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

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Rock Glacier Response to Climate Change in the Argentinian Andes

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Glacial lakes of the Central and Patagonian Andes

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

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

PubMed

Ocampo-Peñuela, Natalia; Pimm, Stuart L

2015-01-01

Conservation and restoration priorities often focus on separate ecosystem problems. Inspired by the November 11th (2011) landslide event near Manizales, and the current poor results of Colombia's Article 111 of Law 99 of 1993 as a conservation measure in this country, we set out to prioritize conservation and restoration areas where landslide prevention would complement bird conservation in the Central Andes. This area is one of the most biodiverse places on Earth, but also one of the most threatened. Using the case of the Rio Blanco Reserve, near Manizales, we identified areas for conservation where endemic and small-range bird diversity was high, and where landslide risk was also high. We further prioritized restoration areas by overlapping these conservation priorities with a forest cover map. Restoring forests in bare areas of high landslide risk and important bird diversity yields benefits for both biodiversity and people. We developed a simple landslide susceptibility model using slope, forest cover, aspect, and stream proximity. Using publicly available bird range maps, refined by elevation, we mapped concentrations of endemic and small-range bird species. We identified 1.54 km(2) of potential restoration areas in the Rio Blanco Reserve, and 886 km(2) in the Central Andes region. By prioritizing these areas, we facilitate the application of Article 111 which requires local and regional governments to invest in land purchases for the conservation of watersheds.

A systematic review of the nutritional adequacy of the diet in the Central Andes.

PubMed

Berti, Peter R; Fallu, Cynthia; Cruz Agudo, Yesmina

2014-11-01

To examine dietary adequacy in the Andean area, including macro- and micronutrient intakes, with a particular focus on rural communities; to highlight nutrition priorities in the Andes; and to identify opportunities for improvement. A comprehensive literature search was conducted, identifying published and grey literature in English and Spanish related to diet in the central Andean countries of Bolivia, Colombia, Ecuador, and Peru. Articles reporting data from dietary surveys or nutrition interventions were included. Thirty-four papers or reports published in 1969-2011 were included in the final review. The mean and variation in intakes by sex and age group of all presented nutrients were collated and the mean of means were calculated. Thiamin, niacin, and vitamin C intakes were usually adequate. Intakes of most other micronutrients, including iron, zinc, vitamin A, riboflavin, vitamin B12, folate, and zinc were low, likely resulting in high levels of inadequacy. Energy intakes were lower than requirements, but it is unlikely to be a common problem, rather, this result was probably due to the known tendency of most dietary survey tools to underreport intake. However, energy from fat intakes was very low, usually less than 20% of the total, and in some settings, less than 10%. The inadequate intake of some micronutrients is common in many developing countries, but the extremely low intake of dietary fat found in the central Andes is not. Increased consumption of animal-source foods would increase fat intakes, while addressing micronutrient deficiencies; however, the impact on the fragile ecosystem of the Andes needs considering. Indigenous crops, such as lupine bean, quinoa, and amaranth are also rich in fat or micronutrients.

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

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

PubMed Central

Ocampo-Peñuela, Natalia

2015-01-01

Conservation and restoration priorities often focus on separate ecosystem problems. Inspired by the November 11th (2011) landslide event near Manizales, and the current poor results of Colombia’s Article 111 of Law 99 of 1993 as a conservation measure in this country, we set out to prioritize conservation and restoration areas where landslide prevention would complement bird conservation in the Central Andes. This area is one of the most biodiverse places on Earth, but also one of the most threatened. Using the case of the Rio Blanco Reserve, near Manizales, we identified areas for conservation where endemic and small-range bird diversity was high, and where landslide risk was also high. We further prioritized restoration areas by overlapping these conservation priorities with a forest cover map. Restoring forests in bare areas of high landslide risk and important bird diversity yields benefits for both biodiversity and people. We developed a simple landslide susceptibility model using slope, forest cover, aspect, and stream proximity. Using publicly available bird range maps, refined by elevation, we mapped concentrations of endemic and small-range bird species. We identified 1.54 km2 of potential restoration areas in the Rio Blanco Reserve, and 886 km2 in the Central Andes region. By prioritizing these areas, we facilitate the application of Article 111 which requires local and regional governments to invest in land purchases for the conservation of watersheds. PMID:25737819

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

PubMed

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

2017-05-16

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

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

PubMed Central

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

2017-01-01

The circulation and exchange of goods and resources at various scales have long been considered central to the understanding of complex societies, and the Andes have provided a fertile ground for investigating this process. However, long-standing archaeological emphasis on typological analysis, although helpful to hypothesize the direction of contacts, has left important aspects of ancient exchange open to speculation. To improve understanding of ancient exchange practices and their potential role in structuring alliances, we examine material exchanges in northwest Argentina (part of the south-central Andes) during 400 BC to AD 1000 (part of the regional Formative Period), with a multianalytical approach (petrography, instrumental neutron activation analysis, laser ablation inductively coupled plasma mass spectrometry) to artifacts previously studied separately. We assess the standard centralized model of interaction vs. a decentralized model through the largest provenance database available to date in the region. The results show: (i) intervalley heterogeneity of clays and fabrics for ordinary wares; (ii) intervalley homogeneity of clays and fabrics for a wide range of decorated wares (e.g., painted Ciénaga); (iii) selective circulation of two distinct polychrome wares (Vaquerías and Condorhuasi); (iv) generalized access to obsidian from one major source and various minor sources; and (v) selective circulation of volcanic rock tools from a single source. These trends reflect the multiple and conflicting demands experienced by people in small-scale societies, which may be difficult to capitalize by aspiring elites. The study undermines centralized narratives of exchange for this period, offering a new platform for understanding ancient exchange based on actual material transfers, both in the Andes and beyond. PMID:28461485

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

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

Central Andes mountains, Chile/Argentina as seen from STS-67

NASA Technical Reports Server (NTRS)

1995-01-01

The Chilean coastline and the arid Atacama Desert stretch the length of the view with the high Andes on the eastern margin where hundreds of volcanoes dot the landscape. The wider (250-350 kilometers) Altiplano ('plains') sector of the Andes appears in the top half of the view, and the narrow (120 kilometers) 'mountain-chain-dominated' sector to the bottom. The northern half of Chile can be seen, with the 'hammer-head' peninsula at the city of Antofagasta, top left. Up welling of cold water as the Humboldt Current immediately offshore gives rise to low stratus cloud. The extensive cloud mass on the right lies beyond the Andes in the low country of Argentina's 'pampas' grasslands and Chaco semi-desert.

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

PubMed

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

2016-07-06

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

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

PubMed

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

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

Mesozoic-Early Cenozoic Retroarc Basin Evolution in Response to Changing Tectonic Regimes, Southern Central Andes

NASA Astrophysics Data System (ADS)

Mackaman-Lofland, C.; Horton, B. K.; Fuentes, F.; Constenius, K. N.; Stockli, D. F.

2017-12-01

Spatial and temporal variations in pre-Andean deformation, inherited lithospheric discontinuities, and subduction geometry have been documented for the southern Central Andes (27-40°S). However, the influence of inherited crustal structures and changing subduction zone dynamics on along-strike (N-S) and across-strike (E-W) variations in upper-plate deformation and basin evolution remains poorly understood. The La Ramada Basin in the High Andes at 32°S preserves the northernmost succession correlated with the well-studied Neuquen Basin to the south. New maximum depositional ages and provenance information provided by detrital zircon U-Pb geochronology refine the chronostratigraphic and provenance framework of La Ramada Basin deposits and improve reconstructions of structural activity and subsidence mechanisms during polyphase basin evolution. Updated along- and across-strike comparisons with Neuquen and intraplate depocenters provide an unparalleled opportunity to examine long-term fluctuations in stress regime, modes of variable plate coupling, structural reactivation, and basin evolution. Zircon U-Pb age distributions constrain Mesozoic-Cenozoic ages of La Ramada clastic units and identify a previously unrecognized period of Paleogene nonmarine deposition. Late Triassic-Jurassic synrift and post-rift deposits record sediment derivation from the eastern half-graben footwall and western Andean volcanic arc during periods of slab rollback and thermal subsidence. Uplift of the Coastal Cordillera and introduction of Coastal Cordillera sediment at 107 Ma represents the first signature of initial Andean uplift associated with accumulation in the La Ramada Basin. Finally, newly identified Paleogene extensional structures and intra-arc deposits in the western La Ramada Basin are correlated with the extensional Abanico Basin system ( 28°S-44°S) to the west in Chile. Development and inversion of this system of intra-arc depocenters suggests that shortening and uplift in

Simulations of the future precipitation climate of the Central Andes using a coupled regional climate model

NASA Astrophysics Data System (ADS)

Nicholls, S.; Mohr, K. I.

2014-12-01

The meridional extent and complex orography of the South American continent contributes to a wide diversity of climate regimes ranging from hyper-arid deserts to tropical rainforests to sub-polar highland regions. Global climate models, although capable of resolving synoptic-scale South American climate features, are inadequate for fully-resolving the strong gradients between climate regimes and the complex orography which define the Tropical Andes given their low spatial and temporal resolution. Recent computational advances now make practical regional climate modeling with prognostic mesoscale atmosphere-ocean coupled models, such as the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system, to climate research. Previous work has shown COAWST to reasonably simulate the both the entire 2003-2004 wet season (Dec-Feb) as validated against both satellite and model analysis data. More recently, COAWST simulations have also been shown to sensibly reproduce the entire annual cycle of rainfall (Oct 2003 - Oct 2004) with historical climate model input. Using future global climate model input for COAWST, the present work involves year-long cycle spanning October to October for the years 2031, 2059, and 2087 assuming the most likely regional climate pathway (RCP): RCP 6.0. COAWST output is used to investigate how global climate change impacts the spatial distribution, precipitation rates, and diurnal cycle of precipitation patterns in the Central Andes vary in these yearly "snapshots". Initial results show little change to precipitation coverage or its diurnal cycle, however precipitation amounts did tend drier over the Brazilian Plateau and wetter over the Western Amazon and Central Andes. These results suggest potential adjustments to large-scale climate features (such as the Bolivian High).

Oscillations and trends of river discharge in the southern Central Andes and linkages with climate variability

NASA Astrophysics Data System (ADS)

Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred R.

2017-12-01

This study analyzes the discharge variability of small to medium drainage basins (102-104 km2) in the southern Central Andes of NW Argentina. The Hilbert-Huang Transform (HHT) was applied to evaluate non-stationary oscillatory modes of variability and trends, based on four time series of monthly-normalized discharge anomaly between 1940 and 2015. Statistically significant trends reveal increasing discharge during the past decades and document an intensification of the hydrological cycle during this period. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be best described by five quasi-periodic statistically significant oscillatory modes, with mean periods varying from 1 to ∼20 y. Moreover, we show that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (∼20 y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (∼2-5 y). Previous studies highlighted a rapid increase in discharge in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. Our results suggest that the rapid discharge increase in the NW Argentine Andes coincides with the periodic enhancement of discharge, which is mainly linked to a negative to positive transition of the PDO phase and TSA variability associated with a long-term increasing trend. We therefore suggest that variations in discharge in this region are largely driven by both natural variability and the effects of global climate change. We furthermore posit that the links between atmospheric and hydrologic processes result from a combination of forcings that operate on different spatiotemporal scales.

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

NASA Astrophysics Data System (ADS)

Iturrizaga, Lasafam; Charrier, Reynaldo

2013-04-01

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

Mountaintops phylogeography: A case study using small mammals from the Andes and the coast of central Chile

PubMed Central

González, Juan F.; Boric-Bargetto, Dusan; Torres-Pérez, Fernando

2017-01-01

We evaluated if two sigmodontine rodent taxa (Abrothrix olivacea and Phyllotis darwini) from the Andes and Coastal mountaintops of central Chile, experienced distributional shifts due to altitudinal movements of habitat and climate change during and after the Last Glacial Maximum (LGM). We tested the hypothesis that during LGM populations of both species experienced altitudinal shifts from the Andes to the lowlands and the coastal Cordillera, and then range retractions during interglacial towards higher elevations in the Andes. These distributional shifts may have left remnants populations on the mountaintops. We evaluated the occurrence of intraspecific lineages for each species, to construct distribution models at LGM and at present, as extreme climatic conditions for each lineage. Differences in distribution between extreme climatic conditions were interpreted as post-glacial distributional shifts. Abrothrix olivacea displayed a lineage with shared sequences between both mountain systems, whereas a second lineage was restricted to the Andes. A similar scenario of panmictic unit in the past was recovered for A. olivacea in the Andes, along with an additional unit that included localities from the rest of its distribution. For P. darwini, both lineages recovered were distributed in coastal and Andean mountain ranges at present as well, and structuring analyses for this species recovered coastal and Andean localities as panmictic units in the past. Niche modeling depicted differential postglacial expansions in the recovered lineages. Results suggest that historical events such as LGM triggered the descending of populations to Andean refuge areas (one of the A. olivacea’s lineages), to the lowlands, and to the coastal Cordillera. Backward movements of populations after glacial retreats may have left isolates on mountaintops of the coastal Cordillera, suggesting that current species distribution would be the outcome of climate change and habitat reconfiguration

Population genetic structure of traditional populations in the Peruvian Central Andes and implications for South American population history.

PubMed

Cabana, Graciela S; Lewis, Cecil M; Tito, Raúl Y; Covey, R Alan; Cáceres, Angela M; Cruz, Augusto F De La; Durand, Diana; Housman, Genevieve; Hulsey, Brannon I; Iannacone, Gian Carlo; López, Paul W; Martínez, Rolando; Medina, Ángel; Dávila, Olimpio Ortega; Pinto, Karla Paloma Osorio; Santillán, Susan I Polo; Domínguez, Percy Rojas; Rubel, Meagan; Smith, Heather F; Smith, Silvia E; Massa, Verónica Rubín de Celis; Lizárraga, Beatriz; Stone, Anne C

2014-01-01

Molecular-based characterizations of Andean peoples are traditionally conducted in the service of elucidating continent-level evolutionary processes in South America. Consequently, genetic variation among "western" Andean populations is often represented in relation to variation among "eastern" Amazon and Orinoco River Basin populations. This west-east contrast in patterns of population genetic variation is typically attributed to large-scale phenomena, such as dual founder colonization events or differing long-term microevolutionary histories. However, alternative explanations that consider the nature and causes of population genetic diversity within the Andean region remain underexplored. Here we examine population genetic diversity in the Peruvian Central Andes using data from the mtDNA first hypervariable region and Y-chromosome short tandem repeats among 17 newly sampled populations and 15 published samples. Using this geographically comprehensive data set, we first reassessed the currently accepted pattern of western versus eastern population genetic structure, which our results ultimately reject: mtDNA population diversities were lower, rather than higher, within Andean versus eastern populations, and only highland Y-chromosomes exhibited significantly higher within-population diversities compared with eastern groups. Multiple populations, including several highland samples, exhibited low genetic diversities for both genetic systems. Second, we explored whether the implementation of Inca state and Spanish colonial policies starting at about ad 1400 could have substantially restructured population genetic variation and consequently constitute a primary explanation for the extant pattern of population diversity in the Peruvian Central Andes. Our results suggest that Peruvian Central Andean population structure cannot be parsimoniously explained as the sole outcome of combined Inca and Spanish policies on the region's population demography: highland populations

Multiethnicity, pluralism, and migration in the south central Andes: An alternate path to state expansion.

PubMed

Goldstein, Paul S

2015-07-28

The south central Andes is known as a region of enduring multiethnic diversity, yet it is also the cradle of one the South America's first successful expansive-state societies. Social structures that encouraged the maintenance of separate identities among coexistent ethnic groups may explain this apparent contradiction. Although the early expansion of the Tiwanaku state (A.D. 600-1000) is often interpreted according to a centralized model derived from Old World precedents, recent archaeological research suggests a reappraisal of the socio-political organization of Tiwanaku civilization, both for the diversity of social entities within its core region and for the multiple agencies behind its wider program of agropastoral colonization. Tiwanaku's sociopolitical pluralism in both its homeland and colonies tempers some of archaeology's global assumptions about the predominant role of centralized institutions in archaic states.

LANDSAT (ERTS) used as a basis for geological volcanological mapping in the central Andes

NASA Technical Reports Server (NTRS)

Kussmaul, S.; Brockman, C. E.

1977-01-01

LANDSAT images of the central Andes (N-Chile, W-Bolivia) were effectively used for volcanological mapping of an area about 160,000 km. The map shown exhibits more and better details than the older small scale geological maps of that area. Even on a scale of 1:1,000,000 details greater than 200 m in size are recognizable. The interpretation of LANDSAT images makes it possible to establish relative age sequences of strato-volcanoes. Finally, the images will also be helpful in prospecting for mineral deposits and geothermal sources.

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

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

River-discharge variability and trends in southeastern Central Andes since 1940

NASA Astrophysics Data System (ADS)

Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred R.

2017-04-01

The southern Central Andes in NW Argentina comprise small to medium drainage basins (102-104 km2) particularly sensitive to climate variability. In this area and in contrast to larger drainage basins such as the Amazon or La Plata rivers, floodplains or groundwater reservoirs either do not exist or are small. This reduces their dampening effect on discharge variability. Previous studies highlighted a rapid discharge increase up to 40% in seven years in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. To better understand the processes that drive variations in river discharge in this region, we analyze discharge variability on different timescales, relying on four time series of monthly discharge between 1940 and 2015. Since river discharge in this complex mountain environment results in a pronounced non-stationary and non-linear character, we apply the Hilbert-Huang Transform (HHT) to evaluate non-stationary oscillatory modes of variability and trends. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be decomposed in four quasi-periodic, statistically significant oscillatory modes, associated with timescales varying from 1 to ˜20y. In addition, statistically significant long-term trends show increasing discharge during the period between 1940 and 2015, documenting an intensification of the hydrological cycle during this period. Furthermore, time-dependent intrinsic correlation (TDIC) analysis shows that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (˜20y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (˜2-5y). Finally, our results suggest that the rapid discharge increased occurred during the 1970s coincides with the periodic enhancement of discharge mainly linked to the rise of the PDO

Upper-crustal Stress Field Variations During the Building of the Central Andes: Constrains on the Activation/deactivation of Megadetachments

NASA Astrophysics Data System (ADS)

Giambiagi, L.; Tassara, A.; Mescua, J.; Suriano, J.; Mahoney, J. B.; Hoke, G. D.; Spagnotto, S. L.; Lossada, A. C.; Mardónez, D.; Mazzitelli, M.; Barrionuevo, M.

2015-12-01

Nowadays, it is broadly accepted that the Central Andes resulted largely from crustal shortening in the last ~45 Ma, driven by horizontal forces as a consequence of subduction of the Nazca plate beneath South America. However, the way this shortening is achieved is still a matter a debate. Structural, seismological, thermochronological, isotopical and sedimentological studies of the Central Andes, together with thermomechanical modeling, suggest that different megadetachments located shallow in the upper crust were active during the construction of the Andes. Constrains on changes in the state of stress in the crust gleaned from more than 1,500 fault-slip data in the arc region provide insights into how and when these megadetachments get activated or deactivated. We used a forward modeling procedure to examine five transects across the Central Andes, at 21.5°, 24°, 30°, 34° and 35°S, with particular emphasis on the relationship between deep and shallow structures. Our kinematic-thermomechanical models show that most of the upper-middle crust has a brittle-elastic behavior particularly for the cold and rigid forearc and foreland regions, and a ductile behavior below the thermally weakened arc region. Our models assume a shallow, sub-horizontal megadetachment located at the shallowest brittle-ductile transition, which concentrates the majority of the horizontal crustal shortening between the fore-arc and the South American craton. During this horizontal shortening, the crust gets thick and topography rises due to buoyancy of the crustal root. The threshold of this thickening is achieved when the bouyancy force equals the horizontal force. At this point, the megadetachment deactives and the crustal root widens eastwards in concert with ductile deformation in the lower crust and the generation of a new megadetachment. By studying changes in the paleostress fields along the arc region, from compression to strike-slip, and strike-slip to extension, associated with �

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

NASA Astrophysics Data System (ADS)

Trachte, Katja; Bendix, Jörg

2013-04-01

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

Multiethnicity, pluralism, and migration in the south central Andes: An alternate path to state expansion

PubMed Central

Goldstein, Paul S.

2015-01-01

The south central Andes is known as a region of enduring multiethnic diversity, yet it is also the cradle of one the South America’s first successful expansive-state societies. Social structures that encouraged the maintenance of separate identities among coexistent ethnic groups may explain this apparent contradiction. Although the early expansion of the Tiwanaku state (A.D. 600–1000) is often interpreted according to a centralized model derived from Old World precedents, recent archaeological research suggests a reappraisal of the socio-political organization of Tiwanaku civilization, both for the diversity of social entities within its core region and for the multiple agencies behind its wider program of agropastoral colonization. Tiwanaku’s sociopolitical pluralism in both its homeland and colonies tempers some of archaeology’s global assumptions about the predominant role of centralized institutions in archaic states. PMID:26195732

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

NASA Astrophysics Data System (ADS)

Sulca, Juan C.

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

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

NASA Astrophysics Data System (ADS)

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

The Irish potato famine pathogen Phytophthora infestans originated in central Mexico rather than the Andes.

PubMed

Goss, Erica M; Tabima, Javier F; Cooke, David E L; Restrepo, Silvia; Fry, William E; Forbes, Gregory A; Fieland, Valerie J; Cardenas, Martha; Grünwald, Niklaus J

2014-06-17

Phytophthora infestans is a destructive plant pathogen best known for causing the disease that triggered the Irish potato famine and remains the most costly potato pathogen to manage worldwide. Identification of P. infestan's elusive center of origin is critical to understanding the mechanisms of repeated global emergence of this pathogen. There are two competing theories, placing the origin in either South America or in central Mexico, both of which are centers of diversity of Solanum host plants. To test these competing hypotheses, we conducted detailed phylogeographic and approximate Bayesian computation analyses, which are suitable approaches to unraveling complex demographic histories. Our analyses used microsatellite markers and sequences of four nuclear genes sampled from populations in the Andes, Mexico, and elsewhere. To infer the ancestral state, we included the closest known relatives Phytophthora phaseoli, Phytophthora mirabilis, and Phytophthora ipomoeae, as well as the interspecific hybrid Phytophthora andina. We did not find support for an Andean origin of P. infestans; rather, the sequence data suggest a Mexican origin. Our findings support the hypothesis that populations found in the Andes are descendants of the Mexican populations and reconcile previous findings of ancestral variation in the Andes. Although centers of origin are well documented as centers of evolution and diversity for numerous crop plants, the number of plant pathogens with a known geographic origin are limited. This work has important implications for our understanding of the coevolution of hosts and pathogens, as well as the harnessing of plant disease resistance to manage late blight.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Volcanic deformation in the Andes

NASA Astrophysics Data System (ADS)

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

2009-05-01

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

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

PubMed Central

Pietrokovsky, Silvia Mónica; Cigliano, Maria Marta; Confalonieri, Viviana Andrea

2017-01-01

The Andean Mountain range has been recognized as one of the biodiversity hotspots of the world. The proposed mechanisms for such species diversification, among others, are due to the elevation processes occurring during the Miocene and the intensive glacial action during the Pleistocene. In this study we investigated the diversification history of the grasshopper Trimerotropis pallidipennis species complex which shows a particularly wide latitudinal and altitudinal distribution range across the northern, central and southern Andes in South America. Many genetic lineages of this complex have been so far discovered, making it an excellent model to investigate the role of the central Andes Mountains together with climatic fluctuations as drivers of speciation. Phylogenetics, biogeographic and molecular clock analyses using a multi-locus dataset revealed that in Peru there are at least two, and possibly four genetic lineages. Two different stocks originated from a common ancestor from North/Central America—would have dispersed toward southern latitudes favored by the closure of the Panama Isthmus giving rise to two lineages, the coastal and mountain lineages, which still coexist in Peru (i.e., T. pallidipennis and T. andeana). Subsequent vicariant and dispersal events continued the differentiation process, giving rise to three to six genetic lineages (i.e., clades) detected in this study, which were geographically restricted to locations dispersed over the central Andes Mountains in South America. Our results provide another interesting example of “island diversification” motored by the topography plus unstable climatic conditions during the Pleistocene, pointing out the presence of a hotspot of diversification in the Andean region of Peru. PMID:28975055

The nature of orogenic crust in the central Andes

NASA Astrophysics Data System (ADS)

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.

Altitudinal variation in fish assemblage diversity in streams of the central Andes of Colombia.

PubMed

Jaramillo-Villa, U; Maldonado-Ocampo, J A; Escobar, F

2010-06-01

This study documents differences in fish assemblages for 32 freshwater streams located between 258 and 2242 m a.s.l. on the eastern slopes of the central range of the Colombian Andes. A total of 2049 fishes belonging to 62 species, 34 genera and 16 families were collected. Species richness declined rapidly with altitude; nearly 90% of the species were recorded between 250 and 1250 m a.s.l. Three of the four physico-chemical variables, of the water, temperature, dissolved oxygen and pH, explained 53.5% of the variation in species richness along the altitudinal gradient, with temperature the most important (37.6%). An analysis of species composition showed that the distinctiveness of the fish fauna increased with elevation, with the greatest turnover observed between 1000 and 1750 m a.s.l. On this altitudinal gradient, turnover was dominated by the loss of species rather than gain, and dominance by just a few species was greater at higher elevations. Turnover was also observed along the altitudinal gradient in the structure of the three functional groups (torrential, pool and pelagic species). The study focused on understanding the pattern of diversity of fish communities inhabiting the Andes in Colombia. Anthropogenic effects on the altitudinal distribution of fish species in the region, however, are largely unknown and would require further investigations.

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

PubMed

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

2007-05-15

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

Late Cretaceous to Cenozoic deformation and exhumation of the Chilean Frontal Cordillera (28°-29°S), Central Andes

NASA Astrophysics Data System (ADS)

Martínez, Fernando; Parra, Mauricio; Arriagada, César; Mora, Andrés; Bascuñan, Sebastián; Peña, Matías

2017-11-01

The Frontal Cordillera in northern Chile is located over the flat-slab subduction segment of the Central Andes. This tectonic province is characterized by a thick-skinned structural style showing evidence of tectonic inversion and basement-involved compressive structures. Field data, U-Pb geochronological and apatite fission track data were used to unravel partially the tectonic history of the area. Previous U-Pb ages of synorogenic deposits exposed on the flanks of basement-core anticlines indicate that Andean deformation started probably during Late Cretaceous with the tectonic inversion of Triassic and Jurassic half-grabens. New U-Pb ages of the synorogenic Quebrada Seca Formation suggest that this deformation continued during Paleocene (66-60 Ma) with the reverse faulting of pre-rift basement blocks. The analysis of new apatite fission-track data shows that a rapid and coeval cooling related to exhumation of the pre-rift basement blocks occurred during Eocene times. This exhumation event is interpreted for first time in the Chilean Frontal Cordillera and it could have occurred simultaneously with the propagation of basement-involved structures. The age of this exhumation event coincides with the Incaic orogenic phase, which is interpreted as the most important to the Central Andes in terms of shortening, uplift and exhumation.

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

PubMed Central

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

2012-01-01

To better describe the genetic diversity of hantaviruses associated with human illness in South America, we screened blood samples from febrile patients in Chapare Province in central Bolivia during 2008–2009 for recent hantavirus infection. Hantavirus RNA was detected in 3 patients, including 1 who died. Partial RNA sequences of small and medium segments from the 3 patients were most closely related to Andes virus lineages but distinct (<90% nt identity) from reported strains. A survey for IgG against hantaviruses among residents of Chapare Province indicated that 12.2% of the population had past exposure to >1 hantaviruses; the highest prevalence was among agricultural workers. Because of the high level of human exposure to hantavirus strains and the severity of resulting disease, additional studies are warranted to determine the reservoirs, ecologic range, and public health effect of this novel strain of hantavirus. PMID:22515983

Mitochondrial Variation among the Aymara and the Signatures of Population Expansion in the Central Andes

PubMed Central

BATAI, KEN; WILLIAMS, SLOAN R.

2015-01-01

Objectives The exploitation of marine resources and intensive agriculture led to a marked population increase early in central Andean prehistory. Constant historic and prehistoric population movements also characterize this region. These features undoubtedly affected regional genetic variation, but the exact nature of these effects remains uncertain. Methods Mitochondrial DNA (mtDNA) hypervariable region I sequence variation in 61 Aymara individuals from La Paz, Bolivia, was analyzed and compared to sequences from 47 other South American populations to test hypotheses of whether increased female effective population size and gene flow influenced the mtDNA variation among central Andean populations. Results The Aymara and Quechua were genetically diverse showing evidence of population expansion and large effective population size, and a demographic expansion model fits the mtDNA variation found among central Andean populations well. Estimated migration rates and the results of AMOVA and multidimensional scaling analysis suggest that female gene flow was also an important factor, influencing genetic variation among the central Andeans as well as lowland populations from western South America. mtDNA variation in south central Andes correlated better with geographic proximity than with language, and fit a population continuity model. Conclusion The mtDNA data suggests that the central Andeans experienced population expansion, most likely because of rapid demographic expansion after introduction of intensive agriculture, but roles of female gene flow need to be further explored. PMID:24449040

Lithologic discrimination of volcanic and sedimentary rocks by spectral examination of Landsat TM data from the Puma, Central Andes Mountains

NASA Technical Reports Server (NTRS)

Fielding, E. J.

1986-01-01

The Central Andes are widely used as a modern example of noncollisional mountain-building processes. The Puna is a high plateau in the Chilean and Argentine Central Andes extending southward from the altiplano of Bolivia and Peru. Young tectonic and volcanic features are well exposed on the surface of the arid Puna, making them prime targets for the application of high-resolution space imagery such as Shuttle Imaging Radar B and Landsat Thematic Mapper (TM). Two TM scene quadrants from this area are analyzed using interactive color image processing, examination, and automated classification algorithms. The large volumes of these high-resolution datasets require significantly different techniques than have been used previously for the interpretation of Landsat MSS data. Preliminary results include the determination of the radiance spectra of several volcanic and sedimentary rock units and the use of the spectra for automated classification. Structural interpretations have revealed several previously unknown folds in late Tertiary strata, and key zones have been targeted to be investigated in the field. The synoptic view of space imagery is already filling a critical gap between low-resolution geophysical data and traditional geologic field mapping in the reconnaissance study of poorly mapped mountain frontiers such as the Puna.

Structural and petrographic constraints on the stratigraphy of the Lapataia Formation, with implications for the tectonic evolution of the Fuegian Andes

NASA Astrophysics Data System (ADS)

Cao, Sebastián J.; Torres Carbonell, Pablo J.; Dimieri, Luis V.

2018-07-01

The structure of the Fuegian Andes central belt is characterized by a first phase of peak metamorphism and ductile deformation, followed by a brittle-ductile thrusting phase including juxtaposition of different (first phase) structural levels; both related to the closure and inversion of the Late Jurassic-Early Cretaceous Rocas Verdes basin. The second phase involved thrust sheets of pre-Jurassic basement, as well as Upper Jurassic and Lower Cretaceous units from the volcanic-sedimentary fill of the basin. Rock exposures in the Parque Nacional Tierra del Fuego reveal a diversity of metamorphic mineral assemblages, dynamic recrystallization grades and associated structures, evidencing a variety of protoliths and positions in the crust during their orogenic evolution. Among the units present in this sector, the Lapataia Formation portrays the higher metamorphic grade reported in the Argentine side of the Fuegian Andes, and since no precise radiometric ages have been established to date, its stratigraphic position remains a matter of debate: the discussion being whether it belongs to the pre-Jurassic basement, or the Upper Jurassic volcanic/volcaniclastic initial fill of the Rocas Verdes basin. The mapping and petrographic/microstructural study of the Lapataia Formation and those of undoubtedly Mesozoic age, allow to characterize the former as a group of rocks with great lithological affinity with the Upper Jurassic metamorphic rocks found elsewhere in the central belt of the Fuegian Andes. The main differences in metamorphic grade are indebted to its deformation at deeper crustal levels, but during the same stages than the Mesozoic rocks. Accordingly, we interpret the regional structure to be associated with the stacking of thrust sheets from different structural levels through the emplacement of a duplex system during the growth of the Fuegian Andes.

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

NASA Astrophysics Data System (ADS)

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

2006-11-01

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

Understanding the influence of orography on the precipitation diurnal cycle and the associated atmospheric processes in the central Andes

NASA Astrophysics Data System (ADS)

Junquas, C.; Takahashi, K.; Condom, T.; Espinoza, J.-C.; Chavez, S.; Sicart, J.-E.; Lebel, T.

2018-06-01

In the tropical Andes, the identification of the present synoptic mechanisms associated with the diurnal cycle of precipitation and its interaction with orography is a key step to understand how the atmospheric circulation influences the patterns of precipitation variability on longer time-scales. In particular we aim to better understand the combination of the local and regional mechanisms controlling the diurnal cycle of summertime (DJF) precipitation in the Northern Central Andes (NCA) region of Southern Peru. A climatology of the diurnal cycle is obtained from 15 wet seasons (2000-2014) of 3-hourly TRMM-3B42 data (0.25° × 0.25°) and swath data from the TRMM-2A25 precipitation radar product (5 km × 5 km). The main findings are: (1) in the NCA region, the diurnal cycle shows a maximum precipitation occurring during the day (night) in the western (eastern) side of the Andes highlands, (2) in the valleys of the Cuzco region and in the Amazon slope of the Andes the maximum (minimum) precipitation occurs during the night (day). The WRF (Weather Research and Forecasting) regional atmospheric model is used to simulate the mean diurnal cycle in the NCA region for the same period at 27 km and 9 km horizontal grid spacing and 3-hourly output, and at 3 km only for the month of January 2010 in the Cuzco valleys. Sensitivity experiments were also performed to investigate the effect of the topography on the observed rainfall patterns. The model reproduces the main diurnal precipitation features. The main atmospheric processes identified are: (1) the presence of a regional-scale cyclonic circulation strengthening during the afternoon, (2) diurnal thermally driven circulations at local scale, including upslope (downslope) wind and moisture transport during the day (night), (3) channelization of the upslope moisture transport from the Amazon along the Apurimac valleys toward the western part of the cordillera.

Structure and Evolution of the Central Andes of Peru

NASA Astrophysics Data System (ADS)

Gonzalez, L.; Pfiffner, O. A.

2009-04-01

Three major units make up the Andes in Peru: (1) The Western Cordillera consists of the Cretaceous Coastal Batholith intruding Jurassic to Cretaceous volcaniclastics (Casma group) in the west, and a fold-and-thrust belt of Mesozoic sediments in the east. Eocene and Miocene volcanics (Calipuy group and equivalents) overly all of these rock types. (2) The Central Highland contains a folded Paleozoic-Mesozoic sedimentary sequence overlain by thick Quaternary deposits. A major fault puts Neoproterozoic basement rocks of the Eastern Cordillera next to these units. (3) In the Eastern Cordillera, Late Paleozoic clastic successions unconformably overly folded Early Paleozoic sediments and a Neoproterozoic basement in the east. Permian (locally Triassic) granitoids intruded these units and were affected by folding and thrusting. In the core of the Eastern Cordillera, Early Cretaceous overly Early or Late Paleozoic strata. To the west, a thrust belt of Paleozoic to Cenozoic strata forms the transition to the foreland of the Brasilian shield. The most external part of this thrust belt involves Pliocene sediments and is referred to as Subandine zone. The Coastal Batholith is internally undeformed. The adjacent fold-and-thrust belt to the east is characterized by tight, nearly isoclinal upright folds with amplitudes of up to 1000 m. At the surface only Cretaceous rocks are observed. Using balancing techniques, a detachment horizon at the base of the Lowermost Cretaceous (Goyallarisquizga group - Oyon Formation) can be proposed. Further east, folds are more open, asymmetric and east verging, Jurassic sediments appear in the cores of the anticlines. The abrupt change in style from upright tight folding in the west to more open folding in the east is explained by a primary difference in the depositional sequence, most probably associated with synsedimentary faulting. The overlying volcanics of the Calipuy group and equivalents are, in turn, only slightly folded. In the Northern

Application of the Landsat Thematic Mapper to the identification of potentially active volcanoes in the Central Andes

NASA Technical Reports Server (NTRS)

Francis, P. W.; De Silva, S. L.

1989-01-01

A systematic study of the potentially active volcanoes in the Central Andes (14 deg S to 28 deg S) was carried out on the basis of Landsat Thematic Mapper images which provided consistent coverage of the area. More than 60 major volcanoes were identified as potentially active, as compared to 16 that are listed in the Catalog of Active Volcanoes of the World (Casertano, 1963; Hantke and Parodi, 1966). Most of these volcanoes are large (up to 6000 m in height) composite cones. Some of them could threaten nearby settlements, especially those in southern Peru, where the volcanoes rise above deep canyons with settlements along them.

Glacier Sensitivity Across the Andes

NASA Astrophysics Data System (ADS)

Sagredo, E. A.; Lowell, T. V.; Rupper, S.

2010-12-01

temperatures, while glaciers located in the wet Patagonian Andes seem to exhibit an opposite behavior. In an intermediate position are those glaciers located in the Tropical Andes, and Tierra del Fuego, which even though still more sensitive to temperature, they can be affected by temperature changes as well. With this regional approach towards the comprehension of climate-glacial dynamic interaction, we expect to contribute to the understanding the causes and mechanism driving former episodes of glacial fluctuations, and in turn, to the development of future scenarios of climate change.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Crustal origin of trench-parallel shear-wave fast polarizations in the Central Andes

NASA Astrophysics Data System (ADS)

Wölbern, I.; Löbl, U.; Rümpker, G.

2014-04-01

In this study, SKS and local S phases are analyzed to investigate variations of shear-wave splitting parameters along two dense seismic profiles across the central Andean Altiplano and Puna plateaus. In contrast to previous observations, the vast majority of the measurements reveal fast polarizations sub-parallel to the subduction direction of the Nazca plate with delay times between 0.3 and 1.2 s. Local phases show larger variations of fast polarizations and exhibit delay times ranging between 0.1 and 1.1 s. Two 70 km and 100 km wide sections along the Altiplano profile exhibit larger delay times and are characterized by fast polarizations oriented sub-parallel to major fault zones. Based on finite-difference wavefield calculations for anisotropic subduction zone models we demonstrate that the observations are best explained by fossil slab anisotropy with fast symmetry axes oriented sub-parallel to the slab movement in combination with a significant component of crustal anisotropy of nearly trench-parallel fast-axis orientation. From the modeling we exclude a sub-lithospheric origin of the observed strong anomalies due to the short-scale variations of the fast polarizations. Instead, our results indicate that anisotropy in the Central Andes generally reflects the direction of plate motion while the observed trench-parallel fast polarizations likely originate in the continental crust above the subducting slab.

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

NASA Astrophysics Data System (ADS)

Pritchard, M. E.; Simons, M.

2001-12-01

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

Monogenetic Arc Volcanism in the Central Andes: The "Hidden" Mafic Component in the Land of Andesite and Ignimbrite

NASA Astrophysics Data System (ADS)

van Alderwerelt, B. M.; Ukstins Peate, I.; Ramos, F. C.

2016-12-01

Faulting in the upper crust of the Central Andes has provided passage for small volumes of mafic magma to reach the surface, providing a window into petrogenetic processes in the region's deep crust and upper mantle. Mafic lavas are rare in the Central Andean region dominated by intermediate-composition arc volcanism and massive sheets of silicic ignimbrite, and provide key data on magmatic origin, evolution, and transport. This work characterizes fault-controlled, within-arc monogenetic eruptive centers representative of the most mafic volcanism in the Altiplano-Puna region of the Andes since (at least) the Mesozoic. Olivine-phyric basaltic andesite (54 wt% SiO2, 7.3 wt% MgO) at Cerro Overo maar and associated dome, La Albóndiga Grande, and an olivine-clinopyroxene flow (53 wt% SiO2, 6.7 wt% MgO) from Cordón de Puntas Negras have been erupted at the intersection of regional structural features and the modern volcanic arc. Bulk magma chemistry, radiogenic isotopes, and microanalyses of mineral and melt inclusion composition provide insight on the composition(s) of mafic magmas being delivered to the lowermost crust and the deep crustal processes which shape central Andean magma. Bulk major and trace elements follow regional arc differentiation trends and are clearly modified by crustal magmatic processes. In contrast, microanalyses reveal a much richer history with olivine-hosted melt inclusions recording multiple distinct magmas, including potential primary melts. Single crystal olivine 87Sr/86Sr from Cerro Overo (0.7041-0.7071) define a broader range than whole rock (0.7062-0.7065), indicating preservation of juvenile melt in olivine-hosted inclusions lost at the whole rock scale. Mineral chemistry (via EMPA) P-T calculations define a petrogenetic history for these endmember lavas. Field mapping, bulk chemistry, and microanalyses outline the generation, storage, transportation, and eventual eruption of the "hidden" mafic component of the Andean arc.

Glaciation in the Andes during the Lateglacial and Holocene

NASA Astrophysics Data System (ADS)

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

2009-10-01

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

Origin of the high plateau in the Central Andes, Bolivia, South America

NASA Astrophysics Data System (ADS)

Lamb, Simon; Hoke, Leonore

1997-08-01

The Bolivian Altiplano, in the Central Andes of South America, is part of the second largest high plateau on Earth. It is an elongate region of subdued relief, ˜1.2 × 105 km2 and ˜4 km above sea level, bounded by the Eastern Cordillera and volcanic arc (Western Cordillera). Here the crust is up to ˜75 km thick. We describe the Cenozoic geological evolution of this region, using a revised chronostratigraphy and an analysis of the crustal and lithospheric structure. Crustal shortening and magmatic addition and, locally, sedimentation are the main mechanisms of Cenozoic crustal thickening, leading to nearly 4 km of surface uplift since the Paleocene. Addition of mafic melts appears to be a first-order mechanism of Cenozoic crustal growth, contributing ˜40% of the crustal thickening beneath the volcanic arc. Removal of the basal part of the lithosphere may have caused two episodes of widespread arc and behind-arc mafic volcanism, at ˜23 Ma and 0 - ˜5 Ma, contributing to the surface uplift. The Altiplano originated as a sedimentary basin, several hundred kilometers wide, between the proto-Western Cordillera and a narrow zone of uplift (proto-Eastern Cordillera) farther east. The latter zone formed by inversion of the center of a wide lacustrine or marine Cretaceous - Paleocene basin close to sea-level at ˜45 Ma. A thickness of 2-4 km of Paleogene continental elastics accumulated in the proto-Altiplano basin. Subsequently, in the Oligocene, we estimate that this region and the western margin of the Eastern Cordillera were technically shortened ˜22% (˜65 km), resulting in ˜9 km of average crustal thickening. The Altiplano basin was rejuvenated at ˜25 Ma and subsequently flooded with up to 8 km thickness of detritus eroded from the uplifting Eastern and Western Cordilleras. Between ˜25 and 5 Ma, folding and thrusting in the western margin of the Eastern Cordillera migrated westward into the center of the Altiplano basin, essentially terminating deposition

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

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

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

NASA Astrophysics Data System (ADS)

Nieto-Moreno, Vanesa; Rohrmann, Alexander; van der Meer, Marcel T. J.; Sinninghe Damsté, Jaap S.; Sachse, Dirk; Tofelde, Stefanie; Niedermeyer, Eva M.; Strecker, Manfred R.; Mulch, Andreas

2016-11-01

Surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature, sometimes complicating paleoaltimetry interpretations. Thus, understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions. Lipid biomarker-based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials, in particular outside semi-arid climate zones where soil carbonates are not abundant but (soil) organic matter has a high preservation potential. Here we present δD values of soil-derived n-alkanes and mean annual air temperature (MAT) estimates based on branched glycerol dialkyl glycerol tetraether (brGDGT) distributions to assess their potential for paleoelevation reconstructions in the southern central Andes. We analyzed soil samples across two environmental and hydrological gradients that include a hillslope (26-28°S) and a valley (22-24°S) transect on the windward flanks of Central Andean Eastern Cordillera in NW Argentina. Our results show that present-day n-alkane δD values and brGDGT-based MAT estimates are both linearly related with elevation and in good agreement with present-day climate conditions. Soil n-alkanes show a δD lapse rate (Δ (δD)) of - 1.64 ‰ / 100 m (R2 = 0.91, p < 0.01) at the hillslope transect, within the range of δD lapse rates from precipitation and surface waters in other tropical regions in the Andes like the Eastern Cordillera in Colombia and Bolivia and the Equatorial and Peruvian Andes. BrGDGT-derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of ΔT = - 0.51 °C / 100 m (R2 = 0.91, p < 0.01), comparable with lapse rates from in situ soil temperature measurements, satellite-derived land-surface temperatures at this transect, and

Trench investigation along the Merida section of the Bocono fault (central Venezuelan Andes), Venezuela

USGS Publications Warehouse

Audemard, F.; Pantosti, D.; Machette, M.; Costa, C.; Okumura, K.; Cowan, H.; Diederix, H.; Ferrer, C.

1999-01-01

The Bocono fault is a major NE-SW-trending, dextral fault that extends for about 500 km along the backbone of the Venezuelan Andes. Several large historical earthquakes in this region have been attributed to the Bocono fault, and some of these have been recently associated with specific parts through paleoseismologic investigations. A new trench study has been performed, 60 km to the northeast of Merida in the central Venezuelan Andes, where the fault forms a releasing bend, comprising two conspicuous late Holocene fault strands that are about 1 km apart. The southern and northern strands carry about 70% and 30% (respectively) of the 7-10 mm/yr net slip rate measured in this sector, which is based on a 40 vs. 85-100 m right-lateral offset of the Late Pleistocene Los Zerpa moraines. A trench excavated on the northern strand of the fault (near Morros de los Hoyos, slightly northeast of Apartaderos) across a twin shutter ridge and related sag pond exposed two main fault zones cutting Late Pleistocene alluvial and Holocene peat deposits. Each zone forms a shutter ridge with peat deposits ponded against the uplifted block. The paleoearthquake reconstruction derived from this trench allow us to propose the occurrence of at least 6-8 earthquakes in the past 9000 yr, yielding a maximum average recurrence interval of about 1100-1500 yr. Based on the northern strands average slip rate (2.6 mm/yr), such as earthquake sequence should have accommodated about 23 m of slip since 9 ka, suggesting that the maximum slip per event ranges between 3 and 4 m. No direct evidence for the large 1812 earthquake has been found in the trench, although this earthquake may have ruptured this section of the fault. Further paleoseismic studies will investigate the possibility that this event occurred in the Bocono fault, but ruptured mainly its southern strand in this region.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Geological evolution of Paniri volcano, Central Andes, northern Chile

NASA Astrophysics Data System (ADS)

Godoy, Benigno; Lazcano, José; Rodríguez, Inés; Martínez, Paula; Parada, Miguel Angel; Le Roux, Petrus; Wilke, Hans-Gerhard; Polanco, Edmundo

2018-07-01

Paniri volcano, in northern Chile, belongs to a volcanic chain trending across the main orientation of the Central Andean volcanic province. Field work mapping, stratigraphic sequences, and one new 40Ar/39Ar and eleven previous published 40Ar/39Ar, and K/Ar ages, indicate that the evolution of Paniri involved eruption of seven volcanic units (Malku, Los Gordos, Las Lenguas, Las Negras, Viscacha, Laguna, and Llareta) during four main stages occurring over more than 1 Myr: Plateau Shield (>800 ka); Main Edifice (800-400 ka); Old Cone (400-250 ka); and New Cone (250-100 ka). Considering glacial and fluvial action, an estimated 85.3 km3 of volcanic material were erupted during the eruptive history of Paniri volcano, giving a bulk eruption rate of 0.061 km3/ka, with major activity in the last 150 kyr (eruption rate of 0.101 km3/ka). Lava flows from Paniri show abundant plagioclase together with subordinate ortho-, and clino-pyroxene, and amphibole as main phenocrysts. Moreover, although true basalts are scarce in the Central Andes, olivine-bearing lavas were erupted at Paniri at ∼400 ka. Also, scarce phenocrysts of biotite, quartz, rutile, and opaque minerals (Fe-Ti oxides) were identified. The groundmass of these flows is composed mainly of glass along with pyroxene and plagioclase microlites. Consolidated and unconsolidated pyroclastic deposits of dacitic composition are also present. The consolidated deposits correspond to vitreous tuffs, whilst unconsolidated deposits are composed of pumice clasts up to 5 cm in diameter. Both pyroclastic deposits are composed of glassy groundmass (up to 80% vol.), and subordinated plagioclase, hornblende, and biotite phenocrysts up to 1 cm in length. Results of twenty-four new, coupled with previous published compositional analyses show that volcanic products of Paniri vary from 57% (basaltic-andesite) to 71% (rhyolite) vol. SiO2, with significant linear correlations between major element-oxide and trace-element concentrations. 87

Carbon accumulation in high-altitude peatlands of the Central Andes of Peru

NASA Astrophysics Data System (ADS)

Llanos, Romina; Moreira-Turcq, Patricia; Huaman, Yizet; Espinoza, Raul; Apaestegui, James; Turcq, Bruno; Willems, Bram

2017-04-01

Despite covering only 6 - 8% of the world's land surface, peatlands contain around one third of the global organic soil carbon (C) and are an important component of the global C cycle. Most studies of peatland C dynamics have been carried out on boreal and subarctic peatlands, but less is known about peatlands at lower latitudes, yet there are significant peatland C stocks in these regions that may be more vulnerable to future climate change because they are closer to the climatic limit of peatland distribution. In South America, peatlands in high altitudes called "bofedales" represent one of the most important water resources and also provide key environmental services that support both Andean mountain biodiversity and the wellbeing of human populations. Nowdays, the need for conservation and wise use of these ecosystems is increasingly being recognized. So, a useable assessment of peatlands in the global C cycle requires accurate estimates of carbon pools and fluxes. In order to understand the impact of different altitudes on the growth, production and carbon accumulation, several short (about 30 cm) peatlands cores were collected in the headwater of the Cachi river basin, in the Central Andes of Peru. Two Distichia muscoides cushion plant-dominated "bofedales" which elevations exceed 4000 m were studied. The sedimentation rates, based on radiocarbon dating of peat samples from the two sites studied, were very variable. Cores from the bofedal located at 4200 m present an age of approximately 55 years, while the site at the highest altitude site has an age of approximately about 450 years. Our results point out very different rates of sedimentation in the two peatlands that may be related to the climatic changes observed during the recent past, with a direct consequence on the carbon accumulation rates. In the determination of the annual growth, we observed that this one presented smaller values in the first centimeters of the peatland with lower elevation, while

Uplift Sequence of the Main Morphoestructural Units of the South Central Andes at 30°S: Insights from a Multidisciplinary Approach

NASA Astrophysics Data System (ADS)

Lossada, A. C.; Mardónez, D.; Suriano, J.; Hoke, G. D.; Fitzgerald, P. G.; Mahoney, J. B.; Giambiagi, L.; Aragon, E.

2015-12-01

The South Central Andes at 30°S represent a key area to understand the Andes geodynamics as it corresponds to the flat slab segment, characterized by a subhorizontal subduction angle, absence of Neogene magmatism and a highly compressive tectonic regime. Under these settings, crustal shortening is believed to be the principal mechanism responsible for the rise of the Andes. However, the sequence of uplift of the different morphoestructural units composing the orogen is not fully understood; neither do the location and time of activity of intracrustal detachments and their connection with shallower structures. We attempt to develop a multidisciplinary analysis that allow us to characterize the timing, magnitude and activity of the principal structures involved in the construction of the Andes at 30°S trough the Coastal Range, the Frontal Cordillera and the Precordillera. The main phase of deformation in the Coastal Range occurred between 60 and 40Ma, based on published thermochronological and structural data. Our structural analyses constrain the Frontal Cordillera uplift between 18 and 13Ma. In the Precordillera area, in turn, we carried out structural, sedimentological and U-Pb provenience studies. Provenience studies and the 12 and 9Ma ages obtained for the youngest zircons indicated that the main thrusts uplifting the western sector of the Precordillera thrust system were activated since 13Ma at this latitude, and not before that time as it was previously suggested. In order to better constrain the exhumation and thermal history of Frontal Cordillera, a thermochronological study is being conducted. Twenty samples for apatite fission tracks (AFT) and apatite (U-Th)/He (AHe) were collected from two vertical profiles located at western sector (Guanta granitoid) and eastern sector (Colanguil granitoid) of the Frontal Cordillera system. Samples are currently being processed, and they are partially reseted, which will allow us to obtain a cooling age. The aim is to

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Sulphur-Rich Melt At Upper Crustal Levels At Cerro La Torta, Central Andes: Evidence From Melt Inclusions Assemblages.

NASA Astrophysics Data System (ADS)

Cannatelli, C.; Godoy, B.; Alvear, B.; Moncada, D.

2016-12-01

Central Andes present some of the biggest and most important porphyry copper ore deposits in the world. Porphyry copper ore formation is related to precipitation of ore minerals from sulphur and chlorine-rich fluids. Genesis of these deposits occurred 4 km below surface, while mineralized fluids are released by magmatic melts located between 5 and 15 km depth (Sillitoe, 2010). Cerro La Torta is part of a cluster of <105 ka rhyodacitic domes related to the waning stage of the Altiplano-Puna Volcanic Complex at Central Andes (Tierney et al., 2016). These domes reflect a crystal-rich mush layer at the upper crust - named Altiplano-Puna Magma Body (APMB) - which is proposed to be a voluminous partially molten body locate at shallow depth (4-25 km), with a thickness up to 11 km (Ward et al., 2014). Cerro La Torta is a crystal-rich ( 40% vol.) dacitic flow with plagioclase, amphibole, biotite, and quartz phenocrysts on a glassy (up to 50% vol.) groundmass. During detailed petrographic observation, two types of Melt Inclusions Assemblages (MIAs) were observed in the plagioclase. Group I is found in the core of crystals, and contains sulphide, pyrite ± bubbles. Group II of bubble-bearing MIAs is observed at the rim of the phenocrysts, with no associated sulphide mineral present. Melt Inclusions size ranges from 10-40 µm, suggesting an intermediate cooling rate (Roedder 1979). Out hypothesis is that during cooling, Group I MIA is trapped as result of a metal sulfur-rich event, leading to the suggestion that sulphide-bearing MIAs from Cerro La Torta are the evidence of mineralized magmas ponding at shallow crustal levels. Furthermore, the presence of MIAs in the mush-type magmas related to the APMB implies that such systems are suitable to porphyry copper ore generation. Roedder, 1979. The Evolution of the Igneous Rocks. 15-57 Sillitoe, 2010. Econ. Geol. 105:3-41 Tierney et al., 2016. Geology 44:683-686. doi:10.1130/G37968.1Ward et al., 2014. Earth Planet Sci Letters 404:43-54

The ash deposits of the 4200 BP Cerro Blanco eruption: the largest Holocene eruption of the Central Andes

NASA Astrophysics Data System (ADS)

Fernandez-Turiel, Jose-Luis; Saavedra, Julio; Perez-Torrado, Francisco-Jose; Rodriguez-Gonzalez, Alejandro; Carracedo, Juan-Carlos; Lobo, Agustin; Rejas, Marta; Gallardo, Juan-Fernando; Osterrieth, Margarita; Carrizo, Julieta; Esteban, Graciela; Martinez, Luis-Dante; Gil, Raul-Andres; Ratto, Norma; Baez, Walter

2015-04-01

We present new data about a major eruption -spreading approx. 110 km3 ashes over 440.000 km2- long thought to have occurred around 4200 years ago in the Cerro Blanco Volcanic Complex (CBVC) in the Central Andes of NW Argentina (Southern Puna, 26°45' S, 67°45' W). This eruption may be the biggest during the past five millennia in the Central Volcanic Zone of the Andes, and possibly one of the largest Holocene eruptions in the world. Discrimination and correlation of pyroclastic deposits of this eruption of Cerro Blanco was conducted comparing samples of proximal (domes, pyroclastic flow and fall deposits) with distal ash fall deposits (up to 400 km from de vent). They have been characterized using optical and electron microscopy (SEM), X-ray diffraction, particle-size distribution by laser diffraction and electron microprobe and HR-ICP-MS with laser ablation for major and trace element composition of glass, feldspars and biotite. New and published 14C ages were calibrated using Bayesian statistics. An one-at-a-time inversion method was used to reconstruct the eruption conditions using the Tephra2 code (Bonadonna et al. 2010, https://vhub.org/resources/tephra2). This method allowed setting the main features of the eruption that explains the field observations in terms of thickness and grain size distributions of the ash fall deposit. The main arguments that justify the correlation are four: 1) Compositional coincidence for glass, feldspars, and biotite in proximal and distal materials; 2) Stratigraphic and geomorphological relationships, including structure and thickness variation of the distal deposits; 3) Geochronological consistency, matching proximal and distal ages; and 4) Geographical distribution of correlated outcrops in relation to the eruption centre at the coordinates of Cerro Blanco. With a magnitude of 7.0 and a volcanic explosivity index or VEI 7, this eruption of ~4200 BP at Cerro Blanco is the largest in the last five millennia known in the Central

Contemporary recent extension and compression in the central Andes

NASA Astrophysics Data System (ADS)

Tibaldi, A.; Bonali, F. L.

2018-02-01

Although extension in the high Andes vs. compression in the lowlands has already been widely discussed in the literature, for the first time we recognized both extensional and contractional structures that developed contemporaneously during late Pliocene-Quaternary times in a wide area of the central Andean chain (about 90,000 km2), where crustal earthquake data are missing. This area comprises north-eastern Chile, south-western Bolivia and north-western Argentina, and extends from the Puna Plateau to the Altiplano-volcanic belt. Late Pliocene-Quaternary folds, with hinge lines trending NNE-SSW to N-S, are mostly located along the westernmost part of the volcanic belt and the eastern part of the Western Cordillera. Locally, there are coeval reverse faults, parallel to the folds, which reach up to the surface; particularly, the Miscanti Ridge, Tolocha Fault and La Casualidad Ridge may be the morphostructural expression of tens-km-long fault-propagation folds, which locally show topographic scarps hundreds of meters high. North and east of the contractional structures, we found evidence of late Pliocene-Quaternary normal faults striking N-S in the southern part of the study area, and NW-SE in the northern part. Well-developed grabens are present in the higher areas of the volcanic belt and in the transition zone with the Puna Plateau. The surface rupture zones of normal fault swarms range 8-24 km in length, with single fault strands up to 18 km long, which are typical of tectonic structures. The distribution in space and time of the studied contractional and extensional structures indicates that they originated in the same time period; we thus address the challenging question regarding the possible origin of the stress sources, by analysing possible causes such as volcanotectonics, high topography, orogeny collapse, and gravitational spreading of the orogen, in relation also with the role played by inherited structures. We finally analyse the relations between the

Andes Altiplano, South America

NASA Image and Video Library

1991-08-11

STS043-151-159 (2-11 August 1991) --- This photograph looks westward over the high plateau of the southern Peruvian Andes west and north of Lake Titicaca (not in field of view). Lima, Peru lies under the clouds just north of the clear coastal area. Because the high Andes have been uplifted 10,000 to 13,000 feet during the past 20 million years, the rivers which cut down to the Pacific Ocean have gorges almost that deep, such as the Rio Ocona at the bottom of the photograph. The eastern slopes of the Andes are heavily forested, forming the headwaters of the Amazon system. Smoke from burning in the Amazon basin fills river valleys on the right side of the photograph. A Linhof camera was used to take this view.

Morphological analysis of Cerro Bravo Volcano, Central Andes of Colombia

NASA Astrophysics Data System (ADS)

Arango-Palacio, E.; Murcia, H. F.; Robayo, C.; Chica, P.; Piedrahita, D. A.; Aguilar-Casallas, C.

2017-12-01

Keywords: Cerro Bravo Volcano, Volcanic landforms, Craters. Cerro Bravo Volcano (CBV) belongs to the San Diego-Cerro Machín Volcano - Tectonic Province in the Central Andes of Colombia. CVB is located 150 km NW from Bogotá, the capital of Colombia, and 25 km E from Manizales city ( 350,00 inhabitants). The volcanic activity of CBV began at 50,000 years ago and has been characterized by produce effusive and explosive (subplinian to plinian) eruptions with dacitic and andesitic in composition products. The effusive activity is evidenced by lava flows and lava domes, while the explosive activity is evidenced by pyroclastic density current deposits and pyroclastic fall deposits; some secondary deposits such as debris avalanches and lahares has been also recognised. Currently, the CBV is considered as a hazard for the Manizales city. In order to characterise the volcanic edifice, a morphological analysis was carried out and a map was created from a digital elevations model (DEM) with 12.5 m resolution as well as aerial photographs. Thus, it was possible to associate the landforms with the evolution of the volcano. Based on this analysis, it was possible to identify the base and top of the CBV edifice as 2400 and 4020 m.a.s.l., respectively, with a diameter in its major axis of 5.8 km. The volcanic edifice has four main craters opening to the north. The craters are apart from each other by heights and distances between 120 m.a.s.l. and 1 km, respectively; this geomorphology is an evidence of different eruptive stages of the volcano construction. Morphological analysis has shown that some craters were created from explosive eruptions, however the different heights between each crater suggest the creation of lava domes and their collapse as a response of the final effusive activity.

Episodic Cenozoic volcanism and tectonism in the Andes of Peru

USGS Publications Warehouse

Noble, D.C.; McKee, E.H.; Farrar, E.; Petersen, U.

