev; Francisco Munizaga; Marcos Zentilli; Reynaldo Charrier

    2009-01-01

    Apatite fission track data for Miocene plutons of the western slope of the Principal Andean Cordillera in central Chile (33-35°S) define a distinct episode of enhanced crustal cooling through the temperature range of the apatite partial annealing zone (~125-60°C) from about 6 to 3 Ma. This cooling episode is compatible with accelerated exhumation of the plutons at the time of Pliocene compressive tectonism, and mass wasting on the western slope of the Principal Andean Cordillera in central Ch...

  7. Geochronologic and paleontologic evidence for a Pacific-Atlantic connection during the late Oligocene-early Miocene in the Patagonian Andes (43-44°S)

    Science.gov (United States)

    Encinas, Alfonso; Pérez, Felipe; Nielsen, Sven N.; Finger, Kenneth L.; Valencia, Victor; Duhart, Paul

    2014-11-01

    Cenozoic marine strata occur in the western, eastern, and central parts of the North Patagonian Andes between ˜43°S and 44°S. Correlation of these deposits is difficult because they occur in small and discontinuous outcrops and their ages are uncertain. In order to better understand the age and sedimentary environment of these strata, we combined U-Pb (LA-MC-ICPMS) geochronology on detrital zircons with sedimentologic and paleontologic (foraminifers and molluscs) studies. Sedimentologic analyses suggest that the Puduhuapi Formation on the western flank of the Andean Cordillera was deposited in a deep-marine setting, the Vargas Formation in the central part of the Andes was deposited at outer-neritic or bathyal depths, and the La Cascada Formation on the eastern flank of the range was deposited in a shallow-marine environment. Geochronologic and paleontologic results indicate that the three marine units were deposited during the late Oligocene-early Miocene interval, although it is not clear whether this occurred during one or more marine incursions in the area. The alluvial(?) conglomeratic deposits of the La Junta Formation, exposed in the proximity of the Vargas Formation outcrops, have a maximum depositional age of ˜26 Ma and could have been deposited during the initial stage of subsidence that affected this region prior to the marine transgression over this area. The occurrence of both Pacific and Atlantic molluscan taxa in the La Cascada and Vargas formations suggests that a marine strait connected both oceans during the accumulation of these units. The new data on the age of the Puduhuapi, Vargas, and La Cascada formations indicate that these units may correlate with lower Miocene marine deposits in the forearc of central and southern Chile (Navidad Formation and equivalent units) and on the eastern flank of the Patagonian Andes (Río Foyel Formation and equivalent units). A late Oligocene-early Miocene age for these marine deposits is a reliable maximum

  8. 77 FR 65574 - Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Draft Comprehensive Conservation...

    Science.gov (United States)

    2012-10-29

    ... Complex. We started this process through a notice in the Federal Register (72 FR 27328; May, 15, 2007... Fish and Wildlife Service Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Draft... assessment (EA) for the Lake Andes National Wildlife Refuge Complex (Complex), which includes Lake Andes...

  9. Multiscale upwelling forcing cycles and biological response off north-central Chile Ciclos multiescala en el forzamiento de la surgencia y respuesta biológica en el centro-norte de Chile

    Directory of Open Access Journals (Sweden)

    JOSÉ RUTLLANT

    2002-03-01

    Full Text Available The physical forcing of the upwelling along the subtropical west coasts of the continents encompasses a broad range of time scales which shape both phytoplankton biomass (Chl-a and primary productivity (carbon fixation changes over any given time interval. The narrow continental shelf and the steep alongshore orography off north-central Chile provide for a unique combination of year-round, upwelling-favorable winds with quasi-weekly upwelling pulses associated with atmospheric coastal-trapped disturbances (coastal lows. This variability is modulated by intraseasonal oscillations in the depth of the thermo/nutricline, produced by coastal-trapped waves in the ocean, upon which annual (seasons and interannual (ENSO cycles are superimposed. During coastal field experiments off Cruz Grande bay (29º S, carried on in November 1987 and 1988 (opposite extremes of the ENSO cycle, mean changes of the phytoplankton-integrated Chl-a (B and carbon fixation rate (PP from the active to the relaxed phases of the local upwelling forcing cycle (phyto-pattern were characterized. Those data were contrasted against similar ones reported off Punta Lengua de Vaca (Coquimbo, 30º S and off Mejillones peninsula (Antofagasta, 23º S, encompassing different seasons and phases of intraseasonal and interannual (ENSO cycles from 1992 to 1997. A "warm" phyto-pattern was schematically characterized by a significant increase in B and a quasi-steady evolution of PP from the active to the relaxed phases of one complete upwelling event. Conversely, relative small changes in B and a significant increase in PP characterized a "cold" phyto-pattern. It is proposed here that the ENSO "cold/warm" signal may be offset by more than one opposite "thermal" condition (seasonal and/or intraseasonal in defining a "warm" or "cold" phyto-pattern associated with a particular cycle of the local upwelling forcingEl forzamiento físico de la surgencia a lo largo de las costas occidentales de los

  10. Satellite-measured interannual variability of turbid river plumes off central-southern Chile: Spatial patterns and the influence of climate variability

    Science.gov (United States)

    Saldías, Gonzalo S.; Largier, John L.; Mendes, Renato; Pérez-Santos, Iván; Vargas, Cristian A.; Sobarzo, Marcus

    2016-08-01

    Ocean color imagery from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the Aqua platform is used to characterize the interannual variability of turbid river plumes off central-southern Chile. Emphasis is placed on the influence of climate fluctuations, namely El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Antarctic Oscillation (AAO). Additional satellite data on wind, boat-based hydrographic profiles, and regional climate indices are used to identify the influence of climate variability on the generation of anomalous turbid river plumes. The evolution of salinity at a coastal station on the 90 m isobath between the Itata and Biobío Rivers shows a freshwater surface layer with salinity < 32.5 and 5-10 m thick during major plume events in 2002, 2005 and 2006. Surface salinity minima are correlated with peaks in turbidy from the normalized water leaving radiance at 555 nm (nLw(555)), both representing turbid river plumes. EOF analysis reveals that major turbid plume events occurred primarily during warm phases of the ENSO and PDO, and negative phases of the AAO, when storm tracks are further north. Anomalously large turbid plumes extend long distances offshore (∼ 70-80 km), and individual plumes coalesce into a continuous plume along the coast that covers the entire continental shelf. Season-specific correlation analyses reveal an increased influence of the AAO on river plumes south of Punta Lavapié in spring-summer (negative correlation). North of this major cape, ENSO and PDO indices have a dominant influence on plumes with positive correlations with the nLw(555) signal in winter (and negative in summer). We discuss the biogeochemical implications of plume events and the importance of long-term and high-resolution ocean color observations for studying the temporal evolution of river plumes.

  11. Seasonal mercury concentrations and δ15N and δ13C values of benthic macroinvertebrates and sediments from a historically polluted estuary in south central Chile

    International Nuclear Information System (INIS)

    The Lenga Estuary is one of the most industrialized sites in south central Chile where the historic operation of chlor-alkali plants resulted in large quantities of mercury (Hg) being deposited into the estuary. This historical contamination may still represent a risk to the biota in the estuary. To investigate this four macroinvertebrates, Neotrypaea uncinata (ghostshrimp), Elminius kingii (barnacle), Hemigrapsus crenulatus (shore crab) and Perinereis gualpensis (ragworm) were collected seasonally from three different sites in the Lenga Estuary and one in a reference estuary (Tubul Estuary), and analyzed for Hg and stable isotopes (δ15N and δ13C). Mercury concentrations in Lenga sediments ranged from 0.4 ± 0.1 to 13 ± 3 mg/kg, while those in Tubul sediments ranged from 0.02 ± 0.01 to 0.07 ± 0.09 mg/kg. Total Hg concentrations of invertebrates were significantly different between estuaries (p 0.05). In contrast, organic Hg concentrations were different by species and season with shore crab muscle tissues exhibiting the greatest percent difference. Site-specific relationships demonstrated that total Hg concentrations in ragworm best reflected the total Hg sediment mercury concentrations. Signatures of δ13C were correlated to the organic Hg % rather than total Hg. This suggests that organic Hg concentrations in these species were related to the carbon sources. -- Highlights: ► Hg in sediments and biota from Lenga Estuary were elevated compared to nearby estuary. ► Invertebrates showed interspecific and seasonal differences in terms of organic Hg %. ► Total Hg levels in the ragworm best reflect Hg sediment gradient in Lenga Estuary. ► Interspecific variation in δ13C signatures indicated different feeding modes. ► Organic forms of Hg in invertebrates were mainly related to the carbon sources.

  12. Biases in determining the diet of jumbo squid Dosidicus gigas (D' Orbigny 1835) (Cephalopoda: Ommastrephidae) off southern-central Chile (34°S-40°S)

    Science.gov (United States)

    Ibáñez, Christian M.; Arancibia, Hugo; Cubillos, Luis A.

    2008-12-01

    The diet of jumbo squid ( Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel ( Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier ( Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake ( Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.

  13. Recruitment Dynamics of the Relict Palm, Jubaea chilensis: Intricate and Pervasive Effects of Invasive Herbivores and Nurse Shrubs in Central Chile.

