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Sample records for andean cordillera central

  1. Petrographic and Geochemical Characterization of the Cambumbia STOCK in Andean Central Cordillera, Colombia

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    Rojas Lequerica, S.; Jaramillo Mejía, J.; Concha Perdomo, A.

    2012-12-01

    The Cambumbia Stock is located on the western flank of the Central Cordillera of the northern Andes. The goals of this study were to petrographic and geochemically characterize the Cambumbia igneous body and to establish its petrogenetic history. 41 samples were collected, 28 for petrographic analysis and 14 for elementary chemical determination by ICP-MS. Petrographically the samples were classified as hornblende and pyroxene-gabbros varying to diorites, gabbronorites and tonalites, the rock texture varies from medium to coarse granular grain, with local microporfiritic texture. It was concluded from the major elements analysis that the samples correspond to the sub-alkaline series with low K content, mainly in the calc-alkaline series, within the gabbros and diorites fields. By using the SiO2 vs TiO2 (Jaramillo, 1980), Th/Yb vs Ta/Yb (Pearce, 1984) (Fig. 1) and Zr/117-Th-Nb/16 (Wood, 1979) diagrams it was determined that these rocks were generated in two geotectonic environments: one type MOR (extension) and other island arc (subduction, compression). Petrographic and geochemical comparisons between the rocks of Cambumbia Stock and Diorite and Gabbro El Pueblito (Giraldo, 2009) (located about 25 km to the north-west) may postulate a possible genetic link between them. 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 (Middle Triassic). This age is consistent with the global event of the extension and fragmentation of Pangea supercontinent. In addition, the mantle nature of the source and the petrogenetic evolution of the magmatic system were established. References GIRALDO, M.I., (2009): Esquema geodinámica de la parte noroccidental de la cordillera Central de Colombia. (Thesis). p.56-68. Universidad Nacional de Colombia, Medellín. JARAMILLO, J.M. (1980): Petrology and geochemistry of the Nevado del Ruiz Volcano northern Andes, Colombia (Thesis). 167 p. University of Houston

  2. Late Cretaceous-Cenozoic Evolution of the Central Andean Foreland Basin System in the Eastern Cordillera to Subandean Zone, Southern Bolivia

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    Calle, A.; Horton, B. K.; Anderson, R. B.; Long, S. P.

    2015-12-01

    Evaluation of foreland basin deposystems and provenance across southern Bolivia reveals punctuated growth of the central Andean orogenic wedge. New and published sedimentology, provenance data, stratigraphy, subcrop mapping, and apatite (U-Th)/He thermochronometry along two transects (19.5, 21°S) from the easternmost Eastern Cordillera (EC) to the western Subandean Zone (SAZ) shed light on Late Cretaceous-Miocene thrust belt and foreland basin dynamics. Sediment dispersal patterns are constrained by paleocurrents, detrital zircon U-Pb geochronology, sandstone petrography, and conglomerate clast compositions. Spatial and temporal changes in the Andean thrust belt are recorded in asymmetric foreland basin thicknesses, facies distributions, and provenance within the EC (Incapampa and Camargo synclines) and SAZ (El Rosal and Entre Rios synclines). The >4 km uppermost Cretaceous-lower Miocene EC succession and ~2.5 km upper Oligocene-Miocene SAZ clastic successions record a shift from fluvial backbulge to pedogenic forebulge deposition. Braided, meandering, and lacustrine foredeep deposition records the most-rapid subsidence, with a later shift to progradational braided and alluvial fan deposition in the wedge-top zone. Growth strata preserved in EC and SAZ wedge-top deposits suggest unsteady eastward advance of the deformation front. Distal foreland deposits show west-directed paleocurrents with >1 Ga detrital zircon populations. Emerging Andean sources are indicated by east-directed paleocurrents, 36-25 Ma), Interandean Zone (IAZ, ~22-7 Ma) and SAZ (<6 Ma) can be linked to eastward passage of a flexural forebulge, recorded as a 50-200 m thick condensed zone in EC and SAZ basin fill. Integrated assessment of basin architecture, provenance, and exhumation highlights the potential influence of pre-Cenozoic IAZ heterogeneities on orogenic wedge growth.

  3. Evolution of clay mineral assemblages in the Tinguiririca geothermal field, Andean Cordillera of central Chile: an XRD and HRTEM-AEM study

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    Vázquez, M.; Nieto, F.; Morata, D.; Droguett, B.; Carrillo-Rosua, F. J.; Morales, S.

    2014-08-01

    HRTEM textural evidence shows that clay minerals in the Tinguiririca geothermal field (Andean Cordillera, central Chile) are the result of direct alteration of former volcanic glass and minerals by hydrothermal fluids at similar temperatures to the present day. They show the classical pattern of diagenetic transformation from smectite at the top to illite at the bottom, with the progressive formation of corrensite and chlorite. The high fluid/rock ratio, disposability of necessary cations and absence of previous detrital phyllosilicates allow the consideration of this area as a natural laboratory to establish the extreme ideal conditions for very low-T reactions. Transformations from smectite to R1 illite-smectite (I-S) and from these to R3 mixed-layers occur respectively at 80-120 °C and 125-180 °C. In spite of ideal genetic conditions, the new-formed minerals show all the defective character and lack of textural and chemical equilibrium previously described in the literature for diagenetic and hydrothermal low-temperature assemblages. Chemistry of smectite-illite phases evolves basically through a diminution of the pyrophyllitic component toward a theoretical muscovite (Si4 + + □ -> Al3 ++ K+). However, a second chemical vector (Si4 ++ Mg2 + → Al3 ++ Al3 +), that is, decreasing of the tschermack component, also contributes to the evolution toward the less Si-more Al rich muscovite in relation to the original smectite. Residual Mg (and Fe) from the latter reaction is consumed in the genesis of chloritic phases. Nevertheless, as a consequence of the lack of chemical equilibrium (probably because of the short time-scale of the geothermal alteration processes), the composition of clay minerals is highly heterogeneous at the level of a single sample. Consequently, the respective fields of smectite, R1 I-S and R3 I-S overlap each other, making the distinction among these three phases impossible based exclusively on chemical data.

  4. DISTRIBUCIÓN DEL AGUA LLUVIA EN TRES BOSQUES ALTOANDINOS DE LA CORDILLERA CENTRAL DE ANTIOQUIA, COLOMBIA RAINFALL DISTRIBUTION IN THREE HIGH ANDEAN FORESTS IN THE CENTRAL CORDILLERA OF COLOMBIA

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    Juan Diego León Peláez

    2010-06-01

    Full Text Available Se estudió la distribución del agua lluvia durante tres años en un bosque climácico de roble (Quercus humboldtii y dos plantaciones forestales, de pino (Pinus patula y ciprés (Cupressus lusitanica ubicados en los Andes colombianos. Los principales ingresos de agua al bosque ocurrieron por la lluvia, cuyo valor medio anual fue 1.700 mm año-1. La precipitación interna tuvo la mayor participación de los flujos hídricos del bosque, siendo máxima en el cipresal (1.486 mm a-1, 90 % y mínima en el pinar (1.389 mm a-1, 81 %, mientras que el escurrimiento cortical fue muy bajo en los tres bosques (1-3 mm a-1, 0,1-0,2 %. La máxima intercepción se presentó en el pinar (329 mm a-1, equivalente al 19 % de la lluvia. A diferencia de estos flujos hídricos del dosel los flujos hídricos del suelo sí mostraron diferencias significativas entre coberturas (P Rainfall distribution was assessed for three years in a mature oak forest (Quercus humboldtii, pine (Pinus patula and cypress (Cupressus lusitanica plantations in the northern part of the colombian Andean mountains. An annual average of 1700 mm was the main water input in the forests, which came from the bulk precipitation. The higher water flows were represented by throughfall, which showed a maximum value in the cypress (1486 mm y¹, 90% and a minimum one in the pine (1389 mm y¹, 81% plantations, respectively. Stemflow was very low in the three forest types (1-3 mm y¹, 0.1-0.2%. The maximum amount of water intercepted by forest crowns was found in the pine plantation (329 mm y¹, which accounted for 19% out of the total rainfall. In opposition to the patterns found for throughfall and stemflow, soil hydric flows did show significant differences among forest types (P<0.05. In the oak forest water infiltration inversely decreased with soil depth; this forest type showed the lowest water losses by deep drainage (2 mm y¹. Finally, throughfall and stemflow were significantly correlated with the

  5. Lithospheric evolution of the Andean fold thrust belt, Bolivia, and the origin of the central Andean plateau

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    McQuarrie, Nadine; Horton, Brian K.; Zandt, George; Beck, Susan; DeCelles, Peter G.

    2005-04-01

    We combine geological and geophysical data to develop a generalized model for the lithospheric evolution of the central Andean plateau between 18° and 20° S from Late Cretaceous to present. By integrating geophysical results of upper mantle structure, crustal thickness, and composition with recently published structural, stratigraphic, and thermochronologic data, we emphasize the importance of both the crust and upper mantle in the evolution of the central Andean plateau. Four key steps in the evolution of the Andean plateau are as follows. 1) Initiation of mountain building by ˜70 Ma suggested by the associated foreland basin depositional history. 2) Eastward jump of a narrow, early fold-thrust belt at 40 Ma through the eastward propagation of a 200-400-km-long basement thrust sheet. 3) Continued shortening within the Eastern Cordillera from 40 to 15 Ma, which thickened the crust and mantle and established the eastern boundary of the modern central Andean plateau. Removal of excess mantle through lithospheric delamination at the Eastern Cordillera-Altiplano boundary during the early Miocene appears necessary to accommodate underthrusting of the Brazilian shield. Replacement of mantle lithosphere by hot asthenosphere may have provided the heat source for a pulse of mafic volcanism in the Eastern Cordillera and Altiplano at 24-23 Ma, and further volcanism recorded by 12-7 Ma crustal ignimbrites. 4) After ˜20 Ma, deformation waned in the Eastern Cordillera and Interandean zone and began to be transferred into the Subandean zone. Long-term rates of shortening in the fold-thrust belt indicate that the average shortening rate has remained fairly constant (˜8-10 mm/year) through time with possible slowing (˜5-7 mm/year) in the last 15-20 myr. We suggest that Cenozoic deformation within the mantle lithosphere has been focused at the Eastern Cordillera-Altiplano boundary where the mantle most likely continues to be removed through piecemeal delamination.

  6. Central Andean crustal structure from receiver function analysis

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    Ryan, Jamie; Beck, Susan; Zandt, George; Wagner, Lara; Minaya, Estela; Tavera, Hernado

    2016-07-01

    The Central Andean Plateau (15°-27°S) is a high plateau in excess of 3 km elevation, associated with thickened crust along the western edge of the South America plate, in the convergent margin between the subducting Nazca plate and the Brazilian craton. We have calculated receiver functions using seismic data from a recent portable deployment of broadband seismometers in the Bolivian orocline (12°-21°S) region and combined them with waveforms from 38 other stations in the region to investigate crustal thickness and crust and mantle structures. Results from the receiver functions provide a more detailed map of crustal thickness than previously existed, and highlight mid-crustal features that match well with prior studies. The active volcanic arc and Altiplano have thick crust with Moho depths increasing from the central Altiplano (65 km) to the northern Altiplano (75 km). The Eastern Cordillera shows large along strike variations in crustal thickness. Along a densely sampled SW-NE profile through the Bolivian orocline there is a small region of thin crust beneath the high peaks of the Cordillera Real where the average elevations are near 4 km, and the Moho depth varies from 55 to 60 km, implying the crust is undercompensated by 5 km. In comparison, a broader region of high elevations in the Eastern Cordillera to the southeast near 20°S has a deeper Moho at 65-70 km and appears close to isostatic equilibrium at the Moho. Assuming the modern-day pattern of high precipitation on the flanks of the Andean plateau has existed since the late Miocene, we suggest that climate induced exhumation can explain some of the variations in present day crustal structure across the Bolivian orocline. We also suggest that south of the orocline at 20°S, the thicker and isostatically compensated crust is due to the absence of erosional exhumation and the occurrence of lithospheric delamination.

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

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    Laura Giambiagi

    2009-04-01

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

  8. Tectonomagmatic Associations on the Central Andean Plateau

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    de Silva, S. L.; Viramonte, J. G.

    2012-12-01

    The Neogene evolution of the Central Andes is characterized by a strong association between plate convergence, mountain building and plateau formation, and magmatism. Plateau uplift by crustal shortening and thickening in the lower crust is broadly coincident with large scale silicic magmatism defined by the Neogene Central Andean ignimbrite province. Of particular interest here are the spatiotemporal correlations between silicic magmatism and tectonic evolution of the Altiplano-Puna plateau. Although magmatism is driven by the subduction-related flux from mantle to crust, the shift to "crustal" magmatism as indicated by elevated crustal isotopic indices after ~10Ma suggests a link between crustal thickening, plateau formation and silicic magmatism. In particular, elevated geotherms associated with crustal thickening and enhanced mantle flux associated with lithospheric delamination may have played a role in thermally preparing the Central Andean crust for enhanced silicic magma production during the extensive Neogene ignimbrite flare-up. Emplacement of these magmas in the upper crust throughout the Neogene may have fuelled a period of significant interaction between magmatism and tectonism on the plateau. With particular reference to the 21° to 24°S segment of the Central Andes, spatial and structural coincidence of calderas of the Altiplano Puna Volcanic Complex with the NW-SE striking Calama-Olacapata-El Toro fault zone suggests significant tectonomagmatic interaction. Location of calderas suggest that these regional faults focused magma intrusion and storage, while spatially and temporally correlated eruption pulses connote a tectonic control. Indeed, current thermomechanical models of magma chamber development and eruption triggering promote a role for external triggering of "perched" upper crustal magma chambers. This might have been achieved by melt-enhanced deformation, or alternatively, significant uplift (~1km) associated with the development of large

  9. U/Pb ages on detrital zircons in the southern central Andes Neogene foreland (36°-37°S): Constraints on Andean exhumation

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    Sagripanti, Lucía; Bottesi, Germán; Naipauer, Maximiliano; Folguera, Andrés; Ramos, Victor A.

    2011-12-01

    U/Pb dating on detrital zircons was performed in the Pampa de Carrizalito depocenter of the Late Miocene foreland basin associated with the Southern Central Andes orogenic front. This reveals Andean and pre-Andean components in magmatic derived zircons inhomogeneously distributed through the sequence. Andean, Grenville, Pampean, Famatinian and Gondwanic components reveal a complex source distribution from either the Main Andes, Coastal Cordillera and basement foreland areas. These are discussed showing different patterns in the context of the Andean orogenic cycle. Cretaceous and Jurassic components that are partly related to Mesozoic batholiths, developed at the western slope of the Andes at these latitudes, have a very contrasting behavior through the sequence: While Jurassic grains are represented from base to top, Cretaceous ones dilute upwardly. This is explained through the progressive uplift of the Southern Central Andes that could have created a barrier to Cretaceous and Jurassic detritus, while the older ones could have had either an alternative source area represented by the inverted rift system of the Huincul Ridge in the foreland area and the Cordillera del Viento in the hinterland area or the reworking of Jurassic sedimentary sequences of the Neuquén basin. Finally, a progressive enrichment in pre-Andean components to the top of the sequence is interpreted as related to the development of a broken foreland and the consequent rapid expansion of the orogenic front at the time of development of a slab shallowing setting in the region as shown by previous works.

  10. Imaging variations in the central Andean mantle and the subducting Nazca slab with teleseismic tomography

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    Scire, Alissa

    The Nazca-South America convergent margin is marked by the presence of the Andean mountain belt, which stretches along the 8000-km long western margin of the South American plate. The subduction zone is characterized by significant along-strike changes in both upper plate structure and slab geometry that make it an ideal region to study the relationship between the subducting slab, the surrounding mantle, and the overriding plate. This dissertation summarizes the results of three finite frequency teleseismic tomography studies of the central Nazca-South America subduction zone which improve our understanding of how along-strike variations in the Andean mountain belt and the subducting Nazca plate interact with each other and with the surrounding mantle. This is accomplished by first focusing on two smaller adjacent regions of the central Andes to explore upper mantle variations and then by using a combined dataset, which covers a larger region, to image the deeply subducted Nazca slab to investigate the fate of the slab. The first study focuses on the central Andean upper mantle under the Altiplano-Puna Plateau where normally dipping subduction of the Nazca plate is occurring (18° to 28°S). The shallow mantle under the Eastern Cordillera is generally fast, consistent with either underthrusting of the Brazilian cratonic lithosphere from the east or a localized "curtain" of delaminating material. Additional evidence for delamination is seen in the form of high amplitude low velocities under the Puna Plateau, consistent with proposed asthenospheric influx following lithospheric removal. In the second study, we explore the transition between normal and flat subduction along the north edge of the Altiplano Plateau (8° to 21°S). We find that the Peruvian flat slab extends further inland along the projection of the Nazca Ridge than was previously proposed and that when re-steepening of the slab occurs, the slab dips very steeply (˜70°) down through the mantle

  11. Active shallow extension in central and eastern Betic Cordillera from CGPS data

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    Galindo-Zaldivar, J.; Gil, A. J.; Sanz de Galdeano, C.; Lacy, M. C.; García-Armenteros, J. A.; Ruano, P.; Ruiz, A. M.; Martínez-Martos, M.; Alfaro, P.

    2015-11-01

    The Betic Cordillera is an Alpine belt formed in the western Mediterranean by the westward displacement of the Alboran Domain in between the Eurasian and African convergent plates. New CGPS data from the central and eastern Betic Cordillera and its foreland-obtained mainly from the Topo-Iberia project-allowed us to precisely determine the rate of tectonic deformation. Most of the displacements of the central and eastern Betics are westward, with a variable southwestward component, in relation to the Eurasian stable plate. While in the Iberian foreland the displacements are extremely low, some deformation related to low compressional deformation occurs in the easternmost foreland basin and eastern Betic Cordillera. The displacement increases substantially southwards and westwards in relation to present-day extensional deformation. Major active discontinuities correspond to the NW-SE normal fault zones, which dip westwards; they are located in Almeria-Tabernas; Balanegra, and western Sierra de Gador; whereas the Padul fault zone located west of Sierra Nevada extends northwards to the Granada Basin. NW-SE extensional faults are also observed to the north, in the Baza Basin. Moreover, the activity of dextral faults along the Sorbas-Tabernas-Alpujarras-Guajares band, generally considered as a transfer fault zone, is evidenced by the displacement data. These results come to demonstrate the low activity or inactivity of the large northern E-W oriented folds of the central and eastern Internal Zone, such as the Sierra de Los Filabres antiform. They also point to the possible residual activity of the northern part of the NE-SW Sierra Nevada antiform, where the maximum relief of the Cordillera is found. Altogether, our data support a heterogeneous present-day westward extension that affects the upper crust of the Betic Cordillera and increases towards the thinned continental crust of the Alboran Sea and towards the west, which is compatible with roll-back subduction along

  12. The Early Andean Magmatic Province (EAMP): 40Ar/ 39Ar dating on Mesozoic volcanic and plutonic rocks from the Coastal Cordillera, northern Chile

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    Oliveros, Verónica; Féraud, Gilbert; Aguirre, Luis; Fornari, Michel; Morata, Diego

    2006-10-01

    The Early Andean Magmatic Province (EAMP), consists of about 150 000 km 3 of volcanic and plutonic units in the Coastal Cordillera of northern Chile and southern Peru and represents a major magmatic Mesozoic event in the world, for which the precise age of the thick volcanic series was unknown. Thirty 40Ar/ 39Ar analyses were carried out on primary mineral phases of volcanic and plutonic rocks from northern Chile (18°30'-24°S). Reliable plateau and "mini plateau" ages were obtained on plagioclase, amphibole and biotite from volcanic and plutonic rocks, despite widespread strong alteration degree. In the Arica, Tocopilla and Antofagasta (700 km apart) regions, the ages obtained on lava flows constrain the volcanic activity between 164 and 150 Ma and no N-S migration of volcanism is observed. The uppermost lava flows of the volcanic sequence at the type locality of the La Negra Formation extruded at ca. 153-150 Ma, suggesting the end of the volcanic activity of the arc at that time. The oldest volcanic activity occurred probably at ca. 175-170 Ma in the Iquique area, although no plateau age could be obtained. The plutonic bodies of the same regions were dated between ca. 160 and 142 Ma, indicating that they were partly contemporaneous with the volcanic activity. At least one volcanic pulse around 160 Ma is evidenced over the entire investigated reach of the EAMP, according to the ages found in Arica, Tocopilla, Michilla and Mantos Blancos regions. The episodic emplacement of huge amounts of subduction related volcanism is observed throughout the whole Andean history and particularly during the Jurassic (southern Peru, northern Chile and southern Argentina). These events probably correspond to periodic extensional geodynamic episodes, as a consequence of particular subduction conditions, such as change of obliquity of the convergence, change in the subduction angle, slab roll back effect or lower convergence rate, that remain to be precisely defined.

  13. Cenozoic stratigraphic development in the north Chilean forearc: Implications for basin development and uplift history of the Central Andean margin

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    Hartley, Adrian J.; Evenstar, Laura

    2010-11-01

    with volcanic activity limited to the periodic eruption of extensive ignimbrite sheets. Alluvial fan, fluvial and lacustrine sedimentation dominated within the endorheic basins from ˜ 8 to 3 Ma. After development of a regional unconformity at 3 Ma a change to isolated evaporite sub-basins took place in the Central Depression with small lacustrine basins developed along the flank of the Western Cordillera. The scale and grain size recorded in the sedimentary systems indicates that a substantial source area was located in the present day area of the Western Cordillera by 30 Ma and that this has persisted to the present day. This area also shed material eastwards into the Altiplano. The presence of such a topographic feature by 30 Ma suggests that a significant proportion of Andean uplift had occurred prior to the Late Miocene. This important uplift phase should be incorporated into any model of Andean uplift. The evidence from the basin-fill succession suggests that sediments accumulated in a basin developed in front of a broad monocline between 38 and 19 Ma and that a transition to a thrust-bounded foreland style basin took place after the development of the unconformity at 19 Ma.

  14. Geometric, Kinematic, and Erosional history of the Central Andean Plateau, northern Bolivia

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    McQuarrie, N.; Barnes, J. B.; Ehlers, T. A.

    2006-12-01

    Latitudinal changes in topography, climate, and thrust-belt geometry in the Central Andes have lead to conflicting hypotheses that climate or tectonics exert a first-order control on the orogens' evolution. Models of climate/tectonic interactions are limited by a lack of detailed observations for both the long-term deformation and erosion history of the Andean fold-thrust belt. We contribute to this problem by combining a sequentially restored, balanced cross section across the northern Bolivia portion of the thrust belt (15-16°S) with 10 new and 51 previously published mineral cooling ages, documenting the timing and magnitude of exhumation across the cross section. The cross section was balanced and restored using the sinuous bed method. The restored section was also sequentially forward modeled using stratigraphic and cooling age constraints. Results indicate the Eastern Cordillera (EC) records the highest magnitudes of shortening (123 km or 55%). The Interandean zone (IAZ) has shortened 48 km or 30%. In both the EC and IAZ individual thrust sheets are tightly folded and have minor offsets of 1-5 km. The fold-thrust belt of the SAZ has multiple levels of detachments allowing for thrust sheets with large 6-17 km of offset. Total shortening in the SAZ is 66 km or 40%. Total shortening for the entire fold-thrust belt in this region is 276 km (39%). New cooling ages support previously published ages that indicate rapid exhumation of the EC from ~40-25 Ma and distributed exhumation of the entire fold-thrust belt from ~15-0 Ma. Cooling ages in the EC and IAZ do not appear affected by individual thrusts. Integrating the sequential reconstructions with a compilation of mineral cooling ages and onlapping sedimentary basins provides a means of comparing independently derived exhumation estimates and determining long term shortening rates. Combined exhumation estimates suggest ~9 km of exhumation in the EC ~5-9 km in the IAZ and 3-4 km in the SAZ. Long term shortening

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

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

    2012-12-01

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

  16. Geochronology, geochemistry and tectonic evolution of the Western and Central cordilleras of Colombia

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    Villagómez, Diego; Spikings, Richard; Magna, Tomas; Kammer, Andreas; Winkler, Wilfried; Beltrán, Alejandro

    2011-08-01

    Autochthonous rocks of the pre-Cretaceous continental margin of NW South America (the Tahami Terrane) are juxtaposed against a series of para-autochthonous rock units that assembled during the Early Cretaceous. Allochthonous, oceanic crust of the Caribbean Large Igneous Province collided with and accreted onto the margin during the Late Cretaceous. We present the first regional-scale dataset of zircon U-Pb LA-ICP-MS ages for intrusive and metamorphic rocks of the autochthonous Tahami Terrane, Early Cretaceous igneous para-autochthonous rocks and accreted oceanic crust. The U-Pb zircon data are complemented by multiphase 40Ar/ 39Ar crystallization and cooling ages. The geochronological data are combined with whole rock major oxide, trace element and REE data acquired from the same units to constrain the tectonic origin of the rock units and terranes exposed in the Western Cordillera, Cauca-Patía Valley and the Central Cordillera of Colombia. The Tahami Terrane includes lower Paleozoic orthogneisses (~ 440 Ma) that may have erupted during the active margin stage of the Rheic Ocean. Basement gneisses were intruded by Permian, continental arc granites during the final assembly of Pangea. Triassic sedimentary rocks were subsequently deposited in rift basins and partially melted during high-T metamorphism associated with rifting of western Pangea during 240-220 Ma. Continental arc magmatism during 180-145 Ma is preserved along the whole length of the Central Cordillera and was followed by an Early Cretaceous out-board step of the arc axis and the inception of the Quebradagrande Arc that fringed the continental margin. Back-stepping of the arc axis may have been caused by the collision of buoyant seamounts, which were coeval with plateau rocks exposed in the Nicoya Peninsular of Costa Rica. Rapid westward drift of South America closed the Quebradagrande basin in the late Aptian and caused medium-high P-T metamorphic rocks of the Arquía Complex to exhume and obduct onto

  17. Andean waterways

    DEFF Research Database (Denmark)

    Rasmussen, Mattias Borg

    , social, and cultural concerns. Set in the highland town of Recuay in Ancash, the book traces the ways in which water affects political and ecological relations as glaciers recede. By looking at the shared waterways of four villages located in the foothills of Cordillera Blanca, it addresses pertinent......Andean Waterways explores the politics of natural resource use in the Peruvian Andes in the context of climate change and neoliberal expansion. It does so through careful ethnographic analysis of the constitution of waterways, illustrating how water becomes entangled in a variety of political...

  18. Geometric, kinematic, and erosional history of the central Andean Plateau, Bolivia (15-17°S)

    Science.gov (United States)

    McQuarrie, Nadine; Barnes, Jason B.; Ehlers, Todd A.

    2008-06-01

    Latitudinal changes in topography, climate, and thrust belt geometry in the central Andes have led to conflicting hypotheses that climate or tectonics exert a first-order control on orogen evolution. The relative roles of climate and tectonics in the evolution of the Andean orogen are difficult to quantify because of a lack of detailed observations for both the long-term deformation and erosion history of the Andean fold-thrust belt. We contribute to the resolution of this problem by presenting a sequentially restored, balanced cross section based on new mapping across the northern Bolivia portion of the thrust belt (15-17°S). The timing and magnitude of exhumation across the cross section are determined by synthesizing 10 new and ˜70 previously published mineral cooling ages. Once balanced and restored, the section was sequentially forward modeled using stratigraphic and cooling age constraints. Results indicate the Eastern Cordillera (EC) records the highest magnitudes of shortening (123 km or 55%). The Interandean zone (IA) has shortened 48 km or 30%. In both the EC and IA individual thrust sheets are tightly folded and have minor offsets of 1-5 km. The Subandes (SA) has multiple levels of detachments allowing for thrust sheets with relatively large offsets (6-17 km). Total shortening in the SA is 66 km or 40%. Total magnitude of shortening for the entire fold-thrust belt in this region is 276 km (40%). New apatite and zircon fission track cooling ages in conjunction with published ages indicate two phases of rapid exhumation; an earlier phase from ˜40 to 25 Ma in the EC and one prior to ˜25 Ma in the IA, followed by distributed exhumation of the entire fold-thrust belt from ˜15-0 Ma. Combined exhumation estimates from the balanced cross section and thermochronology suggest ˜9-11 km of exhumation in the EC, ˜5-9 km in the IA, and ˜3-4 km in the SA. Long-term shortening rates are 7 mm/a for the EC and IA and 4-8 mm/a for the SA. The SA shortening rates

  19. 10Be surface exposure dating reveals strong active deformation in the central Andean backarc interior

    Science.gov (United States)

    García Morabito, Ezequiel; Terrizzano, Carla; Zech, Roland; Willett, Sean; Yamin, Marcela; Haghipour, Negar; Wuethrich, Lorenz; Christl, Marcus; María Cortes, José; Ramos, Victor

    2016-04-01

    Understanding the deformation associated with active thrust wedges is essential to evaluate seismic hazard. How is active faulting distributed throughout the wedge, and how much deformation is taken up by individual structures? We address these questions for our study region, the central Andean backarc of Argentina. We combined a structural and geomorphological approach with surface exposure dating (10Be) of alluvial fans and strath terraces in two key localities at ~32° S: the Cerro Salinas, located in the active orogenic front of the Precordillera, and the Barreal block in the interior of the Andean mountain range. We analysed 22 surface samples and 6 depth profiles. At the thrust front, the oldest terrace (T1) yields an age of 100-130 ka, the intermediate terrace (T2) between 40-95 ka, and the youngest terrace (T3) an age of ~20 ka. In the Andean interior, T1´ dates to 117-146 ka, T2´ to ~70 ka, and T3´ to ~20 ka, all calculations assuming negligible erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Vertical slip rates of fault offsets are 0.3-0.5 mm/yr and of 0.6-1.2 mm/yr at the thrust front and in the Andean interior, respectively. Our results highlight: i) fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone. Internal structures have been active during the last 150 ka, ii) deformation rates in the Andean interior are comparable or even higher that those estimated and reported along the emerging thrust front, iii) distribution of active faulting seems to account for unsteady state conditions, and iv) seismic hazards may be more relevant in the internal parts of the Andean orogen than assumed so far. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary Science Letters 104: 424-439. Stone, J.O., 2000: Air pressure and cosmogenic isotope production. Journal of Geophysical

  20. Three-dimensional inversion of magnetotelluric data from the Central Andean continental margin

    Science.gov (United States)

    Kühn, Christine; Küster, Jonas; Brasse, Heinrich

    2014-12-01

    Magnetotelluric data were collected in the late 1990s in the Central Andes of Chile and Bolivia, with the aim to delineate the electrical conductivity distribution in the subsurface and its relations to subduction processes. In previous studies, these data were interpreted based on 2-D models. The principal result was a vast conductivity zone beneath the Altiplano high plateau at mid and lower crustal depths and a much smaller, though significant conductor associated with the Precordillera Fault System. However, there are some significant 3-D effects in the investigation area, in particular near the coast and on the eastern Altiplano. The aim of this work is to give a reinterpretation based on new 3-D inversion of these data. The 3-D inversion not only provides a better fit to the data compared to 2-D results but furthermore allows to include sites with strong telluric distortion which were ignored in previous studies. We are now able to explain anomalous phases above 90° and induction arrows pointing subparallel to the coast as observed at several sites in the Coastal Cordillera. These strongly distorted data are caused by highly conductive near-surface structures that are partly connected to the Pacific Ocean, forcing currents to flow around the sites. The lower crust beneath the Coastal Cordillera resembles a poorly conductive, nearly homogeneous half-space and is electrically unremarkable. Besides, we can now image the Precordillera conductor as a continuous, elongated feature. The volcanic arc of the Western Cordillera is highly resistive with the exception of a few conductive spots which may be associated with certain individual volcanoes or geothermal resources, respectively. The Altiplano conductor is again the dominant electrical feature in the Central Andes, indicating widespread melting of the middle and lower back-arc crust.

  1. Three new species of Pristimantis (Lissamphibia, Anura from montane forests of the Cordillera Yanachaga in Central Peru

    Directory of Open Access Journals (Sweden)

    William E. Duellman

    2007-12-01

    Full Text Available We describe three additional new species of Pristimantis from the Cordillera Yanachaga, a part of the Andes in central Peru. Analyses of DNA sequences of the mitochondrial rRNA genes show that onespecies is a close relative of P. bipunctatus (P. conspicillatus Group, another is a close relative of P. stictogaster (P. peruvianus Group, and the third is related to several species in the P. unistrigatus Group. The first two species are morphologically similar to their closest relatives but occur at lower elevations. Twenty-nine species of Pristimantis and Phrynopus are known from the vicinity of the Cordillera Yanachaga. The number of species, especially of Pristimantis, is high in the humid montane forestin comparison with other sites in humid montane forests in Peru, but the number is lower than on the western slopes of the Andes in Ecuador.

  2. Shortening Record in the Central Andean Plateau of Southern Peru: Basement Inversion, Thin-skinned Thrusting, and Geomorphic Response

    Science.gov (United States)

    Perez, N.; Horton, B. K.; McQuarrie, N.; Stübner, K.; Ehlers, T. A.

    2015-12-01

    Variations in the inherited structural architecture along western South America influence the timing, magnitude, and style of Andean deformation and topographic evolution. New results from mapping, balanced cross-section construction, apatite and zircon (U-Th)/He thermochronology, and geomorphology spanning the Altiplano, Eastern Cordillera and Subandean zone of southern Peru define the role of Triassic rift inversion on Cenozoic deformation style, thrust belt kinematics, exhumation timing, and spatial variation of canyon incision. A minimum of 130 km (38%) shortening along a 200 km transect accommodated by thin- and thick-skinned structures involved selective reactivation of Triassic normal faults that fed slip to shallower detachments of thin-skinned fold-thrust systems. Map relationships define unique structural domains defined by inherited normal faults. In the Eastern Cordillera, new zircon (U-Th)/He results from a Triassic pluton reveal Oligocene-Miocene (~26-18 Ma) cooling, consistent with previously reported exhumation from ~40 km along strike to the NW. However, rapid ~15 Ma cooling revealed by new apatite (U-Th)/He data is ~11 Myr older than equivalent rocks in a similar structural setting ~40 km to the NW. This suggests a potential middle Miocene shift from synchronous to diachronous exhumation along strike. Modern fluvial profiles constructed along the Eastern Cordillera show a reduction in knickpoint elevations from SE to NW, suggesting more youthful uplift toward the NW, comparable to the spatial trend in apatite (U-Th)/He ages. The deformation front reached the Subandean zone by ~15 Ma, after the majority of reported deformation in the Eastern Cordillera and Altiplano. These variations in exhumation over such distances are consistent with multiple potential scenarios: a northward propagating wave of uplift, spatial variations in climatically driven incision, interactions with mantle dynamics, or complex structural geometries.

  3. Deformation and incision of the western margin of the Central Andean Plateau, S. Peru and N. Chile

    Science.gov (United States)

    Schildgen, T.

    2012-12-01

    The western margin of the Central Andean Plateau in southern Peru and northern Chile hosts a rich geologic and geomorphic record of crustal deformation and river incision that developed during a period of regional plateau uplift. Significant growth of topography likely occurred in the western Central Andes starting at ca. 30 Ma, when the regionally extensive silts and sandstones of the Moquegua and Azapa Group sediments gave way to coarse sandstones and conglomerates. Apatite (U-Th)/He thermochronology, 3D thermal modeling, and infilling volcanic flows show that a subsequent major phase of canyon incision started in the middle reaches of Ocoña Canyon (southern Peru) between 11 and 8 Ma, with ca. 2-km of incision occurring between ca. 11 and 5 Ma. Surface uplift coeval with this incision has been documented in northern Chile, where rotated forearc basin deposits reveal 1 to 2 km of differential uplift between the Coastal Cordillera and the plateau margin that started after 11 to 10 Ma. In contrast with the 11 to 8 Ma onset of incision in the middle reaches of Ocoña Canyon, the currently 1-km-high coastal/piedmont region appears not to have been affected by incision until after 5 Ma, as documented by the 50-km-wide alluvial and colluvial plain that remained occupied by rivers until at least 5 Ma. Apatite (U-Th)/He thermochronology pointing to a final 1-km of incision in the middle reaches of Ocoña Canyon after ca. 5 Ma is supported by apatite 4He/3He thermochonometry, which documents the passage of a km-scale knickpoint through the same region between ca. 7 and 4 Ma. Although river incision provides only a minimum time constraint for the start of surface uplift, the broadly coincident start of incision with the rotation of forearc basin deposits in northern Chile implies a close temporal coupling between the start of surface uplift and the onset of incision in Ocoña Canyon. Furthermore, the delayed incision of the coastal/piedmont region until after 5 Ma shows

  4. Kinematic evolution of Andean fold-thrust structures along the boundary between the Eastern Cordillera and Middle Magdalena Valley basin, Colombia

    Science.gov (United States)

    SáNchez, Javier; Horton, Brian K.; Tesón, Eliseo; Mora, AndréS.; Ketcham, Richard A.; Stockli, Daniel F.

    2012-06-01

    Surface and subsurface data support a kinematic reconstruction of Cenozoic fold-thrust deformation along the Eastern Cordillera-Magdalena Valley transition in Colombia. The La Salina fault (LSF) marks the boundary between west-vergent Eastern Cordillera structures and hinterland deposits of the Middle Magdalena Valley basin. Apatite fission track and (U-Th)/He thermochronological results for the west-directed LSF reveal initial hanging wall exhumation during middle Eocene-early Oligocene (45-30 Ma) shortening, renewed exhumation in the early middle Miocene (18-12 Ma), and accelerated late Miocene-Pliocene (12-3 Ma) exhumation. Vitrinite reflectance data suggest maximum burial of 4-6 km, helping constrain Cenozoic basin architecture. Mapping of the LSF reveals hanging wall Cretaceous-Eocene rocks in a broad anticline-syncline pair with limited faulting and footwall Eocene-Quaternary basin fill in a complex series of tight thrust-related folds. Limited displacement along the westernmost (frontal) thrust suggests that shortening is largely accommodated by east-directed thrusting within a broader triangle zone of a passive-roof duplex (and probable minor strike-slip deformation). In the preferred kinematic restoration, the most recent phase of shortening to transpressional deformation represents out-of-sequence reactivation of the LSF consistent with irregular crosscutting relationships among footwall structures. Earliest exhumation by 45-30 Ma in the Eastern Cordillera fold-thrust belt is correlated with increased sedimentary lithic fragments and high compositional maturity in sandstones of the adjacent Magdalena Valley basin. Exhumation since ˜15 Ma coincided with decreased compositional maturity and elevated accumulation rates for the Real Group. The compositional provenance shifts are attributed to westward advance of fold-thrust deformation into the proximal (eastern) segments of the Magdalena Valley basin.

  5. Size class structure, growth rates, and orientation of the central Andean cushion Azorella compacta

    Directory of Open Access Journals (Sweden)

    Catherine Kleier

    2015-03-01

    Full Text Available Azorella compacta (llareta; Apiaceae forms dense, woody, cushions and characterizes the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was established at 5,250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr−1. Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20° from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant.

  6. Size class structure, growth rates, and orientation of the central Andean cushion Azorella compacta

    Science.gov (United States)

    Trenary, Tim; Graham, Eric A.; Stenzel, William; Rundel, Philip W.

    2015-01-01

    Azorella compacta (llareta; Apiaceae) forms dense, woody, cushions and characterizes the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was established at 5,250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr−1. Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20° from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant. PMID:25802811

  7. Seismic imaging of the upper mantle beneath the northern Central Andean Plateau: Implications for surface topography

    Science.gov (United States)

    Ward, K. M.; Zandt, G.; Beck, S. L.; Wagner, L. S.

    2015-12-01

    Extending over 1,800 km along the active South American Cordilleran margin, the Central Andean Plateau (CAP) as defined by the 3 km elevation contour is second only to the Tibetan Plateau in geographic extent. The uplift history of the 4 km high Plateau remains uncertain with paleoelevation studies along the CAP suggesting a complex, non-uniform uplift history. As part of the Central Andean Uplift and the Geodynamics of High Topography (CAUGHT) project, we use surface waves measured from ambient noise and two-plane wave tomography to image the S-wave velocity structure of the crust and upper mantle to investigate the upper mantle component of plateau uplift. We observe three main features in our S-wave velocity model including (1), a high velocity slab (2), a low velocity anomaly above the slab where the slab changes dip from near horizontal to a normal dip, and (3), a high-velocity feature in the mantle above the slab that extends along the length of the Altiplano from the base of the Moho to a depth of ~120 km with the highest velocities observed under Lake Titicaca. A strong spatial correlation exists between the lateral extent of this high-velocity feature beneath the Altiplano and the lower elevations of the Altiplano basin suggesting a potential relationship. Non-uniqueness in our seismic models preclude uniquely constraining this feature as an uppermost mantle feature bellow the Moho or as a connected eastward dipping feature extending up to 300 km in the mantle as seen in deeper mantle tomography studies. Determining if the high velocity feature represents a small lithospheric root or a delaminating lithospheric root extending ~300 km into the mantle requires more integration of observations, but either interpretation shows a strong geodynamic connection with the uppermost mantle and the current topography of the northern CAP.

  8. BANCO DE SEMILLAS EN UN BOSQUE DE ROBLE DE LA CORDILLERA CENTRAL COLOMBIANA SOIL SEED BANK IN AN OAK FOREST FROM THE COLOMBIAN CENTRAL CORDILLERA

    Directory of Open Access Journals (Sweden)

    Luz Bibiana Moscoso Marín

    2005-12-01

    they stores species ready to germinate when a perturbation occurs or when environmental conditions change to start the successional process. The main objective of this research was to evaluate the spatial variation of seed banks and its relation with the current vegetation in a highland Andean forest dominated by oak (Quercus humbodtii Bonpl. at 2.290 m.a.s.l. in the watershed of the Piedras Blancas stream, in the department of Antioquia, Colombia. We sampled 57 points in a 6.400 m² plot established in that forest. In each point we collected one sample each of litter and soil. We also established five subplots of 160 m²each for sampling vegetation. Seed banks were assessed by the method of direct germination. We obtained 204 trees belonging to 25 families and 41 genera. The most representative tree species were Alfaroa cf. colombiana, Myrcia popayanensis Rich. and Quercus humboldtii Bonpl. We obtained 428 individuals from soil samples and 113 individuals from litter samples in the germination trial, belonging to 20 morpho species. Species composition of the soil seed bank did not reflect the composition of the forest vegetation, and we found mainly herbaceous and shrub vegetation. Litter had 198 seeds m-2 and soil had 4.330 seeds m-2. There was large spatial variation in the amount of seeds in this forest fragment.

  9. A new colorful species of Pristimantis (Anura: Craugastoridae) from the eastern flank of the Cordillera Central in Colombia .

    Science.gov (United States)

    Rivera-Prieto, Diego A; Rivera-Correa, Mauricio; Daza, Juan M

    2014-12-22

    We describe a new species of Pristimantis from the humid forests on the eastern flank of the northern Cordillera Central in Colombia (6º 23' 19.3554" N, 75º 1' 24.0594" W; ca. 1150 m.a.s.l.). Pristimantis jaguensis sp. nov. is characterized by an extraordinary variation in color and is readily distinguished from congeneric species by lacking nuptial pads, discoidal fold and conical calcar tubercles; flanks and belly white to cream without blotches as well as iris yellow ocher to copper with thick brown reticulation and cream sclera. Molecular phylogenetic analyses recovered the new species in a clade with species mostly distributed in Ecuador. Our finding suggests that new taxa can still be discovered in the Middle Magdalena River valley of Colombia despite the extensive sampling this region has received during the last decades. 

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

    Science.gov (United States)

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

    2014-05-01

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

  11. El Rosario: un asentamiento prehispánico en "la sierra de los pijao", municipio de Buga, cordillera Central (Colombia

    Directory of Open Access Journals (Sweden)

    Eduardo Forero Lloreda

    2009-07-01

    In the Colombian Andean Central Range belonging to over the Department of Valle in the origins of Cofre river, at El Rosario (Municipality of Buga, there are certain cultural ar- chaeological characteristics that show the evidence of pre–Hispanic occupation, which occurred close to the moment of the first contact with the Spanish invasion. Historical sources of this contact make reference to the fact that the Central Mountain Range was called “Sierra de los pijaos” or “Sierra alta de los pijaos” and was considered the territorial limit since the foundation chronicles of the city of Buga. This is the same border that was used in those days, when Spanish invaders could not trespass due to the occupation of groups that were against the invasion. There is also information about explorations along the middle river stream Guadalajara –river in the same terri- torial limits; that is, the western branch of the Central Mountain Range. The fact that these establishments are found in the limits of the occupation might mean that the- re are two different patterns. The first one is El Rosario (which shares similarities in style with Chaparral– Tolima and the second one is El Janeiro, which has late charac- teristics of what is known as Cauca Medio and Quimbaya. This document reports the unpublished archaeological explorations for this archaeological Colombian region. Keywords: central mountain range, Sierra de los Pijao, territorial limit, Cauca Valley, late settlements

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

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    CAROLINA VILLAGRÁN

    2001-12-01

    Andean and at high latitudes exist in south-central Chile, between 37 and 43° S. According to Darwin (1859, such "islands" are remnants of glacial populations, which were distributed at lower altitudes and latitudes during glacier advances. Also, in Chile there were expansions of the Andean and southernmost flora into the Longitudinal Valley of Los Lagos region during the last glaciation, which reversed during the Late-glacial (14, 600-10,000 14C years BP and Holocene (after 10,000 14C years BP. Considering this hypothesis, in this study we analyzed two palynological sequences from summits of the Coastal Range of Los Lagos region (Cordillera de Nahuelbuta and Cordillera de Sarao and both were correlated with published high and low altitude records from the Los Lagos and Los Canales regions. The records from the Coastal Range show the following chronological sequence: (1 at the lower and middle Holocene, after 9,040 14C years BP, the Cordillera de Sarao site documents the colonization of Magellanic moorlands and north-Patagonian forest elements, followed by north-Patagonian-Valdivian forest elements during the upper Holocene; (2 the Cordillera de Nahuelbuta site shows the development of conifer forest and Magellanic moorlands during the middle Holocene, ca. 5,430 14C years BP. Other palynological records from the Coastal Range (Cordillera Pelada and Cordillera de Piuchué show the development of both communities during the Late-glacial and lower Holocene. In contrast, the low altitude pollen records from the Los Lagos region indicate that conifers and magellanic moorland elements occupied the Longitudinal Valley during the Last Glacial Maximum (LGM, ca. 22,000 14C years BP. Various pollen profiles from Los Lagos and Los Canales regions evidenced for the late-glacial (14,600-10,000 14C years BP the rapid southern expansion of conifers and other north-Patagonian elements, following the deglaciation of these areas. During the Holocene, Valdivian forest elements invaded the

  13. High-up: a remote reservoir of microbial extremophiles at Central Andean Wetlands

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    Virginia Helena Albarracín

    2015-12-01

    Full Text Available The Central Andes region displays unexplored ecosystems of shallow lakes and salt flats at mean altitudes of 3,700 m. Being isolated and hostile, these so-called High-Altitude Andean Lakes (HAAL are pristine and have been exposed to little human influence. HAAL proved to be a rich source of microbes showing interesting adaptations to life in extreme settings (poly-extremophiles such as alkalinity, high concentrations of arsenic and dissolved salts, intense dryness, large daily ambient thermal amplitude, and extreme solar radiation levels. This work reviews HAAL microbiodiversity, taking into account different microbial niches, such as plankton, benthos, microbial mats and microbialites. The modern stromatolites and other microbialites discovered recently at HAAL are highlighted, as they provide unique modern -though quite imperfect- analogues of environments proxy for an earlier time in Earth’s history (volcanic setting and profuse hydrothermal activity, low atmospheric O2 pressure, thin ozone layer and high UV exposure. Likewise, we stress the importance of HAAL microbes as model poly-extremophiles in the study of the molecular mechanisms underlying their resistance ability against UV and toxic or deleterious chemicals using genome mining and functional genomics. In future research directions, it will be necessary to exploit the full potential of HAAL poly-extremophiles in terms of their biotechnological applications. Current projects heading this way have yielded detailed molecular information and functional proof on novel extremoenzymes: i.e. DNA repair enzymes and arsenic efflux pumps for which medical and bioremediation applications, respectively, are envisaged. But still, much effort is required to unravel novel functions for this and other molecules that dwell in a unique biological treasure despite its being hidden high up, in the remote Andes.

  14. High-Up: A Remote Reservoir of Microbial Extremophiles in Central Andean Wetlands.

    Science.gov (United States)

    Albarracín, Virginia H; Kurth, Daniel; Ordoñez, Omar F; Belfiore, Carolina; Luccini, Eduardo; Salum, Graciela M; Piacentini, Ruben D; Farías, María E

    2015-01-01

    The Central Andes region displays unexplored ecosystems of shallow lakes and salt flats at mean altitudes of 3700 m. Being isolated and hostile, these so-called "High-Altitude Andean Lakes" (HAAL) are pristine and have been exposed to little human influence. HAAL proved to be a rich source of microbes showing interesting adaptations to life in extreme settings (poly-extremophiles) such as alkalinity, high concentrations of arsenic and dissolved salts, intense dryness, large daily ambient thermal amplitude, and extreme solar radiation levels. This work reviews HAAL microbiodiversity, taking into account different microbial niches, such as plankton, benthos, microbial mats and microbialites. The modern stromatolites and other microbialites discovered recently at HAAL are highlighted, as they provide unique modern-though quite imperfect-analogs of environments proxy for an earlier time in Earth's history (volcanic setting and profuse hydrothermal activity, low atmospheric O2 pressure, thin ozone layer and high UV exposure). Likewise, we stress the importance of HAAL microbes as model poly-extremophiles in the study of the molecular mechanisms underlying their resistance ability against UV and toxic or deleterious chemicals using genome mining and functional genomics. In future research directions, it will be necessary to exploit the full potential of HAAL poly-extremophiles in terms of their biotechnological applications. Current projects heading this way have yielded detailed molecular information and functional proof on novel extremoenzymes: i.e., DNA repair enzymes and arsenic efflux pumps for which medical and bioremediation applications, respectively, are envisaged. But still, much effort is required to unravel novel functions for this and other molecules that dwell in a unique biological treasure despite its being hidden high up, in the remote Andes.

  15. High-Up: A Remote Reservoir of Microbial Extremophiles in Central Andean Wetlands

    Science.gov (United States)

    Albarracín, Virginia H.; Kurth, Daniel; Ordoñez, Omar F.; Belfiore, Carolina; Luccini, Eduardo; Salum, Graciela M.; Piacentini, Ruben D.; Farías, María E.

    2015-01-01

    The Central Andes region displays unexplored ecosystems of shallow lakes and salt flats at mean altitudes of 3700 m. Being isolated and hostile, these so-called “High-Altitude Andean Lakes” (HAAL) are pristine and have been exposed to little human influence. HAAL proved to be a rich source of microbes showing interesting adaptations to life in extreme settings (poly-extremophiles) such as alkalinity, high concentrations of arsenic and dissolved salts, intense dryness, large daily ambient thermal amplitude, and extreme solar radiation levels. This work reviews HAAL microbiodiversity, taking into account different microbial niches, such as plankton, benthos, microbial mats and microbialites. The modern stromatolites and other microbialites discovered recently at HAAL are highlighted, as they provide unique modern—though quite imperfect—analogs of environments proxy for an earlier time in Earth's history (volcanic setting and profuse hydrothermal activity, low atmospheric O2 pressure, thin ozone layer and high UV exposure). Likewise, we stress the importance of HAAL microbes as model poly-extremophiles in the study of the molecular mechanisms underlying their resistance ability against UV and toxic or deleterious chemicals using genome mining and functional genomics. In future research directions, it will be necessary to exploit the full potential of HAAL poly-extremophiles in terms of their biotechnological applications. Current projects heading this way have yielded detailed molecular information and functional proof on novel extremoenzymes: i.e., DNA repair enzymes and arsenic efflux pumps for which medical and bioremediation applications, respectively, are envisaged. But still, much effort is required to unravel novel functions for this and other molecules that dwell in a unique biological treasure despite its being hidden high up, in the remote Andes. PMID:26733008

  16. Imaging the Seismic Cycle in the Central Andean Subduction Zone from Geodetic Observations

    Science.gov (United States)

    Ortega-Culaciati, F.; Becerra-Carreño, V. C.; Socquet, A.; Jara, J.; Carrizo, D.; Norabuena, E. O.; Simons, M.; Vigny, C.; Bataille, K. D.; Moreno, M.; Baez, J. C.; Comte, D.; Contreras-Reyes, E.; Delorme, A.; Genrich, J. F.; Klein, E.; Ortega, I.; Valderas, M. C.

    2015-12-01

    We aim to quantify spatial and temporal evolution of fault slip behavior during all stages of the seismic cycle in subduction megathrusts, with the eventual goal of improving our understanding of the mechanical behavior of the subduction system and its implications for earthquake and tsunami hazards. In this work, we analyze the portion of the Nazca-SouthAmerican plates subduction zone affected by the 1868 southern Peru and 1877 northern Chile mega-earthquakes. The 1868 and 1878 events defined a seismic gap that did not experience a large earthquake for over 124 years. Only recently, the 1995 Mw 8.1 Antofagasta, 2001 Mw 8.4 Arequipa, 2007 Mw 7.7 Tocopilla, and 2014 Mw 8.2 Pisagua earthquakes released only a small fraction of the potential slip budget, thereby raising concerns about continued seismic and tsunami hazard. We use over a decade of observations from continuous and campaign GPS networks to analyze inter-seismic strain accumulation, as well as co-seimic deformation associated to the more recent earthquakes in the in the Central Andean region. We obtain inferences of slip (and back-slip) behavior using a consistent and robust inversion framework that accounts for the spatial variability of the constraint provided by the observations on slip across the subduction megathrust. We present an updated inter-seismic coupling model and estimates of pre-, co- and post- seismic slip behavior associated with the most recent 2014 Mw 8.2 Pisagua earthquake. We analyze our results, along with published information on the recent and historical large earthquakes, to characterize the regions of the megathrust that tend to behave aseismically, and those that are capable to accumulate a slip budget (ultimately leading to the generation of large earthquakes), to what extent such regions may overlap, and discuss the potential for large earthquakes in the region.

  17. Along-Strike Variations in Focal Mechanisms of Central Andean Crustal Earthquakes: Northern Peru through the Argentina Sierras Pampeanas

    Science.gov (United States)

    Devlin, S.; Isacks, B. L.

    2003-12-01

    120 shallow focal mechanisms in the crust above the subducted Nazca plate were assembled from the Harvard CMT catalog and published studies covering over 40 years of seismicity. The study area included the Andes crust above three major segments of the subducted plate, the Peruvian and Argentinean flat-slab segments and the intervening segment where the subducted Nazca plate dips more steeply. The most seismically active regions continue to be the thick-skinned foreland thrust belts in the eastern Andes of Peru and the Sierras Pampeanas. The earthquakes there are clearly associated with youthful tectonic structures with strong topographic signatures as revealed by the new 90 m SRTM digital elevation models. The mechanisms are dominantly of the thrust type but include a minority of strike-slip orientations. However the P axes remain consistent. The thin-skinned thrust belts east of the central Andean Plateau show significant activity only near Santa Cruz, Bolivia and northern Argentina; most of the Sub-Andean thrust belt of Bolivia and southern Peru remains aseismic. The central Andean plateau itself also remains aseismic except for the region of southern Peru and two earthquakes in the Puna. The crustal seismicity in southern Peru is largely concentrated on the western side of the plateau. The focal mechanisms show a strong grouping of T axes in a horizontal, north-south orientation. Both normal and strike-slip mechanisms occur in this region, with no obvious correlation with elevation or surface structures. Remarkably, with the exception of one normal fault type mechanism near the Cusco basin, the earthquakes occur in regions of the western parts of the Altiplano that do not exhibit topographic evidence of substantial crustal deformation. These results are consistent with a model in which the Altiplano of southern Peru, with a trend most oblique to the overall direction of convergence, manifests a left-lateral shearing component across the orogen.

  18. Where and When did High Andean Relief Emerge?: Insights From Molecular Phylogenies of Andean Biota

    Science.gov (United States)

    Sempere, T.; Picard, D.; Plantard, O.

    2006-05-01

    Emergence of mountains along the Andean margin created new ecosystems and thus triggered a variety of adaptive biotic radiations, to the point that the Andes are to-day one of the world's major biodiversity hotspots. The rising Andes came to serve as a rain barrier: cloud forests developed along their eastern side due to orographic concentration of the westward-moving Amazonian moisture, and environments became drier in the west, with highland steppes extending above ~2-3 km. Relevant biologic data concerning Andean taxa adapted to these environments might therefore shed some light on the issue of Andean orogeny and surface uplift. Phylogeography (the analysis of phylogenetic trees in terms of biogeographic distributions) and phylochronology (the use of phylogenetic trees as molecular clocks) can be employed to reconstruct syn- orogenic radiations and estimate their timing, respectively. We use published molecular phylogenies that inform on the evolution of a variety of Andean animal and plant taxa, and therefore provide indirect means to assess and approximately date the acquisition of altitude. Phylogeographic analyses of 6 phylogenetic trees concerning unrelated Andean biota coincide in having their basal clades established in areas within the Central Andean Orocline (CAO), 5 of them clearly pointing to southern Peru and/or western Bolivia as the region of origin of the corresponding high-Andean taxa. A histogram of 9 phylochronologic estimates, based on trees concerning unrelated taxa (independently constructed and calibrated), suggests that the 2.0-2.5 km critical altitude was acquired during the 23-17 Ma or 26-16 Ma intervals (depending on the threshold used), confirming some geomorphic and geologic estimates (but conflicting with others). Although more data are needed, these results suggest that it was within the CAO and approximately during the early Miocene that the Andes acquired altitudes sufficient to trigger radiations of cold-adapted taxa, i.e. >~2 km

  19. Calculo Preliminar de la Tasa de Meteorización del Batolito Antioqueño, Cordillera Central, Colombia

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    Carolina Garcia

    2004-12-01

    Full Text Available Este trabajo es una estimación preliminar del tiempo necesario para generar la espesa capa de saprolito que caracteriza el perfil de meteorización actual de un batolito cuarzodiorítico cretácico que aflora en altiplanos de la Cordillera Central de Colombia, entre 5º50' y 7º00' de latitud Norte y 74º50' y 75º35' de longitud Oeste y a alturas entre 750 y 2700 m.Se utilizan datos obtenidos previamente mediante el análisis de la composición química de las aguas superficiales de cuatro cuencas con áreas diferentes, ubicadas sobre el Batolito Antioqueño, al este de Medellín. Los cáculos se hicieron con el método basado en la pérdida de componentes en solución utilizando diferentes valores de solutos. Al utilizar la pérdida de sílice se obtiene un tiempo de meteorización de unos 6 x 10 6 años, comparable con el obtenido mediante la datación de las cenizas volcánicas mas antiguas que recubren la topografía actual y que indican la fecha mínima de configuración de la superficie de erosión.A pesar de resultar de una serie de suposiciones simplificadoras, este resultado es interesante y justifica la realización de determinaciones mas detalladas. Confirma la larga preservación de superficies de erosión antiguas conformadas sobre un saprolito que desde hace varios millones de años no ha sido sometido a una erosión profunda, fenómeno poco común en una zona tectónicamente activa como la estudiada.

  20. Bioprospecting in potato fields in the Central Andean Highlands: screening of rhizobacteria for plant growth-promoting properties.

    Science.gov (United States)

    Ghyselinck, Jonas; Velivelli, Siva L S; Heylen, Kim; O'Herlihy, Eileen; Franco, Javier; Rojas, Mercy; De Vos, Paul; Prestwich, Barbara Doyle

    2013-03-01

    The Central Andean Highlands are the center of origin of the potato plant (Solanum tuberosum). Ages of mutualism between potato plants and soil bacteria in this region support the hypothesis that Andean soils harbor interesting plant growth-promoting (PGP) bacteria. Therefore, the aim of this study was to isolate rhizobacteria from Andean ecosystems, and to identify those with PGP properties. A total of 585 bacterial isolates were obtained from eight potato fields in the Andes and they were screened for suppression of Phytophthora infestans and Rhizoctonia solani. Antagonistic mechanisms were determined and antagonistic isolates were further tested for phosphate solubilization, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of NH3- and indole-3-acetic acid (IAA). PGP was studied in healthy and R. solani diseased plantlets under growth room conditions. Performance was compared to the commercial strain B. subtilis FZB24(®) WG. Isolates were dereplicated with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), and identified with 16S rRNA gene sequencing and multi locus sequence analysis (MLSA). A total of 10% of the isolates were effective antagonists, of which many were able to solubilize phosphate, and produce IAA, ACC deaminase, NH3 and hydrogen cyanide (HCN). During growth room experiments, 23 antagonistic isolates were associated with plant growth-promotion and/or disease suppression. Ten isolates had a statistically significant impact on test parameters compared to the uninoculated control. Three isolates significantly promoted plant growth in healthy plantlets compared to the commercial strain, and seven isolates outperformed the commercial strain in in vitro R. solani diseased plantlets.

  1. The El Abra stadlal in the Eastern Cordillera of Colombia (South America)

    Science.gov (United States)

    Kuhry, P.; Hooghiemstra, H.; van Geel, B.; van der Hammen, T.

    The El Abra stadial is a climatic cooling event defined in the Eastern Cordillera of Colombia, which corresponds both in timing and intensity to the Younger Dryas climatic oscillation of the northern North Atlantic region. The stadial was preceded by the relatively warm Guantiva interstadial and followed by the warm Holocene. Colder climatic conditions during the El Abra stadial caused a 400 m lowering of the upper Andean forest limit below its altitudinal location during the preceding Guantiva interstadial. Translated in temperature change, this represents a drop in mean annual temperature of approximately 2 to 3°C. The lowering of the upper forest limit and inferred temperature change for the El Abra stadial, compared to Late Holocene conditions, are in the order of 600 m and 4°C, respectively. The transition of the Guantiva interstadial to the El Abra stadial has been radiocarbon dated at 11,210 ± 90 BP and 10,820 ± 60 BP. Climatic warming may have started shortly after 10,380 ± 90 BP, and near present-day temperatures were reached at least as early as 8920 ± 100 BP. Maximum cooling was probably attained between 10,800 BP and 10,300 BP. Further (AMS) radiocarbon dating is planned to establish more exactly the timing of the El Abra stadial. A glacial advance of El Abra age, the Bocatoma stade, has been recognized in the highest part of the Colombian Eastern Cordillera, the Sierra Nevada del Cocuy. During this advance, glaciers extended some 700 m lower than at present. A climatic cooling event of El Abra age, associated with shifts of the upper Andean forest limit and glacial advances, has also been recognized in other parts of Andean Colombia, including the Central Cordillera and the Sierra Nevada de Santa Marta.

  2. 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.

  3. Receiver functions and crustal structure of the northwestern Andean region, Colombia

    Science.gov (United States)

    Poveda, Esteban; Monsalve, Gaspar; Vargas, Carlos Alberto

    2015-04-01

    We used the receiver function technique to deduce crustal thickness beneath the northwestern Andean system, using data from the permanent seismic network of Colombia, combined with some of the IRIS and CTBTO stations in Colombia and Ecuador. The estimation of crustal thickness was made using the primary P to s conversion and crustal reverberations. The bulk crustal VP/VS ratio was constrained using a crustal thickness versus VP/VS stacking method, in addition to estimations using a time to depth conversion technique based on results of a modified Wadati diagram analysis. We observed a wide range of crustal thicknesses, including values around 17 km beneath the Malpelo Island on the Pacific Ocean, 20 to 30 km at the coastal Pacific and Caribbean plains of Colombia, 25 to 40 km beneath the eastern plains and foothills, 35 km beneath the Western Cordillera, 45 km at the Magdalena River intermountain valley, 52 to 58 km under the northern Central Cordillera, and reaching almost 60 km beneath some of the volcanoes of the Southern Cordilleran system of Colombia; crustal thickness can be slightly greater than 60 km beneath the plateau of the Eastern Cordillera. The values of VP/VS are particularly high for some of the stations on the volcanic centers, reaching values above 1.79, probably related to the addition of mafic materials to the lower crust, and in the plateau of the Eastern Cordillera near Bogota, where we speculate about the possibility of crustal seismic anisotropy associated with shear zones.

  4. Efecto del secado de las muestras sobre la extracción selectiva de Fe y A1 activos en Andisoles del norte de la cordillera central Colombiana.

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    Jaramillo J. Daniel F.

    2000-12-01

    Full Text Available Muestras secadas al aire y sin secar de cinco perfiles de Andisoles del norte de la cordillera central colombiana fueron sometidas a extracción con oxalato ácido de amonio y con pirofosfato de sodio. En los extractos de oxalato se determinaron A1, Fe y Si y en los de pirofosfato A1 y Fe. El secado de las muestras redujo significativamente al 95% la cantidad de A1 y de Fe extraída con oxalato ácido, dificultando la clasificación de los suelos en el orden Andisol utilizando los parámetros de la taxonomía del USDA.

  5. Composition and provenance of Late Pleistocene-Holocene alluvial sediments of the eastern Andean piedmont between 33 and 34° S (Mendoza Province, Argentina)

    Science.gov (United States)

    Mehl, A.; Blasi, A.; Zárate, M.

    2012-12-01

    The Andean cordillera, and its piedmont in the central western Argentina, has been long considered as one of the main source areas of detritus for the Chaco-Pampean plain sand dune fields and loess/loess-like deposits of central Argentina. The main goal of this study is to evaluate the composition of the late Pleistocene-Holocene alluvial deposits of the Andes cordillera piedmont, from 33° to 34° S. The results are interpreted in the context of the regional geology, tectonic setting of the study area and its implications in the continent-wide perspective of modern alluvial sands proposed by Potter (1994). Sampling was conducted at the alluvial stratigraphic sequences of four study sites along three Andean piedmont arroyos; modal mineralogy in the very fine sand fraction (3 phi to 4 phi) was determined using standard petrographic microscope methods. Q:F:LF average compositions indicate that the Late Pleistocene-Holocene very fine-grained alluvial sands of the Cordillera Frontal piedmont reflects the modern lithic arenites of the Argentine Association reported by Potter (1994). The results show two geologically distinct sources in the catchment areas, volcaniclastic and metamorphic rocks. High concentrations of mica and volcanic glass are likely related to particle morphologies and to the deposition sedimentary environment recorded in the alluvial sequences—floodplains. The overabundance of micas over the volcanic glass in the mid-late Holocene alluvial sequence indicates the drainage of a metamorphic area at the expense of other lithological sources. Source areas are located mainly in the Frontal cordillera, and to a lesser extent, in the piedmont Tertiary deposits, another likely source for the analyzed Quaternary alluvial sediments. The mineralogical signature of the late Pleistocene and Holocene alluvial sequences is in agreement with the composition of the southern Pampean sand mantles, loess and loess-like deposits mainly formed by a volcanic mineral

  6. Early and Middle Holocene evidence for plant use and cultivation in the Middle Cauca River Basin, Cordillera Central (Colombia)

    Science.gov (United States)

    Aceituno, Francisco J.; Loaiza, Nicolás

    2014-02-01

    This paper presents the latest results of research done in the Colombian Andean region known as Middle Cauca River Basin, an important location for the study of the origins of plant use and the dispersal of domesticates throughout the Americas due to its geographical position in northwest South America. We discuss human-environment interactions during Pleistocene/Holocene transition to middle Holocene (ca 10,000-4000 BP), specifically human-plant interaction and environmental factors that led to the adoption of horticultural practices. Three lines of evidence are analyzed: archaeological stratigraphy, lithic technology, and microbotanical remains. Our results suggest that early Holocene environmental stability allowed Middle Cauca settlers to use the diverse local resources for several millennia, altering the local vegetation, and leading to the development of horticultural practices that included the use of both local and foreign plants. These results inform the ongoing debate about the antiquity and nature of plant domestication and dispersals in the Americas.

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

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    CARLOS E. OYARZÚN

    2002-03-01

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

  8. Studies in Neotropical Paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: implications for the uplift history of the Central Andes.

    Science.gov (United States)

    Graham, A; Gregory-Wodzicki, K M; Wright, K L

    2001-09-01

    An assemblage of 33 fossil pollen and spores, recovered from the 3600-m high Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds considerably to our knowledge of three aspects of the region in late Neogene time: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevation of the Central Andes. The plant microfossils recognized are Isoetes, Lycopodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymenophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern spores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cavanillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that this flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano húmedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of ∼10° and 20°C. The Pislepampa flora probably represents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of ∼20°C, a mean annual precipitation between 1000 and 1500 mm, and that part containing most of the identified genera of fossil pollen is found at elevations ∼1200-1400 m. These conditions are thus inferred for the Pislepampa flora; however, because of the uncertainty of the magnitude of global climate change and of possible changes in the ecological range of plant genera, we estimate an error of at least ±1000 m for the paleoelevation estimate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from one-third to one

  9. Detrital Zircon Provenance Record of Pre-Andean to Modern Tectonics in the Northern Andes: Examples from Peru, Ecuador, and Colombia

    Science.gov (United States)

    George, S. W. M.; Jackson, L. J.; Horton, B. K.