1974-01-01

Radiometric and geologic information indicate a complex history of Cenozoic volcanism and tectonism in the central Andes. K-Ar ages on silicic pyroclastic rocks demonstrate major volcanic activity in central and southern Peru, northern Chile, and adjacent areas during the Early and Middle Miocene, and provide additional evidence for volcanism during the Late Eocene. A provisional outline of tectonic and volcanic events in the Peruvian Andes during the Cenozoic includes: one or more pulses of igneous activity and intense deformation during the Paleocene and Eocene; a period of quiescence, lasting most of Oligocene time; reinception of tectonism and volcanism at the beginning of the Miocene; and a major pulse of deformation in the Middle Miocene accompanied and followed through the Pliocene by intense volcanism and plutonism. Reinception of igneous activity and tectonism at about the Oligocene-Miocene boundary, a feature recognized in other circum-Pacific regions, may reflect an increase in the rate of rotation of the Pacific plate relative to fixed or quasifixed mantle coordinates. Middle Miocene tectonism and latest Tertiary volcanism correlates with and probably is genetically related to the beginning of very rapid spreading at the East Pacific Rise. ?? 1974.

Neotectonic reactivation of the western section of the Malargüe fold and thrust belt (Tromen volcanic plateau, Southern Central Andes)

NASA Astrophysics Data System (ADS)

Sagripanti, Lucía; Rojas Vera, Emilio A.; Gianni, Guido M.; Folguera, Andrés; Harvey, Jonathan E.; Farías, Marcelo; Ramos, Victor A.

2015-03-01

This study examines the neotectonic deformation and development of the Tromen massif, a Quaternary retroarc volcanic field located in the western section of the Malargüe fold and thrust belt in the Southern Central Andes. The linkages between neotectonic deformation in the intra-arc zone and the recent retroarc structures of the Tromen volcanic plateau are not clearly understood. These retroarc deformations affect the mid-section of the fold and thrust belt, leaving to the east a 200 km-wide deformed zone that can be considered inactive over the last 12-10 Ma. This out-of-sequence deformation west of the orogenic front area has not been previously addressed in detail. In this study, exhaustive mapping is used to describe and discriminate structures with a neotectonic component from those fossilized by Pleistocene strata. Two balanced cross-sections are constructed showing the distribution of the youngest deformations and their relation to pre-Miocene structures. An important means for evaluating this is the morphometric and morphological analyses that allowed identification of perturbations in the fluvial network associated with active structures. In a broader perspective, neotectonic activity in the fold and thrust belt is discussed and inferred to be caused by local mechanical weakening of the retroarc zone, due to injection of asthenospheric material evidenced by magnetotelluric surveys. Thus, deformation imposed by the oblique convergence between South American and Nazca plates, while to the south being limited to the Liquiñe-Ofqui fault system that runs through the arc zone, in the retroarc area is located at the site of magmatic emplacement, presumably in association with a thermally weakened-upper crust. This control exemplifies the relationship that exists between surficial processes, magmatic emplacement and upper asthenospheric dynamics in the Southern Central Andes.

Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

NASA Astrophysics Data System (ADS)

Bravo, Claudio; Loriaux, Thomas; Rivera, Andrés; Brock, Ben W.

2017-07-01

Glacier melt is an important source of water for high Andean rivers in central Chile, especially in dry years, when it can be an important contributor to flows during late summer and autumn. However, few studies have quantified glacier melt contribution to streamflow in this region. To address this shortcoming, we present an analysis of meteorological conditions and ablation for Universidad Glacier, one of the largest valley glaciers in the central Andes of Chile at the head of the Tinguiririca River, for the 2009-2010 ablation season. We used meteorological measurements from two automatic weather stations installed on the glacier to drive a distributed temperature-index and runoff routing model. The temperature-index model was calibrated at the lower weather station site and showed good agreement with melt estimates from an ablation stake and sonic ranger, and with a physically based energy balance model. Total modelled glacier melt is compared with river flow measurements at three sites located between 0.5 and 50 km downstream. Universidad Glacier shows extremely high melt rates over the ablation season which may exceed 10 m water equivalent in the lower ablation area, representing between 10 and 13 % of the mean monthly streamflow at the outlet of the Tinguiririca River Basin between December 2009 and March 2010. This contribution rises to a monthly maximum of almost 20 % in March 2010, demonstrating the importance of glacier runoff to streamflow, particularly in dry years such as 2009-2010. The temperature-index approach benefits from the availability of on-glacier meteorological data, enabling the calculation of the local hourly variable lapse rate, and is suited to high melt regimes, but would not be easily applicable to glaciers further north in Chile where sublimation is more significant.

Tectonic Evolution of the Central Andes during Mesozoic-Cenozoic times: Insights from the Salar de Atacama Basin

NASA Astrophysics Data System (ADS)

Peña Gomez, M. A.; Bascunan, S. A.; Becerra, J.; Rubilar, J. F.; Gómez, I.; Narea, K.; Martínez, F.; Arriagada, C.; Le Roux, J.; Deckart, K.

2015-12-01

The classic Salar de Atacama Basin, located in the Central Andes of northern Chile, holds a remarkable yet not fully understood record of tectonic events since mid-Cretaceous times. Based on the growing amount of data collected over the last years, such as high-detail maps and U-Pb geochronology, we present an updated model for the development of this area after the Triassic. A major compressional event is recorded around the mid-Late Cretaceous (ca. 107 Ma) with the deposition of synorogenic continental successions reflecting the uplift of the Coastal Cordillera area farther to the west, and effectively initiating the foreland basin. The deformation front migrated eastwards during the Late Campanian (ca. 79 Ma), where it exhumed and deformed the Late Cretaceous magmatic arc and the crystalline basement of Cordillera de Domeyko. The K-T Event (ca. 65 Ma), recently identified in the basin, involved the same source areas, though the facies indicate a closer proximity to the source. The compressional record of the basin is continued by the Eocene Incaic Event (ca. 45 Ma), with deep exhumation of the Cordillera de Domeyko and the cannibalization of previous deposits. A change to an extensional regime during the Oligocene (ca. 28 Ma) is shown by the deposition of more than 4 km of evaporitic and clastic successions. A partial inversion of the basin occurred during the Miocene (ca.10 Ma-present), as shown by the deformation seen in the Cordillera de la Sal. As such, the basin shows that the uplift of the Cordillera de Domeyko was not one isolated episode, but a prolonged and complex event, punctuated by episodes of major deformation. It also highlights the need to take into account the Mesozoic-Cenozoic deformation events for any model trying to explain the building of the modern-day Andes.

Ancient ice islands in salt lakes of the Central Andes

USGS Publications Warehouse

Hurlbert, S.H.; Chang, Cecily C.Y.

1984-01-01

Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.

Three-Dimensional Seismic Image of a Geothermal Prospect: Tinguiririca, Central Andes, Chile

NASA Astrophysics Data System (ADS)

Lira, E.; Comte, D.; Giavelli, A.; Clavero, J. E.; Pineda, G.

2010-12-01

Seismic monitoring has been widely used by the oil and gas industry, as a valuable input for the reservoir characterization. This tool has also been used in geothermal productive systems, particularly to understand permeability controls usually associated to shallow crustal fault systems that are seismically actives. Faults can be considered either “migration path” or “seals” in Petroleum Systems, depending on their activity story (they are carriers while actives and seals when the activity cease due to diagenetic processes in the fault plain). On the other hand, is well known that seismic velocities are strongly related to rock properties, in particular Vp/Vs and VpVs relationship has been successfully used to emphasize the variations in the physical rock properties due to fluid content and porosity. In geothermal systems, P and S-wave velocities are expected to be noticeably affected by massive hydrothermal alteration and/or to the presence of hot water in the fault related fractures of the rocks. In this job, the results of three months of seismic monitoring and a seismic velocity tomography are presented. Sixteen short period continuous recording, three components seismic stations were deployed in an area of approximately 20x10 Km2, and a large 8.8 magnitude earthquake took place during the recording period. The study area corresponds to the Tinguiririca volcanic complex (70°21''W, 35°48''S), in the high mountain of the Central Andes near the Chile-Argentina border. These preliminary results are complemented with some MT profiles, delineating potentially interesting geothermal features.

Crustal-scale electrical conductivity anomaly beneath inflating Lazufre volcanic complex, Central Andes

NASA Astrophysics Data System (ADS)

Budach, Ingmar; Brasse, Heinrich; Díaz, Daniel

2013-03-01

Large-scale surface deformation was observed at Lazufre volcanic center in the Central Andes of Northern Chile/Northwestern Argentina by means of Interferometric Synthetic Aperture Radar (InSAR). Uplift started there after 1998 and increased dramatically in the following years up to a rate of 3 cm/a. Lazufre is now one of the largest deforming volcano systems on Earth, but the cause for uplift - likely influx of magmatic material into the crust - is still poorly understood. In the beginning of 2010 a magnetotelluric survey was conducted to delineate the electrical conductivity distribution in the area. Several long-period magnetotelluric (LMT) sites and two broadband magnetotelluric (BBMT) sites were set up on an EW trending profile crossing the volcanic center; furthermore some LMT sites were arranged circularly around Lazufre complex and adjacent Lastarria volcano. Data were processed using an algorithm for robust and remote reference transfer function estimation. Electrical strike directions were estimated and induction arrows were derived. Although electrical strike is rather ambiguous, in a first step a 2-D resistivity model was calculated. The most prominent feature of this model is a well conducting structure rising from the upper mantle to the shallow crust beneath the center of elevation. This can be interpreted as partial melts ascending from the asthenospheric wedge and feeding a potential magma reservoir beneath Lazufre volcanic center. An improved model is finally achieved by 3-D inversion, supporting this feature. We assume that these rising melts are the source of the observed uplift at Lazufre complex.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

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

NASA Astrophysics Data System (ADS)

Pritchard, M. E.; Simons, M.

2002-12-01

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

Ocean-Atmosphere Coupled Model Simulations of Precipitation in the Central Andes

NASA Technical Reports Server (NTRS)

Nicholls, Stephen D.; Mohr, Karen I.

2015-01-01

The meridional extent and complex orography of the South American continent contributes to a wide diversity of climate regimes ranging from hyper-arid deserts to tropical rainforests to sub-polar highland regions. In addition, South American meteorology and climate are also made further complicated by ENSO, a powerful coupled ocean-atmosphere phenomenon. Modelling studies in this region have typically resorted to either atmospheric mesoscale or atmosphere-ocean coupled global climate models. The latter offers full physics and high spatial resolution, but it is computationally inefficient typically lack an interactive ocean, whereas the former offers high computational efficiency and ocean-atmosphere coupling, but it lacks adequate spatial and temporal resolution to adequate resolve the complex orography and explicitly simulate precipitation. Explicit simulation of precipitation is vital in the Central Andes where rainfall rates are light (0.5-5 mm hr-1), there is strong seasonality, and most precipitation is associated with weak mesoscale-organized convection. Recent increases in both computational power and model development have led to the advent of coupled ocean-atmosphere mesoscale models for both weather and climate study applications. These modelling systems, while computationally expensive, include two-way ocean-atmosphere coupling, high resolution, and explicit simulation of precipitation. In this study, we use the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST), a fully-coupled mesoscale atmosphere-ocean modeling system. Previous work has shown COAWST to reasonably simulate the entire 2003-2004 wet season (Dec-Feb) as validated against both satellite and model analysis data when ECMWF interim analysis data were used for boundary conditions on a 27-9-km grid configuration (Outer grid extent: 60.4S to 17.7N and 118.6W to 17.4W).

Toxoplasma gondii and Neospora caninum seroprevalences in domestic South American camelids of the Peruvian Andes.

PubMed

Chávez-Velásquez, Amanda; Aguado-Martínez, Adriana; Ortega-Mora, Luis M; Casas-Astos, Eva; Serrano-Martínez, Enrique; Casas-Velásquez, Gina; Ruiz-Santa-Quiteria, Jose A; Alvarez-García, Gema

2014-10-01

The objective of this study was to investigate the presence of Toxoplasma gondii- and Neospora caninum-specific antibodies in domestic South American camelids (SAC) (llamas and alpacas) from the Peruvian Andes through a cross-sectional study. A wide panel of serum samples collected from 1,845 llamas and 2,874 alpacas from the two main SAC production areas of Peru was selected. Immunofluorescence antibody technique was employed to detect and titrate specific anti-T. gondii and anti-N. caninum immunoglobulins G in serum samples. The association between T. gondii and N. caninum seroprevalence and the geographical origin (Central and South Peruvian Andes) was evaluated. Anti-T. gondii antibodies were found in 460 (24.9 %) llamas and 706 (24.6 %) alpacas, whereas anti-N. caninum antibodies were detected in 153 (8.3 %) llamas and 425 (14.8 %) alpacas. Toxoplasma gondii infection was strongly associated with the South Peruvian Andes where moderate climate conditions, larger human population, compared to the Central region, and the presence of wildlife definitive hosts could favor horizontal transmission to SAC. In contrast, N. caninum infection was not associated with the geographical region. These results indicate that T. gondii and N. caninum infections are highly and moderately widespread, respectively, in both species of domestic SAC studied in the sampled areas and appropriate control measures should be undertaken to reduce the prevalence of both parasitic infections.

Tierra del Fuego, Argentina, South America

NASA Technical Reports Server (NTRS)

1991-01-01

The Mitre Peninsula is the easternmost tip of Tierra del Fuego, Argentina, (54.5S, 65.5W). Early winter snow can be seen on this south tip of the Andes Mountains. These same mountains continue underwater to Antarctica. The Strait of Magellan, separating the South American mainland from Tierra del Fuego is off the scene to the north and west, but the Strait of LeMaire, separating Tierra del Fuego from the Isla de los Estados can be seen.

Earth observations of the Andes Mountains taken during the STS-97 mission

NASA Image and Video Library

2000-12-10

STS097-715-061 (10 December 2000) This view over the Central Andes Mountains in Argentina and Chile was taken on December 10, 2000 by one of the astronauts aboard the Earth-orbiting Space Shuttle Endeavour. Extending 5500 miles (8850 kilometers) along the western coast of South America from northern Colombia to Cape Horn in southern Chile, the Andes are the longest mountain range, above sea level, and the second highest range in the world. According to NASA scientists studying the STS-97 photo collection, this immense system came into existence nearly 70 million years ago. With numerous active volcanoes and a slow uplift, the building of the Andes Mountains continues today rising four inches (10 centimeters) per century, the scientists say. In this north-looking view, snow covers the higher peaks of the range, some of which rise to over 20000 feet (6100 meters) above sea level. Along the left or western portion of the view, clouds can be seen along coastal areas of Chile. In the bottom left quadrant of the scene, the blue waters of the Paloma Reservoir, a recreational lake, are visible. The folded Tontal Range (bottom center) and the Valle Fertil Range (upper right quadrant and partially cloud covered) of western Argentina can be seen. The rocks of these ranges, the scientists point out, are ancient compared to the younger volcanic peaks and ranges of the Andes. The city of San Juan, Argentina is visible on the eastern (right) base of the Tontal Range in the lower right quadrant of the view.

Compositional variations of ignimbrite magmas in the Central Andes over the past 26 Ma - A multivariate statistical perspective

NASA Astrophysics Data System (ADS)

Brandmeier, M.; Wörner, G.

2016-10-01

Multivariate statistical and geospatial analyses based on a compilation of 890 geochemical and 1200 geochronological data for 194 mapped ignimbrites from the Central Andes document the compositional and temporal patterns of large-volume ignimbrites (so-called "ignimbrite flare-ups") during Neogene times. Rapid advances in computational science during the past decade led to a growing pool of algorithms for multivariate statistics for large datasets with many predictor variables. This study applies cluster analysis (CA) and linear discriminant analysis (LDA) on log-ratio transformed data with the aim of (1) testing a tool for ignimbrite correlation and (2) distinguishing compositional groups that reflect different processes and sources of ignimbrite magmatism during the geodynamic evolution of the Central Andes. CA on major and trace elements allows grouping of ignimbrites according to their geochemical characteristics into rhyolitic and dacitic "end-members" and to differentiate characteristic trace element signatures with respect to Eu anomaly, depletions in middle and heavy rare earth elements (REE) and variable enrichments in light REE. To highlight these distinct compositional signatures, we applied LDA to selected ignimbrites for which comprehensive datasets were available. In comparison to traditional geochemical parameters we found that the advantage of multivariate statistics is their capability of dealing with large datasets and many variables (elements) and to take advantage of this n-dimensional space to detect subtle compositional differences contained in the data. The most important predictors for discriminating ignimbrites are La, Yb, Eu, Al2O3, K2O, P2O5, MgO, FeOt, and TiO2. However, other REE such as Gd, Pr, Tm, Sm, Dy and Er also contribute to the discrimination functions. Significant compositional differences were found between (1) the older (> 13 Ma) large-volume plateau-forming ignimbrites in northernmost Chile and southern Peru and (2) the

A Million-Year Record of Glaciation in the Tropical Andes

NASA Astrophysics Data System (ADS)

Smith, J. A.; Seltzer, G. O.; Rodbell, D. T.; Farber, D. L.; Finkel, R. C.

2004-12-01

We present a longterm record of glaciation in the tropical Andes based on cosmogenic dating (10Be) of boulders on moraines. Well-preserved moraines in deglaciated valleys bordering the Junin Plain in central Peru ( ˜11° S, 76° W, 4000 m) were deposited during several glacial cycles extending back more than one million years before present (1 Myr BP). The presence of boulders with zero-erosion 10Be exposure ages >1 Myr constrains boulder erosion rates to relatively low values. For boulders at high altitudes, however, even low boulder erosion rates (0.3 to 0.5 m/Myr) make calculated old exposure ages markedly older [e.g., ˜20% older for a zero-erosion age of 400,000 10Be years (400 10Be kyr)]. Exposure ages recalculated with boulder erosion rates of 0.3 m/Myr straddle interglacial marine isotope stage (MIS) 11 ( ˜430-390 kyr BP), fall within glacial MIS 12 ( ˜480-430 kyr BP), but skip over glacial MIS 16 ( ˜670-630 kyr BP), perhaps the largest ice volume of the past 2 Myr. Increasing the erosion rate used in the calculations to 0.5 m/Myr moves ages into both MIS 11 and MIS 16. If we assume that the older Andean glaciations were indeed synchronous with global ice volume, our data suggest that boulder preservation cannot be treated as a simple linear process. Conversely, the data may be suggesting correctly that glaciation of the tropical Andes was not synchronous with the global glaciations as inferred from the marine isotope record. Our chronology for the last glacial maximum (LGM) in the region supports the idea of asynchrony between the global ice volume record and the terrestrial record of glaciation in the tropical Andes. The LGM in the Junin region of Peru and in the Cordillera Real of Bolivia (16° S 68° W) occurred ˜34 to 22 10Be kyr BP and was less extensive than older glaciations. Asynchrony between the LGM in the Northern Hemisphere ( ˜21 kyr BP) and the tropical Andes suggests that previous glaciations in the tropical Andes may have been

Jürgen Stock: From One End of the Andes to the Other

NASA Astrophysics Data System (ADS)

Vivas, A. K.; Stock, M. J.

2015-05-01

Jürgen Stock (1923-2004) will always be remembered for his work on astronomical site testing. He led the efforts to find the best place for CTIO, and his work had a large influence in the setting of other observatories in Chile. He was the first director of CTIO (1963-1966). After his time in Chile, he moved to the other end of the Andes and was in charge of the site selection and the construction of the only professional observatory in Venezuela, the Llano del Hato National Observatory.

New Argentine Central-West line taps rich Neuquen gas field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watts, J.

1982-02-01

Argentina's new Central-West gas pipeline consists of 697 miles of 30-in. line and 451 miles of smaller gathering and distribution lines that link the rich Neuquen gas field with cities to the north. A financing package drawn up by 21 banks in the US and Europe allowed Cogasco S.A. to build the line for Gas del Estado across the roadless pampas east of the Andes. Primarily an agricultural country, Argentina had to import all the equipment and materials for the project. Site work began in July, 1980 with 800 workers employed on three spreads; the line was commissioned in November,more » 1981, 15 months ahead of the contract schedule.« less

Hydro-isostatic deflection and tectonic tilting in the central Andes: Initial results of a GPS survey of Lake Minchin shorelines

NASA Technical Reports Server (NTRS)

Bills, Bruce G.; De Silva, Shanaka L.; Currey, Donald R.; Emenger, Robert S.; Lillquist, Karl D.; Donnellan, Andrea; Worden, Bruce

1994-01-01

Sufficiently large lake loads provide a means of probing rheological stratification of the crust and upper mantle. Lake Minchin was the largest of the late Pleistocene pluvial lakes in the central Andes. Prominent shorelines, which formed during temporary still-stands in the climatically driven lake level history, preserve records of lateral variations in subsequent net vertical motions. At its maximum extent the lake was 140 m deep and spanned 400 km N-S and 200 km E-R. The load of surficial water contained in Lake Minchin was sufficient to depress the crust and underlying mantle by 20-40 m, depending on the subjacent rheology. Any other differential vertical motions will also be recorded as departures from horizontality of the shorelines. We recently conducted a survey of shoreline elevations of Lake Minchin with the express intent of monitoring the hydro-isostatic deflection and tectonic tilting. Using real-time differential Global Positioning System (GPS), we measured topographic profiles across suites of shorelines at 15 widely separated locations throughout the basin. Horizontal and vertical accuracies attained are roughly 30 and 70 cm, respectively. Geomorphic evidence suggests that the highest shoreline was occupied only briefly (probably less than 200 years) and radiocarbon dates on gastropod shells found in association with the shore deposits constrain the age to roughly 17 kyr. The basin-side pattern of elevations of the highest shoreline is composed of two distinct signals: (27 +/- 1) m of hydro-isostatic deflection due to the lake load, and a planar tilt with east and north components of (6.8 +/- 0.4) 10(exp -5) and 9-5.3 +/- 0.3) 10(exp -5). This rate of tilting is too high to be plausibly attributed to steady tectonism, and presumably reflects some unresolved combination of tectonism plus the effects of oceanic and lacustrine loads on a laterally heterogeneous substrate. The history of lake level fluctuations is still inadequately known to allow

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

PubMed

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

2015-09-01

The Neotropical ecoregion has been an important place of avian diversification where dispersal and allopatric events coupled with periods of active orogeny and climate change (Late Pliocene-Pleistocene) have shaped the biogeography of the region. In the Neotropics, avian population structure has been sculpted not only by geographical barriers, but also by non-allopatric factors such as natural selection and local adaptation. We analyzed the genetic variation of six co-distributed Phrygilus species from the Central Andes, based on mitochondrial and nuclear markers in conjunction with morphological differentiation. We examined if Phrygilus species share patterns of population structure and historical demography, and reviewed the intraspecific taxonomy in part of their geographic range. Our results showed different phylogeographic patterns between species, even among those belonging to the same phylogenetic clade. P. alaudinus, P. atriceps, and P. unicolor showed genetic differentiation mediated by allopatric mechanisms in response to specific geographic barriers; P. gayi showed sympatric lineages in northern Chile, while P. plebejus and P. fruticeti showed a single genetic group. We found no relationship between geographic range size and genetic structure. Additionally, a signature of expansion was found in three species related to the expansion of paleolakes in the Altiplano region and the drying phase of the Atacama Desert. Morphological analysis showed congruence with molecular data and intraspecific taxonomy in most species. While we detected genetic and phenotypic patterns that could be related to natural selection and local adaptation, our results indicate that allopatric events acted as a major factor in the population differentiation of Phrygilus species. Copyright © 2015 Elsevier Inc. All rights reserved.

The impact of Tibet and the Andes on the climate and isotopic composition of precipitation

NASA Astrophysics Data System (ADS)

Battisti, D. S.; Ding, Q.; Liu, X.; Roe, G.

2012-12-01

We summarize modeling and theoretical evidence for the impact of the high topography in Tibet and the Andes on the climate and the isotopic (δ18O) composition of precipitation, regionally and globally. Tibet controls the seasonal cycle of precipitation over eastern China, mainly via dynamical processes, and has little to no impact on the Indian and southeast Asian monsoons. Tibet is also responsible for the northwesterly winds and extraordinary cold winters in northern China, and contributes to the mid-winter suppression of storminess in the western and central Pacific. The Andes greatly shape the climatological precipitation over South America, and are an important contributor to the annual cycle in sea surface temperature, precipitation and atmospheric circulation throughout the eastern half of the tropical Pacific. We have performed a series of numerical experiments with the isotope-enabled ECHAM 4.6 atmospheric general circulation model to illuminate the impact of the Andes and Tibet on the regional distribution of oxygen isotopes in precipitation. Experiments to be discussed include a world without an elevated Andes circa 12 million years BP, and a series of experiments that prescribed a plausible evolution of the continental geometry and topography for the past 50 million years in and around the Indian Ocean basin. In the latter case, additional idealized experiments are performed to illuminate the separate impacts of topography and continental configuration.

Central Chile

NASA Technical Reports Server (NTRS)

2002-01-01

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

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

PubMed

Pritchard, Matthew E; Simons, Mark

2002-07-11

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

Uplift sequence of the Andes at 30°S: Insights from sedimentology and U/Pb dating of synorogenic deposits

NASA Astrophysics Data System (ADS)

Suriano, J.; Mardonez, D.; Mahoney, J. B.; Mescua, J. F.; Giambiagi, L. B.; Kimbrough, D.; Lossada, A.

2017-04-01

The South Central Andes at 30°S represent a key area to understand the Andes geodynamics as it is in the middle of the flat slab segment and all the morphotectonic units of the Central Andes are well developed. This work is focused in the proximal synorogenic deposits of the Western Precordillera, in the La Tranca valley, in order to unravel the uplift sequence of this belt. Nine facies associations were recognized; most of them represent piedmont facies with local provenance from Precordillera and were deposited in the wedge-top depozone, as is expected for proximal sinorogenic deposits. However there are intercalations of transference fluvial systems, which show mixed provenance indicating that Permo-Triassic igneous rocks were already exposed to the west (Frontal Cordillera). There are also lacustrine deposits which are interpreted as the result of damming by fault activity at east of the studied basin. Finally, two maximum depositional ages at ca. 11 Ma and 8 Ma of these deposits indicate that the onset of uplift of the Precordillera at 30°S is little older than 11 Ma. These data change two previous ideas about the evolution of the Precordillera: its uplift at 30° S is younger than proposed by previous works and it is nearly synchronous along strike.

Oral pathology patterns in late farmers of the Central Andes: A comparative perspective between coastal and highland populations.

PubMed

Pezo-Lanfranco, Luis; Peralta, Arturo; Guillén, Sonia; Eggers, Sabine

2017-10-01

Aiming at future comparisons with earlier hunter-gatherers or transitional populations, this paper intends to characterize and describe the oral pathology pattern of late agriculturalists from Central Andes dating to the Late Intermediate Period (LIP) and Inca periods (1000-1532 CE), and identify differences and/or similarities between coastal and highland populations. Although the botanical inventories of the LIP suggest carbohydrate-rich diets and similar components, it has been hypothesized that coastal and highland populations had, nevertheless, substantially different oral pathology patterns. We evaluated 14 indicators of oral pathology from Los Pinos (n=200) and Armatambo (n=25) sites in the Central Coast and two chronological phases from Laguna de los Cóndores site (LC-Inca, n=23; and LC-LIP, n=55), in the Peruvian northern highlands. The results showed a recurrent pattern of oral pathologies characterized by cervical caries (above 30%), extra-occlusal caries (above 60%), high rates of gross-gross caries, high frequency of ante mortem tooth loss, and signals of periodontal disease among these four populations. The diets of the coast were slightly more abrasive than those of the highlands. Oral pathology patterns were compatible with a slightly more cariogenic diet in the coast than in the highlands. In all four populations, those patterns were modulated by other common factors such as consumption of fermented drinks (maize beer - chicha) and the coca leaf chewing habit. Copyright © 2017 Elsevier GmbH. All rights reserved.

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

PubMed

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

2005-05-01

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

New insights into the tectonic evolution of the Boconó Fault, Mérida Andes, Venezuela

NASA Astrophysics Data System (ADS)

Backé, G.

2006-12-01

The Boconó fault is a major right-lateral strike-slip fault that cuts along strike the Mérida Andes in Venezuela. The uplift of this mountain range started in the Miocene as a consequence of the relative oblique convergence between two lithospheric units named the Maracaibo block to the northwest and the Guyana shield to the southeast. Deformation in the Mérida Andes is partitioned between a strike-slip component along the Boconó fault and shortening perpendicular to the belt. Distinctive features define the Boconó fault: it is shifted southward relative to the chain axis and it does not have a continuous and linear trace but is composed of several fault segments of different orientations striking N35°E to N65°E. Quaternary fault strike-slip motion has been evidenced by various independent studies. However, onset of the strike-slip motion, fault offset and geometry at depth remains a matter of debate. Our work, based on morphostructural analyses of satellite and digital elevation model imagery, provides new data on both the geometry and the tectonic evolution of this major structure. We argue that the Boconó fault affects only the upper crust and connects at depth to a décollement. Consequently, it can not be considered as a plate boundary. The Boconó fault does however form the boundary between two different tectonic areas in the central part of the Mérida Andes as revealed by the earthquake focal mechanisms. South of the Boconó fault, the focal mechanisms are mainly compressional and reverse oblique-slip in agreement with NW SE shortening in the foothills. North of the Boconó fault, extensional and strike-slip deformation dominates. Microtectonic measurements collected in the central part of the Boconó fault are characterized by polyphased tectonics. The dextral shearing along the fault is superimposed to reverse oblique-slip to reverse motion, showing that initiation of transcurrent movement is more likely to have occurred after a certain amount of

3-D modeling of magnetotelluric data in the Paniri-Toconce volcanic chain, Central Andes.

NASA Astrophysics Data System (ADS)

Mancini, R.; Brasse, H.; Diaz, D.

2017-12-01

The research is located in the San Pedro-Toconce volcanic chain in the central volcanic zone of the Andes, North Chile. This area is interesting because of its proximity to several active volcanic centers, the geysers field of El Tatio and the recently opened geothermal plant Cerro Pabellon. Thermobarometry studies made in the area point to magma accumulated at 8 km below Lavas de Chao, and depths greater than 24 km below Toconce and Cerro de Leon. Regional geophysical studies show a distribution of conductive bodies around the complex, but the resolution of these studies at shallow depths are not conclusive. Data from wells show the possible presence of a large geothermal system in the southwest part of the complex, with depths of 2 km. Twenty broadband magnetotelluric (MT) stations were measured in the vicinity of the complex and combined with 15 long period MT stations measured in the 1990s, aiming at characterizing the deep conductive structures previously observed in the area, with magmatic bodies associated with the adjacent volcanic system. The results of a 3-D inversion show several conductive anomalies around the complex. Analyses of conductivity together with the 3-D models obtained indicate the presence of a geothermal system to the southwest of the complex with maximum depths of about 5 km, and two possible magmatic chambers below Paniri volcano and between Paniri and San Pedro volcanoes. In addition, the presence of a highly conductive structure to the east is obtained, associated with the Altiplano-Puna magma body (APMB).

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

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Panoramic View of the Andes Mountains, Chile and Argentina

NASA Technical Reports Server (NTRS)

1992-01-01

This panoramic view of the Andes Mountains of Chile and Argentina (24.5S, 69.5W) is dominated by the yellows and browns of the coastal Atacama Desert and the full width of the Andes altiplano, about 300 miles. Winter snow can be seen capping the 22,000 to 23,000 ft. peaks of the Andes. Wisps of cirrus clouds lie over the altiplano and offshore fog obscures the coast. In the distance, the low Chaco Plain appears green with pastures and agriculture.

A new species of small-eared shrew of the genus Cryptotis (Mammalia, Eulipotyphla, Soricidae) from the northernmost Peruvian Andes.

PubMed

Zeballos, Horacio; Pino, Kateryn; Medina, CÉsar E; Pari, Alexander; ChÁvez, Daniel; Tinoco, NicolÁs; Ceballos, Gerardo

2018-01-31

The northernmost Peruvian Andes, a unique biogeographic region characterized by the confluence of multiple distinct ecosystems (i.e. Amazon basin, Pacific rainforest, the Sechura Desert, the northern and central Andes), is the southernmost geographic range limit of the South American shrews representing the genus Cryptotis. In the northernmost Peruvian Andes, two poorly known species have traditionally been reported (C. peruviensis and C. equatoris). Our study, based on molecular and morphologic traits, confirms the presence of C. peruviensis but also the occurrence of C. montivaga, based on specimens erroneously assigned to C. equatoris. Moreover, a new species of Cryptotis from the páramo and montane forests of the Tabaconas Namballe National Sanctuary near the Ecuadorian border is also described. It is a member of the thomasi group and is distinguished from other South American shrews by a unique set of morphological characters, including large body size, comparatively short tail, simple ectoloph of M3, and large PM4 post protocrista.

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

NASA Astrophysics Data System (ADS)

Civitarese, O.; Fushimi, K. J.; Mosquera, M. E.

2016-12-01

Weakly interacting massive particles (WIMPs) are possible components of the Universe’s dark matter (DM). The detection of WIMPs is signaled by the recoil of the atomic nuclei which form a detector. CoGeNT at the Soudan Underground Laboratory (SUL) and DAMA at the Laboratori Nazionali del Gran Sasso (LNGS) have reported data on annual modulation of signals attributed to WIMPs. Both experiments are located in laboratories in the Northern Hemisphere. DM detectors are planned to operate (or already operate) in laboratories in the Southern Hemisphere, including SABRE at Stawell Underground Physics Laboratory (SUPL) in Australia, and DM-ICE in Antarctica. In this work we have analyzed the dependence of diurnal and annual modulation of signals, pertaining to the detection of WIMP, on the coordinates of the laboratory, for experiments which may be performed in the planned new Agua Negra Deep Experimental Site (ANDES) underground facility, to be built in San Juan, Argentina. We made predictions for NaI and Ge-type detectors placed in ANDES, to compare with DAMA, CoGeNT, SABRE and DM-ICE arrays, and found that the diurnal modulation of the signals, at the ANDES site, is amplified at its maximum value, both for NaI (Ge)-type detectors, while the annual modulation remains unaffected by the change in coordinates from north to south.

U-series disequilibria of trachyandesites from minor volcanic centers in the Central Andes

NASA Astrophysics Data System (ADS)

Huang, Fang; Sørensen, Erik V.; Holm, Paul M.; Zhang, Zhao-Feng; Lundstrom, Craig C.

2017-10-01

Young trachyandesite lavas from minor volcanic centers in the Central Andes record the magma differentiation processes at the base of the lower continental crust. Here we report U-series disequilibrium data for the historical lavas from the Andagua Valley in Southern Peru to define the time-scale and processes of magmatism from melting in the mantle wedge to differentiation in the crust. The Andagua lavas show (230Th)/(238U), (231Pa)/(235U), and (226Ra)/(230Th) above unity except for one more evolved lava with 230Th depletion likely owing to fractional crystallization of accessory minerals. The 226Ra excess indicates that the time elapsed since magma emplacement and differentiation in the deep crust is within 8000 years. Based on the correlations of U-series disequilibria with SiO2 content and ratios of incompatible elements, we argue that the Andagua lavas were produced by mixing of fresh mantle-derived magma with felsic melt of earlier emplaced basalts in the deep crust. Because of the lack of sediment in the Chile-Peru trench, there is no direct link of recycled slabs with 230Th and 231Pa excesses in the Andagua lavas. Instead, 230Th and 231Pa excesses are better explained by in-growth melting in the upper mantle followed by magma differentiation in the crust. Such processes also produced the 226Ra excess and the positive correlations among (226Ra)/(230Th), Sr/Th, and Ba/Th in the Andagua lavas. The time-scale of mantle wedge melting should be close to the half-life of 231Pa (ca. 33 ka), while it takes less than a few thousand years for magma differentiation to form intermediate volcanic rocks at a convergent margin.

Holocene compression in the Acequión valley (Andes Precordillera, San Juan province, Argentina): Geomorphic, tectonic, and paleoseismic evidence

NASA Astrophysics Data System (ADS)

Audemard, M.; Franck, A.; Perucca, L.; Laura, P.; Pantano, Ana; Avila, Carlos R.; Onorato, M. Romina; Vargas, Horacio N.; Alvarado, Patricia; Viete, Hewart

2016-04-01

The Matagusanos-Maradona-Acequión Valley sits within the Andes Precordillera fold-thrust belt of western Argentina. It is an elongated topographic depression bounded by the roughly N-S trending Precordillera Central and Oriental in the San Juan Province. Moreover, it is not a piggy-back basin as we could have expected between two ranges belonging to a fold-thrust belt, but a very active tectonic corridor coinciding with a thick-skinned triangular zone, squeezed between two different tectonic domains. The two domains converge, where the Precordillera Oriental has been incorporated to the Sierras Pampeanas province, becoming the western leading edge of the west-verging broken foreland Sierras Pampeanas domain. This latter province has been in turn incorporated into the active deformation framework of the Andes back-arc at these latitudes as a result of enhanced coupling between the converging plates due to the subduction of the Juan Fernández ridge that flattens the Nazca slab under the South American continent. This study focuses on the neotectonics of the southern tip of this N-S elongated depression, known as Acequión (from the homonym river that crosses the area), between the Del Agua and Los Pozos rivers. This depression dies out against the transversely oriented Precordillera Sur, which exhibits a similar tectonic style as Precordillera Occidental and Central (east-verging fold-thrust belt). This contribution brings supporting evidence of the ongoing deformation during the Late Pleistocene and Holocene of the triangular zone bounded between the two leading and converging edges of Precordillera Central and Oriental thrust fronts, recorded in a multi-episodic lake sequence of the Acequión and Nikes rivers. The herein gathered evidence comprise Late Pleistocene-Holocene landforms of active thrusting, fault kinematics (micro-tectonic) data and outcrop-scale (meso-tectonic) faulting and folding of recent lake and alluvial sequences. In addition, seismically

First results of high-resolution modeling of Cenozoic subduction orogeny in Andes

NASA Astrophysics Data System (ADS)

Liu, S.; Sobolev, S. V.; Babeyko, A. Y.; Krueger, F.; Quinteros, J.; Popov, A.

2016-12-01

The Andean Orogeny is the result of the upper-plate crustal shortening during the Cenozoic Nazca plate subduction beneath South America plate. With up to 300 km shortening, the Earth's second highest Altiplano-Puna Plateau was formed with a pronounced N-S oriented deformation diversity. Furthermore, the tectonic shortening in the Southern Andes was much less intensive and started much later. The mechanism of the shortening and the nature of N-S variation of its magnitude remain controversial. The previous studies of the Central Andes suggested that they might be related to the N-S variation in the strength of the lithosphere, friction coupling at slab interface, and are probably influenced by the interaction of the climate and tectonic systems. However, the exact nature of the strength variation was not explored due to the lack of high numerical resolution and 3D numerical models at that time. Here we will employ large-scale subduction models with a high resolution to reveal and quantify the factors controlling the strength of lithospheric structures and their effect on the magnitude of tectonic shortening in the South America plate between 18°-35°S. These high-resolution models are performed by using the highly scalable parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model). This code is based on finite difference staggered grid approach and employs massive linear and non-linear solvers within the PETSc library to complete high-performance MPI-based parallelization in geodynamic modeling. Currently, in addition to benchmark-models we are developing high-resolution (< 1km) 2D subduction models with application to Nazca-South America convergence. In particular, we will present the models focusing on the effect of friction reduction in the Paleozoic-Cenozoic sediments above the uppermost crust in the Subandean Ranges. Future work will be focused on the origin of different styles of deformation and topography evolution in Altiplano-Puna Plateau and Central

The Largest Holocene Eruption of the Central Andes Found

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

New Elemental and Isotopic Data From Mafic Lavas on the Puna Plateau and Re-Examining the Geochemical Signature of Convective Lithospheric Removal in the Central Andes

NASA Astrophysics Data System (ADS)

Murray, K. E.; Ducea, M. N.; Reiners, P. W.

2009-12-01

Foundering or delamination of the lower lithosphere into the convecting mantle is required by mass balance in convergent orogens such as the central Andes. In the central Andean volcanic zone (CVZ), late Miocene to Recent mafic lavas erupted on the Puna plateau are small volume fissure flows and cinder cones classically cited as evidence of convective lithospheric removal, in concert with a suite of observations including high surface elevation (>4000m) and anomalously thin lithosphere relative to other parts of the CVZ. Mafic lavas provide the best available geochemical window into the recent history of the upper mantle in this and other regions. However, an increasing number of elemental and isotopic data suggest that these melts are less distinct from the neighboring arc magmatism than originally predicted. This observation weakens the hypothesis that there is a distinct geochemical fingerprint for so-called delamination magmatism, while advancing our understanding of the size of delaminating bodies and the timescales over which they detach from the lithosphere and interact with the mantle wedge. In this contribution, we present elemental and radiogenic isotopic data from 20 newly sampled mafic lavas from the Puna plateau (24.5°S to 27°S). Preliminary major element analyses show that the Puna lavas are high-K to shoshonitic in composition, in broad agreement with other mafic lavas sampled though out the region. Several sampled flows contain xenotliths of granitoid composition, which likely represent the crustal end member that contributed to the more evolved lavas. Along with major, trace and rare earth element analyses, we will present 87Sr/86Sr and 143Nd/144Nd data to further characterize source regions of these melts. In sum, these data will allow us to (1) expand the spatial coverage of this dataset in the central Andes, (2) contribute to the effort to parse contributions from the subcontinental lithosphere, asthenosphere, subduction-related fluids, and

Morphologic evolution of the Central Andes of Peru

NASA Astrophysics Data System (ADS)

Gonzalez, Laura; Pfiffner, O. Adrian

2012-01-01

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

Do cacti form soil seed banks? An evaluation using species from the Southern Central Andes.

PubMed

Lindow-López, Lucía; Galíndez, Guadalupe; Sühring, Silvia; Pastrana-Ignes, Valeria; Gorostiague, Pablo; Gutiérrez, Angela; Ortega-Baes, Pablo

2018-06-22

There is controversy over whether cactus species form soil seed banks. Although it is commonly assumed that cacti do not form seed banks, very few studies have evaluated them. In this work, we analyzed whether cactus species form soil seed banks, studying seed distribution, seed density and seed longevity in the Southern Central Andes. Soil samples were collected in two microhabitats (under nurse plants and in bare areas) at 12 selected sites. We determined seed presence-absence, density and distribution for 32 native cactus species. Seed longevity for six of these species was determined through a burial experiment. We recorded viable seeds for 62.5% of the 32 evaluated species, finding variation in seed density between microenvironments and among populations. In some species, the greatest seed density was found under potential nurse plants. Seed germination and seed viability decreased with burial time, with seed longevity always being less than 24 months after burial. Our results show strong evidence that cactus species do form seed banks. Seed density can vary between microenvironments and among populations, suggesting that cactus-nurse plant associations can also be explained by differential seed dispersal and not only by differential establishment. We found that Echinopsis and Gymnocalycium species form short-term seed banks. Our results will help to better understand the population dynamics of cactus species, a focal species group for conservation actions because many of them are threatened by human activities. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

The first ANDES elements: 9-DOF plate bending triangles

NASA Technical Reports Server (NTRS)

Militello, Carmelo; Felippa, Carlos A.

1991-01-01

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

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

PubMed

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

2001-01-01

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

Numerical investigations with WRF about atmospheric features leading to heavy precipitation and flood events over the Central Andes' complex topography

NASA Astrophysics Data System (ADS)

Zamuriano, Marcelo; Brönnimann, Stefan

2017-04-01

It's known that some extremes such as heavy rainfalls, flood events, heatwaves and droughts depend largely on the atmospheric circulation and local features. Bolivia is no exception and while the large scale dynamics over the Amazon has been largely investigated, the local features driven by the Andes Cordillera and the Altiplano is still poorly documented. New insights on the regional atmospheric dynamics preceding heavy precipitation and flood events over the complex topography of the Andes-Amazon interface are added through numerical investigations of several case events: flash flood episodes over La Paz city and the extreme 2014 flood in south-western Amazon basin. Large scale atmospheric water transport is dynamically downscaled in order to take into account the complex topography forcing and local features as modulators of these events. For this purpose, a series of high resolution numerical experiments with the WRF-ARW model is conducted using various global datasets and parameterizations. While several mechanisms have been suggested to explain the dynamics of these episodes, they have not been tested yet through numerical modelling experiments. The simulations captures realistically the local water transport and the terrain influence over atmospheric circulation, even though the precipitation intensity is in general unrealistic. Nevertheless, the results show that Dynamical Downscaling over the tropical Andes' complex terrain provides useful meteorological data for a variety of studies and contributes to a better understanding of physical processes involved in the configuration of these events.

Unexpected climatological behavior of MLT gravity wave momentum flux in the lee of the Southern Andes hot spot

NASA Astrophysics Data System (ADS)

de Wit, R. J.; Janches, D.; Fritts, D. C.; Stockwell, R. G.; Coy, L.

2017-01-01

The Southern Argentina Agile MEteor Radar (SAAMER), located at Tierra del Fuego (53.7°S, 67.7°W), has been providing near-continuous high-resolution measurements of winds and high-frequency gravity wave (GW) momentum fluxes of the mesopause region since May 2008. As SAAMER is located in the lee of the largest seasonal GW hot spot on Earth, this is a key location to study GWs and their interaction with large-scale motions. GW momentum flux climatologies are shown for the first time for this location and discussed in light of these unique dynamics. Particularly, the large eastward GW momentum fluxes during local winter are surprising, as these observations cannot be explained by the direct upward propagation of expected large-amplitude mountain waves (MWs) through the eastward stratospheric jet. Instead, these results are interpreted as secondary GWs propagating away from stratospheric sources over the Andes accompanying MW breaking over the Southern Andes.

Unexpected Climatological Behavior of MLT Gravity Wave Momentum Flux in the Lee of the Southern Andes Hot Spot

NASA Technical Reports Server (NTRS)

DeWit, R. J.; Janches, D.; Fritts, D. C.; Stockwell, R. G.; Coy, L.

2017-01-01

The Southern Argentina Agile MEteor Radar (SAAMER), located at Tierra del Fuego (53.7degS, 67.7degW), has been providing near-continuous high-resolution measurements of winds and high-frequency gravity wave (GW) momentum fluxes of the mesopause region since May 2008. As SAAMER is located in the lee of the largest seasonal GW hot spot on Earth, this is a key location to study GWs and their interaction with large-scale motions. GW momentum flux climatologies are shown for the first time for this location and discussed in light of these unique dynamics. Particularly, the large eastward GW momentum fluxes during local winter are surprising, as these observations cannot be explained by the direct upward propagation of expected large-amplitude mountain waves (MWs) through the eastward stratospheric jet. Instead, these results are interpreted as secondary GWs propagating away from stratospheric sources over the Andes accompanying MW breaking over the Southern Andes.

Epidemiology of Echinococcus granulosus infection in the central Peruvian Andes.

PubMed Central

Moro, P. L.; McDonald, J.; Gilman, R. H.; Silva, B.; Verastegui, M.; Malqui, V.; Lescano, G.; Falcon, N.; Montes, G.; Bazalar, H.

1997-01-01

The prevalence of human, canine, and ovine echinococcosis was determined in an endemic area of the Peruvian Andes where control programmes have not been operational since 1980. Prevalence of infection in humans was determined using portable ultrasound, chest X-rays, and an enzyme-linked immunoelectrotransfer blot (EITB) assay. Canine and ovine echinococcal prevalence was determined by microscopic stool examinations following arecoline purging for tapeworm detection and by examination of the viscera from slaughtered livestock animals, respectively. The prevalence among 407 humans surveyed was 9.1%. The frequency of disease in the liver, lung, and in both organs was 3.4%, 2.0%, and 0.2%, respectively. Portable ultrasound or portable chest X-ray has shown that, compared to adults, children under 11 years had significantly higher seropositive rates without evidence of hydatid disease (P < 0.05). Among the 104 dogs inspected for echinococcus after arecoline purging, 33 (32%) were positive for adult tapeworms. Among the 117 sheep slaughtered at the local abattoir, 102 (87%) had hydatid cysts. The prevalence of human hydatidosis in this endemic area of Peru is one of the highest in the world and nearly five times higher than previously reported in 1980. An increase in echinococcosis prevalence may result after premature cessation of control programmes. PMID:9509628

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

NASA Astrophysics Data System (ADS)

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 <75 µm fraction, and the clay fraction was removed by repeated pipette withdrawal. The <75 µm fraction contains abundant euhedral grains of calcite that are not abraded or corroded, thus reflecting their authigenic origin in Laguna Yuraicocha. The 18O and 13C stratigraphy reveals decadal, century, and millennial-scale variability that is comparable to isotope records from other carbonate lakes and ice cores in the region. The 18O and 13C records generally covary with similar amplitudes; δ13C ranges from -0.5 to 3.5 ‰ (PDB). A pronounced linear trend of δ18O depletion (from -10.5 to -14.5 ‰) spans the length of record and likely reflects a progressive increase in hydrologic balance (i.e., the ratio of precipitation/evaporation) through the middle and late Holocene. This interpretation is consistent with basal core sediment that records pronounced lake low stands, and possible periodic dessication in the early-middle Holocene. The last 1200 yr of record reveals a 2‰ depletion culminating with the most depleted isotopes on record ~ AD 1800 followed by an abrupt 1.5 ‰ enrichment that began ~AD 1900 and continues to the present. These trends match closely the 18O record from the

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Ethnobotany of the Sierra Nevada del Cocuy-Güicán: climate change and conservation strategies in the Colombian Andes.

PubMed

Rodríguez, Mireia Alcántara; Angueyra, Andrea; Cleef, Antoine M; Van Andel, Tinde

2018-05-05

The Sierra Nevada del Cocuy-Güicán in the Colombian Andes is protected as a National Natural Park since 1977 because of its fragile páramo ecosystems, extraordinary biodiversity, high plant endemism, and function as water reservoir. The vegetation on this mountain is threatened by expanding agriculture, deforestation, tourism, and climate change. We present an ethnobotanical inventory among local farmer communities and discuss the effects of vegetation change on the availability of useful plants. We used 76 semi-structured, 4 in-depth interviews, and 247 botanical collections to record the ethnoflora of the farmers and surveyed from the high Andean forest to the super-páramo, including native and introduced species. We organized 3 participative workshops with local children, high school students, and campesinos' women to share the data we acquired in the field and empower local plant conservation awareness. We encountered 174 useful plants, most of them native to the area (68%) and almost one third introduced (32%). The Compositae was the most species-rich family, followed by Lamiaceae, Poaceae, and Rosaceae. The majority of plant species were used as medicine, followed by food, firewood, and domestic tools. Local farmers reported declining numbers of páramo species, which were now only found at higher altitudes than before. Although our informants were worried about the preservation of their natural resources and noticed the effects of climate change, for several commercial species, unsustainable land use and overharvesting seemed to be the direct cause of declining medicinal plant resources rather than climate change. We recommend conservation plans that include vegetation monitoring, people's perceptions on climate change, and participative actions with the communities of the Sierra Nevada del Cocuy-Güicán.

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

NASA Technical Reports Server (NTRS)

Bloom, Arthur L.; Fielding, Eric J.

1986-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

extension is documented in the Central Cordillera of Colombia and Ecuador between 240 Ma and 215 Ma, although extension at this time has not been clearly identified in the Mérida Andes or the Santander Massif. Permian to Triassic cooling is not recorded in the structurally isolated Caparo Block in the southern Mérida Andes, suggesting that it may have constituted a distinct fault block in the Triassic. New fission track data from the Santander Massif suggest that it started exhuming at 40 Ma during a period of accelerated convergence between the Nazca/Farallòn Plate and the western margin of South America. Exhumation in the Santander Massif occurred diachronously since 18 Ma in distinct fault blocks at rates of 0.5-1 km/Ma, and may have been driven by east-west compression as a result of the indentation of the Panama-Chocó terrane to western Colombia.

Structural control on volcanoes and magma paths from local- to orogen-scale: The central Andes case

NASA Astrophysics Data System (ADS)

Tibaldi, A.; Bonali, F. L.; Corazzato, C.

2017-03-01

Assessing the parameters that control the location and geometry of magma paths is of paramount importance for the comprehension of volcanic plumbing systems and geo-hazards. We analyse the distribution of 1518 monogenic and polygenic volcanoes of Miocene-Quaternary age of the Central Volcanic Zone of the Andes (Chile-Bolivia-Argentina), and reconstruct the magma paths at 315 edifices by analysing the morphostructural characteristics of craters and cones. Then we compare these data with outcropping dykes, tectonic structures and state of stress. Most magma paths trend N-S, NW-SE, and NE-SW, in decreasing order of frequency. The N-S and NW-SE paths coexist in the northern and southern part of the study area, whereas N-S paths dominate east of the Salar de Atacama. Outcropping dykes show the same trends. The regional Holocene stress state is given by an E-W greatest horizontal principal stress. N-S and NNE-SSW reverse faults and folds affect deposits of 4.8, 3.2 and 1.3 Ma BP, especially in the central and southern study areas. A few NW-SE left-lateral strike-slip faults are present in the interior of the volcanic arc, part of which belong to the Calama-Olacapato-El Toro fault. The volcanic chain is also affected by several N-S- and NW-SE-striking normal faults that offset Pliocene and Quaternary deposits. The results indicate different scenarios of magma-tectonic interaction, given by N-S normal and reverse faults and N-S fold hinges that guide volcano emplacement and magma paths. Magma paths are also guided by strike-slip and normal NW-SE faults, especially in the northern part of the study area. Zones with verticalized strata, with bedding striking NE-SW, also acted as preferential magma paths. These data suggest that at convergence zones with continental crust, shallow magma paths can be more sensitive to the presence and geometry of upper crustal weakness zones than to the regional state of stress.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

SRTM Colored Height and Shaded Relief: Laguna Mellquina, Andes Mountains, Argentina

NASA Image and Video Library

2001-06-14

This depiction of an area south of San Martin de Los Andes, Argentina, is the first Shuttle Radar Topography Mission SRTM view of the Andes Mountains, the tallest mountain chain in the western hemisphere.

Water and sediment quality of the Lake Andes and Choteau Creek basins, South Dakota, 1983-2000

USGS Publications Warehouse

Sando, Steven Kent; Neitzert, Kathleen M.

2003-01-01

The Bureau of Reclamation has proposed construction of the Lake Andes/Wagner Irrigation Demonstration Project to investigate environmental effects of irrigation of glacial till soils substantially derived from marine shales. During 1983-2000, the U.S. Geological Survey collected hydrologic, water-quality, and sediment data in the Lake Andes and Choteau Creek Basins, and on the Missouri River upstream and downstream from Choteau Creek, to provide baseline information in support of the proposed demonstration project. Lake Andes has a drainage area of about 230 mi2 (square miles). Tributaries to Lake Andes are ephemeral. Water-level fluctuations in Lake Andes can be large, and the lake has been completely dry on several occasions. The outlet aqueduct from Lake Andes feeds into Garden Creek, which enters Lake Francis Case just upstream from Fort Randall Dam on the Missouri River. For Lake Andes tributary stations, calcium, magnesium, and sodium are approximately codominant among the cations, and sulfate is the dominant anion. Dissolved-solids concentrations typically range from about 1,000 mg/L (milligrams per liter) to about 1,700 mg/L. Major-ion concentrations for Lake Andes tend to be higher than the tributaries and generally increase downstream in Lake Andes. Proportions of major ions are similar among the different lake units (with the exception of Owens Bay), with calcium, magnesium, and sodium being approximately codominant among cations, and sulfate being the dominant anion. Owens Bay is characterized by a calcium sulfate water type. Dissolved-solids concentrations for Lake Andes typically range from about 1,400 to 2,000 mg/L. Whole-water nitrogen and phosphorus concentrations are similar among the Lake Andes tributaries, with median whole-water nitrogen concentrations ranging from about 1.6 to 2.4 mg/L, and median whole-water phosphorus concentrations ranging from about 0.5 to 0.7 mg/L. Whole-water nitrogen concentrations in Lake Andes are similar among the

Geomorphic consequences of two large glacier and rock glacier destabilizations in the Central and northern Chilean Andes

NASA Astrophysics Data System (ADS)

Iribarren Anacona, Pablo; Bodin, Xavier

2010-05-01

Mountain areas are occasionaly affected by complex mass movements of high magnitude and large extent, which generally involve water, snow, rock and ice in variable proportions. Those events can take the form of rock avalanche, landslide, debris flow, glacier collapse or a combination of these phenomenons. In the Central Andes of Chile, they affect hardly accessible regions with low population, explaining the scarcity of previous studies. Nevertheless, during the last 30 years, some documented examples of such events in this region have shown that the volume of material involved is in the order of several millions of m³, the areas affected can reach several tenth of km² and the velocity of the movement can exceed several tenths of m/s. In this context, this study intends i) to inventory and to describe the main characteristics of events previously documented in the Central Andes of Chile, and ii) analyse in detail two recent events (2005-2007) never described before which have affected in one case a glacier and in another case a rock glacier. With the objectives of determining the possible chain of triggering factors and interpreting the event's significance in terms of geomorphic, cryogenic and climatic dynamics, we used air photographs, satellite imagery (Landsat TM & ETM+; Quick Bird when available in Google Earth 5.0), data from the closest meteorological stations, glacier mass balance data and seismic records to investigate the collapse of a rock glacier occurred in 2006 on the west-facing flank of the Cerro Las Tórtolas (6160 m asl; 29°58' S. - 69°55' W.), in the arid North of Chile, and the collapse of a glacier that occurred during austral summer 2006-2007 on the South side of the Tinguiririca Volcano (4075 m asl; 34°48' S. - 70°21' W.). The rock glacier collapse of the Cerro Las Tórtolas West flank occurred during the spring of 2006, but signs of destabilization were already observable since the end of 2005. The deposit of the collapsed mass of the

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

NASA Astrophysics Data System (ADS)

Noury, Mélanie; Bernet, Matthias; Sempéré, Thierry

2014-05-01

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

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

NASA Astrophysics Data System (ADS)

Pritchard, M. E.; Simons, M.

2004-02-01

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

Quantifying sediment dynamics on alluvial fans, Iglesia basin, south Central Argentine Andes

NASA Astrophysics Data System (ADS)

Harries, Rebekah; Kirstein, Linda; Whittaker, Alex; Attal, Mikael; Peralta, Silvio

2017-04-01

Qualitative interpretations of environmental change drawn from alluvial fan stratigraphy typically tie the deposition of greater volumes of coarser sediment to wetter climatic periods. For example, step changes in sediment flux and discharge associated with glacial-interglacial cycles are often linked to the progradation and back stepping of a fan's toe (Harvey et al, 2002). Indeed, more recent quantitative stratigraphic models demonstrate changes in the volume and calibre of sediment fluxed from an uplifted catchment can produce predictable shifts in the rate at which fluvial deposits fine downstream (Duller et al. 2010, Armitage et al. 2011). These interpretations, however, make three important assumptions: 1) the volume and calibre of the sediment transferred from an eroding mountain belt to a depositional basin is directly related to climate through some value of time-averaged discharge or catchment wetness; 2) lateral sources of sediment, such as tributaries, do not significantly influence the pattern of deposition in a basin and, similarly, 3) the reworking of older fan surfaces is minimal and does not impact the depositional pattern of younger deposits. Here we demonstrate each of these assumptions underestimates the importance of variance in transportable grain sizes in influencing the local and basin-wide deposited grain size trends. Using the Iglesia basin in the Argentine south Central Andes as a natural laboratory, we compare three large, adjacent, alluvial fan systems whose catchments experience the same background tectonic and climatic forcing. We find regional climate forcing is not expressed uniformly in the downstream grain size fining rates of their modern systems. Furthermore, we observe the variance in transportable grain sizes supplied from each primary catchment and the variance of material introduced by tributaries and fan surfaces downstream can act as first order controls on the rate of downstream fining. We also raise the importance of

The Structure of the Crust and Uppermost Mantle Beneath the Central Andes from Ambient Noise Tomography: Imaging the Neogene to Modern Batholith

NASA Astrophysics Data System (ADS)

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

2012-12-01

The Central Andes of southern Peru, Bolivia, and northern Chile (between ~10°S and ~35°S) comprise the largest orogenic plateau in the world associated with abundant arc volcanism, the Central Andean Plateau (CAP). The goal of this continental-scale Ambient Noise Tomography (ANT) project is to incorporate broadband seismic data from ~20 seismic networks deployed incrementally in the Central and Southern Andes from May 1994 through March 2012, to image the vertically polarized shear-wave velocity (Vsv) structure of the CAP. First-order correlations with our shallow results (~5 km) and the morphotectonic provinces as well as subtler geological features indicate our results are robust. Our major results include mapping a pervasive mid-crustal low-velocity zone (<3.25 km/s) underneath the western portion of the CAP and a locally ultra-low-velocity anomaly (~2.0 km/s) beneath the Altiplano-Puna Volcanic Complex (APVC). The presence of a large and laterality extensive low-velocity zone suggests either a zone of partial melt ("mush") associated with batholith formation at depth, a thermally weakened crust capable of lateral flow, or the presence of aqueous fluids. Magnetotelluric studies that overlap our images do not resolve a high conductivity anomaly across our low-velocity zone as expected in the presence of aqueous fluids or large interconnected zones of partial melt. Therefore, we dismiss them as likely explanations for our imaged low-velocity body outside of the APVC location. Working under the hypothesis that voluminous ignimbrites are the surface expression of batholith formation at depth as exemplified by the APVC, we combine our results with the locations of known Neogene ignimbrite eruptive centers and negative isostatic residual gravity anomalies and suggest the 3.25 km/s shear-wave velocity contour at 15 km depth generally outlines the extent of a Neogene to modern batholith, with isolated pockets of partial melt where velocities dip below 3.0 km/s. A

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

PubMed

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

2000-09-01

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

Diversification of clearwing butterflies with the rise of the Andes.

