WorldWideScience

Sample records for andes iahula 1974-2005

  1. ASTER Andes

    Science.gov (United States)

    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

  2. History of Lake Andes

    Data.gov (United States)

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

  3. Andes 1997 Gravity Data

    Data.gov (United States)

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

  4. Mujeres de los Andes

    OpenAIRE

    Arango, Luz Gabriela; Arizabaleta de García, María Teresa; Bejarano, Nilse; Borchart de Moreno, Christiana; Bucheli, Rocío Vaca; Cervantes, Elvira Llanos; Cisneros, Tatiana; Defossez, Anne-Claire; Fassin, Didier; Giraldo, Fernando Urrea; Li, Dina; Malaver, José; Montúfar, Verónica; Moscoso, Martha; Ortega, Diego Zapata

    2016-01-01

    El Seminario "Mujeres De Los Andes: Condiciones De Vida Y Salud" tuvo lugar en la ciudad de Quito, del 6 al 10 de junio de 1991. Reunió investigadores de distintas disciplinas académicas y actores de variados campos, de cuatro países del área andina-Bolivia, Colombia, Ecuador y Perú-, en los cuales está presente el Instituto Francés de Estudios Andinos, principal instigador del evento. Este libro, que reúne la mayor parte de las ponencias en él presentadas, se inscribe en la línea de las corr...

  5. 78 FR 24228 - Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Final Comprehensive Conservation Plan

    Science.gov (United States)

    2013-04-24

    ... review and comment following the announcement in the Federal Register on October 29, 2012 ] (77 FR 65574... Fish and Wildlife Service Lake Andes National Wildlife Refuge Complex, Lake Andes, SD; Final... conservation plan and finding of no significant impact (FONSI) for the Lake Andes National Wildlife...

  6. The ANDES Deep Underground Laboratory

    CERN Document Server

    Bertou, X

    2013-01-01

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

  7. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1994 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1994 calendar year. The report begins...

  8. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : Updated- 2003 annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 2003 calendar year. The report begins...

  9. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1996 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1996 calendar year. The report begins...

  10. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1997 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1997 calendar year. The report begins...

  11. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1998 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1998 calendar year. The report begins...

  12. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1999 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1999 calendar year. The report begins...

  13. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 1995 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1995 calendar year. The report begins...

  14. Lake Andes National Wildlife Refuge Complex : Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, Lake Andes Wetland Management District : 2000 Annual narrative report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 2000 calendar year. The report begins...

  15. Lake Andes NWR Water Use Report- 1958

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report contains locations and water use at Lake Andes NWR for 1958. The report highlights the weather, water, habitat, and wildlife conditions for the year of...

  16. Global water watch in the Andes

    OpenAIRE

    S. Ruiz-Córdova; B. Duncan

    2001-01-01

    An "offspring" of SANREM Philippines experience, the Water Resources Management and Environmental Education activity in the Andes is approaching problems of water through community-based, participatory research. Forty-three citizens in Ecuador and eleven in Peru have become certified water quality monitors. Under sponsorship of UNORCAC, SANREM's partner in the Andes, a significant portion of water quality data obtained is the result of their efforts. Since July 1999 a time series of 2,800 bac...

  17. Active tectonics of the Andes

    Science.gov (United States)

    Dewey, J. F.; Lamb, S. H.

    1992-04-01

    Nearly 90 mm a -1 of relative plate convergence is absorbed in the Andean plate-boundary zone. The pattern of active tectonics shows remarkable variations in the way in which the plate slip vector is partitioned into displacement and strain and the ways in which compatibility between different segments is solved. Along any traverse across the plate-boundary zone, the sum of relative velocities between points must equal the relative plate motion. We have developed a kinematic synthesis of displacement and strain partitioning in the Andes from 47°S to 5°N relevant for the last 5 Ma based upon: (1) relative plate motion deduced from oceanic circuits giving a roughly constant azimuth between 075 and 080; (2) moment tensor solutions for over 120 crustal earthquakes since 1960; (3) structural studies of deformed Plio-Pleistocene rocks; (4) topographic/geomorphic studies; (5) palaeomagnetic data; and (6) geodetic data. We recognize four neotectonic zones, with subzones and boundary transfer zones, that are partitioned in different ways. These zones are not coincident with the 'classic' zones defined by the presence or absence of a volcanic chain or differences in finite displacements and strains and tectonic form; the long-term segmentation and finite evolution of the Andes may not occur in constantly defined segments in space and time. In Segment 1 (47°-39°S), the slip vector is partitioned into roughly orthogonal Benioff Zone slip with large magnitude/large slip-surface earthquakes and both distributed dextral shear giving clockwise rotations of up to 50° and dextral slip in the curved Liquine-Ofqui Fault System giving 5°-10° of anticlockwise fore-arc rotation. In Segment 2 (39°-20°S), the slip vector is partitioned into Benioff Zone slip roughly parallel with the slip vector, Andean crustal shortening and a very small component of dextral slip, including that on the Atacama Fault System. Between 39° and 34°S, a cross-strike dextral transfer, which deflects

  18. Recreational Fishery Management Plan for Lake Andes National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Current condition of lake Andes (1996) and highlights potential problems and recommendations for improving the lake as a hatchery. Lake Andes was a much larger body...

  19. Formalized morphostructural zoning of the mountain zone of the Andes

    Energy Technology Data Exchange (ETDEWEB)

    Gabrielov, A.M.; Gvishiani, A.D.; Zhidkov, M.P.

    1982-01-01

    A plan is presented for morphostructural zoning of the Andes compiled according to formalized signs for purposes of seismic forecasting. Characteristics are presented for the basic morphostructural subdivisions of the Andes.

  20. Fish Population Investigation: Lake Andes, Charles Mix County

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Brief background on Lake Andes fishing history, and data on current fish populations. Lake Andes was a much larger body of water prior to the construction of an...

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

    Directory of Open Access Journals (Sweden)

    J Fernández

    2008-01-01

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

  2. LANDSAT imagery of the Central Andes

    Science.gov (United States)

    Komer, C. A.; Morgan, P.

    1986-01-01

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

  3. Changing Student Attitudes using Andes, An Intelligent Homework System

    Science.gov (United States)

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

    2007-03-01

    The size of introductory physics lectures often inhibits personal homework assistance and timely corrective feedback. Andes, an intelligent homework help system designed for two semesters of introductory physics, can fill this need by encouraging students to use sound problem solving techniques and providing immediate feedback on each step of a solution. On request, Andes provides principles-based hints based on previous student actions. A multi-year study at the U.S. Naval Academy demonstrates that students using Andes perform better than students working the same problems as graded pencil and paper homeworks. In addition, student attitude surveys show that Andes is preferred over other homework systems. These findings have implications for student attitudes toward, and mastery of, physics. See http://www.andes.pitt.edu for more information.

  4. Annual narrative report: Lake Andes National Wildlife Refuge, Karl Mundt National Wildlife Refuge, and Lake Andes Wetland Management District: Calendar year 1975

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This collection of monthly activity reports summarizes activities on Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR during the 1975 calendar year. Resource...

  5. Lake Andes Easement Refuges: Narrative report: September to December, 1946

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report summarizes activities on Lake Andes NWR between September and December of 1946. Water conditions, waterfowl, furbearers, maintenance and...

  6. Seismological Parameters in the Northern Andes, Venezuela

    Science.gov (United States)

    Sobiesiak, M.; Palme de Osechas, C.; Choy, J. E.; Morandi S., M. T.; Campo, M.; Granado Ruiz, C.

    2001-12-01

    Venezuelas tectonic setting as part of the plate boundary between the Caribbean and the South American plate causes two major seismologically active fault systems: the roughly west - east trending strike slip fault system along the coast with numerous sub-parallel faults and the Bocono fault system, which dominates the Venezuelan southwest - northeast striking Andes. The main Bocono fault reaches a total length of about 500 km and has a width of approximately 100 km between the southern and northern baseline of the mountain slopes which are marked by inverse faults. This is believed to be due to strain partitioning, a concept which seems to apply as well to the Bocono fault system. The whole fault system is characterized by a high seismicity rate of small scale and intermediate event magnitudes ranging from 1.5 to 6.3 in the last fifty years. In this study we would like to present an investigation on 39 focal mechanism solutions and a b-value mapping of the Andean region with the main goal to throw light on the stess and strain situation. For recompiling the focal memchanisms calculated from first motion polarities, various sources had to been used: seismograms from stations of the local and regional networks of the Seismological Center of ULA, the national seismic network operated by FUNVISIS, the seismic network Lago Maracaibo of PDVSA and the local seismic network of DESURCA. For the b-value mapping we used the two catalogues of ULA and DESURCA of which the last one registered more than 6500 events from 1994 to 1999. The set of focal mechanism solutions studied showed normal, strike slip, and reverse faulting mechanisms concentrated in distinct areas of the Bocono fault system and thus resulting in a zonation also supported by the determinations of the azimuths of the maximum horizontal stress SHmax. This hypothesis of the zonation of the Andes region is strongly supported by the results of the b-value mapping. The zonation as seen in the varying major stress

  7. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1989

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1989 calendar year. The report...

  8. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1986

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1986 calendar year. The report...

  9. Lake Andes National Wildlife Refuge : Annual narrative report : Calendar year 1992

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1992 calendar year. The report begins...

  10. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1985

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1985 calendar year. The report...

  11. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1987

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1987 calendar year. The report...

  12. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1990

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1990 calendar year. The report...

  13. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1988

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1988 calendar year. The report...

  14. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1983

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1983 calendar year. The report...

  15. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1984

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1984 calendar year. The report...

  16. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1981 calendar year. The report...

  17. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1982

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Lake Andes WMD, and Karl E. Mundt NWR outlines Refuge accomplishments during the 1982 calendar year. The report...

  18. Lake Andes National Wildlife Refuge Complex : Annual narrative report : Calendar year 1991

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1991 calendar year. The report begins...

  19. Lake Andes National Wildlife Refuge Complex : Annual narrative report : Calendar year 1993

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR, Karl Mundt NWR, and Lake Andes WMD outlines Refuge accomplishments during the 1993 calendar year. The report begins...

  20. The first ANDES elements: 9-DOF plate bending triangles

    Science.gov (United States)

    Militello, Carmelo; Felippa, Carlos A.

    1991-01-01

    New elements are derived to validate and assess the assumed natural deviatoric strain (ANDES) formulation. This is a brand new variant of the assumed natural strain (ANS) formulation of finite elements, which has recently attracted attention as an effective method for constructing high-performance elements for linear and nonlinear analysis. The ANDES formulation is based on an extended parametrized variational principle developed in recent publications. The key concept is that only the deviatoric part of the strains is assumed over the element whereas the mean strain part is discarded in favor of a constant stress assumption. Unlike conventional ANS elements, ANDES elements satisfy the individual element test (a stringent form of the patch test) a priori while retaining the favorable distortion-insensitivity properties of ANS elements. The first application of this formulation is the development of several Kirchhoff plate bending triangular elements with the standard nine degrees of freedom. Linear curvature variations are sampled along the three sides with the corners as gage reading points. These sample values are interpolated over the triangle using three schemes. Two schemes merge back to conventional ANS elements, one being identical to the Discrete Kirchhoff Triangle (DKT), whereas the third one produces two new ANDES elements. Numerical experiments indicate that one of the ANDES element is relatively insensitive to distortion compared to previously derived high-performance plate-bending elements, while retaining accuracy for nondistorted elements.

  1. Out of the Andes: patterns of diversification in clearwing butterflies.

    Science.gov (United States)

    Elias, M; Joron, M; Willmott, K; Silva-Brandão, K L; Kaiser, V; Arias, C F; Gomez Piñerez, L M; Uribe, S; Brower, A V Z; Freitas, A V L; Jiggins, C D

    2009-04-01

    Global biodiversity peaks in the tropical forests of the Andes, a striking geological feature that has likely been instrumental in generating biodiversity by providing opportunities for both vicariant and ecological speciation. However, the role of these mountains in the diversification of insects, which dominate biodiversity, has been poorly explored using phylogenetic methods. Here we study the role of the Andes in the evolution of a diverse Neotropical insect group, the clearwing butterflies. We used dated species-level phylogenies to investigate the time course of speciation and to infer ancestral elevation ranges for two diverse genera. We show that both genera likely originated at middle elevations in the Andes in the Middle Miocene, contrasting with most published results in vertebrates that point to a lowland origin. Although we detected a signature of vicariance caused by the uplift of the Andes at the Miocene-Pliocene boundary, most sister species were parapatric without any obvious vicariant barrier. Combined with an overall decelerating speciation rate, these results suggest an important role for ecological speciation and adaptive radiation, rather than simple vicariance.

  2. Andes hantavirus variant in rodents, southern Amazon Basin, Peru.

    Science.gov (United States)

    Razuri, Hugo; Tokarz, Rafal; Ghersi, Bruno M; Salmon-Mulanovich, Gabriela; Guezala, M Claudia; Albujar, Christian; Mendoza, A Patricia; Tinoco, Yeny O; Cruz, Christopher; Silva, Maria; Vasquez, Alicia; Pacheco, Víctor; Ströher, Ute; Guerrero, Lisa Wiggleton; Cannon, Deborah; Nichol, Stuart T; Hirschberg, David L; Lipkin, W Ian; Bausch, Daniel G; Montgomery, Joel M

    2014-02-01

    We investigated hantaviruses in rodents in the southern Amazon Basin of Peru and identified an Andes virus variant from Neacomys spinosus mice. This finding extends the known range of this virus in South America and the range of recognized hantaviruses in Peru. Further studies of the epizoology of hantaviruses in this region are warranted.

  3. Rapid millennial-scale vegetation changes in the tropical Andes

    NARCIS (Netherlands)

    D.H. Urrego; H. Hooghiemstra; O. Rama-Corredor; B. Martrat; J.O. Grimalt; L. Thompson

    2015-01-01

    We compare eight pollen records reflecting climatic and environmental change from the tropical Andes. Our analysis focuses on the last 50 ka, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extra

  4. Lithospheric scale model of Merida Andes, Venezuela (GIAME Project)

    Science.gov (United States)

    Schmitz, M.; Orihuela, N. D.; Klarica, S.; Gil, E.; Levander, A.; Audemard, F. A.; Mazuera, F.; Avila, J.

    2013-05-01

    Merida Andes (MA) is one of the most important orogenic belt in Venezuela and represents the northern culmination of South America Andes. During the last 60 years, several models have been proposed to explain the shallow and deep structure, using different geological, geophysical, seismological, geochemical and petrologic concepts; nevertheless, most of them have applied local observation windows, and do not represent the major structure of MA. Therefore, a multidisciplinary research group, coordinated by FUNVISIS, in close cooperation with UCV, ULA and PDVSA, is proposed in order to get the outlined goals in the project entitled GIAME ("Geociencia Integral de los Andes de MErida") was established, which aims to generate a lithospheric scale model and the development of a temporal dynamic model for the MA. As a base for lithospheric investigations of the Merida Andes, we are proposing three wide angle seismic profiles across the orogen on three representative sites, in order to determine the inner structure and its relation with the orogen's gravimetric root. To the date, there are no seismic studies at lithospheric scale which cross MA. The wide angle seismic will be complemented with the re-processing and re-interpretation of existing reflection seismic data, which will allow to establish a relationship between MA and its associated flexural basins (Maracaibo and Barinas-Apure basins). Depending on the results of the VENCORP Project (VENezuelan COntinental Reflection Profiling), which might show some reliable results about crustal features and Moho reflectors along three long seismic profiles at Caribbean Moutain system, a reflection seismic profile across the central portion of MA is proposed. Additional tasks, consisting in MA quaternary deformation studies, using research methods like neotectonics and paleoseismology, georadar, numerical modeling, cinematic GPS, SAR interferometry, thermocronology, detailed studies on regional geology, flexural modeling

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

    OpenAIRE

    Barros, Agustina; Monz, Christopher; Pickering, Catherine

    2014-01-01

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

  6. Glacier shrinkage and water resources in the Andes

    Science.gov (United States)

    Francou, Bernard; Coudrain, Anne

    For more than a century glaciers around the world have been melting as air temperatures rise due to a combination of natural processes and human activity. The disappearance of these glaciers can have wide-ranging effects, such as the creation of new natural hazards or changes in stream flow that could threaten water suppliesSome of the most dramatic melting has occurred in the Andes mountain range in South America. To highlight the climatic and glacial change in the Andes and to encourage the scientific community to strengthen the glacier observation network that stretches from Colombia to the Patagonian ice fields, the Instituto Nacional de Recursos Naturales (INRENA), Perú, and the Institute of Research and Development (IRD), France, recently organized the second Symposium on Mass Balance of Andean Glaciers in Huaráz,Perú.

  7. Modeling the Glacial Buzzsaw in the Patagonian Andes

    Science.gov (United States)

    Brandon, M. T.; Tomkin, J. H.

    2006-12-01

    Modeling the Glacial Buzzsaw in the Patagonian Andes The concept of a "glacial buzzsaw" was spawned by Steve Porter's observation in 1977 and 1988 that the "equilibrium line altitude" (ELA) for alpine glaciation in the Andes parallels the summit elevations of the range. The modern ELA in the Patagonian Andes drops from about 4.5 km at 30 S to about 1 km at 50 S, due to colder temperatures at higher latitudes. The summit elevations decrease steadily by a similar amount over this 2200 km distance. The landscape of the western side of the Patagonian Andes clearly shows that it has long been dominated by glacial erosion. Locally preserved tills indicate that alpine glaciation was active at 7 to 4.6 Ma, if not earlier. The idea of a glacial buzzsaw is that erosion by alpine glaciers is aggressive enough to limit the height of a mountain range. Fission-track cooling ages indicate modest long-term erosion rates (~0.5 to 1 km/Ma) for the Patagonian Andes, which precludes the possibility that the range was trimmed down to size by Quaternary- age glaciations. Furthermore, the range shows clear evidence of growth by continental subduction and tectonic accretion along its eastern margin. Evidence for recent tectonic shortening is based on the observation that the range has an approximately constant taper, as expected for a critical wedge. The width of the range decreases southward in parallel with the decreasing summit elevations. We have developed a general analytical model for coupled wedge growth and glacial erosion that accounts for much of the tectonic evolution of the Patagonian Andes. The model is based on an actively accreting wedge that maintains a constant taper geometry. The size of the wedge is controlled by competition between accretion and glacial erosion. Recent work by one of us (JHT) and Gerard Roe shows that the erosional yield caused by alpine glaciation is approximately proportional to the local elevation difference between the summit of the range and the

  8. Crustal-thickness variations in the central Andes

    Science.gov (United States)

    Beck, Susan L.; Zandt, George; Myers, Stephen C.; Wallace, Terry C.; Silver, Paul G.; Drake, Lawrence

    1996-05-01

    We estimated the crustal thickness along an east-west transect across the Andes at lat 20°S and along a north-south transect along the eastern edge of the Altiplano from data recorded on two arrays of portable broadband seismic stations (BANJO and SEDA). Waveforms of deep regional events in the downgoing Nazca slab and teleseismic earthquakes were processed to isolate the P-to-S converted phases from the Moho in order to compute the crustal thickness. We found crustal-thickness variations of nearly 40 km across the Andes. Maximum crustal thicknesses of 70 74 km under the Western Cordillera and the Eastern Cordillera thin to 32 38 km 200 km east of the Andes in the Chaco Plain. The central Altiplano at 20°S has crustal thicknesses of 60 to 65 km. The crust also appears to thicken from north (16°S, 55 60 km) to south (20°S, 70 74 km) along the Eastern Cordillera. The Subandean zone crust has intermediate thicknesses of 43 to 47 km. Crustal-thickness predictions for the Andes based on Airy-type isostatic behavior show remarkable overall correlation with observed crustal thickness in the regions of high elevation. In contrast, at the boundary between the Eastern Cordillera and the Subandean zone and in the Chaco Plain, the crust is thinner than predicted, suggesting that the crust in these regions is supported in part by the flexural rigidity of a strong lithosphere. With additional constraints, we conclude that the observation of Airy-type isostasy is consistent with thickening associated with compressional shortening of a weak lithosphere squeezed between the stronger lithosphere of the subducting Nazca plate and the cratonic lithosphere of the Brazilian craton.

  9. A review of the geology of the Argentinian Fuegian Andes

    Science.gov (United States)

    Olivero, Eduardo B.; Martinioni, Daniel R.

    2001-06-01

    Seven stratigraphic units reflect the tectonic evolution of the Argentinian Fuegian Andes: Basement (Paleozoic-Jurassic); Lemaire Formation (Upper Jurassic); Yahgan-Beauvoir formations (Lower Cretaceous); Cerro Matrero Formation (Upper Cretaceous); Rı´o Claro Formation (Paleocene); La Despedida Group (Eocene); and Cabo Peña Formation (uppermost Eocene-Lower Oligocene). Basement rocks (garnet, quartz-sericite, and chlorite schists; and amphibolites) are unconformably covered by the Lemaire Formation (rhyolites; basalts; slates; and acidic volcaniclastic breccias, tuffs, conglomerates, and turbidites), formed during extensional tectonism. The post-rift Yahgan Formation (deep-marine black mudstones, andesitic volcaniclastic turbidites and tuffs) interfingers northward with the Beauvoir Formation (slope and platform black mudstones), and covers the Lemaire Formation unconformably. The Yahgan Formation represents an andesitic, volcaniclastic apron, coeval with a Pacific volcanic-arc, filling a marginal basin floored with oceanic crust. The Late Cretaceous compressional orogeny resulted in tectonic inversion, closure of the marginal basin, peak metamorphism and folding, and initial uplifting of the Fuegian Andes. By the latest Cretaceous-earliest Paleogene, the Andes were exposed to subaerial erosion, and the lowest Danian Rı´o Claro Formation bears clear evidence of an Andean clastic provenance. The Rı´o Claro Formation represents the first molasse deposits of the foreland stage of evolution of the Fuegian Andes. Earliest Paleogene north-verging thrust propagation deformed the Rı´o Claro Formation and older units, producing northward depocenter migration. La Despedida Group rests unconformably on the Rı´o Claro Formation and is involved in the thrust and fold belt. Important Eocene compression resulted in thrusting of central Andean basement schists and the Lemaire Formation over Lower Cretaceous and continental Paleogene rocks, respectively. In the

  10. Geochemical composition of river loads in the Tropical Andes: first insights from the Ecuadorian Andes

    Science.gov (United States)

    Tenorio Poma, Gustavo; Govers, Gerard; Vanacker, Veerle; Bouillon, Steven; Álvarez, Lenín; Zhiminaicela, Santiago

    2015-04-01

    Processes governing the transport of total suspended material (TSM), total dissolved solids (TDS) and particulate organic carbon (POC) are currently not well known for Tropical Andean river systems. We analyzed the geochemical behavior and the budgets of the particulate and dissolved loads for several sub-catchments in the Paute River basin in the southern Ecuadorian Andes, and examined how anthropogenic activities influenced the dynamics of riverine suspended and dissolved loads. We gathered a large dataset by regularly sampling 8 rivers for their TSM, POC, and TDS. Furthermore, we determined the major elements in the dissolved load and stable isotope composition (δ13C) of both the POC, and the dissolved inorganic carbon (DIC). The rivers that were sampled flow through a wide range of land uses including: 3 nature conservation areas (100 - 300 Km²), an intensive grassland and arable zone (142 Km²); downstream of two cities (1611 and 443 Km²), and 2 degraded basins (286 and 2492 Km²). We described the geochemical characteristics of the river loads both qualitatively and quantitatively. Important differences in TSM, POC and TDS yields were found between rivers: the concentration of these loads increases according with human activities within the basins. For all rivers, TSM, TDS and POC concentrations were dependent on discharge. Overall, a clear relation between TSM and POC (r²=0.62) was observed in all tributaries. The C:N ratios and δ13CPOC suggest that the POC in most rivers is mainly derived from soil organic matter eroded from soils dominated by C3 vegetation (δ13CPOC < -22‰). Low Ca:Si ratios (<1)and high δ13CDIC (-9 to -4) in the Yanuncay, Tomebamba1 and Machángara, rivers suggest that weathering of silica rocks is dominant in these catchments, and that the DIC is mainly derived from the soil or atmospheric CO2. In contrast, the Ca:Si ratio was high for the Burgay and Jadán rivers (1-13), and the low δ13CDIC values (-9 to -15) suggest that

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

    Science.gov (United States)

    Barros, Agustina; Monz, Christopher; Pickering, Catherine

    2015-03-01

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

  12. The Iconography of Painted Ceramics from the Northern Andes Title: La iconografía de la cerámica pintada del norte de los Andes

    OpenAIRE

    Felipe Cárdenas-Arroyo

    1998-01-01

    Felipe Cárdenas-Arroyo, arqueólogo colombiano de la Universidad de Los Andes en Bogotá, erudito de CASVA, especialista en momificación pre-hispánica de huesos humanos.Abstract: Felipe Cárdenas-Arroyo, Colombian archaeologist from the University of Los Andes in Bogotá, CASVA scholar, specialist in pre-Hispanic mummification and human bone.

  13. The largest holocene eruption of the Central Andes found

    OpenAIRE

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

    2013-01-01

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

  14. Giant evaporite belts of the Neogene central Andes

    Science.gov (United States)

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

    1991-04-01

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

  15. Desde los Andes al Orinoco y al Amazonas

    OpenAIRE

    Duque Escobar, Gonzalo

    2015-01-01

    La Orinoquia y la Amazonia con su considerable red hídrica natural y cadena de valor, esperan ver consolidadas dos rutas que pasando por los Andes articulen el Atlántico y el Pacífico, conformando dos corredores logísticos que avanzarían a Bogotá por el río Meta y a Quito por el río Napo; proyectos vitales para la integración de América del Sur y para la identidad y desarrollo de dichas regiones que comprenden el 46,7 % de la superficie sudamericana

  16. Mujeres de los andes: condiciones de vida y salud

    OpenAIRE

    Defossez, Anne-Claire; Bassin, Didier; Viveros, Mara; Sánchez Parga, José; Vaca Bucheli, Rocío; Llanos Cervantes, Elvira; Li, Dina; Urra Giraldo, Fernando; Zapata Arteaga, Diego; Poloni, Jacques; Moscoso, Martha; Bejarano, Nilse; Arango, Luz Gabriela; Palomino, Nancy; Borchart de Moreno, Cristiana

    1992-01-01

    El Seminario "Mujeres de los Andes: condiciones de vida y salud" tuvo lugar en la ciudad de Quito, del 6 al 10 de junio de 1991, reunió investigadores de distintas disciplinas académicas y actores de variados campos, de cuatro países del área andina Bolivia, Colombia, Ecuador y Perú-, en los cuales está presente el Instituto Francés de Estudios Andinos, principal instigador del evento. Este libro, que reúne la mayor parte de las ponencias en él presentadas, se inscribe en la línea de las cor...

  17. Protoplanetary Disk Structure With Grain Evolution: the ANDES Model

    CERN Document Server

    Akimkin, V; Wiebe, D; Semenov, D; Pavlyuchenkov, Ya; Vasyunin, A; Birnstiel, T; Henning, Th

    2013-01-01

    We present a self-consistent model of a protoplanetary disk: 'ANDES' ('AccretioN disk with Dust Evolution and Sedimentation'). ANDES is based on a flexible and extendable modular structure that includes 1) a 1+1D frequency-dependent continuum radiative transfer module, 2) a module to calculate the chemical evolution using an extended gas-grain network with UV/X-ray-driven processes surface reactions, 3) a module to calculate the gas thermal energy balance, and 4) a 1+1D module that simulates dust grain evolution. For the first time, grain evolution and time-dependent molecular chemistry are included in a protoplanetary disk model. We find that grain growth and sedimentation of large grains to the disk midplane lead to a dust-depleted atmosphere. Consequently, dust and gas temperatures become higher in the inner disk (R 50 AU), in comparison with the disk model with pristine dust. The response of disk chemical structure to the dust growth and sedimentation is twofold. First, due to higher transparency a partl...

  18. Did growth of high Andes slow down Nazca plate subduction?

    Science.gov (United States)

    Quinteros, J.; Sobolev, S. V.

    2010-12-01

    The convergence velocity rate of the Nazca and South-American plate and its variations during the last 100 My are quite well-known from the global plate reconstructions. The key observation is that the rate of Nazca plate subduction has decreased by about 2 times during last 20 Myr and particularly since 10 Ma. During the same time the Central Andes have grown to its present 3-4 km height. Based on the thin-shell model, coupled with mantle convection, it was suggested that slowing down of Nazca plate resulted from the additional load exerted by the Andes. However, the thin-shell model, that integrates stresses and velocities vertically and therefore has no vertical resolution, is not an optimal tool to model a subduction zone. More appropriate would be modeling it with full thermomechanical formulation and self-consistent subduction. We performed a set of experiments to estimate the influence that an orogen like the Andes could have on an ongoing subduction. We used an enhanced 2D version of the SLIM-3D code suitable to simulate the evolution of a subducting slab in a self-consistent manner (gravity driven) at vertical crossections through upper mantle, transition zone and shallower lower mantle. The model utilizes non-linear temperature- and stress-dependant visco-elasto-plastic rheology and phase transitions at 410 and 660 km depth. We started from a reference case with a similar configuration as both Nazca and South-America plates. After some Mys of slow kinematicaly imposed subduction, to develop a coherent thermo-mechanical state, subduction was totally dynamic. On the other cases, the crust was slowly thickened artificially during 10 My to generate the Andean topography. Although our first results show no substantial changes on the velocity pattern of the subduction, we, however, consider this result as preliminary. At the meeting we plan to report completed and verified modeling results and discuss other possible cases of the late Cenozoic slowing down of

  19. Lake Andes National Wildlife Refuge: Narrative report: January to April, 1951

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report summarizes activities on Lake Andes National Wildlife Refuge between January and April of 1951. Water conditions, furbearers, and maintenance...

  20. Lake Andes Wetland Management District Annual narrative report: Calendar year 1989

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1989 calendar year. The report begins with an...

  1. Lake Andes Wetland Management District Annual narrative report : Calendar year 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1981 calendar year. The report begins with an...

  2. Lake Andes Wetland Management District Annual narrative report : Calendar year 1982

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1982 calendar year. The report begins with an...

  3. Lake Andes Wetland Management District Annual narrative report: Calendar year 1990

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1990 calendar year. The report begins with an...

  4. Lake Andes Wetland Management District Annual narrative report: Calendar year 1988

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1988 calendar year. The report begins with an...

  5. Lake Assessment Project Report, Lake Andes: Charles Mix County, South Dakota

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Lake Andes was included in the 1998 South Dakota 303(d) list as an impairment-related Total Maximum Daily Load waterbody. In 1922 Congress passed a bill that...

  6. Narrative Report : Lake Andes National Wildlife Refuge [September to December 1952

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes National Wildlife Refuge outlines Refuge accomplishments from September through December of 1952. The report begins by...

  7. Narrative report: January, February, March, and April, 1963: Lake Andes National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from January through April of 1963. The report begins by summarizing the weather...

  8. Lake Andes Waterfowl Production Area: Narrative report: January 1 through December 31, 1967

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR- Waterfowl Production Area outlines Refuge accomplishments during the 1967 calendar year. The report begins by...

  9. Lake Andes Wetlands District: Narrative report: January 1 through December 31, 1968

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetlands District outlines Refuge accomplishments during the 1968 calendar year. The report begins by summarizing the...

  10. Narrative report: Lake Andes National Wildlife Refuge: May 1, to August 31, 1955

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1955. The report begins by summarizing the weather conditions,...

  11. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1970

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1970 calendar year. The report begins by summarizing the weather...

  12. [Lake Andes National Wildlife Refuge: Narrative report: January to April, 1957

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from January through April of 1957. The report begins by summarizing the weather...

  13. Narrative report: Lake Andes National Wildlife Refuge: May 1, to August 31, 1953

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1953. The report begins by summarizing the weather conditions,...

  14. Lake Andes Wetlands District: Narrative report: January 1 through December 31, 1971

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetlands District outlines Refuge accomplishments during the 1971 calendar year. The report begins by summarizing the...

  15. Narrative report: May, June, July, and August, 1962: Lake Andes National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1962. The report begins by summarizing the weather conditions,...

  16. Lake Andes Wetland District: Narrative report: January 1 through December 31, 1970

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetlands District outlines Refuge accomplishments during the 1970 calendar year. The report begins by summarizing the...

  17. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1968

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1968 calendar year. The report begins by summarizing the weather...

  18. Lake Andes [Wetland Management District]: Narrative report: January 1 through December 31, 1972

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetlands District outlines Refuge accomplishments during the 1972 calendar year. The report begins by summarizing the...

  19. Lake Andes Wetlands District: Narrative report: January 1 through December 31, 1969

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetlands District outlines Refuge accomplishments during the 1969 calendar year. The report begins by summarizing the...

  20. Narrative report: Lake Andes National Wildlife Refuge: May 1, to August 31, 1957

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1957. The report begins by summarizing the weather conditions,...

  1. [Lake Andes National Wildlife Refuge: Narrative report: September to December, 1953

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from September through December of 1953. The report begins by summarizing the weather...

  2. Narrative report: Lake Andes National Wildlife Refuge: May 1, to August 31, 1956

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1956. The report begins by summarizing the weather conditions,...

  3. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1969

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1969 calendar year. The report begins by summarizing the weather...

  4. Narrative report: September, October, November, and December, 1962: Lake Andes National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from September through December of 1962. The report begins by summarizing the weather...

  5. Narrative report: Lake Andes National Wildlife Refuge: May 1, to August 31, 1954

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments from May through August of 1954. The report begins by summarizing the weather conditions,...

  6. Narrative report: January 1 through December 31, 1964: Lake Andes National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1964 calendar year. The report begins by summarizing the weather...

  7. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1971

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1971 calendar year. The report begins by summarizing the weather...

  8. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1965

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR and WPA outlines Refuge accomplishments during the 1965 calendar year. The report begins by summarizing the weather...

  9. Lake Andes Wetland Management District: Annual narrative report : Calendar year 1978

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines Refuge accomplishments during the 1978 calendar year. The report begins with an...

  10. Annual narrative report: Lake Andes National Wildlife Refuge and Management District: Calendar year 1974

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report summarizes activities on Lake Andes NWR during the 1974 calendar year. Monthly activities reports are provided. Resource management- including...

  11. Phase 1 Watershed Assessment Final Report: Lake Andes Watershed, Charles Mix County, South Dakota.

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Lake Andes was included in the 1998 South Dakota 303(d) list as an impairment-related Total Maximum Daily Load waterbody. In 1922 Congress passed a bill that...

  12. Lake Andes Wetland Management District: Annual narrative report: Calendar year 1992

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes Wetland Management District outlines Refuge accomplishments during the 1992 calendar year. The report begins with a...

  13. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1980

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1980 calendar year. The report begins with an introduction to the Refuge and...

  14. Lake Andes Wetland Management District: Annual narrative report : Calendar year 1979

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines Refuge accomplishments during the 1979 calendar year. The report begins with an...

  15. Lake Andes Wetland Management District: Annual narrative report : Calendar year 1977

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines Refuge accomplishments during the 1977 calendar year. The report begins with an...

  16. Lake Andes Wetland Management District : Annual narrative report : Calendar year 1980

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes WMD outlines Refuge accomplishments during the 1980 calendar year. The report begins with an introduction to the Refuge and...

  17. Lake Andes National Wildlife Refuge: Annual narrative report: Calendar year 1979

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1979 calendar year. The report begins with an introduction to the Refuge and...

  18. Lake Andes National Wildlife Refuge: Narrative report: January 1 through December 31, 1966

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR outlines Refuge accomplishments during the 1966 calendar year. The report begins by summarizing the weather...

  19. Lake Andes Wetland Management District Annual narrative report: Calendar year 1983

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Lake Andes Wetland Management District outlines District accomplishments during the 1983 calendar year. The report begins with an...

  20. Complex brittle deformation pattern along the Southern Patagonian Andes (Argentina)

    Science.gov (United States)

    Barberón, Vanesa; Sue, Christian; Ronda, Gonzalo; Ghiglione, Matías

    2016-04-01

    The Southern Patagonian Andes is located in the southern extreme of the Pacific subduction zone, where the Antartic oceanic plate sinks underneath South America. The history of the area begins with compression during Paleozoic, Jurassic extension associated to the rift and opening of the South Atlantic Ocean, then a sag stage in the Lower Cretaceous followed by a foreland phase as a result of plate tectonics (Ghiglione et al., 2016). The kinematic study is concentrated in the Argentinean foothills, between 46°40' and 48° SL. We measured around 800 fault planes and their striaes with the sense of movement in order to characterize the stress field. The software used to make the stress inversion were Tensor (Delvaux, 2011) and Multiple Inverse Method MIM (Yamaji et al., 2011). The stress field map was built with the results of the MIM. We present new data from 48 sites located in the northern sector of the Southern Patagonian Andes. The measurements were made in several rocks from Paleozoic to Lower Cretaceous, even though most were taken in pyroclastic jurassic rocks from El Quemado Complex. Paleostress tensors obtained are mostly strike-slip, although a 25% is normal and there are a few compresional. The pattern of faults found is complex. In some sites the tensor can be locally linked to satellite images and observations from the field or be related to a major thrust front. There is no clear correlation between the age and/or lithology with the tensor since the youngest rocks measured are Lower Cretaceous. Probably there are several generations of family faults connected to different and recent tectonic phases then the paleostress tensors might correspond to the latest tectonic events.

  1. ANDES: Statistical tools for the ANalyses of DEep Sequencing

    Directory of Open Access Journals (Sweden)

    Denison Mark R

    2010-07-01

    Full Text Available Abstract Background The advancements in DNA sequencing technologies have allowed researchers to progress from the analyses of a single organism towards the deep sequencing of a sample of organisms. With sufficient sequencing depth, it is now possible to detect subtle variations between members of the same species, or between mixed species with shared biomarkers, such as the 16S rRNA gene. However, traditional sequencing analyses of samples from largely homogeneous populations are often still based on multiple sequence alignments (MSA, where each sequence is placed along a separate row and similarities between aligned bases can be followed down each column. While this visual format is intuitive for a small set of aligned sequences, the representation quickly becomes cumbersome as sequencing depths cover loci hundreds or thousands of reads deep. Findings We have developed ANDES, a software library and a suite of applications, written in Perl and R, for the statistical ANalyses of DEep Sequencing. The fundamental data structure underlying ANDES is the position profile, which contains the nucleotide distributions for each genomic position resultant from a multiple sequence alignment (MSA. Tools include the root mean square deviation (RMSD plot, which allows for the visual comparison of multiple samples on a position-by-position basis, and the computation of base conversion frequencies (transition/transversion rates, variation (Shannon entropy, inter-sample clustering and visualization (dendrogram and multidimensional scaling (MDS plot, threshold-driven consensus sequence generation and polymorphism detection, and the estimation of empirically determined sequencing quality values. Conclusions As new sequencing technologies evolve, deep sequencing will become increasingly cost-efficient and the inter and intra-sample comparisons of largely homogeneous sequences will become more common. We have provided a software package and demonstrated its

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

    Directory of Open Access Journals (Sweden)

    CONSTANZA CASTILLO H.

    2002-01-01

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

  3. An elusive new species of Marsupial Frog (Anura: Hemiphractidae: Gastrotheca from the Andes of northern Peru

    Directory of Open Access Journals (Sweden)

    William E. Duellman

    2013-06-01

    Full Text Available A new species of marsupial frog, genus Gastrotheca, is described from high-elevation grasslands in the Andes in Región Amazonas in northernPeru, where even calling males are well hidden in deep moss. The new species is distinguished from all congeners by its unique color pattern that includes a narrow, blackbordered, yellow middorsal stripe. The species apparently belongs to the Gastrotheca plumbea Group, which ranges in the Andes from northern Colombia to northern Peru.

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

    OpenAIRE

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

    2013-01-01

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

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

    OpenAIRE

    César Aguilar; Niels Valencia

    2011-01-01

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

  6. Vulnerabilidad, resistividad en el campesinado rural de los Andes tropicales

    Directory of Open Access Journals (Sweden)

    Christoph Stadel

    2009-09-01

    Full Text Available Mientras que la colonización agrícola y humana tiene milenios de tradiciones culturales en los Andes tropicales, la agricultura y la superviviencia rural siempre representaban ‘sistemas abiertos’ adaptandose a una gran diversidad de condiciones medioambientales, políticas, culturales, sociales y económicas fluctuando con- tinuamente. Sin embargo, el patrimonio cultural tan variado y rico de los campesinos andinos con sus experiencias y conocimientos en sobrevivir en condiciones locales difíciles y sumamente vulnerables en muchos casos les ayudó a llegar a formas variadas de resistividad y resistencia frente a los estímulos y el estrés internos y externos. Además y dadas las condiciones medio ambientales tan diversas de las regiones andinas con su gran variedad de zonas altitudinales, nichos agrícolas y mosaicos culturales, se ha formado un paisaje rural muy complejo y variado. En este estudio se reconocen y se apoyan las identidades locales y regionales de las formas del uso de las tierras rurales y de las actividades agrícolas, además se examinan los impactos de las influencias supra-regionales y globales que determinan las condiciones climáticas, políticas, económicas y socio-culturales. De esta manera, una alta variabilidad y una baja predictabilidad de las condiciones andinas medioambientales y del desarrollo socio-económico forman los argumentos básicos en este estudio. Se rechaza la validez de un modelo universal del uso de las tierras agrícolas en los Andes así como una exposición inevitable de la agricultura montañesa frente a los riesgos de las fuerzas y los actores globales. Contrariamente, en el artículo se propone toda una serie de modelos locales y regionales para el uso de las tierras rurales que sean flexibles en relación al espacio y al tiempo tomando en cuenta las condiciones locales persistentes así como las nuevas influencias externas. Como resultado de estas consideraciones parece imprescindible

  7. Large slope failures in the La Paz basin, Bolivian Andes

    Science.gov (United States)

    Roberts, N. J.; Hermanns, R. L.; Rabus, B.; Guzmán, M. A.; Minaya, E.; Clague, J. J.

    2014-12-01

    The La Paz basin in the eastern Bolivian Andes has been a hotspot for large-scale, deep-seated gravitational slope deformation during the Holocene. In less than 2 Ma, a network of steep-sided valleys up to 800 m deep formed in sediments of the Altiplano Plateau and underlying basement rocks. We characterize the distribution, extent, mechanisms, and modern activity of large-scale failures within this landscape using optical image interpretation, existing geologic maps, synthetic RADAR interferometry (InSAR), and field investigation. Deposits of nearly 20 landslides larger than 100 Mm3 occur within the basin. Most failures have occurred in weakly lithified Late Miocene to Pliocene sedimentary rocks and include earth flows, translational and rotational landslides, and plug flows. Failures in underlying tectonized Paleozoic sedimentary rocks include bedding-parallel rockslides. The largest failure is the 3 km3 Achcocalla earth flow (ca. 11 ka BP), which ran out ~20 km. Other dated events span the period from the early Holocene to nearly the Colonial historic period. InSAR results show that many large slope failures, including the Achocalla earth flow, are currently moving at rates of a few centimeters to a few decimeters per year. Rapid deposition, shallow burial, and rapid incision of the basin fills produced steep slopes in weak geologic materials that, coupled with groundwater discharge from the valley walls, are the primary controls on instability. In contrast, the Altiplano surface has changed little in 2 Ma and the adjacent slopes of the Cordilleran Real, although steep, are relatively stable. Of the over 100 landslides that have occurred in the city of La Paz since the early twentieth century, most are at the margins of large, deep-seated prehistoric failures, and two of the most damaging historic landslides (Hanko-Hanko, 1582; Pampahasi, 2011) were large-scale reactivations of previously failed slopes. Improved understanding of large, deep-seated landslides in

  8. On recent measurements from the Andes Lidar Observatory

    Science.gov (United States)

    Liu, Alan Z.; Snively, Jonathan; Heale, Christopher; Cao, Bing

    2016-07-01

    The Andes Lidar Observatory is an upper atmosphere observatory located in Cerro Pachón, Chile (30.3S, 70.7W). It houses a Na Wind/Temperature Lidar, an all sky airglow imager, a mesospheric temperature mapper, an infrared imager and a meteor radar. This suite of instrumentation provides comprehensive measurements of the mesopause region and enables detailed study of wave dynamics. With the recent upgrade of the Na lidar, many complex dynamic processes were observed and resolved in detail. I will present several intriguing phenomena seen in the lidar measurement from recent campaigns, and a detailed analysis of a complex wave propagation event, which involved a large vertical wind oscillation exceeding 10 m/s. A nonlinear gravity wave model was able to reproduce most of the observed features. The results suggest that the wave experienced partial reflections at two altitudes and a critical layer in between, resulting in large vertical wind amplitude and multi-layer distribution of wave energy.

  9. Quaternary Glaciations in the Rio Mendoza Valley, Argentine Andes

    Science.gov (United States)

    Espizua, Lydia E.

    1993-09-01

    In the Rio Mendoza valley, five Pleistocene drifts and one Holocene drift are distinguished by multiple relative-age criteria, including surface-rock weathering, development of rock varnish, moraine morphology, soil-profile development, and stratigraphic relationships. Several absolute ages suggest a preliminary chronology. During the oldest (Uspallata) glaciation, a system of valley glaciers flowed 110 km from the Andean drainage divide and 80 km from Cerro Aconcagua to terminate at 1850 m. Drift of this ice advance is older than a widespread tephra dated by fission-track at 360,000 ± 36,000 yr. During the Punta de Vacas advance, ice terminated at 2350 m, while during the subsequent Penitentes advance, the glacier system ended at 2500 m. A travertine layer overlying Penitentes Drift has U-series age of 24,200 ± 2000 yr B.P. The distribution of Horcones Drift, which is inferred to represent the last glacial maximum, delimits an independent ice stream that flowed 22 km down Horcones valley to 2750 m. A later readvance (Almacenes) reached 3250 m. Confluencia Drift is considered to be Neoglacial in age and extends downvalley to 3300 m. The moraine sequence is compared with those studied by Caviedes (1972) along Rio Aconcagua on the Chilean flank of the Andes.

  10. [Medical education at Universidad de los Andes, Santiago, Chile].

    Science.gov (United States)

    Orrego Vicuña, F

    1997-07-01

    Universidad de los Andes School of Medicine started in 1991 with a new medical curriculum aimed at providing a medical education for its students, that is, it attempts to give, together with technical proficiency in medical matters, formation of character and a strong ethical attitude. The curriculum lasts for seven years: five of basic, pre-clinical and clinical theoretical and practical courses, followed by two years of internships in Internal Medicine, Surgery, Obstetrics and Pediatrics, plus a four month period of an elective internship. The courses have an integrated design, in which each matter is presented from multiple perspectives, e.g. in Internal Medicine together with the clinical aspects of disease, the pathophysiology and the pharmacology of the drugs used are presented. Also the Pathology of each disease is given in coordination in the Pathology course. General educational matters such as Anthropology, Psychology, Origin of Living Beings, Theology and Medical Ethics are interspersed in the curriculum. An important feature is the personal counselling system, in which each student may choose an academic counsellor and discuss with him (her) the subjects of his choosing. Clinical practice is given in a system that includes five hospitals and five private clinics that range from general medical practice to Psychiatry or Ophthalmology.

  11. Paleomagnetism of Permian and Triassic rock, central Chilean Andes

    Science.gov (United States)

    Forsythe, Randall D.; Kent, Dennis V.; Mpodozis, Constantino; Davidson, John

    The first paleomagnetic data from Permian and Triassic formations west of the Andean divide are presented. Four formations of Permian or Triassic age in the central Chilean Andes have been investigated: two are located in the coastal ranges, and two are in the main cordillera. Of the formations in the main cordillera (Pastos Blancos and Matahuaico formations), only the Pastos Blancos Formation has yielded characteristic directions. While a fold test is absent, magnetizations are most likely secondary and yield pre-tilt corrected concordant inclinations, but yield declinations discordant 30° clockwise in comparison to the South American apparent polar wander path. Both formations from the coastal ranges (Cifuncho and Pichidangui formations) yielded stable directions. Postfolding magnetizations in the Cifuncho Formation also show declinations discordant 30° clockwise and concordant inclinations. The Pichidangui Formation has two stable components: one of postfolding age is concordant to apparent polar wander path data, and one of probable prefolding (Late Triassic) age is concordant in declination, but discordant in inclination. Further work is needed to better define the prefolding magnetizations in the Pichidangui Formation, but at present these preliminary results are the first paleomagnetic signs of displaced terranes along the Pacific margin of Chile. If correct, the results suggest that the Pichidangui Formation was some 15° of latitude farther south during the Late Triassic and had likely moved northward to its present latitudinal position with respect to cratonic South America by Middle to Late Jurassic.

  12. Active Folding of the Tame Anticline, Eastern Foothills, Colombian Andes

    Science.gov (United States)

    Veloza-Fajardo, G.; Taylor, M. H.; Mora, A.; Stockli, D. F.

    2011-12-01

    We integrate neotectonic mapping and interpretation of seismic reflection profiles to evaluate the kinematics of folding and development of the Quaternary Tame anticline and Cusiana fault at 6.5 N Latitude in the eastern foothills of the Eastern Cordillera of Colombia. The Tame anticline is located approximately 660 km to the east of the Nazca-South America and 810 km to the south of the Caribbean-South America subduction zones plate boundaries in a retroarc foreland basin setting. The Tame anticline is an elongated, N15E trending structure, 14 km long N-S by 6 km wide E-W, that represents the most frontal active structure of the northern Colombian Andes. The Tame fold is related to the east-directed Cusiana fault that day lights to the south. Seismic reflection profiles indicate the Cusiana fault is a listric, west-dipping blind structure. The east flowing antecedent Macaguana creek has incised the Tame fold forming three prominent terrace levels, uplifted approximately 220, 150 and 100 meters, above current river levels. The surfaces were sampled for terrestrial cosmogenic nuclides using the depth profiling approach to account for inheritance. Surface exposure ages from the highest to lowest surfaces are 93.9, 50.8 and 32.4 kyrs at the 1σ level respectively, which were calculated using Monte Carlo methods. Trishear kinematic modeling was used to retrodeform the folding history and based on the surface abandonment ages, we will present shortening rates at millennial timescales.

  13. Structure and tectonic evolution of the Fuegian Andes (southernmost South America) in the framework of the Scotia Arc development

    Science.gov (United States)

    Torres Carbonell, Pablo J.; Dimieri, Luis V.; Olivero, Eduardo B.; Bohoyo, Fernando; Galindo-Zaldívar, Jesús

    2014-12-01

    The major structural and tectonic features of the Fuegian Andes provide an outstanding onshore geological framework that aids in the understanding of the tectonic evolution of the Scotia Arc, mainly known from offshore studies. The orogenic history of the Fuegian Andes (Late Cretaceous-Miocene) is thus compared and integrated with the tectonic history of the Scotia Sea. Late Cretaceous-Paleocene structures in the Fuegian Andes suggest a N-directed contraction consistent with an oroclinal bending of the southernmost South America-Antarctic Peninsula continental bridge. This N-directed contraction in the Fuegian Andes continued during the spreading of the West Scotia Ridge, between 40-50 and 10 Ma ago. The onset of major strike-slip faulting in Tierra del Fuego is considered here to be not older than the late Miocene, consistent with the recent history of the North Scotia Ridge; thus forming part of a tectonic regime superposed to the prior contraction in the Fuegian Andes.

  14. Traditional use of the Andean flicker (Colaptes rupicola as a galactagogue in the Peruvian Andes

    Directory of Open Access Journals (Sweden)

    Froemming Steve

    2006-05-01

    Full Text Available Abstract This paper explores the use of the dried meat and feathers of the Andean Flicker (Colaptes rupicola to increase the milk supply of nursing women and domestic animals in the Andes. The treatment is of preColumbian origin, but continues to be used in some areas, including the village in the southern Peruvian highlands where I do ethnographic research. I explore the factors giving rise to and sustaining the practice, relate it to other galactagogues used in the Andes and to the use of birds in ethnomedical and ethnoveterinary treatments in general, and situate it within the general tendency in the Andes and elsewhere to replicate human relations in the treatment of valuable livestock. The bird's use as a galactagogue appears to be motivated by both metaphorical associations and its perceived efficacy, and conceptually blends human and animal healthcare domains.

  15. Possible future lakes in the Andes of Peru

    Science.gov (United States)

    Colonia, Daniel; Haeberli, Wilfried; Torres, Judith; Giraldez, Claudia; Schauwecker, Simone; Santiago, Alexzander; Cochachin, Alejo; Huggel, Christian

    2015-04-01

    Climate change has caused large losses of glacier mass in the Andes of Peru. Also, given the projected changes in climate, based on different IPCC scenarios for 2050 and 2080, simulations with a tropical glacier-climate model indicate that glaciers will continue to retreat. According to the national Peruvian glacier inventories 43% of glacier area has disappeared between 1970 and 2003-2010 in the 19 snowy mountain ranges and a total of 8 355 new lakes have formed in deglaciating terrain. With glacier retreat new lakes form in parts of the glacier tongue where there is an overdeepening, and these lakes can be a source of natural hazards to downstrean populations. Therefore, the identification of possible future lakes is important to plan for preventive measures concerning possible lake outbursts as well as to understand changes in freshwater storage in the corresponding source areas. Modeling of glacier-bed overdeepenings and possible future lakes forming in such topographic depressions when becoming ice-free was done using the SRTM DEM from the year 2000 with a 90 m resolution and the 2003-2010 glacier outlines from the recently published national glacier inventory of Perú. The GIS-based analysis followed three main steps: (1) identification of flat glacier areas with less than 10° surface slope as a first-order spatial approximation to possible occurrences of glacier-bed overdeepenings; (2) application, using Google Earth, of three morphological indications of glacier-bed overdeepenings following Frey et al. (2010): steepening surface slope, onset of crevasse formation, lateral flow-narrowing; and (3) verification of the results from steps (1) and (2) by comparison with GlabTop modeling of bed topographies following Linsbauer et al. (2012) using the SRTM DEM, contour lines and constructed branch lines for all glaciers. A pilot study has already been carried out for the Cordillera Blanca. The results show that 31 major new lakes may form in the future. The total

  16. Carbon stabilization mechanisms in soils in the Andes

    Science.gov (United States)

    Jansen, Boris; Cammeraat, Erik

    2015-04-01

    The volcanic ash soils of the Andes contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute significant potential sources or sinks of the greenhouse gas CO2. Climate and/or land use change potentially have a strong effect on these large SOM stocks. To clarify the role of chemical and physical stabilisation mechanisms in volcanic ash soils in the montane tropics, we investigated carbon stocks and stabilization mechanisms in the top- and subsoil along an altitudinal transect in the Ecuadorian Andes. The transect encompassed a sequence of paleosols under forest and grassland (páramo), including a site where vegetation cover changed in the last century. We applied selective extraction techniques, performed X-ray diffraction analyses of the clay fraction and estimated pore size distributions at various depths in the top- and subsoil along the transect. In addition, from several soils the molecular composition of SOM was further characterized with depth in the current soil as well as the entire first and the top of the second paleosol using GC/MS analyses of extractable lipids and Pyrolysis-GC/MS analyses of bulk organic matter. Our results show that organic carbon stocks in the mineral soil under forest a páramo vegetation were roughly twice as large as global averages for volcanic ash soils, regardless of whether the first 30cm, 100cm or 200cm were considered. We found the carbon stabilization mechanisms involved to be: i) direct stabilization of SOM in organo-metallic (Al-OM) complexes; ii) indirect protection of SOM through low soil pH and toxic levels of Al; and iii) physical protection of SOM due to a very high microporosity of the soil (Tonneijck et al., 2010; Jansen et al. 2011). When examining the organic carbon at a molecular level, interestingly we found extensive degradation of lignin in the topsoil while extractable lipids were preferentially preserved in the subsoil (Nierop and Jansen, 2009). Both vegetation

  17. Two New Species of Black Flies (Diptera: Simuliidae) from the High Andes of Colombia.

    Science.gov (United States)

    Mantilla, Juan S; Moncada, Ligia I; Matta, Nubia E; Adler, Peter H

    2013-01-01

    The females, males, pupae, and larvae of two new species of Simulium are described and illustrated from a small stream 3950 m above sea level in the Lake Otún area of the Colombian Andes Mountains. Simulium (Pternaspatha) quimbayium n. sp. represents a 630-km northeastern extension of the distributional range of previously known members of the subgenus Pternaspatha, and Simulium (Psilopelmia) machetorum n. sp. represents the highest altitude recorded for a species of the subgenus Psilopelmia. These species illustrate the unique simuliid biodiversity in the páramo ecosystem of the high northern Andes.

  18. Erosion by Ice and Water in the Southern Andes

    Science.gov (United States)

    2002-01-01

    This scene on the remote, rugged Argentine/Chilean border in the far southern Andes Mountains offers numerous, dramatic examples of both erosional processes and features of ice and water. The sharp, glaciated crest of the Cerro San Lorenzo (center) exceeds 12,000 feet and casts a long shadow southeastward. Glaciers on its western flank flow into the valley. This Electronic Still Camera photo was taken from the International Space Station, in December 2000 (late spring) when most of the previous winter's snow had melted below an altitude of 6,000 feet. Lago Pueyrredon, and the other lakes visible here, have been excavated by geologically recent episodes of glacier erosion, when glaciers extended all the way onto the lowland plains (top right). Since the last melting of the glaciers (15,000 years ago) three distinct fan deltas (semicircular features, marked with arrows) have formed where rivers flow into the lake. Counterclockwise currents in the lake-driven by strong winds from the west-have generated thin sand spits from each fan-delta. The largest spit (attached to the largest fan-delta, see right arrow) has isolated an approximately 10-kilometer long segment of the south end of the lake. The river that constructed the largest fan presently discharges turbid water to this isolated basin, giving it a lighter color than the rest of the lake. Glacial data collected over the past 50 years indicate that small ice bodies are disappearing at accelerated rates. (EOS, vol 81, no. 24, June 13, 2000) Predictions are that large fluctuations in land ice, with significant implications to society, are possible in the coming decades and centuries due to natural and anthropogenic climate change. Before glacial data can be used to address critical problems pertaining to the world's economic and environmental health, more detailed information about such glaciers is needed. Image ISS001-ESC-5113 provided by the Earth Sciences and Image Analysis Laboratory, Johnson Space Center.

  19. Morphologic evolution of the Central Andes of Peru

    Science.gov (United States)

    Gonzalez, Laura; Pfiffner, O. Adrian

    2012-01-01

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

  20. High resolution precipitation climatology for the Andes of South Ecuador

    Science.gov (United States)

    Trachte, Katja; Bendix, Jörg

    2014-05-01

    The climate of Ecuador is strongly dominated by the complex structure of the Andes Mountains. Due to their heights and north-south orientation they act like a barrier, which cause delineation between the western and eastern flanks, as well as the inner-Andean areas. Commonly the Ecuadorian climate is classified in three zones, Costa, Interandina and Oriente. Existing precipitation products such as the GPCC or TRMM data are enabled to represent these climate zones, but because of their spatial resolution, they pass to capture the different regimes within a zone. Especially the inner-Andean region (Interandina) with its characteristic complex terrain shows spatially high climate variability. Local circulation systems, e.g. mountain-valley breezes as well as effects of windward and lee-side, drive the climate conditions allowing for the differentiation of air temperature and rainfall distribution on relative small scales. These highly variable patterns are also reflected by the diversity of ecosystems, e.g. rainforest, dry forest and Paramo, in a relative small area. In order to represent the local systems a dynamical downscaling approach for the Ecuadorian region is applied. In doing so the Weather Research and Forecasting (WRF) model is used. A suitable model setup was evaluated within a sensitivity study, where various parametrization schemes were tested. The most suitable physics combination was used for a 30 year hint cast simulation. The poster presents first results of the high resolution climate simulations. On the basis of the spatial distribution of rainfall patterns distinct precipitation regimes within the Interandina will be shown. The aim is to highlight and discuss the importance of the adequately representation of the terrain in mountainous regions like the Andean Mountains.

  1. Cretaceous stratigraphy of sierra de Beauvoir, Fuegian Andes, Argentina

    Directory of Open Access Journals (Sweden)

    Daniel R. Martinioni

    2013-03-01

    Full Text Available The Cretaceous stratigraphy north of Lago Fagnano, Tierra del Fuego, was poorly known until the last decade of the twentieth century. Stratigraphic, sedimentologic, and paleontological observations in sierra de Beauvoir and surroundings enabled the recognition of two main packages of dominant marine mudstone. 1 A more than 450 m thick package of slate, shale and mudstone, constituted by the revised Lower Cretaceous Beauvoir Formation. A type locality in the core of sierra de Beauvoir, with diagnostic Aptian-Albian fossils including inoceramids of the Inoceramus neocomiensis group and Aucellina sp., is proposed for this unit. 2 A more than 1,500 m thick, mudstone-dominated, but sandier upward, package consisting of at least three Upper Cretaceous units. Arroyo Castorera Formation (nom. nov. bears Turonian inoceramids of the I. hobetsensis group and I. cf. lamarcki. Río Rodríguez Formation (nom. nov. has Coniacian inoceramids, cf. Cremnoceramus sp. Policarpo Formation bears poorly preserved ammonites (Grossouvrites sp., Maorites sp., and Diplomoceras sp., together with diagnostic Maastrichtian dinocysts (Manumiella spp. complex, Operculodinium cf. azcaratei, some specimens of Fibrocysta-Exochosphaeridium complex, and Palaeocystodinium granulatum. Both packages were deposited in deep-marine environments and show, as a whole, a coarsening upward trend in the succession of Cretaceous rocks. Beauvoir Formation is part of the back-arc basin-fill of the former Rocas Verdes marginal basin. Arroyo Castorera Formation appears as a transition to the initiating Late Cretaceous Austral foreland basin evolution, clearly represented by turbiditic deposits of Río Rodríguez and Policarpo formations that were progressively accumulated in front of the rising Fuegian Andes.

