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Sample records for cerro castillo patagonia

  1. Extreme Winds in the Pampa del Castillo Plateau, Patagonia, Argentina, with Reference to Wind Farm Settlement.

    NASA Astrophysics Data System (ADS)

    Labraga, Juan C.

    1994-01-01

    Wind farm settlement in Argentina is likely to be initiated in the extended and uniform Pampa del Castillo tablelands (5100 km2) in central cast Patagonia, due to its suitable wind regime and local economic factors. The magnitude of these investments requires not only a detailed wind energy assessment and optimum site selection but also a comprehensive evaluation of the extreme winds experienced in the region.Statistical results, with emphasis on severe winds, of two regional programs of one-year observations at four levels above the ground are presented in this paper. The highest frequencies of hourly mean wind velocities above 40, 60, and 80 km h1 are observed during November and December. The spring power spectrum shows a considerable amount of energy in components with a periodicity ranging from 2.5 to 4 days. Severe wind episodes are usually related to the displacement of low pressure systems from the Atlantic to the Pacific Ocean through the Drake Passage with a periodicity consistent with spectral results. The highest hourly mean wind speed registered in each experimental period (at 60 m AGL) is about 25 m s1. The estimated modal value of the theoretical probability distribution of annual extreme values is in good agreement with observed values. The annual peak gust for an averaging time of 240 s is about 27 m s. The gust factor was computed for different averaging intervals and compared with empirical formulations. Its variation with height and time of year was also analyzed. The general form of the vertical wind profile and its dependence on stability conditions was characterized and compared with that of typical episodes of severe winds.

  2. Validating numerical simulations of snow avalanches using dendrochronology: the Cerro Ventana event in Northern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Casteller, A.; Christen, M.; Villalba, R.; Martínez, H.; Stöckli, V.; Leiva, J. C.; Bartelt, P.

    2008-05-01

    The damage caused by snow avalanches to property and human lives is underestimated in many regions around the world, especially where this natural hazard remains poorly documented. One such region is the Argentinean Andes, where numerous settlements are threatened almost every winter by large snow avalanches. On 1 September 2002, the largest tragedy in the history of Argentinean mountaineering took place at Cerro Ventana, Northern Patagonia: nine persons were killed and seven others injured by a snow avalanche. In this paper, we combine both numerical modeling and dendrochronological investigations to reconstruct this event. Using information released by local governmental authorities and compiled in the field, the avalanche event was numerically simulated using the avalanche dynamics programs AVAL-1D and RAMMS. Avalanche characteristics, such as extent and date were determined using dendrochronological techniques. Model simulation results were compared with documentary and tree-ring evidences for the 2002 event. Our results show a good agreement between the simulated projection of the avalanche and its reconstructed extent using tree-ring records. Differences between the observed and the simulated avalanche, principally related to the snow height deposition in the run-out zone, are mostly attributed to the low resolution of the digital elevation model used to represent the valley topography. The main contributions of this study are (1) to provide the first calibration of numerical avalanche models for the Patagonian Andes and (2) to highlight the potential of textit{Nothofagus pumilio} tree-ring records to reconstruct past snow-avalanche events in time and space. Future research should focus on testing this combined approach in other forested regions of the Andes.

  3. Diverse subaerial and sublacustrine hot spring settings of the Cerro Negro epithermal system (Jurassic, Deseado Massif), Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Guido, Diego M.; Campbell, Kathleen A.

    2012-06-01

    The Late Jurassic (~ 150 Ma) Cerro Negro volcanic-epithermal-geothermal system (~ 15 km2 area), Deseado Massif, Patagonia, Argentina, includes two inferred volcanic emission centers characterized by rhyolitic domes linked along NW-SE regional faults that are associated with deeper level Au/Ag mineralization to the NW, and with shallow epithermal quartz veins and mainly travertine surface hot spring manifestations to the SE. Some travertines are silica-replaced, and siliceous and mixed silica-carbonate geothermal deposits also are found. Five hot spring-related facies associations were mapped in detail, which show morphological and textural similarities to Pleistocene-Recent geothermal deposits at Yellowstone National Park (U.S.A.), the Kenya Rift Valley, and elsewhere. They are interpreted to represent subaerial travertine fissure ridge/mound deposits (low-flow spring discharge) and apron terraces (high-flow spring discharge), as well as mixed silica-carbonate lake margin and shallow lake terrace vent-conduit tubes, stromatolitic mounds, and volcano-shaped cones. The nearly 200 mapped fossil vent-associated deposits at Cerro Negro are on a geographical and numerical scale comparable with subaerial and sublacustrine hydrothermal vents at Mammoth Hot Springs, and affiliated with Yellowstone Lake, respectively. Overall, the Cerro Negro geothermal system yields paleoenvironmentally significant textural details of variable quality, owing to both the differential preservation potential of particular subaerial versus subaqueous facies, as well as to the timing and extent of carbonate diagenesis and silica replacement of some deposits. For example, the western fault associated with the Eureka epithermal quartz vein facilitated early silicification of the travertine deposits in the SE volcanic emission center, thereby preserving high-quality, microbial macro- and micro-textures of this silica-replaced "pseudosinter." Cerro Negro provides an opportunity to reconstruct

  4. The Marianas-San Marcos vein system: characteristics of a shallow low sulfidation epithermal Au-Ag deposit in the Cerro Negro district, Deseado Massif, Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Vidal, Conrado Permuy; Guido, Diego M.; Jovic, Sebastián M.; Bodnar, Robert J.; Moncada, Daniel; Melgarejo, Joan Carles; Hames, Willis

    2016-08-01

    The Cerro Negro district, within the Argentinian Deseado Massif province, has become one of the most significant recent epithermal discoveries, with estimated reserves plus resources of ˜6.7 Moz Au equivalent. The Marianas-San Marcos vein system contains about 70 % of the Au-Ag resources in the district. Mineralization consists of Upper Jurassic (155 Ma) epithermal Au- and Ag-rich veins of low to intermediate sulfidation style, hosted in and genetically related to Jurassic intermediate composition volcanic rocks (159-156 Ma). Veins have a complex infill history, represented by ten stages with clear crosscutting relationships that can be summarized in four main episodes: a low volume, metal-rich initial episode (E1), an extended banded quartz episode with minor mineralization (E2), a barren waning stage episode (E3), and a silver-rich late tectonic-hydrothermal episode (E4). The first three episodes are interpreted to have formed at the same time and probably from fluids of similar composition: a 290-230 °C fluid dominated by meteoric and volcanic waters (-3‰ to -0‰ δ18Owater), with <3 % NaCl equivalent salinity and with a magmatic source of sulfur (-1 to -2 ‰ δ34Swater). Metal was mainly precipitated at the beginning of vein formation (episode 1) due to a combination of boiling at ˜600 to 800 m below the paleowater table, and associated mixing/cooling processes, as evidenced by sulfide-rich bands showing crustiform-colloform quartz, adularia, and chlorite-smectite banding. During episodes 2 and 3, metal contents progressively decrease during continuing boiling conditions, and veins were filled by quartz and calcite during waning stages of the hydrothermal system, and the influx of bicarbonate waters (-6 to -8.5 ‰ δ18Owater). Hydrothermal alteration is characterized by proximal illite, adularia, and silica zone with chlorite and minor epidote, intermediate interlayered illite-smectite and a distal chlorite halo. This assemblage is in agreement with

  5. People first in the Philippines: Gelia Castillo.

    PubMed

    Yabes, C

    1995-01-01

    Gelia Castillo, a specialist in rural sociology whose ideas have influenced policymakers in government, international development circles, and academe, pioneered the concept of participatory development. Born into a poor family, her father convinced her that academic achievement was the key to her future; her academic training includes a Bachelor of Arts in psychology from the University of the Philippines, a Master's in rural sociology from Pennsylvania State University, and a Doctorate from Cornell University. She served as professor of rural sociology at the College of Agriculture, University of the Philippines, and published extensively on women's roles, the sex roles of Filipino adolescents, agricultural school administration, the team approach in community development, rice and potato farming, the changing social images in a developing society, and the protein gap. "Beyond Manila," her most famous book, was the first comprehensive research work on income distribution, employment, labor, education, and migration in the rural Philippines. She underscored the definition of "household" and observed that the role of women and children contributes greatly to the dynamics of society. Her husband, Leopoldo Castillo, an animal nutritionist who is now professor emeritus at the Institute of Animal Science, has long supported his wife's career. The mother of two daughters and one son was the only female member of the board of the International Potato Center for 6 years and served on the boards of the IDRC, the International Service for National Agriculture Research, and the International Council for Research in Agroforestry. At 66, and retired, she believes affirmative action is necessary and that the feminist movement has only helped professional women. PMID:12288549

  6. Carlos Castillo-Chavez: a century ahead.

    PubMed

    Schatz, James

    2013-01-01

    When the opportunity to contribute a short essay about Dr. Carlos Castillo-Chavez presented itself in the context of this wonderful birthday celebration my immediate reaction was por supuesto que sí! Sixteen years ago, I travelled to Cornell University with my colleague at the National Security Agency (NSA) Barbara Deuink to meet Carlos and hear about his vision to expand the talent pool of mathematicians in our country. Our motivation was very simple. First of all, the Agency relies heavily on mathematicians to carry out its mission. If the U.S. mathematics community is not healthy, NSA is not healthy. Keeping our country safe requires a team of the sharpest minds in the nation to tackle amazing intellectual challenges on a daily basis. Second, the Agency cares deeply about diversity. Within the mathematical sciences, students with advanced degrees from the Chicano, Latino, Native American, and African-American communities are underrepresented. It was clear that addressing this issue would require visionary leadership and a long-term commitment. Carlos had the vision for a program that would provide promising undergraduates from minority communities with an opportunity to gain confidence and expertise through meaningful research experiences while sharing in the excitement of mathematical and scientific discovery. His commitment to the venture was unquestionable and that commitment has not waivered since the inception of the Mathematics and Theoretical Biology Institute (MTBI) in 1996.

  7. The Chicana Subject in Ana Castillo's Fiction and the Discursive Zone of Chicana/o Theory

    ERIC Educational Resources Information Center

    Carson, Benjamin D.

    2007-01-01

    In the world of Chicana fiction, Ana Castillo has achieved the kind of status Maxine Hong Kingston has attained within Asian American discourse. Castillo's work is popular not only with the general reading public but in many academic circles as well. What sets Castillo apart from so many other Chicana fiction writers is that she is also a…

  8. Overview of Cerro Prieto studies

    SciTech Connect

    Lippmann, M.J.

    1983-01-01

    The studies performed on the Cerro Prieto geothermal field, Mexico, since the late 1950's are summarized. Emphasis is given to those activities leading to the identification of the sources of heat and mass, the fluid flow paths, and the phenomena occurring in the field in its natural state and under exploitation.

  9. Lightning in Western Patagonia

    NASA Astrophysics Data System (ADS)

    Garreaud, René D.; Gabriela Nicora, M.; Bürgesser, Rodrigo E.; Ávila, Eldo E.

    2014-04-01

    On the basis of 8 years (2005-2012) of stroke data from the World Wide Lightning Location Network we describe the spatial distribution and temporal variability of lightning activity over Western Patagonia. This region extends from ~40°S to 55°S along the west coast of South America, is limited to the east by the austral Andes, and features a hyper-humid, maritime climate. Stroke density exhibits a sharp maximum along the coast of southern Chile. Although precipitation there is largely produced by cold nimbostratus, days with more than one stroke occur up to a third of the time somewhere along the coastal strip. Disperse strokes are also observed off southern Chile. In contrast, strokes are virtually nonexistent over the austral Andes—where precipitation is maximum—and farther east over the dry lowlands of Argentina. Atmospheric reanalysis and satellite imagery are used to characterize the synoptic environment of lightning-producing storms, exemplified by a case study and generalized by a compositing analysis. Lightning activity tends to occur when Western Patagonia is immersed in a pool of cold air behind a front that has reached the coast at ~40°S. Under these circumstances, midlevel cooling occurs before and is more prominent than near-surface cooling, leading to a weakly unstable postfrontal condition. Forced uplift of the strong westerlies impinging on the coastal mountains can trigger convection and produces significant lightning activity in this zone. Farther offshore, large-scale ascent near the cyclone's center may lift near-surface air parcels, fostering shallow convection and dispersing lightning activity.

  10. Geothermal drilling in Cerro Prieto

    SciTech Connect

    Dominguez A., Bernardo

    1982-08-10

    The number of characteristics of the different wells that have been drilled in the Cerro Prieto geothermal field to date enable one to summarize the basic factors in the applied technology, draw some conclusions, improve systems and procedures, and define some problems that have not yet been satisfactorily solved, although the existing solution is the best now available. For all practical purposes, the 100 wells drilled in the three areas or blocks into which the Cerro Prieto field has been divided have been completed. Both exploratory and production wells have been drilled; problems of partial or total lack of control have made it necessary to abandon some of these wells, since they were unsafe to keep in production or even to be used for observation and/or study. The wells and their type, the type of constructed wells and the accumulative meters that have been drilled for such wells are summarized.

  11. Patagonia Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This ASTER images was acquired on May 2, 2000 over the North Patagonia Ice Sheet, Chile near latitude 47 degrees south, longitude 73 degrees west. The image covers 36 x 30 km. The false color composite displays vegetation in red. The image dramatically shows a single large glacier, covered with crevasses. A semi-circular terminal moraine indicates that the glacier was once more extensive than at present. ASTER data are being acquired over hundreds of glaciers worldwide to measure their changes over time. Since glaciers are sensitive indicators of warming or cooling, this program can provide global data set critical to understand climate change.

    This image is located at 46.5 degrees south latitude and 73.9 degrees west longitude.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud

  12. Conscientizacion of the Oppressed Language and the Politics of Humor in Ana Castillo's "So Far from God"

    ERIC Educational Resources Information Center

    Thananopavarn, Susan

    2012-01-01

    This essay explores the relationship between Ana Castillo's novel "So Far from God" (1993) and her development of an activist poetics inspired by Paulo Freire's influential 1970 treatise "Pedagogy of the Oppressed." "So Far from God" may be understood as the practical application of Castillo's theory of "conscienticized poetics"; that is, the…

  13. Stereo Pair: Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, near El Cain, Argentina shows complexly eroded volcanic terrain, with basalt mesas, sinkholes, landslide debris, playas, and relatively few integrated drainage channels. Surrounding this site (but also extending far to the east) is a broad plateau capped by basalt, the Meseta de Somuncura. Here, near the western edge of the plateau, erosion has broken through the basalt cap in a variety of ways. On the mesas, water-filled sinkholes (lower left) are most likely the result of the collapse of old lava tubes. Along the edges of the mesas (several locations) the basalt seems to be sliding away from the plateau in a series of slices. Water erosion by overland flow is also evident, particularly in canyons where vegetation blankets the drainage channels (green patterns, bottom of image). However, overland water flow does not extend very far at any location. This entire site drains to local playas, some of which are seen here (blue). While the water can reach the playas and then evaporate, what becomes of the eroded rock debris? Wind might excavate some of the finer eroded debris, but the fate of much of the missing bedrock remains mysterious.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7 satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The

  14. Anaglyph: Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, near El Cain, Argentina shows complexly eroded volcanic terrain, with basalt mesas, sinkholes, landslide debris, playas, and relatively few integrated drainage channels. Surrounding this site (but also extending far to the east) is a broad plateau capped by basalt, the Meseta de Somuncura. Here, near the western edge of the plateau, erosion has broken through the basalt cap in a variety of ways. On the mesas, water-filled sinkholes (lower left) are most likely the result of the collapse of old lava tubes. Along the edges of the mesas (several locations) the basalt seems to be sliding away from the plateau in a series of slices. Water erosion by overland flow is also evident, particularly in canyons where vegetation blankets the drainage channels (bright patterns, bottom of image). However, overland water flow does not extend very far at any location. This entire site drains to local playas, some of which are seen here (dark lakes with bright shores). While the water can reach the playas and then evaporate, what becomes of the eroded rock debris? Wind might excavate some of the finer eroded debris, but the fate of much of the missing bedrock remains mysterious.

    This anaglyph was generated by first draping a Landsat Thematic Mapper image over a topographic map from the Shuttle Radar Topography Mission, then producing the two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and the right eye with a blue filter.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was

  15. Stereo Pair, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, at Los Menucos, Argentina shows remnants of relatively young volcanoes built upon an eroded plain of much older and contorted volcanic, granitic, and sedimentary rocks. The large purple, brown, and green 'butterfly' pattern is a single volcano that has been deeply eroded. Large holes on the volcano's flanks indicate that they may have collapsed soon after eruption, as fluid molten rock drained out from under its cooled and solidified outer shell. At the upper left, a more recent eruption occurred and produced a small volcanic cone and a long stream of lava, which flowed down a gully. At the top of the image, volcanic intrusions permeated the older rocks resulting in a chain of small dark volcanic peaks. At the top center of the image, two halves of a tan ellipse pattern are offset from each other. This feature is an old igneous intrusion that has been split by a right-lateral fault. The apparent offset is about 6.6 kilometers (4 miles). Color, tonal, and topographic discontinuities reveal the fault trace as it extends across the image to the lower left. However, young unbroken basalt flows show that the fault has not been active recently.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive

  16. Anaglyph, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, at Los Menucos, Argentina shows remnants of relatively young volcanoes built upon an eroded plain of much older and contorted volcanic, granitic, and sedimentary rocks. The large, dark 'butterfly' pattern is a single volcano that has been deeply eroded. Large holes on the volcano's flanks indicate that they may have collapsed soon after eruption, as fluid molten rock drained out from under its cooled and solidified outer shell. At the upper left, a more recent eruption occurred and produced a small volcanic cone and a long stream of lava, which flowed down a gully. At the top of the image, volcanic intrusions permeated the older rocks resulting in a chain of small dark volcanic peaks.

    At the top center of the image, two halves of a light ellipse pattern are offset from each other. This feature is an old igneous intrusion that has been split by a right-lateral fault. The apparent offset is about 6.6 kilometers (4 miles). Tonal and topographic discontinuities reveal the fault trace as it extends across the image to the lower left. However, young unbroken basalt flows show that the fault has not been active recently.

    This anaglyph was generated by first draping a Landsat Thematic Mapper image over a topographic map from the Shuttle Radar Topography Mission, then producing the two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and the right eye with a blue filter.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic mapper image used here was provided to the SRTM project by the United

  17. Geothermal Drilling in Cerro Prieto

    SciTech Connect

    Aguirre, B. D.; Garcia, G. S.

    1981-01-01

    To date, 71 geothermal wells have been drilled in Cerro Prieto. The activity has been divided into several stages, and, in each stage, attempts have been made to correct deficiencies that were gradually detected. Some of these problems have been solved; others, such as those pertaining to well casing, cement, and cementing jobs, have persisted. The procedures for well completion--the most important aspect for the success of a well--that were based on conventional oil well criteria have been improved to meet the conditions of the geothermal reservoir. Several technical aspects that have improved should be further optimized, even though the resolutions are considered to be reasonably satisfactory. Particular attention has been given to the development of a high-temperature drilling fluid capable of being used in drilling through lost circulation zones. Conventional oil well drilling techniques have been used except where hole-sloughing is a problem. Sulfonate lignitic mud systems have been used with good results. When temperatures exceed 300 C (572 F), it has been necessary to use an organic polymer to stabilize the mud properties.

  18. Geohydrology of the Cerro Prieto geothermal aquifer

    SciTech Connect

    Sanchez R, J.; de la Pena L, A.

    1981-01-01

    The most recent information on the Cerro Prieto geothermal aquifer is summarized, with special emphasis on the initial production zone where the wells completed in the Alpha aquifer are located. These wells produce steam for power plant units 1 and 2. Brief comments also are made on the Beta aquifer, which underlies the Alpha aquifer in the Cerro Prieto I area and which extends to the east to what is known as the Cerro Prieto II and Cerro Prieto III areas. The location of the area studied is shown. The Alpha and Beta aquifers differ in their mineralogy and cementing mineral composition, temperatures, and piezometric levels. The difference in piezometric levels indicates that there is no local communication between the two aquifers. This situation has been verified by a well interference test, using well E-1 as a producer in the Beta aquifer and well M-46 as the observation well in the Alpha aquifer. No interference between them was observed. Information on the geology, geohydrology, and geochemistry of Cerro Prieto is presented.

  19. Quantitative Model of the Cerro Prieto Field

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Bodvarsson, G.S.

    1986-01-21

    A three-dimensional model of the Cerro Prieto geothermal field, Mexico, is under development. It is based on an updated version of LBL's hydrogeologic model of the field. It takes into account major faults and their effects on fluid and heat flow in the system. First, the field under natural state conditions is modeled. The results of this model match reasonably well observed pressure and temperature distributions. Then, a preliminary simulation of the early exploitation of the field is performed. The results show that the fluid in Cerro Prieto under natural state conditions moves primarily from east to west, rising along a major normal fault (Fault H). Horizontal fluid and heat flow occurs in a shallower region in the western part of the field due to the presence of permeable intergranular layers. Estimates of permeabilities in major aquifers are obtained, and the strength of the heat source feeding the hydrothermal system is determined.

  20. Quantitative model of the Cerro Prieto field

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Bodvarsson, G.S.

    1986-03-01

    A three-dimensional model of the Cerro Prieto geothermal field, Mexico, is under development. It is based on an updated version of LBL's hydrogeologic model of the field. It takes into account major faults and their effects on fluid and heat flow in the system. First, the field under natural state conditions is modeled. The results of this model match reasonably well observed pressure and temperature distributions. Then, a preliminary simulation of the early exploitation of the field is performed. The results show that the fluid in Cerro Prieto under natural state conditions moves primarily from east to west, rising along a major normal fault (Fault H). Horizontal fluid and heat flow occurs in a shallower region in the western part of the field due to the presence of permeable intergranular layers. Estimates of permeabilities in major aquifers are obtained, and the strength of the heat source feeding the hydrothermal system is determined.

  1. Exploration and development of Cerro Prieto

    SciTech Connect

    Teilman, M.A.; Cordon, U.J.

    1981-01-01

    A brief retrospective of the exploration and field model development at Cerro Prieto are presented. Representative field models are presented for each of the work phases. These models demonstrate how the concept of the field evolved - from a small 2 km/sup 2/ area with a relatively unknown reservoir configuration - to a geothermal resource area over 20 km/sup 2/ where the hydrothermal processes and structural environment are being studied in detail. A model integrating information from these studies was developed.

  2. Accelerator 14C dates for early upper paleolithic (basal Aurignacian) at El Castillo Cave (Spain)

    USGS Publications Warehouse

    Valdes, V.C.; Bischoff, J.L.

    1989-01-01

    Three fragments of charcoal taken from different parts of the lowermost bed containing Aurignacian artifacts at El Castillo Cave yielded AMS dates of 37??7 (?? 1??8) ka bp, 38??5 (?? 1??8) ka bp, and 40??0 (?? 2??1) ka bp (average 38??7 ?? 1??9 ka bp). These dates are almost identical to new AMS dates from l'Arbreda cave in Catalunya on the same cultural horizon (average 38??5 ?? 1??0 ka bp) and are significantly older than the earliest dates for Aurignacian industries in the Aquitaine and in other parts of Central and Western Europe. ?? 1989.

  3. Using glacial morphology to constrain the impact of the Chile active spreading ridge subduction in Central Patagonia

    NASA Astrophysics Data System (ADS)

    Scalabrino, B.; Ritz, J. F.; Lagabrielle, Y.

    2009-04-01

    The Central Patagonian Cordillera is a unique laboratory to study interaction between oceanic and continental lithospheres during the subduction of an active spreading ridge beneath a continent. The subduction of the South Chile spreading Ridge, which separates the Nazca plate from the Antarctic plate, started ca. 15-14 Ma at the southern tip of Patagonia (55°S latitude). The northwards migration of the Chile Triple Junction induces the subduction of several segments especially around 46°S latitude. There, three segments subducted at ca. 6, 3 and 0.3 Ma, leading to the formation of a large asthenospheric slab-window beneath Central Patagonia. Contemporaneously, the Central Patagonia reliefs are undergoing major glacial events since at least 7 Ma. These events are evidenced to the east of the Central Patagonian morphotectonic front within perched relict surfaces. Inset in these perched glacial surfaces are found mid-Pleistocene glacial valleys, as the Lake General Carrera-Buenos Aires amphitheatre (LGCBA), which formed between 1.1 Ma and 16 ka. We used the relationships between the glacial valleys and the volcanism associated with the asthenospheric slab-window to better constraints the structural evolution of the Patagonian Cordillera related to the subduction of the Chili active spreading Ridge. The present work focused within two well-preserved perched flat surfaces named Meseta del Lago Buenos Aires and Meseta del Cerro Galera: (i) The meseta del Lago Buenos Aires defines a plateau made of interbedded units of tills and lavas dated between 12 Ma and 3 Ma. The top surface of the meseta, ˜2000 meters high is dated at 3 Ma, and is shaped by four NE-SW trending glacial lobes characterized with kettles, lineations and moraines. The glacial valleys are beheaded westwards and define perched valleys 200 to 400 meters higher than the western Cordillera. This suggests recent vertical movement along N160 extensive/transtensive corridor located between the morphotectonic

  4. Optical atmospheric extinction over Cerro Paranal

    NASA Astrophysics Data System (ADS)

    Patat, F.; Moehler, S.; O'Brien, K.; Pompei, E.; Bensby, T.; Carraro, G.; de Ugarte Postigo, A.; Fox, A.; Gavignaud, I.; James, G.; Korhonen, H.; Ledoux, C.; Randall, S.; Sana, H.; Smoker, J.; Stefl, S.; Szeifert, T.

    2011-03-01

    Aims: The present study was conducted to determine the optical extinction curve for Cerro Paranal under typical clear-sky observing conditions, with the purpose of providing the community with a function to be used to correct the observed spectra, with an accuracy of 0.01 mag airmass-1. Additionally, this work was meant to analyze the variability of the various components, to derive the main atmospheric parameters, and to set a term of reference for future studies, especially in view of the construction of the Extremely Large Telescope on the nearby Cerro Armazones. Methods: The extinction curve of Paranal was obtained through low-resolution spectroscopy of 8 spectrophotometric standard stars observed with FORS1 mounted at the 8.2 m Very Large Telescope, covering a spectral range 3300-8000 Å. A total of 600 spectra were collected on more than 40 nights distributed over six months, from October 2008 to March 2009. The average extinction curve was derived using a global fit algorithm, which allowed us to simultaneously combine all the available data. The main atmospheric parameters were retrieved using the LBLRTM radiative transfer code, which was also utilised to study the impact of variability of the main molecular bands of O2, O3, and H2O, and to estimate their column densities. Results: In general, the extinction curve of Paranal appears to conform to those derived for other astronomical sites in the Atacama desert, like La Silla and Cerro Tololo. However, a systematic deficit with respect to the extinction curve derived for Cerro Tololo before the El Chichón eruption is detected below 4000 Å. We attribute this downturn to a non standard aerosol composition, probably revealing the presence of volcanic pollutants above the Atacama desert. An analysis of all spectroscopic extinction curves obtained since 1974 shows that the aerosol composition has been evolving during the last 35 years. The persistence of traces of non meteorologic haze suggests the effect of

  5. Freshwater fishes of Patagonia: conservation and fisheries.

    PubMed

    Cussac, V E; Habit, E; Ciancio, J; Battini, M A; Riva Rossi, C; Barriga, J P; Baigún, C; Crichigno, S

    2016-07-01

    The absence of much literature on the Patagonian fish fauna in comparison with that of the neotropics, has previously been blamed on its poor species diversity. Knowledge of the fishes of Patagonia, however, rose sharply at the beginning of the present century, allowing for an understanding of the complex biogeographical history that has led to the present diversity and distribution patterns. There are several new and potential threats to biodiversity and conservation of Patagonian fishes, such as the introduction of exotic species, damming, climate change and changes geared to safeguard economic interests, often acting synergistically. A great amount of new information is now available and the aim of the present review is to articulate this knowledge in a comprehensive way in order to aid in the development of tools to face the increasing challenges posed by environmental change and human activity. Knowledge about fishes of Patagonia has grown at the same time as human actions, and presence.

  6. Freshwater fishes of Patagonia: conservation and fisheries.

    PubMed

    Cussac, V E; Habit, E; Ciancio, J; Battini, M A; Riva Rossi, C; Barriga, J P; Baigún, C; Crichigno, S

    2016-07-01

    The absence of much literature on the Patagonian fish fauna in comparison with that of the neotropics, has previously been blamed on its poor species diversity. Knowledge of the fishes of Patagonia, however, rose sharply at the beginning of the present century, allowing for an understanding of the complex biogeographical history that has led to the present diversity and distribution patterns. There are several new and potential threats to biodiversity and conservation of Patagonian fishes, such as the introduction of exotic species, damming, climate change and changes geared to safeguard economic interests, often acting synergistically. A great amount of new information is now available and the aim of the present review is to articulate this knowledge in a comprehensive way in order to aid in the development of tools to face the increasing challenges posed by environmental change and human activity. Knowledge about fishes of Patagonia has grown at the same time as human actions, and presence. PMID:27284012

  7. Geothermal development in Cerro Prieto Baja California, Mexico (1983)

    SciTech Connect

    Manon M.A.

    1983-09-01

    The actual stage of the expansion program and some of the main characteristics of the Cerro Prieto Geothermal Field are presented. This is similar to the one presented in this same conference back in 1981, but it has been updated.

  8. Analysis of Cerro Prieto production data

    SciTech Connect

    Goyal, K.P.; Miller, C.W.; Lippmann, M.J.; Vonder Haar, S.P.

    1981-01-01

    Heat and mass production data from the Cerro Prieto field are analyzed in order to provide a basis for a detailed quantitative model of the system. It is found, in general, that the production from the individual wells decreased with time. This can be due to a reduction in permeability by silica deposition in the aquifer pores, relative permeability effects in a two-phase flow, and/or a reduced pressure gradient over years of production. Specific increases in the total mass production rate of the field are associated with the increased number of producing wells. Average enthalpy of the produced fluid varied over the years. It first increased, then decreased, and again increased. An increase in enthalpy was usually the result of adding higher enthalpy wells to those already in the field. The decrease in the enthalpy is thought to be mostly due to the mixing of relatively cold water with the geothermal aquifer fluid. Downhole pressures, temperatures and saturations in the flowing wells were calculated from the known wellhead data. Between 1973 and 1980, the pressures and temperatures have decreased by about 15 bars and 20/sup 0/C respectively, and the steam saturations have slightly increased in the near-well regions.

  9. Evaluation of geologic characteristics at Cerro Prieto

    SciTech Connect

    Howard, J.H.; Halfman, S.E.; Vonder Haar, S.P.

    1981-01-01

    Computerized well-log analysis of Cerro Prieto has led to the identification of a relatively large and irregular low-density volume extending from near the surface in the vicinity of Laguna Volcano to greater depths toward the northeast. This low-density volume is located about a plane of symmetry of a self-potential anomaly and a group of northeast trending active faults. The presence of a volume of relatively high-density rock has been recognized at shallow depths in the initially developed part of the resource. It is believed to be due to minerals deposited by cooled, rising geothermal brine. Storativity calculated from well logs at the south end of the western part of the field shows acceptable comparison with storativity calculated from well tests. The amount of fluid produced from the field during the period 1973-1977 is greater than the amount in situ calculated from the completed interval thicknesses. Because this part of the field is still producing today, fluid must be recharging this part of the field.

  10. Production characteristics of some Cerro Prieto wells

    SciTech Connect

    Goyal, K.P.; Halfman, S.E.; Truesdell, A.H.; Howard, J.H.

    1982-08-01

    An areal distribution of heat and mass production in the Cerro Prieto field has been presented for two different times to determine the initial state of the ..cap alpha.. and ..beta.. aquifers and the behavior of the field under production. It was found that, initially, the ..cap alpha.. and ..beta.. aquifers were hot and very hot respectively. Cold boundaries to the field were found to be located toward the west and northeast. Initially, fluid production from most wells was very high. M-53 and some wells southeast of Fault H produced very hot fluids at very high rates. Production from most wells declined over the years, possibly due to scaling in the wellbore, reduced recharge to the aquifer, high resistance to flow due to silica precipitation in the reservoir pores and/or relative permeability effects in the two-phase regions surrounding the wells. In most wells fluid enthalpies declined over the years, perhaps due to mixing with colder waters either drawn in from upper strata and/or from the cold lateral boundaries depending upon well location.

  11. Preface to special issue in honor of Carlos Castillo-Chavez.

    PubMed

    Levin, Simon A

    2013-01-01

    A little more than a quarter-century ago, I received an inquiry from a young Assistant Professor of Applied Mathematics at the University of Tulsa, the honoree of this volume, Carlos Castillo-Chavez. Though he was well situated in a faculty job, he was not satisfied: He was interested in mathematical biology, having written an excellent thesis in population biology with Fred Brauer at Wisconsin entitled Linear and Nonlinear Deterministic Character-Dependent Models with Time Delay in Population Dynamics. But that success had only whetted his appetite to become more deeply embedded in biology, and he was prepared to give up his faculty job to start a postdoctoral fellowship in ecology. It is always difficult to read in such letters what potential exists in the author; but there was something about what Carlos wrote, the obvious sacrifice he was prepared to make, and my regard for Fred Brauer that convinced me that I must meet this fellow. We did meet, for lunch in an LA restaurant, and the qualities that have led to his remarkable career were immediately obvious. I resolved on the spot to make sure he joined our group. Carlos arrived at Cornell shortly thereafter, and did not leave for nearly twenty years.

  12. Palynological analysis of camelid coprolites: seasonality in the use of the site Cerro Casa de Piedra 7 (Santa Cruz, Argentina)

    NASA Astrophysics Data System (ADS)

    Velázquez, Nadia Jimena; Burry, Lidia Susana; Fugassa, Martín Horacio; Civalero, María Teresa; Aschero, Carlos Alberto

    2014-01-01

    Palynological, palaeoparasitological and paleobotanical studies of coprolites found in archaeological sites from Perito Moreno National Park (47°57‧S72°05‧W) yielded information on diet, palaeoenvironment and health. These studies allowed adding evidence to the reconstruction of life history of the hunter-gatherers that inhabited Patagonia during the Holocene. We examined the season of the year when camelid Lama guanicoe coprolites (5400 ± 64 yr 14C BP to 9640 ± 190 yr 14C BP) were deposited at Cerro Casa de Piedra 7 (site CCP7). The study used palynological evidence and comparison with pollen spectra of modern feces collected during summer, fall, winter and spring of 2010. The dominant types were: pollen of Nothofagus, Empetrum rubrum, Asteraceae subfam. Asteroideae, Nassauvia, Caryophyllaceae and Poaceae; fern spores; remains of Eimeria macusaniensis; and plant remains of Poaceae, Festuca pallescens, Stipa speciosa, Armeria maritima, Gaultheria mucronata and E. rubrum. Pollen spectra of modern and fossil feces were used for multivariate analysis. Coprolites associated to fall and winter modern feces. These results and those obtained from pollen concentration values and the presence of pollen types indicators of seasonality, allowed the determination of summer, fall and winter coprolites. However, caution must be taken with the seasonality results of coprolites dated earlier than 9000 years BP since the environmental conditions differed from now. The site was probably a camelid shelter during the unfavorable seasons.

  13. The hydrogeologic-geochemical model of Cerro Prieto revisited

    SciTech Connect

    Lippmann, M.J.; Halfman, S.E.; Truesdell, A.H.; Manon M., A.

    1989-01-01

    As the exploitation of the Cerro Prieto, Mexico, geothermal field continues, there is increasing evidence that the hydrogeologic model developed by Halfman et al. (1984, 1986) presents the basic features controlling the movement of geothermal fluids in the system. At the present time the total installed capacity at Cerro Prieto is 620 MWe requiring the production of more than 10,500 tonnes/hr of a brine-steam mixture. This significant rate of fluid production has resulted in changes in reservoir thermodynamic conditions and in the chemistry of the produced fluids. After reviewing the hydrogeologic-geochemical model of Cerro Prieto, some of the changes observed in the field due to its exploitation are discussed and interpreted on the basis of the model. 21 refs., 11 figs., 1 tab.

  14. Slab-derived melt metasomatism: an example from Patagonia

    NASA Astrophysics Data System (ADS)

    Faccini, Barbara; Coltorti, Massimo; Bonadiman, Costanza; Grégoire, Michel; Siena, Franca

    2010-05-01

    Slab-melts travelling through the mantle wedge induce various kinds of reactions in the peridotite, and, depending on melt/rock ratio, can cause cryptic and/or modal enrichments with the production of orthopyroxene + amphibole and phlogopite at the expense of olivine. The generation of new opx is a peculiar petrographical feature both as crystals formed at the expense of olivine and as fibrous aggregates in the peridotitic matrix, and veins. Ultramafic xenoliths found in Quaternary volcanics at Cerro del Fraile, Patagonia, only 150 km from the trench, represent fragments of the mantle wedge above the subducting Antarctic plate. Samples are protogranular lherzolites, with minor harzburgites, dunites and plagioclase-bearing orthopyroxenites and websterites. Two composite samples are characterized by dunites cut by orthopyroxenite or clinopyroxenite veins. Primary cpx of peridotites (cpx1) and of the clinopyroxenite vein have mg# ranging from 88.5 to 93.5 with very low TiO2 contents, whereas cpx in orthopyroxenites have lower mg# and higher Al2O3 and TiO2 contents. Mg#, Al2O3 and Na2O of peridotitic opx range from 87.9 to 91.4, 1.33 to 4.20 wt% and 0.02 to 0.17 wt%, respectively. Opx in orthopyroxenites and websterites are characterized by lower and more variable mg# (71.9-86.9), higher Al2O3 (2.98-5.35 wt%) and similar Na2O values. Based on trace element contents cpx1 can be divided into two groups. Group1 has convex downward pattern from Gd to Lu, and variable enrichments from Eu to La: (La/Yb)N, 0.05-4.04. It has positive Sr anomaly, variable Th and U contents and a positive Zr-Hf anomaly. Group2 has lower HREE content with respect to Group1 at comparable LREE, leading to higher (La/Yb)N (1.83-14.23). It has the highest Th and U contents, the widest Zr-Hf positive anomalies and a huge Ti through. Cpx of clinopyroxenite vein have a flat REE pattern [(La/Yb)N, 1.24-1.74] with a marked positive Sr spike. Opx in peridotites are of two types (even in the same sample

  15. Gas chemistry and thermometry of the Cerro Prieto geothermal field

    SciTech Connect

    Nehring, N.L.; D'Amore, F.

    1981-01-01

    Geothermal gases at Cerro Prieto are derived from high temperature reactions within the reservoir or are introduced with recharge water. Gases collected from geothermal wells should, therefore, reflect reservoir conditions. Interpretation of gas compositions of wells indicates reservoir temperatures, controls of oxygen and sulfur fugacities, and recharge source and direction.

  16. Preliminary simulation studies related to the Cerro Prieto Field

    SciTech Connect

    Lippmann, M.J.; Bodvarsson, G.S.; Witherspoon, P.A.; Rivera, J.R.

    1980-01-01

    Results of preliminary numerical simulations of the behavior of the Cerro Prieto field are discussed. The purpose of these studies is to examine: (1) the effect of using conventional isothermal methods of well test data analysis for geothermal systems, and (2) the influence of recharge from over under underlying aquifers on the temperature of a producing geothermal reservoir. 8 refs.

  17. Geochemical and isotopic characterization of mantle xenoliths from the back arc region of north Patagonia

    NASA Astrophysics Data System (ADS)

    Mundl, Andrea; Ntaflos, Theodoros; Lukás, Ackerman; Bizimis, Michael; Bjerg, Ernesto; Hauzenberger, Christoph

    2015-04-01

    Mantle xenoliths brought to the surface by alkali basalts in north Patagonia, Argentina, were studied for their geochemical and isotopic compositions. Samples were collected at four different outcrops within the North Patagonian Massif in Rio Negro Province. The studied sample suite from Comallo (COM), Puesto Diaz (PD), Cerro Chenque (CH) and Prahuaniyeu (PRA) comprises anhydrous spinel-harzburgites, spinel-dunites, as well as one PRA spinel-garnet-lherzolite. Bulk rock Al2O3 and CaO compositions of the studied samples lie within a narrow range of 0.68 to 1.31 wt. % and 0.36 to 1.25 wt. %, respectively. Al2O3 and CaO decrease with increasing MgO ranging from 44.7 to 48.0 wt. %. The single spinel-garnet lherzolite has a more fertile composition with CaO, Al2O3 and MgO of 2.78 wt. %, 2.35 wt. % and 42.2 wt. %, respectively. With the exception of the PRA region, the studied mantle xenoliths represent an overall highly depleted lithospheric mantle underneath northern Patagonia (up to 25% melt extraction). The rock forming minerals show concentrations typical for depleted peridotites with mg# that range from 0.91 to 0.92 for olivine and orthopyroxene and mg# from 0.91 to 0.95 for clinopyroxene. Variably elevated clinopyroxene trace element compositions in all studied north Patagonian mantle samples indicate reactions with a chromatographically fractionated melt after the initial melt depletion event. A percolating melt reacts with a strongly depleted mantle peridotite as it propagates through the wall rock and subsequently changes its composition. These melt-rock reactions lead to a compositionally evolving melt and variably altered mantle sections, which is strongly reflected in primitive mantle normalized clinopyroxene trace element patterns. Bulk rock and mineral compositions, on the other hand, suggest that this melt percolation event has not significantly affected major element systematics. Contrary, isotope and HSE systematics also indicate melt-rock reactions. In

  18. Holocene peatland carbon dynamics in Patagonia

    NASA Astrophysics Data System (ADS)

    Loisel, Julie; Yu, Zicheng

    2013-06-01

    Patagonian peatland ecosystems have received very little attention in the scientific literature despite their widespread distribution in the regional landscape and the anthropogenic pressure they experience from the peat extraction industry. The functioning of these southern peatlands is strikingly similar to that of northern peatlands, but they have developed under very different climate boundary conditions. Therefore, studying these ecosystems provides a unique opportunity to test ideas and hypotheses about the sensitivity of carbon-rich peat accumulating ecosystems to climate change, in addition to filling significant data and knowledge gaps. Here we provide a synthesis of detailed peat accumulation records for southern Patagonia using a combination of new peat-core analysis (from 4 sites) and a data review from previously published studies (from 19 sites). We also present the modern climate space (temperature, precipitation, and seasonality ranges) of Patagonian peatlands on the basis of modern peatland distribution and gridded climate data to discuss climate controls of Patagonian peatlands at the present and in the past by inference. Results indicated that Patagonian peatlands occupy a distinct climatological niche that corresponds to an end-member of the northern peatland climate domain, with a mild mean annual temperature (from 3 to 9 °C) and very weak temperature seasonality. We also found that Patagonian peatlands have been efficient land carbon sinks since their initiation, with a mean soil carbon density of 168 kg C m-2 ± 10%. The total carbon pool for these ecosystems was estimated at 7.6 GtC. Modeled peat addition rates to the catotelm in Patagonian peatlands were significantly higher than what has been reported for northern peatlands, but decay coefficients were similar between these two high-latitude regions. These results support the idea that long, mild growing seasons promote peat formation in southern Patagonia. At the regional scale however

  19. Holocene coastal paleoenvironments in Atlantic Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    González Bonorino, G.; Bujalesky, G.; Colombo, F.; Ferrero, M.

    1999-11-01

    The Atlantic shoreline in Patagonia, southernmost South America, is a paraglacial coast that has undergone extensive erosion and retreat since the late Pleistocene, releasing a large volume of sand and gravel to southward littoral drift. Despite regional erosive conditions, accretionary landforms developed during the Holocene in three coastal reentrants. These are, from north to south along a 200 km long shoreline stretch: (1) the cuspate foreland that underlies Bustamante Point, in the Rı´o Gallegos Estuary; (2) the cuspate foreland with incipient spit underlying Dungeness Point, in the eastern Strait of Magellan; (3) the San Sebastián Bay tidal flat; and (4) the El Páramo Spit, partly enclosing the San Sebastián Bay. These accretionary landforms contain a record of relative sea level changes for approximately the past 7 ka, and indicate a tectonically driven drop of about 3 m during growth of Bustamante Point and of 1-2 m in the other areas. Differential sea level fall influenced development of the landforms, with slower rates favoring spit development in the south.

  20. Glaciers in Patagonia: Controversy and prospects

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Alho, P.; Buytaert, W.; Célleri, R.; Cogley, J. G.; Dussaillant, A.; Guido, Z.; Haeberli, W.; Harrison, S.; Leonard, G.; Maxwell, A.; Meier, C.; Poveda, G.; Reid, B.; Reynolds, J.; Rodríguez, C. A. Portocarrero; Romero, H.; Schneider, J.

    2012-05-01

    Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilities—a US7- to 10-billion megaproject—in a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate change—both anthropogenic and natural—is fundamental to glaciology and to glaciers' practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater.

  1. Progress report on LBL's numerical modeling studies on Cerro Prieto

    SciTech Connect

    Halfman-Dooley, S.E.; Lippman, M.J.; Bodvarsson, G.S.

    1989-04-01

    An exploitation model of the Cerro Prieto geothermal system is needed to assess the energy capacity of the field, estimate its productive lifetime and develop an optimal reservoir management plan. The model must consider the natural state (i.e., pre-exploitation) conditions of the system and be able to predict changes in the reservoir thermodynamic conditions (and fluid chemistry) in response to fluid production (and injection). This paper discusses the results of a three-dimensional numerical simulation of the natural state conditions of the Cerro Prieto field and compares computed and observed pressure and temperature/enthalpy changes for the 1973--1987 production period. 16 refs., 24 figs., 2 tabs.

  2. Criteria for determining casing depth in Cerro Prieto

    SciTech Connect

    Olivas M., H.M.; Vaca S., J.M.E.

    1982-08-10

    On the basis of geological data obtained during drilling and its relation to electric logs, together with the problems that arose when drilling through formations until the production zone was reached, it is possible to establish the most suitable manner to line a well and thus formulate an optimum casings program. The main criteria to be taken into consideration in preparing such a program and its application in the drilling of wells programmed in Cerro Prieto to optimize and economize such drilling and achieve suitable techniques for well completion are presented. The criteria are based on the characteristics of the Cerro Prieto field and on casing design factors, as well as a experience gained during drilling in such a field.

  3. Seismic discrimination of a geothermal field: Cerro Prieto

    SciTech Connect

    Blakeslee, S.

    1984-04-01

    Extensive reprocessing of a subset of the seismic reflection data from Cerro Prieto has been performed. The formations and faults identified in the resulting seismic profile were correlated to cross-sections constructed from well log data. The production region coincides with a zone of reflection attenuation. A detailed velocity analysis reveals a lid of high velocity events rimming the reflection attenuation zone. This may prove to be a valuable discriminant for locating a geothermal resource using seismic reflection data.

  4. Near-Ground optical turbulence measurements at Cerro Las Campanas

    NASA Astrophysics Data System (ADS)

    Prieto, G.; Berdja, A.; Thomas-Osip, J. E.

    2011-11-01

    We report preliminary results from Near-Ground optical turbulence measurements carried out at Cerro Las Campanas, the future site of the Giant Magellan Telescope (GMT), using MooSci (Moon Scintillomenter), DIMM (Differential Image Motion Monitor) and MASS (Multiple Aperture Scintillation Sensor), focusing on the effects above the future GMT enclosure. This campaign will continue with future observations of the NGL turbulence in order to better model the adaptive optics performance and aid in the design of the GMT AO instrumentation

  5. Dating thermal events at Cerro Prieto using fission track annealing

    SciTech Connect

    Sanford, S.J.; Elders, W..

    1981-01-01

    Data from laboratory experiments and geologic fading studies were compiled from published sources to produce lines of iso-annealing for apatite in time-temperature space. Fission track ages were calculated for samples from two wells at Cerro Prieto, one with an apparently simple and one with an apparently complex thermal history. Temperatures were estimated by empirical vitrinite reflectance geothermometry, fluid inclusion homogenization and oxygen isotope equilibrium. These estimates were compared with logs of measured borehole temperatures.

  6. Reservoir simulation and geochemical study of Cerro Prieto I wells

    SciTech Connect

    Lippmann, M.J. ); Truesdell, A.H. )

    1990-03-01

    Combined reservoir simulation and geochemical data analysis are used to investigate the effects of recharge and other reservoir processes occurring in the western part of the Cerro Prieto, Mexico, geothermal field (i.e., Cerro Prieto I area). Enthalpy-based temperatures and bottomhole temperatures are calculated based on simplified models of the system, considering different reservoir boundary conditions and zones of contrasting initial temperatures and reservoir properties. By matching the computed trends with geothermometer-based temperature and enthalpy histories of producing wells, the main processes active in the western area of Cerro Prieto are identified. This part of the geothermal system is strongly influenced by nearby groundwater aquifers; cooler waters readily recharge the reservoirs. In response to exploitation, the natural influx of cold water into the shallower alpha reservoir is mainly from the west and down Fault L, while the recharge to the deeper beta reservoir in this part of the field, seems to be only lateral, from the west and possibly south. 11 refs., 12 figs.

  7. Current state of the hydrothermal geochemistry studies at Cerro Prieto

    SciTech Connect

    Fausto L, J.J.; Jimenez S, M.E.; Esquer P, I.

    1981-01-01

    The current state of hydrothermal geochemistry studies being carried out at the field are reported. These studies are based on the results of chemical analysis of water samples collected during 1979 and 1980 at the geothermal wells of the area known as Cerro Prieto I, as well as from those located in the Cerro Prieto II and Cerro Prieto III areas, some of which have only recently started flowing. Data are presented on the chemical variations of the main chemical constituents dissolved in the waters, as well as on the Na/K and Na-K-Ca chemical relations and the temperatures calculated from them and from SiO/sub 2/. Fluid recharge into the reservoir and its direction of flow are interpreted from isotherm contour maps of the field prepared from Na/K and Na-K-Ca geothermometry and from concentration contour maps of some of the main chemical constituents. Well M-43 is discussed as an example of a well affected by well completion problems in its production casing. Its behavior is explained on the basis of the chemical characteristics of the produced water. The chemical changes that have taken place in some of the wells during production are explained by correlating the chemistry with the production mechanisms of the well (steam-water production rates).

  8. Microfossils from Cerro Prieto geothermal wells, Baja California, Mexico

    SciTech Connect

    Cotton, M.L.; Haar, S.V.

    1982-08-10

    To aid in a paleonenvironmental and age reconstruction of the Cerro Prieto reservoir system, 59 samples of well cuttings were analyzed for microfossils. The cuttings were obtained at depths from 351 to 3495m in 14 geothermal wells in the Cerro Prieto field, Baja California, Mexico. Foraminifera was found in 6 samples, ostracodes in 19 samples and mannoplankton as coccoliths in 24 samples. Other groups, such as molluscus, insects, fish skeletal parts, and plant material were occasionally present. Detailed interpretations at this time cannot be made because of poor preservation of samples. This is primarily due to causes: dissolution by geothermal fluids that reach 350/sup 0/C, and the extensive mixing of filled Cretaceous forms (reworked from the Colorado Plateau region) with Tertiary species during drilling. Further studies of ostracodes and foraminifera from colder portions of the wells are needed. The abundant and well-preserved ostracodes indicate marine to backish water inviroments that correspond in part, to lagoonal or estuarine facies. The presence of the mid-Tertiary (15-m.y.-old) marine foraminifera, Cassigerinela chipolensis, in wells M-11 and M-38, 350 to 500m deep, is perplexing. These are not laboratory contaminates and, as yet have not been found in the drilling mud. If further studies confirm their presence at Cerro Prieto, established ideas about the opening of the Gulf of California and about Pacific Coast mid-Tertiary history will need to be rewritten.

  9. Microfossils from Cerro Prieto geothermal wells, Baja California, Mexico

    SciTech Connect

    Cotton, M.L.; Vonder Haar, S.

    1980-01-01

    To aid in a paleoenvironmental and age reconstruction of the Cerro Prieto reservoir system, 59 samples of well cuttings were analyzed for microfossils. The cuttings were obtained at depths from 351 to 3495 m in 14 geothermal wells in the Cerro Prieto field, Baja California, Mexico. We found foraminifera in 6 samples, ostracodes in 19 samples, and nannoplankton as coccoliths in 24 samples. Other groups, such as molluscs, insects, fish skeletal parts, and plant material were occasionally present. Detailed interpretations are not possible at this time because of poor preservation of samples. This is primarily due to causes: dissolution by geothermal fluids that reach 350{sup 0}C, and the extensive mixing of filled Cretaceous forms (reworked from the Colorado Plateau region) with Tertiary species during drilling. Further studies of ostracodes and foraminifera from colder portions of the wells are needed. The abundant and well-preserved ostracodes indicate marine to brackish water environments that correspond, in part, to lagoonal or estuarine facies. The presence of the mid-Tertiary (15-My-old) marine foraminifera, Cassigerinela chipolensis, in wells M-11 and M-38, 350 to 500 m deep, is perplexing. These are not laboratory contaminates and, as yet, have not been found in the drilling mud. If further studies confirm their presence at Cerro Prieto, established ideas about the opening of the Gulf of California and about Pacific Coast mid-Tertiary history will need to be rewritten.

  10. Seismotectonics of the Cerro Prieto Geothermal Field, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Rebollar, C. J.; Reyes, L. M.; Quintanar, L.; Arellano, J. F.

    2002-12-01

    We studied the background seismic activity in the Cerro Prieto geothermal field (CPGF) using a network of 21 digital stations. Earthquakes are located below the exploitation area of the CPGF, between 3 and 12 km depth, within the basement. Earthquakes follow roughly a N30°E trend perpendicular to the Cerro Prieto fault. This activity is located on a horst-like structure below the geothermal field and coincides with the zone of maximum subsidence in the CPGF. Two earthquake swarms occurred along the SE-NW strike of the Cerro Prieto fault and in the neighborhood of the Cerro Prieto volcano. Magnitudes range from -0.3 to 2.5. A Vp/Vs=1.91 ratio of the activity below the volcano suggests a water-saturated medium and/or a partial-melt medium. We calculated 76 focal mechanisms of individual events. On June 1 and September 10, 1999, two earthquakes of Mw 5.2 and 5.3 occurred in the basement at depths of 7.4 and 3.8 km below the CPGF. Maximum peak accelerations above the hypocenter ranged from 128.0 to 432.0 cm/s2. Waveform modeling results in a fault geometries given by strike=236°, dip=60°, rake=-58° (normal) and strike=10°, dip=90°, rake=159° (right lateral strike-slip) for the June and September events. Observed triangular source time function of 0.7 seconds and a double source with a total duration of 1.9 seconds for the June and September events were used to calculate the synthetics seismograms. Static stress drops and seismic moments for the June and September events are: Δ\\sigma=82.5 MPa (825 bars), Mo= 7.65x1016 Nm (7.65x1023 dyne-cm) and Δ\\sigma=31.3 MPa (313 bars) and Mo=1.27x1017 Nm (1.27x1024 dyne-cm). These stress drops are typical of continental events rather than stress drops of events originated in spreading centers. We concluded from the focal mechanisms of the background seismicity and June and September 1999 events, that a complex stress environment exits in the CPGF due to the continual thinning of the crust in the Cerro Prieto basin.

  11. Geologic map of the Patagonia Mountains, Santa Cruz County, Arizona

    USGS Publications Warehouse

    Graybeal, Frederick T.; Moyer, Lorre A.; Vikre, Peter; Dunlap, Pamela; Wallis, John C.

    2015-01-01

    Several spatial databases provide data for the geologic map of the Patagonia Mountains in Arizona. The data can be viewed and queried in ArcGIS 10, a geographic information system; a geologic map is also available in PDF format. All products are available online only.

  12. Shaded relief, color as height Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This topographic image of Patagonia, Argentina shows a spectacular landscape formed by volcanoes, rivers, and wind. The area is located just east of the narrow range of the Andes Mountains, about 100 kilometers (62 miles) east of the border with Chile. Interesting features include basalt-capped mesas with sinkholes (lower center), arcuate ridges of windblown beach sands downwind from a salty desert lake (upper center), young volcanic cones(right), and at least one case of what geologists call 'inverted relief'. This happens when lava flows down a valley in soft material and then the soft material is eroded away leaving the former valley as a ridge of lava. These ridges can be seen on the slopes of the volcano in the upper right. Geologists will use SRTM topographic data to study the interaction of volcanic, climatic and erosional processes.

    This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Colors show the elevation as measured by SRTM. Colors range from blue at the lowest elevations to white at the highest elevations. This image contains about 1100 meters(3600 feet) of total relief. White speckles on the face of some of the mountains are holes in the data caused by steep terrain. These will be filled using coverage from an intersecting pass.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11,2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added

  13. Complete Genome Sequence and Methylome of Salmonella enterica subsp. enterica Cerro, a Frequent Dairy Cow Serovar.

    PubMed

    Haley, Bradd J; Pirone, Cary; Muruvanda, Tim; Brown, Eric; Allard, Marc; Karns, Jeffrey S; Van Kessel, Jo Ann S

    2016-01-28

    Salmonella enterica subsp. enterica serovar Cerro is an infrequent pathogen of humans and other mammals but is frequently isolated from the hindgut of asymptomatic cattle in the United States. To further understand the genomic determinants of S. Cerro specificity for the bovine hindgut, the genome of isolate CFSAN001588 was fully sequenced and deposited in the GenBank database.

  14. Geophysical Investigations of Magma Plumbing Systems at Cerro Negro Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    MacQueen, Patricia Grace

    Cerro Negro near Leon, Nicaragua is a very young (163 years), relatively small basaltic cinder cone volcano that has been unusually active during its short lifespan (recurrence interval 6--7 years), presenting a significant hazard to nearby communities. Previous studies have raised several questions as to the proper classification of Cerro Negro and its relation to neighboring Las Pilas-El Hoyo volcano. Analysis of Bouguer gravity data collected at Cerro Negro has revealed connected positive density anomalies beneath Cerro Negro and Las Pilas-El Hoyo. These findings suggest that eruptions at Cerro Negro may be tapping a large magma reservoir beneath Las Pilas-El Hoyo, implying that Cerro Negro should be considered the newest vent on the Las Pilas-El Hoyo volcanic complex. As such, it is possible that the intensity of volcanic hazards at Cerro Negro may eventually increase in the future to resemble those pertaining to a stratovolcano. Keywords: Cerro Negro; Las Pilas-El Hoyo; Bouguer gravity; magmatic plumbing systems; potential fields; volcano.

  15. Theoretical studies of Cerro Prieto brines chemical equilibria

    SciTech Connect

    Iglesias, E.R.; Weres, O.

    1980-02-01

    A chemical equilibrium model is used, implemented in a compact FORTRAN package called HITEQ, to investigate possible mineral deposition related to prereinjection treatment of Cerro Prieto brines for silica removal. Large saturation ratios of the treated brines with respect to several minerals are indicated by these computations. As a remedy, an inexpensive CO/sub 2/ removal scheme aimed at inhibiting carbonate mineral precipitation is proposed. This scheme is quantitatively discussed with the aid of HITEQ. It is concluded that the proposed treatment is both technically and economically feasible.

  16. Atmospheric conditions at Cerro Armazones derived from astronomical data

    NASA Astrophysics Data System (ADS)

    Lakićević, Maša; Kimeswenger, Stefan; Noll, Stefan; Kausch, Wolfgang; Unterguggenberger, Stefanie; Kerber, Florian

    2016-04-01

    Aims: We studied the precipitable water vapour (PWV) content near Cerro Armazones and discuss the potential use of our technique of modelling the telluric absorbtion lines for the investigation of other molecular layers. The site is designated for the European Extremely Large Telescope (E-ELT) and the nearby planned site for the Čerenkov Telescope Array (CTA). Methods: Spectroscopic data from the Bochum Echelle Spectroscopic Observer (BESO) instrument were investigated by using a line-by-line radiative transfer model (LBLRTM) for the Earth's atmosphere with the telluric absorption correction tool molecfit. All observations from the archive in the period from December 2008 to the end of 2014 were investigated. The dataset completely covers the El Niño event registered in the period 2009-2010. Models of the 3D Global Data Assimilation System (GDAS) were used for further comparison. Moreover, we present a direct comparison for those days for which data from a similar study with VLT/X-Shooter and microwave radiometer LHATPRO at Cerro Paranal are available. Results: This analysis shows that the site has systematically lower PWV values, even after accounting for the decrease in PWV expected from the higher altitude of the site with respect to Cerro Paranal, using the average atmosphere found with radiosondes. We found that GDAS data are not a suitable basis for predicting local atmospheric conditions - they usually systematically overestimate the PWV values. The large sample furthermore enabled us to characterize the site with respect to symmetry across the sky and variation with the years and within the seasons. This technique of studying the atmospheric conditions is shown to be a promising step into a possible monitoring equipment for the CTA. Based on archival observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile and of the Cerro Armazones Observatory facilities of the Ruhr Universität Bochum.Full Table 1

  17. The chronology of hand stencils in European Palaeolithic rock art: implications of new U-series results from El Castillo Cave (Cantabria, Spain).

    PubMed

    García-Diez, Marcos; Garrido, Daniel; Hoffmann, Dirk; Pettitt, Paul; Pike, Alistair; Zilhão, Joao

    2015-07-20

    The hand stencils of European Paleolithic art tend to be considered of pre-Magdalenian age and scholars have generally assigned them to the Gravettian period. At El Castillo Cave, application of U-series dating to calcite accretions has established a minimum age of 37,290 years for underlying red hand stencils, implying execution in the earlier part of the Aurignacian if not beforehand. Together with the series of red disks, one of which has a minimum age of 40,800 years, these motifs lie at the base of the El Castillo parietal stratigraphy. The similarity in technique and colour support the notion that both kinds of artistic manifestations are synchronic and define an initial, non-figurative phase of European cave art. However, available data indicate that hand stencils continued to be painted subsequently. Currently, the youngest, reliably dated examples fall in the Late Gravettian, approximately 27,000 years ago.

  18. The chronology of hand stencils in European Palaeolithic rock art: implications of new U-series results from El Castillo Cave (Cantabria, Spain).

    PubMed

    García-Diez, Marcos; Garrido, Daniel; Hoffmann, Dirk; Pettitt, Paul; Pike, Alistair; Zilhão, Joao

    2015-07-20

    The hand stencils of European Paleolithic art tend to be considered of pre-Magdalenian age and scholars have generally assigned them to the Gravettian period. At El Castillo Cave, application of U-series dating to calcite accretions has established a minimum age of 37,290 years for underlying red hand stencils, implying execution in the earlier part of the Aurignacian if not beforehand. Together with the series of red disks, one of which has a minimum age of 40,800 years, these motifs lie at the base of the El Castillo parietal stratigraphy. The similarity in technique and colour support the notion that both kinds of artistic manifestations are synchronic and define an initial, non-figurative phase of European cave art. However, available data indicate that hand stencils continued to be painted subsequently. Currently, the youngest, reliably dated examples fall in the Late Gravettian, approximately 27,000 years ago. PMID:25615428

  19. Precision gravity studies at Cerro Prieto: a progress report

    SciTech Connect

    Grannell, R.B.; Kroll, R.C.; Wyman, R.M.; Aronstam, P.S.

    1981-01-01

    A third and fourth year of precision gravity data collection and reduction have now been completed at the Cerro Prieto geothermal field. In summary, 66 permanently monumented stations were occupied between December and April of 1979 to 1980 and 1980 to 1981 by a LaCoste and Romberg gravity meter (G300) at least twice, with a minimum of four replicate values obtained each time. Station 20 alternate, a stable base located on Cerro Prieto volcano, was used as the reference base for the third year and all the stations were tied to this base, using four to five hour loops. The field data were reduced to observed gravity values by (1) multiplication with the appropriate calibration factor; (2) removal of calculated tidal effects; (3) calculation of average values at each station, and (4) linear removal of accumulated instrumental drift which remained after carrying out the first three reductions. Following the reduction of values and calculation of gravity differences between individual stations and the base stations, standard deviations were calculated for the averaged occupation values (two to three per station). In addition, pooled variance calculations were carried out to estimate precision for the surveys as a whole.

  20. Exploration and development of the Cerro Prieto geothermal field

    SciTech Connect

    Lippmann, M.J.; Goldstein, N.E.; Halfman, S.E.; Witherspoon, P.A.

    1983-07-01

    A multidisciplinary effort to locate, delineate, and characterize the geothermal system at Cerro Prieto, Baja California, Mexico, began about 25 years ago. It led to the identification of an important high-temperature, liquid-dominated geothermal system which went into production in 1973. Initially, the effort was undertaken principally by the Mexican electric power agency, the Comision Federal de Electricidad (CFE). Starting in 1977 a group of US organizations sponsored by the US Department of Energy, joined CFE in this endeavor. An evaluation of the different studies carried out at Cerro Prieto has shown that: (1) surface electrical resistivity and seismic reflection surveys are useful in defining targets for exploratory drilling; (2) the mineralogical studies of cores and cuttings and the analysis of well logs are important in designing the completion of wells, identifying geological controls on fluid movement, determining thermal effects and inferring the thermal history of the field; (3) geochemical surveys help to define zones of recharge and paths of fluid migration; and (4) reservoir engineering studies are necessary in establishing the characteristics of the reservoir and in predicting its response to fluid production.

  1. Hydrocarbons emissions from Cerro Prieto Geothermal Power Plant, Mexico

    NASA Astrophysics Data System (ADS)

    Navarro, Karina; Navarro-González, Rafael; de la Rosa, José; Peralta, Oscar; Castro, Telma; Imaz, Mireya

    2014-05-01

    One of the most important environmental issues related to the use of geothermal fluids to generate electricity is the emission of non-condensable gases to the atmosphere. Mexico has one of the largest geothermal plants in the world. The facility is located at Cerro Prieto, Baja California, roughly 30 km south of Mexicali and the international boundary between Mexico and United States. The Cerro Prieto power plant has 13 units grouped on four individual powerhouses. Gas samples from 9 units of the four powerhouses were collected during 4 campaigns conducted in May-July, 2010, February, 2012, December, 2012, and May, 2013. Gas samples from the stacks were collected in 1000 ml Pyrex round flasks with Teflon stopcocks, and analyzed by gas chromatography-mass spectrometry. Methane was the most abundant aliphatic hydrocarbon, with a concentration that ranged from less than 1% up to 3.5% of the total gas mixture. Normal alkanes represented the second most abundant species, and displayed a decreasing abundance with increasing carbon number in the homologous series. Isoalkanes were also present as isobutane and isopentane. Cycloalkanes occurring as cyclopentane and cyclohexane, were detected only at trace level. Unsaturated hydrocarbons (alkenes and alkynes) were not detected. Benzene was detected at levels ranging from less than 1% up to 3.4% of the total gas mixture. Other aromatic hydrocarbons detected were toluene, and xylenes, and were present at lower concentrations (

  2. SRTM Radar - Landsat Image Comparison, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    In addition to an elevation model of most of Earth'slandmass, the Shuttle Radar Topography Mission will produce C-band radar imagery of the same area. This imagery is essentially a 10-day snapshot view of the Earth, as observed with 5.8 centimeter wavelength radar signals that were transmitted from the Shuttle, reflected by the Earth, and then recorded on the Shuttle. This six-image mosaic shows two examples of SRTM radar images (center) with comparisons to images acquired by the Landsat 7 satellite in the visible wavelengths (left) and an infrared wavelength (right). Both sets of images show lava flows in northern Patagonia, Argentina. In each case, the lava flows are relatively young compared to the surrounding rock formations.

    In visible light (left) image brightness corresponds to mineral chemistry and -- as expected -- both lava flows appear dark. Generally, the upper flow sits atop much lighter bedrock, providing good contrast and making the edges of the flow distinct. However, the lower flow borders some rocks that are similarly dark, and the flow boundaries are somewhat obscured. Meanwhile, in the radar images (center), image brightness corresponds to surface roughness (and topographic orientation) and substantial differences between the flows are visible. Much of the top flow appears dark, meaning it is fairly smooth. Consequently, it forms little or no contrast with the smooth and dark surrounding bedrock and thus virtually vanishes from view. However, the lower flow appears rough and bright and mostly forms good contrast with adjacent bedrock such that the flow is locally more distinct here than in the visible Landsat view. For further comparison, infrared Landsat images (right) again show image brightnesses related to mineral chemistry, but the lava flows appear lighter than in the visible wavelengths. Consequently, the lower lava flow becomes fairly obscure among the various surrounding rocks, just as the upper flow did in the radar image. The

  3. Paleoparasitological analysis of a raptor pellet from southern Patagonia.

    PubMed

    Fugassa, M H; Sardella, N H; Denegri, G M

    2007-04-01

    Organic remains attributable to one regurgitated pellet were examined. The pellet, belonging to a bird of prey and collected from a cave of Southern Patagonia, was dated at 6,540 +/- 110 yr. With standard paleoparasitological procedures, eggs of Capillaria sp. and a mite, Demodex sp., were found. The parasites found in the pellet belong to a rodent ingested by the bird. The present report constitutes the first paleoparasitological study of a regurgitated pellet. PMID:17539429

  4. Paleoparasitological analysis of a raptor pellet from southern Patagonia.

    PubMed

    Fugassa, M H; Sardella, N H; Denegri, G M

    2007-04-01

    Organic remains attributable to one regurgitated pellet were examined. The pellet, belonging to a bird of prey and collected from a cave of Southern Patagonia, was dated at 6,540 +/- 110 yr. With standard paleoparasitological procedures, eggs of Capillaria sp. and a mite, Demodex sp., were found. The parasites found in the pellet belong to a rodent ingested by the bird. The present report constitutes the first paleoparasitological study of a regurgitated pellet.

  5. Biometric identification of capillariid eggs from archaeological sites in Patagonia.

    PubMed

    Taglioretti, V; Fugassa, M H; Beltrame, M O; Sardella, N H

    2014-06-01

    Numerous eggs of capillariid nematodes have been found in coprolites from a wide range of hosts and in raptor pellets in archaeological samples from Patagonia. The structure and sculpture of the eggshell of these nematodes and their biometry are commonly used for identification. The aim of this study was to determine whether eggs of the genus Calodium with similar morphology, found in different archaeological samples from Patagonia, belong to the same species. For this purpose, capillariid eggs (N= 843) with thick walls and radial striations were studied by permutational multivariate analysis of variance (PERMANOVA). Eggs exhibiting similar shape and structure also showed similar biometry, regardless of the zoological origin of coprolites (P= 0.84), host diet (P= 0.19), character of the archaeological sites (P= 0.67) and chronology (P= 0.66). Thus, they were attributed to the same species. We suggest that an unidentified zoonotic species of the genus Calodium occurred in the digestive tract of a wide range of hosts in Patagonia during the Holocene and that both human and animal populations were exposed to this parasite during the Holocene in the study area.

  6. A review of progress in understanding the fluid geochemistry of the Cerro Prieto geothermal system

    USGS Publications Warehouse

    Truesdell, A.H.; Nehring, N.L.; Thompson, J.M.; Janik, C.J.; Coplen, T.B.

    1984-01-01

    Fluid geochemistry has played a major role in our present understanding of the Cerro Prieto geothermal system. Fluid chemical and isotopic compositions have been used to indicate the origin of water, salts and gases, original subsurface temperature and fluid flow, fluid-production mechanisms, and production-induced aquifer boiling and cold-water entry. The extensive geochemical data and interpretations for Cerro Prieto published from 1964 to 1981 are reviewed and discussed. Fluid geochemistry must continue to play an important role in the further development of the Cerro Prieto field. ?? 1984.

  7. Progress on the biphase turbine at Cerro Prieto

    SciTech Connect

    Cerini, D.; Hays, L.; Studhalter, W.

    1997-12-31

    The status of a Biphase turbine power plant being installed at the Cerro Prieto geothermal field is presented. The major modules for the power plant are completed except for a back pressure steam turbine. The power plant will be started in April 1997 with the Biphase turbine alone followed by the addition of the steam turbine module two months later. The current power plant performance level is 2780 kWe due to a decline in the well. An increase in power output to 4060 kWe by adding the flow from another well is planned. The addition of five Biphase power plants with a total power output of 21.2 megawatts is described.

  8. Properties of Cerro Prieto rock at simulated in situ conditions

    SciTech Connect

    Schatz, J.F.

    1981-01-01

    Rocks from the Cerro Prieto Geothermal Field were tested under simulated in situ conditions in the laboratory to determine their properties and response to pore pressure reduction as would be caused by reservoir production. The primary purpose of the project was to provide information on compaction and creep as they may contribute to surface subsidence. Results show typical compressibilities for reservoir rocks of about 1 x 10/sup -6/ psi/sup -1/ and creep compaction rates of about 1 x 10/sup -9/ sec/sup -1/ when triggered by 1000 psi pore pressure reduction. This creep rate would cause significant porosity reduction if it continued for several years. Therefore it becomes important to learn how to correctly extrapolate such data to long times.

  9. Geochemical evidence of drawdown in the Cerro Prieto geothermal field

    USGS Publications Warehouse

    Truesdell, A.H.; Manon, M.A.; Jimenez, S.M.E.; Sanchez, A.A.; Fausto, L.J.J.

    1979-01-01

    Some wells of the Cerro Prieto geothermal field have undergone changes in the chemistry of fluids produced which reflect reservoir processes. Pressure decreases due to production in the southeastern part of the field have produced both drawdown of lower chloride fluids from an overlying aquifer and boiling in the aquifer with excess steam reaching the wells. These reservoir changes are indicated by changes in fluid chloride concentrations, Na/K ratios and measured enthalpies and by comparisons of aquifer fluid temperatures and chloride concentrations calculated from enthalpy and chemical measurements. Fluid temperatures have not been greatly affected by this drawdown because heat contained in the rock was transferred to the fluid. When this heat is exhausted, fluid temperatures may drop rapidly. ?? 1979.

  10. The origin of the Cerro Prieto geothermal brine

    USGS Publications Warehouse

    Truesdell, A.H.; Thompson, J.M.; Coplen, T.B.; Nehring, N.L.; Janik, C.J.

    1981-01-01

    The Cerro Prieto geothermal brine may have originated from mixing of Colorado River water with seawater evaporated to about six times its normal salinity. This mixture circulated deeply and was heated by magmatic processes. During deep circulation, Li, K, Ca, B, SiO2 and rare alkalis were transferred from rock minerals to the water, and Mg, SO4, and a minor quantity of Na were transferred to the rock. Similar alteration of seawater salt chemistry has been observed in coastal geothermal systems and produced in laboratory experiments. After heating and alteration the brine was further diluted to its present range of composition. Oxygen isotopes in the fluid are in equilibrium with reservoir calcite and have been affected by exploitation-induced boiling and dilution. ?? 1981.

  11. Estudio de seeing en la zona del Cerro Champaqui (I)

    NASA Astrophysics Data System (ADS)

    Diaz, R. J.; Eikenberry, S.; Scott, J.; Levato, H.; Firpo, V.; Farina, C.; Piroddi, D.; Jamud, N.; Bosch, G.; Mudrik, A.; Guzzo, P.; Donoso, V.; Recabarren, P.; Seifer, E.

    We report the results of the most recent seeing feasibility study performed in the region of Cerro Champaqui (2800m) at the mountain range of Sierras Grandes at the Province of Cordoba. We also describe the high frequency DIMM device built for this and other seeing samplings obtained at the provinces of San Juan; San Luis and Cordoba. This work is part of a long term project started in 2006; in search of sites of very low turbulence and suited for near infrared telescopes with active and adaptive optics. Two of the sites have been monitored during a total of 46 nights distributed in six months of the period 2011-2012. The preliminary results suggest the existence of `sub-arcsecond' seeing conditions during extended periods of time in at least one location in the mountain range in the SW of Cordoba and NE of San Luis provinces. FULL TEXT IN SPANISH

  12. Results from two years of resistivity monitoring at Cerro Prieto

    SciTech Connect

    Wilt, M.J.; Goldstein, N.E.

    1981-01-01

    Dipole-dipole resistivity measurements for the combined purposes of reservoir delineation and resistivity monitoring were first made at Cerro Prieto in 1978 and have continued on an annual basis since then. Two 20 km long dipole-dipole lines with permanently emplaced electrodes at one kilometer spacings were established over the field area; one of these lines is remeasured annually. Resistivity measurements are taken using a 25 kW generator capable of up to 80A output and a microprocessor controlled signal averaging receiver; this high power-low noise system is capable of highly accurate measurements even at large transmitter-receiver separations. Standard error calculations for collected data indicate errors less than 5% for all points, but 95% confidence intervals show error limits about 2 to 4 times higher. Analysis of collected data indicate little change in the apparent resistivity of the upper 300 m over the field production zone and that in this section measurements are relatively insensitive to the annual rainfall cycle. Apparent resistivity increases were observed over the older producing zone at Cerro Prieto at depths of 1 km and greater. Large zones of decreasing apparent resistivity were observed flanking the zone of increases on both sides. The increase in apparent resistivity in the production region may be due to an increasing fraction of steam in the reservoir resulting from a production related decline in reservoir pressure. Alternatively the increases may be the result of fresh water influx from the Colorado River. The zone of declining resistivity flanking the area of increase may be due to the movement of saline waters into the reservoir region as a result of the pressure decline. Quantitative modeling of observed changes is impractical owing to the high uncertainty in estimating apparent resistivity changes and the nonuniqueness of models.

  13. Using dental enamel wrinkling to define sauropod tooth morphotypes from the Cañadón Asfalto Formation, Patagonia, Argentina.

    PubMed

    Holwerda, Femke M; Pol, Diego; Rauhut, Oliver W M

    2015-01-01

    The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic-early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by associated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity.

  14. Using Dental Enamel Wrinkling to Define Sauropod Tooth Morphotypes from the Cañadón Asfalto Formation, Patagonia, Argentina

    PubMed Central

    Holwerda, Femke M.; Pol, Diego; Rauhut, Oliver W. M.

    2015-01-01

    The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic–early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by associated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity. PMID:25692466

  15. Evidence for early Pliocene and late Miocene transgressions in southern Patagonia (Argentina): 87Sr/86Sr ages of the pectinid “Chlamys” actinodes (Sowerby)

    NASA Astrophysics Data System (ADS)

    del Río, Claudia J.; Griffin, Miguel; McArthur, John M.; Martínez, Sergio; Thirlwall, Matthew F.

    2013-11-01

    Numerical ages based on 87Sr/86Sr dating of calcitic shells belonging to the pectinid “Chlamys” actinodes (Sowerby) document the only late Miocene (Tortonian) sea flooding event in the Austral Basin at Cabo Buentiempo (8.95 ± 0.82 Ma, 2 s.e.), and provide evidence of the first documented early Pliocene (Zanclean) transgression in Argentina recorded at Cañadón Darwin (5.15 ± 0.18 Ma, 2 s.e., Austral Basin) and at Terraces of Cerro Laciar (5.10 ± 0.21 Ma, 2 s.e.), southern San Jorge Basin). The sedimentary rocks deposited during the Tortonian are correlated with the youngest beds deposited by the “Entrerriense Sea” that covered northern Patagonia. The Zanclean marine episode is correlated with the long-term cycle represented in the Southern Hemisphere by the flooding events recorded in Cockburn and James Ross Islands (Antarctica) and in North-Central Chile.

  16. Using dental enamel wrinkling to define sauropod tooth morphotypes from the Cañadón Asfalto Formation, Patagonia, Argentina.