    Science.gov (United States)

    Fleury, Marina; Marcelo, Wara; Vásquez, Rodrigo A; González, Luis Alberto; Bustamante, Ramiro O

    2015-01-01

    Shrubs can have a net positive effect on the recruitment of other species, especially relict species in dry-stressful conditions. We tested the effects of nurse shrubs and herbivory defoliation on performance (survival and growth) of nursery-grown seedlings of the largest living palm, the relict wine palm Jubaea chilensis. During an 18-month period, a total of more than 300 seedlings were exposed to of four possible scenarios produced by independently weakening the effects of nurse shrubs and browsers. The experiment followed a two-way fully factorial design. We found consistent differences in survival between protected and unprotected seedlings (27.5% and 0.7%, respectively), and herbivory had a dramatic and overwhelmingly negative effect on seedling survival. The invasive rabbit (Oryctolagus cuniculus) is clearly creating a critical bottleneck in the regeneration process and might, therefore, partially explain the general lack of natural regeneration of wine palms under natural conditions. Apparently biotic filters mediated by ecological interactions are more relevant in the early stages of recruitment than abiotic, at least in invaded sites of central Chile. Our data reveal that plant-plant facilitation relationship may be modulated by plant-animal interactions, specifically by herbivory, a common and widespread ecological interaction in arid and semi-arid environments whose role has been frequently neglected. Treatments that protect young wine palm seedlings are mandatory to enable the seedlings to attain a height at which shoots are no longer vulnerable to browsing. Such protection is an essential first step toward the conservation and reintroduction of this emblematic and threatened species. PMID:26218100

  14. Using fecal profiles of bile acids to assess habitat use by threatened carnivores in the Maulino forest of central Chile Empleo del perfil de ácidos biliares fecales para evaluar uso del hábitat por carnívoros amenazados en el bosque maulino de Chile central

    Directory of Open Access Journals (Sweden)

    CARLA GUERRERO

    2006-03-01

    Full Text Available The distribution and habitat use by carnivores can be assessed by studying their tracks or feces. If these methods are to be used confidently, they should not only unequivocally discriminate among species, but should also render the same patterns of spatial distributions. We assessed the fulfillment of these requirements with five carnivores inhabiting the Maulino forest of central Chile: Galictis cuja, Oncifelis guigna, Pseudalopex culpaeus, Pseudalopex griseus, and Puma concolor. Fecal bile acid thin layer chromatographic profiles were assessed, and shown to be species-specific, invariant within samples of a given individual and among individuals of a given species, but consistently different across species. The spatial distribution of feces in mixed stands of native forests and exotic pine plantations in the coastal Maule region of central Chile was compared with the expected distribution according to habitat offer, and also with the expected distribution based on earlier track records. The results revealed that Pseudalopex culpaeus makes extensive use of pine plantations; Oncifelis guigna prefers native forests, and Pseudalopex griseus thrives in pine plantations, native forests, and patches of native forest, in proportion to habitat availability. Results from scat distribution were similar to those obtained by tracks records. Feces and tracks were thus useful indicators of habitat use by carnivores, and could be used complementarily to study species with conservation problemsEl uso del hábitat por carnívoros puede ser examinado a partir de la distribución de sus huellas y fecas. Para que ambas aproximaciones sean usadas en forma segura y complementaria, ellas deberían no solamente discriminar inequívocamente entre especies, sino que también deberían entregar la misma información sobre los patrones de distribución espacial. Analizamos el cumplimiento de estos requisitos con cinco especies de carnívoros en el bosque maulino de Chile

  15. Efecto del reemplazo de la vegetación nativa de ribera sobre la comunidad de macroinvertebrados bentónicos en arroyos de climas templados, Chile central Replacement effect of riparian native vegetation on benthic macroinvertebrates community in temperate climate streams, Central Chile

    Directory of Open Access Journals (Sweden)

    Gabriela Mancilla

    2009-12-01

    Full Text Available El aporte de materia orgánica desde la vegetación ribereña es determinante en la estructura y complejidad de los sistemas fluviales; es identificado como el mayor aporte energético en ríos y una fuente importante de alimento para macroinvertebrados en arroyos de cabecera. No obstante, el paisaje ribereño ha sido altamente degradado por actividades humanas, lo que ha afectado la estructura y composición de las comunidades acuáticas. El presente estudio se desarrolló en Chile central (región del Biobío donde se concentra una intensa actividad forestal con especies exóticas. Se seleccionaron ríos de bajo orden (The organic matter from riparian vegetation is determined by the structure and complexity of streams. It presents a higher energetic input to streams as well as important source of food for macroinvertebrates in head streams. In spite of its importance, riparian landscape has been rapidly degraded by human activity, this affects structure and composition of the aquatic community. The present study was made in Central Chile (Biobio Region which has intensive forest activity with exotic species. Small streams were selected (< 3 order, because they are very particularly sensitive to changes in land use. The sites were grouped identified according to native forest land cover larger than 20% (group 1 and smaller than 20% (group 2. Significant differences (p< 0.05 in Plecoptera abundance (p < 0.05 were found between the two groups. Differences in trophic groups were significant for shredders and predators increased and gathering-collectors decreased their abundance, with native cover smaller than 20%. This showed the dependent on allochthonous material. The vegetation cover and community parameters correlations showed that Diversity (W increased with higher percentage of watershed covered by native vegetation and exotic species mix. Results suggest that a buffer conservation area of native riparian vegetation is necessary in streams

  16. Biomasa en Chile

    OpenAIRE

    Nilsson Cifuentes, Gabriel; Rodríguez Monroy, Carlos

    2012-01-01

    El artículo presenta el desarrollo de la biomasa en Chile, dentro del complejo marco energético existente en el país, el cual, aún no logra potenciar e incentivar el desarrollo de energías renovables y depende fuertemente de los combustibles fósiles, acrecentando el riesgo latente de sufrir una crisis energética, en el mediano plazo, producto de la paulatina incorporación de nuevas centrales generadoras de energías, que satisfagan la creciente demanda energética pronosticada. Este ar...

  17. La fauna de caprélidos (Crustacea: Amphipoda: Caprellidea de la costa de Coquimbo, centro-norte de Chile, con una clave taxonómica para la identificación de las especies The caprellid fauna (Crustacea: Amphipoda: Caprellidea from the coast of Coquimbo, Northern-central Chile, with a taxonomic key for species identification

    Directory of Open Access Journals (Sweden)

    JOSÉ M. GUERRA-GARCÍA

    2001-12-01

    Full Text Available Los caprélidos son comunes y abundantes en muchos hábitats litorales del ambiente marino. Sin embargo este grupo de anfípodos no ha sido muy bien estudiado en la costa chilena. El estudio de los caprélidos se ha visto dificultado por su gran variabilidad morfológica y el hecho de que la literatura así como los especímenes de los museos son difíciles de localizar. El objetivo de este estudio fue entregar las herramientas taxonómicas para la identificación de las especies de crustáceos caprélidos comunes en el centro-norte de la costa de Chile. Se muestrearon distintos hábitats (boyas, bolones intermareales, praderas de algas y fanerógamas marinas y se encontraron seis especies distintas de caprélidos: Caprellina longicollis (Nicolet, 1849, Caprella equilibra Say, 1818, C. scaura Templeton, 1836, C. verrucosa Boeck, 1871; Deutella venenosa Mayer, 1890 y Paracaprella pusilla Mayer, 1890. Caprella scaura, C. verrucosa y D. venenosa fueron muy abundantes sobre las algas, hidrozoos y briozoos asociados a boyas. Caprella equilibra, también presente en boyas, fue más abundante bajo piedras en zonas intermareales rocosas expuestas, donde también se encontraron ejemplares de D. venenosa y de P. pusilla. Caprella scaura también se encontró sobre algas rojas de las playas arenosas, especialmente sobre Gracilaria chilensis y sobre la fanerógama marina Heterozostera tasmanica, donde cohabitó junto a Caprellina longicollis. Paracaprella pusilla constituye una nueva cita para las costas pacíficas sudamericanas, siendo nueva para la fauna de Chile. La especie D. venenosa, que se cita por primera vez después de la descripción original de Mayer en el año 1890, es considerada una especie endémica de la costa central de ChileCaprellids are abundant in many littoral habitats of the marine environment. Nevertheless, this group of amphipods has been scarcely studied along the coast of Chile. The study of the Caprellidea is particularly

  18. New time-constraints on provenance, metamorphism and exhumation of the Bahía Mansa Metamorphic Complex on the Main Chiloé Island, south-central Chile Nuevas restricciones temporales sobre proveniencia, metamorfismo y exhumación del Complejo Metamórfico Bahía Mansa en la Isla Grande de Chiloé, centro-sur de Chile

    OpenAIRE

    Paul Duhart; Alberto C Adriasola

    2008-01-01

    The Coastal Ranges in the western part of the Chiloé Archipelago represent an emerged forearc high at the subduction front of south-central Chile. Prior to the Cenozoic framework of the subducting Farallón and Nazca plates beneath the South American plate, the history of the metamorphic basement in the Coastal Ranges involves episodes of subduction and/or accretion of oceanic and ensialic material along the proto-Pacific margin of Gondwana. Along different segments of the Main Chiloé Island t...

  19. Recent regional shortening in the interior of the orogenic Puna Plateau of the southern central Andes: New InSAR observations from the Salar de Pocitos, Salta, NW Argentina.

    Science.gov (United States)

    Eckelmann, Felix; Motagh, Mahdi; Bookhagen, Bodo; Strecker, Manfred; Freymark, Jessica; Bekeschus, Benjamin; Alonso, Ricardo

    2013-04-01

    The Altiplano-Puna Plateau of the southern central Andes, with an average elevation of about 3.5 km and an area of 500,000 km2, is the world's second highest plateau after the Tibetan plateau. The southern sector of the plateau, the Argentine Puna, is characterized by a pattern of basement-cored ranges with the highest peaks above 6000 m asl and intervening Cenozoic sedimentary basins. Most of the ranges have a nearly N-S trend and enclose the sedimentary basins which exhibit internal drainage and several km-thick continental evaporate and clastic deposits. Like its Cenozoic counterparts this plateau is thought to be characterized by active extension, which superseded contractile deformation in the late Miocene. Often, extensional structures are associated with mafic volcanism. In contrast, the plateau flanks are subjected to sustained contraction and a migration of deformation toward the foreland. Here, we present new Interferometric Synthetic Aperture Radar (InSAR) measurements based on ENVISAT and ERS data to document that the southern central part of the Puna is still dominated by contraction, despite widespread evidence for extensional tectonism. We report a time series of InSAR from the Salar de Pocitos basin spanning about seven years (ENVISAT from 2005 to 2009; ERS from 2002 to 2009). The basin is located at approximately 24.5° S, 67° W, with a minimum elevation of 3650 m asl. In this region, the transition from regional shortening to horizontal extension associated with mafic volcanism is generally assumed to have taken place quite rapidly between 7 and 5 Ma. The Pocitos basin forms a N-S orientated, salt-bearing, hydrologically-isolated basin with a surface area of 435 Km2. To the west, it is bounded by an anticline involving Tertiary and Quaternary sediments; to the east it is bounded by a reverse-faulted range. Late Miocene volcanic edifices delimit the basin to the north, whereas structural blocks close it to the south. The Tertiary and Quaternary

  20. Hábitos alimentarios de Dosidicus gigas (D' Orbigny, 1835) (Cephalopoda: Teuthoidea) frente a la costa centro-sur de Chile Feeding habits of Dosidicus gigas (D'Orbigny, 1835) (Cephalopoda: Teuthoidea) in the central-south coast off Chile

    OpenAIRE

    PATRICIO ULLOA; MARTA FUENTEALBA; VÍCTOR RUIZ

    2006-01-01

    Se estudiaron los hábitos alimentarios del calamar rojo Dosidicus gigas (D'Orbigny, 1835) frente a la costa de Chile centro-sur, durante el invierno del año 2005. Se examinaron un total de 52 estómagos, en todos los cuales había contenido alimentario. Los ejemplares provenían de pescas efectuadas por la flota arrastrera industrial que opera entre 36°39' S y 38°55'S sobre la merluza común Merluccius gayi (Guichenot 1848) y a una profundidad media de 290 m sobre la plataforma continental. Para ...

