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Sample records for central andes chile

  1. Central Chile

    2002-01-01

    The beginning of spring in central Chile looked like this to SeaWiFS. The snow-covered Andes mark the country's eastern border, and phytoplankton blooms and river sediment plumes fill the waters off its west coast. A large eddy due west of Concepcion is highlighted by the phytoplankton it contains.

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

    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

  3. Paleozoic evolution of active margin basins in the southern Central Andes (northwestern Argentina and northern Chile)

    Bahlburg, H.; Breitkreuz, C.

    The geodynamic evolution of the Paleozoic continental margin of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American margin at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin

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

    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

  5. Use of high-resolution satellite images for detection of geological structures related to Central Andes geothermal field, Chile.

    Benavides-Rivas, C. L.; Soto-Pinto, C. A.; Arellano-Baeza, A. A.

    2014-12-01

    Central valley and the border with Argentina in the center, and in the fault system Liquiñe-Ofqui in the South of the country. High resolution images from the LANDSAT 8 satellite have been used to delineate the geological structures related to the potential geothermal reservoirs located at the northern end of the Southern Volcanic Zone of Chile. It was done by applying the lineament extraction technique, using the ADALGEO software, developed by [Soto et al., 2013]. These structures have been compared with the distribution of main geological structures obtained in the field. It was found that the lineament density increases in the areas of the major heat flux indicating that the lineament analysis could be a power tool for the detection of faults and joint zones associated to the geothermal fields. A lineament is generally defined as a straight or slightly curved feature in the landscape visible satellite image as an aligned sequence of pixel intensity contrast compared to the background. The system features extracted from satellite images is not identical to the geological lineaments that are generally determined by ground surveys, however, generally reflects the structure of faults and fractures in the crust. A temporal sequence of eight Landsat multispectral images of Central Andes geothermal field, located in VI region de Chile, was used to study changes in the configuration of the lineaments during 2011. The presence of minerals with silicification, epidotization, and albitization, which are typical for geothrmal reservoirs, was also identified, using their spectral characteristics, and subsequently corroborated in the field. Both lineament analysis and spectral analysis gave similar location of the reservoir, which increases reliability of the results.

  6. Variaciones de un glaciar de montaña en los Andes de Chile central en las últimas dos décadas

    1995-01-01

    Full Text Available VARIATIONS D’UN GLACIER DE MONTAGNE DANS LES ANDES DU CHILI CENTRAL AU COURS DES DEUX DERNIÈRES DÉCENNIES. Les résultats du bilan de masse du glacier Echaurren Norte sont présentés. Il s’agit d’un glacier de montagne de 0,4 km2 situé dans les Andes du Chili central, à 50 km à l’est de Santiago, à une altitude moyenne de 3 750 m. Ce programme de la Direction Générale d’Eaux du Chili a permis de recueillir régulièrement une information sur les bilans de masse pendant 18 ans, entre les années 1975 et 1993. C’est le seul registre de bilan de masse d’un glacier au Chili. L’ablation pendant la période de fonte a été de 252 cm d’eau en moyenne annuelle, avec une accumulation hivernale moyenne de 280 cm d’eau. Le bilan net est positif pour la période, mais on observe une grande variation interannuelle. Le bilan positif du glacier Echaurren Norte contraste avec le recul généralisé des autres glaciers du Chili central. Se presentan resultados del balance de masa del glaciar Echaurren Norte, un glaciar de montaña de 0,4 km2 ubicado a una altitud media de 3 750 m.s.n.m., en los Andes de Chile central, 50 km al este de Santiago. Los datos, recolectados como parte de un programa regular de la Dirección General de Aguas, Chile, cubren un período de 18 años, desde 1975 a 1993 y constituyen el único registro de balance de masa de un glaciar en Chile. La ablación durante el período de deshielo fue de 252 cm eq. en agua anuales en promedio, con una acumulación invernal promedio de 280 cm eq. en agua. El balance neto para el período es positivo, pero existe una gran variación interanual. El balance positivo del glaciar Echaurren Norte contrasta con el retroceso generalizado en otros glaciares de Chile central. VARIATIONS OF A MOUNTAIN GLACIER IN THE CENTRAL CHILEAN ANDES DURING THE LAST TWENTY YEARS. Mass balance results for Echaurren Norte Glacier are presented. This mountain glacier, with an area of 0,4 km2, is located at

  7. Impact of Santiago de Chile urban atmospheric pollution on anthropogenic trace elements enrichment in snow precipitation at Cerro Colorado, Central Andes

    Cereceda-Balic, F.; Palomo-Marín, M. R.; Bernalte, E.; Vidal, V.; Christie, J.; Fadic, X.; Guevara, J. L.; Miro, C.; Pinilla Gil, E.

    2012-02-01

    Seasonal snow precipitation in the Andes mountain range is evaluated as an environmental indicator of the composition of atmospheric emissions in Santiago de Chile metropolitan area, by measuring a set of representative trace elements in snow samples by ICP-MS. Three late winter sampling campaigns (2003, 2008 and 2009) were conducted in three sampling areas around Cerro Colorado, a Central Andes mountain range sector NE of Santiago (36 km). Nevados de Chillán, a sector in The Andes located about 500 km south from the metropolitan area, was selected as a reference area. The experimental results at Cerro Colorado and Nevados de Chillán were compared with previously published data of fresh snow from remote and urban background sites. High snow concentrations of a range of anthropogenic marker elements were found at Cerro Colorado, probably derived from Santiago urban aerosol transport and deposition combined with the effect of mining and smelting activities in the area, whereas Nevados de Chillán levels roughly correspond to urban background areas. Enhanced concentrations in surface snow respect to deeper samples are discussed. Significant differences found between the 2003, 2008 and 2009 anthropogenic source markers profiles at Cerro Colorado sampling points were correlated with changes in emission sources at the city. The preliminary results obtained in this study, the first of this kind in the southern hemisphere, show promising use of snow precipitation in the Central Andes as a suitable matrix for receptor model studies aimed at identifying and quantifying pollution sources in Santiago de Chile.

  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

    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. Glacialmorphological reconstruction of glacier advances and glacial lake outburst floods at the Cachapoal glacier in the Dry Central Andes of Chile (34°S)

    Iturrizaga, Lasafam; Charrier, Reynaldo

    2013-04-01

    Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina

  10. 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

    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

  11. Low-pressure evolution of arc magmas in thickened crust: The San Pedro-Linzor volcanic chain, Central Andes, Northern Chile

    Godoy, Benigno; Wörner, Gerhard; Kojima, Shoji; Aguilera, Felipe; Simon, Klaus; Hartmann, Gerald

    2014-07-01

    Magmatism at Andean Central Volcanic Zone (CVZ), or Central Andes, is strongly influenced by differentiation and assimilation at high pressures that occurred at lower levels of the thick continental crust. This is typically shown by high light to heavy rare earth element ratios (LREE/HREE) of the erupted lavas at this volcanic zone. Increase of these ratios with time is interpreted as a change to magma evolution in the presence of garnet during evolution of Central Andes. Such geochemical signals could be introduced into the magmas be high-pressure fractionation with garnet on the liquidus and/or assimilation from crustal rocks with a garnet-bearing residue. However, lavas erupted at San Pedro-Linzor volcanic chain show no evidence of garnet fractionation in their trace element patterns. This volcanic chain is located in the active volcanic arc, between 22°00‧S and 22°30‧S, over a continental crust ˜70 km thick. Sampled lavas show Sr/Y and Sm/Yb ratios Chile. We relate our geochemical observations to shallow crustal evolution of primitive magmas involving a high degree of assimilation of upper continental crust. We emphasize that low pressure AFC- (Assimilation Fractional Crystallization) type evolution of the San Pedro-Linzor volcanic chain reflects storage, fractionation, and contamination of mantle-derived magmas at the upper felsic crust (<40 km depth). The ascent of mantle-derived magmas to mid-crustal levels is related with the extensional regime that has existed in this zone of arc-front offset since Late-Miocene age, and the relatively thin portion of mafic lower crust observed below the volcanic chain.

  12. Mafic enclaves in dacitic domes and their relation with La Poruña scoria cone, Central Andes, northern Chile

    González-Maurel, O. P.; Gallmeyer, G.; Godoy, B.; Menzies, A.; le Roux, P. J.; Harris, C.

    2017-12-01

    Chao Dacite, Chillahuita, Cerro Pabellón, Chanka, Chac-Inca, and Cerro La Torta (or Tocorpuri) are dacitic domes of late Pleistocene age (30 to 140 ka; Renzulli et al., 2006; Tierney et al., 2016) located in Northern Chilean Central Andean province (NCCA; 17°20'S - 27°40'S). While, La Poruña is a 180 m high basaltic-andesite scoria cone erupted ca. 100 ka (Wörner et al., 2000). This scoria cone is also located at the NCCA, 26 km to the SW of Chanka and 45 km to the NW of Chao Dacite. The dacitic domes are generally porphyritic and highly crystalline lavas (30 - 50 vol % phenocrysts, plagioclase > biotite > amphibole > quartz ≥ accessory), with hyalopilitic or intersertal groundmass. These domes contain mafic enclaves, mostly andesite in composition, with plagioclase > amphibole > biotite ≥ clinopyroxene ≥ olivine ≥ accessory phenocryst (10 - 20 vol %) in a lightly oxidized groundmass with intersertal or intergranular textures. In contrast, La Poruña rocks are mostly aphanitic (75 - 85 vol % groundmass) and highly vesicular, with plagioclase > olivine ≥ clinopyroxene ≥ orthopyroxene phenocrysts in an intersertal or hyalopilitic groundmass. Although petrographically different, the composition (57 wt % SiO2; 580 ppm Sr, 87Sr/86Sr = 0.7066) of mafic enclaves from Cerro Pabellón dome are similar to the lava flows and pyroclastic blocks of La Poruña scoria cone (55 - 59 wt % SiO2; 560 - 610 ppm Sr; 0.7062 - 0.7066 87Sr/86Sr). Based on this data and the eruption ages of these volcanic structures, we suggest that the mafic enclaves and La Poruña magmas are co-genetic. Thus, we propose that the genesis of these mafic enclaves is associated with the origin of less evolved parental magmas erupted in the NCCA, such as those from La Poruña. In this case, the mafic enclaves would represent batches of less evolved magmas that ascended from deeper sources and probably contributed in the eruption of the dacitic domes. Renzulli et al., 2006. In XI Congreso Geol

  13. Mycorrhizal compatibility and symbiotic seed germination of orchids from the Coastal Range and Andes in south central Chile.

    Herrera, Hector; Valadares, Rafael; Contreras, Domingo; Bashan, Yoav; Arriagada, Cesar

    2017-04-01

    Little is known about Orchidaceae plants in Chile and their mycorrhizal associations, a key issue for designing protective actions for endangered species. We investigated root fungi from seven terrestrial orchid species to identify potential mycorrhizal fungi. The main characteristics of Rhizoctonia-like fungi were observed under light microscopy, and isolates were identified through PCR-ITS sequencing. Molecular identification of fungal sequences showed a high diversity of fungi colonizing roots. Fungal ability to germinate seeds of different orchids was determined in symbiotic germination tests; 24 fungal groups were isolated, belonging to the genera Tulasnella, Ceratobasidium, and Thanatephorus. Furthermore, dark septate and other endophytic fungi were identified. The high number of Rhizoctonia-like fungi obtained from adult orchids from the Coastal mountain range suggests that, after germination, these orchids may complement their nutritional demands through mycoheterotrophy. Nonetheless, beneficial associations with other endophytic fungi may also co-exist. In this study, isolated mycorrhizal fungi had the ability to induce seed germination at different efficiencies and with low specificity. Germin ation rates were low, but protocorms continued to develop for 60 days. A Tulasnella sp. isolated from Chloraea gavilu was most effective to induce seed germination of different species. The dark septate endophytic (DSE) fungi did not show any effect on seed development; however, their widespread occurrence in some orchids suggests a putative role in plant establishment.

  14. 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

    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

  15. Evidence for Cenozoic extensional basin development and tectonic inversion south of the flat-slab segment, southern Central Andes, Chile (33° 36°S.L.)

    Charrier, R.; Baeza, O.; Elgueta, S.; Flynn, J. J.; Gans, P.; Kay, S. M.; Muñoz, N.; Wyss, A. R.; Zurita, E.

    2002-04-01

    The mainly volcanic Cenozoic deposits that make up much of the western part of the Principal Cordillera in Central Chile are generally subdivided into two major units: an older Abanico or Coya-Machalí Formation and a younger Farellones Formation. Difficulty in differentiating these units has led to considerable debate. On the basis of the wide distribution, great thickness, and presence of sedimentary intercalations, it has been postulated that these arc volcanics were deposited in an intermontane basin; more recently, it has been proposed that this basin developed under extensional conditions and underwent subsequent tectonic inversion. We present field, geochronologic, geochemical, and thermal maturity data that support the latter interpretation. Collectively, this new information clarifies the stratigraphic, tectonic, and paleogeographic evolution of these deposits. The vast geographic extent of the Abanico Formation and lateral equivalents, which reach from at least 32°30' to 44°S along the Principal Cordillera, its great thickness, and the presence of repeated thick fluvial and lacustrine intercalations all indicate deposition in a large, strongly subsident, and probably north-south oriented basin, developed between middle to late Eocene and Oligocene. The unconformable contact with underlying Mesozoic units observed at several localities indicates that deposition followed a substantial erosional episode during late Cretaceous and/or early Cenozoic time. Basal deposits of the Abanico Formation near Termas del Flaco increase rapidly in thickness to the west. Still further to the west, a thick Abanico section contains, in its upper part, mammal fossils older than those found in the basal deposits near Termas. This evidence indicates a major space of deposition west of this locality, which had been filled before deposition took place at Termas. The east-vergent, high-angle El Fierro thrust fault on the east side of the westward-growing deposits is interpreted

  16. 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

    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

  17. Late Oligocene-Early Miocene compressional tectosedimentary episode and associated land-mammal faunas in the Andes of central Chile and adjacent Argentina (32 37°s)

    Semper, Thierry; Marshall, Larry G.; Rivano, Sergio; Godoy, Estanislao

    1994-01-01

    A reassessment of the geologic and land-mammal fossil evidence used in attribution of a tectosedimentary episode in the Andes between 32 and 37°S to the Middle Eocene "Incaic tectonic phase" of Peru indicates that the episode occurred during Late Oligocene-Early Miocene times(~ 27-20 Ma). From west to east, three structural domains are recognized for this time span in the study area: a volcanic arc (Chile); a thin-skinned, E-verging fold-thrust belt (Cordillera Principal, Chile-Argentina border strip); and a foreland basin (Argentina). Initiation of thrusting in the Cordillera Principal fold-thrust belt produced the coeval initiation of sedimentation in the foreland basin of adjacent Argentina. This onset of foreland deposition postdates strata bearing a Divisaderan Land Mammal Age fauna (i.e. ~ 35-30 Ma) and is marked at ~ 36°30'S by the base of the "Rodados Lustrosos" conglomerates, which are conformably overlain by sedimentary rocks containing a Deseadan Land Mammal Age fauna (i.e. ~ 29-21 Ma). Geologic relationships between the thick volcanic Abanico (Coya-Machalí) and Farellones formations also demonstrate that this tectosedimentary episode practically ended at ~ 20 Ma at least in the volcanic arc, and was therefore roughly coeval with the major tectonic crisis (~ 27-19 Ma) known in northwestern Andean Bolivia some 1500 km to the north. This strongly suggests that a long, outstanding tectonic upheaval affected at least an extended 12-37°S segment of the Andean margin of South America during Late Oligocene and Early Miocene times.

  18. 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

    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

  19. The Amazon-Laurentian connection as viewed from the Middle Proterozoic rocks in the central Andes, western Bolivia and northern Chile

    Tosdal, R.M.

    1996-01-01

    Middle Proterozoic rocks underlying the Andes in western Bolivia, western Argentina, and northern Chile and Early Proterozoic rocks of the Arequipa massif in southern Peru?? from the Arequipa-Antofalla craton. These rocks are discontinuously exposed beneath Mesozoic and Cenozoic rocks, but abundant crystalline clasts in Tertiary sedimentary rocks in the western altiplano allow indirect samples of the craton. Near Berenguela, western Bolivia, the Oligocene and Miocene Mauri Formation contains boulders of granodiorite augen gneiss (1171??20 Ma and 1158??12 Ma; U-Pb zircon), quartzose gneiss and granofels that are inferred to have arkosic protoliths (1100 Ma source region; U-Pb zircon), quartzofeldspathic and mafic orthogneisses that have amphibolite- and granulite-facies metamorphic mineral assemblages (???1080 Ma metamorphism; U-Pb zircon), and undeformed granitic rocks of Phanerozoic(?) age. The Middle Proterozoic crystalline rocks from Berenguela and elsewhere in western Bolivia and from the Middle Proterozoic Bele??n Schist in northern Chile generally have present-day low 206Pb/204Pb ( 15.57), and elevated 208Pb/204Pb (37.2 to 50.7) indicative of high time-averaged Th/U values. The Middle Proterozoic rocks in general have higher presentday 206Pb/204Pb values than those of the Early Proterozoic rocks of the Arequipa massif (206Pb/204Pb between 16.1 and 17.1) but lower than rocks of the southern Arequipa-Antofalla craton (206Pb/204Pb> 18.5), a difference inferred to reflect Grenvillian granulite metamorphism. The Pb isotopic compositions for the various Proterozoic rocks lie on common Pb isotopic growth curves, implying that Pb incorporated in rocks composing the Arequipa-Antofalla craton was extracted from a similar evolving Pb isotopic reservoir. Evidently, the craton has been a coherent terrane since the Middle Proterozoic. Moreover, the Pb isotopic compositions for the Arequipa-Antofalla craton overlap those of the Amazon craton, thereby supporting a link

  20. Black carbon and other light-absorbing impurities in the Andes of Northern Chile

    Rowe, P. M.; Cordero, R.; Warren, S. G.; Pankow, A.; Jorquera, J.; Schrempf, M.; Doherty, S. J.; Cabellero, M.; Carrasco, J. F.; Neshyba, S.

    2015-12-01

    Black carbon (BC) and other light-absorbing impurities in snow absorb solar radiation and thus have the potential to accelerate glacial retreat and snowmelt. In Chile, glaciers and seasonal snow are important sources of water for irrigation and domestic uses. In July 2015 (Austral winter) we sampled snow in the western Andes in a north-south transect of Chile from 18 S to 34 S. Most of the sampled snow had fallen during a single synoptic event, during 11-13 July. The snow was melted and passed through 0.4 micrometer nuclepore filters. Preliminary estimates indicate that (1) the ratio of BC to dust in snow increases going south from Northern to Central Chile, and (2) in snow sampled during the two weeks following the snowstorm, the impurities were concentrated in the upper 5 cm of snow, indicating that the surface layer became polluted over time by dry deposition.

  1. PAH fluxes in the Laja Lake of south central Chile Andes over the last 50 years: Evidence from a dated sediment core

    Quiroz, Roberto; Popp, Peter; Urrutia, Roberto; Bauer, Coretta; Araneda, Alberto; Treutler, Hanns-Christian; Barra, Ricardo

    2005-01-01

    This paper reports the occurrence of polyaromatic hydrocarbons (PAHs) deposition inferred from a sediment core of an Andean lake in south central Chile. Sediments were carefully collected from one of the deepest section of the lake and sliced every 1 cm. The samples were analyzed for PAHs, 137 Cs, 210 Pb, organic carbon and grain-size. The stratigraphic chronology and the sedimentation rates were estimated using the sedimentary signature left by the 137 Cs and 210 Pb fallout as temporal markers. PAHs were quantified by HPLC-fluorescence detection (HPLC-Fluorescence). 15 priority EPA PAHs were analyzed in this study. Based on these results, PAH deposition over the last 50 years was estimated (a period characterized by an important intervention in the area). PAH concentration ranged from 226 to 620 ng g -1 d.w. The highest concentrations of PAHs were found in the core's bottom. The PAH profile is dominated by the presence of perylene indicating a natural source of PAH. In addition, two clear PAH deposition periods could be determined: the most recent with two-four rings PAHs, the older one with five-seven rings predomination. Determined fluxes where 71 to 972 μg m -2 year -1 , dominated by perylene deposition. PAH levels and fluxes are lower compared to the levels found in sediments from remote lakes in Europe and North America. It is concluded that the main source of PAHs into the Laja Lake sediments are of natural origin

  2. A further contribution to the knowledge of two inadequately known species of geophilid centipedes from the Andes of South-Central Chile, currently assigned to the genus Plateurytion Attems, 1909 (Chilopoda: Geophilomorpha).

    Pereira, Luis Alberto

    2015-10-06

    Two poorly known species of geophilid centipedes from the Andes of South-Central Chile, i.e., Plateurytion mundus (Chamberlin, 1955) and Plateurytion zapallar (Chamberlin, 1955) (Myriapoda: Chilopoda: Geophilomorpha), are herein redescribed and illustrated after type specimens of both taxa and new material of the latter, rectifying the condition of the coxosternites of the second maxillae, which are medially joined through a narrow, hyaline and non-areolate membranous isthmus only (instead of "broadly fused as in Pachymerium", as stated by Chamberlin), this being consistent with the current generic assignment of these species under Plateurytion Attems, 1909. New data on many morphological features of specific value, until now unknown, are also given for both taxa. Plateurytion zapallar is reported for the first time from Coquimbo region, 11 Km N of Los Vilos (Elqui province), Valparaíso region, Quebrada Huaquén, Pichicuy (Petorca province), La Campana National Park (Quillota province), and Quebrada el Tigre, Cachagua (Valparíso province). A key for identification of the South American species currently included in Plateurytion is given.

  3. Clumped Isotope Thermometry Reveals Variations in Soil Carbonate Seasonal Biases Over >4 km of Relief in the Semi-Arid Andes of Central Chile

    Burgener, L. K.; Huntington, K. W.; Hoke, G. D.; Schauer, A. J.; Ringham, M. C.; Latorre Hidalgo, C.; Díaz, F.

    2015-12-01

    The application of carbonate clumped isotope thermometry to soil carbonates has the potential to shed new light on questions regarding terrestrial paleoclimate. In order to better utilize this paleoclimate tool, outstanding questions regarding seasonal biases in soil carbonate formation and the relationship between soil carbonate formation temperatures (T(Δ47)) and surface temperatures must be resolved. We address these questions by comparing C, O, and clumped isotope data from Holocene/modern soil carbonates to modern meteorological data. The data were collected along a 170 km transect with >4 km of relief in central Chile (~30°S). Previous studies have suggested that soil carbonates should record a warm season bias and form in isotopic equilibrium with soil water and soil CO2. We identify two discrete climate zones separated by the local winter snow line (~3200 m). Below this boundary, precipitation falls as rain and soil carbonate T(Δ47) values at depths >40 cm resemble summer soil temperatures; at higher elevations, precipitation falls as snow and T(Δ47) values resemble mean annual soil temperatures. Soil carbonates from the highest sample site (4700 m), which is devoid of vegetation and located near perennial snow fields, yield anomalous δ18O, δ13C, and T(Δ47) values, indicative of kinetic isotope effects that we attribute to cryogenic carbonate formation. Our results suggest that soil carbonates from depths temperature and precipitation, and should not be used as paleotemperature proxies. These findings (1) highlight the role of soil moisture in modulating soil carbonate formation and the resulting T(Δ47) values, (2) underscore the importance of understanding past soil moisture conditions when attempting to reconstruct paleotemperatures using carbonate clumped isotope thermometry, and (3) suggest that soil carbonates from high elevation or high latitude sites may form under non-equilibrium conditions.

  4. Oroclinal Bending and Mountain Uplift in the Central Andes

    Mpodozis, C.; Arriagada, C.; Roperch, P.

    2007-05-01

    The large paleomagnetic database now available for the Central Andes permits a good understanding of the overall spatial and temporal variations of rotations. Mesozoic to Early Paleogene rocks along the forearc of northern Chile (23°-28°S) record significant clockwise rotations (>25°) [Arriagada et al., 2006, Tectonics, doi:10.1029/2005TC001923]. Along the forearc of southern Peru, counterclockwise rotations recorded within flat lying red-beds (Moquegua Formation) increase from about -30° at 17.5°S to - 45° at15.5°S and decrease through time from the late Eocene to the late Oligocene-early Miocene [Roperch et al., 2006, Tectonics, doi:10.1029/2005TC001882]. Recently published thermo-chronological studies show evidence for strong exhumation within Bolivian Eastern Cordillera and the Puna plateau starting in the Eocene while structural studies indicate that the majority of crustal shortening in the Eastern Cordillera occurred during the Eocene-Oligocene, although the final stages of deformation may have continued through the Early Miocene. Rotations in the Peruvian and north Chilean forearc thus occurred at the same time than deformation and exhumation/uplift within the Eastern Cordillera. In contrast Neogene forearc rocks in southern Peru and northern Chile do not show evidences of rotation but low magnitude (10°) counterclockwise rotations are usually found in mid to late Miocene rocks from the northern Altiplano. These Neogene rotations are concomitant with shortening in the Sub-Andean zone and sinistral strike-slip faulting along the eastern edge of the northern Altiplano. We interpret the rotation pattern along the southern Peru and north Chile forearc as a result of strong late Eocene- late Oligocene oroclinal bending of the Central Andes associated with shortening gradients along the Eastern Cordillera associated both with the Abancay deflection and the Arica bend. The amount and spatial distribution of pre-Neogene shortening needed to account for

  5. Bofedales: high altitude peatlands of the central Andes Bofedales: turberas de alta montaña de los Andes centrales

    FRANCISCO A SQUEO

    2006-06-01

    Full Text Available There is an exceptional group of alpine peatlands in the world situated in the arid grasslands of the central Andes. The peatlands in northern Chile occur in the most arid part of their range. Members of the Juncaceae are the primary peat-forming plant species. Fresh and mildly saline groundwaters originate from glaciers, snowmelt and rain are the water sources for the northern Chile peatlands. Paleoecological investigations suggest that some peatlands are recent features of the landscape having developed within the last three thousand years or less. These peatlands are unique, extremely fragile water features sensitive to climate changes and human disturbances such as regional mining activity. Much more work is required to develop scientifically based sound management and conservation programs for the rare plants and animals that live in them and to ensure the future livelihoods of the indigenous peoples who depend on themExiste un grupo excepcional de turberas (bofedales de alta montaña en el mundo situados en la estepa árida de los Andes centrales. Los bofedales en el norte de Chile están presentes en la parte más árida de su rango. Las principales especies de plantas responsables de la formación de turba corresponden a miembros de Juncaceae. El agua fresca y medianamente salina de los bofedales proviene de agua subterránea asociada a riachuelos proveniente de glaciares, derretimiento de nieve y lluvia. Investigaciones paleoecológicas sugieren que algunos bofedales son integrantes recientes del paisaje, habiéndose desarrollado durante los últimos tres mil años o menos. Estos bofedales son entidades únicas, extremadamente frágiles por su dependencia del agua, sensibles a los cambios climáticos y vulnerables a la alteración humana tal como la actividad minera en la región. Se requiere mucho más trabajo para desarrollar programas de manejo y conservación, con sólidas bases científicas, de las plantas y animales que viven en

  6. Mountain building in the central Andes

    Kono, Masaru; Fukao, Yoshio; Yamamoto, Akihiko

    1989-04-01

    The Central Andes is the middle part of the Andean chain between about 13°S and 27°S, characterized by the parallel running high mountain chains (the Western and Eastern Cordilleras) at the edges of high plateaus with a height of about 4000 m and a width of 200 to 450 km (the Altiplano-Puna). From the examination of geophysical and geological data in this area, including earthquakes, deformation, gravity anomaly, volcanism, uplift history, and plate motion, we conclude that the continued plate subduction with domination of compressive stress over the entire arc system is the main cause of the tectonic style of the Central Andes. We propose that the present cycle of mountain building has continued in the Cenozoic with the most active phase since the Miocene, and that the present subduction angle (30°) is not typical in that period but that subduction with more shallowly dipping oceanic lithosphere has prevailed at least since the Miocene, because of the young and buoyant slab involved. This situation is responsible for the production of a broad zone of partial melt in the mantle above the descending slab. Addition of volcanic materials was not restricted to the western edge (where active volcanoes of the Western Cordillera exist) but extended to the western and central portion of the Altiplano-Puna. The western half of the Central Andes is essentially isostatic because the heat transferred with the volcanic activities softened the crust there. In the eastern edge, the thermal effect is small, and the crust is strongly pushed by the westward moving South American plate. This caused the shortening of crustal blocks due to reverse faulting and folding in the Eastern Cordillera and Amazonian foreland. The magmatism and crustal accretion are dominant at the western end of the mountain system and decrease eastward, while the compression and consequent crustal shortening are strongest at the eastern end and wane toward west. These two processes are superposed between

  7. Transboundary protected area proposals along the Southern Andes of Chile and Argentina: Status of current efforts

    Peter Keller

    2007-01-01

    An evolving network of protected areas along the southern Andes of Chile and Argentina-the heart of Patagonia-are in various stages of evaluation and potential Transboundary Protected Area designations. This paper examines three such efforts. The first proposal is the North Andean-Patagonia Regional Eco-Corridor, which was the subject of a recent bilateral meeting...

  8. Glacial lakes of the Central and Patagonian Andes

    Wilson, Ryan; Glasser, Neil F.; Reynolds, John M.; Harrison, Stephan; Anacona, Pablo Iribarren; Schaefer, Marius; Shannon, Sarah

    2018-03-01

    The prevalence and increased frequency of high-magnitude Glacial Lake Outburst Floods (GLOFs) in the Chilean and Argentinean Andes suggests this region will be prone to similar events in the future as glaciers continue to retreat and thin under a warming climate. Despite this situation, monitoring of glacial lake development in this region has been limited, with past investigations only covering relatively small regions of Patagonia. This study presents new glacial lake inventories for 1986, 2000 and 2016, covering the Central Andes, Northern Patagonia and Southern Patagonia. Our aim was to characterise the physical attributes, spatial distribution and temporal development of glacial lakes in these three sub-regions using Landsat satellite imagery and image datasets available in Google Earth and Bing Maps. Glacial lake water volume was also estimated using an empirical area-volume scaling approach. Results reveal that glacial lakes across the study area have increased in number (43%) and areal extent (7%) between 1986 and 2016. Such changes equate to a glacial lake water volume increase of 65 km3 during the 30-year observation period. However, glacial lake growth and emergence was shown to vary sub-regionally according to localised topography, meteorology, climate change, rate of glacier change and the availability of low gradient ice areas. These and other factors are likely to influence the occurrence of GLOFs in the future. This analysis represents the first large-scale census of glacial lakes in Chile and Argentina and will allow for a better understanding of lake development in this region, as well as, providing a basis for future GLOF risk assessments.

  9. Relationships between mineralization and silicic volcanism in the central Andes

    Francis, P.W.; Halls, C.; Baker, M.C.W.

    1983-10-01

    Studies of late Tertiary silicic volcanic centers in the Western and Eastern Cordilleras of the Central Andes show that three volcanic environments are appropriate sites for mineralization: (1) ring-fracture extrusions post-dating large calderas; (2) similar extrusions within ignimbrite shields; and (3) isolated, small silicic volcanoes. Subvolcanic tin mineralization in the Eastern Cordillera is located in silicic stocks and associated breccias of Miocene age. The Cerro Rico stock, Potosi, Bolivia, contains tin and silver mineralization and has an intrusion age apparently millions of years younger than that of the associated Kari Kari caldera. Similar age relationships between mineralization and caldera formation have been described from the San Juan province, Colorado. The vein deposits of Chocaya, southern Bolivia, were emplaced in the lower part of an ignimbrite shield, a type of volcanic edifice as yet unrecognized in comparable areas of silicic volcanism. The El Salvador porphyry copper deposit, Chile, is related to silicic stocks which may have been intruded along a caldera ring fracture. Existing models for the genesis of porphyry copper deposits suggest that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. The dome of La Soufriere, Guadeloupe is proposed as a modern analog for the surface expression of subvolcanic mineralization processes, the phreatic eruptions there suggesting the formation of hydrothermal breccia bodies in depth.

  10. On the generation of coastal lows in central Chile

    Rutllant, J.

    1994-07-01

    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

  11. Andes virus infections in the rodent reservoir and in humans vary across contrasting landscapes in Chile

    Torres-Pérez, Fernando; Palma, R. Eduardo; Hjelle, Brian; Ferres, Marcela; Cook, Joseph A.

    2009-01-01

    Hantavirus cardiopulmonary syndrome (HCPS) is an emerging infectious disease first reported in Chile in 1995. Andes hantavirus (ANDV) is responsible for the more than 500 cases of HCPS reported in Chile. Previous work showed that ANDV is genetically differentiated in Chile across contrasting landscapes. To determine whether the reservoir rodent (Oligoryzomys longicaudatus) populations are also geographically segregated, we conducted range-wide spatial genetic analyses of O. longicaudatus in Chile using the mitochondrial DNA cytochrome b gene. Given that landscape structure influences the incidence of hantavirus infections, we also tested 772 O. longicaudatus specimens for antibodies to ANDV captured during the period 2000 − 2006. Population genetic analyses of O. longicaudatus are largely congruent with those reported for ANDV, with the host primarily differentiated according to three defined ecoregions, Mediterranean, Valdivian rain forest and North Patagonian rain forest. Significant differences in the relative prevalence of anti-ANDV antibodies in rodent samples also were found across the three ecoregions. We relate these results to the number of reported human HCPS cases in Chile, and discuss the importance of landscape differences in light of ANDV transmission to humans and among rodent populations. PMID:19632357

  12. Subvolcanic contact metasomatism at El Laco Volcanic Complex, Central Andes Metasomatismo de contacto subvolcánico en el Complejo Volcánico El Laco, Andes centrales

    José A Naranjo

    2010-01-01

    Full Text Available Studies of drill cores from the Pasos Blancos area at El Laco in the central Andes, northern Chile, give evidence of an intense and extensive subvolcanic contact-metasomatic process. This process resulted from shallow-level emplacement of very volatile-rich iron-oxide magma, with discharge of volatiles that resulted in extensive fracturing of overlying volcanic rocks. The brecciated rocks were altered (mainly extensive scapolitization and formation of pyroxene by hot magmatic fluids emitted from the cooling intrusion , and accompanied by magnetite deposition. With time and decreasing temperature, the metasomatic fluids evolved to fluids of hydrothermal character, and a final recent geothermal event took place that deposited superficial gypsum over a large part of the El Laco Volcanic Complex.Estudios realizados en testigos de sondajes en el area de Pasos Blancos en El Laco, en los Andes Centrales del norte de Chile, dan evidencias de un intenso y extenso proceso subvolcánico de metasomatismo de contacto. Este proceso es el resultado de un emplazamiento a poca profundidad de un magma de óxido de fierro muy rico en volátiles y cuya descarga de gases produjo un intenso fracturamiento de las rocas sobrepuestas. Las rocas brechizadas fueron alteradas (principalmente una extensa escapolitización y formación de piroxeno, junto con la depositación de magnetita, por los fluidos magmáticos calientes emitidos por la intrusión durante su enfriamiento. Los fluidos metasomáticos evolucionaron en el tiempo y con la disminución de temperatura, a fluidos de carácter hidrotermal y finalmente tuvo lugar un evento geotérmico reciente, el cual depositó yeso superficial en gran parte del Complejo Volcánico El Laco.

  13. Ecology, genetic diversity, and phylogeographic structure of andes virus in humans and rodents in Chile.

    Medina, Rafael A; Torres-Perez, Fernando; Galeno, Hector; Navarrete, Maritza; Vial, Pablo A; Palma, R Eduardo; Ferres, Marcela; Cook, Joseph A; Hjelle, Brian

    2009-03-01

    Andes virus (ANDV) is the predominant etiologic agent of hantavirus cardiopulmonary syndrome (HCPS) in southern South America. In Chile, serologically confirmed human hantavirus infections have occurred throughout a wide latitudinal distribution extending from the regions of Valparaíso (32 to 33 degrees S) to Aysén (46 degrees S) in southern Patagonia. In this study, we found seropositive rodents further north in the Coquimbo region (30 degrees S) in Chile. Rodent seroprevalence was 1.4%, with Oligoryzomys longicaudatus displaying the highest seroprevalence (5.9%), followed by Abrothrix longipilis (1.9%) and other species exhibiting Chile. Phylogenetic analyses showed two major ANDV South (ANDV Sout) clades, congruent with two major Chilean ecoregions, Mediterranean (Chilean matorral [shrubland]) and Valdivian temperate forest. Human and rodent samples grouped according to geographic location. Phylogenetic comparative analyses of portions of S and medium segments (encoding glycoproteins Gn and Gc) from a subset of rodent specimens exhibited similar topologies, corroborating two major ANDV Sout clades in Chile and suggesting that yet unknown factors influence viral gene flow and persistence throughout the two Chilean ecoregions. Genetic algorithms for recombination detection identified recombination events within the S segment. Molecular demographic analyses showed that the virus is undergoing purifying selection and demonstrated a recent exponential growth in the effective number of ANDV Sout infections in Chile that correlates with the increased number of human cases reported. Although we determined virus sequences from four rodent species, our results confirmed O. longicaudatus as the primary ANDV Sout reservoir in Chile. While evidence of geographic differentiation exists, a single cosmopolitan lineage of ANDV Sout remains the sole etiologic agent for HCPS in Chile.

  14. Hydrological Modeling of Highly Glacierized Basins (Andes, Alps, and Central Asia

    Nina Omani

    2017-02-01

    Full Text Available The Soil and Water Assessment Tool (SWAT was used to simulate five glacierized river basins that are global in coverage and vary in climate. The river basins included the Narayani (Nepal, Vakhsh (Central Asia, Rhone (Switzerland, Mendoza (Central Andes, Argentina, and Central Dry Andes (Chile, with a total area of 85,000 km2. A modified SWAT snow algorithm was applied in order to consider spatial variation of associated snowmelt/accumulation by elevation band across each subbasin. In previous studies, melt rates varied as a function of elevation because of an air temperature gradient while the snow parameters were constant throughout the entire basin. A major improvement of the new snow algorithm is the separation of the glaciers from seasonal snow based on their characteristics. Two SWAT snow algorithms were evaluated in simulation of monthly runoff from the glaciered watersheds: (1 the snow parameters are lumped (constant throughout the entire basin and (2 the snow parameters are spatially variable based on elevation bands of a subbasin (modified snow algorithm. Applying the distributed SWAT snow algorithm improved the model performance in simulation of monthly runoff with snow-glacial regime, so that mean RSR decreased to 0.49 from 0.55 and NSE increased to 0.75 from 0.69. Improvement of model performance was negligible in simulations of monthly runoff from the basins with a monsoon runoff regime.

  15. Hydrological response in catchments whit debris covered glaciers in the semi-arid Andes, Chile

    Caro, A.; McPhee, J.; MacDonell, S.; Pellicciotti, F.; Ayala, A.

    2016-12-01

    Glaciers in the semi-arid Andes Cordillera in Chile have shrank rapidly during the 20th century. Negative mass balance contributes to increase the surface area of debris-covered glaciers. Recent research in Chile suggests that contributions from glaciers to summer season river flow in dry years is very important, however hydrological processes determining the glacier contribution are still poorly understood in the region. This work seeks to determine appropriate parameters for the simulation of melt volume in two watersheds dominated by debris-covered glaciers, in order to understand its variability in time and space, in the area with the largest population in Chile. The hydrological simulation is performed for the Tapado (30°S) and Pirámide (33ºS) glaciers, which can be defined as cold and temperate respectively. To simulate the hydrological behaviour we adopt the physically-based TOPographic Kinematic wave APproximation model (TOPKAPI-ETH). The hydrometeorological records necessary model runs have been collected through fieldwork from 2013 to 2015. Regarding the calibration of the model parameters melting ETI, its observed that the value for TF in Pirámide is a third of the value for Tapado glacier, while SRF is half in Tapado regarding to Pirámide. The runoff in the glaciers, the constant snow and ice storage are higher in Tapado regarding Pirámide. Results show a contribution of glacial outflow to runoff during 2015 of 55% in Tapado and 77% in Pirámide, with maximum contributions between January and March in Tapado and Pirámide between November and March, presenting the relevance of the permanence of snow cover during spring and shelter that provides debris-covered in reducing the melting glacier. The results have allowed to know the relevance of the glacier contribution to mountain streams, allowing to know the calibration parameters most relevant in the hydrology balance of glacier basins in the Andes.

  16. Coupled geohazards at Southern Andes (Copahue-Lanín volcanoes): Chile's GEO supersite proposal

    Lara, Luis E.; Cordova, Loreto

    2017-04-01

    Southern Andes are a young and active mountain belt where volcanism and tectonic processes (and those related to the hydrometeorological conditions controlled by this geological setting) pose a significant threat to the growing communities nearby. This proposal focus on a ca. 200 km long segment of the Southern Andes where 9 stratovolcanoes and 2 distributed volcanic fields are located, just along a tectonic corridor defined by the northern segment of the Liquiñe-Ofqui Faul System (LOFS), a long-lived active strike-slip fault running for 1200 km. Volcanoes in this area take part of the central province of the Andean Southern Volcanic Zone (37-41°S), particularly the northermost portion that is limited at the south by an Andean tranverse fault (Lanalhue Fault, which define the Villarrica-Lanin volcanic chain) and run along the horse-tail array of the LOFS to the north. Most of the stravolcanoes are atop of the LOFS main branch with only 3 exceptions (Callaqui, Tolhuaca and Lanín) 15-20 km away, but related to transverse faults. Hazards in the segment derive from the activity of some of the most active volcanoes in South America (e.g., Villarrica, Llaima), others with long-lasting weak activity (e.g., Copahue) or some volcanoes with low frequency but high magnitude eruptions in the geological record. Only since the beggining of the 20th century 80 eruptions have been recorded in this area. In addition, activity of the LOFS has been detected prior to some eruptions and coeval with some others (e.g., Lonquimay 1989). A strong two-way coupling between tectonics and volcanism has been proposed for the segment but only recently detected by geophysical techniques or numerical modelling. Tectonic triggered landslides are frequent in this region together with debris flows at erupting ice-covered volcanoes or stream headed at high altitude basins. The latter scenario seems to be worst at present because of global climate change. Ground-based monitoring networks for both

  17. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics Granitoides estériles del Mioceno en la franja metalogénica de los Andes Centrales, Chile: geoquímica e isotopía de Nd-Hf y U-Pb

    Katja Deckart

    2010-01-01

    Full Text Available 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 under-taken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32° and 34°S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Mesón 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 32°S, slightly younger mineralized porphyries at Río 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 i-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 CLTUR 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 Río Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening

  18. [Medical specialization in Chile. A centralized vision].

    Clouet-Huerta, Diego E; González, Bárbara; Correa, Katherine

    2017-11-01

    Medical graduates face different postgraduate training options, but their priority is to obtain a primary medical specialty, defined as a specialty that does not derive from other. There are different specialty training programs in Chile, which can be dependent or independent of the Ministry of Health. The information about these programs is available in different Internet sites. However a centralized information service that groups and synthetize these programs is lacking, hampering graduate choice decisions. This article aims to review all specialization program modalities, providing a general vision of the institutional structure and implications that govern the specialization process in Chile.

  19. Tectonic control of erosion in the southern Central Andes

    Val, Pedro; Venerdini, Agostina L.; Ouimet, William; Alvarado, Patricia; Hoke, Gregory D.

    2018-01-01

    Landscape evolution modeling and global compilations of exhumation data indicate that a wetter climate, mainly through orographic rainfall, can govern the spatial distribution of erosion rates and crustal strain across an orogenic wedge. However, detecting this link is not straightforward since these relationships can be modulated by tectonic forcing and/or obscured by heavy-tailed frequencies of catchment discharge. This study combines new and published along-strike average rates of catchment erosion constrained by 10Be and river-gauge data in the Central Andes between 28°S and 36°S. These data reveal a nearly identical latitudinal pattern in erosion rates on both sides of the range, reaching a maximum of 0.27 mm/a near 34°S. Collectively, data on topographic and fluvial relief, variability of rainfall and discharge, and crustal seismicity suggest that the along-strike pattern of erosion rates in the southern Central Andes is largely independent of climate, but closely relates to the N-S distribution of shallow crustal seismicity and diachronous surface uplift. The consistently high erosion rates on either side of the orogen near 34°S imply that climate plays a secondary role in the mass flux through an orogenic wedge where the perturbation to base level is similar on both sides.

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

    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

  1. Influence of spatial resolution on precipitation simulations for the central Andes Mountains

    Trachte, Katja; Bendix, Jörg

    2013-04-01

    The climate of South America is highly influenced by the north-south oriented Andes Mountains. Their complex structure causes modifications of large-scale atmospheric circulations resulting in various mesoscale phenomena as well as a high variability in the local conditions. Due to their height and length the terrain generates distinctly climate conditions between the western and the eastern slopes. While in the tropical regions along the western flanks the conditions are cold and arid, the eastern slopes are dominated by warm-moist and rainy air coming from the Amazon basin. Below 35° S the situation reverses with rather semiarid conditions in the eastern part and temperate rainy climate along southern Chile. Generally, global circulation models (GCMs) describe the state of the global climate and its changes, but are disabled to capture regional or even local features due to their coarse resolution. This is particularly true in heterogeneous regions such as the Andes Mountains, where local driving features, e. g. local circulation systems, highly varies on small scales and thus, lead to a high variability of rainfall distributions. An appropriate technique to overcome this problem and to gain regional and local scale rainfall information is the dynamical downscaling of the global data using a regional climate model (RCM). The poster presents results of the evaluation of the performance of the Weather Research and Forecasting (WRF) model over South America with special focus on the central Andes Mountains of Ecuador. A sensitivity study regarding the cumulus parametrization, microphysics, boundary layer processes and the radiation budget is conducted. With 17 simulations consisting of 16 parametrization scheme combinations and 1 default run a suitable model set-up for climate research in this region is supposed to be evaluated. The simulations were conducted in a two-way nested mode i) to examine the best physics scheme combination for the target and ii) to

  2. Late Paleozoic to Triassic magmatism in the north-central High Andes, Chile: New insights from SHRIMP U-Pb geochronology and O-Hf isotopic signatures in zircon

    Hernández González, Álvaro; Deckart, Katja; Fanning, Mark; Arriagada, César

    2014-05-01

    The Chilean High Andes (28o- 31oS) comprises a vast number of late Paleozoic - Triassic granitoids which give information about the last stages of Gondwana assemblage. Particularly, previous studies determined two tectonic configurations during this time: subduction related compressional setting (late Carboniferous - Late Permian) and non-subduction post-collisional extensional setting (Late Permian - Triassic), as the last stage of Gondwana assemblage. However, new O-Hf isotopic data along new U-Pb SHRIMP ages in zircon have shown that this model should be modified and updated to the new analytical data available. δ18O values indicate a strong change in the tectonic configuration approximately 270 Ma (earliest middle Permian) and thus, units can be divided into 2 mayor groups: late Carboniferous to earliest middle Permian and middle Permian to Triassic. The oldest group shows slightly low values of ɛHfi (ca. +1 to -4) with high δ18O (ca. >6.5 o/oo), indicating an elevated supracrustal component and the addition of less radiogenic continental-like material, which along significant residence time (TDM2: Mesoproterozoic) can be interpreted as magmas formed at depth in a subduction-related continental arc, and contaminated with supracrustal material and/or oceanic sediments transported through the subducted slab to the mantle-wedge. Subsequently, middle Permian - Triassic rocks show a wider range of ɛHfi values (ca. +3 to -3) with relatively low, mantle-like δ18O (ca. 4.5-6.5 o/oo), indicating a source of magmas without the addition of supracrustal material for some plutons, whilst for others, a slight input. The higher positive values of ɛHfi can be related to the influence of new juvenile material in the source of some magmas. This isotopic data can be interpreted as rocks formed as the result of melting of an old thinned mafic crust (with mantle-like δ18O values characteristic of this type of rocks) with limited addition of supracrustal material; in

  3. Seasonal and elevational contrasts in temperature trends in Central Chile between 1979 and 2015

    Burger, F.; Brock, B.; Montecinos, A.

    2018-03-01

    We analyze trends in temperature from 18 temperature stations and one upper air sounding site at 30°-35° S in central Chile between 1979-2015, to explore geographical and season temperature trends and their controls, using regional ocean-atmosphere indices. Significant warming trends are widespread at inland stations, while trends are non-significant or negative at coastal sites, as found in previous studies. However, ubiquitous warming across the region in the past 8 years, suggests the recent period of coastal cooling has ended. Significant warming trends are largely restricted to austral spring, summer and autumn seasons, with very few significant positive or negative trends in winter identified. Autumn warming is notably strong in the Andes, which, together with significant warming in spring, could help to explain the negative mass balance of snow and glaciers in the region. A strong Pacific maritime influence on regional temperature trends is inferred through correlation with the Interdecadal Pacific Oscillation (IPO) index and coastal sea surface temperature, but the strength of this influence rapidly diminishes inland, and the majority of valley, and all Andes, sites are independent of the IPO index. Instead, valley and Andes sites, and mid-troposphere temperature in the coastal radiosonde profile, show correlation with the autumn Antarctic Oscillation which, in its current positive phase, promotes subsidence and warming at the latitude of central Chile.

  4. Steady-state exhumation pattern in the central Andes SE Peru

    Ruiz, G.M.H.; Carlotto, V.; van Heiningen, P.S.; Andriessen, P.A.M.

    2009-01-01

    The Western Cordillera of SE Peru is part of the Central Andes and is situated to the west of the Eastern Andes from which it is separated by the northern termination of the Altiplano - the Inter-Andean Valley. It is a volcanic-volcano-detrital chain that developed in the Palaeogene, and is

  5. AREAS OF ENDEMISM IN THE SOUTHERN CENTRAL ANDES

    Lone Aagesen

    2012-01-01

    Full Text Available Este trabajo analiza la distribución de especies de plantas vasculares endémicas de la porción sur de los Andes centrales (sudoeste de Bolivia y noroeste de Argentina. En el análisis se incluyeron 540 especies endémicas de la región estudiada (aproximadamente 720.600 km2. La mayoría de las especies endémicas se halla en ambientes semiáridos, entre 1500-3500 m s.m., encontrándose principalmente en valles, laderas y mesetas del topográficamente complejo sur de los Andes centrales. Las áreas de endemismos aquí halladas se presentan consecuentemente en ambientes áridos y no en ambientes húmedos subtropicales de las Yungas tucumano-bolivianas, a pesar de que en esta última región la diversidad de plantas vasculares es mayor. Se identificaron un total de 17 patrones de distribución bien definidos, y parcialmente solapados. El patrón de distribución más amplio define un área general de endemismos para los Andes centrales. Esta área se extiende a lo largo de casi toda la región y está delimitada por especies que se distribuyen en ambientes desérticos a sub-húmedos en laderas, valles o regiones altoandinas. Casi todas las restantes áreas de endemismo se encuentran anidadas dentro del patrón de distribución amplio antes citado, superponiéndose en el sentido norte-sur a lo largo de pendientes y valles de los Andes y de las Sierras Pampeanas. A pesar del sesgo observado en la distribución hacia ambientes áridos, aproximadamente la mitad de las especies endémicas están restringidas a unas pocas áreas de alto endemismo, las que se encuentran en yuxtaposición con las zonas más lluviosas de la región. Estas áreas de alto endemismo incluyen los rangos de hábitat más amplios de la región en términos de altitud y precipitación, siendo las especies endémicas igualmente variables en sus requerimientos de humedad y elevación. Las unidades fitogeográficas previamente definidas por diversos autores no fueron encontradas

  6. Changes of glaciers in the Andes of Chile and priorities for future work.

    Pellicciotti, F; Ragettli, S; Carenzo, M; McPhee, J

    2014-09-15

    Glaciers in the Andes of Chile seem to be shrinking and possibly loosing mass, but the number and types of studies conducted, constrained mainly by data availability, are not sufficient to provide a synopsis of glacier changes for the past or future or explain in an explicit way causes of the observed changes. In this paper, we provide a systematic review of changes in glaciers for the entire country, followed by a discussion of the studies that have provided evidence of such changes. We identify a missing type of work in distributed, physically-oriented modelling studies that are needed to bridge the gap between the numerous remote sensing studies and the specific, point scale works focused on process understanding. We use an advanced mass balance model applied to one of the best monitored glaciers in the region to investigate four main research issues that should be addressed in modelling studies for a sound assessment of glacier changes: 1) the use of physically-based models of glacier ablation (energy balance models) versus more empirical models (enhanced temperature index approaches); 2) the importance of the correct extrapolation of air temperature forcing on glaciers and in high elevation areas and the large uncertainty in model outputs associated with it; 3) the role played by snow gravitational redistribution; and 4) the uncertainty associated with future climate scenarios. We quantify differences in model outputs associated with each of these choices, and conclude with suggestions for future work directions. © 2013 Elsevier B.V. All rights reserved.