    PubMed

    Holwerda, Femke M; Pol, Diego; Rauhut, Oliver W M

    2015-01-01

    The early Middle Jurassic is regarded as the period when sauropods diversified and became major components of the terrestrial ecosystems. Not many sites yield sauropod material of this time; however, both cranial and postcranial material of eusauropods have been found in the Cañadón Asfalto Formation (latest Early Jurassic-early Middle Jurassic) in Central Patagonia (Argentina), which may help to shed light on the early evolution of eusauropods. These eusauropod remains include teeth associated with cranial and mandibular material as well as isolated teeth found at different localities. In this study, an assemblage of sauropod teeth from the Cañadón Asfalto Formation found in four different localities in the area of Cerro Condor (Chubut, Argentina) is used as a mean of assessing sauropod species diversity at these sites. By using dental enamel wrinkling, primarily based on the shape and orientation of grooves and crests of this wrinkling, we define and describe three different morphotypes. With the exception of one taxon, for which no cranial material is currently known, these morphotypes match the local eusauropod diversity as assessed based on postcranial material. Morphotype I is tentatively assigned to Patagosaurus, whereas morphotypes II and III correspond to new taxa, which are also distinguished by associated postcranial material. This study thus shows that enamel wrinkling can be used as a tool in assessing sauropod diversity. PMID:25692466

  17. Geochemistry of igneous rocks from the Cerro Prieto geothermal field, northern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Herzig, C. T.

    1990-08-01

    Fractional crystallization of basaltic magma, derived from an oceanic affinity source region present beneath the Salton Trough and emplaced into a pull-apart basin of this continental rift regime, produced a tholeiitic suite of hypabyssal rocks consisting of basalt, andesite and dacite within the Cerro Prieto geothermal field, located in northern Baja California, Mexico. Higher light-rare-earth-element abundances for a basalt from the Cerro Prieto geothermal field in comparison to basalts from the Gulf of California and the East Pacific Rise suggest partial assimilation of crustal materials into the parental magmas generated beneath the Salton Trough. The crustal contaminant may be present near the surface today in the form of granitoids of the Peninsular Ranges batholith, at deeper levels as hydrothermally altered materials near the base of the Salton Trough, or may be a relict feature of Tertiary subduction contained within the upper mantle beneath the Salton Trough. The Sr isotopic compositions of dacites from the nearby Cerro Prieto volcano range from 0.7029 to 0.7036, indicating an oceanic affinity source for these rocks. The suite of hypabyssal rocks of tholeiitic affinity present within the Cerro Prieto geothermal field, related by fractional crystallization, link the dacite volcano of Cerro Prieto to gabbroic plutons inferred to exist beneath the Cerro Prieto geothermal field.

  18. High plant diversity in Eocene South America: Evidence from Patagonia

    USGS Publications Warehouse

    Wilf, P.; Cuneo, N.R.; Johnson, K.R.; Hicks, J.F.; Wing, S.L.; Obradovich, J.D.

    2003-01-01

    Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude ???47??S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.

  19. Gondwanide continental collision and the origin of Patagonia

    NASA Astrophysics Data System (ADS)

    Pankhurst, R. J.; Rapela, C. W.; Fanning, C. M.; Má; rquez, M.

    2006-06-01

    A review of the post-Cambrian igneous, structural and metamorphic history of Patagonia, largely revealed by a five-year programme of U-Pb zircon dating (32 samples), geochemical and isotope analysis, results in a new Late Palaeozoic collision model as the probable cause of the Gondwanide fold belts of South America and South Africa. In the northeastern part of the North Patagonian Massif, Cambro-Ordovician metasediments with a Gondwana provenance are intruded by Mid Ordovician granites analogous to those of the Famatinian arc of NW Argentina; this area is interpreted as Gondwana continental crust at least from Devonian times, probably underlain by Neoproterozoic crystalline basement affected by both Pampean and Famatinian events, with a Cambrian rifting episode previously identified in the basement of the Sierra de la Ventana. In the Devonian (following collision of the Argentine Precordillera terrane to the north), the site of magmatism jumped to the western and southwestern margins of the North Patagonian Massif, although as yet the tectonics of this magmatic event are poorly constrained. This was followed by Early Carboniferous I-type granites representing a subduction-related magmatic are and Mid Carboniferous S-type granites representing crustal anatexis. The disposition of these rocks implies that the North Patagonian Massif was in the upper plate, with northeasterly subduction beneath Gondwana prior to the collision of a southern landmass represented by the Deseado Massif and its probable extension in southeastern Patagonia. This 'Deseado terrane' may have originally rifted off from a similar position during the Cambrian episode. Intense metamorphism and granite emplacement in the upper plate continued into the Early Permian. Known aspects of Late Palaeozoic sedimentation, metamorphism, and deformation in the Sierra de la Ventana and adjacent Cape Fold Belt of South Africa are encompassed within this model. It is also compatible with modern geophysical and

  20. Geology of the Cerro Summit quadrangle, Montrose County, Colorado

    USGS Publications Warehouse

    Dickinson, Robert G.

    1966-01-01

    The Cerro Summit quadrangle covers 58 square miles of dissected plateau on the south flank of the Gunnison uplift in southwestern Colorado. It lies east of the Uncompahgre River valley and south of the Black Canyon of the Gunnison River. Rocks dip gently in most of the quadrangle, but they are locally upturned and faulted on the margin of the Gunnison uplift and are intensely deformed in the core of the uplift. The rocks exposed are of Precambrian, late Mesozoic, and Cenozoic age. Precambrian rocks include metasedimentary schist and gneiss, granitic pegmatite, and olivine gabbro. The oldest Mesozoic rocks exposed are continental, fresh-water, and lagoonal deposits in the Late Jurassic Entrada Sandstone, Wanakah Formation, and Morrison Formation. Channel-fill deposits that unconformably overlie the Jurassic rocks are possibly the Burro Canyon Formation of Early Cretaceous age. Upper Cretaceous rocks include marine and nearshore deposits of the Dakota Sandstone, Mancos Shale, and Pictured Cliffs Sandstone, and the fresh- and brackish-water sandstone, shale, and coal of the Fruitland Formation. Rocks of Late Cretaceous age that crop out in the adjacent Cimarron Ridge area may also have been deposited in this quadrangle but are now eroded; these rocks include the nonmarine Kirtland Shale and an unnamed volcanic conglomerate and tuff breccia. Nine faunal zones in the Mancos Shale help to establish the correct correlation of units in the Upper Cretaceous. The Pictured Cliffs Sandstone, Fruitland Formation, and Kirtland Shale of the Cerro Summit area have been mapped by some geologists as the Mesaverde Formation. Fossils indicate that the rocks are younger than the type Mesaverde. The unnamed volcanic rocks represent major volcanism in nearby areas. A Late Cretaceous (Maestrichtian) age for the volcanism is indicated by palynological evidence and an isotopic age of approximately 66 million years. Middle Tertiary rocks are conglomerate and tuff breccia. Upper Tertiary or

  1. Detailed interpretation of aeromagnetic data from the Patagonia Mountains area, southeastern Arizona

    USGS Publications Warehouse

    Bultman, Mark W.

    2015-01-01

    Euler deconvolution depth estimates derived from aeromagnetic data with a structural index of 0 show that mapped faults on the northern margin of the Patagonia Mountains generally agree with the depth estimates in the new geologic model. The deconvolution depth estimates also show that the concealed Patagonia Fault southwest of the Patagonia Mountains is more complex than recent geologic mapping represents. Additionally, Euler deconvolution depth estimates with a structural index of 2 locate many potential intrusive bodies that might be associated with known and unknown mineralization.

  2. Evidence of recent deep magmatic activity at Cerro Bravo-Cerro Machín volcanic complex, central Colombia. Implications for future volcanic activity at Nevado del Ruiz, Cerro Machín and other volcanoes

    NASA Astrophysics Data System (ADS)

    Londono, John Makario

    2016-09-01

    In the last nine years (2007-2015), the Cerro Bravo-Cerro Machín volcanic complex (CBCMVC), located in central Colombia, has experienced many changes in volcanic activity. In particular at Nevado del Ruiz volcano (NRV), Cerro Machin volcano (CMV) and Cerro Bravo (CBV) volcano. The recent activity of NRV, as well as increasing seismic activity at other volcanic centers of the CBCMVC, were preceded by notable changes in various geophysical and geochemical parameters, that suggests renewed magmatic activity is occurring at the volcanic complex. The onset of this activity started with seismicity located west of the volcanic complex, followed by seismicity at CBV and CMV. Later in 2010, strong seismicity was observed at NRV, with two small eruptions in 2012. After that, seismicity has been observed intermittently at other volcanic centers such as Santa Isabel, Cerro España, Paramillo de Santa Rosa, Quindío and Tolima volcanoes, which persists until today. Local deformation was observed from 2007 at NRV, followed by possible regional deformation at various volcanic centers between 2011 and 2013. In 2008, an increase in CO2 and Radon in soil was observed at CBV, followed by a change in helium isotopes at CMV between 2009 and 2011. Moreover, SO2 showed an increase from 2010 at NRV, with values remaining high until the present. These observations suggest that renewed magmatic activity is currently occurring at CBCMVC. NRV shows changes in its activity that may be related to this new magmatic activity. NRV is currently exhibiting the most activity of any volcano in the CBCMVC, which may be due to it being the only open volcanic system at this time. This suggests that over the coming years, there is a high probability of new unrest or an increase in volcanic activity of other volcanoes of the CBCMVC.

  3. Niche Segregation between Wild and Domestic Herbivores in Chilean Patagonia

    PubMed Central

    Iranzo, Esperanza C.; Traba, Juan; Acebes, Pablo; González, Benito A.; Mata, Cristina; Estades, Cristián F.; Malo, Juan E.

    2013-01-01

    Competition arises when two co-occuring species share a limiting resource. Potential for competition is higher when species have coexisted for a short time, as it is the case for herbivores and livestock introduced in natural systems. Sheep, introduced in the late 19th century in Patagonia, bear a great resemblance in size and diet to the guanaco, the main native herbivore in Patagonia. In such circumstances, it could be expected that the two species compete and one of them could be displaced. We investigated spatial overlap and habitat selection by coexisting sheep and guanaco in winter and in summer. Additionally, we studied habitat selection of the guanaco in a control situation free from sheep, both in summer and winter. We also determined overlap between species in areas with different intensity of use (named preferred and marginal areas) in order to further detect the potential level of competition in the case of overlapping. Guanaco and sheep showed significantly different habitat preferences through all seasons, in spite of their spatial overlap at landscape scale. Additionally, the habitat used by guanaco was similar regardless of the presence or absence of livestock, which further indicates that sheep is not displacing guanaco where they coexist. These results suggest that habitat segregation between guanaco and sheep is due to a differential habitat selection and not to a competitive displacement process. Therefore, the potential for competition is considered low, contrary to what has been previously observed, although this could be a density-dependent result. PMID:23555656

  4. Late Cretaceous Aquatic Plant World in Patagonia, Argentina

    PubMed Central

    Cúneo, N. Rubén; Gandolfo, María A.; Zamaloa, María C.; Hermsen, Elizabeth

    2014-01-01

    In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla) and a monocot (Araceae). Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae). Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form) and the eudicot angiosperm Nelumbo (Nelumbonaceae) are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae), ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America. PMID:25148081

  5. Radon and ammonia transects across the Cerro Prieto geothermal field

    SciTech Connect

    Semprini, L.; Kruger, P.

    1981-01-01

    Radon and ammonia transects, conducted at the Cerro Prieto geothermal field, involve measurement of concentration gradients at wells along lines of structural significance in the reservoir. Analysis of four transects showed radon concentrations ranging from 0.20 to 3.60 nCi/kg and ammonia concentrations from 17.6 to 59.3 mg/l. The data showed the lower concentrations in wells of lowest enthalpy fluid and the higher concentrations in wells of highest enthalpy fluid. Linear correlation analysis of the radon-enthalpy data indicated a strong relationship, with a marked influence by the two-phase conditions of the produced fluid. It appears that after phase separation in the reservoir, radon achieves radioactive equilibrium between fluid and rock, suggesting that the phase separation occurs well within the reservoir. A two-phase mixing model based on radon-enthalpy relations allows estimation of the fluid phase temperatures in the reservoir. Correlations of ammonia concentration with fluid enthalpy suggests an equilibrium partitioning model in which enrichment of ammonia correlates with higher enthalpy vapor.

  6. Cerro Prieto cold water injection: effects on nearby production wells

    SciTech Connect

    Truesdell, A.H.; Lippmann, M.J.; De Leon, J.; Rodriguez, M.H.

    1999-07-01

    The liquid-dominated Cerro Prieto geothermal field of northern Baja California, Mexico has been under commercial exploitation since 1973. During the early years of operation, all waste brines were sent to an evaporation pond built west of the production area. In 1989, cooled pond brines began to be successfully injected into the reservoir along the western boundary of the geothermal system. The injection rate varied over the years, and is at present about 20% of the total fluid extracted. As expected under the continental desert conditions prevailing in the area, the temperature and salinity of the pond brines change with the seasons, being higher during the summer and lower during the winter. The chemistry of pond brines is also affected by precipitation of silica, oxidation of H{sub 2}S and reaction with airborne clays. Several production wells in the western part of the field (CP-I area) showed beneficial effects from injection. The chemical (chloride, isotopic) and physical (enthalpy, flow rate) changes observed in producers close to the injectors are reviewed. Some wells showed steam flow increases, in others steam flow decline rates flattened. Because of their higher density, injected brines migrated downward in the reservoir and showed up in deep wells.

  7. Evolution of the Cerro Prieto reservoirs under exploitation

    SciTech Connect

    Truesdell, A.H.; Lippmann, M.J.; Puente, H.G.

    1997-07-01

    The Cerro Prieto Geothermal field of Baja California (Mexico) has been under commercial production to generate electricity since 1973. Over the years, the large amount of Geothermal fluids extracted (at present about 12,000 tons per hour) to supply steam to the power plants has resulted in a reduction of pressures, changes in reservoir processes, and increased flow of cooler groundwater into the geothermal system. The groundwater recharging the reservoir moves horizontally through permeable layers, as well as vertically through permeable fault zones. In addition, the supply of deep hot waters has continued unabated, and perhaps has increased as reservoir pressure decreased. Since 1989, this natural fluid recharge has been supplemented by injection which presently amounts to about 20% of the fluid produced. Changes in the chemical and physical characteristics of the reservoir fluids due to the drop in pressures and the inflow of cooler groundwaters and injectate have been detected on the basis of wellhead data. These changes point to reservoir processes like local boiling, phase segregation, steam condensation, mixing and dilution. Finally, the study identified areas where fluids are entering the reservoir, as well as indicated their source (i.e. natural Groundwater recharge versus injectate) and established the controlling geologic structures.

  8. Detailed microearthquake studies at the Cerro Prieto geothermal field

    SciTech Connect

    Majer, E.L.; McEvilly, T.V.

    1981-01-01

    There appears to be an increase in seismic activity within the Cerro Prieto production zone since early 1978. The microearthquake activity is now more or less constant at a rate of 2 to 3 events per day. The b-values within the field are significantly higher inside the production zone than are those for events on faults outside of the production region. The earthquakes seem to be controlled by the Hidalgo fault, although slight clustering was observed in the center of the main production region. The earthquakes within the production zone may reflect the reservoir dynamics associated with heat and mass withdrawal. Mechanisms such as volume change, thermal stresses and weakening of materials associated with boiling (i.e., phase changes, dissolution) may all be responsible for the increased seismic activity. Although a small reinjection program has started, the pressure drawdown conditions existing within the field would imply that increased pore pressure resulting from the injection activities is not responsible for the increased seismic activity.

  9. Performance of casings in Cerro Prieto production wells

    SciTech Connect

    Dominguez A, B.; Vital B, F.; Bermejo M, F.; Sanchez G, G.

    1981-01-01

    A careful evaluation of different production casings used at Cerro Prieto from 1964 to date has shown that the following casings have yielded particularly impressive results: 7 5/8-in. diameter, J-55, 26 lb/ft; 7 5/8-in. diameter, K-55, 45.3 lb/ft; and 5-in. diameter, K-55, 23.2 lb/ft. These casings differ from others of the same diameter but lighter weight which were also used at the field. The results are favorable in spite of severe construction problems, especially the loss of circulation during cementing operations, which we encountered in some of the wells where these casings were used. The use of gravity-fed fine sand as packing material and the arrangement of the production and intermediate casings were important in avoiding damage due to tension-compression stresses and, above all, damage due to internal or external corrosion over time. This situation is clearly evidenced if we compare the damage to the above casings with that experienced by grade N-80 production casings, especially in a corrosive environment.

  10. Investigating the subsurface connection beneath Cerro Negro volcano and the El Hoyo Complex, Nicaragua

    NASA Astrophysics Data System (ADS)

    Venugopal, Swetha; Moune, Séverine; Williams-Jones, Glyn

    2016-10-01

    Cerro Negro, the youngest volcano along the Central American Volcanic Belt (CAVB), is a polygenetic cinder cone with relatively frequent basaltic eruptions. The neighbouring El Hoyo complex, of which Las Pilas is the dominant edifice, is a much larger and older complex with milder and less frequent eruptions. Previous studies have suggested a deep link beneath these two closely spaced volcanoes (McKnight, 1995; MacQueen, 2013). Melt inclusions were collected from various tephra samples in order to determine whether a connection exists and to delineate the features of this link. Major, volatile, and trace elemental compositions reveal a distinct geochemical continuum with Cerro Negro defining the primitive endmember and El Hoyo representing the evolved endmember. Magmatic conditions at the time of melt inclusion entrapment were estimated with major and volatile contents: 2.4 kbar and 1170 °C for Cerro Negro melts and 1.3 kbar and 1130 °C for El Hoyo melts with an overall oxygen fugacity at the NNO buffer. Trace element contents are distinct and suggest Cerro Negro magmas fractionally crystallise while El Hoyo magmas are a mix between primitive Cerro Negro melts and residual and evolved El Hoyo magma. Modelling of end member compositions with alphaMELTS confirms the unique nature of El Hoyo magmas as resulting from incremental mixing between Cerro Negro and residual evolved magma at 4 km depth. Combining all available literature data, this study presents a model of the interconnected subsurface plumbing system. This model considers the modern day analogue of the Lemptégy cinder cones in Massif Central, France and incorporates structurally controlled dykes. The main implications of this study are the classification of Cerro Negro as the newest conduit within the El Hoyo Complex as well as the potential re-activation of the El Hoyo edifice.

  11. Salmonella enterica Serotype Cerro Among Dairy Cattle in New York: An Emerging Pathogen?

    PubMed Central

    Warnick, Lorin D.; Elton, Mara; Rodriguez-Rivera, Lorraine D.; Siler, Julie D.; Wright, Emily M.; Gröhn, Yrjo T.; Wiedmann, Martin

    2010-01-01

    Abstract The focus of this study was Salmonella enterica serotype Cerro, a potentially emerging pathogen of cattle. Our objectives were to document the within-herd prevalence of Salmonella Cerro among a sample of New York dairy herds, to describe the antimicrobial resistance patterns and pulsed-field gel electrophoresis types of the isolates, and to elucidate the status of this serotype as a bovine pathogen. Data were collected prospectively from dairy herds throughout New York that had at least 150 lactating cows and that received clinical service from participating veterinarians. Following enrollment, Salmonella surveillance consisted of both environmental screening and disease monitoring within the herd. Herds positive by either environmental or fecal culture were sampled during three visits to estimate the within-herd prevalence of Salmonella. Among 57 enrolled herds, 44 (77%) yielded Salmonella-positive samples during the study period. Of these, 20 herds (46%) were positive for Salmonella Cerro. Upon follow-up sampling for estimation of prevalence, Cerro was identified in 10 of the 20 herds; the median within-herd Cerro prevalence was 17%, with a maximum of 53%. Antimicrobial resistance ranged from zero to nine drugs, and eight (40%) of the Cerro-positive farms generated drug-resistant isolates. Eight XbaI pulsed-field gel electrophoresis types were represented among 116 isolates tested, although 89% of these isolates shared the predominant type. Among herds with clinical cases, cattle that had signs consistent with salmonellosis were more likely to test positive for Cerro than apparently healthy cattle, as estimated by a logistic regression model that controlled for herd as a random effect (odds ratio: 3.9). There is little in the literature concerning Salmonella Cerro, and published reports suggest an absence of disease association in cattle. However, in our region there has been an apparent increase in the prevalence of this serotype among cattle with

  12. Alkaline magmatism in the Amambay area, NE Paraguay: The Cerro Sarambí complex

    NASA Astrophysics Data System (ADS)

    Gomes, C. B.; Velázquez, V. F.; Azzone, R. G.; Paula, G. S.

    2011-07-01

    The Early Cretaceous alkaline magmatism in the northeastern region of Paraguay (Amambay Province) is represented by stocks, plugs, dikes, and dike swarms emplaced into Carboniferous to Triassic-Jurassic sediments and Precambrian rocks. This magmatism is tectonically related to the Ponta Porã Arch, a NE-trending structural feature, and has the Cerro Sarambí and Cerro Chiriguelo carbonatite complexes as its most significant expressions. Other alkaline occurrences found in the area are the Cerro Guazú and the small bodies of Cerro Apuá, Arroyo Gasory, Cerro Jhú, Cerro Tayay, and Cerro Teyú. The alkaline rocks comprise ultramafic-mafic, syenitic, and carbonatitic petrographic associations in addition to lithologies of variable composition and texture occurring as dikes; fenites are described in both carbonatite complexes. Alkali feldspar and clinopyroxene, ranging from diopside to aegirine, are the most abundant minerals, with feldspathoids (nepheline, analcime), biotite, and subordinate Ti-rich garnet; minor constituents are Fe-Ti oxides and cancrinite as the main alteration product from nepheline. Chemically, the Amambay silicate rocks are potassic to highly potassic and have miaskitic affinity, with the non-cumulate intrusive types concentrated mainly in the saturated to undersaturated areas in silica syenitic fields. Fine-grained rocks are also of syenitic affiliation or represent more mafic varieties. The carbonatitic rocks consist dominantly of calciocarbonatites. Variation diagrams plotting major and trace elements vs. SiO 2 concentration for the Cerro Sarambí rocks show positive correlations for Al 2O 3, K 2O, and Rb, and negative ones for TiO 2, MgO, Fe 2O 3, CaO, P 2O 5, and Sr, indicating that fractional crystallization played an important role in the formation of the complex. Incompatible elements normalized to primitive mantle display positive spikes for Rb, La, Pb, Sr, and Sm, and negative for Nb-Ta, P, and Ti, as these negative anomalies are

  13. Examination of the constructional processes of submarine Cerro Azul and the Galapagos Platform

    NASA Astrophysics Data System (ADS)

    Lambert, M. K.; Harpp, K. S.; Geist, D. J.; Fornari, D. J.; Kurz, M. D.; Koleszar, A. M.; Rollins, N. A.

    2004-05-01

    One of the primary goals of the 2001 Drift04 cruise was to examine the constructional processes responsible for the Galapagos platform and to investigate the relationship between the platform and the overlying volcanoes. Cerro Azul volcano is located above the steep escarpment that marks the southwestern limit of the Galapagos platform, at the leading edge of the hotspot. This area is of particular interest in light of a recent seismic tomography experiment by Toomey, Hooft, et al., which suggests that the root of the Galapagos plume is centered between Cerro Azul and adjacent Fernandina Island. During the Drift04 cruise, detailed bathymetric and sidescan sonar studies were carried out across the submarine sector of Cerro Azul and 14 dredges were collected from the same area. Major element analyses of the submarine lavas indicate that the lavas from the platform edge and the subaerial Cerro Azul lavas constitute a suite of petrologically-related lavas. The dredged glasses of the Drift04 cruise have MgO contents of <7.5% and are indistinguishable from published data on Cerro Azul. Whole rock analyses include a highly primitive sample (20 wt% MgO), which probably contains accumulated olivine. All the submarine and subaerial lavas define coherent trends in major element space that are consistent with variable amounts of olivine and olivine+cpx fractionation. Incompatible trace element (ITE) ratios indicate that the mantle source for the submarine platform flows is intermediate in composition between the magmas supplying Fernandina and Cerro Azul. Previous researchers have proposed that two mantle endmembers are interacting across the leading edge of the plume, one focused at Fernandina and the other at Floreana Island. The intermediate ITE ratios of the submarine and subaerial Cerro Azul lavas are consistent both geographically and compositionally with this hypothesis. Naumann and co-workers concluded that the lavas erupted at Cerro Azul were stored in small

  14. Spatial and Temporal Variations of Diffuse Carbon Dioxide Emission From Cerro Negro Volcano, Nicaragua, Central America

    NASA Astrophysics Data System (ADS)

    Galindo, I.; Melián, G.; Salazar, J.; Hernández, P.; Pérez, N.; Strauch, W.

    2002-12-01

    Cerro Negro is a basaltic cinder cone that has erupted 22 times since its birth in 1850. It is part of a group of four young cinder cones NW of Las Pilas volcano. Cerro Negro's most recent activity was on 5 August 1999 when erupted ash clouds at heights of about 7 km. In December 1999, three months after the eruption, a surface flux survey was carried out at Cerro Negro. Soil CO2 efflux values ranged from 0.5 to 35,000 gm-2d-1 and the total diffuse CO2 output was estimated about 2,800 td-1. Soil temperature reached values above 300°C on the NE flank of the volcano (Salazar et al., 2001). The goal of this study is to evaluate how diffuse CO2 degassing rate at Cerro Negro changes through its eruptive cycle and improve its volcano monitoring program. From Febraury 26 to March 11, 2002, a new diffuse CO2 degassing survey was carried out at Cerro Negro. Sampling distribution was similar to the 1999 survey covering an area of (0.6 Km2). Diffuse CO2 emission rates for the 2002 survey showed a wide range of values from 0.3 to 26,500 gm-2d-1. Most of the study area showed soil CO2 efflux values above 110 gm-2d-1, and the highest CO2 efflux rate was observed in the Northeastern sector of the crater. Soil temperature was also recorded during the survey, and the highest value was observed in the NE flank reaching temperatures up to 450°C. The total diffuse CO2 output for the 2002 survey was estimated about 280 td-1, which is one order of magnitude lower than the estimated for the 1999 survey. This significant temporal variation on diffuse CO2 emission rate seems to be clearly related to the eruptive cycle of Cerro Negro. If we consider that the statistically eruptive cycle for Cerro Negro is less than a decade, it is obvious that the December 1999 survey was performed within its post-eruptive period, while the recent 2002 survey was carried out two years and a half after the most recent eruption of Cerro Negro, within its inter-eruptive period. These results suggest that

  15. Gastrointestinal helminths of Commerson's dolphins Cephalorhynchus commersonii from central Patagonia and Tierra del Fuego.

    PubMed

    Berón-Vera, B; Pedraza, S N; Raga, J A; Gil de Pertierra, A; Crespo, E A; Alonso, M K; Goodall RNP

    2001-12-01

    The stomachs and intestines of 9 Commerson's dolphins incidentally caught in trawl nets in central Patagonia and 23 stranded on beaches in Tierra del Fuego were surveyed for helminth parasites. A total of 267 individuals belonging to 4 species of parasites (1 nematode, 3 digeneans) were found in the dolphins from the first area: Anisakis sp. (larvae type 1 = A. simplex), Braunina cordiformis, Hadwenius sp. and Pholeter gastrophilus. In the Tierra del Fuego dolphins, 142 specimens belonging to 3 species (2 nematodes, 1 digenean, 1 cestode) were found: A. simplex, Hadwenius sp. and Strobilocephalus triangularis. Only 2 of the helminth species were shared in the 2 study areas, A. simplex and Hadwenius sp., and both were more common in central Patagonia. Among the species, A. simplex was most prevalent and abundant in both study areas. In Tierra del Fuego, adults of A. simplex appeared in only 1 host. Hadwenius sp., P. gastrophilus and S. triangularis are new host records for Commerson's dolphin. Species diversity and species richness were low in both study areas. Helminth communities were more diverse in central Patagonia (t = 1.97, df = 258, p < 0.05) and species richness was higher in central Patagonia (S = 4). No differences in diversity were observed between females and males of central Patagonia (t = 1.97, df = 139, p < 0.05) and between females of central Patagonia and Tierra del Fuego. The results may suggest some differences in habitat use, diet and sex between Commerson's dolphin populations in the 2 study areas.

  16. Airborne laser altimetry survey of Glaciar Tyndall, Patagonia

    NASA Astrophysics Data System (ADS)

    Keller, Kristian; Casassa, Gino; Rivera, Andrés; Forsberg, Rene; Gundestrup, Niels

    2007-10-01

    The first airborne laser altimetry measurements of a glacier in South America are presented. Data were collected in November of 2001 over Glaciar Tyndall, Torres del Paine National Park, Chilean Patagonia, onboard a Twin Otter airplane of the Chilean Air Force. A laser scanner with a rotating polygon-mirror system together with an Inertial Navigation System (INS) were fixed to the floor of the aircraft, and used in combination with two dual-frequency GPS receivers. Together, the laser-INS-GPS system had a nominal accuracy of 30 cm after data processing. On November 23rd, a total of 235 km were flown over the ablation area of Glaciar Tyndall, with 5 longitudinal tracks with a mean swath width of 300 m, which results in a point spacing of approximately 2 m both along and across track. A digital elevation model (DEM) generated using the laser altimetry data was compared with a DEM produced from a 1975 map (1:50,000 scale — Instituto Geográfico Militar (IGM), Chile). A mean thinning of - 3.1 ± 1.0 m a - 1 was calculated for the ablation area of Glaciar Tyndall, with a maximum value of - 7.7 ± 1.0 m a - 1 at the calving front at 50 m a.s.l. and minimum values of between - 1.0 and - 2.0 ± 1.0 m a - 1 at altitudes close to the equilibrium line altitude (900 m a.s.l.). The thinning rates derived from the airborne survey were similar to the results obtained by means of ground survey carried out at ˜ 600 m of altitude on Glaciar Tyndall between 1975 and 2002, yielding a mean thinning of - 3.2 m a - 1 [Raymond, C., Neumann, T.A., Rignot, E., Echelmeyer, K.A., Rivera, A., Casassa, G., 2005. Retreat of Tyndall Glacier, Patagonia, over the last half century. Journal of Glaciology 173 (51), 239-247.]. A good agreement was also found between ice elevation changes measured with laser data and previous results obtained with Shuttle Radar Topography Mission (SRTM) data. We conclude that airborne laser altimetry is an effective means for accurately detecting glacier elevation

  17. Measured ground-surface movements, Cerro Prieto geothermal field

    SciTech Connect

    Massey, B.L.

    1981-01-01

    The Cerro Prieto geothermal area in the Mexicali Valley, 30 kilometers southeast of Mexicali, Baja California, incurred slight deformation because of the extraction of hot water and steam, and probably, active tectonism. During 1977 to 1978, the US Geological Survey established and measured two networks of horizontal control in an effort to define both types of movement. These networks consisted of: (1) a regional trilateration net brought into the mountain ranges west of the geothermal area from stations on an existing US Geological Survey crustal-strain network north of the international border; and (2) a local net tied to stations in the regional net and encompassing the present and planned geothermal production area. Electronic distance measuring instruments were used to measure the distances between stations in both networks in 1978, 1979 and 1981. Lines in the regional net averaged 25 km. in length and the standard deviation of an individual measurement is estimated to be approx. 0.3 part per million of line length. The local network was measured using different instrumentation and techniques. The average line length was about 5 km. and the standard deviation of an individual measurement approached 3 parts per million per line length. Ground-surface movements in the regional net, as measured by both the 1979 and 1981 resurveys, were small and did not exceed the noise level. The 1979 resurvey of the local net showed an apparent movement of 2 to 3 centimeters inward toward the center of the production area. This apparent movement was restricted to the general limits of the production area. The 1981 resurvey of the local net did not show increased movement attributable to fluid extraction.

  18. Observations on the Use of Manual Signs and Gestures in the Communicative Interactions between Native Americans and Spanish Explorers of North America: The Accounts of Bernal Diaz del Castillo and Alvar Nunez Cabeza de Vaca

    ERIC Educational Resources Information Center

    Bonvillian, John D.; Ingram, Vicky L.; McCleary, Brendan M.

    2009-01-01

    The accounts of two men who participated in several Spanish-led expeditions to the New World in the early 1500s document the frequent use of manual signs and gestures in the initial interactions between European explorers and the indigenous peoples of North America. Bernal Diaz del Castillo described the events that occurred during three…

  19. Interaction of cold-water aquifers with exploited reservoirs of the Cerro Prieto geothermal system

    USGS Publications Warehouse

    Truesdell, Alfred; Lippmann, Marcelo

    1990-01-01

    Cerro Prieto geothermal reservoirs tend to exhibit good hydraulic communication with adjacent cool groundwater aquifers. Under natural state conditions the hot fluids mix with the surrounding colder waters along the margins of the geothermal system, or discharge to shallow levels by flowing up fault L. In response to exploitation reservoir pressures decrease, leading to changes in the fluid flow pattern in the system and to groundwater influx. The various Cerro Prieto reservoirs have responded differently to production, showing localized near-well or generalized boiling, depending on their access to cool-water recharge. Significant cooling by dilution with groundwater has only been observed in wells located near the edges of the field. In general, entry of cool water at Cerro Prieto is beneficial because it tends to maintain reservoir pressures, restrict boiling, and lengthen the life and productivity of wells.

  20. The complete genome sequence and methylome of Salmonella enterica subsp. enterica serovar Cerro, a frequent dairy cow strain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salmonella enterica subsp. enterica serovar Cerro is an infrequent pathogen of humans and other mammals, but is frequently isolated from the hindgut of asymptomatic cattle in the United States. To further understand the genomic determinants of S. Cerro specificity for the bovine hindgut, the genome ...

  1. A late Jurassic pterosaur (Reptilia, Pterodactyloidea) from northwestern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Codorniú, Laura; Gasparini, Zulma; Paulina-Carabajal, Ariana

    2006-03-01

    A small to medium-sized pterodactyloid pterosaur (wingspan approximately 1.10 m) from the Upper Jurassic (middle-late Tithonian) marine deposits of the Vaca Muerta Formation of Patagonia (Los Catutos area, central Neuquén Province, Argentina) is reported. The specimen lacks the skull but constitutes a nearly complete postcranial skeleton, which includes cervical and dorsal vertebrae; a few thoracic ribs; both pectoral girdles; the left pelvic girdle; a proximal right wing (humerus, ulna, and radius) and metacarpal IV; a left wing that lacks only wing phalanx four; and both hindlimbs, the right one without the foot. Ontogenetic features suggest that the new fossil corresponds to a relatively mature individual, probably a subadult. Observed characters support its assignment to the Archaeopteroactyloidea, a basal clade within the Pterodactyloidea. This specimen is the second pterosaur from Los Catutos and the most complete Jurassic pterosaur so far known from South America.

  2. Splendid and Seldom Isolated: The Paleobiogeography of Patagonia

    NASA Astrophysics Data System (ADS)

    Wilf, Peter; Cúneo, N. Rubén; Escapa, Ignacio H.; Pol, Diego; Woodburne, Michael O.

    2013-05-01

    The idea that South America was an island continent over most of the Cenozoic, during which its unusual mammalian faunas evolved in isolation, is outstandingly influential in biogeography. Although large numbers of recent fossil discoveries and related advances require that the original isolation concept be significantly modified, it is still repeated in much current literature. The persistence of the idea inspired us to present here an integrated paleobiogeographic account of mammals, reptiles, and plants from the Jurassic to the Paleogene of Patagonia, which has by far the richest fossil record on the continent. All three groups show distribution patterns that are broadly consistent with South America's long separation history, first from Laurasia by the Late Jurassic, then from Africa and India-Madagascar during the late Early Cretaceous, and finally from Antarctica and Australia during the early-middle Eocene, after which “isolation” finally commenced. We highlight areas of promising future research and provide an updated view of South American isolation.

  3. Phytoseiid mites (Acari: Phytoseiidae) from Patagonia and Tierra del Fuego.

    PubMed

    Ferragut, Francisco; Navia, Denise

    2015-07-28

    Predatory phytoseiid mites have been intensively studied and surveyed in the last decades because of their economic importance as biocontrol agents of agricultural pests. However, many regions of the world remain unexplored and the diversity of the family worldwide is still fragmentary. Up to date no phytoseiid species have been collected in the southernmost part of the Earth down to latitude 45º S. In this study Phytoseiidae were sampled from native vegetation in southern Argentina and Chile in the regions of Patagonia and Tierra del Fuego Island. Thirteen species were collected, five of which were previously described and eight, Chileseius australis n. sp., Neoseiulus mapuche n. sp., Typhlodromips valdivianus n. sp., T. fissuratus n. sp., Amblyseius grandiporus n. sp., A. caliginosus n. sp., Typhlodromus (Anthoseius) anomalos n. sp. and Metaseiulus parabrevicollis n. sp. are proposed as new to science and are described and diagnosed.

  4. Hantavirus reservoir Oligoryzomys longicaudatus spatial distribution sensitivity to climate change scenarios in Argentine Patagonia

    PubMed Central

    Carbajo, Aníbal E; Vera, Carolina; González, Paula LM

    2009-01-01

    Background Oligoryzomys longicaudatus (colilargo) is the rodent responsible for hantavirus pulmonary syndrome (HPS) in Argentine Patagonia. In past decades (1967–1998), trends of precipitation reduction and surface air temperature increase have been observed in western Patagonia. We explore how the potential distribution of the hantavirus reservoir would change under different climate change scenarios based on the observed trends. Methods Four scenarios of potential climate change were constructed using temperature and precipitation changes observed in Argentine Patagonia between 1967 and 1998: Scenario 1 assumed no change in precipitation but a temperature trend as observed; scenario 2 assumed no changes in temperature but a precipitation trend as observed; Scenario 3 included changes in both temperature and precipitation trends as observed; Scenario 4 assumed changes in both temperature and precipitation trends as observed but doubled. We used a validated spatial distribution model of O. longicaudatus as a function of temperature and precipitation. From the model probability of the rodent presence was calculated for each scenario. Results If changes in precipitation follow previous trends, the probability of the colilargo presence would fall in the HPS transmission zone of northern Patagonia. If temperature and precipitation trends remain at current levels for 60 years or double in the future 30 years, the probability of the rodent presence and the associated total area of potential distribution would diminish throughout Patagonia; the areas of potential distribution for colilargos would shift eastwards. These results suggest that future changes in Patagonia climate may lower transmission risk through a reduction in the potential distribution of the rodent reservoir. Conclusion According to our model the rates of temperature and precipitation changes observed between 1967 and 1998 may produce significant changes in the rodent distribution in an equivalent

  5. New SHRIMP U-Pb and 40Ar/39Ar constraints on the crustal stabilization of southern South America, from the margin of the Rio de Plata (Sierra de Ventana) craton to northern Patagonia

    NASA Astrophysics Data System (ADS)

    Tohver, E.; Cawood, P. A.; Rossello, E.; Lopez de Luchi, M. G.; Rapalini, A.; Jourdan, F.

    2008-12-01

    Two models exist to explain the late Paleozoic tectonic history for southern South America: an accretionary model of crustal growth through magmatism and a collisional model involving pre-existing continental elements, namely, the Rio de Plata craton and the possibly allochthonous terrane(s) of Patagonia, the Northern Patagonia Massif and the Deseado Massif. We report new U-Pb and 40Ar/39Ar results from rocks within a posited collision zone between the SW edge of the Rio de Plata craton and the northern margin of the Northern Patagonia Massif. Igneous basement samples from the Sierra de Ventana region, Buenos Aires province, were dated by ion microprobe (SHRIMP) analysis of zircon. A previously unrecognized occurrence of Paleoproterozoic basement indicates that the Rio de Plata craton extends ca.250 km farther west than considered. The majority of the basement rocks are shallow mid-Cambrian granitoids and rhyolites, including the rocks of the Cerro Colorado granite, which is intrusive into the sediments of the Curamalal Gp, signifying that these mature quartzites and conglomerates are older than early Cambrian in age, possibly correlated with the low-grade sedimentary rocks of the Tandilia Range that includes the La Tinta Fm. The 40Ar/39Ar ages from biotite, muscovite, and sericite from three different sheared basement localities demonstrates deformation in the latest Permian (265-260 Ma), ca. 20 Ma after the foreland deposition of the synorogenic Tunas Fm. in the upper Pilahuinco Gp, constrained by 282.4 ± 2.8 Ma zircon ages in volcanic ashbeds. Farther south, along the northern margin of the Northern Patagonian Massif, late Ordovician 40Ar/39Ar cooling ages of granites intrusive into the Cambro-Ordovician Nahuel Niyeu Fm. are consistent with the presence of Ordovician magmatism along the W edge of the Rio de Plata craton. These ages alternate with late Permian 40Ar/39Ar cooling ages from undeformed granites and pegmatites, as well as early Jurassic cross

  6. Subduction of the South Chile active spreading ridge: A 17 Ma to 3 Ma magmatic record in central Patagonia (western edge of Meseta del Lago Buenos Aires, Argentina)

    NASA Astrophysics Data System (ADS)

    Boutonnet, E.; Arnaud, N.; Guivel, C.; Lagabrielle, Y.; Scalabrino, B.; Espinoza, F.

    2010-01-01

    The Chile Triple Junction is a natural laboratory to study the interactions between magmatism and tectonics during the subduction of an active spreading ridge beneath a continent. The MLBA plateau (Meseta del Lago Buenos Aires) is one of the Neogene alkali basaltic plateaus located in the back-arc region of the Andean Cordillera at the latitude of the current Chile Triple Junction. The genesis of MLBA can be related with successive opening of slabs windows beneath Patagonia: within the subducting Nazca Plate itself and between the Nazca and Antarctic plates. Detailed 40Ar/ 39Ar dating and geochemical analysis of bimodal magmatism from the western flank of the MLBA show major changes in the back-arc magmatism which occurred between 14.5 Ma and 12.5 Ma with the transition from calc-alkaline lavas (Cerro Plomo) to alkaline lavas (MLBA) in relation with slab window opening. In a second step, at 4-3 Ma, alkaline felsic intrusions were emplaced in the western flank of the MLBA coevally with the MLBA basalts with which they are genetically related. These late OIB-like alkaline to transitional basalts were generated by partial melting of the subslab asthenosphere of the subducting Nazca plate during the opening of the South Chile spreading ridge-related slab window. These basalts differentiated with small amounts of assimilation in shallow magma chambers emplaced along transtensional to extensional zones. The close association of bimodal magmatism with extensional tectonic features in the western MLBA is a strong support to the model of Patagonian collapse event proposed to have taken place between 5 and 3 Ma as a consequence of the presence of the asthenospheric window (SCR-1 segment of South Chile Ridge) below the MLBA area.

  7. Structural and sedimentological study of the Cerro Prieto geothermal field, Baja California, Mexico

    SciTech Connect

    Vonder Haar, S.

    1981-06-01

    Geophysical and lithologic well logs from over fifty wells have been qualitatively and quantitatively analyzed using both manual and computer interpretation techniques. These logs were studied to make stratigraphic correlations throughout the Cerro Prieto field and to interpret the deltaic depositional environment of the field's lithologic units. Dipmeter and seismic data were of great value in making stratigraphic interpretations and extrapolations. Cross sections were constructed to illustrate lithofacies variations throughout the geothermal field. In turn, these sections were used to construct a three-dimensional model of the Cerro Prieto geothermal reservoir. Petrographic microscopy, scanning electron microscopy, and x-ray diffraction analyses of well-bore cuttings and cores were utilized to determine the degree and distribution of hydrothermal alteration by fluids at temperatures up to 350{sup 0}C, the origins of dissolution porosity, and the relative degree of fracture versus dissolution porosity. The results of these analyses were confirmed by log-derived determinations of formation fluid properties, porosity, and petrophysical properties and by studies of Cerro Prieto cores conducted under in-situ conditions. The results of this research were integrated into the Cerro Prieto reservoir model.

  8. The Cerro Grande Fire - From Wildlife Modeling Through the Fire Aftermath

    SciTech Connect

    Rudell, T. M.; Gille, R. W.

    2001-01-01

    The Cerro Grande Fire developed from a prescribed burn by the National Park Service at Bandelier National Monument near Los Alamos, New Mexico. When the burn went out of control and became a wildfire, it attracted worldwide attention because it threatened the birthplace of the atomic bomb, Los Alamos National Laboratory (LANL). Was LANL prepared for a fire? What lessons have been learned?

  9. The Cerro Grande Fire - From Wildfire Modeling Through the Fire Aftermath

    SciTech Connect

    Rudell, T. M.; Gille, R. W.

    2001-01-01

    The Cerro Grande Fire developed from a prescribed burn by the National Park Service at Bandelier National Monument near Los Alamos, New Mexico. When the burn went out of control and became a wildfire, it attracted worldwide attention because it threatened the birthplace of the atomic bomb, Los Alamos National Laboratory (LANL). Was LANL prepared for a fire? What lessons have been learned?

  10. Summary of recent progress in understanding the Cerro Prieto Geothermal Field, Baja, California, Mexico

    SciTech Connect

    Lippmann, M.J.; Witherspoon, P.A.

    1980-07-01

    Geological and geophysical studies indicate that the Cerro Prieto reservoir is quite heterogeneous due to complex lithofacies fault structures, and hydrothermal alteration. Geochemical investigations have provided clues on the origin of the geothermal fluids, their recharge paths and on the reservoir processes accompanying the exploitation of the field. Well tests have yielded information on the permeability of the reservoir. (MHR)

  11. Metagenomic analysis of the bovine hindgut from Salmonella Kentucky and Cerro-shedding dairy cows

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the United States Salmonella enterica subsp. enterica serovars Kentucky and Cerro are frequently isolated from dairy cows that appear asymptomatic. Although they are not major contributors to the salmonellosis burden, these serovars have been implicated in human clinical cases in recent years. To...

  12. Eruptive Variations During the Emplacement of Cerro Pinto, an Ambitious Rhyolite Dome, Puebla, Mexico

    NASA Astrophysics Data System (ADS)

    Zimmer, B.; Riggs, N.; Carrasco-Nunez, G.

    2006-12-01

    Cerro Pinto is a rhyolite dome complex located in the eastern Trans-Mexican Volcanic Belt. The complex is composed of four tuff rings and four domes that were emplaced in three distinct eruptive stages marked by changes in vent location and eruptive character. Each of these stages contained eruptive sequences that follow simple rhyolite-dome models, in which a pyroclastic phase is followed immediately by effusive dome emplacement. However, some aspects of the eruptive history, such as the occurrence of explosive reactivation and dome destruction through a lateral blast are uncommon in small rhyolitic structures and are more commonly associated with polygenetic structures, such as stratovolcanoes or calderas. In these larger structures, new pulses of magma often initiate reactivation, but at Cerro Pinto the story is different. Major and trace element geochemistry suggest that Cerro Pinto was sourced by a small, isolated magma chamber, unassociated with any surrounding silicic centers and did not experience any change in chemical composition over the course of the eruption. Based on these data and field observations, it is inferred that Cerro Pinto's eruptive variations were not the result of the influx of a new magma batch, but were the result of both phreatomagmatic interactions and the presence of a small magma chamber that was zoned with respect to volatiles. Both of these factors are commonly encountered in volcanologic studies, but documentation of their influence on smaller structures is under represented. Rhyolite domes have long been considered relatively simple volcanic structures with only localized hazard implications. However, the eruptive variations displayed by Cerro Pinto suggest that isolated rhyolite dome evolutions can be much more complex with the potential for explosive reactivation and dome collapse; events that must be taken into consideration when making hazard assessments.

  13. The degassing character of a young volcanic center: Cerro Negro, Nicaragua

    NASA Astrophysics Data System (ADS)

    Lucic, Gregor; Stix, John; Sherwood Lollar, Barbara; Lacrampe-Couloume, Georges; Muñoz, Angélica; Carcache, Martha Ibarra

    2014-09-01

    Cerro Negro volcano is a young basaltic cinder cone which is part of the Nicaraguan volcanic arc. Eruptive activity at Cerro Negro is characterized by explosive strombolian to subplinian eruptions driven by volatile-rich basaltic magma ascending rapidly from various crustal depths (>15 to 6 km) resulting in the onset of precursory activity only ˜30 min before an eruption. In this paper, we present a comprehensive degassing characterization of the volcano over a 4-year period aimed at improving our understanding of the magmatic plumbing network and its relationship with regional tectonics. A total of 124 individual soil gas samples were collected between 2010 and 2013 and analyzed for stable carbon isotopes (δ13C) from CO2. High temperature fumaroles were sampled for δ18O, δD, and 3He/4He isotope analysis, and major degassing zones were mapped using soil CO2 flux measurements. Gases at Cerro Negro are characterized by a strong 3He/4He mantle signature (6.3 to 7.3 RA), magmatic δ13C ratios (-2.3 to -3.0 ‰), meteoric δ18O and δD ratios, and stable CO2 fluxes (31 t d-1). The lack of δ13C fractionation and an increase in the relative mantle component from 2002 to 2012 suggest that the volatile flux at Cerro Negro originates from the mantle and ascends to the surface via a series of crustal fractures that act as permeable conduits. Despite the lack of new eruptions, the hydrothermal system of Cerro Negro continues to evolve due to seasonal inputs of meteoric water, slope failures that expose and bury sites of active degassing, and bursts of regional seismicity that have the potential to open up new conduits for gas release as well as magma. Continuing geophysical and geochemical monitoring of the main edifice and the recently formed south zone is essential, as the volcano remains overdue to erupt.

  14. Dynamics of diffuse CO2 emission and eruptive cycle at Cerro Negro volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Rodriguez, F.; Melian, G.; Barrancos, J.; Padilla, G.; Diaz, M.; Calvo, D.; Nolasco, D.; Perez, N.; Hernandez Perez, P. A.; Ibarra, M.; Strauch, W.; Muñoz, A.

    2009-12-01

    Cerro Negro volcano is the youngest of a group of cinder cones NW of Las Pilas at 25 km from León (Nicaragua) with 685 meters above sea level and one of the most active volcanoes of Nicaragua. It has erupted 21 times since its birth in 1850, with an eruptive cycle about 7-8 years. Since the last eruption, occurred on 5 August 1999, with erupted lava flows and ash clouds together with gas emissions, a research collaboration program between INETER and ITER was established for monitoring diffuse CO2 emissions from Cerro Negro. Since then, ten CO2 surface efflux surveys have been undertaken covering an area of 0,6 km2, in order to evaluate the spatial and temporal variations of CO2 degassing rate in relation with the eruptive cycle of Cerro Negro. Soil CO2 efflux measurements were performed always by means of a portable NDIR sensor according to the accumulation chamber method. A total diffuse CO2 emission output of 1869 t d-1 was estimated for the 1999 survey; just 3 months after the 1999 eruption which can be considered within the post-eruptive phase. For the 2002 and 2003 surveys, considered within the inter-eruptive phase, a clear decreasing tendency on the total diffuse CO2 output was observed, with estimates of 431 and 84 t d-1, respectively. However, during the 2004 a slightly increase on the total diffuse CO2 emission was observed, reaching up to 256 t d-1. The observed relatively increase was addressed to the occurrence of a seismic swarm at Cerro Negro during the survey. The yearly surveys performed at Cerro Negro from 2005 until present, have always shown background levels of CO2 emission, with 68, 38, 45, 10 and 12 t d-1, respectively. The temporal evolution of the diffuse CO2 emissions from Cerro Negro will allow us to determine the typical range of seasonal or other transient departures from its normal or “baseline” behaviour and its relation with the eruptive cycle.

  15. Highly ordered antigorite from Cerro del Almirez HP-HT serpentinites, SE Spain

    NASA Astrophysics Data System (ADS)

    Padrón-Navarta, J. A.; López Sánchez-Vizcaíno, V.; Garrido, C. J.; Gómez-Pugnaire, M. T.; Jabaloy, A.; Capitani, G. C.; Mellini, M.

    2008-11-01

    The Cerro del Almirez ultramafic massif offers an example of high pressure and high temperature antigorite serpentinites. A sharp antigorite-out isograd separates them from Chl-harzburgites, consisting of olivine + enstatite + chlorite. Antigorite is characterized by aluminium contents as high as 4 wt.% Al2O3. The microstructural study shows that, prior to the transformation, antigorite is exceptionally ordered and consists of the polysome m = 17. No polysomatic defect occurs in antigorite forming most of the Cerro del Almirez serpentinites. Close to the antigorite-out isograd, limited disorder features may occur, mainly as (001) twins, reaction rims and reduction of m down to 14-15. Here, local recrystallization phenomena lead to sporadic growth of large antigorite and chlorite crystals.

  16. Occurrences of alunite, prophyllite, and clays in the Cerro La Tiza area, Puerto Rico

    USGS Publications Warehouse

    Hildebrand, Fred Adelbert; Smith, Raymond J.

    1959-01-01

    A deposit of hydrothermally altered rocks in the Cerro La Tiza area located between the towns of Comerio and Aguas Buenas, approximately 25 kilometers southwest of San Juan, Puerto Rico, was mapped and studied to determine the principal minerals, their extent distribution and origin, and the possibility of their economic utilization, especially in Puerto Rico. The Cerro la Tiza area is about 7? kilometers long, has an average width of about 1? kilometers and embraces a total area of approximately 15 square kilometers. The principal mineralized zone, a dike-like mass of light-colored rocks surrounded by dark-colored volcanic country rocks, occupies the crest and upper slopes of east-trending Cerro La Tiza ridge and is believed to be of Late Cretaceous or Eocene age. This zone is approximately 5,300 meters long, 430 meters wide and has an area of approximately 225 hectares (556 acres). The rocks of the mineralized zone are of mixed character and consist mainly of massive quartzose rocks and banded quartz-alunite rocks closely associated with foliated pyrophyllitic, sericitic and clayey rocks. The principal minerals in probably order of abundance are quartz, alunite, pyrophyllite, kaolin group clays (kaolinite and halloysite) and sericite. Minerals of minor abundance are native sulfure, diaspore, svanbergite (?), sunyite (?), hematite, goethite, pyrite, rutile (?) and very small quantities of unidentified minerals. The mineralized zone has broken down to deposits of earth-rock debris of Quaternary age that cover much of the slopes and flanks of Cerro La Tiza. This debris consists generally of fragments and boulders with a very large size range embedded in a clayey matrix. The distribution of the earth-rock debris with respect to the present topography and drainage suggests that it may have undergone at least two cycles of erosion. Underlying the earth-rock debris and completely enclosing the mineralized zone are country rocks of probably Late Cretaceous age. These

  17. H2S and CO2 emissions from Cerro Prieto geothermal power plant, Mexico

    NASA Astrophysics Data System (ADS)

    Peralta, Oscar; Franco, Luis; Castro, Telma; Taran, Yuri; Bernard, Ruben; Inguaggiato, Salvatore; Navarro, Rafael; Saavedra, Isabel

    2014-05-01

    Cerro Prieto geothermal power plant has an operation capacity of 570 MW distributed in four powerhouses being the largest geothermal plant in Mexico. The geothermal field has 149 production wells. It is located in Cerro Prieto, Baja California, 30 km to the south of the Mexico-US border. Two sampling campaigns were performed in December 2012 and May 2013 where geothermal fluids from 46 production wells and 10 venting stacks were obtained and analyzed by gas chromatography coupled to mass spectrometry. Average CO2 and H2S composition of samples from venting stacks were 49.4% and 4.79%, respectively. Based on the chemical composition of samples, the geothermal power plant emits every day from venting stacks 869 tons of CO2, plus 68 tons of H2S, among other non-condensable gases.

  18. Identification of fluid-flow paths in the Cerro Prieto geothermal field

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Zelwer, R.; Howard, J.H.

    1982-05-01

    A hydrogeologic model of the Cerro Prieto geothermal field has been developed based on geophysical and lithologic well logs, downhole temperature, and well completion data from about 90 deep wells. The hot brines seem to originate in the eastern part of the field, flowing in a westward direction and rising through gaps in the shaly layers which otherwise act as partial caprocks to the geothermal resource.

  19. Hydrothermal alteration minerals of Cerro Caliente (Deception Island, Antarctica). Analogies to several assemblages of Mars

    NASA Astrophysics Data System (ADS)

    Prieto-Ballesteros, O.; Gómez, F.; Moreno, M.; de Diego, G.; Fernández-Sampedro, M.; Martín-Redondo, M. P.; Parro, V.

    2013-09-01

    We study the assemblage of minerals formed by hydrothermal alteration at Cerro Caliente, Deception Island, Antarctica. The alteration of the basaltic andesitic rock produces phyllosilicates associated with carbonates, which precipitate impregnating the porous volcanic strata from the fluids released by the fractures. Similar signatures have been observed at several places of Mars, so we use this terrestrial analog to determine the processes acting on Mars.

  20. Fluid flow model of the Cerro Prieto Geothermal Field based on well log interpretation

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Zelwe, R.; Howard, J.H.

    1982-08-10

    The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine the direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.

  1. Fluid flow model of the Cerro Prieto geothermal field based on well log interpretation

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Zelwer, R.; Howard, J.H.

    1982-10-01

    The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine he direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.

  2. The age and constitution of Cerro Campanario, a mafic stratovolcano in the Andes of central Chile

    USGS Publications Warehouse

    Hildreth, W.; Singer, B.; Godoy, E.; Munizaga, F.

    1998-01-01

    Cerro Campanario, a towering landmark on the continental divide near Paso Pehuenche, is a glacially eroded remnant of a mafic stratovolcano that is much younger than previously supposed. Consisting of fairly uniform basaltic andesite, rich in olivine and plagioclase, the 10-15 km3 edifice grew rapidly near the end of the middle Pleistocene, about 150-160 ka, as indicated by 40Ar/39Ar and unspiked K-Ar analyses of its lavas.

  3. Mercury in the biotic compartments of Northwest Patagonia lakes, Argentina.

    PubMed

    Rizzo, A; Arcagni, M; Arribére, M A; Bubach, D; Guevara, S Ribeiro

    2011-06-01

    We report on total mercury (THg) concentrations in the principal components of food webs of selected Northern Patagonia Andean Range ultraoligotrophic lakes, Argentina. The THg contents were determined using Instrumental Neutron Activation Analysis in muscle and liver of four fish species occupying the higher trophic positions (the introduced Salmo trutta, Oncorhynchus mykiss and Salvelinus fontinalis, and the native Percichthys trucha) accounted for eight lakes belonging to Nahuel Huapi and Los Alerces National Parks. We studied the food web components of both the West and East branches of Lake Moreno, including benthic primary producers such as biofilm, mosses, and macrophytes, three plankton fractions, fish, riparian tree leaves, and benthic invertebrates, namely decapods, molluscs, insect larvae, leeches, oligochaetes, and amphipods. Mercury concentrations in fish muscle varied in a wide range, from less than 0.05 to 4 μg g(-1) dry weight (DW), without a distribution pattern among species but showing higher values for P. trucha and S. fontinalis, particularly in Lake Moreno. The THg contents of the food web components of Lake Moreno varied within 4 orders of magnitude, with the lower values ranging from 0.01 to 0.5 μg g(-1) DW in tree leaves, some macrophytes, juvenile salmonids or benthic macroinvertebrates, and reaching concentrations over 200 μg g(-1) DW in the plankton. Juvenile Galaxias maculatus caught in the pelagic area presented the highest THg contents of all fish sampled, reaching 10 μg g(-1) DW, contents that could be associated with the high THg concentrations in plankton since it is their main food source. Although Lake Moreno is a system without local point sources of contamination, situated in a protected area, some benthic organisms presented high THg contents when compared with those from polluted ecosystems.

  4. Organic carbon in glacial fjords of Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Pantoja, Silvio; Gutiérrez, Marcelo; Tapia, Fabián; Abarzúa, Leslie; Daneri, Giovanni; Reid, Brian; Díez, Beatriz

    2016-04-01

    The Southern Ice Field in Chilean Patagonia is the largest (13,000 km2) temperate ice mass in the Southern hemisphere, yearly transporting ca. 40 km3 of freshwater to fjords. This volume of fresh and cold water likely affects adjacent marine ecosystems by changing circulation, productivity, food web dynamics, and the abundance and distribution of planktonic and benthic organisms. We hypothesize that freshwater-driven availability of inorganic nutrient and transport of organic and inorganic suspended matter, as well as microbes, become a controlling factor for productivity in the fjord associated with the Baker river and Jorge Montt glacier. Both appear to be sources of silicic acid, but not of nitrate and particulate organic carbon, especially during summer, when surface PAR and glacier thawing are maximal. In contrast to Baker River, the Jorge Montt glacier is also a source of dissolved organic carbon towards a proglacial fjord and the Baker Channel, indicating that a thorough chemical description of sources (tidewater glacier and glacial river) is needed. Nitrate in fiord waters reaches ca. 15 μM at 25 m depth with no evidence of mixing up during summer. Stable isotope composition of particulate organic nitrogen reaches values as low as 3 per mil in low-salinity waters near both glacier and river. Nitrogen fixation could be depleting δ15N in organic matter, as suggested by the detection at surface waters of nif H genes belonging to diazotrophs near the Montt glacier. As diazotrophs have also been detected in other cold marine waters (e.g. Baltic Sea, Arctic Ocean) as well as glaciers and polar terrestrial waters, there is certainly a potential for both marine and freshwater microbes to contribute and have a significant impact on the Patagonian N and C budgets. Assessing the impact of freshwater on C and N fluxes and the microbial community structure in Patagonian waters will allow understanding future scenarios of rapid glacier melting. This research was funded

  5. Sarcocystosis in wild red deer (Cervus elaphus) in Patagonia, Argentina.

    PubMed

    Reissig, Elizabeth Chang; Moré, Gastón; Massone, Adriana; Uzal, Francisco A

    2016-05-01

    Sarcocystis spp. are protozoan parasites with a heteroxenous life cycle, which produce cysts in the muscle of herbivorous animals. In these animal species, sarcocystosis is frequently asymptomatic, although it may occur with high prevalence. Seven Sarcocystis spp. have been described in red deer (Cervus elephus). The aim of this study was to determine the prevalence of sarcocystosis, and to perform the morphological and molecular characterization of Sarcocystis spp. found in wild red deer of the Nahuel Huapi National Park (NHNP), Patagonia, Argentina. Full necropsies of 62 red deer killed by hunters in the NHNP and neighboring areas were performed. Samples of heart and skeletal muscle were examined histologically and selected samples were also examined by transmission electron microscopy (TEM), PCR and sequencing. Sarcocystis spp. thin walled cysts were detected in 62 % (38/62) of heart, and in 22 % (3/14) of skeletal muscle samples examined histologically. TEM revealed a smooth and thin cyst wall (≤1 μm), with scarce and separated ribbon-like protrusions. A total of three partial and one full 18S ribosomal RNA (rRNA) gene sequences were obtained, and showed the highest identity (≥99 %) with Sarcocystis taeniata, a species described in moose (Alces alces). The morphological and molecular results indicate that red deer in Argentina are frequently infected with S. taeniata, a species for which the definitive host is unknown. The present results also confirm that Sarcocystis spp. using cervids as intermediate host are not host-specific. Further studies are needed to improve the epidemiological knowledge of Sarcocystosis in red deer. PMID:26779923

  6. 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.

  7. A review of the hydrogeologic-geochemical model for Cerro Prieto

    USGS Publications Warehouse

    Lippmann, M.J.; Truesdell, A.H.; Halfman-Dooley, S. E.; Mañónm, A.

    1991-01-01

    With continued exploitation of the Cerro Prieto, Mexico, geothermal field, there is increasing evidence that the hydrogeologic model developed by Halfman and co-workers presents the basic features controlling the movement of geothermal fluids in the system. In mid-1987 the total installed capacity at Cerro Prieto reached 620 MWc, requiring a large rate of fluid production (more than 10,500 tonnes/hr of a brine-steam mixture; August 1988). This significant mass extraction has led to changes in reservoir thermodynamic conditions and in the chemistry of the produced fluids. Pressure drawdown has caused an increase in cold water recharge in the southern and western edges of the field, and local and general reservoir boiling in parts of the geothermal system. After reviewing the hydrogeologic and geochemical models of Cerro Prieto, the exploitation-induced cold water recharge and reservoir boiling (and plugging) observed in different areas of the field, are discussed and interpreted on the basis of these models and schematic flow models that describe the hydrogeology. ?? 1991.

  8. Relationship between water chemistry and sediment mineralogy in the Cerro Prieto geothermal field: a preliminary report

    SciTech Connect

    Valette-Silver, J.N.; Thompson, J.M.; Ball, J.W.

    1981-01-01

    The chemical compositions of waters collected from the Cerro Prieto geothermal production wells and hydrothermal emanations are different. Compared to the Cerro Prieto well waters, the surficial waters generally contain significantly less potassium, slightly less calcium and chloride, and significantly more magnesium and sulfate. In comparison to the unaltered sediments, the changes in the mineralogy of the altered sediments appear to be controlled by the type of emanation (well, spring, mud pot, geyser, fumarole, or cold pool). However, an increase in quartz and potassium feldspar percentages seems to be characteristic of the majority of the sediments in contact with geothermal fluids. Preliminary attempts to model the chemical processes occurring in the Cerro Prieto geothermal field using chemical equilibrium calculations are reported. For this purpose the chemical compositions of thermal waters (well and surficial emanation) were used as input data to make calculations with SOLMNEQ and WATEQ2 computer programs. Then the theoretical mineral composition of altered sediments was predicted and compared to the mineralogy actually observed in the solid samples.

  9. Evolution of the Cerro Prieto geothermal system as interpreted from vitrinite reflectance under isothermal conditions

    SciTech Connect

    Barker, C.E.; Pawlewicz, M.J.; Bostick, N.H.; Elders, W.A.

    1981-01-01

    Temperature estimates from reflectance data in the Cerro Prieto system correlate with modern temperature logs and temperature estimates from fluid inclusion and oxygen isotope geothermometry indicating that the temperature in the central portion of the Cerro Prieto System is now at its historical maximum. Isoreflectance lines formed by contouring vitrinite reflectance data for a given isothermal surface define an imaginary surface that indicates an apparent duration of heating in the system. The 250/sup 0/C isothermal surface has a complex dome-like form suggesting a localized heat source that has caused shallow heating in the central portion of this system. Isoreflectance lines relative to this 250/sup 0/C isothermal surface define a zone of low reflectance roughly corresponding to the crest of the isothermal surface. Comparison of these two surfaces suggest that the shallow heating in the central portion of Cerro Prieto is young relative to the heating (to 250/sup 0/C) on the system margins. Laboratory and theoretical models of hydrothermal convection cells suggest that the form of the observed 250/sup 0/C isothermal surface and the reflectance surface derived relative to it results from the convective rise of thermal fluids under the influence of a regional hydrodynamic gradient that induces a shift of the hydrothermal heating effects to the southwest.

  10. Respiratory tract deposition efficiencies: evaluation of effects from smoke released in the Cerro Grande forest fire.

    PubMed

    Schöllnberger, H; Aden, J; Scott, B R

    2002-01-01

    Forest-fire smoke inhaled by humans can cause various health effects. This smoke contains toxic chemicals and naturally occurring radionuclides. In northern New Mexico, a large wildfire occurred in May 2000. Known as the Cerro Grande Fire, it devastated the town of Los Alamos and damaged Los Alamos National Laboratory (LANL). Residents were concerned about the possible dissemination of radionuclides from LANL via smoke from the fire. To evaluate potential health effects of inhaling radionuclides contained in the smoke from the Cerro Grande Fire, it was first necessary to evaluate how much smoke would deposit in the human respiratory tract. The purpose of this study was to evaluate respiratory-tract deposition efficiencies of airborne forest-fire smoke for persons of different ages exposed while inside their homes. Potential non-radiological health effects of a forest fire are reviewed. The deposition efficiencies presented can be used to evaluate in-home smoke deposition in the respiratory tract and expected radionuclide intake related to forest fires. The impact of smoke exposure on firemen fighting a forest fire is quantitatively discussed and compared. They primarily inhaled forest-fire smoke while outdoors where the smoke concentration was much higher than inside. Radionuclides released at the LANL site via the Cerro Grande Fire were restricted to naturally occurring radionuclides from burning trees and vegetation. Radiation doses from inhaled airborne radionuclides to individuals inside and outside the Los Alamos area were likely very small.

  11. New data on the bottom topography, recent sedimentation and water balance of Cerro Prieto dam, Mexico

    NASA Astrophysics Data System (ADS)

    Yutsis, Vsevolod; Levchenko, Oleg; Lowag, Jens; Krivosheya, Konstantin; de León Gómez, Héctor; Kotsarenko, Anatolyi

    2010-05-01

    Cerro Prieto Dam, a small water reservoir in the NE Mexico, is characterized by very high velocity of recent sedimentation, high sub-bottom seepage and erosion, and as a result, nonlinear water balance. These phenomenons never were studied since construction of the dam in the beginning of 1980th. So the goal of our work was to investigate the bottom topography and also sub-bottom near surface structure using the parametric acoustical effect. High-resolution sub-bottom profiling, using the Innomar SES-2000 compact echosounder, was carried out in Cerro Prieto Dam during February-April of 2008. The survey was conducted onboard of a small motor boat. The SES transducer was mounted on the front side of the boat using light metal pipe, and all electronic equipment was installed on the deck. Accurate positioning of the boat was reached by GPS. Average speed was 8-10 km/h. Innomar's software tool ISE was provides near real-time post-processing of the collected SES data and operation procedure could be corrected on-line. Acoustic signal ensured vertical resolution of 10-15 cm at acceptable penetration up to 15 m. Bathymetry map was compiled assuming average sound velocity of 1450 m/s. The irregular bottom topography of Cerro Prieto dam was discovered. The present elevation of the water surface is about 181 m above see level, and the lake depth varies from 1-2 to 28 m. The SES records show a distinct bottom layer of recent sediments by 0.5 - 4 m thickness which follows reservoir floor topography. Very specific acoustic anomalies, which seem to be related with gas sediments, are observed. The integrated SES, gravity, magnetic and geoelectrical data interpretation allows assuming a series of the superficial fractures focused in a NW direction, perpendicular (NE-SW) to the general deep fault zone. Hydrological balance for the Cerro Prieto water reservoir has been analyzed for last two decades. There are three types of water level fluctuations on the Cerro Prieto dam: long

  12. 1. Fourteen Years Of Diffuse CO2 Monitoring At Cerro Negro Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Barrancos Martinez, Jose; Melián, Gladys; Ibarra, Martha; Álvarez, Julio; Rodríguez, Fátima; Nolasco, Dácil; Padilla, Germán; Calvo, David; Dionis, Samara; Padrón, Eleazar; Hernández, Iñigo; Hernández, Pedro A.; Pérez, Nemesio M.; Muñoz, Angélica

    2013-04-01

    7. Cerro Negro is an active basaltic volcano belonging to the active Central American Volcanic Belt, which includes a 1,100 Km long chain of 41 active volcanoes from Guatemala to Panama. Cerro Negro first erupted in 1850 and has experienced 21 eruptive eruptions with inter eruptive average periods between 7 and 9 years. Since the last eruption occurred on 5 August 1999, with erupted lava flows and ash clouds together with gas emissions, a collaborative research program between INETER and ITER was established for monitoring diffuse CO2 emissions from this volcano. Until 2012, twelve soil CO2 emission surveys covering an area of 0,6 km2 have been performed by means of the accumulation chamber method to evaluate the spatial and temporal variations of CO2 degassing rate in relation to the eruptive cycle of Cerro Negro. A total diffuse CO2 emission output of 1,869 t•d-1 was estimated for the 1999 survey; just 3 months after the 1999 eruption which can be considered within the post-eruptive phase. For the April, 2002 and March, 2008 surveys, considered within the inter-eruptive phase, a clear decreasing tendency on the total diffuse CO2 output was observed, with estimates of 431 and 10 t•d-1, respectively, except a small increment in 2004, to 256 t d-1, associated with an anomalous seismic activity. The higher anomalies are located around the crater of 1995 and 1999. An increasing on the total CO2 emission has been observed, from December 2008 to February 2011, with total diffuse CO2 output estimates from 12 t•d-1 to 43 t•d-1, respectively. These temporal variations show a close relationship between diffuse CO2 emission and the eruptive cycle at Cerro Negro. This relationship indicates that monitoring CO2 emission is an important geochemical tool for the volcanic surveillance at Cerro Negro. References: (1) Rodríguez et al. (2009) AGU Fall Meeting 2009. EOS, AGU,V21-2017 . (2) Padilla et al. (2008). IV Reunión de la Red Española de Volcanología, Almagro 2008

  13. Additional information for Leptoglossus impictus (Stål 1859) (Hemiptera: Heteroptera: Coreidae: Coreinae: Anisoscelini) from Patagonia, Argentina.

    PubMed

    Diez, Fernando; Espindola, Milton Ruiz; Cornelis, Marcela; Coscarón, María Del Carmen

    2016-01-01

    The Patagonian subregion belongs to the Andean region, and is comprised of two provinces: Central Patagonia and Subandean Patagonia. It extends from central Mendoza, widening through Neuquén, Río Negro, Chubut, and Santa Cruz, to northern Tierra del Fuego, and reaches Chile (Morrone 2006). The knowledge of terrestrial Heteroptera in this region is poor and is limited to a few contributions (e.g. Berg 1979, Breddin 1898, Pennington 1920, Faúndez & Carvajal 2011, Faundez 2015). PMID:27395893

  14. Additional information for Leptoglossus impictus (Stål 1859) (Hemiptera: Heteroptera: Coreidae: Coreinae: Anisoscelini) from Patagonia, Argentina.

    PubMed

    Diez, Fernando; Espindola, Milton Ruiz; Cornelis, Marcela; Coscarón, María Del Carmen

    2016-01-25

    The Patagonian subregion belongs to the Andean region, and is comprised of two provinces: Central Patagonia and Subandean Patagonia. It extends from central Mendoza, widening through Neuquén, Río Negro, Chubut, and Santa Cruz, to northern Tierra del Fuego, and reaches Chile (Morrone 2006). The knowledge of terrestrial Heteroptera in this region is poor and is limited to a few contributions (e.g. Berg 1979, Breddin 1898, Pennington 1920, Faúndez & Carvajal 2011, Faundez 2015).

  15. Use of timesat to estimate phenological parameters in Northwestern Patagonia

    NASA Astrophysics Data System (ADS)

    Oddi, Facundo; Minotti, Priscilla; Ghermandi, Luciana; Lasaponara, Rosa

    2015-04-01

    Under a global change context, ecosystems are receiving high pressure and the ecology science play a key role for monitoring and assessment of natural resources. To achieve an effective resources management to develop an ecosystem functioning knowledge based on spatio-temporal perspective is useful. Satellite imagery periodically capture the spectral response of the earth and remote sensing have been widely utilized as classification and change detection tool making possible evaluate the intra and inter-annual plant dynamics. Vegetation spectral indices (e.g., NDVI) are particularly suitable to study spatio-temporal processes related to plant phenology and remote sensing specific software, such as TIMESAT, has been developed to carry out time series analysis of spectral indexes. We used TIMESAT software applied to series of 25 years of NDVI bi-monthly composites (240 images covering the period 1982-2006) from the NOAA-AVHRR sensor (8 x 8 km) to assessment plant pheonology over 900000 ha of shrubby-grasslands in the Northwestern of Patagonia, Argentina. The study area corresponds to a Mediterranean environment and is part of a gradient defined by a sharp drop west-east in the precipitation regime (600 mm to 280 mm). We fitted the temporal series of NDVI data to double logistic functions by least-squares methods evaluating three seasonality parameters: a) start of growing season, b) growing season length, c) NDVI seasonal integral. According to fitted models by TIMESAT, start average of growing season was the second half of September (± 10 days) with beginnings latest in the east (dryer areas). The average growing season length was 180 days (± 15 days) without a clear spatial trend. The NDVI seasonal integral showed a clear trend of decrease in west-east direction following the precipitation gradient. The temporal and spatial information allows revealing important patterns of ecological interest, which can be of great importance to environmental monitoring. In this

  16. Physically Based Mountain Hydrological Modelling using Reanalysis Data in Patagonia

    NASA Astrophysics Data System (ADS)

    Krogh, S.; Pomeroy, J. W.; McPhee, J. P.

    2013-05-01

    Remote regions in South America are often characterized by insufficient observations of meteorology for robust hydrological model operation. Yet water resources must be quantified, understood and predicted in order to develop effective water management policies. Here, we developed a physically based hydrological model for a major river in Patagonia using the modular Cold Regions Hydrological Modelling Platform (CRHM) in order to better understand hydrological processes leading to streamflow generation in this remote region. The Baker River -with the largest mean annual streamflow in Chile-, drains snowy mountains, glaciers, wet forests, peat and semi-arid pampas into a large lake. Meteorology over the basin is poorly monitored in that there are no high elevation weather stations and stations at low elevations are sparsely distributed, only measure temperature and rainfall and are poorly maintained. Streamflow in the basin is gauged at several points where there are high quality hydrometric stations. In order to quantify the impact of meteorological data scarcity on prediction, two additional data sources were used: the ERA-Interim (ECMWF Re-analyses) and CFSR (Climate Forecast System Reanalysis) atmospheric reanalyses. Precipitation temporal distribution and magnitude from the models and observations were compared and the reanalysis data was found to have about three times the number of days with precipitation than the observations did. Better synchronization between measured peak streamflows and modeled precipitation was found compared to observed precipitation. These differences are attributed to: (i) lack of any snowfall observations (so precipitation records does not consider snowfall events) and (ii) available rainfall observations are all located at low altitude (<500 m a.s.l), and miss the occurrence of high altitude precipitation events. CRHM parameterization was undertaken by using local physiographic and vegetation characteristics where available and

  17. Last millenium environmental changes in Lake Bertrand sediments, Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Sacré, V.; Fagel, N.; Schmidt, S.; Alvarez, D.; Araneda, A.; Urrutia, R.

    2012-04-01

    Our study focuses on a multiproxy analysis of sedimentary records from Lago Bertrand (area 50 km2; 227 masl; 46°55'S 72°50'W). Three cores were retrieved during fieldtrips in 2009 and 2011 with an Uwitec gravity corer. One core was collected in the main lake (LBt09, 102 cm) and two others in a lateral extension (LBb11-A, 162 cm and LBb11-B, 156 cm). Data 210Pb and 137Cs give average sedimentation rates of 2 mm/yr for the upper core section from the main lake, allowing a decennial resolution. Our aim is to document the climatic variability during the last millennium in Northern Patagonia and its impact on the environment. Lago Bertrand is separated from a pro-glacial lake (Lago Plomo) by a morainic barrier. The sediments of this lake are mainly composed of clayed silts and very few sandy silts. In the cores from the Eastern branch of Lago Bertrand, X-ray radiographies and magnetic susceptibility profiles evidence well-defined pluri-millimetric laminations with organic-rich layers, especially in the central core section. In the main lake, X-ray radiographies show diffuse pluri-millimetric laminations while magnetic susceptibility profiles do not confirm it. The sediments of the main lake appear more homogeneous with less organic-rich layers. They are characterized by low C/N ratio (10), supporting an important aquatic productivity; high inorganic content (90-95% of the bulk sediment); two peaks in the biological silica profile; and abundant diatoms (50-100 µm). According to the age model, the changes in aquatic productivity occurred between 1700 and 1850 AD. The cores from the Eastern branch of Lago Bertrand are under investigation to confirm the extension of the sedimentological changes observed in the main lake. The main sedimentological change observed in Lago Bertrand occurs during an interval equivalent to a part of the Little Ice Age. A similar biogenic silica-rich layer was also recorded in another relatively distant lake (Lago Thompson at 45°30'S, 72°47

  18. Metasomatism in the lithospheric mantle beneath southern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Kolosova-Satlberger, Olesya; Ntaflos, Theodoros; Bjerg, Ernesto

    2014-05-01

    Mantle xenoliths from Gobernador Gregores, southern Patagonia are spinel- lherzolites, harzburgites and wherlites. A large number of the studied xenoliths have experienced cryptic and modal metasomatism. The xenoliths are mainly coarse-grained with prevalent protogranular texture but equigranular tabular and mosaic textures are present as well. Xenoliths that have undergone modal metasomatism bear hydrous phases such as amphibole, phlogopite ± apatite and melt pockets. The latter are of particular interest because of their unusually large size (up to 1 cm in diameter) and freshness. They consist of second generation olivine, clinopyroxene and spinel ± relict amphibole ± sulfides that are surrounded by a yellowish vesicular glass matrix. The melt pockets are found in amphibole- and/or phlogopite-bearing wehrlites and harzburgites as well as anhydrous lherzolites. Subhedral primary olivines enclosed by melt pockets show in the BSE images a dark grey margin up to 80 microns thick attributed to the reaction of the primatry olivine with melt. Fine grained spinel inclusions are always associated with the dark grey margin, indicating that they belong to the secong generation assemblage. There are considerable differences between first and second generation minerals found in melt pockets. While primary olivine has Fo-contents that range from 88.0 to 93.3, second generation olivines in melt pockets vary from Fo89.3 to Fo94.4. Both primary and second generation cpx are diopsides with the latter systematically enriched in TiO2. The glasses that occur in melt pockets or propagate intergranular have compositions varying from trachyandesite to phonolite. The variable composition of the glass could be attributed to host basalt infiltration and decompressional melting of amphiboles. Some of the studied xenoliths show melt propagation of two compositional different glasses crosscutting primary generation minerals and finally mixing with each other. Microprobe analyses suggest

  19. Reconnaissance study of late quaternary faulting along cerro GoDen fault zone, western Puerto Rico

    USGS Publications Warehouse

    Mann, P.; Prentice, C.S.; Hippolyte, J.-C.; Grindlay, N.R.; Abrams, L.J.; Lao-Davila, D.