  1. The genetic relationship between mafic dike swarms and plutonic reservoirs in the mesozoic of central chile (30A degrees-33A degrees 45'S) : insights from AMS and geochemistry

    OpenAIRE

    C. Creixell; M.A. Parada; D. Morata; Roperch, Pierrich; Arriagada, C

    2009-01-01

    Five mafic dike swarms between 30A degrees and 33A degrees 45'S were studied for their geochemical signature and kinematics of magma flow directions by means of AMS data. In the Coastal Range of central Chile (33A degrees-33A degrees 45'S), Middle Jurassic dike swarms (ConcA(3)n and Cartagena dike swarms, CMDS and CrMDS, respectively) and an Early Cretaceous dike swarm (El Tabo Dike Swarm, ETDS) display the presence of dikes of geochemically enriched (high-Ti) and depleted (low-Ti) basaltic c...

  2. Hydrochemical and isotopic patterns in a calc-alkaline Cu- and Au-rich arid Andean basin: The Elqui River watershed, North Central Chile

    International Nuclear Information System (INIS)

    Highlights: ► Major ions are provided by rock weathering and NaCl recycling. ► Aridity and cal-alkaline lithology effects abate acid drainage. ► Factors affecting hydrochemistry in mineral rich zone are addressed. ► Stable isotopes confirm the meteoric origin of groundwaters. ► High sulfate contents are explained by widespread sulfide minerals. - Abstract: The geochemistry of surface water and groundwater from the Elqui River basin, North-Central Chile, was studied in spring 2007 and fall 2008 to obtain a general understanding of the factors and mechanisms controlling the water chemistry of steep rivers located in mineral-rich, arid to semi arid zones. Besides its uniform intermediate igneous lithology, this basin is known for acid drainage and high As contents in the El Indio Au–Cu–As district, in its Andean head. Abundant tailings deposits are present in the middle part of the basin, where agricultural activities are important. According to the results, the chemical and isotopic composition of the Elqui basin surface water and groundwater is related to uniform calc-alkaline lithology and the major polluting system of the chemically reactive, but closed El Indio mining district. The resulting compositional imprints in surface and ground-water are, (a) high SO4 levels, reaching about 1000 mg/L in the Toro River water, directly draining the mining area; (b) a major depletion of Fe and pollutant metals in surface water after the confluence of the Toro and La Laguna rivers; (c) similar chemical composition of surface and ground-waters that differ in H and O isotopic composition, reflecting the effect of differential evaporation processes downstream of the Puclaro dam; and (d) seasonal variations of Fe, Mn, Cu and Zn in surface water. In contrast, the groundwater chemistry exhibits moderate seasonal changes, mainly in HCO3- content. In spite of the acid drainage pollution, water quality is adequate for human consumption and irrigation. This is a

  3. Charles Darwin in the Andes

    Science.gov (United States)

    Bizzo, Nelio; Bizzo, Luis Eduardo Maestrelli

    2006-01-01

    Considering geological time as an important epistemological obstacle to the construction of ideas on biological evolution, a study was carried out on the so-called "Darwin Papers". The conclusion was that Charles Darwin's excursion in the Andes during March-April 1835 was a crucial step in this regard. An expedition was carried out in March-April…

  4. Streamflow responses in Chile to megathrust earthquakes in the 20th and 21st centuries

    Science.gov (United States)

    Mohr, Christian; Manga, Michael; Wang, Chi-yuen; Korup, Oliver

    2016-04-01

    Both coseismic static stress and dynamic stresses associated with seismic waves may cause responses in hydrological systems. Such responses include changes in the water level, hydrochemistry and streamflow discharge. Earthquake effects on hydrological systems provide a means to study the interaction between stress changes and regional hydrology, which is otherwise rarely possible. Chile is a country of frequent and large earthquakes and thus provides abundant opportunities to study such interactions and processes. We analyze streamflow responses in Chile to several megathrust earthquakes, including the 1943 Mw 8.1 Coquimbo, 1950 Mw 8.2 Antofagasta, 1960 Mw 9.5 Valdivia, 1985 Mw 8.0 Valparaiso, 1995 Mw 8.0 Antofagasta, 2010 Mw 8.8 Maule, and the 2014 Mw 8.2 Iquique earthquakes. We use data from 716 stream gauges distributed from the Altiplano in the North to Tierra del Fuego in the South. This network covers the Andes mountain ranges, the central valley, the Coastal Mountain ranges and (mainly in the more southern parts) the Coastal flats. We combine empirical magnitude-distance relationships, machine learning tools, and process-based modeling to characterize responses. We first assess the streamflow anomalies and relate these to topographical, hydro-climatic, geological and earthquake-related (volumetric and dynamic strain) factors using various classifiers. We then apply 1D-groundwater flow modeling to selected catchments in order to test competing hypotheses for the origin of streamflow changes. We show that the co-seismic responses of streamflow mostly involved increasing discharges. We conclude that enhanced vertical permeability can explain most streamflow responses at the regional scale. The total excess water released by a single earthquake, i.e. the Maule earthquake, yielded up to 1 km3. Against the background of megathrust earthquakes frequently hitting Chile, the amount of water released by earthquakes is substantial, particularly for the arid northern

  5. Fluvio-lacustrine sedimentation and volcanism in a Late Carboniferous tensional intra-arc basin, northern Chile

    Science.gov (United States)

    Breitkreuz, Christoph

    1991-11-01

    Extensive outcrops of Late Carboniferous to Triassic volcanoplutonic magnetic-arc complexes occur in the Andes of northern Chile. In the Salar de Atacama area, terrestrial volcanosedimentary successions include a 200-600 m thick fluvio-lacustrine sequence ("Miembro Medio"). The terrestrial basin which accommodated this sequence formed during the latest Carboniferous on top of the deposits of the pre-existing Carboniferous composite volcanoes. The lower part of the Miembro Medio consists of green limnic and multicoloured alluvial fan deposits; the upper part is made up of red fluvial sedimentary rocks. Basic volcanic rocks occur locally throughout the sequence. The climate is inferred to have been warm and humid. The limnic (freshwater) environment had a minimum extension of 300 × 100 km. Limnic facies is inferred from the existence of fine-parallel-bedded sediments, ooliths and a limnic benthic fauna. Lake-shore deposits prevail in the outcrops. In some sections, the green limnic sequence is followed by red fine-grained floodplain or alluvial plain, and fluvial channel deposits. The framework composition of the Miembro Medio is dominated by volcanogenic detritus presumably eroded from the successions of the previous Late Carboniferous volcanic arc. Another volcanogenic clast type was provided by syndepositional basalto-andesitic phreatomagmatic activity, which also produced peperitic sills, dykes and lavas. The limnic-alluvial fan facies association, the predominance of volcanogenic detritus, and the accompanying intrabasinal basic calc-alkaline volcanism together with the considerable size of the basin point to a ?NW-SE trending half-graben setting controlled by (trans-)tensional arc tectonics. With regard to the Late Carboniferous-Triassic volcanosedimentary successions of northern Chile, this Latest Carboniferous tensional setting is the only feature in this area supporting those models, which inferred an extensional magmatic arc for the entire Central and

  6. Evaluation of Little Ice Age cooling in Western Central Andes, suggested by paleoELAs, in contrast with global warming since late 19th century deduced from instrumental records

    Science.gov (United States)

    Ubeda, Jose; Palacios, David; Campos, Néstor; Giraldez, Claudia; García, Eduardo; Quiros, Tatiana

    2015-04-01

    This paper attempts to evaluate climate cooling (°C) during the glacial expansion phases using the product GTV•ΔELA, where GTV is the vertical air temperature gradient (°C/m) and ΔELA (m) the difference in level observed between the Equilibrium Line Altitude (ELA) reconstructions for current and past glaciers. With this aim the Area x Altitude Balance Ratio-(AABR) method was used to produce reconstructions of present ELAs (2002-2010) and paleoELAs corresponding to the last glacier advance phase. The reconstructions were produced in three study areas located along a N-S transect of the western cordillera in the Central Andes: the south-western sector of the Nevado Hualcán (9°S, 77°W; Giráldez 2011); the southern slope of the Cordillera Pariaqaqa (12°S, 76°W; Quirós, 2013) and the NW, NE, SE and SW quadrants of the Nevado Coropuna (16°S, 72°W; García 2013; Úbeda 2011; Campos, 2012). The three mountains exceed 6000 m altitude, their summit areas are covered by glaciers, and on their slopes there are existing well-conserved moraines deposited by the last advances near the present front of the ice masses. Although there are no absolute dates to confirm this hypothesis, it has been assumed that the last glacial advances occurred during the Little Ice Age (LIA), which the oxygen isotopes of the Nevado Huascarán (9°S, 77°W) date to the period 1500-1890. For the Hualcán and Pariaqaqa the mean global value of the Earth's GTV (6.5°C/km) was used, considered valid for the Tropics. On the Coropuna a GTV=8.4°C/km was used, based on high resolution sensors installed in situ since 2007 (Úbeda 2011). This gradient is approaching the upper limit of the dry adiabatic gradient (9.8°C/km), as the Coropuna region is more arid than the other case study areas. The climate cooling estimates deduced from the product GTV•ΔELA were compared with the global warming shown by the 1880-2012 series, ΔT=0.85°C, and 1850/1900-2003/2012, ΔT=0.78°C. The differences are

  7. Lithospheric scale model of Merida Andes, Venezuela (GIAME Project)

    Science.gov (United States)

    Schmitz, M.; Orihuela, N. D.; Klarica, S.; Gil, E.; Levander, A.; Audemard, F. A.; Mazuera, F.; Avila, J.