    2015-12-01

    Detrital zircon U-Pb age distributions from modern rivers and Mesozoic-Cenozoic basin fill in the northern Andes provide insights into pre-Andean, Andean, and active uplift and exhumation of distinctive sediment source regions. Diagnostic age signatures enable straightforward discrimination of competing sediment sources within the Andean magmatic arc (Western Cordillera-Central Cordillera), retroarc fold-thrust belt (Eastern Cordillera-Subandean Zone), and Amazonian craton (composed of several basement provinces). More complex, however, are the mid/late Cenozoic provenance records generated by recycling of basin fill originally deposited during early/mid Mesozoic extension, late Mesozoic thermal subsidence, and early Cenozoic shortening. Although subject to time-transgressive trends, regionally significant provenance patterns in Peru, Ecuador, and Colombia reveal: (1) Triassic-Jurassic growth of extensional subbasins fed by local block uplifts (with commonly unimodal 300­-150 Ma age peaks); (2) Cretaceous deposition in an extensive postrift setting fed by principally cratonic sources (with common 1800-900 Ma ages); and (3) Cenozoic growth of a broad flexural basin fed initially fed by magmatic-arc rocks (100-0 Ma), then later dominance by thrust-belt sedimentary rocks with progressively greater degrees of basin recycling (yielding diverse and variable age populations from the aforementioned source regions). U-Pb results from modern rivers and smaller subbasins prove useful in evaluating source-to-sink relationships, downstream mixing relationships, hinterland-foreland basin connectivity, paleodrainage integration, and tectonic/paleotopographic reconstructions. Most but not all of the elevated intermontane basins in the modern hinterland of the northern Andes contain provenance records consistent with genesis in a broader foreland basin developed at low elevation. Downstream variations within modern axial rivers and Cenozoic axial basins inform predictive models of

  10. Large along-strike variations in the onset of Subandean exhumation: Implications for Central Andean orogenic growth

    Science.gov (United States)

    Lease, Richard O.; Ehlers, Todd A.; Enkelmann, Eva

    2016-10-01

    Plate tectonics drives mountain building in general, but the space-time pattern and style of deformation is influenced by how climate, geodynamics, and basement structure modify the orogenic wedge. Growth of the Subandean thrust belt, which lies at the boundary between the arid, high-elevation Central Andean Plateau and its humid, low-elevation eastern foreland, figures prominently into debates of orogenic wedge evolution. We integrate new apatite and zircon (U-Th)/He thermochronometer data with previously published apatite fission-track data from samples collected along four Subandean structural cross-sections in Bolivia between 15° and 20°S. We interpret cooling ages vs. structural depth to indicate the onset of Subandean exhumation and signify the forward propagation of deformation. We find that Subandean growth is diachronous south (11 ± 3 Ma) vs. north (6 ± 2 Ma) of the Bolivian orocline and that Subandean exhumation magnitudes vary by more than a factor of two. Similar north-south contrasts are present in foreland deposition, hinterland erosion, and paleoclimate; these observations both corroborate diachronous orogenic growth and illuminate potential propagation mechanisms. Of particular interest is an abrupt shift to cooler, more arid conditions in the Altiplano hinterland that is diachronous in southern Bolivia (16-13 Ma) vs. northern Bolivia (10-7 Ma) and precedes the timing of Subandean propagation in each region. Others have interpreted the paleoclimate shift to reflect either rapid surface uplift due to lithosphere removal or an abrupt change in climate dynamics once orographic threshold elevations were exceeded. These mechanisms are not mutually exclusive and both would drive forward propagation of the orogenic wedge by augmenting the hinterland backstop, either through surface uplift or spatially variable erosion. In summary, we suggest that diachronous Subandean exhumation was driven by piecemeal hinterland uplift, orography, and the outward

  11. Stable water isotope variation in a Central Andean watershed dominated by glacier and snowmelt

    Directory of Open Access Journals (Sweden)

    N. Ohlanders

    2013-03-01

    Full Text Available Central Chile is an economically important region for which water supply is dependent on snow- and ice melt. Nevertheless, the relative contribution of water supplied by each of those two sources remains largely unknown. This study represents the first attempt to estimate the region's water balance using stable isotopes of water in streamflow and its sources. Isotopic ratios of both H and O were monitored during one year in a high-altitude basin with a moderate glacier cover (11.5%. We found that the steep altitude gradient of the studied catchment caused a corresponding gradient in snowpack isotopic composition and that this spatial variation had a profound effect on the temporal evolution of streamflow isotopic composition during snowmelt. Glacier melt and snowmelt contributions to streamflow in the studied basin were determined using a quantitative analysis of the isotopic composition of streamflow and its sources, resulting in a glacier melt contribution of 50–90% for the unusually dry melt year of 2011/2012. This suggests that in (La Niña years with little precipitation, glacier melt is an important water source for central Chile. Predicted decreases in glacier melt due to global warming may therefore have a negative long-term impact on water availability in the Central Andes. The pronounced seasonal pattern in streamflow isotope composition and its close relation to the variability in snow cover and discharge presents a potentially powerful tool to relate discharge variability in mountainous, melt-dominated catchments with related factors such as contributions of sources to streamflow and snowmelt transit times.

  12. Styles of zoning in central Andean ignimbrites - Insights into magma chamber processes

    Science.gov (United States)

    De Silva, S. L.

    1991-01-01

    Data are presented showing that calc-alkaline high-K ignimbrites from the Altiplano-Puna Volcanic Complex of the Central Volcanic Zone of the Andes, showing a variety of compositional zonations. The characteristics of the juvenile material from the zoned and heterogenous ignimbrites suggest that crystallization of the observed phenocrysts occurred in prezoned magma chambers consisting of two or more layers. It is suggested that the width/height ratio of a magma chamber plays a critical role in the control of the style of zonation that may develop in a closed magma chamber.

  13. Provenance of the Miocene Alto Tunuyán Basin (33°40‧S, Argentina) and its implications for the evolution of the Andean Range: Insights from petrography and U-Pb LA-ICPMS zircon ages

    Science.gov (United States)

    Porras, Hernán; Pinto, Luisa; Tunik, Maisa; Giambiagi, Laura; Deckart, Katja

    2016-10-01

    The Alto Tunuyán Foreland Basin in western Argentina is located immediately south of the flat-slab segment of the Central Andes and its evolution is directly related to the propagation of structures to the east. Petrographic and geochronologic studies have been performed to determine the provenance of syntectonic sediments in the basin in order to establish their relationship to the Andean orogenic activity. The analysed detrital and igneous zircons in contrast with previous data, allow us to restrict the basin age between ca. 15 and 6 Ma. Sandstones record two main contributions, one from andesitic volcanic rocks and the other from an acidic igneous source, the first probably corresponding to Miocene volcanic rocks from the Principal Cordillera (Farellones Formation) and the second to Permo-Triassic, acidic, igneous rocks from the Frontal Cordillera (Choiyoi Magmatic Province, CMP). Two secondary sources have been recorded, sedimentary and metamorphic; the first one is represented by Mesozoic rocks in the Principal Cordillera and the second by the Proterozoic/early Carboniferous Guarguaráz Complex (GC) in the Frontal Cordillera, respectively. Sandstones from the lower basin deposits (15-11 Ma) register supply pulses from the Farellones Formation reflecting the unroofing of the Principal Cordillera by uplift pulses during the middle Miocene. Sandstones from the upper basin deposits (ca. 11-9 Ma) record an increase in material derived from the CMP, reflecting important uplift of the Frontal Cordillera. A thick, ca. 9 Ma old ignimbrite within the basin indicates an eruption in the Frontal Cordillera. Detrital zircons from the CMP have been detected also in the lower basin deposits, suggesting either recycling of Mesozoic deposits containing CMP zircons or an early paleorelief of the Frontal Cordillera. The good correlation between the age of the detrital zircons of the CMP and the GC in the lower basin deposits supports recycling of Mesozoic sedimentary deposits.

  14. Depositional and provenance record of the Paleogene transition from foreland to hinterland basin evolution during Andean orogenesis, northern Middle Magdalena Valley Basin, Colombia

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    Moreno, Christopher J.; Horton, Brian K.; Caballero, Victor; Mora, Andrés; Parra, Mauricio; Sierra, Jair

    2011-10-01

    The Central Cordillera and Eastern Cordillera of the northern Andes form the topographic flanks of the north-trending Magdalena Valley Basin. Constraining the growth of these ranges and intervening basin has implications for Andean shortening and the transformation from a foreland to hinterland basin configuration. We present sedimentological, paleocurrent, and sandstone petrographic results from Cenozoic type localities to provide insights into the tectonic history of the northern Middle Magdalena Valley Basin of Colombia. In the Nuevo Mundo Syncline, the mid-Paleocene transition from marine to nonmarine deposystems of the Lisama Formation corresponds with a paleocurrent shift from northward to eastward transport. These changes match detrital geochronological evidence for a contemporaneous shift from cratonic (Amazonian) to orogenic (Andean) provenance, suggesting initial shortening-related uplift of the Central Cordillera and foreland basin generation in the Magdalena Valley by mid-Paleocene time. Subsequent establishment of a meandering fluvial system is recorded in lower-middle Eocene strata of the lower La Paz Formation. Eastward paleocurrents in mid-Paleocene through uppermost Eocene fluvial deposits indicate a continuous influence of western sediment source areas. However, at the upper middle Eocene (˜40 Ma) boundary between the lower and upper La Paz Formation, sandstone compositions show a drastic decrease in lithic content, particularly lithic volcanic fragments. This change is accompanied by a facies shift from mixed channel and overbank facies to thick, amalgamated braided fluvial deposits of possible fluvial megafans, reflecting changes in both the composition and proximity of western sediment sources. We attribute these modifications to the growing influence of exhumed La Cira-Infantas paleohighs in the axial Magdalena Valley, features presently buried beneath upper Eocene-Quaternary basin fill along the western flank of the Nuevo Mundo Syncline. In

  15. Seafloor Geodetic Monitoring of the Central Andean Subduction Zone: The Geosea Array

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    Kopp, H.; Lange, D.; Contreras Reyes, E.; Behrmann, J. H.; McGuire, J. J.; Flueh, E. R.

    2014-12-01

    Seafloor geodesy has been identified as one of the central tools in marine geosciences to monitor seafloor deformation at high resolution. To quantify strain accumulation and assess the resultant hazard potential we urgently need systems to resolve seafloor crustal deformation. The GeoSEA (Geodetic Earthquake Observatory on the Seafloor) array consists of a seafloor transponder network comprising a total of 35 units and a wave glider acting as a surface unit (GeoSURF) to ensure satellite correspondence, data transfer and monitor system health. For horizontal direct path measurements, the system utilizes acoustic ranging techniques with a ranging precision better than 15 mm and long term stability over 2 km distance. Vertical motion is obtained from pressure gauges. Integrated inclinometers monitor station settlement in two horizontal directions. Travel time between instruments and the local water sound velocity will be recorded autonomously subsea without system or human intervention for up to 3.5 years. Data from the autonomous network on the seafloor can be retrieved via the integrated high-speed acoustic telemetry link without recovering the seafloor units. In late 2015 GeoSEA will be installed on the Iquique segment of the South America - Nazca convergent plate boundary to monitor crustal deformation. The Iquique seismic gap experienced the 2014 Mw 8.1 Pisagua earthquake, which apparently occurred within a local locking minimum. It is thus crucial to better resolve resolve strain in the forearc between the mainland and the trench in order to improve our understanding of forearc deformation required for hazard assessment. Mobile autonomous seafloor arrays for continuous measurement of active seafloor deformation in hazard zones have the potential to lead to transformative discoveries of plate boundary/fault zone tectonic processes and address a novel element of marine geophysical research.

  16. Las bioconstrucciones de corales y sus facies asociadas durante el Malm en la Cordillera Ibérica Central (provincia de Zaragoza

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    Meléndez, A.

    1987-08-01

    Full Text Available The differents types of bioconstructions and associated facies in the Central Iberian Chain (Higueruelas Formation, Upper Kimmeridgian have been studied. Biohermes of different thickness (decimetric to metric and less lateral continuity are developped, highly colonized by corals, that are associated to oncolitic, bioclastic and oolitic of high energy facies, in marginal areas, near the litoral developpment. At the same time takes place an important set up of mud mounds, with a small coral colonisation, in protected arcas in a inner shelf, or in outer areas, where the action of the waves is not so effective. The environment protection is been generated in some places due to the appearance of oolitic barrier islands.Se estudian los diferentes tipos de bioconstrucciones de corales, y sus facies asociadas, presentes en el sector central de la rama aragonesa de la Cordillera Ibérica, en la Formación Higueruelas (Kimmeridgiense superior. Se desarrollan biohermos de potencias métricas a decimétricas y escasa continuidad lateral, intensamente colonizados por corales coloniales, que se encuentran asociados a facies oncolíticas, bioclásticas y oolíticas de alta energía en zonas marginales, próximas al desarrollo litoral. Al mismo tiempo tiene lugar una importante instalación de mud mounds, con escasa colonización de corales, en zonas protegidas dentro de la plataforma interna o en zonas más externas, donde la acción del oleaje no es efectiva. La protección del medio viene condicionada en algunos puntos por la aparición de islas barrera oolíticas.

  17. K-Ar geochronology of the late cenozoic volcanic rocks of the Cordillera Occidental, southernmost Peru

    Science.gov (United States)

    Tosdal, Richard M.; Farrar, Edward; Clark, Alan H.

    1981-05-01

    Twenty-four K-Ar radiometric ages are presented for late Cenozoic continental volcanic rocks of the Cordillera Occidental of southernmost Perú (lat. 16° 57'-17° 36'S). Rhyodacitic ignimbrite eruptions began in this transect during the Late Oligocene and continued episodically through the Miocene. The development of andesitic-dacitic strato volcanoes was initiated in the Pliocene and continues to the present. The earliest ignimbrite flows (25.3-22.7 Ma) are intercalated in the upper, coarsely-elastic member of the Moquegua Formation and demonstrate that this sedimentary unit accumulated in a trough, parallel to Andean tectonic trends, largely in the Oligocene. More voluminous ash-flow eruptions prevailed in the Early Miocene (22.8-17.6 Ma) and formed the extensively preserved Huaylillas Formation. This episode was coeval with a major phase of Andean uplift, and the pyroclastics overlie an erosional surface of regional extent incised into a Paleogene volcano-plutonic arc terrain. An age span of 14.2-8.9 Ma (mid-Late Miocene) is indicated for the younger Chuntacala Formation, which again comprises felsic ignimbrite flows, largely restricted to valleys incised into the pre-Huaylillas Formation lithologies, and, at lower altitudes, an extensive aggradational elastic facies. The youngest areally extensive ignimbrites, constituting the Sencca Formation, were extruded during the Late Miocene. In the earliest Pliocene, the ignimbrites were succeeded by more voluminous calcalkaline, intermediate flows which generated numerous large and small stratovolcanoes; these range in age from 5.3 to 1.6 Ma. Present-day, or Holocene, volcanism is restricted to several large stratovolcanoes which had begun their development during the Pleistocene (by 0.7 Ma). The late Oligocene/Early Miocene (ca. 22-23 Ma) reactivation of the volcanic arc coincided with a comparable increase in magmatic activity throughout much of the Cordilleras Occidental and Oriental of the Central Andes.

  18. Evolución de las estructuras andinas en la region del Río Diamante (34º40'LS: vinculación entre la faja corrida y plegada de Malargüe y la cordillera frontal Evolution of the Andean structures at the Río Diamante region (34º40'SL: linkage between the Malargüe fold-and-thrust belt and the Cordillera Frontal

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    Martín M. Turienzo

    2010-11-01

    Full Text Available El estudio de las estructuras andinas en la región del río Diamante y su vinculación con las rocas volcánicas, subvolcánicas y sedimentarias terciarias, permitió establecer un modelo estructural evolutivo para este sector de los Andes. La estructura dominante está conformada por dos sectores que involucran al basamento, entre los cuales se desarrolla un sector con deformación en la cubierta sedimentaria. En el sector occidental, grandes cuñas de basamento asociadas a corrimientos andinos, se propagaron en la cubierta a lo largo de horizontes favorables generando los pliegues y corrimientos del sector central de piel fina. La estructuración de estos dos sectores, que implica un acortamiento de 10 km, tuvo lugar entre los 14,5 Ma y los 10,8 Ma, lo cual representa un importante evento compresivo durante el Mioceno medio (2,7 mm/año. En el sector oriental, la ausencia de despegues eficientes dificultó el desarrollo de cuñas de basamento y en cambio tuvo lugar una importante deformación mediante retrocorrimientos. Numerosos cuerpos subvolcánicos (10,5 Ma a 5,5 Ma presentes en toda la zona donde ocurren los retrocorrimientos sugieren una vinculación entre el magmatismo y el fallamiento antitético. Con la continuidad de la compresión, la falla Carrizalito cortó hacia la superficie montando rocas prejurásicas y mesozoicas sobre terciarias, aunque en la región más austral permanece como una falla ciega que registra sismicidad moderna. Un acortamiento de 4,3 km en el sector oriental ocurrido entre los 10,8 Ma y los 0,5 Ma (0,42 mm/año indica una lentificación de la contracción andina durante el Mioceno tardío-Pleistoceno.The study of the Andean structures at the Río Diamante region and its linkage with the tertiary volcanic, subvolcanic and sedimentary rocks, allow us to propose a structural evolution for this sector of the Andes. Two basement-involved sectors with a thin-skinned sector between them form the dominant structure

  19. Caracterización de superficies de erosión mediante geomorfología cuantitativa, Altiplano Antioqueño, Cordillera Central de Colombia

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    Xavier Bustos

    2013-01-01

    Full Text Available En el presente trabajo se caracterizan treinta y cinco superficies de erosión (SE en la Cordillera Central de Colombia mediante geomorfología cuantitativa y análisis digital de terreno. Utilizando modelos digitales de elevación (MDE se derivaron las curvas hipsométricas para dichas superficies, y se comparan los resultados desde dos ópticas. Primero, mediante técnicas geoestadísticas utilizando subrutinas elaboradas bajo R, en combinación con el Lenguaje de Consulta Estructurado (SQL. Segundo, mediante sus respectivos valores de integral hipsométrica, lo que permitió discriminar el grado de madurez, juventud y vejez de las mismas. Desde un vista geomático este trabajo contribuye en el empleo de Bases de Datos Geográficas (Geodatabase lo que permite optimizar el tiempo y el número de cálculos en el procesamiento, todo esto fue integrado usando Sistemas de Información Geográfica (SIG. Los resultados obtenidos acá permiten caracterizar las superficies y relacionar su morfología con fenómenos físicos y climáticos tales como: levantamiento superficial del terreno, erosión, incisión de ríos y presencia de fallas. Adicionalmente, este enfoque multidisciplinario podría ser utilizado para caracterizar topo-formas remanentes a lo largo de Suramérica, las cuales son de vital importancia ya que contienen información de la interacción de procesos climáticos y tectónicos a lo largo del tiempo geológico.

  20. Landsat TM and ETM+ derived snowline altitudes in the Cordillera Huayhuash and Cordillera Raura, Peru, 1986–2005

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    J. Ramage

    2011-05-01

    Full Text Available The Cordilleras Huayhuash and Raura are remote glacierized ranges in the Andes Mountains of Peru. A robust assessment of modern glacier change is important for understanding how regional change affects Andean communities, and for placing paleo-glaciers in a context relative to modern glaciation and climate. Snowline altitudes (SLAs derived from satellite imagery are used as a proxy for modern (1986–2005 local climate change in a key transition zone in the Andes. Clear sky, dry season Landsat Thematic Mapper (TM and Enhanced Thematic Mapper (ETM+ satellite images from 1986–2005 were used to identify snowline positions, and their altitude ranges were extracted from an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER digital elevation model (DEM. Based on satellite records from 31 glaciers, average snowline altitudes (SLAs, an approximation for the equilibrium line altitude (ELA, for the Cordillera Huayhuash (13 glaciers and Cordillera Raura (18 glaciers from 1986–2005 were 5051 m a.s.l. from 1986–2005 and 5006 m a.s.l. from 1986–2002, respectively. During the same time period, the Cordillera Huayhuash SLA experienced no significant change while the Cordillera Raura SLA rose significantly from 4947 m a.s.l. to 5044 m a.s.l.

  1. Rodent consumption by Philodryas psammophidea (Serpentes: Colubridae, from the inter-andean dry valleys of central Bolivia

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    Quinteros-Muñoz, Oliver

    2010-12-01

    Full Text Available In May 18, 2009 we found an adult female of Philodryas psammophidea (930 mm SVL, at a side of a crop field in the Tabacal valley (18º23'7.42" S – 64º38'7.88" W, 2015 m, Narciso Campero province southern Cochabamba, Bolivia. Ecologically, this valley belongs to the Inter-Andean Dry Forests of Bolivia. In the stomach of the snake probably killed by a settler, there was an adult female of Graomys domorum (Phyllotini; Sigmodontidae, a native rodent species widely distributed in the region.

  2. El frente de corrimiento andino al nivel de los cerros Penitentes y Visera (alta Cordillera de Mendoza: aspectos cronológicos y cartográficos The Andean thrust front in the Cerros Penitentes and Visera (High Cordillera of Mendoza: chronological and cartographic aspects

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    Jean-Claude Vicente

    2009-10-01

    Full Text Available El hallazgo de una iportante fauna de invertebrados marinos del Tithoniano superior a espaldas del cerro Penitentes en la secuencia carbonática basal de la primera escama del frente de corrimiento andino, confirma la lógica tectónica de un despegue de esta unidad a nivel del Yeso Principal y lleva a invalidar ciertas correlaciones litoestratigráficas y bosquejos paleogeográficos asignados a la Formación La Manga. Por otro lado, el análisis de algunos perfiles claves en torno al cerro Penitentes entre la quebrada Vargas y el cerro Visera permite presentar una reinterpretación tectónica del sector. Esta se sustenta en el reconocimiento y la diferenciación de las unidades terciarias básicas representadas por los Conglomerados Penitentes (Mioceno inferior y los Aglomerados Santa María (Mioceno superior en una relación muy similar a la descrita anteriormente al norte de Puente del Inca. El estudio permite seguir las interferencias, en un contexto polifásico, entre las reactivaciones del corrimiento Penitentes de piel fina y un cabalgamiento frontal de piel gruesa que repite la secuencia terciaria. La discordancia entre las secuencias terciarias y el emplazamiento de una klippe de Malm sobre los Conglomerados Penitentes del sinclinal del cerro Visera, conduce a otorgar cierta importancia a la fase del final del Mioceno inferior.The finding of an important marine invertebrate fauna of Upper Tithonian age at the shoulders of the Penitentes hill, in the basal carbonatic sequence of the first Andean wedge confirms the tectonic logic of a detachment of this unit at the level of the Yeso Principal. This allows invalidating certain lithostratigraphic correlations and paleogeographic sketches ascribed to the La Manga Formation. On the other hand, the analysis of some key sections around the Penitentes hill area between the Quebrada de Vargas and the Cerro Visera, allows presenting a tectonic reinterpretation of the sector. This is based on the

  3. The origin and crust/mantle mass balance of Central Andean ignimbrite magmatism constrained by oxygen and strontium isotopes and erupted volumes

    Science.gov (United States)

    Freymuth, Heye; Brandmeier, Melanie; Wörner, Gerhard

    2015-06-01

    Volcanism during the Neogene in the Central Volcanic Zone (CVZ) of the Andes produced (1) stratovolcanoes, (2) rhyodacitic to rhyolitic ignimbrites which reach volumes of generally less than 300 km3 and (3) large-volume monotonous dacitic ignimbrites of up to several thousand cubic kilometres. We present models for the origin of these magma types using O and Sr isotopes to constrain crust/mantle proportions for the large-volume ignimbrites and explore the relationship to the evolution of the Andean crust. Oxygen isotope ratios were measured on phenocrysts in order to avoid the effects of secondary alteration. Our results show a complete overlap in the Sr-O isotope compositions of lavas from stratovolcanoes and low-volume rhyolitic ignimbrites as well as older (>9 Ma) large-volume dacitic ignimbrites. This suggests that the mass balance of crustal and mantle components are largely similar. By contrast, younger (70 km3 Ma-1 km-1 (assuming plutonic/volcanic ratios of 1:5) which are additional to, but within the order of, the arc background magmatic flux. Comparing our results to average shortening rates observed in the Andes, we observe a "lag-time" with large-volume eruptions occurring after accelerated shortening. A similar delay exists between the ignimbrite pulses and the subduction of the Juan Fernandez ridge. This is consistent with the idea that large-volume ignimbrite eruptions occurred in the wake of the N-S passage of the ridge after slab steepening has allowed hot asthenospheric mantle to ascend into and cause the melting of the mantle wedge. In our model, the older large-volume dacitic ignimbrites in the northern part of the CVZ have lower (15-37 %) crustal contributions because they were produced at times when the Central Andean crust was thinner and colder, and large-scale melting in the middle crust could not be achieved. Younger ignimbrite flare-ups further south (22°S) formed with a significantly higher crustal contribution (22-68 %) because at that

  4. Improving glacier volume-area scaling to better quantify tropical Andean glacial water resources from remote sensing

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    Klein, A. G.; Kincaid, J. L.; Dobreva, I. D.

    2014-12-01

    Tropical glaciers are an important component of the water budget for high-altitude catchments in much of the central Andes. The majority of tropical Andean glaciers are small, but it has been suggested that because of their numbers the volume of water they contain is significant. Unfortunately, the ice volume measurements needed to inform decision makers have been made for only a handful of tropical glaciers. In August 2012, with the assistance of the Instituto Geográfico Militar in Bolivia, ground penetrating radar (GPR) and differential Global Positioning System (dGPS) measurements were collected along transects totaling 3,189 m in length on the Charquini SE cirque glacier. This small cirque glacier which is located in the southern portion of the Cordillera Real in Bolivia had an approximate surface area in 2012 of 02.42 square kilometers. Our initial observations indicate that the GPR survey was able to adequately capture the ice bedrock interface. Ordinary Kriging was used to develop maps of surface and subsurface topography from the dGPS and GPR observations. In 2012, the Charquini SE glacier contained a minimum of 3,900,000 cubic meters of ice. This information, along with other recent volume measurements for tropical and sub-tropical Andean glaciers, was used to update earlier volume-area scaling relationships established for these glaciers. This relationship will then be applied to determine the volume of water currently stored in tropical Andean glaciers based on previous research on glaciers areas using remote sensing.

  5. A new minute Andean Pristimantis (Anura: Strabomantidae from Venezuela

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    César L. Barrio-Amorós

    2012-12-01

    Full Text Available A new species of Pristimantis is described from the Venezuelan Andes. The new species is the smallest in its genus known in Venezuela and belongs to the Pristimantis unistrigatus Group. It differs from the rest of Venezuelan Andean congeners in body size (mean male SVL < 21.3 mm, female SVL < 26.3 mm, expanded discs on fingers and toes, absence of dorsolateral folds, and a distinctivecall consisting in 2–5 cricket-like short notes. The new species inhabits the southwestern part of the Cordillera de Mérida in Venezuela and the Venezuelan side of the Cordillera Oriental deColombia, and could be present on the Colombian portion of the cordillera as well.

  6. Magmatic evidence for Neogene lithospheric evolution of the central Andean ``flat-slab'' between 30°S and 32°S

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    Kay, S. M.; Abbruzzi, J. M.

    1996-06-01

    Geochemical data from Andean Miocene magmas erupted through the now volcanically-inactive "flat-slab" between 30°S to 32°S, coupled with geological and geophysical data, illuminate details on magmatic and continental lithospheric evolution over a progressively shallowing subduction zone. Pb, Sr and Nd isotopic and trace-element data show that Main Cordilleran, Precordilleran and Pampean magmas were contaminated in both the mantle and crust, and that the nature of the contaminants varied in time and space, reflecting tectonic events. Contaminants included both "enriched" (high LIL-element, high Sr and Pb, and low Nd isotopic ratios) and "depleted" (low LILE-element, low Sr and Pb, and high Nd isotopic ratios) types. In the western region, Main Cordilleran earlier Miocene lavas had contaminants with less "enriched" signatures than later Miocene lavas. Progressive "enrichment" is attributed to: (a) increasing amounts of sediment and tectonically eroded crust being subducted into the mantle wedge; and (b) contamination in a thickening Main Cordilleran lower crust whose composition was progressively "enriched". This "enrichment" occurred through addition of upper crust by an intracrustal mixing process driven by a propagating wedge tip associated with westward wedging, heating and deformation of crust from beneath the shortening Precordillera thrust belt to the east. Further east, magmas erupted through back-arc crust have more "depleted" signatures. Those erupted in the central part through the evolving Precordilleran thrust belt were contaminated by an older, thinner Grenville (˜ 1100 Ma) basement whose "depleted" signature is unique among Central Andean terranes. Late Miocene Pocho lavas erupted further east in conjunction with uplift of the Sierras Pampeanas show "enrichment" through time. Arguably, these magmas could contain a component mechanically removed from the base of the thinning continental lithosphere to the west, and progressively incorporated into the

  7. Out of Amazonia: the unexpected trans-Andean distribution of Cochranella resplendens (Lynch and Duellman, 1978) (Anura: Centrolenidae).

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    Molina-Zuluaga, Claudia; Cano, Estefany; Restrepo, Adriana; Rada, Marco; Daza, Juan M

    2017-03-02

    The glassfrog genus Cochranella, with nine recognized species, is distributed in the lowlands and mid elevation of the Neotropical forests, from Nicaragua to Bolivia (Guayasamin et al. 2009; Twomey et al. 2014). Four species are trans-Andean-C. granulosa (Taylor 1949) occurs in the lowlands and mountains, at mid elevation, of Central America, C. litoralis (Ruiz-Carranza & Lynch 1996) and C. mache Guayasamin & Bonaccorso 2004 occur in the Pacific lowlands and the western cloud forests of Colombia and Ecuador, and C. euknemos (Savage & Starrett 1967) occurs both in Central America and South America (northwestern Colombia).-The other five species have cis-Andean distributions in the Amazonian slopes and lowlands, from Colombia to Bolivia: C. nola Harvey 1996, C. guayasamini Twomey, Delia & Castroviejo-Fisher 2014, C. resplendens (Lynch & Duellman 1973), C. erminea Torres-Gastello, Suárez-Segovia & Cisneros-Heredia 2007, and C. phryxa Aguayo-Vedia & Harvey 2006. In Colombia, C. resplendens is known from the foothills of the Amazon versant in Caquetá (Malambo et al. 2013) and Putumayo (Lynch & Duellman 1973; Ruiz-Carranza et al. 1996). The species is also known from Ecuador (Lynch & Duellman 1973) and Peru (Twomey et al. 2014). Here, we report two new records of Cochranella resplendens, extending the species distribution beyond the Amazonian lowlands into the northern Cordillera Central in Colombia.

  8. Estructura comunitaria de diatomeas presentes en los sedimentos superficiales de ocho lagos andinos de Chile central Diatoms community structure in superficial sediments of eight Andean lakes of central Chile

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    INGRID E ALVIAL

    2008-03-01

    Full Text Available En este trabajo se analizó la estructura comunitaria de diatomeas depositadas en los sedimentos superficiales de ocho lagos andinos chilenos ubicados entre los 32°49' y 38°48' S. Se encontró un total de 99 taxa de diatomeas, distribuidos en 48 géneros. Del total de taxa, 74 fueron identificados a nivel de especie siendo todos ellos cosmopolitas a excepción de Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis y Pinnularia acidicola, entre otras, que están descritos solo para el Hemisferio Sur. Por otro lado, las muestras analizadas presentaron distinta composición florística de diatomeas. De esta manera, en los ensambles diatomológicos depositados en los sedimentos de las lagunas de altura Ocho, Huifa, Ensueño y Negra ubicadas sobre los 2.860 m del nivel del mar, abundaron especies bentónicas, típicas de aguas oligotróficas y acidas como Achnanthidium exiguum, Achnanthidium minutissimum, Encyonema minutum, Pinnularia acidicola y Planothidium lanceolatum. En los ensambles diatomológicos de los lagos Galletué, Icalma y Laja, ubicados bajo los 1.360 m del nivel del mar, abundaron diatomeas planctónicas, características de aguas alcalinas y mesotróficas como Asterionella formosa, Aulacoseira distans, Aulacoseira granulata, Cyclotella stelligera y Rhopalodia gibbaIn this research the taxonomic structure of diatoms in sediments of high mountain lakes was studied. These lakes are located in Chile between 32°49' and 38°48' S in the Andean Cordillera. A total of 99 diatom taxa distributed in 48 genera were identified and all this taxa are cosmopolitan excepting a Eunotia andinofrequens, Gomphonema punae, Pinnularia araucanensis and Pinnularia acidicola, which are know only for the Southern Hemisphere. The assemblages of diatoms were different in the studied lakes. So the high mountain lakes Ocho, Huifa, Ensueño and Negra, dominated benthic diatoms which are typical of oligotrophic and acid waters as Achnanthidium

  9. Estudio sedimentológico del Keuper inferior, a partir del análisis de facies, en el sector central de la Cordillera Bética. Algunas consideraciones paleogeográficas

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    López Chicano, M.

    1989-12-01

    Full Text Available The lower Keuper of the central sector of Betic Cordillera shows a predominance of clays with variegated colours. They have intercalations of thin layers of sandstones (fine grain, gypsum and carbonates. Through sedimentological and stratigraphic analysis we can conclude that these materials are from a systems tract fluviocoastal further more it allows us to distinguish sorne different facies types which characterize the following subenvironments. They are set in a framework of mud flat, found on a vast tidal coastal lutitic plain. Terrigenous sediments (fine sands from the mainland are deposited on the lutitic plain by ephemeral streams. In this coastal environment there are subenvironments of salt marsh, salt pans, sabkha, coastal lagoons, etc. The distribution in time and space of these facies was mainly controlled by the climate and the frequent incursions of the sea over the coastal plain, facilited by the flat geographical nature of coastline.En el Keuper inferior del sector central de la Cordillera Bética hay un predominio de materiales arcillosos, de colores abigarrados, con niveles intercalados de areniscas de grano fino, yesos y carbonatos. A partir del análisis estratigráfico y sedimentológico se han interpretado estos materiales como pertenecientes a un cortejo fluviocostero. Este análisis ha permitido, previamente, diferenciar diversas asociaciones de facies que caracterizan varios ambientes sedimentarios. Esencialmente, se enmarcan en un mud flat, dentro de una extensa llanura costera parcialmente afectada por mareas. A ésta llegan sedimentos detríticos continentales (arenas finas mediante corrientes fluviales efímeras. Dentro de este mismo medio costero aparecen ambientes de marisma, salt pans, sabkha, laguna, etc. La evolución en el tiempo y en el espacio de estas facies está controlada principalmente por el clima y por las frecuentes ingresiones del mar sobre la llanura costera, las cuales están facilitadas por la

  10. Variables Associated with Utilization of a Centralized Medical Post in the Andean Community of Pampas Grande, Peru

    Science.gov (United States)

    Merry, Stephen P.; Rohrer, James E.; Thacher, Thomas D.; Summers, Matthew R.; Alpern, Jonathan D.; Contino, Robert W.

    2012-01-01

    Context: Integral to the location of health resources is the distance decay of utilization observed in a population. In rural Peru, a nongovernmental organization planning to increase the availability of health services needed this information. Purpose: To determine variables associated with utilization of a central medical clinic and determine…

  11. Late Quaternary geomorphic history of a glacial landscape - new sedimentary and chronological data from the Cordillera de Cochabamba (Bolivia)

    Science.gov (United States)

    May, J.-H.; Preusser, F.; Zech, R.; Ilgner, J.; Veit, H.

    2009-04-01

    Throughout the Central Andes, glacial landscapes have long been used for the reconstruction of Late Quaternary glaciations and landscape evolution. Much work has focused on the Andes in Peru, Chile and the Bolivian Altiplano, whereas relatively little data has been published on glaciation history in the eastern Andean ranges and slopes. Even less is known with regard to the postglacial evolution of these glacial landscapes. In the Cordillera de Cochabamba (Bolivia), local maximum advances probably peaked around 20-25 ka BP and were followed by significant readvances between ~12-16 ka BP. This generally points to temperature controlled maximum glacial advances along the humid eastern slopes of the Central Andes, which is supported by glacier-climate-modelling studies. However, most studies include only marginal information with regard to the complex geomorphic and sedimentary situation in the Cordillera de Cochabamba. Furthermore, the chronological results are afflicted with several methodological uncertainties inherent to surface exposure dating and call for application of alternative, independent age dating methods. Therefore this study aims at i) documenting and interpreting the complex glacial geomorphology of the Huara Loma valley in the Cordillera de Cochabamba (Bolivia), ii) analyzing the involved units of glacial sediments, and iii) improving the chronological framework by applying optically stimulated luminescence (OSL) and radiocarbon dating (14C). For this purpose, geomorphic mapping was combined with field documentation of sedimentary profiles. The involved sediments were subject to geochemical and mineralogical analysis in order to deduce information on their erosional and weathering histories. In addition, the interpretation of OSL ages from glacial and proglacial sediments integrated several methodological procedures with regard to sample preparation and statistical analysis of the measurements in order to increase the degree of confidence. These

  12. Phylogenetic insights into Andean plant diversification

    Directory of Open Access Journals (Sweden)

    Federico eLuebert

    2014-06-01

    Full Text Available Andean orogeny is considered as one of the most important events for the developmentof current plant diversity in South America. We compare available phylogenetic studies anddivergence time estimates for plant lineages that may have diversified in response to Andeanorogeny. The influence of the Andes on plant diversification is separated into four major groups:The Andes as source of new high-elevation habitats, as a vicariant barrier, as a North-Southcorridor and as generator of new environmental conditions outside the Andes. Biogeographicalrelationships between the Andes and other regions are also considered. Divergence timeestimates indicate that high-elevation lineages originated and diversified during or after the majorphases of Andean uplift (Mid-Miocene to Pliocene, although there are some exceptions. Asexpected, Andean mid-elevation lineages tend to be older than high-elevation groups. Mostclades with disjunct distribution on both sides of the Andes diverged during Andean uplift.Inner-Andean clades also tend to have divergence time during or after Andean uplift. This isinterpreted as evidence of vicariance. Dispersal along the Andes has been shown to occur ineither direction, mostly dated after the Andean uplift. Divergence time estimates of plant groupsoutside the Andes encompass a wider range of ages, indicating that the Andes may not benecessarily the cause of these diversifications. The Andes are biogeographically related to allneighbouring areas, especially Central America, with floristic interchanges in both directionssince Early Miocene times. Direct biogeographical relationships between the Andes and otherdisjunct regions have also been shown in phylogenetic studies, especially with the easternBrazilian highlands and North America. The history of the Andean flora is complex and plantdiversification has been driven by a variety of processes, including environmental change,adaptation, and biotic interactions

  13. Glacial areas, lake areas, and snowlines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Directory of Open Access Journals (Sweden)

    M. N. Hanshaw

    2013-02-01

    Full Text Available Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far, yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975–2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 ± 1.70 km2 yr−1 (22-yr average, 1988–2010, with 95% confidence interval. The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 ± 0.18 km2 yr−1 since 1980 (31-yr average, 1980–2011, also with 95% confidence interval; Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000–2011 as compared to the preceding decade (1990–2000; Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61% of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84% of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 yr provide an important spatiotemporal assessment of climate

  14. Glacial areas, lake areas, and snowlines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, M. N.; Bookhagen, B.

    2013-02-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 ± 1.70 km2 yr-1 (22-yr average, 1988-2010, with 95% confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 ± 0.18 km2 yr-1 since 1980 (31-yr average, 1980-2011, also with 95% confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61% of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84% of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 yr provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further studies

  15. Glacial areas, lakes areas, and snowlines from 1975-2012: Status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, Maiana Natania

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: First, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 +/- 1.70 km2/yr (22-year average, 1988-2010, with 95 % confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 +/- 0.18 km2/yr since 1980 (31-year average, 1980-2011, also with 95 % confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61 % of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84 % of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 years provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further

  16. Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    Science.gov (United States)

    Hanshaw, M. N.; Bookhagen, B.

    2014-03-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. Additionally, we have estimated the snow-line altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota (1988 glacial area: 361 km2) have been declining at a rate of 3.99 ± 1.15 km2 yr-1 (22 year average, 1988-2010, with 95% confidence interval (CI), n = 8 images). Since 1980, the Quelccaya Ice Cap (1980 glacial area: 63.1 km2) has been declining at a rate of 0.57 ± 0.10 km2 yr-1 (30 year average, 1980-2010, with 95% CI, n = 14). Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2010) as compared to the preceding decade (1988-1999) with an average increase from 37.5 to 42.3 × 10-3 km2 yr-1 km-2 (13%). Third, glaciers with lower median elevations are declining at higher rates than those with higher median elevations. Specifically, glaciers with median elevations around 5200 m a.s.l. are retreating to higher elevations at a rate of ~1 m yr-1 faster than glaciers with median elevations around 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% of lakes connected to glacial watersheds have either remained stable or shown a roughly synchronous increase in lake area, while 42% of lakes not connected to glacial

  17. Vegetation composition and altitudinal distribution of Andean rain forests in El Angel and Guandera reserves, northern Ecuador

    NARCIS (Netherlands)

    Moscol Olivera, M.C.; Cleef, A.M.

    2009-01-01

    Patterns of vascular plant species composition and structure of the remaining rain forest of the Andean Cordillera in northern Ecuador were studied in two reserves: Guandera and El Angel. Thirty three plots located between 3300 and 3700 in were examined along two altitudinal transects crossing the U

  18. Características de la fauna de braquiópodos del Toarciense superior en el Sector Central de la Cordillera Ibérica (noroeste de España

    Directory of Open Access Journals (Sweden)

    García Joral, F.

    1984-04-01

    Full Text Available Studying brachiopod faunas from the Upper Toarcian beds of the Iberian Range (Central Sector, bring out the few number of species and the local range for the majority of them. In relation with that, populations show characteristics (polymorphism, gregarism and generalism that suggest an unstable environment, probably produced by the progressive isolation of the basin, the shallowing trend and the tectosedimentary instability quoted by differents authors, As a consequence of this situation there is a faunistic turnover for the brachiopods at this time, that could be the origin of some lineages developped in the Western European Dogger.

    En el estudio de la fauna de braquiópodos del Toarciense superior del Sector Central de la Cordillera Ibérica destacan el bajo. número de especies que la componen y el ámbito local de la mayoría de ellas. En relación con esto, las poblaciones muestran unas características (polimorfismo, gregarismo y forma generalizada que sugieren un ambiente inestable, provocado probablemente por el aislamiento progresivo de la cuenca, la tendencia somerizadora y la inestabilidad tectosedimentaria que han señalado diversos autores. La consecuencia de esta situación es una renovación faunística para el grupo en esta edad, que puede haber dado origen a algunas de las ramas filéticas que se desarrollan en el Dogger de Europa Occidental.

  19. Paleogene depositional patterns in the Magdalena Valley and Cordillera Oriental: Implications for deformational phases

    Energy Technology Data Exchange (ETDEWEB)

    Ressetar, R.; Allen, R.B.; Alfonso, C.A. (Univ. of South Carolina, Columbia (United States)); Sarmiento, L. (Instituto Colombiano de Petroleos, Bucaramanga (Colombia)); Ramirez, C.; Laverde, F. (Hocol-Shell, Cartagena (Colombia))

    1993-02-01

    The Paleogene rocks of the Magdalena Valley and the Cordillera Oriental of Colombia represent the synorogenic sedimentary fill of the ancestral Andean foreland basin. Although detailed correlation of the Paleogene is hampered by poor biostratigraphic control, recent field studies document variations between the Upper and Middle Magdalena Valleys in vertical facies succession and paleocurrent direction, suggesting independent depositional systems separated by the Girardot fold belt. In the northern Upper Magdalena Valley, the Paleogene Gualanday Group lies unconformably to paraconformably on marine Upper Cretaceous and Paleocene rocks. Lower and upperconglomeratic units in the Gualanday Group grade eastward into finer grained fluvial sandstones in the western Cordillera Oriental. North of the Girardot belt, conglomerates occur only in the lower part of the Paleogene and grade northeastward into fluvial sandstones. These unconformably overlie rocks as old as Neocomian in a series of en echelon structures on the west flank of the Cordillera Oriental. The structural trends and thickness of the Cretaceous here suggest inversion of the marine depocenter prior to Paleogene deposition. Previous reports of early Paleogene uplift of the Quetame Massif south of Bogota indicate that similar processes acted elsewhere in the Cordillera Oriental. These studies show that the Cordillera Oriental underwent at least one phase of uplift prior to the main inversion in the Neogene.

  20. Caracterización Física, Química y Mineralógica de Suelos con Vocación Forestal Protectora Región Andina Central Colombiana / Physical Chemical and Mineralogical Characterization of Soils with a Protective Forest Vocation, Central Andean Region of Colombia

    Directory of Open Access Journals (Sweden)

    Leyder Echeverri Tafur

    2014-06-01

    Full Text Available Resumen. En la Reserva Forestal Protectora Bosques de la CHEC, ubicada sobre la vertiente occidental de la cordillera central colombiana, municipios de Manizales y Villamaría, departamento de Caldas, se hizo la caracterización física, química y mineralógica de dos perfiles de suelos, descritos sobre dos laderas, con un manejo actual correspondiente a una plantación de aliso (Alnus acuminata y un bosque secundario. Los resultados permitieron establecer,desde el punto de vista físico, el dominio de clase textural areno francosa en la plantación de aliso y franco arenoso en el bosque secundario. Químicamente el suelo del perfil plantado con aliso, presentó valores de pH más bajos, mayor saturación de acidez intercambiable y menor saturación de bases en comparación con el perfil del bosque secundario. En ambos perfiles, el análisis óptico con microscopio petrográfico, permitió observar que los feldespatos, del grupo de las plagioclasas y el vidrio volcánico, se destacan como minerales abundantes en la fracción arena; mientras que en la fracción arcilla, el material no cristalino, seconsidera mineral predominante, seguido de la cristobalita y los feldespatos, según la metodología de difracción de rayos X. Se concluye que la vocación de uso forestal protector, bajo el cual se encuentran sometidos ambos suelos, es el más adecuado, teniendo en cuenta que las limitaciones químicas, dificultan el establecimiento de sistemas de producción agropecuaria. / Abstract. The physical, chemical and mineralogical characterization of two soil profiles on two slopes, with a management currently corresponding to an Andean alder plantation (Alnus acuminata and a secondary forest, was carried out at the Protective Forest Reserve of the CHEC. This reserve is located on the western slope of the Central Mountain Range of the Colombian Andes, in the municipalities of Manizales and Villamaria, Caldas Department. The results

  1. Extreme High Field Strength Element Depletion and Chondritic Nb/Ta in Central Andean Adakite-like Lavas (~27° S, ~68° W)

    Science.gov (United States)

    Goss, A. R.; Kay, S. M.

    2005-12-01

    We present new high precision ICP-MS HFSE data on ~30 samples from the adakite-like Pircas Negras (SiO2 =57-62 %; La/Yb= 20-60; Sr = 600-900 ppm, Cr to 200 ppm) and Dos Hermanos (SiO2 =56-59 %; La/Yb= 57-61; Sr = 1200-1500 ppm, Cr to 60 ppm) andesites from the southernmost Andean Central Volcanic Zone (CVZ). These andesites erupted in a broadened arc as the volcanic front was displaced about 50 km to the east between 8 and 3 Ma and likely reflect melting of a garnet bearing crustal source. Our data reveal a discrete change from chondritic Nb/Ta ratios (19-21) and low Zr/Sm (25-30) in older 8-7 Ma Dos Hermanos lavas to dominantly subchondritic Nb/Ta ratios (11-18) and higher Zr/Sm (30-45) in Hermanos (La/Ta= 90-100) lavas are best explained as hydrous and oxidizing conditions within the mantle wedge initially stabilized Ti-oxides (i.e. rutile) as the arc front migrated. These steeper REE patterns and high La/Ta are a transient feature measured in lavas erupting during the peak of arc migration, as mafic <2 Ma CVZ lavas to the north (~26° S) have lower La/Yb (< 20) and La/Ta (< 40). The observed temporal shift in Nb/Ta coupled with a general increase in Zr/Sm suggests a change from residual rutile to low-Mg amphibole within an eclogitic/granulitic crustal residue during the course of arc migration. A potential factor in explaining these data is that a transient period of increased subduction erosion associated with the migration of the frontal arc transported forearc crustal material into the progressively dehydrating mantle wedge. Partial melting of this eclogitized forearc material contributed to the transient adakite-like nature of the magmas erupted along the margin.

  2. Extreme high field strength element (HFSE) depletion and near-chondritic Nb/Ta ratios in Central Andean adakite-like lavas (~ 28°S, ~ 68°W)

    Science.gov (United States)

    Goss, A. R.; Kay, S. M.

    2009-03-01

    The eruption of andesites with steep REE patterns and high Sr concentrations (adakite-like) in the northernmost Chilean flatslab region of the Central Andes spatially and temporally corresponds with the appearance of a marked HFSE (high field strength element) depletion in these lavas (La/Ta up to 95). Known as the Dos Hermanos and Pircas Negras andesites, these lavas erupted at the beginning (˜ 8 Ma), during (7-3 Ma), and immediately following (3-2 Ma) a period of tectonic instability characterized by eastward migration of the frontal volcanic arc. ICP-MS analyses of the HFSE reveal a range of chondritic (20-18) to subchondritic (18-11) Nb/Ta ratios in these lavas. Evident temporal trace element trends support a change from a rutile-bearing to an amphibole-bearing eclogitic residual assemblage in equilibrium with the mafic precursor magmas of these andesites. This change in residual mineralogy is contemporaneous with the onset of frontal arc migration in the region. Potential eclogitic sources for the Dos Hermanos and Pircas Negras adakitic andesites include mafic Andean lower crust and an additional flux of forearc crust transported to the sub-arc mantle via subduction erosion during the height of arc migration and Pircas Negras magmatism. Batch melting models of rutile- or amphibole-bearing eclogitic arc basalt in tandem with magma mixing calculations generate the observed adakitic signatures and near-chondritic Nb/Ta ratios of these Central Andean andesites.

  3. Orogenesis at the southern tip of the Americas: the structural evolution of the Cordillera Darwin metamorphic complex, southernmost Chile

    Science.gov (United States)

    Cunningham, W. Dickson

    1995-04-01

    New, detailed lithologic and structural data are presented from three separately mapped areas along the southern boundary of the Cordillera Darwin metamorphic complex of southernmost Chile. Cordillera Darwin is a unique uplift because it exposes the highest grade rocks in the Andes south of Peru and averages 1 km higher in elevation than adjacent areas. The structural data indicate that Cordillera Darwin experienced mid-Late Cretaceous trans-pressional deformation with a partitioned strike-slip component localized along the Beagle Channel that forms the southern boundary to the range. Foliation, lineation and fold axis trends indicate NE-SW-directed contraction and NW-SE strike-slip shearing (present directions) during progressive {D1}/{D2} Andean deformation. D2 deformation is marked by outcrop-to 10 km-scale south-southwest-vergent folds. Late Cretaceous-Tertiary brittle-ductile and brittle left-lateral strike-slip faults and shear zones crosscut all {D1}/{D2} structures. Although limited structural evidence for extensional tectonics was documented in this study, apparent normal offsets across both arms of the Beagle Channel and previously documented field evidence for extension from other areas in Cordillera Darwin suggest that transtensional displacements also may have occurred in southern Cordillera Darwin during the Late Cretaceous-Early Tertiary. Cordillera Darwin's position within the evolving Patagonian Orocline adjacent to an evolving Mesozoic-Cenozoic left-lateral transform boundary between the South American and Antarctic plates, and later the South American and Scotia plates, necessitates consideration of the possible effects of regional counterclockwise rotation on development of structures. Regional counterclockwise rotation of Cordillera Darwin may have controlled the temporal and spatial transition of deformational regimes within Cordillera Darwin. Exhumation of the metamorphic core of Cordillera Darwin during the Late Cretaceous-Early Tertiary is

  4. Chagas disease in Andean countries

    Directory of Open Access Journals (Sweden)

    Felipe Guhl

    2007-10-01

    Full Text Available The Andean Countries' Initiative (ACI for controlling Chagas disease was officially created in 1997 within the framework of the Hipolito Unanue Agreement (UNANUE between the Ministries of Health of Colombia, Ecuador, Peru, and Venezuela. Its objective was to interrupt transmission via vector and transfusion in the region, taking into account that there are 12.5 million people at risk in the four Andean countries forming the initiative in the area and around 3 million people are infected by Trypanosoma cruzi. The progress of control activities for the vector species present in the Andean sub-region, for different reasons, has been slow and control interventions have still not been installed in all geographical areas occupied by the target species. This has been partly due to lack of knowledge about these vector populations' biological characteristics, and consequent uncertainty about which are the appropriate control measures and strategies to be implemented in the region. The main vector species present important similarities in Venezuela and Colombia and in Ecuador and Northern Peru and they can be approached in a similar way throughout the whole regions, basing approaches on and adapting them to the current strategies being developed in Venezuela during the 1960s which have been progressively adopted in the Southern Cone and Central-American region. Additional measures are needed for keeping endemic areas free from Rhodnius prolixus silvatic populations, widely spread in the Orinoco region in Colombia and Venezuela. Regarding aetiological treatment, it is worth mentioning that (with the exception of Colombia none of the other countries forming the ACI have registered medicaments available for treating infected young people. There are no suitable follow-up programmes in the sub-region or for treating cases of congenital Chagas disease. An integral and integrated programme encompassing all the aspects including transmission by transfusion which

  5. Constraining the Lithospheric Structure of the Central Andes Using P- and S- wave Receiver Functions

    Science.gov (United States)

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

    2014-12-01

    The Central Andean Plateau (CAP) has elevations in excess of 3 km, and is part of the Andean Cordillera that resulted in part from shortening along the western edge of South America as it was compressed between the subducting Nazca plate and underthrusting Brazilian cratonic lithosphere. We calculated P- and S-wave receiver functions for the Central Andean Uplift and Geodynamics of High Topography (CAUGHT) temporary deployment of broadband seismometers in the Bolivian orocline (12°-20°S) region to investigate crustal thickness and lithospheric structure. Migration of the receiver functions is done using common conversion point (CCP) stacks through a 3D shear velocity model from ambient noise tomography (Ward et al., 2013). The P- and S-wave receiver functions provide similar estimates of the depth to Moho under the CAP. Crustal thicknesses include 60-65 km thick crust underneath the Bolivian Altiplano, crust that varies from ~70 km to ~50 km underneath the Eastern Cordillera and Interandean zone, and thins to 50 to 40 km crust in the Subandes and the edge of the foreland. The variable crustal thickness of the Eastern Cordillera and Interandean zone ranges from >70 km associated with the Los Frailes volcanic field at 19°-20°S to ~55 km beneath the 6 km peaks of the Cordillera Real at ~16°S. From our S-wave receiver functions, that have no multiples that can interfere with deeper structure, we also identify structures below the Moho. Along a SW-NE line that runs near La Paz where we have our highest station density, the S-wave CCP receiver-function stacks show a strong negative polarity arrival at a depth of ~120 km from the eastern edge of the Altiplano to the Subandean zone. We suggest this may be a good candidate for the base of the CAP lithosphere. In addition, above this depth the mantle is strongly layered, suggesting that there is not a simple high velocity mantle lithosphere associated with the continental lithosphere underthrusting the Andean orogen

  6. Miocene orographic uplift forces rapid hydrological change in the southern central Andes

    Science.gov (United States)

    Rohrmann, Alexander; Sachse, Dirk; Mulch, Andreas; Pingel, Heiko; Tofelde, Stefanie; Alonso, Ricardo N.; Strecker, Manfred R.

    2016-10-01

    Rainfall in the central Andes associated with the South American Monsoon and the South American Low-Level Jet results from orographic effects on atmospheric circulation exerted by the Andean Plateau and the Eastern Cordillera. However, despite its importance for South American climate, no reliable records exist that allow decoding the evolution of thresholds and interactions between Andean topography and atmospheric circulation, especially regarding the onset of humid conditions in the inherently dry southern central Andes. Here, we employ multi-proxy isotope data of lipid biomarkers, pedogenic carbonates and volcanic glass from the Eastern Cordillera of NW Argentina and present the first long-term evapotranspiration record. We find that regional eco-hydrology and vegetation changes are associated with initiation of moisture transport via the South American Low-Level Jet at 7.6 Ma, and subsequent lateral growth of the orogen at 6.5 Ma. Our results highlight that topographically induced changes in atmospheric circulation patterns, not global climate change, were responsible for late Miocene environmental change in this part of the southern hemisphere. This suggests that mountain building over time fundamentally controlled habitat evolution along the central Andes.

  7. Temporal variation of the stress field during the construction of the central Andes: Constrains from the volcanic arc region (22-26°S), Western Cordillera, Chile, during the last 20 Ma

    Science.gov (United States)

    Giambiagi, Laura; Alvarez, Pamela; Spagnotto, Silvana

    2016-09-01

    In order to understand the response of the stress field state to intrinsic processes during the construction of the Andes, such as thickening of the continental crust, lithospheric delamination, and/or thermal weakening, we investigate the stress field evolution of the arc region since the last 20 Myr, in the central Andes (22-26.5°S). The 43 reduced paleostress tensors derived from inversion of 682 fault slip data reveal a complex pattern of stress states during the last episode of orogenic construction and topographic uplift. We identify two geodynamic stages: the first stage corresponds to the construction of the Altiplano/Puna plateau and the second one to its gravitational collapse. Four stress states that have prevailed in the Altiplano/Puna plateau since middle Miocene times characterize the transition from one stage to the other. Along the study latitudes, a spatiotemporal change in stress state is clearly observed, which led to an understanding that a change in the stress field may be related not only to the boundary conditions but also to intrinsic factors associated with the construction of the Andean orogeny. Our results suggest that approximately at 13-10 Ma and approximately 8-5 Ma, in the southern Altiplano and northern Puna, and in the southern Puna, respectively, regional elevation and crustal thicknesses reached threshold values necessary to generate the orogenic collapse.

  8. Tectonic repetitions of the Early Cretaceous Agrio Formation in the Chos Malal fold-and-thrust belt, Neuquén Basin, Argentina: Geometry, kinematics and structural implications for Andean building

    Science.gov (United States)

    Turienzo, M.; Sánchez, N.; Dimieri, L.; Lebinson, F.; Araujo, V.

    2014-08-01

    The Neuquén Basin, developed in a retroarc setting in the central-west of Argentina, contains more than 6000 m of Mesozoic marine and continental sedimentary rocks. These rocks were deformed during the Andean orogeny leading to several thick and thin-skinned fold-and-thrust belts. The Early Cretaceous Agrio Formation is composed by a thick marine succession predominantly of black shales in which highlights a thin fluvial-aeolian sandy interval named Avilé Member. The Avilé Member, one of the most important hydrocarbon reservoirs of the Neuquén Basin, constitutes an excellent structural marker. At the Chos Malal fold-and-thrust belt, the strong mechanical anisotropy given by the contrasting lithology of the Avilé Member within the Agrio Formation favored the location of detachments along the shales and ramps affecting the sandstones during the Andean compression. Detailed field mapping at the Chacay Melehue area allowed us to recognize tectonic repetitions of the Avilé Member, which form imbrications in the simplest case whereas in other places constitute a more complex combination of imbrications, including fault-bend folding that duplicates stratigraphic sequences and fault-propagation folding that deforms more intensely the duplicated units. Along three structural cross-sections we illustrate the geometry of these tectonic repetitions of the Agrio Formation, which in the northern area have an eastward-vergence and in the central and southern regions show a clear westward-vergence. A tear fault along the arroyo Chacay Melehue could explain this vergence change. Forward modeling of the structures at the central cross-section, where a backthrust system produced imbrication, duplication and folding of the Agrio Formation, allows us to propose a balanced kinematic reconstruction of this complex structure and to compare the features produced at different stages of the deformation sequence with field observations. Our kinematic interpretation shows that the

  9. Late Eocene to Early Miocene Andean uplift inferred from detrital zircon fission track and U-Pb dating of Cenozoic forearc sediments (15-18°S)

    Science.gov (United States)

    Decou, A.; von Eynatten, H.; Dunkl, I.; Frei, D.; Wörner, G.

    2013-08-01

    Timing, amount, and mechanisms of uplift in the Central Andes have been a matter of debate in the last decade. Our study is based on the Cenozoic Moquegua Group deposited in the forearc basin between the Western Cordillera and the Coastal Cordillera in southern Peru from ˜50 to ˜4 Ma. The Moquegua Group consists mainly of mud-flat to fluvial siliciclastic sediments with upsection increasing grain size and volcanic intercalations. Detrital zircon U-Pb dating and fission track thermochronology allow us to refine previous sediment provenance models and to constrain the timing of Late Eocene to Early Miocene Andean uplift. Uplift-related provenance and facies changes started around 35 Ma and thus predate major voluminous ignimbrite eruptions that started at ˜25 by up to 10 Ma. Therefore magmatic addition to the crust cannot be an important driving factor for crustal thickening and uplift at Late Eocene to Early Oligocene time. Changes in subduction regime and the subducting plate geometry are suggested to control the formation of significant relief in the area of the future Western Cordillera which acts as an efficient large-scale drainage divide between Altiplano and forearc from at least 15.5 to 19°S already at ˜35 Ma. The model integrates the coincidence of (i) onset of provenance change no later than 35 Ma, (ii) drastic decrease in convergence rates at ˜40, (iii) a flat-subduction period at around ˜40 to ˜30 Ma leading to strong interplate coupling, and (iv) strong decrease in volcanic activity between 45 and 30 Ma.

  10. New KAr age determinations of intrusive rocks from the Cordillera Occidental and Altiplano of central Peru: Identification of magmatic pulses and episodes of mineralization

    Science.gov (United States)

    Soler, P.; Bonhomme, M. G.

    The post-Albian evolution of the Andes of central Peru is characterized by igneous activity, both effusive and intrusive, and by at least six distinct episodes of compressional tectonics. New KAr age determinations have been made of intrusive rocks from the Cajatambo-Oyón-Cerro de Pasco area. In conjunction with already published information, these new data permit a better estimate of the ages and the lateral extent of successive Cenozoic magmatic arcs. Metallogenetic implications of the 26.3-29.3 Ma age of mineralized Milpo-Atacocha intrusions are also discussed.

  11. Predicting Polylepis distribution: vulnerable and increasingly important Andean woodlands

    Directory of Open Access Journals (Sweden)

    Brian R. Zutta

    2012-11-01

    Full Text Available Polylepis woodlands are a vital resource for preserving biodiversity and hydrological functions, which will be altered by climate change and challenge the sustainability of local human communities. However, these highaltitude Andean ecosystems are becoming increasingly vulnerable due to anthropogenic pressure including fragmentation, deforestation and the increase in livestock. Predicting the distribution of native woodlands has become increasingly important to counteract the negative effects of climate change through reforestation and conservation. The objective of this study was to develop and analyze the distribution models of two species that form extensive woodlands along the Andes, namely Polylepis sericea and P. weberbaueri. This study utilized the program Maxent, climate and remotely sensed environmental layers at 1 km resolution. The predicted distribution model for P. sericea indicated that the species could be located in a variety of habitats along the Andean Cordillera, while P. weberbaueri was restricted to the high elevations of southern Peru and Bolivia. For both species, elevation and temperature metrics were the most significant factors for predicted distribution. Further model refinement of Polylepis and other Andean species using increasingly available satellite data demonstrate the potential to help define areas of diversity and improve conservation strategies for the Andes.

  12. Qochas on Andean highlands

    CERN Document Server

    Sparavigna, Amelia Carolina

    2011-01-01

    On the Andean highlands, the "qochas" are lakes or ponds of natural or artificial origin. An ancient agricultural technique is based on their use. Linked together by a network of canals, qochas form a system of water and soil management, alternately used for crops or pasture. The concave structure of qochas controls the strong evaporation produced by solar radiation and wind blowing. Qochas can be observed in the satellite imagery of Google Maps.

  13. Utilización de recursos faunísticos y materias primas líticas durante el Holoceno tardío en la cordillera de Chile central: un enfoque integrador desde Caletón Los Queltehues Use of faunal resources and lithic raw materials during the late Holocene in the cordillera of central Chile: an integrative approach from Caletón los Queltehues

    Directory of Open Access Journals (Sweden)

    Rafael Labarca Encina

    2012-07-01

    Full Text Available Este trabajo evalúa, desde una perspectiva tecnológica y conductual, tendencias a largo plazo de cambio y continuidad en las estrategias de aprovechamiento de recursos faunísticos y líticos en contextos de cazadores-recolectores cordilleranos de Chile central. Para esto, tomamos los datos procedentes de un contexto ubicado en la cuenca superior del río Maipo: Caletón Los Queltehues, y escogimos, de su secuencia ocupacional, los componentes Arcaico IV y Alfarero temprano (5000 a 1000 AP. Los resultados de los análisis no arrojaron mayores variaciones entre ambos períodos en términos de taxones explotados, frecuencia de partes esqueletarias, modificaciones culturales y fragmentación de los restos óseos. De manera similar, las materias primas, las categorías morfofuncionales y los tipos de desechos líticos se observaron relativamente constantes. Sólo se registraron cambios en la tasa de la depositación, la frecuencia de modificaciones naturales y la diversidad de actividades de uso/descarte lítico, las que son interpretadas como una tendencia hacia una variación en la recurrencia e intensidad de la ocupación, pero no en cuanto a su funcionalidad.This article evaluates long-term trends in change and continuity of lithic and faunal use strategies in hunter-gatherer contexts in the central Chilean cordillera from technological and behavioral perspectives. The main objective of the analysis is to articulate both lines of evidence from a behavioral and technological perspective in order to infer unknown elements of the function and organization of activities in this kind of archaeological context. As an initial example, the Archaic IV and Early Ceramic (5000-1000 BP components from a classic site located in the upper valley of the Maipo river, Caletón Los Queltehues, were analyzed in detail. The results do not show significant variation between the periods in exploited taxa, skeletal part frequencies, cultural modifications, or

  14. Andean uplift promotes lowland speciation through vicariance and dispersal in Dendrocincla woodcreepers.

    Science.gov (United States)

    Weir, Jason T; Price, Momoko

    2011-11-01

    Andean uplift contributed importantly to the build-up of high Neotropical diversity. Final uplift of the Eastern Cordillera of Colombia separated once-contiguous lowland faunas east and west of the Andes between 5 and 3.5 million years ago (Ma hereafter). We used DNA sequences from several moderate- to fast-evolving mitochondrial and two slow-evolving nuclear genes to generate a well-supported phylogeny of Dendrocincla woodcreepers, a genus with multiple species endemic to lowland regions both east and west of the Andes. A time-calibrated phylogeny and dispersal-vicariance analysis indicated that uplift of the Eastern Cordillera of Colombia resulted in the initial vicariant separation of a widespread lowland form east and west of the Andes at c. 3.6 Ma. This was followed by two separate east-to-west dispersal events over or around the completed Andes, each producing a genetically distinct lineage. Our analysis suggests that Andean uplift promoted the build-up of biodiversity in lowland Neotropical faunas both through vicariance-based speciation during uplift and through dispersal-based speciation following uplift. In contrast to the multiple colonizations of the trans-Andean region by Dendrocincla, the Atlantic Forest was colonized from the Amazon only once, followed by in situ diversification.

  15. Nazca plate subduction, mantle flow and Cordilleras formation

    Science.gov (United States)

    Capitanio, Fabio A.

    2013-04-01

    The Nazca-South America convergence represents a unique natural laboratory to probe our understanding of subduction, mantle flow and stress coupling at Andean-type margins. Here, it is shown that the most fundamental balance of forces associated with the downgoing slab, the upper plates and the mantle can account for the Nazca plate motions, although it does not adequately explain the variations of the Cordilleran tectonics found along the ~6000 km wide margin. Using three-dimensional numerical models it is shown that trench-parallel gradients in both the driving and resisting forces are an essential component of the force balance, and necessary to reproduce the macroscopic features observed. When along-trench buoyancy variations similar to the Nazca plate's are included, the slab dips and upper plate deformations observed in the Nazca slab, in the Cordilleras and South American continent interiors can be reproduced. The models show that gradients in the resisting shear force along the trench can be as relevant, as they modulate the trench retreat to form the concave Bolivian Orocline. Pressure gradients in the mantle follow the Nazca buoyancy gradients, and effectively rearrange the flow introducing a trench-parallel component, similar to what suggested by seismic anisotropy in this area. Although they introduce only secondary variations to the primary subduction and mantle flow dynamics, the regional features of the Nazca and South American plates exert a primary control at the margin-local scale. This suggests that far-field forces, e.g. from spreading Atlantic or large-scale convection, should play a minor role in the formation of the Cordilleras.

  16. Análisis espectral de materiales geológicos en la Cordillera Volcánica Central de Costa Rica y su relación con la detección remota de anomalías

    Directory of Open Access Journals (Sweden)

    Rejas, J. G.

    2014-12-01

    Full Text Available The aim of this work is the comparative study of methods for calculating spectral anomalies from imaging spectrometry in several test areas of the Central Volcanic Range (CVR of Costa Rica. In the detection of anomalous responses it is assumed no prior knowledge of the targets, so that the pixels are automatically separated according to their spectral information significantly differentiated with respect to a background to be estimated, either globally for the full scene, either locally by image segmentation techniques. We used spectral ranges of visible-near infrared (VNIR, shortwave infrared (SWIR and thermal (TIR data cubes hiperepectrales from HyMAP airborne sensors and MASTER. We have designed experiments on natural scenes of the CVC, and semi-urban of different complexity, analyzing the behavior of the standard RX (Reed & Xiaoli, 1990 anomaly detector and different approaches based on imaging and dimensionality reduction. In this paper we propose a new technique for anomaly detection in hyperspectral data called DAFT (Detector de Anomalías de Fondo Térmico, as a Projection Pursuit (Malpica et al., 2008 variant, based on dimensionality reduction by projecting anomalies or targets with unknown spectral signature to the background, in a range thermal spectrum wavelengths. We discuss the results considering their implications on geological processes, as well as their use as terrestrial analogs for planetary exploration.El objetivo del presente trabajo es el estudio de bandas de absorción y reflexión de espectros de materiales geológicos presentes en distintas áreas de test de la Cordillera Volcánica Central (CVC de Costa Rica, y su correlación con el cálculo automático de anomalías a partir de espectrometría de imagen de alta resolución, también llamada teledetección hiperespectral. En la detección de respuestas anómalas se asume un no conocimiento previo de los objetivos. Los píxeles se separan automáticamente en funci

  17. Andean region study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-10-01

    New opportunities for climate change mitigation arising from a higher energy integration among Andean Pact nations were analysed within the framework of the UNEP/GEF Project. Apart from the search for regional mitigation actions, the study was mainly aimed at detecting methodological problems which arise when passing from a strictly national view to the co-ordination of regional actions to deal with climate change. In accordance with the available resources and data, and in view of the mainly methodological nature of the project, it was decided to analyse the opportunities to delve into the energy integration of the Region as regards electricity and natural gas industries and their eventual impact on the emission of greenhouse gases. Although possibilities of setting up electricity and natural gas markets are real, their impacts on GHG emission from the energy system would not prove substantially higher than those which the nations could achieve through the use of their own energy resources, in view that the Andean systems are competitive rather than complementary. More in-depth studies and detail information will be required - unavailable for the present study - to be able to properly evaluate all benefits associated with higher energy integration. Nevertheless, the supply of natural gas to Ecuador seems to be the alternative with the highest impact on GHG emission. If we were to analyse the supply and final consumption of energy jointly, we would most certainly detect additional mitigation options resulting from higher co-operation and co-ordination in the energy field. (EHS)

  18. Volcanism and associated hazards: the Andean perspective

    Science.gov (United States)

    Tilling, R. I.

    2009-12-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

  19. Volcanism and associated hazards: The Andean perspective

    Science.gov (United States)

    Tilling, R.I.

    2009-01-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

  20. The Andean Geotrail (2): An educational project

    Science.gov (United States)

    Galland, O.; Sassier, C.; Vial, M.; Thiberge, P.

