Alto Paraguay Research Articles

Twenty-eight new and significant departmental reptile records for Paraguay

Twenty-eight new distribution records are reported for twenty-seven species of Paraguayan reptiles. Ten of these species are considered threatened at the national level (6 EN, 2 VU, 2 DD). Nineteen new departmental records are documented: Phrynops hilarii (Chelidae) in Misiones department; Homonota marthae, Phyllopezus przewalskii (Phyllodactylidae), Philodryas baroni and P. psammophidea (Colubridae) in Presidente Hayes department; Teius oculatus (Teiidae), Cercosaura schreibersii (Gymnophthalmidae), Ophiodes intermedius (Diploglossidae), Amphisbaena mertensii (Amphisbaenidae), Boiruna maculata and Philodryas aestiva (Colubridae) in Caazapá department; Amphisbaena alba (Amphisbaenidae) in Caaguazú and Cordillera departments; Bothrops moojeni (Viperidae), Eunectes notaeus (Boidae), Helicops leopardinus and Hydrodynastes gigas (Colubridae) in Guairá department; Apostolepis dimidiata, Atractus paraguayensis and Mussurana bicolor (Colubridae) in Itapúa department; and Epicrates crassus (Boidae) and Phalotris nigirilatus (Colubridae) in Concepción department. Significant range extensions of threatened or poorly-known species are also documented: The known distribution of the Endangered Salvator duseni (Teiidae) is extended 128.5 km to the east within Canindeyú department; that of the Vulnerable Boa occidentalis is extended 109.2 km to the southwest within Boquerón department; that of the Vulnerable Epicrates alvarezi (Boidae) is extended 136.6 km to the west within Boquerón department and 172.4 km to the northeast into Alto Paraguay department; that of Caiman yacare (Alligatoridae) is extended 132 km west within Boquerón department to the northern reaches of the Pilcomayo River. We also document an additional specimen of the rare Philodryas agassizii (Colubridae) and confirmation of the occurrence of the disputed form Phalotris “punctatus” in Paraguay.

Carbon cycle of native pasture-based beef cattle production systems in the Pantanal area of the Paraguayan Chaco

The objective of the present study was evaluate the carbon cycle in Paraguayan Pantanal area native grassland ecosystems by measuring pasture growth and simulating animal grazing. For this purpose, soil analyzes, annual productivity and forage quality were carried out in 4 agro ecological sites of a 20,000 ha located in Alto Paraguay Department (21º 1' 29.85”S and 58º 17' 38.55” W), from Dec 21, 2019 to Feb 12, 2020. In the selected location was installed an 8 m x 8 m exclusion cage with three treatments (4 m2 subplots), corresponding to cutting intervals (35, 70 and 105 CI days, respectively). The seasonal dry matter (DM) production and the pasture growth rate, adjusted stocking rate at three production levels (50, 70 and 75% breeding rate, respectively), carbon contained in organic matter (OM), root system and aerial biomass accumulated in ground were evaluated. The data were compared using Tukey test with a 5% probability. The emission of greenhouse gases (GG) per head and per ha was simulated and adjusted to breeding livestock to a total area of 6,600 ha and 5,000 grassland ha. The 35 days CI presented 32% higher productivity than 105 days CI in carbon sequestration. The best capture/emission balance per ha was observed in 35 days CI with the 50% breeding rate, producing 1,481 kg of CO2-e ha-1, intensifying and increasing the breeding rate to 75%, the balance decreases to 1,294 kg of CO2-e ha-1. In all cases, livestock in grassland has presented a positive balance when accounting for GG per unit area.

Mapping of suspended sediment transport using acoustic methods in a Pantanal tributary.