    2013-05-01

    Merida Andes (MA) is one of the most important orogenic belt in Venezuela and represents the northern culmination of South America Andes. During the last 60 years, several models have been proposed to explain the shallow and deep structure, using different geological, geophysical, seismological, geochemical and petrologic concepts; nevertheless, most of them have applied local observation windows, and do not represent the major structure of MA. Therefore, a multidisciplinary research group, coordinated by FUNVISIS, in close cooperation with UCV, ULA and PDVSA, is proposed in order to get the outlined goals in the project entitled GIAME ("Geociencia Integral de los Andes de MErida") was established, which aims to generate a lithospheric scale model and the development of a temporal dynamic model for the MA. As a base for lithospheric investigations of the Merida Andes, we are proposing three wide angle seismic profiles across the orogen on three representative sites, in order to determine the inner structure and its relation with the orogen's gravimetric root. To the date, there are no seismic studies at lithospheric scale which cross MA. The wide angle seismic will be complemented with the re-processing and re-interpretation of existing reflection seismic data, which will allow to establish a relationship between MA and its associated flexural basins (Maracaibo and Barinas-Apure basins). Depending on the results of the VENCORP Project (VENezuelan COntinental Reflection Profiling), which might show some reliable results about crustal features and Moho reflectors along three long seismic profiles at Caribbean Moutain system, a reflection seismic profile across the central portion of MA is proposed. Additional tasks, consisting in MA quaternary deformation studies, using research methods like neotectonics and paleoseismology, georadar, numerical modeling, cinematic GPS, SAR interferometry, thermocronology, detailed studies on regional geology, flexural modeling

  8. Consecuencias de las variaciones microclimáticas sobre la visita de insectos polinizadores en dos especies de Chaetanthera (Asteraceae en los Andes de Chile central Consequences of microclimate variation on insect pollinator visitation in two species of Chaetanthera (Asteraceae in the central Chilean Andes

    Directory of Open Access Journals (Sweden)

    CRISTIAN TORRES-DÍAZ

    2007-12-01

    Full Text Available La actividad de polinizadores puede ser afectada por factores bióticos (e.g., densidad floral en el parche, despliegue floral o por factores abióticos (e.g., temperatura, velocidad de viento, nubosidad. A pesar de la notable variación local, estacional e interanual en temperatura en zonas alpinas, las consecuencias de la variación microclimática local sobre la actividad de los polinizadores han recibido escasa atención en ambientes de alta montaña. En este estudio comparamos las tasas de visita a flores de polinizadores realizadas sobre poblaciones de exposición norte y oeste, en Chaetanthera apiculata (3.100 m de altitud, y en poblaciones de exposición este y oeste en C. lycopodioides (3.300 m de altitud. Se estudiaron los sistemas de reproducción de ambas especies para determinar su nivel de dependencia de un agente de polinización externo. En C. apiculata, la población que crece sobre la ladera de exposición norte estuvo sujeta a mayores temperaturas diurnas (1,8 °C y mayores tasas de visita (7,8 veces que la población sobre la ladera de exposición oeste. En C. lycopodioides, a su vez, la ladera de exposición este fue más cálida (3 °C y más visitada (cuatro veces que la población de exposición oeste. Mientras en C. apiculata, solo Faunula leucoglene (Lepidóptera: Satyridae presentó mayor actividad en la población más cálida, en C. lycopodioides, solo F. leucoglene y Liphantus sp. (Himenóptera: Andrenidae tuvieron mayor actividad en la población más cálida. La tasa de visitas de Faunula leucoglene fue afectada por la temperatura en C. apiculata y C. lycopodioides. Ambas especies, C. apiculata y C. lycopodioides, son parcialmente autocompatibles, y por lo tanto requieren polen exógeno para alcanzar una producción de semillas máxima. Nuestros resultados muestran que en ambientes de alta montaña las tasas de visita de polinizadores son altamente variables y que los factores microclimáticos pueden generar más variación en las tasas de visitas a flores que la densidad de capítulos florales en los parches. Nuestros resultados aportan valiosa información sobre las potenciales consecuencias del cambio climático global en la polinizaciónInsect pollinator activity can be influenced by biotic (e.g., patch floral density and floral display or by abiotic factors (e.g., temperature, wind velocity, cloudiness. In spite of microsite, seasonal and interannual variation in temperature in the alpine zone, the consequences of local microclimatic variation on pollinator activity has been rarely studied in high mountain ecosystems. In this study we compared flower visitation rates on a north-facing slope and a west-facing slope in Chaetanthera apiculata (3,100 m of altitude and on an east-facing slope and a west-facing slope in Chaetanthera lycopodioides (3,300 m of altitude. We studied the breeding system in each species in order to determine level of dependence on external pollinators. While the north-facing slope inhabited by C. apiculata was warmer (1.8 °C and visited (7.8-fold more frequently than the west-facing slope, in C. lycopodioides the east-facing slope was warmer (3 °C and visited more frequently (4-fold than the west-facing slope. In C. apiculata only Faunula leucoglene (Lepidóptera: Satyridae showed higher activity in the warmer population. In C. lycopodioides, F. leucoglene and Liphantus sp. (Himenóptera:Andrenidae showed higher activity rates in the warmer population. Flower visitation rate in Faunula leucoglene was correlated with temperature in C. apiculata and C. lycopodioides. Both C. apiculata and C. lycopodioides are partially self-compatible, and thus require exogenous pollen for maximum seed set. Our results show that in high elevation environments flower visitation rates can be highly variable and that microclimatic conditions can be more important for pollinator variation among populations than head density. Our results offer valuable insights on the potential consequences of global warming on plant pollination at high elevation

  9. Chile ushers in new hydro era

    International Nuclear Information System (INIS)

    The planned construction of two hydroelectric power plants at Peuchen and Mampil, will help to meet Chile's growing electricity demand. Securing finance for the project has been straight forward thanks to the optimal hydrological conditions, rivers with a very strong flow providing a large head of water over short distance. Hydropower plays a central role in Chile's generating capacity providing 70% of total energy consumption. Thus, the future of these projects will be highly successful, it is argued. (UK)

  10. La vertebración territorial en regiones de alta especialización: Valle Central de Chile. Alcances para el desarrollo de zonas rezagadas en torno a los recursos naturales

    Directory of Open Access Journals (Sweden)

    ALBERTO GARCÍA-HUIDOBRO

    2010-04-01

    Full Text Available Los procesos de reestructuración económica y la apertura de los mercados han generado múltiples y variadas consecuencias sobre nuestros territorios. Quizás para Chile, como para otros países latinoamericanos, uno de los más importantes procesos a nivel regional es el desarrollo de espacios altamente especializados o regiones-commodities. Distintos trabajos académicos señalan que interiormente, en conjunto con áreas de gran competitividad, se están generando áreas rezagadas o alejadas de los dinamismos económicos. Por lo tanto: ¿ En qué ha derivado su modelo de vertebración territorial y su sistema de centros poblados ? ¿Cuáles son las características de estas áreas rezagadas ? Y por ende, ¿cuáles son los desafíos a los cuales se enfrentan? El Valle Central de Chile es una de estas áreas donde se evidencia dicha especialización. Por tanto, analizaremos la estructura física territorial en las que han derivado estas regiones y el papel que cumplen sus centros poblados en los nuevos escenarios. A partir de la caracterización de su vertebración territorial avanzaremos hacia la definición de sus zonas menos favorecidas, e intentaremos generar algunas hipótesis que respondan a sus desafíos y requerimientos futuros.Economic restructuring processes and market opening have generated multiple and varied consequences in our territories. Perhaps for Chile, as with other Latin American countries, one of the most important processes at the regional level is the development of highly specialized spaces or commodity-regions. Different academic work indicates that within these spaces, as well as areas of high competitiveness, there are also backward areas with limited economic dynamism. Consequently: What has happened to the model of a territorial spine and system of population center? What are the characteristics of these backward areas? In addition, what are the challenges to be faced? Chile's Central Valley is one of the areas

  11. DETECTION OF LOCAL SITE CONDITIONS INFLUENCING EARTHQUAKE SHOCK AND SECONDARY EFFECTS IN THE VALPARAISO AREA IN CENTRAL-CHILE USING REMOTE SENSING AND GIS METHODS

    OpenAIRE

    Barbara Theilen-Willige; Felipe Barrios Burnett

    2011-01-01

    The potential contribution of remote sensing and GIS techniques to earthquake hazard analysis was investigated in Valparaiso in Chile in order to improve the systematic, standardized inventory of those areas that are more susceptible to earthquake ground motions or to earthquake related secondary effects such as landslides, liquefaction, soil amplifications, compaction or even tsunami-waves. Geophysical, topographical, geological data and satellite images were collected, processed, and integr...

  12. 78 FR 24228 - Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Final Comprehensive Conservation Plan

    Science.gov (United States)

    2013-04-24

    ... review and comment following the announcement in the Federal Register on October 29, 2012 ] (77 FR 65574... Fish and Wildlife Service Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Final... conservation plan and finding of no significant impact (FONSI) for the Lake Andes National Wildlife...

  13. Estimación de la biomasa de langostino amarillo (Cervimunida johni, aplicando Modelo Lineal Generalizado a registros de captura por área barridaen la zona central de Chile Estimating yellow squat lobster (Cervimunida johni biomass by applying a generalized linear model to catch records per swept area in central Chile

    Directory of Open Access Journals (Sweden)

    Cristian Canales

    2012-07-01

    Full Text Available La información obtenida en cruceros de evaluación directa de langostino amarillo (Cervimunida johní realizados en la zona central del Chile (32°-38°S entre 1997 y 2009, permitió modelar los cambios en la densidad anual de este recurso mediante Modelo Lineal Generalizado (MLG. El objetivo de este enfoque fue tanto minimizar el efecto de los distintos criterios y diseños de muestreo que han sido empleados en el tiempo, como también determinar los efectos que explican las variaciones en la densidad de este recurso. Lo anterior permitió estimar el valor esperado de la densidad anual para el cálculo de biomasa mediante el método de "área barrida". Los registros lance a lance de captura por unidad de área barrida (CPUA permitieron la identificación y medición de los focos de abundancia, además de caracterizar la distribución y área que ha ocupado el recurso en el tiempo. El MLG identificó como efectos significativos el año, la zona, la profundidad, y las interacciones anuales de primer orden, explicando con ello el 43% de la devianza residual del modelo. Los principales efectos que explican las variaciones de la CPUA son el año y la interacción año-zona. Se determinó que la zona con mayor abundancia promedio corresponde a la delimitada entre 32° y 34°S, de igual manera que en el rango de profundidad menor a 250 m. Dentro del período analizado, se determinó que la población de este recurso incrementó en biomasa de manera sostenida hasta el 2006, principalmente en la zona norte del área de estudio, seguida de una fuerte reducción que al 2009 equivale al 75% respecto del máximo, reflejada en una biomasa de 11.000 ton.Changes in the annual density of the yellow squat lobster (Cervimunida johni were modeled using a generalized linear model (GLM, using information obtained during direct stock assessment cruises carried out in central Chile (32°-38°S between 1997 and 2009. The purpose of this approach was to minimize the

  14. Botanical Composition of Alpaca (Lama pacos Linn. Diet in a Central Mediterranean Range of Chile Composición Botánica de la Dieta de Alpaca (Lama pacos Linn. en un Pastizal del Secano Mediterráneo de la Zona Central de Chile

    Directory of Open Access Journals (Sweden)