    2009-12-01

    The role of Geosciences in our society is of primary importance. Its implications for humanity relate to major challenges such as climate change, managing energy resources, natural hazard mitigation, and water scarcity. Despite these issues being familiar to specialists, this is in general not the case for the public. In a world, where the impact of human activity is beginning to be seen on the environment, knowledge of the Earth and its history is paramount to make informed decisions that will influence our future. The necessity to educate the global population and raise awareness of Geosciences has led UNESCO to designate 2009 the International Year of the Planet Earth. In the framework of the UNESCO International Year of Planet Earth, we performed an educational project in collaboration with primary, secondary and high schools in France and Norway. Geosciences are not usually studied in schools, but this project allowed more than 600 pupils (from 17 schools) aged 8 to 18 years old to share the geological discoveries of our popular science adventure The Andean Geotrail (see Sassier et al., this session). The main educational goal was to promote Geosciences by illustrating in the field what geology is. Our natural laboratory was the spectacular Andean Cordillera. The secondary goal was to promote careers in geology and highlight their variety by allowing the pupils to meet geologists through portraits of geologists. The teachers of the partner schools used our project as a dynamic complement to their theoretical lessons. To set up this partnership, we obtained the support of the pedagogic supervisors of the French Ministry of National Education. The pedagogical project consisted of three steps: (1) Before the expedition (Oct.-Nov. 2008), we visited the pupils of each partner school to present the project, establish personal contact and engage the pupils in our adventure. (2) During The Andean Geotrail itself (Nov. 2008-Aug. 2009), we continuously documented our

  1. Cretaceous Exhumation of the North American Cordillera Measured through Mineral Multi-Dating: Insights into Basin Filling Models and Orogenic Architecture

    Science.gov (United States)

    Painter, C. S.; Carrapa, B.; DeCelles, P. G.; Gehrels, G. E.; Thomson, S. N.

    2015-12-01

    exhumation rates is observed in South America in the central Andean arc, Puna-Altiplano, and eastern Cordillera zones.

  2. 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.

  3. The Andean Geotrail (1): A scientific adventure

    Science.gov (United States)

    Sassier, C.; Galland, O.; Raufaste, C.; Mair, K.

    2009-12-01

    The role of Geosciences in our society is of primary importance. Its implications for humanity relate to major challenges such as climate change, managing energy resources, natural hazard mitigation, and water scarcity. Despite these issues being familiar to specialists, this is in general not the case for the public. In a world, where the impact of human activity is beginning to be seen on the environment, knowledge of the Earth and its history is paramount to make informed decisions that will influence our future. The necessity to educate the global population and raise awareness of Geosciences has led UNESCO to designate 2009 the International Year of the Planet Earth. In this context and with the label of the UNESCO, we organized and performed a popular science adventure that was followed in real time by both school children and many adults around the world. The Andean Geotrail consisted of a cycling expedition through a spectacular geological environment, the Andean Cordillera. During the nine month expedition, we cycled 8000 km and walked 400 km from Ushuaia in the Southern tip of Argentina to Nazca in Peru to encounter a rich variety of geological environments: active volcanoes, earthquakes, mineral and hydrocarbon deposits, and fantastic geological scenery. All this makes the Andes a great pedagogical natural laboratory. During the expedition, we visited spectacular geological localities that illustrate key Earth Science phenomena (such as mines and hydrocarbon deposits, erupting volcanoes and seismogenically active areas, and national parks) and discovered their implications for the local people. Along the way, we interviewed local geologists and scientists who helped us understand the geology of their areas. We gathered our own observations with those of the local specialists and published essays, articles and photographs on our website and blog (www.georouteandine.fr/English, http://georouteandine.blogspot.com). Seventeen schools in France and Norway

  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. Volcanism and associated hazards: the Andean perspective

    Directory of Open Access Journals (Sweden)

    R. I. Tilling

    2009-12-01

    Full Text Available Andean volcanism occurs within the Andean Volcanic Arc (AVA, which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions" recognized worldwide that have occurred from the Ordovician to the Pleistocene.

    The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru. The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km3 in 1985 of Nevado del Ruiz (Colombia killed about 25 000 people – the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent

  6. Latitudinal variations (18°-23°S) in denudation rates of western Andean Syntaxis, Chile, South America.

    Science.gov (United States)

    Starke, Jessica; Ehlers, Todd A.; Schaller, Mirjam

    2016-04-01

    Keywords: Cosmogenic nuclides, denudation rates, channel steepness, Chi, syntax, North Chile, South Peru Syntaxial regions of orogens (e.g. the western and eastern Himalayan Syntaxes, St. Elias Mountains Alaska) are regions where curved segments of subducting plates meet and the subducting plate is bent forms a rigid indentor. Previous studies of syntaxial regions in the Himalaya and Alaska document localized and rapid deformation and denudation due to vigorous fluvial or glacial erosional processes. In this study we investigate denudation around an arid end-member syntaxial orogen in South America to understand the interactions between climate and tectonic processes in localizing denudation. We present 35 new cosmogenic 10Be analyses of river sediments to quantify spatial variations in erosion along the Andean Coastal Cordillera and Western Cordillera. The sizes of the drainage basin vary from 5 - 5000 square kilometers. These measurements are linked to analysis of digital topography, variations in fluvial steepness indices and Chi- plots. Cosmogenic derived denudation rates range from 2.5 - 130 mm/kyr. Denudation rates decrease generally from the syntaxis (near Arica, Chile) towards the south (near Antofagasta, Chile) and from the Western Cordillera to the Coastal Cordillera. Topographic analysis of channel steepness variations and Chi-plots also document spatial variations in fluvial erosion and are consistent with spatial pattern in cosmogenic derived denudation rates. In summary the results document both a north to south and east to west variation in denudation around the western Andean margin. The spatial pattern of denudation is consistent with recently proposed patterns of syntaxial deformation driven by the geometry of the bent subducting plate. Denudation rates are also likely influenced to a lesser degree by a latitudinal variation in climate along the Andean margin.

  7. Rhyolitic calderas and centers clustered within the active andesitic belt of Ecuador's Eastern Cordillera

    Energy Technology Data Exchange (ETDEWEB)

    Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: pmothes@igepn.edu.ec

    2008-10-01

    In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.

  8. 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

  9. Mountain building at ocean-continent margins - linking mass flux, mechanics, and earthquakes at the Andean margin

    Science.gov (United States)

    Oncken, O.

    2015-12-01

    Deformation at convergent plate boundaries involves various styles of mass flux and of backarc shortening. For the Andes, patterns appear obvious. Long-term mass flux style - i.e. accretionary versus erosive - shows a distinct relationship with forearc as well as backarc deformation mode. Neogene surface deformation exhibits tectonically uplifting areas along the coast driven by interseismically active reverse faulting. Moreover, seismic-cycle vertical displacement is not coincident with long-term vertical motion that probably is superseded by slow basal underplating (southern Chile) or tectonic erosion (northern Chile). Reconstruction clearly indicates that the Central Andean trench has always been underfilled with less than 500 m of sediment. In southern Chile, our data illustrate a similar trend during most of the Cenozoic with a shift around some 6-7 Ma to substantial sediment influx from glaciation of the Patagonian part of the Andean Cordillera. As a consequence, backarc shortening stopped at this latitude, while shortening velocity in the Central Andes was still accelerating. Using latitudinal evolution and variations of shortening rate, orogenic strain accumulation and deformation partitioning in the Andes can be shown to be dominated by distinct factors. The Altiplano-Puna plateaux are characterized by a complete cycle of initial lateral spreading of deformation followed by subsequent localization and acceleration of bulk shortening rate. Estimates of strength evolution based on force balance calculations and critical wedge analysis suggest significant backarc weakening driving this change. Lithosphere-scale failure from strain weakening beyond a critical strain threshold (c. 20%) and fault coalescence with formation of a weak detachment in shales (μeff < 0.1) played a key role in the evolution of the Central Andes. Strain-related lithosphere weakening dominated over the impact of external forcing mechanisms, such as variations of plate convergence

  10. 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.

  11. Cenozoic forearc basin sediments in Southern Peru (15-18°S): Stratigraphic and heavy mineral constraints for Eocene to Miocene evolution of the Central Andes

    Science.gov (United States)

    Decou, A.; von Eynatten, H.; Mamani, M.; Sempere, T.; Wörner, G.

    2011-05-01

    A large sedimentary forearc basin developed in Cenozoic times between the present-day Coastal Cordillera and the Western Cordillera of the Central Andes, called Moquegua basin in southern Peru. The basin is filled by Moquegua Group deposits (~ 50 to 4 Ma) comprising mostly siliciclastic mudstones, sandstones and conglomerates as well as volcanic intercalations. Several facies changes both, along orogenic strike and through time, are described and have led to subdivision into four sedimentary units (Moquegua A, B, C and D). In this paper we present a refined stratigraphic scheme of the Moquegua Group combined with the first provenance analysis of the Moquegua basin based on (i) semi-quantitative analysis of heavy mineral abundance, (ii) electron microprobe (EMP) and laser ablation (LA) ICP-MS analyses of single detrital amphibole and Fe-Ti oxide grains, and (iii) comparative analysis of the different potential source rocks to clearly identify the most likely sources. Results allow us to reconstruct sediment provenance and to relate changes of the erosion-sedimentation system in the Moquegua basin to the evolution of the Andean orogen. At ~ 50 to ~ 40 Ma the Moquegua basin was close to sea level and fed by low energy rivers transporting mainly metamorphic basement and Jurassic-Cretaceous sedimentary detritus from local and distal sources. The latter might be as far as the present Eastern Cordillera. From ~ 35 Ma on the distal sediment sources were cut off by the uplift of the Altiplano and Eastern Cordillera leading to higher energy fluvial systems and increasing importance of local sources, especially the relevant volcanic arcs. From 25 Ma on volcanic arc rocks became the predominant sources for Moquegua Group sediments. The 10 Ma time lag observed between the onset of uplift-induced facies and provenance changes (at ~ 35 Ma) and the onset of intense magmatic activity (at ~ 25 Ma) suggests that magmatic addition was not the main driver for crustal thickening and

  12. 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.

  13. The intersection of climate, tectonic uplift, and regional groundwater flow in the central Andean Plateau: Insight from the accumulation of the massive evaporite deposit in the Salar de Atacama, Chile

    Science.gov (United States)

    Boutt, D. F.; Hynek, S. A.; Corenthal, L.; Munk, L. A.

    2015-12-01

    The Salar de Atacama (SdA), a large endorheic basin adjacent to the Central Andes in the hyperarid Atacama Desert, has accumulated over 1800 km3 of evaporites and a lithium-rich brine since the late Miocene. Focused groundwater discharge in endorheic basins, such as those in the Chilean Altiplano, provide opportunities to investigate mechanisms for closing hydrologic budgets in arid regions. We demonstrate that modern evapotranspiration is 5 to 21 times greater than modern recharge from precipitation in the topographic watershed. Multiple lines of evidence including an adapted chloride mass balance method applied to remotely sensed precipitation estimates and sodium mass balance calculations support this conclusion. We contend that the missing water needed to close the extreme hydrologic imbalance of SdA is sourced from recharge on the orogenic plateau in an area over 4 times larger than the topographic watershed, augmented by transient draining of stored groundwater. Groundwater recharged during wetter periods in the late Pleistocene is still actively draining and discharging from storage without corresponding recharge into the system. Geologic evidence from the volume of evaporites deposited in the basin suggests that the SdA has been receiving significant amounts of fresh inflow waters over at least 7 Ma despite the region being hyperarid over the same time frame. Our conceptualization of the depositional model for evaporite accumulation necessitates the water table being at or close to the land surface. Subsidence associated with basin development has accommodated significant accumulation of these deposits thereby requiring the sustenance of fresh inflow waters during uplift of the Andean plateau. Sustained groundwater discharge to the basin requires long residence times, deep water tables and strong gradients in landscape and climate enabled by an uplifting plateau. The application of steady state assumptions to the modern hydrologic system are unsupported by

  14. Oroclinal Bending and Mountain Uplift in the Central Andes

    Science.gov (United States)

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

    2007-05-01

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

  15. New Paleomagnetic Results and Ar-Ar Geochronology From the Vallenar Region (29oS), N. Chile: Implications for the Timing of Rotations in the Andean Forearc Region.

    Science.gov (United States)

    Gipson, M. J.; Taylor, G. K.; Grocott, J.

    2001-12-01

    The Andean forearc in northern Chile comprises from west to east three tectonomorphic zones - the Coastal Cordillera, the Central Valley and the Precordillera/Chilean Altiplano which lie outboard of the High Andes which represent the present-day active magmatic/volcanic arc. In the Vallenar region the Coastal Cordillera passes directly eastward into the Precordillera with no Central Valley present. The Coastal Cordillera is composed of deformed Palaeozoic sediments intruded by Permo-Triassic plutons, which together comprise the basement of the region. This basement is intruded by Jurassic to Upper Cretaceous plutons of the Coastal Batholith, which is in part overlain by and intruded into Lower Cretaceous arc to back-arc sequences of volcanics and marine limestones. This region is separated from the Upper Cretaceous and Lower Tertiary volcanics and intrusives of the Precordillera to the east by a narrow deformational zone which extends for at least 200km along strike and which we believe to have formed as a result of sinistral transpression. New palaeomagnetic results from the westernmost part of the Lower Cretaceous batholith (n = 7/9 sites, dec = 35.5, inc = -45.0, {α }95 = 4.9), dated to between 130-128 Ma using Ar-Ar geochronology, reveal a well constrained clockwise rotation of 47 {+/-} 7o, consistent with previous results from further north in the Coastal Cordillera. Results from the easternmost pluton of the batholith, dated at 91 Ma, yields a characteristic direction (n = 9 sites, dec = 22.6, inc = -51.1, {α }95 = 4.5) and a rotation of 37 {+/-} 7o. The Coastal Cordillera - Precordillera boundary in this region is marked by an interbedded sequence of red sandstones and andesitic flows (the Punte del Cobre Fm.) overlain by limestones (Chanarcillo Gp.) which are here deformed in a relatively narrow (5-10km wide) fold and thrust belt. The characteristic magnetization of these units (n = 9 sites, dec = 31.5, inc = -50.7, α 95 = 4.3) clearly fails the fold

  16. Cenozoic back-arc magmatism of the southern extra-Andean Patagonia (44° 30' - 52° S: A review of geochemical data and geodynamic interpretations

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    M. D'Orazio

    2004-12-01

    Full Text Available Huge amounts of basaltic s.l. lavas were persistently erupted along the eastern side of the Andean Cordillera, throughout Cenozoic time, forming extensive plateaus, hundreds of monogenetic scoria cones and other volcanic structures in a continental back-arc setting. The igneous products exposed in the southern sector of the extra-Andean Patagonia (44° 30' - 52° S are dominantly mafic with minor slightly evolved compositions and rare highly differentiated products. The many published chemical analyses of these rocks, indicate that the mafic lavas range from strongly silica - undersaturated basanites to oversaturated basaltic andesites, and that most of the lavas have a typical within-plate geochemical signature. However, a number of lavas, generally erupted in the western-central sectors of Patagonia, are characterized by different distributions of the incompatible elements with high LILE/HFSE and LREE/HFSE ratios. The REE distribution modelling suggests a low degree of melting of a deep (> 70 km garnet-bearing source for the alkaline magmas, and a higher degree of melting of the same source, or an even higher degree of melting of an enriched source, for the subalkaline magmas. The available Sr-Nd-Pb isotope compositions clearly attest to a major geographic variation: the southernmost lavas have lower 87Sr/86Sr and higher 143Nd/144Nd and 206Pb/204Pb ratios with respect to those erupted to the north. On the whole, the Sr-Nd-Pb isotope compositions of the southern Patagonia lavas fall within the typical range of within-plate continental magmas; in addition the Pb isotope ratios fall in the range of the Southern Hemisphere Dupal Pb isotope anomaly. The geochemical variations of the southern Patagonia lavas are discussed in terms of different geochemical components: depleted and enriched sub-slab asthenosphere, enriched continental lithospheric mantle, continental crust and subducted materials. The geodynamic significance is interpreted with in the

  17. Preliminary phylogenetic analysis of the Andean clade and the placement of new Colombian blueberries (Ericaceae, Vaccinieae

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    Paola Pedraza-Penalosa

    2015-04-01

    Full Text Available The blueberry tribe Vaccinieae (Ericaceae is particularly diverse in South America and underwent extensive radiation in Colombia where many endemics occur. Recent fieldwork in Colombia has resulted in valuable additions to the phylogeny and as well in the discovery of morphologically noteworthy new species that need to be phylogenetically placed before being named. This is particularly important, as the monophyly of many of the studied genera have not been confirmed. In order to advance our understanding of the relationships within neotropical Vaccinieae and advice the taxonomy of the new blueberry relatives, here we present the most comprehensive phylogenetic analysis for the Andean clade. Anthopterus, Demosthenesia, and Pellegrinia are among the putative Andean genera recovered as monophyletic, while other eight Andean genera were not. The analyses also showed that genera that have been traditionally widely defined are non-monophyletic and could be further split into more discrete groups. Four newly discovered Colombian Vaccinieae are placed in the monophyletic Satyria s.s. and the Psammisia I clade. Although these new species are endemic to the Colombian Western Cordillera and Chocó biogeographic region and three are not known outside of Las Orquídeas National Park, they do not form sister pairs.

  18. [Diversity and dynamics of a high sub-Andean forest from Northern Andes, Colombia].

    Science.gov (United States)

    Restrepo, Jesús Oswaldo Velásquez; Maniguaje, Nancy Lorena; Duque, Alvaro Javier

    2012-06-01

    The sub-Andean forests are characterized by a high biodiversity, but little is known about their natural dynamics. In order to generate new information, this study assessed two permanent plots of one hectare each, in the Northern Andean area of the Western Cordillera, Colombia. Methodology included the evaluation of diversity patterns, above ground biomass (AGB) dynamics, and mortality and recruitment rates. Besides, we used the Fisher's Alpha index to calculate species diversity. Forest dynamics and AGB were evaluated in both plots by means of three censuses carried out within a nine years period. In total, we found 1 664 individuals with diameter at breast height (DBH)> or =10cm belonging to 222 species, 113 genera and 60 families. Mean species richness was of 156 species/ha and a mean Fisher's Alpha index of 56.2/ha. The mortality rate was 0.88% and recruitment was 1.16%, which did not allow to lay any external effect of global warming or climate change on individual forest dynamics. However, the mean AGB was 243.44+/-9.82t/ha, with an annual average increase of 2.9t/ha, a higher value than the one reported in other studies of high sub-Andean forests, which suggests that equilibrium in terms of the AGB have not yet been reached. Besides, according to field observations, a recovery process, from a disturbance that occurred in the past, might be on his way.

  19. Stable isotope variations (δ18O and δD) in modern waters across the Andean Plateau

    Science.gov (United States)

    Bershaw, John; Saylor, Joel E.; Garzione, Carmala N.; Leier, Andrew; Sundell, Kurt E.

    2016-12-01

    Environmental parameters that influence the isotopic composition of meteoric water (δ18O and δD) are well characterized up the windward side of mountains, where orographic precipitation results in a predictable relationship between the isotopic composition of precipitation and elevation. The topographic and climatic evolution of the Andean Plateau and surrounding regions has been studied extensively by exploiting this relationship through the use of paleowater proxies. However, interpretation on the plateau itself is challenged by a poor understanding of processes that fractionate isotopes during vapor transport and rainout, and by the relative contribution of unique moisture sources. Here, we present an extensive dataset of modern surface water samples for the northern Andean Plateau and surrounding regions to elucidate patterns and causes of isotope fractionation in this continental environment. These data show a progressive increase in δ18O of stream water west of the Eastern Cordillera (∼1‰/70 km), almost identical to the rate observed across the Tibetan Plateau, attributed to a larger fraction of recycled water in precipitation and/or increased evaporative enrichment downwind. This may lead to underestimates of paleoelevation, particularly for sites deep into the rainshadow of the Eastern Cordilleran crest. That said, elevation is a primary control on the isotopic composition of surface waters across the entire Andean Plateau and its flanks when considering the most negative δ18O values, highlighting the need for sufficiently large datasets to distinguish minimally evaporated samples. There is a general increase in δ18O on the plateau from north to south, concomitant with an increase in aridity and decrease in convective moistening (amount effect). Lastly, stable isotope and seasonal precipitation patterns suggest easterlies provide the vast majority of moisture that falls as precipitation across the Andean Plateau and Western Cordillera, from Peru to

  20. Fajas oblicuas de deformación neotectónica en Precordillera y Cordillera Frontal (31° 30´ - 33° 30´ LS: controles paleotectónicos Oblique belts of neotectonic deformation in Precordillera and Frontal Cordillera (31 30´ - 33 30´ ls: Paleotectonic controls

    Directory of Open Access Journals (Sweden)

    J.M. Cortés

    2006-12-01

    Full Text Available La Precordillera Sur y las Cerrilladas Pedemontanas de Mendoza, son dos unidades morfotectónicas principales en la vertiente oriental de los Andes centrales, a los 31º30' - 33º30' de latitud sur. Allí, dos cinturones de deformación transpresiva y orientación noroeste, denominados fajas Barreal-Las Peñas y Río Mendoza-Tupungato, se desarrollaron como consecuencia de la gradual somerización de la placa de Nazca en los últimos 20 Ma. Su orientación y compleja geometría estructural resulta de la interferencia de la deformación andina tardío-cenozoica con la estructura de orientación noroeste del rift triásico de la cuenca Cuyana y antiguas zonas de sutura colisional de edad paleozoica. Este trabajo demuestra que los rasgos paleotectónicos del substrato triásico-paleozoico de la Precordillera Sur y del margen oriental de la Cordillera Frontal controlan la configuración morfotectónica y la distribución y reactivación de gran parte de la estructura neotectónica del margen andino a estas latitudes.The Southern Precordillera and Cerrilladas Pedemontanas of Mendoza, Argentina, are two major morphotectonic units in the eastern side of the Central Andes at 31º30' - 33º30' South latitude. There, two regional NW striking structures, called the Barreal - Las Peñas and Río Mendoza - Tupungato belts were developed as a consequence of gradual flattening of the Nazca plate in the last 20 M.yrs. Their orientation and complex structural geometry result from the interference of the Late Cenozoic Andean deformation with the NW-trending rift structure of the Triassic Cuyo basin and ancient collisional suture zones of Paleozoic age. This work demonstrates that paleotectonics features in the Triassic-Paleozoic substratum of the Southern Precordillera and the eastern margin of the Cordillera Frontal control the morphotectonic configuration and neotectonic structural distribution and rejuvenation of the Andes at these latitudes.

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

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    Wenhui He

    2016-05-01

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

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

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    Enrique Arbeláez-Cortés

    2011-06-01

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

  3. Can cosmic ray exposure dating reveal the normal faulting activity of the Cordillera Blanca Fault, Peru?

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    L.L. Siame

    2006-12-01

    Full Text Available The build-up of in situ-produced cosmogenic 10Be within bedrock scarps and escarpments associated to the Cordillera Blanca Normal Fault, Peru, was measured to evaluate, through Cosmic Ray Exposure dating, its normal faulting activity. The highest mountain peaks in Peru belong to the 210 km-long, NW- striking, Cordillera Blanca. Along its western border, the Cordillera Blanca Normal Fault is responsible for a vertical relief over 4.4 km, whose prominent 2 km high escarpment is characterized by ~1 km-high triangular facets corresponding to vertical displacements cumulated during the last 1-2 million years. At a more detailed scale, this fault system exhibits continuous geomorphic evidence of repeated displacements, underlined by 2 to 70 m-high scarps, corresponding to vertical displacements cumulated since Late Pleistocene and Holocene periods. Although microseismicity occurs along the Cordillera Blanca Normal Fault, no major historical or instrumental earthquake has been recorded since the beginning of the Spanish settlement in the 16th century. To evaluate the vertical slip rate along the major 90 km-long central segment of the Cordillera Blanca Normal Fault, the Quaternary fault escarpment (i.e., triangular facet, as well as the bedrock fault scarp, have been sampled for 10Be Cosmic Ray Exposure dating. Even if the uppermost part of the triangular facets have been resurfaced by the Last Glacial Maximum glaciers, our results allow to estimate a vertical slip-rate of 3±1 mm/yr, and suggest at least 2 seismic events during the last 3000 years.

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

    Directory of Open Access Journals (Sweden)

    Julián Andrés Rojas-Morales

    2012-12-01

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

  5. VARIABILIDAD ESPACIAL DE PROPIEDADES QUÍMICAS Y FÍSICAS EN UN TYPIC UDIVITRANDS, ARENOSO DE LA REGIÓN ANDINA CENTRAL COLOMBIANA SPATIAL VARIABILITY OF CHEMICAL AND PHYSICAL PROPERTIES OF A SANDY TYPIC UDIVITRANDS IN THE COLOMBIAN CENTRAL ANDEAN ZONE

    Directory of Open Access Journals (Sweden)

    Franco Humberto Obando Moncayo

    2006-06-01

    Full Text Available Se estudió la variabilidad espacial de propiedades químicas y físicas en un Typic Udivitrands arenoso de la granja experimental Tesorito de la Universidad de Caldas, ubicado en la Cordillera Central Colombiana a 5º 01’47” N, 75º 26’ 03” W y 2280 msnm. El área experimental se localiza en un Piedemonte Coluvial, con un manejo antecedente y actual en pastos, frutales de clima frío moderado y hortalizas. Se realizó un muestreo sistemático en red con una distancia aproximada entre sitios de muestreo de 30 m en un área efectiva de 3,96 ha; para un total de 60 sitios. El análisis geoestadístico se llevó a cabo en tres etapas: 1 análisis exploratorio de los datos utilizando los software Statgraphics Plus v 2.0 y SPSS 9.0, 2 análisis estructural o semivariografía. 3 interpolación por el método Kriging puntual utilizando el paquete geoestadístico GS+ versión 5.3b. Los modelos esférico y exponencial fueron los de mejor ajuste a los modelos experimentales excepto para el DPM, que se ajustó a un modelo lineal (Nugget puro. El alcance para las variables analizadas se encuentra dentro de la distancia máxima ( 350 m del área de muestreo considerada para el cálculo de los semivariogramas, excepto para el fósforo que presento un alcance de 479,4 metros. El alcance fluctuó entre 33,9 m para el Na y 308,5 m para el DPM. La variabilidad espacial de atributos del suelo en el predio experimental es alta, siendo mayor en propiedades químicas, igualmente, permitió visualizar la variabilidad espacial del deterioro estructural del suelo coincidiendo con la zona de mayor variabilidad química.A study of the spatial variability of the chemical and physical properties of a Sandy Typic Udivitrands was conducted in the Tesorito Experimental Farm of Universidad de Caldas, located in the Colombian Central Cordillera at 5º 01’47” N, 75º 26’ 03” W and 2280 m elevation. The experimental plot was located in a Coluvial Piedmont with

  6. Regional polyphase deformation of the Eastern Sierras Pampeanas (Argentina Andean foreland): strengths and weaknesses of paleostress inversion

    Science.gov (United States)

    Traforti, Anna; Zampieri, Dario; Massironi, Matteo; Viola, Giulio; Alvarado, Patricia; Di Toro, Giulio

    2016-04-01

    The Eastern Sierras Pampeanas of central Argentina are composed of a series of basement-cored ranges, located in the Andean foreland c. 600 km east of the Andean Cordillera. Although uplift of the ranges is partly attributed to the regional Neogene evolution (Ramos et al. 2002), many questions remain as to the timing and style of deformation. In fact, the Eastern Sierras Pampeanas show compelling evidence of a long lasting brittle history (spanning the Early Carboniferous to Present time), characterised by several deformation events reflecting different tectonic regimes. Each deformation phase resulted in further strain increments accommodated by reactivation of inherited structures and rheological anisotropies (Martino 2003). In the framework of such a polyphase brittle tectonic evolution affecting highly anisotropic basement rocks, the application of paleostress inversion methods, though powerful, suffers from some shortcomings, such as the likely heterogeneous character of fault slip datasets and the possible reactivation of even highly misoriented structures, and thus requires careful analysis. The challenge is to gather sufficient fault-slip data, to develop a proper understanding of the regional evolution. This is done by the identification of internally consistent fault and fracture subsets (associated to distinct stress states on the basis of their geometric and kinematic compatibility) in order to generate a chronologically-constrained evolutionary conceptual model. Based on large fault-slip datasets collected in the Sierras de Cordoba (Eastern Sierras Pampeanas), reduced stress tensors have been generated and interpreted as part of an evolutionary model by considering the obtained results against: (i) existing K-Ar illite ages of fault gouges in the study area (Bense et al. 2013), (ii) the nature and orientation of pre-existing anisotropies and (iii) the present-day stress field due to the convergence of the Nazca and South America plates (main shortening

  7. Administrative Law in the Andean Community of Nations

    OpenAIRE

    Santos Rodríguez, Jorge Enrique

    2013-01-01

    One of the contemporary tendencies of Administrative Law is the recognition of its existence beyond the borders of a State. Under such premise, this paper aims to demonstrate that in the Andean Community of Nations sufficient elements to consider the existence of an Andean administrative Law. In the Andean statutes and rules, it is possible to identify an administrative function, as well as an administrative organization inside the Andean Integration System; and a system of Andean administrat...

  8. Partitioning of oblique convergence in the Northern Andes subduction zone: Migration history and the present-day boundary of the North Andean Sliver in Ecuador

    Science.gov (United States)

    Alvarado, A.; Audin, L.; Nocquet, J. M.; Jaillard, E.; Mothes, P.; Jarrín, P.; Segovia, M.; Rolandone, F.; Cisneros, D.

    2016-05-01

    Along the Ecuadorian margin, oblique subduction induces deformation of the overriding continental plate. For the last 15 Ma, both exhumation and tectonic history of Ecuador suggest that the northeastward motion of the North Andean Sliver (NAS) was accompanied by an eastward migration of its eastern boundary and successive progressively narrowing restraining bends. Here we present geologic data, earthquake epicenters, focal mechanisms, GPS results, and a revised active fault map consistent with this new kinematic model. All data sets concur to demonstrate that active continental deformation is presently localized along a single major fault system, connecting fault segments from the Gulf of Guayaquil to the eastern Andean Cordillera. Although secondary faults are recognized within the Cordillera, they accommodate a negligible fraction of relative motion compared to the main fault system. The eastern limit is then concentrated rather than distributed as first proposed, marking a sharp boundary between the NAS, the Inca sliver, and the Subandean domain overthrusting the South American craton. The NAS limit follows a northeast striking right-lateral transpressional strike-slip system from the Gulf of Guayaquil (Isla Puná) to the Andean Cordillera and with the north-south striking transpressive faults along the eastern Andes. Eastward migration of the restraining belt since the Pliocene, abandonment of the sutures and reactivation of north-south striking ancient fault zones lead to the final development of a major tectonic boundary south and east of the NAS, favoring its extrusion as a continental sliver, accommodating the oblique convergence of the Nazca oceanic plate toward South America.

  9. Andean settlers rush for Amazonia.

    Science.gov (United States)

    Serra-vega, J

    1990-01-01

    Governments of Andean countries (Peru, Bolivia, Colombia, Ecuador, and Venezuela) have encouraged migration to the Amazon Basin, which has contributed to its destruction. Population pressure, landlessness, and poverty are the inducements to migrate. Efforts to populate the Amazon forest were begun as early as 1964 in Peru without international notice. By 1980, logging was allowed in Peru, and Brazil considered colonization of the Amazon essential to national sovereignty. By 1986, outside of Lima, Peru, a development project originally funded by the World Bank, the InterAmerican Development Bank, and the US, resulted in conflicts between settlers and Indians, in loggers indiscriminately cutting, and in farmers using slash and burn techniques to clear forests. Elsewhere the Peruvian Amazon, in San Ignacio, the population was growing by 5.5%/year. The jungle road that had been started but never completed, Carretera Marginal, destroyed 5 million hectares of primary forest, and much of the 600,000 hectares of arable land gained by the road suffered from inappropriate farming practices which caused massive erosion and laterization of the soils. Food crop production declined, and production of coca for cocaine increased. Coca crops are controlled by the Shining Path guerrillas, who are trying to overthrow the Peruvian government. Devastation of Ecuador around Lago Agrio continues. In Colombia, east of Bogota, forests have disappeared and hills have eroded and silted up rivers and dams. The Andean piedmont in Bolivia has also been devastated by loggers and by slash and burn farming. Southeastern Bolivian forests have been cleared for soya bean cultivation on poor soils. Social and economic crises propel people into the remaining forests. The solution is to ease foreign debt, transfer appropriate technology at affordable prices, refuse to finance destructive development, and help to educate and train scientific researchers. Family planning services are also urgently needed

  10. THE PAIPA VOLCANO, EASTERN CORDILLERA OF COLOMBIA, SOUTH AMERICA (PART II: PETROGRAPHY AND MAJOR ELEMENTS PETROLOGY

    Directory of Open Access Journals (Sweden)

    Cepeda Héctor

    2005-08-01

    Full Text Available Paipa volcano products are mainly pyroclastic pumice and ash flow tuffs, lava domes and pyroclastic block and ash flow tuffs. They are classified as alkaline rhyolites and trachytes and high-K calcalkaline rhyolites. Chemical data show SiO2 values between 68 and 72%, and alkalis (Na2O+K2O content of 7%-10%. Essential minerals are phenocrysts and glomerocrysts of anorthoclase, sanidine up to 1,5 cm and anorthoclase-mantled plagioclase; accessory minerals are red biotite, and hastingsite while trace minerals are augite, zircon, sphene and magnetite. Crystals have disequilibrium textures, such as dissolution embayments, corrosion and reabsortion borders, normal, inverse, oscillating and patchy zonation, together with fibrous borders intercalated with euhedral borders. In correlation with published data of Iza volcanic rocks, Paipa rocks chemical composition confirms that acid and alkaline magmas that have erupted in the Eastern Cordillera of Colombia during the Neogene are strongly different from the calc-alkaline magmas that erupt in the westward active arc (Central Cordillera. Detailed structural, geochemical and geophysical research has to be done in future research to establish the geodynamic framework that governs the volcanism of the Eastern Cordillera.

  11. Identification of aquifer limits inside an Andean Piedmont (between 19,5°S and 20°S - Northern Chile) with TDEM and gauging methods.

    Science.gov (United States)

    Viguier, Benoit; Jourde, Hervé; Leonardi, Véronique; Moya, Claudio; Líra, Elias; Yáñez, Gonzalo; Maringue, José; García-Pérez, Tiaren; Lictevout, Elisabeth

    2016-04-01

    In times of brutal climate changes and water scarcity in arid areas, the management of water resource has become a major issue. In this aim, several studies attempted to quantify the aquifer recharge and hydrodynamic processes. However, the quality of many studies depends on the characterization of aquifer boundaries. In arid areas, the amount of observation points (e.g. wells) and their spatial distribution constrain the understanding of aquifer boundaries spatial variations. In this study, we propose a methodology to characterize both water table level and boundaries of aquifer in such areas where the observation points do not exist. The Andean Piedmont (between 19,5°S and 20°S - Northern Chile) is located in the Pampa del Tamarugal Central Depression and is bounded respectively at the westside and the eastside by the Coastal Cordillera (1100 m a.s.l) and the Precordillera mountain range (4500 m a.s.l). The piedmont and the basin floor are composed of the late-Cenozoic alluvial deposits (hundred meters thick) which contain the Pampa del Tamarugal aquifer. Due to the hyperarid context, this regional aquifer is one of the main strategic groundwater resources in Northern Chile. This aquifer is mainly unconfined and the electrical conductivity of groundwater varies around 3000 μS/cm in the study area. The analysis of resistivity variation with depth, acquired by Time Domain Electromagnetic (TDEM) method in various points inside the piedmont, allow identifying a continuous resistivity contrast (from ≥ 100-40 Ω.m to ≤ 10 Ω.m) that varies over the study area. This continuous resistivity contrast is assumed to be related to the water table of the unconfined aquifer rather than to a lithology contrast. After validation of the observations, a piezometric map was constructed using both the available hydrogeological information and the TDEM results. In the piedmont, river sink were identified; these zones where surface water sinks are correlated with the resistivity

  12. Miocene tectonism and the separation of cis- and trans-Andean river basins: Evidence from Neotropical fishes

    Science.gov (United States)

    Albert, James S.; Lovejoy, Nathan R.; Crampton, William G. R.

    2006-03-01

    The fish fauna of trans-Andean river basins in northwestern South America is ancient and diverse, including 14% (558 of 4,085) of all Neotropical teleost species and representing 88% of the orders and 79% of the families. The evolutionary histories of these lineages provide many examples to test models of the tectonic uplift that isolated the trans-Andean basins. We report the results of two newly compiled data sets of phylogenetic and biogeographic information on the freshwater fishes of the region: (1) species-level phylogenies for 26 Neotropical freshwater teleost taxa, with a minimum of 37 cis-/trans-Andean clades and (2) species distributions for 641 genera of Neotropical freshwater teleosts, with a minimum of 140 cis-/trans-Andean clades. Although it provides only about one-quarter the total number of cis-/trans-Andean clades, species phylogeny preserves a more accurate record of the temporal sequence of basin isolation. Phylogenies using gene sequences also may provide estimates on the timing of lineage divergences. However, the great majority (70%) of available species phylogenies for Neotropical freshwater teleosts employ comparative morphology alone, partly because species-level sampling for most taxa requires collections over large spatial (10 3-10 4 km) scales, and collections of whole specimens for morphological study are readily available for many taxa from natural history museums. Fish species phylogenies are partially concordant with patterns of drainage basin isolation generated from geological data on the Miocene of northwestern South America, which associate the initial rise of the Eastern Cordillera (˜1 2 Ma) with the hydrological isolation of the Magdalena and Pacific Slope regions and the rise of the Merida Andes (˜8 Ma) with the isolation of the modern Maracaibo and Orinoco basins. Although some phylogenies unite taxa from the Maracaibo and cis-Andean Orinoco, a more common set of area relationships occurs between clades exclusive to the

  13. Andean subduction orogeny: feedbacks between tectonics, relief evolution and global climate

    Science.gov (United States)

    Lacassin, Robin; Armijo, Rolando; Coudurier-Curveur, Aurélie; Carrizo, Daniel

    2016-04-01

    The Andean subduction margin, largest tectonic relief on the Earth (13 km vertically from the trench to the Altiplano) has a stepped morphology, which results of the evolution over the past 50 Myr of two parallel flat-ramp thrust systems, at the - previously unidentified - West Andean Thrust (WAT), and at the subduction interface. The evolution of those thrusts appears concomitant with increasing aridity in the Atacama Desert, which keeps a large-scale record of interplaying tectonics and Cenozoic climate change. The coastal morphology is dominated by the Atacama Bench, a giant uplifted terrace at 1-2km asl. Geomorphic and climatic data, numerical experiments of drainage formation are consistent with the development of a flat Atacama morphology close to sea level, interrupted at ≤10 Ma by tectonic uplift prevailing to the present. This suggests recent trench-ward relief growth by incorporation of the coastal Atacama Bench to the Andes reliefs. Thrust splay structures and other complexities above the subduction interface may explain this relief growth, as well as the distribution of asperities under the oceanward forearc, and the down-dip segmentation of coupling and seismicity on the megathrust. Combining those results with geological knowledge at the scale of the whole Central Andes, we show that the Andean orogeny results from protracted processes of bivergent crustal shortening in a wide region squeezed between the rigid Marginal Block and the S America Plate. The overall growth curve of Andean orogeny over the past 50 Myr appears synchronous with the onset of the "ramp-shaped" temperature decrease since the Early Eocene climatic optimum. Andean growth and global cooling may have operated under the same forcing mechanism at plate-scale, involving viscous flow in the mantle. But Andean growth appears modulated by climatic feedbacks causative of stepwise reductions of erosive power over the Andean margin. The first of such events is coeval with Late Eocene

  14. A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate

    Science.gov (United States)

    Bromley, Gordon R. M.; Schaefer, Joerg M.; Hall, Brenda L.; Rademaker, Kurt M.; Putnam, Aaron E.; Todd, Claire E.; Hegland, Matthew; Winckler, Gisela; Jackson, Margaret S.; Strand, Peter D.

    2016-09-01

    Resolving patterns of tropical climate variability during and since the last glacial maximum (LGM) is fundamental to assessing the role of the tropics in global change, both on ice-age and sub-millennial timescales. Here, we present a10Be moraine chronology from the Cordillera Carabaya (14.3°S), a sub-range of the Cordillera Oriental in southern Peru, covering the LGM and the first half of the last glacial termination. Additionally, we recalculate existing 10Be ages using a new tropical high-altitude production rate in order to put our record into broader spatial context. Our results indicate that glaciers deposited a series of moraines during marine isotope stage 2, broadly synchronous with global glacier maxima, but that maximum glacier extent may have occurred prior to stage 2. Thereafter, atmospheric warming drove widespread deglaciation of the Cordillera Carabaya. A subsequent glacier resurgence culminated at ∼16,100 yrs, followed by a second period of glacier recession. Together, the observed deglaciation corresponds to Heinrich Stadial 1 (HS1: ∼18,000-14,600 yrs), during which pluvial lakes on the adjacent Peruvian-Bolivian altiplano rose to their highest levels of the late Pleistocene as a consequence of southward displacement of the inter-tropical convergence zone and intensification of the South American summer monsoon. Deglaciation in the Cordillera Carabaya also coincided with the retreat of higher-latitude mountain glaciers in the Southern Hemisphere. Our findings suggest that HS1 was characterised by atmospheric warming and indicate that deglaciation of the southern Peruvian Andes was driven by rising temperatures, despite increased precipitation. Recalculated 10Be data from other tropical Andean sites support this model. Finally, we suggest that the broadly uniform response during the LGM and termination of the glaciers examined here involved equatorial Pacific sea-surface temperature anomalies and propose a framework for testing the viability

  15. Age and chemical constraints of Volcán Tunupa: Implications for behind arc volcanism in the Bolivian central Andes

    Science.gov (United States)

    salisbury, M. J.; Kent, A. J.; Jiménez, N.; Jicha, B. R.

    2011-12-01

    New 40Ar/39Ar age determinations of groundmass separates and whole-rock geochemical data constrain the Pleistocene eruptive history of Volcán Tunupa, a glacially-dissected composite volcano (~50 km3) situated between the Salar de Uyuni and Salar de Coipasa. Tunupa erupted ~110 km east of the arc front of the Western Cordillera of the central Andes near the eastern edge of the Intersalar Volcanic Field, an arc-perpendicular expression of volcanism that extends to the central Altiplano basin of Bolivia. 40Ar/39Ar age determinations indicate that the edifice was constructed between ~1.40 and 1.55 Ma, whereas nearby Cerro Huayrana lavas erupted ~ 11 Ma. Published ages from the Western Cordillera that are concordant with both Tunupa and Huayrana lavas demonstrate that the central Altiplano lavas are a long-lived expression of behind arc volcanism. The Tunupa lavas define a calc-alkaline trend from trachyandesite to trachydacite (wt.% SiO2 = 60.6 - 63.6; wt.% K2O + Na2O = 7.5 - 8.3) and are overlain by younger, more silicic (wt.% SiO2 = 66) trachydacitic domes. Major element compositions of Tunupa and Huayrana are enriched in FeO and TiO2 compared to the arc front. These lavas are also enriched in high field strength elements, notably Nb and Ta, and are characterized by considerably lower Ba/Nb and La/Ta ratios than arc front lavas in northern Chile. The geochemical and spatiotemporal patterns of the behind arc Tunupa and Huayrana lavas suggest different petrogenetic histories from typical central Andean arc lavas.

  16. Two new Cystoderma species from high Andean Ecuador

    DEFF Research Database (Denmark)

    Saar, I.; Læssøe, Thomas

    2006-01-01

    ABSTRACT: Two new agaric species, Cystoderma andinum and C. papallactae are described from high Andean Ecuador.......ABSTRACT: Two new agaric species, Cystoderma andinum and C. papallactae are described from high Andean Ecuador....

  17. Nuevas manifestaciones ígneas básicas en el flanco occidental de la cordillera oriental, colombia

    OpenAIRE

    2012-01-01

    Se describen y localizan nuevas manifestaciones ígneas básicas en la parte central del flanco occidental de la Cordillera Oriental, las cuales se presentan generalmente a manera de diques y silos.  De acuerdo con los análisis preliminares de los resultados petrográficos y geoquímicos, las rocas corresponden a gabros similares a los reportados anteriormente al sur del área.

  18. Multi-temporal InSAR for Deformation Monitoring of the Granada and Padul Faults and the Surrounding Area (Betic Cordillera, Southern Spain)

    NARCIS (Netherlands)

    Sousa, J.J.; Ruiz, A.M.; Hooper, A.J.; Hanssen, R.F.; Perski, Z.; Bastos, L.C.; Gil, A.J.; Galindo-Zaldivar, J.; Sanz de Galdeano, C.; Alfaro, P.; Garrido, M.S.; Armenteros, J.A.; Gimenez, E.; Aviles, M.

    2014-01-01

    The quantification of low rate active tectonic structures is a major target of geodetic and geological studies to improve the knowledge of seismic hazards. The central Betic Cordillera (southern Spain) is affected by moderately active tectonic structures and seismicity. Part of this seismic activity

  19. Late Miocene increase in precipitation in the Western Cordillera of the Andes between 18-19°S latitudes inferred from shifts in sedimentation patterns

    Science.gov (United States)

    Schlunegger, Fritz; Norton, Kevin P.; Delunel, Romain; Ehlers, Todd A.; Madella, Andrea

    2017-03-01

    Modern climate in the Andes is characterized by strong N-S decreasing trends in precipitation rates. Here we use stratigraphic records to show that this pattern has been established since as early as 12-11 Ma, at least on the western Andean margin of Northern Chile. The stratigraphic architecture on the western Andean margin documents a transition between 19°-20°S latitude where matrix-supported debris flow deposits shift to fluvial conglomerates between 12-11 Ma. The deposition of fluvial sediments has been maintained to the present north of 19°-20°S, while the occurrence of post 11 Ma aeolian sand, matrix-supported breccias with conglomerate interbeds south of these latitudes implies ongoing sedimentation with less water and thus under drier conditions. We relate these changes to the tectonic development of the Andes. Existing palaeoclimate models suggest that an elevated plateau deflects the Andean jet towards the south, thereby focusing moisture from the equatorial Atlantic to the northeastern flanks of the Altiplano. In addition, the formation of the eastern Andean foothills most likely intercepted moisture transport, and shifted it farther to the east, thereby keeping the western Andean margin dry south of 19°-20°S latitudes. The sedimentological data support a strong linkage between orographic precipitation and stratigraphy whereby central Andean deformation controls the distribution of available moisture on the western flank through a combination of orographic precipitation and deflection of air masses.

  20. Administrative Law in the Andean Community of Nations

    Directory of Open Access Journals (Sweden)

    Jorge Enrique Santos Rodríguez

    2013-12-01

    Full Text Available One of the contemporary tendencies of Administrative Law is the recognition of its existence beyond the borders of a State. Under such premise, this paper aims to demonstrate that in the Andean Community of Nations sufficient elements to consider the existence of an Andean administrative Law. In the Andean statutes and rules, it is possible to identify an administrative function, as well as an administrative organization inside the Andean Integration System; and a system of Andean administrative rules and an administrative justice system.

  1. Structure and age of the Lower Magdalena Valley basin basement, northern Colombia: New reflection-seismic and U-Pb-Hf insights into the termination of the central andes against the Caribbean basin

    Science.gov (United States)

    Mora-Bohórquez, J. Alejandro; Ibánez-Mejia, Mauricio; Oncken, Onno; de Freitas, Mario; Vélez, Vickye; Mesa, Andrés; Serna, Lina

    2017-03-01

    Detailed interpretations of reflection seismic data and new U-Pb and Hf isotope geochemistry in zircon, reveal that the basement of the Lower Magdalena Valley basin is the northward continuation of the basement terranes of the northern Central Cordillera, and thus that the Lower Magdalena experienced a similar pre-Cenozoic tectonic history as the latter. New U-Pb and Hf analyses of zircon from borehole basement samples retrieved in the basin show that the southeastern region consists of Permo-Triassic (232-300Ma) metasediments, which were intruded by Late Cretaceous (75-89 Ma) granitoids. In the northern Central Cordillera, west of the Palestina Fault System, similar Permo-Triassic terranes are also intruded by Late Cretaceous felsic plutons and display ESE-WNW-trending structures. Therefore, our new data and analyses prove not only the extension of the Permo-Triassic Tahamí-Panzenú terrane into the western Lower Magdalena, but also the along-strike continuity of the Upper Cretaceous magmatic arc of the northern Central Cordillera, which includes the Antioquia Batholith and related plutons. Hf isotopic analyses from the Upper Cretaceous Bonga pluton suggest that it intruded new crust with oceanic affinity, which we interpret as the northern continuation of a Lower Cretaceous oceanic terrane (Quebradagrande?) into the westernmost Lower Magdalena. Volcanic andesitic basement predominates in the northwestern Lower Magdalena while Cretaceous low-grade metamorphic rocks that correlate with similar terranes in the Sierra Nevada de Santa Marta and Guajira are dominant in the northeast, suggesting that the Tahamí-Panzenú terrane does not extend into the northern Lower Magdalena. Although the northeastern region of the Lower Magdalena has a similar NE-SW fabric as the San Lucas Ridge of the northeastern Central Cordillera and the Sierra Nevada de Santa Marta, lithologic and geochronologic data suggest that the San Lucas terrane terminates to the north against the

  2. Evolving Regional Security in the Andean Region

    Science.gov (United States)

    2004-03-19

    security forces or judicial systems reduces the effectiveness of regional cooperation. Past efforts to achieve consensus among the Andean states have...Trimestre 2001. Nuñez, Joseph. Una Arquitectura para la Seguridad del Siglo XXI par alas Américas: Cooperación Multilateral, Paz y Poder Flexible

  3. Holocene glacier fluctuations in the American Cordillera

    Science.gov (United States)

    Davis, P. Thompson

    In many areas of the American Rocky Mountains (Colorado, Wyoming, Utah, Idaho, Montana), Cascade Range (Washington, Oregon), and the Sierra Nevada (California), radiocarbon ages suggest that ice receded to near present limits before 10 ka BP. A pre-Altithermal readvance or stillstand left moraines ca. 1-3 km beyond and ca. 50-300 m below present glacier margins. At one locality on Glacier Peak in Washington, these deposits are perhaps dated to the early Holocene, but in general these deposits are probably at least 10 ka old. Glacial advances during the Altithermal (ca. 8 to 5 ka BP) elsewhere are rare; radiocarbon evidence for Altithermal glacial advances in the Colorado Front Range is questionable. The earliest radiocarbon-dated Neoglacial advances occurred about 5 ka BP in the Washington Cascades; moraines and related deposits believed to be of early Neoglacial age (i.e. 5 to 3 ka BP) elsewhere are poorly dated. For example, moraines believed to date to the early Neoglacial in Colorado (Triple Lakes) and Wyoming (Temple Lake) are actually late Pleistocene age, based on radiocarbon ages derived from lake sediments at the type localities. Although relative-age data (i.e. lichens, rock weathering, soils) from many areas suggest a three-fold Neoglacial sequence, little supporting radiocarbon evidence is available. However, tephrochronology distinguishes three Neoglacial advances near Mount Rainier in Washington. In most mountain ranges of the western United States, fresh, unweathered, sharp-crested moraines usually adjacent to present ice margins, or near headwalls in empty cirques, date to the Little Ice Age of the last several centuries. However, detailed photographic or other historical records of glacial fluctuations during the last century are rare, and detailed mass balance studies rarer still. Whether or not pre-Little Ice Age glacial fluctuations in the American Cordillera are synchronous must await better radiometric dating of local moraine sequences.

  4. Andean region: measles on the way out.

    Science.gov (United States)

    1996-10-01

    In August 1996, health officials, program managers, epidemiologists, laboratory representatives, UNICEF, Rotary International, and Pan American Health Organization staff attended the VII Andean EPI Meeting in Quito, Ecuador, to review the progress of the Expanded Program on Immunization (EPI). All Andean countries have conducted catch-up measles vaccination campaigns targeting children 9 months to 15 years old. These campaigns achieved 90% vaccine coverage and a strong reduction in measles incidence (only 7 confirmed cases in 1996). Follow-up campaigns were conducted during 1995-1996 in Colombia, Peru, and Chile. They were expected in Bolivia, Ecuador, Peru, and Venezuela during 1997-1999. The Andean countries implemented a national surveillance system for measles in 1995. Meeting representatives made eight recommendations regarding measles. For example, health officials should reach and maintain routine vaccination coverage greater than 95% for children 12-23 months old in each municipality. Laboratory representatives proposed recommendations on uniform criteria for measles diagnosis. The last indigenous wild poliovirus in the Americas was isolated in 1991. Imported wild poliovirus remains a concern. The Andean countries are expanding surveillance of neonatal tetanus activities. Since 1989 the frequency of neonatal tetanus has been falling in the Andean region, especially in Bolivia and Peru. The impact of migration on the control of neonatal tetanus should be a higher priority. Participants repeated the need for systematic use and continuous monitoring of EPI indicators (e.g., vaccination coverage). Three countries plan on analyzing surveys on missed opportunities for vaccination in 1996. Three countries presented progress reports on hepatitis B vaccination and surveillance. Participants issued recommendations on quality control of vaccines. The responsibility for quality control lies with the manufacturers and the government. Vaccines for invasive diseases (e

  5. Carbon storage and long-term rate of accumulation in high-altitude Andean peatlands of Bolivia

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    J.A. Hribljan

    2015-11-01

    Full Text Available (1 The high-altitude (4,500+ m Andean mountain range of north-western Bolivia contains many peatlands. Despite heavy grazing pressure and potential damage from climate change, little is known about these peatlands. Our objective was to quantify carbon pools, basal ages and long-term peat accumulation rates in peatlands in two areas of the arid puna ecoregion of Bolivia: near the village of Manasaya in the Sajama National Park (Cordillera Occidentale, and in the Tuni Condoriri National Park (Cordillera Real. (2 We cored to 5 m depth in the Manasaya peatland, whose age at 5 m was ca. 3,675 yr. BP with a LARCA of 47 g m-2 yr-1. However, probing indicated that the maximum depth was 7–10 m with a total estimated (by extrapolation carbon stock of 1,040 Mg ha-1. The Tuni peat body was 5.5 m thick and initiated ca. 2,560 cal. yr. BP. The peatland carbon stock was 572 Mg ha-1 with a long-term rate of carbon accumulation (LARCA of 37 g m-2 yr-1. (3 Despite the dry environment of the Bolivian puna, the region contains numerous peatlands with high carbon stocks and rapid carbon accumulation rates. These peatlands are heavily used for llama and alpaca grazing.

  6. The feedback between active tectonics, fluid flow and mineralization in an Andean geotermal reservoir

    Science.gov (United States)

    Reich, M.; Arancibia, G.; Perez, P.; Sanchez, P.; Cembrano, J. M.; Stimac, J. A.; Lohmar, S.

    2012-12-01

    In the Andean Cordillera of Central-Southern Chile, geothermal resources occur in close spatial relationship with active volcanism. The nature of the relationship between tectonics and volcanism in this region is the result of interaction between the crustal structures of the basement and the ongoing regional stress field, which is primarily controlled by the oblique convergence of the Nazca and South America Plates. Between 39° and 46°S, the volcanic and geothermal activity is controlled by the NNE-trending, 1,000 km long Liquiñe-Ofqui Fault Zone (LOFZ), an intra-arc dextral strike-slip fault system. Although there is consensus that volcanism (and hence geothermal activity) in southern Chile is largely controlled by the regional-scale tectonic stress field and architecture of the volcanic arc, there is limited scientific information about the role of local kinematic conditions on fluid flow and mineralization during the development and evolution of geothermal reservoirs. In this report, we present the preliminary results of an undergoing structural, mineralogical and geochemical study of the Tolhuaca geothermal system in southern Chile. The Tolhuaca geothermal reservoir formed as a liquid-dominated hydrothermal system, where shallow upflow resulted in near-boiling temperatures in a roughly horizontal liquid reservoir at 100-200 m depth (Melosh et al., 2010, 2012). In an early stage of evolution, hydrothermal brecciation and phase-separation (boiling) episodes penetrated at least 950 m depth into the deeper reservoir, and boiling was followed by steam-heated water invasion that cooled the reservoir. In a later stage, the preliminary conceptual model involves boiling and reheating of the reservoir, forming a system with deep hot brines that is connected to the shallow steam zone by an upflow conduit that is characterized by high-temperature mineralogy. The structural analysis of veins, fault-veins and faults of the Tol-1 drillcore (~1080 m depth) provide insights

  7. Andean uplift and Neogene climate change in the Atacama Desert

    Science.gov (United States)

    Rech, J. A.; Currie, B. S.; Jordan, T. E.

    2006-12-01

    Today the Andean Cordillera and Altiplano provide a major obstacle to atmospheric circulation over South America. The Altiplano Plateau prevents moist air masses from the Amazon Basin from reaching the Atacama Desert, causing the Atacama to be one of the driest places on Earth. Although Neogene sedimentary records from the western flank of the Andes should record the dramatic shift to hyperaridity that resulted from the growth of the Altiplano Plateau, the climatic implications of many sedimentary sequences have been difficult to decipher. The causes of the difficulties are complex, such as the relative influences of tectonics and active volcanism versus climate, and the roles of local as well as regional precipitation on groundwater and on the deposition of paludal sediments in basin centers. Over the last few years our research group has focused on using paleosols and the isotopic composition of palustrine carbonates in the Calama Basin (22°S) to try to identify a local precipitation signal and determine the onset of extreme hyperaridity as a consequence of the growth of the Altiplano. We have determined the soil morphological characteristics, salt chemistry, and mass independent fractionation anomalies (Δ17O values) in dated paleosols to reconstruct a Middle Miocene climatic transition from semi-aridity to extreme hyperaridity in the Atacama Desert. Paleosols along the southeastern margin of the Calama Basin change from calcic Vertisols with root traces, slickensides, and gleyed horizons to an extremely mature salic Gypsisol with pedogenic nitrate. We interpret this transition, which occurred between 19 and 13 Ma, to represent a change in precipitation from >200 mm/yr to Calama Basin also show a marked change during this time period. δ13C values of palustrine carbonates increase from -7 to +7? VPDB and δ18O values increases from -7 to +1? VPDB over the late to Middle Miocene time. This major trend towards more positive values is likely the result of several

  8. Paired Magmatic-Metallogenic Belts in Myanmar - an Andean Analogue?

    Science.gov (United States)

    Gardiner, Nicholas; Robb, Laurence; Searle, Michael; Morley, Christopher

    2015-04-01

    contrasting minerals endowment. The Mogok-Mandalay-Mergui (MMM) Belt hosts crustal-melt S-type granites with significant tin-tungsten mineralization, and contains the historically major tungsten deposit of Mawchi. The Wuntho-Popa Arc comprises I-type granites and granodiorites with porphyry-type copper-gold and epithermal gold mineralization, and includes the world-class Monywa copper mine. Recent U-Pb radiometric age dating has shown the potential for the two belts to be both active from the Late Cretaceous to Eocene. The spatial juxtaposition of these two sub-parallel belts, the implication of contemporary magmatism, and their distinct but consistent metallogenic endowment bears strong similarities to the metallogenic belts of the South American Cordillera. Here we investigate whether they together represent the magmatic and metallogenic expression of an Andean-type setting in Myanmar during the subduction of Neo-Tethys. In this analogue the Wuntho-Popa Arc represents a proximal I-type magmatic belt sited immediately above the eastwards-verging Neo-Tethys subduction zone. Exhibiting porphyry-type copper-gold and epithermal gold mineralization, this would therefore be the Myanmar equivalent of the Andean coastal copper belts. Conversely, the parallel MMM Belt, comprised of more distal crustal-melt S-type tin granites, would have an analogue in the Bolivian tin belt.

  9. Paleontologic and stratigraphic relations of phosphate beds in Upper Cretaceous rocks of the Cordillera Oriental, Colombia

    Science.gov (United States)

    Maughan, Edwin K.; Zambrano O., Francisco; Mojica G., Pedro; Abozaglo M., Jacob; Pachon P., Fernando; Duran R., Raul

    1979-01-01

    Phosphorite crops out in the Cordillera Oriental of the Colombian Andes in rocks of Late Cretaceous age as strata composed mostly of pelletal carbonate fluorapatite. One stratum of Santonian age near the base of the Galembo Member of the La Luna Formation crops out at many places in the Departments of Santander and Norte de Santander and may be of commercial grade. This stratum is more than one meter thick at several places near Lebrija and near Sardinata, farther south it is locally one meter thick or more near the base of the Guadalupe Formation in the Department of Boyaca. Other phosphorite beds are found at higher stratigraphic levels in the Galembo Member and the Guadalupe Formation, and at some places these may be commercial also. A stratigraphically lower phosphorite occurs below the Galembo Member in the Capacho Formation (Cenomanian age) in at least one area near the town of San Andres, Santander. A phosphorite or pebbly phosphate conglomerate derived from erosion of the Galembo Member forms the base of the Umir Shale and the equivalent Colon Shale at many places. Deposition of the apatite took place upon the continental shelf in marine water of presumed moderate depth between the Andean geosyncline and near-shore detrital deposits adjacent to the Guayana shield. Preliminary calculations indicate phosphorite reserves of approximately 315 million metric tons in 9 areas, determined from measurements of thickness, length of the outcrop, and by projecting the reserves to a maximum of 1,000 meters down the dip of the strata into the subsurface. Two mines were producing phosphate rock in 1969; one near Turmeque, Boyaca, and the other near Tesalia, Huila.

  10. Provenance through the limit: integrated provenance from the Devonian sedimentary and basement rocks from the northern segment of the Eastern Cordillera of the Colombian Andes

    Science.gov (United States)

    Cardona, Agustin; Valencia, Victor; Lotero, Andrea; Villafañez, Yohana; Augustsson, Carita; Bayona, German; Ibañez, Mauricio

    2013-04-01

    The provenance record of sedimentary rocks is sometimes the only available archive of the geological evolution in continuously active continental margins where continuous exhumation, erosion and along strike fragmentation of continental margins destroy geological evidences. New integrated provenance constraints from segmented exposures of Devonian rocks of the northern segment of the Eastern Cordillera of Colombia are used to reconstruct overimposed Paleozoic, Mesozoic and Cenozoic paleogeographic scenarios of the northern Andes. Sandstones from deltaic to platform environments are characterized by very high quartz contents, stable to ultrastable heavy minerals and mostly angular fragments. U-Pb detrital zircon geochronology reveals prominent Silurian to Ordovician and Mesoproterozoic (Grenvillian) age populations with minor Devonian zircons. Tourmaline geochemistry and detrital quarz characterization suggest prominent low grade metamorphic sources. These provenance fingerprints can be related to the erosion of the older metasedimentary basement exposed in the same region and record the transition from a terrane collisional event to the formation of a new subduction zone before the final Late Paleozoic events that end in the agglutination of Pangea. The U-Pb detrital record of the Devonian and basement rocks of the Eastern Cordillera are also comparable with Early to Middle Paleozic Paleozoic rocks form the Northern segment of the eastern Peruvian Andes re-inforcing the view of along strike terrane thousand of kilometer transport along the Mesozoic proto-Andean margin. Petrographic and heavy mineral petrofacies and stratigraphic correlation between Devonian localities are also used as piercing points to document Cenozoic ten of kilometers strike slip displacements along the northern termination of the Eastern Cordillera.

  11. Late Glacial-Holocene climatic transition record at the Argentinian Andean piedmont between 33–34° S

    Directory of Open Access Journals (Sweden)

    A. E. Mehl

    2013-10-01

    Full Text Available The Arroyo La Estacada (~33°28' S, 69°02' W, eastern Andean piedmont of Argentina, cuts through an extensive piedmont aggradational unit composed of a dominant late Pleistocene–early Holocene (LP–EH alluvial sequence including several paleosols. The arroyo sedimentary record exhibits a paleosol developed affecting the topmost part of likely Lateglacial aeolian deposits aggraded into a floodplain environment by the end of the late Pleistocene. The paleosol shows variable grade of development in the outcrops along the arroyo probably in relation to fluvial valley paleotopography. Organic matter humification, carbonate accumulation and redox processes were the dominant processes associated with paleosol formation. By the early Holocene, when the formation of the paleosol ended, alluvial aggradation renewed and a higher frequency of flooding events could have affected the arroyo's floodplain environment. A period of relative landscape stability in the Arroyo La Estacada basin is inferred from the paleosol developed by the LP–EH transition in response to a climatic amelioration in the Andes cordillera piedmont after the Late Glacial arid conditions. The renewal of early Holocene alluvial aggradation was probably influenced by the South American Monsoon and resulted in a change in the sedimentary dynamics of the arroyo. The analyzed Late Glacial-Holocene alluvial record of the Andean piedmont constitutes a suitable record of the LP–EH climatic transition at the extra Andean region of Argentina. It is in agreement with regional paleoclimatic evidence along the southern tip of the South American continent, where other sedimentary sequences record similar late Quaternary paleoenvironmental changes over both fluvial and interfluvial areas.

  12. 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.

  13. Varying mechanical coupling along the Andean margin: Implications for trench curvature, shortening and topography

    Science.gov (United States)

    Iaffaldano, G.; Di Giuseppe, E.; Corbi, F.; Funiciello, F.; Faccenna, C.; Bunge, H.-P.

    2012-03-01

    Convergent margins often exhibit spatial and temporal correlations between trench curvature, overriding plate shortening and topography uplift that provide insights into the dynamics of subduction. The Andean system, where the Nazca plate plunges beneath continental South America, is commonly regarded as the archetype of this class of tectonics systems. There is distinctive evidence that the degree of mechanical coupling between converging plates, i.e. the amount of resistive force mutually transmitted in the direction opposite to their motions, may be at the present-day significantly higher along the central Andean margin compared to the northern and southern limbs. However quantitative estimates of such resistance are still missing and would be desirable. Here we present laboratory models of subduction performed to investigate quantitatively how strong lateral coupling variations need to be to result in trench curvature, tectonic shortening and distribution of topography comparable to estimates from the Andean margin. The analogue of a two-layers Newtonian lithosphere/upper mantle system is established in a silicone putty/glucose syrup tank-model where lateral coupling variations along the interface between subducting and overriding plates are pre-imposed. Despite the simplicity of our setup, we estimate that coupling in the central margin as large as 20% of the driving force is sufficient to significantly inhibit the ability of the experimental overriding plate to slide above the subducting one. As a consequence, the central margin deforms and shortens more than elsewhere while the trench remains stationary, as opposed to the advancing lateral limbs. This causes the margin to evolve into a peculiar shape similar to the present-day trench of the Andean system.

  14. Climate Change Impacts in a Colombian Andean Tropical Basin

    Science.gov (United States)

    Ocampo, O. L.; Vélez, J. J.; Londoño, A.

    2012-12-01

    Climate change and climate variability have a large impact on water resources. Developing regions have less capacity to prepare for, respond to, and recover from climate-related hazards and effects, and then, populations may be disproportionately affected. In Colombia, the geographical location and the marked irregularity in the terrain, give as a result, a complex climate. These factors have contributed to the water supply of the territory. Unfortunately, the visualization of abundant and inexhaustible water resources created a great disregard for them. Besides, the water supply is not distributed uniformly across the country, and then there is water-deficit in some areas as Andean Region, where the largest population and the main development centers are located. In recent decades, water conflicts have emerged locally and regionally, which have generated a crisis in the allocation mechanisms and have improved the understanding of the water situation in Colombia. The Second National Communication to CCMNU alerts on possible future consequences of climate change and the need for regional studies for understanding climate change impacts on the fragile ecosystems of high mountains as paramos and fog forest, which are water production regulators. Colombian water resources are greatly affected by changes in rainfall patterns influenced by El Niño and La Niña. The recent disasters in the 2010-2011 rainy seasons have caught the attention of not only the authorities but from the scientific community to explore strategies to improve water management by tracking, anticipating and responding to climate variability and climate change. Whereas sound water management is built upon long-term, the country is undertaking a pilot exercise for the integrated management of water resources, five Basins are selected, among them, is the Chinchiná River Basin; this Andean tropical Basin is located on the western slopes at the central range in the Andes between 4°48 and 5°12 N

  15. A new species of Andean poison frog, Andinobates (Anura: Dendrobatidae), from the northwestern Andes of Colombia.

    Science.gov (United States)

    Amézquita, Adolfo; Márquez, Roberto; Medina, Ricardo; Mejía-Vargas, Daniel; Kahn, Ted R; Suárez, Gustavo; Mazariegos, Luis

    2013-01-01

    The poison frogs of the Colombian Andes, Pacific lowlands and Panama have been recently recognized as a new, monophyletic and well-supported genus: Andinobates. The species richness and distribution within Andinobates remain poorly understood due to the paucity of geographic, genetic and phenotypic data. Here we use a combination of molecular, bioacoustic and morphometric evidence to describe a new species of Andean poison frog: Andinobates cassidyhornae sp. nov. from the high elevation cloud forests of the Colombian Cordillera Occidental, in the northwestern Andes. The new species is associated to the bombetes group and characterized by a unique combination of ventral and dorsal color patterns. Data on 1119 bp from two mitochondrial markers allowed us to reject the null hypotheses that A. cassidyhornae sp. nov. is part of the phenotypically similar and geographically less distant species: A. opisthomelas, A. virolinensis or A. bombetes. The best available phylogenetic trees and the genetic distance to other Andinobates species further support this decision. Altogether, the advertisement call parameters unambiguously separated A. cassidyhornae sp. nov. calls from the calls of the three closest species. The new species adds to a poorly known and highly endangered genus of poison frogs that requires further studies and urgent conservation measures.

  16. Agronomic performance and stability of andean common bean lines with white grains in Brazil

    Directory of Open Access Journals (Sweden)

    Helton Santos Pereira

    2014-06-01

    Full Text Available This work evaluated the effect of genotype by environment interaction in Andean common bean lines with white grains, in Central Southern Brazil, to identify lines with high agronomic performance, stability and adaptability, aiming to meet domestic demand and to increase the Brazilian participation in the foreign market of common bean. Nineteen trials with twelve Andean lines were conducted in 2007, 2008 and 2009, in Central Southern Brazil. Grain yield and other agronomic traits were evaluated. Data were subjected to analysis of variance and of adaptability/stability using Annicchiarico and modified AMMI methods. Significant differences were found between lines for all traits evaluated. Genotype by environment interaction was important for lines with Andean origin and white seed. The utilization of weighted mean of absolute scores and yield with the AMMI results enabled the identification of the most stable and adapted lines. Lines Poroto Alubia, CNFB 16211, Ouro Branco and WAF 160 were stable and adapted, using both methods. CNFB 16211 line presented high agronomic performance, stability and adaptability and therefore this line may be a new cultivar. USWA 70 and WAF 75 lines presented grain size similar to that required by the foreign market and superior to the Brazilian cultivars, besides favorable agronomic traits, and thus these lines may be indicated as new cultivars.