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

    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

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

    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.

  9. Monitoring rock glacier dynamics and ground temperatures in the semiarid Andes (Chile, 30°S)

    Brenning, Alexander; Azócar, Guillermo F.; Bodin, Xavier

    2013-04-01

    Rock glaciers and mountain permafrost are widespread in the high semiarid Andes of Chile, where they concentrate greater amounts of ice than glaciers. Rock glaciers are of particular interest because in some cases the permafrost they contain might be in a degrading in response to climatic warming. This could result in increased dynamics and even to destabilization, which has been observed on some rock glaciers in the studied area. Displacement rates and active-layer temperatures of two rock glaciers as well as ground surface temperatures of the periglacial environment in the upper Elqui valley have been monitored since summer 2009/10 with funding from the Chilean Dirección General de Aguas. Differential GPS measurements of 115 points on the surface of two rock glaciers since April 2010 showed horizontal displacements of up to 1.3 m/a on the Llano de las Liebres rock glacier and up to 1.2 m/a on the Tapado rock glacier. General velocity patterns are consistent with the morphological evidence of activity (e.g., front slopes, looseness of debris) and for the Tapado complex, a clearly distinct activity from the debris-covered glacier was observed. Temperature measurements in four boreholes indicate active-layer depths of about 2.5 m at the highest locations on the Tapado rock glacier (~4400 m a.s.l.) and about 8 m near the front of the Llano rock glacier (3786 m a.s.l.). Spatial patterns of mean ground surface temperature (MGST) were analyzed with regards to influences of elevation, potential incoming solar radiation, location on ice-debris landforms (rock and debris-covered glaciers), and snow cover duration using linear mixed-effects models. While accounting for the other variables, sites with long-lasting snow patches had ~0.4°C lower MGST, and ice-debris landforms had ~0.4-0.6°C lower MGST than general debris surfaces, highlighting important local modifications to the general topographic variation of ground thermal conditions.

  10. Tectonics, hydrothermal zoning, and uranium in the central Andes

    Gabelman, J W

    1961-01-01

    The geological features of the Peruvian Andes are discussed in some detail. The geologic history of the Andrean tectonics was found to be virtually the same as that represented in both North and South American Cordillera. The study indicated that Andrean hydrothermal mineralization occurred intermittently but in close time relation with accompanying deformations from the late Cretaceous or early Tertiary up to the present. The mineralization cycle is discussed as it relates to several metals, particularly uranium. Uranium is believed to occupy the same several temperature--environmental positions in the Andes that it does throughout the rest of the western hemisphere Cordillera. Even though uranium is present in minor quantities in several high-to-moderate-temperature environments, the bulk of uranium present in the cycle is believed to precipitate in the subepithermal environment.

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

    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

  12. Antecedentes geobotánicos de una cuenca andina de Chile Central

    Quintanilla Pérez, V.

    2004-12-01

    Full Text Available Like any other mountain ecosystem; the Andes Mountains show an outstanding phytoecological specificity. This is because of the influence of ecological conditions; as well as the presence of special vegetation groups. These groups of plants show a well defined structure and functionality; arising from the adaptation of biological behavior to the regional altitude. Nevertheless; despite the rigourous climatic conditions; plants do have access to water supplies. A latitudinal vegetation distribution is proposed; based on three vegetation belts: montane; subandine and andine. A remarkable similarity can be noticed between the montane plant communities and those corresponding to the central lower valleys. In addition; the influence of geomorphological processes on plant life and its distribution is presented. Finally; a case study in the highlands of the Andes; Santiago de Chile; is discussed.

    [fr] Comme tous les systèmes de montagne du monde; les Andes du Chili Central présentent une identité phytoécologique; qui se manifeste par l'action des conditions écologiques très particulières et par la présence de groupements végétaux qui montrent une individualité par rapport à ces caractères structurels et fonctionels; résultant de l'adaptation des plantes aux effets de l'altitude; avec des conditions climatiques difficiles; mais pourtant avec la possibilité de profiter des reserves du sol en eau. Dans ces montagnes on a établi une zonation en altitude; et on peut distinguer trois étages: montagnard; subandin et andin. Les seuils altimétriques des étages changent selon les versants; mais tous présentent une certaine richesse d'espèces endémiques. Cependant on remarque les ressemblances floristiques de l'étage montagnard avec les vallées centrales du pays. On présente aussi un aperçu des effets de la dynamique agressive des processus géomorphologiques de montagne sur la vie des plantes; avec une étude de cas dans les

  13. Chile.

    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

  14. Morphologic evolution of the Central Andes of Peru

    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.

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

    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

  16. Early Tertiary Exhumation, Erosion, and Sedimentation in the Central Andes, NW Argentina

    Carrapa, B.; Decelles, P. G.; Gerhels, G.; Mortimer, E.; Strecker, M. R.

    2006-12-01

    Timing of deformation and resulting sedimentation patterns in the Altiplano-Puna Plateau-Eastern Cordillera of the southern Central Andes are the subject of ongoing controversial debate. In the Bolivian Altiplano, sedimentation into a foreland basin system commenced during the Paleocene. Farther south in the Puna and Eastern Cordillera of NW Argentina, a lack of data has precluded a similar interpretation. Early Tertiary non-marine sedimentary rocks are preserved within the present day Puna Plateau and Eastern Cordillera of NW Argentina. The Salar de Pastos Grandes basin in the Puna Plateau contains more than 2 km of Eocene alluvial and fluvial strata in the Geste Formation, deposited in close proximity to orogenic source terrains. Sandstone and conglomerate petrographic data document Ordovician quartzites and minor phyllites and schists as the main source rocks. Detrital zircon U-Pb ages from both the Geste Formation and from underlying Ordovician quartzite cluster in the 900-1200 Ma (Grenville) and late Precambrian-Cambrian (Panafrican) ranges. Sparse late Eocene (~37-34 Ma) grains are also present; their large size, euhedral shape, and decreasing mean ages upsection suggest that these grains are volcanogenic (i.e. ash fall contamination), derived from an inferred magmatic arc to the west. The Eocene ages corroborate mammalian paleontological dates, defining the approximate begin of deposition of the Geste Formation. Alternatively, these young zircons could be of plutonic origin; however, no Eocene plutons are present in the surrounding source rocks and this interpretation is not likely. From W to E, fluvial rocks of the Quebrada de los Colorados Formation show similar sedimentological features as those observed for the Geste Formation, suggesting a genetic link between the two. Detrital zircon U-Pb data show mainly Panafrican ages, with sparse ages in the 860-935 Ma range and a few mid-Proterozoic ages. More importantly, a significant number of late Eocene

  17. Surface uplift in the Central Andes driven by growth of the Altiplano Puna Magma Body.

    Perkins, Jonathan P; Ward, Kevin M; de Silva, Shanaka L; Zandt, George; Beck, Susan L; Finnegan, Noah J

    2016-10-25

    The Altiplano-Puna Magma Body (APMB) in the Central Andes is the largest imaged magma reservoir on Earth, and is located within the second highest orogenic plateau on Earth, the Altiplano-Puna. Although the APMB is a first-order geologic feature similar to the Sierra Nevada batholith, its role in the surface uplift history of the Central Andes remains uncertain. Here we show that a long-wavelength topographic dome overlies the seismically measured extent of the APMB, and gravity data suggest that the uplift is isostatically compensated. Isostatic modelling of the magmatic contribution to dome growth yields melt volumes comparable to those estimated from tomography, and suggests that the APMB growth rate exceeds the peak Cretaceous magmatic flare-up in the Sierran batholith. Our analysis reveals that magmatic addition may provide a contribution to surface uplift on par with lithospheric removal, and illustrates that surface topography may help constrain the magnitude of pluton-scale melt production.

  18. Culture and landslide risk in the Central Andes of Bolivia and Peru

    Nicholas Roberts

    2009-01-01

    Culture and its heritage play a major role in determining landslide risk in the Central Andes. Examples of some of these many possible influences are provided from natural and social science literature and from the author’s recent work in Bolivia. Landslide risk appears to have generally increased throughout the last millennium, due largely to anthropogenic modification of hazard, exposure, vulnerability and coping capacity. These changes result from both local and distant pressures and from ...

  19. Relationships between mineralization and silicic volcanism in the central Andes

    Francis, P. W.; Halls, C.; Baker, M. C. W.

    1983-01-01

    Existing models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.

  20. Facing unprecedented drying of the Central Andes? Precipitation variability over the period AD 1000–2100

    Neukom, Raphael; Salzmann, Nadine; Huggel, Christian; Rohrer, Mario; Calanca, Pierluigi; Acuña, Delia; Christie, Duncan A; Morales, Mariano S

    2015-01-01

    Projected future trends in water availability are associated with large uncertainties in many regions of the globe. In mountain areas with complex topography, climate models have often limited capabilities to adequately simulate the precipitation variability on small spatial scales. Also, their validation is hampered by typically very low station density. In the Central Andes of South America, a semi-arid high-mountain region with strong seasonality, zonal wind in the upper troposphere is a good proxy for interannual precipitation variability. Here, we combine instrumental measurements, reanalysis and paleoclimate data, and a 57-member ensemble of CMIP5 model simulations to assess changes in Central Andes precipitation over the period AD 1000–2100. This new database allows us to put future projections of precipitation into a previously missing multi-centennial and pre-industrial context. Our results confirm the relationship between regional summer precipitation and 200 hPa zonal wind in the Central Andes, with stronger Westerly winds leading to decreased precipitation. The period of instrumental coverage (1965–2010) is slightly dryer compared to pre-industrial times as represented by control simulations, simulations from the past Millennium, ice core data from Quelccaya ice cap and a tree-ring based precipitation reconstruction. The model ensemble identifies a clear reduction in precipitation already in the early 21st century: the 10 year running mean model uncertainty range (ensemble 16–84% spread) is continuously above the pre-industrial mean after AD 2023 (AD 2028) until the end of the 21st century in the RCP2.6 (RCP8.5) emission scenario. Average precipitation over AD 2071–2100 is outside the range of natural pre-industrial variability in 47 of the 57 model simulations for both emission scenarios. The ensemble median fraction of dry years (defined by the 5th percentile in pre-industrial conditions) is projected to increase by a factor of 4 until 2071

  1. Within plate seismicity analysis in the segment between the high Cordillera and the Precordillera of northern Mendoza (Southern Central Andes

    Julián Olivar

    2018-01-01

    Full Text Available Crustal seismicity in northwestern Mendoza Province in Argentina, corresponding to the transition zone between the Chilean-Pampean flat subduction zone (26.5–33.5°S and the Southern Central Andes normal subduction zone to the south, is studied in order to i identify its relationship with the mapped structure, ii determine deformational mechanisms and iii constrain the geometry of the fold and thrust belt in the lower crust. Through this, we aim to determine which are the structures that contribute to Andean construction, east of the Frontal Cordillera in Argentina and at the western Principal Cordillera in Chile. Data from a temporary local seismic network are reprocessed in order to achieve a precise location of hypocenters and, whenever possible, to build focal mechanisms. Results are interpreted and compared with previous seismic studies and structural models. Analyzed seismicity is grouped around the eastern front of Frontal Cordillera, with hypocenters mainly at depths of 25–40 km. Contrastingly, earthquakes in the Principal Cordillera to the west are located at the axial Andean sector and Chilean slope, with depths shallower than 15 km. Obtained focal mechanisms indicate mainly strike-slip displacements, left lateral at Frontal Cordillera and right lateral at Principal Cordillera. Based on these observations, new possible structural models are proposed, where seismogenic sources could be either associated with inherited basement structures from the Cuyania-Chilenia suture; or correspond to deep-blind thrusts linked with a deeper-than-previously-assumed decollement that could be shared between Frontal Cordillera and western Precordillera. This deeper decollement would coincide in turn with the one determined from receiver function analysis for the eastern Sierras Pampeanas in previous works, potentially implying a common decollement all through the fold and thrust belt configuration. Apart from this, a new interpretation of

  2. Mass balance and hydrological contribution of glaciers in northern and central Chile

    MacDonell, Shelley; Vivero, Sebastian; McPhee, James; Ayala, Alvaro; Pellicciotti, Francesca; Campos, Cristian; Caro, Dennys; Ponce, Rodrigo

    2016-04-01

    the course of a season than glacial ice, however there were marked differences between seasons. The modelling studies showed that in the northern (drier) site, during the lower precipitation season, glacier contribution could be as high as 20% verses only approximately 5% in 'wetter' periods. Comparatively, in central Chile, glaciers contributed approximately 15% during 'wetter' periods, and as much as 35% of total streamflow during the extremely dry year. This study suggests that the continuation of long-term glacier monitoring projects in the semi-arid Andes is necessary in order to better constrain hydrological models in these environments.

  3. The effect of offset on fracture permeability of rocks from the Southern Andes Volcanic Zone, Chile

    Pérez-Flores, P.; Wang, G.; Mitchell, T. M.; Meredith, P. G.; Nara, Y.; Sarkar, V.; Cembrano, J.

    2017-11-01

    The Southern Andes Volcanic Zone (SVZ) represents one of the largest undeveloped geothermal provinces in the world. Development of the geothermal potential requires a detailed understanding of fluid transport properties of its main lithologies. The permeability of SVZ rocks is altered by the presence of fracture damage zones produced by the Liquiñe-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF). We have therefore measured the permeability of four representative lithologies from the volcanic basement in this area: crystalline tuff, andesitic dike, altered andesite and granodiorite. For comparative purposes, we have also measured the permeability of samples of Seljadalur basalt, an Icelandic rock with widely studied and reported hydraulic properties. Specifically, we present the results of a systematic study of the effect of fractures and fracture offsets on permeability as a function of increasing effective pressure. Baseline measurements on intact samples of SVZ rocks show that the granodiorite has a permeability (10-18 m2), two orders of magnitude higher than that of the volcanic rocks (10-20 m2). The presence of throughgoing mated macro-fractures increases permeability by between four and six orders of magnitude, with the highest permeability recorded for the crystalline tuff. Increasing fracture offset to produce unmated fractures results in large increases in permeability up to some characteristic value of offset, beyond which permeability changes only marginally. The increase in permeability with offset appears to depend on fracture roughness and aperture, and these are different for each lithology. Overall, fractured SVZ rocks with finite offsets record permeability values consistent with those commonly found in geothermal reservoirs (>10-16 m2), which potentially allow convective/advective flow to develop. Hence, our results demonstrate that the fracture damage zones developed within the SVZ produce permeable regions, especially within the

  4. Climate in the Western Cordillera of the Central Andes over the last 4300 years

    Engel, Zbyněk; Skrzypek, Grzegorz; Chuman, Tomáš; Šefrna, Luděk; Mihaljevič, Martin

    2014-09-01

    The Distichia peat core obtained in the Carhuasanta valley near Nevado Mismi, Cordillera Chila, provides information on climatic and environmental conditions over the last ˜4300 years. The relative changes in the stable carbon isotope composition of plant remains preserved in the core reflect major temperature fluctuations in the Western Cordillera of the southern Peruvian Andes. These temperature variations can be additionally linked with the changes in precipitation patterns by analysing C% and C/N ratio in the core. Relatively warm and moist conditions prevailed from 4280 to 3040 cal. yrs BP (BC 2330-1090) with a short colder dry episode around 3850 cal. yrs BP (BC 1900). The most prominent climate changes recorded in the peat occurred between 3040 and 2750 cal. yrs BP (BC 1090-800) when the initial warming turned to a rapid cooling to temperatures at least 2 °C lower than the mean for the Late Holocene. Initially drier conditions within this event turned to a short wet phase after 2780 cal. yrs BP (BC 830) when the temperature increased again. This event coincides with significant changes in peat and ice core records in the Central Andes matching the timing of the global climate event around 2.8 cal. ka BP. Climatic conditions in the study area became relatively dry and stable after the event for about 800 years. Highly variable temperatures and humidity prevailed during the last 2000 years when an extended warm and relatively humid period occurred between 640 and 155 cal. yrs BP (AD 1310-1795) followed by predominantly colder and drier conditions. The established δ13C peat record represents the first continuous proxy for the temperature in the southern Peruvian Andes dated by the AMS 14C. Distichia peat is wide spread in the Andes and the proposed approach can be applied elsewhere in high altitudes, where no other traditional climate proxies are available.

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

    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

  6. Analysis of La Dehesa paleo-landslide. Central Pre-Andes of Argentina

    Tapia Baldis, Carla; Rothis, Luis Martín; Perucca, Laura; Esper Angillieri, María; Vargas, Horacio; Ponce, David; Allis, Carlos

    2018-04-01

    The main objective of this paper is to consider the influence of Quaternary faults as likely triggering factor for rockslides occurrence in the Central Pre-Andes, a region with intense shallow seismic activity. A rockslide deposit was selected as study case, placed in the western flank of La Dehesa and Talacasto (DT) range (31°3‧37″ S and 68°46‧ 8″ W). Applied methodology includes the characterization of main discontinuities, reconstruction of the topography using a high-resolution digital elevation model, safety factor calculation along the sliding surface and, Newmark displacements estimation for three different hypothetical seismic scenarios, recreated from existing neotectonic local information. Equilibrium-limit method's results confirm that study case, La Dehesa rockslide (LDR), had a stable and safe slope's configuration under static conditions. However, a seismic horizontal coefficient between 0.2 and 0.3 decreases safety factor below the safety threshold. Newmark's displacements for different seismic reconstructed scenarios varies between 4.1 and 15.9 cm, values that agreed with a coherent failure process, likely triggered by Pleistocene to Holocene seismogenic sources in Central Pre-Andes. LDR trigger could be assigned mainly to an earthquake related to La Dehesa Quaternary fault (LDF) activity; however, similar movements produced by neighboring faults should not be discarded. LDR triggering related to climatic conditions is despised. Finally, the methodology presented in this work is easy to reproduce and may be applied to other rockslides located in the mountainous areas of the Central Pre-Andes of Argentina.

  7. Mio-Pliocene aridity in the south-central Andes associated with Southern Hemisphere cold periods.

    Amidon, William H; Fisher, G Burch; Burbank, Douglas W; Ciccioli, Patricia L; Alonso, Ricardo N; Gorin, Andrew L; Silverhart, Perri H; Kylander-Clark, Andrew R C; Christoffersen, Michael S

    2017-06-20

    Although Earth's climate history is best known through marine records, the corresponding continental climatic conditions drive the evolution of terrestrial life. Continental conditions during the latest Miocene are of particular interest because global faunal turnover is roughly synchronous with a period of global glaciation from ∼6.2-5.5 Ma and with the Messinian Salinity Crisis from ∼6.0-5.3 Ma. Despite the climatic and ecological significance of this period, the continental climatic conditions associated with it remain unclear. We address this question using erosion rates of ancient watersheds to constrain Mio-Pliocene climatic conditions in the south-central Andes near 30° S. Our results show two slowdowns in erosion rate, one from ∼6.1-5.2 Ma and another from 3.6 to 3.3 Ma, which we attribute to periods of continental aridity. This view is supported by synchrony with other regional proxies for aridity and with the timing of glacial ‟cold" periods as recorded by marine proxies, such as the M2 isotope excursion. We thus conclude that aridity in the south-central Andes is associated with cold periods at high southern latitudes, perhaps due to a northward migration of the Southern Hemisphere westerlies, which disrupted the South American Low Level Jet that delivers moisture to southeastern South America. Colder glacial periods, and possibly associated reductions in atmospheric CO 2 , thus seem to be an important driver of Mio-Pliocene ecological transitions in the central Andes. Finally, this study demonstrates that paleo-erosion rates can be a powerful proxy for ancient continental climates that lie beyond the reach of most lacustrine and glacial archives.

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

    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

  9. Culture and landslide risk in the Central Andes of Bolivia and Peru

    Nicholas Roberts

    2009-06-01

    Full Text Available Culture and its heritage play a major role in determining landslide risk in the Central Andes. Examples of some of these many possible influences are provided from natural and social science literature and from the author’s recent work in Bolivia. Landslide risk appears to have generally increased throughout the last millennium, due largely to anthropogenic modification of hazard, exposure, vulnerability and coping capacity. These changes result from both local and distant pressures and from contemporaneous and pervious cultural factors. Consequently, holistic examination of landslide risk necessitates consideration of culture and its heritage.

  10. Dynamics of a large, restless, rhyolitic magma system at Laguna del Maule, southern Andes, Chile

    Singer, Brad S.; Andersen, Nathan L.; Le Mével, Hélène; Feigl, Kurt L.; DeMets, Charles; Tikoff, Basil; Thurber, Clifford H.; Jicha, Brian R.; Cardonna, Carlos; Córdova, Loreto; Gil, Fernando; Unsworth, Martyn J.; Williams-Jones, Glyn; Miller, Craig W.; Fierstein, Judith; Hildreth, Edward; Vazquez, Jorge A.

    2014-01-01

    Explosive eruptions of large-volume rhyolitic magma systems are common in the geologic record and pose a major potential threat to society. Unlike other natural hazards, such as earthquakes and tsunamis, a large rhyolitic volcano may provide warning signs long before a caldera-forming eruption occurs. Yet, these signs—and what they imply about magma-crust dynamics—are not well known. This is because we have learned how these systems form, grow, and erupt mainly from the study of ash flow tuffs deposited tens to hundreds of thousands of years ago or more, or from the geophysical imaging of the unerupted portions of the reservoirs beneath the associated calderas. The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007, the crust there has been inflating at an astonishing rate of at least 25 cm/yr. This unique opportunity to investigate the dynamics of a large rhyolitic system while magma migration, reservoir growth, and crustal deformation are actively under way is stimulating a new international collaboration. 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 ca. 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. The next phase of this investigation seeks to enlarge the sets of geophysical and geochemical data and to use these observations in numerical models of system dynamics.

  11. Crustal balance and crustal flux from shortening estimates in the Central Andes

    Hindle, David; Kley, Jonas; Oncken, Onno; Sobolev, Stephan

    2005-01-01

    The Central Andes of South America form the second largest high elevation plateau on earth. Extreme elevations have formed on a noncollisional margin with abundant associated arc magmatism. It has long been thought that the crustal thickness necessary to support Andean topography was not accounted for by known crustal shortening alone. We show that this may in part be due to a two-dimensional treatment of the problem. A three-dimensional analysis of crustal shortening and crustal thickness shows that displacement of material towards the axis of the bend in the Central Andes has added a significant volume of crust not accounted for in previous comparisons. We find that present-day crustal thickness between 12°S and 25°S is accounted for (∼-10% to ∼+3%)with the same shortening estimates, and the same assumed initial crustal thickness as had previously led to the conclusion of a ∼25-35% deficit in shortening relative to volume of crustal material. We suggest that the present-day measured crustal thickness distribution may not match that predicted due to shortening, and substantial redistribution of crust may have occurred by both erosion and deposition at the surface and lower crustal flow in regions of the thermally weakened middle and lower crust.

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

    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

  13. Cold Episodes, Their Precursors and Teleconnections in the Central Peruvian Andes (1958-2009)

    Sulca, J. C.; Vuille, M. F.; Trasmonte, G.; Silva, Y.; Takahashi, K.

    2014-12-01

    The Mantaro valley (MV) is located in the central Peruvian Andes. Occasionally, cold episodes are observed during the austral summer (January-March), which strongly damage crops. However, little is known about the causes and impacts of such cold episodes in the MV. The main goal of this study is thus to characterize cold episodes in the MV and assess their large-scale circulation and teleconnections over South America (SA) during austral summer. To identify cold events in the MV daily minimum temperature for the period 1958-2009 from Huayao station, located within the MV was used. We defined a cold episode as the period when daily minimum temperature drops below the 10-percentile for at least one day. Several gridded reanalysis and satellite products were used to characterize the large-scale circulation, cloud cover and rainfall over SA associated with these events for same period. Cold episodes in the MV are associated with positive OLR anomalies, which extend over much of the central Andes, indicating reduced convective cloud cover during these extremes, but also affirm the large-scale nature of these events. At the same time, northeastern Brazil (NEB) registers negative OLR anomalies, strong convective activity and enhanced cloud cover because displacement of the South Atlantic Convergence Zone (SACZ) toward the northeast of its climatologic position. Further, it is associated with a weakening of the Bolivian High - Nordeste Low (BH-NL) system at upper levels, but also influenced by a low-level migratory high-pressure center develops at 30°S, 50°W; propagating from mid- to low latitudes as part of an extratropical Rossby wave train. In conclusion, cold episodes in the MV appear to be caused by radiative cooling associated with reduced cloudiness, rather than cold air advection. The reduced cloud cover in turn results from a robust large-scale pattern of westerly wind anomalies over central Peruvian Andes, inhibiting moisture influx, convective activity and

  14. Cronología, identidad, urbanismo y estado en los Andes Centrales y surcentrales entre los siglos V a X D.C.: algunas reflexiones finales

    Kaulicke, Peter

    2012-01-01

    Chronology, Identity, Urbanism and State in the Central and South Central Andes between V and X Centuries AD: Some Final ConclusionsThe article doesn´t have an abstract El artículo no presenta resumen

  15. Novel Strain of Andes Virus Associated with Fatal Human Infection, Central Bolivia

    Cruz, Cristhopher D.; Vallejo, Efrain; Agudo, Roberto; Vargas, Jorge; Blazes, David L.; Guevara, Carolina; Laguna-Torres, V. Alberto; Halsey, Eric S.; Kochel, Tadeusz J.

    2012-01-01

    To better describe the genetic diversity of hantaviruses associated with human illness in South America, we screened blood samples from febrile patients in Chapare Province in central Bolivia during 2008–2009 for recent hantavirus infection. Hantavirus RNA was detected in 3 patients, including 1 who died. Partial RNA sequences of small and medium segments from the 3 patients were most closely related to Andes virus lineages but distinct (1 hantaviruses; the highest prevalence was among agricultural workers. Because of the high level of human exposure to hantavirus strains and the severity of resulting disease, additional studies are warranted to determine the reservoirs, ecologic range, and public health effect of this novel strain of hantavirus. PMID:22515983

  16. A new species of iguanid lizard, genus Stenocercus (Squamata, Iguania), from the Central Andes in Peru.

    Venegas, Pablo J; Echevarría, Lourdes Y; García-Burneo, Karla; Koch, Claudia

    2016-12-04

    We describe a new species of Stenocercus from the montane forest of the right margin of the Marañón river in the northern portion of the Central Andes in northern Peru (Amazonas and La Libertad departments), at elevations ranging from 2300 to 3035 m. Stenocercus omari sp. nov. differs from other Stenocercus species, with the exception of S. amydrorhytus, S. chrysopygus, S. cupreus, S. johaberfellneri, S. latebrosus, S. melanopygus, S. modestus, S. ornatissimus, S. orientalis, and S. stigmosus, by having granular scales on the posterior surfaces of thighs, a conspicuous antehumeral fold and by lacking a vertebral crest. However, Stenocercus omari sp. nov. is easily distinguished from the aforementioned species, except S. orientalis, by the presence of prominently keeled dorsal head scales. The new species differs from S. orientalis by lacking a prominent oblique neck fold and by having a distinct deep postfemoral mite pocket.

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

    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.

  18. Calcite Twin Analysis in the Central Andes of Northern Argentina and Southern Bolivia

    Hardesty, E.; Hindle, D.

    2005-12-01

    The use of calcite twinning to infer compression directions and strain axes patterns has been applied widely in both fold and thrust belts, and continental interiors. Calcite twinning is noted to be one of the most precise methods for determining the internal strain of deformed rocks. Until now, such data from the deformed plate boundary of the Central Andes were lacking. This study has examined twinning orientations along the deformed Andean foreland (southern Bolivia and northern Argentina) from -25 to -20 latitude. In the Central Andes, we find an abundance of calcite twins in intervals of the Cretaceous age Yacorite limestone. Twin samples were collected, measured for orientation and type (I and II can be best used for strain analysis), and processed using the Groshong method, to give resultant strain tensors. The orientations of the twin short axes trend mostly NE-SW, which is close to the plate convergence direction. However, in a limited number of samples from the north, adjacent to the southern culmination of the active Subandean fold thrust belt, they trend NW-SE. This difference may be related to the more active, or more recent, shortening of the southern portion of the Eastern Cordillera, south of the culmination of the Subandean belt. This implies that twin short axes vary consistently with respect to geographic location and local tectonic regime. NW-SE trends in the northern region match well with fault kinematic studies in rocks pre-dating the San Juan del Oro unconformity (9-10 Ma). NE-SW trends in the south could correspond to much younger (~1-3 Ma) fault kinematic trends. In the Eastern Cordillera, where there is present day tectonic activity, the plunges of the twin short axes are found to be almost horizontal. This suggests that the twins were formed after folding occurred.

  19. Human effects in Holocene fire dynamics of Central Western Patagonia (~44° S, Chile

    César Méndez

    2016-08-01

    Full Text Available The forest-steppe ecotone of the eastern slope of the Andes in Central Western Patagonia (43°40'-49°15' S, Chile, South America provides a unique area for assessing long and short term dynamics between humans and past environments. Central Western Patagonian was a demographically marginal zone inhabited intermittently and with low intensity by hunter-gatherers during the Holocene. This paper adopts a novel approach in order to assess the relationship between trends in the archaeological, pollen and charcoal records. The recognition of temporal and spatial scales in both archaeology and paleoecology is crucial for defining roles in paleofire records. The main goal of the paper is to assess the role of climate and human beings as potential ignitors of wildfires by acknowledging the scales in which they operate and the different roles either one played in paleofire trends. We investigated a case study in the Cisnes River Valley where the frequencies and magnitudes of fire episodes – reconstructed from macro-charcoal particles from the Lake Shaman intermoraine sequence – can be attributed to human action, while acknowledging the driving role of climate over broader time scales. The Lake Shaman charcoal record spanning the last 19000 cal years is compared to the archaeological record starting at 11500 cal years BP. After comparing paleofires, reconstructed from the charcoal record, with peaks and troughs in the radiocarbon record and archaeological evidence at local and site scales, we argue that this approach provides insights for assessing the timing and magnitude of human effects on the environment. We examine collation and correlation scenarios for comparative trends between the archaeological, pollen and charcoal records. The correlation of occupational events at the El Chueco 1 archaeological site and other sites along the Cisnes River Valley with the results obtained at Lake Shaman is suggestive of a combination of human agency and

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

    Thomson, S.N; Herve, F; Stockhert, B.; Brix, M.R.; Adriasola, A

    2001-01-01

    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. 46 o S, increased cooling and denudation related to transpression induced rock uplift and erosion along

  1. Modeling Soil Organic Carbon Variation Along Climatic and Topographic Trajectories in the Central Andes

    Gavilan, C.; Grunwald, S.; Quiroz, R.; Zhu, L.

    2015-12-01

    The Andes represent the largest and highest mountain range in the tropics. Geological and climatic differentiation favored landscape and soil diversity, resulting in ecosystems adapted to very different climatic patterns. Although several studies support the fact that the Andes are a vast sink of soil organic carbon (SOC) only few have quantified this variable in situ. Estimating the spatial distribution of SOC stocks in data-poor and/or poorly accessible areas, like the Andean region, is challenging due to the lack of recent soil data at high spatial resolution and the wide range of coexistent ecosystems. Thus, the sampling strategy is vital in order to ensure the whole range of environmental covariates (EC) controlling SOC dynamics is represented. This approach allows grasping the variability of the area, which leads to more efficient statistical estimates and improves the modeling process. The objectives of this study were to i) characterize and model the spatial distribution of SOC stocks in the Central Andean region using soil-landscape modeling techniques, and to ii) validate and evaluate the model for predicting SOC content in the area. For that purpose, three representative study areas were identified and a suite of variables including elevation, mean annual temperature, annual precipitation and Normalized Difference Vegetation Index (NDVI), among others, was selected as EC. A stratified random sampling (namely conditioned Latin Hypercube) was implemented and a total of 400 sampling locations were identified. At all sites, four composite topsoil samples (0-30 cm) were collected within a 2 m radius. SOC content was measured using dry combustion and SOC stocks were estimated using bulk density measurements. Regression Kriging was used to map the spatial variation of SOC stocks. The accuracy, fit and bias of SOC models was assessed using a rigorous validation assessment. This study produced the first comprehensive, geospatial SOC stock assessment in this

  2. The Southern Central Andes vertical axis tectonic rotations: relations with the deformation pattern Rotaciones tectónicas según ejes verticales en los Andes Centrales del Sur: relaciones con el patrón de deformación

    Claudia Prezzi

    2012-05-01

    Full Text Available Along the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (~19°S and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP. However, the CARP is a subject of ongoing debate. Recently, the quantity, quality, and geographic distribution of paleomagnetic data have expanded greatly. Such expansion has been accompanied by an increase in the knowledge of the deformation periods in the Andes, allowing a more detailed analysis of the temporal and spatial distribution of the detected rotations. We compiled and analyzed the available Cenozoic paleomagnetic data for the region extending between 19° and 27.5°S. The results suggest the possible existence of different rotational domains with distinct characteristics. We propose that in the Southern Central Andes, a close correlation would exist between the style and the temporal and spatial pattern of deformation and the amount of recorded vertical axis rotations. However, in order to further investigate such relationship, new paleomagnetic studies are necessary, particularly in the Eastern Cordillera domain, in Paleogene rocks cropping out in the Altiplano-Puna and in Neogene rocks of the forearc.En los Andes Centrales se ha identificado un patrón de rotaciones tectónicas según ejes verticales a través de estudios paleomagnéticos. Dichas rotaciones son en sentido antihorario al norte del codo de Arica (~19°S y en sentido horario hacia el sur. Distintos autores han propuesto diferentes hipótesis y modelos para tratar de explicar el Patrón de Rotaciones de los Andes Centrales (PRAC. Sin embargo, el PRAC sigue siendo objeto de debate. Recientemente, la cantidad, calidad y la distribución geográfica de los datos paleomagnéticos ha aumentado de manera notable. Dicho incremento ha sido acompañado por un importante

  3. The Quaternary calc-alkaline volcanism of the Patagonian Andes close to the Chile triple junction: geochemistry and petrogenesis of volcanic rocks from the Cay and Maca volcanoes (˜45°S, Chile)

    D'Orazio, M.; Innocenti, F.; Manetti, P.; Tamponi, M.; Tonarini, S.; González-Ferrán, O.; Lahsen, A.; Omarini, R.

    2003-08-01

    Major- and trace-element, Sr-Nd isotopes, and mineral chemistry data were obtained for a collection of volcanic rock samples erupted by the Cay and Maca Quaternary volcanoes, Patagonian Andes (˜45°S, Chile). Cay and Maca are two large, adjacent stratovolcanoes that rise from the Chiloe block at the southern end of the southern volcanic zone (SVZ) of the Andes. Samples from the two volcanoes are typical medium-K, calc-alkaline rocks that form two roughly continuous, largely overlapping series from subalkaline basalt to dacite. The overall geochemistry of the samples studied is very similar to that observed for most volcanoes from the southern SVZ. The narrow range of Sr-Nd isotope compositions ( 87Sr/ 86Sr=0.70389-0.70431 and 143Nd/ 144Nd=0.51277-0.51284) and the major- and trace-element distributions indicate that the Cay and Maca magmas differentiated by crystal fractionation without significant contribution by crustal contamination. This is in accordance with the thin (Maca magmas is investigated by means of the relative concentration of fluid mobile (e.g. Ba) and fluid immobile (e.g. Nb, Ta, Zr, Y) elements and other relevant trace-element ratios (e.g. Sr/Y). The results indicate that small amounts (Maca volcanoes and that, despite the very young age (Maca magma sources to the northern edge of the slab window generated by the subduction of the Chile ridge under the South American plate, we did not find any geochemical evidence for a contribution of a subslab asthenospheric mantle. However, this mantle has been used to explain the peculiar geochemical features (e.g. the mild alkalinity and relatively low ratios between large ion lithophile and high field strength elements) of the Hudson volcano, which is located even closer to the slab window than the Cay and Maca volcanoes are.

  4. Las ignimbritas del complejo volcánico Coranzuli (Puna Argentina-Andes Centrales

    Martí, J.

    1987-12-01

    Full Text Available The Coranzulí is a large Upper Miocene volcanic complex located on a NE-SW and NW-SE regional faults intersection, at 66º 15' W 23º S, in the Northwest of Argentina in Jujuy province. It corresponds to one of four large volcanic complexes which represent the end of Transversal Volcanic Chaines in La Puna Argentina in the Central Andes. The volcanic activity was characterized by at least four separate ignimbrite eruptions which produced four different ignimbrite sheets. These are well welded, very crystal-rich, lithie poor ignimbrites and have a moderate to high pumice content. The total volume of the Coranzuli ignimbrites exeededs 650 Km3. Preliminary data indicate that the eruption oeeurred from a homogeneous magmatic chamber without zoning. The emplacement characteristics of the ignimbrites and the lack of basal or interbedded plinian fall deposits suggest that the eruptions developed quickly to massive proportions.El Coranzuli es uno de los grandes complejos volcánicos que representan el remate final de las Cadenas Volcánicas Transversales de la Puna Argentina, en los Andes Centrales. Se trata de un complejo volcánico del Mioceno superior situado a los 66º 15' W 23º S en el NW de Argentina en la provincia de Jujuy, en la intersección entre dos fallas regionales de dirección NE-SW y NW-SE, respectivamente. La actividad eruptiva se caracterizó por la existencia de, al menos, cuatro erupciones ignimbríticas que produjeron cuatro diferentes mantos ignimbríticos. Se trata de ignimbritas bien soldadas, muy ricas en cristales, pobre en fragmentos líticos y que presentan un contenido en fragmentos pumíticos de moderado a alto. El volumen total que representan estas ignimbritas supera los 650 km3. Los datos preliminares indican que el magma juvenil deriva de una cámara magmática homogénea no zonada. Las características de emplazamiento de estas ignimbritas, así como la falta de depósitos plinianos de caída en la base o

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

    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. Evidence of Teleconnections between the Peruvian central Andes and Northeast Brazil during extreme rainfall events

    Sulca, J. C.; Vuille, M. F.; Silva, F. Y.; Takahashi, K.

    2013-12-01

    Knowledge about changes in regional circulation and physical processes associated with extreme rainfall events in South America is limited. Here we investigate such events over the Mantaro basin (MB) located at (10°S-13°S; 73°W-76°W) in the central Peruvian Andes and Northeastern Brazil (NEB), located at (9°S-15°S; 39°W-46°W). Occasional dry and wet spells can be observed in both areas during the austral summer season. The main goal of this study is to investigate potential teleconnections between extreme rainfall events in MB and NEB during austral summer. We define wet (dry) spells as periods that last for at least 3 (5) consecutive days with rainfall above (below) the 70 (30) percentile. To identify the dates of ocurrence of these events, we used daily accumulated rainfall data from 14 climate stations located in the Mantaro basin for the period 1965 to 2002. In NEB we defined a rainfall index which is based on average daily gridded rainfall data within the region for the same period. Dry (wet spells) in the MB are associated with positive (negative) OLR anomalies which extend over much of the tropical Andes, indicating the large-scale nature of these events. At 200 hPa anomalous easterly (westerly) zonal winds aloft accompany wet (dry) spells. Composite anomalies of dry spells in MB reveal significant contemporaneous precipitation anomalies of the opposite sign over NEB, which suggest that intraseasonal precipitation variability over the two regions may be dynamically linked. Indeed upper-tropospheric circulation anomalies over the central Andes extend across South America and appear to be tied to an adjustment in the Bolivian High-Nordeste Low system. Dry (wet) spells in NEB are equally associated with a large-scale pattern of positive (negative) OLR anomalies; however, there are no related significant OLR anomalies over the MB during these events. Dry (wet) spells are associated with robust patterns of anomalous wind fields at both low and upper

  7. The role of climate in the accumulation of lithium-rich brine in the Central Andes

    Godfrey, L.V.; Chan, L.-H.; Alonso, R.N.; Lowenstein, T.K.; McDonough, W.F.; Houston, J.; Li, J.; Bobst, A.; Jordan, T.E.

    2013-01-01

    Highlights: • δ 7 Li of waters and rocks in the Central Andes were measured. • Halite/brine partition coefficients of lithium and δ 7 Li of halite were determined. • Li-rich brines have a high component of fluids of geothermal origin. • Removal of lithium by clays is minor relative to other regions of the world. • The weathering flux of lithium and sodium decouple according to climate state. - Abstract: Lithium-rich brine within the sub-surface of the Salar del Hombre Muerto (SHM) salt pan in the Andes of northwestern Argentina has a chemical and isotopic composition which is consistent with Li derived from several sources: the modern halite saturated lagoon, Li-rich salts and brines formed recently, and dissolution of halite which precipitated from ancient saline lakes. SHM lies in the closed basin that includes part of the massive Cerro Galán caldera which is drained by the Río los Patos, which is responsible for 90% of surface runoff into the salar. The low Li isotope composition, +3.4‰, of this river is consistent with significant contributions of geothermal spring water. As water drains through the volcaniclastic deposits which cover a large proportion of the basin, Li removal, as indicated by decreasing Li/Na, occurs but without significant isotope fractionation. This indicates a mechanism of surface sorption onto smectite or ferrihydrite rather than Li incorporation into octahedral structural sites of clays. These observations suggest that conditions in this high altitude desert have limited the dilution of hydrothermal spring water as well as the formation of clay minerals, which jointly have allowed the Li resource to accumulate rapidly. Changes in climate on a multi-millennial time scale, specifically in the hydrologic budget, have resulted in solute accumulation rates that have been variable through time, and decoupled Li and Na fluxes. Inflow to the salar under modern conditions has high Li/Na (7.9 × 10 −3 by wt) with δ 7 Li

  8. A remote sensing assessment of the impact of the 2010 Maule, Chile earthquake (Mw 8.8) on the volcanoes of the southern Andes

    Pritchard, M. E.; Welch, M.; Jay, J.; Button, N.

    2011-12-01

    There are tantalizing, but controversial, indications that great earthquakes affect arc-wide volcanic activity. For example, analysis of historic eruptions at volcanoes of the southern Andes has shown that 3-4 eruptions were likely seismically triggered by Mw > 8 earthquakes in the Chile subduction zone -- particularly the 1906 and 1960 earthquakes (e.g., Watt et al., 2009). However, the 27 February 2010 Mw 8.8 Maule, Chile earthquake that ruptured the subduction zone between the 1960 and 1906 earthquakes does not appear to have triggered 3-4 volcanic eruptions in the same area in the 12 months after the event. In an effort to understand the relation between a large earthquake and volcanic unrest, we use a variety of satellite instruments to look for more subtle (i.e., not leading to eruption), but detectable change in thermal or deformation activity at the volcanoes of the southern Andes after the Maule earthquake and its aftershocks. For all of the volcanoes in the catalog of the Smithsonian Institution (approximately 80), we use nighttime MODIS and ASTER data to assess the thermal activity and ALOS InSAR data to characterize the surface deformation before and after the earthquake. The ALOS InSAR data are not ideal for detecting changes in deformation before and after the earthquake because of the small number of acquisitions in austral summer as well as ionospheric and tropospheric artifacts. We estimate that we could detect deformation > 5 cm/year. Similarly, the ASTER and MODIS data suffer respectively from poor temporal and spatial resolution of thermal anomalies. We update previous InSAR work that identified at least 8 areas of volcanic deformation in the southern Andes related to eruptive processes, subsidence of past lava flows, or surface uplift not associated with an eruption (Fournier et al., 2010). Of greatest interest are the two volcanic areas with the largest deformation signals between 2007-2008 (both > 15 cm/yr in the radar line of sight): Laguna

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

    Ovalle, C.; Arredondo, S.; Aronson, J.; Longeri, L.; Avendano, J.

    1998-01-01

    Results are presented from a 5-year experiment using 15 N-enriched fertilizer to determine N 2 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 N 2 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 N 2 fixation rarely detailed for woody plants in dryland regions. (author)

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

    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.

  11. Genome of Plant Maca (Lepidium meyenii) Illuminates Genomic Basis for High-Altitude Adaptation in the Central Andes.

    Zhang, Jing; Tian, Yang; Yan, Liang; Zhang, Guanghui; Wang, Xiao; Zeng, Yan; Zhang, Jiajin; Ma, Xiao; Tan, Yuntao; Long, Ni; Wang, Yangzi; Ma, Yujin; He, Yuqi; Xue, Yu; Hao, Shumei; Yang, Shengchao; Wang, Wen; Zhang, Liangsheng; Dong, Yang; Chen, Wei; Sheng, Jun

    2016-07-06

    Maca (Lepidium meyenii Walp, 2n = 8x = 64), belonging to the Brassicaceae family, is an economic plant cultivated in the central Andes sierra in Peru (4000-4500 m). Considering that the rapid uplift of the central Andes occurred 5-10 million years ago (Ma), an evolutionary question arises regarding how plants such as maca acquire high-altitude adaptation within a short geological period. Here, we report the high-quality genome assembly of maca, in which two closely spaced maca-specific whole-genome duplications (WGDs; ∼6.7 Ma) were identified. Comparative genomic analysis between maca and closely related Brassicaceae species revealed expansions of maca genes and gene families involved in abiotic stress response, hormone signaling pathway, and secondary metabolite biosynthesis via WGDs. The retention and subsequent functional divergence of many duplicated genes may account for the morphological and physiological changes (i.e., small leaf shape and self-fertility) in maca in a high-altitude environment. In addition, some duplicated maca genes were identified with functions in morphological adaptation (i.e., LEAF CURLING RESPONSIVENESS) and abiotic stress response (i.e., GLYCINE-RICH RNA-BINDING PROTEINS and DNA-DAMAGE-REPAIR/TOLERATION 2) under positive selection. Collectively, the maca genome provides useful information to understand the important roles of WGDs in the high-altitude adaptation of plants in the Andes. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Geomodels of coseismic landslides environments in Central Chile.

    Serey, A.; Sepulveda, S. A.; Murphy, W.; Petley, D. N.

    2017-12-01

    Landslides are a major source of fatalities and damage during strong earthquakes in mountain areas. Detailed geomodels of coseismic landslides environments are essential parts of seismic landslide hazard analyses. The development of a site specific geological model is required, based on consideration of the regional and local geological and geomorphological history and the current ground surface conditions. An engineering geological model is any approximation of the geological conditions, at varying scales, created for the purpose of solving an engineering problem. In our case, the objective is the development of a methodology for earthquake-induced landslide hazard assessment applicable to urban/territorial planning and disaster prevention strategies assessment at a regional scale adapted for the Chilean tectonic conditions. We have developed the only 2 complete inventories of landslides triggered by earthquakes in Chile. The first from the Mw 6.2, shallow crustal Aysén earthquake in 2007. Second one from the Mw 8.8, megathrust subduction Maule earthquake in 2010. From the comparison of these 2 inventories with others from abroad, as well as analysis of large, prehistoric landslide inventories proposed as likely induced by seismic activity we have determined topographic, geomorphological, geological and seismic controlling factors in the occurrence of earthquake-triggered landslides. With the information collected we have defined different environments for generation of coseismic landslides based on the construction of geomodels. As a result we have built several geomodels in the Santiago Cordillera in central Chile (33°S), based upon the San Ramón Fault, a west-vergent reverse fault that outcrops at the edge of Santiago basin recently found to be active and a likely source of seismic activity in the future, with potential of triggering landslides in the Santiago mountain front as well as inland into the Mapocho and Maipo Cordilleran valleys. In conclusion

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

    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

  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

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

    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

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

    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.

  17. Lacustrine sedimentation in an altitude forest site, central Andes, Bolivia. Palaeo-climatic implications

    Sifeddine, A.; Bertaux, J.; Mourguiart, Ph.; Disnar, J.R.; Laggoun-Defarge, F.; Argollo, J.

    1998-01-01

    A sedimentological study of a 755 cm length core sampled in the middle of a marshy depression surrounded by a cloud forest in the central Andes reveals that this site has recorded important environmental variations during the last 50 000 years. For the most part (625 cm) the core is composed of detrital rich sediments deposited during the Upper Pleistocene. The highest amount of detrital influx underlines the Last Glacial Maximum which ranges from ca 29,000 14 C yr B.P. to ca 16,000 14 C yr B.P. (ca 18,500 cal yr B.P.), between two relatively humid phases. The sedimentation of the present Interglacial, starting at ca 12,500 14 C yr B.P. (14,500 cal yr B.P.), is mainly organic, as a consequence of the great development of soils and the forest vegetal cover the catchment area. The maximum extension of this vegetal cover ranging from 12,500 to ca 10,500 14 C yr B.P. (14,500 and 12,400 cal yr B.P.) is followed from 10,500 to 8,000 14 C yr B.P. (12,400 and 8,800 cal yr B.P.) by a drier period is revealed by the occurrence of micro-charcoals in the sediment. Between ca 8,000 and 4,000 14 C yr B.P. (8,800 and 4,500 cal yr B.P.), the sharp increase of micro-charcoals content, likely related to palaeo-fires, underlines an intensification of this dry trend. (authors)

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

    Cooke, Colin A.; Abbott, Mark B.

    2008-01-01

    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 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

  19. Neogene paleoelevation of intermontane basins in a narrow, compressional mountain range, southern Central Andes of Argentina

    Hoke, Gregory D.; Giambiagi, Laura B.; Garzione, Carmala N.; Mahoney, J. Brian; Strecker, Manfred R.

    2014-11-01

    The topographic growth of mountain ranges at convergent margins results from the complex interaction between the motion of lithospheric plates, crustal shortening, rock uplift and exhumation. Constraints on the timing and magnitude of elevation change gleaned from isotopic archives preserved in sedimentary sequences provide insight into how these processes interact over different timescales to create topography and potentially decipher the impact of topography on atmospheric circulation and superposed exhumation. This study uses stable isotope data from pedogenic carbonates collected from seven different stratigraphic sections spanning different tectonic and topographic positions in the range today, to examine the middle to late Miocene history of elevation change in the central Andes thrust belt, which is located immediately to the south of the Altiplano-Puna Plateau, the world's second largest orogenic plateau. Paleoelevations are calculated using previously published local isotope-elevation gradients observed in modern rainfall and carbonate-formation temperatures determined from clumped isotope studies in modern soils. Calculated Neogene basin paleoelevations are between 1 km and 1.9 km for basins that today are located between 1500 and 3400 m elevation. Considering the modern elevation and δ18O values of precipitation at the sampling sites, three of the intermontane basins experienced surface uplift between the end of deposition during the late Miocene and present. The timing of elevation change cannot be linked to any documented episodes of large-magnitude crustal shortening. Paradoxically, the maximum inferred surface uplift in the core of the range is greatest where the crust is thinnest. The spatial pattern of surface uplift is best explained by eastward migration of a crustal root via ductile deformation in the lower crust and is not related to flat-slab subduction.

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

    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.