  2. The nature of orogenic crust in the central Andes

    Science.gov (United States)

    Beck, Susan L.; Zandt, George

    2002-10-01

    The central Andes (16°-22°S) are part of an active continental margin mountain belt and the result of shortening of the weak western edge of South America between the strong lithospheres of the subducting Nazca plate and the underthrusting Brazilian shield. We have combined receiver function and surface wave dispersion results from the BANJO-SEDA project with other geophysical studies to characterize the nature of the continental crust and mantle lithospheric structure. The major results are as follows: (1) The crust supporting the high elevations is thick and has a felsic to intermediate bulk composition. (2) The relatively strong Brazilian lithosphere is underthrusting as far west (65.5°W) as the high elevations of the western part of the Eastern Cordillera (EC) but does not underthrust the entire Altiplano. (3) The subcrustal lithosphere is delaminating piecemeal under the Altiplano-EC boundary but is not completely removed beneath the central Altiplano. The Altiplano crust is characterized by a brittle upper crust decoupled from a very weak lower crust that is dominated by ductile deformation, leading to lower crustal flow and flat topography. In contrast, in the high-relief, inland-sloping regions of the EC and sub-Andean zone, the upper crust is still strongly coupled across the basal thrust of the fold-thrust belt to the underthrusting Brazilian Shield lithosphere. Subcrustal shortening between the Altiplano and Brazilian lithosphere appears to be accommodated by delamination near the Altiplano-EC boundary. Our study suggests that orogenic reworking may be an important part of the "felsification" of continental crust.

  3. Glacier loss and emerging hydrologic vulnerabilities in the Peruvian Andes

    Science.gov (United States)

    Mark, B. G.; McKenzie, J. M.; Baraer, M.; Lagos, P.; Lautz, L.; Carey, M.; Bury, J.; Crumley, R.; Wigmore, O.; Somers, L. D.

    2015-12-01

    Accelerating glacier recession in the tropical Andes is transforming downstream hydrology, while increasing demands for water by end-users (even beyond the watershed limits) is complicating the assessment of vulnerability. Future scenarios of hydro-climatic vulnerability require a better understanding of coupled hydrologic and human systems, involving both multiscale process studies and more robust models of glacier-climate interactions. We synthesize research in two proglacial valleys of glacierized mountain ranges in different regions of Peru that are both in proximity to growing water usage from urban sectors, agriculture, hydroelectric generation, and mining. In both the Santa River watershed draining the Cordillera Blanca and the Shullcas River watershed below Hyuatapallana Mountain in Junin, glaciers have receded over 25% since the 1980s. Historical runoff and glacier data, combined with glacier-climate modeling, show a long-term decrease in discharge resulting from a net loss of stored water. We find evidence that this altered hydrology is transforming proglacial wetland ecology and water quality, even while water resource use has intensified. Beyond glaciers, our results show that over 60% of the dry season base flow in each watershed is groundwater sourced from heterogeneous aquifers. Municipal water supply in Huancayo already relies on 18 groundwater wells. Perceptions of water availability and actual water use practices remain relatively divorced from the actual water resources provided from each mountain range. Critical changes in glacier volume and water supply are not perceived or acknowledged consistently amongst different water users, nor reflected in water management decisions. In order to identify, understand, model, and adapt to climate-glacier-water changes, it is vital to integrate the analysis of water availability and groundwater processes (the domain of hydrologists) with that of water use (the focus for social scientists). Attention must be

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

    Directory of Open Access Journals (Sweden)

    E. Kendrick

    2006-12-01

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

  5. Evolución tectonomagmática de los Andes bolivianos Tectonomagmaticevolution of the Bolivian Andes

    Directory of Open Access Journals (Sweden)

    Néstor Jiménez

    2009-10-01

    Full Text Available Los Andes bolivianos ocuparonuna posición de retroarco durante gran parte del Fanerozoico. En su evoluciónse reconoce una primera etapa, restringida al Paleozoico inferior, en la quehubo una gran transferencia de material sedimentario en la corteza superior, yuna segunda en la que predominó el reciclaje de la masa cortical. A lo largodel Paleozoico inferior, una cuenca marina epicratónica se formó entre elcratón de Amazonia, el macizo Arequipa-Antofalla, y el macizo Pampeanofuncionando inicialmente como cuenca de retroarco y luego como cuenca deantepaís hasta colmatarse en el Paleozoico superior. En este lapso ocurrierontres etapas de deformación: La fase oclóyica (límite Ordovícico-Silúrico decarácter restringido, la fase eohercínica (límite Devónico-Carbonífero, y lafase hercínica (Carbonífero Superior también de influencia areal restringida.En el Mesozoico, se registraron aún breves incursiones marinas antes que en elEoceno comience a edificarse una protocordillera. El solevantamiento general detoda la región centroandina, se inició en el Oligoceno Superior afectando alAltiplano y la Cordillera Oriental actuales. Este solevantamiento ocurrió entres etapas limitadas por la formación de superficies de erosión datadas en 18y 10 Ma. La ladera oeste de la Cordillera Oriental, denominada faja de Huarina,tuvo un rol muy importante en la evolución de la región centroandina. Además decobijar a gran parte del magmatismo de retroarco, en esta faja ocurrió la mayorsubsidencia de la cuenca paleozoica. En esta faja ocurrieron preferentementedurante el Mesozoico, procesos de rifting y de adelgazamiento litosférico. Enel Paleógeno, la faja de Huarinas fue la primera en ser solevantada aislando lacuenca altiplánica del interior del continente, y durante el OligocenoSuperior, se constituyó en el cinturón retrocabalgante del orógeno. Ladeformación en el Altiplano y la Cordillera Oriental concluyó hace 10 Ma cuandose form

  6. Senecio canoi (Compositae), Una especie nueva de los Andes de Perú

    NARCIS (Netherlands)

    Montesinos, Daniel; Gonzáles, Paúl; Navarro, Eduardo

    2015-01-01

    Senecio canoi, a new species of Compositae of the high Andes of Southern Peru, Puno department, is described and illustrated. Senecio canoi is a perennial species differing from others in the ser. Suffruticosi subser. Caespitosi by having tufted habit, oblong-spathulate leaves with toothed margin

  7. A millennium of metallurgy recorded by lake sediments from Morococha, Peruvian Andes.

    Science.gov (United States)

    Cooke, Colin A; Abbott, Mark B; Wolfe, Alexander P; Kittleson, John L

    2007-05-15

    To date, information concerning pre-Colonial metallurgy in South America has largely been limited to the archaeological record of artifacts. Here, we reconstruct a millennium of smelting activity in the Peruvian Andes using the lake-sediment stratigraphy of atmospherically derived metals (Pb, Zn, Cu, Ag, Sb, Bi, and Ti) and lead isotopic ratios (206Pb/ 207Pb) associated with smelting from the Morococha mining region in the central Peruvian Andes. The earliest evidence for metallurgy occurs ca. 1000 A.D., coinciding with the fall of the Wari Empire and decentralization of local populations. Smelting during this interval appears to have been aimed at copper and copper alloys, because of large increases in Zn and Cu relative to Pb. A subsequent switch to silver metallurgy under Inca control (ca. 1450 to conquest, 1533 A.D.) is indicated by increases in Pb, Sb, and Bi, a conclusion supported by further increases of these metals during Colonial mining, which targeted silver extraction. Rapid development of the central Andes during the 20th century raised metal burdens by an order of magnitude above previous levels. Our results represent the first evidence for pre-Colonial smelting in the central Peruvian Andes, and corroborate the sensitivity of lake sediments to pre-Colonial metallurgical activity suggested by earlier findings from Bolivia.

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

    Directory of Open Access Journals (Sweden)

    OSCAR HUMBERTO MARÍN GÓMEZ

    2014-05-01

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

  9. Lichenometric dating using Rhizocarpon subgenus Rhizocarpon in the Patagonian Andes, Argentina

    Science.gov (United States)

    Garibotti, Irene Adriana; Villalba, Ricardo

    2009-05-01

    This study represents the first attempt to develop and apply lichenometric dating curves of Rhizocarpon subgenus Rhizocarpon for dating glacier fluctuations in the Patagonian Andes. Six glaciers were studied along the Patagonian Andes. Surfaces of known ages (historical evidences and tree-ring analyses) were used as control sites to develop indirect lichenometric dating curves. Dating curves developed for the studied glaciers show the same general logarithmic form, indicating that growth rate of subgenus Rhizocarpon decreases over time. The strong west-east precipitation gradient across the Andean Cordillera introduces statistically significant differences in the growth curves, with faster growth rates in the moist west sites than the drier eastern sites. Latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates. Therefore, we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the Patagonian Andes during the past 450 yrs. Application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree-ring analyses. A first chronosequence for moraine formation in the Torrecillas Glacier (42°S) is presented. Our findings confirm the utility of lichenometry to date deglaciated surfaces in the Patagonian Andes.

  10. Unexpectedly high beta-diversity of root-associated fungal communities in the Bolivian Andes

    DEFF Research Database (Denmark)

    Barnes, Christopher James; Maldonado Goyzueta, Carla Brenda; Frøslev, Tobias Guldberg;

    2016-01-01

    Bolivia is one of the most biologically diverse countries on the planet. Between the Andes and the Amazon drainage basin spans the Yungas, a vast forested region shown to be extremely species rich in macro-organisms. However, it remains unclear whether this high diversity is also reflected...

  11. Deformation, deposition, and surface uplift in the hinterland of the Central Andes, Bolivia

    Science.gov (United States)

    Leier, A.; McQuarrie, N.; Garzione, C. N.; Eiler, J. M.

    2011-12-01

    Paleoelevation histories from mountain belts like the Central Andes of Bolivia provide important constraints on the timing and geodynamic mechanisms associated with surface uplift. New stable isotope data from paleosol carbonate nodules in the Altiplano and Eastern Cordillera of the Central Andes of Bolivia indicate a previously undocumented episode of surface uplift occurred in the region between ca. 24 and 17 Ma. Oxygen isotope and clumped-isotope thermometry values from paleosol carbonate in strata >24 Ma suggest paleoelevations as low as sea-level. Paleosol carbonate in strata ca. 17 Ma have oxygen isotope and clumped-isotope thermometry values, which using modern lapse rates, indicate an increase in elevation of approximately 3 km. Relatively undeformed Oligocene and Miocene strata overlap faulted Paleozoic rocks of the Bolivian Eastern Cordillera, indicating deposition and surface uplift post-dated and was decoupled from upper crustal deformation. Together, geological data from the area record an initial period of deformation and exhumation, a subsequent period of sediment deposition and overlap, and then an episode of surface uplift that was not accompanied by upper crustal deformation. We propose accommodation for the Oligocene-Miocene strata was associated with mantle and lowermost crustal processes, and the subsequent increase in surface elevation was an isostatic response to removal of dense material through delamination or drip. Combined with existing data sets in the Central Andes, these new data suggest multiple, regionally-variable, and diachronous periods of surface uplift occurred within the Central Andes during the Cenozoic Era.

  12. Application of remote sensing to understanding fire regimes and biomass burning emissions of the tropical Andes

    NARCIS (Netherlands)

    Oliveras Menor, I.; Anderson, L.O.; Malhi, Y.

    2014-01-01

    In the tropical Andes, there have been very few systematic studies aimed at understanding the biomass burning dynamics in the area. This paper seeks to advance on our understanding of burning regimes in this region, with the first detailed and comprehensive assessment of fire occurrence and the deri

  13. Climate Change in the High Andes:implications and adaptation strategies for small-scale farmers

    NARCIS (Netherlands)

    Perez, C.; Nicklin, C.; Dangles, O.; Vanek, S.; Sherwood, S.G.; Halloy, S.; Garrett, K.A.; Forbes, G.A.

    2010-01-01

    Abstract: Global climate change represents a major threat to sustainable farming in the Andes. Farmers have used local ecological knowledge and intricate production systems to cope, adapt and reorganize to meet climate uncertainty and risk, which have always been a fact of life. Those traditional sy

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

    Science.gov (United States)

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

    2015-09-01

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

  15. Hydrological cycles and trends in the NW Argentine Andes since 1940

    Science.gov (United States)

    Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred

    2016-04-01

    Strong spatiotemporal variability characterizes the hydrometeorological pattern in the NW Argentine Andes, draining parts of the most populated and economically important areas of South America. During the summer monsoon season (DJF), the eastern flanks of the central Andes are characterized by deep convection, exposing them to extreme hydrometeorological events. These often result in floods and landslides with disastrous effects on the local populations. Here, we analyze river discharge to explore long-term hydrological variability in NW Argentine Andes and the linked climate controlling processes. We rely on 13 daily river discharge time series relevant to drainage basins spanning several size orders (102-104 km2) starting in 1914 and define different hydro-climate indices both for the mean and the extreme hydrological events. We apply quantile regression to investigate long-term trends and spectral analysis associated with cross-correlation with SST-based climate indices to identify links to large-scale climate variability modes. River discharge presents a pronounced and coherent variability signal in South America, particularly for wide drainage basins, such as the Amazon and Paraná/La Plata rivers, strongly associated to Pacific and Atlantic Oceans Sea Surface Temperature (SST) anomalies (i.e. ENSO, PDO, AMO). Our analysis evidences that in the NW Argentine Andes, mean discharge values are characterized by statistically significant, mostly positive, long-term trends since 1940, whereas the extreme events present a more non-unidirectional trend pattern. Also, coherent multi-annual to multi-decadal cycles characterizing the discharge pattern have been identified, suggesting that processes linked to SST anomaly-modes strongly control the hydrometeorology variability in the NW Argentina Andes.

  16. Lake Andes National Wildlife Refuge Waterfowl Production Area District: Narrative report: January 1 through December 31, 1966

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Lake Andes NWR- Waterfowl Production Area District outlines Refuge accomplishments during the 1966 calendar year. The report begins...

  17. Thermochronology and tectonics of the Mérida Andes and the Santander Massif, NW South America

    Science.gov (United States)

    van der Lelij, Roelant; Spikings, Richard; Mora, Andrés

    2016-04-01

    New apatite U-Pb and multiphase 40Ar/39Ar data constrain the high to medium temperature (~ 500 °C-~ 300 °C) thermal histories of igneous and metamorphic rocks exposed in the Mérida Andes of Venezuela, and new apatite and zircon fission track data constrain the ~ 500 °C-~ 60 °C thermal histories of pre-Jurassic igneous and metamorphic rocks of the adjacent Santander Massif of Colombia. Computed thermal history envelopes using apatite U-Pb dates and grain size information from an Early Palaeozoic granodiorite in the Mérida Andes suggest that it cooled from > 500 °C to rocks in the Mérida Andes by numerous new muscovite and biotite 40Ar/39Ar plateau dates spanning 257.1 ± 1.0 Ma to 205.1 ± 0.8 Ma. This episode of cooling is not recognised in the Santander Massif, where 40Ar/39Ar data suggest that some Early Palaeozoic rocks cooled below ~ 320 °C in the Early Palaeozoic. However, most data from pre-Jurassic rocks reveal a regional heat pulse at ~ 200 Ma during the intrusion of numerous shallow granitoids, resulting in temperatures in excess of ~ 520 °C, obscuring late Palaeozoic histories. The generally accepted timing of amalgamation of Pangaea along the Ouachita-Marathon suture pre-dates Late Permian to Triassic cooling recorded in basement rocks of the Mérida Andes by > 30 Ma, and its effect on rocks preserved in north-western South America is unknown. We interpret late Permian to Triassic cooling in the Mérida Andes to be driven by exhumation. Previous studies have suggested that a short phase of shortening and anatexis is recorded at ~ 253 Ma in the Maya Block, which may have been adjacent to the basement rocks of the Mérida Andes in the Late Permian. The coeval onset of exhumation in the Mérida Andes may be a result of increased coupling in the magmatic arc, which was located along the western margin of Pangaea. Triassic extension is documented in the Central Cordillera of Colombia and Ecuador between ~ 240 Ma and ~ 215 Ma, although extension at

  18. The Largest Holocene Eruption of the Central Andes Found

    Science.gov (United States)

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

    2013-12-01

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

  19. Screening for new accumulator plants in Andes Range mines

    Science.gov (United States)

    Bech, Jaume; Roca, Núria

    2016-04-01

    accumulated considerable concentrations of Cu and Zn. The species from the genus Bidens (Asteraceae) were able not only to accumulate high shoot As concentrations (> 1000 μg g-1 in B. cynapiifolia from Peru) but also considerable amounts of Pb (B. humilis from Chile). The highest Cu shoot concentrations were found in Mullinum spinosum (870 μg g-1) and in B. cynapiifolia (620 μg g-1). The shoot accumulation of Zn was highest in Baccharis amdatensis (>1900 μg g-1) and in Rumex crispus (1300 μg g-1) from the Ag mine in Ecuador (Bech et al., 2002). In the Peruvian Andes, B. triplinervia can be considered interesting for phytostabilization, due to its capacity to restrict the accumulation of elevated amounts of Pb and Zn in the shoots.

  20. Cenozoic foreland-basin evolution in the northern Andes : insights from thermochronology and basin analysis in the Eastern Cordillera, Colombia

    OpenAIRE

    Parra, Mauricio

    2009-01-01

    The modern foreland basin straddling the eastern margin of the Andean orogen is the prime example of a retro-arc foreland basin system adjacent to a subduction orogen. While widely studied in the central and southern Andes, the spatial and temporal evolution of the Cenozoic foreland basin system in the northern Andes has received considerably less attention. This is in part due to the complex geodynamic boundary conditions, such as the oblique subduction and accretion of the Caribbean plates ...

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

    Science.gov (United States)

    Schlunegger, F.; Norton, K. P.

    2012-04-01

    The deformation style and climate between the eastern and western escarpments of the Central Andes are strikingly different. The eastern side is in a tropical climate; it receives annual precipitation amounts of >3500 mm and experiences active shortening and thrusting, while the western side is one of the driest places on Earth and is deformed by long-wavelength warping. Indeed, climate is so dry that the western slopes can go decades without recorded rainfall. Here we show that the modern distribution of deformation in the Central Andes can be a result of enhanced orographic precipitation pattern beginning ca. 7-10 Ma (Norton and Schlunegger, 2011). Reduced erosion on the western side would have steepened the orogen, forcing deformation to shift to the east where high precipitation amounts would have enhanced erosion. We support this hypothesis with low erosion rates and a well-defined retreating knickzone in the Western Andes, and likewise by high erosion rates and channel morphologies indicative of transient orographic feedbacks in the east. Indeed, erosion rates as measured by cosmogenic nuclides are 0.2 mm yr-1, in the east (Safran et al. 2005). Stream profiles from the Western Escarpment are indicative of slow knickzone retreat in the absence of modern tectonic forcing while streams on the Eastern Escarpment are the product of strong climate-tectonic feedbacks, indicated by steep and strongly concave segments in the orographically-affected reach. Reconstructions of the accretionary wedge geometry and high angle fault movements between the Miocene and today further support an erosion driven shift in the locus of deformation. In particular, at orogenic scales, critical taper calculations indicate that the near cessation of erosion on the western side ca. 7-10 Ma ago shifted the orogen into a super-critical state where deformation only occurs along the basal décollement, while the eastern margin resided in sub-critical to critical conditions and experienced

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

    Science.gov (United States)

    Beckman, Elizabeth J; Witt, Christopher C

    2015-06-01

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

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

    Science.gov (United States)

    Beckman, Elizabeth J; Witt, Christopher C

    2015-06-01

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

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

    Science.gov (United States)

    Latrubesse, Edgardo M.; Restrepo, Juan D.

    2014-07-01

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

  5. Transecta Andina: Estudios de interregionalidad y verticalidad en los Andes del sur del Perú

    OpenAIRE

    Reindel, Markus

    2014-01-01

    Las poblaciones prehispánicas del sur del Perú desarrollaron sistemas socioeconómicos sofisticados que les permitieron adaptarse a la enorme diversidad ecológica de los Andes. Entre la sierra de los Andes y la costa desértica del Pacífico se formó una regionalización muy marcada. Los sistemas económicos correspondientes se reflejan en los restos de los asentamientos prehispánicos de cada región, que hoy en día se pueden detectar con métodos arqueológicos. El proyecto “Transecta Andina” del I...

  6. Illicit crops and armed conflict as constraints on biodiversity conservation in the Andes region.

    Science.gov (United States)

    Fjeldså, Jon; Alvarez, María D; Lazcano, Juan Mario; León, Blanca

    2005-05-01

    Coca, once grown for local consumption in the Andes, is now produced for external markets, often in areas with armed conflict. Internationally financed eradication campaigns force traffickers and growers to constantly relocate, making drug-related activities a principal cause of forest loss. The impact on biodiversity is known only in general terms, and this article presents the first regional analysis to identify areas of special concern, using bird data as proxy. The aim of conserving all species may be significantly constrained in the Santa Marta and Perijá mountains, Darién, some parts of the Central Andes in Colombia, and between the middle Marañón and middle Huallaga valleys in Peru. Solutions to the problem must address the root causes: international drug markets, long-lasting armed conflict, and lack of alternative income for the rural poor.

  7. Interseismic Rates From the CTO cGPS Andes and Nepal Networks

    Science.gov (United States)

    Genrich, J. F.; Galetzka, J.; Chowdhury, F.; Avouac, J.; Simons, M.; Barrientos, S. E.; Comte, D.; Norabuena, E. O.; Sapkota, S. N.

    2009-12-01

    To study crustal deformation at converging plate margins the Caltech Tectonics Observatory (CTO), together with partner institutions in the host countries, operates continuously observing GPS stations in the central Andes (northern Chile and southern Peru) and in Nepal. The currently 20-site Andes network was established in 2005 with 7 stations. Efforts are underway to provide data streaming links at near real time for the majority of sites. The Nepal network started with 10 sites in 2004 and has been expanded to 23 sites in the last couple of years. Dual frequency code and phase data from all sites are processed with the GAMIT/GLOBK processing package. Reliable interseismic velocities are now available for the majority of sites. Network metadata, rinex data files, processed time series and velocity estimates can be found online thru links at the CTO website: tectonics.caltech.edu.

  8. Illicit crops and armed conflict as constraints on biodiversity conservation in the Andes region.

    Science.gov (United States)

    Fjeldså, Jon; Alvarez, María D; Lazcano, Juan Mario; León, Blanca

    2005-05-01

    Coca, once grown for local consumption in the Andes, is now produced for external markets, often in areas with armed conflict. Internationally financed eradication campaigns force traffickers and growers to constantly relocate, making drug-related activities a principal cause of forest loss. The impact on biodiversity is known only in general terms, and this article presents the first regional analysis to identify areas of special concern, using bird data as proxy. The aim of conserving all species may be significantly constrained in the Santa Marta and Perijá mountains, Darién, some parts of the Central Andes in Colombia, and between the middle Marañón and middle Huallaga valleys in Peru. Solutions to the problem must address the root causes: international drug markets, long-lasting armed conflict, and lack of alternative income for the rural poor. PMID:16042278

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

    Directory of Open Access Journals (Sweden)

    E. Kendrick

    2006-12-01

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

  10. What facilitates adaptation? An analysis of community-based adaptation to environmental change in the Andes

    OpenAIRE

    Felipe Murtinho

    2016-01-01

    This study analyses the environmental, socio-economic andinstitutional factors that influence community-based adaptation strategies in 16municipalities in the rural Andes of Colombia. The study focuses specifically onthe factors that influence whether communities decide to take measures to managetheir water and micro-watersheds in response to water scarcity caused by climatevariability and land-use changes. The research uses quantitative and qualitativemethods incorporating data from surveys ...

  11. La implantación de la viruela en los Andes, la historia de un holocausto

    Directory of Open Access Journals (Sweden)

    Uriel García Cáceres

    2003-03-01

    Full Text Available La historia de las epidemias de viruela en los Andes tiene el carácter tétrico del relato de un holocausto. Esta presentación está destinada a resaltar las etapas más importantes del proceso de la implantación de la viruela en las poblaciones andinas en general y, en particular, en el Perú, desde principio del siglo XVI hasta nuestros días.

  12. Foreland shortening and crustal balancing in the Andes at 30°S latitude

    Science.gov (United States)

    Allmendinger, R. W.; Figueroa, D.; Synder, D.; Beer, J.; Mpodozis, C.; Isaacks, B. L.

    1990-08-01

    Excellent surface exposures, known Benioff zone geometry, a dynamic morphology, and the availability of industry seismic reflection data all make the Andes at 30°S an excellent transect for investigating crustal-scale balanced sections. 150-170 km of horizontal shortening has occurred in three major belts located between the trench and the foreland. The thin-skinned, east-verging Precordillera of western Argentina accounts for 60-75% of the total shortening and formed mostly since major volcanism ceased at ˜10 Ma. Industry seismic reflection data show that the décollement of the Precordillera belt is located anomalously deep at ˜15 km. The belt is dominated by fault propagation folds and contains several prominent out-of-sequence thrust faults. Seismic stratigraphie analysis shows that Miocene strata in the Iglesia Valley, located between the Precordillera and the crest of the Andes, accumulated in a piggy-back basin. Onlap relations on the western side indicate that the High Cordillera was uplifted as a major fault bend fold over a buried ramp. Thrusting in the two western belts, both in the High Cordillera of Chile, formed during the waning stages of arc volcanism, 11-16 Ma. and account for 25-40% of the shortening. The observed shortening is probably greater than can be accounted for with reasonable crustal thicknesses, indicating the possibility of continental truncation or erosion along the plate margin or an anomalously thick root held down by the nearly flat subducted Nazca Plate. Our preferred crustal geometry puts the ramp between upper and lower crustal deformation west of the high topography, requiring crustal scale tectonic wedging to thicken the crust beneath the crest of the Andes. This non-unique model provides a simple explanation of the first order morphology of the Andes at this latitude.

  13. Drivers of atmospheric methane uptake by montane forest soils in the southern Peruvian Andes

    OpenAIRE

    Jones, S. P.; T. Diem; L. P. Huaraca Quispe; Cahuana, A. J.; D. S. Reay; Meir, P.; Teh, Y. A.

    2016-01-01

    The soils of tropical montane forests can act as sources or sinks of atmospheric methane (CH4). Understanding this activity is important in regional atmospheric CH4 budgets, given that these ecosystems account for substantial portions of the landscape in mountainous areas like the Andes. Here we investigate the drivers of CH4 fluxes from premontane, lower and upper montane forests, experiencing a seasonal climate, in southeastern Peru. Between February 2011 and June 2013, these so...

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

    Science.gov (United States)

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

    2015-12-01

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

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

    OpenAIRE

    M. E. Pritchard; Simons, M.

    2004-01-01

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

  16. Adaptive Capacity of Rural Communities to Climate Change in the Andes – Bolivia

    OpenAIRE

    Vidaurre de Mulczyk, Marolyn

    2016-01-01

    Climate change is one of the major contributing factors to degradation of ecological services, and these in turn are harming many people and causing poverty mainly in rural areas. The information available and the gain of knowledge on how climate change is affecting livelihood resources in the Bolivian Andes are very limited. This research aims to advance in the understanding of adaptive capacity to social and climate change in rural communities whose livelihoods are dependent upon agricultur...

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

    OpenAIRE

    Hofmann, K; F. K. List;  

    1996-01-01

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

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

    OpenAIRE

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

    2010-01-01

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

  19. Late Quaternary deglacial history of the Mérida Andes, Venezuela

    Science.gov (United States)

    Stansell, Nathan D.; Abbott, Mark B.; Polissar, Pratigya J.; Wolfe, Alexander P.; Bezada, Maximiliano; Rull, Valentí

    2005-10-01

    Radiocarbon-dated sediment cores from seven lakes and two bogs spanning the Cordillera de Mérida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22 750 and 19 960 cal. yr BP. On the wetter southeastern side of the Cordillera de Mérida, glaciers had significantly retreated by 15 700 cal. yr BP, followed by several minor glacial advances and retreats between 14 850 and 13 830 cal. yr BP. At least one major glacial readvance occurred between 13 830 and 10 000 cal. yrBP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Mérida records initial glacial retreat by 14240cal.yrBP. Multiple sites on both sides of the Mérida Andes record a further phase of extensive deglaciation approximately 10000cal.yrBP. However, the north-northwest facing Mucubají catchment remained partially glaciated until ca. 6000cal.yrBP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter-hemispheric deglacial lag in the northern tropics of the order of two thousand years.

  20. Desarrollo del programa de Doctorado en Ingeniería en la Universidad de los Andes

    Directory of Open Access Journals (Sweden)

    2009-05-01

    Full Text Available La Memoria, que la Revista de Ingeniería presenta en este número, recuenta el proceso de constitución del programa de doctorado en la Facultad de Ingeniería de la Universidad de los Andes, el cual cumple en 2009 una década de formación de profesionales a nivel doctoral.

  1. Do climate changes influence dispersal and population dynamics of dragonflies in the western Peruvian Andes?

    OpenAIRE

    Joachim Hoffmann

    2010-01-01

    For nine dragonfly species (five aeshnids and four libellulids) all previous and verifiable data are related to the vertical climate zones and nature regions of the western Peruvian Andes and the Peruvian Pacific coast. Climate changes due to the El Niño and La Niña phenomena, as well as the global climate change have an influence on the different natural regions and also restrict aquatic biotopes. These changes influence the dispersal and behavior of some dragonflies and concer...

  2. Grenvillian remnants in the Northern Andes: Rodinian and Phanerozoic paleogeographic perspectives

    Science.gov (United States)

    Cardona, A.; Chew, D.; Valencia, V. A.; Bayona, G.; Mišković, A.; Ibañez-Mejía, M.

    2010-01-01

    Grenvillian crust is encountered in several basement inliers in the northern Andes of Colombia, Ecuador and Peru and is also represented as a major detrital or inherited component within Neoproterozoic to Paleozoic sedimentary and magmatic rocks. This review of the tectonic and geochronological record of the Grenvillian belt in the northern Andes suggests that these crustal segments probably formed on an active continental margin in which associated arc and back-arc magmatism evolved from ca. 1.25 to 1.16 Ga, possibly extending to as young as 1.08 Ga. The lithostratigraphic and tectonic history of the Grenvillian belt in the northern Andes differs from that of the Sunsas belt on the southwest Amazonian Craton and from the Grenvillian belt of Eastern Laurentia. It is considered that this belt, along with similar terranes of Grenvillian age in Middle America and Mexico define a separate composite orogen which formed on the northwestern margin of the Amazonian Craton. Microcontinent accretion and interaction with the Sveconorwegian province on Baltica is a feasible tectonic scenario, in line with recent paleogeographic reconstructions of the Rodinian supercontinent. Although Phanerozoic tectonics may have redistributed some of these terranes, they are still viewed as para-autocthonous domains that remained in proximity to the margin of Amazonia. Paleogeographic data derived from Phanerozoic rocks suggest that some of the Colombian Grenvillian fragments were connected to northernmost Peru and Ecuador until the Mesozoic, whereas the Mexican terranes where attached to the Colombian margin until Pangea fragmentation in Late Triassic times.

  3. Potential of a Neutrino Detector in the ANDES Underground Laboratory for Geophysics and Astrophysics of Neutrinos

    CERN Document Server

    Machado, P A N; Nunokawa, H; Funchal, R Zukanovich

    2012-01-01

    The construction of the Agua Negra tunnels that will link Argentina and Chile under the Andes, the world longest mountain range, opens the possibility to build the first deep underground labo- ratory in the Southern Hemisphere. This laboratory has the acronym ANDES (Agua Negra Deep Experiment Site) and its overburden could be as large as \\sim 1.7 km of rock, or 4500 mwe, providing an excellent low background environment to study physics of rare events like the ones induced by neutrinos and/or dark matter. In this paper we investigate the physics potential of a few kiloton size liquid scintillator detector, which could be constructed in the ANDES laboratory as one of its possible scientific programs. In particular, we evaluate the impact of such a detector for the studies of geoneutrinos and galactic supernova neutrinos assuming a fiducial volume of 3 kilotons as a reference size. We emphasize the complementary roles of such a detector to the ones in the Northern Hemisphere neutrino facilities through some adv...

  4. Animal-powered tillage erosion assessment in the southern Andes region of Ecuador

    Science.gov (United States)

    Dercon, G.; Govers, G.; Poesen, J.; Sánchez, H.; Rombaut, K.; Vandenbroeck, E.; Loaiza, G.; Deckers, J.

    2007-06-01

    While water erosion has been the focus of past research in the Andes, former studies show that soil erosion could also be related to the methods used in cultivating the fields. The main objective of the present study was to assess (i) tillage erosion caused by the traditional animal-powered "yunta" or ard plough in the Andes and the factors controlling the process and (ii) the implications for soil conservation. Erosion rates were experimentally measured on 27 sites, having slopes from ca. 0% to 60% and soils ranging from Andosols to Cambisols, in the Andes region of Ecuador (Gima, Azuay). Different tillage methods were assessed: (i) tillage parallel to the contour lines ('Paralelo') and (ii) tillage at an angle with the contour lines. Statistical analysis points out that erosion caused by animal-powered tillage is gravity-driven. A strong correlation exists between slope and downslope displacement: furthermore, tillage depth and initial soil condition are important. For the 'Paralelo' tillage method the tillage transportation coefficient ( k) is below 100 kg m - 1 Tillage Pass - 1 , for the combined 'Arado'-'Cruzado' tillage method k may exceed 300 kg m - 1 . Tillage erosion is responsible for the reduction of the slope between the contour strips over a relatively short time period of 20 years, resulting in the formation of terraces and therefore the reduction of the water erosion risk. However, at the same time it may negatively affect soil quality.

  5. Cryptococcus gattii meningoencephalitis in an HIV-negative patient from the Peruvian Andes Meningoencefalite causada por Cryptococcus gattii em um paciente HIV-negativo procedente dos Andes Peruanos

    Directory of Open Access Journals (Sweden)

    Ericson L. Gutierrez

    2010-08-01

    Full Text Available We report a case of an immunocompetent Peruvian patient from the Andes with a one-month history of meningoencephalitis. Cryptococcus gattii was identified from a cerebrospinal fluid culture through assimilation of D-proline and D-tryptophan as the single nitrogen source. Initially, the patient received intravenous antifungal therapy with amphotericin B. The patient was discharged 29 days after hospitalization and continued with oral fluconazole treatment for ten weeks. During this period, the patient showed clinical improvement with slight right-side residual weakness. Through this case report, we confirm the existence of this microorganism as an infectious agent in Peru.Nós reportamos o caso de um paciente peruano immunocompetente proveniente dos Andes com história de um mês com meningoencefalite. Foi identificado o Cryptococcus gattii na cultura de liquido cerebrospinal através da assimilação de D-prolina e D-tryptofano como fonte única de nitrogênio. Inicialmente, o paciente recebeu tratamento antifúngico intravenoso com amfotericina B. O paciente foi liberado 29 dias depois da hospitalização, seguindo tratamento oral durante 10 semanas com fluconazol. Durante este período, o paciente apresentou melhoria clinica e uma leve fraqueza residual direita. Com o reporte do caso, nós confirmamos a existência desse microorganismo como agente infeccioso em nosso país.

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

    Science.gov (United States)

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

    2015-08-01

    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 2071-2100 in

  7. Developing services for climate impact and adaptation baseline information and methodologies for the Andes

    Science.gov (United States)

    Huggel, C.

    2012-04-01

    Impacts of climate change are observed and projected across a range of ecosystems and economic sectors, and mountain regions thereby rank among the hotspots of climate change. The Andes are considered particularly vulnerable to climate change, not only due to fragile ecosystems but also due to the high vulnerability of the population. Natural resources such as water systems play a critical role and are observed and projected to be seriously affected. Adaptation to climate change impacts is therefore crucial to contain the negative effects on the population. Adaptation projects require information on the climate and affected socio-environmental systems. There is, however, generally a lack of methodological guidelines how to generate the necessary scientific information and how to communicate to implementing governmental and non-governmental institutions. This is particularly important in view of the international funds for adaptation such as the Green Climate Fund established and set into process at the UNFCCC Conferences of the Parties in Cancun 2010 and Durban 2011. To facilitate this process international and regional organizations (World Bank and Andean Community) and a consortium of research institutions have joined forces to develop and define comprehensive methodologies for baseline and climate change impact assessments for the Andes, with an application potential to other mountain regions (AndesPlus project). Considered are the climatological baseline of a region, and the assessment of trends based on ground meteorological stations, reanalysis data, and satellite information. A challenge is the scarcity of climate information in the Andes, and the complex climatology of the mountain terrain. A climate data platform has been developed for the southern Peruvian Andes and is a key element for climate data service and exchange. Water resources are among the key livelihood components for the Andean population, and local and national economy, in particular for

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

    Directory of Open Access Journals (Sweden)

    César Aguilar

    2011-07-01

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

  9. Generation of the relationship between glacier area and volume for a tropical glacier in Bolivian Andes

    Science.gov (United States)

    Liu, T.; Kinouchi, T.; Hasegawa, A.; Tsuda, M.; Iwami, Y.; Asaoka, Y.; Mendoza, J.

    2015-12-01

    In Andes, retreat of tropical glaciers is rapid, thus water resources currently available from glacierized catchments would be changed in its volume and temporal variations due to climate change and glacier shrinkage. The relationship between glacier area and volume is difficult to define however which is important to monitor glaciers especially those are remote or inaccessible. Water resources in La Paz and El Alto in Bolivia, strongly depend on the runoff from glacierized headwater catchments in the Cordillera Real, Andes, which is therefore selected as our study region.To predict annual glacier mass balances, PWRI-Distributed Hydrological Model (PWRI-DHM) was applied to simulate runoff from the partially glacierized catchments in high mountains (i.e. Condoriri-Huayna West headwater catchment located in the Cordillera Real, Bolivian Andes). PWRI-DHM is based on tank model concept in a distributed and 4-tank configuration including surface, unsaturated, aquifer, and river course tanks. The model was calibrated and validated with observed meteorological and hydrological data from 2011 to 2014 by considering different phases of precipitation, various runoff components from glacierized and non-glacierized areas, and the retarding effect by glacial lakes and wetlands. The model is then applied with MRI-AGCM outputs from 1987 to 2003 considering the shrinkage of glacier outlines since 1980s derived from Landsat data. Annual glacier mass balance in each 100m-grid was reproduced, with which the glacier area-volume relationship was generated with reasonable initial volume setting. Out study established a method to define the relationship between glacier area and volume by remote sensing information and glacier mass balances simulated by distributed hydrological model. Our results demonstrated that the changing trend of local glacier had a consistency the previous observed glacier area-volume relationship in the Cordillera Real.

  10. Strike-slip faults in the southernmost Andes and the development of the Patagonian orocline

    Science.gov (United States)

    Cunningham, W. Dickson

    1993-02-01

    The Patagonian orocline is the 90° bend in the southernmost Andes between 50°S and 56°S. Paleomagnetic and structural data indicate that the orocline is, at least in part, the product of tectonic rotation. Recent field work in the Beagle Channel region of southernmost Chile provides evidence for widespread left-lateral strike-slip faulting in the internal zones of the mountain belt. Both arms of the Beagle Channel are interpreted to be left-lateral strike-slip faults based on detailed study of mesoscale strike-slip faults (Riedel shears) observed in coastal outcrops. Although much of the evidence indicates Cenozoic brittle strike-slip faulting, other fabric data, including vertical foliation zones containing horizontal quartz stretching lineations and ductile left-lateral kinematic indicators, suggest that Mesozoic ductile strike-slip or oblique-slip shearing also occurred. The implication is that the mid-Cretaceous Andean orogeny involved the transpressional inversion of the Rocas Verdes marginal basin and that transpression has been the dominant deformational regime in the region for the last 120 Ma. Regional left-lateral strike-slip faults are now recognized in all lithotectonic provinces of the southernmost Andes. A statistical study of regional lineament trends using aerial photographs and satellite imagery suggests that many unstudied lineaments are also strike-slip faults. A new model is proposed that integrates the development of strike-slip faulting and the structural evolution and uplift of the southernmost Andes with the rotational development of the orocline. The Patagonian orocline appears to be the product of broad interplate shearing accommodated by strike-slip faulting, block rotation, and contraction and is probably continuing to evolve today.

  11. Geografía, café y prosperidad en los andes occidentales de Colombia

    Directory of Open Access Journals (Sweden)

    Juan Barón

    2011-07-01

    Full Text Available Compuesta por los departamentos de Antioquia, Caldas, Quindío, Risaralda y Valle del Cauca, los Andes Occidentales ha sido por mucho años una de las regiones más prósperas de Colombia. Esta prosperidad se ha traducido en condiciones de vida e infraestructura superiores a las del resto del país. El éxito y bienestar que presentan hoy en día los Andes Occidentales están estrechamente ligados a la concentración de la producción de café, que se dio allí durante gran parte del siglo XX. El arraigo del café en la región no sólo se dio debido a que la geografía ofrecía las condiciones ideales para el cultivo, sino también a las instituciones cafeteras creadas para organizar la industria del café. A pesar de esta prosperidad, el constante descenso del precio internacional del café después del rompimiento del pacto de cuotas de producción en 1989, sumado al estancamiento de la industria manufacturera en algunos departamentos de la región, han afectado las economías departamentales menos diversificadas. Es así como la región de los Andes Occidentales Colombianos presenta las tasas de desempleo más altas del país, tasas que se han visto afectadas aún más con la crisis financiera internacional a través del menor flujo de remesas que los trabajadores oriundos de la región, y residentes en el exterior envían a sus familias.

  12. Do climate changes influence dispersal and population dynamics of dragonflies in the western Peruvian Andes?

    Directory of Open Access Journals (Sweden)

    Joachim Hoffmann

    2010-12-01

    Full Text Available For nine dragonfly species (five aeshnids and four libellulids all previous and verifiable data are related to the vertical climate zones and nature regions of the western Peruvian Andes and the Peruvian Pacific coast. Climate changes due to the El Niño and La Niña phenomena, as well as the global climate change have an influence on the different natural regions and also restrict aquatic biotopes. These changes influence the dispersal and behavior of some dragonflies and concern also loss of habitats as well as alterations of biotic and abiotic factors at and in water. However new waters and habitats also are formed in most nature regions. Specialists like Rhionaeschna peralta, a species of high mountain regions and the Puna, are not able to react to habitat losses by adaptation, while other species such as R. maita and R. marchali do colonize new habitats also in higher altitudes. While the here represented aeshnids change their distribution ranges within the vertical nature regions of the west Andes, this is suspected for three of the four libellulids (Orthemis ferruginea, O. discolor and Pantala flavescens as latitudinally respectively longitudinally immigrations and expansions of their areals. For all species discussed, a seasonally earlier flight beginning is detectable, but for no species an extension of their flight time. Altogether, the above named three libellulid do react more flexibly and faster to the alterations by climate changes than the majority of the five aeshnid species. The influence of increased UV-B and UV-A radiation possibly affects also the site occurrence of some species in high altitudes of the Andes.

  13. Setting practical conservation priorities for birds in the Western Andes of Colombia.

    Science.gov (United States)

    Ocampo-Peñuela, Natalia; Pimm, Stuart L

    2014-10-01

    We aspired to set conservation priorities in ways that lead to direct conservation actions. Very large-scale strategic mapping leads to familiar conservation priorities exemplified by biodiversity hotspots. In contrast, tactical conservation actions unfold on much smaller geographical extents and they need to reflect the habitat loss and fragmentation that have sharply restricted where species now live. Our aspirations for direct, practical actions were demanding. First, we identified the global, strategic conservation priorities and then downscaled to practical local actions within the selected priorities. In doing this, we recognized the limitations of incomplete information. We started such a process in Colombia and used the results presented here to implement reforestation of degraded land to prevent the isolation of a large area of cloud forest. We used existing range maps of 171 bird species to identify priority conservation areas that would conserve the greatest number of species at risk in Colombia. By at risk species, we mean those that are endemic and have small ranges. The Western Andes had the highest concentrations of such species-100 in total-but the lowest densities of national parks. We then adjusted the priorities for this region by refining these species ranges by selecting only areas of suitable elevation and remaining habitat. The estimated ranges of these species shrank by 18-100% after accounting for habitat and suitable elevation. Setting conservation priorities on the basis of currently available range maps excluded priority areas in the Western Andes and, by extension, likely elsewhere and for other taxa. By incorporating detailed maps of remaining natural habitats, we made practical recommendations for conservation actions. One recommendation was to restore forest connections to a patch of cloud forest about to become isolated from the main Andes.

  14. Assembly patterns of mixed-species avian flocks in the Andes.

    Science.gov (United States)

    Colorado, Gabriel J; Rodewald, Amanda D

    2015-03-01

    The relative contribution of deterministic and stochastic processes in the assembly of biotic communities is a central issue of controversy in community ecology. However, several studies have shown patterns of species segregation that are consistent with the hypothesis that deterministic factors such as competition and niche-partitioning structure species assemblages in animal communities. Community assembly provides a theoretical framework for understanding these processes, but it has been seldom applied to social aggregations within communities. In this research, we assessed patterns of non-randomness in Andean mixed-species flocks using three assembly models: (i) co-occurrence patterns; (ii) guild proportionality; and (iii) constant body-size ratios using data from 221 species of resident and Neotropical migrant birds participating in 311 mixed-species flocks at 13 regions distributed in Venezuela, Colombia, Ecuador and Peru. Significant assembly patterns for mixed-species flocks based on co-occurrence models and guild proportionality models suggest that competitive interactions play an important role in structuring this social system in the Andes. Distribution of species among foraging guilds (i.e. insectivore, frugivore, omnivore, nectivore) was generally similar among flocks, though with some regional variation. In contrast, we found little evidence that structuring of mixed-species flocks in the Andes was mediated by body size. Rather, we found greater than expected variance of body-size ratios within flocks, indicating that birds did not segregate morphologically. Overall, our findings suggest that deterministic factors associated to competitive interactions are important contributors to mixed-species flock assemblages across the Andes. PMID:25283441

  15. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    Science.gov (United States)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

    2015-12-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous ~ N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from ~ E-W in the Patagonian Andes to ~ N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin

  16. Proglacial lake sediments, cosmogenic ages and stable isotopes reveal Holocene climate changes in the Peruvian Andes

    Science.gov (United States)

    Stansell, N.; Rodbell, D. T.; Licciardi, J. M.; Abbott, M. B.; Mark, B. G.; Schweinsberg, A.

    2013-12-01

    Sediment records from lakes and cosmogenic ages on moraine boulders in central Peru document the waxing and waning of alpine glaciers since the end of the late glacial stage. These records from the southern tropical Andes tentatively suggest that a brief re-advance occurred during the early Holocene, even though conditions overall were relatively warm and dry from ~12 to 8 ka. The middle Holocene (between 8 and 4 ka) was marked by a shift to cooler, and possibly wetter conditions in certain regions, leading to glacial advances. Although there were multiple periods of brief ice advances that punctuated the overall late Holocene trend, glaciers in multiple valleys generally retreated from ~4.0 ka through the Medieval Climate Anomaly (1.0 to 0.7 ka). This late Holocene pattern of ice retreat occurred during a period when lake level studies, and both lacustrine and speleothem stable isotopic records indicate wetter conditions, suggesting that higher temperatures contributed to the pattern of ice retreat. Following this period of glacial retreat, multiple proxy records suggest that the start of the Little Ice Age (~0.6 to 0.1 ka) was a colder and wetter time throughout much of the tropical Andes. While there is emerging evidence that the strength of the South American Summer Monsoon increased through the Holocene, these shifting precipitation patterns do not fully explain the record of glaciation in Peru. It is likely that sea surface temperature distributions in the tropical Pacific Ocean also affected atmospheric temperature, precipitation and circulation patterns over the Andes. The combined influences of both Atlantic and Pacific ocean and atmospheric influences thus contributed to the observed pattern of glacial variability during the Holocene.

  17. The Glacier Inventory of the Central Andes of Argentina (31°-35°S)

    Science.gov (United States)

    Ferri Hidalgo, L.; Zalazar, L.; Castro, M.; Pitte, P.; Masiokas, M. H.; Ruiz, L.; Villalba, R.; Delgado, S.; Gimenez, M.; Gargantini, H.

    2015-12-01

    The National Law for protection of glaciers in Argentina envisages the development of a National Inventory of Glaciers. All glaciers and periglacial landforms which are important as strategic water resource must be properly identified and mapped. Here we present a detailed and complete glacier and rock glacier inventory of the Central Andes of Argentina between 31° and 35°S. This semi-arid region contains some of the highest mountains of South America and concentrates the second most glacierized area in Argentina after the Patagonian Andes. To develop the inventory, we used remotely sensed data and related techniques complemented with field surveys. Clean ice and perennial snowfields were identified applying an automatic extraction method on medium spatial-resolution images. Debris-covered and rock glaciers were manually digitized on higher spatial-resolution images. With minor modifications, the present digital inventory is consistent with GLIMS standards. For each glacier, we derived 38 database fields, adding five specific attributes for rock glaciers, which are not included in the original GLIMS database. In total we identified 8069 glaciers covering an area of 1768 km2. Debris-covered ice and rock glaciers represent 57% of the total inventoried area. In this region, rock glaciers are a common feature in the arid landscape and constitute an important water reserve at regional scale. Many glaciers were characterized by gradual transition from debris-covered glaciers, in the upper part, to rock glaciers, in the lower sector. The remaining 43% includes clean ice glaciers and permanent snowfields. These are mostly mountain and valley-type glaciers with medium-to-small sizes. This detailed inventory constitutes a valuable contribution to the ongoing global efforts (e.g. WGI, RGI and GLIMS) to map the world's glaciers. It is also the base for ongoing glaciological, climatological and hydrological studies in this portion of southern Andes.

  18. Land Use Change and Hydrologic Processes in High-Elevation Tropical Watersheds of the Northern Andes

    Science.gov (United States)

    Avery, W. A.; Riveros-Iregui, D. A.; Covino, T. P.; Peña, C.

    2013-12-01

    The humid tropics cover one-fifth of the Earth's land surface and generate the greatest amount of runoff of any biome globally, but remain poorly understood and understudied. Humid tropical regions of the northern and central Andes have experienced greater anthropogenic land-use/land-cover (LULC) change than nearly any other high mountain system in the world. Vast expanses of this region are currently undergoing rapid transformation to farmland for production of potatoes and pasture for cattle grazing. Although the humid tropics have some of the highest runoff ratios, precipitation, and largest river flows in the world, there is a lack of scientific literature that addresses hydrologic processes in these regions and very few field observations are available to inform management strategies to ensure the sustainability of water resources of present and future generations. We seek to improve understanding of hydrologic processes and feedbacks in the humid tropics using existing and new information from two high-elevation watersheds that span a LULC gradient in the Andes Mountains of Colombia. One site is located in the preserved Chingaza Natural National Park in Central Colombia (undisturbed). The second site is located ~60 km to the northwest and has experienced considerable LULC change over the last 40 years. Combined, these watersheds deliver over 80% of the water resources to Bogotá and neighboring communities. These watersheds have similar climatological characteristics (including annual precipitation), but have strong differences in LULC which result in substantial differences in hydrologic response and streamflow dynamics. We present an overview of many of the pressing issues and effects that land degradation and climate change are posing to the long-term sustainability of water resources in the northern Andes. Our overarching goal is to provide process-based knowledge that will be useful to prevent, mitigate, or respond to future water crises along the Andean

  19. Subduction Zone Science - Examples of Seismic Images of the Central Andes and Subducting Nazca Slab

    Science.gov (United States)

    Beck, S. L.; Zandt, G.; Scire, A. C.; Ward, K. M.; Portner, D. E.; Bishop, B.; Ryan, J. C.; Wagner, L. S.; Long, M. D.

    2015-12-01

    Subduction has shaped large regions of the Earth and constitute over 55,000 km of convergent plate margin today. The subducting slabs descend from the surface into the lower mantle and impacts earthquake occurrence, surface uplift, arc volcanism and mantle convection as well as many other processes. The subduction of the Nazca plate beneath the South America plate is one example and constitutes the largest present day ocean-continent convergent margin system and has built the Andes, one of the largest actively growing mountain ranges on Earth. This active margin is characterized by along-strike variations in arc magmatism, upper crustal shortening, crustal thickness, and slab geometry that make it an ideal region to study the relationship between the subducting slab, the mantle wedge, and the overriding plate. After 20 years of portable seismic deployments in the Central Andes seismologists have combined data sets and used multiple techniques to generate seismic images spanning ~3000 km of the South American subduction zone to ~800 km depth with unprecedented resolution. For example, using teleseismic P- waves we have imaged the Nazca slab penetrating through the mantle transition zone (MTZ) and into the uppermost lower mantle. Our tomographic images show that there is significant along-strike variation in the morphology of the Nazca slab in the upper mantle, MTZ, and the lower mantle, including possible tears, folding, and internal deformation. Receiver function studies and surface wave tomography have revealed major changes in lithospheric properties in the Andes. Improved seismic images allow us to more completely evaluate tectonic processes in the formation and uplift of the Andes including: (1) overthickened continental crust driven by crustal shortening, (2) changes in slab dip and coupling with the overlying plate (3) localized lithospheric foundering, and (4) large-scale mantle and crustal melting leading to magmatic addition and/or crustal flow. Although

  20. Space geodetic observations of nazca-south america convergence across the central andes

    Science.gov (United States)

    Norabuena; Leffler-Griffin; Mao; Dixon; Stein; Sacks; Ocola; Ellis

    1998-01-16

    Space geodetic data recorded rates and directions of motion across the convergent boundary zone between the oceanic Nazca and continental South American plates in Peru and Bolivia. Roughly half of the overall convergence, about 30 to 40 millimeters per year, accumulated on the locked plate interface and can be released in future earthquakes. About 10 to 15 millimeters per year of crustal shortening occurred inland at the sub-Andean foreland fold and thrust belt, indicating that the Andes are continuing to build. Little (5 to 10 millimeters per year) along-trench motion of coastal forearc slivers was observed, despite the oblique convergence.

  1. Tectonic geomorphology of the Andes with SIR-A and SIR-B

    Science.gov (United States)

    Bloom, Arthur L.; Fielding, Eric J.

    1986-01-01

    Data takes from SIR-A and SIR-B (Shuttle Imaging Radar) crossed all of the principal geomorphic provinces of the central Andes between 17 and 34 S latitude. In conjunction with Thematic Mapping images and photographs from hand-held cameras as well as from the Large Format Camera that was flown with SIR-B, the radar images give an excellent sampling of Andean geomorphology. In particular, the radar images show new details of volcanic rocks and landforms of late Cenozoic age in the Puna, and the exhumed surfaces of tilted blocks of Precambrian crystalline basement in the Sierras Pampeanas.

  2. Muerte en los Andes: sociedad colonial y mortalidad en las haciendas andinas (Ecuador, 1743-1857)

    OpenAIRE

    María José Vilalta

    2015-01-01

    Resumen La vida cotidiana en las haciendas coloniales implicó la introducción de una forma de administración de poblaciones impuesta sobre la sociedad indígena y regulada por las Leyes de Indias. En la zona norte de los Andes, el concertaje de indios y la abundancia de trabajos en la agricultura y en los obrajes fueron factores de atracción que generaron la tendencia a un crecimiento poblacional de larga duración. Más allá del debate inconcluso sobre la catástrofe demográfica en las Indias, e...

  3. The Medieval Climate Anomaly and the Little Ice Age in the eastern Ecuadorian Andes

    OpenAIRE

    Ledru, M.-P.; Jomelli, V; Samaniego, P.; M. Vuille; S. Hidalgo; M. Herrera; Ceron, C.

    2013-01-01

    To better characterize the climate variability of the last millennium in the high Andes, we analyzed the pollen content of a 1150-yr-old sediment core collected in a bog located at 3800 m a.s.l. in the páramo in the eastern Cordillera in Ecuador. An upslope convective index based on the ratio between cloud transported pollen from the Andean forest to the bog (T) and Poaceae pollen frequencies, related to the edaphic moisture of the páramo (P), was defined. This index was use...

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

    Science.gov (United States)

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

    2014-05-01

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

  5. Effect of Vandetanib on Andes virus survival in the hamster model of Hantavirus pulmonary syndrome.

    Science.gov (United States)

    Bird, Brian H; Shrivastava-Ranjan, Punya; Dodd, Kimberly A; Erickson, Bobbie R; Spiropoulou, Christina F

    2016-08-01

    Hantavirus pulmonary syndrome (HPS) is a severe disease caused by hantavirus infection of pulmonary microvascular endothelial cells leading to microvascular leakage, pulmonary edema, pleural effusion and high case fatality. Previously, we demonstrated that Andes virus (ANDV) infection caused up-regulation of vascular endothelial growth factor (VEGF) and concomitant downregulation of the cellular adhesion molecule VE-cadherin leading to increased permeability. Analyses of human HPS-patient sera have further demonstrated increased circulating levels of VEGF. Here we investigate the impact of a small molecule antagonist of the VEGF receptor 2 (VEGFR-2) activation in vitro, and overall impact on survival in the Syrian hamster model of HPS. PMID:27233645

  6. Amalgamation and small-scale gold mining in the ancient Andes

    OpenAIRE

    Brooks, William E.; Schwörbel, Gabriela; Castillo, Luis Enrique

    2013-01-01

    In 1532, the volume of gold provided by Atahualpa, the Inka king, as ransom for his release from the Spanish was hard evidence for the efficient small-scale gold mining that took place before European contact and the number of gold occurrences in the Andes. At Huancavelica, Perú, mercury occurs as a native metal and as cinnabar [HgS], which was used for pigments, funeral preparations, and retorted to obtain mercury. Using Inductively Coupled Plasma analysis (ICP), an average of 15 ppm (parts...

  7. Salud mental y resilencia en estudiantes de Arte, Universidad de los Andes, Venezuela

    OpenAIRE

    González González, Julio César

    2015-01-01

    Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Psiquiatría. Fecha de lectura: 15-04-2015 El presente estudio tuvo como objetivo hacer una evaluación del estado de salud mental y de la capacidad resiliente de los estudiantes de la Escuela de Artes Visuales y Diseño Gráfico de la Facultad de Arte de la Universidad de Los Andes. La muestra estuvo constituida por 318 cursantes entre principio, mitad y final de la carrera, 119 (44.07 %) ...

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

    OpenAIRE

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

    2011-01-01

    We use about two decades of geodetic measurements to characterize interseismic strain build up along the Central Andes subduction zone from Lima, Peru, to Antofagasta, Chile. These measurements are modeled assuming a 3-plate model (Nazca, Andean sliver and South America Craton) and spatially varying interseismic coupling (ISC) on the Nazca megathrust interface. We also determine slip models of the 1996 M(w) = 7.7 Nazca, the 2001 M(w) = 8.4 Arequipa, the 2007 M(w) = 8.0 Pisco and the M(w) = 7....

  9. Back-Arc Extension in the Southern Andes: A Review and Critical Reappraisal

    Science.gov (United States)

    Dalziel, I. W. D.

    1981-03-01

    The interpretation that the mafic 'rocas verdes' (green rocks) complex of the southern Andes represents part of the uplifted floor of a Late Jurassic to Early Cretaceous back-arc basin has proved particularly useful in understanding the geological evolution of the southern Andes, the north Scotia Ridge and the Antarctic Peninsula. Clear field evidence of the back-arc setting of the 'rocas verdes' gabbro-sheeted dyke - pillow lava ophiolitic assemblages has encouraged fruitful petrological and geochemical comparison with mid-ocean ridge and marginal basin basalts, other onshore ophiolite complexes, and Archaean greenstone belts. Uncertainty still surrounds estimates of the original width and depth of the basin, as well as the proportion of new mafic crust, compared with relict sialic crust, in the basin floor. These questions are unresolved, owing mainly to the considerable Lower Cretaceous turbiditic basin infill and the effects of mid-Cretaceous compressional deformation. While the field relations clearly indicate that the 'rocas verdes' basin is not an older piece of ocean floor 'trapped' behind a volcanic arc, it is not yet clear whether the basin is directly subduction-related or falls in the category of back-arc 'leaky transforms' like the proto-Gulf of California or apparent 'rip-off' features like the Andaman Sea.