Generally, fluvial systems are used for different objectives including energy production, water supply, recreation, and navigation. Thus, many impacts must be considered with their use. An understanding of sediment dynamics in fluvial systems is often of value for a variety of objectives, given that erosion and depositional processes can change the fluvial system morphology and can substantially alter the fluvial environment. In this sense, sediment monitoring is important because it helps to explain and quantify sediment dynamics in the environment. Hence, this study presents an innovative sediment monitoring technique: the use of the acoustic Doppler current profiler, commonly used to obtain discharge measurements, to obtain suspended sediment concentration (SSC). This paper aims to describe the application of additional corrections to the ADP-M9 signal to obtain SSC from measurement campaigns that used the ADP only for discharge measurements. The analyses were based on traditional sediment sampling methods and discharge measurements, with the ADP-M9, from 7 field campaigns at the Taquari River, a major tributary from the Alto Paraguay Basin, in the Pantanal Biome, known as the largest freshwater wetland system in the world. The correlation was assessed considering the following: (a) the equipment frequency operation mode (Smart Pulse or Fixed Frequency) and (b) by checking the influence of the sediment attenuation coefficient. Furthermore, extrapolation was conducted in filtered and unmeasured areas of the ADP to map the suspended sediment concentration over the entire cross section. Results indicate that ADP correlations can be an effective tool for estimating SSC in the Taquari River when samples cannot be collected. Correlations could be applied to past and future ADP measurements made at the location where the correlation was created, as long as similar environmental conditions are present as when the correlation was developed. The described technique can expand the amount of sediment data available at a monitoring site even with reduced traditional sampling and by leveraging instruments used for other monitoring purposes.

Chagas Disease Vectors of Paraguay: Entomoepidemiological Aspects of Triatoma sordida (Stål, 1859) and Development of an Identification Key for Paraguayan Triatomines Based on Cytogenetics Data.

Approximately 150,000 people are living with Chagas disease in Paraguay. Although the country has been since 2008 considered as one of the countries that succeeded in interrupted the vector transmission of Chagas by Triatoma infestans in houses of the eastern region, there are nine other species notified in the country that are potential vectors and also deserve attention from vector control programs. Thus, we carried out an entomoepidemiological study of T. sordida in the eastern and western regions of the country and we developed an identification key for Paraguay's triatomines based on cytogenetic data. Between the years 2003 to 2004, 271 specimens of T. sordida were captured in domestic, peridomestic, and wild ecotopes, with 131 insects caught in the eastern (Alto Paraguay, Boquerón and Pte. Hayes) and 140 in the western region of Paraguay (Guairá and Paraguarí). High rates of peridomicillary infestation were observed for both regions. Besides that, the natural infection of the captured insects was detected by optical microscopy in 12% and 10%, and by PCR in 21% and 20% in the eastern and western regions, respectively. Based on cytogenetic data from nine of ten species notified in Paraguay, an identification key was developed to differentiate all taxa. Thus, given the vectorial importance of T. sordida, we highlight the need for continued attention from Paraguay's vector control programs for this species. Further, we provide a taxonomic key that assists in the correct classification of Paraguayan triatomines.

Shortening history of the Neoproterozoic oroclinal bending in Paraguay belt, Central Brazil, based on structural interpretation of field work and high resolution aerogeophysical data