  1. Spatio-Temporal Patterns of the 2010–2015 Extreme Hydrological Drought across the Central Andes, Argentina

    Juan Antonio Rivera

    2017-08-01

    Full Text Available During the period 2010–2015, the semi-arid Central Andes in Argentina (CAA experienced one of the most severe and long-lasting hydrological droughts on record. Since the snowmelt is the most important source of water, the reduced snowfall over the mountains propagated the drought signal through the streamflows in the adjacent foothills east of the Andes ranges. Motivated by the widespread impacts on the socio-economic activities in the region, this study aims to characterize the recent hydrological drought in terms of streamflow deficits. Based on streamflow data from 20 basins, we used the standardized streamflow index (SSI to characterize hydrological droughts during the period 1971–2016. We found that the regional extent of the 2010–2015 hydrological drought was limited to the basins located north of 38° S, with mean duration of 67 months and maximum drought severity exhibiting a heterogeneous pattern in terms of spatial distribution and time of occurrence. The drought event reached extreme conditions in 14 of the 15 basins in the CAA, being record-breaking drought in six of the basins. This condition was likely driven by a cooling in the tropical Pacific Ocean resembling La Niña conditions, which generated a decrease in snowfall over the Andes due to suppressed frontal activity.

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

    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.

  3. Compositional data supports decentralized model of production and circulation of artifacts in the pre-Columbian south-central Andes.

    Lazzari, Marisa; Pereyra Domingorena, Lucas; Stoner, Wesley D; Scattolin, María Cristina; Korstanje, María Alejandra; Glascock, Michael D

    2017-05-16

    The circulation and exchange of goods and resources at various scales have long been considered central to the understanding of complex societies, and the Andes have provided a fertile ground for investigating this process. However, long-standing archaeological emphasis on typological analysis, although helpful to hypothesize the direction of contacts, has left important aspects of ancient exchange open to speculation. To improve understanding of ancient exchange practices and their potential role in structuring alliances, we examine material exchanges in northwest Argentina (part of the south-central Andes) during 400 BC to AD 1000 (part of the regional Formative Period), with a multianalytical approach (petrography, instrumental neutron activation analysis, laser ablation inductively coupled plasma mass spectrometry) to artifacts previously studied separately. We assess the standard centralized model of interaction vs. a decentralized model through the largest provenance database available to date in the region. The results show: ( i ) intervalley heterogeneity of clays and fabrics for ordinary wares; ( ii ) intervalley homogeneity of clays and fabrics for a wide range of decorated wares (e.g., painted Ciénaga); ( iii ) selective circulation of two distinct polychrome wares (Vaquerías and Condorhuasi); ( iv ) generalized access to obsidian from one major source and various minor sources; and ( v ) selective circulation of volcanic rock tools from a single source. These trends reflect the multiple and conflicting demands experienced by people in small-scale societies, which may be difficult to capitalize by aspiring elites. The study undermines centralized narratives of exchange for this period, offering a new platform for understanding ancient exchange based on actual material transfers, both in the Andes and beyond.

  4. Scale of human mobility in the southern Andes (Argentina and Chile): A new framework based on strontium isotopes.

    Barberena, Ramiro; Durán, Víctor A; Novellino, Paula; Winocur, Diego; Benítez, Anahí; Tessone, Augusto; Quiroga, María N; Marsh, Erik J; Gasco, Alejandra; Cortegoso, Valeria; Lucero, Gustavo; Llano, Carina; Knudson, Kelly J

    2017-10-01

    The goal of this article is to assess the scale of human paleomobility and ecological complementarity between the lowlands and highlands in the southern Andes during the last 2,300 years. By providing isotope results for human bone and teeth samples, we assess a hypothesis of "high residential mobility" suggested on the basis of oxygen isotopes from human remains. We develop an isotopic assessment of human mobility in a mountain landscape combining strontium and oxygen isotopes. We analyze bone and teeth samples as an approach to life-history changes in spatial residence. Human samples from the main geological units and periods within the last two millennia are selected. We present a framework for the analysis of bioavailable strontium based on the combination of the geological data with isotope results for rodent samples. The 87 Sr/ 86 Sr values from human samples indicate residential stability within geological regions along life history. When comparing strontium and oxygen values for the same human samples, we record a divergent pattern: while δ 18 O values for samples from distant regions overlap widely, there are important differences in 87 Sr/ 86 Sr values. Despite the large socio-economic changes recorded, 87 Sr/ 86 Sr values indicate a persisting scenario of low systematic mobility between the different geological regions. Our results suggest that strontium isotope values provide the most germane means to track patterns of human occupation of distinct regions in complex geological landscapes, offering a much higher spatial resolution than oxygen isotopes in the southern Andes. © 2017 Wiley Periodicals, Inc.

  5. Imaging the lithospheric structure of the Central Andes from the joint inversion of multiple seismic data sets

    Ward, Kevin Michael

    A lingering question in Cordilleran tectonics is how high plateaus form in the absence of continental collision. The type example of an active Cordilleran high plateau is found in the Central Andes of Peru, Bolivia, Argentina, and Chile. Along this section of the South American Cordillera, tectonics are primarily driven by subduction of the oceanic Nazca Plate beneath the continental South American Plate. Extending over 1,800 km along the active continental margin, the Central Andean Plateau (CAP) reaches a maximum width of around 400 km with several peaks in excess of 6 km. Numerous morphotectonic subdivisions of the CAP highlight the complex along-strike variability of the Plateau providing a natural laboratory for investigating the relative contribution of tectonic processes involved in building and maintaining Cordilleran high plateaus. The scale of this problem extends far beyond the scope of any one geoscientific discipline requiring a multidisciplinary approach. Our contribution to this scientific problem and the focus of the work presented in this dissertation is to better understand the current lithospheric and uppermost mantle structure along the CAP. This is achieved by integrating recent advances in seismic imaging techniques with a growing availability of high-quality seismic data into three distinct studies across the South American continent. In the first study, we present a shear-wave velocity model for the crust below the Altiplano-Puna Volcanic Complex (APVC). The target of this study is to constrain the crustal volume of a large magma reservoir inferred to exist below the APVC. When combined with geological and petrological constraints, the large-volume magma reservoir imaged in this study suggests a significant magmatic contribution to the growth of the Plateau in excess of one kilometer over the last ten million years. In addition to the tectonic contributions of this work, we introduce a new method of jointly inverting surface-wave dispersion

  6. Chile.

    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

  7. Extreme hydrometeorological events in the Peruvian Central Andes during austral summer and their relationship with the large-scale circulation

    Sulca, Juan C.

    In this Master's dissertation, atmospheric circulation patterns associated with extreme hydrometeorological events in the Mantaro Basin, Peruvian Central Andes, and their teleconnections during the austral summer (December-January-February-March) are addressed. Extreme rainfall events in the Mantaro basin are related to variations of the large-scale circulation as indicated by the changing strength of the Bolivian High-Nordeste Low (BH-NL) system. Dry (wet) spells are associated with a weakening (strengthening) of the BH-NL system and reduced (enhanced) influx of moist air from the lowlands to the east due to strengthened westerly (easterly) wind anomalies at mid- and upper-tropospheric levels. At the same time extreme rainfall events of the opposite sign occur over northeastern Brazil (NEB) due to enhanced (inhibited) convective activity in conjunction with a strengthened (weakened) Nordeste Low. Cold episodes in the Mantaro Basin are grouped in three types: weak, strong and extraordinary cold episodes. Weak and strong cold episodes in the MB are mainly associated with a weakening of the BH-NL system due to tropical-extratropical interactions. Both types of cold episodes are associated with westerly wind anomalies at mid- and upper-tropospheric levels aloft the Peruvian Central Andes, which inhibit the influx of humid air masses from the lowlands to the east and hence limit the potential for development of convective cloud cover. The resulting clear sky conditions cause nighttime temperatures to drop, leading to cold extremes below the 10-percentile. Extraordinary cold episodes in the MB are associated with cold and dry polar air advection at all tropospheric levels toward the central Peruvian Andes. Therefore, weak and strong cold episodes in the MB appear to be caused by radiative cooling associated with reduced cloudiness, rather than cold air advection, while the latter plays an important role for extraordinary cold episodes only.

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

    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.

  9. Distinguishing megathrust from intraplate earthquakes using lacustrine turbidites (Laguna Lo Encañado, Central Chile)

    Van Daele, Maarten; Araya-Cornejo, Cristian; Pille, Thomas; Meyer, Inka; Kempf, Philipp; Moernaut, Jasper; Cisternas, Marco

    2017-04-01

    One of the main challenges in seismically active regions is differentiating paleo-earthquakes resulting from different fault systems, such as the megathrust versus intraplate faults in subductions settings. Such differentiation is, however, key for hazard assessments based on paleoseismic records. Laguna Lo Encañado (33.7°S; 70.3°W; 2492 m a.s.l.) is located in the Central Chilean Andes, 50 km east of Santiago de Chile, a metropole with about 7,000,000 inhabitants. During the last century the study area experienced 3 large megathrust earthquakes (1906, 1985 and 2010) and 2 intraplate earthquakes (1945 and 1958) (Lomnitz, 1960). While the megathrust earthquakes cause Modified Mercalli Intensities (MMIs) of VI to VII at the lake (Van Daele et al., 2015), the intraplate earthquakes cause peak MMIs up to IX (Sepúlveda et al., 2008). Here we present a turbidite record of Laguna Lo Encañado going back to 1900 AD. While geophysical data (3.5 kHz subbottom seismic profiles and side-scan sonar data) provides a bathymetry and an overview of the sedimentary environment, we study 15 short cores in order to understand the depositional processes resulting in the encountered lacustrine turbidites. All mentioned earthquakes triggered turbidites in the lake, which are all linked to slumps in proximal areas, and are thus resulting from mass wasting of the subaquatic slopes. However, turbidites linked to the intraplate earthquakes are additionally covered by turbidites of a finer-grained, more clastic nature. We link the latter to post-seismic erosion of onshore landslides, which need higher MMIs to be triggered than subaquatic mass movements (Howarth et al., 2014). While intraplate earthquakes can cause MMIs up to IX and higher, megathrust earthquakes do not cause sufficiently high MMIs at the lake to trigger voluminous onshore landslides. Hence, the presence of these post-seismic turbidites allows to distinguish turbidites triggered by intraplate earthquakes from those

  10. The subduction erosion and mantle source region contamination model of Andean arc magmatism: Isotopic evidence from igneous rocks of central Chile

    Stern, Charles R

    2001-01-01

    Continental crust may be incorporated in mantle-derived Andean magmas as these magmas rise through the crust (Hildreth and Moorbath, 1988), or alternatively, crust may be tectonically transported into the mantle by subduction of trench sediments and subduction erosion of the continental margin, and then added into the mantle source region of Andean magmas (Stern, 1991). Since the mantle has relatively low Sr, Nd, and Pb concentrations compared to continental crust, differences in the isotopic compositions of magmas erupted in different region of the Andes may be produced by relatively small differences in the amount of subducted crust added to the mantle source region of these magmas. By comparison, significantly larger amounts of crust must be assimilated by mantle-derived magmas to produce isotopic differences of similar magnitude. Therefore, constraining the process by which continental crust is incorporated in Andean magmas has important implications for understanding the chemical cycling that takes place in the Andean subduction-related magma factory. Isotopic data suggest the incorporation of a greater proportion of crust in Andean magmas erupted at the northern portion of the Southern Volcanic Zone of central Chile compared to those erupted in the southern portion of the Southern Volcanic Zone of south central Chile (SSVZ) (Stern et al., 1984; Futa and Stern, 1988; Hildreth and Moorbath, 1988). The NSVZ occurs just south of the current locus of the subduction of the Juan Fernandez Ridge. The southward migration of the locus of subduction of this ridge has resulted in decreasing subduction angle below the NSVZ, the eastward migration of the volcanic front of the Andean arc, and an increase in the crustal thickness below the arc. These factors together have caused changes, since the middle Miocene, in the isotopic composition of Andean igneous rocks of central Chile. The data indicate a close chronologic relation between the southward migrations of the locus

  11. Andes 1997 Gravity Data

    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...

  12. Total arsenic, lead, cadmium, copper, and zinc in some salt rivers in the northern Andes of Antofagasta, Chile.

    Queirolo, F; Stegen, S; Mondaca, J; Cortés, R; Rojas, R; Contreras, C; Munoz, L; Schwuger, M J; Ostapczuk, P

    2000-06-08

    The pre-Andes water in the region of Antofagasta is the main drinking and irrigation water source for approximately 3000 Atacameña (indigenous) people. The concentration for soluble elements (filtration in field through a 0.45-microm filter) was: Cd < 0.1 ng/ml; Pb < 0.5 ng/ml; and Zn and Cu between 1 and 10 ng/ml. In particulate material the concentrations were: for Cd < 0.1 ng/ml; for Pb < 0.3 ng/ml; and for Zn and Cu less than 1 ng/ml. The total content of these elements is far below the international recommendations (WHO) and the national standards (N. Ch. 1333 mod. 1987 and 409-1 of 1984). On the other hand, in some rivers a very high arsenic concentration was found (up to 3000 ng/ml) which exceed more than 50 times the national standard. In order to verify the analytical results, inter-laboratory and comparison with different determination methods have been done.

  13. Eocene extensional exhumation of basement and arc rocks along southwesternmost Peru, Central Andes.

    Noury, Mélanie; Bernet, Matthias; Sempéré, Thierry

    2014-05-01

    The overthickened crust of the current Central Andes is commonly viewed as the result of tectonic shortening. However, in the present-day terrestrial forearc and arc of southwesternmost Peru, crustal thickness increases from 30 km along the coastline to >60 km below the active arc, whereas the upper crust exhibits little to no evidence of crustal shortening and, in constrast, many extensional features. How (and when) crustal overthickness was acquired in this region is thus little understood. Because crustal overthickening often results in extensional collapse and/or significant erosion, here we address this issue through a regional-scale study of exhumation using fission-track thermochronology. The limited fission-track data previously available in the area suggested that exhumation began during the Mesozoic. In this study, we present new apatite and zircon fission-track data obtained along the current terrestrial forearc of southwesternmost Peru. This relatively restricted area presents the interest of providing extensive outcrops of Precambrian to Ordovician basement and Early Jurassic to Late Cretaceous arc plutons. In order to compare the chronology of exhumation of these units, we performed extensive sampling for fission-track dating, as well as structural mapping. Our results indicate that the basement rocks and Jurassic plutons that crop out in the Arequipa region, where the crust is now >50 km-thick, experienced a rapid cooling through the 240-110°C temperature range between ~65 and ~35 Ma. This period of rapid exhumation coincided in time with the accumulation of terrestrial forearc deposits (the Lower Moquegua Group), that exhibit many syn-sedimentary extensional features and are bounded by conspicuous normal faults, specifically along the region where intense activity of the main arc between ~90 and ~60 Ma had led to voluminous magma emplacement. This close succession of (1) intense magmatic activity and (2) regional-scale exhumation associated with

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

    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

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

    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 San Juan-Argentina, 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.

  16. Spatial coincidence and similar geochemistry of Late Triassic and Eocene-Oligocene magmatism in the Andes of northern Chile: evidence from the MMH porphyry type Cu-Mo deposit, Chuquicamata District

    Zentilli, Marcos; Maksaev, Victor; Boric, Ricardo; Wilson, Jessica

    2018-04-01

    The MMH porphyry type copper-molybdenum deposit in northern Chile is the newest mine in the Chuquicamata District, one of largest copper concentrations on Earth. Mineralized Eocene-Oligocene porphyry intrusions are hosted by essentially barren Triassic granodiorites. Despite a century of exploitation, geologists still have problems in the mine distinguishing the Triassic granodiorite from the most important ore-carrying Eocene porphyries in the district. To resolve the problem, internally consistent high-quality geochemical analyses of the Triassic and Tertiary intrusives were carried out: explaining the confusion, they show that the rock units in question are nearly identical in composition and thus respond equally to hydrothermal alteration. In detail, the only difference in terms of chemical composition is that the main Eocene-Oligocene porphyries carry relatively less Fe and Ni. Unexpectedly, the mineralized Eocene-Oligocene porphyries have consistently less U and Th than other Tertiary intrusions in the district, a characteristic that may be valuable in exploration. The supergiant copper-molybdenum deposits in the Central Andes were formed within a narrow interval between 45 and 31 Ma, close to 7% of the 200 My duration of "Andean" magmatism, which resulted from subduction of oceanic lithosphere under South America since the Jurassic. Although recent work has shown that subduction was active on the margin since Paleozoic times, pre-Andean (pre-Jurassic) "Gondwanan" magmatism is often described as being very different, having involved crustal melting and the generation of massive peraluminous rhyolites and granites. This study shows that the indistinguishable Late Triassic and Eocene-Oligocene intrusions occupy the same narrow NS geographic belt in northern Chile. If it is accepted that magma character may determine the potential to generate economic Cu-Mo deposits, then Late Triassic volcano-plutonic centres in the same location in the South American margin

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

    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.

  18. The Influence of the Madden-Julian Oscillation (mjo) on Extreme Rainfall Over the Central and Southern Peruvian Andes

    Heidinger, H.; Jones, C.; Carvalho, L. V.

    2015-12-01

    Extreme rainfall is important for the Andean region because of the large contribution of these events to the seasonal totals and consequent impacts on water resources for agriculture, water consumption, industry and hydropower generation, as well as the occurrence of floods and landslides. Over Central and Southern Peruvian Andes (CSPA), rainfall exceeding the 90th percentile contributed between 44 to 100% to the total Nov-Mar 1979-2010 rainfall. Additionally, precipitation from a large majority of stations in the CSPA exhibits statistically significant spectral peaks on intraseasonal time-scales (20 to 70 days). The Madden-Julian Oscillation (MJO) is the most important intraseasonal mode of atmospheric circulation and moist convection in the tropics and the occurrence of extreme weather events worldwide. Mechanisms explaining the relationships between the MJO and precipitation in the Peruvian Andes have not been properly described yet. The present study examines the relationships between the activity and phases of the MJO and the occurrence of extreme rainfall over the CSPA. We found that the frequency of extreme rainfall events increase in the CSPA when the MJO is active. MJO phases 5, 6 and 7 contribute to the overall occurrence of extreme rainfall events over the CSPA. However, how the MJO phases modulate extreme rainfall depends on the location of the stations. For instance, extreme precipitation (above the 90th percentile) in stations in the Amazon basin are slightly more sensitive to phases 2, 3 and 4; the frequency of extremes in stations in the Pacific basin increases in phases 5, 6 and 7 whereas phase 2, 3 and 7 modulates extreme precipitation in stations in the Titicaca basin. Greater variability among stations is observed when using the 95th and 99th percentiles to identify extremes. Among the main mechanisms that explain the increase in extreme rainfall events in the Peruvian Andes is the intensification of the easterly moisture flux anomalies, which

  19. A new species of Alsodes (Anura: Alsodidae) from Altos de Cantillana, central Chile.

    Charrier, Andrés; Correa, Claudio; Castro, Camila; Méndez, Marco A

    2015-02-05

    Based on morphological and molecular evidence (mitochondrial and nuclear sequences) we describe a new species of spiny-chest frog, Alsodes cantillanensis, from central Chile (around 34°S). The type locality, Quebrada Infiernillo, is located in the Coastal Range at approximately 65 km from Santiago (Metropolitan Region), the capital of Chile. The distribution of the new species is included entirely in that of A. nodosus (32-36°S approximately), which was identified as the sister taxon according to molecular phylogenetic analyses. Moreover, both species are sympatric in the type locality. The new species was found in a Nothofagus macrocarpa relict forest potentially threatened by gold mining activities. We identify other threats for its conservation and some biological data needed for understanding the evolution of this species. This discovery reveals the scarce knowledge about biogeography, evolution and ecology of spiny-chest frogs from central Chile

  20. Cold episodes in the Peruvian Central Andes: Composites, Types, and their Impacts over South America (1958-2014)

    Sulca, J. C.; Vuille, M. F.; Roundy, P. E.; Trasmonte, G.; Silva, Y.; Takahashi, K.

    2015-12-01

    The Mantaro basin (MB) is located in the central Peruvian Andes. Occasionally, cold episodes are observed during austral summer (January-March), that strongly damage crops. However, little is known about the causes and impacts of such cold episodes. The main goal of this study is thus to characterize cold episodes in the MB and assess their large-scale circulation and teleconnections over South America (SA) during austral summer. To identify cold events in the MB daily minimum temperature (Tmin) for the period 1958-2014 from Huayao station, located within the MB was used. A cold episode is defined when daily minimum temperature drops below its 10-percentile for at least one day. Additionally, to study the sensitivity between physical mechanisms associated with cold episodes and temperature, cold episodes are classified in three groups: Weak cold episodes (7.5 ≤ Tmin ≤ 10 percentile), strong cold episodes (Tmin ≤ 2.5 percentile), but excluding the 9 coldest events (Tmin ≤ 0 ͦ C), henceforth referred to as extraordinary cold episodes. Several gridded reanalysis were used to characterize the large-scale circulation, cloud cover and rainfall over SA associated with these events. Weak and strong cold episodes in the MB are mainly associated with a weakening of the Bolivian High-Nordeste Low system by tropical-extratropical interactions. Both types of cold episodes are associated with westerly wind anomalies at mid- and upper-tropospheric levels aloft the Peruvian Central Andes, which inhibit the influx of humid air masses from the lowlands to the east and hence limit the development of cloud cover (e.g., positive OLR anomalies over MB). The resulting clear sky conditions cause nighttime temperatures to drop, leading to cold extremes below 10-percentile. Simultaneously, northeastern Brazil (NEB) registers negative OLR anomalies, strong convection and enhanced cloud cover because displacement of the South Atlantic Convergence Zone (SACZ) toward the northeast of

  1. The 2010-2015 megadrought in central Chile: impacts on regional hydroclimate and vegetation

    Garreaud, René D.; Alvarez-Garreton, Camila; Barichivich, Jonathan; Boisier, Juan Pablo; Christie, Duncan; Galleguillos, Mauricio; LeQuesne, Carlos; McPhee, James; Zambrano-Bigiarini, Mauricio

    2017-12-01

    Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in central Chile (western South America, 30-38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large extent. The extraordinary character of the so-called central Chile megadrought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile, but the event was unprecedented to the south of 35° S. ENSO-neutral conditions have prevailed since 2011 (except for the strong El Niño in 2015), contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semi-arid basins we found a decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south, where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year periods on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. We also report some of the measures taken by the central government to relieve the MD effects and the public perception of this event. The understanding of the nature and biophysical impacts of the MD helps as a foundation for preparedness efforts to confront a dry, warm future regional climate scenario.

  2. The 2010–2015 megadrought in central Chile: impacts on regional hydroclimate and vegetation

    R. D. Garreaud

    2017-12-01

    Full Text Available Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in central Chile (western South America, 30–38° S. Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large extent. The extraordinary character of the so-called central Chile megadrought (MD was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile, but the event was unprecedented to the south of 35° S. ENSO-neutral conditions have prevailed since 2011 (except for the strong El Niño in 2015, contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 % of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semi-arid basins we found a decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south, where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year periods on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. We also report some of the measures taken by the central government to relieve the MD effects and the public perception of this event. The understanding of the nature and biophysical impacts of the MD helps as a foundation for preparedness efforts to confront a dry, warm future regional climate scenario.

  3. Diversity patterns and composition of native and exotic floras in central Chile

    Figueroa, Javier A.; Teillier, Sebastián; Castro, Sergio A.

    2011-03-01

    Floristic changes in the Mediterranean region of central Chile brought about by human impact appear to be shared with other climatic regions, although there is a notable absence of empirical studies and available quantitative evidence for the central Chile region. This study examines the cover, richness and composition of native and exotic plant species in a representative area of central Chile. Through floristic characterization of 33 sites sampled using 40 × 40 m plots distributed along transect on which the two farthest sites were separated by 50 km, the floristic richness and cover patterns, as well as the general land use characteristics were evaluated (native matorral, espinal, abandoned farming field, forest plantations, periurban sites, road sites, river bank, and burnt site). We recorded 327 species of plants; 213 species were native and 114 were exotic. The average number of species was heterogeneous in all sites, showing a greater relative native frequency in those sites with a lower level of anthropic intervention. Except for the matorral, the cover of exotic species was greater than that of native species. No relation was found between richness and cover in relation to the different types of land use. The relationship between cover of native and exotic was negative, although for richness did not show relationship. Results show that the exotic species are limited by resources, although they have not completely displaced the native species. The native and exotic floras respond to different spatial distribution patterns, so their presence makes it possible to establish two facts rarely quantified in central Chile: first, that the exotic flora replaces (but does not necessarily displace) the native flora, and second, that at the same time, because of its greater geographic ubiquity and the abundance levels that it achieves, it contributes to the taxonomic and physiognomic homogenization of central Chile.

  4. Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S)

    Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.

    2006-11-01

    This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

  5. The Mass Elevation Effect of the Central Andes and Its Implications for the Southern Hemisphere's Highest Treeline

    Wenhui He

    2016-05-01

    Full Text Available One of the highest treelines in the world is at 4810 m above sea level on the Sajama Volcano in the central Andes. The climatological cause of that exceptionally high treeline position is still unclear. Although it has been suggested that the mass elevation effect (MEE explains the upward shift of treelines in the Altiplano region, the magnitude of MEE has not yet been quantified for that region. This paper defines MEE as the air temperature difference in summer at the same elevation between the inner mountains/plateaus (Altiplano and the free atmosphere above the adjacent lowlands of the Andean Cordillera. The Altiplano air temperature was obtained from the Global Historical Climatology Network-Monthly temperature database, and the air temperature above the adjacent lowlands was interpolated based on the National Center for Environmental Prediction/National Center for Atmospheric Research Reanalysis 1 data set. We analyzed the mean air temperature differences for January, July, and the warm months from October to April. The air temperature was mostly higher on the Altiplano than over the neighboring lowlands at the same altitude. The air temperature difference increased from the outer Andean east-facing slope to the interior of the Altiplano in summer, and it increased from high latitudes to low latitudes in winter. The mean air temperature in the Altiplano in summer is approximately 5 K higher than it is above the adjacent lowlands at the same mean elevation, averaging about 3700 m above sea level. This upward shift of isotherms in the inner part of the Cordillera enables the treeline to climb to 4810 m, with shrub-size trees reaching even higher. Therefore, the MEE explains the occurrence of one of the world’s highest treelines in the central Andes.

  6. Les Andes Centrales Tropicales vues par deux géographes: Isaiah Bowman et Carl Troll

    1978-01-01

    Full Text Available Deux visions des Andes vues par deux géographes, Isaiah BOWMAN et Carl TROLL, au caractère et au milieu intellectuel différents. L'auteur étudie dans l'un et l'autre cas la méthode d'analyse de l'espace géographique et les conclusions tirées par chacun d'eux. I. BOWMAN, Américain, convaincu qu'une économie mercantiliste fondée sur l'exportation permettra aux Etats andins d'accéder à un modèle de développement, décrit les vastes contrées amazoniennes comme un futur El Dorado entre les mains de colons. L'aménagement des basses plaines selon des schémas nord-américains est le pilier de l'économie alors que les Andes abritant les communautés indigènes constituent un frein au développement. De ce fait il laisse de côté l'étude des paysanneries andines. Toute différente est la démarche de Carl TROLL dont la formation à la fois en sciences humaines et naturelles, lui permet de cerner l'espace géographique comme cadre de vie des sociétés. L'utilisation des étages écologiques, le développement de l'Empire Inca fondé sur l'étage des 'punas', la démarche historique des analyses minutieuses de Carl TROLL donne un éclairage nouveau aux relations des sociétés andines et des milieux naturels avec lesquels elles composent. Dos puntos de vista de los Andes por dos geógrafos, Isaiah BOWMAN y Carl TROLL con carácter y medio intelectual distintos. El autor estudia en ambos casos el método de análisis del espacio geográfico y las conclusiones sacadas por cada uno de ellos. I. BOWMAN, americano, convencido que una economía mercantil fundada sobre la exportación permitirá a los estados andinos acceder a un modelo de desarrollo, describe las extensas llanuras amazónicas como un El Dorado futuro entre las manos de los colonos. El desarrollo de las llanuras bajas según esquemas norteamericanos constituye el pilar de la economía mientras los Andes abrigando las comunidades indígenas se comportan como un freno al

  7. Non-volant mammals in a protected area on the Central Andes of Colombia: new records for the Caldas department and the Chinchiná River basin

    Ramírez-Mejía, Andrés; Sánchez, Francisco

    2015-01-01

    The Chinchiná River basin is located on the western slope of the Colombian Central Andes. This basin provides ecosystem services such as water provision for >500,000 people, but has suffered considerable ecosystem degradation, and the information on its biodiversity is limited. We inventoried the non-volant mammals in the Caldas' Central Hydroelectric (CHEC) Reserve in the Chinchiná River basin, in the Caldas department. We detected 18 species of mammals, present the first record of Puma ya...

  8. Magmatic Flow Record From AMS Data La Gloria Pluton, Central Chile

    Gutierrez, F.; Payacan, I. J.; Calderon, S.

    2011-12-01

    La Gloria Pluton (LGP) is a 10 Ma epizonal intrusion in the Southern Andes, located 40 km east of Santiago, in central Chile. 20 km long and 5 km wide LPG has a thickness of 2.5 km, in the form of a NW elongating inverted canoe. LGP intrudes Miocene volcanics as NS extending cluster of Miocene granitoids. LGP was emplaced at the west of an inverse fault system without exhibiting significant post-intrusion deformation. The fault system includes the Laguna Negra Fault and the El Coironal Fault, at its southern and northern ends respectively. LGP has been interpreted to have had a short cooling time, where subsolidus reequilibration was not pervasive, allowing identification of early and late magmatic conditions and suggesting it to be a single closed chamber. LGP is zoned vertically from granodiorite/quartz monzodiorite to quartz monzonite towards the roof, where hornblende and biotite and minor magnetite-ilmenite are omnipresent. AMS samples were collected at 39 sites to determine of the magnetic anisotropy susceptibility tensor. Magnetic fabric is generally oblate and anisotropy values range from 1.3 to 13.9%, consistent with the prescience magnetite and ilmenite. Magnetic lineation (ML) has a NNW trend, a subhorizontal dip and values between 0.4 and 5.3%. Magnetic foliation (MF) has a NW trend and dip varying from vertical at the walls of the intrusive to subhorizontal inside and under the roof. MF values ranges between 0.8 and 13.3%. Since linear trend of MF is restricted to the LGP interior only and can not be caused by a simple inverse fault system, we interpret the AMS results as a consequence of magmatic flow. ML represents the main flow direction, where several shallow plutons intrude at 10Ma in NW direction. MF is consequence of convection, related to cooling and differentiation, and is comparable to numerical simulations of magma fluid-dynamics during differentiation (R4). Two profiles (EW and NS) indicate that MF linear trend is from 29°/km to 50

  9. Kinematics, Exhumation, and Sedimentation of the North Central Andes (Bolivia): An Integrated Thermochronometer and Thermokinematic Modeling Approach

    Rak, Adam J.; McQuarrie, Nadine; Ehlers, Todd A.

    2017-11-01

    Quantifying mountain building processes in convergent orogens requires determination of the timing and rate of deformation in the overriding plate. In the central Andes, large discrepancies in both timing and rate of deformation prevent evaluating the shortening history in light of internal or external forcing factors. Geologic map patterns, age and location of reset thermochronometer systems, and synorogenic sediment distribution are all a function of the geometry, kinematics, and rate of deformation in a fold-thrust-belt-foreland basin (FTB-FB) system. To determine the timing and rate of deformation in the northern Bolivian Andes, we link thermokinematic modeling to a sequentially forward modeled, balanced cross section isostatically accounting for thrust loads and erosion. Displacement vectors, in 10 km increments, are assigned variable ages to create velocity fields in a thermokinematic model for predicting thermochronometer ages. We match both the pattern of predicted cooling ages with the across strike pattern of measured zircon fission track, apatite fission track, and apatite (U-Th)/He cooling ages as well as the modeled age of FB formations to published sedimentary sections. Results indicate that northern Bolivian FTB deformation started at 50 Ma and may have begun as early as 55 Ma. Acceptable rates of shortening permit either a constant rate of shortening ( 4-5 mm/yr) or varying shortening rates with faster rates (7-10 mm/yr) at 45-50 Ma and 12-8 Ma, significantly slower rates (2-4 mm/yr) from 35 to 15 Ma and indicate the northern Bolivian Subandes started deforming between 19 and 14 Ma.

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

    Martín Chávez Hoffmeister

    Full Text Available 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.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.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.

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

    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

  12. Local Perception of Drought Impacts in a Changing Climate: The Mega-Drought in Central Chile

    Paulina Aldunce

    2017-11-01

    Full Text Available Droughts are a recurrent and complex natural hazard whose frequency and magnitude are expected to increase with climate change. Despite the advances in responding and adapting to droughts (with the development of new policies, for example, droughts continue to cause serious impacts and suffering. Developing well-targeted public policies requires further research on adaptation. Specifically, understanding the public perception of drought can help to identify drivers of and barriers to adaptation and options. This research seeks to understand the public perception of drought in central Chile in order to inform adaptation-related policies and decision-making processes. This study focused on the Mega-drought, which was a protracted dry spell afflicting central Chile since 2010.

  13. Nitrification and nitrogen mineralization in agricultural soils contaminated by copper mining activities in Central Chile

    Moya, Héctor; Verdejo, José; Yáñez, Carolina; Álvaro, Juan E.; Sauvé, Sébastien; Neaman, Alexander

    2017-01-01

    Microbiological bioassays of nitrification and nitrogen mineralization have been used for evaluation of soil quality on metal-contaminated soils. We evaluated the effectiveness of nitrification and nitrogen mineralization bioassays as quality indicators of soil degradation caused by metal contamination. We performed standard tests based on protocols of ISO 14238 (2012) and ISO 15685 (2012) on 90 soil samples collected from agricultural areas in central Chile that were historically contaminate...

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

    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.

  15. Topoclimatic modeling for minimum temperature prediction at a regional scale in the Central Valley of Chile

    Santibáñez, F.; Morales, L.; Fuente, J. de la; Cellier, P.; Huete, A.

    1997-01-01

    Spring frost may strongly affect fruit production in the Central Valley of Chile. Minimum temperatures are spatially variable owing to topography and soil conditions. A methodology for forecasting minimum temperature at a regional scale in the Central Valley of Chile, integrating spatial variability of temperature under radiative frost conditions, has been developed. It uses simultaneously a model for forecasting minimum temperatures at a reference station using air temperature and humidity measured at 6 pm, and topoclimatic models, based on satellite infra-red imagery (NOAA/AVHRR) and a digital elevation model, to extend the prediction at a regional scale. The methodological developments were integrated in a geographic information system for geo referencing of a meteorological station with satellite imagery and modeled output. This approach proved to be a useful tool for short range (12 h) minimum temperature prediction by generating thermal images over the Central Valley of Chile. It may also be used as a tool for frost risk assessment, in order to adapt production to local climatological conditions. (author)

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

    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 (propylitic alteration assemblage at greater depth (S2). Boiling, flashing and brecciation occurred later (S3), followed by a final phase of fluid mixing and boiling (S4). The evolution of hydrothermal alteration at Tolhuaca has produced a mineralogical, hydrological and structural vertical segmentation of the system through the development of a low-permeability, low-cohesion clay-rich cap at shallow depth. The quantitative chemical analyses of fluid inclusions and borehole fluids reveal a significant change in chemical conditions during the evolution of Tolhuaca. Whereas borehole (present-day) fluids are rich in Au, B and As, but Cu-poor (B/Na 100.5, As/Na 10- 1.1, Cu/Na 10- 4.2), the paleofluids trapped in fluid inclusions are Cu-rich but poor in B and As (B/Na 10- 1, As/Na 10- 2.5, Cu/Na 10- 2.5 in average). We interpret the fluctuations in fluid chemistry at Tolhuaca as the result of transient supply of metal-rich, magmatically derived fluids where As, Au and Cu are geochemically decoupled. Since these fluctuating physical and chemical conditions at the reservoir produced a mineralogical vertical segmentation of the system that affects the mechanical and hydrological properties of host rock, we explored

  17. Ordenar para controlar. Ordenamiento espacial y control político en las Llanuras del Caribe y en los Andes Centrales Neogranadinos. siglo XVIII

    Beatriz Patiño Millán

    2002-01-01

    Full Text Available Marta Herrera Ángel. Ordenar para Controlar. Ordenamiento espacial y control político en las Llanuras del Caribe y en los Andes Centrales Neogranadinos. Siglo XVIII. Bogotá: Instituto Colombiano de Antropología e Historia - Academia Colombiana de Historia, 2002, pp. 343. En este libro Marta Herrera estudia la estructuración del ordenamiento espacial y político durante el siglo XVIII de las llanuras del Caribe, nombre con el cual denomina el ámbito espacial correspondiente a las gobernaciones de Cartagena y Santa Marta,  y los Andes Centrales, apelativo que utiliza para referirse a los territorios de la provincia de Santafé y la jurisdicción de la ciudad de Tunja.

  18. (Plio-)Pleistocene alluvial-lacustrine basin infill evolution in a strike-slip active zone (Northern Andes, Western-Central Cordilleras, Colombia)

    SUTER, F.; NEUWERTH, R.; GORIN, G.; GUZMÁN, C.

    2009-01-01

    The (Plio)-Pleistocene Zarzal Formation was deposited in the Cauca Depression and Quindío-Risaralda Basin between the Western and Central Cordilleras (Northern Andes). This area is structurally located on the transcurrent Romeral Fault System (RFS). Because of the interaction between the Nazca plate and the Chocó-Panamá block (an active indenter), the RFS strike-slip component changes direction around the study zone (dextral in the south, senestral in the north). Zarzal sediments are the olde...

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

    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., food crops. Following a 2011 investigation of over 75 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

  20. Genetic structure of Quechua-speakers of the Central Andes and geographic patterns of gene frequencies in South Amerindian populations.

    Luiselli, D; Simoni, L; Tarazona-Santos, E; Pastor, S; Pettener, D

    2000-09-01

    A sample of 141 Quechua-speaking individuals of the population of Tayacaja, in the Peruvian Central Andes, was typed for the following 16 genetic systems: ABO, Rh, MNSs, P, Duffy, AcP1, EsD, GLOI, PGM1, AK, 6-PGD, Hp, Gc, Pi, C3, and Bf. The genetic structure of the population was analyzed in relation to the allele frequencies available for other South Amerindian populations, using a combination of multivariate and multivariable techniques. Spatial autocorrelation analysis was performed independently for 13 alleles to identify patterns of gene flow in South America as a whole and in more specific geographic regions. We found a longitudinal cline for the AcP1*a and EsD*1 alleles which we interpreted as the result of an ancient longitudinal expansion of a putative ancestral population of modern Amerindians. Monmonnier's algorithm, used to identify areas of sharp genetic discontinuity, suggested a clear east-west differentiation of native South American populations, which was confirmed by analysis of the distribution of genetic distances. We suggest that this pattern of genetic structures is the consequence of the independent peopling of western and eastern South America or to low levels of gene flow between these regions, related to different environmental and demographic histories. Copyright 2000 Wiley-Liss, Inc.

  1. High-Resolution ∂18O record of middle-late Holocene hydrologic variability from the central Peruvian Andes (Invited)

    Rodbell, D. T.; Abbott, M.; Bird, B. W.; Stansell, N.

    2009-12-01

    Laguna Yuraicocha in the western cordillera of the central Peruvian Andes (12.53°S; 75.50°W; 4460 masl) is dammed by late glacial moraines and is underlain and surrounded by Jurassic and Cretaceous limestone interbedded with siliciclastic rocks. A 6.9 meter-long sediment core from the distal end of the lake is dominated by authigenic calcite (marl) with a mean concentration of 82 weight percent that has accumulated at a rate of ~ 1 mm yr-1 for the past 6200 years. The age model for the core is based on a combination of 210Pb and AMS 14C ages from charcoal; modern lake water is ~1‰ evaporatively enriched from mean regional precipitation. Marl samples were taken with an average sampling interval of 8 years; samples were treated to remove organic matter, sieved to concentrate the clay fraction was removed by repeated pipette withdrawal. The Peru and Bolivia, are especially sensitive to changes in regional moisture balance.

  2. Redescripción y consideraciones biogeográfcas de dos especies de Scotobius (Coleoptera: Tenebrionidae de ambientes montanos del centro de Argentina y Chile Redescription and biogeographic considerations of two species of Scotobius (Coleoptera: Tenebrionidae from mountain environments of central Argentina and Chile

    Violeta A. Silvestro

    2012-12-01

    Full Text Available El género neotropical Scotobius Germar (Tenebrioninae: Scotobiini comprende 61 especies distribuidas desde el centro de Perú y sur de Brasil hasta el sur de Argentina y Chile. En este trabajo, revisamos dos especies de Scotobius que habitan el oeste de las provincias de San Juan, Mendoza y Neuquén (Argentina y en Chile central, a lo largo de la Cordillera de los Andes y las montañas extra-andinas en Argentina: S. punctatus Eschscholtz, 1831 y S. andrassyi Kaszab, 1969. Se proveen redescripciones utilizando nuevos caracteres morfológicos y se proporcionan fotografías de los adultos y de los pronotos. Se consigna la distribución geográfica, rangos altitudinales y las provincias biogeográficas en las que habitan estas especies. Se utiliza un modelo predictivo de distribución de especies para proponer hipótesis sobre los factores que influencian la distribución espacial y que explicarían la alopatría de ambas especies.The Neotropical genus Scotobius Germar (Tenebrioninae: Scotobiini comprises 61 species distributed from central Peru and southern Brazil to southern Argentine and Chile. In this contribution two species of Scotobius: S. punctatus Eschscholtz, 1831 and S. andrassyi Kaszab, 1969, that inhabit in western San Juan, Mendoza, and Neuquén provinces (Argentina and in central Chile, along the “Cordillera de los Andes” and extra-Andean mountains in Argentina, are revised. Redescriptions using new morphological data and photographs of habitus and pronota are provided. This article informs about the geographic distribution, altitudinal ranges and the biogeographic provinces that these species inhabit. A predictive model of species distribution is presented to propose hypothesis about the factors that influence the space distribution and the allopatry of these two species.

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

    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

  4. ASTER Andes

    2000-01-01

    In this image of the Andes along the Chile-Bolivia border, the visible and infrared data have been computer enhanced to exaggerate the color differences of the different materials. The scene is dominated by the Pampa Luxsar lava complex, occupying the upper right two-thirds of the scene. Lava flows are distributed around remnants of large dissected cones, the largest of which is Cerro Luxsar. On the middle left edge of the image are the Olca and Parumastrato volcanoes, which appear in blue due to a lack of vegetation (colored red in this composite). This image covers an area 60 kilometers (37 miles) wide and 60 kilometers (37 miles) long in three bands of the reflected visible and infrared wavelength region. It was acquired on April 7, 2000.The image is located at 21 degrees south latitude, 68.3 degrees west longitude. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples of applications include monitoring glacial advances and retreats

  5. Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

    Dure, Tina; Cisternas, Marco; Horton, Benjamin; Ely, Lisa; Nelson, Alan R.; Wesson, Robert L.; Pilarczyk, Jessica

    2015-01-01

    The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has produced.

  6. Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

    Dure, Tina; Cisternas, Marco; Horton, Benjamin; Ely, Lisa; Nelson, Alan R.; Wesson, Robert L.; Pilarczyk, Jessica

    2015-01-01

    The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has produced.

  7. Facies volcánicas del depósito de avalancha de detritos del volcán Tata Sabaya, Andes Centrales Volcanic facies of the debris avalanche deposit of Tata Sabaya Volcano, Central Andes

    Benigno Godoy

    2012-09-01

    Full Text Available Las avalanchas de detritos, asociadas a colapsos parciales de edificios volcánicos, son fenómenos comunes en la evolución de un volcán. Este tipo de flujos son por inestabilidades, que pueden deberse a factores tales como la existencia de zonas afectadas por alteración hidrotermal, cambios climáticos, terremotos, intrusión de magmas en zonas superficiales (criptodomos y/o diques y/o movimiento de fallas bajo el edificio volcánico o cercanas a él. El producto final de estos flujos -denominado depósito de avalancha de detritos (DAD- presenta morfologías típicas de cerrillos y drenajes cerrados. En los Andes Centrales se han reconocido, al menos, 14 centros volcánicos con depósitos de avalancha asociados, entre los que está el volcán Tata Sabaya (Bolivia. El colapso que ha dado origen a este depósito podría haberse generado por una combinación de actividad sísmica y magmática en el volcán. El depósito asociado al colapso parcial de este volcán se distribuye sobre la parte baja del flanco sur del volcán y sobre la parte noroccidental de la cuenca del salar de Coipasa. Cubre una superficie de más de 230 km² y tiene un volumen estimado de 6±1 km³. Sobre la base de las composiciones litológicas, se ha establecido que el depósito está constituido por 6 tipos distintos de cerrillos, los cuales son: lávicos, piroclásticos, sedimentarios mixtos, brecha piroclástica y andesítico-basálticos. Considerando el tipo predominante de cerrillos y su distribución espacial dentro del depósito, se ha definido 6 facies diferentes (Facies de Bloques Toreva, Facies de Cerrillos Volcánicos, Facies Central, Facies de Cerrillos Sedimentarios, Facies Mixta y Facies de Cerrillos de Brecha Piroclástica. Tomando en cuenta la distribución espacial de estas facies, se propone la estructura del paleovolcán previa a su colapso parcial.Debris avalanches associated with partial sector collapse of volcanic edifices are common phenomena in the

  8. llustrated review of the leaf-mining Nepticulidae of the central Andes (Peru and Bolivia)

    Stonis, Jonas R.; Diškus, Arunas; Remeikis, Andrius

    2017-01-01

    We review forty-five species of Nepticulidae (Lepidoptera) based on an analysis of samples collected in the central Andean region of Peru and Bolivia. Thirteen of these species are new to science, and are named and described here: Stigmella paracosma Remeikis & Stonis, sp. nov., S. expressa...

  9. Environmental evidence of fossil fuel pollution in Laguna Chica de San Pedro lake sediments (Central Chile)

    Chirinos, L. [Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepcion, PO Box 160-C, Concepcion (Chile)]. E-mail: lchirin@pucp.edu.pe; Rose, N.L. [Environmental Change Research Centre, University College London, 26 Bedford Way, London WG1HOAP (United Kingdom); Urrutia, R. [Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepcion, PO Box 160-C, Concepcion (Chile); Munoz, P. [Departamento de Biologia Marina, Universidad Catolica del Norte, Larrondo 1281, Coquimbo (Chile); Torrejon, F. [Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepcion, PO Box 160-C, Concepcion (Chile); Torres, L. [Departamento de Botanica, Universidad de Concepcion, Concepcion (Chile); Cruces, F. [Departamento de Botanica, Universidad de Concepcion, Concepcion (Chile); Araneda, A. [Centro de Ciencias Ambientales EULA-Chile, Universidad de Concepcion, PO Box 160-C, Concepcion (Chile); Zaror, C. [Facultad de Ingenieria Quimica, Universidad de Concepcion, Concepcion (Chile)

    2006-05-15

    This paper describes lake sediment spheroidal carbonaceous particle (SCP) profiles from Laguna Chica San Pedro, located in the Biobio Region, Chile (36{sup o} 51' S, 73{sup o} 05' W). The earliest presence of SCPs was found at 16 cm depth, corresponding to the 1915-1937 period, at the very onset of industrial activities in the study area. No SCPs were found at lower depths. SCP concentrations in Laguna Chica San Pedro lake sediments were directly related to local industrial activities. Moreover, no SCPs were found in Galletue lake (38{sup o} 41' S, 71{sup o} 17.5' W), a pristine high mountain water body used here as a reference site, suggesting that contribution from long distance atmospheric transport could be neglected, unlike published data from remote Northern Hemisphere lakes. These results are the first SCP sediment profiles from Chile, showing a direct relationship with fossil fuel consumption in the region. Cores were dated using the {sup 21}Pb technique. - The lake sediment record of SCPs shows the record of fossil-fuel derived pollution in Central Chile.

  10. Environmental evidence of fossil fuel pollution in Laguna Chica de San Pedro lake sediments (Central Chile)

    Chirinos, L.; Rose, N.L.; Urrutia, R.; Munoz, P.; Torrejon, F.; Torres, L.; Cruces, F.; Araneda, A.; Zaror, C.

    2006-01-01

    This paper describes lake sediment spheroidal carbonaceous particle (SCP) profiles from Laguna Chica San Pedro, located in the Biobio Region, Chile (36 o 51' S, 73 o 05' W). The earliest presence of SCPs was found at 16 cm depth, corresponding to the 1915-1937 period, at the very onset of industrial activities in the study area. No SCPs were found at lower depths. SCP concentrations in Laguna Chica San Pedro lake sediments were directly related to local industrial activities. Moreover, no SCPs were found in Galletue lake (38 o 41' S, 71 o 17.5' W), a pristine high mountain water body used here as a reference site, suggesting that contribution from long distance atmospheric transport could be neglected, unlike published data from remote Northern Hemisphere lakes. These results are the first SCP sediment profiles from Chile, showing a direct relationship with fossil fuel consumption in the region. Cores were dated using the 21 Pb technique. - The lake sediment record of SCPs shows the record of fossil-fuel derived pollution in Central Chile

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

    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

  12. The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Litvak, Vanesa D.; Poma, Stella; Alonso, Ricardo N.; Hinton, Richard; EIMF

    2016-10-01

    The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29-31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U-Pb dating of magmatic zircon, combined with Ar-Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous ( 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene ( 26 Ma) to Early Miocene ( 17 Ma), and Late Miocene ( 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian-Triassic (P

  13. A NEW SPECIES OF CHLEROGAS FROM THE ANDES OF CENTRAL COLOMBIA (HYMENOPTERA: HALICTIDAE

    Engel M

    2009-12-01

    Full Text Available ABSTRACTA new species of the long-headed bee genus Chlerogas Vachal (Halictinae:Augochlorini is described and fi gured from a male captured at high elevation in centralColombia. Chlerogas tatamaensis Engel & Gonzalez, new species, is distinguishedfrom its congeners on the basis of integumental coloration and sculpturing as wellas features of the male terminalia. A revised key to the species of Chlerogas isprovided.

  14. DINÁMICA NUTRICIONAL EN CINCO PARRONES DE DIFERENTE PRODUCTIVIDAD DEL VALLE CENTRAL REGADO DE CHILE

    Ruiz S., Rafael

    2000-01-01

    Se efectuó un estudio comparativo de aspectos nutricionales del suelo y de la planta en 5 parronales de uva de mesa cv. Thompson Seedless con un historial muy diferente de productividad y vigor, en el valle central de Chile, durante 4 años. Durante este período se efectuaron análisis nutricionales mensuales, que incluyeron además de N, P y K total, fracciones de N de reserva como arginina y aminoácidos totales y carbohidratos de reserva en la parte aérea (sarmientos y brotes) y en raíces. El ...

  15. The Effect of Central Bank Policy Decisions on Stock Market Returns in Chile

    Andrés A. Acuña

    2015-06-01

    Full Text Available This paper analyzes the stock-market response to monetary policy decisions made by the Central Bank of Chile.  We use a methodology designed for the study of low frequency events and monthly data from September 2001 to December 2013 to estimate the effect of anticipated and unanticipated changes in the Chilean monetary policy interest rate on stock returns.  In contrast to the research findings in the literature for the U.S., we find no evidence that monetary surprises affect Chilean stock returns.

  16. Terrestrial vertebrates of the Río Clarillo National Reserve, central Chile: representation and conservation

    DÍAZ, IVÁN A.; SARMIENTO, CARLOS; ULLOA, LUIS; MOREIRA, ROGELIO; NAVIA, RAFAEL; VÉLIZ, EDUARDO; PEÑA, CARLOS

    2002-01-01

    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 ...

