The Two Subduction Zones of the Southern Caribbean: Lithosphere Tearing and Continental Margin Recycling in the East, Flat Slab Subduction and Laramide-Style Uplifts in the West

Science.gov (United States)

Levander, A.; Bezada, M. J.; Niu, F.; Schmitz, M.

2015-12-01

The southern Caribbean plate boundary is a complex strike-slip fault system bounded by oppositely vergent subduction zones, the Antilles subduction zone in the east, and a currently locked Caribbean-South American subduction zone in the west (Bilham and Mencin, 2013). Finite-frequency teleseismic P-wave tomography images both the Atlanic (ATL) and the Caribbean (CAR) plates subducting steeply in opposite directions to transition zone depths under northern South America. Ps receiver functions show a depressed 660 discontinuity and thickened transition zone associated with each subducting plate. In the east the oceanic (ATL) part of the South American (SA) plate subducts westward beneath the CAR, initiating the El Pilar-San Sebastian strike slip system, a subduction-transform edge propagator (STEP) fault (Govers and Wortel, 2005). The point at which the ATL tears away from SA as it descends into the mantle is evidenced by the Paria cluster seismicity at depths of 60-110 km (Russo et al, 1993). Body wave tomography and lithosphere-asthenosphere boundary (LAB) thickness determined from Sp and Ps receiver functions and Rayleigh waves suggest that the descending ATL also viscously removes the bottom third to half of the SA continental margin lithospheric mantle as it descends. This has left thinned continental lithosphere under northern SA in the wake of the eastward migrating Antilles subduction zone. The thinned lithosphere occupies ~70% of the length of the El Pilar-San Sebastian fault system, from ~64oW to ~69oW, and extends inland several hundred kilometers. In northwestern SA the CAR subducts east-southeast at low angle under northern Colombia and western Venezuela. The subducting CAR is at least 200 km wide, extending from northernmost Colombia as far south as the Bucaramanga nest seismicity. The CAR descends steeply under Lake Maracaibo and the Merida Andes. This flat slab is associated with three Neogene basement cored, Laramide-style uplifts: the Santa Marta

Chromosomes of South American Bufonidae (Amphibia, Anura Chromosomes of South American Bufonidae (Amphibia, Anura

Directory of Open Access Journals (Sweden)

Brum Zorrilla N.

1973-09-01

Full Text Available Karyotypes of eight of South American Bufonidae were studied: B.ictericus, B. spinulosus spinulosus, B. arenarum, B. g. fernandezae, B. g. d'orbignyi, B. crucifer, B. paracnemis and B. marinus. In all species 2n = 22 chromosomes were found. Neither heteromorphic pairs of chromosomes nor bivalents with characteristic morphology and behavior of sex chromosomesduring male meiosis were observed in any species.Karyotypes of eight of South American Bufonidae were studied: B.ictericus, B. spinulosus spinulosus, B. arenarum, B. g. fernandezae, B. g. d'orbignyi, B. crucifer, B. paracnemis and B. marinus. In all species 2n = 22 chromosomes were found. Neither heteromorphic pairs of chromosomes nor bivalents with characteristic morphology and behavior of sex chromosomesduring male meiosis were observed in any species.

Can north american fish passage tools work for South american migratory fishes?

Directory of Open Access Journals (Sweden)

Claudio Rafael Mariano Baigún

Full Text Available In North America, the Numerical Fish Surrogate (NFS is used to design fish bypass systems for emigrating juvenile salmon as they migrate from hatchery outfalls and rearing habitats to adult habitat in the oceans. The NFS is constructed of three linked modules: 1 a computational fluid dynamics model describes the complex flow fields upstream of dams at a scale sufficiently resolved to analyze, understand and forecast fish movement, 2 a particle tracking model interpolates hydraulic information from the fixed nodes of the computational fluid model mesh to multiple locations relevant to migrating fish, and 3 a behavior model simulates the cognition and behavior of individual fish in response to the fluid dynamics predicted by the computational fluid dynamics model. These three modules together create a virtual reality where virtual fish exhibit realistic dam approach behaviors and can be counted at dam exits in ways similar to the real world. Once calibrated and validated with measured fish movement and passage data, the NFS can accurately predict fish passage proportions with sufficient precision to allow engineers to select one optimum alternative from among many competing structural or operational bypass alternatives. Although South American fish species are different from North American species, it is likely that the basic computational architecture and numerical methods of the NFS can be used for fish conservation in South America. Consequently, the extensive investment made in the creation of the NFS need not be duplicated in South America. However, its use in South America will require that the behavioral response of the continent's unique fishes to hydrodynamic cues must be described, codified and tested before the NFS can be used to conserve fishes by helping design efficient South American bypass systems. To this end, we identify studies that could be used to describe the movement behavior of South American fishes of sufficient detail

Mutation spectrum in South American Lynch syndrome families

DEFF Research Database (Denmark)

Dominguez-Valentin, Mev; Nilbert, Mef; Wernhoff, Patrik

2013-01-01

Genetic counselling and testing for Lynch syndrome have recently been introduced in several South American countries, though yet not available in the public health care system.......Genetic counselling and testing for Lynch syndrome have recently been introduced in several South American countries, though yet not available in the public health care system....

Lithospheric architecture of the South-Western Alps revealed by multiparameter teleseismic full-waveform inversion

Science.gov (United States)

Beller, S.; Monteiller, V.; Operto, S.; Nolet, G.; Paul, A.; Zhao, L.

2018-02-01

The Western Alps, although being intensively investigated, remains elusive when it comes to determining its lithospheric structure. New inferences on the latter are important for the understanding of processes and mechanisms of orogeny needed to unravel the dynamic evolution of the Alps. This situation led to the deployment of the CIFALPS temporary experiment, conducted to address the lack of seismological data amenable to high-resolution seismic imaging of the crust and the upper mantle. We perform a 3-D isotropic full-waveform inversion (FWI) of nine teleseismic events recorded by the CIFALPS experiment to infer 3-D models of both density and P- and S-wave velocities of the Alpine lithosphere. Here, by FWI is meant the inversion of the full seismograms including phase and amplitude effects within a time window following the first arrival up to a frequency of 0.2 Hz. We show that the application of the FWI at the lithospheric scale is able to generate images of the lithosphere with unprecedented resolution and can furnish a reliable density model of the upper lithosphere. In the shallowest part of the crust, we retrieve the shape of the fast/dense Ivrea body anomaly and detect the low velocities of the Po and SE France sedimentary basins. The geometry of the Ivrea body as revealed by our density model is consistent with the Bouguer anomaly. A sharp Moho transition is followed from the external part (30 km depth) to the internal part of the Alps (70-80 km depth), giving clear evidence of a continental subduction event during the formation of the Alpine Belt. A low-velocity zone in the lower lithosphere of the S-wave velocity model supports the hypothesis of a slab detachment in the western part of the Alps that is followed by asthenospheric upwelling. The application of FWI to teleseismic data helps to fill the gap of resolution between traditional imaging techniques, and enables integrated interpretations of both upper and lower lithospheric structures.

Premature mortality patterns among American Indians in South Dakota, 2000-2010.

Science.gov (United States)

Christensen, Mathew; Kightlinger, Lon

2013-05-01

American Indians in South Dakota have the highest mortality rates in the nation compared to other racial and ethnic groups and American Indians in other states. Cause-related and age-specific mortality patterns among American Indians in South Dakota are identified to guide prevention planning and policy efforts designed to reduce mortality within this population, in both South Dakota and other parts of the U.S. Death certificate data from South Dakota (2000-2010), on 5738 American Indians and 70,580 whites, were used to calculate age-specific mortality rates and rate ratios. These values were examined in order to identify patterns among the leading causes of death. Analyses were completed in 2011 and 2012. Within the South Dakota population, 70% of American Indians died before reaching age 70 years, compared to 25% of whites. Fatal injuries and chronic diseases were the leading causes of premature mortality. Nine leading causes of death showed consistent patterns of mortality disparity between American Indians and whites, with American Indians having significantly higher rates of mortality at lower ages. Premature mortality among American Indians in South Dakota is a serious public health problem. Unified efforts at the federal, tribal, state, and local levels are needed to reduce premature death within this population. Copyright © 2013 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

South American climate during the Last Glacial Maximum: Delayed onset of the South American monsoon

Science.gov (United States)

Cook, K. H.; Vizy, E. K.

2006-01-01

The climate of the Last Glacial Maximum (LGM) over South America is simulated using a regional climate model with 60-km resolution, providing a simulation that is superior to those available from global models that do not resolve the topography and regional-scale features of the South American climate realistically. LGM conditions on SST, insolation, vegetation, and reduced atmospheric CO2 on the South American climate are imposed together and individually. Remote influences are not included. Annual rainfall is 25-35% lower in the LGM than in the present day simulation throughout the Amazon basin. A primary cause is a 2-3 month delay in the onset of the rainy season, so that the dry season is about twice as long as in the present day. The delayed onset occurs because the low-level inflow from the tropical Atlantic onto the South American continent is drier than in the present day simulation due to reduced evaporation from cooler surface waters, and this slows the springtime buildup of moist static energy that is needed to initiate convection. Once the monsoon begins in the Southern Hemisphere, LGM rainfall rates are similar to those in the present day. In the Northern Hemisphere, however, rainfall is lower throughout the (shortened) rainy season. Regional-scale structure includes slight precipitation increases in the Nordeste region of Brazil and along the eastern foothills of the Andes, and a region in the center of the Amazon basin that does not experience annual drying. In the Andes Mountains, the signal is complicated, with regions of significant rainfall increases adjacent to regions with reduced precipitation.

Haemotrophic mycoplasmas in South American camelids in Switzerland

OpenAIRE

Kaufmann, C; Meli, Marina L; Robert, N; Willi, Barbara; Hofmann-Lehmann, Regina; Wengi, Nicole; Lutz, Hans; Zanolari, P

2007-01-01

The red blood cell parasite 'Candidatus Mycoplasma haemolamae', formerly Eperythrozoon, is known to be widespread in South American camelids in the USA, causing anaemia in affected animals. Up to now, haemotrophic mycoplasmas were not observed in South American camelids in Europe; however, they were known in a herd of alpacas in Switzerland and to identify them as 'Candidatus M. haemolamae'. Possible ways of transmission are discussed.

Use of along-track magnetic field differences in lithospheric field modelling

DEFF Research Database (Denmark)

Kotsiaros, Stavros; Finlay, Chris; Olsen, Nils

2015-01-01

. Experiments in modelling the Earth's lithospheric magnetic field with along-track differences are presented here as a proof of concept. We anticipate that use of such along-track differences in combination with east–west field differences, as are now provided by the Swarm satellite constellation......We demonstrate that first differences of polar orbiting satellite magnetic data in the along-track direction can be used to obtain high resolution models of the lithospheric field. Along-track differences approximate the north–south magnetic field gradients for non-polar latitudes. In a test case......, using 2 yr of low altitude data from the CHAMP satellite, we show that use of along-track differences of vector field data results in an enhanced recovery of the small scale lithospheric field, compared to the use of the vector field data themselves. We show that the along-track technique performs...

The metallogenic role of east-west fracture zones in South America with regard to the motion of lithospheric plates (with an example from Brazil)

Science.gov (United States)

Kutina, J.; Carter, William D.; Lopez, F.X.

1978-01-01

The role of east-west fracture zones in South America is discussed with regard to global fracturing and the motion of lithospheric plates. A set of major NW-trending lineaments has been derived which show a tendency to be spaced equidistantly and may correspond to a set of east-west fractures in the "pre-drift" position of the South American plate. Statistical analysis of linears in the ERTS-mosaics shows that NW-fractures are also among the most important ones in the Andes region, suggesting that the above major lineaments extend into the basement of the Andes. Some of the old major fractures, trending east-west in the present orientation of South America, are discussed and their NE orientation in the pre-drift position of the plate is considered. An example of structural control of ore deposition in the Brazilian Shield is presented, using the maps of the RADAM Project. It is concluded that the small tin-bearing granitic bodies concentrated in the region of Sao Felix do Xingu in the state of Para represent upper parts of an unexposed granitoid massif which is controlled by the intersection of a major east-west fracture zone probably represents westward extension of the Patos Lineament of the easternmost part of Brazil, connected with the east-west fracture zone of the Para state through the basement of the Maranhao Basin (Sineclise do Maranhao-Piaui). It is expected that the proposed "Patos-Para Lineament" extends further westward and may similarly control, at intersections with fractures of other trends, some mineralization centers in the western part of the state of Para and in the state of Amazonas.

Exploring opportunities and challenges for establishing a South American Space Agency

Science.gov (United States)

Silva-Martinez, Jackelynne P.; Aguilar, Andrés D.; Sarli, Bruno V.; Pardo Spiess, Monika Johanna; Sorice, Andreia F.; Genaro, Gino; Ojeda, Oscar I.

2018-06-01

The idea of establishing a South American Space Agency (SASA) is not new. There have been many discussions about this topic for a couple of decades, including an agreement by the Union of South American Nations to create such a space agency. Roughly 10 years ago, Argentina was the first to propose this collaboration with a military orientation. As the ideas progressed, Brazil was proposed to host its headquarters. However, not much support from the South American region has been given, either financially or logistically. To this day, a South American Space Agency or a similar concept has not yet been established in the region. The Space Generation Advisory Council (SGAC) hosted the first South American Space Generation Workshop in Argentina in 2015, where one of the working groups was tasked to further investigate the feasibility, advantages and challenges of implementing SASA. This paper presents an extension of the main findings from this working group where South American students and young professionals study and present a rationale in favor of SASA, outlining possible solutions and a structure that could be taken into account for its implementation. This paper pays particular attention to the question: Is it possible for countries in South America to establish the kind of cooperation necessary to stimulate the development and application of capabilities in the space sector, which would then enable undertaking missions far beyond the scope of what any single country in South America could do on its own? The existence of SASA would allow access to a common representative agency, which would lower costs, be accessible to all participating countries, and allow engagement with other emerging and established space agencies around the world.

[Endo- and ectoparasites of South American camelids and their control].

Science.gov (United States)

Schmäschke, R

2015-01-01

In a literature review, common endo- and ectoparasites of South American camelids are described, presenting morphological details and clinical signs important for diagnosis. Based on the life cycle of the parasites, possibilities for prophylaxis and therapy are indicated. The review should aid the veterinarian to diagnose and control common parasitic infections in South American camelids.

The continental lithosphere

DEFF Research Database (Denmark)

Artemieva, Irina

2009-01-01

The goal of the present study is to extract non-thermal signal from seismic tomography models in order to distinguish compositional variations in the continental lithosphere and to examine if geochemical and petrologic constraints on global-scale compositional variations in the mantle...... are consistent with modern geophysical data. In the lithospheric mantle of the continents, seismic velocity variations of a non-thermal origin (calculated from global Vs seismic tomography data [Grand S.P., 2002. Mantle shear-wave tomography and the fate of subducted slabs. Philosophical Transactions...... and evolution of Precambrian lithosphere: A global study. Journal of Geophysical Research 106, 16387–16414.] show strong correlation with tectono-thermal ages and with regional variations in lithospheric thickness constrained by surface heat flow data and seismic velocities. In agreement with xenolith data...

Exploration of the South-Eastern Alps lithosphere with 3D refraction seismics project Alp 2002 – data acquisition in Slovenia

Directory of Open Access Journals (Sweden)

Andrej Gosar

2003-06-01

Full Text Available Using combined seismic refraction/wide-angle reflection method project Alp 2002 explored the contact zone between South-Eastern Alps, Dinarides and Pannonian basin. In a network of 12 profiles of 4100 km total length, which are spread over seven countries,1055 portable seismographs were deployed and 31 strong (300 kg explosions fired. In Slovenia 127 seismographs were deployed along five profiles totalling 575 km and two explosions fired near Vojnik and Gradin. The collected data will allow construction of athree-dimensional model of the lithosphere and will contribute to the understanding of the tectonics and geodynamics at the junction of European, Adriatic and Tisza plates.

The Impact of China on South American Political and Economic Development

DEFF Research Database (Denmark)

Christensen, Steen Fryba

2018-01-01

The analysis compares three typologies of South American countries in terms of the impact of China on their political and economic development.......The analysis compares three typologies of South American countries in terms of the impact of China on their political and economic development....

Seismic structure of the lithosphere beneath NW Namibia: Impact of the Tristan da Cunha mantle plume

Science.gov (United States)

Yuan, Xiaohui; Heit, Benjamin; Brune, Sascha; Steinberger, Bernhard; Geissler, Wolfram H.; Jokat, Wilfried; Weber, Michael

2017-01-01

Northwestern Namibia, at the landfall of the Walvis Ridge, was affected by the Tristan da Cunha mantle plume during continental rupture between Africa and South America, as evidenced by the presence of the Etendeka continental flood basalts. Here we use data from a passive-source seismological network to investigate the upper mantle structure and to elucidate the Cretaceous mantle plume-lithosphere interaction. Receiver functions reveal an interface associated with a negative velocity contrast within the lithosphere at an average depth of 80 km. We interpret this interface as the relic of the lithosphere-asthenosphere boundary (LAB) formed during the Mesozoic by interaction of the Tristan da Cunha plume head with the pre-existing lithosphere. The velocity contrast might be explained by stagnated and "frozen" melts beneath an intensively depleted and dehydrated peridotitic mantle. The present-day LAB is poorly visible with converted waves, indicating a gradual impedance contrast. Beneath much of the study area, converted phases of the 410 and 660 km mantle transition zone discontinuities arrive 1.5 s earlier than in the landward plume-unaffected continental interior, suggesting high velocities in the upper mantle caused by a thick lithosphere. This indicates that after lithospheric thinning during continental breakup, the lithosphere has increased in thickness during the last 132 Myr. Thermal cooling of the continental lithosphere alone cannot produce the lithospheric thickness required here. We propose that the remnant plume material, which has a higher seismic velocity than the ambient mantle due to melt depletion and dehydration, significantly contributed to the thickening of the mantle lithosphere.

Aldehyde dehydrogenase polymorphism in North American, South American, and Mexican Indian populations.

Science.gov (United States)

Goedde, H W; Agarwal, D P; Harada, S; Rothhammer, F; Whittaker, J O; Lisker, R

1986-01-01

While about 40% of the South American Indian populations (Atacameños, Mapuche, Shuara) were found to be deficient in aldehyde dehydrogenase isozyme I (ALDH2 or E2), preliminary investigations showed very low incidence of isozyme deficiency among North American natives (Sioux, Navajo) and Mexican Indians (mestizo). Possible implications of such trait differences on cross-cultural behavioral response to alcohol drinking are discussed. PMID:3953578

Mapping lithosphere thickness beneath the Southern Caribbean and Venezuela using body wave reflectivity and surface wave tomography

Science.gov (United States)

Masy, J.; Niu, F.; Levander, A.; Schmitz, M.

2012-12-01

The Caribbean (CAR) and South American (SA) plate boundary in Venezuela is a broad zone of diffuse deformation and faulting. GPS measurements indicate that the CAR is moving approximately 2 cm/yr respect to SA, parallel to the strike slip fault system in the east, but with an oblique convergence component in the west (Weber et al., 2001). Along the central and eastern Venezuela coast, most of the motion is accommodated by both transpression and transtension along the right lateral strike-slip San Sebastian- El Pilar fault system. The main tectonic features of the area include accretionary wedges and coastal thrust belts with their associated foreland basins (e.g. Sierra del Interior and Espino Graben). Southern of the plate boundary is located the Guayana Shield, which is part of the Amazonian Craton, and is an elevated plain consisting of Precambrian rocks. BOLIVAR (Broadband Onshore-Offshore Lithospheric Investigation of Venezuela and the Antilles Arc Region) was a multidisciplinary, international investigation to determine the evolution of the CAR-SA plate boundary (Levander et al., 2006) that included a 47 station broadband seismic array to complement the 40 station Venezuelan national array operated by FUNVISIS. The goal of this study is to map out lithosphere thickness across the region in order to understand its role for the various types of deformations observed at surface. We combined surface wave tomography and body wave reflectivity to locate the depth of the lithosphere-asthenosphere boundary (LAB). To generate a coherent 3D reflectivity volume of the study area, we used both P- and S-wave receiver-function data, as well as the ScS reverberation records of two deep earthquakes occurring in South America. We also measured Rayleigh phase velocities in the frequency range of 20-100 s using the two plane-wave method to remove multi-pathing effects (Forsyth and Li, 2005). Finite-frequency kernels were computed for a total of 63 teleseismic events to improve

Gender, Family, and Community Correlates of Mental Health in South Asian Americans

OpenAIRE

Masood, Nausheen; Okazaki, Sumie; Takeuchi, David T.

2009-01-01

Nationally representative data from the National Latino and Asian American Study (Alegría et al., 2004) was used to examine both disorder prevalence rates and correlates of distress for the South Asian American subgroup (n = 164). South Asian Americans generally appeared to have lower or comparable rates of lifetime and 12-month mood and anxiety disorders when compared with the overall Asian American sample. A multiple-regression model fitted to predict recent psychological distress, with 12-...

Afrikaans, American and British Models for South African English ...

African Journals Online (AJOL)

tions in a national and international context, by comparing the traditions and the roles of the lan- ... The changing linguistic, social, and educational situations in South Africa ... abroad, by the British and American leXicographical traditions. ... interactional styles in the South African social psychology and cross-cultural.

Dynamics of Lithospheric Extension and Residual Topography in Southern Tibet

Science.gov (United States)

Chen, B.; Shahnas, M. H.; Pysklywec, R.; Sengul Uluocak, E.

2017-12-01

Although the north-south (N-S) convergence between India and Eurasia is ongoing, a number of north-south trending rifts (e.g., Tangra Yum Co Rift, Yadong-Gulu Rift and Cona Rift) and normal faulting are observed at the surface of southern Tibet, suggesting an east-west (E-W) extension tectonic regime. The earthquake focal mechanisms also show that deformation of southern Tibet is dominated by E-W extension across these N-S trending rifts. Because the structure of the lithosphere and underlying mantle is poorly understood, the origin of the east-west extension of southern Tibet is still under debate. Gravitational collapse, oblique convergence, and mantle upwelling are among possible responsible mechanisms. We employ a 3D-spherical control volume model of the present-day mantle flow to understand the relationship between topographic features (e.g., rifts and the west-east extension), intermediate-depth earthquakes, and tectonic stresses induced by mantle flow beneath the region. The thermal structure of the mantle and crust is obtained from P and S-wave seismic inversions and heat flow data. Power-law creep with viscous-plastic rheology, describing the behavior of the lithosphere and mantle material is employed. We determine the models which can best reconcile the observed features of southern Tibet including surface heat flow, residual topography with uplift and subsidence, reported GPS rates of the vertical movements, and the earthquake events. The 3D geodynamic modeling of the contemporary mantle flow-lithospheric response quantifies the relative importance of the various proposed mechanism responsible for the E-W extension and deep earthquakes in southern Tibet. The results also have further implications for the magmatic activities and crustal rheology of the region.

“Liting it up”: Popular Culture, Indo-Pak Basketball, and South Asian American Institutions

Directory of Open Access Journals (Sweden)

Stanley Ilango Thangaraj

2010-08-01

Full Text Available South Asian American participants of a co-ethnic basketball league, known as Indo-Pak Basketball, utilized urban basketball vernacular through the phrase “liting it up” to identify individuals scoring points in great numbers. The person “liting it up” becomes visible and receives recognition. Accordingly, I want to “lite up” the scholarship on South Asian America whereby situating South Asian American religious sites and cultural centers as key arenas for “Americanization” through US popular culture. I situate sport as a key element of popular culture through which South Asian American communities work out, struggle through, and contest notions of self. Informed by an Anthropology of Sport, ethnography of South Asian American communities in Atlanta takes place alongside an examination of the North American Indo-Pak Basketball circuit. Accordingly, my findings indicate that such community formation has also taken shape at the intersections of institutions, gender, and sexuality whereby excluding queers, women, and other communities of color.

The lithosphere-asthenosphere Italy and surroundings

CERN Document Server

Panza, G F; Chimera, G; Pontevivo, A; Raykova, R

2003-01-01

The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineat...

Gender, family, and community correlates of mental health in South Asian Americans.

Science.gov (United States)

Masood, Nausheen; Okazaki, Sumie; Takeuchi, David T

2009-07-01

Nationally representative data from the National Latino and Asian American Study (Alegría et al., 2004) was used to examine both disorder prevalence rates and correlates of distress for the South Asian American subgroup (n = 164). South Asian Americans generally appeared to have lower or comparable rates of lifetime and 12-month mood and anxiety disorders when compared with the overall Asian American sample. A multiple-regression model fitted to predict recent psychological distress, with 12-month diagnosis as a covariate, found gender differences. For women, lack of extended family support was related to higher levels of distress, whereas for men, greater conflict with family culture, and a lower community social position (but higher U.S. social position) predicted higher distress scores. Findings suggest that mental health services consider a broad framework of psychological functioning for South Asian Americans that reflect their gendered, familial, and sociopolitical realities.

Gender, Family, and Community Correlates of Mental Health in South Asian Americans

Science.gov (United States)

Masood, Nausheen; Okazaki, Sumie; Takeuchi, David T.

2014-01-01

Nationally representative data from the National Latino and Asian American Study (Alegría et al., 2004) was used to examine both disorder prevalence rates and correlates of distress for the South Asian American subgroup (n = 164). South Asian Americans generally appeared to have lower or comparable rates of lifetime and 12-month mood and anxiety disorders when compared with the overall Asian American sample. A multiple-regression model fitted to predict recent psychological distress, with 12-month diagnosis as a covariate, found gender differences. For women, lack of extended family support was related to higher levels of distress, whereas for men, greater conflict with family culture, and a lower community social position (but higher U.S. social position) predicted higher distress scores. Findings suggest that mental health services consider a broad framework of psychological functioning for South Asian Americans that reflect their gendered, familial, and sociopolitical realities. PMID:19594255

Exploring Hybrid Identities: South Asian American Women Pursue a Career in Teaching

Science.gov (United States)

Shah, Amita Roy

2013-01-01

This study explores how second-generation South Asian American women negotiated their hybrid identities to pursue a career in teaching. Many South Asian Americans have not pursued a career in teaching because of various external and internal factors that have influenced their sense of identity, academic achievement, and professional career path…

Ecogeographical Variation in Skull Shape of South-American Canids: Abiotic or Biotic Processes?

Science.gov (United States)

de Moura Bubadué, Jamile; Cáceres, Nilton; Dos Santos Carvalho, Renan; Meloro, Carlo

Species morphological changes can be mutually influenced by environmental or biotic factors, such as competition. South American canids represent a quite recent radiation of taxa that evolved forms very disparate in phenotype, ecology and behaviour. Today, in the central part of South America there is one dominant large species (the maned wolf, Chrysocyon brachyurus ) that directly influence sympatric smaller taxa via interspecific killing. Further south, three species of similar sized foxes ( Lycalopex spp.) share the same habitats. Such unique combination of taxa and geographic distribution makes South American dogs an ideal group to test for the simultaneous impact of climate and competition on phenotypic variation. Using geometric morphometrics, we quantified skull size and shape of 431 specimens belonging to the eight extant South American canid species: Atelocynus microtis , Cerdocyon thous , Ch. brachyurus , Lycalopex culpaeus , L. griseus , L. gymnocercus , L. vetulus and Speothos venaticus . South American canids are significantly different in both skull size and shape. The hypercarnivorous bush dog is mostly distinct in shape from all the other taxa while a degree of overlap in shape-but not size-occurs between species of the genus Lycalopex . Both climate and competition impacts interspecific morphological variation. We identified climatic adaptations as the main driving force of diversification for the South American canids. Competition has a lower degree of impact on their skull morphology although it might have played a role in the past, when canid community was richer in morphotypes.

The lithosphere-asthenosphere: Italy and surroundings

International Nuclear Information System (INIS)

Panza, G.F.; Aoudia, A.; Pontevivo, A.; Chimera, G.; Raykova, R.

2003-02-01

The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by surface wave velocity tomography and non-linear inversion. Maps of the Moho depth, of the thickness of the lithosphere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, identified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the principal recent volcanoes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria a lithospheric doubling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenosphere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea, likely attesting the fragmentation of Adria. (author)

Gravity anomalies and flexure of the lithosphere at the Middle Amazon Basin, Brazil

Science.gov (United States)

Nunn, Jeffrey A.; Aires, Jose R.

1988-01-01

The Middle Amazon Basin is a large Paleozoic sedimentary basin on the Amazonian craton in South America. It contains up to 7 km of mainly shallow water sediments. A chain of Bouguer gravity highs of approximately +40 to +90 mGals transects the basin roughly coincident with the axis of maximum thickness of sediment. The gravity highs are flanked on either side by gravity lows of approximately -40 mGals. The observed gravity anomalies can be explained by a steeply sided zone of high density in the lower crust varying in width from 100 to 200 km wide. Within this region, the continental crust has been intruded/replaced by more dense material to more than half its original thickness of 45-50 km. The much wider sedimentary basin results from regional compensation of the subsurface load and the subsequent load of accumulated sediments by flexure of the lithosphere. The observed geometry of the basin is consistent with an elastic lithosphere model with a mechanical thickness of 15-20 km. Although this value is lower than expected for a stable cratonic region of Early Proterozoic age, it is within the accepted range of effective elastic thicknesses for the earth. Rapid subsidence during the late Paleozoic may be evidence of a second tectonic event or lithospheric relaxation which could lower the effective mechanical thickness of the lithosphere. The high-density zone in the lower crust, as delineated by gravity and flexural modeling, has a complex sinuous geometry which is narrow and south of the axis of maximum sediment thickness on the east and west margins and wide and offset to the north in the center of the basin. The linear trough geometry of the basin itself is a result of smoothing by regional compensation of the load in the lower crust.

The South American fruit fly, Anastrepha fraterculus (Wiedemann) in Brazil

International Nuclear Information System (INIS)

Zucchi, R.A.; Araujo, E.L.; Canal D, N.A.; Uchoa F, M.A.

1999-01-01

Anastrepha fraterculus, the South American fruit fly, is the most common and economically important pest for the fruit-bearing species in the Neotropical region. However, there are some species that are close to A. fraterculus and, sometimes they can be erroneously identified as A. fraterculus. The separation of A. fraterculus from A. obliqua, A. sororcula and A. zenildae, species closely related to South American fruit fly, is discussed. Also, information on the host plants and braconid parasitoids for A. fraterculus in Brazil is presented. (author)

South American Youth : Regional Democracy-Building Dialogue ...

International Development Research Centre (IDRC) Digital Library (Canada)

This project will undertake a comparative analysis of South American youth in the Mercosur countries (Argentina, Brazil, Paraguay and Uruguay) and their perception of rights, democracy and regional integration. Researchers will examine the meaning that young people, adults and mediators of youth demands attribute to ...

Insight into American tourists’ experiences with weather in South Africa

Directory of Open Access Journals (Sweden)

Giddy Julia K.

2017-12-01

Full Text Available Weather and climate are often important factors determining the success of a tourism destination and resultant satisfaction among tourists. This is particularly true for South Africa due the predominance of outdoor tourist attractions. Increasing numbers of international tourists have visited South Africa since the fall of apartheid, particularly those from the United States (U.S., which is an important market for South African tourism. Therefore, this paper seeks to examine a sample of American tourists’ experience with day-to-day weather and climatic conditions in South Africa. The results show that although respondents did not feel that climatic conditions were an important factor in motivations to visit the country, the day-to-day weather did often impact the enjoyment of their visit. Most notably, weather controlled their ability to participate in outdoor activities. In correlating accounts of unpleasant weather conditions with the meteorological records, a close association emerged, particularly for excessively high temperatures. This indicates that the experiences of American tourists are an accurate indication of climatic unsuitability for tourism, which poses threats to the South African outdoor tourism sector.

Phylogenetic reconstruction of South American felids defined by protein electrophoresis.

Science.gov (United States)

Slattery, J P; Johnson, W E; Goldman, D; O'Brien, S J

1994-09-01

Phylogenetic associations among six closely related South American felid species were defined by changes in protein-encoding gene loci. We analyzed proteins isolated from skin fibroblasts using two-dimensional electrophoresis and allozymes extracted from blood cells. Genotypes were determined for multiple individuals of ocelot, margay, tigrina, Geoffroy's cat, kodkod, and pampas cat at 548 loci resolved by two-dimensional electrophoresis and 44 allozyme loci. Phenograms were constructed using the methods of Fitch-Margoliash and neighbor-joining on a matrix of Nei's unbiased genetic distances for all pairs of species. Results of a relative-rate test indicate changes in two-dimensional electrophoresis data are constant among all South American felids with respect to a hyena outgroup. Allelic frequencies were transformed to discrete character states for maximum parsimony analysis. Phylogenetic reconstruction indicates a major split occurred approximately 5-6 million years ago, leading to three groups within the ocelot lineage. The earliest divergence led to Leopardus tigrina, followed by a split between an ancestor of an unresolved trichotomy of three species (Oncifelis guigna, O. geoffroyi, and Lynchailuris colocolo) and a recent common ancestor of Leopardus pardalis and L. wiedii. The results suggest that modern South American felids are monophyletic and evolved rapidly after the formation of the Panama land bridge between North and South America.

Close relationship of Plasmodium sequences detected from South American pampas deer (Ozotoceros bezoarticus to Plasmodium spp. in North American white-tailed deer

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Masahito Asada

2018-04-01

Full Text Available We report, for the first time, the presence of ungulate malaria parasites in South America. We conducted PCR-based surveys of blood samples of multiple deer species and water buffalo from Brazil and detected Plasmodium sequences from pampas deer (Ozotoceros bezoarticus samples. Phylogenic analysis revealed that the obtained sequences are closely related to the Plasmodium odocoilei clade 2 sequence from North American white-tailed deer (Odocoileus virginianus. Nucleotide differences suggest that malaria parasites in South American pampas deer and North American P. odocoilei clade 2 branched more recently than the Great American Interchange. Keywords: Malaria, Pampas deer, South America, Plasmodium odocoilei, Brazil

Lithosphere erosion atop mantle plumes

Science.gov (United States)

Agrusta, R.; Arcay, D.; Tommasi, A.

2012-12-01

Mantle plumes are traditionally proposed to play an important role in lithosphere erosion. Seismic images beneath Hawaii and Cape Verde show a lithosphere-asthenosphere-boundary (LAB) up to 50 km shallower than the surroundings. However, numerical models show that unless the plate is stationary the thermo-mechanical erosion of the lithosphere does not exceed 30 km. We use 2D petrological-thermo-mechanical numerical models based on a finite-difference method on a staggered grid and marker in cell method to study the role of partial melting on the plume-lithosphere interaction. A homogeneous peridotite composition with a Newtonian temperature- and pressure-dependent viscosity is used to simulate both the plate and the convective mantle. A constant velocity, ranging from 5 to 12.5 cm/yr, is imposed at the top of the plate. Plumes are created by imposing a thermal anomaly of 150 to 350 K on a 50 km wide domain at the base of the model (700 km depth); the plate right above the thermal anomaly is 40 Myr old. Partial melting is modeled using batch-melting solidus and liquidus in anhydrous conditions. We model the progressive depletion of peridotite and its effect on partial melting by assuming that the melting degree only strictly increases through time. Melt is accumulated until a porosity threshold is reached and the melt in excess is then extracted. The rheology of the partially molten peridotite is determined using viscous constitutive relationship based on a contiguity model, which enables to take into account the effects of grain-scale melt distribution. Above a threshold of 1%, melt is instantaneously extracted. The density varies as a function of partial melting degree and extraction. Besides, we analyze the kinematics of the plume as it impacts a moving plate, the dynamics of time-dependent small-scale convection (SSC) instabilities developing in the low-viscosity layer formed by spreading of hot plume material at the lithosphere base, and the resulting thermal

New views on American colonization: critical tests from South America

Directory of Open Access Journals (Sweden)

O'Rourke, Dennis

2007-01-01

Full Text Available The traditional view of colonization of the Americas as a migration across Beringia and subsequent dispersal southward following the last glacial maximum is being increasingly questioned. In North America, archaeological links to Siberia are tenuous and genetic data are more consistent with an earlier entry of people into the Americas, from Central rather than Northeast Siberia. An entry of populations into the Americas prior to the last glacial maximum forces a reconsideration not only of timing, but also geographic points of entry and speed of dispersal, based on ecological theory. A number of emerging alternative hypotheses on the colonization of the Americas predict early entry and dispersal of people into South America - earlier than, or coeval with, initial dispersal in North America. The study of genetic, morphological, and archaeological variation across South America is critical to testing these new, alternative hypotheses of Native American origins. I will review the evidence for emerging, alternative views of American Colonization, and suggest ways in which data from South American populations and prehistory will be crucial in testing them.

South American Field Experience: An Initiative in International Education. The Implementation Journal for the South American Field Experience.

Science.gov (United States)

Martin, William J.

A description is provided of Williamsport Area Community College's (WACC's) South American Field Experience program, a travel/study program for faculty and staff designed to provide a variety of learning experiences through a three week trip to Peru, Chile, Argentina, and Brazil. Chapter I presents an overview of the development of the project,…

Iberian (South American) Model of Judicial Review: Toward Conceptual Framework

Science.gov (United States)

Klishas, Andrey A.

2016-01-01

The paper explores Latin American countries legislation with the view to identify specific features of South American model of judicial review. The research methodology rests on comparative approach to analyzing national constitutions' provisions and experts' interpretations thereof. The constitutional provisions of Brazil, Peru, Mexico, and…

Crust-Lithosphere-Asthenosphere Dynamics in Mantle Plume Provinces with Emphasis on the Galapagos =

Science.gov (United States)

Orellana, Felipe

Hotspot tracks, which most geoscientists attribute to the effects of mantle plumes on the overlying lithospheric plates, are characterized by distinct bathymetry, gravity signatures, structural geology, volcanology, petrology, and geochemistry; motivating us to try to understand the dynamics behind the space-time-histories of these systems. Making use of classical geodynamic paradigms, such as highly-viscous fluids (Stokes flow, for the mantle and/or lithosphere), elastic plate behavior, and heat flow, we develop conceptual frameworks to explain a number of distinct hotspot track features, and present quantitative models aimed at elucidating their origins. There is much diversity among the population of mantle plume hotspot tracks on the Earth's oceanic crust. For example, there are marked differences in the style of their bathymetry, as well as in their gravimetric signals, and also in the isotopic signature of extruded lavas. At the same time, important underlying differences are given by the age of the lithospheric plates under which the mantle plumes are impinging, lithospheric elastic thickness, the heat (or buoyancy) flux of individual mantle plumes, their melt production, crustal thickening, the proximity of spreading centers, etc. In the first chapter of this dissertation, making use of scaling theory, we show that for most oceanic hotspot tracks, the character of bathymetric expression (primarily rough vs. smooth topography) can be explained by three independent primary underlying factors - plate thickness, or equivalently plate age; plate speed; and plume buoyancy flux - combined into a single parameter, R, the ratio of plume heat flux to the effective thermal capacity of the moving plate overlying the plume. The Galapagos archipelago (off the west coast of equatorial South America), part of a >20 Ma old hotspot track formed by the underlying Galapagos mantle plume, currently exhibits a broad geographic distribution of volcanic centers of surprisingly

Is There Really A North American Plate?

Science.gov (United States)

Krill, A.

2011-12-01

Lithospheric plates are typically identified from earthquake epicenters and evidence such as GPS movements. But no evidence indicates a plate boundary between the North American and South American Plates. Some plate maps show them separated by a transform boundary, but it is only a fracture zone. Other maps show an "undefined plate boundary" or put no boundary between these two plates (check Google images). Early plate maps showed a single large American Plate, quite narrow east of the Caribbean Plate (Le Pichon 1968, Morgan 1968). The North and South American Plates became established by the leading textbook Earth (Press & Siever 1974). On their map, from a Scientific American article by John Dewey (1972), these new plates were separated by an "uncertain plate boundary." The reasons for postulating a North American Plate were probably more psychological than geological. Each of the other continents of the world had its own plate, and North American geologists naturally wanted theirs. Similarly, European geographers used to view Europe as its own continent. A single large plate should again be hypothesized. But the term American Plate would now be ambiguous ("Which plate, North or South?") Perhaps future textbook authors could call it the "Two-American Plate." Textbook authors ultimately decide such global-tectonic matters. I became aware of textbook authors' opinions and influence from my research into the history of Alfred Wegener's continental drift (see Fixists vs. Mobilists by Krill 2011). Leading textbook author Charles Schuchert realized that continental drift would abolish his cherished paleogeographic models of large east-west continents (Eria, Gondwana) and small oceans (Poseiden, Nereis). He and his junior coauthors conspired to keep drift evidence out of their textbooks, from the 1934-editions until the 1969-editions (Physical Geology by Longwell et al. 1969, Historical Geology by Dunbar & Waage 1969). Their textbooks ruled in America. Textbooks

Thermodynamic, geophysical and rheological modeling of the lithosphere underneath the North Atlantic Porcupine Basin (Ireland).

Science.gov (United States)

Botter, C. D.; Prada, M.; Fullea, J.

2017-12-01

The Porcupine is a North-South oriented basin located southwest of Ireland, along the North Atlantic continental margin, formed by several rifting episodes during Late Carboniferous to Early Cretaceous. The sedimentary cover is underlined by a very thin continental crust in the center of the basin (10 in the South. In spite of the abundant literature, most of the oil and gas exploration in the Porcupine Basin has been targeting its northern part and is mostly restricted to relatively shallow depths, giving a restrained overview of the basin structure. Therefore, studying the thermodynamic and composition of the deep and broader structures is needed to understand the processes linked to the formation and the symmetry signature of the basin. Here, we model the present-day thermal and compositional structure of the continental crust and lithospheric mantle underneath the Porcupine basin using gravity, seismic, heat flow and elevation data. We use an integrated geophysical-petrological framework where most relevant rock properties (density, seismic velocities) are determined as a function of temperature, pressure and composition. Our modelling approach solves simultaneously the heat transfer, thermodynamic, geopotential, seismic and isostasy equations, and fit the results to all available geophysical and petrological observables (LitMod software). In this work we have implemented a module to compute self-consistently a laterally variable lithospheric elastic thickness based on mineral physics rheological laws (yield strength envelopes over the 3D volume). An appropriate understanding of local and flexural isostatic behavior of the basin is essential to unravel its tectonic history (i.e. stretching factors, subsidence etc.). Our Porcupine basin 3D model is defined by four lithological layers, representing properties from post- and syn-rift sequences to the lithospheric mantle. The computed yield strength envelopes are representative of hyperextended lithosphere and

Rifting Thick Lithosphere - Canning Basin, Western Australia

Science.gov (United States)

Czarnota, Karol; White, Nicky

2016-04-01

The subsidence histories and architecture of most, but not all, rift basins are elegantly explained by extension of ~120 km thick lithosphere followed by thermal re-thickening of the lithospheric mantle to its pre-rift thickness. Although this well-established model underpins most basin analysis, it is unclear whether the model explains the subsidence of rift basins developed over substantially thick lithosphere (as imaged by seismic tomography beneath substantial portions of the continents). The Canning Basin of Western Australia is an example where a rift basin putatively overlies lithosphere ≥180 km thick, imaged using shear wave tomography. Subsidence modelling in this study shows that the entire subsidence history of the account for the observed subsidence, at standard crustal densities, the lithospheric mantle is required to be depleted in density by 50-70 kg m-3, which is in line with estimates derived from modelling rare-earth element concentrations of the ~20 Ma lamproites and global isostatic considerations. Together, these results suggest that thick lithosphere thinned to > 120 km is thermally stable and is not accompanied by post-rift thermal subsidence driven by thermal re-thickening of the lithospheric mantle. Our results show that variations in lithospheric thickness place a fundamental control on basin architecture. The discrepancy between estimates of lithospheric thickness derived from subsidence data for the western Canning Basin and those derived from shear wave tomography suggests that the latter technique currently is limited in its ability to resolve lithospheric thickness variations at horizontal half-wavelength scales of <300 km.

Desi Women on the Forty Acres: Exploring Intergenerational Issues and Identity Development of South Asian American College Students

Science.gov (United States)

Ruzicka, Smita Sundaresan

2011-01-01

South Asian Americans are one of the fastest growing sub-groups within the Asian American population in the United States today. Between 1960 and 1990, the South Asian American population witnessed an increase of approximately 900% (Leonard, 1997). This increase in population also corresponds with the increase in South Asian American students…

Craton stability and continental lithosphere dynamics during plume-plate interaction

Science.gov (United States)

Wang, H.; Van Hunen, J.; Pearson, D.

2013-12-01

Survival of thick cratonic roots in a vigorously convecting mantle system for billions of years has long been studied by the geodynamical community. A high cratonic root strength is generally considered to be the most important factor. We first perform and discuss new numerical models to investigate craton stability in both Newtonian and non-Newtonian rheology in the stagnant lid regime. The results show that only a modest compositional rheological factor of Δη=10 with non-Newtonian rheology is required for the survival of cratonic roots in a stagnant lid regime. A larger rheological factor (100 or more) is needed to maintain similar craton longevity in a Newtonian rheology environment. Furthermore, chemical buoyancy plays an important role on craton stability and its evolution, but could only work with suitable compositional rheology. During their long lifespan, cratons experienced a suite of dynamic, tectonothermal events, such as nearby subduction and mantle plume activity. Cratonic nuclei are embedded in shorter-lived, more vulnerable continental areas of different thickness, composition and rheology, which would influence the lithosphere dynamic when tectonothermal events happen nearby. South Africa provides a very good example to investigate such dynamic processes as it hosts several cratons and there are many episodic thermal events since the Mesozoic as indicated by a spectrum of magmatic activity. We numerically investigate such an integrated system using the topographic evolution of cratons and surrounding lithosphere as a diagnostic observable. The post-70Ma thinning of pericratonic lithosphere by ~50km around Kaapvaal craton (Mather et al., 2011) is also investigated through our numerical models. The results show that the pericratonic lithosphere cools and grows faster than cratons do, but is also more likely to be effected by episodic thermal events. This leads to surface topography change that is significantly larger around the craton than within

South American Youth and Integration : Typical Situations and Youth ...

International Development Research Centre (IDRC) Digital Library (Canada)

South American Youth and Integration : Typical Situations and Youth ... IDRC partner the World Economic Forum is building a hub for inclusive growth ... Brazil, Paraguay and Uruguay) and their perception of rights, democracy and regional.

Lithospheric expression of geological units in central and eastern North America from full waveform tomography

Science.gov (United States)

Yuan, Huaiyu; French, Scott; Cupillard, Paul; Romanowicz, Barbara

2014-09-01

The EarthScope TA deployment has provided dense array coverage throughout the continental US and with it, the opportunity for high resolution 3D seismic velocity imaging of both lithosphere and asthenosphere in the continent. Building upon our previous long-period waveform tomographic modeling in North America, we present a higher resolution 3D isotropic and radially anisotropic shear wave velocity model of the North American lithospheric mantle, constructed tomographically using the spectral element method for wavefield computations and waveform data down to 40 s period. The new model exhibits pronounced spatial correlation between lateral variations in seismic velocity and anisotropy and major tectonic units as defined from surface geology. In the center of the continent, the North American craton exhibits uniformly thick lithosphere down to 200-250 km, while major tectonic sutures of Proterozoic age visible in the surface geology extend down to 100-150 km as relatively narrow zones of distinct radial anisotropy, with Vsv >Vsh. Notably, the upper mantle low velocity zone is present everywhere under the craton between 200 and 300 km depth. East of the continental rift margin, the lithosphere is broken up into a series of large, somewhat thinner (150 km) high velocity blocks, which extend laterally 200-300 km offshore into the Atlantic Ocean. Between the craton and these deep-rooted blocks, we find a prominent narrow band of low velocities that roughly follows the southern and eastern Laurentia rift margin and extends into New England. We suggest that the lithosphere along this band of low velocities may be thinned due to the combined effects of repeated rifting processes and northward extension of the hotspot related Bermuda low-velocity channel across the New England region. We propose that the deep rooted high velocity blocks east of the Laurentia margin represent the Proterozoic Gondwanian terranes of pan-African affinity, which were captured during the Rodinia

Anthropozoonotic Endoparasites in Free-Ranging ?Urban? South American Sea Lions (Otaria flavescens)

OpenAIRE

Hermosilla, Carlos; Silva, Liliana M. R.; Navarro, Mauricio; Taubert, Anja

2016-01-01

The present study represents the first report on the gastrointestinal endoparasite fauna of a free-ranging “urban” colony of South American sea lions (Otaria flavescens) living within the city of Valdivia, Chile. A total of 40 individual faecal samples of South American sea lions were collected during the year 2012 within their natural habitat along the river Calle-Calle and in the local fish market of Valdivia. Coprological analyses applying sodium acetate acetic formalin methanol (SAF) tech...