PubMed

De-Silva, Donna Lisa; Elias, Marianne; Willmott, Keith; Mallet, James; Day, Julia J

2016-01-01

Despite the greatest butterfly diversity on Earth occurring in the Neotropical Andes and Amazonia, there is still keen debate about the origins of this exceptional biota. A densely sampled calibrated phylogeny for a widespread butterfly subtribe, Oleriina (Nymphalidae: Ithomiini) was used to estimate the origin, colonization history and diversification of this species-rich group. Neotropics. Ancestral elevation and biogeographical ranges were reconstructed using data generated from detailed range maps and applying the dispersal-extinction-cladogenesis model using stratified palaeogeographical time slice matrices. The pattern of diversification through time was examined by comparing constant and variable rate models. We also tested the hypothesis that a change in elevation is associated with speciation. The Oleriina likely originated in the Andes in the Early to Middle Miocene and rapidly diversified to include four genera all of which also originated in the Andes. These clades, together with four species groups, experienced varying spatial and temporal patterns of diversification. An overall early burst and decreasing diversification rate is identified, and this pattern is reflected for most subclades. Changes in the palaeogeological landscape, particularly the prolonged uplift of the Andes, had a profound impact on the diversification of the subtribe. The Oleriina mostly remained within the Andes and vicariant speciation resulted in some instances. Dynamic dispersal occurred with the disappearance of geological barriers such as the Acre System and the subtribe exploited newly available habitats. Our results confirm the role of the Andean uplift in the evolution of Neotropical biodiversity.

Seismicity and active tectonics of the Andes and the origin of the Altiplano

NASA Technical Reports Server (NTRS)

Molnar, P.

1982-01-01

Large earthquakes and active deformation on the Andes were studied. Earthquakes on the east side of the Andes were generally found to reflect east-west crustal shortening. These earthquakes seem to occur throughout the crust and do not reflect a detachment and low angle thrusting of the sedimentary cover onto the Brazilian shield. Instead they imply deformation of the basement. The rate of shortening is compatible with construction of the Andes by crustal shortening since the late Cretaceous, and the surface geology, at least qualitatively, is considered to reflect this process. Andean margins are considered to be a result of crustal shortening. The crustal shortening in the sub-Andes occurs concurrently with normal faulting at high elevations in parts of the Andes. The normal faulting is associated with the buoyancy of the thick crust. Crustal shortening thickens the crust and work is done against gravity. When the crustal thickness and elevation reach limiting values, the range grows laterally by further thrusting on the margins.

Climate Variability and Surface Processes in Tectonically Active Orogens: Insights From the Southern Central Andes and the Northwest Himalaya

NASA Astrophysics Data System (ADS)

Strecker, M. R.; Bookhagen, B.

2008-12-01

The Southern Central Andes of NW Argentina and the NW Himalaya are important orographic barriers that intercept moisture-bearing winds associated with monsoonal circulation. Changes in both atmospheric circulation systems on decadal to millennial timescales fundamentally influence differences in the amount and location of rainfall in both orogens. In India, the eastern arm of the monsoonal circulation draws moisture from the Bay of Bengal and transports humid air masses along the southern Himalayan front to the northwest. There, at the end of the monsoonal conveyer belt, rainfall is diminished and moisture typically does not reach far into the orogen interior. Similar conditions apply to the NW Argentine Andes, which are located within the precipitation regime of the South American Monsoon. Here, pronounced local relief blocks humid air masses from the Amazon region, resulting in extreme gradients in rainfall that leave the orogen interior dry. However, during negative ENSO years (La Niña) and intensified Indian Summer Monsoon years, moisture penetrates farther into the Andean and Himalayan orogens, respectively. Structurally pre- conditioned valley systems may enhance this process and funnel moisture far into the orogen interior. The greater availability of moisture increases runoff, lateral scouring of mountin streams, and ultimately triggers intensified hillslope processes on decadal to centennial timescales. In both environments, the scenario of intensified present-day surface processes and rates is analogous to protracted episodes of enhanced mass removal from hillslopes via deep-seated landslides during the early Holocene and late Pleistocene. Apparently, these episodes were also associated with transient storage of voluminous conglomerates and lacustrine deposits in narrow intermontane basins. Subsequently, these deposits were incised, partly removed, and the fluvial systems adjusted themselves to the pre-depositional base levels through a readjustment and

Receiver Function Study of the Crustal Structure Beneath the Northern Andes (colombia)

NASA Astrophysics Data System (ADS)

Poveda, E.; Monsalve, G.; Vargas-Jimenez, C. A.

2013-05-01

We have investigated crustal thickness beneath the Northern Andes with the teleseismic receiver function technique. We used teleseismic data recorded by an array of 18 broadband stations deployed by the Colombian Seismological Network, and operated by the Colombian Geological Survey. We used the primary P-to-S conversion and crustal reverberations to estimate crustal thickness and average Vp/Vs ratio; using Wadati diagrams, we also calculated the mean crustal Vp/Vs ratio around stations to further constrain the crustal thickness estimation. In northern Colombia, near the Caribbean coast, the estimated crustal thickness ranges from 25 to 30 km; in the Middle Magdalena Valley, crustal thickness is around 40 km; beneath the northern Central Cordillera, the Moho depth is nearly 40 km; at the Ecuador-Colombia border, beneath the western flank of the Andes, the estimated thickness is about 46 km. Receiver functions at a station at the craton in South East Colombia, near the foothills of the Eastern Cordillera, clearly indicate the presence of the Moho discontinuity at a depth near 36 km. The greatest values of crustal thickness occur beneath a plateau (Altiplano Cundiboyacense) on the Eastern Cordillera, near the location of Bogota, with values around 58 km. Receiver functions in the volcanic areas of the south-western Colombian Andes do not show a systematic signal from the Moho, indicating abrupt changes in Moho geometry. Signals at stations on the Eastern Cordillera near Bogota reveal a highly complex crustal structure, with a combination of sedimentary layers up to 9 km thick, dipping interfaces, low velocity layers, anisotropy and/or lateral heterogeneity that still remain to be evaluated. This complexity obeys to the location of these stations at a region of a highly deformed fold and thrust belt.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Southern rim of Pacific Ocean basin: southern Andes to southern Alps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalziel, I.W.D.; Garrett, S.W.; Grunow, A.M.

1986-07-01

Between the southern Andes of Tierra del Fuego and the southern Alps of New Zealand lies the least accessible and geologically least explored part of the Pacific Ocean basin. A joint United Kingdom-United States project was initiated in 1983 to elucidate the geologic history and structure of the Pacific margin of Antarctica from the Antarctic Peninsula to Pine Island Bay at approximately lone. 105/sup 0/W. The first season (1983-1984) of this West Antarctic Tectonics Project was spent in the Ellsworth-Whitmore crustal block, and the second (1984-1985) in the Thurston Island crustal block. The project involves structural and general field geology,more » petrology, geochemistry, paleomagnetism, and airborne geophysics (magnetics and radar ice echo sounding). A final geologic season will be spent in the Pensacola Mountains of the Transantarctic Range in 1987-1988.« less

Antibody to HTLV‐I in Indigenous Inhabitants of the Andes and Amazon Regions in Colombia

PubMed Central

Zamora, Tomas; Zaninovic, Vladimir; Kajiwara, Masaharu; Komoda, Haruko; Hayami, Masanori

1990-01-01

To explore the HTLV‐I‐carrying groups among the indigenous inhabitants in South America, a sero‐epidemiological study on HTLV‐I focusing on hinterland villages isolated from others in the Andes and Amazon regions was conducted. Five (2.9%) out of 171 subjects showed positive for HTLV‐I antibody in the gelatin particle agglutination (PA) test. Two out of 5 positives with high antibody titer (≫× 1024) in the PA test also showed a positive immunofluorescence (IF) test and anti‐HTLV‐I‐specific protein products, p19, p24, p28, gp46, and p53 in sera by the Western blotting (WB) test. One of three negatives in the IF test showed positive antibodies to p19 and p24 by the WB test. Finally, two were confirmed as HTLV‐I carriers and one was suspected of being a carrier. All three are Paez Indians from the central Andes; 53‐ and 34‐year‐old women and a 35‐year‐old man. The results show that HTLV‐1 carriers exist among isolated indigenous people in South America. PMID:1975804

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

USGS Publications Warehouse

Futa, K.; Stern, C.R.

1988-01-01

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

SRTM Perspective of Colored Height and Shaded Relief Laguna Mellquina, Andes Mountains, Argentina

NASA Image and Video Library

2001-06-22

This depiction of an area south of San Martin de Los Andes, Argentina, is the first Shuttle Radar Topography Mission SRTMview of the Andes Mountains, the tallest mountain chain in the western hemisphere.

Ubinas Volcano Activity in Peruvian Andes

NASA Image and Video Library

2014-05-01

On April 28, 2014, NASA Terra spacecraft spotted signs of activity at Ubinas volcano in the Peruvian Andes. The appearance of a new lava dome in March 2014 and frequent ash emissions are signs of increasing activity at this volcano.

Charles Darwin in the Andes

ERIC Educational Resources Information Center

Bizzo, Nelio; Bizzo, Luis Eduardo Maestrelli

2006-01-01

Considering geological time as an important epistemological obstacle to the construction of ideas on biological evolution, a study was carried out on the so-called "Darwin Papers". The conclusion was that Charles Darwin's excursion in the Andes during March-April 1835 was a crucial step in this regard. An expedition was carried out in…

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Tectonic deformation of the Andes and the configuration of the subducted slab in central Peru: Results from a micro-seismic experiment

NASA Technical Reports Server (NTRS)

Suarez, G.; Gagnepain, J. J.; Cisternas, A.; Hatzfeld, D.; Molnar, P.; Ocola, L.; Roecker, S. W.; Viode, J. P.

1983-01-01

The vast majority of the microearthquakes recorded occurred to the east: on the Huaytapallana fault in the Eastern Cordillera or in the western margin of the sub-Andes. The sub-Andes appear to be the physiographic province subjected to the most intense seismic deformation. Focal depths for the crustal events here are as deep as 50 km, and the fault plane solutions, show thrust faulting on steep planes oriented roughly north-south. The Huaytapallana fault in the Cordillera Oriental also shows relatively high seismicity along a northeast-southwest trend that agrees with the fault scarp and the east dipping nodal plane of two large earthquakes that occurred on this fault in 1969. The recorded microearthquakes of intermediate depth show a flat seismic zone about 25 km thick at a depth of about 100 km. This agrees with the suggestion that beneath Peru the slab first dips at an angle of 30 deg to a depth of 100 km and then flattens following a quasi-horizontal trajectory. Fault plane solutions of intermediate depth microearthquakes have horizontal T axes oriented east-west.

Glaciological studies in the central Andes using AIRSAR/TOPSAR

NASA Technical Reports Server (NTRS)

Forster, Richard R.; Klein, Andrew G.; Blodgett, Troy A.; Isacks, Bryan L.

1993-01-01

The interaction of climate and topography in mountainous regions is dramatically expressed in the spatial distribution of glaciers and snowcover. Monitoring existing alpine glaciers and snow extent provides insight into the present mountain climate system and how it is changing, while mapping the positions of former glaciers as recorded in landforms such as cirques and moraines provide a record of the large past climate change associated with the last glacial maximum. The Andes are an ideal mountain range in which to study the response of snow and ice to past and present climate change. Their expansive latitudinal extent offers the opportunity to study glaciers in diverse climate settings from the tropical glaciers of Peru and Bolivia to the ice caps and tide-water glaciers of sub-polar Patagonia. SAR has advantages over traditional passive remote sensing instruments for monitoring present snow and ice and differentiating moraine relative ages. The cloud penetrating ability of SAR is indispensable for perennially cloud covered mountains. Snow and ice facies can be distinguished from SAR's response to surface roughness, liquid water content and grain size distribution. The combination of SAR with a coregestered high-resolution DEM (TOPSAR) provides a promising tool for measuring glacier change in three dimensions, thus allowing ice volume change to be measured directly. The change in moraine surface roughness over time enables SAR to differentiate older from younger moraines. Polarimetric SAR data have been used to distinguish snow and ice facies and relatively date moraines. However, both algorithms are still experimental and require ground truth verification. We plan to extend the SAR classification of snow and ice facies and moraine age beyond the ground truth sites to throughout the Cordillera Real to provide a regional view of past and present snow and ice. The high resolution DEM will enhance the SAR moraine dating technique by discriminating relative ages

Convective initiation in the vicinity of the subtropical Andes

NASA Astrophysics Data System (ADS)

Rasmussen, K. L.; Houze, R.

2014-12-01

Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. An investigation of the most intense storms for 11 years of TRMM Precipitation Radar (PR) data shows a tendency for squall lines to initiate and develop in this region with the canonical leading convective line/trailing stratiform structure. The synoptic environment and structures of the extreme convection and MCSs in subtropical South America are similar to those found in other regions of the world, especially the United States. In subtropical South America, however, the topographical influence on the convective initiation and maintenance of the MCSs is unique. A capping inversion in the lee of the Andes is important in preventing premature triggering. The Andes and other mountainous terrain of Argentina focus deep convective initiation in a narrow region. Subsequent to initiation, the convection often evolves into propagating mesoscale convective systems similar to those seen over the Great Plains of the U. S. and produces damaging tornadoes, hail, and floods across a wide agricultural region. Numerical simulations conducted with the NCAR Weather Research and Forecasting (WRF) Model extend the observational analysis and provide an objective evaluation of storm initiation, terrain effects, and development mechanisms. The simulated mesoscale systems closely resemble the storm structures seen by the TRMM Precipitation Radar as well as the overall shape and character of the storms shown in GOES satellite data. A sensitivity experiment with different configurations of topography, including both decreasing and increasing the height of the Andes Mountains, provides insight into the significant influence of orography in focusing convective initiation in this region. Lee cyclogenesis and a strong low-level jet are modulated by the height of the Andes Mountains and directly affect the character

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

PubMed

Barros, Agustina; Monz, Christopher; Pickering, Catherine

2015-03-01

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

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

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

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

PubMed

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

2011-11-01

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

Multiproxy Holocene paleoclimate records from the southern Peruvian Andes - what new can we learn from the stable carbon isotope composition of high altitude organic matter deposits?

NASA Astrophysics Data System (ADS)

Skrzypek, Grzegorz; Engel, Zbyněk

2015-04-01

Interpretation of the Central Andean paleoclimate over the last millennia still represents a research challenge demanding deeper studies [1,2]. Several high-resolution paleoclimate proxies for the last 10,000 years have been developed for the northern hemisphere. However, similar proxies are very limited for South America, particularly for high altitudes where, for example, tree-ring chronologies are not available and instrumental records are very limited. Consequently, our knowledge of high altitude climate changes in arid regions of the Peruvian Andes mainly relies on ice-core and lake deposit studies. In our study, we used a new alternative proxy for interpretation of palaeoclimate conditions based on a peat core taken from the Carhuasanta Valley at the foot of Nevado Mismi in the southern Peruvian Andes (15° 30'S, 71° 43'W, 4809m a.s.l.). The stable carbon isotope composition (δ13C) of Distichia peat reflects mainly the relative variation of the mean air temperature during subsequent growing seasons [3], and allows reconstructions of palaeotemperature changes. In contrast, peat organic carbon concentration (C % wt) records mainly wetness in the valley, directly corresponding to the changes in runoff in the upper part of the catchment. The most prominent climate changes recorded in the peat over last 4ka occurred between 3040 and 2750 cal. yrs BP. The initial warming turned to a very rapid cooling to temperatures at least 2° C lower than the mean for the Late Holocene. Initially drier conditions within this event turned to a short wet phase after 2780 cal. yrs BP, when the temperature increased again. This event coincides with significant changes in peat and ice core records in the Central Andes that match the timing of the global climate event around 2.8 cal. ka BP. Climatic conditions in the study area became relatively dry and stable after the event for about 800 years. Highly variable temperatures and humidity prevailed during the last 2000 years, when

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

NASA Astrophysics Data System (ADS)

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

2006-12-01

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

Deglaciation chronology in the Mérida Andes from cosmogenic 10Be dating, (Gavidia valley, Venezuela)

NASA Astrophysics Data System (ADS)

Angel, Isandra; Audemard M., Franck A.; Carcaillet, Julien; Carrillo, Eduardo; Beck, Christian; Audin, Laurence

2016-11-01

In the Mérida Andes, a detailed deglaciation history reconstruction is difficult to achieve due to scattered deglaciation chronologies available. This paper contributes with 24 exposure ages of glacial landforms sampled in the Gavidia valley. Exposure ages were obtained based on terrestrial cosmogenic nuclide 10Be dating. Results indicate deglaciation mainly occurred between ∼21 ka and 16.5 ka and the complete deglaciation occurred at ∼16.0 ka. The glacier retreated in two different phases. The oldest one occurred since the LGM until middle OtD or the local climate event El Caballo Stadial. The youngest phase occurred at ages younger than ∼16.5 ka until complete deglaciation. A combination of topographic features and changes in the paleoclimate conditions at the end of the El Caballo Stadial seems leaded the fastest former glacier extinction. The topographic feature which seems contributed to the fastest glacier extinction was the low valley bottom slopes. In addition, exposure ages of the Gavidia valley were integrated with deglaciation chronologies from the central Mérida Andes to compare deglaciation histories. Asynchronous deglaciation histories were observed. Local paleotemperatures and paleoprecipitations contrasts, different valleys aspects, insolation and catchments steepness could explain different deglaciation histories.

Andes Virus and First Case Report of Bermejo Virus Causing Fatal Pulmonary Syndrome

PubMed Central

Della Valle, Marcelo González; Alai, María Garcia; Cortada, Pedro; Villagra, Mario; Gianella, Alberto

2002-01-01

Two suspected hantavirus pulmonary syndrome (HPS) cases from Bolivia were confirmed by enzyme-linked immunosorbent assay. (ELISA)-ANDES was performed using N-Andes recombinant antigen serology in May and July 2000. Clot RNAs from the two patients were subjected to reverse transcription–polymerase chain reaction (PCR) amplification and sequencing. We describe two characterized cases of HPS. One was caused by infection with Bermejo virus and the other with Andes Nort viral lineage, both previously obtained from Oligoryzomys species. This is the first report of molecular identification of a human hantavirus associated with Bermejo virus. PMID:11971782

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

PubMed

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

1998-10-01

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

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)

NASA Astrophysics Data System (ADS)

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.

Races of Heliconius erato (Nymphalidae: Heliconiinae) found on different sides of the Andes show wing size differences

USDA-ARS?s Scientific Manuscript database

Differences in wing size in geographical races of Heliconius erato distributed over the western and eastern sides of the Andes are reported on here. Individuals from the eastern side of the Andes are statistically larger in size than the ones on the western side of the Andes. A statistical differenc...

Modeling potential distribution of Oligoryzomys longicaudatus, the Andes virus (Genus: Hantavirus) reservoir, in Argentina.

PubMed

Andreo, Verónica; Glass, Gregory; Shields, Timothy; Provensal, Cecilia; Polop, Jaime

2011-09-01

We constructed a model to predict the potential distribution of Oligoryzomys longicaudatus, the reservoir of Andes virus (Genus: Hantavirus), in Argentina. We developed an extensive database of occurrence records from published studies and our own surveys and compared two methods to model the probability of O. longicaudatus presence; logistic regression and MaxEnt algorithm. The environmental variables used were tree, grass and bare soil cover from MODIS imagery and, altitude and 19 bioclimatic variables from WorldClim database. The models performances were evaluated and compared both by threshold dependent and independent measures. The best models included tree and grass cover, mean diurnal temperature range, and precipitation of the warmest and coldest seasons. The potential distribution maps for O. longicaudatus predicted the highest occurrence probabilities along the Andes range, from 32°S and narrowing southwards. They also predicted high probabilities for the south-central area of Argentina, reaching the Atlantic coast. The Hantavirus Pulmonary Syndrome cases coincided with mean occurrence probabilities of 95 and 77% for logistic and MaxEnt models, respectively. HPS transmission zones in Argentine Patagonia matched the areas with the highest probability of presence. Therefore, colilargos presence probability may provide an approximate risk of transmission and act as an early tool to guide control and prevention plans.

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

Late Quaternary deglacial history of the Mérida Andes, Venezuela

NASA Astrophysics Data System (ADS)

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

2005-10-01

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

New host and lineage diversity of avian haemosporidia in the northern Andes

PubMed Central

Harrigan, Ryan J; Sedano, Raul; Chasar, Anthony C; Chaves, Jaime A; Nguyen, Jennifer T; Whitaker, Alexis; Smith, Thomas B

2014-01-01

The northern Andes, with their steep elevational and climate gradients, are home to an exceptional diversity of flora and fauna, particularly rich in avian species that have adapted to divergent ecological conditions. With this diversity comes the opportunity for parasites to exploit a wide breadth of avian hosts. However, little research has focused on examining the patterns of prevalence and lineage diversity of avian parasites in the Andes. Here, we screened a total of 428 birds from 19 species (representing nine families) and identified 133 infections of avian haemosporidia (31%), including lineages of Plasmodium, Haemoproteus, and Leucocytozoon. We document a higher prevalence of haemosporidia at higher elevations and lower temperatures, as well as an overall high diversity of lineages in the northern Andes, including the first sequences of haemosporidians reported in hummingbirds (31 sequences found in 11 species within the family Trochilidae). Double infections were distinguished using PHASE, which enables the separation of distinct parasite lineages. Results suggest that the ecological heterogeneity of the northern Andes that has given rise to a rich diversity of avian hosts may also be particularly conducive to parasite diversification and specialization. PMID:25469161

New fission-track age constraints on the exhumation of the central Santander Massif: Implications for the tectonic evolution of the Northern Andes, Colombia

NASA Astrophysics Data System (ADS)

Amaya, Sergio; Zuluaga, Carlos Augusto; Bernet, Matthias

2017-06-01

The Late Cretaceous to late Neogene exhumation history of the central Santander Massif in the Northern Andes of Colombia is controlled by the geodynamic interactions between the Caribbean, South American and Nazca plates, as well as the Neogene collision and accretion of the Panama arc. Slab-breakoff of the Caribbean plate, with the tip of the slab tear presently being located beneath Bucaramanga, and the east-west oriented Caldas tear are the main structures relating seismic activity and Late Miocene to Pleistocene magmatic/hydrothermal activity and associated gold mineralization in the central Santander Massif. Here we present new apatite (AFT) and zircon fission-track (ZFT) data from 18 samples collected along two profiles in the California-Vetas block (including the Rio Charta), to the south of the Rio Charta fault, and from Bucaramanga to Picacho on the western flank of the central Santander Massif. The fission-track data are used for time-temperature history modelling and for estimating long-term average exhumation rates. The California-Vetas block in the central Santander Massif to the north of the Rio Charta fault cooled rapidly at a rate of about 24 °C/Myr between 10 and 5 Ma. Fast cooling was not related to post-magmatic cooling or hydrothermal activity, but rather to exhumation, with rates based on apatite fission-track cooling ages on the order of 0.3-0.4 km/Myr. However, long-term average exhumation rates since the Late Cretaceous, based on zircon fission-track data, were only on the order of 0.1-0.2 km/Myr. Our data indicate that next to the Rio Charta fault also the Surata fault contributed to the exhumation of the California-Vetas block. The western flank of the central Santander Massif, shows a more complete thermal history along the Bucaramanga-Picacho profile, with the exposure of an exhumed zircon fission-track partial annealing zone. Thermal history modelling of zircon fission-track data of this profile shows that after burial and heating from

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

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

NASA Astrophysics Data System (ADS)

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

2010-03-01

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

First GPS baseline results from the North Andes

NASA Technical Reports Server (NTRS)

Kellogg, James N.; Freymueller, Jeffrey T.; Dixon, Timothy H.; Neilan, Ruth E.; Ropain, Clemente

1990-01-01

The CASA Uno GPS experiment (January-February 1988) has provided the first epoch baseline measurements for the study of plate motions and crustal deformation in and around the North Andes. Two dimensional horizontal baseline repeatabilities are as good as 5 parts in 10 to the 8th for short baselines (100-1000 km), and better than 3 parts in 10 to the 8th for long baselines (greater than 1000 km). Vertical repeatabilities are typically 4-6 cm, with a weak dependence on baseline length. The expected rate of plate convergence across the Colombia Trench is 6-8cm/yr, which should be detectable by the repeat experiment planned for 1991. Expected deformation rates within the North Andes are of the order of 1 cm/yr, which may be detectable with the 1991 experiment.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

del Maule and Cordón Caulle (which began a major eruption in June, 2011). The deformation rate at Laguna del Maule continues through 2011 at a similar high rate, accumulating more than 60 cm of vertical deformation since 2007 -- making it one of the largest deformation signals without recent eruption yet observed. The rate of uplift at Laguna del Maule seems to be unchanged before and after the 2010 Maule earthquake. The spatial and temporal deformation at Cordón Caulle is complex as noted by Fournier et al., 2010, but does not appear to have been changed by the Maule earthquake either. The reasons that the 2010 Maule earthquake did not strongly affect the closest volcanic arc in the southern Andes remains a mystery. Comparison with the 2004 Sumatra (Mw 9.2) and the 2011 Japan (Mw 9.0) earthquakes and their closest volcanic arcs could provide clues to the elusive links between large earthquakes and volcanic unrest.

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

NASA Astrophysics Data System (ADS)

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

2006-12-01

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

Regional climate of the Subtropical Central Andes using high-resolution CMIP5 models. Part II: future projections for the twenty-first century

NASA Astrophysics Data System (ADS)

Zazulie, Natalia; Rusticucci, Matilde; Raga, Graciela B.

2017-12-01

In Part I of our study (Zazulie et al. Clim Dyn, 2017, hereafter Z17) we analyzed the ability of a subset of fifteen high-resolution global climate models (GCMs) from the Coupled Model Intercomparison Project phase 5 to reproduce the past climate of the Subtropical Central Andes (SCA) of Argentina and Chile. A subset of only five GCMs was shown to reproduce well the past climate (1980-2005), for austral summer and winter. In this study we analyze future climate projections for the twenty-first century over this complex orography region using those five GCMs. We evaluate the projections under two of the representative concentration pathways considered as future scenarios: RCP4.5 and RCP8.5. Future projections indicate warming during the twenty-first century over the SCA region, especially pronounced over the mountains. Projections of warming at high elevations in the SCA depend on altitude, and are larger than the projected global mean warming. This phenomenon is expected to strengthen by the end of the century under the high-emission scenario. Increases in winter temperatures of up to 2.5 °C, relative to 1980-2005, are projected by 2040-2065, while a 5 °C warming is expected at the highest elevations by 2075-2100. Such a large monthly-mean warming during winter would most likely result in snowpack melting by late winter-early spring, with serious implication for water availability during summer, when precipitation is a minimum over the mountains. We also explore changes in the albedo, as a contributing factor affecting the net flux of energy at the surface and found a reduction in albedo of 20-60% at high elevations, related to the elevation dependent warming. Furthermore, a decrease in winter precipitation is projected in central Chile by the end of the century, independent of the scenario considered.

Glacier shrinkage and water resources in the Andes

NASA Astrophysics Data System (ADS)

Francou, Bernard; Coudrain, Anne

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

Dating the last Neanderthals in Central Iberia - New evidence from Abrigo del Molino, Segovia, Spain

NASA Astrophysics Data System (ADS)

Kehl, Martin; Álvarez-Alonso, David; de Andrés-Herrero, María; Díez-Herrero, Andrés; Klasen, Nicole; Rojo-Hernández, Julio; Weniger, Gerd-Christian

2017-04-01

The timing of Neanderthal disappearance in the Iberian Peninsula is a hotly debated subject in Palaeolithic archaeology. Several studies suggested a late survival in South and Central Iberia until about 32,000 year ago (ka), but were probably subject to significant age underestimation due to contamination of dating samples and/or lack of stratigraphic integrity. More recently, Late Neanderthal presence was dated to no later than 38 ka. In Central Iberia, few archaeological sites contain Mousterian levels attesting occupation by Neanderthals. The newly discovered rock shelter of Abrigo del Molino contains chronologically well-constraint Mousterian levels, which, according to radiocarbon dating on bone, place the latest Neanderthal occupation to around 42-44 ka and within Greenland interstadial 11. Accumulation of these levels took place after deposition of fluvial and slope sediments, dated to around 46 ± 3.5 ka using luminescence techniques, and probably correlating with Greenland stadial 13 including Heinrich event 5. Micromorphological evidence of banded sediment fabrics suggests frost dynamics pointing to cold climate conditions during that time in Central Spain. Abrigo del Molino thus provides a detailed and chronologically well-constrained record on Late Neanderthal presence and morphodynamic change in Central Iberia during times of millennial-scale climate changes. The site gives further evidence for an early rather than late disappearance of Neanderthals in Iberia.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

Hantavirus pulmonary syndrome: encephalitis caused by virus Andes.

PubMed

Talamonti, Lionel; Padula, Paula J; Canteli, María Sol; Posner, Federico; Marczeski, Fanny Pires; Weller, Carlos

2011-04-01

Hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome (HPS) are rodent-borne emerging diseases caused by members of the genus Hantavirus, family Bunyaviridae. Some species of hantavirus may cause encephalitis, but this is the first report in Andes virus associated to HPS.

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

PubMed

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

2011-05-01

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

Ethnographic model of acoustic use of space in the southern Andes for an archaeo-musicological investigation

NASA Astrophysics Data System (ADS)

Perez de Arce, Jose

2002-11-01

Studies of ritual celebrations in central Chile conducted in the past 15 years show that the spatial component of sound is a crucial component of the whole. The sonic compositions of these rituals generate complex musical structures that the author has termed ''multi-orchestral polyphonies.'' Their origins have been documented from archaeological remains in a vast region of southern Andes (southern Peru, Bolivia, northern Argentina, north-central Chile). It consists of a combination of dance, space walk-through, spatial extension, multiple movements between listener and orchestra, and multiple relations between ritual and ambient sounds. The characteristics of these observables reveal a complex schematic relation between space and sound. This schema can be used as a valid hypothesis for the study of pre-Hispanic uses of acoustic ritual space. The acoustic features observed in this study are common in Andean ritual and, to some extent are seen in Mesoamerica as well.

Two scales of inflation at Lastarria-Cordon del Azufre volcanic complex, central Andes, revealed from ASAR-ENVISAT interferometric data

NASA Astrophysics Data System (ADS)

Froger, J.-L.; Remy, D.; Bonvalot, S.; Legrand, D.

2007-03-01

ASAR-ENVISAT Interferometric Synthetic Aperture Radar (InSAR) data collected over the Lastarria-Cordon del Azufre complex (Chile-Argentina) between March 2003 and May 2005 show the persistence of the large wavelength ground inflation revealed by Pritchard and Simons in 2002 from the analysis of ERS InSAR data [Nature 418 (2002) 167-170]. After reducing the tropospheric contribution in the interferograms using a combination of data network adjustment and analysis of MODIS images, we produced an accurate interferometric time series showing a 2 yr long temporal evolution of the ground displacements patterns. Two distinct inflating signals are detected. The main signal covers an elliptical area with a 45 km NNE-SSW major axis and a 37 km minor axis. It is correlated with a regional topographic dome. We estimated its maximum inflation rate to ˜ 2.5 cm yr - 1 . We inverted the InSAR data for a range of source geometries (spherical, prolate ellipsoids, penny-shaped cracks). The inferred source parameters for 2003-2005 period are consistent with an over-pressured reservoir at shallow to intermediate crustal depths (7-15 km), with an average volumetric rate of inflation of about 14 × 10 6 m 3 yr - 1 . In addition to this main signal a new feature highlighted by the ASAR data is short wavelength inflation (6 km wide) at the location of Lastarria volcano on the northern margin of the large wavelength signal. We explain this short wavelength signal by a spherical over-pressured source lying 1000 m below the summit of Lastarria volcano. We estimate the average volumetric rate of inflation during the observation period to be ˜ 35 × 10 3 m 3 yr - 1 . It is remarkable that both volumetric variations for the large and small inflations exhibit the same evolution during the 2003-2005 period, suggesting that both processes could be related. On the basis of the inversion results and of arguments provided by field evidences and a morpho-structural analysis of the Digital Elevation

Reflections on Andes' Goal-Free User Interface

ERIC Educational Resources Information Center

VanLehn, Kurt

2016-01-01

Although the Andes project produced many results over its 18 years of activity, this commentary focuses on its contributions to understanding how a goal-free user interface impacts the overall design and performance of a step-based tutoring system. Whereas a goal-aligned user interface displays relevant goals as blank boxes or empty locations that…

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

NASA Astrophysics Data System (ADS)

Haberland, Christian; Rietbrock, Andreas

2001-06-01

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

Between Andes and Amazon: the genetic profile of the Arawak-speaking Yanesha.

PubMed

Barbieri, Chiara; Heggarty, Paul; Yang Yao, Daniele; Ferri, Gianmarco; De Fanti, Sara; Sarno, Stefania; Ciani, Graziella; Boattini, Alessio; Luiselli, Donata; Pettener, Davide

2014-12-01

The Yanesha are a Peruvian population who inhabit an environment transitional between the Andes and Amazonia. They present cultural traits characteristic of both regions, including in the language they speak: Yanesha belongs to the Arawak language family (which very likely originated in the Amazon/Orinoco lowlands), but has been strongly influenced by Quechua, the most widespread language family of the Andes. Given their location and cultural make-up, the Yanesha make for an ideal case study for investigating language and population dynamics across the Andes-Amazonia divide. In this study, we analyze data from high and mid-altitude Yanesha villages, both Y chromosome (17 STRs and 16 SNPs diagnostic for assigning haplogroups) and mtDNA data (control region sequences and 3 SNPs and one INDEL diagnostic for assigning haplogroups). We uncover sex-biased genetic trends that probably arose in different stages: first, a male-biased gene flow from Andean regions, genetically consistent with highland Quechua-speakers and probably dating back to Inca expansion; and second, traces of European contact consistent with Y chromosome lineages from Italy and Tyrol, in line with historically documented migrations. Most research in the history, archaeology and linguistics of South America has long been characterized by perceptions of a sharp divide between the Andes and Amazonia; our results serve as a clear case-study confirming demographic flows across that 'divide'. © 2014 The Authors. American journal of physical Anthropology published by Wiley Periodocals, Inc.

The Decline of Austrocedrus Forests in Patagonia (Mal del Ciprés): Another Phytophthora-Caused Forest Disease

Treesearch

Alina Greslebin; Everett Hansen

2009-01-01

Austrocedrus chilensis, an indigenous Cupressaceae of the Patagonian Andes forests, is suffering a disease that has been called "Mal del Ciprés" (MDC). This disease was first reported more than 50 years ago but, in spite of many studies, its causes remained unclear until recently. The disease begins in the root system, the distribution...

Mechanisms of crustal shortening in the foreland of the central Andes, Argentina: insights from data-driven three-dimensional gravity, thermal and rheological modelling

NASA Astrophysics Data System (ADS)

Meeßen, Christian; Scheck-Wenderoth, Magdalena; Sippel, Judith; Strecker, Manfred

2017-04-01

Thin- and thick-skinned deformation styles in the foreland of the central Andes are the result of ongoing crustal shortening since the early Neogene. The mechanisms proposed for these different styles range from variations in subduction angle of the Nazca plate, lithospheric thickening to variations in temperature and strength of the crystalline crust. The latter hypothesis states a cold and strong lithosphere in the foreland of the Altiplano Plateau, facilitating thin-skinned shortening. In contrast, the foreland of the Puna plateau is proposed to be characterized by a warm lithosphere and strong upper crust, resulting in thick-skinned deformation. Whilst this hypothesis has been confirmed in numerical thermomechanical experiments, there is no evidence for this mechanism from data integrative modelling. We test this hypothesis by means of three-dimensional data integrative gravity, thermal and rheological modelling. Therefore, we constructed a lithospheric-scale density model of the foreland of northern Argentina and southern Bolivia using gravity forward modelling and inversion techniques. Into this density model we implemented sediment isopachs, data from receiver functions and densities from shear-wave velocities of the upper mantle. The model was verified using the observed Bouguer gravity anomaly. By assigning thermal and rheological properties to the modelled units we are able to quantify the strength of the lithosphere and test the predictions by the thermomechanical models.

Switching from pure- into simple-shear mode during uplift of the Altiplano plateau (Central Andes)

NASA Astrophysics Data System (ADS)

Babeyko, A. Yu.; Sobolev, S. V.

2003-04-01

The Altiplano plateau of the Central Andes is the second greatest plateau in the world after Tibet with an average elevation of about 4 km formed as a result of ocean-continent collision between subducting Nasca plate on the west and Brazilian shield on the east. According to the well known Isacks (1988) scenario, the Cenozoic evolution of the plateau started ca. 30 Ma in response to the retreat of the flat-subducted Nasca plate. Astenospheric material, which replaced the retreated plate, thermally thinned and softened the overlying lithosphere. The Altiplano crust, being pushed by the Brazilian shield from the east, was first shortened in a pure-shear mode and reached 60-70 km in thickness. At ca. 8-10 Ma deformation changed to a simple-shear mode: it was ceased in the upper crust of the plateau and migrated eastwards, into the Subandean, while the plateau itself continued to grow due to ongoing shortening in the lower crust. We employ numerical 2D thermomechanical modelling to test the above scenario and to evaluate the key parameters, which account for the transition from pure- to simple- shear style of the lithosphere-scale deformation under pure-shear boundary condition. As a numerical tool we use explicit finite difference/finite element lagrangian code with markers tracking material properties. The model contains rheologically different layers representing sediments, felsic and mafic crust, lithospheric mantle, and astenosphere. Rheological laws are Mohr-Coloumb elasto-plastic with softening and Maxwell visco-elastic with nonlinear power-law creep. Initial and boundary conditions simulate thermal activation of the Altiplano lithosphere by upwelling astenosphere as well as its westward pushing by the cold Brazilian shield with constant velocity. We found that model shortening always occurs in a pure-shear mode unless the uppermost crust of the Brazilian shield becomes during the deformation considerably weaker than the Altiplano upper crust (drop of friction

Snowpack variations since AD 1150 in the Andes of Chile and Argentina (30°-37°S) inferred from rainfall, tree-ring and documentary records

NASA Astrophysics Data System (ADS)

Masiokas, M. H.; Villalba, R.; Christie, D. A.; Betman, E.; Luckman, B. H.; Le Quesne, C.; Prieto, M. R.; Mauget, S.

2012-03-01

The Andean snowpack is the main source of freshwater and arguably the single most important natural resource for the populated, semi-arid regions of central Chile and central-western Argentina. However, apart from recent analyses of instrumental snowpack data, very little is known about the long term variability of this key natural resource. Here we present two complementary, annually-resolved reconstructions of winter snow accumulation in the southern Andes between 30°-37°S. The reconstructions cover the past 850 years and were developed using simple regression models based on snowpack proxies with different inherent limitations. Rainfall data from central Chile (very strongly correlated with snow accumulation values in the adjacent mountains) were used to extend a regional 1951-2010 snowpack record back to AD 1866. Subsequently, snow accumulation variations since AD 1150 were inferred from precipitation-sensitive tree-ring width series. The reconstructed snowpack values were validated with independent historical and instrumental information. An innovative time series analysis approach allowed the identification of the onset, duration and statistical significance of the main intra- to multi-decadal patterns in the reconstructions and indicates that variations observed in the last 60 years are not particularly anomalous when assessed in a multi-century context. In addition to providing new information on past variations for a highly relevant hydroclimatic variable in the southern Andes, the snowpack reconstructions can also be used to improve the understanding and modeling of related, larger-scale atmospheric features such as ENSO and the PDO.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

Glacier loss and hydro-social risks in the Peruvian Andes

NASA Astrophysics Data System (ADS)

Mark, Bryan G.; French, Adam; Baraer, Michel; Carey, Mark; Bury, Jeffrey; Young, Kenneth R.; Polk, Molly H.; Wigmore, Oliver; Lagos, Pablo; Crumley, Ryan; McKenzie, Jeffrey M.; Lautz, Laura

2017-12-01

Accelerating glacier recession in tropical highlands and in the Peruvian Andes specifically is a manifestation of global climate change that is influencing the hydrologic cycle and impacting water resources across a range of socio-environmental systems. Despite predictions regarding the negative effects of long-term glacier decline on water availability, many uncertainties remain regarding the timing and variability of hydrologic changes and their impacts. To improve context-specific understandings of the effects of climate change and glacial melt on water resources in the tropical Andes, this article synthesizes results from long-term transdisciplinary research with new findings from two glacierized Peruvian watersheds to develop and apply a multi-level conceptual framework focused on the coupled biophysical and social determinants of water access and hydro-social risks in these settings. The framework identifies several interacting variables-hydrologic transformation, land cover change, perceptions of water availability, water use and infrastructure in local and regional economies, and water rights and governance-to broadly assess how glacier change is embedded with social risks and vulnerability across diverse water uses and sectors. The primary focus is on the Santa River watershed draining the Cordillera Blanca to the Pacific. Additional analysis of hydrologic change and water access in the geographically distinct Shullcas River watershed draining the Huaytapallana massif towards the city of Huancayo further illuminates the heterogeneous character of hydrologic risk and vulnerability in the Andes.

Andes Altiplano, Northwest Argentina, South America

NASA Technical Reports Server (NTRS)

1993-01-01

This view of the Andes Altiplano in northwest Argentina (25.5S, 68.0W) is dominated by heavily eroded older and inactive volcano peaks. The altiplano is a high altitude cold desert like the Tibetan Plateau but smaller in area. It is an inland extension of the hyperarid Atacama Desert of the west coast of South America and includes hundreds of volcanic edifices (peaks, cinder cones, lava flows, debris fields, lakes and dry lake beds (salars).

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

NASA Astrophysics Data System (ADS)

Bahlburg, H.; Breitkreuz, C.

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

Synchronous interhemispheric Holocene climate trends in the tropical Andes

PubMed Central

Polissar, Pratigya J.; Abbott, Mark B.; Wolfe, Alexander P.; Vuille, Mathias; Bezada, Maximiliano

2013-01-01

Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate. PMID:23959896

Use and legacy of mercury in the Andes.

PubMed

Cooke, Colin A; Hintelmann, Holger; Ague, Jay J; Burger, Richard; Biester, Harald; Sachs, Julian P; Engstrom, Daniel R

2013-05-07

Both cinnabar (HgS) and metallic mercury (Hg(0)) were important resources throughout Andean prehistory. Cinnabar was used for millennia to make vermillion, a red pigment that was highly valued in pre-Hispanic Peru; metallic Hg(0) has been used since the mid-16th century to conduct mercury amalgamation, an efficient process of extracting precious metals from ores. However, little is known about which cinnabar deposits were exploited by pre-Hispanic cultures, and the environmental consequences of Hg mining and amalgamation remain enigmatic. Here we use Hg isotopes to source archeological cinnabar and to fingerprint Hg pollution preserved in lake sediment cores from Peru and the Galápagos Islands. Both pre-Inca (pre-1400 AD) and Colonial (1532-1821 AD) archeological artifacts contain cinnabar that matches isotopically with cinnabar ores from Huancavelica, Peru, the largest cinnabar-bearing district in Central and South America. In contrast, the Inca (1400-1532 AD) artifacts sampled are characterized by a unique Hg isotopic composition. In addition, preindustrial (i.e., pre-1900 AD) Hg pollution preserved in lake sediments matches closely the isotopic composition of cinnabar from the Peruvian Andes. Industrial-era Hg pollution, in contrast, is distinct isotopically from preindustrial emissions, suggesting that pre- and postindustrial Hg emissions may be distinguished isotopically in lake sediment cores.

Out of Amazonia again and again: episodic crossing of the Andes promotes diversification in a lowland forest flycatcher

PubMed Central

Miller, Matthew J; Bermingham, Eldredge; Klicka, John; Escalante, Patricia; do Amaral, Fabio S. Raposo; Weir, Jason T; Winker, Kevin

2008-01-01

Most Neotropical lowland forest taxa occur exclusively on one side of the Andes despite the availability of appropriate habitat on both sides. Almost all molecular phylogenies and phylogenetic analyses of species assemblages (i.e. area cladograms) have supported the hypothesis that Andean uplift during the Late Pliocene created a vicariant barrier affecting lowland lineages in the region. However, a few widespread plant and animal species occurring in lowland forests on both sides of the Andes challenge the generality of this hypothesis. To understand the role of the Andes in the history of such organisms, we reconstructed the phylogeographic history of a widespread Neotropical flycatcher (Mionectes oleagineus) in the context of the other four species in the genus. A molecular phylogeny based on nuclear and mitochondrial sequences unambiguously showed an early basal split between montane and lowland Mionectes. The phylogeographic reconstruction of lowland taxa revealed a complex history, with multiple cases in which geographically proximate populations do not represent sister lineages. Specifically, three populations of M. oleagineus west of the Andes do not comprise a monophyletic clade; instead, each represents an independent lineage with origins east of the Andes. Divergence time estimates suggest that at least two cross-Andean dispersal events post-date Andean uplift. PMID:18285279

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

PubMed Central

Froemming, Steve

2006-01-01

This paper explores the use of the dried meat and feathers of the Andean Flicker (Colaptes rupicola) to increase the milk supply of nursing women and domestic animals in the Andes. The treatment is of preColumbian origin, but continues to be used in some areas, including the village in the southern Peruvian highlands where I do ethnographic research. I explore the factors giving rise to and sustaining the practice, relate it to other galactagogues used in the Andes and to the use of birds in ethnomedical and ethnoveterinary treatments in general, and situate it within the general tendency in the Andes and elsewhere to replicate human relations in the treatment of valuable livestock. The bird's use as a galactagogue appears to be motivated by both metaphorical associations and its perceived efficacy, and conceptually blends human and animal healthcare domains. PMID:16677398

The ANDES Deep Underground Laboratory in South America: status and prospects

NASA Astrophysics Data System (ADS)

Bertou, Xavier

2017-01-01

The construction of the Agua Negra tunnel through the Andes between Argentina and Chile is a unique opportunity to build a world class deep underground laboratory in the southern hemisphere, with 1750 m of rock overburden. At 30 degrees latitude south, far from nuclear power plants, it provides a unique site for Dark Matter searches and Neutrino experiments, and can host multidisciplinary experiments with a specific focus on Earth sciences given its location in a peculiar geoactive region. Its operation is foreseen to be coordinated by an international consortium and to start in 2026. In this presentation the current status of the Agua Negra tunnel and the ANDES initiative will be reviewed, and the scientific programme of the planned laboratory will be discussed.

Characterizing Magmatic Sources in the Central Andes Volcanic Zone with a Regional InSAR Time Series Survey

NASA Astrophysics Data System (ADS)

Henderson, S. T.; Pritchard, M. E.

2011-12-01

The Central Andes Volcanic Zone (CVZ) contains many intriguing areas of ongoing crustal deformation detectable with InSAR. Foremost among these are the 1-2cm/yr radar line-of-sight (LOS) inflations near Uturuncu Volcano in Bolivia and the Lazufre volcanic area spanning the border of Chile and Argentina (Pritchard and Simons 2002). These two deformation sources are intriguing in that they are long-lived (>10yrs), have large diameters (>50km), and have modeled sources at mid-crustal depths (10-20km). For Uturuncu, the best-fitting source depths coincide with the seismically imaged Altiplano-Puna Magma Body (eg. Chimielowsi et al. 1999, Zandt et al. 2003). Regional InSAR time series analysis enables the spatial and temporal comparison of the Uturuncu and Lazufre signals with other deformations in a sub-region of the CVZ from 1992 to the present. Our study focuses on volcanic deformation, but we also resolve non-magmatic deformation signals including landslides and salars. The study region benefits from a large InSAR dataset of 631 ERS and ENVISAT interferograms, distributed between two descending tracks and two ascending tracks, covering up to 870 kilometers along the volcanic arc. We employ an inversion method based on the SBAS algorithm (Berardino 2002), but modified to avoid interpolation across dates with incoherent values. This modification effectively deals with the heterogeneous spatial extents and data gaps present in individual interferograms for long tracks. With our time series results we investigate the timing of possible magma migrations and we explore the parameters of forward models that match observations. Results indicate continuing monotonic inflation styles at Uturuncu and Lazufre with maximum LOS uplift at 1.0cm/yr and 2.5cm/yr respectively (Pritchard and Simons 2004, Froger et al. 2007, Ruch et al. 2009). We discuss evidence for 2mm/yr broad LOS deflation collocated with the Uturuncu inflation signal and comment on possible models for its origin

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

NASA Astrophysics Data System (ADS)

Huggel, C.

2012-04-01

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

Impact of glaciations on the long-term erosion in Southern Patagonian Andes

NASA Astrophysics Data System (ADS)

Simon-Labric, Thibaud; Herman, Frederic; Baumgartner, Lukas; Shuster, David L.; Braun, Jean; Reiners, Pete W.; Valla, Pierre G.; Leuthold, Julien

2014-05-01

The Southern Patagonian Andes are an ideal setting to study the impact of Late-Cenozoic climate cooling and onset of glaciations impact on the erosional history of mountain belts. The lack of tectonic activity during the last ~12 Myr makes the denudation history mainly controlled by surface processes, not by tectonics. Moreover, the glaciations history of Patagonia shows the best-preserved records within the southern hemisphere (with the exception of Antarctica). Indeed, the dry climate on the leeward side of Patagonia and the presence of lava flows interbedded with glacial deposits has allowed an exceptional preservation of late Cenozoic moraines with precise dating using K-Ar analyses on lava flow. The chronology of moraines reveals a long history covering all the Quaternary, Pliocene, and up to the Upper Miocene. The early growth of large glaciers flowing on eastern foothills started at ~7-6 Myr, while the maximum ice-sheet extent dates from approximately 1.1 Myr. In order to quantify the erosion history of the Southern Patagonian Andes and compare it to the glaciations sediment record, we collected samples along an age-elevation profile for low-temperature thermochronology in the eastern side of the mountain belt (Torres del Paine massif). The (U-Th)/He age-elevation relationship shows a clear convex shape providing an apparent long-term exhumation rate of ~0.2 km/Myr followed by an exhumation rate increase at ~6 Myr. Preliminary results of 4He/3He thermochronometry for a subset of samples complete the erosion history for the Plio-Pleistocene epoch. We used inverse procedure predicting 4He distributions within an apatite grain using a radiation-damage and annealing model to quantify He-diffusion kinetics in apatite. The model also allows quantifying the impact of potential U-Th zonation throughout each apatite crystal. Inversion results reveal a denudation history composed by a pulse of denudation at ~6 Ma, as suggested by the age-elevation relationship

Hydrologic Variability During the Last 10,000 Years in the Tropical Andes

NASA Astrophysics Data System (ADS)

Seltzer, G.; Rodbell, D.; Burns, S.; Edwards, R.; Chen, H.

2003-12-01

The apparent increase in frequency of strong El Niño events in the mid Holocene as recorded around the tropical Pacific (e.g., Moy et al., 2002, Nature) has prompted the search for additional records to help identify the mechanism(s) behind tropical climatic variability on interannual and longer time scales. Lake Junin is a large lake (300 km2) in the Peruvian Andes (11° S, 4100 masl) that has rapidly accumulated authigenic carbonate over the last 10,000 years. A 14C and U/Th dated time series of δ 18Ocalcite with an average sample spacing of ˜30 years shows up to +/-2‰ (VPDB) deviations from an overall decreasing trend. The δ 18O of source precipitation to the region, as recorded in the Nevado Huascaran (9° S) and Nevado Sajama (18° S) ice-cores, reveals no decadal-centennial changes over the same time period and a long-term Holocene trend of <3‰ (VSMOW). It is likely that large changes in the hydrologic balance (precipitation minus evaporation) of Lake Junin led to relatively rapid and large changes in δ 18Ocalcite . The hydrologic changes at Lake Junin can be correlated with El Niño events recorded in lake sediments in southern Ecuador, lake level records from Lake Titicaca, and the amount of ice-rafted debris in North Atlantic sediments. The variability in precipitation in the tropical Andes is likely a result of the interplay between air masses that deliver moisture to the Andes from the east and the upper tropospheric westerlies that are impacted by sea-surface temperatures in the eastern tropical Pacific(Vuille et al., 2000, JGR). Climatic conditions are generally drier in the tropical Andes during intervals marked by an increased frequency in El Niño Southern Oscillation warm events and cooler North Atlantic sea-surface temperatures.

Utility of multiple chemical techniques in archaeological residential mobility studies: case studies from Tiwanaku- and Chiribaya-affiliated sites in the Andes.

PubMed

Knudson, Kelly J; Price, T Douglas

2007-01-01

In the south central Andes, archaeologists have long debated the extent of Tiwanaku colonization during the Middle Horizon (AD 500-1000). We tested the hypotheses regarding the nature of Tiwanaku influence using strontium isotope, trace element concentration, and oxygen isotope data from archaeological human tooth enamel and bone from Tiwanaku- and Chiribaya-affiliated sites in the south central Andes. Strontium isotope analysis of 25 individuals buried at the Tiwanaku-affiliated Moquegua Valley site of Chen Chen demonstrates that it was likely a Tiwanaku colony. In contrast, no immigrants from the Lake Titicaca Basin were present in 27 individuals analyzed from the San Pedro de Atacama cemeteries of Coyo Oriental, Coyo-3, and Solcor-3; it is likely that these sites represent economic and religious alliances, but not colonies. However, strontium isotope analysis alone cannot distinguish movement between the Tiwanaku- and Chiribaya-affiliated sites in the Moquegua and Ilo Valleys of southern Peru. Analyzing oxygen isotope and trace element concentration data and comparing it with strontium isotope data from the same individuals provides a more detailed picture of residential mobility in the Tiwanaku and Chiribaya polities. In addition to monitoring diagenetic contamination, trace element concentration data identified movement during adulthood for certain individuals. However, these data could not distinguish movement between the Moquegua and Ilo Valleys. While oxygen isotope data could clearly distinguish the high-altitude sites from others, more data is needed to characterize the local oxygen isotope ratios of these regions. These data demonstrate the potential for archaeological reconstruction of residential mobility through multiple lines of evidence. (c) 2006 Wiley-Liss, Inc

Assessing groundwater recharge mechanisms in the Pampa del Tamarugal Basin of northern Chile's Atacama Desert

NASA Astrophysics Data System (ADS)

Jayne, R., Jr.; Pollyea, R.; Dodd, J. P.; Olson, E. J.; Swanson, S.

2015-12-01

The hyper-arid Atacama Desert in northern Chile is one of the driest inhabited places on Earth receiving little to no rain (<5 mm/yr). Within the Tarapacá Region of the Atacama Desert, the Pampa del Tamarugal Aquifer (PTA) is the primary source of water for agriculture, industry, mining, and residential uses. The PTA covers 5,000 km2, and is located in the Pampa del Tamarugal Basin, which is situated between the Andes and the Coastal Cordillera, and is filled with ~1700m of Miocene and younger sediments. The source of recharge for the PTA originates as precipitation in the high Andes, which can receive up to 400 mm/yr of precipitation; however, the mechanisms and magnitude of recharge to the PTA are still poorly understood. Here, we present a regional scale, non-isothermal 2-D numerical groundwater model is developed to analyze the time scales and geological controls on fluid flow paths recharging the PTA. Results from this work suggest that (1) both shallow groundwater flow and deep (>1km) hydrothermal fluid circulation are responsible for recharging the PTA; (2) topography and geothermal gradients are the main driving factors for regional groundwater flow; (3) the Altos de Pica member 4, an ignimbrite layer in the sedimentary basin controls both heat and fluid flow in the western part of the basin, this is evident due to the presence of convection cells and meteoric water upwelling and presenting itself as surface water (salars); and (4) it takes meteoric water 100,000 years to travel from the high Andes to reach Pica and 1,000,000 years for salar formation. In addition, this work provides a theoretical basis for the spatial distribution of highly alkaline surface water bodies, known as salars in the western Atacama Desert.

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

NASA Astrophysics Data System (ADS)

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

Paraphyly of Cinclodes fuscus (Aves: Passeriformes: Furnariidae): Implications for taxonomy and biogeography

USGS Publications Warehouse

Sanin, Camilo; Cadena, Carlos Daniel; Maley, James M.; Lijtmaer, Dario A.; Tubaro, Pablo L.; Chesser, R. Terry

2009-01-01

The Andes are a hotspot of global avian diversity, but studies on the historical diversification of Andean birds remain relatively scarce. Evolutionary studies on avian lineages with Andean–Patagonian distributions have focused on reconstructing species-level phylogenies, whereas no detailed phylogeographic studies on widespread species have been conducted. Here, we describe phylogeographic patterns in the Bar-winged Cinclodes (Cinclodes fuscus), a widespread and common species of ovenbird (Furnariidae) that breeds from Tierra del Fuego to the northern Andes. Traditionally, C. fuscus has been considered a single species composed of nine subspecies, but its long and narrow range suggests the possibility of considerable genetic variation among populations. Sequences of two mitochondrial genes revealed three discrete and geographically coherent groups of C. fuscus, occupying the southern, central, and northern Andes. Surprisingly, phylogenetic analyses indicated that these groups were more closely related to other species of Cinclodes than to each other. Relationships of the southern and northern C. fuscus clades to other species of Cinclodes were straightforward; in combination with available information on plumage, behavioral, and vocal variation, this suggests that each should be recognized as a distinct biological species. The central Andean group was paraphyletic with respect to C. oustaleti, and relationships among these taxa and C. olrogi were poorly resolved. We suggest that the central Andean C. fuscus should also be considered a different species, pending new information to clarify species limits in this group. These new phylogenetic data, along with recently developed methods, allowed us to review the biogeography of the genus, confirming southern South America and the central Andes as important areas for the diversification of these birds.

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

PubMed

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

2014-02-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-09-01

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

Impact of surface processes and climate variability on clumped isotope thermometry of soil carbonates, southern Central Andes, Argentina (Invited)

NASA Astrophysics Data System (ADS)

Huntington, K. W.; Peters, N.; Roe, G.; Hoke, G. D.; Eiler, J.

2010-12-01

Soil carbonates archive a potentially rich record of past climate, but rates of pedogenic carbonate formation, erosion, and deposition impact how the isotopic composition and formation temperature of carbonate-bearing paleosols reflect the local environmental conditions under which they form. We investigate these processes using conventional stable isotope (δ18O and δ13C) and clumped isotope thermometry data for Quaternary pedogenic carbonates from the southern Central Andes at ~33°S, Argentina. The study area spans over 2 km of relief in the Río Mendoza and Río de las Cuevas valleys, accessing a range of mean annual temperature conditions and vegetative cover and exhibiting large seasonal variations in temperature, precipitation, and soil moisture. Variations in soil conditions influence carbonate precipitation and dissolution reactions and the rate and depth of pedogenic carbonate formation. Because soil temperature varies predictably as a function of depth in the soil and seasonal and secular variations in air temperature, clumped isotope thermometry of samples collected in soil pits offers a direct way to estimate the seasonality of pedogenic carbonate formation and potential biases in the long-term climate record. We explore potential complications due to the effects of radiative solar heating on the relationship between air and soil temperatures by examining clumped isotope thermometry results in the context of site-to-site variations in vegetative cover. Temperature estimates from clumped isotope thermometry of pedogenic carbonate collected 5-110 cm below geomorphically stable soil surfaces from 1200-3400 m a.s.l. are compared to temperature profiles predicted by simple rule-based models of soil carbonate formation. The models use climate reanalysis daily diagnostic data (soil temperature, soil moisture, and latent heat flux as a proxy for evaporation) and weather station data as input to assess how varying rates of pedogenic carbonate formation

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

PubMed

Pereira, Luis Alberto

2015-10-06

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

Andes Hantavirus Variant in Rodents, Southern Amazon Basin, Peru

PubMed Central

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

2014-01-01

We investigated hantaviruses in rodents in the southern Amazon Basin of Peru and identified an Andes virus variant from Neacomys spinosus mice. This finding extends the known range of this virus in South America and the range of recognized hantaviruses in Peru. Further studies of the epizoology of hantaviruses in this region are warranted. PMID:24447689

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

NASA Astrophysics Data System (ADS)

Khazaradze, G.; Klotz, J.

2001-12-01

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

A high-altitude peatland record of environmental changes in the NW Argentine Andes (24 ° S) over the last 2100 years

NASA Astrophysics Data System (ADS)

Schittek, Karsten; Kock, Sebastian T.; Lücke, Andreas; Hense, Jonathan; Ohlendorf, Christian; Kulemeyer, Julio J.; Lupo, Liliana C.; Schäbitz, Frank

2016-05-01

High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies, and sensitivity to climatic and/or human-induced changes. Especially within the Central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP), located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF), stable isotope and element content analyses (δ13C, δ15N, TN and TOC) were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatlands' past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that in situ moisture changes were coupled to the migration of the Intertropical Convergence Zone (ITCZ). A period of sustained dry conditions prevailed from around 150 BC to around AD 150. A more humid phase dominated between AD 200 and AD 550. Afterwards, the climate was characterised by changes between drier and wetter conditions, with droughts at around AD 650-800 and AD 1000-1100. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption) seems to have had an impact on climatic settings in the Central Andes. In the past, the peatland recovered from climatic perturbations. Today, CTP is heavily degraded by human interventions, and the peat deposit is becoming increasingly susceptible to erosion and incision.

Trauma and violence in the Wari empire of the Peruvian Andes: warfare, raids, and ritual fights.

PubMed

Tung, Tiffiny A

2007-07-01

This study examines bioarchaeological evidence for violence during the period of Wari imperialism in the Peruvian Andes through analysis of skeletal trauma from three populations dating to AD 650-800. The samples are from contemporaneous archaeological sites: Conchopata, a Wari heartland site in central highland Peru; Beringa, a community of commoners in the Majes valley of the southern Wari hinterland; and La Real, a high status mortuary site, also in the Majes valley. Given the expansionist nature of Wari and its military-related iconography and weaponry, it is hypothesized that Wari imperialism was concomitant with greater levels of violence relative to other prehispanic groups in the Andes. It is also hypothesized that differential articulation with the Wari empire (e.g., heartland vs. hinterland groups) affected the frequency and patterning of trauma. Results show that cranial trauma frequency of the three Wari era samples is significantly greater than several other Andean skeletal populations. This suggests that Wari rule was associated with high levels of violence, though it may not have always been related to militarism. The three adult samples show similar frequencies of cranial trauma (Conchopata = 26%; Beringa = 33%; La Real = 31%). This may suggest that differential positioning in the Wari empire had little effect on exposure to violence. Sex-based differences in cranial trauma frequencies are present only at La Real, but wound patterning differs between the sexes: females display more wounds on the posterior of the cranium, while males show more on the anterior. These data suggest that Wari rule may have contributed to violence. (c) 2007 Wiley-Liss, Inc.