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Science.gov (United States)

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

    2009-12-01

    Laguna Yuraicocha in the western cordillera of the central Peruvian Andes (12.53°S; 75.50°W; 4460 masl) is dammed by late glacial moraines and is underlain and surrounded by Jurassic and Cretaceous limestone interbedded with siliciclastic rocks. A 6.9 meter-long sediment core from the distal end of the lake is dominated by authigenic calcite (marl) with a mean concentration of 82 weight percent that has accumulated at a rate of ~ 1 mm yr-1 for the past 6200 years. The age model for the core is based on a combination of 210Pb and AMS 14C ages from charcoal; modern lake water is ~1‰ evaporatively enriched from mean regional precipitation. Marl samples were taken with an average sampling interval of 8 years; samples were treated to remove organic matter, sieved to concentrate the Andes. Subcentennial variance in 18O with an ~2‰ amplitude is persistent throughout the record. Time series analysis reveals strength in the 5-12 year window, which may record the influence of ENSO on the hydrologic balance of the region through its effect on the strength of the South American summer monsoon. Spectral strength is also present in the 40-200 year periodicity and this spectral component appears to weaken in the last millennium. The progressive increase in hydrologic balance during the middle-late Holocene is consistent with glacial geologic evidence for the onset of neoglaciation in the Peruvian Andes, including the dramatic reformation of the Quelccaya Ice Cap ~5100 years ago. This appears to confirm the notion that Andean glaciers, especially those in the southern and western cordillera of Peru and Bolivia, are especially sensitive to changes in regional moisture balance.

  19. Tropical high-altitude Andean lakes located above the tree line attenuate UV-A radiation more strongly than typical temperate alpine lakes.

    Science.gov (United States)

    Aguilera, Ximena; Lazzaro, Xavier; Coronel, Jorge S

    2013-09-01

    Tropical high-altitude Andean lakes are physically harsh ecosystems. Located above the treeline (≥4000 m a.s.l.), they share common features with temperate alpine lakes, which impose extreme conditions on their aquatic organisms: e.g., strong winds, broad diel variations in water temperature, and intense solar ultraviolet radiation (UVR). However, because of their latitude, they differ in two major ecological characteristics: they lack ice cover during the winter and they do not present summer water column stratification. We sampled 26 tropical high-altitude Andean lakes from three regions of the Bolivian Eastern Andes Cordillera during the wet period (austral summer). We performed an ordination to better describe the typology of Andean lakes in relation to the environmental variables, and we assessed the relationships among them, focussing on the UV-A transparency (360 nm) throughout the water column. We found a positive correlation between UV-A transparency calculated as Z(1%) (the depth which reaches 1% of the surface UV-A), the lake maximum depth and Secchi transparency (r = 0.61). Z(1%) of UV-A was smaller in shallow lakes than in deep lakes, indicating that shallow lakes are less transparent to UV-A than deep lakes. We hypothesize that, compared to shallow lakes, deep lakes (maximum depth > 10 m) may have lower dissolved organic carbon (DOC) concentrations (that absorb UV radiation) due to lower temperature and reduced macrophyte cover. Based on our data, tropical high-altitude Andean lakes are less transparent to UV-A (K(d) range = 1.4-11.0 m(-1); Z(1%) depth range = 0.4-3.2 m) than typical temperate alpine lakes (1-6 m(-1), 3-45 m, respectively). Moreover, they differ in vertical profiles of UV-A, chlorophyll-a, and temperature, suggesting that they may have a distinct ecological functioning. Such peculiarities justify treating tropical high-altitude Andean lakes as a separate category of alpine lakes. Tropical high-altitude Andean lakes have been poorly

  20. The recycled orogenic sand provenance from an uplifted thrust belt, Betic Cordillera, Southern Spain

    OpenAIRE

    Critelli, Salvatore; Arribas Mocoroa, José; Le Pera, Emilia; Tortosa, A; Marsaglia, Kathleen M.; Latter, Kelly K.

    2003-01-01

    The Betic Cordillera of southern Spain represents an uplifted foreland fold–thrust belt. Source rock types of the Betic Cordillera include metamorphic (mainly phyllite, schist, quartzite, and gneiss), sedimentary (siliciclastic and carbonate), volcanic (felsic to intermediate pyroclasts), and mantle-derived (peridotite, gabbro, serpentinite, and serpentine schist) rocks. The fluvial systems range that transect the Betic Cordillera are the major detrital source of sediment ...

  1. 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.

  2. Growth and gravitational collapse of a mountain front of the Eastern Cordillera of Colombia

    Science.gov (United States)

    Kammer, Andreas; Montana, Jorge; Piraquive, Alejandro

    2016-04-01

    The Eastern Cordillera of Colombia is bracketed between the moderately east-dipping flank of the Central Cordillera on its western and the gently bent Guayana shield on its eastern side. It evolved as a response to a considerable displacement transfer from the Nazca to the Southamerican plate since the Oligocene break-up of the Farallon plate. One of its distinctive traits refers to its significant shortening by penetrative strain at lower and folding at higher structural levels, approximating a wholesale pure-shear in analogy to a vice model or a crustal welt sandwiched between rigid buttresses. This contrasting behavior may be explained by the spatial coincidence between Neogene mountain belt and a forebulge that shaped the foreland trough during a Cretaceous subduction cycle and was very effective in localizing a weakening of the backarc region comprised between two basin margin faults. In this paper we examine a two-phase evolution of the Eastern mountain front. Up to the late Miocene deformation was restrained by the inherited eastern basin margin fault and as the cordilleran crust extruded, a deformation front with an amplitude similar the present structural relief of up to 10.000 m may have built up. In the Pliocene convergence changed from a roughly strike-perpendicular to an oblique E-W direction and caused N-S trending faults to branch off from the deformation front. This shortening was partly driven by a gravitational collapse of the Miocene deformation front, that became fragmented by normal faults and extruded E on newly formed Pliocene thrust faults. Normal faults display displacements of up to 3000 m and channelized hydrothermal fluids, leading to the formation of widely distributed fault breccias and giving rise to a prolific Emerald mineralization. In terms of wedge dynamics, the Pliocene breaching of the early formed deformation front helped to establish a critical taper.

  3. The magmatic history of the Vetas-California mining district, Santander Massif, Eastern Cordillera, Colombia

    Science.gov (United States)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Valencia, Víctor; Hart, Craig J. R.

    2013-08-01

    The Vetas-California Mining District (VCMD), located in the central part of the Santander Massif (Colombian Eastern Cordillera), based on U-Pb dating of zircons, records the following principal tectono-magmatic events: (1) the Grenville Orogenic event and high grade metamorphism and migmatitization between ˜1240 and 957 Ma; (2) early Ordovician calc-alkalic magmatism, which was synchronous with the Caparonensis-Famatinian Orogeny (˜477 Ma); (3) middle to late Ordovician post-collisional calc-alkalic magmatism (˜466-436 Ma); (4) late Triassic to early Jurassic magmatism between ˜204 and 196 Ma, characterized by both S- and I-type calc-alkalic intrusions and; (5) a late Miocene shallowly emplaced intermediate calc-alkaline intrusions (10.9 ± 0.2 and 8.4 ± 0.2 Ma). The presence of even younger igneous rocks is possible, given the widespread magmatic-hydrothermal alteration affecting all rock units in the area. The igneous rocks from the late Triassic-early Jurassic magmatic episodes are the volumetrically most important igneous rocks in the study area and in the Colombian Eastern Cordillera. They can be divided into three groups based on their field relationships, whole rock geochemistry and geochronology. These are early leucogranites herein termed Alaskites-I (204-199 Ma), Intermediate rocks (199-198 Ma), and late leucogranites, herein referred to as Alaskites-II (198-196 Ma). This Mesozoic magmatism is reflecting subtle changes in the crustal stress in a setting above an oblique subduction of the Panthalassa plate beneath Pangea. The lower Cretaceous siliciclastic Tambor Formation has detrital zircons of the same age populations as the metamorphic and igneous rocks present in the study area, suggesting that the provenance is related to the erosion of these local rocks during the late Jurassic or early Cretaceous, implying a local supply of sediments to the local depositional basins.

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

    Directory of Open Access Journals (Sweden)

    Violeta A. Silvestro

    2012-12-01

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

  5. Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson Glacier

    Science.gov (United States)

    Chisolm, R. E.; Mckinney, D. C.; Gomez, J.; Voss, K.

    2012-12-01

    Tropical glaciers are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glacier mass balance. This study presents GPR data taken in July 2012 at the Arteson glacier in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson glacier, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson glacier. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson glacier, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating glacier are key to assessing the flood risk from this dynamic three-lake system. Because the glacier mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson glacier and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of

  6. Climatic forcing of asymmetric orogenic evolution in the Eastern Cordillera of Colombia

    NARCIS (Netherlands)

    Mora, A.; Parra, M.; Strecker, M.R.; Sobel, R.A.; Hooghiemstra, H.; Torres, V.; Vallejo Jaramillo, J.

    2008-01-01

    New apatite fission-track data, paleoelevation estimates from paleobotany, and recently acquired geological data from the Eastern Cordillera of Colombia document the onset of increased exhumation rates in the northeastern Andes at ca. 3 Ma. The Eastern Cordillera forms an efficient orographic barrie

  7. A new species of salamander (Bolitoglossa: Plethodontidae from the Cordillera Oriental of the Colombian Andes

    Directory of Open Access Journals (Sweden)

    Andrés R. Acosta-Galvis

    2012-01-01

    Full Text Available Eight species of salamanders are recognized to Cordillera Oriental of Colombia. Here we describe a new species of the genus Bolitoglossa, named Bolitoglossa guaneae sp. nov. The highest number of species of this genus is found in the cloud forests located in the western flank of the Cordillera Oriental.

  8. Birds of Two Oceans? Trans-Andean and Divergent Migration of Black Skimmers (Rynchops niger cinerascens from the Peruvian Amazon.

    Directory of Open Access Journals (Sweden)

    Lisa C Davenport

    Full Text Available Seasonal flooding compels some birds that breed in aquatic habitats in Amazonia to undertake annual migrations, yet we know little about how the complex landscape of the Amazon region is used seasonally by these species. The possibility of trans-Andes migration for Amazonian breeding birds has largely been discounted given the high geographic barrier posed by the Andean Cordillera and the desert habitat along much of the Pacific Coast. Here we demonstrate a trans-Andes route for Black Skimmers (Rynchops niger cinerascens breeding on the Manu River (in the lowlands of Manu National Park, Perú, as well as divergent movement patterns both regionally and across the continent. Of eight skimmers tracked with satellite telemetry, three provided data on their outbound migrations, with two crossing the high Peruvian Andes to the Pacific. A third traveled over 1800 km to the southeast before transmissions ended in eastern Paraguay. One of the two trans-Andean migrants demonstrated a full round-trip migration back to its tagging location after traveling down the Pacific Coast from latitude 9° South to latitude 37° S, spending the austral summer in the Gulf of Arauco, Chile. This is the first documentation of a trans-Andes migration observed for any bird breeding in lowland Amazonia. To our knowledge, this research also documents the first example of a tropical-breeding waterbird migrating out of the tropics to spend the non-breeding season in the temperate summer, this being the reverse pattern with respect to seasonality for austral migrants in general.

  9. Soil organic matter dynamics at the paramo and puna highlands in the Andean mountains

    Science.gov (United States)

    Ángeles Muñoz, M.; Faz, Ángel; Mermut, Ahmet R.; Zornoza, Raúl

    2014-05-01

    Mountains and uplands represent the most diverse and fragile ecosystems in the world, cover about 20% of the terrestrial surface and are distributed across all continents and major ecoregions. The Andean Plateau is the main mountain range of the American continent and one of the largest in the world with more than 7,500 km. The soil organic matter is a corner stone in the fertility management of the Andean agriculture as well as in the erosion control. However, its role is still much unknown in these ecosystems. Moreover, the influence of current global climatic change on soil organic C reservoirs and dynamics is still not clearly understood. The aim of this work was to review the soil C dynamics and the implication of the soil organic matter in the fertility management, erosion control, conservation of biodiversity and global climate change to improve the knowledge on the mountain Andean highlands. Climate, landscape, soil C pools, biomass and management were studied. In general, the Andean climate is affected by three main factors: ocean currents, winds and orography characterized by an abrupt topography. The entire Andean belt is segmented into the Northern, Central and Southern Andes. Northern Andes are called paramo and are characterized by humid climate while Central and Southern Andes dryer zones are called puna. Most of the region is tectonically and volcanically active. Sedimentary rocks predominated in the paramo while sedimentary, igneous and metamorphic ones prevailed in the puna. The most common soils were Andosols, Regosols, Umbrisols and Histosols. The cold and wet climate and the low atmospheric pressure favored organic matter accumulation in the soil. The accumulation of organic matter is further enhanced by the formation of organomineral complexes strongly resistant to the microbial breakdown mainly in the paramo. High organic C contents were observed in the paramo (10%) oppositely to the low contents found in the dryer puna (1%). The C/N ratio

  10. Nuclear ribosomal internal transcribed spacer 1 (ITS1) variation in the Anastrepha fraterculus cryptic species complex (Diptera, Tephritidae) of the Andean region

    Science.gov (United States)

    The nuclear ribosomal internal transcribed spacer 1 (ITS1) was sequenced for Anastrepha fraterculus (Wiedemann, 1830) originating from 85 collections from the northern and central Andean countries of South America including Argentina (Tucumán), Bolivia, Perú, Ecuador, Colombia, and Venezuela. The IT...

  11. The new Andean Regional Office of Astronomy for Development (ROAD)

    Science.gov (United States)

    Char, Farid; Forero-Romero, Jaime

    2015-08-01

    The Andean Regional Office of Astronomy for Development (ROAD) is a new effort in South America to serve several goals in astronomical development. Six countries (Bolivia, Colombia, Chile, Ecuador, Perú and Venezuela) will work together, representing a common language block in the Andean region and focusing on develop strategies to strengthen the professional research, education and popularization of astronomy. Our current Working Structure comprises a ROAD Coordinator and Coordinators per Task Force, as well as Organizing Committees, Collaborators and Volunteers.The participating institutions of this new ROAD have been involved in many projects involving each of the current OAD’s Task Forces: research, schools and children and public, exploring educational activities/material to be shared among the Andean countries, standardizing the knowledge and creating inspirational experiences. We expect to generate many efforts in order to bring a more homogeneous activity in each Andean country, taking into account the special role of Chile in global astronomy, due to its great conditions for astronomy and the involvement of many professional observatories, universities and astronomy institutions.Our current (and upcoming) most relevant activities includes: Andean Schools on Astronomy, Andean Graduate Program and Massive Open Online Courses (TF1); Virtual Training Sessions and Teaching material for the visually impaired students; Annual TF2 meeting to gather all the collaborators (TF2); Development for planetariums and Communicating Astronomy with the Public (TF3). The Andean region, in the other hand, will also be involved in at least two important events: the CAP Meeting in May 2016 and the XV LARIM in October 2016 (both in Colombia); and Chile will bid to host the XXXI IAU GA in 2021, with the aim of show the great advances in astronomical development from the Andean region and South America.

  12. Thermal and exhumation history of the Coastal Cordillera arc of northern Chile revealed by thermochronological dating

    Science.gov (United States)

    Juez-Larré, Joaquim; Kukowski, Nina; Dunai, Tibor J.; Hartley, Adrian J.; Andriessen, Paul A. M.

    2010-11-01

    The thermal and erosional history of convergent plate boundaries is important for understanding the links between subduction, arc magmatism, genesis of ore deposits, topography and climate of orogenic belts. Unlike the continent-continent collision that formed many of the largest orogenic belts known today, the Central Andes of South America is a unique case where an oceanic-continent collision has given rise to the Earth's longest and second tallest orogenic belt. Over the last thirty years a plethora of models have been suggested in an attempt to explain how a plateau-type orogen formed at the leading edge of western South America. In the Central Andes most research have focussed attention on the study of the evolution of the arc and backarc, since continuous subduction erosion of the forearc has left little trace of the interplate dynamics that initiated the orogenic belt. In this article, we present a new insight into the thermal and exhumation history of the forearc along the Coastal Cordillera of northern Chile based on biotite K-Ar, apatite fission-track, and apatite/zircon (U-Th)/He dating. We collected diorite samples in a 2 km thick crustal section at the coastal cliff (~ 22°S), and a sea level isoelevation profile between 21 and 27°S. Results from all three dating methods show that the cooling of Coastal Cordillera took place shortly after emplacement during a period of rifting in Jurassic times. Cooling took place in two episodes, mainly in Late Jurassic-Early Cretaceous (~ 118-152 Ma) but also during Late Cretaceous (60-80 Ma) due to the resumption of compression, rift closure, arc uplift, exhumation, eastward migration of magmatic arc activity, and thermal relaxation. The youngest apatite (U-Th)/He ages reveal a cooling event, never reported previously, between 40 and 50 Ma (Eocene). This thermal event affected a > 500 km long and > 1 km thick section of the Coastal Cordillera in northern Chile. Rock cooling recorded in the Eocene cannot be

  13. Multiple glacial culminations from the Lateglacial to the late Holocene in central and southern Peru (Invited)

    Science.gov (United States)

    Licciardi, J. M.; Schaefer, J. M.; Rodbell, D. T.; Stansell, N.; Schweinsberg, A.; Finkel, R. C.; Zimmerman, S. R.

    2013-12-01

    Fluctuations in small tropical mountain glaciers serve as sensitive indicators of variations in past and present-day climate. Most of the world's modern tropical glaciers reside in the Peruvian Andes, where a growing number of well-dated glacial records have recently been developed. As additional records are documented, regional patterns of late Pleistocene to Holocene glacial activity have begun to emerge. Here we present a compilation of new and previously obtained 10Be surface exposure ages from boulders on well-preserved moraine successions in two glaciated Andean ranges: the Cordillera Vilcabamba of southern Peru (13°20'S, 72°32'W) and the Huaguruncho massif (10°32'S, 75°56'W), located in central Peru ~450 km northwest of the Vilcabamba. A high-resolution composite chronology that merges >100 10Be measurements on moraine sequences in five glaciated drainages of the Cordillera Vilcabamba reveals the occurrence of at least five discrete glacial culminations from the Lateglacial to the late Holocene. At the Huaguruncho massif, >20 10Be exposure ages obtained from moraine sequences in a south-facing cirque indicate at least three major glacial stages spanning the Lateglacial to the Little Ice Age. The moraine ages at Huaguruncho are broadly correlative with the Vilcabamba moraine chronologies, with some dated moraine belts exhibiting geomorphic expressions that closely resemble those of their coeval counterparts in the Vilcabamba. A recurring finding in both field areas is a mismatch between basal radiocarbon ages from bog and lake sediments and 10Be exposure ages on outboard moraines, which enclose the depositional basins. These age discrepancies suggest that cosmogenic 10Be production rates scaled to high altitudes in the tropics are substantially lower than previous estimates. While we anticipate that future refinements to scaled isotope production rates may significantly affect correlation of 10Be exposure ages in the high Andes with ages derived from

  14. Andean tectonics: Implications for Satellite Geodesy

    Science.gov (United States)

    Allenby, R. J.

    1984-09-01

    Current knowledge and theories of large scale Andean tectonics as they relate to site planning for the NASA Crustal Dynamics Program's proposed high precision geodetic measurements of relative motions between the Nazca and South American plates are summarized. The Nazca Plate and its eastern margin, the Peru-Chile Trench, is considered a prototype plate marked by rapid motion, strong seismicity and well defined boundaries. Tectonic activity across the Andes results from the Nazca Plate subducting under the South American plate in a series of discrete platelets with different widths and dip angles. This in turn, is reflected in the tectonic complexity of the Andes which are a multitutde of orogenic belts superimposed on each other since the Precambrian. Sites for Crustal Dynamics Program measurements are being located to investigate both interplate and extraplate motions. Observing operations have already been initiated at Arequipa, Peru and Easter Island, Santiago and Cerro Tololo, Chile. Sites under consideration include Iquique, Chile; Oruro and Santa Cruz, Bolivia; Cuzco, Lima, Huancayo and Bayovar, Peru; and Quito and the Galapagos Islands, Ecuador. Based on scientific considerations, Santa Cruz, Huancayo (or Lima), Quito and the Galapagos Islands should be replaced by Isla San Felix, Chile; Brazilia or Petrolina, Brazil; and Guayaquil, Ecuador. If resources permit, additional important sites would be Buenaventura and Villavicencio or Puerto La Concordia, Colombia; and Mendoza and Cordoba, Argentina.

  15. Nuclear ribosomal internal transcribed spacer 1 (ITS1) variation in the Anastrepha fraterculus cryptic species complex (Diptera, Tephritidae) of the Andean region

    OpenAIRE

    Sutton, Bruce D.; Steck, Gary J.; Norrbom, Allen L.; Rodriguez, Erick J.; Srivastava,Pratibha; Alvarado, Norma Nolazco; Colque, Fredy; Landa, Erick Yábar; Sánchez,Juan José Lagrava; Quisberth, Elizabeth; Peñaranda, Emilio Arévalo; Clavijo, P. A. Rodriguez; Alvarez-Baca,Jeniffer K.; Zapata,Tito Guevara; Ponce, Patricio

    2015-01-01

    Abstract The nuclear ribosomal internal transcribed spacer 1 (ITS1) was sequenced for Anastrepha fraterculus (Wiedemann, 1830) originating from 85 collections from the northern and central Andean countries of South America including Argentina (Tucumán), Bolivia, Perú, Ecuador, Colombia, and Venezuela. The ITS1 regions of additional specimens (17 collections) from Central America (México, Guatemala, Costa Rica, and Panamá), Brazil, Caribbean Colombia, and coastal Venezuela were sequenced and t...

  16. Holocene denudation and landscape deformation in the Cordillera Blanca, Peru

    Science.gov (United States)

    Hodson, K. R.; Hall, S. R.; Michalak, M.; Farber, D.; Hourigan, J. K.

    2012-12-01

    Active orogenic systems are subject to a host of processes that influence their topographic and structural evolution. Broadly speaking, these processes can be divided into two general groups: tectonics and climate. Both are capable of inducing profound changes within an orogen, although many specifics regarding their forcings, interactions, and feedbacks remain unclear. Here, we address the evolution of the Cordillera Blanca Mountain Range of northern Peru: an elevated, high-relief, 200km long string of glaciated peaks along the spine of the Andes. The striking Cordillera Blanca Detachment Fault (CBDF) is actively facilitating the production of several kilometers of relief along the western flank of the range, and abundant records of past glaciations span from >440 ka to the present. Thus, tectonics (active faulting) and climate (glacial erosion) are operating in tandem to produce some of the highest topography in the western hemisphere, affording the opportunity to investigate their potential interactions. Through the use of cosmogenic 10Be, low temperature thermochronology and digital terrain analysis we characterize the rates of landscape change as well as the present morphology. Significant variation in range elevation (maximum, mean, modal and minimum), relief (local and within basins) and slope (maximum, mean and minimum) exist along the strike of the range, potentially reflecting variable displacement along the CBDF, varying degrees of glacial erosion along the mountain range, or some combination of the two. The morphology of the adjacent supradetachment basin varies as well, containing zones with distinct styles of faulting and basin growth likely defined by the segmentation history of the CBDF. New thermochronologic data extends the current dataset, which we combine with 10Be basin-averaged erosion rates from basins along the range. These two datasets constrain the exhumational and erosional history of the range-forming Cordillera Blanca Batholith from the

  17. 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.

  18. Recent glacier retreat and climate trends in Cordillera Huaytapallana, Peru

    Science.gov (United States)

    López-Moreno, J. I.; Fontaneda, S.; Bazo, J.; Revuelto, J.; Azorin-Molina, C.; Valero-Garcés, B.; Morán-Tejeda, E.; Vicente-Serrano, S. M.; Zubieta, R.; Alejo-Cochachín, J.

    2014-01-01

    We analyzed 19 annual Landsat Thematic Mapper images from 1984 to 2011 to determine changes of the glaciated surface and snow line elevation in six mountain areas of the Cordillera Huaytapallana range in Peru. In contrast to other Peruvian mountains, glacier retreat in these mountains has been poorly documented, even though this is a heavily glaciated area. These glaciers are the main source of water for the surrounding lowlands, and melting of these glaciers has triggered several outburst floods. During the 28-year study period, there was a 55% decrease in the surface covered by glaciers and the snowline moved upward in different regions by 93 to 157 m. Moreover, several new lakes formed in the recently deglaciated areas. There was an increase in precipitation during the wet season (October-April) over the 28-year study period. The significant increase in maximum temperatures may be related to the significant glacier retreat in the study area. There were significant differences in the wet season temperatures during El Niño (warmer) and La Niña (colder) years. Although La Niña years were generally more humid than El Niño years, these differences were not statistically significant. Thus, glaciers tended to retreat at a high rate during El Niño years, but tended to be stable or increase during La Niña years, although there were some notable deviations from this general pattern. Climate simulations for 2021 to 2050, based on the most optimistic assumptions of greenhouse gas concentrations, forecast a continuation of climate warming at the same rate as documented here. Such changes in temperature might lead to a critical situation for the glaciers of the Cordillera Huaytapallana, and may significantly impact the water resources, ecology, and natural hazards of the surrounding areas.

  19. On the Nature of Cross-Linguistic Transfer: A Case Study of Andean Spanish

    Science.gov (United States)

    Muntendam, Antje G.

    2013-01-01

    This paper presents the results of a study on cross-linguistic transfer in Andean Spanish word order. In Andean Spanish the object appears in preverbal position more frequently than in non-Andean Spanish, which has been attributed to an influence from Quechua (a Subject-Object-Verb language). The high frequency of preverbal objects could be…

  20. Constraining the crustal root geometry beneath the Rif Cordillera (North Morocco)

    Science.gov (United States)

    Diaz, Jordi; Gil, Alba; Carbonell, Ramon; Gallart, Josep; Harnafi, Mimoun

    2016-04-01

    The analyses of wide-angle reflections of controlled source experiments and receiver functions calculated from teleseismic events provide consistent constraints of an over-thickened crust beneath the Rif Cordillera (North Morocco). Regarding active source data, we investigate now offline arrivals of Moho-reflected phases recorded in RIFSIS project to get new estimations of 3D crustal thickness variations beneath North Morocco. Additional constrains on the onshore-offshore transition are derived from onland recording of marine airgun shots from the coeval Gassis-Topomed profiles. A regional crustal thickness map is computed from all these results. In parallel, we use natural seismicity data collected throughout TopoIberia and PICASSO experiments, and from a new RIFSIS deployment, to obtain teleseismic receiver functions and explore the crustal thickness variations with a H-κ grid-search approach. The use of a larger dataset including new stations covering the complex areas beneath the Rif Cordillera allow us to improve the resolution of previous contributions, revealing abrupt crustal changes beneath the region. A gridded surface is built up by interpolating the Moho depths inferred for each seismic station, then compared with the map from controlled source experiments. A remarkably consistent image is observed in both maps, derived from completely independent data and methods. Both approaches document a large modest root, exceeding 50 km depth in the central part of the Rif, in contrast with the rather small topographic elevations. This large crustal thickness, consistent with the available Bouguer anomaly data, favor models proposing that the high velocity slab imaged by seismic tomography beneath the Alboran Sea is still attached to the lithosphere beneath the Rif, hence pulling down the lithosphere and thickening the crust. The thickened area corresponds to a quiet seismic zone located between the western Morocco arcuate seismic zone, the deep seismicity area

  1. Nuclear ribosomal internal transcribed spacer 1 (ITS1) variation in the Anastrepha fraterculus cryptic species complex (Diptera, Tephritidae) of the Andean region

    Science.gov (United States)

    Sutton, Bruce D.; Steck, Gary J.; Norrbom, Allen L.; Rodriguez, Erick J.; Srivastava, Pratibha; Alvarado, Norma Nolazco; Colque, Fredy; Landa, Erick Yábar; Sánchez, Juan José Lagrava; Quisberth, Elizabeth; Peñaranda, Emilio Arévalo; Clavijo, P. A. Rodriguez; Alvarez-Baca, Jeniffer K.; Zapata, Tito Guevara; Ponce, Patricio

    2015-01-01

    Abstract The nuclear ribosomal internal transcribed spacer 1 (ITS1) was sequenced for Anastrepha fraterculus (Wiedemann, 1830) originating from 85 collections from the northern and central Andean countries of South America including Argentina (Tucumán), Bolivia, Perú, Ecuador, Colombia, and Venezuela. The ITS1 regions of additional specimens (17 collections) from Central America (México, Guatemala, Costa Rica, and Panamá), Brazil, Caribbean Colombia, and coastal Venezuela were sequenced and together with published sequences (Paraguay) provided context for interpretation. A total of six ITS1 sequence variants were recognized in the Andean region comprising four groups. Type I predominates in the southernmost range of Anastrepha fraterculus. Type II predominates in its northernmost range. In the central and northern Andes, the geographic distributions overlap and interdigitate with a strong elevational effect. A discussion of relationships between observed ITS1 types and morphometric types is included. PMID:26798259

  2. Peculiar seismotectonic characteristics of Nazca's subducted slab, in the Andean region: Why do they exist?

    Science.gov (United States)

    Berrocal, J.; Fernandes, C.

    2007-05-01

    The peculiar morphology of Wadati-Benioff Zone (WBZ) beneath Andean region presents controversial seismotectonic characteristics of the subducting Nazca plate beneath South American plate: WBZ with an almost flat behaviour under Central-Northern Peru region, and beneath Central Chile region, intercalated with steeply portion of the slab; the almost completely aseismic portion between 300 and 500 km of depth; the existence of deep earthquakes in South American and their controversial focal mechanism. There are several hypotheses trying to explain a suitable origin for those deep earthquakes that occur in depths between 500 and almost 700 km, where the occurrence of brittle failure is improbable to exist due to the presence of high temperature and pressure conditions at those depths. We propose in this work - based mainly in the spatial distribution of relocated hypocentres, and in the joint interpretation with recent published results related to seismotectonic aspects of Andean region - a top-to- northwest shear of the portion of Nazca subducting plate between 24°S and 01°S, in such an amount that its deepest corresponding extremes, at around 600 km of depth, seem to be presently, under latitudes between 29°S and 06°S, respectively. The proposed northwestern displacement of South American plate may be provoking that shear process of Nazca slab, which should be larger at shallower depths of the slab, and limited to those latitudes below the Andean region. The NW displacement of Nazca slab could explain the existence of flat subduction beneath Central-Northern Peru region as a consequence of a probable northwards migration of the buoyant Nazca ridge after subduction under South American plate in around 15°S. Similar explanation could be used for the flat WBZ beneath Central Chile and the Juan Fernandez ridge. This hypothesis permits to infer for some very deep South American earthquakes shear, planar mechanisms at high pressure, some times as almost horizontal

  3. La cordillera como elemento significativo que permite entender la condición del narrador en Al oído de la cordillera

    OpenAIRE

    2015-01-01

    La obra de Ignacio Piedrahíta es un relato de viaje que narra la travesía de un hombre desde Colombia hasta Tierra del Fuego en la Argentina. A través del recorrido el narrador reflexiona sobre sí a partir de la observación de la naturaleza. De allí que este trabajo busque: primero destacar cómo el espacio-tiempo de la cordillera, estructura la forma y el contenido de la obra; segundo, entender la cordillera como un texto permite los efectos de meditación y de narrativa de la experiencia del ...

  4. Lead isotopic evidence for evolutionary changes in magma-crust interaction, Central Andes, southern Peru

    Energy Technology Data Exchange (ETDEWEB)

    Barreiro, B.A. (California Univ., Santa Barbara (USA). Dept. of Geological Sciences); Clark, A.H. (Queen' s Univ., Kingston, Ontario (Canada). Dept. of Geological Sciences)

    1984-07-01

    Lead isotopic measurements were made on Andean igneous rocks of Jurassic to Recent age in Moquegua and Tacna Departments, southernmost Peru, to clarify the petrogenesis of the rocks and, in particular, to investigate the effect of crustal thickness on rock composition. This location in the Cordillera Occidental is ideal for such a study because the ca. 2 Ga Precambrian basement rocks (Arequipa massif) have a distinct Pb isotopic signature which is an excellent tracer of crustal interaction, and because geomorphological research has shown that the continental crust was here thickened drastically in the later Tertiary.

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

    Directory of Open Access Journals (Sweden)

    F. Martínez

    2015-08-01

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

  6. Postmodern Anthropology: Reflections from Andean Ethnohistory

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    Villarías-Robles, Juan J. R.

    2008-06-01

    Full Text Available The postmodern perspective, which began its influence on studies of Prehispanic Peru in the 1980s, has resulted —as chief positive effect— in reflection and debate concerning the written sources for apprehending such cultural otherness, the so-called “Chronicles of the West Indies”: a perspective accompanied by new editions of these texts. The author of the present article expresses his own reflection on such change in theory and method. He argues that, with regard to self-reflectivity on its epistemological foundations, the new perspective is not entirely original in the long history of Andean ethnohistory; in effect, this approach is almost as old as the field itself. What is indeed original is the cognitive relativism that surfaced in some extreme forms of the discussion. It was an unfortunate development, however: when not denying, as a matter of principle, the very possibility of understanding that cultural otherness, arguments masked actual interpretations or explanations of its features that were protected, ipso facto, from a rigorous process of validation.

    La perspectiva posmoderna, que empezó a ser influyente en los estudios del Perú prehispánico en la década de 1980, ha tenido como principal efecto positivo la reflexión y el debate sobre las fuentes originales de conocimiento de esa alteridad cultural, las llamadas genéricamente “Crónicas de Indias”: una perspectiva acompañada de nuevas ediciones de tales textos. El autor del presente artículo hace aquí su propia reflexión sobre este cambio teórico y metodológico. Plantea que, en lo que tiene de discusión sobre sus bases epistemológicas, no es del todo original en la larga historia de la etnohistoria peruanista. Es, de hecho, casi tan antiguo como ella. Lo que sí ha sido original es el relativismo cognitivo que ha acompañado a algunas expresiones extremas de la discusión. Pero fue ésta una novedad desafortunada: cuando no negaba por principio la

  7. Andean shrublands of Moquegua, South Peru: Prepuna plant communities

    NARCIS (Netherlands)

    Montesinos, D.B.; Cleef, A.M.; Sykora, K.V.

    2012-01-01

    A syntaxonomic overview of shrubland vegetation in the southern Andean regions of Peru is presented. For each plant community, information is given on physiognomy, floristic diversity, ecology and geographical distribution. The shrub vegetation on the slopes of the upper Tambo river valley includes

  8. The astronomy of Andean myth: The history of a cosmology

    Science.gov (United States)

    Sullivan, William F.

    It is shown that Andean myth, on one level, represents a technical language recording astronomical observations of precession and, at the same time, an historical record of simultaneous social and celestial transformations. Topographic and architectural terms of Andean myth are interpreted as a metaphor for the organization of and locations on the celestial sphere. Via ethoastronomical date, mythical animals are identified as stars and placed on the celestial sphere according to their topographical location. Tested in the planetarium, these arrays generate cluster of dates - 200 B.C. and 650 A.D. Analysis of the names of Wiraqocha and Manco Capac indicates they represent Saturn and Jupiter and that their mythical meeting represents their conjunction in 650 A.D. The astronomy of Andean myth is then used as an historical tool to examine how the Andean priest-astronomers recorded the simultaneous creation of the avllu and of this distinctive astronomical system about 200 B.C. The idea that the agricultural avllu, with its double descent system stressing the importance of paternity, represents a transformation of society from an earlier matrilineal/horticultural era is examined in light of the sexual imagery employed in myth. Wiraqocha's androgyny and the division of the celestial sphere into male (ecliptic) and female (celestial equator = earth) are interpreted as cosmological validations of the new social structure.

  9. Andean grasslands are as productive as tropical cloud forests

    NARCIS (Netherlands)

    Oliveras Menor, I.; Girardin, C.; Doughty, C.E.; Cahuana, N.; Arenas, C.E.; Oliver, V.; Huaraca Huasco, W.; Malhi, Y.

    2014-01-01

    We aim to assess net primary productivity (NPP) and carbon cycling in Andean tropical alpine grasslands (puna) and compare it with NPP of tropical montane cloud forests. We ask the following questions: (1) how do NPP and soil respiration of grasslands vary over the seasonal cycle? (2) how do burning

  10. Andean Uplift in the Context of Global Climate Change

    Science.gov (United States)

    Jeffery, Louise; Poulsen, Chris; Ehlers, Todd; Insel, Nadja

    2010-05-01

    The two primary causes of South American climate change over the last 40 million years are global climate change and the uplift of the Andes Mountains. Quantifying spatial and temporal variations in climate over the duration of Andean surface uplift is necessary for interpreting palaeoclimate, erosion and palaeoelevation records from the region. This study utilises an atmospheric general circulation model (GCM) to investigate the magnitude and relative importance of 1) global climate and 2) Andean surface uplift to South American climate during the last 40Ma. Combined with knowledge from the geologic record, the results constrain the controls on, and timing of, landscape development. Three different atmospheric CO2 levels (1, 2 and 4x pre-industrial levels - 280ppm) are used to simulate the range of global climate since the early Cenozoic. Surface uplift of the Andes is examined with simulations at three different Andean elevations (100%, 50% and 5% of modern heights). The importance of feedbacks associated with global climate change is assessed with additional simulations incorporating 1) no Antarctic Ice Sheet and 2) an equilibrium vegetation model coupled to the climate model. Initial results show that the elevation of the Andes exerts a much stronger control on South American precipitation than does the atmospheric CO2 level. The presence of the Andes leads to an increase in annual average precipitation rates of up to 8 mm/day at 20⁰S on the eastern flanks of the mountain range. An increase in CO2 levels from 1x to 4x pre-industrial levels increases the intensity of the global hydrological cycle with annual average precipitation rates increasing by up to 5mm/day. At 50% and 5% Andean elevation, precipitation patterns over South America are independent of atmospheric CO2 concentration. However, at 100% Andean elevation South American precipitation is sensitive to high (4x) CO2 levels. Most large-scale circulation patterns over South America are consistent

  11. Elevation-dependent changes in n-alkane δD and soil GDGTs across the South Central Andes

    Science.gov (United States)

    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 alkane δD values and MAT reconstructions based on brGDGTs distributions from the hillslope transect (Δ (δD) = - 1.64 ‰ / 100 m, R2 = 0.91, p < 0.01 and ΔT = - 0.51 °C / 100 m, R2 = 0.91, p < 0.01) track the direct effects of orography on precipitation and temperature and hence the combined effects of local and regional hydrology as well as elevation.

  12. To what extent do natural disturbances contribute to Andean plant diversity? A theoretical outline from the wettest and driest parts of the tropical Andes

    Science.gov (United States)

    Richter, M.

    2009-10-01

    This paper deals with natural disturbances and their impact on vascular plant enrichment at two climatically contrasting Andean ranges, i.e. the perhumid Cordillera Real in southern Ecuador and the arid Cordillera de Atacama in northern Chile. In the first case, main triggers for an additional input of pioneer species during succession stages initiated by perturbations are landslides, mudflows, and, to a lesser extent, cohort mortality, floods, and wildlife damages. Droughts and wind are stressors, which reduce plant growth but hardly plant diversity, in contrast to enhanced UV radiation with its mutagen effect. Though stress effects are similar in the Atacama, disturbance regimes differ considerably in this dry mountain environment. Here, most perturbations are of small dimension such as nitrogen inputs by feces of Lamoids and burrow activities of tuco-tuco mice, both of them fostering nitrophilous plant communities. Flooding, gelifluction, and other denudation processes such as sheet wash occur too, however, do not charge species enrichment in the dry Andes. Although the perhumid study site represents one of the world's plant diversity "hotspots" and, by contrast, the arid one a comparatively "coldspot", pioneer species during successive stages after natural disturbances contribute in a similar percentage to the total plant inventories (appr. 10% of the species numbers). Relatively seen, natural disturbances are most important for species enrichment in the Atacama (200-500 species per 10 000 km2), while most other ecological factors delimit plant survival. Instead, plant life at the Ecuadorian study area benefits from many climatic and edaphic site conditions, and consequently, disturbances are considered only one of many driving forces for its hotspot status (>5000 species per 10 000 km2).

  13. Active rollback in the Gibraltar Arc: Evidences from CGPS data in the western Betic Cordillera

    Science.gov (United States)

    Gonzalez-Castillo, L.; Galindo-Zaldivar, J.; de Lacy, M. C.; Borque, M. J.; Martinez-Moreno, F. J.; García-Armenteros, J. A.; Gil, A. J.

    2015-11-01

    The Gibraltar Arc, located in the western Mediterranean Sea, is an arcuate Alpine orogen formed by the Betic and Rif Cordilleras, separated by the Alboran Sea. New continuous GPS data (2008-2013) obtained in the Topo-Iberia stations of the western Betic Cordillera allow us to improve the present-day deformation pattern related to active tectonics in this collision area between the Eurasian and African plates. These data indicate a very consistent westward motion of the Betic Cordillera with respect to the relatively stable Iberian Massif foreland. The displacement in the Betics increases toward the south and west, reaching maximum values in the Gibraltar Strait area (4.27 mm/yr in Ceuta, CEU1, and 4.06 mm/yr in San Fernando, SFER), then progressively decreasing toward the northwestern mountain front. The recent geological structures and seismicity evidence moderate deformation in a roughly NW-SE to WNW-ESE compressional stress setting in the mountain frontal areas, and moderate extension toward the internal part of the cordillera. The mountain front undergoes progressive development of folds affecting at least up to Pliocene deposits, with similar recent geological and geodetical rates. This folded strip helps to accommodate the active deformation with scarce associated seismicity. The displacement pattern is in agreement with the present-day clockwise rotation of the tectonic units in the northern branch of the Gibraltar Arc. Our data support that the westward emplacement of the Betic Cordillera continues to be active in a rollback tectonic scenario.

  14. How do subduction processes contribute to forearc Andean uplift? Insights from numerical models

    Science.gov (United States)

    Martinod, J.; Regard, V.; Letourmy, Y.; Henry, H.; Hassani, R.; Baratchart, S.; Carretier, S.

    2016-05-01

    We present numerical models to study how changes in the process of subduction may explain the observed Quaternary uplift of the Andean forearc region. Indeed, most segments of the South American Pacific coasts between 16 and 32° S have been uplifting since the Lower Pleistocene, following a period of stability of the forearc region. Models confirm that local uplift is expected to occur above ridges, this phenomenon being predominant in central Peru where the Nazca Ridge is subducting. We investigate the effects of slab pull, interplate friction and convergence velocity on the vertical displacements of the overriding plate. We propose that the global tendency to coastal uplift is accompanying the deceleration of the Nazca-South America convergence that occurred in the Pleistocene. In contrast, forearc subsidence may accompany increasing convergence velocities, as suggested by the subsidence history of the South America active margin.

  15. Lizards on ice: evidence for multiple refugia in Liolaemus pictus (Liolaemidae) during the last glacial maximum in the Southern Andean beech forests.

    Science.gov (United States)

    Vera-Escalona, Iván; D'Elía, Guillermo; Gouin, Nicolás; Fontanella, Frank M; Muñoz-Mendoza, Carla; Sites, Jack W; Victoriano, Pedro F

    2012-01-01

    Historical climate changes and orogenesis are two important factors that have shaped intraspecific biodiversity patterns worldwide. Although southern South America has experienced such complex events, there is a paucity of studies examining the effects on intraspecific diversification in this part of the world. Liolaemus pictus is the southernmost distributed lizard in the Chilean temperate forest, whose genetic structure has likely been influenced by Pleistocene glaciations. We conducted a phylogeographic study of L. pictus in Chile and Argentina based on one mitochondrial and two nuclear genes recovering two strongly divergent groups, Northern and Southern clades. The first group is distributed from the northernmost limit of the species to the Araucanía region while the second group is distributed throughout the Andes and the Chiloé archipelago in Southern Chile. Our results suggest that L. pictus originated 751 Kya, with divergence between the two clades occurring in the late Pleistocene. Demographic reconstructions for the Northern and Southern clades indicate a decrease in effective population sizes likely associated with Pleistocene glaciations. Surprisingly, patterns of genetic variation, clades age and historical gene flow in populations distributed within the limits of the Last Glacial Maximum (LGM) are not explained by recent colonization. We propose an "intra-Andean multiple refuge" hypothesis, along with the classical refuge hypothesis previously proposed for the biota of the Chilean Coastal range and Eastern Andean Cordillera. Our hypothesis is supported by niche modelling analysis suggesting the persistence of fragments of suitable habitat for the species within the limits of the LGM ice shield. This type of refuge hypothesis is proposed for the first time for an ectothermic species.

  16. Lizards on ice: evidence for multiple refugia in Liolaemus pictus (Liolaemidae during the last glacial maximum in the Southern Andean beech forests.

    Directory of Open Access Journals (Sweden)

    Iván Vera-Escalona

    Full Text Available Historical climate changes and orogenesis are two important factors that have shaped intraspecific biodiversity patterns worldwide. Although southern South America has experienced such complex events, there is a paucity of studies examining the effects on intraspecific diversification in this part of the world. Liolaemus pictus is the southernmost distributed lizard in the Chilean temperate forest, whose genetic structure has likely been influenced by Pleistocene glaciations. We conducted a phylogeographic study of L. pictus in Chile and Argentina based on one mitochondrial and two nuclear genes recovering two strongly divergent groups, Northern and Southern clades. The first group is distributed from the northernmost limit of the species to the Araucanía region while the second group is distributed throughout the Andes and the Chiloé archipelago in Southern Chile. Our results suggest that L. pictus originated 751 Kya, with divergence between the two clades occurring in the late Pleistocene. Demographic reconstructions for the Northern and Southern clades indicate a decrease in effective population sizes likely associated with Pleistocene glaciations. Surprisingly, patterns of genetic variation, clades age and historical gene flow in populations distributed within the limits of the Last Glacial Maximum (LGM are not explained by recent colonization. We propose an "intra-Andean multiple refuge" hypothesis, along with the classical refuge hypothesis previously proposed for the biota of the Chilean Coastal range and Eastern Andean Cordillera. Our hypothesis is supported by niche modelling analysis suggesting the persistence of fragments of suitable habitat for the species within the limits of the LGM ice shield. This type of refuge hypothesis is proposed for the first time for an ectothermic species.

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

    Directory of Open Access Journals (Sweden)

    Reynaldo Charrier

    2009-10-01

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

  18. Foreland sedimentary record of Andean mountain building during advancing and retreating subduction

    Science.gov (United States)

    Horton, Brian K.

    2016-04-01

    As in many ocean-continent (Andean-type) convergent margins, the South American foreland has long-lived (>50-100 Myr) sedimentary records spanning not only protracted crustal shortening, but also periods of neutral to extensional stress conditions. A regional synthesis of Andean basin histories is complemented by new results from the Mesozoic Neuquén basin system and succeeding Cenozoic foreland system of west-central Argentina (34-36°S) showing (1) a Late Cretaceous shift from backarc extension to retroarc contraction and (2) an anomalous mid-Cenozoic (~40-20 Ma) phase of sustained nondeposition. New detrital zircon U-Pb geochronological results from Jurassic through Neogene clastic deposits constrain exhumation of the evolving Andean magmatic arc, retroarc thrust belt, foreland basement uplifts, and distal eastern craton. Abrupt changes in sediment provenance and distal-to-proximal depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, post-extensional thermal subsidence, punctuated tectonic inversion involving thick- and thin-skinned shortening, alternating phases of erosion and rapid accumulation, and overlapping igneous activity. U-Pb age distributions define the depositional ages of several Cenozoic stratigraphic units and reveal a major late middle Eocene-earliest Miocene (~40-20 Ma) hiatus in the Malargüe foreland basin. This boundary marks an abrupt shift in depositional conditions and sediment sources, from Paleocene-middle Eocene distal fluviolacustrine deposition of sediments from far western volcanic sources (Andean magmatic arc) and subordinate eastern cratonic basement (Permian-Triassic Choiyoi igneous complex) to Miocene-Quaternary proximal fluvial and alluvial-fan deposition of sediments recycled from emerging western sources (Malargüe fold-thrust belt) of Mesozoic basin fill originally derived from basement and magmatic arc sources. Neogene eastward advance of the fold-thrust belt involved thick

  19. Dynamic Paleogeography of the Jurassic Andean Basin: pattern of regression and general considerations on main features

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    J-C. Vicente

    2006-09-01

    Full Text Available Following examination of the evolution of the Jurassic Andean retroarc basin at a global scale for the Central Andes, this paper analyses the pattern of the regressive process, and discusses some general features concerning Andean Jurassic Paleogeography. The early Upper Jurassic regression obeys to an exactly reverse pattern as the one evidenced for the Lower Jurassic transgressive process. Sectors with late transgressions become those with early regressions while those with early transgressions show later regressions. This fact may indicate that the Norte Chico Isthmus (29°S to 30°30'S was a precociously emerged zone from the Bajocian. This carries again a split up between the Tarapacá and Aconcagua-Neuquén basins until their complete drying up in the Late Oxfordian following their restricted circulation. This evaporitic late stage presents great analogy with the Mediterranean «Messinian crisis» and gives evidence of a general tectonic and magmatic control on the straits. The local transgressions observed on the cratonic margin of the central part of these shrinking basins were due to shifting of water masses resulting from the regressive process on the northern and southern margins. Comparison between the main stages of transgression and regression allows some quantification concerning velocities of displacement of coastlines, specifically lengthwise. The permanence of paleogeographic and structural features over the time argues for an indisputable tectonic heritage. In the dynamic framework of this typical barred retroarc basin where arc magmatic activity has contributed considerably to variation on sediment supply and changing bathymetry of the seaways connecting with the Pacific Ocean, evidence for an assumed global eustatic cycle remains questionable or very subordinated.

  20. mtDNA and Y-chromosome diversity in Aymaras and Quechuas from Bolivia: different stories and special genetic traits of the Andean Altiplano populations.

    Science.gov (United States)

    Gayà-Vidal, Magdalena; Moral, Pedro; Saenz-Ruales, Nancy; Gerbault, Pascale; Tonasso, Laure; Villena, Mercedes; Vasquez, René; Bravi, Claudio M; Dugoujon, Jean-Michel

    2011-06-01

    Two Bolivian samples belonging to the two main Andean linguistic groups (Aymaras and Quechuas) were studied for mtDNA and Y-chromosome uniparental markers to evaluate sex-specific differences and give new insights into the demographic processes of the Andean region. mtDNA-coding polymorphisms, HVI-HVII control regions, 17 Y-STRs, and three SNPs were typed in two well-defined populations with adequate size samples. The two Bolivian samples showed more genetic differences for the mtDNA than for the Y-chromosome. For the mtDNA, 81% of Aymaras and 61% of Quechuas presented haplogroup B2. Native American Y-chromosomes were found in 97% of Aymaras (89% hg Q1a3a and 11% hg Q1a3*) and 78% of Quechuas (100% hg Q1a3a). Our data revealed high diversity values in the two populations, in agreement with other Andean studies. The comparisons with the available literature for both sets of markers indicated that the central Andean area is relatively homogeneous. For mtDNA, the Aymaras seemed to have been more isolated throughout time, maintaining their genetic characteristics, while the Quechuas have been more permeable to the incorporation of female foreigners and Peruvian influences. On the other hand, male mobility would have been widespread across the Andean region according to the homogeneity found in the area. Particular genetic characteristics presented by both samples support a past common origin of the Altiplano populations in the ancient Aymara territory, with independent, although related histories, with Peruvian (Quechuas) populations.

  1. Investigation of a measles outbreak in Cordillera, Northern Philippines, 2013

    Science.gov (United States)

    Zapanta, Ma Justina; de los Reyes, Vikki Carr; Tayag, Enrique; Magpantay, Rio

    2016-01-01

    Introduction Measles is a highly infectious viral illness that remains one of the leading causes of death among children worldwide. In the Philippines, decreasing routine vaccination coverage from 2007 to 2011 led to local measles outbreaks. A team investigated a measles outbreak reported in Cordillera of the Philippines in May 2013. Methods Measles case data with symptom onset from 2 February to 27 May 2013 were obtained from official sources and verified on site. Data included age, sex, residential address, signs and symptoms and vaccination status. Active case-findings were also conducted for contacts of these cases. The living environments of the cases were investigated. A survey was conducted with the cases and caregivers to understand their knowledge and attitudes about measles. Results There were 50 measles cases identified with an age range from six months to 32 years (median: 16 years). Thirty-two were male (64%). Twenty (40%) were hospitalized with one death. Thirty-two (64%) cases were laboratory confirmed, and 36 (72%) received a single dose of measles vaccine. Overcrowded living environments were observed among many cases. The majority of respondents (46/48, 96%) knew about measles, but there were misconceptions about the cause of measles and how it can be prevented and managed. Conclusion This measles outbreak occurred in an area with low immunization coverage. Achieving 95% measles immunization coverage and strengthening routine immunization strategies to address high-risk populations are recommended. Also, we recommend health education campaigns to include components that address misconceptions about measles. PMID:27766180

  2. Investigation of a measles outbreak in Cordillera, northern Philippines, 2013

    Directory of Open Access Journals (Sweden)

    Paola Katrina Ching

    2016-07-01

    Full Text Available Introduction: Measles is a highly infectious viral illness that remains one of the leading causes of death among children worldwide. In the Philippines, decreasing routine vaccination coverage from 2007 to 2011 led to local measles outbreaks. A team investigated a measles outbreak reported in Cordillera of the Philippines in May 2013. Methods: Measles case data with symptom onset from 2 February to 27 May 2013 were obtained from official sources and verified on site. Data included age, sex, residential address, signs and symptoms and vaccination status. Active case-findings were also conducted for contacts of these cases. The living environments of the cases were investigated. A survey was conducted with the cases and caregivers to understand their knowledge and attitudes about measles. Results: There were 50 measles cases identified with an age range from six months to 32 years (median: 16 years. Thirty-two were male (64%. Twenty (40% were hospitalized with one death. Thirty-two (64% cases were laboratory confirmed, and 36 (72% received a single dose of measles vaccine. Overcrowded living environments were observed among many cases. The majority of respondents (46/48, 96% knew about measles, but there were misconceptions about the cause of measles and how it can be prevented and managed. Conclusion: This measles outbreak occurred in an area with low immunization coverage. Achieving 95% measles immunization coverage and strengthening routine immunization strategies to address high-risk populations are recommended. Also, we recommend health education campaigns to include components that address misconceptions about measles.

  3. Technical analysis of four archaeological andean painted textiles

    OpenAIRE

    2016-01-01

    This project investigates the materials and manufacturing techniques used to create four archaeological Andean painted textiles in the collection of the National Museum of the American Indian, Smithsonian Institution. The textiles are attributed to Peru but have minimal provenience. Building on previous work by other scholars on similar archaeological textiles, the materials and manufacturing techniques are identified and characterized by observation, documentation, and scientific analysis. S...

  4. State dilemmas in applying the Previous Consultation Law in the Andean Region

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    Rafael Barrio de Mendoza

    2013-12-01

    Full Text Available The Peruvian government enacted a new law granting consultation rights to indigenous peoples as a mechanism to enhance social inclusion in the country. The law generated debates about the criteria to identify indigenous population in the Andean region. Why does this law have problems granting consultation rights to Andean people? This paper aims to answer the question by reviewing historically the different Andean identities and analyzing the current international debate on indigenity. Our main argument is that the government intrying to apply the law is structuring a restrictive model that is hardlyable to grasp the complexity and dynamism of Andean identities.

  5. Erosion of particulate organic material from an Andean river and its delivery to the Amazon Basin

    Science.gov (United States)

    Clark, Kathryn; Hilton, Robert; West, A. Joshua; Robles Caceres, Arturo; Grocke, Darren; Marthews, Toby; Asner, Greg; New, Mark; Mahli, Yadvinder

    2016-04-01

    Organic carbon and nutrients discharged by mountainous rivers can play an important role in biogeochemical cycles from regional to global scales. The eastern Andes host productive forests on steep, rapidly eroding slopes, a combination that is primed to deliver sediment, carbon and nutrients to the lowland Amazon River. We quantify clastic sediment and particulate organic carbon (POC) discharge for the Kosñipata River, Peru, an Andean tributary of the Madre de Dios River, using suspended sediment samples and discharge measurements over one year at two gauging stations. Calculations of sediment yield on the basis of this data suggest that the Madre de Dios basin may have erosion rates ˜10 times greater than the Amazon Basin average. The total POC yield over the sampling period was up to five times higher than the yield in the lowland Amazon Basin, with most POC (70-80%) exported between December and March in the wet season. We use radiocarbon, stable C isotopes and C/N ratios to distinguish between the erosion and discharge of POC from sedimentary rocks (petrogenic POC) and POC eroded from the modern terrestrial biosphere, from vegetation and soil (biospheric POC). We find that biospheric POC discharge was significantly enhanced during flood events, over that of clastic sediment and petrogenic POC. The ultimate fate of the eroded POC may play a central role in the net carbon budget of Andean forest. In these forests, net productivity minus heterotrophic respiration is close to zero at the scale of forest plots, and the erosion of biospheric POC by this Andean river is sufficiently rapid that its fate downstream (sedimentary burial/preservation versus oxidation/degradation) may determine whether the mountain forest is a carbon sink or source to the atmosphere. In addition, the measured discharge of petrogenic POC suggests that fluxes from the Andes may be considerably higher than measured downstream in the Madeira River. If this petrogenic POC is oxidised rather

  6. Integración regional andina en salud Health in Andean regional integration

    Directory of Open Access Journals (Sweden)

    Carlos A. Agudelo

    2007-01-01

    Full Text Available A pesar su historia compartida, los países de la Región Andina presentan una diversidad social y política que genera realidades sanitarias heterogéneas y procesos de integración complejos. Se han dado por décadas procesos generales, como la Asociación Latinoamericana de Libre Comercio y la Asociación Latinoamericana de Integración, o de alcance regional como la Comunidad Andina de Naciones, la Comunidad del Caribe y el Mercado Común Centroamericano. En el campo específico de la salud se cuenta con un instrumento en la Región Andina, el Convenio Hipólito Unánue, creado en 1971. Estos procesos de integración se han concentrado en los aspectos económicos, con base en acuerdos de preferencias arancelarias, los cuales han generado, en el largo plazo, un intercambio comercial apreciable. En el campo de la salud se ha avanzado menos, en términos de procesos que ponen en común experiencias nacionales, conocimientos y capacidades. El análisis de las experiencias de integración en salud muestra que esta depende de las fortalezas de cada país y, en gran parte, de los procesos políticos nacionales.Despite their shared history, the Andean countries are socially and politically diverse, with heterogeneous health realities and complex integration processes. General developments such as the Latin American Free Trade Association and Latin American Integration Association have existed for decades, along with others of a regional scope, like the Andean Community of Nations, Caribbean Community, and Central American Common Market. The health field has a specific instrument in the Andean Region called the Hipólito Unánue Agreement, created in 1971. Integration processes have concentrated on economic aspects, based on preferential customs agreements that have led to an important long-term increase in trade. Less progress has been made in the field of health in terms of sharing national experiences, knowledge, and capabilities. Analysis of

  7. Evaporite deposits of Bogota area, Cordillera Oriental, Colombia

    Science.gov (United States)

    McLaughlin, Donald H.

    1972-01-01

    Four evaporite-bearing stratigraphic zones are known in Cretaceous strata of the Cordillera Oriental of Colombia north and east of Bogota. The easternmost and oldest zone is probably of Berriasian to Valanginian age. The next oldest is probably late Barremian to early Aptian in age. The third appears to be Aptian. The westernmost and best known sequence in the Sabana de Bogota is Turonian to early Coniacian in age. This youngest sequence contains the thickest salt deposits known in Colombia and is probably the most widespread geographically. Most of the rock salt exposed in the three accessible mines (at Zipaquira, Nemocon, and Upin) has a characteristic lamination of alternating slightly argillaceous and highly argillaceous salt layers of varied but moderate thickness. Black, calcareous claystone, commonly very pyritic, is interbedded conformably with the laminated salt in many places throughout the deposits. Fragments of black claystone derived from the thinner interbeds are ubiquitous in all deposits, both as concordant breccia zones and as isolated clasts. Anhydrite is scarce at Zipaquira and apparently even rarer at Nemocon and Upin. Gypsum is produced at three small deposits in the oldest evaporite zone where it probably was concentrated by leaching of salt initially associated with it. The two intervening evaporite zones are not exposed, but their existence and distribution are indicated by brine springs and locally by "rute," a distinctive black, calcareous mud formed by the leaching of salt beds. Fossils show that the youngest salt-claystone zone, in the Sabana de Bogota, is contemporary with associated hematitic sandstone and siltstone, and with carbonaceous and locally coaly claystone. Although evidence is poor, this same facies relation probably exists within the other three evaporite zones. All salt deposits in this study probably are associated with anticlines, a relation best exemplified by the deposits on the Sabana de Bogota. Within these

  8. Uptake of Hg2+ by picocyanobacteria in natural water from four Andean lakes

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    Diéguez M.C.

    2014-07-01

    Full Text Available In lake food webs, planktonic bacteria and algae represent the greatest bioconcentration step for Hg2+ and monomethyl-Hg (MeHg. As they are the most abundant organisms in planktonic trophic webs and also the main food resource for herbivorous plankton, they can mobilize large amounts of Hg to higher trophic levels. In Andean Patagonian lakes (Argentina, dissolved organic matter (DOM concentration and character, coupled with photo-reactions, play a central role in the complexation of Hg2+ in the water column and can even regulate the uptake of Hg2+ by planktonic algae. In this investigation we evaluated the DOM character of natural waters (NW from four Andean lakes and studied its influence on the uptake of 197Hg2+ in a strain of the picocyanobacteria Synechococcus by using Hg2+ labeled with 197Hg2+. The uptake of radiolabeled Hg2+ by Synechococcus showed different magnitude in NW of lakes Moreno, El Trébol, Morenito and Escondido. Increasing lake DOM concentration reduced the bioavailability of Hg2+ as indicated by the lower uptakes rates found in NW with higher complexity and concentration of the DOM pool. Uptakes of Hg2+ by this picocyanobacteria contrasted among NW from pelagic (surface and bottom and littoral compartments of Lake Escondido which suggest that the entry of this metal may be highly variable even in the same environment. The study of the uptake of radiolabeled Hg2+ in a set of dilutions of NW from Lake Escondido demonstrated that the bioavailability of Hg2+ decrease with increasing DOM concentration.

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

    Science.gov (United States)

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

    2016-10-01

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

  10. GPS velocities and the construction of the Eastern Cordillera of the Colombian Andes

    Science.gov (United States)

    Mora-Páez, Héctor; Mencin, David J.; Molnar, Peter; Diederix, Hans; Cardona-Piedrahita, Leonardo; Peláez-Gaviria, Juan-Ramón; Corchuelo-Cuervo, Yuli

    2016-08-01

    GPS velocities across the northeast trending Eastern Cordillera of Colombia show oblique convergence at 8.8 ± 1.7 mm/yr, consisting of 8.0 ± 1.7 mm/yr of right-lateral strike-slip shear along the mountain range and 3.7 ± 0.3 mm/yr of northwest southeast shortening. Faster convergence occurs only at the northeast end of the Cordillera, where its eastern edge trends northwest and the highest mountains lie. The strike-slip shear corroborates geologic work suggesting such movement southwest and northeast of the range. Given the ~200 km width of the Eastern Cordillera, the ~100-150 km of crustal shortening inferred from balanced cross sections and implied by recent estimates of crustal thickness would require ~25-40 Myr of shortening at ~4 mm/yr. The present-day GPS measurements, therefore, are inconsistent with the inference, based on paleobotanical observations that the entire Eastern Cordillera rose 1500-2500 m since 3-6 Ma and called for a different interpretation of those data.

  11. Structural analysis of the Cordillera Blanca detachment: Geometry, kinematics and fault rocks

    Science.gov (United States)

    Shaw, C. A.; Jessup, M. J.; Hughes, C. A.; Newell, D. L.

    2015-12-01

    The Cordillera Banca Detachment (CBD) in the north-central Peruvian Andes is recognized as a rare example of active extension parallel to the direction of shortening within a convergent orogenic setting. Despite longstanding interest in the geodynamic significance of the CBD relatively little work has been done to characterize the basic geometry, kinematics and evolution of the detachment or the petrology and distribution of brittle and ductile tectonites within the fault zone. This contribution presents preliminary results of a basic structural analysis of the CBD based on field observations, laboratory results, and GIS analysis. Basic structural observations of fault geometry and kinematics are needed to constrain the regional geodynamic role of the CBD. The NNW topographic trace of the CBD is defined by faceted ridges up to 2000 m in height. The lower slopes of the facets are locally cut by steep fault scarps that offset quaternary glacial moraines, debris fans and colluvium. The shear zone comprises both brittle and ductile tectonites including mylonite series rocks, pseudotachylyte, and breccia - often highly silicified. Highly polished mirrored surfaces are observed locally. Deformation mechanisms show a consistent progression from plastic in structurally lower positions to brittle in structurally higher positions. Evidence for overprinting deformation mechanisms is preserved in many samples. The shear zone ranges up to about 200 m thick. The average orientation of mylonitic foliation and fault slip surfaces (strike/dip = 140/30) and lineations/slickenlines (plunge-trend = 35-235) is quite consistent along the ~200 km detachment, but some systematic variation along strike may be related to concave fault segments or corrugations. Slip indicators are nearly down-dip with a minor left-lateral or right-lateral component in some locations. Offsets in marker horizons constrain total offset between about 4500 m near the central section of the fault to near zero

  12. The time-space distribution of Eocene to Miocene magmatism in the central Peruvian polymetallic province and its metallogenetic implications

    Science.gov (United States)

    Bissig, Thomas; Ullrich, Thomas D.; Tosdal, Richard M.; Friedman, Richard; Ebert, Shane

    2008-07-01

    Eocene to late Miocene magmatism in the central Peruvian high-plain (approx. between Cerro de Pasco and Huancayo; Lats. ˜10.2-12°S) and east of the Cordillera Occidental is represented by scattered shallow-level intrusions as well as subaerial domes and volcanic deposits. These igneous rocks are calc-alkalic and range from basalt to rhyolite in composition, and many of them are spatially, temporally and, by inference, genetically associated with varied styles of major polymetallic mineralization. Forty-four new 40Ar- 39Ar and three U/Pb zircon dates are presented, many for previously undated intrusions. Our new time constraints together with data from the literature now cover most of the Cenozoic igneous rocks of this Andean segment and provide foundation for geodynamic and metallogenetic research. The oldest Cenozoic bodies are of Eocene age and include dacitic domes to the west of Cerro de Pasco with ages ranging from 38.5 to 33.5 Ma. South of the Domo de Yauli structural dome, Eocene igneous rocks occur some 15 km east of the Cordillera Occidental and include a 39.34 ± 0.28 Ma granodioritic intrusion and a 40.14 ± 0.61 Ma rhyolite sill, whereas several diorite stocks were emplaced between 36 and 33 Ma. Eocene mineralization is restricted to the Quicay high-sulfidation epithermal deposit some 10 km to the west of Cerro de Pasco. Igneous activity in the earliest Oligocene was concentrated up to 70 km east of the Cordillera Occidental and is represented by a number of granodioritic intrusions in the Milpo-Atacocha area. Relatively voluminous early Oligocene dacitic to andesitic volcanism gave rise to the Astabamba Formation to the southeast of Domo de Yauli. Some stocks at Milpo and Atacocha generated important Zn-Pb (-Ag) skarn mineralization. After about 29.3 Ma, magmatism ceased throughout the study region. Late Oligocene igneous activity was restricted to andesitic and dacitic volcanic deposits and intrusions around Uchucchacua (approx. 25 Ma) and felsic

  13. Can cosmic ray exposure dating reveal the normal faulting activity of the Cordillera Blanca Fault, Peru? ¿Dataciones por exposición de rayos cósmicos revelan fallamiento activo normal en la falla de la Cordillera Blanca, Perú?

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    L.L. Siame

    2006-12-01

    Full Text Available The build-up of in situ-produced cosmogenic 10Be within bedrock scarps and escarpments associated to the Cordillera Blanca Normal Fault, Peru, was measured to evaluate, through Cosmic Ray Exposure dating, its normal faulting activity. The highest mountain peaks in Peru belong to the 210 km-long, NW- striking, Cordillera Blanca. Along its western border, the Cordillera Blanca Normal Fault is responsible for a vertical relief over 4.4 km, whose prominent 2 km high escarpment is characterized by ~1 km-high triangular facets corresponding to vertical displacements cumulated during the last 1-2 million years. At a more detailed scale, this fault system exhibits continuous geomorphic evidence of repeated displacements, underlined by 2 to 70 m-high scarps, corresponding to vertical displacements cumulated since Late Pleistocene and Holocene periods. Although microseismicity occurs along the Cordillera Blanca Normal Fault, no major historical or instrumental earthquake has been recorded since the beginning of the Spanish settlement in the 16th century. To evaluate the vertical slip rate along the major 90 km-long central segment of the Cordillera Blanca Normal Fault, the Quaternary fault escarpment (i.e., triangular facet, as well as the bedrock fault scarp, have been sampled for 10Be Cosmic Ray Exposure dating. Even if the uppermost part of the triangular facets have been resurfaced by the Last Glacial Maximum glaciers, our results allow to estimate a vertical slip-rate of 3±1 mm/yr, and suggest at least 2 seismic events during the last 3000 years.La acumulación in situ de 10Be cosmogénico en las rocas intrusivas de las escarpas de la falla normal de la Cordillera Blanca del Perú han sido medidas para evaluar, su actividad de fallamiento normal., con edades de exposición a los rayos cósmicos. Los más altos picos en el Perú conforman la Cordillera Blanca que se extiende con una longitud de 210 km según una orientación NO. A lo largo de su l

  14. Tomographic images of subducted oceans matched to the accretionary records of orogens - Case study of North America and relevance to Central Asia

    Science.gov (United States)

    Sigloch, Karin; Mihalynuk, Mitchell G.; Hosseini, Kasra

    2016-04-01

    Accretionary orogens are the surface record of subduction on the 100-million-year timescale; they aggregate buoyant crustal welts that resisted subduction. The other record of subduction is found in the deep subsurface: oceanic lithosphere preserved in the mantle that records ocean basin closure between successive generations of arcs. Seismic tomography maps out these crumpled paleo-oceans down to the core-mantle boundary, where slab accumulates. One such accumulation of enormous scale is under Eastern Asia, recording the assembly of the Central Asian Orogenic Belt (CAOB). Deep CAOB slab has hardly been explored because tomographic image resolution in the lowermost mantle is limited, but this is rapidly improving. We present new images of the CAOB slabs from our P-wave tomography that includes core-diffracted waves as a technical novelty. The previous slab blur sharpens into the type of elongated geometries expected to trace paleo-trench lines. Since the North American Cordillera is younger than the CAOB (mostly 10,000 km long. North America converged on the two microcontinents by westward subduction of two intervening basins (which we name Mezcalera and Angayucham oceans), culminating in diachronous suturing between ~150 Ma and ~50 Ma. Hence geophysical subsurface evidence negates the widely accepted "Andean-style" model of Farallon-beneath-continent subduction since at least 180 Ma, and supports a Jura-Cretaceous paleogeography closer to today's Southwestern Pacific, or to the Paleozoic CAOB. Though advocated since the 1970's by a minority of geologists, this scenario had not gained wide acceptance due to a record obscured by overprinting, margin-parallel translation, and oroclinal bending. The new subsurface evidence provides specific indications where to seek the decisive Mezcalera-Angayucham suture. The suture is evident in a trail of collapsed Jura-Cretaceous basin relics that run the length of the Cordillera. Reference: Sigloch, K., & Mihalynuk, M. G. (2013

  15. Metals and altitude drive genetic diversity of chironomids in Andean streams

    NARCIS (Netherlands)

    Loayza-Muro, R.A.; de Baat, M.; Palomino, E.J.; Kuperus, P.; Kraak, M.H.S.; Admiraal, W.; Breeuwer, H.