Different phases of the orogen's evolutionary history can be geometrically restored by identifying associated tectonic features in the thrust-and-fold belts in the foreland basin. The geometry and fold styles allow understanding the rate of crustal shortening of the Paraguay Belt Neoproterozoic oroclinal. We suggest that high resolution airborne geophysical data provides critical information to understand the tectonic history of Brasiliano fold belts. Geophysical studies integrated to structural analysis in field mapping may unveil the crustal architecture as well as the sequence of events of rocks exposed in two structural windows of the basement in the region of Planalto da Serra and Nova Xavantina, in the state of Mato Grosso, northern segment of the Paraguay Belt, Central Brazil.The evolutive history of rocks exposed southwards of the Amazonian craton margin represents extensional tectonics followed by the development of a passive margin. It is estimated that the original width of the depositional space was ~350 km during the formation of the hyperextended platform and, after the intense shortening during the Brasiliano orogenesis, the oroclinal was restricted to ~130 km wide, in the post-deformation phase. Planalto da Serra region is characterized by asymmetrical, harmonic folds with thickened hinge zones. They show variable styles between tight and isoclinal and form pairs of EW and NE anticlines and synclines. In Nova Xavantina structural window, the magnetic lineaments mark important lithospheric discontinuities represented by the Campinápolis (CAL) and General Carneiro (GCL) lineaments, which seem to be the deep basement faults that controlled the extension and where the rift axial zone developed. The Transbrasiliano Lineament (TBL) is a major shear zone that controls the secondary lineaments propagation, forming a network of folds and drag faults, with lateral escapes and vertical movement. Between the two main lineaments occurred the deposition of sediments and volcanic successions related to Nova Xavantina Metavolcanosedimentary Sequence representing a marginal ocean basin. The transition from EW trending features of the Paraguay Belt to NE trend Araguaia Belt lies within Nova Xavantina region and is marked by the direct influence of TBL. TBL is evident in the magnetic images, forming a mosaic of different crustal blocks and corresponding to various curvilinear shear zones with unidirectional trend N30-45E. It is composed of mega-sigmoids interlaced with mainly dextral kinematics, within shallow and deep levels.During the Neoproterozoic orogeny, a foreland basin system was formed in response to the flexural subsidence due to the tectonic inversion of the basin. Several depocenters were formed and served as accumulation sites for the deposition of sediments of the Alto Paraguay Group (Raizama, Sepotuba and Diamantino formations). Gravimetric data allowed individualization of the foreland basin system, which is characterized by four discrete depozones (back-bulge, forebulge, foredeep and wedge-top), between the Amazonian Craton and the inner structural zone.

STRUCTURAL, STRATIGRAPHIC AND METALLOGENETIC ASPECTS OF THE PARAGUAY FOLD AND THRUST BELT: IMPLICATIONS FOR GOLD MINERALIZATION AND COLLAGE OF THE GONDWANA

ABSTRACT - Paraguay Belt occupies the western portion of the Tocantins Province, surrounding the Southeast of the Amazonian Craton and the eastern border of the Rio Apa Block, suggesting continuity with Tucavaca Belt in Bolivia. The rocks of the Paraguay belt were initially deposited in a glaciomarine environment in sites proximal to the cratonic area and deeper marine under the influence of turbidite flows in distal sites (Cuiabá Group, Bauxi and Puga Formation). The cap carbonates, thick limestone and dolostone succession of the Araras Group and siltstones and diamictites of the Serra Azul Formation related to Glaskiers glaciation overlay these diamictites (related to Marinoan glaciation). On the top there are terrigenous sediments of the Alto Paraguay Group, represented by sandstones of Raizama and claystones of Diamantino formations, respectively. The belt can be divided into three distinct structural zones: The Internal Domain is comprised of turbidite and glaciogenic sequences. Glaciogenic rocks on the base and carbonaceous and terrigenous sediments on the top occur in the External Domain. Horizontal platformal cover on the Amazonian Craton rocks are characterized by open folds. Structural studies allowed characterization of continuous deformational phases: the main deformational phase generated regional inverse folds with a NE-SW trend and fan geometry. Several regionally widespread lode-type gold deposits related to four types of the quartz veins were identified: type 1 is in concordance to bedding, type 2 is parallel to Sn, type 3 is parallel to Sn+2, and vertical Type 4 (Au-rich) is orthogonal to Sn. Late deformation developed in the Cuiabá region, recorded the closure of the ocean and the invertion where the hydrothermal fluids are the responsible for the orebodies formation.
 Keywords: Paraguay Belt, Structural, Stratigraphy, Metalogenesis.

Prevalence of comorbidity tuberculosis and diabetes mellitus in Paraguay, 2016 and 2017Prevalência de comorbidade tuberculose-diabetes mellitus no Paraguai, 2016 e 2017