Genetic continuity after the collapse of the Wari empire: mitochondrial DNA profiles from Wari and post-Wari populations in the ancient Andes.

PubMed

Kemp, Brian M; Tung, Tiffiny A; Summar, Marshall L

2009-09-01

The Wari empire flourished in the central, highland Peruvian Andes from AD 600-1000, and although the events that led to its demise are unknown, archaeological evidence indicates that Wari control waned at the end of the first millennium. Here, we test the hypothesis that, despite the major shift in social and political organization at the fall of the Wari empire, the mitochondrial DNA (mtDNA) composition of populations from the Ayacucho Basin, the former imperial heartland of the empire, remained essentially unchanged. Results show that mtDNA haplogroup frequencies among the Wari and post-Wari groups differ, but the difference is not statistically significant (chi2 = 5.886, df = 3, P = 0.1172). This is the first study in the Andes to use haplotypic data to evaluate the observed genetic distance between two temporally distinct prehispanic populations (F(ST) = 0.029) against modeled expectations of four possible evolutionary scenarios. None of these simulations allowed the rejection of continuity. In total, at both the haplogroup and haplotype levels these data do not allow us to reject the hypothesis that post-Wari individuals sampled in this study are the maternal descendants of those sampled from the Wari era site of Conchopata. However, genetic homogeneity in the mitochondrial gene pool, as seen in the late prehispanic southern Andes, may also characterize our study region. But, prior to this research, this was unknown. If our new data show mtDNA homogeneity, then this could limit the detection of female migration if, in fact, it occurred. Nonetheless, the novel mtDNA data presented here currently do not support the hypothesis that there was an influx of genetically distinct females into the former Wari heartland after the Wari collapse. Copyright 2009 Wiley-Liss, Inc.

Late Pleistocene equilibrium-line reconstructions in the northern Peruvian Andes

USGS Publications Warehouse

Rodbell, D.T.

1992-01-01

ELA reconstructions using the toe-to-headwall-altitude ratio method for paleoglaciers in the Cordilleras Blanca and Oriental, northern Peruvian Andes indicate that ELAs during the last glacial maximum (LGM; marine isotope stage 2)) were c.4300 m in the Cordillera Blanca, c.3900-3600 m on the west side of the Cordillera Oriental, and c.3200 m on the east (Amazon Basin) side of the Cordillera Oriental. Comparison with estimated modern ELAs and glaciation thresholds indicate that ELA depression ranged from c.700 m in the Cordillera Blanca to c.1200 m on the east side of the Cordillera Oriental. Palynological evidence for drier conditions during the LGM in the tropical Andes suggests that ELA depression of this amount involved a temperature reduction (>5-6??C) that greatly exceeded the tropical sea-surface temperature depression estimates of CLIMAP (<2??C). The west to east increase in ELA depression during the LGM indicates that the steep modern precipitation gradients may have been even steeper during the LGM. -from Author

3D dynamics of crustal deformation driven by oblique subduction: Northern and Central Andes

NASA Astrophysics Data System (ADS)

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

2017-04-01

The geometry and relative motion of colliding plates will affect how and where they deform. In oblique subduction systems, factors such as the dip angle of the subducting plate and the convergence obliquity, as well as the presence of weak zones in the overriding plate, all influence how oblique convergence is partitioned onto various fault systems in the overriding plate. The partitioning of strain into margin-normal slip on the plate-bounding fault and horizontal shearing on a strike-slip system parallel to the margin is mainly controlled by the margin-parallel shear forces acting on the plate interface and the strength of the continental crust. While these plate interface forces are influenced by the dip angle of the subducting plate (i.e., the length of plate interface in the frictional domain) and the obliquity angle between the normal to the plate margin and the plate convergence vector, the strength of the continental crust in the upper plate is strongly affected by the presence or absence of weak zones such as regions of arc volcanism, pre-existing fault systems, or boundaries of stronger crustal blocks. In order to investigate which of these factors are most important in controlling how the overriding continental plate deforms, we compare results of lithospheric-scale 3D numerical geodynamic experiments from two regions in the north-central Andes: the Northern Volcanic Zone (NVZ; 5°N - 3°S) and adjacent Peruvian Flat Slab Segment (PFSS; 3°S -14°S). The NVZ is characterized by a 35° subduction dip angle with an obliquity angle of about 40°, extensive volcanism and significant strain partitioning in the continental crust. In contrast, the PFSS is characterized by flat subduction (the slab flattens beneath the continent at around 100 km depth for several hundred kilometers), an obliquity angle of about 20°, no volcanism and minimal strain partitioning. The plate geometry and convergence obliquity for these regions are incorporated in 3D (1600 x 1600 x

Assessment of snow modeling decisions in the extra-tropical Andes Cordillera

NASA Astrophysics Data System (ADS)

Mendoza, P. A.; Musselman, K. N.; Raleigh, M. S.; Clark, M. P.; McPhee, J. P.

2017-12-01

Improving model realism is an ongoing challenge for the cryosphere research community, not only to advance process understanding, but also to quantify and reduce uncertainty under global warming conditions. This work attempts to characterize the interplay and impact of user decisions about snow model structure and parameter specification on model uncertainty. Snow simulations were conducted in the extra-tropical Andes - a mountainous region that acts as a natural reservoir for Central Chile and Western Argentina. To address this topic, we apply the Structure for Unifying Multiple Modeling Alternatives (SUMMA) to simulate seasonal snowpack dynamics at three sites with different hydroclimatic regimes (semi-arid, Mediterranean, and temperate humid). Results are verified against extensive ground-based observations. Site elevations decrease from north to south, whereas precipitation amounts increase with latitude. Results highlight the impact of different windflow and snow transport decisions on model skill during the accumulation period, and different parameterizations (e.g., albedo decay) on spring simulations. We anticipate that the outcomes from this study will have important implications on current and future research, in particular on the configuration of snow models used to quantify the availability of water resources in this region.

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

NASA Astrophysics Data System (ADS)

Monnier, Sébastien; Kinnard, Christophe

2017-08-01

Three glacier-rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955-2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr-1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr-1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere

Crustal seismicity associated to rpid surface uplift at Laguna del Maule Volcanic Complex, Southern Volcanic Zone of the Andes

NASA Astrophysics Data System (ADS)

Cardona, Carlos; Tassara, Andrés; Gil-Cruz, Fernando; Lara, Luis; Morales, Sergio; Kohler, Paulina; Franco, Luis

2018-03-01

Laguna del Maule Volcanic Complex (LMVC, Southern Andes of Chile) has been experiencing large rates (ca. 30 cm/yr) of surface uplift as detected since 2008 by satellite geodetic measurements. Previous works have modeled the source of this deformation as an inflating rectangular sub-horizontal sill underlying LMVC at 5 km depth, which is supposedly related to an active process of magmatic replenishment of a shallow silicic reservoir. However little is known about the tectonic context on which this activity is taking place, particularly its relation with crustal seismicity that could help understanding and monitoring the current deformation process. Here we present the first detailed characterization of the seismic activity taking place at LMVC and integrate it with structural data acquired in the field in order to illuminate the possible connection between the ongoing process of surface uplift and the activation of crustal faults. Our main finding is the recognition of repetitive volcano-tectonic (VT) seismic swarms that occur periodically between 2011 and 2014 near the SW corner of the sill modeled by InSAR studies. A cross-correlation analysis of the waveforms recorded for these VT events allows identifying three different seismic families. Families F1 and F3 share some common features in the stacked waveform and its locations, which markedly differ from those of family F2. Swarms belonging to this later family are more energetic and its energy was increasing since 2011 to a peak in January 2013, which coincide with maximum vertical velocities detected by local GPS stations. This points to a common process relating both phenomena. The location of VT seismic swarms roughly coincides with the intersection of a NE-SW lineament with a WNW-ESE lineament. The former shows clear field evidences of dextral strike-slip that are fully consistent with one nodal plane of focal mechanism for well-recorded F2 events. The conjugate nodal plane of these focal mechanisms could

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

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

GT-9A - EARTH SKY - CENTRAL COASTAL AREA OF PERU

NASA Image and Video Library

1966-06-05

S66-38298 (5 June 1966) --- The central coastal area of Peru as seen from the Gemini-9A spacecraft during its 35th revolution of Earth. The body of water is the Pacific Ocean. The mountains are in the Cordillera Blanca range of the Andes. The 22,205-feet Huascaran is the highest peak in the area. The image was taken with a modified 70mm Hasselblad camera, using Eastman Kodak, Ektachrome MS (S.O. 217) color film Photo credit: NASA

Solar and Volcanic Modulation of Little Ice Age Climate in the Tropical Andes, Venezuela

NASA Astrophysics Data System (ADS)

Polissar, P. J.; Abbott, M. B.; Wolfe, A. P.; Rull, V.; Bezada, M.

2004-12-01

The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here, we report a 1500-year reconstruction of climate history in the Venezuelan Andes using lake sediment records from four sites. This reconstruction is based upon accelerator mass spectrometry (AMS) radiocarbon and Pb-210 dating, sedimentology, magnetic susceptibility, geochemistry, pollen and stable isotope (C, N) measurements. In the Laguna Mucubaji watershed four distinct glacial advances occurred between 1250 and 1810 A.D. The earliest advance began during an extended period of higher global volcanic activity. The subsequent three advances were coincident with minima in solar activity (reconstructed from Be-10 and C-14 records). The Mucubají glacial activity in the Venezuelan Andes coincides with other records of Little Ice Age (LIA) glacial advances in S. America. Comparison of modern glacier equilibrium line altitudes (ELAs) in Venezuela with the Mucubaji LIA glacier ELA indicates an ELA depression of at least 300 m. Both a decline in temperature and increase in precipitation are required to explain the ELA depression. The precipitation increase is supported by increased catchment erosion recorded in L. Blanca sediments. Pollen records from two sites in the Venezuelan Andes also indicate wetter and colder conditions during the LIA.

Evolution of the Chos Malal and Agrio fold and thrust belts, Andes of Neuquén: Insights from structural analysis and apatite fission track dating

NASA Astrophysics Data System (ADS)

Rojas Vera, E. A.; Mescua, J.; Folguera, A.; Becker, T. P.; Sagripanti, L.; Fennell, L.; Orts, D.; Ramos, V. A.

2015-12-01

The Chos Malal and Agrio fold and thrust belts are located in the western part of the Neuquén basin, an Andean retroarc basin of central-western Argentina. Both belts show evidence of tectonic inversion at the western part during Late Cretaceous times. The eastern part is dominated by late Miocene deformation which also partially reactivated the western structures. This work focuses on the study of the regional structure and the deformational event that shaped the relief of this part of the Andes. Based on new field work and structural data and previously published works a detailed map of the central part of the Neuquén basin is presented. Three regional structural cross sections were surveyed and balanced using the 2d Move™ software. In order to define a more accurate uplift history, new apatite fission track analyses were carried on selected structures. These data was used for new thermal history modeling of the inner part of the Agrio and Chos Malal fold and thrust belts. The results of the fission track analyses improve the knowledge of how these fold and thrust belts have grown trough time. Two main deformational events are defined in Late Cretaceous to Paleocene and Late Miocene times. Based on this regional structural analysis and the fission track data the precise location of the orogenic front for the Late Cretaceous-Paleocene times is reconstructed and it is proposed a structural evolution of this segment of the Andes. This new exhumation data show how the Late Cretaceous to Paleocene event was a continuous and uninterrupted deformational event.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

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

NASA Astrophysics Data System (ADS)

Singer, B. S.

2014-12-01

The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007 the crust here has been inflating at an astonishing rate of 25 cm/yr. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ~20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. Swarms of volcano-tectonic and long period earthquakes, mostly of M < 2, have occurred beneath the most recent rhyolite coulees on the southwestern and southern margins of the 20 km diameter ring of silicic vents. With support from the US NSF and the Chilean government (SERNAGEOMIN and OVDAS) we are seizing the unique opportunity to investigate, over the next 5 years, the dynamics of this large rhyolitic system while magma migration, reservoir growth, and crustal deformation are actively underway. This collaboration involves scientists and students at: University of Wisconsin-Madison, Georgia Tech, Cornell, University of Alberta, Simon Fraser University, University of Chile-Santiago, CONICET/University of San Juan-Argentina, Nanyang Technological University-Singapore, SERNAGEOMIN, OVDAS, USGS, and SEGEMAR-Argentina. Team members will be introduced in this presentation. Our approach includes augmenting the OVDAS array of 6 permanent seisic stations with 40 additional instruments to conduct tomographic, receiver function and ambient noise studies. We continue to collect 4-D gravity data from 37 stations. Surface deformation is monitored via cGPS at 5 permanent receivers and InSAR data. A magnetotelluric survey across the Andes at 36o S is planned. Geochemical studies include mineral zoning and U-Th disequilibrium of zircons to constrain the timing of magma intrusion and

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

NASA Astrophysics Data System (ADS)

Ward, Kevin Michael

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

Hybrid Literacies: The Case of a Quechua Community in the Andes

ERIC Educational Resources Information Center

de la Piedra, Maria Teresa

2009-01-01

Drawing on data from an ethnographic study in a Quechua rural community in the Peruvian Andes, this article examines hybrid literacy practices among bilingual rural speakers in the context of the household and the community. I examine the coexistence of two types of textual practices that operate side by side, at times integrated in the same…

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

NASA Astrophysics Data System (ADS)

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

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

NASA Astrophysics Data System (ADS)

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

2012-04-01

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

Distribution models and species discovery: the story of a new Solanum species from the Peruvian Andes

PubMed Central

Särkinen, Tiina; Gonzáles, Paúl; Knapp, Sandra

2013-01-01

Abstract A new species of Solanum sect. Solanum from Peru is described here. Solanum pseudoamericanum Särkinen, Gonzáles & S.Knapp sp. nov. is a member of the Morelloid clade of Solanum, and is characterized by the combination of mostly forked inflorescences, flowers with small stamens 2.5 mm long including the filament, and strongly exerted styles with capitate stigmas. The species was first thought to be restricted to the seasonally dry tropical forests of southern Peru along the dry valleys of Río Pampas and Río Apurímac. Results from species distribution modelling (SDM) analysis with climatic predictors identified further potential suitable habitat areas in northern and central Peru. These areas were visited during field work in 2013. A total of 17 new populations across the predicted distribution were discovered using the model-based sampling method, and five further collections were identified amongst herbarium loans. Although still endemic to Peru, Solanum pseudoamericanum is now known from across northern, central and southern Peru. Our study demonstrates the usefulness of SDM for predicting new occurrences of rare plants, especially in the Andes where collection densities are still low in many areas and where many new species remain to be discovered. PMID:24399901

Distribution models and species discovery: the story of a new Solanum species from the Peruvian Andes.

PubMed

Särkinen, Tiina; Gonzáles, Paúl; Knapp, Sandra

2013-01-01

A new species of Solanum sect. Solanum from Peru is described here. Solanum pseudoamericanum Särkinen, Gonzáles & S.Knapp sp. nov. is a member of the Morelloid clade of Solanum, and is characterized by the combination of mostly forked inflorescences, flowers with small stamens 2.5 mm long including the filament, and strongly exerted styles with capitate stigmas. The species was first thought to be restricted to the seasonally dry tropical forests of southern Peru along the dry valleys of Río Pampas and Río Apurímac. Results from species distribution modelling (SDM) analysis with climatic predictors identified further potential suitable habitat areas in northern and central Peru. These areas were visited during field work in 2013. A total of 17 new populations across the predicted distribution were discovered using the model-based sampling method, and five further collections were identified amongst herbarium loans. Although still endemic to Peru, Solanum pseudoamericanum is now known from across northern, central and southern Peru. Our study demonstrates the usefulness of SDM for predicting new occurrences of rare plants, especially in the Andes where collection densities are still low in many areas and where many new species remain to be discovered.

High-resolution paleoclimate records of Holocene hydroclimatic variability in the Eastern Colombian Andes from Lago de Tota

NASA Astrophysics Data System (ADS)

Ahmed, M. N.; Bird, B. W.; Escobar, J.; Polissar, P. J.

2017-12-01

The Northern Hemisphere (NH) South American Monsoon (SAM) is a significant source of precipitation for the North Andes (north of 0˚) and has major control over regional hydroclimate variability. Holocene-length histories of NH SAM variability are few compared to the Southern Hemisphere (SH), limiting understanding of how these systems are connected on orbital and shorter timescales. Here, we present multi-proxy lake-sediment-based paleoclimate and paleohydrologic reconstructions from Lago de Tota, Colombia, using sedimentological, geochemical and leaf-wax hydrogen isotopic indicators from radiometically dated cores. The results indicate periods of wet and dry climate phases during the past 9000 BP with an average Holocene sedimentation rate 33cm/kyr. An increase in total organic matter (TOM) content and finer grain-size distributions was observed from 8000 to 3200 BP, suggesting a period of high lake level. This was followed by lower TOM and coarser grain sizes, suggesting lower lake levels from 3200 BP to the present. Although Tota's lake level pattern is antiphased with other lake level reconstructions from the NH and SH Andes, it is consistent with hypothesized changes in atmospheric convection over the Andes during the Holocene and the way in which they would be modified by the so-called dry island effect in the Colombian Andes. This suggests that a common forcing mechanism can be invoked to explain differing millennial-scale Andean hydroclimate changes, namely atmospheric convection. Orbital and Pacific atmosphere-forcing are therefore likely to have played a significant role in driving pan-Andean hydroclimate variability based on their inter-hemispheric influence on Andean convection.

Characterizing the Linkages Between landform and Precipitation Regime in the Sierra Madre Meridional and in the Andes

NASA Astrophysics Data System (ADS)

Giovannettone, J. P.; Barros, A. P.

2005-12-01

Mountains play an important role in the hydrologic cycle in many parts of the world. About 25% of the world's population lives in mountainous terrain, and 60% of people rely on freshwater from mountainous regions for drinking water and other purposes. This is especially the case in the western US, in Central America and along the Andes. Whereas quantitative estimation of precipitation in mountainous regions is of critical importance, sparse raingauge networks and the operational difficulties of ground-based radar in the vicinity of high terrain, leave us without substantive observations to work with. By contrast, satellites provide a unique opportunity to look at large regions simultaneously and at high resolution. Although terrain complexity can also cause substantial uncertainty in the interpretation of remotely-sensed data, there is great value in the small-scale structure captured by high spatial resolution sensors. A comprehensive study including surface measurements, observations from the NASA TRMM satellite, and coupled land-atmosphere modeling to characterize the diurnal cycle of precipitation over the Sierra Madre Meridional (east of Mexico City) and over the Andes is currently under way. The objective of this work is to investigate the role of landform as the organizing principle of convective activity in mountainous regions and to determine whether this spatial organization can be linked to the diurnal cycle of rainfall. For this purpose, TRMM data were analyzed over the Sierra Madre and Andes Mountains using an algorithm developed by Nesbitt et al. (2000) to determine the location of precipitation features (PF's) over a time period extending from 1998 to 2004. The algorithm uses two types of data provided by the TRMM satellite: the near-surface precipitation radar (PR) and the TRMM Microwave Imager (TMI) polarization-corrected temperatures (PCT's) at 85.5 GHz. A PF is defined as an area of 75 km2 or greater in which reflectivities are greater than 20 d

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago

NASA Astrophysics Data System (ADS)

Eichler, A.; Gramlich, G.; Kellerhals, T.; Tobler, L.; Rehren, Th.; Schwikowski, M.

2017-01-01

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200-800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700-50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures.

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago.

PubMed

Eichler, A; Gramlich, G; Kellerhals, T; Tobler, L; Rehren, Th; Schwikowski, M

2017-01-31

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200-800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700-50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures.

Ice-core evidence of earliest extensive copper metallurgy in the Andes 2700 years ago

PubMed Central

Eichler, A.; Gramlich, G.; Kellerhals, T.; Tobler, L.; Rehren, Th.; Schwikowski, M.

2017-01-01

The importance of metallurgy for social and economic development is indisputable. Although copper (Cu) was essential for the wealth of pre- and post-colonial societies in the Andes, the onset of extensive Cu metallurgy in South America is still debated. Comprehensive archaeological findings point to first sophisticated Cu metallurgy during the Moche culture ~200–800 AD, whereas peat-bog records from southern South America suggest earliest pollution potentially from Cu smelting as far back as ~2000 BC. Here we present a 6500-years Cu emission history for the Andean Altiplano, based on ice-core records from Illimani glacier in Bolivia, providing the first complete history of large-scale Cu smelting activities in South America. We find earliest anthropogenic Cu pollution during the Early Horizon period ~700–50 BC, and attribute the onset of intensified Cu smelting in South America to the activities of the central Andean Chiripa and Chavin cultures ~2700 years ago. This study provides for the first time substantial evidence for extensive Cu metallurgy already during these early cultures. PMID:28139760

Volcanic impediments in the progressive development of pre-Columbian civilizations in the Ecuadorian Andes

NASA Astrophysics Data System (ADS)

Hall, Minard L.; Mothes, Patricia A.

2008-10-01

Archaeological investigations in Ecuador have proposed that there appear to be hiatus or anomalous jumps in the progressive development of pre-Columbian indigenous cultures, based upon the fact that their ceramics and tools demonstrate abrupt advances in their sophistication at several horizons in the soil profile. Because some of these horizons are clearly associated with volcanic ash layers, archaeologists have sought a causal relation with volcanism, that is, the eruptive events or their products severely interfered with the early inhabitants, resulting in their abandonment of certain areas. Geological studies of the young volcanoes in the Ecuadorian Andes carried out during the past two decades now allow us to make a more thorough evaluation of the role of volcanism during the Holocene. This contribution briefly describes the principal Holocene volcanic events and the distribution of the corresponding eruptive products found along the InterAndean Valley, from southern Colombia to central Ecuador. Only those events that were sufficiently large that they could have had a detrimental effect on the valley's early residents are discussed. Dacitic and rhyolitic ash flows, as well as numerous debris flows (lahars) have occurred frequently and their deposits cover many valleys and floodplains, where early inhabitants probably settled. The enormous Chillos Valley lahar, associated with the 4500 yBP eruption of Cotopaxi volcano, buried soils containing ceramics of the early Formative Period. However, the greatest impact upon mankind was probably not these short-lived violent events, but rather the burying of settlements and agricultural fields by ash fallout, the effect of which may have lasted hundreds of years. Ash fall layers are observed in pre-Columbian cultural horizons in the soil profile, occurring in the InterAndean Valley, the lower flanks of the Andes, and along Ecuador's Pacific coast, the oldest corresponding to the 5800 yBP eruption of Cotopaxi. This brief

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

PubMed

Nina, Nélida; Quispe, Cristina; Jiménez-Aspee, Felipe; Theoduloz, Cristina; Feresín, Gabriela Egly; Lima, Beatriz; Leiva, Elba; Schmeda-Hirschmann, Guillermo

2015-10-06

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

A new species of Alopoglossus lizard (Squamata, Gymnophthalmidae) from the tropical Andes, with a molecular phylogeny of the genus

PubMed Central

Torres-Carvajal, Omar; Lobos, Simón E.

2014-01-01

Abstract We describe a new species of Alopoglossus from the Pacific slopes of the Andes in northern Ecuador based on morphological and molecular evidence. The new species differs most significantly from all other congeners in having a double longitudinal row of widened gular scales, lanceolate dorsal scales in transverse rows, 29–32 dorsal scales in a transverse row at midbody, and 4 longitudinal rows of ventrals at midbody. It is most similar in morphology to A. festae, the only species of Alopoglossus currently recognized in western Ecuador. We analyze the phylogenetic relationships among species of Alopoglossus based on the mitochondrial gene ND4. Cis-Andean [east of the Andes] and Trans-Andean [west of the Andes] species are nested in two separate clades, suggesting that the uplift of these mountains had an important effect in the diversification of Alopoglossus. In addition, we present an updated key to the species of Alopoglossus. PMID:24899852

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Sensitivity of modelled snow cover to turbulent flux parameterization and forcing data: a case study in a high altitude basin of the dry Andes, northern Chile

NASA Astrophysics Data System (ADS)

Kinnard, C.; Irarrazaval, I.; Campos, C.; Gascoin, S.; MacDonell, S.; Macdonell, S.; Herrero, J.

2016-12-01

Snow cover in the central-northern Andes of Chile is the main runoff source, providing water for the irrigation of cultures in the fertile valleys downstream. The prospect of adverse climate warming impacts on the hydrological cycle calls for a better understanding of the snow cover dynamics in response to climate, an aspect that has been little studied in the dry Andes. The heterogeneous and often thin snow cover, as well as the paucity of long-term hydrometeorological data makes snow modelling a challenging task in these regions. In this work we applied a physically-based, spatially-distributed snow model (Wimmed) to the La Laguna headwater catchment in the dry Andes (30°S, 70°W) during three hydrological years (2010-2013) when forcing data was available. Model testing at the point scale revealed a large sensitivity of simulated snow depths to the choice of snow roughness parameter (z0), which controls turbulent fluxes, while wind-induced snow erosion at the station in 2010 and 2011 complicated model validation. The inclusion of a mean wind speed map from a previous simulation with the WRF atmospheric model was found to improve the simulation results, while excluding the highest mountain ridge weather station had detrimental effects on the results. A snow roughness (z0) of 1 mm yielded the best comparison between the simulated and observed snow depth at the reference weather station, and between the simulated and MODIS-derived snow cover at the catchment scale. The simulation resulted in large sublimation losses (up to 4 mm day-1), corresponding to more than 80% of snow ablation in the catchment. While such high sublimation rates have been reported before in this region, remaining uncertainties in precipitation data and snow compaction processes call for more detailed studies and increased instrumentation in order to improve future modelling efforts.

Air temperature change in the northern and southern tropical Andes linked to North-Atlantic stadials and Greenland interstadials

NASA Astrophysics Data System (ADS)

Urrego, Dunia H.; Hooghiemstra, Henry

2016-04-01

We use eight pollen records reflecting climatic and environmental change from northern and southern sites in the tropical Andes. Our analysis focuses on the signature of millennial-scale climate variability during the last 30,000 years, in particular the Younger Dryas (YD), Heinrich stadials (HS) and Greenland interstadials (GI). We identify rapid responses of the vegetation to millennial-scale climate variability in the tropical Andes. The signature of HS and the YD are generally recorded as downslope migrations of the upper forest line (UFL), and are likely linked to air temperature cooling. The GI1 signal is overall comparable between northern and southern records and indicates upslope UFL migrations and warming in the tropical Andes. Our marker for lake level changes indicates a north to south difference that could be related to moisture availability. The direction of air temperature change recorded by the Andean vegetation is consistent with millennial-scale cryosphere and sea surface temperature records from the American tropics, but suggests a potential difference between the magnitude of temperature change in the ocean and the atmosphere.

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

PubMed

Ocampo-Peñuela, Natalia; Pimm, Stuart L

2014-10-01

We aspired to set conservation priorities in ways that lead to direct conservation actions. Very large-scale strategic mapping leads to familiar conservation priorities exemplified by biodiversity hotspots. In contrast, tactical conservation actions unfold on much smaller geographical extents and they need to reflect the habitat loss and fragmentation that have sharply restricted where species now live. Our aspirations for direct, practical actions were demanding. First, we identified the global, strategic conservation priorities and then downscaled to practical local actions within the selected priorities. In doing this, we recognized the limitations of incomplete information. We started such a process in Colombia and used the results presented here to implement reforestation of degraded land to prevent the isolation of a large area of cloud forest. We used existing range maps of 171 bird species to identify priority conservation areas that would conserve the greatest number of species at risk in Colombia. By at risk species, we mean those that are endemic and have small ranges. The Western Andes had the highest concentrations of such species-100 in total-but the lowest densities of national parks. We then adjusted the priorities for this region by refining these species ranges by selecting only areas of suitable elevation and remaining habitat. The estimated ranges of these species shrank by 18-100% after accounting for habitat and suitable elevation. Setting conservation priorities on the basis of currently available range maps excluded priority areas in the Western Andes and, by extension, likely elsewhere and for other taxa. By incorporating detailed maps of remaining natural habitats, we made practical recommendations for conservation actions. One recommendation was to restore forest connections to a patch of cloud forest about to become isolated from the main Andes. © 2014 Society for Conservation Biology.

Evaluation of Little Ice Age cooling in Western Central Andes, suggested by paleoELAs, in contrast with global warming since late 19th century deduced from instrumental records

NASA Astrophysics Data System (ADS)

Ubeda, Jose; Palacios, David; Campos, Néstor; Giraldez, Claudia; García, Eduardo; Quiros, Tatiana

2015-04-01

This paper attempts to evaluate climate cooling (°C) during the glacial expansion phases using the product GTV•ΔELA, where GTV is the vertical air temperature gradient (°C/m) and ΔELA (m) the difference in level observed between the Equilibrium Line Altitude (ELA) reconstructions for current and past glaciers. With this aim the Area x Altitude Balance Ratio-(AABR) method was used to produce reconstructions of present ELAs (2002-2010) and paleoELAs corresponding to the last glacier advance phase. The reconstructions were produced in three study areas located along a N-S transect of the western cordillera in the Central Andes: the south-western sector of the Nevado Hualcán (9°S, 77°W; Giráldez 2011); the southern slope of the Cordillera Pariaqaqa (12°S, 76°W; Quirós, 2013) and the NW, NE, SE and SW quadrants of the Nevado Coropuna (16°S, 72°W; García 2013; Úbeda 2011; Campos, 2012). The three mountains exceed 6000 m altitude, their summit areas are covered by glaciers, and on their slopes there are existing well-conserved moraines deposited by the last advances near the present front of the ice masses. Although there are no absolute dates to confirm this hypothesis, it has been assumed that the last glacial advances occurred during the Little Ice Age (LIA), which the oxygen isotopes of the Nevado Huascarán (9°S, 77°W) date to the period 1500-1890. For the Hualcán and Pariaqaqa the mean global value of the Earth's GTV (6.5°C/km) was used, considered valid for the Tropics. On the Coropuna a GTV=8.4°C/km was used, based on high resolution sensors installed in situ since 2007 (Úbeda 2011). This gradient is approaching the upper limit of the dry adiabatic gradient (9.8°C/km), as the Coropuna region is more arid than the other case study areas. The climate cooling estimates deduced from the product GTV•ΔELA were compared with the global warming shown by the 1880-2012 series, ΔT=0.85°C, and 1850/1900-2003/2012, ΔT=0.78°C. The differences are

Linking climate variations with the hydrological cycle over the semi-arid Central Andes of Argentina. Past, present and future, with emphasis on streamflow droughts.

NASA Astrophysics Data System (ADS)

Rivera, Juan Antonio; Araneo, Diego; Penalba, Olga; Villalba, Ricardo

2017-04-01

In the Central Andes of Argentina (CAA, located between 28° and 38°S), an arid to semi-arid region, the irrigation and a variety of socio-economical activities are highly dependent on river streamflows. Permanent and semi-permanent rivers originate mainly from snowmelt and glacier ablation, enabling the development of large agricultural oasis and the construction of numerous dams and reservoirs for irrigation and power generation. Most of its 2.5 million inhabitants and the main economic activities are located in a small irrigated fraction of the territory, where the variations in the timing and amount of water resources largely determine the socio-economic vulnerability of the region. In this context, the links between climatic variability and the hydrological cycle were assessed considering daily streamflow records from 21 streamgauges in the main rivers of the study area. Principal component analysis of annual hydrographs from 1931 to 2015 allowed to discriminate between precipitation- and temperature-related components associated with variations in snow accumulation (51% of variance) and advances/delays of the streamflow annual peak (16% of variance), respectively. The components related to intraseasonal variability account for 7% and 6% of variance, respectively, mixing both precipitation and thermal factors. The contribution of the precipitation-related component was the main driver of the 2010-15 streamflow drought conditions, although the thermal contribution was relevant during specific seasonal drought events. Based on an empirical decomposition methodology we identified the main modes of streamflow drought variability, which are linked to El Niño-Southern Oscillation on interannual time scales and the Pacific Decadal Oscillation (PDO) for the decadal variations. This result shows the influence of the tropical Pacific Ocean in the development of streamflow drought conditions and its relevance for potential predictability of hydroclimatic variations

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

PubMed

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

2013-12-01

Lepidium meyenii (Maca) is a plant that grows at over 4,000 m above sea level in the central Peruvian Andes. The hypocotyls of this plant are traditionally consumed for their nutritional and medicinal properties. The aim of this study was to determine the health status based on a health related quality of life (HRQL) questionnaire (SF-20) and serum levels of interleukin 6 (IL-6) in subjects that are maca consumers. For this, a cross-sectional study was designed to be performed in 50 subjects from Junin (4,100 m): 27 subjects were maca consumers and 23 were non-consumers. The SF-20 survey is used to obtain a summary measure of health status. The stand up from a chair and sit down (SUCSD) test (to assess lower-extremity function), hemoglobin measurement, blood pressure, sexual hormone levels, serum IL-6 levels and the score of chronic mountain sickness (CMS) were evaluated. Testosterone/estradiol ratio (P <0.05), IL-6 (P < 0.05) and CMS score were lower, whereas the health status score was higher, in maca consumers when compared to non-consumers (P < 0.01). A greater proportion of maca consumers successfully completed the SUCSD test compared to non-consumers (P < 0.01), showing a significant association with lower values of serum IL-6 (P < 0.05). In conclusion, consumption of maca was associated with low serum IL-6 levels and in turn with better health status scores in the SF-20 survey and low chronic mountain sickness scores.

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

PubMed Central

Gonzales, Gustavo F.; Gasco, Manuel; Lozada, Ivan

2013-01-01

Lepidium meyenii (Maca) is a plant that grows at over 4000 meters above sea level in the central Peruvian Andes. The hypocotyls of this plant are traditionally consumed for their nutritional and medicinal properties. The aim of this study was to determine the health status based on a health related quality of life (HRQL) questionnaire (SF-20) and serum levels of interleukin 6 (IL-6) in subjects that are maca consumers. For this, a cross-sectional study was designed to be performed in 50 subjects from Junin (4100 m): 27 subjects were maca consumers and 23 were non-consumers. The SF-20 survey is used to obtain a summary measure of health status. The stand up from a chair and sit down (SUCSD) test (to assess lower-extremity function), hemoglobin measurement, blood pressure, sexual hormone levels, serum IL-6 levels and the score of chronic mountain sickness (CMS) were evaluated. Testosterone/estradiol ratio (P≪0.05), IL-6 (P<0.05) and CMS score were lower, whereas the health status score was higher, in maca consumers when compared to non-consumers (P<0.01). A greater proportion of maca consumers successfully completed the SUCSD test compared to non-consumers (P<0.01), showing a significant association with lower values of serum IL-6 (P<0.05). In conclusion, consumption of maca was associated with low serum IL-6 levels and in turn with better health status scores in the SF-20 survey and low chronic mountain sickness scores. PMID:23934543

Entire Western Hemisphere visible from Apollo 8 spacecraft

NASA Image and Video Library

1968-12-22

AS08-16-2593 (21-27 Dec. 1968) --- A striking view from the Apollo 8 spacecraft showing nearly the entire Western Hemisphere, from the mouth of the St. Lawrence River, including nearby Newfoundland, extending to Tierra del Fuego at the southern tip of South America. Central America is clearly outlined. Nearly all of South America is covered by clouds, except the high Andes Mountain chain along the west coast. A small portion of the bulge of West Africa shows along the sunset terminator.

Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

NASA Astrophysics Data System (ADS)

Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

2014-12-01

Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

Combining numerical modeling and stable isotope values to quantify groundwater recharge from the Chilean Andes to the Pampa del Tamarugal Basin, Atacama Desert, northern Chile

NASA Astrophysics Data System (ADS)

Dodd, J. P.; Pollyea, R.

2014-12-01

The Atacama Desert of northern Chile is one of the driest regions on Earth and receives less than 5mm of precipitation annually. The Pampa del Tamarugal (PdT) Basin contains the largest aquifer system in the region, yet the mechanisms and timing of aquifer recharge and continental-scale groundwater flux are poorly understood. Although there is little debate that the source of groundwater recharge is the higher elevation regions of the Andean Altiplano to the east of the PdT Basin, there remains much uncertainty surrounding the mechanisms and timing of aquifer recharge and continental-scale groundwater flux. Most recharge models of the PdT focus on surface water runoff and alluvial fan recharge on shorter time scales, but many of these models explicitly neglect deep flow pathways. Previous investigators have combined the thermal aquifer profile and 14C groundwater ages to propose an alternative conceptual model in which cold meteoric water infiltrates deep into the Cordillera before circulating upward into the PdT by thermal convection through fault-controlled migration pathways. Although this conceptual model provides a convincing theoretical argument for deep fluid circulation, it cannot constrain the magnitude of this deep recharge flux. In this work, we revisit deep-flow conceptual model by combining the spatial distribution of hydrogen and oxygen isotope values as groundwater tracers with a non-isothermal model of continental scale groundwater flow through a two-dimensional transect from the Chilean Andes to the PdT Basin. This work provides first-order estimates on the contribution of deep groundwater circulation within the PdT Aquifer, while providing a framework for (1) quantifying boundary conditions for high resolution models of groundwater resources within the PdT Aquifer, (2) assessing the influence of variable future climate scenarios for groundwater availability in the region, and (3) further integrating conservative tracers and numerical models for

A modelling study of the seasonal snowpack energy balance at three sites along the Andes Cordillera. Regional climate and local effects.

NASA Astrophysics Data System (ADS)

McPhee, James; Mengual, Sebastian; MacDonell, Shelley

2017-04-01

Seasonal snowpack melt constitutes the main water source for large portions of extratropical South America, including central Chile and Western Argentina. The properties and distribution of snow in the Andes are threatened by rapid climate change, characterised by warming and drying. This study provides a first attempt at detailed description of the energy balance of the seasonal snowpack and its variability along a latitudinal gradient, which is also correlated with an elevation and precipitation gradient, in the Andes Cordillera. The Snowpack model was validated at semi-arid, Mediterranean and temperate humid sites, where meteorological and snowpack properties have been observed since year 2013. Site elevations decrease from north to south, whereas precipitation climatology increases with latitude. Results show that turbulent energy exchange becomes relatively more important in periods of low snow accumulation, with sensible heat fluxes having a greater effect in cooling the snowpack at the high-altitude, low latitude site. Likewise, daily melt-freeze cycles are important in maintaining positive cold contents throughout the accumulation season at this site, and contribute to extending the duration of snow cover despite low accumulation and high radiation loads. In contrast, the southernmost, lowest elevation site shows smaller daily temperature amplitude and a much more preponderant radiation component to the energy balance. This modelling exercise highlights the nonlinearities of snow dynamics at different geographical settings in a sparsely monitored mountain area of the world, as well as the need for further understanding in order to evaluate the sensitivity of snow-dominated watersheds to global warming and climate change.

Cenozoic basin thermal history reconstruction and petroleum systems in the eastern Colombian Andes

NASA Astrophysics Data System (ADS)

Parra, Mauricio; Mora, Andres; Ketcham, Richard A.; Stockli, Daniel F.; Almendral, Ariel

2017-04-01

Late Mesozoic-Cenozoic retro-arc foreland basins along the eastern margin of the Andes in South America host the world's best detrital record for the study of subduction orogenesis. There, the world's most prolific petroleum system occur in the northernmost of these foreland basin systems, in Ecuador, Colombia and Venezuela, yet over 90% of the discovered hydrocarbons there occur in one single province in norteastern Venezuela. A successful industry-academy collaboration applied a multidisciplinary approach to the study of the north Andes with the aim of investigating both, the driving mechanisms of orogenesis, and its impact on hydrocarbon accumulation in eastern Colombia. The Eastern Cordillera is an inversion orogen located at the leading edge of the northern Andes. Syn-rift subsidence favored the accumulation of km-thick organic matter rich shales in a back-arc basin in the early Cretaceous. Subsequent late Cretaceous thermal subsidence prompted the accumulation of shallow marine sandstones and shales, the latter including the Turonian-Cenomanian main hydrocarbon source-rock. Early Andean uplift since the Paleocene led to development of a flexural basin, filled with mainly non-marine strata. We have studied the Meso-Cenozoic thermal evolution of these basins through modeling of a large thermochronometric database including hundreds of apatite and zircon fission-track and (U-Th)/He data, as well as paleothermometric information based on vitrinite reflectance and present-day temperatures measured in boreholes. The detrital record of Andean construction was also investigated through detrital zircon U-Pb geochronometry in outcrop and borehole samples. A comprehensive burial/exhumation history has been accomplished through three main modeling strategies. First, one-dimensional subsidence was used to invert the pre-extensional lithospheric thicknesses, the magnitude of stretching, and the resulting heat flow associated to extension. The amount of eroded section and

A glacial record of the last termination in the southern tropical Andes

NASA Astrophysics Data System (ADS)

Bromley, G. R.; Schaefer, J. M.; Winckler, G.; Hall, B. L.; Todd, C. E.; Rademaker, K.

2012-12-01

The last glacial termination represents the highest-magnitude climate change of the last hundred thousand years. Accurate resolution of events during the termination is vital to our understanding of how - and why - the global climate system transitions from a full glacial to interglacial state, as well as the causes of abrupt climate change during the late-glacial period. Palaeoclimate data from low latitudes, though relatively sparse, are particularly valuable, since the tropical ocean and atmosphere likely play a crucial role in Quaternary climate variability on all timescales. We present a detailed glacier record from the Andes of southern Peru (15°S), resolved with 3He surface-exposure dating and spanning the last glacial maximum and termination. Our dataset reveals that glaciers in this part of the Southern Hemisphere maintained their Late Pleistocene maxima for several millennia and that the onset of the termination may have occurred relatively late. Deglaciation was punctuated by two major advances during the late-glacial period. Following the glacial-interglacial transition, our preliminary chronologic and morphologic data suggest that, in contrast to the Northern Hemisphere, glaciers in the southern tropical Andes have experienced overall shrinkage during the Holocene.

New evidence for late mesozoic-early Cenozoic evolution of the Chilean Andes in the upper Tinguiririca valley (35 °S), central Chile

NASA Astrophysics Data System (ADS)

Charrier, Reynaldo; Wyss, AndréR.; Flynn, John J.; Swisher, Carl C.; Norell, Mark A.; Zapatta, Franyo; McKenna, Malcolm C.; Novacek, Michael J.

1996-11-01

New geologic, paleontologic and isotopic geochronometric results from the Termas del Flaco region in the upper Tinguiririca River valley in central Chile demand considerable revision of the accepted geotectonic history of the Andean Main Range in this region. A diverse, transitional Eocene-Oligocene aged, land-mammal fauna was recovered from several sites in volcaniclastic sediments of the Coya-Machalí (=Abanico) Formation. Major results of our study include: 1) The 1000 + m thick studied deposits, previously attributed to the Cretaceous Colimapu Formation, belong to the Coya-Machalí (=Abanico) Formation. Radioisotopic data from levels immediately above (31.5 Ma) and below (37.S Ma) the fossiliferous horizon indicate a latest Eocene to early Oligocene age for the basal part of the formation and the fauna contained in it. 2) The fossiliferous unit rests with slight angular offset on different Mesozoic units: "Brownish-red Clastic Unit" (BRCU) and Baños del Flaco Formation; in a limited area it also overlies a white tuff dated at 104 Ma. 3) The contacts just discussed (none of which is attributable to faulting), demonstrate the existence of two, or possibly three, unconformities in the region. 4) Sedimentological criteria argue against reference of the BRCU to the Colimapu Formation, and imply correlation of the former unit to basal levels with in the late Cretaceous Neuquén Group of western Argentina. 5) The Coya-Machalí Formation, previously viewed as representing the western volcanic equivalent of Riográndico Supercycle deposits of western Argentino, is likely coeval to much younger units in that region such as the Agua de la Piedra Formation. 6) Paleomagnetic results from the fossil producing horizon indicate about 20 ° of post-early Oligocene, counterclockwise rotation. 7) Fossil mammals from the Coya-Machalí Formation near Termas del Flaco represent a distinct biochronologic interval not heretofore clearly recognized from elsewhere on the continent

Molecular identification of vectors of Leishmania in Colombia: mitochondrial introgression in the Lutzomyia townsendi series.

PubMed

Testa, J M; Montoya-Lerma, J; Cadena, H; Oviedo, M; Ready, P D

2002-12-01

The identity of the sandfly vectors of Leishmania braziliensis in Valle del Cauca Department, Colombia, was originally given as Lutzomyia townsendi, but then changed to L. youngi, another member of the L. townsendi series (Verrucarum group) with isomorphic females. To identify members of this series in Valle del Cauca, we analyzed the nuclear gene elongation factor-alpha (EF-alpha) and the mitochondrial gene cytochrome b (Cyt b). DNA sequences from the L. verrucarum series (L. columbiana, L. evansi and L. ovallesi) were used as outgroups. Flies from two locations on the western cordillera of the Andes were identified as L. townsendi s.s., according to male morphology and distinctive gene lineages. In the third location, on the central cordillera of the Andes, most specimens were identified as belonging to a geographical population of L. youngi, according to male morphology, an EF-alpha lineage shared with L. youngi from the Venezuelan-type locality, and a distinctive Cyt b sub-lineage. All other specimens were identified as L. youngi with the introgressed Cyt b sequences of L. townsendi. Such interspecific introgression implies that vectorial traits and ecological associations may no longer be viewed as fixed properties of different morphospecies.

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

NASA Astrophysics Data System (ADS)

Brenning, Alexander; Muenchow, Jannes

2016-04-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Racialization of the Bilingual Student in Higher Education: A Case from the Peruvian Andes

ERIC Educational Resources Information Center

Zavala, Virginia

2011-01-01

In the Andes, a phonological transference known as "motoseo" has acquired ideological weight. People think that bilingual speakers of Quechua and Spanish "confuse" the vowels when speaking Spanish and that they are inferior to the ones who do not. In this article, I analyze the ideological agenda of the racialized verbal…

SRTM Perspective of Colored Height and Shaded Relief Laguna Mellquina, Andes Mountains, Argentina

NASA Technical Reports Server (NTRS)

2001-01-01

This depiction of an area south of San Martin de Los Andes, Argentina, is the first Shuttle Radar Topography Mission (SRTM)view of the Andes Mountains, the tallest mountain chain in the western hemisphere. This particular site does not include the higher Andes peaks, but it does include steep-sided valleys and other distinctive landforms carved by Pleistocene glaciers. Elevations here range from about 700 to 2,440 meters (2,300 to 8,000 feet). This region is very active tectonically and volcanically, and the landforms provide a record of the changes that have occurred over many thousands of years. Large lakes fill the broad mountain valleys, and the spectacular scenery here makes this area a popular resort destination for Argentinians.

Three visualization methods were combined to produce this image: shading, color coding of topographic height and a perspective view. The shade image was derived by computing topographic slope in the north-south direction. Northern slopes appear bright and southern slopes appear dark, as would be the case at noon at this latitude in the southern hemisphere. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow, red, and magenta, to white at the highest elevations. The perspective is toward the west, 20 degrees off horizontal with 2X vertical exaggeration. The back (west) edge of the data set forms a false skyline within the Andes Range.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission aboard Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and

Landscape-based discretization for modeling of hydrological processes in the semi-arid Andes Cordillera: a case study in Morales Basin

NASA Astrophysics Data System (ADS)

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

2017-12-01

Improved understanding of cryosphere processes in the Subtropical Andes is essencial to secure water supply in Central Chile. An ongoing challenge is to identify the main controls on snow accumulation and ablation at multiple scales. In this study, we use the Cold Regions hydrological model (CRHM) to simulate the evolution of seasonal snow cover in the basin of the Estero Morales between the period 2000-2016. The model was forced with radiation, temperature, humidity, wind and precipitation data obtained from downscaled Era-Interim outputs. The basin was disaggregated spatially through representative hydrological processes and and geomorphological into HRU's. 22% of snow in the basin is subject to reallocation by topographic effects, while net short wave radiation would explain major changes in snowmelt. 80% of summer runoff comes from glacial melting, while temperature and soil properties are key factors controlling infiltration and contribution to the runoff at all times of the year. The model results indicate that 78.2% of precipitation corresponds to snow while 21.8% to rain. The flow rates of snowmelting are the main component in the water balance, accounting for approximately 62.8% of the total rainfall. It is important to point out that during the total period of modeling (2010-2016), it was noted that the 23.08% of the total annual flow corresponds to glacial melting, however for the period 2010 - 2015 this percentage increases to 45.3%, in spite of this were not observed variations in the volume of subsurface and groundwater flow. This suggests first: that systems such as analyzed in this article, have a great importance because they are fragile in terms of response and the ground due to its topographic features (such as slope and conductivity) is not able to store large percentages of resources until the end of the summer season; and second, to understand that mountain systems with presence of glaciers, naturally are regulated compared to sudden changes

"Nervios" and "Modern Childhood": Migration and Shifting Contexts of Child Life in the Ecuadorian Andes.

ERIC Educational Resources Information Center

Pribilsky, Jason

2001-01-01

Argues that beyond explanations predicated on psychological ideas of separation and attachment, "nervios," a depression-like disorder among children in the southern Ecuadorian Andes, reflects the limits of children's abilities to accept terms of family life increasingly defined through transnational migration and new consumption…

A new fossil mammal assemblage from the southern Chilean Andes: implications for geology, geochronology, and tectonics

NASA Astrophysics Data System (ADS)

Flynn, John J.; Novacek, Michael J.; Dodson, Holly E.; Frassinetti, Daniel; McKenna, Malcolm C.; Norell, Mark A.; Sears, Karen E.; Swisher, Carl C.; Wyss, André R.

2002-07-01

A diverse (36 taxa), new fossil terrestrial mammal assemblage has been recovered from the Santacrucian South American Land Mammal 'Age' (SALMA; latest Early Miocene) in the southern Andes of Chile. This is the westernmost high latitude mammal fauna known in South America and the first in a string of new mammal assemblages discovered in Chile after a lapse of nearly a century. The terrestrial mammal-bearing sequence conformably overlies a marine section of Late Oligocene to Early Miocene age. The combined marine-terrestrial sequence, as well as a locality with fossil whales and bracketing basalts, bear significantly on theories regarding the extent of the late Tertiary Patagonian epicontinental seaway and the onset of later Cenozoic phases of uplift in the southern Andes. Uplift in this region likely began by Santacrucian SALMA (˜16-17.5 Ma) time, but it remains uncertain whether this occurred in two phases (Pehuenchic and Quechuic) or one. These discoveries substantiate propositions of sharp geologic contrasts north and south of the Lago General Carrera/Lago Buenos Aires area (Magellanes basin to the south and Río Mayo embayment to the north). Minimum estimates of uplift rate are approximately 0.05-0.07 mm/yr (but as high as 0.22 mm/yr), comparable to or slightly lower than those from other parts of the Andes (e.g. Bolivia). The timing and location of uplift may be correlated with major plate tectonic events associated with the Chile Margin Triple Junction.

A Holocene Lake Record from Laguna Del Maule (LdM) in the Chilean Andes: Climatic and Volcanic Controls on Lake Depositional Dynamics

NASA Astrophysics Data System (ADS)

Valero-Garces, B. L.; Frugone Alvarez, M.; Barreiro-Lostres, F.; Carrevedo, M. L.; Latorre Hidalgo, C.; Giralt, S.; Maldonado, A.; Bernárdez, P.; Prego, R.; Moreno-Caballud, A.

2014-12-01

Central Chile is a tectonically active, drought-prone region sensitive to latitudinal variations in large-scale cold fronts associated with fluctuations of the Pacific subtropical high. Holocene high-resolution records of climate and volcanic events could help inform more on the frequency of extensive droughts as well as volcanic and seismic hazards. LdM is a high altitude, volcanic lake located in the Transition Southern Volcanic Zone (~36°S, 2200 m.a.s.l). The LdM volcanic field is a very seismically and volcanically active zone in the Andes, with several caldera-forming eruptions over the last 1.5 Ma, and intense postglacial activity. In 2013, we recovered over 40 m of sediment cores at four sites of LdM and collected > 20 km of seismic lines. The cores were imaged, their physical and geochemical properties analysed with a Geotek MSCL and XRF scanner respectively, and sampled for TOC, TIC, TS, TN, BioSi, and bulk mineralogy. The chronology was constructed with a Bayesian age-depth model including 210Pb-137Cs, the Quizapú volcanic ash (1932 AD) and 17 AMS 14C dates. The 4.8 m long composite sequence spans the Late glacial and Holocene.Sediments are massive to banded, quartz and plagioclase-rich silts with variable diatom (BioSi, 15- 30 %) and organic matter content (TOC, 1-5 %). Four main units have been defined based on sedimentological and geochemical composition. The transition from Unit 4 to 3 is ascribed to the onset of the Holocene; Unit 2 spans the mid Holocene, and Unit 1 the last 4 ka. Higher (lower) TOC, Br/Ti and Fe/Mn ratios in units 1 and 3 (2 and 4) suggest higher (lower) organic productivity in the lake and dominant oxic (anoxic) conditions at the bottom of the lake. Up to 17 ash and lapilli layers mark volcanic events, mostly grouped in units 1 and 3. Periods of higher lake productivity (units 1 and 3) are synchronous to higher frequency of volcanic events. Some climate transitions (LIA, 4ka, 8ka and 11ka) are evident in the LdM sequence

The influence of topography on vertical velocity of air in relation to severe storms near the Southern Andes Mountains

NASA Astrophysics Data System (ADS)

de la Torre, A.; Pessano, H.; Hierro, R.; Santos, J. R.; Llamedo, P.; Alexander, P.

2015-04-01

On the basis of 180 storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range at southern mid-latitudes, we consider those registered in the northern and central crop areas (oases). The regions affected by these storms are currently protected by an operational hail mitigation project. Differences with previously reported storms detected in the southern oasis are highlighted. Mendoza is a semiarid region situated roughly between 32S and 37S at the east of the highest Andes top. It forms a natural laboratory where different sources of gravity waves, mainly mountain waves, occur. In this work, we analyze the effects of flow over topography generating mountain waves and favoring deep convection. The joint occurrence of storms with hail production and mountain waves is determined from mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properly represent diverse structures observed in the region are considered in detail. A continuous wavelet transform is applied to each variable and profile to detect the main oscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radar echo, time and location are determined. The necessary energy to lift a parcel to its level of free convection is tested from the Convective Available Potential Energy and Convection Inhibition. This last parameter is compared against the mountain waves' vertical kinetic energy. The time evolution and vertical structure of vertical velocity and equivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able to provide the necessary energy to lift the air parcel and trigger convection. A simple conceptual scheme linking the dynamical factors taking place before and during storm development is proposed.

Geographical Information Systems risk assessment models for zoonotic fascioliasis in the South American Andes region.

PubMed

Fuentes, M V; Sainz-Elipe, S; Nieto, P; Malone, J B; Mas-Coma, S

2005-03-01

The WHO recognises Fasciola hepatica to be an important human health problem. The Andean countries of Peru, Bolivia and Chile are those most severely affected by this distomatosis, though areas of Ecuador, Colombia and Venezuela are also affected. As part of a multidisciplinary project, we present results of use of a Geographical Information Systems (GIS) forecast model to conduct an epidemiological analysis of human and animal fasciolosis in the central part of the Andes mountains. The GIS approach enabled us to develop a spatial and temporal epidemiological model to map the disease in the areas studied and to classify transmission risk into low, moderate and high risk areas so that areas requiring the implementation of control activities can be identified. Current results are available on a local scale for: (1) the northern Bolivian Altiplano, (2) Puno in the Peruvian Altiplano, (3) the Cajamarca and Mantaro Peruvian valleys, and (4) the Ecuadorian provinces of Azuay, Cotopaxi and Imbabura. Analysis of results demonstrated the validity of a forecast model that combines use of climatic data to calculate of forecast indices with remote sensing data, through the classification of Normalized Difference Vegetation Index (NDVI) maps.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

Occurrence of psilocybin and psilocin in Psilocybe pseudobullacea (Petch) Pegler from the Venezuelan Andes.

PubMed

Marcano, V; Morales Méndez, A; Castellano, F; Salazar, F J; Martinez, L

1994-07-08

Using thin-layer chromatographic and spectroscopic (UV) methods two Psilocybe species from the Venezuelan Andes were analysed for the hallucinogens psilocybin and psilocin. These species are: P. montana (Pers. ex Fr.) Kumm and P. pseudobullacea (Petch) Pegler. Both hallucinogens were found in P. pseudobullacea, while P. montana was found to be exempt of these compounds.

Central and South America GPS geodesy - CASA Uno

NASA Technical Reports Server (NTRS)

Kellogg, James N.; Dixon, Timothy H.

1990-01-01

In January 1988, scientists from over 25 organizations in 13 countries and territories cooperated in the largest GPS campaign in the world to date. A total of 43 GPS receivers collected approximately 590 station-days of data in American Samoa, Australia, Canada, Colombia, Costa Rica, Ecuador, New Zealand, Norway, Panama, Sweden, United States, West Germany, and Venezuela. The experiment was entitled CASA Uno. Scientific goals of the project include measurements of strain in the northern Andes, subduction rates for the Cocos and Nazca plates beneath Central and South America, and relative motion between the Caribbean plate and South America. A second set of measurements are planned in 1991 and should provide preliminary estimates of crustal deformation and plate motion rates in the region.

Fired glaciofluvial sediment in the northwestern Andes: Biotic aspects of the Black Mat

NASA Astrophysics Data System (ADS)

Mahaney, William C.; Krinsley, David; Langworthy, Kurt; Kalm, Volli; Havics, Tony; Hart, Kris M.; Kelleher, Brian P.; Schwartz, Stephane; Tricart, Pierre; Beukens, Roelf

2011-05-01

Fired glaciofluvial beds in outwash considered to date from the onset of the Younger Dryas Event (~ 12.9 ka) in the northwestern Venezuelan Andes are considered equivalent to the Black Mat deposits described in other areas of North and South America and Europe. It may be equivalent to sediment recovered from other sites containing beds with spikes of cosmic nuclides and charcoal indicating the presence of widespread fire, one of the signatures of the Black Mat conflagration that followed the proposed breakup of Comet Encke or an unknown asteroid over the Laurentide Icesheet at 12.9 ka. In the northern Andes at Site MUM7B, sediment considered coeval with the Black Mat contains glassy carbon spherules, tri-coatings of C welded onto quartz and feldspar covered with Fe and Mn. Monazite with excessive concentrations of REEs, platinum metals including Ru and Rh, possible pdf's, and disrupted/brecciated and microfractured quartz and feldspar from impacting ejecta and excessive heating summarize the data obtained so far. The purpose of this paper is to document the physical character, mineralogy and biotic composition of the Black Mat.

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

NASA Astrophysics Data System (ADS)

McPhee, James; Videla, Yohann

2014-05-01

The 5000-km2 upper Maipo River Basin, in central Chile's Andes, has an adequate streamgage network but almost no meteorological or snow accumulation data. Therefore, hydrologic model parameterization is strongly subject to model errors stemming from input and model-state uncertainty. In this research, we apply the Cold Regions Hydrologic Model (CRHM) to the basin, force it with reanalysis data downscaled to an appropriate resolution, and inform a parsimonious basin discretization, based on the hydrologic response unit concept, with distributed data on snowpack properties obtained through snow surveys for two seasons. With minimal calibration the model is able to reproduce the seasonal accumulation and melt cycle as recorded in the one snow pillow available for the basin, and although a bias in maximum accumulation persists, snowpack persistence in time is appropriately simulated based on snow water equivalent and snow covered area observations. Blowing snow events were simulated by the model whenever daily wind speed surpassed 8 m/s, although the use of daily instead of hourly data to force the model suggests that this phenomenon could be underestimated. We investigate the representation of snow redistribution by the model, and compare it with small-scale observations of wintertime snow accumulation on glaciers, in a first step towards characterizing ice distribution within a HRU spatial discretization. Although built at a different spatial scale, we present a comparison of simulated results with distributed snow depth data obtained within a 40 km2 sub-basin of the main Maipo watershed in two snow surveys carried out at the end of winter seasons 2011 and 2012, and compare basin-wide SWE estimates with a regression tree extrapolation of the observed data.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, Steven K.; Sobieniak-Wiseman, L. Cheyanne; Kageyama, Stacy A.

2008-01-01

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

Late Pleistocene glacial fluctuations in Cordillera Oriental, subtropical Andes

NASA Astrophysics Data System (ADS)

Martini, Mateo A.; Kaplan, Michael R.; Strelin, Jorge A.; Astini, Ricardo A.; Schaefer, Joerg M.; Caffee, Marc W.; Schwartz, Roseanne

2017-09-01

The behavior of subtropical glaciers during Middle to Late Pleistocene global glacial maxima and abrupt climate change events, specifically in Earth's most arid low-latitude regions, remains an outstanding problem in paleoclimatology. The present-day climate of Cordillera Oriental, in arid northwestern Argentina, is influenced by shifts in subtropical climate systems, including the South American Summer Monsoon. To understand better past glacier-subtropical climates during the global Last Glacial Maximum (LGM, 26.5-19 ka) and other time periods, we combined geomorphic features with forty-two precise 10Be ages on moraine boulders and reconstructed paleo-equilibrium line altitudes (ELA) at Nevado de Chañi (24°S) in the arid subtropical Andes. We found a major glacial expansion at ∼23 ± 1.6 ka, that is, during the global LGM. Additional glacial expansions are observed before the global LGM (at ∼52-39 ka), and after, at 15 ± 0.5 and 12 ± 0.6 ka. The ∼15 ka glacial event was found on both sides of Chañi and the ∼12 ka event is only recorded on the east side. Reconstructed ELAs of the former glaciers exhibit a rise from east to west that resembles the present subtropical climate trajectory from the Atlantic side of the continent; hence, we infer that this climate pattern must have been present in the past. Based on comparison with other low-latitude paleoclimate records, such as those from lakes and caves, we infer that both temperature and precipitation influenced past glacial occurrence in this sector of the arid Andes. Our findings also imply that abrupt deglacial climate events associated with the North Atlantic, specifically curtailed meridional overturning circulation and regional cooling, may have had attendant impacts on low subtropical Southern Hemisphere latitudes, including the climate systems that affect glacial activity around Nevado de Chañi.