  10. Temperature and Rainfall Variability in the Northern Andes Over the Past Two Millennia

    Science.gov (United States)

    Shanahan, T. M.; Bixler, C. W.; Mora, A.

    2014-12-01

    Recent studies of tropical glaciers have shown that most are retreating rapidly, with some of the most dramatic changes occurring since the mid-1970s, most likely as a result of increasing global temperatures. However, a longer-term perspective is needed to place these changes in the context of natural climate variability. To better understand the climatological factors driving long-term variations in the mass balance of tropical glaciers, we reconstructed changes in precipitation and temperature in the northern tropical Andes using variations in the hydrogen isotope composition of sedimentary leaf waxes and branched GDGT distributions in a high-resolution varved sediment record from Lago Chingaza, Colombia. Br-GDGT derived temperatures are significantly correlated with instrumental temperature data and indicate that recent warming in the northern tropical Andes is unprecedented over the past two millennia. Furthermore, the magnitude of warming since the Little Ice Age is substantially larger than suggested by high latitude temperature reconstructions. Hydrogen isotope data indicated that colder conditions during the Little Ice Age were accompanied by a decrease in rainfall, likely associated with a southward shift in the position of the ITCZ. Over the past few centuries, warmer temperatures were accompanied by an increase in rainfall and a northward expansion of the tropical rainbelt. Together, these data suggest that the dominant control on the retreat of Andean glaciers has been the unprecedented rate and magnitude of recent warming.

  11. Albedo changes, Milankovitch forcing, and late quaternary climate changes in the central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Kull, C.; Grosjean, M. [Swiss Federal Inst. of Tech., Zurich (Switzerland). Dept. of Geography

    1998-11-01

    Late quaternary humidity changes resulted in substantial modifications of the land surface characteristics in the Altiplano of the Atacama desert, central Andes. Reconstructions of surface albedo, top-of-atmosphere (TOA) albedo, and shortwave net radiation in the Andes of northern Chile for 20,14,10,7 and 0 ka suggest that surface and TOA albedo increased substantially during periods of relatively humid environmental conditions (i.e., with large palaeolakes, glaciers and dense vegetation). The decrease of summer shortwave net radiation and seasonality during the late-glacial/early Holocene humid phase (14 to 10 ka) due to Earth`s surface and atmospheric characteristics added to the effect of orbitally driven negative deviations of southern Hemisphere austral summer insolation and minimum seasonality at 20 S. Therefore, in situ radiative forcing is, in contrast to the Northern Hemisphere tropics, not a suitable explanation for enhanced convective precipitation and, ultimately, humid climatic conditions. Our results suggest that late Quaternary humidity changes on the Altiplano reflect a collective response to (1) environmental changes in the source area of the moisture (e.g., reexpansion of the rain forest and increased release of latent heat over Amazonia and the Chaco, warm sea surface temperatures in the E Pacific) and, (2) large-scale circulation patterns and wave structures in the upper troposphere (strength and position of the Bolivian high, divergent flow stimulating convection over the Altiplano), or that they even reflect a response to (3) interhemispherical teleconnections. (orig.) With 5 figs., 2 tabs., 45 refs.

  12. Bare Rocks and Fallen Angels: Environmental Change, Climate Perceptions and Ritual Practice in the Peruvian Andes

    Directory of Open Access Journals (Sweden)

    Karsten Paerregaard

    2013-05-01

    Full Text Available One of the many dimensions of globalization is climate change that in recent years has caused much concern in the developed world. The aim of this article is to explore how people living on the margins of the global world conceive climate change. Drawing on ethnographic field data from the 1980s and today it examines how the ritual practice and the religious belief of a rural community in the Peruvian Andes has changed during the last 27 years and how the villagers perceive this change. It argues that the villagers traditionally conceive the environment as co-habited by humans and non-humans but that recent environmental change in the Andes has caused a shift in this world-view. Today, many villagers have adopted the global vocabulary on climate change and are concerned with their own impact in the environment. However, the villagers reject the idea that it is human activities in other parts of the world that cause environmental problems in their community and claim that these must be addressed locally. It suggests that even though the villagers’ reluctance to subscribe to the global discourse of climate change makes them look like the companions of climate skeptics in the developed world, their reasons are very different.

  13. Thermal physiology, disease, and amphibian declines on the eastern slopes of the Andes.

    Science.gov (United States)

    Catenazzi, Alessandro; Lehr, Edgar; Vredenburg, Vance T

    2014-04-01

    Rising temperatures, a widespread consequence of climate change, have been implicated in enigmatic amphibian declines from habitats with little apparent human impact. The pathogenic fungus Batrachochytrium dendrobatidis (Bd), now widespread in Neotropical mountains, may act in synergy with climate change causing collapse in thermally stressed hosts. We measured the thermal tolerance of frogs along a wide elevational gradient in the Tropical Andes, where frog populations have collapsed. We used the difference between critical thermal maximum and the temperature a frog experiences in nature as a measure of tolerance to high temperatures. Temperature tolerance increased as elevation increased, suggesting that frogs at higher elevations may be less sensitive to rising temperatures. We tested the alternative pathogen optimal growth hypothesis that prevalence of the pathogen should decrease as temperatures fall outside the optimal range of pathogen growth. Our infection-prevalence data supported the pathogen optimal growth hypothesis because we found that prevalence of Bd increased when host temperatures matched its optimal growth range. These findings suggest that rising temperatures may not be the driver of amphibian declines in the eastern slopes of the Andes. Zoonotic outbreaks of Bd are the most parsimonious hypothesis to explain the collapse of montane amphibian faunas; but our results also reveal that lowland tropical amphibians, despite being shielded from Bd by higher temperatures, are vulnerable to climate-warming stress.

  14. Rainfall and Cloud Dynamics in the Andes: A Southern Ecuador Case Study

    Directory of Open Access Journals (Sweden)

    Lenin Campozano

    2016-01-01

    Full Text Available Mountain regions worldwide present a pronounced spatiotemporal precipitation variability, which added to scarce monitoring networks limits our understanding of the generation processes involved. To improve our understanding of clouds and precipitation dynamics and cross-scale generation processes in mountain regions, we analyzed spatiotemporal rainfall patterns using satellite cloud products (SCP in the Paute basin (900–4200 m a.s.l. and 6481 km2 in the Andes of Ecuador. Precipitation models, using SCP and GIS data, reveal the spatial extension of three regimes: a three-modal (TM regime present across the basin, a bimodal (BM regime, along sheltered valleys, and a unimodal (UM regime at windward slopes of the eastern cordillera. Subsequently, the spatiotemporal analysis using synoptic information shows that the dry season of the BM regime during boreal summer is caused by strong subsidence inhibiting convective clouds formation. Meanwhile, in UM regions, low advective shallow cap clouds mainly cause precipitation, influenced by water vapor from the Amazon and enhanced easterlies during boreal summer. TM regions are transition zones from UM to BM and zones on the windward slopes of the western cordillera. These results highlight the suitability of satellite and GIS data-driven statistical models to study spatiotemporal rainfall seasonality and generation processes in complex terrain, as the Andes.

  15. Bird conservation would complement landslide prevention in the Central Andes of Colombia

    Directory of Open Access Journals (Sweden)

    Natalia Ocampo-Peñuela

    2015-02-01

    Full Text Available Conservation and restoration priorities often focus on separate ecosystem problems. Inspired by the November 11th (2011 landslide event near Manizales, and the current poor results of Colombia’s Article 111 of Law 99 of 1993 as a conservation measure in this country, we set out to prioritize conservation and restoration areas where landslide prevention would complement bird conservation in the Central Andes. This area is one of the most biodiverse places on Earth, but also one of the most threatened. Using the case of the Rio Blanco Reserve, near Manizales, we identified areas for conservation where endemic and small-range bird diversity was high, and where landslide risk was also high. We further prioritized restoration areas by overlapping these conservation priorities with a forest cover map. Restoring forests in bare areas of high landslide risk and important bird diversity yields benefits for both biodiversity and people. We developed a simple landslide susceptibility model using slope, forest cover, aspect, and stream proximity. Using publicly available bird range maps, refined by elevation, we mapped concentrations of endemic and small-range bird species. We identified 1.54 km2 of potential restoration areas in the Rio Blanco Reserve, and 886 km2 in the Central Andes region. By prioritizing these areas, we facilitate the application of Article 111 which requires local and regional governments to invest in land purchases for the conservation of watersheds.

  16. Two new species of Leptanilloides Mann, 1823 (Formicidae: Dorylinae from the Andes of southern Ecuador

    Directory of Open Access Journals (Sweden)

    Thibaut Delsinne

    2015-10-01

    Full Text Available Two new species of Leptanilloides are described: L. copalinga Delsinne & Donoso sp. nov., and L. prometea Delsinne & Donoso sp. nov., based on workers collected in the leaf litter and soil of the Andes of southern Ecuador. Both species belong to the L. biconstricta species-group (formally diagnosed here. The metatibial gland, considered a synapomorphy for Dorylinae, is observed in L. prometea sp. nov. but seems absent in L. copalinga sp. nov. We provide a COI DNA barcode for both species and a revised key for the worker caste of all known species in the genus. We also describe a single male identified as a potential new Leptanilloides species on the basis of morphology. Furthermore, its mitochondrial COI gene sequence does not match any previously barcoded species. However, we refrain from giving it a specific name because of our lack of knowledge about the worker caste. So far, half of the 14 Leptanilloides species have been discovered above 1500 m in the mountain forests or páramos of the Ecuadorian Andes, confirming, if needed, the biological significance of these threatened habitats.

  17. Petrofabric Interpretations Supported by Magnetic Anisotropy Observations for the Clavijo Intrusion, Colombian Andes

    Science.gov (United States)

    MacDonald, W. D.; Muggleton, S.; Estrada, J. J.; Sierra, G. M.

    2002-12-01

    Remanent magnetization studies on Late Tertiary shallow intrusions in allochthonous terranes of the Colombian Andes suggest two apparent modes of rotation, about vertical axes and about horizontal axes, as reported previously. The horizontal axes trend perpendicular to the regional structural trends, to judge by the dispersed remanence directions along vertical planes parallel to major strike-slip faults. Two distinct zones have been recognized, between Medellin and Manizales, and between Cali and Pasto (Risnes, 1995), extending approximately 600 km along the Andes. Research on the Clavijo body indicates the importance of combining studies of remanence with those of anisotropy of susceptibility (AMS) and of isothermal remanence (AIRM), and petrofabric studies, in interpreting the remanence directions in tectonically disturbed regions. In this body, hydrothermal alteration is associated with increased within-site scatter of AMS axes. Within-site remanence directions are however not dispersed by such alteration, while between-site remanence directions are affected. New results from electron-microprobe analyses of fresh and hydrothermally altered ferromagnetic (s.l.) and paramagnetic minerals are compared with the respective remanence and susceptibility anisotropies of altered and unaltered sites. A major objective is to determine if vertical flow directions in these shallow intrusions can be recognized, and thus utilized for tilt-corrections of remanence and improved tectonic interpretations. Risnes, K., 1995, Terre et Environnement, v. 2, 169 p., Dept. Mineralogy, Univ. Geneva.

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

    Science.gov (United States)

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

    2013-12-01

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

  19. Kas Arnold Rüütel valetas süümevannet andes? / Anneli Ammas, Garel Püüa

    Index Scriptorium Estoniae

    Ammas, Anneli, 1962-

    2006-01-01

    Autorite hinnangul tekib 31. augustil Eesti Ekspressis ilmunud artikli põhjal, milles käsitleti Johannes Hindi represseerimist, küsimus, kas Arnold Rüütel on valetanud Eesti Vabariigile korduvalt süümevannet andes. TÜ professori Kalle Meruski seisukoht. Lisa: Rüütel käskis kontrolli tugevdada

  20. A new species of Eretris Thieme (Lepidoptera: Nymphalidae, Satyrinae) from the Elbow of the Andes region in Bolivia.

    Science.gov (United States)

    Pyrcz, Tomasz W; Gareca, Yuvinka

    2009-01-01

    A new species of cloud forest butterfly, Eretris julieta n. sp. is described from a region of south-central Bolivia known as the Elbow of the Andes. It is the southernmost known representative of the genus, hitherto known only from a restricted area of interandean valleys in the department of Santa Cruz. Its affinities with other congeners are evaluated.

  1. Uplift and volcanism of the SE Colombian Andes in relation to Neogene sedimentation in the Upper Magdalena Valley.

    NARCIS (Netherlands)

    Wiel, van der A.M.

    1991-01-01

    The present study deals with the relation between Neogene uplift and volcanism of the SE Colombian Andes and sedimentation processes in the Upper Magdalena Valley. The southernmost part of the Upper Magdalena Valley, the S. Neiva Basin, is located between latitudes 2°08'-2°31 N and longitudes 75°22'

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

    Science.gov (United States)

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

    2015-11-01

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

  3. Ensayos metodologicos para la investigacion de reservorios de Leishmania spp en los Andes venezolanos Methodological assay for research of reservoirs of Leishmania spp. in the Venezuelan Andes

    Directory of Open Access Journals (Sweden)

    Ana Lugo Yarbuh

    1982-12-01

    Full Text Available Se describen dos técnicas, presuntiva y confirmativa, para la investigación de mamíferos que pudieran ser reservorios de Leishmania que parasitan al hombre. Se investigan los cambios en los títulos de inmovilización y aglutinación de promastigotos de cultivo por los sueros de animales normales y expuestos una o varias veces a la inoculación intradérmica de pequeñas dosis de promastigotos vivos. Se registra una caída de los títulos de aglutinación en los sueros de hamsteres, de Holochilus venezuelae y de Didelphis marsupialis después de la inoculación con L. mexicana mexicana de Panamá y de L. gamhami de la región de los Andes venezolanos. Se discute la natureza de estos fenómenos. Se han hecho xenodiagnósticos con Lutzomyia townsendi en Holochilus venezuelae y Sigmodon hispidus infectados experimentalmente com L. mexicana mexicana, L. mexicana amazonensis, L. braziliensis y L. garnhami. Las pruebas fueron leidas mediante el examen microscópico de las gotitas de heces excretadas entre las 108 y 132 horas después de la ingesta infectante, tras colorearlas con Giemsa. Se obtuvieron resultados positivos en 23% de los experimentos usando mamíferos con lesiones localizadas, dejando a los flebótomos ingurgitarse libremente sobre animales anestesiados que poseian una hasta varias lesiones localizadas.Presumptive and confirmative techniques for searching mammals which could be reservoirs for Leishmania parasites from man are described. The changes of immobilising and agglutinating titers for promastigotes from culture by sera from normal and exposed mammals after single or repeated intradermal inoculation of promastigotes are described. A fall in titers of agglunation is observed in sera from hamsters, Holochilus venezuelae and Didelphis marsupialis after inoculation with L. mexicana mexicana from Panama and L. garnhami from the Venezuelan Andes region. The nature of this phenomenon is discussed. Xenodiagnoses were made with

  4. The Bolivian Orocline and its implications for the origin of the central Andes

    Science.gov (United States)

    Arriagada, C.

    2015-12-01

    The tectonic evolution of the Central Andes includes a complex combination of thrusting, wrenching and block rotation leading progressively to the curvature of the orogenic system of the South American continental margin at 18ºS (Bolivian Orocline). Tectonic deformation in the Bolivian Orocline cannot be realistically restored using information from balanced cross sections alone, as the deformation includes an important component of block rotation, associated to counterclockwise block rotation in southern Peru and clockwise rotation in northern Chile. Recent work shows that block rotations in the forearc are essentially pre-early Miocene, predating the onset of Neogene shortening in the Sub Andean zone. Most rotations in the forearc of northern Chile where acquired through a single tectonic event during the Paleogene-early Miocene which probably coincides with the Eocene orogen-wide Incaic event which affected large regions of the central Andes between ca. 50 and 40 Ma. Results from 2D restoration experiments support the hypothesis of the Paleogene formation of the Bolivian Orocline, as a consequence of differential shortening, concentrated in the Eastern Cordillera of Bolivia, southern Peru and northwestern Argentina. Within the southern central Andes four additional curvatures including striking changes in the pattern of rotations have been discovered. From north to south these are the Antofagasta-Calama Lineament, Vallenar, Maipo and Arauco oroclines. However, an important part of rotation needs to be balanced, in the forearc region, by two major conjugate oblique shear zones (Abancay Deflection and Antofagasta-Calama Lineament). These structural features are probably related to inherited lithospheric discontinuities associated with the accretion of basement terranes which could be responsible for producing and delimitating significant and abrupt changes in the magnitude of the Central Andean Rotation Pattern along the margin. While shortening and crustal

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

    Science.gov (United States)

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

    2015-04-01

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

  6. Analysis of the Geographical Distribution of Gerridae (Hemiptera, Gerromorpha in the Andes of Southwestern Colombia

    Directory of Open Access Journals (Sweden)

    Dora Nancy Padilla Gil

    2013-06-01

    Full Text Available We present the geographical and altitudinal distribution of the Gerridae family on the western slopes of the Western Cordillera of Andes in southwestern Colombia. The specimens were captured in different water bodies, eight sampling sites, during 2009 and 2010. Taxonomic composition was analyzed with respect to geographical and altitudinal range, biomes and the similarity between areas. The geographical distribution of the Gerridae is related to geographic area, foothills and Plain Pacific, altitudinal range (0-2000 masl and features of type of biome. The communities of Gerridae from Pacific Plain are in the same zonobioma but differ in taxonomic composition due to differences in water bodies and microhabitats own. On the other hand we show the inverse relationship between altitude and species richness. ANÁLISIS DE LA DISTRIBUCIÓN GEOGRÁFICA DE LAS GERRIDAE (HEMIPTERA, GERROMORPHA EN LOS ANDES DEL SUROESTE DE COLOMBIA Se presentan la distribución geográfica y altitudinal las Gerridae en la vertiente occidental de la Cordillera Occidental, suroccidente de los Andes de Colombia. La captura de especimenes se realizó en cuerpos de agua en ocho sitios de muestreo, durante los años 2009 y 2010. Se analizó la composición taxonómica respecto al rango geográfico y altitudinal, los biomas y la similitud entre áreas. La distribución geográfica de las Gerridae esta relacionada con el área geográfica, rango altitudinal (0-2000m y tipo de bioma. Las especies de la Planicie del Pacífico a pesar de encontrarse en el mismo Zonobioma difieren en su composición taxonómica debido a diferencias en los cuerpos de agua y michohábitats característicos. Se evidencia la relación inversa entre la altitud y la riqueza de especies.

  7. Modelling increased landslide susceptibility near highways in the Andes of southern Ecuador

    Science.gov (United States)

    Brenning, Alexander; Muenchow, Jannes

    2016-04-01

    Modelling increased landslide susceptibility near highways in the Andes of southern Ecuador A. Brenning (1), J. Muenchow (1) (1) Department of Geography, Friedrich Schiller University Jena, Loebdergraben 32, 07743 Jena, Germany Mountain roads are affected by and also affect themselves landslide suceptibility. Especially in developing countries, inadequate drainage systems and mechanical destabilization of hillslopes by undercutting and overloading are known processes through which road construction and maintenance can enhance landslide activity within the immediate surroundings of road infrastructure. In the Andes of southern Ecuador, strong precipitation gradients as well as lithological differences provide an excellent study site in which the relationship between highways and landslide susceptibility and its regional differentiation can be studied. This study uses Generalized Additive Models (GAM) to investigate patterns of landslide susceptibility along two paved interurban highways in the tropical Andes of southern Ecuador. The relationship of landslides to distance from road is modeled while accounting for topographic, climatic and lithological predictors as possible confounders and modifiers, focusing on the odds ratio of landslide occurrence at 25 m versus 200 m distance from the highway. Spatial attention is given to uncertainties in estimated odds ratios of landslide occurrence using spatial block bootstrap techniques. The GAM is able to represent nonlinear additive terms as well as bivariate smooth interaction terms, providing a good tradeoff between model complexity and interpretability. The estimated odds of landslide occurrence were 18-21 times higher near the highway than at 200 m distance, based on different analyses, with lower 95% confidence limits always >13. (Semi-) parametric estimates confirmed this general range of values but suggests slightly higher odds ratios (95% confidence interval: 15.5-25.3). Highway-related effects were observed to

  8. What facilitates adaptation? An analysis of community-based adaptation to environmental change in the Andes

    Directory of Open Access Journals (Sweden)

    Felipe Murtinho

    2016-02-01

    Full Text Available This study analyses the environmental, socio-economic andinstitutional factors that influence community-based adaptation strategies in 16municipalities in the rural Andes of Colombia. The study focuses specifically onthe factors that influence whether communities decide to take measures to managetheir water and micro-watersheds in response to water scarcity caused by climatevariability and land-use changes. The research uses quantitative and qualitativemethods incorporating data from surveys to 104 water user associations,precipitation and land-use data, municipal socio-economic information, and semistructured interviews with key informants. The results reveal 1 the links betweenenvironmental change and the type of adaptation that communities implement,and 2 how, in face of water scarcity changes, external funding facilitatesadaptation. The findings of this study contributes to the common-pool resourceand adaptation literatures by highlighting the important role that external actorsmay have in shaping collective action to adapt to environmental change.

  9. Pablo Palacio: Corporal Violence on Impossible Identities in the Zone of the Andes

    Directory of Open Access Journals (Sweden)

    Falconí Travez, Diego Fernando

    2012-01-01

    Full Text Available Pablo Palacio was an Ecuadorian writer who, in the 1920’s, built within his narrative a catalog of rare bodies with ambiguous and disturbing sexualities, characterizations that are quite different from ones portrayed in the Andean tradition to which Palacio belongs. Nonetheless one of the most issues striking facts of these characters is that their bodies are disciplined by certain discourses of power in a violent way. This paper explores trough literary theory such abuse and violence on women and homosexual identities in two of his stories. The aim of the paper is to investigate issues such as violence, economy of representation, its relationship with the literary text and vulnerability, as a sine qua non norm of abuse, in certain bodies in the area of the Andes.

  10. Controls on continental strain partitioning above an oblique subduction zone, Northern Andes

    Science.gov (United States)

    Schütt, Jorina M.; Whipp, David M., Jr.

    2016-04-01

    Strain partitioning is a common process at obliquely convergent plate margins dividing oblique convergence into margin-normal slip on the plate-bounding fault and horizontal shearing on a strike-slip system parallel to the subduction margin. In subduction zones, strain partitioning in the upper continental plate is mainly controlled by the shear forces acting on the plate interface and the strength of the continental crust. The plate interface forces are influenced by the subducting plate dip angle and the obliquity angle between the normal to the plate margin and the convergence velocity vector, and the crustal strength of the continent is strongly affected by the presence or absence of a volcanic arc, with the presence of the volcanic arcs being common at steep subduction zones. Along the ˜7000 km western margin of South America the convergence obliquity, subduction dip angles and presence of a volcanic arc all vary, but strain partitioning is only observed along parts of it. This raises the questions, to what extent do subduction zone characteristics control strain partitioning in the overriding continental plate, and which factors have the largest influence? We address these questions using lithospheric-scale 3D numerical geodynamic experiments to investigate the influence of subduction dip angle, convergence obliquity, and weaknesses in the crust owing to the volcanic arc on strain partitioning behavior. We base the model design on the Northern Volcanic Zone of the Andes (5° N - 2° S), characterized by steep subduction (˜ 35°), a convergence obliquity between 31° -45° and extensive arc volcanism, and where strain partitioning is observed. The numerical modelling software (DOUAR) solves the Stokes flow and heat transfer equations for a viscous-plastic creeping flow to calculate velocity fields, thermal evolution, rock uplift and strain rates in a 1600 km x 1600 km box with depth 160 km. Subduction geometry and material properties are based on a

  11. Senecio canoi (Compositae, una especie nueva de los Andes de Perú

    Directory of Open Access Journals (Sweden)

    Montesinos-Tubée, Daniel B.

    2015-12-01

    Full Text Available Senecio canoi, a new species of Compositae of the high Andes of Southern Peru, Puno department, is described and illustrated. Senecio canoi is a perennial species differing from others in the ser. Suffruticosi subser. Caespitosi by having tufted habit, oblong-spathulate leaves with toothed margin, glabrous, and white flowers.Se describe e ilustra una nueva especie de Compositae, Senecio canoi, de la región altoandina del sur de Perú, departamento de Puno. Senecio canoi es una especie perenne que se diferencia de otras especies de la ser. Suffruticosi subser. Caespitosi por tener el hábito cespitoso, hojas oblongo-espatuladas, glabras, con margen dentado y flores blancas.

  12. Landsat Thematic Mapper observations of debris avalanche deposits in the Central Andes

    Science.gov (United States)

    Francis, P. W.; Wells, G. L.

    1988-01-01

    Remote sensing with the Landsat Thematic Mapper of debris avalanche deposits in the Central Andes between 18 and 27 deg S revealed, for the first time, the presence of 28 breached volcanic cones and 11 major volcanic debris avalanche deposits, several of which cover areas in excess of 100 sq km. It is concluded that such avalanche deposits are normal products of the evolution of large composite volcanoes, comparable with lava and pyroclastic flow deposits. A statistical survey of 578 composite volcanoes in the same area indicated that a majority of cones which achieve edifice heights between 2000 and 3000 m may undergo sector collapse. The paper describes morphological criteria for identifying breached composite cones and volcanic debris avalanches using orbital images.

  13. Tecnología apropiada: Sus inicios en la Universidad de los Andes

    Directory of Open Access Journals (Sweden)

    Revista de Ingeniería

    2007-05-01

    Full Text Available El origen de la tecnología apropiada en la Universidad de los Andes debe entenderse no sólo a partir de las inquietudes de algunos profesores de la Facultad de Ingeniería, sino que debe leerse en sintonía con una serie de eventos de índole nacional e internacional que permitieron su desarrollo. En los años 70, Estados Unidos sufrió una crisis energética, ante la cual se debió buscar alternativas que pudieran suplir la necesidad de energía y la dificultad de remplazar el petróleo. Se generó, entonces, un movimiento cuyo objetivo era desarrollar energías renovables basadas en recursos naturales.

  14. Mapping advanced argillic alteration zones with ASTER and Hyperion data in the Andes Mountains of Peru

    Science.gov (United States)

    Ramos, Yuddy; Goïta, Kalifa; Péloquin, Stéphane

    2016-04-01

    This study evaluates Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Hyperion hyperspectral sensor datasets to detect advanced argillic minerals. The spectral signatures of some alteration clay minerals, such as dickite and alunite, have similar absorption features; thus separating them using multispectral satellite images is a complex challenge. However, Hyperion with its fine spectral bands has potential for good separability of features. The Spectral Angle Mapper algorithm was used in this study to map three advanced argillic alteration minerals (alunite, kaolinite, and dickite) in a known alteration zone in the Peruvian Andes. The results from ASTER and Hyperion were analyzed, compared, and validated using a Portable Infrared Mineral Analyzer field spectrometer. The alterations corresponding to kaolinite and alunite were detected with both ASTER and Hyperion (80% to 84% accuracy). However, the dickite mineral was identified only with Hyperion (82% accuracy).

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

    CERN Document Server

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

    2010-01-01

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

  16. How well do Important Bird Areas represent species and minimize conservation conflict in the tropical Andes?

    DEFF Research Database (Denmark)

    O´Dea, Niall; Bastos Araujo, Miguel; Whittaker, Robert J.

    2006-01-01

    then compare the performance of the expert-driven Important Bird Areas (IBA) scheme against a hypothetical protected-areas network identified with a systematic reserve selection algorithm seeking to maximize at-risk bird species representation. Our aim is to assess the degree to which: IBAs contain a higher......Where high species richness and high human population density coincide, potential exists for conflict between the imperatives of species conservation and human development. We examine the coincidence of at-risk bird species richness and human population in the countries of the tropical Andes. We...... richness of at-risk species than would be expected by chance, IBAs contain more people than would be expected by chance, and IBAs are congruent with complementary areas that maximize species representation with an equivalent number of sites. While the correlation of richness and population was low...

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

    Science.gov (United States)

    Arriagada, C. A.

    2013-05-01

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

  18. Altitudinal changes in diversity of macroinvertebrates from small streams in the Ecuadorian Andes

    DEFF Research Database (Denmark)

    Jacobsen, Dean

    2003-01-01

    Altitudinal patterns in diversity of macroinvertebrate families at different spatial scales (stone, stream and altitude) were studied by collecting stone samples from six streams at each of the three altitudes: lowlands (400m), midlands (2000m) and highlands (3800 m), in the equatorial Andes...... was dominated by insects, mainly Ephemeroptera, Trichoptera and Diptera at all three altitudes. Odonata and Hemiptera were relatively rich in lowland streams, scarcely present in the midland streams and absent in the highland streams (as was the case for the less diverse orders Lepidoptera and Megaloptera....... In contrast, beta diversity (taxon turnover among streams) increased with altitude. The higher richness in the lowland streams appeared at the smallest spatial scale (stone), and was therefore not due to higher beta diversity among stones within streams. Local richness was nearly linearly related to regional...

  19. Geologic evolution of the Cordillera Darwin orogenic core complex, Southern Andes

    Science.gov (United States)

    Nelson, E. P.

    1981-08-01

    Located in the east-west trending Andes of Tierra del Fuego is a structural culmination exposing deeper crustal levels than in surrounding areas, termed an orogenic core complex because of the localization there of relatively high-grade metamorphism, intense polyphase deformation, and differential uplift. Strongly deformed and regionally metamorphosed pre-Late Jurassic basement rocks mainly of sedimentary origin are unconformably overlain by a cover sequence of Upper Jurassic silicic-intermediate volcanic rocks (Tobifera Formation) and Lower Cretaceous clastic sedimentary rocks (Yahgan Formation). The D1 and D2 phases produced major and minor fold structures, extension and intersection lineations, and axial planar and transposition foliations in complex patterns similar to those in other collision-type orogens. The Darwin and Beagle suites show affinities with S- and I-type granitic suites respectively.

  20. The Major Cellular Sterol Regulatory Pathway Is Required for Andes Virus Infection

    Science.gov (United States)

    Riblett, Amber M.; Didigu, Chukwuka A.; Wilen, Craig B.; Malani, Nirav; Male, Frances; Lee, Fang-Hua; Bushman, Frederic D.; Cherry, Sara; Doms, Robert W.; Bates, Paul; Briley, Kenneth

    2014-01-01

    The Bunyaviridae comprise a large family of RNA viruses with worldwide distribution and includes the pathogenic New World hantavirus, Andes virus (ANDV). Host factors needed for hantavirus entry remain largely enigmatic and therapeutics are unavailable. To identify cellular requirements for ANDV infection, we performed two parallel genetic screens. Analysis of a large library of insertionally mutagenized human haploid cells and a siRNA genomic screen converged on components (SREBP-2, SCAP, S1P and S2P) of the sterol regulatory pathway as critically important for infection by ANDV. The significance of this pathway was confirmed using functionally deficient cells, TALEN-mediated gene disruption, RNA interference and pharmacologic inhibition. Disruption of sterol regulatory complex function impaired ANDV internalization without affecting virus binding. Pharmacologic manipulation of cholesterol levels demonstrated that ANDV entry is sensitive to changes in cellular cholesterol and raises the possibility that clinically approved regulators of sterol synthesis may prove useful for combating ANDV infection. PMID:24516383

  1. The major cellular sterol regulatory pathway is required for Andes virus infection.

    Directory of Open Access Journals (Sweden)

    Josiah Petersen

    2014-02-01

    Full Text Available The Bunyaviridae comprise a large family of RNA viruses with worldwide distribution and includes the pathogenic New World hantavirus, Andes virus (ANDV. Host factors needed for hantavirus entry remain largely enigmatic and therapeutics are unavailable. To identify cellular requirements for ANDV infection, we performed two parallel genetic screens. Analysis of a large library of insertionally mutagenized human haploid cells and a siRNA genomic screen converged on components (SREBP-2, SCAP, S1P and S2P of the sterol regulatory pathway as critically important for infection by ANDV. The significance of this pathway was confirmed using functionally deficient cells, TALEN-mediated gene disruption, RNA interference and pharmacologic inhibition. Disruption of sterol regulatory complex function impaired ANDV internalization without affecting virus binding. Pharmacologic manipulation of cholesterol levels demonstrated that ANDV entry is sensitive to changes in cellular cholesterol and raises the possibility that clinically approved regulators of sterol synthesis may prove useful for combating ANDV infection.

  2. Demonstration of two pulses of Paleogene deformation in the Andes of Peru

    Science.gov (United States)

    Noble, D.C.; Sebrier, M.; Megard, F.; McKee, E.H.

    1985-01-01

    New radiometric ages of about 25 m.y. on volcanic materials in a marine intercalation within clastic continental strata of the Upper Moquegua Formation near Caraveli, southern Peru, together with an age of 25.3 ?? 0.4 m.y obtained by Tosdal et al. from a locality about 300 km to the ESE, show that the formation contains strata of late Oligocene as well as Miocene age, and demonstrate that the coastal region was at a low elevation during latest Oligocene time. Because the unconformities between the Upper Moquegua Formation and the underlying Lower Moquegua Formation, and between the Lower Moquegua Formation and underlying Paleocene rocks cannot both represent the same tectonic event, two discrete Paleogene events must be present in the Andes of Peru. Although the exact timing of these events is uncertain, the unconformities are likely to be of Paleocene and middle Eocene age or possibly of middle Eocene and Oligocene age. ?? 1985.

  3. Privatizing Water in the Chilean Andes: The Case of Las Vegas de Chiu-Chiu

    Directory of Open Access Journals (Sweden)

    Manuel Prieto

    2015-08-01

    Full Text Available The Chilean water model has been described as a textbook example of a free-market water system. This article contributes to the critiques of this model by showing the effect of its implementation in the Atacameño community of Chiu-Chiu, located in the Atacama Desert in the south-central Andes. In this community, the privatization of water rights ignored local water management practices that had produced a high-altitude wetland (known as a vega. This led to the inhabitants’ dispossession of crucial water rights and to wetland degradation. This process belies statements that the Chilean model relies on an unregulated market and instead highlights the state’s role in marginalizing local irrigation practices by reducing the water consumption of the indigenous population while keeping the copper mining industry (the main source of Chilean income and related growing urban populations supplied with water.

  4. Palm harvest impact in the western Amazon, Andes and Pacific lowlands

    DEFF Research Database (Denmark)

    Balslev, Henrik

    2011-01-01

    forest formations and determine the number of species and individuals of all palm species. The genetic structure of useful palm species is studied to determine how much harvesting of the species contributes to genetic erosion of their populations, and whether extraction can be made without harm. We......Palms are the most useful group of plants in tropical American forests and in this project we study the effect of extraction and trade of palms on forests in the western Amazon, Andes, and Pacific lowlands. We determine the size of the resource by making palm community studies in the different...... determine how much palms are used for subsistence purposes by carrying out quantitative, ethnobotanical research in different forest types and we also study trade patterns for palm products from local markets to markets that involve export to other countries and continents. We study different ways in which...

  5. Synchronous fire activity in the tropical high Andes: an indication of regional climate forcing.

    Science.gov (United States)

    Román-Cuesta, R M; Carmona-Moreno, C; Lizcano, G; New, M; Silman, M; Knoke, T; Malhi, Y; Oliveras, I; Asbjornsen, H; Vuille, M

    2014-06-01

    Global climate models suggest enhanced warming of the tropical mid and upper troposphere, with larger temperature rise rates at higher elevations. Changes in fire activity are amongst the most significant ecological consequences of rising temperatures and changing hydrological properties in mountainous ecosystems, and there is a global evidence of increased fire activity with elevation. Whilst fire research has become popular in the tropical lowlands, much less is known of the tropical high Andean region (>2000 masl, from Colombia to Bolivia). This study examines fire trends in the high Andes for three ecosystems, the Puna, the Paramo and the Yungas, for the period 1982-2006. We pose three questions: (i) is there an increased fire response with elevation? (ii) does the El Niño- Southern Oscillation control fire activity in this region? (iii) are the observed fire trends human driven (e.g., human practices and their effects on fuel build-up) or climate driven? We did not find evidence of increased fire activity with elevation but, instead, a quasicyclic and synchronous fire response in Ecuador, Peru and Bolivia, suggesting the influence of high-frequency climate forcing on fire responses on a subcontinental scale, in the high Andes. ENSO variability did not show a significant relation to fire activity for these three countries, partly because ENSO variability did not significantly relate to precipitation extremes, although it strongly did to temperature extremes. Whilst ENSO did not individually lead the observed regional fire trends, our results suggest a climate influence on fire activity, mainly through a sawtooth pattern of precipitation (increased rainfall before fire-peak seasons (t-1) followed by drought spells and unusual low temperatures (t0), which is particularly common where fire is carried by low fuel loads (e.g., grasslands and fine fuel). This climatic sawtooth appeared as the main driver of fire trends, above local human influences and fuel build

  6. Disappearance of the glacier on Mama Cotacachi: ethnoecological research and climate change in the Ecuadorian Andes

    Directory of Open Access Journals (Sweden)

    Rhoades, R.

    2008-12-01

    Full Text Available A first documented case study of a disappearing glacier in the snow capped volcano Cotacahi in Ecuador is presented with the studies belonging to the social sciences in relation to climate change and its impact on the population of the Equatorial Andes. With the use of multiple source methodology, including ethnographic analyzes, visual representations, repetitive photography, critical mapping by the local communities, longitudinal surveys, even archival research, as well as interviews to social actors and utilization of spatial data in a geographical information system (GIS. It is concluded that the documented disappearance of the glacier on the Cotacahi serves as an urgent call for action to the important dearth of social research related to global change from the ethnoecological perspective, with a cultural, local approach.

    Se presenta el primer estudio documentado de la desaparición del glaciar del nevado Cotacachi en el Ecuador, con los estudios que corresponden a las ciencias sociales en relación con el cambio climático y su impacto en la población de los Andes ecuatoriales. Mediante el uso de una metodología que incluye análisis etnográficos, representaciones visuales, fotografía repetitiva, mapeo crítico por parte de las comunidades locales, encuestas longitudinales e incluso investigación de archivos, así como también entrevistas a actores sociales, y utilización de los datos espaciales en un sistema de información geográfica (SIG. Se concluye que la desaparición documentada del glaciar del Cotacachi sirve como una llamada de atención urgente a la importante falta de investigaciones sociales relacionadas con el cambio global desde el punto de vista etnoecológico, con un enfoque cultural local.

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

    Science.gov (United States)

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

    2015-08-01

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

  8. Reconstruction of Late Cretaceous Magmatic Arcs in the Northern Andes: Single Versus Multiple Arc Systems

    Science.gov (United States)

    Cardona, A.; Jaramillo, J. S.; Leon, S.; Hincapie, S.; Mejia, D.; Patino, A. M.; Vanegas, J.; Zapata, S.; Valencia, V.; Jimenez, G.; Monsalve, G.

    2014-12-01

    Although magmatic rocks are major tracers of the geological evolution of convergent margins, pre-collisional events such as subduction erosion, collisional thrusting or late collisional strike slip segmentation may difficult the recognizing of multiple arc systems and therefore the existence of paleogeographic scenarios with multiple subduction systems. New field, U-Pb geochronology and whole rock geochemistry constraints from the northwestern segment of the Central Cordillera in the states of Antioquia and Caldas (Colombia) are used to understand the nature of the Late Cretaceous arc magmatism and evaluate the existence of single or multiple Pacific and Caribbean arc systems in the growth of the Northwestern Andes. The new results integrated with additional field and published information is used to suggest the existence of at least three different magmatic arcs. (1) An Eastern Continental arc built within a well defined Permian to Triassic continental crust that record a protracted 90-70 Ma magmatic evolution, (2) a 90-80 arc formed within attenuated continental crust and associated oceanic crust, (3) 90-88 Ma arc formed over a Late Cretaceous plateau crust. The eastern arcs were formed as part of double eastern vergent subduction system, where the most outboard arc represent a fringing arc formed over detached fragments of continental crust, whereas the easternmost continental arc growth by the closure an subduction of and older and broad Triassic to Early Jurassic back-arc ocean. Its closure also end up in ophiolite emplacement. The third allochtonous oceanic arc was formed over the Caribbean plateau crust and was accreted to the continental margin in the Late Cretaceous. Ongoing paleomagnetic, deformational, gravimetric and basin analysis will be integrate to test this model and understand the complex Late Cretaceous tectonic evolution of the Northern Andes.

  9. High-resolution satellite-gauge merged precipitation climatologies of the Tropical Andes

    Science.gov (United States)

    Manz, Bastian; Buytaert, Wouter; Zulkafli, Zed; Lavado, Waldo; Willems, Bram; Robles, Luis Alberto; Rodríguez-Sánchez, Juan-Pablo

    2016-02-01

    Satellite precipitation products are becoming increasingly useful to complement rain gauge networks in regions where these are too sparse to capture spatial precipitation patterns, such as in the Tropical Andes. The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (TPR) was active for 17 years (1998-2014) and has generated one of the longest single-sensor, high-resolution, and high-accuracy rainfall records. In this study, high-resolution (5 km) gridded mean monthly climatological precipitation is derived from the raw orbital TPR data (TRMM 2A25) and merged with 723 rain gauges using multiple satellite-gauge (S-G) merging approaches. The resulting precipitation products are evaluated by cross validation and catchment water balances (runoff ratios) for 50 catchments across the Tropical Andes. Results show that the TPR captures major synoptic and seasonal precipitation patterns and also accurately defines orographic gradients but underestimates absolute monthly rainfall rates. The S-G merged products presented in this study constitute an improved source of climatological rainfall data, outperforming the gridded TPR product as well as a rain gauge-only product based on ordinary Kriging. Among the S-G merging methods, performance of inverse distance interpolation of satellite-gauge residuals was similar to that of geostatistical methods, which were more sensitive to gauge network density. High uncertainty and low performance of the merged precipitation products predominantly affected regions with low and intermittent precipitation regimes (e.g., Peruvian Pacific coast) and is likely linked to the low TPR sampling frequency. All S-G merged products presented in this study are available in the public domain.

  10. Reasons for an outstanding plant diversity in the tropical Andes of Southern Ecuador

    Directory of Open Access Journals (Sweden)

    Michael Richter

    2009-06-01

    Full Text Available Long-term field studies in the scope of a multidisciplinary project in southern Ecuador revealed extraordinary high species numbers of many organismic groups. This article discusses reasons for the outstanding vascular plant diversity using a hierarchical scale-oriented top-down approach (Grüninger 2005, from the global scale to the local microscale. The global scale explains general (paleo- ecological factors valid for most parts of the humid tropics, addressing various hypotheses and theories, such as the “greater effective evolutionary time”, constant input of “accidentals”, the “seasonal variability hypothesis”, the “intermediate disturbance hypothesis”, and the impact of soil fertility. The macroscale focuses on the Andes in northwestern South America. The tropical Andes are characterised by many taxa of restricted range which is particularly true for the Amotape-Huancabamba region, i.e. the so called Andean Depression, which is effective as discrete phytogeographic transition as well as barrier zone. Interdigitation of northern and southern flora elements, habitat fragmentation, geological and landscape history, and a high speciation rate due to rapid genetic radiation of some taxa contribute to a high degree of diversification. The mesoscale deals with the special environmental features of the eastern mountain range, the Cordillera Real and surrounding areas in southern Ecuador. Various climatic characteristics, the orographic heterogeneity, the geologic and edaphic conditions as well as human impact are the most prominent factors augmenting plant species diversity. On microscale, prevailing regimes of disturbance and environmental stresses, the orographic basement, as well as the general role on the various mountain chains are considered. Here, micro-habitats e.g. niches for epiphytes, effects of micro-relief patterns, and successions after small-sized disturbance events are screened. Direct effects of human impact are

  11. A statistical study of Weinmannia pollen trajectories across the Andes

    Directory of Open Access Journals (Sweden)

    C. F. Pérez

    2009-10-01

    Full Text Available Recent airborne pollen records data from Northern Patagonia (San Carlos de Bariloche, Argentina, Lat. 41.1435° S, Long. 71.375° W, 800 m elevation suggest that pollen transport takes place from the west to the east slope of the Andes. However, the atmospheric characteristics responsible of this transport have not yet been studied. The aim of this paper is to assess potential source areas and to describe the involved atmospheric mechanisms of the trans-Andean pollen transport. Methodology relies on the analysis of backward trajectories of air masses calculated with the HYSPLIT 4.9 regional model for particular days where airborne pollen of Weinmannia trichosperma Cav. was detected east of the Andes. This pollen type was selected because it is found regularly at localities in eastern Patagonia beyond its present-day distribution. Weinmannia's substantial presence during early Holocene times would also benefit from better knowledge of its transport mechanisms. Correspondence between atmospheric trajectories and the position of sources was checked using GIS maps. Mode T, Principal Component Analysis (PCA with Varimax rotation was used to identify the main spatial structure of geopotential height anomalies producing the calculated trajectories. Eighty-eight cases showed that the calculated directions of trajectories trended from the Northwest to Southwest passing over the Chilean region of W. trichosperma distribution. PCs results showed two patterns of negative anomalies over southern Patagonia. The prevailing circulation pattern which drives airborne transport is the presence of a trough located south of 37 to 40° S with its axis over western Patagonia. The synoptic situations for two cases highly correlated with principal component scores were described.

  12. Gene expression in the Andes; relevance to neurology at sea level.

    Science.gov (United States)

    Appenzeller, Otto; Minko, Tamara; Pozharov, Vitaly; Bonfichi, Maurizio; Malcovati, Luca; Gamboa, Jorge; Bernardi, Luciano

    2003-03-15

    Chronic mountain sickness (CMS), a maladaptation syndrome to chronic hypoxia, occurs in the Andes. Gene expression differences in Andeans could explain adaptation and maladaptation to hypoxia, both of which are relevant to neurology at sea level. Expression of genes responsive to cellular oxygen concentration, hypoxia-inducible factor-1alpha (HIF-1alpha), three splicing variants of vascular endothelial growth factor (VEGF) and von Hippel-Lindau protein (pVHL) was measured by reverse transcription polymerase chain reaction (RT-PCR) in 12 Cerro de Pasco (CP) (altitude 4338 m) natives and 15 CMS patients in CP. Thirteen high altitude natives living in Lima and five Lima natives were sea level controls. A CMS score (CMS-sc) was assigned clinically. Expression was related to the clinical assessment. High expression of HIF-1alpha and VEGF-121 was found in CMS (P<0.001). Samples from CP had higher expression than those from Lima (P<0.001). Expression of HIF-1alpha and VEGF-121 was related to age (P<0.001); adjusting for age did not abolish the group effect. Higher CMS-sc was related to expression independent of age (P<0.001). VEGF-165 and -189 were expressed only in CMS. Birth altitude had no effect on gene expression. pVHL was not quantifiable.HIF-1alpha and VEGF-121 participate in adaptation to hypoxia. The high levels may explain blood vessel proliferation in Andeans and hold lessons for patients at sea level. VEGF-165 expression suggests that it contributes to preservation of neuronal function in human chronic hypoxia. VHL mutations may mark those destined to develop neural crest tumors which are common in the Andes.

  13. Drivers of atmospheric methane uptake by montane forest soils in the southern Peruvian Andes

    Science.gov (United States)

    Jones, Sam P.; Diem, Torsten; Huaraca Quispe, Lidia P.; Cahuana, Adan J.; Reay, Dave S.; Meir, Patrick; Arn Teh, Yit

    2016-07-01

    The soils of tropical montane forests can act as sources or sinks of atmospheric methane (CH4). Understanding this activity is important in regional atmospheric CH4 budgets given that these ecosystems account for substantial portions of the landscape in mountainous areas like the Andes. We investigated the drivers of net CH4 fluxes from premontane, lower and upper montane forests, experiencing a seasonal climate, in south-eastern Peru. Between February 2011 and June 2013, these soils all functioned as net sinks for atmospheric CH4. Mean (standard error) net CH4 fluxes for the dry and wet season were -1.6 (0.1) and -1.1 (0.1) mg CH4-C m-2 d-1 in the upper montane forest, -1.1 (0.1) and -1.0 (0.1) mg CH4-C m-2 d-1 in the lower montane forest, and -0.2 (0.1) and -0.1 (0.1) mg CH4-C m-2 d-1 in the premontane forest. Seasonality in CH4 exchange varied among forest types with increased dry season CH4 uptake only apparent in the upper montane forest. Variation across these forests was best explained by available nitrate and water-filled pore space indicating that nitrate inhibition of oxidation or diffusional constraints imposed by changes in water-filled pore space on methanotrophic communities may represent important controls on soil-atmosphere CH4 exchange. Net CH4 flux was inversely related to elevation; a pattern that differs to that observed in Ecuador, the only other extant study site of soil-atmosphere CH4 exchange in the tropical Andes. This may result from differences in rainfall patterns between the regions, suggesting that attention should be paid to the role of rainfall and soil moisture dynamics in modulating CH4 uptake by the organic-rich soils typical of high-elevation tropical forests.

  14. Proliferation of Hydroelectric Dams in the Andean Amazon and Implications for Andes-Amazon Connectivity

    Science.gov (United States)

    Finer, Matt; Jenkins, Clinton N.

    2012-01-01

    Due to rising energy demands and abundant untapped potential, hydropower projects are rapidly increasing in the Neotropics. This is especially true in the wet and rugged Andean Amazon, where regional governments are prioritizing new hydroelectric dams as the centerpiece of long-term energy plans. However, the current planning for hydropower lacks adequate regional and basin-scale assessment of potential ecological impacts. This lack of strategic planning is particularly problematic given the intimate link between the Andes and Amazonian flood plain, together one of the most species rich zones on Earth. We examined the potential ecological impacts, in terms of river connectivity and forest loss, of the planned proliferation of hydroelectric dams across all Andean tributaries of the Amazon River. Considering data on the full portfolios of existing and planned dams, along with data on roads and transmission line systems, we developed a new conceptual framework to estimate the relative impacts of all planned dams. There are plans for 151 new dams greater than 2 MW over the next 20 years, more than a 300% increase. These dams would include five of the six major Andean tributaries of the Amazon. Our ecological impact analysis classified 47% of the potential new dams as high impact and just 19% as low impact. Sixty percent of the dams would cause the first major break in connectivity between protected Andean headwaters and the lowland Amazon. More than 80% would drive deforestation due to new roads, transmission lines, or inundation. We conclude with a discussion of three major policy implications of these findings. 1) There is a critical need for further strategic regional and basin scale evaluation of dams. 2) There is an urgent need for a strategic plan to maintain Andes-Amazon connectivity. 3) Reconsideration of hydropower as a low-impact energy source in the Neotropics. PMID:22529979

  15. Proliferation of hydroelectric dams in the Andean Amazon and implications for Andes-Amazon connectivity.

    Directory of Open Access Journals (Sweden)

    Matt Finer

    Full Text Available Due to rising energy demands and abundant untapped potential, hydropower projects are rapidly increasing in the Neotropics. This is especially true in the wet and rugged Andean Amazon, where regional governments are prioritizing new hydroelectric dams as the centerpiece of long-term energy plans. However, the current planning for hydropower lacks adequate regional and basin-scale assessment of potential ecological impacts. This lack of strategic planning is particularly problematic given the intimate link between the Andes and Amazonian flood plain, together one of the most species rich zones on Earth. We examined the potential ecological impacts, in terms of river connectivity and forest loss, of the planned proliferation of hydroelectric dams across all Andean tributaries of the Amazon River. Considering data on the full portfolios of existing and planned dams, along with data on roads and transmission line systems, we developed a new conceptual framework to estimate the relative impacts of all planned dams. There are plans for 151 new dams greater than 2 MW over the next 20 years, more than a 300% increase. These dams would include five of the six major Andean tributaries of the Amazon. Our ecological impact analysis classified 47% of the potential new dams as high impact and just 19% as low impact. Sixty percent of the dams would cause the first major break in connectivity between protected Andean headwaters and the lowland Amazon. More than 80% would drive deforestation due to new roads, transmission lines, or inundation. We conclude with a discussion of three major policy implications of these findings. 1 There is a critical need for further strategic regional and basin scale evaluation of dams. 2 There is an urgent need for a strategic plan to maintain Andes-Amazon connectivity. 3 Reconsideration of hydropower as a low-impact energy source in the Neotropics.

  16. On the Nature of Severe Orographic Thunderstorms near the Andes in Subtropical South America

    Science.gov (United States)

    Rasmussen, Kristen Lani Emi

    Identifying common features and differences between the mechanisms producing extreme convection near major mountain ranges of the world is an essential step toward a general understanding of orographic precipitation on a global scale. The overarching objective of this dissertation is to understand and examine orographic convective processes in general, while specifically focusing on systems in the lee of the Andes Mountains. Diagnosing the key ingredients necessary for generating high impact weather near extreme topography is crucial to our understanding of orographic precipitating systems. An investigation of the most intense storms in 11 years of TRMM Precipitation Radar (PR) data has shown a tendency for squall lines to initiate and develop east of the Andes with a mesoscale organization similar to storms in the U.S. Great Plains (Rasmussen and Houze 2011). In subtropical South America, however, the topographical influence on the convective initiation and maintenance of the mesoscale convective systems (MCSs) is unique. The Andes and other mountainous terrain of Argentina focus deep convective initiation in the foothills of western Argentina (Romatschke and Houze 2010; Rasmussen and Houze 2011). Subsequent to initiation, the convection often evolves into propagating MCSs similar to those seen over the U.S. Great Plains sometimes producing damaging tornadoes, hail and floods across a wide agricultural region (Rasmussen and Houze 2011; Rasmussen et al. 2014b). The TRMM satellite was designed to determine the spatial and temporal variation of tropical and subtropical rainfall amounts and storm structures around the globe with the goal of understanding the factors controlling the precipitation. However, the TRMM PR algorithm significantly underestimates surface rainfall in deep convection over land (Nesbitt et al. 2004; Iguchi et al. 2009; Kozu et al. 2009). When the algorithm rates are compared to a range of conventional Z-R relations, the rain bias tends to be

  17. Ethnoecology of the tropical Andes avian indicators of landscape change in highland Ecuador.

    Directory of Open Access Journals (Sweden)

    Sarmiento, F. O.

    2005-12-01

    Full Text Available Four Andean birds offer clues to rethink the ethnoecology of neotropical cloud forests, challenging the notion of conservation based only in water resources and biodiversity. Using both archaeological and actuoecological evidence, the role of humans in shaping high Andean landscapes' location and maintenance is argued as an important factor for conservation priorities of tropical montane cloud forests, particularly in the equatorial mountains. Avian examples demonstrate intricate linkages of culture and nature in the tropical Andes. Traditional knowledge associated to ornithological clues, helps understanding the dynamics of cultural landscapes, with birds as proxy of synergisms affecting the complexities of both, nature and culture. A paradox of conservation is highlighted with avian indicators. The four selected species were cases where landscape change and biodiversity help in determining ethnoecological insights. Unlike the preservation of absolute nature reserves, landscape stewardship, conservation easements and cultural la^tdscapes are listed as options for inclusion in the repertoire of conservation scenarios for cloud forests survival, which includes sacred places and spiritual domains as intangibles worth protecting in the Tropical Andes.

    [fr] Quatre oiseaux andins nous donnent des raisons pour repenser Vethnoécologie des forêts néotropicales humides, ce qui met en question l'idée de la conservation basée sur les ressources d'eau et la biodiversité seules. En se servant des évidences archéologiques et écologiques actuelles, on soutient que les êtres humains ont un rôle dans la formation des hauts paysages andins. On soutient aussi que l'entretien est un facteur important dans la conservation des forêts tropicales humides en montagne, surtout dans les montagnes équatoriales. Les exemples aviaires démontrent les liens compliqués entre la culture et la nature dans les Andes tropicales. Les connaissances

  18. Evapofacieshalítica en el Salar del Rincón, departamento Los Andes, Salta Halitefacies in the salar del Rincon, Andes Department, Salta

    Directory of Open Access Journals (Sweden)

    Alberto Ovejero Toledo

    2009-06-01

    Full Text Available El salar delRincón se encuentra ubicado en el departamento Los Andes, provincia de Salta enel extremo noroeste de la Puna Austral, a una altura media de 3.660 m s.n.m. Eneste trabajo se dan a conocer los resultados de la correlación de sondeos, quepermitieron determinar facies de halita, texturas, estructuras, materialesclásticos intersticiales, mineralogía, composición química de la salmuera y losparámetros hidráulicos del acuífero, determinados a lo largo de una transectaeste-oeste que cubre aproximadamente 30 km². La fase cristalina estácompuesta mayoritariamente de halita, con yeso, mirabilita, thenardita,glauberita, hidroglauberita, eugsterita, calcita y ulexita solo en el sectoroeste de la transecta. Se identificaron las siguientes evapofacies halítica:costra salina, geodas y halita bandeada. Las texturas observadas incluyen:cristales hoppers, pirámides chevron, halita intersticial muddyhalite y halita cloudy. La composición de la salmuera es denaturaleza clorurada sódica con variaciones en profundidad de sulfato y borato.Los cationes son Ca, Mg, Li y K, la relación K/Li es de 20/1. El cálculo dereserva a nivel de recurso mineral, en sectores con distinta porosidad eficaz,dio para Li+ 208,2 kt y para K+ 4231,9 kt (> 30 %; yLi+ 14,9 kt y K+ 302, 9 kt (Salar del Rincón is located at 3,660 m.a.s.l. in the Andes district, Salta province, andnortheast of the Southern Puna. This paper shows the results of theborehole correlation that helped determine the halite facies, textures,structures, interstitial clastic material, mineralogy, chemical composition ofthe brine and the aquifer hydraulic parameters determineted in an E-W transectthat covers approximately 30 km². The crystalline phase is mainlymade up of halite with gypsum, mirabilite, thenardite, glauberite,hydroglauberite, eugsterite, calcite, and ulexite only in the western area oftransect. The following halite evapofacies were identified: saline crust,geodes and banded

  19. Migraciones en la puna: su relación con el uso de los recursos naturales del departamento Los Andes Migraciones en la puna: su relación con el uso de los recursos naturales del departamento Los Andes

    OpenAIRE

    Barbarán, Francisco R.; Humberto Arias

    2009-01-01

    From an historic and demographic perspective, as well as the use of natural resources, we analyzed the relationship between human migrations and the economic activities of Los Andes Department, West of the Salta Province, in NW Argentina. Using the residual method, we calculated migratory balances between Argentinean population censuses carried out in 1947,1960, 1970, 1980 and 2001. The migratory balances were negative for all the periods studied. When the train started to run through Ramal C...

  20. 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

    OpenAIRE

    JOHN H. CAROTHERS; Jaksic, Fabián M

    2001-01-01

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

  1. Nuclear Data for Safe Operation and Waste Transmutation: ANDES (Accurate Nuclear Data for nuclear Energy Sustainability); Datos nucleares para la operacion segura y la transmutacion de residuos: Andes (Datos Nucleares Precisos para la Sostenibilidad de la Energia Nuclear)

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, E. M.

    2014-07-01

    Nuclear research within the 7th Framework Program (FP7 and FP7+2) of EURATOM has devoted a significant fraction of its efforts to the development of advanced nuclear fuel cycles and reactor concepts, mainly fast reactors, aiming to improve the long term sustainability by reduction of the final wastes, optimal use of natural resources and improvement of safety in the present and future nuclear installations. The new design need more accurate basic nuclear data for isotopes, like minor actinides, potentially playing an important role in the operation, fuel concept, safety or final wastes of those reactors and fuel cycles. Four projects, ANDES, ERINDA, EUFRAT and CHANDA, supported by EURATOM within the FP7 and FP7+2, have put together most of the European Nuclear Data community to respond efficiently and in a coordinated way to those needs. This paper summarizes the objectives, and main achievements of ANDES, the project responsible for most of the measurements and technical achievements that was coordinated by CIEMAT. Indeed, CIEMAT has coordinated the nuclear data R and D projects within EURATOM during the last 7 years (NUDATRA domain of EUROTRANS, and ANDES) and will continue this coordination in the CHANDA project till 2017. (Author)

  2. Identificación, caracterización y dinámica de las geoformas glaciales y periglaciales en la Cordillera de los Andes a través de sensores remotos

    OpenAIRE

    Falaschi, Daniel

    2015-01-01

    El presente trabajo de Tesis Doctoral tuvo el objetivo de estudiar los glaciares y glaciares de escombros en tres regiones montañosas a lo largo de la Cordillera de los Andes Argentina: Monte San Lorenzo (Provincia de Santa Cruz), Volcán Domuyo (Provincia de Neuquén), y Nevados de Cachi (Provincia de Salta). Cada uno de estos sitios presenta características climáticas propias, representativas de tres porciones particulares de los Andes: Andes Patagónicos Meridionales, Andes Centrales Meridion...

  3. A Stepwise, Participatory Approach to Design and Implement Community Based Adaptation to Drought in the Peruvian Andes

    OpenAIRE

    Ralph Lasage; Sanne Muis; Carolina S. E. Sardella; Michiel A. van Drunen; Peter H. Verburg; Aerts, Jeroen C.J.H.