RESUMENObjetivo.Estimar la prevalencia nacional y regional de la comorbilidad tuberculosis (TB) y diabetes mellitus (DM) e identificar los factores asociados con esta comorbilidad en Paraguay.Métodos.Estudio transversal en pacientes con TB notificada en 2016 y 2017 y registrados en la base de datos del Programa Nacional de Control de la TB. La prevalencia de DM, definida por autonotificación, se estimó en pacientes con TB. Para conocer los factores asociados con la comorbilidad TB-DM se empleó un modelo multivariante de regresión binomial para ajustar las razones de prevalencia (RP) según los errores estándar por el clúster de región sanitaria.Resultados.Entre 2016 y 2017 se notificaron 5 315 casos de TB. La prevalencia de la comorbilidad TB-DM fue 6,3% en 2016, 6,0% en 2017 y 6,2% en ambos años. Fue más alta en Itapúa (9,2%), Alto Paraguay (8,0%), Alto Paraná (7,5%), Central (7,4%) y Asunción (7,2%). La mediana de edad de personas con DM fue más alta que la de las que no tenían DM (55 y 33 años; P < 0,001). Tener una edad mayor de 45 años (RP = 18,3), el sexo femenino, antecedente de hipertensión arterial (HTA) (RP = 2,17), baciloscopía de diagnóstico de tres cruces (RP 1,98), y antecedente de enfermedad pulmonar obstructiva crónica (EPOC) (RP 1,68) estuvieron asociados con mayor comorbilidad. En cambio, se asociaron con menor comorbilidad pertenecer a la población indígena (RP = 0,26), la infección por el virus de la inmunodeficiencia humana (RP = 0,44), historia de adicción a drogas (RP = 0,49), el sexo masculino (RP = 0,64), y la TB extrapulmonar (RP = 0,75).Conclusiones.La prevalencia de la comorbilidad de TB y DM en Paraguay, por autonotificación, fue 6,2% en el periodo 2016-2017 y varió entre las regiones sanitarias. La edad, una alta carga bacilar al diagnóstico y la comorbilidad con HTA y EPOC se asociaron a una mayor comorbilidad. Estos hallazgos permitirán priorizar grupos de población para aumentar rendimiento del cribado, diagnóstico, tratamiento y prevención de la comorbilidad TB-DM en Paraguay.

Vectores de Trypanosoma cruzi en ambientes domésticos y silvestres de las comunidades Ayoreo Totobiegosode del Alto Paraguay

La enfermedad de Chagas es hasta hoy día endémica en el Chaco paraguayo, perjudicando principalmente a las poblaciones rurales o de menores recursos económicos, representando así las comunidades indígenas algunas de las poblaciones más vulnerables. El objetivo de este trabajo fue determinar la presencia de triatominos vectores de Trypanosoma cruzi en las comunidades indígenas Ayoreo Totobiegosode Chaidi y Aocojadi del Alto Paraguay. Se evaluaron características de las viviendas y su relación con la permanencia de vectores. La búsqueda de vectores se realizó en el intradomicilio y peridomicilio de las viviendas, y mediante la instalación de una trampa de luz en un ambiente silvestre adyacente a una de las comunidades. Para la búsqueda de flagelados fueron examinadas al microscopio óptico las heces de los triatominos colectados. Se realizó la técnica de xenocultivo para los insectos positivos. Fueron encontrados e identificados triatominos tanto en los ambientes domésticos como en el ambiente silvestre en la zona de las comunidades del Pueblo Ayoreo Totobiegosode del Alto Paraguay: Chaidi y Aocojadi, durante el periodo de colecta del 2016. Los triatominos identificados en este estudio, Triatoma sordida y Triatoma guasayana, son propios de ambientes silvestres, aunque durante ciertas épocas del año actúan como especies intrusivas invadiendo las áreas domésticas. Se detectó la infección natural con T. cruzi-like en un ejemplar proveniente de la comunidad Chaidi, sin descartar la posibilidad de que el parásito se encuentre circulando en Aocojadi. La investigación contribuye a considerar el riesgo de exposición a la enfermedad que tiene la población local, debido a que hasta el momento de este estudio no se cuenta con información sobre la presencia o ausencia de circulación de T. cruzi en estas comunidades.

Pluteus Fr. (Pluteaceae, Agaricales) in Paraguay: morphological studies and new records

Four species of Pluteus Fr. are documented based on recently collected specimens from Alto Paraguay and Central Department, which correspond to the Pantanal and Humid Chaco ecoregions, respectively. Pluteus fibulatus Singer, P. longistriatus (Peck) Peck, P. petasatus (Fr.) Gillet, and P. triplocystis Singer are newly recorded species of the mycobiota of Paraguay; P. triplocystis is also a newly recorded for South America. Descriptions and photographs of both macro- and microscopic features of each species are included along with a brief discussion on their taxonomy, ecology, and distribution.