10-Be Constraints on the Timing of the Last Glacial Maximum and Deglaciation in the Northern Peruvian Andes

NASA Astrophysics Data System (ADS)

Shakun, J. D.; Clark, P. U.; Marcott, S. A.; Brook, E. J.; Caffee, M. W.

2007-12-01

Eighteen 10Be ages were determined on quartzite boulders from two latest Pleistocene moraines in the northern Peruvian Andes at 7°S. Pleistocene moraines in this area are only a few hundred meters below the highest summits and represent small glaciers sensitive to climate change. A moraine corresponding to the local Last Glacial Maximum (LGM) yields a mean age of 19.2 +/- 1.1 10Be ka using the scaling of Lal (1991) and the production rate of Stone (2000). This age agrees fairly well with the onset of deglaciation inferred from other records in the tropical Andes including 10Be dating of moraines in the Cordillera Blanca, glaciogenic sediment input into Lakes Junin and Titicaca, and Huascaran d18O, as well as the initiation of warming seen in many marine records throughout the tropics at ~19 ka. These data do not seem to support an early local LGM in the tropical Andes, although ongoing cosmogenic work at our field site seeks to better clarify this issue. A deglacial moraine in an adjacent valley has a mean age of 15.8 +/- 1.4 10Be ka and best represents the timing of ice withdrawal from this region. Numerous other moraines throughout Peru and northern Bolivia have also been dated to ~15 10Be ka (Farber et al, 2005; Smith et al, 2005). Other records from the southern tropics indicate drying at this time, perhaps in response to a northward shift of the intertropical convergence zone associated with a resumption of thermohaline circulation, which may explain this deglacial event. While Schaefer et al. (2006) found a near-synchronous termination of the LGM in the mid-latitudes of both the Northern and Southern Hemispheres at ~17 10Be ka, the ~15 10Be ka age of moraines from the tropical Andes may indicate an asynchronous onset of the last deglaciation between the low and mid-latitudes.

Knowledge and Learning in the Andes: Ethnographic Perspectives. Liverpool Latin American Studies, New Series 3.

ERIC Educational Resources Information Center

Stobart, Henry, Ed.; Howard, Rosaleen, Ed.

This book presents research into the ways in which Indigenous peoples of the Andes create, transmit, maintain, and transform their knowledge, and the related processes of teaching and learning. Most chapters are based on papers delivered at a round-table conference at the University of Cambridge (England) in 1996 and include contributions from…

Two new species of Andean gymnophthalmid lizards of the genus Euspondylus (Reptilia, Squamata) from central and southern Peru

PubMed Central

Chávez, Germán; Siu-Ting, Karen; Duran, Vilma; Venegas, Pablo J

2011-01-01

Abstract Two new species of lizards assigned to the genus Euspondylus from the montane forests of the Peruvian Andes in the Pasco Department (central Peru) and Ayacucho Department (southern Peru) both at elevations of 2550 and 3450 m, respectively, are described. The new species are distinguishable from all other Peruvian and Ecuadorian species of Euspondylus by a unique combination of morphometric, scalation and color pattern characteristics. Natural history data for the new species and for Euspondylus spinalis are also provided. PMID:21852931

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

NASA Astrophysics Data System (ADS)

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

2006-12-01

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

Glacier change and glacial lake outburst flood risk in the Bolivian Andes

NASA Astrophysics Data System (ADS)

Kougkoulos, Ioannis; Cook, Simon J.; Edwards, Laura A.; Dortch, Jason; Hoffmann, Dirk

2017-04-01

Glaciers of the Bolivian Andes represent an important water resource for Andean cities and mountain communities, yet relatively little work has assessed changes in their extent over recent decades. In many mountain regions, glacier recession has been accompanied by the development of proglacial lakes, which can pose a glacial lake outburst flood (GLOF) hazard. However, no studies have assessed the development of such lakes in Bolivia despite recent GLOF incidents here. Our mapping from satellite imagery reveals an overall areal shrinkage of 228.1 ± 22.8 km2 (43.1%) across the Bolivian Cordillera Oriental between 1986 and 2014. Shrinkage was greatest in the Tres Cruces region (47.3%), followed by the Cordillera Apolobamba (43.1%) and Cordillera Real (41.9%). A growing number of proglacial lakes have developed as glaciers have receded, in accordance with trends in most other deglaciating mountain ranges, although the number of ice-contact lakes has decreased. The reasons for this are unclear, but the pattern of lake change has varied significantly throughout the study period, suggesting that monitoring of future lake development is required as ice continues to recede. Ultimately, we use our 2014 database of proglacial lakes to assess GLOF risk across the Bolivian Andes. We identify 25 lakes that pose a potential GLOF threat to downstream communities and infrastructure. We suggest that further studies of potential GLOF impacts are urgently required.

Glacier change and glacial lake outburst flood risk in the Bolivian Andes

NASA Astrophysics Data System (ADS)

Cook, Simon J.; Kougkoulos, Ioannis; Edwards, Laura A.; Dortch, Jason; Hoffmann, Dirk

2016-10-01

Glaciers of the Bolivian Andes represent an important water resource for Andean cities and mountain communities, yet relatively little work has assessed changes in their extent over recent decades. In many mountain regions, glacier recession has been accompanied by the development of proglacial lakes, which can pose a glacial lake outburst flood (GLOF) hazard. However, no studies have assessed the development of such lakes in Bolivia despite recent GLOF incidents here. Our mapping from satellite imagery reveals an overall areal shrinkage of 228.1 ± 22.8 km2 (43.1 %) across the Bolivian Cordillera Oriental between 1986 and 2014. Shrinkage was greatest in the Tres Cruces region (47.3 %), followed by the Cordillera Apolobamba (43.1 %) and Cordillera Real (41.9 %). A growing number of proglacial lakes have developed as glaciers have receded, in accordance with trends in most other deglaciating mountain ranges, although the number of ice-contact lakes has decreased. The reasons for this are unclear, but the pattern of lake change has varied significantly throughout the study period, suggesting that monitoring of future lake development is required as ice continues to recede. Ultimately, we use our 2014 database of proglacial lakes to assess GLOF risk across the Bolivian Andes. We identify 25 lakes that pose a potential GLOF threat to downstream communities and infrastructure. We suggest that further studies of potential GLOF impacts are urgently required.

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

NASA Astrophysics Data System (ADS)

Rasmussen, Kristen Lani Emi

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

Deglaciation in the High Andes - a Record from Laguna Piuray (Cusco, Peru)

NASA Astrophysics Data System (ADS)

Nederbragt, A.; Thurow, J.; Brumsack, H.; Lowe, J.; Pearce, R.; Ramsey, C.

2007-12-01

The Peruvian Andes lie in a crucial location for paleoclimate investigation. Fluctuating Pacific and Atlantic air masses compete for long-term dominance of the region, with the El-Nino Southern Oscillation (ENSO) system causing further variability. A laminated glacial/interglacial sediment sequence (6m) exposed around the shores of Laguna Piuray, near Cusco, offers not only the potential to reconstruct the climate history of the area but also to test for strength and frequency of the Atlantic monsoonal and Pacific ENSO influence. A suite of continuous cores was collected from deep trenches. The sedimentary record is characterized by postglacial diatom-rich chalk overlying organic-rich clayey chalk. Between these units are 3 distinct organic layers (80% TOC) deposited between 12-14 cal. kyr BP (14C). The base of the record is probably as old as 25kyrs (U/Th). We obtained a multi- proxy record of the section including continuous XRF scanning data of the entire sequence, and stable isotopes, XRF, XRD, TOC, biogenic opal, and carbonate analysis of discrete samples as well as a relative paleotemperature record from analyses of soil biomarkers. All the data profiles we obtained show a pronounced increase in temperature and decrease in precipitation at 13.8kyrs and are in good correlation with published regional Andean records using single proxies. Our results confirm that the Deglaciation Cold Reversal in central South America is not identical to the Younger Dryas event in the Northern Hemisphere.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

Cave stalagmite records show strong evidence of abrupt changes in summer monsoons during Heinrich events, but we lack rigorous constraints on the amount of wetting or drying occurring in monsoon regions. Studies on shoreline deposits of closed-basin lakes can establish quantitative bounds on water balance changes through mapping-based estimates of lake volume variations. We present new dating constraints on lake level variations in Agua Caliente I and Laguna Loyoques, two closed-basin, high-altitude paleolakes on the Altiplano-Puna plateau of the Central Andes (23.1°S, 67.4°W, 4250 masl). Because this area receives >70% of its total annual precipitation during austral summer, the region is ideally suited to capture a pure response to changes in the South American summer monsoon (SASM). The plateau is home to several small (<40 km2) lakes surrounded by well-preserved paleoshorelines that indicate past wetter conditions. Agua Caliente I is unique, having multiple shorelines encrusted with biologically-mediated calcium carbonate "tufa" deposits. Initial U-Th dating of these massive shoreline tufas reveals that these deposits are dateable to within ±50 to 300 years due to high U concentrations and low initial Th content (as indicated by high 230Th/232Th). Our U-Th dates show that Agua Caliente I was greater in lake surface area during two periods: 17.5-14.5 kyrs BP, coincident with Heinrich Event 1 (HE1), and 24-23 kyrs BP, roughly coincident with the Last Glacial Maximum (LGM). At these times, Agua Caliente I also overflowed into a neighboring lake basin (Loyoques) through an 8-km long southeast-trending stream channel. Thus, during HE1 and the LGM, the lake was ~9 times larger in surface area relative to modern. Hydrologic modeling constrained by paleotemperature estimates is used to provide bounds for these past precipitation changes. We also tentatively explore physical mechanisms linking Heinrich events and the regional hydroclimate by comparing freshwater

Radiogenic isotopes of arc lavas constrain uplift of the Andes

NASA Astrophysics Data System (ADS)

Scott, Erin; Allen, Mark B.; Macpherson, Colin; McCaffrey, Ken; Davidson, Jon; Saville, Christopher

2017-04-01

Orogenic plateaux are an ultimate expression of continental tectonics, but the timings and mechanisms of their formation are far from understood. The elevation history of the Andes is of particular importance for climatic reconstructions, as they pose the only barrier to atmospheric circulation in the Southern Hemisphere. Many varied techniques have been utilized over the last two decades to constrain Andean Plateau (AP) surface uplift. Two conflicting schools of thought are prominent: (1) recent, rapid rise since 10-6 Ma (Late Miocene), and (2) slow, continued uplift from 40 Ma. We propose a new, independent, approach to constrain AP surface uplift through time. By comparing isotopic compositions of Andean Quaternary arc lavas to present day crustal thickness and topography, we show that Sr and Nd isotopes are effective discriminants for the modern extent of the AP. As previously described, these isotopic systems are sensitive to crustal contamination, which in turn relates to crustal thickness, and, via isostasy, to regional surface elevation. We apply this relationship to a new compilation of published, age corrected, isotopic compositions of arc lavas, to constrain the surface uplift history of the Andes from the Jurassic to present day. Our results are consistent with significant AP surface uplift beginning in the Mid to Late Paleogene. We show that by 23 Ma, the AP was established at close to its modern elevations between at least 16-28 deg. S, thereby predating models for Late Miocene surface uplift. Between 23-10 Ma, surface uplift propagated south of 28 deg. S by a further 400 km. Our model has implications for understanding magma plumbing systems in regions of thick, wide crust, especially other orogenic plateaux.

Diatom Assemblages on Lacustrine Sediments from the Tropical Andes, Southern Peru: Modern Analogs for Ancient Environments

NASA Astrophysics Data System (ADS)

Tapia, P. M.; Vargas, J.; Beal, S. A.; Stroup, J. S.; Kelly, M. A.

2012-12-01

Diatom analysis of surface sediments from 17 high-altitude lakes (~3,100-5,000 m asl) in the Cuzco area, Peru, reveals several potential environmental settings that have been observed in biostratigraphy records from lakes in the tropical Andes. The sedimentation rates in several lakes from this area range between 1 and 1.6 mm yr-1 during the late Quaternary, thus we assume our surface samples represent conditions spanning from 6 to 10 years for the top 1cm. Physical and chemical analysis show a high variability in water depth (0.5-12.3 m), pH (7.5-9.7), temperature (4.6-16.5 °C) and conductivity (5.6-3205 μS cm -1), as well as cationic (Na+, K+, Mg2+, Ca2+, Al3+, Mn3+, Fe3+) and anionic (F-, Cl-, Br-, SO42-) composition. Most of the lakes were oligotrophic (PO43-and NO32- below limit of detection) with the exception of nitrite. Principle Component Analysis suggests that the sites follows a strong gradient in conductivity + anions & cations (Axis 1, explaining 51.61 % of variance), and pH + water depth (Axis 2, 17.36 %). Diatoms are quite abundant (108-1010 valves g dry sed-1) in these samples, indicating oligotrophic to mesotrophic conditions and fresh to brackish waters, sometimes forming almost monospecific associations. Applications of these assemblages may be found in the Lake Junin, Central Peruvian Andes. The high abundance (92%) of the pennate diatom Denticula elegans from Site PLS-9 is similar at the Junin Biozone JU-3 that covers most of the Holocene. This species prospers in shallow (1.3-m), high conductivity (3205 μS cm-1) and alkaline (pH 9.39) waters with high values in Ca, Mg and sulfate. Similarly, the dominance (95%) of the centric diatom Discotella stelligera at Site PLS-8 resemble Biozone JU-2, ~17,000 cal yr BP, with deeper (10.9 m), lower conductivity (48.8 μS cm-1) and slightly-alkaline (pH 7.82) waters, with at least 2 orders of magnitude lower in chemical parameters than Site PLS-9. These findings encourage the survey of additional modern

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Person-to-Person Transmission of Andes Virus

PubMed Central

Bellomo, Carla; San Juan, Jorge; Pinna, Diego; Forlenza, Raul; Elder, Malco; Padula, Paula J.

2005-01-01

Despite the fact that rodents are considered to be the infectious source of hantavirus for humans, another route of transmission was demonstrated. Andes virus (ANDV) has been responsible for most of the cases recorded in Argentina. Person-to-person transmission of ANDV Sout lineage was described during an outbreak of hantavirus pulmonary syndrome in southwest Argentina. In this study, we analyzed 4 clusters that occurred in 2 disease-endemic areas for different ANDV lineages. We found new evidence of interhuman transmission for ANDV Sout lineage and described the first event in which another lineage, ANDV Cent BsAs, was implicated in this mechanism of transmission. On the basis of epidemiologic and genetic data, we concluded that person-to-person spread of the virus likely took place during the prodromal phase or shortly after it ended, since close and prolonged contact occurred in the events analyzed here, and the incubation period was 15–24 days. PMID:16485469

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Stability characteristics of the mesopause region above the Andes

NASA Astrophysics Data System (ADS)

Yang, F.; Liu, A. Z.

2017-12-01

The structure and seasonal variations of static and dynamic (shear) instabilities in the upper atmosphere (80 to 110 km) are examined using 3-year high-resolution wind and temperature data obtained with the Na Lidar at Andes Lidar Observatory (30S,71W). The stabilities are primarily determined by background temperature and wind, but strongly affected by tidal and gravity wave variations. Gravity waves perturb the atmosphere, causing intermittent unstable layers. The stabilities are characterized by their vertical and seasonal distributions of probability of instabilities. As have been found in previous studies, there is a correlation between high static stability (large N2) and strong vertical wind shear. The mechanism for this relationship is investigated in the context of gravity waves interacting with varying background.

Investigations on vertical crustal movements in the Venezuelan Andes by gravimetric methods

NASA Technical Reports Server (NTRS)

Drewes, H.

1978-01-01

A precise gravimetric network has been installed in the Venezuelan Andes to study eventual gravity changes due to vertical tectonic movements. The design and the measurements of the network are described and the accuracy is estimated. In the center of the region a local gravity network has been reobserved three times. The detected variations are discussed. In order to obtain a genuine statement as far as possible about the significance of observed gravity changes, requirements for the procedure of monitoring precise gravity networks are pointed out.

New GPS velocity field in the northern Andes (Peru - Ecuador - Colombia): heterogeneous locking along the subduction, northeastwards motion of the Northern Andes

NASA Astrophysics Data System (ADS)

Nocquet, J.; Mothes, P. A.; Villegas Lanza, J.; Chlieh, M.; Jarrin, P.; Vallée, M.; Tavera, H.; Ruiz, G.; Regnier, M.; Rolandone, F.

2010-12-01

Rapid subduction of the Nazca plate beneath the northen Andes margin (~6 cm/yr) results in two different processes: (1) elastic stress is accumulating along the Nazca/South American plate interface which is responsible for one of the largest megathrust earthquake sequences during the last century. The 500-km-long rupture zone of the 1906 (Mw= 8.8) event was partially reactivated by three events from the 1942 (Mw = 7.8), 1958 (Mw = 7.7), to the 1979 (Mw = 8.2). However, south of latitude 1°S, no M>8 earthquake has been reported in the last three centuries, suggesting that this area is slipping aseismically (2) permanent deformation causes opening of the Gulf of Guayaquil, with northeastwards motion of the Northern Andean Block (NAB). We present a new GPS velocity field covering the northern Andes from south of the Gulf of Guayaquil to the Caribbean plate. Our velocity field includes new continuously-recording GPS stations installed along the Ecuadorian coast, together with campaign sites observed since 1994 in the CASA project (Kellogg et al., 1989). We first estimate the long-term kinematics of the NAB in a joint inversion including GPS data, earthquake slip vectors, and quaternary slip rates on major faults. The inversion provides an Euler pole located at long. -107.8°E, lat. 36.2°N, 0.091°/Ma and indicates little internal deformation of the NAB (wrms=1.2 mm/yr). As a consequence, 30% of the obliquity of the Nazca/South America motion is accommodated by transcurrent to transpressive motion along the eastern boundary of the NAB. Residual velocities with respect to the NAB are then modeled in terms Models indicate a patchwork of highly coupled asperities encompassed by aseismic patches over the area of rupture of the M~8.8 1906 earthquake. Very low coupling is found along the southern Ecuadorian and northern Peru subduction.

On geographic barriers and Pleistocene glaciations: Tracing the diversification of the Russet-crowned Warbler (Myiothlypis coronata) along the Andes

PubMed Central

2018-01-01

We studied the phylogeography and plumage variation of the Russet-crowned Warbler (Myiothlypis coronata), from Venezuela to Bolivia, with focus on populations from Ecuador and northern Peru. We analyzed sequences of mitochondrial and nuclear genes, geographic distributions, as well as photographs of specimens deposited at museum collections. Phylogenetic analyses identified three major lineages formed by populations from: Venezuela and Colombia (M. c. regulus), Ecuador and northern Peru (M. elata, M. castaneiceps, M. orientalis, M. c. chapmani), and central Peru and Bolivia (M. c. coronata). We found further population structure within M. c. regulus and M. c. coronata, and population structure and complexity of plumage variation within the Ecuador-northern Peru lineage. Time-calibrated trees estimated that most intraspecific variation originated during the Pleistocene; however, this pattern may not be attributed to an increase in diversification rate during that period. We discuss these results in the context of the importance of geographic-ecological barriers in promoting lineage diversification along the Andes and put forward a preliminary taxonomic proposal for major lineages identified in this study. PMID:29522515

On geographic barriers and Pleistocene glaciations: Tracing the diversification of the Russet-crowned Warbler (Myiothlypis coronata) along the Andes.

PubMed

Prieto-Torres, David A; Cuervo, Andrés M; Bonaccorso, Elisa

2018-01-01

We studied the phylogeography and plumage variation of the Russet-crowned Warbler (Myiothlypis coronata), from Venezuela to Bolivia, with focus on populations from Ecuador and northern Peru. We analyzed sequences of mitochondrial and nuclear genes, geographic distributions, as well as photographs of specimens deposited at museum collections. Phylogenetic analyses identified three major lineages formed by populations from: Venezuela and Colombia (M. c. regulus), Ecuador and northern Peru (M. elata, M. castaneiceps, M. orientalis, M. c. chapmani), and central Peru and Bolivia (M. c. coronata). We found further population structure within M. c. regulus and M. c. coronata, and population structure and complexity of plumage variation within the Ecuador-northern Peru lineage. Time-calibrated trees estimated that most intraspecific variation originated during the Pleistocene; however, this pattern may not be attributed to an increase in diversification rate during that period. We discuss these results in the context of the importance of geographic-ecological barriers in promoting lineage diversification along the Andes and put forward a preliminary taxonomic proposal for major lineages identified in this study.

[Possible health effects associated with Pre-Columbian metallurgy].

PubMed

Idrovo, Alvaro Javier

2005-09-01

In the Old World, several researchers have indicated that adverse health effects were associated with exposure to arsenic, and that this influenced a change in the use of copper-arsenic alloys to others less toxic. This hypothesis was evaluated for three Pre-Columbian metallurgy traditions: Central Andes, Intermediate Area, and West Mexico. The metal artifacts from the Central Andes showed arsenic concentrations similar to those in the Old World (0.5%-1.0%). In the Intermediate Area the values were smallest; however, in West Mexico the arsenic content was very high (7%-25%). In Central Andes arsenical bronze was used initially, but copper-tin alloys when introduced were preferred and distributed throughout the Inca Empire. Osteological and artistic evidences of foot amputations among Moche individuals from Central Andes support the presence of "black foot disease" (a condition associated with arsenic poisoning) among Pre-Columbian populations. In conclusion, the adverse effects of arsenic have been observed in the New World, and that these effects promoted a change toward the use of less toxic alloys.

Glacier monitoring and glacier-climate interactions in the tropical Andes: A review

NASA Astrophysics Data System (ADS)

Veettil, Bijeesh Kozhikkodan; Wang, Shanshan; Florêncio de Souza, Sergio; Bremer, Ulisses Franz; Simões, Jefferson Cardia

2017-08-01

In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to

High Resolution Simulations of Pollution Vertical Stratification over Santiago and its Transport to the Chilean Andes

NASA Astrophysics Data System (ADS)

Orfanoz-Cheuquelaf, A. P.; Gallardo, L.; Huneeus, N.; Lambert, F.

2015-12-01

Santiago, Chile (33.5 S, 70.5 W, 500 m.a.s.l., population 7 millions) is a large city situated in a basin surrounded by the Andes in the East and smaller mountain ranges to the North, West, and South. It is plagued by abnormally high pollution levels for its size due to climatological and topological features. To date, it is unclear how far the urban pollution plume reaches up the mountain. Here we explore the region's complex atmospheric circulation and particularly the transport of black carbon (BC) using a state of the art numerical model (WRF-Chem, Weather Research and Forecasting model).Observations indicate the presence of multiple layers within the boundary layer, as well as the occurrence of uncoupled layers above the boundary layer. Here we explore mechanisms within our simulation that may explain these features. Our results suggest that they may correspond to residual layers that are produced by recirculation along mountain slopes due to the complex terrain around the city.In late August 2013, a short multi-platform measuring campaign (DIVERSOL) took place in the Santiago basin, providing the first vertical profiles of BC, accompanied by meteorological soundings. We analyze the dispersion of a quasi-passive tracer (carbon monoxide) of black carbon in our simulation to improve our understanding of the governing mixing and transport processes. We also perform sensitivity studies with respect to vertical resolution and turbulence schemes, contrasting our results against DIVERSOL data. Our simulations suggest that pollutants emitted in Santiago could reach the high regions of Andes mountains during the afternoon circulation, thus affecting local glaciers. With an entire year of simulation we find that the stratification of pollutants within the basin displays a seasonal signal, as well as a capacity to reach the Chilean Andes and affect the Andean cryosphere.

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

NASA Astrophysics Data System (ADS)

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

2013-12-01

The Denver Professional Chapter of Engineers Without Borders (EWB) has begun conducting erosion control projects in the Kichwa communities of Malingua Pamba in the Andes Mountains south of Quito, Ecuador. In many high elevation areas in this region, erosion of volcanic soils on steep hillsides (i.e., < 40%) is severe and often associated with roads, water supply systems, and loss of native cloud forests followed by burning and cultivation of food crops. Following a 2011 investigation of over 75 erosion sites, the multidisciplinary Erosion Control team traveled to Malingua Pamba in October 2012 to conduct final design and project implementation at 5 sites. In partnership with the local communities, we installed woody cloud forest species, grass (sig-sig) contour hedges, erosion matting, and rock structures (toe walls, plunge pools, bank armoring, cross vanes, contour infiltration ditches, etc.) to reduce incision rates and risk of slump failures, facilitate aggradation, and hasten revegetation. In keeping with the EWB goal of project sustainability, we used primarily locally available resources. High school students of the community grew 5000 native trees and some naturalized shrubs in a nursery started by the school principal, hand weavers produced jute erosion mats, and rocks were provided by a nearby quarry. Where possible, local rock was harvested from landslide areas and other local erosion features. Based on follow up reports and photographs from the community and EWB travelers, the approach of using locally available materials installed by the community is successful; plants are growing well and erosion control structures have remained in place throughout the November to April rainy season. The community has continued planting native vegetation at several additional erosion sites. Formal monitoring will be conducted in October 2013, followed by analysis of data to determine if induced meandering and other low-maintenance erosion control techniques are working

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

NASA Astrophysics Data System (ADS)

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

2013-08-01

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

The current tectonic motion of the Northern Andes along the Algeciras Fault System in SW Colombia

NASA Astrophysics Data System (ADS)

Velandia, Francisco; Acosta, Jorge; Terraza, Roberto; Villegas, Henry

2005-04-01

Riedel, synthetic and antithetic type faults, principal displacement zones (PDZ), pull-apart basins (such as lazy-S shaped releasing bend, extensive and rhomboidal shaped and releasing sidestep basins) and minor folds located oblique to the main trace of the Algeciras Fault System (AFS) are interpreted from Landsat TM 5 images and geological mapping. These tectonic features are affecting Quaternary deposits and are related to major historical earthquakes and recent registered seismic events, indicating neotectonic activity of the structure. The AFS is classified as a right lateral wrench complex structure, with an important vertical component in which sedimentary cover and basement rocks are involved. In addition, the system represents a simple shear caused by the oblique convergence between the Nazca Plate and the northern Andes. The transpressive boundary in SW Colombia was previously located along the Eastern Frontal Fault System. However, this paper shows that the AFS constitutes the actual boundary of the current transpressive regime along the Northern Andes, which begins at the Gulf of Guayaquil in Ecuador and continues into Colombia and Venezuela.

Changes in Andes snow cover from MODIS data, 2000-2016

NASA Astrophysics Data System (ADS)

Saavedra, Freddy A.; Kampf, Stephanie K.; Fassnacht, Steven R.; Sibold, Jason S.

2018-03-01

The Andes span a length of 7000 km and are important for sustaining regional water supplies. Snow variability across this region has not been studied in detail due to sparse and unevenly distributed instrumental climate data. We calculated snow persistence (SP) as the fraction of time with snow cover for each year between 2000 and 2016 from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensors (500 m, 8-day maximum snow cover extent). This analysis is conducted between 8 and 36° S due to high frequency of cloud (> 30 % of the time) south and north of this range. We ran Mann-Kendall and Theil-Sens analyses to identify areas with significant changes in SP and snowline (the line at lower elevation where SP = 20 %). We evaluated how these trends relate to temperature and precipitation from Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) and University of Delaware datasets and climate indices as El Niño-Southern Oscillation (ENSO), Southern Annular Mode (SAM), and Pacific Decadal Oscillation (PDO). Areas north of 29° S have limited snow cover, and few trends in snow persistence were detected. A large area (34 370 km2) with persistent snow cover between 29 and 36° S experienced a significant loss of snow cover (2-5 fewer days of snow year-1). Snow loss was more pronounced (62 % of the area with significant trends) on the east side of the Andes. We also found a significant increase in the elevation of the snowline at 10-30 m year-1 south of 29-30° S. Decreasing SP correlates with decreasing precipitation and increasing temperature, and the magnitudes of these correlations vary with latitude and elevation. ENSO climate indices better predicted SP conditions north of 31° S, whereas the SAM better predicted SP south of 31° S.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

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

PubMed

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

2016-08-16

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

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

PubMed Central

Pellicciotti, Francesca

2016-01-01

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

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

PubMed

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

2014-04-01

Rising temperatures, a widespread consequence of climate change, have been implicated in enigmatic amphibian declines from habitats with little apparent human impact. The pathogenic fungus Batrachochytrium dendrobatidis (Bd), now widespread in Neotropical mountains, may act in synergy with climate change causing collapse in thermally stressed hosts. We measured the thermal tolerance of frogs along a wide elevational gradient in the Tropical Andes, where frog populations have collapsed. We used the difference between critical thermal maximum and the temperature a frog experiences in nature as a measure of tolerance to high temperatures. Temperature tolerance increased as elevation increased, suggesting that frogs at higher elevations may be less sensitive to rising temperatures. We tested the alternative pathogen optimal growth hypothesis that prevalence of the pathogen should decrease as temperatures fall outside the optimal range of pathogen growth. Our infection-prevalence data supported the pathogen optimal growth hypothesis because we found that prevalence of Bd increased when host temperatures matched its optimal growth range. These findings suggest that rising temperatures may not be the driver of amphibian declines in the eastern slopes of the Andes. Zoonotic outbreaks of Bd are the most parsimonious hypothesis to explain the collapse of montane amphibian faunas; but our results also reveal that lowland tropical amphibians, despite being shielded from Bd by higher temperatures, are vulnerable to climate-warming stress. © 2013 Society for Conservation Biology.

Diversification in the Andes: age and origins of South American Heliotropium lineages (Heliotropiaceae, Boraginales).

PubMed

Luebert, Federico; Hilger, Hartmut H; Weigend, Maximilian

2011-10-01

The uplift of the Andes was a major factor for plant diversification in South America and had significant effects on the climatic patterns at the continental scale. It was crucial for the formation of the arid environments in south-eastern and western South America. However, both the timing of the major stages of the Andean uplift and the onset of aridity in western South America remain controversial. In this paper we examine the hypothesis that the Andean South American groups of Heliotropium originated and diversified in response to Andean orogeny during the late Miocene and a the subsequent development of aridity. To this end, we estimate divergence times and likely biogeographical origins of the major clades in the phylogeny of Heliotropium, using both Bayesian and likelihood methods. Divergence times of all Andean clades in Heliotropium are estimated to be of late Miocene or Pliocene ages. At least three independent Andean diversification events can be recognized within Heliotropium. Timing of the diversification in the Andean lineages Heliotropium sects.Heliothamnus, Cochranea, Heliotrophytum, Hypsogenia, Plagiomeris, Platygyne clearly correspond to a rapid, late Miocene uplift of the Andes and a Pliocene development of arid environments in South America. Copyright © 2011 Elsevier Inc. All rights reserved.

Assimilating Non-linear Effects of Customized Large-Scale Climate Predictors on Downscaled Precipitation over the Tropical Andes

NASA Astrophysics Data System (ADS)

Molina, J. M.; Zaitchik, B. F.

2016-12-01

Recent findings considering high CO2 emission scenarios (RCP8.5) suggest that the tropical Andes may experience a massive warming and a significant precipitation increase (decrease) during the wet (dry) seasons by the end of the 21st century. Variations on rainfall-streamflow relationships and seasonal crop yields significantly affect human development in this region and make local communities highly vulnerable to climate change and variability. We developed an expert-informed empirical statistical downscaling (ESD) algorithm to explore and construct robust global climate predictors to perform skillful RCP8.5 projections of in-situ March-May (MAM) precipitation required for impact modeling and adaptation studies. We applied our framework to a topographically-complex region of the Colombian Andes where a number of previous studies have reported El Niño-Southern Oscillation (ENSO) as the main driver of climate variability. Supervised machine learning algorithms were trained with customized and bias-corrected predictors from NCEP reanalysis, and a cross-validation approach was implemented to assess both predictive skill and model selection. We found weak and not significant teleconnections between precipitation and lagged seasonal surface temperatures over El Niño3.4 domain, which suggests that ENSO fails to explain MAM rainfall variability in the study region. In contrast, series of Sea Level Pressure (SLP) over American Samoa -likely associated with the South Pacific Convergence Zone (SPCZ)- explains more than 65% of the precipitation variance. The best prediction skill was obtained with Selected Generalized Additive Models (SGAM) given their ability to capture linear/nonlinear relationships present in the data. While SPCZ-related series exhibited a positive linear effect in the rainfall response, SLP predictors in the north Atlantic and central equatorial Pacific showed nonlinear effects. A multimodel (MIROC, CanESM2 and CCSM) ensemble of ESD projections revealed

Changing Precipitation Patterns or Waning Glaciers? Identifying Water Supply Vulnerabilities to Climate Change in the Bolivian Andes

NASA Astrophysics Data System (ADS)

Guido, Z. S.; McIntosh, J. C.; Papuga, S. A.

2010-12-01

The Bolivian Andes have become an iconic example for the impacts of climate change. Glaciers are rapidly melting and some have already completely disappeared. More than 75 percent of the water consumed by 2 million people living on the flanks of the Bolivian Andes comes from mountains and it is often cited that the dwindling ice threatens the water supply of the expanding and destitute population living in the twin cities of La Paz and El Alto. However, the wet and the warm seasons and the cold and dry seasons coincide, causing high precipitation and ice melt—and therefore high streamflows—to occur only in the austral summer (October-March); during the austral winter, cold conditions limit glacier melt. This suggests that reductions in the water supply could be influenced more by changing precipitation amounts than continued glacial mass-wasting. We hypothesize that precipitation is the principal component of groundwater recharge for the aquifers at the base of the central Cordillera Real. Oxygen and hydrogen isotopes from rivers partially fed by glaciers, groundwater, and glacial melt water can help determine the relative contribution of precipitation and glacial melt to important water supplies. During the dry season in August 2010, we sampled 23 sites that follow the flow path of water in the Condiriri watershed, beginning in the glacial headwaters and ending several kilometers upriver from Lake Titicaca. We collected five samples at the toe of the Pequeño Alpamayo glacier and four samples from three tributary rivers that drain glaciated headwaters, which include meltwater from the Pequeño Alpamayo glacier. W also collected 14 water samples from shallow and deep wells in rural communities within 40 kilometers of the glaciers. If the isotopic values of groundwater are similar to rain values, as we suspect, precipitation is likely the largest contributor to groundwater resources in the region and will suggest that changing precipitation patterns present the

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

Treesearch

Peter Keller

2007-01-01

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

Paleoindian settlement of the high-altitude Peruvian Andes.

PubMed

Rademaker, Kurt; Hodgins, Gregory; Moore, Katherine; Zarrillo, Sonia; Miller, Christopher; Bromley, Gordon R M; Leach, Peter; Reid, David A; Álvarez, Willy Yépez; Sandweiss, Daniel H

2014-10-24

Study of human adaptation to extreme environments is important for understanding our cultural and genetic capacity for survival. The Pucuncho Basin in the southern Peruvian Andes contains the highest-altitude Pleistocene archaeological sites yet identified in the world, about 900 meters above confidently dated contemporary sites. The Pucuncho workshop site [4355 meters above sea level (masl)] includes two fishtail projectile points, which date to about 12.8 to 11.5 thousand years ago (ka). Cuncaicha rock shelter (4480 masl) has a robust, well-preserved, and well-dated occupation sequence spanning the past 12.4 thousand years (ky), with 21 dates older than 11.5 ka. Our results demonstrate that despite cold temperatures and low-oxygen conditions, hunter-gatherers colonized extreme high-altitude Andean environments in the Terminal Pleistocene, within about 2 ky of the initial entry of humans to South America. Copyright © 2014, American Association for the Advancement of Science.

New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes

PubMed Central

Langer, Max C.; Rincón, Ascanio D.; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W. M.

2014-01-01

Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary. PMID:26064540

New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes.

PubMed

Langer, Max C; Rincón, Ascanio D; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W M

2014-10-01

Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U-Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal-vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic-Jurassic boundary.

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

NASA Astrophysics Data System (ADS)

Riveros-Iregui, D. A.; Peña, C.

2015-12-01

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

Detrital provenance constraints from the Austral (Magallanes) Basin on dynamic changes in orogenic paleogeography during Cenozoic growth and denudation of the Patagonian Andes

NASA Astrophysics Data System (ADS)

Fosdick, J. C.; Leonard, J. S.; Bostelmann, J. E.; Ugalde, R.; Schwartz, T.

2015-12-01

The topographic development of the Patagonian Andes is influenced by crustal shortening, magmatism, asthenospheric mantle upwelling, climate, and erosion - yet knowledge of how these processes interact is hindered by an incomplete understanding of the timing and tempo of deformation and erosion. We report new detrital zircon U/Pb geochronology and sedimentology from the Cenozoic Austral (Magallanes) foreland basin in Argentina and Chile (near 51°S) that record changes in orogenic paleogeography during uplift of the Patagonian Andes. Near Cerro Castillo, Chile, zircons from deltaic and estuarine sandstones of the Cerro Dorotea Fm. indicate sedimentation ~60-61 Ma, revising the long-held Danian age assignment based on the foraminiferal content. Lower Eocene (47-46 Ma) zircons constrain the age of the overlying unit, the deltaic lower Río Turbio Fm., which shares sedimentological, paleontological, and provenance affinity with the northern Man Aike Fm. Deposition of the upper Río Turbio Fm. in Argentina occurred during the Eocene-Oligocene transition ~33-34 Ma and continued until ~26 Ma. Deposition of the Río Guillermo Fm. resumed ~23.5 Ma with the first occurrence of fluvial sedimentation that continued until the marine Patagonian transgression ~21-19 Ma at this location. Detrital zircon ages reveal upsection reduction in Late Jurassic and Paleozoic igneous sources, variable contributions of Late Cretaceous zircons, and younging of arc-derived zircons. Combined with published bedrock thermochronology and structural data, we suggest that early Miocene faulting and exhumation of the thrust-belt resulted in drainage reorganization and eastward shift in the drainage divide to the central domain, isolating the retroarc basin from the Jurassic Tobífera thrust sheets. Revised timing of sedimentation and changes in upland source areas during Paleocene-Miocene time reveals a complex relationship between basin evolution, Cenozoic climate, and phases of Andean tectonic

Spatio-temporal variability of snow water equivalent in the extra-tropical Andes Cordillera from distributed energy balance modeling and remotely sensed snow cover

NASA Astrophysics Data System (ADS)

Cornwell, E.; Molotch, N. P.; McPhee, J.

2016-01-01

Seasonal snow cover is the primary water source for human use and ecosystems along the extratropical Andes Cordillera. Despite its importance, relatively little research has been devoted to understanding the properties, distribution and variability of this natural resource. This research provides high-resolution (500 m), daily distributed estimates of end-of-winter and spring snow water equivalent over a 152 000 km2 domain that includes the mountainous reaches of central Chile and Argentina. Remotely sensed fractional snow-covered area and other relevant forcings are combined with extrapolated data from meteorological stations and a simplified physically based energy balance model in order to obtain melt-season melt fluxes that are then aggregated to estimate the end-of-winter (or peak) snow water equivalent (SWE). Peak SWE estimates show an overall coefficient of determination R2 of 0.68 and RMSE of 274 mm compared to observations at 12 automatic snow water equivalent sensors distributed across the model domain, with R2 values between 0.32 and 0.88. Regional estimates of peak SWE accumulation show differential patterns strongly modulated by elevation, latitude and position relative to the continental divide. The spatial distribution of peak SWE shows that the 4000-5000 m a.s.l. elevation band is significant for snow accumulation, despite having a smaller surface area than the 3000-4000 m a.s.l. band. On average, maximum snow accumulation is observed in early September in the western Andes, and in early October on the eastern side of the continental divide. The results presented here have the potential of informing applications such as seasonal forecast model assessment and improvement, regional climate model validation, as well as evaluation of observational networks and water resource infrastructure development.

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

NASA Astrophysics Data System (ADS)

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

Duck plague in free-flying waterfowl observed during the Lake Andes epizootic

USGS Publications Warehouse

Proctor, S.J.; Pearson, G.L.; Leibovitz, Louis

1975-01-01

The first major epizootic of duck plague in free-flying waterfowl occurred at Lake Andes, South Dakota, in January and February, 1973. Duck plague was diagnosed in black ducks, mallards, pintail-mallard hybrids, redheads, common mergansers, common golden eyes, canvasbacks, American widgeon, wood ducks, and Canada geese, indicating the general susceptibility of ducks to duck plague. Clinical signs observed in mallards were droopiness, polydipsia, lethargy, reduced wariness, weakness, reluctance to fly, swimming in circles, bloody diarrhea, bloody fluid draining from the nares and bill, and terminal convulsions.Because the mallard was the most numerous and heavily infected species during the Lake Andes epizootic, gross and microscopic lesions of the gastrointestinal tract, liver, spleen, thymus, bursa of Fabricius, heart, lung, bone marrow, pancreas, and ovaries were described. Lesions of the esophagus and cloaca were in the stratified submucosal glands. In the small and large intestine, lesions were located in lymphocytic aggregates, lamina propria, and crypt epithelium. Hemorrhages and necrosis of hepatocytes and bile duct epithelium were noted in the liver. Diffuse necrosis of lymphocytic and reticuloendothelial tissue were evident in the spleen, bursa of Fabricius, and thymus. Hemorrhages in other tissues such as the lung and heart were often associated with lymphoid nodules, while those in organs such as the pancreas were associated with acinar necrosis. Intranuclear inclusion bodies were seen in stratified squamous epithelium of the esophagus and cloaca, crypt epithelium of the intestine, hepatocytes, bile duct epithelium, cells of Hassel's corpuscles, splenic periarteriolar reticular cells, and epithelial cells in the bursa of Fabricius.

East of the Andes: The genetic profile of the Peruvian Amazon populations.

PubMed

Di Corcia, T; Sanchez Mellado, C; Davila Francia, T J; Ferri, G; Sarno, S; Luiselli, D; Rickards, O

2017-06-01

Assuming that the differences between the Andes and the Amazon rainforest at environmental and historical levels have influenced the distribution patterns of genes, languages, and cultures, the maternal and paternal genetic reconstruction of the Peruvian Amazon populations was used to test the relationships within and between these two extreme environments. We analyzed four Peruvian Amazon communities (Ashaninka, Huambisa, Cashibo, and Shipibo) for both Y chromosome (17 STRs and 8 SNPs) and mtDNA data (control region sequences, two diagnostic sites of the coding region, and one INDEL), and we studied their variability against the rest of South America. We detected a high degree of genetic diversity in the Peruvian Amazon people, both for mtDNA than for Y chromosome, excepting for Cashibo people, who seem to have had no exchanges with their neighbors, in contrast with the others communities. The genetic structure follows the divide between the Andes and the Amazon, but we found a certain degree of gene flow between these two environments, as particularly emerged with the Y chromosome descent cluster's (DCs) analysis. The Peruvian Amazon is home to an array of populations with differential rates of genetic exchanges with their neighbors and with the Andean people, depending on their peculiar demographic histories. We highlighted some successful Y chromosome lineages expansions originated in Peru during the pre-Columbian history which involved both Andeans and Amazon Arawak people, showing that at least a part of the Amazon rainforest did not remain isolated from those exchanges. © 2017 Wiley Periodicals, Inc.

The extended tracking network and indications of baseline precision and accuracy in the North Andes

NASA Technical Reports Server (NTRS)

Freymueller, Jeffrey T.; Kellogg, James N.

1990-01-01

The CASA Uno Global Positioning System (GPS) experiment (January-February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400-1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day-to-day rms repeatabilities for the same baselines. The mean solutions obtained by using tracking stations in North America and the Pacific agreed at the 2-3 millimeter level with those using tracking stations in North America and Europe. The agreement of the extended tracking network solutions suggests that a broad distribution of tracking stations provides better geometric constraints on the satellite orbits and that solutions are not sensitive to changes in tracking network configuration when an extended network is use. A comparison of the results from the North Andes and a baseline in North America suggests that the use of a geometrically strong extended tracking network is most important when the network of interest is far from North America.

A new species of Platydecticus (Orthoptera: Tettigoniidae: Tettigoniinae; Nedubini) from the Andes of Chile.

PubMed

Sánchez, Alejandro Vera

2015-11-10

A new species of the genus Platydecticus is described based on adult male and female specimens and the egg. The new species, Platydecticus diaguita, inhabits the Andes Range at 27º S latitude, above 3000 m elevation. Both sexes are easily identifiable by genital morphology characters and by the external characters of the fastigium of the vertex and the reduced number of spines in the hind tibia. It is also the smallest species described for the genus.

Indian hospitals and government in the colonial Andes.

PubMed

Ramos, Gabriela

2013-04-01

This article examines the reception of the early modern hospital among the indigenous people of the Andes under Spanish colonial rule. During the period covered by this study (sixteenth to mid-eighteenth centuries), the hospital was conceived primarily as a manifestation of the sovereign’s paternalistic concern for his subjects’ spiritual well being. Hospitals in the Spanish American colonies were organised along racial lines, and those catering to Indians were meant to complement the missionary endeavour. Besides establishing hospitals in the main urban centres, Spanish colonial legislation instituted hospitals for Indians in provincial towns and in small rural jurisdictions throughout the Peruvian viceroyalty. Indian hospitals often met with the suspicion and even hostility of their supposed beneficiaries, especially indigenous rulers. By conceptualising the Indian hospital as a tool of colonial government, this article investigates the reasons behind its negative reception, the work of adaptation that allowed a few of them to thrive, and the eventual failure of most of these institutions.

Active Tectonics in the Central Chilean Andes: 3D Tomography Based on the Aftershock Sequence of the 28 August 2004 Shallow Crustal Earthquake

NASA Astrophysics Data System (ADS)

Comte, D.; Farias, M.; Charrier, R.; Gonzalez, A.

2008-12-01

Most of the seismological research in the Andes has been mainly oriented to the detection and understanding of the seismicity associated with megathrust earthquakes that characterize the subduction environment that governs the Andean tectonics. However, deployments of temporary networks have allowed the detection of intense crustal seismicity beneath the Chilean forearc-arc region. The temporary seismic network deployed along the Las Leñas and Pangal river valleys (34°25'S), between January and May 2004 permitted to better constrain the abundant shallow intra-continental seismicity previously detected in that region. Although most of the seismicity is randomly distributed in the region, several microearthquakes occur along the trace of the major El Fierro fault-system. This system is well recognized between 33°30' and 35°15'S and is located at or close to the eastern contact between Mesozoic and Cenozoic deposits in the Principal Cordillera and, locally, below active volcanoes, being considered to have participated in the extension and tectonic inversion of a widely extended (>600 km long) Cenozoic basin along the Principal Cordillera. Further south, at 35°S, a Mw=6.5 strike-slip shallow earthquake occurred on August 28, 2004, near of the headwater of the Teno river, close to the Planchon volcano. A 3D detailed Vp and Vs velocities determination was obtained along the 2004 earthquake aftershock area. The aftershocks are distributed along one branch of the El Fierro fault system, with a NNE-SSW direction and depths lower than 15 km. The rupture zone coincides with a sharp contrast in Vp and Vs, also in coincidence with the presence of hydrothermal fluids, gypsum diapers and the volcanic arc, suggesting rheological contrast controlling deformation. At the surface, this zone present an intense contractive deformation produced during the Neogene, which differs from what can be observed in other regions. Present day deformation related to seismicity has no

Slow life histories in lizards living in the highlands of the Andes Mountains.

PubMed

Boretto, Jorgelina M; Cabezas-Cartes, Facundo; Ibargüengoytía, Nora R

2018-05-01

In the highlands of the Andes, lizards must balance precisely the allocation of energy for growth and reproduction to ensure their survival. We studied the individuals' age, growth rates, age at sexual maturity, and maximum life span of the viviparous lizard Phymaturus antofagastensis, endemic of cold and harsh environments at high altitudes in the Andes Mountains of Catamarca province, Argentina. We also estimated key life history parameters like reproductive effort, lifetime reproductive effort, net reproductive rate, and relative reproductive time in P. antofagastensis as well as in other Phymaturus to compare the interplay among growth, maintenance, and reproduction in species that live across a latitudinal and altitudinal gradient. We found that females and males of P. antofagastensis mature late in life, at 6-7 years old, respectively, and some individuals reached 20 years of age. Adult females showed higher specific growth rates than males and an adult life span of 9 years which, due to their biennial reproduction, results in an estimated production of only four litters in life. This species exhibits one of the highest lifetime reproductive efforts described for lizards. Our results indicate the existence of a tradeoff between the number of reproductive events throughout life and reproductive effort devoted to each event in Phymaturus, related to the phylogenetic group. The palluma group shows low reproductive effort but high number of reproductive events throughout their lives, whereas the patagonicus group shows high reproductive efforts in low number of reproductive events.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Pío del Río-Hortega: A Visionary in the Pathology of Central Nervous System Tumors

PubMed Central

Ramon y Cajal Agüeras, Santiago

2016-01-01

The last 140 years have seen considerable advances in knowledge of central nervous system tumors. However, the main tumor types had already been described during the early years of the twentieth century. The studies of Dr. Pío del Río Hortega have been ones of the most exhaustive histology and cytology-based studies of nervous system tumors. Río Hortega's work was performed using silver staining methods, which require a high level of practical skill and were therefore difficult to standardize. His technical aptitude and interest in nervous system tumors played a key role in the establishment of his classification, which was based on cell lineage and embryonic development. Río Hortega's approach was controversial when he proposed it. Current classifications are not only based on cell type and embryonic lineage, as well as on clinical characteristics, anatomical site, and age. PMID:26973470

Comparative Phylogeography of Direct-Developing Frogs (Anura: Craugastoridae: Pristimantis) in the Southern Andes of Colombia

PubMed Central

García-R, Juan C.; Crawford, Andrew J.; Mendoza, Ángela María; Ospina, Oscar; Cardenas, Heiber; Castro, Fernando

2012-01-01

The Andes of South America hosts perhaps the highest amphibian species diversity in the world, and a sizable component of that diversity is comprised of direct-developing frogs of the genus Pristimantis (Anura: Craugastoridae). In order to better understand the initial stages of species formation in these frogs, this study quantified local-scale spatial genetic structuring in three species of Pristimantis. DNA sequences of two mitochondrial gene fragments (16S and COI) were obtained from P. brevifrons, P. palmeri and P. jubatus at different locations in the Cordillera Occidental. We found high levels of genetic diversity in the three species, with highly structured populations (as measured by F ST) in P. brevifrons and P. palmeri while P. jubatus showed panmixia. Large effective population sizes, inferred from the high levels of genetic diversity, were found in the three species and two highly divergent lineages were detected within P. jubatus and P. palmeri. Estimated divergence times among populations within P. brevifrons and P. palmeri coincide with the Pleistocene, perhaps due to similar responses to climatic cycling or recent geological history. Such insights have important implications for linking alpha and beta diversity, suggesting regional scale patterns may be associated with local scale processes in promoting differentiation among populations in the Andes. PMID:23049941

Moraine preservation and boulder erosion in the tropical Andes: interpreting old surface exposure ages in glaciated valleys

NASA Astrophysics Data System (ADS)

Smith, Jacqueline A.; Finkel, Robert C.; Farber, Daniel L.; Rodbell, Donald T.; Seltzer, Geoffrey O.

2005-10-01

Cosmogenic dating provides a long-awaited means of directly dating glacial deposits that pre-date the last glacial cycle. Although the potential benefits of longer chronologies are obvious, the greater uncertainty associated with older cosmogenic ages may be less readily apparent. We illustrate the challenges of developing and interpreting a long chronology using our data from the Peruvian Andes. We used surface exposure dating with cosmogenic radionuclides (CRNs; 10Be and 26Al) to date 140 boulders on moraines in valleys bordering the Junin Plain (11° S, 76° W) in central Peru. Our chronology spans multiple glacial cycles and includes exposure ages greater than 1 million years, which indicate that long-term rates of boulder erosion have been very low. Interpreting the chronology of moraines for glaciations that predate the last glacial cycle is complicated by the need to consider boulder erosion and exhumation, surface uplift, and inheritance of CRNs from previous exposure intervals. As an example, we recalculate exposure ages using our boulder erosion rates (0.3-0.5 metres per million years) and estimated surface uplift rates to emphasise both the challenges involved in interpreting old surface exposure ages and the value of chronological data, even with large uncertainties, when reconstructing the palaeoclimate of a region.

Seasonal and high-resolution variability in hydrochemistry of the Andes-Amazon

NASA Astrophysics Data System (ADS)

Burt, E.; West, A. J.

2017-12-01

Stream hydrochemistry acts as a record of integrated catchment processes such as the amount of time it takes precipitation to flow through the subsurface and become streamflow (water transit times), water-rock interaction and biogeochemical cycling. Although it is understood that sampling interval affects observed patterns in hydrochemistry, most studies collect samples on a weekly, bi-weekly or monthly schedule due to lack of resources or the difficulty of maintaining automated sampling devices. Here, we attempt to combine information from two sampling time scales, comparing a year-long hydrochemical time series to data from a recent sub-daily sampling campaign. Starting in April 2016, river, soil and rain waters have been collected every two weeks at five small catchments spanning the tropical Andes and Amazon - a natural laboratory for its gradients in topography, erosion rates, precipitation, temperature and flora. Between January and March, 2017, we conducted high frequency sampling for approximately one week at each catchment, sampling at least every four hours including overnight. We will constrain young water fractions (Kirchner, 2016) and storm water fluxes for the experimental catchments using stable isotopes of water as conservative tracers. Major element data will provide the opportunity to make initial constraints on geochemical and hydrologic coupling. Preliminary results suggest that in the Amazon, hydrochemistry patterns are dependent on sampling frequency: the seasonal cycle in stable isotopes of water is highly damped, while the high resolution sampling displays large variability. This suggests that a two-week sampling interval is not frequent enough to capture rapid transport of water, perhaps through preferential flow networks. In the Andes, stable isotopes of water are highly damped in both the seasonal and high resolution cycle, suggesting that the catchment behaves as a "well-mixed" system.

Northern Chile and Andes Mountains seen from STS-61 Shuttle Endeavour

NASA Image and Video Library

1993-12-09

STS061-101-023 (8 Dec 1993) --- This color photograph is a spectacular, panoramic (southeastern view) shot that features the northern half of the country of Chile and the Andes Mountains of South America. The Atacama Desert, one of the driest regions on earth, is clearly visible along the northern Chilean coast. This desert extends from roughly Arica in the north to the city of Caldera in the south, a distance of six hundred miles. Some parts of this very arid region go for more than twenty years without measurable precipitation. It is an area of dramatic and abrupt elevation changes. For example, from the waters edge there is an escarpment of the coastal plateau that rises like an unbroken wall two or three thousand feet above the Pacific Ocean. From the coastal plateau, there is an even more dramatic increase in elevation -- from two thousand feet above sea level to an average elevation of thirteen thousand feet above sea level in the Bolivian Altiplano. This elevation change occurs within a one hundred to two hundred mile distance from the Pacific Ocean. The north-south trending spine of the Andes Mountains can be seen on this photograph. Several of the volcanic peaks in this mountain chain exceed 20,000 feet above sea level. Interspersed with these volcanic peaks, numerous dry lake beds (salars) can be seen as highly reflective surfaces. The largest of these salars (Salar de Uyuni) is visible at the edge of the Hubble Space Telescope (HST). Offshore, the cold Peruvian current produces low stratus clouds that can be found along this coastline at certain times of the year. This is the same type of meteorological phenomena that is found along the southern California coast and the Skeleton coast of southwestern Africa.

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

Holocene environmental changes in the highlands of the southern Peruvian Andes (14° S) and their impact on pre-Columbian cultures

NASA Astrophysics Data System (ADS)

Schittek, K.; Mächtle, B.; Schäbitz, F.; Forbriger, M.; Wennrich, V.; Reindel, M.; Eitel, B.

2014-04-01

Within palaeoenvironmental studies, high-altitude peatlands of the Andes still remain relatively unexploited, although they offer an excellent opportunity for high-resolution chronologies, on account of their high accumulation rates and abundant carbon for dating. Especially in the central Andes, additional high-quality proxy records are still needed due to the lack of continuous and well-dated records, which show a significant variability on sub-centennial to decadal precision scales. To widen the current knowledge on climatic and environmental changes in the western Andes of southern Peru, we present a new, high-resolution 8600 year-long record from Cerro Llamoca peatland, a high-altitude Juncaceous cushion peatland in the headwaters of Río Viscas, a tributary to Río Grande de Nasca. A 10.5 m core of peat with intercalated sediment layers was examined for all kinds of microfossils, including fossil charred particles. We chose homogeneous peat sections for pollen analysis at a high temporal resolution. The inorganic geochemistry was analysed in 2 mm resolution using an ITRAX X-ray fluorescence (XRF) core scanner. We interpret the increase of Poaceae pollen in our record as an expansion of Andean grasslands during humid phases. Drier conditions are indicated by a significant decrease of Poaceae pollen and higher abundances of Asteraceae pollen. The results are substantiated by changes in arsenic contents and manganese/iron ratios, which turned out as applicable proxies for in situ palaeo-redox conditions. The mid-Holocene period of 8.6-5.6 ka is characterized by a series of episodic dry spells alternating with spells that are more humid. After a pronounced dry period at 4.6-4.2 ka, conditions generally shifted towards a more humid climate. We stress a humid/relatively stable interval between 1.8-1.2 ka, which coincides with the florescence of the Nasca culture in the Andean foreland. An abrupt turnover to a sustained dry period occurs at 1.2 ka, which coincides

Precipitation changes over the eastern Bolivian Andes inferred from speleothem (δ18O) records for the last 1400 years

NASA Astrophysics Data System (ADS)

Apaéstegui, James; Cruz, Francisco William; Vuille, Mathias; Fohlmeister, Jens; Espinoza, Jhan Carlo; Sifeddine, Abdelfettah; Strikis, Nicolas; Guyot, Jean Loup; Ventura, Roberto; Cheng, Hai; Edwards, R. Lawrence

2018-07-01

Here we present high-resolution δ18O records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in δ18O during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative δ18O values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian δ18O record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased δ18O values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the δ18O reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA.

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

NASA Astrophysics Data System (ADS)

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

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

NASA Astrophysics Data System (ADS)

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 (<10 Ma) large-volume dacitic ignimbrites from the southern portion of the Central Andes have distinctly more radiogenic Sr and heavier O isotopes and thus contrast with older dacitic ignimbrites in northernmost Chile and southern Peru. Results of assimilation and fractional crystallization (AFC) models show that the largest chemical changes occur in the lower crust where magmas acquire a base-level geochemical signature that is later modified by middle to upper crustal AFC. Using geospatial analysis, we estimated the volume of these ignimbrite deposits throughout the Central Andes during the Neogene and examined the spatiotemporal pattern of so-called ignimbrite flare-ups. We observe a N-S migration of maximum ages of the onset of large-volume "ignimbrite pulses" through time: Major pulses occurred at 19-24 Ma (e.g. Oxaya, Nazca Group), 13-14 Ma (e.g. Huaylillas and Altos de Pica ignimbrites) and <10 Ma (Altiplano and Puna ignimbrites). Such "flare-ups" represent magmatic production rates of 25 to >70 km3 Ma-1 km-1 (assuming plutonic/volcanic ratios of 1

Magnetic signatures of the orogenic crust of the Patagonian Andes with implication for planetary exploration

NASA Astrophysics Data System (ADS)

Díaz Michelena, Marina; Kilian, Rolf

2015-11-01

The Patagonian Andes represent a good scenario of study because they have outcrops of diverse plutonic rocks representative of an orogenic crust on Earth and other planets. Furthermore, metamorphic surface rocks provide a window into deeper crustal lithologies. In such remote areas, satellite and aerial magnetic surveys could provide important geological information concerning exposed and not exposed rocks, but they integrate the magnetic anomalies in areas of kilometres. For the southernmost Andes long wavelength satellite data show clear positive magnetic anomalies (>+100 nT) for the Patagonian Batholith (PB), similar as parts of the older martian crust. This integrated signal covers regions with different ages and cooling histories during magnetic reversals apart from the variability of the rocks. To investigate the complex interplay of distinct magnetic signatures at short scale, we have analysed local magnetic anomalies across this orogen at representative sites by decimeter-scale magnetic ground surveys. As expected, the investigated sites have positive and negative local anomalies. They are related to surface and subsurface rocks, and their different formation and alternation processes including geomagnetic inversions, distinct Curie depths of the magnetic carriers, intracrustal deformation among other factors. Whole rock chemistry (ranging from 45 to >80 wt.% SiO2 and from 1 to 18 wt.% FeOtot.), magnetic characteristics (susceptibilities, magnetic remanence and Königsberger ratios) as well as the composition and texture of the magnetic carriers have been investigated for representative rocks. Rocks of an ultramafic to granodioritic intrusive suite of the western and central PB contain titanomagnetite as major magnetic carrier. Individual magnetic signatures of these plutonic rocks reflect their single versus multidomain status, complex exolution processes with ilmenite lamella formations and the stoichiometric proportions of Cr, Fe and Ti in the oxides. At

Expression profiling of lymph node cells from deer mice infected with Andes virus.

PubMed

Schountz, Tony; Shaw, Timothy I; Glenn, Travis C; Feldmann, Heinz; Prescott, Joseph

2013-04-09

Deer mice (Peromyscus maniculatus) are the principal reservoir hosts of Sin Nombre virus (SNV), the cause of the great majority of hantavirus cardiopulmonary syndrome (HCPS) cases in North America. SNV, like all hantaviruses with their reservoirs, causes persistent infection without pathology in deer mice and appear to elicit a regulatory T cell response. Deer mice are also susceptible to Andes virus (ANDV), which causes the great majority of HCPS cases in South America, but they clear infection by 56 days post infection without signs of disease. We examined lymph node cell responses of deer mice infected with ANDV to determine expression profiles upon in vitro recall challenge with viral antigen. Because the deer mouse genome is currently unannotated, we developed a bioinformatics pipeline to use known lab mouse (Mus musculus) cDNAs to predict genes within the deer mouse genome and design primers for quantitative PCR (http://dna.publichealth.uga.edu/BlastPrimer/BlastPrimer.php). Of 94 genes examined, 20 were elevated, the plurality of which were Th2-specific, whereas 12 were downregulated. Other expressed genes represented Th1, regulatory T cells and follicular helper T cells, and B cells, but not Th17 cells, indicating that many cellular phenotypes participate in the host response to Andes virus. The ability to examine expression levels of nearly any gene from deer mice should allow direct comparison of infection with SNV or ANDV to determine the immunological pathways used for clearance of hantavirus infection in a reservoir host species.