    2015-01-01

    The livelihoods of people in the Andes are expected to be affected by climate change due to their dependence on glacier water. The observed decrease in glacier volume over the last few decades is likely to accelerate during the current century, which will affect water availability in the region. This paper presents an approach for participatory development of community-based adaptation measures to cope with the projected impacts of climate change. It combines in an innovative manner participa...

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

    OpenAIRE

    Zapata Henao, Sebastian

    2015-01-01

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

  5. Quantitative Temperature Reconstructions from Holocene and Late Glacial Lake Sediments in the Tropical Andes using Chironomidae (non-biting midges)

    Science.gov (United States)

    Matthews-Bird, F.; Gosling, W. D.; Brooks, S. J.; Montoya, E.; Coe, A. L.

    2014-12-01

    Chironomidae (non-biting midges) is a family of two-winged aquatic insects of the order Diptera. They are globally distributed and one of the most diverse families within aquatic ecosystems. The insects are stenotopic, and the rapid turnover of species and their ability to colonise quickly favourable habitats means chironomids are extremely sensitive to environmental change, notably temperature. Through the development of quantitative temperature inference models chironomids have become important palaeoecological tools. Proxies capable of generating independent estimates of past climate are crucial to disentangling climate signals and ecosystem response in the palaeoecological record. This project has developed the first modern environmental calibration data set in order to use chironomids from the Tropical Andes as quantitative climate proxies. Using surface sediments from c. 60 lakes from Bolivia, Peru and Ecuador we have developed an inference model capable of reconstructing temperatures, with a prediction error of 1-2°C, from fossil assemblages. Here we present the first Lateglacial and Holocene chironomid-inferred temperature reconstructions from two sites in the tropical Andes. The first record, from a high elevation (4153 m asl) lake in the Bolivian Andes, shows persistently cool temperatures for the past 15 kyr, punctuated by warm episodes in the early Holocene (9-10 kyr BP). The chironomid-inferred Holocene temperature trends from a lake sediment record on the eastern Andean flank of Ecuador (1248 m asl) spanning the last 5 millennia are synchronous with temperature changes in the NGRIP ice core record. The temperature estimates suggest along the eastern flank of the Andes, at lower latitudes (~1°S), climate closely resemble the well-established fluctuations of the Northern Hemisphere for this time period. Late-glacial climate fluctuations across South America are still disputed with some palaeoecological records suggesting evidence for Younger Dryas

  6. Assessment of soil fertility change and sustainability of agroecological management in different land use systems of the southern Ecuadorian Andes

    OpenAIRE

    Bahr, Etienne

    2015-01-01

    The thesis was conducted to investigate soil fertility changes and assess the sustainability of agroecological management in different land-use systems of the southern Ecuadorian Andes using quantitative and qualitative methods. Ecuador still holds the highest deforestation rate of all Latin American countries which also has a large impact in the research area by forest conversion into agricultural land. Agricultural land-use systems in the research area are multifaceted due to heterogeneous ...

  7. Direction and timing of uplift propagation in the Peruvian Andes deduced from molecular phylogenetics of highland biotaxa

    OpenAIRE

    Picard, D; Sempéré, Thierry; Plantard, O.

    2008-01-01

    Physical paleoaltimetric methods are increasingly used to estimate the amount and timing of surface uplift in orogens. Because the rise of mountains creates new ecosystems and triggers evolutionary changes biological data may also be used to assess the development and timing of regional surface uplift. Here we apply this idea to the Peruvian Andes through a molecular phylogeographic and phylochronologic analysis of Globodera pallida. a potato parasite nematode that requires cool temperatures ...

  8. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils

    OpenAIRE

    Olivero, Eduardo B.; Francisco A. Medina; María I. López C.

    2009-01-01

    The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul), Maorites sp., and Pachydiscus (Neodesmoceras) sp....

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

    OpenAIRE

    ARRIAGADA, César; Cobbold, Peter,; Roperch, Pierrick

    2006-01-01

    19 p.; International audience; The Salar de Atacama basin lies in the inner fore arc of northern Chile. Topographically and structurally, it is a first-order feature of the central Andes. The sedimentary fill of the basin constrains the timing and extent of crustal deformation since the mid-Cretaceous. We have studied good exposures along the western edge of the basin and have correlated them with seismic reflection sections and data from an exploration well. Throughout most of its history, t...

  10. Age of Terrestrial Biomarkers in Fluvial Transit Across the Andes-Amazon Reveal Timescales of Carbon Storage and Turnover

    Science.gov (United States)

    Ponton, C.; Feakins, S. J.; West, A. J.; Galy, V.

    2014-12-01

    Environmental signatures carried by fluvially-exported terrestrial organic matter are shaped by storage, remineralization and replacement at various spatial and temporal scales. Uncertainties in the timescales of these processes are key caveats in the accurate interpretation of sedimentary records. As part of a multi-isotope leaf wax biomarker project, we report the age of biomarkers transported by rivers from mountain to floodplain across the Andes-Amazon transition in southern Peru. We tracked the age of organic carbon using the radiocarbon (14ΔC) composition of plant leaf waxes extracted from particulate organic carbon (POC) in river suspended sediments. Leaf waxes from POC are younger in mountain headwaters (1000 yrs). Downstream aging is associated with the greater storage potential and residence times in lowland mineral soils and sedimentary sequences that include Pleistocene age eroding river terraces. Given three key observations that 1) carbon loading in suspended sediment does not substantively change from Andes to Amazon, 2) ~80% of sediment is sourced in the Andes, and 3) age increases downstream (this study); we find proof of the decoupling of organic carbon from sediment, which we attribute to loss of Andean carbon and replacement during transport.

  11. Mycorrhizal and Dark-Septate Fungi in Plant Roots above 4270 Meters Elevation in the Andes and Rocky Mountains

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Steven K. [University of Colorado; Sobieniak-Wiseman, L. Cheyanne [University of Colorado; Kageyama, Stacy A. [Oregon State University; Halloy, Stephen [Instituto de Ecologia, Universidad Mayor de San Andres, La Paz, Bolivia; Schadt, Christopher Warren [ORNL

    2008-01-01

    Arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) fungi were quantified in plant roots from high-elevation sites in the Cordillera Vilcanota of the Andes (Per ) and the Front Range of the Colorado Rocky Mountains (U.S.A.). At the highest sites in the Andes (5391 m) AM fungi were absent in the two species of plants sampled (both Compositae) but roots of both were heavily colonized by DSE fungi. At slightly lower elevations (5240 5250 m) AM fungi were present in roots while DSE fungi were rare in plants outside of the composite family. At the highest sites sampled in Colorado (4300 m) AM fungi were present, but at very low levels and all plants sampled contained DSE fungi. Hyphae of coarse AM fungi decreased significantly in plant roots at higher altitude in Colorado, but no other structures showed significant decreases with altitude. These new findings indicate that the altitudinal distribution of mycorrhizal fungi observed for European mountains do not necessarily apply to higher and drier mountains that cover much of the Earth (e.g. the Himalaya, Hindu Kush, Andes, and Rockies) where plant growth is more limited by nutrients and water than in European mountains. This paper describes the highest altitudinal records for both AM and DSE fungi, surpassing previous reported altitudinal maxima by about 1500 meters.

  12. ISOSTATICALLY DISTURBED TERRAIN OF NORTHWESTERN ANDES MOUNTAINS FROM SPECTRALLY CORRELATED FREE-AIR AND GRAVITY TERRAIN DATA

    Directory of Open Access Journals (Sweden)

    Hernández P Orlando

    2006-12-01

    Full Text Available Recently revised models on global tectonics describe the convergence of the North Andes, Nazca, Caribbean and South American Plates and their seismicity, volcanism, active faulting and extreme
    topography. The current plate boundaries of the area are mainly interpreted from volcanic and seismic datasets with variable confidence levels. New insights on the isostatic state and plate boundaries of
    the northwestern Andes Mountains can be obtained from the spectral analysis of recently available gravity and topography data.
    Isostatically disturbed terrain produces free-air anomalies that are highly correlated with the gravity effects of the terrain. The terrain gravity effects (TGE and free air gravity anomalies (FAGA of the
    Andes mountains spectral correlation data confirms that these mountains are isostatically disturbed. Strong negative terrain-correlated FAGA along western South America and the Greater and Lesser Antilles are consistent with anomalously deepened mantle displaced by subducting oceanic plates.

    Inversion of the compensated terrain gravity effects (CTGE reveals plate subduction systems with alternating shallower and steeper subduction angles. The gravity modeling highlights crustal
    deformation from plate collision and subduction and other constraints on the tectonism of the plate boundary zones for the region.

  13. TRMM- and GPM-based precipitation analysis and modelling in the Tropical Andes

    Science.gov (United States)

    Manz, Bastian; Buytaert, Wouter; Zulkafli, Zed; Onof, Christian

    2016-04-01

    Despite wide-spread applications of satellite-based precipitation products (SPPs) throughout the TRMM-era, the scarcity of ground-based in-situ data (high density gauge networks, rainfall radar) in many hydro-meteorologically important regions, such as tropical mountain environments, has limited our ability to evaluate both SPPs and individual satellite-based sensors as well as accurately model or merge rainfall at high spatial resolutions, particularly with respect to extremes. This has restricted both the understanding of sensor behaviour and performance controls in such regions as well as the accuracy of precipitation estimates and respective hydrological applications ranging from water resources management to early warning systems. Here we report on our recent research into precipitation analysis and modelling using various TRMM and GPM products (2A25, 3B42 and IMERG) in the tropical Andes. In an initial study, 78 high-frequency (10-min) recording gauges in Colombia and Ecuador are used to generate a ground-based validation dataset for evaluation of instantaneous TRMM Precipitation Radar (TPR) overpasses from the 2A25 product. Detection ability, precipitation time-series, empirical distributions and statistical moments are evaluated with respect to regional climatological differences, seasonal behaviour, rainfall types and detection thresholds. Results confirmed previous findings from extra-tropical regions of over-estimation of low rainfall intensities and under-estimation of the highest 10% of rainfall intensities by the TPR. However, in spite of evident regionalised performance differences as a function of local climatological regimes, the TPR provides an accurate estimate of climatological annual and seasonal rainfall means. On this basis, high-resolution (5 km) climatological maps are derived for the entire tropical Andes. The second objective of this work is to improve the local precipitation estimation accuracy and representation of spatial patterns of

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

    Science.gov (United States)

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

    2013-04-01

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

  15. The Basement of the Andes: the Gondwana-Laurentia Connections Revisited

    Science.gov (United States)

    Ramos, V. A.

    2009-05-01

    The research performed in the last decade in the basement of the Andes have shown that the Precambrian and Paleozoic rocks have recorded a series of igneous and metamorphic events through time. These episodes can be grouped in discrete orogenic events, which have different paleogeographic distribution and intensity. The first and most important orogenic event is widely distributed along the margin and correspond to the Sunsas-Grenville orogen. Evidence of metamorphism and associated magmatic rocks are found from Colombia to the southernmost Patagonia. This episode produced the amalgamation of Amazonia, Pampia and Patagonia, among other cratonic blocks, to form Rodinia. The Rodinia break-up leaved several cratonic blocks accreted in the Gondwana side, such as Marañón, Arequipa, and Antofalla, although the generalized extension of this period produced crustal attenuation, rifted basins, and limited oceanic realms during late Proterozoic times. The Brasiliano-Pampean orogeny reamalgamated these blocks against the Gondwana margin. A new episode of break-up produced the dispersal of several Gondwanian blocks, separation along some previous sutures, crustal attenuation and magmatism in Late Cambrian times, until the new amalgamation occurred in Middle Late Ordovician times. These processes led to the Famatinian orogeny when metamorphism and arc magmatism was widely spread along the continental margin, as seen in Chibcha, Marañón, Arequipa and Sierras Pampeanas. Besides the re-accretion of some parautochthonous terranes, new exotic blocks were derived from Laurentia, such as the Cuyania terrane, which finally collided against the Andean proto-margin at ~ 460 Ma to form the Argentine Precordillera and surrounding regions. Late accretion in Early to Middle Devonian times of Chilenia and related terranes formed most of the basement of Central Andes. Final collision between Laurentia and Gondwana in the Late Carboniferous - Early Permian times to form the Alleghanides

  16. Lateglacial temperature reconstruction in the Eastern Tropical Andes (Bolivia) inferred from paleoglaciers and paleolakes

    Science.gov (United States)

    Martin, L.; Blard, P. H.; Lave, J.; Prémaillon, M.; Jomelli, V.; Brunstein, D.; Lupker, M.; Charreau, J.; Mariotti, V.; Condom, T.; Bourles, D. L.

    2015-12-01

    Recent insights shed light on the global mechanisms involved in the abrupt oscillations of the Earth climate for the Late Glacial Maximum (LGM) to Holocene period (Zhang et al., 2014; Banderas et al., 2015). Yet the concomitant patterns of regional climate reorganization on continental areas are for now poorly documented. Particularly, few attempts have been made to propose temporal reconstructions of the regional climate variables in the High Tropical Andes, a region under the direct influence of the upper part of the troposphere. We present new glacial chronologies from the Zongo (16.3°S - 68.1°W, Bolivia) and Wara-Wara (17.3°S - 66.1°W, Bolivia) valleys based on Cosmic Ray Exposure dating (CRE) from an exceptional suite of recessive moraines. These new data permitted to refine existing chronologies (Smith et al., 2005 ; Zech et al., 2010): the Zongo valley is characterized by an older local last glacial maximum than the Wara Wara valley. Both sites however exhibit similar glacier behaviours, with a progressive regression between 18 ka and the Holocene. In both sites, glaciers recorded stillstand episodes synchronous with the cold events of the Norther Hemisphere (Henrich 1 event, Younger Dryas). Since the nearby Altiplano basin registered lake level variations over the same period, we were able to apply a joint modelling of glaciers Equilibrium Line Altitude (ELA) and lake budget. This permits to derive a temporal evolution of temperature and precipitation for both sites. These new reconstructions show for both sites that glaciers of the Eastern Tropical Andes were both influenced by the major climatic events of the Northern and Southern Hemispheres. However, precipitation variability is more influenced by the Northern Atlantic events. This observation is in good agreement with the theories suggesting that North Hemisphere cold events are coeval with an important southward deflexion of the Intertropical Convergence Zone (ITCZ) due to the inter

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

    Science.gov (United States)

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

    2016-04-01

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

  18. Lichenometric Dating of Little Ice Age Moraines in the Cordillera Vilcabamba, Southern Peruvian Andes

    Science.gov (United States)

    Taggart, J. R.; Licciardi, J. M.

    2008-12-01

    Lateral and end moraines deposited by two valley glaciers were mapped on the south side of Nevado Tucarhuay (5910 m asl) and on the east side of Nevado Salcantay (6271 m asl) in the Cordillera Vilcabamba in the southern Peruvian Andes (~13°S latitude). The geomorphic expression of outer and inner moraine sequences in these two drainages mimics that of a previously studied pair of moraines in the upper Rio Blanco valley on the south side of Nevado Salcantay. Cosmogenic 10Be surface exposure dating has yielded ages of 9.0 ± 0.3 ka and 195 ± 24 years, respectively, for these outer and inner Rio Blanco moraines. In all three valleys, prominent outer moraines occur ~3-5 km from headwalls and inner moraine ridges are found ~2.5-3 km from headwalls. Recessional moraines found exclusively on the east side of Salcantay indicate multiple early- to late-Holocene glacier pauses, rather than continuous retreat, prior to the latest Holocene glacier readvance. Diameters of the lichen Rhizocarpon subgenus Rhizocarpon were measured on moraine boulders from the inner moraines in all three valleys. Lichen diameters on the two undated inner moraines are consistent with diameters on the inner 10Be-dated Rio Blanco moraine, which signifies similar lichenometric ages and supports synchronous glacier culminations in all three drainages during the Little Ice Age. The new lichen measurements and age estimates provide a critical link between previous lichen studies in the Cordillera Blanca to the north and in the Cordillera Real to the south, thereby increasing spatial coverage of terrestrial paleoclimate information. Moreover, the extensive lichen measurements gathered on the inner 10Be-dated Rio Blanco moraine define a new control point for the Rhizocarpon subgenus Rhizocarpon growth curve in the tropical Peruvian- Bolivian Andes, which will increase the accuracy of lichenometric age estimates in this region. 10Be exposure dating of the inner moraines in adjacent valleys is underway

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

    Science.gov (United States)

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

    2013-12-01

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

  20. Methane fluxes from a wet puna ecosystem in the Peruvian Andes

    Science.gov (United States)

    Jones, Sam; Diem, Torsten; Priscila Huaraca Quispe, Lidia; Quispe Ccahuana, Adan Julian; Meir, Patrick; Arn Teh, Yit

    2014-05-01

    Discrepancies exist between top-down and bottom-up estimates of the tropical South American atmospheric methane budget. This suggests that current source-sink inventories fail to adequately characterise the landscapes of the region. This may be particularly true of Andean environments where very few field observations have been made. The high tropical Andes, between tree and permanent snow-lines, is home to diverse grass, shrub and giant rosette dominated ecosystems known variously from Venezuela to northern Chile and Argentina as paramo, jalca and puna. In humid regions these are characterised by wet, organic-rich mineral soils, peat-forming wetlands and shallow lakes. Such conditions are likely to promote methane production and potentially represent a regionally significant source to the atmosphere that should be considered. We report on methane fluxes from a bunch-grass dominated puna habitat at 3500 m above sea level in south-eastern Peru. Mean annual temperature and precipitation are 11 °C and 2500 mm, respectively. Temperature is aseasonal but experiences considerable diurnal variations with overnight frosting common-place. In contrast, rainfall is intensely episodic and has a pronounced wet season between September and March. Sampling encompassed a range of topographic features, such as grassland on freely draining, gently inclined or steep slopes and depressions containing bogs, over a 3 ha ridge to basin transition. Monthly sampling was carried out between January 2011 and June 2013 to investigate seasonal variability in methane fluxes. Intensive sampling campaigns were conducted to investigate spatial and short-term variations on a daily basis in two nine-day campaigns during wet and dry season. The site was a net source of methane to the atmosphere during the period of study. Methane fluxes were dominated by emissions from bogs, whereas, freely draining grassland exhibited weak source or marginal sink activity. Temporal variations were most notable at

  1. Intra- and interspecific tree growth across a long altitudinal gradient in the Peruvian Andes.

    Science.gov (United States)

    Rapp, Joshua M; Silman, Miles R; Clark, James S; Girardin, Cecile A J; Galiano, Darcy; Tito, Richard

    2012-09-01

    Tree growth response across environmental gradients is fundamental to understanding species distributional ecology and forest ecosystem ecology and to predict future ecosystem services. Cross-sectional patterns of ecosystem properties with respect to climatic gradients are often used to predict ecosystem responses to global change. Across sites in the tropics, primary productivity increases with temperature, suggesting that forest ecosystems will become more productive as temperature rises. However, this trend is confounded with a shift in species composition and so may not reflect the response of in situ forests to warming. In this study, we simultaneously studied tree diameter growth across the altitudinal ranges of species within a single genus across a geographically compact temperature gradient, to separate the direct effect of temperature on tree growth from that of species compositional turnover. Using a Bayesian state space modeling framework we combined data from repeated diameter censuses and dendrometer measurements from across a 1700-m altitudinal gradient collected over six years on over 2400 trees in Weinmannia, a dominant and widespread genus of cloud forest trees in the Andes. Within species, growth showed no consistent trend with altitude, but higher-elevation species had lower growth rates than lower-elevation species, suggesting that species turnover is largely responsible for the positive correlation between productivity and temperature in tropical forests. Our results may indicate a significant difference in how low- and high-latitude forests will respond to climate change, since temperate and boreal tree species are consistently observed to have a positive relationship between growth and temperature. If our results hold for other tropical species, a positive response in ecosystem productivity to increasing temperatures in the Andes will depend on the altitudinal migration of tree species. The rapid pace of climate change, and slow observed

  2. Control tectónico de la red de drenaje de los Andes del norte argentino

    Directory of Open Access Journals (Sweden)

    R. Mon

    2005-09-01

    Full Text Available Los ríos transversales que drenan la vertiente oriental de los Andes del norte argentino muestran bruscos desvíos hacia cursos longitudinales, inmediatamente al oeste de la traza de grandes cabalgamientos o de los bordes de láminas levantadas por fallas ubicadas en el lado opuesto de ellos. Los ríos desviados colectan otros ríos transversales antes de emerger en la dirección opuesta y de atravesar el frente montañoso. El desvío de los ríos se interpreta como la respuesta al levantamiento progresivo y al crecimiento lateral de cinturones fallados o de anticlinales propagados a lo largo de fallas ciegas. La mayor parte de los ríos de la región fueron desviados, pocos de ellos mantuvieron sus cursos a través de las estructuras en desarrollo. La reorganización del drenaje por el desarrollo de una topografía controlada estructuralmente influyó en la ubicación y en la concentración de los desagües de los ríos en el frente montañoso. Este segmento de los Andes, que se extiende a lo largo de más de 600 km, tiene sólo tres desagües representados por los ríos troncales Bermejo, Juramento y Salí-Dulce. El drenaje evolucionó desde el levantamiento de la Puna (12- 15 Ma, después de la regresión marina final. El desvío de los ríos puede haber empezado después del levantamiento de la Cordillera Oriental (10 Ma y prosiguió con el levantamiento de nuevas montañas hacia el este. El levantamiento de las cadenas montañosas avanzó de oeste a este. Los cinturones más orientales del Sistema Subandino y de las Sierras Pampeanas septentrionales se levantaron después de los 3 Ma. El levantamiento rápido de los obstáculos tectónicos puede explicar la tendencia al desvío de los ríos de esta región.

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

    Science.gov (United States)

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

    2011-12-01

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

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

    Science.gov (United States)

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

    2011-12-01

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

  5. Aridity changes in the temperate-Mediterranean transition of the Andes since ad 1346 reconstructed from tree-rings

    Energy Technology Data Exchange (ETDEWEB)

    Christie, Duncan A.; Quesne, Carlos le [Universidad Austral de Chile, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); Boninsegna, Jose A.; Morales, Mariano S.; Villalba, Ricardo [Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales, IANIGLA, Departamento de Dendrocronologia e Historia Ambiental, Mendoza (Argentina); Cleaveland, Malcolm K.; Stahle, David W. [University of Arkansas Fayetteville, Tree-Ring Laboratory, Department of Geosciences, Fayetteville, AR (United States); Lara, Antonio [Universidad Austral de Chile, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); Universidad Austral de Chile, Forest Ecosystem Services under Climatic Fluctuations (Forecos), Valdivia (Chile); Mudelsee, Manfred [Climate Risk Analysis, Hanover (Germany); Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany)

    2011-04-15

    The Andes Cordillera acts as regional ''Water Towers'' for several countries and encompasses a wide range of ecosystems and climates. Several hydroclimatic changes have been described for portions of the Andes during recent years, including glacier retreat, negative precipitation trends, an elevation rise in the 0 isotherm, and changes in regional streamflow regimes. The Temperate-Mediterranean transition (TMT) zone of the Andes (35.5 -39.5 S) is particularly at risk to climate change because it is a biodiversity hotspot with heavy human population pressure on water resources. In this paper we utilize a new tree-ring network of Austrocedrus chilensis to reconstruct past variations in regional moisture in the TMT of the Andes by means of the Palmer Drought Severity Index (PDSI). The reconstruction covers the past 657 years and captures interannual to decadal scales of variability in late spring-early summer PDSI. These changes are related to the north-south oscillations in moisture conditions between the Mediterranean and Temperate climates of the Andes as a consequence of the latitudinal position of the storm tracks forced by large-scale circulation modes. Kernel estimation of occurrence rates reveals an unprecedented increment of severe and extreme drought events during the last century in the context of the previous six centuries. Moisture conditions in our study region are linked to tropical and high-latitude ocean-atmospheric forcing, with PDSI positively related to Nino-3.4 SST during spring and strongly negatively correlated with the Antarctic Oscillation (AAO) during summer. Geopotential anomaly maps at 500-hPa show that extreme dry years are tightly associated with negative height anomalies in the Ross-Amundsen Seas, in concordance with the strong negative relationship between PDSI and AAO. The twentieth century increase in extreme drought events in the TMT may not be related to ENSO but to the positive AAO trend during late-spring and

  6. Agriculture at the Edge: Landscape Variability of Soil C Stocks and Fluxes in the Tropical Andes

    Science.gov (United States)

    Riveros-Iregui, D. A.; Peña, C.

    2015-12-01

    Paramos, or tropical alpine grasslands occurring right above the forest tree-line (2,800 - 4,700 m), are among the most transformed landscapes in the humid tropics. In the Tropical Andes, Paramos form an archipelago-like pattern from Northern Colombia to Central Peru that effectively captures atmospheric moisture originated in the Amazon-Orinoco basins, while marking the highest altitude capable of sustaining vegetation growth (i.e., 'the edge'). This study investigates the role of land management on mediating soil carbon stocks and fluxes in Paramo ecosystems of the Eastern Cordillera of Colombia. Observations were collected at a Paramo site strongly modified by land use change, including active potato plantations, pasture, tillage, and land abandonment. Results show that undisturbed Paramos soils have high total organic carbon (TOC), high soil water content (SWC), and low soil CO2 efflux (RS) rates. However, Paramo soils that experience human intervention show lower TOC, higher and more variable RS rates, and lower SWC. This study demonstrates that changes in land use in Paramos affect differentially the accumulation and exchange of soil carbon with the atmosphere and offers implications for management and protection strategies of what has been deemed the fastest evolving biodiversity ecosystem in the world.

  7. Calculated WIMP signals at the ANDES laboratory: comparison with northern and southern located dark matter detectors

    CERN Document Server

    Civitarese, O; Mosquera, M E

    2016-01-01

    Weakly Interacting Massive Particles (WIMP) are possible components of the Universe's Dark Matter. The detection of WIMP is signalled by the recoil of the atomic nuclei which form a detector. CoGeNT at the Soudan Underground Laboratory (SUL) and DAMA at the Laboratori Nazionali del Gran Sasso (LNGS) have reported data on annual modulation of signals attributed to WIMP. Both experiments are located in laboratories of the northern hemisphere. Dark matter detectors are planned to operate (or already operate) in laboratories of the southern hemisphere, like SABRE at Stawell Underground Physics Laboratory (SUPL) in Australia, and DM-ICE in the South Pole. In this work we have analysed the dependence of diurnal and annual modulation of signals, pertaining to the detection of WIMP, on the coordinates of the laboratory, for experiments which may be performed in the planned new underground facility ANDES (Agua Negra Deep Experimental Site), to be built in San Juan, Argentina. We made predictions for NaI and Ge-type de...

  8. Caracterización de semillas de lupino (Lupinus mutabilis sembrado en los Andes de Colombia

    Directory of Open Access Journals (Sweden)

    Eduar Ortega-David

    2010-01-01

    Full Text Available En este trabajo se identificaron las propiedades físicas, composicionales y fisicoquímicas de la semilla de Lupino (Lupinus mutabilis cultivado en Nariño (Andes de Colombia. Su composición se determinó realizando análisis proximales de semilla completa, tegumento y cotiledones. Además se determinó el contenido de minerales y su composición elemental. Se estableció cuantitativamente el contenido de alcaloides presentes y su perfil composicional. Se determinaron propiedades físicas como la forma y el tamaño de la semilla. Se determinaron las propiedades fisicoquímicas como la capacidad de retención de agua y el pH. Las cantidades de nutrientes de la semilla son menores que los valores reportados en la literatura. Se presenta una variación en cuanto al perfil de alcaloides, siendo la esparteína la segunda sustancia de mayor presencia. La hidratación de la semilla conduce a un incremento de 1.72 veces su tamaño original. Se puede sugerir que la proteína posee afinidad hidrofílica evidenciada por la elevada capacidad de retención de agua de la semilla. La identificación de estas propiedades permite reconocer el potencial de la semilla para su futuro aprovechamiento.

  9. Nazca - South America Convergence and Motion of the North Andes Block

    Science.gov (United States)

    La Femina, P. C.; Mora-paez, H.; Mothes, P. A.; Ruiz, G.

    2012-12-01

    The North Andes block (NAB) is a hypothesized tectonic block that moves (escapes) north-northeast relative to a stable South American reference frame. The motion of this block is thought to be derived by the collision of the Carnegie Ridge in southern Ecuador and/or by oblique convergence and high degrees of interplate coupling north of the ridge (i.e., strain partitioning). We investigate the kinematics of NAB motion utilizing a velocity field based on new continuous GPS networks and existing episodic GPS data in Ecuador and Colombia. The new velocity field and published earthquake slip vectors are inverted to solve for the Euler vector of the NAB and interseismic elastic strain accumulation on block-bounding faults using a block modeling approach. At the latitude of Ecuador, the NAB is rigid with transpressional deformation accommodating northeastward motion along its boundary with South America. In central to northern Colombia, the NAB is dissected by several prominent shear zones. We test a suite of block models to investigate the tectonic nature of the NAB and the style of faulting in the upper plate accommodating block motion. Through the estimation of elastic strain accumulation on all block-bounding faults, we improve the understanding of interseismic coupling along a convergent margin capable of producing M>8 earthquakes and upper plate faults capable of generating M>6 earthquakes.

  10. The powers of water-user associations: on multiplicity, fluidity, and durability in the Peruvian Andes

    Directory of Open Access Journals (Sweden)

    Andres Verzijl

    2015-03-01

    Full Text Available In this article we use insights from institutional bricolage and actor network theory to make sense of an Andean water user association (WUA and its bricoleurs in the Region of Ayacucho, Peru. Rather than being designed and clearly defined, we see natural resource institutions as continuously performed and patched together, through heterogeneous elements and practices, by those that live, experience and enact these institutions every day and by those who make sense of them. We present three cases, three supra-community efforts to secure water livelihoods, in which the Ayacucho water user association is enacted differently. Similar actors and practices like, water law, local customs, water bodies, and ecological services are performed in alternate ways for diverse purposes. It is this range of co-existing performances or enactments and the fluidity of actors and bricoleurs which enables an institution to adapt and adjust. We hold that an Andean WUA can be a bureaucratic imposition, but in many ways the WUA is something else too: a strategic ally; a prerequisite for subsidy consideration, a marketplace for exchanging goods and services and more. In the setting of the contemporary Peruvian Andes, the durability of natural resource institutions can be understood through the fluidity and multiplicity of performances and purposes. This has normative and political implications for researchers and policymakers as to what enactment they consider and target.

  11. Tectonic geomorphology of large normal faults bounding the Cuzco rift basin within the southern Peruvian Andes

    Science.gov (United States)

    Byers, C.; Mann, P.

    2015-12-01

    The Cuzco basin forms a 80-wide, relatively flat valley within the High Andes of southern Peru. This larger basin includes the regional capital of Cuzco and the Urubamba Valley, or "Sacred Valley of the Incas" favored by the Incas for its mild climate and broader expanses of less rugged and arable land. The valley is bounded on its northern edge by a 100-km-long and 10-km-wide zone of down-to-the-south systems of normal faults that separate the lower area of the down-dropped plateau of central Peru and the more elevated area of the Eastern Cordillera foldbelt that overthrusts the Amazon lowlands to the east. Previous workers have shown that the normal faults are dipslip with up to 600 m of measured displacements, reflect north-south extension, and have Holocene displacments with some linked to destructive, historical earthquakes. We have constructed topographic and structural cross sections across the entire area to demonstrate the normal fault on a the plateau peneplain. The footwall of the Eastern Cordillera, capped by snowcapped peaks in excess of 6 km, tilts a peneplain surface northward while the hanging wall of the Cuzco basin is radially arched. Erosion is accelerated along the trend of the normal fault zone. As the normal fault zone changes its strike from east-west to more more northwest-southeast, normal displacement decreases and is replaced by a left-lateral strike-slip component.

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

    Science.gov (United States)

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

    2014-12-01

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

  13. Neotropical Andes hot springs harbor diverse and distinct planktonic microbial communities.

    Science.gov (United States)

    Delgado-Serrano, Luisa; López, Gina; Bohorquez, Laura C; Bustos, José R; Rubiano, Carolina; Osorio-Forero, César; Junca, Howard; Baena, Sandra; Zambrano, María M

    2014-07-01

    Microbial explorations of hot springs have led to remarkable discoveries and improved our understanding of life under extreme conditions. The Andean Mountains harbor diverse habitats, including an extensive chain of geothermal heated water sources. In this study, we describe and compare the planktonic microbial communities present in five high-mountain hot springs with distinct geochemical characteristics, at varying altitudes and geographical locations in the Colombian Andes. The diversity and structure of the microbial communities were assessed by pyrosequencing the V5 - V6 region of the 16S rRNA gene. The planktonic communities varied in terms of diversity indexes and were dominated by the bacterial phyla Proteobacteria, Aquificae, Chloroflexi, Cyanobacteria, Firmicutes, Nitrospirae, and Thermotogae, with site-specific bacterial taxa also observed in some cases. Statistical analyses showed that these microbial communities were distinct from one another and that they clustered in a manner consistent with physicochemical parameters of the environment sampled. Multivariate analysis suggested that pH and sulfate were among the main variables influencing population structure and diversity. The results show that despite their geographical proximity and some shared geochemical characteristics, there were few shared operational taxonomic units (OTUs) and that community structure was influenced mainly by environmental factors that have resulted in different microbial populations.

  14. Effects of loadingeunloading and wettingedrying cycles on geomechanical behaviors of mudrocks in the Colombian Andes

    Institute of Scientific and Technical Information of China (English)

    Mario Camilo Torres-Suarez; Adolfo Alarcon-Guzman; Rafael Berdugo-De Moya

    2014-01-01

    The mudrocks in the Colombian Andes, particularly those exhibiting low cementation (bonding), are susceptible to degradation when the environmental conditions change, which are challenging issues for engineering works. In this paper, the changes in physico-mechanical properties of mudrocks were moni-tored in laboratory, and some influential factors on the mechanical competence of geomaterials were studied. The geotechnical characteristics and experimental designs were developed from physical, chem-ical, mechanical and compositional points of view. In the tests, the techniques such as vapor equilibrium technique (VET) were employed to apply wettingedrying cycles and to control relative humidity (suction-controlled) and loadingeunloading cycles through ultrasonic wave velocities technique. The results show that the main failure mechanisms for the laminated mudrocks start on the microscopic scale by fissures coalescence, exhibiting physico-chemical degradation as well;the global geomechanical behavior presents a state between a ductile, like rock, and a fragile, like soil. The obtained results can provide engineering values according to monitoring laboratory set, when compared with in situ conditions.

  15. Methodology for Evaluating the Quality of Ecosystem Maps: A Case Study in the Andes

    Directory of Open Access Journals (Sweden)

    Dolors Armenteras

    2016-08-01

    Full Text Available Uncertainty in thematic maps has been tested mainly in maps with discrete or fuzzy classifications based on spectral data. However, many ecosystem maps in tropical countries consist of discrete polygons containing information on various ecosystem properties such as vegetation cover, soil, climate, geomorphology and biodiversity. The combination of these properties into one class leads to error. We propose a probability-based sampling design with two domains, multiple stages, and stratification with selection of primary sampling units (PSUs proportional to the richness of strata present. Validation is undertaken through field visits and fine resolution remote sensing data. A pilot site in the center of the Colombian Andes was chosen to validate a government official ecosystem map. Twenty primary sampling units (PSUs of 10 × 15 km were selected, and the final numbers of final sampling units (FSUs were 76 for the terrestrial domain and 46 for the aquatic domain. Our results showed a confidence level of 95%, with the accuracy in the terrestrial domain varying between 51.8% and 64.3% and in the aquatic domain varying between 75% and 92%. Governments need to account for uncertainty since they rely on the quality of these maps to make decisions and guide policies.

  16. Caracterización de semillas de lupino (Lupinus mutabilis sembrado en los Andes de Colombia

    Directory of Open Access Journals (Sweden)

    Ortega-David Eduar

    2010-03-01

    Full Text Available En este trabajo se identificaron las propiedades físicas, composicionales y fisicoquímicas de la semilla de Lupino (Lupinus mutabilis cultivado en Nariño (Andes de Colombia. Su composición se determinó realizando análisis proximales de semilla completa, tegumento y cotiledones. Además se determinó el contenido de minerales y su composición elemental. Se estableció cuantitativamente el contenido de alcaloides presentes y su perfil composicional. Se determinaron propiedades físicas como la forma y el tamaño de la semilla. Se determinaron las propiedades fisicoquímicas como la capacidad de retención de agua y el pH. Las cantidades de nutrientes de la semilla son menores que los valores reportados en la literatura. Se presenta una variación en cuanto al perfil de alcaloides, siendo la esparteína la segunda sustancia de mayor presencia. La hidratación de la semilla conduce a un incremento de 1.72 veces su tamaño original. Se puede sugerir que la proteína posee afinidad hidrofílica evidenciada por la elevada capacidad de retención de agua de la semilla. La identificación de estas propiedades permite reconocer el potencial de la semilla para su futuro aprovechamiento.

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

    Directory of Open Access Journals (Sweden)

    S. MacDonell

    2013-04-01

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

  18. Long-term carbon accumulation in two tropical mountain peatlands, Andes Mountains, Ecuador

    Directory of Open Access Journals (Sweden)

    R.A. Chimner

    2008-03-01

    Full Text Available Tropical peatlands form in at least two distinct altitudinal zones, namely lowlands and high mountains. Unlike lowland tropical peatlands, which are typically forested, tropical mountain peatlands are dominated by cushion plants, bryophytes and herbaceous plants. Tropical mountain peatlands are poorly understood and little information is available on their ages, whether their peat bodies are relicts or actively accumulating carbon, the amount of carbon they contain, or the rate at which they can accumulate carbon. Our objective in this paper is to quantify carbon accumulation rates in two peatlands in the Andes Mountains of Ecuador, South America. At each site, we collected peat cores which were analysed for bulk density, mineral content and % C and we calculated the amount of carbon stored. Due to the high amount of mineral sediment in the Cotopaxi peatland, carbon dating was not done at this site. The Cayambre-Coca peat body was 4 m thick, ca. 3,000 years old, and had accumulated 140 kgC m-2. The approximate long-term rate of carbon accumulation (LARCA is 46 gC m-2 yr-1. However, a significant part of the depth of accumulation is due to high levels of mineral sediment input from steep side slopes and volcanic ash input.

  19. Gravity Wave and Turbulence Transport of Heat and Na in the Mesopause Region over the Andes

    Science.gov (United States)

    Guo, Yafang; Liu, Alan Z.

    2016-07-01

    The vertical heat and Na fluxes induced by gravity waves and turbulence are derived based on over 600 hours of observations from the Na wind/temperature lidar located at Andes lidar Observatory (ALO), Cerro Pachón, Chile. In the 85-100 km region, the annual mean vertical fluxes by gravity waves show downward heat transport with a maximum of 0.78K m/s at 90 km, and downward Na transport with a maximum of 210 m/s/cm3 at 94km. The maximum cooing rate reaches -24 K/d at 94km. The vertical fluxes have strong seasonal variations, with large differences in magnitudes and altitudes of maximum fluxes between winter and summer. The vertical fluxes due to turbulence eddies are also derived with a novel method that relates turbulence fluctuations of temperature and vertical wind with photon count fluctuations at very high resolution (25 m, 6 s). The results show that the vertical transports are comparable to those by gravity waves and they both play significant roles in the atmospheric thermal structure and constituent distribution. This direct measure of turbulence transport also enables estimate of the eddy diffusivity for heat and constituent in the mesopause region.

  20. The Basement of the Central Andes: The Arequipa and Related Terranes

    Science.gov (United States)

    Ramos, Victor A.

    2008-05-01

    The basement of the Central Andes provides insights for the dispersal of Rodinia, the reconstruction of Gondwana, and the dynamics of terrane accretion along the Pacific. The Paleoproterozoic Arequipa terrane was trapped during collision between Laurentia and Amazonia in the Mesoproterozoic. Ultrahigh-temperature metamorphism correlates with the collapse of the Sunsás-Grenville orogen after 1000 Ma and is related to slab break-off and dispersal of Rodinia. The Antofalla terrane separated in the Neoproterozoic, forming the Puncoviscana basin. Its closure was coeval with the collision of the eastern Sierras Pampeanas. The rift-drift transitions of the early Paleozoic clastic platform showed a gradual younging to the north, in agreement with counterclockwise rotation based on paleomagnetic data of Antofalla. North of Arequipa arc magmatism and high-grade metamorphism are linked to collision of the Paracas terrane in the Ordovician, during the Famatinian orogeny in the Sierras Pampeanas. The early Paleozoic history of the Arequipa massif is explained by a backarc, which further south changed to open oceanic conditions and subsequent collision. The Antofalla terrane reaccreted to the continental margin by the late Ordovician. These accretions and subsequent separations during the Mesoproterozoic, Neoproterozoic early Cambrian, and late Cambrian middle Ordovician are explained by changes in absolute motion of the Gondwana supercontinent during plate global reorganization.

  1. Does external funding help adaptation? Evidence from community-based water management in the Colombian Andes.

    Science.gov (United States)

    Murtinho, Felipe; Eakin, Hallie; López-Carr, David; Hayes, Tanya M

    2013-11-01

    Despite debate regarding whether, and in what form, communities need external support for adaptation to environmental change, few studies have examined how external funding impacts adaptation decisions in rural resource-dependent communities. In this article, we use quantitative and qualitative methods to assess how different funding sources influence the initiative to adapt to water scarcity in the Colombian Andes. We compare efforts to adapt to water scarcity in 111 rural Andean communities with varied dependence on external funding for water management activities. Findings suggest that despite efforts to use their own internal resources, communities often need external support to finance adaptation strategies. However, not all external financial support positively impacts a community's abilities to adapt. Results show the importance of community-driven requests for external support. In cases where external support was unsolicited, the results show a decline, or "crowding-out," in community efforts to adapt. In contrast, in cases where communities initiated the request for external support to fund their own projects, findings show that external intervention is more likely to enhance or "crowds-in" community-driven adaptation.

  2. Low temperature resistance in saplings and ramets of Polylepis sericea in the Venezuelan Andes

    Science.gov (United States)

    Rada, Fermín; García-Núñez, Carlos; Rangel, Sairo

    2009-09-01

    The frequent occurrence of all year-round below zero temperatures in tropical high mountains constitutes a most stressful climatic factor that plants have to confront. Polylepis forests are found well above the continuous forest line and are distributed throughout the Andean range. These trees require particular traits to overcome functional limitations imposed on them at such altitudes. Considering seedling and sapling stages as filter phases in stressful environments, some functional aspects of the regeneration of Polylepis sericea, a species associated to rock outcrops in the Venezuelan Andes, were studied. We characterized microclimatic conditions within a forest, in a forest gap and surrounding open páramo and determined low temperature resistance mechanisms in seedlings, saplings and ramets. Conditions in the forest understory were more stable compared to the forest gaps and open surrounding páramo. Minimum temperatures close to the ground were 3.6 °C lower in the open páramo compared to the forest understory. Maximum temperatures were 9.0 °C higher in the open páramo. Ice nucleation and injury temperatures occurred between -6 and -8 °C for both ramets and saplings, an evidence of frost avoidance to low nighttime temperatures. In this particular forest, this resistance ability is determinant in their island-like distribution in very specific less severe temperature habitats.

  3. New isotopic ages and the timing of orogenic events in the Cordillera Darwin, southernmost Chilean Andes

    Science.gov (United States)

    Hervé, F.; Nelson, E.; Kawashita, K.; Suárez, M.

    1981-10-01

    The Cordillera Darwin, a structural culmination in the Andes of Tierra del Fuego, exposes an orogenic core zone that has undergone polyphase deformation and metamorphism. Some of the classic problems of orogenic zones have remained unanswered in the Cordillera Darwin: the age of deformed plutonic rocks, the distinction of structurally reactivated basement and metamorphosed cover rocks, and the timing of orogenic events. This study addresses and partially answers these questions. A well-constrained Rb-Sr isochron age of157±8m.y. and an initial 87Sr/ 86Sr ratio of 0.7087 obtained from a pre-tectonic granitic suite suggest a genetic relation between this suite and Upper Jurassic silicic volcanic rocks in the cover sequence (Tobifera Formation), and also suggest involvement of continental crust in formation of these magmas. A poorly constrained Rb-Sr isochron age of240±40m.y. obtained from supposed basement schists is consistent with field relations in the area which suggest a late Paleozoic/early Mesozoic metamorphism for these pre-Late Jurassic rocks. However, because of scatter in the data and the uncertainties involved in dating metasedimentary rocks, the significance of the isotopic age is dubious. Compilation of previously published ages in the area [9] with new mineral ages reported here indicate that "early Andean" orogenic events occurred between 100 and 84 m.y. ago, and that subduction-related magmatism has contributed, probably discontinuously, to the crustal evolution of the region throughout the Mesozoic.

  4. Estimates of Carbon Reservoirs in High-Altitude Wetlands in the Colombian Andes

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    Enrique Javier Peña

    2009-10-01

    Full Text Available The observed increase in emission of greenhouse gases, with attendant effects on global warming, have raised interests in identifying sources and sinks of carbon in the environment. Terrestrial carbon (C sequestration involves capture of atmospheric C through photosynthesis and storage in biota, soil and wetlands. Particularly, wetland systems function primarily as long-term reservoirs for atmospheric carbon dioxide (CO2 and as sources of atmospheric methane (CH4. The objective of this study was to evaluate the patterns of carbon reservoirs in two high-altitude wetlands in the central Andean mountain of Colombia. Carbon cycle in both systems is related mainly with the plant biomass dynamics from the littoral zone. Thus, total organic carbon concentrate an average up to 329 kg of N ha-1 and 125 kg of P ha-1 every year vs only 17 kg N ha-1 and 6 kg P ha-1 in the water column of the limnetic zone in the wetland, evidencing spatial differences in carbon concentrations for these types of ecosystems. Results revealed that these systems participate in the balance and sequestration of carbon in the Colombian Andes.

  5. Aguapanela, a new tarantula genus from the Colombian Andes (Araneae, Theraphosidae).

    Science.gov (United States)

    Perafán, Carlos; Cifuentes, Yeimy; Estrada-Gomez, Sebastián

    2015-01-01

    A new monotypic genus of Theraphosidae is described from Colombia: Aguapanela Perafán & Cifuentes gen. nov. with only the type species Aguapanela arvi Perafán, Cifuentes & Estrada sp. nov., from Caldas and Medellin, Antioquia, Colombian Andes. The new genus differs from other theraphosid spiders mainly in the presence of stridulatory setae on the palps and legs I and II, together with the presence of type III and IV urticating setae. Males lack a tibial apophysis on leg I and have a simple palpal bulb with the subtegulum less extended than usual in Theraphosinae, elongated curved embolus, ventrally concave, and with two prolateral keels very flat and developed on the dorsal edge. The female spermathecae have two digitiform elongated and granulated seminal receptacles attached to a semicircular wide membranous base. We describe, diagnose and illustrate the new genus and give some biological remarks. Morphological, systematic and biogeographic aspects are discussed. Chromatographic and electrophoretic profiles of its venom are analyzed. PMID:26624422

  6. De Los ríos profundos a Lituma en los andes: La respuesta de Mario Vargas Llosa a José María Arguedas

    Directory of Open Access Journals (Sweden)

    Marie-Madeleine Gladieu

    2011-05-01

    Full Text Available La novela de Mario Vargas Llosa Lituma en los Andes1 poco tiene que ver, aparentemente, con el mundo narrativo de José María Arguedas: las nuevas aventuras de un personaje ficticio bien conocido de los lectores, presente en varias obras anteriores de aquel autor, en nada se asemejan a las del niño Ernesto ni a las de otro protagonista arguediano. Los Andes sirven de decorado para los dos relatos, pero entre la naturaleza y los pueblos que se suceden en Los ríos profundos2en toda su diversidad, y los paisajes hoscos y siempre peligrosos por los que cruza Lituma, apenas reconoce el lector aquella parte del sur peruano. Algunos detalles, sin embargo, al examinar bien el texto y el contexto de Lituma en los Andes, llaman la atención.

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Directory of Open Access Journals (Sweden)

    M. H. Masiokas

    2015-09-01

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

  9. Holocene changes in monsoon precipitation in the Andes of NE Peru based on δ18O speleothem records

    Science.gov (United States)

    Bustamante, M. G.; Cruz, F. W.; Vuille, M.; Apaéstegui, J.; Strikis, N.; Panizo, G.; Novello, F. V.; Deininger, M.; Sifeddine, A.; Cheng, H.; Moquet, J. S.; Guyot, J. L.; Santos, R. V.; Segura, H.; Edwards, R. L.

    2016-08-01

    Two well-dated δ18O-speleothem records from Shatuca cave, situated on the northeastern flank of the Peruvian Andes (1960 m asl) were used to reconstruct high-resolution changes in precipitation during the Holocene in the South American Summer Monsoon region (SASM). The records show that precipitation increased gradually throughout the Holocene in parallel with the austral summer insolation trend modulated by the precession cycle. Additionally the Shatuca speleothem record shows several hydroclimatic changes on both longer- and shorter-term time scales, some of which have not been described in previous paleoclimatic reconstructions from the Andean region. Such climate episodes, marked by negative excursions in the Shatuca δ18O record were logged at 9.7-9.5, 9.2, 8.4, 8.1, 5.0, 4.1, 3.5, 3.0, 2.5, 2.1 and 1.5 ka b2k, and related to abrupt multi-decadal events in the SASM. Some of these events were likely associated with changes in sea surface temperatures (SST) during Bond events in the North Atlantic region. On longer time scales, the low δ18O values reported between 5.1-5.0, 3.5-3.0 and 1.5 ka b2k were contemporaneous with periods of increased sediment influx at Lake Pallcacocha in the Andes of Ecuador, suggesting that the late Holocene intensification of the monsoon recorded at Shatuca site may also have affected high altitudes of the equatorial Andes further north. Numerous episodes of low SASM intensity (dry events) were recorded by the Shatuca record during the Holocene, in particular at 10.2, 9.8, 9.3, 6.5, 5.1, 4.9, 2.5 and 2.3 ka b2k, some of them were synchronous with dry periods in previous Andean records.

  10. Da Amazônia ao Pacífico cruzando os Andes

    Directory of Open Access Journals (Sweden)

    Enrique Amayo Zevallos

    1993-04-01

    Full Text Available A Área Amazônica (AA é compartilhada por oito países sul-americanos independentes. Desde os tempos coloniais sentiu-se a necessidade da construção de uma via de união da AA com o Oceano Pacífico. Mas os Andes, em termos técnicos e econômicos, foram barreira insuperável até as últimas décadas do século XIX. Nos últimos anos, para o Brasil - país que tem perto de 60% da AA -, esta via vem se tornando cada vez mais importante em termos de exportação, especialmente para o mercado japonês, de grãos, madeira, polpa de madeira etc., ao mesmo tempo em que o Japão também deseja acesso direto à AA. Brasil e Peru, segundo país da AA, com a maior e mais ocidental costa no Pacífico, têm desenvolvido projetos para a construção de uma estrada, contando para isso com apoio financeiro oferecido pelo Japão em diversas oportunidades. Tais projetos tentam conciliar não apenas os interesses de Brasil e Peru, mas também os da Bolívia, país mediterrâneo que poderia finalmente ter acesso livre à costa do Pacífico. Os Estados Unidos, porém, opõem-se a construção da mencionada via e, o projeto está a espera de que o financiamento anteriormente aventado permita sua concretização. Parece que, na construção da projetada estrada, interesses estratégicos das grandes potências mundiais estão envolvidos.The Amazon Area (AA is shared by 8 independent south american countries. Since colonial times it was felt the need of a road linking the AA to the Pacific Ocean. Up to the last decades of the 19th Century the Andes were, in technical and economical terms, almost an insuperable challenge. In the last years for Brazil, the country that has about 60% of the AA, that road has become almost a need for exporting grains, timber, woodpulp etc. (mainly to Japan. And Japan also wants an acess to that area. So, Brasil, together with Peru - the second, after Brazil, AA country that has the largest and westernmost coast in the Pacific - have

  11. Abundance and Morphological Effects of Large Woody Debris in Forested Basins of Southern Andes

    Science.gov (United States)

    Andreoli, A.; Comiti, F.; Lenzi, M. A.

    2006-12-01

    The Southern Andes mountain range represents an ideal location for studying large woody debris (LWD) in streams draining forested basins thanks to the presence of both pristine and managed woodland, and to the general low level of human alteration of stream corridors. However, no published investigations have been performed so far in such a large region. The investigated sites of this research are three basins (9-13 km2 drainage area, third-order channels) covered by Nothofagus forests: two of them are located in the Southern Chilean Andes (the Tres Arroyos in the Malalcahuello National Reserve and the Rio Toro within the Malleco Natural Reserve) and one basin lies in the Argentinean Tierra del Fuego (the Buena Esperanza basin, near the city of Ushuaia). Measured LWD were all wood pieces larger than 10 cm in diameter and 1 m in length, both in the active channel and in the adjacent active floodplain. Pieces forming log jams were all measured and the geometrical dimensions of jams were taken. Jam type was defined based on Abbe and Montgomery (2003) classification. Sediment stored behind log-steps and valley jams was evaluated approximating the sediment accumulated to a solid wedge whose geometrical dimensions were measured. Additional information relative to each LWD piece were recorded during the field survey: type (log, rootwad, log with rootwads attached), orientation to flow, origin (floated, bank erosion, landslide, natural mortality, harvest residuals) and position (log-step, in-channel, channel-bridging, channel margins, bankfull edge). In the Tres Arroyos, the average LWD volume stored within the bankfull channel is 710 m3 ha-1. The average number of pieces is 1,004 per hectare of bankfull channel area. Log-steps represent about 22% of all steps, whereas the elevation loss due to LWD (log-steps and valley jams) results in 27% loss of the total stream potential energy. About 1,600 m3 of sediment (assuming a porosity of 20%) is stored in the main channel

  12. Near-surface temperature lapse rates in a mountainous catchment in the Chilean Andes

    Science.gov (United States)

    Ayala; Schauwecker, S.; Pellicciotti, F.; McPhee, J. P.

    2011-12-01

    In mountainous areas, and in the Chilean Andes in particular, the irregular and sparse distribution of recording stations resolves insufficiently the variability of climatic factors such as precipitation, temperature and relative humidity. Assumptions about air temperature variability in space and time have a strong effect on the performance of hydrologic models that represent snow processes such as accumulation and ablation. These processes have large diurnal variations, and assumptions that average over longer time periods (days, weeks or months) may reduce the predictive capacity of these models under different climatic conditions from those for which they were calibrated. They also introduce large uncertainties when such models are used to predict processes with strong subdiurnal variability such as snowmelt dynamics. In many applications and modeling exercises, temperature is assumed to decrease linearly with elevation, using the free-air moist adiabatic lapse rate (MALR: 0.0065°C/m). Little evidence is provided for this assumption, however, and recent studies have shown that use of lapse rates that are uniform in space and constant in time is not appropriate. To explore the validity of this approach, near-surface (2 m) lapse rates were calculated and analyzed at different temporal resolution, based on a new data set of spatially distributed temperature sensors setup in a high elevation catchment of the dry Andes of Central Chile (approx. 33°S). Five minutes temperature data were collected between January 2011 and April 2011 in the Ojos de Agua catchment, using two Automatic Weather Stations (AWSs) and 13 T-loggers (Hobo H8 Pro Temp with external data logger), ranging in altitude from 2230 to 3590 m.s.l.. The entire catchment was snow free during our experiment. We use this unique data set to understand the main controls over temperature variability in time and space, and test whether lapse rates can be used to describe the spatial variations of air

  13. Vernal Point and Seismic Activity in Tibet Mountains and Andes Mountains

    Science.gov (United States)

    Chavez-Sumarriva, Israel; Chavez-Campos, Teodosio; Chavez S, Nadia

    2014-05-01

    The gravitational influence of the sun and moon on the equatorial bulges of the mantle of the rotating earth causes the precession of the earth. The retrograde motion of the vernal point through the zodiacal band is 26,000 years and passes through each constellation in an average of 2000 years (Milankovitch subcycle). The vernal point retrogrades one precessional degree approximately in 72 years (Gleissberg-cycle), and approximately enters into the Aquarius constellation (declination 11.5° S) on March 20, 1940. On earth this entry was verify through: a) stability of the magnetic equator in the south central zone of Peru and in the north zone of Bolivia (11.5º South latitude) since 1940 b) the greater intensity of equatorial electrojet (EEJ) in Peru and Bolivia since 1940. Besides, there was a long history of studies of coupling between earthquake-ionosphere. In IUGG (Italy-2007), Cusco was proposed as a prime meridian that was based on: (1) the new prime meridian (72º W == 0º) was parallel to the Andes and its projection the meridian (108° E == 180º) intersects the Tibetan plate (Asia). (2) On earth these two areas present the greatest thickness of the crust with an average depth of 70 kilometers. The aim was to synchronize the earth sciences phenomena (e.g. geology, geophysics, etc.). The coordinate system had the vernal point from meridian (72º W== 0º) and March 20, 1940. The retrograde movement of the vernal point was the first precessional degree (2012 = 1940 + 72). The west coast of South America (parallel to meridian 72º W== 0º) was a segment of the circum-pacific seismic belt where more than two thirds of major earthquakes in the world happened. During the first precessional degree (1940 +72 ==2012) seismic activity were: (a) near the new prime meridian (72° W == 0°) occurs in: (a1) Haiti (18.4° N, 72.5° W), January 12, 2010 with magnitude of 7.0 Mw. (a2) Chile (36.28° S, 73.23° W), February 27, 2010 with Magnitude of 8.8 Mw. (a3) Chile (35

  14. Long-lasting wrenching tectonism in the Fuegian Andes: An overview

    Science.gov (United States)

    Sue, Christian; Ghiglione, Matias

    2016-04-01

    Beyond its formal beauty, the geodynamic complexity of the connection between the Southernmost Andes and the Scotia plate, through the active Magallanes-Fagnano Fault system (MFF) and North Scotia Ridge (NSR), ask for proper geodynamic model(s), which could account for the discrepencies between long-term and actual co-seismic deformation and earthquake recurrence time. We focus here on the most recent and current deformation of the region, including a synthesis on the fault system carving the area, together with a critical review of the available kinematic and micro-tectonic data, an overview of the seismicity and paleoseismicity leading to current fault mechanism and actual seismic deformation, which then could be compared to geodetically-related deformation observed by GPS. Fault kinematic studies are coherent with main shortening consistently oriented NE-SW, without significant rotation of the axes across the orogen. These observation, together with the stability of the stress pattern and orientation of the shortening axes on a bigger scale reflects a steady E-W to NNE-SSW σ1/shortening direction since middle Eocene times, reflecting that the global left-lateral motion between Antarctica-Scotia-South America plate circuit, is the main driving forced for the entire area and in particular for the southernmost Andes, over the last 40 or 50 Ma. In terms of seismicity, elastic rebound theory predicts that the major earthquakes on a fault are time dependent, as they are linked to a period of built-up energy (interseismic) with abrupt relaxation stages (coseismic). Regarding both the short-term geodetic and the long-term geological observation, slip rates of the MFF system are pretty low (c.a. 5 mm/yr). Therefore, the time span between major earthquakes should be larger than the one obtained over the last 2 or 3 centuries. Considering a simple tectonic setting of a pure left-lateral strike-slip fault with a constant 5 mm/yr slip rate able to generate ~6 m of left

  15. Effects of post-harvest treatments on the carbohydrate composition of yacon roots in the Peruvian Andes

    OpenAIRE

    Graefe, Sophie; M. Hermann; Manrique, I.; Golombek, S.; Bürkert, Andreas

    2004-01-01

    Yacon (Smallanthus sonchifolius [Poepp. & Endl.] H. Robinson) is an under-exploited native root crop of the Andes, which stores oligofructans (fructo-oligosaccharides, FOS) as its main component of dry matter (DM). FOS are of increasing economic interest because of their low caloric value in human diets and bifidogenic benefits on colon health. Two on-farm experiments were conducted to: (i) determine the effect of shaded, short-term storage at 1990 and 2930 m a.s.l. in the Andean highlands...

  16. New and Evolving Seismic Images of the Central Andes and Subducting Nazca Slab: 20 Years of Portable Seismology Results

    Science.gov (United States)

    Beck, S. L.