Short wavelength lateral variability of lithospheric mantle beneath the Middle Atlas (Morocco) as recorded by mantle xenoliths

Science.gov (United States)

El Messbahi, Hicham; Bodinier, Jean-Louis; Vauchez, Alain; Dautria, Jean-Marie; Ouali, Houssa; Garrido, Carlos J.

2015-05-01

The Middle Atlas is a region where xenolith-bearing volcanism roughly coincides with the maximum of lithospheric thinning beneath continental Morocco. It is therefore a key area to study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy that is required to explain the Moroccan topography. Samples from the two main xenolith localities, the Bou Ibalghatene and Tafraoute maars, have been investigated for their mineralogy, microstructures, crystallographic preferred orientation, and whole-rock and mineral compositions. While Bou Ibalghatene belongs to the main Middle Atlas volcanic field, in the 'tabular' Middle Atlas, Tafraoute is situated about 45 km away, on the North Middle Atlas Fault that separates the 'folded' Middle Atlas, to the South-East, from the 'tabular' Middle Atlas, to the North-West. Both xenolith suites record infiltration of sub-lithospheric melts that are akin to the Middle Atlas volcanism but were differentiated to variable degrees as a result of interactions with lithospheric mantle. However, while the Bou Ibalghatene mantle was densely traversed by high melt fractions, mostly focused in melt conduits, the Tafraoute suite records heterogeneous infiltration of smaller melt fractions that migrated diffusively, by intergranular porous flow. As a consequence the lithospheric mantle beneath Bou Ibalghaten was strongly modified by melt-rock interactions in the Cenozoic whereas the Tafraoute mantle preserves the record of extensional lithospheric thinning, most likely related to Mesozoic rifting. The two xenolith suites illustrate distinct mechanisms of lithospheric thinning: extensional thinning in Tafraoute, where hydrous incongruent melting triggered by decompression probably played a key role in favouring strain localisation, vs. thermal erosion in Bou Ibalghatene, favoured and guided by a dense network of melt conduits. Our results lend support to the suggestion that lithospheric thinning beneath the Atlas

“Liting it up”: Popular Culture, Indo-Pak Basketball, and South Asian American Institutions

OpenAIRE

Stanley Ilango Thangaraj

2010-01-01

South Asian American participants of a co-ethnic basketball league, known as Indo-Pak Basketball, utilized urban basketball vernacular through the phrase “liting it up” to identify individuals scoring points in great numbers. The person “liting it up” becomes visible and receives recognition. Accordingly, I want to “lite up” the scholarship on South Asian America whereby situating South Asian American religious sites and cultural centers as key arenas for “Americanization” through US popula...

The water economy of South American desert rodents: from integrative to molecular physiological ecology.

Science.gov (United States)

Bozinovic, Francisco; Gallardo, Pedro

2006-01-01

Rodents from arid and semi-arid habitats live under conditions where the spatial and temporal availability of free water is limited, or scarce, thus forcing these rodents to deal with the problem of water conservation. The response of rodents to unproductive desert environments and water deficits has been intensively investigated in many deserts of the world. However, current understanding of the cellular, systemic and organismal physiology of water economy relies heavily on short-term, laboratory-oriented experiments, which usually focus on responses at isolated levels of biological organization. In addition, studies in small South American mammals are scarce. Indeed xeric habitats have existed in South America for a long time and it is intriguing why present day South American desert rodents do not show the wide array of adaptive traits to desert life observed for rodents on other continents. Several authors have pointed out that South American desert rodents lack physiological and energetic specialization for energy and water conservation, hypothesizing that their success is based more on behavioral and ecological strategies. We review phenotypic flexibility and physiological diversity in water flux rate, urine osmolality, and expression of water channels in South American desert-dwelling rodents. As far as we know, this is the first review of integrative studies at cellular, systemic and organismal levels. Our main conclusion is that South American desert rodents possess structural as well as physiological systems for water conservation, which are as remarkable as those found in "classical" rodents inhabiting other desert areas of the world.

Radioactive mineral potential of carbonatites in western parts of the South American shields

International Nuclear Information System (INIS)

Premoli, C.; Kroonenberg, S.B.

1984-01-01

During the last eight years at least six carbonatites or clusters of carbonatites have been discovered in the western parts of the South American cratons. In contrast to the carbonatites of the eastern part of the South American shields, which have been well studied and placed in a tectonic context together with the West African carbonatite provinces, those of the western part of the South American cratons have received litte attention. This paper is a compilation of published and original data on these occurrences, their geology, geochemistry, structural setting and radioactive mineral potential. An exploration strategy is devised based on experiences in this rainforest-clad area and the peculiar genetic aspect of carbonatites. Some details of a possibly new uranium mineral encountered in Cerro Cora carbonatite are given. (author)

The electrical lithosphere in Archean cratons: examples from Southern Africa

Science.gov (United States)

Khoza, D. T.; Jones, A. G.; Muller, M. R.; Webb, S. J.

2011-12-01

lithospheric geotherm. Preferential alignment of graphite and/or interstitial sulphides along grain boundaries facilitated by deep shear movement during crustal extension and thinning could account for the high conductive region within the DGC. The Congo and Kalahari cratons are characterised by very thick and resistive lithosphere, approximately 220 km and 160 km respectively and both their cratonic roots appear to be thrusted underneath the DGC. The Archean-Proterozoic basement inliers, which are part of the Congo craton nuclei are geologically mapped within the DGC in northern Namibia, further suggesting that the craton extend far south into the orogenic belt.

South Asian American Perspectives on Overweight, Obesity, and the Relationship Between Weight and Health

OpenAIRE

Tang, Joyce W.; Mason, Maryann; Kushner, Robert F.; Tirodkar, Manasi A.; Khurana, Neerja; Kandula, Namratha R.

2012-01-01

Introduction Compared with other racial groups, South Asian adults develop type 2 diabetes and cardiovascular disease at a lower body mass index (BMI). Perceptions of weight and the effect of weight on health can influence weight-loss attempts but are not well described in this population. The objective of this study was to examine perceptions of weight appropriateness and the effect of weight on health among South Asian Americans. Methods We recruited 75 South Asian American adults from a si...

Southward Ejection of Subcontinental Lithosphere and large-scale Asthenospheric Enrichment beneath central Chile resulting from Flat Subduction

Science.gov (United States)

Jacques, G.; Hoernle, K.; Schaefer, B. F.; Hauff, F.; Gill, J.; Holm, P. M.; Bindeman, I. N.; Folguera, A.; Lara, L.; Ramos, V. A.

2015-12-01

Flat subduction is a common process in subduction zones, causing crustal shortening and thickening and possibly subduction erosion. These processes can lead to the contamination of asthenospheric melts either by lithospheric assimilation (e.g. MASH) or by subduction erosion of lithosphere into the asthenospheric source. We present new major and trace element and Sr-Nd-Pb-Hf-O-Os isotope data for a transect of Quaternary volcanic rocks across the Northern Southern Volcanic Front (NSVZ) of Chile at ~33.5°S, just south of the area of flat subduction, extending from the volcanic front (VF) to the rear arc (RA). The newly discovered calc-alkaline to alkaline RA rocks are more mafic (MgO~4-9wt.%) than the VF rocks (MgO~2.0-4.5wt.%). Both groups have overlapping Sr-Nd-Hf isotopic compositions that are more enriched than lavas from further south in the SVZ with two RA trachybasalts displaying extreme 87Sr/86Sr (0.710), eNd (-6) and eHf (-9). The RA samples, however, have less radiogenic Pb isotopic compositions with the two extreme RA trachybasalt samples having the least radiogenic Pb. The 207Pb/204Pb vs. Nd/Pb, Ce/Pb and Nb/U form good inverse linear correlations extending from subducted sediments to a mantle-like component. Mesozoic/Paleozoic crust and Grenvillian Argentinian lower crust do not fall on or along an extension of these arrays. The ol, plag and groundmassd18O (normalized to melt) of samples covering the full range in Sr-Nd-Pb-Hf isotopic composition lie within the mantle range (5.5-5.9). High Os abundances (~330ppt) in radiogenic Os (187Os/188Os=0.18) samples are not consistent with derivation from a mantle plume or continental crust. eNd and eHf increase to the south along the VF, e.g. eHf ranges from -9 to +10, forming an excellent linear correlation (r2=0.99), indicating that the enriched component is present in the source for >1000km to at least ~43°S. We propose that flattening of the Pampean slab 1) triggered subduction erosion of enriched

Numerical simulations of the mantle lithosphere delamination

Science.gov (United States)

Morency, C.; Doin, M.-P.

2004-03-01

Sudden uplift, extension, and increased igneous activity are often explained by rapid mechanical thinning of the lithospheric mantle. Two main thinning mechanisms have been proposed, convective removal of a thickened lithospheric root and delamination of the mantle lithosphere along the Moho. In the latter case, the whole mantle lithosphere peels away from the crust by the propagation of a localized shear zone and sinks into the mantle. To study this mechanism, we perform two-dimensional (2-D) numerical simulations of convection using a viscoplastic rheology with an effective viscosity depending strongly on temperature, depth, composition (crust/mantle), and stress. The simulations develop in four steps. (1) We first obtain "classical" sublithospheric convection for a long time period (˜300 Myr), yielding a slightly heterogeneous lithospheric temperature structure. (2) At some time, in some simulations, a strong thinning of the mantle occurs progressively in a small area (˜100 km wide). This process puts the asthenosphere in direct contact with the lower crust. (3) Large pieces of mantle lithosphere then quickly sink into the mantle by the horizontal propagation of a detachment level away from the "asthenospheric conduit" or by progressive erosion on the flanks of the delaminated area. (4) Delamination pauses or stops when the lithospheric mantle part detaches or when small-scale convection on the flanks of the delaminated area is counterbalanced by heat diffusion. We determine the parameters (crustal thicknesses, activation energies, and friction coefficients) leading to delamination initiation (step 2). We find that delamination initiates where the Moho temperature is the highest, as soon as the crust and mantle viscosities are sufficiently low. Delamination should occur on Earth when the Moho temperature exceeds ˜800°C. This condition can be reached by thermal relaxation in a thickened crust in orogenic setting or by corner flow lithospheric erosion in the

Tenancy and African American Marriage in the Postbellum South.

Science.gov (United States)

Bloome, Deirdre; Muller, Christopher

2015-10-01

The pervasiveness of tenancy in the postbellum South had countervailing effects on marriage between African Americans. Tenancy placed severe constraints on African American women's ability to find independent agricultural work. Freedwomen confronted not only planters' reluctance to contract directly with women but also whites' refusal to sell land to African Americans. Marriage consequently became one of African American women's few viable routes into the agricultural labor market. We find that the more counties relied on tenant farming, the more common was marriage among their youngest and oldest African American residents. However, many freedwomen resented their subordinate status within tenant marriages. Thus, we find that tenancy contributed to union dissolution as well as union formation among freedpeople. Microdata tracing individuals' marital transitions are consistent with these county-level results.

STUDIES ON SOUTH AMERICAN YELLOW FEVER

Science.gov (United States)

Davis, Nelson C.; Shannon, Raymond C.

1929-01-01

Yellow fever virus from M. rhesus has been inoculated into a South American monkey (Cebus macrocephalus) by blood injection and by bites of infected mosquitoes. The Cebus does not develop the clinical or pathological signs of yellow fever. Nevertheless, the virus persists in the Cebus for a time as shown by the typical symptoms and lesions which develop when the susceptible M. rhesus is inoculated from a Cebus by direct transfer of blood or by mosquito (A. aegypti) transmission. PMID:19869607

The evolutionary history of Lygodactylus lizards in the South American open diagonal.

Science.gov (United States)

Lanna, Flávia M; Werneck, Fernanda P; Gehara, Marcelo; Fonseca, Emanuel M; Colli, Guarino R; Sites, Jack W; Rodrigues, Miguel T; Garda, Adrian A

2018-06-12

The Pleistocenic Arc Hypothesis (PAH) posits that South American Seasonally Dry Tropical Forests (SDTF) were interconnected during Pleistocene glacial periods, enabling the expansion of species ranges that were subsequently fragmented in interglacial periods, promoting speciation. The lizard genus Lygodactylus occurs in Africa, Madagascar, and South America. Compared to the high diversity of African Lygodactylus, only two species are known to occur in South America, L. klugei and L. wetzeli, distributed in SDTFs and the Chaco, respectively. We use a phylogenetic approach based on mitochondrial (ND2) and nuclear (RAG-1) markers covering the known range of South American Lygodactylus to investigate (i) if they are monophyletic relative to their African congeners, (ii) if their divergence is congruent with the fragmentation of the PAH, and (iii) if cryptic diversity exists within currently recognized species. Maximum likelihood and Bayesian phylogenetic analyses recovered a well-supported monophyletic South American Lygodactylus, presumably resulting from a single trans-Atlantic dispersal event 29 Mya. Species delimitation analyses supported the existence of five putative species, three of them undescribed. Divergence times among L. klugei and the three putative undescribed species, all endemic to the SDTFs, are not congruent with the fragmentation of the PAH. However, fragmentation of the once broader and continuous SDTFs likely influenced the divergence of L. wetzeli in the Chaco and Lygodactylus sp. 3 (in a SDTF enclave in the Cerrado). Copyright © 2018. Published by Elsevier Inc.

The contribution of the Precambrian continental lithosphere to global H2 production.

Science.gov (United States)

Lollar, Barbara Sherwood; Onstott, T C; Lacrampe-Couloume, G; Ballentine, C J

2014-12-18

Microbial ecosystems can be sustained by hydrogen gas (H2)-producing water-rock interactions in the Earth's subsurface and at deep ocean vents. Current estimates of global H2 production from the marine lithosphere by water-rock reactions (hydration) are in the range of 10(11) moles per year. Recent explorations of saline fracture waters in the Precambrian continental subsurface have identified environments as rich in H2 as hydrothermal vents and seafloor-spreading centres and have suggested a link between dissolved H2 and the radiolytic dissociation of water. However, extrapolation of a regional H2 flux based on the deep gold mines of the Witwatersrand basin in South Africa yields a contribution of the Precambrian lithosphere to global H2 production that was thought to be negligible (0.009 × 10(11) moles per year). Here we present a global compilation of published and new H2 concentration data obtained from Precambrian rocks and find that the H2 production potential of the Precambrian continental lithosphere has been underestimated. We suggest that this can be explained by a lack of consideration of additional H2-producing reactions, such as serpentinization, and the absence of appropriate scaling of H2 measurements from these environments to account for the fact that Precambrian crust represents over 70 per cent of global continental crust surface area. If H2 production via both radiolysis and hydration reactions is taken into account, our estimate of H2 production rates from the Precambrian continental lithosphere of 0.36-2.27 × 10(11) moles per year is comparable to estimates from marine systems.

Impact of lithospheric rheology on surface topography

Science.gov (United States)

Liao, K.; Becker, T. W.

2017-12-01

The expression of mantle flow such as due to a buoyant plume as surface topography is a classical problem, yet the role of rheological complexities could benefit from further exploration. Here, we investigate the topographic expressions of mantle flow by means of numerical and analytical approaches. In numerical modeling, both conventional, free-slip and more realistic, stress-free boundary conditions are applied. For purely viscous rheology, a high viscosity lithosphere will lead to slight overestimates of topography for certain settings, which can be understood by effectively modified boundary conditions. Under stress-free conditions, numerical and analytical results show that the magnitude of dynamic topography decreases with increasing lithosphere thickness (L) and viscosity (ηL), as L-1 and ηL-3. The wavelength of dynamic topography increases linearly with L and (ηL/ ηM) 1/3. We also explore the time-dependent interactions of a rising plume with the lithosphere. For a layered lithosphere with a decoupling weak lower crust embedded between stronger upper crust and lithospheric mantle, dynamic topography increases with a thinner and weaker lower crust. The dynamic topography saturates when the decoupling viscosity is 3-4 orders lower than the viscosity of upper crust and lithospheric mantle. We further explore the role of visco-elastic and visco-elasto-plastic rheologies.

Cultural Patterns of South Asian and Southeast Asian Americans.

Science.gov (United States)

Mathews, Rachel

2000-01-01

An overview of South Asian and Southeast Asian Americans is discussed to aid teachers in understanding behaviors exhibited by Asian students. Culture influences in the following areas are explored: family relationships, respect for age, social interaction, communication style, family expectations, humility, school situations, decision making, and…

2009 South American benchmarking study: natural gas transportation companies

Energy Technology Data Exchange (ETDEWEB)

Jordan, Nathalie [Gas TransBoliviano S.A. (Bolivia); Walter, Juliana S. [TRANSPETRO, Rio de Janeiro, RJ (Brazil)

2009-07-01

In the current business environment large corporations are constantly seeking to adapt their strategies. Benchmarking is an important tool for continuous improvement and decision-making. Benchmarking is a methodology that determines which aspects are the most important to be improved upon, and it proposes establishing a competitive parameter in an analysis of the best practices and processes, applying continuous improvement driven by the best organizations in their class. At the beginning of 2008, GTB (Gas TransBoliviano S.A.) contacted several South American gas transportation companies to carry out a regional benchmarking study in 2009. In this study, the key performance indicators of the South American companies, whose reality is similar, for example, in terms of prices, availability of labor, and community relations, will be compared. Within this context, a comparative study of the results, the comparative evaluation among natural gas transportation companies, is becoming an essential management instrument to help with decision-making. (author)

78 FR 50135 - CNC Development, Ltd., Exousia Advanced Materials, Inc., and South American Minerals, Inc.; Order...

Science.gov (United States)

2013-08-16

... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] CNC Development, Ltd., Exousia Advanced Materials, Inc., and South American Minerals, Inc.; Order of Suspension of Trading August 14, 2013. It... securities of South American Minerals, Inc. because it has not filed any periodic reports since it filed a...

Implications for anomalous mantle pressure and dynamic topography from lithospheric stress patterns in the North Atlantic Realm

Science.gov (United States)

Schiffer, Christian; Nielsen, Søren Bom

2016-08-01

With convergent plate boundaries at some distance, the sources of the lithospheric stress field of the North Atlantic Realm are mainly mantle tractions at the base of the lithosphere, lithospheric density structure and topography. Given this, we estimate horizontal deviatoric stresses using a well-established thin sheet model in a global finite element representation. We adjust the lithospheric thickness and the sub-lithospheric pressure iteratively, comparing modelled in plane stress with the observations of the World Stress Map. We find that an anomalous mantle pressure associated with the Iceland and Azores melt anomalies, as well as topography are able to explain the general pattern of the principle horizontal stress directions. The Iceland melt anomaly overprints the classic ridge push perpendicular to the Mid Atlantic ridge and affects the conjugate passive margins in East Greenland more than in western Scandinavia. The dynamic support of topography shows a distinct maximum of c. 1000 m in Iceland and amounts <150 m along the coast of south-western Norway and 250-350 m along the coast of East Greenland. Considering that large areas of the North Atlantic Realm have been estimated to be sub-aerial during the time of break-up, two components of dynamic topography seem to have affected the area: a short-lived, which affected a wider area along the rift system and quickly dissipated after break-up, and a more durable in the close vicinity of Iceland. This is consistent with the appearance of a buoyancy anomaly at the base of the North Atlantic lithosphere at or slightly before continental breakup, relatively fast dissipation of the fringes of this, and continued melt generation below Iceland.

The continental lithosphere: a geochemical perspective

International Nuclear Information System (INIS)

Hawkesworth, C.J.; Person, G.; Turner, S.P.; Calsteren, P. Van; Gallagher, K.

1993-01-01

The lithosphere is the cool strong outler layer of the Earth that is effectively a boundary layer to the convecting interior. The evidence from mantle xenoliths and continental basalts is that the lower continental crust and uppermost mantle are different beneath Archaen and proterozoic areas. Mantle xenoliths from Archaen terrains, principally the Kaapvaal craton in southern Africa, are significantly depleted in Fe and other major elements which are concentrated in basalts. Nd and Os isotope data on inclusions in diamonds and peridoties respectively, indicate that such mantle is as old as the overlying Archaen crust. Since it appears to have been coupled to the overlying crust, and to have been isolated from the homogenising effects of convection for long periods of time, it is inferred to be within the continental lithosphere. The mantle lithosphere beneath Proterozoic and younger areas is less depleted in major elements, and so it is more fertile, less buoyant, and therefore thinner, than the Archaen mantle lithosphere. (author). 136 refs, 14 figs

South American collaboration in scientific publications on leishmaniasis: bibliometric analysis in SCOPUS (2000-2011).

Science.gov (United States)

Huamaní, Charles; Romaní, Franco; González-Alcaide, Gregorio; Mejia, Miluska O; Ramos, José Manuel; Espinoza, Manuel; Cabezas, César

2014-01-01

Evaluate the production and the research collaborative network on Leishmaniasis in South America. A bibliometric research was carried out using SCOPUS database. The analysis unit was original research articles published from 2000 to 2011, that dealt with leishmaniasis and that included at least one South American author. The following items were obtained for each article: journal name, language, year of publication, number of authors, institutions, countries, and others variables. 3,174 articles were published, 2,272 of them were original articles. 1,160 different institutional signatures, 58 different countries and 398 scientific journals were identified. Brazil was the country with more articles (60.7%) and Oswaldo Cruz Foundation (FIOCRUZ) had 18% of Brazilian production, which is the South American nucleus of the major scientific network in Leishmaniasis. South American scientific production on Leishmaniasis published in journals indexed in SCOPUS is focused on Brazilian research activity. It is necessary to strengthen the collaboration networks. The first step is to identify the institutions with higher production, in order to perform collaborative research according to the priorities of each country.

Seismic Constraints on the Lithosphere-Asthenosphere Boundary Beneath the Izu-Bonin Area: Implications for the Oceanic Lithospheric Thinning

Science.gov (United States)

Cui, Qinghui; Wei, Rongqiang; Zhou, Yuanze; Gao, Yajian; Li, Wenlan

2018-01-01

The lithosphere-asthenosphere boundary (LAB) is the seismic discontinuity with negative velocity contrasts in the upper mantle. Seismic detections on the LAB are of great significance in understanding the plate tectonics, mantle convection and lithospheric evolution. In this paper, we study the LAB in the Izu-Bonin subduction zone using four deep earthquakes recorded by the permanent and temporary seismic networks of the USArray. The LAB is clearly revealed with sP precursors (sdP) through the linear slant stacking. As illustrated by reflected points of the identified sdP phases, the depth of LAB beneath the Izu-Bonin Arc (IBA) is about 65 km with a range of 60-68 km. The identified sdP phases with opposite polarities relative to sP phases have the average relative amplitude of 0.21, which means a 3.7% velocity drop and implies partial melting in the asthenosphere. On the basis of the crustal age data, the lithosphere beneath the IBA is located at the 1100 °C isotherm calculated with the GDH1 model. Compared to tectonically stable areas, such as the West Philippine Basin (WPB) and Parece Vela Basin (PVB) in the Philippine Sea, the lithosphere beneath the Izu-Bonin area shows the obvious lithospheric thinning. According to the geodynamic and petrological studies, the oceanic lithospheric thinning phenomenon can be attributed to the strong erosion of the small-scale convection in the mantle wedge enriched in volatiles and melts.

The helium flux from the continents and ubiquity of low-3He/4He recycled crust and lithosphere

Science.gov (United States)

Day, James M. D.; Barry, Peter H.; Hilton, David R.; Burgess, Ray; Pearson, D. Graham; Taylor, Lawrence A.

2015-03-01

New helium isotope and trace-element abundance data are reported for pyroxenites and eclogites from South Africa, Siberia, and the Beni Bousera Massif, Morocco that are widely interpreted to form from recycled oceanic crustal protoliths. The first He isotope data are also presented for Archaean peridotites from the Kaapvaal (South Africa), Slave (Canada), and Siberian cratons, along with recently emplaced off-craton peridotite xenoliths from Kilbourne Hole, San Carlos (USA) and Vitim (Siberia), to complement existing 3He/4He values obtained for continental and oceanic peridotites. Helium isotope compositions of peridotite xenoliths vary from 7.3 to 9.6 RA in recently (volcanics that contain a contribution from asthenospheric sources. Using the new He isotope data for cratonic peridotites and assuming that significant portions (>50%) of the Archaean and Proterozoic continental lithospheric mantle are stable and unaffected by melt or fluid infiltration on geological timescales (>0.1 Ga), and that U and Th contents vary between cratonic lithosphere and non-cratonic lithosphere, calculations yield a 3He flux of 0.25-2.2 atoms/s/cm2 for the continental lithospheric mantle. These estimates differ by a factor of ten from non-cratonic lithospheric mantle and are closer to the observed 3He flux from the continents (<1 atoms/s/cm2). Pyroxenites and eclogites from the continental regions are all characterized by 3He/4He (0.03-5.6 RA) less than the depleted upper mantle, and relatively high U and Th contents. Together with oceanic and continental lithospheric peridotites, these materials represent reservoirs with low time-integrated 3He/(U + Th) in the mantle. Pyroxenites and eclogites are also characterized by higher Fe/Mg, more radiogenic Os-Pb isotope compositions, and more variable δ18O values (∼3‰ to 7‰), compared with peridotitic mantle. These xenoliths are widely interpreted to be the metamorphic/metasomatic equivalents of recycled oceanic crustal protoliths. The

Y-chromosome lineages in native South American population.

Science.gov (United States)

Blanco-Verea, A; Jaime, J C; Brión, M; Carracedo, A

2010-04-01

The present work tries to investigate the population structure and variation of the Amerindian indigenous populations living in Argentina. A total of 134 individuals from three ethnic groups (Kolla, Mapuche and Diaguitas) living in four different regions were collected and analysed for 26 Y-SNPs and 11 Y-STRs. Intra-population variability was analysed, looking for population substructure and neighbour populations were considered for genetic comparative analysis, in order to estimate the contribution of the Amerindian and the European pool, to the current population. We observe a high frequency of R1b1 and Q1a3a* Y-chromosome haplogroups, in the ethnic groups Mapuche, Diaguita and Kolla, characteristic of European and Native American populations, respectively. When we compare our native Argentinean population with other from the South America we also observe that frequency values for Amerindian lineages are relatively lower in our population. These results show a clear Amerindian genetic component but we observe a predominant European influence too, suggesting that typically European male lineages have given rise to the displacement of genuinely Amerindian male lineages in our South American population. Copyright 2009 Elsevier Ireland Ltd. All rights reserved.

Gravity and magnetic modelling in the Vrancea Zone, south-eastern Carpathians: Redefinition of the edge of the East European Craton beneath the south-eastern Carpathians

Science.gov (United States)

Bocin, A.; Stephenson, R.; Matenco, L.; Mocanu, V.

2013-11-01

A 2D gravity and magnetic data model has been constructed along a 71 km densely observed profile, called DACIA PLAN GRAV MAN's. The profile crosses part of the nappe pile of the south-eastern Carpathians and includes the seismically active Vrancea Zone and was acquired with the objective to illuminate the basement structure and affinity in this area. The modelling approach was to create an initial model from well constrained geological information, integrate it with previous seismic ray tracing and tomographic models and then alter it outside the a priori constraints in order to reach the best fit between observed and calculated potential field anomalies. The results support a realignment of the position of the TTZ (Tornquist-Teisseyre Zone), the profound tectonic boundary within Europe that separates Precambrian cratonic lithosphere of the East European Craton (EEC) from younger accreted lithosphere of Phanerozoic mobile belts to its west. The TTZ is shown to lie further to the south-west than was previously inferred within Romania, where it is largely obscured by the Carpathian nappes. The crust of the EEC beneath the south-eastern Carpathians is inferred to terminate along a major crustal structure lying just west of the Vrancea seismogenic zone. The intermediate depth seismicity of the Vrancea Zone therefore lies within the EEC lithosphere, generally supporting previously proposed models invoking delamination of cratonic lithosphere as the responsible mechanism.

Lithospheric processes

International Nuclear Information System (INIS)

Baldridge, W.S.

2000-01-01

The authors used geophysical, geochemical, and numerical modeling to study selected problems related to Earth's lithosphere. We interpreted seismic waves to better characterize the thickness and properties of the crust and lithosphere. In the southwestern US and Tien Shari, crust of high elevation is dynamically supported above buoyant mantle. In California, mineral fabric in the mantle correlate with regional strain history. Although plumes of buoyant mantle may explain surface deformation and magmatism, our geochemical work does not support this mechanism for Iberia. Generation and ascent of magmas remains puzzling. Our work in Hawaii constrains the residence of magma beneath Hualalai to be a few hundred to about 1000 years. In the crust, heat drives fluid and mass transport. Numerical modeling yielded robust and accurate predictions of these processes. This work is important fundamental science, and applies to mitigation of volcanic and earthquake hazards, Test Ban Treaties, nuclear waste storage, environmental remediation, and hydrothermal energy

Lithospheric processes

Energy Technology Data Exchange (ETDEWEB)

Baldridge, W. [and others

2000-12-01

The authors used geophysical, geochemical, and numerical modeling to study selected problems related to Earth's lithosphere. We interpreted seismic waves to better characterize the thickness and properties of the crust and lithosphere. In the southwestern US and Tien Shari, crust of high elevation is dynamically supported above buoyant mantle. In California, mineral fabric in the mantle correlate with regional strain history. Although plumes of buoyant mantle may explain surface deformation and magmatism, our geochemical work does not support this mechanism for Iberia. Generation and ascent of magmas remains puzzling. Our work in Hawaii constrains the residence of magma beneath Hualalai to be a few hundred to about 1000 years. In the crust, heat drives fluid and mass transport. Numerical modeling yielded robust and accurate predictions of these processes. This work is important fundamental science, and applies to mitigation of volcanic and earthquake hazards, Test Ban Treaties, nuclear waste storage, environmental remediation, and hydrothermal energy.

An introduction to South American camelids

International Nuclear Information System (INIS)

Urquieta, B.; Rojas, J.R.

1990-01-01

The South American camelids - the domesticated alpaca and llama, and the wild vicuna and guanaco - which belong to the Camelidae family of the Artiodactyla order are of considerable sociological, economic and ecological importance to the native populations living in the high plateau (altiplano) of the central Andes. Owing to their biological characteristics they are able to provide meat, wool, hides and transportation without disrupting the fragile ecosystem. Increasing interest is being taken in these animals, both in their native lands of Argentina, Bolivia, Chile and Peru and in other parts of the world. (author). 55 refs, 5 figs

The impact of the subtropical South Atlantic SST on South American precipitation

Directory of Open Access Journals (Sweden)

A. S. Taschetto

2008-11-01

Full Text Available The Community Climate Model (CCM3 from the National Center for Atmospheric Research (NCAR is used to investigate the effect of the South Atlantic sea surface temperature (SST anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed.

A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM and spring (SON precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF and winter (JJA rainfall. While the Inter-tropical Convergence Zone (ITCZ region is dominated by external variance, the South Atlantic Convergence Zone (SACZ over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent.

An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño – Southern Oscillation (ENSO. Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic branch during MAM. Both local and

The fossil record of South American short-faced bears (Ursidae, Tremarctinae)

OpenAIRE

Bond, Mariano; Tonni, Eduardo Pedro; Soibelzon, Leopoldo Héctor

2005-01-01

The present study includes a review of the geographic and stratigraphic distribution of short-faced bears (Ursidae, Tremarctinae) in South America. In addition, the authors discuss biogeographic hypotheses regarding the origin of South American tremarctines. The Tremarctinae subfamily is distributed exclusively in America, from Alaska to southern Patagonia. Its biochron comprises the temporal lapse between Late Miocene and recent times; the first record of Tremarctinae in North America corres...

Upper mantle beneath foothills of the western Himalaya: subducted lithospheric slab or a keel of the Indian shield?

Science.gov (United States)

Vinnik, L.; Singh, A.; Kiselev, S.; Kumar, M. Ravi

2007-12-01

The fate of the mantle lithosphere of the Indian Plate in the India-Eurasia collision zone is not well understood. Tomographic studies reveal high P velocity in the uppermost mantle to the south of the western Himalaya, and these high velocities are sometimes interpreted as an image of subducting Indian lithosphere. We suggest that these high velocities are unrelated to the ongoing subduction but correspond to a near-horizontal mantle keel of the Indian shield. In the south of the Indian shield upper-mantle velocities are anomalously low, and relatively high velocities may signify a recovery of the normal shield structure in the north. Our analysis is based on the recordings of seismograph station NIL in the foothills of the western Himalaya. The T component of the P receiver functions is weak relative to the Q component, which is indicative of a subhorizontally layered structure. Joint inversion of the P and S receiver functions favours high uppermost mantle velocities, typical of the lithosphere of Archean cratons. The arrival of the Ps converted phase from 410 km discontinuity at NIL is 2.2 s earlier than in IASP91 global model. This can be an effect of remnants of Tethys subduction in the mantle transition zone and of high velocities in the keel of the Indian shield. Joint inversion of SKS particle motions and P receiver functions reveals a change in the fast direction of seismic azimuthal anisotropy from 60° at 80-160 km depths to 150° at 160-220 km. The fast direction in the lower layer is parallel to the trend of the Himalaya. The change of deformation regimes at a depth of 160 km suggests that this is the base of the lithosphere of the Indian shield. A similar boundary was found with similar techniques in central Europe and the Tien Shan region, but the base of the lithosphere in these regions is relatively shallow, in agreement with the higher upper-mantle temperatures. The ongoing continental collision is expressed in crustal structure: the crust

Lithosphere structure and subsidence evolution of the conjugate S-African and Argentine margins

Science.gov (United States)

Dressel, Ingo; Scheck-Wenderoth, Magdalena; Cacace, Mauro; Götze, Hans-Jürgen; Franke, Dieter

2016-04-01

The bathymetric evolution of the South Atlantic passive continental margins is a matter of debate. Though it is commonly accepted that passive margins experience thermal subsidence as a result of lithospheric cooling as well as load induced subsidence in response to sediment deposition it is disputed if the South Atlantic passive margins were affected by additional processes affecting the subsidence history after continental breakup. We present a subsidence analysis along the SW African margin and offshore Argentina and restore paleobathymetries to assess the subsidence evolution of the margin. These results are discussed with respect to mechanisms behind margin evolution. Therefore, we use available information about the lithosphere-scale present-day structural configuration of these margins as a starting point for the subsidence analysis. A multi 1D backward modelling method is applied to separate individual subsidence components such as the thermal- as well as the load induced subsidence and to restore paleobathymetries for the conjugate margins. The comparison of the restored paleobathymetries shows that the conjugate margins evolve differently: Continuous subsidence is obtained offshore Argentina whereas the subsidence history of the SW African margin is interrupted by phases of uplift. This differing results for both margins correlate also with different structural configurations of the subcrustal mantle. In the light of these results we discuss possible implications for uplift mechanisms.

Global thermal models of the lithosphere

Science.gov (United States)

Cammarano, F.; Guerri, M.

2017-12-01

Unraveling the thermal structure of the outermost shell of our planet is key for understanding its evolution. We obtain temperatures from interpretation of global shear-velocity (VS) models. Long-wavelength thermal structure is well determined by seismic models and only slightly affected by compositional effects and uncertainties in mineral-physics properties. Absolute temperatures and gradients with depth, however, are not well constrained. Adding constraints from petrology, heat-flow observations and thermal evolution of oceanic lithosphere help to better estimate absolute temperatures in the top part of the lithosphere. We produce global thermal models of the lithosphere at different spatial resolution, up to spherical-harmonics degree 24, and provide estimated standard deviations. We provide purely seismic thermal (TS) model and hybrid models where temperatures are corrected with steady-state conductive geotherms on continents and cooling model temperatures on oceanic regions. All relevant physical properties, with the exception of thermal conductivity, are based on a self-consistent thermodynamical modelling approach. Our global thermal models also include density and compressional-wave velocities (VP) as obtained either assuming no lateral variations in composition or a simple reference 3-D compositional structure, which takes into account a chemically depleted continental lithosphere. We found that seismically-derived temperatures in continental lithosphere fit well, overall, with continental geotherms, but a large variation in radiogenic heat is required to reconcile them with heat flow (long wavelength) observations. Oceanic shallow lithosphere below mid-oceanic ridges and young oceans is colder than expected, confirming the possible presence of a dehydration boundary around 80 km depth already suggested in previous studies. The global thermal models should serve as the basis to move at a smaller spatial scale, where additional thermo-chemical variations

Low Seismic Attenuation in Southern New England Lithosphere Implies Little Heating by the Upwelling Asthenosphere

Science.gov (United States)

Lamoureux, J. M.; Menke, W. H.

2017-12-01

The Northern Appalachian Anomaly (NAA) is a patch of the asthenosphere in southern New England that is unusually hot given its passive margin setting. Previous research has detected large seismic wave delays that imply a temperature of 770 deg C higher than the mantle below the adjacent craton at the same depth. A key outstanding issue is whether the NAA interacts with the lithosphere above it (e.g. by heating it up). We study this issue using Po and So waves from two magnitude >5.5 earthquakes near the Puerto Rico Trench. These waves, propagating in the cold oceanic lithosphere at near Moho speeds, deliver high frequency energy to the shallow continental lithosphere. We hypothesized that: (1) once within the continental lithosphere, Po and So experience attenuation with distance that can be quantified by a quality factor Q, and that (2) any heating of the lithosphere above the NAA would lead to a higher Q than in regions further north or south along the continental margin. Corresponding Po and So velocities would also be lower. The decay rates of Po and So are estimated using least-squares applied to RMS coda amplitudes measured from digital seismograms from stations in northeastern North America, corrected for instrument response. A roughly log-linear decrease in amplitude is observed, corresponding to P and S wave quality factors in the range of 394-1500 and 727-6847, respectively. Measurements are made for four margin-perpendicular geographical bands, with one band overlapping the NAA. We detect no effect on these amplitudes by the NAA; 95% confidence bounds overlap in every case; Furthermore, all quality factors are much higher than the 100 predicted by lab experiments for near-solidus mantle rocks. These results suggest that the NAA is not causing significant heating of the lithosphere above it. The shear velocities, however, are about 10% slower above the NAA - an effect that may be fossil, reflecting processes that occurred millions of years ago.

Ancient Continental Lithosphere Dislocated Beneath Ocean Basins Along the Mid-Lithosphere Discontinuity: A Hypothesis

Science.gov (United States)

Wang, Zhensheng; Kusky, Timothy M.; Capitanio, Fabio A.

2017-09-01

The documented occurrence of ancient continental cratonic roots beneath several oceanic basins remains poorly explained by the plate tectonic paradigm. These roots are found beneath some ocean-continent boundaries, on the trailing sides of some continents, extending for hundreds of kilometers or farther into oceanic basins. We postulate that these cratonic roots were left behind during plate motion, by differential shearing along the seismically imaged mid-lithosphere discontinuity (MLD), and then emplaced beneath the ocean-continent boundary. Here we use numerical models of cratons with realistic crustal rheologies drifting at observed plate velocities to support the idea that the mid-lithosphere weak layer fostered the decoupling and offset of the African continent's buoyant cratonic root, which was left behind during Meso-Cenozoic continental drift and emplaced beneath the Atlantic Ocean. We show that in some cratonic areas, the MLD plays a similar role as the lithosphere-asthenosphere boundary for accommodating lateral plate tectonic displacements.

Potential use of the sterile insect technique against the South American fruit fly

International Nuclear Information System (INIS)

Ortiz, G.

1999-01-01

The Latin American countries have a strong interest in increasing fruit production and quality to facilitate commercialization within and outside the region. Various fruit fly control programmes in South America and their objectives and benefits are described here. Specific priorities to improve fruit fly control and eradication technologies include strengthening of quarantine, development of pre- and post-phytosanitary measures, and harmonization of the most effective and advanced technical procedures/methodologies to control fruit flies. A subregional strategy to control fruit flies in South America would promote technical co-operation among the South American countries and strengthen the activities of less advanced fruit fly programmes. Effective use can be made of local/regional infrastructure, expertise, sterile fly production and human/technical resources. In Argentina, advanced technology related to the use of medfly genetic sexing strains for SIT programmes has been successfully introduced. Joint efforts between technicians and scientists would contribute to developing new technology to control important pests in South America. (author)

Mercury's Lithospheric Magnetization

Science.gov (United States)

Johnson, C.; Phillips, R. J.; Philpott, L. C.; Al Asad, M.; Plattner, A.; Mast, S.; Kinczyk, M. J.; Prockter, L. M.

2017-12-01

Magnetic field data obtained by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have been used to demonstrate the presence of lithospheric magnetization on Mercury. Larger amplitude fields resulting from the core dynamo and the strongly time-varying magnetospheric current systems are first estimated and subtracted from the magnetic field data to isolate lithospheric signals with wavelengths less than 500 km. These signals (hereafter referred to as data) are only observed at spacecraft altitudes less than 120 km, and are typically a few to 10 nT in amplitude. We present and compare equivalent source dipole magnetization models for latitudes 35°N to 75°N obtained from two distinct approaches to constrain the distribution and origin of lithospheric magnetization. First, models that fit either the data or the surface field predicted from a regional spherical harmonic representation of the data (see Plattner & Johnson abstract) and that minimize the root mean square (RMS) value of the magnetization are derived. Second, models in which the spatial distribution of magnetization required to fit the data is minimized are derived using the approach of Parker (1991). As seen previously, the largest amplitudes of lithospheric magnetization are concentrated around the Caloris basin. With this exception, across the northern hemisphere there are no overall correlations of magnetization with surface geology, although higher magnetizations are found in regions with darker surfaces. Similarly, there is no systematic correlation of magnetization signatures with crater materials, although there are specific instances of craters with interiors or ejecta that have magnetizations distinct from the surrounding region. For the latter case, we observe no correlation of the occurrence of these signatures with crater degradation state (a proxy for age). At the lowest spacecraft altitudes (source depths less than O(10 km) are unlikely in most regions

SOUTH AMERICAN COLLABORATION IN SCIENTIFIC PUBLICATIONS ON LEISHMANIASIS: BIBLIOMETRIC ANALYSIS IN SCOPUS (2000-2011

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Charles Huamaní

2014-09-01

Full Text Available Objectives: Evaluate the production and the research collaborative network on Leishmaniasis in South America. Methods: A bibliometric research was carried out using SCOPUS database. The analysis unit was original research articles published from 2000 to 2011, that dealt with leishmaniasis and that included at least one South American author. The following items were obtained for each article: journal name, language, year of publication, number of authors, institutions, countries, and others variables. Results: 3,174 articles were published, 2,272 of them were original articles. 1,160 different institutional signatures, 58 different countries and 398 scientific journals were identified. Brazil was the country with more articles (60.7% and Oswaldo Cruz Foundation (FIOCRUZ had 18% of Brazilian production, which is the South American nucleus of the major scientific network in Leishmaniasis. Conclusions: South American scientific production on Leishmaniasis published in journals indexed in SCOPUS is focused on Brazilian research activity. It is necessary to strengthen the collaboration networks. The first step is to identify the institutions with higher production, in order to perform collaborative research according to the priorities of each country.

Piecewise delamination of Moroccan lithosphere from beneath the Atlas Mountains

Science.gov (United States)

Bezada, M. J.; Humphreys, E. D.; Davila, J. M.; Carbonell, R.; Harnafi, M.; Palomeras, I.; Levander, A.

2014-04-01

The elevation of the intracontinental Atlas Mountains of Morocco and surrounding regions requires a mantle component of buoyancy, and there is consensus that this buoyancy results from an abnormally thin lithosphere. Lithospheric delamination under the Atlas Mountains and thermal erosion caused by upwelling mantle have each been suggested as thinning mechanisms. We use seismic tomography to image the upper mantle of Morocco. Our imaging resolves the location and shape of lithospheric cavities and of delaminated lithosphere ˜400 km beneath the Middle Atlas. We propose discontinuous delamination of an intrinsically unstable Atlas lithosphere, enabled by the presence of anomalously hot mantle, as a mechanism for producing the imaged structures. The Atlas lithosphere was made unstable by a combination of tectonic shortening and eclogite loading during Mesozoic rifting and Cenozoic magmatism. The presence of hot mantle sourced from regional upwellings in northern Africa or the Canary Islands enhanced the instability of this lithosphere. Flow around the retreating Alboran slab focused upwelling mantle under the Middle Atlas, which we infer to be the site of the most recent delamination. The Atlas Mountains of Morocco stand as an example of large-scale lithospheric loss in a mildly contractional orogen.

Perspectives of the mercosur parliament performance according to south american political organization

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Clarissa Franzoi Dri

2007-04-01

Full Text Available The signature of the MERCOSUR Parliament Constitutive Protocol, in 2005, has opened new parliamentary perspectives to the integration process which takes place in the South Cone. The nomination “parliament”, the universal suffrage prevision and new legislative and control functions evidence possibilities for an outstanding actuation. But is it possible to consider that this new organ was created in the middle of political conditions favorable to an effective functionality? Looking for traces to an answer, the paper examines political and electoral characteristics common to the South American States. First, we study the daily relations between the Executive and Legislative Powers in South American presidential regimes. Then, we verify to what extent the proportional open-list electoral system, largely used in the election of the lower houses members in the continent, influences such relations. At the end, we discuss the new assembly perspectives of effectiveness based on the regional characteristics studied.

Electricity consumption and economic growth in seven South American countries

International Nuclear Information System (INIS)

Yoo, Seung-Hoon; Kwak, So-Yoon

2010-01-01

This paper attempts to investigate the causal relationship between electricity consumption and economic growth among seven South American countries, namely Argentina, Brazil, Chile, Columbia, Ecuador, Peru, and Venezuela using widely accepted time-series techniques for the period 1975-2006. The results indicate that the causal nexus between electricity consumption and economic growth varies across countries. There is a unidirectional, short-run causality from electricity consumption to real GDP for Argentina, Brazil, Chile, Columbia, and Ecuador. This means that an increase in electricity consumption directly affects economic growth in those countries. In Venezuela, there is a bidirectional causality between electricity consumption and economic growth. This implies that an increase in electricity consumption directly affects economic growth and that economic growth also stimulates further electricity consumption in that country. However, no causal relationships exist in Peru. The documented evidence from seven South American countries can provide useful information for each government with regard to energy and growth policy.

Evolving electrical SCLM models of the Australian continent - results of the South Australia AusLAMP deployment

Science.gov (United States)

Robertson, K. E.; Thiel, S.; Heinson, G. S.

2017-12-01

The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is an Australian initiative to map the Australian continental lithosphere using magnetotelluric (MT) stations to obtain a resistivity model of the subsurface. It is a joint project between Geoscience Australia, state surveys, and Universities. We present new MT 3D inversion results of the largest coherent array of the AusLAMP MT deployments to date covering two-thirds of South Australia, funded largely by the Geological Survey of South Australia with additional funding by Geoscience Australia and The University of Adelaide. The model extends across the South Australian Gawler Craton, including the Eucla Basin to the west of the craton and the Flinders Ranges and Curnamona Province to the east. The MT array covers parts of the Australian lithosphere, which has been largely unexplored with seismic tomography methods and provide a unique insight into the tectonic evolution of the continent. We incorporate 284 long-period (10s-10,000s) MT stations separated roughly every half degree latitude and longitude across an area spanning 1200 km x 800 km, south of latitude -28.5 degrees and from longitude 129 degrees to 141 degrees. We invert 24 discrete periods of the impedance tenor between 7 s and 13,000 s, and 22 different periods of the tipper data between 7s-8000 s period. The results show a heterogeneous lower crust and mantle lithosphere with a primarily resistive mantle (>1000 Ωm) lithosphere in the central and western part of the Gawler Craton and Eucla Domain. The model shows a generally NS oriented electric LAB offset from deeper cratonic lithosphere in the west to a shallow lithosphere along the eastern margin of the Gawler Craton extending further east towards the Proterozoic and Phanerozoic eastern part of Australia. The lower crust is generally resistive with elongated lower crustal conductivity anomalies, which are associated with major translithospheric shear zones likely existent

The American South in the Atlantic World

DEFF Research Database (Denmark)

decisively shaped the history and culture of the American South from colonial times to the modern era. The essays in this interdisciplinary volume examine a wide range of topics, including race, migration, religion, law, slavery, emancipation, literature, memoir, popular culture, and ethnography. At a time...... when there is growing emphasis on globalizing southern studies the collection both demonstrates and critiques the value of Atlantic World perspectives on the region. Equally important, the mix of case studies and state-of-the field essays combines the latest historical thinking on the South’s myriad...