How typical are the last 20,000 years of climatic and vegetation change in the tropical Andes?

NASA Astrophysics Data System (ADS)

Gosling, W. D.; Urrego, D. H.; Hanselman, J. A.; Valencia, B.; Bush, M. B.; Silman, M. R.

2006-12-01

A consensus of global circulation models highlights the southern tropical Andes as the biodiversity hotspot most likely to experience biome shift in the next century. The pace of the ongoing change finds its nearest parallel in that of the Younger Dryas at high latitudes. However, in the tropical Andes of Peru and Bolivia we find that there was no such rapid temperature change within the last 40,000 years. Rates of temperature change across the deglacial interval (which may begin as early as c. 22,000 cal. yr BP) are one to two orders of magnitude slower than those forecasted for the next century, and differed little from those of the full glacial. Indeed, the fastest rates of vegetation change are responses to Holocene drought and human activity, not Pleistocene/Holocene warming. Sedimentary data from long records on the Altiplano provide records of earlier interglacials (MIS 5e, 7 and 9), but do not have the chronological control to provide assessments of rate of change. Nevertheless, those records do provide evidence of marked similarities in the development of each interglacial, with some divergence seen at full interglacial conditions.

Ecotypic differentiation under farmers' selection: Molecular insights into the domestication of Pachyrhizus Rich. ex DC. (Fabaceae) in the Peruvian Andes.

PubMed

Delêtre, Marc; Soengas, Beatriz; Vidaurre, Prem Jai; Meneses, Rosa Isela; Delgado Vásquez, Octavio; Oré Balbín, Isabel; Santayana, Monica; Heider, Bettina; Sørensen, Marten

2017-06-01

Understanding the distribution of crop genetic diversity in relation to environmental factors can give insights into the eco-evolutionary processes involved in plant domestication. Yam beans ( Pachyrhizus Rich. ex DC.) are leguminous crops native to South and Central America that are grown for their tuberous roots but are seed-propagated. Using a landscape genetic approach, we examined correlations between environmental factors and phylogeographic patterns of genetic diversity in Pachyrhizus landrace populations. Molecular analyses based on chloroplast DNA sequencing and a new set of nuclear microsatellite markers revealed two distinct lineages, with strong genetic differentiation between Andean landraces (lineage A) and Amazonian landraces (lineage B). The comparison of different evolutionary scenarios for the diversification history of yam beans in the Andes using approximate Bayesian computation suggests that Pachyrhizus ahipa and Pachyrhizus tuberosus share a progenitor-derivative relationship, with environmental factors playing an important role in driving selection for divergent ecotypes. The new molecular data call for a revision of the taxonomy of Pachyrhizus but are congruent with paleoclimatic and archeological evidence, and suggest that selection for determinate growth was part of ecophysiological adaptations associated with the diversification of the P. tuberosus - P. ahipa complex during the Mid-Holocene.

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

PubMed

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.

Long-term carbon accumulation in Andes peatlands

NASA Astrophysics Data System (ADS)

Huaman, Yizet; Moreira-turq, Patricia; Willems, Bram; Espinoza, Raul; Turq, Bruno; Apaéstegui, James; Llanos, Romina

2017-04-01

High-altitude peatlands of the Andes still remain relatively unexplored since most of the studies on carbon capture in tropical soils have focused on peatlands in low altitude areas, leaving aside the importance of the study of high mountain wetlands, currently called "bofedales" located between 3000 and 5000 masl, covering most of the Andes mountains in South America. These peatlands in turn may also represent important paleoclimatic records. In this study, we investigated three peatland cores (APA-01, APA2-01, and APA2-02) at different altitudes (4210 m, 4420 m and 4432 m, respectively) in high Andean Peatlands of southern Peru. The peatland studied is located at the headwater basin Cachi River, in the town of Ayacucho, Peru. The aim of this study was to evaluate the role played by past climatic changes on the peatlands carbon accumulation. Each core was sectioned centimeter by centimeter and sub samples (n = 31) were collected for radiocarbon dating by AMS (acceleration mass spectrometer) and were used to create a sedimentological model based on the program Clam2.2R. The concentrations of carbon and nitrogen were determined from a C / H / N elemental analyzer and the stable carbon and nitrogen isotopes (δ13C and δ15N) were also analyzed. The bulk density was determined based on the volume occupied by the sediment (g /cm3). Finally, the carbon accumulation rate (gC m-2año-1) was determined. The three cores were characterized by two sedimentary units, the results present in the first sedimentary unit of APA01 an average long-term carbon accumulation rate of 59 gC m-2año-1, APA2-01 with 32 gC m-2año-1 and finally APA2-02 with 24 gC m-2año-1; for the second sedimentary unit we have: APA01 on average 17 gC m-2año-1, APA2-01 with 33 gC m-2año-1 and finally APA2-02 with 49 gC m-2año-1. In conclusion, we can say that the carbon accumulation rate for the first sedimentary unit of the three cores decreases as the altitude increases; on the other hand, we have the

Fragmentation of Andes-to-Amazon connectivity by hydropower dams

PubMed Central

Anderson, Elizabeth P.; Jenkins, Clinton N.; Heilpern, Sebastian; Maldonado-Ocampo, Javier A.; Carvajal-Vallejos, Fernando M.; Encalada, Andrea C.; Rivadeneira, Juan Francisco; Hidalgo, Max; Cañas, Carlos M.; Ortega, Hernan; Salcedo, Norma; Maldonado, Mabel; Tedesco, Pablo A.

2018-01-01

Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems—the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services. PMID:29399629

Fragmentation of Andes-to-Amazon connectivity by hydropower dams.

PubMed

Anderson, Elizabeth P; Jenkins, Clinton N; Heilpern, Sebastian; Maldonado-Ocampo, Javier A; Carvajal-Vallejos, Fernando M; Encalada, Andrea C; Rivadeneira, Juan Francisco; Hidalgo, Max; Cañas, Carlos M; Ortega, Hernan; Salcedo, Norma; Maldonado, Mabel; Tedesco, Pablo A

2018-01-01

Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems-the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

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

NASA Astrophysics Data System (ADS)

Lara, Luis E.; Cordova, Loreto

2017-04-01

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

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

PubMed

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

2017-04-24

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

Nevado del Huila, Columbia

NASA Technical Reports Server (NTRS)

2007-01-01

Nevado del Huila Volcano in Colombia is actually a volcanic chain running north to south, capped by a glacier. With peaks ranging in height from 2,600 to 5,780 meters (8,530 to 18,960 feet), Nevado del Huila is a stratovolcano composed of alternating layers of hardened lava, solidified ash, and volcanic rocks. Its first recorded eruption occurred in the mid-sixteenth century. The long-dormant volcano erupted again in mid-April 2007. A few months before the eruption, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image of Nevado del Huila, on February 23, 2007. In this image, the bright white area just east of the central summit is ice. Immediately west of the summit are bare rocks, appearing as blue-gray. West of those rocks, white reappears, but this patch of white results from clouds hovering in the nearby valley. In the east, the colors turn to brown (indicating bare rock) and bright green (indicating vegetation). ASTER photographed Nevado del Huila near the end of a long phase of quietude. On April 17, 2007, local authorities recorded seismic activity associated with rock fracturing on the volcano's central summit, according to the ReliefWeb Website. Activity intensified the following day with an eruption and mudflows, forcing thousands of nearby residents to evacuate. As the Associated Press reported, the eruption caused avalanches and floods that wiped away both houses and bridges. It marked the volcano's first recorded eruption since the Spanish colonized the area five centuries earlier. NASA image created by Jesse Allen, using data provided courtesy of the NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

Remote sensing and climate data as a key for understanding fasciolosis transmission in the Andes: review and update of an ongoing interdisciplinary project.

PubMed

Fuentes, Màrius V

2006-11-01

Fasciolosis caused by Fasciola hepatica in various South American countries located on the slopes of the Andes has been recognized as an important public health problem. However, the importance of this zoonotic hepatic parasite was neglected until the last decade. Countries such as Peru and Bolivia are considered to be hyperendemic areas for human and animal fasciolosis, and other countries such as Chile, Ecuador, Colombia and Venezuela are also affected. At the beginning of the 1990s a multidisciplinary project was launched with the aim to shed light on the problems related to this parasitic disease in the Northern Bolivian Altiplano. A few years later, a geographic information system (GIS) was incorporated into this multidisciplinary project analysing the epidemiology of human and animal fasciolosis in this South American Andean region. Various GIS projects were developed in some Andean regions using climatic data, climatic forecast indices and remote sensing data. Step by step, all these GIS projects concerning the forecast of the fasciolosis transmission risk in the Andean mountain range were revised and in some cases updated taking into account new data. The first of these projects was developed on a regional scale for the central Chilean regions and the proposed model was validated on a local scale in the Northern Bolivian Altiplano. This validated mixed model, based on both fasciolosis climatic forecast indices and normalized difference vegetation index values from Advanced Very High Resolution Radiometer satellite sensor, was extrapolated to other human and/or animal endemic areas of Peru and Ecuador. The resulting fasciolosis risk maps make it possible to show the known human endemic areas of, mainly, the Peruvian Altiplano, Cajamarca and Mantaro Peruvian valleys, and some valleys of the Ecuadorian Cotopaxi province. Nevertheless, more climate and remote sensing data, as well as more accurate epidemiological reports, have to be incorporated into these GIS

Andes Virus M Genome Segment is Not Sufficient to Confer the Virulence Associated With Andres Virus in Syrian Hamsters

DTIC Science & Technology

2004-01-01

Hantavirus ; Reassortant; Hantavirus pulmonary syndrome ; HamsterIntroduction Hantaviruses are members of the Bunyaviridae...Andes virus (ANDV), members of the genus Hantavirus , in the family Bunyaviridae, are causative agents of hantavirus pulmonary syndrome (HPS) in North and...in humans: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) (Lee et al., 1982; Nichol et al., 1993). Almost

Updated azca (Farallon)—South America relative motions during the last 40 My: implications for mountain building in the central Andean region

NASA Astrophysics Data System (ADS)

Somoza, R.

1998-05-01

Recently published seafloor data around the Antarctica plate boundaries, as well as calibration of the Cenozoic Magnetic Polarity Time Scale, allow a reevaluation of the Nazca (Farallon)-South America relative convergence kinematics since late Middle Eocene time. The new reconstruction parameters confirm the basic characteristics determined in previous studies. However, two features are notable in the present data set: a strong increase in convergence rate in Late Oligocene time, and a slowdown during Late Miocene time. The former is coeval with the early development of important tectonic characteristics of the present Central Andes, such as compressional failure in wide areas of the region, and the establishment of Late Cenozoic magmatism. This supports the idea that a relationship exists between strong acceleration of convergence and mountain building in the Central Andean region.

Variations in the Crust-Mantle Transition Beneath the Andean Cordillera and Implications for Orogenic Processes.

NASA Astrophysics Data System (ADS)

Koch, C.; Isaacs, D.; Delph, J. R.; Beck, S. L.

2017-12-01

The South American Andes, generated along an active oceanic-continental convergent margin between the Nazca and South American plates, make up the world's longest arc and encompass the second highest orogenic plateau on Earth. Along-strike variations in shortening, slab subduction angle, and volcanism, along with other tectonic processes, have created extraordinarily complex topography, crustal thickness, and compositional variations reflected in the seismic characteristics of the region. Ps receiver functions (PRFs) have been widely used to investigate the Andes, and these studies provide a wealth of information regarding the structure of the Andean crust and the continental Moho beneath the orogen. However, these studies have focused largely on individual networks or latitudinal segments of the Andes, and a regional-scale model that combines all available data has yet to be analyzed, hence it is hard to compare the amplitudes of conversions at the major discontinuities. This study compiles and analyzes all available data from permanent and temporary seismic networks from (1989-2017) to create a continuous, high spatial resolution common conversion point (CCP) volume for the Andes. In total, receiver functions were calculated for over 1500 seismic stations in the Andes, enabling us to obtain high-resolution, regional-scale CCP images of the continental Moho beneath the Andes from Colombia to southern Chile. The resulting CCP volume shows strong lateral variations in P-to-S conversion amplitudes at the base of the crust, indicating a complex and variable crust-mantle transition. In some places, the back-arc of the central Andes is characterized by relatively thick crust (60 - 75 km) and a broad, low amplitude Moho conversion indicative of a gradational Moho possibly due to the eclogitization of the lower crust. Combined with other geophysical data, this may suggest these are sites of ongoing delamination in the central Andes. Additionally, in the central Andes

Characterisation of the sedimentary processes responsible for the filling and excavation of two intra mountainous basins (Agua Amarga and Collon Cura) in the Andes of Neuquén (Argentina) during the Neogene

NASA Astrophysics Data System (ADS)

Bonnel, C.; Huyghe, D.; Nivière, B.; Messager, G.; Dhont, D.; Fasentieux, B.; Hervouët, Y.; Xavier, J.-P.

2012-04-01

Intramontane basins constitute potential good recorders of orogenic systems deformation history through the documentation of their remnant sedimentary filling and observation of syntectonic growth strata. In this work, we focus on the Neuquén basin, located on the eastern flank of the Andes between 32°S and 41°S latitude. It has been structured since the late Triassic, first as back arc basin and as compressive foreland basin since the upper Cretaceous. Most of the sedimentary filling is composed of Mesozoic sediments, which have been importantly studied because of their hydrocarbon potential. On the contrary, Cenozoic tectonic and sedimentologic evolutions remain poorly documented in regard to the Mesozoic. The structural inheritance is very important and strongly influences the deformation and shortening rates from the North to the South of the basin. Thus, the northern part exhibits a classical configuration from the western high Andes, to younger fold and thrust belts and piggy-back basins to the East. On the contrary, no fold and thrust belt exist in the southern part of the basin and the deformation is restricted to the internal domain. Nevertheless, contemporaneous intramontane basins (the Agua Amarga to the North and the Collon Cura basin to the South) existed in these two parts of the basin and seem to have followed a similar evolution despite of a different structural context. To the North, the partial closing of the Agua Amarga basin by the growth of the Chuihuidos anticlines during the Miocene is characterised by the deposition of a fining upward continental sequence of ~250 m thick, from lacustrine environment at the base to alluvial and fluviatile environments in the upper part of the section. In the Collon Cura, the sedimentary filling, due to the rising of the Piedra del Aguila basement massif, reach at maximum 500 m and consist in fluvial tuffaceous material in the lower part to paleosoils and coarse conglomeratic fluvial deposits in the upper

Regionalisation of Hydrological Indices to Assess Land-Use Change Impacts in the Tropical Andes

NASA Astrophysics Data System (ADS)

Buytaert, W.; Ochoa Tocachi, B. F.

2014-12-01

Andean ecosystems are major water sources for cities and communities located in the Tropical Andes; however, there is a considerable lack of knowledge about their hydrology. Two problems are especially important: (i) the lack of monitoring to assess the impacts of historical land-use and cover change and degradation (LUCCD) at catchment scale, and (ii) the high variability in climatic and hydrological conditions that complicate the evaluation of land management practices. This study analyses how a reliable LUCCD impacts assessment can be performed in an environment of high variability combined with data-scarcity and low-quality records. We use data from participatory hydrological monitoring activities in 20 catchments distributed along the tropical Andes. A set of 46 hydrological indices is calculated and regionalized by relating them to 42 physical catchment properties. Principal Component Analysis (PCA) is performed to maximise available data while minimising redundancy in the sets of variables. Hydrological model parameters are constrained by estimated indices, and different behavioural predictions are assembled to provide a generalised response on which we assess LUCCD impacts. Results from this methodology show that the attributed effects of LUCCD in pair-wise catchment comparisons may be overstated or hidden by different sources of uncertainty, including measurement inaccuracies and model structural errors. We propose extrapolation and evaluation in ungauged catchments as a way to regionalize LUCCD predictions and to provide statistically significant conclusions in the Andean region. These estimations may deliver reliable knowledge to evaluate the hydrological impact of different watershed management practices.

Evolutionary persistence in Gunnera and the contribution of southern plant groups to the tropical Andes biodiversity hotspot.

PubMed

Bacon, Christine D; Velásquez-Puentes, Francisco J; Hinojosa, Luis Felipe; Schwartz, Thomas; Oxelman, Bengt; Pfeil, Bernard; Arroyo, Mary T K; Wanntorp, Livia; Antonelli, Alexandre

2018-01-01

Several studies have demonstrated the contribution of northern immigrants to the flora of the tropical Andes-the world's richest and most diverse biodiversity hotspot. However, much less is known about the biogeographic history and diversification of Andean groups with southern origins, although it has been suggested that northern and southern groups have contributed roughly equally to the high Andean (i.e., páramo) flora. Here we infer the evolutionary history of the southern hemisphere plant genus Gunnera , a lineage with a rich fossil history and an important ecological role as an early colonising species characteristic of wet, montane environments. Our results show striking contrasts in species diversification, where some species may have persisted for some 90 million years, and whereas others date to less than 2 Ma since origination. The outstanding longevity of the group is likely linked to a high degree of niche conservatism across its highly disjunct range, whereby Gunnera tracks damp and boggy soils in cool habitats. Colonisation of the northern Andes is related to Quaternary climate change, with subsequent rapid diversification appearing to be driven by their ability to take advantage of environmental opportunities. This study demonstrates the composite origin of a mega-diverse biota.

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

PubMed

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

2015-02-01

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

Preliminary assessment of a Cretaceous-Paleogene Atlantic passive margin, Serrania del Interior and Central Ranges, Venezuela/Trinidad

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pindell, J.L.; Drake, C.L.; Pitman, W.C.

1991-03-01

For several decades, Cretaceous arc collision was assumed along northern Venezuela based on isotopic ages of metamorphic minerals. From subsidence histories in Venezuelan/Trinidadian basins, however, it is now clear that the Cretaceous metamorphic rocks were emplaced southeastward as allochthons above an autochthonous suite of rocks in the Cenozoic, and that the pre-Cenozoic autochthonous rocks represent a Mesozoic passive margin. The passive margin rocks have been metamorphosed separately during overthrusting by the allochthons in central Venezuela, but they are uplifted but not significantly metamorphosed in Eastern Venezuela and Trinidad. There, in the Serrania del Interior and Central Ranges of Venezuela/Trinidad, Mesozoic-Paleogenemore » passive margin sequences were uplifted in Neogene time, when the Caribbean Plate arrived from the west and transpressionally inverted the passive margin. Thus, this portion of South America's Atlantic margin subsided thermally without tectonism from Jurassic to Eocene time, and these sections comprise the only Mesozoic-Cenozoic truly passive Atlantic margin in the Western Hemisphere that is now exposed for direct study. Direct assessments of sedimentological, depositional and faunal features indicative of, and changes in, water depth for Cretaceous and Paleogene time may be made here relative to a thermally subsiding passive margin without the complications of tectonism. Work is underway, and preliminary assessments presented here suggest that sea level changes of Cretaceous-Paleogene time are not as pronounced as the frequent large and rapid sea level falls and rises that are promoted by some.« less

Cosmogenic 10Be Dating of Early and Latest Holocene Moraines on Nevado Salcantay in the Southern Peruvian Andes

NASA Astrophysics Data System (ADS)

Licciardi, J. M.; Schaefer, J. M.; Lund, D. C.

2007-12-01

A two-fold sequence of nested lateral and end moraines was mapped in a glacial trough emanating from the southwest flank of Nevado Salcantay (6271 m; ~13°S latitude), the highest peak in the Cordillera Vilcabamba of southern Peru. The field area is situated 25 km due south of the archaeological site of Machu Picchu. Outer and inner moraines in the sequence were deposited by valley glaciers that terminated ~5 km and ~3 km, respectively, from their headwall on the Salcantay summit massif. Cosmogenic 10Be surface exposure dating of granitic boulders sampled on the Salcantay moraines is underway and has provided the first numerical ages for these deposits. Initial results indicate ages of 8.1 ± 0.1 10Be ka for the outer moraine and 200 ± 20 10Be years for the sharp-crested inner moraine. These ages are derived using the CRONUS-Earth 10Be exposure age calculator (version 2.0) and expressed with respect to the Lal- Stone production rate scaling scheme using the standard atmosphere. The outer and inner moraine ages correspond to glacial events during the early and latest Holocene, respectively. Further 10Be dating of the mapped moraines and similar deposits observed in adjacent drainages on Nevado Salcantay is anticipated to yield a high-resolution chronology of valley glaciation in this segment of the southern Peruvian Andes. The new results bridge an important gap between existing Andean glacier records to the north and south, and complement available ice core and lacustrine paleoclimate records in the vicinity, thereby expanding spatial and temporal coverage for identifying patterns of Holocene climate change in the tropical Andes. Notably, the inner moraine age correlates with the timing of the Little Ice Age as defined in northern mid- and high latitude glacier records, and suggests considerable expansion of valley glaciers in the southern Peruvian Andes during this climatic minimum. Apart from their paleoclimatic significance, the initial results also demonstrate

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

NASA Astrophysics Data System (ADS)

Byers, C.; Mann, P.

2015-12-01

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

The high Andes, gene flow and a stable hybrid zone shape the genetic structure of a wide-ranging South American parrot

PubMed Central

2011-01-01

Background While the gene flow in some organisms is strongly affected by physical barriers and geographical distance, other highly mobile species are able to overcome such constraints. In southern South America, the Andes (here up to 6,900 m) may constitute a formidable barrier to dispersal. In addition, this region was affected by cycles of intercalating arid/moist periods during the Upper/Late Pleistocene and Holocene. These factors may have been crucial in driving the phylogeographic structure of the vertebrate fauna of the region. Here we test these hypotheses in the burrowing parrot Cyanoliseus patagonus (Aves, Psittaciformes) across its wide distributional range in Chile and Argentina. Results Our data show a Chilean origin for this species, with a single migration event across the Andes during the Upper/Late Pleistocene, which gave rise to all extant Argentinean mitochondrial lineages. Analyses suggest a complex population structure for burrowing parrots in Argentina, which includes a hybrid zone that has remained stable for several thousand years. Within this zone, introgression by expanding haplotypes has resulted in the evolution of an intermediate phenotype. Multivariate regressions show that present day climatic variables have a strong influence on the distribution of genetic heterogeneity, accounting for almost half of the variation in the data. Conclusions Here we show how huge barriers like the Andes and the regional environmental conditions imposed constraints on the ability of a parrot species to colonise new habitats, affecting the way in which populations diverged and thus, genetic structure. When contact between divergent populations was re-established, a stable hybrid zone was formed, functioning as a channel for genetic exchange between populations. PMID:21672266

An Ancestral Language to Speak with the "Other": Closing down Ideological Spaces of a Language Policy in the Peruvian Andes

ERIC Educational Resources Information Center

Zavala, Virginia

2014-01-01

Using a multilayered, ethnographic and critical approach to language policy and planning, this article examines a language policy favoring Quechua in Apurímac in the Southern Peruvian Andes, which is being imagined as an integrated community unified by the local language. This study presents a case in which top-down policies open up ideological…

Neotectonics in the foothills of the southernmost central Andes (37°-38°S): Evidence of strike-slip displacement along the Antiñir-Copahue fault zone

NASA Astrophysics Data System (ADS)

Folguera, AndréS.; Ramos, VíCtor A.; Hermanns, Reginald L.; Naranjo, José

2004-10-01

The Antiñir-Copahue fault zone (ACFZ) is the eastern orogenic front of the Andes between 38° and 37°S. It is formed by an east vergent fan of high-angle dextral transpressive and transtensive faults, which invert a Paleogene intra-arc rift system in an out of sequence order with respect to the Cretaceous to Miocene fold and thrust belt. 3.1-1.7 Ma volcanic rocks are folded and fractured through this belt, and recent indicators of fault activity in unconsolidated deposits suggest an ongoing deformation. In spite of the absence of substantial shallow seismicity associated with the orogenic front, neotectonic studies show the existence of active faults in the present mountain front. The low shallow seismicity could be linked to the high volumes of retroarc-derived volcanic rocks erupted through this fault system during Pliocene and Quaternary times. This thermally weakened basement accommodates the strain of the Antiñir-Copahue fault zone, absorbing the present convergence between the South America and Nazca plates.

British medicine in the Peruvian Andes: the travels of Archibald Smith M.D. (1820-1870).

PubMed

Lossio, Jorge

2006-01-01

This article traces the travels of the Scottish physician Archibald Smith through the Peruvian Andes between the 1820s and 1860s. Despite his prominent role in the nineteenth-century Peruvian medical scene, almost nothing has been written on Archibald Smith. By exploring Smith's medical activities, publications, and debates, this article intends to uncover unexplored areas of Peruvian medical history, such as the animosity between local and foreign physicians during the post-Independence war era and the important role played by medical geography as a scientific discipline for redefining ethnical and regional issues.

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

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

Climate dynamics of South America during summer: Connections between the large-scale circulation and regional precipitation

NASA Astrophysics Data System (ADS)

Lenters, Johh Derick

1997-05-01

Relationships between the large-scale circulation and regional precipitation over South America during austral summer are examined using a GCM, linear model, and observational analyses. Emphasis is placed on understanding the origin of upper-tropospheric circulation features such as the Bolivian high and its effects on South American precipitation variability, particularly on the Central Andean Altiplano. Results from the linear model indicate that the Bolivian high and 'Nordeste low' are generated in response to precipitation over the Amazon basin, Central Andes, and South Atlantic convergence zone (SACZ), with African precipitation also playing a crucial role in the formation of the low. The direct mechanical and sensible heating effects of the Andes are minimal, acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the Central Andes. In the GCM the effects of the Andes include a strengthening of the Bolivian high and northward shift of the Nordeste low, primarily through changes in the precipitation field. The position of the Bolivian high is primarily determined by Amazonian precipitation and is little affected by the removal of the Andes. Strong subsidence to the west of the high is found to be important for the maintenance of the high's warm core, while large-scale convective overshooting to the east is responsible for a layer of cold air above the high. Observations from eight summer seasons reveal a close relationship between precipitation variability in the Central Andes and the position and intensity of the Bolivian high. The physical mechanisms of this connection are explored using composite, EOF, and correlation techniques. On intraseasonal to interannual timescales, rainy episodes on the Altiplano are found to be associated with warm, moist, poleward flow along the eastern flank of the Andes, often in conjunction with extratropical disturbances and a westward displacement of the SACZ. Corresponding to this

Mapping hydrological signatures in the tropical Andes using a network of paired catchments

NASA Astrophysics Data System (ADS)

Ochoa-Tocachi, B. F.; Buytaert, W.; De Bièvre, B.

2016-12-01

The complexity and data scarcity of tropical Andean catchments make regional hydrological predictions very challenging. The strong spatiotemporal patterns of the local climate contrast with the inadequate coverage, especially of remote areas, by the national monitoring networks. We present an approach to regionalize the hydrological impacts of land-use and land-cover (LUC) using a network of 24 headwater catchments in a pairwise comparison approach. We monitored precipitation and streamflow through an informal partnership of stakeholders in the Andes, known as iMHEA. Using a `trading-space-for-time' approach, our design aims at strengthening the statistical significance of LUC signals. To test our hypothesis, we summarized the hydrological responses using a set of indices, which are then regionalized against catchment properties including land-use. Lastly, the regionalization model is then used to generate distributed maps of hydrological signatures in ungauged areas. Our results clearly reflect the dominant regional climate patterns of the tropical Andes and the associated wide spectrum of hydrological responses. Although the hydrological impacts of LUC are equally diverse, we find consistent trends within different biomes. Contrary to earlier studies, we find that incorporating LUC variables in the regionalization increases significantly the performance of the regression model and its predictive capacity, which makes it possible to generate regional maps that predict the dynamics and propagation of streamflow signatures in complex regions with an explicit report of uncertainty. We attribute the robust regionalization results to the regional pairwise setup that covers diverse physiographic characteristics, contrasting LUC types, and degrees of conservation/alteration. As such, it may be a useful strategy to optimize data collection, leverage commonly available geographical information, and understand the major controls of hydrological response in data

Intraplate Stresses Within the North Andes Block; an Enigma Soon to be Clarified

NASA Astrophysics Data System (ADS)

Trenkamp, R.; Mora P., H.

2008-05-01

High precision geodesy (GPS) has given earth scientists the unprecedented opportunity for studying the kinematics and dynamics of present day deformation processes at both plate boundary zones and within areas of wide plate boundary deformation. Global Positioning System (GPS) data from northwestern South America collected between 1991 and 2007 reveal wide plate margin deformation along a 1400 km length of the North Andes associated with the oblique subduction of the Nazca plate at the Colombia-Ecuador trench (CET) and ongoing collision with the Panama microplate. Also associated with this oblique subduction at the CET is the escape of the North Andes block (NAB). The NAB is delineated by the Bocono-East Andean fault systems and the Dolores Guayaquil Megasheare to the east, the South Caribbean deformed belt on the north and the CET and Panama on the west. Within the subduction complex at the CET many damaging earthquakes have occurred in the past, including the 1906-1979 mega-sequence of four earthquakes with moment magnitudes between 7.5 and 8.8. and two moment magnitude 7.1 earthquakes north of the mega-sequence rupture zone that have ruptured the same point within a 13 year time-span. Within the NAB many damaging crustal earthquakes have occurred which is most recently exemplified by the December 5, 1999 Armenia earthquake and the spectacular sequence known as the Bucaramanga nest. Much of the deformation of the NAB is constrained within the S-N and W-E trending fault systems within the NAB which contribute to the continuing seismic hazards within the system. Although the GPS data has been collected intermittently in the past, the many first order observations have been useful for developing strategies for future more extensive occupations and have led to the funding through INGEOMINAS of the Colombian national permanent GPS array; GEORED Geodesia: Red de Estudios de Deformacion.

Nutritional status, physical performance and disability in the elderly of the Peruvian Andes.

PubMed

Tramontano, Alessandra; Veronese, Nicola; Giantin, Valter; Manzato, Enzo; Rodriguez-Hurtado, Diana; Trevisan, Caterina; De Zaiacomo, Francesca; Sergi, Giuseppe

2016-12-01

Although nutritional status plays an important part in the physical performance and disability of older people, this relationship has been little studied in developing countries. A study on the effects of nutritional status on the physical performance and functional status of elderly people living in rural areas of the Peruvian Andes. The study concerned 222 people aged ≥65 years living in a rural area of the Peruvian Andes. The Mini-Nutritional Assessment (MNA) was used to classify participants as malnourished (MNA <= 17), at risk of malnutrition (MNA 18-23), or well-nourished (MNA>= 24). The short physical performance battery (SPPB) and six-minute walking test (6MWT) were used to measure participants' physical performance. Disabilities were investigated by assessing participants' self-reported difficulty in performing one or more basic activities of daily living (ADL), and instrumental activities of daily living (IADL). The prevalence of malnutrition was 9.4 %, and more than half of our samples were at risk of malnutrition. After adjusting for potential confounders, malnourished individuals performed significantly worse than the other MNA groups in the SPPB (p for trend=0.001), 6MWT and IADL (p for trend < 0.0001 for both outcomes), but not in the ADL (p for trend = 0.23). Taking the well-nourished for reference, and after adjusting for potential confounders, malnutrition was significantly associated with disability in IADL (OR 5.36, 95 % CI 1.02-56.94; p = 0.05), and poor performance in the 6MWT (OR 2.73, 95 % CI 1.06-12.08; p = 0.03) and SPPB (OR 4.94, 95 % CI 1.01-24.07; p = 0.04). Poor nutritional status was found significantly associated with poor physical performance and poor functional status in elderly Peruvian individuals.

Membrane triangles with corner drilling freedoms. II - The ANDES element

NASA Technical Reports Server (NTRS)

Felippa, Carlos A.; Militello, Carmelo

1992-01-01

This is the second article in a three-part series on the construction of 3-node, 9-dof membrane elements with normal-to-its-plane rotational freedoms (the so-called drilling freedoms) using parametrized variational principles. In this part, one such element is derived within the context of the assumed natural deviatoric strain (ANDES) formulation. The higher-order strains are obtained by constructing three parallel-to-sides pure-bending modes from which natural strains are obtained at the corner points and interpolated over the element. To attain rank sufficiency, an additional higher-order 'torsional' mode, corresponding to equal hierarchical rotations at each corner with all other motions precluded, is incorporated. The resulting formulation has five free parameters. When these parameters are optimized against pure bending by energy balance methods, the resulting element is found to coalesce with the optimal EFF element derived in Part I. Numerical integration as a strain filtering device is found to play a key role in this achievement.

Peltephilidae and Mesotheriidae (Mammalia) from late Miocene strata of Northern Chilean Andes, Caragua

NASA Astrophysics Data System (ADS)

Montoya-Sanhueza, Germán; Moreno, Karen; Bobe, René; Carrano, Matthew T.; García, Marcelo; Corgne, Alexandre

2017-04-01

Until now, only one Cenozoic fossil mammal from the Chilean Precordillera (Arica and Parinacota Region) has been reported, Caraguatypotherium munozi (Mesotheriidae: Notoungulata). In this study, we describe a fourth specimen of C. munozi and a new armadillo species, Epipeltephilus caraguensis (Peltephilidae: Cingulata), both collected from a new site closer to the fossiliferous outcrops of the Caragua area (Serravallian - Tortonian). E. caraguensis differs from other members of the family in having: two sulci in the articular surface of the mobile osteoderm; having a tubular, rough and raised anterior edge; a conspicuous transverse depression; and four widely spaced foramina. This taxon represents the youngest known peltephilid from intermediate latitudes and indicates a wide geographic distribution (Patagonia to Central Andes) of the family just prior to its extinction. The new mesothere specimen is 19% larger than previous records. The revision of the dental features of C. munozi allowed the identification of an ambiguous trait in its original diagnosis, i.e. an enamel fracture was misinterpreted with the presence of a posterior sulcus on the talonid of the m3, suggesting that further taxonomic and systematic revision for the Caragua mesothere is necessary. Although the fossil record from the Caragua area is still scarce, mesotheriines seem to be abundant at this latitude, just as has been observed at several early to late Miocene sites such as Chucal (Chile), Cerdas and Nazareno (Bolivia), as well as in southern regions such as Arroyo Chasicó and Mendoza (Argentina). The presence of a new peltephilid species in Caragua sustains the hypothesis of provincialism during the Miocene in intermediate latitudes. Our findings also provide further support for probable faunal movements between intermediate and higher latitudes rather than to lower ones.

Tracing oxidative weathering from the Andes to the lowland Amazon Basin using dissoved rhenium

NASA Astrophysics Data System (ADS)

Dellinger, M.; Hilton, R. G.; West, A. J.; Torres, M.; Burton, K. W.; Clark, K. E.; Baronas, J. J.

2016-12-01

Over long timescales (>105 yrs), the abundance of carbon dioxide (CO2) in the atmosphere is determined by the balance of the major carbon sources and sinks. Among the major carbon sources, the oxidation of organic carbon contained within sedimentary rocks ("petrogenic" carbon, or OCpetro) is thought to result in CO2 emission of similar magnitude to that released by volcanism. Rhenium (Re) has been proposed as a proxy for tracing OCpetro oxidation. Here we investigate the source, behavior and flux of dissolved and particulate rhenium (Re) in the Madre de Dios watershed (a major Andean tributary of the Amazon River) and the lowlands, aiming to characterize the behavior of Re in river water and quantify the flux of CO2 released by OCpetro oxidation. Measured Re concentrations in Andean rivers range from 0.07 to 1.55 ppt. In the Andes, Re concentration do not change significantly with water discharge, whereas in the lowlands, Re concentration decrease at high water discharge. Mass balance calculation show that more than 70% of the dissolved Re is sourced from the oxidation of OCpetro the Andes-floodplain system. We calculate dissolved Re flux over a hydrological year to estimate the rates of oxidative weathering, and the associated CO2 release from OCpetro. Rates are high in the Andean headwaters, consistent with estimates from other mountain rivers with similar rates of physical erosion. We find evidence that a significant amount of additional oxidation (Re flux) happens during floodplain transport. These results have important implications for improving our understanding of the source and processes controlling Re in rivers, and allowing us to quantify long-term OCpetro cycling in large river basins.

Magnetic Mineralogy as Indicator of dry Conditions in Lacustrine Sediments From Santa María del Oro, Nayarit, Central Mexico

NASA Astrophysics Data System (ADS)

Ortega, B.; Vazquez, G.; Rodriguez, A.

2007-05-01

Combined magnetic and geochemical analysis were conducted on laminated sediments from Santa Maria del Oro, a crater lake in Nayarit (Mexico), to build up a model of paleoenvironmental conditions for the late Holocene. The occurrence of a severe drought at the end of the archeological Classic period (100 - 900 AD) has been documented in sites of central Mexico (Zirahuen lake and Lerma basin), the Gulf of Mexico coast (Los Tuxtlas) and the Yucatan peninsula. The effects of this climatic event are considered to have stressed the social and political situation in the Yucatan area and other sites in Mesoamerica, and resulted in the "collapse" of the Maya civilization. Santa Maria del Oro sediments between ca. 600 - 1140 AD are characterized by repeated sequences of ocher silt laminae with high inorganic carbon content, authigenic siderite, and low concentration of SD magnetic minerals, followed upward by an increase of concentrations of fine grained SD and SP ferrimagnetic minerals in brown silt laminae. This sequence is considered to represent dissolution-precipitation cycles of magnetic minerals in low erosion, concentrated waters and anoxic water-sediment interface environments. Dissolution of magnetite occurs in reductive conditions, which are considered as warmer and dryer periods. Above the ocher silt, precipitation of fine grained magnetite occurs when conditions change to oxic environments. Ostracode C and O isotopy document a negative precipitation/evaporation balance during this time period.

Primer registro para Peru del genero Nielsonia Young, 1977 (Hemiptera: Cicadellidae: Cicadellinae: Cicadellini)

USDA-ARS?s Scientific Manuscript database

En este articulo se reporta por primera vez para el Peru una especies del genero Nielsonia Young, 1977, de material procedente del Departamento de Tumbes. El genero ha sido reportada anteriormente de Ecuador, como unico registro para Sudamerica, y America Central. El unico especimen hembra encontra...

Prevalence of sarcopenia and associated factors in the healthy older adults of the Peruvian Andes.

PubMed

Tramontano, Alessandra; Veronese, Nicola; Sergi, Giuseppe; Manzato, Enzo; Rodriguez-Hurtado, Diana; Maggi, Stefania; Trevisan, Caterina; De Zaiacomo, Francesca; Giantin, Valter

To assess the prevalence of sarcopenia and associated factors in a population of older people living in a rural area of the Peruvian Andes. The study concerned 222 people aged ≥65 years. Sarcopenia was diagnosed on the basis of skeletal muscle mass, measured using bioimpedance analysis, and gait speed, measured with the 4-m walking test, as recommended by the International Working Group on sarcopenia. Self-reported physical activity, the Short Physical Performance Battery, and the Six-Minute Walking Test also contributed information on participants' physical performance status. Disabilities were investigated by assessing participants' self-reported difficulties in performing one or more basic or instrumental activities of daily living. The prevalence of sarcopenia was 17.6%. Compared with participants without sarcopenia, individuals who were found sarcopenic were significantly older, female and were less frequently farmers, had fewer children, had a worse nutritional status, a significantly lower physical performance, and higher levels of disability in the instrumental activities of daily living. After adjusting for potential confounders, age, female sex, a low body mass index, a self-reported low physical activity level, a worse Six-Minute Walking Test scores, and a low number of children were significantly associated with sarcopenia. The prevalence of sarcopenia seems to be quite high among community-dwelling older subjects in the Peruvian Andes. Age, female sex, a low body mass index, little physical activity, a poor Six-Minute Walking Test scores, and a low number of children could be associated with this condition. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Fault-controlled development of shallow hydrothermal systems: Structural and mineralogical insights from the Southern Andes

NASA Astrophysics Data System (ADS)

Roquer, T.; Arancibia, G.; Rowland, J. V.; Iturrieta, P. C.; Morata, D.; Cembrano, J. M.

2017-12-01

Paleofluid-transporting systems can be recognized as meshes of fracture-filled veins in eroded zones of extinct hydrothermal systems. Here we conducted meso-microstructural analysis and mechanical modeling from two exhumed exposures of the faults governing regional tectonics of the Southern Andes: the Liquiñe-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF). A total of 107 fractures in both exposures were analyzed. The ATF specific segment shows two tectonic solutions that can be modeled as Andersonian and non-Andersonian tectonic regimes: (1) shear (mode II/III) failure occurs at differential stresses > 28 MPa and fluid pressures < 40-80% lithostatic in the Andersonian regime; and (2) sporadic hybrid extensional + shear (modes I + II/III) failure occurs at differential stresses < 20 MPa and anomalously high fluid pressures > 85-98% lithostatic in the non-Andersonian regime. Additionally, the LOFS exposure cyclically fails in extension (mode I) or extension + shear (modes I + II/III) in the Andersonian regime, at differential stresses < 28 MPa and fluid pressures > 40-80% lithostatic. In areas of spatial interaction between ATF and LOFS, these conditions might favor: (1) the storage of overpressured fluids in hydrothermal systems associated with the ATF faults, and (2) continuous fluid flow through vertical conduits in the LOFS faults. These observations suggest that such intersections are highly probable locations for concentrated hydrothermal activity, which must be taken into consideration for further geothermal exploration. ACKNOWLEDGEMENTS. PhD CONICYT grants, Centro de Excelencia en Geotermia de los Andes (CEGA-FONDAP/CONICYT Project #15090013), FONDECYT Project #1130030 and Project CONICYT REDES #140036.

Mid-Holocene Drought in the Andes and Associated Impacts on Hydrology of the Amazon River

NASA Astrophysics Data System (ADS)

de Toledo, M. B.; Bush, M. B.; Figueiredo, A. G.

2007-05-01

Pollen, charcoal, and radiocarbon analyses were performed on a 2m-long sediment core obtained from Lake Tapera (coastal Amapa) to provide the paleoenvironmental history of this part of Amazonia. Detrended Correspondence Analysis was applied to the pollen data to improve visualization of sample distribution and similarity. The chronology was based on seven AMS radiocarbon dates, which allowed the establishment of a basal age (8,060 yrs BP) and identification of a sedimentary hiatus lasting 5,500 years (c. 7,100-1600 yrs BP) in Lake Tapera. Because the timing of the hiatus overlapped with the highest Holocene sea-level (5,000 yrs BP), which would have increased the local water table preventing the lake from drying out, it is clear that sea-level was not important in maintaining the lake level. As Lake Tapera apparently depended on riverine flood waters, the sedimentary gap was probably caused by reduced Amazon River discharge, due to an extremely dry period in the Andes (8,000-5,000 years BP), when precipitation levels markedly decreased. One of the impacts of this drought in the Andes was a c. 100m drop in Lake Titicaca water depth. The contrasting presence before and after the hiatus of Andean pollen (river transported) in the record of Lake Tapera supports this interpretation. The pollen analysis also shows that when sedimentation resumed in 1,620 cal. years BP, vegetation around the lake was changed from forest into savanna. This record demonstrates the need to improve our understanding of climate changes and the extent of their associated impacts on the environment.

Social networks, market transactions, and reputation as a central resource. The Mercado del Mar, a fish market in central Mexico

PubMed Central

Hernández, Juan M.

2017-01-01

Fish consumption in Mexico is considered low (around 12 kg per person per year) and non-homogeneously distributed across the country. One of the reasons for this situation is the scarcity of wholesale selling sites. In this context, the Mercado del Mar (MM), located in Guadalajara city, Jalisco, is the second biggest wholesale fish market in Mexico, with a distribution of about 500 tons per day and a variety of about 350 different species of fish. In this paper, we argue that MM has accumulated social capital, which is formed from two main resources: buyer and seller relationships, and reputation. Specifically, the MM manages a broad and intensive interaction among business actors and the already achieved reputation allows the MM to adapt to market changes. To validate our hypotheses, an empirical study was conducted in 2015 by means of interviews to fish wholesalers in the MM and a sample of their suppliers and buyers. For simplicity we have only considered fresh water fish. We have followed snow-ball sampling as the survey strategy. Results show that the MM has responded to fish market dynamics organizing a complex network of buyers and suppliers whose relationships can be explained in the form of strong and weak ties. At the same time, reputation has been the central resource to build this social capital and also gives place to market transactions. Additionally, the strategic position of Guadalajara city and the well-connected routes have facilitated fish bulking and distribution in the region. PMID:29016637

Social networks, market transactions, and reputation as a central resource. The Mercado del Mar, a fish market in central Mexico.

PubMed

Pedroza-Gutiérrez, Carmen; Hernández, Juan M

2017-01-01

Fish consumption in Mexico is considered low (around 12 kg per person per year) and non-homogeneously distributed across the country. One of the reasons for this situation is the scarcity of wholesale selling sites. In this context, the Mercado del Mar (MM), located in Guadalajara city, Jalisco, is the second biggest wholesale fish market in Mexico, with a distribution of about 500 tons per day and a variety of about 350 different species of fish. In this paper, we argue that MM has accumulated social capital, which is formed from two main resources: buyer and seller relationships, and reputation. Specifically, the MM manages a broad and intensive interaction among business actors and the already achieved reputation allows the MM to adapt to market changes. To validate our hypotheses, an empirical study was conducted in 2015 by means of interviews to fish wholesalers in the MM and a sample of their suppliers and buyers. For simplicity we have only considered fresh water fish. We have followed snow-ball sampling as the survey strategy. Results show that the MM has responded to fish market dynamics organizing a complex network of buyers and suppliers whose relationships can be explained in the form of strong and weak ties. At the same time, reputation has been the central resource to build this social capital and also gives place to market transactions. Additionally, the strategic position of Guadalajara city and the well-connected routes have facilitated fish bulking and distribution in the region.

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

PubMed

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.

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

PubMed Central

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

Reproductive pattern of the large fruit-eating bat, Artibeus amplus (Chiroptera: Phyllostomidae) in the Venezuelan Andes.

PubMed

Ruiz-Ramoni, Damián; Ramoni-Perazzi, Paolo; Muñoz-Romo, Mariana

2017-03-01

Bimodal polyestry is the most common reproductive pattern in tropical bats, and it consists in producing one offspring per female twice a year. Reproductive patterns are closely related to rainfall regimes, frequently occurring twice a year in tropical regions. The goal of our study was to determine the reproductive pattern of the large fruit-eating bat, Artibeus amplus Handley, 1987 in a cave in the Venezuelan Andes inhabited by a large, stable colony. Thus, in this study we describe for the first time this important biological aspect of this unknown Neotropical bat species through the examination of external reproductive characteristics of males (inguinal or scrotal testes) and females (pregnant, lactating, post-lactating), based on 211 individuals (120 males and 91 females) captured between September 2008 and August 2009, in Cueva del Parque Las Escaleras, Estado Táchira, Venezuela. During this period of monthly sampling for a full year, most males displayed large scrotal testes, averaging 10 mm maximum length. The examination of females indicated that although pregnancy was first observed in November 2008, it reached a maximum during January and February 2009. Although adult males with scrotal testes throughout the year could imply that females have more than one pregnancy, our results suggested a seasonally monoestrous reproductive pattern for A. amplus. This study represents the first report of reproductive pattern for this poorly-known Neotropical frugivorous species. The observed monoestrous reproductive pattern supports the existence of synchronization between precipitation and reproduction. This synchronization has been frequently observed in most species of fruit bats. In this study, Artibeus amplus presumably adjust the parturition to anticipate the rainy season, as a strategy that allows maintenance of offspring during high availability of fruits.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

Pedological and mineralogical investigations on a soil-paleosoil sequence within Andosols in the Western Cordillera of the Peruvian Andes (region Laramate, 14.5S)

NASA Astrophysics Data System (ADS)

Leceta Gobitz, Fernando; Mächtle, Bertil; Schukraft, Gerd; Meyer, Hans-Peter; Eitel, Bernhard

2016-04-01

An integrated research project of environmental sciences focuses on a group of four Andosol profiles in Western flank of the Peruvian southern Andes. Aim of this study is to contribute to the reconstruction of the paleo environmental conditions in the Western Cordillera of the Peruvian Andes. Standard pedological and sedimentological analysis has been conducted in order to identify morphological and geochemical features generated by climatic variations during the middle and late Holocene. Though a provenance analysis of sediments, all potential lithological sources around the town of Laramate are being examined under the scanning electron microscope, in order to find significant mineralogical associations downward the soil-profile. Preliminary results reveal two edaphic cycles within a soil-paleo soil-sequence: a relative poor developed "Ah" topsoil, mostly composed by fine grain sediments, is underlain by a well preserved "2Ah" paleo soil; a "2Bwt" subsoil exhibits signs of alteration and clay translocation; parent material in slight weathered statement at "2C" culminates the sequence. Mineralogical analytical data supports the premise, that materials in the uppermost horizons are relatable to distal geological units of the Western and Eastern Cordillera, therefore also related to other described aeolian archives from the region: "Desert Margin Loess" at the Andean foot-zone and "Mixed Loess" in the Puna grassland. The amphibole varieties Actinolite, Mg-Hornblende and Edenite could be only distinguished within the soil sediments. The fluvial transport to its current position is excluded, insofar mentioned varieties stem from the granodiorites of Coastal Batholite (downstream the study area), and the vulcanites of the Anta und Andahuaylas Formation (eastward the continental divide). References: Eitel, B., et al. (2005). "Geoarchaeological evidence from desert loess in the Nazca-Palpa region, southern Peru : Palaeoenvironmental changes and their impact on Pre

Study of the Seismic Cycle of large Earthquakes in central Peru: Lima Region

NASA Astrophysics Data System (ADS)

Norabuena, E. O.; Quiroz, W.; Dixon, T. H.

2009-12-01

Since historical times, the Peruvian subduction zone has been source of large and destructive earthquakes. The more damaging one occurred on May 30 1970 offshore Peru’s northern city of Chimbote with a death toll of 70,000 people and several hundred US million dollars in property damage. More recently, three contiguous plate interface segments in southern Peru completed their seismic cycle generating the 1996 Nazca (Mw 7.1), the 2001 Atico-Arequipa (Mw 8.4) and the 2007 Pisco (Mw 7.9) earthquakes. GPS measurements obtained between 1994-2001 by IGP-CIW an University of Miami-RSMAS on the central Andes of Peru and Bolivia were used to estimate their coseismic displacements and late stage of interseismic strain accumulation. However, we focus our interest in central Peru-Lima region, which with its about 9’000,000 inhabitants is located over a locked plate interface that has not broken with magnitude Mw 8 earthquakes since May 1940, September 1966 and October 1974. We use a network of 11 GPS monuments to estimate the interseismic velocity field, infer spatial variations of interplate coupling and its relation with the background seismicity of the region.

Distributional ecology of Andes hantavirus: a macroecological approach.

PubMed

Astorga, Francisca; Escobar, Luis E; Poo-Muñoz, Daniela; Escobar-Dodero, Joaquin; Rojas-Hucks, Sylvia; Alvarado-Rybak, Mario; Duclos, Melanie; Romero-Alvarez, Daniel; Molina-Burgos, Blanca E; Peñafiel-Ricaurte, Alexandra; Toro, Frederick; Peña-Gómez, Francisco T; Peterson, A Townsend

2018-06-22

Hantavirus pulmonary syndrome (HPS) is an infection endemic in Chile and Argentina, caused by Andes hantavirus (ANDV). The rodent Oligoryzomys longicaudatus is suggested as the main reservoir, although several other species of Sigmodontinae are known hosts of ANDV. Here, we explore potential ANDV transmission risk to humans in southern South America, based on eco-epidemiological associations among: six rodent host species, seropositive rodents, and human HPS cases. We used ecological niche modeling and macroecological approaches to determine potential geographic distributions and assess environmental similarity among rodents and human HPS cases. Highest numbers of rodent species (five) were in Chile between 35° and 41°S latitude. Background similarity tests showed niche similarity in 14 of the 56 possible comparisons: similarity between human HPS cases and the background of all species and seropositive rodents was supported (except for Abrothrix sanborni). Of interest among the results is the likely role of O. longicaudatus, Loxodontomys micropus, Abrothrix olivaceus, and Abrothrix longipilis in HPS transmission to humans. Our results support a role of rodent species' distributions as a risk factor for human HPS at coarse scales, and suggest that the role of the main reservoir (O. longicaudatus) may be supported by the broader rodent host community in some areas.

Holocene Multi-Decadal to Millennial-Scale Hydrologic Variability on the South American Altiplano

NASA Astrophysics Data System (ADS)

Fritz, S. C.; Baker, P. A.; Ekdahl, E.; Burns, S.

2006-12-01

On orbital timescales, lacustrine sediment records in the tropical central Andes show massive changes in lake level due to mechanisms related to global-scale drivers, varying at precessional timescales. Here we use stable isotopic and diatom records from two lakes in the Lake Titicaca drainage basin to reconstruct multi- decadal to millennial scale precipitation variability during the last 7000 to 8000 years. The records are tightly coupled at multi-decadal to millennial scales with each other and with lake-level fluctuations in Lake Titicaca, indicating that the lakes are recording a regional climate signal. A quantitative reconstruction of precipitation from stable isotopic data indicates that the central Andes underwent significant wet to dry alternations at multi- centennial frequencies with an amplitude of 30 to 40% of total precipitation. A strong millennial-scale component, similar in duration to periods of increased ice rafted debris flux in the North Atlantic, is observed in both lake records, suggesting that tropical North Atlantic sea-surface temperature (SST) variability may partly control regional precipitation. No clear relationship is evident between these records and the inferred ENSO history from Lago Pallcacocha in the northern tropical Andes. In the instrumental period, regional precipitation variability on inter-annual timescales is clearly influenced by Pacific modes; for example, most El Ninos produce dry and warm conditions in this part of the central Andes. However, on longer timescales, the control of tropical Pacific modes is less clear. Our reconstructions suggest that the cold intervals of the Holocene Bond events are periods of increased precipitation in the central Andes, thus indicating an anti-phasing of precipitation variation in the southern tropics of South America relative to the Northern Hemisphere monsoon region.

The importance of place names in the search for ecosystem-like concepts in indigenous societies: an example from the Bolivian Andes.

PubMed

Boillat, Sébastien; Serrano, Elvira; Rist, Stephan; Berkes, Fikret

2013-03-01

This paper aims to deepen the search for ecosystem-like concepts in indigenous societies by highlighting the importance of place names used by Quechua indigenous farmers from the central Bolivian Andes. Villagers from two communities in the Tunari Mountain Range were asked to list, describe, map and categorize the places they knew on their community's territory. Results show that place names capture spatially explicit units which integrate biotic and abiotic nature and humans, and that there is an emphasis on topographic terms, highlighting the importance of geodiversity. Farmers' perspectives differ from the classical view of ecosystems because they 'humanize' places, considering them as living beings with agency. Consequently, they do not make a distinction between natural and cultural heritage. Their perspective of the environment is that of a personalized, dynamic relationship with the elements of the natural world that are perceived as living entities. A practical implication of the findings for sustainable development is that since places names make the links between people and the elements of the landscape, toponymy is a tool for ecosystem management rooted in indigenous knowledge. Because place names refer to holistic units linked with people's experience and spatially explicit, they can be used as an entry point to implement an intercultural dialogue for more sustainable land management.

The Importance of Place Names in the Search for Ecosystem-Like Concepts in Indigenous Societies: An Example from the Bolivian Andes

NASA Astrophysics Data System (ADS)

Boillat, Sébastien; Serrano, Elvira; Rist, Stephan; Berkes, Fikret

2013-03-01

This paper aims to deepen the search for ecosystem-like concepts in indigenous societies by highlighting the importance of place names used by Quechua indigenous farmers from the central Bolivian Andes. Villagers from two communities in the Tunari Mountain Range were asked to list, describe, map and categorize the places they knew on their community's territory. Results show that place names capture spatially explicit units which integrate biotic and abiotic nature and humans, and that there is an emphasis on topographic terms, highlighting the importance of geodiversity. Farmers' perspectives differ from the classical view of ecosystems because they `humanize' places, considering them as living beings with agency. Consequently, they do not make a distinction between natural and cultural heritage. Their perspective of the environment is that of a personalized, dynamic relationship with the elements of the natural world that are perceived as living entities. A practical implication of the findings for sustainable development is that since places names make the links between people and the elements of the landscape, toponymy is a tool for ecosystem management rooted in indigenous knowledge. Because place names refer to holistic units linked with people's experience and spatially explicit, they can be used as an entry point to implement an intercultural dialogue for more sustainable land management.

Mountain building processes in the Central Andes

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Mountain building processes in the Central Andes

NASA Astrophysics Data System (ADS)

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

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

An evening at "La Clinica del Pueblo".

PubMed

Shefsky, M L

1986-01-01

This article describes a typical evening at the Clinica del Pueblo in the Hispanic neighborhood of Adams-Morgan in Washington, D.c. The Clinical del Pueblo began operating in 1983 in response to the urgen medical needs of Central American refugees arriving in the Washington D.c. area. The refugees bring with them severe trauma, fear, and health problems caused by the civil was and exacerbated by inadequate or non-existant health services. Approximately 80,000 Salvadoran refugees live in the area. They do not receive adequate health care for 3 reasons. 1) Because the US goverment is unwilling to recognize them as true refugees, they live with the constant threat of deportatin back to the violence from which they have fled. 2) Refugees lack the ability to pay for private care. 3) Langauage and culture create frightening barriers to health care for the refugees. For those who do seek care, these barriers can lead to the inadequate or incomplete diagnoses and poor compliance and follow-up. Plenty International and the Central American Refugee Center responded to these problems by organizing a free clinic to provide not only medical care but also a training course for volunteers. The director of the clinic organizes the course, the classes are taught by a variety of people including the clinic's volunteer physicians, nurses, and public health educators as well as graduates of previus training courses and people from the wider community. The services of the clinic reach only a small portion of the population in need. However, the fact that free medical services are now available to some Central American refugees make the Clinica del Pueblo an important program.

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

PubMed Central

Finer, Matt; Jenkins, Clinton N.

2012-01-01

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

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

PubMed

Finer, Matt; Jenkins, Clinton N

2012-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Landslide susceptibility near highways is increased by one order of magnitude in the Andes of southern Ecuador, Loja province

NASA Astrophysics Data System (ADS)

Brenning, A.; Schwinn, M.; Ruiz-Páez, A. P.; Muenchow, J.

2014-03-01

Mountain roads in developing countries are known to increase landslide occurrence due to often inadequate drainage systems and mechanical destabilization of hillslopes by undercutting and overloading. This study empirically investigates landslide initiation frequency along two paved interurban highways in the tropical Andes of southern Ecuador across different climatic regimes. Generalized additive models (GAM) and generalized linear models (GLM) were used to analyze the relationship between mapped landslide initiation points and distance to highway while accounting for topographic, climatic and geological predictors as possible confounders. A spatial block bootstrap was used to obtain non-parametric confidence intervals for the odds ratio of landslide occurrence near the highways (25 m distance) compared to a 200 m distance. The estimated odds ratio was 18-21 with lower 95% confidence bounds > 13 in all analyses. Spatial bootstrap estimation using the GAM supports the higher odds ratio estimate of 21.2 (95% confidence interval: 15.5-25.3). The highway-related effects were observed to fade at about 150 m distance. Road effects appear to be enhanced in geological units characterized by Holocene gravels and Laramide andesite/basalt. Overall, landslide susceptibility was found to be more than one order of magnitude higher in close proximity to paved interurban highways in the Andes of southern Ecuador.

Landslide susceptibility near highways is increased by 1 order of magnitude in the Andes of southern Ecuador, Loja province

NASA Astrophysics Data System (ADS)

Brenning, A.; Schwinn, M.; Ruiz-Páez, A. P.; Muenchow, J.

2015-01-01

Mountain roads in developing countries are known to increase landslide occurrence due to often inadequate drainage systems and mechanical destabilization of hillslopes by undercutting and overloading. This study empirically investigates landslide initiation frequency along two paved interurban highways in the tropical Andes of southern Ecuador across different climatic regimes. Generalized additive models (GAM) and generalized linear models (GLM) were used to analyze the relationship between mapped landslide initiation points and distance to highway while accounting for topographic, climatic, and geological predictors as possible confounders. A spatial block bootstrap was used to obtain nonparametric confidence intervals for the odds ratio of landslide occurrence near the highways (25 m distance) compared to a 200 m distance. The estimated odds ratio was 18-21, with lower 95% confidence bounds >13 in all analyses. Spatial bootstrap estimation using the GAM supports the higher odds ratio estimate of 21.2 (95% confidence interval: 15.5-25.3). The highway-related effects were observed to fade at about 150 m distance. Road effects appear to be enhanced in geological units characterized by Holocene gravels and Laramide andesite/basalt. Overall, landslide susceptibility was found to be more than 1 order of magnitude higher in close proximity to paved interurban highways in the Andes of southern Ecuador.

Diversity of bacteria producing pigmented colonies in aerosol, snow and soil samples from remote glacial areas (Antarctica, Alps and Andes)

NASA Astrophysics Data System (ADS)

González-Toril, E.; Amils, R.; Delmas, R. J.; Petit, J.-R.; Komárek, J.; Elster, J.