    2005-01-01

    The Cerro GoDen fault zone is associated with a curvilinear, continuous, and prominent topographic lineament in western Puerto Rico. The fault varies in strike from northwest to west. In its westernmost section, the fault is ???500 m south of an abrupt, curvilinear mountain front separating the 270- to 361-m-high La CaDena De San Francisco range from the Rio A??asco alluvial valley. The Quaternary fault of the A??asco Valley is in alignment with the bedrock fault mapped by D. McIntyre (1971) in the Central La Plata quadrangle sheet east of A??asco Valley. Previous workers have postulated that the Cerro GoDen fault zone continues southeast from the A??asco Valley and merges with the Great Southern Puerto Rico fault zone of south-central Puerto Rico. West of the A??asco Valley, the fault continues offshore into the Mona Passage (Caribbean Sea) where it is characterized by offsets of seafloor sediments estimated to be of late Quaternary age. Using both 1:18,500 scale air photographs taken in 1936 and 1:40,000 scale photographs taken by the U.S. Department of Agriculture in 1986, we iDentified geomorphic features suggestive of Quaternary fault movement in the A??asco Valley, including aligned and Deflected drainages, apparently offset terrace risers, and mountain-facing scarps. Many of these features suggest right-lateral displacement. Mapping of Paleogene bedrock units in the uplifted La CaDena range adjacent to the Cerro GoDen fault zone reveals the main tectonic events that have culminated in late Quaternary normal-oblique displacement across the Cerro GoDen fault. Cretaceous to Eocene rocks of the La CaDena range exhibit large folds with wavelengths of several kms. The orientation of folds and analysis of fault striations within the folds indicate that the folds formed by northeast-southwest shorTening in present-day geographic coordinates. The age of Deformation is well constrained as late Eocene-early Oligocene by an angular unconformity separating folDed, Deep

  20. Session 10: The Cerro Prieto Geothermal Field, Mexico: The Experiences Gained from Its Exploration and Development

    SciTech Connect

    Lippman, M.J.; Goldstein, N.E.; Halfman, S.E.; Witherspoon, P.A.

    1983-12-01

    The Cerro Prieto case study demonstrated the value of a multidisciplinary effort for exploring and developing a geothermal field. There was no problem in recognizing the geothermal potential of the Cerro Prieto area because of the many obvious surface manifestations. However, the delineation of the geothermal reservoir at depth was not so straightforward. Wells drilled near the abundant surface manifestations only produced fluids of relatively low enthalpy. Later it was determined that these zones of high heat loss corresponded to discharge areas where faults and fractures allowed thermal fluids to leak to the surface, and not to the main geothermal reservoir. The early gravity and seismic refraction surveys provided important information on the general structure of the area. Unaware of the existence of a higher density zone of hydrothermally altered sediments capping the geothermal reservoir, CFE interpreted a basement horst in the western part of the field and hypothesized that the bounding faults were controlling the upward flow of thermal fluids. Attempting to penetrate the sedimentary column to reach the ''basement horst'', CFE discovered the {alpha} geothermal reservoir (in well M-5). The continuation of the geothermal aquifer (actually the {beta} reservoir) east of the original well field was later confirmed by a deep exploration well (M-53). The experience of Cerro Prieto showed the importance of chemical ratios, and geothermometers in general, in establishing the subsurface temperatures and fluid flow patterns. Fluid chemical and isotopic compositions have also been helpful to determine the origin of the fluids, fluid-production mechanisms and production induced effects on the reservoir.

  1. The Cerro Negro accumulation of Venezuela's Orinoco Belt - the favorable convergence of several geological processes

    SciTech Connect

    Swanson, D.C. ); Tarache, C. )

    1993-02-01

    The Cerro Negro Area is a major part of eastern Venezuela's Orinoco Belt. Here upper Eocene fluvial-deltaic deposits of the Oficina Fm. reservoir billions of barrels of heavy oil, much of which is in valley-fill deposits. Maturation, migration and accumulation of these hydrocarbons in thick, porous and permeable sandstones were the logical conclusion to several major geological events in eastern Venezuela during the Tertiary. In the Cerro Negro Area, Cretaceous clastics were deposited on an igneous and metamorphic basement after which the sea withdrew northward toward the axial part of the Eastern Venezuelan Basin. The basement and Cretaceous deposits were weathered and eroded during the Eocene, Oligocene, and early Miocene, forming the unconformity on which the Oficina Fm. is deposited. Historic reconstruction begins with this unconformity, a paleotopographic surface strongly influencing the character and distribution of the overlying Oficina Fm. As relative sea level fell and gradients increased, streams incised into the shelf while transporting great amounts of coarse clastic load northward. At Cerro Negro, a mature topography of low ridges and hills were developed with differential elevations of several hundred feet. During the Miocene, a sea transgressed across the stream-etched unconformity. Streams carrying large amounts of clastic load encountered an elevating sea level. They consequently dropped their coarse load, forming long, linear, transgressive, valley-fill deposits. By Late Miocene, hydrocarbons generated in the deeper basin began to migrate southward through the long linear fluvial-deltaic clastic conduits that were separated laterally and vertically into complex [open quotes]plumbing systems.[close quotes] As the hydrocarbons moved shelfward, normal faults cut the conduits into numerous reservoir segments. The timing between migration and faulting is critical to present-day hydrocarbon distribution in these segments.

  2. Vitrinite reflectance geothermometry and apparent heating duration in the Cerro Prieto geothermal field

    USGS Publications Warehouse

    Barker, C.E.; Elders, W.A.

    1981-01-01

    Vitrinite reflectance measured in immersion oil (Ro) on kerogen extracted from hydrothermally altered mudstones in borehole M-84 at the Cerro Prieto geothermal field exhibit an increase in mean reflectance (Ro) from 0.12 per cent at 0.24 km depth to 4.1 per cent at 1.7 km depth. Downhole temperatures measured over this interval increase from about 60?? to 340??C. These Ro data plotted against temperature fall along an exponential curve with a coefficient of determination of about 0.8. Other boreholes sampled in the field show similar relationships. A regression curve calculated for temperature and Ro in borehole M-105 correctly predicts temperatures in other boreholes within the central portion of the geothermal system. The correlation between the reflectance values and logged temperature, together with consistent temperature estimates from fluid inclusion and oxygen isotope geothermometry, indicates that changes in Ro are an accurate and sensitive recorder of the maximum temperature attained. Therefore, vitrinite reflectance can be used in this geothermal system to predict the undisturbed temperature in a geothermal borehole during drilling before it regains thermal equilibrium. Although existing theoretical functions which relate Ro to temperature and duration of heating are inaccurate, empirical temperature-Ro curves are still useful for geothermometry. A comparison of temperature-Ro regression curves derived from nine boreholes within the Cerro Prieto system suggests that heating across the central portion of the field occurred penecontemporaneously, but varies near margins. Boreholes M-93 and M-94 appear to have cooled from their maximum temperatures, whereas M-3 and Prian-1 have only recently been heated. Comparison of the temperature-Ro data from the Salton Sea, California, geothermal system indicates that the duration of heating has been longer there than at the Cerro Prieto field. ?? 1981.

  3. Modeling discharge requirements for deep geothermal wells at the Cerro Prieto geothermal field, MX

    SciTech Connect

    Menzies, Anthony J.; Granados, Eduardo E.; Puente, Hector Gutierrez; Pierres, Luis Ortega

    1995-01-26

    During the mid-l980's, Comision Federal de Electricidad (CFE) drilled a number of deep wells (M-200 series) at the Cerro Prieto geothermal field, Baja California, Mexico to investigate the continuation of the geothermal reservoir to the east of the Cerro Prieto-II and III production areas. The wells encountered permeability at depths ranging from 2,800 to 4,400 m but due to the reservoir depth and the relatively cold temperatures encountered in the upper 1,000 to 2,000 m of the wells, it was not possible to discharge some of the wells. The wells at Cerro Prieto are generally discharged by injecting compressed air below the water level using 2-3/8-inch tubing installed with either a crane or workover rig. The objective of this technique is to lift sufficient water out of the well to stimulate flow from the reservoir into the wellbore. However, in the case of the M-200 series wells, the temperatures in the upper 1,000 to 2,000 m are generally below 50 C and the heat loss to the formation is therefore significant. The impact of heat loss on the stimulation process was evaluated using both a numerical model of the reservoir/wellbore system and steady-state wellbore modeling. The results from the study indicate that if a flow rate of at least 300 liters/minute can be sustained, the well can probably be successfully stimulated. This is consistent with the flow rates obtained during the successful stimulations of wells M-202 and M-203. If the flow rate is closer to 60 liters/minute, the heat loss is significant and it is unlikely that the well can be successfully discharged. These results are consistent with the unsuccessful discharge attempts in wells M-201 and M-205.

  4. Preliminary plasma spectrometric analyses for selected elements in some geothermal waters from Cerro Prieto, Mexico

    USGS Publications Warehouse

    Ball, J.W.; Jenne, E.A.

    1983-01-01

    As part of a cooperative study with Dr. Alfred Truesdell, water samples collected from geothermal power production wells at Cerro Prieto, Mexico, were analyzed for selected elements by d.c. argon plasma emission spectroscopy. Spectral interferences due to the presence of high concentrations of Ca, Si, Na and K in these water affected the apparent concentration values obtained. These effects were evaluated and correction techniques were developed and applied to the analytical values. Precipitates present in the samples at the time of analysis adversely affected the accuracy, precision and interpretability of the data. (USGS)

  5. Two-dimensional modeling of apparent resistivity pseudosections in the Cerro Prieto region

    SciTech Connect

    Vega, R.; Martinez, M.

    1981-01-01

    Using a finite-difference program (Dey, 1976) for two-dimensional modeling of apparent resistivity pseudosections obtained by different measuring arrays, four apparent resistivity pseudosections obtained at Cerro Prieto with a Schlumberger array by CFE personnel were modeled (Razo, 1978). Using geologic (Puente and de la Pena, 1978) and lithologic (Diaz, et al., 1981) data from the geothermal region, models were obtained which show clearly that, for the actual resistivity present in the zone, the information contained in the measured pseudosections is primarily due to the near-surface structure and does not show either the presence of the geothermal reservoir or the granitic basement which underlies it.

  6. First results from optical turbulence measurements at Cerro Las Campanas in 2010

    NASA Astrophysics Data System (ADS)

    Berdja, A.; Prieto, G.; Thomas-Osip, J. E.

    2011-09-01

    We report preliminary results from optical turbulence measurements carried out in 2010 at Cerro Las Campanas, the future site for the Giant Magellan Telescope (GMT). The instruments involved are MooSci, a lunar scintillometer for the near-ground optical turbulence profile, Differential Image Motion Monitor (DIMM) for the whole atmosphere total seeing, and MASS Multiple Aperture Scintillation Sensor (MASS) for high-altitude optical turbulence estimation. The main purpose of these measurements is to anticipate the optical turbulence strength above the future GMT enclosure, and to provide a means to model the future adaptive optics performance. We also discuss the significance of such a combination of instruments and some hypothetical limitations.

  7. Four Years of Optical Turbulence Monitoring at the Cerro Tololo Inter-American Observatory (CTIO)

    NASA Astrophysics Data System (ADS)

    Els, S. G.; Schöck, M.; Bustos, E.; Seguel, J.; Vasquez, J.; Walker, D.; Riddle, R.; Skidmore, W.; Travouillon, T.; Vogiatzis, K.

    2009-08-01

    The optical turbulence conditions as measured between 2004 through the end of 2008 above Cerro Tololo, their seasonal as well as nocturnal behavior, are presented. A comparison with the MASS-DIMM system of the Thirty Meter Telescope site testing was conducted and identifies an artificially increased seeing component in the data collected by the CTIO-DIMM system under northerly winds. Evidence is shown that this increased turbulence is caused by the telescope dome. A correction for this effect is attempted and applied to the CTIO-DIMM data. The MASS data of this comparison campaign allow constraints to be set on the general assumption of uniform turbulent layers above a site.

  8. Cerro Papayo: an astronomical, calendrical and traditional landmark in Ancient Mexico.

    NASA Astrophysics Data System (ADS)

    Galindo Trejo, J.; Aguilera, T.; Montero García, I. A.

    Cerro Papayo is a peculiar formed hill (almost perfect semisphere, 3,630 m) situated at the east side of the Valley of Mexico. According to surface reconnaissance there is on its cusp a prehispanic site and a modern shrine dedicated to the Virgin of Guadalupe. Its striking appearance and its unobstructed visibility from anyplace in the Valley were used, since preclassic up to postclassic periods, to mark at sunrise the moment of precise astronomical, calendrical and traditional events. The present work shows observational evidence from Cuicuilco, the Templo Mayor of Tenochtitlan and Tepeyacac.

  9. Boiling and condensation processes in the Cerro Prieto beta reservoir under exploitation

    SciTech Connect

    Truesdell, A. , Menlo Park, CA ); Manon, A.; Quijano, L. ); Coplen, T. ); Lippmann, M. )

    1992-01-01

    The deep Cerro Prieto (Baja California, Mexico) beta reservoir is offset vertically by the southwest-northeast trending, normal H fault. Under exploitation pressures in the upthrown block have decreased strongly resulting in boiling and high-enthalpy production fluids. Significant differences in fluid chemical and isotopic compositions are observed in the two parts of the reservoir and particularly in an anomalous zone associated with the H fault. These differences result from intense boiling and adiabatic steam condensation, as well as from leakage of overlying cooler water along the fault.

  10. Recent drainage events of glacial Lake Cachet 2, Patagonia

    NASA Astrophysics Data System (ADS)

    Casassa, G.; Wendt, J.; Wendt, A.; Escobar, F.; Lopez, P.; Carrasco, J.; Rivera, A.; Leidich, J.

    2009-04-01

    Lake Cachet 2 (47°12' S, 73°15' W, 422 m a.s.l.) is a proglacial lake of 4 km2 located on the eastern margin of the Northern Patagonia Icefield (3,953 km2, Rivera et al., 2007), which is dammed on its southern margin by Colonia Glacier. Until April 2008 there was no historical evidence of catastrophic flooding of this lake. In 2008 three sudden drainage events occurred at Lake Cachet 2 (April 6-7; October 7-8 and 21-22 December). During each event the flood wave traveled down Colonia River to the confluence with Baker River, then affected Baker River to a distance of up to 25 km upstream from the confluence and downstream all the way to its mouth on the Pacific Ocean fjords at Caleta Tortel (100 km to the southwest), transporting abundant sediments. In April the runoff of Baker River close to the confluence with Colonia River increased from a base level of 1,200 m3/s on April 7 to a peak runoff of 3,570 m3/s within a period of less than 48 hours, resulting in a river level increase of 4.5 m and an associated water temperature drop from 8°C to 4°C. In October the base level was 573 m3/s, with a peak runoff of 3,007 m3/s, a river level increase of 4.7 m and a water temperature drop from 7.3°C to 4.8°C, while in December the corresponding values were 1,145 m3/s, 3,052 m3/s, 11°C and 8°C. The flood affected roads, bridges, farms and cattle, fortunately not resulting in any human damage. Similar floods had been reported on Colonia River several decades ago, the last having occurred in the 1970s, all of which originated at that time at glacial Lake Arco, located south of Colonia Glacier. Airborne and ground explorations carried out after each event in 2008 confirmed that the floods originated at Lake Cachet 2, draining under Colonia Glacier for a distance of 8 km and emerging at the front of the glacier. As a result parts of the glacier front collapsed after each event, where large ice fractures could be observed. During the October event a complete drainage of

  11. SRTM Anaglyph: Meseta de Somuncura, Patagonia, Argentina (Near Los Menucos)

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Meseta de Somuncura is a semi-arid basalt plateau in northern Patagonia. This view of the northwestern part of the plateau, near Los Menucos, Argentina, shows numerous depressions where the upper basalt layers are missing or collapsed. Collapse occurs above voids in the underlying rock. These voids might have been caused by lava tubes carrying away molten lava from under the cooled and solidified surface of a lava flow. Alternatively, voids might result when ground water dissolves carbonate (limestone) or evaporite (salt) deposits that the lava may be covering.

    Many of the depressions have salty lakes. Light wind streaks downwind (eastward) from the lakes show that salt crystals blow off the lake beds during dry times. Some eroded sand and silt debris from the basalt must also blow downwind, but the degree to which wind plays a role in the erosion of the depressions is not clear.

    This anaglyph was generated by first draping a Landsat Thematic Mapper image over a topographic map from the Shuttle Radar Topography Mission, then producing the two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and the right eye with a blue filter.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11

  12. SRTM Stereo Pair: Meseta de Somuncura, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Meseta de Somuncura is a semi-arid basalt plateau in northern Patagonia. This view of the northwestern part of the plateau, near Los Menucos, Argentina, shows numerous depressions where the upper basalt layers are missing or collapsed. Collapse occurs above voids in the underlying rock. These voids might have been caused by lava tubes carrying away molten lava from under the cooled and solidified surface of a lava flow. Alternatively, voids might result when ground water dissolves carbonate (limestone) or evaporite (salt) deposits that the lava may be covering.

    Many of the depressions have salty lakes. Light wind streaks downwind (eastward) from the lakes show that salt crystals blow off the lake beds during dry times. Some eroded sand and silt debris from the basalt must also blow downwind, but the degree to which wind plays a role in the erosion of the depressions is not clear.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission

  13. Metasomatism in the lithospheric mantle beneath southern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Kolosova-Satlberger, Olesya; Ntaflos, Theodoros; Bjerg, Ernesto

    2015-04-01

    Mantle xenoliths from Gobernador Gregores, southern Patagonia are spinel- lherzolites, harzburgites and wehrlites. Composite xenoliths consisting of websterites, olivine-websterites and spinel- lherzolites or harzburgites are present as well. The lithospheric mantle beneath Gobernador Gregores region was affected by multiple modal metasomatic events as can be inferred by the presence of amphibole, phlogopite and apatite. The existence of amphibole as inclusion in clinopyroxene suggests dehydration reaction of peridotites, which previously experienced modal metasomatism. This textural evidence records the earliest detectable metasomatic event. A second distinct modal metasomatic event consists of disseminated up to 6 mm in diameter coarse grained amphiboles (100*mg# =89.9) which show breakdown reactions and pseudomorphic replacement by glass and fine grained second generation of olivine, clinopyroxene and spinel. The intensity of the breakdown reaction is variable. In most cases amphibole occurs as a relict within these pseudomorphs. However, melt pockets of up to 10 mm in diameter are abundant, irregular in shape and having the same minerals such as in the pseudomorphs, indicate clearly amphibole breakdown because remnants of it were found enclosed by second generation clinopyroxene. Similar breakdown reactions experienced the phlogopite in the samples where is present. The Phlogopite (100*mg# =88.6) breakdown produces the same mineral phases as the amphibole. The second generation minerals formed after breakdown of amphibole and phlogopite show minor differences in their composition. However, the chemical composition of glass varies considerably. The glasses formed after breakdown of amphibole and phlogopite have trachyandesitic and tephriphonolitic composition, respectively. Some harzburgites and composite xenoliths reveal another metasomatic event: peridotite, enriched in orthopyroxene (mainly orthopyroxenite veinlets, rare websterite), suggests interaction with

  14. Geochronology of type Santacrucian (Middle Tertiary) Land Mammal Age, Patagonia, Argentina

    SciTech Connect

    Marshall, L.G.; Drake, R.E.; Curtis, G.H.; Butler, R.F.; Flanagan, K.M.; Naeser, C.W.

    1986-07-01

    Mammal-bearing lacustrine and tuffaceous sediments from three localities of the Santa Cruz Formation, type fauna of the Santacrucian Land Mammal Age, in Patagonia, southern Argentina, are calibrated by radioisotope dating with the aid of magnetostratigraphy. The strata range from about 17.6 Ma to perhaps 16.0 Ma, and are thus of late-early Miocene age. The Santacrucian Land Mammal Age ranges from about 18.0 Ma to about 15.0 Ma.

  15. An apparent outbreak of cutaneous papillomatosis in merino sheep in patagonia, Argentina.

    PubMed

    Uzal, F A; Latorraca, A; Ghoddusi, M; Horn, M; Adamson, M; Kelly, W R; Schenkel, R

    2000-04-01

    A retrospective study was performed on skin samples from an outbreak of cutaneous papillomatosis in Merino sheep that occurred in 1995. The samples were processed for routine histology, electron microscopy and immunocytochemistry for papilloma viruses. Particles of approximately 55 nm diameter were found in some nuclei of the stratum granulosum cells, while immunocytochemistry gave positive staining of cell nuclei in this layer. This study confirms that papillomas associated with papillomaviruses occur in sheep in Patagonia. PMID:10836278

  16. 222Radon Concentration Measurements biased to Cerro Prieto Fault for Verify its Continuity to the Northwest of the Mexicali Valley.

    NASA Astrophysics Data System (ADS)

    Lazaro-Mancilla, O.; Lopez, D. L.; Reyes-Lopez, J. A.; Carreón-Diazconti, C.; Ramirez-Hernandez, J.

    2009-05-01

    The need to know the exact location in the field of the fault traces in Mexicali has been an important affair due that the topography in this valley is almost flat and fault traces are hidden by plow zone, for this reason, the southern and northern ends of the San Jacinto and Cerro Prieto fault zones, respectively, are not well defined beneath the thick sequence of late Holocene Lake Cahuilla deposits. The purpose of this study was to verify if Cerro Prieto fault is the continuation to the southeast of the San Jacinto Fault proposed by Hogan in 2002 who based his analysis on pre-agriculture geomorphy, relocation and analysis of regional microseismicity, and trench exposures from a paleoseismic site in Laguna Xochimilco, Mexicali. In this study, four radon (222Rn) profiles were carried out in the Mexicali Valley, first, to the SW-NE of Cerro Prieto Volcano, second, to the W-E along the highway Libramiento San Luis Río Colorado-Tecate, third, to the W-E of Laguna Xochimilco and fourth, to the W-E of the Colonia Progreso. The Radon results allow us to identify in the Cerro Prieto profile four regions where the values exceed 100 picocuries per liter (pCi/L), these regions can be associated to fault traces, one of them associated to the Cerro Prieto Fault (200 pCi/L) and other related with Michoacán de Ocampo Fault (450 pCi/L). The profile Libramiento San Luis Río Colorado-Tecate, show three regions above 100 pCi/L, two of them related to the same faults. In spite of the results of the Laguna Xochimilco, site used by Hogan (2002), the profile permit us observe three regions above the 100 pCi/L, but we can associate only one of the regions above this level to the Michoacán de Ocampo Fault, but none region to the Cerro Prieto Fault. Finally in spite of the Colonia Progreso is the shortest profile with only five stations, it shows one region with a value of 270 pCi/L that we can correlate with the Cerro Prieto Fault. The results of this study allow us to think in the

  17. Impacts of the Cerro Grande fire on Homestead era and Manhattan Project properties at Los Alamos National Laboratory.

    SciTech Connect

    McGehee, E. D.; Isaacson, J.

    2001-01-01

    In May of 2000, the Cerro Grande Fire burned approximately 8,000 acres of Department of Energy (DOE) managed land at the Los Alamos National Laboratory (LANL). Although the fire was generally of low intensity, it impacted a significant number of LANL's cultural resources. Historic wooden properties were affected more heavily than prehistoric archaeological sites. This paper will provide an overview of the Homestead and Manhattan Project Periods at LANL and will discuss the effects of the Cerro Grande Fire on historic wooden properties. Post-fire cultural resource management issues will also be discussed.

  18. Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity, Low Extinction, and a Classopollis Spike

    PubMed Central

    Barreda, Viviana D.; Cúneo, Nestor R.; Wilf, Peter; Currano, Ellen D.; Scasso, Roberto A.; Brinkhuis, Henk

    2012-01-01

    Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis. PMID:23285049

  19. Cretaceous/Paleogene floral turnover in Patagonia: drop in diversity, low extinction, and a Classopollis spike.

    PubMed

    Barreda, Viviana D; Cúneo, Nestor R; Wilf, Peter; Currano, Ellen D; Scasso, Roberto A; Brinkhuis, Henk

    2012-01-01

    Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis. PMID:23285049

  20. Pomacea canaliculata (Mollusca, Gastropoda) in Patagonia: potential role of climatic change in its dispersion and settlement.

    PubMed

    Darrigran, G; Damborenea, C; Tambussi, A

    2011-02-01

    Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) shows a large native distribution range in South America, reaching as far south as 37º S (Buenos Aires, Argentina). This species was deliberately introduced into Southeast Asia around 1980 and subsequently underwent a rapid intentional or accidental dispersal into many countries in the region. It was also introduced into North and Central America and Hawaii. In this contribution we record the presence of P. canaliculata in Patagonia, assessing the possible influence of climatic change in the new establishment of this species there. Three samplings (between September 2004 and April 2005) were carried out at 38º 58' 20.2" S-68º 11' 27.3" W. In the sampling we found two adult specimens of P. canaliculata and numerous egg clutches. Pomacea canaliculata is naturally distributed in the Plata and Amazon Basins. The southern boundary of this species has been established as the isotherms of 14 ºC and 16 ºC in Buenos Aires province, and precipitations of 900 to 600 mm/year. This study also analysed variations in annual temperature and precipitation in Patagonia. Average temperatures show an increase over the years, although not constantly. Important modifications in precipitation regime in northern Patagonia, triggered by global climatic changes, could be beneficial for the settlement of populations of P. canaliculata in this new area, where precipitation increased enough to reach values similar to those in the southernmost area of distribution of this species.

  1. Analysis of heavy oils: Method development and application to Cerro Negro heavy petroleum

    SciTech Connect

    Carbognani, L.; Hazos, M.; Sanchez, V. ); Green, J.A.; Green, J.B.; Grigsby, R.D.; Pearson, C.D.; Reynolds, J.W.; Shay, J.Y.; Sturm, G.P. Jr.; Thomson, J.S.; Vogh, J.W.; Vrana, R.P.; Yu, S.K.T.; Diehl, B.H.; Grizzle, P.L.; Hirsch, D.E; Hornung, K.W.; Tang, S.Y.

    1989-12-01

    On March 6, 1980, the US Department of Energy (DOE) and the Ministry of Energy and Mines of Venezuela (MEMV) entered into a joint agreement which included analysis of heavy crude oils from the Venezuelan Orinoco oil belt.The purpose of this report is to present compositional data and describe new analytical methods obtained from work on the Cerro Negro Orinoco belt crude oil since 1980. Most of the chapters focus on the methods rather than the resulting data on Cerro Negro oil, and results from other oils obtained during the verification of the method are included. In addition, published work on analysis of heavy oils, tar sand bitumens, and like materials is reviewed, and the overall state of the art in analytical methodology for heavy fossil liquids is assessed. The various phases of the work included: distillation and determination of routine'' physical/chemical properties (Chapter 1); preliminary separation of >200{degree}C distillates and the residue into acid, base, neutral, saturated hydrocarbon and neutral-aromatic concentrates (Chapter 2); further separation of acid, base, and neutral concentrates into subtypes (Chapters 3-5); and determination of the distribution of metal-containing compounds in all fractions (Chapter 6).

  2. Cerro de Pasco and other massive sulfide deposits of central Peru

    SciTech Connect

    Cheney, E.S.

    1985-01-01

    The famous Cerro de Pasco Pb-Zn-Ag deposit historically has been considered to be hydrothermally derived from an adjacent Tertiary volcanic vent. However, texturally massive pyrite-chert and pyrite-sphalerite-galena in the deposit have the same strike and cross folds as the adjacent pre-Tertiary strata. Both the deposit and the strata are cut by one of the large Longitudinal Faults. Both dikes and pyrite-enargite veins associated with the vent cut the massive sulfides; fragments of massive pyrite occur in the vent. A few examples of laminated pyrite and chert, banded pyrite and chert, banded pyrite and sphalerite, and banded pyrite, sphalerite, and galena are preserved in the massive sulfide portion of the deposit. The deposit has the composition and zoning patterns typical of shale-hosted massive sulfides. Cerro de Pasco probably in part of the pelitic Devonian Excelsior formation. The Colquijirca deposit 8 km to the south and the San Cristobal district 110 km to the south likewise have been considered to be Tertiary volcanic hydrothermal deposits. Colquijirca consists of stratigraphically controlled mantos of layered pyrite, chert and tuff in the Tertiary Calera formation. The mantos of the San Cristobal district are along the upper contact of the pyritic, Permian, Catalina felsic volcanic rocks; some ore consists of laminated pyrite and sphalerite. Tertiary plutons are conspicuously absent at San Cristobal, and the ores are brecciated by Tertiary folding.

  3. Reservoir Simulation on the Cerro Prieto Geothermal Field: A Continuing Study

    SciTech Connect

    Castaneda, M.; Marquez, R.; Arellano, V.; Esquer, C.A.

    1983-12-15

    The Cerro Prieto geothermal field is a liquid-dominated geothermal reservoir of complex geological and hydrological structure. It is located at the southern end of the Salton-Mexicali trough which includes other geothermal anomalies as Heber and East Mesa. Although in 1973, the initial power plant installed capacity was 75 MW of electrical power, this amount increased to 180 MW in 1981 as field development continued. It is expected to have a generating capacity of 620 MW by the end of 1985, when two new plants will be completely in operation. Questions about field deliverability, reservoir life and ultimate recovery related to planned installations are being presently asked. Numerical modeling studies can give very valuable answers to these questions, even at the early stages in the development of a field. An effort to simulate the Cerro Prieto geothermal reservoir has been undergoing for almost two years. A joint project among Comision Federal de Electricidad (CFE), Instituto de Investigaciones Electricas (IIE) and Intercomp of Houstin, Texas, was created to perform reservoir engineering and simulation studies on this field. The final project objective is tosimulate the behavior of the old field region when production from additional wells located in the undeveloped field zones will be used for feeding the new power plants.

  4. Dating thermal events at Cerro Prieto using fission-track annealing

    SciTech Connect

    Sanford, S.J.; Elders, W.A.

    1981-01-01

    The duration of heating in the Cerro Prieto reservoir was estimated by relating the fading of spontaneous fission tracks in detrital apatite to observed temperatures. The rate of fading is a function of both time and temperature. The apparent fission track age of the detrital apatites then, is a function of both their source age and their time-temperature history. Data from laboratory experiments and geologic fading studies were compiled from published sources to produce lines of iso-annealing for apatite in time-temperature space. Fission track ages were calculated for samples from two wells at Cerro Prieto, one with an apparently simple and one with an apparently complex thermal history. Temperatures were estimated by empirical vitrinite reflectance geothermometry, fluid inclusion homogenization and oxygen isotope equilibrium. These estimates were compared with logs of measured borehole temperatures. The temperature in well T-366, where complete annealing first occurs, was estimated to be between 160 and 180{sup 0}C. Complete annealing at these temperatures requires 10{sup 4} and 10{sup 3} years, respectively. Well M-94 has an apparently complex thermal history. Geothermometers in this well indicate temperatures some 50 to 100{sup 0}C higher than those measured directly in the borehole. Fission tracks are partially preserved in M-94 where paleotemperatures were as high as 200{sup 0}C and are erased where geothermometers indicate temperatures of 250{sup 0}C. This implies a thermal event less than 10{sup 1} years and greater than 10{sup 0} years in duration.

  5. A first shallow firn-core record from Glaciar La Ollada, Cerro Mercedario, central Argentine Andes

    NASA Astrophysics Data System (ADS)

    Bolius, David; Schwikowski, Margit; Jenk, Theo; Gäggeler, Heinz W.; Casassa, Gino; Rivera, Andrés

    In January 2003, shallow firn cores were recovered from Glaciar Esmeralda on Cerro del Plomo (33°14‧ S, 70°13‧ W; 5300 ma.s.l.), central Chile, and from Glaciar La Ollada on Cerro Mercedario (31°58‧ S, 70°07‧ W; 6070 ma.s.l.), Argentina, in order to find a suitable archive for paleoclimate reconstruction in a region strongly influenced by the El Niño-Southern Oscillation. In the area between 28° S and 35° S, the amount of winter precipitation is significantly correlated to the Southern Oscillation Index, with higher values during El Niño years. Glaciochemical analysis indicates that the paleo-record at Glaciar La Ollada is well preserved, whereas at Glaciar Esmeralda the record is strongly influenced by meltwater formation and percolation. A preliminary dating of the Mercedario core by annual-layer counting results in a time-span of 17 years (1986-2002), yielding an average annual net accumulation of 0.45 m w.e.

  6. High Holocene lake levels in eastern Patagonia (Argentina) as a result of persistent Atlantic rainfall (Invited)

    NASA Astrophysics Data System (ADS)

    Ariztegui, D.; Compagnucci, R.; Agosta, E. A.

    2013-12-01

    Today's precipitation in central Patagonia, Argentina, mostly follows the intensity of the Westerlies. However, the extraordinary persistence of daily easterly winds can trigger episodes of intense rainfall reflected as water level variations in Lago Cardiel, a closed lacustrine basin located at 49°S. Meteorological data from 11-20 March 2002 at nearby Gobernador Gregores station recorded a heavy rain spell of 50mm accounting for 30% of the mean annual rainfall (167mm/year). The synoptic situation during this interval shows rainfall produced by wet air mass advection from the Atlantic. The weather surface maps for these days display a cyclone incoming at 45°S to the west of western Patagonia together with a concomitant anticyclone to the southwest, while a cyclogenesis initiates in eastern Patagonia. This pressure dipole produced east-north-eastern winds at the lake latitude and a generalized drop in the Westerlies intensity almost across the entire Patagonia. This is shown in distant stations such as Bariloche(41.9°S) and Rio Gallegos (51.4°S) in northwestern and southeastern Patagonia, respectively, as well as in Chilean stations such as Balmaceda (45.9°S) and Chile Chico (46.9°S). Similar pressure anomalies along with changes in wind intensity and direction have been previously simulated for the Austral winter (JJA) during the middle Holocene (7.0 to 4.5 kcal yrs BP). Thus, weaker Westerlies along with a higher frequency of the dipole-type atmospheric circulation than at present increased the described easterly winds-triggered rainfall. This inference agrees with high lake levels in the Lago Cardiel record along with more negative - Atlantic type - oxygen isotopic composition of authigenic carbonates. An increase in the frequency of this climatic configuration during longer time intervals could further explain the extreme lake highstands reconstructed for the early Holocene, and the contemporaneous negative isotopic signature of the carbonates. It could

  7. Subduction of the South-Chile active spreading ridge: a 17 Ma to 3 Ma magmatic record in central Patagonia (western edge of Meseta del Lago Buenos Aires, Argentina)

    NASA Astrophysics Data System (ADS)

    Boutonnet, Emmanuelle; Arnaud, Nicolas; Guivel, Christèle; Lagabrielle, Yves; Scalabrino, Bruno; Espinoza, Felipe

    2010-05-01

    The Chile Triple Junction is a natural laboratory to study the interactions between magmatism and tectonics during the subduction of an active spreading ridge beneath a continent. The MLBA plateau (Meseta del Lago Buenos Aires) is one of the Neogene alkali basaltic plateaus located in the back-arc region of the Andean Cordillera at the latitude of the current Chile Triple Junction. The genesis of MLBA can be related with successive opening of slabs windows beneath Patagonia: within the subducting Nazca Plate itself and between the Nazca and Antarctic plates. Detailed 40Ar/39Ar dating and geochemical analysis of bimodal magmatism from the western flank of the MLBA show major changes in the back-arc magmatism which occurred between 14.5 Ma and 12.5 Ma with the transition from calc-alkaline lavas (Cerro Plomo) to alkaline lavas (MLBA) in relation with slab window opening. In a second step, at 4- 3 Ma, alkaline felsic intrusions were emplaced in the western flank of the MLBA coevally with the MLBA basalts with which they are genetically related. These late OIB-like alkaline to transitional basalts were generated by partial melting of the subslab asthenosphere of the subducting Nazca plate during the opening of the South Chile spreading ridge-related slab window. These basalts differentiated with small amounts of assimilation in shallow magma chambers emplaced along transtensional to extensional zones. The close association of bimodal magmatism with extensional tectonic features in the western MLBA is a strong support to the model of Patagonian collapse event proposed to have taken place between 5 and 3 Ma as a consequence of the presence of the asthenospheric window (SCR-1 segment of South Chile Ridge) below the MLBA area.

  8. Extension of the Cerro Prieto field and zones in the Mexicali Valley with geothermal possibilities in the future

    SciTech Connect

    Fonseca L, H.L.; de la Pena L, A.; Puente C, I.; Diaz C, E.

    1981-01-01

    This study concerns the possible extension of the Cerro Prieto field and identification of other zones in the Mexicali Valley with geothermal development potential by assessing the structural geologic conditions in relation to the regional tectonic framework and the integration of geologic and geophysical surveys carried out at Cerro Prieto. This study is based on data obtained from the wells drilled to date and the available geological and geophysical information. With this information, a geologic model of the field is developed as a general description of the geometry of what might be the geothermal reservoir of the Cerro Prieto field. In areas with geothermal potential within the Mexicali Valley, the location of irrigation wells with anomalous temperatures was taken as a point of departure for subsequent studies. Based on this initial information, gravity and magnetic surveys were made, followed by seismic reflection and refraction surveys and the drilling of 1200-m-deep multiple-use wells. Based on the results of the final integration of these studies with the geology of the region, it is suggested that the following areas should be explored further: east of Cerro Prieto, Tulecheck, Riito, Aeropuerto-Algodones, and San Luis Rio Colorado, Sonora.

  9. VTEM airborne EM, aeromagnetic and gamma-ray spectrometric data over the Cerro Quema high sulphidation epithermal gold deposits, Panama

    NASA Astrophysics Data System (ADS)

    Kwan, Karl; Prikhodko, Alexander; Legault, Jean M. Plastow, Geoffrey C.; Kapetas, John; Druecker, Michael

    2016-03-01

    In March 2012, a helicopter-borne versatile time-domain electromagnetic (VTEM), magnetic and radiometric survey was flown over the Cerro Quema high sulphidation (HS) epithermal gold deposits and the surrounding area. The Cerro Quema deposits are located in the Azuero Peninsula, Panama, approximately 8 km east of Güerita. The gold mineralisation is associated with clay-pyrite alterations topped by an acid-leached resistive cap, and the principal ores are pyrite-rich sulphides located within mineralised vuggy silica rocks. The geophysical data over the Cerro Quema deposits have been analysed. The electromagnetic (EM) responses over the deposits are characterised by resistivity highs and chargeability lows, surrounded by resistivity lows and chargeability highs. Radiometric Th/K ratio highs and magnetic susceptibility lows are observed over the deposits. These geophysical signatures over the Cerro Quema deposits are characteristic responses from HS epithermal gold deposits. The success of the VTEM survey points to the applicability of the regional helicopter electromagnetic, magnetic and gamma-ray spectrometry (EM-Mag-Spec) surveys for the exploration of similar HS epithermal gold deposits to depths < 500 m in weathered terrains.

  10. The Organic Chemistry of Volcanoes: Case Studies at Cerro Negro, Nicaragua and Oldoinyo Lengai, Tanzania

    NASA Astrophysics Data System (ADS)

    Teague, A. J.; Seward, T. M.; Gize, A. P.; Hall, T.

    2005-12-01

    Though it has long been known that volcanoes emit organic compounds within their fumarolic gases, it is only in recent years that a concerted attempt has been made to catalogue and quantify the species and fluxes. Two general lines of interest dominate this study. Firstly, volcanic gases represent some of the most likely environments in which the precursor molecules necessary for the origin of life were synthesised. The existence of an active, abiotic, organic chemistry in such settings today is fundamental to our understanding of the early Earth. Secondly, the presence of halogenated organic compounds is of interest to the atmospheric sciences, particularly with respect to their ozone depleting potential. It is clear that natural sources of halocarbons must exist, and though current natural fluxes are low with respect to the anthropogenic signature, volcanogenic halocarbons may have proved to be significant during the eruption of supervolcanoes and continental flood basalts. In this study, gases were collected from fumaroles in the craters of two, very different, active volcanoes. Cerro Negro, a young basaltic cinder cone belonging to the Central American Volcanic Belt, could be defined as a typical subduction zone volcano. Gases were collected from Cerro Negro during March 2003 and 2004 from a single fumarole discharging close to the crater floor. In contrast, Oldoinyo Lengai is the world's only active carbonatite volcano and represents the most extreme case of alkali volcanism in the East African Rift system. Fieldwork was conducted in the northern summit crater of Lengai over 8 days in October 2003. In this period, the volcano was in near continuous eruption and gases were sampled from two fumaroles situated within 20m of the eruptive centre, though measured gas temperatures were low at around 195°C. Organic compounds were collected using a variety of activated carbon, molecular sieve type adsorbents, packed into glass cartridges. The water and acid matrix of

  11. Microfaunal evidence of age and depositional environments of the Cerro Prieto section (Plio-Pleistocene), Baja California, Mexico

    SciTech Connect

    Ingle, J.C. Jr.

    1982-01-01

    Microfossils including benthic and planktic foraminifera, ostracodes, calcareous algae, fish skeletal material, and fragments of pelecypods were found in 14 core samples from depths of 185 to 1952 m in the Cerro Prieto geothermal field, providing evidence of both the age and depositional history of sediments comprising the 3000-m-thick Pliocene and Pleistocene section in this area. Ostracodes of brackish water and marine origin constitute the most common microfossils present in this sequence occurring in 8 samples; in situ littoral and neritic species of benthic foraminifera occur in 5 samples with planktic species present in 2 samples. Distributional patterns of ostracodes and foraminifera together with previously analyzed lithofacies (Lyons and van de Kamp, 1980) indicate that the Cerro Prieto section represents an intertonguing complex of alluvial, deltaic, estuarine, and shallow marine environments deposited along the front of the Colorado River delta as it prograded across the Salton Trough during Pliocene and Pleistocene time. Foraminiferal evidence indicates that a sand and shale unit commonly present at depths between 700 and 1100 m represents a significant mid-Pleistocene marine incursion in the Cerro Prieto area. Tentative correlation of the Cerro Prieto section with the well dated Palm Springs Formation of the Imperial Valley, California area suggests that the Pliocene/Pleistocene boundary occurs at a depth of approximately 2000 m in the area of well M-93. Reworked specimens of Cretaceous foraminifera and fragments of the Cretaceous pelecypod Inoceramus were found in five samples further substantiating the Colorado Plateau provenance of a significant portion of the Colorado River deltaic sediments in the Cerro Prieto area.

  12. Comments on some of the drilling and completion problems in Cerro Prieto geothermal wells

    SciTech Connect

    Dominguez A, B.; Sanchez G, G.

    1981-01-01

    From 1960 to the present, 85 wells with a total drilling length exceeding 160,000 m have been constructed at Cerro Prieto, a modest figure compared to an oil field. This activity took place in five stages, each characterized by changes and modifications required by various drilling and well-completion problems. Initially, the technical procedures followed were similar to those used in the oil industry. However, several problems emerged as a result of the relatively high temperatures found in the geothermal reservoir. The various problems that have been encountered can be considered to be related to drilling fluids, cements and cementing operations, lithology, geothermal fluid characteristics, and casings and their accessories. As the importance of high temperatures and the characteristics of the geothermal reservoir fluids were better understood, the criteria were modified to optimize well-completion operations, and satisfactory results have been achieved to date.

  13. Geological interpretation of self-potential data from the Cerro Prieto geothermal field

    SciTech Connect

    Corwin, R.F.; Fitterman, D.V.

    1980-02-01

    A source mechanism based on concepts of irreversible thermodynamics and consisting of heat or fluid flow along a north-south trending zone of faulting is proposed for the self-potential anomaly measured over the Cerro Prieto geothermal reservoir. The source region is represented by a vertical plane of that separates regions of differing streaming potential or thermoelectric coupling coefficients. The coupling coefficient contrast could be caused by vertical offset of rock units along faults. The depth to the top of the source plane is about 1.3 km, its vertical extent is about 11 km, and its length along strike is about 10 km. Geological, geophysical, and mineralogical evidence supports the existence of an important north-south geological trend roughly corresponding in location to the proposed self-potential source plane.

  14. Dynamics of a geothermal field traced by noble gases: Cerro Prieto, Mexico

    SciTech Connect

    Mazor, E.; Truesdell, A.H.

    1981-01-01

    Noble gases have been measured mass spectrometrically in samples collected during 1977 from producing wells at Cerro Prieto. Positive correlations between concentrations of radiogenic (He, /sup 40/Ar) and atmospheric noble gases (Ne, Ar, and Kr) suggest the following dynamic model: the geothermal fluids originated from meteoric water penetrated to more than 2500 m depth (below the level of first boiling) and mixed with radiogenic helium and argon-40 formed in the aquifer rocks. Subsequently, small amounts of steam were lost by a Raleigh process (0 to 3%) and mixing with shallow cold water occurred (0 to 30%). Noble gases are sensitive tracers of boiling in the initial stages of 0 to 3% steam separation and complement other tracers, such as Cl or temperature, which are effective only beyond this range.

  15. [Reptiles from Cerro Colorado and its surroundings, Cumana, Sucre State, Venezuela].

    PubMed

    Oliveros, O; Prieto, A; Comejo, P

    2000-01-01

    An inventory of the reptiles that inhabit in Cerro Colorado and its surroundings, was performed from March, 1994 to March, 1995. There were reported 8 species of snakes and 7 of lizards enclosed in 4 and 5 families repectively. Aspects observed were ecolology as habitat, activity, reproduction and relative abundance. The more abundant species of lizards were: Cnemidophorus femniscatus, Ameiva bifrontata, (Teiidae), Tropidurus hispidus (Tropiduridae), Gonatodes vittatus and Hemidactylus mabouia (Gekkonidae) and the ophidians: Leptodeira annulata and Mastigodryas amarali (Colubridae). It is believed that the changes occurred in the zone influenced the increase of the relative abundance of the species Leptotyphlops goudotii (Leptotyphlopidae) arid Gymnophthalmus speciosus(Gymnophthalmidae) and perhaps in the disappearance of others that have been reported at the xerophitic or semixerophitic zones of the Sucre State of Venezuela. PMID:11220219

  16. Structure and age of the Cerro de Pasco Cu-Zn-Pb-Ag deposit, Peru

    NASA Astrophysics Data System (ADS)

    Cheney, E. S.

    1991-04-01

    The world-famous Cu-Zn-Pb-Ag deposit at Cerro de Pasco, Peru, consists of texturally massive pyrite, texturally massive sphalerite-galena-pyrite, and veins containing pyrite and enargite. Historically the deposit has been considered to be the hydrothermal product of the adjacent Miocene volcanic and intrusive complex (locally known as the “Vent”). However, both the texturally massive sulfides of the deposit and the pre-Miocene strata are cut by the Longitudinal fault, one of the largest faults in the district, but the Vent is not. Imbrication by the Longitudinal fault zone (duplex structures) has thickened the deposit so that it is amenable to open-pit mining. Dikes and pyrite-enargite veins pass from the Vent into the massive sulfides; fragments of massive pyrite occur in the Vent. Thus, no matter what their origin, the texturally massive sulfides are older and, therefore, genetically unrelated to the Vent.

  17. Underground warmed environments at cold regions. The case of Cerro Caliente in Deception island, Antarctica

    NASA Astrophysics Data System (ADS)

    Prieto-Ballesteros, O.; Gómez, F.; Moreno, M.; de Diego, G.; Fernandez-Sampedro, M.; Martín-Redondo, M. P.; Parro, V.

    2012-09-01

    Hydrothermal and cold environments constitute two extremes for life and are relevant to evaluate the present or past life on Mars. Deception Island (Antarctica) is an excellent place to study the cold and warm underground habitats and their interfaces. They are extreme environments that have interest as terrestrial analogues to Mars. Cerro Caliente, a 107 m high hill has been selected because the geothermal activity present at its summit. Some drills at the same ground materials but with different thermal regimes were performed at this place. Samples from the cores are being studied to understand the interactions between the cold and warm environments. The description of the area and the preliminary results of the sample analysis will be presented during the session.

  18. Update of the hydrogeologic model of the Cerro Prieto field based on recent well data

    SciTech Connect

    Halfman, S.E.; Manon, A.; Lippmann, M.J.

    1986-01-01

    The hydrogeologic model of the Cerro Prieto geothermal field in Baja California, Mexico has been updated and modified on the basis of geologic and reservoir engineering data from 21 newly completed wells. Previously, only two reservoirs had been discovered: the shallow ..cap alpha.. reservoir and the deeper ..beta.. reservoir. Recently, three deep wells drilled east of the main wellfield penetrated a third geothermal reservoir (called the ..gamma.. reservoir) below the sandstones corresponding to the ..beta.. reservoir in the main part of the field. The new well data delimit the ..beta.. reservoir, confirm the important role of Fault H in controlling the flow of geothermal fluids, and enable us to refine the hydrogeologic model of the field.

  19. Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field

    SciTech Connect

    Valette-Silver, J.N.; Esquer P., I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

    1981-01-01

    A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields.

  20. Preliminary studies of brine reinjection at the Cerro Prieto Geothermal Field

    SciTech Connect

    Rivera, J.R.; Mercado, S.G.; Tsang, C.F.

    1980-01-01

    At the present time, Units 1 and 2 of the Cerro Prieto power plant generate 75 MW of power. For this purpose, about 2200 t/h of fluids are produced. At present, a number of studies are being conducted to evaluate alternative methods of injection. The methods being considered are: cold or hot injection with open, closed or mixed systems. For each of these systems, laboratory tests will be carried out using columns packed with different grain-sized sands. The sands used are from alluvial fans of the Cucapa range. The purpose of these tests is to establish the scale-forming tendencies of the water when injected under different conditions. 5 refs.

  1. A new MOS mask cutter facility at Gemini/Cerro Tololo observatories

    NASA Astrophysics Data System (ADS)

    Wyman, Robert T.; Trancho, Gelys; Tighe, Roberto

    2010-07-01

    The installation and commissioning of a new laser cutter facility in La Serena, Chile is a cooperative effort between Gemini Observatory and the Cerro Tololo Inter-American Observatory. This system enables the cutting of aluminum and carbon fiber slit masks for three multi-object spectrographs operating in Chile: GMOS-S, Flamingos-2, and Goodman spectrograph. Selection of the new laser cutter tool was based on slit mask specifications developed for two materials. Prior to the commissioning all slit mask production was performed at Gemini's Northern base facility with a similar laser cutter system. The new facility supports two observatories and enhances the capabilities for both. This paper will discuss the observatory arrangement with respect to mask data tracking and handling. The laser system and facility will be discussed along with mask cutting performance, process development and manufacturing methods.

  2. Mercury in freshwater fish and clams from the Cerro Prieto geothermal field of Baja California, Mexico

    SciTech Connect

    Gutierrez-Galindo, E.A.; Munoz, G.F.; Flores, A.A.

    1988-08-01

    Several reports have expressed concern about the potential toxicity hazards and environmental contamination of mercury emissions from geothermal fields in Hawaii, New Zealand, Iceland, California and Mexico. Inorganic mercury discharged from the sources may accumulate in the sediments of rivers or lakes and, after microbiological methylation may become concentrated in the edible tissue of fish. This study involves assessment of geothermal mercury pollution arising from Cerro Prieto. For this purpose the fish Tilapia mossambica and the clam Corbicula fluminea were collected from the freshwater courses of the Mexicali Valley. Reports indicated that in 1982, 13 t of T. mossambica were destinated for human consumption. A further aim was to provide base line data and information relevant to the level of mercury contamination for the Mexicali Valley.

  3. Burn Severities, Fire Intensities, and Impacts to Major Vegetation Types from the Cerro Grande Fire

    SciTech Connect

    Balice, Randy G.; Bennett, Kathryn D.; Wright, Marjorie A.

    2004-12-15

    The Cerro Grande Fire resulted in major impacts and changes to the ecosystems that were burned. To partially document these effects, we estimated the acreage of major vegetation types that were burned at selected burn severity levels and fire intensity levels. To accomplish this, we adopted independently developed burn severity and fire intensity maps, in combination with a land cover map developed for habitat management purposes, as a basis for the analysis. To provide a measure of confidence in the acreage estimates, the accuracies of these maps were also assessed. In addition, two other maps of comparable quality were assessed for accuracy: one that was developed for mapping fuel risk and a second map that resulted from a preliminary application of an evolutionary computation software system, called GENIE.

  4. Results of the latest transient well pressure tests at Cerro Prieto

    SciTech Connect

    Abril G, A.; Vargas G, C.

    1981-01-01

    The equipment used in the interference and two-rate flow tests carried out at the Cerro Prieto geothermal field during 1980 are described. The results of two interference tests are presented, one between wells M-110 and M-104, and the other between wells M-7 and Q-757. The data was interpreted using type curve matching analysis. Results of two-rate flow tests carried out in wells M-102 and M-7 are also discussed. A technique for making two-rate flow tests is proposed. This approach, which attempts to avoid the uncertainty of present flow-rate measurements, makes use of devices for direct measurements of separated water and steam. Conclusions based on the above interpretations and recommendations for future tests are presented.

  5. Dynamics of a geothermal field traced by noble gases: Cerro Prieto, Mexico

    USGS Publications Warehouse

    Mazor, E.; Truesdell, A.H.

    1984-01-01

    Noble gases have been measured mass spectrometrically in samples collected during 1977 from producing wells at Cerro Prieto. Positive correlations between concentrations of radiogenic (He and 40Ar) and atmospheric noble gases (Ne, Ar and Kr) suggest the following dynamic model: the geothermal fluids originated from meteoric water that penetrated to more than 2500 m depth (below the level of first boiling) and mixed with radiogenic He and 40Ar formed in the aquifer rocks. Subsequently, small amounts of steam were lost by a Raleigh process (0 - 30%) and mixing with shallow cold water occurred (0 - 30%). Noble gases are sensitive tracers of boiling in the initial stages of 0 - 3% steam separation and complement other tracers, such as C1 or temperature, which are effective only beyond this range. ?? 1984.

  6. Did stresses from the Cerro Prieto Geothermal Field influence the El Mayor-Cucapah rupture sequence?

    NASA Astrophysics Data System (ADS)

    Trugman, Daniel T.; Borsa, Adrian A.; Sandwell, David T.

    2014-12-01

    The Mw 7.2 El Mayor-Cucapah (EMC) earthquake ruptured a complex fault system in northern Baja California that was previously considered inactive. The Cerro Prieto Geothermal Field (CPGF), site of the world's second largest geothermal power plant, is located approximately 15 km to the northeast of the EMC hypocenter. We investigate whether anthropogenic fluid extraction at the CPGF caused a significant perturbation to the stress field in the EMC rupture zone. We use Advanced Land Observing Satellite interferometric synthetic aperture radar data to develop a laterally heterogeneous model of fluid extraction at the CPGF and estimate that this extraction generates positive Coulomb stressing rates of order 15 kPa/yr near the EMC hypocenter, a value which exceeds the local tectonic stressing rate. Although we cannot definitively conclude that production at the CPGF triggered the EMC earthquake, its influence on the local stress field is substantial and should not be neglected in local seismic hazard assessments.

  7. Mathematical Modeling of the Dynamics of Salmonella Cerro Infection in a US Dairy Herd

    NASA Astrophysics Data System (ADS)

    Chapagain, Prem; van Kessel, Jo Ann; Karns, Jeffrey; Wolfgang, David; Schukken, Ynte; Grohn, Yrjo

    2006-03-01

    Salmonellosis has been one of the major causes of human foodborne illness in the US. The high prevalence of infections makes transmission dynamics of Salmonella in a farm environment of interest both from animal and human health perspectives. Mathematical modeling approaches are increasingly being applied to understand the dynamics of various infectious diseases in dairy herds. Here, we describe the transmission dynamics of Salmonella infection in a dairy herd with a set of non-linear differential equations. Although the infection dynamics of different serotypes of Salmonella in cattle are likely to be different, we find that a relatively simple SIR-type model can describe the observed dynamics of the Salmonella enterica serotype Cerro infection in the herd.

  8. Simultaneous observations of the phase-locked 2 day wave at Adelaide, Cerro Pachon, and Darwin

    NASA Astrophysics Data System (ADS)

    Walterscheid, R. L.; Hecht, J. H.; Gelinas, L. J.; MacKinnon, A.; Vincent, R. A.; Reid, I. M.; Franke, S. J.; Zhao, Y.; Taylor, M. J.; Pautet, P. D.

    2015-03-01

    The Southern Hemisphere summer 2 day wave (TDW) is the most dramatic large-scale event of the upper mesosphere. The winds accelerate over ~1 week, may attain > 70 m/s, and are often accompanied by a near disappearance of the diurnal tide and stabilization of the period close to 48 h. We denote this as the phase-locked 2 day wave (PL/TDW). We have examined airglow and meteor radar (MR) wind data from the Andes Lidar Observatory (Cerro Pachon, Chile:30°S, 289.3°E), MR data from Darwin (12.5°S, 131°E) and airglow and medium frequency radar data from the University of Adelaide (34.7°S, 138.6°E) for the behavior of the TDW during the austral summers of 2010, 2012, and 2013. The Cerro Pachon and Adelaide sites are located at similar latitudes separated in longitude by about 120°. We find a remarkable coincidence between the TDW oscillations at Chile and Adelaide for the period January-February 2010. The oscillations are nearly in phase in terms of local time and the minima and maxima repeat at nearly the same local time from cycle to cycle consistent with a phase-locked wave number 3 TDW. Data for this and other years (including Darwin) show that the amplitude of the diurnal tide decreases when the TDW is largest and that this occurs when the period is close to 48 h. These observations support the proposal that the PL/TDW is a subharmonic parametric instability wherein the diurnal tide transfers energy to a TDW that is resonant at nearly 48 h.

  9. Geomorphical and Geochronological Constrains of the Last Glacial Period in Southern Patagonia, Southern South America

    NASA Astrophysics Data System (ADS)

    García, J.; Hall, B. L.; Kaplan, M. R.; Vega, R. M.; Binnie, S. A.; Hein, A.; Gómez, G. N.; Ferrada, J. J.

    2013-12-01

    Despite the outer limits of the former Patagonian ice sheet (PIS, ~38-55S) having been extensively mapped, it remains unknown if the Patagonian glaciers fluctuated synchronously or asynchronously during the last glacial period. Previous work has revealed asynchronous spatiotemporal ice dynamics along the eastern and western ice-margins at the end of the last glaciation but it is not well understood if the northern and southern parts of the PIS reached concurrent maximum glaciation during the last glacial cycle. The Patagonian Andes is the only landmass involving the southern westerly wind belt latitudinal range, which is thought to have played a key role in past glacial and climate changes. Therefore, reconstructing southern Andes glacier history constitutes a key element for understanding the cause of glaciations in Patagonia and the role of the westerlies in climate change. Here, we discuss paleoglaciological and paleoclimatological implications of new 10Be and 14C data obtained from moraines and strategically selected mires in two contiguous glacially molded basins of south Patagonia (48-55S): Torres del Paine (51S) and Última Esperanza (52S). In this region, we focused our 10Be cosmogenic-dating efforts in the previously undated outer moraines deposited (supposedly) during the last glacial cycle. In order to crosscheck cosmogenic data we collected boulders embedded in moraines and cobbles from the main glaciofluvial plains grading from the outermost moraines. Geomorphic and cosmogenic dating affords evidence for glacial maximum conditions occurring between 40-50 ka (ka = thousand of years before present) in southern Patagonia, which is different from other chronologies within southern South America. We obtained 14C basal ages from sites located within moraine depressions and on former paleolake shorelines and thus these may provide key data on deglaciation and debated regional paleolake history.

  10. Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments

    NASA Astrophysics Data System (ADS)

    Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Hein, Andrew S.; Rodés, Ángel

    2015-11-01

    The timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing, but this requires robust glacial chronologies. In parts of southernmost Patagonia, dating pre-global Last Glacial Maximum (gLGM) ice limits has proven difficult due to post-deposition processes affecting the build-up of cosmogenic nuclides in moraine boulders. Here we provide ages for the Río Cullen and San Sebastián glacial limits of the former Bahía Inútil-San Sebastián (BI-SSb) ice lobe on Tierra del Fuego (53-54°S), previously hypothesised to represent advances during Marine Isotope Stages (MIS) 12 and 10, respectively. Our approach uses cosmogenic 10Be and 26Al exposure dating, but targets glacial outwash associated with these limits and uses depth-profiles and surface cobble samples, thereby accounting for surface deflation and inheritance. The data reveal that the limits formed more recently than previously thought, giving ages of 45.6 ka (139.9/-14.3) for the Río Cullen, and 30.1 ka (+45.6/-23.1) for the San Sebastián limits. These dates indicate extensive glaciation in southern Patagonia during MIS 3, prior to the well-constrained, but much less extensive MIS 2 (gLGM) limit. This suggests the pattern of ice advances in the region was different to northern Patagonia, with the terrestrial limits relating to the last glacial cycle, rather than progressively less extensive glaciations over hundreds of thousands of years. However, the dates are consistent with MIS 3 glaciation elsewhere in the southern mid-latitudes, and the combination of cooler summers and warmer winters with increased precipitation, may have caused extensive glaciation prior to the gLGM.

  11. Outburst floods of glacial lakes in Patagonia: is there an increasing trend?

    NASA Astrophysics Data System (ADS)

    Casassa, Gino; Wendt, Jens; Wendt, Anja; López, Paulina; Schuler, Thomas; Maas, Hans-Gerd; Carrasco, Jorge; Rivera, Andrés.

    2010-05-01

    Glaciers in Patagonia are temperate and many of them are receding at an accelerated rate, with a consequent enlargement of glacial lakes. We will review the occurrence of Glacial Lake Outburst Floods (GLOFs) recorded during the last century in Patagonia (Northern and Southern Patagonia icefields), and analyse them in view of the general warming of 0.5°C affecting the region during the last 40 years. Special attention will be devoted to Lake Cachet 2 (47°12' S, 73°15' W, 422 m a.s.l.) which has experienced 6 GLOF events during the last 2 years: April 6-7 2008, October 7-8 2008, 21-22 December 2008, 5 March 2009, 16 September 2009 and 5-6 January 2010. Lake Cachet 2 has an area of 4 km2, located on the eastern margin of the Northern Patagonia Icefield, being dammed on its southern margin by Colonia Glacier. Prior to the April 2008 event there had been no historical record of catastrophic flooding of this lake. Each event resulted in a flood wave of which travelled down Colonia River to the confluence with Baker River in a period of less than 48 hours, where it reached peak flows of approximately 2,000 m3/s. Here we present airborne and ground explorations carried out in the period 2008-2009 which confirm that the Lake Cachet 2 floods drain through an englacial tunnel under Colonia Glacier for a distance of 8 km, emerging at the front of the glacier. We propose that the lake started draining in 2008 as a result of the weakening of the ice dam produced by long-term thinning of Colonia Glacier. Measurements of the empty lake bed were performed with the CECS airborne laser scanner onboard a helicopter, which show that the maximum water volume of the lake is 200 x 106 m3. Modelling of the flood events has been carried out based on the subglacial flood model of Clarke (2003), showing that a semi-circular subglacial tunnel attaining a maximum dimension of 15 m can evacuate Lake Cachet 2 in approximately 48 hours, with peak flows on the order of 4000 m3/s. Preliminary

  12. Magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

    USGS Publications Warehouse

    Rodriguez, Brian D.; Sampson, Jay A.

    2010-01-01

    The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size and resistivity of the mineralized area beneath overburden, a regional east-west magnetotelluric sounding profile was acquired. This is a data release report of the magnetotelluric sounding data collected along the east-west profile; no interpretation of the data is included.

  13. Paleoenvironmental setting and description of an estuarine oyster reef in the Eocene of Patagonia, southern Argentina

    NASA Astrophysics Data System (ADS)

    Raising, Martín Rodríguez; Casadío, Silvio; Pearson, Nadine; Mángano, Gabriela; Buatois, Luis; Griffin, Miguel

    2014-12-01

    A middle Eocene Crassostrea sp. reef near Río Turbio, southwestern Patagonia (Argentina), represents the earliest record of an oyster reef associated with estuarine facies in the southern hemisphere, and also one of the few known worldwide occurring in Paleogene rocks. The reef grew in an outer estuary environment subject to periodic changes in salinity and may have reached a maturing phase. The Río Turbio reef - by its dimensions, geometry, and substrate lithology- would have been located in a tidal channel convergence area. This reef provides new evidence suggesting that estuaries served as refuges for Crassostrea populations allowing them to disperse into fully marine environments many times throughout the Cenozoic.

  14. Audio-magnetotelluric survey to characterize the Sunnyside porphyry copper system in the Patagonia Mountains, Arizona

    USGS Publications Warehouse

    Sampson, Jay A.; Rodriguez, Brian D.

    2010-01-01

    The Sunnyside porphyry copper system is part of the concealed San Rafael Valley porphyry system located in the Patagonia Mountains of Arizona. The U.S. Geological Survey is conducting a series of multidisciplinary studies as part of the Assessment Techniques for Concealed Mineral Resources project. To help characterize the size, resistivity, and skin depth of the polarizable mineral deposit concealed beneath thick overburden, a regional east-west audio-magnetotelluric sounding profile was acquired. The purpose of this report is to release the audio-magnetotelluric sounding data collected along that east-west profile. No interpretation of the data is included.

  15. Rime Mushrooms - Extreme Rime Ice Buildup on Mountain Summits of Southern Patagonia

    NASA Astrophysics Data System (ADS)

    Whiteman, C. D.

    2015-12-01

    The Southern Patagonian Andes are known among mountain climbers for a meteorological phenomenon that occurs there but is unknown in many other mountain areas. The phenomenon is the buildup of rime ice in large bulbous or mushroom-shaped accretions on the windward side of projecting mountain summits, ridges and exposed near-vertical rock faces. These "ice mushrooms" have never been investigated scientifically. This talk will introduce the audience to ice mushrooms, describe where they are found, consider the meteorological factors leading to their formation, and illustrate how they are negotiated by mountain climbers using photographs and descriptions from Southern Patagonia.

  16. The Odonata (Insecta) of Patagonia: a synopsis of their current status with illustrated keys for their identification.

    PubMed

    Muzón, Javier; Pessacq, Pablo; Lozano, Federico

    2014-01-01

    Patagonia is a vast landmass with a distinctive environmental and biotic heterogeneity. Its Odonata biodiversity is the best known of South America, and it is composed of 36 species, of which more than 50% are endemic. We summarize the main taxonomic, distributional and biological information including illustrated keys for adults and known larvae, and distributional maps. PMID:24872061

  17. Eastern Andean environmental and climate synthesis for the last 2000 years BP from terrestrial pollen and charcoal records of Patagonia

    NASA Astrophysics Data System (ADS)

    Sottile, G. D.; Echeverria, M. E.; Mancini, M. V.; Bianchi, M. M.; Marcos, M. A.; Bamonte, F. P.

    2015-06-01

    The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation system that dominates the dynamics of Southern Hemisphere mid-latitude climate. Little is known about climatic changes in the Southern South America in comparison to the Northern Hemisphere due to the low density of proxy records, and adequate chronology and sampling resolution to address environmental changes of the last 2000 years. Since 2009, new pollen and charcoal records from bog and lakes in northern and southern Patagonia at the east side of the Andes have been published with an adequate calibration of pollen assemblages related to modern vegetation and ecological behaviour. In this work we improve the chronological control of some eastern Andean previously published sequences and integrate pollen and charcoal dataset available east of the Andes to interpret possible environmental and SWW variability at centennial time scales. Through the analysis of modern and past hydric balance dynamics we compare these scenarios with other western Andean SWW sensitive proxy records for the last 2000 years. Due to the distinct precipitation regimes that exist between Northern (40-45° S) and Southern Patagonia (48-52° S) pollen sites locations, shifts on latitudinal and strength of the SWW results in large changes on hydric availability on forest and steppe communities. Therefore, we can interpret fossil pollen dataset as changes on paleohydric balance at every single site by the construction of paleohydric indices and comparison to charcoal records during the last 2000 cal yrs BP. Our composite pollen-based Northern and Southern Patagonia indices can be interpreted as changes in latitudinal variation and intensity of the SWW respectively. Dataset integration suggest poleward SWW between 2000 and 750 cal yrs BP and northward-weaker SWW during the Little Ice Age (750-200 cal yrs BP). These SWW variations are synchronous to Patagonian fire activity major shifts. We found an in phase

  18. Benthic methylmercury production in lacustrine ecosystems of Nahuel Huapi National Park, Patagonia, Argentina

    USGS Publications Warehouse

    Ribeiro, Guevara S.; Catan, S.P.; Marvin-DiPasquale, M.

    2009-01-01

    Seasonal trends of benthic methylmercury (methyl-Hg) production were examined in both littoral and open water sites of three lakes (Escondido, Moreno, and Morenito) in the North Andean Patagonia region of Argentina. Potentials of methyl-Hg production were measured by amending sediment samples with inorganic 197Hg(II), incubating for either 24 and 32 h at room temperature, and subsequently assaying the radiolabelled organomercury produced. Seasonal variations of benthic methyl-Hg production were studied but no significant correlation was observed. Lake littoral sites exhibited up to two fold higher methyl-Hg production potentials in most cases. Sediment from lakes Moreno and Morenito generally exhibited much lower (up to 10 fold) methyl-Hg production potentials than those from Lake Escondido, possibly due to differences in particulate and dissolved organic matter quantity and quality, which is higher in Lake Escondido and primarily allochthonous, whereas in lakes Moreno and Morenito is primarily autochthonous. This study represents the first to directly examine benthic microbial Hg(II)-methylation in aquatic ecosystems of Patagonia. ?? 2009 Elsevier Ltd. All rights reserved.

  19. Last glacial maximum environments in northwestern Patagonia revealed by fossil small mammals

    NASA Astrophysics Data System (ADS)

    Tammone, Mauro N.; Hajduk, Adan; Arias, Pablo; Teta, Pablo; Lacey, Eileen A.; Pardiñas, Ulyses F. J.

    2014-07-01

    Comparisons of historical and modern assemblages of mammals can yield important insights into patterns and processes of environmental change. Here, we present the first analyses of small mammal assemblages present in northern Patagonia during the last glacial maximum (LGM). Using remains obtained from owl pellets excavated from an archeological cave site (Arroyo Corral I, levels VII-V, carbon dates of 22,400-21,530 cal yr BP), we generate estimates of the minimum number of individuals for all species detected; these estimates, in turn are used to determine relative species abundances. Comparisons of these data with similar analyses of small mammal remains obtained from a second archeological site (ACoII, levels IV-V, carbon dates of 10,010-9220 cal yr BP) as well as from modern owl pellets reveal pronounced changes in relative species abundance since the LGM. In particular, Euneomys chinchilloides and Ctenomys sociabilis - the predominant species during the LGM - declined markedly, suggesting a change from open, bare habitat punctuated by patches of wet meadows and shrubs to the more densely vegetated mosaic of ecotone habitats found in this region today. These data provide important new insights into the environmental changes that have occurred in northern Patagonia over the last 20,000 years.

  20. Wildland-Urban Interface Fires and Socioeconomic Conditions: A Case Study of a Northwestern Patagonia City

    NASA Astrophysics Data System (ADS)

    de Torres Curth, Monica; Biscayart, Carolina; Ghermandi, Luciana; Pfister, Gabriela

    2012-04-01

    In many regions of the world, fires are primarily of anthropogenic origin. In northwestern Patagonia, the number of fires is not correlated with meteorological variables, but is concentrated in urban areas. This study was conducted in the wildland-urban interface (WUI) area of San Carlos de Bariloche (Patagonia, Argentina), within the Nahuel Huapi National Park. WUI fires are particularly problematic because, besides people and goods, they represent a danger to protected areas. We studied the relationship between fire records and socioeconomic indicators within the WUI of San Carlos de Bariloche. We conducted a Multiple Correspondence Factorial Analysis and an Ascendant Hierarchical Classification of the city neighborhoods. The results show that the neighborhoods in Bariloche can be divided into three classes: High Socioeconomic Fire Risk neighborhoods, including neighborhoods with the highest fire rates, where people have low instruction level, high levels of unsatisfied basic needs and high unemployment levels; Low Socioeconomic Fire Risk neighborhoods, that groups neighborhoods which present the opposite characterization, and Moderate Socioeconomic Fire Risk neighborhoods, which are more heterogeneous. Once neighborhoods were classified, a Socioeconomic Fire Risk map was generated, supplementing the existing WUI Fire Danger map. Our results emphasize the relevance of socioeconomic variables to fire policies.

  1. Saccharomyces eubayanus and Saccharomyces uvarum associated with the fermentation of Araucaria araucana seeds in Patagonia.

    PubMed

    Rodríguez, M Eugenia; Pérez-Través, Laura; Sangorrín, Marcela P; Barrio, Eladio; Lopes, Christian A

    2014-09-01

    Mudai is a traditional fermented beverage, made from the seeds of the Araucaria araucana tree by Mapuche communities. The main goal of the present study was to identify and characterize the yeast microbiota responsible of Mudai fermentation as well as from A. araucana seeds and bark from different locations in Northern Patagonia. Only Hanseniaspora uvarum and a commercial bakery strain of Saccharomyces cerevisiae were isolated from Mudai and all Saccharomyces isolates recovered from A. araucana seed and bark samples belonged to the cryotolerant species Saccharomyces eubayanus and Saccharomyces uvarum. These two species were already reported in Nothofagus trees from Patagonia; however, this is the first time that they were isolated from A. araucana, which extends their ecological distribution. The presence of these species in A. araucana seeds and bark samples, led us to postulate a potential role for them as the original yeasts responsible for the elaboration of Mudai before the introduction of commercial S. cerevisiae cultures. The molecular and genetic characterization of the S. uvarum and S. eubayanus isolates and their comparison with European S. uvarum strains and S. eubayanus hybrids (S. bayanus and S. pastorianus), allowed their ecology and evolution us to be examined.

  2. Flavonols, alkaloids, and antioxidant capacity of edible wild berberis species from patagonia.

    PubMed

    Ruiz, Antonieta; Zapata, Moises; Sabando, Constanza; Bustamante, Luis; von Baer, Dietrich; Vergara, Carola; Mardones, Claudia

    2014-12-24

    There are 20 species of the Berberidaceae family described in Chile, whose fruits are edible and show high anthocyanin and hydroxycinnamic acid levels. Berberis microphylla G. Forst, commonly known as calafate, is the most extensively distributed. Flavonols and alkaloids in seed, pulp, skin, and whole calafate berry extracts and other Berberis were studied using HPLC-DAD-ESI-MS/MS and HPLC with fluorescence detector. Berry samples from different locations in Chilean Patagonia, including different phenological stages, were systematically addressed. Results were compared with other organs of the plant and with other Berberis species. Total flavonol concentration in calafate (n = 65) was 1.33 ± 0.54 μmol/g. Glycosyl metabolites of quercetin and isorhamnetin were the most abundant. Similar profiles were observed in calafate from distinct locations, but important differences were observed for the other edible Berberis species. Calafate pulp and skin have higher flavonol concentrations than seeds, and the maturation process reduced its levels. TEACCUPRAC and TEACABTS of whole calafate extracts and fractions are also explored. Finally, only berberine was detected in the fruit (0.001%), mainly in seeds. Results contribute to the promotion of this berry as a superfruit from Patagonia.

  3. Repeated Glacial-Lake Outburst Floods in Patagonia: An Increasing Hazard?

    NASA Astrophysics Data System (ADS)

    Dussaillant, A.; Benito, G.; Buytaert, W.; Carling, P.; Gonzalez, F.; Link, O.; Meier, C.

    2009-04-01

    Patagonian glaciers are recording one of the fastest glacial retreats on Earth, inferred to be a direct response to recorded climate change in South America. The dynamic response of the region's glaciers to climate change was evident when two self-similar glacial-lake outburst floods occurred in April and October 2008, the largest floods from this glacier on record. On each occasion, the lake Cachet 2, in the Northern Patagonia Ice-Field, dammed by the Colonia glacier, released about 200 million m3 water into the Colonia river. The lake is refilling rapidly, such that further outbreak floods can be expected. This paper anticipates future events, by providing an assessment of the hydraulic properties of the 2008 events. Pipeflow calculations of the subglacial tunnel drainage and hydraulic models of the river flood give consistent results, with an estimated peak discharge of between 2500 and 3000 m3s-1. However, geomorphological analysis of the Colonia valley shows evidence of former catastrophic outburst floods, with flood discharges possibly as high as 16,000 m3s-1. Given the impacts of climate change on glacier dynamics in the area, the frequency and high magnitude jökulhlaups may increase future flood risks for infrastructure and population, particularly relevant in view of the current development of hydropower projects in Chilean Patagonia.

  4. Solar ultraviolet radiation and its impact on aquatic systems of Patagonia, South America.

    PubMed

    Villafañe, V E; Helbling, E W; Zagarese, H E

    2001-03-01

    Solar ultraviolet radiation (UVR, 280-400 nm) is known to cause a number of detrimental effects in aquatic organisms. The area of Patagonia, which is sometimes under the influence of the Antarctic ozone "hole", occasionally receives enhanced levels of ultraviolet B radiation (UV-B, 280-315 nm). Great efforts have been put into creating a database for UVR climatology by installing a variety of instruments in several localities in the region. However, no comparable effort has been made to determine the impact of normal and enhanced levels of solar UVR upon organisms. Most of the photobiological research in aquatic systems of Patagonia has focused on determining the effects of solar UVR in phytoplankton photosynthesis, DNA damage, and mortality, fecundity and repair mechanisms in zooplanktonic species. Some work has also been done with fish larvae and interactions between species at low trophic levels of the aquatic food web. The results of these studies indicate that in order to assess the overall impact of UVR in a certain waterbody, it is also necessary to consider other variables, such as changes in cloudiness, ozone concentrations, differential sensitivity of organisms, and depth of the upper mixed layer/epilimnion. All factors that can preclude or benefit the acclimation of species to solar radiation.