    2014-12-01

    Beno Gutenberg first identified a seismic low velocity zone in the upper mantle that we now refer to as the asthenosphere that is still the focus of many studies in active tectonic regions. The upper-most mantle is very heterogeneous and occupies the depth range where much of the tectonic action occurs especially in subduction zones and convergent margins. The central South American convergent margin is the result of the subduction of the Nazca Plate beneath the South American Plate and includes the Andes, one of the largest actively growing mountain ranges on Earth. The South American subduction zone has two regions of "flat" subduction in Peru and central Chile and Argentina separated by a segment of "normal" subduction and an active magmatic arc. The central Andean plateau has an average elevation of 3-4 km and some of the thickest crust on Earth with deformation reaching ~800 km inland. This active margin is characterized by along-strike variations in magmatism, upper crustal shortening, crustal thickness, and slab geometry that make it an ideal region to study the relationship between the subducting slab, the mantle wedge, and the overriding plate. After 20 years of portable seismic deployments in the Central Andes seismologists have generated unprecedented seismic images spanning ~3000 km of the Andean lithosphere, the subducting Nazca slab, and the surrounding mantle. Seismic travel-time, ambient noise and earthquake surface-wave tomography, receiver function imaging, and joint receiver function - surface wave dispersion inversions have produced along strike images of the Central Andes from the surface to a depth of ~700 km. These new images were made possible by PI-driven portable broadband seismic deployments and data sharing by many international groups. I will highlight images of along-strike variations in crustal properties and thickness, mantle lithospheric structure, and slab geometry. These seismic images allow us to more completely evaluate the role

  17. El cambio climático y los recursos hídricos en los Andes tropicales

    OpenAIRE

    Mathias Vuille

    2013-01-01

    En este documento se describen los desafíos que plantea el uso actual y futuro del agua en los Andes tropicales, comenzando por un análisis del ciclo hidrológico proyectado presente y futuro, así como los efectos previstos sobre los servicios ambientales que suministran los glaciares y la vegetación de los humedales. Luego se abordarán en detalle las tensiones y conflictos que existen en este momento en relación con el uso del agua desde una perspectiva socioeconómica. Por último, se hará hin...

  18. The Andes Hantavirus NSs Protein Is Expressed from the Viral Small mRNA by a Leaky Scanning Mechanism

    OpenAIRE

    Vera-Otarola, Jorge; Solis, Loretto; Soto-Rifo, Ricardo; Ricci, Emiliano P.; Pino, Karla; Tischler, Nicole D.; Ohlmann, Théophile; Darlix, Jean-Luc; López-Lastra, Marcelo

    2012-01-01

    The small mRNA (SmRNA) of all Bunyaviridae encodes the nucleocapsid (N) protein. In 4 out of 5 genera in the Bunyaviridae, the smRNA encodes an additional nonstructural protein denominated NSs. In this study, we show that Andes hantavirus (ANDV) SmRNA encodes an NSs protein. Data show that the NSs protein is expressed in the context of an ANDV infection. Additionally, our results suggest that translation initiation from the NSs initiation codon is mediated by ribosomal subunits that have bypa...

  19. A study of stratospheric GW fluctuations and sporadic E at midlatitudes with focus on possible orographic effect of Andes

    Science.gov (United States)

    Hocke, Klemens; Tsuda, Toshitaka; de la Torre, Alejandro

    2002-10-01

    Longitudinal dependences of stratospheric gravity wave (GW) fluctuations and lower ionospheric irregularities (sporadic E) at midlatitudes are studied by means of radio occultation data of the Global Positioning System/Meteorology Experiment (GPS/MET) satellite mission. The zonal average of temperature variance of GW fluctuations with vertical scales less than 7 km at northern midlatitudes is observed to be similar to that at southern midlatitudes, but there is a significant interhemispheric difference in the longitudinal dependence of GW fluctuations. The GPS/MET data at northern midlatitudes show a rapid change of the gravity wave distribution from 25 to 35 km height, resulting in a broad maximum of temperature variance located over the Atlantic and Eurasia. We only find in the wave distribution at h = 25 km some weak traces of possible orographic effects. On the other hand, the distribution of GW fluctuations at southern midlatitudes has a strong and sharp maximum over Andes, which is obviously due to orographic wave generation by the interaction of surface wind with the Andean mountain ridge. This observation of the new GPS radio occultation technique is in agreement with previous measurements of spaceborne microwave and infrared limb sounders. The amplitude of the average wave field increases with height over Andes, while the amplitude maximum moves westward, against the prevailing wind. The temperature fluctuations have an apparent, dominant vertical wavelength of around 6 km. In situ measurements by a balloon-borne rawinsonde at Ushuaia, Argentina (54.7°S, 68.1°W) are compared to a simultaneous GPS/MET temperature profile. The balloon observations of temperature and horizontal wind are interpreted by a large amplitude mountain wave propagating to the upper stratosphere. Wave characteristics and atmospheric background conditions are investigated in detail for this mountain wave observation. Finally, the GPS/MET experiment indicates enhanced sporadic E in

  20. Cenozoic crustal shortening and thickening contributions to Andean orogenesis: Preliminary results from structural mapping in the southern Peruvian Andes

    Science.gov (United States)

    Perez, N.; Horton, B. K.

    2012-12-01

    Estimates of Cenozoic crustal shortening and thickening from the southern Peruvian Andes are necessary to address ongoing debates regarding growth of the Andes and Altiplano plateau. However, limited regional studies in southern Peru prevent accurate assessments of the structural contributions to high topography. This study provides new structural mapping along a >200 km transect spanning the northernmost Altiplano to Subandes at 13-15.5°S and fills the gap between existing central Peruvian and northern Bolivian studies. New stratigraphic data, fault relationships and fold orientations are used to create an updated geologic map and provide insights into the style, timing and magnitude of crustal deformation. Preliminary cross sections accompanying these map transects illustrate deformation style and provide first-order estimates of shortening. Further cross section analyses will be balanced and provide estimates of total crustal shortening and associated thickening in southern Peru. The study transect is subdivided into belts according to the age of exposed rocks and style of deformation. From west to east these belts include: Cretaceous strata dominated by tight folds, closely spaced faults and multiple detachments; Permo-Triassic strata dominated by thicker thrust sheets and fault-fold orientations departing from typical Andean trends; and Paleozoic rocks characterized by thick thrust sheets and deformation focused near major faults. The Cretaceous belt is composed of marine limestones and upward coarsening, siltstone to coarse sandstone progradational sequences. Disharmonic and detachment folds in the Cretaceous section demonstrate the importance of interbedded gypsum and mudstone layers. Fault relationships suggest local shortening during the Early Cretaceous. The Permo-Triassic belt is composed of thick Permian carbonates (Copacabana Formation) and interbedded sandstones, conglomerates and volcanics of the Mitu Formation. This study defines the orientation of

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

    Science.gov (United States)

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

    2016-07-01

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

  2. A 2,300-year-long annually resolved record of the South American summer monsoon from the Peruvian Andes

    OpenAIRE

    Bird, Broxton W.; Abbott, Mark B.; Vuille, Mathias; Donald T. Rodbell; Stansell, Nathan D.; Rosenmeier, Michael F.

    2011-01-01

    Decadal and centennial mean state changes in South American summer monsoon (SASM) precipitation during the last 2,300 years are detailed using an annually resolved authigenic calcite record of precipitation δ18O from a varved lake in the Central Peruvian Andes. This unique sediment record shows that δ18O peaked during the Medieval Climate Anomaly (MCA) from A.D. 900 to 1100, providing evidence that the SASM weakened considerably during this period. Minimum δ18O values occurred during the Litt...

  3. Assessment of Paleozoic terrane accretion along the southern central Andes using detrital zircon geochronology

    Science.gov (United States)

    McKenzie, R.; Horton, B. K.; Fuentes, F.; Fosdick, J. C.; Capaldi, T.; Stockli, D. F.; Alvarado, P. M.

    2015-12-01

    Two distinct Paleozoic terranes known as Cuyania and Chilenia occupy the southern central Andes of Argentina and Chile. Because the proposed terrane boundaries coincide with major structural elements of the modern Andean system at 30-36°S, it is important to understand their origins and potential role in guiding later Andean deformation. The Cuyania terrane of western Argentina encompasses the Precordillera (PC) and a thick-skinned thrust block of the western Sierras Pampeanas, persisting southward to the San Rafael Basin (SRB). Although recently challenged, Cuyania has been long considered a piece of southern Laurentia that rifted away during the early Cambrian and collided with the Argentine margin during the Ordovician. Chilenia is situated west of Cuyania and includes the Frontal Cordillera (FC) and Andean magmatic arc. This less-studied terrane was potentially accreted during an enigmatic Devonian orogenic event. We present new detrital zircon U-Pb age data from siliciclastic sedimentary rocks that span the entire Paleozoic to Triassic from the FC, PC, and SRB. Cambrian rocks of the PC exhibit similar zircon age distributions with prominent ~1.4 and subordinate ~1.1 Ga populations, which are distinct from other Paleozoic strata. Plutonic rocks with these ages are common in southern Laurentia, whereas ~1.4 Ga zircons are uncommon in South American age distributions. This supports a Laurentian origin for Cuyania in isolation from Argentina during the Cambrian. Upper Paleozoic strata from the PC, FC, and SRB all yield similar age data suggesting shared provenance across the proposed Cuyania-Chilenia suture. Age distributions also notably lack Devonian-age grains. The regional paucity of Devonian plutonic rocks and detrital zircon casts doubt on a possible arc system between these terranes at this time, a key requisite for the mid-Paleozoic transfer and accretion of Chilenia to the Argentine margin. Collectively, these data question the precise boundaries of the

  4. Validation of TRMM multi-satellite precipitation analysis (TMPA) products in the Peruvian Andes

    Science.gov (United States)

    Mantas, V. M.; Liu, Z.; Caro, C.; Pereira, A. J. S. C.

    2015-09-01

    The relevance of accurate and timely rainfall estimates cannot be overstated. The rainfall gauge network is still insufficient across significant areas worldwide. Rainfall estimates from spaceborne sensors present an opportunity to supplement the existing network and enable the development of critical, near real time applications. However, the societal benefits of such systems can only be realized if the estimates are properly validated and the performance of existing products accurately described. In this study, two products generated by the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) are validated for the Peruvian Andes. This is a region of complex topography that poses significant challenges to the retrieval of rainfall values from space. The TMPA products, both research grade (3B42V7) and near real time (3B42RT), are compared against in situ data. Different observation lengths are studied and the results are analyzed in light of geographic, topographic and climatic constraints. The Time Series of the science grade product were also studied under Dynamic Time Warping and Hierarchical Clustering to streamline inter-tile comparisons. The TMPA products show a good agreement with the gauge values, especially for more prolonged observation periods (over 8 days). The validation results display a strong regional dependence as a consequence of differences in the climate and topography. This region-specific performance calls for additional, detailed case studies and localized validation efforts. Overall the TMPA was found to perform adequately and provide quality information for a number of applications requiring timely estimates in convenient formats.

  5. Plant leaf wax biomarkers capture gradients in hydrogen isotopes of precipitation from the Andes and Amazon

    Science.gov (United States)

    Feakins, Sarah J.; Bentley, Lisa Patrick; Salinas, Norma; Shenkin, Alexander; Blonder, Benjamin; Goldsmith, Gregory R.; Ponton, Camilo; Arvin, Lindsay J.; Wu, Mong Sin; Peters, Tom; West, A. Joshua; Martin, Roberta E.; Enquist, Brian J.; Asner, Gregory P.; Malhi, Yadvinder

    2016-06-01

    Plant leaf waxes have been found to record the hydrogen isotopic composition of precipitation and are thus used to reconstruct past climate. To assess how faithfully they record hydrological signals, we characterize leaf wax hydrogen isotopic compositions in forest canopy trees across a highly biodiverse, 3 km elevation range on the eastern flank of the Andes. We sampled the dominant tree species and assessed their relative abundance in the tree community. For each tree we collected xylem and leaf samples for analysis of plant water and plant leaf wax hydrogen isotopic compositions. In total, 176 individuals were sampled across 32 species and 5 forest plots that span the gradient. We find both xylem water and leaf wax δD values of individuals correlate (R2 = 0.8 and R2 = 0.3 respectively) with the isotopic composition of precipitation (with an elevation gradient of -21‰ km-1). Minimal leaf water enrichment means that leaf waxes are straightforward recorders of the isotopic composition of precipitation in wet climates. For these tropical forests we find the average fractionation between source water and leaf wax for C29n-alkanes, -129 ± 2‰ (s.e.m., n = 136), to be indistinguishable from that of temperate moist forests. For C28n-alkanoic acids the average fractionation is -121 ± 3‰ (s.e.m., n = 102). Sampling guided by community assembly within forest plots shows that integrated plant leaf wax hydrogen isotopic compositions faithfully record the gradient of isotopes in precipitation with elevation (R2 = 0.97 for n-alkanes and 0.60 for n-alkanoic acids). This calibration study supports the use of leaf waxes as recorders of the isotopic composition of precipitation in lowland tropical rainforest, tropical montane cloud forests and their sedimentary archives.

  6. Quantifying modern erosion rates and river-sediment contamination in the Bolivian Andes

    Science.gov (United States)

    Vezzoli, Giovanni; Ghielmi, Giacomo; Mondaca, Gonzalo; Resentini, Alberto; Villarroel, Elena Katia; Padoan, Marta; Gentile, Paolo

    2013-08-01

    We use petrographic, mineralogical and geochemical data on modern river sediments of the Tupiza basin in the Bolivian Andes to investigate the relationships among human activity, heavy-metal contamination of sediments and modern erosion rates in mountain fluvial systems. Forward mixing model was used to quantify the relative contributions from each main tributary to total sediment load of the Tupiza River. The absolute sediment load was estimated by using the Pacific Southwest Inter Agency Committee model (PSIAC, 1968) after two years of geological field surveys (2009; 2010), together with data obtained from the Instituto Nacional del Agua public authority (INA, 2007), and suspended-load data from Aalto et al. (2006). Our results indicate that the sediment yield in the drainage basin is 910 ± 752 ton/km2year and the mean erosion rate is 0.40 ± 0.33 mm/year. These values compare well with erosion rates measured by Insel et al. (2010) using 10Be cosmogenic radionuclide concentrations in Bolivian river sediments. More than 40% of the Tupiza river load is produced in the upper part of the catchment, where highly tectonized and weathered rocks are exposed and coupled with sporadic land cover and intense human activity (mines). In the Rio Chilco basin strong erosion of upland valleys produce an increase of erosion (˜10 mm/year) and the influx of large amounts of sediment by mass wasting processes. The main floodplain of the Tupiza catchment represents a significant storage site for the heavy metals (˜657 ton/year). Fluvial sediments contain zinc, lead, vanadium, chromium, arsenic and nickel. Since the residence time of these contaminants in the alluvial plain may be more than 100 years, they may represent a potential source of pollution for human health.

  7. Unexpectedly High Beta-Diversity of Root-Associated Fungal Communities in the Bolivian Andes.

    Science.gov (United States)

    Barnes, Christopher J; Maldonado, Carla; Frøslev, Tobias G; Antonelli, Alexandre; Rønsted, Nina

    2016-01-01

    Bolivia is one of the most biologically diverse countries on the planet. Between the Andes and the Amazon drainage basin spans the Yungas, a vast forested region shown to be extremely species rich in macro-organisms. However, it remains unclear whether this high diversity is also reflected in microbial diversity. Here we assess the genetic, taxonomic and functional diversity of root-associated fungi surrounding Cinchona calisaya trees, a typical element of the intermediate altitudes of the Bolivian Yungas. We determine the relative effects of edaphic properties, climate, and geography in regulating fungal community assembly. We show that α-diversity for these fungal communities was similar to temperate and arid ecosystems, averaging 90.1 operational taxonomic units (OTUs) per sample, with reads predominantly assigned to the Ascomycota phylum and with a saprotrophic lifestyle. ß-diversity was calculated as the distance-decay rate, and in contrast to α-diversity, was exceptionally high with a rate of -0.407. Soil properties (pH and P) principally regulated fungal community assembly in an analogous manner to temperate environments, with pH and phosphorus explaining 7.8 and 7.2% of community variation respectively. Surprisingly, altitude does not influence community formation, and there is limited evidence that climate (precipitation and temperature) play a role. Our results suggest that sampling should be performed over a wide geographical and environmental range in order to capture the full root-associated fungal diversity in subtropical regions. This study sheds further light on the diversity and distribution of the world's "hidden biodiversity." PMID:27630629

  8. Evapofacieshalítica en el Salar del Rincón, departamento Los Andes, Salta

    Directory of Open Access Journals (Sweden)

    Alberto Ovejero Toledo

    2009-06-01

    Full Text Available El salar delRincón se encuentra ubicado en el departamento Los Andes, provincia de Salta enel extremo noroeste de la Puna Austral, a una altura media de 3.660 m s.n.m. Eneste trabajo se dan a conocer los resultados de la correlación de sondeos, quepermitieron determinar facies de halita, texturas, estructuras, materialesclásticos intersticiales, mineralogía, composición química de la salmuera y losparámetros hidráulicos del acuífero, determinados a lo largo de una transectaeste-oeste que cubre aproximadamente 30 km². La fase cristalina estácompuesta mayoritariamente de halita, con yeso, mirabilita, thenardita,glauberita, hidroglauberita, eugsterita, calcita y ulexita solo en el sectoroeste de la transecta. Se identificaron las siguientes evapofacies halítica:costra salina, geodas y halita bandeada. Las texturas observadas incluyen:cristales hoppers, pirámides chevron, halita intersticial muddyhalite y halita cloudy. La composición de la salmuera es denaturaleza clorurada sódica con variaciones en profundidad de sulfato y borato.Los cationes son Ca, Mg, Li y K, la relación K/Li es de 20/1. El cálculo dereserva a nivel de recurso mineral, en sectores con distinta porosidad eficaz,dio para Li+ 208,2 kt y para K+ 4231,9 kt (> 30 %; yLi+ 14,9 kt y K+ 302, 9 kt (< 10 %. Los contenidos deLi+ y K+ en toda la transecta son 223,1 kt y 4534,8 ktrespectivamente. El estudio permitió determinar una concentración promedio de0,4 g/l de litio y 8 g/l de potasio.

  9. Engineering masterpieces : from the Andes to Siberia, Canadian talent is in demand

    Energy Technology Data Exchange (ETDEWEB)

    Jaremko, G.

    2001-03-05

    Canadian oilfields are a prime breeding ground for talent, technology and industrial management. This paper described how Canadian talent was recognized in 2001 for three major projects which included a cold-ocean production platform in the Sea of Okhotsk in Siberia, a mountain pipeline project in South America, and an in-situ underground extraction technology in the oilsands of Alberta. The cold-ocean production platform project was recruited by Sakhalin Energy Investment Co., an international consortium originally led by Marathon Oil Co which is now led by Royal Dutch Shell. The oil production platform is stationed 16 kilometres offshore of Sakhalin Island in the Sea of Okhotsk. Sakhalin Energy bought and converted the Molikpaq, an innovative platform made in the 1980s for the Beaufort Sea by Gulf Canada Resources Ltd. The second project included Calgary's Hydroconsult EN3 Services Ltd. which was responsible for the construction of the 940-km GasAtacama 24-inch diameter pipeline between gas fields in northern Argentina and Chile through a 4,000 metre high mountain pass through the Andes. The formidable terrain meant that riverbeds were the only practical route. Pipeline was laid under the rivers, deep enough to escape the forces of wet-season runoff. During the construction, local irrigation systems were kept going with pumps. The final project involved an innovative technology known as steam assisted gravity drainage (SAGD) for enhanced recovery of the Alberta oilsands. Compared to strip-mining, SAGD has several advantages. The process separates the oil from the sand beneath the ground with paris of heat-injection and production wells. The system avoids the use of huge machinery, vast open pits and lake-size waste water ponds. The challenge is to ensure that environmental effects are monitored during the lifespan of any project. 6 figs.

  10. Wide-Angle Seismic Experiment Across the Oeste Fault Zone, Central Andes, Northern Chile.

    Science.gov (United States)

    Lorenzo, J. M.; Yáñez, G. A.; Vera, E. E.; Sepúlveda, J.

    2008-12-01

    From December 6-21, 2007, we conducted a 3-component, radio-telemetric, seismic survey along a ~ 15-km wide E-W transect in the Central Andes, at a latitude of ~ 22.41° S, centered north of the city of Calama (68.9° W), Chile. The study area is sandwiched between the Central Depression in the west and the Andean Western Cordillera of Chile. Recording stations, nominally spaced at intervals of either 125 or 250 m collected up to 3.5 s of refracted seismic arrivals at maximum source-receiver offsets exceeding 15 km. Ten shothole sources, spaced 2-6 km apart focused energy on the shallow (0-3 km), crustal, Paleogene-age structures. Preliminary, tomographic inversions of refracted first arrivals show the top of a shallow ( 600 km), strike-slip fault zone known as the Oeste fault. Turning ray densities suggest the base of the overlying velocity gradient unit (VP, 2-4 km/s) dips inwardly from both east and west directions toward the Oeste fault to depths of almost 1 km. Plate reorganization commencing at least by the latter half of the Oligocene led from oblique to more orthogonal convergence between the South American and the Nazca (Farallon) Plates. We interpret previously mapped, older, minor faults as being generated within the right-lateral, orogen-parallel, Oeste strike-slip fault zone, and postdated by Neogene, N-S striking thrust faults. In this context we also interpret that the spatial distribution of velocity units requires an period of extensional activity that may (1) postdate the transpressional strike slip fault activity of the Neogene, (2) be related to a later releasing bend through the translation and interaction of rigid blocks hidden at depth or even (3) be the consequence of inelastic failure from the result of flexural loading.

  11. Moderate, strong and strongest earthquake-prone areas in the Caucasus, California and the Andes

    Science.gov (United States)

    Dzeboev, Boris; Gvishiani, Alexei

    2016-04-01

    We present this study on recognition of areas of possible occurrence of strong earthquakes. The study deals with the earthquake-prone areas in three regions with different geological and tectonic structures located in different parts of the world. The authors created a new method (FCAZ - Fuzzy Clustering and Zoning) for recognition of highly seismic areas, where epicenters of earthquakes with magnitude M≥M0 can occur. The magnitude threshold M0 depends on the seismic activity of the region. The objects of clustering are earthquake epicenters. The new method allows us to implement uniformly necessary clustering of the recognition objects respectively for moderate, strong and strongest events. Suggested approach consists of two steps: clustering of known earthquake epicenters by the original DPS (Discrete Perfect Sets) algorithm and delineating highly seismic zones around the recognized clusters by another original E2XT algorithm. By means of this method we detected the areas of possible occurrence of the epicenters of strong earthquakes in the Caucasus (M≥5), in California (M≥6.5) and in the mountain belt of the Andes (M≥7.75). The latter case relates to the possible areas of natural disaster occurence. Reliability of the results is confirmed by numerous control experiments, including individual and complete seismic history. Two strongest recent Chilean earthquakes occurred in 2014 and 2015 after the moment the results were published. Their epicenters belong to the zone recognized as high seismically hazardous. It is a strong independent argument which confirms the reliability of the results. The presented results integrate most recent outcomes of more than 40 years of research in pattern recognition and systems analysis for seismic zoning implemented in Russian Academy of Science. This research is supported by the Russian Science Foundation (project № 15-17-30020).

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

    Science.gov (United States)

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

    2016-04-01

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

  13. Multi-sensor geophysical constraints on crustal melt in the central Andes: the PLUTONS project

    Science.gov (United States)

    Pritchard, M. E.; Comeau, M. J.; West, M. E.; Christensen, D. H.; Mcfarlin, H. L.; Farrell, A. K.; Del Potro, R.; Gottsmann, J.; McNutt, S. R.; Michelfelder, G.; Diez, M.; Elliott, J.; Henderson, S. T.; Keyson, L.; Delgado, F.; Unsworth, M. J.

    2015-12-01

    The central Andes is a key global location to quantify storage, transport, and volumes of magma in the Earth's crust as it is home to the world's largest zone of partial melt (the Altiplano-Puna Magma or Mush Body, APMB) as well as the more recently documented Southern Puna Magma Body (SPMB). We describe results from the recently completed international PLUTONS project that focused inter-disciplinary study on two sites of large-scale surface uplift that presumably represent ongoing magmatic intrusions in the mid to upper crust - Uturuncu, Bolivia (in the center of the APMB) and Lazufre on the Chile-Argentina border (on the edge of the SPMB). In particular, a suite of geophysical techniques (seismology, gravity, surface deformation, and electro-magnetic methods) have been used to infer the current subsurface distribution and quantity of partial melts in combination with geochemical and lab studies on samples from the area. Both Uturuncu and Lazufre show separate geophysical anomalies in the upper and mid/lower crust (e.g., low seismic velocity, low resistivity, etc.) indicating multiple distinct reservoirs of magma and/or hydrothermal fluids with different properties. The characteristics of the geophysical anomalies differ somewhat depending on the technique used - reflecting the different sensitivity of each method to subsurface melt of different compositions, connectivity, and volatile content. For example, the depth to the top of the APMB is shallower in a joint ambient noise tomography and receiver function analysis compared to a 3D magnetotelluric inversion. One possibility is that the seismic methods are detecting brines above the APMB that do not have a large electromagnetic signature. Comparison of the geophysical measurements with laboratory experiments at the APMB indicate a minimum of 4-25% melt averaged over the region is needed -- higher melt volumes are permitted by the gravity and MT data and may exist in small regions. However, bulk melt values above

  14. Hydrogen Isotope Biogeochemistry of Plant Biomarkers in Tropical Trees from the Andes to Amazon

    Science.gov (United States)

    Feakins, S. J.; Ponton, C.; West, A. J.; Malhi, Y.; Goldsmith, G.; Salinas, N.; Bentley, L. P.

    2014-12-01

    Plant leaf waxes are well known biomarkers for terrestrial vegetation. Generally, their hydrogen isotopic composition (D/H) records the isotopic composition of precipitation, modulated by leaf water processes and a large biosynthetic fractionation. In addition, the D/H of methoxyl groups on tree wood lignin is an emerging technique thought to record the D/H of source waters, without leaf water complications. Using each of these biomarkers as proxies requires understanding D/H fractionations in plant systems, but few studies have directly studied hydrogen isotope biogeochemistry in tropical plants. An approach that has proven helpful is the paired analysis of plant waters and plant biomarkers: in order that fractionations can be directly computed rather than assumed. This presents logistical challenges in remote tropical forest environments. We report on a unique dataset collected by tree-climbers from 6 well-studied vegetation plots across a 4km elevation transect in the Peruvian Andes and Amazonia. We have measured the D/H of stem water and leaf water, and we compare these to precipitation isotopes and stream waters. The goal of the plant water studies is to understand plant water uptake and stem-leaf water isotopic offsets which can vary due to both transpiration and foliar uptake of water in tropical montane forests. We are in the process of measuring the D/H of plant biomarkers (n-alkanoic acids, n-alkanes and lignin methoxyl) in order to assess how these water isotopic signals are encoded in plant biomarkers. We compare the species-specific modern plant insights to the plant leaf wax n-alkanoic acid D/H that we have recently reported from soils and river sediments from the same region, in order to understand how signals of plant biogeochemistry are integrated into geological sedimentary archives. Progress and open questions in tropical isotope biogeochemistry will be discussed at the meeting.

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

    Science.gov (United States)

    Suvires, Graciela M.

    2014-11-01

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

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

    Science.gov (United States)

    Cooke, Colin A; Abbott, Mark B

    2008-04-15

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

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

    International Nuclear Information System (INIS)

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

  18. Unexpectedly High Beta-Diversity of Root-Associated Fungal Communities in the Bolivian Andes

    Science.gov (United States)

    Barnes, Christopher J.; Maldonado, Carla; Frøslev, Tobias G.; Antonelli, Alexandre; Rønsted, Nina

    2016-01-01

    Bolivia is one of the most biologically diverse countries on the planet. Between the Andes and the Amazon drainage basin spans the Yungas, a vast forested region shown to be extremely species rich in macro-organisms. However, it remains unclear whether this high diversity is also reflected in microbial diversity. Here we assess the genetic, taxonomic and functional diversity of root-associated fungi surrounding Cinchona calisaya trees, a typical element of the intermediate altitudes of the Bolivian Yungas. We determine the relative effects of edaphic properties, climate, and geography in regulating fungal community assembly. We show that α-diversity for these fungal communities was similar to temperate and arid ecosystems, averaging 90.1 operational taxonomic units (OTUs) per sample, with reads predominantly assigned to the Ascomycota phylum and with a saprotrophic lifestyle. ß-diversity was calculated as the distance-decay rate, and in contrast to α-diversity, was exceptionally high with a rate of −0.407. Soil properties (pH and P) principally regulated fungal community assembly in an analogous manner to temperate environments, with pH and phosphorus explaining 7.8 and 7.2% of community variation respectively. Surprisingly, altitude does not influence community formation, and there is limited evidence that climate (precipitation and temperature) play a role. Our results suggest that sampling should be performed over a wide geographical and environmental range in order to capture the full root-associated fungal diversity in subtropical regions. This study sheds further light on the diversity and distribution of the world's “hidden biodiversity.” PMID:27630629

  19. The Tropical Andes without Snow and Ice - Impacts, Uncertainties and Challenges Ahead

    Science.gov (United States)

    Vuille, M. F.

    2015-12-01

    Climate change has lead to significant glacier retreat in the tropical Andes over the past several decades. Despite the apparent hiatus in warming along the Pacific coast, temperature continues to rise at higher elevations, putting smaller glaciers in lower lying mountain ranges on the verge of complete disappearance. As a result water availability and water quality in glacier-fed river systems will be reduced during the dry season. The lack of a seasonal snow cover in the tropics, which provides for an additional hydrologic buffer in mid-latitude mountain ranges, further exacerbates the situation. Altered precipitation regimes, including changes in total precipitation amount, changes in the rain/snow ratio, or changes in the wet season length will also affect water availability, but projections of these changes are currently fraught with uncertainty. The importance of glacier-fed water supply varies between regions and depends on the presence of other water regulators (reservoirs, wetlands), the length of the dry season and the trajectory of water demand (population growth, expanding economic activities). Here we will review downscaled CMIP5 model results for some of these mountain ranges and discuss the consequences of future warming and projected precipitation changes for the Andean cryosphere, while considering uncertainties associated with downscaling methodology, model dependency and choice of emission scenario. Adaptation strategies will be evaluated in the light of these results, discussing the need to pursue no-regret strategies, when implementing water conservation measures. Lessons learned from past adaptation and capacity building activities in the region will be discussed, emphasizing a) the need to strengthen the institutional standing of authorities involved in glacier research, b) alignment of capacity building and international cooperation with the national and regional needs and c) improvements to long-term climate and glacier monitoring programs

  20. Elevational Ranges of Montane Birds and Deforestation in the Western Andes of Colombia.

    Directory of Open Access Journals (Sweden)

    Natalia Ocampo-Peñuela

    Full Text Available Deforestation causes habitat loss, fragmentation, degradation, and can ultimately cause extinction of the remnant species. Tropical montane birds face these threats with the added natural vulnerability of narrower elevational ranges and higher specialization than lowland species. Recent studies assess the impact of present and future global climate change on species' ranges, but only a few of these evaluate the potentially confounding effect of lowland deforestation on species elevational distributions. In the Western Andes of Colombia, an important biodiversity hotspot, we evaluated the effects of deforestation on the elevational ranges of montane birds along altitudinal transects. Using point counts and mist-nets, we surveyed six altitudinal transects spanning 2200 to 2800 m. Three transects were forested from 2200 to 2800 m, and three were partially deforested with forest cover only above 2400 m. We compared abundance-weighted mean elevation, minimum elevation, and elevational range width. In addition to analysing the effect of deforestation on 134 species, we tested its impact within trophic guilds and habitat preference groups. Abundance-weighted mean and minimum elevations were not significantly different between forested and partially deforested transects. Range width was marginally different: as expected, ranges were larger in forested transects. Species in different trophic guilds and habitat preference categories showed different trends. These results suggest that deforestation may affect species' elevational ranges, even within the forest that remains. Climate change will likely exacerbate harmful impacts of deforestation on species' elevational distributions. Future conservation strategies need to account for this by protecting connected forest tracts across a wide range of elevations.

  1. Elevational Ranges of Montane Birds and Deforestation in the Western Andes of Colombia.

    Science.gov (United States)

    Ocampo-Peñuela, Natalia; Pimm, Stuart L

    2015-01-01

    Deforestation causes habitat loss, fragmentation, degradation, and can ultimately cause extinction of the remnant species. Tropical montane birds face these threats with the added natural vulnerability of narrower elevational ranges and higher specialization than lowland species. Recent studies assess the impact of present and future global climate change on species' ranges, but only a few of these evaluate the potentially confounding effect of lowland deforestation on species elevational distributions. In the Western Andes of Colombia, an important biodiversity hotspot, we evaluated the effects of deforestation on the elevational ranges of montane birds along altitudinal transects. Using point counts and mist-nets, we surveyed six altitudinal transects spanning 2200 to 2800 m. Three transects were forested from 2200 to 2800 m, and three were partially deforested with forest cover only above 2400 m. We compared abundance-weighted mean elevation, minimum elevation, and elevational range width. In addition to analysing the effect of deforestation on 134 species, we tested its impact within trophic guilds and habitat preference groups. Abundance-weighted mean and minimum elevations were not significantly different between forested and partially deforested transects. Range width was marginally different: as expected, ranges were larger in forested transects. Species in different trophic guilds and habitat preference categories showed different trends. These results suggest that deforestation may affect species' elevational ranges, even within the forest that remains. Climate change will likely exacerbate harmful impacts of deforestation on species' elevational distributions. Future conservation strategies need to account for this by protecting connected forest tracts across a wide range of elevations.

  2. In vitro and in vivo activity of ribavirin against Andes virus infection.

    Directory of Open Access Journals (Sweden)

    David Safronetz

    Full Text Available Pathogenic hantaviruses are a closely related group of rodent-borne viruses which are responsible for two distinct diseases in humans, hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome (HPS, otherwise known as hantavirus cardiopulmonary syndrome, HCPS. The antiviral effect of ribavirin against Old World hantaviruses, most notably Hantaan virus, is well documented; however, only a few studies have addressed its inhibitory effect on New World hantaviruses. In the present study, we demonstrate that ribavirin is highly active against Andes virus (ANDV, an important etiological agent of HPS, both in vitro and in vivo using a lethal hamster model of HPS. Treatment of ANDV infected Vero E6 cells with ribavirin resulted in dose-dependent reductions in viral RNA and protein as well as virus yields with a half maximal inhibitory concentration between 5 and 12.5 µg ml(-1. In hamsters, treatment with as little as 5 mg kg(-1 day(-1 was 100% effective at preventing lethal HPS disease when therapy was administered by intraperitoneal injection from day 1 through day 10 post-infection. Significant reductions were observed in ANDV RNA and antigen positive cells in lung and liver tissues. Ribavirin remained completely protective when administered by intraperitoneal injections up to three days post-infection. In addition, we show that daily oral ribavirin therapy initiated 1 day post-infection and continuing for ten days is also protective against lethal ANDV disease, even at doses of 5 mg kg(-1 day(-1. Our results suggest ribavirin treatment is beneficial for postexposure prophylaxis against HPS-causing hantaviruses and should be considered in scenarios where exposure to the virus is probable. The similarities between the results obtained in this study and those from previous clinical evaluations of ribavirin against HPS, further validate the hamster model of lethal HPS and demonstrate its usefulness in screening antiviral agents against

  3. Land Cover Change in the Andes of Southern Ecuador—Patterns and Drivers

    Directory of Open Access Journals (Sweden)

    Giulia F. Curatola Fernández

    2015-03-01

    Full Text Available In the megadiverse tropical mountain forest in the Andes of southern Ecuador, a global biodiversity hotspot, the use of fire to clear land for cattle ranching is leading to the invasion of an aggressive weed, the bracken fern, which is threatening diversity and the provisioning of ecosystem services. To find sustainable land use options adapted to the local situation, a profound knowledge of the long-term spatiotemporal patterns of land cover change and its drivers is necessary, but hitherto lacking. The complex topography and the high cloud frequency make the use of remote sensing in this area a challenge. To deal with these conditions, we pursued specific pre-processing steps before classifying five Landsat scenes from 1975 to 2001. Then, we quantified land cover changes and habitat fragmentation, and we investigated landscape changes in relation to key spatial elements (altitude, slope, and distance from roads. Good classification results were obtained with overall accuracies ranging from 94.5% to 98.5% and Kappa statistics between 0.75 and 0.98. Forest was strongly fragmented due to the rapid expansion of the arable frontier and the even more rapid invasion by bracken. Unexpectedly, more bracken-infested areas were converted to pastures than vice versa, a practice that could alleviate pressure on forests if promoted. Road proximity was the most important spatial element determining forest loss, while for bracken the altitudinal range conditioned the degree of invasion in deforested areas. The annual deforestation rate changed notably between periods: ~1.5% from 1975 to 1987, ~0.8% from 1987 to 2000, and finally a very high rate of ~7.5% between 2000 and 2001. We explained these inconstant rates through some specific interrelated local and national political and socioeconomic drivers, namely land use policies, credit and tenure incentives, demography, and in particular, a severe national economic and bank crisis.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-04-15

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

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

    Science.gov (United States)

    Cooke, Colin A; Abbott, Mark B

    2008-04-15

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

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

    Science.gov (United States)

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

    2016-08-01

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

  7. Stratigraphic and Petrological Constraints of Cretaceous Subduction Initiation and Arc-Continent Collision in the Northern Andes

    Science.gov (United States)

    Leon, S.; Cardona, A.; Mejia, D.; Parra, M.

    2014-12-01

    Middle to Late-Cretaceous orogenic events in the northern Andes have been commonly reconstructed from the analysis of inland basins or the integration of regional scale thermochronological, geochronological and geochemical datasets from the accreted blocks. In contrast, limited studies have been developed on the stratigraphic and deformational record of magmatic and sedimentary sequences exposed near the suture zones. New field and petrologic data are used to characterize an ophiolite type sequence that outcrops in the western flank from the northwestern segment of the Central Cordillera of Colombia. Stratigraphic analysis indicate the existence of Albian-Aptian deep marine pelitic sequence interbedded with minor chert and thin quartz sandstone beds that apparently change to a volcanic dominate stratigraphy. Deformed ophiolite-like mafic and ultramafic plutonic rocks and isolated pillow lavas are also exposed to the east in fault contact with the pelitic sequence. The pelitic and interlayered volcanic rocks represent the growth of an extensional Early-Cretaceous basin that followed a Late-Jurassic magmatic quiescence in the Northern Andes. The volcano-sedimentary record is probably related to the growth of a fore-arc basin in a new subduction zone that extends until the Late Cretaceous. The deformation and obduction of the ophiolitic association and the fore-arc basin were probably triggered by the Late Cretaceous collision with an allocthonous plateau-arc associated to the migration of the Caribbean plate.

  8. Tectonomagmatic characteristics of the back-arc portion of the Calama-Olacapato-El Toro Fault Zone, Central Andes

    Science.gov (United States)

    Acocella, V.; Gioncada, A.; Omarini, R.; Riller, U.; Mazzuoli, R.; Vezzoli, L.

    2011-06-01

    Post-20 Ma magmatism in the Central Andes is either localized in the magmatic arc or distributed east of it, on the Altiplano-Puna Plateau. Here there is a distinct concentration of magmatic centers on NW-SE trending lineaments, such as the Calama-Olacapato-El Toro (COT), that extends into the Eastern Cordillera to the east of the Puna. Understanding the possible genetic relationship between prominent structures and magmatic centers on these lineaments is important to elucidate the tectonomagmatic evolution of the Central Andes. We investigated the back-arc area of the COT using remote sensing, geological, structural, and petrochemical data. Our study demonstrates that this portion of the COT consists of NW-SE striking faults, formed under overall left-lateral transtension that decreases in activity toward the COT termini. Deformation on the COT occurred during and after activity of prominent N-S striking transpressive fault systems and is coeval with magmatism, which is focused on the central COT. The most evolved magmatic rocks, with an upper crustal imprint, are exposed on the central COT, whereas more primitive, mantle-derived mafic to moderately evolved magmatic rocks, are found toward the COT termini. This points to a genetic relationship between upper crustal deformation and magmatic activity that led to enhanced magma storage in the central COT. COT magmas may result either from slab steepening or episodic delamination of the asthenospheric mantle.

  9. Landscape-scale changes in forest structure and functional traits along an Andes-to-Amazon elevation gradient

    Science.gov (United States)

    Asner, G. P.; Anderson, C. B.; Martin, R. E.; Knapp, D. E.; Tupayachi, R.; Sinca, F.; Malhi, Y.

    2014-02-01

    Elevation gradients provide opportunities to explore environmental controls on forest structure and functioning. We used airborne imaging spectroscopy and lidar (light detection and ranging) to quantify changes in three-dimensional forest structure and canopy functional traits in twenty 25 ha landscapes distributed along a 3300 m elevation gradient from lowland Amazonia to treeline in the Peruvian Andes. Elevation was positively correlated with lidar-estimated canopy gap density and understory vegetation cover, and negatively related to canopy height and the vertical partitioning of vegetation in canopies. Increases in canopy gap density were tightly linked to increases in understory plant cover, and larger gaps (20-200 m2) produced 25-30 times the response in understory cover than did smaller gaps (soil increased, with elevation. Scaling of gap size to gap frequency (λ) was, however, nearly constant along the elevation gradient. When combined with other canopy structural and functional trait information, this suggests near-constant canopy turnover rates from the lowlands to treeline, which occurs independent of decreasing biomass or productivity with increasing elevation. Our results provide the first landscape-scale quantification of forest structure and canopy functional traits with changing elevation, thereby improving our understanding of disturbance, demography and ecosystem processes in the Andes-to-Amazon corridor.

  10. Landscape-scale changes in forest structure and functional traits along an Andes-to-Amazon elevation gradient

    Directory of Open Access Journals (Sweden)

    G. P. Asner

    2013-09-01

    Full Text Available Elevation gradients provide opportunities to explore environmental controls on forest structure and functioning, but plot-based studies have proven highly variable due to limited geographic scope. We used airborne imaging spectroscopy and LiDAR (light detection and ranging to quantify changes in three-dimensional forest structure and canopy functional traits in a series of 25 ha landscapes distributed along a 3300 m elevation gradient from lowland Amazonia to treeline in the Peruvian Andes. Canopy greenness, photosynthetic fractional cover and exposed non-photosynthetic vegetation varied as much across lowland forests (100–200 m as they did from the lowlands to the Andean treeline (3400 m. Elevation was positively correlated with canopy gap density and understory vegetation cover, and negatively related to canopy height and vertical profile. Increases in gap density were tightly linked to increases in understory plant cover, and larger gaps (20–200 m2 produced 25–30 times the response in understory cover than did smaller gaps (2. Scaling of gap size to gap frequency was, however, relatively constant along the elevation gradient, which when combined with other canopy structural information, indicates equilibrium turnover patterns from the lowlands to treeline. Our results provide a first landscape-scale quantification of forest structure and canopy functional traits with changing elevation, thereby improving our understanding of disturbance, demography and ecosystem processes in the Andes-to-Amazon corridor.

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

    Science.gov (United States)

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

    2004-06-01

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

  12. Long-Term Single-Dose Efficacy of a Vesicular Stomatitis Virus-Based Andes Virus Vaccine in Syrian Hamsters

    Directory of Open Access Journals (Sweden)

    Joseph Prescott

    2014-01-01

    Full Text Available Andes virus (ANDV is highly pathogenic in humans and is the primary etiologic agent of hantavirus cardiopulmonary syndrome (HCPS in South America. Case-fatality rates are as high as 50% and there are no approved vaccines or specific therapies for infection. Our laboratory has recently developed a replication-competent recombinant vesicular stomatitis virus (VSV-based vaccine that expressed the glycoproteins of Andes virus in place of the native VSV glycoprotein (G. This vaccine is highly efficacious in the Syrian hamster model of HCPS when given 28 days before challenge with ANDV, or when given around the time of challenge (peri-exposure, and even protects when administered post-exposure. Herein, we sought to test the durability of the immune response to a single dose of this vaccine in Syrian hamsters. This vaccine was efficacious in hamsters challenged intranasally with ANDV 6 months after vaccination (p = 0.025, but animals were not significantly protected following 1 year of vaccination (p = 0.090. The decrease in protection correlated with a reduction of measurable neutralizing antibody responses, and suggests that a more robust vaccination schedule might be required to provide long-term immunity.

  13. CENOZOIC EXHUMATION OF THE ANTIOQUEÑO PLATEAU, NORTHERN ANDES, COLOMBIA, FROM APATITE LOW-TEMPERATURE THERMOCHRONOLOGY

    Science.gov (United States)

    Restrepo-Moreno, S. A.; Foster, D. A.; O'Sullivan, P. B.; Donelick, R.; Stockli, D. F.

    2009-12-01

    The Antioqueño plateau (AP), in the northernmost Cordillera Central, Colombia, is the most extensive and best preserved relict surface in the Northern Andes. Apatite (U-Th)/He (AHe) and fission track (AFT) results from twenty two samples, collected from paleocrustal depths along two vertical profiles in canyons dissecting the AP, constrain Cenozoic erosional exhumation of this segment of the Andean range. The two profiles exhibit excellent reproducibility of AHe and AFT data. Helium ages increase with elevation from ~22-49 Ma. A marked inflection point in the AHe age-elevation plots at 25 Ma defines the bottom of the post-Oligocene He partial retention zone (PRZ). Virtually invariant ages at ~25 Ma record onset of rapid exhumation in the AP. A more subtle slope change in the PRZ at ~43 Ma is interpreted as a minor exhumation pulse. AFT better defines timing and intensity of Eocene exhumation. AFT ages for both profiles vary from ~30-49 Ma and are consistently older than AHe ages. AFT data display invariant ages (±2σ) between 1500-2400 m elevations while confined track length data exhibit uni-modal distributions with a mean track length of ~14.2 μm. Both facts indicate rapid cooling. This is further supported by virtually concordant AFT and AHe ages for both profiles between 1500 to 2200 m implying that rocks were exhumed from temperatures >120°C to below AHe closure temperature 60°C. Assuming a geothermal gradient of ~25°C/km this corresponds to exhumation rates in the order of 0.5 mm/y, comparable in intensity to the Miocene pulse defined by AHe. Integrated thermal modeling show an episode of rapid cooling at ~43-49 Ma. AFT profiles show an apparent inflection point at ~1400 m, which defines the upper boundary of an apatite partial annealing zone (PAZ) exhumed during the 43-49 Ma cooling event. The position of the PAZ and PRZ relative to the present erosional surface point to average erosion rates of ~0.03 mm/yr, which constitute very low denudation rates

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

    Science.gov (United States)

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

    2012-12-01

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

  15. Glacial recession in the Tropical Andes from the Little Ice Age: the case of Ampato Volcanic Complex (Southern Peru

    Science.gov (United States)

    Alcalá, J.; Palacios, D.; Zamorano, J. J.

    2010-03-01

    Data published over the last decade reveal substantial glacial recession in the tropical Andes since the Little Ice Age (LIA), (Ramirez, et al., 2001; Rabatel, et al., 2005; Rabatel, et al., 2008; Vuille, et al., 2008; Hastenrath, 2009; Jomelli, et al., 2009), and a growing rate of recession since the 1980’s caused by global warming (Ramirez, et al., 2001; Vuille, et al., 2008). Today there is great interest in the evolution of these ice masses due to heightened awareness of climate change and of the strategic importance that glaciers have as a hydrologic resource for communities in arid climate zones in the tropical Andes (Mark, 2008; Vuille et al., 2008). Cordillera Blanca forms part of the Andes Mountains of northern Peru, and is a chosen site for many studies on glacier evolution. Vuille et al. 2008 determined that a considerable area of ice mass was lost at Huascarán-Chopicalqui glacier (18% from 1920-1970) and Astesonraju glacier (20% from 1962-2003). Studies at Coropuna volcano, which has the most extensive glacier field in the western range of southern Peru, also report a strong melting trend that began with only minimal recession from 1955-1986 (4%), but increased to 14% from 1986-2007 (Úbeda et al., 2009). Only a few of the Andes glaciers are consistently monitored, and the most comprehensive data are for Chacaltaya and Zongo glaciers (16º S) in Bolivia. Since the maximum LIA, Chacaltaya has lost 89% of its surface area, particularly in recent years. By 1983, the totaled loss was five times the shrinkage for the period 1940-1963 (Ramirez, et al., 2001). Zongo glacier maintained equilibrium from 1956-1975, but later experienced a period dominated by continuous recession (Soruco, et al., 2009). This study expands current knowledge of glacier evolution since the LIA in the Central Volcanic Zone (CVZ; 14º - 27º S) (Stern, 2004) of the Andes. The study site was chosen in an area that had never been used for preliminary research of this type, concretely

  16. The Real of Community, the Desire for Development and the Performance of Egalitarianism in the Peruvian Andes: A Materialist–Utopian Account

    NARCIS (Netherlands)

    Vries, de P.A.

    2015-01-01

    The paper proposes a materialist–utopian perspective for explaining the persistence of community in the Andes by drawing upon Lacanian theory and the thought of the Peruvian Marxist José Carlos Mariátegui. What characterizes the Andean comunidad are not notions of belonging and identity, but the exi

  17. The ethno-politics of water security: contestations of ethnicity and gender in strategies to control water in the Andes of Peru

    NARCIS (Netherlands)

    Vera-Delgado, J.

    2011-01-01

    This thesis is the result of a multidisciplinary research which tries to explain water injustices and the threats to water rights access and control experienced by indigenous peasants of the Peruvian Andes. It attempts to contribute to the analysis of the interactions between ethnicity and gender, a

  18. Mallas y flujos : acción colectiva, cambio social, quinua y desarrollo regional indígena en los Andes Bolivianos

    NARCIS (Netherlands)

    Laguna, P.

    2011-01-01

    This thesis studies collective action and social change in indigenous rural organisations (IRO) in the Bolivian Andes. I focus on the effects and importance that these organisations have in the historical process of regional development as social spaces that encapsulate different projects of social,

  19. Killing the snake of poverty : local perceptions of poverty and well-being and people’s capabilities to improve their lives in the Southern Andes of Peru

    NARCIS (Netherlands)

    A. Miyashita

    2009-01-01

    Despite the generalised image of comuneros of the Southern Andes of Peru as living in poverty, a closer examination of the daily lives of the campesinos provides a more dynamic perspective. Some households claim that their lives are improving, others that their lives are the same, while many report

  20. SANREM CRSP LTR4: Adapting to change in the Andes: Practices and strategies to address market and climate risks in vulnerable ecosystems

    OpenAIRE

    Valdivia, Corinne

    2008-01-01

    This presentation describes the work of the SANREM CRSP Long term research activity 4 (LTRA-4), "Adapting to Change in the Andes: Practices and Strategies to Address Market and Climate Risks in Vulnerable Ecosystems." The objectives of the project are to address: LTRA-4 (Practices and Strategies for Vulnerable Agro-Ecosystems)

  1. A new genus of Toads (Amphibia: Anura: Bufonidae) from the Pacific Slopes of the Andes in Northern Ecuador and Southern Colombia, with the description of two new species

    NARCIS (Netherlands)

    Hoogmoed, M.S.

    1985-01-01

    The genus Andinophryne, characterized by the presence of an omosternum, an externally visible tympanum, elongate parotoids and extensively webbed hands and feet is described from the Pacific versant of the Andes in northwestern Ecuador and southwestern Colombia. Two new species, Andinophryne colomai

  2. Paleoclimatic reconstruction in the Bolivian Andes from oxygen isotope analysis of lake sediment cellulose

    International Nuclear Information System (INIS)

    Cellulose-inferred lake water δ18O (δ18Olw) records from Lago Potosi, a seasonally-closed lake in a watershed that is not currently glaciated, and Lago Taypi Chaka Kkota, an overflowing lake in a glaciated watershed, provide the basis for late Pleistocene and Holocene paleoclimatic reconstruction in the Bolivian Andes. Deconvolution of the histories of changing evaporative isotopic enrichment from source water δ18O in the lake sediment records is constrained by comparison to the Sajama ice core oxygen isotope profile. At Lago Potosi, the δ18Olw record appears to be dominantly controlled by evaporative 18O-enrichment, reflecting shifts in local effective moisture. Using an isotope-mass balance model, a preliminary quantitative reconstruction of summer relative humidity spanning the past 11,500 cal yr is derived from the Lago Potosi Π18Olw record. Results indicate that the late Pleistocene was moist with summer relative humidity values estimated at 10-20% greater than present. Increasing aridity developed in the early Holocene with maximum prolonged dryness spanning 7500 to 6000 cal yr BP at Lago Potosi, an interval characterized by summer relative humidity values that may have been 20% lower than present. Highly variable but dominantly arid conditions persist in the mid- to late Holocene, with average summer relative humidity values estimated at 15% below present, which then increase to about 10-20% greater than present by 2000 cal yr BP. Slightly more arid conditions characterize the last millennium with summer relative humidity values ranging from 5-10% lower than present. Similar long-term variations are evident in the Lago Taypi Chaka Kkota δ18Olw profile, except during the early Holocene when lake water evaporative 18Oenrichment in response to low relative humidity appears to have been offset by enhanced inflow from 18O-depleted snowmelt or groundwater from the large catchment. Close correspondence occurs between the isotope-inferred paleohumidity

  3. Chemical Mineralogy, Geochemical Characterization and Petrography of the Cambumbia Stock, Northern Andes, South America, Colombia

    Science.gov (United States)

    Rojas Lequerica, Salvador; María Jaramillo Mejía, José; Concha Perdomo, Ana Elena; Jimenez Quintero, Camilo

    2013-04-01

    The Cambumbia Stock is located on the western flank of the Central Cordillera of the northern Andes, South America. The goals of this study were to characterize the mineral chemistry, the geochemical composition and the petrography of the Cambumbia igneous body and to establish its petrogenesis. We collected 41 samples, selected 28 for thin section petrographic analysis, 14 for whole rock elementary chemical determination by ICP-MS and 4 for chemical mineralogy by LA-ICP(JEOL JXA-8200). Petrographically the samples were classified as 30 % hornblende-gabbro, 30% pyroxene-gabbros, 10% diorites, 10% olivine-gabbro, 7% gabbronorites, 7% tonalities and 3% norite, 3% wehrlite, the rock varies from medium to coarse hipidiomorfic and holocristaline texture, with local microporfiritic texture. Spot elemental chemical analysis of the some minerals in 4 samples show the range of the major elemental composition is plagioclase (labradorite), clinopyroxene (augite), horblende (magnesiohornblende), olivine (fayalite())Chemical mineralogy shows the variety of minerals in this rock, essential minerals correspond to bytownite, augite, magnesio-honblende, fallaite and titanite. We conclude base on the SiO2 Vs Total Alkalis graph that the samples correspond to the sub-alkaline series with low K content, mainly in the calc-alkaline series. By using the SiO2 vs TiO2, Th/Yb vs Ta/Yb and Zr/117-Th-Nb/16 diagrams it was determined that these rocks were generated in two geotectonic environments: one type MOR (extension) and other island arc (subduction, compression). Recently, a U/Pb age was obtained by the Universidad de Caldas in zircon in 2009 (not published data), yielded an age of 233.41 ± 3.4 Ma (Carnian - Upper Triassic). Petrographic geochemical and geochronology comparisons between the rocks of Cambumbia Stock and Diorite and Gabbro El Pueblito (located about 25 km to the north-west) and with U/Pb age 231 ± 8 may postulate a possible genetic link between them. These ages are

  4. Leaf Wax δ13C Varies with Elevation in the Peruvian Andes and Western Amazonia

    Science.gov (United States)

    Wu, M. S.; Feakins, S. J.; Ponton, C.; Peters, T.; West, A. J.; Galy, V.; Bentley, L. P.; Salinas, N.; Shenkin, A.; Martin, R.; Asner, G. P.; Malhi, Y.

    2015-12-01

    Plant leaf wax carbon isotopic composition (δ13Cwax) reflects the net isotopic effects associated with diffusion into the leaf, fixation of carbon by Rubisco and biosynthesis of individual leaf wax biochemicals. As declining pCO2 with elevation affects the first two fractionations, we expect to find an isotopic gradient in δ13Cwax, if the fractionation of leaf wax biosynthesis is constant. To test this, we report δ13Cwax values from 500 samples of leaves collected by tree-climbers from the upper canopy from 9 forest-inventory plots spanning a 3.5km elevation transect in the Peruvian Andes and western Amazonia during the CHAMBASA field campaign. These samples provide a unique opportunity to study the relationship between δ13Cwax and pCO2 in diverse species across this remote tropical montane forest and lowland rainforest. The very wet climate throughout (2-5 m rainfall per year) minimizes fractionation effects due to stomatal restrictions (i.e. water use efficiency) that may be an important factor elsewhere. Preliminary results show δ13Cwax values on average increase with elevation by ~1.5‰/km, a trend consistent with bulk plant δ13C in previous studies. The mean epsilon between bulk and C29 n-alkane is -7.3±2.2‰. Inter-sample differences are large on the order of 10‰. Shaded leaves and understory leaves are found to be depleted relative to sunlit leaves, presumably due to a lower photosynthetic rate and use of respired CO2 in the understory. C29 n-alkanes are on average ~2.5‰ more depleted than C30 n-alkanoic acids, indicating fractionation during selective decarboxylation. We further compare results from plants with soil and river sediments to provide insights into how leaf wax signals are archived in soils and exported from the landscape. We find a ~1.4‰/km gradient in forest soils similar to plants. We observe a ~2‰ offset between C29 n-alkane in plant leaves and in soils across the elevation profile, which is likely a signal of degradation

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

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2004-02-01

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

  6. Poder y sociedad en los Andes: Manuel Isidoro Belzu, un caudillo popular. Bolivia, 1848-1855

    Directory of Open Access Journals (Sweden)

    Luis Javier Ortíz Mesa

    2012-10-01

    Full Text Available Normal 0 21 false false false ES-CO X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} En este ensayo quiero referirme a un gobernante boliviano, Manuel Isidoro Belzu, presidente entre los años de 1848 y 1855. Con una larga carrera militar de casi 25 años, en un ambiente de permanente inestabilidad política y con una fascinante estrategia, Belzu ha sido percibido por algunos historiadores y literatos como un «Caudillo del Pueblo», otros lo calificaron como un demagogo y algunos más como el presidente para la Bolivia de entonces. Manuel Isidoro Belzu nació al tiempo que se vislumbraba la Bolivia Republicana en 1808. Fue un hombre pobre como muchos de sus conciudadanos, predominantemente indígenas. No obstante, Belzu fue un mestizo, expresión de los cambios raciales que desde la Colonia se produjeron en la población de la Audiencia de Charcas cuya sede y capital fue Chuquisaca o Sucre, donde tuvo asiento el emporio minero más importante y productivo de los Andes, el Cerro Rico de Potosí.

  7. The Medieval Climate Anomaly and the Little Ice Age in the eastern Ecuadorian Andes

    Science.gov (United States)

    Ledru, M.-P.; Jomelli, V.; Samaniego, P.; Vuille, M.; Hidalgo, S.; Herrera, M.; Ceron, C.