2008-04-01

Four different communities and one culture of pigmented microbial assemblages were obtained by incubation in mineral medium of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas). Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. The phylogenetic comparison with the currently available rDNA database allowed the identification of sequences belonging to Proteobacteria (Alpha-, Beta- and Gamma-proteobacteria), Actinobacteria and Bacteroidetes phyla. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified) and the maritime Antarctic soil the poorest (only one). Snow samples from Col du midi (Alps) and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones). These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteria clone). The only microorganism identified in the maritime Antarctica soil (Brevundimonas sp.) was also detected in the Antarctic aerosol. The two snow samples from the Alps only shared one common microorganism. Most of the identified microorganisms have been detected previously in cold environments (Dietzia kujamenisi, Pseudonocardia Antarctica, Hydrogenophaga palleronii and Brebundimonas sp.), marine sediments (Aquiflexus balticus, Pseudomonas pseudoalkaligenes, Pseudomonas sp. and one uncultured Alphaproteobacteria), and soils and rocks (Pseudonocardia sp., Agrobactrium sp., Limnobacter sp. and two uncultured Alphaproteobacetria clones). Air current dispersal is the best model to explain the presence of very specific microorganisms, like those

Nail haemorrhages in native highlanders of the Peruvian Andes

PubMed Central

Heath, Donald; Harris, Peter; Williams, David; Krüger, Hever

1981-01-01

Nail haemorrhages are of interest to the chest physician and cardiologist. While the common type in the distal part of the nail is produced by the minor trauma of daily life, the rarer form—scattered through the nail substance—appears to be related to hypoxaemia brought about by heart and lung disease. We thought it would be of interest to study a population which was naturally hypoxaemic because of living at high altitude. Accordingly we have studied the frequency and types of nail haemorrhage in Quechua Indians who are permanently exposed to the hypobaric hypoxia of the Andes. We found the haemorrhages to be common both in mestizos living on the coastal plain and in the native highlanders. They appeared to increase in frequency with altitude but were of the distal type and would thus seem to be the result of minor trauma as at sea level. However, just as in cases of cyanotic congenital heart disease at low altitude, those with exaggerated hypoxaemia and pronounced elevation of haematocrit—namely, subjects with Monge's disease (chronic mountain sickness)—had scattered haemorrhages in the nail substance. Images

Description of Lutzomyia velezi, a new species of phlebotomine sand fly (Diptera: Psychodidae) from the Department of Antioquia, Colombia.

PubMed

Bejarano, Eduar Elías; Vivero, Rafael José; Uribe, Sandra

2010-05-01

The phlebotomine sand fly Lutzomyia velezi sp.nov. was described and illustrated from male specimens collected by light trap in the Reserva Natural Cañon del Río Claro in the Central Cordillera of the Colombian Andes. The new species belongs to the series sanguinaria of the subgenus Helcocyrtomyia, which is represented in Colombia by Lutzomyia cirrita, Lutzomyia hartmanni, Lutzomyia sanguinaria, Lutzomyia scorzai, Lutzomyia sp. of Pichindé and Lutzomyia tortura. The new species can be differentiated from others of the subgenus by the combination of the following characteristics: long antennal ascoids, reaching level of the papilla, coxite with a single basal seta and fifth palpomere longer than or equal to the sum of the lengths of the third and fourth palpomeres.

The Andes Virus Nucleocapsid Protein Directs Basal Endothelial Cell Permeability by Activating RhoA

PubMed Central

Gorbunova, Elena E.; Simons, Matthew J.; Gavrilovskaya, Irina N.

2016-01-01

ABSTRACT Andes virus (ANDV) predominantly infects microvascular endothelial cells (MECs) and nonlytically causes an acute pulmonary edema termed hantavirus pulmonary syndrome (HPS). In HPS patients, virtually every pulmonary MEC is infected, MECs are enlarged, and infection results in vascular leakage and highly lethal pulmonary edema. We observed that MECs infected with the ANDV hantavirus or expressing the ANDV nucleocapsid (N) protein showed increased size and permeability by activating the Rheb and RhoA GTPases. Expression of ANDV N in MECs increased cell size by preventing tuberous sclerosis complex (TSC) repression of Rheb-mTOR-pS6K. N selectively bound the TSC2 N terminus (1 to 1403) within a complex containing TSC2/TSC1/TBC1D7, and endogenous TSC2 reciprocally coprecipitated N protein from ANDV-infected MECs. TSCs normally restrict RhoA-induced MEC permeability, and we found that ANDV infection or N protein expression constitutively activated RhoA. This suggests that the ANDV N protein alone is sufficient to activate signaling pathways that control MEC size and permeability. Further, RhoA small interfering RNA, dominant-negative RhoA(N19), and the RhoA/Rho kinase inhibitors fasudil and Y27632 dramatically reduced the permeability of ANDV-infected MECs by 80 to 90%. Fasudil also reduced the bradykinin-directed permeability of ANDV and Hantaan virus-infected MECs to control levels. These findings demonstrate that ANDV activation of RhoA causes MEC permeability and reveal a potential edemagenic mechanism for ANDV to constitutively inhibit the basal barrier integrity of infected MECs. The central importance of RhoA activation in MEC permeability further suggests therapeutically targeting RhoA, TSCs, and Rac1 as potential means of resolving capillary leakage during hantavirus infections. PMID:27795403

Stratotype for the Mérida Glaciation at Pueblo Llano in the northern Venezuelan Andes

NASA Astrophysics Data System (ADS)

Mahaney, W. C.; Milner, M. W.; Voros, J.; Kalm, V.; Hütt, G.; Bezada, M.; Hancock, R. G. V.; Aufreiter, S.

2000-12-01

The Mérida Glaciation (cf. Wisconsinan, Weichselian) as proposed by Schubert (1974b) culminated at about 18 ka during the last glacial maximum (LGM) and ended at about 13 ka as indicated by 14C dating and correlation with the Cordillera Oriental of Colombia. Moraines of an early stade of Mérida Glaciation reached to 2800 m a.s.l. and were largely overrun or eradicated by the maximum Wisconsinan advance (LGM); where they outcrop, the older moraines are characterized by eroded, weathered glacial diamictons and outwash fans. At Pueblo Llano in the central Mérida Andes (Cordillera de Trujillo), older to younger beds of contorted glacitectonized diamict, overlying beds of bouldery till and indurated outwash, all belong to the early Mérida stade. Overlying the early Mérida stade, deposits of rhythmically bedded glaciolacustrine sediments are in turn overlain with contorted sand and silt beds capped with outwash. Above the outwash terrace a loop moraine of LGM age completely encircles the margins of the basin. A stream cut exposed by catastrophic (tectonic or surge?) release of meltwater displays a lithostratigraphic succession that is bereft of organic material for radiocarbon dating. Five optically-stimulated luminescence (OSL) dates place the maximum age of the lowest till at 81 ka. Particle size distributions allow clear distinctions between major lithic units. Heavy mineral analysis of the middle and lower coarse units in the section provide information on sediment sourcing and on major lithostratigraphic divisions. Trace element concentrations provide information on the relative homogeneity of the deposits. The HREE (heavy rare earth element) concentrations allow discrimination of the lower till from the rest of the section; the LREE (light rare earth element) concentrations highlight differences between the lower till, LGM till, and the rest of the section.

Changes in denudation rates and erosion processes in the transition from a low-relief, arid orogen interior to a high-relief, humid mountain-front setting, Toro Basin, southern Central Andes

NASA Astrophysics Data System (ADS)

Tofelde, S.; Düsing, W.; Schildgen, T. F.; Wittmann, H.; Alonso, R. N.; Strecker, M. R.

2017-12-01

In tectonically active mountain belts positive correlations between denudation rates and hillslope angles are commonly observed, supporting the notion that landscape morphology may reflect tectonic forcing. However, this relationship generally breaks down at 30°, when hillslopes reach threshold angles. Beyond this threshold, faster denudation may occur by an increased contribution from mass-wasting processes. We test this idea in the 4000 km2 Toro Basin, a fault-bounded basin in the Eastern Cordillera of the southern Central Andes. This N-S oriented basin is located between low-relief, arid conditions in the orogen interior (N) and a high-relief, humid setting at its fluvial outlet (S). We measured in-situ produced 10Be concentration in fluvial sediments, which can be converted into basin-mean denudation rates, assuming a spatially uniform contribution of sediment from the catchment. However, in landslide-influenced areas, this assumption is often violated. Previous studies have suggested that clast-size material is mainly contributed by mass-wasting processes, whereas sand is derived from a broad range of erosional processes. Hence, a combination of clast and sand samples can reveal information about the basin-mean denudation rate as well as the contribution of mass-wasting processes. We sampled 13 pebble (1-3 cm) and sand (250-500 µm) pairs across the basin. The sand-derived denudation rates increase from N to S, ranging from 0.010 mm/yr to 1.337 mm/yr, and reveal a non-linear positive correlation with median basin slope. The clast/sand ratios also increase from N to S, indicating amplified mass-wasting processes with increasing slopes. To test if our ratios represent a real shift in erosional processes, we mapped different erosional processes in the study area (e.g. deep-seated landslides, scree erosion,.., diffusion). We assume that today's distribution of processes has not changed over the integration time of 10Be derived denudation rates. This detailed

Payenia volcanic province in the Southern Andes: An appraisal of an exceptional Quaternary tectonic setting

NASA Astrophysics Data System (ADS)

Ramos, Victor A.; Folguera, Andrés

2011-04-01

The Southern Volcanic Zone of the Andes has a Quaternary basaltic province along the retroarc which has a unique tectonic setting. The Payenia volcanic province covers an area larger than 40,000 km 2 between 33°30' and 38° South latitudes, with an estimated volcanic volume of about 8387 km 3 erupted through more than 800 volcanic centers in the last ~ 2 Ma. The mainly basaltic province developed above the San Rafael Block is subdivided in three segments characterized by the Cerro Nevado, Llancanelo, Payún Matru, Tromen and Auca Mahuida volcanic fields, together with hundreds of minor monogenetic basaltic centers. The analysis of the different segments shows the formation of a common basalt plateau with intraplate signature from south to north between 2.0 and 1.7 Ma, which reached the 35°S to the north. Above this plateau monogenetic centers as Nihuil Vn. 1.433 Ma and Cerro Chato at 1.352 Ma are developed, followed by the large polygenetic center of Cerro Nevado (3980 m a.s.l.) at 1.320 Ma. This plateau was broken by a series of normal faults that produced volcanic cone alignments such as the NNW-trending Mancha Jarilla lineament in the central part at about 1.0 Ma. Extension shifted to the eastern margin of the San Rafael Block, which concentrates tens of monogenetic centers between 0.9 and 0.7 Ma. Extension then migrated towards the foothills in the west, where many monogenetic cones were erupted through NW-trending normal faults between 0.5 and 0.435 Ma. The collapse of the large Diamante Caldera at 0.445 Ma coincides with that period. Subsequent volcanism was concentrated in (1) the Payún Matru volcanic field, with the eruption of Cerro Payén between 0.272 and 0.261 Ma; the Payún Matru shield volcano, with polygenetic eruptions at least since the last 0.233 Ma and with the caldera formation bracketed between 0.168 ± 0.004 Ma and 0.082 ± 0.001 Ma, followed by several eruptions until 7000 yrs, and even historical ones; and in (2) the Tromen volcano, where

Long-term human response to uncertain environmental conditions in the Andes

PubMed Central

Dillehay, Tom D.; Kolata, Alan L.

2004-01-01

Human interaction with the physical environment has increasingly transformed Earth-system processes. Reciprocally, climate anomalies and other processes of environmental change of natural and anthropogenic origin have been affecting, and often disrupting, societies throughout history. Transient impact events, despite their brevity, can have significant long-term impact on society, particularly if they occur in the context of ongoing, protracted environmental change. Major climate events can affect human activities in critical conjunctures that shape particular trajectories of social development. Here we report variable human responses to major environmental events in the Andes with a particular emphasis on the period from anno Domini 500–1500 on the desert north coast of Perú. We show that preindustrial agrarian societies implemented distinct forms of anticipatory response to environmental change and uncertainty. We conclude that innovations in production strategies and agricultural infrastructures in these indigenous societies reflect differential social response to both transient (El Niño–Southern Oscillation events) and protracted (desertification) environmental change. PMID:15024122

Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 years

NASA Astrophysics Data System (ADS)

Gayo, E. M.; Latorre, C.; Santoro, C. M.; Maldonado, A.; de Pol-Holz, R.

2011-10-01

Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally well-preserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ~21° S, 1000 m a.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050-680, 1615-1350 and 2500-2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 years. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 years represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the

Hydroclimate variability in the low-elevation Atacama Desert over the last 2500 yr

NASA Astrophysics Data System (ADS)

Gayo, E. M.; Latorre, C.; Santoro, C. M.; Maldonado, A.; de Pol-Holz, R.

2012-02-01

Paleoclimate reconstructions reveal that Earth system has experienced sub-millennial scale climate changes over the past two millennia in response to internal/external forcing. Although sub-millennial hydroclimate fluctuations have been detected in the central Andes during this interval, the timing, magnitude, extent and direction of change of these events remain poorly defined. Here, we present a reconstruction of hydroclimate variations on the Pacific slope of the central Andes based on exceptionally well-preserved plant macrofossils and associated archaeological remains from a hyperarid drainage (Quebrada Maní, ∼21° S, 1000 m a.s.l.) in the Atacama Desert. During the late Holocene, riparian ecosystems and farming social groups flourished in the hyperarid Atacama core as surface water availability increased throughout this presently sterile landscape. Twenty-six radiocarbon dates indicate that these events occurred between 1050-680, 1615-1350 and 2500-2040 cal yr BP. Regional comparisons with rodent middens and other records suggest that these events were synchronous with pluvial stages detected at higher-elevations in the central Andes over the last 2500 yr. These hydroclimate changes also coincide with periods of pronounced SST gradients in the Tropical Pacific (La Niña-like mode), conditions that are conducive to significantly increased rainfall in the central Andean highlands and flood events in the low-elevation watersheds at inter-annual timescales. Our findings indicate that the positive anomalies in the hyperarid Atacama over the past 2500 yr represent a regional response of the central Andean climate system to changes in the global hydrological cycle at centennial timescales. Furthermore, our results provide support for the role of tropical Pacific sea surface temperature gradient changes as the primary mechanism responsible for climate fluctuations in the central Andes. Finally, our results constitute independent evidence for comprehending the

Intra-to multidecadel variations of snowpack and streamflow records in the Andes of Chile and Argentina between 30 degrees and 37 degrees S.

USDA-ARS?s Scientific Manuscript database

Regional composites of winter snowpack (1951-2008) and mean annual river discharges (1906-2007) are used to evaluate the main intra- to multi-decadal hydrologic variations in the Andes of Chile and Argentina between 30° and 37°S. The streamflow record shows a non-significant negative trend but two s...

Description of Pintomyia limafalcaoae and Pintomyia antioquiensis, two new species of phlebotomine sand fly (Diptera, Psychodidae) from the Colombian Andes.

PubMed

Wolff, Marta; Galati, Eunice Aparecida Bianchi

2002-04-01

Two new species of phlebotomine sand fly from Colombian Andes are described, belonging to the subgenus Pifanomyia of the genus Pintomyia. P. (P.) limafalcaoae sp. nov. for which both sexes are described, is assigned to the series pia while P. (P.) antioquiensis sp. nov., known only from the male, is included in the series verrucarum. The subgenus Pifanomyia is characterized and identification keys presented for the two new species.

On the Origin of the Bolivian High and Related Circulation Features of the South American Climate.

NASA Astrophysics Data System (ADS)

Lenters, J. D.; Cook, K. H.

1997-03-01

The climatological structure in the upper-tropospheric summertime circulation over South America is diagnosed using a GCM (with and without South American topography), a linear model, and observational data. Emphasis is placed on understanding the origin of observed features such as the Bolivian high and the accompanying `Nordeste low' to the east. Results from the linear model indicate that these two features are generated in response to precipitation over the Amazon basin, central Andes, and South Atlantic convergence zone, with African precipitation also playing a crucial role in the formation of the Nordeste low. The direct mechanical and sensible heating effects of the Andes are minimal, acting only to induce a weak lee trough in midlatitudes and a shallow monsoonal circulation over the central Andes. In the GCM, the effects of the Andes include a strengthening of the Bolivian high and northward shift of the Nordeste low, primarily through changes in the precipitation field. The position of the Bolivian high is primarily determined by Amazonian precipitation and is little affected by the removal of the Andes. Strong subsidence to the west of the high is found to be important for the maintenance of the high's warm core, while large-scale convective overshooting to the east is responsible for a layer of cold air above the high.

The N Terminus of Andes Virus L Protein Suppresses mRNA and Protein Expression in Mammalian Cells

PubMed Central

Heinemann, Patrick; Schmidt-Chanasit, Jonas

2013-01-01

Little is known about the structure and function of the 250-kDa L protein of hantaviruses, although it plays a central role in virus genome transcription and replication. When attempting to study Andes virus (ANDV) L protein in mammalian cells, we encountered difficulties. Even in a strong overexpression system, ANDV L protein could not be detected by immunoblotting. Deletion analysis revealed that the 534 N-terminal amino acid residues determine the low-expression phenotype. Inhibition of translation due to RNA secondary structures around the start codon, rapid proteasomal degradation, and reduced half-life time were excluded. However, ANDV L protein expression could be rescued upon mutation of the catalytic PD-E-K motif and further conserved residues of the putative endonuclease at the N terminus of the protein. In addition, wild-type ANDV L rather than expressible L mutants suppressed the level of L mRNA, as well as reporter mRNAs. Wild-type L protein also reduced the synthesis of cellular proteins in the high-molecular-weight range. Using expressible ANDV L mutants as a tool for localization studies, we show that L protein colocalizes with ANDV N and NSs but not Gc protein. A fraction of L protein also colocalized with the cellular processing (P) body component DCP1a. Overall, these data suggest that ANDV L protein possesses a highly active endonuclease at the N terminus suppressing the level of its own as well as heterologous mRNAs upon recombinant expression in mammalian cells. PMID:23576516

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

NASA Astrophysics Data System (ADS)

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

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

Effect of Moxidectin Treatment at Peripartum on Gastrointestinal Parasite Infections in Ewes Raised under Tropical Andes High Altitude Conditions

PubMed Central

Vargas-Duarte, J. J.; Lozano-Márquez, H.; Grajales-Lombana, H. A.; Manrique-Perdomo, C.; Martínez-Bello, D. A.; Saegerman, C.; Raes, M.; Kirschvink, N.

2015-01-01

This study tested the impact of moxidectin at peripartum on nematode fecal egg count (FEC) and clinical parameters on ewes in the high altitude tropical Andes of Colombia. FEC and clinical evaluations were performed on 9 occasions in 43 naturally infected ewes before and during gestation and after lambing. Moxidectin (Mox, 200 µg kg−1) was applied at late pregnancy (T 1, n = 15) or 48 hours after parturition (T 2, n = 14). 14 untreated ewes served as controls (C). Suckling lambs (n = 58) remained untreated and underwent four clinical and parasitological evaluations until 8 weeks after birth. Mox efficacy equaled 99.3% (T 1) and 96.9% (T 2). Highest mean FEC value reflecting periparturient nematode egg rise (PPER) was recorded in C ewes at 4–6 weeks after lambing. Significant FEC reductions were found in T 1 (94.8%) and T 2 (96.7%) ewes (p < 0.05). All lambs showed a significant and ewes-group independent increase in FEC before weaning (p < 0.05). Clinical parameters (anemia and diarrhea) showed time- and treatment-related differences (p < 0.05). Monitoring of FEC and clinical parameters linked to gastrointestinal parasite infections allowed demonstrating that postpartum or preweaning are two critical periods to nematode infection for sheep raised under tropical Andes high altitude conditions. Use of Mox as anthelmintic treatment prevented PPER. PMID:26078913

Erosion of organic carbon from the Andes and its effects on ecosystem carbon dioxide balance

NASA Astrophysics Data System (ADS)

Clark, K. E.; Hilton, R. G.; West, A. J.; Robles Caceres, A.; Gröcke, D. R.; Marthews, T. R.; Ferguson, R. I.; Asner, G. P.; New, M.; Malhi, Y.

2017-03-01

Productive forests of the Andes are subject to high erosion rates that supply to the Amazon River sediment and carbon from both recently photosynthesized biomass and geological sources. Despite this recognition, the source and discharge of particulate organic carbon (POC) in Andean Rivers remain poorly constrained. We collected suspended sediments from the Kosñipata River, Peru, over 1 year at two river gauging stations. Carbon isotopes (14C, 13C, and 12C) and nitrogen to organic carbon ratios of the suspended sediments suggest a mixture of POC from sedimentary rocks (POCpetro) and from the terrestrial biosphere (POCbiosphere). The majority of the POCbiosphere has a composition similar to surface soil horizons, and we estimate that it is mostly younger than 850 14C years. The suspended sediment yield in 2010 was 3500 ± 210 t km-2 yr-1, >10 times the yield from the Amazon Basin. The POCbiosphere yield was 12.6 ± 0.4 t C km-2 yr-1 and the POCpetro yield was 16.1 ± 1.4 t C km-2 yr-1, mostly discharged in the wet season (December to March) during flood events. The river POCbiosphere discharge is large enough to play a role in determining whether Andean forests are a source or sink of carbon dioxide. The estimated erosional discharge of POCpetro from the Andes is much larger ( 1 Mt C yr-1) than the POCpetro discharge by the Madeira River downstream in the Amazon Basin, suggesting that oxidation of POCpetro counters CO2 drawdown by silicate weathering. The flux and fate of Andean POCbiosphere and POCpetro need to be better constrained to fully understand the carbon budget of the Amazon River basin.

Variation in freshwater fish assemblages along a regional elevation gradient in the northern Andes, Colombia

PubMed Central

Carvajal-Quintero, Juan D; Escobar, Federico; Alvarado, Fredy; Villa-Navarro, Francisco A; Jaramillo-Villa, Úrsula; Maldonado-Ocampo, Javier A

2015-01-01

Studies on elevation diversity gradients have covered a large number of taxa and regions throughout the world; however, studies of freshwater fish are scarce and restricted to examining their changes along a specific gradient. These studies have reported a monotonic decrease in species richness with increasing elevation, but ignore the high taxonomic differentiation of each headwater assemblage that may generate high β-diversity among them. Here, we analyzed how fish assemblages vary with elevation among regional elevation bands, and how these changes are related to four environmental clines and to changes in the distribution, habitat use, and the morphology of fish species. Using a standardized field sampling technique, we assessed three different diversity and two structural assemblage measures across six regional elevation bands located in the northern Andes (Colombia). Each species was assigned to a functional group based on its body shape, habitat use, morphological, and/or behavioral adaptations. Additionally, at each sampling site, we measured four environmental variables. Our analyses showed: (1) After a monotonic decrease in species richness, we detected an increase in richness in the upper part of the gradient; (2) diversity patterns vary depending on the diversity measure used; (3) diversity patterns can be attributed to changes in species distribution and in the richness and proportions of functional groups along the regional elevation gradient; and (4) diversity patterns and changes in functional groups are highly correlated with variations in environmental variables, which also vary with elevation. These results suggest a novel pattern of variation in species richness with elevation: Species richness increases at the headwaters of the northern Andes owing to the cumulative number of endemic species there. This highlights the need for large-scale studies and has important implications for the aquatic conservation of the region. PMID:26257874

Deglacial palaeoclimate at Puerto del Hambre, subantarctic Patagonia, Chile

NASA Astrophysics Data System (ADS)

Heusser, Calvin J.; Heusser, Linda E.; Lowell, Thomas V.; Moreira M., Andrés; Moreira M., Simón

2000-02-01

The primary objective of this study is to further substantiate multistep climatic forcing of late-glacial vegetation in southern South America. A secondary objective is to establish the age of deglaciation in Estrecho de Magallanes-Bahía Inútil. Pollen assemblages at 2-cm intervals in a core of the mire at Puerto del Hambre (53°3621S, 70°5553W) provide the basis for reconstructing the vegetation and a detailed account of palaeoclimate in subantarctic Patagonia. Chronology over the 262-cm length of core is regulated by 20 AMS radiocarbon dates between 14 455 and 10 089 14C yr BP. Of 13 pollen assemblage zones, the earliest representing the Oldest Dryas chronozone (14 455-13 000 14C yr BP) records impoverished steppe with decreasing frequencies and loss of southern beech (Nothofagus). Successive 100-yr-long episodes of grass/herbs and of heath (Empetrum/Ericaceae) before 14 000 14C yr BP infer deglacial successional communities under a climate of increased continentality prior to the establishment of grass-dominated steppe. The Bølling-Allerød (13 000-11 000 14C yr BP) is characterised by mesic grassland under moderating climate that with abrupt change to heath dominance after 12 000 14C yr BP was warmer and not as humid. At the time of the Younger Dryas (11 000-10 000 14C yr BP), grass steppe expanded with a return of colder, more humid climate. Later, with gradual warming, communities were invaded by southern beech. The Puerto del Hambre record parallels multistep, deglacial palaeoclimatic sequences reported elsewhere in the Southern Andes and at Taylor Dome in Antarctica. Deglaciation of Estrecho de Magallanes-Bahía Inútil is dated close to 14 455 14C yr BP, invalidating earlier dates of between 15 800 and 16 590 14C yr BP.

Geochemistry and isotopic signatures of Paleogene plutonic and detrital rocks of the Northern Andes of Colombia: A record of post-collisional arc magmatism

NASA Astrophysics Data System (ADS)

Bustamante, Camilo; Cardona, Agustín; Archanjo, Carlos J.; Bayona, Germán; Lara, Mario; Valencia, Victor

2017-04-01

Between the Late Cretaceous and Paleogene, the Northern Andes experienced subduction and collision due to the convergence between the oceanic Caribbean Plate and the continental margin of Ecuador and Colombia. Subduction-related calc-alkaline plutonic rocks form stocks of limited areal expression or local batholiths that consist mostly of diorites and granodiorites. We investigated two stocks (Hatillo and Bosque) exposed in the Central Cordillera of Colombia that had U-Pb zircon crystallization ages between 60 and 53 Ma. Relatively low radiogenic Sr, Nd and Pb isotopes from selected samples account for a heterogeneous crustal source, whereas negative anomalies of Nb and Ti, high LREE/HREE and Sr/Y > 28 ratios indicate that the magmas were emplaced in a continental magmatic arc setting. ƐHf(i) values of the dated zircons were between - 4 and + 7 and suggest some contamination of the magmas during their ascent through the crust. The high Sr/Y ratios recorded both in the investigated plutons as well as in other Paleogene plutons in the Central Cordillera suggest that the magmas differentiate in high-pressure conditions (garnet stability field). This differentiation probably occurred at the base of a thickened crust through the Mesozoic subduction and accretion of oceanic arcs to the continental margin during the Lower Cretaceous and Paleocene. The existence of other Paleogene granitoids with evidence of shallower differentiation signatures may be also an inheritance of along strike variations in the Northern Andean continental crust due to Cretaceous to Paleogene oblique convergence. The Hf isotope results from Paleogene detrital zircons from volcanoclastic rocks of the eastern Colombian basins reinforce the possibility of a distal magmatic focus.

Sensitivity of glaciation in the arid subtropical Andes to changes in temperature, precipitation, and solar radiation

NASA Astrophysics Data System (ADS)

Vargo, L. J.; Galewsky, J.; Rupper, S.; Ward, D. J.

2018-04-01

The subtropical Andes (18.5-27 °S) have been glaciated in the past, but are presently glacier-free. We use idealized model experiments to quantify glacier sensitivity to changes in climate in order to investigate the climatic drivers of past glaciations. We quantify the equilibrium line altitude (ELA) sensitivity (the change in ELA per change in climate) to temperature, precipitation, and shortwave radiation for three distinct climatic regions in the subtropical Andes. We find that in the western cordillera, where conditions are hyper-arid with the highest solar radiation on Earth, ELA sensitivity is as high as 34 m per % increase in precipitation, and 70 m per % decrease in shortwave radiation. This is compared with the eastern cordillera, where precipitation is the highest of the three regions, and ELA sensitivity is only 10 m per % increase in precipitation, and 25 m per % decrease in shortwave radiation. The high ELA sensitivity to shortwave radiation highlights the influence of radiation on mass balance of high elevation and low-latitude glaciers. We also consider these quantified ELA sensitivities in context of previously dated glacial deposits from the regions. Our results suggest that glaciation of the humid eastern cordillera was driven primarily by lower temperatures, while glaciations of the arid Altiplano and western cordillera were also influenced by increases in precipitation and decreases in shortwave radiation. Using paleoclimate records from the timing of glaciation, we find that glaciation of the hyper-arid western cordillera can be explained by precipitation increases of 90-160% (1.9-2.6× higher than modern), in conjunction with associated decreases in shortwave radiation of 7-12% and in temperature of 3.5 °C.

High-Resolution Modeling of ENSO-Induced Precipitation in the Tropical Andes: Implications for Proxy Interpretation.

NASA Astrophysics Data System (ADS)

Kiefer, J.; Karamperidou, C.

2017-12-01

Clastic sediment flux into high-elevation Andean lakes is controlled by glacial processes and soil erosion caused by high precipitation events, making these lakes suitable archives of past climate. To wit, sediment records from Laguna Pallcacocha in Ecuador have been interpreted as proxies of ENSO variability, owing to increased precipitation in the greater region during El Niño events. However, the location of the lake's watershed, the presence of glaciers, and the different impacts of ENSO on precipitation in the eastern vs western Andes have challenged the suitability of the Pallcacocha record as an ENSO proxy. Here, we employ WRF, a high-resolution regional mesoscale weather prediction model, to investigate the circulation dynamics, sources of moisture, and resulting precipitation response in the L. Pallcacocha region during different flavors of El Niño and La Niña events, and in the presence or absence of ice caps. In patricular, we investigate Eastern Pacific (EP), Central Pacific (CP), coastal El Niño, and La Niña events. We validate the model simulations against spatially interpolated station measurements and reanalysis data. We find that during EP events, moisture is primarily advected from the Pacific, whereas during CP events, moisture primarily originates from the Atlantic. More moisture is available during EP events, which implies higher precipitation rates. Furthermore, we find that precipitation during EP events is mostly non-convective in contrast to primarily convective precipitation during CP events. Finally, a synthesis of the sedimentary record and the EP:CP ratio of accumulated precipitation and specific humidity in the L. Pallcacocha region allows us to assess whether past changes in the relative frequency of the two ENSO flavors may have been recorded in paleoclimate archives in this region.

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

PubMed

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

2016-08-01

Hantavirus pulmonary syndrome (HPS) is a severe disease caused by hantavirus infection of pulmonary microvascular endothelial cells leading to microvascular leakage, pulmonary edema, pleural effusion and high case fatality. Previously, we demonstrated that Andes virus (ANDV) infection caused up-regulation of vascular endothelial growth factor (VEGF) and concomitant downregulation of the cellular adhesion molecule VE-cadherin leading to increased permeability. Analyses of human HPS-patient sera have further demonstrated increased circulating levels of VEGF. Here we investigate the impact of a small molecule antagonist of the VEGF receptor 2 (VEGFR-2) activation in vitro, and overall impact on survival in the Syrian hamster model of HPS. Copyright © 2016. Published by Elsevier B.V.

The Andes hantavirus NSs protein is expressed from the viral small mRNA by a leaky scanning mechanism.

PubMed

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

2012-02-01

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

Rain-fed agriculture thrived despite climate degradation in the pre-Hispanic arid Andes

PubMed Central

Cruz, Pablo; Winkel, Thierry; Ledru, Marie-Pierre; Bernard, Cyril; Egan, Nancy; Swingedouw, Didier; Joffre, Richard

2017-01-01

Archaeological research suggests significant human occupation in the arid Andean highlands during the 13th to 15th centuries, whereas paleoclimatic studies reveal prolonged drier and colder conditions during that period. Which subsistence strategy supported local societies in this harsh environment? Our field and aerial surveys of archaeological dwelling sites, granaries, and croplands provide the first evidence of extended pre-Hispanic agriculture supporting dense human populations in the arid Andes of Bolivia. This unique agricultural system associated with quinoa cultivation was unirrigated, consisting of simple yet extensive landscape modifications. It relied on highly specific environmental knowledge and a set of water-saving practices, including microterracing and biennial fallowing. This intense agricultural activity developed during a period of unfavorable climatic change on a regional and global scale, illustrative of efficient adaptive strategies to cope with this climatic change. PMID:29279865

Description and molecular diagnosis of a new species of Brunfelsia (Solanaceae) from the Bolivian and Argentinean Andes

PubMed Central

Filipowicz, Natalia; Nee, Michael H.; Renner, Susanne S.

2012-01-01

Abstract Brunfelsia plowmaniana N.Filipowicz & M.Nee sp. nov., a species from humid and cloud forests of the Bolivian and Argentinean Andes, is described and provided with a molecular diagnosis, using provisions available in the recently approved International Code of Nomenclature for algae, fungi and plants. Specimens belonging to the new species were previously placed in the polymorphic Brunfelsia uniflora (Pohl) D.Don, which a molecular phylogeny revealed as polyphyletic. Revision of numerous collections revealed clear morphological differences between the new species and Brunfelsia uniflora, the type locality of which is in the state of São Paulo, Brazil. PMID:22461731

First web-based database on total phenolics and oxygen radical absorbance capacity (ORAC) of fruits produced and consumed within the south Andes region of South America.

PubMed

Speisky, Hernan; López-Alarcón, Camilo; Gómez, Maritza; Fuentes, Jocelyn; Sandoval-Acuña, Cristian

2012-09-12

This paper reports the first database on antioxidants contained in fruits produced and consumed within the south Andes region of South America. The database ( www.portalantioxidantes.com ) contains over 500 total phenolics (TP) and ORAC values for more than 120 species/varieties of fruits. All analyses were conducted by a single ISO/IEC 17025-certified laboratory. The characterization comprised native berries such as maqui ( Aristotelia chilensis ), murtilla ( Ugni molinae ), and calafate ( Barberis microphylla ), which largely outscored all other studied fruits. Major differences in TP and ORAC were observed as a function of the fruit variety in berries, avocado, cherries, and apples. In fruits such as pears, apples, apricots, and peaches, a significant part of the TP and ORAC was accounted for by the antioxidants present in the peel. These data should be useful to estimate the fruit-based intake of TP and, through the ORAC data, their antioxidant-related contribution to the diet of south Andes populations.

Evolution of the east-central San Jose del Cabo basin, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

McTeague, M. S.; Umhoefer, P. J.; Schwennicke, T.; Ingle, J. C.; Cortes Martinez, M.

2006-12-01

The San Jose del Cabo basin at the southern tip of the Baja California peninsula records the early tectonic evolution of the west side of the Gulf of California. This study focused on the east central margin of the basin. The basal La Calera Formation unconformably overlies Cretaceous granite and consists of conglomerate, pebbly sandstone and conglomerate, and sandstone deposited in alluvial fans and fan-deltas. Deposition of the La Calera Formation was from ca. 9-14 Ma. The lower member of the Trinidad Formation was deposited beginning ca. 9-13 Ma and consists of sandstone, mudstone, and shelly mudstone deposited in nearshore and estuarine environments. These age estimates are based on sedimentation rates and foraminifera and coccoliths from the NN 11A nannozone (7.4 8.6 Ma, GTS 2004). The middle member of the Trinidad Formation consists of deeper water mudstones deposited by turbidity currents and suspension settling in a shelf to slope and conglomerates deposited by submarine debris flows on the shelf. The basin began earlier than previously thought. The oldest marine rocks are ca.9-13 Ma, while sedimentation on the east side began at ca. 9-14 Ma, synchronous with estimates of initiation of offset on the San Jose del Cabo fault. The Zapote fault is a down-to-the-east normal and sinistral-oblique fault that exposes a wedge of granite and older strata in the footwall to the west. The fault was active during sedimentation in the late Miocene and possibly later. The fault divides the study area into an eastern hanging wall subbasin and western footwall subbasin. The eastern subbasin formed an embayment in the eastern margin of the Cabo basin. A regional flooding surface (ca. 8 Ma) can be correlated across the fault that marks a major marine incursion. Depositional systems evolved rapidly from coarse-grained terrestrial systems to fine-grained marine and estuarine systems. The Cabo basin provides an excellent analogue for comparison with offshore basins, which are

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

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

PubMed

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

2014-06-01

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

A measurement of the cosmic microwave background from the high Chilean Andes

NASA Astrophysics Data System (ADS)

Miller, Amber Dawn

A measurement of the angular spectrum of the Cosmic Microwave Background (CMB) between l = 50 and l = 400 is described. Data were obtained using HEMT radiometers at 30 and 40 GHz with angular resolutions of ≈1 deg and ≈0.7 deg respectively and with SIS based receivers at 144 GHz with angular resolution of ≈0.2 deg. Observations were made from Cerro Toco in the Chilean altiplano at an altitude of 17,000 feet in the Northern Chilean Andes. We find that the angular spectrum rises from l = 50 to a peak at l ≈ 200 and falls off at higher angular scales. A peak in the angular spectrum with amplitude, deltaTl ≈ 85muK is thus located for the first time with a single instrument at l ≈ 200. In addition, we find that the detected anisotropy has the spectrum of the CMB. Cosmological implications of this result are discussed.

A new species of Notodiaptomus from the Ecuadorian Andes (Copepoda, Calanoida, Diaptomidae).

PubMed

Alonso, Miguel; Dos Santos-Silva, Edinaldo N; Jaume, Damià

2017-01-01

Notodiaptomus cannarensis sp. n. is described from a reservoir on the Amazonian slope of the Ecuadorian Andes. The new species is unique among diaptomid calanoid copepods in the display of hypertrophied, symmetrical wing-like extensions at each side of the female composite genital somite. Furthermore, it displays a female urosome reduced to only two somites due to the incorporation of abdominal somites III and IV to the composite genital double-somite, and a male right fifth leg with the outer spine of second exopodal segment recurved and implanted proximally on margin. It differs from any other Notodiaptomus in the display of a large rectangular lamella on proximal segment of exopod of male right fifth leg. The species is currently known only from Mazar reservoir, a eutrophic water body placed above 2127 m a.s.l. on the River Paute (Cañar Province; southern Ecuador), where it is the most common crustacean in the water column.

A new species of Notodiaptomus from the Ecuadorian Andes (Copepoda, Calanoida, Diaptomidae)

PubMed Central

Alonso, Miguel; dos Santos-Silva, Edinaldo N.; Jaume, Damià

2017-01-01

Abstract Notodiaptomus cannarensis sp. n. is described from a reservoir on the Amazonian slope of the Ecuadorian Andes. The new species is unique among diaptomid calanoid copepods in the display of hypertrophied, symmetrical wing-like extensions at each side of the female composite genital somite. Furthermore, it displays a female urosome reduced to only two somites due to the incorporation of abdominal somites III and IV to the composite genital double-somite, and a male right fifth leg with the outer spine of second exopodal segment recurved and implanted proximally on margin. It differs from any other Notodiaptomus in the display of a large rectangular lamella on proximal segment of exopod of male right fifth leg. The species is currently known only from Mazar reservoir, a eutrophic water body placed above 2127 m a.s.l. on the River Paute (Cañar Province; southern Ecuador), where it is the most common crustacean in the water column. PMID:29134016

What controls deformation in a bent three-dimensional orogen? An example from the Bolivian Andes

NASA Astrophysics Data System (ADS)

Kaislaniemi, L.; Whipp, D. M., Jr.

2017-12-01

The width of orogens is thought to be affected by both erosional intensity and strength of the rocks. Along-strike variation of the orogen width can be expected to reflect shifts in these factors. An example of such variation can be found around the Bolivian orocline, which is a change in the orientation of the central Andes, in central Bolivia, from N-S south of 18°S to roughly NW-SE in the north. This bend coincides with 50% reduction in the width of the orogen east of the Altiplano, an approximately eight-fold increase in the annual precipitation, and the presence of a basement arch that reduces the thickness of relatively weak Paleozoic sediments upon which the orogen detaches. This has led to uncertainty about whether the growth of the orogen is controlled primarily by climate (erosion) or tectonics (strength of the basal detachment). We study deformation in a segmented orogen using 3D geodynamic models to understand how along-strike variations in rainfall and basal detachment strength affect orogen deformation and growth of the frontal part of the Andean fold-and-thrust belt (FTB). We calculate the visco-plastic deformation in the retro-wedge of an Andean-style orogen using the finite element software DOUAR (Braun et al. 2008) coupled to the surface process model FastScape (Braun & Willett 2013). The model design includes the basement, the Altiplano, and the FTB east of the plateau. A weak basal detachment zone is prescribed. Strain softening allows development of new faults and free evolution of the detachment zone. The effects of varying rock strength and varying precipitation are considered to determine the primary control(s) on the geometry and evolution of curved orogens. Results show that both increased precipitation and stronger detachment zone can explain differences in the width of the FTB, as reflected in the topography. These factors, however, lead to different structural evolution of the orogen: Weak basal detachment zone promotes growth of the

Improving Regional Security in Central America: Military Engagement Options for Nicaragua

DTIC Science & Technology

2002-12-01

Diálogo Centro-americano San José, Costa Rica No. 38 Marzo-Abril 1999 Ejércitos para preservar la paz y la democracia . Pedro Joaquín Chamorro...del Foro Civil Centroamericano para la Defensa y la Seguridad (FOCADES). (Declaration of Managua: Declaration of Managua: Constitution of the Central...State. Isacson, Adam 1998. Seguridad Cooperativa en Centroamérica. (Cooperative Security in Central America) Diálogo Centro-americano No. 35

Magmatism and the Shallowing of the Chilean Flatslab in the Central Andes

NASA Astrophysics Data System (ADS)

Kay, S. M.

2014-12-01

The magmatic history of the flatslab region between the Central and Southern Andean volcanic zones reflects shallowing of the slab, lithospheric thinning, narrowing of the asthenospheric wedge, crustal thickening and forearc removal by subduction erosion. Newly revised contours on the northern margin of the modern flatslab (Mulcahy et al. 2014) show the flattest part extends from ~28° to 33°S and is bounded by Pleistocene volcanic activity. An eastward broadening of the magmatic arc began after 18 Ma as westward drift of South America accelerated, but the most distinctive retroarc magmatism occurred after near normal subduction of the southward drifting Juan Fernandez Ridge began at ~11 Ma and ended as magmatism ceased in the Pampean ranges, ~ 700 km east of the trench at ~4.7 Ma. Recent seismic work in the retroarc area indicate a ~60 km thick crust under the Precordillera fold-thrust belt with transitions at ~20 and ~40 km that are considered to be the top of crystalline basement and an eclogitic facies transition. Chemical constraints from ~15-7 Ma magmatic rocks suggest eclogization is related to crustal thickening over the shallowing slab in accord with field relations for major thrusting in the region by ~8-7 Ma. High Ba/Th ratios in <9 Ma volcanic rocks are interpreted to reflect phengite breakdown in the mantle wedge with the fluids facilitating eclogization of the lower crust. Evidence for mantle melt contributions in the magmas up until ~7 Ma comes from more primitive isotopic values in 1088-1251 Ma amphibolite and granulite facies xenoliths (eNd = 0 to -3; 87Sr/86Sr =704-0.710) than in Miocene volcanic rocks (eNd = 0-1.7; 0.70325-0.70345; zircon eHf ~ 0). From ~8 to 3 Ma, the active volcanic arc front near 28°S and 33°S was translated ~ 40-50 km eastward in a suspected response to forearc removal by subduction erosion. Given the position of the arc and distance to the trench, the same amount of forearc was likely removed in the intervening flatslab

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

NASA Astrophysics Data System (ADS)

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.

Domestication and human demographic history in South America.

PubMed

Perez, S Ivan; Postillone, María Bárbara; Rindel, Diego

2017-05-01

The early groups of hunter-gatherers who peopled South America faced significant ecological changes in their trophic niche for a relatively short period after the initial peopling. In particular, the incorporation of cultigens during the Holocene led to a wider trophic niche and probably to an increased carrying capacity of the environment. Here, we study the relationship between the incorporation of domestic resources during the Holocene and the demographic dynamics of human populations at a regional scale in South America. We employ mitochondrial DNA (mtDNA), radiocarbon data and Bayesian methods to estimate differences in population size, human occupation and explore the demographic changes of human populations in three regions (i.e., South-Central Andes, Northwest, and South Patagonia). We also use archaeological evidence to infer the main diet changes in these regions. The absolute population size during the later Late Holocene was fifteen times larger in the South-Central Andes than in Northwest Patagonia, and two times larger in the latter region than in South Patagonia. The South-Central Andes display the earlier and more abrupt population growth, beginning about 9000 years BP, whereas Northwest Patagonia exhibits a more slow growth, beginning about 7000-7500 years BP. South Patagonia represents a later and slower population increase. In this work we uncovered a well-supported pattern of the demographic change in the populations from South-Central Andes and Patagonia, obtained on the basis of different data and quantitative approaches, which suggests that the incorporation of domestic resources was paramount for the demographic expansion of these populations during the Holocene. © 2017 Wiley Periodicals, Inc.

ON the interaction of the north andes plate with the caribbean and south american plates in northwestern south america from gps geodesy and seismic data

NASA Astrophysics Data System (ADS)

Pérez, Omar J.; Wesnousky, Steven G.; De La Rosa, Roberto; Márquez, Julio; Uzcátegui, Redescal; Quintero, Christian; Liberal, Luis; Mora-Páez, Héctor; Szeliga, Walter

2018-06-01

We examine the hypocentral distribution of seismicity and a series of geodetic velocity vectors obtained from Global Positioning System (GPS) observations between 1994 and 2015 both off-shore and mainland northwestern South America [66° W - 77° W; 8° N - 14° N]. Our analysis, that includes a kinematic block modeling, shows that east of the Caribbean-South American-North Andes plates triple junction at ˜68° W; 10.7° N, right-lateral easterly oriented shear motion (˜19.6 ± 2.0 mm/yr) between the Caribbean and South-America plates is split along two easterly striking, right-lateral strike slip subparallel fault zones: the San Sebastián fault that runs offshore the Venezuelan coast and slips about 17.0 ± 0.5 mm/yr, and the La Victoria fault, located onshore to the south, which is accumulating strain equivalent to 2.6 ± 0.4 mm/yr. West of the triple junction, relative right-lateral motion between the Caribbean and South American plates is mostly divided between the Morrocoy and Boconó fault systems which strike northwest and southwest from the triple junction, respectively, and bound the intervening North Andes plate that shows an easterly oriented geodetic slip of 15.0 ± 1.0 mm/yr relative to the South American plate. Slip on the Morrocoy fault is right-lateral and transtensional. Motion across the Boconó fault is also right-lateral but instead transpressional, divided between ˜9 to 11 mm/yr of right-slip on the Boconó fault and 2 to 5 mm/yr of convergence across adjacent and subparallel thrust faults. Farther west of the triple junction, ˜800 km away in northern Colombia, the Caribbean plate subducts to the southeast beneath the North Andes plate at a geodetically estimated rate of ˜5-7 mm/yr.

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

USGS Publications Warehouse

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

2014-01-01

Explosive eruptions of large-volume rhyolitic magma systems are common in the geologic record and pose a major potential threat to society. Unlike other natural hazards, such as earthquakes and tsunamis, a large rhyolitic volcano may provide warning signs long before a caldera-forming eruption occurs. Yet, these signs—and what they imply about magma-crust dynamics—are not well known. This is because we have learned how these systems form, grow, and erupt mainly from the study of ash flow tuffs deposited tens to hundreds of thousands of years ago or more, or from the geophysical imaging of the unerupted portions of the reservoirs beneath the associated calderas. The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007, the crust there has been inflating at an astonishing rate of at least 25 cm/yr. This unique opportunity to investigate the dynamics of a large rhyolitic system while magma migration, reservoir growth, and crustal deformation are actively under way is stimulating a new international collaboration. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ca. 20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. The next phase of this investigation seeks to enlarge the sets of geophysical and geochemical data and to use these observations in numerical models of system dynamics.

The Panama North Andes Plate Bounday Zone from Interpreted Radar Images, Geologic Mapping and Geophysical Anomalies

NASA Astrophysics Data System (ADS)

Hernandez, O.; Alexander, G. C.; Garzon, F.

2013-05-01

Satellite geodetics shows the existence of the rigid Panama microplate converging on west to east with The North Andean block. Seismic studies indicate that this plate boundary zone has compressive east-west stresses. Interpretation from magnetic and gravity data suggest that the thickness of the sedimentary sequence of The Atrato basin, reaches 10.5 km and that the Mande magmatic arc is a tectonic pillar, bounded by faults. The interpretation of seismic lines shows the basement of the Urabá Basin is affected by normal faults that limit blocks sunk and raised, a sedimentary sequence that is wedged against the Mande magmatic arc and becomes thicker towards the east. It also shows a thrust fault that connects Neogene sediments of Sinu fold belt with the Urabá Basin. The collision of the Panama arc with the Western Cordillera leads to the existence of a low-angle subduction zone inclined to the east involving the partition of the oceanic plate, drawing up of a trench and subducting plate bending. Before the Panama arc collision with the Western Cordillera, granitic intrusion had occurred that gave rise to the Mande magmatic arc, causing bending and rise of the oceanic crust. This effort generated tensional bending at the top of the crust that led to the formation of raised and sunken blocks bounded by normal faults, within which lies the tectonic pillar which forms the Mande magmatic arc. Upon the occurrence of the collision, it was launched the end of the connection between the Pacific Ocean and Caribbean Sea and the formation of the Uraba forearc basins and the Atrato basin. Panama - North Andes Plate boundary Zone 2d Modeling of the Panama - North Andes Plate Bounday Zone

Carbon stabilization mechanisms in soils in the Andes

NASA Astrophysics Data System (ADS)

Jansen, Boris; Cammeraat, Erik

2015-04-01

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

Cenozoic intraplate tectonics in Central Patagonia: Record of main Andean phases in a weak upper plate

NASA Astrophysics Data System (ADS)

Gianni, G. M.; Echaurren, A.; Folguera, A.; Likerman, J.; Encinas, A.; García, H. P. A.; Dal Molin, C.; Valencia, V. A.

2017-11-01

Contraction in intraplate areas is still poorly understood relative to similar deformation at plate margins. In order to contribute to its comprehension, we study the Patagonian broken foreland (PBF) in South America whose evolution remains controversial. Time constraints of tectonic events and structural characterization of this belt are limited. Also, major causes of strain location in this orogen far from the plate margin are enigmatic. To unravel tectonic events, we studied the Cenozoic sedimentary record of the central sector of the Patagonian broken foreland (San Bernardo fold and thrust belt, 44°30‧S-46°S) and the Andes (Meseta de Chalia, 46°S) following an approach involving growth-strata detection, U-Pb geochronology and structural modeling. Additionally, we elaborate a high resolution analysis of the effective elastic thickness (Te) to examine the relation between intraplate contraction location and variations in lithospheric strength. The occurrence of Eocene growth-strata ( 44-40 Ma) suggests that contraction in the Andes and the Patagonian broken foreland was linked to the Incaic phase. Detection of synextensional deposits suggests that the broken foreland collapsed partially during Oligocene to early Miocene. During middle Miocene times, the Quechua contractional phase produced folding of Neogene volcanic rocks and olistostrome deposition at 17 Ma. Finally, the presented Te map shows that intraplate contraction related to Andean phases localized preferentially along weak lithospheric zones (Te < 15 km). Hence, the observed strain distribution in the PBF appears to be controlled by lateral variations in the lithospheric strength. Variations in this parameter could be related to thermo-mechanical weakening produced by intraplate rifting in Paleozoic-Mesozoic times.

Tectonic, volcanic, and climatic geomorphology study of the Sierras Pampeanas Andes, northwestern Argentina

NASA Technical Reports Server (NTRS)

Bloom, A. L.; Strecker, M. R.; Fielding, E. J.

1984-01-01

A proposed analysis of Shuttle Imaging Radar-B (SIR-B) data extends current research in the Sierras Pampeanas and the Puna of northwestern Argentina to the determination - by the digital analysis of mountain-front sinuousity - of the relative age and amount of fault movement along mountain fronts of the late-Cenozoic Sierras Pampeanas basement blocks; the determination of the age and history of the boundary across the Andes at about 27 S latitude between continuing volcanism to the north and inactive volcanism to the south; and the determination of the age and extent of Pleistocene glaciation in the High Sierras, as well as the comparative importance of climatic change and tectonic movements in shaping the landscape. The integration of these studies into other ongoing geology projects contributes to the understanding of landform development in this active tectonic environment and helps distinguish between climatic and tectonic effects on landforms.

Human T-lymphotropic virus type 1 infection is frequent in rural communities of the southern Andes of Peru.

PubMed

Ita, Fanny; Mayer, Erick F; Verdonck, Kristien; Gonzalez, Elsa; Clark, Daniel; Gotuzzo, Eduardo

2014-02-01

To evaluate the presence of human T-lymphotropic virus type 1 (HTLV-1) infection in isolated rural communities in the southern Andes of Peru. We conducted a cross-sectional study in five communities located in three provinces in Ayacucho, Peru. The five communities are located at >3000 meters above sea level and are mainly rural, and more than 85% of the population speaks Quechua. Volunteers aged 12 years and older were included. Clinical and epidemiological data were collected, along with a blood sample for serological testing. We included 397 participants; their median age was 41 years (interquartile range 31-57 years) and 69% were women. According to our definitions, 98% were of Quechua origin. HTLV-1 was diagnosed in 11 people: 0/164 in Cangallo, 3/154 (2%) in Vilcashuaman, and 8/79 (10%) in Parinacochas. There were no cases of HTLV-2. All the HTLV-1-positive participants were born in Ayacucho and were of Quechua origin; they ranged in age from 29 to 87 years (median 56 years) and 10/11 were women. Ten were apparently healthy, and one woman was diagnosed with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Three out of 11 had a family member with a lower limb impairment compatible with HAM/TSP. The fact that HTLV-1 infection was present in two out of three provinces suggests that HTLV-1 could be highly endemic in the southern Andes in the Quechua population. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

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

PubMed

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

2017-10-01

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

Glacial Lake Growth and Associated Glacier Dynamics: Case Study from the Himalayas, Andes, Alaska and New Zealand

NASA Astrophysics Data System (ADS)

Binger, D. J.; Haritashya, U. K.; Kargel, J. S.; Shugar, D. H.

2016-12-01

Glacial lake growth and associated glacier dynamics: Case study from the Himalayas, Andes, Alaska and New Zealand David J. Binger1, Umesh K. Haritashya1 and Jeffrey S. Kargel21University of Dayton, Dayton, OH 2University of Arizona, Tucson, AZ As a result of climate change most of the world's alpine glaciers are undergoing measurable retreat and dynamic changes. The result of accelerated melting has led to the formation and growth of potentially dangerous glacial lakes. In this study, alpine glaciers and associated lakes from the Himalayas, Andes, Alaska and New Zealand, showing similar geomorphological settings were analyzed to compare differences in regional proglacial lake growth and its relationship with glacier dynamics. Specifically, we analyzed the surface area growth of the lakes, retreat of glacier terminus, changes in glacier velocity, surface temperature and potential glacial lake outburst flood triggers. Using Landsat and ASTER satellite images, Cosi - Corr software, and in house thermal mapping, 10 glaciers were analyzed and compared. Results show a substantial increase in proglacial lake surface area, accelerated velocity and significant calving of the glaciers. Glacier surface temperatures varied by location, with some remaining constant and others 2°C - 4°C increases; although increased surface temperature did not always show a direct correlation with increasing retreat rate. Lakes with high rates of surface area growth paired with glaciers with increased velocity and calving could prove to be unsustainable and lead to an increased risk for glacial lake outburst floods. Overall, result show the changing dynamics of the alpine glaciers in different mountain regions and the growth of their proglacial lakes.

Methane fluxes from a wet puna ecosystem in the Peruvian Andes

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

Patterns of Diversity and Abundance of Carrion Insect Assemblages in the Natural Park “Hoces del Río Riaza” (Central Spain)

PubMed Central

Baz, Arturo; Cifrián, Blanca; Martín-Vega, Daniel

2014-01-01

Abstract The patterns of diversity and abundance of the carrion insect species in the different habitats of the Natural Park “Hoces del Río Riaza” (central Spain) were studied with the use of carrion-baited traps. Representativeness of the inventories was assessed with the calculation of randomized species richness curves and nonparametric estimators. Coleoptera families, Silphidae and Dermestidae, and Diptera families, Calliphoridae and Muscidae, were dominant in every sampling habitat, but differences in the patterns of diversity and abundance were found. Lusitanian oakwood and riparian forest were the most diverse habitats with high abundance of saprophagous species, whereas more open (i.e., exposed to continuous sunlight during the day) habitats showed lower diversity values and a different species composition and distribution of species abundance, favoring thermophilous species and necrophagous species with high tolerance to different environmental conditions. Differences in the bioclimatical features of the sampled habitats are suggested to explain the composition and diversity of the carrion insect assemblages in different environments. PMID:25368080

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

PubMed Central

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

2012-01-01

The small mRNA (SmRNA) of all Bunyaviridae encodes the nucleocapsid (N) protein. In 4 out of 5 genera in the Bunyaviridae, the smRNA encodes an additional nonstructural protein denominated NSs. In this study, we show that Andes hantavirus (ANDV) SmRNA encodes an NSs protein. Data show that the NSs protein is expressed in the context of an ANDV infection. Additionally, our results suggest that translation initiation from the NSs initiation codon is mediated by ribosomal subunits that have bypassed the upstream N protein initiation codon through a leaky scanning mechanism. PMID:22156529

Quaternary deformation in the central Neuquén basin (35°-37°S), Argentina: evidences for active strain partitioning.

NASA Astrophysics Data System (ADS)

Niviere, B.; Backé, G.

2006-12-01

The tectonic evolution of the Central Andes is a consequence of the relative convergence between the Nazca and the South American plates. The Neuquén basin is located in the southernmost part of the Central Andes, between latitudes 32°S and 40°S. The present day geometry of the basin has been inherited from different compressive pulses, separated by times of relative tectonic quiescence since the late Cretaceous. The complex tectonic evolution of the area has often been explained by changes in the geometry of the subducted plate. The last broad scale tectonic event in the Neuquén basin is the Miocene compressive stage referred to as the Quechua phase. The tectonic evolution of the outer part of the Neuquén Basin from the late Miocene onwards is still a matter of debate. For instance, strain partitioning has been described in the inner part of the basin, which corresponds to the modern arc area close to the Chile Argentina border. The strain regime in the foreland between 35°S and 37°S is more uncertain. Extensional tectonic features have been described in different areas of the basin, leading to the formulation of a possible orogenic collapse in response to the steepening of the oceanic slab that followed a late Miocene shallow subduction. This model accounts for the occurrence of large Pleistocene to Quaternary back-arc volcanism in the Neuquén basin. However, field structural data and borehole breakout analysis strongly support on-going compression in the basin. Our study is based on the morphostructural analysis of remote sensing data (satellite and digital elevation model images) complemented by field work. Here we show that strike-slip faulting and localized extension in the outer zone of the basin is coeval with active thrusting and folding. This can be explained by strain partitioning or segmentation processes due to the oblique convergence between the Nazca and the South American plates.

A 22,000-year record of monsoonal precipitation from northern Chile's Atacama Desert

USGS Publications Warehouse

Betancourt, J.L.; Latorre, C.; Rech, J.A.; Quade, Jay; Rylander, K.A.

2000-01-01

Fossil rodent middens and wetland deposits from the central Atacama Desert (22° to 24°S) indicate increasing summer precipitation, grass cover, and groundwater levels from 16.2 to 10.5 calendar kiloyears before present (ky B.P.). Higher elevation shrubs and summer-flowering grasses expanded downslope across what is now the edge of Absolute Desert, a broad expanse now largely devoid of rainfall and vegetation. Paradoxically, this pluvial period coincided with the summer insolation minimum and reduced adiabatic heating over the central Andes. Summer precipitation over the central Andes and central Atacama may depend on remote teleconnections between seasonal insolation forcing in both hemispheres, the Asian monsoon, and Pacific sea surface temperature gradients. A less pronounced episode of higher groundwater levels in the central Atacama from 8 to 3 ky B.P. conflicts with an extreme lowstand of Lake Titicaca, indicating either different climatic forcing or different response times and sensitivities to climatic change.

A 22,000-Year Record of Monsoonal Precipitation from Northern Chile's Atacama Desert.

PubMed

Betancourt; Latorre; Rech; Quade; Rylander

2000-09-01

Fossil rodent middens and wetland deposits from the central Atacama Desert (22 degrees to 24 degrees S) indicate increasing summer precipitation, grass cover, and groundwater levels from 16.2 to 10.5 calendar kiloyears before present (ky B.P.). Higher elevation shrubs and summer-flowering grasses expanded downslope across what is now the edge of Absolute Desert, a broad expanse now largely devoid of rainfall and vegetation. Paradoxically, this pluvial period coincided with the summer insolation minimum and reduced adiabatic heating over the central Andes. Summer precipitation over the central Andes and central Atacama may depend on remote teleconnections between seasonal insolation forcing in both hemispheres, the Asian monsoon, and Pacific sea surface temperature gradients. A less pronounced episode of higher groundwater levels in the central Atacama from 8 to 3 ky B.P. conflicts with an extreme lowstand of Lake Titicaca, indicating either different climatic forcing or different response times and sensitivities to climatic change.

Antioxidant Activity, Total Phenolics Content, Anthocyanin, and Color Stability of Isotonic Model Beverages Colored with Andes Berry (Rubus glaucus Benth) Anthocyanin Powder

PubMed Central

Estupiñan, D.C.; Schwartz, S.J.; Garzón, G.A.