  17. Attenuation tomography in the western central Andes: A detailed insight into the structure of a magmatic arc

    Haberland, Christian; Rietbrock, Andreas

    2001-06-01

    High-quality data from 1498 local earthquakes recorded by the PISCO '94 (Proyecto de Investigatión Sismológica de la Cordillera Occidental, 1994) and ANCORP '96 (Andean Continental Research Project, 1996) temporary seismological networks allowed the detailed determination of the three-dimensional (3-D) attenuation structure (Qp-1) beneath the recent magmatic arc in the western central Andes (20° to 24°S). Assuming a frequency-independent Qp-1 in a frequency band between 1 and 30 Hz, whole path attenuation (t*) was estimated from the amplitude spectra of the P waves using spectral ratios and a spectral inversion technique. The damped least squares inversion (tomography) of the data reveals a complex attenuation structure. Crust and mantle of the forearc and subducting slab are generally characterized by low attenuation (Qp > 1000). Crust and mantle beneath the magmatic arc show elevated attenuation. The strongest anomaly of extremely low Qp is found in the crust between 22° and 23°S beneath the recent volcanic arc (Qp < 100). N-S variations can be observed: The western flank of the crustal attenuation anomaly follows the curved course of the volcanic front. North of 21°S the attenuation is less developed. In the northern part of the study area the low-Qp zone penetrates in the forearc mantle down to the subducting slab. In the south a deeper zone of high attenuation is resolved between 23° and 24°S directly above the subducting slab. Low Qp in the mantle correlates with earthquake clusters. The strong crustal attenuation is confined to the distribution of young ignimbrites and silicic volcanism and is interpreted as a thermally weakened zone with partial melts. The attenuation pattern in the upper mantle might reflect the variable extent of the asthenosphere and maps variations of subduction-related hydration processes in the mantle wedge from slab-derived fluids.

  18. Unraveling the diversification history of grasshoppers belonging to the “Trimerotropis pallidipennis” (Oedipodinae: Acrididae species group: a hotspot of biodiversity in the Central Andes

    Noelia Verónica Guzmán

    2017-09-01

    Full Text Available The Andean Mountain range has been recognized as one of the biodiversity hotspots of the world. The proposed mechanisms for such species diversification, among others, are due to the elevation processes occurring during the Miocene and the intensive glacial action during the Pleistocene. In this study we investigated the diversification history of the grasshopper Trimerotropis pallidipennis species complex which shows a particularly wide latitudinal and altitudinal distribution range across the northern, central and southern Andes in South America. Many genetic lineages of this complex have been so far discovered, making it an excellent model to investigate the role of the central Andes Mountains together with climatic fluctuations as drivers of speciation. Phylogenetics, biogeographic and molecular clock analyses using a multi-locus dataset revealed that in Peru there are at least two, and possibly four genetic lineages. Two different stocks originated from a common ancestor from North/Central America—would have dispersed toward southern latitudes favored by the closure of the Panama Isthmus giving rise to two lineages, the coastal and mountain lineages, which still coexist in Peru (i.e., T. pallidipennis and T. andeana. Subsequent vicariant and dispersal events continued the differentiation process, giving rise to three to six genetic lineages (i.e., clades detected in this study, which were geographically restricted to locations dispersed over the central Andes Mountains in South America. Our results provide another interesting example of “island diversification” motored by the topography plus unstable climatic conditions during the Pleistocene, pointing out the presence of a hotspot of diversification in the Andean region of Peru.

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

    Garcia Nestor; Galeano Gloria

    2009-01-01

    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.

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

    Falabella, Fernanda; Planella, M.Teresa; Aspillaga, Eugenio; Sanhueza, Lorena; Tykot, Robert H

    2007-01-01

    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 [es

  1. Diet, dietary selectivity and density of South American grey fox, Lycalopex griseus, in Central Chile.

    Muñoz-Pedreros, Andrés; Yáñez, José; Norambuena, Heraldo V; Zúñiga, Alfredo

    2018-01-01

    The South American grey fox Lycalopex griseus is a canid widely distributed in southern South America; however, some aspects of its biology are still poorly known. We studied the diet and density of L. griseus in the Lago Peñuelas Biosphere Reserve, in Central Chile. The trophic niche breadth was B = 6.16 (B sta = 0.47) and prey diversity was H' = 2.46 (H max ' = 3.17, J' = 0.78). The highest proportions of prey consumed in the diet were Oryctolagus cuniculus (52.21%) and other mammals (32.78%). We compared these results with a latitudinal gradient of diet results for this species in Chile. L. griseus eats mostly mammals (>90% of total prey), consuming the rodent Phyllotis darwini and reptiles in the northern zone; Oryctolagus cuniculus, Octodon degus and Abrocoma bennetti in the central zone; Abrothrix spp. and lagomorphs in the southern zone; and Lepus capensis and Ovis aries in the austral zone. The estimated density of L. griseus in Lago Peñuelas NR was 1.3 foxes/km 2 . © 2017 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  2. A 600-year-long stratigraphic record of tsunamis in south-central Chile

    Hong, Isabel; Dura, Tina; Ely, Lisa L.; Horton, Benajamin P.; Nelson, Alan R.; Cisternas, Marco; Nikitina, Daria; Wesson, Robert L.

    2017-01-01

    The stratigraphy within coastal river valleys in south-central Chile clarifies and extends the region’s history of large, earthquakes and accompanying tsunamis. Our site at Quidico (38.1°S, 73.3°W) is located in an overlap zone between ruptures of magnitude 8–9 earthquakes in 1960 and 2010, and, therefore, records tsunamis originating from subduction-zone ruptures north and south of the city of Concepción. Hand-dug pits and cores in a 3-m-thick sequence of freshwater peat in an abandoned meander (a little-examined depositional environment for tsunami deposits) and exposures along the Quidico River show five sand beds that extend as much as 1.2 km inland. Evidence for deposition of the beds by tsunamis includes tabular sand beds that are laterally extensive (>100 m), well sorted, fine upward, have sharp lower contacts, and contain diatom assemblages dominated by brackish and marine taxa. Using eyewitness accounts of tsunami inundation, 137Cs analyses, and 14C dating, we matched the upper four sand beds with historical tsunamis in 2010, 1960, 1835, and 1751. The oldest prehistoric bed dates to 1445–1490 CE and correlates with lacustrine and coastal records of similar-aged earthquakes and tsunamis in south-central Chile.

  3. Viability of Green Roofs as a Flood Mitigation Element in the Central Region of Chile

    Daniel Mora-Melià

    2018-04-01

    Full Text Available Population increase and urban development over the last 20 years in Chile have outgrown most rainwater drainage and evacuation systems. Many cities located in the central region suffer from frequent floods in some of their sectors during winter rainfall events. In addition, the lack of green spaces in these cities leads to biodiversity loss, increasing temperatures, greater energy demands, etc. Green roofs offer a solution that can mitigate climate change by reducing the runoff in cities with extensive, highly impermeable areas. This work analyses the installation of green roofs as a potential solution to the sectorial floods suffered by many cities in central Chile. The methodology includes the identification of conflictive sectors in the city of Curicó, hydrological modelling with the Storm Water Management Model (SWMM software, the consideration of different distributions and types of green roof surfaces, and computational simulations to determine the feasibility of green roofs for preventing floods. The results show that, for moderate rainfall events, all studied sectors could avoid flooding if at least 50% of the surrounding area had green roofs (irrespective of the type of green roof. In contrast, in the presence of strong rainfall events, only some semi-extensive and extensive green roofs covering 60% to 95% of the surrounding area, respectively, could prevent flooding.

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

    Schueftan, Alejandra; González, Alejandro D.

    2013-01-01

    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 m 3 /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%

  5. Field Survey of the 2015 Ilapel Tsunami in North Central Chile

    Lagos, M.; Fritz, H. M.

    2016-12-01

    The magnitude Mw 8.3 earthquake in north-central Chile on September 16, 2015 generated a tsunami that rapidly flooded coastal areas. The tsunami impact was concentrated in Coquimbo region, while the regions of Valparaiso and Atacama were also affected. Fortunately, ancestral knowledge from the past tsunamis in the region, as well as tsunami education and evacuation exercises prompted most coastal residents to spontaneously evacuate to high ground after the earthquake. The event caused 11 fatalities: 8 were associated with the tsunami, while 3 were attributed to building collapses caused by the earthquake. The international scientist joined the local effort from September 20 to 26, 2015. The international tsunami survey team (ITST) interviewed numerous eyewitnesses and documented flow depths, runup heights, inundation distances, sediment deposition, damage patterns, performance of the navigation infrastructure and impact on the natural environment. The ITST covered a 500 km stretch of coastline from Caleta Chañaral de Aceituno (28.8° S) south of Huasco down to Llolleo near San Antonio (33.6° S). We surveyed more than 40 locations and recorded more than 100 tsunami and runup heights with differential GPS and integrated laser range finders. The tsunami impact peaked at Caleta Totoral near Punta Aldea with both tsunami and runup heights exceeding 10 m as surveyed on September 22. Runup exceeded 10 m at a second uninhabited location some 15 km south of Caleta Totoral. A significant variation in tsunami impact was observed along the coastlines of central Chile at local and regional scales. The tsunami occurred in the evening hours limiting the availability of eyewitness video footages. Observations from the 2015 Chile tsunami are compared with recent Chilean tsunamis. The tsunami was characterized by rapid arrival within minutes in the nearfield requiring spontaneous self-evacuation as warning messages did not reach some of the hardest hit fishing villages prior to

  6. Along and Across Arc Variation of the Central Andes by Single Crystal Trace Element Analaysis

    Michelfelder, G.; Sundell, T.; Wilder, A.; Salings, E. E.

    2017-12-01

    Along arc and across arc geochemical variations at continental volcanic arcs are influenced by a number of factors including the composition and thickness of the continental crust, mantle heterogeneity, and fluids from the subducted slab. Whole rock geochemical trends along and across the arc front of the Central Volcanic Zone (CVZ) have been suggested to be primarily influenced by the composition and thickness of the crust. In the CVZ, Pb isotopic domains relate volcanic rock compositions to the crustal basement and systematically varies with crustal age. It has been shown repeatedly that incompatible trace element trends and trace element ratios can be used to infer systematic geochemical changes. However, there is no rule linking magmatic process or chemical heterogeneity/ homogeneity as a result of large crustal magma storage reservoirs such as MASH zones to the observed variation. Here we present a combination of whole rock major- and trace element data, isotopic data and in situ single crystal data from plagioclase, pyroxene and olivine for six stratovolcanoes along the arc front and in the back arc of the CVZ. We compare geochemical trends at the whole and single crystal scale. These volcanoes include lava flows and domes from Cerro Uturuncu in the back-arc, Aucanquilcha, Ollagüe, San Pedro-San Pablo, Lascar, and Lazufre from the arc front. On an arc-wide scale, whole rock samples of silicic lavas from these six composite volcanoes display systematically higher K2O, LILE, REE and HFSE contents and 87Sr/86Sr ratios with increasing distance from the arc-front. In contrast, the lavas have systematically lower Na2O, Sr, and Ba contents; LILE/HFSE ratios; 143Nd/144Nd ratios; and more negative Eu anomalies. Silicic magmas along the arc-front reflecting melting of young, mafic composition source rocks with the continental crust becoming increasingly older and more felsic toward the east. These trends are paralleled in the trace element compositions of plagioclase

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

    Planchuelo, Ana M.; Fuentes, Esteban P.

    2005-01-01

    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 encontrado...

  8. Glaciation in the Andes during the Lateglacial and Holocene

    Rodbell, Donald T.; Smith, Jacqueline A.; Mark, Bryan G.

    2009-10-01

    This review updates the chronology of Andean glaciation during the Lateglacial and the Holocene from the numerous articles and reviews published over the past three decades. The Andes, which include some of the world's wettest and driest mountainous regions, offer an unparalleled opportunity to elucidate spatial and temporal patterns of glaciation along a continuous 68-degree meridional transect. The geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad-scale atmospheric circulation and consequent regional moisture patterns. Glaciers in the tropical Andes and in the mid-latitude Andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical Andes. Broad-scale temporal and spatial patterns of glaciation during the Lateglacial are apparent. In the southernmost Andes, the Lateglacial chronology appears to have a strong Antarctic signature with the best-dated moraines correlating closely with the Antarctic Cold Reversal. The southernmost Andes do not appear to have experienced a significant ice advance coeval with the Younger Dryas (YD) climatic reversal. At the other end of the Andes, from ˜0 to 9°N, a stronger YD connection may exist, but critical stratigraphic and geochronologic work is required before a YD ice advance can be fully demonstrated. In the central Andes of Peru, well-dated moraines record a significant ice readvance at the onset of the YD, but ice was retreating during much of the remaining YD interval. The spatial-temporal pattern of Holocene glaciation exhibits tantalizing but incomplete evidence for an Early to Mid-Holocene ice advance(s) in many regions, but not in the arid subtropical Andes, where moraines deposited during or slightly prior to the Little Ice Age (LIA) record the most extensive advance of the Holocene. In many regions, there is strong evidence for Neoglacial

  9. 100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina

    Tofelde, Stefanie; Schildgen, Taylor F.; Savi, Sara; Pingel, Heiko; Wickert, Andrew D.; Bookhagen, Bodo; Wittmann, Hella; Alonso, Ricardo N.; Cottle, John; Strecker, Manfred R.

    2017-09-01

    Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic 10Be depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 ± 7 and 487 ± 34 ka. Depositional ages of the conglomerates, determined by four 26Al/10Be burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 ± 141 to 936 ± 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at ∼1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two

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

    Rutlant, J.; Aceituno, P.

    1991-05-01

    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. El Niño effects on soil seed bank dynamics in north-central Chile.

    Gutiérrez, Julio R; Meserve, Peter L

    2003-03-01

    The soil seed bank was monitored in four 75x75 m plots over 6 years (1990-1995) in an arid thorn scrub community in north-central Chile. Sixty-six species were identified. Total seed densities ranged from 2,000 to 42,000/m(2). Average mass of shrub seeds was significantly greater than that of other growth-forms. Between 70 and 90% of the seeds were less than 1 mg, with those in the 0.51-1.00 mg size class being most numerous. Seed densities were highly variable between years as well as within years, but were also closely associated with plant cover patterns and rainfall regime. Higher seed densities were found in wet years, and in samples taken in early summer and early autumn (i.e., after seed set); the lowest seed densities were in late winter (i.e., after annual plant germination). The annual plant species with the highest cover were also the most abundant in the soil seed bank and exhibited the largest seed density fluctuations. In general, seed densities were 5- to 10-fold higher during the 1991-1992 El Niño/southern oscillation (ENSO) years than non-ENSO years, showing the importance of this phenomenon for seed bank replenishment in the arid region of Chile.

  12. Add-on conservation benefits of marine territorial user rights fishery policies in central Chile.

    Gelcich, Stefan; Godoy, Natalio; Prado, Luis; Castilla, Juan Carlos

    2008-01-01

    To combine the rational use of marine benthic resources and economic development of small-scale fishers, Chile passed legislation in 1991 establishing a comanagement policy that grants exclusive territorial user rights for fisheries (TURFs) to artisanal fisher organizations in well-defined inshore coastal areas, known as Management and Exploitation Areas for Benthic Resources (MEABRs). In general the policy has been proclaimed a management and economic success because benthic resource abundances have increased inside MEABRs in comparison with open-access areas. However, there is a lack of studies assessing the impact of this management policy on nontargeted subtidal species and community assemblages and the policy's implications for biodiversity and conservation. This study starts to fill this gap and links the allocation of TURFs for benthic resources with add-on conservation benefits for species that are not directly linked with the fishery policy. Comparative subtidal surveys inside vs. outside MEABRs were used to assess the effects of three MEABRs on managed targeted benthic species, biodiversity (species richness), and community assemblages in central Chile. Surveys focused exclusively on subtidal kelp forest habitats dominated by Lessonia trabeculata, spanning 4-12 m in depth and with similar levels of habitat complexity. The study comprised: (1) quantification of kelp forest complexity, (2) understory survey of sessile species, (3) quantification of conspicuous benthic macroinvertebrates, including those under management, and (4) quantification of reef-fish species inside the kelp habitat. Results showed population enhancement of target-managed invertebrates inside MEABRs. Moreover, reef-fish species were significantly more diverse and abundant inside MEABRs, and community assemblages of nontarget benthic invertebrates and reef fish were significantly different inside vs. outside MEABRs. The comanagement of inshore benthic resources in Chile, through MEABRs

  13. Influencia del fenómeno ENSO sobre la precipitación nival en el sector andino de Chile central durante el invierno

    1998-01-01

    Full Text Available INFLUENCE DU PHÉNOMÈNE ENSO SUR LES PRÉCIPITATIONS NEIGEUSES DANS LE CENTRE DU CHILI ANDIN AU COURS DE L’HIVER AUSTRAL. On analyse l’influence du phénomène El Niño/Oscillation du Sud (ENSO sur les précipitations nivales dans les Andes du Chili central au cours de l’hiver. Pour cela, on a utilisé l’information obtenue sur des sites spécifiques (routes de neige situées entre 30° et 38° S et les anomalies de Température de Surface de la Mer (TSM du bloc Niño 3, comme indicateur de l’importance des événements chauds ou froids dans le Pacifique équatorial central. Au nord de 35°S, l’accumulation de neige tend à être supérieure à la normale quand l’anomalie moyenne de TSM dépasse +1°C au cours de la période mai-août. Dans ce même secteur, on enregistre une précipitation inférieure à la normale les hivers caractérisés par une anomalie de TSM inférieure à -0,5°C. Dans la zone située au sud de 35° S, l’influence du phénomène ENSO sur l’accumulation de neige n’est plus significative. Se analiza la influencia del fenómeno El Niño/Oscilación del Sur (ENSO sobre la precipitación nival en los Andes de Chile central durante el invierno. Para esto, se utiliza información de rutas de nieve localizadas entre 30° y 38° S, y de anomalías de temperatura superficial del mar (TSM en la región Niño 3 como un indicador de la magnitud de los eventos cálidos y fríos en el Pacífico ecuatorial central. En la región al norte de 35° S, la acumulación de nieve durante el invierno tiende a ser superior a lo normal cuando la magnitud de la anomalía media de TSM en el periodo mayo-agosto supera +1,0° C. En este mismo sector se verifica que durante los inviernos caracterizados por una anomalía de TSM inferior a -0,5° C, suele registrarse una precipitación nival inferior a lo normal. En el sector al sur de los 35° S, la influencia del fenómeno ENSO sobre la acumulación de nieve durante el invierno no es

  14. Nueva localidad para Alsodes tumultuosus Veloso, Iturra & Galleguillos, 1979 (Amphibia, Alsodidae en la Cordillera de los Andes, Region de O’Higgins, Chile

    Diego Ramírez Álvarez

    2015-06-01

    Full Text Available Alsodes tumultuosus Veloso, Iturra & Galleguillos, 1979 es un anfibio endémico de Chile, descrito y hasta hace poco conocido únicamente en su localidad tipo, los arroyos cordilleranos del Sector La Parva, en la región Metropolitana. En este artículo se detalla el hallazgo de una nueva localidad para esta especie, en la región de O’Higgins, aproximadamente a 100 kilómetros al sur de La Parva. Este hallazgo, sugiere la ampliación del rango de distribución de esta especie al cordón cordillerano Andino de la región de O’Higgins, y señala la necesidad de efectuar mayores prospecciones e investigación de la especie, que permitan definir claramente su estado de conservación en Chile.

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

    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

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

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

    1997-12-31

    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. A 60,000-year record of hydrologic variability in the Central Andes from the hydrogen isotopic composition of leaf waxes in Lake Titicaca sediments

    Fornace, Kyrstin L.; Hughen, Konrad A.; Shanahan, Timothy M.; Fritz, Sherilyn C.; Baker, Paul A.; Sylva, Sean P.

    2014-12-01

    A record of the hydrogen isotopic composition of terrestrial leaf waxes (δDwax) in sediment cores from Lake Titicaca provides new insight into the precipitation history of the Central Andes and controls of South American Summer Monsoon (SASM) variability since the last glacial period. Comparison of the δDwax record with a 19-kyr δD record from the nearby Illimani ice core supports the interpretation that precipitation δD is the primary control on δDwax with a lesser but significant role for local evapotranspiration and other secondary influences on δDwax. The Titicaca δDwax record confirms overall wetter conditions in the Central Andes during the last glacial period relative to a drier Holocene. During the last deglaciation, abrupt δDwax shifts correspond to millennial-scale events observed in the high-latitude North Atlantic, with dry conditions corresponding to the Bølling-Allerød and early Holocene periods and wetter conditions during late glacial and Younger Dryas intervals. We observe a trend of increasing monsoonal precipitation from the early to the late Holocene, consistent with summer insolation forcing of the SASM, but similar hydrologic variability on precessional timescales is not apparent during the last glacial period. Overall, this study demonstrates the relative importance of high-latitude versus tropical forcing as a dominant control on glacial SASM precipitation variability.

  18. New evidences on the presence of Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, in the Late Pleistocene of Central Chile

    Labarca, R.; Alberdi, M.T.; Prado, J.L.; Mansilla, P.; Mourgues, F.A.

    2016-07-01

    This paper contextualizes, describes and taxonomically assigned cranial and dental Gomphotheriidae materials from the El Trebal 1, late Pleistocene form central Chile. Starting from metric and morphological variables fossils are included in Stegomastodon platensis. Taxonomic implications of this finding as well as some regional paleoenvironmental history are discussed. (Author)

  19. Behaviour of Southern sea lions in presence of killer whales during fishing operations in Central Chile

    Luis Hückstädt

    2004-06-01

    Full Text Available The killer whale is an opportunistic top-predator of ecosystems worldwide and its diet varies locally and seasonally, which is reflected in diverse feeding behaviours associated with its prey. We report the occurrence of killer whales presumably predating on southern sea lions associated with the jack mackerel fishing fleet in central Chile. The presence of killer whales was recorded during 4 fishing sets. All sightings consisted of 3-5 individual pods of females and calves. The number of sea lions was not significantly affected by the presence of killer whales, but their behaviour was, by reducing the number of behavioural displays, as they stopped feeding and resting activities and stayed close to the hull of the vessel after net retrieval ended. We propose that killer whales could be using the fishery as an indirect source of prey to benefit from the aggregation of sea lions around the vessel, far away from land.

  20. Seismicity preliminary results in a geothermal and volcano activity area: study case Liquiñe-Ofqui fault system in Southern Andes, Chile

    Estay, N. P.; Yáñez Morroni, G.; Crempien, J. G. F.; Roquer, T.

    2017-12-01

    Fluid transport through the crust takes place in domains with high permeability. For this reason, fault damage zones are a main feature where fluids may circulate unimpeded, since they have much larger permeability than normal country rocks. With the location of earthquakes, it is possible to infer fault geometry and stress field of the crust, therefore we can determine potential places where fluid circualtion is taking place. With that purpose, we installed a seismic network in an active volcanic-geothermal system, the Liquiñe-Ofqui Fault System (LOFS), located in Puyuhuapi, Southern Andes (44°-45°S). This allowed to link epicentral seismicity, focal mechanisms and surface expression of fluid circulation (hot-springs and volcanos). The LOFS is composed by two NS-striking dextral master faults, and several secondary NE-striking dextral and normal faults. Surface manifestation of fluid circulation in Puyuhuapi area are: 1) six hot-springs, most of them spatially associated with different mapped faults; 2) seven minor eruptive centers aligned over a 10-km-along one of the master NS-striking fault, and; 3) the Melimouyu strato-volcano without any spatial relationship with mapped faults. The network consists of 6 short period seismometers (S31f-2.0a sensor of IESE, with natural frequency of 2Hz), that were installed between July 2016 and August 2017; also 4 permanent broad-band seismometers (Guralp 6TD/ CD 24 sensor) which belong to the Volcano Observatory of Southern Andes (OVDAS). Preliminary results show a correlation between seismicity and surface manifestation of fluid circulation. Seismicity has a heterogeneous distribution: most of the earthquake are concentrated is the master NS-striking fault with fluid circulation manifestations; however along the segments without surface manifestation of fluids do not have seismicity. These results suggest that fluid circulation mostly occur in areas with high seismicity, and thus, the increment in fluid pressure enhances

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

    Schueftan, Alejandra; González, Alejandro D.

    2015-01-01

    Major cities in South-central Chile suffer high levels of particulate matter PM 10 and PM 2.5 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 PM 2.5 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

  2. Large-Scale Controls and Characteristics of Fire Activity in Central Chile, 2001-2015

    McWethy, D. B.; Pauchard, A.; García, R.; Holz, A.; González, M.; Veblen, T. T.; Stahl, J.

    2016-12-01

    In recent decades, fire activity has increased in many ecosystems worldwide, even where fuel conditions and natural ignitions historically limited fire activity, and this increase begs questions of whether climate change, land-use change, and/or altered vegetation are responsible. Increased frequency of large fires in these settings has been attributed to drier-than-average summers and longer fire seasons as well as fuel accumulation related to ENSO events, raising concerns about the trajectory of post-fire vegetation dynamics and future fire regimes. In temperate and Mediterranean forests of central Chile, recent large fires associated with altered ecosystems, climate variability and land-use change highlight the risk and hazard of increasing fire activity yet the causes and consequences are poorly understood. To better understand characteristics of recent fire activity, key drivers of fire occurrence and the spatial probability of wildfire we examined the relationship between fire activity derived from MODIS satellite imagery and biophysical, land-cover and land-use variables. The probability of fire occurrence and annual area burned was best predicted by seasonal precipitation, annual temperature and land cover type. The likelihood of fire occurrence was greatest in Matorral shrublands, agricultural lands (including pasture lands) and Pinus and Eucalyptus plantations, highlighting the importance of vegetation type and fuel flammability as a critical control on fire activity. Our results suggest that land-use change responsible for the widespread presence of highly flammable vegetation and projections for continued warming and drying will likely combine to promote the occurrence of large fires in central Chile in the future.

  3. Synoptic aspects of the central Chile rainfall variability associated with the southern oscillation

    Rutllant, J.; Fuenzalida, H.

    1988-07-01

    Central Chile winter rainfall patterns show a positive anomaly during the developing stage of warm events associated to the negative phase of the Southern Oscillation. On the other hand, cold events during the positive phase of the Southern Oscillation, correspond quite closely to dry conditions. However, several dry years seem to precede or follow warm events without being necessarily classified as cold events. A synoptic characterization of major winter storms during the development of the most recent warm events in 1972, 1982 and 1987, is presented. Dry winter months during cold-event years are described in terms of average 500 hPa contour anomaly fields. Significant departures from this general behavior, as storms not associated to warm events and extended dry periods during otherwise wet winters, are also analyzed. It is found that major winter storms occurring during the developing phase of warm events are related to hemispheric types of blocking and anomaly patterns where sonal wavenumber 4 and a particular phase of wavenumber 3 dominate. The blockings, located in the Bellingshausen sea area, split the westerly flow diverting the storm tracks towards central Chile. Cold years, often immediately preceding or following a warm event, bring dry conditions in the study area due to a well developed subtropical anticyclonic belt and predominantly sonal westerly flow. Superimposed on these general conditions, anomaly contour patterns in southern South America reveal opposite signs with respect to those associated to warm events. Heavy winter storms not coinciding with warm events show local types of blocking in the Antartic peninsula area, with meridionally or slightly NE-SW oriented troughs and ridges. Extended dry spells and rainfall episodes during warm-event winters seem to be connected with alternating subtropical anomalies moving east with an intraseasonal time scale, superimposed on the aforementioned anomaly pattern at high latitudes. 21 refs, 17 figs, 1 tab

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

    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

  5. 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

    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

  6. Boron isotopic composition of tertiary borate deposits in the Puna Plateau of the Central Andes, NW Argentina

    Kasemann, Simone; Franz, Gerhard; Viramonte, Jose G.; Alonso, Ricardo N.

    1998-01-01

    Full text: The most important borate deposits in South America are concentrated in the Central Andes. The Neogene deposits are located in the Puna Plateau of N W Argentina. These continental deposits are stratiform in the tectonically deformed Tertiary rocks. The largest borate accumulations Tincalayu, Sijes and Loma Blanca are part of the Late Miocene Sijes Formation, composed by different evaporitic and clastic units. In the main borate units of each location different phases of borates dominate. In Tincalayu the mayor mineral is borax with minor amounts of kernite and other rare borate minerals (ameginite, rivadavite, etc.). The principal minerals in Loma Blanca are borax with minor ulexite and inyoite. In the two main units of Sijes hydroboracite and colemanite are the major minerals; inyoite and ulexite appear subordinately. The deposition of the borates is due to a strong evaporation in playa lakes, which were fed by boron bearing thermal fluids (Alonso and Viramonte 1990). From Loma Blanca we determined δ 11 B values of ulexite (- 6.3 %0), inyoite (-12.7 %0) and terrugite (-16.2 %0); and from Tincalayu the δ 11 B values of borax (-10.5 %0), tincal (-12.2 %0) kernite (-11.7 %0) and inderite (-15.4 %0). The borates of Sijes are hydroboracite (-16.8 %0 to -17.2 %0), ulexite (-22.4 %0) and inyoite (-28.5 %0 to -29.6 %0). In order to get information about the δ 11 B values and pH of a boron solution we analysed the thermal spring of Antuco. It has a δ 11 B of -12.5%0 at a pH of 7.9. The presently forming ulexite deposit has a δ 11 B of -22.4%0. Borates within one depositional unit show a decreasing δ 11 B value sequence from the Na-Borates to the Ca-Borates related to the boron coordination of the minerals (Oi et al. 1989). The difference in the δ 11 B values excludes the precipitation in equilibrium from solutions with constant pH. According to results from previous work on Neogene borates (Turkey, USA) we interpret the borate succession due to

  7. Investigating Crustal Scale Fault Systems Controlling Volcanic and Hydrothermal Fluid Processes in the South-Central Andes, First Results from a Magnetotelluric Survey

    Pearce, R.; Mitchell, T. M.; Moorkamp, M.; Araya, J.; Cembrano, J. M.; Yanez, G. A.; Hammond, J. O. S.

    2017-12-01

    At convergent plate boundaries, volcanic orogeny is largely controlled by major thrust fault systems that act as magmatic and hydrothermal fluid conduits through the crust. In the south-central Andes, the volcanically and seismically active Tinguiririca and Planchon-Peteroa volcanoes are considered to be tectonically related to the major El Fierro thrust fault system. These large scale reverse faults are characterized by 500 - 1000m wide hydrothermally altered fault cores, which possess a distinct conductive signature relative to surrounding lithology. In order to establish the subsurface architecture of these fault systems, such conductivity contrasts can be detected using the magnetotelluric method. In this study, LEMI fluxgate-magnetometer long-period and Metronix broadband MT data were collected at 21 sites in a 40km2 survey grid that surrounds this fault system and associated volcanic complexes. Multi-remote referencing techniques is used together with robust processing to obtain reliable impedance estimates between 100 Hz and 1,000s. Our preliminary inversion results provide evidence of structures within the 10 - 20 km depth range that are attributed to this fault system. Further inversions will be conducted to determine the approximate depth extent of these features, and ultimately provide constraints for future geophysical studies aimed to deduce the role of these faults in volcanic orogeny and hydrothermal fluid migration processes in this region of the Andes.

  8. Resignificación de la muerte en los Andes: La festividad de Wiñay Pacha o todas las almas en Santiago de Chile

    Francisca Fernández Droguett

    2014-12-01

    Full Text Available Desde el 2009 diversas organizaciones y agrupaciones de danza y música andina, han comenzado a conmemorar el día de difuntos en la ciudad de Santiago, denominándola Wiñay Pacha o Todas Almas. El siguiente artículo tiene por objetivo caracterizar esta práctica festiva desde los elementos culturales que configuran la visión de la muerte de los pueblos indígenas de Los Andes, a través de la vivencia del duelo y la forma de conmemorar a los difuntos, para luego reflexionar el modo en que se ha ido resignificando en el contexto urbano, mediante la revisión de su origen como festividad y su expresión como reivindicación de otros modos de vivenciar la muerte. La investigación se aborda desde una aproximación etnográfica, utilizando para la recopilación de datos la revisión bibliográfica, observación participante y entrevistas en profundidad.

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

    Rabbia, O.M.; Hernandez, L.B.; King, R.W.; Lopez Escobar, L

    2001-01-01

    The giant El Teniente porphyry Cu-Mo deposit is located in the Andes foothills of Central Chile (34 o S). In simplistic terms, the igneous rocks at the mine can be grouped in two major units: a felsic suite of silicic intrusives (the porphyries; SiO 2 ≥56wt%) with subvertical stock-like to dyke shapes, and a mafic volcanic to subvolcanic sequence (the Farellones formation; SiO 2 <≤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

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

    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

  11. Del santuario al caserío: acerca de la neolitización en la Cordillera de los Andes Centrales

    1988-01-01

    Full Text Available Les faits archéologiques mis en évidence sur le site de Piruru ouvrent des perspectives nouvelles sur la sédentarisation et l'apparition du village dans les Andes centrales. Piruru présente, au Précéramique Final (3000/2500 - 1800/1500 av.JC, une longue période de construction à des fins religieuses avant que n'existent, au Formatif Initial et Moyen (1800/1500 - 800/600 av.JC, des structures à usage domestique. Cette antériorité de l'architecture publique et cérémonielle, observable à l'échelle régionale, permet de proposer l'hypothèse qu'au Précéramique Final, les sanctuaires montagnards jouent un rôle catalyseur, non seulement dans la naissance et le développement de l'architecture, mais aussi dans l'organisation spatiale des communautés en cours de sédentarisation. Durant la longue occupation du Précéramique Final, plus de 1000 ans, les premières phases de la séquence de Piruru montrent l'existence de petits temples, qui sont les plus anciens connus actuellement dans les Andes centrales. Ensuite, la phase plus récente du temple P1 permet de relier Piruru aux autres sanctuaires connus, et de définir la tradition Mito, courant religieux qui se manifeste dans les Andes d'Ancash et de Huánuco, durant la deuxième partie du Précéramique Final. Au Formatif Initial, dans le même temps où la céramique est introduite sur le site, Piruru devient un petit habitat groupé, premier exemple connu à ce jour en montagne. Au cours d'un processus long de plus de 700 ans, les transformations dans l'organisation globale de l'habitat indiquent un degré croissant de sédentarité, et montrent le passage d'un hameau utilisé de façon saisonnière à un village habité de façon permanente, la sédentarité paraissant acquise au début du Formatif Moyen. Los hechos arqueológicos puestos en evidencia en el sitio de Piruru ofrecen nuevas perspectivas sobre la sedentarización y la aparición de la aldea en los Andes centrales

  12. Economic evaluation of a crop rotation portfolio for irrigated farms in central Chile

    Jorge González U

    2013-09-01

    Full Text Available The sustainable use of productive resources by agricultural producers in the central valley of Chile should be compatible with economic results so that producers can select an appropriate rotation or succession of annual crops and pasture. The objective of this work was to evaluate the economic behavior of four food crop and supplementary forage rotations using indicators of profitability and profit variability. Productive data were used from a long-term experiment (16 yr in the central valley of Chile under conditions of irrigation. With productive data and information on historic input/output prices, the real net margin per rotation (RNMR and its coefficient of variation (CV were determined. The results indicated that the highest economic benefits and greatest economic stability were obtained with rotations that only included crops, namely sugar beet (Beta vulgaris L. subsp. vulgaris-wheat (Triticum aestivum L.-bean (Phaseolus vulgaris L.-barley (Hordeum vulgare L. (CR2 and corn (Zea mays L.-wheat-bean-barley (CR4. These rotations included crops with low CV of the net margin, such as wheat, barley and beans, with values between 0.31 and 0.34. The rotations with crops and pasture, sugar beet-wheat-red clover (Trifolium pratense L. (2 (CR1 and corn-wheat-red clover (2 (CR3 had lower net margins and more variability of this indicator. Red clover had the highest CV value (1.00. The selection of crops for rotations and their sequence were determining factors in the economic behavior of rotations, affecting the level of RNMR and the degree of inter-annual variability of this indicator. Thus, differences among rotations of 47% in net margin were determined (CR2 vs. CR1, which only differed in the replacement of pasture with red clover (2 by bean-barley. The economic analysis based on the net margin and its variability allow for discriminating among rotations, providing valuable information for producers in deciding which crops to use in rotations.

  13. Megathrust earthquakes in Central Chile: What is next after the Maule 2010 earthquake?

    Madariaga, R.

    2013-05-01

    The 27 February 2010 Maule earthquake occurred in a well identified gap in the Chilean subduction zone. The event has now been studied in detail using both far-field, near field seismic and geodetic data, we will review this information gathered so far. The event broke a region that was much longer along strike than the gap left over from the 1835 Concepcion earthquake, sometimes called the Darwin earthquake because he was in the area when the earthquake occurred and made many observations. Recent studies of contemporary documents by Udias et al indicate that the area broken by the Maule earthquake in 2010 had previously broken by a similar earthquake in 1751, but several events in the magnitude 8 range occurred in the area principally in 1835 already mentioned and, more recently on 1 December 1928 to the North and on 21 May 1960 (1 1/2 days before the big Chilean earthquake of 1960). Currently the area of the 2010 earthquake and the region immediately to the North is undergoing a very large increase in seismicity with numerous clusters of seismicity that move along the plate interface. Examination of the seismicity of Chile of the 18th and 19th century show that the region immediately to the North of the 2010 earthquake broke in a very large megathrust event in July 1730. this is the largest known earthquake in central Chile. The region where this event occurred has broken in many occasions with M 8 range earthquakes in 1822, 1880, 1906, 1971 and 1985. Is it preparing for a new very large megathrust event? The 1906 earthquake of Mw 8.3 filled the central part of the gap but it has broken again on several occasions in 1971, 1973 and 1985. The main question is whether the 1906 earthquake relieved enough stresses from the 1730 rupture zone. Geodetic data shows that most of the region that broke in 1730 is currently almost fully locked from the northern end of the Maule earthquake at 34.5°S to 30°S, near the southern end of the of the Mw 8.5 Atacama earthquake of 11

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

    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

  15. Disentangling the role of Natural Variability and Climate Change in the aggravation of Droughts in central Chile

    Garreaud, R. D.; Boisier, J. P.; Rondanelli, R. F.

    2016-12-01

    Among other climate extreme events, droughts (annual rainfall deficit larger than 25%) have punctuated the hydro-climate history of central Chile (30-40°S) with profoundly negative effects on physical (e.g., water storage depletion), ecological (e.g., increase in forest fires) and human systems (e.g., major distress in rural communities). In this presentation we show that intense but short-lived (1 or 2 years long) droughts are associated with anticyclonic (cyclonic) anomalies over the subtropical south Pacific (Amudsen sea), reduced synoptic-scale variability in that area and weakening of the westerly winds impinging the west coast of South America. These large-scale anomalies often occurs in connection with the cold phase of ENSO (La Niña events). Of particular interest is an uninterrupted rainfall deficit since 2010 to date, referred to as the central Chile mega-drought (MD) in virtue of its unprecedented character in term of duration, spatial extent and coincidence with warm air temperatures. The protracted MD shares some of the climate features of the historical events but for the prevalence of near-neutral ENSO years with the exception of 2010 (La Niña) and 2015 (intense El Niño). Thus, we use a suite of fully-coupled and SST-forced climate simulations to disentangle natural and anthropogenic contributions to current mega drought as well as to shed light in the physical link between global climate change and rainfall deficit in central Chile drought. It turns out that anthropogenic climate change accounts for about a third of the drought as it forces SAM towards its positive polarity. The later enhances a dipole of geopotential height over the South Pacific that is conducive to dry conditions in central Chile.

  16. Altitudinal and interannual variation in seedling survival of tree species in central Chile: implications for sclerophyllous forest restoration

    Becerra, Pablo I; Smith-Ramírez, Cecilia; Armesto, Juan J

    2016-01-01

    An important issue in ecological restoration of forest ecosystems is to establish where reforestation is more limited by ecological factors and thus where additional treatments (e.g. irrigation, shading) are more needed. Population growth, density and reproduction in plants have frequently been documented to decrease with altitude, although in semiarid regions, initial increases up to middle elevations and then decreasing upward have been reported. In the semiarid region of central Chile, the...

  17. Recuperación de la biomasa mediante la sucesión secundaria, Cordillera Central de los Andes, Colombia

    Jorge Ignacio del Valle

    2011-09-01

    Full Text Available En bosques secundarios premontanos tropicales es escasa la información sobre el tiempo requerido para recuperar la biomasa aérea y subterránea de los primarios. Por lo tanto, establecimos 33 parcelas de 0.1ha entre 550 y 1 700m en bosques secundarios que cubrían estadios serales de 3 a 36 años y estimamos la biomasa de las plantas y de las raíces gruesas con ecuaciones locales. Así como la biomasa de las pasturas y barbechos por cosecha de 54 y 18 parcelas, respectivamente. También se calculó la edad de las parcelas con informantes locales, sensores remotos, C14 y anillos de crecimiento. En cada parcela medimos la biomasa aérea viva por hectárea (Bav y la de las raíces gruesas por hectárea (Brg. Modelamos la Bav y Brg en función de la edad mediante la ecuación de von Bertalanfy con asíntotas de 247t/ha (Bav y 66t/ha (Brg resultantes de la medición de 33 parcelas de 0.1ha en los bosques primarios. Con la razón Brg/Bav=f(t estimamos 87 años para que los bosques secundarios recuperen la Bav existente en los primarios y 217 años para recuperar la Brg. La tasa máxima de crecimiento instantáneo de la Bav fue 6.95t/ha/año a los 10 años y la tasa media máxima de crecimiento 6.26t/ha/año a los 17 años. La media ponderada de la tasa de crecimiento absoluto de la Bav alcanzó 4.57t/ha/año y la relativa 10% anual. La razón Brg/Bav inicialmente aumenta muy aceleradamente hasta 4-5 años (25%, luego disminuye hasta 25 años (18% para luego incrementar hasta 26.7Biomass recovery through secondary succession in the Cordillera Central de los Andes, Colombia. Estimations on biomass recovery rates by secondary tropical forests are needed to understand the complex tropical succession, and their importance on CO2 capture, to offset the warming of the planet. We conducted the study in the Porce River Canyon between 550 and 1 700m.a.s.l. covering tropical and premontane moist belts. We established 33 temporary plots of 50mx20m in secondary

  18. The 1985 central chile earthquake: a repeat of previous great earthquakes in the region?

    Comte, D; Eisenberg, A; Lorca, E; Pardo, M; Ponce, L; Saragoni, R; Singh, S K; Suárez, G

    1986-07-25

    A great earthquake (surface-wave magnitude, 7.8) occurred along the coast of central Chile on 3 March 1985, causing heavy damage to coastal towns. Intense foreshock activity near the epicenter of the main shock occurred for 11 days before the earthquake. The aftershocks of the 1985 earthquake define a rupture area of 170 by 110 square kilometers. The earthquake was forecast on the basis of the nearly constant repeat time (83 +/- 9 years) of great earthquakes in this region. An analysis of previous earthquakes suggests that the rupture lengths of great shocks in the region vary by a factor of about 3. The nearly constant repeat time and variable rupture lengths cannot be reconciled with time- or slip-predictable models of earthquake recurrence. The great earthquakes in the region seem to involve a variable rupture mode and yet, for unknown reasons, remain periodic. Historical data suggest that the region south of the 1985 rupture zone should now be considered a gap of high seismic potential that may rupture in a great earthquake in the next few tens of years.

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

    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.

  20. Surgical implantation of intra-abdominal radiotransmitters in marine otters (Lontra felina) in central Chile.

    Soto-Azat, Claudio; Boher, Francisca; Fabry, Mauricio; Pascual, Paulo; Medina-Vogel, Gonzalo

    2008-10-01

    Six free-ranging marine otters (Lontra felina) were livetrapped on the central coast of Chile and implanted with specially designed radiotransmitters as part of a spatial ecology study. Marine otters frequent the rocky seashore, often squeezing their narrow bodies through cracks and crevices and grooming themselves on the rocks. They are also among the smallest of the otter species, weighing between 3.4 kg and 4.5 kg. For these reasons, the transmitter used was small, rectangular, and flat, measuring 3.5 x 3.2 x 1.0 cm. They were implanted using a ventral midline approach to minimize contact between the skin incision and sharp-edged rocks. Surgical incisions healed within 2 wk. The transmitters functioned well, but the duration varied from 62 days to 143 days instead of the 240 days predicted by the manufacturer. All six marine otters reestablished in their home ranges, and survey results suggest they survived well beyond the life of the transmitters.

  1. Sexuality behind bars in the female central penitentiary of Santiago, Chile: Unlocking the gendered binary.

    Castro Madariaga, Francisca Alejandra; Gómez Garcés, Belén Estefanía; Carrasco Parra, Alicia; Foster, Jennifer

    2017-01-01

    We explore what it means to promote healthy sexuality for incarcerated women. We report upon the experiences of ten inmates in the Female Central Penitentiary of Santiago, Chile, regarding their sexuality within prison. We used a qualitative, descriptive research approach. Individual and semistructured interviews were conducted with women from different sections of the prison over a 2-month period. Participants highlighted the site for conjugal visits, the Venusterio, as a place of privacy and sexual expression between couples from outside prison. Motivated by loneliness, need of protection, and desire for affection, participants enacted alternate gender and sexual identities and sexual orientation. Some previously heterosexual women became 'machos', women taking on dominant masculine identities. Women found a paradoxical freedom to express a malleable and fluid sexual identity, an identity that might not go outside the prison. Informed by Judith Butler's idea of performativity, we argue that women could enact both different gender and sexual identities in search of satisfying their affective and erotic desires while under the duress of incarceration. The findings suggest a need for a more fluid understanding of gender and sexuality, especially for those midwives and nurses who strive to promote sexual health, not only reproductive health. © 2017 John Wiley & Sons Ltd.

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

    Rutllant, J.

    1994-07-01

    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

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

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

    2015-06-17

    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 health problems, frequency of supper with the family, the degree of agreement with respect to family being an important source of happiness (p food consumption in fast food outlets (p health, family and eating, and the family interaction associated with eating may play an important role in overall satisfaction with life.

  4. Impact of Land Use Change on the Temperate Forest of South Central Chile

    Fernandez, A.; Fuentes, R.; Jaque, E.; Fernandez, S.

    2017-12-01

    Chilean temperate forests is a biological hotspot because its high diversity and endemism. Nevertheless, in the last few decades the spatial extent of this forest has been decimated, portraying potentially harmful impacts on the regional biodiversity. In this work, we present our ongoing study on the rate of temperate forest shrinkage and their causes in a section of the BioBío region (37°S), South Central Chile. We derived land cover maps from satellite imagery acquired over 20 years (1990 and 2010) and assessed the effects of changes in land use on native forest. Between 1990 and 2010, there was a 59% reduction in native forest area, which is equivalent to an annual forest loss rate of 4.4% per year. Forest fragmentation was associated with a decrease in forest patch size and proximity, and an increase in the number of forest patches. During this study period native forest loss was correlated with an expansion of plantations of exotic species, which in turn was associated with substantial changes in the spatial configuration of the landscape. We will also present an update of this pattern including the period 2010-2017. The assessment of deforestation and fragmentation provides a basis for future research on the impacts of forest fragmentation on the different components of biodiversity. We suggest that conservation strategies and land use planning are necessary in the study area; this should consider the spatial pattern of native forest patches and the change of these over time at a landscape level.

  5. Seismic influence in the Quaternary uplift of the Central Chile coastal margin, preliminary results.

    Valdivia, D.; del Valle, F.; Marquardt, C.; Elgueta, S.

    2017-12-01

    In order to quantify the influence of NW striking potentially seismogenic normal faults over the longitudinal variation of the Central Chile Coastal margin uplift, we measured Quaternary marine terraces, which represent the tectonic uplift of the coastal margin. Movement in margin oblique normal faults occurs by co-seismic extension of major subduction earthquakes and has occurred in the Pichilemu fault, generating a 7.0 Mw earthquake after the 2010 8.8 Mw Maule earthquake.The coastal area between 32° and 34° S was selected due to the presence of a well-preserved sequence of 2 to 5 Quaternary marine terraces. In particular, the margin oblique normal NW-trending, SW-dipping Laguna Verde fault, south of Valparaiso (33° S) puts in contact contrasting morphologies: to the south, a flat coast with wide marine terraces is carved in both, Jurassic plutonic rocks and Neogene semi-consolidated marine sediments; to the north, a steeper scarp with narrower marine terraces, over 120 m above the corresponding ones in the southern coast, is carved in Jurassic plutonic rocks.We have collected over 6 months microseimic data, providing information on seismic activity and underground geometry of the Laguna Verde fault. We collected ca. 100 systematic measurements of fringes at the base of paleo coastal scarps through field mapping and a 5 m digital elevation model. These fringes mark the maximum sea level during the terrace's carving.The heights of these fringes range between 0 and 250 masl. We estimate a 0.7 mm/yr slip rate for the Laguna Verde fault based on the height difference between corresponding terraces north- and southward, with an average uplift rate of 0.3 mm/yr for the whole area.NW striking normal faults, besides representing a potential seismic threat to the near population on one of the most densely populated areas of Chile, heavily controls the spatial variation of the coastal margin uplift. In Laguna Verde, the uplift rate differs more than three times northward

  6. Identifying role of subtropical southeast Pacific SST anomalies on precipitation dynamics in Central Chile

    Bozkurt, D.; Garreaud, R.

    2014-12-01

    Central Chile (CC, western South America coasts, 28°S- 38°S) is the heartland of Chile with the highest population and important economic activities. The region is characterized by semiarid Mediterranean climate with a marked precipitation gradient along the coast from north to south, mostly due to the positioning of the South Pacific Subtropical Anticyclone and the midlatitude westerlies belt. Although there are several diagnostic studies that focus on the impact of tropical Pacific SST on CC precipitation variability via atmospheric teleconnections, less attention has been placed on impacts of subtropical southeast (SE) Pacific SST on precipitation. The later region is immediately adjacent to CC and it interferes with the overpassing atmospheric systems. In particular we want to assess the impact of a consistent cooling over the SE Pacific during the last 30 years. This study is being tackled by a combination of observational and reanalysis datasets together with numerical simulations. Observational dataset includes gridded dataset of CRU, TRMM and GPCP. Moreover, Reynolds SST data V2 based on AVHRR infrared satellite SST data is used for analyzing spatial and temporal changes in SST. Current modelling experiment includes a control simulation, used as reference, and sensitivity simulation that involves perturbations to SST over subtropical SE Pacific for a normal year austral winter (2001) season. A number of simulations with different initial conditions have been carried out by employing ICTP-RegCM4. The domain for simulations was centered at 82oW and 32oW with 288x288 grid cells on 20 km spatial resolution. Preliminary results indicate that the response of precipitation in CC to SST anomalies in the subtropical SE Pacific exhibits more or less linear behavior. In the colder SST experiments, drier conditions dominate over CC, which is possibly related with the intensification of South Pacific Subtropical Anticyclone (SPSA) or a reduction in the available

  7. Beliefs about the causes of schizophrenia among Aymara and non-Aymara patients and their primary caregivers in the Central-Southern Andes.

    Caqueo-Urízar, Alejandra; Breslau, Joshua; Gilman, Stephen E

    2015-02-01

    The aim of this study is to investigate differences in the beliefs about the causes of schizophrenia between Aymara and non-Aymara patients with schizophrenia and their primary caregivers. Ethnic background plays an important role in the formation of beliefs regarding the causes of schizophrenia, and there have been no prior studies on such beliefs among the Aymara, an indigenous community with a population of about 2 million people living in the Andes. We focused on three systems of beliefs distinguished in the literature: biological, psychosocial and magical-religious. The sample comprised 253 patients (n=117 Aymara, and n=136 non-Aymara) of public mental health centers in Chile (33.6%), Peru (33.6%) and Bolivia (32.8%) with a diagnosis of schizophrenia, and each patient's primary caregiver. We administered to patients and caregivers a questionnaire with scales assessing the perceived causes of schizophrenia. Linear regression models were fitted to compare differences in the levels of causal beliefs between Aymara and non-Aymara patients and caregivers, and to identify socio-demographic and clinical predictors of different types of beliefs about the causes of schizophrenia. Adjusted for socio-demographic and clinical covariates, levels of psychosocial beliefs were significantly higher for Aymara caregivers (0.33, 95% confidence interval (CI)=0.05, 0.62) than non-Aymara caregivers. Contrary to expectations, beliefs about the causes of schizophrenia among Aymara are not more magical-religious than those of their non-Aymara counterparts. It may be necessary for mental health staff members to evaluate beliefs about the disorder, especially in ethnic minorities, before applying a standard model of treatment. © The Author(s) 2014.