  5. Molecular evidence for a novel encapsulated genotype of Trichinella from Patagonia, Argentina.

    PubMed

    Krivokapich, Silvio J; Prous, Cinthia L Gonzalez; Gatti, Graciana M; Confalonieri, Viviana; Molina, Viviana; Matarasso, Hugo; Guarnera, Eduardo

    2008-10-01

    At present, Trichinella spiralis is the only species of this genus reported from South America. Herein, we detail a molecular analysis of a new encapsulated isolate of muscle larvae of Trichinella, found in a mountain lion (Puma concolor) coming from the Patagonia, Argentina. We studied three DNA regions previously probed to be useful for the identification of all eleven recognized Trichinella genotypes: expansion segment 5 (ES5), cytochrome c-oxidase subunit I (COI) and 5S ribosomal DNA intergenic spacer region (5S ISR). BLAST searches with these DNA sequences showed that the mitochondrial and nuclear ribosomal regions most closely resemble other Trichinella sequences available in GenBank. However, they did not exactly match any of the eleven recognized genotypes. The phylogenetic analysis from COI and 5S ISR sequences showed that the mountain lion isolate is grouped with encapsulated members, in concordance with morphological data. Furthermore, this new isolate was located at the base of the encapsulated genotypes, signifying that it is an old genotype that could have emerged earliest in this group. These data strongly suggest that this isolate from the Patagonia represents the twelfth genotype (T12) described in the genus Trichinella. Nevertheless, further studies are necessary to adequately establish this isolate as a unique genotype. PMID:18650017

  6. Description of a New Galapagos Giant Tortoise Species (Chelonoidis; Testudines: Testudinidae) from Cerro Fatal on Santa Cruz Island.

    PubMed

    Poulakakis, Nikos; Edwards, Danielle L; Chiari, Ylenia; Garrick, Ryan C; Russello, Michael A; Benavides, Edgar; Watkins-Colwell, Gregory J; Glaberman, Scott; Tapia, Washington; Gibbs, James P; Cayot, Linda J; Caccone, Adalgisa

    2015-01-01

    The taxonomy of giant Galapagos tortoises (Chelonoidis spp.) is currently based primarily on morphological characters and island of origin. Over the last decade, compelling genetic evidence has accumulated for multiple independent evolutionary lineages, spurring the need for taxonomic revision. On the island of Santa Cruz there is currently a single named species, C. porteri. Recent genetic and morphological studies have shown that, within this taxon, there are two evolutionarily and spatially distinct lineages on the western and eastern sectors of the island, known as the Reserva and Cerro Fatal populations, respectively. Analyses of DNA from natural populations and museum specimens, including the type specimen for C. porteri, confirm the genetic distinctiveness of these two lineages and support elevation of the Cerro Fatal tortoises to the rank of species. In this paper, we identify DNA characters that define this new species, and infer evolutionary relationships relative to other species of Galapagos tortoises.

  7. Description of a New Galapagos Giant Tortoise Species (Chelonoidis; Testudines: Testudinidae) from Cerro Fatal on Santa Cruz Island

    PubMed Central

    Chiari, Ylenia; Garrick, Ryan C.; Russello, Michael A.; Benavides, Edgar; Watkins-Colwell, Gregory J.; Glaberman, Scott; Tapia, Washington; Gibbs, James P.; Cayot, Linda J.; Caccone, Adalgisa

    2015-01-01

    The taxonomy of giant Galapagos tortoises (Chelonoidis spp.) is currently based primarily on morphological characters and island of origin. Over the last decade, compelling genetic evidence has accumulated for multiple independent evolutionary lineages, spurring the need for taxonomic revision. On the island of Santa Cruz there is currently a single named species, C. porteri. Recent genetic and morphological studies have shown that, within this taxon, there are two evolutionarily and spatially distinct lineages on the western and eastern sectors of the island, known as the Reserva and Cerro Fatal populations, respectively. Analyses of DNA from natural populations and museum specimens, including the type specimen for C. porteri, confirm the genetic distinctiveness of these two lineages and support elevation of the Cerro Fatal tortoises to the rank of species. In this paper, we identify DNA characters that define this new species, and infer evolutionary relationships relative to other species of Galapagos tortoises. PMID:26488886

  8. Relationshipe Between Self-potential Anomalies and Hydraulic Flow In A Geothermal System: Application To Cerro-prieto, Baja California

    NASA Astrophysics Data System (ADS)

    Saracco, G.; Revil, A.; Pessel, M.

    The Cerro Prieto geothermal field is located in the alluvial plain of the Mexicali Valley, northern Baja California, Mexico, at about 35 km southeast of the city of Mexicali. The Cerro Prieto geothermal field is one of several high temperature water-dominated geothermal fields within the Salton Trough. We analyze here the self-potential distri- bution at the ground surface in order to determine the pattern of fluid flow in te sub- surface of this geothermal field. Various methods of analysis of self-potential anoma- lies are employed to reach this purpose. We use density probability tomography of monopolar and dipolar electrical sources and an Euler-type analysis. The hydraulic flow pattern found in this geothermal field is in agreement with that detemined from the heat flux inside the structure.

  9. Evidence for a modulation of the intraseasonal summer temperature in Eastern Patagonia by the Madden-Julian Oscillation

    NASA Astrophysics Data System (ADS)

    Jacques-Coper, Martín.; Brönnimann, Stefan; Martius, Olivia; Vera, Carolina S.; Cerne, S. Bibiana

    2015-08-01

    We describe the relationship between the intraseasonal component of surface air temperature (SAT) variability in Eastern Patagonia and the Madden-Julian Oscillation (MJO) during austral summer based on ~50 years of daily instrumental records, the Twentieth Century Reanalysis, and a century-long MJO index reconstruction. Our results show that the summer SAT variability in Patagonia is highly driven by the intraseasonal activity (~80%), especially by that associated with the MJO. The active MJO phases modulate the spatial mean intraseasonal temperature signal in Eastern Patagonia with ~1.5°C of amplitude. In most of the region, the warmest (coldest) conditions are found during active phase 8 (4). These opposite states of the temperature perturbations are related to almost inverse midlevel circulation anomalies over southern South America and the southwest Atlantic, which are part of a large-scale Rossby-like wave train of alternating circulation anomalies extended along the South Pacific. The corresponding outgoing longwave radiation anomalies suggest that these structures may be triggered by anomalous convection in the tropics. Furthermore, we show that intraseasonal heat waves in southeastern Patagonia tend to occur during active MJO phase 8. These events are also induced by a wave train pattern over the South Pacific, associated with other intraseasonal variability sources. Hence, as shown in a case study, circulation anomalies over the South Pacific triggered, in general, by tropical convection variability and, in particular, by the MJO activity may constructively interact with circulation patterns resulting from the extratropical dynamics, eventually leading to intraseasonal heat waves in southeastern Patagonia.

  10. Oxygen isotope exchange in rocks and minerals from the Cerro Prieto geothermal system: Indicators of temperature distribution and fluid flow

    SciTech Connect

    Williams, A.E.; Elders, W.A.

    1981-01-01

    Oxygen isotopic compositions have been measured in drill cuttings and core samples from more than 40 wells ranging in depth to more than 3.5 km in the Cerro Prieto geothermal field. Profiles of isotopic ratios versus sampling depths provide information on the three-dimensional distribution of temperature and fluid flow. These parameters also indicate variations in the history of hydrothermal processes in different areas of the geothermal field.

  11. The Cerro Aguas Calientes caldera, NW Argentina: an example of a tectonically controlled, polygenetic, collapse caldera, and its regional significance

    NASA Astrophysics Data System (ADS)

    Petrinovic, Ivan A.; Martí, Joan; Aguirre-Diaz, Gerardo J.; Guzmán, Silvina R.; Geyer, Adelina; Grosse, Pablo; Salado Paz, Natalia

    2010-05-01

    Polygenetic, silicic collapse calderas such as Cerro Galán, Pastos Grandes, La Pacana, Vilama, Negra Muerta, Farallón Negro, Cerro Guacha, among others are common in the central Andes. Here we describe in detail the Cerro Aguas Calientes caldera in NW Argentina, which comprises two caldera-forming episodes occurred at 17.15 Ma and 10.3 Ma, respectively. We analyse the significance of its structural setting, composition, size and the subsidence style of both caldera episodes. Our results reveal that the caldera eruptions had a tectonic trigger. In both cases, an homogeneous dacitic crystal-rich (>60 vol. % of crystals) reservoir of batholitic size became unstable due to the effect of increasing regional transpression, favouring local dilation throughout minor strike slip faults from which ring faults nucleated and permitted caldera collapse. Both episodes are similar in shape, location and products of the resulting calderas. The 17.15 Ma caldera has an elliptical shape (17 × 14 km) and is elongated in a N30° trend; both intracaldera and extracaldera ignimbrites covered an area of around 620 km2 with a minimum volume estimate of 138 km3 (DRE). The 10.3 Ma episode generated another elliptical caldera (19 ×14 km), with the same orientation as the previous one, from which intracaldera and outflow ignimbrites covered a total area of about 1,700 km2, representing a minimum eruption volume of 341 km3 (DRE). In this work we discuss the significance of the Cerro Aguas Calientes caldera in comparison with other well known examples from the central Andes in terms of tectonic setting, eruption mechanisms, and volumes of related ignimbrites. We suggest that our kinematic model is a common volcano-tectonic scenario during the Cenozoic in the Puna and Altiplano, which may be applied to explain the origin of other large calderas in the same region.

  12. ANALYSIS OF RECHARGE COOLDOWN AT THE WESTERN BOUNDARY OF CERRO PRIETO I GEOTHERMAL FIELD

    SciTech Connect

    Kruger, P.; Lam, S.; Hunsbedt, A.; Esquer, C.; Marquez, R.; Hernandez, L. Cobo, J.

    1985-01-22

    Extensive study of the Cerro Prieto geothermal field has provided much geologic and thermodynamic data of its structurally-complex, liquid-dominated reservoir. Several of the studies investigated the resource characteristics of fluid and energy flow. An early report by Mercado (1975) showed that the heat source for the part of the reservoir under development, now called Cerro Prieto I (CPI), originated in the eastern part of the field. Subsequent studies confirmed the flow of hot water from the east. A summary of several experimental and numerical studies of fluid and energy transport in the field was given by Lippmann and Bodvarsson (1983). The hydrogeologic model of Halfman et al. (1982) shows hot-water flow from the east divided into a shallow (alpha) aquifer at about 120Om and a deeper (beta) aquifer at about 170Om depth. A cross section along an east-west direction shows a central upflow to the two aquifers and uncertain geology beyond the western border of the field near well M-9. It also shows a fault dividing the line of border wells at M-29 from the inner wells at M-25 to the east. The hydrogeology of the field was described by Sanchez and de la Pena (1981) as an alluvial unit from the surface to about 700 m over the production zone and a shale-sandstone unit comprising an upper, shallow (alpha) aquifer bounded below by a basement horst overlying a deeper (beta) aquifer. To date, much of the cumulative production at Cerro Prieto I has been from the alpha aquifer. Piezometric level measurements over the first 5 years of operation showed a decline in the western zone beyond the production wells. Over the 10-year period of continuous production, a significant temperature decline has been observed along the westernmost line of wells. Several investigations of the recharge characteristics of the field have been reported. Mercado (1975) and Elders et al. (1984) indicated a flow of cold groundwater from the east. Mercado also noted that cold water was entering

  13. Xenoliths of Cerro las Mercedes, Costa Rica: a Geochemical Record of Arc History?

    NASA Astrophysics Data System (ADS)

    Lindsay, F. N.; Gazel, E.; Herzberg, C. T.; Carr, M. J.; Feigenson, M. D.

    2006-12-01

    Over 70 ultramafic xenoliths, many with diameters of at least 3cm, open a window into the mantle beneath Cerro las Mercedes, Costa Rica. This quaternary vent is 70km behind the active volcanic front and near the northern boundary of the Caribbean Plateau. Both xenoliths and host lava remain well preserved in spite of substantial soil development in a rain forest environment. We analyzed the host lava and a subset of 30 rocks for bulk and mineral chemistry, which include both peridotite and pyroxenite populations. The host rock is Plio-Quaternary potassic alkaline basalt; depleted in SiO2 and Al2O3 and enriched in MgO and P2O5 relative to both present day and Miocene volcanics. In terms of trace elements, the host basalt has enriched LREEs and relative depletion of HFSEs, typical of island-arc basalt, both present and past. The coarse-grained pyroxenites have trace element chemistry akin to the volcanic front lavas of Costa Rica, although they are closer to chondritic values. Truly, they are more similar to basalts from Sarapiquí Miocene arc than to present day volcanic front basalts. Although there is enrichment in incompatible elements such as Ba and U and depletions in HFSEs, common in island arc basalts, the pyroxenites have a strong positive Pb anomaly that is characteristic only of the Miocene arc, not present day lavas. We interpret the pyroxenites as cumulates. The peridotite population includes dunites, spinel lherzolites and lherzolites. These rocks have Mg-numbers ranging from 87 to 92 and Cr-numbers ranging from 6 to 61. Whole rock geochemistry indicates that the peridotite xenoliths are fragments of mantle associated with the western Caribbean Plateau. SiO2, FeO, Al2O3 and MgO contents of several Cerro Mercedes peridotites are similar to those expected of hot residues that would form in a plume environment. Trace elements reveal some samples with enrichment of Ba and U, and depletion in Nb and Ta indicating variable extents of melt-rock reaction and

  14. Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field, Baja, California, Mexico

    SciTech Connect

    Valette-Silver, J.N.; Esquer-Patino, I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

    1981-01-01

    Surface emissions from the Cerro Prieto geothermal reservoir are restricted to a 100 km/sup 2/ area on the western side of the field, near the volcano Cerro Prieto and the lake Laguna Vulcano. Some 57 surface emissions, explored in 1979, were classified into hot springs, mud pots, pools, fumaroles and geysers (Valette and Esquer-Patino, 1979). A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180/sup 0/C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristics of the discharge from high intensity geothermal fields.

  15. Intense Seismic Activity at Chiles and Cerro Negro Volcanoes on the Colombia-Ecuador Border

    NASA Astrophysics Data System (ADS)

    Torres, R. A.; Cadena, O.; Gomez, D.; Ruiz, M. C.; Prejean, S. G.; Lyons, J. J.; White, R. A.

    2015-12-01

    The region of Chiles and Cerro Negro volcanoes, located on the Colombian-Ecuadorian border, has experienced an ongoing seismic swarm beginning in Aug. 2013. Based on concern for local residents and authorities, a cooperative broadband monitoring network was installed by the Servicio Geológico Colombiano in Colombia and the Instituto Geofísico of the Escuela Politécnica Nacional in Ecuador. Since November 2013 more than 538,000 earthquakes were recorded; although since May 2015 the seismicity has decreased significantly to an average of 70 events per day. Three large earthquake swarms with increasing energy occurred in Aug.-Oct. 2013, March-May 2014, and Sept.-Dec. 2014. By the end of 2014, roughly 400 earthquakes greater than M 3 had occurred with a maximum rate of 8000 earthquakes per day. The largest earthquake was a 5.6 ML on Oct. 20, 2014. This event produced an InSAR coseismic deformation of ~23 cm (S. Ebmeier, personal communication). Most events are typical brittle failure volcano-tectonic (VT) earthquakes that are located in a cluster beneath the southern flank of Chiles volcano, with depths between 1.5 and 10 km. Although the great majority of earthquakes are VT, some low-frequency (LF, ~0.5 Hz) and very-low-frequency (VLF) events have occurred. Particle motion analysis suggests that the VLF source migrated with time. While a VLF on Oct. 15, 2014 was located south of Chiles volcano, near the InSAR source, the VLF registered on Feb. 14, 2015 was likely located very close to Chiles Volcano. We infer that magma intrusion and resulting fluid exsolution at depths greater than 5 km are driving seismicity in the Chiles-Cerro Negro region. However earthquakes are failing in a manner consistent with regional tectonics. Relative relocations reveal a structure consistent with mapped regional faults. Thus seismicity is likely controlled by an interaction of magmatic and tectonic processes. Because the regional stress field is highly compressional and the volcanoes

  16. The age and thermal history of Cerro Rico de Potosi, Bolivia

    USGS Publications Warehouse

    Cunningham, C.G.; Zartman, R.E.; McKee, E.H.; Rye, R.O.; Naeser, C.W.; Sanjines, V.O.; Ericksen, G.E.; Tavera, V.F.

    1996-01-01

    Cerro Rico de Potosi, Bolivia, is the world's largest silver deposit and has been mined since the sixteenth century for silver, and for tin and zinc during the twentieth century, together with by-product copper and lead. The deposit consists primarily of veins that cut an altered igneous body that we interpret to be a dacitic volcanic dome and its underlying tuff ring and explosion breccia. The deposit is compositionally and thermally zoned, having a core of cassiterite, wolframite, bismuthinite, and arsenopyrite surrounded by a peripheral, lower-temperature mineral assemblage consisting principally of sphalerite, galena, lead sulfosalt, and silver minerals. The low-temperature assemblage also was superim-posed on the high-temperature assemblage in response to cooling of the main hydrothermal system. Both the dacite dome and the ore fluids were derived from a larger magmatic hydrothermal source at depth. The dome was repeatedly fractured by recurrent movement on the fault system that guided its initial emplacement. The dome was extruded at 13.8 ?? 0.2 Ma (2??), based on U-Th-Pb dating of zircon. Mineralization and alteration occurred within about 0.3 my of dome emplacement, as indicated by a 40Ar/39Ar date of 13.76 ?? 0.10 Ma (1??) for sericite from the pervasive quartz-sericite-pyrite alteration associated with the main-stage, high-temperature, mineralization. The last thermal event able to reset zircon fission tracks occurred no later than 12.5 ?? 1.1 Ma (1??). as indicated by fission-tract dating. Minor sericite. and magmatic-steam alunite veins, were episodically formed around 11 Ma and between 8.3 and 5.7 Ma; the younger episodes occurring at the time of extensional fracturing at Cerro Rico and widespread volcanism in the adjacent Los Frailes volcanic field. None of these younger events appear to be signific-ant thermal/mineralizing events: the exceptionally flat thermal release pattern of 39Ar from sericite and the results of the fission-tract dating of

  17. Photosynthesis within Mars' volcanic craters?: Insights from Cerro Negro Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Rogers, K. L.; Hynek, B. M.; McCollom, T. M.

    2011-12-01

    Discrete locales of sulfate-rich bedrocks exist on Mars and in many cases represent the products of acid-sulfate alteration of martian basalt. In some places, the products have been attributed to hydrothermal processes from local volcanism. In order to evaluate the habitability of such an environment, we are investigating the geochemical and biological composition of active fumaroles at Cerro Negro Volcano, Nicaragua, where fresh basaltic cinders similar in composition to martian basalts are altered by acidic, sulfur-bearing gases. Temperatures at active fumaroles can reach as high as 400°C and the pH of the steam ranges from <0 to 5. Adjacent to some fumaroles, silica is being precipitated from condensing steam on the crater walls and endolithic photosynthetic mats are found at 1-2 cm depth within these silica deposits. We have analyzed one of these mats, Monkey Cheek (T=65°C, pH ~4.5), for both Archaeal and Bacterial diversity. Cloning of PCR-amplified 16S rRNA genes reveals a diverse community of Bacteria, with eight phyla represented. The most common bacterial sequences belonged to the Cyanobacteria and Ktedonobacteria, however Actinobacteria, alpha-Proteobacteria and Acidobacteria were also identified. Many of the cyanobacterial sequences were similar to those of the eukaryotic Cyanidiales, red algae that inhabit acidic, geothermal environments. Many of sequences related to Ktedonobacteria and Actinobacteria have also been found in acid mine drainage environments. The Archaeal community was far less diverse, with sequences matching those of unclassified Desulfurococcales and unclassified Thermoprotei. These sequences were more distant from isolated species than the bacterial sequences. Similar bacterial and archaeal communities have been found in hot spring environments in Yellowstone National Park, Greenland, Iceland, New Zealand and Costa Rica. Some of Mars' volcanoes were active for billions of years and by analogy to Cerro Negro, may have hosted

  18. The Cerro Tololo Inter-American Observatory Summer Student Programs in La Serena, Chile

    NASA Astrophysics Data System (ADS)

    Kaleida, Catherine C.; Smith, C.; Van Der Bliek, N. S.; James, D.

    2014-01-01

    The Cerro Tololo Inter-American Observatory (CTIO) offers positions for U.S. and Chilean student interns during the Chilean summer months of January-March (northern winter semester) at the CTIO offices in La Serena, Chile. CTIO is part of the National Optical Astronomy Observatory (NOAO) of the United States, focused on the development of astronomy in the southern hemisphere. Six undergraduate research assistantships are offered for U.S. physics and astronomy undergraduate students through the NSF-funded Research Experiences for Undergraduates (REU) program. The CTIO-funded Prácticas de Investigación en Astronomía (PIA) program is run concurrently with the REU program, and offers two research assistantships for Chilean undergraduate or 1st or 2nd year masters students, also at the CTIO offices in La Serena, Chile. The CTIO REU and PIA programs provide exceptional opportunities for students considering a career in astronomy to engage in substantive research activities with scientists working at the forefront of contemporary astrophysics. Student participants work on specific research projects in close collaboration with members of the CTIO scientific and technical staff, such as galaxy clusters, gravitational lensing, supernovae, planetary nebulae, stellar populations, star clusters, star formation, variable stars and interstellar medium. The CTIO REU and PIA programs emphasize observational techniques and provide opportunities for direct observational experience using CTIO's state-of-the-art telescopes and instrumentation. The programs run for 10 weeks, from mid-January to the end of March. A two-night observing run on Cerro Tololo and a field trip to another observatory in Chile are included for students of both programs. These positions are full time, and those selected will receive a modest stipend and subsidized housing on the grounds of the offices of CTIO in La Serena, as well as travel costs to and from La Serena. In addition, the students have the

  19. Arterial oxygen saturation in healthy newborns delivered at term in Cerro de Pasco (4340 m) and Lima (150 m)

    PubMed Central

    Gonzales, Gustavo F; Salirrosas, Amelia

    2005-01-01

    Background High altitude is associated with both low pulse oxygen saturation at birth and more pre-term deliveries. The present study was performed to determine pulse oxygen saturation in newborns at term in Cerro de Pasco (4340 m) and Lima (150 m) to test the hypothesis that low pulse oxygen saturation at birth at high altitudes was not observed at term deliveries. Methods The present study was designed to determine pulse oxygen saturation values through 1 minute to 24 hours and values of Apgar score at 1 and 5 minutes in newborns delivered at term in Cerro de Pasco (4340 m) and Lima (150 m). Pulse oxygen saturation was recorded in 39 newborns from Cerro de Pasco (4340 m) and 131 from Lima (150 m) at 1, 2, 3, 4, 5, 10, 15, 30 minutes and 1, 2, 8 and 24 hours after delivery. Apgar score was assessed at 1 and 5 minutes after birth. Neurological score was assessed at 24 h of birth by Dubowitz exam. Results Pulse oxygen saturation increased significantly from 1 to 15 min after birth at sea level and from 1 to 30 minutes at Cerro de Pasco. Thereafter, it increased slightly such that at 30 min at sea level and at 60 minutes in Cerro de Pasco it reached a plateau up to 24 hours after birth. At all times, pulse oxygen saturation was significantly higher at sea level than at high altitude (P < 0.01). At 1 minute of life, pulse oxygen saturation was 15% lower at high altitude than at sea level. Apgar score at 1 minute was significantly lower at high altitude (P < 0.05). Neurological score at 24 hours was also lower at high altitude than at sea level. Head circumference, and Apgar score at 5 minutes were similar at sea level and at high altitude (P:NS). Incidence of low birth-weight (<2500 g) at high altitude (5.4%) was similar to that observed at sea level (2.29%) (P:NS). Incidences of low pulse oxygen saturation (<30%), low Apgar score at first minute (<7) and low neurological score at 24 h (<19) were significantly higher at high altitude than at sea level (P < 0.0001; P

  20. Simultaneous Observations of the Phase-Locked Two Day Wave at Adelaide and Cerro Pachon

    NASA Astrophysics Data System (ADS)

    Walterscheid, R. L.; Hecht, J. H.; Vincent, R. A.; Franke, S. J.; Taylor, M. J.; Pautet, P.; Zhao, Y.

    2013-12-01

    The phase locked two day wave (PL/TDW) during austral summer is the most dramatic large scale event of the upper mesosphere. The PL/TDW wave can achieve amplitudes exceeding 70 m/s and involve the entire southern hemisphere and much of the northern hemisphere. The winds accelerate over a period of about 1 week and are accompanied by a near disappearance of the diurnal tide and stabilization of the two-day wave period at close to 48 hours. We have examined meteor wind data from the Andes Lidar Observatory at Cerro Pachon, Chile (30S, 70.1W) and MF radar data from the University of Adelaide (34.7S, 138.6E) located at similar latitudes. We find a remarkable coincidence between the oscillations. When adjustments for the separation in longitude are made the oscillations are nearly in phase. The amplitude of the oscillation is significantly greater at Chili, where winds approach 100 m/s. The diurnal tide is greatly diminished at both locations. These observations support the explanation that the PL/TDW is a subharmonic parametric instability of the diurnal tide (Walterscheid and Vincent, JGR, 1996). We will also present analysis of airglow data for the two-day wave at both locations.

  1. Gas chemistry and thermometry of the Cerro Prieto, Mexico, geothermal field

    USGS Publications Warehouse

    Nehring, N.L.; D'Amore, F.

    1984-01-01

    Gas compositions of Cerro Prieto wells in 1977 reflected strong boiling in the reservoir around wells M-20 and M-25. This boiling zone appeared to be collapsing in 1982 when a number of wells in this area of the field were shut-in. In 1977 and 1982, gas compositions also showed boiling zones corresponding to faults H and L postulated by Halfman et al. (1982). Four gas geothermometers were applied, based on reservoir equilibria and calculated fugacities. The Fisher - Tropsch reaction predicted high temperatures and appeared to re-equilibrate slowly, whereas the H2S reaction predicted low temperatures and appeared to re-equilibrate rapidly. Hydrogen and NH3 reactions were intermediate. Like gas compositions, the geothermometers reflected reservoir processes, such as boiling. Surface gas compositions are related to well compositions, but contain large concentrations of N2 originating from air dissolved in groundwater. The groundwater appears to originate in the east and flow over the production field before mixing with reservoir gases near the surface. ?? 1984.

  2. Soil mercury levels in the area surrounding the Cerro Prieto geothermal complex, MEXICO.

    PubMed

    Pastrana-Corral, M A; Wakida, F T; García-Flores, E; Rodriguez-Mendivil, D D; Quiñonez-Plaza, A; Piñon-Colin, T D J

    2016-08-01

    Even though geothermal energy is a renewable energy source that is seen as cost-effective and environmentally friendly, emissions from geothermal plants can impact air, soil, and water in the vicinity of geothermal power plants. The Cerro Prieto geothermal complex is located 30 km southeast of the city of Mexicali in the Mexican state of Baja California. Its installed electricity generation capacity is 720 MW, being the largest geothermal complex in Mexico. The objective of this study was to evaluate whether the emissions generated by the geothermal complex have increased the soil mercury concentration in the surrounding areas. Fifty-four surface soil samples were collected from the perimeter up to an approximate distance of 7660 m from the complex. Additionally, four soil depth profiles were performed in the vicinity of the complex. Mercury concentration in 69 % of the samples was higher than the mercury concentration found at the baseline sites. The mercury concentration ranged from 0.01 to 0.26 mg/kg. Our results show that the activities of the geothermal complex have led to an accumulation of mercury in the soil of the surrounding area. More studies are needed to determine the risk to human health and the ecosystems in the study area.

  3. A Climatology of Ripple Instabilities in the OH Airglow at Cerro Pachon, Chile

    NASA Astrophysics Data System (ADS)

    Gelinas, L. J.; Hecht, J. H.; Walterscheid, R. L.; Rudy, R. J.

    2015-12-01

    Airglow imaging provides a unique means by which to study many wave-related phenomena in the 80 to 100 km altitude regime. Observations reveal quasi-monochromatic disturbances associated with atmospheric gravity waves (AGWs) as well as small-scale instabilities often called ripples. Ripples are wavelike features that resemble AGWs in appearance, but have short horizontal wavelengths (<15 km) and short lifetimes (a few tens of minutes). The end product of the breakdown of ripples is turbulence, leading to increased eddy diffusion. Thus, ripple observations may help refine our understanding of the occurrence of turbulence in the upper Mesosphere and Lower Thermosphere. The Aerospace Corporation's Nightglow Imager (ANI) is located at the Andes Lidar Observatory near the crest of Cerro Pachon, Chile. ANI observes nighttime OH emission (near 1.6 microns) every 2 seconds over an approximate 73 degree field of view, which allows the study of AGW and ripple features over very short temporal and spatial scales. An automated wave detection algorithm is used to identify ripple and quasi monochromatic wave features in the ANI data. Ripples are characterized by their wavelength, orientation, drift speed and location in the image. Quasi-monochromatic waves are quantified by wavelength, wave period and propagation direction. We present a climatology of ripple instabilities at Chile, including comparisons to the background quasi-monochromatic wave field. Lidar and radar data are used to determine the background wind and temperatures, which allows comparisons between ripple observations and evanescent regions and potentially unstable regions identified by Richardson number.

  4. Cerro Prieto Contents of the Technical Information Files Generated at the Field

    SciTech Connect

    Olmos, Miguel Angel Ayuso

    1987-01-20

    The creation of a computer data bank for the Cerro Prieto Geothermal Field, resulted from the need for fast and flexible management of the increasing and voluminous information generated from the large number of wells drilled in recent years. The data are needed for updating the thermodynamic evolution of the field in order to define field history and validate mathematical analyses applications. This data bank compiles 20 files with all technical information issued from the time of initial field exploration to the end of 1986. To use the data bank, a series of programs and subroutines were created simultaneously for data base management to allow access and add new data as well as data analysis and data graphics. Tables of global statistics of the informations contained in the 20 files are shown in the paper, as an example of one application of the general use of the data base. For particular and specific applications, depending on users’ needs for the data. 3 tabs., 1 fig.

  5. Model of the heat source of the Cerro Prieto magma-hydrothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.; Cox, B.

    1982-08-10

    Earlier studies at Cerro Prieto by UCR have led to the development of a qualitative model for field flow in the geothermal system before it was drilled and perturbed by production. Current efforts are directed towards numerical modelling of heat and mass transfer in the system in this undisturbed state. A two-dimensional model assumes that the heat sources were a single basalt/gabbro intrusion which provided heat to the system as it cooled. After compiling various information on the physical properties of the reservoir, the enthalpy contained in two 1cm thick section across the reservoir orthogonal to each other was calculated. Next various shapes, sizes and depths for the intrusion as initial conditions and boundary conditions for the calculation of heat transfer were considered. A family of numerical models which so far gives the best matches to the conditions observed in the field today have in common a funnel-shaped intrusion with a top 4km wide emplaced at a depth of 5km some 30,000 to 50,000 years ago, providing heat to the geothermal system. Numerical modelling is still in progress. Although none of the models so far computed may be a perfect match for the thermal history of the reservoir, they all indicate that the intrusive heat source is young, close and large.

  6. Hydrothermal flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Schiffman, P.; Williams, A.E.

    1984-01-01

    This detailed three-dimensional model of the natural flow regime of the Cerro Prieto geothermal field, before steam production began, is based on patterns of hydrothermal mineral zones and light stable isotopic ratios observed in rock samples from more than 50 deep wells, together with temperature gradients, wireline logs and other data. At the level so far penetrated by drilling, this hydrothermal system was heated by a thermal plume of water close to boiling, inclined at 45/sup 0/, rising from the northeast and discharging to the west. To the east a zone of cold water recharge overlies the inclined thermal plume. Fission track annealing studies show the reservoir reached 170/sup 0/C only 10/sup 4/ years ago. Oxygen isotope exchange data indicate that a 12 km/sup 3/ volume of rock subsequently reacted with three times its volume of water hotter than 200/sup 0/C. Averaged over the duration of the heating event this would require a flow velocity through a typical cross-section of the reservoir of about 6 m/year. The heat in storage in that part of the reservoir hotter than 200/sup 0/C and shallower than 3 km depth is equivalent to that which would be released by the cooling of about 1 or 2 km/sup 3/ of basalt or gabbro magma.

  7. Model for the heat source of the Cerro Prieto magma-hydrothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.; Cox, B.

    1981-01-01

    Earlier studies at Cerro Prieto led to the development of a qualitative model for fluid flow in the geothermal system before it was drilled and perturbed by production. Current efforts are directed towards numerical modeling of heat and mass transfer in the system in this undisturbed state. This one-dimensional model assumes that the heat source was a single basalt/gabbro intrusion which provided heat to the system as it cooled. After compilation of various information of the physical properties of the reservoir, the enthalpy contained in two 1 cm thick sections across the reservoir orthogonal to each other was calculated. Various shapes, sizes and depths for the intrusion were considered as initial conditions and boundary conditions for the calculations of heat transfer. A family of numerical models which so far gives the best matches to the conditions observed in the field today have in common a funnel-shaped intrusion with a top 4 km wide emplaced at a depth of 5 km some 30,000 to 50,000 years ago, providing heat to the geothermal system.

  8. The Final Days of Paracas in Cerro del Gentil, Chincha Valley, Peru

    PubMed Central

    2016-01-01

    This article describes and analyzes a highly significant archaeological context discovered in a late Paracas (400–200 BCE) sunken patio in the monumental platform mound of Cerro Gentil, located in the Chincha Valley, Peru. This patio area was used for several centuries for ritual activities, including large-scale feasting and other public gatherings. At one point late in this historical sequence people deposited a great deal of objects in what is demonstrably a single historical event. This was quickly followed by a series of minor events stratigraphically immediately above this larger event. This entire ritual process included the consumption of liquids and food, and involved the offering of whole pottery, pottery fragments, botanical remains, bone, lithics, baskets, pyro-engraved gourds, mummies, and other objects. We interpret these events as an “abandonment ceremony” or “termination ritual” during the late Paracas period, one that may have lasted for weeks or even months. The subsequent Topará occupation at the site (ca. 200 BCE- AD 100) involved the architectural enhancement of the mound area, but the pattern of use of the patio itself ended. Such a termination ritual signals a reorganization in the regional political structure of Paracas society. PMID:27144824

  9. Durability of various cements in a well of the Cerro Prieto geothermal field

    SciTech Connect

    Krause, Ralph F., Jr.; Kukacka, Larry E.

    1982-10-08

    The durability of each of 16 different cements was evaluated by both room temperature compressive strength and water permeability measurements, following various periods of treatment of the cements in flowing geothermal fluid of the Cerro Prieto field of Mexico. Some of these cements were selected through a Department of Energy program to develop improved cements for geothermal well completion while the others were contributed by several other institutions interested in the tests. Two types of specimens of the cements were used in the tests: (a) 50 mm cubes which were precured 1 da in molds under water in an autoclave at 200 C and 20 MPa and (b) cement slurries which were prepared and cast in sandstone cups at the field. Federal de Electricidad a set of both types of specimens was installed in baskets which were placed 700 m downhole a well at 214 C, and an identical set of specimens was installed in special aboveground vessels near the wellhead. Following periods of 1 da. 3 mo, 6 mo. and 12 mo, specimens were withdrawn from the geothermal treatment and divided evenly between the Instituto de Investigaciones Electricas and the National Bureau of Standards for property measurements. This paper gives the downhole results by the latter laboratory. Final values will be published when the results of both laboratories are collated and reviewed.

  10. Curve Number and Peakflow Responses Following the Cerro Grande Fire on a Small Watershed.

    SciTech Connect

    Springer, E. P.; Hawkins, Richard H.

    2005-01-01

    The Curve Number (CN) method is routinely used to estimate runoff and peakflows following forest fires, but there has been essentially no literature on the estimated value and temporal variation of CNs following wildland fires. In May 2000, the Cerro Grande Fire burned the headwaters of the major watersheds that cross Los Alamos National Laboratory, and a stream gauging network presented an opportunity to assess CNs following the fire. Analysis of rainfall-runoff events indicated that the pre-fire watershed response was complacent or limited watershed area contributed to runoff. The post-fire response indicated that the complacent behavior continued so the watershed response was not dramatically changed. Peakflows did increase by 2 orders of magnitude following the fire, and this was hypothesized to be a function of increase in runoff volume and changes in watershed network allowing more efficient delivery of runoff. More observations and analyses following fires are needed to support definition of CNs for post-fire response and mitigation efforts.

  11. Measurements of air contaminants during the Cerro Grande fire at Los Alamos National Laboratory

    SciTech Connect

    Eberhart, Craig

    2010-08-01

    Ambient air sampling for radioactive air contaminants was continued throughout the Cerro Grande fire that burned part of Los Alamos National Laboratory. During the fire, samples were collected more frequently than normal because buildup of smoke particles on the filters was decreasing the air flow. Overall, actual sampling time was 96% of the total possible sampling time for the May 2000 samples. To evaluate potential human exposure to air contaminants, the samples were analyzed as soon as possible and for additional specific radionuclides. Analyses showed that the smoke from the fire included resuspended radon decay products that had been accumulating for many years on the vegetation and the forest floor that burned. Concentrations of plutonium, americium, and depleted uranium were also measurable, but at locations and concentrations comparable to non-fire periods. A continuous particulate matter sampler measured concentrations that exceeded the National Ambient Air Quality Standard for PM-10 (particles less than 10 micrometers in diameter). These high concentrations were caused by smoke from the fire when it was close to the sampler.

  12. A simulation of the Cerro Hudson SO[sub 2] cloud

    SciTech Connect

    Schoeberl, M.R.; Lait, L.R.; Newman, P.A.; Krueger, A.J. ); Doiron, S.D. )

    1993-02-20

    An isentropic trajectory model is used to simulate the evolution of the southern hemisphere SO[sub 2] cloud associated with the eruption of Cerro Hudson. By matching the parcel trajectories with total ozone mapping spectrometer SO[sub 2] retrievals, the principal stratospheric injection region is determined to be between 11 and 16 km in altitude. This region is characterized by weak wind shears and is located just poleward of the subtropical jet in the outer fringe of the stratospheric polar vortex. The lack of wind shear in the injection region explains the slow zonal dispersal of the SO[sub 2] cloud which was still clearly observed 19 days after the eruption. The trajectory model simulation of the SO[sub 2] cloud shows good agreement with observations for 7 days after the eruption. Using the potential vorticity and potential temperature estimates of the initial eruption cloud, the cloud position relative to the polar night jet is shown to be nearly fixed up to September 2, 1991, which was as long as the cloud was observed. This result suggests that the lower stratopsheric polar and mid-latitude regions are nearly isolated from each other during the late August period. 9 refs., 5 figs.

  13. The Final Days of Paracas in Cerro del Gentil, Chincha Valley, Peru.

    PubMed

    Tantaleán, Henry; Stanish, Charles; Rodríguez, Alexis; Pérez, Kelita

    2016-01-01

    This article describes and analyzes a highly significant archaeological context discovered in a late Paracas (400-200 BCE) sunken patio in the monumental platform mound of Cerro Gentil, located in the Chincha Valley, Peru. This patio area was used for several centuries for ritual activities, including large-scale feasting and other public gatherings. At one point late in this historical sequence people deposited a great deal of objects in what is demonstrably a single historical event. This was quickly followed by a series of minor events stratigraphically immediately above this larger event. This entire ritual process included the consumption of liquids and food, and involved the offering of whole pottery, pottery fragments, botanical remains, bone, lithics, baskets, pyro-engraved gourds, mummies, and other objects. We interpret these events as an "abandonment ceremony" or "termination ritual" during the late Paracas period, one that may have lasted for weeks or even months. The subsequent Topará occupation at the site (ca. 200 BCE- AD 100) involved the architectural enhancement of the mound area, but the pattern of use of the patio itself ended. Such a termination ritual signals a reorganization in the regional political structure of Paracas society.

  14. Preliminary isotopic studies of fluids from the Cerro Prieto geothermal field

    USGS Publications Warehouse

    Truesdell, A.H.; Rye, R.O.; Pearson, F.J.; Olson, E.R.; Nehring, N.L.; Whelan, J.F.; Huebner, M.A.; Coplen, T.B.

    1979-01-01

    Preliminary isotopic studies of Cerro Prieto geothermal fluids and earlier studies of Mexicali Valley ground waters suggest local recharge of the geothermal system from the area immediately to the west. Oxygen isotope exchange of water with reservoir rock minerals at temperatures increasing with depth has produced fluids with oxygen-18 contents increasing with depth, and pressure drawdown in the southeastern part of the field has allowed lower oxygen-18 fluids to invade the production aquifer from above. The contents of tritium and carbon-14 in the fluid suggest only that the age of the fluid is between 50 and 10,000 years. The isotopic compositions of carbon and sulfur are consistent with a magmatic origin of these elements but a mixed sedimentary-organic origin appears more likely for carbon and is also possible for sulfur. Investigations of the isotopic compositions of geothermal and cold ground waters continue and are being expanded as fluids become available and as separation and analysis methods are improved. ?? 1979.

  15. Research Experiences for Undergraduates at Cerro Tololo Inter-American Observatory

    NASA Astrophysics Data System (ADS)

    Hoard, D. W.; Smith, R. C.

    1999-12-01

    Each year, Cerro Tololo Inter-American Observatory (CTIO) hosts a Research Experiences for Undergraduates (REU) program funded by the National Science Foundation. In general, REU programs bring a group of undergraduate students to the host institute for 10 weeks, where they are teamed-up with staff members to perform research projects. Unlike REU programs at other U.S. institutions, the CTIO program takes place outside the United States and during the southern summer/northern winter months. This offers students not only a chance to perform research and participate in the day-to-day life at a major astronomical observatory, but also provides a unique exposure to a foreign culture and an option for students who can take advantage of a non-traditional work experience during the academic year. CTIO REU students also benefit from interaction with their Chilean counterparts participating in the Prácticas de Investigación en Astronomía, an REU-like program operated by CTIO for Chilean undergraduates. Since 1995, CTIO has hosted 16 REU students (with 4 more coming in 2000). Thirteen (and counting) publications have resulted from CTIO REU projects; all 4 REU students in the 1999 program attended the 194th AAS meeting to present posters based on their projects. We present here an overview of the REU program at CTIO.

  16. Research Experiences for Undergraduates at Cerro Tololo Inter-American Observatory

    NASA Astrophysics Data System (ADS)

    Hoard, D. W.; Smith, R. C.

    2000-12-01

    Each year, Cerro Tololo Inter-American Observatory (CTIO), located in La Serena, Chile, hosts a Research Experiences for Undergraduates (REU) Program funded by the National Science Foundation. In general, REU programs bring a group of undergraduate students to the host institute for 10 weeks, where they are teamed-up with staff members to perform research projects. Unlike REU programs at other U.S. institutions, the CTIO program takes place outside the United States and during the southern summer/northern winter months of January--March. This offers students not only a chance to perform research and participate in the day-to-day life at a major astronomical observatory, but also provides a unique exposure to a foreign culture and an option for students who can take advantage of a non-traditional work experience during the academic year. CTIO REU students also benefit from interaction with their Chilean counterparts participating in the Prácticas de Investigación en Astronomía, an REU-like program operated by CTIO for Chilean undergraduates. Since 1995, CTIO has hosted 20 REU students (with 4 more coming in 2001). Twenty (and counting) publications have resulted from CTIO REU projects. In addition, since 1999, 100% of the CTIO REU students have presented the results of their research projects at meetings of the American Astronomical Society. We present here an overview of the REU program at CTIO.

  17. Long-term dipole-dipole resistivity monitoring at the Cerro Prieto geothermal field

    SciTech Connect

    Wilt, M.; Goldstein, N.E.; Sasaki, Y.

    1984-04-01

    Dipole-dipole resistivity measurements for the combined purposes of reservoir delineation and reservoir monitoring were first made at Cerro Prieto in 1978 and have continued on approximately an annual basis since then. Two 20 km-long dipole-dipole lines with permanently emplaced electrodes at 1-km spacings were established over the field area. Resistivity remeasurements have been made on one line at 6- to 18-month intervals using a 25 kW generator capable of up to 80A output and a microprocessor-controlled signal-averaging receiver. This high-power, low-noise system provides highly accurate measurements even at large transmitter receiver separations. Standard error calculations for collected data indicate errors less than 5% for all points. Results from four years of monitoring (1979-1983) indicate a 5% average annual increase in apparent resistivity over the present production area, and larger decreases in apparent resistivity in the region to the east. The increase in resistivity in the production zone is most likely due to dilution of reservoir fluids with fresher water, as evidenced by a drop in chloride content of produced waters. The area of decreasing resistivity east of the reservoir is associated with a steeply dipping conductive body, a zone of higher thermal gradients and an increase in shale thickness in the section. Decreasing resistivity in this area may be caused by an influx of high temperature, saline water from depths of 3/sup +/ km through a sandy gap in the shales.

  18. Two-dimensional inversion of resistivity monitoring data from the Cerro Prieto geothermal field

    SciTech Connect

    Goldstein, N.E.; Sasaki, Y.; Wilt, M.J.

    1985-03-01

    Two-dimensional iterative, least-squares inversions were performed on dc resistivity data obtained over the Cerro Prieto geothermal field at five successive times during the 1979-1983 period. The data were taken on a 20-km-long control line centered over the production region. Inversions were performed on the apparent resistivities after they were converted to percent changes in apparent resistivity relative to the base year data of 1979. The resulting solutions gave the percent change in resistivity within each of 47 rectangular blocks representing the reservoir and recharge regions. These changes are compared to and found consistent with hydrogeologic and recharge models proposed by other workers on the basis of geophysical well logs, well cuttings, well production, geochemical and reservoir engineering data. The solutions support the model of a reservoir that is being recharged mainly by cooler, less saline water, causing changes in both pore fluid resistivity and the extent of boiling near the wells. There may be a component of high-temperature recharge from below and to the east, but flow may be impeded by a two-phase zone. Notwithstanding the various sources of error and uncertainty in the data acquisition and 2-D inversions, repetitive, high precision dc resistivity monitoring seems to be a useful method for assessing reservoir conditions when used in conjunction with production and reservoir engineering data and analyses. 17 refs., 6 figs.

  19. Soil mercury levels in the area surrounding the Cerro Prieto geothermal complex, MEXICO.

    PubMed

    Pastrana-Corral, M A; Wakida, F T; García-Flores, E; Rodriguez-Mendivil, D D; Quiñonez-Plaza, A; Piñon-Colin, T D J

    2016-08-01

    Even though geothermal energy is a renewable energy source that is seen as cost-effective and environmentally friendly, emissions from geothermal plants can impact air, soil, and water in the vicinity of geothermal power plants. The Cerro Prieto geothermal complex is located 30 km southeast of the city of Mexicali in the Mexican state of Baja California. Its installed electricity generation capacity is 720 MW, being the largest geothermal complex in Mexico. The objective of this study was to evaluate whether the emissions generated by the geothermal complex have increased the soil mercury concentration in the surrounding areas. Fifty-four surface soil samples were collected from the perimeter up to an approximate distance of 7660 m from the complex. Additionally, four soil depth profiles were performed in the vicinity of the complex. Mercury concentration in 69 % of the samples was higher than the mercury concentration found at the baseline sites. The mercury concentration ranged from 0.01 to 0.26 mg/kg. Our results show that the activities of the geothermal complex have led to an accumulation of mercury in the soil of the surrounding area. More studies are needed to determine the risk to human health and the ecosystems in the study area. PMID:27418073

  20. Subsurface Connections and Magma Mixing as revealed by Olivine- and Pyroxene-Hosted Melt Inclusions from Cerro Negro Volcano and the Las Pilas-El Hoyo Complex, Nicaragua.

    NASA Astrophysics Data System (ADS)

    Venugopal, S.; Moune, S.; Williams-Jones, G.

    2015-12-01

    Cerro Negro, the youngest volcano in the Central American Volcanic Belt, is a polygenetic cinder cone with relatively frequent explosive basaltic eruptions. Las Pilas, on the other hand, is a much larger and older complex with milder and less frequent eruptions. Based on historical data, these two closely spaced volcanoes have shown concurrent eruptive behavior, suggesting a subsurface connection. To further investigate this link, melt inclusions, which are blebs of melt trapped in growing crystals, were the obvious choice for optimal comparison of sources and determination of pre-eruptive volatile contents and magmatic conditions. Olivine-hosted inclusions were chosen for both volcanoes and pyroxene-hosted inclusions were also sampled from Las Pilas to represent the evolved melt. Major, volatile and trace elements reveal a distinct geochemical continuum with Cerro Negro defining the primitive end member and Las Pilas representing the evolved end member. Volatile contents are high for Cerro Negro (up to 1260 ppm CO2, 4.27 wt% H2O and 1700 ppm S) suggesting that volatile exsolution is likely the trigger for Cerro Negro's explosive eruptions. Las Pilas volatile contents are lower but consistent with degassing and evolutionary trends shown by major oxides. Trace element contents are rather unique and suggest Cerro Negro magmas fractionally crystallize while Las Pilas magmas are the products of mixing. Magmatic conditions were estimated with major and volatile contents: at least 2.4 kbar and 1170 °C for Cerro Negro melts and 1.3 kbar and 1130 °C for Las Pilas melts with an overall oxygen fugacity at the NNO buffer. In combination with available literature data, this study suggests an interconnected subsurface plumbing system and thus Cerro Negro should be considered as the newest vent within the Las Pilas-El Hoyo Complex.

  1. Complex palaeosol ichnofabrics from Late Jurassic-Early Cretaceous volcaniclastic successions of Central Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Bedatou, Emilio; Melchor, Ricardo N.; Genise, Jorge F.

    2009-06-01

    Late Jurassic-Early Cretaceous volcaniclastic continental deposits from central Patagonia, Argentina were analyzed for an integral characterization of palaeosol ichnofabrics. These units contain complex continental ichnofabrics that were also recorded in other late Jurassic-late Miocene extended volcaniclastic successions from Patagonia. According to a recently proposed method, ichnofabric, pedofabric and original bedding of selected intervals were measured separately in order to determinate the degree in which the deposits are affected by soil features besides the ichnofabrics. Four recurrent ichnofabrics were recognized in studied palaeosols: the Loloichnus, large Taenidium- Beaconites, diffuse boxwork, and Dagnichnus ichnofabrics. The Loloichnus ichnofabric is characterized by sub-vertical Loloichnusbaqueroensis and subordinate, similarly arrenged large Taenidiumbarretti and Beaconitescoronus.L.baqueroensis is a crayfish dwelling structure while large T.barretti and B.coronus are assigned to locomotion of the same organisms. Root traces are additional components of this ichnofabric. The large Taenidium- Beaconites ichnofabric is formed by large, irregular and curved T.barretti and B.coronus and by L.baqueroensis in low proportion. This ichnofabric is also assigned to crayfish activity. The diffuse boxwork ichnofabric is characterized by a pervasive and intricate three-dimensional boxwork of burrows; occasionally joined to subspherical chambers (possible Castrichnus). The diffuse boxwork is interpreted as an earthworm burrow system and the associated chambers are probably for aestivation. Rare and scattered discrete trace fossils in this ichnofabric include L.baqueroensis, T.barretti and B.coronus. The Dagnichnus ichnofabric is formed by Dagnichnustitoi, root traces and, subordinately, Loloichnusbaqueroensis, Cellicalichnusmeniscatus and tangled groups of meniscate burrows. D.titoi and C.meniscatus has been interpreted as crayfish breeding structures and the

  2. A multi-proxy lacustrine record of Holocene climate change in SW Patagonia, Chile

    NASA Astrophysics Data System (ADS)

    LeRoy, S. L.; Mucciarone, D. A.; Dunbar, R. B.

    2014-12-01

    One of the largest uncertainties in the Holocene ocean-atmosphere carbon cycle is the role of the Southern Ocean (SO) and subpolar seas in controlling atmospheric CO2 levels. The strength and position of the westerly winds is thought to control rates of CO2 exchange as well as depth of ventilation. Secondarily, through their control on the large scale geostrophic circulation, the westerlies influence the position of major ocean frontal boundaries as well as stratification in the Southern Ocean - additional controls on SO carbon uptake. However, little is known about westerly wind variability over the Holocene. Southern Patagonia is an ideal locality for addressing this uncertainty, as it is the only major landmass that extends into the southern westerly wind field. In particular, lake and fjord environments hold potential for reconstructing precipitation, which is closely correlated with westerly wind strength in this region. Here we present a multi-proxy lacustrine sediment core record from Lago Sarmiento (51.06˚S, 72.91˚W), a large, closed-basin lake in southwest Chilean Patagonia. We observe highly variable C:N ratios between ~12,500 and ~6,000 14C yr BP, indicating recurrent transitions from grassland to forest. We measured a steady increase in the C:N ratio from ~6,000 14C yr BP to present, indicating a sustained shift from grassland to the modern Nothofagus forest and more humid conditions. We observe a general decreasing trend in bulk carbonate δ18O since ~4,000 14C yr BP, which we interpret as a progressive increase in westerly wind intensity and associated tendency towards positive water balance. Weight percent bulk carbonate varies greatly, with a strong decreasing trend in the early Holocene, followed by an increasing trend during the mid-Holocene, and a dip followed by a short rise in the late Holocene. Comparison with other records from southern Patagonia and Antarctica is improving our understanding of the forcing mechanisms driving changes in the

  3. Impact of solar ultraviolet radiation on marine phytoplankton of Patagonia, Argentina.

    PubMed

    Helbling, E Walter; Barbieri, Elena S; Marcoval, M Alejandra; Gonçalves, Rodrigo J; Villafañe, Virginia E

    2005-01-01

    Patagonia area is located in close proximity to the Antarctic ozone "hole" and thus receives enhanced ultraviolet B (UV-B) radiation (280-315 nm) in addition to the normal levels of ultraviolet A (UV-A; 315-400 nm) and photosynthetically available radiation (PAR; 400-700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer-fall), (2) bloom season (winter-early spring) and (3) postbloom season (late spring-summer). Small-size cells characterize the pre- and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by microplankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV-B when inhibition is normalized by irradiance (i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages (i.e. during the pre- but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions (e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses

  4. Impact of solar ultraviolet radiation on marine phytoplankton of Patagonia, Argentina.

    PubMed

    Helbling, E Walter; Barbieri, Elena S; Marcoval, M Alejandra; Gonçalves, Rodrigo J; Villafañe, Virginia E

    2005-01-01

    Patagonia area is located in close proximity to the Antarctic ozone "hole" and thus receives enhanced ultraviolet B (UV-B) radiation (280-315 nm) in addition to the normal levels of ultraviolet A (UV-A; 315-400 nm) and photosynthetically available radiation (PAR; 400-700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer-fall), (2) bloom season (winter-early spring) and (3) postbloom season (late spring-summer). Small-size cells characterize the pre- and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by microplankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV-B when inhibition is normalized by irradiance (i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages (i.e. during the pre- but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions (e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses

  5. Patagonian and Antarctic dust as recorded in the sediments of Laguna Potrok Aike (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Haberzettl, Torsten; Stopp, Annemarie; Lisé-Pronovost, Agathe; Gebhardt, Catalina; Ohlendorf, Christian; Zolitschka, Bernd; von Eynatten, Hilmar; Kleinhanns, Ilka; Pasado Science Team

    2010-05-01

    Although an increasing number of terrestrial paleoclimatic records from southern South America has been published during the last decade, these archives mostly cover the Lateglacial and/or the Holocene. Only little is known about the Patagonian climate before the Last Glacial Maximum. Here, we present a continuous, high-resolution magnetic susceptibility record for the past 48 ka from the maar lake Laguna Potrok Aike (51°58' S, 70°23' W, southern Patagonia, Argentina). Magnetic susceptibility serves as an excellent parameter for the parallelization of sediment cores all over Laguna Potrok Aike including sediment cores taken within the ICDP (International Continental Scientific Drilling Program) project PASADO (Potrok Aike maar lake Sediment Archive Drilling prOject). Additionally, magnetic susceptibility is assumed to be a proxy for dust deposition in this lake. Distinct similarities were found between the independently dated magnetic susceptibility record from Laguna Potrok Aike and the non-sea-salt calcium (nss-Ca) flux from the EPICA Dome C ice core record (75°06'S, 123°24'E) the latter being a proxy for mineral dust deposition in Antarctica [1]. Comparison of the two records and variations in grain size of the Laguna Potrok Aike sediment records indicate a relatively high aeolian activity in southern South America during the glacial period. During the Holocene climatic conditions driving sediment deposition seem to have been more variable and less dominated by wind compared to glacial times. Although the source of the dust found in Antarctic ice cores often has been attributed to Patagonia [2], we present the first evidence for contemporaneity of aeolian deposition in both the target area (Antarctica) and the major source area (Patagonia). Considering the similarities of the two records, magnetic susceptibility might yield the potential for chronological information: transfer of the ice core age model to a lacustrine sediment record. This would be important

  6. A gigantic, exceptionally complete titanosaurian sauropod dinosaur from southern Patagonia, Argentina.

    PubMed

    Lacovara, Kenneth J; Lamanna, Matthew C; Ibiricu, Lucio M; Poole, Jason C; Schroeter, Elena R; Ullmann, Paul V; Voegele, Kristyn K; Boles, Zachary M; Carter, Aja M; Fowler, Emma K; Egerton, Victoria M; Moyer, Alison E; Coughenour, Christopher L; Schein, Jason P; Harris, Jerald D; Martínez, Rubén D; Novas, Fernando E

    2014-01-01

    Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death. PMID:25186586

  7. Dermatoglyphics in Araucanian Indians from Patagonia and multivariate comparisons with other Argentinian aboriginal populations.

    PubMed

    Demarchi, D A; Giordano, A R; Marcellino, A J

    1997-04-01

    Digital and palmar dermatoglyphics are reported for 94 Araucanian Indians from the Argentinian Patagonia. All the traits analyzed present values within the range of variation found in South Amerindians. The principal finding is the different behavior observed for the digital and palmar traits of the individuals of the tribe. Although finger variables show high sexual and bimanual variation (especially in males), palmar traits exhibit extreme homogeneity. Multiple discriminant analyses from palmar data and finger ridge counts separately were carried out with three other Argentinian Indian populations from the Gran Chaco. The results indicate high discrimination between the populations in both palmar variables and finger ridge counts. However, although the nature of interpopulation relationships obtained from palmar data conforms to the ethnohistorical and geographic patterns, no clear picture emerges when the finger ridge counts are used.

  8. Marine pollution effects on the southern surf crab Ovalipes trimaculatus (Crustacea: Brachyura: Polybiidae) in Patagonia Argentina.

    PubMed

    Lezcano, Aníbal Hernán; Rojas Quiroga, María Laura; Liberoff, Ana Laura; Van der Molen, Silvina

    2015-02-28

    We compared the carapace shape and thickness as well as the energy density of Ovalipes trimaculatus inhabiting areas comprising a gradient of marine pollution: high, moderate and undetected, in the Nuevo gulf (Patagonia Argentina). The carapace shape was evaluated by means of individual asymmetry scores (=fluctuating asymmetry) whereas the carapace thickness was assessed by measuring the carapace dry weight. The energy density was analyzed through its negative relationship with water content in muscle tissue. The individual asymmetry scores as well as the percentage of water content in muscle tissue were proportional to the marine pollution gradient, whereas the carapaces thickness did not differ among sampling sites. Our results are consistent with previous findings and demonstrate the direct effect of marine pollution on other taxa different from gastropods, cephalopods and polyplacophora and add to long-standing concerns about detrimental effects caused by marine pollution on the benthic community of the Nuevo gulf.

  9. Linked canopy, climate, and faunal change in the Cenozoic of Patagonia.

    PubMed

    Dunn, Regan E; Strömberg, Caroline A E; Madden, Richard H; Kohn, Matthew J; Carlini, Alfredo A

    2015-01-16

    Vegetation structure is a key determinant of ecosystems and ecosystem function, but paleoecological techniques to quantify it are lacking. We present a method for reconstructing leaf area index (LAI) based on light-dependent morphology of leaf epidermal cells and phytoliths derived from them. Using this proxy, we reconstruct LAI for the Cenozoic (49 million to 11 million years ago) of middle-latitude Patagonia. Our record shows that dense forests opened up by the late Eocene; open forests and shrubland habitats then fluctuated, with a brief middle-Miocene regreening period. Furthermore, endemic herbivorous mammals show accelerated tooth crown height evolution during open, yet relatively grass-free, shrubland habitat intervals. Our Patagonian LAI record provides a high-resolution, sensitive tool with which to dissect terrestrial ecosystem response to changing Southern Ocean conditions during the Cenozoic. PMID:25593182

  10. A new late Cenozoic species of Abertella (Echinoidea: Clypeasteroida) from Patagonia.

    PubMed

    Kroh, Andreas; Mooi, Rich; Del Río, Claudia; Neumann, Christian

    2013-01-01

    A new species of abertellid sand dollar, Abertella miskellyi n. sp., is described from the Miocene Camarones Formation of Patagonia, southern Argentina. The new taxon corroborates the existence of the genus in South America, given that Abertella is most common in the southeastern USA and the eastern coast of Central America. It is characterized by a unique basicoronal circle, in which the interambulacral basicoronal plates are very heterogeneous in size (small in interambulacrum 5, largest in interambulacra 2 and 3). Additionally, it features disjunct oral interambulacra involving two ambulacral plates in some of the interambulacra rather than one, thus being the most disjunct of all known species of Abertella. A key to the species of the genus is provided. PMID:24614477

  11. Cystobasidiomycetes yeasts from Patagonia (Argentina): description of Rhodotorula meli sp. nov. from glacial meltwater.

    PubMed

    Libkind, Diego; Sampaio, José Paulo; van Broock, Maria

    2010-09-01

    A basidiomycetous yeast, strain CRUB 1032(T), which formed salmon-pink colonies, was isolated from glacial meltwater in Patagonia, Argentina. Morphological, physiological and biochemical characterization indicated that this strain belonged to the genus Rhodotorula. Molecular taxonomic analysis based on the 26S rDNA D1/D2 domain and internal transcribed spacer region sequences showed that strain CRUB 1032(T) represents an undescribed yeast species, for which the name Rhodotorula meli sp. nov. is proposed (type strain is CRUB 1032(T)=CBS 10797(T)=JCM 15319(T)). Phylogenetic analysis showed that Rhodotorula lamellibrachii was the closest known species, which, together with R. meli, formed a separate cluster related to the Sakaguchia clade within the Cystobasidiomycetes. Additional Patagonian yeast isolates of the class Cystobasidiomycetes are also investigated in the present work. PMID:19880630

  12. A new late Cenozoic species of Abertella (Echinoidea: Clypeasteroida) from Patagonia.

    PubMed

    Kroh, Andreas; Mooi, Rich; Del Río, Claudia; Neumann, Christian

    2013-01-22

    A new species of abertellid sand dollar, Abertella miskellyi n. sp., is described from the Miocene Camarones Formation of Patagonia, southern Argentina. The new taxon corroborates the existence of the genus in South America, given that Abertella is most common in the southeastern USA and the eastern coast of Central America. It is characterized by a unique basicoronal circle, in which the interambulacral basicoronal plates are very heterogeneous in size (small in interambulacrum 5, largest in interambulacra 2 and 3). Additionally, it features disjunct oral interambulacra involving two ambulacral plates in some of the interambulacra rather than one, thus being the most disjunct of all known species of Abertella. A key to the species of the genus is provided.

  13. Linked canopy, climate, and faunal change in the Cenozoic of Patagonia.

    PubMed

    Dunn, Regan E; Strömberg, Caroline A E; Madden, Richard H; Kohn, Matthew J; Carlini, Alfredo A

    2015-01-16

    Vegetation structure is a key determinant of ecosystems and ecosystem function, but paleoecological techniques to quantify it are lacking. We present a method for reconstructing leaf area index (LAI) based on light-dependent morphology of leaf epidermal cells and phytoliths derived from them. Using this proxy, we reconstruct LAI for the Cenozoic (49 million to 11 million years ago) of middle-latitude Patagonia. Our record shows that dense forests opened up by the late Eocene; open forests and shrubland habitats then fluctuated, with a brief middle-Miocene regreening period. Furthermore, endemic herbivorous mammals show accelerated tooth crown height evolution during open, yet relatively grass-free, shrubland habitat intervals. Our Patagonian LAI record provides a high-resolution, sensitive tool with which to dissect terrestrial ecosystem response to changing Southern Ocean conditions during the Cenozoic.

  14. New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods.

    PubMed

    Canale, Juan I; Scanferla, Carlos A; Agnolin, Federico L; Novas, Fernando E

    2009-03-01

    A nearly complete skeleton of the new abelisaurid Skorpiovenator bustingorryi is reported here. The holotype was found in Late Cenomanian-Early Turonian outcrops of NW Patagonia, Argentina. This new taxon is deeply nested within a new clade of South American abelisaurids, named Brachyrostra. Within brachyrostrans, the skull shortening and hyperossification of the skull roof appear to be correlated with a progressive enclosure of the orbit, a set of features possibly related to shock-absorbing capabilities. Moreover, the development of horn-like structures and differential cranial thickening appear to be convergently acquired within Abelisauridae. Based on the similarities between Skorpiovenator and carcharodontosaurid tooth morphology, we suggest that isolated teeth originally referred as post-Cenomanian Carcharodontosauridae most probably belong to abelisaurids.

  15. A gigantic, exceptionally complete titanosaurian sauropod dinosaur from southern Patagonia, Argentina.

    PubMed

    Lacovara, Kenneth J; Lamanna, Matthew C; Ibiricu, Lucio M; Poole, Jason C; Schroeter, Elena R; Ullmann, Paul V; Voegele, Kristyn K; Boles, Zachary M; Carter, Aja M; Fowler, Emma K; Egerton, Victoria M; Moyer, Alison E; Coughenour, Christopher L; Schein, Jason P; Harris, Jerald D; Martínez, Rubén D; Novas, Fernando E

    2014-09-04

    Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death.

  16. First paleoparasitological record of acanthocephalan eggs from Northwestern Patagonia (Late Holocene, Argentina).

    PubMed

    Beltrame, María Ornela; Fernández, Fernando Julián; Sardella, Norma Haydeé

    2015-06-01

    Eggs representative of an acanthocephalan were found in an ancient fragment of raptor pellet, probably belonged to the barn owl, Tyto alba, from the archeological site named "Epullán Chica cave." This site is a cave located at the southern of Neuquén Province, Patagonia, Argentina. The fragment of pellet was found in a layer with charcoals dated at 1980±80 years B.P. A total of 56 eggs were found. Eggs were brown colored and thick-shelled, and presented four membranes, the outer lightly sculpted. The embryos presented hooks in one extremity. Measurements ranged from 87.5 to 107.5μm long and 50 to 57.5μm wide. Eggs were very well-preserved, and were identified as belonged to Class Archiacanthocephala, Order Oligacanthorhynchida, Family Oligacanthorhynchidae, probably Macracanthorhynchus Travassos, 1917, or an unidentified species. This is the first report of small mammal acanthocephalans from ancient material worldwide.

  17. Marine pollution effects on the southern surf crab Ovalipes trimaculatus (Crustacea: Brachyura: Polybiidae) in Patagonia Argentina.

    PubMed

    Lezcano, Aníbal Hernán; Rojas Quiroga, María Laura; Liberoff, Ana Laura; Van der Molen, Silvina

    2015-02-28

    We compared the carapace shape and thickness as well as the energy density of Ovalipes trimaculatus inhabiting areas comprising a gradient of marine pollution: high, moderate and undetected, in the Nuevo gulf (Patagonia Argentina). The carapace shape was evaluated by means of individual asymmetry scores (=fluctuating asymmetry) whereas the carapace thickness was assessed by measuring the carapace dry weight. The energy density was analyzed through its negative relationship with water content in muscle tissue. The individual asymmetry scores as well as the percentage of water content in muscle tissue were proportional to the marine pollution gradient, whereas the carapaces thickness did not differ among sampling sites. Our results are consistent with previous findings and demonstrate the direct effect of marine pollution on other taxa different from gastropods, cephalopods and polyplacophora and add to long-standing concerns about detrimental effects caused by marine pollution on the benthic community of the Nuevo gulf. PMID:25293645

  18. New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods.

    PubMed

    Canale, Juan I; Scanferla, Carlos A; Agnolin, Federico L; Novas, Fernando E

    2009-03-01

    A nearly complete skeleton of the new abelisaurid Skorpiovenator bustingorryi is reported here. The holotype was found in Late Cenomanian-Early Turonian outcrops of NW Patagonia, Argentina. This new taxon is deeply nested within a new clade of South American abelisaurids, named Brachyrostra. Within brachyrostrans, the skull shortening and hyperossification of the skull roof appear to be correlated with a progressive enclosure of the orbit, a set of features possibly related to shock-absorbing capabilities. Moreover, the development of horn-like structures and differential cranial thickening appear to be convergently acquired within Abelisauridae. Based on the similarities between Skorpiovenator and carcharodontosaurid tooth morphology, we suggest that isolated teeth originally referred as post-Cenomanian Carcharodontosauridae most probably belong to abelisaurids. PMID:19057888

  19. Vegetation dynamics and disturbance regimes in northern Patagonia, Argentina: The roles of humans and climate variation

    SciTech Connect

    Veblen, T.T.; Kitzberger, T.; Villalba, R. )

    1993-06-01

    In northern Patagonia (c. 40[degrees] S.), we examined the roles of human activities and climate variation in the modification of disturbance regimes and vegetation dynamics along a gradient from Andean rainforest to the Patagonian steppe. Human-set fires and introduced herbivores (livestock and deer) have had dramatic impacts on the vegetation, the nature of which varies according to position along the macro-scale gradient. For example, European settlement resulted in increased fire frequency in the wet forest district whereas near the steppe fire frequency declined. Climate variability also has had important influences through the alteration of fire regimes and by directly influencing tree mortality and regeneration. The nature and consequences of the influences of climate variation are also distinct for different portions of the macro-scale environmental gradient.

  20. Bonitasaura salgadoi gen. et sp. nov.: a beaked sauropod from the Late Cretaceous of Patagonia

    NASA Astrophysics Data System (ADS)

    Apesteguía, Sebastián

    2004-10-01

    Ornithischian and theropod dinosaurs were morphologically diverse during the Cretaceous. In contrast, sauropods were relatively more conservative. The anatomy of Bonitasaura salgadoi, a new 9-m titanosaurian sauropod from Upper Cretaceous beds of Patagonia, suggests that sauropod anatomical diversity would have included unexpected items. Its unusual, rectangular lower jaw possesses narrow, anteriorly restricted teeth and shows evidence of a sharp keratinous sheath over the non-dentigerous region that probably worked to guillotine plant material. This discovery definitely demonstrates that titanosaurs acquired a mandibular configuration similar to that of some basal diplodocoids, as had already been suggested by the lower jaw of the controversial genus Antarctosaurus. This oral configuration, plus the beak-like structure and the skull shape, resemble some traits more commonly seen in Laurasian ornithischians, mostly unexpressed in southern continents. A high sauropod morphological diversity seems to be in agreement with the poorly represented ornithischian clades of the southern hemisphere.

  1. Lack of founding Amerindian mitochondrial DNA lineages in extinct aborigines from Tierra del Fuego-Patagonia.

    PubMed

    Lalueza, C; Pérez-Pérez, A; Prats, E; Cornudella, L; Turbón, D

    1997-01-01

    Ancient DNA from bones and teeth of 60 individuals from four extinct human populations from Tierra del Fuego-Patagonia (Selknam, Yamana, Kaweskar and Aonikenk) has been extracted and the mitochondrial DNA (mtDNA) amplified by using the polymerase chain reaction. High-resolution analysis of endonuclease restriction site variation in the mtDNA and sequencing of its hypervariable non-coding control region, revealed complete absence of two of the four primary mitochondrial haplotype groups present in contemporary Amerinds, namely A and B. In contrast, haplogroups C and D were found in all but one sample with frequencies of approximately 38% and 60%. These results, together with the decreasing incidence of group A in more southerly latitudes in the American continent and the absence of cluster B above 55 degrees North in America and Asia, argue that the first settlers entering America 21000-14000 years ago already lacked both mtDNA lineages.

  2. Cretaceous Small Scavengers: Feeding Traces in Tetrapod Bones from Patagonia, Argentina

    PubMed Central

    de Valais, Silvina; Apesteguía, Sebastián; Garrido, Alberto C.

    2012-01-01

    Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem. PMID:22253800

  3. Catchment similarity and classification in areas of high hydrologic gradients: the case of Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Dussaillant, A.; Buytaert, W.; Maturana, O.; Arias, M.

    2009-04-01

    The Baker River Basin is located in Patagonia, Southern South America, with a total drainage area of 26,726 km2 (second-largest river basin in Chile). The Baker River has the highest mean annual discharge rate of all Chilean rivers (1,133 m3/s), and flows out of Bertrand Lake, which in turn receives the draining waters from the General Carrera Lake (surface area of about 1800 km2, Latin America's second largest). Geology and climate gradients are even more extreme than in the rest of the country, from mountain to sea, and sometimes having mean annual rainfalls change from 8000 mm to 400 mm in less than 60 km. Bigger basins, like the Baker, have Eastern sub-basins with even a semi-arid character, whereas Western sub-catchments drain from ice fields. Thus, flow regimes may have very diverse characters in combination. And regarding sediment, although many rivers are born in lakes (many bi-national), they have important profile slopes and plenty of sediment available (partly due to glacial deposits). In spite of this huge natural variability, there is scant data due to low resources and remoteness: few meteorological and flow stations (having few decades or much shorter data series), and lack of stations in Western areas, linked to mountainous terrain, glaciers, and the ice fields. Nevertheless, decisions are being made with what seems extremely limited hydro-meteorological, streamflow, and in general, river data. In fact, Chile is currently in a crossroad due to mega projects being planned in Aysén, Chilean Patagonia (at least 5 hydropower dams producing more than 2000 MW). We characterize streamflows for ungauged basins, such as floods, mean annual flows, and flow duration curves, which can then be used related to a more sustainable design and operation of dams for hydropower. Relations extracted from gauged catchments to their geomorphologic characteristics and indices will be used to transfer those relations to ungauged catchments.

  4. The tectonographic development of Patagonia and its relevance to hydrocarbon exploration

    SciTech Connect

    Light, M.P.R.; Urien, C.M.; Maslanyj, M.P.; Keeley, M.L.; Hoggs, S.L.

    1993-02-01

    Patagonia accreted successively from the southwest onto the southern margin of the Proterozoic Plata Craton and Brazilian Guapore Shield between the Late Proterozoic and Early Devonian. The thrust-like stacking of terranes onto the southern termination of the Pelotas Terrane is considered to have developed a pervasive northwest to north-trending fabric. During the Permo-Triassic the northwest to north-trending fabric of the Patagonian Plate was re-activated by dextral strike-slip movement causing extension. The deformation was caused by oblique subduction and accretion of the madre Dos Dios to Pichidangui Terranes along its western margin. To the northeast the more competent shield underwent compression (Ventania-Gond-wanide Folding) and extension occurred parallel to the axis of the embryo South Atlantic, where a shallow sea transgressed. Ridge on its western side, now preserved on the facing shelf margins of Argentina and Namibia. In the Late Triassic-Lower Jurassic, the Malvinas and Microplate was situated south of the Transkei (South Africa) and an intracratonic basin separated it from two sutures formed at the margin of the Argentine Shelf and along the axis of the West Malvinas Basin. Subduction/arc activity on the west flank of this intracratonic basin, in association with trench pull is believed to have initiated Late Triassic-Early Jurassic strike slip extension and volcanicity in Patagonia. This exploited the pervasive northwest and north-trending Paleozoic fabric. By the Mid-Jurassic the Malvinas Microplate had docked with the eastern margin of the Patagonian Shelf and was undergoing clockwise rotation between the Malvinas-Agulhas and Burwood Bank-Scotia Ridge dextral strike-slip systems. Rifting had now progressed southwestwards to the Pacific and north eastwards to the Colorado and Outeniqua Basins.

  5. Fire affects size and shape of Fabiana imbricata Shurblands in northwestern Patagonia

    NASA Astrophysics Data System (ADS)

    Oddi, Facundo; Ghermandi, Luciana

    2010-05-01

    Fire is a major environmental ecological agent acting in the landscape configuration and a factor that models vegetation in Mediterranean environments. Fire impacts differently in the landscape due to the intrinsic heterogeneity of the environments and the characteristics associated with each fire event. After fire, density of patches may be increased and the size of them may be reduced because fire generates areas of different successional stages. Landscape ecology seems to be the ideal theoretical approach to study the fire impact in fire prone environments. Landscape ecology has been greatly favoured by a significant progress in the last years of geographic information technologies (GIT) (remote sensing, GIS, GPS). The study area of this work is the San Ramon ranch (22,000 ha) located in Northwester Patagonia in the ecotone between the sub Antarctic forest in the West and the Patagonian steppe in the East. We studied sectors of the ranch with different fire recurrence in the last 40 years and we mapped Fabiana imbricata shrubland with GPS. This specie is a native shrub characteristic of Northwester Patagonia grasslands and its dynamic is not very known. Shrublands compete for the space with palatable grasses that are used for forage and livestock production, the main economic resource of the region. We analysed the mapped patches with GIS software, and we assessed landscape metrics to determine differences between sites with different fire recurrence. In the future we foresee the integrated use of satellite imagery with different resolution to add to GIS other important spatial variables (topography, hydrography, aspect, soil) to develop models that can explain landscape metrics, spatial configuration and the potential shrub invasion in the grassland.

  6. Cultural Transmission of Traditional Knowledge in two populations of North-western Patagonia

    PubMed Central

    Eyssartier, Cecilia; Ladio, Ana H; Lozada, Mariana

    2008-01-01

    Background In the present study we have investigated the cultural transmission of two types of traditional plant knowledge in two communities of North-western Patagonia, Argentina. In the Pilcaniyeu community, we studied the transmission of traditional knowledge related to horticultural practices in home-gardens, greenhouses and gardens; while in the community of Cuyin Manzano, we studied wild plant gathering customs. Methods Ethnobotanical fieldwork was conducted by means of semi-structured interviews, in which we investigated which plants are used, at what life history phase was learned, modes of transmission and who the principal transmitters were in childhood and adulthood. In both communities, each of this three aspects related to cultural transmission were categorized and the frequencies of each category were obtained. The total number of species recorded in each community was also calculated. Frequencies were analyzed with the Chi-square test of independence. Results and discussion In both communities, transmission of traditional plant knowledge begins at an early age, as a family custom, in which women play a predominant role. Wild plant use and horticultural knowledge continue to be learned during adulthood. This was particularly registered associated with horticultural learning, which receives greater influence from extension agents who are introducing new practices and technology. This outside influence, which implies novelty, could imply syncretism but also traditional knowledge loss. Conclusion Given the remarkable acculturation processes occurring at present in rural communities of Northwestern Patagonia, it might be of vital importance to document traditional knowledge of ancient practices. Moreover, it could be interesting to share our results with both populations in order to encourage participatory activities within the communities which could enhance traditional knowledge horizontal transmission, particularly among elder adults and youngsters

  7. The chronology of the Last Glacial Maximum and deglacial events in central Argentine Patagonia

    NASA Astrophysics Data System (ADS)

    Hein, Andrew S.; Hulton, Nicholas R. J.; Dunai, Tibor J.; Sugden, David E.; Kaplan, Michael R.; Xu, Sheng

    2010-05-01

    This paper evaluates the chronology of the last glacial cycle and deglaciation in the Lago Pueyrredón valley of central Patagonia, 47.5° S, Argentina. The valley was a major outlet of the former Patagonian Ice Sheet and the moraines that record its fluctuations are an important proxy record of climate change in southern South America. Such moraines are well-preserved in the Lago Pueyrredón valley owing in part to the semi-arid environment east of the mountain front. Here, we provide the first direct chronology for the age of the "Rio Blanco" moraine system by utilizing cosmogenic-nuclide surface exposure ages. Boulders on the moraines give 10Be exposure ages that indicate the Last Glacial Maximum (LGM) maximum extent occurred by 27-25 ka. Subsequent advances occurred at 23-22 ka, 20-18 ka, and ca. 18-17 ka. Initial deglaciation began after ca. 18-17 ka and was interrupted as evidenced by the Lago Columna moraines up-valley. Subsequently the outlet glaciers occupying both the Lago Pueyrredón basin (Chilean name: Lago Cochrane) and the Lago Buenos Aires basin (Chilean name: Lago General Carrera) to the north, rapidly retreated more than 80 km at around 16.5-15 ka. The timing of the LGM maximum extent and the onset of deglaciation occurred broadly synchronously throughout Patagonia. Deglaciation resulted in a series of interconnected glacier-dammed lakes in the region that initially drained toward the Atlantic Ocean and later drained to the Pacific Ocean as a consequence of disintegrating ice in the Andes.