Permeability Barrier Generation in the Martian Lithosphere

Science.gov (United States)

Schools, Joe; Montési, Laurent

2015-11-01

Permeability barriers develop when a magma produced in the interior of a planet rises into the cooler lithosphere and crystallizes more rapidly than the lithosphere can deform (Sparks and Parmentier, 1991). Crystallization products may then clog the porous network in which melt is propagating, reducing the permeability to almost zero, i.e., forming a permeability barrier. Subsequent melts cannot cross the barrier. Permeability barriers have been useful to explain variations in crustal thickness at mid-ocean ridges on Earth (Magde et al., 1997; Hebert and Montési, 2011; Montési et al., 2011). We explore here under what conditions permeability barriers may form on Mars.We use the MELTS thermodynamic calculator (Ghiorso and Sack, 1995; Ghiorso et al., 2002; Asimow et al., 2004) in conjunction with estimated Martian mantle compositions (Morgan and Anders, 1979; Wänke and Dreibus, 1994; Lodders and Fegley, 1997; Sanloup et al., 1999; Taylor 2013) to model the formation of permeability barriers in the lithosphere of Mars. In order to represent potential past and present conditions of Mars, we vary the lithospheric thickness, mantle potential temperature (heat flux), oxygen fugacity, and water content.Our results show that permeability layers can develop in the thermal boundary layer of the simulated Martian lithosphere if the mantle potential temperature is higher than ~1500°C. The various Martian mantle compositions yield barriers in the same locations, under matching variable conditions. There is no significant difference in barrier location over the range of accepted Martian oxygen fugacity values. Water content is the most significant influence on barrier development as it reduces the temperature of crystallization, allowing melt to rise further into the lithosphere. Our lower temperature and thicker lithosphere model runs, which are likely the most similar to modern Mars, show no permeability barrier generation. Losing the possibility of having a permeability

Spirits of the Air: Birds and American Indians in the South

Directory of Open Access Journals (Sweden)

E. N. Anderson

2010-08-01

Full Text Available Review of Spirits of the Air: Birds and American Indians in the South. Shepard Krech III. 2009. University of Georgia Press, Athens. Pp. 245, copiously illustrated. $44.95 (hardbound. ISBN-13 978-0-8203-2815-7.

Ocean-atmosphere forcing of South American tropical paleoclimate, LGM to present

Science.gov (United States)

Baker, P. A.; Fritz, S. C.; Dwyer, G. S.; Rigsby, C. A.; Silva, C. G.; Burns, S. J.

2012-12-01

Because of many recent terrestrial paleoclimatic and marine paleoceanographic records, late Quaternary South American tropical paleoclimate is as well understood as that anywhere in the world. While lessons learned from the recent instrumental record of climate are informative, this record is too short to capture much of the lower frequency variability encountered in the paleoclimate records and much of the observed paleoclimate is without modern analogue. This paleoclimate is known to be regionally variable with significant differences both north and south of the equator and between the western high Andes and eastern lowlands of the Amazon and Nordeste Brazil. Various extrinsic forcing mechanisms affected climate throughout the period, including global concentrations of GHGs, Northern Hemisphere ice sheet forcing, seasonal insolation forcing of the South American summer monsoon (SASM), millennial-scale Atlantic forcing, and Pacific forcing of the large-scale Walker circulation. The magnitude of the climate response to these forcings varied temporally, largely because of the varying amplitude of the forcing itself. For example, during the last glacial, large-amplitude north Atlantic forcing during Heinrich 1 and the LGM itself, led to wet (dry) conditions south (north) of the equator. During the Holocene, Atlantic forcing was lower amplitude, thus seasonal insolation forcing generally predominated with a weaker-than-normal SASM during the early Holocene resulting in dry conditions in the south-western tropics and wet conditions in the eastern lowlands and Nordeste; in the late Holocene seasonal insolation reached a maximum in the southern tropics and climate conditions reversed.

Lithosphere mantle density of the North China Craton based on gravity data

Science.gov (United States)

Xia, B.; Artemieva, I. M.; Thybo, H.

2017-12-01

Based on gravity, seismic and thermal data we constrained the lithospheric mantle density at in-situ and STP condition. The gravity effect of topography, sedimentary cover, Moho and Lithosphere-Asthenosphere Boundary variation were removed from free-air gravity anomaly model. The sedimentary covers with density range from 1.80 g/cm3 with soft sediments to 2.40 g/cm3 with sandstone and limestone sediments. The average crustal density with values of 2.70 - 2.78 g/cm3 which corresponds the thickness and density of the sedimentary cover. Based on the new thermal model, the surface heat flow in original the North China Craton including western block is > 60 mW/m2. Moho temperature ranges from 450 - 600 OC in the eastern block and in the western block is 550 - 650 OC. The thermal lithosphere is 100 -140 km thick where have the surface heat flow of 60 - 70 mW/m2. The gravity effect of surface topography, sedimentary cover, Moho depth are 0 to +150 mGal, - 20 to -120 mGal and +50 to -200 mGal, respectively. By driving the thermal lithosphere, the gravity effect of the lithosphere-asthenosphere boundary ranges from 20 mGal to +200 mGal which shows strong correction with the thickness of the lithosphere. The relationship between the gravity effect of the lithosphere-asthenosphere boundary and the lithosphere thickness also for the seismic lithosphere, and the value of gravity effect is 0 to +220 mGal. The lithospheric mantle residual gravity which caused by lithospheric density variation range from -200 to +50 mGal by using the thermal lithosphere and from -250 to +100 mGal by driving the seismic lithosphere. For thermal lithosphere, the lithospheric mantle density with values of 3.21- 3.26 g/cm3 at in-situ condition and 3.33 - 3.38 g/cm3 at STP condition. Using seismic lithosphere, density of lithosphere ranges from 3.20 - 3.26 g/cm3 at in-situ condition and 3.31 - 3.41 g/cm3 at STP condition. The subcontinental lithosphere of the North China Craton is highly heterogeneous

A bayesian approach to genome/linguistic relationships in native South Americans.

Science.gov (United States)

Amorim, Carlos Eduardo Guerra; Bisso-Machado, Rafael; Ramallo, Virginia; Bortolini, Maria Cátira; Bonatto, Sandro Luis; Salzano, Francisco Mauro; Hünemeier, Tábita

2013-01-01

The relationship between the evolution of genes and languages has been studied for over three decades. These studies rely on the assumption that languages, as many other cultural traits, evolve in a gene-like manner, accumulating heritable diversity through time and being subjected to evolutionary mechanisms of change. In the present work we used genetic data to evaluate South American linguistic classifications. We compared discordant models of language classifications to the current Native American genome-wide variation using realistic demographic models analyzed under an Approximate Bayesian Computation (ABC) framework. Data on 381 STRs spread along the autosomes were gathered from the literature for populations representing the five main South Amerindian linguistic groups: Andean, Arawakan, Chibchan-Paezan, Macro-Jê, and Tupí. The results indicated a higher posterior probability for the classification proposed by J.H. Greenberg in 1987, although L. Campbell's 1997 classification cannot be ruled out. Based on Greenberg's classification, it was possible to date the time of Tupí-Arawakan divergence (2.8 kya), and the time of emergence of the structure between present day major language groups in South America (3.1 kya).

Daily and seasonal activity patterns of free range South-American rattlesnake (Crotalus durissus).

Science.gov (United States)

Tozetti, Alexandro M; Martins, Marcio

2013-09-01

This study aimed at describing daily and seasonal variation in the activity of a population of South-American rattlesnakes (Crotalus durissus) in a savanna like habitat (Cerrado) in Southeastern Brazil. Seasonal and daily activities of snakes were evaluated by the number of captures of snakes during road surveys, accidental encounters, and relocations by radio-tracking. Our results show that climatic variables such as air temperature and rainfall have little influence on the activity pattern of rattlesnakes. Our findings indicate that rattlesnakes spend most of the day resting and most of the night in ambush posture. The South-American rattlesnake is active throughout the year with a discrete peak in activity of males during the matting season. The possibility of maintaining activity levels even during the coldest and driest season can facilitate the colonization of several habitats in South America. This possibility currently facilitates the colonization of deforested areas by rattlesnakes.

DESTRUCTION OF THE LITHOSPHERE: FAULTBLOCK DIVISIBILITY AND ITS TECTONOPHYSICAL REGULARITIES

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Semen I. Sherman

2012-01-01

Full Text Available A new concept is proposed concerning the origin and inception of ‘initial’ faults and formation of large blocks as a result of cooling of the Archaean lithosphere, during which Benard cells had formed (Fig. 5. At locations where cooling convection currents went down, partial crystallization took place, stresses were localized, and initial fault occurred there. The systems of such fault developed mainly in two directions and gradually formed an initial block pattern of the lithosphere. This pattern is now represented by the largest Archaean faults acting as boundaries of the lithospheric plates and large intraplate blocks (Fig. 6. This group of faults represents the first scaletime level of destruction of the lithosphere. Large blocks of the first (and may be the second order, which are located on the viscous foundation, interacted with each other under the influence of the sublithospheric movements or endogenous sources and thus facilitated the occurrence of high stresses inside the blocks. When the limits of strength characteristics of the block medium were exceeded, the intrablock stresses were released and caused formation of fractures/faults and blocks of various ranks (Fig. 14. This large group, including faultblock structures of various ranks and ages, comprises the second level of the scaletime destruction of the lithosphere.The intense evolution of ensembles of faults and blocks of the second scaletime level is facilitated by shortterm activation of faultblock structures of the lithosphere under the influence of strain waves. Periods of intensive shortterm activation are reliably detected by seismic monitoring over the past fifty years. Investigations of periodical processes specified in the geological records over the post-Proterozoic periods [Khain, Khalilov, 2009] suggest that in so far uninvestigated historical and more ancient times, the top of the lithosphere was subject to wave processes that �

Formation and temporal evolution of the Kalahari sub-cratonic lithospheric mantle: Constraints from Venetia xenoliths, South Africa

NARCIS (Netherlands)

Hin, R.C.; Morel, M.L.A.; Nebel, O.; Mason, P.R.D.; van Westrenen, W.; Davies, G.R.

2009-01-01

The ~533 Ma Venetia Diamond Mine is located between the Kaapvaal and Zimbabwe Cratons and the study of selected xenoliths provides the opportunity to investigate the temporal evolution of the sub-continental lithospheric mantle (SCLM) underneath southern Africa, as well as the extent and potentially

The westward drift of the lithosphere: A tidal ratchet?

Directory of Open Access Journals (Sweden)

A. Carcaterra

2018-03-01

Full Text Available Is the westerly rotation of the lithosphere an ephemeral accidental recent phenomenon or is it a stable process of Earth's geodynamics? The reason why the tidal drag has been questioned as the mechanism determining the lithospheric shift relative to the underlying mantle is the apparent too high viscosity of the asthenosphere. However, plate boundaries asymmetries are a robust indication of the ‘westerly’ decoupling of the entire Earth's outer lithospheric shell and new studies support lower viscosities in the low-velocity layer (LVZ atop the asthenosphere. Since the solid Earth tide oscillation is longer in one side relative to the other due to the contemporaneous Moon's revolution, we demonstrate that a non-linear rheological behavior is expected in the lithosphere mantle interplay. This may provide a sort of ratchet favoring lowering of the LVZ viscosity under shear, allowing decoupling in the LVZ and triggering the westerly motion of the lithosphere relative to the mantle.

New species of Bidessonotus Régimbart, 1895 with a review of the South American species (Coleoptera, Adephaga, Dytiscidae, Hydroporinae, Bidessini

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Kelly Miller

2016-10-01

Full Text Available The South American species of the New World genus Bidessonotus Régimbart, 1895 are reviewed with descriptions of seven new species. This brings the total number of valid Bidessonotus species to 37, making it the largest Bidessini genus in the New World. The new species are B. annae sp. n. (Venezuela, B. josiahi sp. n. (Venezuela, B. palecephalus sp. n. (Venezuela, B. reductus sp. n. (Venezuela, B. septimus sp. n. (Venezuela, B. spinosus sp. n. (Venezuela, and B. valdezi sp. n. (Guyana, Suriname. New distribution records are provided for many other South American Bidessonotus species. The main diagnostic features of Bidessonotus species are in the male genitalia, and these are illustrated for all South American species. Diagnostic features, distributions (including distribution maps, and additional comments are provided for all South American species.

Petrology of Serpentinites and Rodingites in the Oceanic Lithosphere

OpenAIRE

Klein, Frieder

2009-01-01

Serpentinization, steatitization, and rodingitization are consequences of seawater reaction with lithospheric mantle. These processes take place coevally within the oceanic lithosphere and are related to circulation pathways, lithologic makeup of rocks along the flow path, fluid flux, and temperature. While the boundary conditions are set by the history of magmatic and tectonic accretion of the lithosphere, fluid-rock equilibria determine what reactions take place and where in the system. Pet...

Lithospheric structure of southern Indian shield and adjoining oceans: integrated modelling of topography, gravity, geoid and heat flow data

Science.gov (United States)

Kumar, Niraj; Zeyen, H.; Singh, A. P.; Singh, B.

2013-07-01

For the present 2-D lithospheric density modelling, we selected three geotransects of more than 1000 km in length each crossing the southern Indian shield, south of 16°N, in N-S and E-W directions. The model is based on the assumption of local isostatic equilibrium and is constrained by the topography, gravity and geoid anomalies, by geothermal data, and where available by seismic data. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ˜40 km beneath the Dharwar Craton, and ˜39 km beneath the Southern Granulite Terrane to about 15-20 km beneath the adjoining oceans. The lithospheric thickness varies significantly along the three profiles from ˜70-100 km under the adjoining oceans to ˜130-135 km under the southern block of Southern Granulite Terrane including Sri Lanka and increasing gradually to ˜165-180 km beneath the northern block of Southern Granulite Terrane and the Dharwar Craton. This step-like lithosphere-asthenosphere boundary (LAB) structure indicates a normal lithospheric thickness beneath the adjoining oceans, the northern block of Southern Granulite Terrane and the Dharwar Craton. The thin lithosphere below the southern block of Southern Granulite Terrane including Sri Lanka is, however, atypical considering its age. Our results suggest that the southern Indian shield as a whole cannot be supported isostatically only by thickened crust; a thin and hot lithosphere beneath the southern block of Southern Granulite Terrane including Sri Lanka is required to explain the high topography, gravity, geoid and crustal temperatures. The widespread thermal perturbation during Pan-African (550 Ma) metamorphism and the breakup of Gondwana during late Cretaceous are proposed as twin cause mechanism for the stretching and/or convective removal of the lower part of lithospheric mantle and its replacement by hotter and lighter asthenosphere in the southern block of Southern Granulite Terrane including Sri Lanka

Antarctic Lithosphere Studies: Progress, Problems and Promise

Science.gov (United States)

Dalziel, I. W. D.; Wilson, T. J.

2017-12-01

In the sixty years since the International Geophysical Year, studies of the Antarctic lithosphere have progressed from basic geological observations and sparse geophysical measurements to continental-scale datasets of radiometric dates, ice thickness, bedrock topography and characteristics, seismic imaging and potential fields. These have been augmented by data from increasingly dense broadband seismic and geodetic networks. The Antarctic lithosphere is known to have been an integral part, indeed a "keystone" of the Pangea ( 250-185Ma) and Gondwanaland ( 540-180 Ma) supercontinents. It is widely believed to have been part of hypothetical earlier supercontinents Rodinia ( 1.0-0.75 Ga) and Columbia (Nuna) ( 2.0-1.5 Ga). Despite the paucity of exposure in East Antarctica, the new potential field datasets have emboldened workers to extrapolate Precambrian geological provinces and structures from neighboring continents into Antarctica. Hence models of the configuration of Columbia and its evolution into Rodinia and Gondwana have been proposed, and rift-flank uplift superimposed on a Proterozoic orogenic root has been hypothesized to explain the Gamburtsev Subglacial Mountains. Mesozoic-Cenozoic rifting has imparted a strong imprint on the West Antarctic lithosphere. Seismic tomographic evidence reveals lateral variation in lithospheric thickness, with the thinnest zones within the West Antarctic rift system and underlying the Amundsen Sea Embayment. Upper mantle low velocity zones are extensive, with a deeper mantle velocity anomaly underlying Marie Byrd Land marking a possible mantle plume. Misfits between crustal motions measured by GPS and GIA model predictions can, in part, be linked with the changes in lithosphere thickness and mantle rheology. Unusually high uplift rates measured by GPS in the Amundsen region can be interpreted as the response of regions with thin lithosphere and weak mantle to late Holocene ice mass loss. Horizontal displacements across the TAM

Daily and seasonal activity patterns of free range South-American rattlesnake (Crotalus durissus

Directory of Open Access Journals (Sweden)

ALEXANDRO M. TOZETTI

2013-09-01

Full Text Available This study aimed at describing daily and seasonal variation in the activity of a population of South-American rattlesnakes (Crotalus durissus in a savanna like habitat (Cerrado in Southeastern Brazil. Seasonal and daily activities of snakes were evaluated by the number of captures of snakes during road surveys, accidental encounters, and relocations by radio-tracking. Our results show that climatic variables such as air temperature and rainfall have little influence on the activity pattern of rattlesnakes. Our findings indicate that rattlesnakes spend most of the day resting and most of the night in ambush posture. The South-American rattlesnake is active throughout the year with a discrete peak in activity of males during the matting season. The possibility of maintaining activity levels even during the coldest and driest season can facilitate the colonization of several habitats in South America. This possibility currently facilitates the colonization of deforested areas by rattlesnakes.

Combined constraints on the structure and physical properties of the East Antarctic lithosphere from geology and geophysics.

Science.gov (United States)

Reading, A. M.; Staal, T.; Halpin, J.; Whittaker, J. M.; Morse, P. E.

2017-12-01

The lithosphere of East Antarctica is one of the least explored regions of the planet, yet it is gaining in importance in global scientific research. Continental heat flux density and 3D glacial isostatic adjustment studies, for example, rely on a good knowledge of the deep structure in constraining model inputs.In this contribution, we use a multidisciplinary approach to constrain lithospheric domains. To seismic tomography models, we add constraints from magnetic studies and also new geological constraints. Geological knowledge exists around the periphery of East Antarctica and is reinforced in the knowledge of plate tectonic reconstructions. The subglacial geology of the Antarctic hinterland is largely unknown but the plate reconstructions allow the well-posed extrapolation of major terranes into the interior of the continent, guided by the seismic tomography and magnetic images. We find that the northern boundary of the lithospheric domain centred on the Gamburtsev Subglacial Mountains has a possible trend that runs south of the Lambert Glacier region, turning coastward through Wilkes Land. Other periphery-to-interior connections are less well constrained and the possibility of lithospheric domains that are entirely sub-glacial is high. We develop this framework to include a probabilistic method of handling alternate models and quantifiable uncertainties. We also show first results in using a Bayesian approach to predicting lithospheric boundaries from multivariate data.Within the newly constrained domains, we constrain heat flux (density) as the sum of basal heat flux and upper crustal heat flux. The basal heat flux is constrained by geophysical methods while the upper crustal heat flux is constrained by geology or predicted geology. In addition to heat flux constraints, we also consider the variations in friction experienced by moving ice sheets due to varying geology.

African American Medical Culture in the Antebellum South: As Remembered in the WPA Narratives

OpenAIRE

Barber, Daniel

2015-01-01

This project examines the oral accounts of former slaves, as recorded in the WPA narratives in the 1930s, to study the development of African American medical culture in the Antebellum South. Through an examination of these transcribed memories, my research investigates how African American praxes with medicinal flora, healing techniques, and spiritual harmony, reflected their ethnomedical and cosmological ideologies. The duality of these ideologies represents an African American medical iden...

Does the "mantle" helium signature provide useful information about lithospheric architecture of Tibet/Himalaya?

Science.gov (United States)

Klemperer, S. L.; Liu, T.; Hilton, D. R.; Karlstrom, K. E.; Crossey, L. J.; Zhao, P.

2015-12-01

Measurements of 3He/4He > 0.1*Ra (where Ra = 3He/4He in Earth's atmosphere) in geothermal fluids are conventionally taken to represent derivation from a mantle source. 3He/4He values 0.1*Ra may still be argued to result from mantle-derived 3He previously stored in the crust. However, our growing regional database of widely spaced observations of 3He/4He > 0.1*Ra, from the Karakoram Fault in the west to the Sangri-Cona rift and Yalaxiangbo Dome in the east, and from south of the Yarlung-Zangbo suture (YZS) to north of the Banggong-Nujiang suture, makes such special pleading increasingly implausible. The observation of 3He/4He > 0.1*Ra at the YZS and even within the Tethyan Himalaya south of the YZS cannot represent melting of Indian mantle close to the Moho unless existing thermal models are grossly in error. The source of 3He close to the YZS is likely either asthenosphere accessed by faults and shear zones that cut through subducting Indian lithospheric mantle; or incipient melt of Asian lithospheric mantle at the Moho north of the northern edge of underthrust India (the "mantle suture") which must therefore lie close to the YZS. Thus far we have barely tapped the rich potential that helium-isotope data offer for understanding transit of mantle volatiles through some of Earth's thickest (and ductilely flowing) crust.

Post-processing scheme for modelling the lithospheric magnetic field

Directory of Open Access Journals (Sweden)

V. Lesur

2013-03-01

Full Text Available We investigated how the noise in satellite magnetic data affects magnetic lithospheric field models derived from these data in the special case where this noise is correlated along satellite orbit tracks. For this we describe the satellite data noise as a perturbation magnetic field scaled independently for each orbit, where the scaling factor is a random variable, normally distributed with zero mean. Under this assumption, we have been able to derive a model for errors in lithospheric models generated by the correlated satellite data noise. Unless the perturbation field is known, estimating the noise in the lithospheric field model is a non-linear inverse problem. We therefore proposed an iterative post-processing technique to estimate both the lithospheric field model and its associated noise model. The technique has been successfully applied to derive a lithospheric field model from CHAMP satellite data up to spherical harmonic degree 120. The model is in agreement with other existing models. The technique can, in principle, be extended to all sorts of potential field data with "along-track" correlated errors.

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

Science.gov (United States)

Ward, Kevin Michael

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

In situ rheology of the oceanic lithosphere along the Hawaiian ridge

Science.gov (United States)

Pleus, A.; Ito, G.; Wessel, P.; Frazer, L. N.

2017-12-01

Much of our quantitative understanding of lithospheric rheology is based on rock deformation experiments carried out in the laboratory. The accuracy of the relationships between stress and lithosphere deformation, however, are subject to large extrapolations, given that laboratory strain rates (10-7 s-1) are much greater than geologic rates (10-15 to 10-12 s-1). In situ deformation experiments provide independent constraints and are therefore needed to improve our understanding of natural rheology. Zhong and Watts [2013] presented such a study around the main Hawaiian Islands and concluded that the lithosphere flexure requires a much weaker rheology than predicted by laboratory experiments. We build upon this study by investigating flexure around the older volcanoes of the Hawaiian ridge. The ridge is composed of a diversity of volcano sizes that loaded seafloor of nearly constant age (85+/-8 Ma); this fortunate situation allows for an analysis of flexural responses to large variations in applied loads at nearly constant age-dependent lithosphere thermal structure. Our dataset includes new marine gravity and multi-beam bathymetry data collected onboard the Schmidt Ocean Institute's R/V Falkor. These data, along with forward models of lithospheric flexure, are used to obtain a joint posterior probability density function for model parameters that control the lithosphere's flexural response to a given load. These parameters include the frictional coefficient constraining brittle failure in the shallow lithosphere, the activation energy for the low-temperature plasticity regime, and the geothermal gradient of the Hawaiian lithosphere. The resulting in situ rheological parameters may be used to verify or update those derived in the lab. Attaining accurate lithospheric rheological properties is important to our knowledge, not only of the evolution of the Hawaiian lithosphere, but also of other solid-earth geophysical problems, such as oceanic earthquakes, subduction

Updated Reference Model for Heat Generation in the Lithosphere

Science.gov (United States)

Wipperfurth, S. A.; Sramek, O.; Roskovec, B.; Mantovani, F.; McDonough, W. F.

2017-12-01

Models integrating geophysics and geochemistry allow for characterization of the Earth's heat budget and geochemical evolution. Global lithospheric geophysical models are now constrained by surface and body wave data and are classified into several unique tectonic types. Global lithospheric geochemical models have evolved from petrological characterization of layers to a combination of petrologic and seismic constraints. Because of these advances regarding our knowledge of the lithosphere, it is necessary to create an updated chemical and physical reference model. We are developing a global lithospheric reference model based on LITHO1.0 (segmented into 1°lon x 1°lat x 9-layers) and seismological-geochemical relationships. Uncertainty assignments and correlations are assessed for its physical attributes, including layer thickness, Vp and Vs, and density. This approach yields uncertainties for the masses of the crust and lithospheric mantle. Heat producing element abundances (HPE: U, Th, and K) are ascribed to each volume element. These chemical attributes are based upon the composition of subducting sediment (sediment layers), composition of surface rocks (upper crust), a combination of petrologic and seismic correlations (middle and lower crust), and a compilation of xenolith data (lithospheric mantle). The HPE abundances are correlated within each voxel, but not vertically between layers. Efforts to provide correlation of abundances horizontally between each voxel are discussed. These models are used further to critically evaluate the bulk lithosphere heat production in the continents and the oceans. Cross-checks between our model and results from: 1) heat flux (Artemieva, 2006; Davies, 2013; Cammarano and Guerri, 2017), 2) gravity (Reguzzoni and Sampietro, 2015), and 3) geochemical and petrological models (Rudnick and Gao, 2014; Hacker et al. 2015) are performed.

First South American Agathis (Araucariaceae), Eocene of Patagonia.

Science.gov (United States)

Wilf, Peter; Escapa, Ignacio H; Cúneo, N Rubén; Kooyman, Robert M; Johnson, Kirk R; Iglesias, Ari

2014-01-01

Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that range over lowland to upper montane rainforests from New Zealand to Sumatra. Exploitation of its timber and copal has greatly reduced the genus's numbers. The early fossil record of Agathis comes entirely from Australia, often presumed to be its area of origin. Agathis has no previous record from South America. We describe abundant macrofossils of Agathis vegetative and reproductive organs, from early and middle Eocene rainforest paleofloras of Patagonia, Argentina. The leaves were formerly assigned to the New World cycad genus Zamia. Agathis zamunerae sp. nov. is the first South American occurrence and the most complete representation of Agathis in the fossil record. Its morphological features are fully consistent with the living genus. The most similar living species is A. lenticula, endemic to lower montane rainforests of northern Borneo. Agathis zamunerae sp. nov. demonstrates the presence of modern-aspect Agathis by 52.2 mya and vastly increases the early range and possible areas of origin of the genus. The revision from Zamia breaks another link between the Eocene and living floras of South America. Agathis was a dominant, keystone element of the Patagonian Eocene floras, alongside numerous other plant taxa that still associate with it in Australasia and Southeast Asia. Agathis extinction in South America was an integral part of the transformation of Patagonian biomes over millions of years, but the living species are disappearing from their ranges at a far greater rate.

Mitogenomic phylogeny, diversification, and biogeography of South American spiny rats

DEFF Research Database (Denmark)

Fabre, Pierre-Henri; Upham, Nathan S.; Emmons, Louise H.

2017-01-01

Echimyidae is one of the most speciose and ecologically diverse rodent families in the world, occupying a wide range of habitats in the Neotropics. However, a resolved phylogeny at the genus-level is still lacking for these 22 genera of South American spiny rats, including the coypu (Myocastorina...... Atlantic and Amazonian Forests and (2) the Northern uplift of the Andes....

South American Guidelines for Cardiovascular Disease Prevention and Rehabilitation

Directory of Open Access Journals (Sweden)

AH Herdy

2014-08-01

Full Text Available In this document, the Inter-American Committee of Cardiovascular Prevention and Rehabilitation, together with the South American Society of Cardiology, aimed to formulate strategies, measures, and actions for cardiovascular disease prevention and rehabilitation (CVDPR. In the context of the implementation of a regional and national health policy in Latin American countries, the goal is to promote cardiovascular health and thereby decrease morbidity and mortality. The study group on Cardiopulmonary and Metabolic Rehabilitation from the Department of Exercise, Ergometry, and Cardiovascular Rehabilitation of the Brazilian Society of Cardiology has created a committee of experts to review the Portuguese version of the guideline and adapt it to the national reality. The mission of this document is to help health professionals to adopt effective measures of CVDPR in the routine clinical practice. The publication of this document and its broad implementation will contribute to the goal of the World Health Organization (WHO, which is the reduction of worldwide cardiovascular mortality by 25% until 2025. The study group's priorities are the following: • Emphasize the important role of CVDPR as an instrument of secondary prevention with significant impact on cardiovascular morbidity and mortality; • Join efforts for the knowledge on CVDPR, its dissemination, and adoption in most cardiovascular centers and institutes in South America, prioritizing the adoption of cardiovascular prevention methods that are comprehensive, practical, simple and which have a good cost/benefit ratio; • Improve the education of health professionals and patients with education programs on the importance of CVDPR services, which are directly targeted at the health system, clinical staff, patients, and community leaders, with the aim of decreasing the barriers to CVDPR implementation.

Explaining and improving breast cancer information acquisition among African American women in the Deep South.

Science.gov (United States)

Anderson-Lewis, Charkarra; Ross, Levi; Johnson, Jarrett; Hastrup, Janice L; Green, B Lee; Kohler, Connie L

2012-06-01

A major challenge facing contemporary cancer educators is how to optimize the dissemination of breast cancer prevention and control information to African American women in the Deep South who are believed to be cancer free. The purpose of this research was to provide insight into the breast cancer information-acquisition experiences of African American women in Alabama and Mississippi and to make recommendations on ways to better reach members of this high-risk, underserved population. Focus group methodology was used in a repeated, cross-sectional research design with 64 African American women, 35 years old or older who lived in one of four urban or rural counties in Alabama and Mississippi. Axial-coded themes emerged around sources of cancer information, patterns of information acquisition, characteristics of preferred sources, and characteristics of least-preferred sources. It is important to invest in lay health educators to optimize the dissemination of breast cancer information to African American women who are believed to be cancer free in the Deep South.

SPECIFIC FEATURES OF DEFORMATION OF THE CONTINENTAL AND OCEANIC LITHOSPHERE AS A RESULT OF THE EARTH CORE NORTHERN DRIFT

Directory of Open Access Journals (Sweden)

Mikhail A. Goncharov

2012-01-01

drifting (Figures 26, and 27.By comparing the equations that describe the model of the northern drift of the lithosphere and the model of the core drift towards the North Pole, it is possible to establish a quantitative ‘bridge’ between the structures of meridional compression of the lithosphere and the core drifting structures.Conclusions based on the model of the northern drift of the lithosphere conform to many independent data and concepts, such as disturbance of the isostatic equilibrium of the Antarctica lithosphere and its high standing; the anomalously wide shelf of the Arctic ocean (Figure 28а and the increased thickness of the sediment cover, that is rich in hydrocarbons, in combination with the ultralow velocity of spreading in Gakkel Ridge; the approximately equal areas of Antarctica and the Arctic ocean as antipodes (Figure 28б; elongation (according to GPS data of the parallels in the Southern hemisphere, and their shortening in the Northern hemisphere (Figure 26; radial (relative to the South Pole rifts and other lineaments in Antarctica (Figures 29, and 30; the sub-concentric (relative to the same pole system of spreading around Antarctica, which develops northward into the submeridional system including three ‘trunks’ at a distance of about 90° (Figure 31.Due to the higher velocity of the northern drift of the lithosphere within the band with the middle meridian 100° E – 80° W, wherein the main mass of the continental lithosphere is concentrated and whose two ‘poles’ are marked by the axes of the African and Pacific superplumes (Figures 3, 4, 5, and 32, the following specific features have developed: maximum elongation of the Antarctic continent in the Southern (‘stretched’ hemisphere (Figure 28 б; maximum shortening of the Arctic ocean in the Northern (‘compressed’ hemisphere (Figure 28а; maximum spreading velocity in the SouthEastern Indian Ridge (Figure 33; maximum northern component of the horizontal displacements velocity

English or Perish: How Contemporary South Korea Received, Accommodated, and Internalized English and American Modernity

Science.gov (United States)

Lee, JongHwa; Han, Min Wha; McKerrow, Raymie E.

2010-01-01

This paper discusses the positionality of English in South Korea as a form of symbolic capital that represents the discursive power of Americanism and East Asian Social Darwinism. By employing Bourdieu's and Foucault's theoretical orientations, this paper traces how South Korean linguistic policies to incorporate English loan words coincide with…

Depth to the bottom of magnetic layer in South America and its relationship to Curie isotherm, Moho depth and seismicity behavior

Directory of Open Access Journals (Sweden)

Javier Idárraga-García

2018-01-01

After comparing our results with the Moho depths reported by other authors, we have found that the Curie isotherm is deeper than Moho in most of the South American Platform (northward to ∼20°S, which is located in the stable cratonic area at the east of the Andes. This is evidence that the lithospheric mantle here is magnetic and contributes to the long wavelength magnetic signal. Also, our results support the hypothesis that the Curie isotherm may be acting as a boundary above which most of the crustal seismicity is concentrated. Below this boundary the occurrence of seismic events decreases dramatically.

The rapid cooling of the Nansha Block, southern South China Sea

Science.gov (United States)

Dong, M.; Zhang, J.

2017-12-01

Since the Late Cretaceous and Cenozoic, the Nansha Block has experienced a series of tectonic process and separated from South China continent to the south. As an exotic micro-continental, Nansha Block has an obvious different lithospheric rheology property from surrounding region. The lithosphere and mantle dynamic and rheology are mainly controlled by temperature. Therefore, we calculated the 3D temperature field and geothermal gradient of Nansha Block's upper mantle by using the S-wave velocity structure from surface wave tomography. The results show that the depth where temperature of 1300° as the lithospheric thickness is in close correspondence with the top of the seismic low velocity zone. The temperature of the upper mantle in Nansha Block is significantly lower than that of surrounding. It implies that Nansha Block experienced a rapid cooling event. We propose that the rapid cooling can be partly attributed to three reasons: 1) Nansha Block is a relatively stable block with no interior geothermal activity. 2) No external heat source to provide energy. 3) Abnormal mantle convection under Nansha Block accelerated the cooling.

Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

Science.gov (United States)

Plasman, M.; Tiberi, C.; Ebinger, C.; Gautier, S.; Albaric, J.; Peyrat, S.; Déverchère, J.; Le Gall, B.; Tarits, P.; Roecker, S.; Wambura, F.; Muzuka, A.; Mulibo, G.; Mtelela, K.; Msabi, M.; Kianji, G.; Hautot, S.; Perrot, J.; Gama, R.

2017-07-01

Rifting in a cratonic lithosphere is strongly controlled by several interacting processes including crust/mantle rheology, magmatism, inherited structure and stress regime. In order to better understand how these physical parameters interact, a 2 yr long seismological experiment has been carried out in the North Tanzanian Divergence (NTD), at the southern tip of the eastern magmatic branch of the East African rift, where the southward-propagating continental rift is at its earliest stage. We analyse teleseismic data from 38 broad-band stations ca. 25 km spaced and present here results from their receiver function (RF) analysis. The crustal thickness and Vp/Vs ratio are retrieved over a ca. 200 × 200 km2 area encompassing the South Kenya magmatic rift, the NTD and the Ngorongoro-Kilimanjaro transverse volcanic chain. Cratonic nature of the lithosphere is clearly evinced through thick (up to ca. 40 km) homogeneous crust beneath the rift shoulders. Where rifting is present, Moho rises up to 27 km depth and the crust is strongly layered with clear velocity contrasts in the RF signal. The Vp/Vs ratio reaches its highest values (ca. 1.9) beneath volcanic edifices location and thinner crust, advocating for melting within the crust. We also clearly identify two major low-velocity zones (LVZs) within the NTD, one in the lower crust and the second in the upper part of the mantle. The first one starts at 15-18 km depth and correlates well with recent tomographic models. This LVZ does not always coexist with high Vp/Vs ratio, pleading for a supplementary source of velocity decrease, such as temperature or composition. At a greater depth of ca. 60 km, a mid-lithospheric discontinuity roughly mimics the step-like and symmetrically outward-dipping geometry of the Moho but with a more slanting direction (NE-SW) compared to the NS rift. By comparison with synthetic RF, we estimate the associated velocity reduction to be 8-9 per cent. We relate this interface to melt ponding

A proof of concept study to assess the potential of PCR testing to detect natural Mycobacterium bovis infection in South American camelids.

Science.gov (United States)

Crawshaw, Timothy R; Chanter, Jeremy I; McGoldrick, Adrian; Line, Kirsty

2014-02-07

Cases of Mycobacterium bovis infection South American camelids have been increasing in Great Britain. Current antemortem immunological tests have some limitations. Cases at post mortem examination frequently show extensive pathology. The feasibility of detecting Mycobacterium bovis DNA in clinical samples was investigated. A sensitive extraction methodology was developed and used on nasal swabs and faeces taken post-mortem to assess the potential for a PCR test to detect Mycobacterium bovis in clinical samples. The gross pathology of the studied South American camelids was scored and a significantly greater proportion of South American camelids with more severe pathology were positive in both the nasal swab and faecal PCR tests. A combination of the nasal swab and faecal PCR tests detected 63.9% of all the South American camelids with pathology that were tested. The results suggest that antemortem diagnosis of Mycobacterium bovis in South American camelids may be possible using a PCR test on clinical samples, however more work is required to determine sensitivity and specificity, and the practicalities of applying the test in the field.

Seismic imaging of lithospheric discontinuities and continental evolution

Science.gov (United States)

Bostock, M. G.

1999-09-01

Discontinuities in physical properties within the continental lithosphere reflect a range of processes that have contributed to craton stabilization and evolution. A survey of recent seismological studies concerning lithospheric discontinuities is made in an attempt to document their essential characteristics. Results from long-period seismology are inconsistent with the presence of continuous, laterally invariant, isotropic boundaries within the upper mantle at the global scale. At regional scales, two well-defined interfaces termed H (˜60 km depth) and L (˜200 km depth) of continental affinity are identified, with the latter boundary generally exhibiting an anisotropic character. Long-range refraction profiles are frequently characterized by subcontinental mantle that exhibits a complex stratification within the top 200 km. The shallow layering of this package can behave as an imperfect waveguide giving rise to the so-called teleseismic Pn phase, while the L-discontinuity may define its lower base as the culmination of a low velocity zone. High-resolution, seismic reflection profiling provides sufficient detail in a number of cases to document the merging of mantle interfaces into lower continental crust below former collisional sutures and magmatic arcs, thus unambiguously identifying some lithospheric discontinuities with thrust faults and subducted oceanic lithosphere. Collectively, these and other seismic observations point to a continental lithosphere whose internal structure is dominated by a laterally variable, subhorizontal layering. This stratigraphy appears to be more pronounced at shallower lithospheric levels, includes dense, anisotropic layers of order 10 km in thickness, and exhibits horizontal correlation lengths comparable to the lateral dimensions of overlying crustal blocks. A model of craton evolution which relies on shallow subduction as a principal agent of craton stabilization is shown to be broadly compatible with these characteristics.

Evaluation of insulin resistance in two kinds of South American camelids: llamas and alpacas.

Science.gov (United States)

Araya, A V; Atwater, I; Navia, M A; Jeffs, S

2000-10-01

Insulin resistance was evaluated in South American camelids, llamas and alpacas, by use of the minimal model test and the insulin tolerance test. Animals were catheterized for long-term studies and tamed to minimize stress during evaluation. Results indicated a low insulin sensitivity index (SI) = 0 to 0.97, median = 0.39 x 10(-4) min/uIU x ml, about a fifth the value in other mammals and humans. The KITT was between 1.43 and 3.19 %/min, also significantly lower than that reported for humans. Glycosylated hemoglobin concentration was 6%, and HbAlc concentration was 5.5%; red blood cell lifetime, as measured by use of the 51Cr method, was 120 days, similar to the value in humans. We concluded that llamas and alpacas have naturally higher blood glucose concentration than do humans and other mammals during the glucose tolerance test. Using the same mathematical tools to evaluate glucose metabolism as those used in people, South American camelids appear to be resistant to insulin. Thus, the South American camelid may be a useful new animal model for the study of sugar metabolism and various facets of diabetes mellitus, especially protection from the deleterious effects of glycosylation.

Lithosphere and upper-mantle structure of the southern Baltic Sea estimated from modelling relative sea-level data with glacial isostatic adjustment

Science.gov (United States)

Steffen, H.; Kaufmann, G.; Lampe, R.

2014-06-01

During the last glacial maximum, a large ice sheet covered Scandinavia, which depressed the earth's surface by several 100 m. In northern central Europe, mass redistribution in the upper mantle led to the development of a peripheral bulge. It has been subsiding since the begin of deglaciation due to the viscoelastic behaviour of the mantle. We analyse relative sea-level (RSL) data of southern Sweden, Denmark, Germany, Poland and Lithuania to determine the lithospheric thickness and radial mantle viscosity structure for distinct regional RSL subsets. We load a 1-D Maxwell-viscoelastic earth model with a global ice-load history model of the last glaciation. We test two commonly used ice histories, RSES from the Australian National University and ICE-5G from the University of Toronto. Our results indicate that the lithospheric thickness varies, depending on the ice model used, between 60 and 160 km. The lowest values are found in the Oslo Graben area and the western German Baltic Sea coast. In between, thickness increases by at least 30 km tracing the Ringkøbing-Fyn High. In Poland and Lithuania, lithospheric thickness reaches up to 160 km. However, the latter values are not well constrained as the confidence regions are large. Upper-mantle viscosity is found to bracket [2-7] × 1020 Pa s when using ICE-5G. Employing RSES much higher values of 2 × 1021 Pa s are obtained for the southern Baltic Sea. Further investigations should evaluate whether this ice-model version and/or the RSL data need revision. We confirm that the lower-mantle viscosity in Fennoscandia can only be poorly resolved. The lithospheric structure inferred from RSES partly supports structural features of regional and global lithosphere models based on thermal or seismological data. While there is agreement in eastern Europe and southwest Sweden, the structure in an area from south of Norway to northern Germany shows large discrepancies for two of the tested lithosphere models. The lithospheric

Intestinal helminths in lowland South American Indians: some evolutionary interpretations.

Science.gov (United States)

Confalonieri, U; Ferreira, L F; Araújo, A

1991-12-01

Data on intestinal parasite infections for South American Indians in prehistoric times as revealed by coprolite analysis are being used to support transoceanic migration routes from the Old World to the New World. These same findings on modern semi-isolated aborigines, considered persisting prehistoric patterns, are also of great importance as indicators of pre-Columbian peopling of South America. This is the case for the Lengua Indians from Paraguay, studied in the 1920s, and the Yanomami and the Salumã from Brazil, studied in the 1980s. The intestinal parasitic profile of these groups can be empirically associated with culture change, but no clear correlations with the population biology of their hosts can be made at present because of scarcity of data.

Spatial variations of effective elastic thickness of the Lithosphere in the Southeast Asia regions

Science.gov (United States)

Shi, Xiaobin; Kirby, Jon; Yu, Chuanhai; Swain, Chris; Zhao, Junfeng

2016-04-01

The effective elastic thickness Te corresponds to the thickness of an idealized elastic beam that would bend similarly to the actual lithosphere under the same applied loads, and could provide important insight into rheology and state of stress. Thus, it is helpful to improve our understanding of the relationship between tectonic styles, distribution of earthquakes and lithospheric rheology in various tectonic settings. The Southeast Asia, located in the southeastern part of the Eurasian Plate, comprises a complex collage of continental fragments, volcanic arcs, and suture zones and marginal oceanic basins, and is surrounded by tectonically active margins which exhibit intense seismicity and volcanism. The Cenozoic southeastward extrusion of the rigid Indochina Block due to the Indo-Asian collision resulted in the drastic surface deformation in the western area. Therefore, a high resolution spatial variation map of Te might be a useful tool for the complex Southeast Asia area to examine the relationships between surface deformation, earthquakes, lithospheric structure and mantle dynamics. In this study, we present a high-resolution map of spatial variations of Te in the Southeast Asia area using the wavelet method, which convolves a range of scaled wavelets with the two data sets of Bouguer gravity anomaly and topography. The topography and bathymetry grid data was extracted from the GEBCO_08 Grid of GEBCO digital atlas. The pattern of Te variations agrees well with the tectonic provinces in the study area. On the whole, low lithosphere strength characterizes the oceanic basins, such as the South China Sea, the Banda sea area, the Celebes Sea, the Sulu Sea and the Andaman Sea. Unlike the oceanic basins, the continental fragments show a complex pattern of Te variations. The Khorat plateau and its adjacent area show strong lithosphere characteristics with a Te range of 20-50 km, suggesting that the Khorat plateau is the strong core of the Indochina Block. The West

A New Model of Lithosphere Deformation Beneath the Okinawa Trough Based on Gravity Data

Institute of Scientific and Technical Information of China (English)

ZHAO Lihong; JIANG Xiaodian; ZHANG Weigang

2002-01-01

The Ryukyu trench-arc system can be divided into two types according to its subduction model. The normal sub-duction in the northern part of the Philippine Sea plate creates a hinge sedimentary wedge with large deformation at the col-lision front, while the oblique subduction in the southern part gives rise to a smaller accretion with small deformation thanthat in the northern part. The mechanisms that cause the distinction between these two types have been analysed and calcu-lated by using gravity data based on the lithosphere rheology and the stress state of the lithosphere in the subduction bound-ary. The two types of subduction model are associated with the internal extension in the southern Okinawa Trough and thesmall extension in the northern part. The difference of the stress state between the two types of subduction model is alsomanifested in other tectonic features, such as topography, volcanic activity and crust movement. Modeling bathymetric andgravity data from this area suggests that the oblique subduction of low angle, together with smooth geometry of the overlyingplate crust, results in small stress released on the south of the trench by the subduction plate. The intraplate faults in thesouthern Okinawa Trough behind the trench stand in surplus intensive stress. On the other hand, the normal subduction ofhigh angle, together with strong undulation geometry of the overlying crust, results in more intensive stress released in thenorthern Ryukyu Trench than that in the south. The intraplate faults in the northern Okinawa Trough behind the northernRyukyu Trench stand in small stress.

Phylogenetic reconstruction of South American felids defined by protein electrophoresis

OpenAIRE

Pecon Slattery, J.; Johnson, W. E.; Goldman, D.; O'Brien, S. J.

1994-01-01

Phylogenetic associations among six closely related South American felid species were defined by changes in protein-encoding gene loci. We analyzed proteins isolated from skin fibroblasts using two-dimensional electrophoresis and allozymes extracted from blood cells. Genotypes were determined for multiple individuals of ocelot, margay, tigrina, Geoffroy's cat, kodkod, and pampas cat at 548 loci resolved by two-dimensional electrophoresis and 44 allozyme loci. Phenograms were constructed using...

Global model for the lithospheric strength and effective elastic thickness

OpenAIRE

Magdala Tesauro; Mikhail Kaban; S. A. P. L. Cloetingh

2013-01-01

Global distribution of the strength and effective elastic thickness (Te) of the lithosphere are estimated using physical parameters from recent crustal and lithospheric models. For the Te estimation we apply a new approach, which provides a possibility to take into account variations of Young modulus (E) within the lithosphere. In view of the large uncertainties affecting strength estimates, we evaluate global strength and Te distributions for possible end-member ‘hard’ (HRM) and a ‘soft’ (SR...