Análisis multitemporal del cambio de uso de la tierra en el Departamento de Alto Paraguay, Paraguay

Análisis multitemporal del cambio de uso de la tierra en el Departamento de Alto Paraguay, Paraguay

New Records and Range Extension of Bryophytes for Paraguay

Abstract We present the first records for Paraguay for 24 species of bryophytes (one hornwort, eight liverworts and 15 mosses). Another 47 new regional records enhance the list of bryodiversity for the departments of Alto Paraguay, Alto Parana, Amambay, Caaguazu, Canindeyu, Central, Concepcion, Cordillera, Paraguari, Presidente Hayes and one new record for the capital district, Asuncion.

First record of Liolaemus azarai and Hemidactylus mabouia for Ñeembucú Department, Paraguay

Here, we present the first record of Liolameus azarai and Hemidactylus mabouia for the Neembucu Department, and Manciola guaporicola for the Alto Paraguay Department, all in Paraguay. These data were the result of recent fieldwork in Paraguay and contribute to knowledge about the distribution of these lizards in this country.

Conexiones inestables, imprevistas y pérdidas: expandiendo la arena política en la cooperación para el desarrollo y comunidades indígenas en el Chaco paraguayo

The article is a reflection on the definition of the political arena in the Paraguayan context and beyond. In particular, it provides a close look on the way in which this arena gets stretched and blurred in the space of encounter between indigenous communities and development institutions in two specific case studies. The first is the case of the maskoy communities of Alto Paraguay, where the absence of “developmental” forms of indigenous organizations parallels a strong re-enactment of collective ceremonies that are not considered political by non-indigenous observers but they certainly are if we try to reformulate “the political” according to other ontological premises. In the second case, the Sanapana and Enxet community of Xakmok Kasek works with an advocacy ngo to reclaim a part of their ancestral land before the Paraguayan Parliament through an expropriation law project against the landowner who holds the land title. At reaching point of discussion of the law project, the community ask the ngo an additional support to hold a shamans’ meeting to act upon the lawmakers. The example show once more that politics that not reduces its realm to the actions of humans alone. Both cases also altogether demonstrate the feeble developmental attempts to separate “human” from “nature” and the limitations of advocacy ngo endeavours to fully understand politics as cosmopraxis. Thus, the indigenous challenges to the “modern” limits of the political arena, which provokes tensions and misunderstandings, ask to slow down reasoning and re-imagine a configuration for future alliances and political practices

Distribution and status of the Rufous-tailed Jacamar Galbula ruficauda (Aves: Galbulidae) in Paraguay

Rufous-tailed Jacamar Galbula ruficauda is known from few records in Paraguay, all during the last 20 years. The species has been recorded in the northern Chaco and Paraguayan Pantanal, with all confirmed records from Alto Paraguay department. Here we summarise all reports and localities of the species in Paraguay to date. The species is categorized as Data Deficient at the national level, but may be more widely distributed than is currently recognised.

Late-stage magmatic to deuteric/metasomatic accessory minerals from the Cerro Boggiani agpaitic complex (Alto Paraguay Alkaline Province)

This work describes rare accessory minerals in volcanic and subvolcanic silica-undersaturated peralkaline and agpaitic rocks from the Permo-Triassic Cerro Boggiani complex (Eastern Paraguay) in the Alto Paraguay Alkaline Province. These accessory phases consist of various minerals including Th-U oxides/silicates, Nb-oxide, REE-Sr-Ba bearing carbonates-fluorcarbonates-phosphates-silicates and Zr-Na rich silicates. They form a late-stage magmatic to deuteric/metasomatic assemblage in agpaitic nepheline syenites and phonolite dykes/lava flows made of sodalite, analcime, albite, fluorite, calcite, ilmenite-pyrophanite, titanite and zircon. It is inferred that carbonatitic fluids rich in F, Na and REE percolated into the subvolcanic system and metasomatically interacted with the Cerro Boggiani peralkaline and agpaitic silicate melts at the thermal boundary layers of the magma chamber, during and shortly after their late-stage magmatic crystallization and hydrothermal deuteric alteration.