    G Castellaro

    2008-06-01

    Full Text Available The re-introduction of domestic South American camelids (alpacas and llamas in the central zone of Chile makes it necessary to study their behaviour and adaptability. Since it is fundamental to characterize the camelid’s diet, the present work had as an objective the determination of the plant species selected by the alpacas (Lama pacos Linn. in different phenological stages (vegetative, reproductive and dry season. The study was carried out over three years in a paddock of 2.5 ha of sparse shrubland dominated by Acacia caven (Mol. Mol. and annual species in the herbaceous stratum, which were continually grazed by five male alpacas. The botanical composition and the forage dry matter available for grazing in the pasture was evaluated. Botanical composition of diets was estimated with the microhistological technique, using dung samples collected directly from the rectum. During the vegetative season, the most consumed plant species were annual and perennial grasses. In the reproductive season, the most important components of the diet were woody plant species, annual grasses and forbs. In the dry season, the diet was composed of a high percentage of woody plant species.La reintroducción de camélidos sudamericanos domésticos (alpaca y llamas en la zona central de Chile, hace necesario estudiar su comportamiento y adaptabilidad. En este contexto, la caracterización de la dieta es fundamental. Por ello, el presente trabajo tuvo como objetivo determinar las especies vegetales seleccionadas por las alpacas en diferentes etapas fenológicas del pastizal (vegetativo, reproductivo y seco. El estudio se realizó durante tres temporadas en un potrero de 2,5 ha ocupado por un matorral claro dominado por Acacia caven (Mol. Mol. y especies anuales en el estrato herbáceo, las cuales fueron pastoreadas continuamente por cinco alpacas macho. En la pradera se evaluó la composición botánica y la disponibilidad de la materia seca bajo pastoreo. La

  15. Shoreline changes in Concón and Algarrobo bays, central Chile, using an adjustment model Cambios en la línea litoral de las bahías de Algarrobo y Concón, Chile central, a través de un modelo de ajuste

    Directory of Open Access Journals (Sweden)

    Carolina Martinez

    2007-11-01

    Full Text Available Adjustment models for both Algarrobo and Concón bays, central Chile, are presented herein; the results show a nearly logarithmic spiral shape for the shore. Spatial-temporal variations in the shorelines of both bays were found based on aerial photographs from different years. The results indicate important variations in the relative position of the Concón Bay shoreline between 1945 and 2006, with extreme oscillations (-368 to 123.8 m only occurring in the proximal zone, where the Aconcagua Estuary is located. On the other hand, the spatial-temporal variations in the Algarrobo Bay shoreline between 1967 and 2006 are moderate (131 in the proximal and -73 in the distal zone. Whereas Concón Bay exhibits a stable state of equilibrium for the past 60 years, if the estuary zone is excluded, Algarrobo Bay presents a stable state with a tendency for growth in the proximal zone and retreat in the distal zone. The results are discussed in terms of coastal changes associated with highly urbanized shorelines and applications for coastal area management that are derived from the modelsSe presentan los resultados de la aplicación de un modelo de ajuste para las bahías de Algarrobo y Concón en Chile central, cuya forma se aproxima a una espiral logarítmica. A partir del uso de fotografías aéreas correspondientes a diferentes años, se determinaron las variaciones espacio-temporales de la línea litoral en ambas bahías. Los resultados indican que la bahía de Concón ha presentado importantes variaciones en la posición relativa de su línea litoral para el período 1945 a 2006, únicamente en su zona proximal, lugar en donde se localiza el estuario Aconcagua con oscilaciones extremas entre -368 m y 123,8 m. En la bahía de Algarrobo, las variaciones espacio-temporales de la línea litoral son de magnitud moderada para el período comprendido entre 1967 y 2006, presentando valores extremos de 131 m en la zona proximal y de -73 m en la zona distal

  16. Using 137Cs and 210Pbex and other sediment source fingerprints to document suspended sediment sources in small forested catchments in south-central Chile

    International Nuclear Information System (INIS)

    A study of the impact of forest harvesting operations on sediment mobilization from forested catchments has been undertaken in south-central Chile. The study focused on two sets of small paired catchments (treatment and control), with similar soil type, but contrasting mean annual rainfall, located about 400 km apart at Nacimiento (1200 mm yr−1) and Los Ulmos (2500 mm yr−1). The objective was to study the changes in the relative contribution of the primary sources of fine sediment caused by forestry operations. Attention focused on the pre-harvest and post-harvest periods and the post-replanting period was included for the Nacimiento treatment catchment. The sediment source fingerprinting technique was used to document the contributions of the potential sources. Emphasis was placed on discriminating between the forest slopes, forest roads and channel erosion as potential sources of fine sediment and on assessing the relative contributions of these three sources to the sediment yield from the catchments. The fallout radionuclides (FRNs) 137Cs and excess lead-210, the environmental radionuclides 226Ra and 40K and soil organic matter (SOM) were tested as possible fingerprints for discriminating between potential sediment sources. The Kruskal–Wallis test and discriminant function analysis were used to guide the selection of the optimum fingerprint set for each catchment and observation period. Either one or both of the FRNs were selected for inclusion in the optimum fingerprint for all datasets. The relative contribution of each sediment source to the target sediment load was estimated using the selected fingerprint properties, and a mixing model coupled with a Monte Carlo simulation technique that takes account of uncertainty in characterizing sediment source properties. The goodness of fit of the mixing model was tested by comparing the measured and simulated fingerprint properties for the target sediment samples. In the Nacimiento treatment catchment the

  17. Relaciones entre la distribución de recursos pelágicos pequeños y la temperatura superficial del mar registrada con satélites NOAA en la zona central de Chile Relationships between the small pelagic resources distribution and the sea surface temperatures recorded by NOAA satellites from Chile central zone

    Directory of Open Access Journals (Sweden)

    Eleuterio Yáñez R

    1996-01-01

    Full Text Available Se realiza un estudio exploratorio para determinar la posibilidad de introducir el uso de imágenes de temperatura superficial del mar (TSM, confeccionadas con datos de satélites NOAA, en las pesquerías de recursos pelágicos pequeños de la zona central de Chile. Se determinan significativas relaciones entre los rendimientos de las especies analizadas y los gradientes térmicos (GRT en forma particular. Estos se asocian a aguas oceánicas en el caso del jurel (Trachurus murphyi, y a surgencias costeras en relación con la anchoveta (Engraulis ringens y sardina común (Clupea bentincki. Se concluye que el uso de imágenes de TSM-NOAA puede jugar un papel importante en la operación de flotas, particularmente de las del tipo de embarcaciones consideradas en el presente trabajo.A survey study was conducted to assess the possibility of introducing the use of sea surface temperatures (SST, obtained from NOAA satellite data, for the small pelagic fisheries resources. Relationships between species yields and thermal gradients (TGR were found significant. Jack mackerel (Trachurus murphyi yields were largely related with a strong thermal gradient next to oceanic waters, while anchovy (Engraulis ringens and common sardine (Clupea bentincki yields were mainly associated to the development of coastal upwelling events. It is concluded that the use of SST-NOAA images can play an important role in fleet operations, particularly in the case ot the type of boats considered in this paper.

  18. Litterfall, litter decomposition and nitrogen mineralization in old-growth evergreen and secondary deciduous Nothofagus forests in south-central Chile Aporte, descomposición de hojarasca y mineralización de nitrógeno en bosques siempreverdes de antiguo crecimiento y bosques secundarios deciduos, centro-sur de Chile

    Directory of Open Access Journals (Sweden)

    JEROEN STAELENS

    2011-03-01

    Full Text Available South Chilean forest ecosystems represent one of the largest areas of old-growth temperate rainforests remaining in the Southern hemisphere and have a high ecological value, but suffer from deforestation, invasion by exotic species, fragmentation, and increasing atmospheric nitrogen (N deposition. To support sustainable forest management, more knowledge is required on nutrient cycling of these ecosystems. Therefore, a descriptive study of nutrient dynamics was done in four Valdivian rainforests in the lower Andes range of south Chile: old-growth and altered evergreen stands and unmanaged and managed secondary deciduous stands. Time series were measured for (i mass (four year and nutrient content (N, K, Ca, and Mg; one year of litterfall, (ii decomposition and nutrient dynamics (N, C, K, Ca, Mg, and P; one year of leaf litter and Saxegothaea conspicua bark litter, and (iii in situ topsoil net N mineralization (one year. Litterfall in the four stands ranged from 3.5 to 5.8 ton ha-1 yr-1, was temporarily lower in the managed than in the unmanaged deciduous stand and had a different seasonality in the evergreen stands than in the deciduous stands. Leaf litter decomposed faster (on average 32 % mass loss after one year than bark litter (8 % but without significant differences between leaf litter types. Net N in evergreen leaf litter decreased during decomposition but increased in deciduous leaf litter. Net soil N mineralization was fastest in the pristine evergreen stand, intermediate in the deciduous stands and slowest in the altered evergreen forest. Given the absence of replicated stands, the definite impact of forest type or management regime on the internal nutrient cycling cannot be demonstrated. Nevertheless, the results suggest that management can affect nutrient turnover by altering species composition and forest structure, while recent (five years selective logging in secondary deciduous forest did not affect litter decomposition or N

  19. Constrasting styles of erosion along the western slope of the Central Andean Plateau

    Science.gov (United States)

    Hoke, G. D.; Isacks, B. L.; Jordan, T. E.

    2002-12-01

    We examine the western slope of the central Andes Mountains between 17S and 30S in an effort to elucidate the effects of along strike climate variability on landscape process and form. This region is most opportune for study because the mountain front is, to a first order, a relatively simple monoclinal structure and several lines of evidence point towards the general stability of today's observed climatic zones since 15 Ma. In the central part of the study region (22-25S), relict landscape preservation is extremely good, much of the relict middle Miocene surface (erosional and depositional) between 18S and 25S remains intact. This surface becomes progressively more dissected moving north and south of the central segment. We present data from satellite imagery and geomorphic analyses of a 90 m digital elevation model, which suggest that three independent erosion styles exist in the study area (excluding the central region where no significant rivers exist). The first order differences in erosional style are accounted for predominantly by where precipitation is falling. In southern Peru and northern Chile, almost all moisture is in the form of high elevation, easterly-sourced precipitation falling on the Altiplano Plateau and Western Cordillera. This results in groundwater controlled drainage networks in northern Chile and the existence of a large active salar, the Salar de Atacama, which apparently has trapped groundwater originating from the plateau. Available geologic evidence shows that these features are of greater antiquity than the Pleistocene glacial period in the Central Andes. South of 27S, westerly derived, orographically enhanced precipitation falls directly on the mountain front producing an erosional regime more typical of actively eroding mountain fronts.