Diversity and disparity of sparassodonts (Metatheria) reveal non-analogue nature of ancient South American mammalian carnivore guilds

Science.gov (United States)

Dolgushina, Tatiana; Wesley, Gina

2018-01-01

This study investigates whether terrestrial mammalian carnivore guilds of ancient South America, which developed in relative isolation, were similar to those of other continents. We do so through analyses of clade diversification, ecomorphology and guild structure in the Sparassodonta, metatherians that were the predominant mammalian carnivores of pre-Pleistocene South America. Body mass and 16 characters of the dentition are used to quantify morphological diversity (disparity) in sparassodonts and to compare them to extant marsupial and placental carnivores and extinct North American carnivoramorphans. We also compare trophic diversity of the Early Miocene terrestrial carnivore guild of Santa Cruz, Argentina to that of 14 modern and fossil guilds from other continents. We find that sparassodonts had comparatively low ecomorphological disparity throughout their history and that South American carnivore palaeoguilds, as represented by that of Santa Cruz, Argentina, were unlike modern or fossil carnivore guilds of other continents in their lack of mesocarnivores and hypocarnivores. Our results add to a growing body of evidence highlighting non-analogue aspects of extinct South American mammals and illustrate the dramatic effects that historical contingency can have on the evolution of mammalian palaeocommunities. PMID:29298933

Thinning of heterogeneous lithosphere: insights from field observations and numerical modelling

Science.gov (United States)

Petri, B.; Duretz, T.; Mohn, G.; Schmalholz, S. M.

2017-12-01

The nature and mechanisms of formation of extremely thinned continental crust (N Italy) and in the Southern Alps (N Italy) were selected for their exceptional level of preservation of rift-related structures. This situation enables us to characterize (1) the pre-rift architecture of the continental lithosphere, (2) the localization of rift-related deformation in distinct portion of the lithosphere and (3) the interaction between initial heterogeneities of the lithosphere and rift-related structures. In a second stage, these observations are integrated in high-resolution, two-dimensional thermo-mechanical models taking into account various patterns of initial mechanical heterogeneities. Our results show the importance of initial pre-rift architecture of the continental lithosphere during rifting. Key roles are given to high-angle and low-angle normal faults, anastomosing shear-zones and decoupling horizons. We propose that during the first stages of thinning, deformation is strongly controlled by the complex pre-rift architecture of the lithosphere, localized along major structures responsible for the lateral extrusion of mid to lower crustal levels. This extrusion juxtaposes mechanically stronger levels in the hyper-thinned continental crust, being exhumed by subsequent low-angle normal faults. Altogether, these results highlight the critical role of the extraction of mechanically strong layers of the lithosphere during the extreme thinning of the continental lithosphere and allows to propose a new model for the formation of continental passive margins.

Estimating lithospheric properties at Atla Regio, Venus

Science.gov (United States)

Phillips, Roger J.

1994-01-01

Magellan spehrical harmonic gravity and topography models are used to estimate lithospheric properties at Alta Regio, Venus, a proposed hotspot with dynamic support from mantle plume(s). Global spherical harmonic and local representations of the gravity field share common properties in the Atla region interms of their spectral behavior over a wavelength band from approximately 2100 to approximately 700 km. The estimated free-air admittance spectrum displays a rather featureless long-wavelength portion followed by a sharp rise at wavelengths shorter than about 1000 km. This sharp rise requires significant flexural support of short-wavelength structures. The Bouguer coherence also displays a sharp drop in this wavelength band, indicating a finite flexural rigidity of the lithosphere. A simple model for lithospheric loading from above and below is introduced (D. W. Forsyth, 1985) with four parameters: f, the ratio of bottom loading to top loading; z(sub m), crustal thickness; z(sub l) depth to bottom loading source; and T(sub e) elastic lithosphere thickness. A dual-mode compensation model is introduced in which the shorter wavelengths (lambda approximately less than 1000 km) might be explained best by a predominance of top loading by the large shield volcanoes Maat Mons, Ozza Mons, and Sapas Mons, and the longer wavelengths (lambda approximately greater than 1500 km) might be explained best by a deep depth of compensation, possibly representing bottom loading by a dynamic source. A Monte Carlo inversion technique is introduced to thoroughly search out the four-space of the model parameters and to examine parameter correlation in the solutions. Venus either is a considerabe deficient in heat sources relative to Earth, or the thermal lithosphere is overthickened in response to an earlier episode of significant heat loss from the planet.

Characterizing Lithospheric Thickness in Australia using Ps and Sp Scattered Waves

Science.gov (United States)

Ford, H. A.; Fischer, K. M.; Rychert, C. A.

2008-12-01

The purpose of this study is to constrain the morphology of the lithosphere-asthenosphere boundary throughout Australia using scattered waves. Prior surface wave studies have shown a correlation between lithospheric thickness and the three primary geologic provinces of Australia, with the shallowest lithosphere located beneath the Phanerozoic province to the east, and the thicker lithosphere located beneath the Proterozoic and Archean regions. To determine lithospheric thickness, waveform data from twenty permanent broadband stations spanning mainland Australia and the island of Tasmania were analyzed using Ps and Sp migration techniques. Waveform selection for each station was based on epicentral distance (35° to 80° for Ps and 55° to 80° for Sp), and event depth (no greater than 300 km for Sp). For both Ps and Sp a simultaneous deconvolution was performed on the data for each of the twenty stations, and the resulting receiver function for each station was migrated to depth. Data were binned with epicentral distance to differentiate direct discontinuity phases from crustal reverberations (for Ps) and other teleseismic arrivals (for Sp). Early results in both Ps and Sp show a clear Moho discontinuity at most stations in addition to sharp, strong crustal reverberations seen in many of the Ps images. In the eastern Phanerozoic province, a strong negative phase at 100-105 km is evident in Ps for stations CAN and EIDS. The negative phase lies within a depth range that corresponds to the negative velocity gradient between fast lithosphere and slow asthenosphere imaged by surface waves. We therefore think that it is the lithosphere- asthenosphere boundary. On the island of Tasmania, a negative phase at 70-75 km in Ps images at stations TAU and MOO also appears to be the lithosphere-asthenosphere boundary. In the Proterozoic and Archean regions of the Australian continent, initial results for both Ps and Sp migration indicate clear crustal phases, but significantly

The tectonic setting of the Caribbean region and the K/T turnover of the South American land-mammal fauna

Energy Technology Data Exchange (ETDEWEB)

Ortiz-Jaureguizar, E.; Pascual, R.

2011-07-01

According to the fossil record, a biotic interchange of land vertebrates (e.g. booid snakes, dinosaurs and mammals) occurred between the Americas during the Late Cretaceous-Early Palaeocene. The arrival of North American immigrants (particularly marsupials and placental) during the latest Cretaceous-earliest Palaeocene had a profound influence on the composition of the South American mammal communities. During the Late Cretaceous these communities were dominated by native groups of Pangeic lineages, which represented more than 95% of the known genera, but during the Early Palaeocene 70% of South American mammals were derived from North American immigrants that had arrived during the Late Cretaceous-earliest Palaeocene, and by the Late Palaeocene all the South American mammals (with the possible exception of the xenarthrans) were descendants of these North American immigrants. In spite of the fact that no geological evidence is currently available to support the existence of a continuous land connection between the Americas during the Late Cretaceousearly Palaeocene, the fossil record is substantial enough to point to a temporary inter-American connection that permitted the beginning of a land-mammal exchange by the end of the Cretaceous. This interpretation is supported by recent geographic reconstructions of the Caribbean region. (Author)

Three-dimensional lithospheric density distribution of China and surrounding regions

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Chuantao Li

2014-01-01

Full Text Available In this paper, we analyze lithospheric density distribution of China and surrounding regions on the basis of 30′ × 30′ gravity data and 1° × 1° P-wave velocity data. Firstly, we used the empirical equation between the density and the P-wave velocity difference as the base of the initial model of the Asian lithospheric density. Secondly, we calculated the gravity anomaly, caused by the Moho discontinuity and the sedimentary layer discontinuity, by the Parker formula. Thirdly, the gravity anomaly of the spherical harmonics with 2–40 order for the anomalous body below the lithosphere is calculated based on the model of EGM96. Finally, by using Algebra Reconstruction Techniques (ART, the inversion of 30′ × 30′ residual lithospheric Bouguer gravity anomaly caused by the lithosphere yields a rather detailed structural model. The results show that the lithospheric density distribution of China and surrounding regions has a certain connection with the tectonic structure. The density is relatively high in the Philippine Sea plate, Japan Sea, the Indian plate, the Kazakhstan shield and the Western Siberia plain, whereas the Tibetan Plateau has low-density characteristics. The minimum value of density lies in the north of Philippines, in the Taiwan province and in the Ryukyu island arc.

Towards an improved determination of Earth’s lithospheric field from satellite observations

DEFF Research Database (Denmark)

Kotsiaros, Stavros; Olsen, Nils; Finlay, Chris

Perhaps one of the biggest difficulties in modelling the Earth’s lithospheric magnetic field is the separation of contributions from sources of internal and external origin. In particular, the determination of smaller-scale lithospheric magnetic field features is problematic because the lithosphe......Perhaps one of the biggest difficulties in modelling the Earth’s lithospheric magnetic field is the separation of contributions from sources of internal and external origin. In particular, the determination of smaller-scale lithospheric magnetic field features is problematic because...

Lithospheric Strength Beneath the Zagros Mountains of Southwestern Iran

Science.gov (United States)

Adams, A. N.; Nyblade, A.; Brazier, R.; Rodgers, A.; Al-Amri, A.

2006-05-01

The Zagros Mountain Belt of southwestern Iran is among the most seismically active mountain belts in the world. Early seismic studies of this area found that the lithosphere underlying the Zagros Mountains follows the "jelly sandwich" model, having a strong upper crust and a strong lithospheric mantle, separated by a weak lower crust. More recent studies, which analyzed earthquakes originating within the Zagros Mountains that were recorded at teleseismic distances, however, found that these earthquakes occurred only within the upper crust, thus indicating that the strength of the Zagros Mountains' lithosphere lies only within the upper crust, in accordance with the "creme brulee" lithospheric model. Preliminary analysis of regionally recorded earthquakes that originated within the Zagros Mountains is presented here. Using earthquakes recorded at regional distances will allow the analysis of a larger dataset than has been used in previous studies. Preliminary results show earthquakes occurring throughout the crust and possibly extending into the upper mantle.

S-Wave's Velocities of the Lithosphere-Asthenosphere System in the Caribbean Region

International Nuclear Information System (INIS)

Gonzalez, O'Leary; Alvarez, Jose Leonardo; Moreno, Bladimir; Panza, Giuliano F.

2010-06-01

An overview of the S-wave velocity (Vs) structural model of the Caribbean is presented with a resolution of 2 o x2 o . As a result of the frequency time analysis (FTAN) of more than 400 trajectories epicenter-stations in this region, new tomographic maps of Rayleigh waves group velocity dispersion at periods ranging from 10 s to 40 s have been determined. For each 2 o x2 o cell, group velocity dispersion curves were determined and extended to 150 s adding data from a larger scale tomographic study (Vdovin et al., 1999). Using, as independent a priori information, the available geological and geophysical data of the region, each dispersion curve has been mapped, by non-linear inversion, into a set of Vs vs. depth models in the depth range from 0 km to 300 km. Due to the non-uniqueness of the solutions for each cell a Local Smoothness Optimization (LSO) has been applied to the whole region to identify a tridimensional model of Vs vs. depth in cells of 2 o x2 o , thus satisfying the Occam razor concept. Through these models some main features of the lithosphere and asthenosphere are evidenced, such as: the west directed subduction zone of the eastern Caribbean region with a clear mantle wedge between the Caribbean lithosphere and the subducted slab; the complex and asymmetric behavior of the crustal and lithospheric thickness in the Cayman ridge; the diffused presence of oceanic crust in the region; the presence of continental type crust in the South America, Central America and North America plates, as well as the bottom of the upper asthenosphere that gets shallower going from west to east. (author)

Magnetotelluric investigations of the lithosphere beneath the central Rae craton, mainland Nunavut, Canada

Science.gov (United States)

Spratt, Jessica E.; Skulski, Thomas; Craven, James A.; Jones, Alan G.; Snyder, David B.; Kiyan, Duygu

2014-03-01

New magnetotelluric soundings at 64 locations throughout the central Rae craton on mainland Nunavut constrain 2-D resistivity models of the crust and lithospheric mantle beneath three regional transects. Responses determined from colocated broadband and long-period magnetotelluric recording instruments enabled resistivity imaging to depths of > 300 km. Strike analysis and distortion decomposition on all data reveal a regional trend of 45-53°, but locally the geoelectric strike angle varies laterally and with depth. The 2-D models reveal a resistive upper crust to depths of 15-35 km that is underlain by a conductive layer that appears to be discontinuous at or near major mapped geological boundaries. Surface projections of the conductive layer coincide with areas of high grade, Archean metasedimentary rocks. Tectonic burial of these rocks and thickening of the crust occurred during the Paleoproterozoic Arrowsmith (2.3 Ga) and Trans-Hudson orogenies (1.85 Ga). Overall, the uppermost mantle of the Rae craton shows resistivity values that range from 3000 Ω m in the northeast (beneath Baffin Island and the Melville Peninsula) to 10,000 Ω m beneath the central Rae craton, to >50,000 Ω m in the south near the Hearne Domain. Near-vertical zones of reduced resistivity are identified within the uppermost mantle lithosphere that may be related to areas affected by mantle melt or metasomatism associated with emplacement of Hudsonian granites. A regional decrease in resistivities to values of 500 Ω m at depths of 180-220 km, increasing to 300 km near the southern margin of the Rae craton, is interpreted as the lithosphere-asthenosphere boundary.

Satellite gravity gradient views help reveal the Antarctic lithosphere

Science.gov (United States)

Ferraccioli, F.; Ebbing, J.; Pappa, F.; Kern, M.; Forsberg, R.

2017-12-01

Here we present and analyse satellite gravity gradient signatures derived from GOCE and superimpose these on tectonic and bedrock topography elements, as well as seismically-derived estimates of crustal thickness for the Antarctic continent. The GIU satellite gravity component images the contrast between the thinner crust and lithosphere underlying the West Antarctic Rift System and the Weddell Sea Rift System and the thicker lithosphere of East Antarctica. The new images also suggest that more distributed wide-mode lithospheric and crustal extension affects both the Ross Sea Embayment and the less well known Ross Ice Shelf segment of the rift system. However, this pattern is less clear towards the Bellingshousen Embayment, indicating that the rift system narrows towards the southern edge of the Antarctic Peninsula. In East Antarctica, the satellite gravity data provides new views into the Archean to Mesoproterozoic Terre Adelie Craton, and clearly shows the contrast wrt to the crust and lithosphere underlying both the Wilkes Subglacial Basin to the east and the Sabrina Subglacial Basin to the west. This finding augments recent interpretations of aeromagnetic and airborne gravity data over the region, suggesting that the Mawson Continent is a composite lithospheric-scale entity, which was affected by several Paleoproterozoic and Mesoproterozoic orogenic events. Thick crust is imaged beneath the Transantarctic Mountains, the Terre Adelie Craton, the Gamburtsev Subglacial Mountains and also Eastern Dronning Maud Land, in particular beneath the recently proposed region of the Tonian Oceanic Arc Superterrane. The GIA and GIU components help delineate the edges of several of these lithospheric provinces. One of the most prominent lithospheric-scale features discovered in East Antarctica from satellite gravity gradient imaging is the Trans East Antarctic Shear Zone that separates the Gamburtsev Province from the Eastern Dronning Maud Land Province and appears to form the

Influence of Surface Processes over Africa on the Atlantic Marine ITCZ and South American Precipitation.

Science.gov (United States)

Hagos, Samson M.; Cook, Kerry H.

2005-12-01

Previous studies show that the climatological precipitation over South America, particularly the Nordeste region, is influenced by the presence of the African continent. Here the influence of African topography and surface wetness on the Atlantic marine ITCZ (AMI) and South American precipitation are investigated.Cross-equatorial flow over the Atlantic Ocean introduced by north south asymmetry in surface conditions over Africa shifts the AMI in the direction of the flow. African topography, for example, introduces an anomalous high over the southern Atlantic Ocean and a low to the north. This results in a northward migration of the AMI and dry conditions over the Nordeste region.The implications of this process on variability are then studied by analyzing the response of the AMI to soil moisture anomalies over tropical Africa. Northerly flow induced by equatorially asymmetric perturbations in soil moisture over northern tropical Africa shifts the AMI southward, increasing the climatological precipitation over northeastern South America. Flow associated with an equatorially symmetric perturbation in soil moisture, however, has a very weak cross-equatorial component and very weak influence on the AMI and South American precipitation. The sensitivity of the AMI to soil moisture perturbations over certain regions of Africa can possibly improve the skill of prediction.

Time, Space, and National Belonging in The Namesake: Redrawing South Asian American Citizenship in the Shadow of 9/11

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Sue Brennan

2011-03-01

Full Text Available The terms of national belonging after 9/11 for South Asian Americans have taken shape through a vague and depoliticized discourse around ethnic identity, one in which the clichés of multiculturalism and melting-pot nationalism stand in for the specific socioeconomic and historical conditions that helped form the South Asian diaspora in the US. This paper explores the ways in which Jhumpa Lahiri’s novel The Namesake and its cinematic adaptation by filmmaker Mira Nair challenge the erasure of South Asian American citizenship following 9/11. Recounting the journey of a young Bengali graduate student and his wife migrating to the US in the late 1960s, each text speaks back to the erasure of South Asian American citizenship through the materialization of time in space: while Lahiri foregrounds the state itself in producing the rhythms through which immigrants are assimilated into the nation, Nair creates a narrative world in which filmic space materializes many, and often competing, histories, unifying multiple temporalities and histories through the representations of space. I argue that the cinematic adaptation of The Namesake generates a new spatiotemporal state of affairs, one in which the iconography of 9/11 both challenges post-9/11 racial logics and destabilizes the singular, progressive, and institutionalized temporality through which Lahiri writes South Asian American immigrants back into nation.

Geodynamic inversion to constrain the non-linear rheology of the lithosphere

Science.gov (United States)

Baumann, T. S.; Kaus, Boris J. P.

2015-08-01

One of the main methods to determine the strength of the lithosphere is by estimating it's effective elastic thickness. This method assumes that the lithosphere is a thin elastic plate that floats on the mantle and uses both topography and gravity anomalies to estimate the plate thickness. Whereas this seems to work well for oceanic plates, it has given controversial results in continental collision zones. For most of these locations, additional geophysical data sets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to understand the dynamics of the lithosphere as this also requires knowledge of the rheology of the lithosphere. Laboratory experiments suggest that rocks deform in a viscous manner if temperatures are high and stresses low, or in a plastic/brittle manner if the yield stress is exceeded. Yet, the experimental results show significant variability between various rock types and there are large uncertainties in extrapolating laboratory values to nature, which leaves room for speculation. An independent method is thus required to better understand the rheology and dynamics of the lithosphere in collision zones. The goal of this paper is to discuss such an approach. Our method relies on performing numerical thermomechanical forward models of the present-day lithosphere with an initial geometry that is constructed from geophysical data sets. We employ experimentally determined creep-laws for the various parts of the lithosphere, but assume that the parameters of these creep-laws as well as the temperature structure of the lithosphere are uncertain. This is used as a priori information to formulate a Bayesian inverse problem that employs topography, gravity, horizontal and vertical surface velocities to invert for the unknown material parameters and temperature structure. In order to test the general methodology

Space geodesy validation of the global lithospheric flow

Science.gov (United States)

Crespi, M.; Cuffaro, M.; Doglioni, C.; Giannone, F.; Riguzzi, F.

2007-02-01

Space geodesy data are used to verify whether plates move chaotically or rather follow a sort of tectonic mainstream. While independent lines of geological evidence support the existence of a global ordered flow of plate motions that is westerly polarized, the Terrestrial Reference Frame (TRF) presents limitations in describing absolute plate motions relative to the mantle. For these reasons we jointly estimated a new plate motions model and three different solutions of net lithospheric rotation. Considering the six major plate boundaries and variable source depths of the main Pacific hotspots, we adapted the TRF plate kinematics by global space geodesy to absolute plate motions models with respect to the mantle. All three reconstructions confirm (i) the tectonic mainstream and (ii) the net rotation of the lithosphere. We still do not know the precise trend of this tectonic flow and the velocity of the differential rotation. However, our results show that assuming faster Pacific motions, as the asthenospheric source of the hotspots would allow, the best lithospheric net rotation estimate is 13.4 +/- 0.7 cm yr-1. This superfast solution seems in contradiction with present knowledge on the lithosphere decoupling, but it matches remarkably better with the geological constraints than those retrieved with slower Pacific motion and net rotation estimates. Assuming faster Pacific motion, it is shown that all plates move orderly `westward' along the tectonic mainstream at different velocities and the equator of the lithospheric net rotation lies inside the corresponding tectonic mainstream latitude band (~ +/-7°), defined by the 1σ confidence intervals.

Human consumption of a vagrant South American Fur Seal Arctocephalus australis (Carnivora: Otariidae in Brazil

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S. Siciliano

2016-04-01

Full Text Available The South American Fur Seal Arctocephalus australis is one of the most widely distributed South American otariid species. In Brazil, during austral winter months specimens of A. australis are regularly found along the Rio Grande do Sul and Santa Catarina coasts. Occasionally, vagrants have been recorded along the southeastern coast but rarely moves north of Rio de Janeiro, at 23°S. On 01 May 2015, fishermen noticed in the surf zone an unidentified large animal in Ilhéus, Bahia, northeastern Brazil. Severely wounded, it was still alive when first spotted. Numerous shark bites were observed in the rostrum and flippers, the peduncle was severely lacerated and the intestines were protruding. The specimen was identified as an adult of South American Fur Seal based on the combination of the characteristic coloration of the pelage, head shape, body size, the relatively large eye size, and mainly due to the pronounced three cusped teeth in post canines. Fishermen decided to butcher the carcass and share the meat among their companions. The present record, however, is of special concern as human consumption South American Fur Seal seems to be unusual in Brazil. Pieces of meat were shared among fishermen. In addition, small pieces of blubber were used as bait in the local shark long-line fishery. Consumption of an injured and presumably weak marine mammal carcass points to an increasing risk of contact between potentially harmful viruses, bacteria and fungi and humans. This note represents an alert to public health specialists and wildlife authorities in Brazil. It calls the urgency of an outreach campaign advertising to the potential risks of ingesting bushmeat either from land or aquatic sources. 

petrography, compositional characteristics and stable isotope

African Journals Online (AJOL)

PROF EKWUEME

African and South American lithospheric plates (Burke et al., 1971). The basin ...... Tectonic evolution Cretaceous stratigraphy of the. Dahomey Basin.Journal of Mining and Geology, ... theory and application of trace element technique.

Tectonothermal events of southeastern Brazil: Implications for consolidation of the South American platform

International Nuclear Information System (INIS)

Hackspacher, P.C.; Fetter, A.H; Dantas, E.L; Hadler Neto, J.C; Ribeiro, L.F.B; Tello, C.E.S

2001-01-01

The tectonothermal history of the South American Platform and it consolidation have to be analyzed considering different tectonic and stabilization stages. For that propose we have studied the Precambrian basement southwest of the city of Sao Paulo, which was consolidated and deformed during the Brasiliano Orogeny and later affected by Phanerozoic tectonics. Geological data from a northwest/southeast transect between Sao Roque and Jundiai - SP, were obtained through U/Pb, K/Ar and Ar/Ar mineral and whole rock studies. Metamorphic PT values, relation of brittle-ductile zone of felsic crustal rocks and fission track ages were also obtained. Such data were plotted on a temperature-time plot representing a preliminary overview of the geological evolution of this part of the South American platform. Recently dated highly deformed metaplutons from the Ribeira Belt suggest that convergence that preceded collision was underway by around 650 Ma. Low-grade (rarely reaching 4000 o C) metasediments and metavolcanics of the Sao Roque Group, interpreted to be a backarc basin that formed during active Brasiliano collision, yield a crystallization age of 627 Ma (Hackspacher et al., 2000). Syn-collisional granitoids with U/Pb zircon and monazite ages of 625 Ma (Janasi, 1999) provide more constraints on the timing of active collision. Temperatures of these calc-alkaline rocks can be considered around 650 o C. U/Pb zircon and monazite ages between 610 and 595 Ma obtained igneous bodies associated with transpressional tectonics place age constraints on the transition to a transpressional regime, with crystallization temperature around 580 o C. Related strike-slip shear zones in brittle-ductile transition, present K-Ar ages on biotite and hornblende between 600 and 580 Ma. The temperature interval for these greenschist grade shear zones is estimated between 450 and 300 o C. Apatite Fission Track Analysis (AFTA) near the Jundiuvira Shear Zone present a corrected Fission Track Age of 477

Helminth parasites of South American fishes: current status and characterization as a model for studies of biodiversity.

Science.gov (United States)

Luque, J L; Pereira, F B; Alves, P V; Oliva, M E; Timi, J T

2017-03-01

The South American subcontinent supports one of the world's most diverse and commercially very important ichthyofauna. In this context, the study of South American fish parasites is of increased relevance in understanding their key roles in ecosystems, regulating the abundance or density of host populations, stabilizing food webs and structuring host communities. It is hard to estimate the number of fish parasites in South America. The number of fish species studied for parasites is still low (less than 10%), although the total number of host-parasite associations (HPAs) found in the present study was 3971. Monogeneans, with 835 species (1123 HPAs, 28.5%), and trematodes, with 662 species (1127 HPAs, 30.9%), are the more diverse groups. Data gathered from the literature are useful to roughly estimate species richness of helminths from South American fish, even though there are some associated problems: the reliability of information depends on accurate species identification; the lack of knowledge about life cycles; the increasing number of discoveries of cryptic species and the geographically biased number of studies. Therefore, the closest true estimations of species diversity and distribution will rely on further studies combining both molecular and morphological approaches with ecological data such as host specificity, geographical distribution and life-cycle data. Research on biodiversity of fish parasites in South America is influenced by problems such as funding, taxonomic impediments and dispersion of research groups. Increasing collaboration, interchange and research networks in the context of globalization will enable a promising future for fish parasitology in South America.

Excerpt from The Red Land to the South: American Indian Writers and Indigenous Mexico

Directory of Open Access Journals (Sweden)

James H. Cox

2013-09-01

Full Text Available Excerpted from James H. Cox, The Red Land to the South: American Indian Writers and Indigenous Mexico (Minneapolis: University of Minnesota Press, 2012.Reprinted with permission from University of Minnesota Press.

Curare: the South American arrow poison.

Science.gov (United States)

Lee, M R

2005-02-01

The history of curare is both curious and convoluted. A product of South American culture it emerged in the sixteenth century from the mists of antiquity at the same time as quinine, coca, and chocolate. Like quinine, at first came the extract but no plant, and later the plant but no chemical compound. It took more than 300 years and the efforts of many explorers and scientists to resolve the problem. These included Condamine, Humboldt, Brodie, Waterton, Bernard, Dale, Walker, and King. Finally, the pure compound d-tubocurarine was isolated from the liana Chondrodendron and synthesised. Its specific physiological action was blockade of the effect of acetylcholine at the neuro-muscular junction. Such a paralytic poison could be used to kill oneself or others. The bizarre plot to kill the Prime Minister, Lloyd George, during the First World War is described. Fortunately this nefarious plan was thwarted by the Secret Service!

Global model for the lithospheric strength and effective elastic thickness

Science.gov (United States)

Tesauro, Magdala; Kaban, Mikhail K.; Cloetingh, Sierd A. P. L.

2013-08-01

Global distribution of the strength and effective elastic thickness (Te) of the lithosphere are estimated using physical parameters from recent crustal and lithospheric models. For the Te estimation we apply a new approach, which provides a possibility to take into account variations of Young modulus (E) within the lithosphere. In view of the large uncertainties affecting strength estimates, we evaluate global strength and Te distributions for possible end-member 'hard' (HRM) and a 'soft' (SRM) rheology models of the continental crust. Temperature within the lithosphere has been estimated using a recent tomography model of Ritsema et al. (2011), which has much higher horizontal resolution than previous global models. Most of the strength is localized in the crust for the HRM and in the mantle for the SRM. These results contribute to the long debates on applicability of the "crème brulée" or "jelly-sandwich" model for the lithosphere structure. Changing from the SRM to HRM turns most of the continental areas from the totally decoupled mode to the fully coupled mode of the lithospheric layers. However, in the areas characterized by a high thermal regime and thick crust, the layers remain decoupled even for the HRM. At the same time, for the inner part of the cratons the lithospheric layers are coupled in both models. Therefore, rheological variations lead to large changes in the integrated strength and Te distribution in the regions characterized by intermediate thermal conditions. In these areas temperature uncertainties have a greater effect, since this parameter principally determines rheological behavior. Comparison of the Te estimates for both models with those determined from the flexural loading and spectral analysis shows that the 'hard' rheology is likely applicable for cratonic areas, whereas the 'soft' rheology is more representative for young orogens.

Synthetic Analysis of the Effective Elastic Thickness of the Lithosphere in China

Science.gov (United States)

Lu, Z.; Li, C.

2017-12-01

Effective elastic thickness (Te) represents the response of the lithosphere to a long-term (larger than 105 years) geological loading and reflects the deformation mechanism of plate and its thermodynamic state. Temperature and composition of the lithosphere, coupling between crust and lithospheric mantle, and lithospheric structures affect Te. Regional geology in China is quite complex, influenced by the subduction of the Pacific and Philippine Sea plates in the east and the collision of the Eurasia plate with the India-Australia plate in the southwest. Te can help understand the evolution and strength of the lithospheres in different areas and tectonic units. Here we apply the multitaper coherence method to estimate Te in China using the topography (ETOPO1) and Bouguer gravity anomalies (WGM2012) , at different window sizes (600km*600km, 800km*800km, 1000km*1000km) and moving steps. The lateral variation of Te in China coincides well with the geology. The old stable cratons or basins always correspond to larger Te, whereas the oceanic lithosphere or active orogen blocks tend to get smaller Te. We further correlate Te to curie-point depths (Zb) and heat flow to understand how temperature influences the strength of the lithosphere. Despite of a complex correlation between Te and Zb, good positive correlations are found in the North China Block, Tarim Basin, and Lower Yangtze, showing strong influence of temperature on lithospheric strength. Conversely, the Tibetan Plateau, Upper and Middle Yangtze, and East China Sea Basin even show negative correlation, suggesting that lithospheric structures and compositions play more important roles than temperature in these blocks. We also find that earthquakes tend to occur preferably in a certain range of Te. Deeper earthquakes are more likely to occur where the lithosphere is stronger with larger Te. Crust with a larger Te may also have a deeper ductile-brittle boundary, along which deep large earthquakes tend to cluster.

Splendid oddness: revisiting the curious trophic relationships of South American Pleistocene mammals and their abundance

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RICHARD A. FARIÑA

2014-03-01

Full Text Available The South American Pleistocene mammal fauna includes great-sized animals that have intrigued scientists for over two centuries. Here we intend to update the knowledge on its palaeoecology and provide new evidence regarding two approaches: energetics and population density and relative abundance of fossils per taxa. To determine whether an imbalance exists, population density models were applied to several South American fossil faunas and the results compared to those that best describe the palaeoecology of African faunas. The results on the abundance study for Uruguay and the province of Buenos Aires during the Lujanian stage/age reveal that bulk-feeding ground sloths (Lestodon and Glossotherium were more represented in the first territory, while the more selective Scelidotherium and Megatherium were more abundant in the second. Although the obtained values were corrected to avoid size-related taphonomic biases, linear regressions of abundance vs. body mass plots did not fit the expected either for first or second consumers. South American Pleistocene faunas behave differently from what models suggest they should. Changes in sea level and available area could account for these differences; the possibility of a floodplain in the area then emerged could explain seasonal changes, which would modify the calculations of energetics and abundance.

Coping with Discrimination: The Subjective Well-Being of South Asian American Women

Science.gov (United States)

Liang, Christopher T. H.; Nathwani, Anisha; Ahmad, Sarah; Prince, Jessica K.

2010-01-01

The relationship between coping strategies used by South Asian American women and subjective well-being (SWB) was studied. Second-generation women were found to use more support compared with 1st-generation women. Problem-solving coping was inversely related to age. Avoidance coping was found to predict SWB when controlling for age and…

Digenetic trematodes in South American sea lions from southern Brazilian waters.

Science.gov (United States)

Pereira, E M; Müller, G; Secchi, E; Pereira, J; Valente, A L S

2013-10-01

The aim of this work was to perform a systematic study to detect and quantify the digenetic trematode infections in South American sea lions from the southern Brazilian coast. Twenty-four South American sea lions, Otaria flavescens (Carnivora: Otaridae), were found dead along the coast of Rio Grande do Sul State, Brazil, between June 2010 and September of 2011. Two trematode species were found in the intestines of O. flavescens, i.e., Stephanoprora uruguayense (Digenea: Echinostomatidae) and Ascocotyle (Phagicola) longa (Digenea: Heterophyidae). Ascocotyle (P.) longa reached a prevalence of 33.3% and mean intensity of 248,500, whereas S. uruguayense showed a prevalence of 4.2% and mean intensity of 202. The 2 trematode species infecting sea lions were likely transmitted by feeding on mullets, Mugil platanus, that commonly harbor heterophyid metacercariae. The present work is the first report of digenetic trematodes infecting O. flavescens in Brazil. The high prevalence and mean intensity values of the 2 trematode species infecting sea lions in the present study suggest caution in human consumption of mullets and other fish, which can be infected with the metacercariae of these trematodes known to have zoonotic potential.

The Lithosphere in Italy: Structure and Seismicity

International Nuclear Information System (INIS)

Brandmayr, Enrico; Blagoeva Raykova, Reneta; Zuri, Marco; Romanelli, Fabio; Doglioni, Carlo; Panza, Giuliano Francesco

2010-07-01

We propose a structural model for the lithosphere-asthenosphere system for the Italic region by means of the S-wave velocity (V S ) distribution with depth. To obtain the velocity structure the following methods are used in the sequence: frequency-time analysis (FTAN); 2D tomography (plotted on a grid 1 o x 1 o ); non-linear inversion; smoothing optimization method. The 3D V S structure (and its uncertainties) of the study region is assembled as a juxtaposition of the selected representative cellular models. The distribution of seismicity and heat flow is used as an independent constraint for the definition of the crustal and lithospheric thickness. The moment tensor inversion of recent damaging earthquakes which occurred in the Italic region is performed through a powerful non-linear technique and it is related to the different rheologic-mechanic properties of the crust and uppermost mantle. The obtained picture of the lithosphere-asthenosphere system for the Italic region confirms a mantle extremely vertically stratified and laterally strongly heterogeneous. The lateral variability in the mantle is interpreted in terms of subduction zones, slab dehydration, inherited mantle chemical anisotropies, asthenospheric upwellings, and so on. The western Alps and the Dinarides have slabs with low dip, whereas the Apennines show a steeper subduction. No evidence for any type of mantle plume is observed. The asymmetric expansion of the Tyrrhenian Sea, which may be interpreted as related to a relative eastward mantle flow with respect to the overlying lithosphere, is confirmed. (author)

Prevalence and genetic diversity of haematozoa in South American waterfowl and evidence for intercontinental redistribution of parasites by migratory birds

Science.gov (United States)

Smith, Matthew M.; Ramey, Andy M.

2015-01-01

To understand the role of migratory birds in the movement and transmission of haematozoa within and between continental regions, we examined 804 blood samples collected from eleven endemic species of South American waterfowl in Peru and Argentina for infection by Haemoproteus, Plasmodium, and/or Leucocytozono blood parasites. Infections were detected in 25 individuals of six species for an overall apparent prevalence rate of 3.1%. Analysis of haematozoa mitochondrial DNA revealed twelve distinct parasite haplotypes infecting South American waterfowl, four of which were identical to lineages previously observed infecting ducks and swans sampled in North America. Analysis of parasite mitochondrial DNA sequences revealed close phylogenetic relationships between lineages originating from waterfowl samples regardless of continental affiliation. In contrast, more distant phylogenetic relationships were observed between parasite lineages from waterfowl and passerines sampled in South America for Haemoproteus and Leucocytozoon, suggesting some level of host specificity for parasites of these genera. The detection of identical parasite lineages in endemic, South American waterfowl and North American ducks and swans, paired with the close phylogenetic relationships of haematozoa infecting waterfowl on both continents, provides evidence for parasite redistribution between these regions by migratory birds.

Anthropozoonotic Endoparasites in Free-Ranging "Urban" South American Sea Lions (Otaria flavescens).

Science.gov (United States)

Hermosilla, Carlos; Silva, Liliana M R; Navarro, Mauricio; Taubert, Anja

2016-01-01

The present study represents the first report on the gastrointestinal endoparasite fauna of a free-ranging "urban" colony of South American sea lions (Otaria flavescens) living within the city of Valdivia, Chile. A total of 40 individual faecal samples of South American sea lions were collected during the year 2012 within their natural habitat along the river Calle-Calle and in the local fish market of Valdivia. Coprological analyses applying sodium acetate acetic formalin methanol (SAF) technique, carbol fuchsin-stained faecal smears and Giardia/Cryptosporidium coproantigen ELISAs, revealed infections with 8 different parasites belonging to protozoan and metazoan taxa with some of them bearing anthropozoonotic potential. Thus, five of these parasites were zoonotic (Diphyllobothriidae gen. sp., Anisakidae gen. sp., Giardia, Cryptosporidium, and Balantidium). Overall, these parasitological findings included four new parasite records for Otaria flavescens, that is, Giardia, Cryptosporidium, Balantidium, and Otostrongylus. The current data serve as a baseline for future monitoring studies on anthropozoonotic parasites circulating in these marine mammals and their potential impact on public health.

Numerical modeling of continental lithospheric weak zone over plume

Science.gov (United States)

Perepechko, Y. V.; Sorokin, K. E.

2011-12-01

The work is devoted to the development of magmatic systems in the continental lithosphere over diffluent mantle plumes. The areas of tension originating over them are accompanied by appearance of fault zones, and the formation of permeable channels, which are distributed magmatic melts. The numerical simulation of the dynamics of deformation fields in the lithosphere due to convection currents in the upper mantle, and the formation of weakened zones that extend up to the upper crust and create the necessary conditions for the formation of intermediate magma chambers has been carried out. Thermodynamically consistent non-isothermal model simulates the processes of heat and mass transfer of a wide class of magmatic systems, as well as the process of strain localization in the lithosphere and their influence on the formation of high permeability zones in the lower crust. The substance of the lithosphere is a rheologic heterophase medium, which is described by a two-velocity hydrodynamics. This makes it possible to take into account the process of penetration of the melt from the asthenosphere into the weakened zone. The energy dissipation occurs mainly due to interfacial friction and inelastic relaxation of shear stresses. The results of calculation reveal a nonlinear process of the formation of porous channels and demonstrate the diversity of emerging dissipative structures which are determined by properties of both heterogeneous lithosphere and overlying crust. Mutual effect of a permeable channel and the corresponding filtration process of the melt on the mantle convection and the dynamics of the asthenosphere have been studied. The formation of dissipative structures in heterogeneous lithosphere above mantle plumes occurs in accordance with the following scenario: initially, the elastic behavior of heterophase lithosphere leads to the formation of the narrow weakened zone, though sufficiently extensive, with higher porosity. Further, the increase in the width of

Arthroscopic approach and intraarticular anatomy of the stifle in South American camelids.

Science.gov (United States)

Pentecost, Rebecca L; Niehaus, Andrew J; Santschi, Elizabeth

2012-05-01

To describe a cranial arthroscopic approach to the stifle of South American camelids and to report our clinical experience with camelid stifle arthroscopy. Experimental study and retrospective case series. (1) Cadaveric alpaca hindlimbs (n = 18; 9 alpacas); (2) 1 alpaca and 1 llama Polymethylmethacrylate joint casts (n = 2) were made to define stifle joint dimensions. Cadaveric stifle joints (n = 16) were evaluated arthroscopically to determine arthroscopic portal locations, describe the intraarticular anatomy, and report potential complications. An alpaca and a llama with stifle joint disease had diagnostic arthroscopy. Successful entry into the stifle joint was achieved in 16 cadaver limbs. Observed structures were: the suprapatellar pouch, articular surface of the patella, femoral trochlear ridges and groove, cranial aspect of the femoral condyles (n = 16); distal aspect of the cranial and proximal aspect of the caudal cruciate ligaments (14); and cranial aspects of the medial and lateral menisci (11), and cranial meniscotibial and intermeniscal ligaments (8). Stifle arthroscopy allowed for joint evaluation and removal of osteochondral fragments in 1 alpaca and 1 llama with naturally occurring stifle disease. Complications of cadaver or live procedures included minor cartilage scoring (3 stifles) and subcutaneous periarticular fluid accumulation (8 stifles). Arthroscopy provides a safe approach for diagnosis and treatment of stifle lesions in South American camelids. Copyright 2012 by The American College of Veterinary Surgeons.

Impact of the lithosphere on dynamic topography: Insights from analogue modeling

OpenAIRE

Sembroni, Andrea; Kiraly, Agnes; Faccenna, Claudio; Funiciello, Francesca; Becker, Thorsten W.; Goblig, Jan; Fernandez, Manel

2017-01-01

Density anomalies beneath the lithosphere are expected to generate dynamic topography at the Earth's surface due to the induced mantle flow stresses which scale linearly with density anomalies, while the viscosity of the upper mantle is expected to control uplift rates. However, limited attention has been given to the role of the lithosphere. Here we present results from analogue modeling of the interactions between a density anomaly rising in the mantle and the lithosphere in a Newtonian sys...

Sarcoptic Mange in a South American Gray Fox (Chilla Fox; Lycalopex griseus ), Chile.

Science.gov (United States)

Verdugo, Claudio; Espinoza, Angelo; Moroni, Manuel; Valderrama, Rocio; Hernandez, Carlos

2016-07-01

Mange, a prevalent disease of dogs in Chile, is also a serious threat to wildlife. We report a case of sarcoptic mange in a South American gray fox or chilla fox ( Lycalopex griseus ). Further research is needed to understand the impact of mange in wildlife populations.

Lithospheric layering in the North American craton revealed by including Short Period Constraints in Full Waveform Tomography

Science.gov (United States)

Roy, C.; Calo, M.; Bodin, T.; Romanowicz, B. A.

2017-12-01

Recent receiver function studies of the North American craton suggest the presence of significant layering within the cratonic lithosphere, with significant lateral variations in the depth of the velocity discontinuities. These structural boundaries have been confirmed recently using a transdimensional Markov Chain Monte Carlo approach (TMCMC), inverting surface wave dispersion data and converted phases simultaneously (Calò et al., 2016; Roy and Romanowicz 2017). The lateral resolution of upper mantle structure can be improved with a high density of broadband seismic stations, or with a sparse network using full waveform inversion based on numerical wavefield computation methods such as the Spectral Element Method (SEM). However, inverting for discontinuities with strong topography such as MLDS's or LAB, presents challenges in an inversion framework, both computationally, due to the short periods required, and from the point of view of stability of the inversion. To overcome these limitations, and to improve resolution of layering in the upper mantle, we are developing a methodology that combines full waveform inversion tomography and information provided by short period seismic observables. We have extended the 30 1D radially anisotropic shear velocity profiles of Calò et al. 2016 to several other stations, for which we used a recent shear velocity model (Clouzet et al., 2017) as constraint in the modeling. These 1D profiles, including both isotropic and anisotropic discontinuities in the upper mantle (above 300 km depth) are then used to build a 3D starting model for the full waveform tomographic inversion. This model is built after 1) homogenization of the layered 1D models and 2) interpolation between the 1D smooth profiles and the model of Clouzet et al. 2017, resulting in a smooth 3D starting model. Waveforms used in the inversion are filtered at periods longer than 30s. We use the SEM code "RegSEM" for forward computations and a quasi-Newton inversion

Global model for the lithospheric strength and effective elastic thickness

NARCIS (Netherlands)

Tesauro, M.; Kaban, M.K.; Cloetingh, S.A.P.L.

2013-01-01

Global distribution of the strength and effective elastic thickness (Te) of the lithosphere are estimated using physical parameters from recent crustal and lithospheric models. For the Te estimation we apply a new approach, which provides a possibility to take into account variations of Young

The South India Precambrian crust and shallow lithospheric mantle ...

Indian Academy of Sciences (India)

Regional geothermal-barometry in the granulite facies terrane of South India; Contrib. Mineral. Petrol. 73. 221–244. Raith M, Karmakar S and Brown M 1997 Ultra high temparature metamorphism and multi-stage decom- pressional of saphirrine granulite from the Palni-. Hill ranges, southern India; J. Metamorph. Geol. 15.

Ectoparasites from the South American sea lion (Otaria flavescens from Peruvian coast

Directory of Open Access Journals (Sweden)

Luis A. Gomez-Puerta

2015-10-01

Full Text Available Two species of ectoparasites were collected from a South American sea lion (Otaria flavescens found stranded on the beaches of Chorrillos in Lima, Peru. The ectoparasites were identified as Antarctophthirus microchir (Phthiraptera and Orthohalarachne attenuata (Acari. Some morphological characteristics are described in this report. The finding of these ectoparasites is the first records in Peru.

Preliminary three-dimensional model of mantle convection with deformable, mobile continental lithosphere

Science.gov (United States)

Yoshida, Masaki

2010-06-01

Characteristic tectonic structures such as young orogenic belts and suture zones in a continent are expected to be mechanically weaker than the stable part of the continental lithosphere with the cratonic root (or cratonic lithosphere) and yield lateral viscosity variations in the continental lithosphere. In the present-day Earth's lithosphere, the pre-existing, mechanically weak zones emerge as a diffuse plate boundary. However, the dynamic role of a weak (low-viscosity) continental margin (WCM) in the stability of continental lithosphere has not been understood in terms of geophysics. Here, a new numerical simulation model of mantle convection with a compositionally and rheologically heterogeneous, deformable, mobile continental lithosphere is presented for the first time by using three-dimensional regional spherical-shell geometry. A compositionally buoyant and highly viscous continental assemblage with pre-existing WCMs, analogous to the past supercontinent, is modeled and imposed on well-developed mantle convection whose vigor of convection, internal heating rate, and rheological parameters are appropriate for the Earth's mantle. The visco-plastic oceanic lithosphere and the associated subduction of oceanic plates are incorporated. The time integration of the advection of continental materials with zero chemical diffusion is performed by a tracer particle method. The time evolution of mantle convection after setting the model supercontinent is followed over 800 Myr. Earth-like continental drift is successfully reproduced, and the characteristic thermal interaction between the mantle and the continent/supercontinent is observed in my new numerical model. Results reveal that the WCM protects the cratonic lithosphere from being stretched by the convecting mantle and may play a significant role in the stability of the cratonic lithosphere during the geological timescale because it acts as a buffer that prevents the cratonic lithosphere from undergoing global

The rheological structure of the lithosphere in the Eastern Marmara region, Turkey

Science.gov (United States)

Oruç, Bülent; Sönmez, Tuba

2017-05-01

The aim of this work is to propose the geometries of the crustal-lithospheric mantle boundary (Moho) and lithosphere-asthenosphere boundary (LAB) and the 1D thermal structure of the lithosphere, in order to establish a rheological model of the Eastern Marmara region. The average depths of Moho and LAB are respectively 35 km and 51 km from radially averaged amplitude spectra of EGM08 Bouguer anomalies. The geometries of Moho and LAB interfaces are estimated from the Parker-Oldenburg gravity inversion algorithm. Our results show the Moho depth varies from 31 km at the northern part of North Anatolian Fault Zone (NAFZ) to 39 km below the mountain belt in the southern part of the NAFZ. The depth to the LAB beneath the same parts of the region ranges from 45 km to 55 km. Having lithospheric strength and thermal boundary layer structure, we analyzed the conditions of development of lithosphere thinning. A two-dimensional strength profile has been estimated for rheology model of the study area. Thus we suggest that the rheological structure consists of a strong upper crust, a weak lower crust, and a partly molten upper lithospheric mantle.

Lithospheric-scale centrifuge models of pull-apart basins

Science.gov (United States)

Corti, Giacomo; Dooley, Tim P.