    2013-02-01

    To better characterize the climate variability of the last millennium in the high Andes, we analyzed the pollen content of a 1150-yr-old sediment core collected in a bog located at 3800 m a.s.l. in the páramo in the eastern Cordillera in Ecuador. An upslope convective index based on the ratio between cloud transported pollen from the Andean forest to the bog (T) and Poaceae pollen frequencies, related to the edaphic moisture of the páramo (P), was defined. This index was used to distinguish changes in the atmospheric moisture from the soil moisture content of the páramo and their associated patterns of interdecadal El Niño-Southern Oscillation (ENSO) variability and South American summer monsoon (SASM) activity. Results show that between 850 and 1250 AD, the Medieval Climate Anomaly interval was warm and moist with a high transported pollen/Poaceae pollen (T/P) index linked to high ENSO variability and weak SASM activity. Between 1250 and 1550 AD, a dry climate prevailed, characterized by an abrupt decrease in the T/P index and therefore no upslope cloud convection, related to lower ENSO variability and with significant impact on the floristic composition of the páramo. During the Little Ice Age, two phases were observed: first, a wet phase between 1550 and 1750 AD linked to low ENSO variability in the Pacific and warm south equatorial Atlantic sea surface temperatures (SSTs) favored the return of a wet páramo, and then a cold and dry phase between 1750 and 1800 AD associated with low ENSO variability and weak SASM activity resulted in drying of the páramo. The current warm period marks the beginning of a climate characterized by high convective activity - the highest in the last millennium - and weaker SASM activity modifying the water storage of the páramo. Our results show that the páramo is progressively losing its capacity for water storage and that the interdecadal variability of both tropical Pacific and Atlantic SSTs matter for Andean climate

  8. The Medieval Climate Anomaly and the Little Ice Age in the eastern Ecuadorian Andes

    Directory of Open Access Journals (Sweden)

    M.-P. Ledru

    2013-02-01

    Full Text Available To better characterize the climate variability of the last millennium in the high Andes, we analyzed the pollen content of a 1150-yr-old sediment core collected in a bog located at 3800 m a.s.l. in the páramo in the eastern Cordillera in Ecuador. An upslope convective index based on the ratio between cloud transported pollen from the Andean forest to the bog (T and Poaceae pollen frequencies, related to the edaphic moisture of the páramo (P, was defined. This index was used to distinguish changes in the atmospheric moisture from the soil moisture content of the páramo and their associated patterns of interdecadal El Niño–Southern Oscillation (ENSO variability and South American summer monsoon (SASM activity. Results show that between 850 and 1250 AD, the Medieval Climate Anomaly interval was warm and moist with a high transported pollen/Poaceae pollen (T/P index linked to high ENSO variability and weak SASM activity. Between 1250 and 1550 AD, a dry climate prevailed, characterized by an abrupt decrease in the T/P index and therefore no upslope cloud convection, related to lower ENSO variability and with significant impact on the floristic composition of the páramo. During the Little Ice Age, two phases were observed: first, a wet phase between 1550 and 1750 AD linked to low ENSO variability in the Pacific and warm south equatorial Atlantic sea surface temperatures (SSTs favored the return of a wet páramo, and then a cold and dry phase between 1750 and 1800 AD associated with low ENSO variability and weak SASM activity resulted in drying of the páramo. The current warm period marks the beginning of a climate characterized by high convective activity – the highest in the last millennium – and weaker SASM activity modifying the water storage of the páramo. Our results show that the páramo is progressively losing its capacity for water storage and that the interdecadal variability of both tropical Pacific and Atlantic SSTs matter for

  9. Application of enzyme leach soil analysis for epithermal gold exploration in the Andes of Ecuador

    Energy Technology Data Exchange (ETDEWEB)

    Williams, T.M.; Gunn, A.G. [British Geological Survey, Nottingham (United Kingdom)

    2002-07-01

    Enzyme Leach (EL) soil surveys were undertaken over known epithermal Au mineralisation at El Mozo and Llano Largo, Azuay, Ecuador to assess the utility of the technique for identifying such deposits in the Ecuadorian Andes. The results indicate the development of both apical- and oxidation-type EL anomalies over auriferous structures at the two sites, the former systematically incorporating Au, and the latter Cl and Br. The spectrum of elements responsive to mineralisation at El Mozo (Cl, Br, I, La, Ce, Nd, Cu, Pb, Au, As, Sb, Ag, Zr, Sr) was found to be considerably greater than at Llano Largo (Cl, Br, Au, As, Sb, Ag, Zn), probably reflecting the contrasting high- and low-sulphidation assemblages of the two prospects. Ratios of EL versus aqua-regia extractable trace element concentrations ranged from 1: < 100 for Mn to 1: >400 for chalcophile elements such as Pb, Sb, As, Bi and Ag. Strong correlations between the concentrations of several analytes (including Mn, Sr, Cu, Co, As) extracted by the two procedures indicate, however, that EL datasets are extensively influenced by bulk matrix composition. Spatial variations of EL extractable Mn were found to exert no major influence on apical or oxidation suite anomaly patterns at El Mozo. However, Mn-normalisation of halogen data for Llano Largo elucidated otherwise obscure oxidation features, potentially related to Au mineralisation. Ratios between elements subject to apical enrichment and those of the oxidation suite (e.g. Cl/Au and Bi/Br) were found to highlight known Au targets with improved clarity. The formation mechanism of the recorded Au anomalies is uncertain, but may involve physical enrichment of Au in the soil during pedogenesis with subsequent in-situ formation of (EL soluble) Au halide complexes. The strength of such apical features is, in part, probably a function of the minimal depths to mineralisation which characterise El Mozo and Llano Largo. Oxidation halos formed by volatile non-metallic elements

  10. The Medieval Climate Anomaly and the Little Ice Age in the Eastern Ecuadorian Andes

    Directory of Open Access Journals (Sweden)

    M.-P. Ledru

    2012-09-01

    Full Text Available To better characterize the climate variability of the last millennium in the high Andes, we analysed the pollen content of a 1100-yr-old sediment core collected in a bog located at 3800 m a.s.l. in the páramo in the Eastern Cordillera in Ecuador. An upslope convective index based on the ratio between cloud transported pollen from the andean forest to the bog (T and Poaceae pollen frequencies, related to the edaphic moisture of the páramo (P, was defined to distinguish the atmospheric moisture from the soil moisture content of the páramo. Results showed that between 900 AD and 1230 AD, the Medieval Climate Anomaly interval was warm and moist with high T/P index linked to a high ENSO variability and a weak South American Summer Monsoon (SASM activity. Between 1230 and 1650 AD, a dry climate prevailed characterized by an abrupt decrease in the T/P index related to lower ENSO variability with significant impact on the floristic composition of the páramo. During the Little Ice Age, two phases were observed, first a wet phase between 1650 and 1750 AD linked to low ENSO variability in the Pacific and warm south equatorial Atlantic SSTs favored the return of a wet páramo, and a cold and dry phase between 1750 and 1810 AD associated with low ENSO variability and weak SASM activity resulting in drying of the páramo. The Current Warm Period marks the beginning of a climate characterized by high convective activity, the highest in the last millennium, and weaker SASM activity modifying the water stock of the páramo. Our results show that the páramo is progressively loosing its capacity for water storage and that the variability of both tropical Pacific and Atlantic SSTs matters for Andean climate patterns although many teleconnection mechanisms are still poorly understood.

  11. Regional distance shear-coupled PL propagation within the northern Altiplano, central Andes

    Science.gov (United States)

    Swenson, Jennifer L.; Beck, Susan L.; Zandt, George

    1999-12-01

    Properties of the shear-coupled P wavetrain (SPL) from regional earthquakes provide important information about the structure of the crust and upper mantle. We investigate broad-band seismic data from intermediate-depth earthquakes and develop a grid search technique using synthetic seismograms to study the sensitivity of SPL and to model the crustal structure of the northern Altiplano, central Andes. Waveforms from an earthquake that occurred on 1994 December 12 within the Nazca slab beneath the Altiplano display a clear SPL wavetrain at the temporary stations deployed during the BANJO and SEDA experiments. We relocate this event and determine the moment tensor by inverting the complete long-period waveforms. With these source parameters fixed, we perform sensitivity analyses using a reflectivity technique to compute synthetic seismograms at a distance of 313 km (BANJO station 2, SALI). We find that, at this distance, the long-period SPL wavetrain is sensitive to the following model parameters, in order of decreasing sensitivity: crustal VP/VS, mantle VP/VS, average crustal velocity, crustal thickness, focal depth, distance (location), crustal Qα and Qβ, and mantle velocity. We develop a grid search method to investigate the four parameters of the crust/upper mantle model to which the synthetic seismograms are most sensitive at SALI (crustal VP/VS, mantle VP/VS, average crustal velocity, crustal thickness). Trade-offs exist among all four of the model parameters, resulting in a range of acceptable crustal models that provide excellent fits between the data and synthetic seismograms in the passband of 15-100 s at a single station. However, by using data at a range of distances (150-450 km) we find that the model that provides the best overall fit between the data and synthetic seismograms, and thus best approximates the average characteristics of the crust and upper mantle structure of the northern Altiplano, is characterized by an average crustal velocity of 6

  12. Variation of the upper mantle velocity structure along the central-south Andes

    Science.gov (United States)

    Liang, Xiaofeng; Sandvol, Eric; Shen, Yang; Gao, Haiying

    2014-05-01

    Variations in the subduction angle of the Nazca plate beneath the South American plate has lead to different modes of deformation and volcanism along the Andean active margin. The volcanic gap between the central and southern Andean volcanic zones is correlated with the Pampean flat-slab subduction zone, where the subducting Nazca slab changes from a 30-degree dipping slab beneath the Puna plateau to a horizontal slab beneath the Sierras Pampeanas, and then to a 30-degree dipping slab beneath the south Andes from north to south. The Pampean flat-slab subduction correlates spatially with the track of the Juan Fernandez Ridge, and is associated with the inboard migration of crustal deformation. A major Pliocene delamination event beneath the southern Puna plateau has previously been inferred from geochemical and geological and preliminary geophysical data. The mechanisms for the transition between dipping- and flat-subduction slab and the mountain building process of the central Andean plateau are key issues to understanding the Andean-type orogenic process. We use a new frequency-time normalization approach with non-linear stacking to extract very-broadband (up to 300 second) empirical Green's functions (EGFs) from continuous seismic records. The long-period EGFs provide the deeper depth-sensitivity needed to constrain the mantle structure. The broadband waveform data are from 393 portable stations of four temporary networks: PUNA, SIEMBRA, CHARGE, RAMP, East Sierras Pampeanas, BANJO/SEDA, REFUCA, ANCORP, and 31 permanent stations accessed from both the IRIS DMC and GFZ GEOFON DMC. A finite difference waveform propagation method is used to generate synthetic seismograms from 3-D velocity model. We use 3-D traveltime sensitivity kernels, and traveltime residuals measurement by waveform cross-correlation to directly invert the upper mantle shear-wave velocity structure. The preliminary model shows strong along-strike velocity variations within in the mantle wedge and

  13. Broadband regional waveform modeling to investigate crustal structure and tectonics of the central Andes

    Science.gov (United States)

    Swenson, Jennifer Lyn

    We use broadband regional waveform modeling of earthquakes in the central Andes to determine seismic properties of the Altiplano crust. Properties of the shear-coupled P-wavetrain (SPL ) from intermediate-depth events provide particularly important information about the structure of the crust. We utilize broadband seismic data recorded at the BANJO and SEDA stations, and synthetic seismograms computed with a reflectivity technique to study the sensitivity of SPL to crustal and upper mantle parameters at regional distances. We find that the long-period SPL-wavetrain is most sensitive to crustal and mantle Poisson's ratios, average crustal velocity, and crustal thickness. A comprehensive grid search method developed to investigate these four parameters suggests that although trade-offs exist between model parameters, models of the Altiplano which provide the best fit between the data and synthetic seismograms are characterized by low Poisson's ratios, low average crustal velocity and thick crust. We apply our grid search technique and sensitivity analysis results to model the full waveforms from 6 intermediate-depth and 2 shallow-focus earthquakes recorded at regional distances by BANJO and SEDA stations. Results suggest that the Altiplano crust is much thicker (55--65 km) and slower (5.75--6.25 km/s) than global average values. Low crustal and mantle Poisson's ratios together with the lack of evidence for a high-velocity lower crust suggests a bulk felsic crustal composition, resulting in an overall weak crust. Our results favor a model of crustal thickening involving large-scale tectonic shortening of a predominantly felsic crust. To better understand the mechanics of earthquake rupture along the South American subduction zone, we have analyzed broadband teleseismic P-waves and utilize single- and multi-station inversion techniques to constrain source characteristics for the 12 November 1996 Peru subduction zone earthquake. Aftershock locations, intensity reports

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

    Directory of Open Access Journals (Sweden)

    Claudia B. Prezzi

    2009-10-01

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

  15. Tomographic imaging of the Nazca slab and surrounding mantle in the mantle transition zone beneath the Central Andes

    Science.gov (United States)

    Scire, A. C.; Biryol, C. B.; Zandt, G.; Beck, S. L.; Wagner, L. S.; Long, M. D.; Minaya, E.; Tavera, H.

    2013-12-01

    The central Andes in South America is an ideal location to investigate the interaction between a subducting slab and the surrounding mantle to the base of the mantle transition zone (MTZ). We used finite-frequency teleseismic P-wave tomography to image velocity anomalies in the mantle from 100 - 700 km between 10° and 28°S in the central Andes by combining data from twelve separate networks deployed in the region between 1994 and 2013. P- and PKIKP- (diffracted PKP) arrivals were picked in multiple frequency bands for earthquakes at distances between 30° and 90° and between 155° to 180° from the array, respectively. The tomographic algorithm used calculates approximate finite frequency kernels for each ray, providing additional sampling for each model layer to potentially increase the resolution of our images. The trench-parallel, fast anomaly which appears to correspond with the subducting Nazca slab is the most prominent anomaly in our tomograms. Variations in the width of the slab anomaly in the deeper parts of the model show evidence for deformation of the slab between 300 and 660 km. Our results show localized thickening of the Nazca slab in the MTZ north of 14°S, between 16° and 18°S, and south of 25°S, in agreement with the idea that the Nazca slab stagnates at least temporarily in the transition zone before resuming subduction into the lower mantle. Our images of the deeply subducted Nazca slab also show evidence of varying degrees of thinning in the mantle transition zone, particularly at 20° and 24°S, possibly indicating that the stress state changes along strike as the slab deforms in the MTZ before resuming subduction into the lower mantle. We also image along-strike variations in the sub-slab mantle in the MTZ including a strong low velocity anomaly between 22° and 28°S which is similar to those seen in other subduction zones, and is interpreted as either a local thermal anomaly or a region of hydrated material in the MTZ. A similar

  16. Direction and timing of uplift propagation in the Peruvian Andes deduced from molecular phylogenetics of highland biotaxa

    Science.gov (United States)

    Picard, Damien; Sempere, Thierry; Plantard, Olivier

    2008-07-01

    Physical paleoaltimetric methods are increasingly used to estimate the amount and timing of surface uplift in orogens. Because the rise of mountains creates new ecosystems and triggers evolutionary changes, biological data may also be used to assess the development and timing of regional surface uplift. Here we apply this idea to the Peruvian Andes through a molecular phylogeographic and phylochronologic analysis of Globodera pallida, a potato parasite nematode that requires cool temperatures and thus thrives above 2.0-2.5 km in these tropical highlands. The Peruvian populations of this species exhibit a clear evolutionary pattern with deeper, more ancient lineages occurring in Andean southern Peru and shallower, younger lineages occurring progressively northwards. Genetically diverging G. pallida populations thus progressively colonized highland areas as these were expanding northwards, demonstrating that altitude in the Peruvian Andes was acquired longitudinally from south to north, i.e. in the direction of decreasing orogenic volume. This phylogeographic structure is recognized in other, independent highland biotaxa, and point to the Central Andean Orocline (CAO) as the region where high altitudes first emerged. Moreover, molecular clocks relative to Andean taxa, including the potato-tomato group, consistently estimate that altitudes high enough to induce biotic radiation were first acquired in the Early Miocene. After calibration by geological and biological tie-points and intervals, the phylogeny of G. pallida is used as a molecular clock, which estimates that the 2.0-2.5 km threshold elevation range was reached in the Early Miocene in southernmost Peru, in the Middle and Late Miocene in the Abancay segment (NW southern Peru), and from the latest Miocene in central and northern Peru. Although uncertainties attached to phylochronologic ages are significantly larger than those derived from geochronological methods, these results are fairly consistent with coeval

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

    Directory of Open Access Journals (Sweden)

    Moisés Arce

    2006-01-01

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

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

    Science.gov (United States)

    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

  19. Diversity of bacteria producing pigmented colonies in aerosol, snow and soil samples from remote glacial areas (Antarctica, Alps and Andes

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    E. González-Toril

    2008-04-01

    Full Text Available Four different communities and one culture of pigmented microbial assemblages were obtained by incubation in mineral medium of samples collected from high elevation snow in the Alps (Mt. Blanc area and the Andes (Nevado Illimani summit, Bolivia, from Antarctic aerosol (French station Dumont d'Urville and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. The phylogenetic comparison with the currently available rDNA database allowed the identification of sequences belonging to Proteobacteria (Alpha-, Beta- and Gamma-proteobacteria, Actinobacteria and Bacteroidetes phyla. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified and the maritime Antarctic soil the poorest (only one. Snow samples from Col du midi (Alps and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones. These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteria clone. The only microorganism identified in the maritime Antarctica soil (Brevundimonas sp. was also detected in the Antarctic aerosol. The two snow samples from the Alps only shared one common microorganism. Most of the identified microorganisms have been detected previously in cold environments (Dietzia kujamenisi, Pseudonocardia Antarctica, Hydrogenophaga palleronii and Brebundimonas sp., marine sediments (Aquiflexus balticus, Pseudomonas pseudoalkaligenes, Pseudomonas sp. and one uncultured Alphaproteobacteria, and soils and rocks (Pseudonocardia sp.,

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

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    Lohengrin A. Cavieres

    2000-06-01

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

  1. Implicaciones criminológicas de los casos legales recibidos en una unidad de Psiquiatría: Resultados preliminares/ Legal cases received in a Psychiatric unit and it’s criminological implications: Preliminary results

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    Odalis Tibisay Parra Izarra (Venezuela

    2014-01-01

    Full Text Available Se realiza un estudio descriptivo de tipo cuantitativo y de carácter retrospectivo, de la frecuencia con la que las instituciones de control social formal refieren “casos legales” a la Unidad de Psiquiatría del Instituto Autónomo Hospital Universitario de Los Andes (IAHULA, en Mérida, Venezuela, desde 1996 hasta el 2009, encontrando un aumento exponencial de estas demandas en el transcurso de los catorce años estudiados, con un total de 2216 referencias, correspondiendo el mayor número al Consejo de Protección del Niño, Niña y Adolescente (CPNNA (55%, como también a quien la Consulta Externa de Psiquiatría le envió el mayor número de respuestas (42%, de igual manera el CPNNA fue la institución con más solicitudes de evaluación psicológica (50,6%. El delito no fue mencionado en la gran mayoría (88,1% de referencias legales de las instituciones de control social formal. Concluyendo que hay pertinencia criminológica en los “casos legales” referidos a la Unidad de Psiquiatría del IAHULA y, se sugiere, que un profesional como el criminólogo clínico, de ser considerado en ambas instancias, pudiera fungir de puente entre la Unidad de Psiquiatría y las instituciones de control social formal. There is realized a descriptive study of quantitative type and of retrospective character, of the frequency with which the institutions of social formal control recount “legal cases” to the Psychiatry Unit of the IAHULA, in Merida, Venezuela, from 1996 until 2009, finding an exponential increase of these demands in the course of fourteen studied years, with a total of 2216 references, corresponding the major number to the Protection Advice of the Child, Girl and Teenager (PACGT (55%, since also to whom the External Consultation of Psychiatry sent the major number of answers (42%, of equal way PACGT it was the Institution with more requests of psychological evaluation (50,6%. The crime was not mentioned in the great majority (88

  2. 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)

    Science.gov (United States)

    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.

  3. Landslides in the Andes and the need to communicate on an interandean level on landslide mapping and research

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    Reginald L Hermanns

    2012-09-01

    Full Text Available Landslides in the Andes are some of the highest natural threats to society with single events killing up to several thousand people. Landslide mapping and landslide research became a more widely spread discipline in geosciences in the Andean countries. However efforts today by far do not match the threat and both more investigations and more mapping activities are needed to support decision makers in land use planning. In this communication we discussed five key issues that we suggest to focus on in upcoming years: Impact of climatic change on landslides occurrence, landslides susceptibility and hazard maps, prediction of megalandslides, seismically triggered landslides, and temporal spatial distribution of mud and debris flows potential.

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

    OpenAIRE

    Coutand, Isabelle

    1999-01-01

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

  5. Procesos de isomorfismo en la Facultad de Administración de la Universidad de los Andes.

    Directory of Open Access Journals (Sweden)

    Alexánder Guzmán Vásquez

    2010-05-01

    Full Text Available En este artículo partimos de los siguientes interrogantes: ¿Ha cambiado la relación entre las facultades de Administración en Colombia y sus profesores en los últimos 15 años? Y si efectivamente ha cambiado ¿por qué se han presentado estos cambios? Buscando respuestas revisamos literatura en teoría organizacional y observamos la experiencia de la Facultad de Administración de la Universidad de los Andes. Gracias a lo anterior planteamos la coexistencia de procesos de isomorfi smo en las organizaciones, la presencia de mecanismos que facilitan el desarrollo de estos procesos y resaltamos la importancia del aprendizaje organizacional para el éxito de los mismos.

  6. A new species of the Pristimantis orestes group (Amphibia: Strabomantidae) from the high Andes of Ecuador, Reserva Mazar.

    Science.gov (United States)

    Guayasamin, Juan M; Arteaga, Alejandro F

    2013-02-21

    We describe a new Pristimantis from La Libertad and Rumiloma, Reserva Mazar, Andes of Southeastern Ecuador, at elevations between 2895-3415 m. This species is assigned to the P. orestes group, from whose members it differs by its small body size (adult males ≤ 18.1 mm; adult females ≤ 23.7 mm), usually reticulated ventral pattern, and visible tympanum. The vocalization of the new species consists of a series of calls; each call is composed by a pulsed, non-modulated note in frequency, and with a dominant frequency of 3122-3171 Hz. A molecular phylogeny based on a fragment of the mitochondrial gene 12S shows that the new species is sister to Pristimantis simonbolivari.

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

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    R. Zech

    2010-10-01

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

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

    Directory of Open Access Journals (Sweden)

    R. Zech

    2011-01-01

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

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

    Science.gov (United States)

    Bookhagen, B.; Strecker, M. R.

    2013-12-01

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

  10. Modelling and monitoring vegetation and evapotranspiration on an anthropogenic grassland succession in the Andes of Ecuador

    Science.gov (United States)

    Silva, B.; Bendix, J.

    2012-04-01

    In the eastern Andes of southern Ecuador the infestation of pasture (mostly C4-grass Setaria sphacelata) by the aggressive bracken fern (Pteridium sp.) still is an unsolved problem. Environmental and exogenous factors and direct plant competition have been hypothesized to drive bracken occurrence. Special attention is given to pasture burning, which stimulates bracken growth, and is common in the relative dry season (Oct-Dec). However, no knowledge is available for a quantitative hypothesis investigation on bracken occurrence under current and future local climate. In this work a modeling approach is presented, in which initial investigations support the application of a two-big-leaf model, and parameterization and model forcing are made with extensive data on physiological traits and on the physical environment. Our main aims here are (i) to show field investigations on a plant scale, which are the basis for a proper model parameterization; and (ii) to provide initialization data, which is based on estimation of green leaf area index from very-high and high resolution optical remote sensing (air-photos and Quickbird images); (iii) to simulate vegetation succession after burn on an experimental site, using in situ climate data and future climate-change scenarios. The modeling approach is based in the main on the vegetation dynamic model called Southern Bracken Competition Model (SoBraCoMo), which has been coupled to a hydrological model written on the catchment model framework (CMF), to simulate soil-vegetation dynamics. Main initialization variables are biochemical parameters (quantum and carboxylation efficiency) and the green leaf area index (green-LAI). Forcing data include soil, leaf and air temperature, soil and air humidity and radiation. The model has been developed and tested on the experimental site (2100 m asl) in the Rio San Francisco Valley, Ecuador. Simulation results on the burn experiment of 2009 showed that stimulation by fire could not boost fern

  11. Evolución tectonomagmática de los Andes bolivianos

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    Néstor Jiménez

    2009-10-01

    Full Text Available Los Andes bolivianos ocuparonuna posición de retroarco durante gran parte del Fanerozoico. En su evoluciónse reconoce una primera etapa, restringida al Paleozoico inferior, en la quehubo una gran transferencia de material sedimentario en la corteza superior, yuna segunda en la que predominó el reciclaje de la masa cortical. A lo largodel Paleozoico inferior, una cuenca marina epicratónica se formó entre elcratón de Amazonia, el macizo Arequipa-Antofalla, y el macizo Pampeanofuncionando inicialmente como cuenca de retroarco y luego como cuenca deantepaís hasta colmatarse en el Paleozoico superior. En este lapso ocurrierontres etapas de deformación: La fase oclóyica (límite Ordovícico-Silúrico decarácter restringido, la fase eohercínica (límite Devónico-Carbonífero, y lafase hercínica (Carbonífero Superior también de influencia areal restringida.En el Mesozoico, se registraron aún breves incursiones marinas antes que en elEoceno comience a edificarse una protocordillera. El solevantamiento general detoda la región centroandina, se inició en el Oligoceno Superior afectando alAltiplano y la Cordillera Oriental actuales. Este solevantamiento ocurrió entres etapas limitadas por la formación de superficies de erosión datadas en 18y 10 Ma. La ladera oeste de la Cordillera Oriental, denominada faja de Huarina,tuvo un rol muy importante en la evolución de la región centroandina. Además decobijar a gran parte del magmatismo de retroarco, en esta faja ocurrió la mayorsubsidencia de la cuenca paleozoica. En esta faja ocurrieron preferentementedurante el Mesozoico, procesos de rifting y de adelgazamiento litosférico. Enel Paleógeno, la faja de Huarinas fue la primera en ser solevantada aislando lacuenca altiplánica del interior del continente, y durante el OligocenoSuperior, se constituyó en el cinturón retrocabalgante del orógeno. Ladeformación en el Altiplano y la Cordillera Oriental concluyó hace 10 Ma cuandose form

  12. Amazon River dissolved load: temporal dynamics and annual budget from the Andes to the ocean.

    Science.gov (United States)

    Moquet, Jean-Sébastien; Guyot, Jean-Loup; Crave, Alain; Viers, Jérôme; Filizola, Naziano; Martinez, Jean-Michel; Oliveira, Tereza Cristina; Sánchez, Liz Stefanny Hidalgo; Lagane, Christelle; Casimiro, Waldo Sven Lavado; Noriega, Luis; Pombosa, Rodrigo

    2016-06-01

    The aim of the present study is to estimate the export fluxes of major dissolved species at the scale of the Amazon basin, to identify the main parameters controlling their spatial distribution and to identify the role of discharge variability in the variability of the total dissolved solid (TDS) flux through the hydrological cycle. Data are compiled from the monthly hydrochemistry and daily discharge database of the "Programa Climatologico y Hidrologico de la Cuenca Amazonica de Bolivia" (PHICAB) and the HYBAM observatories from 34 stations distributed over the Amazon basin (for the 1983-1992 and 2000-2012 periods, respectively). This paper consists of a first global observation of the fluxes and temporal dynamics of each geomorphological domain of the Amazon basin. Based on mean interannual monthly flux calculations, we estimated that the Amazon basin delivered approximately 272 × 10(6) t year(-1) (263-278) of TDS during the 2003-2012 period, which represents approximately 7 % of the continental inputs to the oceans. This flux is mainly made up by HCO3, Ca and SiO2, reflecting the preferential contributions of carbonate and silicate chemical weathering to the Amazon River Basin. The main tributaries contributing to the TDS flux are the Marañon and Ucayali Rivers (approximately 50 % of the TDS production over 14 % of the Amazon basin area) due to the weathering of carbonates and evaporites drained by their Andean tributaries. An Andes-sedimentary area-shield TDS flux (and specific flux) gradient is observed throughout the basin and is first explained by the TDS concentration contrast between these domains, rather than variability in runoff. This observation highlights that, under tropical context, the weathering flux repartition is primarily controlled by the geomorphological/geological setting and confirms that sedimentary areas are currently active in terms of the production of dissolved load. The log relationships of concentration vs discharge have

  13. El alto de Copahue - Pino Hachado y la fosa de Loncopué: un comportamiento tectónico episódico, Andes neuquinos (37º - 39ºS The Copahue-Pino Hachado high and the Loncopuè trough: An episodic tectonic behaviour, Neuquén Andes (37º- 39ºS

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    E. García Morabito

    2005-12-01

    Full Text Available Los Andes de la parte central de Neuquén (38º-39ºS, enmarcados en los Andes Centrales Australes (35º-39ºS, han poseído una cronología de levantamiento similar al resto de los Andes Patagónicos Septentrionales (39º-46ºS construyéndose a través de sucesivas fases de alzamiento en el Cretácico medio, Eoceno medio y Mioceno superior. Sin embargo, se han diferenciado con respecto al resto de los Andes Patagónicos, ubicados hacia el sur, en lo relativo a las distintas fases de relajamiento extensional que han sufrido, tanto en el Oligoceno superior como en el Plio-Cuaternario. Existen evidencias que sugieren un comportamiento episódico de la faja plegada y corrida neuquina dado por regímenes tectónicos compresivos seguidos por estadios de extensión generalizados al menos desde el Cretácico medio. El estudio de dos unidades morfoestructurales desarrolladas entre los 37º y los 39ºS ejemplifican este comportamiento peculiar, el alto de Copahue - Pino Hachado ubicado en la zona limítrofe argentino-chilena y su extensión hacia el norte en territorio chileno, en la laguna de la Laja, y la fosa de Loncopué en el retroarco. El estudio de la estructura miocena a cuaternaria y la descripción detallada de la estratigráfía de este sector cordillerano han aportado un nuevo cuadro de evolución para este sector de los Andes.The Andes located in the central Neuquén (38º-39ºS, which belong to the southern Central Andes (35º-39ºS, have recorded a similar chronology of uplift than the neighbor northern Patagonian Andes (39º-46ºS. Both areas have been formed trough successive phases of contraction in the Late Cretaceous, Middle Eocene and Late Miocene respectively. However, the Neuquén Andes have experienced two discrete phases of orogenic relaxation, during the Late Oligocene and Pliocene-Quaternary, which make then distinctive respect to the area located to the south. Field studies have shown new evidences of an episodic behavior of

  14. Fluctuations of Glaciar Esperanza Norte in the North Patagonian Andes of Argentina during the past 400 yr

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    L. Ruiz

    2011-11-01

    Full Text Available The number of studies of Little Ice Age (LIA glacier fluctuations in Southern South America has increased in recent years but is largely biased towards sites in the South Patagonian Andes. In this paper we present a detailed record of length and areal fluctuations of Glaciar Esperanza Norte (GEN, in the North Patagonian Andes of Argentina, during the past four centuries. The GEN record was reconstructed through the dendro-geomorphological dating of moraines and the analysis of satellite imagery, aerial photographs and documentary material complemented with extensive field surveys. The maximum LIA extent at GEN was associated with an outer moraine dated to the mid 17th century. At least 19 subsequent readvances or standstills evidenced by morainic ridges were identified inside the most extensive LIA moraine. The dating and spacing of these moraines and the additional information available indicate that the ice front retreated much more rapidly during the 20th century than during earlier centuries. Comparison with the record of LIA fluctuations of Glaciar Frías, an ice mass of similar characteristics located 110 km to the north of GEN, shows a similar pattern of recession over the past 400 yr. Both glacier records have the peak LIA event occurring roughly during the same interval and show a minor readvance during the 1970s, but there are still a few discrepancies in the dating of some inner moraines. These differences may be due to local, specific factors or associated with the inherent uncertainties in the dating of the moraines. The chronologies of GEN and Frías are among the most detailed currently available in Patagonia, but a larger number of study sites is needed to develop robust, regionally representative glacier chronologies. Detailed glaciological, geomorphological and meteorological data are also needed to understand the glacier-climate relationships in this region and develop reliable paleoclimatic reconstructions.

  15. Cenozoic uplift of the Central Andes in northern Chile and Bolivia - reconciling paleoaltimetry with the geological evolution.

    Science.gov (United States)

    Lamb, S. H.

    2015-12-01

    The Cenozoic geological evolution of the Central Andes, along two transects between ~17.5°S and 21°S, is compared with paleo-topography, determined from published paleo-altimetry studies. Surface and rock uplift are quantified using simple 2-D models of crustal shortening and thickening, together with estimates of sedimentation, erosion and magmatic addition. Prior to ~25 Ma, during a phase of amagmatic flat-slab subduction, thick skinned crustal shortening and thickening was focused in the Eastern and Western Cordilleras, separated by a broad basin up to 300 km wide and close to sea level, which today comprises the high Altiplano. Surface topography in the Eastern Cordillera appears to be ~1 km lower than anticipated from crustal thickening, which may be due to the pull-down effect of the subducted slab, coupled to the overlying lithosphere by a cold mantle wedge. Oligocene steepening of the subducted slab is indicated by the initiation of the volcanic arc at ~27 - 25 Ma, and widespread mafic volcanism in the Altiplano between 25 and 20 Ma. This may have resulted in detachment of mantle lithosphere and possibly dense lower crust, triggering 1 - 1.5 km of rapid uplift (over Altiplano and western margin of the Eastern Cordillera and establishing the present day lithospheric structure beneath the high Andes. Since ~25 Ma, surface uplift has been the direct result of crustal shortening and thickening, locally modified by the effects of erosion, sedimentation and magmatic addition from the mantle. The rate of crustal shortening and thickening varies with location and time, with two episodes of rapid shortening in the Altiplano, lasting < 5 Myrs, that are superimposed on a long term history of ductile shortening in the lower crust, driven by underthrusting of the Brazilian Shield on the eastern margin.

  16. Spatiotemporal characteristics and synchronization of extreme rainfall in South America with focus on the Andes Mountain range

    Science.gov (United States)

    Boers, Niklas; Bookhagen, Bodo; Marwan, Norbert; Kurths, Jürgen

    2016-01-01

    The South American Andes are frequently exposed to intense rainfall events with varying moisture sources and precipitation-forming processes. In this study, we assess the spatiotemporal characteristics and geographical origins of rainfall over the South American continent. Using high-spatiotemporal resolution satellite data (TRMM 3B42 V7), we define four different types of rainfall events based on their (1) high magnitude, (2) long temporal extent, (3) large spatial extent, and (4) high magnitude, long temporal and large spatial extent combined. In a first step, we analyze the spatiotemporal characteristics of these events over the entire South American continent and integrate their impact for the main Andean hydrologic catchments. Our results indicate that events of type 1 make the overall highest contributions to total seasonal rainfall (up to 50 %). However, each consecutive episode of the infrequent events of type 4 still accounts for up to 20 % of total seasonal rainfall in the subtropical Argentinean plains. In a second step, we employ complex network theory to unravel possibly non-linear and long-ranged climatic linkages for these four event types on the high-elevation Altiplano-Puna Plateau as well as in the main river catchments along the foothills of the Andes. Our results suggest that one to two particularly large squall lines per season, originating from northern Brazil, indirectly trigger large, long-lasting thunderstorms on the Altiplano Plateau. In general, we observe that extreme rainfall in the catchments north of approximately 20°S typically originates from the Amazon Basin, while extreme rainfall at the eastern Andean foothills south of 20°S and the Puna Plateau originates from southeastern South America.

  17. Spatiotemporal variability of modern precipitation δ18O in the central Andes and implications for paleoclimate and paleoaltimetry estimates

    Science.gov (United States)

    Fiorella, Richard P.; Poulsen, Christopher J.; Pillco Zolá, Ramiro S.; Barnes, Jason B.; Tabor, Clay R.; Ehlers, Todd A.

    2015-05-01

    Understanding the patterns of rainfall isotopic composition in the central Andes is hindered by sparse observations. Despite limited observational data, stable isotope tracers have been commonly used to constrain modern-to-ancient Andean atmospheric processes, as well as to reconstruct paleoclimate and paleoaltimetry histories. Here, we present isotopic compositions of precipitation (δ18Op and δDp) from 11 micrometeorological stations located throughout the Bolivian Altiplano and along its eastern flank at ~21.5°S. We collected and isotopically analyzed 293 monthly bulk precipitation samples (August 2008 to April 2013). δ18Op values ranged from -28.0‰ to 9.6‰, with prominent seasonal cycles expressed at all stations. We observed a strong relationship between the δ18Op and elevation, though it varies widely in time and space. Constraints on air sourcing estimated from atmospheric back trajectory calculations indicate that continental-scale climate dynamics control the interannual variability in δ18Op, with upwind precipitation anomalies having the largest effect. The impact of precipitation anomalies in distant air source regions to the central Andes is in turn modulated by the Bolivian High. The importance of the Bolivian High is most clearly observed on the southern Bolivian Altiplano. However, monthly variability among Altiplano stations can exceed 10‰ in δ18Op on the plateau and cannot be explained by elevation or source variability, indicating a nontrivial role for local scale effects on short timescales. The strong influence of atmospheric circulation on central Andean δ18Op requires that paleoclimate and paleoaltimetry studies consider the role of South American atmospheric paleocirculation in their interpretation of stable isotopic values as proxies.

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

    Science.gov (United States)

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

    2014-06-01

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

  19. GOCE satellite derived gravity and gravity gradient corrected for topographic effect in the South Central Andes region

    Science.gov (United States)

    Álvarez, Orlando; Gimenez, Mario; Braitenberg, Carla; Folguera, Andres

    2012-08-01

    Global gravity field models, derived from satellite measurements integrated with terrestrial observations, provide a model of the Earth's gravity field with high spatial resolution and accuracy. The Earth Gravity Model EGM08, a spherical harmonic expansion of the geopotential up to degree and order 2159, has been used to calculate two functionals of the geopotential: the gravity anomaly and the vertical gravity gradient applied to the South Central Andes area. The satellite-only field of the highest resolution has been developed with the observations of satellite GOCE, up to degree and order 250. The topographic effect, a fundamental quantity for the downward continuation and validation of satellite gravity gradiometry data, was calculated from a digital elevation model which was converted into a set of tesseroids. This data is used to calculate the anomalous potential and vertical gravity gradient. In the Southern Central Andes region the geological structures are very complex, but not well resolved. The processing and interpreting of the gravity anomaly and vertical gradients allow the comparison with geological maps and known tectonic structures. Using this as a basis, a few features can be clearly depicted as the contact between Pacific oceanic crust and the Andean fold and thrust belt, the seamount chains over the Oceanic Nazca Plate, and the Famatinian and Pampean Ranges. Moreover the contact between the Rio de la Plata craton and the Pampia Terrain is of great interest, since it represents a boundary that has not been clearly defined until now. Another great lineament, the Valle Fertil-Desaguadero mega-lineament, an expression of the contact between Cuyania and Pampia terranes, can also be clearly depicted. The authors attempt to demonstrate that the new gravity fields can be used for identifying geological features, and therefore serve as useful innovative tools in geophysical exploration.

  20. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils

    Directory of Open Access Journals (Sweden)

    Eduardo B. Olivero

    2009-04-01

    Full Text Available The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul, Maorites sp., and Pachydiscus (Neodesmoceras sp. to further constrain the Cretaceous stratigraphy of the eastern Fuegian Andes. In addition, new records of distinctive trace fossils and ichnofabric are meaningful for stratigraphic division and delineation of paleoenvironmental settings in these Cretaceous mudstones. The Lower Cretaceous ichnoassemblage of Chondrites targioni (Brongniart and Zoophycos isp. is consistent with the inferred slope-volcaniclastic apron settings of the Yahgan Formation; Nereites missouriensis (Weller reflects distal basin plain depositional settings for the Beauvoir Formation. In the Upper Cretaceous, the "Estratos de Buen Suceso" record the earliest extensively bioturbated horizons, reflecting prolonged well-oxygenated bottom conditions. In the Bahía Thetis Formation, organic-rich, channel margin or distal basin slaty mudstones record the last occurrence of inoceramid bivalves in the Austral Basin; the generalized absence of trace fossils is consistent with dysoxic bottom conditions. The thoroughly bioturbated Policarpo Formation, records a marked change in paleoceanographic conditions. The strong contrast in the intensity of bioturbation between the Upper Campanian-Maastrichtian Bahía Thetis Formation, almost devoid of trace fossils, and the highly bioturbated Maastrichtian-Danian Policarpo Formation reflects a change from dysoxic-anoxic to well ventilated conditions, probably associated with a cooling trend of bottom waters in the austral deep oceans.

  1. Evaluación del estado de conservación de los bosques montanos en los Andes tropicales

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    N. Tejedor Garavito

    2012-01-01

    Full Text Available Los Andes tropicales constituyen una región única con una alta diversidad de hábitats, producto de complejos gradientes espaciales y ambientales. Los bosques montanos de esta región son considerados como una prioridad global de conservación, debido principalmente a su elevada riqueza biológica y de endemismos. Sin embargo su biodiversidad es de las menos conocidas de toda la región tropical, aunque se reconoce la amplia gama de servicios ambientales que prestan, incluyendo la regulación del clima regional y la captura y almacenamiento de carbono. Este artículo ofrece una perspectiva general del estado de conservación de los bosques montanos tropicales andinos y de los retos que esta implica. Asimismo, proporciona información sobre sus amenazas, identificando aquéllas que con mayor probabilidad sean responsables de aumentar el riesgo de extinción de especies. Se resalta la necesidad de disponer de más información sobre el estado de conservación de las especies para identificar las futuras prioridades de conservación en la región. La reciente iniciativa de la "Lista Roja y planeación para la conservación de especies de árboles montanos de los Andes Tropicales", formada por delegados de varios países de la región, constituirá una sólida base para el desarrollo y enfoque de políticas y respuestas de manejo dirigidas a la reducción de la deforestación y pérdida de especies en estos bosques, incluyendo acciones para promover la creación de áreas protegidas, restauración forestal y manejo forestal sostenible.

  2. The Plutón Diorítico Moat: Mildly alkaline monzonitic magmatism in the Fuegian Andes of Argentina

    Science.gov (United States)

    González Guillot, M.; Escayola, M.; Acevedo, R.; Pimentel, M.; Seraphim, G.; Proenza, J.; Schalamuk, I.

    2009-12-01

    The Plutón Diorítico Moat (Moat Dioritic Pluton, PDM) is the largest of several isolated Cretaceous plutons exposed in the Fuegian Andes of Argentina. It is made of a large variety of rock types ranging from ultramafic bodies (pyroxenites and hornblendites) to syenites. The petrological diversity is thought to have been originated by fractional crystallization of a mantle-derived magma combined with minor assimilation of continental crust (AFC). Its geochemical characteristics indicate a mildly-alkaline monzonitic affinity, contrasting with the typical calc-alkaline plutons of the Southern Patagonian Batholith (PB) to the south, in the Chilean archipelago. The PDM original magma is arc-related and its crystallization, as indicated by the Rb-Sr mineral isochron age of 115 ± 3 Ma, is coeval with some plutons of the PB. Therefore a similar tectonic regime is assumed for the emplacement of these plutonic bodies, both south and north of the Beagle channel. Differences in magma sources and degree of partial melting are inferred to account for the contrasting lithological and geochemical characteristics of the PB and PDM. The data suggest that the original magmas of the PDM were generated at greater depths in the mantle, by a smaller degree of partial melting, compared with the PB. The Barros Arana basalts, exposed to the north in Chile, forming a back-arc volcanic complex, display the same mildly-alkaline shoshonitic affinity, and are considered in this study as the volcanic equivalents of the PDM. All the plutons in the Argentinean Fuegian Andes display similar lithological and geochemical characteristics and are, therefore, grouped in this work under the name of Magmatismo Potásico Fueguino ( Fuegian Potassic Magmatism).

  3. Observational evidences on the modulation of the South American Low Level Jet east of the Andes according the ENSO variability

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    G. A. M. Silva

    2009-02-01

    Full Text Available The differences on the phase and wavelength of the quasi-stationary waves over the South America generated by El Niño (EN and La Niña (LN events seem to affect the daily evolution of the South American Low Level Jet east of the Andes (SALLJ. For the austral summer period of 1977–2004 the SALLJ episodes detected according to Bonner criterion 1 show normal to above-normal frequency in EN years, and in LN years the episodes show normal to below-normal frequency.

    During EN and LN years the SALLJ episodes were associated with positive rainfall anomalies over the La Plata Basin, but more intense during LN years. During EN years the increase in the SALLJ cases were associated to intensification of the Subtropical Jet (SJ around 30° S and positive Sea Level Pressure (SLP anomalies over the western equatorial Atlantic and tropical South America, particularly over central Brazil. This favored the intensification of the northeasterly trade winds over the northern continent and it channeled by the Andes mountain to the La Plata Basin region where negative SLP are found. The SALLJ cases identified during the LN events were weaker and less frequent when compared to those for EN years. In this case the SJ was weaker than in EN years and the negative SLP anomalies over the tropical continent contributed to the inversion of the northeasterly trade winds. Also a southerly flow anomaly was generated by the geostrophic balance due to the anomalous blocking over southeast Pacific and the intense cyclonic transient over the southern tip of South America. As result the warm tropical air brought by the SALLJ encounters the cold extratropical air from the southerly winds over the La Plata basin. This configuration can increase the conditional instability over the La Plata basin and may explain the more intense positive rainfall anomalies in SALLJ cases during LN years than in EN years.

  4. Late Cretaceous-early Eocene counterclockwise rotation of the Fueguian Andes and evolution of the Patagonia-Antarctic Peninsula system

    Science.gov (United States)

    Poblete, F.; Roperch, P.; Arriagada, C.; Ruffet, G.; Ramírez de Arellano, C.; Hervé, F.; Poujol, M.

    2016-02-01

    The southernmost Andes of Patagonia and Tierra del Fuego present a prominent arc-shaped structure: the Patagonian Bend. Whether the bending is a primary curvature or an orocline is still matter of controversy. New paleomagnetic data have been obtained south of the Beagle Channel in 39 out of 61 sites. They have been drilled in Late Jurassic and Early Cretaceous sediments and interbedded volcanics and in mid-Cretaceous to Eocene intrusives of the Fuegian Batholith. The anisotropy of magnetic susceptibility was measured at each site and the influence of magnetic fabric on the characteristic remanent magnetizations (ChRM) in plutonic rocks was corrected using inverse tensors of anisotropy of remanent magnetizations. Normal polarity secondary magnetizations with west-directed declination were obtained in the sediments and they did not pass the fold test. These characteristic directions are similar to those recorded by mid Cretaceous intrusives suggesting a remagnetization event during the normal Cretaceous superchron and describe a large (> 90°) counterclockwise rotation. Late Cretaceous to Eocene rocks of the Fueguian Batholith, record decreasing counterclockwise rotations of 45° to 30°. These paleomagnetic results are interpreted as evidence of a large counterclockwise rotation of the Fueguian Andes related to the closure of the Rocas Verdes Basin and the formation of the Darwin Cordillera during the Late Cretaceous and Paleocene. The tectonic evolution of the Patagonian Bend can thus be described as the formation of a progressive arc from an oroclinal stage during the closure of the Rocas Verdes basin to a mainly primary arc during the final stages of deformation of the Magallanes fold and thrust belt. Plate reconstructions show that the Antarctic Peninsula would have formed a continuous margin with Patagonia between the Early Cretaceous and the Eocene, and acted as a non-rotational rigid block facilitating the development of the Patagonian Bend.

  5. The interaction between parent material, climate and volcanism as the major soil forming factor in the Ecuadorian high Andes region

    Science.gov (United States)

    Buytaert, W.; Duyck, H.; Dercon, G.; Deckers, J.; Wyseure, G.

    2003-04-01

    The high Andes region of Ecuador and Colombia (>3500m a.s.l.) is covered by the so-called páramo ecosystem, characterised by a cold climate, a typical grass or small shrub vegetation and volcanic soils. Soil profiles of the paramo in the Austro Ecuatoriano, South Ecuador, were studied in order to reveal genetic relationships with geology, volcanic ash deposits, climate and land use. A gradual diminuation of Andic properties was found, related to the distance of the pedon to the active volcanoes of the Northern Volcanic Zone of the Andes. Pedons in the north of the region, closer to these volcanoes (Sangay, Tungurahua) are classified as non-allophanic Histic Andosols. The influence of the vicinity of the volcanoes leads to a higher oxalate extractable aluminium and iron. The genesis of the Andosols seems to be strongly related to the presence and thickness of volcanic ash depositions. The limit of these depositions is situated south of the city of Cuenca. Pedons further to the south are classified as Histosols. However, they also have clear Andic properties. Several differences in chemical properties between the Western and Eastern cordilleras where found, that are most probable related with a difference in mother material, and maybe also a different climatic regime. Correlation of the chemical properties with land use reveals that no chemical differences can be found that are invoked by occupying natural Andosols for agricultural purposes, within the first five years of cultivation. At last, the conclusions were used to revisit the World Reference Base for Soil Resources in order to sharpen up differenciation between Andosols and Histosols.

  6. Determinación de procesos y áreas de riesgos en los Andes centrales de Chile mediterráneo: Casos de estudio

    Directory of Open Access Journals (Sweden)

    Quintanilla, Víctor

    1994-12-01

    Full Text Available ln the course of the Mountain Hazards Mapping Project in the Central Andes from Chile (Project FONDECYT Nº 482-91 natural hazards were assessed and mapped in the Aconcagua Bassin Test area of the high Andes (2.500 to 4.000 m.. Various geomorphic hazard processes (avalanches, rockfalls, landslide hazards, water activity were mapped on the scale 1:50.000 with a simplified legend. The mountainous area seems to be relatively stable and the rock substratum (mainly granitic is resistant to weathering. The greatest hazards are avalanches and landslides, which have a long recurrence interval and are difficult to predict, although their source areas can be identified.

    [es] Durante la realización del proyecto de Cartografía de Riesgos de Montaña en los Andes Centrales de Chile (Proyecto FONDECYT nº 482- 91 se cartografiaron los riesgos naturales en la cuenca del Aconcagua, altos Andes (2.500 a 4.000 m. Varios riesgos geomorfológicos (avalanchas, caídas de piedras, erosión hídrica fueron cartografiados a escala 1:50.000 con una leyenda simplificada. Las áreas de montaña parecen relativamente estables y el sustrato rocoso (principalmente granítico es resistente a la meteorización.
    Los mayores riesgos son las avalanchas y los deslizamientos, que tienen un largo periodo de recurrencia y son difíciles de predecir, aunque sus áreas fuente pueden ser fácilmente identificadas.
    [fr] Durant la réalisation du projet de cartographie des risques de montagne dans les Andes Centrales du Chili (Projet FONDECYT nº 482-91 on a réalisé des cartographies des risques naturels dans le bassin de Aconcagua, Hautes Andes (2500 à 4000 m. Des risques géomorphologiques variés (avalanches, chutes de pierres, érosion hydrique ont été représentés au 1:50.000ième avec une légende simplifiée. Les zones de montagne paraissent relativement stables et la roche mère (principalement granitique est résistante à la d

  7. Review article of the current state of glaciers in the tropical Andes: a multi-century perspective on glacier evolution and climate change

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    A. Rabatel

    2012-07-01

    Full Text Available The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the LIA (mid 17th–early 18th century. In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the computed global average. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from −0.2 m w.e. in the period 1964–1975 to −0.76 m w.e. in the period 1976–2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that as a percentage, this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia showed that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance variability at the interannual to decadal time scale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession. On the other hand, temperature increased at a significant rate of 0.10 °C decade−1 in the last 70 yr. The higher frequency of El Niño events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the

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

    Directory of Open Access Journals (Sweden)

    A. G. Martínez

    2008-04-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-10-01

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

  10. Spatio-temporal variability of snow water equivalent in the extra-tropical Andes Cordillera from distributed energy balance modeling and remotely sensed snow cover

    OpenAIRE

    E. Cornwell; Molotch, N. P.; McPhee, J

    2016-01-01

    Seasonal snow cover is the primary water source for human use and ecosystems along the extratropical Andes Cordillera. Despite its importance, relatively little research has been devoted to understanding the properties, distribution and variability of this natural resource. This research provides high-resolution (500 m), daily distributed estimates of end-of-winter and spring snow water equivalent over a 152 000 km2 domain that includes the mountainous reaches of central Chi...

  11. Spatio-temporal variability of snow water equivalent in the extra-tropical Andes cordillera from a distributed energy balance modeling and remotely sensed snow cover

    OpenAIRE

    E. Cornwell; Molotch, N. P.; McPhee, J

    2015-01-01

    Seasonal snow cover is the primary water resource precursor for human use and environmental sustain along the extratropical Andes Cordillera. Despite its importance, relatively little research has been devoted to understanding the properties, distribution and variability of this natural resource. This research provides high-resolution distributed estimates of end-of-winter and spring snow water equivalent over a 152 000 km2 domain that includes the mountainous reaches of ...

  12. Assessment of the Impacts of Climate Change on Mountain Hydrology : Development of a Methodology through a Case Study in the Andes of Peru

    OpenAIRE

    Vergara, Walter; Deeb, Alejandro; Leino, Irene; Kitoh, Akio; Escobar, Marisa

    2011-01-01

    The objective of study of the impacts of climate change on mountain hydrology is to develop a methodology to assess the net impacts of climate change on the hydrological response in mountainous regions. This is done through a case study in the Peruvian Andes. There are few examples of predictions of the impact of climate change on resource availability and even fewer examples of the applic...

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

    OpenAIRE

    Monnier, S.; C. Kinnard

    2016-01-01

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

  14. 40Ar/39Ar ages from blueschists of the Jambaló region, Central Cordillera of Colombia : implications on the styles of accretion in the Northern Andes

    OpenAIRE

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

    2011-01-01

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

  15. Extension of the analytic nodal diffusion solver ANDES to triangular-Z geometry and coupling with COBRA-IIIc for hexagonal core analysis.

    OpenAIRE

    Lozano Montero, Juan Andrés; Jiménez Escalante, Javier; García Herranz, Nuria; Aragonés Beltrán, José María

    2010-01-01

    In this paper the extension of the multigroup nodal diffusion code ANDES, based on the Analytic Coarse Mesh Finite Difference (ACMFD) method, from Cartesian to hexagonal geometry is presented, as well as its coupling with the thermal–hydraulic (TH) code COBRA-IIIc for hexagonal core analysis. In extending the ACMFD method to hexagonal assemblies, triangular-Z nodes are used. In the radial plane, a direct transverse integration procedure is applied along the three directions that are orthog...

  16. Le lait des Andes vaut-il de l'or ? Logiques paysannes et insertion marchande de la production fromagère andine

    OpenAIRE

    Aubron, Claire

    2006-01-01

    In Peru, milk and farm cheese made from it both participate in elaborating the agricultural income of numerous Andean peasant families. Based upon a detailed study of the adoption of this dairy orientation by a peasant community of the western side of the central Andes, this thesis explores the issue of Andean dairy farming, using the methodological frame of Compared Agriculture. In the dry and uneven mountainous environment of the area, setting-up irrigation systems allowed landowners that l...

  17. Distribución y conservación de especies amenazadas en Mesoamérica, Chocó y Andes tropicales Distribution and conservation of endangered species in Mesoamerica, Chocó and Tropical Andes

    Directory of Open Access Journals (Sweden)

    María Cecilia Londoño-Murcia

    2011-09-01

    Full Text Available En este estudio se modeló el nicho ecológico proyectado como distribución potencial de 313 especies amenazadas en Mesoamérica, Chocó y los Andes tropicales, según las listas de la UICN. De estas especies, 285 fueron plantas y 28 fueron vertebrados terrestres. La superposición de las distribuciones de las especies amenazadas cubrió prácticamente toda la región. Ecuador mostró cerca del 30% de su área con 50 especies. Colombia, Costa Rica, Guatemala, Nicaragua y Panamá mostraron > 50, aunque en 50% de su área. El Salvador y Honduras, de 11 a 20 en > 50% de su área y México de 1 a 5 especies en > 50% de su área. La distribución de estas especies en áreas transformadas (agricultura y áreas urbanas varió del 11al 30%; El Salvador, Panamá y Guatemala mostraron > 50% de la distribución; Colombia, Honduras y México This study modeled ecological niches projected as potential distributions for 313 endangered species listed in the IUCN for Mesoamerica, Chocó and Tropical Andes, of which 285 were plants, and 28 terrestrial vertebrates. Overlapping of endangered species distributions covered most of the region. Ecuador showed close to 30% of its area with 50 endangered species. Colombia, Costa Rica, Guatemala, Nicaragua y Panama showed more than 50 endangered species in 50% of its area with endangered species (21 to 50 species were Costa Rica, Ecuador, Nicaragua and Panama. El Salvador and Honduras showed > 50% of its area with 11 to 20 endangered species; Mexico showed 50% of endangered species in transformed areas; Colombia, Honduras and Mexico showed < 40%, and Belize and Ecuador showed < 25% of endangered species in transformed areas, respectively. El Salvador, Honduras, Panama, Nicaragua and Mexico showed a high proportion of endangered species in transformed areas for the Classes Amphibia, Liliopsida, Polipodiopsida, and the Orders Asterales, Fabales, Laurales, Myrtales, Scrophulariales and Rubiales. Less than 35% of endangered

  18. Religión, género y construcción de una sexualidad en los Andes (Siglos XVI y XVII. Una acercamiento provisional

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    Armas Asin, Fernando

    2001-12-01

    Full Text Available This study emphasizes the conceptual changes in regard to sex, sexuality and general genre relations in the Andes, in the 16th and 17th centuries, in the context of the establishment of the colonial society. It is analyzed the way in which a new discourse on the body was developed as a consequence of the deeply represive baroque culture. This culture recreated religious values which controlled every aspect of the daily life. It also enforced a rigid legislation which ruled through society as a whole.

    El estudio busca enfatizar los cambios conceptuales que se produjeron en torno al sexo, la sexualidad, y, en términos generales, en las relaciones de género en los Andes en los siglos XVI y XVII, en un contexto de establecimiento de la sociedad colonial. Se analiza cómo se construyó un nuevo discurso sobre el cuerpo en los Andes como consecuencia de la cultura barroca, profundamente represiva. Dicha cultura recreó valores religiosos que controlaban todos los aspectos de la vida diaria, además de poner en marcha una legislación muy rígida que reguló toda la sociedad.

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

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    JOHN H. CAROTHERS

    2001-09-01

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

  20. Breeding system of Embothrium coccineum (Proteaceae in two populations on different slopes of the Andes Sistema reproductivo de Embothrium coccineum (Proteaceae en dos poblaciones ubicadas en diferentes laderas de los Andes

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    ADRIANA E ROVERE

    2006-06-01

    Full Text Available Plant breeding systems are considered to reflect species' life history characteristics, selection due to biotic or abiotic factors, pollination conditions, or a combination of these. Reproductive systems may vary over ecological gradients. The breeding system of the ornithophilous Embothrium coccineum (Proteaceae from temperate South America was studied by pollination treatments: manual self-pollination, manual cross-pollination, automatic self-pollination, and natural pollination. These treatments were conducted in a coastal western and an Andean eastern population. Embothrium coccineum was found to be self-incompatible and highly dependent on the pollinating agent at both sites. However, pollen limitations were greater in the coastal population, as breeding efficiency was lower. Populations have different floral visitors whose identity differentially affects reproductive efficiency and pollen flow in E. coccineumLos sistemas de compatibilidad reproductiva en las plantas son considerados una manifestación de la historia de vida, de la selección ante factores abióticos ó bióticos, de las condiciones de polinización o una de combinación de esos factores. El sistema reproductivo de una especie puede variar a lo largo de un gradiente ecológico-ambiental. El sistema reproductivo de Embothrium coccineum (Proteaceae, un árbol ornitófilo endémico de los bosques templados de sur de Sudamérica, fue estudiado mediante experimentos de polinización: autopolinización manual, polinización manual cruzada, autopolinización automática y polinización natural en flores descubiertas. Este trabajo se realizó en una población costera al oeste de la cordillera de los Andes y una población andina ubicada al este de la cordillera de los Andes. En ambas poblaciones se encontró que E. coccineum es autoimcompatible y altamente dependiente de los agentes polinizadores en ambos sitios. Sin embargo, la limitación por polen fue mayor en la poblaci

  1. Aplicación de tres índices bióticos en el río San Juan, Andes, Colombia (Application of three biotic indexes in the river San Juan, Andes, Colombia

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    Mailedt Paola Murillo Torrentes

    2016-09-01

    Full Text Available Durante los meses de febrero, mayo, agosto y octubre del año 2014, se evaluó la calidad del agua del río San Juan. Para tal fin se establecieron seis puntos de muestreo donde se recolectaron muestras de agua y macroinvertebrados acuáticos para los análisis fisicoquímicos e hidrobiológicos. Se aplicaron y modificaron los índices bióticos EPT (efemerópteros, plecópteros, tricópteros, BMWP/Col (Biological Monitoring Working Party y ASPT (Average Score per Taxon basados en las comunidades de macroinvertebrados acuáticos capturados. Los resultados de las variables fisicoquímicas y los índices bióticos indican que las estaciones E1 y E2 son las que presentan menor grado de contaminación, en las demás estaciones disminuye considerablemente la calidad del agua debido a las actividades económicas desarrolladas en el sector y a su cercanías con el casco urbano del municipio de Andes. De los tres índices analizados, el ASPT modificado y adaptado al río San Juan es el que mejor se relaciona con las condiciones ambientales del río en tanto las características de los macroinvertebrados acuáticos recolectados y analizados en el trayecto objeto de estudio. (Abstract. During the months of February, May, August and October 2014, the water quality of the San Juan River was assessed. To this aim, six sampling points were established, where water samples and macroinvertebrates for physical-chemical and hydrobiological analysis were collected. Three biotic indexes were applied and one modified: EPT (Ephemeroptera, Plecoptera, Trichoptera, BMWP / Col (Biological Monitoring Working Party and ASPT (Average Score per Taxon based on the captured communities of aquatic macroinvertebrates. The results of the physical-chemical variables and biotic indixes indicate that E1 and E2 stations are those with lower degree of contamination, other stations considerably decreased water quality due to economic activities around, and the short distance with the

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

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

    2003-04-01

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

  3. Elevation-dependent changes in n-alkane δD and soil GDGTs across the South Central Andes

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    Nieto-Moreno, Vanesa; Rohrmann, Alexander; van der Meer, Marcel T. J.; Sinninghe Damsté, Jaap S.; Sachse, Dirk; Tofelde, Stefanie; Niedermeyer, Eva M.; Strecker, Manfred R.; Mulch, Andreas

    2016-11-01

    Surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature, sometimes complicating paleoaltimetry interpretations. Thus, understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions. Lipid biomarker-based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials, in particular outside semi-arid climate zones where soil carbonates are not abundant but (soil) organic matter has a high preservation potential. Here we present δD values of soil-derived n-alkanes and mean annual air temperature (MAT) estimates based on branched glycerol dialkyl glycerol tetraether (brGDGT) distributions to assess their potential for paleoelevation reconstructions in the southern central Andes. We analyzed soil samples across two environmental and hydrological gradients that include a hillslope (26-28°S) and a valley (22-24°S) transect on the windward flanks of Central Andean Eastern Cordillera in NW Argentina. Our results show that present-day n-alkane δD values and brGDGT-based MAT estimates are both linearly related with elevation and in good agreement with present-day climate conditions. Soil n-alkanes show a δD lapse rate (Δ (δD)) of - 1.64 ‰ / 100 m (R2 = 0.91, p < 0.01) at the hillslope transect, within the range of δD lapse rates from precipitation and surface waters in other tropical regions in the Andes like the Eastern Cordillera in Colombia and Bolivia and the Equatorial and Peruvian Andes. BrGDGT-derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of ΔT = - 0.51 °C / 100 m (R2 = 0.91, p < 0.01), comparable with lapse rates from in situ soil temperature measurements, satellite-derived land-surface temperatures at this transect, and

  4. Bimodal volcanism in a tectonic transfer zone: Evidence for tectonically controlled magmatism in the southern Central Andes, NW Argentina

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    Petrinovic, I. A.; Riller, U.; Brod, J. A.; Alvarado, G.; Arnosio, M.