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

    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

  9. 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

    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

  10. ANDES: An Underground Laboratory in South America

    Dib, Claudio O.

    ANDES (Agua Negra Deep Experiment Site) is an underground laboratory, proposed to be built inside the Agua Negra road tunnel that will connect Chile (IV Region) with Argentina (San Juan Province) under the Andes Mountains. The Laboratory will be 1750 meters under the rock, becoming the 3rd deepest underground laboratory of this kind in the world, and the first in the Southern Hemisphere. ANDES will be an international Laboratory, managed by a Latin American consortium. The laboratory will host experiments in Particle and Astroparticle Physics, such as Neutrino and Dark Matter searches, Seismology, Geology, Geophysics and Biology. It will also be used for the development of low background instrumentation and related services. Here we present the general features of the proposed laboratory, the current status of the proposal and some of its opportunities for science.

  11. Source contributions to PM10 and arsenic concentrations in Central Chile using positive matrix factorization

    Hedberg, Emma; Gidhagen, Lars; Johansson, Christer

    Sampling of particles (PM10) was conducted during a one-year period at two rural sites in Central Chile, Quillota and Linares. The samples were analyzed for elemental composition. The data sets have undergone source-receptor analyses in order to estimate the sources and their abundance's in the PM10 size fraction, by using the factor analytical method positive matrix factorization (PMF). The analysis showed that PM10 was dominated by soil resuspension at both sites during the summer months, while during winter traffic dominated the particle mass at Quillota and local wood burning dominated the particle mass at Linares. Two copper smelters impacted the Quillota station, and contributed to 10% and 16% of PM10 as an average during summer and winter, respectively. One smelter impacted Linares by 8% and 19% of PM10 in the summer and winter, respectively. For arsenic the two smelters accounted for 87% of the monitored arsenic levels at Quillota and at Linares one smelter contributed with 72% of the measured mass. In comparison with PMF, the use of a dispersion model tended to overestimate the smelter contribution to arsenic levels at both sites. The robustness of the PMF model was tested by using randomly reduced data sets, where 85%, 70%, 50% and 33% of the samples were included. In this way the ability of the model to reconstruct the sources initially found by the original data set could be tested. On average for all sources the relative standard deviation increased from 7% to 25% for the variables identifying the sources, when decreasing the data set from 85% to 33% of the samples, indicating that the solution initially found was very stable to begin with. But it was also noted that sources due to industrial or combustion processes were more sensitive for the size of the data set, compared to the natural sources as local soil and sea spray sources.

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

    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

  13. Nematode community structure along a central Chile margin transect influenced by the oxygen minimum zone

    Neira, Carlos; King, Ian; Mendoza, Guillermo; Sellanes, Javier; De Ley, Paul; Levin, Lisa A.

    2013-08-01

    Nematodes are among the metazoans most tolerant of low-oxygen conditions and play major roles in seafloor ecosystem processes. Nematode communities were studied in sediments off Concepción, Central Chile, spanning the outer shelf within the OMZ (122 m) to the mid-lower continental slope (972 m) beneath the OMZ. The total density and biomass of nematodes (core depth 0-10 cm) ranged from 677 to 2006 ind. 10 cm-2, and 168.4 to 506.5 μg DW 10 cm-2, respectively. Among metazoan meiofaunal taxa, nematodes predominated at all sites both in terms of relative abundance (83.7-99.4%) and biomass (53.8-88.1%), followed by copepods, nauplii and polychaetes. Nematodes were represented by 33 genera distributed among 17 families, with densities greatest at low oxygen sites (122-364 m; ~2000 ind. 10 cm-2). Nematode generic and trophic diversity, and individual biomass were lowest, and Rank 1 dominance was highest, at the most oxygen-depleted site (122 m), despite the fact that the organic carbon content of the sediment was maximal at this depth. At the most oxygenated slope sites (827 and 972 m), all of Wieser's nematode feeding groups were represented. In contrast, at the lowest-oxygen site, only selective deposit (bacterial) feeders (1A) were present, indicating a reduction in trophic complexity. A large percentage of nematodes inhabited subsurface sediment layers (>1 cm). At deeper, more oxygenated sites (827 and 972 m), nematode individual biomass increased downcore, while within the OMZ, nematode biomass was low and remained relatively uniform through the sediment column. The concentration of nematodes in deeper sediment layers, the vertical distribution of the feeding groups, as well as the high nutritional quality of the deeper layers, suggest a differential resource partitioning of the food available, which may reduce interspecific competition.

  14. Postfire responses of the woody flora of Central Chile: Insights from a germination experiment.

    Gómez-González, Susana; Paula, Susana; Cavieres, Lohengrin A; Pausas, Juli G

    2017-01-01

    Fire is a selective agent shaping plant traits and community assembly in fire-prone ecosystems. However, in ecosystems with no fire history, it can be a cause of land degradation when it is suddenly introduced by humans, as plant species may not be able to respond to such novel disturbance. Unlike other Mediterranean-type ecosystems (MTE) of the world, natural fires have not been frequent during the Quaternary in the matorral of Central Chile, and thus, plant adaptive responses are expected to be uncommon. We evaluated the effect of heat shock on seed survival and germination of 21 native woody plants of the Chilean matorral and compiled information on smoke-stimulation and resprouting, to evaluate the importance of fire-adaptive responses in the context of the other MTE. We found that in the Chilean woody flora negative seed responses to fire cues were more frequent than positive responses. Although resprouting is a relatively widespread trait, fire-stimulated germination is not as common in the Chilean matorral as in other MTE. The seeds of seven endemic species were strongly damaged by fire cues and this should be considered in post-fire restoration planning. However, our results also showed that many species were resistant to elevated doses of heat shock and in some, germination was even stimulated. Thus, future research should focus on the evolutionary causes of these responses. These findings could help to develop strategies for fire management in the Chilean matorral. In addition, they will improve our understanding of the evolutionary forces that shaped this plant community and to better frame this region among the other MTE worldwide.

  15. Postfire responses of the woody flora of Central Chile: Insights from a germination experiment.

    Susana Gómez-González

    Full Text Available Fire is a selective agent shaping plant traits and community assembly in fire-prone ecosystems. However, in ecosystems with no fire history, it can be a cause of land degradation when it is suddenly introduced by humans, as plant species may not be able to respond to such novel disturbance. Unlike other Mediterranean-type ecosystems (MTE of the world, natural fires have not been frequent during the Quaternary in the matorral of Central Chile, and thus, plant adaptive responses are expected to be uncommon. We evaluated the effect of heat shock on seed survival and germination of 21 native woody plants of the Chilean matorral and compiled information on smoke-stimulation and resprouting, to evaluate the importance of fire-adaptive responses in the context of the other MTE. We found that in the Chilean woody flora negative seed responses to fire cues were more frequent than positive responses. Although resprouting is a relatively widespread trait, fire-stimulated germination is not as common in the Chilean matorral as in other MTE. The seeds of seven endemic species were strongly damaged by fire cues and this should be considered in post-fire restoration planning. However, our results also showed that many species were resistant to elevated doses of heat shock and in some, germination was even stimulated. Thus, future research should focus on the evolutionary causes of these responses. These findings could help to develop strategies for fire management in the Chilean matorral. In addition, they will improve our understanding of the evolutionary forces that shaped this plant community and to better frame this region among the other MTE worldwide.

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

    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. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. First detection and characterization of Salmonella spp. in poultry and swine raised in backyard production systems in central Chile.

    Alegria-Moran, R; Rivera, D; Toledo, V; Moreno-Switt, A I; Hamilton-West, C

    2017-11-01

    Little is known about Salmonella serovars circulating in backyard poultry and swine populations worldwide. Backyard production systems (BPS) that raise swine and/or poultry are distributed across Chile, but are more heavily concentrated in central Chile, where industrialized systems are in close contact with BPS. This study aims to detect and identify circulating Salmonella serovars in poultry and swine raised in BPS. Bacteriological Salmonella isolation was carried out for 1744 samples collected from 329 BPS in central Chile. Faecal samples were taken from swine, poultry, geese, ducks, turkeys and peacocks, as well as environmental faecal samples. Confirmation of Salmonella spp. was performed using invA-polymerase chain reaction (PCR). Identification of serovars was carried out using a molecular serotyping approach, where serogroups were confirmed by a multiplex PCR of Salmonella serogroup genes for five Salmonella O antigens (i.e., D, B, C1, C2-C3, and E1), along with two PCR amplifications, followed by sequencing of fliC and fljB genes. A total of 25 samples (1·4% of total samples) from 15 BPS (4·6 % of total sampled BPS) were found positive for Salmonella. Positive samples were found in poultry (chickens and ducks), swine and environmental sources. Molecular prediction of serovars on Salmonella isolated showed 52·0% of S. Typhimurium, 16·0% of S. Infantis, 16·0% S. Enteritidis, 8·0% S. Hadar, 4·0% S. Tennessee and 4·0% S. Kentucky. Poor biosecurity measures were found on sampled BPS, where a high percentage of mixed confinement systems (72·8%); and almost half of the sampled BPS with improper management of infected mortalities (e.g. selling the carcasses of infected animals for consumption). Number of birds other than chickens (P = 0·014; OR = 1·04; IC (95%) = 1·01-1·07), mixed productive objective (P = 0·030; OR = 5·35; IC (95%) = 1·24-27·59) and mixed animal replacement origin (P = 0017; OR = 5·19; IC (95%) = 1·35-20·47) were detected as

  18. Glacial Hazards in Chile: Processes, Assessment, Mitigation and Risk Management Strategies

    Glasser, N. F.; Wilson, R.; Casassa, G., Sr.; Reynolds, J.; Harrison, S.; Shannon, S. R.; Schaefer, M.; Iribarran, P.

    2017-12-01

    Glacial Lake Outburst Floods (GLOFs) are capable of travelling considerable distances from their source and they represent one of the most important glacial hazards. In line with observations in other parts of the world, the frequency of GLOF events in Chile has increased in recent decades highlighting the need to quantify the flood risk posed to downstream areas. This poster presents the work of the `Glacial Hazards in Chile' project which aims to (1) better understand the processes that govern the development of GLOFs in Chile, (2) estimate the socio-economic effects of GLOFs in Chile, and (3) provide a GLOF risk assessment framework that can be applied to Chile and other lower income countries globally. As an initial step towards the completion of these aims, we have recently compiled the first glacial lake inventory for the central and Patagonian Andes, which details the temporal development of glacial lakes in this region over the past three decades. This analysis was used to identify two lakes of interest that were visited during a fieldwork expedition in February 2017. The first of these, Lago Chileno in Patagonia, has recently produced a large GLOF causing significant damage to the downstream floodplain, whilst the second was identified as one of the fastest growing lakes in the central Andes. Both these lakes were surveyed using aerial imagery acquired with a drone and a custom-built bathymetry boat, data from which will help to improve our understanding of the physical processes associated with glacial lake development and failure within the Chilean Andes.

  19. 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

    EDUARDO F. PAVEZ

    2001-01-01

    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 hem...

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

    Schuller, P.; Sepulveda, A.; Trumper, R.E.; Castillo, A.

    2000-01-01

    The objective of the present study was to evaluate the applicability of the 137 Cs 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 137 Cs 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 137 Cs method at adjacent points. The 137 Cs 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) [es

  1. Tsunami Rapid Assessment Using High Resolution Images and Field Surveys: the 2010 , Central Chile, and the 2011, Tohoku Tsunamis

    Ramirez-Herrera, M.; Navarrete-Pacheco, J.; Lagos, M.; Arcas, D.

    2013-12-01

    Recent extreme tsunamis have shown their major socioeconomic impact and imprint in the coastal landscape. Extensive destruction, erosion, sediment transport and deposition resculpted coastal landscape within few minutes along hundreds of kilometers of the Central Chile, in 2010, and the Northeast coast of Japan, in 2011. In the central coast of Chile, we performed a post-tsunami survey a week after the tsunami due to access restrictions. Our observations focus on the inundation and geomorphic effects of the 2010 tsunami and included an air reconnaissance flight, analysis of pre- and post-event low fly air-photographs and Google Earth satellite images, together with ground reconnaissance and mapping in the field, including topographic transects, during a period of 13 days. Eyewitness accounts enabled us to confirm our observations on effects produced by the tsunami along ~ 500km along the coastline landscape in central Chile For the Tohoku case study, we assessed in a day tsunami inundation distances and runup heights using satellite data (very high resolution satellite images from the GeoEye1 satellite and from the DigitalGlobe worldview through the Google crisis response project, SRTM and ASTER GDEM) of the Tohoku region, Northeast Japan. Field survey data by Japanese, other international scientists and us validated our results. The rapid assessment of damage using high-resolution images has proven to be an excellent tool neccessary for effcient postsunami surveys as well as for rapid assessment of areas with access restrictions. All countries, in particular those with less access to technology and infrastructure, can benefit from the use of freely available satellite imagery and DEMs for an initial, pre-field survey, rapid estimate of inundated areas, distances and runup, tsunami effects in the coastal geomorphology and for assisting in hazard management and mitigation after a natural disaster. These data provide unprecedented opportunities for rapid assessment

  2. Estimating Monthly Solar Radiation in South-Central Chile Estimación de Radiación Solar Mensual en la Zona Centro Sur de Chile

    José Álvarez

    2011-12-01

    Full Text Available Solar radiation is a key component in process-based models. The amount of this energy depends on the location, time of the year, and atmospheric conditions. Several equations and models have been developed for different conditions using historical data from weather station networks or satellite measurements. However, solar radiation estimates are too local since they rely on weather stations or have a resolution that is too coarse when working with satellites. In this study, we estimated monthly global solar radiation for the south-central region of Chile using the r.sun model and validated it with observations from automatic weather stations. We analyzed the performance of global radiation results with the Hargreaves-Samani (HS and Bristow-Campbell (BC models. Estimates from a calibrated rsun model accounted for 89% of the variance (r² = 0.89 in monthly mean values for 15 locations in the research area. The model performed very well for a wide area and conditions in Chile when we compared it with the HS and BC models. Our estimates of global solar radiation using the rsun model could be improved through calibration of ground measurements and more precise cloudiness estimates as they become available. With additional procedures, the rsun model could be used to provide spatial estimates of daily, weekly, monthly, and yearly solar radiation.La radiación solar es un componente clave en los modelos basados en procesos. La cantidad de esta energía depende de la ubicación, época del año, y también de las condiciones atmosféricas. Varias ecuaciones y modelos han sido desarrollados para diferentes condiciones, utilizando datos históricos de las redes de estaciones meteorológicas o de las mediciones por satélite. Sin embargo, las estimaciones de la radiación solar son demasiado locales con estaciones meteorológicas, o con una resolución muy gruesa cuando se trabaja con satélites. En el presente estudio se estimó radiación solar global

  3. HLA-A, -B, -DRB1 allele and haplotype frequencies of 920 cord blood units from Central Chile.

    Schäfer, Christian; Sauter, Jürgen; Riethmüller, Tobias; Kashi, Zahra Mehdizadeh; Schmidt, Alexander H; Barriga, Francisco J

    2016-08-01

    We present human leukocyte antigen (HLA) haplotype and allele/antigenic group frequencies derived from a data set of 920 umbilical cord blood units collected in Central Chile. HLA-A and -B genotypes were typed using sequence specific oligonucleotide probe methods while HLA-DRB1 genotypes were obtained from sequencing-based typing. The most frequent haplotype is A*29~B*44~DRB1*07:01 with an estimated frequency of 2.1%. Copyright © 2016 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

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

    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.

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

    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

  6. 2017 Valparaíso earthquake sequence and the megathrust patchwork of central Chile

    Nealy, Jennifer L.; Herman, Matthew W.; Moore, Ginevra L.; Hayes, Gavin P.; Benz, Harley M.; Bergman, Eric A.; Barrientos, Sergio E.

    2017-01-01

    In April 2017, a sequence of earthquakes offshore Valparaíso, Chile, raised concerns of a potential megathrust earthquake in the near future. The largest event in the 2017 sequence was a M6.9 on 24 April, seemingly colocated with the last great-sized earthquake in the region—a M8.0 in March 1985.

  7. Role of maca (Lepidium meyenii) consumption on serum interleukin-6 levels and health status in populations living in the Peruvian Central Andes over 4000 m of altitude.

    Gonzales, Gustavo F; Gasco, Manuel; Lozada-Requena, Ivan

    2013-12-01

    Lepidium meyenii (Maca) is a plant that grows at over 4,000 m above sea level in the central Peruvian Andes. The hypocotyls of this plant are traditionally consumed for their nutritional and medicinal properties. The aim of this study was to determine the health status based on a health related quality of life (HRQL) questionnaire (SF-20) and serum levels of interleukin 6 (IL-6) in subjects that are maca consumers. For this, a cross-sectional study was designed to be performed in 50 subjects from Junin (4,100 m): 27 subjects were maca consumers and 23 were non-consumers. The SF-20 survey is used to obtain a summary measure of health status. The stand up from a chair and sit down (SUCSD) test (to assess lower-extremity function), hemoglobin measurement, blood pressure, sexual hormone levels, serum IL-6 levels and the score of chronic mountain sickness (CMS) were evaluated. Testosterone/estradiol ratio (P maca consumers when compared to non-consumers (P maca consumers successfully completed the SUCSD test compared to non-consumers (P maca was associated with low serum IL-6 levels and in turn with better health status scores in the SF-20 survey and low chronic mountain sickness scores.

  8. Surnames and genetic structure of a high-altitude Quechua community from the Ichu River Valley, Peruvian Central Andes, 1825-1914.

    Pettener, D; Pastor, S; Tarazona-Santos, E

    1998-10-01

    Changes in isolation, inbreeding, population subdivision, and isonymous relationships are examined in six Quechua communities from the upper valley of the Ichu River in the Peruvian Central Andes (3700 m). All marriages registered between 1825 and 1914 in the Parish of Santa Ana were analyzed. The data (1680 marriages) were divided into 2 periods (1825-1870 and 1871-1914) and into the 6 villages that constitute the parish. Endogamy rates are between 81% and 100%, indicating high levels of reproductive isolation. The inbreeding indicated by isonymy (Ft, Fr, and Fn) is lower than in other mountain populations studied. Isonymy values, calculated from the different surname combinations made possible by the Ibero-American Surnames System, indicate a strong rejection of consanguineous marriages, particularly between patrilineal relatives, in agreement with the parental structure typical of Andean populations. The comparison between observed and expected repeated-pair values reveals a moderate level of subdivision within populations, which could be related to cultural and socioeconomic factors. Nonmetric multidimensional scaling was used to investigate temporal changes in the isonymous relationships among the communities. The results reveal a decrease in the interpopulational variability measured by surnames, in agreement with an increase in exogamy. Surnames and data contained in historical and demographic records yield reliable information, and they can be used to reconstruct the biological history of Amerindian populations over the last few centuries.

  9. Body size, composition, and blood pressure of high-altitude Quechua from the Peruvian Central Andes (Huancavelica, 3,680 m).

    Toselli, S; Tarazona-Santos, E; Pettener, D

    2001-01-01

    Although much information is available about the effects of high altitude on physiological characteristics, less is know about its effect on body composition. In the present study, anthropometric and body composition variables were investigated in a sample of 77 adult Quechua males from the Peruvian Central Andes (Huancavelica, 3,680 m). The subjects are shorter in relation to body weight than other ethnic groups, whereas body proportions are macrocormic (indicating a long trunk relative to the lower extremities), with intermediate values of the acromial-iliac index. All skinfold thicknesses are low (approximately 15th percentiles of NHANES reference values for the triceps and subscapular skinfolds), but tend to be higher than in the other Quechua populations. Similar results are obtained when percentage fat is estimated. Somatotypes are dominant in mesomorphy with very low ectomorphy. Comparison with a sample of high-altitude Kirghiz (3,200 m), previously studied with the same methods, shows higher values in the Peruvian sample for all variables related to adiposity. The presence of low adiposity in the Quechua population could be associated with stresses of the high-altitude environment. Mean values of blood pressure are very low and there is no correlation with age.

  10. Late Cenozoic basin evolution and fold-thrust deformation in the southern Central Andes: Initial constraints from synorogenic deposits of the Precordillera, Argentina

    Levina, M.; Horton, B. K.; Fuentes, F.; Stockli, D. F.

    2012-12-01

    In the Precordillera region of the Argentine Andes, Cenozoic shortening associated with flattening of the Pampean segment of the subducting Nazca plate has resulted in a series of thin skinned fold-thrust systems that partitioned and uplifted Cenozoic foreland basin deposits. The kinematic and temporal evolution of the Andean Precordillera can be approached through detailed analyses of the sedimentary fill now preserved in intermontane regions and the bedrock low-temperature thermochronology of the fold-thrust belt. In this project, we focus on Neogene foreland basin fill exposed in the central and eastern Precordillera along the San Juan River (Quebrada Albarracín and Pachaco regions), on the western flank of the Sierra Talacasto, and in the Loma de las Tapias area near the Ullum dam. The sedimentary successions exposed in these regions record the hinterland development of the Frontal Cordillera (detrital zircon provenance and composition of sandstone and conglomeratic units), regional volcanism (pyroclastic flows and tuffaceous sandstone units), and initial construction of the Precordillera (fault cutoff relationships, growth strata, and paleocurrent changes). We investigate the development and subsequent partitioning and deformation of these synorogenic sections using sediment provenance (detrital zircon U-Pb geochronology, conglomerate clast counts, sandstone petrography, and paleocurrent measurements), facies analysis of measured stratigraphic successions, and initial apatite (U-Th)/He cooling histories to constrain the age of uplift-induced exhumation of successive thrust sheets in the Andean Precordillera.

  11. Effects of diet and water supply on energy intake and water loss in a mygalomorph spider in a fluctuating environment of the central Andes.

    Canals, M; Figueroa, D; Alfaro, C; Kawamoto, T; Torres-Contreras, H; Sabat, P; Veloso, C

    2011-11-01

    The metabolic and water evaporation strategies in spiders may be part of a set of physiological adaptations to tolerate low or unpredictable food availability, buffering spiders against environmental fluctuations such as those of the high mountains of the central Andes. The aim of this study is to analyze experimentally the variations in metabolic rate and the rate of evaporative water with food and/or water restriction in a high mountain mygalomorph spider population (Paraphysa sp.). We found that the low metabolism of this spider was not affected by water restriction, but its metabolism was depressed after 3 weeks of food deprivation. The spider did not show seasonal metabolic changes but it presented seasonal changes in the rate of evaporative water loss at high temperatures. Females with egg sacs reduced their metabolic rate and evaporative water at high temperatures. These findings constitute a set of possible adaptations to a highly fluctuating Mediterranean environment, which is completely covered with snow for many months and then progresses rapidly to a very dry climate with high temperatures. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Limitación de la conservación de variedades nativas por variedades mejoradas: Estudio de caso de la papa en los Andes centrales del Ecuador

    MSc. María Cecilia Dávila

    2018-04-01

    Full Text Available La conservación de la biodiversidad para la alimentación y la agricultura, es una actividad importante a nivel mundial para asegurar la seguridad alimentaria y nutricional, pero dicha actividad está siendo limitada por varios factores. Este estudio de caso analiza cómo la adopción de variedades mejoradas de papa limita la conservación de la diversidad de las variedades nativas a nivel de granja o chakra en seis comunidades indígenas en los Andes centrales ecuatorianos. Los resultados muestran que la adopción de variedades mejoradas ha desplazado una amplia gama de variedades locales tradicionales de los campos de agricultores que, junto con las condiciones socioeconómicas y ambientales que caracterizaron el sitio de estudio, han socavado la diversidad genética de variedades cultivadas de papa en las fincas. Palabras clave: Conservación en finca, diversidad de papa, variedades mejoradas, variedades nativas.

  13. Coupling of microbial nitrogen transformations and climate in sclerophyll forest soils from the Mediterranean Region of central Chile.

    Pérez, Cecilia A; Armesto, Juan J

    2018-06-01

    The Mediterranean region of central Chile is experiencing extensive "mega-droughts" with detrimental effects for the environment and economy of the region. In the northern hemisphere, nitrogen (N) limitation of Mediterranean ecosystems has been explained by the decoupling between N inputs and plant uptake during the dormant season. In central Chile, soils have often been considered N-rich in comparison to other Mediterranean ecosystems of the world, yet the impacts of expected intensification of seasonal drought remain unknown. In this work, we seek to disentangle patterns of microbial N transformations and their seasonal coupling with climate in the Chilean sclerophyll forest-type. We aim to assess how water limitation affects microbial N transformations, thus addressing the impact of ongoing regional climate trends on soil N status. We studied four stands of the sclerophyll forest-type in Chile. Field measurements in surface soils showed a 67% decline of free-living diazotrophic activity (DA) and 59% decrease of net N mineralization rates during the summer rainless and dormant season, accompanied by a stimulation of in-situ denitrification rates to values 70% higher than in wetter winter. Higher rates of both free-living DA and net N mineralization found during spring, provided evidence for strong coupling of these two processes during the growing season. Overall, the experimental addition of water in the field to litter samples almost doubled DA but had no effect on denitrification rates. We conclude that coupling of microbial mediated soil N transformations during the wetter growing season explains the N enrichment of sclerophyll forest soils. Expected increases in the length and intensity of the dry period, according to climate change models, reflected in the current mega-droughts may drastically reduce biological N fixation and net N mineralization, increasing at the same time denitrification rates, thereby potentially reducing long-term soil N capital

  14. Pesticide residues in leafy vegetables and human health risk assessment in North Central agricultural areas of Chile.

    Elgueta, Sebastian; Moyano, Stella; Sepúlveda, Paulina; Quiroz, Carlos; Correa, Arturo

    2017-06-01

    To investigate pesticide residue concentrations and potential human health risk, a study was conducted in 118 leafy vegetable samples collected in 2014-2015 from the North Central agricultural areas of Chile. The pesticide residues were determined using the multiresidue QuEChERS method by gas chromatography as well as high-performance liquid chromatography. The results indicated that 27% of the total samples contained pesticide residues above the maximum residue limits of each active ingredient. The maximum estimated daily intake obtained for carbon disulphide (CS 2 ), methamidophos, azoxystrobin and cypermethrin were 0.57, 0.07, 0.06 and 0.05 mg kg -1 , respectively, which was higher than their acceptable daily intake. It is concluded that inhabitants of the North Central agricultural area of Chile are not exposed to health risks through the consumption of leafy vegetables with the exception of methamidophos. Nevertheless, the high levels of methamidophos detected in leafy vegetables could be considered a potential chronic health risk.

  15. New stratigraphic, chronologic, and magnetic fabric constraints for Neogene and Quaternary ignimbrites in the Central Andes (South Peru)

    De La Rupelle, A.; Thouret, J. C.; Cubukcu, H. E.; Jicha, B.; Bréard, E.; Gerbe, M.-C.; Le Pennec, J.-L.; Diot, H.; Boivin, P.

    2012-04-01

    Central Andean deformation history in southern Peru is recorded in Neogene volcanic units of Ocoña and Cotahuasi canyons that cut across the western Cordillera. Acceleration (100 km3) Nazca (c.24.6 Ma), Alpabamba (19.4-18.0 Ma), and Huaylillas (14.25-12.7 Ma) ignimbrite sheets preceded the canyon incision, whereas sheets of smaller volume (Peru, stratigraphy, chronology, AMS, fabric, Neogene, Quaternary.

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

    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

  17. Automated recognition of quasi-planar ignimbrite sheets and paleo-surfaces via robust segmentation of DTM - examples from the Western Cordillera of the Central Andes

    Székely, B.; Karátson, D.; Koma, Zs.; Dorninger, P.; Wörner, G.; Brandmeier, M.; Nothegger, C.

    2012-04-01

    The Western slope of the Central Andes between 22° and 17°S is characterized by large, quasi-planar landforms with tilted ignimbrite surfaces and overlying younger sedimentary deposits (e.g. Nazca, Oxaya, Huaylillas ignimbrites). These surfaces were only modified by tectonic uplift and tilting of the Western Cordillera preserving minor now fossilized drainage systems. Several deep, canyons started to form from about 5 Ma ago. Due to tectonic oversteepening in a arid region of very low erosion rates, gravitational collapses and landslides additionally modified the Andean slope and valley flanks. Large areas of fossil surfaces, however, remain. The age of these surfaces has been dated between 11 Ma and 25 Ma at elevations of 3500 m in the Precordillera and at c. 1000 m near the coast. Due to their excellent preservation, our aim is to identify, delineate, and reconstruct these original ignimbrite and sediment surfaces via a sophisticated evaluation of SRTM DEMs. The technique we use here is a robust morphological segmentation method that is insensitive to a certain amount of outliers, even if they are spatially correlated. This paves the way to identify common local planar features and combine these into larger areas of a particular surface segment. Erosional dissection and faulting, tilting and folding define subdomains, and thus the original quasi-planar surfaces are modified. Additional processes may create younger surfaces, such as sedimentary floodplains and salt pans. The procedure is tuned to provide a distinction of these features. The technique is based on the evaluation of local normal vectors (perpendicular to the actual surface) that are obtained by determination of locally fitting planes. Then, this initial set of normal vectors are gradually classified into groups with similar properties providing candidate point clouds that are quasi co-planar. The quasi co-planar sets of points are analysed further against other criteria, such as number of minimum

  18. Canyon incision chronology based on ignimbrite stratigraphy and cut-and-fill sediment sequences in SW Peru documents intermittent uplift of the western Central Andes

    Thouret, Jean-Claude; Gunnell, Yanni; Jicha, Brian R.; Paquette, Jean-Louis; Braucher, Régis

    2017-12-01

    Based on an 40Ar/39Ar- and U/Pb-based chronostratigraphy of ignimbrite sheets and the geomorphological features of watersheds, river profiles and slope deposits in the Ocoña-Cotahuasi-Marán (OCM) and Colca valleys of southwest Peru, we reconstruct the valley incision history of the western Central Andes over the last c. 25 Myr. We further document the Pleistocene and Holocene evolution of deep valleys on the basis of 14 10Be surface-exposure ages obtained on debris-avalanche deposits and river straths. The data suggest that uplift was gradual over the past 25 Myr, but accelerated after c. 9 Ma. Valley incision started around 11-9 Ma and accelerated between 5 and 4 Ma. Incision was followed by several pulses of valley cut-and-fill after 2.3 Ma. Evidence presented suggest that the post-5 Ma sequence of accelerated canyon incision probably resulted from a combination of drainage piracy from the Cordilleran drainage divide towards the Altiplano, accentuated flexural tilting of the Western Cordillera towards the SE, and increased rainfall on the Altiplano after late Miocene uplift of the Eastern Cordillera. The valley deepening and slope steepening driven by tectonic uplift gave rise to large occurrences of rockslope failure. The collapsed rock masses periodically obstructed the canyons, thus causing abrupt changes in local base levels and interfering with the steadiness of fluvial incision. As a result, channel aggradation has prevailed in the lower-gradient, U-shaped Pacific-rim canyons, whereas re-incision through landslide deposits has occurred more rapidly across the steeper V-shaped, upper valleys. Existing canyon knickpoints are currently arrested at the boundary between the plutonic bedrock and widespread outcrops of middle Miocene ignimbritic caprock, where groundwater sapping favouring rock collapse may be the dominant process driving headward erosion.

  19. Essential oils of medicinal plants from the central andes of Argentina: chemical composition, and antifungal, antibacterial, and insect-repellent activities.

    Lima, Beatriz; López, Sandra; Luna, Lorena; Agüero, María B; Aragón, Liliana; Tapia, Alejandro; Zacchino, Susana; López, María L; Zygadlo, Julio; Feresin, Gabriela E

    2011-05-01

    The antifungal, antibacterial, and insect-repellent activities of the essential oils (EOs) of Acantholippia seriphioides, Artemisia mendozana, Gymnophyton polycephalum, Satureja parvifolia, Tagetes mendocina, and Lippia integrifolia, collected in the Central Andes area, province of San Juan, Argentina, were investigated. The dermatophytes Microsporum gypseum, Trichophyton mentagrophytes, and T. rubrum were inhibited by the EOs of G. polycephalum, L. integrifolia, and S. parvifolia, with minimum inhibitory concentrations (MICs) between 31.2 and 1000 μg/ml. Moreover, all EOs presented moderate activity against the bacteria tested, and the L. integrifolia and G. polycephalum EOs showed excellent repellent properties against Triatoma infestans, the Chagas disease vector, with repellency values between 60 and 100%. The A. seriphioides, G. polycephalum, and L. integrifolia EOs, obtained by hydrodistillation, were characterized by GC-FID and GC/MS analyses. The highest number of components (40) was identified in L. integrifolia EO, which, along with that of A. seriphioides, contained important amounts of oxygenated monoterpenes (44.35 and 29.72%, resp.). Thymol (27.61%) and carvacrol (13.24%) were the main components of A. seriphioides EO, and borneol, lippifoli-1(6)-en-5-one, and terpinen-4-ol (>8.5%) were the principal compounds of L. integrifolia EO. These results support the idea that oxygenated monoterpenes are the bioactive fractions of the EOs. Finally, the study shows that these Andean species might be used to treat superficial fungal infections and to improve the local Chagas disease situation by vector-control. Copyright © 2011 Verlag Helvetica Chimica Acta AG, Zürich.

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

    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.

  1. Illustrated review of the leaf-mining Nepticulidae of the central Andes (Peru and Bolivia).

    Stonis, Jonas R; Diškus, Arūnas; Remeikis, Andrius; Karsholt, Ole; Torres, Nixon Cumbicus

    2017-04-24

    We review forty-five species of Nepticulidae (Lepidoptera) based on an analysis of samples collected in the central Andean region of Peru and Bolivia. Thirteen of these species are new to science, and are named and described here: Stigmella paracosma Remeikis & Stonis, sp. nov., S. expressa Remeikis & Stonis, sp. nov., S. acalyphae Diškus & Stonis, sp. nov., S. lepida Diškus & Stonis, sp. nov., S. misera Diškus & Stonis, sp. nov., S. inca Diškus & Stonis, sp. nov., S. eiffeli Diškus & Stonis, sp. nov., S. arequipica Remeikis & Stonis, sp. nov., S. coronaria Diškus & Stonis, sp. nov., S. azulella Diškus & Stonis, sp. nov., S. sparsella Diškus & Stonis, sp. nov., Manoneura forcipis Diškus & Stonis, sp. nov., and Acalyptris murex Diškus & Stonis, sp. nov. Some of the central Andean species are recorded here as leaf-miners on Euphorbiaceae (Acalypha), Fabaceae (Collaea), Rosaceae (Polylepis), Malvaceae (Sida), Calceolariaceae (Calceolaria), Lamiaceae (Clinopodium), and Asteraceae (Ageratina and Trixis). We create eleven new species groups based on morphological characters designated in Stigmella and one in Acalyptris. A pictorial key to the species groups and distribution maps are provided. All new species are illustrated with 150 photographs and drawings of the adults and genitalia, and, where known and/or available, photographs of host-plants and leaf-mines.

  2. 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

    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

  3. 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

    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

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

    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.

  5. Late Quaternary evolution of the San Antonio Submarine Canyon in the central Chile forearc (∼33°S)

    Laursen, Jane; Normark, William R.

    2002-01-01

    Hydrosweep swath-bathymetry and seismic-reflection data reveal the morphology, sedimentary processes, and structural controls on the submarine San Antonio Canyon. The canyon crosses the forearc slope of the central Chile margin for more than 150 km before it empties into the Chile Trench near 33°S latitude. In its upper reaches, the nearly orthogonal segments of the San Antonio Canyon incise ∼1 km into thick sediment following underlying margin-perpendicular basement faults and along the landward side of a prominent margin-parallel thrust ridge on the outer mid-slope. At a breach in the outer ridge, the canyon makes a sharp turn into the San Antonio Reentrant. Resistance to erosion of outcropping basement at the head of the reentrant has prevented the development of a uniformly sloping thalweg, leaving gentle gradients (6°) across the lower slope. Emergence of an obstruction across the head of the San Antonio Reentrant has trapped sediment in the mid-slope segments of the canyon. Presently, little sediment appears to reach the Chile Trench through the San Antonio Canyon. The development of the San Antonio Canyon was controlled by the impact of a subducted seamount, which formed the San Antonio Reentrant and warped the middle slope along its landward advancing path. Incision of the canyon landward of the outer mid-slope ridge may be ascribed to a combination of headward erosion and entrenchment by captured unconfined turbidity currents. Flushing of the canyon was likely enhanced during the lowered sea level of the last glaciation. Where the canyon occupies the triangular embayment of the reentrant at the base of the slope, sediment has ponded behind a small accretionary ridge. On the trench floor opposite the San Antonio Canyon mouth, a 200-m-thick levee–overbank complex formed on the left side of a distributary channel emanating from a breach in the accretionary ridge. Axial transfer of sediment was inhibited to the north of the San Antonio Canyon mouth

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

    1977-08-01

    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

  7. 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

    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

  8. Is there redundancy in bioengineering for molluscan assemblages on the rocky shores of central Chile? ¿Existe redundancia en la bioingeniería de los ensambles de moluscos de las costas rocosas de Chile central?

    BRENDAN P KELAHER

    2007-06-01

    Full Text Available Bioengineers modify habitats via their own physical structures and substantially increase local diversity in marine ecosystems. On rocky shores, there are large overlaps in the composition of communities associated with bioengineers that form complex mat-like habitats. We investigated the potential for redundancy in habitat provision by these types of habitats by comparing diverse molluscan assemblages associated with Perumytilus purpuratus mussel beds and algal turfs of Corallina officinalis var. chilenis, Gelidium chilense and Gastroclonium cylindricum. At three times between September 2003 and January 2004, we sampled the molluscan assemblages associated with each bioengineer at similar tidal heights on two rocky shores on the coast of central Chile. Of the 31 molluscan species identified, 30 were found in Corallina and 19-22 were identified from the other habitats. The pool of species found associated with each bioengineer overlapped greatly, demonstrating the potential for redundancy in habitat provision and little habitat-specificity. However, multivariate and univariate analyses showed all bioengineers except Gastroclonium contained a unique molluscan assemblage for at least one time of sampling because of variation in frequency of occurrence, richness and total abundance. Recent studies have highlighted many anthropogenic and natural processes that directly influence the diversity and composition of bioengineering species on rocky shores. We demonstrate that the loss of any particular bioengineer would not substantially alter the overall pool of molluscan species on the rocky shores of Chile. The loss of any bioengineer except Gastroclonium would, however, result in decreased local biodiversity because the molluscan assemblages in Perumytilus, Corallina and Gelidium, each contained a significantly different community structure for at least one time of samplingEn los ecosistemas marinos los organismos bioingenieros modifican habitats a

  9. 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

    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

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

    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 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

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

    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.

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

    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.

  13. Phosphorus fractions and sorption dynamics in the sediments of two Ca-SO4 water reservoirs in the central Argentine Andes

    José Gabriel León; Fernando Luis Pedrozo; Pedro Félix Temporetti

    2017-01-01

    Phosphorus (P) fractionation and sorption behavior were studied in the sediments of two calcium-sulfate (Ca-SO4:Ca2+170 mg L-1;SO42-400 mg L-1) water reservoirs in the southern central Argentine Andes-El Carrizal Reservoir (ECR),which stratifies in summer and El Nihuil Reservoir (ENR),which is vertically mixed throughout the year. Sediment size classes reflected the lithology of both basins and the reservoirs relative location:ECR (downstream from a valley adjacent to a mountain environment) had higher clay proportions while the sand fraction was more important in ENR (just next to a mountain environment). In both reservoirs, the chemical composition revealed low alteration and calcium enrichment. Total P content was relatively high (1.1–1.6 mg P kg-1 dry weight) as expected from the contribution of marine formations. P fractionation was dominated by Ca-P (ECR, 69%and ENR, 63%) followed by organic-P (23%) in summer-anoxic ECR and by iron/aluminum (Fe/Al)-P (27%) in oxic ENR. Batch experiments showed that sorption behavior in ECR had a typical Langmuir isotherm plot while in ENR that model fitted only at low dissolved P values (<5 mg P L-1) and co-precipitation evidence was observed at higher P con-centrations. It is proposed that lower Fe/Al-P content in anoxic (ECR) vs. oxic (ENR) sediments results from the P released from iron-bound phosphorus due to sulfate reduction-ferrous sulfide formation in an anoxic environment. This condition should enable ECR sediments to adsorb P into fresh oxidized iron, and ENR sediments to co-precipitate P with calcium due to Fe/Al-P saturation, as observed in batch experiments. This paper constitutes the first description of phosphorus content and dynamics in reser-voir sediments in arid central western Argentina, where water sulfate concentrations are naturally high due to basin lithology.

  14. Applying an ecosystem service approach to unravel links between ecosystems and society in the coast of central Chile.

    de Juan, Silvia; Gelcich, Stefan; Ospina-Alvarez, Andres; Perez-Matus, Alejandro; Fernandez, Miriam

    2015-11-15

    Ecosystem-based management implies understanding feedbacks between ecosystems and society. Such understanding can be approached with the Drivers-Pressures-State change-Impacts-Response framework (DPSIR), incorporating stakeholders' preferences for ecosystem services to assess impacts on society. This framework was adapted to six locations in the central coast of Chile, where artisanal fisheries coexist with an increasing influx of tourists, and a set of fisheries management areas alternate with open access areas and a no-take Marine Protected Area (MPA). The ecosystem services in the study area were quantified using biomass and species richness in intertidal and subtidal areas as biological indicators. The demand for ecosystem services was elicited by interviews to the principal groups of users. Our results evidenced decreasing landings and a negative perception of fishermen on temporal trends of catches. The occurrence of recreational fishing was negligible, although the consumption of seafood by tourists was relatively high. Nevertheless, the consumption of organisms associated to the study system was low, which could be linked, amongst other factors, to decreasing catches. The comparison of biological indicators between management regimens provided variable results, but a positive effect of management areas and the MPA on some of the metrics was observed. The prioritising of ecosystem attributes by tourists was highly homogenous across the six locations, with "scenic beauty" consistently selected as the preferred attribute, followed by "diversity". The DPSIR framework illustrated the complex interactions existing in these locations, with weak linkages between society's priorities, existing management objectives and the state of biological communities. Overall, this work improved our knowledge on relations between components of coastal areas in central Chile, of paramount importance to advance towards an ecosystem-based management in the area. Copyright © 2015

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

    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

  16. Upper pliocene-lower pleistocene 40Ar/39Ar ages of Pudahuel ignimbrite (Diamante-Maipo volcanic complex), Central Chile (33.50S)

    Wall, R.M.; Lara, L.E.; Perez de Arce, C

    2001-01-01

    The Pudahuel Ignimbrite (Wall et al., 1996) is a characteristic pyroclastic flow deposit placed in the Central Depression, within the Maipo, Mapocho and Cachapoal valleys and, in the eastern side of the Andes, at Yaucha and Papagayos rivers as well (Harrington, 1989; Guerstein, 1993). Close to Santiago, Pudahuel Ignimbrite reaches 40 m in thickness (Dragicevic, 1962) which decreces up to 5 m 60 km to the west. The deposit is compounded by ash and lapilli size pumice within a cineritic matrix with shards, crystals and pumice fragments. Facies of both, laminar and turbulent flow regime can be distinguished, the latter prevailing near topographic barriers and on river plain floors. There, traction structures like cross-bedding and important amount of litic clasts are characteristic. Pumices are rhyolitic in composition (ca. 75% SiO 2 ; Stern et al., 1984; Guerstein, 1993) and have few 0.5-2 mm long biotite crystals. Two 40 Ar/ 39 Ar step-heating experiments on biotite from pumices of two localities, Maipu (Santiago) and Bollenar (Melipilla), show plateau ages of 2.3±0.3 Ma (RW-371) and 2.2±0.3 Ma (RW-1009). In both cases, the first step of the experiment indicates loss of Ar from the cristal rims wich was removed for the plateau calculus only in the second case. For the RW-371 sample an inverse isocrone age of 1.4±0.8 Ma (MSWD: 0.98) was obtained. Previously, the Pudahuel Ignimbrite was dated by Stern et al. (1984) in ca. 450 ka using zircon fission-tracks. Although inconsistent with our new ages, these pleistocene age seemed coherent with the discovery of an Antifer (deer) bone by Tavera (1978) within the ignimbrite close to Santiago. Nevertheless, as was apointed by Tavera (1978) himself, the Antifer genus is recognized in Argentina in the Pliocene-Quaternary interval and make possible a review of the well known 'pleistocene' mammal vertebrate associations in Chile. Another consequence of the new possible pliocene ages is that, since the ignimbrite does not show

  17. Preliminary Depositional and Provenance Records of Mesozoic Basin Evolution and Cenozoic Shortening in the High Andes, La Ramada Fold-Thrust Belt, Southern-Central Andes (32-33°S)

    Mackaman-Lofland, C.; Horton, B. K.; Fuentes, F.; Constenius, K. N.; McKenzie, R.; Alvarado, P. M.

    2015-12-01

    The Argentinian Andes define key examples of retroarc shortening and basin evolution above a zone of active subduction. The La Ramada fold-thrust belt (RFTB) in the High Andes provides insights into the relative influence and temporal records of diverse convergent margin processes (e.g. flat-slab subduction, convergent wedge dynamics, structural inversion). The RFTB contains Mesozoic extensional basin strata deformed by later Andean shortening. New detrital zircon U-Pb analyses of Mesozoic rift sediments reveal: (1) a dominant Permo-Triassic age signature (220-280 Ma) associated with proximal sources of effective basement (Choiyoi Group) during Triassic synrift deposition; (2) upsection younging of maximum depositional ages from Late Triassic through Early Cretaceous (230 to 100 Ma) with the increasing influence of western Andean arc sources; and (3) a significant Late Cretaceous influx of Paleozoic (~350-550 Ma) and Proterozoic (~650-1300 Ma) populations during the earliest shift from back-arc post-extensional subsidence to upper-plate shortening. The Cenozoic detrital record of the Manantiales foreland basin (between the Frontal Cordillera and Precordillera) records RFTB deformation prior to flat-slab subduction. A Permo-Triassic Choiyoi age signature dominates the Miocene succession, consistent with sources in the proximal Espinacito range. Subordinate Mesozoic (~80-250 Ma) to Proterozoic (~850-1800 Ma) U-Pb populations record exhumation of the Andean magmatic arc and recycling of different structural levels in the RFTB during thrusting/inversion of Mesozoic rift basin strata and subjacent Paleozoic units. Whereas maximum depositional ages of sampled Manantiales units cluster at 18-20 Ma, the Estancia Uspallata basin (~50 km to the south) shows consistent upsection younging of Cenozoic populations attributed to proximal volcanic centers. Ongoing work will apply low-temperature thermochronology to pinpoint basin accumulation histories and thrust timing.

  18. Serie Documentos Nº2 - Investigaciones en Antropología Urbana (U. Central de Chile

    Verónica Tapia Barría

    2007-09-01

    Full Text Available Una de las características principales del desarrollo de la investigación antropológica urbana en Chile es justamente el hecho de constituirse como un espacio en construcción, que obedece más bien a un conjunto de esfuerzos independientes que a la formulación de programas de investigación formales. Dichos esfuerzos son mayormente protagonizados por investigadores jóvenes, que desde sus particulares ópticas y objetos de interés han ido perfilando el carácter de lo que podríamos denominar antropología urbana chilena.

  19. Los costos de la expedición militar a Chile, 1815-1818

    Beatriz Bragoni

    2016-09-01

    Full Text Available Este trabajo explora las estrategias utilizadas para financiar la creación y el sostenimiento del Ejército de los Andes y los instrumentos fiscales utilizados para conseguirlo. El análisis de los distintos rubros que integraban las cajas del ejército permite examinar el peso de los recursos aportados por el gobierno central y por la jurisdicción cuyana. Asimismo, analiza el destino de los fondos a través del estudio de los presupuestos del ejército, con el objetivo de ponderar el peso que tuvieron los salarios en el total de los gastos militares durante la etapa previa al cruce de los Andes, y en la posterior, cuando el ejército estaba en Chile bajo severas condiciones fiscales de los gobiernos patriotas.

  20. Circulation, échange et production de poteries dans les Andes Centrales au deuxième millénaire AV. J.C

    1990-01-01

    Full Text Available Sont présentés tout d’abord les quatre types céramiques définis pour la séquence Pirwa de Piruru (1600/1500 - 800/600 av. J.C.. Puis, après quelques réflexions méthodologiques à propos de la détermination de groupes céramiques pertinents, particulièrement durant le Formatif Initial, Piruru Pirwa est replacé dans le contexte culturel de la cordillère centre-andine, des changements significatifs étant constatés entre les phases Pirwa II et III. Les analyses céramologiques montrent que trois types sont importés et que le quatrième résulte d’une production locale. Les variations dans l’organisation globale de l’habitat Pirwa II et Pirwa III permettent de proposer l’hypothèse que l’activité céramique, c’est-à-dire la production de vaisselles, pourrait, dans l’exemple de Piruru, dépendre de la sédentarité. Circulación, intercambio y producción de cerámica en los Andes Centrales durante el segundo milenio a. C. En primer lugar, se presentan los cuatro tipos cerámicos definidos para la secuencia Pirwa de Piruru (1600/1500 - 800/600 a.C.. Luego, después de unas reflexiones metodológicas acerca de la determinación de grupos cerámicos pertinentes, especialmente durante el período Formativo Inicial, se sitúa Piruru Pirwa en el contexto cultural de la sierra central, notando cambios significativos entre las fases Pirwa II y Pirwa III. Los análisis ceramológicos muestran que tres tipos son importados, y que el cuarto es resultado de una producción local. Tomando en cuenta las variaciones en la organización general del asentamiento Pirwa II y Pirwa III, se plantea la hipótesis que la actividad cerámica, es decir la producción alfarera, en Piruru, podría vincularse al sedentarismo. Circulation, exchange and production of wares in the Central Highlands of Peru during the secund millenium B.C. In this paper, four ceramic types are defined and described for the Piruru Pirwa sequence (1600/1500 - 800/600 a C, and

  1. Volcanic hotspots of the central and southern Andes as seen from space by ASTER and MODVOLC between the years 2000-2011

    Jay, J.; Pritchard, M. E.; Mares, P. J.; Mnich, M. E.; Welch, M. D.; Melkonian, A. K.; Aguilera, F.; Naranjo, J.; Sunagua, M.; Clavero, J. E.

    2011-12-01

    We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for temperature anomalies between 2000-2011 from two different spacebourne sensors: 1) those automatically detected by the MODVOLC algorithm (Wright et al., 2004) from MODIS and 2) manually identified hotspots in nighttime images from ASTER. Based on previous work, we expected to find 8 thermal anomalies (volcanoes: Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Puyehue-Cordón Caulle, Chiliques). We document 31 volcanic areas with pixel integrated temperatures of 4 to more than 100 K above background in at least two images, and another 29 areas that have questionable hotspots with either smaller anomalies or a hotspot in only one image. Most of the thermal anomalies are related to known activity (lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to be active. A handful of volcanoes exhibit temporal variations in the magnitude and location of their temperature anomaly that can be related to both documented and undocumented pulses of activity. Our survey reveals that low amplitude volcanic hotspots detectable from space are more common than expected (based on lower resolution data) and that these features could be more widely used to monitor changes in the activity of remote volcanoes. We find that the shape, size, magnitude, and location on the volcano of the thermal anomaly vary significantly from volcano to volcano, and these variations should be considered when developing algorithms for hotspot identification and detection. We compare our thermal results to satellite InSAR measurements of volcanic deformation and find that there is no simple relationship between deformation and thermal anomalies - while 31 volcanoes have continuous hotspots, at least 17 volcanoes in the same area have exhibited deformation, and these lists do not completely overlap. In

  2. Eruption and Degassing Processes in a Supervolcanic System: The Volatile Record Preserved in Melt Inclusions from the 3.49Ma Tara Ignimbrite in the Central Andes

    Grocke, S.; de Silva, S. L.; Schmitt, A. K.; Wallace, P. J.