  8. Historical records of mercury in southern latitudes over 1600 years: Lake Futalaufquen, Northern Patagonia.

    PubMed

    Daga, Romina; Ribeiro Guevara, Sergio; Pavlin, Majda; Rizzo, Andrea; Lojen, Sonja; Vreča, Polona; Horvat, Milena; Arribére, María

    2016-05-15

    Mercury is released to the environment from natural and anthropogenic sources, and through atmospheric transport is distributed globally. Lake Futalaufquen (42.8°S) is an oligotrophic lake located in Los Alerces National Park (Northern Patagonia), providing a remote and unpolluted study system. A lacustrine sedimentary sequence revealed 1600 years of Hg deposition, identifying natural baselines and marked peaks not correlated with long-range atmospheric transport. Organic matter and catchment erosion were discarded as Hg drivers. Natural background, pre-1300 CE Hg concentrations, ranged between 27 and 47 ng g(-1) (accumulation rates from 8 to 15μg m(-2) y(-1)). From 1300 CE on, the Hg background profile did not follow the generally increasing Hg pattern observed in both Southern and Northern Hemisphere since pre-industrial times. It was not until the last century that a 1.6-fold increase is observed in the Hg accumulation rate, considered among the lowest increments in southern South America. Noteworthy local/regional sources of Hg for this area, along with global transport, are forest fires and volcanic activity. Between approx. 1340 and 1510 CE, sharp increase in Hg concentration and accumulation rate (up to 204 ng g(-1) and 51 μg m(-2) y(-1), respectively) were clearly associated with extended fire episodes. Furthermore, high Hg peaks during the last 300 years were associated with volcanic eruptions in northernmost Patagonia together with fairly irregular fire episodes, caused by anthropogenic burning by settling population in the Andes. PMID:26938317

  9. Stable oxygen isotopes (delta18(O)) in Austrocedrus chilensis tree rings reflect climate variability in northwestern Patagonia, Argentina.

    PubMed

    Roig, F A; Siegwolf, R; Boninsegna, J A

    2006-11-01

    The stable oxygen isotope (delta (18)O) composition of Austrocedrus chilensis (D. Don) Endl. (Cupressaceae) tree rings potentially provide retrospective views of changes in environment and climate in the semi-arid lands of Patagonia. We report the development of the first annually resolved delta (18)O tree-ring chronology obtained from natural forests of the foothills of the northwestern Patagonian Andes. The isotope record spans between 1890 and 1994 AD. We explore the probable links between this record and the climate of the region. Air temperatures during summer conditions are significantly, but not strongly, inversely correlated with annual delta (18)O values from Austrocedrus tree rings. The strongest correlations are between the southern oscillation index (SOI) and the tree rings. The existence of millennial-age Austrocedrus trees in northern Patagonia provides interesting possibilities for examining these climate-related isotopic signals over most of the last 1,000 years.

  10. Detection of Salmonella enterica in Magellanic penguins (Spheniscus magellanicus) of Chilean Patagonia: evidences of inter-species transmission.

    PubMed

    Dougnac, C; Pardo, C; Meza, K; Arredondo, C; Blank, O; Abalos, P; Vidal, R; Fernandez, A; Fredes, F; Retamal, P

    2015-04-01

    Patagonia in southern South America is among the few world regions where direct human impact is still limited but progressively increasing, mainly represented by tourism, farming, fishing and mining activities. The sanitary condition of Patagonian wildlife is unknown, in spite of being critical for the assessment of anthropogenic effects there. The aim of this study was the characterization of Salmonella enterica strains isolated from wild colonies of Magellanic penguins (Spheniscus magellanicus) located in Magdalena Island and Otway Sound, in Chilean Patagonia. Eight isolates of Salmonella were found, belonging to Agona and Enteritidis serotypes, with an infection rate of 0·38%. Resistance to ampicillin, cefotaxime, ceftiofur and tetracycline antimicrobials were detected, and some of these strains showed genotypic similarity with Salmonella strains isolated from humans and gulls, suggesting inter-species transmission cycles and strengthening the role of penguins as sanitary sentinels in the Patagonian ecosystem.

  11. Detection of Salmonella enterica in Magellanic penguins (Spheniscus magellanicus) of Chilean Patagonia: evidences of inter-species transmission.

    PubMed

    Dougnac, C; Pardo, C; Meza, K; Arredondo, C; Blank, O; Abalos, P; Vidal, R; Fernandez, A; Fredes, F; Retamal, P

    2015-04-01

    Patagonia in southern South America is among the few world regions where direct human impact is still limited but progressively increasing, mainly represented by tourism, farming, fishing and mining activities. The sanitary condition of Patagonian wildlife is unknown, in spite of being critical for the assessment of anthropogenic effects there. The aim of this study was the characterization of Salmonella enterica strains isolated from wild colonies of Magellanic penguins (Spheniscus magellanicus) located in Magdalena Island and Otway Sound, in Chilean Patagonia. Eight isolates of Salmonella were found, belonging to Agona and Enteritidis serotypes, with an infection rate of 0·38%. Resistance to ampicillin, cefotaxime, ceftiofur and tetracycline antimicrobials were detected, and some of these strains showed genotypic similarity with Salmonella strains isolated from humans and gulls, suggesting inter-species transmission cycles and strengthening the role of penguins as sanitary sentinels in the Patagonian ecosystem. PMID:25148565

  12. Temporal Evolution of a Seismic Swarm at Chiles - Cerro Negro volcanic complex

    NASA Astrophysics Data System (ADS)

    Ruiz, Mario

    2015-04-01

    The increasing seismic activity in the area of the Chiles - Cerro Negro volcanic complex, located on the Ecuador-Colombian border, has been jointly monitored by the Instituto Geofisico - Ecuador and the Observatorio Vulcanologico y Sismologico de Pasto (OVSP), a division of the Servicio Geologico Colombiano. Since April 2013, three seismic swarms have been detected in this area, and more than 400.000 events have been recorded since November 2013. The largest and most recent swarm has a daily average of 3894 events between March and the 12th of December 2014. Currently a seismic network of 13 short- and broad-band stations (5 Colombian, 8 Ecuadorian) was deployed in this area. High quality epicenters of seismic events with magnitudes Ml>2.0, RMS<0.75 s, Gap < 180° and 10 or more phases are located in an area 1-4 km south of Chiles volcano with shallow depths (up to 14 km). Most events have magnitudes between 1.0 to 4.0. Fifteen events have magnitudes larger than 4.0 including an event that occurred on October 20, 2014. This event had a local magnitude of 5.7 and an oblique (strike-slip with some thrusting) focal mechanism. Waveforms and spectral patterns define these events as volcano-tectonic. However, events with moderate to large magnitudes (above 3.0) contain pronounced very-long-period components. Position time series recorded by a dual-frequency GPS receiver at the SE flank of Chiles show a slight departure from the normal tectonic trend beginning with the appearance of the last seismic swarm on or around September 30, 2014. This trend is subsequently punctuated by a sharp deformation transient related to the coseismic displacement of the October 20 event. After more than a year of very anomalous seismic activity and concurrent minor deformation, no evidence of surficial volcanic activity has been documented.

  13. Downwelling Far-Infrared Radiance Spectra Measured by FIRST at Cerro Toco, Chile

    NASA Astrophysics Data System (ADS)

    Mast, J. C.; Mlynczak, M. G.; Cageao, R.; Kratz, D. P.; Latvakoski, H.; Johnson, D. G.; Mlawer, E. J.; Turner, D. D.

    2015-12-01

    The Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument is a Fourier transform spectrometer developed by NASA Langley Research Center in collaboration with the Space Dynamics Laboratory and the Harvard-Smithsonian Center for Astrophysics. FIRST was initially developed for measuring the far-infrared portion of Earth's longwave spectrum as a balloon borne instrument and later was reconfigured to operate as a ground-based instrument. In its current ground-based configuration FIRST was deployed at 17500 ft on Cerro Toco, a mountain in the Atacama Desert of Chile, from August to October, 2009. There the integrated precipitable water (IPW) was as low as 0.02 cm. FIRST measurements from days with IPW between 0.024 and 0.035 cm during the campaign are presented here between 200 cm-1 and 800 cm-1. Significant spectral development in the far-IR is observed over the entire 200 cm-1 to 800 cm-1 band. Water vapor and temperature profiles from radiosonde and GVRP measurements are used as inputs to the AER Line-by-Line Radiative Transfer Model (LBLRTM) utilizing the AER v3.2 line parameter database. Uncertainties in both the measured and modeled radiances are accounted for in this study. The residual LBLRTM - FIRST is calculated to assess agreement between the measured and modeled spectra. Measured and model radiances generally agree to within the combined uncertainties for wavenumbers greater than 360 cm-1. At wavenumbers less than 360 cm-1 persistent troughs in the residual are present outside of the combined uncertainties. These features are present on different days and at different water vapor amounts. Possible solutions for these features are discussed.

  14. Shallow earthquake inhibits unrest near Chiles-Cerro Negro volcanoes, Ecuador-Colombian border

    NASA Astrophysics Data System (ADS)

    Ebmeier, Susanna K.; Elliott, John R.; Nocquet, Jean-Mathieu; Biggs, Juliet; Mothes, Patricia; Jarrín, Paúl; Yépez, Marco; Aguaiza, Santiago; Lundgren, Paul; Samsonov, Sergey V.

    2016-09-01

    Magma movement or reservoir pressurisation can drive swarms of low-magnitude volcano-tectonic earthquakes, as well as occasional larger earthquakes (>M5) on local tectonic faults. Earthquakes >M5 near volcanoes are challenging to interpret in terms of evolving volcanic hazard, but are often associated with eruptions, and in some cases enhance the ascent of magma. We present geodetic observations from the first episode of unrest known to have occurred near Chiles and Cerro Negro de Mayasquer volcanoes on the Ecuador-Colombian border. A swarm of volcano-tectonic seismicity in October 2014 culminated in a Mw 5.6 earthquake south of the volcanoes. Satellite radar data spanning this earthquake detect displacements that are consistent with dextral oblique slip on a reverse fault at depths of 1.4-3.4 km within a SSW-NNE trending fault zone that last ruptured in 1886. GPS station measurements capture ∼20 days of uplift before the earthquake, probably originating from a pressure source ∼10-15 km south of Volcán Chiles, at depths exceeding 13 km. After the Mw 5.6 earthquake, uplift ceased and the rate of seismicity began to decrease. Potential mechanisms for this decline in activity include a decrease in the rate of movement of magma into the shallow crust, possibly caused by the restriction of fluid pathways. Our observations demonstrate that an earthquake triggered during volcanic unrest can inhibit magmatic processes, and have implications for the hazard interpretation of the interactions between earthquakes and volcanoes.

  15. Planning and Analysis of Fractured Rock Injection Tests in the Cerro Brillador Underground Laboratory, Northern Chile

    NASA Astrophysics Data System (ADS)

    Fairley, J. P., Jr.; Oyarzún L, R.; Villegas, G.

    2015-12-01

    Early theories of fluid migration in unsaturated fractured rock hypothesized that matrix suction would dominate flow up to the point of matrix saturation. However, experiments in underground laboratories such as the ESF (Yucca Mountain, NV) have demonstrated that liquid water can migrate significant distances through fractures in an unsaturated porous medium, suggesting limited interaction between fractures and unsaturated matrix blocks and potentially rapid transmission of recharge to the sat- urated zone. Determining the conditions under which this rapid recharge may take place is an important factor in understanding deep percolation processes in arid areas with thick unsaturated zones. As part of an on-going, Fondecyt-funded project (award 11150587) to study mountain block hydrological processes in arid regions, we are plan- ning a series of in-situ fracture flow injection tests in the Cerro Brillador/Mina Escuela, an underground laboratory and teaching facility belonging to the Universidad la Serena, Chile. Planning for the tests is based on an analytical model and curve-matching method, originally developed to evaluate data from injection tests at Yucca Mountain (Fairley, J.P., 2010, WRR 46:W08542), that uses a known rate of liquid injection to a fracture (for example, from a packed-off section of borehole) and the observed rate of seepage discharging from the fracture to estimate effective fracture aperture, matrix sorptivity, fracture/matrix flow partitioning, and the wetted fracture/matrix interac- tion area between the injection and recovery points. We briefly review the analytical approach and its application to test planning and analysis, and describe the proposed tests and their goals.

  16. Mexicali aquifer and its relation with the Colorado river and the Cerro Prieto geothermal reservoir

    NASA Astrophysics Data System (ADS)

    Ramirez-Hernandez, J.; Reyes-Lopez, J. A.; Carreon-Diazconti, C.; Lazaro-Mancilla, O.

    2008-05-01

    Until some years ago the Colorado River has been the main recharge source of the Mexicali and the Imperial Valley aquifers. River discharge interruption after the constructions of dams upstream (i.e. Parker, Davis and Hoover) and the creation of great irrigation systems in both Valleys have modified their dynamics. Currently, the distribution of water recharge is the network of irrigation and drainage channels that distribute water to more than 500.000 ha. The chemical quality of the recharge water also has changed because the irrigation run-off water has become more mineralized. On the other hand, the intense steam exploitation of the Cerro Prieto geothermal reservoir has inverted the flow direction from the Volcano Lagoon area that until the 60s constituted the discharge zone of the aquifer and the geothermal reservoir. In this work, changes in the aquifer water recharge regime, the phreatic level and the water chemical quality are analyzed. It was found that after the reduction of the annual water extraction from aquifer up to 750X106 m3, the static levels have reached a dynamic balance that could be altered if water seepage from the irrigation channels, specially from the All American Channel, is reduced. The total dissolved solids (TDS) concentration has increased from 1000 ppm in 1970 to 1800 ppm in 2005. The water of recent infiltration, the gradual cooling of the shallowest strata of the geothermal reservoir, and the almost total disappearance of the hydrothermal surface manifestations are evidences of groundwater flow inversion. The new source of groundwater recharge due to seepage of evaporation disposal geothermal brine pond is documented. This pond incorporates water with a very different chemical composition to the groundwater system. Therefore, mineralization of the shallow aquifer layers and the soil contamination process are identified. It was concluded that the aquifer hydrodynamics in the Valley of Mexicali depends on the irrigation system more

  17. Regional and local networks of horizontal control, Cerro Prieto geothermal area

    USGS Publications Warehouse

    Massey, B.L.

    1979-01-01

    The Cerro Prieto geothermal area in the Mexicali Valley 30 km southeast of Mexicali, Baja California, is probably deforming due to (1) the extraction of large volumes of steam and hot water, and (2) active tectonism. Two networks of precise horizontal control were established in Mexicali Valley by the U.S. Geological Survey in 1977 - 1978 to measure both types of movement as they occur. These networks consisted of (1) a regional trilateration net brought into the mountain ranges west of the geothermal area from survey stations on an existing U.S. Geological Survey crustal-strain network north of the international border, and (2) a local net tied to stations in the regional net and encompassing the area of present and planned geothermal production. Survey lines in this net were selected to span areas of probable ground-surface movements in and around the geothermal area. Electronic distance measuring (EDM) instruments, operating with a modulated laser beam, were used to measure the distances between stations in both networks. The regional net was run using a highly precise long-range EDM instrument, helicopters for transportation of men and equipment to inaccessible stations on mountain peaks, and a fixed wing airplane flying along the line of sight. Precision of measurements with this complex long-range system approached 0-2 ppm of line length. The local net was measured with a medium-range EDM instrument requiring minimal ancillary equipment. Precision of measurements with this less complex system approached 3 ppm for the shorter line lengths. The detection and analysis of ground-surface movements resulting from tectonic strains or induced by geothermal fluid withdrawal is dependent on subsequent resurveys of these networks. ?? 1979.

  18. Public health surveillance after a volcanic eruption: lessons from Cerro Negro, Nicaragua, 1992.

    PubMed

    Malilay, J; Real, M G; Ramirez Vanegas, A; Noji, E; Sinks, T

    1996-09-01

    The eruption of the Cerro Negro volcano near León, Nicaragua, on 9 April 1992 distributed an estimated 1.7 million tons of ash over a 200 square kilometer area. An assessment was conducted to evaluate the health effects on approximately 300,000 residents, using routine data obtained by the national epidemiologic surveillance system. It was found that rates of visits to health care facilities for acute diarrheal and respiratory illnesses increased in two study communities, one within and one near the disaster zone. Specifically, visits for acute diarrhea were nearly 6 times more numerous than before the eruption in both communities, while visits for acute respiratory diseases were 3.6 times more frequent in Malpaisillo (the community near the disaster zone) and 6.0 times more frequent in Telica (the community within it). Most of the visits were for infants and children less than 5 years old. Increased diarrheal disease morbidity, which commonly occurs after volcanic eruptions, demands detailed investigation of the type and quality of water supplies following heavy ashfall. Ash-related respiratory problems should be further examined to determine the spectrum of such diseases and the timing of illness onsets among infants and other special population subgroups. Data collected on health conditions before and after an eruption by passive surveillance can be used to detect eruption-related morbidity. Systems already in place, such as Nicaragua's national epidemiologic surveillance system, can be modified or extended so as to increase their sensitivity to new cases and hence their ability to provide appropriate notification to medical relief agencies. PMID:8897722

  19. Structural control on geothermal circulation in the Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Argentina)

    NASA Astrophysics Data System (ADS)

    Giordano, Guido; Pinton, Annamaria; Cianfarra, Paola; Baez, Walter; Chiodi, Agostina; Viramonte, José; Norini, Gianluca; Groppelli, Gianluca

    2013-01-01

    The reconstruction of the stratigraphical-structural framework and the hydrogeology of geothermal areas is fundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermal fluids and for planning the exploitation of the field. The Cerro Tuzgle-Tocomar geothermal volcanic area (Puna plateau, Central Andes, NW Argentina) has a high geothermal potential. It is crossed by the active NW-SE trans-Andean tectonic lineament known as the Calama-Olacapato-Toro (COT) fault system, which favours a high secondary permeability testified by the presence of numerous springs. This study presents new stratigraphic and hydrogeological data on the geothermal field, together with the analysis from remote sensed image analysis of morphostructural evidences associated with the structural framework and active tectonics. Our data suggest that the main geothermal reservoir is located within or below the Pre-Palaeozoic-Ordovician basement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged by infiltration in the ridges above 4500 m a.s.l., where basement rocks are in outcrop. Below 4500 m a.s.l., the reservoir is covered by the low permeable Miocene-Quaternary units that allow a poor circulation of shallow groundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regional structures, particularly NW-SE COT-parallel lineaments, intersect with secondary structures, such as at the Tocomar field. Away from the main tectonic features, such as at the Cerro Tuzgle field, the less developed network of faults and fractures allows only a moderate upwelling of geothermal fluids and a mixing between hot and shallow cold waters. The integration of field-based and remote-sensing analyses at the Cerro Tuzgle-Tocomar area proved to be effective in approaching the prospection of remote geothermal fields, and in defining the conceptual model for geothermal circulation.

  20. Volcano-ice-sea interaction in the Cerro Santa Marta area, northwest James Ross Island, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Calabozo, Fernando M.; Strelin, Jorge A.; Orihashi, Yuji; Sumino, Hirochika; Keller, Randall A.

    2015-05-01

    We present here the results of detailed mapping, lithofacies analysis and stratigraphy of the Neogene James Ross Island Volcanic Group (Antarctic Peninsula) in the Cerro Santa Marta area (northwest of James Ross Island), in order to give constraints on the evolution of a glaciated volcanic island. Our field results included recognition and interpretation of seventeen volcanic and glacial lithofacies, together with their vertical and lateral arrangements, supported by four new unspiked K-Ar ages. This allowed us to conclude that the construction of the volcanic pile in this area took place during two main eruptive stages (Eruptive Stages 1 and 2), separated from the Cretaceous bedrock and from each other by two major glacial unconformities (U1 and U2). The U1 unconformity is related to Antarctic Peninsula Ice sheet expansion during the late Miocene (before 6.2 Ma) and deposition of glacial lithofacies in a glaciomarine setting. Following this glacial advance, Eruptive Stage 1 (6.2-4.6 Ma) volcanism started with subaerial extrusion of lava flows from an unrecognized vent north of the study area, with eruptions later fed from vent/s centered at Cerro Santa Marta volcano, where cinder cone deposits and a volcanic conduit/lava lake are preserved. These lava flows fed an extensive (> 7 km long) hyaloclastite delta system that was probably emplaced in a shallow marine environment. A second unconformity (U2) was related to expansion of a local ice cap, centered on James Ross Island, which truncated all the eruptive units of Eruptive Stage 1. Concomitant with glacier advance, renewed volcanic activity (Eruptive Stage 2) started after 4.6 Ma and volcanic products were fed again by Cerro Santa Marta vents. We infer that glaciovolcanic eruptions occurred under a moderately thin (~ 300 m) glacier, in good agreement with previous estimates of paleo-ice thickness for the James Ross Island area during the Pliocene.

  1. The Usefulness of Edible and Medicinal Fabaceae in Argentine and Chilean Patagonia: Environmental Availability and Other Sources of Supply

    PubMed Central

    Molares, Soledad; Ladio, Ana

    2012-01-01

    Fabaceae is of great ethnobotanical importance in indigenous and urban communities throughout the world. This work presents a revision of the use of Fabaceae as a food and/or medicinal resource in Argentine-Chilean Patagonia. It is based on a bibliographical analysis of 27 ethnobotanical sources and catalogues of regional flora. Approximately 234 wild species grow in Patagonia, mainly (60%) in arid environments, whilst the remainder belong to Sub-Antarctic forest. It was found that 12.8% (30 species), mainly woody, conspicuous plants, are collected for food or medicines. Most of the species used grow in arid environments. Cultivation and purchase/barter enrich the Fabaceae offer, bringing it up to a total of 63 species. The richness of native and exotic species, and the existence of multiple strategies for obtaining these plants, indicates hybridization of knowledge and practices. Only 22% of the total species used are mentioned in bothcontexts of food and medicine, reflecting low-use complementation. This study suggests a significant ecological appearance and a high level of availability in shops and exchange networks in Patagonia, highlighting the need to consider the full set of environmental and socioeconomic factors in research related to the use and cultural importance of plants in regional contexts. PMID:22194774

  2. Geomagnetic field for the past 5 Myr recorded in lava flows from British Columbia, Patagonia, and Mexico

    NASA Astrophysics Data System (ADS)

    Mejia, Victoria

    2005-11-01

    Paleosecular variation (PSV) and time averaged field (TAF) results recorded in lava flows younger than 5 million years are presented. The targeted areas of studies are several volcanic fields from British Columbia (mainly the Silverthrone, Garibaldi, and Wells Park volcanic fields), Southern Patagonia (the Pali-Aike volcanic field and Meseta Viscachas lavas), and Mexico (the Trans-Mexican volcanic belt and several volcanic areas in San Luis Potosi). The purpose of this investigation was to obtain high quality paleomagetic data suitable to test the presence or absence of permanent non dipolar components of the field that have been interpreted from studies carried out with less rigor. The mean directions in the areas of British Columbia and Patagonia (roughly at 50° N and 50° S latitude) coincide with the expected geocentric axial dipole (GAD) at these areas. The presence of a quadrupolar component of the field is difficult to discard because it is expected to produce only about 1° shallower inclinations. The mean direction in the area of Mexico coincides with a GAD plus a 5% quadrupole. The VGP scatter in the three areas of study coincides with Model G. The asymmetry between the northern and southern hemisphere of the present magnetic field and particularly the 20° inclination anomaly relative to GAD in Patagonia, are not observed in the paleomagnetic data obtained, implying that the present field configuration is relatively recent. The results confirm that axial components prevail in the time-averaged field.

  3. TITAN2D simulations of pyroclastic flows at Cerro Machín Volcano, Colombia: Hazard implications

    NASA Astrophysics Data System (ADS)

    Murcia, H. F.; Sheridan, M. F.; Macías, J. L.; Cortés, G. P.

    2010-03-01

    Cerro Machín is a dacitic tuff ring located in the central part of the Colombian Andes. It lies at the southern end of the Cerro Bravo-Cerro Machín volcanic belt. This volcano has experienced at least six major explosive eruptions during the last 5000 years. These eruptions have generated pyroclastic flows associated with Plinian activity that have traveled up to 8 km from the crater, and pyroclastic flows associated with Vulcanian activity with shorter runouts of 5 km from the source. Today, some 21,000 people live within a 8 km radius of Cerro Machín. The volcano is active with fumaroles and has shown increasing seismic activity since 2004, and therefore represents a potentially increasing threat to the local population. To evaluate the possible effects of future eruptions that may generate pyroclastic density currents controlled by granular flow dynamics we performed flow simulations with the TITAN2D code. These simulations were run in all directions around the volcano, using the input parameters of the largest eruption reported. The results show that an eruption of 0.3 km 3 of pyroclastic flows from a collapsing Plinian column would travel up to 9 km from the vent, emplacing a deposit thicker than 60 m within the Toche River valley. Deposits >45 m thick can be expected in the valleys of San Juan, Santa Marta, and Azufral creeks, while 30 m thick deposits could accumulate within the drainages of the Tochecito, Bermellón, and Coello Rivers. A minimum area of 56 km 2 could be affected directly by this kind of eruption. In comparison, Vulcanian column-collapse pyroclastic flows of 0.1 km 3 would travel up to 6 km from the vent depositing >45 m thick debris inside the Toche River valley and more than 30 m inside the valleys of San Juan, Santa Marta, and Azufral creeks. The minimum area that could be affected directly by this kind of eruption is 33 km 2. The distribution and thickness of the deposits obtained by these simulations are consistent with the hazard

  4. Production induced boiling and cold water entry in the Cerro Prieto geothermal reservoir indicated by chemical and physical measurements

    SciTech Connect

    Grant, M.A.; Truesdell, A.H.; Manon, A.

    1981-01-01

    Chemical and physical data suggest that the relatively shallow western part of the Cerro Prieto reservoir is bounded below by low permeability rocks, and above and at the sides by an interface with cooler water. There is no continuous permeability barrier around or immediately above the reservoir. Permeability within the reservoir is dominantly intergranular. Mixture with cooler water rather than boiling is the dominant cooling process in the natural state, and production causes displacement of hot water by cooler water, not by vapor. Local boiling occurs near most wells in response to pressure decreases, but no general vapor zone has formed.

  5. Movement of geothermal fluid in the Cerro Prieto field as determined from well log and reservoir engineering data

    SciTech Connect

    Halfman, S.E.; Lippmann, M.J.; Zelwer, R.

    1982-01-01

    A hydrogeologic model of the Cerro Prieto geothermal field in its undisturbed state, developed on the basis of well log and reservoir engineering data, is discussed. According to this model, geothermal fluid enters the field from the east through a deep (>10,000 ft) sandstone aquifer which is overlain by a thick shale unit which locally prevents the upward migration of the fluid. As it flows westward, the fluid gradually rises through faults and sandy gaps in the shale unit. Eventually, some of the fluid leaks to the surface in the western part of the field, while the rest mixes with surrounding colder waters.

  6. Some aspects of the response of geothermal reservoirs to brine reinjection with application to the Cerro Prieto Field

    SciTech Connect

    Tsang, C.F.; Bodvarsson, G.S.; Lippmann, M.J.; Rivera, J.R.

    1980-01-01

    In this paper, preliminary results of two reinjection studies will be described: (1) Initial investigation of several possible reinjection patterns for the Cerro Prieto geothermal field have been made based on a method developed by Gringarten and Sauty (1975). The resulting data show what may be expected from different reinjection schemes and may provide useful guidelines for the eventual choice of an optimal well arrangement. A numerical model was used to study the injection pressure expected when colder water is injected into a hot reservoir. 3 refs.

  7. Production induced boiling and cold water entry in the Cerro Prieto geothermal reservoir indicated by chemical and physical measurements

    USGS Publications Warehouse

    Grant, M.A.; Truesdell, A.H.; Manon, M.A.

    1984-01-01

    Chemical and physical data suggest that the relatively shallow, western part of the Cerro Prieto reservoir is bounded below by low permeability rocks, and above and at the sides by an interface with cooler water. There is no continuous permeability barrier around or immediately above the reservoir. Permeability within the reservoir is dominantly intergranular. Mixture with cooler water rather than boiling is the dominant cooling process in the natural state, and production causes displacement of hot water by cooler water, not by vapour. Local boiling occurs near most wells in response to pressure decreases, but no general vapour zone has formed. ?? 1984.

  8. Production induced boiling and cold water entry in the Cerro Prieto geothermal reservoir indicated by chemical and physical measurements

    SciTech Connect

    Grant, M.A.; Manon, A.; Truesdell, A.H.

    1984-01-01

    Chemical and physical data suggest that the relatively shallow, western part of the Cerro Prieto reservoir is bounded below by low permeability rocks, and above and at the sides by an interface with cooler water. There is no continuous permeability barrier around or immediately above the reservoir. Permeability within the reservoir is dominantly intergranular. Mixture with cooler water rather than boiling is the dominant cooling process in the natural state, and production causes displacement of hot water by cooler water, not by vapour. Local boiling occurs near most wells in response to pressure decreases, but no general vapour zone has formed.

  9. Fault Length Vs Fault Displacement Evaluation In The Case Of Cerro Prieto Pull-Apart Basin (Baja California, Mexico) Subsidence

    NASA Astrophysics Data System (ADS)

    Glowacka, E.; Sarychikhina, O.; Nava Pichardo, F. A.; Farfan, F.; Garcia Arthur, M. A.; Orozco, L.; Brassea, J.

    2013-05-01

    The Cerro Prieto pull-apart basin is located in the southern part of San Andreas Fault system, and is characterized by high seismicity, recent volcanism, tectonic deformation and hydrothermal activity (Lomnitz et al, 1970; Elders et al., 1984; Suárez-Vidal et al., 2008). Since the Cerro Prieto geothermal field production started, in 1973, significant subsidence increase was observed (Glowacka and Nava, 1996, Glowacka et al., 1999), and a relation between fluid extraction rate and subsidence rate has been suggested (op. cit.). Analysis of existing deformation data (Glowacka et al., 1999, 2005, Sarychikhina 2011) points to the fact that, although the extraction changes influence the subsidence rate, the tectonic faults control the spatial extent of the observed subsidence. Tectonic faults act as water barriers in the direction perpendicular to the fault, and/or separate regions with different compaction, and as effect the significant part of the subsidence is released as vertical displacement on the ground surface along fault rupture. These faults ruptures cause damages to roads and irrigation canals and water leakage. Since 1996, a network of geotechnical instruments has operated in the Mexicali Valley, for continuous recording of deformation phenomena. To date, the network (REDECVAM: Mexicali Valley Crustal Strain Measurement Array) includes two crackmeters and eight tiltmeters installed on, or very close to, the main faults; all instruments have sampling intervals in the 1 to 20 minutes range. Additionally, there are benchmarks for measuring vertical fault displacements for which readings are recorded every 3 months. Since the crackmeter measures vertical displacement on the fault at one place only, the question appears: can we use the crackmeter data to evaluate how long is the lenth of the fractured fault, and how quickly it grows, so we can know where we can expect fractures in the canals or roads? We used the Wells and Coppersmith (1994) relations between

  10. Noble gas composition of subcontinental lithospheric mantle: An extensively degassed reservoir beneath Southern Patagonia

    NASA Astrophysics Data System (ADS)

    Jalowitzki, Tiago; Sumino, Hirochika; Conceição, Rommulo V.; Orihashi, Yuji; Nagao, Keisuke; Bertotto, Gustavo W.; Balbinot, Eduardo; Schilling, Manuel E.; Gervasoni, Fernanda

    2016-09-01

    Patagonia, in the Southern Andes, is one of the few locations where interactions between the oceanic and continental lithosphere can be studied due to subduction of an active spreading ridge beneath the continent. In order to characterize the noble gas composition of Patagonian subcontinental lithospheric mantle (SCLM), we present the first noble gas data alongside new lithophile (Sr-Nd-Pb) isotopic data for mantle xenoliths from Pali-Aike Volcanic Field and Gobernador Gregores, Southern Patagonia. Based on noble gas isotopic compositions, Pali-Aike mantle xenoliths represent intrinsic SCLM with higher (U + Th + K)/(3He, 22Ne, 36Ar) ratios than the mid-ocean ridge basalt (MORB) source. This reservoir shows slightly radiogenic helium (3He/4He = 6.84-6.90 RA), coupled with a strongly nucleogenic neon signature (mantle source 21Ne/22Ne = 0.085-0.094). The 40Ar/36Ar ratios vary from a near-atmospheric ratio of 510 up to 17700, with mantle source 40Ar/36Ar between 31100-6800+9400 and 54000-9600+14200. In addition, the 3He/22Ne ratios for the local SCLM endmember, at 12.03 ± 0.15 to 13.66 ± 0.37, are higher than depleted MORBs, at 3He/22Ne = 8.31-9.75. Although asthenospheric mantle upwelling through the Patagonian slab window would result in a MORB-like metasomatism after collision of the South Chile Ridge with the Chile trench ca. 14 Ma, this mantle reservoir could have remained unhomogenized after rapid passage and northward migration of the Chile Triple Junction. The mantle endmember xenon isotopic ratios of Pali-Aike mantle xenoliths, which is first defined for any SCLM-derived samples, show values indistinguishable from the MORB source (129Xe/132Xe =1.0833-0.0053+0.0216 and 136Xe/132Xe =0.3761-0.0034+0.0246). The noble gas component observed in Gobernador Gregores mantle xenoliths is characterized by isotopic compositions in the MORB range in terms of helium (3He/4He = 7.17-7.37 RA), but with slightly nucleogenic neon (mantle source 21Ne/22Ne = 0.065-0.079). We

  11. Late Holocene environmental changes in a mesotidal estuary from Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Espinosa, Marcela; Escandell, Alejandra; Velez Agudelo, Camilo

    2016-04-01

    Two sediment records from the lower valley of Negro River, Patagonia, Argentina (41°01´S; 62°47'W) spanning for the last 2000 cal yrs BP were analyzed according to diatoms and sediments contents. The river originates at the junction of the Neuquén and the Limay Rivers, Northern Patagonia, and discharges more than 1000 m3/s to the South Atlantic Ocean. Mesotidal conditions dominate at the inlet (2.95 m) affecting the lower valley (about 20 km) where salinity decreases drastically in the last 2 km. Fossil diatom assemblages and grain size were studied from two cores located at 1.5 km (Villarino site) and 12 km (Criadero site) from the inlet. Samples for modern diatom analyses were collected from the littoral zone at eleven sites along the river. Physical and chemical variables were quantified representing the maximum heterogeneity along the aquatic environment. Turbidity, salinity, conductivity, pH and temperature data were obtained in situ during summer and winter. In addition, a surface sediment sample was taken for grain size analysis and organic matter content, and water samples were taken to analyze nutrients and major ions following standard methods. The diatom content of modern sediment samples were studied in order to achieve ecological information useful as modern analogous for Patagonian rivers. Diatom zones were characterized by constrained incremental sum of squares cluster analysis (single linkage, Euclidean distance) in the fossil sequences. Fossil and modern diatom assemblages were compared with Detrended Correspondence Analysis (DCA). A total of 77 samples (modern and fossils) were analyzed and more than 200 taxa were identified. Diatom assemblages showed distinct abundance patterns in relation to salinity with a shift from communities dominated by marine/brackish taxa in lower sites to communities dominated by freshwater taxa in the middle and upper course of the river. The record of Criadero core (12 km from the inlet) began 2000 cal yrs BP with

  12. Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina

    NASA Astrophysics Data System (ADS)

    Rossello, E. A.; Massabie, A. C.; López-Gamundí, O. R.; Cobbold, P. R.; Gapais, D.

    1997-12-01

    Paleozoic sediments are present in three regions in eastern central Argentina: (1) the Sierras Australes of Buenos Aires, (2) Sierras Septentrionales of Buenos Aires and (3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation. Exposures of these rocks are scattered, variably deformed, and isolated by younger sediments deposited in basins related to the Mesozoic through Tertiary opening of the South Atlantic such as the offshore Colorado Basin. The Sierras Australes of Buenos Aires outcrops are the best preserved. They are mostly located along the Sierras Australes foldbelt, with minor outliers distributed in the adjacent Claromec-basin. The Tunas Formation (early-early late? Permian) is the uppermost unit of the Pillahuincó Group (late Carboniferous-Permian) and is crucial to the understanding of the tectono-sedimentary evolution of the region during the late Paleozoic. The underlying units of the Pillahuincó Group (Sauce Grande, Piedra Azul and Bonete Formations) exhibit a depositional and compositional history characterized by glaciomarine sedimentation and postglacial transgression. They are also characterized by rather uniform quartz-rich compositions indicative of a cratonic provenance from the La Plata craton to the NE. In contrast, the sandstone-rich Tunas Formation has low quartz contents, and abundant volcanic and metasedimentary fragments; paleocurrents are consistently from the SW. Glassrich tuffs are interbedded with sandstone in the upper half of the Tunas Formation. The age of the deformation in the Sierras Australes is Permian and early-middle Triassic. This is based on metamorphic events indicated by formation of illite at 282 ± 3 Ma, 273 ± 8 Ma, 265 ± 3 Ma, and 260 ± 3 Ma ( {K}/{Ar} illite) in the Silurian Curamalal Group. Evidence of syntectonic magmatism is provided by a radiometric date of 245 ± 12 Ma ( {K}/{Ar} hornblende) for the López Lecube Granite

  13. Late Holocene environmental changes recorded in the sediments of Lago Thompson, Northern Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Fagel, Nathalie; Nuttin, Laurence; Bertrand, Sébastien; Borgniet, Geoffrey; Schmidt, Sabine; Araneda, Alberto; Torrejon, Fernando; Urrutia, Roberto

    2010-05-01

    We investigate the sedimentary record of Lago Thompson, a small lake (area 1.1 km2, watershed ~8 km2) located at an elevation of 750 masl in Northern Chilean Patagonia (45.38 °S, 71.47°W). At Present, the climate conditions around the lake are relatively dry, with annual precipitation averaging 500 mm. The goal of this study is to evaluate the natural climate variability over the Last Millennium in Northern Chilean Patagonia and its impact on the environment. The coring site was selected after a bathymetric survey using an echo-sounder. Several short cores were retrieved in 2008 using an Uwitec gravity corer: the length of the cores ranges between 124 and 132 cm. The preliminary age model is based on 4 AMS radiocarbon ages measured on bulk sediment and organic macro-remains. The radiocarbon ages demonstrate that the sediment cores cover the last 850 to 950 years. This sediment record, which is characterized by accumulation rates ranging between 1 and 3 mm/yr, can therefore be studied at decennial to centennial resolution. To reconstruct past changes in climate and the environment, we conducted a multiproxy study combining sedimentological, mineralogical and geochemical analyses (LOI 105, 550 and 950°C, biogenic silica content, magnetic susceptibility, tephrostratigraphy, bulk organic geochemistry, bulk mineralogy by X-ray diffraction, and inorganic geochemistry by ITRAX core scanner and ICP-AES). Visual descriptions and X-ray radiographies demonstrate that the sediment record is relatively undisturbed. The sediment is composed of light brown organic-rich clayey material. The lower part of the core (below 75 cm) is finely laminated whereas the upper part is more homogeneous. Magnetic susceptibility values highlight two tephra layers that represent explosive eruptions of volcanoes from the southern volcanic zone of Chile (Hudson, Cay, or Macá volcanoes). The biogenic silica content of the sediment retrieved in Lago Thompson is high (40 to 80%), and probably

  14. Enhanced Southern Westerly Activity During the Last Glacial Interglacial Transition in SW Patagonia

    NASA Astrophysics Data System (ADS)

    Moreno, P. I.; Villa-Martinez, R. P.; Cardenas, M. L.; Moy, C. M.

    2008-12-01

    Much of the ongoing controversy regarding synchrony or bipolar asynchrony has centered on the timing and structure of temperature changes during the Last Glacial Interglacial Transition (LGIT) in the southern mid- latitudes, in particular the Patagonian region (40°-56°S) of South America. South America is the only continuous continental landmass in the Southern Hemisphere that intersects the entire westerly wind belt and lies in the critical climatic interface between mid- to high latitudes. The region between 50°- 55°S is of particular interest considering its proximity to the polar front and the southern margin of the westerly winds, and the possibility of monitoring paleoclimate changes at or near this important oceanic- atmospheric boundary. Present and past climate studies, including modeling simulations, have emphasized that interactions between changes in the Antarctic Circumpolar Current, the southern westerly winds, sea ice, and the polar front are important drivers for deep ocean circulation changes, variations in atmospheric CO2, and equator-to-pole temperature and pressure gradients. Yet, the behavior of the westerly winds and the adjacent Southern Ocean during the LGIT is still poorly understood despite their fundamental influence on modern hemispheric and global climate. In this study we compare sediment cores from small closed-basin lakes and a bog from the Ultima Esperanza area of SW Patagonia (52°S), an area affected solely by the southern westerlies. Lake sediment cores from three lakes show lacustrine sedimentation over the last 17,000 years. In contrast, the Dumestre bog shows subaerial peat deposition since 15 ka interrupted by a prominent lacustrine phase dated between 14.5-11.5 ka. During this interval palynological records indicate the preponderance of cold-resistant herbs, along with aquatic taxa, followed by a rapid expansion of Nothofagus woodlands/forests, a lake regressive phase in Dumestre, and disappearance of laminated calcite

  15. The origin of pyroxene megacrysts in alkali basalts from Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Ntaflos, Theo; Bjerg, Ernesto; Gregoire, Michel

    2015-04-01

    Clinopyroxene and othopyroxene megacrysts have been brought to the surface together with mantle xenoliths by Neogene and Quaternary alkali basalts from the back-arc environment in Patagonia. The collected megacrysts are from Pali Aike Volcanic Field (El Ruido, maar) and the Gobernador Gregores cinder cone in southern Patagonia, and from the Laguna Fria outcrop in northern Patagonia. The most frequent pyroxene megacrysts are augites (twelve samples), one diopside and two enstatites. Enstatites were found in El Ruido and Laguna Fria. The augites are magnesian rich with MG# that vary from 73.1 to 75.3 in Gobernador Gregores, fairly constant at 76.6 in El Ruido and from 74.0 to 78.6 in Laguna Fria. The MG# of diopside is 91.1 and the two enstatites, one from Gobernador Gregores and the other from Laguna Fria, have MG#s 78.3 and 82.5 respectively. The Na2O and TiO2 contents in augites vary from 0.99 to 2.06 wt% and from 0.69 to 1.86 wt% repectively. Systematically, the Gobernador Gregores augites have the highest TiO2 and Na2O contents. The primitive mantle normalized REE abundances have concave upwards patterns. While the Gobernador Gregores augites have (La/Y)N ratios that vary from 2.4 to 3.8, the El Ruido and Laguna Fria augites have ratios that vary from 0.91 to 1.74. The enstatites from both localities have similar MREE but they differ markedly in their LREE (in GG LaN=0.04xPM and in El Ruido LAN=0.14) and in their HREE (in Gobernador Gregores YbN=0.25 and in El Ruido YBN=0.6). The AL IV/AL VI in all augites is high and vary from 0.75 to1.07 suggesting that they have been formed at - more than 30 km depth. The calculated minimum equilibrium temperatures vary between 1260 to 1320°C. Pressure estimates for augites, with exception of the El Ruido augites with a pressure of 1.65 GP, vary between 1.27 and 1.47 GPa. Especially the pressure estimates from Gobernador Gregores megacrysts vary within a small interval from 1.29 to 1.36 GPa indicating an isobaric

  16. Paleomagnetism in the Determination of the Emplacement Temperature of Cerro Colorado Tuff Cone, El Pinacate Volcanic Field, Sonora, Mexico.

    NASA Astrophysics Data System (ADS)

    Rodriguez Trejo, A.; Alva-Valdivia, L. M.; Vidal Solano, J. R.; Garcia Amador, B.; Gonzalez-Rangel, J. A.

    2014-12-01

    Cerro Colorado Maar is located at the World Heritage Site, biosphere reserve El Pinacate and Gran Desierto del Altar, at the NNW region of Sonora, Mexico (in El Pinacate Volcanic Field). It is a tuff cone, about 1 km diameter, result of several phreatomagmatic episodes during the late Quaternary. We report paleomagnetic and rock magnetic properties from fusiform volcanic bombs obtained from the borders of Cerro Colorado. This study is based in the thermoremanent magnetization TRM normally acquired by volcanic rocks, which can be used to estimate the emplacement temperature range. We performed the experiments on 20 lithic fragments (10 cm to 20 cm approximately), taking 6-8 paleomagnetic cores from each. Rock magnetic experiments (magnetic susceptibility vs. temperature (k-T), hysteresis curves and FORC analysis, shows that the main magnetic mineral carriers of magnetization are titanomagnetite and titanohematite in different levels of intergrowth. The k-T curves suggest in many cases, only one magnetic phase, but also in other cases a second magnetic phase. Thermal demagnetization was used to demagnetize the specimens in detailed short steps and make a well-defined emplacement temperature determination ranges. We found that temperature emplacement determination range for these two magnetic phases is between 350-450 °C, and 550-580 °C, respectively. These results are consistent with those expected in an eruption of Surtsey type, showing a distinct volcanic activity compared to the other craters from El Pinacate volcanic field.

  17. Gases in steam from Cerro Prieto geothermal wells with a discussion of steam/gas ratio measurements

    USGS Publications Warehouse

    Nehring, N.L.; Fausto, L.J.J.

    1979-01-01

    As part of a joint USGS-CFE geochemical study of Cerro Prieto, steam samples were collected for gas analyses in April, 1977. Analyses of the major gas components of the steam were made by wet chemistry (for H2O,CO2,H2S and NH3) and by gas chromatography (He,H2,Ar,O2,N2 and hydrocarbons). The hydrocarbon gases in Cerro Prieto steam closely resemble hydrocarbons in steam from Larderello, Italy and The Geysers, California which, although they are vapor-dominated rather than hot-water geothermal systems, also have sedimentary aquifer rocks. These sedimentary geothermal hydrocarbons are characterized by the presence of branched C4-6 compounds and a lack of unsaturated compounds other than benzene. Relatively large amounts of benzene may be characteristic of high-temperature geothermal systems. All hydrocarbons in these gases other than methane most probably originate from the thermal metamorphosis of organic matter contained in the sediments. ?? 1979.

  18. Storm Water Quality in Los Alamos Canyon following the Cerro Grande Fire

    SciTech Connect

    M. Johansen; B. Enz; B. Gallaher; K. Mullen; D. Kraig

    2001-04-01

    In May 2000, the Cerro Grande Fire burned about 7400 acres of forest on the Los Alamos National Laboratory (LANL) and about 10,000 acres in watersheds above LANL on Santa Fe National Forest lands. The resulting burned landscapes raised concerns of increased storm water runoff and transport of contaminants by runoff in the canyons traversing LANL. On June 2 and 3, 2000, rain fell in the Los Alamos Canyon watershed generating storm water runoff in the canyon bottom. This event was important in that it was the first significant runoff on LANL following the fire and occurred in a canyon containing known legacy waste sites. Samples from this runoff were analyzed for radionuclide, metal, inorganic, and organic constituents. Results show radionuclide concentrations at or below previous (pre-fire) maximum levels at locations on LANL and downstream. However, greater concentrations of some fallout-associated radionuclides (cesium-137 and strontium-90) were seen arriving on LANL from upstream areas compared to pre-fire conditions. Tests indicate most of the radionuclides in the samples were bound to sediments, not dissolved in water. Most radionuclide concentrations in sediments were below LANL Screening Action Levels, with cesium-137 and strontium-90 as exceptions. Most radionuclide concentrations in samples taken at LANL's downstream boundary were greater than those taken upstream, indicating the presence of contributing sources on LANL. For comparison purposes, doses were calculated on a mrem per liter of unfiltered water basis for 11 radionuclides commonly associated with atmospheric fallout and with LANL operations. The maximum dose was 0.094 mrem per liter unfiltered water and was largely associated with plutonium-239/240. In contrast, all filtered samples had total doses less than 0.001 mrem per liter. Compared to past data, potential doses were not increased by the fire during this initial runoff event. Of the 25 metals tested for, seven were above pre-fire levels

  19. A process for fire-related debris flow initiation, Cerro Grande fire, New Mexico

    USGS Publications Warehouse

    Cannon, S.H.; Bigio, E.R.; Mine, E.

    2001-01-01

    In this study we examine factors that pertain to the generation of debris flows from a basin recently burned by wildfire. Throughout the summer 2000 thunderstorm season, we monitored rain gauges, channel cross-sections, hillslope transects, and nine sediment-runoff traps deployed in a steep, 0??15 km2 basin burned by the May 2000 Cerro Grande fire in New Mexico. Debris flows were triggered in the monitored basin during a rainstorm on July 16, 2000, in response to a maximum 30 min rainfall intensity of 31 mm h-1 (return period of approximately 2 years). Eleven other storms occurred before and after the July storm; these storms resulted in significant runoff, but did not generate debris flows. The debris flows generated by the July 16 storm initiated on a broad, open hillslope as levee-lined rills. The levees were composed of gravel- and cobble-sized material supported by an abundant fine-grained matrix. Debris-flow deposits were observed only on the hillslopes and in the first and second-order drainages of the monitored basin. No significant amounts of channel incision were measured following the passage of the debris flows, indicating that most of the material in the flows originated from the hillslopes. Sediment-runoff concentrations of between 0??23 and 0??81 kg 1-1 (with a mean of 0-42 kg 1-1) were measured from the hillslope traps following the debris-flow-producing storm. These concentrations, however, were not unique to the July 16 storm. The materials entrained by the July 16 storm contained a higher proportion of silt- plus clay-sized materials in the <2 mm fraction than the materials collected from storms that produced comparable sediment-runoff concentrations but not debris flows. The difference in materials demonstrates the critical role of the availability of fine-grained wood ash mantling the hillslopes in the runoff-dominated generation of post-wildfire debris flows. The highest sediment-runoff concentrations, again not unique to debris

  20. The last millenia sedimentary record of Lake Esponja, Northern Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Fagel, Nathalie; Araneda, Alberto; Alvarez, Denisse; Perfetti-Bolaño, Alessandra; Billy, Isabelle; Martinez, Philippe; Schmidt, Sabine; Urrutia, Roberto

    2016-04-01

    We evaluate the climate and environmental variability of Northern Chilean Patagonia during the Last Millennia, using a multi-proxy analysis of a sediment core from Lago Esponja (45°09'S, 72°08'W). The lake is located in the region of Aysen del General Carlos Ibanez del Campo, in NW Patagonia. The study focuses on a multiproxy analysis of sedimentary records. The longest core (150 cm long) was collected in 2014 at 40 m depth. The sediment, which is composed of light brown organic-rich clayey silt, was analyzed for sedimentology (grain size, magnetic susceptibility organic matter and biogenic silica content), mineralogy (X-ray diffraction) and geochemistry (elemental and isotopic analyses of C and N, XRF core-scaner at 1 mm resolution). The radiocarbon ages, measured on 3 macro-remains, demonstrate that the core covers the last 6.700 years. The sedimentation rate ranges between 0.1 mm/yr in the lower section (100-150 cm) and 0.4 mm/yr in the upper meter. Visual descriptions and Scopix radiographies show that the sediment record is finely laminated except a massive decimetric coarser and darker layer corresponding to a tephra (estimated age 700AD±50). Magnetic susceptibility (confirmed by scopix radiographies) highlights the presence of 8 additional millimetric tephra layers. The biogenic silica content of the sediment is low (mean 5%). Diatom assemblage is dominated by benthic and acidophilous species, with high saprobic values. None marked changes were observed regarding the dynamic of the lake. The high organic matter content (mean 15%) and its high C/N ratio (12.7) throughout the core indicate inputs of allochtonous and terrestrial organic matter. Such parameters present high sediment variability also marked by changes in the chemical composition. The laminations reflect changes in the allochtonous sedimentary inputs, with high terrestrial inputs during wetter conditions in relation with the Westerlies. The sedimentary records of Lago Esponja will be compared

  1. Neogene kinematic history of Nazca-Antarctic-Phoenix slab windows beneath Patagonia and the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Breitsprecher, Katrin; Thorkelson, Derek J.

    2009-01-01

    The Patagonian slab window is a subsurface tectonic feature resulting from subduction of the Nazca-Antarctic spreading-ridge system (Chile Rise) beneath southern South America. The geometry of the slab window had not been rigorously defined, in part because of the complex nature of the history of ridge subduction in the southeast Pacific region, which includes four interrelated spreading-ridge systems since 20 Ma: first, the Nazca-Phoenix ridge beneath South America, then simultaneous subduction of the Nazca-Antarctic and the northern Phoenix-Antarctic spreading-ridge systems beneath South America, and the southern Phoenix-Antarctic spreading-ridge system beneath Antarctica. Spreading-ridge paleo-geographies and rotation poles for all relevant plate pairs (Nazca, Phoenix, Antarctic, South America) are available from 20 Ma onward, and form the mathematical basis of our kinematic reconstruction of the geometry of the Patagonia and Antarctic slab windows through Neogene time. At approximately 18 Ma, the Nazca-Phoenix-Antarctic oceanic (ridge-ridge-ridge) triple junction enters the South American trench; we recognize this condition as an unstable quadruple junction. Heat flow at this junction and for some distance beneath the forearc would be considerably higher than is generally recognized in cases of ridge subduction. From 16 Ma onward, the geometry of the Patagonia slab window developed from the subduction of the trailing arms of the former oceanic triple junction. The majority of the slab window's areal extent and geometry is controlled by the highly oblique (near-parallel) subduction angle of the Nazca-Antarctic ridge system, and by the high contrast in relative convergence rates between these two plates relative to South America. The very slow convergence rate of the Antarctic slab is manifested by the shallow levels achieved by the slab edge (< 45 km); thus no point on the Antarctic slab is sufficiently deep to generate "normal" mantle-derived arc-type magmas

  2. History of views on the relative positions of Antarctica and South America: A 100-year tango between Patagonia and the Antarctic Peninsula

    USGS Publications Warehouse

    Miller, H.

    2007-01-01

    Discussion of continental drift around Antarctica began nearly 100 years ago. While the Gondwana connections of Antarctica to Africa and Australia have been well defined for decades, the relative pre-drift positions of the Antarctic Peninsula and Patagonia continue to be subjects of controversy. Certainly older figures, which showed a paleo-position of the Peninsula crossing over continental crust of the Falkland Plateau or even South Africa or Patagonia, are out of consideration now. But contradictory opinions remain over the relative paleo-position of the Peninsula as a more or less straight prolongation of the Patagonian Andes, versus a position parallel to Patagonia along the Pacific coast. Geological reasons are found for both opinions, but geophysical observations on the adjacent ocean floors, particularly the evolution of the Weddell Sea crust, speak for the last-mentioned reconstruction.

  3. Paleomagnetism of the Quaternary Cerro Prieto, Crater Elegante, and Salton Buttes volcanic domes in the northern part of the Gulf of California rhombochasm

    SciTech Connect

    de Boer, J.

    1980-02-01

    Deviating thermomagnetic directions in volcanics representing the second and fifth or sixth pulse of volcanism suggest that the Cerro Prieto volcano originated about 110,000 years B.P. and continued to be active intermittently until about 10,000 years ago.

  4. An integrated model for the natural flow regime in the Cerro Prieto hydrothermal system based upon petrological and isotope geochemical criteria

    SciTech Connect

    Elders, W.A.; Williams, A.E.; Hoagland, J..

    1981-01-01

    Studies of cuttings and cores at Cerro Prieto have now been extended to more than 50 boreholes. The aims of this petrological and isotopic work are to determine the shape of the reservoir, its physical properties, and its temperature distribution and flow regime before the steam field was produced.

  5. Land subsidence in the Cerro Prieto Geothermal Field, 1 Baja California, Mexico, from 1994 to 2005. An integrated analysis of DInSAR, levelingand geological data.

    SciTech Connect

    Sarychikhina, O; Glowacka, E; Mellors, R; Vidal, F S

    2011-03-03

    Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994- 1997 and 1997-2006) and detailed geological information in order to improve the understanding of temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area coincides with the Cerro Prieto pull-apart basin. In addition, the spatial pattern of the subsidence as well as changes in rate are highly correlated with the development of the Cerro Prieto Geothermal Field.

  6. Land subsidence in the Cerro Prieto Geothermal Field, Baja California, Mexico, from 1994 to 2005: An integrated analysis of DInSAR, leveling and geological data

    NASA Astrophysics Data System (ADS)

    Sarychikhina, Olga; Glowacka, Ewa; Mellors, Robert; Vidal, Francisco Suárez

    2011-07-01

    Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to the local infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994-1997 and 1997-2006) and detailed geological information in order to improve understanding of the temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area coincides with the Cerro Prieto pull-apart basin. In addition, the changes in spatial pattern and rate of the subsidence are correlated with the development of the Cerro Prieto Geothermal Field.

  7. Gamma irradiation as a phytosanitary treatment for fresh pome fruits produced in Patagonia

    NASA Astrophysics Data System (ADS)

    Pérez, J.; Lires, C.; Horak, C.; Pawlak, E.; Docters, A.; Kairiyama, E.

    2009-07-01

    Argentina produces 1.8 million tons/year of apples ( Malus domestica L.) and pears ( Pyrus communis L.) in the Patagonia region. Cydia pomonella, codling moth, and Grapholita molesta, Oriental fruit moth, ( Lepidoptera: Tortricidae) are quarantine pests in pome fruits. Irradiation is a promising phytosanitary treatment because a dose of 200 Gy completely prevents pest adult emergence. A pilot irradiation process of commercially packaged 'Red Delicious' apples and 'Packham's Triumph' pears was performed in an irradiation facility with a Cobalt 60 source. Quality analyses were carried out at 0, 2, 4, 6 and 8 months of storage (1 °C, RH 99%) to evaluate fruit tolerance at 200, 400 and 800 Gy. Irradiation at 200 and 400 Gy had no undesirable effects on fruit quality (pulp firmness, external colour, soluble solids content (SSC), titratable acidity (TA) and sensory evaluations). Irradiation of 'Red Delicious' apples and 'Packham's Triumph' pears can be applied as a commercial quarantine treatment with a minimum absorbed dose of 200 Gy (to control codling moth and Oriental fruit moth) and <800 Gy (according to quality results).

  8. Rodent community structure and Andes virus infection in sylvan and peridomestic habitats in northwestern Patagonia, Argentina.

    PubMed

    Piudo, Luciana; Monteverde, Martin J; Walker, R Susan; Douglass, Richard J

    2011-03-01

    Modifications of natural habitat in peridomestic rural areas could affect original rodent community composition, diversity, and evenness. In zoonoses such as hantavirus pulmonary syndrome, the presence of a diverse community can dilute the impact of the principal reservoir, reducing risk to humans. The goal of this study was to examine rodent community composition, abundance of Andes virus (ANDV) host (Oligoryzomys longicaudatus), ANDV prevalence, and temporal variability associated with rural peridomestic settings in Patagonia, Argentina. We trapped rodents in peridomestic settings and nearby sylvan areas for 2 years. The numerically dominant species differed between peridomestic and sylvan settings. O. longicaudatus was the most abundant species in peridomestic settings (>50% of individuals). Diversity and evenness in peridomestic settings fluctuated temporally, with an abrupt decline in evenness coinciding with peaks in ANDV prevalence. The probability of finding an ANDV-positive mouse in peridomestic settings was 2.44 times greater than in sylvan habitats. Changes in rodent communities in peridomestic settings may increase the probability for human exposure to ANDV because those settings promote the presence of O. longicaudatus with high ANDV antibody prevalence. High O. longicaudatus relative abundance in an unstable community associated with peridomestic settings may favor intraspecific contact, leading to a higher probability of virus transmission. PMID:21332352

  9. Nuisance ecology: do scavenging condors exact foraging costs on pumas in Patagonia?

    PubMed

    Elbroch, L Mark; Wittmer, Heiko U

    2013-01-01

    Predation risk describes the energetic cost an animal suffers when making a trade off between maximizing energy intake and minimizing threats to its survival. We tested whether Andean condors (Vultur gryphus) influenced the foraging behaviors of a top predator in Patagonia, the puma (Puma concolor), in ways comparable to direct risks of predation for prey to address three questions: 1) Do condors exact a foraging cost on pumas?; 2) If so, do pumas exhibit behaviors indicative of these risks?; and 3) Do pumas display predictable behaviors associated with prey species foraging in risky environments? Using GPS location data, we located 433 kill sites of 9 pumas and quantified their kill rates. Based upon time pumas spent at a carcass, we quantified handling time. Pumas abandoned >10% of edible meat at 133 of 266 large carcasses after a single night, and did so most often in open grasslands where their carcasses were easily detected by condors. Our data suggested that condors exacted foraging costs on pumas by significantly decreasing puma handling times at carcasses, and that pumas increased their kill rates by 50% relative to those reported for North America to compensate for these losses. Finally, we determined that the relative risks of detection and associated harassment by condors, rather than prey densities, explained puma "giving up times" (GUTs) across structurally variable risk classes in the study area, and that, like many prey species, pumas disproportionately hunted in high-risk, high-resource reward areas.

  10. Radar remote sensing of wind-driven land degradation processes in northeastern Patagonia.

    PubMed

    del Valle, H F; Blanco, P D; Metternicht, G I; Zinck, J A

    2010-01-01

    Wind-driven land degradation negatively impacts on rangeland production and infrastructure in the Valdes Peninsula, northeastern Patagonia. The Valdes Peninsula has the most noticeable dunefields of the Patagonian drylands. Wind erosion has been assessed at different scales in this region, but often with limited data. In general, terrain features caused by wind activity are better discriminated by active microwaves than by sensors operating in the visible and infrared regions of the electromagnetic spectrum. This paper aims to analyze wind-driven land degradation processes that control the radar backscatter observed in different sources of radar imagery. We used subsets derived from SIR-C, ERS-1 and 2, ENVISAT ASAR, RADARSAT-1, and ALOS PALSAR data. The visibility of aeolian features on radar images is mostly a function of wavelength, polarization, and incidence angle. Stabilized sand deposits are clearly observed in radar images, with defined edges but also signals of ongoing wind erosion. One of the most conspicuous features corresponds to old track sand dunes, a mixture of active and inactive barchanoid ridges and parabolic dunes. This is a clear example of deactivation of migrating dunes under the influence of vegetation. The L-band data reveal details of these sand ridges, whereas the C-band data only allow detecting a few of the larger tracks. The results of this study enable us to make recommendations about the utility of some radar sensor configurations for wind-driven land degradation reconnaissance in mid-latitude regions.

  11. Microbial life in a fjord: metagenomic analysis of a microbial mat in Chilean patagonia.

    PubMed

    Ugalde, Juan A; Gallardo, Maria J; Belmar, Camila; Muñoz, Práxedes; Ruiz-Tagle, Nathaly; Ferrada-Fuentes, Sandra; Espinoza, Carola; Allen, Eric E; Gallardo, Victor A

    2013-01-01

    The current study describes the taxonomic and functional composition of metagenomic sequences obtained from a filamentous microbial mat isolated from the Comau fjord, located in the northernmost part of the Chilean Patagonia. The taxonomic composition of the microbial community showed a high proportion of members of the Gammaproteobacteria, including a high number of sequences that were recruited to the genomes of Moritella marina MP-1 and Colwelliapsycherythraea 34H, suggesting the presence of populations related to these two psychrophilic bacterial species. Functional analysis of the community indicated a high proportion of genes coding for the transport and metabolism of amino acids, as well as in energy production. Among the energy production functions, we found protein-coding genes for sulfate and nitrate reduction, both processes associated with Gammaproteobacteria-related sequences. This report provides the first examination of the taxonomic composition and genetic diversity associated with these conspicuous microbial mat communities and provides a framework for future microbial studies in the Comau fjord. PMID:24015199

  12. Latest Pleistocene and Holocene glacial events in the Colonia valley, Northern Patagonia Icefield, southern Chile

    USGS Publications Warehouse

    Nimick, David A.; Mcgrath, Daniel; Mahan, Shannon; Friesen, Beverly A.; Leidich, Jonathan

    2016-01-01

    The Northern Patagonia Icefield (NPI) is the primary glaciated terrain worldwide at its latitude (46.5–47.5°S), and constraining its glacial history provides unique information for reconstructing Southern Hemisphere paleoclimate. The Colonia Glacier is the largest outlet glacier draining the eastern NPI. Ages were determined using dendrochronology, lichenometry, radiocarbon, cosmogenic 10Be and optically stimulated luminescence. Dated moraines in the Colonia valley defined advances at 13.2 ± 0.95, 11.0 ± 0.47 and 4.96 ± 0.21 ka, with the last being the first constraint on the onset of Neoglaciation for the eastern NPI from a directly dated landform. Dating in the tributary Cachet valley, which contains an ice-dammed lake during periods of Colonia Glacier expansion, defined an advance at ca. 2.95 ± 0.21 ka, periods of advancement at 810 ± 49 cal a BP and 245 ± 13 cal a BP, and retreat during the intervening periods. Recent Colonia Glacier thinning, which began in the late 1800s, opened a lower-elevation outlet channel for Lago Cachet Dos in ca. 1960. Our data provide the most comprehensive set of Latest Pleistocene and Holocene ages for a single NPI outlet glacier and expand previously developed NPI glacial chronologies.

  13. Detrital zircons U-Pb SHRIMP ages and provenance of La Modesta Formation, Patagonia Argentina

    NASA Astrophysics Data System (ADS)

    Moreira, Pilar; Fernández, Raúl; Hervé, Francisco; Fanning, C. Mark; Schalamuk, Isidoro A.

    2013-11-01

    This paper summarizes the geology of the Paleozoic La Modesta Formation in Patagonia, Argentina, and presents new SHRIMP U-Pb dating of detrital zircons from muscovite-chlorite schist and tourmalinite. Also complementary geochemical and lead isotopic data are presented, indicating that the protoliths were formed from upper crustal rocks by the contribution of a large input from recycled (or felsic) sources. The maximum age of sedimentation of La Modesta Formation is about 446 ± 6 Ma. The basin closure (or eventually a paleocurrent shift) occurs at Lower Devonian before the exhumation of the Middle-Devonian granitoids of the Rio Deseado Complex (Deseado Massif). Many of the detrital zircons are igneous and record Ordovician ages, with a prominent Lower Ordovician-age peak at approximately 473 Ma. Most favourable candidates to provide the younger zircons in the basin would Ordovician granites of the Rio Deseado Complex (Deseado Massif) and Punta Sierra Plutonic Complex (Somun Cura Massif). Older zircons have peaks of different importance (including Brasiliano and Grenvillian ages) between 530 and 700, 750-1500, 1750-2000 and 2550-2700 Ma. La Modesta Formation is also a potential area of materials (detrital zircon) to the basin where the rocks of the Eastern Andean Metamorphic Complex and equivalent formations of the Andean region were generated. xml:lang="fr"

  14. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean

    PubMed Central

    Glasser, Neil F.; Jansson, Krister N.; Duller, Geoffrey A. T.; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface “hosing” to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  15. Origin of melt pockets in mantle xenoliths from southern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Aliani, Paola; Ntaflos, Theodoros; Bjerg, Ernesto

    2009-12-01

    Peridotite mantle xenoliths collected north of Gobernador Gregores, Patagonia, affected by cryptic and modal metasomatism bear melt pockets of unusually large size. Melt pockets consist of second generation olivine (ol2), clinopyroxene (cpx2) and spinel (sp2) ± relict amphibole (amph) immersed in a yellowish vesicular glass matrix. Amphibole breakdown was responsible for melt pocket generation as suggested by textural evidence and proved by consistent mass-balance calculations: amph → cpx2 + ol2 + sp2 + melt. Composition of calculated amphibole in amphibole-free melt pockets is very similar to that measured in amphibole-bearing melt pockets from the same xenolith, i.e. amphibole was consumed in the melt pocket generation process. In melt pockets devoid of relict amphibole, mass-balance calculations show remarkable differences between the calculated amphibole and the measured amphibole compositions in melt pockets from the same xenolith. The participation of minor proportions of a consumed reactant phase could be a reasonable explanation. In some samples the calculated phase proportion of glass is in excess compared to modal estimations based on backscattered electron images, probably because a portion of the generated melt was able to migrate out of the melt pockets. Compositional inhomogeneity of cpx2 and variable Ti Kd in cpx2 vs. glass in the same melt pocket reflect fast nucleation and growth and disequilibrium crystallisation, respectively. This and the difference between forsterite content in calculated equilibrium olivine and second generation olivine, suggest that mineral equilibrium was inhibited by rapid quenching of melt pockets.

  16. Rodent Community Structure and Andes Virus Infection in Sylvan and Peridomestic Habitats in Northwestern Patagonia, Argentina

    PubMed Central

    Monteverde, Martin J.; Walker, R. Susan; Douglass, Richard J.

    2011-01-01

    Abstract Modifications of natural habitat in peridomestic rural areas could affect original rodent community composition, diversity, and evenness. In zoonoses such as hantavirus pulmonary syndrome, the presence of a diverse community can dilute the impact of the principal reservoir, reducing risk to humans. The goal of this study was to examine rodent community composition, abundance of Andes virus (ANDV) host (Oligoryzomys longicaudatus), ANDV prevalence, and temporal variability associated with rural peridomestic settings in Patagonia, Argentina. We trapped rodents in peridomestic settings and nearby sylvan areas for 2 years. The numerically dominant species differed between peridomestic and sylvan settings. O. longicaudatus was the most abundant species in peridomestic settings (>50% of individuals). Diversity and evenness in peridomestic settings fluctuated temporally, with an abrupt decline in evenness coinciding with peaks in ANDV prevalence. The probability of finding an ANDV-positive mouse in peridomestic settings was 2.44 times greater than in sylvan habitats. Changes in rodent communities in peridomestic settings may increase the probability for human exposure to ANDV because those settings promote the presence of O. longicaudatus with high ANDV antibody prevalence. High O. longicaudatus relative abundance in an unstable community associated with peridomestic settings may favor intraspecific contact, leading to a higher probability of virus transmission. PMID:21332352

  17. Microbial Life in a Fjord: Metagenomic Analysis of a Microbial Mat in Chilean Patagonia

    PubMed Central

    Ugalde, Juan A.; Gallardo, Maria J.; Belmar, Camila; Muñoz, Práxedes; Ruiz-Tagle, Nathaly; Ferrada-Fuentes, Sandra; Espinoza, Carola; Allen, Eric E.; Gallardo, Victor A.

    2013-01-01

    The current study describes the taxonomic and functional composition of metagenomic sequences obtained from a filamentous microbial mat isolated from the Comau fjord, located in the northernmost part of the Chilean Patagonia. The taxonomic composition of the microbial community showed a high proportion of members of the Gammaproteobacteria, including a high number of sequences that were recruited to the genomes of Moritella marina MP-1 and Colwelliapsycherythraea 34H, suggesting the presence of populations related to these two psychrophilic bacterial species. Functional analysis of the community indicated a high proportion of genes coding for the transport and metabolism of amino acids, as well as in energy production. Among the energy production functions, we found protein-coding genes for sulfate and nitrate reduction, both processes associated with Gammaproteobacteria-related sequences. This report provides the first examination of the taxonomic composition and genetic diversity associated with these conspicuous microbial mat communities and provides a framework for future microbial studies in the Comau fjord. PMID:24015199

  18. Scale-dependent analysis of an otter-crustacean system in Argentinean Patagonia

    NASA Astrophysics Data System (ADS)

    Cassini, Marcelo H.; Fasola, Laura; Chehébar, Claudio; MacDonald, David W.

    2009-05-01

    The Southern river otter or ‘huillin’, Lontra provocax, is an endangered species endemic of the Andean Patagonian region of Argentina and Chile. It feeds almost exclusively on the genera of macro-crustacea: Aegla and Sammastacus. The aim of this study was to analyse the role of food availability on the huillin’s distribution using a scale-dependent analysis of crustacean and otter distributions. We compared the distributions of otters and macro-crustaceans along a north-south regional gradient, between river basins of northern Patagonia, in an altitudinal gradient within a river basin, and between habitat types within a lake. We investigated the distribution of otters by sign surveys along lake shores, river banks and marine coasts, and of crustaceans using surveys in the water, undigested remains in mink ( Mustela vison) scats, presence of external skeletons at the waterside and through interviews with local people. Our results show that there were heterogeneities in the distributions of macro-crustaceans at four scales and these were generally reflected in the distributions of freshwater otters. We conclude that the main factor limiting the distributions of L. provocax in freshwater environments is the availability of macro-crustaceans. This paper shows how scale-dependent type analyses of population distribution serves as a method for identifying key environmental factors for species for which the use of long-term demographies is unfeasible.

  19. Bacterial composition of microbial mats in hot springs in Northern Patagonia: variations with seasons and temperature.

    PubMed

    Mackenzie, Roy; Pedrós-Alió, Carlos; Díez, Beatriz

    2013-01-01

    Seasonal shifts in bacterial diversity of microbial mats were analyzed in three hot springs (39-68 °C) of Patagonia, using culture-independent methods. Three major bacterial groups were detected in all springs: Phyla Cyanobacteria and Bacteroidetes, and Order Thermales. Proteobacteria, Acidobacteria and Green Non-Sulfur Bacteria were also detected in small amounts and only in some samples. Thermophilic filamentous heterocyst-containing Mastigocladus were dominant Cyanobacteria in Porcelana Hot Spring and Geyser, and Calothrix in Cahuelmó, followed by the filamentous non-heterocyst Leptolyngbya and Oscillatoria. Bacteroidetes were detected in a wide temperature range and their relative abundance increased with decreasing temperature in almost all samples. Two Meiothermus populations with different temperature optima were found. Overall, fingerprinting analysis with universal bacterial primers showed high similarities within each hot spring despite differences in temperature. On the other hand, Cahuelmó Hot Spring showed a lower resemblance among samples. Porcelana Hot Spring and Porcelana Geyser were rather similar to each other, possibly due to a common geological substrate given their geographic proximity. This was even more evident with specific cyanobacterial primers. The different geological substrate and the seawater influence in Cahuelmó might have caused the differences in the microbial community structure with the other two hot springs.

  20. An assessment of oil pollution in the coastal zone of patagonia, Argentina.

    PubMed

    Commendatore, Marta Graciela; Esteves, José Luis

    2007-11-01

    The Patagonian coast is considered a relatively pristine environment. However, studies conducted along coastal Patagonia have showed hydrocarbon pollution mostly concentrated at ports that have fishing, oil loading, general merchant, and/or tourist activities. A high value of total aliphatic hydrocarbons (TAH) was found at the Rawson fishing port (741 microg/g dw). In other ports with and without petroleum-related activities, hydrocarbon values were approximately 100 microg/g dw. The highest values for TAH and total aromatic hydrocarbons (TArH) were found in Faro Aristizábal, north of San Jorge gulf (1304 and 737 microg/g dw, respectively). This is very likely the result of petroleum-related activities at the Comodoro Rivadavia, Caleta Cordova, and Caleta Olivia ports located within this gulf. In other coastal areas away from potential anthropogenic sources, hydrocarbon values were less than 2 and 3 microg/g dw for TAH and TArH, respectively. This review of published and unpublished information suggests that ports are important oil pollution sources in the Patagonian coast. More detailed studies are needed to evaluate the area affected by port activities, to understand the mechanisms of hydrocarbon distribution in surrounding environments, and to assess bioaccumulation in marine organisms. Despite that some regulations exist to control oil pollution derived from port and docked vessel activities, new and stricter management guidelines should be implemented.

  1. Shell shape variation in the Nassariid Buccinanops globulosus in northern Patagonia

    NASA Astrophysics Data System (ADS)

    Avaca, María Soledad; Narvarte, Maite; Martín, Pablo; van der Molen, Silvina

    2013-09-01

    Morphological variation among natural populations is a phenomenon commonly observed in marine invertebrates and well studied, particularly, in shelled gastropods. The nassariid Buccinanops globulosus is interesting to study shell shape variation because it exhibits strong interpopulation differences in life history features, including maximum size, fecundity and growth rate. In this study, we examined the pattern of variation in size and shell shape among populations and between sexes of B. globulosus (Bahía San Antonio 40°29'S 63°01'W, Playa Villarino 40°45'S 64°40'W and Bahía Nueva 42°46'S 65°02'W). In particular, we used geometric morphometric techniques to test: (1) whether the two components of shell morphology (size and shape) are independent and (2) whether shape differences between sexes are consistently found among populations, regardless of their body sizes. Our results show shell shape variation between the populations of B. globulosus of northern Patagonia. Intra-specific shell shape variation is affected by body size, indicating allometry. Regardless of the size differences, individuals from Playa Villarino have high-spired shells, and shorter apertures and wider columellar area than individuals from the other populations. Also, sex-related shape differences were consistently found at each population, thus suggesting a common sexual dimorphism in shell morphology for this species. The functional significance of the variability found is discussed in terms of the flexibility of developmental programmes for morphology as well as the evolution of phenotypic plasticity.

  2. The Domuyo volcanic system: An enormous geothermal resource in Argentine Patagonia

    NASA Astrophysics Data System (ADS)

    Chiodini, Giovanni; Liccioli, Caterina; Vaselli, Orlando; Calabrese, Sergio; Tassi, Franco; Caliro, Stefano; Caselli, Alberto; Agusto, Mariano; D'Alessandro, Walter

    2014-03-01

    A geochemical survey of the main thermal waters discharging in the southwestern part of the Domuyo volcanic complex (Argentina), where the latest volcanic activity dates to 0.11 Ma, has highlighted the extraordinarily high heat loss from this remote site in Patagonia. The thermal water discharges are mostly Na-Cl in composition and have TDS values up to 3.78 g L- 1 (El Humazo). A simple hydrogeochemical approach shows that 1,100 to 1,300 kg s- 1 of boiling waters, which have been affected by shallow steam separation, flow into the main drainage of the area (Rio Varvarco). A dramatic increase of the most conservative species such as Na, Cl and Li from the Rio Varvarco from upstream to downstream was observed and related solely to the contribution of hydrothermal fluids. The equilibrium temperatures of the discharging thermal fluids, calculated on the basis of the Na-K-Mg geothermometer, are between 190 °C and 230 °C. If we refer to a liquid originally at 220 °C (enthalpy = 944 J g- 1), the thermal energy release can be estimated as high as 1.1 ± 0.2 GW, a value that is much higher than the natural release of heat in other important geothermal fields worldwide, e.g., Mutnovsky (Russia), Wairakei (New Zealand) and Lassen Peak (USA). This value is the second highest measured advective heat flux from any hydrothermal system on Earth after Yellowstone.