2015-11-01

We present here the results of the first lithospheric-scale centrifuge models of pull-apart basins. The experiments simulate relative displacement of two lithospheric blocks along two offset master faults, with the presence of a weak zone in the offset area localising deformation during strike-slip displacement. Reproducing the entire lithosphere-asthenosphere system provides boundary conditions that are more realistic than the horizontal detachment in traditional 1 g experiments and thus provide a better approximation of the dynamic evolution of natural pull-apart basins. Model results show that local extension in the pull-apart basins is accommodated through development of oblique-slip faulting at the basin margins and cross-basin faults obliquely cutting the rift depression. As observed in previous modelling studies, our centrifuge experiments suggest that the angle of offset between the master fault segments is one of the most important parameters controlling the architecture of pull-apart basins: the basins are lozenge shaped in the case of underlapping master faults, lazy-Z shaped in case of neutral offset and rhomboidal shaped for overlapping master faults. Model cross sections show significant along-strike variations in basin morphology, with transition from narrow V- and U-shaped grabens to a more symmetric, boxlike geometry passing from the basin terminations to the basin centre; a flip in the dominance of the sidewall faults from one end of the basin to the other is observed in all models. These geometries are also typical of 1 g models and characterise several pull-apart basins worldwide. Our models show that the complex faulting in the upper brittle layer corresponds at depth to strong thinning of the ductile layer in the weak zone; a rise of the base of the lithosphere occurs beneath the basin, and maximum lithospheric thinning roughly corresponds to the areas of maximum surface subsidence (i.e., the basin depocentre).

The South American Mailed Catfishes of the genus Pseudoloricaria Bleeker, 1862 (Pisces, Siluriformes, Loricariidae)

NARCIS (Netherlands)

Isbrücker, I.J.H.; Nijssen, H.

1976-01-01

Two species of South American Mailed Catfishes of the genus Pseudoloricaria Bleeker, 1862 are redescribed and figured from type-specimens and additional material: Pseudoloricaria laeviuscula (Valenciennes, 1840), and Pseudoloricaria punctata (Regan, 1904). Since the provenance of the holotype of P.

Metamorphism and Shear Localization in the Oceanic and Continental Lithosphere: A Local or Lithospheric-Scale Effect?

Science.gov (United States)

Montesi, L.

2017-12-01

Ductile rheologies are characterized by strain rate hardening, which favors deformation zones that are as wide as possible, thus minimizing strain rate and stress. By contrast, plate tectonics and the observation of ductile shear zones in the exposed middle to lower crust show that deformation is often localized, that is, strain (and likely strain rate) is locally very high. This behavior is most easily explained if the material in the shear zone is intrinsically weaker than the reference material forming the wall rocks. Many origins for that weakness have been proposed. They include higher temperature (shear heating), reduced grain size, and fabric. The latter two were shown to be the most effective in the middle crust and upper mantle (given observational limits restricting heating to 50K or less) but they were not very important in the lower crust. They are not sufficient to explain the generation of narrow plate boundaries in the oceans. We evaluate here the importance of metamorphism, especially related to hydration, in weakening the lithosphere. Serpentine is a major player in the dynamics of the oceanic lithosphere. Although its ductile behavior is poorly constrained, serpentine is likely to behave in a brittle or quasi-plastic manner with a reduced coefficient of friction, replacing stronger peridotite. Serpentinization sufficiently weakens the oceanic lithosphere to explain the generation of diffuse plate boundaries and, combined with grain size reduction, the development of narrow plate boundaries. Lower crust outcrops, especially in the Bergen Arc (Norway), display eclogite shear zones hosted in metastable granulites. The introduction of water triggered locally a metamorphic reaction that reduces rock strength and resulted in a ductile shear zone. The presence of these shear zones has been used to explain the weakness of the lower crust perceived from geodesy and seismic activity. We evaluate here how much strain rate may increase as a result of

Structure of the lithosphere-asthenosphere system in the vicinity of the Tristan da Cunha hot spot as seen by surface waves

Science.gov (United States)

Bonadio, Raffaele; Geissler, Wolfram H.; Ravenna, Matteo; Lebedev, Sergei; Celli, Nicolas L.; Jokat, Wilfried; Jegen, Marion; Sens-Schönfelder, Christoph; Baba, Kiyoshi

2017-04-01

Tristan da Cunha is a volcanic island located above a hotspot in the South Atlantic. The deep mantle plume origin of the hotspot volcanism at the island is supported by anomalous geochemical data (Rohde et al., 2013 [1]) and global seismological evidences (French and Romanovicz, 2015 [2]). However, until recently, due to lack of local geophysical data in the South Atlantic and especially around Tristan da Cunha, the existence of a plume has not yet been confirmed. Therefore, an Ocean Bottom Seismometer experiment was carried out in 2012 and 2013 in the vicinity of the archipelago, with the aim of obtaining geophysical data that may help to get some more detailed insights into the structure of the upper mantle, possibly confirming the existence of a plume. In this work we study the shear wave velocity structure of the lithosphere-asthenosphere system beneath the Island. Rayleigh surface wave phase velocity dispersion curves have been obtained using a recent powerful implementation of the inter-station cross-correlation method (Meier et al., 2004 [3]; Soomro et al., 2016 [4]). The measured dispersion curves are used to invert for the 1D shear wave velocity structure beneath the study area and to obtain phase velocity tomographic maps. Our results show a pronounced low shear wave velocity anomaly between 70 and 120 km depth beneath the area; the lid shows high velocity, suggesting a cold, depleted and dehydrated shallow lithosphere, while the deeper lithosphere shows a velocity structure similar to young or rejuvenated Pacific oceanic lithosphere (Laske et al., 2011 [5]; Goes et al., 2012 [6]). Below the base of the lithosphere, shear wave velocities appear to be low, suggesting thermal effects and partial melting (as confirmed by petrological data). Decreasing velocities within the lithosphere south-westward reflect probably a thermal imprint of an underlying mantle plume. References [1] J.K. Rohde, P. van den Bogaard, K. Hoernle, F. Hauff, R. Werner, Evidence for an

A deforestation-induced tipping point for the South American monsoon system

Science.gov (United States)

Boers, Niklas; Marwan, Norbert; Barbosa, Henrique M. J.; Kurths, Jürgen

2017-01-01

The Amazon rainforest has been proposed as a tipping element of the earth system, with the possibility of a dieback of the entire ecosystem due to deforestation only of parts of the rainforest. Possible physical mechanisms behind such a transition are still subject to ongoing debates. Here, we use a specifically designed model to analyse the nonlinear couplings between the Amazon rainforest and the atmospheric moisture transport from the Atlantic to the South American continent. These couplings are associated with a westward cascade of precipitation and evapotranspiration across the Amazon. We investigate impacts of deforestation on the South American monsoonal circulation with particular focus on a previously neglected positive feedback related to condensational latent heating over the rainforest, which strongly enhances atmospheric moisture inflow from the Atlantic. Our results indicate the existence of a tipping point. In our model setup, crossing the tipping point causes precipitation reductions of up to 40% in non-deforested parts of the western Amazon and regions further downstream. The responsible mechanism is the breakdown of the aforementioned feedback, which occurs when deforestation reduces transpiration to a point where the available atmospheric moisture does not suffice anymore to release the latent heat needed to maintain the feedback.

A lithospheric perspective on structure and evolution of Precambrian cratons

DEFF Research Database (Denmark)

Artemieva, Irina

2012-01-01

The purpose of this chapter is to provide a summary of geophysical data on the structure of the stable continental lithosphere and its evolution since the Archean. Here, the term lithosphere is used to define the outer layer of the Earth which includes the crust and uppermost mantle, forms the ro...

South American energy integration: new perspectives; Novas perspectivas para a integracao energetica sul-americana

Energy Technology Data Exchange (ETDEWEB)

Silva, Jose Malhaes da [Malhaes da Silva Consultoria Ltda., Rio de Janeiro, RJ (Brazil); Salomao, Luiz Alfredo [Universidade Candido Mendes, Rio de Janeiro, RJ (Brazil). Escola de Politicas Publicas e Governo

2008-07-01

This paper analyses the South American energy integration, the advantages related to this process as well as the existing obstacles . What is the scope in terms of projects and initiatives, and the role of political and institutional barriers to be overcome. (author)

Double subduction of continental lithosphere, a key to form wide plateau

Science.gov (United States)

Replumaz, Anne; Funiciello, Francesca; Reitano, Riccardo; Faccenna, Claudio; Balon, Marie

2016-04-01

The mechanisms involved in the creation of the high and wide topography, like the Tibetan Plateau, are still controversial. In particular, the behaviour of the indian and asian lower continental lithosphere during the collision is a matter of debate, either thickening, densifying and delaminating, or keeping its rigidity and subducting. But since several decades seismicity, seismic profiles and global tomography highlight the lithospheric structure of the Tibetan Plateau, and make the hypotheses sustaining the models more precise. In particular, in the western syntaxis, it is now clear that the indian lithosphere subducts northward beneath the Hindu Kush down to the transition zone, while the asian one subducts southward beneath Pamir (e.g. Negredo et al., 2007; Kufner et al., 2015). Such double subduction of continental lithospheres with opposite vergence has also been inferred in the early collision time. Cenozoic volcanic rocks between 50 and 30 Ma in the Qiangtang block have been interpreted as related to an asian subduction beneath Qiangtang at that time (De Celles et al., 2011; Guillot and Replumaz, 2013). We present here analogue experiments silicone/honey to explore the subduction of continental lithosphere, using a piston as analogue of far field forces. We explore the parameters that control the subductions dynamics of the 2 continental lithospheres and the thickening of the plates at the surface, and compare with the Tibetan Plateau evolution. We show that a continental lithosphere is able to subduct in a collision context, even lighter than the mantle, if the plate is rigid enough. In that case the horizontal force due to the collision context, modelled by the piston push transmitted by the indenter, is the driving force, not the slab pull which is negative. It is not a subduction driving by the weight of the slab, but a subduction induced by the collision, that we could call "collisional subduction".

Lithospheric controls on magma composition along Earth's longest continental hotspot track.

Science.gov (United States)

Davies, D R; Rawlinson, N; Iaffaldano, G; Campbell, I H

2015-09-24

Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep mantle to its surface. It has long been recognized that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, so far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot track, a 2,000-kilometre-long track in eastern Australia that displays a record of volcanic activity between 33 and 9 million years ago, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (1) standard basaltic compositions in regions where lithospheric thickness is less than 110 kilometres; (2) volcanic gaps in regions where lithospheric thickness exceeds 150 kilometres; and (3) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the sub-continental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

Imaging Canary Island hotspot material beneath the lithosphere of Morocco and southern Spain

Science.gov (United States)

Miller, Meghan S.; O'Driscoll, Leland J.; Butcher, Amber J.; Thomas, Christine

2015-12-01

The westernmost Mediterranean has developed into its present day tectonic configuration as a result of complex interactions between late stage subduction of the Neo-Tethys Ocean, continental collision of Africa and Eurasia, and the Canary Island mantle plume. This study utilizes S receiver functions (SRFs) from over 360 broadband seismic stations to seismically image the lithosphere and uppermost mantle from southern Spain through Morocco and the Canary Islands. The lithospheric thickness ranges from ∼65 km beneath the Atlas Mountains and the active volcanic islands to over ∼210 km beneath the cratonic lithosphere in southern Morocco. The common conversion point (CCP) volume of the SRFs indicates that thinned lithosphere extends from beneath the Canary Islands offshore southwestern Morocco, to beneath the continental lithosphere of the Atlas Mountains, and then thickens abruptly at the West African craton. Beneath thin lithosphere between the Canary hot spot and southern Spain, including below the Atlas Mountains and the Alboran Sea, there are distinct pockets of low velocity material, as inferred from high amplitude positive, sub-lithospheric conversions in the SRFs. These regions of low seismic velocity at the base of the lithosphere extend beneath the areas of Pliocene-Quaternary magmatism, which has been linked to a Canary hotspot source via geochemical signatures. However, we find that this volume of low velocity material is discontinuous along strike and occurs only in areas of recent volcanism and where asthenospheric mantle flow is identified with shear wave splitting analyses. We propose that the low velocity structure beneath the lithosphere is material flowing sub-horizontally northeastwards beneath Morocco from the tilted Canary Island plume, and the small, localized volcanoes are the result of small-scale upwellings from this material.

War, religion, and white supremacy in comparative perspective: South Africa and the American South

Directory of Open Access Journals (Sweden)

R M�ller

2004-10-01

Full Text Available The southern states of the United States of America and South Africa share a number of analogous historical realities. One of these, which is the main subject of� this article,� is� the way in which the memory of a lost war had fused cultural mythology and religious symbolism to provide a foundation for the formation and maintenance of attitudes of white supremacy in both contexts.� This article seeks to achieve a historical� understanding of the complex interrelationship between the development of cultural identity and Protestant Christianity by� focusing on these issues in the histories of the Afrikaner and the white American Southerner in comparative perspective.�

Distributional patterns of the South American species of Hyalella (Amphipoda: Hyalellidae)

OpenAIRE

De los Ríos-Escalante, Patricio; Morrone, Juan J; Rivera, Reinaldo

2012-01-01

Distributional patterns of the South American species of the freshwater amphipod genus Hyalella were analysed using a panbiogeographic approach. Five generalized tracks were found: (1) northern Andes to Lake Titicaca (H. dielaii, H. meinerti, H. dybowskii, H.jelskii, H. lubominsky, and H. pauperocavae; (2) lake Titicaca (H. armata, H. cuprea, H. latinamus, H. lucifugax, H. montforti, H. neveulemairei, H. robusta, H. tiwanaku, H. simplex simplex, and H. solida); (3) central Andes (H. fossamanc...

U.S. foreign policy, the south american integration, and the case of the military bases in Colombia

OpenAIRE

Iglesias Cavicchioli, Manuel

2010-01-01

This article analyzes the nature of the conflict generated in South America by the adoption of the new military agreement between the U.S. and Colombia. The article will evaluate the political and the geostrategic implications of this agreement, especially its repercussions for the regional integration process of South America. It will also analyze the stances of the local actors in order to consider prospective scenarios, and will assess the U.S. approach to South American int...

Characterising East Antarctic Lithosphere and its Rift Systems using Gravity Inversion

Science.gov (United States)

Vaughan, Alan P. M.; Kusznir, Nick J.; Ferraccioli, Fausto; Leat, Phil T.; Jordan, Tom A. R. M.; Purucker, Michael E.; Golynsky, A. V. Sasha; Rogozhina, Irina

2013-04-01

Since the International Geophysical Year (1957), a view has prevailed that East Antarctica has a relatively homogeneous lithospheric structure, consisting of a craton-like mosaic of Precambrian terranes, stable since the Pan-African orogeny ~500 million years ago (e.g. Ferracioli et al. 2011). Recent recognition of a continental-scale rift system cutting the East Antarctic interior has crystallised an alternative view of much more recent geological activity with important implications. The newly defined East Antarctic Rift System (EARS) (Ferraccioli et al. 2011) appears to extend from at least the South Pole to the continental margin at the Lambert Rift, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. New analysis of RadarSat data by Golynsky & Golynsky (2009) indicates that further rift zones may form widely distributed extension zones within the continent. A pilot study (Vaughan et al. 2012), using a newly developed gravity inversion technique (Chappell & Kusznir 2008) with existing public domain satellite data, shows distinct crustal thickness provinces with overall high average thickness separated by thinner, possibly rifted, crust. Understanding the nature of crustal thickness in East Antarctica is critical because: 1) this is poorly known along the ocean-continent transition, but is necessary to improve the plate reconstruction fit between Antarctica, Australia and India in Gondwana, which will also better define how and when these continents separated; 2) lateral variation in crustal thickness can be used to test supercontinent reconstructions and assess the effects of crystalline basement architecture and mechanical properties on rifting; 3) rift zone trajectories through East Antarctica will define the geometry of zones of crustal and lithospheric thinning at plate-scale; 4) it is not clear why or when the crust of East Antarctica became so thick and elevated, but knowing this can be used to test models of

Time, Space, and National Belonging in The Namesake: Redrawing South Asian American Citizenship in the Shadow of 9/11

Directory of Open Access Journals (Sweden)

Sue Brennan

2011-03-01

Full Text Available

The terms of national belonging after 9/11 for South Asian Americans have taken shape through a vague and depoliticized discourse around ethnic identity, one in which the clichés of multiculturalism and melting-pot nationalism stand in for the specific socioeconomic and historical conditions that helped form the South Asian diaspora in the US. This paper explores the ways in which Jhumpa Lahiri’s novel The Namesake and its cinematic adaptation by filmmaker Mira Nair challenge the erasure of South Asian American citizenship following 9/11. Recounting the journey of a young Bengali graduate student and his wife migrating to the US in the late 1960s, each text speaks back to the erasure of South Asian American citizenship through the materialization of time in space: while Lahiri foregrounds the state itself in producing the rhythms through which immigrants are assimilated into the nation, Nair creates a narrative world in which filmic space materializes many, and often competing, histories, unifying multiple temporalities and histories through the representations of space. I argue that the cinematic adaptation of The Namesake generates a new spatiotemporal state of affairs, one in which the iconography of 9/11 both challenges post-9/11 racial logics and destabilizes the singular, progressive, and institutionalized temporality through which Lahiri writes South Asian American immigrants back into nation.

Prevalence of neurodevelopmental disorders among low-income African Americans at a clinic on Chicago's south side.

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Bell, Carl C; Chimata, Radhika

2015-05-01

This study examined the point prevalence of neurodevelopmental disorders among predominantly low-income, African-American psychiatric patients at Jackson Park Hospital's Family Medicine Clinic on Chicago's South Side. Using active case ascertainment methodology, the authors assessed the records of 611 psychiatric patients visiting the clinic between May 23, 2013, and January 14, 2014, to identify those with DSM-5 neurodevelopmental disorders. A total of 297 patients (49%) met criteria for a neurodevelopmental disorder during childhood. Moreover, 237 (39%) had clinical profiles consistent with neurobehavioral disorder associated with prenatal alcohol exposure, and 53 (9%) had other neurodevelopmental disorders. The authors disagreed on the specific type of neurodevelopmental disorder of seven (1% of 611) of the 297 patients with neurodevelopmental disorders. A high prevalence of neurodevelopmental disorders was found among low-income predominantly African-American psychiatric patients on Chicago's South Side. If replicated, these findings should bring about substantial changes in medical practice with African-American patients.

Fossil plume head beneath the Arabian lithosphere?

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Stein, Mordechai; Hofmann, Albrecht W.

1992-12-01

Phanerozoic alkali basalts from Israel, which have erupted over the past 200 Ma, have isotopic compositions similar to PREMA ("prevalent mantle") with narrow ranges of initial ɛ Nd(T) = +3.9-+5.9; 87Sr/ 86Sr(T)= 0.70292-0.70334; 206Pb/ 204Pb(T)= 18.88-19.99; 207Pb/ 204Pb(T)= 15.58-15.70; and 208Pb/ 204Pb(T)= 38.42-39.57. Their Nb/U(43 ± 9) and Ce/Pb(26 ± 6) ratios are identical to those of normal oceanic basalts, demonstrating that the basalts are essentially free of crustal contamination. Overall, the basalts are chemically and isotopically indistinguishable from many ordinary plume basalts, but no plume track can be identified. We propose that these and other, similar, magmas from the Arabian plate originated from a "fossilized" head of a mantle plume, which was unable to penetrate the continental lithosphere and was therefore trapped and stored beneath it. The plume head was emplaced some time between the late Proterozoic crust formation and the initiation of the Phanerozoic magmatic cycles. Basalts from rift environments in other continental localities show similar geochemistry to that of the Arabian basalts and their sources may also represent fossil plume heads trapped below the continents. We suggest that plume heads are, in general, characterized by the PREMA isotopic mantle signature, because the original plume sources (which may have HIMU or EM-type composition) have been diluted by overlying mantle material, which has been entrained by the plume heads during ascent. On the Arabian plate, rifting and thinning of the lithosphere caused partial melting of the stored plume, which led to periodic volcanism. In the late Cenozoic, the lithosphere broke up and the Red Sea opened. N-MORB tholeiites are now erupting in the central trough of the Red Sea, where the lithosphere has moved apart and the fossil plume has been exhausted, whereas E-MORBs are erupting in the northern and southern troughs, still tapping the plume reservoir. Fossil plumes, which are

Lithospheric flexural strength and effective elastic thicknesses of the Eastern Anatolia (Turkey) and surrounding region

Science.gov (United States)

Oruç, Bülent; Gomez-Ortiz, David; Petit, Carole

2017-12-01

The Lithospheric structure of Eastern Anatolia and the surrounding region, including the northern part of the Arabian platform is investigated via the analysis and modeling of Bouguer anomalies from the Earth Gravitational Model EGM08. The effective elastic thickness of the lithosphere (EET) that corresponds to the mechanical cores of the crust and lithospheric mantle is determined from the spectral coherence between Bouguer anomalies and surface elevation data. Its average value is 18.7 km. From the logarithmic amplitude spectra of Bouguer anomalies, average depths of the lithosphere-asthenosphere boundary (LAB), Moho, Conrad and basement in the study area are constrained at 84 km, 39 km, 16 km and 7 km, respectively. The geometries of the LAB and Moho are then estimated using the Parker-Oldenburg inversion algorithm. We also present a lithospheric strength map obtained from the spatial variations of EET determined by Yield Stress Envelopes (YSE). The EET varies in the range of 12-23 km, which is in good agreement with the average value obtained from spectral analysis. Low EET values are interpreted as resulting from thermal and flexural lithospheric weakening. According to the lithospheric strength of the Eastern Anatolian region, the rheology model consists of a strong but brittle upper crust, a weak and ductile lower crust, and a weak lower part of the lithosphere. On the other hand, lithosphere strength corresponds to weak and ductile lower crust, a strong upper crust and a strong uppermost lithospheric mantle for the northern part of the Arabian platform.

A comparative study between South African serial killers and their American counterparts

OpenAIRE

2009-01-01

M.A. This dissertation explores the similarities and differences between South African serial killers and their American counterparts. Seven male candidates, each having committed their reign of terror within the relevant time period, have been included. The candidates compared well in home environments, number of friendships, emotional maturity, abuse undergone, temperament, and anti-social behaviour. Differences were found in comparing family bonding, wealth and education. This dissertat...

Anthropozoonotic Endoparasites in Free-Ranging “Urban” South American Sea Lions (Otaria flavescens

Directory of Open Access Journals (Sweden)

Carlos Hermosilla

2016-01-01

Full Text Available The present study represents the first report on the gastrointestinal endoparasite fauna of a free-ranging “urban” colony of South American sea lions (Otaria flavescens living within the city of Valdivia, Chile. A total of 40 individual faecal samples of South American sea lions were collected during the year 2012 within their natural habitat along the river Calle-Calle and in the local fish market of Valdivia. Coprological analyses applying sodium acetate acetic formalin methanol (SAF technique, carbol fuchsin-stained faecal smears and Giardia/Cryptosporidium coproantigen ELISAs, revealed infections with 8 different parasites belonging to protozoan and metazoan taxa with some of them bearing anthropozoonotic potential. Thus, five of these parasites were zoonotic (Diphyllobothriidae gen. sp., Anisakidae gen. sp., Giardia, Cryptosporidium, and Balantidium. Overall, these parasitological findings included four new parasite records for Otaria flavescens, that is, Giardia, Cryptosporidium, Balantidium, and Otostrongylus. The current data serve as a baseline for future monitoring studies on anthropozoonotic parasites circulating in these marine mammals and their potential impact on public health.

Anthropozoonotic Endoparasites in Free-Ranging “Urban” South American Sea Lions (Otaria flavescens)

Science.gov (United States)

Silva, Liliana M. R.; Navarro, Mauricio; Taubert, Anja

2016-01-01

The present study represents the first report on the gastrointestinal endoparasite fauna of a free-ranging “urban” colony of South American sea lions (Otaria flavescens) living within the city of Valdivia, Chile. A total of 40 individual faecal samples of South American sea lions were collected during the year 2012 within their natural habitat along the river Calle-Calle and in the local fish market of Valdivia. Coprological analyses applying sodium acetate acetic formalin methanol (SAF) technique, carbol fuchsin-stained faecal smears and Giardia/Cryptosporidium coproantigen ELISAs, revealed infections with 8 different parasites belonging to protozoan and metazoan taxa with some of them bearing anthropozoonotic potential. Thus, five of these parasites were zoonotic (Diphyllobothriidae gen. sp., Anisakidae gen. sp., Giardia, Cryptosporidium, and Balantidium). Overall, these parasitological findings included four new parasite records for Otaria flavescens, that is, Giardia, Cryptosporidium, Balantidium, and Otostrongylus. The current data serve as a baseline for future monitoring studies on anthropozoonotic parasites circulating in these marine mammals and their potential impact on public health. PMID:27051860

Weak depth and along-strike variations in stretching from a multi-episodic finite stretching model: Evidence for uniform pure-shear extension in the opening of the South China Sea

Science.gov (United States)

Chen, Lin; Zhang, Zhongjie; Song, Haibin

2013-12-01

The South China Sea is widely believed to have been opened by seafloor spreading during the Cenozoic. The details of its lithospheric extension are still being debated, and it is unknown whether pure, simple, or conjunct shears are responsible for the opening of the South China Sea. The depth-dependent and along-strike extension derived from the single-stage finite stretching model or instantaneous stretching model is inconsistent with the observation that the South China Sea proto-margins have experienced multi-episodic extension since the Late Cretaceous. Based on the multi-episodic finite stretching model, we present the amount of lithosphere stretching at the northern continental margin of the South China Sea for different depth scales (upper crust, whole crust and lithosphere) and along several transects. The stretching factors are estimated by integrating seven deep-penetration seismic profiles, the Moho distribution derived from gravity modeling, and the tectonic subsidence data for 41 wells. The results demonstrate that the amount of stretching increases rapidly from 1.1 at the continent shelf to over 3.5 at the lower slope, but the stretching factors at the crust and lithosphere scales are consistent within error (from the uncertainty in paleobathymetry and sea-level change). Furthermore, the along-strike variation in stretching factor is within the range of 1.11-1.9 in west-east direction, accompanied by significant west-east differences in the thickness of high-velocity layers (HVLs) within the lowermost crust. This weak along-strike variation of the stretching factor is most likely produced by the preexisting contrasts in the composition and thermal structure of the lithosphere. The above observations suggest that the continental extension in the opening of the South China Sea mainly takes the form of a uniform pure shear rather than depth-dependent stretching.

Extensional and compressional instabilities in icy satellite lithospheres

International Nuclear Information System (INIS)

Herrick, D.L.; Stevenson, D.J.

1990-01-01

The plausibility of invoking a lithospheric instability mechanism to account for the grooved terrains on Ganymede, Encedalus, and Miranda is presently evaluated in light of the combination of a simple mechanical model of planetary lithospheres and asthenospheres with recent experimental data for the brittle and ductile deformation of ice. For Ganymede, high surface gravity and warm temperatures render the achievement of an instability sufficiently great for the observed topographic relief virtually impossible; an instability of sufficient strength, however, may be able to develop on such smaller, colder bodies as Encedalus and Miranda. 15 refs

Global variations in gravity-derived oceanic crustal thickness: Implications on oceanic crustal accretion and hotspot-lithosphere interactions

Science.gov (United States)

Lin, J.; Zhu, J.

2012-12-01

We present a new global model of oceanic crustal thickness based on inversion of global oceanic gravity anomaly with constrains from seismic crustal thickness profiles. We first removed from the observed marine free-air gravity anomaly all gravitational effects that can be estimated and removed using independent constraints, including the effects of seafloor topography, marine sediment thickness, and the age-dependent thermal structure of the oceanic lithosphere. We then calculated models of gravity-derived crustal thickness through inversion of the residual mantle Bouguer anomaly using best-fitting gravity-modeling parameters obtained from comparison with seismically determined crustal thickness profiles. Modeling results show that about 5% of the global crustal volume (or 9% of the global oceanic surface area) is associated with model crustal thickness 8.6 km and is interpreted to have been affected by excess magmatism. The percentage of oceanic crustal volume that is associated with thick crustal thickness (>8.6 km) varies greatly among tectonic plates: Pacific (33%), Africa (50%), Antarctic (33%), Australia (30%), South America (34%), Nazca (23%), North America (47%), India (74%), Eurasia (68%), Cocos (20%), Philippine (26%), Scotia (41%), Caribbean (89%), Arabian (82%), and Juan de Fuca (21%). We also found that distribution of thickened oceanic crust (>8.6 km) seems to depend on spreading rate and lithospheric age: (1) On ocean basins younger than 5 Ma, regions of thickened crust are predominantly associated with slow and ultraslow spreading ridges. The relatively strong lithospheric plate at slow and ultraslow ridges might facilitate the loading of large magmatic emplacements on the plate. (2) In contrast, crustal thickness near fast and intermediately fast spreading ridges typically does not exceed 7-8 km. The relatively weak lithosphere at fast and intermediately fast ridges might make it harder for excess magmatism to accrete. We further speculate that

Electrical structure of the lithosphere across the Western Paraná suture zone: the role of a Neoproterozoic-Cambrian subduction in generating the Paraná Magmatic Province

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Dragone, G. N.; Bologna, M.; Gimenez, M. E.; Alvarez, O.; Lince Klinger, F. G.; Correa-Otto, S.; Ussami, N.

2017-12-01

The Paraná Magmatic Province (PMP) together with the Etendeka Province (EP) in Africa is one of the Earth's largest igneous provinces originated prior to the Western Gondwanaland break-up and the inception of the South Atlantic Ocean in the Lower Cretaceous. Geochemical data of PMP-EP basalts collected since late 1980's indicate the origin of PMP-EP by melting of a heterogeneous and enriched subcontinental lithospheric mantle with fast rate of eruption (borders of the PMP, the Western Paraná suture zone (WPS in Fig. 1). We discuss the electrical properties of the lithosphere along three MT profiles across the WPS. MT-A profile (Padilha et al., 2015, JGR) extends from Rio Apa craton towards the center of PMP (high-TiO2 basalts). Profile MT-B extends from Tebicuary craton towards the center of PMP (low-TiO2) and profile MT-C extends from Rio de la Plata craton towards the southern PMP (low- and high-TiO2). All profiles show a resistive ( 104 ohm m) and thick (> 150 km) lithosphere in the cratonic areas whereas the electrical lithosphere is thinner (<100 km) with alternating high and low resistivities within PMP. Vertically elongated and high electrical conductivity anomalies ( 10 ohm m) centered at 40 km depth occur along the -30 mGal contour line in the three profiles, and are interpreted as the location of the suture and former subduction zone. We will discuss the correlation between geochemical and petrological characteristics of basalts and the electrical properties of the lithospheric mantle underneath.

Lithospheric strucutre and relationship to seismicity beneath the Southeastern US using reciever functions

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Cunningham, E.; Lekic, V.

2017-12-01

Despite being on a passive margin for millions of years, the Southeastern United States (SEUS) contains numerous seismogenic zones with the ability to produce damaging earthquakes. However, mechanisms controlling these intraplate earthquakes are poorly understood. Recently, Biryol et al. 2016 use P-wave tomography suggest that upper mantle structures beneath the SEUS correlate with areas of seismicity and seismic quiescence. Specifically, thick and fast velocity lithosphere beneath North Carolina is stable and indicative of areas of low seismicity. In contrast, thin and slow velocity lithosphere is weak, and the transition between the strong and weak lithosphere may be correlated with seismogenic zones found in the SEUS. (eg. Eastern Tennessee seismic zone and the Central Virginia seismic zone) Therefore, I systematically map the heterogeneity of the mantle lithosphere using converted seismic waves and quantify the spatial correlation between seismicity and lithospheric structure. The extensive network of seismometers that makes up the Earthscope USArray combined with the numerous seismic deployments in the Southeastern United States allows for unprecedented opportunity to map changes in lithospheric structure across seismogenic zones and seismic quiescent regions. To do so, I will use both P-to-s and S-to-p receiver functions (RFS). Since RFs are sensitive to seismic wavespeeds and density discontinuities with depth, they particularly useful for studying lithospheric structure. Ps receiver functions contain high frequency information allowing for high resolution, but can become contaminated by large sediment signals; therefore, I removed sediment multiples and correct for time delays of later phases using the method of Yu et. al 2015 which will allow us to see later arriving phases associated with lithospheric discontinuities. S-to-p receiver functions are not contaminated by shallow layers, making them ideal to study deep lithospheric structures but they can

Power law olivine crystal size distributions in lithospheric mantle xenoliths

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Armienti, P.; Tarquini, S.

2002-12-01

Olivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic-porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 μm and applying stereological corrections based on the Schwartz-Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2-25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts. A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than 1 mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in rheological models and evaluation of metasomatic models.

Continental lithosphere of the Arabian Plate: A geologic, petrologic, and geophysical synthesis

Science.gov (United States)

Stern, Robert J.; Johnson, Peter

2010-07-01

The Arabian Plate originated ˜ 25 Ma ago by rifting of NE Africa to form the Gulf of Aden and Red Sea. It is one of the smaller and younger of the Earth's lithospheric plates. The upper part of its crust consists of crystalline Precambrian basement, Phanerozoic sedimentary cover as much as 10 km thick, and Cenozoic flood basalt (harrat). The distribution of these rocks and variations in elevation across the Plate cause a pronounced geologic and topographic asymmetry, with extensive basement exposures (the Arabian Shield) and elevations of as much as 3000 m in the west, and a Phanerozoic succession (Arabian Platform) that thickens, and a surface that descends to sea level, eastward between the Shield and the northeastern margin of the Plate. This tilt in the Plate is partly the result of marginal uplift during rifting in the south and west, and loading during collision with, and subduction beneath, the Eurasian Plate in the northeast. But a variety of evidence suggests that the asymmetry also reflects a fundamental crustal and mantle heterogeneity in the Plate that dates from Neoproterozoic time when the crust formed. The bulk of the Plate's upper crystalline crust is Neoproterozoic in age (1000-540 Ma) reflecting, in the west, a 300-million year process of continental crustal growth between ˜ 850 and 550 Ma represented by amalgamated juvenile magmatic arcs, post-amalgamation sedimentary and volcanic basins, and granitoid intrusions that make up as much as 50% of the Shield's surface. Locally, Archean and Paleoproterozoic rocks are structurally intercalated with the juvenile Neoproterozoic rocks in the southern and eastern parts of the Shield. The geologic dataset for the age, composition, and origin of the upper crust of the Plate in the east is smaller than the database for the Shield, and conclusions made about the crust in the east are correspondingly less definitive. In the absence of exposures, furthermore, nothing is known by direct observation about the

Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle.

Science.gov (United States)

Prieto, Germán A; Froment, Bérénice; Yu, Chunquan; Poli, Piero; Abercrombie, Rachel

2017-03-01

Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of temperature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. On the basis of complete earthquake energy balance estimates using broadband waveforms and temperature estimates using surface heat flow and shear wave velocities, we argue that this earthquake occurred in response to ductile deformation at temperatures above 750°C. The high stress drop, low rupture velocity, and low radiation efficiency are all consistent with a dissipative mechanism. Our results imply that earthquake nucleation in the lithospheric mantle is not exclusively limited to the brittle regime; weakening mechanisms in the ductile regime can allow earthquakes to initiate and propagate. This finding has significant implications for understanding deep earthquake rupture mechanics and rheology of the continental lithosphere.

Subduction initiation, recycling of Alboran lower crust, and intracrustal emplacement of subcontinental lithospheric mantle in the Westernmost Mediterranean

Science.gov (United States)

Varas-Reus, María Isabel; Garrido, Carlos J.; Bosch, Delphine; Marchesi, Claudio; Hidas, Károly; Booth-Rea, Guillermo; Acosta-Vigil, Antonio

2015-04-01

Unraveling the tectonic settings and processes involved in the annihilation of subcontinental mantle lithosphere is of paramount importance for our understanding of the endurance of continents through Earth history. Unlike ophiolites -- their oceanic mantle lithosphere counterparts -- the mechanisms of emplacement of the subcontinental mantle lithosphere in orogens is still poorly known. The emplacement of subcontinental lithospheric mantle peridotites is often attributed to extension in rifted passive margins or continental backarc basins, accretionary processes in subduction zones, or some combination of these processes. One of the most prominent features of the westernmost Mediterranean Alpine orogenic arcs is the presence of the largest outcrops worldwide of diamond facies, subcontinental mantle peridotite massifs; unveiling the mechanisms of emplacement of these massifs may provide important clues on processes involved in the destruction of continents. The western Mediterranean underwent a complex Alpine evolution of subduction initiation, slab fragmentation, and rollback within a context of slow convergence of Africa and Europe In the westernmost Mediterranean, the alpine orogeny ends in the Gibraltar tight arc, which is bounded by the Betic, Rif and Tell belts that surround the Alboran and Algero-Balearic basins. The internal units of these belts are mostly constituted of an allochthonous lithospheric domain that collided and overthrusted Mesozoic and Tertiary sedimentary rocks of the Mesozoic-Paleogene, South Iberian and Maghrebian rifted continental paleomargins. Subcontinental lithospheric peridotite massifs are intercalated between polymetamorphic internal units of the Betic (Ronda, Ojen and Carratraca massifs), Rif (Beni Bousera), and Tell belts. In the Betic chain, the internal zones of the allochthonous Alboran domain include, from bottom to top, polymetamorphic rock of the Alpujarride and Malaguide complexes. The Ronda peridotite massif -- the

Lithospheric thermal-rheological structure of the Ordos Basin and its geodynamics

Science.gov (United States)

Pan, J.; Huang, F.; He, L.; Wu, Q.

2015-12-01

The study on the destruction of the North China Craton has always been one of the hottest issues in earth sciences.Both mechanism and spatial variation are debated fiercely, still unclear.However, geothermal research on the subject is relatively few. Ordos Basin, located in the west of the North China Craton, is a typical intraplate. Based on two-dimensional thermal modeling along a profile across Ordos Basin from east to west, obtained the lithospheric thermal structure and rheology. Mantle heat flow in different regions of Ordos Basin is from 21.2 to 24.5 mW/m2. In the east mantle heat flow is higher while heat flow in western region is relatively low. But mantle heat flow is smooth and low overall, showing a stable thermal background. Ratio of crustal and mantle heat flow is between 1.51 and 1.84, indicating that thermal contribution from shallow crust is lower than that from the mantle. Rheological characteristics along the profile are almost showed as "jelly sandwich" model and stable continental lithosphere structure,which is represent by a weak crust portion but a strong lithospheric mantle portion in vertical strength profile. Based on above , both thermal structure and lithospheric rheology of Ordos Basin illustrate that tectonic dynamics environment in the west of North China Craton is relatively stable. By the study on lithospheric thermal structure, we focus on the disparity in thickness between the thermal lithosphere and seismic lithosphere.The difference in western Ordos Basin is about 140km, which decreases gradually from Fenwei graben in the eastern Ordos Basin to the Bohai Bay Basin.That is to say the difference decreases gradually from the west to the east of North China Craton.The simulation results imply that viscosity of the asthenosphere under North China Craton also decreases gradually from west to east, confirming that dehydration of the Pacific subduction is likely to have great effect on the North China Craton.

Prosopis pod production - comparison of North American, South American, Hawaiian, and African germplasm in young plantations

Energy Technology Data Exchange (ETDEWEB)

Felker, P.; Clark, P.R.; Osborn, J.F.; Cannell, G.H.

Prosopis pod production was compared in 3 field trials in southern California, i.e., a typical orchard planting, an irrigation trial, and a heat/drought stress trial. Thirteen species representing North American, South American, Hawaiian, and African germplasm were evaluated. Hawaiian and African accessions were eliminated from the irrigation trial by a minus 5/sup 0/C temperature. The most productive pod producers were P. velutina accessions from southern Arizona. In the fifth season, 5 trees of the most productive accession, i.e. P. velutina 32 had a mean pod production of 7.2 kg/tree with a range of 3.2-12.2 kg/tree. P. chilensis and P. alba trees of the same age were much larger but had less pod production. Pod production estimates of 3000-4000 kg/ha were obtained in the dry irrigation treatment by P. velutina 20 which received 370 mm rainfall in the year preceding harvest.

Determination of intrinsic attenuation in the oceanic lithosphere-asthenosphere system

Science.gov (United States)

Takeuchi, Nozomu; Kawakatsu, Hitoshi; Shiobara, Hajime; Isse, Takehi; Sugioka, Hiroko; Ito, Aki; Utada, Hisashi

2017-12-01

We recorded P and S waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS. The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere.

evaluation of lateritic soil using 2-d electrical resistivity methods at ...

African Journals Online (AJOL)

Global Journal

The purpose of this study is to search for laterite which is of immense economic ... African and South American lithospheric plates (Burke,. 1971). It is bounded on the ... a number of boreholes (Omatsola and Adegoke 1980,. 1981). During the ...

Analysis of Lithospheric Stresses Using Satellite Gravimetry: Hypotheses and Applications to North Atlantic

Science.gov (United States)

Minakov, A.; Medvedev, S.

2017-12-01

Analysis of lithospheric stresses is necessary to gain understanding of the forces that drive plate tectonics and intraplate deformations and the structure and strength of the lithosphere. A major source of lithospheric stresses is believed to be in variations of surface topography and lithospheric density. The traditional approach to stress estimation is based on direct calculations of the Gravitational Potential Energy (GPE), the depth integrated density moment of the lithosphere column. GPE is highly sensitive to density structure which, however, is often poorly constrained. Density structure of the lithosphere may be refined using methods of gravity modeling. However, the resulted density models suffer from non-uniqueness of the inverse problem. An alternative approach is to directly estimate lithospheric stresses (depth integrated) from satellite gravimetry data. Satellite gravity gradient measurements by the ESA GOCE mission ensures a wealth of data for mapping lithospheric stresses if a link between data and stresses or GPE can be established theoretically. The non-uniqueness of interpretation of sources of the gravity signal holds in this case as well. Therefore, the data analysis was tested for the North Atlantic region where reliable additional constraints are supplied by both controlled-source and earthquake seismology. The study involves comparison of three methods of stress modeling: (1) the traditional modeling approach using a thin sheet approximation; (2) the filtered geoid approach; and (3) the direct utilization of the gravity gradient tensor. Whereas the first two approaches (1)-(2) calculate GPE and utilize a computationally expensive finite element mechanical modeling to calculate stresses, the approach (3) uses a much simpler numerical treatment but requires simplifying assumptions that yet to be tested. The modeled orientation of principal stresses and stress magnitudes by each of the three methods are compared with the World Stress Map.

Constraints on Composition, Structure and Evolution of the Lithosphere

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Bianchini, Gianluca; Bonadiman, Costanza; Aulbach, Sonja; Schutt, Derek

2015-05-01

The idea for this special issue was triggered at the Goldschmidt Conference held in Florence (August 25-30, 2013), where we convened a session titled "Integrated Geophysical-Geochemical Constraints on Composition and Structure of the Lithosphere". The invitation to contribute was extended not only to the session participants but also to a wider spectrum of colleagues working on related topics. Consequently, a diverse group of Earth scientists encompassing geophysicists, geodynamicists, geochemists and petrologists contributed to this Volume, providing a comprehensive overview on the nature and evolution of lithospheric mantle by combining studies that exploit different types of data and interpretative approaches. The integration of geochemical and geodynamic datasets and their interpretation represents the state of the art in our knowledge of the lithosphere and beyond, and could serve as a blueprint for future strategies in concept and methodology to advance our knowledge of this and other terrestrial reservoirs.

Seismic and Thermal Structure of the Arctic Lithosphere, From Waveform Tomography and Thermodynamic Modelling

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Lebedev, S.; Schaeffer, A. J.; Fullea, J.; Pease, V.

2015-12-01

Thermal structure of the lithosphere is reflected in the values of seismic velocities within it. Our new tomographic models of the crust and upper mantle of the Arctic are constrained by an unprecedentedly large global waveform dataset and provide substantially improved resolution, compared to previous models. The new tomography reveals lateral variations in the temperature and thickness of the lithosphere and defines deep boundaries between tectonic blocks with different lithospheric properties and age. The shape and evolution of the geotherm beneath a tectonic unit depends on both crustal and mantle-lithosphere structure beneath it: the lithospheric thickness and its changes with time (these determine the supply of heat from the deep Earth), the crustal thickness and heat production (the supply of heat from within the crust), and the thickness and thermal conductivity of the sedimentary cover (the insulation). Detailed thermal structure of the basins can be modelled by combining seismic velocities from tomography with data on the crustal structure and heat production, in the framework of computational petrological modelling. The most prominent lateral contrasts across the Arctic are between the cold, thick lithospheres of the cratons (in North America, Greenland and Eurasia) and the warmer, non-cratonic blocks. The lithosphere of the Canada Basin is cold and thick, similar to old oceanic lithosphere elsewhere around the world; its thermal structure offers evidence on its lithospheric age and formation mechanism. At 150-250 km depth, the central Arctic region shows a moderate low-velocity anomaly, cooler than that beneath Iceland and N Atlantic. An extension of N Atlantic low-velocity anomaly into the Arctic through the Fram Strait may indicate an influx of N Atlantic asthenosphere under the currently opening Eurasia Basin.

Neotropics and natural ingredients for pharmaceuticals: why isn't South American biodiversity on the crest of the wave?

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Desmarchelier, Cristian

2010-06-01

Despite the advent of biotechnology and modern methods of combinatorial chemistry and rational drug design, nature still plays a surprisingly important role as a source of new pharmaceutical compounds. These are marketed either as herbal drugs or as single active ingredients. South American tropical ecosystems (or the Neotropics) encompass one-third of the botanical biodiversity of the planet. For centuries, indigenous peoples have been using plants for healing purposes, and scientists are making considerable efforts in order to validate these uses from a pharmacological/phytochemical point of view. However, and despite the unique plant diversity in the region, very few natural pharmaceutical ingredients from this part of the world have reached the markets in industrialized countries. The present review addresses the importance of single active ingredients and herbal drugs from South American flora as natural ingredients for pharmaceuticals; it highlights the most relevant cases in terms of species of interest; and discusses the key entry barriers for these products in industrialized countries. It explores the reasons why, in spite of the region's competitive advantages, South American biodiversity has been a poor source of natural ingredients for the pharmaceutical industry. (c) 2010 John Wiley & Sons, Ltd.

Experimental infection of two South American reservoirs with four distinct strains of Trypanosoma cruzi

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Roellig, Dawn M.; McMillan, Katherine; Ellis, Angela E.; Vandeberg, John L.; Champagne, Donald E.; Yabsley, Michael J.