    2006-04-01

    This field-based and analytical laboratory study focuses on the genetic relationship between bimodal volcanic centres and fault types of an important tectonic transfer zone in the southern Central Andes, the NW-SE striking Calama-Olacapato-Toro (COT) volcanic belt. More specifically, tectono-magmatic relationships are examined for the 0.55 Ma Tocomar, the 0.78 Ma San Jerónimo and the 0.45 Ma Negro de Chorrillos volcanic centres in the Tocomar area (66°30 W-24°15 S). Structures of the COT volcanic belt, notably NW-SE striking strike-slip faults and NE-SW trending normal faults, accommodated differential shortening between major N-S striking thrust faults on the Puna Plateau. We present evidence that bimodal volcanism was contemporaneous with activity of these fault types in the COT volcanic belt, whereby eruption and composition of the volcanic rocks in the Tocomar and San Jerónimo-Negro de Chorrillos areas appear to have been controlled by the kinematics of individual faults. More specifically, rhyolitic centres such as the Tocomar are associated with normal faults, whereas shoshonitic-andesitic monogenetic volcanoes, e.g., the San Jerónimo and Negro de Chorrillos centres, formed at strike-slip dominated faults. Thus, the eruption of higher viscous rhyolite magmas appears to have been facilitated in tectonic settings characterized by horizontal dilation whereas ascent and effusive volcanic activity of less viscous and hot basaltic andesites to shoshonites were controlled by subvertical strike-slip faults. While the Tocomar rhyolites are interpreted to be derived from an anatectic crustal source, geochemical characteristics of the San Jerónimo and Negro de Chorrillos shoshonitic andesites are in agreement with a deeper source. This suggests that the composition of erupted volcanic rocks as well as their spatial distribution in the Tocomar area is controlled by the activity of specific fault types. Such volcano-tectonic relationships are also evident from older

  5. Thicknesses and volumes of glaciers in the Andes of Peru estimated with satellite data and digital terrain information

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    Torres, Judith; Colonia, Daniel; Haeberli, Wilfried; Giráldez, Claudia; Frey, Holger; Huggel, Christian

    2014-05-01

    The glaciers in the tropical Andes of Peru have been melting at an unprecedented rate in recent years and generally after the Little Ice Age, a cold period that lasted from the 16th to the 19th century. Knowledge of glacier thicknesses and volumes is necessary for evaluating possible future scenarios of glacier shrinkage and of water supply to the Andean populations under conditions of continued warming. Calculation of glacier volumes for 19 mountain ranges in Perú has been based on two ice- thickness modeling methods including an area-related approach with different parameterizations and a slope-dependent approach. Both methods allow for rapid treatment of regional data obtained from satellite imagery and a Digital Elevation Model, integrated into a Geographic Information System. In addition, glacier outlines were obtained from the glacier inventory compiled by the Unit of Glaciology and Water Resources (UGRH) - National Water Authority (ANA) that used satellite imagery (ASTER, SPOT and LISS III from 2003 to 2010) and topographic information acquired from the cartography of the National Geographical Institute (IGN). The volume-area scaling approach resulted in glacier volume of 35.00 km3 and a total volume of 34.39 km3 resulted from the slope-dependent thickness with a thickness approximately 30 m. Estimated results also show a loss of the total ice surface ~42% and glacier volume loss about ~38% in both methods based on the first Glacier Inventory of Peru (from aerial photographs 1962 -1970) performed by HIDRANDINA SA. The results also indicate that volume estimations are subject to large uncertainties. Field measurements of glacier thickness are scarce and locally restricted due to rugged topography, high altitude and heavy crevassing of glaciers. Possibilities of calibrating and validating the applied model approaches are therefore limited. New possibilities nevertheless come into play with slope-dependent approaches, which lead beyond area-related average

  6. Hydrological interaction between glacier and páramos in the tropical Andes: implications for water resources availability

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    Villacís, Marcos; Cadier, Eric; Mena, Sandra; Anaguano, Marcelo; Calispa, Marlon; Maisisncho, Luis; Galárraga, Remigio; Francou, Bernard

    2010-05-01

    Preliminary hydro glacier estimates indicate that glacier contribution to the average annual consumption (5.6 m3 s-1) of the city of Quito (Capital of Ecuador, ~2'500.000 inhabitants, 2800 masl) represents only about 2%-4% of the total supply for human consumption. However, at the local level at the Antizana volcano (0°28'S, 78°09'W), the mass balance analysis of the system composed by the Humboldt catchment (area of 15.1 km2, 15% of glaciarized area, 5% of moraines area, 80% of the area is páramo-endemic ecosystem of the tropical Andes, range from 5670 masl to 4000 masl) and Los Crespos catchment (area of 2.4 km2, 67% glaciarized area, 27% moraines area, range from 5670 masl to 4500 masl), which is nested into the Humboldt catchment, allows us to identify that due to the presence of the glacier reservoirs there is an additional contribution of 24% to the annual volume at the Humboldt catchment and it helps to regulate the runoff during the dry season, where the daily additional glacier contribution from November to February in some cases could reach t 40%. The Humboldt catchment has similar physiographic characteristics than the sites where new diversions will be built in the future in order to satisfy the increasing demand of water for human consumption of the city of Quito and its surrounding populations. Based on detail hydrological observations (every 15 minutes measurements) during 2005 to 2009 and sporadic environmental trace analysis during the same period, the annual percentage of glacier contribution from the Humboldt catchment could potentially be as high as 37% due in part to the glacier melt contribution that gets infiltrated over 4750 masl it is then delivered around 4100 masl through underground circulation. Some of the sites where the glacier contribution reaches de surface has been identified through field work and the glacier origin of this water have been confirmed using a conductivity measurement, which seems to be a good indicator in when

  7. Compositional variations of ignimbrite magmas in the Central Andes over the past 26 Ma - A multivariate statistical perspective

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    Brandmeier, M.; Wörner, G.

    2016-10-01

    Multivariate statistical and geospatial analyses based on a compilation of 890 geochemical and ~ 1200 geochronological data for 194 mapped ignimbrites from the Central Andes document the compositional and temporal patterns of large-volume ignimbrites (so-called "ignimbrite flare-ups") during Neogene times. Rapid advances in computational science during the past decade led to a growing pool of algorithms for multivariate statistics for large datasets with many predictor variables. This study applies cluster analysis (CA) and linear discriminant analysis (LDA) on log-ratio transformed data with the aim of (1) testing a tool for ignimbrite correlation and (2) distinguishing compositional groups that reflect different processes and sources of ignimbrite magmatism during the geodynamic evolution of the Central Andes. CA on major and trace elements allows grouping of ignimbrites according to their geochemical characteristics into rhyolitic and dacitic "end-members" and to differentiate characteristic trace element signatures with respect to Eu anomaly, depletions in middle and heavy rare earth elements (REE) and variable enrichments in light REE. To highlight these distinct compositional signatures, we applied LDA to selected ignimbrites for which comprehensive datasets were available. In comparison to traditional geochemical parameters we found that the advantage of multivariate statistics is their capability of dealing with large datasets and many variables (elements) and to take advantage of this n-dimensional space to detect subtle compositional differences contained in the data. The most important predictors for discriminating ignimbrites are La, Yb, Eu, Al2O3, K2O, P2O5, MgO, FeOt, and TiO2. However, other REE such as Gd, Pr, Tm, Sm, Dy and Er also contribute to the discrimination functions. Significant compositional differences were found between (1) the older (> 13 Ma) large-volume plateau-forming ignimbrites in northernmost Chile and southern Peru and (2) the

  8. Holocene compression in the Acequión valley (Andes Precordillera, San Juan province, Argentina): Geomorphic, tectonic, and paleoseismic evidence

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    Audemard, M.; Franck, A.; Perucca, L.; Laura, P.; Pantano, Ana; Avila, Carlos R.; Onorato, M. Romina; Vargas, Horacio N.; Alvarado, Patricia; Viete, Hewart

    2016-04-01

    The Matagusanos-Maradona-Acequión Valley sits within the Andes Precordillera fold-thrust belt of western Argentina. It is an elongated topographic depression bounded by the roughly N-S trending Precordillera Central and Oriental in the San Juan Province. Moreover, it is not a piggy-back basin as we could have expected between two ranges belonging to a fold-thrust belt, but a very active tectonic corridor coinciding with a thick-skinned triangular zone, squeezed between two different tectonic domains. The two domains converge, where the Precordillera Oriental has been incorporated to the Sierras Pampeanas province, becoming the western leading edge of the west-verging broken foreland Sierras Pampeanas domain. This latter province has been in turn incorporated into the active deformation framework of the Andes back-arc at these latitudes as a result of enhanced coupling between the converging plates due to the subduction of the Juan Fernández ridge that flattens the Nazca slab under the South American continent. This study focuses on the neotectonics of the southern tip of this N-S elongated depression, known as Acequión (from the homonym river that crosses the area), between the Del Agua and Los Pozos rivers. This depression dies out against the transversely oriented Precordillera Sur, which exhibits a similar tectonic style as Precordillera Occidental and Central (east-verging fold-thrust belt). This contribution brings supporting evidence of the ongoing deformation during the Late Pleistocene and Holocene of the triangular zone bounded between the two leading and converging edges of Precordillera Central and Oriental thrust fronts, recorded in a multi-episodic lake sequence of the Acequión and Nikes rivers. The herein gathered evidence comprise Late Pleistocene-Holocene landforms of active thrusting, fault kinematics (micro-tectonic) data and outcrop-scale (meso-tectonic) faulting and folding of recent lake and alluvial sequences. In addition, seismically

  9. Controls on the isotopic composition of surface water and precipitation in the Northern Andes, Colombian Eastern Cordillera

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    Saylor, Joel E.; Mora, Andrés; Horton, Brian K.; Nie, Junsheng

    2009-12-01

    Empirical datasets provide the constraints on the variability and causes of variability in stable isotope compositions (δD or δ 18O) of surface water and precipitation that are essential not only for models of modern and past climate but also for investigations of paleoelevation. This study presents stable isotope data for 76 samples from four elevation transects and three IAEA GNIP stations in the Eastern Cordillera of Colombia and the northern Andean foreland. These data are largely consistent with theories of stable isotope variability developed based on a global dataset. On a monthly basis, the precipitation-amount effect exerts the dominant control on δD p and δ 18O p values at the IAEA GNIP stations. At the Bogotá station (2547 m), the δD p and δ 18O p values vary seasonally, with isotopic minima correlating with maxima in precipitation-amount. Although surface water samples from Eastern Cordilleran streams and rivers fall on the Global Meteoric Water Line, samples from three of four lakes (2842-3459 m) have evaporatively elevated δD sw and δ 18O sw values. The IAEA GNIP station data averaged over multiple years, combined with stream and river water data, define vertical lapse rates of -1.8‰ km -1 for Δδ 18O and -14.6‰ km -1 for ΔδD, and are a close fit to a common thermodynamically based Rayleigh distillation model. Elevation uncertainties for these relationships are also evaluated. Comparison of this Colombian dataset with the elevation uncertainties generated by the thermodynamically based model shows that the model underestimates uncertainty at high Δδ 18O and ΔδD values while overestimating it for low Δδ 18O and ΔδD values. This study presents an independent, empirical assessment of stable isotope-based elevation uncertainties for the northern Andes based on a dataset of sufficient size to ensure statistical integrity. These vertical lapse rates and associated uncertainties form the basis for stable isotope paleoelevation studies

  10. Migraciones en la puna: su relación con el uso de los recursos naturales del departamento Los Andes Migraciones en la puna: su relación con el uso de los recursos naturales del departamento Los Andes

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    Francisco R. Barbarán

    2009-12-01

    Full Text Available From an historic and demographic perspective, as well as the use of natural resources, we analyzed the relationship between human migrations and the economic activities of Los Andes Department, West of the Salta Province, in NW Argentina. Using the residual method, we calculated migratory balances between Argentinean population censuses carried out in 1947,1960, 1970, 1980 and 2001. The migratory balances were negative for all the periods studied. When the train started to run through Ramal C-14, the workers who built it have to find jobs somewhere else. At the same time, the railway made easier for the natives, to find better economicopportunities out of the Puna. The close of mine La Casualidad by the end of the 70’s, the low creation of jobs by the remaining mining operations, focused in to hire qualified technicians no available in Los Andes and the privatization of the railway in early 90’s, were important factors of emigration. Despite of cattle rising as the main economic activity in rural areas, it is practiced without any technology of management. The overgrazing caused for that reason, has reduced almost to the half the quantity of sheep by inhabitant between 1947 and 2001. That is why the local people have to press more on the wildlife, trading illegally with vicuña (Vicugna vicugna fiber. Despite of a touristic development plan, a law promoting sheep rising and a census of vicuña population carried out by the provincial government, these recent actions should be part of a development project of regional scale, oriented to the sustainable use of the natural resources of Los Andes Department. That project would create jobs and discourage emigration.Desde una perspectiva histórica, demográfica y del uso de los recursos naturales, analizamos la relación existente entre las migraciones humanas y las actividades económicas en el departamento Los Andes, ubicado al W de la provincia de Salta, en el Noroeste Argentino. Usando el m

  11. Resilience and adaptations of rural communities and agricultural land use in the tropical Andes: Coping with environmental and socio-economic changes

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    Stadel, Ch.

    2008-12-01

    Full Text Available In spite of a long settlement history of the tropical Andes, rural farming communities have always been exposed to conditions of ecological and economic vulnerability, risks, and even disasters. This has resulted, at certain times and in some regions, to a destabilization of livelihoods and to a manifestation of various forms of marginalization, to poverty or outmigration. However, Andean communities , over a long time, have given admirable testimonies of resilience and adaptations in the face of adverse conditions or new challenges. This paper examines the potentials and different facets of resilience and adaptation strategies of the rural campesinado in the tropical Andes. It emphasizes the proven traditional concepts of verticality, complementarity, reciprocity, and mutual community support, which to date support the feasibility and sustainability of Andean farming and community survival. In spite of this recognition, it is argued that Andean rural livelihoods always had to adapt to new developments, to threats and challenges, as well as to opportunities and alternative potentials. In the face of an almost ubiquitous penetration of modernization, new technologies, and economic and cultural globalization, the fundamental question arises, whether this can be considered as a path to progress and development, or as a threat to the survival of small-scale farming and rural community living. The paper concludes by formulating, albeit in a tentative form, some general suggestions for ‘development’ approaches and for research priorities in the rural Andes.

    A pesar de una tradición muy extensa del asentamiento humano en los Andes tropicales, las comunidades campesinas siempre enfrentaron condiciones de vulnerabilidad ecológica y económica, con varios riesgos, y aun desastres. Eso ha resultado, en diversos tiempos y en algunas regiones, en una estabilización de la superviviencia humana y en varias manifestaciones de marginalización, de

  12. Reactividad potencial de las rocas andesíticas de Cabo de Gata (SE de España

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    Soriano, J.

    2010-06-01

    Full Text Available Andesitic rocks produce an alkali-silica reaction with the components of the interstitial phase of concrete. This reaction can be considered as belonging to the slow-kinetic type, since the incongruent dissolution of the rock-forming minerals leads to the late formation of siliceous calc-alkaline gel. As a conquence, the conventional mortar-bar method does not detect such reaction until 90 days later.

    Las rocas andesíticas producen una reacción álcalis-sílice con los componentes de la fase intersticial del hormigón. Esta reacción puede encuadrarse dentro de las de cinética lenta, ya que la disolución incongruente de los minerales constituyentes de las rocas, da lugar a la formación tardía de geles silicocalco-alcalinos. En consecuencia, la utilización convencional del método de ensayo de barras de mortero no detecta la reacción hasta transcurridos al menos 90 días.

  13. Zonda downslope winds in the central Andes of South America in a 20-year climate simulation with the Eta model

    Science.gov (United States)

    Antico, Pablo L.; Chou, Sin Chan; Mourão, Caroline

    2015-12-01

    The Zonda wind is a local version of the alpine foehn in the central Andes Mountains in South America. It blows on the eastern slopes and produces an extremely warm and dry condition in Argentina. In this study, the occurrence of Zonda wind events during a 20-year simulation from the regional Eta model is analyzed and results are compared to previous studies of Zonda wind events based on weather observations. We define a set of parameters to account for the zonal pressure gradient across the mountain, vertical movement, and air humidity typical of Zonda wind events. These parameters are applied to characterize Zonda wind events in model run and to classify them as surface-level or high-level episodes. The resulting annual distribution of Zonda occurrences based on composite analyses shows a preference for winter and spring with rare occurrences during summer. For the surface-level Zonda wind events, the highest frequency occurs during spring. Whereas surface-level Zonda wind episodes more commonly initiate in the afternoon, high-level Zonda wind events show no preference for a given initiation time. Our results are mostly in agreement with previous observational results.

  14. Effects of loading–unloading and wetting–drying cycles on geomechanical behaviors of mudrocks in the Colombian Andes

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    Mario Camilo Torres-Suarez

    2014-06-01

    Full Text Available The mudrocks in the Colombian Andes, particularly those exhibiting low cementation (bonding, are susceptible to degradation when the environmental conditions change, which are challenging issues for engineering works. In this paper, the changes in physico-mechanical properties of mudrocks were monitored in laboratory, and some influential factors on the mechanical competence of geomaterials were studied. The geotechnical characteristics and experimental designs were developed from physical, chemical, mechanical and compositional points of view. In the tests, the techniques such as vapor equilibrium technique (VET were employed to apply wetting–drying cycles and to control relative humidity (suction-controlled and loading–unloading cycles through ultrasonic wave velocities technique. The results show that the main failure mechanisms for the laminated mudrocks start on the microscopic scale by fissures coalescence, exhibiting physico-chemical degradation as well; the global geomechanical behavior presents a state between a ductile, like rock, and a fragile, like soil. The obtained results can provide engineering values according to monitoring laboratory set, when compared with in situ conditions.

  15. The role of the Antofagasta-Calama Lineament in ore deposit deformation in the Andes of northern Chile

    Science.gov (United States)

    Palacios, Carlos; Ramírez, Luis E.; Townley, Brian; Solari, Marcelo; Guerra, Nelson

    2007-02-01

    During the Late Jurassic-Early Oligocene interval, widespread hydrothermal copper mineralization events occurred in association with the geological evolution of the southern segment of the central Andes, giving rise to four NS-trending metallogenic belts of eastward-decreasing age: Late Jurassic, Early Cretaceous, Late Paleocene-Early Eocene, and Late Eocene-Early Oligocene. The Antofagasta-Calama Lineament (ACL) consists of an important dextral strike-slip NE-trending fault system. Deformation along the ACL system is evidenced by a right-lateral displacement of the Late Paleocene-Early Eocene metallogenic belts. Furthermore, clockwise rotation of the Early Cretaceous Mantos Blancos copper deposit and the Late Paleocene Lomas Bayas porphyry copper occurred. In the Late Eocene-Early Oligocene metallogenic belt, a sigmoidal deflection and a clockwise rotation is observed in the ACL. The ACL is thought to have controlled the emplacement of Early Oligocene porphyry copper deposits (34-37 Ma; Toki, Genoveva, Quetena, and Opache), whereas it deflected the Late Eocene porphyry copper belt (41-44 Ma; Esperanza, Telégrafo, Centinela, and Polo Sur ore deposits). These observations suggest that right-lateral displacement of the ACL was active during the Early Oligocene. We propose that the described structural features need to be considered in future exploration programs within this extensively gravel-covered region of northern Chile.

  16. Selection of astrophysical/astronomical/solar sites at the Argentina East Andes range taking into account atmospheric components

    Science.gov (United States)

    Piacentini, R. D.; García, B.; Micheletti, M. I.; Salum, G.; Freire, M.; Maya, J.; Mancilla, A.; Crinó, E.; Mandat, D.; Pech, M.; Bulik, T.

    2016-06-01

    In the present work we analyze sites in the Argentinian high Andes mountains as possible places for astrophysical/astronomical/solar observatories. They are located at: San Antonio de los Cobres (SAC) and El Leoncito/CASLEO region: sites 1 and 2. We consider the following atmospheric components that affect, in different and specific wavelength ranges, the detection of photons of astronomical/astrophysical/solar origin: ozone, microscopic particles, precipitable water and clouds. We also determined the atmospheric radiative transmittance in a day near the summer solstice at noon, in order to confirm the clearness of the sky in the proposed sites at SAC and El Leoncito. Consequently, all the collected and analyzed data in the present work, indicate that the proposed sites are very promising to host astrophysical/astronomical/solar observatories. Some atmospheric components, like aerosols, play a significant role in the attenuation of light (Cherencov and/or fluorescence) detected in cosmic rays (particles or gamma photons) astrophysical observatories, while others, like ozone have to be considered in astronomical/solar light detection.

  17. Evidence of the excitation of a ring-like gravity wave in the mesosphere over the Andes Lidar Observatory

    Science.gov (United States)

    Vargas, Fabio; Swenson, Gary; Liu, Alan; Pautet, Dominique

    2016-08-01

    On 23 March 2012, our all-sky imager recorded a concentric, ring-like gravity wave pattern. The wave arose within the area covered by images of both OH and O(1S) nightglow emissions taken at the Andes Lidar Observatory (ALO), Chile (30.3°S, 70.7°W). We have estimated the observed and intrinsic parameters of the event and located the wave source within the lower mesosphere altitude range using a reverse ray tracing method. By the analysis of GOES and LIS satellite images, we have not found evidence of neither convective nor lightning activity nearby ALO, indicating that the source of the ring-like wave was not directly in the troposphere. The absence of tropospheric activity and the height of the source of the event suggest that a secondary wave generation mechanism might be the cause of the ring-like wave. The secondary wave mechanism was likely triggered by a breaking, larger-scale primary wave excited by deep convection ˜1400 km northeast of ALO over Bolivia, as determined by a forward ray tracing scheme.

  18. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes.

    Science.gov (United States)

    Langer, Max C; Rincón, Ascanio D; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W M

    2014-10-01

    Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U-Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal-vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic-Jurassic boundary.

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

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    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.

  20. Comparison of Three Supervised Learning Methods for Digital Soil Mapping: Application to a Complex Terrain in the Ecuadorian Andes

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    Martin Hitziger

    2014-01-01

    Full Text Available A digital soil mapping approach is applied to a complex, mountainous terrain in the Ecuadorian Andes. Relief features are derived from a digital elevation model and used as predictors for topsoil texture classes sand, silt, and clay. The performance of three statistical learning methods is compared: linear regression, random forest, and stochastic gradient boosting of regression trees. In linear regression, a stepwise backward variable selection procedure is applied and overfitting is controlled by minimizing Mallow’s Cp. For random forest and boosting, the effect of predictor selection and tuning procedures is assessed. 100-fold repetitions of a 5-fold cross-validation of the selected modelling procedures are employed for validation, uncertainty assessment, and method comparison. Absolute assessment of model performance is achieved by comparing the prediction error of the selected method and the mean. Boosting performs best, providing predictions that are reliably better than the mean. The median reduction of the root mean square error is around 5%. Elevation is the most important predictor. All models clearly distinguish ridges and slopes. The predicted texture patterns are interpreted as result of catena sequences (eluviation of fine particles on slope shoulders and landslides (mixing up mineral soil horizons on slopes.

  1. Paleoecological potential of mid-altitude peat deposits in the Tropical Andes: evidence from subfossil wood and palynology

    Science.gov (United States)

    Gonzalez Arango, Catalina; Andres Ayala Usma, David; Boom, Arnoud; Archila, Sonia; Montes, Camilo

    2016-04-01

    The understanding of past climatic and ecological phenomena at mid-altitudes in the tropical Andes is limited by the lack of ancient lakes and other well preserved paleoclimatological archives. During the opening of a main road a decade ago in the Central Cordillera of Colombia, some buried peat deposits became exposed within the Pereira Volcanodetritic Fan (~2000 m.a.s.l), revealing a rich resource of organic remains, including big fragments of subfossil trees and micro and macro plant remains ideal for multiproxy analysis. Radiocarbon dating and palynological analysis suggest that the deposit dates back to the last glacial period. We present the first δ13C results of a subfossil wood sample with visible tree rings, that was identified as a member of the genus Chrysochlamys (Clusiaceae) and that revealed a periodic signal that might be attributed to climatic variability. A clear seasonal pattern arises suggesting a different climatic configuration, most likely related to a broader migrational range of the ITCZ related to higher eccentricity. Pollen analysis reveals the prevalence of montane Andean forests and Paramo elements (today ca. 1200 meters higher) indicating much colder climates than today. These first findings indicate that mid-altitude Andean peats are highly sensitive to climatic variability and provide an excellent opportunity to study ancient environmental phenomena at extremely high resolution.

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

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    M. V. Mackern

    2009-12-01

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

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

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

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    Francisco J. Meza

    2013-03-01

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

  4. Genetic Variations in the TP53 Pathway in Native Americans Strongly Suggest Adaptation to the High Altitudes of the Andes.

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    Vanessa Cristina Jacovas

    Full Text Available The diversity of the five single nucleotide polymorphisms located in genes of the TP53 pathway (TP53, rs1042522; MDM2, rs2279744; MDM4, rs1563828; USP7, rs1529916; and LIF, rs929271 were studied in a total of 282 individuals belonging to Quechua, Aymara, Chivay, Cabanaconde, Yanke, Taquile, Amantani, Anapia, Uros, Guarani Ñandeva, and Guarani Kaiowá populations, characterized as Native American or as having a high level (> 90% of Native American ancestry. In addition, published data pertaining to 100 persons from five other Native American populations (Surui, Karitiana, Maya, Pima, and Piapoco were analyzed. The populations were classified as living in high altitude (≥ 2,500 m or in lowlands (< 2,500 m. Our analyses revealed that alleles USP7-G, LIF-T, and MDM2-T showed significant evidence that they were selected for in relation to harsh environmental variables related to high altitudes. Our results show for the first time that alleles of classical TP53 network genes have been evolutionary co-opted for the successful human colonization of the Andes.

  5. Genetic Variations in the TP53 Pathway in Native Americans Strongly Suggest Adaptation to the High Altitudes of the Andes

    Science.gov (United States)

    Peréz, Orlando; de Azevedo, Soledad; Macedo, Gabriel Souza; Sandoval, José Raul; Salazar-Granara, Alberto; Villena, Mercedes; Dugoujon, Jean-Michel; Bisso-Machado, Rafael; Petzl-Erler, Maria Luiza; Salzano, Francisco Mauro; Ashton-Prolla, Patricia; Ramallo, Virginia; Bortolini, Maria Cátira

    2015-01-01

    The diversity of the five single nucleotide polymorphisms located in genes of the TP53 pathway (TP53, rs1042522; MDM2, rs2279744; MDM4, rs1563828; USP7, rs1529916; and LIF, rs929271) were studied in a total of 282 individuals belonging to Quechua, Aymara, Chivay, Cabanaconde, Yanke, Taquile, Amantani, Anapia, Uros, Guarani Ñandeva, and Guarani Kaiowá populations, characterized as Native American or as having a high level (> 90%) of Native American ancestry. In addition, published data pertaining to 100 persons from five other Native American populations (Surui, Karitiana, Maya, Pima, and Piapoco) were analyzed. The populations were classified as living in high altitude (≥ 2,500 m) or in lowlands (< 2,500 m). Our analyses revealed that alleles USP7-G, LIF-T, and MDM2-T showed significant evidence that they were selected for in relation to harsh environmental variables related to high altitudes. Our results show for the first time that alleles of classical TP53 network genes have been evolutionary co-opted for the successful human colonization of the Andes. PMID:26382048

  6. Late Quaternary vegetation, fire and climate history reconstructed from two cores at Cerro Toledo, Podocarpus National Park, southeastern Ecuadorian Andes

    Science.gov (United States)

    Brunschön, Corinna; Behling, Hermann

    2009-11-01

    The last ca. 20,000 yr of palaeoenvironmental conditions in Podocarpus National Park in the southeastern Ecuadorian Andes have been reconstructed from two pollen records from Cerro Toledo (04°22'28.6"S, 79°06'41.5"W) at 3150 m and 3110 m elevation. Páramo vegetation with high proportions of Plantago rigida characterised the last glacial maximum (LGM), reflecting cold and wet conditions. The upper forest line was at markedly lower elevations than present. After ca. 16,200 cal yr BP, páramo vegetation decreased slightly while mountain rainforest developed, suggesting rising temperatures. The trend of increasing temperatures and mountain rainforest expansion continued until ca. 8500 cal yr BP, while highest temperatures probably occurred from 9300 to 8500 cal yr BP. From ca. 8500 cal yr BP, páramo vegetation re-expanded with dominance of Poaceae, suggesting a change to cooler conditions. During the late Holocene after ca. 1800 cal yr BP, a decrease in páramo indicates a change to warmer conditions. Anthropogenic impact near the study site is indicated for times after 2300 cal yr BP. The regional environmental history indicates that through time the eastern Andean Cordillera in South Ecuador was influenced by eastern Amazonian climates rather than western Pacific climates.

  7. Snow water equivalent spatiotemporal variability estimation in the Andes Cordillera through distributed energy balance modeling and intensive-study catchments.

    Science.gov (United States)

    McPhee, J. P.; Cornwell, E.; Molotch, N. P.

    2015-12-01

    Seasonal snow cover is the primary water resource precursor for human use and environmental sustain along the extratropical Andes Cordillera. This research provides high-resolution distributed estimates of end-of-winter and spring snow water equivalent over a 152,000-km2 domain, based on remotely sensed snow cover and a simplified snowpack energy balance model. Important data for model validation was obtained through a sustained effort aimed at monitoring snow conditions throughout the domain from newly installed sensors and snow surveys. Peak SWE estimates show an overall coefficient of determination R2 of 0.61 compared to observations at 12 automatic snow water equivalent sensors distributed across the model domain between latitudes 30º S and 37º S, with R2 values between 0.32 and 0.88. Estimated patterns of snow accumulation reflect appropriately the dominant effect of elevation, and suggest that the current government operational snow observation network may be inadequate under future climate change scenarios. Several insights can be obtained by analyzing the shortcomings of the modeling results when compared with high-resolution time series of energy and mass balance, as well as with distributed SWE observations obtained at experimental catchments. The results presented here have the potential of informing applications such as seasonal forecast model assessment and improvement, regional climate model validation, as well as evaluation of observational networks and water resource infrastructure development.

  8. A new species of Cryptotis (Mammalia, Eulipotyphla, Soricidae) from the Sierra de Perijá, Venezuelan-Colombian Andes

    Science.gov (United States)

    Quiroga-Carmona, Marcial; Woodman, Neal

    2015-01-01

    The Sierra de Perijá is the northern extension of the Cordillera Oriental of the Andes and includes part of the border between Colombia and Venezuela. The population of small-eared shrews (Mammalia, Eulipotyphla, Soricidae, Cryptotis) inhabiting the Sierra de Perijá previously was known from only a single skull from an individual collected in Colombia in 1989. This specimen had been referred to alternatively as C. thomasi and C. meridensis, but more precise definition of the known Colombian and Venezuelan species of Cryptotis has since excluded the Sierra de Perijá population from any named species. The recent collection of a specimen from the Venezuelan slope of Sierra de Perijá, prompted us to re-evaluate the taxonomic status of this population and determine its relationship with other Andean shrews. Our examination of the available specimens revealed that they possess a unique suite of morphological and morphometrical characters, and we describe the Sierra de Perijá population as a new species in the South American C. thomasi species group. Recognition of this new species adds to our knowledge of this genus in South America and to the biodiversity of the Sierra de Perijá.

  9. Climate Warming and Soil Carbon in Tropical Forests: Insights from an Elevation Gradient in the Peruvian Andes

    Science.gov (United States)

    Nottingham, Andrew T.; Whitaker, Jeanette; Turner, Benjamin L.; Salinas, Norma; Zimmermann, Michael; Malhi, Yadvinder; Meir, Patrick

    2015-01-01

    The temperature sensitivity of soil organic matter (SOM) decomposition in tropical forests will influence future climate. Studies of a 3.5-kilometer elevation gradient in the Peruvian Andes, including short-term translocation experiments and the examination of the long-term adaptation of biota to local thermal and edaphic conditions, have revealed several factors that may regulate this sensitivity. Collectively this work suggests that, in the absence of a moisture constraint, the temperature sensitivity of decomposition is regulated by the chemical composition of plant debris (litter) and both the physical and chemical composition of preexisting SOM: higher temperature sensitivities are found in litter or SOM that is more chemically complex and in SOM that is less occluded within aggregates. In addition, the temperature sensitivity of SOM in tropical montane forests may be larger than previously recognized because of the presence of “cold-adapted” and nitrogen-limited microbial decomposers and the possible future alterations in plant and microbial communities associated with warming. Studies along elevation transects, such as those reviewed here, can reveal factors that will regulate the temperature sensitivity of SOM. They can also complement and guide in situ soil-warming experiments, which will be needed to understand how this vulnerability to temperature may be mediated by altered plant productivity under future climatic change. PMID:26955086

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

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    M. Rodriguez

    2014-07-01

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

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

    Science.gov (United States)

    Pellicciotti, Francesca

    2016-01-01

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

  12. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes

    Science.gov (United States)

    Langer, Max C.; Rincón, Ascanio D.; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W. M.

    2014-01-01

    Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary. PMID:26064540

  13. Largest explosive eruption in historical times in the Andes at Huaynaputina volcano, a.d. 1600, southern Peru

    Science.gov (United States)

    Thouret, Jean-Claude; Davila, Jasmine; Eissen, Jean-Philippe

    1999-05-01

    The largest explosive eruption (volcanic explosivity index of 6) in historical times in the Andes took place in a.d. 1600 at Huaynaputina volcano in southern Peru. According to chronicles, the eruption began on February 19 with a Plinian phase and lasted until March 6. Repeated tephra falls, pyroclastic flows, and surges devastated an area 70 × 40 km2 west of the vent and affected all of southern Peru, and earthquakes shook the city of Arequipa 75 km away. Eight deposits, totaling 10.2 13.1 km3 in bulk volume, are attributed to this eruption: (1) a widespread, ˜8.1 km3 pumice-fall deposit; (2) channeled ignimbrites (1.6 2 km3) with (3) ground-surge and ash-cloud-surge deposits; (4) widespread co-ignimbrite ash layers; (5) base-surge deposits; (6) unconfined ash-flow deposits; (7) crystal-rich deposits; and (8) late ash-fall and surge deposits. Disruption of a hydrothermal system and hydromagmatic interactions are thought to have fueled the large-volume explosive eruption. Although the event triggered no caldera collapse, ring fractures that cut the vent area point to the onset of a funnel-type caldera collapse.

  14. Nitrogen and Carbon Cycling in Deforested and Pristine Upland (2400m) Forest Catchments in the Peruvian Andes

    Science.gov (United States)

    Townsend-Small, A.; Haberer, J.; McClain, M.; Ramos, O.; Gardner, W.; McCarthy, M.; Brandes, J.

    2001-12-01

    Nitrogen and carbon cycling were examined within two upland (2400m) forest catchments in the Peruvian Andes. One catchment was partially deforested within the last 3 years, while the other has remained untouched. Tracer amended samples were analyzed to determine the pathways and rates of nitrogen cycling in streams draining each catchment. Both streams exhibited very low inorganic nitrogen levels, on the order of 1 to 2 uM. A large percentage (>1/3) of the total fixed nitrogen flux from these systems was in the form of particulates. Preliminary results suggest a very high rate of nitrogen cycling in these systems. Isotopic measurements of plant samples from both catchments also suggest that these forests are highly efficient in trapping and using atmospheric nitrogen sources. The partially deforested catchment had significantly more species using C4 and CAM carbon fixation pathways. Leaf litter from both streams and leaves from trees in the area were also analyzed for carbon and nitrogen isotopes to compare and contrast nitrogen and carbon cycling between the two sites. This and other data to be presented suggest that deforestation has subtle but significant effects upon the ability of tropical upland forests to retain and use nutrients.

  15. Arquitectura precerámica en la cordillera de los Andes, Piruru frene a la diversidad de los datos

    Directory of Open Access Journals (Sweden)

    Elisabeth Bonnier

    1988-12-01

    Full Text Available Los datos sobre la arquitectura precerámica en la cordilleraandina provienen de cinco sitios: La Galgada, Piruru, Huaricoto, Shillacotoy Kotosh. Contexto arqueológico y rasgos arquitectónicos específicos permitenidentificar la función ceremonial de esta arquitectura. La descripciónde las construcciones religiosas pone en evidencia un conjunto pertinente decaracteres comunes. El espacio ceremonial, construido y sin construir, se articulaalrededor del doble elemento arquitectónico fundamental, el fogón yel piso. Para analizar el piso a dos niveles, dos neologismos, pericausto y epicaustohan sido creados. El análisis arquitectónico muestra que el piso es elespacio sagrado por excelencia. Los fechados 14C de los sitios estudiadosdestacan la larga duración del Precerámico Final con arquitectura. A la luz delos últimos trabajos en Piruru y de los cambios arquitectónicos perceptiblesen este sitio, la hipótesis, formulada a principios de este decenio, sobre ·taexistencia de una tradición religiosa única propia de los Andes Centrales, seestá reconsiderando.

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

    Science.gov (United States)

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

    2016-08-16

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

  17. A Stepwise, Participatory Approach to Design and Implement Community Based Adaptation to Drought in the Peruvian Andes

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    Ralph Lasage

    2015-02-01

    Full Text Available The livelihoods of people in the Andes are expected to be affected by climate change due to their dependence on glacier water. The observed decrease in glacier volume over the last few decades is likely to accelerate during the current century, which will affect water availability in the region. This paper presents an approach for participatory development of community-based adaptation measures to cope with the projected impacts of climate change. It combines in an innovative manner participatory design with physical measurements, modeling and a vulnerability analysis. Vulnerability to drought is made operational for households in a catchment of the Ocoña River basin in Peru. On the basis of a household survey (n = 94 we explore how a vulnerability index (risk divided by response efficacy can be used to assess the distribution of vulnerability over households, and how socio-economic factors determine this vulnerability. Water entitlement, area of irrigated land, income and education are all significantly correlated with vulnerability to drought. The research showed that the main source of spring water is local rainwater, and that water use efficiency is low. The selected adaptation measures aimed to increase water availability close to farmland, and increase water use efficiency of farmers and households.

  18. Soluble iron inputs to the Southern Ocean through recent andesitic to rhyolitic volcanic ash eruptions from the Patagonian Andes

    Science.gov (United States)

    Simonella, L. E.; Palomeque, M. E.; Croot, P. L.; Stein, A.; Kupczewski, M.; Rosales, A.; Montes, M. L.; Colombo, F.; García, M. G.; Villarosa, G.; Gaiero, D. M.

    2015-08-01

    Patagonia, due to its geographic position and the dominance of westerly winds, is a key area that contributes to the supply of nutrients to the Southern Ocean, both through mineral dust and through the periodic deposits of volcanic ash. Here we evaluate the characteristics of Fe dissolved (into soluble and colloidal species) from volcanic ash for three recent southern Andes volcanic eruptions having contrasting features and chemical compositions. Contact between cloud waters (wet deposition) and end-members of andesitic (Hudson volcano) and rhyolitic (Chaitén volcano) materials was simulated. Results indicate higher Fe release and faster liberation rates in the andesitic material. Fe release during particle-seawater interaction (dry deposition) has higher rates in rhyolitic-type ashes. Rhyolitic ashes under acidic conditions release Fe in higher amounts and at a slower rate, while in those samples containing mostly glass shards, Fe release was lower and faster. The 2011 Puyehue eruption was observed by a dust monitoring station. Puyehue-type eruptions can contribute soluble Fe to the ocean via dry or wet deposition, nearly reaching the limit required for phytoplankton growth. In contrast, the input of Fe after processing by an acidic eruption plume could raise the amount of dissolved Fe in surface ocean waters several times, above the threshold required to initiate phytoplankton blooms. A single eruption like the Puyehue one represents more than half of the yearly Fe flux contributed by dust.

  19. On Darwin's footsteps across the Andes: Tithonian-Neocomian fossil invertebrates from the Piuquenes pass Tras las huellas de Darwin a través de los Andes: invertebrados fósiles del Tithoniano-Neocomiano del paso de Piuquenes

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    Beatriz Aguirre-Urreta

    2009-04-01

    Full Text Available The aim of this work is to summarize the modern knowledge of the geology of the Piuquenes Pass, in the Main Andes of Argentina and Chile, and to describe a small fauna of Tithonian-Neocomian invertebrates mostly represented by ammonites. The present knowledge of the region is compared with Darwin's, as expressed in his famous book on the Geology of South America.El objetivo de este trabajo es presentar una breve revisión moderna de la geología del Paso de Piuquenes en los Andes Principales de Chile y Argentina y describir una pequeña fauna de invertebrados del Tithoniano-Neocomiano compuesta principalmente por amonites. Se compara también el conocimiento de esta región con la referida por Darwin en su famoso libro sobre la geología de América del Sur.

  20. How do two Lupinus species respond to temperature along an altitudinal gradient in the Venezuelan Andes? ¿Cómo responden dos especies de Lupinus a la temperatura en un gradiente altitudinal en los Andes venezolanos?

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    FERMÍN RADA

    2008-09-01

    Full Text Available Temperature determines plant formations and species distribution along altitudinal gradients. Plants in the tropical high Andes, through different physiological and morphological characteristics, respond to freezing night temperatures and high daytime energy inputs which occur anytime of the year. The main objective of this study was to characterize day and night temperature related responses of two Lupinus species with different altitudinal ranges (L. meridanus, 1,800-3,600 and L. eromonomos, 3,700-4,300 m of altitude. Are there differences in night low temperature resistance mechanisms between the species along the gradient? How do these species respond, in terms of optimum temperature for photosynthesis, to increasing altitude? Lupinus meridanus shows frost avoidance, in contrast to L. eromonomos, which tolerates freezing at higher altitudes. Optimum temperature for photosynthesis decreases along the gradient for both species. Maximum C0(2 assimilation rates were higher in L. meridanus, while L. eromonomos showed decreasing C0(2 assimilation rates at the higher altitude. In most cases, measured daily leaf temperature is always within the 80 % of optimum for photosynthesis. L. meridanus7 upper distribution limit seems to be restricted by cold resistance mechanisms, while L. eromonomos7 to a combination of both cold resistance and to C0(2 assimilation responses at higher altitudes.La temperatura determina las formaciones vegetales y la distribución de especies a lo largo de gradientes altitudinales. Las plantas en los altos Andes tropicales, a través de diferentes características morfológicas y fisiológicas, responden a temperaturas congelantes nocturnas y altas entradas energéticas durante el día en cualquier momento del año. El objetivo principal de este estudio fue caracterizar las respuestas relacionadas con temperaturas diurnas y nocturnas en dos especies de Lupinus con diferente distribución altitudinal (L. meridanus, 1

  1. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils Estratigrafía de las fangolitas del Cretácico en los Andes Fueguinos orientales: Nuevos datos de cuerpos y trazas fósiles

    OpenAIRE

    Olivero, Eduardo B.; Francisco A. Medina; María I. López C.

    2009-01-01

    The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul), Maorites sp., and Pachydiscus (Neodesmoceras) sp....

  2. LA CUEVA ALIHUÉN, NUEVOS REGISTROS DE PINTURAS RUPESTRES EN LA VEGA DE MAIPÚ (SAN MARTÍN DE LOS ANDES, PATAGONIA, ARGENTINA (The Alihuén Cave, New Records of Cave Paintings in the Maipú Valley (San Martín de los Andes, Patagonia, Argentina

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    Alberto Enrique Pérez

    2014-06-01

    Full Text Available Se presenta el resultado de las nuevas investigaciones de pinturas rupestres en la vega Maipú, San Martín de los Andes, Neuquén, Argentina; donde se destaca la presencia de motivos zoomorfos, especialmente camélidos, de escasa representación hasta la fecha en el registro zooarqueológico local. El sitio Cueva Alihuén amplía la diversidad de motivos y técnicas de las pinturas rupestres de la vega Maipú, lo que nos permite plantear aspectos tanto biogeográficos respecto a la fauna como sobre la circulación de información y movilidad. Ambos aspectos nos permiten, nuevamente, aunar ambas vertientes de la cordillera de los Andes, compartiendo, integrando y complementando cada vez más características con el resto de los sitios que componen la cuenca hidrográfica de Valdivia, cuyo sector inferior constituye nuestra área de estudio. ENGLISH: New results from research on the cave paintings of the Maipú Valley, San Martín de los Andes, Neuquén, Argentina, highlight the presence of zoomorphic motifs, especially camelids which have been underrepresented in the local zooarchaeological record. The Alihuén cave site expands the range of motifs and techniques known from the cave paintings of the Maipú Valley that allows us to raise issues regarding both biogeographic wildlife, and on the flow of information and human mobility. These aspects allow us to share and integrate the increasingly complementary features on both sides of the Andes with the rest of the sites that comprise the Valdivia River basin, whose lower section composed our study area.

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

    Science.gov (United States)

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

    2015-12-01

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

  4. The high Andes, gene flow and a stable hybrid zone shape the genetic structure of a wide-ranging South American parrot

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    Schaefer H Martin

    2011-06-01

    Full Text Available Abstract Background While the gene flow in some organisms is strongly affected by physical barriers and geographical distance, other highly mobile species are able to overcome such constraints. In southern South America, the Andes (here up to 6,900 m may constitute a formidable barrier to dispersal. In addition, this region was affected by cycles of intercalating arid/moist periods during the Upper/Late Pleistocene and Holocene. These factors may have been crucial in driving the phylogeographic structure of the vertebrate fauna of the region. Here we test these hypotheses in the burrowing parrot Cyanoliseus patagonus (Aves, Psittaciformes across its wide distributional range in Chile and Argentina. Results Our data show a Chilean origin for this species, with a single migration event across the Andes during the Upper/Late Pleistocene, which gave rise to all extant Argentinean mitochondrial lineages. Analyses suggest a complex population structure for burrowing parrots in Argentina, which includes a hybrid zone that has remained stable for several thousand years. Within this zone, introgression by expanding haplotypes has resulted in the evolution of an intermediate phenotype. Multivariate regressions show that present day climatic variables have a strong influence on the distribution of genetic heterogeneity, accounting for almost half of the variation in the data. Conclusions Here we show how huge barriers like the Andes and the regional environmental conditions imposed constraints on the ability of a parrot species to colonise new habitats, affecting the way in which populations diverged and thus, genetic structure. When contact between divergent populations was re-established, a stable hybrid zone was formed, functioning as a channel for genetic exchange between populations.

  5. Tectonic and climate driven fluctuations in the stratigraphic base level of a Cenozoic continental coal basin, northwestern Andes

    Science.gov (United States)

    Silva Tamayo, J. C.; Sierra, G. M.; Correa, L. G.

    2008-12-01

    amalgamation and promoted both, high preservation of geomorphic elements and high diversity of sedimentary facies. This resulted in the most symmetric stratigraphic cycles of the entire Amagá Formation. The final stage of evolution of the Amagá Basin was related to the early stage of development of the late Miocene northwestern Andes tholeitic volcanism (from ˜10 to ˜8 Ma). The extensive thrusting and folding associated to this volcanism reduced the subsidence rates along the basin and thus the accommodation space. This permitted the development of highly aggradational braided rivers and promoted channels amalgamation. Little preservation of low energy facies, poor preservation of the geomorphic elements and a complete obliteration of important swamp deposits (coal beds) within the basin are reflected by the most asymmetric stratigraphic cycles of the whole formation. The presence of greenish/reddish flood plain deposits and Alfisols suggests a dry climate during this depositional stage. The presence of channel sandstones with high contents of volcanic rock fragments supports a dry climate, and suggests an incipient phase of the Combia tholeiitic magmatism present during deposition of the Amagá Formation. The subsequent eastward migration of the NW Andes magmatic arc (after ˜8 Ma) may have produced basin inversion and suppressed deposition along the Amagá Basin.

  6. The Role of Crustal Tectonics in Volcano Dynamics (ROCTEVODY) along the Southern Andes: seismological study with emphasis on Villarrica Volcano

    Science.gov (United States)

    Mora-Stock, Cindy; Tassara, Andrés

    2016-04-01

    The Southern Andean margin is intrinsically related to the Liquiñe-Ofqui Fault Zone (LOFZ), a 1000 km-long dextral strike-slip arc-parallel fault on which most of the volcanic centers of the Southern Volcanic Zone (SCVZ) of the Andes are emplaced. At large spatial (102 - 103 km) and temporal (105 - 107 yr) scales, regional tectonics linked to partitioning of the oblique convergence controls the distribution of magma reservoirs, eruption rates and style, as well as the magma evolution. At small scales in space (transiently change the regional stress field, thus leading to eruptions and fault (re)activation. However, the mechanisms by which the interaction between (megathrust and crustal) earthquakes and volcanic eruptions actually occur, in terms of generating the relationships and characteristics verified at the long term, are still poorly understood. Since 2007, the Southern Andean margin has presented an increase of its tectonic and eruptive activity with several volcanic crisis and eruptions taking place in association with significant seismicity clusters and earthquakes both in the megathrust and the LOFZ. This increased activity offers a unique opportunity to improve our understanding of the physical relation between contemporary tectono-volcanic processes and the long-term construction of the LOFZ-SVZ system. Taking advantage of this opportunity by means of an integrated analysis of geodetic and seismological data through finite element numerical modeling at the scale of the entire margin and for selected cases is the main goal of project Active Tectonics and Volcanism at the Southern Andes (ACT&VO-SA, see Tassara et al. this meeting). Into the framework of the ACT&VO-SA project, the complementary ROCTEVODY-Villarrica project concentrates on the role that inherited crustal structures have in the volcano dynamics. The focus is on Villarrica volcano, which is emplaced at the intersection of the main NNE-branch of the LOFZ and the NW-SE inherited Mocha

  7. A GIS-based Spatial Analysis of Volcanoes in the Central Andes: Insights Into Factors Controlling Volcano Spacing.

    Science.gov (United States)

    Savant, S. S.; de Silva, S. L.

    2005-12-01

    Volcano spacing has received little attention since the mid-70's when studies undertaken by Vogt (1974; EPSL) and then Marsh (1979; J Geol) suggested a regular spacing of volcanoes in arcs that ranged from 50 to 75 km for different arcs. The spacing was thought to be influenced by the thickness of the lithosphere or gravitational (Rayleigh-Taylor) instabilities related to source layer thickness and viscosity respectively. We have revisited these ideas through a detailed study of volcano distribution in the Central Volcanic Zone (CVZ) of the Andes where volcano spacing was thought to be around 70 km. The CVZ was selected as it is the type example of continental arc volcanism, built on an extremely thick crust of up to 70 km. The availability of a comprehensive dataset describing the relative age, location, and geomorphic characteristics of each volcano (Volcanoes of the Central Andes, de Silva and Francis, 1990, Springer Verlag) made this a compelling case study. The ready availability of ARC GIS Geographic Information Systems software and the geospatial analysis tools therein, allowed a comprehensive spatial analysis of the volcanoes to be conducted. Of the 1,118 volcanoes of ages from 23Ma to active in the CVZ, we focused on the 106 active and potentially active large composite volcanoes that define the modern arc. These volcanoes are related in time and thus to a consistent set of tectonic factors. The frequency distribution of inter-volcano distances shows a peak frequency in the 10 - 30 km range (71%) with subordinate between 40-80 km (19%) and 80 - 120 km (10%). The characteristic spacing is thus much smaller than the characteristic spacing of 70 km found previously and is consistent with Baker (1974; EPSL). The primary cause appears to be clustering of volcanoes into groups. The density of volcanoes is variable along the arc with regularly spaced clusters of two to three volcanoes in northern and southern parts of the arc (13 r°S to 19 r°S and 24 r° to 27

  8. Pedological and mineralogical investigations on a soil-paleosoil sequence within Andosols in the Western Cordillera of the Peruvian Andes (region Laramate, 14.5S)

    Science.gov (United States)

    Leceta Gobitz, Fernando; Mächtle, Bertil; Schukraft, Gerd; Meyer, Hans-Peter; Eitel, Bernhard

    2016-04-01

    An integrated research project of environmental sciences focuses on a group of four Andosol profiles in Western flank of the Peruvian southern Andes. Aim of this study is to contribute to the reconstruction of the paleo environmental conditions in the Western Cordillera of the Peruvian Andes. Standard pedological and sedimentological analysis has been conducted in order to identify morphological and geochemical features generated by climatic variations during the middle and late Holocene. Though a provenance analysis of sediments, all potential lithological sources around the town of Laramate are being examined under the scanning electron microscope, in order to find significant mineralogical associations downward the soil-profile. Preliminary results reveal two edaphic cycles within a soil-paleo soil-sequence: a relative poor developed "Ah" topsoil, mostly composed by fine grain sediments, is underlain by a well preserved "2Ah" paleo soil; a "2Bwt" subsoil exhibits signs of alteration and clay translocation; parent material in slight weathered statement at "2C" culminates the sequence. Mineralogical analytical data supports the premise, that materials in the uppermost horizons are relatable to distal geological units of the Western and Eastern Cordillera, therefore also related to other described aeolian archives from the region: "Desert Margin Loess" at the Andean foot-zone and "Mixed Loess" in the Puna grassland. The amphibole varieties Actinolite, Mg-Hornblende and Edenite could be only distinguished within the soil sediments. The fluvial transport to its current position is excluded, insofar mentioned varieties stem from the granodiorites of Coastal Batholite (downstream the study area), and the vulcanites of the Anta und Andahuaylas Formation (eastward the continental divide). References: Eitel, B., et al. (2005). "Geoarchaeological evidence from desert loess in the Nazca-Palpa region, southern Peru : Palaeoenvironmental changes and their impact on Pre

  9. Infection of human monocyte-derived dendritic cells by ANDES Hantavirus enhances pro-inflammatory state, the secretion of active MMP-9 and indirectly enhances endothelial permeability

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    Lopez-Lastra Marcelo

    2011-05-01

    Full Text Available Abstract Background Andes virus (ANDV, a rodent-borne Hantavirus, is the major etiological agent of Hantavirus cardiopulmonary syndrome (HCPS in South America, which is mainly characterized by a vascular leakage with high rate of fatal outcomes for infected patients. Currently, neither specific therapy nor vaccines are available against this pathogen. ANDV infects both dendritic and epithelial cells, but in despite that the severity of the disease directly correlates with the viral RNA load, considerable evidence suggests that immune mechanisms rather than direct viral cytopathology are responsible for plasma leakage in HCPS. Here, we assessed the possible effect of soluble factors, induced in viral-activated DCs, on endothelial permeability. Activated immune cells, including DC, secrete gelatinolytic matrix metalloproteases (gMMP-2 and -9 that modulate the vascular permeability for their trafficking. Methods A clinical ANDES isolate was used to infect DC derived from primary PBMC. Maturation and pro-inflammatory phenotypes of ANDES-infected DC were assessed by studying the expression of receptors, cytokines and active gMMP-9, as well as some of their functional status. The ANDES-infected DC supernatants were assessed for their capacity to enhance a monolayer endothelial permeability using primary human vascular endothelial cells (HUVEC. Results Here, we show that in vitro primary DCs infected by a clinical isolate of ANDV shed virus RNA and proteins, suggesting a competent viral replication in these cells. Moreover, this infection induces an enhanced expression of soluble pro-inflammatory factors, including TNF-α and the active gMMP-9, as well as a decreased expression of anti-inflammatory cytokines, such as IL-10 and TGF-β. These viral activated cells are less sensitive to apoptosis. Moreover, supernatants from ANDV-infected DCs were able to indirectly enhance the permeability of a monolayer of primary HUVEC. Conclusions Primary human DCs

  10. Una visión del átomo desde los estudiantes de educación de la universidad de los Andes-Venezuela

    OpenAIRE

    Escalona Tapia, J.; Rondón, P.; López, W.; Rincón, G; Ordaz Obando, A.; Barboza Molina, J.; Rivas, C.

    2009-01-01

    La concepción de átomo contiene elementos filosóficos y experimentales, y su explicación supone abstracciones no siempre fáciles de realizar. Por ello, este trabajo tuvo por objetivo evidenciar las concepciones sobre el átomo que poseen los estudiantes de la Universidad de Los Andes-Venezuela. La metodología involucró 44 estudiantes a los que se les pidió responder a una pregunta abierta, durante 4 semestres consecutivos. Las conclusiones indican que algunas respuestas de los estudiantes resp...

  11. PÉROU - Justice et citoyenneté dans les Andes péruviennes : histoire et rôle des Rondes paysannes en contexte minier

    OpenAIRE

    Piccoli, Emmanuelle

    2015-01-01

    Depuis plus de trente ans, les Rondes assurent, pour des centaines de milliers de personnes des Andes péruviennes, l’ordre, la justice et la gestion quotidienne de la vie rurale. Fruit de l’effort de mobilisation des paysans de la région, dynamique communautaire remarquable, elles sont, par-delà l’État, les organisations sociales emblématiques, spécialement de la région du Nord, et elles assurent justice, vigilance et politique communautaires. Les conflits miniers qui secouent la région, nota...

  12. Vulnerability assessment in a participatory approach to design and implement community based adaptation to drought in the Peruvian Andes

    Science.gov (United States)

    Lasage, Ralph; Muis, Sanne; Sardella, Carolina; van Drunen, Michiel; Verburg, Peter; Aerts, Jeroen

    2015-04-01

    The livelihoods of people in the Andes are expected to be affected by climate change due to their dependence on glacier meltwater during the growing season. The observed decrease in glacier volume over the last few decades is likely to accelerate during the current century, which will affect water availability in the region. This paper presents the implementation of an approach for the participatory development of community-based adaptation measures to cope with the projected impacts of climate change, which was implemented jointly by the local community and by a team consisting of an NGO, Peruvian ministry of environment, research organisations and a private sector organisation. It bases participatory design on physical measurements, modelling and a vulnerability analysis. Vulnerability to drought is made operational for households in a catchment of the Ocoña river basin in Peru. On the basis of a household survey we explore how a vulnerability index (impacts divided by the households' perceived adaptive capacity) can be used to assess the distribution of vulnerability over households in a sub catchment. The socio-economic factors water entitlement, area of irrigated land, income and education are all significantly correlate with this vulnerability to drought. The index proved to be appropriate for communicating about vulnerability to climate change and its determining factors with different stakeholders. The water system research showed that the main source of spring water is local rainwater, and that water use efficiency in farming is low. The adaptation measures that were jointly selected by the communities and the project team aimed to increase water availability close to farmland, and increase water use efficiency, and these will help to reduce the communities vulnerability to drought.

  13. Mass balance evolution on two glaciers in the ecuadorian Andes (0°28'S) since the mid-20th century

    Science.gov (United States)

    Basantes, Ruben; Rabatel, Antoine; Alvarez, Danilo; Francou, Bernard; Galarraga, Remigio; Maisincho, Luis; Caceres, Bolivar

    2014-05-01

    The glacier mass balance evolution on two glaciers (Antisana Glacier 12 and Antisana Glacier 15α) in the tropical Andes is presented. To this end, photogrammetry technique was applied on aerial images taken at five dates: 1956, 1965, 1979, 1997 and 2009. For each date, digital elevation models (DEMs) were generated with an average vertical accuracy of ±2.2 m. The spatiotemporal volume variation of the glaciers is calculated through the elevations differences between DEMs and a density factor. The outcomes show that after 1970s the glaciers have experimented a strong recession even if a noticeable increase in mass was detected between 1965 and 1979. From 1979 to 1997, the ablation rates have dramatically increased and the average annual mass balance reached very negative values (-1.1 m w.e. yr-1 for Antisana Glacier 15α and -0.8 m w.e. yr-1 for Antisana Glacier 12). In the last study period, from 1997 to 2009, the glaciers average annual mass balances were less negative (-0.6 m w.e. yr-1 for Antisana Glacier 12 and -0.2 m w.e. yr-1 for Antisana Glacier 15α). The later matched with the period of conventional observations allowing compare the results given by both methodologies, i.e. geodetic and glaciological methods. However, some morphological constraints affecting the figures observed in the glaciological mass balance must be considered. Finally, we performed an analysis of the relationship between the glacier changes and the climate conditions over the study periods in order to understand how climate has impacted the glacier retreat in this region. For such an aim, local climate variables, i.e. temperature and precipitation, as well as regional indices, i.e. Pacific Decadal Oscillation (PDO) and Multivariate ENSO Index (MEI) have been used. The outcomes show a high correlation between the climate signals and the glacier behavior at both annual and decadal time scales.