  3. Gregarious bamboo flowering opens a window of opportunity for regeneration in a temperate forest of Patagonia.

    PubMed

    Giordano, Carla V; Sánchez, Rodolfo A; Austin, Amy T

    2009-03-01

    Rare gregarious flowering of understorey bamboo species occurs in temperate and subtropical forests around the world, but the ecological consequences of this phenomenon for forest regeneration are not well understood.Field experiments were conducted in an old-growth temperate forest in Patagonia,Argentina after a massive bamboo flowering event, to examine whether light quality and other changes in microhabitats could affect seed germination and growth of overstorey species. Germination of southern beech (Nothofagus obliqua) was positively correlated with red:far red (R:FR) ratios in a range of microhabitats generated by the death of the understorey bamboo (Chusquea culeou). Experimental modification of understorey R:FR ratios to mimic alternative light environments reversed this germination response in plots with senescent understorey, but not in plots with live bamboo. Laboratory incubations demonstrated a significant interaction between R:FR ratios and thermal amplitude in promoting seed germination. Microhabitats also significantly affected the growth of emerged seedlings. Microenvironmental changes generated by this flowering event appear to have opened a window of opportunity for germination and growth of overstorey species.We demonstrate that natural gradients in light quality associated with this ecological phenomenon are a major component affecting forest regeneration in this ecosystem.

  4. Interactions among four parasite species in an amphipod population from Patagonia.

    PubMed

    Rauque, C A; Semenas, L

    2013-03-01

    Parasites commonly share their hosts with specimens of the same or different parasite species, resulting in multiple parasites obtaining resources from the same host. This could potentially lead to conflicts between co-infecting parasites, especially at high infection intensities. In Pool Los Juncos (Patagonia, Argentina), the amphipod Hyalella patagonica is an intermediate host to three parasites that mature in birds (the acanthocephalan Pseudocorynosoma sp. and larval stages of two Cyclophyllidea cestodes), in addition to a microsporidian (Thelohania sp.), whose life cycle is unknown, but very likely to be monoxenous. The aim of this study was to describe interactions between these parasite species in their amphipod host population. Amphipods were collected monthly between June 2002 and January 2004 to assess parasite infection. Infection prevalence and mean intensity were greatest in larger male amphipods for all parasite species. We also found a positive association between Thelohania sp. and both Pseudocorynosoma sp. and Cyclophyllidea sp. 1 infections, though Pseudocorynosoma sp. and Cyclophyllidea sp. 1 were negatively associated with each other. We conclude that contrasting associations between parasite species may be associated with competition for both food intake and space in the haemocoel.

  5. Bacterial composition of microbial mats in hot springs in Northern Patagonia: variations with seasons and temperature.

    PubMed

    Mackenzie, Roy; Pedrós-Alió, Carlos; Díez, Beatriz

    2013-01-01

    Seasonal shifts in bacterial diversity of microbial mats were analyzed in three hot springs (39-68 °C) of Patagonia, using culture-independent methods. Three major bacterial groups were detected in all springs: Phyla Cyanobacteria and Bacteroidetes, and Order Thermales. Proteobacteria, Acidobacteria and Green Non-Sulfur Bacteria were also detected in small amounts and only in some samples. Thermophilic filamentous heterocyst-containing Mastigocladus were dominant Cyanobacteria in Porcelana Hot Spring and Geyser, and Calothrix in Cahuelmó, followed by the filamentous non-heterocyst Leptolyngbya and Oscillatoria. Bacteroidetes were detected in a wide temperature range and their relative abundance increased with decreasing temperature in almost all samples. Two Meiothermus populations with different temperature optima were found. Overall, fingerprinting analysis with universal bacterial primers showed high similarities within each hot spring despite differences in temperature. On the other hand, Cahuelmó Hot Spring showed a lower resemblance among samples. Porcelana Hot Spring and Porcelana Geyser were rather similar to each other, possibly due to a common geological substrate given their geographic proximity. This was even more evident with specific cyanobacterial primers. The different geological substrate and the seawater influence in Cahuelmó might have caused the differences in the microbial community structure with the other two hot springs. PMID:23208511

  6. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean.

    PubMed

    Glasser, Neil F; Jansson, Krister N; Duller, Geoffrey A T; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface "hosing" to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  7. Muscular reconstruction and functional morphology of the forelimb of early Miocene sloths (Xenarthra, Folivora) of Patagonia.

    PubMed

    Toledo, Néstor; Bargo, M Susana; Vizcaíno, Sergio F

    2013-02-01

    Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being registered mainly from Santacrucian Age deposits in southern-most shores of Patagonia, Argentina. Their postcranial skeleton differs markedly in shape from those of their closest living relatives (arboreal forms of less than 10 kg), Bradypus and Choloepus. In order to gain insight on functional properties of the Santacrucian sloths forelimb, musculature was reconstructed and a comparative, qualitative morphofunctional analysis was performed, allowing proposing hypotheses about biological role of the limb in substrate preferences, and locomotor strategies. The anatomy of the forelimb of Santacrucian sloths resembles more closely extant anteaters such as Tamandua and Myrmecophaga, due to the robustness of the elements, development of features related to attachment of ligaments and muscles, and conservative, pentadactylous, and strong-clawed manus. The reconstructed forelimb musculature was very well developed and resembles that of extant Pilosa (especially anteaters), although retaining the basic muscular configuration of generalized mammals. This musculature allowed application of powerful forces, especially in adduction of the forelimb, flexion and extension of the antebrachium, and manual prehension. These functional properties are congruent with both climbing and digging activities, and provide support for proposed Santacrucian sloths as good climbing mammals, possibly arboreal or semiarboreal, being also capable diggers. Their climbing strategies were limited, thus these forms relied mainly on great muscular strength and curved claws of the manus to move cautiously on branches.

  8. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana.

    PubMed

    Apesteguía, Sebastián; Novas, Fernando E

    2003-10-01

    Sphenodontian reptiles successfully radiated during Triassic and Jurassic times, but were driven almost to extinction during the Cretaceous period. The sparse Early Cretaceous record of sphenodontians has been interpreted as reflecting the decline of the group in favour of lizards, their suspected ecological successors. However, recent discoveries in Late Cretaceous beds in Patagonia partially modify this interpretation. Numerous skeletons of a new sphenodontian, Priosphenodon avelasi gen. et sp. nov., were collected from a single locality in the Cenomanian-Turonian Candeleros Formation, where it is more abundant than any other tetrapod group recorded in the quarry (for example, Crocodyliformes, Serpentes, Dinosauria and Mammalia). Adult specimens of Priosphenodon reached one metre in length, larger than any previously known terrestrial sphenodontian. Here we propose, using available evidence, that sphenodontians were not a minor component of the Cretaceous terrestrial ecosystems of South America, and that their ecological replacement by squamates was delayed until the early Tertiary. The new discovery helps to bridge the considerable gap in the fossil record (around 120 million years) that separates the Early Cretaceous sphenodontians from their living relatives (Sphenodon). PMID:14534584

  9. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia.

    PubMed

    Rauhut, Oliver W M; Remes, Kristian; Fechner, Regina; Cladera, Gerardo; Puerta, Pablo

    2005-06-01

    Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic. PMID:15931221

  10. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana.

    PubMed

    Apesteguía, Sebastián; Novas, Fernando E

    2003-10-01

    Sphenodontian reptiles successfully radiated during Triassic and Jurassic times, but were driven almost to extinction during the Cretaceous period. The sparse Early Cretaceous record of sphenodontians has been interpreted as reflecting the decline of the group in favour of lizards, their suspected ecological successors. However, recent discoveries in Late Cretaceous beds in Patagonia partially modify this interpretation. Numerous skeletons of a new sphenodontian, Priosphenodon avelasi gen. et sp. nov., were collected from a single locality in the Cenomanian-Turonian Candeleros Formation, where it is more abundant than any other tetrapod group recorded in the quarry (for example, Crocodyliformes, Serpentes, Dinosauria and Mammalia). Adult specimens of Priosphenodon reached one metre in length, larger than any previously known terrestrial sphenodontian. Here we propose, using available evidence, that sphenodontians were not a minor component of the Cretaceous terrestrial ecosystems of South America, and that their ecological replacement by squamates was delayed until the early Tertiary. The new discovery helps to bridge the considerable gap in the fossil record (around 120 million years) that separates the Early Cretaceous sphenodontians from their living relatives (Sphenodon).

  11. First paleoparasitological record of acanthocephalan eggs from Northwestern Patagonia (Late Holocene, Argentina).

    PubMed

    Beltrame, María Ornela; Fernández, Fernando Julián; Sardella, Norma Haydeé

    2015-06-01

    Eggs representative of an acanthocephalan were found in an ancient fragment of raptor pellet, probably belonged to the barn owl, Tyto alba, from the archeological site named "Epullán Chica cave." This site is a cave located at the southern of Neuquén Province, Patagonia, Argentina. The fragment of pellet was found in a layer with charcoals dated at 1980±80 years B.P. A total of 56 eggs were found. Eggs were brown colored and thick-shelled, and presented four membranes, the outer lightly sculpted. The embryos presented hooks in one extremity. Measurements ranged from 87.5 to 107.5μm long and 50 to 57.5μm wide. Eggs were very well-preserved, and were identified as belonged to Class Archiacanthocephala, Order Oligacanthorhynchida, Family Oligacanthorhynchidae, probably Macracanthorhynchus Travassos, 1917, or an unidentified species. This is the first report of small mammal acanthocephalans from ancient material worldwide. PMID:25757369

  12. Food partitioning and spatial subsidy in shelter-limited fishes inhabiting patchy reefs of Patagonia.

    PubMed

    Galván, D E; Botto, F; Parma, A M; Bandieri, L; Mohamed, N; Iribarne, O O

    2009-12-01

    The diets of the most conspicuous reef-fish species from northern Patagonia, the carnivorous species Pseudopercis semifasciata, Acanthistius patachonicus, Pinguipes brasilianus and Sebastes oculatus were studied. Pinguipes brasilianus had the narrowest diet and most specialized feeding strategy, preying mostly on reef-dwelling organisms such as sea urchins, limpets, bivalves, crabs and polychaetes. The diet of A. patachonicus was characterized by the presence of reef and soft-bottom benthic organisms, mainly polychaetes, crabs and fishes. Pseudopercis semifasciata showed the broadest spectrum of prey items, preying upon reef, soft-bottom and transient organism (mainly fishes, cephalopods and crabs). All S. oculatus guts were empty, but stable-isotope analyses suggested that this species consumed small fishes and crabs. In general, P. brasilianus depended on local prey populations and ate different reef-dwelling prey than the other species. Pseudopercis semifasciata, A. patachonicus and probably S. oculatus, however, had overlapping trophic niches and consumed resources from adjacent environments. The latter probably reduces the importance of food as a limiting resource for these reef-fish populations, facilitating their coexistence in spite of their high trophic overlap. PMID:20738509

  13. An assessment of oil pollution in the coastal zone of patagonia, Argentina.

    PubMed

    Commendatore, Marta Graciela; Esteves, José Luis

    2007-11-01

    The Patagonian coast is considered a relatively pristine environment. However, studies conducted along coastal Patagonia have showed hydrocarbon pollution mostly concentrated at ports that have fishing, oil loading, general merchant, and/or tourist activities. A high value of total aliphatic hydrocarbons (TAH) was found at the Rawson fishing port (741 microg/g dw). In other ports with and without petroleum-related activities, hydrocarbon values were approximately 100 microg/g dw. The highest values for TAH and total aromatic hydrocarbons (TArH) were found in Faro Aristizábal, north of San Jorge gulf (1304 and 737 microg/g dw, respectively). This is very likely the result of petroleum-related activities at the Comodoro Rivadavia, Caleta Cordova, and Caleta Olivia ports located within this gulf. In other coastal areas away from potential anthropogenic sources, hydrocarbon values were less than 2 and 3 microg/g dw for TAH and TArH, respectively. This review of published and unpublished information suggests that ports are important oil pollution sources in the Patagonian coast. More detailed studies are needed to evaluate the area affected by port activities, to understand the mechanisms of hydrocarbon distribution in surrounding environments, and to assess bioaccumulation in marine organisms. Despite that some regulations exist to control oil pollution derived from port and docked vessel activities, new and stricter management guidelines should be implemented. PMID:17929085

  14. An Assessment of Oil Pollution in the Coastal Zone of Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Commendatore, Marta Graciela; Esteves, José Luis

    2007-11-01

    The Patagonian coast is considered a relatively pristine environment. However, studies conducted along coastal Patagonia have showed hydrocarbon pollution mostly concentrated at ports that have fishing, oil loading, general merchant, and/or tourist activities. A high value of total aliphatic hydrocarbons (TAH) was found at the Rawson fishing port (741 μg/g dw). In other ports with and without petroleum-related activities, hydrocarbon values were approximately 100 μg/g dw. The highest values for TAH and total aromatic hydrocarbons (TArH) were found in Faro Aristizábal, north of San Jorge gulf (1304 and 737 μg/g dw, respectively). This is very likely the result of petroleum-related activities at the Comodoro Rivadavia, Caleta Cordova, and Caleta Olivia ports located within this gulf. In other coastal areas away from potential anthropogenic sources, hydrocarbon values were less than 2 and 3 μg/g dw for TAH and TArH, respectively. This review of published and unpublished information suggests that ports are important oil pollution sources in the Patagonian coast. More detailed studies are needed to evaluate the area affected by port activities, to understand the mechanisms of hydrocarbon distribution in surrounding environments, and to assess bioaccumulation in marine organisms. Despite that some regulations exist to control oil pollution derived from port and docked vessel activities, new and stricter management guidelines should be implemented.

  15. A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs.

    PubMed

    Pol, Diego; Rauhut, Oliver W M

    2012-08-22

    Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.

  16. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia.

    PubMed

    Rauhut, Oliver W M; Remes, Kristian; Fechner, Regina; Cladera, Gerardo; Puerta, Pablo

    2005-06-01

    Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic.

  17. A Middle Jurassic heterodontosaurid dinosaur from Patagonia and the evolution of heterodontosaurids

    NASA Astrophysics Data System (ADS)

    Pol, Diego; Rauhut, Oliver W. M.; Becerra, Marcos

    2011-05-01

    Heterodontosauridae is a morphologically divergent group of dinosaurs that has recently been interpreted as one of the most basal clades of Ornithischia. Heterodontosaurid remains were previously known from the Early Jurassic of southern Africa, but recent discoveries and studies have significantly increased the geographical and temporal range for this clade. Here, we report a new ornithischian dinosaur from the Middle Jurassic Cañadón Asfalto Formation in central Patagonia, Argentina. This new taxon, Manidens condorensis gen. et sp. nov., includes well-preserved craniomandibular and postcranial remains and represents the only diagnostic ornithischian specimen yet discovered in the Jurassic of South America so far. Derived features of its anatomy indicate that Manidens belongs to Heterodontosauridae, as the sister taxon of Heterodontosaurus and other South African heterodontosaurids. The presence of posterior dentary teeth with high crowns but lacking extensive wear facets in Manidens suggests that this form represents an intermediate stage in the development of the remarkable adaptations to herbivory described for Heterodontosaurus. The dentition of Manidens condorensis also has autapomorphies, such as asymmetrically arranged denticles in posterior teeth and a mesially projected denticle in the posteriormost teeth. At an estimated total length of 60-75 cm, Manidens furthermore confirms the small size of basal heterodontosaurids.

  18. A Middle Jurassic heterodontosaurid dinosaur from Patagonia and the evolution of heterodontosaurids.

    PubMed

    Pol, Diego; Rauhut, Oliver W M; Becerra, Marcos

    2011-05-01

    Heterodontosauridae is a morphologically divergent group of dinosaurs that has recently been interpreted as one of the most basal clades of Ornithischia. Heterodontosaurid remains were previously known from the Early Jurassic of southern Africa, but recent discoveries and studies have significantly increased the geographical and temporal range for this clade. Here, we report a new ornithischian dinosaur from the Middle Jurassic Cañadón Asfalto Formation in central Patagonia, Argentina. This new taxon, Manidens condorensis gen. et sp. nov., includes well-preserved craniomandibular and postcranial remains and represents the only diagnostic ornithischian specimen yet discovered in the Jurassic of South America so far. Derived features of its anatomy indicate that Manidens belongs to Heterodontosauridae, as the sister taxon of Heterodontosaurus and other South African heterodontosaurids. The presence of posterior dentary teeth with high crowns but lacking extensive wear facets in Manidens suggests that this form represents an intermediate stage in the development of the remarkable adaptations to herbivory described for Heterodontosaurus. The dentition of Manidens condorensis also has autapomorphies, such as asymmetrically arranged denticles in posterior teeth and a mesially projected denticle in the posteriormost teeth. At an estimated total length of 60-75 cm, Manidens furthermore confirms the small size of basal heterodontosaurids.

  19. Nuisance Ecology: Do Scavenging Condors Exact Foraging Costs on Pumas in Patagonia?

    PubMed Central

    Elbroch, L. Mark; Wittmer, Heiko U.

    2013-01-01

    Predation risk describes the energetic cost an animal suffers when making a trade off between maximizing energy intake and minimizing threats to its survival. We tested whether Andean condors (Vultur gryphus) influenced the foraging behaviors of a top predator in Patagonia, the puma (Puma concolor), in ways comparable to direct risks of predation for prey to address three questions: 1) Do condors exact a foraging cost on pumas?; 2) If so, do pumas exhibit behaviors indicative of these risks?; and 3) Do pumas display predictable behaviors associated with prey species foraging in risky environments? Using GPS location data, we located 433 kill sites of 9 pumas and quantified their kill rates. Based upon time pumas spent at a carcass, we quantified handling time. Pumas abandoned >10% of edible meat at 133 of 266 large carcasses after a single night, and did so most often in open grasslands where their carcasses were easily detected by condors. Our data suggested that condors exacted foraging costs on pumas by significantly decreasing puma handling times at carcasses, and that pumas increased their kill rates by 50% relative to those reported for North America to compensate for these losses. Finally, we determined that the relative risks of detection and associated harassment by condors, rather than prey densities, explained puma “giving up times” (GUTs) across structurally variable risk classes in the study area, and that, like many prey species, pumas disproportionately hunted in high-risk, high-resource reward areas. PMID:23301093

  20. Environmental effects on grass-endophyte associations in the harsh conditions of south Patagonia.

    PubMed

    Novas, M Victoria; Collantes, Marta; Cabral, Daniel

    2007-07-01

    Cool-season grasses are frequently infected by Neotyphodium endophytes and this association is often considered as a mutualistic symbiosis. We examined the incidence of Neotyphodium in populations of Bromus setifolius, Phleum alpinum and Poa spiciformis, native and wide-spread grasses from south Patagonia, Argentina. The incidence of 36 populations of Bromus setifolius was studied in association with climatic and soil variables. 31 populations of Ph. alpinum were sampled in five different plant communities. Seventeen populations of P. spiciformis were sampled in three different plant communities. The association between incidence and climatic variables in Ph. alpinum and between incidence and soil fertility in P. spiciformis was investigated. In B. setifolius endophyte incidence was positively correlated with annual average rainfall contrary to the results found in Ph. alpinum. All the populations of P. spiciformis were infected by endophytes and the incidence was associated with plant community. The Neotyphodium-grass interaction is variable in natural populations, supporting the increasing evidence that the Neotyphodium-host interaction depends, in many cases, on the environmental conditions. Field observations suggest that in detrimental low growth conditions the association is not favoured, leading to a decrease in the endophyte frequency of infection or even to the complete loss of the association.

  1. A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids.

    PubMed

    Novas, Fernando E; de Valais, Silvina; Vickers-Rich, Pat; Rich, Tom

    2005-05-01

    The Cretaceous Carcharodontosauridae is the latest clade of carnosaurs, including the largest predatory dinosaurs yet recorded. Albeit spectacular for their size, the skeletal anatomy of these theropods remains poorly-known, and their diversity was until recently restricted to two Cenomanian species: the highly derived Giganotosaurus carolinii, from southern South America, and the incompletely known Carcharodontosaurus saharicus, from northern Africa. Here we describe an older and basal member of the group, Tyrannotitan chubutensis gen. et sp. nov., from Aptian strata of Patagonia, Argentina. The new taxon gives new insights into the systematics and evolution of carcharodontosaurids and offers a better understanding of the evolution of Southern theropod faunas. We suggest that carcharodontosaurids radiated in Gondwana sharing with spinosaurids the role of top-predators until their extinction in Cenomanian-Turonian times. During this interval, the diplodocoid sauropods and giant titanosaurians went extinct (probably as part of a global-scale crisis), and the smaller abelisaurid theropods took dominance, reigning until the end of the Cretaceous. Electronic Supplementary Material is available.

  2. Drainage network over the migrating front of dynamic uplift in Patagonia

    NASA Astrophysics Data System (ADS)

    Jeandet, Louise; Robert, Xavier; Audin, Laurence; Husson, Laurent; Guillaume, Benjamin

    2016-04-01

    Dynamic topography disturbs the regional morphology at long wavelength and with very low topographic gradients. Nevertheless, fluvial erosion and the drainage pattern should respond to the spatial and temporal topographic variations. In Patagonia, the mid-Miocene, opening and northward migration of an asthenospheric window beneath the South American plate triggered a northward propagating wave of dynamic topography. Based on a morphometric analysis, we explore the long-wavelength response of the drainage system to the recent dynamics of the continental lithosphere. Our analysis of Patagonian rivers (stream profile analysis) and basins (R/Sr analysis) shows a transient state of the drainage network responding to a likely recent signal that prevails at the latitudes of the Chile Triple Junction in Argentina. Moreover, the distribution of the perturbation signal among the drainage network shows a South-to-North gradient, with the low Strahler order tributaries more affected with increasing latitudes. We interpret this observation as the differential timing of response to a Northward propagating signal of dynamic topography. We further use the geometry of the drainage network combined to numerical model predictions to infer the characteristic response time of the surface processes. While the main tributaries respond within ~1-3 Ma, the lower order remain disturbed for longer times. This observation is further supported by the persistently high mean elevation where incision is high, which we take as indicative of the fact that erosion has not yet thoroughly achieved its resurfacing action.

  3. Four species of digeneans, including Allocreadium patagonicum sp. n. (Allocreadiidae), from freshwater fishes of Patagonia, Argentina.

    PubMed

    Shimazu, T; Urawa, S; Coria, C O

    2000-01-01

    Four species of adult digeneans are reported from freshwater fishes of two lakes in Neuquén, Patagonia, Argentina. Allocreadium patagonicum sp. n. (Allocreadiidae) is described from the intestine of Percichthys colhuapiensis MacDonagh and Percichthys trucha (Cuvier et Valenciennes) (Percichthyidae) from Lago Aluminé. Three species redescribed are: Acanthostomoides apophalliformis Szidat, 1956 (Acanthostomidae) from the intestine of P. colhuapiensis and P. trucha from Lago Aluminé and of Salmo trutta (Linnaeus) (Salmonidae) from Lago Huechulafquén; Deropegus patagonicus (Szidat, 1956) comb. n. (= Genarches patagonicus Szidat, 1956) (Derogenidae) from the stomach of P. colhuapiensis, P. trucha, Oncorhynchus mykiss (Walbaum) (Salmonidae) and Salvelinus fontinalis (Mitchill) (Salmonidae) from Lago Aluminé and of S. trutta from Lago Huechulafquén; and Austrocreadium papilliferum Szidat, 1956 from the intestine of P. trucha from Lago Aluminé. The genus Polylekithum Arnold, 1934 is considered a synonym of the genus Allocreadium Looss, 1900. The genus Austrocreadium Szidat, 1956 is removed to the family Homalometridae.

  4. A palaeoparasitological analysis of rodent coprolites from the Cueva Huenul 1 archaeological site in Patagonia (Argentina).

    PubMed

    Beltrame, María Ornela; Sardella, Norma Haydée; Fugassa, Martín Horacio; Barberena, Ramiro

    2012-08-01

    The aim of the present study was to examine the parasite fauna present in rodent coprolites collected from Cueva Huenul 1 (CH1), northern Neuquén (Patagonia, Argentina), an archaeological site that provides stratified sequences of archaeological and palaeontological remains dating from the Late Pleistocene/Early Holocene Transition to the Late Holocene period. Twenty rodent coprolites collected from different sedimentary units from the site, with ages ranging from 13.844 ± 75-1.416 ± 37 years BP, were examined for parasites. Each coprolite was processed as a whole: rehydrated, homogenised, spontaneously sedimented and examined using light microscopy. The coprolites and the eggs of any parasites present were described, measured and photographed. In all, 158 parasite eggs were found in 10 coprolites. The faeces were positive for Viscachataenia quadrata Denegri, Dopchiz, Elissondo & Beveridge and Monoecocestus sp. Beddard (Cestoda: Anoplocephalidae) and for Heteroxynema (Cavioxyura) viscaciae Sutton & Hugot (Nematoda: Oxyuridae). The coprolites examined were tentatively attributed to Lagidium viscacia Molina (Mammalia, Rodentia, Caviomorpha, Chinchillidae). The life cycles of these parasites are discussed.

  5. Analysis of admixture and genetic structure of two Native American groups of Southern Argentinean Patagonia.

    PubMed

    Sala, Andrea; Corach, Daniel

    2014-03-01

    Argentinean Patagonia is inhabited by people that live principally in urban areas and by small isolated groups of individuals that belong to indigenous aboriginal groups; this territory exhibits the lowest population density of the country. Mapuche and Tehuelche (Mapudungun linguistic branch), are the only extant Native American groups that inhabit the Argentinean Patagonian provinces of Río Negro and Chubut. Fifteen autosomal STRs, 17 Y-STRs, mtDNA full length control region sequence and two sets of Y and mtDNA-coding region SNPs were analyzed in a set of 434 unrelated individuals. The sample set included two aboriginal groups, a group of individuals whose family name included Native American linguistic root and urban samples from Chubut, Río Negro and Buenos Aires provinces of Argentina. Specific Y Amerindian haplogroup Q1 was found in 87.5% in Mapuche and 58.82% in Tehuelche, while the Amerindian mtDNA haplogroups were present in all the aboriginal sample contributors investigated. Admixture analysis performed by means of autosomal and Y-STRs showed the highest degree of admixture in individuals carrying Mapuche surnames, followed by urban populations, and finally by isolated Native American populations as less degree of admixture. The study provided novel genetic information about the Mapuche and Tehuelche people and allowed us to establish a genetic correlation among individuals with Mapudungun surnames that demonstrates not only a linguistic but also a genetic relationship to the isolated aboriginal communities, representing a suitable proxy indicator for assessing genealogical background.

  6. Origin of the DUPAL anomaly in mantle xenoliths of Patagonia (Argentina) and geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Mazzucchelli, Maurizio; Cipriani, Anna; Hémond, Christophe; Zanetti, Alberto; Bertotto, Gustavo Walter; Cingolani, Carlos Alberto

    2016-04-01

    The sub-continental lithospheric mantle of South America has been known for some time to carry the DUPAL isotope anomaly as seen in volcanics from the Paraná volcanic province. However, this has not allowed discriminating whether the DUPAL anomaly is a primary feature of the mantle source or acquired during the upwelling and emplacement of the primary magmas. We discovered mantle xenoliths from the Tres Lagos location in Patagonia that carry evidence of percolation by metasomatic melts that imparted the DUPAL isotope anomaly signature. We discuss a model that requires four isotope components (LCC, EM2, HIMU and DM) to account for the Sr, Nd and Pb isotope variability of our samples. We propose that upwelling of hot astenosphere during the Miocene could have triggered the melting of the LCC and EM2 components carrying the DUPAL anomaly, previously entrained in the subcontinental mantle by subduction. These ascending melts would have then metasomatised the local SCLM characterised by DMM and HIMU geochemical affinity generating the hybrid DUPAL-bearing mantle sampled by the Tres Lagos xenoliths.

  7. Environmental effects on grass-endophyte associations in the harsh conditions of south Patagonia.

    PubMed

    Novas, M Victoria; Collantes, Marta; Cabral, Daniel

    2007-07-01

    Cool-season grasses are frequently infected by Neotyphodium endophytes and this association is often considered as a mutualistic symbiosis. We examined the incidence of Neotyphodium in populations of Bromus setifolius, Phleum alpinum and Poa spiciformis, native and wide-spread grasses from south Patagonia, Argentina. The incidence of 36 populations of Bromus setifolius was studied in association with climatic and soil variables. 31 populations of Ph. alpinum were sampled in five different plant communities. Seventeen populations of P. spiciformis were sampled in three different plant communities. The association between incidence and climatic variables in Ph. alpinum and between incidence and soil fertility in P. spiciformis was investigated. In B. setifolius endophyte incidence was positively correlated with annual average rainfall contrary to the results found in Ph. alpinum. All the populations of P. spiciformis were infected by endophytes and the incidence was associated with plant community. The Neotyphodium-grass interaction is variable in natural populations, supporting the increasing evidence that the Neotyphodium-host interaction depends, in many cases, on the environmental conditions. Field observations suggest that in detrimental low growth conditions the association is not favoured, leading to a decrease in the endophyte frequency of infection or even to the complete loss of the association. PMID:17466027

  8. Spatial dynamics of Fabiana imbricata shrublands in northwestern Patagonia in relation to natural fires

    NASA Astrophysics Data System (ADS)

    Oddi, F. J.; Dudinszky, N.; Ghermandi, L.

    2010-05-01

    Fire is a critical disturbance in the structuring and functioning of most Mediterranean ecosystems. In northwestern Patagonia, vegetation patterns are strongly influenced by fire and environmental heterogeneity. Dendroecology, together with satellite imagery and GIS, have been demonstrated to be useful tools in studies that relate to fire effects with patches, patterns and species dynamics at landscape scale. Such studies can be approached from landscape ecology, which has evolved in the last years supported by the development of remote sensing and GIS technologies. This study evaluates the spatial dynamic of F. imbricata in response to fire using remote sensing, GIS and dendrochronology techniques, at landscape scale. Two sites were evaluated and one of them was affected by fire in the year 1999. The digital processing images (using the NBR spectral index) and the dendroecological analysis verified this. A fire, occurring in 1978, was also detected by the analysis of F. imbricata growth rings. The relation between F. imbricata shrubland dynamics and spatial configuration with fire, land topography and hydrography was established in the study area.

  9. New species of dictyostelids from Patagonia and Tierra del Fuego, Argentina.

    PubMed

    Vadell, Eduardo M; Cavender, James C; Romeralo, Maria; Edwards, Sally M; Stephenson, Steven L; Baldauf, Sandra L

    2011-01-01

    In late Jan and early Feb 2005 samples for isolation of dictyostelid cellular slime molds (dictyostelids) were collected in five different provinces and from six national parks (all located 39-55°S) in Patagonia and Tierra del Fuego, Argentina. Southern beech (Nothofagus) forests represented the primary vegetation type investigated, but some samples were obtained from Patagonian steppe, alpine meadows, Valdivian temperate rainforests and coniferous forests dominated by Araucaria, Austrocedrus and Fitzroya. Among the dictyostelids isolated from the samples we collected were seven species new to science. These species (Dictyostelium austroandinum, D. chordatum, D. fasciculoideum, D. gargantuum, D. leptosomopsis, D. valdivianum and Polysphondylium patagonicum) are described herein on the basis of both morphology and molecular (SSU rDNA) data. One of the new species, D. gargantuum, is one of the largest representatives of the group reported to date. Another unusual species, D. chordatum, produces long interwoven sorocarps that do not appear to respond to a spacing gas similar to the condition first noted in D. implicatum.

  10. Muscular reconstruction and functional morphology of the forelimb of early Miocene sloths (Xenarthra, Folivora) of Patagonia.

    PubMed

    Toledo, Néstor; Bargo, M Susana; Vizcaíno, Sergio F

    2013-02-01

    Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being registered mainly from Santacrucian Age deposits in southern-most shores of Patagonia, Argentina. Their postcranial skeleton differs markedly in shape from those of their closest living relatives (arboreal forms of less than 10 kg), Bradypus and Choloepus. In order to gain insight on functional properties of the Santacrucian sloths forelimb, musculature was reconstructed and a comparative, qualitative morphofunctional analysis was performed, allowing proposing hypotheses about biological role of the limb in substrate preferences, and locomotor strategies. The anatomy of the forelimb of Santacrucian sloths resembles more closely extant anteaters such as Tamandua and Myrmecophaga, due to the robustness of the elements, development of features related to attachment of ligaments and muscles, and conservative, pentadactylous, and strong-clawed manus. The reconstructed forelimb musculature was very well developed and resembles that of extant Pilosa (especially anteaters), although retaining the basic muscular configuration of generalized mammals. This musculature allowed application of powerful forces, especially in adduction of the forelimb, flexion and extension of the antebrachium, and manual prehension. These functional properties are congruent with both climbing and digging activities, and provide support for proposed Santacrucian sloths as good climbing mammals, possibly arboreal or semiarboreal, being also capable diggers. Their climbing strategies were limited, thus these forms relied mainly on great muscular strength and curved claws of the manus to move cautiously on branches. PMID:23193102

  11. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean.

    PubMed

    Glasser, Neil F; Jansson, Krister N; Duller, Geoffrey A T; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-02-12

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface "hosing" to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate.

  12. Trace elements deposition in the Tierra del Fuego region (south Patagonia) by using lichen transplants after the Puyehue-Cordón Caulle (north Patagonia) volcanic eruption in 2011.

    PubMed

    Conti, Marcelo Enrique; Jasan, Raquel; Finoia, Maria Grazia; Iavicoli, Ivo; Plá, Rita

    2016-04-01

    Lichen Usnea barbata transplants were tested as a biomonitor of atmospheric deposition in an apparently pristine environment that is Tierra del Fuego region (Patagonia, Argentina). The present survey is connected with the volcanic eruption that started in north Patagonia on June 4, 2011 from the Puyehue-Cordón Caulle volcano, Chile (north Patagonia, at 1700 km of distance of our sampling sites). Lichens were collected in September 2011 (one month of exposure) and September 2012 (1 year of exposure) in 27 sites covering the northern region of the province where trees are not present. The atmospheric deposition of 27 elements by using Neutron Activation Analysis (NAA) was determined in the collected samples. The first aim of the study was to evaluate the influence of the volcanic eruption on the regional atmospheric deposition comparing our results with baseline data we determined in U. barbata in 2006 in the same sites. The second aim was to test possible patterns of bioaccumulation between the two sampling campaigns after the volcanic eruption. With respect to 2006 baseline levels, we found significant higher levels for As, Ba, Co, Cr, Cs, Na, Sb and U in lichens collected after 1 month of exposure (first sampling campaign--2011). Between the two sampling campaigns (2011-2012) after the eruption, lichens reflected the natural contamination by volcanic ashes with significantly higher median levels of Br, Cr, Fe, K, Na, Sc, and Se. Results confirmed the very good aptitude of U. barbata to reflect the levels of elements in the environment at global scale and to reflect the volcanic emissions at distant places. Volcanic eruptions cause the emission in the atmosphere of elevated levels of particulate matter. In this regard, our findings demonstrate the importance to evaluate the metal composition of the particles to avoid possible health effects. PMID:26637301

  13. Trace elements deposition in the Tierra del Fuego region (south Patagonia) by using lichen transplants after the Puyehue-Cordón Caulle (north Patagonia) volcanic eruption in 2011.

    PubMed

    Conti, Marcelo Enrique; Jasan, Raquel; Finoia, Maria Grazia; Iavicoli, Ivo; Plá, Rita

    2016-04-01

    Lichen Usnea barbata transplants were tested as a biomonitor of atmospheric deposition in an apparently pristine environment that is Tierra del Fuego region (Patagonia, Argentina). The present survey is connected with the volcanic eruption that started in north Patagonia on June 4, 2011 from the Puyehue-Cordón Caulle volcano, Chile (north Patagonia, at 1700 km of distance of our sampling sites). Lichens were collected in September 2011 (one month of exposure) and September 2012 (1 year of exposure) in 27 sites covering the northern region of the province where trees are not present. The atmospheric deposition of 27 elements by using Neutron Activation Analysis (NAA) was determined in the collected samples. The first aim of the study was to evaluate the influence of the volcanic eruption on the regional atmospheric deposition comparing our results with baseline data we determined in U. barbata in 2006 in the same sites. The second aim was to test possible patterns of bioaccumulation between the two sampling campaigns after the volcanic eruption. With respect to 2006 baseline levels, we found significant higher levels for As, Ba, Co, Cr, Cs, Na, Sb and U in lichens collected after 1 month of exposure (first sampling campaign--2011). Between the two sampling campaigns (2011-2012) after the eruption, lichens reflected the natural contamination by volcanic ashes with significantly higher median levels of Br, Cr, Fe, K, Na, Sc, and Se. Results confirmed the very good aptitude of U. barbata to reflect the levels of elements in the environment at global scale and to reflect the volcanic emissions at distant places. Volcanic eruptions cause the emission in the atmosphere of elevated levels of particulate matter. In this regard, our findings demonstrate the importance to evaluate the metal composition of the particles to avoid possible health effects.

  14. A re-appraisal of the stratigraphy and volcanology of the Cerro Galán volcanic system, NW Argentina

    USGS Publications Warehouse

    Folkes, Christopher B.; Wright, Heather M.; Cas, Ray A.F.; de Silva, Shanaka L.; Lesti, Chiara; Viramonte, Jose G.

    2011-01-01

    From detailed fieldwork and biotite 40Ar/39Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60–4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km3 Lower Merihuaca Ignimbrite to a maximum of ~390 km3 (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km3 (DRE), approximately two thirds of the commonly quoted value.

  15. Groundmass Crystallization of A'a and Pahoehoe flows of Cerro Azul, Galapagos and Mauna Loa, Hawaii

    NASA Astrophysics Data System (ADS)

    Teasdale, R.; Geist, D.; Wanless, D.; Cashman, K.

    2001-12-01

    Crystallinities of 1998 lavas from Cerro Azul, Galapagos are distinguished from 1843 Mauna Loa, Hawaii lavas by higher modal proportions of groundmass plagioclase crystals. In both cases, a'a lava was erupted first, followed by emplacement of pahoehoe flows. The 1843 Mauna Loa eruption lasted 90 days and produced both a'a and inflated pahoehoe flows (1). The 1998 Galapagos flows were emplaced over the course of 37 days, and the transition from a'a to pahoehoe flow morphology corresponds with decreased eruption rate during the last week of the eruption. Samples were collected along the length of flows from both volcanoes. Modal groundmass plagioclase increases down-flow for each flow type from each volcano. A'a and pahoehoe flows of Cerro Azul consistently have higher crystallinities (41% and 14%) than equivalent flow types at Mauna Loa (29% and 7%). Whereas Cerro Azul groundmass crystals are exclusively plagioclase, the groundmass of Mauna Loa lavas consists of plagioclase and pyroxene crystals, similar to Kilauea lavas. Proportions of plagioclase crystals and flow morphologies are consistent with predictions that groundmass crystal morphology plays a significant role in the development of crystal networks and yield strength, which instigates the development of a'a flow morphology (2, 3). Galapagos volcanoes tend to have more a'a than their Hawaiian counterparts Mauna Loa and Kilauea. Volcano slopes do not appear to control the proportion of each flow type (4); rather, abundance of groundmass plagioclase appears to be the distinguishing factor. An important distinction between the two systems is that Galapagos lavas have consistently higher Al2O3 content than Hawaiian volcanoes. High Al203 results in a comparatively high abundance of groundmass plagioclase, and may partly explain the prevalence of a'a. We note that while the relative abundance of a'a and pahoehoe flow morphologies on other volcanoes is rarely quantified, Mount Etna is also distinguished by abundant

  16. Variations in trace element partition coefficients in sanidine in the Cerro Toledo Rhyolite, Jemez Mountains, New Mexico: Effects of composition, temperature, and volatiles

    SciTech Connect

    Stix, J. ); Gorton, M.P. )

    1990-10-01

    Trace element partition coefficients have been measured for one plagioclase and five sanidine mineral separates from the Cerro Toledo Rhyolite, New Mexico. Sanidine partition coefficients vary substantially and systematically within the Cerro Toledo Rhyolite. Partition coefficients for Ca, Sr, Zn, La, and Eu are lowest in the most evolved rhyolites, whereas Sm and HREE partition coefficients are highest. Rubidium partition coefficients remain constant, while those for Ba, Ce, and Th are variable. Variations of the Sr, Zn, La, and Eu partition coefficients are correlated with the Ca contents and partition coefficients of the sanidines. Calcium may have controlled the distribution of these elements in the sanidine by modifying the feldspar structure. The low Ca partition coefficients in sanidines for the most evolved rhyolites may be the consequence of modification of the melt structure, possibly due to increased volatile contents at the top of the magma chamber(s) during evolution of the Cerro Toledo Rhyolite. The Zn and La partition coefficients between sanidine and melt also may have been controlled by this change in melt structure. Modelling using major elements and the constant Rb partition coefficient for sanidine indicates 70% crystallization of magma during Cerro Toledo Rhyolite time by removal of 68% sanidine and 32% quartz. Estimates of the volume (1) of initial parental magma and (2) of the magma that crystallized during this period are 11,670 km{sup 3} and 8,170 km{sup 3}, respectively. The average intrusion rate of silicic magma during Cerro Toledo Rhyolite activity was 35 {times} 10{sup {minus}3} km{sup 3}/a.

  17. Eruptive history of the youngest Mexican Shield and Mexico's most voluminous Holocene eruption: Cerro El Metate

    NASA Astrophysics Data System (ADS)

    Oryaëlle Chevrel, Magdalena; Guilbaud, Marie-Noelle; Siebe, Claus

    2016-04-01

    Small to medium-sized shield volcanoes are an important component of many volcanic fields on Earth. The Trans-Mexican Volcanic Belt, one of the most complex and active continental arcs worldwide, displays a large number of such medium-sized volcanoes. In particular the Michoacán-Guanajuato Volcanic Field (MGVF) situated in central Mexico, is the largest monogenetic volcanic field in the world and includes more than 1000 scoria cones and about four hundred medium-sized volcanoes, also known as Mexican shields. The Mexican shields nevertheless represent nearly 70% of the total volume erupted since 1 Ma and hence played a considerable role in the formation of the MGVF. However, the source, storage, and transport as well as the physical properties (density, viscosity, volatile content, etc.) of the magmas involved in these eruptions remain poorly constrained. Here, we focus on Cerro El Metate, the youngest monogenetic andesite shield volcano of the field. New C14 dates for the eruption yield a young age (~AD 1250), which briefly precedes the initial rise of the Tarascan Empire (AD 1350-1521) in this region. This volcano has a minimum volume of ~9.2 km3 DRE, and its viscous lava flows were emplaced during a single eruption over a period of ~35 years covering an area of 103 km2. By volume, this is certainly the largest eruption during the Holocene in Mexico, and it is the largest andesitic effusive eruption known worldwide for this period. Such a large volume of lava erupted in a relatively short time had a significant impact on the environment (modification of the hydrological network, forest fires, etc.), and hence, nearby human populations probably had to migrate. Its eruptive history was reconstructed through detailed mapping, and geochemical and rheological analyses of its thick hornblende-bearing andesitic flows. Early and late flows have distinct morphologies, chemical and mineralogical compositions, and isotopic signatures which show that these lavas were fed by

  18. 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

  19. Burning down the brewery: Establishing and evacuating an ancient imperial colony at Cerro Baúl, Peru

    PubMed Central

    Moseley, Michael E.; Nash, Donna J.; Williams, Patrick Ryan; deFrance, Susan D.; Miranda, Ana; Ruales, Mario

    2005-01-01

    Before the Inca reigned, two empires held sway over the central Andes from anno Domini 600 to 1000: the Wari empire to the north ruled much of Peru, and Tiwanaku to the south reigned in Bolivia. Face-to-face contact came when both colonized the Moquegua Valley sierra in southern Peru. The state-sponsored Wari incursion, described here, entailed large-scale agrarian reclamation to sustain the occupation of two hills and the adjacent high mesa of Cerro Baúl. Monumental buildings were erected atop the mesa to serve an embassy-like delegation of nobles and attendant personnel that endured for centuries. Final evacuation of the Baúl enclave was accompanied by elaborate ceremonies with brewing, drinking, feasting, vessel smashing, and building burning. PMID:16293691

  20. Results of the first order leveling surveys in the Mexicali Valley and at the Cerro Prieto field

    SciTech Connect

    de la Pena L, A.

    1981-01-01

    The results obtained from the third leveling survey carried out by the Direccion General de Geografia del Territorio Nacional (previously DETENAL) during November and December 1979 are presented. Calculations of the changes in field elevation and plots showing comparisons of the 1977, 1978, and 1979 surveys are also presented. Results from a second order leveling survey performed to ascertain the extent of ground motion resulting from the 8 June 1980 earthquake are presented. This magnitude ML = 6.7 earthquake with epicenter located 15 km southeast of the Guadalupe Victoria village, caused fissures on the surface, the formation of small sand volcanos, and the ejection of ground water in the vicinity of the Cerro Prieto field. This leveling survey was carried out between benchmark BN-10067 at the intersection of the Solfatara canal and the Sonora-Baja California railroad, and benchmark BN-10055 located at the Delta station.

  1. Curie point depth from spectral analysis of aeromagnetic data from Cerro Prieto geothermal area, Baja California, México

    NASA Astrophysics Data System (ADS)

    Espinosa-Cardeña, J. M.; Campos-Enriquez, J. O.

    2008-10-01

    Using aeromagnetic data acquired in the area from the Cerro Prieto geothermal field, we estimated the depth to the Curie point isotherm, interpreted as the base of the magnetic sources, following statistical spectral-based techniques. According to our results the Curie point isotherm is located at a depths ranging from 14 to 17 km. Our result is somewhat deeper than that obtained previously based only in 2-D and 3-D forward modeling of previous low-quality data. However, our results are supported by independent information comprising geothermal gradients, seismicity distribution in the crust, and gravity determined crustal thickness. Our results imply a high thermal gradient (ranging between 33 and 38 °C/km) and high heat flow (of about 100 mW/m 2) for the study area. The thermal regime for the area is inferred to be similar to that from the Salton trough.

  2. Constraining the Paleogene of South America: Magnetostratigraphy and paleoclimate proxy records from Cerro Bayo (Provincia de Salta, Argentina)

    NASA Astrophysics Data System (ADS)

    Hyland, E.; Cotton, J. M.; Sheldon, N. D.

    2012-12-01

    Records of rapid climatic and ecological shifts in the past are crucial for understanding global systems and for predicting future impacts of climate change. Transient and broad scale hyperthermal events during the Paleogene, such as the Paleocene-Eocene Thermal Maximum (PETM) and Early Eocene Climatic Optimum (EECO), have been studied extensively through both marine records and a significant terrestrial record from North America. Despite this, little evidence exists from the climatic and ecological histories of other major landmasses, which limits the effectiveness of global climate response predictions. Here we present an integrated paleoenvironmental reconstruction of the early Paleogene from a site in central South America (Cerro Bayo, Argentina), including a new magnetostratigraphic age model, pedological and sedimentological interpretation, whole rock geochemical climate proxies, isotopic environmental proxies, and microfloral assemblages. Cerro Bayo is a 235-meter terrestrial section that exposes the Tunal, Mealla, and Maiz Gordo Formations, and based on magnetostratigraphic interpolation spans roughly 58—50 Mya, including both the PETM and EECO events. These formations are composed primarily of reddish sandstone and siltstone, much of which exhibits features characteristic of a moderate degree of pedogenesis (i.e., Inceptisols and Alfisols). High-resolution climate proxies derived from paleosol geochemical compositions highlight rapid increases in mean annual temperature (>5°C) and precipitation (>300 mm yr-1) during the PETM, as well as more gradual increasing temperature and precipitation trends leading up to the EECO. Carbon isotope stratigraphy through the section also indicates a sizable negative excursion (~4‰) during the PETM, and generally positive isotopic trends during the early Eocene. Phytolith biostratigraphy also details changes in local vegetation composition during climatic events that corresponds to similar patterns seen in terrestrial

  3. Analysis of the Nuevo Leon magnetic anomaly and its possible relation to the Cerro Prieto magmatic-hydrothermal system

    SciTech Connect

    Goldstein, N.E.; Wilt, M.J.; Corrigan, D.J.

    1982-10-01

    The broad dipolar magnetic anomaly whose positive peak is centered near Ejido Nuevo Leon, some 5 km east of the Cerro Prieto I Power Plant, has long been suspected to have a genetic relationship to the thermal source of the Cerro Prieto geothermal system. This suspicion was reinforced after several deep geothermal wells, drilled to depths of 3 to 3.5 km over the anomaly, intersected an apparent dike-sill complex consisting mainly of diabase but with minor rhyodacite. A detailed fit of the observed magnetic field to a computer model indicates that the source may be approximated by a tabular block 4 by 6 km in area, 3.7 km in depth, 2.3 km thick, and dipping slightly to the north. Mafic dike chips from one well, NL-1, were analyzed by means of electron microprobe analyses which showed tham to contain a titanomagnetite that is paramagnetic at in-situ temperature conditions. As the dike mineralogy does not account for the magnetic anomaly, the magnetic source is believed to be a deeper, magnetite-rich assemblage of peridotite-gabbro plutons. the suite of igneous rocks was probably passively emplaced at a shallow depth in response to crustal extension and thinning brought on by strike-slip faulting. The bottom of the magnetic source body, at an estimated depth of 6 km, is presumed to be at or near that of the Curie isotherm (575/sup 0/C) for magnetite, the principal ferromagnetic mineral in peridotitic-gabbroic rocks. The geological model derived from the magnetic study is generally supported by other geophysical data. In particular, earthquake data suggest dike injection is occurring at depths of 6 to 11 km in an area beneath the magnetic source. Thus, it is possible that heat for the geothermal field is being maintained by continuing crustal extension and magmatic activity.

  4. Analysis of the Nuevo Leon Magnetic Anomaly and its possible relation to the Cerro Prieto magmatic-hydrothermal system

    SciTech Connect

    Goldstein, N.E.; Corrigan, D.J.; Wilt, M.J.

    1984-01-01

    The broad dipolar magnetic anomaly whose positive peak is centered near Ejido Nuevo Leon, some 5 km east of the Cerro Prieto I power plant, has long been suspected to have a genetic relationship to the thermal source of the Cerro Prieto geothermal system. This suspicion was reinforced after several deep geothermal wells, drilled to depths of 3-3.5 km over the anomaly, intersected an apparent dike-sill complex consisting mainly of diabase but with minor rhyodacite. A detailed fit of the observed magnetic field to a computer model indicates that the source may be approximated by a tabular block 4 x 6 km in area, 3.7 km in depth, 2.3 km thick, and dipping slightly to the north. Mafic dike chips from one well, NL-1, were analysed by means of electron microprobe analyses which showed them to contain a titanomagnetite that is paramagnetic at in situ temperature conditions. As the dike mineralogy does not account for the magnetic anomaly, the magnetic source is believed to be a deeper, magnetite-rich assemblage of peridotite-gabbro plutons. The suite of igneous rocks was probably emplaced at a shallow depth in response to crustal extension and thinning brought on by en echelon strike-slip faulting. The bottom of the magnetic source body, at an estimated depth of 6 km, is presumed to be at or near that of the Curie isotherm (575/sup 0/C) for magnetite, the principal ferromagnetic mineral in peridotiticgabbroic rocks. The geological model derived from the magnetic study is generally supported by other geophysical data. In particular, earthquake data suggest dike injection is occurring at depths of 6-11 km in an area beneath the magnetic source. Thus, it is possible that heat for the geothermal field is being maintained by continuing crustal extension and magmatic activity.

  5. The Cerro Aguas Calientes caldera, NW Argentina: An example of a tectonically controlled, polygenetic collapse caldera, and its regional significance

    NASA Astrophysics Data System (ADS)

    Petrinovic, I. A.; Martí, J.; Aguirre-Díaz, G. J.; Guzmán, S.; Geyer, A.; Paz, N. Salado

    2010-07-01

    Polygenetic, silicic collapse calderas are common in the central Andes. Here we describe in detail the Cerro Aguas Calientes caldera in NW Argentina, which comprises two caldera-forming episodes that occurred at 17.15 Ma and 10.3 Ma. We analyse the significance of its structural setting, composition, size and the subsidence style of both caldera episodes. We find that the caldera eruptions had a tectonic trigger. In both cases, an homogeneous dacitic crystal-rich (>60 vol.% of crystals) reservoir of batholithic size became unstable due to the effect of increasing regional transpression, which favoured local dilation through minor strike-slip faults from which ring faults nucleated and permitted caldera collapse. Both calderas are similar in shape, location and products. The 17.15 Ma caldera has an elliptical shape (17 × 14 km) elongated in a N30° trend; both intracaldera and extracaldera ignimbrites covered an area of around 620 km 2 with a minimum volume estimate of 140 km 3 (DRE). The 10.3 Ma episode generated another elliptical caldera (19 × 14 km), with the same orientation as the previous one, from which intracaldera and outflow ignimbrites covered a total area of about 1700 km 2, representing a minimum eruption volume of 350 km 3(DRE). In this paper we discuss the significance of the Cerro Aguas Calientes caldera in comparison with other well known examples from the central Andes in terms of tectonic setting, eruption mechanisms, and volumes of related ignimbrites. We suggest that our kinematic model is a common volcano-tectonic scenario during the Cenozoic in the Puna and Altiplano, which may be applied to explain the origin of other large calderas in the same region.

  6. Environmental Niche Overlap between Common and Dusky Dolphins in North Patagonia, Argentina

    PubMed Central

    Svendsen, Guillermo Martín; Romero, María Alejandra; Williams, Gabriela Noemí; Gagliardini, Domingo Antonio; Crespo, Enrique Alberto; Dans, Silvana Laura; González, Raúl Alberto

    2015-01-01

    Research on the ecology of sympatric dolphins has increased worldwide in recent decades. However, many dolphin associations such as that between common dolphins (Delphinus delphis) and dusky dolphins (Lagenorhynchus obscurus) are poorly understood. The present study was conducted in the San Matías Gulf (SMG) ecosystem (North Patagonia, Argentina) where a high diet overlap among both species was found. The main objective of the present work was to explore the niche overlap of common and dusky dolphins in the habitat and temporal dimensions. The specific aims were (a) to evaluate the habitat use strategies of both species through a comparison of their group attributes (social composition, size and activity), and (b) to evaluate their habitat preferences and habitat overlap through Environmental Niche modeling considering two oceanographic seasons. To accomplish these aims, we used a historic database of opportunistic and systematic records collected from 1983 to 2011. Common and dusky dolphins exhibited similar patterns of group size (from less than 10 to more than 100 individuals), activity (both species use the area to feed, nurse, and copulate), and composition (adults, juveniles, and mothers with calves were observed for both species). Also, both species were observed travelling and feeding in mixed-species groups. Specific overlap indices were higher for common dolphins than for dusky dolphins, but all indices were low, suggesting that they are mainly segregated in the habitat dimension. In the case of common dolphins, the best habitats were located in the northwest of the gulf far from the coast. In the warm season they prefer areas with temperate sea surface and in the cold season they prefer areas with relatively high variability of sea surface temperature. Meanwhile, dusky dolphins prefer areas with steep slopes close to the coast in the southwestern sector of the gulf in both seasons. PMID:26091542

  7. Centennial and millennial-scale hydroclimate changes in northwestern Patagonia since 16,000 yr BP

    NASA Astrophysics Data System (ADS)

    Moreno, Patricio I.; Videla, Javiera

    2016-10-01

    We examine hydroclimate changes at centennial/millennial timescales since 16,000 yr BP in northwestern Patagonia based on the pollen and charcoal record from Lago El Salto, a small closed-basin lake located in the Chilean Lake District (41°38‧48.02″S, 73° 5‧48.42″W). We observe cold/wet conditions between 14,500-16,000 yr BP, followed by further cooling with increased precipitation until 13,000 yr BP, enhanced precipitation seasonality and/or variability between 11,600-13,000 yr BP, and an extended warm-and-dry interval between 7600 and 11,300 yr BP with peak paleofire activity. Colder-and-wetter than present conditions and muted paleofire activity prevail between 5300 and 7600 yr BP, followed by alternating cold/wet and centennial-scale warm/dry phases starting at 5300 yr BP with three conspicuous megadroughts since 2500 yr BP. The most recent megadrought occurred during the Medieval Climate Anomaly. We identify a cold reversal that spans the Antarctic Cold Reversal (ACR) and the Younger Dryas (YD) chrons with stronger-than-present westerly influence during the former and enhanced variability during the latter. These results extend the northern limit of strong cooling and increase in precipitation during the ACR and the southern limit of influence of strong hydrologic variations during the YD in terrestrial environments, suggesting an overlap in the spheres of influence of processes originating from southern and northern polar latitudes. An extended warm southern westerly wind (SWW)-minimum interval is evident between 7600 and 11,300 yr BP, followed by a rapid shift to cool-moist conditions between 5300 and 7600 yr BP brought by a mid-Holocene SWW maximum. Since then we observe centennial-scale hydroclimate variability, which has driven biodiversity and fire-regime shifts of evergreen temperate rainforests.

  8. Melting glacier impacts the community structure of Bacteria, Fungi and Archaea in Chilean Patagonia fjord system

    NASA Astrophysics Data System (ADS)

    Gutiérrez, Marcelo, ,, Dr.; Galand, Pierre; Moffat, Carlos; Pantoja, Silvio

    2014-05-01

    microbial composition and therefore the heterotrophic activity in the Chilean Patagonia fjord ecosystem. This research was funded by FONDECYT grant 11110515.

  9. The phylogenetic position of poroid Hymenochaetaceae (Hymenochaetales, Basidiomycota) from Patagonia, Argentina.

    PubMed

    Rajchenberg, Mario; Pildain, María Belén; Bianchinotti, María V; Barroetaveña, Carolina

    2015-01-01

    Six poroid Hymenochaetaceae from Patagonia, Argentina, were studied phylogenetically with nuc rDNA internal transcribed spacer (ITS) and partial 28S rDNA sequences, together with morphological data. Two new genera and a new species are introduced as well as two new combinations proposed. Arambarria destruens gen. et sp. nov. is proposed for a taxon fruiting on fallen or standing, dead Diostea juncea and Lomatia hirsuta and previously recorded erroneously as Inocutis jamaicensis; it is distinguished by annual, effused to effused-reflexed basidiomes forming pilei, a monomitic hyphal system, thick-walled and yellowish basidiospores (brownish chestnut in potassium hydroxide solution), lack of a granular core in the context and lack of setoid elements. Nothophellinus gen. nov. is proposed to accommodate Phellinus andinopatagonicus, the main white wood-rotting polypore of standing Nothofagus pumilio and also an important wood-decayer of other Nothofagus species from southern Argentina and Chile. It is morphologically similar to Phellopilus (type species P. nigrolimitatus) but differs by lacking setae. The new combinations Pseudoinonotus crustosus and Phellinopsis andina are proposed for Inonotus crustosus and Phellinus andinus, respectively. Phellinus livescens, which decays the sapwood of several standing Nothofagus species, is closely related to Phellinus uncisetus, a Neotropical species related to Fomitiporia; for the time being P. livescens is retained in Phellinus sensu lato. An unidentified taxon responsible for a white heart-rot in living Austrocedrus chilensis grouped with Phellinus caryophyllii and Fulvifomes inermis, but its generic affinities remain ambiguous. Transmission electron microscopy studies confirm this unidentified taxon has an imperforate parenthesome, which is typical of the Hymenochaetaceae.

  10. Litter and soil properties are not altered by invasive deer browsing in forests of NW Patagonia

    NASA Astrophysics Data System (ADS)

    Relva, María Andrea; Castán, Elisa; Mazzarino, María Julia

    2014-01-01

    It is largely accepted that large mammalian herbivores can indirectly influence ecosystem properties by changing the quantity and quality of litter inputs to soil through selective browsing on plant communities. However, idiosyncratic effects (positive, neutral and negative) have been found for different vegetation types, herbivory and soil properties. In this study we tested whether browsing by exotic deer introduced into Patagonian forests 90 years ago alters physical, chemical and biological soil properties and litter quantity and quality. As in many terrestrial ecosystems, N is the main nutrient that limits plant growth in Patagonia. Consequently, any disturbance that alters the N cycle, such as changes in the type or intensity of herbivory, is expected to affect these forest ecosystems. We compared soil and total litter from inside and outside five 7-yr old exclosures located on Isla Victoria, Parque Nacional Nahuel Huapi, Argentina. Despite introduced deer has significantly affected the composition, abundance and structure of the understory vegetation, we found no differences between browsed and unbrowsed areas in the physical (bulk density, moisture), chemical (pH, base cations, organic C and total N) and biological (potential microbial respiration and net N mineralization) soil properties. This could be attributable to the high capacity of volcanic soils to stabilize organic matter, buffering disturbance-induced changes. However, the quantity and quality (C, N and C/N ratio) of total litter were also not different between browsed and unbrowsed areas. Although non-significant differences were found between treatments in both compartments, litter and soil, most variables showed a slight trend toward higher values in unbrowsed areas. This suggests that 7 years of browsing exclusion would be not enough to detect changes induced by browsing, particularly in highly stable volcanic soils.

  11. Environmental impacts on offspring survival during the lambing period in central Patagonia

    NASA Astrophysics Data System (ADS)

    Coronato, F.

    Weather conditions are the main factors affecting the survival rate of newborn lambs. In the windy climate of Patagonia, the influence of weather conditions is exacerbated as the wind speed increases noticeably in spring. If the wind increases faster than the temperature rises, wind chill conditions worsen temporarily. This departure from the predictable improvement in bioclimatic conditions as the season moves towards summer may coincide with lambing, if this is not adequately regulated. This paper explores bioclimatic conditions during the 2-month period in which lambing may take place (i.e. mid-September to mid-November), and identifies the unfavourable period that occurs in the second fortnight of October. Starting from the Mount and Brown (Agric Meteorol 27:241-255, 1982) model to assess thermal stress in sheep by means of common meteorological records, a simpler model was developed employing in long-term records. For 2-week averages of temperature (Tf), wind speed (Vf) and total precipitation (Pf), the average heat loss in sheep (HLf) was 40.40-2.07Tf+5.64Vf+0.04Pf. (r2=0.95). A 24-year series of Tf, Vf and Pf data was employed in the calculation of HLf, and results showed this parameter was significantly higher in the second fortnight in October. HLf values were classified into four groups (from ''very good'' to ''very bad'' conditions); once again, significant differences appeared in the second fortnight in October. Finally, HLf during the lambing period was correlated to the percentage of lambs surviving 2 months later. Significant differences between the survival of lambs born under ''very bad'' and ''very good'' conditions were found, but intermediate HLf conditions did not show a clear pattern. The survival rate was best correlated to HLf in the fortnight preceding lambing (P<0.05). This suggests that bioclimatic conditions during late pregnancy are at least as important as conditions during lambing in determining the survival lambs.

  12. Mountain frozen grounds as small amplitude thermal proxy in southern continental Patagonia

    NASA Astrophysics Data System (ADS)

    Ruiz, Sebastian; Beriain, Eneko; Izagirre, Eñaut; Bockheim, James; Pedro, Cid-Agüero

    2015-04-01

    Frozen grounds are an important element of the cryosphere, covering between a 20-25% of the global area. Frozen grounds are becoming a relevant object of research in the southern hemisphere, being most studies focused mainly on Antarctica. With the exception of seasonally frozen grounds, perennially frozen ground is found in continental South America, for example, in high altitude terrains from 4.600m a.s.l. in central Chile. However, scarce or not information regarding permafrost on Southern Patagonia has been reported. One of the aims of this study was to establish mountain permafrost existence at 1.200m in the southern limit of the Southern Patagonian Ice-Field, a geographically active area surrounded by different kinds of glaciers on fast retreat. The area of study presents several features of past cryogenic activity such as undefined polygonal grounds with a thick clast border and sandy-loam interior. A scarce vegetal cover is limited to lichen and moss communities. The analyzed soil does not represent a thermal barrier that may avoid heat wave dynamic along the ground profile. There was neither significant snow-cover during winter nor a vegetation layer enough to consider as insulation for the analyzed ground. Oscillations above 0°C were evidenced down to 1.8m depth during winter of 2014, ruling out the existence of permafrost at that lower limit. Year round thermal dynamic down to 1.8m in the ground profile is presented as one result of the monitoring. Small amplitude temperature fluctuations were registered upon monitoring. These minimal amplitudes were stable throughout several months and as such serve as an interesting proxy for recent and long-term climatic thermal fluctuation. The influence of winds coming from nearby glaciers highly affects near-surface amplitude. This interaction was studied. The present work is part of an ongoing monitoring network along South America that intends to fill the gap between tropical Andes and the Antarctic Peninsula.

  13. An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

    PubMed Central

    Apesteguía, Sebastián; Smith, Nathan D.; Juárez Valieri, Rubén; Makovicky, Peter J.

    2016-01-01

    Background Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit. Methodology/ Principal Findings A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton. Conclusions/ Significance Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa. PMID:27410683

  14. A Water Resources Management Model to Evaluate Climate Change Impacts in North-Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Bucciarelli, L. F.; Losano, F. T.; Marizza, M.; Cello, P.; Forni, L.; Young, C. A.; Girardin, L. O.; Nadal, G.; Lallana, F.; Godoy, S.; Vallejos, R.

    2014-12-01

    Most recently developed climate scenarios indicate a potential future increase in water stress in the region of Comahue, located in the North-Patagonia, Argentina. This region covers about 140,000 km2 where the Limay River and the Neuquén River converge into the Negro River, constituting the largest integrated basins in Argentina providing various uses of water resources: a) hydropower generation, contributing 15% of the national electricity market; b) fruit-horticultural products for local markets and export; c) human and industrial water supply; d) mining and oil exploitation, including Vaca Muerta, second world largest reserves of shale gas and fourth world largest reserves of shale-oil. The span of multiple jurisdictions and the convergence of various uses of water resources are a challenge for integrated understanding of economically and politically driven resource use activities on the natural system. The impacts of climate change on the system could lead to water resource conflicts between the different political actors and stakeholders. This paper presents the results of a hydrological simulation of the Limay river and Neuquén river basins using WEAP (Water Evaluation and Planning) considering the operation of artificial reservoirs located downstream at a monthly time step. This study aims to support policy makers via integrated tools for water-energy planning under climate uncertainties, and to facilitate the formulation of water policy-related actions for future water stress adaptation. The value of the integrated resource use model is that it can support local policy makers understand the implications of resource use trade-offs under a changing climate: 1) water availability to meet future growing demand for irrigated areas; 2) water supply for hydropower production; 3) increasing demand of water for mining and extraction of unconventional oil; 4) potential resource use conflicts and impacts on vulnerable populations.

  15. Environmental Niche Overlap between Common and Dusky Dolphins in North Patagonia, Argentina.

    PubMed

    Svendsen, Guillermo Martín; Romero, María Alejandra; Williams, Gabriela Noemí; Gagliardini, Domingo Antonio; Crespo, Enrique Alberto; Dans, Silvana Laura; González, Raúl Alberto

    2015-01-01

    Research on the ecology of sympatric dolphins has increased worldwide in recent decades. However, many dolphin associations such as that between common dolphins (Delphinus delphis) and dusky dolphins (Lagenorhynchus obscurus) are poorly understood. The present study was conducted in the San Matías Gulf (SMG) ecosystem (North Patagonia, Argentina) where a high diet overlap among both species was found. The main objective of the present work was to explore the niche overlap of common and dusky dolphins in the habitat and temporal dimensions. The specific aims were (a) to evaluate the habitat use strategies of both species through a comparison of their group attributes (social composition, size and activity), and (b) to evaluate their habitat preferences and habitat overlap through Environmental Niche modeling considering two oceanographic seasons. To accomplish these aims, we used a historic database of opportunistic and systematic records collected from 1983 to 2011. Common and dusky dolphins exhibited similar patterns of group size (from less than 10 to more than 100 individuals), activity (both species use the area to feed, nurse, and copulate), and composition (adults, juveniles, and mothers with calves were observed for both species). Also, both species were observed travelling and feeding in mixed-species groups. Specific overlap indices were higher for common dolphins than for dusky dolphins, but all indices were low, suggesting that they are mainly segregated in the habitat dimension. In the case of common dolphins, the best habitats were located in the northwest of the gulf far from the coast. In the warm season they prefer areas with temperate sea surface and in the cold season they prefer areas with relatively high variability of sea surface temperature. Meanwhile, dusky dolphins prefer areas with steep slopes close to the coast in the southwestern sector of the gulf in both seasons.

  16. Sr-isotope chronostratigraphy of Paleogene-Neogene marine deposits: Austral Basin, southern Patagonia (Argentina)

    NASA Astrophysics Data System (ADS)

    Parras, Ana; Dix, George R.; Griffin, Miguel

    2012-08-01

    The Paleogene to Neogene San Julián and Monte León formations underlie the central and eastern parts of the Austral Basin (Patagonia, Argentina), and represent coastal plain to shallow shelf systems within a retroarc foreland basin east of the Andes. The formations are characterized by prominent occurrences of thin (<1 m) densely compacted fossil concentrations, including the large oyster Crassostrea? hatcheri. Formation ages have been problematic given macrofaunal provincialism effectively precluding precise extrabasinal correlations. A Sr-isotope chronostratigraphy based on fossil shell calcite from oysters, pectinids and brachiopods is presented for a regional NE-SW-oriented transect extending ˜200 km along strike of the Austral Basin. The Paleogene-Neogene boundary (˜23 Ma) may occur within the uppermost San Julián Formation (22.68 Ma, with a range between 22.22 and 23.22 Ma), coincident with a prominent glauconitic interval, or in a meteorically altered erosional paleosurface that caps this formation and may correlate with an eustatic sea level fall coincident with the global boundary. The younger Monte León Formation is entirely of early Neogene (Aquitanian to early Burdigalian) age, with ages of 22.12 Ma (21.68-22.58) at the base to 17.91 Ma (17.51-18.29) at the top. The proposed new chronostratigraphic framework forms a foundation for future differentiation of local, regional, and global sedimentary patterns in the Austral Basin during the Paleogene/Neogene transition; in particular, with contemporaneous basins and tectonic blocks across the southern polar region, such as in Australia, New Zealand, and Antarctica.

  17. Late Holocene covariability of the southern westerlies and sea surface temperature in northern Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Bertrand, Sébastien; Hughen, Konrad; Sepúlveda, Julio; Pantoja, Silvio

    2014-12-01

    The climate of Chilean Patagonia is strongly influenced by the southern westerlies, which control the amount and latitudinal distribution of precipitation in the southern Andes. In austral summer, the Southern Westerly Wind Belt (SWWB) is restricted to the high latitudes. It expands northward in winter, which results in a strong precipitation seasonality between ˜35 and 45°S. Here, we present a new precipitation seasonality proxy record from Quitralco fjord (46°S), where relatively small latitudinal shifts of the SWWB result in large changes in precipitation seasonality. Our 1400 yr record is based on sedimentological and geochemical data obtained on a sediment core collected in front of a small river that drains the Patagonian Andes, which makes this site particularly sensitive to changes in river discharge. Our results indicate Fe/Al and Ti/Al values that are low between 600 and 1200 CE, increasing at 1200-1500 CE, and high between 1500 and 1950 CE. Increasing Fe/Al and Ti/Al values reflect a decrease in mean sediment grain-size from 30 to 20 μm, which is interpreted as a decrease in seasonal floods resulting from an equatorward shift of the SWWB. Our results suggest that, compared to present-day conditions, the SWWB was located in a more poleward position before 1200 CE. It gradually shifted towards the equator in 1200-1500 CE, where it remained in a sustained position until 1950 CE. This pattern is consistent with most precipitation records from central and southern Chile. The comparison of our record with published regional sea surface temperature (SST) reconstructions for the late Holocene shows that equatorward shifts of the SWWB are systematically coeval with decreasing SSTs and vice versa, which resembles fluctuations over glacial-interglacial timescales. We argue that the synchronicity between SST and SWWB changes during the last 1400 years represents the response of the SWWB to temperature changes in the Southern Hemisphere.

  18. Iridium, platinum and rhodium baseline concentration in lichens from Tierra del Fuego (South Patagonia, Argentina).

    PubMed

    Pino, Anna; Alimonti, Alessandro; Conti, Marcelo Enrique; Bocca, Beatrice

    2010-10-01

    Lichen samples of Usnea barbata were used as possible biomonitors of the atmospheric background level of iridium (Ir), platinum (Pt) and rhodium (Rh) in the remote region of Tierra del Fuego (South Patagonia, Argentina). Lichens were collected in 2006 at 53 sites covering 7 different areas of the region (24 transplanted lichens of the northern region and 29 native lichen samples of the central-southern region). A microwave acidic digestion procedure was used to mineralize the samples and a sector field inductively coupled plasma mass spectrometry method was developed to quantify the elements. The study of the influence of interferences on analyte signals and a quality control procedure were carried out. The analytical protocol was further applied to evaluate Ir, Pt and Rh bioaccumulation in lichens. The detection limits obtained were 0.010 ng g⁻¹, 0.013 ng g⁻¹ and 0.030 ng g⁻¹ for Ir, Pt and Rh, respectively. Recoveries at different fortification levels were between 96.3% and 106% and precision was 3.3% on average. The metals concentration (as dry weight) spanned the following ranges: Ir, <0.010-1.011 ng g⁻¹; Pt, 0.016-2.734 ng g⁻¹; and Rh, 0.063-1.298 ng g⁻¹. Data on 7 areas were similar suggesting that no specific source, for example traffic or anthropogenic activity, influenced directly the metal concentrations in Tierra del Fuego. Values detected are more likely influenced by the long-range atmospheric transport of these pollutants and, in comparison with densely populated areas in the world, they can represent the baseline for low impacted areas.

  19. Peat decomposition records in three pristine ombrotrophic bogs in southern Patagonia

    NASA Astrophysics Data System (ADS)

    Broder, T.; Blodau, C.; Biester, H.; Knorr, K. H.

    2012-04-01

    Ombrotrophic bogs in southern Patagonia have been examined with regard to paleoclimatic and geochemical research questions but knowledge about organic matter decomposition in these bogs is limited. Therefore, we examined peat humification with depth by Fourier Transformed Infrared (FTIR) measurements of solid peat, C/N ratio, and δ13C and δ15N isotope measurements in three bog sites. Peat decomposition generally increased with depth but distinct small scale variation occurred, reflecting fluctuations in factors controlling decomposition. C/N ratios varied mostly between 40 and 120 and were significantly correlated (R2 > 0.55, p < 0.01) with FTIR-derived humification indices. The degree of decomposition was lowest at a site presently dominated by Sphagnum mosses. The peat was most strongly decomposed at the driest site, where currently peat-forming vegetation produced less refractory organic material, possibly due to fertilizing effects of high sea spray deposition. Decomposition of peat was also advanced near ash layers, suggesting a stimulation of decomposition by ash deposition. Values of δ13C were 26.5 ± 2‰ in the peat and partly related to decomposition indices, while δ15N in the peat varied around zero and did not consistently relate to any decomposition index. Concentrations of DOM partly related to C/N ratios, partly to FTIR derived indices. They were not conclusively linked to the decomposition degree of the peat. DOM was enriched in 13C and in 15N relative to the solid phase probably due to multiple microbial modifications and recycling of N in these N-poor environments. In summary, the depth profiles of C/N ratios, δ13C values, and FTIR spectra seemed to reflect changes in environmental conditions affecting decomposition, such as bog wetness, but were dominated by site specific factors, and are further influenced by ash deposition and possibly by sea spray input.

  20. Draft Whole-Genome Sequence of Sphingobium sp. 22B, a Polycyclic Aromatic Hydrocarbon–Degrading Bacterium from Semiarid Patagonia, Argentina

    PubMed Central

    Macchi, M.; Morelli, I. S.; Coppotelli, B. M.

    2016-01-01

    Sphingobium sp. 22B is a polycyclic aromatic hydrocarbon–degrading strain isolated from Patagonia, Argentina, with capabilities to withstand the environmental factors of that semiarid region. The draft genome shows the presence of genes related with responses to carbon starvation and drying environmental conditions. PMID:27257204

  1. High-temperature emplacement of the Cerro Galán and Toconquis Group ignimbrites (Puna plateau, NW Argentina) determined by TRM analyses

    NASA Astrophysics Data System (ADS)

    Lesti, Chiara; Porreca, Massimiliano; Giordano, Guido; Mattei, Massimo; Cas, Raymond A. F.; Wright, Heather M. N.; Folkes, Chris B.; Viramonte, Josè

    2011-12-01

    Estimates of pyroclastic flow emplacement temperatures in the Cerro Galán ignimbrite and Toconquis Group ignimbrites were determined using thermal remanent magnetization of lithic clasts embedded within the deposits. These ignimbrites belong to the Cerro Galán volcanic system, one of the largest calderas in the world, in the Puna plateau, NW Argentina. Temperature estimates for the 2.08-Ma Cerro Galán ignimbrite are retrieved from 40 sites in 14 localities (176 measured clasts), distributed at different distances from the caldera and different stratigraphic heights. Additionally, temperature estimates were obtained from 27 sample sites (125 measured clasts) from seven ignimbrite units forming the older Toconquis Group (5.60-4.51 Ma), mainly outcropping along a type section at Rio Las Pitas, Vega Real Grande. The paleomagnetic data obtained by progressive thermal demagnetization show that the clasts of the Cerro Galán ignimbrite have one single magnetic component, oriented close to the expected geomagnetic field at the time of emplacement. Results show therefore that most of the clasts acquired a new magnetization oriented parallel to the magnetic field at the moment of the ignimbrite deposition, suggesting that the clasts were heated up to or above the highest blocking temperature ( T b) of the magnetic minerals ( T b = 580°C for magnetite; T b = 600-630°C for hematite). We obtained similar emplacement temperature estimations for six out of the seven volcanic units belonging to the Toconquis Group, with the exception of one unit (Lower Merihuaca), where we found two distinct magnetic components. The estimation of emplacement temperatures in this latter case is constrained at 580-610°C, which are lower than the other ignimbrites. These estimations are also in agreement with the lowest pre-eruptive magma temperatures calculated for the same unit (i.e., 790°C; hornblende-plagioclase thermometer; Folkes et al. 2011b). We conclude that the Cerro Gal

  2. Configuration of the mudstones, gray- and coffee-colored shale lithologic units, zones of silica and epidote, and their relation to the tectonics of the Cerro Prieto geothermal field

    SciTech Connect

    Cobo R, J.M.

    1981-01-01

    Based on well cuttings, five lithological units have been recognized within the area of what is now the Cerro Prieto geothermal field. These five units are described. Differences in origin, mineralogy, grading, color, compaction, etc., are shown.