2010-01-01

SUMMARY Trypanosoma cruzi (Tc), the causative agent of Chagas disease, is a diverse species with 2 primary genotypes, TcI and TcII, with TcII further subdivided into 5 subtypes (IIa–e). This study evaluated infection dynamics of 4 genetically and geographically diverse T. cruzi strains in 2 South American reservoirs, degus (Octodon degus) and grey short-tailed opossums (Monodelphis domestica). Based on prior suggestions of a genotype-host association, we hypothesized that degus (placental) would more readily become infected with TcII strains while short-tailed opossums (marsupial) would be a more competent reservoir for a TcI strain. Individuals (n = 3) of each species were intraperitoneally inoculated with T. cruzi trypomastigotes of TcIIa [North America (NA)-raccoon (Procyon lotor) origin], TcI [NA-Virginia opossum (Didelphis virginiana)], TcIIb [South America (SA)-human], TcIIe (SA-Triatoma infestans), or both TcI and TcIIa. Parasitaemias in experimentally infected degus peaked earlier (7–14 days post-inoculation (p.i.)) compared with short-tailed opossums (21–84 days p.i.). Additionally, peak parasitaemias were higher in degus; however, the duration of detectable parasitaemias for all strains, except TcIIa, was greater in short-tailed opossums. Infections established in both host species with all genotypes, except for TcIIa, which did not establish a detectable infection in short-tailed opossums. These results indicate that both South American reservoirs support infections with these isolates from North and South America; however, infection dynamics differed with host and parasite strain. PMID:20128943

Lithospheric discontinuities beneath the U.S. Midcontinent - signatures of Proterozoic terrane accretion and failed rifting

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Chen, Chen; Gilbert, Hersh; Fischer, Karen M.; Andronicos, Christopher L.; Pavlis, Gary L.; Hamburger, Michael W.; Marshak, Stephen; Larson, Timothy; Yang, Xiaotao

2018-01-01

Seismic discontinuities between the Moho and the inferred lithosphere-asthenosphere boundary (LAB) are known as mid-lithospheric discontinuities (MLDs) and have been ascribed to a variety of phenomena that are critical to understanding lithospheric growth and evolution. In this study, we used S-to-P converted waves recorded by the USArray Transportable Array and the OIINK (Ozarks-Illinois-Indiana-Kentucky) Flexible Array to investigate lithospheric structure beneath the central U.S. This region, a portion of North America's cratonic platform, provides an opportunity to explore how terrane accretion, cratonization, and subsequent rifting may have influenced lithospheric structure. The 3D common conversion point (CCP) volume produced by stacking back-projected Sp receiver functions reveals a general absence of negative converted phases at the depths of the LAB across much of the central U.S. This observation suggests a gradual velocity decrease between the lithosphere and asthenosphere. Within the lithosphere, the CCP stacks display negative arrivals at depths between 65 km and 125 km. We interpret these as MLDs resulting from the top of a layer of crystallized melts (sill-like igneous intrusions) or otherwise chemically modified lithosphere that is enriched in water and/or hydrous minerals. Chemical modification in this manner would cause a weak layer in the lithosphere that marks the MLDs. The depth and amplitude of negative MLD phases vary significantly both within and between the physiographic provinces of the midcontinent. Double, or overlapping, MLDs can be seen along Precambrian terrane boundaries and appear to result from stacked or imbricated lithospheric blocks. A prominent negative Sp phase can be clearly identified at 80 km depth within the Reelfoot Rift. This arrival aligns with the top of a zone of low shear-wave velocities, which suggests that it marks an unusually shallow seismic LAB for the midcontinent. This boundary would correspond to the top of a

Ichthyophonus sp. (Ichthyophonae, Ichthyophonida) infection in a South American amphibian, the hylid frog Hypsiboas pulchellus.

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Borteiro, Claudio; Verdes, José Manuel; Cruz, Juan Carlos; Sabalsagaray, María Jesús; Kolenc, Francisco; Martínez Debat, Claudio; Ubilla, Martín

2015-04-01

We report infection by Ichthyophonus sp. in a South American amphibian, the hylid frog Hypsiboas pulchellus in Uruguay. This frog had a large subcutaneous mass over the urostyle and dorsal musculature comprised of parasitic cysts with mild granulomatous inflammation but otherwise appeared healthy.

Climate change and American Bullfrog invasion: what could we expect in South America?

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Javier Nori

Full Text Available BACKGROUND: Biological invasion and climate change pose challenges to biodiversity conservation in the 21(st century. Invasive species modify ecosystem structure and functioning and climatic changes are likely to produce invasive species' range shifts pushing some populations into protected areas. The American Bullfrog (Lithobates catesbeianus is one of the hundred worst invasive species in the world. Native from the southeast of USA, it has colonized more than 75% of South America where it has been reported as a highly effective predator, competitor and vector of amphibian diseases. METHODOLOGY/PRINCIPAL FINDINGS: We modeled the potential distribution of the bullfrog in its native range based on different climate models and green-house gases emission scenarios, and projected the results onto South America for the years of 2050 and 2080. We also overlaid projected models onto the South American network of protected areas. Our results indicate a slight decrease in potential suitable area for bullfrog invasion, although protected areas will become more climatically suitable. Therefore, invasion of these sites is forecasted. CONCLUSION/SIGNIFICANCE: We provide new evidence supporting the vulnerability of the Atlantic Forest Biodiversity Hotspot to bullfrog invasion and call attention to optimal future climatic conditions of the Andean-Patagonian forest, eastern Paraguay, and northwestern Bolivia, where invasive populations have not been found yet. We recommend several management and policy strategies to control bullfrog invasion and argue that these would be possible if based on appropriate articulation among government agencies, NGOs, research institutions and civil society.

Stigma of poverty. The discursive construction of ­"South" term in Latin American countries

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GÓMEZ QUINTERO, Juan David

2014-05-01

Full Text Available This article reflects a general knowledge and a macro-paradigmatic contribution of developmentalist discourses, in particular, its modernist and Eurocentric roots. In particular we analyze the artificiality of the discursive construction of certain categories that represent geopolitical stigma of poverty, such as ­Third World® or ­South® or ­underdeveloped® adopted in the field of international relations and the development cooperation. It notes that there are not metaphors opposite (North-South in its own right, the ­South® is not the opposite of the ­North®, but its negative extension, as evidenced by the imaginarium of most Latin American countries. The metaphors that stigmatize poverty are symbolic discourse used to define in a European way the identity of the winner (rich people.

Gallbladder cancer: South American experience.

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Arroyo, Gerardo F; Gentile, Alberto; Parada, Luis A

2016-10-01

Large differences in terms of incidence and mortality due to gallbladder cancer (GBC) have been reported worldwide. Moreover, it seems that GBC has unique characteristics in South America. We surveyed the literature looking for information about the epidemiology, basic and translational research, and clinical trials performed in South America in order to critically analyze the magnitude of this health problem in the region. Compared to other geographic areas, age-standardized mortality rates (ASMR) for GBC in women are very high, particularly in many western areas of South America. Genetic, as well as dietary and environmental factors likely contribute to the pathogenesis of this disease in the area. Compared to other regions the profile of abnormalities of key genes such as KRAS and TP53 in GBC seems to slightly differ in South America, while the clinical behavior appears to be similar with a median overall survival (OS) of 6.5 to 8 months in advanced GBC. In contrast to Europe and USA, prophylactic cholecystectomy is a common practice in western areas of South America. GBC particularly affects women in South America, and represents a significant public health problem. It appears to have peculiarities that pose an urgent need for additional research aimed to discover risk factors, molecular events associated with its development and new treatment options for this lethal disease.

The lithosphere-asthenosphere system in the Calabrian Arc and surrounding seas

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Panza, G F [Department of Earth Sciences, University of Trieste, Trieste (Italy); [Abdus Salam International Centre for Theoretical Physics, SAND Group, Trieste (Italy)]. E-mail: panza@dst.univ.trieste.it; Pontevivo, A [Department of Earth Sciences, University of Trieste, Trieste (Italy)

2002-10-01

Through the non-linear inversion of Surface-Wave Tomography data, using as a priori constraints seismic data from literature, it has been possible to define a fairly detailed structural model of the lithosphere-asthenosphere system (thickness, S-wave and P-wave velocities of the crust and of the upper mantle layers) in the Calabrian Arc region (Southern Tyrrhenian Sea, Calabria and the Northern-Western part of the Ionian Sea). The main features identified by our study are: (1) a very shallow (less then 10 km deep) crust-mantle transition in the Southern Tyrrhenian Sea and very low S-wave velocities just below a very thin lid in correspondence of the submarine volcanic bodies in the study area; (2) a shallow and very low S-wave velocity layer in the mantle in the areas of Aeolian islands, of Vesuvius, Ischia and Phlegraean Fields, representing their shallow-mantle magma source; (3) a thickened continental crust and lithospheric doubling in Calabria; (4) a crust about 25 km thick and a mantle velocity profile versus depth consistent with the presence of a continental rifled, now thermally relaxed, lithosphere in the investigated part of the Ionian Sea; (5) the subduction of the Ionian lithosphere towards NW below the Tyrrhenian Basin; (6) the subduction of the Adriatic lithosphere underneath the Vesuvius and Phlegraean Fields. (author)

Magma explains low estimates of lithospheric strength based on flexure of ocean island loads

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Buck, W. Roger; Lavier, Luc L.; Choi, Eunseo

2015-04-01

One of the best ways to constrain the strength of the Earth's lithosphere is to measure the deformation caused by large, well-defined loads. The largest, simple vertical load is that of the Hawaiian volcanic island chain. An impressively detailed recent analysis of the 3D response to that load by Zhong and Watts (2013) considers the depth range of seismicity below Hawaii and the seismically determined geometry of lithospheric deflection. These authors find that the friction coefficient for the lithosphere must be in the normal range measured for rocks, but conclude that the ductile flow strength has to be far weaker than laboratory measurements suggest. Specifically, Zhong and Watts (2013) find that stress differences in the mantle lithosphere below the island chain are less than about 200 MPa. Standard rheologic models suggest that for the ~50 km thick lithosphere inferred to exist below Hawaii yielding will occur at stress differences of about 1 GPa. Here we suggest that magmatic accommodation of flexural extension may explain Hawaiian lithospheric deflection even with standard mantle flow laws. Flexural stresses are extensional in the deeper part of the lithosphere below a linear island load (i.e. horizontal stresses orthogonal to the line load are lower than vertical stresses). Magma can accommodate lithospheric extension at smaller stress differences than brittle and ductile rock yielding. Dikes opening parallel to an island chain would allow easier downflexing than a continuous plate, but wound not produce a freely broken plate. The extensional stress needed to open dikes at depth depends on the density contrast between magma and lithosphere, assuming magma has an open pathway to the surface. For a uniform lithospheric density ρL and magma density ρM the stress difference to allow dikes to accommodate extension is: Δσxx (z) = g z (ρM - gρL), where g is the acceleration of gravity and z is depth below the surface. For reasonable density values (i.e. �

Interaction between mantle and crustal detachments: a non-linear system controlling lithospheric extension

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Rosenbaum, G.; Regenauer-Lieb, K.; Weinberg, R. F.

2009-12-01

We use numerical modelling to investigate the development of crustal and mantle detachment faults during lithospheric extension. Our models simulate a wide range of rift systems with varying values of crustal thickness and heat flow, showing how strain localization in the mantle interacts with localization in the upper crust and controls the evolution of extensional systems. Model results reveal a richness of structures and deformation styles, which grow in response to a self-organized mechanism that minimizes the internal stored energy of the system by localizing deformation at different levels of the lithosphere. Crustal detachment faults are well developed during extension of overthickened (60 km) continental crust, even when the initial heat flow is relatively low (50 mW/m2). In contrast, localized mantle deformation is most pronounced when the extended lithosphere has a normal crustal thickness (30-40 km) and an intermediate (60-70 mW/m2) heat flow. Results show a non-linear response to subtle changes in crustal thickness or heat flow, characterized by abrupt and sometime unexpected switches in extension modes (e.g. from diffuse rifting to effective lithospheric-scale rupturing) or from mantle- to crust-dominated strain localization. We interpret this non-linearity to result from the interference of doming wavelengths. Disharmony of crust and mantle doming wavelengths results in efficient communication between shear zones at different lithospheric levels, leading to rupturing of the whole lithosphere. In contrast, harmonious crust and mantle doming inhibits interaction of shear zones across the lithosphere and results in a prolonged rifting history prior to continental breakup.

Understanding the Association of Type 2 Diabetes Mellitus in Breast Cancer Among African American and European American Populations in South Carolina.

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Samson, Marsha E; Adams, Swann Arp; Orekoya, Olubunmi; Hebert, James R

2016-09-01

In South Carolina, the co-occurrence of diabetes mellitus (DM) and breast cancer (BrCA) is much more prevalent among African American populations than among European American populations. The underlying relationship between diabetes and breast cancer may influence breast cancer survival. The purpose of this investigation is to examine the effect of diabetes on developing breast cancer and to reduce racial disparities in breast cancer outcomes. Study participants included women of European American (EA) and African American (AA) ethnicity from both the Medicaid ICD-9 designations and the South Carolina Central Cancer Registry (SCCCR). A historical prospective cohort design was used to determine the risk of developing breast cancer among women of different ethnicities with and without DM. The chi-square test was used to determine the significance of the association; the logistic model was used to assess the relationship between breast cancer and other factors among EA and AA women. Menopause may have protective properties for AA compared to EA women. AA women have twice the odds of not surviving from each breast cancer stage compared to EA women with respect to their breast cancer stage. Adherence to diabetes medication may contribute to lower breast cancer death in EA. This study illustrates the discrepancy between EA and AA women in terms of breast cancer survival. AA women bear a higher disease burden than EA women. To create ethnic-appropriate public health policies, it is imperative that we understand the effect of comorbidities on breast cancer and how we can prevent them from occurring.

Mitochondrial control region haplotypes of the South American sea lion Otaria flavescens (Shaw, 1800).

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Artico, L O; Bianchini, A; Grubel, K S; Monteiro, D S; Estima, S C; Oliveira, L R de; Bonatto, S L; Marins, L F

2010-09-01

The South American sea lion, Otaria flavescens, is widely distributed along the Pacific and Atlantic coasts of South America. However, along the Brazilian coast, there are only two nonbreeding sites for the species (Refúgio de Vida Silvestre da Ilha dos Lobos and Refúgio de Vida Silvestre do Molhe Leste da Barra do Rio Grande), both in Southern Brazil. In this region, the species is continuously under the effect of anthropic activities, mainly those related to environmental contamination with organic and inorganic chemicals and fishery interactions. This paper reports, for the first time, the genetic diversity of O. flavescens found along the Southern Brazilian coast. A 287-bp fragment of the mitochondrial DNA control region (D-loop) was analyzed. Seven novel haplotypes were found in 56 individuals (OFA1-OFA7), with OFA1 being the most frequent (47.54%). Nucleotide diversity was moderate (π = 0.62%) and haplotype diversity was relatively low (67%). Furthermore, the median joining network analysis indicated that Brazilian haplotypes formed a reciprocal monophyletic clade when compared to the haplotypes from the Peruvian population on the Pacific coast. These two populations do not share haplotypes and may have become isolated some time back. Further genetic studies covering the entire species distribution are necessary to better understand the biological implications of the results reported here for the management and conservation of South American sea lions.

Seismic anisotropy and compositionally induced velocity anomalies in the lithosphere above mantle plumes: a petrological and microstructural study of mantle xenoliths from French Polynesia

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Tommasi, Andréa; Godard, Marguerite; Coromina, Guilhem; Dautria, Jean-Marie; Barsczus, Hans

2004-11-01

In addition to thermal erosion, plume/lithosphere interaction may induce significant changes in the lithosphere chemical composition. To constrain the extent of this process in an oceanic environment and its consequences on the lithosphere seismic properties, we investigated the relationship between petrological processes and microstructure in mantle xenoliths from different hotspots tracks in South Pacific Superswell region: the Austral-Cook, Society, and Marquesas islands in French Polynesia. Olivine forsterite contents in the studied spinel peridotites vary continuously from Fo91 to Fo83. Dunites and wehrlites display the lowest forsterite contents. Their microstructure and high Ni contents preclude a cumulate origin, suggesting that these rocks result from melt/rock reactions involving olivine precipitation and pyroxene dissolution. In addition, lherzolites and wehrlites display evidence of late crystallization of clinopyroxene, which may result from a near-solidus melt-freezing reaction. These data suggest that the lithosphere above a mantle plume undergoes a complex sequence of magmatic processes that significantly change its composition. These compositional changes, particularly iron enrichment in olivine, result in lower P- and S-waves velocities. Relative to normal lithospheric mantle, compositionally induced seismic anomalies may attain -2.2% for S-waves and -1% for P-waves. Smaller negative anomalies for P-waves are due to a higher sensitivity to modal composition. Conversely, crystal-preferred orientations (CPO) and seismic anisotropy are little affected by these processes. Lherzolites and harzburgites, independent from composition, show high-temperature porphyroclastic microstructures and strong olivine CPO. Dunites and wehrlites display annealing microstructures to which is associated a progressive dispersion of the olivine CPO. Very weak, almost random olivine CPO is nevertheless rare, suggesting that CPO destruction is restricted to domains of

Lithosphere erosion and continental breakup : Interaction of extension, plume upwelling and melting

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Lavecchia, Alessio; Thieulot, Cedric; Beekman, Fred; Cloetingh, Sierd; Clark, Stuart

2017-01-01

We present the results of thermo-mechanical modelling of extension and breakup of a heterogeneous continental lithosphere, subjected to plume impingement in presence of intraplate stress field. We incorporate partial melting of the extending lithosphere, underlying upper mantle and plume, caused by

Using natural laboratories and modeling to decipher lithospheric rheology

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Sobolev, Stephan

2013-04-01

Rheology is obviously important for geodynamic modeling but at the same time rheological parameters appear to be least constrained. Laboratory experiments give rather large ranges of rheological parameters and their scaling to nature is not entirely clear. Therefore finding rheological proxies in nature is very important. One way to do that is finding appropriate values of rheological parameter by fitting models to the lithospheric structure in the highly deformed regions where lithospheric structure and geologic evolution is well constrained. Here I will present two examples of such studies at plate boundaries. One case is the Dead Sea Transform (DST) that comprises a boundary between African and Arabian plates. During the last 15- 20 Myr more than 100 km of left lateral transform displacement has been accumulated on the DST and about 10 km thick Dead Sea Basin (DSB) was formed in the central part of the DST. Lithospheric structure and geological evolution of DST and DSB is rather well constrained by a number of interdisciplinary projects including DESERT and DESIRE projects leaded by the GFZ Potsdam. Detailed observations reveal apparently contradictory picture. From one hand widespread igneous activity, especially in the last 5 Myr, thin (60-80 km) lithosphere constrained from seismic data and absence of seismicity below the Moho, seem to be quite natural for this tectonically active plate boundary. However, surface heat flow of less than 50-60mW/m2 and deep seismicity in the lower crust ( deeper than 20 km) reported for this region are apparently inconsistent with the tectonic settings specific for an active continental plate boundary and with the crustal structure of the DSB. To address these inconsistencies which comprise what I call the "DST heat-flow paradox", a 3D numerical thermo-mechanical model was developed operating with non-linear elasto-visco-plastic rheology of the lithosphere. Results of the numerical experiments show that the entire set of

The impact of lateral variations in lithospheric thickness on glacial isostatic adjustment in West Antarctica

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Nield, Grace A.; Whitehouse, Pippa L.; van der Wal, Wouter; Blank, Bas; O'Donnell, John Paul; Stuart, Graham W.

2018-04-01

Differences in predictions of Glacial Isostatic Adjustment (GIA) for Antarctica persist due to uncertainties in deglacial history and Earth rheology. The Earth models adopted in many GIA studies are defined by parameters that vary in the radial direction only and represent a global average Earth structure (referred to as 1D Earth models). Over-simplifying actual Earth structure leads to bias in model predictions in regions where Earth parameters differ significantly from the global average, such as West Antarctica. We investigate the impact of lateral variations in lithospheric thickness on GIA in Antarctica by carrying out two experiments that use different rheological approaches to define 3D Earth models that include spatial variations in lithospheric thickness. The first experiment defines an elastic lithosphere with spatial variations in thickness inferred from seismic studies. We compare the results from this 3D model with results derived from a 1D Earth model that has a uniform lithospheric thickness defined as the average of the 3D lithospheric thickness. Irrespective of deglacial history and sub-lithospheric mantle viscosity, we find higher gradients of present-day uplift rates (i.e. higher amplitude and shorter wavelength) in West Antarctica when using the 3D models, due to the thinner-than-1D-average lithosphere prevalent in this region. The second experiment uses seismically-inferred temperature as input to a power-law rheology thereby allowing the lithosphere to have a viscosity structure. Modelling the lithosphere with a power-law rheology results in behaviour that is equivalent to a thinner-lithosphere model, and it leads to higher amplitude and shorter wavelength deformation compared with the first experiment. We conclude that neglecting spatial variations in lithospheric thickness in GIA models will result in predictions of peak uplift and subsidence that are biased low in West Antarctica. This has important implications for ice-sheet modelling

Radial anisotropy of the North American upper mantle based on adjoint tomography with USArray

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Zhu, Hejun; Komatitsch, Dimitri; Tromp, Jeroen

2017-10-01

We use seismic data from USArray to image the upper mantle underneath the United States based on a so-called `adjoint tomography', an iterative full waveform inversion technique. The inversion uses data from 180 regional earthquakes recorded by 4516 seismographic stations, resulting in 586 185 frequency-dependent measurements. Three-component short-period body waves and long-period surface waves are combined to simultaneously constrain deep and shallow structures. The transversely isotropic model US22 is the result of 22 pre-conditioned conjugate-gradient iterations. Approximate Hessian maps and point-spread function tests demonstrate good illumination of the study region and limited trade-offs among different model parameters. We observe a distinct wave-speed contrast between the stable eastern US and the tectonically active western US. This boundary is well correlated with the Rocky Mountain Front. Stable cratonic regions are characterized by fast anomalies down to 250-300 km, reflecting the thickness of the North American lithosphere. Several fast anomalies are observed beneath the North American lithosphere, suggesting the possibility of lithospheric delamination. Slow wave-speed channels are imaged beneath the lithosphere, which might indicate weak asthenosphere. Beneath the mantle transition zone of the central US, an elongated north-south fast anomaly is observed, which might be the ancient subducted Farallon slab. The tectonically active western US is dominated by prominent slow anomalies with magnitudes greater than -6 per cent down to approximately 250 km. No continuous lower to upper mantle upwellings are observed beneath Yellowstone. In addition, our results confirm previously observed differences between oceans and continents in the anisotropic parameter ξ = (βh/βv)2. A slow wave-speed channel with ξ > 1 is imaged beneath the eastern Pacific at depths from 100 to 200 km, reflecting horizontal shear within the asthenosphere. Underneath continental

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

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

2011-10-01

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

Second-generation bioethanol from industrial wood waste of South American species

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María E. Vallejos

2017-09-01

Full Text Available There is a global interest in replacing fossil fuels with renewable sources of energy. The present review evaluates the significance of South-American wood industrial wastes for bioethanol production. Four countries have been chosen for this review, i.e., Argentina, Brazil, Chile, and Uruguay, based on their current or potential forestry industry. It should be noted that although Brazil has a global bioethanol market share of 25%, its production is mainly first-generation bioethanol from sugarcane. The situation in the other countries is even worse, in spite of the fact that they have regulatory frameworks in place already allowing the substitution of a percentage of gasoline by ethanol. Pines and eucalyptus are the usually forested plants in these countries, and their industrial wastes, as chips and sawdust, could serve as promising raw materials to produce second-generation bioethanol in the context of a forest biorefinery. The process to convert woody biomass involves three stages: pretreatment, enzymatic saccharification, and fermentation. The operational conditions of the pretreatment method used are generally defined according to the physical and chemical characteristics of the raw materials and subsequently determine the characteristics of the treated substrates. This article also reviews and discusses the available pretreatment technologies for eucalyptus and pines applicable to South-American industrial wood wastes, their enzymatic hydrolysis yields, and the feasibility of implementing such processes in the mentioned countries in the frame of a biorefinery.

IMPROVING MASS REARING TECHNOLOGY FOR SOUTH AMERICAN FRUIT FLY (DIPTERA:TEPHRITIDAE

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Raimundo Braga Sobrinho

2006-01-01

Full Text Available Studies on availability of suitable and economic diets for adults and larvae of the South American fruit fly Anastrepha fraterculus (Wiedemann, 1830 were carried out at the Entomology Unit of the FAO/IAEA Agriculture and Biotechnology Laboratories in Seibersdorf, Austria with the aim to find the best diets to fit in a large scale mass rearing production. The best diet for adult was the combination of Hydrolysate Corn Protein + Yeast Hydrolysate Enzymatic + Sugar (3:1:3. This diet resulted in the highest numbers of egg/female/day, spermatozoid in the spermathecae, percentages of egg hatch, the lowest mortality rate of adults and the highest average mating duration compared with the standard adult diet based on Yeast Hydrolysate Enzymatic + Sugar (1:3. Among eleven larval diets tested, diets based on sugarcane and sugarbeet bagases plus 7% brewer yeast, 8% sugar, 0.2% sodium benzoate, 0.8% of hydrochloric acid and 60% water (adjusted, yielded the highest percentages of egg hatching, pupal recovery, pupal weight and adult emergence. There was no statistical difference with the standard larval diet based on wheat germ 3%, corncob 15%, corn flower 8%, brewer yeast 6%, sugar 8%, sodium benzoate 0.23%, hydrochloric acid 0.63%, nipagin 0.14% and water 59% (adjusted. The significant performance of these adult and larval diets open discussion for future researches on improvement of rearing techniques required for the establishment of sterile insect technique (SIT program focused on the South American fruit fly.

Analysis of the genetic ancestry of patients with oral clefts from South American admixed populations.

Science.gov (United States)

Vieira-Machado, Camilla D; de Carvalho, Flavia M; Santana da Silva, Luiz C; Dos Santos, Sidney E; Martins, Claudia; Poletta, Fernando A; Mereb, Juan C; Vieira, Alexandre R; Castilla, Eduardo E; Orioli, Iêda M

2016-08-01

Increased susceptibility to cleft lip, with or without cleft palate (CL±P) has been observed in South America, as related to Amerindian ancestry, using epidemiological data, uniparental markers, and blood groups. In this study, it was evaluated whether this increased risk remains when Amerindian ancestry is estimated using autosomal markers and considered in the predictive model. Ancestry was estimated through genotyping 62 insertion and deletion (INDEL) markers in sample sets of patients with CL±P, patients with cleft palate (CP), and controls, from Patagonia in southern Argentina and Belém in northern Brazil. The Amerindian ancestry in patients from Patagonia with CL±P was greater than in controls although it did not reach statistical significance. The European ancestry in patients with CL±P from Belém and in patients with CP from Belém and Patagonia was higher than in controls and statistically significant for patients with CP who were from Belém. This high contribution of European genetic ancestry among patients with CP who were from Belém has not been previously observed in American populations. Our results do not corroborate the currently accepted risks for CL±P and CP estimated by epidemiological studies in the North American populations and probably reflect the higher admixture found in South American ethnic groups when compared with the same ethnic groups from the North American populations. © 2016 Eur J Oral Sci.

Highly Structured Duets in the Song of the South American Hornero

Science.gov (United States)

Laje, Rodrigo; Mindlin, Gabriel B.

2003-12-01

The South American Hornero (Furnarius rufus) is a suboscine bird widely known for its mud-made, oven-looking nest. Beyond their architectural skills, the male and female Horneros sing in highly structured duets. The analysis of field recordings reported in this work reveals that as the male increases the note production rate the female responds by switching to different locking states: the ones predicted by the theory of nonlinear forced oscillators. This gives the duet a most appealing rhythm, and unveils the nonlinear nature of the underlying brain activity needed to generate the song.

PARTICULATE ORGANIC CARBON, cloud amount/frequency and other data from COLUMBUS ISELIN in the North American Coastline-South and South Atlantic Ocean from 1990-05-23 to 1990-06-13 (NODC Accession 9100150)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Data was collected from R/V COLUMBUS ISELIN in South Atlantic Ocean and North American Coast line-South during the Amazon Shelf Sediment Study (AMASSEDS) between May...

Prosopis pod production: comparison of North American, South American, Hawaiin, and African germplasm in young plantations

Energy Technology Data Exchange (ETDEWEB)

Felker, P.; Clark, P.R.; Osborn, J.F.; Cannell, G.H.

Prosopis pod production was compared in 3 field trials in southern California, i.e., a typical orchard planting, an irrigation trial, and a heat/drought stress trial. Thirteen species representing North American, South American, Hawaiian, and African germplasm were evaluated. Hawaiian and African accessions were eliminated from the irrigation trial by a minus 5/sup 0/C temperature. The most productive pod producers were P. velutina accessions from southern Arizona. In the fifth season, 5 trees of the most productive accession, i.e., P. velutina 32 had a mean pod production of 7.2 kg/tree with a range of 3.2-12.2 kg/tree. P. chilensis and P. alba trees of the same age were much larger but had less pod production. Trees in the driest irrigation treatment had the greatest pod production. Pod production estimates of 3000-4000 kg/ha were obtained in the dry irrigation treatment by P. velutina 20 which received 370 mm rainfall in the year preceding harvest. 32 references, 1 figure, 6 tables.

Sub-Moho Reflectors, Mantle Faults and Lithospheric Rheology

Science.gov (United States)

Brown, L. D.

2013-12-01

One of the most unexpected and dramatic observations from the early years of deep reflection profiling of the continents using multichannel CMP techniques was the existing of prominent reflections from the upper mantle. The first of these, the Flannan thrust/fault/feature, was traced by marine profiling of the continental margin offshore Britain by the BIRPS program, which soon found them to be but one of several clear sub-crustal discontinuities in that area. Subsequently, similar mantle reflectors have been observed in many areas around the world, most commonly beneath Precambrian cratonic areas. Many, but not all, of these mantle reflections appear to arise from near the overlying Moho or within the lower crust before dipping well into the mantle. Others occur as subhorizontal events at various depths with the mantle, with one suite seeming to cluster at a depth of about 75 km. The dipping events have been variously interpreted as mantle roots of crustal normal faults or the deep extension of crustal thrust faults. The most common interpretation, however, is that these dipping events are the relicts of ancient subduction zones, the stumps of now detached Benioff zones long since reclaimed by the deeper mantle. In addition to the BIRPS reflectors, the best known examples include those beneath Fennoscandia in northern Europe, the Abitibi-Grenville of eastern Canada, and the Slave Province of northwestern Canada (e.g. on the SNORCLE profile). The most recently reported example is from beneath the Sichuan Basin of central China. The preservation of these coherent, and relatively delicate appearing, features beneath older continental crust and presumably within equally old (of not older) mantle lithosphere, has profound implications for the history and rheology of the lithosphere in these areas. If they represent, as widely believe, some form of faulting with the lithosphere, they provide corollary constraints on the nature of faulting in both the lower crust and

Interaction between mantle and crustal detachments: A nonlinear system controlling lithospheric extension

Science.gov (United States)

Rosenbaum, Gideon; Regenauer-Lieb, Klaus; Weinberg, Roberto F.

2010-11-01

We use numerical modeling to investigate the development of crustal and mantle detachments during lithospheric extension. Our models simulate a wide range of extensional systems with varying values of crustal thickness and heat flow, showing how strain localization in the mantle interacts with localization in the upper crust and controls the evolution of extensional systems. Model results reveal a richness of structures and deformation styles as a response to a self-organized mechanism that minimizes the internal stored energy of the system by localizing deformation. Crustal detachments, here referred as low-angle normal decoupling horizons, are well developed during extension of overthickened (60 km) continental crust, even when the initial heat flow is relatively low (50 mW m-2). In contrast, localized mantle deformation is most pronounced when the extended lithosphere has a normal crustal thickness (30-40 km) and an intermediate heat flow (60-70 mW m-2). Results show a nonlinear response to subtle changes in crustal thickness or heat flow, characterized by abrupt and sometimes unexpected switches in extension modes (e.g., from diffuse extensional deformation to effective lithospheric-scale rupturing) or from mantle- to crust-dominated strain localization. We interpret this nonlinearity to result from the interference of doming wavelengths in the presence of multiple necking instabilities. Disharmonic crust and mantle doming wavelengths results in efficient communication between shear zones at different lithospheric levels, leading to rupturing of the whole lithosphere. In contrast, harmonic crust and mantle doming inhibits interaction of shear zones across the lithosphere and results in a prolonged history of extension prior to continental breakup.

Three new South American mailed catfishes of the genera Rineloricaria and Loricariichthys (Pisces, Siluriformes, Loricariide)

NARCIS (Netherlands)

Isbrücker, I.J.H.; Nijssen, H.

1979-01-01

Three new species belonging to two different genera of South American mailed catfishes of the subfamily Loricariinae are described and figured. A discussion of and comparative notes on related species are added. Rineloricaria formosa n. sp. is described from the Río Inírida/Río Orinoco drainage in

Lithospheric structure of the westernmost Mediterranean inferred from finite frequency Rayleigh wave tomography S-velocity model.

Science.gov (United States)

Palomeras, Imma; Villasenor, Antonio; Thurner, Sally; Levander, Alan; Gallart, Josep; Harnafi, Mimoun

2016-04-01

The Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin, constitute the westernmost Mediterranean. From north to south this region consists of the Pyrenees, the result of interaction between the Iberian and Eurasian plates; the Iberian Massif, a region that has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes) and the Atlas Mountains, resulting from post-Oligocene subduction roll-back and Eurasian-Nubian plate convergence. In this study we analyze data from recent broad-band array deployments and permanent stations on the Iberian Peninsula and in Morocco (Spanish IberArray and Siberia arrays, the US PICASSO array, the University of Munster array, and the Spanish, Portuguese, and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km, comparable to USArray. We have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. The model shows differences in the crust for the different areas, where the highest shear velocities are mapped in the Iberian Massif crust. The crustal thickness is highly variable ranging from ~25 km beneath the eastern Betics to ~55km beneath the Gibraltar Strait, Internal Betics and Internal Rif. Beneath this region a unique arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere has been removed beneath these areas

Native South American genetic structure and prehistory inferred from hierarchical modeling of mtDNA.

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Lewis, Cecil M; Long, Jeffrey C

2008-03-01

Genetic diversity in Native South Americans forms a complex pattern at both the continental and local levels. In comparing the West to the East, there is more variation within groups and smaller genetic distances between groups. From this pattern, researchers have proposed that there is more variation in the West and that a larger, more genetically diverse, founding population entered the West than the East. Here, we question this characterization of South American genetic variation and its interpretation. Our concern arises because others have inferred regional variation from the mean variation within local populations without taking into account the variation among local populations within the same region. This failure produces a biased view of the actual variation in the East. In this study, we analyze the mitochondrial DNA sequence between positions 16040 and 16322 of the Cambridge reference sequence. Our sample represents a total of 886 people from 27 indigenous populations from South (22), Central (3), and North America (2). The basic unit of our analyses is nucleotide identity by descent, which is easily modeled and proportional to nucleotide diversity. We use a forward modeling strategy to fit a series of nested models to identity by descent within and between all pairs of local populations. This method provides estimates of identity by descent at different levels of population hierarchy without assuming homogeneity within populations, regions, or continents. Our main discovery is that Eastern South America harbors more genetic variation than has been recognized. We find no evidence that there is increased identity by descent in the East relative to the total for South America. By contrast, we discovered that populations in the Western region, as a group, harbor more identity by descent than has been previously recognized, despite the fact that average identity by descent within groups is lower. In this light, there is no need to postulate separate founding

Mitochondrial control region haplotypes of the South American sea lion Otaria flavescens (Shaw, 1800

Directory of Open Access Journals (Sweden)

L.O. Artico

2010-09-01

Full Text Available The South American sea lion, Otaria flavescens, is widely distributed along the Pacific and Atlantic coasts of South America. However, along the Brazilian coast, there are only two nonbreeding sites for the species (Refúgio de Vida Silvestre da Ilha dos Lobos and Refúgio de Vida Silvestre do Molhe Leste da Barra do Rio Grande, both in Southern Brazil. In this region, the species is continuously under the effect of anthropic activities, mainly those related to environmental contamination with organic and inorganic chemicals and fishery interactions. This paper reports, for the first time, the genetic diversity of O. flavescens found along the Southern Brazilian coast. A 287-bp fragment of the mitochondrial DNA control region (D-loop was analyzed. Seven novel haplotypes were found in 56 individuals (OFA1-OFA7, with OFA1 being the most frequent (47.54%. Nucleotide diversity was moderate (π = 0.62% and haplotype diversity was relatively low (67%. Furthermore, the median joining network analysis indicated that Brazilian haplotypes formed a reciprocal monophyletic clade when compared to the haplotypes from the Peruvian population on the Pacific coast. These two populations do not share haplotypes and may have become isolated some time back. Further genetic studies covering the entire species distribution are necessary to better understand the biological implications of the results reported here for the management and conservation of South American sea lions.

Lithosphere destabilization by melt percolation during pre-oceanic rifting: Evidence from Alpine-Apennine ophiolitic peridotites

Science.gov (United States)

Piccardo, Giovanni; Ranalli, Giorgio

2017-04-01

Orogenic peridotites from Alpine-Apennine ophiolite Massifs (Lanzo, Voltri, External and Internal Ligurides, - NW Italy, and Mt. Maggiore - Corsica) derive from the mantle lithosphere of the Ligurian Tethys. Field/structural and petrologic/geochemical studies provide constraints on the evolution of the lithospheric mantle during pre-oceanic passive rifting of the late Jurassic Ligurian Tethys ocean. Continental rifting by far-field tectonic forces induced extension of the lithosphere by means of km-scale extensional shear zones that developed before infiltration of melts from the asthenosphere (Piccardo and Vissers, 2007). After significant thinning of the lithosphere, the passively upwelling asthenosphere underwent spinel-facies decompression melting along the axial zone of the extensional system. Silica-undersaturated melt fractions percolated through the lithospheric mantle via diffuse/focused porous flow and interacted with the host peridotite through pyroxenes-dissolving/olivine-precipitating melt/rock reactions. Pyroxene dissolution and olivine precipitation modified the composition of the primary silica-undersaturated melts into derivative silica-saturated melts, while the host lithospheric spinel lherzolites were transformed into pyroxene-depleted/olivine-enriched reactive spinel harzburgites and dunites. The derivative liquids interacted through olivine-dissolving/orthopyroxene+plagioclase-crystallizing reactions with the host peridotites that were impregnated and refertilized (Piccardo et al., 2015). The saturated melts stagnated and crystallized in the shallow mantle lithosphere (as testified by diffuse interstitial crystallization of euhedral orthopyroxene and anhedral plagioclase) and locally ponded, forming orthopyroxene-rich/olivine-free gabbro-norite pods (Piccardo and Guarnieri, 2011). Reactive and impregnated peridotites are characterized by high equilibration temperatures (up to 1250 °C) even at low pressure, plagioclase-peridotite facies

South American regional ionospheric maps computed by GESA: A pilot service in the framework of SIRGAS

Science.gov (United States)

Brunini, C.; Meza, A.; Gende, M.; Azpilicueta, F.

2008-08-01

SIRGAS (Geocentric Reference Frame for the Americas) is an international enterprise of the geodetic community that aims to realize the Terrestrial Reference Frame in the America's countries. In order to fulfill this commitment, SIRGAS manages a network of continuously operational GNSS receivers totalling around one hundred sites in the Caribbean, Central, and South American region. Although the network was not planed for ionospheric studies, its potential to be used for such a purpose was recently recognized and SIRGAS started a pilot experiment devoted to establish a regular service for computing and releasing regional vertical TEC (vTEC) maps based on GNSS data. Since July, 2005, the GESA (Geodesia Espacial y Aeronomía) laboratory belonging to the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata computes hourly maps of vertical Total Electron Content (vTEC) in the framework of the SIRGAS pilot experiment. These maps exploit all the GNSS data available in the South American region and are computed with the LPIM (La Plata Ionospheric Model). LPIM implements a de-biasing procedure that improves data calibration in relation to other procedures commonly used for such purposes. After calibration, slant TEC measurements are converted to vertical and mapped using local-time and modip latitude. The use of modip latitude smoothed the spatial variability of vTEC, especially in the South American low latitude region and hence allows for a better vTEC interpolation. This contribution summarizes the results obtained by GESA in the framework of the SIRGAS pilot experiment.

Life in the lithosphere, kinetics and the prospects for life elsewhere.

Science.gov (United States)

Cockell, Charles S

2011-02-13

The global contiguity of life on the Earth today is a result of the high flux of carbon and oxygen from oxygenic photosynthesis over the planetary surface and its use in aerobic respiration. Life's ability to directly use redox couples from components of the planetary lithosphere in a pre-oxygenic photosynthetic world can be investigated by studying the distribution of organisms that use energy sources normally bound within rocks, such as iron. Microbiological data from Iceland and the deep oceans show the kinetic limitations of living directly off igneous rocks in the lithosphere. Using energy directly extracted from rocks the lithosphere will support about six orders of magnitude less productivity than the present-day Earth, and it would be highly localized. Paradoxically, the biologically extreme conditions of the interior of a planet and the inimical conditions of outer space, between which life is trapped, are the locations from which volcanism and impact events, respectively, originate. These processes facilitate the release of redox couples from the planetary lithosphere and might enable it to achieve planetary-scale productivity approximately one to two orders of magnitude lower than that produced by oxygenic photosynthesis. The significance of the detection of extra-terrestrial life is that it will allow us to test these observations elsewhere and establish an understanding of universal relationships between lithospheres and life. These data also show that the search for extra-terrestrial life must be accomplished by 'following the kinetics', which is different from following the water or energy.

Genetic Differentiation within the Puccinia triticina Population in South America and Comparison with the North American Population Suggests Common Ancestry and Intercontinental Migration

Science.gov (United States)

Leaf rust, caused by Puccinia triticina is the most prevalent and widespread disease of wheat in South America. The objective of this study was to determine the number of genetically differentiated groups of P. triticina that are currently present in South America, and to compare the South American ...

Samovar: a thermomechanical code for modeling of geodynamic processes in the lithosphere-application to basin evolution

DEFF Research Database (Denmark)

Elesin, Y; Gerya, T; Artemieva, Irina

2010-01-01

We present a new 2D finite difference code, Samovar, for high-resolution numerical modeling of complex geodynamic processes. Examples are collision of lithospheric plates (including mountain building and subduction) and lithosphere extension (including formation of sedimentary basins, regions...... of extended crust, and rift zones). The code models deformation of the lithosphere with viscoelastoplastic rheology, including erosion/sedimentation processes and formation of shear zones in areas of high stresses. It also models steady-state and transient conductive and advective thermal processes including...... partial melting and magma transport in the lithosphere. The thermal and mechanical parts of the code are tested for a series of physical problems with analytical solutions. We apply the code to geodynamic modeling by examining numerically the processes of lithosphere extension and basin formation...

Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

Science.gov (United States)

Artemieva, Irina

2014-05-01

This presentation reports a 1 deg ×1 deg global thermal model for the continental lithosphere (TC1). The model is digitally available from the author's web-site: www.lithosphere.info. Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliable data on borehole heat flow measurements (Artemieva and Mooney, 2001), checked with the original publications for data quality, and corrected for paleo-temperature effects where needed. These data are supplemented by cratonic geotherms based on xenolith data. Since heat flow measurements cover not more than half of the continents, the remaining areas (ca. 60% of the continents) are filled by the statistical numbers derived from the thermal model constrained by borehole data. Continental geotherms are statistically analyzed as a function of age and are used to estimate lithospheric temperatures in continental regions with no or low quality heat flow data. This analysis requires knowledge of lithosphere age globally. A compilation of tectono-thermal ages of lithospheric terranes on a 1 deg × 1 deg grid forms the basis for the statistical analysis. It shows that, statistically, lithospheric thermal thickness z (in km) depends on tectono-thermal age t (in Ma) as: z=0.04t+93.6. This relationship formed the basis for a global thermal model of the continental lithosphere (TC1). Statistical analysis of continental geotherms also reveals that this relationship holds for the Archean cratons in general, but not in detail. Particularly, thick (more than 250 km) lithosphere is restricted solely to young Archean terranes (3.0-2.6 Ga), while in old Archean cratons (3.6-3.0 Ga) lithospheric roots do not extend deeper than 200-220 km. The TC1 model is presented by a set of maps, which show significant thermal heterogeneity within continental upper mantle. The strongest lateral temperature variations (as large as 800 deg C) are typical of the shallow mantle (depth less than 100 km). A map of the

Fission-track dating of South American natural glasses: an overview

Energy Technology Data Exchange (ETDEWEB)

Bigazzi, G. [Istituto di Geoscienze e Georisorse, C.N.R., Via G. Moruzzi, 1, 56124 Pisa (Italy)]. E-mail: g.bigazzi@igg.cnr.it; Hadler Neto, J.C. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-970 Campinas SP (Brazil); Iunes, P.J. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-970 Campinas SP (Brazil); Osorio Araya, A.M. [Departamento de Fisica, Quimica e Biologia, Universidade do Estado de Sao Paulo, UNESP, 19060-900 Presidente Prudente SP (Brazil)

2005-12-01

Although many glass-bearing horizons can be found in South American volcanic complexes or sedimentary series, only a relatively few tephra and obsidian-bearing volcanic fields have been studied using the fission-track (FT) dating method. Among them, the volcanics located in the Sierra de Guamani (east of Quito, Ecuador) were studied by several authors. Based upon their ages, obsidians group into three clusters: (1) very young obsidians, {approx}0.2Ma old (2) intermediate-age obsidians, {approx}0.4-{approx}0.8Ma old, and (3) older obsidians, {approx}1.4-{approx}1.6Ma old. The FT method is also an efficient alternative technique for identification of the sources of prehistoric obsidian artefacts. Provenance studies carried out in South America have shown that the Sierra de Guamani obsidian occurrences were important sources of raw material for tool making during pre-Columbian times. Glasses originated from these sources were identified in sites distributed over relatively wide areas of Ecuador and Colombia. Only a few systematic studies on obsidians in other sectors were carried out. Nevertheless, very singular glasses have been recognised in South America, such as Macusanite (Peru) and obsidian Quiron (Argentina), which are being proposed as additional reference materials for FT dating. Analyses of tephra beds interstratified with sedimentary deposits revealed the performance of FT dating in tephrochronological studies. A remarkable example is the famous deposit outcropping at Farola Monte Hermoso, near Bahia Blanca (Buenos Aires Province), described for the first time by the middle of the 19th century by Charles Darwin. Considering the large number of volcanic glasses that were recognised in volcanic complexes and in sedimentary series, South America is a very promising region for the application of FT dating. The examples given above show that this technique may yield important results in different disciplinary fields.

Fission-track dating of South American natural glasses: an overview

International Nuclear Information System (INIS)

Bigazzi, G.; Hadler Neto, J.C.; Iunes, P.J.; Osorio Araya, A.M.

2005-01-01

Although many glass-bearing horizons can be found in South American volcanic complexes or sedimentary series, only a relatively few tephra and obsidian-bearing volcanic fields have been studied using the fission-track (FT) dating method. Among them, the volcanics located in the Sierra de Guamani (east of Quito, Ecuador) were studied by several authors. Based upon their ages, obsidians group into three clusters: (1) very young obsidians, ∼0.2Ma old (2) intermediate-age obsidians, ∼0.4-∼0.8Ma old, and (3) older obsidians, ∼1.4-∼1.6Ma old. The FT method is also an efficient alternative technique for identification of the sources of prehistoric obsidian artefacts. Provenance studies carried out in South America have shown that the Sierra de Guamani obsidian occurrences were important sources of raw material for tool making during pre-Columbian times. Glasses originated from these sources were identified in sites distributed over relatively wide areas of Ecuador and Colombia. Only a few systematic studies on obsidians in other sectors were carried out. Nevertheless, very singular glasses have been recognised in South America, such as Macusanite (Peru) and obsidian Quiron (Argentina), which are being proposed as additional reference materials for FT dating. Analyses of tephra beds interstratified with sedimentary deposits revealed the performance of FT dating in tephrochronological studies. A remarkable example is the famous deposit outcropping at Farola Monte Hermoso, near Bahia Blanca (Buenos Aires Province), described for the first time by the middle of the 19th century by Charles Darwin. Considering the large number of volcanic glasses that were recognised in volcanic complexes and in sedimentary series, South America is a very promising region for the application of FT dating. The examples given above show that this technique may yield important results in different disciplinary fields

Thermal classification of lithospheric discontinuities beneath USArray

Science.gov (United States)

Hansen, Steven M.; Dueker, Ken; Schmandt, Brandon

2015-12-01

Broadband seismic data from the United States were processed into Ps and Sp receiver function image volumes for the purpose of constraining negative velocity gradients (NVG) at depths between the Moho and 200 km. Moho depth picks from the two independent datasets are in good agreement, however, large discrepancies in NVG picks occur and are attributed to free-surface multiples which obscure deep NVG arrivals in the Ps data. From the Sp data, shallow NVG are found west of the Rockies and in the central US while deep and sporadic NVG are observed beneath the Great Plains and northern Rockies. To aid the interpretation of the observed NVG arrivals, the mantle thermal field is estimated by mapping surface wave tomography velocities to temperature assuming an anelastic olivine model. The distribution of temperature versus NVG depth is bi-modal and displays two distinct thermal populations that are interpreted to represent both the lithosphere-asthenosphere boundary (LAB) and mid-lithosphere discontinuities (MLD). LAB arrivals occur in the western US at 60-85 km and 1200-1400 °C depth suggesting that they manifest partial melt near the base of the thermal plate. MLD arrivals primarily occur at 70-110 km depth and 700-900 °C and we hypothesize that these arrivals are caused by a low-velocity metasomatic layer containing phlogopite resulting from magma crystallization products that accumulate within long-lived thick lithosphere.