    2014-01-01

    1. Andean streams cover steep altitude gradients and locally leach metal-rich bedrock, creating highly selective habitat conditions. Chironomids are among the few dominant insect taxa present under the harshest conditions in Andean high altitude streams, but it remains unclear whether their dominanc

  16. Cenozoic back-arc magmatism of the southern extra-Andean Patagonia (44° 30' - 52° S: A review of geochemical data and geodynamic interpretations Magmatismo de retroarco cenozoico de la Patagonia extra-andina austral (44° 30' - 52° S: Una revisión de los datos geoquímicos e interpretaciones geodinámicas

    Directory of Open Access Journals (Sweden)

    M. D'Orazio

    2004-12-01

    Full Text Available Huge amounts of basaltic s.l. lavas were persistently erupted along the eastern side of the Andean Cordillera, throughout Cenozoic time, forming extensive plateaus, hundreds of monogenetic scoria cones and other volcanic structures in a continental back-arc setting. The igneous products exposed in the southern sector of the extra-Andean Patagonia (44° 30' - 52° S are dominantly mafic with minor slightly evolved compositions and rare highly differentiated products. The many published chemical analyses of these rocks, indicate that the mafic lavas range from strongly silica - undersaturated basanites to oversaturated basaltic andesites, and that most of the lavas have a typical within-plate geochemical signature. However, a number of lavas, generally erupted in the western-central sectors of Patagonia, are characterized by different distributions of the incompatible elements with high LILE/HFSE and LREE/HFSE ratios. The REE distribution modelling suggests a low degree of melting of a deep (> 70 km garnet-bearing source for the alkaline magmas, and a higher degree of melting of the same source, or an even higher degree of melting of an enriched source, for the subalkaline magmas. The available Sr-Nd-Pb isotope compositions clearly attest to a major geographic variation: the southernmost lavas have lower 87Sr/86Sr and higher 143Nd/144Nd and 206Pb/204Pb ratios with respect to those erupted to the north. On the whole, the Sr-Nd-Pb isotope compositions of the southern Patagonia lavas fall within the typical range of within-plate continental magmas; in addition the Pb isotope ratios fall in the range of the Southern Hemisphere Dupal Pb isotope anomaly. The geochemical variations of the southern Patagonia lavas are discussed in terms of different geochemical components: depleted and enriched sub-slab asthenosphere, enriched continental lithospheric mantle, continental crust and subducted materials. The geodynamic significance is interpreted with in the

  17. Integration, migration and sustainable development in the Andean group of nations.

    Science.gov (United States)

    Leon, R; Kratochwil, H

    1993-04-01

    This paper, which was presented at the 1993 meeting of the International Organization for Migration, summarizes past and recent progress in Andean integration and migration arrangements. Changes in the strategy of the Andean group of nations (GAN) have occurred in the adjustment to prevailing conditions at the subregional and international level. GAN includes Bolivia, Colombia, Ecuador, Peru, and Venezuela. The Andean Pact originated with the signing of the Cartegena Agreement in 1969. Members approved the Andean Strategic Design in 1989, which loosened up trade integration and the movement of capital, services, and persons across shared borders. The Strategic Design also addressed issues resulting from economic and social integration. A statement of migratory patterns among GAN, Andean integration during 1969-89, and the goals and operation of the Andean Strategic Design and integration are discussed in some detail. The Galapagos Declaration and the La Paz Statement of 1990 are also described. The present situation with Andean integration is based on the following meetings of Andean nations: the First Meeting of Migration Officials of the Andean Group of Nations in March 1991, the Second Meeting of Migration Officials in September 1991, and bilateral agreements between Andean nations. Seven basic conclusions are drawn: 1) the strategy is an institutional, deliberate, programmed process; 2) integration within GAN is the culmination of a joint, coordinated directive of achievement of sustainable development in the subregion which aims to reduce the economic gaps between the North and the South, to lessen the impact of protected markets of the North and their migration barriers, and to improve the possibility of development of technologically sophisticated human capital; 3) subregional policies are more sensitive to short-term change in domestic politics; 4) integration and migration can be sustained better with deliberate planning; 5) implementation is dependent on

  18. Regional Analysis of the Hazard Level of Glacial Lakes in the Cordillera Blanca, Peru

    Science.gov (United States)

    Chisolm, Rachel E.; Jhon Sanchez Leon, Walter; McKinney, Daene C.; Cochachin Rapre, Alejo

    2016-04-01

    The Cordillera Blanca mountain range is the highest in Peru and contains many of the world's tropical glaciers. This region is severely impacted by climate change causing accelerated glacier retreat. Secondary impacts of climate change on glacier retreat include stress on water resources and the risk of glacial lake outburst floods (GLOFs) from the many lakes that are forming and growing at the base of glaciers. A number of GLOFs originating from lakes in the Cordillera Blanca have occurred over the last century, several of which have had catastrophic impacts on cities and communities downstream. Glaciologists and engineers in Peru have been studying the lakes of the Cordillera Blanca for many years and have identified several lakes that are considered dangerous. However, a systematic analysis of all the lakes in the Cordillera Blanca has never before been attempted. Some methodologies for this type of systematic analysis have been proposed (eg. Emmer and Vilimek 2014; Wang, et al. 2011), but as yet they have only been applied to a few select lakes in the Cordillera Blanca. This study uses remotely sensed data to study all of the lakes of the Glacial Lake Inventory published by the Glaciology and Water Resources Unit of Peru's National Water Authority (UGRH 2011). The objective of this study is to assign a level of potential hazard to each glacial lake in the Cordillera Blanca and to ascertain if any of the lakes beyond those that have already been studied might pose a danger to nearby populations. A number of parameters of analysis, both quantitative and qualitative, have been selected to assess the hazard level of each glacial lake in the Cordillera Blanca using digital elevation models, satellite imagery, and glacier outlines. These parameters are then combined to come up with a preliminary assessment of the hazard level of each lake; the equation weighting each parameter draws on previously published methodologies but is tailored to the regional characteristics

  19. A Re-Appraisal of the Early Andean Human Remains from Lauricocha in Peru

    Science.gov (United States)

    Kuzminsky, Susan; Rohland, Nadin; Santos, Fabrício R.; Kaulicke, Peter; Valverde, Guido; Richards, Stephen M.; Nordenfelt, Susanne; Seidenberg, Verena; Mallick, Swapan; Cooper, Alan; Reich, David; Haak, Wolfgang

    2015-01-01

    The discovery of human remains from the Lauricocha cave in the Central Andean highlands in the 1960’s provided the first direct evidence for human presence in the high altitude Andes. The skeletons found at this site were ascribed to the Early to Middle Holocene and represented the oldest known population of Western South America, and thus were used in several studies addressing the early population history of the continent. However, later excavations at Lauricocha led to doubts regarding the antiquity of the site. Here, we provide new dating, craniometric, and genetic evidence for this iconic site. We obtained new radiocarbon dates, generated complete mitochondrial genomes and nuclear SNP data from five individuals, and re-analyzed the human remains of Lauricocha to revise the initial morphological and craniometric analysis conducted in the 1960’s. We show that Lauricocha was indeed occupied in the Early to Middle Holocene but the temporal spread of dates we obtained from the human remains show that they do not qualify as a single contemporaneous population. However, the genetic results from five of the individuals fall within the spectrum of genetic diversity observed in pre-Columbian and modern Native Central American populations. PMID:26061688

  20. SENP1, but not fetal hemoglobin, differentiates Andean highlanders with chronic mountain sickness from healthy individuals among Andean highlanders.

    Science.gov (United States)

    Hsieh, Matthew M; Callacondo, David; Rojas-Camayo, Jose; Quesada-Olarte, Jose; Wang, Xunde; Uchida, Naoya; Maric, Irina; Remaley, Alan T; Leon-Velarde, Fabiola; Villafuerte, Francisco C; Tisdale, John F

    2016-06-01

    Chronic mountain sickness (CMS) results from chronic hypoxia. It is unclear why certain highlanders develop CMS. We hypothesized that modest increases in fetal hemoglobin (HbF) are associated with lower CMS severity. In this cross-sectional study, we found that HbF levels were normal (median = 0.4%) in all 153 adult Andean natives in Cerro de Pasco, Peru. Compared with healthy adults, the borderline elevated hemoglobin group frequently had symptoms (headaches, tinnitus, cyanosis, dilatation of veins) of CMS. Although the mean hemoglobin level differed between the healthy (17.1 g/dL) and CMS (22.3 g/dL) groups, mean plasma erythropoietin (EPO) levels were similar (healthy, 17.7 mIU/mL; CMS, 12.02 mIU/mL). Sanger sequencing determined that single-nucleotide polymorphisms in endothelial PAS domain 1 (EPAS1) and egl nine homolog 1 (EGLN1), associated with lower hemoglobin in Tibetans, were not identified in Andeans. Sanger sequencing of sentrin-specific protease 1 (SENP1) and acidic nuclear phosphoprotein 32 family, member D (ANP32D), in healthy and CMS individuals revealed that non-G/G genotypes were associated with higher CMS scores. No JAK2 V617F mutation was detected in CMS individuals. Thus, HbF and other classic erythropoietic parameters did not differ between healthy and CMS individuals. However, the non-G/G genotypes of SENP1 appeared to differentiate individuals with CMS from healthy Andean highlanders.

  1. A new catfish species of the genus Trichomycterus (Siluriformes: Trichomycteridae from the río Orinoco versant of Páramo de Cruz Verde, Eastern Cordillera of Colombia

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    Carlos DoNascimiento

    Full Text Available A new Trichomycterus is described from a highland tributary of the río Meta (Orinoco basin, along the east flank of Páramo de Cruz Verde, Eastern Cordillera of Colombia. The new species is distinguished from most of its congeners by having a reduced posterior cranial fontanel, restricted to the parieto-supraoccipital, cleithrum pierced by several foramina, and an unique combination of four irregular rows of conic teeth in premaxilla and dentary, 13-14 opercular odontodes, 41-43 interopercular odontodes, 6-7 branchiostegal rays, 40 or 41 free vertebrae, 14-18 ribs, first ray of pectoral fin slightly projected as a short filament, 7-8 branched pectoral-fin rays, dorsal-fin origin at same level of pelvic-fin insertion, anal-fin origin posterior to dorsal-fin base, caudal-fin margin slightly rounded, a single upper hypural plate (3+4+5, and coloration pattern consisting in ground color dark brown with a thin mid-lateral dark stripe. Phylogenetic relationships of the new species based on the shared presence of derived features related to posterior cranial fontanel and cleithrum are discussed. The new species is also compared to the only two described species from Andean tributaries of río Orinoco basin.

  2. A Comparative Analysis of Seismological and Gravimetric Crustal Thicknesses below the Andean Region with Flat Subduction of the Nazca Plate

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    Mario E. Gimenez

    2009-01-01

    Full Text Available A gravimetric study was carried out in a region of the Central Andean Range between 28∘ and 32∘ south latitudes and from 72∘ and 66∘ west longitudes. The seismological and gravimetrical Moho models were compared in a sector which coincides with the seismological stations of the CHARGE project. The comparison reveals discrepancies between the gravity Moho depths and those obtained from seismological investigations (CHARGE project, the latter giving deeper values than those resulting from the gravimetric inversion. These discrepancies are attenuated when the positive gravimetric effect of the Nazca plate is considered. Nonetheless, a small residuum of about 5 km remains beneath the Cuyania terrane region, to the east of the main Andean chain. This residuum could be gravimetrically justified if the existence of a high density or eclogitized portion of the lower crust is considered. This result differed from the interpretations from Project “CHARGE” which revealed that the entire inferior crust extending from the Precordillera to the occidental “Sierras Pampeanas” could be “eclogitized”. In this same sector, we calculated the effective elastic thickness (Te of the crust. These results indicated an anomalous value of Te = 30 km below the Cuyania terrane. This is further conclusive evidence of the fact that the Cuyania terrane is allochthonous, for which also geological evidences exist.

  3. Climate change forces new ecological states in tropical Andean lakes.

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    Neal Michelutti

    Full Text Available Air temperatures in the tropical Andes have risen at an accelerated rate relative to the global average over recent decades. However, the effects of climate change on Andean lakes, which are vital to sustaining regional biodiversity and serve as an important water resource to local populations, remain largely unknown. Here, we show that recent climate changes have forced alpine lakes of the equatorial Andes towards new ecological and physical states, in close synchrony to the rapid shrinkage of glaciers regionally. Using dated sediment cores from three lakes in the southern Sierra of Ecuador, we record abrupt increases in the planktonic thalassiosiroid diatom Discostella stelligera from trace abundances to dominance within the phytoplankton. This unprecedented shift occurs against the backdrop of rising temperatures, changing atmospheric pressure fields, and declining wind speeds. Ecological restructuring in these lakes is linked to warming and/or enhanced water column stratification. In contrast to seasonally ice-covered Arctic and temperate alpine counterparts, aquatic production has not increased universally with warming, and has even declined in some lakes, possibly because enhanced thermal stability impedes the re-circulation of hypolimnetic nutrients to surface waters. Our results demonstrate that these lakes have already passed important ecological thresholds, with potentially far-reaching consequences for Andean water resources.

  4. Andean rural children's views of the environment: A qualitative study

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    Maurial, Mahia

    Andean rural children's drawings and narratives about their crops and the immediate biological environment are rich tools to understand local views of the environment. Children's drawings and narratives were collected and linked to interviews as well as participant observation gathered from parents, leaders and teachers. The research sites are the community of Willca and the school of Mayu. Fieldwork was completed in 1998. In the conceptual framework I distinguish between two dissimilar knowledges, school knowledge and local knowledge. These knowledges produce two dissimilar views of the environment. I further analyze relationships of knowledge and power and argue that school knowledge overpowers local knowledge. Concomitantly, I studied set of ideas associated with two knowledges aforementioned: superacion (surpass) and regeneration (Apffel-Marglin 1995). Although these ideas coexist in peoples' minds they are not linked or effectively connected. In order to link local knowledge and school knowledge together, I propose the integration of environmental studies and art education to enhance a local sense of place (Blandy et. al 1993) in Andean and other schools. This will contribute to grassroots educational policy.

  5. Andesita Cerro Bola: Nueva unidad vinculada al magmatismo mioceno de la Cordillera de Olivares, San Juan, Argentina (30°35´S; 69°30´O Cerro Bola Andesite: New unit linked to the Miocene magmatism of the Olivares Cordillera, San Juan (30°35' S ; 68°30' W

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    A.F. Wetten

    2005-03-01

    Full Text Available El área de estudio se halla en la zona de Tocota, inmediatamente al este de la Cordillera de Olivares, en el borde oriental de la Cordillera Frontal, provincia de San Juan. En ella se encuentran unidades ígneas y sedimentarias del ciclo gondwánico, las que fueron intruidas y cubiertas en relación discordante por cuerpos subvolcánicos y volcánicos asignados anteriormente al ciclo ándico en sentido amplio, los cuales constituyen el principal objeto del presente estudio. Estos cuerpos han sido mapeados a fin de poder caracterizarlos adecuadamente, en el contexto estratigráfico de la región. Los afloramientos de interés han sido reconocidos en el cerro Bola y alrededores, donde se observan distribuidos irregularmente, cubriendo un área superior a 5 km². Las rocas, de coloración gris clara y composición andesítica - fenoandesítica, presentan estructuras de domo y colada. Estos afloramientos serían correlacionables con la unidad volcánica Pircas (Mioceno, la que aflora al oeste, y conformarían un evento magmático posterior al de pórfidos de diferente composición situados tanto en el arroyo Chita como en el cerro Divisadero. La extensión del área involucrada, la uniformidad litológica, el bajo grado de alteración y una edad radimétrica obtenida por el método K/Ar, fueron considerados para proponer a estas volcanitas como una unidad litoestratigráfica de edad miocena superior, con la denominación de Andesita Cerro Bola.The study area is located in the region of Tocota Creek, close to the Cordillera Olivares, eastern border of the Frontal Range, San Juan province. In this place, igneous and sedimentary units belonging to the Gondwanic cycle, were recognized. These units were intruded and unconformably covered by subvolcanic and volcanic bodies, which were commonly referred to the Tertiary or Andean cycle. The study of these bodies is the main proposal of this work. These bodies had been mapped in order to characterize them

  6. Extreme high prevalence of a defective mannose-binding lectin (MBL2 genotype in native South American West Andean populations.

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    José Raul Sandoval

    Full Text Available Mannose-binding lectin (MBL is one of the five recognition molecules in the lectin complement pathway. Common variant alleles in the promoter and structural regions of the human MBL gene (MBL2 influence the stability and serum concentration of the protein. Epidemiological studies have shown that MBL2 variant alleles are associated with susceptibility to and the course of different types of infectious and inflammatory conditions. However, it has been suggested that these alleles are maintained in different populations due to selected advantages for carriers. We investigated the MBL2 allelic variation in indigenous individuals from 12 different West Central South America localities spanning from the desert coast, high altitude Andean plates and the Amazon tropical forest within the territories of Peru (n = 249 (Departments of Loreto, Ucayali, Lambayeque, Junin, Ayacucho, Huancayo and Puno, and Ecuador (n = 182 (Region of Esmeraldas and Santo Domingo de los Colorados. The distribution of MBL2 genotypes among the populations showed that the defective variant LYPB haplotype was very common. It showed the highest frequencies in Puno (Taquile (0.80, Amantani (0.80 and Anapia (0.58 islander communities of the Lake Titicaca, but lower frequencies of 0.22 in Junin (Central Andean highland and Ucayali (Central Amazonian forest, as well as 0.27 and 0.24 in the Congoma and Cayapa/Chachis populations in the Amazonian forest in Ecuador were also observed. Our results suggest that the high prevalence of the MBL2 LYPB variant causing low levels of functional MBL in serum may mainly reflect a random distribution due to a population bottleneck in the founder populations.

  7. Extreme high prevalence of a defective mannose-binding lectin (MBL2) genotype in native South American West Andean populations.

    Science.gov (United States)

    Sandoval, José Raul; Madsen, Hans O; De Stefano, Gianfranco; Descailleaux-Dulanto, Jaime; Velazquez-Reinoso, Margarita; Ñique, Cesar; Fujita, Ricardo; Garred, Peter

    2014-01-01

    Mannose-binding lectin (MBL) is one of the five recognition molecules in the lectin complement pathway. Common variant alleles in the promoter and structural regions of the human MBL gene (MBL2) influence the stability and serum concentration of the protein. Epidemiological studies have shown that MBL2 variant alleles are associated with susceptibility to and the course of different types of infectious and inflammatory conditions. However, it has been suggested that these alleles are maintained in different populations due to selected advantages for carriers. We investigated the MBL2 allelic variation in indigenous individuals from 12 different West Central South America localities spanning from the desert coast, high altitude Andean plates and the Amazon tropical forest within the territories of Peru (n = 249) (Departments of Loreto, Ucayali, Lambayeque, Junin, Ayacucho, Huancayo and Puno), and Ecuador (n = 182) (Region of Esmeraldas and Santo Domingo de los Colorados). The distribution of MBL2 genotypes among the populations showed that the defective variant LYPB haplotype was very common. It showed the highest frequencies in Puno (Taquile (0.80), Amantani (0.80) and Anapia (0.58) islander communities of the Lake Titicaca), but lower frequencies of 0.22 in Junin (Central Andean highland) and Ucayali (Central Amazonian forest), as well as 0.27 and 0.24 in the Congoma and Cayapa/Chachis populations in the Amazonian forest in Ecuador were also observed. Our results suggest that the high prevalence of the MBL2 LYPB variant causing low levels of functional MBL in serum may mainly reflect a random distribution due to a population bottleneck in the founder populations.

  8. Nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal: el caso de los pequeños propietarios forestales de la Cordillera de Nahuelbuta (Chile)

    OpenAIRE

    Sergio Monrroy-Concha; Jimmy M. Pincheira Ulbrich

    2013-01-01

    Se evaluó el nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal que poseen los pequeños propietarios forestales en dos territorios de la Cordillera de Nahuelbuta, en Chile. Para ello, se aplicó una encuesta a 53 personas (10% de las viviendas), que abordó cinco temas centrales: (1) uso del bosque nativo, (2) participación en redes sociales y acceso a la información, (3) conocimiento general de la Ley, (4) conocimiento respecto a la administración y (5) fomento de la Ley...

  9. 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...

  10. Oblique transpression in the western thrust front of the Colombian Eastern Cordillera

    Science.gov (United States)

    Acosta, J.; Lonergan, L.; Coward, M. P.

    2004-11-01

    New kinematic data reveal that the main faults of the western foothills of the Colombian Eastern Cordillera are a series of left-lateral to oblique thrusts that are offset by steeply dipping, northwest-trending, left-lateral, strike-slip faults. Kinematic data were collected from the main structures that dominate the 350-km length of the western foothills of the Eastern Cordillera, north of Bogota (La Salina-Bituima, Cambrás, Dos Hermanos-Alto del Trigo, and Bucaramanga faults). These data indicate that transpression is responsible for the Cenozoic formation of the folds and thrusts that deform the Mesozoic and Cenozoic sedimentary sequences of the Middle Magdalena Valley. Kinematic and structural data suggest that the La Salina-Bituima fault changed from a reverse fault to a fault with a left-lateral, strike-slip sense of displacement during middle to late Miocene times. As it propagated, a transpressive zone was generated in the western foothills of the Eastern Cordillera, with the development of arcuate, oblique-reverse secondary faults on the leading edge of the Magdalena basin (e.g. Cambrás, Dos Hermanos). This development implies that during the Neogene (?), the tectonics of the western foothills were dominated by nonplanar deformation with shortening accompanied by significant left-lateral, strike-slip displacements. These new data indicate that the oblique convergence vector imposed by convergence among the Nazca, Caribbean, and South American plates is not fully partitioned in space but instead must be distributed in a diffuse zone of transpressional deformation along the western margin of the Eastern Cordillera and its associated foreland basin.

  11. The Columbia Plateau Revealed; Low Temperature Thermochronology Across the Canadian Cordillera and Links to Lithospheric Delamination.

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    Guest, B.; Bacque, D.; Miles, N.; Stockli, D. F.

    2014-12-01

    Active deformation and mountain building in the Canadian Cordillera ceased in the Paleogene, a period during which this orogen was among the highest on earth. The present morphology, relief and altitude of the mountains and the foothills in the adjacent foreland belt are the result of a feedback relationship between erosion and isostatic compensation. Our low temperature thermochronology data (U-Th/He ages on zircon and apatite) were collected from 5 sample-transects spanning the Intermontane, Omineca, Foreland, and Foothills belts along a Jasper-Vancouver transect. The data show rapid cooling (>15℃/Ma) from >180℃ to RMT) during the Eocene (56 - 33 Ma). In the Foreland and Foothills belts to the east of the RMT the data show modest cooling (~4℃/Ma) during the latest Cretaceous to Early Eocene (~80Ma - 55 Ma) followed by rapid cooling (~15℃/Ma) between ~55 Ma and ~45 Ma transitioning to slower cooling (~1℃/Ma) after 45 Ma. This cooling pattern is consistent with rapid regional uplift and exhumation across the interior belts of the Cordillera during a regional transition from contraction to extension in the early to middle Eocene. At the same time in the Foreland and Foothills belts, during a period of accelerated cooling, contraction was continuing. The combination of rapid exhumation and extension in the interior belts and rapid exhumation and contraction in the Foreland and Foothills belts is similar to what is observed around the Altiplano and Tibetan plateaus. This suggests that the Canadian Cordillera is a fossil plateau (Columbia Plateau) that formed in the Eocene. The lack of a mantle lithosphere beneath the interior belts of the Canadian Cordillera (west of the RMT) and the regional extent of rapid exhumation suggests that the Columbia Plateau formed in response to a large-scale lithosphere removal event; possibly wholesale delamination.

  12. Reducing risks from hazardous glacier lakes in the Cordillera Blanca (Peru): Six decades of experience and perspectives for the future

    Science.gov (United States)

    Portocarrero, Cesar; Cochachin, Alejo; Frey, Holger; González, Cesar; Haeberli, Wilfried; Huggel, Christian

    2016-04-01

    Outbursts from glacier lakes at various spatial and temporal scales have had marked geomorphological effects in many mountain ranges. In many glacierized Andean mountain regions substrates of human settlements made out of flood and debris-flow deposits are testimonies of such events. Examples in the Cordillera Blanca, Peru, are the towns of Caraz, Carhuaz or parts of Huaraz. Continued glacier shrinking since the end of the Little Ice Age caused the formation or enlargement of numerous lakes. The outburst of Laguna Palcacocha, destroying the centre of Huaraz and causing more than 1800 losses of life in December 1941, marked the beginning of systematic risk reduction work in Peru. Corresponding efforts included glacier and lake inventories, hazard assessments, definition of high-risk situations, and completion of engineering work for lake-level lowering in more than 30 cases. The latter comprises outlet reinforcements on morainic dams as well as artificial tunnels in bedrock thresholds. This work has been remarkably efficient as documented in the latest case of the Laguna Huallcacocha (Carhuaz-Ancash), where the earlier made installations withstood the erosive power of an impact wave from an ice avalanche in 2015. In the case of the Laguna 513, the impact wave and far-reaching flood caused by a rock/ice avalanche from Nevado Hualcán in April 2010 showed that the risk had been essentially reduced by the preventive lake-level lowering in the early 1990s but not to zero. Risk assessments, planning, construction and non-structural risk reduction efforts continue. Work is in progress to increase the safety of Laguna Palcacocha where extensive assessments and model calculations had been carried out. Risks related to rock/ice avalanches into lakes from steep icy slopes and related to de-buttressing processes as well as long-term permafrost degradation increases. Based on morphological indications and numerical modelling (GlabTop) an inventory of possible future lakes

  13. Along-Strike Variations in Crustal Seismicity in the Central Andes and Geodynamic Implications

    Science.gov (United States)

    Metcalf, K.; Pearson, D. M.; Kapp, P. A.; McGroder, M.; Kendall, J. J.

    2011-12-01

    For the central Andes, we compiled relocated crustal earthquakes (magnitude ≥ 4.5) from the EHB Bulletin and Nipress et al. [2007] and focal mechanisms from the Global CMT catalog and published literature [Alvarado et al., 2005]. These data were plotted in map, cross section, and 3D views in the context of local tomography [Koulakov et al., 2006] and lithospheric boundaries [Tassara et al., in prep]. The results imply major along-strike variations in the mechanisms of crustal deformation. At the latitude of the Altiplano, there is scarce forearc seismicity. The thin-skinned Bolivian retroarc thrust belt shows no seismic events (magnitude ≥ 4.5), suggesting that it is deforming aseismically or locked. In contrast, at the latitude of the Puna to the south (20-25°S), crustal seismicity is more prevalent in both the forearc and retroarc. Within this region, active deformation in the Coastal Cordillera near Antofagasta is occurring along steeply east-dipping normal faults at 15-41 km depth; this is the only part of the central Andean forearc that displays prominent extension. Outboard of this, thrust events at ~15 km depth in the forearc wedge display gently dipping nodal planes, and may be signatures of underplating crust that was tectonically eroded at the trench. Underplating is a likely process by which this region of the forearc has undergone ~1 km of surface uplift during the Neogene. Seismicity with thrust or reverse and oblique focal mechanisms in the retroarc wedge is localized beneath the frontal part of the thick-skinned Eastern Cordilleran thrust belt and the Santa Barbara ranges. Seismicity along discrete, east- and west-dipping planes occurs to near Moho depths (~50 km). While retroarc crustal seismicity continues to the south toward the Juan Fernandez flat slab, there is a concentration of seismic events in the retroarc at the latitude (22-23°S) where there is prominent normal faulting in the forearc. We interpret the compiled data to suggest that

  14. Forward modeling of δ18O in Andean ice cores

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    Hurley, J. V.; Vuille, M.; Hardy, D. R.

    2016-08-01

    Tropical ice core archives are among the best dated and highest resolution from the tropics, but a thorough understanding of processes that shape their isotope signature as well as the simulation of observed variability remain incomplete. To address this, we develop a tropical Andean ice core isotope forward model from in situ hydrologic observations and satellite water vapor isotope measurements. A control simulation of snow δ18O captures the mean and seasonal trend but underestimates the observed intraseasonal variability. The simulation of observed variability is improved by including amount effects associated with South American cold air incursions, linking synoptic-scale disturbances and monsoon dynamics to tropical ice core δ18O. The forward model was calibrated with and run under present-day conditions but can also be driven with past climate forcings to reconstruct paleomonsoon variability. The model is transferable and may be used to render a (paleo)climatic context at other ice core locations.

  15. An Outbreak of Bartonella bacilliformis in an Endemic Andean Community.

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    Nuria Sanchez Clemente

    Full Text Available Bartonellosis affects small Andean communities in Peru, Colombia and Ecuador. Research in this area has been limited.Retrospective review of 191 cases of bartonellosis managed in Caraz District Hospital, Peru, during the last outbreak (2003.The majority of cases (65% were 14 years old and younger. There was a peak in acute cases after the rainy season; chronic cases presented more constantly throughout the year. The sensitivity of blood smear against blood culture in acute disease was 25%. The most commonly used treatment for chronic disease was rifampicin; chloramphenicol was used to treat most acute cases. Complications arose in 6.8% and there were no deaths.Diagnostic and treatment algorithms for acute and chronic bartonellosis have been developed without a strong evidence base. Preparation of ready-to-go operational research protocols for future outbreaks would strengthen the evidence base for diagnostic and treatment strategies and enhance opportunities for control.

  16. Spatial random downscaling of rainfall signals in Andean heterogeneous terrain

    Science.gov (United States)

    Posadas, A.; Duffaut Espinosa, L. A.; Yarlequé, C.; Carbajal, M.; Heidinger, H.; Carvalho, L.; Jones, C.; Quiroz, R.

    2015-07-01

    Remotely sensed data are often used as proxies for indirect precipitation measures over data-scarce and complex-terrain areas such as the Peruvian Andes. Although this information might be appropriate for some research requirements, the extent at which local sites could be related to such information is very limited because of the resolution of the available satellite data. Downscaling techniques are used to bridge the gap between what climate modelers (global and regional) are able to provide and what decision-makers require (local). Precipitation downscaling improves the poor local representation of satellite data and helps end-users acquire more accurate estimates of water availability. Thus, a multifractal downscaling technique complemented by a heterogeneity filter was applied to TRMM (Tropical Rainfall Measuring Mission) 3B42 gridded data (spatial resolution ~ 28 km) from the Peruvian Andean high plateau or Altiplano to generate downscaled rainfall fields that are relevant at an agricultural scale (spatial resolution ~ 1 km).

  17. A new Andean species of Philodryas (Dipsadidae, Xenodontinae) from Ecuador.

    Science.gov (United States)

    Zaher, Hussam; Arredondo, Juan C; Valencia, Jorge H; Arbeláez, Ernesto; Rodrigues, Miguel T; Altamirano-Benavides, Marco

    2014-04-04

    We describe a new species of Philodryas from the highlands of southern Ecuador. The new species is distinguished from all known species of Philodryas by a unique combination of coloration, scalation, and hemipenial characters. The new species resembles Philodryas simonsii in color pattern. However, they differ notoriously by their hemipenial morphology. The three other trans-Andean members of the genus (Philodryas simonsii, Philodryas chamissonis, and Philodryas tachymenoides), along with the new species, compose a probably monophyletic group that may be characterized by the presence of ungrooved postdiastemal teeth in the maxilla. Unlike most species of the genus Philodryas, the new species shows a restricted distribution, being apparently endemic to a small region of high-altitude (3150-4450m) grasslands in the southern Andes of Ecuador.

  18. Large-scale patterns of turnover and Basal area change in Andean forests.

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    Selene Báez

    Full Text Available General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century.

  19. Revisiting the Andean butterfly Eryphanis zolvizora group (Lepidoptera, Nymphalidae: one or several species?

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    Patrick Blandin

    2014-01-01

    Full Text Available Eryphanis zolvizora (Hewitson, 1877 is a rare Andean endemic butterfly, described from Bolivia, which has been historically classified either as a unique species, or as part of a group of three allopatric species from Bolivia, Ecuador and Colombia. In this paper, the group is revised using more than 200 specimens housed in 34 European, and North and South American public and private collections. For the first time, the presence of the group in Western Ecuador and Venezuela is confirmed, and important data on Peruvian populations are provided. In some populations, individual variations of genitalia are observed. Nevertheless, male genitalia allow the distinction of four geographical groups. Considering also habitus characters, eight taxa are distinguished and considered to be subspecies, of which five are new: Eryphanis zolvizora inca ssp. nov., Eryphanis zolvizora chachapoya ssp. nov., Eryphanis zolvizora casagrande ssp. nov.., Eryphanis zolvizora reyi ssp. nov., and Eryphanis zolvizora isabelae ssp. nov.  In the present state of knowledge, these taxa are allopatric, except for a possible geographic overlap in central Peru, where data are insufficient to prove sympatry. The “several subspecies vs. several species” dilemma is discussed, considering its impact for conservation action and policies.

  20. Large-Scale Patterns of Turnover and Basal Area Change in Andean Forests

    Science.gov (United States)

    Blundo, Cecilia; Aguilar, Manuel; Aguirre, Nikolay; Aquirre, Zhofre; Álvarez, Esteban; Cuesta, Francisco; Farfán-Ríos, William; García-Cabrera, Karina; Grau, Ricardo; Linares-Palomino, Reynaldo; Malizia, Lucio R.; Cruz, Omar Melo; Osinaga, Oriana; Reynel, Carlos; Silman, Miles R.

    2015-01-01

    General patterns of forest dynamics and productivity in the Andes Mountains are poorly characterized. Here we present the first large-scale study of Andean forest dynamics using a set of 63 permanent forest plots assembled over the past two decades. In the North-Central Andes tree turnover (mortality and recruitment) and tree growth declined with increasing elevation and decreasing temperature. In addition, basal area increased in Lower Montane Moist Forests but did not change in Higher Montane Humid Forests. However, at higher elevations the lack of net basal area change and excess of mortality over recruitment suggests negative environmental impacts. In North-Western Argentina, forest dynamics appear to be influenced by land use history in addition to environmental variation. Taken together, our results indicate that combinations of abiotic and biotic factors that vary across elevation gradients are important determinants of tree turnover and productivity in the Andes. More extensive and longer-term monitoring and analyses of forest dynamics in permanent plots will be necessary to understand how demographic processes and woody biomass are responding to changing environmental conditions along elevation gradients through this century. PMID:25973977

  1. Genetic diversity of Phytophthora infestans in the Northern Andean region

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    Grünwald Niklaus J

    2011-02-01

    Full Text Available Abstract Background Phytophthora infestans (Mont. de Bary, the causal agent of potato late blight, is responsible for tremendous crop losses worldwide. Countries in the northern part of the Andes dedicate a large proportion of the highlands to the production of potato, and more recently, solanaceous fruits such as cape gooseberry (Physalis peruviana and tree tomato (Solanum betaceum, all of which are hosts of this oomycete. In the Andean region, P. infestans populations have been well characterized in Ecuador and Peru, but are poorly understood in Colombia and Venezuela. To understand the P. infestans population structure in the Northern part of the Andes, four nuclear regions (ITS, Ras, β-tubulin and Avr3a and one mitochondrial (Cox1 region were analyzed in isolates of P. infestans sampled from different hosts in Colombia and Venezuela. Results Low genetic diversity was found within this sample of P. infestans isolates from crops within several regions of Colombia and Venezuela, revealing the presence of clonal populations of the pathogen in this region. We detected low frequency heterozygotes, and their distribution patterns might be a consequence of a high migration rate among populations with poor effective gene flow. Consistent genetic differentiation exists among isolates from different regions. Conclusions The results here suggest that in the Northern Andean region P. infestans is a clonal population with some within-clone variation. P. infestans populations in Venezuela reflect historic isolation that is being reinforced by a recent self-sufficiency of potato seeds. In summary, the P. infestans population is mainly shaped by migration and probably by the appearance of variants of key effectors such as Avr3a.

  2. [Elaboration and evaluation of infant food based on Andean crops].

    Science.gov (United States)

    Repo-Carrasco, R; Hoyos, N L

    1993-06-01

    The Andes mountain range of South America is one of the most important centres for crop domestication, potato, corn, and lesser known grains such as quinua, cañihua, kiwicha and tarwi are indigenous of these highlands. These Andean grains have adapted perfectly to the climatic and geographical conditions present, whereas other grains have not been able to survive. In addition to their hardiness, they also have a high nutritional value. Bearing in mind on one hand, the high nutritional value of these indegenous products, and on the other hand the high rate of child malnutrition prevalent in the population, it was considered important to look for new variations in their processing which would facilitate their consumption by the poor working classes, especially the children. Accordingly three different flour mixtures were developed based on these Andean grains, the mixtures were then subjected to bromatological and biological analysis. The three new flour mixtures were: Quinua-Cañihua-Broad Bean (Q-C-B), Quinua-Kiwicha-Bean (Q-K-B) and Kiwicha-Rice (K-R). The protein content of these mixtures varied between 11.35-15.46 g/100g, the mixture K-R having the lowest protein level and the Q-C-B having the highest. The Q-K-B mixture had the highest chemical score, PER and NPU value. This PER value of 2.59 was higher than the value of casein which was 2.50. In addition this mixture had a chemical score of 0.94 and a NPU value of 59.38. The Q-C-B mixture had a chemical score of 0.88 and its PER, NPU and Digestibility values were 2.36, 47.24 and 79.2 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  3. Geochemical variations in the Quaternary Andean back-arc volcanism, southern Mendoza, Argentina

    Science.gov (United States)

    Espanon, Venera R.; Chivas, Allan R.; Kinsley, Leslie P. J.; Dosseto, Anthony

    2014-11-01

    The Payenia Basaltic Province (PBP) is located 450 km east of the Chile-Peru trench in central west Argentina, behind the Andean arc front, constituting the back-arc. In order to evaluate the influence of the subducting slab as well as the magmatic source of this region, two volcanic fields located at comparable distance to the trench, having abundant basaltic products and similar eruptive timeframes were chosen. The Llancanelo (LLVF) and the Payún Matrú (PMVF) volcanic fields are part of the PBP and exhibit abundant basaltic activity during the Pleistocene. The geochemical data suggest that the LLVF has some arc signatures which have been described as weak as they are not as pronounced as in the Andean arc. The weak arc signature is not derived from slab dehydration as high Th enrichment relative to U cannot be explained by this process. We relate the Th enrichment as well as the lack of large residual garnet signatures, to slab sediments in the source. In the case of the PMVF, no arc signature has been inferred despite being only 30 km south of the LLVF. However the PMVF has a composition similar to that of the local intraplate end member, represented by the Rio Colorado volcanic field. The two volcanic fields, LLVF and PMVF, show indications of lower crustal assimilation as they trend towards the lower continental crust end member in Nb/U vs Ce/Pb and Nb/Yb vs Th/Yb diagrams. The geochemical differences between the LLVF and the PMVF as well as between several volcanic fields are illustrated using spatial distribution maps of geochemical ratios. Using this new approach, the decrease in arc signature can be traced in the back-arc and the higher enrichment in high field strength elements (HFSE) relative to large ion lithophile elements (LILE) in the PMVF compared to the LLVF is explicitly shown. These geospatial maps provide a graphical manner to illustrate the presence of two distinct types of volcanism (OIB-like and arc-like) occurring in the same Quaternary

  4. Climatic and lacustrine morphometric controls of diatom paleoproductivity in a tropical Andean lake

    Science.gov (United States)

    Bao, R.; Hernández, A.; Sáez, A.; Giralt, S.; Prego, R.; Pueyo, J. J.; Moreno, A.; Valero-Garcés, B. L.

    2015-12-01

    The coupling of lake dynamics with catchment biogeochemistry is considered the key element controlling primary production in mountain lakes at time scales of a few decades to millennia, yet little is known on the impacts of the morphometry of lakes throughout their ontogeny. As Lake Chungará (Central Andean Altiplano, northern Chile) experienced long-term lake-level fluctuations that strongly modified its area:volume ratio, it is an ideal system for exploring the relative roles that long-term climatic shifts and lake morphometry play on biosiliceous lacustrine productivity. In this paper, we review previous data on the percent contents of total organic carbon, total inorganic carbon, total nitrogen, total biogenic silica, isotopic composition of organic matter, carbonates, and diatom frustules, as well as data on the abundance of the chlorophycean Botryococcus braunii in this lake for the period 12,400-1300 cal yr BP. We also include new data on organic carbon and biogenic silica mass accumulation rates and the diatom assemblage composition of an offshore core dated using 14C and U/Th. Biosiliceous productivity in Lake Chungará was influenced by shifts in allochthonous nutrient inputs related to variability in precipitation. Humid phases dated at approx. 12,400 to 10,000 and 9600 to 7400 cal yr BP coincide with periods of elevated productivity, whereas decreases in productivity were recorded during arid phases dated at approx. 10,000 to 9600 and 7400 to 3550 cal yr BP (Andean mid-Holocene Aridity Period). However, morphometry-related in-lake controls led to a lack of a linear response of productivity to precipitation variability. During the late Glacial to early Holocene, lowstands facilitated complete water column mixing, prompting episodic massive blooms of a large centric diatom, Cyclostephanos cf. andinus. Thus, moderate productivity could be maintained, regardless of aridity, by this phenomenon of morphometric eutrophy during the early history of the lake

  5. 78 FR 21002 - Andean Trade Preference Act (ATPA), as Amended: Request for Public Comments Regarding Beneficiary...

    Science.gov (United States)

    2013-04-08

    ... From the Federal Register Online via the Government Publishing Office TRADE REPRESENTATIVE Andean.... The original ATPA allowed Bolivia, Ecuador, Colombia, and Peru to be considered as beneficiary... November 25, 2008, the President determined that Bolivia no longer satisfied the eligibility...

  6. The role of western Mediterranea tectonic evolution in the geometry of a karstic domain in the Betic Cordilleras (Sierra Gorda, Spain): Importance of a tardy extensional regime

    Science.gov (United States)

    Pistre, Séverin; Lopez-Chicano, Manuel; Pulido-Bosch, Antonio; Drogue, Claude

    1999-01-01

    Located in the central part of the Betic Cordilleras, the large carbonate Sierra Gorda Massif provides an example of a west-Mediterranean karstic aquifer. In spite of a complex polyphased tectonic history, the fracturing presents, from aerial views and at outcrop scale a quite organised geometry. Four fracture directions are found over the massif: N000-010, N050-070, N090-100 and N140-170. The statistical and geostatistical approach allows the characteristics (lengths, orientations) and the spatial structure for each fracture set to be determined. The NOOO-010 and N140-170 sets are grouped in packets whereas the two other sets are grouped in bands. The microtectonic study describes the evolution of the massif in the geodynamic context of this part of Mediterranea, distinguishing three recent stages of brittle tectonic activity in the massif: a WNW-ESE Middle Miocene compression, then a NNW-SSE to NW-SE compression with a poorly wrenching regime, and finally a probably pre-Quaternary N-S radial distension. This last stage is essential for the karstification of the massif and groundwater circulation. From the combined analysis of fracture network geometry and palaeostresses a multiple porosity model in agreement with hydrological observations made inside the massif can be proposed: in particular, the hectometric N090-100 (and N050-070) fractures which are essential for the network connectivity, and have a major drainage role at aquifer scale, while the N000-010 and N140-170 ones have a more local drainage role. This extensive tardy regime, which is for the first time described separately from the internal zones of the Cordilleras, must be considered as a significant phenomenon on a regional scale, and henceforth integrated in future geodynamic schemes of this part of Mediterranea.

  7. A tectonically controlled basin-fill within the Valle del Cauca, West-Central Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Rine, J.M.; Keith, J.F. Jr.; Alfonso, C.A.; Ballesteros, I.; Laverde, F.; Sacks, P.E.; Secor, D.T. Jr. (Univ. of South Carolina, Columbia (United States)); Perez, V.E.; Bernal, I.; Cordoba, F.; Numpaque, L.E. (Ecopetrol, Bogota (Colombia))

    1993-02-01

    Tertiary strata of the Valle del Cauca reflect a forearc/foreland basin tectonic history spanning a period from pre-uplift of the Cordillera Central to initiation of uplift of the Cordillera Occidental. Stratigraphy of the Valle del Cauca begins with Jurassic-Cretaceous rocks of exotic and/or volcanic provenance and of oceanic origin. Unconformably overlying these are Eocene to Oligocene basal quartz-rich sandstones, shallow marine algal limestones, and fine-grained fluvial/deltaic mudstones and sandstones with coalbeds. These Eocene to Oligocene deposits represent a period of low tectonic activity. During late Oligocene to early Miocene, increased tectonic activity produced conglomeratic sediments which were transported from east to west, apparently derived from uplift of the Cordillera Central, and deposited within a fluvial to deltaic setting. East-west shortening of the Valle del Cauca basin folded the Eocene to early Miocene units, and additional uplift of the Cordillera Central during the later Miocene resulted in syn-tectonic deposition of alluvial fans. After additional fold and thrust deformation of the total Eocene-Miocene basin-fill, tectonic activity abated and Pliocene-Quaternary alluvial and lacustrine strata were deposited. Within the framework of this depositional and tectonic history of the Valle del Cauca, hydrocarbon exploration strategies can be formulated and evaluated.

  8. Orogeny and drainage in the Lerma Valley region (Eastern Cordillera, Salta, Argentina) during the late Pleistocene

    OpenAIRE

    Gustavo González Bonorino; Liliana Del Valle Abascal

    2016-01-01

    En el Pleistoceno tardío, luego de la incipiente elevación de las serranías subandinas, la contracción retornó al interior del orógeno. En aquel tiempo un piedemonte conectaba los contrafuertes occidentales de la Cordillera Oriental (sierras de Lesser y Obispo) con la llanura subandina, a través de la región que hoy7 ocupan el valle de Lerma y la serranía Mojotoro-Castillejo. La contracción dio origen a las elevaciones interiores en la sierra de Vaqueros y los Cerrillos de San Miguel, y luego...

  9. Surgimiento de nuevas formas de violencias urbanas en Pereira : Caso Organización la Cordillera

    OpenAIRE

    2012-01-01

    El presente trabajo de investigación contiene la presentación de los resultados de la indagación sobre el fenómeno de nuevas violencias urbanas. El estudio se realizó en la ciudad de Pereira (Risaralda), sobre las nuevas formas de organización criminal, representada por la Organización la Cordillera, en el manejo del narcotráfico, narcomenudeo y violencia cotidiana en los barrios marginales de la ciudad. Específicamente, el estudio se centra en indagar las neo violencias monopolizadas por est...

  10. ASPECTOS ECOLOGICOS DE UNA POBLACION DE ROEDORES EN LA CORDILLERA ORIENTAL COLOMBIANA

    OpenAIRE

    2013-01-01

    Distribution, abundancy, demographic structure, type of spatial pattems and home range of a population ofThomasomys laniger (Thomas, 1895) (RODENTIA: CRICETIDAE) from Valledel Frailejón (Frailejon valley) in Chingaza Natural National Park, on the Oriental mountain chain (cordillera Oriental) in Department of Cundinamarca, were studied from January to December of 1992.· The variation ofthe population pattems according to seasonality based on frecuency of capture ofmice in diferent trapping pha...

  11. Hydrodynamic Modeling of Flash Floods in an Andean Stream: Challenges for Assessing Flood Hazards in Mountain Rivers

    Science.gov (United States)

    Contreras, M. T.; Escauriaza, C. R.

    2015-12-01

    Rain-induced flash floods are common events in regions close to the southern Andes, in north and central Chile. Rapid urban development combined to the changing climate and ENSO effects have resulted in an alarming proximity of flood-prone streams to densely populated areas in the Andean foothills, increasing the risk for cities and infrastructure. Simulations of rapid floods in these complex watersheds are particularly challenging, especially if there is insufficient geomorphological and hydrometeorological data. In the Quebrada de Ramón, an Andean stream that passes through a highly populated area in the east part of Santiago, Chile, previous events have demonstrated that sediment concentration, flow resistance, and the characteristic temporal and spatial scales of the hydrograph, are important variables to predict the arrival time of the peak discharge, flow velocities and the extension of inundated areas. The objective of this investigation is to improve our understanding of the dynamics of flash floods in the Quebrada de Ramón, quantifying the effects of these factors on the flood propagation. We implement a two-dimensional model based on the shallow water equations (Guerra et al. 2014) modified to account for hyperconcentrated flows over natural topography. We evaluate events of specific return periods and sediment concentrations, using different methodologies to quantify the flow resistance in the channel and floodplains. Through this work we provide a framework for future studies aimed at improving hazard assessment, urban planning, and early warning systems in urban areas near mountain streams with limited data, and affected by rapid flood events. Work supported by Fondecyt grant 1130940 and CONICYT/FONDAP grant 15110017.

  12. Dynamic paleogeography of the Jurassic Andean Basin: pattern of transgression and localisation of main straits through the magmatic arc

    Directory of Open Access Journals (Sweden)

    J-C. Vicente

    2005-03-01

    Full Text Available The paleogeographic evolution of the Jurassic Andean retroarc basin is examined at a global scale for the Central Andes. In this paper, it is called for the striking continuity and lasting of the active volcanic arc. Both direct and indirect sedimentologic evidences allow to locate the western border (insular of the basin and opposite it with the eastern border (cratonic. Emphasis is placed on the volcaniclastic deposits and synsedimentary structures associated with this insular border. It is concluded that the arc magmatic activity has contributed considerably in sediment supply to the basin. Extent and continuity of the arc implies to locate the straits connecting with the Paleopacific. Systematic check of the time of transgressions coupled with sequential facies analysis provides a dynamic outlook of the transgressive process. Sectors with early transgression allow to distinguish two main gulfs of passage through the arc from which waters have progressed lengthwise at the same time northward and southward in a narrow retroarc furrow : the first at latitude of Taltal (25°S, the second at latitude of Curepto (35°S. Both initiated in the upper Triassic and extended during the Hettangian. The evolution as separate basins (Tarapacá and Aconcagua-Neuquén ended by fusion in middle Pliensbachian giving rise to a continuous elongated basin from Chubut to northern Peru. The remarkable continuity and narrowness of the Andean Basin leaves no doubt about its tectonic control. This stems to its geotectonic setting as a typical retroarc basin adjacent to a very active magmatic arc and explains the extreme mobility of its insular margin characterized by a huge volcanoclastic apron with associated debris flows and turbidites.

  13. Changing Hydrology in Glacier-fed High Altitude Andean Peatbogs

    Science.gov (United States)

    Slayback, D. A.; Yager, K.; Baraer, M.; Mohr, K. I.; Argollo, J.; Wigmore, O.; Meneses, R. I.; Mark, B. G.

    2012-12-01

    Montane peatbogs in the glacierized Andean highlands of Peru and Bolivia provide critical forage for camelids (llama and alpaca) in regionally extensive pastoral agriculture systems. During the long dry season, these wetlands often provide the only available green forage. A key question for the future of these peatbog systems, and the livelihoods they support, is the impact of climate change and glacier recession on their hydrology, and thus forage production. We have already documented substantial regional glacier recession, of, on average, approximately 30% of surface area over the past two decades. As glaciers begin to retreat under climate change, there is initially a period of increased meltwater outflow, culminating in a period of "peak water", and followed by a continual decline in outflows. Based on previous work, we know that some glaciers in the region have already passed peak water conditions, and are now declining. To better understand the impacts of these processes on peatbog hydrology and productivity, we have begun collecting a variety of surface data at several study sites in both Bolivia and Peru. These include precipitation, stream flow, water levels, water chemistry and isotope analyses, and peatbog biodiversity and biomass. These measurements will be used in conjunction with a regional model driven by satellite data to predict likely future impacts. We will present the results from these initial surface measurements, and an overview of satellite datasets to be used in the regional model.

  14. Mechanisms of O2 transport in Andean dogs.

    Science.gov (United States)

    Banchero, N; Cruz, J; Bustinza, J

    1975-04-01

    Using previously inserted catheters, 11 dogs native to high altitude (7.5-23 kg bwt) were studied standing and unsedated in Cerro de Pasco, Peru at 4350 meters. Hemoglobin (Hb), hematocrit (Hct), O2 and CO2 contents, PO2, PCO2 and pH were measured in simultaneously obtained arterial and mixed venous blood samples. Blood pressures were measured in the pulmonary artery and the left ventricle and cardiac output (Q) was determined by dye dilution. Moderately higher values for Hb and Hct were found in these dogs. Hb-O2 affinity was no different than that found in sea level dogs: the P50 in the Andean dogs was 31.6 mm Hg at 38 degrees C and pH of 7.4. Because of the low barometric pressure at 4350 m (458 mmHg) the partial pressures of oxygen in inspired and in alveolar air were lower than at sea level: 84.3 and 56.4 mm Hg, respectively. PAO2 and PVO2, were 55.5 and 32.9 mm Hg while the SAO2 and SVO2 were 79.5 and 50.7%, respectively. Marked hyperventilation was observed (PACO2, 25.6 mm Hg) however, pH was normal. Cardiac output was normal (average 162 plus or minus 39 ml/min/kg). Moderate pulmonary arterial hypertension was observed in the presence of normal left ventricular end diastolic pressure suggesting increased pulmonary vascular resistance.

  15. Cerebral vasoreactivity in Andeans and headache at sea level.

    Science.gov (United States)

    Appenzeller, O; Passino, C; Roach, R; Gamboa, J; Gamboa, A; Bernardi, L; Bonfichi, M; Malcovati, L

    2004-04-15

    Headache is common in Cerro de Pasco (CP), Peru (altitude 4338 m) and was present in all patients with chronic mountain sickness (CMS) in CP reported here. Forty-seven percent of inhabitants report headache. Twenty-four percent of men have migraine with aura, with an average of 65 attacks a year. We assessed vasoreactivity of the cerebral vessels to CO2 by rebreathing and to NO by the administration of isosorbite dinitrate (IDN), a nitric oxide (NO) donor, using transcranial Doppler ultrasound in the middle cerebral artery (MCA) in natives of CP, some of whom suffered from CMS. We repeated the measurements in Lima (altitude 150 m) in the same subjects within 24 h of arrival. Vasodilatation in the middle cerebral artery supply territory in response to CO2 and NO, both physiologic vasodilators, is defective in Andean natives at altitude and in the same subjects at sea level. Incapacitating migraine can occur with impaired cerebral vasoreactivity to physiologic vasodilators. We propose that susceptibility to migraine might depend in part on gene expression with consequent alterations of endothelial function.

  16. JURASSIC PALEONTOLOGICAL HERITAGE OF MURCIA (BETIC CORDILLERA, SOUTH-EASTERN SPAIN

    Directory of Open Access Journals (Sweden)

    GREGORIO ROMERO

    2004-03-01

    Full Text Available Jurassic rocks of the External and Internal Zones of the Betic Cordillera are widespread in the province of Murcia. Four areas are considered of special interest for stratigraphical and paleontological analysis: a Sierra Quípar and b Sierras Lúgar-Corque (External Subbetic, c Sierra Ricote (Median Subbetic and d Sierra Espuña (Malaguide Complex. The first two contain Jurassic sections including Sinemurian-Tithonian deposits, and major stratigraphic discontinuities, containing significant cephalopod concentrations of taphonomic and taxonomic interest, occuring in the Lower-Upper Pliensbachian, Lower/Middle Jurassic and Middle/Upper Jurassic boundaries. These areas are also relevant for biostratigraphical analysis of the Middle-Upper Jurassic interval. In the Sierra de Ricote, the Mahoma section is of especial interest for the study of Lías/Dogger transition. Casa Chimeneas section constitutes the best Subbetic site for the analysis of the Lower/Upper Bajocian boundary. In the La Bermeja-Casas de Vite area, the Bajocian-Tithonian interval is well-represented, including a parastratotype of the Radiolarite Jarropa Formation. Finally, the Malvariche section in Sierra Espuña represents the best Jurassic succession of Internal Zones of the Betic Cordillera and could be considered as a reference section for this Betic Domain. In this paper a heritage evaluation has been carried out for these classical jurassic sections with the object of protecting these sites according to the legal framework prevailing in the province of Murcia.

  17. Latest extension of the Laujar fault in a convergence setting (Sierra Nevada, Betic Cordillera)

    Science.gov (United States)

    Martínez-Martos, Manuel; Galindo-Zaldívar, Jesus; Sanz de Galdeano, Carlos; García-Tortosa, Francisco Juan; Martínez-Moreno, Francisco José; Ruano, Patricia; González-Castillo, Lourdes; Azañón, José Miguel

    2017-02-01

    The present-day relief of the Betic Cordillera formed since the Late Miocene through the regional N-S to NW-SE Africa-Eurasia convergence that developed large folds. The Laujar Fault Zone is a south-dipping E-W oriented structure located at the northern boundary of the Alpujarran Corridor Neogene intramontane basin, which separates Sierra Nevada and Sierra de Gador antiforms, in the Internal Zones of the Betic Cordillera. The fault zone acted in a first stage as a dextral strike-slip fault. Currently it moves as a normal fault evidenced by striated calcretes, also in agreement with regional continuous GPS (CGPS) data that support the hypothesis of an active N-S extension in the fault area. In order to analyse the deep geometry of the Laujar Fault Zone, we combined several geophysical techniques (gravity, magnetic, electric resistivity tomography and audio-magnetotelluric data) with field geological observations. Fault surfaces seem to join at a southward-dipping shallow detachment level, including faults covered by the sedimentary infill. The fault zone was developed in a previously weakened area by wrench faults parallel to the Alpujarran Corridor. The recent normal activity of this fault zone may be a consequence of a change in the Africa-Eurasia convergence orientation, which implies a decrease in the N-S compression component. This structure along the southern limb of Sierra Nevada antiform evidences the gravitational collapse of previously thickened crust in a regional compressional context simultaneous to metamorphic core uplift.

  18. Un nuevo Eleutherodactylus (Anura, Leptodactylidae de la Cordillera de Mérida, Andes de Venezuela

    Directory of Open Access Journals (Sweden)

    Chacón-Ortiz, A.

    2004-06-01

    Full Text Available A new frog of the genus Eleutherodactylus is described from the Cordillera de Mérida, Venezuelan Andes. The species is distinguished from others by its moderate size, first finger equal or shorter than second, basal webbing on toes, and dominant colour immaculate brown or with a few spots. The species is compared with the groups unistrigatus and conspicillatus, but not assigned to either of them. A distribution map and a sonogram (of the song are presented. Comments about current knowledge of frogs of the genus Eleutherodactylus in Venezuela are provided.Se describe una nueva rana del género Eleutherodactylus de la Cordillera de Mérida, Andes de Venezuela. La especie se distingue del resto de congéneres por su tamaño moderado, primer dedo de la mano igual o más corto que el segundo, palmeadura pedal basal, y color dominante marrón uniforme o con pocas manchas. Se compara la especie con los grupos unistrigatus y conspicillatus, pero no se asigna a ninguno de ellos. Se presenta un mapa de distribución y un sonograma del canto. Se comenta brevemente sobre el conocimiento actual de las ranas del género Eleutherodactylus en Venezuela.

  19. Subduction system and flat slab beneath the Eastern Cordillera of Colombia

    Science.gov (United States)

    Chiarabba, Claudio; De Gori, Pasquale; Faccenna, Claudio; Speranza, Fabio; Seccia, Danilo; Dionicio, Viviana; Prieto, Germán. A.

    2016-01-01

    Seismicity at the northern terminus of the Nazca subduction is diffused over a wide area containing the puzzling seismic feature known as the Bucaramanga nest. We relocate about 5000 earthquakes recorded by the Colombian national seismic network and produce the first 3-D velocity model of the area to define the geometry of the lithosphere subducting below the Colombian Andes. We found lateral velocity heterogeneities and an abrupt offset of the Wadati-Benioff zone at 5°N indicating that the Nazca plate is segmented by an E-W slab tear, that separates a steeper Nazca segment to the south from a flat subduction to the north. The flat Nazca slab extends eastward for about 400 km, before dip increases to ˜50° beneath the Eastern Cordillera, where it yields the Bucaramanga nest. We explain this puzzling locus of intermediate-depth seismicity located beneath the Eastern Cordillera of Colombia as due to a massive dehydration and eclogitization of a thickened oceanic crust. We relate the flat subducting geometry to the entrance at the trench at ca. 10 Ma of a thick - buoyant oceanic crust, likely a volcanic ridge, producing a high coupling with the overriding plate. Sub-horizontal plate subduction is consistent with the abrupt disappearance of volcanism in the Andes of South America at latitudes > 5°N.

  20. Estimating detection and density of the Andean cat in the high Andes

    Science.gov (United States)

    Reppucci, Juan; Gardner, Beth; Lucherini, Mauro

    2011-01-01

    The Andean cat (Leopardus jacobita) is one of the most endangered, yet least known, felids. Although the Andean cat is considered at risk of extinction, rigorous quantitative population studies are lacking. Because physical observations of the Andean cat are difficult to make in the wild, we used a camera-trapping array to photo-capture individuals. The survey was conducted in northwestern Argentina at an elevation of approximately 4,200 m during October–December 2006 and April–June 2007. In each year we deployed 22 pairs of camera traps, which were strategically placed. To estimate detection probability and density we applied models for spatial capture–recapture using a Bayesian framework. Estimated densities were 0.07 and 0.12 individual/km2 for 2006 and 2007, respectively. Mean baseline detection probability was estimated at 0.07. By comparison, densities of the Pampas cat (Leopardus colocolo), another poorly known felid that shares its habitat with the Andean cat, were estimated at 0.74–0.79 individual/km2 in the same study area for 2006 and 2007, and its detection probability was estimated at 0.02. Despite having greater detectability, the Andean cat is rarer in the study region than the Pampas cat. Properly accounting for the detection probability is important in making reliable estimates of density, a key parameter in conservation and management decisions for any species.

  1. A new species of Andean semiaquatic lizard of the genus Potamites (Sauria, Gymnophtalmidae from southern Peru

    Directory of Open Access Journals (Sweden)

    Germán Chávez

    2012-01-01

    Full Text Available We describe a new lizard species of the genus Potamites from the montane forests of the Cordillera de Vilcabamba (Cusco region and Apurimac River valley (Ayacucho region, between 1500 and 2000 meters of elevation, in southern Peru. The new species is distinguishable from all other species of the genus mainly byhighly keeled scattered scales on dorsum and females lacking femoral pores.

  2. Exploring the potential of an Andean fruit: an interdisciplinary study on the cape gooseberry (Physalis peruviana L.) value chain

    NARCIS (Netherlands)

    Olivares Tenorio, Mary Luz

    2017-01-01

    Cape gooseberry is a fruit cultivated in Andean countries. Currently it is available some international markets, besides the domestic Andean market. Colombia is the major producer and export country at the moment. The value chain of cape gooseberry faces several barriers of technological and governa

  3. Brain blood flow in Andean and Himalayan high-altitude populations: evidence of different traits for the same environmental constraint

    NARCIS (Netherlands)

    G.F.A. Jansen; B. Basnyat

    2011-01-01

    Humans have populated the Tibetan plateau much longer than the Andean Altiplano. It is thought that the difference in length of occupation of these altitudes has led to different responses to the stress of hypoxia. As such, Andean populations have higher hematocrit levels than Himalayans. In contras

  4. Evolución de las cuencas sinorogénicas de la Cordillera Principal entre 35°- 36° S, Malargüe Evolution of the foreland basins in the Cordillera Principal, at 35º - 36º S. Malargüe

    Directory of Open Access Journals (Sweden)

    J. Silvestro

    2005-12-01

    Full Text Available La faja plegada y corrida de Malargüe se encuentra localizada en el extremo sur de la Cordillera Principal a los 35°-36° S. Los estratos de crecimiento preservados en cuencas sintectónicas registraron la cinemática de plegamiento de la faja plegada durante el Cenozoico. La cuenca Pinchera-Ventana, ubicada en el sector oeste del área, está rellena por dos secuencias volcaniclásticas cubiertas por basaltos. En el sector occidental de esta cuenca, las secuencias se adelgazan hacia los anticlinales de La Valenciana y Torrecillas en el oeste y hacia los retrocorrimientos de La Brea en el este, desarrollando discordancias progresivas observadas en el campo. En el sector oriental de la cuenca, el arreglo de facies, la composición de los clastos y la presencia de discordancias sugieren una proveniencia desde el anticlinal Bardas Blancas en el oeste. Dataciones radimétricas de los niveles andesíticos basales (15,1 Ma y de los basaltos al techo (6,7 Ma limitan la edad de esta cuenca al Mioceno medio y superior. La cuenca Malargüe desarrollada en el sector oriental del área de estudio, está rellena por dos secuencias sintectónicas volcaniclásticas, cubiertas por una secuencia postectónica. El análisis sísmico de las secuencias de crecimiento muestra un arreglo divergente relacionado al levantamiento del anticlinal Malargüe en el oeste de la cuenca y un triángulo de crecimiento hacia el este relacionado al levantamiento del anticlinal Chacay. La datación de niveles andesíticos basales en 5,04 Ma y la secuencia postectónica al tope, limitan la edad de la cuenca entre el Mioceno superior y Cuaternario. Estas observaciones indican que los depocentros sedimentarios migraron hacia el antepaís conjuntamente con el avance de la faja plegada en igual sentido.The Andean fold-and-thrust belt of Malargüe is located in the foothills of Cordillera Principal at 35º-36º S. The geometry and age of the growth strata preserved in syntectonic

  5. Regeneración Natural del Roble Negro (Colombobalanus excelsa, Fagaceae en Dos Poblaciones de la Cordillera Oriental de los Andes, Colombia Natural Regeneration of Black Oak (Colombobalanus excelsa, Fagaceae in Two Populations from the Cordillera Oriental of the Colombian Andes

    Directory of Open Access Journals (Sweden)

    César Augusto Parra Aldana

    2011-12-01

    Full Text Available Colombobalanus excelsa es una especie endémica de la zona andina de Colombia, con cuatro poblaciones aisladas que forman rodales homogéneos denominados robledales negros. Se encuentra en categoría vulnerable de amenaza, debido principalmente a la conversión del bosque para usos agropecuarios; observaciones en campo indican que la regeneración natural bajo su propia cobertura es escasa. Se propone responder las siguientes preguntas: 1. ¿La estructura del bosque evidencia deficiencias en la regeneración natural de dos poblaciones de roble negro localizadas en la cordillera oriental de los Andes? 2. ¿El reclutamiento de fhmoreno@unal.edu.co está limitado por la disponibilidad y viabilidad de las semillas en las dos poblaciones estudiadas? Con este objetivo se establecieron 16 transectos permanentes de 0,1 ha para evaluar la estructura de adultos (DAP>10 cm y de la regeneración natural. Durante un año se realizó monitoreo sobre las épocas de fructificación, lluvia de semillas, germinación y banco de semillas. Los resultados muestran un suministro extremadamente bajo de renuevos y propágulos de roble negro, lo cual potencialmente puede poner en riesgo la persistencia de estos bosques. Esta situación obedece a diversos factores involucrados en el proceso de regeneración: desde baja producción de semillas de los árboles adultos, altos niveles de depredación pre-dispersión, alta proporción de semillas vacías, baja viabilidad de las semillas sanas, hasta alta mortalidad de las semillas sanas y viables que llegan al suelo. Si bien todos estos factores actúan en cascada, el último de ellos es quizás el que ejerce un efecto más dramático en el bajo éxito reproductivo de esta especie.Colombobalanus excelsa is an endemic species of the Andean region of Colombia, with four isolated populations, forming pure stands called black oak forests. It has been classified in the threat category ''Vulnerable'', mainly due to conversion of

  6. DNA Barcoding Survey of Anurans across the Eastern Cordillera of Colombia and the Impact of the Andes on Cryptic Diversity.

    Science.gov (United States)

    Guarnizo, Carlos E; Paz, Andrea; Muñoz-Ortiz, Astrid; Flechas, Sandra V; Méndez-Narváez, Javier; Crawford, Andrew J

    2015-01-01

    Colombia hosts the second highest amphibian species diversity on Earth, yet its fauna remains poorly studied, especially using molecular genetic techniques. We present the results of the first wide-scale DNA barcoding survey of anurans of Colombia, focusing on a transect across the Eastern Cordillera. We surveyed 10 sites between the Magdalena Valley to the west and the eastern foothills of the Eastern Cordillera, sequencing portions of the mitochondrial 16S ribosomal RNA and cytochrome oxidase subunit 1 (CO1) genes for 235 individuals from 52 nominal species. We applied two barcode algorithms, Automatic Barcode Gap Discovery and Refined Single Linkage Analysis, to estimate the number of clusters or "unconfirmed candidate species" supported by DNA barcode data. Our survey included ~7% of the anuran species known from Colombia. While barcoding algorithms differed slightly in the number of clusters identified, between three and ten nominal species may be obscuring candidate species (in some cases, more than one cryptic species per nominal species). Our data suggest that the high elevations of the Eastern Cordillera and the low elevations of the Chicamocha canyon acted as geographic barriers in at least seven nominal species, promoting strong genetic divergences between populations associated with the Eastern Cordillera.

  7. Strong lateral strength contrasts in the mantle lithosphere of continents: A case study from the hot SW Canadian Cordillera

    NARCIS (Netherlands)

    Hardebol, N.J.; Beekman, F.; Cloetingh, S.A.P.L.