  3. The ground-dwelling arthropod community of Península Valdés in Patagonia, Argentina.

    PubMed

    Cheli, Germán H; Corley, J C; Bruzzone, O; Brío, M Del; Martínez, F; Román, N Martínez; Ríos, I

    2010-01-01

    This is the first study based on a planned and intensive sampling effort that describes the community composition and structure of the ground-dwelling arthropod assemblage of Península Valdés (Patagonia). It was carried out using pitfall traps, opened for two weeks during the summers of 2005, 2006 and 2007. A total of 28,111 individuals were caught. Ants(Hymenoptera: Formicidae) dominated this community, followed by beetles (Coleoptera) and spiders (Araneae). The most abundant species were Pheidole bergi Mayr (Hymenoptera:Formicidae) and Blapstinus punctulatus Solier (Coleoptera: Tenebrionidae). Two new species were very recently described as new based on specimens collected during this study: Valdesianacuriosa Carpintero, Dellapé & Cheli (Hemiptera, Miridae) and Anomaloptera patagonica Dellapé& Cheli (Hemiptera, Oxycarenidae). The order Coleoptera was the most diverse taxa. The distribution of abundance data was best described by the logarithmic series model both at the family and species levels, suggesting that ecological relationships in this community could be controlled by a few factors. The community was dominated by predators from a trophic perspective. This suggests that predation acts as an important factor driving the distribution and abundances of surface-dwelling arthropods in this habitat and as such serves as a key element in understanding desert, above-ground community structure. These findings may also be useful for management and conservation purposes in arid Patagonia. PMID:20572783

  4. Hb Wilde and Hb Patagonia: two novel elongated beta-globin variants causing dominant beta-thalassemia.

    PubMed

    Scheps, Karen G; Hasenahuer, Marcia A; Parisi, Gustavo; Fornasari, María S; Pennesi, Sandra P; Erramouspe, Beatriz; Basack, Felisa N; Veber, Ernesto S; Aversa, Luis; Elena, Graciela; Varela, Viviana

    2015-06-01

    We describe here the molecular and hematological characteristics of novel frameshift mutations in exon 2 of the HBB gene (in heterozygous state) found in two Argentinean pediatric patients with dominant β-thalassemia-like features. In Hb Wilde, HBB:c.270_273delTGAG(p.Glu90Cysfs*67), we detected the deletion of the third base of the codon 89 (T) and the codon 90 (GAG), whereas in Hb Patagonia, HBB:c.296_297dupGT(p.Asp99Trpfs*59), the frameshift mutation was due to a duplication of a 'GT' dinucleotide after the second base of codon 98 (GTG). The Hb Patagonia and Hb Wilde mutations would result in elongated β-globin chains with modified C-terminal sequences and a total of 155 and 157 amino acids residues, respectively. Based on bioinformatics and structural analysis, as well as protein modeling, we predict that the elongated β-globins would affect the formation of the αβ dimers and their stability, which would further support the mechanism for the observed clinical features in both patients. PMID:25284604

  5. The Ground-Dwelling Arthropod Community of Península Valdés in Patagonia, Argentina

    PubMed Central

    Cheli, Germán H.; Corley, J. C.; Bruzzone, O.; del Brío, M.; Martínez, F.; Román, N. Martínez; Ríos, I.

    2010-01-01

    This is the first study based on a planned and intensive sampling effort that describes the community composition and structure of the ground-dwelling arthropod assemblage of Península Valdés (Patagonia). It was carried out using pitfall traps, opened for two weeks during the summers of 2005, 2006 and 2007. A total of 28, 111 individuals were caught. Ants (Hymenoptera: Formicidae) dominated this community, followed by beetles (Coleoptera) and spiders (Araneae). The most abundant species were Pheidole bergi Mayr (Hymenoptera: Formicidae) and Blapstinus punctulatus Solier (Coleoptera: Tenebrionidae). Two new species were very recently described as new based on specimens collected during this study: Valdesiana curiosa Carpintero, Dellapé & Cheli (Hemiptera, Miridae) and Anomaloptera patagonica Dellapé & Cheli (Hemiptera, Oxycarenidae). The order Coleoptera was the most diverse taxa. The distribution of abundance data was best described by the logarithmic series model both at the family and species levels, suggesting that ecological relationships in this community could be controlled by a few factors. The community was dominated by predators from a trophic perspective. This suggests that predation acts as an important factor driving the distribution and abundances of surface-dwelling arthropods in this habitat and as such serves as a key element in understanding desert, above-ground community structure. These findings may also be useful for management and conservation purposes in arid Patagonia. PMID:20572783

  6. Hb Wilde and Hb Patagonia: two novel elongated beta-globin variants causing dominant beta-thalassemia.

    PubMed

    Scheps, Karen G; Hasenahuer, Marcia A; Parisi, Gustavo; Fornasari, María S; Pennesi, Sandra P; Erramouspe, Beatriz; Basack, Felisa N; Veber, Ernesto S; Aversa, Luis; Elena, Graciela; Varela, Viviana

    2015-06-01

    We describe here the molecular and hematological characteristics of novel frameshift mutations in exon 2 of the HBB gene (in heterozygous state) found in two Argentinean pediatric patients with dominant β-thalassemia-like features. In Hb Wilde, HBB:c.270_273delTGAG(p.Glu90Cysfs*67), we detected the deletion of the third base of the codon 89 (T) and the codon 90 (GAG), whereas in Hb Patagonia, HBB:c.296_297dupGT(p.Asp99Trpfs*59), the frameshift mutation was due to a duplication of a 'GT' dinucleotide after the second base of codon 98 (GTG). The Hb Patagonia and Hb Wilde mutations would result in elongated β-globin chains with modified C-terminal sequences and a total of 155 and 157 amino acids residues, respectively. Based on bioinformatics and structural analysis, as well as protein modeling, we predict that the elongated β-globins would affect the formation of the αβ dimers and their stability, which would further support the mechanism for the observed clinical features in both patients.

  7. Southern Annular Mode-like changes in southwestern Patagonia at centennial timescales over the last three millennia.

    PubMed

    Moreno, Patricio I; Vilanova, I; Villa-Martínez, R; Garreaud, R D; Rojas, M; De Pol-Holz, R

    2014-01-01

    Late twentieth-century instrumental records reveal a persistent southward shift of the Southern Westerly Winds during austral summer and autumn associated with a positive trend of the Southern Annular Mode (SAM) and contemporaneous with glacial recession, steady increases in atmospheric temperatures and CO2 concentrations at a global scale. However, despite the clear importance of the SAM in the modern/future climate, very little is known regarding its behaviour during pre-Industrial times. Here we present a stratigraphic record from Lago Cipreses (51°S), southwestern Patagonia, that reveals recurrent ~200-year long dry/warm phases over the last three millennia, which we interpret as positive SAM-like states. These correspond in timing with the Industrial revolution, the Mediaeval Climate Anomaly, the Roman and Late Bronze Age Warm Periods and alternate with cold/wet multi-centennial phases in European palaeoclimate records. We conclude that SAM-like changes at centennial timescales in southwestern Patagonia represent in-phase interhemispheric coupling of palaeoclimate over the last 3,000 years through atmospheric teleconnections.

  8. Liver fluke (Fasciola hepatica) naturally infecting introduced European brown hare (Lepus europaeus) in northern Patagonia: phenotype, prevalence and potential risk.

    PubMed

    Cuervo, Pablo F; Cataldo, Sophia Di; Fantozzi, M Cecilia; Deis, Erika; Isenrath, Gabriela Diaz; Viberti, Gabriela; Artigas, Patricio; Peixoto, Raquel; Valero, M Adela; Sierra, Roberto Mera Y; Mas-Coma, Santiago

    2015-09-01

    Fascioliasis has recently been included in the WHO list of Neglected Zoonotic Diseases. Besides being a major veterinary health problem, fascioliasis has large underdeveloping effects on the human communities affected. Though scarcely considered in fascioliasis epidemiology, it is well recognized that both native and introduced wildlife species may play a significant role as reservoirs of the disease. The objectives are to study the morphological characteristics of Fasciola hepatica adults and eggs in a population of Lepus europaeus, to assess liver fluke prevalence, and to analyze the potential reservoir role of the European brown hare in northern Patagonia, Argentina, where fascioliasis is endemic. Measures of F. hepatica found in L. europaeus from northern Patagonia demonstrate that the liver fluke is able to fully develop in wild hares and to shed normal eggs through their faeces. Egg shedding to the environment is close to the lower limit obtained for pigs, a domestic animal whose epidemiological importance in endemic areas has already been highlighted. The former, combined with the high prevalence found (14.28%), suggest an even more important role in the transmission cycle than previously considered. The results obtained do not only remark the extraordinary plasticity and adaptability of this trematode species to different host species, but also highlight the role of the European brown hare, and other NIS, as reservoirs capable for parasite spillback to domestic and native cycle, representing a potentially important, but hitherto neglected, cause of disease emergence.

  9. Southern Annular Mode-like changes in southwestern Patagonia at centennial timescales over the last three millennia

    NASA Astrophysics Data System (ADS)

    Moreno, Patricio I.; Vilanova, I.; Villa-Martínez, R.; Garreaud, R. D.; Rojas, M.; de Pol-Holz, R.

    2014-07-01

    Late twentieth-century instrumental records reveal a persistent southward shift of the Southern Westerly Winds during austral summer and autumn associated with a positive trend of the Southern Annular Mode (SAM) and contemporaneous with glacial recession, steady increases in atmospheric temperatures and CO2 concentrations at a global scale. However, despite the clear importance of the SAM in the modern/future climate, very little is known regarding its behaviour during pre-Industrial times. Here we present a stratigraphic record from Lago Cipreses (51°S), southwestern Patagonia, that reveals recurrent ~200-year long dry/warm phases over the last three millennia, which we interpret as positive SAM-like states. These correspond in timing with the Industrial revolution, the Mediaeval Climate Anomaly, the Roman and Late Bronze Age Warm Periods and alternate with cold/wet multi-centennial phases in European palaeoclimate records. We conclude that SAM-like changes at centennial timescales in southwestern Patagonia represent in-phase interhemispheric coupling of palaeoclimate over the last 3,000 years through atmospheric teleconnections.

  10. Southern Annular Mode-like changes in southwestern Patagonia at centennial timescales over the last three millennia.

    PubMed

    Moreno, Patricio I; Vilanova, I; Villa-Martínez, R; Garreaud, R D; Rojas, M; De Pol-Holz, R

    2014-01-01

    Late twentieth-century instrumental records reveal a persistent southward shift of the Southern Westerly Winds during austral summer and autumn associated with a positive trend of the Southern Annular Mode (SAM) and contemporaneous with glacial recession, steady increases in atmospheric temperatures and CO2 concentrations at a global scale. However, despite the clear importance of the SAM in the modern/future climate, very little is known regarding its behaviour during pre-Industrial times. Here we present a stratigraphic record from Lago Cipreses (51°S), southwestern Patagonia, that reveals recurrent ~200-year long dry/warm phases over the last three millennia, which we interpret as positive SAM-like states. These correspond in timing with the Industrial revolution, the Mediaeval Climate Anomaly, the Roman and Late Bronze Age Warm Periods and alternate with cold/wet multi-centennial phases in European palaeoclimate records. We conclude that SAM-like changes at centennial timescales in southwestern Patagonia represent in-phase interhemispheric coupling of palaeoclimate over the last 3,000 years through atmospheric teleconnections. PMID:25007832

  11. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.; Schläppi, M.; Santibañez, P.; Rivera, A.; Casassa, G.

    2012-12-01

    Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000 to 2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16´40´´ S, 73°21´14´´ W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16% ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4 to 7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  12. Effects of the Cerro Grande Fire (Smoke and Fallout Ash) on Soil Chemical Properties Within and Around Los Alamos National Laboratory

    SciTech Connect

    Fresquez, P.R.; Velasquez, W.R.; Naranjo, L. Jr.

    2000-11-01

    Soil surface (0- to 2-in. depth) samples were collected from areas within and around Los Alamos National Laboratory (LANL) just after the Cerro Grande fire, analyzed for radionuclides, radioactivity, and trace elements (heavy metals), and compared to soil samples collected in 1999 from the same sites. In addition, many types of organic substances (volatile and semivolatile organic compounds, organochlorine pesticides, polychlorinated biphenyls, high explosives, and dioxin and dioxin-like compounds) were assessed in soils from LANL, perimeter, and regional sites after the fire. Results show that impacts to regional, perimeter, and on-site (mesa top) areas from smoke and fallout ash as a result of the Cerro Grande fire were minimal.

  13. U-Th-Pb zircon dating of the 13.8-Ma dacite volcanic dome at Cerro Rico de Potosi, Bolivia

    USGS Publications Warehouse

    Zartman, R.E.; Cunningham, C.G.

    1995-01-01

    The temporal relationship between the extrusion of the Miocene dacite volcanic dome at Cerro Rico de Potasi, Bolivia, and the associated Ag-Sn mineralization has an important bearing on the heat and metal sources for this world class mineral deposit. The present study uses U-Th-Pb dating of sparse zircon contained in the dacite to demonstrate that, at most, only several hundred thousand years separate dome emplacement from main stage mineralization. -from Authors

  14. Cerro Grande Fire Impact to Water Quality and Stream Flow near Los Alamos National Laboratory: Results of Four Years of Monitoring

    SciTech Connect

    B.M. Gallaher; R.J. Koch

    2004-09-15

    In May 2000, the Cerro Grande fire burned about 7400 acres of mixed conifer forest on the Los Alamos National Laboratory (LANL), and much of the 10,000 acres of mountainside draining onto LANL was severely burned. The resulting burned landscapes raised concerns of increased storm runoff and transport of contaminants by runoff in the canyons traversing LANL. The first storms after the fire produced runoff peaks that were more than 200 times greater than prefire levels. Total runoff volume for the year 2000 increased 50% over prefire years, despite a decline in total precipitation of 13% below normal and a general decrease in the number of monsoonal thunderstorms. The majority of runoff in 2000 occurred in the canyons at LANL south of Pueblo Canyon (70%), where the highest runoff volume occurred in Water Canyon and the peak discharge occurred in Pajarito Canyon. This report describes the observed effects of the Cerro Grande fire and related environmental impacts to watersheds at and near Los Alamos National Laboratory (LANL) for the first four runoff seasons after the fire, from 2000 through 2003. Spatial and temporal trends in radiological and chemical constituents that were identified as being associated with the Cerro Grande fire and those that were identified as being associated with historic LANL discharges are evaluated with regard to impacts to the Rio Grande and area reservoirs downstream of LANL. The results of environmental sampling performed by LANL, the New Mexico Environment Department (NMED), and U.S. Geological Survey (USGS) after the Cerro Grande fire are included in the evaluation. Effects are described for storm runoff, baseflow, stream sediments, and area regional reservoir sediment.

  15. 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.

  16. Geographic Information System (GIS) Emergency Support for the May 2000 Cerro Grande Wildfire, Los Alamos, New Mexico, USA

    SciTech Connect

    C.R.Mynard; G.N.Keating; P.M.Rich; D.R. Bleakly

    2003-05-01

    In May 2000 the Cerro Grande wildfire swept through Los Alamos, New Mexico, burning approximately 17,400 ha (43,000 acres) and causing evacuation of Los Alamos National Laboratory (LANL) and the communities of Los Alamos and White Rock. An integral part of emergency response during the fire was the use of geographic information system (GIS) technology, which continues to be used in support of post-fire restoration and environmental monitoring. During the fire Laboratory GIS staff and volunteers from other organizations worked to produce maps and provide support for emergency managers, including at an emergency GIS facility in Santa Fe. Subsequent to the fire, Laboratory GIS teams supported the multiagency Burned Area Emergency Rehabilitation (BAER) team to provide GIS data and maps for planning mitigation efforts. The GIS teams continue to help researchers, operations personnel, and managers deal with the tremendous changes caused by the fire. Much of the work is under the auspices of the Cerro Grande Rehabilitation Project (CGRP) to promote recovery from fire damage, improve information exchange, enhance emergency management, and conduct mitigation activities. GIS efforts during the fire provided important lessons about institutional matters, working relationships, and emergency preparedness. These lessons include the importance of (1) an integrated framework for assessing natural and human hazards in a landscape context; (2) a strong GIS capability for emergency response; (3) coordinated emergency plans for GIS operations; (4) a method for employees to report their whereabouts and receive authoritative information during an evacuation; (5) GIS data that are complete, backed-up, and available during an emergency; (6) adaptation of GIS to the circumstances of the emergency; (7) better coordination in the GIS community; (8) better integration of GIS into LANL operations; and (9) a central data warehouse for data and metadata. These lessons are important for planning

  17. Tracking tectonic activity and climate change in Southernmost Patagonia - The Lago Fagnano record

    NASA Astrophysics Data System (ADS)

    Waldmann, N.; Ariztegui, D.; Anselmetti, F. S.; Austin, J. A.; Moy, C.; Dunbar, R.

    2005-12-01

    The climate of southernmost Patagonia is influenced by the westerly winds, the Southern Ocean circumpolar flow, and the South Pacific gyre. Therefore, continental sediment records from this area are ideal to track high-latitude climate variability through time. Located at 55° S in Tierra del Fuego, Lago Fagnano occupies the deepest of a chain of tectonic depressions along the Fagnano-Magallanes fault system. Fagnano is the biggest (~110 km long), southernmost non-ice covered lake in the world. In March 2005, >800 km of geophysical data were acquired in the lake, combining simultaneously 3.5 kHz (pinger) single-channel with 1 in3 airgun multi-channel systems. These data provide a unique opportunity to look at the most recent lacustrine sediments with high-resolution, while imaging the oldest sediments at the same time. Preliminary interpretations show that the lake is divided into two sub-basins: a deep eastern sub-basin (~200 m water depth), and a shallower western sub-basin (~100 m). The seismic survey penetrated more than several tens of meters of sediments, exhibiting both lacustrine and glacial provenance, probably comprising the LGM and the Holocene. Seismic reflectors indicate the presence of neo-tectonic structures affecting even the most recent sedimentary package, including some mega-turbidites, suggesting continuing tectonic impact on sedimentation. Gravity cores from both sub-basins reveal a regular alternation of light and dark laminae with abundant diatom content. Ultra-high resolution X-ray fluorescence micro-profiles show fluctuations at mm scale in major and trace elements that may indicate seasonal influx changes into the basin. These core data will provide a unique record of decadal changes in regional climate that will be compared with other marine and continental archives to improve our understanding of the forcing mechanisms behind climate change that can be further used to validate the outcome of ocean and atmospheric climatic models for the

  18. Ongoing calving-frontal dynamics of glaciers in the Northern Patagonia Icefield, Chile

    NASA Astrophysics Data System (ADS)

    Bown, F.; Rivera, A.; Burger, F.; Carrión, D.; Cisternas, S.; Gacitúa, G.; Pena, M.; Oberreuter, J.; Silva, R.; Uribe, J. A.; Wendt, A.; Zamora, R.

    2013-05-01

    compared with ongoing thinning rates due to higher ablation. In the long term perspective, San Rafael is a good example of the tidewater calving cycle described for several glaciers in Alaska and Patagonia. At the eastern side glaciers, frontal retreats have been bigger than at San Rafael in recent years, but in the long term (since the Little Ice Age), San Rafael experienced a much stronger frontal recession (more than 12 km). This contrasting calving behavior between eastern and western margin glaciers, is only enhancing ice losses differences, but not changing ongoing receding trends.;

  19. Novel aromatic ring-hydroxylating dioxygenase genes from coastal marine sediments of Patagonia

    PubMed Central

    Lozada, Mariana; Riva Mercadal, Juan P; Guerrero, Leandro D; Di Marzio, Walter D; Ferrero, Marcela A; Dionisi, Hebe M

    2008-01-01

    Background Polycyclic aromatic hydrocarbons (PAHs), widespread pollutants in the marine environment, can produce adverse effects in marine organisms and can be transferred to humans through seafood. Our knowledge of PAH-degrading bacterial populations in the marine environment is still very limited, and mainly originates from studies of cultured bacteria. In this work, genes coding catabolic enzymes from PAH-biodegradation pathways were characterized in coastal sediments of Patagonia with different levels of PAH contamination. Results Genes encoding for the catalytic alpha subunit of aromatic ring-hydroxylating dioxygenases (ARHDs) were amplified from intertidal sediment samples using two different primer sets. Products were cloned and screened by restriction fragment length polymorphism analysis. Clones representing each restriction pattern were selected in each library for sequencing. A total of 500 clones were screened in 9 gene libraries, and 193 clones were sequenced. Libraries contained one to five different ARHD gene types, and this number was correlated with the number of PAHs found in the samples above the quantification limit (r = 0.834, p < 0.05). Overall, eight different ARHD gene types were detected in the sediments. In five of them, their deduced amino acid sequences formed deeply rooted branches with previously described ARHD peptide sequences, exhibiting less than 70% identity to them. They contain consensus sequences of the Rieske type [2Fe-2S] cluster binding site, suggesting that these gene fragments encode for ARHDs. On the other hand, three gene types were closely related to previously described ARHDs: archetypical nahAc-like genes, phnAc-like genes as identified in Alcaligenes faecalis AFK2, and phnA1-like genes from marine PAH-degraders from the genus Cycloclasticus. Conclusion These results show the presence of hitherto unidentified ARHD genes in this sub-Antarctic marine environment exposed to anthropogenic contamination. This information

  20. A Sedimentological Multi-Proxy Study of Late Holocene Climate Change in Southern Patagonia

    NASA Astrophysics Data System (ADS)

    Hutchinson, E. C.; Leroy, S. L.; Dunbar, R. B.

    2014-12-01

    The southern hemisphere westerlies force and respond to circulation and heat exchange with the Southern Ocean, which in turn plays a large role in global climate change. Southern Patagonia is the only significant land mass in the path of the southern westerlies, so it is an ideal location to examine variability of this wind system and its relation to regional and global climate. Precipitation and wind strength exhibit a strong positive correlation, and we take advantage of this relationship to use a paleoclimate archive to probe past changes in the wind field. We examined a 3.6m long sediment core from Lago Sarmiento (51.06˚S, 72.91˚W) in Torres del Paine National Park, Chile, for indicators of past environmental change. Here we present a high resolution, multi-proxy record of regional paleoclimate that includes physical, biological, and chemical data sets. We measured magnetic susceptibility, weight percent organic carbon and nitrogen, δ13C of bulk sediment, and weight percent carbonate of the core. These results provide information about precipitation, relative wind strength, volcanic activity, and biological productivity in and around Lago Sarmiento over the past 4,000 years. Our age model for the core is based in part on tephrochronology. We identified three tephras, or volcanic ashes, in the core at 68-71, 110-112, and 284-286cm that are supported visually and with magnetic susceptibility measurements. Analysis of the C:N ratio of the Lago Sarmiento core demonstrates a long-term increase in the deposition of terrestrial organic matter in Lago Sarmiento over time, perhaps indicating a change from grassland to woodland due to increased precipitation. The largest excursions in the C:N ratio occur at 20, 53, 139-140, 225-226, and 252cm. The average δ13C of organic carbon is -24.81‰, and large decreases occur at 9, 45, 180, 245-246, and 252-253cm, which could indicate overturning events in the lake. The average weight percent carbonate is 18%, with large

  1. Ice elevation and areal changes of glaciers from the Northern Patagonia Icefield, Chile

    NASA Astrophysics Data System (ADS)

    Rivera, Andrés; Benham, Toby; Casassa, Gino; Bamber, Jonathan; Dowdeswell, Julian A.

    2007-10-01

    High thinning rates (up to - 4.0 ± 0.97 m a - 1 ) have been measured at Campo de Hielo Patagónico Norte (CHN) or Northern Patagonia Icefield, Chile between 1975 and 2001. Results have been obtained by comparing a Digital Elevation Model (DEM) derived from regular cartography compiled by Instituto Geográfico Militar of Chile (IGM) based upon 1974/1975 aerial photographs and a DEM generated from Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) satellite images acquired in September 2001. A complete cloud-free Landsat ETM+ satellite image mosaic acquired in March 2001 was used to update the available glacier inventory of the CHN, including all glaciers larger than 0.5 km 2 (48 new glaciers). A new delineation of ice divides was also performed over the accumulation areas of glaciers sharing the high plateau where the existing regular cartography exhibits poor coverage of topographic information. This updated glacier inventory produced a total ice area for 2001 of 3953 km 2, which represents a decrease of 3.4 ± 1.5% (140 ± 61 km 2 of ice) with respect to the total ice area of the CHN in 1979 calculated from a Landsat MSS satellite image. Almost 62% of the total area change between 1979 and 2001 took place in glaciers located at the western margin of the CHN, where the maximum area loss was experienced by Glaciar San Quintín with 33 km 2. At the southern margin, Glaciar Steffen underwent the largest ice-area loss (12 km 2 or 2.6% of the 1979 area), whilst at the eastern margin the greatest area loss took place in Glaciares Nef (7.9 km 2, 5.7% of the 1979 area) and Colonia (9.1 km 2, 2.7% of the 1979 area). At the northern margin of the CHN the lower debris-covered ablation area of Glaciar Grosse collapsed into a new freshwater lake formed during the late 1990s. The areal changes measured at the CHN are much larger than previously estimated due to the inclusion of changes experienced in the accumulation areas. The CHN as a whole is

  2. Correlation and paleoenvironments of middle Paleogene marine beds based on dinoflagellate cysts in southwestern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Guerstein, G. Raquel; González Estebenet, M. Sol; Alperín, Marta I.; Casadío, Silvio A.; Archangelsky, Sergio

    2014-07-01

    An understanding of paleonvironmental and paleoceanographic evolution of the Southwestern Atlantic Ocean during the Palaeogene is prevented by the lack of precise tools to date and correlate the sedimentary units. Palynological samples collected in the upper portion of the Man Aike Formation, which crops out southern Lago Argentino area, in the southwest of the Austral Basin (50°21‧45″S-72°14‧30″W), contain well preserved marine organic dinoflagellate cysts, which are potentially important biostratigraphic and paleoenvironmental indicators. Herein we describe the composition of the Man Aike Formation's dinoflagellate cyst assemblages and compare them to similar assemblages collected in the same basin in the upper member of the Río Turbio Formation using Compositional Statistical Analysis. The dinoflagellate cyst assemblages from the upper part of the Man Aike Formation are highly correlated to the assemblages from the upper member of the Río Turbio Formation from outcropping sections (51°31‧13″S-72°15‧11″W) and with the lower part of sediment cores drilled by Yacimientos Carboníferos Fiscales in the Río Turbio Formation area. These dinoflagellate cyst assemblages show a very low correlation with the assemblages from the upper part of the Yacimientos Carboníferos Fiscales's cores. The comparison of our results with the high-resolution Southern Pacific Ocean dinoflagellate cyst zonation for the late Palaeocene to late Eocene allow us to date some of the dinoflagellate events recorded in formations of southwestern Patagonia. The assemblages from the Man Aike Formation and the lower part of the upper member of the Río Turbio Formation relate to the zones SPDZ11 and SPDZ12 and are assigned to the mid-middle Eocene (late Lutetian to early Bartonian). The biostratigraphy proposed herein constrains the age of the Man Aike Formation and equivalent units based on calcareous microfossil data, mollusks affinities and 87Sr/86Sr isotopic values to an

  3. A new peat bog testate amoeba transfer function and quantitative palaeohydrological reconstructions from southern Patagonia

    NASA Astrophysics Data System (ADS)

    van Bellen, S.; Mauquoy, D.; Payne, R.; Roland, T. P.; Hughes, P. D.; Daley, T. J.; Street-Perrot, F. A.; Loader, N.

    2013-12-01

    Testate amoebae have been used extensively as proxies for environmental change and palaeoclimate reconstructions in European and North American peatlands. The presence of these micro-organisms in surface samples is generally significantly linked to the local water table depth (WTD) and preservation of the amoeba shells downcore allows for millennial length water table reconstructions. Peat bog archive records in southern Patagonia are increasingly the focus of palaeoecological research due to the possibility of detecting changes in the Southern Westerlies. These Sphagnum magellanicum-dominated peat bogs are characterised by a wide range of water table depths, from wet hollows to high hummocks (>100 cm above the water table). Here we present the first transfer function for this region along with ~2k-year palaeorecords from local peat bogs. A modern dataset (155 samples) was sampled along transects from five bogs in 2012 and 2013. Measurements of WTD, pH and conductivity were taken for all samples. The transfer function model was based on the 2012 dataset, while the 2013 samples served as an independent test set to validate the model. Besides the standard leave-one-out cross-validation, we applied leave-one-site-out and leave-one transect-out cross-validation, which are effective means of verifying the degree of clustering in the dataset. To ensure that the environmental gradient had been evenly sampled we quantified the root-mean-squared error of prediction (RMSEP) individually for segments of this gradient. Ordinations showed a clear hydrological gradient in amoeba assemblages, with the dominant Assulina muscorum at the dry end and Amphitrema wrightianum and Difflugia globulosa at the wet end. Canonical correspondence analysis showed that WTD was the most important environmental variable, accounting for 18% of the variance in amoeba assemblages. A weighted averaging-partial least squares model showed best performance in cross-validation, using the 2013 data as an

  4. Oceanographic Processes in Chilean Fjords of Patagonia: From small to large-scale studies

    NASA Astrophysics Data System (ADS)

    Iriarte, José L.; Pantoja, Silvio; Daneri, Giovanni

    2014-12-01

    northward expansion of the subantarctic water, the impact of these changes on physical dynamics, biogeochemical and plankton properties are still unclear. The information presented in this Special Issue (SI) will be important to the understanding and modeling of future changes in the marine carbon cycle in Subantarctic zones off Patagonia.

  5. Annual burned area across a precipitation gradient in northwestern patagonia steppe

    NASA Astrophysics Data System (ADS)

    Oddi, Facundo; Ghermandi, Luciana; Lasaponara, Rosa

    2013-04-01

    study area in relation to precipitation gradient establishing two zones (wet and xeric). To delimit area of wildfires on Landsat scenes we used the NBR index. Then, we calculated the annual burned area in each zone, compared the annual burned area between zones and also explored relationships between that variable of the fire regime and precipitation/temperature data. We expect to contribute to the discussions about the importance of drought/fuel on the fire activity across the productivity/aridity gradient, specifically on Mediterranean environments. Finally, with this work we expect to improve future management and conservation practices in Northwestern Patagonia grasslands.

  6. Jurassic hot spring deposits of the Deseado Massif (Patagonia, Argentina): Characteristics and controls on regional distribution

    NASA Astrophysics Data System (ADS)

    Guido, Diego M.; Campbell, Kathleen A.

    2011-06-01

    The Deseado Massif, Santa Cruz Province, Argentinean Patagonia, hosts numerous Middle to Late Jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs (sinters and travertines, respectively), hydrothermal breccias, quartz veins, and widespread hydrothermal silicification. They indicate pauses in explosive volcanic activity, marking the final stages in the evolution of an extensive Jurassic (ca. 178-151 Ma) volcanic complex set in a diffuse extensional back-arc setting heralding the opening of the Atlantic Ocean. Published paleo-hot spring sites for the Deseado Massif, plus additional sites identified during our recent field studies, reveal a total of 23 locations, five of which were studied in detail to determine their geologic and facies associations. They show structural, lithologic, textural and biotic similarities with Miocene to Recent hot spring systems from the Taupo and Coromandel volcanic zones, New Zealand, as well as with modern examples from Yellowstone National Park, U.S.A. These comparisons aid in the definition of facies assemblages for Deseado Massif deposits - proximal, middle apron and distal siliceous sinter and travertine terraces and mounds, with preservation of many types of stromatolitic fabrics - that likely were controlled by formation temperature, pH, hydrodynamics and fluid compositions. Locally the mapped hot spring deposits largely occur in association with reworked volcaniclastic lacustrine and/or fluvial sediments, silicic to intermediate lava domes, and hydrothermal mineralization, all of which are related to local and regional structural lineaments. Moreover, the numerous geothermal and significant epithermal (those with published minable resources) deposits of the Deseado Massif geological province mostly occur in four regional NNW and WNW hydrothermal-structural belts (Northwestern, Northern, Central, and Southern), defined here by alignment of five or more hot

  7. A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

    NASA Technical Reports Server (NTRS)

    Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-01-01

    The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the

  8. Origin and evolution of the Laguna Potrok Aike maar (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Gebhardt, A. C.; de Batist, M.; Niessen, F.; Anselmetti, F. S.; Ariztegui, D.; Ohlendorf, C.; Zolitschka, B.

    2009-04-01

    Laguna Potrok Aike, a maar lake in southern-most Patagonia, is located at about 110 m a.s.l. in the Pliocene to late Quaternary Pali Aike Volcanic Field (Santa Cruz, southern Patagonia, Argentina) at about 52°S and 70°W, some 20 km north of the Strait of Magellan and approximately 90 km west of the city of Rio Gallegos. The lake is almost circular and bowl-shaped with a 100 m deep, flat plain in its central part and an approximate diameter of 3.5 km. Steep slopes separate the central plain from the lake shoulder at about 35 m water depth. At present, strong winds permanently mix the entire water column. The closed lake basin contains a sub saline water body and has only episodic inflows with the most important episodic tributary situated on the western shore. Discharge is restricted to major snowmelt events. Laguna Potrok Aike is presently located at the boundary between the Southern Hemispheric Westerlies and the Antarctic Polar Front. The sedimentary regime is thus influenced by climatic and hydrologic conditions related to the Antarctic Circumpolar Current, the Southern Hemispheric Westerlies and sporadic outbreaks of Antarctic polar air masses. Previous studies demonstrated that closed lakes in southern South America are sensitive to variations in the evaporation/precipitation ratio and have experienced drastic lake level changes in the past causing for example the desiccation of the 75 m deep Lago Cardiel during the Late Glacial. Multiproxy environmental reconstruction of the last 16 ka documents that Laguna Potrok Aike is highly sensitive to climate change. Based on an Ar/Ar age determination, the phreatomagmatic tephra that is assumed to relate to the Potrok Aike maar eruption was formed around 770 ka. Thus Laguna Potrok Aike sediments contain almost 0.8 million years of climate history spanning several past glacial-interglacial cycles making it a unique archive for non-tropical and non-polar regions of the Southern Hemisphere. In particular, variations of

  9. Origin and evolution of the Laguna Potrok Aike maar (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Gebhardt, A. C.; de Batist, M.; Niessen, F.; Anselmetti, F. S.; Ariztegui, D.; Ohlendorf, C.; Zolitschka, B.

    2009-04-01

    Laguna Potrok Aike, a maar lake in southern-most Patagonia, is located at about 110 m a.s.l. in the Pliocene to late Quaternary Pali Aike Volcanic Field (Santa Cruz, southern Patagonia, Argentina) at about 52°S and 70°W, some 20 km north of the Strait of Magellan and approximately 90 km west of the city of Rio Gallegos. The lake is almost circular and bowl-shaped with a 100 m deep, flat plain in its central part and an approximate diameter of 3.5 km. Steep slopes separate the central plain from the lake shoulder at about 35 m water depth. At present, strong winds permanently mix the entire water column. The closed lake basin contains a sub saline water body and has only episodic inflows with the most important episodic tributary situated on the western shore. Discharge is restricted to major snowmelt events. Laguna Potrok Aike is presently located at the boundary between the Southern Hemispheric Westerlies and the Antarctic Polar Front. The sedimentary regime is thus influenced by climatic and hydrologic conditions related to the Antarctic Circumpolar Current, the Southern Hemispheric Westerlies and sporadic outbreaks of Antarctic polar air masses. Previous studies demonstrated that closed lakes in southern South America are sensitive to variations in the evaporation/precipitation ratio and have experienced drastic lake level changes in the past causing for example the desiccation of the 75 m deep Lago Cardiel during the Late Glacial. Multiproxy environmental reconstruction of the last 16 ka documents that Laguna Potrok Aike is highly sensitive to climate change. Based on an Ar/Ar age determination, the phreatomagmatic tephra that is assumed to relate to the Potrok Aike maar eruption was formed around 770 ka. Thus Laguna Potrok Aike sediments contain almost 0.8 million years of climate history spanning several past glacial-interglacial cycles making it a unique archive for non-tropical and non-polar regions of the Southern Hemisphere. In particular, variations of

  10. Diplodon shells from Northwest Patagonia as continental proxy archives: Oxygen isotopic results and sclerochronological analyses

    NASA Astrophysics Data System (ADS)

    Soldati, A. L.; Beierlein, L.; Jacob, D. E.

    2009-04-01

    Freshwater mussels of the genus Diplodon (Bivalvia, Hyriidae) are the most abundant bivalve (today and in the past) in freshwater bodies at both sides of the South-Andean Cordillera. There are about 25 different Diplodon genera in Argentina and Chile that could be assigned almost completely to the species Diplodon chilensis (Gray, 1828) and two subspecies: D. ch. chilensis and D. ch. patagonicus; this latter species is found in Argentina between Mendoza (32˚ 52' S; 68˚ 51' W) and Chubut (45˚ 51' S; 67˚ 28' W), including the lakes and rivers of the target area, the Nahuel Huapi National Park (Castellanos, 1960). Despite their wide geographic distribution, Diplodon species have only rarely been used as climate archives in the southern hemisphere. Kaandorp et al. (2005) demonstrated for Diplodon longulus (Conrad 1874) collected from the Peruvian Amazonas that oxygen isotopic patterns in the shells could be used in order to reconstruct the precipitation regime and dry/wet seasonal of the monsoonal system in Amazonia. Although this study demonstrated the potential of Diplodon in climatological and ecological reconstructions in the southern hemisphere, as of yet, no systematic study of Diplodon as a multi-proxy archive has been undertaken for the Patagonian region. In this work we present sclerochronological analyses supported by ^18Oshell in recent mussel of Diplodon chilensis patagonicus (D'Orbigny, 1835) collected at Laguna El Trébol (42°S-71°W, Patagonia Argentina), one of the best studied water bodies in the region for paleoclimate analysis. Water temperature was measured every six hours for one year using a temperature sensor (Starmon mini®) placed at 5m depth in the lake, close to a mussel bank. Additionally, ^18Owater was measured monthly for the same time range.g^18Oshell values obtained by micro-milling at high spatial resolution in the growth increments of three Diplodon shells were compared to these records, and to air temperature and

  11. Velafrons coahuilensis, a new labeosaurine haddrosaurid (Dinosauria: Ornithopoda) from the Late Campanian Cerro del Pueblo formation, Coahuila, Mexico

    USGS Publications Warehouse

    Gates, Terry A.; Sampson, Scott D.; de Jesus, Carlos R. Delgado; Zanno, Lindsay E.; Eberth, David; Hernandez-Rivera, Rene; Aguillon-Martinez, Martha C.; Kirkland, James I.

    2007-01-01

    A new lambeosaurine hadrosaurid, Velafrons coahuilensis, is described as the first lambeosaurine from the Cerro del Pueblo Formation of Coahuila, Mexico, and the first lambeosaurine genus to be named from North America in more than 70 years. Although the holotype specimen is a juvenile individual—as evidenced by its incomplete crest development and relative size compared to other North American lambeosaurines—ontogeny independent autapomor-phies have been identified including quadrate with narrow quadratojugal notch and a postorbital with well developed, dorsally positioned squamosal process. Additionally, this taxon is unique in that the prefrontal is not dorsally deflected and anteroposteriorly expanded as in other lambeosaurine taxa of its size, but rather retains the frontal-prefrontal “clamp” present in smaller individuals of other taxa. Phylogenetic analysis places Velafrons in a polytomy with numerous other fan-crested lambeosaurines. The crest structure of Velafrons more closely resembles that of Corythosaurus and Hypacrosaurus because it possesses an anteriorly projecting nasal process over the dorsal premaxilla process. Biogeo-graphically, Velafrons is one of three distinct hadrosaurids known from approximately 73.5 Ma—two lambeosaurines and one hadrosaurine—all restricted to the southern region of the Western Interior Basin of North America.

  12. Effects of pressure drawdown and recovery on the Cerro Prieto beta reservoir in the CP-III area

    SciTech Connect

    Truesdell, A.H.; Lippmann, M.J.

    1998-02-01

    The production characteristics of wells in the northwestern Cerro Prieto III area changed greatly when the Cp-III power plant went on line in 1986. Fluid extraction in the field more than doubled and reservoir-wide boiling started immediately, greatly increasing the enthalpy of produced fluids. Some well fluids showed a decrease in chloride due to adiabatic steam condensation in the well and separator, and others were enriched in chloride due to boiling. As reservoir drawdown increased, entrance of cooler and more dilute groundwaters into the reservoir became evident (i.e., condensation stopped, and there was a decrease in enthalpy and chloride in produced fluids). Although some groundwater inflow was from the leaky western margin of the reservoir, the majority is in the northeast, inferred to be local and downward, possibly through more permeable zones associated with the normal fault H. This natural recharge and some reinjection have slowed and possibly reversed pressure drawdown throughout CP-III. Enthalpy has decreased and liquid saturation has increased as the steam-rich zone in the upper part of the reservoir has either disappeared or become thinner.

  13. The Cerro Bitiche Andesitic Field: petrological diversity and implications for magmatic evolution of mafic volcanic centers from the northern Puna

    NASA Astrophysics Data System (ADS)

    Maro, Guadalupe; Caffe, Pablo J.

    2016-07-01

    The Cerro Bitiche Andesitic Field (CBAF) is one of the two largest mafic volcanic fields in northern Puna (22-24° S) and is spatially and temporally associated with ignimbrites erupted from some central Andean Altiplano-Puna Volcanic Complex calderas. The CBAF comprises seven scoria cones and widespread high-K calcalkaline lava flows that cover an area of 200 km2. Although all erupted rocks have a relatively narrow chemical range (56-62 % SiO2, 3-6 % MgO), there is a broad diversity of mineral compositions and textures. The least evolved lavas (˜58-61 % SiO2) are high-Mg andesites with scarce (<10 %) microphenocrysts of either olivine or orthopyroxene. The small compositional range and low phenocryst content indicate evolution controlled by low percentages (<10 %) of fractional crystallization of olivine and clinopyroxene of magmas similar to the least evolved rocks from the field, accompanied by assimilation during rapid ascent through the crust. Evolved andesites (˜62 wt% SiO2), on the other hand, are porphyritic rocks with plagioclase + orthopyroxene + biotite and ubiquitous phenocryst disequilibrium textures. These magmas were likely stored in crustal reservoirs, where they experienced convection caused by mafic magma underplating, magma mixing, and/or assimilation. Trace element and mineral compositions of CBAF lavas provide evidence for complex evolution of distinct magma batches.

  14. Late Quaternary vegetation, fire and climate history reconstructed from two cores at Cerro Toledo, Podocarpus National Park, southeastern Ecuadorian Andes

    NASA Astrophysics Data System (ADS)

    Brunschön, Corinna; Behling, Hermann

    2009-11-01

    The last ca. 20,000 yr of palaeoenvironmental conditions in Podocarpus National Park in the southeastern Ecuadorian Andes have been reconstructed from two pollen records from Cerro Toledo (04°22'28.6"S, 79°06'41.5"W) at 3150 m and 3110 m elevation. Páramo vegetation with high proportions of Plantago rigida characterised the last glacial maximum (LGM), reflecting cold and wet conditions. The upper forest line was at markedly lower elevations than present. After ca. 16,200 cal yr BP, páramo vegetation decreased slightly while mountain rainforest developed, suggesting rising temperatures. The trend of increasing temperatures and mountain rainforest expansion continued until ca. 8500 cal yr BP, while highest temperatures probably occurred from 9300 to 8500 cal yr BP. From ca. 8500 cal yr BP, páramo vegetation re-expanded with dominance of Poaceae, suggesting a change to cooler conditions. During the late Holocene after ca. 1800 cal yr BP, a decrease in páramo indicates a change to warmer conditions. Anthropogenic impact near the study site is indicated for times after 2300 cal yr BP. The regional environmental history indicates that through time the eastern Andean Cordillera in South Ecuador was influenced by eastern Amazonian climates rather than western Pacific climates.

  15. Monitoring and modeling land subsidence at the Cerro Prieto Geothermal Field, Baja California, Mexico, using SAR interferometry

    NASA Astrophysics Data System (ADS)

    Carnec, Claudie; Fabriol, Hubert

    Images derived from repeat-pass spaceborne interferometric synthetic aperture radar (InSAR) systems offer the possibility of mapping surface deformation of small spatial extent and monitoring its spatio-temporal evolution. A slow local subsidence has been detected at the Cerro Prieto geothermal field from images acquired by the European Space Agency remote sensing satellites ERS-1/2 between 1993 and 1997. Although agricultural activity in the area limited the investigation, interferometric monitoring revealed that the ground deformation is associated with the withdrawal of geothermal fluid and agreed with the leveling data. Modeling of the subsidence was carried out assuming elastic deformation in a half-space from simple point sources, of which five were necessary to reproduce the fringe patterns observed on the interferograms. The depths and locations of three of the sources are compatible with the location of the known reservoir. The study improves prior knowledge of the displacement field and of the mecanisms involved in the subsidence phenomenon.

  16. Results of chemical and stable isotopic analyses of water samples collected in the Patagonia Mountains, southern Arizona

    USGS Publications Warehouse

    Wanty, Richard B.; Shanks, Wayne C.; Lamothe, Paul; Meier, A.L.; Lichte, Fred; Briggs, Paul H.; Berger, Byron R.

    2001-01-01

    Water samples were collected in the Patagonia Mountains in February, 1997. Most of the samples were collected from portals of abandoned mines, or from stream drainages immediately downstream from abandoned mines. Most of the samples have low pH ( 1000 mg/L). Anion composition of the water samples is dominated by sulfate, while cation compositions range from calcium-dominated to mixed calcium-magnesium or calcium-sodium-dominated waters. Metals such as iron, manganese, copper, zinc, and aluminum contribute a significant portion (>10%) of the cation content to the water samples. Because of the low pH?s, protons contribute up to several percent of the cation character of the waters in some of the samples. The data are presented in tabular and graphical formats, with descriptions of data quality and brief descriptions of results.

  17. A new species of Ascocotyle (Trematoda: Heterophyidae) from the South American sea lion, Otaria flavescens, off Patagonia, Argentina.

    PubMed

    Hernández-Orts, Jesús Servando; Montero, Francisco Esteban; Crespo, Enrique Alberto; García, Néstor Aníbal; Raga, Juan Antonio; Aznar, Francisco Javier

    2012-08-01

    We describe a new heterophyid species, Ascocotyle (Ascocotyle) patagoniensis n. sp., based on specimens collected from the intestines of the South American sea lion Otaria flavescens from Patagonia (Argentina). Ascocotyle (A.) patagoniensis n. sp. is distinguished from the other species of the subgenus by the number of circumoral spines, which are arranged in 2 rows of 18 to 23. The new species also differs from the other species in having a gonotyl without papillae. The specimens exhibited the widest seminal receptacle described for a species of this subgenus. Species of the subgenus Ascocotyle usually infect fish-eating birds or mammals in freshwater or brackish habitats. Ascocotyle (A.) patagoniensis n. sp. is the first species of the subgenus described from a marine mammal. However, no metacercariae of Ascocotyle spp. were found in 542 marine teleosts from 20 species collected in the same locality. The life cycle of the marine species from the Ascocotyle -complex infecting pinnipeds remains elusive. PMID:22375817

  18. New record of anoplocephalid eggs (Cestoda: Anoplocephalidae) collected from rodent coprolites from archaeological and paleontological sites of Patagonia, Argentina.

    PubMed

    Beltrame, María Ornela; Fugassa, Martín Horacio; Barberena, Ramiro; Sauthier, Daniel Edgardo Udrizar; Sardella, Norma Haydée

    2013-10-01

    Results of paleoparasitological examination of rodent coprolites collected from archaeological and paleontological sites from Patagonia, Argentina, are present. Each coprolite was processed, rehydrated, homogenized, spontaneously sedimented and examined using light microscope. Coprolites and eggs were described, measured and photographed, and were compared with current faeces of Lagidium viscacia. Eggs with morphological features, attributed to an anoplocephalid cestode were found in samples collected from Cueva Huenul 1 (36°56'45″S, 69°47'32″W, Neuquén Province, Holocene) and Los Altares Profile (43º53'35″S, 68º23'21″W, Chubut Province, Late Holocene). These are the first findings of this anoplocephalid from faecal material from patagonic rodents.

  19. Epidemiological studies on intestinal helminth parasites of the patagonian grey fox (Pseudalopex griseus) in Tierra del Fuego, Patagonia Argentina.

    PubMed

    Zanini, Fabián; Laferrara, Miguel; Bitsch, Matías; Pérez, Héctor; Elissondo, Maria Celina

    2006-03-31

    The present work was performed to study the intestinal helminths of the patagonian grey fox (Pseudalopex griseus) and to obtain information about its possible role in the sylvatic life cycle of Echinococcu granulosus in Tierra del Fuego, Patagonia Argentina. Eighty-one foxes were captured and subject to post-mortem analysis. Thirty-one foxes (38.3%) harboured helminths. A total of six helminth species were recovered. Only one adult of E. granulosus was found in the studied samples. The current study is the first report of the intestinal helminths of the patagonian grey fox in Tierra del Fuego, Argentina and showed that this specie is probably not an important reservoir host for E. granulosus.

  20. The sedimentology and dynamics of crater-affiliated wind streaks in western Arabia Terra, Mars and Patagonia, Argentina

    USGS Publications Warehouse

    Rodriguez, J.A.P.; Tanaka, K.L.; Yamamoto, A.; Berman, D.C.; Zimbelman, J.R.; Kargel, J.S.; Sasaki, S.; Jinguo, Y.; Miyamoto, H.

    2010-01-01

    Wind streaks comprise recent aeolian deposits that have been extensively documented on Venus, Earth and Mars. Martian wind streaks are among the most abundant surface features on the planet and commonly extend from the downwind margins of impact craters. Previous studies of wind streaks emerging from crater interior deposits suggested that the mode of emplacement was primarily related to the deposition of silt-sized particles as these settled from plumes. We have performed geologic investigations of two wind streaks clusters; one situated in western Arabia Terra, a region in the northern hemisphere of Mars, and another in an analogous terrestrial site located in southern Patagonia, Argentina, where occurrences of wind streaks emanate from playas within maar craters. In both these regions we have identified bedforms in sedimentary deposits on crater floors, along wind-facing interior crater margins, and along wind streaks. These observations indicate that these deposits contain sand-sized particles and that sediment migration has occurred via saltation from crater interior deposits to wind streaks. In Arabia Terra and in Patagonia wind streaks initiate from crater floors that contain lithic and evaporitic sedimentary deposits, suggesting that the composition of wind streak source materials has played an important role in development. Spatial and topographic analyses suggest that regional clustering of wind streaks in the studied regions directly correlates to the areal density of craters with interior deposits, the degree of proximity of these deposits, and the craters' rim-to-floor depths. In addition, some (but not all) wind streaks within the studied clusters have propagated at comparable yearly (Earth years) rates. Extensive saltation is inferred to have been involved in its propagation based on the studied terrestrial wind streak that shows ripples and dunes on its surface and the Martian counterpart changes orientation toward the downslope direction where it

  1. Study of cloud enhanced surface UV radiation at the atmospheric observatory of Southern Patagonia, Río Gallegos, Argentina

    NASA Astrophysics Data System (ADS)

    Wolfram, Elian A.; Salvador, Jacobo; Orte, Facundo; Bulnes, Daniela; D'Elia, Raul; Antón, Manuel; Alados-Arboledas, Lucas; Quel, Eduardo

    2013-05-01

    Ozone and ultraviolet (UV) radiation are two important issues in the study of Earth's atmosphere. The anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth's surface, mainly through the Antarctic ozone hole. Also clouds have been identified as the main modulator of UV amount over short time scales. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as a consequence the surface UV radiation may be higher than during an equivalent clear sky scenario. In particular this situation can be important when a low ozone column and partially cloud coverered skies occur simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an atmospheric remote sensing site near the city of Río Gallegos (51°55'S, 69°14'W). In this paper, the impact of clouds on UV radiation is investigated by the use of ground based measurements from the passive remote sensing instruments operating at this site, mainly broad and moderate narrow band filter radiometers. Cloud modification factors (CMF, ratio between the measured UV radiation in a cloudy sky and the simulated radiation under cloud-free conditions) are evaluated for the study site. CMFs higher than 1 are found during spring and summer time, when lower total ozone columns, higher solar elevations and high cloud cover occur simultaneously, producing extreme erythemal irradiance at the ground surface. Enhancements as high as 25% were registered. The maximum duration of the enhancement was around 30 minutes. This produces dangerous sunbathing conditions for the Río Gallegos citizen.

  2. Multi-century tree-ring based reconstruction of the Neuquén River streamflow, northern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Mundo, I. A.; Masiokas, M. H.; Villalba, R.; Morales, M. S.; Neukom, R.; Le Quesne, C.; Urrutia, R. B.; Lara, A.

    2011-10-01

    In most cases, gauged river flow records in southern South America exist for only a few decades, hampering the detection of long-term, decadal to centennial-scale cycles and trends. Long streamflow series can be reconstructed from tree-ring records, offering the opportunity of extending the limited hydrological instrumental data for several centuries or millennia. In northern Patagonia, Argentina, the Neuquén River has great importance for local and national socio-economic activities such as hydroelectric power generation, agriculture and tourism. In this study, new and updated tree-ring chronologies from Araucaria araucana and Austrocedrus chilensis are used to reconstruct the October-June mean streamflow for the Neuquén River and place the period of gauged flows, 1903-2009, in a long-term, multi-century context. The reconstruction covers the period 1346-2000 AD and was developed through a nested principal components regression approach using a network of 43 tree-ring chronologies grouped in composite series. Analyses of the frequency, intensity, and duration of droughts and pluvial events indicate that the 20th century contains some of the driest and wettest annual to decadal-scale events in the past millennium, but longer and more severe events can also be observed in previous centuries. Blackman-Tukey and Singular Spectral Analyses identified various multi-decadal quasiperiodic oscillations with a dominant 6.8-year cycle explaining ca. 23.6% of the total variance in the Neuquén River streamflow reconstruction. We also found that the Neuquén River discharges are related to variations in the Southern Annular Mode (SAM), a measure of air mass exchanges between middle and high latitudes in the Southern Hemisphere. This association is consistent with previous studies which indicate a strong connection between rainfall patterns in northern Patagonia and SAM activity.

  3. Multi-century tree-ring based reconstruction of the Neuquén River streamflow, northern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Mundo, I. A.; Masiokas, M. H.; Villalba, R.; Morales, M. S.; Neukom, R.; Le Quesne, C.; Urrutia, R. B.; Lara, A.

    2012-04-01

    In most cases, gauged river flow records in southern South America extend for only a few decades, hampering the detection of long-term, decadal to centennial-scale cycles and trends. Long streamflow series can be reconstructed from tree-ring records, offering the opportunity of extending the limited hydrological instrumental data to several centuries. In northern Patagonia, Argentina, the Neuquén River has great importance for local and national socio-economic activities such as hydroelectric power generation, agriculture and tourism. In this study, new and updated tree-ring chronologies from Araucaria araucana and Austrocedrus chilensis are used to reconstruct the October-June mean streamflow for the Neuquén River and place the period of gauged flows (1903-2009), in a long-term, multi-century context. The reconstruction covers the period 1346-2000 AD and was developed from a network of 43 tree-ring chronologies, grouped in composite series, using a nested principal component regression approach. Analyses of the frequency, intensity, and duration of droughts and pluvial events indicate that the 20th century contains some of the driest and wettest annual to decadal-scale events in the last 654 yr, but longer and more severe events were recorded in previous centuries. Blackman-Tukey and singular spectral analyses identified quasiperiodic oscillations from 3.5 to 17.5 yr. A dominant 6.8-yr cycle explains ca. 23.6% of the total variance in the Neuquén River streamflow reconstruction. Correlation analyses showed that discharges of the Neuquén River are related to variations in the Southern Annular Mode (SAM), a measure of air mass exchanges between middle and high latitudes in the Southern Hemisphere. This association is consistent with previous studies that indicate a strong correlation between rainfall in northern Patagonia and SAM variations.

  4. Isotopic and fluid-inclusion constraints on the formation of polymetallic vein deposits in the central Argentinian Patagonia

    NASA Astrophysics Data System (ADS)

    Dejonghe, Léon; Darras, Benoît; Hughes, Guillermo; Muchez, Philippe; Scoates, James S.; Weis, Dominique

    2002-03-01

    The lead isotope compositions of galena and the fluid-inclusion systematics of nine barite-bearing polymetallic (Au, Ag, Pb, Zn) deposits of the central Argentinian Patagonia (Chubut and Rio Negro provinces) have been investigated to constrain the compositions and sources of the mineralizing fluids. Most of the deposits occur as veins, with less common wall-rock disseminations and/or stockworks, and are low-sulfidation epithermal deposits hosted in Jurassic volcanic rocks. Fluid-inclusion homogenization temperatures (Th) from quartz and sphalerite from the deposits fall within the range of 100-300 °C, with the highest measured average temperatures for the most eastern deposits (Mina Angela - 298 °C; Cañadón Bagual - 343 °C). The salinities of the hydrothermal fluids at all deposits were low to moderate (≤10.4 equiv. wt% NaCl). Three groups of ore deposits can be defined on the basis of 206Pb/204Pb ratios for galena and these show a general decrease from west to east (from 18.506 to 18.000). The central Argentinian Patagonia deposits have distinctly less radiogenic lead isotope compositions than similar deposits from Peru and Chile, except for the porphyry copper deposits of central and southern Peru. Galena from the Mina Angela deposit is characterized by very low radiogenic lead isotope compositions (18.000<206Pb/204Pb<18.037 and 38.03<208Pb/204Pb<38.09) and reflects interaction with Precambrian basement. The geographic trend in lead isotope compositions of both galena and whole rocks indicates a crustal contribution which increases eastwards, also reflected in the strontium-neodymium isotope systematics of the host lavas. Finally, due to the lack of precise age determinations for the central Patagonian polymetallic deposits, a potential link with Andean porphyry copper systems remains an open question.

  5. Vegetation, Fire and Climate Over the Last 2000 Yrs in Central West Patagonia (45°S)

    NASA Astrophysics Data System (ADS)

    Villa-Martinez, R. P.; Simi, E. I.; Moreno, P. I.

    2014-12-01

    We report high-resolution pollen and charcoal records from lake sediments obtained from Lago Mellizas and Lago Churrasco to reconstruct the history of vegetation, fire and past variations of the southern westerly winds (SWW) over the last 2000 years. Both sites are located near to the climate-modulated forest-steppe ecotone in central west Patagonia. In this region the SWW are the only source of precipitation and is ideal for reconstructing past changes in atmospheric circulation. This is facilitated by the marked west-east precipitation gradient across the Patagonian Andes that induces a zonation of the regional vegetation which can be used for inferring past changes in precipitation regimes based on fossil pollen records. Furthermore, the Chilean-European colonization process in central west Patagonia started early in the 20th century, allowing characterization of natural vegetation and climate variability in the absence of human disturbance until the end of the 19th century. The pollen records shows dominance of Nothofagus deciduous forests with minor fluctuations and low herb and aquatics abundances, which suggest humid climate conditions. We detect a major change in the pollen stratigraphy at 200 cal yr BP, when started a sustained decreasing trend in Nothofagus, along with increases of Poaceae and aquatics plants (Cyperaceae, Myriophyllum). We interpret these changes as a forest opening and centripetal expansion of littoral environments toward the lake center driven by lake-level lowering in response to lowered precipitation brought by the SWW. Pinus, Rumex, Plantago, which indicate human perturbation, increase in 1900 AD. Macroscopic charcoal increases at 1750, 1400, 850-700, 500, and 200 cal yr BP, suggesting local fires, followed by sharp increases during the last 100 years. We interpret the pre-20th century charcoal peaks as dry intervals with lowered SWW influence. Acknowledgement: Fondecyt 1121141, Fondap 15110009, and ICM grants P02-51 and NC120066.

  6. Late Cretaceous-early Eocene counterclockwise rotation of the Fueguian Andes and evolution of the Patagonia-Antarctic Peninsula system

    NASA Astrophysics Data System (ADS)

    Poblete, F.; Roperch, P.; Arriagada, C.; Ruffet, G.; Ramírez de Arellano, C.; Hervé, F.; Poujol, M.

    2016-02-01

    The southernmost Andes of Patagonia and Tierra del Fuego present a prominent arc-shaped structure: the Patagonian Bend. Whether the bending is a primary curvature or an orocline is still matter of controversy. New paleomagnetic data have been obtained south of the Beagle Channel in 39 out of 61 sites. They have been drilled in Late Jurassic and Early Cretaceous sediments and interbedded volcanics and in mid-Cretaceous to Eocene intrusives of the Fuegian Batholith. The anisotropy of magnetic susceptibility was measured at each site and the influence of magnetic fabric on the characteristic remanent magnetizations (ChRM) in plutonic rocks was corrected using inverse tensors of anisotropy of remanent magnetizations. Normal polarity secondary magnetizations with west-directed declination were obtained in the sediments and they did not pass the fold test. These characteristic directions are similar to those recorded by mid Cretaceous intrusives suggesting a remagnetization event during the normal Cretaceous superchron and describe a large (> 90°) counterclockwise rotation. Late Cretaceous to Eocene rocks of the Fueguian Batholith, record decreasing counterclockwise rotations of 45° to 30°. These paleomagnetic results are interpreted as evidence of a large counterclockwise rotation of the Fueguian Andes related to the closure of the Rocas Verdes Basin and the formation of the Darwin Cordillera during the Late Cretaceous and Paleocene. The tectonic evolution of the Patagonian Bend can thus be described as the formation of a progressive arc from an oroclinal stage during the closure of the Rocas Verdes basin to a mainly primary arc during the final stages of deformation of the Magallanes fold and thrust belt. Plate reconstructions show that the Antarctic Peninsula would have formed a continuous margin with Patagonia between the Early Cretaceous and the Eocene, and acted as a non-rotational rigid block facilitating the development of the Patagonian Bend.

  7. Geophysical characterization of two circular structures at Bajada del Diablo (Patagonia, Argentina): Indication of impact origin

    NASA Astrophysics Data System (ADS)

    Prezzi, Claudia B.; Orgeira, María Julia; Acevedo, Rogelio D.; Ponce, Juan Federico; Martinez, Oscar; Rabassa, Jorge O.; Corbella, Hugo; Vásquez, Carlos; González-Guillot, Mauricio; Subías, Ignacio

    2012-02-01

    An impact origin has been proposed for the circular structures found in Bajada del Diablo, Patagonia, Argentina. Taking into account its extension and the number of impact structures, Bajada del Diablo would be the largest meteoritic impact areas known on Earth, being an extremely interesting area for the research of impact events and processes. Moreover, the global distribution of known impact structures shows a surprising asymmetry. Particularly, South America has only seven described areas. It is evident that this situation is an artifact, highlighting the importance of intensifying the research in the least studied areas such as Argentina. Circular structures in Bajada del Diablo have been identified on two rock types: the Quiñelaf eruptive complex and Pampa Sastre Formation. In the first case, circular structures are placed in olivine basalts. On the other hand, Pampa Sastre Formation (late Pliocene/early Pleistocene) corresponds to conglomerate layers with basalt clasts boulder and block in size in a coarse sandy matrix. With the aim of further the investigation of the proposed impact origin for these circular structures, we carried out detailed topographic, magnetic and electromagnetic ground surveys in two circular structures ("8" and "A") found in Pampa Sastre conglomerates. Both circular structures are simple, bowl-shaped with rim diameters of 300 m and maximum depths of 10 m. They have been partially filled in by debris flows from the rims and wind-blown sands. Two preliminary magnetic profiles have also been carried out in circular structure "G" found in Quiñelaf basalts. The magnetic anomalies show a circular pattern with a slightly negative and relatively flat signal in the circular structures' bases. Furthermore in the circular structures' rims, high-amplitude, conspicuous and localized (short wavelength) anomalies are observed. Such large amplitude and short wavelength anomalies are not detected outside the circular structures. For all used

  8. High potential of nitrogen fixation in pristine, ombrotrophic bogs in Southern Patagonia

    NASA Astrophysics Data System (ADS)

    Knorr, Klaus-Holger; Horn, Marcus A.; Bahamonde Aguilar, Nelson A.; Borken, Werner

    2015-04-01

    Nitrogen (N) input in pristine peatlands occurs via natural input of inorganic N through atmospheric deposition or biological dinitrogen (N2) fixation. However, N2 fixation is to date mostly attributed to bacteria and algae associated to Sphagnum and its contribution to plant productivity and peat buildup has been often underestimated in previous studies. Based on net N storage, exceptionally low N deposition, and high abundance of vascular plants at pristine peatlands in Southern Patagonia, we hypothesized that there must be a high potential of non-symbiotic N2 fixation not limited to the occurrence of Sphagnum. To this end, we chose two ombrotrophic bogs with spots that are dominated either by Sphagnum or by vascular, cushion-forming plants and sampled peat from different depths for incubation with 15N2 to determine N2 fixation potentials. Moreover, we analyzed 15N2 fixation by a nodule-forming, endemic conifer inhabiting the peatlands. Results from 15N2 uptake were compared to the conventional approach to study N2 fixation by the acetylene reduction assay (ARA). Using 15N2 as a tracer, high non-symbiotic N2 fixation rates of 0.3-1.4 μmol N g-1 d-1 were found down to 50 cm under micro-oxic conditions (2 vol.%) in samples from both plots either covered by Sphagnum magellanicum or by vascular cushion plants. Peat N concentrations suggested a higher potential of non-symbiotic N2 fixation under cushion plants, likely because of the availability of easily decomposable organic compounds as substrates and oxic conditions in the rhizosphere. In the Sphagnum plots, high N2 fixation below 10 cm depth would rather reflect a potential fixation that may switch on during periods of low water levels when oxygen penetrates deeper into the peat. 15N natural abundance of live Sphagnum from 0-10 cm pointed to N uptake solely from atmospheric deposition and non-symbiotic N2 fixation. 15N signatures of peat from the cushion plant plots indicated additional N supply from N

  9. Depositional Environments of Late Danian Plant Localities: Chubut Provice, Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Comer, E.; Slingerland, R. L.; Wilf, P.

    2010-12-01

    Diverse, well-preserved macroflora are observed within Cretaceous and Paleocene sediments of Chubut Province, Patagonia, Argentina. These macroflora are the most well preserved early Paleocene flora from Gondwana and add new insight into the diversity and environments of that epoch. Two major sites of fossil preservation, Palacio de los Loros and Parque Provincial Ormachea, sit near the top of the Late Danian (65.5-61.7 Ma) Salamanca Formation. Understanding the depositional history of the Salamanca is important in characterizing paleoenvironments in which these flora lived and relating these Patagonian macroflora to concurrent Paleocene flora within the Gondwanan supercontinent. During a two week field season, twenty stratigraphic sections were measured along the outcrop belt at Palacio de los Loros and Ormachea Park as well as two minor sites; Las Flores, and Rancho Grande. Photo mosaics, laser ranger data, and stratigraphic columns were merged with elevated geologic maps and imported into Fledermaus to generate a 3-D visualization of facies relationships. Rock samples were also collected and will be thin sectioned and analyzed for petrography and grain size. The Salamanca Fm. consists of 7 facies, listed here in stratigraphically ascending order: 1)Transgressive sands, 2)Wispy-bedded claystone, 3)Banco Verde, 4)White Cross bedded sandstone, 5)Accretion set siltstone, 6)Transitional silty claystone and 7)Banco Negro. Based on these facies, the Salamanca Fm. is interpreted as a marine-shelf to brackish, tide-dominated, estuarine deposit. The base of the Salamanca Fm. rests on an unconformity representing a marine flooding surface and lower sections of the Salamanca, facies 1 and 2, contain abundant glauconite and fossils indicative of a marine shelf environment. These facies give way upwards to bi-directional trough cross bedded sandstones interspersed with flaser bedded sandy siltstones (facies 3 and 4) indicating a less marine estuary with strong flow regimes

  10. Recent acceleration of ice loss in the Northern Patagonia Icefield based on an updated decennial evolution

    NASA Astrophysics Data System (ADS)

    López, P.; Casassa, G.

    2011-12-01

    Ice elevation changes of the Northern Patagonia Icefield (NPI) were analyzed by comparing three Digital Elevation Models (DEM) corresponding to 1975 (constructed based on topographic maps), the SRTM DEM of 2000 yr and a SPOT 5 DEM of 2005. In addition, the glacier length fluctuations and the surface area evolution between 2001 and 2011 of 25 glaciers of the NPI were studied: the information extracted from the Landsat ETM+ satellite image of 11 March 2001 was compared to the measurements performed based on the Landsat ETM+ satellite image of 19 February 2011. From a global point of view, the majority of the studied glaciers thinned, retreated and lost surface between 2001 and 2011, only few glaciers (Leones, Nef, Pared Sur and Soler) located on the eastern side of the NPI have been stable. Glaciers located on the western side of the NPI suffered a stronger wasting compared to the glaciers located on the eastern side. Overall, over the ablation areas of the NPI (below 1150 m a.s.l.) a more rapid thinning of 2.6 m yr-1 occurred between 2000 and 2005 yr compared to the period 1975-2000, in which a mean thinning of 1.7 m yr-1 was measured for the same zones of the NPI. For the whole period (1975-2005) the most important thinning of the ablation areas has been estimated for HPN-1 Glacier (4.4 m yr-1) followed by Benito (3.4 m yr-1), Fraenkel (2.4 m yr-1), Gualas (2.1 m yr-1) and Acodado glaciers, all of them located on the western side of the NPI. Between 2001 and 2011, a noteworthy retreat of 1.9 km was experienced by Gualas Glacier and by Reichert Glacier with 1.6 km, both located on the north-western side of the NPI. On the south-western side of the NPI, during the same decennia, Steffen Glacier experienced a remarkable retreat of 1.6 km as well. During the 2001-2011 period, Steffen Glacier more than doubled its rate of retreat (compared to the 1979-2001 period) and experienced the disintegration of its main front as well as a lateral tongue that retreated 3.1 km. The

  11. Unravelling the collapse mechanisms at a Jurassic caldera of the Chon Aike silicic LIP in Southern Patagonia (47° 15 'S, 71° 40'W), Argentina

    NASA Astrophysics Data System (ADS)

    Sruoga, P.; Japas, S.; Salani, F.; Kleiman, L.; Graffigna, M.

    2008-10-01

    La Peligrosa Caldera is located at Sierra Colorada (47° 15'S, 71° 40' W) in the Chon-Aike silicic LIP. It represents an unique window to understand the eruptive mechanisms that prevailed throughout the ignimbritic flare-up in Southern Patagonia during middle to late Jurassic times. Key pieces of lithologic and structural evidences are taken into account to reconstruct the volcanic structure.

  12. Molecular phylogenetic relationships of the lizard clade Liolaemus elongatus (Iguania: Liolaemini) with the description of a new species from an isolated volcanic peak in northern Patagonia.

    PubMed

    Avila, Luciano Javier; Medina, Cintia Debora; Perez, Cristian Hernan Fulvio; Sites, Jack W; Morando, Mariana

    2015-01-01

    A new species of the Andean-Patagonian Liolaemus elongatus clade is described. Liolaemus crandalli sp. nov. differs from other members of its clade by a combination of coloration characters, scale counts and genetic traits. Liolaemus crandalli sp. nov. is known only from an isolated volcanic mountain in northwestern Patagonia above 1500 m.a.s.l. unconnected with other habitat suitable for species of the Liolaemus elongatus clade. PMID:25947719

  13. Columnar jointing in vapor-phase-altered, non-welded Cerro Galán Ignimbrite, Paycuqui, Argentina

    USGS Publications Warehouse

    Wright, Heather M.; Lesti, Chiara; Cas, Ray A.F.; Porreca, Massimiliano; Viramonte, Jose G.; Folkes, Christopher B.; Giordano, Guido

    2011-01-01

    Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0 × 10−3–8.5 × 10−2°C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.

  14. Hydrothermal-flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.

    1982-01-01

    This detailed three-dimensional model of the natural flow regime of the Cerro Prieto geothermal field, before steam production began, is based on patterns of hydrothermal mineral zones and light stable isotopic ratios observed in rock samples from more than fifty deep wells, together with temperature gradients, wireline logs and other data. At the level so far penetrated by drilling, this hydrothermal system was heated by a thermal plume of water close to boiling, inclined at 45/sup 0/, rising from the northeast and discharging to the west. To the east a zone of cold water recharge overlies the inclined thermal plume. Fission track annealing studies shows that the reservoir reached 170/sup 0/C only 10/sup 4/ years ago. Oxygen isotope exchange data indicate that a 12 km/sup 3/ volume of rock subsequently reacted with three times its volume of water hotter than 200/sup 0/C. Averaged over the duration of the heating event this would require a flow velocity of about 6 m/year through the pores of a typical cross section of the reservoir having an average porosity of 10%. Although this is an extensional tectonic environment of leaky transform faulting in which repeated intrusions of basalt magma are likely, for simplicity of computation possible heat sources were modelled as simple two dimensional basalt intrusions of various sizes, shapes and locations. We have calculated a series of two-dimensional convective heat transfer models, with different heat sources and permeability distributions. The models which produce the best fit for the temperature distributions observed in the field today have in common a heat source which is a funnel-shaped basalt intrusion, 4 km wide at the top, emplaced at a depth of 5 km to 6 km about 40,000 to 50,000 years ago.

  15. The life cycle of instability features measured from the Andes Lidar Observatory over Cerro Pachon on 24 March 2012

    NASA Astrophysics Data System (ADS)

    Hecht, J. H.; Wan, K.; Gelinas, L. J.; Fritts, D. C.; Walterscheid, R. L.; Rudy, R. J.; Liu, A. Z.; Franke, S. J.; Vargas, F. A.; Pautet, P. D.; Taylor, M. J.; Swenson, G. R.

    2014-07-01

    The Aerospace Corporation's Nightglow Imager (ANI) observes nighttime OH emission (near 1.6 μm) every 2 s over an approximate 73° field of view. ANI had previously been used to study instability features seen over Maui. Here we describe observations of instabilities seen from 5 to 8 UT on 24 March 2012 over Cerro Pachon, Chile, and compare them with previous results from Maui, with theory, and with Direct Numerical Simulations (DNS). The atmosphere had reduced stability because of the large negative temperature gradients measured by a Na lidar. Thus, regions of dynamical and convective instabilities are expected to form, depending on the value of the Richardson number. Bright primary instabilities are formed with a horizontal wavelength near 9 km and showed the subsequent formation of secondary instabilities, rarely seen over Maui, consistent with the primaries being dynamical instabilities. The ratio of the primary to secondary horizontal wavelength was greater over Chile than over Maui. After dissipation of the instabilities, smaller-scale features appeared with sizes in the buoyancy subrange between 1.5 and 6 km. Their size spectra were consistent with the model of Weinstock (1978) if the turbulence is considered to be increasing. The DNS results produce secondary instabilities with sizes comparable to what is seen in the images although their spectra are somewhat steeper than is observed. However, the DNS results also show that after the complete decay of the primary features, scale sizes considerably smaller than 1 km are produced and these cannot be seen by the ANI instrument.

  16. Soft-bottom crustacean assemblages in Mediterranean marine caves: the cave of Cerro Gordo (Granada, Spain) as case study

    NASA Astrophysics Data System (ADS)

    Navarro-Barranco, C.; Guerra-García, J. M.; Sánchez-Tocino, L.; García-Gómez, J. C.

    2012-12-01

    Although marine caves are priority conservation areas according to the Directive 92/43/CEE of the European Community, there is a lack of studies dealing with their soft-bottom communities. For a case study, we selected the Cerro Gordo cave at 15 m depth. Three different zones were defined: a semi-dark 25-m long entrance area, a dark intermediate area of 35 m, and the final zone at 90 m from the entrance. Sediment samples were taken from these zones as well as from outside the cave (control) by SCUBA diving. Six rectangular cores of 10 × 250 cm2 were collected in each site for macrofaunal study, and three more replicates were taken to analyze physico-chemical parameters. The granulometry showed a clear gradient from medium sands outside the cave to silt and clay in the inner zone. Measurements of the crustacean assemblages showed that the number of species and abundance were significantly higher outside the cave (30-40 species, >4,000 ind m-2) than inside (5-10 species, <1,000 ind m-2). Multivariate analyses showed a clear difference in species composition between outside and inside the cave. Caprellids, tanaids, cumaceans, and decapods were only found outside the cave, while gammarids and isopods were present both outside and inside the cave. The gammarid Siphonoecetes sabatieri and the tanaid Apseudes latreilli were the dominant species outside the cave, while the gammarids Harpinia pectinata, Harpinia crenulata, and Harpinia ala were dominant inside. The present study represents an increase in depth range and geographic distribution for Kupellonura mediterranea and Monoculodes packardi. This is the first description of soft-bottom crustacean communities from submarine caves of southern Spain.

  17. Observations of a Breakdown of a Mountain Wave Near 84 km Altitude Over Cerro Pachon Chile from the Andes Lidar Observatory

    NASA Astrophysics Data System (ADS)

    Hecht, J. H.; Gelinas, L. J.; Rudy, R. J.; Walterscheid, R. L.; Taylor, M. J.; Pautet, P. D.; Fritts, D. C.; Smith, S. M.; Franke, S. J.; Mlynczak, M. G.

    2015-12-01

    Mountain waves are produced by flow over orography. They propagate almost vertically, and are characterized by nearly zero velocity phase speed. The altitude to which they typically propagate is not well documented. They are thought to mainly dissipate by absorption in a critical layer although large-amplitude wave breakdown is also thought to occur. There have been almost no direct observations of the breakdown of mountain waves in the upper mesosphere and lower thermosphere. The region over Cerro Pachon Chile (a 2715 meter mountain in the Andes where large astronomical telescopes are located) is especially favorable to the production of mountain waves. In 2009 Smith and colleagues reported on the first observations of such waves propagating into the mesopause region (85 to 95 km) from El Leoncito Argentina, where waves over Cerro Pachon could be seen using airglow observations. The Aerospace Corporation's Nightglow Imager (ANI) is located at the Andes Lidar Observatory near the crest of Cerro Pachon. ANI observes nighttime OH emission (near 1.6 microns) every 2 seconds over an approximate 73 degree field of view. ANI had previously been used to the breakdown of Kelvin-Helmholtz instability features not associated with a specific gravity wave. Here we present OH airglow observations, originating near 84 km, from 22 UT to 3 UT on 8/9 July 2012 that show the breakdown of a mountain wave into instability features that subsequently dissipate into turbulence. These multi-hour observations provide the most detailed images to date of the breakdown of a mountain wave. The causes for, and the results of, the breakdown of this mountain wave are discussed.

  18. Cerro Toledo Rhyolite, Jemez Volcanic Field, New Mexico: {sup 40}Ar/{sup 39}Ar geochronology of eruptions between two caldera-forming events

    SciTech Connect

    Spell, T.L. |; McDougall, I.; Doulgeris, A.P.

    1996-12-01

    The Cerro Toledo Rhyolite comprises a group of domes and tephra which were erupted during the interval between two caldera-forming ignimbrites, the Tshirege Member and Otowi Member of the Bandelier Tuff, in the Jemez Volcanic Field, New Mexico. To provide a chronologic framework for geochemical and isotopic studies on these rhyolites, which record the evolution of the Bandelier magma system during this interval, a {sup 40}Ar/{sup 39}Ar geochronology study was undertaken. Pumice from major pyroclastic fall deposits within the rhyolite tephra and samples from the rhyolite domes were dated as well as the stratigraphically bracketing Bandelier Tuff. The {sup 40}Ar/{sup 39}Ar ages for the two members of the Bandelier Tuff Yield and interval of 380{+-}20 k.y. between these caldera forming eruptions. During this interval nine major pyroclastic pumice units were deposited in the sections studies, for which six yield isochron ages, one a weighted mean age, one a maximum age, and one no reliable age due to lack of sanidine. {sup 40}Ar/{sup 39}Ar dates on pumice fall units within the Cerro Toledo Rhyolite tephra indicate that eruptive activity occurred at > 1.59, 1.54, 1.48, 1.37 and 1.22 Ma. {sup 40}Ar/{sup 39}Ar dating of Cerro Toledo Rhyolite domes indicates these were erupted within the caldera at 1.54, 1.45, 1.38-1.34, and 1.27 Ma. The dates obtained indicate that eruptive activity occurred throughout the 380 k.y. interval between the two members of the Bandelier Tuff, but suggest that eruptions producing both tephra and domes occurred during discrete intervals at ca. 1.54, 1.48 and 1.38-1.34 Ma. 43 refs., 5 figs., 3 tabs.

  19. The geological and structural evolution of the Cerro Tuzgle Quaternary stratovolcano in the back-arc region of the Central Andes, Argentina

    NASA Astrophysics Data System (ADS)

    Norini, G.; Cogliati, S.; Baez, W.; Arnosio, M.; Bustos, E.; Viramonte, J.; Groppelli, G.