  14. Validity and reliability of the Short Physical Performance Battery (SPPB: a pilot study on mobility in the Colombian Andes.

    Directory of Open Access Journals (Sweden)

    José Fernando Gómez Montes

    2013-09-01

    Full Text Available Normal 0 21 false false false ES-CO JA X-NONE Objectives: To assess the validity (convergent and construct and reliability of the Short Physical Performance Battery (SPPB among non-disabled adults between 65 to 74 years of age residing in the Andes Mountains of Colombia.Methods: Design: Validation study; Participants: 150 subjects aged 65 to 74 years recruited from elderly associations (day-centers in Manizales, Colombia.Measurements: The SPPB tests of balance, including time to walk 4 meters and time required to stand from a chair 5 times were administered to all participants.  Reliability was analyzed with a 7-day interval between assessments and use of repeated ANOVA testing. Construct validity was assessed using factor analysis and by testing the relationship between SPPB and depressive symptoms, cognitive function, and self rated health (SRH, while the concurrent validity was measured through relationships with mobility limitations and disability in Activities of Daily Living (ADL. ANOVA tests were used to establish these associations.Results: Test-retest reliability of the SPPB was high: 0.87 (CI95%: 0.77-0.96. A one factor solution was found with three SPPB tests. SPPB was related to self-rated health, limitations in walking and climbing steps and to indicators of disability, as well as to cognitive function and depression. There was a graded decrease in the mean SPPB score with increasing disability and poor health.Conclusion: The Spanish version of SPPB is reliable and valid to assess physical performance among older adults from our region.  Future studies should establish their clinical applications and explore usage in population studies.

  15. The Calama-Olacapato-El Toro fault system in the Puna Plateau, Central Andes: Geodynamic implications and stratovolcanoes emplacement

    Science.gov (United States)

    Norini, Gianluca; Baez, Walter; Becchio, Raul; Viramonte, Jose; Giordano, Guido; Arnosio, Marcelo; Pinton, Annamaria; Groppelli, Gianluca

    2013-11-01

    The structural evolution of the Puna Plateau is characterized by the activity of both orogen-parallel and orogen-oblique faults. Understanding the possible relationship between these two structural styles, their geodynamic implications and the influence on the migration of magmas is important to get insights into the tectonic and magmatic evolution of the Central Andes. In this study, we present a structural analysis of the orogen-oblique Calama-Olacapato-El Toro fault system and the surrounding orogen-parallel thrust faults in the central-eastern Puna Plateau. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the tectonic features in the studied area. We propose a three-dimensional geometrical reconstruction of the main fault planes showing their attitude and intersections at depth. The study indicates that the crust underwent simultaneous deformation along both the vertical transcurrent Calama-Olacapato-El Toro fault system and the low-angle thrust faults, and that the back-arc portion of the Calama-Olacapato-El Toro fault system developed as a transfer zone among the main N-striking thrusts. Our model considers that both orogen-parallel and orogen-oblique fault systems should be regarded as parts of the same tectonic system, accommodating crustal shortening of a thickened crust. The study suggests that the tectonic control on the magma and fluid circulation in the crust is mainly related to the geometry of the fault planes and the orientation of the stress field, with a previously unrecognized important role played by the orogen-parallel thrust faults on the emplacement of the stratovolcanoes.

  16. Continental underthrusting and obduction during the Cretaceous closure of the Rocas Verdes rift basin, Cordillera Darwin, Patagonian Andes

    Science.gov (United States)

    Klepeis, Keith; Betka, Paul; Clarke, Geoffrey; Fanning, Mark; Hervé, Francisco; Rojas, Lisandro; Mpodozis, Constantino; Thomson, Stuart

    2010-06-01

    The Patagonian Andes record a period of Cretaceous-Neogene orogenesis that began with the compressional inversion of a Late Jurassic rift called the Rocas Verdes basin. Detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of ˜148 Ma, suggesting that the basin opened approximately simultaneously along its length during the Late Jurassic. Structural data and U-Pb isotopic ages on zircon from granite plutons near the Beagle Channel (55°S) show that basin inversion involved two stages of shortening separated by tens of millions of years. An initial stage created a small (˜60 km wide) thrust wedge that placed the basaltic floor of the Rocas Verdes basin on top of adjacent continental crust prior to ˜86 Ma. Structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in Cordillera Darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of ˜35 km beneath a coeval volcanic arc. A subsequent stage of out-of-sequence thrusting, culminating in the Paleogene, shortened basement and Upper Jurassic igneous rock in the internal part of the belt by at least ˜50 km, forming a bivergent thrust wedge. This latter period coincided with the exhumation of rocks in Cordillera Darwin and expansion of the fold-thrust belt into the Magallanes foreland basin. This orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi-oceanic rift basin.

  17. Modern and long-term evaporation of central Andes surface waters suggests paleo archives underestimate Neogene elevations

    Science.gov (United States)

    Fiorella, Richard P.; Poulsen, Christopher J.; Pillco Zolá, Ramiro S.; Jeffery, M. Louise; Ehlers, Todd A.

    2015-12-01

    Central Andean paleoelevations reconstructed from stable isotope and paleofloral data imply a large magnitude (>2 km) Miocene-to-modern surface uplift. However, the isotopic relationships between precipitation, surface waters, and soil waters upon which these reconstructions are based remain poorly constrained for both past, and in many cases, modern conditions. We quantify the relationships between central Andean precipitation and surface waters by measuring the isotopic composition of 249 stream water samples (δ18O and δD) collected between April 2009 and October 2012. The isotopic compositions of stream waters match precipitation along the eastern flank. In contrast, Altiplano surface waters possess a lower δD-δ18O slope (4.59 vs ∼8 for meteoric waters) not observed in precipitation, which signals heavy isotope evaporative enrichment in surface waters. Paleoclimate models indicate that highly evaporative conditions have persisted on the plateau throughout Andean uplift, and that conditions may have been more evaporative when the Andes were lower. Thus, more ancient proxy materials may have a greater evaporative bias than previously recognized and paleoelevation reconstructions from stable isotope based central Andean plateau proxy materials likely overstate Miocene-to-present surface uplift. We propose Altiplano paleoelevations of 1-2 km at 24.5 Ma, 1.5-2.9 km by 11.45 Ma, and modern elevations by ∼6 Ma based on the lightest isotopic compositions observed in Altiplano proxy materials, which are least likely to be influenced by evaporation. These constraints limit total late-Miocene-to-modern uplift to <2.2 km, are more consistent with crustal shortening records, and suggest that plateau uplift may have been more spatially uniform than suggested by previous interpretations of stable isotope proxies.

  18. Early Cenozoic Shortening and Foreland Basin Sedimentation in the Marañon Fold-thrust Belt, Central Peruvian Andes

    Science.gov (United States)

    Jackson, L. J.; Carlotto, V.; Horton, B. K.; Rosell, L. N.

    2015-12-01

    The Marañon fold-thrust belt in the westernmost Andes of Peru has long been considered a robust signature of early Cenozoic shortening in the Andean orogenic belt. However, the structural details and potential records of coeval synorogenic sedimentation remain elusive. We report results from new geologic mapping (1:50,000), cross-section construction, and U-Pb geochronology for the Matucana-Ticlio region at 11-12°S along the Lima-La Oroya highway. Zircon U-Pb age data from volcanic rocks and clastic basin fill provide a maximum depositional age of ~43 Ma for a middle Eocene syndeformational unit that we identify as the Anta Formation, which overlies the Paleocene Casapalca Formation. Sedimentary lithofacies and unconformable relationships within the volcaniclastic Anta Formation reveal mixed fluvial, alluvial-fan, and volcanic depositional conditions during shortening accommodated by a NE-verging thrust/reverse fault and corresponding backthrust (here named the Chonta fault system). Our cross-section reconstruction and geochronological data indicate that the region is a critical, possibly unique, zone of the broader NE-directed Marañon fold-thrust belt where pre-Neogene synorogenic sediments and their associated structures are preserved. We interpret this combined structural and basin system as an Eocene-age (Incaic) frontal thrust belt and corresponding foredeep to wedge-top depozone in central Peru. As one of the better-constrained segments of the Marañon fold-thrust belt, this zone provides insight into potential linkages with elusive early Cenozoic (Incaic) structures and foreland basin fill of the Western Cordillera and Altiplano farther south in the central Andean plateau.

  19. Co-Infection by Chytrid Fungus and Ranaviruses in Wild and Harvested Frogs in the Tropical Andes.

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    Robin W Warne

    Full Text Available While global amphibian declines are associated with the spread of Batrachochytrium dendrobatidis (Bd, undetected concurrent co-infection by other pathogens may be little recognized threats to amphibians. Emerging viruses in the genus Ranavirus (Rv also cause die-offs of amphibians and other ectotherms, but the extent of their distribution globally, or how co-infections with Bd impact amphibians are poorly understood. We provide the first report of Bd and Rv co-infection in South America, and the first report of Rv infections in the amphibian biodiversity hotspot of the Peruvian Andes, where Bd is associated with extinctions. Using these data, we tested the hypothesis that Bd or Rv parasites facilitate co-infection, as assessed by parasite abundance or infection intensity within individual adult frogs. Co-infection occurred in 30% of stream-dwelling frogs; 65% were infected by Bd and 40% by Rv. Among terrestrial, direct-developing Pristimantis frogs 40% were infected by Bd, 35% by Rv, and 20% co-infected. In Telmatobius frogs harvested for the live-trade 49% were co-infected, 92% were infected by Bd, and 53% by Rv. Median Bd and Rv loads were similar in both wild (Bd = 101.2 Ze, Rv = 102.3 viral copies and harvested frogs (Bd = 103.1 Ze, Rv = 102.7 viral copies. While neither parasite abundance nor infection intensity were associated with co-infection patterns in adults, these data did not include the most susceptible larval and metamorphic life stages. These findings suggest Rv distribution is global and that co-infection among these parasites may be common. These results raise conservation concerns, but greater testing is necessary to determine if parasite interactions increase amphibian vulnerability to secondary infections across differing life stages, and constitute a previously undetected threat to declining populations. Greater surveillance of parasite interactions may increase our capacity to contain and mitigate the impacts of these and

  20. Effects of soil chemistry on tropical forest biomass and productivity at different elevations in the equatorial Andes.

    Science.gov (United States)

    Unger, Malte; Homeier, Jürgen; Leuschner, Christoph

    2012-09-01

    The dependence of aboveground biomass and productivity of tropical forests on soil fertility is not fully understood, since previous studies yielded contrasting results. Here, we quantify aboveground biomass (AGB) and stem wood production, and examine the impact of soil chemistry on these parameters in mature tropical forest stands of the equatorial Andes in Ecuador. In 80 plots of 0.04 ha at four elevation levels (500, 1,000, 1,500 and 2,000 m a.s.l., total sample area = 3.2 ha), we measured ten important soil chemical parameters, inventoried all trees ≥10 cm dbh and monitored stem diameter growth with dendrometer tapes in 32 plots. Top canopy height and stem density significantly decreased from 500 to 2,000 m, while tree basal area increased and AGB remained invariant (344 ± 17 Mg DM ha(-1), mean ± SE) with elevation. Wood specific gravity (WSG) showed a significant, but small, decrease. Stem wood production decreased from 4.5 to 3.2 Mg DM ha(-1) year(-1) along the transect, indicating a higher biomass turnover at lower elevations. The only soil variable that covaried with AGB was exchangeable K in the topsoil. WSG increased with decreases in N mineralisation rate, soil pH and extractable Ca and P concentrations. Structural equation modelling (SEM) revealed that nitrogen availability acts on stem wood production only indirectly through a negative relation between N mineralisation rate and WSG, and a positive effect of a lowered WSG on stem growth. The SEM analysis showed neither direct nor indirect effects of resin-extractable P on wood production, but a negative P influence on AGB. We conclude that nitrogen availability significantly influences productivity in these Andean forests, but both N and P are affecting wood production mainly indirectly through alterations in WSG and stem density; the growth-promoting effect of N is apparently larger than that of P. PMID:22410639

  1. Spatial components of bird diversity in the Andes of Colombia: implications for designing a regional reserve system.

    Science.gov (United States)

    Kattan, Gustavo H; Franco, Padu; Saavedra-Rodríguez, Carlos A; Valderrama, Carlos; Rojas, Vladimir; Osorio, Daniel; Martínez, Jesús

    2006-08-01

    Beta diversity, or the turnover in species composition among sampling sites in a region, is an important criterion for obtaining adequate representation of regional biodiversity in systems of protected areas. Recently, the additive model for partitioning regional (gamma) diversity (in opposition to the multiplicative model) has been proposed because it allows a direct measure of the contribution of beta diversity to gamma diversity. We determined avian beta diversity along latitudinal (among neighboring river drainages) and elevational axes in a 1347-km2 region on the western slope of the Central Cordillera of the Colombian Andes, where a regional system of protected areas is being designed. We then compared avian beta diversity between sites based on rapid versus long-term (>1 year) inventories and between fragmented sites versus continuous forest. Overall, beta diversity represented 63.1% of gamma diversity among 16 sites. Elevational differences in species composition accounted for 43.3% of regional diversity, whereas differences among drainages accounted for 19.8%. A complementary cluster analysis showed that sites grouped by elevational zones. Rapid inventories overestimated beta diversity because of sampling effects, but the effect was biologically small. Estimators of species richness derived from species accumulation curves provided a useful alternative to compensate for undersampling in short-term surveys. Forest fragmentation increased beta diversity because of differential local extinction of populations. Nevertheless, in our region, forest fragments contributed to gamma diversity because they contained complementary sets of species. More importantly, they contained populations of special-interest species. Although the region is relatively small, our analyses indicate that spatial differentiation of the biota is an important factor for deciding number and location of protected areas in the Andean region.

  2. Experimental Andes virus infection in deer mice: characteristics of infection and clearance in a heterologous rodent host.

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    Jessica R Spengler

    Full Text Available New World hantaviruses can cause hantavirus cardiopulmonary syndrome with high mortality in humans. Distinct virus species are hosted by specific rodent reservoirs, which also serve as the vectors. Although regional spillover has been documented, it is unknown whether rodent reservoirs are competent for infection by hantaviruses that are geographically separated, and known to have related, but distinct rodent reservoir hosts. We show that Andes virus (ANDV of South America, carried by the long tailed pygmy rice rat (Oligoryzomys longicaudatus, infects and replicates in vitro and in vivo in the deer mouse (Peromyscus maniculatus, the reservoir host of Sin Nombre virus (SNV, found in North America. In experimentally infected deer mice, viral RNA was detected in the blood, lung, heart and spleen, but virus was cleared by 56 days post inoculation (dpi. All of the inoculated deer mice mounted a humoral immune response by 14 dpi, and produced measurable amounts of neutralizing antibodies by 21 dpi. An up-regulation of Ccl3, Ccl4, Ccl5, and Tgfb, a strong CD4⁺ T-cell response, and down-regulation of Il17, Il21 and Il23 occurred during infection. Infection was transient with an absence of clinical signs or histopathological changes. This is the first evidence that ANDV asymptomatically infects, and is immunogenic in deer mice, a non-natural host species of ANDV. Comparing the immune response in this model to that of the immune response in the natural hosts upon infection with their co-adapted hantaviruses may help clarify the mechanisms governing persistent infection in the natural hosts of hantaviruses.

  3. Atomic Structure and Biochemical Characterization of an RNA Endonuclease in the N Terminus of Andes Virus L Protein.

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    Yaiza Fernández-García

    2016-06-01

    Full Text Available Andes virus (ANDV is a human-pathogenic hantavirus. Hantaviruses presumably initiate their mRNA synthesis by using cap structures derived from host cell mRNAs, a mechanism called cap-snatching. A signature for a cap-snatching endonuclease is present in the N terminus of hantavirus L proteins. In this study, we aimed to solve the atomic structure of the ANDV endonuclease and characterize its biochemical features. However, the wild-type protein was refractory to expression in Escherichia coli, presumably due to toxic enzyme activity. To circumvent this problem, we introduced attenuating mutations in the domain that were previously shown to enhance L protein expression in mammalian cells. Using this approach, 13 mutant proteins encompassing ANDV L protein residues 1-200 were successfully expressed and purified. Protein stability and nuclease activity of the mutants was analyzed and the crystal structure of one mutant was solved to a resolution of 2.4 Å. Shape in solution was determined by small angle X-ray scattering. The ANDV endonuclease showed structural similarities to related enzymes of orthobunya-, arena-, and orthomyxoviruses, but also differences such as elongated shape and positively charged patches surrounding the active site. The enzyme was dependent on manganese, which is bound to the active site, most efficiently cleaved single-stranded RNA substrates, did not cleave DNA, and could be inhibited by known endonuclease inhibitors. The atomic structure in conjunction with stability and activity data for the 13 mutant enzymes facilitated inference of structure-function relationships in the protein. In conclusion, we solved the structure of a hantavirus cap-snatching endonuclease, elucidated its catalytic properties, and present a highly active mutant form, which allows for inhibitor screening.

  4. Atomic Structure and Biochemical Characterization of an RNA Endonuclease in the N Terminus of Andes Virus L Protein.

    Science.gov (United States)

    Fernández-García, Yaiza; Reguera, Juan; Busch, Carola; Witte, Gregor; Sánchez-Ramos, Oliberto; Betzel, Christian; Cusack, Stephen; Günther, Stephan; Reindl, Sophia

    2016-06-01

    Andes virus (ANDV) is a human-pathogenic hantavirus. Hantaviruses presumably initiate their mRNA synthesis by using cap structures derived from host cell mRNAs, a mechanism called cap-snatching. A signature for a cap-snatching endonuclease is present in the N terminus of hantavirus L proteins. In this study, we aimed to solve the atomic structure of the ANDV endonuclease and characterize its biochemical features. However, the wild-type protein was refractory to expression in Escherichia coli, presumably due to toxic enzyme activity. To circumvent this problem, we introduced attenuating mutations in the domain that were previously shown to enhance L protein expression in mammalian cells. Using this approach, 13 mutant proteins encompassing ANDV L protein residues 1-200 were successfully expressed and purified. Protein stability and nuclease activity of the mutants was analyzed and the crystal structure of one mutant was solved to a resolution of 2.4 Å. Shape in solution was determined by small angle X-ray scattering. The ANDV endonuclease showed structural similarities to related enzymes of orthobunya-, arena-, and orthomyxoviruses, but also differences such as elongated shape and positively charged patches surrounding the active site. The enzyme was dependent on manganese, which is bound to the active site, most efficiently cleaved single-stranded RNA substrates, did not cleave DNA, and could be inhibited by known endonuclease inhibitors. The atomic structure in conjunction with stability and activity data for the 13 mutant enzymes facilitated inference of structure-function relationships in the protein. In conclusion, we solved the structure of a hantavirus cap-snatching endonuclease, elucidated its catalytic properties, and present a highly active mutant form, which allows for inhibitor screening. PMID:27300328

  5. Utilizing NASA Earth Observations to Model Volcanic Hazard Risk Levels in Areas Surrounding the Copahue Volcano in the Andes Mountains

    Science.gov (United States)

    Keith, A. M.; Weigel, A. M.; Rivas, J.

    2014-12-01

    Copahue is a stratovolcano located along the rim of the Caviahue Caldera near the Chile-Argentina border in the Andes Mountain Range. There are several small towns located in proximity of the volcano with the two largest being Banos Copahue and Caviahue. During its eruptive history, it has produced numerous lava flows, pyroclastic flows, ash deposits, and lahars. This isolated region has steep topography and little vegetation, rendering it poorly monitored. The need to model volcanic hazard risk has been reinforced by recent volcanic activity that intermittently released several ash plumes from December 2012 through May 2013. Exposure to volcanic ash is currently the main threat for the surrounding populations as the volcano becomes more active. The goal of this project was to study Copahue and determine areas that have the highest potential of being affected in the event of an eruption. Remote sensing techniques were used to examine and identify volcanic activity and areas vulnerable to experiencing volcanic hazards including volcanic ash, SO2 gas, lava flow, pyroclastic density currents and lahars. Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Landsat 8 Operational Land Imager (OLI), EO-1 Advanced Land Imager (ALI), Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topography Mission (SRTM), ISS ISERV Pathfinder, and Aura Ozone Monitoring Instrument (OMI) products were used to analyze volcanic hazards. These datasets were used to create a historic lava flow map of the Copahue volcano by identifying historic lava flows, tephra, and lahars both visually and spectrally. Additionally, a volcanic risk and hazard map for the surrounding area was created by modeling the possible extent of ash fallout, lahars, lava flow, and pyroclastic density currents (PDC) for future eruptions. These model results were then used to identify areas that should be prioritized for disaster relief and evacuation orders.

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

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    S. MacDonell

    2013-09-01

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

  7. Long-term effects of climate and land cover change on freshwater provision in the tropical Andes

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    A. Molina

    2015-06-01

    Full Text Available Andean headwater catchments play a pivotal role to supply fresh water for downstream water users. However, few long-term studies exist on the relative importance of climate change and direct anthropogenic perturbations on flow regimes. In this paper, we assess multi-decadal change in freshwater provision based on long time series (1974–2008 of hydrometeorological data and land cover reconstructions for a 282 km2 catchment located in the tropical Andes. Three main land cover change trajectories can be distinguished: (1 rapid decline of native vegetation in montane forest and páramo ecosystems in ~1/5 or 20% of the catchment area, (2 expansion of agricultural land by 14% of the catchment area, (3 afforestation of 12% of native páramo grasslands with exotic tree species in recent years. Given the strong temporal variability of precipitation and streamflow data related to El Niño–Southern Oscillation, we use empirical mode decomposition techniques to detrend the time series. The long-term increasing trend in rainfall is remarkably different from the observed changes in streamflow that exhibit a decreasing trend. Hence, observed changes in streamflow are not the result of long-term climate change but very likely result from direct anthropogenic disturbances after land cover change. Partial water budgets for montane cloud forest and páramo ecosystems suggest that the strongest changes in evaporative water losses are observed in páramo ecosystems, where progressive colonization and afforestation of high alpine grasslands leads to a strong increase in transpiration losses.

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

    Science.gov (United States)

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

    2016-03-01

    -term history of convergent margin deformation in the Andes.

  9. A 2,300-year-long annually resolved record of the South American summer monsoon from the Peruvian Andes.

    Science.gov (United States)

    Bird, Broxton W; Abbott, Mark B; Vuille, Mathias; Rodbell, Donald T; Stansell, Nathan D; Rosenmeier, Michael F

    2011-05-24

    Decadal and centennial mean state changes in South American summer monsoon (SASM) precipitation during the last 2,300 years are detailed using an annually resolved authigenic calcite record of precipitation δ(18)O from a varved lake in the Central Peruvian Andes. This unique sediment record shows that δ(18)O peaked during the Medieval Climate Anomaly (MCA) from A.D. 900 to 1100, providing evidence that the SASM weakened considerably during this period. Minimum δ(18)O values occurred during the Little Ice Age (LIA) between A.D. 1400 and 1820, reflecting a prolonged intensification of the SASM that was regionally synchronous. After the LIA, δ(18)O increased rapidly, particularly during the current warm period (CWP; A.D. 1900 to present), indicating a return to reduced SASM precipitation that was more abrupt and sustained than the onset of the MCA. Diminished SASM precipitation during the MCA and CWP tracks reconstructed Northern Hemisphere and North Atlantic warming and a northward displacement of the Intertropical Convergence Zone (ITCZ) over the Atlantic, and likely the Pacific. Intensified SASM precipitation during the LIA follows reconstructed Northern Hemisphere and North Atlantic cooling, El Niño-like warming in the Pacific, and a southward displacement of the ITCZ over both oceans. These results suggest that SASM mean state changes are sensitive to ITCZ variability as mediated by Western Hemisphere tropical sea surface temperatures, particularly in the Atlantic. Continued Northern Hemisphere and North Atlantic warming may therefore help perpetuate the recent reductions in SASM precipitation that characterize the last 100 years, which would negatively impact Andean water resources. PMID:21555548

  10. Environmental and climatic history in the NW Argentine Andes (24° S over the last 2100 years inferred from a high-altitude peatland record

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    K. Schittek

    2015-05-01

    Full Text Available High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies and sensitivity to climatic and/or human-induced changes. Especially within the central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP, which is located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF, stable isotope and element content analyses (δ13C, δ15N, TN and TOC were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatland's past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that Northern Hemisphere temperature oscillations were extensive and affected the southward migration of the Intertropical Convergence Zone (ITCZ, and hence, the intensity of moisture flux within the South American Summer Monsoon (SASM belt. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption seems to have had an impact on climatic settings in the central Andes. In the past, the peatland recovered from climatic perturbations. Nowadays, CTP is heavily degraded by human interventions, and the peat deposit becomes increasingly susceptible to erosion and incision.

  11. Paleomagnetism in the Precordillera of northern Chile (22°30'S): implications for the history of tectonic rotations in the Central Andes

    Science.gov (United States)

    Somoza, Rubén; Tomlinson, Andrew

    2002-01-01

    Widespread clockwise rotations in Mesozoic and Lower Tertiary rocks of northern Chile have been interpreted as the sum of two rotational events separated in time: an early rotation related to local deformation plus a late rotation related to wholesale rotation of northern Chile linked to Late Cenozoic oroclinal bending in the Central Andes. In this paper we report new paleomagnetic data from Cretaceous, upper Oligocene and Miocene sedimentary rocks in the Precordillera of northern Chile. The results suggest that all these rocks acquired their remanence at or close to the time of deposition. The lack of rotation in undeformed lower Miocene strata clearly indicates that clockwise rotations found in underlying, faulted and folded Cretaceous rocks were completed before the Late Cenozoic. Results from nearby localities in deformed upper Oligocene strata would argue for little (˜5°) rotation since the late Oligocene. Data from widely separated Miocene localities covering an area of about 5000 km 2 in the Calama basin strongly suggest that northern Chile did not undergo significant wholesale rotation during the Late Cenozoic. This, together with previous paleomagnetic evidence against Neogene rigid-body-like rotation of the southern Peruvian forearc, suggests that the curved shape of the Central Andean forearc was not significantly enhanced during the Late Cenozoic. By inference, all of the rotation in most Mesozoic and Lower Tertiary rocks of northern Chile was accomplished in the Cretaceous and/or Early Cenozoic, when the locus of deformation in the Central Andes was localized in the present forearc region.

  12. The effect of drainage on organic matter accumulation and plant communities of high-altitude peatlands in the Colombian tropical Andes

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    J.C. Benavides

    2014-04-01

    Full Text Available The tropical Andes store and regulate water outflow that serves nearly 60 million people. Most of the water is for un-managed agricultural irrigation. In this work I report how the drainage of peatlands has adversely affected the development of plant communities and recent carbon accumulation in a páramo massif at 2500 to 3800 m altitude in the northern Andes. I surveyed vegetation and water chemistry in 26 peatlands with differing intensities of drainage. Peat cores to 50 cm from two sites with contrasting drainage histories were dated using 210Pb, and used to compare historical vegetation changes and carbon accumulation rates. (A Species composition was much affected by drainage, which resulted in a reduction in cover of Sphagnum and other peat-forming species, and the encroachment of sedges and Juncus effusus. The ability of peat to store water and carbon was also reduced in drained peatlands. Vegetation records show a shift towards sedge-Juncus communities around 50 years ago when agricultural use of water increased. (B Peat and carbon accumulation rates were lower in drained sites, indicating either greater decomposition rates of the upper peat column or lower production by the changed plant communities. The ecological services offered by peatlands to agrarian communities downstream are important. Measures to prevent peatland destruction are needed urgently.

  13. 10Be dating of river terraces of Santo Domingo river, on Southeastern flank of the Mérida Andes, Venezuela: Tectonic and climatic implications

    Science.gov (United States)

    Guzmán, Oswaldo; Vassallo, Riccardo; Audemard, Franck; Mugnier, Jean-Louis; Oropeza, Javier; Yepez, Santiago; Carcaillet, Julien; Alvarado, Miguel; Carrillo, Eduardo

    2013-12-01

    In this study, we discuss the first cosmogenic 10Be dating of river terraces located in the lower reaches of the Santo Domingo river (Southeastern flank of the Mérida Andes, Western Venezuela). The geomorphic observations and dating allowed the restoration of the temporal evolution of incision rate, which was analysed in terms of tectonic, climatic and geomorphic processes. The long-term incision rate in the area has been constantly around 1.1 mm/a over the last 70 ka. Taking into account the geologic and geomorphologic setting, this value can be converted into the Late Pleistocene uplift rate of the Southeastern flank of the Mérida Andes. Our results show that the process of terraces formation in the lower reaches of the Santo Domingo river occurred at a higher frequency (103-104 years) than a glacial/interglacial cycle (104-105 years). According to the global and local climate curve, these terraces were abandoned during warm to cold transitions.

  14. Niche shifts and range expansions along cordilleras drove diversification in a high-elevation endemic plant genus in the tropical Andes.

    Science.gov (United States)

    Kolář, Filip; Dušková, Eva; Sklenář, Petr

    2016-09-01

    The tropical Andes represent one of the world's biodiversity hot spots, but the evolutionary drivers generating their striking species diversity still remain poorly understood. In the treeless high-elevation Andean environments, Pleistocene glacial oscillations and niche differentiation are frequently hypothesized diversification mechanisms; however, sufficiently densely sampled population genetic data supporting this are still lacking. Here, we reconstruct the evolutionary history of Loricaria (Asteraceae), a plant genus endemic to the Andean treeless alpine zone, based on comprehensive population-level sampling of 289 individuals from 67 populations across the entire distribution ranges of its northern Andean species. Partly incongruent AFLP and plastid DNA markers reveal that the distinct genetic structure was shaped by a complex interplay of biogeography (spread along and across the cordilleras), history (Pleistocene glacial oscillations) and local ecological conditions. While plastid variation documents an early split or colonization of the northern Andes by at least two lineages, one of which further diversified, a major split in the AFLP data correlate with altitudinal ecological differentiation. This suggests that niche shifts may be important drivers of Andean diversification not only in forest-alpine transitions, but also within the treeless alpine zone itself. The patterns of genetic differentiation at the intraspecific level reject the hypothesized separation in spatially isolated cordilleras and instead suggest extensive gene flow among populations from distinct mountain chains. Our study highlights that leveraging highly variable markers against extensive population-level sampling is a promising approach to address mechanisms of rapid species diversifications.

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

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    A. Lavenu

    2006-12-01

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

  16. Aproximaciones Biológicas y Fisicoquímicas en el tratamiento de contaminantes: un resumen del aporte de la Universidad de los Andes

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    Jenny Dussan Garzón

    2009-11-01

    Full Text Available Este resumen pretende dar una visión global de los aportes de la Universidad de los Andes en el tratamiento de aguas y suelos con la presencia de compuestos de difícil degradación o tiempo de vida media prolongado, tales como fármacos (Ciclofosfamida, lodos aceitosos y derivados de la industria del petróleo (Tolueno, Xileno, Fenol derivados de la industria textil, química y pesticidas (Bisphenol A, AMBI, Glifosato, Isoproturon y Metobromuron, usando tecnologías ya sea basadas en procesos biológicos (biorremediación y bioadsorción o de oxidación avanzada (foto-Fenton. /This summary intends to give a global view of the Universidad de los Andes contributions related to the water and soil treatment in the presence of recalcitrant or long half-life aquatic pollutants such as drugs (Cyclophosphamide, oil sludge and petroleum (Toluene, Xylene and Phenol, textile, chemical (Bisphenol A, AMBI and pesticides (Glyphosate, Isoproturon, and Metobromuron industry derived products based on biological (bioremediation and bioadsortion and advanced oxidation (Photo-Fenton approaches.

  17. First web-based database on total phenolics and oxygen radical absorbance capacity (ORAC) of fruits produced and consumed within the south Andes region of South America.

    Science.gov (United States)

    Speisky, Hernan; López-Alarcón, Camilo; Gómez, Maritza; Fuentes, Jocelyn; Sandoval-Acuña, Cristian

    2012-09-12

    This paper reports the first database on antioxidants contained in fruits produced and consumed within the south Andes region of South America. The database ( www.portalantioxidantes.com ) contains over 500 total phenolics (TP) and ORAC values for more than 120 species/varieties of fruits. All analyses were conducted by a single ISO/IEC 17025-certified laboratory. The characterization comprised native berries such as maqui ( Aristotelia chilensis ), murtilla ( Ugni molinae ), and calafate ( Barberis microphylla ), which largely outscored all other studied fruits. Major differences in TP and ORAC were observed as a function of the fruit variety in berries, avocado, cherries, and apples. In fruits such as pears, apples, apricots, and peaches, a significant part of the TP and ORAC was accounted for by the antioxidants present in the peel. These data should be useful to estimate the fruit-based intake of TP and, through the ORAC data, their antioxidant-related contribution to the diet of south Andes populations. PMID:22512599

  18. Phytogeography of the vascular páramo flora of Ramal de Guaramacal (Andes, Venezuela and its ties to other páramo floras

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    Cuello, Nidia L.

    2010-12-01

    Full Text Available Ramal de Guaramacal is an outlier and lower elevation mountain range located at the northeastern end of the Venezuelan Andes. Phytogeographical patterns and affinities of the low altitude and wet vascular páramo flora of Ramal de Guaramacal, have been studied with emphasis in to the analysis of the floristic connections of the Guaramacal páramo flora with the neighboring dry páramos of the Sierra Nevada de Mérida and other páramo floras of the northern Andes and Central America. A total of 252 vascular plant taxa belonging to 150 genera and 69 families were recorded from the study area. The most species rich families are Asteraceae, Poaceae, Ericaceae and Orchidaceae, followed by the ferns families Grammitidaceae and Lycopodiacae. The most diverse genera are the ferns Elaphoglossum, Huperzia and Hymenophyllum. The analysis of generic phytogeographical composition of páramo flora showed that 52.8% of the genera are Tropical. The Temperate component is represented by 33.3% of the genera and the Cosmopolitan component is represented by 13.9% of the genera. The Neo - tropical montane element (38.9% is high in Guaramacal páramo, the Páramo endemic element (1.9% and the Andean alpine element (0.9% and represented by only one genus (Lachemilla are low compared to other páramo areas. The vascular flora of Páramo de Guaramacal is largely composed of (1 a group of Neotropical widespread distributed species (32%, (2 a group of Andean distributed species (49%, part of them confined to the Northern Andes and part widespread in the Andes from Colombia to Bolivia, and (3 a group of Venezuelan endemics (19%. From an eight páramo flora comparative dataset, the closest relationships among páramos is observed between the generic páramo floras of the Colombian Cordillera Oriental of Sumapáz and Sierra Nevada del Cocuy, which are both closely related to that of the Sierra Nevada de Mérida in Venezuela. The generic páramo flora of

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

    NARCIS (Netherlands)

    Gilvonio Perez, J.M.

    2009-01-01

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

  20. Luchas y defensas escondidas. Pluralismo legal y cultural como una práctica de resistencia creativa en la gestión local del agua en los Andes

    NARCIS (Netherlands)

    Boelens, R.A.

    2011-01-01

    En los Andes, los derechos de agua se materializan en procesos de lucha social. El artículo examina cómo la lucha por el agua de los colectivos locales no puede comprenderse sin su enraizamiento en subcorrientes dinámicas: los cimientos multicapas, a menudo ocultos, de los derechos de agua. Aquí se

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

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    M. ANGÉLICA CASANOVA-KATNY

    2006-03-01

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

  2. Restoration of badlands through applying bio-engineering techniques in active gully systems: Evidence from the Ecuadorian Andes

    Science.gov (United States)

    Borja, P.; Vanacker, V.; Alvarado, D.; Govers, G.

    2012-04-01

    A better insight in the processes controlling sediment generation, transport and deposition in badlands is necessary to enhance restoration of degraded soils through eco-engineering techniques. In this study, we evaluate the effect of different bio-engineering measures on soil and slope stability. Five micro-catchments (of 0.2 to 5 ha) were selected within a 3 km2 area in the lower part of the Loreto catchment (Southern Ecuadorian Andes). The micro-catchments differ only by land cover and degree of implementation of soil and water conservation measures. Bio-engineering techniques were used to construct dikes made of fascines of wooden sticks and earth-filled tires in active gully beds, where they are most efficient to reduce water and sediment transport. The experimental design consists of three micro-catchments within highly degraded lands: (DI) micro-catchment with bio-engineering measures concentrated in the active gully beds, (DF) with reforestation of Eucalyptus trees, and (DT) reference situation without any conservation measures. Two micro-catchments were monitored in agricultural lands with (AI) and without (AT) bio-engineering measures in the active gully beds. All catchments were equipped with San Dimas flumes to measure water flow, and sediment traps to monitor sediment export. In the (active) gully beds, various parameters related to gully stability (soil water content, bed elevation, vegetation cover, sedimentation/erosion) were monitored at weekly intervals. First results show that bio-engineering techniques are efficient to stabilize active gully beds through a reduction of the rapid concentration of excess rainfall and the sediment production and transfer. Fascines made of wooden sticks are far more efficient than earth-filled tires. Sediment deposition behind dikes is strongly dependent on precedent rainfall events, and the slope and vegetation cover of the gully floor. The sediment deposited facilitates colonization of the gully floor by native

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

    Science.gov (United States)

    Bustamante, Andres; Juliani, Caetano

    2011-10-01

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

  4. Timing of Accretion and Mountain-Building in The Northern Andes of Colombia through Low-Temperature Thermochonology

    Science.gov (United States)

    Vinasco, C. J.; Restrepo-Moreno, S. A.; Marín, M. I.; Botero, M.; Bermudez, M. A.; Min, K. K.; Foster, D. A.; Noriega, S., Sr.; Montoya, E., Sr.; Londoño, L., Sr.; Bernet, M.

    2015-12-01

    Orogenic configuration of the Northern Andes is closely associated to accretional processes since the Upper Cretaceous. In Colombia, the regional boundary between a Paleozoic continental domain to the east and Cretaceous accreted terrenes to the west is well exposed in several E-W sections near Medellin City and along the Cauca River, which occupies a major depression located between the Central and Western cordilleras. The area is dominated by the N-S trending Romeral Fault System (RFS) that can be traced to southern Ecuador. Relationships between the RFS and W-SW verging thrust system are unknown, although they represent key components of a transpressional orogeny. To understand timing of accretion and associated mountain building processes, we performed (U-Th)/He and fission track dating on samples derived from vertical profiles in cordilleran massifs. Samples were collected along four vertical profiles on two distinct litho-tectonic units: (1) three vertical profiles in the older eastern realm corresponding to metamorphic basement rocks of the Paleozoic Paleo-continental margin and associated Cretaceous intrusives, and (2) one vertical profile in the Mande batholith, Eocene in age at the eastern portion of the Panama Chocó Block (PCB) . The resulting zircon (U-Th)/He (ZHe) ages show a clear contrast between the ancient eastern realm (~50-60 Ma) and the Mande Batholith (~30-40 Ma). Apatite (U-Th)/He (AHe) ages also show a strong contrast with 23-42 Ma for the eastern realm and a well defined cluster at ~4 Ma for the Mande Batholith. These preliminary results suggest distinctive cooling histories for the two litho-tectonic blocks. The Mande batholith (western block) records both the late Eocene and Pliocene events whereas the ancient eastern block does not preserve any of these events. The Paleocene events recorded by the eastern block are probably related to the Laramic orogenetic phase. Finally, elevation-invariable ZHe ages from the ancient eastern block

  5. Stress patterns of the Plio-Quaternary brittle deformation along the Calama-Olacapato-El Toro Fault, Central Andes

    Science.gov (United States)

    Lanza, F.; Tibaldi, A.; Waite, G. P.; Corazzato, C.; Bonali, F.; Nardin, A.

    2012-04-01

    Understanding the geometry and kinematics of the major structures of an orogen is essential to elucidate its style of deformation, as well as its tectonic evolution. We describe the temporal and spatial changes in the state of stress of the trans-orogen area of the Calama-Olacapato-El Toro (COT) Fault Zone in the Central Andes, at about 24° S within the northern portion of the Puna Plateau between the Argentina-Chile border. The importance of the COT derives principally from the Quaternary-Holocene activity recognized on some segments, which may shed new light on its possible control on Quaternary volcanism and on the seismic hazard assessment of the area. Field geological surveys along with kinematic analysis and numerical inversion of ~ 280 new fault-slip measurements have revealed that this portion of the COT consists mainly of NW-SE striking faults, which have been reactivated under three different kinematic regimes: 1) a Miocene transpressional phase with the maximum principal stress (σ1) chiefly trending NW-SE; 2) an extensional phase that started by 9 Ma, with a horizontal NW-SE-trending minimum principal stress (σ3) - permutations between σ2 and σ3 axes have been recognized at three sites - and 3) a left-lateral strike-slip phase with an ~ ENE-WSW σ1 and a ~ NNW-SSE σ3 dating to the late Pliocene-Quaternary. Spatially, in the Quaternary, the left-lateral component decreases toward the westernmost tip of the COT, where it transitions to extension; this produced to a N-S horst and graben structure. Hence, even if trascurrence is still active in the eastern portion of the COT, as focal mechanisms of crustal earthquakes indicate, our study demonstrates that extension is becoming the predominant structural style of deformation, at least in the western region. These major temporal and spatial changes in the tectonic regimes are attributed in part to changes in the magnitude of the boundary forces due to subduction processes. The overall perpendicular

  6. Landscape structure and live fences in Andes Colombian agrosystems: upper basin of the Cane-Iguaque River.

    Science.gov (United States)

    Otero, Javier; Onaindia, Miren

    2009-12-01

    Changes in land use have generated a new landscape configuration in the Andino orobiome (mountain range) of the tropical Andes, resulting in a mosaic of cultivation and pastures interrupted by small fragments of forest and live fences. This has resulted in an ongoing decrease in the biodiversity of this biome. In the upper basin of the Cane-Iguaque River (Villa de Levya-Boyacá, Colombia), located 2,600-3,000 m above the Cordillera Oriental, over three time periods in 1960, 1984, and 2004, we characterized the structure, patterns, and evolution of the overall landscape and of the live fences (used as tools in biodiversity conservation and considered to be desirable alternatives to nonlive fences in farming production systems) within an agricultural landscape. To do this, we interpreted high-resolution satellite images using a landscape ecology approach and applied landscape map metrics. We found that the natural forests have been transformed by pastures and cultivation, and that although live fences cover only a small portion of the total landscape (4.6%), they have an important effect on landscape structure and biodiversity. There has been an increase in live fences, especially between 1960 and 1984, as well as an increase in their density. However, there has been a reduction in the average length of live fences over the periods that we studied. This could be due in part to changes in the types of agricultural products that have been cultivated in recent years, with an increase in potatoes and a decrease in other vegetables, and also by resource extraction of timber and fuel wood. In the studied area, agricultural production was sustained while biodiversity conservation was improved by the use of live fences. Therefore, live fences should be considered not only as part of an agriculturally productive area, but also as an important element of a multi-functional landscape that contributes to the maintenance of biodiversity and provides resources of economic and

  7. Constraining age and rate of deformation in the northern Bolivian Andes from cross sections, cooling ages, and thermokinematic modeling

    Science.gov (United States)

    McQuarrie, N.; Ehlers, T. A.; Rak, A. J.

    2015-12-01

    A critical component in assessing the viability of proposed plate tectonic or geodynamic processes in regions of convergence is the expected or predicted age and rate of deformation in the overriding plate. Commonly, age of deformation is inferred through geochronology of foreland basin and wedge-top sedimentary rocks and bedrock thermochronometer cooling signals. In Bolivia the original pulse of deformation of the fold-thrust belt is argue to be as young as 38-25 Ma based on the age of synorogenic strata or as old as 65-45 Ma due to proposed foreland basin rocks deposited in the Bolivian Altiplano. The large discrepancies in proposed age, rate and magnitude of deformation through the Bolivian Andes limit our ability to relate age and rate of shortening to internal geodynamic or external plate tectonic processes. We evaluate permissible ranges in age of initiation and rate of deformation through a forward kinematic model of the northern Bolivian fold-thrust belt. Each step of deformation accounts for isostatic loading from thrust faults and subsequent erosional of structural highs. The kinematic model predicts an evolution of flexural basins into which synorogenic sediments are deposited allowing us to fully integrate age of exhumation and deposition to age and magnitude of deformation. By assigning an age to each deformation step, we create a range of velocity vectors that are input into the thermokinematic model Pecube, which predicts thermochronometer cooling histories based on kinematics, topography, thermal parameters and shortening rates. We match the pattern of predicted ages with the across strike pattern of measured zircon fission track, apatite fission track and apatite (U-Th)/ He cooling ages. The sensitivity of modeled thermochronologic data to the age at which deformation initiates indicate that northern Bolivian EC started deforming at 50 Ma and may have begun as early as 55 Ma. The acceptable velocity envelope for the modeled section permits either a

  8. Composition of microbial communities in aerosol, snow and ice samples from remote glaciated areas (Antarctica, Alps, Andes

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    J. Elster

    2007-06-01

    Full Text Available Taxonomical and ecological analyses were performed on micro-autotrophs (cyanobacteria and algae together with remnants of diatom valves, micro-fungi (hyphae and spores, bacteria (rod, cocci and red clusters, yeast, and plant pollen extracted from various samples: Alps snow (Mt. Blank area, Andean snow (Illimani, Bolivia, Antarctic aerosol filters (Dumont d'Urville, Terre Adélie, and Antarctic inland ice (Terre Adélie. Three methods for ice and snow sample's pre-concentration were tested (filtration, centrifugation and lyophilisation. Afterwards, cultivation methods for terrestrial, freshwater and marine microorganisms (micro-autotrophs and micro-fungi were used in combination with liquid and solid media. The main goal of the study was to find out if micro-autotrophs are commonly transported by air masses, and later stored in snow and icecaps around the world. The most striking result of this study was the absence of culturable micro-autotrophs in all studied samples. However, an unusual culturable pigmented prokaryote was found in both alpine snow and aerosol samples. Analyses of many samples and proper statistical analyses (PCA, RDA- Monte Carlo permutation tests showed that studied treatments highly significantly differ in both microbial community and biotic remnants composition F=9.33, p=0.001. In addition, GLM showed that studied treatments highly significantly differ in numbers of categories of microorganisms and remnants of biological material F=11.45, p=0.00005. The Antarctic aerosol samples were characterised by having red clusters of bacteria, the unusual prokaryote and yeasts. The high mountain snow from the Alps and Andes contained much more culturable heterotrophs. The unusual prokaryote was very abundant, as were coccoid bacteria, red clusters of bacteria, as well as yeasts. The Antarctic ice samples were quite different. These samples had higher numbers of rod bacteria and fungal hyphae. The microbial communities and

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

    Science.gov (United States)

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

    2015-04-01

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

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

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2001-12-01

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

  11. The impact of rise of the Andes and Amazon landscape evolution on diversification of lowland terra-firme forest birds

    Science.gov (United States)

    Aleixo, A.; Wilkinson, M. J.

    2011-12-01

    Since the 19th Century, the unmatched biological diversity of Amazonia has stimulated a diverse set of hypotheses accounting for patterns of species diversity and distribution in mega-diverse tropical environments. Unfortunately, the evidence supporting particular hypotheses to date is at best described as ambiguous, and no generalizations have emerged yet, mostly due to the lack of comprehensive comparative phylogeographic studies with thorough trans-Amazonian sampling of lineages. Here we report on spatial and temporal patterns of diversification estimated from mitochondrial gene trees for 31 lineages of birds associated with upland terra-firme forest, the dominant habitat in modern lowland Amazonia. The results confirm the pervasive role of Amazonian rivers as primary barriers separating sister lineages of birds, and a protracted spatio-temporal pattern of diversification, with a gradual reduction of earlier (1st and 2nd) and older (> 2 mya) splits associated with each lineage in an eastward direction (the easternmost tributaries of the Amazon, the Xingu and Tocantins Rivers, are not associated with any splits older than > 2 mya). This "younging-eastward" pattern may have an abiotic explanation related to landscape evolution. Triggered by a new pulse of Andean uplift, it has been proposed that modern Amazon basin landscapes may have evolved successively eastward, away from the mountain chain, starting ~10 mya. This process was likely based on the deposition of vast fluvial sediment masses, known as megafans, which apparently extended in series progressively eastward from Andean sources. The effects on drainage patterns are apparent from the location of axial rivers such as the Negro / Orinoco and Madeira which lie at the distal ends of major megafan ramparts at cratonic margins furthest from the Andes. Megafan extension plausibly explains the progressive extinction of the original Pebas wetland of west-central Amazonia by the present fluvial landsurfaces where

  12. Landscape structure and live fences in Andes Colombian agrosystems: upper basin of the Cane-Iguaque River.

    Science.gov (United States)

    Otero, Javier; Onaindia, Miren

    2009-12-01

    Changes in land use have generated a new landscape configuration in the Andino orobiome (mountain range) of the tropical Andes, resulting in a mosaic of cultivation and pastures interrupted by small fragments of forest and live fences. This has resulted in an ongoing decrease in the biodiversity of this biome. In the upper basin of the Cane-Iguaque River (Villa de Levya-Boyacá, Colombia), located 2,600-3,000 m above the Cordillera Oriental, over three time periods in 1960, 1984, and 2004, we characterized the structure, patterns, and evolution of the overall landscape and of the live fences (used as tools in biodiversity conservation and considered to be desirable alternatives to nonlive fences in farming production systems) within an agricultural landscape. To do this, we interpreted high-resolution satellite images using a landscape ecology approach and applied landscape map metrics. We found that the natural forests have been transformed by pastures and cultivation, and that although live fences cover only a small portion of the total landscape (4.6%), they have an important effect on landscape structure and biodiversity. There has been an increase in live fences, especially between 1960 and 1984, as well as an increase in their density. However, there has been a reduction in the average length of live fences over the periods that we studied. This could be due in part to changes in the types of agricultural products that have been cultivated in recent years, with an increase in potatoes and a decrease in other vegetables, and also by resource extraction of timber and fuel wood. In the studied area, agricultural production was sustained while biodiversity conservation was improved by the use of live fences. Therefore, live fences should be considered not only as part of an agriculturally productive area, but also as an important element of a multi-functional landscape that contributes to the maintenance of biodiversity and provides resources of economic and

  13. Inferring late-Holocene climate in the Ecuadorian Andes using a chironomid-based temperature inference model

    Science.gov (United States)

    Matthews-Bird, Frazer; Brooks, Stephen J.; Holden, Philip B.; Montoya, Encarni; Gosling, William D.

    2016-06-01

    Presented here is the first chironomid calibration data set for tropical South America. Surface sediments were collected from 59 lakes across Bolivia (15 lakes), Peru (32 lakes), and Ecuador (12 lakes) between 2004 and 2013 over an altitudinal gradient from 150 m above sea level (a.s.l) to 4655 m a.s.l, between 0-17° S and 64-78° W. The study sites cover a mean annual temperature (MAT) gradient of 25 °C. In total, 55 chironomid taxa were identified in the 59 calibration data set lakes. When used as a single explanatory variable, MAT explains 12.9 % of the variance (λ1/λ2 = 1.431). Two inference models were developed using weighted averaging (WA) and Bayesian methods. The best-performing model using conventional statistical methods was a WA (inverse) model (R2jack = 0.890; RMSEPjack = 2.404 °C, RMSEP - root mean squared error of prediction; mean biasjack = -0.017 °C; max biasjack = 4.665 °C). The Bayesian method produced a model with R2jack = 0.909, RMSEPjack = 2.373 °C, mean biasjack = 0.598 °C, and max biasjack = 3.158 °C. Both models were used to infer past temperatures from a ca. 3000-year record from the tropical Andes of Ecuador, Laguna Pindo. Inferred temperatures fluctuated around modern-day conditions but showed significant departures at certain intervals (ca. 1600 cal yr BP; ca. 3000-2500 cal yr BP). Both methods (WA and Bayesian) showed similar patterns of temperature variability; however, the magnitude of fluctuations differed. In general the WA method was more variable and often underestimated Holocene temperatures (by ca. -7 ± 2.5 °C relative to the modern period). The Bayesian method provided temperature anomaly estimates for cool periods that lay within the expected range of the Holocene (ca. -3 ± 3.4 °C). The error associated with both reconstructions is consistent with a constant temperature of 20 °C for the past 3000 years. We would caution, however, against an over-interpretation at this stage. The reconstruction can only

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

    Science.gov (United States)

    Bookhagen, Bodo; Strecker, Manfred; Olen, Stephanie

    2016-04-01

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

  15. Eruptive history of Chimborazo volcano (Ecuador): A large, ice-capped and hazardous compound volcano in the Northern Andes

    Science.gov (United States)

    Samaniego, Pablo; Barba, Diego; Robin, Claude; Fornari, Michel; Bernard, Benjamin

    2012-04-01

    New fieldwork, radiometric and whole-rock chemical data permit the reconstruction of the main eruptive stages of the Chimborazo compound volcano, the highest summit of the Northern Andes. Chimborazo is composed of three successive edifices. The Basal Edifice (CH-I) was active from ~ 120 to 60 ka and resulted in a large, mostly effusive edifice which was built up during two stages of cone-building, terminating with the formation of a dome complex. This edifice was affected by a huge sector collapse around 65-60 ka which produced a major debris avalanche that spread out into the Riobamba basin, covering about 280 km2 with an average thickness of 40 m and a total volume of ~ 10-12 km3. After the emplacement of the Riobamba debris avalanche, eruptive activity resumed at the eastern outlet of the avalanche scar and was responsible for the construction of a less voluminous, Intermediary Edifice (CH-II), whose current remnants are the Politécnica and Martínez peaks. This edifice developed from 60 to 35 ka. Lastly, eruptive activity shifted to the west, leading to the construction of the morphologically well-preserved Young Cone (CH-III) which currently forms the highest summit (Whymper). The average eruptive rate of Chimborazo volcano is 0.5-0.7 km3/ka. However, looking at the three successive edifices individually, we estimate that there has been a progressive decrease in magma output rate from the Basal Edifice (0.7-1.0 km3/ka), through the Intermediary Edifice (0.4-0.7 km3/ka) to the Young Cone (~ 0.1 km3/ka). However, during the main cone-building stages, the peak eruption rates are markedly higher, indicating significant variations in the magma output rate during the lifespan of this arc volcano. During the Holocene, the Chimborazo eruptive activity consisted of small-volume explosive events that occurred at quite regular intervals, between about 8000 and 1000 yr ago. Since the last eruption occurred between the early part of the 5th century and the end of the 7th

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

    International Nuclear Information System (INIS)

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

  17. Response of regional climate and glacier ice proxies to El Niño-Southern Oscillation (ENSO in the subtropical Andes

    Directory of Open Access Journals (Sweden)

    E. Dietze

    2008-02-01

    Full Text Available El Niño-Southern Oscillation (ENSO is an important element of earth's ocean-climate system. To further understand its past variability, proxy records from climate archives need to be studied. Ice cores from high alpine glaciers may contain high resolution ENSO proxy information, given the glacier site is climatologically sensitive to ENSO. We investigated signals of ENSO in the climate of the subtropical Andes in the proximity of Cerro Tapado glacier (30°08' S, 69°55' W, 5550 m a.s.l., where a 36 m long ice core was drilled in 1999 (Ginot, 2001. We used annual and semi-annual precipitation and temperature time series from regional meteorological stations and interpolated grids for correlation analyses with ENSO indices and ice core-derived proxies (net accumulation, stable isotope ratio δ18O, major ion concentrations. The total time period investigated here comprises 1900 to 2000, but varies with data sets. Only in the western, i.e. Mediterranean Andes precipitation is higher (lower during El Niño (La Niña events, especially at higher altitudes, due to the latitudinal shift of frontal activity during austral winters. However, the temperature response to ENSO is more stable in space and time, being higher (lower during El Niño (La Niña events in most of the subtropical Andes all year long. From a northwest to southeast teleconnection gradient, we suggest a regional water vapour feedback triggers temperature anomalies as a function of ENSO-related changes in regional pressure systems, Pacific sea surface temperature and tropical moisture input. Tapado glacier ice proxies are found to be predominantly connected to eastern Andean summer rain climate, which contradicts previous studies and the modern mean spatial boundary between subtropical summer and winter rain climate derived from the grid data. The only ice core proxy showing a response to ENSO is the major ion concentrations, via local temperature indicating

  18. Reconstructing hydroclimatic variability of the Bermejo River (Subtropical Andes of Argentina-Bolivia) through Archival Documents - 17th to 20th centuries

    Science.gov (United States)

    Del Rosario Prieto, M.; Cueto, C.

    2009-09-01

    The purpose of this paper is to use climatic history for contributing to the general objectives of the IAI -CRN II-047 Project. It will reconstruct, from archival documents, the hydroclimatic variability occurring in the high basin of the Bermejo River during the last centuries and its effects on the floods and swellings in the middle basin. The Río Bermejo in the Southern Andes, is a binational (Argentina-Bolivia) river that contributes the largest proportion of the sediment load to the La Plata basin. Its headwaters are in the Subtropical Andes, near Tarija, Bolivia (22?00'14"S, 64?57'38"W). The main headwater tributaries are the Río Grande de Tarija, in Bolivia and the Iruya and San Francisco Rivers in Argentina. When the river abandons the mountain and turns eastwards (Gran Chaco), it acquires the characteristics of typical lowland rivers, widens its course, and occupies a large, low sedimentary plain with vast floodland areas. Quite often during very high sediment discharge the main river avulses and changes its course, creating big alluvial plains that are occupied for many years. Administrative documents from the colonial and republican periods have provided useful information to reconstruct climate and hydrology of the region. Documents from the Archivo General de Indias in Seville, Archivo Nacional de Bolivia and Archivo General de la Nación (Argentina) have been used to identify extreme floods and swellings in the high and middle-basin of the Rio Bermejo from the 17th century to the first decades of the 20th century. Old maps of the region, reports from annals, chronicles, priests' and travelers' descriptions were also used. Diaries written by the military, explorers and government officials in charge of discovering and taking possession of the territory also provide important sources of information. The archival documents show abrupt hydrological changes in response to the climatic fluctuations in the headwaters region. These records document

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

    Directory of Open Access Journals (Sweden)

    M. L. M. Scheel

    2011-08-01

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

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

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

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

  20. Late Quaternary Glaciations in the Central Peruvian Andes (10°-11°S) and Evidence for a Link to Heinrich Events

    Science.gov (United States)

    Smith, J. A.; Farber, D. L.; Finkel, R. C.; Rodbell, D. T.; Seltzer, G. O.

    2009-05-01

    Seven cosmogenic 10Be ages from a moraine in the Santuario Nacional Bosque de Piedras de Huayllay (BP) in the Western Cordillera of the central Peruvian Andes (10°59'S, 76°20'W, 4180-4200 masl) are consistent with 10Be ages on moraines in both the Eastern Cordillera (40-45 km to the east) and Nevado Jeulla Rajo (NJR) massif (10°00'S, 77°16'W) at the southern end of the Cordillera Blanca (150 km to the northwest). In the BP, 10Be ages are ~14-15 ka on four ignimbrite boulders, ~26 and ~20 ka on two quartz boulders, and ~45 ka on ignimbrite bedrock below the trimline in the valley wall. In the Eastern Cordillera bordering Lake Junin, the most extensive glaciations are >150 ka, but end moraines farther upvalley date to the local last glacial maximum (LLGM; 25-30 ka) and a late-glacial stillstand or readvance (14-18 ka). In NJR, 10Be ages indicate that the largest lateral moraines were deposited during similar intervals (27-32 ka and 14-18 ka). Avulsion of a glacial valley preserved an older, smaller pair of lateral moraines (56-65 ka) in NJR; correlative moraines were apparently not preserved in the Junin valleys. We have found no moraines in NJR that date to the global LGM (ca. 19-24 ka), but see some evidence for an advance ca. 40-48 ka. Outwash deposits (ca. 43-50 ka) located beyond the termini of NJR moraines are underlain by lodgement till that extends ca. 6 km across the Conococha Plain, suggesting that at least one older glaciation was far more extensive than any of the late Quaternary NJR advances dated by 10Be (ages calculated using CRONUS-Earth Online Calculator v. 2.2, Lal/Stone time-dependent scaling, and zero erosion). The timing of glacial advances in the central Peruvian Andes since 70 ka suggests a correlation to Heinrich events and associated southward shifts of the Intertropical Convergence Zone (ITCZ) in the Atlantic Ocean. We propose that Peruvian glaciers typically expanded when southward migration of the ITCZ resulted in increased