    2010-12-01

    Analysis of H2O and CO2 in quartz and sanidine-hosted melt inclusions from one of the youngest supervolcanic eruptions in the Altiplano Puna Volcanic Complex (APVC) in the Central Andes provides information on crystallization depths and eruption and degassing processes. At least 740 km3 of high-K, metaluminous, rhyodacite to rhyolite magma erupted from the Guacha Caldera in southwest Bolivia, producing three phases of the 3.49 Ma Tara Ignimbrite: a Plinian fall-deposit, an extensive ignimbrite, and several post-caldera domes. Infrared spectroscopic analyses of quartz-hosted melt inclusions from Tara Plinian pumice have H2O contents of ~4.5 wt % and variable CO2 contents (110-300 ppm), corresponding to vapor saturation pressures up to 180 MPa. In contrast, sanidine-hosted melt inclusions from the Plinian-fall deposit contain bubbles, lower water contents (1.4-2.2 wt %) and lower CO2 (87-143 ppm). These vesiculated melt inclusions and low volatile contents suggest that the sanidine crystals leaked on their ascent to the surface and therefore do not record accurate pre-eruptive melt volatile contents. In contrast, quartz-hosted melt inclusions from post-caldera dome samples contain lower H2O contents of 2.5-3.5 wt % (average 2.9 wt %) and no detectable CO2, corresponding to vapor saturation pressures of 50-90 MPa. These data indicate that the preeruptive plinian stage Tara magma was vapor saturated at the time of melt inclusion entrapment and stored between 5-6 km, while those from the post-caldera domes were trapped at 2-3 km. Differences in CO2 between Plinian and dome melt inclusions require that the post-caldera dome quartzes represent a different generation of crystals that grew as the magma slowly rose and progressively degassed at 2-3 km. During this shallow crystallization, the magma evolved further and eventually fed the post-caldera domes, one of which is a high-Si rhyolite. Consistent with this interpretation, melt inclusions from post-caldera dome samples

  3. Natural dam failure in the eastern slope of the Central Andes of Argentina. Numerical modelling of the 2005 Santa Cruz river outburst flood

    Penna, I.; Daicz, S.; Zlotnik, S.; Derron, M.-H.; Jaboyedoff, M.

    2012-04-01

    In the Central Andes of Argentina, ephemeral river blockage due to landslides deposition are common phenomena. During the first fortnight of January 2005, 11.5 * 106m3 of rock collapsed from the east slope of the Santa Cruz valley (San Juan province, Argentina). The rock mass displaced from 4300 m a.s.l., down to the valley bottom, at 2900 m a.s.l., and ran up the opposite flank of the valley. This produced the blockage of the Santa Cruz river and generated the Los Erizos lake. The rapid snow melting during the spring season caused the increase of the water level of the reservoir, leading to a process of overtopping on November 12th of 2005. 30 * 106m3 of water were released from the reservoir and the consequent outburst flood displaced along 250 km. From local reports of arrival times, we estimated that the outburst flood reduced its velocity from around 40 km/h near the source area to 6 km/h in its distal section. A road, bridges, and a mining post where destroyed. 75 tourists had to be rescued from the mountains using helicopters, and people from two localities had to be evacuated. Near its distal part, the flood damaged the facilities of the Caracoles power dam, which was under construction, and its inauguration had to be delayed one year due to the damage. The outburst flood produced changes in the morphology of the valley floor along almost all its path (erosion of alluvial fans, talus and terraces, and deposition of boulders). The most significant changes occurred in the first 70 km, especially upstream narrow sections, showing the importance of the backwater effects due to hydraulic ponding. In this work we carried out numerical simulations to obtain the velocity patterns of the flood, and compared them with those obtained from local reports. Furthermore, we analyze the relationship between the dynamics of the flood with the patterns of erosion and deposition near the source area.

  4. Analogue modeling of rotational orogenic wedges: implications for the Neogene structural evolution of the Southern Central Andes (33°-35°S)

    Herrera, S. S.; Farías, M.; Pinto, L.; Yagupsky, D. L.; Guzman, C.; Charrier, R.

    2017-12-01

    Structural evolution of the southernmost Central Andes is a major subject of debate. Overall vergence within the range and how intra-continental subduction prompts Andean orogeny are controversial topics. Between 33°-35° S, strike of the western slope main structures shifts southwards, from N-S to NNE-SSW, defining the Maipo Orocline. Likely, width of the Principal Cordillera increases southwards. Despite, a progressive southward decrease in orogenic volume has been determined for the segment. To understand such latitudinal variations, and to provide explanations for overall vergence, we carry out analogue models of contractional wedges to explore upper-crustal thrust system development with a progressive variation of the convergence vector. The model setup consisted of a fixed plate on which a mobile plate generated a velocity discontinuity. The upper-crust was simulated using low-cohesive quartz sand. The mobile plate was fixed at its northern end to a pivot, thus progressively incrementing shortening and the obliquity of convergence southwards. PIV photogrammetry recorded wedge evolution. A classical doubly-vergent wedge was formed, consisting of a steep 35° dipping, static thrust on the retro-side, an uplifted core, and an incipient forward-breaking, 25° critically tapered imbricated thrust fan on the pro-side, wider (in plan-view) where the imposed shortening reached the maximum. The resulting wedge is reminiscent of: the steep western Andean slope, in which the bordering thrust has maintained its present position during the Neogene; and the east-vergent fold-and-thrust belt of the eastern slope. The asymmetrical doubly vergence of the model suggests west-directed subduction of the South American continent beneath the orogen. The southward width increase is geometrically comparable to the natural analogue, yet we observe a flat contrast with orogenic shortening and volume estimates for the region. This can be attributed to the fact that uplift and erosion

  5. The Pliocene Horcón Formation, Central Chile: a case study of earthquake-induced landslide susceptibility

    Valdivia, D.; Elgueta, S.; Hodgkin, A.; Marquardt, C.; del Valle, F.; Yáñez Morroni, G.

    2017-12-01

    Stability slope analysis is typically focused on modeling using cohesion and friction angle parameters but in earthquake-induced landslides, susceptibility is correlated more to lithological and stratigraphic parameters. In sedimentary deposits whose cohesion and diagenesis are very low, the risk of landslides increases. The Horcón Formation, which crops out continuously along cliffs in Central Chile between 32.5° and 33°S, is a Miocene-Pliocene well preserved, horizontally stratified unit composed of marine strata which overlies Paleozoic-Mesozoic igneous basement. During the Quaternary, the sequence was tectonically uplifted 80 meters and covered by unconsolidated eolian deposits. Given that Seismotectonic and Barrier-Asperity models suggest the occurrence of a forthcoming megathrust earthquake in a segment which includes this area, the Horcón Formation constitutes a good case study to characterize the susceptibility of this type of sediment for mass movements triggered by earthquakes. Field mapping, stratigraphic and sedimentological studies, including petrographic analyses to determine lithological composition and paragenesis of diagenetic events, have been carried out along with limited gravimetric profiling and CPTU drill tests. High resolution digital elevation modeling has also been applied. This work has led to the recognition of a shallow marine lithofacies association composed of weakly lithified fossiliferous and bioturbated medium to fine grained litharenite, mudstone, and fine conglomerate. The low grade of diagenesis in the sedimentary deposits was in response to a short period of burial and a subsequent accelerated uplift evidenced along the coast of Chile during the Quaternary. We have generated a predictive model of landslide susceptibility for the Horcón Formation and for the overlying Quaternary eolian deposits incorporating variables such as composition and diagenesis of lithofacies, slope, structures, weathering and landcover. The model

  6. Dendrohydrology and water resources management in south-central Chile: lessons from the Río Imperial streamflow reconstruction

    Fernández, Alfonso; Muñoz, Ariel; González-Reyes, Álvaro; Aguilera-Betti, Isabella; Toledo, Isadora; Puchi, Paulina; Sauchyn, David; Crespo, Sebastián; Frene, Cristian; Mundo, Ignacio; González, Mauro; Vignola, Raffaele

    2018-05-01

    Streamflow in south-central Chile (SCC, ˜ 37-42° S) is vital for agriculture, forestry production, hydroelectricity, and human consumption. Recent drought episodes have generated hydrological deficits with damaging effects on these activities. This region is projected to undergo major reductions in water availability, concomitant with projected increases in water demand. However, the lack of long-term records hampers the development of accurate estimations of natural variability and trends. In order to provide more information on long-term streamflow variability and trends in SCC, here we report findings of an analysis of instrumental records and a tree-ring reconstruction of the summer streamflow of the Río Imperial ( ˜ 37° 40' S-38° 50' S). This is the first reconstruction in Chile targeted at this season. Results from the instrumental streamflow record ( ˜ 1940 onwards) indicated that the hydrological regime is fundamentally pluvial with a small snowmelt contribution during spring, and evidenced a decreasing trend, both for the summer and the full annual record. The reconstruction showed that streamflow below the average characterized the post-1980 period, with more frequent, but not more intense, drought episodes. We additionally found that the recent positive phase of the Southern Annular Mode has significantly influenced streamflow. These findings agree with previous studies, suggesting a robust regional signal and a shift to a new hydrological scenario. In this paper, we also discuss implications of these results for water managers and stakeholders; we provide rationale and examples that support the need for the incorporation of tree-ring reconstructions into water resources management.

  7. 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

    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

  8. 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

    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

  9. 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

    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

  10. Macrobenthic zonation caused by the oxygen minimum zone on the shelf and slope off central Chile

    Gallardo, V. A.; Palma, M.; Carrasco, F. D.; Gutiérrez, D.; Levin, L. A.; Cañete, J. I.

    2004-10-01

    The relationship between macrobenthic (⩾300 μm) zonation and the oxygen minimum zone (OMZ: O 2Chile. Four study sites were sampled during March-April 1999 for abiotic factors, macrofaunal density, biomass, mean individual size, and diversity. Within the OMZ (122-206 m), the macrofaunal density was high (16,478-21,381 individuals m -2) and 69-89% of the organisms were soft-bodied. Density was highest (21,381 individuals m -2), biomass lowest (16.95 g wet weight m -2), and individual size smallest (0.07 mg C individuals -1) at the shelf break site (206 m). Polychaete worms made up 71% of the total abundance, crustaceans 16%, and mollusks only 2%. Total abundance beneath the OMZ (mid-slope site, ˜840 m) was 49% crustaceans and 43% polychaetes. Although existing literature originally led to the hypothesis that both diversity and biomass within the OMZ would be lower than beneath the OMZ, in the present study this was only true for diversity. Biomass distribution, on the other hand, was concave along the depth gradient; the highest values were near the upper edge of (122 m) and beneath (840 m) the OMZ. Indices of the macrofaunal community structure varied in relation to bottom-water oxygen concentration, chlorophyll- a, phaeopigments, and sulfide concentration, but not in relation to grain size, C, N, mud, porosity, redox potential, a bottom-water temperature.

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

    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.

  12. Variaciones glaciales durante el Holoceno en Patagonia Central, Aisén, Chile: evidencias geomorfológicas Holocene glacial variations in Central Patagonia, Aisén, Chile: geomorphological evidences

    María Mardones

    2011-07-01

    Full Text Available Durante el Holoceno, avances y retrocesos glaciares geomorfológicamente registrados caracterizan la Patagonia. Este artículo presenta la evolución geomorfológica y las evidencias de fluctuaciones glaciales holocénicas de una región patagónica, que servirán de referencia para el estudio de la evolución paleoclimática Postglacial del extremo sur de Sudamérica. El área de trabajo es la cuenca del río Blanco (45°30'S, en la Patagonia Central (Región de Aisén, Chile. Dataciones radiométricas de sedimentos orgánicos de morrenas terminales aportan antecedentes preliminares de dos avances glaciares: el primero, representado por la morrena frontal del lago Elizalde, arroja una edad inferior a 9.370±50 años 14C AP (10.700 a 10.480 cal. años AP, lo que cronológicamente ubica este evento glaciar en el Holoceno Temprano. Esta progresión del hielo es 100 a 200 años más antigua que aquella observada inmediatamente al sur del área de estudio, en el margen oriental del lago General Carrera (o lago Buenos Aires en Argentina y aproximadamente 100 años más joven, que la registrada en la morrena de Puerto Banderas I (lago Argentino, 50°S. Este resultado sugiere un patrón de comportamiento de los glaciares de Patagonia Central diferente a aquel observado por otros investigadores en la Región de Los Lagos (41°S y en la Región de Magallanes (54°S, donde no se registran huellas de reavances glaciares durante el Holoceno Temprano. Luego de un importante retroceso hacia el oeste, un reavance glaciar más reciente se habría producido en el valle del río Quetro (afluente del río Blanco, a una edad inferior a 2.250±40 AP (2.340 a 2.150 cal. años AP, comparable con el estadio frío del Neoglacial Medio, verificado en distintos puntos de la Patagonia. Confrontando estos resultados con registros palinológicos previamente publicados por otros autores, interpretamos que las causas de ambas fluctuaciones glaciales son variaciones regionales

  13. Reabsorción de nitrógeno y fósforo foliar en árboles de bosques montanos en los Andes centrales de Colombia

    Miguel Vera

    1999-06-01

    Full Text Available Se determinaron las concentraciones y los porcentajes de reabsorción de nitrógeno y fósforo foliar en cinco especies de árboles de un bosque montano bajo (BMB a 1850 m.s.n.m. y en cinco de un bosque montano alto (BMA a 2800 m.s.n.m en la Cordillera Central colombiana, asi como la disponibilidad de nitrógeno y fósforo del suelo. Los porcentajes de reabsorción de N y P no fueron significativamente diferentes entre las especies de estos dos bosques. A pesar de esto, se observó que la reabsorción de P foliar tendió a ser mayor en las especies del BMB donde la concentración de P en el suelo fue significativamente más baja (3.2 ppm vs. 9.0 ppm. Cuando la reabsorción de P foliar se expresó como función de la concentración en hojas maduras en 12 tipos de bosques montanos tropicales, se encontró una correlación negativa y estadísticamente significativa. Estos resultados sugieren que los porcentajes de reabsorción de P foliar en bosques montanos estarían controlados parcialmente por la disponibilidad del elemento.Mature leaves and litterfall were collected between November 1992 and February 1993 from one to three individuals of five canopy tree species of a lower montane rain forest (LMRF at 1850 m. and five canopy tree species of an upper montane rain forest (UMRF at 2800 m. in the Central Andes of Colombia, to determine the concentrations and percentage retranslocation of nitrogen and phosphorus. The availability of these two nutrients was measured in the soils, by means of extracts of NH3-NH4, NO2-NO3 and PO4, and incubations of surface soil samples (0-10 cm to measure the rates of nitrogen mineralization and nitrification. In the species of the LMRF the average concentration of N in mature leaves (1.19 % dry weight and litterfall (0.87 % was significantly higher than in mature leaves (0.90 % and litterfall (0.59 % of the tree species of the UMRF. Percentage retranslocation of N and P were not significantly different between the

  14. Morphological evolution of the Maipo River in central Chile: Influence of instream gravel mining

    Arróspide, Felipe; Mao, Luca; Escauriaza, Cristián

    2018-04-01

    Instream gravel mining is one of the most important causes of channel degradation in South America, specifically in rivers located near large metropolitan areas with rapidly growing cities, where no river management strategies exist. In the western region of the continent, many of these rivers belong to Andean systems, in which significant parts of the watersheds are located in mountain areas at high altitude, with considerable seasonal rainfall variability and steep channel slopes. In these rivers, gravel mining has produced significant incision of the channels with serious physical and ecological consequences, affecting habitats, modifying the supply and transport of sediments, and amplifying the risk to infrastructure in and around the channel during floods. In spite of the degraded conditions of many channels, no quantitative studies of the geomorphic impacts of gravel mining have been carried out in the region, mostly because of the insufficient and sparse data available. In this investigation we perform an analysis of the morphodynamic evolution in a section of the Maipo River in the metropolitan region of Santiago, Chile. This river is economically the most important in the country, as it provides drinking and irrigation water to urban and rural areas, is utilized by the energy generation industry, and runs along and below critical infrastructure. We have collected and analyzed data from 1954 to 2015, during which the city population increased by more than 5 million inhabitants whose presence accelerated land use changes. The analysis shows a rapid morphological evolution of the channel where in 31 years effects such as: river sections showing incision of up to 20 m, an increase of the area affected by gravel mining from 86.62 to 368.13 ha, and a net erosion volume of 39.4 million m3 can be observed. This work yields quantitative information on the consequences of gravel mining in the Maipo River, providing the necessary data to develop an integrated

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

    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

  16. Operational Constraints on Hydropeaking and its Effects on the Hydrologic and Thermal Regime of a River in Central Chile

    Olivares, M. A.; Guzman, C.; Rossel, V.; De La Fuente, A.

    2013-12-01

    Hydropower accounts for about 44% of installed capacity in Chile's Central Interconnected System, which serves most of the Chilean population. Hydropower reservoir projects can affect ecosystems by changing the hydrologic regime and water quality. Given its volumen regulation capacity, low operation costs and fast response to demand fluctuations, reservoir hydropower plants commonly operate on a load-following or hydropeaking scheme. This short-term operational pattern produces alterations in the hydrologic regime downstream the reservoir. In the case of thermally stratified reservoirs, peaking operations can affect the thermal structure of the reservoir, as well as the thermal regime downstream. In this study, we assessed the subdaily hydrologic and thermal alteration donwstream of Rapel reservoir in Central Chile for alternative operational scenarios, including a base case and several scenarios involving minimum instream flow (Qmin) and maximum hourly ramping rates (ΔQmax). Scenarios were simulated for the stratification season of summer 2009-2012 in a grid-wide short-term economic dispatch model which prescribes hourly power production by every power plant on a weekly horizon. Power time series are then translated into time series of turbined flows at each hydropower plants. Indicators of subdaily hydrologic alteration (SDHA) were computed for every scenario. Additionally, turbined flows were used as input data for a three-dimensional hydrodynamic model (CWR-ELCOM) of the reservoir which simulated the vertical temperature profile in the reservoir and the outflow temperature. For the time series of outflow temperatures we computed several indicators of subdaily thermal alteration (SDTA). Operational constraints reduce the values of both SDHA and SDTA indicators with respect to the base case. When constraints are applied separately, the indicators of SDHA decrease as each type of constraint (Qmin or ΔQmax) becomes more stringent. However, ramping rate

  17. The invasive species Ulex europaeus (Fabaceae) shows high dynamism in a fragmented landscape of south-central Chile.

    Altamirano, Adison; Cely, Jenny Paola; Etter, Andrés; Miranda, Alejandro; Fuentes-Ramirez, Andres; Acevedo, Patricio; Salas, Christian; Vargas, Rodrigo

    2016-08-01

    Ulex europaeus (gorse) is an invasive shrub deemed as one of the most invasive species in the world. U. europaeus is widely distributed in the south-central area of Chile, which is considered a world hotspot for biodiversity conservation. In addition to its negative effects on the biodiversity of natural ecosystems, U. europaeus is one of the most severe pests for agriculture and forestry. Despite its importance as an invasive species, U. europaeus has been little studied. Although information exists on the potential distribution of the species, the interaction of the invasion process with the spatial dynamic of the landscape and the landscape-scale factors that control the presence or absence of the species is still lacking. We studied the spatial and temporal dynamics of the landscape and how these relate to U. europaeus invasion in south-central Chile. We used supervised classification of satellite images to determine the spatial distribution of the species and other land covers for the years 1986 and 2003, analysing the transitions between the different land covers. We used logistic regression for modelling the increase, decrease and permanence of U. europaeus invasion considering landscape variables. Results showed that the species covers only around 1 % of the study area and showed a 42 % reduction in area for the studied period. However, U. europaeus was the cover type which presented the greatest dynamism in the landscape. We found a strong relationship between changes in land cover and the invasion process, especially connected with forest plantations of exotic species, which promotes the displacement of U. europaeus. The model of gorse cover increase presented the best performance, and the most important predictors were distance to seed source and landscape complexity index. Our model predicted high spread potential of U. europaeus in areas of high conservation value. We conclude that proper management for this invasive species must take into account

  18. Nucleation process and dynamic inversion of the Mw 6.9 Valparaíso 2017 earthquake in Central Chile

    Ruiz, S.; Aden-Antoniow, F.; Baez, J. C., Sr.; Otarola, C., Sr.; Potin, B.; DelCampo, F., Sr.; Poli, P.; Flores, C.; Satriano, C.; Felipe, L., Sr.; Madariaga, R. I.

    2017-12-01

    The Valparaiso 2017 sequence occurred in mega-thrust Central Chile, an active zone where the last mega-earthquake occurred in 1730. An intense seismicity occurred 2 days before of the Mw 6.9 main-shock. A slow trench ward movement observed in the coastal GPS antennas accompanied the foreshock seismicity. Following the Mw 6.9 earthquake the seismicity migrated 30 Km to South-East. This sequence was well recorded by multi-parametric stations composed by GPS, Broad-Band and Strong Motion instruments. We built a seismic catalogue with 2329 events associated to Valparaiso sequence, with a magnitude completeness of Ml 2.8. We located all the seismicity considering a new 3D velocity model obtained for the Valparaiso zone, and compute the moment tensor for events with magnitude larger than Ml 3.5, and finally studied the presence of repeating earthquakes. The main-shock is studied by performing a dynamic inversion using the strong motion records and an elliptical patch approach to characterize the rupture process. During the two days nucleation stage, we observe a compact zone of repeater events. In the meantime a westward GPS movement was recorded in the coastal GPS stations. The aseismic moment estimated from GPS is larger than the foreshocks cumulative moment, suggesting the presence of a slow slip event, which potentially triggered the 6.9 mainshock. The Mw 6.9 earthquake is associated to rupture of an elliptical asperity of semi-axis of 10 km and 5 km, with a sub-shear rupture, stress drop of 11.71 MPa, yield stress of 17.21 MPa, slip weakening of 0.65 m and kappa value of 1.70. This sequence occurs close to, and with some similar characteristics that 1985 Valparaíso Mw 8.0 earthquake. The rupture of this asperity could stress more the highly locked Central Chile zone where a mega-thrust earthquake like 1730 is expected.

  19. Late magmatic stage of the zoned Caleu pluton (Central Chile): insights from zircon crystallization conditions

    Molina, P. G.; Parada, M.; Gutierrez, F. J.; Chang-Qiang, M.; Jianwei, L.; Yuanyuan, L.

    2012-12-01

    (IV)/Ce(III) decrease with temperature gives rise to separate trends for each zone, suggesting an independent unbuffered development at time of zircon formation. Taking into account variations in zircon ages, morphologies and crystallization ranges in the collected samples, it is suggested that zircon crystallization took place independent of the magma composition. Furthermore, old inherited zircon grains in the GDZ could be antecrysts, or products of a restricted and not major host rock assimilation, owing to the impossibility of basaltic magmas to saturate zircon crystals, and the isotopically depleted signature. This study is financed by CONICYT-FONDAP grant 15090013, Centro de Excelencia en Geotermia de los Andes (CEGA); and the CONICYT PBCT-PDA07, Programa Bicentenario de Ciencia y Tecnología.

  20. 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

    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

  1. Estimation of the fustal diameter on the central knotty cylinder in oak basal logs, Chile

    Patricio Corvalán Vera

    2018-01-01

    Full Text Available In order to determine the diameter of the central knotted cylinder both alive and dead, a total of 60 trees belonging to the upper quartile of diametric classes in unmanaged renewal of N. obliqua from the Maule foothills were sampled. It is assumed that these are determined by the lowest living and dead branch present in tree height, respectively. We analyzed the relationships between the diameter of the central knotty cylinder, and the diameters at the lower end of logs 1.2, 2.4 and 3.6 m above the stump, the normal diameter and the insertion height of the first branch. From the analysis it is deduced that: i the diameter of the live and dead central knotted cylinder increases linearly with the normal diameter of the tree, ii that the diameter at the smaller end of the logs increases as it does and decreases as increases in height above the ground and iii that the fustal diameter on the dead central knotty cylinder increases linearly with the normal diameter and the insertion height of the lowest dead branch of the tree, allowing to determine the zone of occlusion of the knots of the tree.

  2. Andes: An intelligent homework helper

    van de Sande, Brett; Vanlehn, Kurt; Treacy, Don; Shelby, Bob; Wintersgill, Mary

    2007-03-01

    Andes (www.andes.pitt.edu) is an intelligent tutor homework system designed for use as the homework portion of an introductory physics course. It encourages students to use good problem solving techniques and provides immediate feedback on each step of a problem solution along with hints on request. I will discuss how Andes works, from a student perspective, and present research demonstrating its effectiveness as a pedagogical tool. Then, I will discuss using Andes as a tool for conducting education research, briefly reviewing several studies conducted using Andes. Finally, I will show how logs of student solutions to Andes problems can be used to develop cognitive models of student learning.

  3. 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

    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

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

    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

  5. Caries experience and use of dental services in rural and urban adults and older adults from central Chile.

    Quinteros, Maria E; Cáceres, Dante D; Soto, Alex; Mariño, Rodrigo J; Giacaman, Rodrigo A

    2014-10-01

    To determine whether there is a relationship between the use of dental services and caries experience in adults and older adults from central Chile. A sample of 453 adults, 35-44 years of age, and 438 older adults, 65-74 years of age, was interviewed and examined using World Health Organisation (WHO) methods. Sociodemographic variables were also registered. Caries experience was assessed using the Decayed, Missing and Filled teeth (DMFT) index. Multiple linear regression models were used to determine whether there was an association between the independent variables and caries experience. Caries prevalence was 99.6% for adults [DMFT score = 14.89 (±6.16)] and 99.8% for older adults [DMFT score = 25.68 (±6.49)]. Less than half of the population - 41.7% of adults and 31.5% of older adults - received dental care. Regardless of the age group, there were no differences in the DMFT score between those who received and those who did not receive attention (P > 0.05). When the DMFT findings were analysed in greater detail, people who received dental care and urban participants had more fillings (P dental damage from caries. Although rurality and use of services do not seem to affect caries experience, they are associated with differences in fillings and missing teeth. © 2014 FDI World Dental Federation.

  6. Intraseasonal patterns in coastal plankton biomass off central Chile derived from satellite observations and a biochemical model

    Gomez, Fabian A.; Spitz, Yvette H.; Batchelder, Harold P.; Correa-Ramirez, Marco A.

    2017-10-01

    Subseasonal (5-130 days) environmental variability can strongly affect plankton dynamics, but is often overlooked in marine ecology studies. We documented the main subseasonal patterns of plankton biomass in the coastal upwelling system off central Chile, the southern part of the Humboldt System. Subseasonal variability was extracted from temporal patterns in satellite data of wind stress, sea surface temperature, and chlorophyll from the period 2003-2011, and from a realistically forced eddy-resolving physical-biochemical model from 2003 to 2008. Although most of the wind variability occurs at submonthly frequencies (< 30 days), we found that the dominant subseasonal pattern of phytoplankton biomass is within the intraseasonal band (30-90 days). The strongest intraseasonal coupling between wind and plankton is in spring-summer, when increased solar radiation enhances the phytoplankton response to upwelling. Biochemical model outputs show intraseasonal shifts in plankton community structure, mainly associated with the large fluctuations in diatom biomass. Diatom biomass peaks near surface during strong upwelling, whereas small phytoplankton biomass peaks at subsurface depths during relaxation or downwelling periods. Strong intraseasonally forced changes in biomass and species composition could strongly impact trophodynamics connections in the ecosystem, including the recruitment of commercially important fish species such as common sardine and anchovy. The wind-driven variability of chlorophyll concentration was connected to mid- and high-latitude atmospheric anomalies, which resemble disturbances with frequencies similar to the tropical Madden-Julian Oscillation.

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

    Zolezzi, J.M.; Garay, A.; Reveco, M.

    2010-01-01

    The energy proposal of this research suggests the use of places with abundant wind resources for the production of H 2 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 H 2 in the future. The study concludes that by the year 2030 the cost of the H 2 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 H 2 in a very competitive position as a fuel. (author)

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

    Barrena, J.; Nahuelhual, L.; Engler, A.; Echeverria, R.; Cofre, G.

    2013-06-01

    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. (Author) 40 refs.

  9. Environmental factors in infancy and ulcerative colitis in the Central South of Chile: a case-control study.

    Boneberger, Anja; Weiss, Eduardo Hebel; Calvo, Mario; Torres, Lilibeth; Wagner, Johanna; Kabesch, Michael; Radon, Katja

    2011-10-01

    Evidence for the role of the hygiene hypothesis and the development of Ulcerative Colitis (UC) is unclear. We aimed to explore the association between environmental factors in infancy and UC. A hospital-based case-control study (52 UC cases, response: 77%, 174 age- , sex and place of living matched controls, response: 62%) was carried out in the Central South of Chile in 2009/2010. Patients or parents underwent a personal interview about early life experiences. High paternal education (adjusted Odds Ratio (aOR): 2.1; 95% CI: 1.0-4.5) as proxy for socioeconomic status was positively associated with case status in the final multivariate logistic regression model. Likewise, having older siblings was a risk factor for UC (aOR: 2.2; 95%CI: 1.1.-4.4). The importance for some early life environmental factors in the development of UC was established. However, the role of the hygiene hypothesis could not be confirmed for all environmental factors. Copyright © 2011 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.

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

    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.

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

    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.

  12. Urban airborne matter in central and southern Chile: Effects of meteorological conditions on fine and coarse particulate matter

    Yáñez, Marco A.; Baettig, Ricardo; Cornejo, Jorge; Zamudio, Francisco; Guajardo, Jorge; Fica, Rodrigo

    2017-07-01

    Air pollution is one of the major global environmental problems affecting human health and life quality. Many cities of Chile are heavily polluted with PM2.5 and PM10, mainly in the cold season, and there is little understanding of how the variation in particle matter differs between cities and how this is affected by the meteorological conditions. The objective of this study was to assess the effect of meteorological variables on respirable particulate matter (PM) of the main cities in the central-south valley of Chile during the cold season (May to August) between 2014 and 2016. We used hourly PM2.5 and PMcoarse (PM10- PM2.5) information along with wind speed, temperature and relative humidity, and other variables derived from meteorological parameters. Generalized additive models (GAMs) were fitted for each of the eight cities selected, covering a latitudinal range of 929 km, from Santiago to Osorno. Great variation in PM was found between cities during the cold months, and that variation exhibited a marked latitudinal pattern. Overall, the more northerly cities tended to be less polluted in PM2.5 and more polluted in PMcoarse than the more southerly cities, and vice versa. The results show that other derived variables from meteorology were better related with PM than the use of traditional daily means. The main variables selected with regard to PM2.5 content were mean wind speed and minimum temperature (negative relationship). Otherwise, the main variables selected with regard to PMcoarse content were mean wind speed (negative), and the daily range in temperature (positive). Variables derived from relative humidity contributed differently to the models, having a higher effect on PMcoarse than PM2.5, and exhibiting both negative and positive effects. For the different cities the deviance explained by the GAMs ranged from 37.6 to 79.1% for PM2.5 and from 18.5 to 63.7% for PMcoarse. The percentage of deviance explained by the models for PM2.5 exhibited a

  13. Emission factors of particulate matter, polycyclic aromatic hydrocarbons, and levoglucosan from wood combustion in south-central Chile.

    Jimenez, Jorge; Farias, Oscar; Quiroz, Roberto; Yañez, Jorge

    2017-07-01

    In south-central Chile, wood stoves have been identified as an important source of air pollution in populated areas. Eucalyptus (Eucalyptus globulus), Chilean oak (Nothofagus oblique), and mimosa (Acacia dealbata) were burned in a single-chamber slow-combustion wood stove at a controlled testing facility located at the University of Concepción, Chile. In each experiment, 2.7-3.1 kg of firewood were combusted while continuously monitoring temperature, exhaust gases, burn rate, and collecting particulate matter samples in Teflon filters under isokinetic conditions for polycyclic aromatic hydrocarbon and levoglucosan analyses. Mean particulate matter emission factors were 2.03, 4.06, and 3.84 g/kg dry wood for eucalyptus, oak, and mimosa, respectively. The emission factors were inversely correlated with combustion efficiency. The mean emission factors of the sums of 12 polycyclic aromatic hydrocarbons in particle phases were 1472.5, 2134.0, and 747.5 μg/kg for eucalyptus, oak, and mimosa, respectively. Fluoranthene, pyrene, benzo[a]anthracene, and chrysene were present in the particle phase in higher proportions compared with other polycyclic aromatic hydrocarbons that were analyzed. Mean levoglucosan emission factors were 854.9, 202.3, and 328.0 mg/kg for eucalyptus, oak, and mimosa, respectively. Since the emissions of particulate matter and other pollutants were inversely correlated with combustion efficiency, implementing more efficient technologies would help to reduce air pollutant emissions from wood combustion. Residential wood burning has been identified as a significant source of air pollution in populated areas. Local wood species are combusted for home cooking and heating, which releases several toxic air pollutants, including particulate matter, carbon monoxide, and polycyclic aromatic hydrocarbons. Air pollutant emissions depend on the type of wood and the technology and operational conditions of the wood stove. A better understanding of emissions from

  14. K-Ar dating celadonite: A contribution to timing of a very low-grade metamorphism in the Central Andes of Chile

    Belmar, M; Schmidt, S.; Frey, M

    2001-01-01

    Clay minerals have been used in several studies to date very low-grade metamorphism processes and hydrothermal episodes. The technique of using the K-Ar isotopic dating was demonstrated by many authors (e.g. Hunziker et al., 1986; Clauer et al., 1995; Kirschner et al 1995; Zhao et al., 1997; Glasmacher et al., 2001). White mica and illitic materials of different size are usually analysed, whereasceladonite mineral with high potassium content has been low developed and few data are published. Successful dating of continental Andean celadonite could mean that is possible to date the very low-grade metamorphism (zeolites facies) in which celadonites are very often observed (au)

  15. Efectos del cambio climático sobre especies de plantas vasculares del sur de los Andes Centrales: un estudio en el noroeste de Argentina (NOA)

    Godoy Bürki, Ana Carolina

    2017-01-01

    La región de los Andes Tropicales es considerada como una región muy vulnerable al cambio climático porque presenta una alta diversidad y endemismo y porque posee una gran variabilidad altitudinal. Si bien se ha efectuado un gran número de predicciones sobre los cambios que ocurrirán en el clima, pocos estudios evaluaron el impacto que éste tendrá sobre las distribuciones de las especies. En este estudio se estima el efecto del cambio climático sobre la distribución y la conservación de espec...

  16. DISPERSION LARVAL Y PATRONES DE CONECTIVIDAD EN PECES LITORALES DE CHILE CENTRAL

    MANZUR, LIDIA ELENA

    2013-01-01

    En estudios de ecología marina, uno de los temas centrales es la conectividad o intercambio de individuos entre poblaciones marinas. Para muchas especies bentónicas con ciclos de vida complejo, este intercambio ocurre en los estadios larvales pelágicos. El pequeño tamaño de las larvas y su comportamiento, la dificultad en realizar seguimientos desde la eclosión de huevos hasta el asentamiento y las condiciones oceanográficas en las cuales se desarrollan estas especies, dificultan el entendimi...

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

    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 ...

  18. Tithonian age of dinosaur fossils in central Patagonian, Chile: U-Pb SHRIMP geochronology

    Suárez, Manuel; De La Cruz, Rita; Fanning, Mark; Novas, Fernando; Salgado, Leonardo

    2016-11-01

    Three Tithonian concordant U-Pb SHRIMP zircon ages of 148.7 ± 1.4, 147.9 ± 1.5 and 147.0 ± 1.0 from tuffs intercalated in a clastic sedimentary succession with exceptional dinosaur bones including the new taxon Chilesaurus diegosuarezi gen. et sp. nov. exposed in central Chilean Patagonia (ca. 46°30'S) are reported herein. The fossiliferous beds accumulated in a synvolcanic fan delta reaching a shallow marine basin as indicated by glauconite present in some of the beds, and coeval with the beginning of the transgression of the Aysén Basin.

  19. Evidence for an Early-Middle Miocene age of the Navidad Formation (central Chile: Paleontological, paleoclimatic and tectonic implications Evidencias de una edad miocena temprana-media de la Formación Navidad: Implicancias paleontológicas, paleoclimáticas y tectónicas

    Néstor M Gutiérrez

    2013-01-01

    Full Text Available The age of the Navidad Formation in central Chile has always been controversial, mainly due to the conflicting age ranges indicated by its macro- and microfossils. Macrofossils are generally interpreted as having been reworked from older, Early to Middle Miocene strata, whereas a Late Miocene-Pliocene age has been accepted on the basis of planktonic foraminifer index species. The results of this study, however, indicate that the macrofossils occur in situ, which necessitates a complete revision of the geochronological data. It is concluded that the evidence for an Early to Middle Miocene age is overwhelming, and that the planktonic foraminifer index species must have appeared in the SE Pacific earlier than elsewhere. These include Globoturborotalia apertura, Globorotalia puncticulata (Deshayes, Globorotalia spheriomizea (Walters, Neogloboquadrina pachyderma (Ehrenberg, and Neogloboquadrina acostaensis (Blow. An Early to Middle Miocene age for the Navidad Formation correlates well with a reinterpretation of its depo-sitional environment as a continental shelf instead of a deepwater continental slope, global and regional paleoclimatic events, and the tectonic development of the Andes Range.La edad de la Formación Navidad en Chile central siempre ha sido controversial, debido a los distintos rangos de edad indicados por los macro- y microfósiles. En general, se considera que los macro-fósiles han sido retrabajados de estratos del Mioceno Temprano a Medio, y se aceptó una edad miocena tardía para esta unidad sobre la base de especies indicadoras de foraminíferos planctónicos. Sin embargo, los resultados de este estudio indican que los macrofósiles ocurren in situ, lo cual hace necesario una revisión completa de los datos geocronológicos. Se concluye que la evidencia por una edad miocena temprana a media es contundente, y que los foraminíferos planctónicos que indicarían una edad miocena tardía aparecieron más temprano en el SE del oc

  20. 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

    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

  1. 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

    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

  2. Sr and Nd isotopic and trace element compositions of Quaternary volcanic centers of the Southern Andes

    Futa, K.; Stern, C.R.

    1988-01-01

    Isotopic compositions of samples from six Quaternary volcanoes located in the northern and southern extremities of the Southern Volcanic Zone (SVZ, 33-46??S) of the Andes and from four centers in the Austral Volcanic Zone (AVZ, 49-54??S) range for 87Sr 86Sr from 0.70280 to 0.70591 and for 143Nd 144Nd from 0.51314 to 0.51255. The ranges are significantly greater than previously reported from the southern Andes but are different from the isotopic compositions of volcanoes in the central and northern Andes. Basalts and basaltic andesites from three centers just north of the Chile Rise-Trench triple junction have 87Sr 86Sr, 143Nd 144Nd, La Yb, Ba La, and Hf Lu that lie within the relatively restricted ranges of the basic magmas erupted from the volcanic centers as far north as 35??S in the SVZ of the Andes. The trace element and Sr and Nd isotopic characteristics of these magmas may be explained by source region contamination of subarc asthenosphere, with contaminants derived from subducted pelagic sediments and seawater-altered basalts by dehydration of subducted oceanic lithosphere. In the northern extremity of the SVZ between 33?? and 34??S, basaltic andesites and andesites have higher 87Sr 86Sr, Rb Cs, and Hf Lu, and lower 143Nd 144Nd than basalts and basaltic andesites erupted farther south in the SVZ, which suggests involvement of components derived from the continental crust. In the AVZ, the most primitive sample, high-Mg andesite from the southernmost volcanic center in the Andes (54??S) has Sr and Nd isotopic compositions and K Rb and Ba La similar to MORB. The high La Yb of this sample suggests formation by small degrees of partial melting of subducted MORB with garnet as a residue. Samples from centers farther north in the AVZ show a regionally regular northward increase in SiO2, K2O, Rb, Ba, Ba La, and 87Sr 86Sr and decrease in MgO, Sr, K Rb, Rb Cs, and 143Nd 144Nd, suggesting increasingly greater degrees of fractional crystallization and associated intra

  3. Meteorological Conditions of Floods In The Chilean Andes Mountains

    Vergara, J.

    Catastrophic floods occurred on mountains River during 2000 and 2001. The meteo- rological conditions of flood during the last five years have analyzed. For example, the flood of June 29 of 2000 occurred after one of extremely wettest June of the last 40 years were snowfall was 991cm in the Aconcagua Valley. Infrequently storms activ- ity generated a huge snowfall and rainfall over the Andes mountains on June of 2000 (1525mm in El Maule Valley) and the end of the unusually period, the flood was trig- gered by rising temperatures on the mountains and heavy rain (199mm in 24 hours) fall over the fresh snow on the morning of June 29 and floods wave developed and moved down along of the all river located on Central part of Chile, the foods peak was 2970.5m3/s on the El Maule basin in the morning of June 29. The regional meteoro- logical models with the hydrological forecasting was used for alert of the floods.

  4. MORFOMETRÍA COMPARADA DE SEMILLAS DE NICOTIANA (SOLANACEAE E IDENTIFICACIÓN DE SEMILLAS CARBONIZADAS PROVENIENTES DE UN SITIO ARQUEOLÓGICO EN CHILE CENTRAL

    M. Teresa Planella

    2012-01-01

    Full Text Available La presencia frecuente de pipas para fumar en sitios arqueológicos del Período Alfarero Temprano deChile central y las evidencias en relación con la costumbre de fumar especies de Nicotiana halladas en sitios prehispánicos de otros lugares de las Américas, muestran la necesidad de contar con una metodología para identificar las especies de este género usadas en Chile. En este trabajo se ha realizado un estudio morfométrico en semillas de especies de Nicotiana que sirve de referencia para comparaciones con semillas de origen arqueológico. La forma y tamaño de la semilla, el patrón de ornamentación dado por las células epidérmicas y la ubicación del hilum resultaron ser caracteres relevantes para identificaciones confiables. Utilizando estos caracteres, se determinaron como N. corymbosa a las semillas recuperadas en el sitio arqueológico Las Morrenas 1, ubicado en Chile central.

  5. 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

    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

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

    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

  7. MUJER, TRABAJO Y FAMILIA. TENSIONES, RUPTURAS Y CONTINUIDADES EN SECTORES RURALES DE CHILE CENTRAL

    Julia Fawaz Yissi

    2012-01-01

    Full Text Available Este artículo examina la incorporación de la mujer rural al mercado laboral y sus efectos por un lado en las estructuras y dinámicas familiares y, por otro, en el mundo de las significaciones que mujeres rurales construyen en torno al trabajo, a los patrones de organización familiar y a la compatibilización trabajo/familia. El análisis combina una perspectiva estructural, a través de datos cuantitativos obtenidos de estadísticas oficiales y una encuesta a una muestra de mujeres rurales; y una perspectiva cualitativa, centrada en los significados construidos por ellas, información obtenida a través de grupos de discusión y entrevistas. Nuestra hipótesis postula que la creciente incorporación de la mujer rural al mundo del trabajo instala nuevas percepciones sobre los roles de género al interior de la familia y en la sociedad y nuevas concepciones de lo femenino, constituyendo así un factor central en la construcción de "nuevos" modelos familiares rurales y en la negociación de arreglos familiares más igualitarios.

  8. Numerical modeling perspectives on zircon crystallization and magma reservoir growth at the Laguna del Maule volcanic field, central Chile

    Andersen, N. L.; Dufek, J.; Singer, B. S.

    2017-12-01

    Magma reservoirs in the middle to upper crust are though to accumulate incrementally over 104 -105 years. Coupled crystallization ages and compositions of zircon are a potentially powerful tracer of reservoir growth and magma evolution. However, complex age distributions and disequilibrium trace element partitioning complicate the interpretation of the zircon record in terms of magmatic processes. In order to make quantitative predictions of the effects of magmatic processes that contribute reservoir growth and evolution—such as cooling and crystallization, magma recharge and mixing, and rejuvenation and remelting of cumulate-rich reservoir margins—we develop a model of zircon saturation and growth within a numerical framework of coupled thermal transfer, phase equilibrium, and magma dynamics. We apply this model to the Laguna del Maule volcanic field (LdM), located in central Chile. LdM has erupted at least 40 km3 of rhyolite from 36 vents distributed within a 250 km2 lake basin. Ongoing unrest demonstrates the large, silicic magma system beneath LdM remains active to this day. Zircon from rhyolite erupted between c. 23 and 1.8 ka produce a continuous distribution of 230Th-238U ages ranging from eruption to 40 ka, as well as less common crystal domains up to 165 ka and rare xenocrysts. Zircon trace element compositions fingerprint compositionally distinct reservoirs that grew within the larger magma system. Despite the dominantly continuous distributions of ages, many crystals are characterized by volumetrically substantial, trace element enriched domains consistent with rapid crystal growth. We utilize numerical simulations to assess the magmatic conditions required to catalyze these "blooms" of crystallization and the magma dynamics that contributed to the assembly of the LdM magma system.

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

    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.

  10. Seasonal and annual variation in Chilean hake Merluccius gayi spawning locations and egg size off central Chile

    Landaeta, Mauricio F.; Castro, Leonardo R.

    2012-01-01

    Variability in Chilean hake reproductive tactics off central Chile was assessed by analyzing ichthyoplankton samples from nine oceanographic cruises (1996-2005) and through experimental trials with early life stages (eggs, yolk-sac larvae) during the main (austral spring) and secondary (late summer-early autumn) spawning seasons. Abundant eggs in the plankton (1300-2000 eggs per 10 m 2) and historical adult reproductive data showed the highest reproductive activity in austral spring, with large egg aggregations near shelf break (50-100 m depth). Large, recently spawned eggs (1.15-1.20 mm diameter) were advected nearshore by coastward subsurface flows in the spring upwelling season. Experimental trials indicated that recently hatched larvae (3.4-3.5 mm) consumed their yolk-sac (0.17-0.41 mm 3) in 3-4 days at 10-12 °C; plankton sampling indicated that larval hake remained at mid-depth (50-100 m) without showing daily vertical migrations until completing their caudal fin formation (∼15 mm). During the secondary reproductive peak, hake spawned nearshore, when smaller eggs (0.95-1.13 mm) and recently hatched larvae (2.2-2.6 mm notochord length) occurred in surface waters (0-10 m depth). Their relatively large yolk-sac volumes (0.57 ± 0.11 mm 3) provided endogenous nourishment for at least 5 days at 10 °C, according to experiments. In the field, preflexion larvae occurred mainly in the mixed layer (0-25 m) and started ontogenetic daily vertical migrations at 7 mm. A strong decline occurred after 2002 in the adult Chilean hake biomass (estimated by hydroacoustic surveys) and body size, coinciding with variations in spawning locations (more coastward in early spring 2004 and 2005) and decline in egg size. Thus, recent variations in Chilean hake reproductive tactics may reflect an indirect effect of declines in the parental population size.

  11. How coastal upwelling influences spatial patterns of size-structured diversity of copepods off central-southern Chile (summer 2009)

    Hidalgo, Pamela; Escribano, Ruben; Fuentes, Marcelo; Jorquera, Erika; Vergara, Odette

    2012-01-01

    This study assessed the structure of the copepod community in the upper 200 m of the coastal upwelling region off central-southern Chile in late summer 2009. Vertically stratified zooplankton samples and hydrographic variables were obtained from 42 stations over the continental shelf and oceanic areas. The survey took place during active upwelling, reflected by a cold upwelling plume extending out to 150 km offshore. A total of 62 copepod species were found. Of these, Oithona similis and Paracalanusindicus accounted for ca. 60% of the whole community. Species richness ( R) and the Shannon-Wiener diversity index ( H‧) were estimated, and the latter was additionally modified to incorporate the effect of copepod size on diversity ( H‧ s). Samples were analyzed for two depth strata (0-50, 50-200 m) and for day vs. night conditions. Significant effects of day vs. night and strata on R, H‧ and H‧ s indicated that diel vertical migration between these two layers was an important source of variation in the zooplankton community. H‧ s seemed to represent copepod diversity better than R and H‧ over the spatial scale. H‧ s was also closely linked to colder upwelled water and the depth of the oxygen minimum zone following a principal component analysis. A positive relationship was even detected between depth of the oxygen minimum zone and H‧ s when strata and day/night effects were excluded. Our findings suggested that the coastal upwelling process could be an important driver of copepod diversity in this region. Upwelling leads to changes in the depth of the oxygen minimum zone and these changes impact the community composition due to species-dependent tolerances to low oxygen water.

  12. Temporal variability and phylogenetic characterization of planktonic anammox bacteria in the coastal upwelling ecosystem off central Chile

    Galán, Alexander; Molina, Verónica; Belmar, Lucy; Ulloa, Osvaldo

    2012-01-01

    The phylogenetic affiliation and temporal variability in the abundance of planktonic anammox bacteria were studied at a time-series station above the continental shelf off central Chile (∼36°S; bottom depth 93 m), a wind-driven, seasonal upwelling area, between August 2006 and April 2008. The study was carried out by cloning and sequencing the 16S rRNA gene and by using catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). Our results showed the presence of a single anammox bacteria-like ribotype during both upwelling and non-upwelling seasons, which was phylogenetically associated with a recently described oxygen-minimum-zone subcluster within the Candidatus Scalindua clade. Moreover, clear differences were observed in the temporal and vertical distribution of anammox cells. During the upwelling season (austral spring-summer), relatively high abundances (∼5500 cells mL -1) and large cells (0.8 μm 3-75.7 fg C cell -1) were found below 20 m depth. In contrast, during the non-upwelling season (austral fall-winter), lower abundances (∼600 cells mL -1) and smaller cells (0.1 μm 3-22.8 fg C cell -1) were found, predominantly associated with the bottom layer. Overall, our results indicate that the abundance and vertical distribution of anammox planktonic assemblages are related to the occurrence of seasonal, wind-driven, coastal upwelling, which in turn appears to offer favorable conditions for the development of these microorganisms. The dominance of a unique anammox bacteria-like ribotype could be related to the high environmental variability observed in the system, which prevents the establishment of other anammox lineages.

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

    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.

  14. Ammonium production off central Chile (36°S by photodegradation of phytoplankton-derived and marine dissolved organic matter.

    Angel Rain-Franco

    Full Text Available We investigated the production of ammonium by the photodegradation of dissolved organic matter (DOM in the coastal upwelling system off central Chile (36°S. The mean penetration of solar radiation (Z1% between April 2011 and February 2012 was 9.4 m, 4.4 m and 3.2 m for Photosynthetically Active Radiation (PAR; 400-700 nm, UV-A (320-400 nm and UV-B (280-320 nm, respectively. Ammonium photoproduction experiments were carried out using exudates of DOM obtained from cultured diatom species (Chaetoceros muelleri and Thalassiosira minuscule as well as natural marine DOM. Diatom exudates showed net photoproduction of ammonium under exposure to UVR with a mean rate of 0.56±0.4 µmol L(-1 h(-1 and a maximum rate of 1.49 µmol L(-1 h(-1. Results from natural marine DOM showed net photoproduction of ammonium under exposure to PAR+UVR ranging between 0.06 and 0.2 µmol L(-1 h(-1. We estimated the potential contribution of photochemical ammonium production for phytoplankton ammonium demand. Photoammonification of diatom exudates could support between 117 and 453% of spring-summer NH4(+ assimilation, while rates obtained from natural samples could contribute to 50-178% of spring-summer phytoplankton NH4(+ requirements. These results have implications for local N budgets, as photochemical ammonium production can occur year-round in the first meters of the euphotic zone that are impacted by full sunlight.

  15. 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

    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

  16. Different Phases of Earthquake Cycle Reflected in GPS Measured Crustal Deformations along the Andes

    Khazaradze, G.; Klotz, J.