    2013-01-01

    This study aims at quantifying the 3-D variability in lithosphere strength of the south-eastern Canadian Cordillera and adjacent craton to the east. Strength is calculated in a forward manner, starting from rheological laws of brittle and ductile deformation. The work flow calculates a temperature m

  8. Transference of some microsatellite molecular markers from Fabaceae family to Andean Lupin (Lupinus mutabilis Sweet

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    Michelle C. Chirinos-Arias

    2015-03-01

    Full Text Available In order to analyze transferibility of 15 microsatellite primers from Fabaceae family to Lupinus mutabilis Sweet "andean lupine" chosen to present transferability between species and genera, by its high rate of polymorphic content (PIC and high degree of observed and expected heterozygosity. DNA was extracted of 300 andean lupines plants, PCR conditions were standardized by gradients of master mix components. Primers for screening were run on 3% agarose gel with some samples. Finally population was amplified and run on 6% polyacrylamide gel for its highest resolution. Only 6.67% of primers were amplified, but they were monomorphic, so they cannot be used for molecular characterization. We proposed eight microsatellite primers for andean lupin wich should be probed in laboratory conditions.

  9. How widely is the Andean type of continental margin represented in the Archean

    Science.gov (United States)

    Burke, Kevin

    1988-01-01

    Application of the principle of uniformitarianism to the Archean was discussed in a search for evidence of Archean-type continental margins in Archean rocks. The author cautioned that Archean rocks represent only 2 percent of the current exposure of the continents, half of which is in the North American Superior Province. Care must be taken in interpreting the global tectonic significance of relatively small exposures of Archean rocks, such as South India. Andean margins were characterized by their elongate shape, magmatic associations, and isotopic signatures. Although the compositional evidence alone will always be ambiguous, it was suggested that supporting structural evidence may aid in the identification of Archean Andean margins. Andean margin remains have been recognized in the Superior Province of Canada by these criteria, and the author suggested that the Closepet granite of South India may represent another example.

  10. Ice-sheet control of continental erosion in central and southern Chile (36°-41°S) over the last 30,000 years

    Science.gov (United States)

    Muratli, Jesse M.; Chase, Zanna; McManus, James; Mix, Alan

    2010-11-01

    Bulk sediment chemistry from three Chilean continental margin Ocean Drilling Program sites constrains regional continental erosion over the past 30,000 years. Sediments from thirteen rivers that drain the (mostly igneous) Andes and the (mostly metamorphic) Coast Range, along with existing rock chemistry datasets, define terrestrial provenance for the continental margin sediments. Andean river sediments have high Mg/Al relative to Coast-Range river sediments. Near 36°S, marine sediments have high-Mg/Al (i.e. more Andean) sources during the last glacial period, and lower-Mg/Al (less Andean) sources during the Holocene. Near 41°S a Ti-rich source, likely from coast-range igneous intrusions, is prevalent during Holocene time, whereas high-Mg/Al Andean sources are more prevalent during the last glacial period. We infer that there is a dominant ice-sheet control of sediment sources. At 36°S, Andean-sourced sediment decreased as Andean mountain glaciers retreated after ˜17.6 ka, coincident with local oceanic warming and southward retreat of the Patagonian Forest and, by inference, westerly winds. At 41°S Andean sediment dominance peaks and then rapidly declines at ˜19 ka, coincident with local oceanic warming and the earliest deglacial sea-level rise. We hypothesize that this decreased flux of Andean material in the south is related to rapid retreat of the marine-based portion of the Patagonian Ice Sheet in response to global sea-level rise, as the resulting flooding of the southern portion of the Central Valley created a sink for Andean sediments in this region. Reversal of the decreasing deglacial Mg/Al trend at 41°S from 14.5 to 13.0 ka is consistent with a brief re-advance of the Patagonian ice sheet coincident with the Antarctic Cold Reversal.

  11. Diverging responses of tropical Andean biomes under future climate conditions.

    Science.gov (United States)

    Tovar, Carolina; Arnillas, Carlos Alberto; Cuesta, Francisco; Buytaert, Wouter

    2013-01-01

    Observations and projections for mountain regions show a strong tendency towards upslope displacement of their biomes under future climate conditions. Because of their climatic and topographic heterogeneity, a more complex response is expected for biodiversity hotspots such as tropical mountain regions. This study analyzes potential changes in the distribution of biomes in the Tropical Andes and identifies target areas for conservation. Biome distribution models were developed using logistic regressions. These models were then coupled to an ensemble of 8 global climate models to project future distribution of the Andean biomes and their uncertainties. We analysed projected changes in extent and elevational range and identified regions most prone to change. Our results show a heterogeneous response to climate change. Although the wetter biomes exhibit an upslope displacement of both the upper and the lower boundaries as expected, most dry biomes tend to show downslope expansion. Despite important losses being projected for several biomes, projections suggest that between 74.8% and 83.1% of the current total Tropical Andes will remain stable, depending on the emission scenario and time horizon. Between 3.3% and 7.6% of the study area is projected to change, mostly towards an increase in vertical structure. For the remaining area (13.1%-17.4%), there is no agreement between model projections. These results challenge the common believe that climate change will lead to an upslope displacement of biome boundaries in mountain regions. Instead, our models project diverging responses, including downslope expansion and large areas projected to remain stable. Lastly, a significant part of the area expected to change is already affected by land use changes, which has important implications for management. This, and the inclusion of a comprehensive uncertainty analysis, will help to inform conservation strategies in the Tropical Andes, and to guide similar assessments for other

  12. Diverging Responses of Tropical Andean Biomes under Future Climate Conditions

    Science.gov (United States)

    Tovar, Carolina; Arnillas, Carlos Alberto; Cuesta, Francisco; Buytaert, Wouter

    2013-01-01

    Observations and projections for mountain regions show a strong tendency towards upslope displacement of their biomes under future climate conditions. Because of their climatic and topographic heterogeneity, a more complex response is expected for biodiversity hotspots such as tropical mountain regions. This study analyzes potential changes in the distribution of biomes in the Tropical Andes and identifies target areas for conservation. Biome distribution models were developed using logistic regressions. These models were then coupled to an ensemble of 8 global climate models to project future distribution of the Andean biomes and their uncertainties. We analysed projected changes in extent and elevational range and identified regions most prone to change. Our results show a heterogeneous response to climate change. Although the wetter biomes exhibit an upslope displacement of both the upper and the lower boundaries as expected, most dry biomes tend to show downslope expansion. Despite important losses being projected for several biomes, projections suggest that between 74.8% and 83.1% of the current total Tropical Andes will remain stable, depending on the emission scenario and time horizon. Between 3.3% and 7.6% of the study area is projected to change, mostly towards an increase in vertical structure. For the remaining area (13.1%–17.4%), there is no agreement between model projections. These results challenge the common believe that climate change will lead to an upslope displacement of biome boundaries in mountain regions. Instead, our models project diverging responses, including downslope expansion and large areas projected to remain stable. Lastly, a significant part of the area expected to change is already affected by land use changes, which has important implications for management. This, and the inclusion of a comprehensive uncertainty analysis, will help to inform conservation strategies in the Tropical Andes, and to guide similar assessments for

  13. Chromosome identification in the Andean common bean accession G19833 (Phaseolus vulgaris L., Fabaceae

    Directory of Open Access Journals (Sweden)

    Sarah Altrock

    2011-01-01

    Full Text Available Characterization of all chromosomes of the Andean G19833 bean genotype was carried out by fluorescent in situ hybridization. Eleven single-copy genomic sequences, one for each chromosome, two BACs containing subtelomeric and pericentromeric repeats and the 5S and 45S ribosomal DNA (rDNA were used as probes. Comparison to the Mesoamerican accession BAT93 showed little divergence, except for additional 45S rDNA sites in four chromosome pairs. Altogether, the results indicated a relative karyotypic stability during the evolution of the Andean and Mesoamerican gene pools of P. vulgaris.

  14. Diversity and ecological ranges of plant species from dry inter-Andean valleys

    DEFF Research Database (Denmark)

    Quintana, Catalina

    of Ecuadorian dry inter-Andean valleys vegetation, including information related to the physical settings as well as to the vegetation and flora of the valleys. 2) This chapter unveils the influence of disturbance, water availability and low temperature in shaping species composition and occurrence. We found...... found on steep slopes and in ravines. These areas of original dry valley vegetation preserve many wild relatives of cultivated plants on the one hand and old lineages of other wild plant groups. Dry inter-Andean valleys (DIAVs) in Ecuador therefore makeup a biodiversity hot spot for both plants...

  15. Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

    Science.gov (United States)

    Bellin, N.; Vanacker, V.; Kubik, P.

    2012-04-01

    In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

  16. Influence of cranial deformation on facial morphology among prehistoric South Central Andean populations.

    Science.gov (United States)

    Rhode, Matthew P; Arriaza, Bernardo T

    2006-08-01

    Calculating biodistances among South American populations using cranial measurements is often hindered, as many available skeletal collections exhibit deformation. Acknowledging vault modifications, researchers have sought measurements in other regions which are unaffected by deformation. In the 1970s, a set of 10 "relatively" unaffected facial measurements was identified in Argentinean crania that later became the basis of numerous South American biodistance studies. These measurements include: minimum frontal breadth, bizygomatic breadth, orbit height, orbit breadth, palate breath, palate length, upper facial height, basion-prosthion length, nasal height, and nasal breadth. Palate length was excluded from the present analysis due to considerable measurement error. The suitability of these measurements in populations other than Argentineans has not been rigorously tested. Using a sample of 350 prehistoric crania from the Museo Arqueológico San Miguel de Azapa (MASMA, Arica, Chile), this project tested the hypothesis that these measurements are unaffected by either annular or tabular deformation. Results obtained from MANOVA analysis indicate this hypothesis cannot be fully supported. Among males, only 3 of the 9 measurements are unaffected by either form of deformation (palate breadth, basion-prosthion length, and nasal breadth), while analysis of females indicates that 4 of the 9 measurements remain unaltered (minimum frontal breadth, orbit breadth, basion-prosthion length, and nasal breadth). Additionally, analogous to the vault, facial measurements display patterns consistent with the deformation applied. Two implications can be drawn from this research: 1) previous studies using these measurements must be interpreted cautiously, and 2) researchers using these measurements must explicitly test their suitability in each population.

  17. Sequence-modified primers for the differential RT-PCR detection of Andean potato latent and Andean potato mild mosaic viruses in quarantine tests.

    Science.gov (United States)

    Koenig, Renate; Ziebell, Heiko

    2014-05-01

    To enable the differential PCR detection of Andean potato latent virus (APLV) and Andean potato mild mosaic virus (APMMV) strains, sense primers were designed that correspond to regions directly upstream of the coat protein genes. Their differentiating power was increased by A->C or T->C replacements in their 3'-terminal parts. Together with the broad-specificity antisense primer EM3, primer AL-a-mod3C detected all APLV strains tested, but none of the APMMV strains. Primer AM-a-mod4C yielded PCR products with all APMMV preparations, but also with some APLV preparations. Sequence analysis revealed that this was not due to a lack of primer specificity, but to the sensitive detection of contaminating APMMV in some of our APLV preparations.

  18. 40Ar/39Ar and K/Ar dating of low grade metamorphism: examples on metabasites from Central Chile

    Science.gov (United States)

    Aguirre, L.; Feraud, G.; Fuentes, F.; Delbar, M.; Morata, D.

    2003-04-01

    from Chacana. Thus, an apparently reliable time interval of about 25 and 22 Ma between the volcanic and the metamorphic events could be obtained in Bustamante and Chacana respectively. K-Ar celadonite ages ranging from 101 ± 3 to 108 ± 4 Ma have been obtained for Jurassic lavas from the Andean Cordillera c. 200 km south from Santiago whereas celadonite in Oligocene lavas from the same region gave a K-Ar age of 19.1 ± 0.8 Ma. These values suggest the existence of two metamorphic events of Cretaceous and Miocene age.

  19. The Unusual Nature of Recent Snowpack Declines in the North American Cordillera

    Science.gov (United States)

    Pederson, Gregory T.; Gray, Stephen T.; Woodhouse, Connie A.; Betancourt, Julio L.; Fagre, Daniel B.; Littell, Jeremy S.; Watson, Emma; Luckman, Brian H.; Graumlich, Lisa J.

    2011-07-01

    In western North America, snowpack has declined in recent decades, and further losses are projected through the 21st century. Here, we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff-generating areas of the Colorado, Columbia, and Missouri River drainages. Over the past millennium, late 20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky Mountains and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming that is due to positive reinforcement of the anthropogenic warming by decadal variability. The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western United States.

  20. Precambrian crust beneath the Mesozoic northern Canadian Cordillera discovered by Lithoprobe seismic reflection profiling

    Science.gov (United States)

    Cook, Frederick A.; Clowes, Ronald M.; Snyder, David B.; van der Velden, Arie J.; Hall, Kevin W.; Erdmer, Philippe; Evenchick, Carol A.

    2004-04-01

    The Cordillera in northern Canada is underlain by westward tapering layers that can be followed from outcrops of Proterozoic strata in the Foreland belt to the lowermost crust of the orogenic interior, a distance of as much as 500 km across strike. They are interpreted as stratified Proterozoic rocks, including ˜1.8-0.7 Ga supracrustal rocks and their basement. The layering was discovered on two new deep seismic reflection profiles in the Yukon (Line 3; ˜650 km) and northern British Columbia (Line 2; ˜1245 km in two segments) that were acquired as part of the Lithoprobe Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) transect. In the Mackenzie Mountains of the eastern Yukon, the layering in Line 3 is visible between 5.0 and 12.0 s (˜15 to 36 km depth). It is followed southwestward for nearly 650 km (˜500 km across strike) and thins to less than 1.0 s (˜3.0-3.5 km thickness) near the Moho at the Yukon-Alaska international boundary. In the northern Rocky Mountains of British Columbia, the upper part of the layering on Line 2 correlates with outcrops of Proterozoic (1.76-1.0 Ga) strata in the Muskwa anticlinorium. At this location, the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for ˜700 km (˜300 km across strike). It disappears as a thin taper at the base of the crust ˜150 km east of the coast of the Alaskan panhandle. The only significant disruption in the layering occurs at the Tintina fault zone, a late to postorogenic strike-slip fault with up to 800 km of displacement, which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles (˜300 km apart). The base of the layered reflection zone coincides with the Moho, which exhibits variable character and undulates in a series of broad arches with widths of ˜150 km. In general, the mantle appears to have few reflections. However, at the southwest end of Line 3 near the Alaska

  1. Holocene Paleoglacier History of Glaciar Dalla Vedova, Cordillera DARWIN, Tierra del Fuego, Chile

    Science.gov (United States)

    Reynhout, S.

    2015-12-01

    Southernmost South America is unique in its position immediately north of the present-day Antarctic Convergence, making it ideally suited for the evaluation of Antarctic influences on terrestrial paleoclimate. Here we present a glacial geomorphic interpretation of the paleoglacial history of Glaciar Dalla Vedova in Bahía Blanca, Cordillera Darwin, Chile (53°S). This interpretation is further constrained by radiocarbon dating, cosmogenic dating, dendrochronology, and historical photogrammetry. Preliminary field work suggests that Holocene glacier fluctuations have been constrained to within 3 km of the present glacier boundary, punctuated by rapid recent glacier retreat over the past century. By comparing the observed chronology with the record contained further north in Patagonia, we will evaluate possible mechanisms of regional climate variability over the Holocene across southernmost South America.

  2. Graptolitos ordovícicos en el Sur de la Cordillera frontal de Mendoza

    Directory of Open Access Journals (Sweden)

    Hugo Tickyj

    2009-04-01

    Full Text Available En el flanco sudoriental de la Cordillera Frontal mendocina aflora un conjunto plegado de metasedimentitas conocido como Formación Las Lagunitas, cuyos afloramientos se extienden entre los ríos Diamante por el sur y Tunuyán por el norte, alcanzando un ancho máximo de 15 km a la latitud del volcán Maipo. El perfil estudiado en el arroyo Cortaderas (34º23'S está compuesto por una secuencia silicoclástica marina integrada por tres conjuntos litológicos, que de este a oeste son: a areniscas gruesas a medias, bien seleccionadas, y areniscas conglomerádicas, b vaques de grano grueso a fino y c areniscas finas a medias, con intercalaciones de pelitas negras laminadas. En la última unidad fueron colectados graptolitos en regular estado de preservación. Su estudio sistemático permitió definir una asociación correspondiente a la Biozona de Climacograptus bicornis, por lo que la Formación Las Lagunitas es asignada al Ordovícico Superior (Sandbiano o Caradociano. La completa extensión cronoestratigráfica de la Formación Las Lagunitas no ha sido establecida, debido a que en el perfil estudiado no es clara la relación entre la unidad portadora de graptolitos y el resto de la secuencia. Este registro de graptolitos en el sur de la Cordillera Frontal mendocina constituye un aspecto novedoso para el análisis del Ordovícico, con implicancias en el contexto de la evolución tectónica de las cuencas sedimentarias ordovícicas del oeste argentino.Outcrops of a folded sedimentary unit known as the Las Lagunitas Formation lie along the southeastern part of the Frontal Cordillera of Mendoza Province. The main exposures of the unit lie between the Diamante River in the south and Tunuyán in the north, reaching 15 km wide at the latitude of the Maipo volcano. At the Cortaderas Creek (34º23'S the studied section is a marine siliciclastic sequence comprising three lithological units: a well-sorted, coarse- to medium-grained sandstones and

  3. Remains of early Ordovician mantle-derived magmatism in the Santander Massif (Colombian Eastern Cordillera)

    Science.gov (United States)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Cottle, John M.; Hart, Craig J. R.

    2012-10-01

    An Early Ordovician magmatic event has been documented in the Santander Massif (north-Eastern Cordillera, Colombia). Three U/Pb laser ablation ages of 477 ± 2 Ma (Arenig), were obtained from metamorphosed and foliated calc-alkaline diorites. The 176Hf/177Hf values in zircons from these meta-diorites, yielded epsilon Hf values (ɛHft) > 0 (Mean = 2 ± 1, at 477 Ma). These data allow interpretation of the origin of these zircons from a radiogenic initial Hf isotope source, which is characteristic of the Earth's mantle. This, together with the fact that the rocks have been affected subsequently by tectonometamorphic processes, suggests that the early Ordovician diorites have been emplaced in a supra-subduction tectonic setting, related to onset of the Iapetus Ocean closure.

  4. Measurements of light absorbing particulates on the glaciers in the Cordillera Blanca, Peru

    Directory of Open Access Journals (Sweden)

    C. G. Schmitt

    2014-10-01

    Full Text Available Glaciers in the tropical Andes have been rapidly losing mass since the 1970s. In addition to the documented increase in air temperature, increases in light absorbing particulates deposited on glaciers could be contributing to the observed glacier loss. Here we report on measurements of light absorbing particulates sampled from glaciers during three surveys in the Cordillera Blanca in Peru. During three research expeditions in the dry seasons (May–August of 2011, 2012 and 2013, two hundred and forty snow samples were collected from fifteen mountain peaks over altitudes ranging from 4800 to nearly 6800 m. Several mountains were sampled each of the three expeditions and some mountains were sampled multiple times during the same expedition. Collected snow samples were melted and filtered in the field then later analyzed using the Light Absorption Heating Method (LAHM, a new technique that measures the ability of particulates on filters to absorb visible light. LAHM results have been calibrated using filters with known amounts of fullerene soot, a common industrial surrogate for black carbon (BC. As sample filters often contain dust in addition to BC, results are presented in terms of effective Black Carbon (eBC. During the 2013 survey, snow samples were collected and kept frozen for analysis with a Single Particle Soot Photometer (SP2. Calculated eBC mass from the filter analysis and the SP2 refractory Black Carbon (rBC results were well correlated (r2 = 0.92. These results indicate that a substantial portion of the light absorbing particulates in the more polluted areas were likely BC. The three years of data show that glaciers in the Cordillera Blanca Mountains close to human population centers have substantially higher levels of eBC (as high as 70 ng g−1 than remote glaciers (as low as 2.0 ng g−1 eBC, indicating that population centers can influence local glaciers by sourcing BC.

  5. Crustal shortening and Eocene extension in the southeastern Canadian Cordillera: Some thermal and rheological considerations

    Science.gov (United States)

    Liu, Mian; Furlong, Kevin P.

    1993-06-01

    Metamorphic core complexes in the southeastern Canadian Cordillera were formed during Eocene crustal extension, shortly (within a few millions of years) after Late Jurassic-Paleocene crustal shortening. Thermal-rheological modeling, constrained by geological and geochronological studies of the Valhalla core complex and other core complexes in this region, is used to investigate two major problems concerning the formation of these core complexes: (1) the dynamic links between crustal shortening and extension and (2) the cooling history and unroofing rates during extension. Thermal-rheological effects associated with crustal shortening are integrated through the history of crustal compression, since crustal shortening in this region was a long and slow process and cannot be treated as an instantaneous event. Our results suggest that crustal shortening may have played an important role in Eocene extension in the southeastern Canadian Cordillera by (1) producing a thickened and therefore unstable crust and (2) thermally weakening the lithosphere. However, heat generated by crustal shortening is not enough to account for the thermal state of the Valhalla complex, and additional heat sources at depth may be necessary. We then investigate thermal evolution during extension in both a simple shear model and a progressive pure stretching model. We show that the geotherm in an extensional region is time-and space-dependent and is affected by many variables including the preextensional thermal history and the mode of extension. Thus caution needs to be exercised when inferring unroofing rates from thermochronologic data. The cooling history of the Valhalla core complex may be explained by unroofing at rates of 1-2 mm/yr.

  6. Ethno-botanical survey of edible wild fruits in Benguet, Cordillera administrative region, the Philippines

    Institute of Scientific and Technical Information of China (English)

    Racquel Tan Chua-Barcelo

    2014-01-01

    Objective: To conduct a survey on the common name/s, traditional uses and cultural importance of the edible wild fruits in different municipalities of Benguet, Cordillera administrative region. Methods: Interviews using questionnaires with barangay leaders and indigenous people were conducted with 176 key informants from June 2011 to July 2013. Results: A total of 36 fruit species were found in different municipalities of Benguet. These fruit species belong to 27 genera and 20 families. Among the 13 municipalities of Benguet, Kibungan has the highest number of species. There are many uses of wild fruits which ranged from food (snack/dessert/table food), forage (especially for birds, monkeys and wild animals such as cloud rat and grass eaters), offertory, processed/preserved (as jam, jellies, candies, juice and wine), condiment or ingredient (for cooking), source of dye or ink, decoration (to garnish food) and as medicine to common ailments or health problems. Based on the inventory and calculated cultural importance index, Garcinia binucao (balokok) belonging to Clusiaceae is the most abundant fruit, hence it is the commonly used fruit for various purposes such as food, forage, processing/preservation and condiment/ingredient; Vaccinium myrtoides (ayusip) for offerings and as source of dye/ink; Saurauia elegans (uyok) for decoration, and, Antidesma bunius (bugnay) for medicine. Conclusions: Benguet province in the Cordillera region provides a diversity of edible wild fruits. The data gathered from the study signifies that collection, processing and utilization of edible wild fruits are still part of the daily activities of the people in Benguet.

  7. Graptolitos ordovícicos en el Sur de la Cordillera frontal de Mendoza

    Directory of Open Access Journals (Sweden)

    Hugo Tickyj

    2009-04-01

    Full Text Available En el flanco sudoriental de la Cordillera Frontal mendocina aflora un conjunto plegado de metasedimentitas conocido como Formación Las Lagunitas, cuyos afloramientos se extienden entre los ríos Diamante por el sur y Tunuyán por el norte, alcanzando un ancho máximo de 15 km a la latitud del volcán Maipo. El perfil estudiado en el arroyo Cortaderas (34º23'S está compuesto por una secuencia silicoclástica marina integrada por tres conjuntos litológicos, que de este a oeste son: a areniscas gruesas a medias, bien seleccionadas, y areniscas conglomerádicas, b vaques de grano grueso a fino y c areniscas finas a medias, con intercalaciones de pelitas negras laminadas. En la última unidad fueron colectados graptolitos en regular estado de preservación. Su estudio sistemático permitió definir una asociación correspondiente a la Biozona de Climacograptus bicornis, por lo que la Formación Las Lagunitas es asignada al Ordovícico Superior (Sandbiano o Caradociano. La completa extensión cronoestratigráfica de la Formación Las Lagunitas no ha sido establecida, debido a que en el perfil estudiado no es clara la relación entre la unidad portadora de graptolitos y el resto de la secuencia. Este registro de graptolitos en el sur de la Cordillera Frontal mendocina constituye un aspecto novedoso para el análisis del Ordovícico, con implicancias en el contexto de la evolución tectónica de las cuencas sedimentarias ordovícicas del oeste argentino.

  8. CO2-rich thermomineral groundwater in the Betic Cordilleras, southeastern Spain: Genesis and tectonic implications

    Science.gov (United States)

    Cerón, J. C.; Martín-Vallejo, M.; García-Rossell, L.

    The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological setting, physical and chemical characteristics, and 13C-isotope content. The study area is about 60km northeast of Almería city, in southeastern Spain. The thermomineral waters are plentiful and are related to regional geothermal anomalies. Temperatures of 20 -41°C, high bicarbonate concentrations (183-1824mg/L), and high amounts of PCO2 (aguas termales con elevados contenidos en CO2 de las Cordilleras Béticas han sido estudiadas en relación con los aspectos geológicos e hidrogeológicos, sus características físicas y químicas, y sus contenidos en 13C. El área de estudio se encuentra aproximadamente a 60km al noreste de la ciudad de Almería, en el sureste de España. Las aguas termominerales son numerosas y están relacionadas con anomalías geotermales regionales. El agua subterránea tiene una temperatura comprendida entre 20-41°C, alta concentración de bicarbonatos (entre 183-1824mg/L) y elevada PCO2 (agua subterránea origina problemas en los sondeos y en el uso del agua. El carácter hidrotermal de este área estaría relacionado con su actividad neotectónica.

  9. Timing and Style of Deformation in the Floresta Massif, Axial Eastern Cordillera, Colombia

    Science.gov (United States)

    Saylor, J.; Stockli, D. F.; Mora, A.

    2009-12-01

    The Floresta Massif is one of the largest exposures of Paleozoic and Pre-Cambrian rocks in the Eastern Cordillera. Estimates for the age of onset of shortening-related deformation in the Eastern Cordillera range from late Cretaceous to late Miocene (e.g., Hoorn et al., 1995; Bayona et al., 2008; Parra et al., 2009). The massif is typically interpreted as being exhumed along a high-angle reverse fault (the Soapaga fault) that reactivated Mesozoic extensional structures (e.g., Kammer and Sanchez, 2006). We examined these dual linked issued with new zircon U/Th-He (ZHe) data, new geological mapping and previously published apatite fission track (AFT) data from the Floresta Massif and the associated footwall strata. Previously, an overturned Paleozoic - Cretaceous sequence was mapped emplaced on Tertiary strata along the Soapaga fault. However, new geologic mapping identifies two previously unrecognized thrusts which place, from west to east, Paleozoic strata on Jurassic strata (Fault 3), Jurassic strata on Cretaceous strata (Fault 2) and Cretaceous strata on Tertiary strata (along the previously identified Fault 1). These results are confirmed by AFT and ZHe data. ZHe ages show no resetting in the Tertiary footwall strata, but show partial resetting in the Cretaceous strata and full resetting in the Jurassic and Paleozoic strata. Similarly, AFT data show older ages in the Cretaceous strata than in the Jurassic or Paleozoic strata. Fully reset ZHe ages from Jurassic strata show that exhumation of the Floresta Massif was ongoing by at least the early Oligocene (~ 30 Ma). However, this deformation post-dates an older episode of deformation associated with partially reset ZHe ages in the Cretaceous strata. Based on a decrease in lag time in detrital ZHe data, we infer that the earlier episode of deformation occurred in the mid - late Eocene (45 - 35 Ma).

  10. Characterization of Two Microbial Isolates from Andean Lakes in Bolivia

    Science.gov (United States)

    Demergasso, C.; Blamey, J.; Escudero, L.; Chong, G.; Casamayor, E. O.; Cabrol, N. A.; Grin, E. A.; Hock, A.; Kiss, A.; Borics, G.

    2004-01-01

    We are currently investigating the biological population present in the highest and least explored perennial lakes on earth in the Bolivian and Chilean Andes, including several volcanic crater lakes of more than 6000 m elevation, in combination of microbiological and molecular biological methods. Our samples were collected in saline lakes of the Laguna Blanca Laguna Verde area in the Bolivian Altiplano and in the Licancabur volcano crater (27 deg. 47 min S/67 deg. 47 min. W) in the ongoing project studying high altitude lakes. The main goal of the project is to look for analogies with Martian paleolakes. These Bolivian lakes can be described as Andean lakes following the classification of Chong. We have attempted to isolate pure cultures and phylogenetically characterize prokaryotes that grew under laboratory conditions. Sediment samples taken from the Licancabur crater lake (LC), Laguna Verde (LV), and Laguna Blanca (LB) were analyzed and cultured using enriched liquid media under both aerobic and anaerobic conditions. All cultures were incubated at room temperature (15 to 20 C) and under light exposure. For the reported isolates, 36 hours incubation were necessary for reaching optimal optical densities to consider them viable cultures. Ten serial dilutions starting from 1% inoculum were required to obtain a suitable enriched cell culture to transfer into solid media. Cultures on solid medium were necessary to verify the formation of colonies in order to isolate pure cultures. Different solid media were prepared using several combinations of both trace minerals and carbohydrates sources in order to fit their nutrient requirements. The microorganisms formed individual colonies on solid media enriched with tryptone, yeast extract and sodium chloride. Cells morphology was studied by optical and electronic microscopy. Rodshape morphologies were observed in most cases. Total bacterial genomic DNA was isolated from 50 ml late-exponential phase culture by using the CTAB

  11. Allantoplacental ultrastructure of an Andean population of Mabuya (Squamata, Scincidae).

    Science.gov (United States)

    Ramírez-Pinilla, Martha Patricia; De Pérez, Gloria; Carreño-Escobar, J Fernando

    2006-10-01

    Mabuya species are highly matrotrophic viviparous lizards with Type IV epitheliochorial allantoplacenta. The allantoplacenta of an Andean population of this genus, currently assigned to Mabuya sp., possesses specializations related to histotrophic nutrition at the embryonic hemisphere (placentome, paraplacentome, and chorionic areolas), while at the abembryonic hemisphere it has a mixed function: histotrophic transfer (absorptive plaques) and hemotrophic nutrition (gas exchange in respiratory segments). These placental specializations were studied using high-resolution light microscopy and transmission electron microscopy, and were compared with those found in other squamate reptiles and eutherian mammals. Cytological features of the placentome suggest that this is an important region for nutritional provision; the paraplacentome also shows characteristics for nutrient transfer, especially lipids. Chorionic areolas allow the absorption of glandular products, as well as uterine and chorionic cellular debris produced by lysis of some cells of both epithelia during areola formation. In the absorptive plaques both uterine and chorionic epithelia are firmly attached and their cellular apices exhibit electron-dense granules that could be related to autocrine and paracrine functions. The short interhemal distance found in the respiratory segments confirms their role in gas exchange. A common feature of all regional specializations in the Mabuya sp. allantoplacenta is the presence of lipids in the interacting chorionic and uterine epithelia, suggesting that lipids are transferred throughout the entire embryonic chamber; placental transfer of lipids may be the principal fetal energy and lipid source in this species. In spite of this feature, each one of the specialized areas of the allantoplacenta has different features suggesting particular functions in the transfer of nutrients (as ions, lipids, proteins, amino acids, sugar, water, and gases), and in the possible

  12. Assessment of satellite rainfall products over the Andean plateau

    Science.gov (United States)

    Satgé, Frédéric; Bonnet, Marie-Paule; Gosset, Marielle; Molina, Jorge; Hernan Yuque Lima, Wilson; Pillco Zolá, Ramiro; Timouk, Franck; Garnier, Jérémie

    2016-01-01

    Nine satellite rainfall estimations (SREs) were evaluated for the first time over the South American Andean plateau watershed by comparison with rain gauge data acquired between 2005 and 2007. The comparisons were carried out at the annual, monthly and daily time steps. All SREs reproduce the salient pattern of the annual rain field, with a marked north-south gradient and a lighter east-west gradient. However, the intensity of the gradient differs among SREs: it is well marked in the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis 3B42 (TMPA-3B42), Precipitation Estimation from remotely Sensed Information using Artificial Neural Networks (PERSIANN) and Global Satellite Mapping of Precipitation (GSMaP) products, and it is smoothed out in the Climate prediction center MORPHing (CMORPH) products. Another interesting difference among products is the contrast in rainfall amounts between the water surfaces (Lake Titicaca) and the surrounding land. Some products (TMPA-3B42, PERSIANN and GSMaP) show a contradictory rainfall deficit over Lake Titicaca, which may be due to the emissivity contrast between the lake and the surrounding lands and warm rain cloud processes. An analysis differentiating coastal Lake Titicaca from inland pixels confirmed this trend. The raw or Real Time (RT) products have strong biases over the study region. These biases are strongly positive for PERSIANN (above 90%), moderately positive for TMPA-3B42 (28%), strongly negative for CMORPH (- 42%) and moderately negative for GSMaP (- 18%). The biases are associated with a deformation of the rain rate frequency distribution: GSMaP underestimates the proportion of rainfall events for all rain rates; CMORPH overestimates the proportion of rain rates below 2 mm day- 1; and the other products tend to overestimate the proportion of moderate to high rain rates. These biases are greatly reduced by the gauge adjustment in the TMPA-3B42, PERSIANN and CMORPH products, whereas a

  13. Marcos Zapata's "Last Supper": a feast of European religion and Andean culture.

    Science.gov (United States)

    Zendt, Christina

    2010-01-01

    In Marcos Zapata's 1753 painting of the Last Supper in Cuzco, Peru, Christian symbolism is filtered through Andean cultural tradition. Zapata was a late member of the Cuzco School of Painting, a group comprised of few European immigrants and handfuls of mestizo and Indian artists. The painters in Cuzco learned mostly from prints of European paintings, and their style tends to blend local culture into the traditional painting of their conquistadors. Imagery was the most successful tool used by the Spaniards in their quest to Christianize the Andean population. By teaching locals to paint Christian subjects, they were able to infuse Christianity into Andean traditions. Zapata's rendering of the Last Supper utilizes this cultural blending while staying true to the Christian symbolism within the subject. Instead of the traditional lamb, Zapata's Last Supper features a platter of cuy, or guinea pig, an Andean delicacy stocked with protein as well as cultural significance. Cuy was traditionally a sacrificial animal at Inca agricultural festivals and in this way it offers poignant parallel to the lamb, as a traditional Christian sacrificial animal.

  14. The electronic procurement in the framework of the Andean Community. State of the art

    Directory of Open Access Journals (Sweden)

    William David Hernández Martínez

    2010-12-01

    Full Text Available The article is structured as a brief survey of the academic and policy approach on the unification or harmonization of regulations about electronic commerce, specifically relating the electronic contracts, in Latin America, with special emphasis on the Andean Community of Nations as a proposed work on the development of modern trends of international trade law.

  15. Taxonomic and functional assignment of cloned sequences from high Andean forest soil metagenome

    NARCIS (Netherlands)

    Montaña, José Salvador; Jiménez Avella, Diego; Angel, Tatiana; Hernández, Mónica; Baena, Sandra

    2012-01-01

    Total metagenomic DNA was isolated from high Andean forest soil and subjected to taxonomical and functional composition analyses by means of clone library generation and sequencing. The obtained yield of 1.7 μg of DNA/g of soil was used to construct a metagenomic library of approximately 20,000 clon

  16. A novel cold active esterase derived from Colombian high Andean forest soil metagenome

    NARCIS (Netherlands)

    Jiménez, Diego Javier; Montaña, José Salvador; Alvarez, Diana; Baena, Sandra

    2012-01-01

    In order to search new lipolytic enzymes and conduct bioprospecting of microbial communities from high Andean forest soil, a metagenomic library of approximately 20,000 clones was constructed in Escherichia coli using plasmid p-Bluescript II SK+. The library covered 80 Mb of the metagenomic DNA main

  17. Forests of the tropical eastern Andean flank during the middle Pleistocene

    NARCIS (Netherlands)

    Cárdenas, M.L.; Gosling, W.D.; Pennington, R.T.; Poole, I.; Sherlock, S.C.; Mothes, P.

    2014-01-01

    Inter-bedded volcanic and organic sediments from Erazo (Ecuador) indicate the presence of four different forest assemblages on the eastern Andean flank during the middle Pleistocene. Radiometric dates (40Ar-39Ar) obtained from the volcanic ash indicate that deposition occurred between 620,000 and 19

  18. Persistence of chironomids in metal polluted Andean high altitude streams: does melanin play a role?

    NARCIS (Netherlands)

    Loayza Muro, R.A.; Marticorena-Ruíz, J.K.; Palomino, E.J.; Merritt, C.; de Baat, M.L.; van Gemert, M.; Verweij, R.A.; Kraak, M.H.S.; Admiraal, W.

    2013-01-01

    In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple

  19. 77 FR 24555 - Andean Trade Preference Act (ATPA), as Amended: Request for Public Comments Regarding Beneficiary...

    Science.gov (United States)

    2012-04-24

    ... From the Federal Register Online via the Government Publishing Office OFFICE OF THE UNITED STATES...., provides trade benefits for eligible Andean countries. The original Act allowed only Bolivia, Ecuador... Bolivia no longer satisfies the eligibility criteria related to counternarcotics and suspended...

  20. 75 FR 19669 - Andean Trade Preference Act (ATPA), as Amended: Request for Public Comments Regarding Beneficiary...

    Science.gov (United States)

    2010-04-15

    ... From the Federal Register Online via the Government Publishing Office OFFICE OF THE UNITED STATES... eligible Andean countries. In Proclamation 7616 of October 31, 2002, the President designated Bolivia... President determined that Bolivia no longer satisfies the eligibility criteria related to...

  1. Formal Law and Local Water Control in the Andean Region: A Fiercely Contested Field

    NARCIS (Netherlands)

    Vos, de H.; Boelens, R.A.; Bustamente, R.R.

    2006-01-01

    Water access and control rights of peasant and indigenous communities in Andean countries are threatened. Vertical state law and intervention practices, as well as new privatization policies generally ignore, discriminate or undermine local normative frameworks. Recognition of diverse local rights a

  2. Institutional reform in the Andean irrigation sector: enabling policies for strengthening local rights and water management

    NARCIS (Netherlands)

    Cremers, L.; Ooijevaar, M.; Boelens, R.A.

    2005-01-01

    For centuries, local and indigenous water rights and rules in the Andean region have been largely neglected and discriminated against. The process of undermining local communities' water access and control rights continues up to today and not only is it headed by powerful local, national and interna

  3. The abiotic and biotic drivers of rapid diversification in Andean bellflowers (Campanulaceae).

    Science.gov (United States)

    Lagomarsino, Laura P; Condamine, Fabien L; Antonelli, Alexandre; Mulch, Andreas; Davis, Charles C

    2016-06-01

    The tropical Andes of South America, the world's richest biodiversity hotspot, are home to many rapid radiations. While geological, climatic, and ecological processes collectively explain such radiations, their relative contributions are seldom examined within a single clade. We explore the contribution of these factors by applying a series of diversification models that incorporate mountain building, climate change, and trait evolution to the first dated phylogeny of Andean bellflowers (Campanulaceae: Lobelioideae). Our framework is novel for its direct incorporation of geological data on Andean uplift into a macroevolutionary model. We show that speciation and extinction are differentially influenced by abiotic factors: speciation rates rose concurrently with Andean elevation, while extinction rates decreased during global cooling. Pollination syndrome and fruit type, both biotic traits known to facilitate mutualisms, played an additional role in driving diversification. These abiotic and biotic factors resulted in one of the fastest radiations reported to date: the centropogonids, whose 550 species arose in the last 5 million yr. Our study represents a significant advance in our understanding of plant evolution in Andean cloud forests. It further highlights the power of combining phylogenetic and Earth science models to explore the interplay of geology, climate, and ecology in generating the world's biodiversity.

  4. The Rise and Fall of Andean Empires: El Nino History Lessons.

    Science.gov (United States)

    Wright, Kenneth R.

    2000-01-01

    Provides information on El Nino and the methods for investigating ancient climate record. Traces the rise and fall of the Andean empires focusing on the climatic forces that each empire (Tiwanaku, Wari, Moche, and Inca) endured. States that modern societies should learn from the experiences of these ancient civilizations. (CMK)

  5. Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution, Population Size and Extinction Risk

    Science.gov (United States)

    Naveda-Rodríguez, Adrián; Vargas, Félix Hernán; Kohn, Sebastián; Zapata-Ríos, Galo

    2016-01-01

    The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation. PMID:26986004

  6. Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution, Population Size and Extinction Risk.

    Science.gov (United States)

    Naveda-Rodríguez, Adrián; Vargas, Félix Hernán; Kohn, Sebastián; Zapata-Ríos, Galo

    2016-01-01

    The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.

  7. Reconciling Local and Global Agendas in Sustainable Development: Participatory Research with Indigenous Andean Communities

    Institute of Scientific and Technical Information of China (English)

    Robert E. Rhoades; Virginia Nazarea

    2006-01-01

    This paper discusses participatory research in the Andes and presents a case study in Cotacachi, Ecuador, where sustainability scientists and indigenous people seek common ground in their respective but drastically different research and social agendas. Participatory research based on Andean experiences pre-dated and inspired much of the later international movement in agriculture, health, and conservation. Andean communities have a long history in demanding that outsiders address the needs of the community as a condition for carrying out scientific or applied activities. What an Andean community, however, sees as relevant may or may not practiced throughout much of the world. In fact,overzealous participatory researchers are just as bothersome as their predecessors bearing long questionnaires. More important to Andean people is an equitable relationship with researchers and developers in which exchanges of value are made. A research is drawn. In the case of the SANREM project in Cotacachi, Ecuador, scientists carried out enriching research activities of interest to local people as a way to generate social capital for conducting basic research which does not have an obvious, immediate local benefit. The requested research did not have a conventional participatory methodology but provided valuable products (educational opportunity,germplasm, community visualization tools, and information) to the indigenous community in exchange for time and resources to conduct research on more basic natural resource questions. We argue that in the Andean context the key to reconciling the needs of scientists and of local needs is seeking new forms of equitable collaboration which reach beyond the present and now somewhat tired discourse of ‘participation'.

  8. Andean Condor (Vultur gryphus in Ecuador: Geographic Distribution, Population Size and Extinction Risk.

    Directory of Open Access Journals (Sweden)

    Adrián Naveda-Rodríguez

    Full Text Available The Andean Condor (Vultur gryphus in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.

  9. Identifying signatures of natural selection in Tibetan and Andean populations using dense genome scan data.

    Directory of Open Access Journals (Sweden)

    Abigail Bigham

    2010-09-01

    Full Text Available High-altitude hypoxia (reduced inspired oxygen tension due to decreased barometric pressure exerts severe physiological stress on the human body. Two high-altitude regions where humans have lived for millennia are the Andean Altiplano and the Tibetan Plateau. Populations living in these regions exhibit unique circulatory, respiratory, and hematological adaptations to life at high altitude. Although these responses have been well characterized physiologically, their underlying genetic basis remains unknown. We performed a genome scan to identify genes showing evidence of adaptation to hypoxia. We looked across each chromosome to identify genomic regions with previously unknown function with respect to altitude phenotypes. In addition, groups of genes functioning in oxygen metabolism and sensing were examined to test the hypothesis that particular pathways have been involved in genetic adaptation to altitude. Applying four population genetic statistics commonly used for detecting signatures of natural selection, we identified selection-nominated candidate genes and gene regions in these two populations (Andeans and Tibetans separately. The Tibetan and Andean patterns of genetic adaptation are largely distinct from one another, with both populations showing evidence of positive natural selection in different genes or gene regions. Interestingly, one gene previously known to be important in cellular oxygen sensing, EGLN1 (also known as PHD2, shows evidence of positive selection in both Tibetans and Andeans. However, the pattern of variation for this gene differs between the two populations. Our results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection. These data suggest a genetic role in high-altitude adaption and provide a basis for future genotype/phenotype association

  10. Shifts in leaf litter breakdown along a forest-pasture-urban gradient in Andean streams.

    Science.gov (United States)

    Iñiguez-Armijos, Carlos; Rausche, Sirkka; Cueva, Augusta; Sánchez-Rodríguez, Aminael; Espinosa, Carlos; Breuer, Lutz

    2016-07-01

    Tropical montane ecosystems of the Andes are critically threatened by a rapid land-use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest-pasture-urban) on stream physico-chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico-chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land-use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf-shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land-use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of

  11. Chronic hypoxia in Andeans; are there lessons for neurology at sea level?

    Science.gov (United States)

    Appenzeller, Otto; Minko, Tamara; Qualls, Clifford; Pozharov, Vitaly; Gamboa, Jorge; Gamboa, Alfredo; Pakunlu, Rafica I

    2006-08-15

    Hypoxia is implicated in aging and neurodegenerative diseases. We posited that changes in gene expression induced by ambient hypoxia at altitude may be neuroprotective to natives of these regions. We studied 30 men. Twenty natives of Cerro de Pasco (CP), altitude 4,338 m were examined in CP; then transported within 6 h to Lima (150 m-sea level) and examined 1 h after arrival. They were assessed by a Chronic Mountain Sickness-score (CMS-sc) in CP, 10 were normal Andeans and 10 had chronic mountain sickness (CMS), a sudden inexplicable loss of adaptation to their native environment. RNA was extracted from venous blood white cells. The Andeans were compared to 10 normal US men living at 1500 m using RT-PCR. We focused on the cyto-neuro-protective genes, Ataxia telangiectasia mutated (ATM), heme-oxygenase-1 (HMOX 1), heat shock protein-70 (HSP-70), heat shock protein-90 (HSP-90), and the neuroprotective enzyme, nicotinamide mononucleotide adenylyl transferase 1 (Nnmat 1). CMS patients had significantly higher levels of gene expression (HMOX-1, HSP-70, ATM) than Andean controls in CP. HSP-90 and Nmnat 1, however, were higher in Andean controls in all locations. Significant reductions of all gene products, within an hour of arriving in normoxia in Lima, were found. In Andean controls, the gene products in Lima fell to levels approaching US controls. Correlation and regression methods showed men with high expression of all gene products had an average CMS-sc=19.8; those with low expression a normal score (9.4, P=0.02). ATM expression was related to age (P<0.001). The natural experiment that unfolds in the mountainous regions of the world provides opportunities to study neuroprotection in intact humans.

  12. An Andean tectonic cycle:From crustal thickening to extension in a thin crust (34º-37ºSL)

    Institute of Scientific and Technical Information of China (English)

    Victor A. Ramos; Vanesa D. Litvak; Andrés Folguera; Mauro Spagnuolo

    2014-01-01

    Several orogenic cycles of mountain building and subsequent collapse associated with periods of shal-lowing and steepening of subduction zones have been recognized in recent years in the Andes. Most of them are characterized by widespread crustal delamination expressed by large calderas and rhyolitic flare-up produced by the injection of hot asthenosphere in the subduction wedge. These processes are related to the increase of the subduction angle during trench roll-back. The Payenia paleoflat-slab, in the southern Central Andes of Argentina and Chile (34º~37º S) recorded a complete cycle from crustal thickening and mountain uplift to extensional collapse and normal faulting, which are related to changes in the subduction geometry. The early stages are associated with magmatic expansion and migration, subsequent deformation and broken foreland. New ages and geochemical data show the middle to late Miocene expansion and migration of arc volcanism towards the foreland region was associated with important deformation in the Andean foothills. However, the main difference of this orogenic cycle with the previously described cycles is that the steepening of the oceanic subducted slab is linked to basaltic flooding of large areas in the retroarc under an extensional setting. Crustal delamination is concentrated only in a narrow central belt along the cordilleran axis. The striking differences between the two types of cycles are interpreted to be related to the crustal thickness when steepening the subducting slab. The crustal thickness of the Altiplano is over 60e80 km, whereas Payenia is less than 42 km in the axial part, and near 30 km in the retroarc foothills. The final extensional regime associated with the slab steepening favors the basaltic flooding of more than 8400 km3 in an area larger than 40,000 km2, through 800 central vents and large fissures. These characteristics are unique in the entire present-day Andes.

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

    Directory of Open Access Journals (Sweden)

    MADELEINE LAMBOROT

    2001-03-01

    Full Text Available Chromosomal genotypes were scored from 359 Liolaemus monticola lizards of the "northern, 2n = 38-40" chromosomal race from 21 locality samples between the Maipo (and one of its tributaries and the Aconcagua (and one of its tributaries ribers, plus a sample from the interracial hybridization zone, and some representative locality samples of the "southern 2n = 34" and the "multiple fission 2n = 42-44" chromosomal races for comparisons. The first seven variable chromosomal pairs were coded as Mendelian genotypes and statistically summarized by several clustering and population genetic algorithms. Spatial and temporal differentiation was assessed by chromosome frequencies, chromosomal diversity and heterozygosity. While no differentiation was found for diversity in the "northern 2n = 38-40" race, chromosomal frequencies and heterozygosity showed significant spatial differentiation that permit distinguishing between the coastal, Andean and transversal mountain range populations. The sample of Cuesta Chacabuco may represent a hybrid zone between the other two range samples. The origin of the chromosomal rearrangements, the population cytogenetics, and the recombination patterns resulting from chromosomal heterozygosity are compared in these chromosomal races, thus expanding the geographical area. These patterns are discussed with respect to the evolution of this complex in Chile and the importance of the riverine barriers in central ChileSe cuantificaron los "genotipos" cromosómicos para 359 lagartijas de 21 muestras poblacionales de la raza "Norte, 2n = 38-40" comprendida entre los ríos: río Maipo y uno de sus afluentes el río Yeso y río Aconcagua (y uno de sus afluentes el río Juncal. Con fines comparativos agregamos una muestra de la zona de hibridación interracial, algunas muestras representativas de la raza "Sur 2n = 34" y una de la raza "múltiples fisiones 2n = 42-44". Los siete primeros pares cromosómicos variables fueron codificados

  14. The Genetic History of Peruvian Quechua‐Lamistas and Chankas: Uniparental DNA Patterns among Autochthonous Amazonian and Andean Populations

    Science.gov (United States)

    Sandoval, José R.; Lacerda, Daniela R.; Acosta, Oscar; Jota, Marilza S.; Robles‐Ruiz, Paulo; Salazar‐Granara, Alberto; Vieira, Pedro Paulo R.; Paz‐y‐Miño, César; Fujita, Ricardo

    2016-01-01

    Summary This study focuses on the genetic history of the Quechua‐Lamistas, inhabitants of the Lamas Province in the San Martin Department, Peru, who speak their own distinct variety of the Quechua family of languages. It has been suggested that different pre‐Columbian ethnic groups from the Peruvian Amazonia, like the Motilones or “shaven heads”, assimilated the Quechua language and then formed the current native population of Lamas. However, many Quechua‐Lamistas claim to be direct descendants of the Chankas, a famous pre‐Columbian indigenous group that escaped from Inca rule in the Andes. To investigate the Quechua‐Lamistas and Chankas’ ancestries, we compared uniparental genetic profiles (17 STRs of Q‐M3 Y‐chromosome and mtDNA complete control region haplotypes) among autochthonous Amazonian and Andean populations from Peru, Bolivia and Ecuador. The phylogeographic and population genetic analyses indicate a fairly heterogeneous ancestry for the Quechua‐Lamistas, while they are closely related to their neighbours who speak Amazonian languages, presenting no direct relationships with populations from the region where the ancient Chankas lived. On the other hand, the genetic profiles of self‐identified Chanka descendants living in Andahuaylas (located in the Apurimac Department, Peru, in the Central Andes) were closely related to those living in Huancavelica and the assumed Chanka Confederation area before the Inca expansion. PMID:26879156

  15. The best for the guest: high Andean nurse cushions of Azorella madreporica enhance arbuscular mycorrhizal status in associated plant species.

    Science.gov (United States)

    Casanova-Katny, M Angélica; Torres-Mellado, Gustavo Adolfo; Palfner, Goetz; Cavieres, Lohengrin A

    2011-10-01

    Positive interactions between cushion plant and associated plants species in the high Andes of central Chile should also include the effects of fungal root symbionts. We hypothesized that higher colonization by arbuscular mycorrhizal (AM) fungi exists in cushion-associated (nursling) plants compared with conspecific individuals growing on bare ground. We assessed the AM status of Andean plants at two sites at different altitudes (3,200 and 3,600 ma.s.l.) in 23 species, particularly in cushions of Azorella madreporica and five associated plants; additionally, AM fungal spores were retrieved from soil outside and beneath cushions. 18 of the 23 examined plant species presented diagnostic structures of arbuscular mycorrhiza; most of them were also colonized by dark-septate endophytes. Mycorrhization of A. madreporica cushions showed differences between both sites (68% and 32%, respectively). In the native species Hordeum comosum, Nastanthus agglomeratus, and Phacelia secunda associated to A. madreporica, mycorrhization was six times higher than in the same species growing dispersed on bare ground at 3,600 ma.s.l., but mycorrhiza development was less cushion dependent in the alien plants Cerastium arvense and Taraxacum officinale at both sites. The ratio of AM fungal spores beneath versus outside cushions was also 6:1. The common and abundant presence of AM in cushion communities at high altitudes emphasizes the importance of the fungal root symbionts in such situations where plant species benefit from the microclimatic conditions generated by the cushion and also from well-developed mycorrhizal networks.

  16. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    Science.gov (United States)

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

    2007-10-01

    Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

  17. 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.

  18. Downscaling reanalysis data to high-resolution variables above a glacier surface (Cordillera Blanca, Peru)

    Science.gov (United States)

    Hofer, Marlis; Mölg, Thomas; Marzeion, Ben; Kaser, Georg

    2010-05-01

    Recently initiated observation networks in the Cordillera Blanca provide temporally high-resolution, yet short-term atmospheric data. The aim of this study is to extend the existing time series into the past. We present an empirical-statistical downscaling (ESD) model that links 6-hourly NCEP/NCAR reanalysis data to the local target variables, measured at the tropical glacier Artesonraju (Northern Cordillera Blanca). The approach is particular in the context of ESD for two reasons. First, the observational time series for model calibration are short (only about two years). Second, unlike most ESD studies in climate research, we focus on variables at a high temporal resolution (i.e., six-hourly values). Our target variables are two important drivers in the surface energy balance of tropical glaciers; air temperature and specific humidity. The selection of predictor fields from the reanalysis data is based on regression analyses and climatologic considerations. The ESD modelling procedure includes combined empirical orthogonal function and multiple regression analyses. Principal component screening is based on cross-validation using the Akaike Information Criterion as model selection criterion. Double cross-validation is applied for model evaluation. Potential autocorrelation in the time series is considered by defining the block length in the resampling procedure. Apart from the selection of predictor fields, the modelling procedure is automated and does not include subjective choices. We assess the ESD model sensitivity to the predictor choice by using both single- and mixed-field predictors of the variables air temperature (1000 hPa), specific humidity (1000 hPa), and zonal wind speed (500 hPa). The chosen downscaling domain ranges from 80 to 50 degrees west and from 0 to 20 degrees south. Statistical transfer functions are derived individually for different months and times of day (month/hour-models). The forecast skill of the month/hour-models largely depends on

  19. Four New Species of Nepenthes L. (Nepenthaceae from the Central Mountains of Mindanao, Philippines

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    Thomas Gronemeyer

    2014-06-01

    Full Text Available Together with the islands of Sumatra (Indonesia and Borneo (Indonesia, Malaysia, the Philippines are the main center of diversity for carnivorous pitcher plants of the genus, Nepenthes L. Nepenthes are the largest of all carnivorous plants, and the species with the biggest pitchers are capable of trapping and digesting small amphibians and even mammals. The central cordillera of Mindanao Island in the south of the Philippines is mostly covered with old, primary forest and is the largest remaining cohesive, untouched area of wilderness in the Philippines. In a recent field exploration of two areas of the central cordillera, namely Mount Sumagaya and a section of the Pantaron range, four new taxa of Nepenthes were discovered. These four remarkable new species, N. pantaronensis, N. cornuta, N. talaandig and N. amabilis, are described, illustrated and assessed.

  20. Recent evolution and degradation of the bent Jatunraju glacier (Cordillera Blanca, Peru)

    Science.gov (United States)

    Emmer, Adam; Loarte, Edwin C.; Klimeš, Jan; Vilímek, Vít

    2015-01-01

    This article brings new insight into the recent evolution and degradation of the bent Jatunraju glacier in the northern part of the Cordillera Blanca, Peru. Analysis of topographical maps, aerial photos and satellite images covering a period of 66 years and a field survey performed in June 2013 and May 2014 helped to describe the geomorphological setting and ongoing processes. Recent evolution and degradation processes are also deduced from surface movements. Historical geodetic measurements (1967-1968; 1977-1984) and current LANDSAT images (2001-2013) were used to estimate surface velocities and changes in surface velocities over time. Our investigation showed that the most significant changes happened at an altitude of between 4300 and 4450 m asl. A significant decrease in surface velocities and increase in debris thickness indicate that this part of Jatunraju turned from a debris-covered glacier into an ice-cored rock glacier during the analyzed period. Particular parts of the article describe the cycle of formation and extinction of supraglacial lakes and the melting of buried (debris-covered) ice. A scenario of future evolution is outlined and discussed as well. We assume that ice degradation within the debris-covered glacier will continue and that the altitude of its presence will increase hand-in-hand with the changing environment.

  1. Faulted hybrid joints: an example from the Campo de Dalias (Betic Cordilleras, Spain)

    Science.gov (United States)

    Marín-Lechado, Carlos; Galindo-Zaldívar, Jesús; Rodríguez-Fernández, Luís. Roberto; González-Lodeiro, Francisco

    2004-11-01

    The development of hybrid and faulted joints has not been studied in detail in natural outcrops. This field study in the Campo de Dalias (Betic Cordilleras) establishes the distinctive features of these structures as compared with those predicted by theoretical studies. Hybrid joints appear as two sets of vertical joints forming variable angles, but generally about 25°, with opening directions orthogonal to joint planes. Their development requires low differential stresses with a tensile minimum stress. The main criteria that indicate the existence of faulted joints are: (1) the presence of subvertical fault planes with oblique slip forming a complex pattern of dextral and sinistral faults developed under a single stress regime; (2) faults with similar geometries as joints in the same outcrop, showing an inconsistent cross-cutting relationship; and (3) the development of small basins with variable polarity of asymmetric wedge filling. A permutation in stress orientation since the Tortonian in the Campo de Dalias was responsible for the development of a faulted hybrid joint system, with a constant ENE-WSW extension trend and a switch of σ1 between NNW-SSE and vertical.

  2. Glacier Retreat in the Cordillera Quimza Cruz (Tres Cruces), Bolivia from 1975 to present

    Science.gov (United States)

    Klein, A. G.; Kincaid, J. L.; Brooks, R. M.

    2008-12-01

    The glaciers in the Cordillera Quimza Cruz (Tres Cruces) and two smaller Bolivian massifs represent the southernmost tropical glaciers found along the eastern margin of the Andes. Their marginal location makes them of particular interest. The extent of glaciers in the mid 1970s was determined though digitization of the published glacier inventory of Bolivia. In 1975, extent of glaciers in the Tres Cruces region was approximately 55.4 square kilometers. More recent extents were determined from Landsat and ASTER satellite images. Cloud-free Landsat images from 1986, 1992 and 2000 were georegistered and surface reflectances were computed. Normalized Difference Snow Index (NDSI) images were then computed and thresholded to create binary maps of snow- and glacier-covered pixels. From 1975 through 2000, the Tres Cruces Region lost a significant amount of its glacier area. Of the area identified as being glacier covered in 1975 only 27.4 square kilometers (49%) were identified as containing snow and ice in Landsat images from 2000. The glacier retreat time series is being updated as part of an ongoing undergraduate research program. More recent retreat mapped from multiple ASTER images from 2000-2006 indicates that glacier recession is continuing. Changes in glacier hypsometries indicate that much of the areal loss has occurred at lower altitudes. The influence of aspect on glacier retreat is the next area of investigation.

  3. Serological survey of leptospiral infections in sheep, goats and dogs in Cordillera province, Bolivta.

    Science.gov (United States)

    Ciceroni, L; Bartoloni, A; Pinto, A; Guglielmetti, P; Valdez Vasquez, C; Gamboa Barahona, H; Roselli, M; Giannico, F; Paradisi, F

    1997-01-01

    A serological survey for antibodies to Leptospira spp. was conducted on sheep, goat and dog serum samples collected in three localities in Cordillera province in the southern part of the Santa Cruz Department (Bolivia) in 1992. A total of 98 sheep, 218 goats and 43 dogs were tested against 29 leptospiral serovars using the microscopic agglutination test. At the time of blood collection all of the examined animals appeared healthy and presented no clinical sign suggestive of leptospirosis. Antibody prevalences, as determined by positive results at a 1:100 dilution or higher, was 14.3% in sheep, 19.7% in goats, and 14.0% in dogs. Agglutinins against six serovars (poi. shermani, pomona, canicola, javanica, djasiman) were found in positive animals. The highest serological prevalence in sheep and goats was recorded for serovar poi, followed by pomona in sheep and shermani in goats. Titres to shermani were the commonest in dogs. The results of this survey indicate that leptospiral infection is common in south-east Bolivia and that serovars of several serogroups concur in the etiology.

  4. Estructura y riqueza de plantas arborescentes en Un Bosque de Niebla de la Cordillera Central (Tolima, Colombia

    Directory of Open Access Journals (Sweden)

    Campo Kurmen Juan Manuel

    2006-06-01

    Full Text Available Se presenta el estudio de la estructura, la riqueza y la composición florística del componente arborescente de un
    bosque entresacado, en la vereda Dantas, municipio de Ibagué, Tolima, Colombia, con base en el mues-treo de
    los individuos con DAP 2,5 cm en 0,1 ha. El bosque se caracteriza por la escasez de lianas y de hemiepífitas,
    ausencia de familias típicas de bosques de niebla colombianos entre los 2.000 y 2.500 msnm (Araceae, Ericaceae,
    Myrtaceae, Meliaceae y Aquifoliaceae y por un incremento en la riqueza de familias como Sabiaceae y Euphorbiaceae.
    Comparado con otros bosques de niebla de los Andes colombianos y del neotrópico, éste presenta una de las
    más bajas densidades de tallos (237 individuos con DAP ³ 2,5 cm por 0,1 ha y una proporción de árboles grandes
    muy alta (39,7% individuos con DAP 10 cm por 0,1 ha. Aparentemente, los efectos de la extracción selectiva
    de maderas sobre la riqueza, la estructura y la composición, son la disminución de la densidad y la riqueza de lianas, mayor riqueza de Sabiaceae y Euphorbiaceae y mayor densidad de especies secundarias como Hedyosmum goudotianum Slms-Laubach var. goudatianum, Miconia resima Naud. y Palicourea calophlebia Standl.

  5. Tectónica extensional cretácica en la subcuenca de Oliete (Cordillera Ibérica central)

    OpenAIRE

    1997-01-01

    The control of the extensional tectonics on the geometry of the Oliete Subbasin during Early Barremian-Basal Aptian (Early Cretaceous) is examinated. Both, the main NW-SE trending of the basin, its asymetrical geometry and the location of the depocenters was controlled by the reactivation of NW-SE and NE-SW Late Variscan faults, and the formation of new faults. We propose that the general geometry of the basin is controlled by a flexion in the cover, with some associated minor normal faults. ...

  6. Coca: The History and Medical Significance of an Ancient Andean Tradition

    Directory of Open Access Journals (Sweden)

    Amy Sue Biondich

    2016-01-01

    Full Text Available Coca leaf products are an integral part of the lives of the Andean peoples from both a cultural and traditional medicine perspective. Coca is also the whole plant from which cocaine is derived. Coca products are thought to be a panacea for health troubles in regions of South America. This review will examine the toxicology of whole coca and will also look at medicinal applications of this plant, past, present, and future.

  7. 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.

  8. Antihypertensive and antioxidant activity of atomized andean purple corn (Zea mayz L) hydroalcoholic extract in rats

    OpenAIRE

    Arroyo, Jorge; Facultad de Medicina, Universidad Nacional Mayor de San Marcos. Lima, Perú. Químico farmaceútico.; Raez, Ernesto; Facultad de Medicina, Universidad Nacional Mayor de San Marcos. Lima, Perú. Médico patólogo.; Rodríguez, Miguel; Facultad de Odontología, Universidad Nacional Mayor de San Marcos. Lima, Perú. Odontólogo.; Chumpitaz, Víctor; Facultad Odontología, Universidad Nacional Mayor de San Marcos. Lima, Perú. Odontólogo.; Burga, Jonny; Facultad de Odontología, Universidad Nacional Mayor de San Marcos. Lima, Perú. Odontólogo.; De la Cruz, Walter; Facultad de Farmacia y Bioquímica, Universidad Nacional Mayor de San Marcos. Lima, Perú. Médico.; Valencia, José; Facultad de Farmacia y Bioquímica, Universidad Nacional Mayor de San Marcos. Lima, Perú. Químico Farmacéutico.

    2008-01-01

    Objectives. To determine the antihypertensive and antioxidant activity of the atomized hydroalcoholic extract of Zea mays L. (Andean purple corn) in rats with induced hypertension. Material and methods. We used five groups of six Holtzmann rats each, one without hypertension (negative control) and four with hypertension induced by L-NAME: positive control and three groups for the doses of 250, 500 and 1000 mg/kg, respectively. The treatment was carried out orally once a day for 25 days. Th...

  9. Three-dimensional density model of the Nazca plate and the Andean continental margin

    Science.gov (United States)

    Tassara, AndréS.; GöTze, Hans-Jürgen; Schmidt, Sabine; Hackney, Ron

    2006-09-01

    We forward modeled the Bouguer anomaly in a region encompassing the Pacific Ocean (85°W) and the Andean margin (60°W) between northern Peru (5°S) and Patagonia (45°S). The three-dimensional density model that reproduces the gravity field is a continental-scale representation of density structure to 410 km depth that characterizes the mantle and crust of the oceanic Nazca plate, subducted slab and continental margin with a minimum number of bodies. We predefined the density of each body after studying the dependency of density on composition of crustal and mantle materials and pressure-temperature conditions appropriate for the Andean setting. A database of independent geophysical information constrains the geometry of the top of the subducted slab, locally the Moho of the oceanic and continental crusts and, indirectly, the lithosphere-asthenosphere boundary underneath the continental plate. Other boundaries, notably the intracrustal density discontinuity separating upper from lower crust below the continent, were not constrained and their geometry is the result of fitting the observed and calculated Bouguer anomaly during forward modeling. This contribution presents the model to the Andean geoscientific community and contains some tools, like a sensitivity analysis, that helps potential users of the model to interpret its results. We describe and discuss some of these results in order to illustrate the application of the model to the study of a wide range of phenomena (e.g., modification of oceanic plate structure by hot spots, shape of the subducted slab, thermal structure of the continental lithosphere, compensation mechanism and formation of orogenic relieve, causes of Andean segmentation).

  10. Large Differences in Bacterial Community Composition among Three Nearby Extreme Waterbodies of the High Andean Plateau.

    Science.gov (United States)

    Aguilar, Pablo; Acosta, Eduardo; Dorador, Cristina; Sommaruga, Ruben

    2016-01-01

    The high Andean plateau or Altiplano contains different waterbodies that are subjected to extreme fluctuations in abiotic conditions on a daily and an annual scale. The bacterial diversity and community composition of those shallow waterbodies is largely unexplored, particularly, of the ponds embedded within the peatland landscape (i.e., Bofedales). Here we compare the small-scale spatial variability (Altiplano peatland ponds represent a hitherto unknown source of microbial diversity.

  11. Invertebrate metacommunity structure and dynamics in an andean glacial stream network facing climate change

    DEFF Research Database (Denmark)

    Cauvy-Fraunié, Sophie; Espinosa, Rodrigo; Andino, Patricio

    2015-01-01

    theory as a conceptual framework to better understand how river network structure influences the spatial organization of aquatic communities in glacierized catchments. At 51 stream sites in an Andean glacierized catchment (Ecuador), we sampled benthic macroinvertebrates, measured physico...... community variation. Overland spatial variables based on geographical and altitudinal distances significantly affected community variation. Watercourse spatial variables based on glaciality distances had a unique significant effect on community variation. Within alpine catchment, glacial meltwater affects...

  12. Prevalence of the metabolic syndrome in Peruvian Andean hispanics: the PREVENCION study.

    Science.gov (United States)

    Medina-Lezama, Josefina; Zea-Diaz, Humberto; Morey-Vargas, Oscar L; Bolaños-Salazar, Juan F; Muñoz-Atahualpa, Edgar; Postigo-MacDowall, Mauricio; Corrales-Medina, Fernando; Valdivia-Ascuña, Zoila; Cuba-Bustinza, Carolina; Paredes-Díaz, Sheyla; Villalobos-Tapia, Paola; Chirinos-Pacheco, Julio; Goldberg, Ronald B; Chirinos, Julio A

    2007-11-01

    Data regarding the prevalence of metabolic syndrome (MTS) in Andean populations are limited. We evaluated the prevalence of MTS according to American Heart Association/National Heart, Lung and Blood Institute criteria among 1878 subjects in the PREVENCION study in Peru. In women, the most common component was low HDL cholesterol (60.9%) followed by abdominal obesity (36.9%). In men, the most common component was elevated triglycerides (52.0%) followed by low HDL cholesterol (32.5%), whereas the prevalence of abdominal obesity was 14%. Abnormal fasting glucose was the least common component in men (5.4%) and women (5.0%). The prevalence of MTS was significantly higher in women compared to men (23.2% versus 14.3%) and increased steeply with age, particularly in women (por=30kg/m2) instead of waist circumference as a component of the MTS lead to equivalent prevalence estimates of MTS in men but significantly underestimated the prevalence in women. The MTS is highly prevalent among Peruvian Andeans, particularly in older women. The pattern of MTS components in this Andean population is characterized by a high prevalence of dyslipidemia and a relatively low prevalence of elevated fasting glucose. Further studies are required to characterize genetic and environmental determinants of these patterns.