    2014-09-01

    The aim of our paper is to contribute to a better knowledge of the volcanism in the back-arc region of the Central Andes and its relationships with the basement geology, the stress field and the tectonic evolution, by studying in detail the stratigraphy and the structure of the Quaternary Cerro Tuzgle stratovolcano in the Puna Plateau. Field mapping and remote sensing analysis reveal the stratigraphic architecture, the geological evolution and the volcanotectonic interactions in the Cerro Tuzgle area. For the first time in a volcano of the Puna Plateau, synthemic units bounded by unconformity surfaces have been defined, unrevealing the temporal and spatial relationships between constructive and destructive phases of the volcano history. Our study indicates that after the emplacement of a small ignimbrite deposit and of few scattered lava domes, the central Cerro Tuzgle volcano built up throughout three distinct phases of edifice construction. The first of these constructive phases ended with a previously unreported destructive event, consisting of ≈ 0.5 km3, catastrophic sector collapse of the volcanic edifice, whose stratigraphic position and main characteristics have been identified. The study suggests that the regional stress regime and the topography of the substrata are the main non-magmatic factors controlling the constructive and destructive phases of the volcano, including the directions of magmatic intrusions, faulting and gravitational sector failure of the volcano. The integration of synthemic stratigraphy and volcanotectonic analysis in the study of volcanic edifices showed to be an effective methodological approach for the understanding of the magmatic and tectonic evolution of the Puna Plateau.

  20. Carbon and nitrogen isotope composition of core catcher samples from the ICDP deep drilling at Laguna Potrok Aike (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Luecke, Andreas; Wissel, Holger; Mayr*, Christoph; Oehlerich, Markus; Ohlendorf, Christian; Zolitschka, Bernd; Pasado Science Team

    2010-05-01

    The ICDP project PASADO aims to develop a detailed paleoclimatic record for the southern part of the South American continent from sediments of Laguna Potrok Aike (51°58'S, 70°23'W), situated in the Patagonian steppe east of the Andean cordillera and north of the Street of Magellan. The precursor project SALSA recovered the Holocene and Late Glacial sediment infill of Laguna Potrok Aike and developed the environmental history of the semi-arid Patagonian steppe by a consequent interdisciplinary multi-proxy approach (e.g. Haberzettl et al., 2007). From September to November 2008 the ICDP deep drilling took place and successfully recovered in total 510 m of sediments from two sites resulting in a composite depth of 106 m for the selected main study Site 2. A preliminary age model places the record within the last 50.000 years. During the drilling campaign, the core catcher content of each drilled core run (3 m) was taken as separate sample to be shared and distributed between involved laboratories long before the main sampling party. A total of 70 core catcher samples describe the sediments of Site 2 and will form the base for more detailed investigations on the palaeoclimatic history of Patagonia. We here report on the organic carbon and nitrogen isotope composition of bulk sediment and plant debris of the core catcher samples. Similar investigations were performed for Holocene and Late Glacial sediments of Laguna Potrok Aike revealing insights into the organic matter dynamics of the lake and its catchment as well as into climatically induced hydrological variations with related lake level fluctuations (Mayr et al., 2009). The carbon and nitrogen content of the core catcher fine sediment fraction (<200 µm) is low to very low (around 1 % and 0.1 %, respectively) and requires particular attention in isotope analysis. The carbon isotope composition shows comparably little variation around a value of -26.0 per mil. The positive values of the Holocene and the Late

  1. Bathymetry of Patagonia glacier fjords and glacier ice thickness from high-resolution airborne gravity combined with other data

    NASA Astrophysics Data System (ADS)

    An, L.; Rignot, E.; Rivera, A.; Bunetta, M.

    2012-12-01

    The North and South Patagonia Ice fields are the largest ice masses outside Antarctica in the Southern Hemisphere. During the period 1995-2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.105 ± 0.001 mm/yr. In more recent years, the glaciers have been thinning more quickly than can be explained by warmer air temperatures and decreased precipitation. A possible cause is an increase in flow speed due to enhanced ablation of the submerged glacier fronts. To understand the dynamics of these glaciers and how they change with time, it is critical to have a detailed view of their ice thickness, the depth of the glacier bed below sea or lake level, how far inland these glaciers remain below sea or lake level, and whether bumps or hollows in the bed may slow down or accelerate their retreat. A grid of free-air gravity data over the Patagonia Glaciers was collected in May 2012 and October 2012, funded by the Gordon and Betty Moore Foundation (GBMF) to measure ice thickness and sea floor bathymetry. This survey combines the Sander Geophysics Limited (SGL) AIRGrav system, SGL laser altimetry and Chilean CECS/UCI ANDREA-2 radar. To obtain high-resolution and high-precision gravity data, the helicopter operates at 50 knots (25.7 m/s) with a grid spacing of 400m and collects gravity data at sub mGal level (1 Gal =1 Galileo = 1 cm/s2) near glacier fronts. We use data from the May 2012 survey to derive preliminarily high-resolution, high-precision thickness estimates and bathymetry maps of Jorge Montt Glacier and San Rafael Glacier. Boat bathymetry data is used to optimize the inversion of gravity over water and radar-derived thickness over glacier ice. The bathymetry maps will provide a breakthrough in our knowledge of the ice fields and enable a new era of glacier modeling and understanding that is not possible at present because ice thickness is not known.

  2. CO2 and CH4 fluxes of contrasting pristine bogs in southern Patagonia (Tierra del Fuego, Argentina)

    NASA Astrophysics Data System (ADS)

    Münchberger, Wiebke; Blodau, Christian; Kleinebecker, Till; Pancotto, Veronica

    2015-04-01

    South Patagonian peatlands cover a wide range of the southern terrestrial area and thus are an important component of the terrestrial global carbon cycle. These extremely southern ecosystems have been accumulating organic material since the last glaciation up to now and are - in contrast to northern hemisphere bogs - virtually unaffected by human activities. So far, little attention has been given to these pristine ecosystems and great carbon reservoirs which will potentially be affected by climate change. We aim to fill the knowledge gap in the quantity of carbon released from these bogs and in what controls their fluxes. We study the temporal and spatial variability of carbon fluxes in two contrasting bog ecosystems in southern Patagonia, Tierra del Fuego. Sphagnum-dominated bog ecosystems in Tierra del Fuego are similar to the ones on the northern hemisphere, while cushion plant-dominated bogs can almost exclusively be found in southern Patagonia. These unique cushion plant-dominated bogs are found close to the coast and their occurrence changes gradually to Sphagnum-dominated bogs with increasing distance from the coast. We conduct closed chamber measurements and record relevant environmental variables for CO2 and CH4 fluxes during two austral vegetation periods from December to April. Chamber measurements are performed on microforms representing the main vegetation units of the studied bogs. Gas concentrations are measured with a fast analyzer (Los Gatos Ultraportable Greenhouse Gas Analyzer) allowing to accurately record CH4 fluxes in the ppm range. We present preliminary results of the carbon flux variability from south Patagonian peat bogs and give insights into their environmental controls. Carbon fluxes of these two bog types appear to be highly different. In contrast to Sphagnum-dominated bogs, cushion plant-dominated bogs release almost no CH4 while their CO2 flux in both, photosynthesis and respiration, can be twice as high as for Sphagnum

  3. Intestinal helminth fauna of the South American sea lion Otaria flavescens and fur seal Arctocephalus australis from northern Patagonia, Argentina.

    PubMed

    Hernández-Orts, J S; Montero, F E; Juan-García, A; García, N A; Crespo, E A; Raga, J A; Aznar, F J

    2013-09-01

    We report on the intestinal helminth fauna of 56 South American sea lions, Otaria flavescens, and 5 South American fur seals, Arctocephalus australis, from northern Patagonia, Argentina. A total of 97,325 helminth specimens were collected from sea lions. Gravid individuals were represented by 6 species of parasites: 1 digenean (Ascocotyle (Ascocotyle) patagoniensis), 1 cestode (Diphyllobothrium spp.), 3 nematodes (Uncinaria hamiltoni, Contracaecum ogmorhini s.s., Pseudoterranova cattani) and 1 acanthocephalan (Corynosoma australe). In addition, third-stage larvae of 2 nematodes (Contracaecum sp. and Anisakis sp. type I) and 3 juvenile acanthocephalans (Andracantha sp., Profilicollis chasmagnathi and Corynosoma cetaceum) were also collected. Andracantha sp., C. ogmorhini s.s. and P. chasmagnathi represent new host records. A total of 1516 helminth specimens were collected from fur seals. Gravid individuals were represented by three species of parasites, namely, Diphyllobothrium spp., C. ogmorhini s.s. and C. australe. In addition, larvae of Contracaecum sp. and P. cattani, juveniles of C. cetaceum and immature cestodes (Tetrabothriidae gen. sp.) were also collected. Corynosoma australe was the most prevalent and abundant parasite in both hosts, accounting for >90% of all specimens. Sea lions and furs seals from northern Patagonia harbour the intestinal helminth communities that could be predicted for otariids, i.e. the combination of species of the genera Corynosoma, Diphyllobothrium, Pseudoterranova, Contracaecum and, in pups, Uncinaria. Additionally, both species of otariid are apparently unsuitable hosts (i.e. non-hosts) for as many as five parasite taxa. The inclusion or exclusion of these species affects estimation of species richness at both component community (11 versus 6 species in sea lions; 7 versus 3 species in fur seals) and infracommunity (mean: 3.1 versus 2.6 in sea lions; 2.2 versus 1.7 species) levels. Information about the reproductive status of

  4. Geochemistry of the Neoproterozoic (800-767 Ma) Cerro Bori orthogneisses, Dom Feliciano Belt in Uruguay: tectonic evolution of an ancient continental arc

    NASA Astrophysics Data System (ADS)

    Lenz, C.; Porcher, C. C.; Fernandes, L. A. D.; Masquelin, H.; Koester, E.; Conceição, R. V.

    2013-10-01

    The Cerro Bori orthogneisses, crystallized between ca. 800 and 767 Ma, are composed of a sequence of mafic gneisses, with dioritic-gabbroic and dioritic composition tectonically interleaved with a sequence of tonalitic and granodioritic gneisses. These rocks intruded the Chafalote paragneisses (metapelites, semipelites, carbonate and mafic rocks) and they were metamorphosed of high P-T conditions at ca. 676-654 Ma. This paper presents the first major and trace geochemical signatures, as well as Sm and Pb isotopic composition for the Cerro Bori orthogneisses, which allow distinguishing three different groups of rocks. Type I rocks are mafic gneisses with tholeiitic affinity, whereas the Type II rocks are tonalitic and granodioritic gneisses with calc-alkaline affinity. The third type is composed of biotite-rich mafic gneisses with potassic and ultrapotassic affinities. All the three types of rocks have negative ℰND values (between -2.12 and -6.67) and old TDM ages (between 1.2 and 2.0 Ga), indicating that the process of crustal assimilation/contamination was an important process, together with fractional crystallization. An continental arc tectonic setting is suggested to this association of rocks between 800 and 767 Ma. This subduction suggests the existence of an ocean between Rio de La Plata and adjacent cratons during the break up of the Rodinia supercontinent.

  5. Proposed Future Disposition of Certain Cerro Grande Fire Flood and Sediment Retention Structures at Los Alamos National Laboratory, Los Alamos, New Mexico

    SciTech Connect

    N /A

    2002-08-07

    This environmental assessment (EA) has been prepared to analyze the environmental consequences resulting from the future disposition of certain flood retention structures built in the wake of the Cerro Grande Fire within the boundaries of Los Alamos National Laboratory (LANL). In May 2000, a prescription burn, started on Federally-administered land to the northwest of LANL, blew out of control and was designated as a wildfire. This wildfire, which became known as the Cerro Grande Fire, burned approximately 7,650 acres (3,061 hectares) within the boundaries of LANL before it was extinguished. During the fire a number of emergency actions were undertaken by the Department of Energy (DOE), National Nuclear Security Administration (NNSA) to suppress and extinguish the fire within LANL; immediately thereafter, NNSA undertook additional emergency actions to address the post-fire conditions. Due to hydrophobic soils (non-permeable soil areas created as a result of very high temperatures often associated with wild fires) and the loss of vegetation from steep canyon sides caused by the fire, surface runoff and soil erosion on hillsides above LANL were greatly increased over prefire levels. The danger to LANL facilities and structures and homes located down-canyon from the burned area was magnified.

  6. Metamorphic evolution of the Río de la Plata Craton in the Cinco Cerros area, Buenos Aires Province, Argentina

    NASA Astrophysics Data System (ADS)

    Massonne, Hans-Joachim; Dristas, Jorge A.; Martínez, Juan Cruz

    2012-10-01

    A metapelite and an interlayered granite were studied from the Cinco Cerros area ca. 65 km WNW of the city of Mar del Plata. Garnet in these samples is slightly zoned with core and rim compositions of pyr17(gro + andr)6spes1.5alm75.5 and pyr13.5(gro + andr)5.5spes2alm80, respectively, in the metapelite. Corresponding compositions in the granite are pyr15(gro + andr)3.5spes3.5alm78 and pyr11(gro + andr)3.5spes4.5alm81. We used the PERPLE_X computer software package to calculate P-T pseudosections. From the pseudosection of the metapelite P-T conditions of 6.7 kbar and 670 °C were derived for an early metamorphic stage. Subsequently, a pressure release occurred at decreasing temperatures. The final metamorphic P-T conditions recorded by the studied rock are 4.5 kbar and 600 °C compatible with the absence of cordierite, staurolite, and an Al2SiO5-phase. Garnet in the granitoid crystallized between 715 and 690 °C at a pressure around 7.7 kbar. U-Th-Pb age dating with the electron microprobe was performed. 16 analyses of monazite in the metapelite formed three clusters resulting in ages of I: 2073 ± 11.4 (1σ) Ma, II: 1913 ± 11.0 (1σ) Ma, and III: 1805 ± 20.8 (1σ) Ma. Thus, the Paleoproterozoic metamorphic event can be related to the Trans-Amazonian cycle and was followed by slow cooling. As our study area is close to the margin of the Río de la Plata Craton, where abundant magmatic arc-derived plutonic rocks are outcropping, we interpret the derived P-T data as follows: A heating event (not recorded by the studied rocks) resulted from magmas that intruded during the Trans-Amazonian cycle. This event was followed by slow exhumation, probably caused by erosion, accompanied by thermal relaxation.

  7. Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de la Muerte, Costa Rica.

    PubMed

    Avalos, Gerardo; Soto, Alejandra; Alfaro, Willy

    2012-03-01

    Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant) and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis), dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads), and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon). Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of captured

  8. Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de la Muerte, Costa Rica.

    PubMed

    Avalos, Gerardo; Soto, Alejandra; Alfaro, Willy

    2012-03-01

    Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant) and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis), dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads), and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon). Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of captured

  9. Rock-magnetism and ore microscopy of the magnetite-apatite ore deposit from Cerro de Mercado, Mexico

    NASA Astrophysics Data System (ADS)

    Alva-Valdivia, L. M.; Goguitchaichvili, A.; Urrutia-Fucugauchi, J.; Caballero-Miranda, C.; Vivallo, W.

    2001-03-01

    Rock-magnetic and microscopic studies of the iron ores and associated igneous rocks in the Cerro de Mercado, Mexico, were carried out to determine the magnetic mineralogy and origin of natural remanent magnetization (NRM), related to the thermo-chemical processes due to hydrothermalism. Chemical remanent magnetization (CRM) seems to be present in most of investigated ore and wall rock samples, replacing completely or partially an original thermoremanent magnetization (TRM). Magnetite (or Ti-poor titanomagnetite) and hematite are commonly found in the ores. Although hematite may carry a stable CRM, no secondary components are detected above 580°, which probably attests that oxidation occurred soon enough after the extrusion and cooling of the ore-bearing magma. NRM polarities for most of the studied units are reverse. There is some scatter in the cleaned remanence directions of the ores, which may result from physical movement of the ores during faulting or mining, or from perturbation of the ambient field during remanence acquisition by inhomogeneous internal fields within these strongly magnetic ore deposits. The microscopy study under reflected light shows that the magnetic carriers are mainly titanomagnetite, with significant amounts of ilmenite-hematite minerals, and goethite-limonite resulting from alteration processes. Magmatic titanomagnetites, which are found in igneous rocks, show trellis, sandwich, and composite textures, which are compatible with high temperature (deuteric) oxy-exsolution processes. Hydrothermal alteration in ore deposits is mainly indicated by martitization in oxide minerals. Grain sizes range from a few microns to >100 mm, and possible magnetic state from single to multidomain, in agreement with hysteresis measurements. Thermal spectra, continuous susceptibility measurements, and IRM (isothermal remanent magnetization) acquisition suggest a predominance of spinels as magnetic carriers, most probably titanomagnetites with low

  10. Recycling of water, carbon, and sulfur during subduction of serpentinites: A stable isotope study of Cerro del Almirez, Spain

    USGS Publications Warehouse

    Alt, Jeffrey C.; Garrido, Carlos J.; Shanks, Wayne C.; Turchyn, Alexandra; Padrón-Navarta, José Alberto; López Sánchez-Vizcaíno, Vicente; Gómez Pugnaire, María Teresa; Marchesi, Claudio

    2012-01-01

    We use the concentrations and isotope compositions of water, carbon, and sulfur in serpentinites and their dehydration products to trace the cycling of volatiles during subduction. Antigorite serpentinites from the Cerro del Almirez complex, Spain, contain 9–12 wt.% H2O and 910 ± 730 ppm sulfur, and have bulk δ18O values of 8.6 ± 0.4‰, δD = − 54 ± 5‰, and δ34S = 5.0‰, consistent with serpentinization at temperatures of ~ 200 °C by seawater hydrothermal fluids in a seafloor setting. The serpentinites were dehydrated to chlorite–harzburgite (olivine + orthopyroxene + chlorite) at 700 °C and 1.6–1.9 GPa during subduction metamorphism, resulting in loss of water, and sulfur. The chlorite–harzburgites contain 5.7 ± 1.9 wt.% H2O, and have bulk δ18O = 8.0 ± 0.9‰, and δD = − 77 ± 11‰. The rocks contain 650 ± 620 ppm sulfur having δ34S = 1.2‰. Dehydration of serpentinite resulted in loss of 5 wt.% H2O having δ18O = 8–10‰ and δD = − 27 to − 65‰, and loss of 260 ppm sulfur as sulfate, having δ34S = 14.5‰. The contents and δ13C of total carbon in the two rock types overlap, with a broad trend of decreasing carbon contents and δ13C from ~ 1300 to 200 ppm and − 9.6 to − 20.2‰. This reflects mixing between reduced carbon in the rocks (210 ppm, δ13C ≈ − 26‰) and seawater-derived carbonate (δ13C ≈ − 1‰). Our results indicate: 1) Serpentinized oceanic peridotites carry significant amounts of isotopically fractionated water, carbon and sulfur into subduction zones; 2) Subduction of serpentinites to high P and T results in loss of water, and sulfur, which can induce melting and contribute to 18O, D, and 34S enrichments and oxidation of the sub-arc mantle wedge; and 3) Isotopically fractionated water, carbon, and sulfur in serpentinite dehydration products are recycled deeper into the mantle where they can contribute to isotope heterogeneities and may be significant for volatile budgets of the deep Earth.

  11. Differential use of the Argentine shelf by wintering adults and juveniles southern giant petrels, Macronectes giganteus, from Patagonia

    NASA Astrophysics Data System (ADS)

    Blanco, Gabriela S.; Quintana, Flavio

    2014-08-01

    To study habitat use and at-sea movements of southern giant petrels (SGP) during non-breeding period, we deployed 15 satellite transmitters (six adults, nine juveniles) at Isla Arce and Isla Gran Robredo colonies in Patagonia, Argentina. Birds were instrumented during 81.4 ± 37 days. Adult birds used 74% of the Argentine shelf concentrating mainly at the shelf break, middle shelf waters, and the surroundings of the colony. After fledging, juveniles spread to the Argentine, Uruguayan and Brazilian shelves within the South Atlantic. Adults alternated at-sea excursions (12 ± 5 days) with periods at the colony of 3 ± 0.3 days. Contrarily, juveniles moved first to the shelf break and then traveled northwards reaching the south of Brazil. There was some spatial overlap between age classes, but only during the first 30 days after juveniles had fledged; thereafter there was not overlap between the areas used by both age classes. The Argentine shelf is widely used by different species offering a suitable environment for foraging; this may be why adults SGP from Patagonian colonies spend all year-round within the Argentine shelf. The identification of used areas of non-breeding SGP fills a gap in the species knowledge contributing not only to the preservation the species, but also to the management of marine areas globally recognized as important for many other Procellariiformes.

  12. Bacillus patagoniensis sp. nov., a novel alkalitolerant bacterium from the rhizosphere of Atriplex lampa in Patagonia, Argentina.

    PubMed

    Olivera, Nelda; Siñeriz, Faustino; Breccia, Javier D

    2005-01-01

    A Gram-positive, rod-shaped, spore-forming bacterium (PAT 05T) was isolated from the rhizosphere of the perennial shrub Atriplex lampa in north-eastern Patagonia, Argentina. Its overall biochemical and physiological characteristics indicated that this strain should be placed in the alkaliphilic Bacillus group. Strain PAT 05T grew at pH 7-10 (optimum pH 8), but not at pH 6. Its DNA G+C content was 39.7 mol%. Sequence analysis of the 16S rRNA gene of PAT 05T revealed the closest match (99.6 % similarity) with Bacillus sp. DSM 8714. The highest level of DNA-DNA relatedness (88.6 %) was also found with this strain. On the basis of 16S rRNA gene sequence similarity and phylogenetic analysis, G+C content and DNA-DNA hybridization data, strain PAT 05T is related at the species level to Bacillus sp. DSM 8714, a member of a group referred as phenon 4a by Nielsen et al. [Nielsen, P., Fritze, D. & Priest, F. G. (1995). Microbiology 141, 1745-1761], which still lacks taxonomic standing. These results support the proposal of strain PAT 05T (=DSM 16117T=ATCC BAA-965T) as the type strain of Bacillus patagoniensis sp. nov. PMID:15653916

  13. Contaminants in the southern tip of South America: Analysis of organochlorine compounds in feathers of avian scavengers from Argentinean Patagonia.

    PubMed

    Martínez-López, E; Espín, S; Barbar, F; Lambertucci, S A; Gómez-Ramírez, P; García-Fernández, A J

    2015-05-01

    The aim of this study was to assess the exposure to organochlorine compounds (OC) in 91 primary wing feathers of avian scavengers, Turkey vulture (Cathartes aura), American black vulture (Coragyps atratus) and Southern crested caracaras (Polyborus plancus) from the southern tip of South America, in the Argentinean Patagonia. We analyzed for a series of OC including hexachlorocyclohexane (HCH) isomers, endosulfan, aldrin, dieldrin, endrin, dichlorodiphenyltrichloroethane (p,p'-DDT), dichlorodiphenyldichloroethane (p,p'-DDD), dichlorodiphenyldichloroethylene (p,p'-DDE), heptachlor and heptachlor-epoxide. This is the first study on OC in feathers of three terrestrial top carnivores from South America. OC concentrations found in the studied species were much higher than those found in feathers of raptors from Europe and Asia, which likely indicate their high use in the region, specifically in agriculture, and other possible uses of OC in this area. ∑HCH had the highest median concentration, followed by ∑Drins, ∑DDT, ∑Heptachlor, and ∑Endosulfan, similar to those reported in several food samples in Argentina. On the other hand, differences in OC profiles between species and areas may be related to feeding and migratory habits, as well as the molt period. Three individuals showed ∑DDT (DDT, DDD and DDE) concentrations in feathers related to sublethal effects. However, this comparison should be used with caution due to problems with extrapolating such data across tissues and species.

  14. South american geochronology: radiometric time scale for middle to late tertiary mammal-bearing horizons in patagonia.

    PubMed

    Marshall, L G; Pascual, R; Curtis, G H; Drake, R E

    1977-03-25

    Radiometric (potassium-argon) age determinations for basalts and tuffs associated with middle to late Tertiary mammal-bearing horizons in Patagonia, southern Argentina, permit refinement of boundaries and hiatuses between beds of Deseadan (early Oligocene) through Friasian (middle to late Miocene) age. At two localities beds of Deseadan age are overlain by basalts, which gave dates of 33.6 and 35.4 million years ago; 34.0 million years ago is tentatively accepted as a terminal date for known Deseadan. At several localities beds of Colhuehuapian age are underlain by basalts, which gave dates ranging from 28.8 to 24.3 million years ago; 25.0 million years is tentatively taken as a basal age for known Colhuehuapian. The paleontological hiatus between known Deseadan and known Colhuehuapian is thus in the order of 9.0 million years. Two tuffs from the Santa Cruz Formation (Santacrucian) gave ages of 21.7 and 18.5 million years. Plagioclase and biotite concentrates of an ignimbrite from the Collón Curá Formation (Friasian) gave ages ranging from 15.4 to 14.0 million years. PMID:17738414

  15. Porosity and permeability in volcanic rocks: a case study on the Serie Tobı´fera, South Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Sruoga, P.; Rubinstein, N.; Hinterwimmer, G.

    2004-04-01

    The Middle to Late Jurassic Serie Tobı´fera belongs to the Chon-Aike Province and extends all over Patagonia and the Antarctic Peninsula. It consists largely of ignimbrites, epiclastics and rhyolitic lavas and was considered only a minor reservoir rock for oil with fracture permeability. Petrographic and petrophysical data in selected core samples from the Austral Basin were collected to determine the processes controlling the porosity and permeability of these volcanic rocks. The sequence of processes occurring during cooling and in the post-cooling stages can modify, sometimes substantially, their original petrophysic characteristics. The results show that the highest porosity and permeability occur in rocks with quench fractured glasses and in non-welded ignimbrites with gas-pipe structures, followed by autobrecciated rhyolites. Welded ignimbrites, massive glasses and fresh rhyolites have the lowest permeabilities. The new data indicate that tectonic fracturing is not as significant as was considered before and application of these concepts are relevant in the assesment of volcanic reservoir quality.

  16. Gelidivirgula Patagoniensis Gen. Nov., Sp. Nov., A Novel Psychrotolerant, Sporeforming Anaerobe Isolated from Magellanic Penguin Guano in Patagonia, Chile

    NASA Technical Reports Server (NTRS)

    Pikuta, Elena V.; Hoover, Richard B.; Marsic, Damien; Whitman, William B.; Tang, Jane; Krader, Paul

    2003-01-01

    A novel obligately anaerobic, psychrotrophic bacterium, strain PPP2(sup T), was isolated from guano of the Magellanic penguin (Spheniscus magellanicus) in Patagonia, Chile. The Gram-positive, sporeforming, straight rods with sizes 0.6-0.9 x 3.0-5.0 microns, are motile by peritrichous flagella. Growth was observed to occur within the pH range 6.0-9.5 (optimum pH x), and temperature range 2-28 C (optimum 20 C). The novel isolate does not require NaCl for growth, but is halotolerant and growth was observed between 0 and 7 % NaCl (w/v) with optimum at 0.5 % (w/v). The new isolate is a catalase negative chemoorganohetherotroph with fermentative metabolism and uses as substrates: peptone, Bacto-tryptone, Casamino acids, and yeast extract. The major metabolic products are: acetate, butyrate, ethanol, and hydrogen is a minor gas product.. Strain PPP2 was sensitive to ampicillin, tetracycline, chloramphenicol, rifampin, kanamycin, and gentamycin. The G+C content of the DNA is 43.6 mol%. On the basis of 16S rDNA gene sequences and phenotypic characteristics, it is proposed that the strain PPP2(sup T) (= ATCC BAA-755(sup T) = JSM ...(sup T)) is assigned to the new genus Gelidivirgula gen. nov., as a representative of the new species, Gelidivirgula patagonensis sp. nov.

  17. Bacillus patagoniensis sp. nov., a novel alkalitolerant bacterium from the rhizosphere of Atriplex lampa in Patagonia, Argentina.

    PubMed

    Olivera, Nelda; Siñeriz, Faustino; Breccia, Javier D

    2005-01-01

    A Gram-positive, rod-shaped, spore-forming bacterium (PAT 05T) was isolated from the rhizosphere of the perennial shrub Atriplex lampa in north-eastern Patagonia, Argentina. Its overall biochemical and physiological characteristics indicated that this strain should be placed in the alkaliphilic Bacillus group. Strain PAT 05T grew at pH 7-10 (optimum pH 8), but not at pH 6. Its DNA G+C content was 39.7 mol%. Sequence analysis of the 16S rRNA gene of PAT 05T revealed the closest match (99.6 % similarity) with Bacillus sp. DSM 8714. The highest level of DNA-DNA relatedness (88.6 %) was also found with this strain. On the basis of 16S rRNA gene sequence similarity and phylogenetic analysis, G+C content and DNA-DNA hybridization data, strain PAT 05T is related at the species level to Bacillus sp. DSM 8714, a member of a group referred as phenon 4a by Nielsen et al. [Nielsen, P., Fritze, D. & Priest, F. G. (1995). Microbiology 141, 1745-1761], which still lacks taxonomic standing. These results support the proposal of strain PAT 05T (=DSM 16117T=ATCC BAA-965T) as the type strain of Bacillus patagoniensis sp. nov.

  18. Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra, Folivora) of Patagonia.

    PubMed

    Toledo, Néstor; Bargo, M Susana; Vizcaíno, Sergio F

    2015-05-01

    This article presents a morphofunctional analysis of the hind limb of Santacrucian (Early Miocene) sloths from southernmost Patagonia (Argentina). These fossil sloths were mid sized to large animals, ranging from 40 to 120 kg, and their postcranial skeleton was markedly different in shape compared with that of extant tree sloths, which vary from 2 to 10 kg. The functional anatomy of the hind limb of Santacrucian sloths was compared with that of living xenarthrans (tree sloths, anteaters, and armadillos), which involved reconstruction of the hind limb musculature and comparative and qualitative morphofunctional analyses, and hypotheses on the biological role of the hind limb in terms of preferences in substrate, posture, and strategies of locomotion were formulated. The hind limb of Santacrucian sloths bears strong resemblances to that of living South American anteaters in stoutness of skeletal elements, form of the characteristics related to muscular and ligamentous attachments, and conservative, pentadactylous strong-clawed pes. The musculature was very well developed, allowing powerful forces, principally in entire limb adduction, crus flexion and extension, pes extension, and toe prehension. These functional features, together with those of the forelimb, are congruent with climbing behavior, and support the hypothesis that Santacrucian sloths were good but slow climbing mammals. However, their climbing strategies were limited, owing principally to their comparatively large body size, and they relied to a large extent on their powerful musculature and curved manual and pedal unguals for both moving and standing on the arboreal supports. PMID:25644288

  19. Modeling volcanic ash resuspension - application to the 14-18 October 2011 outbreak episode in Central Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Folch, A.; Mingari, L.; Osores, M. S.; Collini, E.

    2013-09-01

    Volcanic fallout deposits from the June 2011 Cordón Caulle eruption in Central Patagonia were remobilized in several occasions months after their emplacement. In particular, during 14-18 October 2011, an intense outbreak episode generated huge volcanic clouds that were dispersed across Argentina, causing multiple impacts in the environment, affecting the air quality and disrupting airports. Fine ash particles in volcanic fallout deposits can be resuspended under favourable meteorological conditions, particularly during strong wind episodes in arid environments having low soil moisture and poor vegetation coverage. In opposition to eruption-formed ash clouds, modeling of resuspension-formed ash clouds has received little attention. In consequence, there are no emission schemes specially developed and calibrated for volcanic ash, and no operational product exists to model and forecast the formation and dispersal of resuspension ash clouds. Here we implement three dust emission schemes of increasing complexity in the FALL3D tephra dispersal model and use the 14-18 October 2011 outbreak episode as a model test case. We calibrate the emission schemes and validate the results of the coupled WRF-ARW/FALL3D modeling system using satellite imagery and measurements of visibility (a quantity related to total suspended particle concentration at surface) and particulate matter (PM10) concentration at several meteorological and air quality stations sparse across Argentina and Uruguay. Our final goal is to test the capability of the modeling system to become, in the near future, an operational forecast product for volcanic ash resuspension events.

  20. South american geochronology: radiometric time scale for middle to late tertiary mammal-bearing horizons in patagonia.

    PubMed

    Marshall, L G; Pascual, R; Curtis, G H; Drake, R E

    1977-03-25

    Radiometric (potassium-argon) age determinations for basalts and tuffs associated with middle to late Tertiary mammal-bearing horizons in Patagonia, southern Argentina, permit refinement of boundaries and hiatuses between beds of Deseadan (early Oligocene) through Friasian (middle to late Miocene) age. At two localities beds of Deseadan age are overlain by basalts, which gave dates of 33.6 and 35.4 million years ago; 34.0 million years ago is tentatively accepted as a terminal date for known Deseadan. At several localities beds of Colhuehuapian age are underlain by basalts, which gave dates ranging from 28.8 to 24.3 million years ago; 25.0 million years is tentatively taken as a basal age for known Colhuehuapian. The paleontological hiatus between known Deseadan and known Colhuehuapian is thus in the order of 9.0 million years. Two tuffs from the Santa Cruz Formation (Santacrucian) gave ages of 21.7 and 18.5 million years. Plagioclase and biotite concentrates of an ignimbrite from the Collón Curá Formation (Friasian) gave ages ranging from 15.4 to 14.0 million years.

  1. Utility of high-altitude infrared spectral data in mineral exploration: Application to Northern Patagonia Mountains, Arizona

    USGS Publications Warehouse

    Berger, B.R.; King, T.V.V.; Morath, L.C.; Phillips, J.D.

    2003-01-01

    Synoptic views of hydrothermal alteration assemblages are of considerable utility in regional-scale minerals exploration. Recent advances in data acquisition and analysis technologies have greatly enhanced the usefulness of remotely sensed imaging spectroscopy for reliable alteration mineral assemblages mapping. Using NASA's Airborne Visible Infrared Imaging Spectrometer (AVIRIS) sensor, this study mapped large areas of advanced argillic and phyllic-argillic alteration assemblages in the southeastern Santa Rita and northern Patagonia mountains, Arizona. Two concealed porphyry copper deposits have been identified during past exploration, the Red Mountain and Sunnyside deposits, and related published hydrothermal alteration zoning studies allow the comparison of the results obtained from AVIRIS data to the more traditional field mapping approaches. The AVIRIS mapping compares favorably with field-based studies. An analysis of iron-bearing oxide minerals above a concealed supergene chalcocite deposit at Red Mountain also indicates that remotely sensed data can be of value in the interpretation of leached caps above porphyry copper deposits. In conjunction with other types of geophysical data, AVIRIS mineral maps can be used to discriminate different exploration targets within a region.

  2. Muscular reconstruction and functional morphology of the hind limb of santacrucian (Early Miocene) sloths (Xenarthra, Folivora) of Patagonia.

    PubMed

    Toledo, Néstor; Bargo, M Susana; Vizcaíno, Sergio F

    2015-05-01

    This article presents a morphofunctional analysis of the hind limb of Santacrucian (Early Miocene) sloths from southernmost Patagonia (Argentina). These fossil sloths were mid sized to large animals, ranging from 40 to 120 kg, and their postcranial skeleton was markedly different in shape compared with that of extant tree sloths, which vary from 2 to 10 kg. The functional anatomy of the hind limb of Santacrucian sloths was compared with that of living xenarthrans (tree sloths, anteaters, and armadillos), which involved reconstruction of the hind limb musculature and comparative and qualitative morphofunctional analyses, and hypotheses on the biological role of the hind limb in terms of preferences in substrate, posture, and strategies of locomotion were formulated. The hind limb of Santacrucian sloths bears strong resemblances to that of living South American anteaters in stoutness of skeletal elements, form of the characteristics related to muscular and ligamentous attachments, and conservative, pentadactylous strong-clawed pes. The musculature was very well developed, allowing powerful forces, principally in entire limb adduction, crus flexion and extension, pes extension, and toe prehension. These functional features, together with those of the forelimb, are congruent with climbing behavior, and support the hypothesis that Santacrucian sloths were good but slow climbing mammals. However, their climbing strategies were limited, owing principally to their comparatively large body size, and they relied to a large extent on their powerful musculature and curved manual and pedal unguals for both moving and standing on the arboreal supports.

  3. The glacial geomorphology of the Lago Buenos Aires and Lago Puerreydón ice lobes, Central Patagonia

    NASA Astrophysics Data System (ADS)

    Bendle, Jacob; Thorndycraft, Varyl; Palmer, Adrian

    2016-04-01

    Patagonia is ideally located for reconstructions of late Quaternary ice-climate interaction(s) in the Southern Hemisphere mid-latitudes, yet many questions remain concerning post-LGM ice sheet retreat dynamics across the region. While modern-day glaciation is restricted to three small icefields (the North and South Patagonian and Cordillera Darwin icefields), during the Quaternary, and at the LGM, episodes of significant ice advance culminated in an expansive Patagonian ice sheet (PIS) centered over the southern Andes, for which a long and well-preserved landform record exists. Previous mapping in the region has either aimed to achieve regional coverage, necessarily omitting more subtle/complex features suggestive of certain ice-marginal processes, or has focused on the identification of palaeo-ice limits (e.g. moraine ridges) for geochronological applications, with little attention given to other (e.g. glaciofluvial, glaciolacustrine) features that are significant for understanding post-LGM ice sheet retreat dynamics. This poster presents a comprehensive and highly detailed (<30m spatial resolution) map of the glacial geomorphology of the Lago Buenos Aires (46.4°S) and Lago Puerreydón (47.2°S) ice lobes, major outlet glaciers of the central sector of the former PIS. The map allows refined reconstructions of glacial and, in particular, deglacial ice-marginal processes, and will underpin further analysis on the retreat history of the palaeo-ice lobes using high-resolution lithostratigraphic (varve) analyses.

  4. Response of biomarkers in amphibian larvae to in situ exposures in a fruit-producing region in North Patagonia, Argentina.

    PubMed

    Rosenbaum, Enrique A; Duboscq, Leonardo; Soleño, Jimena; Montagna, Cristina M; Ferrari, Ana; Venturino, Andrés

    2012-10-01

    The authors evaluated biomarker responses in caged larvae of the amphibian Rhinella arenarum in water channels during fruit production season and compared them with those elicited by a transient exposure to azinphos methyl (AzM) (0.02-2 mg/L; 4 h), the main pesticide applied in the Alto Valle region, Patagonia, Argentina, taking into account the maximum environmental concentration detected in superficial water (22.5 µg/L). The traditional biomarkers of organophosphate exposure, acetylcholinesterase (AChE) and carboxylesterase, were inhibited in tadpoles after one week of exposure in channels potentially receiving pesticide drift, whereas the antioxidant glutathione (GSH) and the detoxifying activity of GSH S-transferase (GST) were induced. In a two-week monitoring study, AChE activity was induced in larvae exposed at the agricultural site, and carboxylesterase showed an inhibition followed by return to control values, suggesting an exposure-recovery episode. Antioxidant glutathione levels were first depleted and then surpassed control levels, whereas GST activity was continuously induced. These responses were mimicked in the laboratory by 2 mg/L AzM-pulse exposure, which notably exceeds the expected environmental concentrations. The results draw attention to the complexity of responses after pesticide exposure, strongly depending on exposure time-concentration and recovery periods, among other possible factors, and support the necessity of the integrated use of biomarkers to assess exposure episodes in agricultural areas.

  5. Are the oxygen isotopic compositions of Fitzroya cupressoides and Nothofagus pumilio cellulose promising proxies for climate reconstructions in northern Patagonia?

    NASA Astrophysics Data System (ADS)

    Lavergne, Aliénor; Daux, Valérie; Villalba, Ricardo; Pierre, Monique; Stievenard, Michel; Vimeux, Françoise; Srur, Ana Marina

    2016-03-01

    Tree ring δ18O chronologies from two native species (Fitzroya cupressoides and Nothofagus pumilio) in northern Patagonia were developed to assess their potential for paleoclimate reconstructions. The five annually resolved cellulose δ18O chronologies (two for F. cupressoides and three for N. pumilio) are located on the Andes along the steep west-to-east precipitation gradient. Over the common 60 years long interval, the five site-δ18Ocell chronologies exhibit a strong common signal as indicated by the significant mean intercorrelation (r = 0.61, p < 0.05) and the high percentage (65%) of total variance explained by the first empirical orthogonal function. Although correlation analyses reveal that the two mean species-δ18Ocell chronologies are mainly modulated by December-May temperature, the N. pumilio chronology shows a greater sensitivity to record temperature variations (r = 0.57, p < 0.05). The δ18Ocell of N. pumilio contains a regional temperature signal representative of a large area in southern South America under the influence of the Southern Annular Mode. This study indicates that δ18Ocell in N. pumilio is a promising proxy to reconstruct past variations in temperature in South America south of 38°S.

  6. The flooding of the San Matías Gulf: The Northern Patagonia sea-level curve

    NASA Astrophysics Data System (ADS)

    Isla, Federico Ignacio

    2013-12-01

    Northern Patagonia is characterised by tectonic depressions below present sea level. Some of them are today flooded by the sea; others remain emerged although they are at altitudes of - 50 m (Bajo del Gualicho), - 35 m (Salinas Grandes) and - 7 m (Salina La Piedra). San Matías Gulf also was such an emerged depression below contemporary mean sea level during the Late Pleistocene. It flooded between 11,500 and 11,000 years ago, when the sea level surpassed the sill of the gulf (today 50 m below mean sea level) during postglacial sea-level rise. In those days, shrublands extended on the slopes of the tectonic depression. In-situ pieces of woods dredged from the bottom of the gulf at depths of 70 m gave a conventional age of 11,310 ± 150 years BP. We used the wood, together with dated shells from the continental shelf, and shells and organic matter dated from the San Blas, Negro and Chubut coastal plains to construct a sea-level curve. Sea level rise surpassed the present level somewhat before 6000 years BP, reaching a maximum stand of + 6 m. It has since gently diminished towards present sea level.

  7. Persistence of a Mesozoic, non-therian mammalian lineage (Gondwanatheria) in the mid-Paleogene of Patagonia

    NASA Astrophysics Data System (ADS)

    Goin, Francisco J.; Tejedor, Marcelo F.; Chornogubsky, Laura; López, Guillermo M.; Gelfo, Javier N.; Bond, Mariano; Woodburne, Michael O.; Gurovich, Yamila; Reguero, Marcelo

    2012-06-01

    We describe two isolated molariforms recovered from early-middle Eocene (early Lutetian) levels of northwestern Patagonia, Argentina. Comparisons with major lineages of therian and non-therian mammals lead us to refer them to a new genus and species of Gondwanatheria (Allotheria). There is a single root supporting each tooth that is very short, wide, rounded, and covered by cementum; the steep sidewalls, lack of a neck between the crown and root, and the heavily worn stage in both molariforms suggest that they were of a protohypsodont type. Both teeth are strongly worn at their centers, all along their length, with the labial edge less worn than the lingual; they show strong transverse crests that alternate with lingual grooves. The protohypsodont aspect of the teeth, as well as the strong, transverse crests, are suggestive of sudamericid affinities; on the other hand, the thin enamel layer and the occlusal pattern formed by the crests and grooves shows more similarities to molariform teeth of the Ferugliotheriidae. The new taxon adds evidence regarding the (1) extensive radiation of the Gondwanatheria throughout the Southern Hemisphere, (2) persistence of several lineages well after the Cretaceous/Paleogene boundary, and (3) early evolution of hypsodont types among South American herbivorous mammals.

  8. Intestinal parasites and the environment: frequency of intestinal parasites in children of Neuquén, Patagonia, Argentina.

    PubMed

    Soriano, S V; Barbieri, L M; Pierángeli, N B; Giayetto, A L; Manacorda, A M; Castronovo, E; Pezzani, B C; Minvielle, M; Basualdo, J A

    2001-01-01

    The frequency of intestinal parasites (IP) in 69 children between 2 and 14 years of age was studied within the city of Neuquén, Patagonia, Argentina in relation to socioeconomic, cultural and environmental conditions. Soil type was determined and contamination with IP was investigated in 75 soil samples. Frequency of IP in children was 50.7%. Blastocystis hominis was the most frequent species (24.6%). Simultaneous infection with 2 to 4 species was found in 47,5% of the infected children. Statistical association was found between parasitic infection and family hygienic level (p < 0.001). Socioeconomic level was defined as lower middle class, however, infrastructure and public services were adequate. The climate is continental semiarid and the soil is sandy with a low organic matter level. Intestinal protozoan organisms were found in 33.3% of soil samples and Sarcocystis sp. was the most frequent species (14.6%). The parasites present in soil are related to the environmental conditions that allow their viability and development. Socioeconomic and cultural factors are important for the appearance and spread of IP in communities where sanitary conditions and infrastructure are adequate.

  9. Heterogeneous distribution of human cystic echinococcosis after a long-term control program in Neuquén, Patagonia Argentina.

    PubMed

    Pierangeli, Nora B; Soriano, Silvia V; Roccia, Irene; Giménez, Juan; Lazzarini, Lorena E; Grenóvero, María S; Menestrina, Carlos; Basualdo, Juan A

    2007-06-01

    The present study is the first comprehensive analysis of human cystic echinococcosis (CE) epidemiological data carried out in the province of Neuquén, Patagonia Argentina, after 34 years of uninterrupted control program. A retrospective study of all the official records of confirmed human CE cases between 1995 and 2004 was carried out. A total of 1107 cases were reported. The overall mean annual incidence (MAI) was 24.4 per 100,000 inhabitants for the total population and 9.7/100,000 in the 0-14 year group. Distribution of cases by age and sex as well as frequency of cyst locations was analysed. Children accounted for 13.3% of total cases, indicating active transmission of the disease. Territorial distribution of cases was highly heterogeneous: MAI per 100,000 ranged from 7.9 in the Metropolitan Sanitary Area to 78.4 in the western rural areas. Higher values were recorded in small communities as Pilo Lil (800/100,000). MAI showed a significant decrease from 1995 to 1999 (43.9-18.8) but remains stable from 2000 to 2004 (15.9-15.5). These results suggest that standard control measures, despite long-term implementation, are not able to produce a sustained improvement of the epidemiological status of the disease. Further studies about local transmission cycles, definite and intermediate hosts present, Echinococcus granulosus strains or cultural behaviours in small communities are required in order to adequate the control actions in Neuquén.

  10. [Assessment of the MSP-PCR technique for the molecular characterization of Rhodotorula mucilaginosa isolates from northwestern Patagonia].

    PubMed

    Libkind, D

    2007-01-01

    The rapid identification of environmental or clinical yeast isolates is important for biodiversity studies and the detection of probable pathogens. Rhodotorula mucilaginosa is a ubiquitous and pigmented yeast capable of infecting immunocompromised patients. In this study, we evaluated the Micro/mini satellite-primed PCR (MSP-PCR) fingerprinting method for the characterization and identification of R. mucilaginosa isolates from natural environments in northwestern Patagonia. There were selected 110 putative R. mucilaginosa isolates from 200 environmental pigmented yeast isolates on the basis of phenotypic criteria. (GTG)5, (GAC)5 and M13 primers were initially evaluated in representative R. mucilaginosa isolates. (GTG)5 allowed a good grouping of these isolates and, at the same time, a good differentiation among closely related species, and thus was selected for subsequent studies. R. mucilaginosa isolates (87%) presented similar (> 60%) MSP-PCR profiles to those of the reference strain CBS 316T. The MSP-PCR technique was effective, both, for the characterization and identification of a large number of R. mucilaginosa environmental isolates as well as for the detection of polymorphisms within the species.

  11. Population structure of the snail Buccinanops globulosum (Prosobranchia, Nassariidae) in San Matías Gulf, Patagonia Argentina: Isolated enclaves?

    NASA Astrophysics Data System (ADS)

    Narvarte, Maite; Willers, Valeria; Avaca, María Soledad; Echave, María Eugenia

    2008-10-01

    In San Matías Gulf (Patagonia, Argentina), Buccinanops globulosum is typically distributed in two different areas: the intertidal-subtidal zone of Playa Villarino, where conch length reaches up to 60 mm, and the inner channel of San Antonio Bay, where individuals are not larger than 30 mm. It is suggested that both populations of B. globulosum constitute independent enclaves adapted to the local conditions and with a different population structure. This comparative study focuses on the population structure, sex ratios, growth, and size at maturity at the two sites. The data collected reveal that the individuals in San Antonio ranged from 5 to 29 mm whereas those in Villarino ranged from 4 to 61 mm. It was also observed that in San Antonio Bay, generally males outnumbered females whereas exactly the opposite occurred in Villarino. In addition, females were larger and showed a faster growth than males in both study areas. The number of egg capsules on each female ranged from 8 to 25 in San Antonio Bay and from 5 to 66 in Villarino. Size at maturity of females in San Antonio Bay was estimated at 14.47 mm and maximum estimated length at 6 years old was 33 mm. The same parameters in the individuals from Villarino were 45 and 65 mm, respectively. The comparative analysis of the above-mentioned features poses the question of whether these two populations represent either different species or different forms of the same species.

  12. New records of late Holocene tephras from Lake Futalaufquen (42.8°S), northern Patagonia

    NASA Astrophysics Data System (ADS)

    Daga, Romina; Ribeiro Guevara, Sergio; Arribére, María

    2016-03-01

    In regions with limited knowledge of the historical volcanic record, like remote areas in the Andean Southern Volcanic Zone, the definition of reliable age-depth models for lake sequences represents a valuable tool for tephra layers dating. In Lake Futalaufquen (42.8°S), Northern Patagonia, a short sedimentary sequence was extracted after the AD 2008 Chaitén eruption with the purpose to analyze the records of volcanic eruptions at these poorly studied latitudes. The sequence was dated by 210Pb, 137Cs, and 14C techniques. Five tephras were identified for the last 1600 years, restricted to the last 5 centuries. Sedimentology, morphology, and geochemical properties allowed the characterization of the tephras and their correlation with tephras recently identified proximal to the sources, mainly from Chaitén and Huequi volcanoes, and Michinmahuida accessory cones, representing the first distal records reported of these tephras. Furthermore, tephras modeled ages obtained by the sequence age-depth model shrink the ages for the volcanic events, like a potential cycle of activity from Michinmauida accessory cones during AD 1530 ± 55, one eruption from Huequi volcano at AD 1695 ± 50, and a possible recent eruption from Chaitén at AD 1775 ± 40. Additionally, the work contributes to improve the regional volcanic records knowledge, basic for volcanic hazard assessment.

  13. Heavy metal and trace elements in riparian vegetation and macrophytes associated with lacustrine systems in Northern Patagonia Andean Range.

    PubMed

    Juárez, Andrea; Arribére, María A; Arcagni, Marina; Williams, Natalia; Rizzo, Andrea; Ribeiro Guevara, Sergio

    2016-09-01

    Vegetation associated with lacustrine systems in Northern Patagonia was studied for heavy metal and trace element contents, regarding their elemental contribution to these aquatic ecosystems. The research focused on native species and exotic vascular plant Salix spp. potential for absorbing heavy metals and trace elements. The native species studied were riparian Amomyrtus luma, Austrocedrus chilensis, Chusquea culeou, Desfontainia fulgens, Escallonia rubra, Gaultheria mucronata, Lomatia hirsuta, Luma apiculata, Maytenus boaria, Myrceugenia exsucca, Nothofagus antarctica, Nothofagus dombeyi, Schinus patagonicus, and Weinmannia trichosperma, and macrophytes Hydrocotyle chamaemorus, Isöetes chubutiana, Galium sp., Myriophyllum quitense, Nitella sp. (algae), Potamogeton linguatus, Ranunculus sp., and Schoenoplectus californicus. Fresh leaves were analyzed as well as leaves decomposing within the aquatic bodies, collected from lakes Futalaufquen and Rivadavia (Los Alerces National Park), and lakes Moreno and Nahuel Huapi (Nahuel Huapi National Park). The elements studied were heavy metals Ag, As, Cd, Hg, and U, major elements Ca, K, and Fe, and trace elements Ba, Br, Co, Cr, Cs, Hf, Na, Rb, Se, Sr, and Zn. Geochemical tracers La and Sm were also determined to evaluate contamination of the biological tissues by geological particulate (sediment, soil, dust) and to implement concentration corrections. PMID:27255321

  14. A new species of Haplosporidium Caullery & Mesnil, 1899 in the marine false limpet Siphonaria lessonii (Gastropoda: Siphonariidae) from Patagonia.

    PubMed

    Ituarte, Cristián; Bagnato, Estefanía; Siddall, Mark; Cremonte, Florencia

    2014-05-01

    A new species of Haplosporidium Caullery & Mesnil, 1899 parasitising the pulmonate gastropod Siphonaria lessonii Blainville in Patagonia, Argentina, is described based on morphological (scanning and transmission electron microscopy) and sequence (small subunit ribosomal RNA gene) data. Different stages of sporulation were observed as infections disseminated in the digestive gland. Haplosporidium patagon n. sp. is characterised by oval or slightly subquadrate spores with an operculum that is ornamented with numerous short digitiform projections of regular height, perpendicular to and covering its outer surface. The operculum diameter is slightly larger than the apical diameter of the spore. Neither the immature nor mature spores showed any kind of projections of the exosporoplasm or of the spore wall. Regarding phylogenetic affinities, the new species was recovered as sister to an undescribed species of Haplosporidium Caullery & Mesnil, 1899 from the polychaete family Syllidae Grube from Japanese waters. The morphological characters (ornamentation of the operculum, spore wall structure, shape and size of spores, and the lack of spore wall projections) corroborate it as an as yet undescribed species of Haplosporidium and the first for the phylum in marine gastropods of South America. Siphonaria lessonii is the only known host to date.

  15. Optical Flow Applied to Time-Lapse Image Series to Estimate Glacier Motion in the Southern Patagonia Ice Field

    NASA Astrophysics Data System (ADS)

    Lannutti, E.; Lenzano, M. G.; Toth, C.; Lenzano, L.; Rivera, A.

    2016-06-01

    In this work, we assessed the feasibility of using optical flow to obtain the motion estimation of a glacier. In general, former investigations used to detect glacier changes involve solutions that require repeated observations which are many times based on extensive field work. Taking into account glaciers are usually located in geographically complex and hard to access areas, deploying time-lapse imaging sensors, optical flow may provide an efficient solution at good spatial and temporal resolution to describe mass motion. Several studies in computer vision and image processing community have used this method to detect large displacements. Therefore, we carried out a test of the proposed Large Displacement Optical Flow method at the Viedma Glacier, located at South Patagonia Icefield, Argentina. We collected monoscopic terrestrial time-lapse imagery, acquired by a calibrated camera at every 24 hour from April 2014 until April 2015. A filter based on temporal correlation and RGB color discretization between the images was applied to minimize errors related to changes in lighting, shadows, clouds and snow. This selection allowed discarding images that do not follow a sequence of similarity. Our results show a flow field in the direction of the glacier movement with acceleration in the terminus. We analyzed the errors between image pairs, and the matching generally appears to be adequate, although some areas show random gross errors related to the presence of changes in lighting. The proposed technique allowed the determination of glacier motion during one year, providing accurate and reliable motion data for subsequent analysis.

  16. Did Patagonia collide against Gondwana in the Late Paleozoic? Some Insights From Magnetic Fabrics of Granitoids in the North Patagonian Massif.

    NASA Astrophysics Data System (ADS)

    Rapalini, A. E.; Lopez de Luchi, M. G.; Tomezzoli, R. N.

    2008-05-01

    The Paleozoic tectonic evolution of Patagonia has been a matter of much debate in the last two decades. There is no consensus on whether the North Patagonian Massif (NPM) was accreted by a frontal collision to Gondwana in the Late Paleozoic or if it shared a similar paleotectonic evolution with other Gondwana blocks during the Paleozoic. Different geologic, geochronologic, geophysical and structural data have been interpreted either as supporting or refuting the collisional model. Paleomagnetic data obtained so far is consistent with an authochtonous evolution since the Devonian, but it does not rule out relative displacements of up to 1500 km between Patagonia and Gondwana.Therefore, a Late Paleozoic frontal collision cannot be definitely ruled out on the basis of paleomagnetic data alone. As part of a muldisciplinary research project a magnetic fabric study, by means of the anisotropy of magnetic susceptibility (AMS), was carried out on Late Paleozoic granitoids exposed in northeastern NPM. Two main composite units were studied, the highly to variably foliated Yaminue Complex, poorly dated as Late Carboniferous and ranging in composition from tonalite to leuco-granite, and the much less deformed granodiorites to monzoganites of the Early Permian (283 Ma) Navarrete complex. While the former is composed of both ferro and paramagnetic units, with a dominance of the latter; the Navarrete plutons are basically ferromagnetic. Directional and scalar AMS results joined with meso and microstructural studies permitted the characterization of the deformational and magmatic fabric of the different units. An evolutionary picture of the succesive intrusive events in NPM emerged which confirms an important NNE-SSW contractional event associated with intrusion of the different units that compose the Yaminue Complex. This event ended before the intrusion of the Navarrete Complex, which is governed by a different stress regime. Our results fit the hypothesis of a collisional event

  17. A new genus and species of isanthid sea anemone (Cnidaria: Anthozoa: Actiniaria) from Chilean Patagonia, Anthoparactis fossii n. gen. et sp

    NASA Astrophysics Data System (ADS)

    Häussermann, Verena; Rodríguez, Estefanía

    2014-09-01

    We describe a new genus and species of sea anemone from Chilean Patagonia. Anthoparactis fossii n. gen. et sp. adds another acontiate genus and species to the family Isanthidae Carlgren, 1938. Anthoparactis n. gen. differs from the other isanthid genera in having the same number of mesenteries distally and proximally, acontia with basitrichs only, and a column with verrucae distally. Anthoparactis fossii n. sp. differs from the most similar species, Isoparactis fionae Lauretta et al., 2013, in the number of cycles of mesenteries and tentacles, structures of the column, colour pattern of the oral disc, cnidae, and geographical distribution. Isanthidae now includes seven genera and 11 species.

  18. Description of the 5th instar nymph of Oenopiella punctaria (Stål, 1859) Hemiptera: Heteroptera: Pentatomidae), with new distributional records
    from Southern Patagonia.

    PubMed

    Faúndez, Eduardo I; Carvajal, Máriom A

    2016-01-01

    The 5th instar nymph of Oenopiella punctaria (Stål, 1859) is described and illustrated for the first time, together with new distributional records from Patagonia. The new records are from Santa Cruz Province (Argentina), and the Magallanes Region (Chile). The latter is the southernmost record for this species and also for the Carpocorini in South America. In light of the new data, the biogeography of Oenopiella is discussed, and it is concluded that an Andean origin may be possible. PMID:27395875

  19. Mapping the edge of the Cerros del Rio volcanic field, New Mexico: a piece of the puzzle to understanding a potential geothermal resource

    NASA Astrophysics Data System (ADS)

    Pellerin, L.; Gallegos, M.; Goebel, M.; Murphy, B. S.; Smith, J.; Soto, D.; Swiatlowski, J.; Volk, C.; Welch, M.; Feucht, D. W.; Hollingshaus, B.; Bedrosian, P. A.; McPhee, D. K.

    2012-12-01

    The Cerros del Rio volcanic field located west of Santa Fe, New Mexico spans the southwestern part of the Espanola Basin with the Rio Grande to the west. Underlying the volcanics are the Santa Fe Group sediments, which contain the Ancha Formation, an important aquifer in the region. High temperature gradients in water wells reveal a potential geothermal prospect. In 2012 the Summer of Applied Geophysical Experience (SAGE) program acquired transient electromagnetic (TEM), audiomagnetotelluric (AMT), gravity and ground magnetic data to determine the buried eastern margin of the volcanic field and the connectivity related to the underlying sediments. The roughly EW 5-km long transect was sited from USGS aeromagnetic data to cross the boundary of the Cerros del Rio volcanic field. TEM data collected at ten stations, at 200-400 m spacing, along the transect employed an in-loop configuration with a square 100 m x 100 m transmitter loop and both a Zonge receiver coil and a 5 m square receiver loop. The 5 m loop allowed for the recovery of early-time data that was saturated when using the Zonge coil. AMT data were acquired at eight stations, at 400-500 m spacing, using the Geometric Stratagem system recording from 92 kHz to 10 Hz; a horizontal magnetic dipole transmitter was used to augment low signal strength at around 1 kHz. Gravity data along the profile were acquired using CG-3 and CG-5 Scintrex gravimeters with a station interval >250 m. Magnetic data were acquired with a Geometrics Cesium vapor G-858 magnetometer for about 3500 m along the profile at a 0.5 second sampling rate. Two volcanic flows interbedded with Ancha Formation and overlying Santa Fe Group sediments were identified in both the TEM and AMT modeling. High surface resistivity zones (>300 ohm-m) with depths ranging from ~100 to 300 m define the volcanic flows and correspond to high densities (2.3 to 2.55 g/cm3), while low resistivity zones (<30 ohm-m) correspond to lower densities (~2.1 g/cm3). High

  20. Quaternary eruptive history and hazard-zone model at Nevado del Tolima and Cerro Machin volcanoes, Colombia

    NASA Astrophysics Data System (ADS)

    Thouret, J. C.; Cantagrel, J.-M.; Robin, C.; Murcia, A.; Salinas, R.; Cepeda, H.

    1995-07-01

    areas potentially affected by future eruptions both at Nevado del Tolima and at active Cerro Machin 12 km southward. The extent of areas likely to be affected by tephra-falls, debris flows, pyroclastic flows or surges, debris avalanches and lava flows is shown. Subplinian and plinian eruptions of Nevado del Tolima were used to represent the moderate and large events to be expected. 300,000 people live within a 35-km distance from those volcanoes, which have exhibited a behaviour more explosive than Nevado del Ruiz. Despite the small-sized ice cap, debris flows are the most probable hazard for even a minor eruption, because of the very steep slope gradient, and because of probable interactions of hot eruptive products with ice and snow. Additionally, scoria flows and debris avalanches can be directed toward the southeast and could be transformed into debris flows that would devastate the Combeima valley and suburbs of Ibaguécity, where about 50,000 people live

  1. Operation and Performance of a Biphase Turbine Power Plant at the Cerro Prieto Geothermal Field (Final Report)

    SciTech Connect

    Hays, Lance G.

    2000-09-01

    A full scale, wellhead Biphase turbine was manufactured and installed with the balance of plant at Well 103 of the Cerro Prieto geothermal resource in Baja, California. The Biphase turbine was first synchronized with the electrical grid of Comision Federal de Electricidad on August 20, 1997. The Biphase power plant was operated from that time until May 23, 2000, a period of 2 years and 9 months. A total of 77,549 kWh were delivered to the grid. The power plant was subsequently placed in a standby condition pending replacement of the rotor with a newly designed, higher power rotor and replacement of the bearings and seals. The maximum measured power output of the Biphase turbine, 808 kWe at 640 psig wellhead pressure, agreed closely with the predicted output, 840 kWe. When combined with the backpressure steam turbine the total output power from that flow would be increased by 40% above the power derived only from the flow by the present flash steam plant. The design relations used to predict performance and design the turbine were verified by these tests. The performance and durability of the Biphase turbine support the conclusion of the Economics and Application Report previously published, (Appendix A). The newly designed rotor (the Dual Pressure Rotor) was analyzed for the above power condition. The Dual Pressure Rotor would increase the power output to 2064 kWe by incorporating two pressure letdown stages in the Biphase rotor, eliminating the requirement for a backpressure steam turbine. The power plant availability was low due to deposition of solids from the well on the Biphase rotor and balance of plant problems. A great deal of plant down time resulted from the requirement to develop methods to handle the solids and from testing the apparatus in the Biphase turbine. Finally an online, washing method using the high pressure two-phase flow was developed which completely eliminated the solids problem. The availability of the Biphase turbine itself was 100

  2. Controls on volatile content and distribution in the continental upper mantle of Southern Gondwana (Patagonia & W. Antarctica)

    NASA Astrophysics Data System (ADS)

    Rooks, Eve; Gibson, Sally; Petrone, Chiara; Leat, Phillip

    2015-04-01

    Water content is known to affect many physical and chemical properties of the upper mantle, including melting temperature and viscosity. Water is hosted by hydrous phases, such as amphibole and phlogopite, and also by more dominant, nominally-anhydrous mantle minerals (e.g. olivine and pyroxene). The latter have the potential to incorporate hundreds of ppm of water in point defects, and may explain geophysical observations such as seismic and conductivity anomalies in the upper mantle [1]. However, the significance of the reported concentrations of H2O in nominally anhydrous minerals in mantle xenoliths is still a subject of debate primarily due to the effects of post-entrainment loss [1,2]. Unlike H2O and Li, F is less susceptible to post entrainment loss and can potentially be used to constrain the source of volatiles. We present high-precision SIMS analyses of H2O, Li and F in mantle xenoliths hosted by recently-erupted (5-10 Ka) alkali basalts from south Patagonia and the Antarctic Peninsula. These two regions formed part of the southern margin of the Gondwana supercontinent, prior to break-up, and were located above long-lived subduction zones for at least 200 M.yr., making them highly-appropriate to investigating long term evolution of the sub-continental lithospheric mantle in this setting. The xenoliths are well characterised peridotites, sourced from the off-craton spinel- and spinel-garnet facies lithospheric mantle (40-80 km). Samples are relatively dry: H2O contents of olivine span 0-49 ppm, orthopyroxene 150-235 ppm and clinopyroxene 100-395 ppm. West Antarctic samples are more hydrated than Patagonian samples, on average. These H2O concentrations fall within the global measured range for off-craton mantle minerals [4]. We attribute low H2O concentrations in olivine to diffusive loss, either by exchange with the host magma, shallow level degassing or during cooling [2]. F shows less variability than H2O and is most highly concentrated in clinopyroxenes

  3. Recent Vertical Deformation in Mexicali Valley and its Relationship with Tectonics, Seismicity, and the Exploitation of the Cerro Prieto Geothermal Field, Mexico

    NASA Astrophysics Data System (ADS)

    Glowacka, E.; González, J.; Fabriol, H.

    The interpretation of the results of regional and local leveling which began in 1977 in the Mexicali Valley and the local short profile precision leveling which started in 1994 are discussed. The relation of vertical deformations around the Cerro Prieto Geothermal Field (CPGF) and along the Imperial fault, with local tectonics and seismicity in the Mexicali Valley, is reviewed. Also the relation between vertical deformation and fluid operation in the CPGF is analyzed. The subsidence observed in the field seems to be induced by fluid extraction. The way in which fluid production influences surface changes along the Imperial fault is not clear. The possibility that seismicity is triggering subsidence in the area and vertical movement on the Imperial fault is discussed.

  4. Active metasomatism in the Cerro Prieto geothermal system, Baja California, Mexico: A telescoped low-pressure, low-temperature metamorphic facies series

    NASA Astrophysics Data System (ADS)

    Schiffman, P.; Elders, W. A.; Williams, A. E.; McDowell, S. D.; Bird, D. K.

    1984-01-01

    In the Cerro Prieto geothermal field, carbonate-cemented, quartzofeldspathic sediments of the Colorado River delta are being actively metasomatized into calc-silicate metamorphic rocks by reaction with alkali chloride brines between 200 and 370 °C, at low fluid and lithostatic pressures and low oxygen fugacities. Our petrologic investigations of drill cores and cuttings from more than 50 wells in this field identified a prograde series of zones that include as index minerals wairakite, epidote, prehnite, and clinopyroxene. Associated divariant mineral assemblages are indicative of a very low pressure, low-temperature metamorphic facies series spanning the clay-carbonate, zeolite, greenschist, and amphibolite facies. This hydro-thermal facies series, which is now recognized in other active geothermal systems, is characterized by temperature-telescoped dehydration and decarbonation. Its equivalent can now be sought in fossil hydrothermal systems.

  5. Assessment of Argentinean Patagonia pollution: PBDEs, OCPs and PCBs in different matrices from the Río Negro basin.

    PubMed

    Miglioranza, Karina S B; Gonzalez, Mariana; Ondarza, Paola M; Shimabukuro, Valeria M; Isla, Federico I; Fillmann, Gilberto; Aizpún, Julia E; Moreno, Víctor J

    2013-05-01

    This work reports the occurrence and distribution of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in soil, sediment, suspended particle matter (SPM), streamwater and macrophytes, along the Río Negro basin, Argentinean Patagonia. The clear predominance of OCPs among all matrices indicates the impact of agriculture on the watershed. The highest levels were found for pp'-DDE which represented up to 95% in agricultural soils (42.0-1.27x10(3) ng/g d.w) from the Upper Valley (upstream), where long and historical intensive fruit cultures have been settled and represent a hot spot of legacy pesticides for the environment. The insecticide endosulfan, currently in use, was also found in all matrices. Levels ranged between 0.3 and 708.0 ng/g d.w, being the highest concentrations those of SPM from the Middle Valley, just before the delta area, where pesticides would be retained leading to lower concentrations as was observed downstream. PCB (#153, 138, 110, 101) and PBDE (BDE-47) levels were directly related with the presence of hydroelectric power plants, dams and dumping sites, mainly settled in the Upper Valley (0.8 ng/g and 15.1 ng/g d.w for PBDEs and PCBs, respectively). Although there was a decreasing gradient of these pollutant concentrations through the river flow, downstream urban areas enhanced PCB concentrations in the aquatic environment. More efforts and monitoring programs are highly required to control and reduce soil erosion in order to prevent the availability of forbidden pollutants in the environment. PMID:23523725

  6. Titanium and oxygen isotope diffusion in quartz-phenocrysts from a Jurassic rhyolite, Chon Aike Province (Fitz Roy, Patagonia)

    NASA Astrophysics Data System (ADS)

    Seitz, S.; Putlitz, B.; Baumgartner, L. P.; Escrig, S.; Meibom, A.; Leresche, S.; Vennemann, T. W.

    2014-12-01

    The volcanic El Quemado Complex was deposited during the breakup of Gondwana during the Middle and Late Jurassic. It is part of a large silicic igneous province, which includes the Chon Aike Province in Southern Patagonia and related rocks from the Antarctic Peninsula [1]. The Complex consists of rhyolitic and dacitic ignimbrites and air-fall tuffs, intercalated with andesitic to rhyolitic lava flows. New LA-ICPMS U/Pb-dates of zircons from the Fitz Roy area yield ages between 148 and 153Ma. No inherited zircons were found, suggesting that the temperature of 850°C calculated from zircon saturation is a minimum temperature. Lava flows are typically rich in quartz phenocrysts, which preserved magmatic trace element zoning, as revealed by cathodoluminescence (CL): light cores are surrounded by several darker and lighter zones towards the rim. The δ18O-values for quartz of between 11 to 14 ‰ are compatible with a crustal source for the magma and the SIMS analyses of phenocrysts reveal no zoning in O-isotope compositions. High-resolution Ti-profiles were obtained by NanoSIMS with a beam size of ~200 nm and a minimum step size of ~120 nm. Several lines perpendicular to the magmatic zoning of the quartz-phenocrysts were measured. The profiles show sharp changes in the 48Ti/29Si-ratio over a distance of 5 μm, which correlate with CL-intensity changes. The profiles can be used for diffusion chronometry. The distances obtained from NanoSIMS profiles were used to calculate maximum diffusional relaxation times. Assuming a step function as initial condition and extrusion temperatures from zircon saturation of 850°C, we obtain a maximum residence time for the quartz-phenocrysts of 3.5 years. [1] Pankhurst R.J., Riley T.R., Fanning C.M., Kelley S.P., 2000. J. Pet., 41, 605-625.

  7. Relationship between Bajo Pobre and Chon Aike formations (Deseado Massif, Patagonia, Argentina):a melt inclusions study

    NASA Astrophysics Data System (ADS)

    Busà, T.; Bellieni, G.; Fernandez, R.; Hecheveste, H.; Piccirillo, E. M.

    2003-04-01

    The Deseado Massif covers the centre-east of the Santa Cruz Province, in the extra-Andean Patagonia. Although the Deseado Massif is mainly composed of silicic volcanic rocks (Chon Aike Formation, CA; 151.5 ±0.5 - 177.8 ±0.4 Ma), mafic and intermediate volcanites (Bajo Pobre Formation, BP; 152.7 ±0.5 and 164 ±0.3 Ma) outcrop largely in the central part of the Massif. In this paper quarz-trapped melt inclusions (rhyolitic in composition) from selected samples of the BP and the CA are analysed. On the basis of major elements content, for BP the sequence from andesite (BP whole rock) to ryholite (trapped as inclusions in quartz) can be modelled by simple fractional crystallisation of ortho- and clinopyroxene, plagioclase, quartz and apatite. As regards trace elements, a good calculated/measured ratio (around 1 ±0.2) is obtained assuming only a relatively high apatite fractionation. Since the apatite fractionation amount is not acceptable for major elements, the evolution of BP Formation cannot be modelled by a simple process of fractional crystallisation, and a contamination process probably occurred. The sequence from BP to CA cannot be modelled by fractional crystallisation. 30% batch melting of BP andesite (BP whole rock) produces a magma from which the CA ryholites (trapped as inclusions in quartz) can be obtained by Rayleigh fractional crystallisation of ortho- and clinopyroxene, plagioclase, magnetite, quartz, apatite and small amounts of zircon and minor allanite. Since the latter one was not observed in the analysed sample, a contamination process during magma evolution cannot be completely excluded. Finally, on the basis of the different trace elements concentration (Nb anomaly, different content in LILE, B/Be and B/Nb), it is possible to suppose that, at the time of the BP and CA emplacement, a changing in the tectonic setting, from subduction to a lithospheric extension, was active.

  8. Comparative study of the female gametogenic cycle in three populations of Buccinanops globulosus (Caenogastropoda: Nassariidae) from Patagonia

    NASA Astrophysics Data System (ADS)

    Avaca, María Soledad; Martín, Pablo; van der Molen, Silvina; Narvarte, Maite

    2015-03-01

    The populations of Buccinanops globulosus from three different sites of northern Patagonia were compared in the female reproductive cycle over a 2-year study period (September 2006-August 2008). These populations differed in demographic and life-history traits (sex ratios, size frequency distributions, growth rates and fecundity). Also, two of these populations show imposex-affected females (Bahía San Antonio, BSA and Bahía Nueva, BN), whereas the other (Playa Villarino, PV) is imposex-free and constitutes a commercial fishery ground for this species. The gametogenic activity of this species has not been studied earlier. Females showed the same gonadal stages in the three populations; however, there were differences in the female size at which each gonadal stage occurred. Monthly variation in gonadal stages and in oocyte size indicated that females of B. globulosus showed a seasonal gametogenic pattern without the occurrence of a resting period. Evacuation of mature oocytes (up to 252.5 µm) occurred mainly from September to December (austral spring) in BSA and PV and from December to March (austral summer) in BN. Gonad maturation and the presence of females carrying egg capsules in the field coincided with changes in water surface temperature and a longer day length. Our results indicate that the occurrence of imposex in the populations studied apparently does not affect the gametogenic activity in females. This study provides further insights into the reproductive biology of B. globulosus. The identification of population variation in reproductive traits should lead to more effective management of the species.

  9. Trichococcus Patagoniensis sp. nov., a Facultative Anaerobe that grows at -5 C, Isolated from Penguin Guano in Chilean Patagonia

    NASA Technical Reports Server (NTRS)

    Pikuta, Elena V.; Hoover, Richard B.; Bej, Asim K.; Marsic, Damien; Whitman, William B.; Krader, Paul E.; Tang, Jane

    2006-01-01

    A novel, extremely psychrotolerant, facultative anaerobe, strain PmagGl(sup T), was isolated from guano of Magellanic penguins (Spheniscus magellanicus) collected in Chilean Patagonia. Gram-variable, motile cocci with a diameter of 1.3-2.0 micrometers were observed singularly or in pairs, short chains and irregular conglomerates. Growth occurred within the pH range 6.0-10.0, with optimum growth at pH 8.5. The temperature range for growth of the novel isolate was from -5 to 35 C, with optimum growth at 28-30 C. Strain PmagG1(sup T) did not require NaCl, as growth was observed in the presence of 0-6.5% NaCl with optimum growth at 0.5% (w/v). Strain PmagGl(sup T) was a catalase-negative chemo-organoheterotroph that used sugars and some organic acids as substrates. The metabolic end products were lactate, formate, acetate, ethanol and Con. Strain PmagG1(sup T) was sensitive to ampicillin, tetracycline, chloramphenicol, rifampicin, kanamycin and gentamicin. The G+C content of its genomic DNA was 45.8 mol%. 16S rRNA gene sequence analysis showed 100 % similarity of strain PmagG1(sup T) with Trichococcus collinsii ATCC BAA-296(sup T), but DNA-DNA hybridization between them demonstrated relatedness values of less than 45 plus or minus 1%. Another phylogenetically closely related species, Trichococcus pasteurii, showed 99.85 % similarity by 16s rRNA sequencing and DNA-DNA hybridization showed relatedness values of 47 plus or minus 1.5%. Based on genotypic and phenotypic characteristics, the novel species Trichococcus patagoniensis sp. nov. is proposed, with strain PmagG1(sup T) (=ATCC BAA-756(sup T)=JCM 12176(sup T)=CIP 108035(sup T)) as the type strain.

  10. Fire responses to postglacial climate change and human impact in northern Patagonia (41-43°S).

    PubMed

    Iglesias, Virginia; Whitlock, Cathy

    2014-12-23

    Forest/steppe boundaries are among the most dynamic ecosystems on Earth and are highly vulnerable to changes in climate and land use. In this study we examine the postglacial history of the Patagonian forest/steppe ecotone (41-43°S) to better understand its sensitivity to past variations in climate, disturbance, and human activity before European colonization. We present regional trends in vegetation and biomass burning, as detected by generalized additive models fitted to seven pollen and charcoal records, and compare the results with other paleoenvironmental data, as well as archeological and ecological information to (i) estimate postglacial fire trends at regional scales, (ii) assess the evolution of climate-vegetation-fire linkages over the last 18,000 calibrated (cal) years B.P., and (iii) evaluate the role of humans in altering pre-European landscapes and fire regimes. Pollen and charcoal data indicate that biomass burning was relatively low during warm/dry steppe-dominated landscapes in the late glacial/Early Holocene transition and increased as more humid conditions favored forest development after ca. 10,000 cal years B.P. Postglacial fire activity was thus limited by fuel availability associated with sparse vegetation cover rather than by suitable climate conditions. In contrast to extensive burning by European settlers, variations in indigenous population densities were not associated with fluctuations in regional or watershed-scale fire occurrence, suggesting that climate-vegetation-fire linkages in northern Patagonia evolved with minimal or very localized human influences before European settlement. PMID:25489077

  11. Exploring the Diversity and Antimicrobial Potential of Marine Actinobacteria from the Comau Fjord in Northern Patagonia, Chile

    PubMed Central

    Undabarrena, Agustina; Beltrametti, Fabrizio; Claverías, Fernanda P.; González, Myriam; Moore, Edward R. B.; Seeger, Michael; Cámara, Beatriz

    2016-01-01

    Bioprospecting natural products in marine bacteria from fjord environments are attractive due to their unique geographical features. Although, Actinobacteria are well known for producing a myriad of bioactive compounds, investigations regarding fjord-derived marine Actinobacteria are scarce. In this study, the diversity and biotechnological potential of Actinobacteria isolated from marine sediments within the Comau fjord, in Northern Chilean Patagonia, were assessed by culture-based approaches. The 16S rRNA gene sequences revealed that members phylogenetically related to the Micrococcaceae, Dermabacteraceae, Brevibacteriaceae, Corynebacteriaceae, Microbacteriaceae, Dietziaceae, Nocardiaceae, and Streptomycetaceae families were present at the Comau fjord. A high diversity of cultivable Actinobacteria (10 genera) was retrieved by using only five different isolation media. Four isolates belonging to Arthrobacter, Brevibacterium, Corynebacterium and Kocuria genera showed 16S rRNA gene identity <98.7% suggesting that they are novel species. Physiological features such as salt t