    2001-12-01

    The South American Geodynamic Activities (SAGA) project was initiated in 1993 by the GeoForschungsZentrum together with host organizations in Argentina and Chile with the main objective of studying the kinematics and dynamics of present-day deformation processes along the central and southern Andes. Currently the SAGA network consists of 230 geodetic markers spanning more than 2000 km long distance from Peru/Chile border in the north to Cape Horn in the south. The majority of the observed crustal deformation field is relatively homogenous: roughly parallel to the plate convergence direction and decreasing in magnitude away from the deformation front. This pattern is characteristic for the \\textit{inter-seismic} phase of earthquake deformation cycle and can be explained by the elastic strain accumulation due to locking of the thrust interface between the subducting Nazca and the overriding South America plates. However, in addition to the dominant inter-seismic signal, close examination of the observed velocity field also reveals significant spatial and temporal variations, contrary to the commonly used assumption of constant deformation rates. This variation is especially pronounced for the measurements in the vicinity of the 1995 Mw8.0 Antofagasta earthquake (22{° }S-26{° }S). Here, after capturing up to 1 meters of \\textit{co-seismic} displacements associated with this event, the analysis of data obtained during the three following field campaigns (1996-1999), reveals highly time dependent deformation pattern. This can be explained by the decreasing importance of \\textit{post-seismic} effects of the Antofagasta event relative to the increasing dominance of the inter-seismic phase of subduction. Perhaps, even more interesting time dependent observations have been detected in the southern part the SAGA network (38{° }S-43{° }S).Here, after 35 years of the occurrence of the 1960 Mw9.5 Chile earthquake, we still see the continuing post-seismic effects of this

  17. Effects of seasonal variability in across- and alongshore transport of anchoveta ( Engraulis ringens) larvae on model-based pre-recruitment indices off central Chile

    Parada, Carolina; Colas, Francois; Soto-Mendoza, Samuel; Castro, Leonardo

    2012-01-01

    An individual-based model (IBM) of anchoveta ( Engraulis ringens) larvae was coupled to a climatological hydrodynamic (Regional Oceanic Modeling System, ROMS) model for central-southern Chile to answer the question as to whether or not across- and alongshore transport off central-southern Chile enhances retention in the spawning areas during the winter and summer reproductive periods, using model-based pre-recruitment indices (simulated transport success to nursery areas). The hydrodynamic model validation showed that ROMS captures the mean Seas Surface Temperature and Eddie Kinetic Energy observed in satellite-based data over the entire region. The IBM was used to simulate the transport of eggs and larvae from spawning zones in central Chile (Constitución, Dichato, Gulf of Arauco and Lebu-Corral) to historical nursery areas (HRZ, region between 35°S and 37°S). Model results corroborated HRZ as the most successful pre-recruitment zone (particles originated in the Dichato and Gulf of Arauco spawning areas), as well as identifying Lebu-Corral as a zone of high retention with a high associated pre-recruitment index (particles originated in the Lebu-Corral spawning zone). The highest pre-recruitment values were mainly found in winter. The Constitución and Dichato spawning zones displayed a typical summer upwelling velocity pattern, while the Gulf of Arauco in summertime showed strong offshore and alongshore velocity components. The Lebu-Corral region in winter presented important near-surface cross-shore transport towards the coast (associated with downwelling events), this might be one of the major mechanisms leading to high retention levels and a high pre-recruitment index for Lebu-Corral spawning zone. The limitations of the modeling approach are discussed and put into perspective for future work.

  18. Spatiotemporal variation patterns of plants and animals in San Carlos de Apoquindo, central Chile Patrones de variación espaciotemporal de plantas y animales en San Carlos de Apoquindo, Chile central

    FABIÁN M. JAKSIC

    2001-06-01

    Full Text Available I summarize what is known about the mediterranean ecosystem represented in San Carlos de Apoquindo (33º 23' S, 70º 31' W, a rugged area of 835 ha located ca. 20 km east of downtown Santiago on the Andean foothills. This site attracted numerous researchers during 1976-1990 because of its proximity to Santiago and its relatively protected status. I review the literature, and provide unpublished information on this site. A total of 132 literature entries describe the ecology of San Carlos de Apoquindo, in about 30 topics. The shrub and herbaceous vegetation have been well studied, but little is known about the respective seed banks. Among animals, small mammals, rabbits, and avian and mammalian predators are the best investigated, whereas epigean arthropods, amphibians, lizards, snakes, passerine birds, and scavengers of all types are the least studied. Thematically, interactions from plant/climate, to plant/soil, to plant/herbivore, to herbivore/predator interactions, and to decomposition of animal carcasses, have been addressed. But gross inequalities exist on the thoroughness with which each topic has been researched. The best studied aspects deal with plant/herbivore and herbivore/predator interactions. Up to now, no description existed of soils and climate in the area, which I present in this paper. Taking advantage of the long-term aspect of the research at the site, I highlight temporal variation patterns. And because of the different landscape aspects present at the site, I also highlight data that depict such spatial variability. In general, San Carlos de Apoquindo has contributed greatly to the understanding of ecological processes in central Chile. I call for renewed efforts at studying this site's ecology from an ecosystem perspectiveResumo lo que se conoce acerca del ecosistema mediterráneo representado en San Carlos de Apoquindo (33º 23' S, 70º 31' O, un área con alto relieve y de 835 ha localizada ca. 20 km al Este del centro

  19. 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

    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

  20. Construcción rural como representación. Infraestructura agrícola menor en el valle central de Chile

    Juan Paulo Alarcón

    2017-01-01

    Los gallineros, secadores de maíz, bodegas, caballerizas, etc. del valle central de Chile son construcciones menores que funcionan como infraestructuras que complementan la producción agrícola básica y de pequeña escala que allí se desarrolla con lo cual su resolución, que roza lo arcaico, está desprovista de un germen disciplinar. Estas construcciones, si bien pueden ser la culminación material de una idea, más bien se plantean como la representación en sí misma de un proyecto, en un es...

  1. Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile

    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

  2. Combined impact of ocean acidification and corrosive waters in a river-influenced coastal upwelling area off Central Chile

    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

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

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

    2008-02-01

    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 elemental sulfur, were analyzed at high resolution in the top 20 cm. All stations were characterized by high rates of sulfate reduction, but only the sediments within the Bay of Concepción contained dissolved sulfide. Due to advection and/or in-situ reoxidation of sulfide, dissolved sulfate was close to bottom water values. Whereas the concentrations of sulfite and thiosulfate were mostly in the submicromolar range, elemental sulfur was by far the dominant sulfur intermediate. Although the large nitrate- and sulfur-storing bacteria Thioploca were abundant, the major part of S 0 was located extracellularly. The distribution of sulfur species and dissolved iron suggests the reaction of sulfide with FeOOH as an important pathway for sulfide oxidation and sulfur intermediate formation. This is in agreement with the sulfur isotope composition of co-existing elemental sulfur and iron monosulfides. In the Bay of Concepción, sulfur isotope data suggest that pyrite formation proceeds via the reaction of FeS with polysulfides or H 2S. At the shelf stations, on the other hand, pyrite was significantly depleted in 34S relative to its potential precursors FeS and S 0. Isotope mass balance considerations suggest further that pyritization at depth includes light sulfide, potentially originating from bacterial sulfur disproportionation. The δ 34S-values of pyrite down to -38‰ vs. V-CDT are among the lightest found in organic-rich marine sediments. Seasonal variations in the sulfur isotope composition of dissolved sulfate indicated a dynamic non-steady-state sulfur cycle in the surface sediments. The 18O content of porewater sulfate increased with depth at all sites compared to the

  4. Decision analysis applied to the fishery of the sea snail Concholepas concholepas from central northern coast of Chile

    Tam, J.; Palma, W.; Riofrio, M.; Aracena, O.; Lepez, M.I.

    1996-01-01

    Formal decision analysis was applied to the management of loco (Concholepas concholepas, Fam. Muricidae) in Chile, 29-35 degrees S. Four interested groups were considered "Fishers", "Scientists", "Buyers" and the "State", along with three fishing effort levels and four subobjectives. The method was found to encourage the emergence of a consensus (here: halving of effort), and is recommended for use in other fisheries.

  5. Future Temperatures and Precipitations in the Arid Northern-Central Chile: A Multi-Model Downscaling Approach

    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

  6. Fires in Chile

    2002-01-01

    On February 5, 2002, the dense smoke from numerous forest fires stretched out over the Pacific Ocean about 400 miles south of Santiago, Chile. This true-color Moderate-resolution Imaging Spectroradiometer (MODIS) image shows the fires, which are located near the city of Temuco. The fires are indicated with red dots (boxes in the high-resolution imagery). The fires were burning near several national parks and nature reserves in an area of the Chilean Andes where tourism is very popular. Southeast of the fires, the vegetation along the banks of the Rio Negro in Argentina stands out in dark green. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  7. 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

    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

  8. Flaxseed Response To N, P, and K Fertilization in South Central Chile Respuesta a la Fertilización N, P y K en Lino Oleaginoso en la Zona Centro Sur de Chile

    Marisol Berti

    2009-06-01

    Full Text Available Flaxseed (Linum usitatissimum L. is a minor crop in Chile. There is interest to increase the number of crops on the current rotation in South Central Chile and also to increase oilseed feedstocks for salmon feed. There is little information published about seed yield and oil content response to N, P, and K fertilizers on flaxseed in Chile. The objective of this study was to determine the effect of N, P, and K fertilization on flaxseed yield, oil content, and composition. The study was conducted at two locations during two growing seasons (environments, in Chillán 2004-2005, 2005-2006, and in Osorno 2004-2005, 2006-2007. Treatments were four levels of N (0, 100, 200, and 300 kg N ha-1, three levels of P (0,100, and 200 kg P2O5 ha-1, and two levels of K (0 and 150 kgK2O ha-1. The design was a randomized complete block with a factorial arrangement of three factors (N, P, and K and four replicates. According to the results, flaxseed yield improved as N rates increased. Physical optimum rate (rate at which maximum seed yield is obtained was different depending on the location and year. Nitrogen rate increased oil content and yield up to 200 kg N ha-1. Oil composition was not affected by N, P, and K rates, or their interactions. The P and K nutrients did not have an effect on seed yield, oil content, oil yield, and oil composition.El lino oleaginoso (Linum usitatissimum L. es un cultivo menor en Chile. En la zona centro sur existe interés por ampliar las alternativas para la rotación de cultivos, así como la necesidad de satisfacer la demanda por semillas oleaginosas para la alimentación de salmones. En Chile no hay información relacionada con la respuesta del lino frente a la fertilización. El objetivo del estudio fue evaluar el efecto de N, P y K sobre el rendimiento de semillas y contenido de aceite en lino cultivado en dos localidades: Chillán (temporadas 2004-2005 y 2005-2006 y Osorno (temporadas 2004-2005 y 2006-2007 (ambientes. Los

  9. Magellanic Woodpeckers in three national parks of central-southern Chile: habitat effects and population variation over the last two decades

    Pablo M. Vergara

    2017-12-01

    Full Text Available A major challenge for protected areas is providing wildlife with enough suitable habitat to cope with stochastic environment and increased pressure from the surrounding landscapes. In this study, we addressed changes in local populations of Magellanic Woodpeckers (Campephilus magellanicus occupying three national parks of central-southern Chile. We compared the breeding and postbreeding abundance of woodpeckers during the 1990s with the present (2016 abundance (n = 4 years, and assessed the extent to which abundance was explained by forest type and quality of foraging habitat (as quantified through the plant senescence reflectance index; PSRI. Results show a distinctive temporal variation in woodpecker abundance at each park, with local populations of Magellanic Woodpeckers declining by 42.2% in Conguillío National Park, but increasing by 34.3% in Nahuelbuta National Park. Woodpeckers responded to forest conditions within each park such that their abundance increased with high quality of foraging habitat, i.e., large PSRI values, and the presence of old-growth Monkey puzzle (Araucaria araucana - Nothofagus pumilio mixed forest. Anecdotal evidence suggests that populations of woodpeckers in Conguillío National Park might have responded negatively to large-scale disturbances from recent forest fires affecting part of the forest area within park. Because stochastic events seemed to strongly mediate population changes, our findings suggest that regional conservation of Magellanic Woodpeckers requires expanding the current conservation area network in central-southern Chile.

  10. Presencia de Antifer ultra Ameghino (=Antifer niemeyeri Casamiquela (Artiodactyla, Cervidae en el Pleistoceno tardío-Holoceno temprano de Chile central (30-35°S Presence of Antifer ultra Ameghino (=Antifer niemeyeri Casamiquela in the late Pleistocene-early Holocene of Central Chile (30-35°S

    Rafael Labarca E

    2011-01-01

    Full Text Available El presente trabajo discute el estatus taxonómico de la especie Antifer niemeyeri Casamiquela, 1984, definida a partir de astas completas procedentes de la laguna Taguatagua y la quebrada de Quereo (Pleistoceno tardío-Holoceno temprano, en Chile central (30-35°S. Se concluye, a partir de un estudio morfológico y morfométrico detallado, que Antifer niemeyeri debe ser considerado sinónimo de Antifer ultra Ameghino, 1889 dados los caracteres anatómicos compartidos con esta especie. Los resultados amplían la distribución geográfica del taxón, que previamente se registraba en Argentina, Uruguay y sur de Brasil, y confirman su biocrón para el Pleistoceno tardío-Holoceno temprano (edad Lu-janense, aun cuando las fechas radiocarbónicas de Chile central (ca. 9.900 años 14C AP corresponden a las más tardías para la especie. A la luz de la evidencia paleoclimática disponible, se vincula A ultra durante el Pleistoceno de Chile central a ambientes cálidos y abiertos. Considerando estos requerimientos, se discute su posible vía de ingreso al actual territorio chileno a través de corredores ubicados hacia el sur del macizo andino, y su coexistencia con Hippocamelus bisulcus Molina, 1782. De acuerdo a la información estratigráfica y paleoambiental, se postula que ambas especies habrían sido alopátridas, por lo menos en el área de estudio.This paper discusses the taxonomic status of Antifer niemeyeri Casamiquela, 1984, defined from complete antlers from Taguatagua lake and Quereo canyon, both located in central Chile (30-35°S. From a detailed morphological and moiphometrical study, it is concluded that Antifer niemeyeri should be considered synonymous with Antifer ultra Ameghino, 1889, due to the anatomical characters shared between both forms. These results expand the geographical distribution of this taxa previously recorded in Argentina, Uruguay and southern Brazil, confirming their late Pleistocene-early Holocene biochron, in spite

  11. Influence of inherited structures on the growth of basement-cored ranges, basin inversion and foreland basin development in the Central Andes, from apatite fission-track and apatite Helium thermochronology.

    Zapata, S.; Sobel, E. R.; Del Papa, C.; Jelinek, A. R.; Muruaga, C.

    2017-12-01

    The Central Andes in NW of Argentina is part of a long-lived subduction zone, active since the Paleozoic. This region experienced several tectonic cycles; each of which created an unique set of structures and may have reactivated preexisting structures. These inherited structures may exert a first-order control over the different foreland deformational styles observed along the strike in the Central Andes. Our study area is located between 26°S and 28°S on the transition between the broken foreland (Santa Barbara system), which expresses a combination of thin-skin and thick-skin styles, and the Sierras Pampeanas, which is deform in a thick-skin style. The Cumbres Calchaquies range and the associated Choromoro Basin are located in the northern part of the study area, and are the southern expression of the Santa Barbara system. Published thermochronology data suggest that the rocks from the basement experienced Late Cretaceous and Late Miocene exhumation; the associated sedimentary rocks within the Choromoro basin experienced Paleogene and Late Miocene deformational phases. In contrast, the Sierra Aconquija range, located immediately south on the transition to the Sierras Pampeanas (thick skin) foreland basin, exhibit larger amounts of Miocene exhumation and lack of Cretaceous exhumation; the associated sedimentary rocks from the Tucuman basin have not been deformed since the Cretaceous. Our goal is to understand the evolution of the structural blocks and the structures responsible for the along strike changes in foreland basin deformational styles and their relation with inherited structures from previous tectonic cycles. We are obtaining new apatite U-Th/He and fission track data to reconstruct the thermal history of the basement, accompanied by U-Pb geochronology and stratigraphy to constrain the evolution of the associated sedimentary basins. Preliminary results combined with published data suggest that inherited structures within the study area have evolved

  12. Delineation of the High Enthalpy Reservoirs of the Sierra Nevada Volcanic Geothermal System, South-Central Chile

    Alam, M.; Muñoz, M.; Parada, M.

    2011-12-01

    Geothermal system associated with the Pleistocene-Holocene Sierra Nevada volcano (SNVGS) in the Araucanía Region of Chile has surface manifestations from the north-western flank of the volcano, up to Manzanar and Malalcahuello. Baños del Toro, located on the northwestern flank of the volcano, has numerous fumaroles and acid pools (acid sulfate waters, T=~90°C, pH=2.1, TDS=3080 mg/L); while Aguas de la Vaca, near the base of the volcano, has a bubbling spring (chloride-sulfate waters, T=~60°C, pH=7.0, TDS=950 mg/L). Five shallow (Geotermia) of the Ministry of Energy and Mining, Government of Chile.

  13. Infrastructure development and agricultural exposure to climate variability and change: lessons from the Limarí basin in Central Chile

    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

  14. The genus Callophyllis (Kallymeniaceae, Rhodophyta from the central-south Chilean coast (33° to 41° S, with the description of two new species El género Callophyllis (Kallymeniaceae, Rhodophyta de la costa central y sur de Chile (33° a 41° S, con la descripción de dos nuevas especies

    NATALIA ARAKAKI

    2011-12-01

    Full Text Available The taxonomic status of the species in the genus Callophyllis Kützing (Kallymeniaceae, Rhodophyta from central-south Chile (33° to 41° S is examined on the basis of morphological and molecular evidence. Of the four species originally cited for central Chile, C. variegata, C. pinnata, C. atrosanguinea and C. laciniata, only the presence of C. variegata has been confirmed in this study. C. pinnata reported from Chile is found to be different from C. pinnata described from California, and it is here newly described as C. concepcionensis sp. nov. C. atrosanguinea from southern Chile (including C. linguata from the Antarctic Peninsula is distinct from the species called C. atrosanguinea from central-south Chile, the latter which is here described as C. macrostiolata sp. nov. C. variegata, C. concepcionensis and C. macrostiolata are distinguished from one another by their external habit, the nature and distribution of their cystocarps, and the female reproductive morphology. Comparative rbcL sequence analysis corroborates the distinction of these taxa from central-south Chile and their relationships to other species worldwide.Se examina el estatus taxonómico de las especies del género Callophyllis Kützing (Kallymeniaceae, Rhodophyta de la costa centro-sur de Chile (33° a 41° S en base a caracteres morfológicos y moleculares. De las cuatro especies citadas para Chile central, C. variegata, C. pinnata, C. atrosanguinea y C. laciniata, solo la presencia de C. variegata ha sido confirmada en este estudio. C. pinnata de Chile muestra diferencias con C. pinnata descrita para California y con el resto de las especies de Callophyllis hasta ahora conocidas, constituyendo así una nueva especie, C. concepcionensis sp. nov. C. atrosanguinea del sur de Chile (incluyendo C. linguata de la Península Antártica muestra diferencias con la especie llamada C. atrosanguinea de la costa centro-sur de Chile, esta última especie es descrita como C. macrostiolata

  15. 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

    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.

  16. Patrón de actividad y abundancia de aves en un relleno sanitario de Chile central Abundance and activity-pattern of birds at a landfill in central Chile

    GABRIEL LOBOS; PATRICIO BOBADILLA; ALEJANDRA ALZAMORA; ROBERTO F THOMSON

    2011-01-01

    Los rellenos sanitarios constituyen un foco de atracción para la avifauna, aunque las implicancias de esta relación no han sido exploradas en el país. Nosotros monitoreamos la actividad de aves en un relleno sanitario ubicado en las proximidades de la ciudad de Santiago, capital administrativa de Chile. Las principales aves en el área fueron la gaviota dominicana (Larus dominicanus Lichtenstein), el tiuque (Milvago chimango Vieillot), la garza boyera {Buculbus ibis Linnaeus) y el águila (Gera...

  17. 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

    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.

  18. Development and implementation of a monitoring and information system to increase water use efficiency in arid and semi-arid areas in Limarí, Central Chile (WEIN

    E. Berger

    2016-10-01

    Full Text Available The project WEIN was funded by the Federal Ministry of Education and Research (BMBF | Berlin, Germany in the framework of the high-tech strategy of Germany's program "KMU-Innovativ". The project started in 2012 and was completed in 2014. In the scope of the project, an integrated system for analysis, monitoring and information at river basin level was developed, which provides relevant information for all stakeholders that are concerned with water resource issues. The main objective of the project was to improve water use efficiency and hence ensure the agricultural production in the region. The pilot region, in which this system was implemented, is the semi-arid Limarí basin in Northern Central Chile. One of the main parts of the project was the development and implementation of a web- and app-based irrigation water ordering and accounting system for local farmers.

  19. Aucas en la ciudad de Santiago. La rebelión mapuche de 1723 y el miedo al «otro» en Chile central

    Contreras Cruces, Hugo

    2013-06-01

    Full Text Available Within the context of the so-called indigenous rebellion in 1723, this article reconstructs the actions carried out to suppress an alleged rebel attack on the city of Santiago in October of that year, an attack which never occurred, but nevertheless brought to jail over one hundred Indians, inhabitants of the nearby city areas, and most of whom were immigrants who had come from the border of the river Biobio or from within the Araucania. This process is studied from the perspective of fear of the «other» who was in this case an indigenous migrant carrying language, customs and religion all of which were mostly incomprehensible to the hispanocriollos of central Chile, thereby making them immediately to appear suspicious and be referred to as «Auca», or rebel.En el contexto de la llamada rebelión general indígena de 1723, este artículo reconstituye las acciones llevadas a cabo para reprimir un supuesto ataque rebelde a la ciudad de Santiago en octubre de dicho año, el cual nunca llegó a realizarse, pero que llevó a la cárcel a más de una centena de indios que habitaban en las cercanías de la ciudad, la mayoría de los cuales eran inmigrantes venidos de la frontera del río Biobío o desde el interior de la Araucanía. Dicho proceso se estudia desde la perspectiva del miedo al «otro», en este caso al indígena migrante, portador de un idioma, costumbres y una religiosidad mayormente incomprensibles para los hispanocriollos de Chile central, lo que los convertía inmediatamente en sospechosos y se les calificaba como «aucas» o rebeldes.

  20. Precipitation history of the central Atacama Desert since the Miocene as reconstructed from clay pan records of the Costal Cordillera/ N Chile

    Wennrich, V.; Melles, M.; Diederich, J. L.; Fernández Galego, E.; Ritter, B.; Brill, D.; Niemann, K.; Rolf, C.; Dunai, T. J.

    2017-12-01

    Hyperaridity is a major limitation of Earth-surface processes and biological activity in the Atacama Desert of N Chile, one of the oldest and the driest deserts on Earth. But even the hyperarid core of the Atacama Desert of N Chile has experienced sever precipitation events, e.g., during the flash floods in 2015. On geological timescales, the overall aridity that is postulated to have lasted at least since the early Miocene was punctuated by distinct pluvial events. Such wetter conditions, e.g. during the Miocene, caused widespread lake-formation in the Central Depression and Coastal Cordillera, but also caused amplified surface processes, changes in vegetation dynamics, and enabled the dispersal of species. Unfortunately, due to the limited number and heterogeneous appearance of climate archives from the central Atacama, it's longer-scale precipitation history is still a matter of controversy. This study aims to study continuous longterm (Pleistocene-Miocene) paleoclimatic and environmental records from the hyperarid core of the Atacama Desert covering the last >10 Ma. Therefor we investigate clay pans records from endorheic basins in the Coastal Cordillera mostly formed by blocking of drainage by tectonic movement. The clay pans under study are located along a latitudinal transect across the hyperarid core of the Atacama, and thus, are assumed to have recorded local and regional precipitation variations on different timescales. The investigated sequences exhibit significant changes in the sedimentological, geochemical, and mineralogical properties due to changes in precipitation, but also in the weathering and erosion in the catchments. Diatom and phytolith remains preserved in these records clearly point to significant water bodies during the wettest periods and a significant vegetation cover. The results shed a new light on the timing, frequency, and the driving mechanisms of the intervening pluvial phases.

  1. Construcción rural como representación. Infraestructura agrícola menor en el valle central de Chile

    Juan Paulo Alarcón

    2017-11-01

    Full Text Available Los gallineros, secadores de maíz, bodegas, caballerizas, etc. del valle central de Chile son construcciones menores que funcionan como infraestructuras que complementan la producción agrícola básica y de pequeña escala que allí se desarrolla con lo cual su resolución, que roza lo arcaico, está desprovista de un germen disciplinar. Estas construcciones, si bien pueden ser la culminación material de una idea, más bien se plantean como la representación en sí misma de un proyecto, en un estado pendiente de resolución, que se ha ido forjando generación tras generación. Esparcidas en el territorio, representan tanto el carácter agrícola de la zona, como la inteligencia desplegada a lo largo del tiempo, determinada por las condiciones geográficas, culturales y sociales, en un contexto de escasez. Si bien tiene antecedentes en las edificaciones residenciales primitivas, se origina como tipo en la reforma agraria, cuando se reparten las tierras en superficies pequeñas que promueven el desarrollo de la agricultura menor. Las construcciones rurales en el valle central de Chile son en sí mismo la representación de su proyecto y, como manifestaciones, representan una actividad comunal, un territorio, un paisaje, un modelo económico, un ideal político.

  2. Contrasting Climate Change Impact on River Flow from Glacierised Catchments in the Himalayan and Andes Mountains

    Pellicciotti, F.; Ragettli, S.; Immerzeel, W. W. W.

    2016-12-01

    Glaciers and glacierised catchments in mountainous regions react to a changing climate in different manners depending on climate and glacier characteristics. Despite the key role of mountain ranges as natural water towers, their hydrological balance and future changes in glacier runoff associated with climate warming remain poorly understood because of high meteorological variability, physical inaccessibility and the complex interplay between climate, cryosphere and hydrological processes. We use a state-of-the art glacio-hydrological model informed by data from high altitude observations and the latest CMIP5 climate change scenarios to quantify the climate change impact on glaciers and runoff for two contrasting catchments vulnerable to changes in the cryosphere. The two catchments are located in the Central Andes of Chile and in the Nepalese Himalaya in close vicinity of densely populated areas. Although both sites are projected to experience a strong decrease in glacier area, they show remarkably different hydrological responses. Icemelt is on a rising limb in Langtang at least until 2041-2050 and starts to decrease afterwards, while in Juncal icemelt was already beyond its tipping point at the beginning of the 21st century. This contrasting response can be explained by differences in the elevation distribution of the glaciers in the two regions. In Juncal, many glaciers are melting up to the highest elevations already during the reference period (2000-2010) and increasing melt rates due to higher air temperatures cannot compensate the loss of glacier area. In Langtang, large sections of the glaciers at high elevations are currently not exposed to melt, but will be in the future, thus compensating for the loss of glacier area at lower elevations. As a result of these changes and projected changes in precipitation, in Juncal runoff will sharply decrease in the future and the runoff seasonality is sensitive to projected climatic changes. In Langtang, future water

  3. 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

    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.

  4. 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

    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

  5. On the intraspecific variation in morphometry and shape of sagittal otoliths of common sardine, Strangomera bentincki, off central-southern Chile

    Sandra Curin-Osorio

    2012-11-01

    Full Text Available Size and shape of fish otoliths are species-specific, but some species also display intraspecific variations. The common sardine, Strangomera bentincki, is a small pelagic fish inhabiting a seasonal upwelling ecosystem off central-southern Chile, having two discrete spawning sites along its latitudinal distribution. Otoliths of specimens were collected from commercial catches in Talcahuano and Corral, representing the central and south spawning zones. On the basis of otolith images, size-based shape descriptors were used to detect ontogenetic variation, and morphometric variables (length, breadth, area, perimeter and weight were used to detect geographical differences in size and shape of otoliths. Outline analysis was studied on the basis of elliptic Fourier descriptors through multivariate statistical procedures. Size-based shape descriptors showed that otolith shape starts to be stable for fish larger than 12 cm total length, which keep an elliptical form. Morphometric variables for fish larger than 12 cm revealed intraspecific variation between central and south zones, which were associated with otolith weight and breadth. Outline analysis did not reveal significant spatial differences, but extreme intraspecific variation was due to the antirostrum, excisure, and posterior part of otoliths. Intraspecific variation in otolith size could be linked to differences in each spawning habitat and related to geographical origin, whose differences are not clearly identified. It is concluded that intraspecific variability in morphometric variables of sardine otoliths revealed geographic differences in size that are not attributable to allometric effects, and that otolith shape was similar between specimens from different geographic origin.

  6. Volcanic deformation in the Andes

    Riddick, S.; Fournier, T.; Pritchard, M.

    2009-05-01

    We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

  7. Patrón de actividad y abundancia de aves en un relleno sanitario de Chile central Abundance and activity-pattern of birds at a landfill in central Chile

    GABRIEL LOBOS

    2011-03-01

    Full Text Available Los rellenos sanitarios constituyen un foco de atracción para la avifauna, aunque las implicancias de esta relación no han sido exploradas en el país. Nosotros monitoreamos la actividad de aves en un relleno sanitario ubicado en las proximidades de la ciudad de Santiago, capital administrativa de Chile. Las principales aves en el área fueron la gaviota dominicana (Larus dominicanus Lichtenstein, el tiuque (Milvago chimango Vieillot, la garza boyera {Buculbus ibis Linnaeus y el águila (Geranoaetus melanoleucus Swann. La gaviota dominicana alcanzó los valores de abundancia más altos (entre 358 y 1950 individuos por día y destacó por su comportamiento bimodal, directamente relacionado con los niveles de operación en el relleno sanitario. En el caso del águila se registró una conducta carroñera cleptoparásita sobre los tiuques, estos últimos seleccionan desechos orgánicos (pescados, tripas, carne, que les son usurpados por ellas. Finalmente señalamos medidas simples de manejo que deberían disminuir los números de aves en este tipo de actividad industrial.Landfills are considered an attractive habitat for several bird species; however, implications of this condition have not yet been explored in the country. We monitored birds' activity patterns that use a landfill located in the vicinity of Santiago, Chile's capital. Main birds recorded in the area were, Kelp gull (Larus dominicanus Lichtenstein, Chimango caracara (Milvago chimango Vieillot, Cattle egret (Buculbus ibis Linnaeus and Black Chested Eagle (Geranoaetus melanoleucus Swann. Kelp Gull was the most abundant species, (with values between 358 to 1950 individuals per day and that also displayed a bimodal behavior linked directly to the landfill operation levels. In the case of Black Chested Eagle, we observed a kleptoparasitic behavior over Chimango Caracara which selected organic offal (fishes, innards, meat for its feeding and that are stolen by the eagle. Finally we

  8. 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

    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

  9. The Glaciation of the Ecuadorian Andes

    Schubert, Carlos

    This pleasing book fills the gap in the knowledge about Pleistocene and recent glaciation between Colombia and Peru. A significant amount of data exists already for Colombia and Venezuela and for Peru, Bolivia, and, particularly, Chile. Hastenrath has now given us a description of glaciers and glaciation underneath the equator in the Andes.The book begins with brief summaries of the physiography and the atmospheric circulation, which give the general setting of Ecuador. Then follow detailed descriptions of the glaciers and glacial morphology of all the important mountains of the Western and Eastern Cordilleras. These are well illustrated, and a particularly useful feature is the comparison of old photographs and paintings of glaciers with modern photographs, many taken by the author. All illustrate the spectacular retreat of the glaciers in the Ecuadorian Andes during the last century and correlate quite well with observations elsewhere. This retreat is snown quantitatively in Table 4, in terms of decrease in glacier-covered area since the glacial advance of moraine stage III. The area of present-day glaciers is about 10% of the area during that stage (compared with about 1.5% in the Sierra Nevada de Mérida, Venezuela). A series of maps show the glacial morphology of the mountains (unfortunately, some of the maps have been included within the binding, thus losing some information; they could have been reduced somewhat to fit a single page or, if too large, could have been included in the pocket, together with the map of Chimborazo-Carihuairazo).

  10. Presence of the tunicate Asterocarpa humilis on ship hulls and aquaculture facilities in the coast of the Biobío Region, south central Chile

    Javier Pinochet

    2017-08-01

    Full Text Available Non-native ascidians are important members of the fouling community associated with artificial substrata and man-made structures. Being efficient fouling species, they are easily spread by human-mediated transports (e.g., with aquaculture trade and maritime transports. This is exemplified by the ascidian Asterocarpa humilis which displays a wide distribution in the Southern Hemisphere and has been recently reported in the Northern Hemisphere (NW Europe. In continental Chile, its first report dates back from 2000 for the locality of Antofagasta (23°S. Although there was no evidence about the vectors of introduction and spread, nor the source, some authors suggested maritime transport by ship hulls and aquaculture devices as putative introduction pathways and vectors. In the present study, we report for the first time the presence of A. humilis on the hull of an international ship in a commercial port in Concepción bay (36°S, south central Chile. We also found one individual associated to a seashell farm, 70 km far from Concepción bay. Further individuals were subsequently identified within Concepción bay: one juvenile settled upon international harbor pilings and a dozen individuals along aquaculture seashell longlines. For the first specimens sampled, species identification was ascertained using both morphological criteria and molecular barcoding, using the mitochondrial gene cytochrome c oxidase subunit I (COI and a nuclear gene (ribosomal RNA 18S. The nuclear 18S gene and the mitochondrial gene COI clearly assigned the specimens to A. humilis, confirming our morphological identification. Two haplotypes were obtained with COI corresponding to haplotypes previously obtained with European and Northern Chilean specimens. The present study thus reports for the first time the presence of A. humilis in the Araucanian ecoregion, documenting the apparent expansion of this non-native tunicate in Chile over 2,000 km, spanning over three ecoregions

  11. Geomorphic evidence for post-10 Ma uplift of the western flank of the central Andes 18°30'-22°S

    Hoke, Gregory D.; Isacks, Bryan L.; Jordan, Teresa E.; Blanco, NicoláS.; Tomlinson, Andrew J.; Ramezani, Jahandar

    2007-10-01

    The western Andean mountain front forms the western edge of the central Andean Plateau. Between 18.5° and 22°S latitude, the mountain front has ˜3000 m of relief over ˜50 km horizontal distance that has developed in the absence of major local Neogene deformation. Models of the evolution of the plateau, as well as paleoaltimetry estimates, all call for continued large-magnitude uplift of the plateau surface into the late Miocene (i.e., younger than 10 Ma). Longitudinal river profiles from 20 catchments that drain the western Andean mountain front contain several streams with knickpoint-bounded segments that we use to reconstruct the history of post-10 Ma surface uplift of the western flank of the central Andean Plateau. The generation of knickpoints is attributed to tectonic processes and is not a consequence of base level change related to Pacific Ocean capture, eustatic change, or climate change as causes for creating the knickpoint-bounded stream segments observed. Minor valley-filling alluvial gravels intercalated with the 5.4 Ma Carcote ignimbrite suggest uplift related river incision was well under way by 5.4 Ma. The maximum age of river incision is provided by the regionally extensive, approximately 10 Ma El Diablo-Altos de Pica paleosurface. The river profiles reveal that relative surface uplift of at least1 km occurred after 10 Ma.

  12. Long-term responses of sandy beach crustaceans to the effects of coastal armouring after the 2010 Maule earthquake in South Central Chile

    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.

  13. REE Distribution in Cultivated and No Cultivated Soils in Two Viticultural Areas of Central Chile: Mineralogical, Pedological and Anthropic Influences

    Castillo, P.; Townley, B.; Aburto, F.

    2017-12-01

    Within the scope of a Corfo-Innova Project (I+D Wines of Chile-University of Chile) we have recognized remarkable REE patterns in soils of two vineyards located in traditional vinicultural areas: Casablanca and Santa Cruz. Both vineyards have granitic parent rock, with similar petrographic features and REE patterns. We studied REE distribution on twelve cultivated soil profiles at each vineyard, where a full mineralogical, geochemical and pedogenic sampling and characterization was performed. To establish the effect of management no cultivated soil profiles were included from each vineyard location. REE in soil samples were measured by ICP-MS using two digestion methods: lithium metaborate/tetraborate fusion to obtain REE contents in total soil and MMI® partial extraction technique for REE contents on bioavailable phases.Soils display similar signatures of REEs respect to the rock source at both vineyards, but showing relative enrichments in soils of Casablanca and depletion in soils of Santa Cruz. Bioavailable phase data indicates a relative depletion of LREEs compared to HREEs and different anomalies for Ce (positive vs negative) in different areas of the same vineyard. Similar patterns of soils and parent rock suggest that REEs are adequate tracers of lithological source. Enrichments and/or depletions of REE patterns in soils respect to the rock source and Ce anomalies, evidence differential pedogenetic processes occurring at each sampled site. Results of bioavailable phase are coherent with the immobilization and fractionation of LREEs by stable minerals within soils as clays and Fe oxides. Mineralogical results in soil thin sections of Casablanca evidence the occurrence of Ti phases as sphene, ilmenite and rutile, which probably control the relative REE enrichment, since these minerals are considered more stable under pedogenic conditions.Finally, cultivated soils show a depleted but analogous pattern of REE regarding to no cultivated soil, indicating the

  14. Determination of trace elements in Pre-Hispanic ceramics from Chile's Central Zone using instrumental neutron activation analysis

    Andonie, O; Munoz, L; Kohnnenkamp, I; Falabella, F

    2000-01-01

    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

  15. Cenozoic sedimentation and exhumation of the foreland basin system preserved in the Precordillera thrust belt (31-32°S), southern central Andes, Argentina

    Levina, Mariya; Horton, Brian K.; Fuentes, Facundo; Stockli, Daniel F.

    2014-09-01

    Andean retroarc compression associated with subduction and shallowing of the oceanic Nazca plate resulted in thin-skinned thrusting that partitioned and uplifted Cenozoic foreland basin fill in the Precordillera of west-central Argentina. Evolution of the central segment of the Precordillera fold-thrust belt is informed by new analyses of clastic nonmarine deposits now preserved in three intermontane regions between major east directed thrust faults. We focus on uppermost Oligocene-Miocene basin fill in the axial to frontal Precordillera at 31-32°S along the Río San Juan (Albarracín and Pachaco sections) and the flank of one of the leading thrust structures (Talacasto section). The three successions record hinterland construction of the Frontal Cordillera, regional arc volcanism, and initial exhumation of Precordillera thrust sheets. Provenance changes recorded by detrital zircon U-Pb age populations suggest that initial shortening in the Frontal Cordillera coincided with an early Miocene shift from eolian to fluvial accumulation in the adjacent foreland basin. Upward coarsening of fluvial deposits and increased proportions of Paleozoic clasts reflect cratonward (eastward) advance of deformation into the Precordillera and resultant structural fragmentation of the foreland basin into isolated intermontane segments. Apatite (U-Th)/He thermochronometry of basin fill constrains to 12-9 Ma the most probable age of uplift-induced exhumation and cooling of Precordillera thrust sheets. This apparent pulse of exhumation is evident in each succession, suggestive of rapid, large-scale exhumation by synchronous thrusting above a single décollement linking major structures of the Precordillera.

  16. Magma flow recorded by magmatic and magnetic fabrics in a shallow granitic pluton: La Gloria Pluton, central Chile

    Payacán, I. J.; Gutiérrez, F. J.; Gelman, S. E.; Bachmann, O.; Parada, M. A.

    2013-12-01

    To better understand the dynamics of a small, shallow, silicic magma reservoir, magmatic and magnetic (AMS) fabrics are compared in samples obtained from La Gloria Pluton (LGP), a 10 Ma granitic intrusion located in southern Andes. The magnetic fabric of LGP, mainly given by magnetite, is characterized by oblate shapes. Magnetic lineations have a NW trend with subhorizontal dip, following the main pluton elongation, while magnetic foliation planes have dips varying gradually from vertical at the walls to subhorizontal toward the center and the roof of the pluton. On the basis of numerical simulations, magnetic fabric was interpreted to represent the shear record induced by magmatic convection along solidification fronts as the reservoir reached its rheological locking point. Magmatic fabric (mineral orientation) was determined on 12 samples along the pluton. Three mutually orthogonal thin sections were produced for each sample, perpendicular to the AMS tensor axes. Size and orientation of individual crystals were obtained by image analysis. A 2-D tensor for two mineral groups (plagioclase and amphibole+biotitie) was defined in each mineral plane projecting the crystal lengths on the main crystal orientation (given by Bingham statistics). A 3-D magmatic fabric tensor was obtained. In order to compare the magmatic and magnetic fabrics, magmatic anisotropy parameters were defined similar to the AMS tensors. Magmatic fabric and anisotropy parameter values vary depending on the location inside the pluton: (1) Samples located at the borders exhibit vertical foliations and lineations with a NW trend, similar to the magnetic fabric tensors and higher anisotropy values for plagioclase than amphibole+biotite,; (2) samples located at the center of the LGP commonly present subvertical foliations/lineations, which differ from the magnetic fabric, and higher magmatic anisotropy degree values for amphibole+biotite than plagioclase. Based on numerical simulations of the fluid

  17. Las sociedades anónimas cruzan los Andes: los inversores chilenos en Neuquén al comenzar el siglo XX

    Graciela Blanco

    2012-08-01

    Full Text Available El territorio de Neuquén, en el norte de la Patagonia, atrajo la mirada de diversos inversores privados a partir del avance militar que realizó el Estado nacional sobre los grupos indígenas y de la conquista de las tierras del sur argentino; tierras que fueron ofrecidas a particulares en propiedad o arrendamiento en condiciones muy beneficiosas. Este trabajo analiza la conformación en Chile, en los primeros años del siglo XX, de sociedades anónimas que explicitaban como objetivo central la intención de comprar tierras a ambos lados de la Cordillera de los Andes para la explotación agroganadera y la comercialización, y estudia específicamente el origen, itinerario y organización productiva de una de esas sociedades en Neuquén.Neuquen territory, in the north of the Patagonia, attracted the look of diverse investors after from the military advance that realized the national State on the indigenous groups and of the conquest of the lands of the Argentine's south, lands that were offered to individuals in property or lease in very beneficial conditions. This work analyzes the conformation in Chile, in the first years of the 20th century, of joint-stock companies that stated explicitly as central aim the intention of buying lands on both sides of the Mountain chain of the Andes for the agricultural and livestock exploitation and the commercialization, and there studies specifically the origin, itinerary and productive organization of one of these companies in Neuquen.

  18. Leaf litter is essential for seed survival of the endemic endangered tree Pouteria splendens (Sapotaceae from central Chile

    G. J. Sotes

    2018-01-01

    Full Text Available Pouteria splendens (A.DC. Kuntze, the Chilean lúcumo, is an endemic tree and the only member of the Sapotaceae family in Chile. It is considered an endangered species as a consequence of its restricted distribution and small population size. Currently, individuals of P. splendens are immersed in a heterogeneous landscape with rocky mounds and plains located in areas densely populated by humans. Natural regeneration in the species seems to be low, despite the fact that plants are able to produce fruits. The species produces brightly colored fleshy drupes. There is no information about the dispersal pattern and the fate of the seeds. In this work we investigate (i the seed dispersal pattern and (ii the effect of tree canopy and the presence of leaf litter on seed survival, both in rocky mounds and plains. Results indicated an extremely low distance of seed dispersal, with most of the seeds falling down under the canopy. Seed survival under the canopy without leaf litter was very low and even zero in rocky mounds. Nevertheless, the presence of leaf litter covering the seeds increased survival in both habitats. Outside the canopy, seed survival only increased in plains. We suggest that future conservation programs should focus on protecting both adult plants and leaf litter under trees.

  19. Origin of fumarolic fluids from Tupungatito Volcano (Central Chile): interplay between magmatic, hydrothermal, and shallow meteoric sources

    Benavente, Oscar; Tassi, Franco; Gutiérrez, Francisco; Vaselli, Orlando; Aguilera, Felipe; Reich, Martin

    2013-08-01

    Tupungatito is a poorly known volcano located about 100 km eastward of Santiago (Chile) in the northernmost sector of the South Volcanic Zone. This 5,682 m high volcano shows intense fumarolic activity. It hosts three crater lakes within the northwestern portion of the summit area. Chemical compositions of fumarolic gases and isotopic signatures of noble gases (3He/4He and 40Ar/36Ar are up to 6.09 Ra and 461, respectively), and steam (δ18O and δD) suggest that they are produced by mixing of fluids from a magmatic source rich in acidic gas compounds (SO2, HCl, and HF), and meteoric water. The magmatic-hydrothermal fluids are affected by steam condensation that controls the outlet fumarolic temperatures (contamination from the subducting slab, (2) the sedimentary basement, and (3) limited contribution from crustal sediments. Gas geothermometry based on the kinetically rapid H2-CO equilibria indicates equilibrium temperatures 200 °C and redox conditions are consistent with those inferred by the presence of the SO2-H2S redox pair, typical of fluids that have attained equilibrium in magmatic environment. A comprehensive conceptual geochemical model describing the circulation pattern of the Tupungatito hydrothermal-magmatic fluids is proposed. It includes fluid source regions and re-equilibration processes affecting the different gas species due to changing chemical-physical conditions as the magmatic-hydrothermal fluids rise up toward the surface.

  20. Quechua II contraction in the Ayacucho intermontane basin: Evidence for rapid and episodic Neogene deformation in the Andes of central Perú

    Wise, James M.; Noble, Donald C.; Zanetti, Kathleen A.; Spell, Terry L.

    2008-12-01

    In the Ayacucho basin of central Perú the regional Quechua II contractional deformation is bracketed by 40Ar/ 39Ar isotopic age determinations to a maximum duration of about 300,000 years, and probably less than 150,000 years, centered on 8.7 Ma. The strongly deformed Huanta Formation beneath the Quechua II angular unconformity was deposited during a period of extension that began before 9.05 ± 0.05 Ma. Deposition of a thick succession of alluvial fan deposits interbedded with flows of basaltic andesite in the Tingrayoc Member continued up to about 8.76 ± 0.05 Ma with the later part of the sedimentary record reflected by lacustrine deposits of the Mayocc Member. The upper limit on contractional deformation is constrained by an age of 8.64 ± 0.05 Ma on a unit of tuff near the base of the Puchcas volcanics, which in places was deposited upon near-vertical beds of the Huanta Formation. The Ayacucho Formation was deposited, locally unconformably, upon the Puchcas volcanics beginning slightly before 7.65 ± 0.10 Ma. Extended periods of neutral to tensional stress interrupted by rapid well-developed pulses of contractional deformation demonstrate the episodic behavior of Andean orogeny in Perú. The very short duration for the Quechua II event implies that driving forces for episodic deformation may be related to coupling along the orogen boundaries and strain accumulation and release mechanisms in the continental crust instead of much longer-term variations in the configuration of converging plates.

  1. 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

    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

  2. Rock Glacier Response to Climate Change in the Argentinian Andes

    Drewes, J.; Korup, O.; Moreiras, S.

    2017-12-01

    Rock glaciers are bodies of frozen debris and ice that move under the influence of gravity in permafrost areas. Rock glaciers may store a large amount of sediments and play an important role as prime movers of debris in the Andean sediment cascade. However, little is known about how much sediment and water rock glaciers may store at the mountain-belt scale, and the few existing estimates vary considerably. We address this question for the Argentinian Andes, for which a new glacial inventory containing more than 6500 rock glaciers gives us the opportunity to analyse their relevance within the sediment cascade. We examine the inventory for catchments in five sub-regions, i.e. the Desert Andes (22°-31°S); the Central Andes (31°-36°S); the Northern Andes of Patagonia (36°-45°S); the Southern Andes of Patagonia (45°-52°S); and Tierra del Fuego (52°-55°S), together with climate variables of the WorldClim datasets, and digital topographic data, to estimate how rock-glacier extents may change under different past and future climate scenarios. We observe for the northern Desert Andes that rock glacier toes are at 4000 to 5000 m a.s.l. and a mean annual temperature range of 3° and 8°C, though most rock glaciers are in areas with mean annual temperatures between -5 and 5°C, marking a distinct thermal niche. Rock glaciers are traditionally viewed as diagnostic of sporadic alpine permafrost and their toes are often near the annual mean 0°C isotherm. However, we find that only rock glaciers in the southern Desert Andes and Central Andes are located where annual mean temperature is -2°C. Future scenarios project an increase of > four degrees in these areas, which may further degrade ground ice and potentially change the rates at which rock glaciers advance. Where active rock glaciers become inactive their coarse material, which was formerly bound by ice, may be released into the sediment cascade, whereas accelerating or rapidly downwasting rock glaciers may either

  3. Natural gas across the Andes : a case study of an international business venture

    Figueroa, E.B.; Smith, B.

    2002-07-01

    This book describes the challenges and complexities of constructing the GasAndes pipeline from Argentinian gas fields across the Andes to Santiago in Chile. The project was a joint international effort between Canada's NOVA Corporation, Chile's Gasco and Gener, and Argentina's Compania General de Combustibles and Techint Compania Tecnica Internacional. The book relates how NOVA Gas International, together with its partners, accomplished the task of constructing the first major natural gas pipeline across the Andes mountains despite significant challenges such as steep mountain slopes, many river crossings, high altitude, high winds and bitter cold. It describes how the partnership developed and how political and socio-economic issues were dealt with. It demonstrates how business practices were modified to deal with local conditions and to ensure that the fragile environment of the Andean meadows was protected. It also describes how the builders of the pipeline addressed the concerns of communities along the pipeline route. The pipeline was constructed at a time when democracy was returning and market economies were shifting from a reduced role of government in the energy sector. The 463 km GasAndes pipeline has been in operation since August 7, 1997. refs., tabs., figs.

  4. Distribution and Diversity of Pathogenic Leptospira Species in Peri-domestic Surface Waters from South Central Chile.

    Meghan R Mason

    2016-08-01

    Full Text Available Leptospirosis is a neglected zoonosis affecting animals and humans caused by infection with Leptospira. The bacteria can survive outside of hosts for long periods of time in soil and water. While identification of Leptospira species from human cases and animal reservoirs are increasingly reported, little is known about the diversity of pathogenic Leptospira species in the environment and how surveillance of the environment might be used for monitoring and controlling disease.Water samples (n = 104 were collected from the peri-domestic environment of 422 households from farms, rural villages, and urban slums participating in a broader study on the eco-epidemiology of leptospirosis in the Los Rios Region, Chile, between October 2010 and April 2012. The secY region of samples, previously detected as pathogenic Leptospira by PCR, was amplified and sequenced. Sequences were aligned using ClustalW in MEGA, and a minimum spanning tree was created in PHYLOViZ using the goeBURST algorithm to assess sequence similarity. Sequences from four clinical isolates, 17 rodents, and 20 reference strains were also included in the analysis. Overall, water samples contained L. interrogans, L. kirschneri, and L. weilii, with descending frequency. All species were found in each community type. The distribution of the species differed by the season in which the water samples were obtained. There was no evidence that community-level prevalence of Leptospira in dogs, rodents, or livestock influenced pathogen diversity in the water samples.This study reports the presence of pathogenic Leptospira in the peri-domestic environment of households in three community types and the differences in Leptospira diversity at the community level. Systematic environmental surveillance of Leptospira can be used for detecting changes in pathogen diversity and to identify and monitor contaminated areas where an increased risk of human infection exists.