  13. Estimating Aboveground Biomass and Carbon Stocks in Periurban Andean Secondary Forests Using Very High Resolution Imagery

    Directory of Open Access Journals (Sweden)

    Nicola Clerici

    2016-07-01

    Full Text Available Periurban forests are key to offsetting anthropogenic carbon emissions, but they are under constant threat from urbanization. In particular, secondary Neotropical forest types in Andean periurban areas have a high potential to store carbon, but are currently poorly characterized. To address this lack of information, we developed a method to estimate periurban aboveground biomass (AGB—a proxy for multiple ecosystem services—of secondary Andean forests near Bogotá, Colombia, based on very high resolution (VHR GeoEye-1, Pleiades-1A imagery and field-measured plot data. Specifically, we tested a series of different pre-processing workflows to derive six vegetation indices that were regressed against in situ estimates of AGB. Overall, the coupling of linear models and the Ratio Vegetation Index produced the most satisfactory results. Atmospheric and topographic correction proved to be key in improving model fit, especially in high aerosol and rugged terrain such as the Andes. Methods and findings provide baseline AGB and carbon stock information for little studied periurban Andean secondary forests. The methodological approach can also be used for integrating limited forest monitoring plot AGB data with very high resolution imagery for cost-effective modelling of ecosystem service provision from forests, monitoring reforestation and forest cover change, and for carbon offset assessments.

  14. Introduction and Establishment of Pissodes castaneus (Coleoptera: Curculionidae) in the Andean Patagonia of Argentina.

    Science.gov (United States)

    Pereyra, V A; Gomez, C A; La Manna, L; Roux, G; Lanteri, A A; Vallejos, N C; Marvaldi, A E

    2016-02-01

    The pine weevils that occur in plantations of Pinus spp. in Andean Patagonia of Argentina belong to the species Pissodes castaneus (De Geer), a Eurasian endemic species, according to the identification based on molecular and morphological characters. Sequences of the mitochondrial Cytochrome oxidase subunit I and nuclear genes (28 S rDNA and ITS2) were obtained for individuals of 13 afforestations, covering the entire distribution area of the established populations in the Andean Patagonia of Argentina. Sequence comparison with representative species of the genus (European, North American, and Chinese species) shows that Patagonian specimens are conspecific to those of P. castaneus sequenced from Europe. Phylogenetic analyses indicate that all terminals from Patagonia form a monophyletic unit without evident subclades, eliminating the possibility of existence of more than one species of Pissodes Germar in this area, including cryptic ones. Moreover, the very low genetic divergence between the Patagonian populations suggests that it is plausible that P. castaneus was introduced into Patagonia from just one location. Mitochondrial DNA analysis shows that Patagonian terminals group together with a French haplotype and are clearly separated from other P. castaneus individuals represented in our sample, and reveal that established populations in Andean Patagonia originated via a limited introduction.

  15. A regional perspective on the diversity and conservation of tropical Andean fishes.

    Science.gov (United States)

    Anderson, Elizabeth P; Maldonado-Ocampo, Javier A

    2011-02-01

    The tropical Andes harbor an extraordinarily varied concentration of species in a landscape under increasing pressure from human activities. Conservation of the region's native plants and animals has received considerable international attention, but the focus has been on terrestrial biota. The conservation of freshwater fauna, particularly the conservation of fishes, has not been emphasized. Tropical Andean fishes are among the most understudied vertebrates in the world. We estimate that between 400 and 600 fish species inhabit the diverse aquatic environments in the region. Nearly 40% of these species are endemic. Tropical Andean fishes are vulnerable to ongoing environmental changes related to deforestation, water withdrawals, water pollution, species introductions, and hydropower development. Additionally, their distributions and population dynamics may be affected by hydrologic alterations and warmer water temperatures associated with projected climate change. Presently, at least three species are considered extinct, some populations are endangered, and some species are likely to decline or disappear. The long-term persistence of tropical Andean fishes will depend on greater consideration of freshwater systems in regional conservation initiatives.

  16. Distribution of Lutzomyia ayacuchensis, the vector of Andean-type cutaneous leishmaniasis, at different altitudes on the Andean slope of Ecuador.

    Science.gov (United States)

    Gomez, Eduardo A; Kato, Hirotomo; Mimori, Tatsuyuki; Hashiguchi, Yoshihisa

    2014-09-01

    Distribution of the vector species is a major risk factor for the endemicity of leishmaniasis. In the present study, the vertical distribution of Lutzomyia (Lu.) ayacuchensis, the vector of Leishmania (Leishmania) mexicana in the Ecuadorian Andes, was surveyed at different altitudes (300-2500m above sea level) of the Andean slope. The vector species Lu. ayacuchensis was identified at an altitude of 650m and a higher areas, and higher distribution ratio of the species was observed at higher altitudes. In addition, high ratios of L. (L.) mexicana infection were detected in higher areas, but none in lower populations of sand flies. Since an association between sand fly populations and vector competence is suggested in Lu. ayacuchensis, haplotype analysis was performed on the species from different altitudes of the study areas; however, no apparent difference was observed among populations. These results suggested that Lu. ayacuchensis in Andean slope areas of Ecuador has the potential to transmit L. (L.) mexicana and spread leishmaniasis in these areas.

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

    Science.gov (United States)

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

    1994-01-01

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

  18. Dinámica e implicancia del aluvión de la laguna 513, Cordillera Blanca, Ancash, Perú Dinamics and implications of the laguna 513 Aluvion, Cordillera Blanca, Ancash Perú

    Directory of Open Access Journals (Sweden)

    Patricio Valderrama

    2012-09-01

    Full Text Available La Cordillera Blanca, al norte de Perú, es la zona con más actividad geodinámica externa en Perú. En ella ocurrieron grandes flujos de detritos de origen glaciar, varios de ellos fueron grandes desastres y cobraron miles de vidas. El 11 de abril del 2010, la laguna 513, ubicada en el centro de la Cordillera Blanca, sufrió un desembalse parcial por la caída de un gran bloque de hielo y rocas del nevado Hualcán (5500 m.s.n.m.. Este evento pese a ser de dimensiones considerables, no generó grandes pérdidas ni afectó alguna ciudad importante. Mediante simulaciones numéricas de flujo se estudió su dinámica, se determinó sus volúmenes y su turbulencia así como también explicamos e papel de la morfología de la zona en la desaceleración del flujo, su encausamiento en un valle fluvial y su posterior comportamiento como crecida de río. Las simulaciones realizadas mediante FLO2D se validan mediante comparaciones con imágenes de satélite post evento y datos de campo.The Cordillera Blanca in northern Peru is the most external geodynamics active areas in Perú. There have been occurred the biggest glacier source debris flow in the Peruvian history, most of them became on major disasters and claimed thousands of lives. On April 11th, 2010, the Laguna 513, located in the center of the Cordillera Blanca, suffered a partial GLOF due a massive rock and ice fall from Nevado Hualcán (5500 masl. This event, despite being of considerable size, did not generate large losses or affect any major city. Using numerical simulations we study the dynamics of the consequent GLOF and debris flow. We determined the volume and turbulence as well as also explained the role of the geomorphology of the area in the flow deceleration process and the river flood subsequent behavior. The FLO 2D simulations are validated with post event satellite image and field data.

  19. Pertinent spatio-temporal scale of observation to understand sediment yield control factors in the Andean Region: the case of the Santa River (Peru

    Directory of Open Access Journals (Sweden)

    S. B. Morera

    2013-01-01

    Full Text Available Hydro-sedimentology development is a great challenge in Peru due to limited data as well as sparse and confidential information. Consequently, little is known at present about the relationship between the El Niño Southern Oscillation (ENSO, precipitation, runoff, land use and the sediment transport dynamics. The aim of this paper is to bridge this gap in order to quantify and understand the signal of magnitude and frequency of the sediment fluxes from the central western Andes; also, to identify the main erosion control factor and its relevance.

    The Tablachaca River (3132 km2 and the Santa River (6815 km2, two mountainous Andean catchments that are geographically close to each other, both showed similar statistical daily rainfall and discharge variability but high contrast in sediment yield (SY. In order to investigate which factors are of importance, the continuous water discharge and hourly suspended sediment concentrations (SSC of the Santa River were studied. Firstly, the specific sediment yield (SSY at the continental Andes range scale for the Pacific side is one of the highest amounts (2204 t km2 yr−1. Secondly, no relationship between the water discharge (Q and El Niño/La Niñ a events is found over a 54 yr time period. However, the Santa Basin is highly sensitive during mega Niños (1982–1983 and 1997–1998. Lastly, dispersed micro-mining and mining activity in specific lithologies are identified as the major factors that control the high SSY. These remarks make the Peruvian coast key areas for future research on Andean sediment rates.

  20. Late Cenozoic Deformation of the Coastal Cordillera, Northern Chilean Forearc, 18- 25°S

    Science.gov (United States)

    Allmendinger, R. W.; González, G.; Loveless, J. P.; Carrizo, D.

    2007-12-01

    Overlying the only part of the South American continental crust that is in direct contact with the subducting Nazca Plate, the Coastal Cordillera of northern Chile and southern Peru should provide the most complete geological record of the coupling between the two plates. This record of coupling is exquisitely preserved in the hyperarid Atacama Desert. This preservation is both one of the major advantages and major challenges of working in this region: On the positive side, exposure of geomorphic surfaces is complete and unencumbered by erosion or vegetation, and brittle saline soils preserve subtle deformation features that would quickly be obliterated in more humid environments. On the negative side, ancient geomorphic features are just as fresh as Recent one and the lack of organic material precludes radiocarbon dating, a traditional tool of paleoseismology. During the last several years, we have concentrated on documenting three fundamental characteristics of late Cenozoic forearc deformation: (1) NS shortening on reverse faults striking at a high angle to, and dextral-reverse faults striking oblique to, the continental margin; (2) N-striking normal faults of the forearc and their reactivation, locally, as reverse faults; and (3) extensive suites of tension cracks. Reverse faults striking at a high angle to the margin are present between 19 and 21.5°S, straddling the topographic symmetry plane that marks the axis of the Bolivian orocline. Limited dating of tuffs and surfaces shows that these structures have been active for at least the last 6 Ma. At least 5 of these structures -- Atajaña, Pisagua, Iquique north and south, and Barranco Alto -- cut the Pleistocene marine terraces of the coastal platform, producing 20 to 50 m of vertical offset. A forearc crustal earthquake just south of Pisagua in March 2007 demonstrates that margin parallel shortening continues to the present and that permanent deformation occurs during the interseismic part of the plate

  1. Structure of Sierra Blanca (Alpujarride Complex, west of the Betic Cordillera

    Directory of Open Access Journals (Sweden)

    Andreo, B.

    1995-04-01

    Full Text Available Sierra Blanca, situated in the SW of Málaga, forms part of the Blanca unit, belonging to the Alpujarride Complex of the Betic Cordillera. Its lithologic sequences are made up of a group of migmatites, gneisses and schists and an upper formation of marbles (white dolomitic and the bottom and blue calcareous towards the top, linked with a transitional contact. The structure of Sierra Blanca is comprised of folds, generally isoclinal, with reversed limbs and with important tectonic transpositions, the direction of which is approximately E-W in the eastern area and N-S and E-W in the West. In both areas the folds present opposing vergences, consistently towards the interior of the sierra. The origin of these structures is explained with a model of westerly movements of the Blanca unit, in relation to the Los Reales unit, with the formation of frontal and lateral folds. In its advancement, the western part of Sierra Blanca underwent an important anti-clockwise rotation responsible for the co-existence of folds in N-S and E-W directions. These structures occurred under ductile conditions, owing to the presence of important overthrusting peridotitic masses of the Los Reales unit. This model of westerly displacement is inserted in the process undergone by the Betic-Rif Internal Zones (with Blanca and Los Reales units included which occurred at the end of the Oligocene-Early Miocene when the Gibraltar arch began to be formed.Sierra Blanca, situada al SW de Málaga, forma parte de la unidad de Blanca que pertenece al complejo Alpujárride de la Cordillera Bética. Su secuencia litológica está compuesta por un conjunto inferior de migmatitas, gneises y esquistos, y por una formación superior de mármoles, blancos dolomíticos en la base y mármoles calizos azules hacia la parte superior, entre los que existe un tránsito gradual. La estructura de Sierra Blanca está formada por pliegues, generalmente isoclinales, con flancos invertidos que muestran

  2. Slope deformations in high-mountain regions as observed by InSAR: Examples from the Cordillera Blanca, Peru

    Science.gov (United States)

    Frey, Holger; Strozzi, Tazio; Caduff, Rafael; Huggel, Christian; Klimeš, Jan; Vilímek, Vít; Wiesmann, Andreas; Kääb, Andreas; Cochachin, Alejo; Plummer, Stephen

    2016-04-01

    Steep topography, the world's highest concentration of tropical glaciers, numerous glacial lakes and strong seismic activity combined with a densely populated valley bottom in the Rio Santa basin characterize the Cordillera Blanca in Peru. Besides glacier-related processes, a variety of landslide types and processes is present outside the glaciated areas, favoured by the steep terrain, geological conditions, sparse vegetation, intense precipitation, and strong seismicity. This combination of high hazard potentials and vulnerabilities results in a long list of natural disasters. Information on surface displacements is very valuable for early detection of emerging hazard potentials and their assessment. Interferometric processing of SAR data (InSAR) provides the possibility to remotely detect different types of surface displacement processes, also in remote locations where no other monitoring data are available. This contribution, developed under the ESA-funded S:GLA:MO project (sglamo.gamma-rs.ch), shows the potential of InSAR products for hazard assessments and glaciological investigations in high-mountain regions. We present a selection of different surface displacements as observed in the Cordillera Blanca based on InSAR data: a landslide zone near the Rampac Grande village, where in 2009 a landslide caused casualties and property loss; a landslide at the entry of the Santa Cruz Valley, northern Cordillera Blanca, where the displacement history could be reconstructed over five years; surface displacements at the interior moraine slopes surrounding Laguna Palcacocha, a major glacier lake above the city of Huaraz, which are compared to and complemented by geophysical investigations in the field; surface displacements at the moraine damming Laguna Safuna Alta, a glacier lake in the northern part of the Cordillera Blanca; glacier velocities across the entire Cordillera Blanca, revealing ice flow velocities of more than 200 m yr-1 at certain locations at the end of

  3. Documenting and describing the redox evolution of the Neoproterozoic ocean: lessons from the Canadian Cordillera (Invited)

    Science.gov (United States)

    Johnston, D. T.; Poulton, S. W.; Langmuir, C. H.; MacDonald, F. A.; Chen, Z.; Knoll, A.

    2009-12-01

    The geological record of the Neoproterozoic preserves evidence for large-scale perturbations in Earth’s climate and changes in tectonic configuration. During the terminal Proterozoic, and within the context of these changes, Earth’s fluid envelope achieved a level of oxygenation that allowed for the evolution and subsequent radiation of complex multi-cellular life. As such, better constraining the geochemical evolution of the oceans and atmosphere throughout the entire Neoproterozoic will allow for a more mechanistic understanding of the links between changing environmental chemistry and biological innovation. Further, it will provide information on the relative timing of these changes and, where robust dates are available, estimates on the absolute rates of change (both chemical and biological). To this end, our ongoing work has focused on constructing high stratigraphic resolution geochemical records through mixed lithological packages of sedimentary rocks from eastern Alaska and the Canadian Cordillera. Here, we present detailed chemostratigraphic reconstructions of redox sensitive proxies, including Fe-speciation and trace element budgets, that provide an integrated window into Neoproterozoic marine oxidant budgets. These oxidant budgets then allow for the modeling of the relative influence of different aerobic and anaerobic microbial processes on the overall carbon cycle. Taken together, it is this cascade of microbial processes that drives remineralization reactions, the sum of which serves to counter-act organic carbon export, which is ultimately responsible for the buildup of O2. This simple framework serves as the foundation for our interpretation of Neoproterozoic biogeochemistry and informs our view of late Precambrian marine ecosystems. This approach can be further applied to more specific, and perhaps even more anomalous intervals of Neoproterozoic Earth history, including the Cryogenian Bitter Springs event and the Ediacaran Shuram anomaly; both

  4. East-west thrusting and anomalous magnetic declinations in the Sierra Gorda, Betic Cordillera, southern Spain

    Science.gov (United States)

    Platzman, E. S.

    1994-01-01

    Structural and palaeomagnetic studies in the Sierra Gorda (Sierra de Loja), located in the External zone of the Betic Cordillera, indicate that westward-directed thrusting is not associated with significant rotations about a vertical axis. Detailed mapping and slip vector analysis show that the Sierra Gorda is a thrust complex composed of three thrust sheets. The uppermost thrust places Early Jurassic pelagic carbonates on top of Jurassic to Oligocene sediments that form a large doubly-plunging footwall syncline. The eastern limb of this syncline has been overturned and is tectonically thinned as a result of the overthrusting. Palaeomagnetic results from Mesozoic and Tertiary sediments both within and around the perimeter of the Sierra Gorda indicate that: (1) the average remanence vector of the seven Late Jurassic localities sampled within the Sierra Gorda has a direction (D = 328° and I = 38°) that is not significantly different from the expected declination for the Upper Jurassic of stable Iberia; and (2) there is no significant difference between the remanences in the two upper thrust sheets indicating that differential rotation did not occur during the initiation and displacement on the thrusts. In contrast, the one Late Jurassic site that was sampled to the west of the Sierra Gorda is rotated, like the rest of the Subbetics, 60° clockwise of the reference direction. The unrotated directions obtained in the Sierra suggest, either that it has rotated in a clockwise sense concordant with the rest of the Subbetic zone and has then been backrotated, or that it has never rotated relative to stable Iberia. In the latter, simpler hypothesis the unrotated declinations may be explained in terms of orthogonal convergence along an irregular continental margin.

  5. New method for assessing the potential hazardousness of glacial lakes in the Cordillera Blanca, Peru

    Directory of Open Access Journals (Sweden)

    A. Emmer

    2014-02-01

    Full Text Available This paper presents a new and easily repeatable objective method for assessing the potential hazardousness of glacial lakes within the Peruvian region of Cordillera Blanca (excluding ice-dammed lakes, which do not reach significant volumes in this region. The presented method was designed to meet four basic principles, which we considered as being crucial. These are: (a principle of regional focus; (b principle of objectivity; (c principle of repeatability; and (d principle of multiple results. Potential hazardousness is assessed based on a combination of decision trees for clarity and numerical calculation for objectivity. A total of seventeen assessed characteristics are used, of which seven have yet to be used in this context before. Also, several ratios and calculations are defined for the first time. We assume that it is not relevant to represent the overall potential hazardousness of a particular lake by one result (number, thus the potential hazardousness is described in the presented method by five separate results (representing five different glacial lake outburst flood scenarios. These are potentials for: (a dam overtopping resulting from a dynamic slope movement into the lake; (b dam overtopping following the flood wave originating in a lake situated upstream; (c dam failure resulting from a dynamic slope movement into the lake; (d dam failure following the flood wave originating in a lake situated upstream; and (e dam failure following a heavy earthquake. All of these potentials theoretically range from 0 to 1. The presented method was verified on the basis of assessing the pre-flood conditions of seven lakes which have produced ten glacial lake outburst floods in the past and ten lakes which have not. A comparison of these results showed that the presented method successfully identifies the potentially hazardous lakes.

  6. Fluid flow along North American Cordillera detachments determined from stable isotope and high resolution chemical analyses

    Science.gov (United States)

    Quilichini, A.; Teyssier, C.; Mulch, A.; Nachlas, W.

    2009-12-01

    Fluid flow is likely a major parameter controlling the dynamics of extensional detachment zones. Buoyancy-driven fluid flow is generated by high heat flow beneath the detachment zone, where heat is advected by crustal thinning and magma intrusions. This hydrothermal convective flow is focused in the detachment zone for the duration of activity of the detachment at relatively high temperature (300-500°C), resulting in very significant fluid-rock interaction and isotopic exchange. Quantifying sources and fluid flux in detachments is a challenge because permeability of ductilely deforming rocks is poorly understood. In order to solve these problems, we studied two different Eocene extensional systems in the North American Cordillera: the quartzitic detachment which borders the Kettle dome metamorphic core complex (WA), and the quartzo-feldspathic Bitterroot shear zone along the Idaho batholith (MT). The Kettle Dome detachment provides a continuous section of ~200 m thick quartzite mylonite where high-resolution sampling (~5 m) indicates that Deuterium isotopic ratios that are obtained from synkinematic muscovite grains are consistent with a meteoric fluid source (-130 per mil). In the Bitterroot shear zone, Coyner (2003) reported similar Deuterium isotopic ratios (down to -140 per mil) in muscovite from mylonites and ultramylonites. Microprobe analyses were obtained for white mica porphyroclasts by performing transects perpendicular to the basal (001) cleavage in order to determine intragrain chemical zoning. Preliminary results for the Kettle dome indicate increasing phengite composition with depth, suggesting enhanced activity of the Tschermak exchange. The variations of the phengitic signature in muscovite indicates that temperature diminuish downsection, which is contradictory with the results obtained by the Qz-Ms oxygen isotope thermometer along the Kettle section. Our recent work provides geologic data for numerical models that address the permeability of

  7. Ensayo de zonación sismotectónica en la Cordillera Ibérica. Depresión del Ebro y borde sur Pirenáico

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    Simon, J. L.

    1987-12-01

    Full Text Available Spatial relations between recent (Pliocene and Quaternary structures and seismic activity in the Iberian Chain, Ebro Basin and Outer Pyrenean Sierras are analysed. Starting from these relations, a seismotectonic zonation defining four main regions (Eastern Iberian Chain, Middle Iberian Chain, Outer Pyrenean Sierras-Carneros-Demanda Massif and Central sector of the Ebro Basin is stablished. Several zones and subzones with homogeneous characteristics from the seismotectonic point of view are differenciated within each of these four main regions. This zonation is the basis of an attempt to calculate seismic risk with a deterministic criterion.Se analizan las relaciones espaciales entre estructuras recientes (pliocenas y cuaternarias y actividad sísmica en el área de la Cordillera Ibérica, Depresión del Ebro y Sierras Exteriores Pirenaicas. A partir de ellas se realiza una zonación sismotectónica, definiendo cuatro regiones principales (Ibérica Oriental, Ibérica central, Sierras Exteriores-Macizo de Cameros-Demanda y sector central de la Depresión del Ebro y, en cada una de ellas, diferentes zonas y subzonas con características homogéneas desde el punto de vista sismotectónico. Esta zonación constituye la base de un ensayo de cálculo de riesgo sísmico con criterio determinista.

  8. An enigmatic frog of the genus Atelopus (Family Bufonidae) from Parque Nacional Chirripó, Cordillera de Talamanca, Costa Rica.

    Science.gov (United States)

    Savage, Jay M; Bolaños, Federico

    2009-01-01

    A distinctive new species of Atelopus is described from Parque Nacional Chirrip6 Grande, Cordillera de Talamanca (3,400-3,500 m). It closely resembles populations of the Atelopus ignescens complex from the Andes of northern Ecuador and southern Colombia. It differs most significantly from these frogs in the pattern of spiculae and coni development on the throat, chest, hands and feet. The Costa Rican species appears to be an outlier of the complex inexplicably separated geographically from its nearest allies by an over land distance of about 1,600 km.

  9. Soil charcoal analysis as a climato-stratigraphical tool: The key case of Cordillera Real, northern Andes

    Energy Technology Data Exchange (ETDEWEB)

    Di Pasquale, G. [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Impagliazzo, S., E-mail: stefania.impagliazzo@unina.i [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Lubritto, C. [CIRCE, Dipartimento di Scienze Ambientali, II Universita di Napoli, and INNOVA, via Vivaldi, 43, 81100 Caserta (Italy); Marziano, M. [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy); Passariello, I. [CIRCE, Dipartimento di Scienze Ambientali, II Universita di Napoli, and INNOVA, via Vivaldi, 43, 81100 Caserta (Italy); Ermolli, E. Russo [Dipartimento di Arboricoltura Botanica e Patologia Vegetale, Universita di Napoli Federico II, Via Universita 100, 80055 Portici (Italy)

    2010-04-15

    The present study represents the first attempt of reconstructing fire history through soil charcoal dating. The investigated area is located in the Guandera Biological Reserve (western Cordillera Real, northern Ecuador). Six AMS radiocarbon dating, performed at the base of five soil profiles allowed a fire phase to be identified during the Pleistocene-Holocene transition. A strong correspondence was highlighted between the age of the Guandera fires and the El Abra stadial, which is considered the Younger Dryas equivalent in South America. This local evidence of fires contributes to define the geographic area in which the El Abra stadial was recorded and suggests a wider use of the soil charcoal analysis.

  10. The great Atacama flood of 2001 and its implications for Andean hydrology

    Science.gov (United States)

    Houston, John

    2006-02-01

    In February 2001, widespread flooding occurred throughout the Atacama Desert of northern Chile and southern Peru. It was particularly severe in the Río Loa basin, where roads and bridges were disrupted and the town of Calama inundated. The instantaneous peak flow in the Río Salado, a tributary of the Río Loa, reached 310 m3 s-1, an order of magnitude higher than any previously recorded event. The flood is estimated to have a return period of 100-200 years and is shown to have been caused by intense, long-duration rainfall in the western Cordillera associated with La Niña. The surface water response is typical of arid areas and highly dependent on antecedent conditions, but is quite different in perennial and ephemeral catchments. Ephemeral flood flows suffer high transmission losses, recharging phreatic aquifers. Perennial rivers have lower runoff coefficients, but baseflow levels remained high after the event for several months due to bank storage rebound and interflow. Extremely high energies of 3000 W m-2 were generated by the floods in the Cordillera, becoming less in the Precordillera and downstream. Erosion and sediment transport were consequently highest in the upper and middle reaches of the rivers, with mixed erosion-deposition in the lowest reach. The new insights gained from the interpretation and quantification of this event have important implications for palaeoenvironmental analysis, hazard management, water resource evaluation and the palaeohydrological evolution of the Andes.

  11. The interplay between tectonics and volcanism: a key to unravel the nature of Andean geothermal systems

    Science.gov (United States)

    Cembrano, J. M.

    2013-05-01

    Field mapping combined with seismic data document the interplay between tectonics and volcanism in the Andes. In the Central Volcanic Zone (CVZ) of northern Chile (22-24°S), Pleistocene east-west shortening and a thick crust (50-70 km) are associated with major composite dacitic-andesitic volcanoes and a few monogenetic basaltic eruptive centers. CVZ stratovolcanoes are devoided of flank vents; clusters of minor eruptive centers are uncommon. Composite volcanoes and minor eruptive centers are coeval with a NS-striking system of reverse faults and fault-propagation folds. Although dextral strike-slip crustal seismicity is recorded between 18 and 21°S, evidence for long-term, margin-parallel strike-slip deformation is absent. In contrast, volcanoes of the Southern Volcanic Zone (SVZ), between 38 and 46°S are built on a much thinner crust (30-40 km) during intra-arc dextral transpression. Crustal seismicity shows dextral strike-slip focal mechanisms. There, a wide variety of volcanic forms and compositions coexist along the same volcanic arc. Volcanoes range from single monogenetic cones lying on master faults to major composite volcanoes organized into either NE- or NW-trending chains, oblique to the continental margin. Flank vents and elongated clusters of minor eruptive centers are common. Compositions range from primitive basalts at minor eruptive centers, to highly evolved magmas at mature stratovolcanoes. I hypothesize that the kinematics of fault-fracture networks under which magma is transported through the crust is one fundamental factor controlling the wide variety of volcanic forms, volcanic alignment patterns and rock compositions along a single volcanic arc. As a first approximation, a thicker crust favors magma differentiation processes whereas a thinner crust prevents it. Likewise, whereas bulk intra-arc compression (vertical σ3) enhances longer residence times of magmas in the CVZ, strike-slip deformation (horizontal σ3) in SVZ provides

  12. Genetic, Cytogenetic and Morphological Trends in the Evolution of the Rhodnius (Triatominae: Rhodniini) Trans-Andean Group

    Science.gov (United States)

    Díaz, Sebastián; Panzera, Francisco; Jaramillo-O, Nicolás; Pérez, Ruben; Fernández, Rosina; Vallejo, Gustavo; Saldaña, Azael; Calzada, Jose E.; Triana, Omar; Gómez-Palacio, Andrés

    2014-01-01

    The Rhodnius Pacific group is composed of three species: Rhodnius pallescens, R. colombiensis and R. ecuadoriensis, which are considered important vectors of trypanosomes (Trypanosoma cruzi and T. rangeli) infecting humans. This group is considered as a recent trans-Andean lineage derived from the widespread distributed sister taxa R. pictipes during the later uplift of northern Andes mountain range. The widest spread species R. pallescens may be a complex of two divergent lineages with different chromosomal attributes and a particular biogeographical distribution across Central America and Colombia with several southern populations in Colombia occupying the same sylvatic habitat as its sister species R. colombiensis. Although the taxonomy of Rhodnius Pacific group has been well studied, the unresolved phylogenetic and systematic issues are the target of this paper. Here we explore the molecular phylogeography of this species group analyzing two mitochondrial (ND4 and cyt b) and one nuclear (D2 region of ribosomal 28S gene) gene sequences. The molecular analyses suggest an early divergence of the species R. ecuadoriensis and R. colombiensis, followed by a recent expansion of R. pallescens lineages. The phylogenetic relationship between sympatric R. pallescens Colombian lineage and R. colombiensis was further explored using wing morphometry, DNA genome size measurements, and by analyzing chromosomal behavior of hybrids progeny obtained from experimental crosses. Our results suggest that the diversification of the two R. pallescens lineages was mainly influenced by biogeographical events such as (i) the emergence of the Panama Isthmus, while the origin and divergence of R. colombiensis was associated with (ii) the development of particular genetic and chromosomal features that act as isolation mechanisms from its sister species R. pallescens (Colombian lineage). These findings provide new insights into the evolution of the Rhodnius Pacific group and the underlying

  13. Genetic, cytogenetic and morphological trends in the evolution of the Rhodnius (Triatominae: Rhodniini trans-Andean group.

    Directory of Open Access Journals (Sweden)

    Sebastián Díaz

    Full Text Available The Rhodnius Pacific group is composed of three species: Rhodnius pallescens, R. colombiensis and R. ecuadoriensis, which are considered important vectors of trypanosomes (Trypanosoma cruzi and T. rangeli infecting humans. This group is considered as a recent trans-Andean lineage derived from the widespread distributed sister taxa R. pictipes during the later uplift of northern Andes mountain range. The widest spread species R. pallescens may be a complex of two divergent lineages with different chromosomal attributes and a particular biogeographical distribution across Central America and Colombia with several southern populations in Colombia occupying the same sylvatic habitat as its sister species R. colombiensis. Although the taxonomy of Rhodnius Pacific group has been well studied, the unresolved phylogenetic and systematic issues are the target of this paper. Here we explore the molecular phylogeography of this species group analyzing two mitochondrial (ND4 and cyt b and one nuclear (D2 region of ribosomal 28S gene gene sequences. The molecular analyses suggest an early divergence of the species R. ecuadoriensis and R. colombiensis, followed by a recent expansion of R. pallescens lineages. The phylogenetic relationship between sympatric R. pallescens Colombian lineage and R. colombiensis was further explored using wing morphometry, DNA genome size measurements, and by analyzing chromosomal behavior of hybrids progeny obtained from experimental crosses. Our results suggest that the diversification of the two R. pallescens lineages was mainly influenced by biogeographical events such as (i the emergence of the Panama Isthmus, while the origin and divergence of R. colombiensis was associated with (ii the development of particular genetic and chromosomal features that act as isolation mechanisms from its sister species R. pallescens (Colombian lineage. These findings provide new insights into the evolution of the Rhodnius Pacific group and the

  14. Constraints on the origin and evolution of magmas in the Payún Matrú Volcanic Field, Quaternary Andean Back-arc of Western Argentina

    NARCIS (Netherlands)

    Hernando, I.R.; Aragón, E.; Frei, R.; González, P.D.; Spakman, W.

    2014-01-01

    The Payún Matrú Volcanic Field (Pleistocene–Holocene) is located in the Andean back-arc of the Southern Volcanic Zone, western Argentina, and is contemporaneous with the Andean volcanic arc at the same latitude. It includes two polygenetic, mostly trachytic volcanoes: Payún Matrú (with a summit cald

  15. 'Andean-centred' genera in the short-branch clade of Annonaceae: testing biogeographical hypotheses using phylogeny reconstruction and molecular dating

    NARCIS (Netherlands)

    Pirie, M.D.; Chatrou, L.W.; Mols, J.B.; Erkens, R.H.J.; Oosterhof, J.

    2006-01-01

    Aim We test biogeographical hypotheses regarding the origin of Andean-centred plant groups by reconstructing phylogeny in the short-branch clade (SBC) of Annonaceae, and estimating the timing of diversifications in four apparently Andean-centred genera: Cremastosperma R.E.Fr., Klarobelia Chatrou, Ma

  16. Juruá Orogeny: Brazil and Andean Countries

    Directory of Open Access Journals (Sweden)

    Mario Vicente Caputo

    Full Text Available Seismic data from Petrobras (Brazilian state-owned petroleum company show wide deformation and many reverse faults throughout the Solimões and Acre basins of northern Brazil. This deformation was observed for the first time in the Juruá River in 1976 in the Solimões Basin, and it increases toward Acre and Subandean basins from Argentine and Chile to Colombia and Venezuela. Structural inversions, block uplifts, and asymmetrical folds are attributed to compression and shearing stresses along this wide area. The severe diastrophism seen in the Juruá River area is of Late Jurassic (Kimmeridgian age. It probably coincided with the final separation between Laurasia and Gondwana continents and the initial opening of the Central Atlantic Ocean. In Peru and neighboring countries, the same Late Jurassic orogeny is also present. It occurs in the form of widespread regional uplifts, structural inversions, tilting, faults and asymmetrical folds beneath a pronounced regional parallel or angular unconformity of latest Jurassic age, marking a first-order sequence boundary above the Upper Jurassic Sarayaquillo Formation and equivalent formations, as well as above older formations. The depositional hiatus at the upper part of the Jurassic System is attributed to reorganization of stress fields that resulted in basin inversions, followed by widespread peneplanation. The uppermost Jurassic or lower Cretaceous beds, deposited above this regional unconformity, were not affected by this tectonism in Brazilian and Subandean basins. The stratigraphy of Peruvian Subandean sedimentary basins is similar to that of the Acre Basin.

  17. Genetic control of the seed coat colour of Middle American and Andean bean seeds.

    Science.gov (United States)

    Possobom, Micheli Thaise Della Flora; Ribeiro, Nerinéia Dalfollo; Zemolin, Allan Emanoel Mezzomo; Arns, Fernanda Daltrozo

    2015-02-01

    Seed coat colour of bean seeds is decisive for acceptance of a cultivar. The objectives of this research were to determine whether there is maternal effect for "L", a* and b* colour parameters in Middle American and Andean bean seeds; to obtain estimates of heritability and gain with selection for "L", a* and b* values; and select recombinants with the seed coat colour required by the market demand. Thus, controlled crossings were carried out between the Middle American lines CNFP 10104 and CHC 01-175, and between the Andean lines Cal 96 and Hooter, for obtaining F1, F1 reciprocal, F2 and F2 reciprocal generations for each hybrid combination. Parents and generations were evaluated in two field experiments (2012 normal rainy and 2013 dry seasons) in the state of Rio Grande do Sul, Brazil. Seed coat colour was quantified with a portable colorimeter. Genetic variability for "L" (luminosity), chromaticity a* (green to red shade), and chromaticity b* (blue to yellow shade) values was observed in seeds with F2 seed coat of Middle American and Andean beans. "L", a* and b* values in bean seeds presented maternal effects. High broad-sense heritability are observed for luminosity (h(2)b: 76.66-95.07%), chromaticity a* (h(2)b: 73.08-89.31%), and chromaticity b* (h(2)b: 88.63-92.50%) values in bean seeds. From the crossings, it was possible to select bean seeds in early generation for the black group, and for carioca and cranberry types (dark or clear background) which present the colour required by the market demand.

  18. Identifying positive selection candidate loci for high-altitude adaptation in Andean populations

    Directory of Open Access Journals (Sweden)

    Bigham Abigail W

    2009-12-01

    Full Text Available Abstract High-altitude environments (>2,500 m provide scientists with a natural laboratory to study the physiological and genetic effects of low ambient oxygen tension on human populations. One approach to understanding how life at high altitude has affected human metabolism is to survey genome-wide datasets for signatures of natural selection. In this work, we report on a study to identify selection-nominated candidate genes involved in adaptation to hypoxia in one highland group, Andeans from the South American Altiplano. We analysed dense microarray genotype data using four test statistics that detect departures from neutrality. Using a candidate gene, single nucleotide polymorphism-based approach, we identified genes exhibiting preliminary evidence of recent genetic adaptation in this population. These included genes that are part of the hypoxia-inducible transcription factor (HIF pathway, a biochemical pathway involved in oxygen homeostasis, as well as three other genomic regions previously not known to be associated with high-altitude phenotypes. In addition to identifying selection-nominated candidate genes, we also tested whether the HIF pathway shows evidence of natural selection. Our results indicate that the genes of this biochemical pathway as a group show no evidence of having evolved in response to hypoxia in Andeans. Results from particular HIF-targeted genes, however, suggest that genes in this pathway could play a role in Andean adaptation to high altitude, even if the pathway as a whole does not show higher relative rates of evolution. These data suggest a genetic role in high-altitude adaptation and provide a basis for genotype/phenotype association studies that are necessary to confirm the role of putative natural selection candidate genes and gene regions in adaptation to altitude.

  19. Prevalence and patterns of hypertension in Peruvian Andean Hispanics: the PREVENCION study.

    Science.gov (United States)

    Medina-Lezama, Josefina; Zea-Diaz, Humberto; Morey-Vargas, Oscar L; Bolaños-Salazar, Juan F; Postigo-Macdowall, Mauricio; Paredes-Díaz, Sheyla; Corrales-Medina, Fernando; Valdivia-Ascuña, Zoila; Cuba-Bustinza, Carolina; Villalobos-Tapia, Paola; Muñoz-Atahualpa, Edgar; Chirinos-Pacheco, Julio; Raij, Leopoldo; Chirinos, Julio A

    2007-01-01

    Cardiovascular disease is emerging as a leading cause of morbidity and mortality in Latin America. Population-based data regarding the prevalence of hypertension and hypertension subtypes in Andean Hispanic populations are scarce. The authors performed a population-based study that included 1878 Peruvian Andean adults to determine: (1) the prevalence, awareness, and control of hypertension and (2) the relative frequency of hypertension subtypes (systolic vs. diastolic). The prevalence of hypertension was 15.7% (95% confidence interval [CI], 14.0%-17.4%), did not differ by gender, and increased steeply with age, particularly in women. Awareness, treatment, and control rates were 47.9%, 39.5%, and 14%, respectively. Diastolic blood pressure increased until age 50 years and reached a plateau thereafter, whereas mean arterial pressure continued to increase with age even after age 50 years. Furthermore, in sharp contrast with the United States population, the predominant type of hypertension was systodiastolic (41.7%; 95% CI, 35.1%-48.5%). Isolated systolic hypertension accounted for only 29.3% of cases (95% CI, 23.9%-35.4%) and was responsible for a minority of cases in all age groups before age 70 years. Hypertension subtypes in this Andean population seem to differ significantly from those present in the United States population, with a much larger proportion of systodiastolic and diastolic hypertension even with advanced age. These differences result from interactions between hemodynamic and structural factors, and further studies aimed at characterizing their genetic and environmental determinants and implications in end-organ damage and prognosis in this population may contribute to understanding the pathophysiology of hypertension.

  20. Deforestation and benthic indicators: how much vegetation cover is needed to sustain healthy Andean streams?

    Science.gov (United States)

    Iñiguez-Armijos, Carlos; Leiva, Adrián; Frede, Hans-Georg; Hampel, Henrietta; Breuer, Lutz

    2014-01-01

    Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

  1. Deforestation and benthic indicators: how much vegetation cover is needed to sustain healthy Andean streams?

    Directory of Open Access Journals (Sweden)

    Carlos Iñiguez-Armijos

    Full Text Available Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS, we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%. Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

  2. Analysis of the drought resilience of Andosols on southern Ecuadorian Andean páramos

    Directory of Open Access Journals (Sweden)

    V. Iñiguez

    2015-11-01

    Full Text Available The neotropical Andean grasslands above 3500 m a.s.l. known as "páramo" offer remarkable ecological services for the Andean region. Most important is the water supply – of excellent quality – to many cities and villages established in the lowlands of the inter-Andean valleys and to the coast. However, the páramo ecosystem is under constant and increased threat by human activities and climate change. In this paper we study the resilience of its soils for drought periods during the period 2007–2013. In addition, field measurements and hydrological conceptual modelling at the catchment-scale are comparing two contrasting catchments in the southern Ecuadorian Andes. Both were intensively monitored during two and a half years (2010–2012 in order to analyse the temporal variability of the soil moisture storage. A typical catchment on the páramo at 3500 m a.s.l. was compared to a lower grassland one at 2600 m a.s.l. The main aim was to estimate the resilience capacity of the soils during a drought period and the recovery during a subsequent wet period. Local soil water content measurements in the top soil (first 30 cm through TDR were used as a proxy for the catchment's average soil moisture storage. The local measurements were compared to the average soil water storage as estimated by the probabilistic soil moisture (PDM model. This conceptual hydrological model with 5 parameters was calibrated and validated for both catchments. The study reveals the extraordinary resilience capacity of this type of shallow organic soils during the droughts in 2009 and 2010. During these droughts, the soil water content dropped from a normal value of about 0.80 to ~ 0.60 cm3 cm−3, while the recovery time was only two to three months.

  3. Volcanism subprogram: Volcanological interpretation of the northern part of the Occidental Cordillera of Bolivia, utilizing ERTS imagery

    Science.gov (United States)

    Brockmann, C. E. (Principal Investigator); Kussmaul, S.

    1973-01-01

    The author has identified the following significant results. In the present study, 6 ERTS-1 images have been interpreted on a 1:1 million scale (black and white) with the respective field reconnaissance. The area studied is located in the region bordering with Chile and includes the western part of the Bolivian Altiplano, the volcano Cordillera (western cordillera) and the northern part of Chile to the Pacific Coast. The greater part of this region is formed by Pliocene/Pleistocene volcani rock, which is discordant with the Tertiary sediments with intercalations of calcareous tuff. The ERTS-1 imagery permits the tracing of regional boundaries of the great volcanic formations and the alinements of the volcanic bodies along the fault zones. They also permit a clear examination of the volcanic apparatus, including their secondary forms, such as lava flows, parasitic cones, and lava domes. Because of the great scale, it is not possible to identify either the small structures or those of low relief. On the basis of the interpretation of the images, it is possible to give an idea of the relative age of the volcanoes.

  4. Tectonic and unroofing history of Neogene Manantiales foreland basin deposits, Cordillera Frontal (32°30'S), San Juan Province, Argentina

    Science.gov (United States)

    Pérez, Daniel J.

    2001-12-01

    The Miocene Manantiales foreland basin is located in Cordillera Frontal of San Juan, between 32°30' and 33°S. The unroofing study of the synorogenic Miocene deposits provides information about the structural evolution of Cordón de La Ramada fold-and-thrust belt. These Tertiary deposits are represented by the Chinches Formation and comprise seven members (Tc0-Tc6). They are the result of the uplift of Mesozoic sequences that crop out in La Ramada fold-and-thrust belt of the Cordillera Principal. Quaternary deposits unconformably overlying the Chinches Formation are composed of granitic and rhyolitic blocks, and represent the final uplift of the Cordón del Espinacito and a series of out-of-sequence thrusts. The unroofing studies also provide sufficient information to establish the out-of-sequence timing of the deformation at this latitude. Initial deposition of the Tertiary deposits can be dated at about 20 Ma, or early Miocene. Andesitic lavas dated in 9.2±0.3, 10.7±0.7, and 12.7±0.7 Ma unconformably overlie the structure of La Ramada fold-and-thrust belt. These facts constrain the uplift of the High Andes between 20 and 10 Ma at this latitude. The unconformity between Tertiary and Quaternary deposits suggests final uplift during Pliocene-Pleistocene times.

  5. Landscape evolution within a retreating volcanic arc, Costa Rica, Central America

    Science.gov (United States)

    Marshall, Jeffrey S.; Idleman, Bruce D.; Gardner, Thomas W.; Fisher, Donald M.

    2003-05-01

    Subduction of hotspot-thickened seafloor profoundly affects convergent margin tectonics, strongly affecting upper plate structure, volcanism, and landscape evolution. In southern Central America, low-angle subduction of the Cocos Ridge and seamount domain largely controls landscape evolution in the volcanic arc. Field mapping, stratigraphic correlation, and 40Ar/39Ar geochronology for late Cenozoic volcanic rocks of central Costa Rica provide new insights into the geomorphic response of volcanic arc landscapes to changes in subduction parameters (slab thickness, roughness, dip). Late Neogene volcanism was focused primarily along the now-extinct Cordillera de Aguacate. Quaternary migration of the magmatic front shifted volcanism northeastward to the Caribbean slope, creating a new topographic divide and forming the Valle Central basin. Stream capture across the paleo Aguacate divide led to drainage reversal toward the Pacific slope and deep incision of reorganized fluvial networks. Pleistocene caldera activity generated silicic ash flows that buried the Valle Central and descended the Tárcoles gorge to the Orotina debris fan at the coast. Growth of the modern Cordillera Central accentuated relief along the new divide, establishing the Valle Central as a Pacific slope drainage basin. Arc migration, relocation of the Pacific-Caribbean drainage divide, and formation of the Valle Central basin resulted from slab shallowing as irregular, hotspot-thickened crust entered the subduction zone. The geomorphic evolution of volcanic arc landscapes is thus highly sensitive to changes in subducting plate character.

  6. Plasma soluble erythropoietin receptor is decreased during sleep in Andean highlanders with Chronic Mountain Sickness

    OpenAIRE

    Villafuerte, Francisco C.; Corante, Noemí; Anza-Ramírez, Cecilia; Figueroa-Mujíca, Rómulo; Vizcardo-Galindo, Gustavo; Mercado, Andy; Macarlupú, José Luis; León-Velarde, Fabiola

    2016-01-01

    Excessive erythrocytosis (EE) is the main sign of Chronic Mountain Sickness (CMS), a highly prevalent syndrome in Andean highlanders. Low pulse O2 saturation (SpO2) during sleep and serum androgens have been suggested to contribute to EE in CMS patients. However, whether these factors have a significant impact on the erythropoietin (Epo) system leading to EE is still unclear. We have recently shown that morning soluble Epo receptor (sEpoR), an endogenous Epo antagonist, is decreased in CMS pa...

  7. Physics in the Andean Countries: A Perspective from Condensed Matter, Novel Materials and Nanotechnology

    Science.gov (United States)

    Prieto, P.

    2009-05-01

    We will discuss the current state of R&D in the fields of condensed matter, novel materials, and nanotechnology in the Andean nations. We will initially consider Latin America and the Caribbean (LAC) to then visualize individual developments, as well as those for the region as a whole in these fields of knowledge in each of the nations constituting the Andean Region (Bolivia, Ecuador, Chile, Venezuela, Peru, and Colombia). Based on Science & Technology watch exercises in the countries involved, along with the Iberian American and Inter-American Science & Technology Network of Indicators (Red de indicadores de Ciencia y Tecnolog'ia (RICYT) iberoamericana e interamericana)1, we will reveal statistical data that will shed light on the development in the fields mentioned. As will be noted, total R&D investment in Latin American and Caribbean countries remained constant since 1997. In spite of having reached a general increase in publications without international collaboration in LAC nations, the countries with greatest research productivity in Latin America (Argentina, Mexico, Brazil, and Chile) have strengthened their international collaboration with the United States, France, Germany, and Italy through close links associated with the formation processes of their researchers. Academic and research integration is evaluated through joint authorship of scientific articles, evidencing close collaboration in fields of research. This principle has been used in the creation of cooperation networks among participating nations. As far as networks of research on condensed matter, novel materials, and nanotechnology, the Andean nations have not consolidated a regional network allowing permanent and effective cooperation in research and technological development; as would be expected, given their idiomatic and cultural similarities, their historical background, and geographical proximity, which have been integrating factors in other research areas or socio-economic aspects. This

  8. [Decriminalizing traditional Andean medicine: an interview with Walter Álvarez Quispe].

    Science.gov (United States)

    Quispe, Walter Álvarez; Loza, Carmen Beatriz

    2014-01-01

    Walter Álvarez Quispe, a Kallawaya healer and biomedical practitioner specializing in general surgery and gynecology, presents the struggle of traditional and alternative healers to get their Andean medical systems depenalized between 1960 and 1990. Bolivia was the first country in Latin America and the Caribbean to decriminalize traditional medicine before the proposals of the International Conference on Primary Health Care (Alma-Ata, 1978). The data provided by the interviewee show that the successes achieved, mainly by the Kallawayas, stem from their own independent initiative. These victories are not the result of official policies of interculturality in healthcare, although the successes achieved tend to be ascribed to them.

  9. Vascular Endothelial Growth Factor-A Is Associated with Chronic Mountain Sickness in the Andean Population

    OpenAIRE

    Espinoza, Jose R.; Alvarez, Giancarlo; León-Velarde, Fabiola; Ju Preciado, Hugo F.; Macarlupu, Jose-Luis; Rivera-Ch, Maria; Rodriguez, Jorge; Favier, Judith; Gimenez-Roqueplo, Anne-Paule; Richalet, Jean-Paul

    2014-01-01

    Espinoza, Jose R., Giancarlo Alvarez, Fabiola León-Velarde, Hugo F. Ju Preciado, Jose-Luis Macarlupu, Maria Rivera-Ch, Jorge Rodriguez, Judith Favier, Anne-Paule Gimenez-Roqueplo, and Jean-Paul Richalet. Vascular endothelial growth factor-A is associated with chronic mountain sickness in Andean population. High Alt Med Biol. 15:146–154, 2014.—A study of chronic mountain sickness (CMS) with a candidate gene—vascular endothelial growth factor A (VEGFA)—was carried out in a Peruvian population l...

  10. Role of carbon and climate in forming the Páramo, an Andean evolutionary hotspot

    Science.gov (United States)

    Hill, Daniel

    2015-04-01

    According to a number of genetic diversification measures the Páramo grasslands of the high equatorial Andes show the greatest rates of speciation on the planet. This is probably driven by contrasting ranges of the ecosystem between glacial and interglacial periods of the Pleistocene. During the warm interglacial periods the treeline is high in the Andes restricting the Páramos to the highest regions of the Andean mountain chain, while in the cool glacial periods the Páramo areas expand and probably coalesce, bringing isolated populations into contact with each other. The origin of the Páramo ecosystem is placed close to the end of the Pliocene and has been related to the finale of regional Andean mountain building. However, this formation date is also coincident with the global cooling at the end of the Pliocene, as Northern Hemisphere glaciation and the bipolar Pleistocene ice ages begin. Furthermore, it is estimated that atmospheric CO2 concentrations dropped from the 400 ppmv typical of the Pliocene to values more typical of the Pleistocene at around this time. Global climate model simulations, coupled with a high resolution biome model, give us the opportunity to test these competing hypotheses for the formation of the Páramo ecosystem. A series of HadCM3 climate model simulations are presented here varying the height of the highest altitude Andes and the global climate from its pre-industrial state to the Pliocene. The climate are topographic changes are varied both independently and together. These climatologies are then used to drive a high-resolution biome model, BIOME4, and simulate the impact on Andean vegetation. These models seem to reproduce the observed changes in high altitude grassland biomes during the Pliocene. The climate and biome modelling presented here show that the climate changes associated with the Plio-Pleistocene boundary are the primary cause of the initial formation of this unique and important ecosystem. Although the reduction

  11. ZONIFICACIÓN AGROECOLÓGICA DE LA CORDILLERA DE GUANIGUANICO

    Directory of Open Access Journals (Sweden)

    F. Soto

    2007-01-01

    Full Text Available El desarrollo de un país necesita de una planificación de la actividad agrícola, que si se quiere que sea económicamente rentable, debe ceñirse a la realidad ecológica de las áreas de producción. En este sentido, la zonificación agroecológica es una de las principales herramientas para disminuir los riesgos a los que está sometida la agricultura. Teniendo en cuenta estos elementos, se procedió a realizar la zonificación agroecológica de la cordillera de Guaniguanico. Se tuvo información de ocho estaciones meteorológicas y 62 pluviómetros de la red del Instituto Nacional de Recursos Hidráulicos, con lo cual se llevó a cabo la zonificación climática; se estudiaron 371 000 ha, en las que se obtuvo información de más de 500 perfiles con planillas completas, lo que permitió caracterizar los suelos desde los puntos de vista físico, químico y mineralógico. Se utilizaron diferentes Sistemas de Información Geográfica (SIG, para establecer las relaciones entre los distintos parámetros estudiados y llegar a la zonificación agroecológica. A partir del análisis de la información sobre el comportamiento de los cultivos, se establecieron las bases para la zonificación, tomándose como elementos fundamentales del clima la temperatura y la lluvia; ambos se combinaron y se definieron los potenciales de rendimiento para cada condición. El otro elemento discriminante fue el suelo; en primer lugar, se tuvieron en cuenta los tipos de suelo y su aptitud para el cultivo y posteriormente se consideró la profundidad efectiva.

  12. Transverse Zones in the Eastern Cordillera (Colombia): An example in the Zipaquira Anticline

    Science.gov (United States)

    Garcia Delgado, H. S.; Jimenez, G.

    2014-12-01

    model for the Eastern Cordillera. Our goal is related the ZA and the transverse zones using Anisotropy of Magnetic Susceptibility (AMS) and paleomagnetism to unraveal the kinematic evolution of the anticline and the temporal relationship between the transverse zones and the ZA.

  13. Pollen-based 17-kyr forest dynamics and climate change from the Western Cordillera of Colombia: no-analogue associations and temporarely lost biomes

    NARCIS (Netherlands)

    Velásquez-R., C.A.; Hooghiemstra, H.

    2013-01-01

    A 17 kyr long pollen record from the unexplored Western Cordillera of Colombia (Páramo de Frontino; 3460 m elevation) shows vegetation change and inferred climate dynamics at ~ 125 yr resolution. The cold and wet Lateglacial showed well-defined stadials and interstadials. At the transition to the Ho

  14. Two new trans-Andean species of Imparfinis Eigenmann & Norris, 1900 (Siluriformes: Heptapteridae from Colombia

    Directory of Open Access Journals (Sweden)

    Armando Ortega-Lara

    Full Text Available Two new species of Imparfinis are described from the trans-Andean region of Colombia. Imparfinis timana is diagnosed by having longer anal fin base (12.4-15.5% in SL, in combination with long adipose fin (24.6-31.3% in SL, 5-6 gill rakers on the first ceratobranchial, 42-43 vertebrae and additional measurements. Imparfinis usmai is distinguished by the combination of first ray of dorsal fin longest, but not projected as a long filament, long adipose fin (21.1-27.0% in SL, maxillary barbel exceeding pelvic-fin base, 39-40 vertebrae, upper caudal-fin lobe pointed and longer than lower lobe, lower lobe rounded, 7-8 gill rakers on the first ceratobranchial, as well as additional measurements. Imparfinis timana is only known from río Guarapas, a small tributary of the upper course of the río Magdalena. Imparfinis usmai is broadly distributed in the upper basin of ríos Cauca and Magdalena, and in the lower Patía river basin. The restricted distribution of I. nemacheir to trans-Andean drainages (Atrato, Magdalena, and Lago de Maracaibo is also discussed.

  15. An Andean radiation: polyploidy in the tree genus Polylepis (Rosaceae, Sanguisorbeae).

    Science.gov (United States)

    Schmidt-Lebuhn, A N; Fuchs, J; Hertel, D; Hirsch, H; Toivonen, J; Kessler, M

    2010-11-01

    The Andean tree genus Polylepis (Rosaceae) is notorious for the high morphological plasticity of its species and the difficulty in their circumscription. The evolutionary mechanisms that have driven diversification of the genus are still poorly understood, with factors as diverse as ecological specialisation, reticulate evolution, polyploidisation and apomixis being proposed to contribute. In the present study, chromosome counts, flow cytometry and stomata guard cell size measurements were employed to document for the first time the presence of polyploidy in the genus and to infer ploidy levels for most species. Inferred ploidy levels show a clear progression from diploidy in cloud forest species to polyploidy (tetra- to octoploidy) in the morphologically and ecologically specialised incana group, indicating that polyploidisation may have played a major role in speciation processes and the colonisation of novel habitats during the Andean uplift. At least two species of Polylepis comprise populations with varying degrees of ploidy. More extensive studies are needed to obtain a better understanding of the prevalence and effects of intraspecific polyploidy in the genus.

  16. Composition and diversity of High Andean in the Fauna Production Reserve Chimborazo, Ecuador

    Directory of Open Access Journals (Sweden)

    Jorge Caranqui

    2016-03-01

    Full Text Available The present study inquire the floristic diversity of 9 sampling in four plots of 1 m² of high andean in several locations in the “Reserva de Producción de Fauna Chimborazo”. For the development of this study, we used an adaptation of the method of plots “Gloria”. With coverage (% in each of the plots, Further the diversity indices and similarity with respective analysis were obtained. The data obtained reflect a diversity that can range from medium to low, believe that this is due to anthropogenic activities that have taken place in these ecosistems. With the presence mostly Calamagrostis intermedia, it could establish that the type of vegetation is herbaceous in high andean is higher percentage; is the species that is almost always present in most types of vegetation of the RPF Chimborazo and high dominance that influences the results of low floristic diversity indices was found in the analysis. As a result the most abundant family Asteraceae is well Poaceae.

  17. La vegetación azonal paramunade la Cordillera Oriental colombiana: síntesis fitosociológica preliminar

    Directory of Open Access Journals (Sweden)

    Rangel Churio Orlando

    2006-06-01

    Full Text Available El presente estudio aplica el uso de herramientas sistematizadas y los conceptos clásicos de la fitosociología en la identificación, caracterización y síntesis preliminar de las unidades de vegetación azonal presentes en la cordillera Oriental, revisando las propuestas anteriores de clasificación y analizando conjuntamente la información obtenida de 500 levantamientos realizados en la cordillera por numerosos investigadores entre 1976 y 2001 abarcando el área comprendida entre las regiones paramunas de Almorzadero al norte, Sumapaz al sur y occidente y la Sierra Nevada del Cocuy al oriente, distribuidos entre los límites con la vegetación de bosque altoandino (3.000 m hasta el superpáramo (4.435 m, incluyendo algunas localidades extrazonales (2.800 m. Se diferenciaron en total 136 unidades de vegetación distribuidas en seis clases, cinco órdenes, 17 alianzas, 61 asociaciones, 13  subasociaciones y 34 variantes, además, de 14  comunidades, agrupadas en cuatro tipos principales
    de vegetación: acuática y de ribera, cojines de pantano, herbácea de pantanos y turberas, y arbustiva de matorrales y chuscales. Los páramos del centro de la cordillera comparten la mayor riqueza de alianzas (diez,
    seguidos por los de la región Sur (nueve y los de Chingaza (ocho; la mayor riqueza de asociaciones se concentra en los páramos del sur y centro de la cordillera y en la región de la Sierra Nevada del Cocuy (25, 21 y 18 respectivamente. La vegetación de cinco alianzas presenta distribución restringida, tres de ellas existentes
    en la región de Tota, una en el centro de la cordillera y la restante en la región de Chingaza; el mayor número
    de asociaciones con distribución restringida se presenta en los páramos del Centro de la cordillera (diez, en la
    región de Tota (siete y en la región Sur (cinco. La vegetación de las alianzas Ditricho-Isoetion y Oreobolio-Plantagion posee amplia distribución a lo largo de

  18. Timing of uplift in the Argentine Frontal Cordillera (34-32.5°S), through (U-Th)/He Thermochronology

    Science.gov (United States)

    Graber, N. R.; Hoke, G. D.; Metcalf, J. R.

    2010-12-01

    We use the apatite (U-Th)/He low temperature thermochronometer to study the rock uplift history in the Frontal Cordillera of Argentina between 32.5-34°S, where an abrupt transition in the subduction angle of the Nazca Plate occurs. The Andes in our study area are composed of three major physiographic and tectonic provinces, which have been uplifted as the deformation front stepped eastward over the last 20 Ma. From west to east they are the Principal Cordillera, Frontal Cordillera and Precordillera. The thin-skinned Aconcagua fold-thrust-belt, which today comprises the Principal Cordillera was active between ~20-8 Ma. The thick-skinned Frontal Cordillera began uplifting around 9 Ma. Finally, in the northern part of the study area, uplift and deformation of the Precordillera commenced between 5-2 Ma. South of 33°S, in the absence of the Precordillera, the total amount of crustal shortening is half that of the north, despite similar average and peak range elevations. Remnants of a regionally extensive paleolandscape are preserved in both areas. Two age-elevation profiles were collected from the granitic Permo-Triassic Choiyoi Group in the headwaters of the Rio Tunuyán (south of 33°S) and Rio Mendoza (north of 33°S). In the Tunyán area, 7 samples were collected between 2600 and 4500 m, with paleolandscape remnants at an elevation of ~5000 m. Total local relief in the Río Mendoza sampling area is 2800 m, from which the lower 1400 m were sampled between elevations of 2100 and 3500 m. We aim to constrain 1) the timing of the initiation of deformation-related exhumation of the proximal foredeep associated with the Aconcagua fold and thrust belt and 2) the rate of rock uplift induced river incision of the Rio Mendoza and Rio Tunyán as a proxy for surface uplift.

  19. New thermo and geochronological constraints on the Pliocene-Pleistocene eruption history of the Paipa-Iza volcanic complex, Eastern Cordillera, Colombia

    Science.gov (United States)

    Bernet, Matthias; Urueña, Cindy; Amaya, Sergio; Peña, Mary L.

    2016-11-01

    The Paipa-Iza volcanic complex is the only volcanic edifice in the Eastern Cordillera of Colombia. Zircon fission-track and Usbnd Pb data from deposits of two eruption epochs presented in this study constrain the time of volcanic activity between 5.9 Ma in the late Miocene and at least 1.8 Ma during the early Pleistocene. These ages correspond to 3.6 to 4.7 Ma zircon fission-track ages reported from tephra deposits of the Tierra Negra region to the southwest of the Paipa-Iza volcanic complex in the Eastern Cordillera. A 4 Myr period of volcanic activity is longer than the previously documented 2.5 Ma to 1.9 Ma activity in the Paipa-Iza area. Therefore, our data show that the Paipa-Iza volcanic complex was active during the entire Pliocene phase of rapid surface uplift, when the Eastern Cordillera reached its present-day elevation. Unclear is if the magma chamber of the Paipa-Iza volcanic complex was passively uplifted with the rest of the Eastern Cordillera, or if magmatism contributed to surface uplift. Hydrothermal activity and steep thermal gradients in the study area today indicate that a magma chamber is still present at depth. In both the zircon fission-track and Usbnd Pb data of this study the recycling of zircon from underlying Mesozoic sedimentary rocks is evident in the wide age spectra. The fission-track data show that many recycled zircons were affected at least by partial annealing, but further research is needed for constraining the thermal impact of the Paipa-Iza volcanism on the Eastern Cordillera.

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

    Directory of Open Access Journals (Sweden)

    Jose Úbeda Palenque

    2008-12-01

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

  1. Phenolic compound contents and antioxidant activity in plants with nutritional and/or medicinal properties form the Peruvian Andean region

    NARCIS (Netherlands)

    Chirinos, R.; Pedreschi Plasencia, R.P.; Rogez, H.

    2013-01-01

    Total phenolic compounds (TPC) and antioxidant activities using different assays (DPPH, ABTS and ORAC) in fruits, grains, leaves, seeds, roots and tubers from 27 different Peruvian Andean plants used in folk medicine or/and as food by the native population were evaluated in order to use these as nat

  2. Landscape genetics, historical isolation and cross-Andean gene flow in the wax palm, Ceroxylon echinulatum (Arecaceae)

    DEFF Research Database (Denmark)

    Trénel, P.; Hansen, Michael Møller; Nordmand, S.

    2008-01-01

    and landscape genetics of the Andean wax palm Ceroxylon echinulatum (Arecaceae) that occurs in two narrow bands of montane forests on each side of the Andes in Ecuador and northeastern Peru. First, we tested the hypothesis of C. echinulatum being a geographic cline species crossing the Andes in the Amotape...

  3. Contextual Analysis of the Decision To Adopt a Regional Satellite System: The Case of the Andean CONDOR.

    Science.gov (United States)

    Ferreira, Leonardo; Mody, Bella

    Acknowledging the importance of communications in economic development, this paper discusses the rationale behind the decision of the Andean Pact nations of Bolivia, Colombia, Ecuador, Peru, and Venezuela to develop a regional satellite communication system to be known as CONDOR. The application of contextual theorizing to the decision-making…

  4. The volcanism of the western part of the Los Frailes Meseta (Bolivia): a representative example of the Andean volcanism since the Upper Oligocene; Le volcanisme de la bordure occidentale de la Meseta de Los Frailes (Bolivie): un jalon representatif du volcanisme andin depuis l`Oligocene superieur

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, L. [Nancy-1 Univ., 54 (France); Jimenez, N.

    1996-12-31

    The Los Frailes Meseta (Bolivia) is one of the large tertiary ignimbritic fields of the inner volcanic arc from Central Andes (Central Volcanic Zone. CVZ), in contact zone between the Altiplano to the west and the Eastern Cordillera to the east. Field observations and mineralogical and geochemical studies (major and trace elements) lead to distinguish two types of volcanism in the western border to the Meseta. During the Middle Miocene and Pliocene, the volcanic activity can be subdivided into three pyroclastic emission cycles, the Larco, Coroma and Pliocene ignimbrites, the first two being separated by the Quechua 2 orogeny. All these ignimbrites are very similar and correspond to peraluminous rhyolites to rhyodacites. In the studies area, the Coroma cycle is the only one where an ignimbrite-less evolved resurgent dome association can be observed. Beside these ignimbrites, isolated small lava flows and domes overlay and/or intrude all the other formations. They are meta-aluminous lavas with a shoshonitic affinity. A quaternary age can be attributed to his second volcanism. These two volcanic types are well-known in the CVZ and are related to the different deformation stages, either compressional or extensional, which occur alternately in the Cordillera since 26 Ma. (authors). 61 refs., 12 figs., 3 tabs.

  5. Coarse Grain Progradation in a Foreland basin: Application of Detrital Zircon Double Dating to Cenozoic Stratigraphy, Eastern Cordillera, Colombia.

    Science.gov (United States)

    Odoh, S.; Saylor, J. E.; Higuera-Diaz, C.; Lapen, T. J.; Copeland, P.

    2015-12-01

    Progradation of coarse clastic material into distal foreland basins has been attributed to both 1) enhanced sediment production during rapid tectonic exhumation and 2) sediment reworking during tectonic quiescence. The Floresta and Medina basins in the Eastern Cordillera record deposition of alternating coarse- and fine-grained clastic strata in medial and distal (respectively) Cenozoic foreland basins. The Medina Basin records the continued eastward progradation of the deformation front in the Neogene. We use detrital zircon U-Pb (ZPb) and (U-Th)/He (ZHe) analyses from the Paleogene Floresta Basin and the entire Cenozoic Medina Basin record to evaluate the effects of episodic thrust-belt exhumation and wide-spread deposition of coarse-grained sediments in the adjacent foreland basin. Both ZPb and ZHe systems are applied to individual grains (double dating) to constrain source area and up-section variations in exhumation rates. Changes in exhumation rate or introduction of new sediment sources are recorded as changes in lag time (ZHe age - depositional age). Analysis of 6 samples from the Floresta Basin shows a decrease in lag time during deposition of the coarse-grained middle Eocene Picacho Formation and upper Paleocene Socha Sandstone suggesting that Paleogene deposition of coarse-grained intervals in this medial location corresponds to an increase in exhumation rate. However, initial results from the Medina basin are less clear as there is evidence for Paleocene volcanic input but no clear evidence for thrust-belt related sediment until the Oligocene-early Miocene. We interpret the evidence for different sediment sources for Eocene strata in the axial Eastern Cordillera (Floresta) versus the Eastern foothills (Medina) as indicative of separation of these two regions by an emergent forebulge. Exhumation rate and granularity appear to be inversely correlated in post-Oligocene strata, though confirmation of initial interpretations awaits larger samples sizes

  6. Review Article: Lake and breach hazard assessment for moraine-dammed lakes: an example from the Cordillera Blanca (Peru

    Directory of Open Access Journals (Sweden)

    A. Emmer

    2013-06-01

    Full Text Available Glacial lake outburst floods (GLOFs and related debris flows represent a significant threat in high mountainous areas across the globe. It is necessary to quantify this threat so as to mitigate their catastrophic effects. Complete GLOF hazard assessment incorporates two phases: the probability of water release from a given glacial lake is estimated through lake and breach hazard assessment while the endangered areas are identified during downstream hazard assessment. This paper outlines a number of methods of lake and breach hazard assessment, which can be grouped into three categories: qualitative, of which we outline eight; semi-quantitative, of which we outline two; and quantitative, of which we outline three. It is considered that five groups of critical parameters are essential for an accurate regionally focused hazard assessment method for moraine-dammed lakes in the Cordillera Blanca. These comprise the possibility of dynamic slope movements into the lake, the possibility of a flood wave from a lake situated upstream, the possibility of dam rupture following a large earthquake, the size of the dam freeboard (or ratio of dam freeboard, and a distinction between natural dams and those with remedial work. It is shown that none of the summarised methods uses all these criteria with, at most, three of the five considered by the outlined methods. A number of these methods were used on six selected moraine-dammed lakes in the Cordillera Blanca: lakes Quitacocha, Checquiacocha, Palcacocha, Llaca, Rajucolta, and Tararhua. The results have been compared and show that each method has certain advantages and disadvantages when used in this region. These methods demonstrate that the most hazardous lake is Lake Palcacocha.

  7. Landscape genetics, historical isolation and cross-Andean gene flow in the wax palm, Ceroxylon echinulatum (Arecaceae).

    Science.gov (United States)

    Trénel, Philipp; Hansen, Michael M; Normand, Signe; Borchsenius, Finn

    2008-08-01

    Knowledge of the role of landscapes in shaping genetic connectivity and divergence is essential for understanding patterns of biogeography and diversity. This is particularly relevant for the Andes region, a major biodiversity hotspot of relatively recent origin. We examined the phylogeography and landscape genetics of the Andean wax palm Ceroxylon echinulatum (Arecaceae) that occurs in two narrow bands of montane forests on each side of the Andes in Ecuador and northeastern Peru. First, we tested the hypothesis of C. echinulatum being a geographic cline species crossing the Andes in the Amotape-Huancabamba zone (AHZ) of southern Ecuador/northern Peru, as indicated by observations on fruit morphology. Second, we assessed the timeframe of cross-Andean divergence, and third, we investigated the impact of contemporary and historical landscape features on observed spatio-genetic patterns. Individual-based Bayesian clustering (BC) identified a northeastern, southeastern, southwestern, and northwestern cluster, with areas of genetic discontinuity coinciding with the Andes and the Giron-Paute deflection. F-statistics derived from BC suggested an east-to-west dispersal history. Population-based analyses revealed strong genetic structuring at both small and large geographic scales. Interpopulation relationships and Mantel tests strongly supported the cline model with cross-Andean dispersal in the AHZ. Along the cline, gene flow measured as F(ST) was mainly limited by distance, with less but significant impact of climatic friction. Coalescent analysis revealed that cross-Andean divergence took place during the Quaternary. Significant historical isolation (R(ST) > F(ST)) was found in the southwestern population. The current study illustrates a joint effect of founder dynamics, divergence by distance and historical isolation on patterns of Andean diversity and distribution.