IAEA Helps Remove Highly Radioactive Material from Five South American Countries

International Nuclear Information System (INIS)

2018-01-01

The International Atomic Energy Agency (IAEA) has helped remove 27 disused highly radioactive sources from five South American countries in a significant step forward for nuclear safety and security in the region. It was the largest such project ever facilitated by the IAEA. The material, mainly used for medical purposes such as treating cancer and sterilizing instruments, was transported to Germany and the United States for recycling. Canada, where some of the sources were manufactured, funded the project upon requests for IAEA support from Bolivia, Ecuador, Paraguay, Peru and Uruguay. The sealed Cobalt-60 and Caesium-137 sources pose safety and security risks when no longer in use, according to Raja Adnan, Director of the IAEA’s Division of Nuclear Security. “The removal of this large number of radioactive sources has significantly reduced those risks in the five countries,” Adnan said. In recent years, the IAEA has assisted Bosnia and Herzegovina, Cameroon, Costa Rica, Honduras, Lebanon, Morocco, Tunisia and Uzbekistan in the removal of disused sources. The South American operation was the largest the IAEA has so far coordinated in terms of both the number of highly radioactive sources and countries involved. While nuclear safety and security are national responsibilities, the IAEA helps Member States upon request to meet these responsibilities through training, technical advice, peer reviews and other advisory services. Such efforts may include support for Member States in implementing the safe and cost-effective recovery, conditioning, storage, disposal or transportation of disused sealed radioactive sources (DSRS).

On the Implications of A Priori Constraints in Transdimensional Bayesian Inversion for Continental Lithospheric Layering

Science.gov (United States)

Roy, C.; Romanowicz, B. A.

2017-12-01

Monte Carlo methods are powerful approaches to solve nonlinear problems and are becoming very popular in Earth sciences. One reason being that, at first glance, no constraints or explicit regularization of model parameters are required. At second glance, one might realize that regularization is done through a prior. The choice of this prior, however, is subjective, and with its choice, unintended or undesired extra information can be injected into the problem. The principal criticism of Bayesian methods is that the prior can be "tuned" in order to get the expected solution. Consequently, detractors of the Bayesian method could easily argue that the solution is influenced by the form of the prior distribution, which choice is subjective. Hence, models obtained with Monte Carlo methods are still highly debated. Here we investigate the influence of a priori constraints (i.e., fixed crustal discontinuities) on the posterior probability distributions of estimated parameters, that is, vertical polarized shear velocity VSV and radial anisotropy ξ, in a transdimensional Bayesian inversion for continental lithospheric structure. We follow upon the work of Calò et al. (2016), who jointly inverted converted phases (P to S) without deconvolution and surface wave dispersion data, to obtain 1-D radial anisotropic shear wave velocity profiles in the North American craton. We aim at verifying whether the strong lithospheric layering found in the stable part of the craton is robust with respect to artifacts that might be caused by the methodology used. We test the hypothesis that the observed midlithospheric discontinuities result from (1) fixed crustal discontinuities in the reference model and (2) a fixed Vp/Vs ratio. The synthetic tests on two Earth models show that a fixed Vp/Vs ratio does not introduce artificial layering, even if the assumed value is slightly wrong. This is an important finding for real data inversion where the true value is not always available or accurate

Grandparent caregiving among rural African Americans in a community in the American South: challenges to health and wellbeing.

Science.gov (United States)

Clottey, Emmanuel N; Scott, Alison J; Alfonso, Moya L

2015-01-01

An increasing number of grandparents in rural USA are serving as primary caregivers for their grandchildren because of parental incarceration, addiction, joblessness, or illness. Low-income, African American women from the South are overrepresented in this growing population. There is a paucity of research exploring the challenges faced by rural grandparent caregivers, and past studies have not explicitly addressed the potential consequences of rural grandparent caregiving for health. The purpose of this qualitative study was to explore grandparent caregiving among rural, low-income, African American grandmothers in a community in the American South, and to identify challenges to health that arose in that context. McLeroy's social ecological model (SEM) was used to examine these challenges at multiple levels of influence. This qualitative interview-based study was conducted in a high-poverty community in rural Georgia. In-depth interviews were conducted with African American grandparent caregivers and key informants from local community-based organizations. A key informant assisted in identifying initial interview participants, and then snowball sampling was used to recruit additional participants. Interview questions were grouped under five domains (intrapersonal, interpersonal, community, organizational, and policy), according to the levels of the SEM. Iterative content analysis of interview transcripts was utilized. Transcripts were coded to identify text segments related to each domain of the SEM, which were grouped together for analysis by domain. Reflexive memo-writing aided in development of themes, and data quality was assessed using Lincoln and Guba's trustworthiness criteria. Rural African American grandparent caregivers faced a range of challenges to health. Direct physical challenges included chronic pain that interfered with sleep and daily functioning, mobility issues exacerbated by child care, and the pressure of managing their own medical conditions

Mantle Earthquakes in Thinned Proterozoic Lithosphere: Harrat Lunayyir, Saudi Arabia

Science.gov (United States)

Blanchette, A. R.; Klemperer, S. L.; Mooney, W. D.; Zahran, H. M.

2017-12-01

Harrat Lunayyir is an active volcanic field located in the western Arabian Shield 100 km outside of the Red Sea rift margin. We use common conversion point (CCP) stacking of P-wave receiver functions (PRFs) to show that the Moho is at 38 km depth, close to the 40 km crustal thickness measured in the center of the craton, whereas the lithosphere-asthenosphere boundary (LAB) is at 60 km, far shallower than the 150 km furthest in the craton. We locate 67 high-frequency earthquakes with mL ≤ 2.5 at depths of 40-50 km below the surface, located clearly within the mantle lid. The occurrence of earthquakes within the lithospheric mantle requires a geothermal temperature profile that is below equilibrium. The lithosphere cannot have thinned to its present thickness earlier than 15 Ma, either during an extended period of rifting possibly beginning 24 Ma or, more likely, as part of the second stage of rifting following collision between Arabia and Eurasia.

Disparities in Birth Weight and Gestational Age by Ethnic Ancestry in South American countries

Science.gov (United States)

Wehby, George L.; Gili, Juan A.; Pawluk, Mariela; Castilla, Eduardo E.; López-Camelo, Jorge S.

2015-01-01

Objective We examine disparities in birth weight and gestational age by ethnic ancestry in 2000–2011 in eight South American countries. Methods The sample included 60480 singleton live-births. Regression models were estimated to evaluate differences in birth outcomes by ethnic ancestry controlling for time trends. Results Significant disparities were found in seven countries. In four countries – Brazil, Ecuador, Uruguay, and Venezuela – we found significant disparities in both low birth weight and preterm birth. Disparities in preterm birth alone were observed in Argentina, Bolivia, and Colombia. Several differences in continuous birth weight, gestational age, and fetal growth rate were also observed. There were no systematic patterns of disparities between the evaluated ethnic ancestry groups across the study countries, in that no racial/ethnic group consistently had the best or worst outcomes in all countries. Conclusions Racial/ethnic disparities in infant health are common in several South American countries. Differences across countries suggest that racial/ethnic disparities are driven by social and economic mechanisms. Researchers and policymakers should acknowledge these disparities and develop research and policy programs to effectively target them. PMID:25542227

Strain localization at the margins of strong lithospheric domains: insights from analogue models

NARCIS (Netherlands)

Calignano, Elisa; Sokoutis, Dimitrios; Willingshofer, Ernst; Gueydan, Frederic; Cloetingh, Sierd

The lateral variation of the mechanical properties of continental lithosphere is an important factor controlling the localization of deformation and thus the deformation history and geometry of intra-plate mountain belts. A series of three-layer lithospheric-scale analog models, with a strong domain

Robust high resolution models of the continental lithosphere: Methodology and application to Asia

NARCIS (Netherlands)

Stolk, W.|info:eu-repo/dai/nl/323259170

2013-01-01

Asia is a key natural laboratory for the study of active intra-continental deformation in far-field response to the ongoing collision ofIndiaandEurasia. The resulting tectonic processes strongly depend on the thermo-mechanical structure of the lithosphere. This lithosphere can be separated into

Change in the foraging strategy of female South American sea lions (Carnivora: Pinnipedia after parturition

Directory of Open Access Journals (Sweden)

Massimiliano Drago

2010-08-01

Full Text Available This study tests the hypothesis that female South American sea lions shift from off-shore, pelagic prey to coastal, benthic prey after parturition in order to reduce the foraging trip duration and hence the time pups remain unattended on the beach during early lactation. The δ13C and δ15N values of the serum and blood cells of 26 South American sea lion suckling pups from northern Patagonia were used to track the dietary changes of their mothers from late pregnancy to early lactation, after correction for differential isotopic fractionation between tissues. Primary producers and potential prey species were also analysed to establish a baseline for interpreting the stable isotope concentration of serum and blood cells. Isotopic ratios revealed a generalized increase in the consumption of coastal-benthic prey after parturition. Such a generalized post-partum shift will allow females to spend more time on land and look after their pups. The effects of this foraging strategy on the nutritional quality of the female’s diet are discussed.

The South American fruit fly, Anastrepha fraterculus (Wied.); advances in artificial rearing, taxonomic status and biological studies. Proceedings of a workshop

Energy Technology Data Exchange (ETDEWEB)

1999-01-01

One of the fruit flies of major concern, because of its economic and quarantine importance in the Americas, is the exotic Mediterranean fruit fly, Ceratitis capitata, which is established throughout the Central and South American countries, excluding Chile. Chile, Mexico and the USA have conducted multi-million dollar campaigns to prevent the establishment of this and other exotic fruit flies in their respective territories, in support of the development of important fruit production and export industries. Other important fruit fly species, which are native to the American continent, are those of the genus Anastrepha. In this group, of most economic importance are A. obliqua and A. ludens for Mexico and some Central American countries and A. fraterculus and A. obliqua for South America. In this publication, attention is focused on A. fraterculus, the South American fruit fly. This species, as it is presently recognized, occurs from Mexico to Argentina and is reported from approximately 80 host plants, including commercial fruits of economic importance, such as mango, citrus, guava, apple and coffee. As A. fraterculus if considered to be of high economic and quarantine importance in many countries in South America, it is justifiable to recommend and promote the implementation of activities to strengthen knowledge of the species and develop techniques for its control and/or eradication. The development of sterile insect technique (SIT) and other biological control methods are very encouraging alternatives, as can be seen from examples in Mexico and the USA, where these approaches are in use against A. ludens and A. obliqua Refs, figs, tabs

The South American fruit fly, Anastrepha fraterculus (Wied.); advances in artificial rearing, taxonomic status and biological studies. Proceedings of a workshop

International Nuclear Information System (INIS)

1999-01-01

One of the fruit flies of major concern, because of its economic and quarantine importance in the Americas, is the exotic Mediterranean fruit fly, Ceratitis capitata, which is established throughout the Central and South American countries, excluding Chile. Chile, Mexico and the USA have conducted multi-million dollar campaigns to prevent the establishment of this and other exotic fruit flies in their respective territories, in support of the development of important fruit production and export industries. Other important fruit fly species, which are native to the American continent, are those of the genus Anastrepha. In this group, of most economic importance are A. obliqua and A. ludens for Mexico and some Central American countries and A. fraterculus and A. obliqua for South America. In this publication, attention is focused on A. fraterculus, the South American fruit fly. This species, as it is presently recognized, occurs from Mexico to Argentina and is reported from approximately 80 host plants, including commercial fruits of economic importance, such as mango, citrus, guava, apple and coffee. As A. fraterculus if considered to be of high economic and quarantine importance in many countries in South America, it is justifiable to recommend and promote the implementation of activities to strengthen knowledge of the species and develop techniques for its control and/or eradication. The development of sterile insect technique (SIT) and other biological control methods are very encouraging alternatives, as can be seen from examples in Mexico and the USA, where these approaches are in use against A. ludens and A. obliqua

Implications for anomalous mantle pressure and dynamic topography from lithospheric stress patterns in the North Atlantic Realm

DEFF Research Database (Denmark)

Schiffer, Christian; Nielsen, Søren Bom

2016-01-01

With convergent plate boundaries at some distance, the sources of the lithospheric stress field of the North Atlantic Realm are mainly mantle tractions at the base of the lithosphere, lithospheric density structure and topography. Given this, we estimate horizontal deviatoric stresses using a wel...

Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

Science.gov (United States)

Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

2018-05-01

The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic

Rheological structure of the lithosphere in plate boundary strike-slip fault zones

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Chatzaras, Vasileios; Tikoff, Basil; Kruckenberg, Seth C.; Newman, Julie; Titus, Sarah J.; Withers, Anthony C.; Drury, Martyn R.

2016-04-01

How well constrained is the rheological structure of the lithosphere in plate boundary strike-slip fault systems? Further, how do lithospheric layers, with rheologically distinct behaviors, interact within the strike-slip fault zones? To address these questions, we present rheological observations from the mantle sections of two lithospheric-scale, strike-slip fault zones. Xenoliths from ˜40 km depth (970-1100 ° C) beneath the San Andreas fault system (SAF) provide critical constraints on the mechanical stratification of the lithosphere in this continental transform fault. Samples from the Bogota Peninsula shear zone (BPSZ, New Caledonia), which is an exhumed oceanic transform fault, provide insights on lateral variations in mantle strength and viscosity across the fault zone at a depth corresponding to deformation temperatures of ˜900 ° C. Olivine recrystallized grain size piezometry suggests that the shear stress in the SAF upper mantle is 5-9 MPa and in the BPSZ is 4-10 MPa. Thus, the mantle strength in both fault zones is comparable to the crustal strength (˜10 MPa) of seismogenic strike-slip faults in the SAF system. Across the BPSZ, shear stress increases from 4 MPa in the surrounding rocks to 10 MPa in the mylonites, which comprise the core of the shear zone. Further, the BPSZ is characterized by at least one order of magnitude difference in the viscosity between the mylonites (1018 Paṡs) and the surrounding rocks (1019 Paṡs). Mantle viscosity in both the BPSZ mylonites and the SAF (7.0ṡ1018-3.1ṡ1020 Paṡs) is relatively low. To explain our observations from these two strike-slip fault zones, we propose the "lithospheric feedback" model in which the upper crust and lithospheric mantle act together as an integrated system. Mantle flow controls displacement and the upper crust controls the stress magnitude in the system. Our stress data combined with data that are now available for the middle and lower crustal sections of other transcurrent fault

Brightness of venous blood in South American camelids: implications for jugular catheterization.

Science.gov (United States)

Grint, Nicola; Dugdale, Alexandra

2009-01-01

To compare the brightness of South American camelid venous blood to that of Equidae. Prospective clinical evaluation. Twelve South American camelids (eight llamas, four alpacas), eight horses and ponies (control group). Appropriately sized catheters were placed in the jugular vein of each animal under local anaesthesia. The blood spilt before the catheter was capped was caught on a white tile. A sample of blood was drawn for blood-gas analysis. The brightness of the blood (both on the tile and in the syringe) was matched to a colour chart (1 = darkest red, 8 = brightest red) by a single observer under bright light conditions. Packed cell volume (PCV) and partial pressure of oxygen (PvO(2)) in the blood were also measured on the syringe blood. Normally distributed data were compared using a two tailed t-test, and non-normally distributed data were compared using a Mann-Whitney U-test. Significance was set at p Camelid venous blood was significantly brighter red than that of horses and ponies both on the white tile (p = 0.0003) and in the syringe (p = 0.0001). PCV was significantly lower in camelids (32 +/- 4%) compared with horses (37 +/- 5%). Partial pressure of oxygen values were similar between groups. Jugular venous blood in alpacas and llamas is significantly brighter red than that of horses. Colour should not be used as a sole determinant of venous or arterial catheterization in this species.

Deformation of the Pannonian lithosphere and related tectonic topography: a depth-to-surface analysis

NARCIS (Netherlands)

Dombrádi, E.

2012-01-01

Fingerprints of deep-seated, lithospheric deformation are often recognised on the surface, contributing to topographic evolution, drainage organisation and mass transport. Interactions between deep and surface processes were investigated in the Carpathian-Pannonian region. The lithosphere beneath

Imaging Lithospheric-scale Structure Beneath Northern Altiplano in Southern Peru and Northern Bolivia

Science.gov (United States)

Kumar, A.; Wagner, L. S.; Beck, S. L.; Zandt, G.; Long, M. D.

2014-12-01

The northern Altiplano plateau of southern Peru and northern Bolivia is one of the highest topographic features on the Earth, flanked by Western and Eastern Cordillera along its margin. It has strongly influenced the local and far field lithospheric deformation since the early Miocene (Masek et al., 1994). Previous studies have emphasized the importance of both the crust and upper mantle in the evolution of Altiplano plateau (McQuarrie et al., 2005). Early tomographic and receiver function studies, south of 16° S, show significant variations in the crust and upper mantle properties in both perpendicular and along strike direction of the Altiplano plateau (Dorbath et. al., 1993; Myers et al., 1998; Beck and Zandt, 2002). In order to investigate the nature of subsurface lithospheric structure below the northern Altiplano, between 15-18° S, we have determined three-dimensional seismic tomography models for Vp and Vs using P and S-wave travel time data from two recently deployed local seismic networks of CAUGHT and PULSE. We also used data from 8 stations from the PERUSE network (PERU Subduction Experiment). Our preliminary tomographic models show a complex variation in the upper mantle velocity structure with depth, northwest and southeast of lake Titicaca. We see the following trend, at ~85 km depth, northwest of lake Titicaca: low Vp and Vs beneath the Western Cordillera, high Vs beneath the Altiplano and low Vp and Vs beneath the Eastern Cordillera. This low velocity anomaly, beneath Eastern Cordillera, seems to coincide with Kimsachata, a Holocene volcano in southern Peru. At depth greater than ~85 km: we find high velocity anomaly beneath the Western Cordillera and low Vs beneath the Altiplano. This high velocity anomaly, beneath Western Cordillera, coincides with the well-located Wadati-Benioff zone seismicity and perhaps represents the subducting Nazca slab. On the southeast of lake Titicaca, in northern Bolivia, we see a consistently high velocity anomaly

Partial delamination of continental mantle lithosphere, uplift-related crust mantle decoupling, volcanism and basin formation: a new model for the Pliocene Quaternary evolution of the southern East-Carpathians, Romania

Science.gov (United States)

Chalot-Prat, F.; Girbacea, R.

2000-11-01

A geodynamic model is proposed for the Mid-Miocene to Quaternary evolution of the southern East-Carpathians in order to explain the relationships between shallow and deep geological phenomena that occurred synchronously during late-collision tectonics. In this area, an active volcanic zone cross-cuts since 2 My the suture between the overriding Tisza-Dacia and subducting European continental plates. Mafic calc-alkaline and alkaline magmas (south Harghita and Persani volcanoes) erupted contemporaneously. These magmas were supplied by partial melting of the mantle lithosphere of the subducting, and not of the overriding, plate. In an effort to decipher this geodynamically a-typical setting of magma generation, the spatial and temporal distribution of shallow and deep phenomena was successively examined in order to establish the degree of their interdependence. Our model indicates that intra-mantle delamination of the subducting European plate is the principal cause of a succession of events. It caused upwelling of the hot asthenosphere below a thinned continental lithosphere of the Carpathians, inducing the uplift of the lithosphere and its internal decoupling at the Moho level by isostatic and mostly thermal effects. During this uplift, the crust deformed flexurally whilst the mantle deformed in a ductile way. This triggered decompressional partial melting of the uppermost mantle lithosphere. Flexural deformation of the crust induced its fracturing, allowing for the rapid ascent of magmas to the surface, as well as reactivation of an older detachment horizon at the base of the Carpathian nappe stack above which the Brasov, Ciuc and Gheorghieni hinterland basins formed by extension and gravity spreading. The rapid subsidence of the Focsani foreland basin is controlled by the load exerted on the lithosphere by the delaminated mantle slab that is still attached to it. In this model, crust-mantle decoupling, magma genesis and volcanism, local near-surface hinterland

Localization instability and the origin of regularly- spaced faults in planetary lithospheres

Science.gov (United States)

Montesi, Laurent Gilbert Joseph

2002-10-01

Brittle deformation is not distributed uniformly in planetary lithospheres but is instead localized on faults and ductile shear zones. In some regions such as the Central Indian Basin or martian ridged plains, localized shear zones display a characteristic spacing. This pattern can constrain the mechanical structure of the lithosphere if a model that includes the development of localized shear zones and their interaction with the non- localizing levels of the lithosphere is available. I construct such a model by modifying the buckling analysis of a mechanically-stratified lithosphere idealization, by allowing for rheologies that have a tendency to localize. The stability of a rheological system against localization is indicated by its effective stress exponent, ne. That quantity must be negative for the material to have a tendency to localize. I show that a material deforming brittly or by frictional sliding has ne mechanical properties. When this model is subjected to horizontal extension or compression, infinitesimal perturbation of its interfaces grow at a rate that depends on their wavelength. Two superposed instabilities develop if ne Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

Amount of Asian lithospheric mantle subducted during the India/Asia collision

OpenAIRE

Replumaz, A.; Guillot, S.; Villaseñor, Antonio; Negredo, A. M.

2013-01-01

Body wave seismic tomography is a successful technique for mapping lithospheric material sinking into the mantle. Focusing on the India/Asia collision zone, we postulate the existence of several Asian continental slabs, based on seismic global tomography. We observe a lower mantle positive anomaly between 1100 and 900 km depths, that we interpret as the signature of a past subduction process of Asian lithosphere, based on the anomaly position relative to positive anomalies related to Indian c...

Mantle weakening and strain localization: Implications for the long-term strength of the continental lithosphere

OpenAIRE

Précigout , Jacques; Gueydan , Frédéric

2009-01-01

International audience; Mechanics of the continental lithosphere require the presence of a high-strength uppermost mantle that defines the "jelly sandwich" model for lithosphere strength layering. However, in deforming regions, growing numbers of geological and geophysical data predict a sub-Moho mantle strength lower than the crustal strength, or a "crème brûlée" model. To reconcile these two opposite views of lithosphere strength layering, we account for a new olivine rheology, which could ...

American Indian Parents’ Assessment of and Concern About Their Kindergarten Child’s Weight Status, South Dakota, 2005-2006

OpenAIRE

Arcan, Chrisa; Hannan, Peter J.; Himes, John H.; Fulkerson, Jayne A.; Holy Rock, Bonnie; Smyth, Mary; Story, Mary

2012-01-01

Introduction Obesity is highly prevalent among American Indians, and effective prevention efforts require caregiver involvement. We examined American Indian (AI) parents' assessment of and level of concern about their kindergarten child's weight status. Methods We collected baseline data (fall of 2005 and fall of 2006) on children and their parents or caregivers for a school-based obesity prevention trial (Bright Start) on an AI reservation in South Dakota. The current study uses 413 parent-c...

Lu-Hf isotope constraints on plume-lithosphere interaction during emplacement of the Bushveld Large Igneous Province at 2.06 Ga: Implications for the structure and evolution of the Kaapvaal Craton's lithospheric mantle

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Zirakparvar, N. A.; Mathez, E. A.; Rajesh, H.; Vervoort, J. D.; Choe, S.

2016-12-01

The Bushveld Large Igneous Province (B-LIP) comprises a diverse array of >30 magma bodies that intruded the Kaapvaal Craton at 2.06 Ga. In this talk we use zircon and bulk-rock Lu-Hf isotope data to show that the B-LIP formed in response to the arrival of a plume(s) from the deep mantle. New zircon Hf isotope compositions for four B-LIP bodies yield intrusion-specific average ɛHf (2.06 Ga) values that range from -20.7 ± 2.8 to -2.7 ± 2.8, largely consistent with literature zircon data for other B-LIP intrusions. Bulk-rock solution ɛHf (2.06 Ga) values for a variety of B-LIP intrusions range from -2.1 ± 0.2 to -10.6 ± 0.2. Because the most radiogenic Hf isotope compositions across the entire B-LIP are nearly primordial with an ɛHf (2.06 Ga) close to 0, it is likely that the heat source of the B-LIP was a plume(s) from deep mantle. The Hf isotope data further suggests that individual intrusions in the B-LIP can be grouped into four categories based on their ultimate sources: 1) melts generated in subduction and plume modified continental lithospheric mantle; 2) melts generated by melting of a mafic-ultramafic reservoir composed of older ( 2.7 Ga) plume-related material trapped in the Kaapvaal lithosphere; 3) melts generated in the mid- to upper crust; and 4) melts generated from the 2.06 Ga mantle plume itself. The presence of 2.7 Ga mafic-ultramafic material in the Kaapvaal lithosphere may have acted to strengthen the lithosphere so that it was able to resist being dispered by the arrival of the B-LIP plume at 2.06 Ga. Because the B-LIP extends into a 2.7 Ga aged suture zone between the Kaapvaal and Zimbabwe cratons, it is also possible to understand the role of the lithospheric mantle in producing the Lu-Hf signatures observed in the various B-LIP intrusions as a function of two different types of the continental lithosphere: The very old lithosphere comprising the Kaapvaal Craton and the somewhat younger lithosphere comprising the suture zone. A basic

Cefazolin high-inoculum effect in methicillin-susceptible Staphylococcus aureus from South American hospitals.

Science.gov (United States)

Rincón, Sandra; Reyes, Jinnethe; Carvajal, Lina Paola; Rojas, Natalia; Cortés, Fabián; Panesso, Diana; Guzmán, Manuel; Zurita, Jeannete; Adachi, Javier A; Murray, Barbara E; Nannini, Esteban C; Arias, Cesar A

2013-12-01

Clinical failures with cefazolin have been described in high-inoculum infections caused by methicillin-susceptible Staphylococcus aureus (MSSA) producing type A β-lactamase. We investigated the prevalence of the cefazolin inoculum effect (InE) in MSSA from South American hospitals, since cefazolin is used routinely against MSSA due to concerns about the in vivo efficacy of isoxazolyl penicillins. MSSA isolates were recovered from bloodstream (n = 296) and osteomyelitis (n = 68) infections in two different multicentre surveillance studies performed in 2001-02 and 2006-08 in South American hospitals. We determined standard-inoculum (10(5)cfu/mL) and high-inoculum (10(7) cfu/mL) cefazolin MICs. PFGE was performed on all isolates that exhibited a cefazolin InE. Multilocus sequence typing (MLST) and sequencing of part of blaZ were performed on representative isolates. The overall prevalence of the cefazolin InE was 36% (131 isolates). A high proportion (50%) of MSSA isolates recovered from osteomyelitis infections exhibited the InE, whereas it was observed in 33% of MSSA recovered from bloodstream infections. Interestingly, Ecuador had the highest prevalence of the InE (45%). Strikingly, 63% of MSSA isolates recovered from osteomyelitis infections in Colombia exhibited the InE. MLST revealed that MSSA isolates exhibiting the InE belonged to diverse genetic backgrounds, including ST5, ST8, ST30 and ST45, which correlated with the prevalent methicillin-resistant S. aureus clones circulating in South America. Types A (66%) and C (31%) were the most prevalent β-lactamases. Our results show a high prevalence of the cefazolin InE associated with type A β-lactamase in MSSA isolates from Colombia and Ecuador, suggesting that treatment of deep-seated infections with cefazolin in those countries may be compromised.

Lithospheric Strength and Stress State: Persistent Challenges and New Directions in Geodynamics

Science.gov (United States)

Hirth, G.

2017-12-01

The strength of the lithosphere controls a broad array of geodynamic processes ranging from earthquakes, the formation and evolution of plate boundaries and the thermal evolution of the planet. A combination of laboratory, geologic and geophysical observations provides several independent constraints on the rheological properties of the lithosphere. However, several persistent challenges remain in the interpretation of these data. Problems related to extrapolation in both scale and time (rate) need to be addressed to apply laboratory data. Nonetheless, good agreement between extrapolation of flow laws and the interpretation of microstructures in viscously deformed lithospheric mantle rocks demonstrates a strong foundation to build on to explore the role of scale. Furthermore, agreement between the depth distribution of earthquakes and predictions based on extrapolation of high temperature friction relationships provides a basis to understand links between brittle deformation and stress state. In contrast, problems remain for rationalizing larger scale geodynamic processes with these same rheological constraints. For example, at face value the lab derived values for the activation energy for creep are too large to explain convective instabilities at the base of the lithosphere, but too low to explain the persistence of dangling slabs in the upper mantle. In this presentation, I will outline these problems (and successes) and provide thoughts on where new progress can be made to resolve remaining inconsistencies, including discussion of the role of the distribution of volatiles and alteration on the strength of the lithosphere, new data on the influence of pressure on friction and fracture strength, and links between the location of earthquakes, thermal structure, and stress state.

COMPOSITIONAL AND THERMAL DIFFERENCES BETWEEN LITHOSPHERIC AND ASTHENOSPHERIC MANTLE AND THEIR INFLUENCE ON CONTINENTAL DELAMINATION

Directory of Open Access Journals (Sweden)

A. I. Kiselev

2015-01-01

Full Text Available The lower part of lithosphere in collisional orogens may delaminate due to density inversion between the asthenosphere and the cold thickened lithospheric mantle. Generally, standard delamination models have neglected density changes within the crust and the lithospheric mantle, which occur due to phase transitions and compositional variations upon changes of P-T parameters. Our attention is focused on effects of phase and density changes that may be very important and even dominant when compared with the effect of a simple change of the thermal mantle structure. The paper presents the results of numerical modeling for eclogitization of basalts of the lower crust as well as phase composition changes and density of underlying peridotite resulted from tectonic thickening of the lithosphere and its foundering into the asthenosphere. As the thickness of the lower crust increases, the mafic granulite (basalt passes into eclogite, and density inversion occurs at the accepted crust-mantle boundary (P=20 kbar because the newly formed eclogite is heavier than the underlying peridotite by 6 % (abyssal peridotite, according to [Boyd, 1989]. The density difference is a potential energy for delamination of the eclogitic portion of the crust. According to the model, P=70 kbar and T=1300 °C correspond to conditions at the lower boundary of the lithosphere. Assuming the temperature adiabatic distribution within the asthenosphere, its value at the given parameters ranges from 1350 °C to 1400 °C. Density inversion at dry conditions occurs with the identical lithospheric and asthenospheric compositions at the expense of the temperature difference at 100 °C with the density difference of only 0.0022 %. Differences of two other asthenospheric compositions (primitive mantle, and lherzolite KH as compared to the lithosphere (abyssal peridotite are not compensated for by a higher temperature. The asthenospheric density is higher than that of the lithospheric base

Global strength and elastic thickness of the lithosphere

NARCIS (Netherlands)

Tesauro, M.; Kaban, M.K.; Cloetingh, S.A.P.L.

2012-01-01

Thestrengthand effective elasticthickness (Te) ofthelithosphere control its response to tectonic and surface processes. Here, we present the first globalstrengthand effective elasticthickness maps, which are determined using physical properties from recent crustal and lithospheric models. Pronounced

Adhesive and invasive capacities of Edwarsiella tarda isolated from South American sea lion

OpenAIRE

Fernández, Araceli; Paz Villanueva, María; González, Mario; Fernández, Fabiola; Latif, Fadua; Flores, Sandra Nonier; Fernández, Heriberto

2014-01-01

Edwarsiella tarda is a zoonotic bacterium that can be isolated from humans, animals and the environment. Although E. tarda is primarily considered a fish pathogen, it is the only species of its genus considered to be pathogenic for humans as well. A survey of zoonotic intestinal bacteria in fresh feces from South American sea lions (SASL) Otaria flavescens, reported E. tarda as the most frequently isolated species. In this study, we used HEp-2 cells to establish in vitro the adherence and inv...

Large-scale variation in lithospheric structure along and across the Kenya rift

Science.gov (United States)

Prodehl, C.; Mechie, J.; Kaminski, W.; Fuchs, K.; Grosse, C.; Hoffmann, H.; Stangl, R.; Stellrecht, R.; Khan, M.A.; Maguire, Peter K.H.; Kirk, W.; Keller, Gordon R.; Githui, A.; Baker, M.; Mooney, W.; Criley, E.; Luetgert, J.; Jacob, B.; Thybo, H.; Demartin, M.; Scarascia, S.; Hirn, A.; Bowman, J.R.; Nyambok, I.; Gaciri, S.; Patel, J.; Dindi, E.; Griffiths, D.H.; King, R.F.; Mussett, A.E.; Braile, L.W.; Thompson, G.; Olsen, K.; Harder, S.; Vees, R.; Gajewski, D.; Schulte, A.; Obel, J.; Mwango, F.; Mukinya, J.; Riaroh, D.

1991-01-01

The Kenya rift is one of the classic examples of a continental rift zone: models for its evolution range from extension of the lithosphere by pure shear1, through extension by simple shear2, to diapiric upwelling of an asthenolith3. Following a pilot study in 19854, the present work involved the shooting of three seismic refraction and wide-angle reflection profiles along the axis, across the margins, and on the northeastern flank of the rift (Fig. 1). These lines were intended to reconcile the different crustal thickness estimates for the northern and southern parts of the rift4-6 and to reveal the structure across the rift, including that beneath the flanks. The data, presented here, reveal significant lateral variations in structure both along and across the rift. The crust thins along the rift axis from 35 km in the south to 20 km in the north; there are abrupt changes in Mono depth and uppermost-mantle seismic velocity across the rift margins, and crustal thickening across the boundary between the Archaean craton and PanAfrican orogenic belt immediately west of the rift. These results suggest that thickened crust may have controlled the rift's location, that there is a decrease in extension from north to south, and that the upper mantle immediately beneath the rift may contain reservoirs of magma generated at greater depth.

Seismic investigation of an ocean-continent transition zone in the northern South China Sea

Science.gov (United States)

Zhu, J.; Qiu, X.; Xu, H.; Zhan, W.; Sun, Z.

2011-12-01

Rifted continental margins and basins are mainly formed by the lithospheric extension. Thined lithosphere of passive continental margins results in decompression melt of magma and created oceanic crust and thined ocean-continent transition (OCT) zone. Two refraction profiles used ocean bottom seismometers deployed in the broad continental shelf and three multi-channel seismic reflection lines in the northern South China Sea, acquired by the ship "Shiyan 2" of the South China Sea Institute of Oceanology, Chinese Academy of Sciences in 2010, are processed and interpreted in this study. Seismic reflection lines cut through the Dongsha rise, Zhu-1 and Zhu-2 depression within a Tertiary basin, Pear River Mouth basin (called as Zhujiangkou basin). These tectonic features are clear imaged in the seismic reflection records. Numerous normal faults, cutted through the basement and related to the stretch of the northern South China Sea margin, are imaged and interpreted. Reflection characteristics of the ocean-continent transition (OCT) zone are summaried and outlined. The COT zone is mainly divided into the northern syn-rift subsidence zone, central volcano or buried volcano uplift zone and tilt faulted block near the South Chia Sea basin. Compared to the previous seismic reflection data and refraction velocity models, the segmentation range of the OCT zone is outlined, from width of about 225 km in the northeastern South China Sea , of 160 km in the central to of 110 km in the north-central South China Sea. Based on the epicenter distribution of sporadic and large than 6 magnitude earthquakes, it suggests the OCT zone in the northern South China Sea at present is still an active seismic zone.

The Tetramerium lineage (Acanthaceae: Justicieae) does not support the Pleistocene Arc hypothesis for South American seasonally dry forests.

Science.gov (United States)

Côrtes, Ana Luiza A; Rapini, Alessandro; Daniel, Thomas F

2015-06-01

The Tetramerium lineage (Acanthaceae) presents a striking ecological structuring in South America, with groups concentrated in moist forests or in seasonally dry forests. In this study, we investigate the circumscription and relationships of the South American genera as a basis for better understanding historic interactions between dry and moist biomes in the Neotropics. We dated the ancestral distribution of the Tetramerium lineage based on one nuclear and four plastid DNA regions. Maximum parsimony, maximum likelihood, and Bayesian inference analyses were performed for this study using 104 terminals. Phylogenetic divergences were dated using a relaxed molecular clock approach and ancestral distributions obtained from dispersal-vicariance analyses. The genera Pachystachys, Schaueria, and Thyrsacanthus are nonmonophyletic. A dry forest lineage dispersed from North America to South America and reached the southwestern part of the continent between the end of the Miocene and beginning of the Pleistocene. This period coincides with the segregation between Amazonian and Atlantic moist forests that established the geographic structure currently found in the group. The South American genera Pachystachys, Schaueria, and Thyrsacanthus need to be recircumscribed. The congruence among biogeographical events found for the Tetramerium lineage suggests that the dry forest centers currently dispersed throughout South America are relatively old remnants, probably isolated since the Neogene, much earlier than the Last Glacial Maximum postulated by the Pleistocene Arc hypothesis. In addition to exploring the Pleistocene Arc hypothesis, this research also informs evolution in a lineage with numerous geographically restricted and threatened species. © 2015 Botanical Society of America, Inc.

Seismological Constraints on Lithospheric Evolution in the Appalachian Orogen

Science.gov (United States)

Fischer, K. M.; Hopper, E.; Hawman, R. B.; Wagner, L. S.

2017-12-01

Crust and mantle structures beneath the Appalachian orogen, recently resolved by seismic data from the EarthScope SESAME Flexible Array and Transportable Array, provide new constraints on the scale and style of the Appalachian collision and subsequent lithospheric evolution. In the southern Appalachians, imaging with Sp and Ps phases reveals the final (Alleghanian) suture between the crusts of Laurentia and the Gondwanan Suwannee terrane as a low angle (Kellogg, 2017) isostatic arguments indicate crustal thicknesses were 15-25 km larger at the end of the orogeny, indicating a thick crustal root across the region. The present-day residual crustal root beneath the Blue Ridge mountains is estimated to have a density contrast with the mantle of only 104±20 kg/m3. This value is comparable to other old orogens but lower than values typical of young or active orogens, indicating a loss of lower crustal buoyancy over time. At mantle depths, the negative shear velocity gradient that marks the transition from lithosphere to asthenosphere, as illuminated by Sp phases, varies across the Appalachian orogen. This boundary is shallow beneath the northeastern U.S. and in the zone of Eocene volcanism in Virginia, where low velocity anomalies occur in the upper mantle. These correlations suggest recent active lithosphere-asthenosphere interaction.

Global equivalent magnetization of the oceanic lithosphere

Science.gov (United States)

Dyment, J.; Choi, Y.; Hamoudi, M.; Lesur, V.; Thebault, E.

2015-11-01

As a by-product of the construction of a new World Digital Magnetic Anomaly Map over oceanic areas, we use an original approach based on the global forward modeling of seafloor spreading magnetic anomalies and their comparison to the available marine magnetic data to derive the first map of the equivalent magnetization over the World's ocean. This map reveals consistent patterns related to the age of the oceanic lithosphere, the spreading rate at which it was formed, and the presence of mantle thermal anomalies which affects seafloor spreading and the resulting lithosphere. As for the age, the equivalent magnetization decreases significantly during the first 10-15 Myr after its formation, probably due to the alteration of crustal magnetic minerals under pervasive hydrothermal alteration, then increases regularly between 20 and 70 Ma, reflecting variations in the field strength or source effects such as the acquisition of a secondary magnetization. As for the spreading rate, the equivalent magnetization is twice as strong in areas formed at fast rate than in those formed at slow rate, with a threshold at ∼40 km/Myr, in agreement with an independent global analysis of the amplitude of Anomaly 25. This result, combined with those from the study of the anomalous skewness of marine magnetic anomalies, allows building a unified model for the magnetic structure of normal oceanic lithosphere as a function of spreading rate. Finally, specific areas affected by thermal mantle anomalies at the time of their formation exhibit peculiar equivalent magnetization signatures, such as the cold Australian-Antarctic Discordance, marked by a lower magnetization, and several hotspots, marked by a high magnetization.

The extending lithosphere (Arthur Holmes Medal Lecture)

Science.gov (United States)

Brun, Jean-Pierre

2017-04-01

Extension of the lithosphere gives birth to a wide range of structures, with characteristic widths between 10 and 1000 km, which includes continental rifts, passive margins, oceanic rifts, core complexes, or back-arc basins. Because the rheology of rocks strongly depends on temperature, this variety of extensional structures falls in two broad categories of extending lithospheres according to the initial Moho temperature TM. "Cold extending systems", with TM 750°C and crustal-dominated strength, lead, depending on strain rate, to either wide rifts or metamorphic core complexes. A much less quoted product of extension is the exhumation of high-pressure (HP ) metamorphic rocks occurring in domains of back-arc extension driven by slab rollback (e.g. Aegean; Appennines-Calabrian) or when the subduction upper plate undergoes extension for plate kinematics reasons (e.g. Norwegian Caledonides; Papua New Guinea). In these tectonic environments, well-documented pressure-temperature-time (P - T - t) paths of HP rocks show a two-stage retrogression path whose the first part corresponds to an isothermal large pressure drop ΔP proportional to the maximum pressure Pmax recorded by the rocks. This linear relation between ΔP and Pmax, which likely results from a stress switch between compression and extension at the onset of exhumation, is in fact observed in all HP metamorphism provinces worldwide, suggesting that the exhumation of HP rocks in extension is a general process rather than an uncommon case. In summary, the modes and products of extension are so diverse that, taken all together, they constitute a very versatile natural laboratory to decipher the rheological complexities of the continental lithosphere and their mechanical implications.

Implications of a visco-elastic model of the lithosphere for calculating yield strength envelopes

NARCIS (Netherlands)

Ershov, A.V.; Stephenson, R.A.

2006-01-01

The dominant deformation mechanism in the ductile part of the lithosphere is creep. From a mechanical point of view, creep can be modelled as a viscous phenomenon. On the other hand, yield-strength envelopes (YSEs), commonly used to describe lithosphere rheology, are constructed supposing creep to

A numerical model of mantle convection with deformable, mobile continental lithosphere within three-dimensional spherical geometry

Science.gov (United States)

Yoshida, M.

2010-12-01

A new numerical simulation model of mantle convection with a compositionally and rheologically heterogeneous, deformable, mobile continental lithosphere is presented for the first time by using three-dimensional regional spherical-shell geometry (Yoshida, 2010, Earth Planet. Sci. Lett.). The numerical results revealed that one of major factor that realizes the supercontinental breakup and subsequent continental drift is a pre-existing, weak (low-viscosity) continental margin (WCM) in the supercontinent. Characteristic tectonic structures such as young orogenic belts and suture zones in a continent are expected to be mechanically weaker than the stable part of the continental lithosphere with the cratonic root (or cratonic lithosphere) and yield lateral viscosity variations in the continental lithosphere. In the present-day Earth's lithosphere, the pre-existing, mechanically weak zones emerge as a diffuse plate boundary. However, the dynamic role of the WCM in the stability of continental lithosphere has not been understood in terms of geophysics. In my numerical model, a compositionally buoyant and highly viscous continental assemblage with pre-existing WCMs, analogous to the past supercontinent, is modeled and imposed on well-developed mantle convection whose vigor of convection, internal heating rate, and rheological parameters are appropriate for the Earth's mantle. The visco-plastic oceanic lithosphere and the associated subduction of oceanic plates are incorporated. The time integration of the advection of continental materials with zero chemical diffusion is performed by a tracer particle method. The time evolution of mantle convection after setting the model supercontinent is followed over 800 Myr. Earth-like continental drift is successfully reproduced, and the characteristic thermal interaction between the mantle and the continent/supercontinent is observed in my new numerical model. Results reveal that the WCM protects the cratonic lithosphere from being

The lithospheric mantle below southern West Greenland

DEFF Research Database (Denmark)

Sand, Karina Krarup; Waight, Tod Earle; Pearson, D. Graham

2009-01-01

Geothermobarometry of primarily garnet lherzolitic xenoliths from several localities in southern West Greenland is applied to address the diamond potential, pressure and temperature distribution and the stratigraphy of the subcontinental lithospheric mantle ~600 Ma ago. The samples are from kimbe...... into the reworked Archean North of the Naqssugtoqidian deformation front....

Peeling back the lithosphere: Controlling parameters, surface expressions and the future directions in delamination modeling

Science.gov (United States)

Göğüş, Oğuz H.; Ueda, Kosuke

2018-06-01

Geodynamical models investigate the rheological and physical properties of the lithosphere that peels back (delaminates) from the upper-middle crust. Meanwhile, model predictions are used to relate to a set of observations in the geological context to the test the validity of delamination. Here, we review numerical and analogue models of delamination from these perspectives and provide a number of first-order topics which future modeling studies may address. Models suggest that the presence of the weak lower crust that resides between the strong mantle lithosphere (at least 100 times more viscous/stronger) and the strong upper crust is necessary to develop delamination. Lower crustal weakening may be induced by melt infiltration, shear heating or it naturally occurs through the jelly sandwich type strength profile of the continental lithosphere. The negative buoyancy of the lithosphere required to facilitate the delamination is induced by the pre-existing ocean subduction and/or the lower crustal eclogitization. Surface expression of the peeling back lithosphere has a distinct transient and migratory imprint on the crust, resulting in rapid surface uplift/subsidence, magmatism, heating and shortening/extension. New generation of geodynamical experiments can explain how different types of melting (e.g hydrated, dry melting) occurs with delamination. Reformation of the lithosphere after removal, three dimensional aspects, and the termination of the process are key investigation areas for future research. The robust model predictions, as with other geodynamic modeling studies should be reconciled with observations.

Detachments of the subducted Indian continental lithosphere based on 3D finite-frequency tomographic images

Science.gov (United States)

Liang, X.; Tian, X.; Wang, M.

2017-12-01

Indian plate collided with Eurasian plate at 60 Ma and there are about 3000 km crustal shortening since the continental-continental collision. At least one third of the total amount of crustal shortening between Indian and Eurasian plates could not be accounted by thickened Tibetan crust and surface erosion. It will need a combination of possible transfer of lower crust to the mantle by eclogitization and lateral extrusion. Based on the lithosphere-asthenosphere boundary images beneath the Tibetan plateau, there is also at least the same amount deficit for lithospheric mantle subducted into upper/lower mantle or lateral extrusion with the crust. We have to recover a detailed Indian continental lithosphere image beneath the plateau in order to explain this deficit of mass budget. Combining the new teleseismic body waves recorded by SANDWICH passive seismic array with waveforms from several previous temporary seismic arrays, we carried out finite-frequency tomographic inversions to image three-dimensional velocity structures beneath southern and central Tibetan plateau to examine the possible image of subducted Indian lithosphere in the Tibetan upper mantle. We have recovered a continuous high velocity body in upper mantle and piece-wised high velocity anomalies in the mantle transition zone. Based on their geometry and relative locations, we interpreted these high velocity anomalies as the subducted and detached Indian lithosphere at different episodes of the plateau evolution. Detachments of the subducted Indian lithosphere should have a crucial impact on the volcanism activities and uplift history of the plateau.

Natural Infection of the South American Tapir ( Tapirus terrestris ) by Theileria equi.

Science.gov (United States)

Da Silveira, Alexandre Welzel; De Oliveira, Gustavo Gomes; Menezes Santos, Leandro; da Silva Azuaga, Lucas Bezerra; Macedo Coutinho, Claudia Regina; Echeverria, Jessica Teles; Antunes, Tamires Ramborger; do Nascimento Ramos, Carlos Alberto; Izabel de Souza, Alda

2017-04-01

Theileria equi is a tick-borne piroplasm considered endemic in equines in Brazil. The cohabitation of domestic and wild animals in areas of extensive cattle breeding favors the close contact between different species and the sharing of vectors and, consequently, pathogens. We report the natural infection of a young South American tapir ( Tapirus terrestris ) by T. equi in Mato Grosso do Sul, Brazil. Although it was not possible to associate the clinical and hematologic status of the animal with the infection by the protozoan parasite, our report represents an alert on the sharing of pathogens between domestic and wild animals.

AIRSAR South American deployment: Operation plan, version 3.0

Science.gov (United States)

Kobrick, M.