  5. Distribution and Diversity of Pathogenic Leptospira Species in Peri-domestic Surface Waters from South Central Chile.

    Mason, Meghan R; Encina, Carolina; Sreevatsan, Srinand; Muñoz-Zanzi, Claudia

    2016-08-01

    Leptospirosis is a neglected zoonosis affecting animals and humans caused by infection with Leptospira. The bacteria can survive outside of hosts for long periods of time in soil and water. While identification of Leptospira species from human cases and animal reservoirs are increasingly reported, little is known about the diversity of pathogenic Leptospira species in the environment and how surveillance of the environment might be used for monitoring and controlling disease. Water samples (n = 104) were collected from the peri-domestic environment of 422 households from farms, rural villages, and urban slums participating in a broader study on the eco-epidemiology of leptospirosis in the Los Rios Region, Chile, between October 2010 and April 2012. The secY region of samples, previously detected as pathogenic Leptospira by PCR, was amplified and sequenced. Sequences were aligned using ClustalW in MEGA, and a minimum spanning tree was created in PHYLOViZ using the goeBURST algorithm to assess sequence similarity. Sequences from four clinical isolates, 17 rodents, and 20 reference strains were also included in the analysis. Overall, water samples contained L. interrogans, L. kirschneri, and L. weilii, with descending frequency. All species were found in each community type. The distribution of the species differed by the season in which the water samples were obtained. There was no evidence that community-level prevalence of Leptospira in dogs, rodents, or livestock influenced pathogen diversity in the water samples. This study reports the presence of pathogenic Leptospira in the peri-domestic environment of households in three community types and the differences in Leptospira diversity at the community level. Systematic environmental surveillance of Leptospira can be used for detecting changes in pathogen diversity and to identify and monitor contaminated areas where an increased risk of human infection exists.

  6. A New, Continuous 5400 Yr-long Paleotsunami Record from Lake Huelde, Chiloe Island, South Central Chile.

    Kempf, P.; Moernaut, J.; Vandoorne, W.; Van Daele, M. E.; Pino, M.; Urrutia, R.; De Batist, M. A. O.

    2014-12-01

    After the last decade of extreme tsunami events with catastrophic damage to infrastructure and a horrendous amount of casualties, it is clear that more and better paleotsunami records are needed to improve our understanding of the recurrence intervals and intensities of large-scale tsunamis. Coastal lakes (e.g. Bradley Lake, Cascadia; Kelsey et al., 2005) have the potential to contain long and continuous sedimentary records, which is an important asset in view of the centennial- to millennial-scale recurrence times of great tsunami-triggering earthquakes. Lake Huelde on Chiloé Island (42.5°S), Chile, is a coastal lake located in the middle of the Valdivia segment, which is known for having produced the strongest ever instrumentally recorded earthquake in 1960 AD (MW: 9.5), and other large earthquakes prior to that: i.e. 1837 AD, 1737 AD (no report of a tsunami) and 1575 AD (Lomnitz, 1970, 2004, Cisternas et al., 2005). We present a new 5400 yr-long paleotsunami record with a Bayesian age-depth model based on 23 radiocarbon dates that exceeds all previous paleotsunami records from the Valdivia segment, both in terms of length and of continuity. 18 events are described and a semi-quantitative measure of the event intensity at the study area is given, revealing at least two predecessors of the 1960 AD event in the mid to late Holocene that are equal in intensity. The resulting implications from the age-depth model and from the semi-quantitative intensity reconstruction are discussed in this contribution.

  7. 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

    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

  8. 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

    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

  9. Southward Ejection of Subcontinental Lithosphere and large-scale Asthenospheric Enrichment beneath central Chile resulting from Flat Subduction

    Jacques, G.; Hoernle, K.; Schaefer, B. F.; Hauff, F.; Gill, J.; Holm, P. M.; Bindeman, I. N.; Folguera, A.; Lara, L.; Ramos, V. A.

    2015-12-01

    Flat subduction is a common process in subduction zones, causing crustal shortening and thickening and possibly subduction erosion. These processes can lead to the contamination of asthenospheric melts either by lithospheric assimilation (e.g. MASH) or by subduction erosion of lithosphere into the asthenospheric source. We present new major and trace element and Sr-Nd-Pb-Hf-O-Os isotope data for a transect of Quaternary volcanic rocks across the Northern Southern Volcanic Front (NSVZ) of Chile at ~33.5°S, just south of the area of flat subduction, extending from the volcanic front (VF) to the rear arc (RA). The newly discovered calc-alkaline to alkaline RA rocks are more mafic (MgO~4-9wt.%) than the VF rocks (MgO~2.0-4.5wt.%). Both groups have overlapping Sr-Nd-Hf isotopic compositions that are more enriched than lavas from further south in the SVZ with two RA trachybasalts displaying extreme 87Sr/86Sr (0.710), eNd (-6) and eHf (-9). The RA samples, however, have less radiogenic Pb isotopic compositions with the two extreme RA trachybasalt samples having the least radiogenic Pb. The 207Pb/204Pb vs. Nd/Pb, Ce/Pb and Nb/U form good inverse linear correlations extending from subducted sediments to a mantle-like component. Mesozoic/Paleozoic crust and Grenvillian Argentinian lower crust do not fall on or along an extension of these arrays. The ol, plag and groundmassd18O (normalized to melt) of samples covering the full range in Sr-Nd-Pb-Hf isotopic composition lie within the mantle range (5.5-5.9). High Os abundances (~330ppt) in radiogenic Os (187Os/188Os=0.18) samples are not consistent with derivation from a mantle plume or continental crust. eNd and eHf increase to the south along the VF, e.g. eHf ranges from -9 to +10, forming an excellent linear correlation (r2=0.99), indicating that the enriched component is present in the source for >1000km to at least ~43°S. We propose that flattening of the Pampean slab 1) triggered subduction erosion of enriched

  10. Reproductive patterns in demersal crustaceans from the upper boundary of the OMZ off north-central Chile

    Gallardo, María de los Ángeles; González López, Andrés E.; Ramos, Marcel; Mujica, Armando; Muñoz, Praxedes; Sellanes, Javier; Yannicelli, Beatriz

    2017-06-01

    Pleuroncodes monodon (Crustacea: Munididae) supports one of the main trawling fisheries over the continental shelf off Chile between 25°S and 37°S within the upper boundary of the oxygen minimum zone (OMZ). Although the reproductive cycle of P. monodon has been described, the relationship between this key biological process and the variability of the OMZ has not been comprehensibly addressed neither for P. monodon nor for other OMZ resident species. In this study a set of 14 quasi-monthly oceanographic cruises carried out between June 2010 and November 2011 were conducted over the continental shelf off Coquimbo (30°S) to investigate the temporal variability of: i) dissolved oxygen concentration, temperature and chlorophyll-a at relevant depths ii) the presence and proportion of occurrence of P. monodon ovigerous females and juveniles from benthic trawls; iii) the presence of different stage larvae in the plankton, and iv) similar biological data for other species from the OMZ and shallower depths crustaceans. During summer months oxygen levels and bottom temperature were lower than in winter, while chlorophyll-a concentration was maximum in summer coinciding with an active (but not maximum) upwelling season. P. monodon maximum egg carrying occurred in winter during periods of increased oxygenation. Egg carrying females were never found at depths where oxygen concentration was below 0.5 ml L-1, while over 50% of the autumn and spring cohorts of juveniles occurred at oxygen concentrations below that level. The depth range occupied by ovigerous females was more restricted than the rest of the population and their depth of occurrence followed the variability of the upper OMZ. The larval release period of OMZ resident species extends over late winter and spring, and its main peak precedes that of coastal species (spring) and the spring-summer chlorophyll-a maximum. We propose that for OMZ resident species, brood carrying during warmer and more oxygenated conditions

  11. A Method for Optimal Allocation between Instream and Offstream Uses in the Maipo River in Central Chile

    Génova, P. P.; Olivares, M. A.

    2016-12-01

    Minimum instream flows (MIF) have been established in Chile with the aim of protecting aquatic ecosystems. In practice, since current water law only allocates water rights to offstream water uses, MIF becomes the only instrument for instream water allocation. However, MIF do not necessarily maintain an adequate flow for instream uses. Moreover, an efficient allocation of water for instream uses requires the quantification of the benefits obtained from those uses, so that tradeoffs between instream and offstream water uses are properly considered. A model of optimal allocation between instream and offstream uses is elaborated. The proposed method combines two pieces of information. On one hand, benefits of instream use are represented by qualitative recreational benefit curves as a function of instream flow. On the other hand, the opportunity cost given by lost benefits of offstream uses is employed to develop a supply curve for instream flows. We applied this method to the case of the Maipo River, where the main water uses are recreation, hydropower production and drinking water. Based on available information we obtained the qualitative benefits of various recreational activities as a function of flow attributes. Then we developed flow attributes curves as a function of instream flow for a representative number of sections in the river. As a result we obtained the qualitative recreational benefit curve for each section. The marginal cost curve for instream flows was developed from the benefit functions of hydropower production interfering with recreation in the Maipo River. The purpose of this supply curve is to find a range of instream flow that will provide a better quality condition for recreation experience at a lower opportunity cost. Results indicate that offstream uses adversely influence recreational activities in the Maipo River in certain months of the year, significantly decreasing the quality of these in instream uses. As expected, the impact depends

  12. U-series in zircon and 40Ar/39Ar geochronology reveal the most recent stage of a supervolcanic cycle in the Altiplano-Puna Volcanic Complex, Central Andes

    Tierney, C.; de Silva, S. L.; Schmitt, A. K.; Jicha, B.; Singer, B. S.

    2010-12-01

    The ignimbrite flare up that produced the Altiplano-Puna Volcanic Complex of the Central Andes is characterized by episodic supervolcanism over a ~10 Ma time-span that climaxed about 4Ma. Since peak activity, the temporal and spatial record of volcanism suggests a waning of the system with only one other supervolcanic eruption at 2.6Ma. The most recent phase of volcanism from the APVC comprises a series of late Pleistocene domes that share a general petrochemical resemblance to the ignimbrites. New U-series data on zircons and high precision 40Ar/39Ar age determinations reveal that these effusive eruptions represent a temporally coherent magmatic episode. The five largest domes (Chao, Chillahuita, Chanka, Chascon-Runtu Jarita, and Tocopuri) have a combined volume >40 km3, and are distributed over an elliptical area of over 3000km2 centered at 22°S 68°W. They are crystal rich (>50%) dacites to rhyolites. New 40Ar/39Ar age determinations on biotite for the domes range range from 108±6 to 190±50 ka. However, 40Ar/39Ar ages from sanidine for some of the domes are more precise and span from 87±4 to 97±2 ka. We therefore interpret the eruption age of all these domes to be ~90 - 100 ka. This is consistent with SIMS U-series crystallization ages from the rims of 66 zircon crystals from four of the domes that reveal a fairly continuous spread of ages from ~90 ka to >300 ka with potentially common peaks in zircon ages at 100 ka and ~200 ka. U-Pb dating on the interiors of some of these zircon crystals indicates crystallization ages of up to 1.5 Ma. The common peaks of zircon crystallization between domes suggest that magma that fed these domes shared a larger regional source. Furthermore, the large volume of this potential source and the crystal-rich nature of the lava imply that this source was likely a large body of crystal-mush. The continuous nature of the zircon rim age population indicates that the residence time of this magma body was likely >200kyr. Potential

  13. Seasonal mercury concentrations and δ15N and δ13C values of benthic macroinvertebrates and sediments from a historically polluted estuary in south central Chile.

    Díaz-Jaramillo, Mauricio; Muñoz, Claudia; Rudolph, Ignacio; Servos, Mark; Barra, Ricardo

    2013-01-01

    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 (δ(15)N and δ(13)C). 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 (p0.05). 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 δ(13)C 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. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Nitrospina-like bacteria are the main drivers of nitrite oxidation in the seasonal upwelling area of the Eastern South Pacific (Central Chile ∼36°S).

    Levipan, Héctor A; Molina, Verónica; Fernandez, Camila

    2014-12-01

    Aerobic nitrite oxidation in marine environments plays a key role in the nitrification process. Marine bacteria involved in this nitrate-producing process have however been seldom studied compared with the ammonia-oxidizing community. Here, we report for the first time the community structure of aerobic nitrite-oxidizing bacteria (NOB) in the seasonal upwelling and oxygen-deficient area off Central Chile. Analysis of 16S rRNA by tag pyrosequencing was combined with specific quantitative polymerase chain reaction (qPCR) and reverse transcription qPCR in summer and wintertime. Nitrospina-like bacteria were the only known NOB detected by means of pyrosequencing between 30 and 80 m depth, accounting for up to 5% of total bacteria. This guild was represented by 11 and 7 operational taxonomic units (97% cut-off) in winter and summertime respectively. Nitrospina-like bacteria were phylogenetically related to sequences retrieved from coastal upwelling, oxygen minimum zones and deep-sea environments. This group was also detected by qPCR with abundances that increased with depth throughout the water column. Importantly, Nitrospina from surface layers showed low abundances but high 16S rRNA : rDNA ratios and mainly in summertime. Overall, our results highlight the seasonal variability between the structure and physiological state of this community and suggest a significant role of Nitrospina in the nitrogen cycle of seasonal upwelling areas.

  15. Stable isotope evidence for formation from magmatic fluids of the mineralized breccias in the Los Bronces and El Teniente copper deposits, Central Chile

    Skewes, M.A; Arevalo, A; Holmgren, C.; Stern, C.R

    2001-01-01

    The giant Miocene and Pliocene Rio Blanco-Los Bronces (Warnaars et al., 1985; Serrano et al., 1996; Vargas et al., 1999) and El Teniente (Camus, 1975; Cuadra, 1986; Skewes and Arevalo, 2000) copper deposits of central Chile are among the largest copper deposits in the world. Hypogene copper ore is more significant than supergene ore in these deposits, and most of the hypogene copper occurs in the matrix of multiple clusters of breccias (Skewes and Stern, 1994; 1995). The origin of the large mineralized breccia pipes in these and other Andean copper deposits has been attributed to the explosive expansion of magmatic aqueous fluids derived from cooling plutons (Emmons, 1938; Kents, 1964; Warnaars et al., 1985; Sillitoe, 1985; Skewes and Stern, 1994, 1995). Warnaars et al. (1985) and Skewes and Stern (1996) suggested that mineral deposition in the matrix of these breccias took place by the rapid cooling of the same magmatic fluids that generated the brecciation. Highly saline, high-temperature magmatic fluid inclusions occur in quartz and tourmaline in the matrix of these breccias (Holmgren et al., 1988; Vargas et al., 1999; Skewes et al., 2001) (au)

  16. Impact of forest fires on the concentrations of polychlorinated dibenzo-p-dioxin and dibenzofurans in coastal waters of central Chile.

    Salamanca, Marco; Chandía, Cristian; Hernández, Aldo

    2016-12-15

    The relationship between the occurrence of forest fires in central Chile and the total concentration of dioxins and furans (PCDD/F) in nearby coastal waters was analyzed. The data for this analysis was obtained from a long-term environmental monitoring program (PROMNA) in the Bio-Bio Region. Quantification of PCDD/F was performed using HRGC/HRMS at the MSS laboratory in England. Between 2006 and 2014, peaks were observed in February 2007 and 2012. These concentration maxima coincided with major forest fires in the Bio-Bio Region and particularly with those in the Itata River Basin. The January 2012 fires generated an intense short-term response that was associated with atmospheric transport which increases medium toxicity furan-type congeners concentrations (TCDF, PCDF and HxCDF) and six months later a concentration increase of low toxicity dioxin-type congeners was observed (OCDD, HpCDD and HxCDD) coinciding with maximum winter river flow. These results suggest that forest fires near the coastal zone are responsible for increases in PCDD/F concentration observed in the study area. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. 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

    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

  18. Effects of massive wind power integration on short-term water resource management in central Chile - a grid-wide study

    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

  19. Mountain building processes in the Central Andes

    Bloom, A. L.; Isacks, B. L.

    False color composite images of the Thematic Mapper (TM) bands 5, 4, and 2 were examined to make visual interpretations of geological features. The use of the roam mode of image display with the International Imaging Systems (IIS) System 600 image processing package running on the IIS Model 75 was very useful. Several areas in which good comparisons with ground data existed, were examined in detail. Parallel to the visual approach, image processing methods are being developed which allow the complete use of the seven TM bands. The data was organized into easily accessible files and a visual cataloging of the quads (quarter TM scenes) with preliminary registration with the best available charts for the region. The catalog has proved to be a valuable tool for the rapid scanning of quads for a specific investigation. Integration of the data into a complete approach to the problems of uplift, deformation, and magnetism in relation to the Nazca-South American plate interaction is at an initial stage.

  20. Rock glaciers, Central Andes, Argentina, Version 1

    National Aeronautics and Space Administration — Primary rock glaciers are fed by avalanche chutes. At the El Salto rock glacier, surveys have been undertaken in order to determine the creep rate. Between 1981 and...

  1. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics

    Deckart, Katja; Godoy, Estanislao; Bertens, Alfredo; Jerez, Daniela; Saeed, Ayesha

    2010-01-01

    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 32 o and 34 o S. 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 32 o S, 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

  2. 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

    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

  3. Charles Darwin in the Andes

    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…

  4. Chile; Staff Report for the 2003 Article IV Consultation

    International Monetary Fund

    2003-01-01

    Chile has successfully resisted contagion from neighboring countries difficulties. Chile's inflation targeting framework has successfully anchored inflation expectations and increased the economy's resilience to external shocks while maintaining price stability. The floating exchange rate regime is an essential part of the macroeconomic policy framework and continues to serve Chile well. The interest in recapitalizing the central bank is welcomed. Executive Directors commend Chile for the tra...

  5. Low-grade metamorphism of Cambro-Ordovician successions in the Famatina belt, Southern-Central Andes: Burial-inversion history linked to the evolution of the proto-Andean Gondwana margin Metamorfismo de bajo grado de sucesiones cambro-ordovícicas en el cinturón del Famatina, Andes Centrales de Argentina: Historia de enterramiento-exhumación ligada a la evolución del margen proto-andino de Gondwana

    Gilda Collo

    2011-07-01

    Full Text Available The metamorphic P-T conditions of low-grade units from the Famatina belt, Central Andes of Argentina, were estimated through petrography, X-ray diffraction, and electron microscopy. For the Middle-Upper Cambrian Negro Peinado Formation a tectono-metamorphic event associated with intense intrafoliar folding, with estimated temperatures between 290 and 400°C (KIcis: 0.16-0.27A°29, biotite blastesis and compositional homogeneity in dioctahedral micas and intermediate pressure conditions (white mica b parameter: 9.010Á-9.035Á, was recognized. The Achavil Formation (Middle-Upper Cambrian presents a main metamorphic event associated with temperatures between 200 and 290°C (KIcis: 0.26-0.41A°29 and intermediate- to low-pressure conditions (white mica b parameter values: 8.972Á-9.017Á. Some illitic substitution in dioctahedral micas also indicates lower metamorphic grade than the Negro Peinado Formation. For Upper Cambrian to Middle Ordovician sequences a burial metamorphic pattern, with a progressive decrease in metamorphic grade from Volcancito Formation to Cerro Morado Group (ca. 490-465 Ma; KIcis: 0.31-0.69A°29 and absence of tendency changes linked to strati-graphic discontinuities was proposed. Mica and chlorite are the main phyllosilicates in the oldest units, while Ilt/ Sme (R3 mixed-layer is almost the only one in the youngest. White mica b parameter indicates intermediate- to low-pressure conditions for all these sequences. This burial metamorphic pattern presents a marked break as the youngest Ordovician unit (La Aguadita Formation, after ca. 452 Ma records higher metamorphic conditions (IKcis: 0.28-0.19A°29 than units from the Ordovician arc, with estimated temperatures between 270 and 330°C and intermediate-pressure conditions. Our results indicate that basin contraction and inversion processes related to the Ordovician Ocloyic Orogeny involved at least two well-discriminated and not superposed metamorphic episodes in this region

  6. Diversidad de la familia Carabidae (Coleoptera en Chile Diversity of the family Carabidae (Coleoptera in Chile

    SERGIO ROIG-JUÑENT

    2001-09-01

    Full Text Available Carabidae constituye dentro de los coléopteros chilenos, la cuarta familia en importancia por su cantidad de especies. El presente trabajo incluye una breve compilación acerca de la historia de la familia y de las primeras expediciones realizadas en Chile. También se realizan comparaciones de la diversidad de carábidos chilenos con respecto a otros países y el Neotrópico. Para Chile, se conocen 21 tribus, con 95 géneros y 365 especies, que representan el 38,8, 28,8 y 7,9 % de la fauna del Neotrópico, respectivamente. Chile posee un bajo número de tribus comparado con otros países, sin embargo, constituye un área importante por la presencia de seis tribus relictuales, principalmente pangeicas o gondwánicas. Chile posee 18 géneros endémicos (18,5 % de su fauna de Carabidae, 28 cuya distribución está restringida a Chile y Argentina y seis restringidos a Chile, Argentina y Uruguay. La cantidad de especies presentes en Chile es inferior a la que poseen otros países de América del Sur, pero la cantidad de especies endémicas es muy alta (204 y representa el 55,8 % de su fauna de carábidos. El alto grado de endemismo que posee Chile con respecto a otros países de América del Sur puede deberse a su condición de aislamiento, siendo las barreras más importantes la región desértica del norte y la cordillera de Los Andes. Este hecho también se vislumbra por la ausencia de importantes tribus neotropicales como Galeritini, Scaritini y Brachinini. También se incluyen en este trabajo claves para la identificación de todas las tribus y géneros presentes en Chile, como así también una breve descripción acerca de la diversidad y ambientes en los que se encuentra cada géneroThe family Carabidae is the fourth largest Coleoptera family in Chile. The present work includes a brief compilation on the taxonomic history of the family and the first expeditions to Chile. In addition, knowledge of carabid diversity in Chile is compared with

  7. 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

    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

  8. 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

    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

  9. Exploitation rates of two benthic resources across management regimes in central Chile: Evidence of illegal fishing in artisanal fisheries operating in open access areas

    Andreu-Cazenave, Miguel; Subida, Maria Dulce; Fernandez, Miriam

    2017-01-01

    There is an urgent need to quantify the impacts of artisanal fisheries and define management practices that allow for the recovery and conservation of exploited stocks. The extent of illegal catch is particularly critical as a driver of overexploitation in artisanal fisheries. However, the lack of data at proper spatial scales limits the evaluation of illegal fishing and effectiveness of management practices. We used a catch curve analysis to estimate total instantaneous mortality as a proxy of fishing pressure in the artisanal benthic fishery in central Chile. We compared the patterns of total mortality in fishing grounds under the well-studied territorial use rights for fisheries system (TURF) immersed in a landscape of open access areas (OAA; no access restriction), and from these patterns determined the extent of illegal fishing in open access areas focusing on the two most frequently extracted resources: locos (Concholepas concholepas) and keyhole limpets (Fissurella spp.). The beauty of this seascape is the presence of the no-take (NT) area of Las Cruces as control (no fishing), allowing us to estimate natural mortality. Loco exploitation is banned in OAAs. However, loco mortality in OAAs was 92% higher than in the NT, and 42% higher than in TURFs. Keyhole limpet mortality was similar between TURFs and the NT, but doubled in OAAs. We also found strong differences in mortality among fishing grounds with the same level of protection (i.e. TURFs), and over time. Our results highlight (a) the high level of illegal fishing that may occur in artisanal fisheries under traditional management regimes, and (b) that TURFs can be effective to reduce fishing mortality. However, large variability among TURFs suggests the need for a deeper understanding of the drivers of success of TURFs. PMID:28666013

  10. Seasonal mercury concentrations and δ15N and δ13C values of benthic macroinvertebrates and sediments from a historically polluted estuary in south central Chile

    Díaz-Jaramillo, Mauricio; Muñoz, Claudia; Rudolph, Ignacio; Servos, Mark; Barra, Ricardo

    2013-01-01

    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 (δ 15 N and δ 13 C). 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 δ 13 C 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 δ 13 C signatures indicated different feeding modes. ► Organic forms of Hg in invertebrates were mainly related to the carbon sources.

  11. Exploitation rates of two benthic resources across management regimes in central Chile: Evidence of illegal fishing in artisanal fisheries operating in open access areas.

    Andreu-Cazenave, Miguel; Subida, Maria Dulce; Fernandez, Miriam

    2017-01-01

    There is an urgent need to quantify the impacts of artisanal fisheries and define management practices that allow for the recovery and conservation of exploited stocks. The extent of illegal catch is particularly critical as a driver of overexploitation in artisanal fisheries. However, the lack of data at proper spatial scales limits the evaluation of illegal fishing and effectiveness of management practices. We used a catch curve analysis to estimate total instantaneous mortality as a proxy of fishing pressure in the artisanal benthic fishery in central Chile. We compared the patterns of total mortality in fishing grounds under the well-studied territorial use rights for fisheries system (TURF) immersed in a landscape of open access areas (OAA; no access restriction), and from these patterns determined the extent of illegal fishing in open access areas focusing on the two most frequently extracted resources: locos (Concholepas concholepas) and keyhole limpets (Fissurella spp.). The beauty of this seascape is the presence of the no-take (NT) area of Las Cruces as control (no fishing), allowing us to estimate natural mortality. Loco exploitation is banned in OAAs. However, loco mortality in OAAs was 92% higher than in the NT, and 42% higher than in TURFs. Keyhole limpet mortality was similar between TURFs and the NT, but doubled in OAAs. We also found strong differences in mortality among fishing grounds with the same level of protection (i.e. TURFs), and over time. Our results highlight (a) the high level of illegal fishing that may occur in artisanal fisheries under traditional management regimes, and (b) that TURFs can be effective to reduce fishing mortality. However, large variability among TURFs suggests the need for a deeper understanding of the drivers of success of TURFs.

  12. Exploitation rates of two benthic resources across management regimes in central Chile: Evidence of illegal fishing in artisanal fisheries operating in open access areas.

    Miguel Andreu-Cazenave

    Full Text Available There is an urgent need to quantify the impacts of artisanal fisheries and define management practices that allow for the recovery and conservation of exploited stocks. The extent of illegal catch is particularly critical as a driver of overexploitation in artisanal fisheries. However, the lack of data at proper spatial scales limits the evaluation of illegal fishing and effectiveness of management practices. We used a catch curve analysis to estimate total instantaneous mortality as a proxy of fishing pressure in the artisanal benthic fishery in central Chile. We compared the patterns of total mortality in fishing grounds under the well-studied territorial use rights for fisheries system (TURF immersed in a landscape of open access areas (OAA; no access restriction, and from these patterns determined the extent of illegal fishing in open access areas focusing on the two most frequently extracted resources: locos (Concholepas concholepas and keyhole limpets (Fissurella spp.. The beauty of this seascape is the presence of the no-take (NT area of Las Cruces as control (no fishing, allowing us to estimate natural mortality. Loco exploitation is banned in OAAs. However, loco mortality in OAAs was 92% higher than in the NT, and 42% higher than in TURFs. Keyhole limpet mortality was similar between TURFs and the NT, but doubled in OAAs. We also found strong differences in mortality among fishing grounds with the same level of protection (i.e. TURFs, and over time. Our results highlight (a the high level of illegal fishing that may occur in artisanal fisheries under traditional management regimes, and (b that TURFs can be effective to reduce fishing mortality. However, large variability among TURFs suggests the need for a deeper understanding of the drivers of success of TURFs.

  13. Recruitment Dynamics of the Relict Palm, Jubaea chilensis: Intricate and Pervasive Effects of Invasive Herbivores and Nurse Shrubs in Central Chile.

    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.

  14. Temporal and spatial variability of biological nitrogen fixation off the upwelling system of central Chile (35-38.5°S)

    Fernandez, Camila; González, Maria Lorena; Muñoz, Claudia; Molina, Veronica; Farias, Laura

    2015-05-01

    Although N2 fixation could represent a supplementary source of bioavailable nitrogen in coastal upwelling areas and underlying oxygen minimum zones (OMZs), the limited data available prevent assessing its variability and biogeochemical significance. Here we report the most extensive N2 fixation data set gathered to date in the upwelling area off central Chile (36°S). It covers interannual to high frequency time scales in an area of about 82,500 km2 in the eastern South Pacific (ESP). Because heterotrophic N2 fixation may be regulated by DOM availability in the ESP, we conducted experiments at different oxygen conditions and included DOM amendments in order to test diazotrophic activity. Rates in the euphotic zone showed strong temporal variability which resulted in values reaching 0.5 nmol L-1 d-1 in 2006 (average 0.32 ± 0.17 nmol L-1 d-1) and up to 126.8 nmol L-1 d-1 (average 24.75 ± 37.9 nmol L-1 d-1) in 2011. N2 fixation in subsurface suboxic conditions (1.5 ± 1.16 nmol L-1 d-1) also occurred mainly during late summer and autumn while virtually absent in winter. The diversity of diazotrophs was dominated by heterotrophs, with higher richness in surface compared to OMZ waters. Rates in oxygen depleted conditions could exceed values obtained in the euphotic layer, but rates were not dependent on the availability of dissolved organic matter. N2 fixation also showed a positive correlation with total chlorophyll and the C:N ratio of phytoplankton, but not to the P excess compared to N. We conclude that the diazotrophic community responds to the composition of phytoplankton rather than the extent of N deficiency and the availability of bulk DOM in this system.

  15. Spatial structure of the zooplankton community in the coastal upwelling system off central-southern Chile in spring 2004 as assessed by automated image analysis

    Manríquez, Karen; Escribano, Ruben; Riquelme-Bugueño, Ramiro

    2012-01-01

    Size spectra of the mesozooplankton community was studied under the influence of coastal upwelling during austral spring 2004 in the coastal upwelling zone off central-southern Chile. Size spectra were derived from the ZooImage analysis of digitalized zooplankton samples obtained from the upper 200 m during a survey carried out under active upwelling (November 2004). An upwelling filament extended up to 180 km offshore, and the upper boundary of the oxygen minimum zone (1 mL O 2 L -1) varied between 20 m (nearshore) and 300 m depth (oceanic). The community descriptors (slope of the size spectra, size class index, abundance of size classes) were derived from the size spectra. Stepwise multiple regression analysis found significant correlations between these descriptors and oceanographic variables (temperature, dissolved oxygen, chlorophyll-a, OMZ depth). These data suggest an upwelling-dependent zooplankton distribution characterized by aggregations in a mid-shelf zone, where the log-normalized size spectra become flatter due to an increased abundance of larger size classes (>3 mm). In contrast, the inshore and offshore zones were dominated by small (zone coincided with moderate levels of chlorophyll-a (ca. 1 μg L -1) and the OMZ depth near 200 m. These spatial patterns and slopes of the size spectra however, were subjected to a significant day vs. night effect mostly explained by the diel vertical migration of the euphausiid Euphausia mucronata. This migration can descend below 200 m during the daylight, causing the larger size classes to disappear from the size spectrum and resulting in a steeper slope. Time-dependent effects must, therefore, be considered when examining the spatial patterns of zooplankton in coastal upwelling zones.

  16. Climate change impacts on municipal, mining, and agricultural water supplies in Chile

    Daniel G. Neary; Pablo Garcia-Chevesich

    2008-01-01

    Agricultural and municipal water supply interests in Chile rely heavily on streams which flow from the Andes Mountains. The highly productive Copiapo agricultural region, on the southern edge of the Atacama Desert, is a major supplier of fruit and other crops for the Northern American market during winter. This region relies entirely on snow and icemelt streams to...

  17. 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

    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

  18. Quaternary Tectonic Tilting Governed by Rupture Segments Controls Surface Morphology and Drainage Evolution along the South-Central Coast of Chile

    Echtler, H. P.; Bookhagen, B.; Melnick, D.; Strecker, M.

    2004-12-01

    The Chilean coast represents one of the most active convergent margins in the Pacific rim, where major earthquakes (M>8) have repeatedly ruptured the surface, involving vertical offsets of several meters. Deformation along this coast takes place in large-scale, semi-independent seismotectonic segments with partially overlapping transient boundaries. They are possibly related to reactivated inherited crustal anisotropies; internal seismogenic deformation may be accommodated by structures that have developed during accretionary wedge evolution. Seismotectonic segmentation and the identification of large-scale rupture zones, however, are based on limited seismologic und geodetic observations over short timespans. In order to better define the long-term behavior and deformation rates of these segments and to survey the tectonic impact on the landscape on various temporal and spatial scales, we investigated the south-central coast of Chile (37-38S). There, two highly active, competing seismotectonic compartments influence the coastal and fluvial morphology. A rigorous analysis of the geomorphic features is a key for an assessment of the tectonic evolution during the Quaternary and beyond. We studied the N-S oriented Santa María Island (SMI), 20 km off the coast and only ~70km off the trench, in the transition between the two major Valdivia (46-37S) and Concepción (38-35S) rupture segments. The SMI has been tectonically deformed throughout the Quaternary and comprises two tilt domains with two topographic highs in the north and south that are being tilted eastward. The low-lying and flat eastern part of the island is characterized by a set of emergent Holocene strandlines related to coseismic uplift. We measured detailed surface morphology of these strandlines and E-W traversing ephemeral stream channels with a laser-total station and used these data to calibrate and validate high-resolution, digital imagery. In addition, crucial geomorphic markers were dated by the

  19. 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

    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

  20. Common catabolic enzyme patterns in a microplankton community of the Humboldt Current System off northern and central-south Chile: Malate dehydrogenase activity as an index of water-column metabolism in an oxygen minimum zone

    González, R. R.; Quiñones, R. A.

    2009-07-01

    An extensive subsurface oxygen minimum zone off northern and central-south Chile, associated with the Peru-Chile undercurrent, has important effects on the metabolism of the organisms inhabiting therein. Planktonic species deal with the hypoxic and anoxic environments by relying on biochemical as well as physiological processes related to their anaerobic metabolisms. Here we characterize, for the first time, the potential enzymatic activities involved in the aerobic and anaerobic energy production pathways of microplanktonic organisms (oxygen concentration and microplanktonic biomass in the oxygen minimum zone and adjacent areas of the Humboldt Current System water column. Our results demonstrate significant potential enzymatic activity of catabolic pathways in the oxygen minimum zone. Malate dehydrogenase had the highest oxidizing activity of nicotinamide adenine dinucleotide (reduced form) in the batch of catabolic enzymatic activities assayed, including potential pyruvate oxidoreductases activity, the electron transport system, and dissimilatory nitrate reductase. Malate dehydrogenase correlated significantly with almost all the enzymes analyzed within and above the oxygen minimum zone, and also with the oxygen concentration and microplankton biomass in the water column of the Humboldt Current System, especially in the oxygen minimum zone off Iquique. These results suggest a possible specific pattern for the catabolic activity of the microplanktonic realm associated with the oxygen minimum zone spread along the Humboldt Current System off Chile. We hypothesize that malate dehydrogenase activity could be an appropriate indicator of microplankton catabolism in the oxygen minimum zone and adjacent areas.

  1. 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

    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

  2. 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

    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

  3. Germán Rodríguez Arias y el cine central de Chillán (1945. Una historia del exilio catalán en Chile

    David Caralt

    2011-08-01

    El presente artículo reivindica la figura de Rodríguez Arias y su aportación a la historia de la arquitectura chilena, explica su llegada a Chile y los motivos del encargo del Cine Central en base a una aproximación desde lo específico de la “arquitectura del exilio”. La parte final del texto se concentra en el discurrir del edificio y su estado actual de conservación.

  4. Hydrochemical and isotopic patterns in a calc-alkaline Cu- and Au-rich arid Andean basin: The Elqui River watershed, North Central Chile

    Oyarzún, Jorge; Carvajal, María José; Maturana, Hugo; Núñez, Jorge; Kretschmer, Nicole; Amezaga, Jaime M.; Rötting, Tobias S.; Strauch, Gerhard; Thyne, Geoffrey; Oyarzún, Ricardo

    2013-01-01

    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 SO 4 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 HCO 3 - content. In spite of the acid drainage pollution, water quality is adequate for human consumption and irrigation. This is a

  5. Tourism in Chile | CTIO

    Program PIA Program GO-FAAR Program Other Opportunities Tourism Visits to Tololo Astro tourism in Chile Tourism in Chile Information for travelers Visit Tololo Media Relations News Press Release Publications ‹› You are here CTIO Home » Outreach » Tourism » Tourism in Chile Tourism in Chile Map of

  6. Distribution and abundance of the South American sea lion Otaria flavescens (Carnivora: Otariidae along the central coast off Chile Distribución y abundancia del lobo marino común Otaria flavescens (Carnivora: Otariidae en la costa de Chile central

    MARITZA SEPÚLVEDA

    2011-03-01

    Full Text Available The onshore distribution and abundance of the South American sea lion Otaria flavescens along the central Chilean coast was estimated during the period January-February 2007. Additionally, changes in population abundance during the period 1970-2007 were examined. Population surveys were based on photographs taken from boats or aircraft. A total of 16301 sea lions (CI = 16209-16375 were counted in 33 colonies (6 breeding and 27 non-breeding sites. After correction to account for the proportion of individuals at sea and for pups not seen at the time of the survey, the mean estimated abundance was 18179 (95 % CI = 17777-18851 sea lions. Population trend analysis showed that from 1970 to 1985, South American sea lions showed a positive increase of approximately 2.1 % yr-1. Nevertheless, between 1985 and 1997 and between 1997 and 2007, the estimated number of sea lions showed a stable or slightly negative trend of 0.4 ± 0.1 % yr-1and 0.5 ± 0.1 % yr-1, respectively. We suggest that the overexploitation and decline of the principal fisheries in Central Chile could adversely impact the abundance and distribution of the South American sea lion in the study area.Se estimó la distribución y la abundancia poblacional del lobo marino común Otaria flavescens en la costa de Chile central durante los meses de enero y febrero de 2007. Adicionalmente, se analizaron los cambios en la abundancia de esta especie durante el período 1970-2007. Los censos poblacionales se basaron en fotografías tomadas desde embarcaciones menores o desde avionetas. Se contabilizaron un total de 16301 lobos marinos (IC = 16209-16375 en 33 colonias (6 reproductivas y 27 no reproductivas. Después de corregir por la proporción de animales en el agua y por crías no registradas al momento del censo, se estimó una abundancia promedio de 18179 (95 % CI = 17777-18851 lobos marinos en el área de estudio. El análisis de tendencia poblacional presentó que desde 1970 a 1985 la

  7. Streamflow responses in Chile to megathrust earthquakes in the 20th and 21st centuries

    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

  8. Weather Type classification over Chile; patterns, trends, and impact in precipitation and temperature

    Frias, T.; Trigo, R. M.; Garreaud, R.

    2009-04-01

    The Andes Cordillera induces considerable disturbances on the structure and evolution of the pressure systems that influences South America. Different weather types for southern South America are derived from the daily maps of geopotential height at 850hPa corresponding to a 42 year period, spanning from 1958 to 2000. Here we have used the ECWMF ERA-40 reanalysis dataset to construct an automated version of the Lamb Weather type (WTs) classification scheme (Jones et al., 1993) developed for the UK. We have identified 8 basic WTs (Cyclonic, Anticyclonic and 6 main directional types) following a similar methodology to that previously adopted by Trigo and DaCamara, 2000 (for Iberia). This classification was applied to two regions of study (CLnorth and CLsouth) which differ 20° in latitude, so that the vast Chile territory could be covered. Then were assessed the impact of the occurrence of this weather types in precipitation in Chile, as well as in the distribution of precipitation and temperature fields (reanalysis data) in southern half of South America. The results allow to conclude that the precipitation in central region of Chile is largely linked with the class occurrence (concerning CLnorth) of cyclonic circulation and of West quadrant (SW, W and NW), despite of it's relatively low frequency. In CLsouth, for its part, it is verified that the most frequent circulation is from the west quadrant, although the associated amount of rainfall is lower than in CLnorth. There was also a general decrease of precipitation at local weather stations chosen in the considered period of study, particularly in austral winter.

  9. Modernitet og forbrugskultur i Chile

    Cristoffanini, Pablo Rolando

    2012-01-01

    I de sidste årtier er Chile blevet et egentligt forbrugersamfund. Udbredelsen af forbrugskulturen og forbrugerismen er centrale fænomener i chilenernes dagligliv og har nået et omfang, som har konsekvenser for de borgere, der ikke kan deltage fuldt ud heri, noget som er typisk for et samfund med en...... ujævn økonomisk udvikling og med store sociale forskelle. Denne proces er ikke et produkt af en stille, fredelig og naturlig samfundsudvikling, således som magteliten og de toneangivende intellektuelle i Chile har fremstillet det. Som jeg vil vise, er skabelsen af et egentlig forbrugssamfund knyttet til...... til i dag. Ifølge disse er Chile blevet et moderne samfund netop i kraft af, at Chile er et ægte forbrugersamfund med alt, hvad dette indebærer, såvel materielt som symbolsk. For det tredje er billedet af Chile som en ”supermoderne” nation i den latinamerikanske kontekst en udbredt forestilling hos...

  10. Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

    Muñoz,Marcia; Aguirre,Luis; Vergara,Mario; Demant,Alain; Fuentes,Francisco; Fock,Andrés

    2010-01-01

    In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'S), an Upper Oligocene-Lower Miocene volcanic series belonging to the Abanico Formation (Late Eocene-Early Miocene) is exposed. The rock successions outcropping in both areas, ca. 3,300 m total thickness, have been affected by very low-grade, non-deformative metamorphism in the prehnite-pumpellyite facies. This is represented by the widespread development of secondary mineral assemblages compo...

  11. Effect of the Andes Cordillera on Precipitation from a Midlatitude Cold Front

    2009-09-01

    fall) 2008. As shown later, the event had typical features and produced 30–50 mm of rainfall in central Chile. Our analysis is based on in situ and...collective comments and suggestions have greatly improved the manuscript. We also thank Direccion de Aguas of Chile, and Mr. Dan Dawson of the

  12. Formation of post-fire water-repellent layers in Monterrey pine (Pinus radiata D. Don) plantations in south-central Chile

    P. Garcia-Chevesich; R. Pizarro; C. L. Stropki; P. Ramirez de Arellano; P. F. Ffolliott; L. F. DeBano; Dan Neary; D. C. Slack

    2010-01-01

    A wildfire burned about 15,000 ha of Monterrey Pine (Pinus radiata D. Don) plantations near Yungay, Chile, in January of 2007. Post-fire water repellency (hydrophobicity) was measured using the water-drop-penetration-time (WDPT) method at depths of 0, 5, and 10 mm from the soil surface. These measurements were collected on burned sites of both young (4-years old) and...

  13. 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

    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

  14. Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state Metamorfismo de facies prehnita-pumpellyita en la Formación Abanico del Cenozoico, Andes centrales de Chile (33°50'S): controles químicos y de escala sobre las asociaciones minerales, el progreso de la reacción y el estado de equilibrio

    Marcia Muñoz; Luis Aguirre; Mario Vergara; Alain Demant; Francisco Fuentes; Andrés Fock

    2010-01-01

    In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'S), an Upper Oligocene-Lower Miocene volcanic series belonging to the Abanico Formation (Late Eocene-Early Miocene) is exposed. The rock successions outcropping in both areas, ca. 3,300 m total thickness, have been affected by very low-grade, non-deformative metamorphism in the prehnite-pumpellyite facies. This is represented by the widespread development of secondary mineral assemblages compo...

  15. Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S: chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state Metamorfismo de facies prehnita-pumpellyita en la Formación Abanico del Cenozoico, Andes centrales de Chile (33°50'S: controles químicos y de escala sobre las asociaciones minerales, el progreso de la reacción y el estado de equilibrio

    Marcia Muñoz

    2010-01-01

    Full Text Available In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'S, an Upper Oligocene-Lower Miocene volcanic series belonging to the Abanico Formation (Late Eocene-Early Miocene is exposed. The rock successions outcropping in both areas, ca. 3,300 m total thickness, have been affected by very low-grade, non-deformative metamorphism in the prehnite-pumpellyite facies. This is represented by the widespread development of secondary mineral assemblages composed of epidote, mixed-layer chlorite-smectite, albite, quartz, white mica, and titanite. These mineral assemblages also contain pumpellyite, prehmte or prehnite+actinolite in a few samples. Chemical characteristics, such as low compositional variability of mixed-layer chlorite-smectite and actino-lite independent from the metadomain where these phases are hosted, along with a high proportion of chlorite layers in the former, suggest that these phases closely represent the whole rock effective bulk composition. On the contrary, pumpellyite compositions show a higher variability and a strong metadomain control evidencing its lower equilibration kinetics and leaving only those that grow in the rock matrix as the more closely representative of a whole rock effective bulk compositional control. Mineral assemblages from both areas show evidence of having been formed during the same metamorphic event where reactions have ocurred equivalently between them. However, local differences in chemical variables controlling this process are recognizable. A higher CO2 concentration in the fluids during the metamorphism in the El Volcán area than in the Rodeo de los Bueyes area is suggested by the scarce development of prehnite and the ubiquitous presence of calcite in the metamorphic assemblages of the former. Pressure and temperature of this metamorphic event have been roughly estimated to be lower than 2-3 kbar and 320°C, respectively.En las areas de El Volcán y Rodeo de los Bueyes, Cordillera Principal al este de Santiago (33°50'S, aflora una serie volcánica del Oligoceno Superior-Mioceno Inferior perteneciente a la Formación Abanico (Eoceno Tardío-Mioceno Temprano. Las sucesiones de roca expuestas en ambas areas, de ca. 3.300 m de espesor total, fueron afectadas por metamorfismo no deformativo de muy bajo grado en facies prehnita-pumpellyita. Esto está representado en el desarrollo extensivo de arreglos de minerales secundarios formados por epidota, inter-estratificados de clorita-esmectita, albita, cuarzo, mica blanca, y titanita. Estos arreglos minerales contienen además pumpellyita, prehnita o prehnita+actinolita en algunas muestras. Las características químicas tales como una baja variabilidad composicional de los interestratificados de clorita-esmectita y actinolita independientemente del dominio donde se hospedan estas fases, junto con una alta proporción de capas de clorita en las primeras, sugieren que estas fases representan cercanamente la composición efectiva de la roca total. Por el contrario, la composición de las pum-pellyitas muestra una mayor variabilidad y un fuerte control del metadominio donde éstas se desarrollan evidenciando una baja cinética de equilibrio y dejando sólo a aquellas desarrolladas en la matriz como formadas bajo un control composicional efectivo de la roca total. Los arreglos minerales de ambas areas muestran evidencias de haberse formado bajo un mismo evento metamórñco bajo el cual las reacciones se han desarrollado de manera equivalente. Aún así se reconocen diferencias químicas locales que controlan este proceso. Una mayor concentración de CO2 en los fluidos durante el metamorfismo en el area de El Volcán, con respecto al area de Rodeo de los Bueyes, se ve representada en la presencia escasa de prehnita, y abundante de calcita, en sus asociaciones minerales. La presion y temperatura de este evento metamórfico han sido gruesamente estimadas en valores inferiores a 2-3 kbar y 320°C, respectivamente.

  16. Organic Matter Reduces Copper Toxicity for the Earthworm Eisenia fetida in Soils from Mining Areas in Central Chile Materia Orgánica Reduce la Toxicidad del Cobre para la Lombriz Eiseniafetida en Suelos de Áreas Mineras en Chile Central

    Gonzalo Ávila

    2009-06-01

    Full Text Available The Aconcagua River basin (Central Chile is one of the most important agricultural areas in the country. However, several copper (Cu mining operations are located in the basin. The objective of the study was to determine Cu toxicity for the earthworm Eisenia fetida (Savigny 1826 in the agricultural soils of the basin. We determined the production of cocoons and juveniles of earthworms in the studied soils. The soils differed in the concentrations of organic matter (OM, range 2-6%, pH (range 7.3-8.3, texture (from loamy sand to clay loam, and total Cu concentrations (range 230-960 mg kg-1. Concentrations of Cu and OM in the soils were the variables that determined the earthworms’ biological response. In contrast, pH and texture did not affect this response. Cocoon and juvenile production decreased considerably in soils with elevated Cu concentrations (>500 mg kg-1, regardless of OM concentrations. Cocoon production decreased in the soils with Cu concentrations below 500 mg kg-1 when OM concentrations were below 3.5%. In contrast, cocoon production did not vary when OM concentrations were above 3.5%. The same effect of OM was observed on juvenile production. In this case, the threshold for OM concentration was 2.5%. It was concluded that it is important to consider OM concentrations in order to predict the biological response of earthworms in these soils.La cuenca del Río Aconcagua (Chile Central es una de las más importantes áreas agrícolas en el país. Por otro lado, varias industrias de la minería de cobre (Cu se encuentran ubicadas en esta cuenca. El objetivo del estudio fue determinar la toxicidad de Cu para la lombriz Eiseniafetida (Savigny 1826 en los suelos agrícolas de la cuenca. Se determinó la producción de capullos y juveniles de la lombriz en suelos estudiados. Los suelos se diferenciaron por las concentraciones de materia orgánica (MO, rango 2-6%, pH (rango 7,3-8,3, textura (entre arenoso franca y franco arcillosa y

  17. 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

    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

  18. Using 137Cs and 210Pbex and other sediment source fingerprints to document suspended sediment sources in small forested catchments in south-central Chile

    Schuller, P.; Walling, D.E.; Iroumé, A.; Quilodrán, C.; Castillo, A.; Navas, A.

    2013-01-01

    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) 137 Cs and excess lead-210, the environmental radionuclides 226 Ra and 40 K 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

  19. Imaging the Laguna del Maule Volcanic Field, central Chile using magnetotellurics: Evidence for crustal melt regions laterally-offset from surface vents and lava flows

    Cordell, Darcy; Unsworth, Martyn J.; Díaz, Daniel

    2018-04-01

    Magnetotelluric (MT) data were collected at the Laguna del Maule volcanic field (LdMVF), located in central Chile (36°S, 70.5°W), which has been experiencing unprecedented upward ground deformation since 2007. These data were used to create the first detailed three-dimensional electrical resistivity model of the LdMVF and surrounding area. The resulting model was spatially complex with several major conductive features imaged at different depths and locations around Laguna del Maule (LdM). A near-surface conductor (C1; 0.5 Ωm) approximately 100 m beneath the lake is interpreted as a conductive smectite clay cap related to a shallow hydrothermal reservoir. At 4 km depth, a strong conductor (C3; 0.3 Ωm) is located beneath the western edge of LdM. The proximity of C3 to the recent Pleistocene-to-Holocene vents in the northwest LdMVF and nearby hot springs suggests that C3 is a hydrous (>5 wt% H2O), rhyolitic partial melt with melt fraction >35% and a free-water hydrothermal component. C3 dips towards, and is connected to, a deeper conductor (C4; 1 Ωm). C4 is located to the north of LdM at >8 km depth below surface and is interpreted as a long-lived, rhyolitic-to-andesitic magma reservoir with melt fractions less than 35%. It is hypothesized that the deeper magma reservoir (C4) is providing melt and hydrothermal fluids to the shallower magma reservoir (C3). A large conductor directly beneath the LdMVF is not imaged with MT suggesting that any mush volume beneath LdM must be anhydrous (10 km) as it moves from the deep magma reservoir (C4) to create small, ephemeral volumes of eruptible melt (C3). It is hypothesized that there may be a north-south contrast in physical processes affecting the growth of melt-rich zones since major conductors are imaged in the northern LdMVF while no major conductors are detected beneath the southern vents. The analysis and interpretation of features directly beneath the lake is complicated by the surface conductor C1 which attenuates

  20. 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

    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

  1. Chile ushers in new hydro era

    Moxon, S.

    1997-01-01

    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)

  2. Chile Energy Policy Review 2009

    NONE

    2009-10-22

    Since 1990, Chile has been the fastest growing economy in Latin America thanks to sound economic management and integration into the global economy. Chile can also be proud of its energy policy achievements. The pioneering privatisation and liberalisation of its electricity sector in the 1980s was the foundation for a competitive energy sector, which has sustained the rapid growth of the Chilean economy over the past two decades. Nonetheless, Chile faces the continuing challenge of finding additional energy supplies to fuel economic growth. Chile has limited fossil energy resources and depends on imports to meet three-quarters of its energy needs. The country's electricity sector has faced three periods of significant stress over the past decade. The last episode took place in 2007/2008, when the loss of natural gas imports from Argentina was further exacerbated by a drought in the central system, where hydropower normally accounts for over half of electricity generation. Drawing on the experience of IEA member countries, the Review assesses Chile's major energy challenges and provides recommendations. Six main themes emerge: the successful liberalisation of the power sector in the 1980s; the essential role played by the state in ensuring energy security; the re-formulation of Chile's long-term energy policy; the proposed reorganisation of the institutional framework; greater independence for th