  20. Mortalidad natural de larvas de merluza común (Merluccius gayi gayi frente a Chile centro-sur en relación a su distribución espacial y grado de agregación Natural mortality of chilean hake (Merluccius gayi gayi larvae of central-south Chile in relation to their spatial distribution and patchiness

    Directory of Open Access Journals (Sweden)

    Cristian Vargas

    1996-01-01

    Full Text Available Existe escasa información sobre la ecología y sobrevivencia de estados larvales de merluza común frente a las costas de la VIII Región, Chile. Debido a que la agregación puede ser un factor determinante en la depredación de larvas de peces, en el presente trabajo se estudia su influencia en la mortalidad natural instantánea de larvas de merluza común (Merluccius gayi gayi Guichenot, 1848, estimada a través del modelo mortalidad-agregación de McGurk (1986. Las muestras (red bongo 500µ fueron obtenidas durante un crucero efectuado en la zona costera del centro-sur de Chile (36º22'S _ 37º10'S durante septiembre de 1991. La tasa de mortalidad natural instantánea fluctuó entre 0,1 y 0,38 d-1 para larvas en un rango de tallas de 4 a 11 mm de longitud estándar. Los valores de mortalidad obtenidos a través del modelo de interacción mortalidad-agregación (McGurk, 1986, revelaron que la distribución espacial (agregación podría influenciar considerablemente a la mortalidad, especialmente en larvas de mayor longitud (> 9 mm.At the present time limited information is available about ecology and survival of Chilean hake larvae off coast from VIII Region, Chile. Because spatial patchiness of larvae may be an important factor on the predation of fish larvae, its influence on the instantaneous natural mortality of larval Chilean hake (Merluccius gayi gayi Guichenot, 1848 was studied using the mortality-patchiness model (McGurk, 1986. Samples (bongo net 500µ were taken during a survey carried out in the coastal zone off Central-South Chile (36º22'S _ 37º10'S during september 1991. The natural mortality for larvae between 4 to 11 mm of standard length fluctuated between 0,1 and 0,38 d-1. The mortality values obtained using the mortality-patchiness model (McGurk, 1986, showed that the spatial distribution (patchiness would influence the larval mortality, specially in the largest ones (> 9 mm.

  1. Abanico East Formation: petrology and geochemistry of volcanic rocks behind the Cenozoic arc front in the Andean Cordillera, central Chile (33°50'S

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    Marcia Muñoz

    2006-01-01

    Full Text Available The stratigraphy, chemistry and age of rocks assigned to the eastern portion of the Abanico Formation exposed along the El Volcán river valley, Principal Cordillera east of Santiago (30º50'S/70º12'-70º5'W, are reported and discussed. This ca. 3,300 m thick succession is mainly composed of basalts, basaltic andesites and volcaniclastic rocks. 40Ar/39Ar radiometric dates on plagioclase from the lava flows yield Oligocene-lower Miocene ages with a maximum age of 34.3 ±0.4 Ma for the lower part and a plateau age of 21.4±1.0 Ma for the upper part of the succession. The lava flows show calc-alkaline affinities and have chemical characteristics that are typical of arc volcanic rocks erupted in an active continental margin. A temporal chemical evolution in the sequence is indicated by upward increases in concentrations of LILE and LREE elements and LaN/YbN ratios. This pattern can be attributed to increasing contributions of fluids derived from the subducted lithosphere with time. A chemical comparison of these rocks with Oligocene-lower Miocene volcanic rocks from the Cerro Abanico and Chacabuco areas on the western border of the Principal Cordillera, east of Santiago, and at the northern end of the Central Depression reveals west to east compositional variations. From west to east these variations include: (1 increasing LILE and LREE concentrations, LaN/YbN ratios and Sr and Nd initial isotopic ratios, and (2 decreasing LILE/HFSE and LREE/HFSE ratios. These pattern can be attributed to a west to east decrease in the contribution of slab derived fluids and increase in the influence of crustal contamination processesLa formación Abanico Este: petrología y geoquímica de las rocas volcánicas detrás del arco Cenozoico en la Cordillera Andina, Chile central (33º50'S. Se presentan los resultados del estudio de la estratigrafía, química y edades de rocas asignadas a la franja oriental de la Formación Abanico expuestas en la ladera sur del R

  2. Low prevalence of Factor V Leiden and the prothrombin G20210A mutation in a healthy population from the central-south region of Chile Baixa prevalência do Fator V Leiden e da mutação da protrombina G20210A em uma população sã da região centro-sul do Chile

    OpenAIRE

    Iván Palomo; Fabian Segovia; Daniela Parra; Marcelo Alarcón; Edgardo Rojas

    2009-01-01

    Thrombosis is a result of the interaction between predisposing genetic polymorphisms and acquired risk factors. The two prothrombotic polymorphisms which are most frequently associated with thrombosis are factor V (FV) Leiden and the prothrombin (PT) G20210A mutation. The objective of this work was to investigate the prevalence of both factors in the central-south region of Chile. Determination of the frequency was carried out by means of a genetic analysis of 1200 healthy, non-native individ...

  3. Nuevo esquema estratigráfico para los depósitos marinos mio-pliocenos del área de Navidad (33º00'-34º30'S, Chile central New stratigrafic scheme for the Mio-Pliocene marine deposits of the Navidad area (33º00'-34º30'S, central Chile

    Directory of Open Access Journals (Sweden)

    Alfonso Encinas

    2006-07-01

    Full Text Available Varios autores han propuesto diferentes esquemas estratigráficos para los depósitos sedimentarios neógenos marinos que afloran en la zona costera de Chile central entre Valparaíso (~33°00'S y Punta Topocalma (~34°30'S, sin que exista un consenso al respecto. Tampoco existe acuerdo respecto a las correlaciones entre los depósitos que afloran en la parte norte de dicha zona, entre Valparaíso y San Antonio (~33°30'S con aquellos que aparecen en la parte sur, entre San Antonio y Punta Topocalma. Sobre la base de nuevos estudios estratigráficos, sedimentológicos y paleontológicos se propone, de manera formal, un nuevo esquema estratigráfico para estos depósitos. De acuerdo con este nuevo esquema se definen la Formación Navidad (Mioceno Superior-Plioceno Inferior y las formaciones Licancheu, Rapel y La Cueva (Plioceno. Se propone la elevación de las tres primeras unidades (Navidad, Licancheu y Rapel, generalmente consideradas como miembros en clasificaciones anteriores, al rango de formaciones debido a que se encuentran separadas por discontinuidades (paraconformidades de escala regional. En el presente trabajo se definen estas unidades, se revisan los esquemas anteriores y se justifica la proposición de este nuevo esquemaDifferent stratigraphic schemes have been proposed by various authors for the Neogene marine sedimentary deposits cropping out along the central Chilean coast between Valparaíso (~33°00'S and Punta Topocalma (~34°30'S, without any consensus having been reached. Neither does any agreement exist with respect to the correlation between the deposits cropping out in the northern part of this area, between San Antonio (~33°30'S and Valparaíso, and those of the southern part, between San Antonio and Punta Topocalma. Based on new stratigraphic, sedimentologic and paleontologic studies we propose a formal, new stratigraphic classification for this area. According to this scheme we define the Navidad Formation (Upper

  4. Liolaemus carlosgarini and Liolaemus riodamas (Squamata: Liolaemidae), two new species of lizards lacking precloacal pores, from Andean areas of central Chile.

    Science.gov (United States)

    Esquerré, Damien; Núñez, Herman; Scolaro, José Alejandro

    2013-01-01

    Most of the lizards of the Liolaemus genus present precloacal pores in males, with few exceptions in species of the lineomaculatus and neuquensis groups, and in the elongatus-kriegi complex. The elongatus-kriegi complex, belonging to the Liolaemus (sensu stricto) subgenus, is composed of medium sized, saxicolous, viviparous and insectivorous or omnivorous lizards, distributed between the Andean and Patagonian zones of Chile and Argentina. We reviewed the taxonomic history of this group, and we describe two new species, Liolaemus carlosgarini, found in the vicinity of the Maule Lagoon, in the Maule Region, Chile, and Liolaemus riodamas, described from the population that was originally designated as Liolaemus cf ceii, from Las Damas River, near the Termas del Flaco locality, in the Libertador Bernardo O'Higgins Region, thereby based on this research L. ceii is eliminated from the species belonging to Chile. Both species have as a diagnostic character the absence of precloacal pores, and we suggest here their presumptive systematic relationships in Liolaemus. We analyzed ten species of Liolaemus, in order to perform a phylogenetic analysis based on external morphology, using mostly squamation and morphometric characters. The analysis was performed using PAUP, with the Maximum Parsimony criterion. In addition, through diaphanisation, we studied and described the osteology of the new species. We conclude that species lacking precloacal pores do not form a monophyletic group, and that constructing a phylogeny using only external morphology, at least for this group of reptiles, is insufficient to establish solid phyletic relationships. Other sort of characters should complement the morphological ones. PMID:26131484

  5. Borage (Borago officinalis L. Response to N, P, K, and S Fertilization in South Central Chile Respuesta de Borraja (Borago officinalis L. a la Fertilización con N, P, K, y S en el Centro Sur de Chile

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    Marisol T. Berti

    2010-06-01

    Full Text Available Borage (Borago officinalis L. is an oilseed with a high gamma-linolenic acid (GLA content in its seed. The objective of this study was to determine the response of borage seed yield, oil content, and fatty acid composition to N, P, K, and S fertilizer treatments. Three experiments were conducted in Osorno (40º22’ S, 73º04’ W; 72 m.a.s.l., Chile. The first experiment was conducted during the 2005-2006 growing season, with four N rates (0, 100, 200, and 300 kg N ha-1, three P rates (0, 60, and 120 kg P2O5 ha-1 and two K rates (0 and 150 kg K2O ha-1. The second experiment was conducted in 2006-2007 and evaluated only the effect of four N rates (0, 50, 100 and 150 kg N ha-1 was evaluated because there was no response to P and K in the first experiment. The third experiment was conducted in the 2005-2006 and 2006-2007 and evaluated only two rates of S, 0 and 40 kg S ha-1. Seed yield was not affected by N, P, K, or their interactions in any of the experiments. As N rates increased GLA content increased. Mean seed yield increased to 98 kg ha-1 when applying 40 kg S ha-1. Results indicate that borage has a higher response to S applications than N. Further research is needed to determine the interactions between N and S applications, given that the experiments were conducted on soils with high P and K levels.La borraja (Borago officinalis L. es una oleaginosa con alto contenido de ácido gamma-linolénico (GLA en su semilla. El objetivo de este estudio fue determinar la respuesta en rendimiento de semillas, contenido y composición del aceite de borraja, a la fertilización con N, P, K y S. Tres experimentos fueron conducidos en Osorno (40º22’ S, 73º04’ O; 72 m.s.n.m., Chile. El primer experimento fue conducido en la temporada 2005-2006, con cuatro dosis de N (0, 100, 200 y 300 kg N ha-1, tres dosis de P (0, 60 y 120 kg P2O5 ha-1 y dos dosis de K (0 y 150 kg K2O ha-1. El segundo experimento fue conducido en el 2006-2007, cuando sólo se

  6. Cenozoic foreland-basin evolution in the northern Andes : insights from thermochronology and basin analysis in the Eastern Cordillera, Colombia

    OpenAIRE

    Parra, Mauricio

    2009-01-01

    The modern foreland basin straddling the eastern margin of the Andean orogen is the prime example of a retro-arc foreland basin system adjacent to a subduction orogen. While widely studied in the central and southern Andes, the spatial and temporal evolution of the Cenozoic foreland basin system in the northern Andes has received considerably less attention. This is in part due to the complex geodynamic boundary conditions, such as the oblique subduction and accretion of the Caribbean plates ...