Five new species, one new genus, two synonymies, and new distributional records in Cerambycidae (Coleoptera).

Five new species, and one new genus of Cerambycidae are described: Drycothaea vulcanica sp. nov. (Calliini), from Ecuador (Holotype male deposited in AMNH: Napo, 29.X.1988, J.S. Miller leg.); Perissomerus machadoi sp. nov. (Neoibidionini), from Paraguay (Holotype male deposited in MZSP: Alto Paraguay, 30.XI.2002, Di Iorio leg.); Cacostola carinata sp. nov. (Onciderini), from Brazil (Holotype female deposited in MZSP: Rio Grande do Norte, IX.2008, D.R.R. Fernandes et al. leg.); Ypomacena gen. nov. (Apomecynini) from Brazil to include Y. monnei sp. nov. (Holotype male deposited in MNRJ: Bahia, XI.1970, Roppa leg.), and Y. gibbosa sp. nov. (Holotype female deposited in MNRJ: Rio de Janeiro, 31.X.1969, Alvarenga & Seabra leg.). Dorcasta prolongata Fisher, 1947 is proposed as a new synonym of Bebelis lignea (Bates, 1866). Bisaltes (Bisaltes) fuchsi Breuning, 1971 is proposed as a new synonym of Bisaltes (Bisaltes) buquetii Thomson, 1868. Additionally, sixteen new states records for Brazil, and three country records for Bolivia are provided.

High frequency peritidal cycles of the upper Araras Group: Implications for disappearance of the neoproterozoic carbonate platform in southern Amazon Craton

The Araras Group is an extensive carbonate platform developed at the southeastern margin of the Amazon Craton during the Neoproterozoic. The Nobres Formation corresponds to the upper unit of the Neoproterozoic Araras Group. It is exposed in road cuts and quarries in the Northern Paraguay Belt, and is characterized by meter-scale shallowing upward cycles. Forty-four fourth-to fifth-order parasequence cycles are enclosed into three third order sequences/megacycles, unconformably overlain by siliciclastic deposits of the Alto Paraguay Group. The cycles are generally of peritidal type, limited by exposure surfaces composed of asymmetrical tidal flat/sabkha lithofacies in the basal Nobres Formation. They consist of fine dolostone, intraclastic dolostones with megaripples, stromatolites biostrome, sandy dolostone with enterolithic structures and silicified evaporite molds. Upsection, the cycles progressively become symmetrical, comprising arid tidal flat deposits with abundant stromatolite biostrome, fine-grained sandstone and rare evaporitic molds. The stacking patterns for hundreds of meters indicate continuous and recurrent generation of accommodation space, probably triggered by subsidence concomitant with relative sea-level changes. Palynomorphs found in the upper part of Nobres Formation comprehend spheroidal forms, such as Leiospharidia, rare filamentous and acanthomorphous acritarchs, mostly Tanarium correlated to the Ediacaran Complex Acantomorph Palynoflora of ∼580–570 Ma. Previous data of carbon isotopes and paleogeographic reconstructions, and also the presence of evaporites and storm-influenced deposits in the Araras Group, suggest a wet to tropical setting for Amazonia during the Mid-Ediacaran, which is incompatible with previous claims for Gaskiers-related glacial sedimentation in the region. During the final stages of evolution of the Araras carbonate platform, a progressive input of terrigenous has occurred in the peritidal setting likely due tectonic activity in the vicinity of the basin and the rapid uplift of source areas to the west and to the east of the basin preceding the progradation of the siliciclastic fluvial-coastal environments related to the Alto Paraguay sedimentation. This event resulted in erosion of shallow carbonate basins and, potentially, the demise and disintegration of the Neoproterozoic carbonate platforms in southern Amazon Craton.