  8. Two new cis-Andean species of the South American catfish genus Megalonema allied to trans-Andean Megalonema xanthum, with description of a new subgenus (Siluriformes: Pimelodidae

    Directory of Open Access Journals (Sweden)

    John G. Lundberg

    Full Text Available A revised diagnosis of the pimelodid catfish genus Megalonema is given based on synapomorphic features of the Weberian complex and gas bladder. Megalonema xanthum from the Magdalena River is redescribed. Two new cis-Andean species of Megalonema are described, M. amaxanthum n. sp. from the Amazon River basin, and M. orixanthum n. sp. from the Orinoco River basin. These three species are differentially diagnosed by shape and size of the supraoccipital posterior process, adipose-fin shape, vertebral counts, eye size, premaxillary bone shape and dentition, length of the anal-fin base, width between the posterior nostrils and presence/absence of dentations on the pectoral spine. Eretmomegalonema new subgenus is established for M. xanthum, M. amaxanthum and M. orixanthum and supported by the uniquely synapomorphic paddle-like structure of its pelvic fin and hypertrophied basipterygium. Unambiguous synapomorphies indicate a sister-group relationship between M. amaxanthum and M. orixanthum, with M. xanthum basal to this pair. This topology is congruent with the Neogene origins of separate Magdalena, Amazon and Orinoco basins suggesting vicariant control of diversification of Eretmomegalonema.

  9. Ecological Resilience and Resistance in the Hyper Diverse Forests on the Eastern Andean Flank (Mera, Ecuador)

    Science.gov (United States)

    Keen, H. F.; Gosling, W. D.; Montoya, E.; Sherlock, S.; Mothes, P. A.

    2014-12-01

    Today the Neotropics contain some of the world's most biodiverse and threatened ecosystems. Sediments obtained from two radiocarbon infinite (>48,000 years) stratigraphic sections on the eastern Andean flank, provide new insight into the relationship between biodiversity and disturbance during the Pleistocene (~200,000 years). Pollen analysis of modern and fossil material indicates that hyper diverse forest vegetation has been a feature of the Andean flank landscape for 100,000 years (pollen richness: modern = 44, fossil = 48). Correlation of past vegetation with disturbance events (volcanic and fluvial) indicates the response of hyper-diverse forest to past landscape scale change. Pollen records from near Mera (01°27 S, 78°06 W; 1117 m asl) indicate two major changes in the pollen assemblage, with forest communities dominated by: i) Hedyosmum-Alnus-Ilex, and ii) Combretaceae-Melastomataceae-Myrtaceae. These two pollen assemblages most closely resemble modern vegetation cloud forest (2500-3400m asl) and lower montane rain forest (700-2499 m asl) respectively. Sedimentary evidence suggests that at least 21 volcanic events and three changes in the local fluvial regime perturbed the regional landscape during the period of deposition. However, there is no evidence for volcanic or fluvial disturbance events causing a persistent change in vegetation community. Volcanic events (tephra deposits) are associated with increased fire (charcoal particles), and changes in vegetation (pollen grains); however, within ~50cm of sediment accumulation above each tephra, pollen assemblages revert to pre-deposition compositions. Increased fluvial influence (gravel deposits) is associated with elevated input of pollen from taxa today found at higher elevations (Podocarpus-Celtis). The input of high elevation taxa concomitant with fluvial deposits is most likely indicative of an increase in long-distance transport of pollen along water courses originating in the Andes. Our data indicate

  10. Provenance of the late Proterozoic to early Cambrian metaclastic sediments of the Sierra de San Luis (Eastern Sierras Pampeanas) and Cordillera Oriental, Argentina

    Science.gov (United States)

    Drobe, Malte; López de Luchi, Mónica G.; Steenken, André; Frei, Robert; Naumann, Rudolf; Siegesmund, Siegfried; Wemmer, Klaus

    2009-10-01

    Provenance studies have been performed utilising major and trace elements, Nd systematics, whole rock Pb-Pb isotopes and zircon U/Pb SHRIMP data on metasedimentary rocks of the Sierra de San Luis (Nogolí Metamorphic Complex, Pringles Metamorphic Complex, Conlara Metamorphic Complex and San Luis Formation) and the Puncoviscana Formation of the Cordillera Oriental. The goal was the characterisation of the different domains in the study area and to give insights to the location of the source rocks. An active continental margin setting with typical composition of the upper continental crust is depicted for all the complexes using major and trace elements. The Pringles Metamorphic Complex shows indications for crustal recycling, pointing to a bimodal provenance. Major volcanic input has to be rejected due to Th/Sc, Y/Ni and Cr/V ratios for all units. The ɛNd (540 Ma) data is lower for the San Luis Formation and higher for the Conlara Metamorphic Complex, as compared to the other units, in which a good consistency is given. This is similar to the TDM ages, where the metapsammitic samples of the San Luis Formation are slightly older. The spread of data is largest for the Pringles Metamorphic Complex, again implying two different sources. The whole rock 207Pb/ 206Pb isotopic data lies in between the South American and African sources, excluding Laurentian provenances. The whole rock Pb-Pb data is almost indistinguishable in the different investigated domains. Only the PMC shows slightly elevated 208Pb/ 204Pb values. Possible source rocks for the different domains could be the Quebrada Choja in the Central Arequipa-Antofalla domain, the Southern domain of the Arequipa-Antofalla basement, the Brazilian shield or southern Africa. Zircon SHRIMP data point to a connection between the Puncoviscana Formation and the Conlara Metamorphic Complex. Two maxima around 600 Ma and around 1000 Ma have been determined. The Nogolí Metamorphic Complex and the Pringles Metamorphic Complex

  11. Paleomagnetism and magnetic fabric of the Eastern Cordillera of Colombia: Evidence for oblique convergence and non-rotational reactivation of a Mesozoic intra-continental rift

    Science.gov (United States)

    Jiménez Díaz, G.; Speranza, F.; Faccenna, C.; Bayona, G.; Mora, A.

    2012-12-01

    The Eastern Cordillera of Colombia (EC) is a double-verging mountain system inverting a Mesozoic rift, and bounded by major reverse faults that locally involve crystalline and metamorphic Precambrian-Lower Paleozoic basement rocks, as well as Upper Paleozoic-Cenozoic sedimentary and volcanic sequences. In map view the EC is a curved mountain belt with a regional structural strike that ranges from NNE in the southern part to NNW in the northern part. The origin of its curvature has not been studied or discussed so far. We report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) investigation of the EC, in order to address to test its non-rotational vs. oroclinal nature. Fifty-eight sites were gathered from Cretaceous to Miocene marine and continental strata, both from the southern and northern parts of the EC; additionally, we examined the southern Maracaibo plate, at the junction between the Santander Massif and the Merida Andes of Colombia (Cucuta zone). Twenty-three sites reveal no rotation of the EC range with respect to stable South America. In contrast, a 35°±9° clockwise rotation is documented in four post-Miocene magnetically overprinted sites from the Cucuta zone. Magnetic lineations from AMS analysis do not trend parallel to the chain, but are oblique to the main strike of the orogenic belt. By also considering GPS evidence of a ~1 cm/yr ENE displacement of central-western Colombia accommodated by the EC, we suggest that the late Miocene-recent deformation occurred by a ENE oblique convergence reactivating a NNE rift zone. Our data show that the EC is a non-rotational chain, and that the locations of the Mesozoic rift and the mountain chain roughly correspond. One possible solution is that the oblique shortening is partitioned in pure dip-slip shear characterizing thick-skinned frontal thrust sheets (well-known along both chain fronts), and by range-parallel right-lateral strike-slip fault(s), which have not been identified

  12. Nazca-South America interactions and the late Eocene-late Oligocene flat-slab episode in the central Andes

    Science.gov (United States)

    O'Driscoll, Leland J.; Richards, Mark A.; Humphreys, Eugene D.

    2012-04-01

    The most prominent features of the Andean range are the Altiplano and Puna plateaus, which were constructed by crustal shortening and uplift over the past ˜45 Myr. The early construction of these plateaus may have controlled subsequent growth of the orogen. Proposed models have suggested that an abrupt acceleration in relative motion between the Nazca plate and the South American plate at ˜30 Ma may have led to compression of the continent. However, the major plate motion change occurred at 25-23 Ma, and paleomagnetic rotations and crustal shortening of the Andean forearc require that the Arica Bend formed prior to about 25 Ma. Inferred history of flat-slab subduction along the Altiplano section of the Andean margin and the structure of the adjacent South American cratonic shield combine to suggest an alternate scenario, based partly upon geodynamic models of oceanic-continental plate interactions in subduction zones. We propose that central Andean tectonism may have been controlled by two distinct regimes of subduction: (1) oblique subduction along the central Andean margin during the late Eocene and Oligocene accompanied by downdip alignment with the center of the Amazonian Shield (flat-slab activity in this phase of orogenesis may have been caused by a combination of cratonic root enhanced tectonics and oceanic plateau subduction) and (2) an abrupt transition to trench-normal subduction after ˜25 Ma toward the more distal São Francisco Craton was accompanied by a return to normal angle subduction. Similar interactions are hypothesized to have occurred during the Laramide Orogeny in western North America.

  13. An Andean tectonic cycle: From crustal thickening to extension in a thin crust (34°–37°SL

    Directory of Open Access Journals (Sweden)

    Victor A. Ramos

    2014-05-01

    Full Text Available Several orogenic cycles of mountain building and subsequent collapse associated with periods of shallowing and steepening of subduction zones have been recognized in recent years in the Andes. Most of them are characterized by widespread crustal delamination expressed by large calderas and rhyolitic flare-up produced by the injection of hot asthenosphere in the subduction wedge. These processes are related to the increase of the subduction angle during trench roll-back. The Payenia paleoflat-slab, in the southern Central Andes of Argentina and Chile (34°–37°S recorded a complete cycle from crustal thickening and mountain uplift to extensional collapse and normal faulting, which are related to changes in the subduction geometry. The early stages are associated with magmatic expansion and migration, subsequent deformation and broken foreland. New ages and geochemical data show the middle to late Miocene expansion and migration of arc volcanism towards the foreland region was associated with important deformation in the Andean foothills. However, the main difference of this orogenic cycle with the previously described cycles is that the steepening of the oceanic subducted slab is linked to basaltic flooding of large areas in the retroarc under an extensional setting. Crustal delamination is concentrated only in a narrow central belt along the cordilleran axis. The striking differences between the two types of cycles are interpreted to be related to the crustal thickness when steepening the subducting slab. The crustal thickness of the Altiplano is over 60–80 km, whereas Payenia is less than 42 km in the axial part, and near 30 km in the retroarc foothills. The final extensional regime associated with the slab steepening favors the basaltic flooding of more than 8400 km3 in an area larger than 40,000 km2, through 800 central vents and large fissures. These characteristics are unique in the entire present-day Andes.

  14. Spatial modeling of cutaneous leishmaniasis in the Andean region of Colombia

    Science.gov (United States)

    Pérez-Flórez, Mauricio; Ocampo, Clara Beatriz; Valderrama-Ardila, Carlos; Alexander, Neal

    2016-01-01

    The objective of this research was to identify environmental risk factors for cutaneous leishmaniasis (CL) in Colombia and map high-risk municipalities. The study area was the Colombian Andean region, comprising 715 rural and urban municipalities. We used 10 years of CL surveillance: 2000-2009. We used spatial-temporal analysis - conditional autoregressive Poisson random effects modelling - in a Bayesian framework to model the dependence of municipality-level incidence on land use, climate, elevation and population density. Bivariable spatial analysis identified rainforests, forests and secondary vegetation, temperature, and annual precipitation as positively associated with CL incidence. By contrast, livestock agroecosystems and temperature seasonality were negatively associated. Multivariable analysis identified land use - rainforests and agro-livestock - and climate - temperature, rainfall and temperature seasonality - as best predictors of CL. We conclude that climate and land use can be used to identify areas at high risk of CL and that this approach is potentially applicable elsewhere in Latin America. PMID:27355214

  15. [Possibilities of Lupinus mutabolis and Lupinus albus in the Andean countries].

    Science.gov (United States)

    Gross, R; von Baer, E

    1977-12-01

    Lupinus albus and Lupinus mutabilis may achieve importance among the andean countries in which soy bean can not grow due to ecological reasons. Both lupin varieties are outstanding because of their high protein and oil content. Its alkaloid content limits the lupins usage; however the bitter substances can be eliminated by means of genetic selection or technological processing. Beside the intoxication caused by alkaloids exists the lupinosis, which is caused by a micotoxin. This disease can be observed when animals pasture forages which suffered under a secundary attack of fungus. According to the results obtained up to date other antimetabolic substances present in the legums have no significant importance. The lupin seed flour is adequate for animal consumption, being used for this effect in different countries. Starting next year there exist the prospects of employing Lupinus mutabilis as an oil source in Peru and Lupinus albus as proteic flour in Chile.

  16. Temporal patterns of diversification in Andean Eois, a species-rich clade of moths (Lepidoptera, Geometridae).

    Science.gov (United States)

    Strutzenberger, P; Fiedler, K

    2011-04-01

    The timing of the origin of present day Neotropical animal diversity is still a matter of debate. For a long time, a preponderance of glacial (i.e. Pleistocene) radiations has been proposed. However, recent data from molecular clock studies indicate a preglacial origin for most of the examined taxa. We performed a fossil-calibrated molecular dating analysis of the genus Eois, which is a major component of one of the world's most diverse assemblages of herbivorous insects. We found that diversification of Eois took place in the Miocene following a pattern best explained by density-dependent diversification. A strong slowdown of diversification towards the present was detected. Diversification of Eois does overlap with increased Andean uplift and diversification of the most commonly used host plant genus Piper. These findings match the patterns found for the majority of Neotropical tetrapods and for three other unrelated, ecologically different lepidopteran genera.

  17. Invertebrate metacommunity structure and dynamics in an andean glacial stream network facing climate change

    DEFF Research Database (Denmark)

    Cauvy-Fraunié, Sophie; Espinosa, Rodrigo; Andino, Patricio;

    2015-01-01

    theory as a conceptual framework to better understand how river network structure influences the spatial organization of aquatic communities in glacierized catchments. At 51 stream sites in an Andean glacierized catchment (Ecuador), we sampled benthic macroinvertebrates, measured physico......-chemical and food resource conditions, and calculated geographical, altitudinal and glaciality distances among all sites. Using partial redundancy analysis, we partitioned community variation to evaluate the relative strength of environmental conditions (e.g., glaciality, food resource) vs. spatial processes (e.......g., overland, watercourse, and downstream directional dispersal) in organizing the aquatic metacommunity. Results revealed that both environmental and spatial variables significantly explained community variation among sites. Among all environmental variables, the glacial influence component best explained...

  18. Mercury Contamination in an Indicator Fish Species from Andean Amazonian Rivers Affected by Petroleum Extraction.

    Science.gov (United States)

    Webb, Jena; Coomes, Oliver T; Mainville, Nicolas; Mergler, Donna

    2015-09-01

    Elevated mercury (Hg) concentrations in fish from Amazonia have been associated with gold-mining, hydroelectric dams and deforestation but few studies consider the role of petroleum extraction. Hg levels were determined in fish samples collected in three river basins in Ecuador and Peru with contrasting petroleum exploitation and land-use characteristics. The non-migratory, piscivorous species, Hoplias malabaricus, was used as a bioindicator. The rate of Hg increase with body weight for this species was significantly higher on the Corrientes River, near the site of a recent oil spill, than on the other two rivers. In the absence of substantial deforestation and other anthropogenic sources in the Corrientes River basin, this finding suggests that oil contamination in Andean Amazonia may have a significant impact on Hg levels in fish.

  19. ANDEAN COSMOLOGY AND RELIGION: A HISTORICAL DYNAMICS OF ENCOUNTERS, MISSED CONNECTIONS AND REUNIONS

    Directory of Open Access Journals (Sweden)

    Avelar Araujo Santos Junior

    2009-06-01

    Full Text Available Religiosity of contemporary Andean indigenous peoples is constituted by a complex interaction between theology and the original items from the Christianized and ideologies historically produced phenomena such as taxation, interpenetration, removal, syncretism, resistance and reinvention. Embedded in this context was developed as a way of enhancing identity particular worldview is quite representative of their feelings and attitudes about the world, mainly in what it says respect to their territory and their community experiences and patterns of reciprocity in the socialization of traditions. Thus, our proposal in this article is to analyze some of the different elements of the symbolic representation, mythological and ritualistic of these communities, characterized by persistent conflict between a hegemonic dominance of the creative and creative autonomy.

  20. The Sabethines of Northern Andean Coffee-Growing Regions of Colombia.

    Science.gov (United States)

    Suaza-Vasco, Juan; López-Rubio, Andrés; Galeano, Juan; Uribe, Sandra; Vélez, Iván; Porter, Charles

    2015-06-01

    Sampling for sabethine mosquitoes occurred intermittently from September 2007 to April 2013 in 17 municipalities, located in 5 departments (divisions) in the northern Andean coffee-growing regions of Colombia. Of the 9 genera within the Sabethini tribe known to occur in the Neotropical region, 6 were encountered including 15 species: Jonhbelkinia ulopus, Limatus durhamii, Sabethes ignotus, Sa. luxodens, Sa. undosus, Shannoniana fluviatilis, Trichoprosopon compressum, Tr. digitatum, Tr. evansae, Tr. pallidiventer s.l., Tr. pallidiventer s.s., Wyeomyia arthrostigma, Wy. oblita, Wy. ulocoma, and Wy. undulata. The species Sa. luxodens and Wy. undulata constitute new records for Colombia. These records broaden the knowledge of this important group that includes some important species related to the arbovirus transmission. Records are from the northern Colombian Andes, a region noted for coffee cultivation and ecotourism.

  1. An Environmental Watch System for the Andean countries: El Observatorio Andino

    CERN Document Server

    Muñoz, Ángel G; Velasquez, Ramon; Monterrey, Luis; Leon, Gloria; Ruiz, Franklyn; Recalde, Cristina; Cadena, Jaime; Mejia, Raul; Paredes, Marcos; Bazo, Juan; Reyes, Carmen; Carrasco, Gualberto; Castellon, Yaruska; Villarroel, Claudia; Quintana, Juan; Urdaneta, Avel

    2010-01-01

    An experimental Environmental Watch System, the so-called Observatorio Andino-OA (Observatorio Andino), has been implemented in Venezuela, Colombia, Ecuador, Peru, Bolivia, and Chile over the past two years. The OA is a collaborative and regional network that aims to monitor several environmental variables and develop accurate forecasts based on different scientific tools. Its overall goal is to improve risk assessments, set up Early Warning Systems, support decision-making processes, and provide easily- and intuitively-understandable spatial maps to end-users. The initiative works under the scientific and logistic coordination of the Centro de Modelado Cient\\'ifico (CMC) at Zulia University, Venezuela, and the Centro Internacional para la Investigaci\\'on del Fen\\'omeno 'El Ni\\~no' (CIIFEN), and is operated at a local level by the National Weather Services (NWSs) of the aforementioned six Andean nations. The OA provides several freely-available model outputs including meteorological and hydrological forecasts...

  2. Fajas oblicuas de deformación neotectónica en Precordillera y Cordillera Frontal (31° 30´ - 33° 30´ LS: controles paleotectónicos

    Directory of Open Access Journals (Sweden)

    J.M. Cortés

    2006-12-01

    Full Text Available La Precordillera Sur y las Cerrilladas Pedemontanas de Mendoza, son dos unidades morfotectónicas principales en la vertiente oriental de los Andes centrales, a los 31º30' - 33º30' de latitud sur. Allí, dos cinturones de deformación transpresiva y orientación noroeste, denominados fajas Barreal-Las Peñas y Río Mendoza-Tupungato, se desarrollaron como consecuencia de la gradual somerización de la placa de Nazca en los últimos 20 Ma. Su orientación y compleja geometría estructural resulta de la interferencia de la deformación andina tardío-cenozoica con la estructura de orientación noroeste del rift triásico de la cuenca Cuyana y antiguas zonas de sutura colisional de edad paleozoica. Este trabajo demuestra que los rasgos paleotectónicos del substrato triásico-paleozoico de la Precordillera Sur y del margen oriental de la Cordillera Frontal controlan la configuración morfotectónica y la distribución y reactivación de gran parte de la estructura neotectónica del margen andino a estas latitudes.

  3. Description of a New Species of the Andean Butterfly Genus Forsterinaria Gray (Lepidoptera: Nymphalidae) with Considerations on an Apparently New Structure in Male Genitalia.

    Science.gov (United States)

    Zubek, A; Pyrcz, T W; Boyer, P

    2014-02-01

    The butterfly genus Forsterinaria Gray is the only strictly montane representative of the diverse Neotropical subtribe Euptychiina (Nymphalidae, Satyrinae), with 24 described species. Recent research in some of the most isolated and highly diverse Andean regions, such as central Peru, show that its total species richness is still underestimated. An example is the new species described here, Forsterinaria emo n. sp., which is particularly interesting because of an unusual structure discovered in its male genitalia which consists of a bunch of bristle-like processes, composing a fringe-like formation on the dorsum of the tegumen. No similar, homologous structure was found in any congener, nor indeed, in any species of diurnal Lepidoptera. Scanning electron microscope studies revealed that the microstructure of the processes resembles a membrane lining the tegumen. Its function is unknown but two hypotheses are discussed based on a comparative study with other genital structures of butterflies. We argue that it may help stabilizing the partners in the process of mating or it may serve as a 'mating plug', preventing the female from multiple copulations.

  4. Acceleration and novelty: community restoration speeds recovery and transforms species composition in Andean cloud forest.

    Science.gov (United States)

    Wilson, Sarah Jane; Rhemtulla, Jeanine M

    2016-01-01

    Community-based tropical forest restoration projects, often promoted as a win-win solution for local communities and the environment, have increased dramatically in number in the past decade. Many such projects are underway in Andean cloud forests, which, given their extremely high biodiversity and history of extensive clearing, are understudied. This study investigates the efficacy of community-based tree-planting projects to accelerate cloud forest recovery, as compared to unassisted natural regeneration. This study takes place in northwest Andean Ecuador, where the majority of the original, highly diverse cloud forests have been cleared, in five communities that initiated tree-planting projects to restore forests in 2003. In 2011, we identified tree species along transects in planted forests (n = 5), naturally regenerating forests (n = 5), and primary forests (n = 5). We also surveyed 120 households about their restoration methods, tree preferences, and forest uses. We found that tree diversity was higher in planted than in unplanted secondary forest, but both were less diverse than primary forests. Ordination analysis showed that all three forests had distinct species compositions, although planted forests shared more species with primary forests than did unplanted forests. Planted forests also contained more animal-dispersed species in both the planted canopy and in the unplanted, regenerating understory than unplanted forests, and contained the highest proportion of species with use value for local people. While restoring forest increased biodiversity and accelerated forest recovery, restored forests may also represent novel ecosystems that are distinct from the region's previous ecosystems and, given their usefulness to people, are likely to be more common in the future.

  5. DNA Barcoding of an Assembly of Montane Andean Butterflies (Satyrinae): Geographical Scale and Identification Performance.

    Science.gov (United States)

    Marín, M A; Cadavid, I C; Valdés, L; Álvarez, C F; Uribe, S I; Vila, R; Pyrcz, T W

    2017-01-23

    DNA barcoding is a technique used primarily for the documentation and identification of biological diversity based on mitochondrial DNA sequences. Butterflies have received particular attention in DNA barcoding studies, although varied performance may be obtained due to different scales of geographic sampling and speciation processes in various groups. The montane Andean Satyrinae constitutes a challenging study group for taxonomy. The group displays high richness, with more of 550 species, and remarkable morphological similarity among taxa, which renders their identification difficult. In the present study, we evaluated the effectiveness of DNA barcodes in the identification of montane Andean satyrines and the effect of increased geographical scale of sampling on identification performance. Mitochondrial sequences were obtained from 104 specimens of 39 species and 16 genera, collected in a forest remnant in the northwest Andes. DNA barcoding has proved to be a useful tool for the identification of the specimens, with a well-defined gap and producing clusters with unambiguous identifications for all the morphospecies in the study area. The expansion of the geographical scale with published data increased genetic distances within species and reduced those among species, but did not generally reduce the success of specimen identification. Only in Forsterinaria rustica (Butler, 1868), a taxon with high intraspecific variation, the barcode gap was lost and low support for monophyly was obtained. Likewise, expanded sampling resulted in a substantial increase in the intraspecific distance in Morpho sulkowskyi (Kollar, 1850); Panyapedaliodes drymaea (Hewitson, 1858); Lymanopoda obsoleta (Westwood, 1851); and Lymanopoda labda Hewitson, 1861; but for these species, the barcode gap was maintained. These divergent lineages are nonetheless worth a detailed study of external and genitalic morphology variation, as well as ecological features, in order to determine the potential

  6. Phlebotomine sandflies (Diptera: Psychodidae in a sub-Andean forest from the Norte de Santander, Colombia

    Directory of Open Access Journals (Sweden)

    Richard Hoyos-López

    2016-01-01

    Full Text Available Background & objectives: The recognition of communities of arthropods with medical importance in natural systems constitutes an important step in the prediction of possible epidemic events and/or emergence of infectious diseases in the human population. This is due to anthropogenic impact in natural areas and landscape modification, which changes the dynamics of pathogenic agents, reservoirs, and vector insects. In this study, an inventory was compiled of species of the genus Lutzomyia present in sub-Andean forest from the confluence of the Pamplonita River basin. Methods: CDC-light and Shannon traps were used for collecting adult phlebotomine sandflies during the month of October 2013 in a sub-Andean forest from river basin Pamplonita. All specimens were identified using morphological keys. The epidemiological relevance of each species was reported using a literature review about natural infection or vector incrimination with Leishmania species or other pathogens microorganism. Results: A total of 2755 specimens belonging to eight species of the genus Lutzomyia were collected. Out of the eight species, seven belonged to the group verrucarum (Lutzomyia sp - townsendi series, L. ovallesi, L. spinicrassa, L. serrana, L. townsendi, L. nuneztovari and L. pia, while one belonged to the subgenus Helcocyrtomyia (L. hartmanni. A new registry of L. townsendi was observed for the Norte de Santander department. Interpretation & conclusion: The appreciable diversity of the verrucarum group observed in this area suggest further investigation on the biogeography and evolution of this group, and epidemiological risk for human populations around this area, as there are reports of Leishmania natural infection and favourable conditions for domestication of phlebotomines in rural towns.

  7. Hydrological connectivity of alluvial Andean valleys: a groundwater/surface-water interaction case study in Ecuador

    Science.gov (United States)

    Guzmán, Pablo; Anibas, Christian; Batelaan, Okke; Huysmans, Marijke; Wyseure, Guido

    2016-06-01

    The Andean region is characterized by important intramontane alluvial and glacial valleys; a typical example is the Tarqui alluvial plain, Ecuador. Such valley plains are densely populated and/or very attractive for urban and infrastructural development. Their aquifers offer opportunities for the required water resources. Groundwater/surface-water (GW-SW) interaction generally entails recharge to or discharge from the aquifer, dependent on the hydraulic connection between surface water and groundwater. Since GW-SW interaction in Andean catchments has hardly been addressed, the objectives of this study are to investigate GW-SW interaction in the Tarqui alluvial plain and to understand the role of the morphology of the alluvial valley in the hydrological response and in the hydrological connection between hillslopes and the aquifers in the valley floor. This study is based on extensive field measurements, groundwater-flow modelling and the application of temperature as a groundwater tracer. Results show that the morphological conditions of a valley influence GW-SW interaction. Gaining and losing river sections are observed in narrow and wide alluvial valley sections, respectively. Modelling shows a strong hydrological connectivity between the hillslopes and the alluvial valley; up to 92 % of recharge of the alluvial deposits originates from lateral flow from the hillslopes. The alluvial plain forms a buffer or transition zone for the river as it sustains a gradual flow from the hills to the river. Future land-use planning and development should include concepts discussed in this study, such as hydrological connectivity, in order to better evaluate impact assessments on water resources and aquatic ecosystems.

  8. Genome-Wide Association Study of Anthracnose Resistance in Andean Beans (Phaseolus vulgaris.

    Directory of Open Access Journals (Sweden)

    Grady H Zuiderveen

    Full Text Available Anthracnose is a seed-borne disease of common bean (Phaseolus vulgaris L. caused by the fungus Colletotrichum lindemuthianum, and the pathogen is cosmopolitan in distribution. The objectives of this study were to identify new sources of anthracnose resistance in a diverse panel of 230 Andean beans comprised of multiple seed types and market classes from the Americas, Africa, and Europe, and explore the genetic basis of this resistance using genome-wide association mapping analysis (GWAS. Twenty-eight of the 230 lines tested were resistant to six out of the eight races screened, but only one cultivar Uyole98 was resistant to all eight races (7, 39, 55, 65, 73, 109, 2047, and 3481 included in the study. Outputs from the GWAS indicated major quantitative trait loci (QTL for resistance on chromosomes, Pv01, Pv02, and Pv04 and two minor QTL on Pv10 and Pv11. Candidate genes associated with the significant SNPs were detected on all five chromosomes. An independent QTL study was conducted to confirm the physical location of the Co-1 locus identified on Pv01 in an F4:6 recombinant inbred line (RIL population. Resistance was determined to be conditioned by the single dominant gene Co-1 that mapped between 50.16 and 50.30 Mb on Pv01, and an InDel marker (NDSU_IND_1_50.2219 tightly linked to the gene was developed. The information reported will provide breeders with new and diverse sources of resistance and genomic regions to target in the development of anthracnose resistance in Andean beans.

  9. 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

  10. Monitoring adherence to the international code of conduct: highly hazardous pesticides in central Andean agriculture and farmers' rights to health.

    Science.gov (United States)

    Orozco, Fadya A; Cole, Donald C; Forbes, Greg; Kroschel, Jürgen; Wanigaratne, Susitha; Arica, Denis

    2009-01-01

    The WHO has advocated monitoring adherence to the Food and Agriculture Organization's Code of Conduct to reduce use of highly hazardous pesticides in lower and middle income countries. We re-framed Code articles in terms of farmers' rights and drew on survey data, farmer focus group results, and direct observations of agrochemical stores in Ecuador and Peru to construct indicators reflecting respect for such rights. Use of highly (Ia and Ib) and moderately (II) hazardous pesticides was common. Worse indicators were observed in places with lower education, greater poverty, and more use of indigenous languages. Limited government enforcement capacity, social irresponsibility of the pesticide industry, and lack of farmers' knowledge of the Code were all factors impeding respect for farmers' rights. Addressing the power imbalance among social actors requires informed farmer and farmworker participation in monitoring adherence and active involvement of non-governmental organizations and municipal governments.

  11. Climbing in the high volcanoes of central Mexico

    Science.gov (United States)

    Secor, R. J.

    1984-01-01

    A chain of volcanoes extends across central Mexico along the 19th parallel, a line just south of Mexico City. The westernmost of these peaks is Nevado de Colima at 4,636 feet above sea level. A subsidiary summit of Nevado de Colima is Volcan de Colima, locally called Fuego (fire) it still emits sulphurous fumes and an occasional plume of smoke since its disastrous eruption in 1941. Parictuin, now dormant, was born in the fall of 1943 when a cornfield suddenly erupted. Within 18 months, the cone grew more than 1,700 feet. Nevado de Toluca is a 15,433-foot volcanic peak south of the city of Toluca. Just southeast of Mexico City are two high volcanoes that are permanently covered by snow: Iztaccihuatl (17,342 fet) and Popocatepetl (17,887 feet) Further east is the third highest mountain in North America: 18,700-foot Citlateptl, or El Pico de Orizaba. North of these high peaks are two volcanoes, 14, 436-foot La Malinche and Cofre de Perote at 14,048 feet. This range of mountains is known variously as the Cordillera de Anahuac, the Sierra Volcanica Transversal, or the Cordillera Neovolcanica. 

  12. 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.

  13. Flujos de detritos recientes en la cordillera frontal de Mendoza: Un ejemplo de riesgo natural en la ruta 7 Recent debris flows in the Frontal Cordillera of Mendoza: an example of natural risk on the Road 7

    Directory of Open Access Journals (Sweden)

    Emmanuel Wick

    2010-06-01

    Full Text Available Se expone un estudio sobre los flujos de detritos ocurridos en enero de 2005, en el km 1.118,5 de la ruta nacional 7 en la provincia de Mendoza. La zona se ubica en la Cordillera Frontal, próxima al límite con la Precordillera. Se realizó un mapa geomorfológico detallado, sobre la base de una imagen Quickbird del año 2006. Además, se hicieron cálculos de volúmenes, velocidades y caudales, con mediciones en el campo y con ayuda de un sistema de información geográfico (SIG. El estudio de la geomorfología permitió proponer tres escenarios para el caso de un nuevo evento, a partir de los cuáles se creó un mapa de susceptibilidad a los flujos de detritos para el tramo de ruta analizado. Finalmente, se proponen medidas de protección y de mitigación ante la posibilidad de recurrencia de estos eventos en el sector.In this paper is presented a study dealing with the debris flows that reached the national road 7 in January 2005, in the km 1,118.5, Mendoza province. The area is located in the Frontal Cordillera near the limit of the Precordillera. A detailed geomorphologic map has been realized for this study using a Quickbird satellite imagery of the year 2006. Various calculations of volumes, velocities and peak discharges have been performed with the field data and using a geographic information system (GIS. The geomorphologic survey has permitted to propose three propagation scenarios in case of a new event. These allowed creating a map of debris flows susceptibility for the stretch of the road that has been studied. Finally, it has been proposed protection and mitigation measures, based on the results of the study, to protect the road from a new event.

  14. Plantas Fósiles del Grupo Choiyoi, Cordillera Frontal a la Latitud del río Mendoza Fossil plants from the Choiyoi Group, Frontal Cordillera at the latitude of the Mendoza River

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    Magdalena Koukharsky

    2011-06-01

    Full Text Available En este trabajo se dan a conocer los primeros restos fósiles hallados en sedimentitas, cuyo componente clástico es de origen volcánico, intercaladas en la Formación Tambillos del Grupo Choiyoi, Cordillera Frontal de Mendoza. Los mismos consisten en abundantes improntas de Sphenophyta en estado de preservación regular a malo. En la zona estudiada, las rocas de la Formación Tambillos, que son dominantemente volcánicas ácidas y de edad pérmica temprana a media según correlaciones regionales, se depositaron sobre una discordancia erosiva labrada en lavas andesíticas intensamente propilitizadas que se atribuyen a la Formación Portezuelo del Cenizo. Los restos vegetales se encuentran a unos 23 metros de la base, contenidos en niveles de areniscas finas y pelitas depositadas en un ambiente fluvial (microdelta, en los bordes de un lago y fueron coetáneas con los primeros episodios de volcanismo riolítico en la región. Si bien la flora encontrada no permite definir la edad, las formas presentes son comunes en niveles del Carbonífero superior-Pérmico y Triásico de Argentina.In this contribution we report the discovery of the first fossil remains in sedimentary strata belonging to the Tambillos Formation, Choiyoi Group, Cordillera Frontal of Mendoza. In the studied area the Tambillos Formation, which is formed dominantly by acid volcanics rocks of alleged Early to the Middle Permian, were deposited over an erosive unconformity on top of propilytic andesites of the Portezuelo del Cenizo Formation. The vegetal remains were found about 23 meters from the base of the formation, hosted in fine-grained sandstones and shales that were deposited in a fluvial environment (microdelta, along the borders of a lake during the first episodes of the rhyolitic volcanism of the region. The fossil flora includes abundant, poorly preserved impressions of Sphenophyta that does not permit to assign a precise age, although these forms are common in the Upper

  15. 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.

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

    Science.gov (United States)

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

    2012-04-01

    Central Andean deformation history in southern Peru is recorded in Neogene volcanic units of Ocoña and Cotahuasi canyons that cut across the western Cordillera. Acceleration (100 km3) Nazca (c.24.6 Ma), Alpabamba (19.4-18.0 Ma), and Huaylillas (14.25-12.7 Ma) ignimbrite sheets preceded the canyon incision, whereas sheets of smaller volume (welded, eutaxitic, crystal-rich facies overlain by a thick, multi-bedded ash-flow tuff and a lithic-rich, indurated flow unit. The Huaylillas ignimbrite sheet comprises a strongly welded, crystal-rich, lithic-poor, columnar lithofacies, with devitrified pumice. The Caraveli ignimbrite sheet has a jointed vitrophyre overlain by a welded, blocky, crystal-rich flow unit. A vacuolar, saccharolytic unit forms the top of the sequence. The Lower Sencca ignimbrite sheet comprises of a basal vitrophyre and a slightly welded, fibrous pumice-rich flow unit, which grades into a welded, vapor-phase unit that contains more crystals than pumice and lithics. The Upper Sencca ignimbrite sheet consists of a black vitrophyre, grading into a strongly welded, crystal-rich, eutaxitic cooling unit. The latter is capped by a slightly welded unit, and an indurated pumice-rich, crystal-poor vapour-phase facies. Quaternary valley-fill termed Las Lomas consists of unwelded, crystal-poor pumice-flow deposits. Eighteen new 40Ar/39Ar analyses have been carried out on feldspar/glass separates from pumice and lavas. Results for the Caraveli ignimbrite (9.35±0.06 Ma), Upper Barroso lavas (2.24±0.45 Ma) and Upper Sencca ignimbrite (2.00-2.06±0.09 Ma) are in good agreement with previous data. New ages for the Lower Barroso lavas (7.32±0.05; 5.36±0.12 Ma) and Lower Sencca ignimbrites (5.13±0.01, 5.09±0.03, 4.65±0.11, 4.36 ± 0.16) extend their temporal history towards older times. Lower Barroso lava flow activity occurred as early as~7.3 and lasted until 5.4 Ma just before the Lower Sencca eruptions. The Lower Sencca ignimbrites spanned at least 1.5 Ma and

  17. Analysis of Genetic Variability among thirty accessions of Andean Lupin (Lupinus mutabilis Sweet using ISSR molecular markers

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    Michelle C. Chirinos-Arias

    2015-03-01

    Full Text Available In order to make the genetic variability analysis among thirty accessions of andean lupine (L. mutabilis Sweet belonging to Agrarian Innovation National Institute (INIA Seed Bank. DNA was extracted from 300 plants and we made bulks. We standardized amplification protocol of Inter Simple Sequence Repeat (ISSR primers, we chose the most polymorphic primers to run in acrylamide gel. We found 255 ISSR loci with 8 primers. It was found high genetic variability of the samples under study by ISSR markers. Also observed relatively high polymorphism for autogamous species such as andean lupine. Finally phenograms showed a relationship with the geographical location, possibly due to in situ gene flow due to the exchange or sale of seeds in markets near the collection area.

  18. Evaluation of indigenous grains from the Peruvian Andean region for antidiabetes and antihypertension potential using in vitro methods.

    Science.gov (United States)

    Ranilla, Lena Galvez; Apostolidis, Emmanouil; Genovese, Maria Ines; Lajolo, Franco Maria; Shetty, Kalidas

    2009-08-01

    The health-relevant functionality of 10 thermally processed Peruvian Andean grains (five cereals, three pseudocereals, and two legumes) was evaluated for potential type 2 diabetes-relevant antihyperglycemia and antihypertension activity using in vitro enzyme assays. Inhibition of enzymes relevant for managing early stages of type 2 diabetes such as hyperglycemia-relevant alpha-glucosidase and alpha-amylase and hypertension-relevant angiotensin I-converting enzyme (ACE) were assayed along with the total phenolic content, phenolic profiles, and antioxidant activity based on the 1,1-diphenyl-2-picrylhydrazyl radical assay. Purple corn (Zea mays L.) (cereal) exhibited high free radical scavenging-linked antioxidant activity (77%) and had the highest total phenolic content (8 +/- 1 mg of gallic acid equivalents/g of sample weight) and alpha-glucosidase inhibitory activity (51% at 5 mg of sample weight). The major phenolic compound in this cereal was protocatechuic acid (287 +/- 15 microg/g of sample weight). Pseudocereals such as Quinoa (Chenopodium quinoa Willd) and Kañiwa (Chenopodium pallidicaule Aellen) were rich in quercetin derivatives (1,131 +/- 56 and 943 +/- 35 microg [expressed as quercetin aglycone]/g of sample weight, respectively) and had the highest antioxidant activity (86% and 75%, respectively). Andean legumes (Lupinus mutabilis cultivars SLP-1 and H-6) inhibited significantly the hypertension-relevant ACE (52% at 5 mg of sample weight). No alpha-amylase inhibitory activity was found in any of the evaluated Andean grains. This in vitro study indicates the potential of combination of Andean whole grain cereals, pseudocereals, and legumes to develop effective dietary strategies for managing type 2 diabetes and associated hypertension and provides the rationale for animal and clinical studies.

  19. Variability in New Shortening Estimates from Southern Peru (12-14S); Implications for Mass Balance of the Andean Plateau.

    Science.gov (United States)

    Gotberg, N.; McQuarrie, N.

    2008-12-01

    One of the fundamental questions of interest with regards to the Andean Plateau is the mass balance of material needed to create and sustain a 3-4 km high plateau. Is crustal shortening sufficient to support an isostatically compensated crust of 60-70km? We present new estimates of shortening across the northern margin of the Andean Plateau. The cross section extent, from the eastern edge of the volcanic arc to foreland basin, is approximately one half of the physiographic width of the Andean Plateau in Peru. Cross sectional shortening estimates in southern Peru (12-14°S) provide a best estimate of 123 km or 40% shortening with an absolute minimum estimate of 86 km or 30% and absolute maximum estimate of 275 km or 60%. We determined the maximum and minimum shortening estimates using the cross sectional area and possible variations in assumptions made about the amount of erosion, detachment dip, involvement of basement thrusts and displacement along faults. The best estimate of shortening is well short of the required 240-300km of shortening needed in order to account for a 60-70km thick crust under the entire plateau. This suggests that for an isostatically equilibrated crust either 1) there is a significant amount of shortening (~150km) in the western half of the plateau which, is hidden by the volcanic arc or 2) crustal material is being added to the Peruvian section of the Andean Plateau either through lower crustal flow or a process of magmatic underplating followed by differentiation and delamination.

  20. ARTE EN LA ZONA DE HISTÉRESIS: QUEBRADA. LAS CORDILLERAS EN ANDAS DE GUADALUPE SANTA CRUZ Art in the Zone of Hysteresis: Quebrada. Las cordilleras en andas, by Guadalupe Santa Cruz

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    Cecilia Ojeda

    2007-12-01

    Full Text Available Este libro de Guadalupe Santa Cruz plantea el problema del desmedrado estatus del arte en un horizonte cultural dominado por la industria del entretenimiento. De este reconocimiento y del diseño vanguardista del libro en sí -concebido como un puente entre el arte y la vida, o como un instrumento de conocimiento privilegiado de lo real- surge una tensión característica del arte contemporáneo. Dicha tensión ha sido definida como el punto de histéresis de la obra artística en la que ésta tiende a conservar una propiedad en ausencia del estímulo que la ha generado, tensión artística que se examina en este ensayo.Quebrada. Las cordilleras en andas examines the issue of the artwork’s diminished status within a landscape dominated by the entertainment industry. From this knowledge and the vanguard design of the book itself -as an instrument of the real-arises a tension that is characteristic of contemporary art. This tension has been compared to the point of hysteresis of an element, in which like a magnetic material it, the work of art, preserves one of its properties in the absence of its stimulus. This essay examines how this tension is produced in the work by Guadalupe Santa Cruz.

  1. Mantle to Surface Fluid Transfer Above a Flat Slab Subduction Zone: Isotopic Evidence from Hot Springs in the Cordillera Blanca, Peru

    Science.gov (United States)

    Newell, D. L.; Jessup, M. J.; Hilton, D. R.; Shaw, C. A.; Hughes, C. A.

    2015-12-01

    Thermal springs in the Cordillera Blanca, Peru, provide geochemical evidence for deeply circulated hydrothermal fluids that carry significant mantle-derived helium. The Cordillera Blanca is a ~200 km-long NNW-SSE trending mountain range in the Peruvian Andes located above an amagmatic flat-slab subduction segment. The west side of the range is bounded by the Cordillera Blanca detachment that preserves a progression of top to the west ductile shear to brittle normal faulting since ~5 Ma. We report aqueous and stable isotope geochemical results from fluid and gas samples collected in 2013 and 2015 from 13 hot springs emanating from the Cordillera Blanca detachment and associated hanging wall faults. Most springs are vigorously bubbling (degassing), and range in temperature, pH, and conductivity from 17-89 °C, 5.95-8.87, and 0.17-21.5 mS, respectively. The hottest springs issue directly from the northern segment of the detachment. Geochemically, springs are CO2-rich, alkaline-chloride to alkaline-carbonate waters, with elevated trace metal contents including Fe, Cu, As, Zn, Sb, and Tl. Notably, As contents are ≤11 ppm, indicating that thermal waters may be adversely impacting local water quality. Water δ18O and δD, trends in elemental chemistry, and cation geothermometry collectively demonstrate mixing of hot (200-260 °C) saline fluid with cold meteoric recharge along the fault. Helium isotope ratios (3He/4He) for dissolved gases in the hot springs range from 0.62 to 1.98 RC/RA, indicating the presence of ~25% mantle-derived helium, assuming mixing of an asthenospheric end-member with the crustal helium reservoir. CO2/3He and carbon stable isotope ratios indicate a carbon source derived from mixing of crustal sources with minor mantle carbon. Overall, the volatile signature overlaps with orogen-wide datasets where crustal overprinting has modified mantle contributions at active arc volcanoes. Given the long duration since active magmatism in the Cordillera

  2. Dark Adaptation at High Altitude: An Unexpected Pupillary Response to Chronic Hypoxia in Andean Highlanders.

    Science.gov (United States)

    Healy, Katherine; Labrique, Alain B; Miranda, J Jaime; Gilman, Robert H; Danz, David; Davila-Roman, Victor G; Huicho, Luis; León-Velarde, Fabiola; Checkley, William

    2016-09-01

    Healy, Katherine, Alain B. Labrique, J. Jaime Miranda, Robert H. Gilman, David Danz, Victor G. Davila-Roman, Luis Huicho, Fabiola León-Velarde, and William Checkley. Dark adaptation at high altitude: an unexpected pupillary response to chronic hypoxia in Andean highlanders. High Alt Med Biol. 17:208-213, 2016.-Chronic mountain sickness is a maladaptive response to high altitude (>2500 m above sea level) and is characterized by excessive erythrocytosis and hypoxemia resulting from long-term hypobaric hypoxia. There is no known early predictor of chronic mountain sickness and the diagnosis is based on the presence of excessive erythrocytosis and clinical features. Impaired dark adaptation, or an inability to visually adjust from high- to low-light settings, occurs in response to mild hypoxia and may serve as an early predictor of hypoxemia and chronic mountain sickness. We aimed to evaluate the association between pupillary response assessed by dark adaptometry and daytime hypoxemia in resident Andean highlanders aged ≥35 years living in Puno, Peru. Oxyhemoglobin saturation (SpO2) was recorded using a handheld pulse oximeter. Dark adaptation was quantitatively assessed as the magnitude of pupillary contraction to light stimuli of varying intensities (-2.9 to 0.1 log-cd/m(2)) using a portable dark adaptometer. Individual- and stimulus-specific multilevel analyses were conducted using mixed-effect models to elicit the relationship between SpO2 and pupillary responsiveness. Among 93 participants, mean age was 54.9 ± 11.0 years, 48% were male, 44% were night blind, and mean SpO2 was 89.3% ± 3.4%. The magnitude of pupillary contraction was greater with lower SpO2 (p dark-adapted conditions was exaggerated with hypoxemia and may serve as an early predictor of chronic mountain sickness. This unexpected association is potentially explained as an excessive and unregulated sympathetic response to hypoxemia at altitude.

  3. Flujos de detritos recientes en la cordillera frontal de Mendoza: Un ejemplo de riesgo natural en la ruta 7

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    Emmanuel Wick

    2010-06-01

    Full Text Available Se expone un estudio sobre los flujos de detritos ocurridos en enero de 2005, en el km 1.118,5 de la ruta nacional 7 en la provincia de Mendoza. La zona se ubica en la Cordillera Frontal, próxima al límite con la Precordillera. Se realizó un mapa geomorfológico detallado, sobre la base de una imagen Quickbird del año 2006. Además, se hicieron cálculos de volúmenes, velocidades y caudales, con mediciones en el campo y con ayuda de un sistema de información geográfico (SIG. El estudio de la geomorfología permitió proponer tres escenarios para el caso de un nuevo evento, a partir de los cuáles se creó un mapa de susceptibilidad a los flujos de detritos para el tramo de ruta analizado. Finalmente, se proponen medidas de protección y de mitigación ante la posibilidad de recurrencia de estos eventos en el sector.

  4. Late Quaternary Glacial Chronology in the Cordillera de Talamanca, Costa Rica, Investigated Using Cosmogenic Cl-36 Surface Exposure Dating

    Science.gov (United States)

    Li, Y.; Potter, R.; Horn, S.; Orvis, K. H.

    2015-12-01

    The role of the tropics in past and future climate change has garnered significant attention in recent decades, but debate still exists over climate linkages between the tropics and the middle and high latitudes. Glaciers in tropical mountains are highly sensitive indicators of climate, and glacial landforms left behind by past glacier fluctuations provide key evidence of paleoclimate trends and their forcing mechanisms. We investigated late Quaternary glacial chronology from two glaciated valleys on the Chirripó massif in the Cordillera de Talamanca, Costa Rica. Previous studies in this highland have constrained the most recent deglaciation to 12.4-9.7 ka cal BP based on radiocarbon dates on basal sediments of glacial lakes within the cirque at the head of the Morrenas Valley. However, no studies have been conducted to constrain the ages of the moraines located down valley. We dated the formation ages of these moraines in the Morrenas and Talari valleys using cosmogenic Cl-36 surface exposure dating. Our results indicate a major glacial event ~21-18 ka, broadly synchronous with the global Last Glacial Maximum (LGM). Glaciers during this period advanced 3.2-3.4 km down valley on both sides of the Chirripó massif. Our ages also suggest periods of glacial retreat or standstills ~18-10 ka before complete deglaciation of this highland ~10 ka. These results provide insight into the timing and extent of glacial events in this tropical highland that is of critical importance for reconstructing regional and global climate patterns.

  5. On the lag time between internal strain and basement involved thrust induced exhumation: The case of the Colombian Eastern Cordillera

    Science.gov (United States)

    Mora, Andrès; Blanco, Vladimir; Naranjo, Julian; Sanchez, Nelson; Ketcham, Richard A.; Rubiano, Jorge; Stockli, Daniel F.; Quintero, Isaid; Nemčok, Michal; Horton, Brian K.; Davila, Hamblet

    2013-07-01

    Thrust sheets accumulate internal strain before they start moving along discrete fault planes. However, there are no previous studies evaluating the time difference between initiation of strain and fault displacement. In this paper we use observations from the Eastern Cordillera of Colombia to evaluate this interval. We utilize multiple thermochronometers and paleothermometers to refine the timing of deformation. Based on these new data we build time-temperature path estimates that together with geometric outcrop-based structural analysis and fluid inclusions allow us to assign relative timing to features associated with strain, such as cleavage, veins and certain types of fractures, and compare that with the timing of thrusting. We find that cleavage was only formed close to maximum paleotemperatures, almost coeval with the onset of thrust-induced denudation by the Late Oligocene. The corresponding structural level of fold-related veins suggest that they were formed later but still when the country rocks were at temperatures higher than 160 °C, mostly during the Early Miocene and still coexisted with the latest stages of cleavage formation. Our data show that the main period of strain hardening was short (probably a few million years) and occurred before first-order basement thrusting was dominant, but was associated with second-order folding.

  6. Plantas Fósiles del Grupo Choiyoi, Cordillera Frontal a la Latitud del río Mendoza

    Directory of Open Access Journals (Sweden)

    Magdalena Koukharsky

    2011-06-01

    Full Text Available En este trabajo se dan a conocer los primeros restos fósiles hallados en sedimentitas, cuyo componente clástico es de origen volcánico, intercaladas en la Formación Tambillos del Grupo Choiyoi, Cordillera Frontal de Mendoza. Los mismos consisten en abundantes improntas de Sphenophyta en estado de preservación regular a malo. En la zona estudiada, las rocas de la Formación Tambillos, que son dominantemente volcánicas ácidas y de edad pérmica temprana a media según correlaciones regionales, se depositaron sobre una discordancia erosiva labrada en lavas andesíticas intensamente propilitizadas que se atribuyen a la Formación Portezuelo del Cenizo. Los restos vegetales se encuentran a unos 23 metros de la base, contenidos en niveles de areniscas finas y pelitas depositadas en un ambiente fluvial (microdelta, en los bordes de un lago y fueron coetáneas con los primeros episodios de volcanismo riolítico en la región. Si bien la flora encontrada no permite definir la edad, las formas presentes son comunes en niveles del Carbonífero superior-Pérmico y Triásico de Argentina.

  7. Deployable centralizers

    Energy Technology Data Exchange (ETDEWEB)

    Grubelich, Mark C.; Su, Jiann-Cherng; Knudsen, Steven D.

    2017-02-28

    A centralizer assembly is disclosed that allows for the assembly to be deployed in-situ. The centralizer assembly includes flexible members that can be extended into the well bore in situ by the initiation of a gas generating device. The centralizer assembly can support a large load carrying capability compared to a traditional bow spring with little or no installation drag. Additionally, larger displacements can be produced to centralize an extremely deviated casing.

  8. 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.

  9. Human impact on the hydrology of the Andean páramos

    Science.gov (United States)

    Buytaert, Wouter; Célleri, Rolando; De Bièvre, Bert; Cisneros, Felipe; Wyseure, Guido; Deckers, Jozef; Hofstede, Robert

    2006-11-01

    This paper analyses the problems involved in the conservation and management of the hydrological system of the South American páramo. The páramo consists of a collection of neotropical alpine grassland ecosystems covering the upper region of the northern Andes. They play a key role in the hydrology of the continent. Many of the largest tributaries of the Amazon basin have their headwaters in the páramo. It is also the major water source for the Andean highlands and a vast area of arid and semi-arid lowlands, where páramo water is used for domestic, agricultural and industrial consumption, and the generation of hydropower. Recently, the páramo is increasingly used for intensive cattle grazing, cultivation, and pine planting, among others. These activities, as well as global phenomena such as climate change, severely alter the hydrological regime. A review on the state of knowledge of its hydrology is given in a first part. In a second part, the impact of human activities and climate change on the hydrology of the páramo is discussed.

  10. Diversification of the rainfrog Pristimantis ornatissimus in the lowlands and Andean foothills of Ecuador

    Science.gov (United States)

    Hutter, Carl R.; Tapia, Elicio E.; Culebras, Jaime; Peñafiel, Nicolás; Pyron, R. Alexander; Morochz, Carlos; Funk, W. Chris; Arteaga, Alejandro

    2017-01-01

    Geographic barriers and elevational gradients have long been recognized as important in species diversification. Here, we illustrate an example where both mechanisms have shaped the genetic structure of the Neotropical rainfrog, Pristimantis ornatissimus, which has also resulted in speciation. This species was thought to be a single evolutionary lineage distributed throughout the Ecuadorian Chocó and the adjacent foothills of the Andes. Based on recent sampling of P. ornatissimus sensu lato, we provide molecular and morphological evidence that support the validity of a new species, which we name Pristimantis ecuadorensis sp. nov. The sister species are elevational replacements of each other; the distribution of Pristimantis ornatissimus sensu stricto is limited to the Ecuadorian Chocó ecoregion (< 1100 m), whereas the new species has only been found at Andean localities between 1450–1480 m. Given the results of the Multiple Matrix Regression with Randomization analysis, the genetic difference between P. ecuadorensis and P. ornatissimus is not explained by geographic distance nor environment, although environmental variables at a finer scale need to be tested. Therefore this speciation event might be the byproduct of stochastic historic extinction of connected populations or biogeographic events caused by barriers to dispersal such as rivers. Within P. ornatissimus sensu stricto, morphological patterns and genetic structure seem to be related to geographic isolation (e.g., rivers). Finally, we provide an updated phylogeny for the genus, including the new species, as well as other Ecuadorian Pristimantis. PMID:28329011

  11. Investigation Into the Humaneness of Slaughter Methods for Guinea Pigs (Cavia porcelus) in the Andean Region.

    Science.gov (United States)

    Limon, Georgina; Gonzales-Gustavson, Eloy A; Gibson, Troy J

    2016-01-01

    Guinea pigs (Cavia porcelus) are an important source of nonhuman animal protein in the Andean region of South America. Specific guidelines regarding the welfare of guinea pigs before and during slaughter have yet to be developed. This study critically assessed the humaneness of 4 different stunning/slaughter methods for guinea pigs: cervical neck dislocation (n = 60), electrical head-only stunning (n = 83), carbon dioxide (CO2) stunning (n = 21), and penetrating captive bolt (n = 10). Following cervical neck dislocation, 97% of guinea pigs had at least 1 behavioral or cranial/spinal response. Six percent of guinea pigs were classified as mis-stunned after electrical stunning, and 1% were classified as mis-stunned after captive bolt. Increased respiratory effort was observed during CO2 stunning. Apart from this finding, there were no other obvious behavioral responses that could be associated with suffering. Of the methods assessed, captive bolt was deemed the most humane, effective, and practical method of stunning guinea pigs. Cervical neck dislocation should not be recommended as a slaughter method for guinea pigs.

  12. Cliffs used as communal roosts by Andean condors protect the birds from weather and predators.

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    Sergio A Lambertucci

    Full Text Available The quality and availability of resources influence the geographical distribution of species. Social species need safe places to rest, meet, exchange information and obtain thermoregulatory benefits, but those places may also serve other important functions that have been overlooked in research. We use a large soaring bird that roosts communally in cliffs, the Andean condor (Vultur gryphus, as a model species to elucidate whether roost locations serve as a refuge from adverse weather conditions (climatic refuge hypothesis, CRH, and/or from predators or anthropogenic disturbances (threats refuge hypothesis, TRH. The CRH predicts that communal roosts will face in the opposite direction from where storms originate, and will be located in climatically stable, low precipitation areas. The TRH predicts that communal roosts will be large, poorly accessible cliffs, located far from human-made constructions. We surveyed cliffs used as communal roosts by condors in northwestern Patagonia, and compared them with alternative non-roosting cliffs to test these predictions at local and regional scales. We conclude that communal roosting places provide refuge against climate and disturbances such as, for instance, the threats of predators (including humans. Thus, it is not only the benefits gained from being aggregated per se, but the characteristics of the place selected for roosting that may both be essential for the survival of the species. This should be considered in management and conservation plans given the current scenario of global climate change and the increase in environmental disturbances.

  13. Whole-Genome Sequencing Uncovers the Genetic Basis of Chronic Mountain Sickness in Andean Highlanders

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    Zhou, Dan; Udpa, Nitin; Ronen, Roy; Stobdan, Tsering; Liang, Junbin; Appenzeller, Otto; Zhao, Huiwen W.; Yin, Yi; Du, Yuanping; Guo, Lixia; Cao, Rui; Wang, Yu; Jin, Xin; Huang, Chen; Jia, Wenlong; Cao, Dandan; Guo, Guangwu; Gamboa, Jorge L.; Villafuerte, Francisco; Callacondo, David; Xue, Jin; Liu, Siqi; Frazer, Kelly A.; Li, Yingrui; Bafna, Vineet; Haddad, Gabriel G.

    2013-01-01

    The hypoxic conditions at high altitudes present a challenge for survival, causing pressure for adaptation. Interestingly, many high-altitude denizens (particularly in the Andes) are maladapted, with a condition known as chronic mountain sickness (CMS) or Monge disease. To decode the genetic basis of this disease, we sequenced and compared the whole genomes of 20 Andean subjects (10 with CMS and 10 without). We discovered 11 regions genome-wide with significant differences in haplotype frequencies consistent with selective sweeps. In these regions, two genes (an erythropoiesis regulator, SENP1, and an oncogene, ANP32D) had a higher transcriptional response to hypoxia in individuals with CMS relative to those without. We further found that downregulating the orthologs of these genes in flies dramatically enhanced survival rates under hypoxia, demonstrating that suppression of SENP1 and ANP32D plays an essential role in hypoxia tolerance. Our study provides an unbiased framework to identify and validate the genetic basis of adaptation to high altitudes and identifies potentially targetable mechanisms for CMS treatment. PMID:23954164

  14. The Corregidores of the Colca Valley, Peru: Imperial Administration in an Andean Region

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    Cook, Noble David

    2003-12-01

    Full Text Available The corregidor de los indios was introduced into the Viceroyalty of Peru by Governor García de Castro in 1565. The institution was designed to limit the power of the encomendero elite and to improve administration and justice in the Andean countryside. Here we examine the impact of the reforms at the local level, the corregimiento of Los Collaguas in the Colca Valley, located between Cuzco and Arequipa. Althought the Crown was largely successful in weakening the encomienda, possibility of graft corrupted all but a handful of corregidores. The residencia did check some of those abuses.

    El gobernador García de Castro fue quien introdujo (1565 el corregidor de los indios en el virreinato del Perú. El corregimiento fue establecido para limitar el poder de los encomenderos y mejorar la administración y la justicia en los sitios rurales, y al mismo tiempo incrementar la colección del tributo. En este trabajo examinamos el impacto de las reformas en el corregimiento de los Collaguas situado en el hermoso valle del río Colca entre Arequipa y Cuzco. Aunque la corona fue más exitosa en debilitar la encomienda, la posibilidad de soborno corrompió a la mayoría de los corregidores.

  15. Phytosynthesis of gold nanoparticles using Andean Ajı′ (Capsicum baccatum L.

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    Brajesh Kumar

    2015-12-01

    Full Text Available This article covers the importance of Andean Ajı′/Chilli (Capsicum baccatum L. mediated synthesis of gold nanoparticles (AuNPs, which favors for green chemistry and escape us from the use of hazardous chemicals. UV–visible spectroscopy was used to monitor the quantitative formation of AuNPs. Further, as synthesized AuNPs were characterized using Transmission electron microscopy, Dynamic Light Scattering, and X-ray diffraction. It produced spherical AuNPs at λmax = 540 nm of average size 23.9 ± 9.7 nm without any aggregation. Ajı′ extract (aq was the good reducing and capping agent in terms of conversion to Au3+ to AuNPs. The synthesized AuNPs, also enhancing the photocatalytic degradation of methylene blue (>50%, k = 1.9585 × 10−3 min−1 under direct solar light irradiation. In addition, the experimental approach is benign, ecofriendly, and inexpensive for industrial-scale production of nanoparticles using Aji extract as natural bioreductant.

  16. Karyotypic variation in the Andean rodent Phyllotisxanthopygus (Waterhouse, 1837) (Rodentia, Cricetidae, Sigmodontinae).

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    Labaroni, Carolina Alicia; Malleret, Matías Maximiliano; Novillo, Agustina; Ojeda, Agustina; Rodriguez, Daniela; Cuello, Pablo; Ojeda, Ricardo; Dardo Martí; Lanzone, Cecilia

    2014-01-01

    Phyllotisxanthopygus (Waterhouse, 1837) is an Andean rodent endemic to South America. Despite its wide geographical distribution in Argentina, few individuals have been studied on the cytogenetic level and only through conventional staining. In this work, chromosome characterization of Argentine samples of this species was performed using solid staining, C-banding and base-specific fluorochromes. Twenty two specimens were analyzed, collected in the provinces of Jujuy, Catamarca, and the north and south of Mendoza. All studied specimens showed 2n=38, having mostly the bi-armed autosomes, metacentric or submetacentric. Fundamental Number varied between 70 and 72. These changes were due to the presence of chromosome heteromorphisms in individuals from southern Mendoza and Jujuy. C-banding revealed pericentromeric blocks of constitutive heterochromatin in most chromosomes. Acrocentric chromosomes involved in heteromorphisms showed high variation in the amount of heterochromatin within and among populations. Additionally, banding with fluorochromes (DAPI and chromomycin A3) revealed homologous localization of AT and GC rich regions among chromosomes of the different populations analyzed. Comparisons among heteromorphic pairs suggested, however, that the variation might be the result of complex chromosome rearrangements, involving possibly amplifications and/or deletions of heterochromatic segments. These results are in accordance with molecular studies that indicate genetic variability within and among the populations of this taxon.

  17. Transplacental nutrient transfer during gestation in the Andean lizard Mabuya sp. (Squamata, Scincidae).

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    Ramírez-Pinilla, Martha Patricia; Rueda, Elkin Darío; Stashenko, Elena

    2011-02-01

    Mabuya skinks have the most specialized allantoplacenta and the greatest degree of placentotrophy known among the Reptilia. Their recently ovulated eggs are microlecithal (1-2 mm) and lack fatty yolk platelets; thus, virtually all of the nutrients for embryonic development must pass across the placenta. We quantified the net uptake of nutrients during gestation in an Andean population of Mabuya and compared these results with other matrotrophic skinks and eutherian mammals. Total dry and wet masses, ash and organic content, ions (calcium, potassium, sodium, magnesium, iron), lipids (cholesterol, vitamin E and fatty acids in the major lipid classes-triacylglycerol, phospholipids, cholesteryl ester, free fatty acids), nitrogen (an index of protein) were measured during the different developmental stages throughout gestation, and in neonates. A significant net uptake of inorganic and organic matter was found. This uptake begins slowly during early gestation but accelerates during the last third of gestation when the growth of the embryo is maximal and the allantoplacenta has developed its greatest complexity. The drastic reduction of egg size in this clade is related to the great reduction in the contribution of lecithotrophic nutrients to the embryo, an obligatory placentotrophy from early developmental stages, and the highest placental complexity known in the Reptilia. All of these features converge with features found in eutherian mammals.

  18. [Floristic composition and distribution of the Andean subtropical riparian forests of Lules River, Tucuman, Argentina].

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    Sirombra, Martín G; Mesa, Leticia M

    2010-03-01

    We studied the floristic composition and distribution of the riparian forest of two hydrographical systems in a subtropical Andean region. Using uni and multivariate techniques, we tested the hypotheses that a differentiable riparian forest exists, composed by native vegetation typical of the Yungas phytogeographical province, and that the distribution of vegetation varied significantly with geomorphologic characteristics. Parallel transects along the water courses were used to collect presence-absence data of vegetation in eleven sites. Detrended Correspondence Analysis defined a group of common riparian species for the studied area (Solanum riparium, Phenax laevigatus, Tipuana tipu, Cestrum parqui, Carica quercifolia, Acacia macracantha, Celtis iguanaea, Juglans australis, Pisoniella arborescens, Baccharis salicifolia, Cinnamomum porphyrium and Eugenia uniflora) and identified two reference sites. The distribution of the riparian vegetation varied significantly with the geomorphic characteristics along the studied sites. Riparian habitats were composed by native and exotic species. A distinct riparian flora, different in structure and function from adjacent terrestrial vegetation, could not be identified. Riparian species were similar to the adjacent terrestrial strata. These species would not be limited by the proximity to the river. Anthropogenic impacts were important factors regulating the introduction and increase of exotic vegetation. The lack of regulation of some activities in the zone could cause serious problems in the integrity of this ecosystem.

  19. Probabilistic estimation of glacier volume and glacier bed topography: the Andean glacier Huayna West

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    V. Moya Quiroga

    2013-08-01

    Full Text Available Glacier retreat will increase sea level and decrease fresh water availability. Glacier retreat will also induce morphologic and hydrologic changes due to the formation of glacial lakes. Hence, it is important not only to estimate glacier volume, but also to understand the spatial distribution of ice thickness. There are several approaches for estimating glacier volume and glacier thickness. However, it is not possible to select an optimal approach that works for all locations. It is important to analyse the relation between the different glacier volume estimations and to provide confidence intervals of a given solution. The present study presents a probabilistic approach for estimating glacier volume and its confidence interval. Glacier volume of the Andean glacier Huayna West was estimated according to different scaling relations. Besides, glacier volume and glacier thickness were estimated assuming plastic behaviour. The present study also analysed the influence of considering a variable glacier density due to ice firn densification. It was found that the different estimations are described by a lognormal probability distribution. Considering a confidence level of 90%, the estimated glacier volume is 0.0275 km3 ± 0.0052 km3. Considering a confidence level of 90%, the estimated glacier thickness is 24.98 m with a confidence of ±4.67 m. The mean basal shear stress considering plastic behaviour is 82.5 kPa. The reconstruction of glacier bed topography showed the future formation of a glacier lake with a maximum depth of 32 m.

  20. Gut Microbiome of an 11th Century A.D. Pre-Columbian Andean Mummy.

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    Tasha M Santiago-Rodriguez

    Full Text Available The process of natural mummification is a rare and unique process from which little is known about the resulting microbial community structure. In the present study, we characterized the microbiome of paleofeces, and ascending, transverse and descending colon of an 11th century A.D. pre-Columbian Andean mummy by 16S rRNA gene high-throughput sequencing and metagenomics. Firmicutes were the most abundant bacterial group, with Clostridium spp. comprising up to 96.2% of the mummified gut, while Turicibacter spp. represented 89.2% of the bacteria identified in the paleofeces. Microbiome profile of the paleofeces was unique when compared to previously characterized coprolites that did not undergo natural mummification. We identified DNA sequences homologous to Clostridium botulinum, Trypanosoma cruzi and human papillomaviruses (HPVs. Unexpectedly, putative antibiotic-resistance genes including beta-lactamases, penicillin-binding proteins, resistance to fosfomycin, chloramphenicol, aminoglycosides, macrolides, sulfa, quinolones, tetracycline and vancomycin, and multi-drug transporters, were also identified. The presence of putative antibiotic-resistance genes suggests that resistance may not necessarily be associated with a selective pressure of antibiotics or contact with European cultures. Identification of pathogens and antibiotic-resistance genes in ancient human specimens will aid in the understanding of the evolution of pathogens as a way to treat and prevent diseases caused by bacteria, microbial eukaryotes and viruses.

  1. Vicuña conservation and poverty alleviation? Andean communities and international fibre markets

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    Gabriela Lichtenstein

    2009-09-01

    Full Text Available Vicuna (Vicugna vicugna fiber is produced by extremely low-income communities that inhabit the harsh environment of the Andes in Arge