  7. Isotope hydrology in northern Chile

    International Nuclear Information System (INIS)

    Environmental isotope analyses were done on samples from aquifers in the Pampa del Tamarugal and the Salar de Atacama drainage basin in northern Chile. In the Pampa it is possible to delineate individual groundwater bodies on the basis of their 18O and deuterium contents and, in some cases, to relate these to specific recharge areas. A marked displacement from the meteoric water line indicates that river recharge is an important mechanism for groundwater renewal. Groundwater ages appear high at distance from the Andes and much of the water found in the Pampa may have to be treated as a non-renewable resource. The groundwaters, springs and rivers of the Salar de Atacama drainage basin vary between -6.09 and -8.06%. No difference between the different waters can be recognized and an evaporative isotope enrichment indicates that also here river recharge is an important process. Some groundwaters adjacent to the Salar are very salty but 18O and deuterium data show that these waters are not refluxed brines but simply salty freshwater. The 14C contents in groundwaters and springs are very low but their delta13C values are high. It is concluded that this is probably due to the uptake of volcanic CO2. 14C age dating is thus not possible unless the delta13C values of all possible carbon sources can be defined and the geochemical evolution of the groundwaters is better understood. (author)

  8. DETECTION OF LOCAL SITE CONDITIONS INFLUENCING EARTHQUAKE SHOCK AND SECONDARY EFFECTS IN THE VALPARAISO AREA IN CENTRAL-CHILE USING REMOTE SENSING AND GIS METHODS

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    Barbara Theilen-Willige

    2011-01-01

    Full Text Available The potential contribution of remote sensing and GIS techniques to earthquake hazard analysis was investigated in Valparaiso in Chile in order to improve the systematic, standardized inventory of those areas that are more susceptible to earthquake ground motions or to earthquake related secondary effects such as landslides, liquefaction, soil amplifications, compaction or even tsunami-waves. Geophysical, topographical, geological data and satellite images were collected, processed, and integrated into a spatial database using Geoinformation Systems (GIS and image processing techniques. The GIS integrated evaluation of satellite imageries, of digital topographic data and of various open-source geodata can contribute to the acquisition of those specific tectonic, geomorphologic/ topographic settings influencing local site conditions in Valparaiso, Chile. Using the weighted overlay techniques in GIS, susceptibility maps were produced indicating areas, where causal factors influencing near- surface earthquake shock occur aggregated. Causal factors (such as unconsolidated sedimentary layers within a basin’s topography, higher groundwater tables, etc. summarizing and interfering each other, rise the susceptibility of soil amplification and of earthquake related secondary effects. This approach was used as well to create a tsunami flooding susceptibility map. LANDSAT Thermal Band 6-imageries were analysed to get information of surface water currents in this area.

  9. Across the southern Andes on fin: glacial refugia, drainage reversals and a secondary contact zone revealed by the phylogeographical signal of Galaxias platei in Patagonia.

    Science.gov (United States)

    Zemlak, Tyler S; Habit, Evelyn M; Walde, Sandra J; Battini, Miguel A; Adams, Emily D M; Ruzzante, Daniel E

    2008-12-01

    We employed DNA sequence variation at two mitochondrial (control region, COI) regions from 212 individuals of Galaxias platei (Pisces, Galaxiidae) collected throughout Patagonia (25 lakes/rivers) to examine how Andean orogeny and the climatic cycles throughout the Quaternary affected the genetic diversity and phylogeography of this species. Phylogenetic analyses revealed four deep genealogical lineages which likely represent the initial division of G. platei into eastern and western lineages by Andean uplift, followed by further subdivision of each lineage into separate glacial refugia by repeated Pleistocene glacial cycles. West of the Andes, refugia were likely restricted to the northern region of Patagonia with small relicts in the south, whereas eastern refugia appear to have been much larger and widespread, consisting of separate northern and southern regions that collectively spanned most of Argentinean Patagonia. The retreat of glacial ice following the last glacial maximum allowed re-colonization of central Chile from nonlocal refugia from the north and east, representing a region of secondary contact between all four glacial lineages. Northwestern glacial relicts likely followed pro-glacial lakes into central Chilean Patagonia, whereas catastrophic changes in drainage direction (Atlantic --> Pacific) for several eastern palaeolakes were the likely avenues for invasions from the east. These mechanisms, combined with evidence for recent, rapid and widespread population growth could explain the extensive contemporary distribution of G. platei throughout Patagonia. PMID:19017262

  10. Remote sensing and climate data as a key for understanding fasciolosis transmission in the Andes: review and update of an ongoing interdisciplinary project

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    Màrius V. Fuentes

    2006-11-01

    Full Text Available Fasciolosis caused by Fasciola hepatica in various South American countries located on the slopes of the Andes has been recognized as an important public health problem. However, the importance of this zoonotic hepatic parasite was neglected until the last decade. Countries such as Peru and Bolivia are considered to be hyperendemic areas for human and animal fasciolosis, and other countries such as Chile, Ecuador, Colombia and Venezuela are also affected. At the beginning of the 1990s a multidisciplinary project was launched with the aim to shed light on the problems related to this parasitic disease in the Northern Bolivian Altiplano. A few years later, a geographic information system (GIS was incorporated into this multidisciplinary project analysing the epidemiology of human and animal fasciolosis in this South American Andean region. Various GIS projects were developed in some Andean regions using climatic data, climatic forecast indices and remote sensing data. Step by step, all these GIS projects concerning the forecast of the fasciolosis transmission risk in the Andean mountain range were revised and in some cases updated taking into account new data. The first of these projects was developed on a regional scale for the central Chilean regions and the proposed model was validated on a local scale in the Northern Bolivian Altiplano. This validated mixed model, based on both fasciolosis climatic forecast indices and normalized difference vegetation index values from Advanced Very High Resolution Radiometer satellite sensor, was extrapolated to other human and/or animal endemic areas of Peru and Ecuador. The resulting fasciolosis risk maps make it possible to show the known human endemic areas of, mainly, the Peruvian Altiplano, Cajamarca and Mantaro Peruvian valleys, and some valleys of the Ecuadorian Cotopaxi province. Nevertheless, more climate and remote sensing data, as well as more accurate epidemiological reports, have to be

  11. Spatio-temporal variability of snow water equivalent in the extra-tropical Andes Cordillera from distributed energy balance modeling and remotely sensed snow cover

    Science.gov (United States)

    Cornwell, E.; Molotch, N. P.; McPhee, J.

    2016-01-01

    Seasonal snow cover is the primary water source for human use and ecosystems along the extratropical Andes Cordillera. Despite its importance, relatively little research has been devoted to understanding the properties, distribution and variability of this natural resource. This research provides high-resolution (500 m), daily distributed estimates of end-of-winter and spring snow water equivalent over a 152 000 km2 domain that includes the mountainous reaches of central Chile and Argentina. Remotely sensed fractional snow-covered area and other relevant forcings are combined with extrapolated data from meteorological stations and a simplified physically based energy balance model in order to obtain melt-season melt fluxes that are then aggregated to estimate the end-of-winter (or peak) snow water equivalent (SWE). Peak SWE estimates show an overall coefficient of determination R2 of 0.68 and RMSE of 274 mm compared to observations at 12 automatic snow water equivalent sensors distributed across the model domain, with R2 values between 0.32 and 0.88. Regional estimates of peak SWE accumulation show differential patterns strongly modulated by elevation, latitude and position relative to the continental divide. The spatial distribution of peak SWE shows that the 4000-5000 m a.s.l. elevation band is significant for snow accumulation, despite having a smaller surface area than the 3000-4000 m a.s.l. band. On average, maximum snow accumulation is observed in early September in the western Andes, and in early October on the eastern side of the continental divide. The results presented here have the potential of informing applications such as seasonal forecast model assessment and improvement, regional climate model validation, as well as evaluation of observational networks and water resource infrastructure development.

  12. Quinua in Chile

    OpenAIRE

    Martinez, Enrique A.; Fuentes, Francisco F.; Chia, Eduardo; Namdar-Irani, Mina; Olguin, Pablo; Saa, Constanza; Thomet, Max; Vidal, Alejandra

    2015-01-01

    The biogeography of quinoa (Chenopodium quinua Willd.) provides a comprehensive view of a crop that is relatively minor in Chilean agriculture, despite growing in a large geographical area (18°–47°S). Quinoa’s genetic diversity illustrates that it is a vital crop in the South American Andes region. It was domesticated in various geographical zones, which generated a wide variety of adaptative morphological and environmental features. Specific adaptations in each macrozone throughout the Andes...