The Early Triassic magmatism of the Alto ParaguayProvince, Central South America: Paleomagneticand ASM data

Abstract A paleomagnetic studystudywork was carriedout on the Alto Paraguay Province (APP), a belt of alkalinecomplexes that parallel the Paraguay river for morethan 40 km at the border of Brazil and Paraguay. Theprovince is well dated by 40Ar/39Ar method giving ages inthe range 240–250 Ma with a preferred age of 241 Ma. Intrusiverocks are predominant but the stocks may be toppedby lava flows and ignimbrites. Paleomagnetic work onstocks, dikes and flows of the APP identified normal andreversed magnetic components which are carried mainlyby titanomagnetites. The calculated paleomagnetic polelocated at 319ºE 78ºS (α95 = 6º; k = 23) is in agreementwith other South American poles of Permo-Triassic age.Most of the sampling sites showed large variations in rockmagnetization, but similar patterns in the variation of thewithin-site magnetizations, mainly in dikes, suggest geomagneticpolarity transition records. The magnetizationdata along with the anisotropy of magnetic susceptibilitydeterminations suggested that the South and North areasof the province have different evolution characteristics.

Investigating mid‐Ediacaran glaciation and final Gondwana amalgamation using coupled sedimentology and 40Ar/ 39Ar detrital muscovite provenance from the Paraguay Belt, Brazil

AbstractUnderstanding the evolution of the northern Paraguay Belt, Brazil, is critical in two current controversies: (i) the number, timing and significance of Ediacaran glaciations; and (ii) the timing of amalgamation of South American Gondwana. The Neoproterozoic Alto Paraguay Group forms much of the northern Paraguay Belt. The Serra Azul Formation, within this Group, contains unequivocal evidence for a glacial influence on sedimentation, including multi‐directional striations on sandstone clasts and striated, polished and bullet‐shaped mudstone clasts. However, the age of the Serra Azul Formation is not well‐constrained. The northern Paraguay Belt also formed after the traditionally accepted time for amalgamation of South American Gondwana. If the orogen represents closure of an ocean, then this traditional view is incorrect. A significant number of single grain 40Ar/39Ar detrital muscovite cooling ages (ca 120) from the Alto Paraguay Group are presented. The three youngest grains from the Serra Azul Formation yield a weighted mean age of 640 ± 15 Myr, providing a robust maximum depositional age for this formation. This age, when considered with other data, suggests that the Serra Azul Formation developed in a mid‐Ediacaran glaciation consistent with that expressed in the Gaskiers Formation of Newfoundland, Canada. Cryogenian 40Ar/39Ar detrital muscovite ages from the Alto Paraguay Group are hard to reconcile with the known geology of Amazonia and are interpreted as being sourced from the evolving orogen to the east – from an arc terrane, possibly the Goiás–Paranapanema Massif. Detrital muscovites in the upper part of the Alto Paraguay Group are as young as 544 ± 7 Myr, consistent with mounting evidence that indicates a Cambrian age for orogenesis within the Paraguay Belt during the final amalgamation of Gondwana. This article suggests that the data best support a model where ocean closure in the region continued until Ediacaran/Cambrian times, with final ocean closure represented by orogenesis in the Paraguay–Araguaia orogen.

A Paraguayan Case Study on the Production of Electricity from Fuel Cells for Distributed Generation

The result of a preliminary economic evaluation of distributed generation of electricity with a molten carbonate fuel cell (MCFC) in Paraguay is presented in this work. For this purpose, a mathematical model that represents the main technical and economic characteristics involved in the operation of MCFCs was applied. The model is applied in a horizon of 20 years and shows how costs are influenced by the projected energy demand increase of the studied population and by the decrease of MCFC unit cost due to technological advances and mass production. The studied population is Bahía Negra district in the department of Alto Paraguay. The results show that the generation cost of electricity by MCFC is high, US$ 290/MWh and US$ 270/MWh, for conservative and optimistic scenarios, respectively. However, in these situations, the feasibility analysis of electricity supply to isolated communities with low living standards and in developing countries based only on the comparison and quantification in monetary terms is not enough. This is because there are intangible benefits that are difficult to quantify and, therefore, to express in monetary terms. For example, it is very difficult to quantify in monetary terms the improvements in environmental conditions and quality of life of the community. Finally, the use of fuel cells for distributed generation of electricity in rural areas of Paraguay is feasible if the social and environmental aspects are considered, not just economics.