2013-01-01

The stability of anthocyanin (ACN) freeze-dried powders from Andes berry (Rubus glaucus Benth) as affected by storage, addition of maltodextrin as a carrier agent, and illumination was evaluated in isotonic model beverages. The ethanolic ACN extract was freeze dried with and without maltodextrin DE 20. Isotonic model beverages were colored with freeze-dried ACN powder (FDA), freeze-dried ACN powder with maltodextrin (MFDA), and red nr 40. Beverages were stored in the dark and under the effect of illumination. Half life of the ACNs, changes in color, total phenolics content (TPC), and antioxidant activity were analyzed for 71 d. Addition of maltodextrin and absence of light stabilized the color of beverages and improved ACN and TPC stability during storage. The antioxidant activity of the beverages was higher when they were colored with MFDA and highly correlated with ACN content. There was no correlation between antioxidant activity and TPC. It is concluded that addition of maltodextrin DE 20 as a carrier agent during freeze-drying improves the color and stability of nutraceutical antioxidants present in Andes berry extract. This suggests a protective enclosing of ACNs within a maltodextrin matrix with a resulting powder that could serve as a supplement or additive to naturally color and to enhance the antioxidant capacity of isotonic beverages. PMID:21535712

Provenance of Cretaceous-Pliocene Clastic Sediments in the Tachira Saddle, Western Venezuela, and Implications for Sediment Dispersal Patterns in the Northern Andes

NASA Astrophysics Data System (ADS)

Gomez, Ali Ricardo

Northwestern South America is highly deformed due to the transpressive plate boundary associated with complex interactions between the Caribbean plate, the South American plate, the Nazca plate and the Panama arc. Previous studies suggest that the Cenozoic uplift of the Merida Andes and Eastern Cordillera of Colombia affected sediment dispersal patterns in the region, shifting from a Paleocene foreland basin configuration to the modern isolated basins. Well-exposed Cretaceous to Pliocene strata in the Tachira Saddle provides a unique opportunity to test proposed sediment dispersal patterns in the region. U-Pb detrital zircon geochronology and supplementary XRD heavy mineral data are used together to document the provenance of the Tachira Saddle sediments and refine the sediment dispersal patterns in the region. Results from the U-Pb detrital zircon geochronology show that there are six age groups recorded in these samples. Two groups are related to the Precambrian Guyana shield terranes and Putumayo basement in the Eastern Cordillera, and four groups are related to different magmatic episodes occurring during the Andean orogenic process. The transition between the Cretaceous passive margin and the Paleocene foreland basin and the initial uplift of the Eastern Cordillera and the uplift of the Merida Andes by the Early Miocene were also recorded in the Tachira saddle detrital zircon signature.

Antioxidant activity, total phenolics content, anthocyanin, and color stability of isotonic model beverages colored with Andes berry (Rubus glaucus Benth) anthocyanin powder.

PubMed

Estupiñan, D C; Schwartz, S J; Garzón, G A

2011-01-01

The stability of anthocyanin (ACN) freeze-dried powders from Andes berry (Rubus glaucus Benth) as affected by storage, addition of maltodextrin as a carrier agent, and illumination was evaluated in isotonic model beverages. The ethanolic ACN extract was freeze dried with and without maltodextrin DE 20. Isotonic model beverages were colored with freeze-dried ACN powder (FDA), freeze-dried ACN powder with maltodextrin (MFDA), and red nr 40. Beverages were stored in the dark and under the effect of illumination. Half life of the ACNs, changes in color, total phenolics content (TPC), and antioxidant activity were analyzed for 71 d. Addition of maltodextrin and absence of light stabilized the color of beverages and improved ACN and TPC stability during storage. The antioxidant activity of the beverages was higher when they were colored with MFDA and highly correlated with ACN content. There was no correlation between antioxidant activity and TPC. It is concluded that addition of maltodextrin DE 20 as a carrier agent during freeze-drying improves the color and stability of nutraceutical antioxidants present in Andes berry extract. This suggests a protective enclosing of ACNs within a maltodextrin matrix with a resulting powder that could serve as a supplement or additive to naturally color and to enhance the antioxidant capacity of isotonic beverages.

Validation of recent geopotential models in Tierra Del Fuego

NASA Astrophysics Data System (ADS)

Gomez, Maria Eugenia; Perdomo, Raul; Del Cogliano, Daniel

2017-10-01

This work presents a validation study of global geopotential models (GGM) in the region of Fagnano Lake, located in the southern Andes. This is an excellent area for this type of validation because it is surrounded by the Andes Mountains, and there is no terrestrial gravity or GNSS/levelling data. However, there are mean lake level (MLL) observations, and its surface is assumed to be almost equipotential. Furthermore, in this article, we propose improved geoid solutions through the Residual Terrain Modelling (RTM) approach. Using a global geopotential model, the results achieved allow us to conclude that it is possible to use this technique to extend an existing geoid model to those regions that lack any information (neither gravimetric nor GNSS/levelling observations). As GGMs have evolved, our results have improved progressively. While the validation of EGM2008 with MLL data shows a standard deviation of 35 cm, GOCO05C shows a deviation of 13 cm, similar to the results obtained on land.

Reply to comments on: "Tethyan calpionellids in the Neuquén Basin (Argentine Andes), their significance in defining the Jurassic/Cretaceous boundary and pathways for Tethyan-Eastern Pacific connections" by Kietzmann & Iglesia Llanos

NASA Astrophysics Data System (ADS)

López-Martínez, Rafael; Aguirre-Urreta, Beatriz; Lescano, Marina; Concheyro, Andrea; Vennari, Verónica; Ramos, Victor A.

2018-07-01

The comments by Kietzmann & Iglesia Llanos (Comment on "Tethyan calpionellids in the Neuquén Basin (Argentine Andes), their significance in defining the Jurassic/Cretaceous boundary and pathways for Tethyan-Eastern Pacific connections" by R. López-Martínez, B. Aguirre-Urreta, M. Lescano, A. Concheyro, V. Vennari and V. Ramos) on our paper published in the Journal of South American Earth Sciences 78 (2017): 116-125, provide a worthy opportunity to further clarify our observations and interpretations regarding the importance of precise biostratigraphic studies in the definition of the Jurassic/Cretaceous boundary in the Argentine Andes. These include the calpionellids as primary markers, the classic and widespread nannofossils bioevents as secondary markers, together with a detailed ammonite zonation.

Diversity of extremophilic bacteria in the sediment of high-altitude lakes located in the mountain desert of Ojos del Salado volcano, Dry-Andes.

PubMed

Aszalós, Júlia Margit; Krett, Gergely; Anda, Dóra; Márialigeti, Károly; Nagy, Balázs; Borsodi, Andrea K

2016-09-01

Ojos del Salado, the highest volcano on Earth is surrounded by a special mountain desert with extreme aridity, great daily temperature range, intense solar radiation, and permafrost from 5000 meters above sea level. Several saline lakes and permafrost derived high-altitude lakes can be found in this area, often surrounded by fumaroles and hot springs. The aim of this study was to gain information about the bacterial communities inhabiting the sediment of high-altitude lakes of the Ojos del Salado region located between 3770 and 6500 m. Altogether 11 sediment samples from 4 different altitudes were examined with 16S rRNA gene based denaturing gradient gel electrophoresis and clone libraries. Members of 17 phyla or candidate divisions were detected with the dominance of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes. The bacterial community composition was determined mainly by the altitude of the sampling sites; nevertheless, the extreme aridity and the active volcanism had a strong influence on it. Most of the sequences showed the highest relation to bacterial species or uncultured clones from similar extreme environments.

Genetic diversity of Mycobacterium tuberculosis isolates from central India.

PubMed

Desikan, Prabha; Chauhan, D S; Sharma, Pragya; Panwalkar, Nikita; Chourey, Manju; Patidar, Mohan Lal; Yadav, Priyanka; Chandrasekaran, V; Ohri, B S

2016-04-01

There is a paucity of data available on genetic biodiversity of Mycobacterium tuberculosis isolates from central India. The present study was carried out on isolates of M. tuberculosis cultured from diagnostic clinical samples of patients from Bhopal, central India, using spoligotyping as a method of molecular typing. DNA was extracted from 340 isolates of M. tuberculosis from culture, confirmed as M. tuberculosis by molecular and biochemical methods and subjected to spoligotyping. The results were compared with the international SITVIT2 database. Sixty five different spoligo international type (SIT) patterns were observed. A total of 239 (70.3%) isolates could be clustered into 25 SITs. The Central Asian (CAS) and East African Indian (EAI) families were found to be the two major circulating families in this region. SIT26/CAS1_DEL was identified as the most predominant type, followed by SIT11/EAI3_IND and SIT288/CAS[2]. Forty (11.8%) unique (non-clustered) and 61 (17.9%) orphan isolates were identified in the study. There was no significant association of clustering with clinical and demographic characteristics of patients. Well established SITs were found to be predominant in our study. SIT26/CAS1_DEL was the most predominant type. However, the occurrence of a substantial number of orphan isolates may indicate the presence of active spatial and temporal evolutionary dynamics within the isolates of M. tuberculosis.

Potato-associated arbuscular mycorrhizal fungal communities in the Peruvian Andes.

PubMed

Senés-Guerrero, Carolina; Torres-Cortés, Gloria; Pfeiffer, Stefan; Rojas, Mercy; Schüßler, Arthur

2014-08-01

The world's fourth largest food crop, potato, originates in the Andes. Here, the community composition of arbuscular mycorrhizal fungi (AMF) associated with potato in Andean ecosystems is described for the first time. AMF were studied in potato roots and rhizosphere soil at four different altitudes from 2,658 to 4,075 m above mean sea level (mamsl) and in three plant growth stages (emergence, flowering, and senescence). AMF species were distinguished by sequencing an approx. 1,500 bp nuclear rDNA region. Twenty species of AMF were identified, of which 12 came from potato roots and 15 from rhizosphere soil. Seven species were found in both roots and soil. Interestingly, altitude affected species composition with the highest altitude exhibiting the greatest species diversity. The three most common colonizers of potato roots detected were Funneliformis mosseae, an unknown Claroideoglomus sp., and Rhizophagus irregularis. Notably, the potato-associated AMF diversity observed in this Andean region is much higher than that reported for potato in other ecosystems. Potato plants were colonized by diverse species from 8 of the 11 Glomeromycota families. Identification of the AMF species is important for their potential use in sustainable management practices to improve potato production in the Andean region.

Spatial abundance models and seasonal distribution for guanaco (Lama guanicoe) in central Tierra del Fuego, Argentina.

PubMed

Flores, Celina E; Deferrari, Guillermo; Collado, Leonardo; Escobar, Julio; Schiavini, Adrián

2018-01-01

Spatially explicit modelling allows to estimate population abundance and predict species' distribution in relation to environmental factors. Abiotic factors are the main determinants of a herbivore´s response to environmental heterogeneity on large spatiotemporal scales. We assessed the influence of elevation, geographic location and distance to the coast on the seasonal abundance and distribution of guanaco (Lama guanicoe) in central Tierra del Fuego, by means of spatially explicit modelling. The estimated abundance was 23,690 individuals for the non-breeding season and 33,928 individuals for the breeding season. The factors influencing distribution and abundance revealed to be the elevation for the non-breeding season, and the distance to the coast and geographic location for the breeding season. The southwest of the study area presented seasonal abundance variation and the southeast and northeast presented high abundance during both seasons. The elevation would be the driving factor of guanaco distribution, as individuals move to lower areas during the non-breeding season and ascend to high areas during the breeding season. Our results confirm that part of the guanaco population performs seasonal migratory movements and that the main valleys present important wintering habitats for guanacos as well as up-hill zones during summer. This type of study would help to avoid problems of scale mismatch and achieve better results in management actions and is an example of how to assess important seasonal habitats from evaluations of abundance and distribution patterns.

Spatial abundance models and seasonal distribution for guanaco (Lama guanicoe) in central Tierra del Fuego, Argentina

PubMed Central

Deferrari, Guillermo; Collado, Leonardo; Escobar, Julio; Schiavini, Adrián

2018-01-01

Spatially explicit modelling allows to estimate population abundance and predict species’ distribution in relation to environmental factors. Abiotic factors are the main determinants of a herbivore´s response to environmental heterogeneity on large spatiotemporal scales. We assessed the influence of elevation, geographic location and distance to the coast on the seasonal abundance and distribution of guanaco (Lama guanicoe) in central Tierra del Fuego, by means of spatially explicit modelling. The estimated abundance was 23,690 individuals for the non-breeding season and 33,928 individuals for the breeding season. The factors influencing distribution and abundance revealed to be the elevation for the non-breeding season, and the distance to the coast and geographic location for the breeding season. The southwest of the study area presented seasonal abundance variation and the southeast and northeast presented high abundance during both seasons. The elevation would be the driving factor of guanaco distribution, as individuals move to lower areas during the non-breeding season and ascend to high areas during the breeding season. Our results confirm that part of the guanaco population performs seasonal migratory movements and that the main valleys present important wintering habitats for guanacos as well as up-hill zones during summer. This type of study would help to avoid problems of scale mismatch and achieve better results in management actions and is an example of how to assess important seasonal habitats from evaluations of abundance and distribution patterns. PMID:29782523

Molecular method for the detection of Andes hantavirus infection: validation for clinical diagnostics

PubMed Central

Vial, Cecilia; Martinez-Valdebenito, Constanza; Rios, Susana; Martinez, Jessica; Vial, Pablo; Ferres, Marcela; Rivera, Juan Carlos; Perez, Ruth; Valdivieso, Francisca

2016-01-01

Hantavirus Cardiopulmonary Syndrome is a severe disease caused by exposure to New World hantaviruses. Early diagnosis is difficult due to the lack of specific initial symptoms. Anti-hantavirus antibodies are usually negative until late in the febrile prodrome or the beginning of cardiopulmonary phase while Andes hantavirus (ANDV) RNA genome can be detected before symptoms onset. We analyzed the effectiveness of RTqPCR as a diagnostic tool detecting ANDV-Sout genome in peripheral blood cells from 78 confirmed hantavirus patients and 166 negative controls. Our results indicate that RTqPCR had a low detection limit (~10 copies), with a specificity of 100% and a sensitivity of 94.9%. This suggests the potential for establishing RT-qPCR as the assay of choice for early diagnosis, promoting early effective care of patients and improve other important aspects of ANDV infection management, such as compliance of biosafety recommendations for health personnel in order to avoid nosocomial transmission. PMID:26508102

Person-to-Person Household and Nosocomial Transmission of Andes Hantavirus, Southern Chile, 2011

PubMed Central

Martinez-Valdebenito, Constanza; Calvo, Mario; Vial, Cecilia; Mansilla, Rita; Marco, Claudia; Palma, R. Eduardo; Vial, Pablo A.; Valdivieso, Francisca; Mertz, Gregory

2014-01-01

Andes hantavirus (ANDV) causes hantavirus cardiopulmonary syndrome in Chile and is the only hantavirus for which person-to-person transmission has been proven. We describe an outbreak of 5 human cases of ANDV infection in which symptoms developed in 2 household contacts and 2 health care workers after exposure to the index case-patient. Results of an epidemiologic investigation and sequence analysis of the virus isolates support person-to-person transmission of ANDV for the 4 secondary case-patients, including nosocomial transmission for the 2 health care workers. Health care personnel who have direct contact with ANDV case-patients or their body fluids should take precautions to prevent transmission of the virus. In addition, because the incubation period of ANDV after environmental exposure is longer than that for person-to-person exposure, all persons exposed to a confirmed ANDV case-patient or with possible environmental exposure to the virus should be monitored for 42 days for clinical symptoms. PMID:25272189

A new high-altitude species of centipede from the Andes of Ecuador (Chilopoda, Geophilomorpha, Schendylidae).

PubMed

Pereira, Luis Alberto

2018-01-18

Pectiniunguis aequatorialis sp. nov. (Chilopoda: Geophilomorpha: Schendylidae) is described and illustrated on the basis of specimens collected in the Cayambe-Coca Ecological Reserve in the High Andes of Ecuador. The new species is characterized by having ventral pore-fields on the anterior region of the trunk only, a trait that is shared by a single Neotropical congener: Pectiniunguis ascendens Pereira, Minelli Barbieri, 1994 to which it is similar and is compared taxonomically. This is only the second report of a species of the genus Pectiniunguis Bollman, 1889 from mainland Ecuador. The other taxon is Pectiniunguis roigi Pereira, Foddai Minelli, 2001, so far only known from the type locality, Limoncocha (Sucumbíos Province), and herein reported for the first time from Parque Nacional Sumaco Napo-Galeras (Napo Province).

Earth observations taken from shuttle orbiter Atlantis during STS-84 mission

NASA Image and Video Library

1997-05-18

STS084-727-053 (15-24 May 1997) --- This view of Lima, Peru is among a very few photographed by astronauts who have orbited Earth since the early 1960's. Francisco Pizarro founded the city of Lima in 1535. Lima is located 13 kilometers (8 miles) inland from the Peruvian coast and is surrounded by coastal desert and the Andes mountains. Suburbs of Lima extend in all directions except to the east, where the Andes prohibits growth. The three rivers, Chillion to the northeast of Lima, the Rimac which runs through the northern part of the city, and the Mala to the southeast, all drain the central Andes. The island off the coast is San Lorenzo.

Observations of the Breakdown of Mountain Waves Over the Andes Lidar Observatory at Cerro Pachon on 8/9 July 2012

NASA Astrophysics Data System (ADS)

Hecht, J. H.; Fritts, D. C.; Wang, L.; Gelinas, L. J.; Rudy, R. J.; Walterscheid, R. L.; Taylor, M. J.; Pautet, P. D.; Smith, S.; Franke, S. J.

2018-01-01

Although mountain waves (MWs) are thought to be a ubiquitous feature of the wintertime southern Andes stratosphere, it was not known whether these waves propagated up to the mesopause region until Smith et al. (2009) confirmed their presence via airglow observations. The new Andes Lidar Observatory at Cerro Pachon in Chile provided the opportunity for a further study of these waves. Since MWs have near-zero phase speed, and zero wind lines often occur in the winter upper mesosphere (80 to 100 km altitude) region due to the reversal of the zonal mean and tidal wind, MW breakdown may routinely occur at these altitudes. Here we report on very high spatial/temporal resolution observations of the initiation of MW breakdown in the mesopause region. Because the waves are nearly stationary, the breakdown process was observed over several hours; a much longer interval than has previously been observed for any gravity wave breakdown. During the breakdown process observations were made of initial horseshoe-shaped vortices, leading to successive vortex rings, as is also commonly seen in Direct Numerical Simulations (DNS) of idealized and multiscale gravity wave breaking. Kelvin-Helmholtz instability (KHI) structures were also observed to form. Comparing the structure of observed KHI with the results of existing DNS allowed an estimate of the turbulent kinematic viscosity. This viscosity was found to be around 25 m2/s, a value larger than the nominal viscosity that is used in models.

High-resolution dynamic downscaling of CMIP5 output over the Tropical Andes

NASA Astrophysics Data System (ADS)

Reichler, Thomas; Andrade, Marcos; Ohara, Noriaki

2015-04-01

Our project is targeted towards making robust predictions of future changes in climate over the tropical part of the South American Andes. This goal is challenging, since tropical lowlands, steep mountains, and snow covered subarctic surfaces meet over relatively short distances, leading to distinct climate regimes within the same domain and pronounced spatial gradients in virtually every climate quantity. We use an innovative approach to solve this problem, including several quadruple nested versions of WRF, a systematic validation strategy to find the version of WRF that best fits our study region, spatial resolutions at the kilometer scale, 20-year-long simulation periods, and bias-corrected output from various CMIP5 simulations that also include the multi-model mean of all CMIP5 models. We show that the simulated changes in climate are consistent with the results from the global climate models and also consistent with two different versions of WRF. We also discuss the expected changes in snow and ice, derived from off-line coupling the regional simulations to a carefully calibrated snow and ice model.

Fluctuations of Glaciar Esperanza Norte in the North Patagonian Andes of Argentina during the past 400 yr

NASA Astrophysics Data System (ADS)

Ruiz, L.; Masiokas, M. H.; Villalba, R.

2011-11-01

The number of studies of Little Ice Age (LIA) glacier fluctuations in Southern South America has increased in recent years but is largely biased towards sites in the South Patagonian Andes. In this paper we present a detailed record of length and areal fluctuations of Glaciar Esperanza Norte (GEN), in the North Patagonian Andes of Argentina, during the past four centuries. The GEN record was reconstructed through the dendro-geomorphological dating of moraines and the analysis of satellite imagery, aerial photographs and documentary material complemented with extensive field surveys. The maximum LIA extent at GEN was associated with an outer moraine dated to the mid 17th century. At least 19 subsequent readvances or standstills evidenced by morainic ridges were identified inside the most extensive LIA moraine. The dating and spacing of these moraines and the additional information available indicate that the ice front retreated much more rapidly during the 20th century than during earlier centuries. Comparison with the record of LIA fluctuations of Glaciar Frías, an ice mass of similar characteristics located 110 km to the north of GEN, shows a similar pattern of recession over the past 400 yr. Both glacier records have the peak LIA event occurring roughly during the same interval and show a minor readvance during the 1970s, but there are still a few discrepancies in the dating of some inner moraines. These differences may be due to local, specific factors or associated with the inherent uncertainties in the dating of the moraines. The chronologies of GEN and Frías are among the most detailed currently available in Patagonia, but a larger number of study sites is needed to develop robust, regionally representative glacier chronologies. Detailed glaciological, geomorphological and meteorological data are also needed to understand the glacier-climate relationships in this region and develop reliable paleoclimatic reconstructions.

Socioeconomic status and chronic child malnutrition: Wealth and maternal education matter more in the Peruvian Andes than nationally.

PubMed

Urke, Helga B; Bull, Torill; Mittelmark, Maurice B

2011-10-01

This study investigated the association of parents' socioeconomic status (SES) with child stunting in the Peruvian Andes and in Peru nationally. It was hypothesized that the relationship of SES to child stunting would be weaker in the Andean compared with the national sample. This is consistent with earlier research indicating that the relationship of SES to health may be weak in poor regions. The data were from the Demographic and Health Survey 2004 to 2006. Two samples of children 3 to 60 months old were compared: a national sample (n = 1426) and an Andean sample (n = 543). Malnutrition was measured using the indicator "stunting," which is small stature for age. Socioeconomic status was measured using parental education, occupation, and household wealth index (WI). In both samples, SES was significantly related to stunting. The odds of stunting in the poorest WI quintile were significantly higher than in the richest quintile. The same pattern was observed in children of mothers having incomplete primary education compared with children of mothers having complete secondary or higher education. The odds of stunting were significantly lower in children of mothers working at home compared with mothers in professional occupations. The associations of WI and maternal education with stunting were significantly stronger in the Andean compared with the national sample; the study did not find support for the hypothesis. Even in very poor regions such as the Andes, SES may be associated with child health, suggesting the importance of public health measures to overcome the health disadvantages experienced by children living in low SES households. Copyright © 2011 Elsevier Inc. All rights reserved.

Concentration and distribution of heavy metals in two Andisols of the Azuay Andes (Ecuador)

NASA Astrophysics Data System (ADS)

Bech, Jaume; Roca, Núria; Ugalde, Sandra; Tonon, Luis; Larriva, Giovani

2013-04-01

At present many governmental and environmental bureaus are interested in establishing reliable soil quality criteria for heavy metals to enable the detection of polluted sites. To evaluate the variation of heavy metal natural concentration and to assess heavy metal contamination in soils, it is necessary to survey heavy metal baseline levels in order to understand their migration and distribution during pedogenesis. Many nationwide projects report elemental baseline values in soils. Baseline levels of heavy metals in soils have also been determined at local scales. Data is scarce on qualitative and quantitative trace elements content of Ecuatorian soils. The soils in the Azuay Andes (S of Ecuador) are thought to be generally non-contaminated. The objective of this study is to determine and evaluate the natural concentrations and distribution of seven heavy metals (Cd, Co, Cr, Cu, Ni, Pb and Zn) in Andisol of Azuay Andes. Soil samples were grounded in an agate mill prior to pseudototal heavy metal analysis. Cadmium, Co, Cr, Cu, Ni, Pb and Zn were determined by a masses spectrometer (MS-ICP) after aqua regia extraction according to ISO standard procedures. Soil particle size distribution, organic carbon, electrical conductivity and pH have been previously determined. Andisols are dominated by amorphous aluminium silicates and Al-organic complexes. The soils of volcanic area usually have an Ah-Bh-Bhs/Bw-C horizon sequence. The Ah horizon is dark-coloured and normally very high in organic matter, ranging from 6.4 to 15.2 %. A strong rise in pH upon addition of a fluoride solution is used to signal the presence of allophane. The pH usually rises to 10.5 bellow 20 cm. The range of total soil values in mgkg-1 is as follows: Cd (0.03-0.3), Co (0.8-5), Cr (7-15), Cu (9-25), Ni (2-4), Pb (11-41) and Zn (12-37). All heavy metal contents, except for Cd, are strongly correlated with pH. For the pseudototal fraction, there was significant difference between the soil horizons in

Conjoint Analysis of the Surface and Atmospheric Water Balances of the Andes-Amazon System

NASA Astrophysics Data System (ADS)

Builes-Jaramillo, Alejandro; Poveda, Germán

2017-04-01

Acknowledging the interrelation between the two branches of the hydrological cycle, we perform a comprehensive analysis of the long-term mean surface and atmospheric water balances in the Amazon-Andes River basins system. We estimate the closure of the water budgets based on the long-term approximation of the water balance equations, and estimate the imbalance between both atmospheric and surface budgets. The analysis was performed with observational and reanalysis datasets for the entire basin, for several sub-catchments inside the entire Amazon River basin and for two physical and geographical distinctive subsystems of the basin, namely upper Andean the low-lying Amazon River basin. Our results evidence that for the entire Amazon River basin the surface water balance can be considered to be in balance (P = 2225 mm.yr-1, ET= 1062 mm.yr-1, R= 965 mm.yr-1), whereas for the separated subsystems it not so clear, showing high discrepancies between observations and reanalysis datasets. In turn, the atmospheric budget does not close regardless of datasets or geographical disaggregation. Our results indicate that the amount of imbalance of the atmospheric branch of the water balance depends on the evaporation data source used. The imbalance calculated as I=(C/R)-1, where C is net moisture convergence (C= -∇Q where ∇Q is the net vertically integrated moisture divergence) and R the runoff,represents the difference between the two branches of the hydrological cycle. For the entire Amazon River basin we found a consistent negative imbalance driven by higher values of runoff, and when calculated for monthly time scales the imbalance is characterized by a high dependence on the Amazon dry season. The separated analysis performed to the Andes and Low-lying Amazonia subsystems unveils two shortcomings of the available data, namely a poor quality of the representation of surface processes in the reanalysis models (including precipitation and evapotranspiration), and the

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

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

PubMed

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

2012-09-01

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

Bagua Basin: an Archive of the Tectonic Evolution of the Northern Peruvian Andes.

NASA Astrophysics Data System (ADS)

Moreno, F.; Garzione, C. N.; George, S. W. M.; Williams, L. A.

2017-12-01

The Cenozoic sediments of the intermontane Bagua Basin contain the record of the orogenic history of the northern Peruvian Andes. This Andean segment is constituted by a relatively narrow and low elevation orogen compared to the Central Andean Plateau. Understanding the similarities and differences of the tectonic evolution between these two provinces provides insights into the processes that govern the evolution of fold-thrust belts and orogenic plateaus. We use stratigraphic and sedimentologic field observations, detrital zircons (DZ) provenance analysis and stable isotopes paleoenvironmental analysis to reconstruct the regional tectonic history. Our results reveal the evolution of Bagua Basin, as a foreland basin related to the Andean belt since late Cretaceous time. The late Cretaceous Fundo el Triunfo Fm. records shelf deposits in a backbulge setting associated with a distant orogenic load. The Early Cretaceous DZ signature contained in these deposits reveal the early exhumation of Mesozoic rocks in the forebulge. The Paleocene fluvial deposits of the Rentema Fm. and the estuarine deposits of the Eocene Series record the transition to a forebulge setting. The Jurassic and Triassic DZ signature contained in the Paleocene and Eocene deposits reveal the continued exhumation of Mesozoic rocks during forebulge migration. The fluvial-floodplain succession of the Sambimera Fm. overlays the Eocene Series, recording intermediate and proximal foredeep deposition. Sambimera deposits contains sin-depositional Cenozoic DZ populations that reveal strong magmatism in the west. Comparison of δ18O and δ13C values from Sambimera and Rentema pedogenic carbonate nodules (δ18O -9‰ vs. -5‰ and δ13C -12.5‰ vs. -10‰) suggests that the Sambimera fluvial-floodplain system was more distal from the shoreline, based on the relatively negative δ18O values, and deposited in a drier climate, based on the relatively positive δ13C values. A four million year unconformity

Rapid Geodetic Shortening Across the Eastern Cordillera of NW Argentina Observed by the Puna-Andes GPS Array

NASA Astrophysics Data System (ADS)

McFarland, Phillip K.; Bennett, Richard A.; Alvarado, Patricia; DeCelles, Peter G.

2017-10-01

We present crustal velocities for 29 continuously recording GPS stations from the southern central Andes across the Puna, Eastern Cordillera, and Santa Barbara system for the period between the 27 February 2010 Maule and 1 April 2014 Iquique earthquakes in a South American frame. The velocity field exhibits a systematic decrease in magnitude from 35 mm/yr near the trench to <1 mm/yr within the craton. We forward model loading on the Nazca-South America (NZ-SA) subduction interface using back slip on elastic dislocations to approximate a fully locked interface from 10 to 50 km depth. We generate an ensemble of models by iterating over the percentage of NZ-SA convergence accommodated at the subduction interface. Velocity residuals calculated for each model demonstrate that locking on the NZ-SA interface is insufficient to reproduce the observed velocities. We model deformation associated with a back-arc décollement using an edge dislocation, estimating model parameters from the velocity residuals for each forward model of the subduction interface ensemble using a Bayesian approach. We realize our best fit to the thrust-perpendicular velocity field with 70 ± 5% of NZ-SA convergence accommodated at the subduction interface and a slip rate of 9.1 ± 0.9 mm/yr on the fold-thrust belt décollement. We also estimate a locking depth of 14 ± 9 km, which places the downdip extent of the locked zone 135 ± 20 km from the thrust front. The thrust-parallel component of velocity is fit by a constant shear strain rate of -19 × 10-9 yr-1, equivalent to clockwise rigid block rotation of the back arc at a rate of 1.1°/Myr.

Ancient DNA Analysis Suggests Negligible Impact of the Wari Empire Expansion in Peru's Central Coast during the Middle Horizon.

PubMed

Valverde, Guido; Barreto Romero, María Inés; Flores Espinoza, Isabel; Cooper, Alan; Fehren-Schmitz, Lars; Llamas, Bastien; Haak, Wolfgang

2016-01-01

The analysis of ancient human DNA from South America allows the exploration of pre-Columbian population history through time and to directly test hypotheses about cultural and demographic evolution. The Middle Horizon (650-1100 AD) represents a major transitional period in the Central Andes, which is associated with the development and expansion of ancient Andean empires such as Wari and Tiwanaku. These empires facilitated a series of interregional interactions and socio-political changes, which likely played an important role in shaping the region's demographic and cultural profiles. We analyzed individuals from three successive pre-Columbian cultures present at the Huaca Pucllana archaeological site in Lima, Peru: Lima (Early Intermediate Period, 500-700 AD), Wari (Middle Horizon, 800-1000 AD) and Ychsma (Late Intermediate Period, 1000-1450 AD). We sequenced 34 complete mitochondrial genomes to investigate the potential genetic impact of the Wari Empire in the Central Coast of Peru. The results indicate that genetic diversity shifted only slightly through time, ruling out a complete population discontinuity or replacement driven by the Wari imperialist hegemony, at least in the region around present-day Lima. However, we caution that the very subtle genetic contribution of Wari imperialism at the particular Huaca Pucllana archaeological site might not be representative for the entire Wari territory in the Peruvian Central Coast.

On the quality of climate proxies derived from newspaper reports - a case study

NASA Astrophysics Data System (ADS)

Gallego, D.; García-Herrera, R.; Prieto, R.; Peña-Ortiz, C.

2008-02-01

One of the main problems in climate reconstruction from documentary sources is the evaluation of the quality of non instrumental meteorological records in absence of instrumental observations to perform a calibration. In these cases it is mandatory to envision different approaches to assess the climatic signal in a reconstruction. This work is aimed to test the consistency of a snow frequency reconstruction in the central Argentinean Andes by studying the synoptic patterns related to the occurrence of precipitation in this area. While the original reconstruction covers the period between 1885 and 1996, the insufficiency of overlapping instrumental data limited the calibration to a short 15-year interval. In this paper we evaluate the performance of the reconstructed series for the entire 45-year period between 1958 and 1996 by analyzing the displacement in the jet stream and the patterns of geopotential height related to anomalies in the reconstructed snow frequency series. Previous works have linked the precipitation in the central Andes to the ENSO through the Pacific South American mode. We also have found this connection between ENSO and the reconstructed precipitation. Finally, it is shown that the ENSO relationship is the cause of a significant link between the precipitation anomalies in the central Argentinean Andes and the ice extent around the Antarctic Peninsula.

Glacial and volcanic evolution on Nevado Coropuna (Tropical Andes) based on cosmogenic 36Cl surface exposure dating

NASA Astrophysics Data System (ADS)

Úbeda, J.; Palacios, D.; Vázquez-Selém, L.

2012-04-01

flow of 6 ka, to the East, where we dated two units similar to the previous one at 2 and <1ka. Bromley, G.R. et al., 2009. Relative timing of last glacial maximum and late-glacial events in the central tropical Andes. Quaternary Science Reviews, 1-13. Bromley, R.M. et al., 2011. Glacier fluctuations in the southern Peruvian Andes during the late-glacial period, constrained with cosmogenic 3He. Journal of Quaternary Science, 26 (1): 37-43. Fritz, S.C. et al., 2007. Lake Titicaca 370KYr LT01-2B Sediment Database. Lake Titicaca 370KYr LT01-2B Sediment Data. IGBP PAGES/World Data Center-A for Paleoclimatology Data Contribution Series # 92-008. NOAA/NGDC Paleoclimatology Program. Boulder (EEUU). Lea, D.W. et al., 2006. Galápagos TR163-22 Foraminiferal ^18O and Mg/Ca Data and SST Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2006-090. NOAA/NCDC Paleoclimatology Program, Boulder (EEUU). Research funded by CGL2009-7343 project, Government of Spain.

Alluvial to lacustrine sedimentation in an endorheic basin during the Mio-Pliocene: The Toro Negro Formation, Central Andes of Argentina

NASA Astrophysics Data System (ADS)

Ciccioli, Patricia L.; Marenssi, Sergio A.; Amidon, William H.; Limarino, Carlos O.; Kylander-Clark, Andrew

2018-07-01

A 2400 m-thick sedimentary column belonging to the Toro Negro Formation was recorded along the Quebrada del Yeso, Sierra de Los Colorados (Vinchina Basin), La Rioja province, NW Argentina. The Vinchina basin is a good example of a closed basin surrounded by the Precordillera fold and thrust belt to the west and basement-cored blocks to the north, south (Western Sierras Pampeanas) and east (Sierra de Famatina). Seven facies associations (FA) are described and interpreted to represent fluvial, lacustrine and alluvial environments developed in the southern part of the Vinchina basin from the Late Miocene until the earliest Pleistocene. The depositional evolution of the formation was divided in four phases. Phase I (∼7-6.6 Ma) represents sedimentation in medial (FA I) to distal (FA II) parts of a southward directed distributive fluvial system with a retrogradational pattern. During phase II (6.6-6.1Ma), the distributive fluvial system was replaced by a mixed clastic-evaporitic shallow lake (FA III) in a high aggradational basin. In phase III (∼6.1-5 Ma) the eastward progradation of a fluvial system (FA IV) was recorded as a distal clastic wedge. Finally, phase IV (∼5-2.4Ma) records two depositional cycles of proximal clastic wedge progradation of fluvial-dominated piedmonts (FAV, FAVII) from the southwest (Sierra de Umango) and/or the west (Precordillera) with an intervening playa lake (FA VI). Two new U-Pb ages obtained from zircons in volcanic ash layers confirm the Late Miocene age of the lower member of the Toro Negro Formation and permit a tight correlation with the central part of the basin (Quebrada de La Troya section). The sedimentation rate calculated for the dated lacustrine-fluvial interval is higher than the corresponding one in La Troya area suggesting a higher subsidence in the southern part of the basin. During the Late Miocene (∼7-6.6Ma) the ephemeral drainage was controlled by an arid to semiarid climate and initially dissipated mostly

The Flying Telescope: How to Reach Remote Areas in the Colombian Andes for Astronomy Outreach

NASA Astrophysics Data System (ADS)

Seidel, M. K.; Buelhoff, K.

2016-12-01

The project Cielo y Tierra, Spanish for Sky and Earth, was undertaken in order to bring astronomy and ecology to remote villages throughout Colombia using sustainable transport. This transport included three horses and two paragliders. The innovative approach of the expedition helped to keep an extremely low budget whilst making it possible to cross the Colombian Andes from northeast to southwest. This article will show how projects like these can succeed, the need for this kind of project, and the possible impact, with this project reaching more than 1500 people. We hope to encourage others not to be afraid of going into countries like Colombia on a low-budget educational expedition. The success of this project shows that outreach and education projects are possible in these remote areas where little or no governmental or other support reaches.

Understanding Recent Trends in Freezing Level Height over the Tropical Andes Mountains of South America: An Investigation of Reanalysis Products and GEOSCCM Integrations.

NASA Astrophysics Data System (ADS)

Zaitchik, B. F.; Russell, A.; Gnanadesikan, A.

2015-12-01

As the global climate warms, the height of the 0°C isotherm - aka the freezing level height (FLH) - rises, especially over mountainous regions. Over the past few decades, FLH in the tropical Andes Mountains of South America has been rising at a rate that is 2 to 3 times faster than would be expected considering the zonally-averaged upper troposphere temperature trends and the recent cooling of Pacific Ocean sea surface temperatures. Rising FLH could have devastating impacts in this region where most of the dry season runoff comes from seasonal snow melt and glacial melt. Yet, is unclear why FLH is rising so rapidly in this particular area and what the quantitative implications will be for tropical Andean water resources. Reanalysis products tend to disagree on the spatial pattern and strength of FLH changes which confounds the issue by making it difficult to uncover the driving mechanisms of these local changes in FLH. Indeed, there are several possible factors that may be contributing to the unprecedented rise in FLH over the Andes (above and beyond the normally expected effects of greenhouse gases) of which the most likely actors are: changes in the state of the tropical Pacific Ocean, changes in sea surface temperatures in the Atlantic Ocean, shifts in the Hadley cell, indirect effects of stratospheric ozone depletion and recent recovery, and local thermodynamic land-atmosphere feedbacks. To better understand the changes in FLH, which will ultimately contribute to the effort to predict effects on Andean water resources, we analyze FLH in several forcing-separated integrations of the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM). By separating out the various forcings (greenhouse gases, sea surface temperatures, ozone depleting substances, volcanic eruptions, and solar fluctuations), we are able to develop hypotheses for mechanistic drivers of FLH changes which can be rigorously tested. These efforts will contribute to the understanding of

Early neogene history of the central American arc from Bocas del Toro, western Panama

USGS Publications Warehouse

Coates, Anthony G.; Aubry, Marie-Pierre; Berggren, William A.; Collins, Laurel S.; Kunk, Michael J.

2003-01-01

A newly discovered sequence of lower to middle Miocene rocks from the eastern Bocas del Toro archipelago, western Panama, reveals the timing and environment of the earliest stages in the rise of the Isthmus of Panama in this region. Two new formations, the Punta Alegre Formation (lower Miocene, Aquitanian to Burdigalian) and the Valiente Formation (middle Miocene, Langhian to Serravallian), are here named and formally described. The Punta Alegre Formation contains a diagnostic microfauna of benthic and planktic foraminifera and calcareous nannofossils that indicate deposition in a 2000-m-deep pre-isthmian neotropical ocean from as old as 21.5–18.3 Ma. Its lithology varies from silty mudstone to muddy foraminiferal ooze with rare thin microturbidite layers near the top. The Valiente Formation, which ranges in age from 16.4 to ca. 12.0 Ma, lies with slight angular unconformity on the Punta Alegre Formation and consists of five lithofacies: (1) columnar basalt and flow breccia, (2) pyroclastic deposits, (3) coarse-grained volcaniclastic deposits, (4) coral-reef limestone with diverse large coral colonies, and (5) marine debris-flow deposits and microturbidites. These lithofacies are interpreted to indicate that after ca. 16 Ma a volcanic arc developed in the region of Bocas del Toro and that by ca. 12 Ma an extensively emergent archipelago of volcanic islands had formed. 39Ar/40Ar dating of basalt flows associated with the fossiliferous sedimentary rocks in the upper part of the Valiente Formation strongly confirms the ages derived from planktic foraminifera and nannofossils. Paleobathymetric analysis of the two new formations in the Valiente Peninsula and Popa Island, in the Bocas del Toro archipelago, shows a general shallowing from lower- through upper-bathyal to upper-neritic and emergent laharic and fluviatile deposits from ca. 19 to 12 Ma. The overlying nonconformable Bocas del Toro Group contains a lower transgressive sequence ranging from basal nearshore

Altitudinal gradients, midwinter melt, and wind effects on snow accumulation in semiarid midlatitude Andes under La Niña conditions

NASA Astrophysics Data System (ADS)

Ayala, A.; McPhee, J.; Vargas, X.

2014-04-01

The Andes Cordillera remains a sparsely monitored and studied snow hydrology environment in comparison to similar mountain ranges in the Northern Hemisphere. In order to uncover some of the key processes driving snow water equivalent (SWE) spatial variability, we present and analyze a distributed SWE data set, sampled at the end of accumulation season 2011. Three representative catchments across the region were monitored, obtaining measurements in an elevation range spanning 2000 to 3900 m asl and from 32.4° to 34.0°S in latitude. Climatic conditions during this season corresponded to a moderate La Niña phenomenon, which is generally correlated with lower-than normal accumulation. Collected measurements can be described at the regional and watershed extents by altitudinal gradients that imply an increase by a factor of two in snow depth between 2200 and 3000 m asl, though with significant variability at the upper sites. In these upper sites, we found north-facing, wind-sheltered slopes showing 25% less average SWE values than south-facing, wind-exposed ones. This suggests that under these conditions, solar radiation dominated wind transport effects in controlling end-of-winter variability. Nevertheless, we found clusters of snow depth measurements above 3000 m asl that can be explained by wind exposure differences. This is the first documented snow depth data set of this spatial extent for this region, and it is framed within an ongoing research effort aimed at improving understanding and modeling of snow hydrology in the extratropical Andes Cordillera.

Evaluation of ERTS-1 data applications to geologic mapping, structural analysis and mineral resource inventory of South America with special emphasis on the Andes Mountain region

NASA Technical Reports Server (NTRS)

Carter, W. D. (Principal Investigator)

1973-01-01

The author has identified the following significant results. ERTS-1 data is ideally suited for small-scale geologic mapping and structural analysis of remote, inaccessible areas such as the Andes of South America. The synoptic view of large areas, low sun-angle and multispectral nature of the images provide the right ingredients for improving existing geologic and other maps of the regions. In most areas it has been possible to compile geologic, drainage, and cultural interpretive overlays to individual scenes mainly using MSS bands 4, 5, and 7. A test image mosaic using MSS band 6 is being compiled for Test Area 7 (La Paz, Bolivia). It will be at a scale of 1:1,000,000 and cover 4 x 6 degrees of latitude and longitude and will serve as a compilation base on which to join the overlays. Repetitive data shows changes in river channels and sedimentation plumes, changes in lake shorelines, and surface moisture distribution. Vegetation and snow line changes in the Andes have been recognized. A year of seasonal data, however, has not yet been acquired due to tape recorder failure.

Ancient DNA Analysis Suggests Negligible Impact of the Wari Empire Expansion in Peru’s Central Coast during the Middle Horizon

PubMed Central

Barreto Romero, María Inés; Flores Espinoza, Isabel; Cooper, Alan; Fehren-Schmitz, Lars

2016-01-01

The analysis of ancient human DNA from South America allows the exploration of pre-Columbian population history through time and to directly test hypotheses about cultural and demographic evolution. The Middle Horizon (650–1100 AD) represents a major transitional period in the Central Andes, which is associated with the development and expansion of ancient Andean empires such as Wari and Tiwanaku. These empires facilitated a series of interregional interactions and socio-political changes, which likely played an important role in shaping the region’s demographic and cultural profiles. We analyzed individuals from three successive pre-Columbian cultures present at the Huaca Pucllana archaeological site in Lima, Peru: Lima (Early Intermediate Period, 500–700 AD), Wari (Middle Horizon, 800–1000 AD) and Ychsma (Late Intermediate Period, 1000–1450 AD). We sequenced 34 complete mitochondrial genomes to investigate the potential genetic impact of the Wari Empire in the Central Coast of Peru. The results indicate that genetic diversity shifted only slightly through time, ruling out a complete population discontinuity or replacement driven by the Wari imperialist hegemony, at least in the region around present-day Lima. However, we caution that the very subtle genetic contribution of Wari imperialism at the particular Huaca Pucllana archaeological site might not be representative for the entire Wari territory in the Peruvian Central Coast. PMID:27248693

The Relative Impact of Climate Change on the Extinction Risk of Tree Species in the Montane Tropical Andes.

PubMed

Tejedor Garavito, Natalia; Newton, Adrian C; Golicher, Duncan; Oldfield, Sara

2015-01-01

There are widespread concerns that anthropogenic climate change will become a major cause of global biodiversity loss. However, the potential impact of climate change on the extinction risk of species remains poorly understood, particularly in comparison to other current threats. The objective of this research was to examine the relative impact of climate change on extinction risk of upper montane tree species in the tropical Andes, an area of high biodiversity value that is particularly vulnerable to climate change impacts. The extinction risk of 129 tree species endemic to the region was evaluated according to the IUCN Red List criteria, both with and without the potential impacts of climate change. Evaluations were supported by development of species distribution models, using three methods (generalized additive models, recursive partitioning, and support vector machines), all of which produced similarly high AUC values when averaged across all species evaluated (0.82, 0.86, and 0.88, respectively). Inclusion of climate change increased the risk of extinction of 18-20% of the tree species evaluated, depending on the climate scenario. The relative impact of climate change was further illustrated by calculating the Red List Index, an indicator that shows changes in the overall extinction risk of sets of species over time. A 15% decline in the Red List Index was obtained when climate change was included in this evaluation. While these results suggest that climate change represents a significant threat to tree species in the tropical Andes, they contradict previous suggestions that climate change will become the most important cause of biodiversity loss in coming decades. Conservation strategies should therefore focus on addressing the multiple threatening processes currently affecting biodiversity, rather than focusing primarily on potential climate change impacts.

The Relative Impact of Climate Change on the Extinction Risk of Tree Species in the Montane Tropical Andes

PubMed Central

Tejedor Garavito, Natalia; Newton, Adrian C.; Golicher, Duncan; Oldfield, Sara

2015-01-01

There are widespread concerns that anthropogenic climate change will become a major cause of global biodiversity loss. However, the potential impact of climate change on the extinction risk of species remains poorly understood, particularly in comparison to other current threats. The objective of this research was to examine the relative impact of climate change on extinction risk of upper montane tree species in the tropical Andes, an area of high biodiversity value that is particularly vulnerable to climate change impacts. The extinction risk of 129 tree species endemic to the region was evaluated according to the IUCN Red List criteria, both with and without the potential impacts of climate change. Evaluations were supported by development of species distribution models, using three methods (generalized additive models, recursive partitioning, and support vector machines), all of which produced similarly high AUC values when averaged across all species evaluated (0.82, 0.86, and 0.88, respectively). Inclusion of climate change increased the risk of extinction of 18–20% of the tree species evaluated, depending on the climate scenario. The relative impact of climate change was further illustrated by calculating the Red List Index, an indicator that shows changes in the overall extinction risk of sets of species over time. A 15% decline in the Red List Index was obtained when climate change was included in this evaluation. While these results suggest that climate change represents a significant threat to tree species in the tropical Andes, they contradict previous suggestions that climate change will become the most important cause of biodiversity loss in coming decades. Conservation strategies should therefore focus on addressing the multiple threatening processes currently affecting biodiversity, rather than focusing primarily on potential climate change impacts. PMID:26177097

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

USGS Publications Warehouse

Tosdal, R.M.

1996-01-01

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

Geochemistry and organic facies of La Luna-Tres Esquinas cycle: Maturity, biomarkers and kerogen issues

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivares, C.; Lorente, M.A.; Cassani, F.

1996-08-01

Four surface sections from the Venzuelan Andes were chosen for this study. The results show interesting trends for exploration of the Andean Belt. In the Eastern Andes (Trujillo), sections San Lazaro and Chejende yield thick, post-mature, highly tectonically disturbed La Luna Formation. San Lazaro section has a fault contact showing La Luna post-mature, inertinitic shales in contact with gray shales, ftanites and carbonates bearing marginally mature, highly fluorescent organic gels. Biomarkers show a high level of hopanes, predominance of C27/C29, and S/R ratio=64% characteristic of marine, moderate mature organic matter. Chejende section has almost the same pattern of marine organicmore » matter (COT=9%) but post-mature. In the Central Andes (Merida), El Valle and San Javier sections yield extremely rich source rocks with very different organic matter. El Valle section (Tres Esquinas Member) has very rich structured algal matter (COT=8%), marginally mature, which is correlated with a short term carbon isotope ({delta}{sup 13}C) fluctuation found in the Campanian-Santonian (anoxic?) cycle. The abundance of C27/C29, and high levels of hopanes are related to marine anoxic conditions. The San Javier section shows evidence of a very rich type I/II kerogen, bearing algal-bacterial amorphous masses, marginally mature and rich (COT=3%); this pattern matches with the abundance of C27/C29 as well as with the ratio S/R=64%, which means moderate maturity. From these results, two provinces can be separated today: a highly tectonized, post-mature, Eastern Andes Province and a very rich, marginally mature, Central Andes Province.« less

Volcano-stratigraphy and 40Ar/ 39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of southeast Peru

NASA Astrophysics Data System (ADS)

Cheilletz, Alain; Clark, Alan H.; Farrar, Edward; Pauca, Guido Arroyo; Pichavant, Michel; Sandeman, Hamish A.

1992-04-01

A total of 1400 m of ignimbritic ash-flow tuffs distributed in five cross-sections and extending from the pre-Neogene base to the uppermost flows were studied in the Miocene Macusani ignimbrite basin (southeast Peru). Volcano-stratigraphic interpolation and precise 40Ar/ 39Ar dating of sanidine, biotite, and rhyolitic glass from the ash-flow tuffs give rise to a southwest-northeast correlation chart subdivided into six volcanic cycles or fundamental cooling units i.e., (1) 10.0 ± 0.5; (2) 7.8-8.0 ± 0.1; (3) 7.5 ± 0.1; (4) 7.3 ± 0.1; (5) 6.8-7.0 ± O.1; and (6) 6.7 ± O.1 Ma. These delimit two brief e 10 ± 1 and 7 ± 1 Ma, which are sensibly synchronous with the Quechua 2 and Quechua 3 compressional events characterizing the tectonic regime in the Central Andes. This close relationship between tectonic pulses and felsic magmatic activity adds a supplementary constraint to models of the Miocene tectono-magmatic evolution of the Cordillera Oriental. The stratigraphic relationships of the uranium mineralization of the Macusani field are defined for the first time: the stratiform-stratabound occurrences are restricted to three main cooling units dated at 7.8, 7.5 and 6.9-6.8 Ma which constitute a maximum age for uranium deposition.

The Little Ice Age in the tropical Andes

NASA Astrophysics Data System (ADS)

Jomelli, V.; Cooley, D.; Naveau, P.; Rabatel, A.

2003-12-01

The period known as the Little Ice Age, from the 17th to the 19th century, brought a cooling of around 0.5 degrees Celsius as well as varyingly humid episodes Eurasia and North America. Because of a lack of long paleoclimatic time series in the tropical Andes, it is still unclear if similar cooling occurred over these tropical and Southern Hemisphere regions. Furthermore, if changes did take place, it is currently not well established if they were temporally synchronous or shifted with respect of the variations in the Northern Hemisphere or the globe. To look into this important climatic question and for advancing our understanding of the past climate links between the tropics and higher latitudes, 25 glaciers located in Bolivia and in Peru were carefully selected. Glacial activity and environmental changes were analyzed using lichenometry. Largest lichen diameters were measured in the different glacial basins. To better analyze these maximum diameters and to more appropriately represent uncertainty and the character of this collected data, age estimates of the different moraine systems were derived using extreme value theory rather than the traditional averaging. The results reveal two particular phases of glacier growth, 1550-1600 and 1800-1850. These two phases have also been identified in other proxy records, such as ice-cores and documentary data (particularly from church chronicles). In order to understand the climatic changes that could have contributed to the glacial variations, a simple model based on both precipitations and temperatures is applied to estimate mass balance questions in the basins. A cooling of the order of 0.5 C seems to be the most consistent with the data. Finally, these findings are compared with the better-known histories of Northern Hemisphere mid-latitude glaciers.

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

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

Reconstructing climate variability using tree rings and glacier fluctuations in the southern Chilean Andes

NASA Astrophysics Data System (ADS)

Aravena, Juan-Carlos

This thesis investigates climate variability in southern South America (south of 40°S) during the last 400 years using instrumental data, tree rings and glacier fluctuations. The dominant spatial and temporal patterns of a network of 25 homogeneous instrumental rainfall records were analyzed and used to define four regional precipitation series (1950-2000): northwestern Patagonia, central Patagonia, Patagonian plains-Atlantic, and southern Patagonia. Time series analysis of these regional patterns shows marked decadal variability for northwestern and central Patagonia, 3-7 year oscillations for Patagonian plains-Atlantic region, and a strong biannual oscillatory mode for southern Patagonia. Regional rainfall appears to be strongly influenced by Antarctic circulation modes (Antarctic Oscillation Index) while the ENSO influence on rainfall variability is less evident. Highly significant correlation of precipitation on the west coast of Patagonia with the pressure gradient between the subtropical eastern Pacific and the high-latitude south eastern Pacific is confirmed. A new network of 18 tree-ring chronologies from Pilgerodendron uviferum, an endemic conifer, was developed from sites along the western flank of the southern Andes. Highly significant series inter-correlation values ranged between 0.44 and 0.629 while mean sensitivity values ranged between 0.186 and 0.252. The series have relatively few missing rings (0.77-0.12% in individual chronologies). The oldest Pilgerodendron sampled to date was 859 years old while the chronology length ranged between 239 and 633 years. Ring-width series are correlated with precipitation but there were difficulties developing strong precipitation/ring-width relationships for individual stations/sites. However, two regional rainfall reconstructions were developed based on the inverse correlation between Pilgerodendron radial growth and the precipitation of northwestern and southern Patagonia. The reconstruction for spring

The acid and alkalinity budgets of weathering in the Andes-Amazon system: Insights into the erosional control of global biogeochemical cycles

NASA Astrophysics Data System (ADS)

Torres, Mark A.; West, A. Joshua; Clark, Kathryn E.; Paris, Guillaume; Bouchez, Julien; Ponton, Camilo; Feakins, Sarah J.; Galy, Valier; Adkins, Jess F.

2016-09-01

The correlation between chemical weathering fluxes and denudation rates suggests that tectonic activity can force variations in atmospheric pCO2 by modulating weathering fluxes. However, the effect of weathering on pCO2 is not solely determined by the total mass flux. Instead, the effect of weathering on pCO2 also depends upon the balance between 1) alkalinity generation by carbonate and silicate mineral dissolution and 2) sulfuric acid generation by the oxidation of sulfide minerals. In this study, we explore how the balance between acid and alkalinity generation varies with tectonic uplift to better understand the links between tectonics and the long-term carbon cycle. To trace weathering reactions across the transition from the Peruvian Andes to the Amazonian foreland basin, we measured a suite of elemental concentrations (Na, K, Ca, Mg, Sr, Si, Li, SO4, and Cl) and isotopic ratios (87Sr/86Sr and δ34S) on both dissolved and solid phase samples. Using an inverse model, we quantitatively link systematic changes in solute geochemistry with elevation to downstream declines in sulfuric acid weathering as well as the proportion of cations sourced from silicates. With a new carbonate-system framework, we show that weathering in the Andes Mountains is a CO2 source whereas foreland weathering is a CO2 sink. These results are consistent with the theoretical expectation that the ratio of sulfide oxidation to silicate weathering increases with increasing erosion. Altogether, our results suggest that the effect of tectonically-enhanced weathering on atmospheric pCO2 is strongly modulated by sulfide mineral oxidation.

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

NASA Astrophysics Data System (ADS)

Ramos, Yuddy; Goïta, Kalifa; Péloquin, Stéphane

2016-04-01

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

Fluctuations of Glaciar Esperanza Norte in the north Patagonian Andes of Argentina during the past 400 yr

NASA Astrophysics Data System (ADS)

Ruiz, L.; Masiokas, M. H.; Villalba, R.

2012-06-01

The number of studies of Little Ice Age (LIA) glacier fluctuations in southern South America has increased in recent years but is largely biased towards sites in the south Patagonian Andes. In this paper we present a detailed record of length and areal fluctuations of Glaciar Esperanza Norte (GEN) in the north Patagonian Andes of Argentina during the past four centuries. The GEN record was reconstructed through the dendro-geomorphological dating of moraines and the analysis of satellite imagery, aerial photographs and documentary material complemented with extensive field surveys. The maximum LIA extent at GEN was associated with an outer moraine dated to the mid 17th century. At least 19 subsequent readvances or standstills evidenced by morainic ridges were identified inside the most extensive LIA moraine. The dating and spacing of these moraines and the additional information available indicate that the ice front retreated much more rapidly during the 20th century than during earlier centuries. Comparison with the record of LIA fluctuations of Glaciar Frías, an ice mass of similar characteristics located 110 km to the north of GEN, shows a similar pattern of recession over the past 400 yr. Both glacier records have the peak LIA event occurring roughly during the same interval (early-mid 17th century) and show a minor readvance during the 1970s, but there are still a few discrepancies in the dating of some inner moraines. These differences may be due to local, specific factors or associated with the inherent uncertainties in the dating of the moraines. The chronologies of GEN and Frías are among the most detailed currently available in Patagonia, but a larger number of study sites is needed to develop robust, regionally representative glacier chronologies. Detailed glaciological, geomorphological and meteorological data are also needed to understand the glacier-climate relationships in this region and develop reliable paleoclimatic reconstructions.

The Cuernos del Paine mountains in Torres del Paine National Park, Chile, during NASA's AirSAR 2004 campaign

NASA Image and Video Library

2004-03-11

The Cuernos del Paine mountains in Torres del Paine National Park, Chile, during NASA's AirSAR 2004 campaign. AirSAR 2004 is a three-week expedition in Central and South America by an international team of scientists that is using an all-weather imaging tool, called the Airborne Synthetic Aperture Radar (AirSAR), located onboard NASA's DC-8 airborne laboratory. Scientists from many parts of the world are combining ground research with NASA's AirSAR technology to improve and expand on the quality of research they are able to conduct. Founded in 1959, Torres del Paine National Park encompasses 450,000 acres in the Patagonia region of Chile. This region is being studied by NASA using a DC-8 equipped with an Airborne Synthetic Aperture Radar (AirSAR) developed by scientists from NASA’s Jet Propulsion Laboratory. This is a very sensitive region that is important to scientists because the temperature has been consistently rising causing a subsequent melting of the region’s glaciers. AirSAR will provide a baseline model and unprecedented mapping of the region. This data will make it possible to determine whether the warming trend is slowing, continuing or accelerating. AirSAR will also provide reliable information on ice shelf thickness to measure the contribution of the glaciers to sea level.

Keeping watch over Colombia’s slumbering volcanoes

USGS Publications Warehouse

Ordoñez, Milton; López, Christian; Alpala, Jorge; Narváez, Lourdes; Arcos, Dario; Battaglia, Maurizio

2015-01-01

Located in the Central Cordillera (Colombian Andes), Nevado del Ruiz is a volcanic complex, topped by glaciers, rising 5,321 m above sea level. A relatively small explosive eruption from Ruiz's summit crater on November 13, 1985, generated an eruption column and sent a series of pyroclastic flows and surges across the volcano's ice-covered summit. Pumice and meltwater produced by the hot pyroclastic flows and surges swept into gullies and channels on the slopes of Ruiz as a series of lahars. Within two hours of the beginning of the eruption, lahars had traveled 100 km and left behind a wake of destruction: more than 25,000 people were killed (23,000 in the town of Armero and 2,000 in the town of Chinchiná), about 5,000 injured, and more than 5,000 homes destroyed along the Chinchiná, Gualí, and Lagunillas rivers.

The interaction between parent material, climate and volcanism as the major soil forming factor in the Ecuadorian high Andes region

NASA Astrophysics Data System (ADS)

Buytaert, W.; Duyck, H.; Dercon, G.; Deckers, J.; Wyseure, G.

2003-04-01

The high Andes region of Ecuador and Colombia (>3500m a.s.l.) is covered by the so-called páramo ecosystem, characterised by a cold climate, a typical grass or small shrub vegetation and volcanic soils. Soil profiles of the paramo in the Austro Ecuatoriano, South Ecuador, were studied in order to reveal genetic relationships with geology, volcanic ash deposits, climate and land use. A gradual diminuation of Andic properties was found, related to the distance of the pedon to the active volcanoes of the Northern Volcanic Zone of the Andes. Pedons in the north of the region, closer to these volcanoes (Sangay, Tungurahua) are classified as non-allophanic Histic Andosols. The influence of the vicinity of the volcanoes leads to a higher oxalate extractable aluminium and iron. The genesis of the Andosols seems to be strongly related to the presence and thickness of volcanic ash depositions. The limit of these depositions is situated south of the city of Cuenca. Pedons further to the south are classified as Histosols. However, they also have clear Andic properties. Several differences in chemical properties between the Western and Eastern cordilleras where found, that are most probable related with a difference in mother material, and maybe also a different climatic regime. Correlation of the chemical properties with land use reveals that no chemical differences can be found that are invoked by occupying natural Andosols for agricultural purposes, within the first five years of cultivation. At last, the conclusions were used to revisit the World Reference Base for Soil Resources in order to sharpen up differenciation between Andosols and Histosols.