  13. Patrones reproductivos del lobo marino común, Otaria flavescens (Shaw 1800, en el centro-sur de Chile Breeding patterns in southern sea lions, Otaria flavescens (Shaw 1800, in south-central Chile

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    HÉCTOR J PAVÉS

    2005-12-01

    Full Text Available El desfase latitudinal de los eventos reproductivos en Otaria flavescens sugiere la existencia de una adaptación fisiológica y conductual a condiciones ambientales locales. La identificación de cambios en los patrones conductuales intraespecíficos frente a modificaciones ambientales sugieren una relación entre estos. Se pretende revisar los patrones reproductivos del O. flavescens, determinando la existencia de una sincronización y estabilidad en ellos durante las temporadas 1996-1997 y 1997-1998 en la colonia de Punta Lobería, Chile. Se realizaron observaciones directas de las agrupaciones y conductas reproductivas empleando binoculares, y apoyadas por el uso de material fílmico y fotográfico. Los resultados evidenciaron modificaciones en, (a el número de harenes (de 28 disminuye a 19, (b la distribución espacial de los harenes (70 % de los harenes durante 1997-1998 se establecieron en el lado norte de la playa reproductiva, durante la temporada anterior estos se distribuyeron a lo largo de toda la playa, (c proporción etaria (un macho: 12 hembras: un juvenil: siete cachorros, desciende a un macho: nueve hembras: dos juveniles: seis cachorros, (d índice de poliginia (de 12,4 a 7,8 HPMT y de 11 a 9 HP, y (e la población organizada en harenes (disminución del 10,3 %. Estas variaciones estarían relacionadas con la reducción del espacio óptimo para el establecimiento de harenes debido a la incorporación de suelo/roca posterior a un derrumbe invernal. Los patrones conductuales reproductivos que se mantuvieron invariables durante las temporadas fueron, (a la estacionalidad de los harenes (constitución durante la cuarta semana de diciembre y disolución en la cuarta semana de febrero, (b el período de partos (inicio durante la segunda semana de enero, finalización durante la cuarta semana de enero, y (c el período de cópulas (inicio durante la tercera semana de enero, finalización durante la segunda semana de febrero. Por lo

  14. Revisiting chlorophyll data along the coast in north-central Chile, considering multiscale environmental variability Reinterpretando datos de clorofila en la costa centro-norte de Chile, considerando variabilidad ambiental de multiescala

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    VIVIAN MONTECINO

    2006-06-01

    Full Text Available Phytoplankton abundance in the surface mixed layer of the coastal ocean responds to environmental changes at various time scales. Here the "warm", "cold" and "neutral" phases of "three environmental cycles" have been jointly considered to assess chlorophyll-a (Chl-a biomass variability for both the active and relaxed phases of the local, wind-driven coastal upwelling: (i the interannual ENSO cycle (ii the annual (seasonal cycle and (iii the intraseasonal cycle associated with equatorially-sourced, ocean trapped-waves along the coast in northern Chile. The main goal of this study is to quantitatively assess the variability of the depth- integrated Chl-a biomass in the euphotic zone (¾Chl-a in terms of an overall "environmental condition" over a 50 km upwelling sensitive coastal strip, revisiting published and unpublished Chl-a ship (Cship = Chl-a + Phaeopigments data. All possible "environmental conditions" combinations were further ranked into seven "environmental indices" ranging from 0 ("absolutely cold" to 6 ("absolutely warm". Out of 332 samples of ¾Chl-a, 198/134 were obtained during active/relaxed upwelling conditions from which 24/38 and 30/36 samples were associated with the simultaneous occurrence of at least two "cold"/"warm" phases of the three environmental cycles ("cold"/"warm" environmental conditions, respectively. Lower ¾Chl-a values during "cold" and "warm" environmental conditions relative to the "neutral" ones reached statistical significance for both active and relaxed conditions (144/60 samples respectively. Higher turbulent mixing during "cold" environmental conditions and a deeper nutricline during "warm" ones would explain lower ¾Chl-a-values. Satellite chlorophyll (Csat data obtained in clear skies (active upwelling only, showed a similar distribution to those of ¾Chl-a when classified into the corresponding "environmental indices". These results suggest that during "neutral" (transitional "environmental conditions

  15. The High Andean Cordillera of central Argentina and Chile along the Piuquenes Pass-Cordon del Portillo transect: Darwin's pioneering observations compared with modern geology

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    Laura Giambiagi

    2009-04-01

    Full Text Available The geological observations made by Darwin in 1835 during his crossing of the Andes from Santiago to Mendoza via the Piuquenes Pass and Cordón del Portillo are compared with the present geological knowledge of the Cordillera Principal and Cordillera Frontal at 33°-34°S. The analysis of the complex stratigraphy of the Cordillera Principal, the imbricated structure of the Aconcagua fold and thrust belt, as well as the stratigraphy and structure of the inter mountain foreland Tunuyán Basin, allows to assess the pioneer observations of Darwin. He recognized the old metamorphic basement and the granitoids and volcanic sequences of late Paleozoic to Triassic age of the Cordillera Frontal, established the Cretaceous age of the marine successions cropping out along the eastern Cordillera Principal and studied the conglomeratic deposits associated with the uplift of the Cordillera in the Alto Tunuyán Basin. Based on the study of clast provenance of the synorogenic deposits of the Alto Tunuyán Basin, Darwin recognized that the Cordillera Frontal was uplifted later than the Cordillera Principal. The present knowledge of this sector of the Andean Cordillera confirms his pioneer observations and show that Darwin was one of the first scientists ever in realizing that in an orogenic system the sequence of uplift and deformation proceeds from hinterland towards foreland, according to a process that is exceptionally well-illustrated along the Piuquenes-Cordón del Portillo transect.

  16. Spatio-temporal distribution of spionids (Polychaeta-Spionidae in an estuarine system in south-central Chile Distribución espacio-temporal de los espiónidos (Polychaeta-Spionidae en un sistema de estuarios del centro sur de Chile

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    MAURICIO DÍAZ-JARAMILLO

    2008-12-01

    Full Text Available This study is based on the identification and distribution of spionid polychaetes in relation to abiotic characteristics of the environment at the mouth of the Valdivia-Tornagaleones estuary in south-central Chile. Four samplings were carried out in 2005, in which eight species were identified including Aquilaspio peruana, Boccardia polybranchia, Carazziella carrascoi, Dipolydora socialis, Minuspio patagónica, Rhynchospio glutaea, Scolelepis quinquedentata and Spiophanes sp. As it is typical of other estuaries in south central Chile, spionids were an important component of the macroinfauna of the Valdivia estuary. The distribution of the Spionidae family in the system showed higher species richness in the outer reach of the estuary but higher abundance (number of specimens at the inner reach. The distributional pattern of the polychaetes did not vary throughout the year, exhibiting strong spatial zonation with three significantly different assemblages. Minuspio patagónica, A. peruana and C. carrascoi contributed to the similarity between these three groups, as well as to the formation of a general component in the macroinfauna. Sedimentological and depth variables, as well as sedimentary organic material were only marginally related to the distribution of spionids. Results showed that bottom salinity was the environmental variable responsible for spatial differentiation of spionids in the three groups, which permit to differentiate the outer-reach species from those in the internal area of the estuary. The significant contribution of spionids to the total component of macroinfauna in the studied area shows that these species are a significant component of the estuarine and transition areas in the southwest Pacific coast.El estudio se desarrolla en base a la identificación y distribución de Spionidae y su relación con las características abióticas del medio, en la desembocadura del sistema estuarial Valdivia-Tornagaleones (Chile. Se

  17. Effect of Compost Application on Some Properties of a Volcanic Soil from Central South Chile Efecto de la Aplicación de Compost sobre Algunas Propiedades de un Suelo Volcánico de La Región Centro-Sur de Chile

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    Pedro José Valarini

    2009-09-01

    Full Text Available Soil compost application is a common soil management practice used by small farmers of Central-South Chile that produces positive effects on soil properties and also promotes presence and activity of arbuscular mycorrhizal fungi (AMF. This fungi form symbiosis with plant roots improving plant nutrition, as well as producing glomalin, a glycoprotein that has been associated with soil aggregation stability. Therefore, the aim of this study was to evaluate, in an Ultisol from Central-South Chile, the effect of different doses of compost on some soil characteristics at the end of the third year of a crop sequence including wheat (Triticum aestivum L., bean (Phaseolus vulgaris L., and grassland (Lolium multiflorum Lam. associated with Trifolium repens L.. Studied soil characteristics included chemical (pH, available-P, organic C, biological (C and N biomass, AMF spore number, root colonization percentage, mycelium length, and glomalin content, as well as physical parameters (water holding capacity [WHC], and water stable aggregates [WSA]. Results showed that, in general, compost application increased soil pH, mycorrizal roots, mycelium length, glomalin levels, and WSA. Significant relationships were found between C and N biomass, C biomass and WSA, C biomass and glomalin, WSA and WHC, among others. Results suggest that compost application to this type of soil is a feasible option as a fertilizer substitute, and a way to avoid soil erosion by small local farmers involved in organic agriculture.La aplicación de compost al suelo, práctica habitual en predios de pequeños agricultores de la región centro-sur de Chile, produce efectos positivos en sus propiedades y promueve la presencia y actividad de los hongos micorrícicos arbusculares (AMF. Estos hongos forman simbiosis con las raíces de las plantas mejorando su nutrición y además producen una glicoproteína llamada glomalina, la cual ha sido relacionada con la estabilidad de los agregados de

  18. Parasites of the Green-backed Firecrown (Sephanoides sephaniodes) in Chile Parásitos del picaflor chico (Sephanoides sephaniodes) en Chile

    OpenAIRE

    Daniel González-Acuña; Carolina Silva; Marta Soto; Sergei Mironov; Lucila Moreno; González-Gómez, Paulina L.; Hasan Badrul; Mike Kinsella

    2011-01-01

    Gastrointestinal and external parasites from 12 Green-backed Firecrown (Sephanoides sephaniodes) were collected between January 2004 and December 2008 from the Biobío Region south-central Chile and Santiago (central Chile). Helminths collected included 1 trematode species (Mosesia sp.) and 1 cestode species (Hymenolepis trinidadensis). The mite Proctophyllodes huitzilopchtlii was the only ectoparasite species found. All these parasites represent new records for Chile and the first parasites r...

  19. La dieta y fauna de endoparásitos del pejesapo Gobiesox marmoratus Jenyns, 1842 (Pisces: Gobiesocidae en el litoral central de Chile están conectadas pero no correlacionadas Feeding habits and endoparasite fauna of the clingfish Gobiesox marmoratus Jenyns, 1842 (Pisces: Gobiesocidae on the central coast of Chile are intertwined, but not correlated

    Directory of Open Access Journals (Sweden)

    M. Cecilia Pardo-Gandarillas

    2004-12-01

    similarity is documented in the composition of the endoparasitic fauna and the diet of the clingfish G. marmoratus Jenyns, 1842, between three localities off the central coast of Chile separated about 400 km from their nearest neighbor(s. Clingfish in the samples were similar between localities in total body length. The parasite fauna was composed by 16 metazoan taxa (including five Myxozoa. Parasites were found in 38.8 % of the 108 clingfish examined, whereas 32.4 % of the fish in the samples had stomach contents, where 37 prey items were recognized. The even rarer cases of co-occurrence of parasites and prey impeded the search of correlations between both type of variables, such as that between the dietary width and parasite richness. Composition of parasite infracommunities and diet changed along host ontogeny. The diet of juvenile and adult clingfish consisted mainly of amphipods, decapod crustaceans and mollusks at the three localities. The numerical descriptors of the diet and of infracommunities (total abundance, diversity and richness are similar between the localities and along the host ontogeny. The composition of the endoparasitic fauna necessarily depends on the diet of the clingfish, but there is no statistical correlation between both variables. This can be due to the small maximum body size reached by the adults, to the short length of the digestive tract, to the differences in the rate and frequency at which parasites and prey enter and stay in the hosts, to the level of taxonomic resolution attained in prey and/or parasites, and to having decided to include or not rare prey/parasites in the analyses

  20. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1997 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1997 calendar year. The report begins...

  1. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : Updated- 2003 annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 2003 calendar year. The report begins...