1993-01-01

The United States National Aeronautics and Space Administration (NASA) and the Brazilian Commission for Space Activities (COBAE) are undertaking a joint experiment involving NASA's DC-8 research aircraft and the Airborne Synthetic Aperture Radar (AIRSAR) system during late May and June 1993. The research areas motivating these activities are: (1) fundamental research in the role of soils, vegetation, and hydrology in the global carbon cycle; and (2) in cooperation with South American scientists, airborne remote sensing research for the upcoming NASA Spaceborne Imaging Radar (SIR)-C/X-SAR flights on the Space Shuttle. A flight schedule and plans for the deployment that were developed are included. Maps of the site locations and schematic indications of flight routes and dates, plots showing swath locations derived from the flight requests and generated by flight planning software, and, most importantly, a calendar showing which sites will be imaged each day are included.

Linking plate reconstructions with deforming lithosphere to geodynamic models

Science.gov (United States)

Müller, R. D.; Gurnis, M.; Flament, N.; Seton, M.; Spasojevic, S.; Williams, S.; Zahirovic, S.

2011-12-01

While global computational models are rapidly advancing in terms of their capabilities, there is an increasing need for assimilating observations into these models and/or ground-truthing model outputs. The open-source and platform independent GPlates software fills this gap. It was originally conceived as a tool to interactively visualize and manipulate classical rigid plate reconstructions and represent them as time-dependent topological networks of editable plate boundaries. The user can export time-dependent plate velocity meshes that can be used either to define initial surface boundary conditions for geodynamic models or alternatively impose plate motions throughout a geodynamic model run. However, tectonic plates are not rigid, and neglecting plate deformation, especially that of the edges of overriding plates, can result in significant misplacing of plate boundaries through time. A new, substantially re-engineered version of GPlates is now being developed that allows an embedding of deforming plates into topological plate boundary networks. We use geophysical and geological data to define the limit between rigid and deforming areas, and the deformation history of non-rigid blocks. The velocity field predicted by these reconstructions can then be used as a time-dependent surface boundary condition in regional or global 3-D geodynamic models, or alternatively as an initial boundary condition for a particular plate configuration at a given time. For time-dependent models with imposed plate motions (e.g. using CitcomS) we incorporate the continental lithosphere by embedding compositionally distinct crust and continental lithosphere within the thermal lithosphere. We define three isostatic columns of different thickness and buoyancy based on the tectonothermal age of the continents: Archean, Proterozoic and Phanerozoic. In the fourth isostatic column, the oceans, the thickness of the thermal lithosphere is assimilated using a half-space cooling model. We also

Coalescent Simulation and Paleodistribution Modeling for Tabebuia rosealba Do Not Support South American Dry Forest Refugia Hypothesis.

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Warita Alves de Melo

Full Text Available Studies based on contemporary plant occurrences and pollen fossil records have proposed that the current disjunct distribution of seasonally dry tropical forests (SDTFs across South America is the result of fragmentation of a formerly widespread and continuously distributed dry forest during the arid climatic conditions associated with the Last Glacial Maximum (LGM, which is known as the modern-day dry forest refugia hypothesis. We studied the demographic history of Tabebuia rosealba (Bignoniaceae to understand the disjunct geographic distribution of South American SDTFs based on statistical phylogeography and ecological niche modeling (ENM. We specifically tested the dry forest refugia hypothesis; i.e., if the multiple and isolated patches of SDTFs are current climatic relicts of a widespread and continuously distributed dry forest during the LGM. We sampled 235 individuals across 18 populations in Central Brazil and analyzed the polymorphisms at chloroplast (trnS-trnG, psbA-trnH and ycf6-trnC intergenic spacers and nuclear (ITS nrDNA genomes. We performed coalescence simulations of alternative hypotheses under demographic expectations from two a priori biogeographic hypotheses (1. the Pleistocene Arc hypothesis and, 2. a range shift to Amazon Basin and other two demographic expectances predicted by ENMs (3. expansion throughout the Neotropical South America, including Amazon Basin, and 4. retraction during the LGM. Phylogenetic analyses based on median-joining network showed haplotype sharing among populations with evidence of incomplete lineage sorting. Coalescent analyses showed smaller effective population sizes for T. roseoalba during the LGM compared to the present-day. Simulations and ENM also showed that its current spatial pattern of genetic diversity is most likely due to a scenario of range retraction during the LGM instead of the fragmentation from a once extensive and largely contiguous SDTF across South America, not supporting the

Coalescent Simulation and Paleodistribution Modeling for Tabebuia rosealba Do Not Support South American Dry Forest Refugia Hypothesis.

Science.gov (United States)

de Melo, Warita Alves; Lima-Ribeiro, Matheus S; Terribile, Levi Carina; Collevatti, Rosane G

2016-01-01

Studies based on contemporary plant occurrences and pollen fossil records have proposed that the current disjunct distribution of seasonally dry tropical forests (SDTFs) across South America is the result of fragmentation of a formerly widespread and continuously distributed dry forest during the arid climatic conditions associated with the Last Glacial Maximum (LGM), which is known as the modern-day dry forest refugia hypothesis. We studied the demographic history of Tabebuia rosealba (Bignoniaceae) to understand the disjunct geographic distribution of South American SDTFs based on statistical phylogeography and ecological niche modeling (ENM). We specifically tested the dry forest refugia hypothesis; i.e., if the multiple and isolated patches of SDTFs are current climatic relicts of a widespread and continuously distributed dry forest during the LGM. We sampled 235 individuals across 18 populations in Central Brazil and analyzed the polymorphisms at chloroplast (trnS-trnG, psbA-trnH and ycf6-trnC intergenic spacers) and nuclear (ITS nrDNA) genomes. We performed coalescence simulations of alternative hypotheses under demographic expectations from two a priori biogeographic hypotheses (1. the Pleistocene Arc hypothesis and, 2. a range shift to Amazon Basin) and other two demographic expectances predicted by ENMs (3. expansion throughout the Neotropical South America, including Amazon Basin, and 4. retraction during the LGM). Phylogenetic analyses based on median-joining network showed haplotype sharing among populations with evidence of incomplete lineage sorting. Coalescent analyses showed smaller effective population sizes for T. roseoalba during the LGM compared to the present-day. Simulations and ENM also showed that its current spatial pattern of genetic diversity is most likely due to a scenario of range retraction during the LGM instead of the fragmentation from a once extensive and largely contiguous SDTF across South America, not supporting the South

Water in the oceanic lithosphere: Salt Lake Crater xenoliths, Oahu, Hawaii

Science.gov (United States)

Peslier, A. H.; Bizimis, M.

2010-12-01

water contents increase with increasing degree of depletion and decrease with LREE/HREE ratios which is inconsistent with the incompatible behavior of H. Calculated water contents of melts in equilibrium with Cpx or Opx range from 1.4 to 3.8 wt % which is higher than that of all Hawaiian lavas. Calculated melts in equilibrium with Cpx and Opx have variable but mostly high H_{2}O/Ce ratios (194 to 1146) consistent with those of rejuvenated stage lavas from Niihau and the South Arch volcanic field, but unlike the drier shield building stage tholeiites. Whether the high water contents recorded in Salt Lake Crater xenoliths were acquired before and/or during interaction of the oceanic lithosphere with the Hawaiian plume will be discussed.

Water in the Oceanic Lithosphere: Salt Lake Crater Xenoliths, Oahu, Hawaii

Science.gov (United States)

Peslier, Anne H.; Bizimis, Michael

2010-01-01

contents increase with increasing degree of depletion and decrease with LREE/HREE ratios which is inconsistent with the incompatible behavior of H. Calculated water contents of melts in equilibrium with Cpx or Opx range from 1.4 to 3.8 wt % which is higher than that of all Hawaiian lavas. Calculated melts in equilibrium with Cpx and Opx have variable but mostly high H_{2}O/Ce ratios (194 to 1146) consistent with those of rejuvenated stage lavas from Niihau and the South Arch volcanic field, but unlike the drier shield building stage tholeiites. Whether the high water contents recorded in Salt Lake Crater xenoliths were acquired before and/or during interaction of the oceanic lithosphere with the Hawaiian plume will be discussed.

Garnet Pyroxenites from Kaula, Hawaii: Implications for Plume-Lithosphere Interaction

Science.gov (United States)

Bizimis, M.; Garcia, M. O.; Norman, M. D.

2006-12-01

The presence of garnet pyroxenite xenoliths on Oahu and Kaula Islands, Hawaii, provides the rare opportunity to investigate the composition of the deeper oceanic mantle lithosphere and the nature of plume-lithosphere interaction in two dimensions, downstream from the center of the Hawaiian plume. Kaula (60 miles SW of Kauai) is on the same bathymetric shallow as Kauai and the Kaula-Niihau-Kauai islands form a cross-trend relationship to the Hawaiian Island ridge. Here, we present the first Sr-Nd isotope data on clinopyroxenes (cpx) from Kaula pyroxenites, and we compare them with the Salt Lake Crater (SLC) pyroxenites from Oahu. The Kaula cpx major element compositions overlap those of the (more variable) SLC pyroxenites (e.g. Mg# = 0.79-0.83), except for their higher Al2O3 contents (9% vs. 5-8%) than the SLC. The Kaula cpx are LREE enriched with elevated Dy/Yb ratios, similar to the SLC pyroxenites and characteristic of the presence of garnet that preferentially incorporates the HREE. In Sr-Nd isotope space, the Kaula pyroxenite compositions (87Sr/86Sr= 0.70312-0.70326, ɛNd= 7.2-8.6) overlap those of both the Oahu-Kauai post erosional lavas and the SLC pyroxenites, falling at the isotopically depleted end of the Hawaiian lava compositions. The depleted Sr-Nd isotope compositions of the Kaula pyroxenites suggest that they are not related to the isotopically enriched shield stage Hawaiian lavas, either as a source material (i.e. recycled eclogite) or as cumulates. Their elevated 87Sr/86Sr ratios relative to MORB also suggests that they are not likely MORB-related cumulates. The similarities between the Oahu and Kaula pyroxenites, some 200 km apart, suggest the widespread presence of pyroxenitic material in the deeper (>60km) Pacific lithosphere between Oahu and Kaula-Kauai, as high pressure cumulates from melts isotopically similar to the secondary Hawaiian volcanism. The presence of this material within the lower lithosphere is consistent with seismic observations

Using crustal thickness and subsidence history on the Iberia-Newfoundland margins to constrain lithosphere deformation modes during continental breakup

Science.gov (United States)

Jeanniot, Ludovic; Kusznir, Nick; Manatschal, Gianreto; Mohn, Geoffroy

2014-05-01

Observations at magma-poor rifted margins such as Iberia-Newfoundland show a complex lithosphere deformation history during continental breakup and seafloor spreading initiation leading to complex OCT architecture with hyper-extended continental crust and lithosphere, exhumed mantle and scattered embryonic oceanic crust and continental slivers. Initiation of seafloor spreading requires both the rupture of the continental crust and lithospheric mantle, and the onset of decompressional melting. Their relative timing controls when mantle exhumation may occur; the presence or absence of exhumed mantle provides useful information on the timing of these events and constraints on lithosphere deformation modes. A single lithosphere deformation mode leading to continental breakup and sea-floor spreading cannot explain observations. We have determined the sequence of lithosphere deformation events for two profiles across the present-day conjugate Iberia-Newfoundland margins, using forward modelling of continental breakup and seafloor spreading initiation calibrated against observations of crustal basement thickness and subsidence. Flow fields, representing a sequence of lithosphere deformation modes, are generated by a 2D finite element viscous flow model (FeMargin), and used to advect lithosphere and asthenosphere temperature and material. FeMargin is kinematically driven by divergent deformation in the upper 15-20 km of the lithosphere inducing passive upwelling beneath that layer; extensional faulting and magmatic intrusions deform the topmost upper lithosphere, consistent with observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996). Buoyancy enhanced upwelling, as predicted by Braun et al. (2000) is also kinematically included in the lithosphere deformation model. Melt generation by decompressional melting is predicted using the parameterization and methodology of Katz et al. (2003). The distribution of lithosphere deformation, the

Late Miocene extensional systems in northern Tunisia and their relation with SE directed delamination of the African subcontinental mantle lithosphere

Science.gov (United States)

Booth-Rea, Guillermo; Gaidi, Seif; Melki, Fetheddine; Pérez-Peña, Vicente; Marzougui, Wissem; Azañón, Jose Miguel; Galve, Jorge Pedro

2017-04-01

Recent work has proposed the delamination of the subcontinental mantle lithosphere under northern Tunisia during the late Miocene. This process is required to explain the present location of the Tunisian segment of the African slab, imaged by seismic tomography, hanging under the Gulf of Gabes to the south of Tunisia. Thus, having retreated towards the SE several hundred km from its original position under the Tellian-Atlas nappe contact that crops out along the north of Tunisia. However, no tectonic structures have been described which could be related to this mechanism of lithospheric mantle peeling. Here we describe for the first time extensional fault systems in northern Tunisia that strongly thinned the Tellian nappes, exhuming rocks from the Tunisian Atlas in the core of folded extensional detachments. Two normal fault systems with sub-orthogonal extensional transport occur. These were active during the late Miocene associated to the extrusion of 13 Ma granodiorite and 9 Ma rhyodacite in the footwall of the Nefza detachment. We have differentiated an extensional system formed by low-angle normal faults with NE- and SW-directed transport cutting through the Early to Middle Miocene Tellian nappen stack and a later system of low and high-angle normal faults that cuts down into the underlying Tunisian Atlas units with SE-directed transport, which root in the Nefza detachment. Both normal fault systems have been later folded and cut by thrusts during Plio-Quaternary NW-SE directed compression. These findings change the interpretation of the tectonic evolution of Tunisia that has always been framed in a transpressive to compressive setting, manifesting the extensional effects of Late Miocene lithospheric mantle delamination under northern Tunisia.

Antiviral activity of some South American medicinal plants.

Science.gov (United States)

Abad, M J; Bermejo, P; Sanchez Palomino, S; Chiriboga, X; Carrasco, L

1999-03-01

Folk medicinal plants are potential sources of useful therapeutic compounds including some with antiviral activities. Extracts prepared from 10 South American medicinal plants (Baccharis trinervis, Baccharis teindalensis, Eupatorium articulatum, Eupatorium glutinosum, Tagetes pusilla, Neurolaena lobata, Conyza floribunda, Phytolacca bogotensis, Phytolacca rivinoides and Heisteria acuminata) were screened for in vitro antiviral activity against herpes simplex type I (HSV-1), vesicular stomatitis virus (VSV) and poliovirus type 1. The most potent inhibition was observed with an aqueous extract of B. trinervis, which inhibited HSV-1 replication by 100% at 50-200 micrograms/mL, without showing cytotoxic effects. Good activities were also found with the ethanol extract of H. acuminata and the aqueous extract of E. articulatum, which exhibited antiviral effects against both DNA and RNA viruses (HSV-1 and VSV, respectively) at 125-250 micrograms/mL. The aqueous extracts of T. pusilla (100-250 micrograms/mL), B. teindalensis (50-125 micrograms/mL) and E. glutinosum (50-125 micrograms/mL) also inhibited the replication of VSV, but none of the extracts tested had any effect on poliovirus replication.

Quantifying the humanitarian and economic impact of earthquakes on South American capital cities (Invited)

Science.gov (United States)

Zoback, M. L.; Cabrera, C.; Pomonis, A.; Baca, A.; Brunner, I.; Cheung, G.; Chen, A.; Nagel, B.; Carrasco, S.

2009-12-01

By 2000, an estimated 80% of South America’s population lived in urban areas (Veblen et al., The Physical Geography of South America, Oxford University Press, 2007). A significant fraction of those urban dwellers resides in the capital cities which are major economic centers and act as magnets for rural poor and refugees. This population concentration includes many residents living in extreme poverty in substandard and informal housing, often on the margins of these capital cities and sometimes on steep slopes, greatly compounding the vulnerability to natural hazards. We are analyzing the humanitarian and economic risk for six of the seismically most-at-risk South American capitals along the northern and western plate boundaries of South America: Caracas, Venezuela; Bogotá, Colombia; Quito, Ecuador; Lima, Perú; La Paz, Bolivia; and Santiago, Chile. Impacts are provided in the form of expected losses for a specific “likely” scenario earthquake and in a probabilistic format using exceedance probability curves (probability of exceeding a given loss in different return periods). Impacts to be quantified include: total economic losses, potential fatalities, potential serious injuries, and the number of displaced households. Probabilistic seismic hazard was developed in collaboration with numerous South American experts and includes subduction interface, intraslab, background crustal and, where available, active fault sources. A significant challenge for this study is to accurately account for the exposure and vulnerability of populations living in the informal, shanty areas. Combining analysis of aerial imagery and on-the-ground reconnaissance, we define between 20-30 “inventory districts” of relatively uniform construction styles within each capital. Statistical distributions of the different construction types and their characteristics (height, occupancy, year built, average value) are estimated for each district. In addition, working with local graduate

Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

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Y. Sahai

2009-12-01

Full Text Available The response of the ionospheric F-region in the South American sector during the super geomagnetic storms on 29 and 30 October 2003 is studied in the present investigation. In this paper, we present ionospheric sounding observations during the period 29–31 October 2003 obtained at Palmas (a near equatorial location and Sao Jose dos Campos (a location under the southern crest of the equatorial ionospheric anomaly, Brazil, along with observations during the period 27–31 October 2003 from a chain of GPS stations covering the South American sector from Imperatriz, Brazil, to Rio Grande, Argentina. Also, complementary observations that include sequences of all-sky images of the OI 777.4 and 630.0 nm emissions observed at El Leoncito, Argentina, on the nights of 28–29 (geomagnetically quiet night and 29–30 (geomagnetically disturbed night October 2003, and ion densities observed in the South American sector by the DMSP F13, F14 and F15 satellites orbiting at about 800 km on 29 and 30 October 2003 are presented. In addition, global TEC maps derived from GPS observations collected from the global GPS network of International GPS Service (IGS are presented, showing widespread and drastic TEC changes during the different phases of the geomagnetic disturbances. The observations indicate that the equatorial ionospheric irregularities or plasma bubbles extend to the Argentinean station Rawson (geom. Lat. 33.1° S and map at the magnetic equator at an altitude of about 2500 km.

Factors Associated with Toothache among African American Adolescents Living in Rural South Carolina

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Wiegand, Ryan E.; Hill, Elizabeth G.; Magruder, Kathryn M.; Slate, Elizabeth H.; Salinas, Carlos F.; London, Steven D.

2012-01-01

Objective The aim of this study is to explore behavioral factors associated with toothache among African American adolescents living in rural South Carolina. Methods Using a self-administered questionnaire, data were collected on toothache experience in the past 12 months, oral hygiene behavior, dental care utilization, and cariogenic snack and non-diet soft drink consumption in a convenience sample of 156 African American adolescents aged 10-18 years old living in rural South Carolina. Univariable and multivariable logistic regression analyses were used to assess the associations between reported toothache experience and socio-demographic variables, oral health behavior, and snack consumption. Results Thirty-four percent of adolescents reported having toothache in the past 12 months. In univariable modeling, age, dental visit in the last two years, quantity and frequency of cariogenic snack consumption, and quantity of non-diet soft drink consumption were each significantly associated with experiencing toothache in the past 12 months (all p-values cariogenic snacks, and number of cans of non-diet soft drink consumed during the weekend significantly increased the odds of experiencing toothache in the past 12 months (all p-values ≤ 0.01). Conclusion Findings indicate age, frequent consumption of cariogenic snacks and number of cans of non-diet soft drinks are related to toothache in this group. Public policy implications related to selling cariogenic snacks and soft drink that targeting children and adolescents especially those from low income families are discussed. PMID:22085328

Structure of the mantle lithosphere in continental collision zones of Europe, North America and China from S-receiver functions

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Kind, R.; Shen, X.

2017-12-01

Seismic tomography and receiver functions are the most common methods to study the structure of the mantle lithosphere. We use S-receiver functions to study continent-continent collision zones in Europe, North America and China. In order to avoid possible numerical problems caused by filtering effects (side lobes) we process the data practically without filtering (also excluding deconvolution). Side lobes are still a fundamental question to check the reality of the Mid-Lithospheric Discontinuity (MLD). We use openly available data of mostly permanent seismic broadband stations from the European portal EIDA, from IRIS and from the Chinese Seismic Network. We obtained several ten thousands of useful records in each region by visual and fully automatic processing. We observed the MLD in all cratonic regions near 100 km depth and the Lithosphere-Asthenosphere Boundary (LAB) partly in cratonic regions near 200 km depth. The observation of the cratonic LAB with converted waves requires a relatively sharp discontinuity which excludes temperature as only cause of the LAB. In younger tectonic active regions we observed the LAB near 100 km depth. TheLAB and MLD are in collision zones significantly structured. In central Europe we observed the deep cratonic LAB reaching far to the west of the Tornquist-Teisseyre Zone below Phanerozoic cover. Below the northern edge of the Bohemian Massif seems to be a tear in the LAB leading to a jump in its depth of about 100 km. In North America we see north of Yellowstone a smooth deepening of the western LAB from about 100 km depth to 200 km depth at the Mid-Continental Rift System. Similarly to the LAB jump below the Bohemian Massif in Europe, we see below the Sevier Thrust Belt also a jump of about 100 km in the LAB depth. In China we see the cratonic LAB deepening to the south-west far below eastern Tibet. Below the craton in north-east China is only the shallow LAB/MLD visible. These observations in three continents show that the

Building and Modification of the Continental Lithosphere: the History of the Contiguous U.S. as told by MLDs and LABs

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Hopper, E.; Fischer, K. M.

2016-12-01

The lithosphere preserves a record of past and present tectonic processes in its internal structures and its boundary with the underlying asthenosphere. We use common conversion point stacked Sp converted waves recorded by EarthScope's Transportable Array, as well as other available permanent and temporary broadband stations, to image such structures in the lithospheric mantle of the contiguous U.S. In the tectonically youngest western U.S., a shallow, sharp velocity gradient at the base of the lithosphere suggests a boundary defined by ponded melt. The lithosphere thickens with age of volcanism, implying the lithosphere is a melt-mitigated, conductively cooling thermal boundary layer. Beneath older, colder lithosphere where melt fractions are likely much lower, the velocity gradient at the base of such a layer should be a more diffuse, primarily thermal boundary. This is consistent with observations in the eastern U.S. where the lithosphere-asthenosphere boundary (LAB) is locally sharp and shallower only in areas of inferred enhanced upwelling - such as ancient hot spot tracks and areas of inferred delamination. In the cratonic interior, the LAB is even more gradual in depth, and is transparent to Sp waves with dominant periods of 10 s. Although seismic imaging only provides a snapshot of the lithosphere as it is today, preserved internal structures extend the utility of this imaging back into deep geological time. Ancient accretion within the cratonic lithospheric mantle is preserved as dipping structures associated with relict subducted slabs from Paleoproterozoic continental accretion, suggesting that lateral accretion was integral to the cratonic mantle root formation process. Metasomatism, melt migration and ponding below a carbonated peridotite solidus explain a sub-horizontal mid-lithospheric discontinuity (MLD) commonly observed at 70-100 km depth. This type of MLD is strongest in Mesoproterozoic and older lithosphere, suggesting that it formed more

Electromagnetic study of lithospheric structure in Trans-European Suture Zone in Poland

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Jóźwiak, Waldemar; Ślęzak, Katarzyna; Nowożyński, Krzysztof; Neska, Anne

2016-04-01

The area covered by magnetotelluric surveys in Poland is mostly related to the Trans-European Suture Zone (TESZ), the largest tectonic boundary in Europe. Numerous 1D, 2D, and pseudo-3D and 3D models of the electrical resistivity distribution were constructed, and a new interpretation method based on Horizontal Magnetic Tensor analysis has been applied recently. The results indicate that the TESZ is a lithospheric discontinuity and there are noticeable differences in geoelectric structures between the East European Craton (EEC), the transitional zone (TESZ), and the Paleozoic Platform (PP). The electromagnetic sounding is a very efficient tool for recognizing the lithospheric structure especially it helps in identification of important horizontal (or lateral) inhomogeneities in the crust. Due to our study we can clearly determine the areas of the East European Craton of high resistivity, Paleozoic Platform of somewhat lower resistivity value, and transitional TESZ of complicated structure. At the East European Craton, we observe very highly resistive lithosphere, reaching 220-240 km depth. Underneath, there is distinctly greater conductivity values, most probably resulting from partial melting of rocks; this layer may represent the asthenosphere. The resistivity of the lithosphere under the Paleozoic Platform is somewhat lower, and its thickness does not exceed 150 km. The properties of the lithosphere in the transition zone, under the TESZ, differ significantly. The presented models include prominent, NW-SE striking conductive lineaments. These structures, that related with the TESZ, lie at a depth of 10-30 km. They are located in a mid-crustal level and they reach the boundary of the EEC. The structures we initially connect to the Variscan Deformation Front (VDF) and the Caledonian Deformation Front (CDF). The differentiation of conductivity visible in the crust continues in the upper mantle.

Central plane of the ring current responsible for geomagnetic disturbance in the South-American region

International Nuclear Information System (INIS)

Kane, R.P.; Trivedi, N.B.

1981-01-01

Using hourly values of H, D, Z from a network of South American stations, operative during the IGY-IGC, the latitude dependence of storm effects was studied. It was found that whereas there were considerable distortions due to conductivity anomalies under the Andes, there was also evidence of latitudinal excursions of overhead current system, not only from storm to storm but even during the course of the same storm

Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

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Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

2017-08-01

Subduction of carbonated crust is widely believed to generate a flux of carbon into the base of the continental lithospheric mantle, which in turn is the likely source of widespread volcanic and non-volcanic CO2 degassing in active tectonic intracontinental settings such as rifts, continental margin arcs and back-arc domains. However, the magnitude of the carbon flux through the lithosphere and the budget of stored carbon held within the lithospheric reservoir are both poorly known. We provide new constraints on the CO2 budget of the lithospheric mantle below the Pannonian Basin (Central Europe) through the study of a suite of xenoliths from the Bakony-Balaton Highland Volcanic Field. Trails of secondary fluid inclusions, silicate melt inclusions, networks of melt veins, and melt pockets with large and abundant vesicles provide numerous lines of evidence that mantle metasomatism affected the lithosphere beneath this region. We obtain a quantitative estimate of the CO2 budget of the mantle below the Pannonian Basin using a combination of innovative analytical and modeling approaches: (1) synchrotron X-ray microtomography, (2) NanoSIMS, Raman spectroscopy and microthermometry, and (3) thermodynamic models (Rhyolite-MELTS). The three-dimensional volumes reconstructed from synchrotron X-ray microtomography allow us to quantify the proportions of all petrographic phases in the samples and to visualize their textural relationships. The concentration of CO2 in glass veins and pockets ranges from 0.27 to 0.96 wt.%, higher than in typical arc magmas (0-0.25 wt.% CO2), whereas the H2O concentration ranges from 0.54 to 4.25 wt.%, on the low end for estimated primitive arc magmas (1.9-6.3 wt.% H2O). Trapping pressures for vesicles were determined by comparing CO2 concentrations in glass to CO2 saturation as a function of pressure in silicate melts, suggesting pressures between 0.69 to 1.78 GPa. These values are generally higher than trapping pressures for fluid inclusions

Abnormal lithium isotope composition from the ancient lithospheric mantle beneath the North China Craton.

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Tang, Yan-Jie; Zhang, Hong-Fu; Deloule, Etienne; Su, Ben-Xun; Ying, Ji-Feng; Santosh, M; Xiao, Yan

2014-03-04

Lithium elemental and isotopic compositions of olivines in peridotite xenoliths from Hebi in the North China Craton provide direct evidence for the highly variable δ(7)Li in Archean lithospheric mantle. The δ(7)Li in the cores of olivines from the Hebi high-Mg# peridotites (Fo > 91) show extreme variation from -27 to +21, in marked deviation from the δ(7)Li range of fresh MORB (+1.6 to +5.6) although the Li abundances of the olivines are within the range of normal mantle (1-2 ppm). The Li abundances and δ(7)Li characteristics of the Hebi olivines could not have been produced by recent diffusive-driven isotopic fractionation of Li and therefore the δ(7)Li in the cores of these olivines record the isotopic signature of the subcontinental lithospheric mantle. Our data demonstrate that abnormal δ(7)Li may be preserved in the ancient lithospheric mantle as observed in our study from the central North China Craton, which suggest that the subcontinental lithospheric mantle has experienced modification of fluid/melt derived from recycled oceanic crust.

On the use of the South-American neutron monitors

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Cordaro, E. G. [Santiago de Chile Univ., Santiago de Chile (Chile). Facultad de Ciencias Fisicas y Matematicas, Dept. de Fisica, Lewis Research Center; Storini, M. [Consiglio Nazionale delle Ricerche, Istituto di Fisica dello Spazio Interplanetario, Rome (Italy); Rome Univ. Tre, Rome (Italy). Dipt. di Fisica, Raggi Cosmici

2001-10-01

Cosmic ray scientific community deserves special attention to the Chacaltaya site for its over 5 km altitude. In this site, a neutron monitor of the IGY type operated from 1960 to 1969, and the one of the NM-64 type since 1966 (16.31{sup 0}S, 291.85{sup 0}E, height: about 5200 m a.s.l.). It was discussed the relevance of such kind of detector when it is integrated with the other South-American neutron monitors: a) LARC (62.20{sup 0}S, 301.04{sup 0}E, height: 40 m a.s.l., King George Island, Antarctica; operating since 1991); b) Los Cerrillos (33.45{sup 0}S, 289.40{sup 0}E, height: 570 m a. s. l., Santiago, Chile; to be installed in the near future); c) Huancayo (12.03{sup 0}S, 284.67{sup 0}E, height: 3400 m a.s.l., Huancayo, Peru; hoping to recover its acquired data).

Contrast of lithospheric dynamics across the southern and eastern margins of the Tibetan Plateau: a numerical study

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Sun, Yujun; Fan, Taoyuan; Wu, Zhonghai

2018-05-01

Both of the southern and eastern margins of the Tibetan Plateau are bounded by the cratonic blocks (Indian plate and Sichuan basin). However, there are many differences in tectonic deformation, lithospheric structure and surface heat flow between these two margins. What dynamics cause these differences? With the constraints of the lithospheric structure and surface heat flow across the southern and eastern margins of Tibetan Plateau, we constructed 2-D thermal-mechanical finite-element models to investigate the dynamics across these two margins. The results show that the delamination of mantle lithosphere beneath the Lhasa terrane in Oligocene and the rheological contrast between the Indian and Tibetan crust are the two main factors that control the subduction of the Indian plate. The dynamics across the eastern margin of the Tibetan Plateau are different from the southern margin. During the lateral expansion of the Tibetan Plateau, pure shear thickening is the main deformation characteristic for the Songpan-Ganzi lithosphere. This thickening results in the reduction of geothermal gradient and surface heat flow. From this study, it can be seen that the delamination of the mantle lithosphere and the rheological contrast between the Tibetan Plateau and its bounding blocks are the two main factors that control the lithospheric deformation and surface heat flow.

Dinosaur speed demon: the caudal musculature of Carnotaurus sastrei and implications for the evolution of South American abelisaurids.

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W Scott Persons

Full Text Available In the South American abelisaurids Carnotaurus sastrei, Aucasaurus garridoi, and, to a lesser extent Skorpiovenator bustingorryi, the anterior caudal ribs project at a high dorsolateral inclination and have interlocking lateral tips. This unique morphology facilitated the expansion of the caudal hypaxial musculature at the expense of the epaxial musculature. Distinct ridges on the ventrolateral surfaces of the caudal ribs of Aucasaurus garridoi are interpreted as attachment scars from the intra caudofemoralis/ilio-ischiocaudalis septa, and confirm that the M. caudofemoralis of advanced South American abelisaurids originated from a portion of the caudal ribs. Digital muscle models indicate that, relative to its overall body size, Carnotaurus sastrei had a substantially larger M. caudofemoralis than any other theropod yet studied. In most non-avian theropods, as in many extant sauropsids, the M. caudofemoralis served as the primary femoral retractor muscle during the locomotive power stroke. This large investment in the M. caudofemoralis suggests that Carnotaurus sastrei had the potential for great cursorial abilities, particularly short-burst sprinting. However, the tightly interlocking morphology of the anterior caudal vertebrae implies a reduced ability to make tight turns. Examination of these vertebral traits in evolutionary context reveals a progressive sequence of increasing caudofemoral mass and tail rigidity among the Abelisauridae of South America.

Lithospheric structure of northwest Africa: Insights into the tectonic history and influence of mantle flow on large-scale deformation

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Miller, Meghan S.; Becker, Thorsten

2014-05-01

Northwest Africa is affected by late stage convergence of Africa with Eurasia, the Canary Island hotspot, and bounded by the Proterozoic-age West African craton. We present seismological evidence from receiver functions and shear-wave splitting along with geodynamic modeling to show how the interactions of these tectonic features resulted in dramatic deformation of the lithosphere. We interpret seismic discontinuities from the receiver functions and find evidence for localized, near vertical-offset deformation of both crust-mantle and lithosphere-asthenosphere interfaces at the flanks of the High Atlas. These offsets coincide with the locations of Jurassic-aged normal faults that have been reactivated during the Cenozoic, further suggesting that inherited, lithospheric-scale zones of weakness were involved in the formation of the Atlas. Another significant step in lithospheric thickness is inferred within the Middle Atlas. Its location corresponds to the source of regional Quaternary alkali volcanism, where the influx of melt induced by the shallow asthenosphere appears restricted to a lithospheric-scale fault on the northern side of the mountain belt. Inferred stretching axes from shear-wave splitting are aligned with the topographic grain in the High Atlas, suggesting along-strike asthenospheric shearing in a mantle channel guided by the lithospheric topography. Isostatic modeling based on our improved lithospheric constraints indicates that lithospheric thinning alone does not explain the anomalous Atlas topography. Instead, an mantle upwelling induced by a hot asthenospheric anomaly appears required, likely guided by the West African craton and perhaps sucked northward by subducted lithosphere beneath the Alboran. This dynamic support scenario for the Atlas also suggests that the timing of uplift is contemporaneous with the recent volcanismin the Middle Atlas.

Lateral heterogeneity and vertical stratification of cratonic lithospheric keels: a case study of the Siberian craton

DEFF Research Database (Denmark)

Artemieva, Irina; Cherepanova, Yulia; Herceg, Matija

2014-01-01

by regional xenolith P-T arrays,lithosphere density heterogeneity as constrained by free-board and satellite gravity data, and the non-thermalpart of upper mantle seismic velocity heterogeneity based on joint analysis of thermal and seismic tomography data.Density structure of the cratonic lithosphere...... and strongly depleted lithospheric mantle of the Archean nuclei, particularly below the Anabar shield.Since we cannot identify the depth distribution of density anomalies, we complement the approach by seismicdata. An analysis of temperature-corrected seismic velocity structure indicates strong vertical...

Evolution of naturally occurring 5'non-coding region variants of Hepatitis C virus in human populations of the South American region

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García-Aguirre Laura

2007-08-01

Full Text Available Abstract Background Hepatitis C virus (HCV has been the subject of intense research and clinical investigation as its major role in human disease has emerged. Previous and recent studies have suggested a diversification of type 1 HCV in the South American region. The degree of genetic variation among HCV strains circulating in Bolivia and Colombia is currently unknown. In order to get insight into these matters, we performed a phylogenetic analysis of HCV 5' non-coding region (5'NCR sequences from strains isolated in Bolivia, Colombia and Uruguay, as well as available comparable sequences of HCV strains isolated in South America. Methods Phylogenetic tree analysis was performed using the neighbor-joining method under a matrix of genetic distances established under the Kimura-two parameter model. Signature pattern analysis, which identifies particular sites in nucleic acid alignments of variable sequences that are distinctly representative relative to a background set, was performed using the method of Korber & Myers, as implemented in the VESPA program. Prediction of RNA secondary structures was done by the method of Zuker & Turner, as implemented in the mfold program. Results Phylogenetic tree analysis of HCV strains isolated in the South American region revealed the presence of a distinct genetic lineage inside genotype 1. Signature pattern analysis revealed that the presence of this lineage is consistent with the presence of a sequence signature in the 5'NCR of HCV strains isolated in South America. Comparisons of these results with the ones found for Europe or North America revealed that this sequence signature is characteristic of the South American region. Conclusion Phylogentic analysis revealed the presence of a sequence signature in the 5'NCR of type 1 HCV strains isolated in South America. This signature is frequent enough in type 1 HCV populations circulating South America to be detected in a phylogenetic tree analysis as a distinct

Estimation of Water Within the Lithospheric Mantle of Central Tibet from Petrological-Geophysical Investigations

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Vozar, J.; Fullea, J.; Jones, A. G.

2013-12-01

Investigations of the lithosphere and sub-lithospheric upper mantle by integrated petrological-geophysical modeling of magnetotelluric (MT) and seismic surface-wave data, which are differently sensitive to temperature and composition, allows us to reduce the uncertainties associated with modeling these two data sets independently, as commonly undertaken. We use selected INDEPTH MT data, which have appropriate dimensionality and large penetration depths, across central Tibet for 1D modeling. Our deep resistivity models from the data can be classified into two different and distinct groups: (i) the Lhasa Terrane and (ii) the Qiangtang Terrane. For the Lhasa Terrane group, the models show the existence of upper mantle conductive layer localized at depths of 200 km, whereas for the Qiangtang Terrane, this conductive layer is shallower at depths of 120 km. We perform the integrated geophysical-petrological modeling of the MT and surface-wave data using the software package LitMod. The program facilitates definition of realistic temperature and pressure distributions within the upper mantle for given thermal structure and oxide chemistry in the CFMAS system. This allows us to define a bulk geoelectric and seismic model of the upper mantle based on laboratory and xenolith data for the most relevant mantle minerals, and to compute synthetic geophysical observables. Our results suggest an 80-120 km-thick, dry lithosphere in the central part of the Qiangtang Terrane. In contrast, in the central Lhasa Terrane the predicted MT responses are too resistive for a dry lithosphere regardless its thickness; according to seismic and topography data the expected lithospheric thickness is about 200 km. The presence of small amounts of water significantly decreases the electrical resistivity of mantle rocks and is required to fit the MT responses. We test the hypothesis of small amounts of water (ppm scale) in the nominally anhydrous minerals of the lithospheric mantle. Such a small

High resolution 3-D shear wave velocity structure in South China from surface wave tomography

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Ning, S.; Guo, Z.; Chen, Y. J.

2017-12-01

Using continuous data from a total of 638 seismic stations, including 484 from CEArray between 2008 and 2013 and 154 from SINOPROBE between 2014 and 2015, we perform both ambient noise and earthquake Rayleigh wave tomography across South China. Combining Rayleigh wave phase velocity between 6and 40s periods from ambient noise tomography and Rayleigh wave phase velocity between 20and 140s from teleseismic two-plane-wave tomography, we obtain phase velocity maps between 6 and140 s periods. We then invert Rayleigh wave phase velocity to construct a 3-D shear wave velocity structure of South China by Markov Chain Monte Carlo method. Similar to other inversion results, our results correspond topography well. Moreover, our results also reveal that velocity structure of the eastern South China in mantle depth is similar to eastern North China, the core of the western South China, Sichuan Block (SB),still exists thick lithosphere. However, owing to much more data employed and some data quality control techniques in this research, our results reveal more detailed structures. Along Qinling-Dabie Orogenic Belt (QDOB), North-South Gravity Lineament (NSGL) and the Sichuan-Yunnan Rhombic Block (SYRB), there are obvious high speed anomalies in depths of 10-20 km, which possibly imply ancient intrusions. Moreover, it seems that Tancheng-Lujiang Fault Zone (TLFZ) has already cut through QDOB, forming a deep fracture cutting through the crust of the whole China continent. Although SB still exists thick lithosphere, there are indications for thermal erosion. At the same time, the lithosphere of the central SYRB seems to be experiencing delamination process, obviously forming a barrier to prevent the hot Tibetan Plateau (TP) mantle material from flowing further southeast. Upwelling hot mantle material possibly triggered by this delamination process might be the cause of the Emeishan Large Igneous Province. There exists an intercontinental low velocity layer in the crust of the TP

Global map of lithosphere thermal thickness on a 1 deg x 1 deg grid - digitally available

DEFF Research Database (Denmark)

Artemieva, Irina

2014-01-01

with no or low quality heat flow data. This analysis requires knowledge oflithosphere age globally.A compilation of tectono-thermal ages of lithospheric terranes on a 1 deg 1 deg grid forms the basis forthe statistical analysis. It shows that, statistically, lithospheric thermal thickness z (in km) depends......This presentation reports a 1 deg 1 deg global thermal model for the continental lithosphere (TC1). The modelis digitally available from the author’s web-site: www.lithosphere.info.Geotherms for continental terranes of different ages (early Archean to present) are constrained by reliabledata...... on borehole heat flow measurements (Artemieva and Mooney, 2001), checked with the original publicationsfor data quality, and corrected for paleo-temperature effects where needed. These data are supplemented bycratonic geotherms based on xenolith data.Since heat flow measurements cover not more than half...

Gravity signals from the lithosphere in the Central European Basin System

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Yegorova, T.; Bayer, U.; Thybo, H.; Maystrenko, Y.; Scheck-Wenderoth, M.; Lyngsie, S. B.

2007-01-01

We study the gravity signals from different depth levels in the lithosphere of the Central European Basin System (CEBS). The major elements of the CEBS are the Northern and Southern Permian Basins which include the Norwegian-Danish Basin (NDB), the North-German Basin (NGB) and the Polish Trough (PT). An up to 10 km thick sedimentary cover of Mesozoic-Cenozoic sediments, hides the gravity signal from below the basin and masks the heterogeneous structure of the consolidated crust, which is assumed to be composed of domains that were accreted during the Paleozoic amalgamation of Europe. We performed a three-dimensional (3D) gravity backstripping to investigate the structure of the lithosphere below the CEBS. Residual anomalies are derived by removing the effect of sediments down to the base of Permian from the observed field. In order to correct for the influence of large salt structures, lateral density variations are incorporated. These sediment-free anomalies are interpreted to reflect Moho relief and density heterogeneities in the crystalline crust and uppermost mantle. The gravity effect of the Moho relief compensates to a large extent the effect of the sediments in the CEBS and in the North Sea. Removal of the effects of large-scale crustal inhomogeneities shows a clear expression of the Variscan arc system at the southern part of the study area and the old crust of Baltica further north-east. The remaining residual anomalies (after stripping off the effects of sediments, Moho topography and large-scale crustal heterogeneities) reveal long wavelength anomalies, which are caused mainly by density variations in the upper mantle, though gravity influence from the lower crust cannot be ruled out. They indicate that the three main subbasins of the CEBS originated on different lithospheric domains. The PT originated on a thick, strong and dense lithosphere of the Baltica type. The NDB was formed on a weakened Baltica low-density lithosphere formed during the Sveco

Lateral heterogeneity and vertical stratification of cratonic lithospheric keels: examples from Europe, Siberia, and North America

DEFF Research Database (Denmark)

Artemieva, Irina; Cherepanova, Yulia; Herceg, Matija

of the Precambrian lithosphere based on surface heat flow data, (ii) non-thermal part of upper mantle seismic velocity heterogeneity based on a joint analysis of thermal and seismic tomography data, and (iii) lithosphere density heterogeneity as constrained by free-board and satellite gravity data. The latter...... of the Gondwanaland does not presently exceed 250 km depth. An analysis of temperature-corrected seismic velocity structure indicates strong vertical and lateral heterogeneity of the cratonic lithospheric mantle, with a pronounced stratification in many Precambrian terranes; the latter is supported by xenolith data...

Earth's evolving subcontinental lithospheric mantle: inferences from LIP continental flood basalt geochemistry

Science.gov (United States)

Greenough, John D.; McDivitt, Jordan A.

2018-04-01

Archean and Proterozoic subcontinental lithospheric mantle (SLM) is compared using 83 similarly incompatible element ratios (SIER; minimally affected by % melting or differentiation, e.g., Rb/Ba, Nb/Pb, Ti/Y) for >3700 basalts from ten continental flood basalt (CFB) provinces representing nine large igneous provinces (LIPs). Nine transition metals (TM; Fe, Mn, Sc, V, Cr, Co, Ni, Cu, Zn) in 102 primitive basalts (Mg# = 0.69-0.72) from nine provinces yield additional SLM information. An iterative evaluation of SIER values indicates that, regardless of age, CFB transecting Archean lithosphere are enriched in Rb, K, Pb, Th and heavy REE(?); whereas P, Ti, Nb, Ta and light REE(?) are higher in Proterozoic-and-younger SLM sources. This suggests efficient transfer of alkali metals and Pb to the continental lithosphere perhaps in association with melting of subducted ocean floor to form Archean tonalite-trondhjemite-granodiorite terranes. Titanium, Nb and Ta were not efficiently transferred, perhaps due to the stabilization of oxide phases (e.g., rutile or ilmenite) in down-going Archean slabs. CFB transecting Archean lithosphere have EM1-like SIER that are more extreme than seen in oceanic island basalts (OIB) suggesting an Archean SLM origin for OIB-enriched mantle 1 (EM1). In contrast, OIB high U/Pb (HIMU) sources have more extreme SIER than seen in CFB provinces. HIMU may represent subduction-processed ocean floor recycled directly to the convecting mantle, but to avoid convective homogenization and produce its unique Pb isotopic signature may require long-term isolation and incubation in SLM. Based on all TM, CFB transecting Proterozoic lithosphere are distinct from those cutting Archean lithosphere. There is a tendency for lower Sc, Cr, Ni and Cu, and higher Zn, in the sources for Archean-cutting CFB and EM1 OIB, than Proterozoic-cutting CFB and HIMU OIB. All CFB have SiO2 (pressure proxy)-Nb/Y (% melting proxy) relationships supporting low pressure, high % melting

Phylogeny of Amazona barbadensis and the Yellow-headed Amazon complex (Aves: Psittacidae): a new look at South American parrot evolution.

Science.gov (United States)

Urantówka, Adam Dawid; Mackiewicz, Paweł; Strzała, Tomasz

2014-01-01

The Yellow-shouldered Amazon (Amazona barbadensis) is the sole parrot of the genus Amazona that inhabits only dry forests. Its population has been dropping; therefore it has been the topic of many studies and conservation efforts. However, the phylogenetic relationship of this species to potential relatives classified within the Yellow-Headed Amazon (YHA) complex are still not clear. Therefore, we used more extensive data sets, including the newly sequenced mitochondrial genome of A. barbadensis, to conduct phylogenetic analyses. Various combinations of genes and many phylogenetic approaches showed that A. barbadensis clustered significantly with A. ochrocephala ochrocephala from Colombia and Venezuela, which created the Northern South American (NSA) lineage, clearly separated from two other lineages within the YHA complex, the Central (CA) and South American (SA). Tree topology tests and exclusion of rapidly evolving sites provided support for a NSA+SA grouping. We propose an evolutionary scenario for the YHA complex and its colonization of the American mainland. The NSA lineage likely represents the most ancestral lineage, which derived from Lesser Antillean Amazons and colonized the northern coast of Venezuela about a million years ago. Then, Central America was colonized through the Isthmus of Panama, which led to the emergence of the CA lineage. The southward expansion to South America and the origin of the SA lineage happened almost simultaneously. However, more intensive or prolonged gene flow or migrations have led to much weaker geographic differentiation of genetic markers in the SA than in the CA lineage.

The energy geopolitics interests: the Initiative for South American Regional Integration - ISARI; Os interesses da geopolitica energetica: a Iniciativa para Integracao Regional Sul Americana - IIRSA

Energy Technology Data Exchange (ETDEWEB)

Jeronymo, Alexandre; Roig, Carla de Almeida; Guerra, Sinclair Mallet Guy [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Programa de Pos-Graduacao em Energia], e-mail: alexandre.jeronymo@ufabc.edu.br, e-mail: carla.roig@ufabc.edu.br, e-mail: sguerra@ufabc.edu.br

2008-07-01

This work adds itself to the debates on the project Integration of South America Regional Infrastructure - ISARI. Its focus is related with Energy Geopolitics and the South America integration under the world system of commodities production. The ISARI, as a project oriented to the viability of low value aggregated which should be transported from the south american continent for consumption at the world market.

Seismic evidence of the lithosphere-asthenosphere boundary beneath Izu-Bonin area

Science.gov (United States)

Cui, H.; Gao, Y.; Zhou, Y.

2016-12-01

The lithosphere-asthenosphere boundary (LAB), separating the rigid lithosphere and the ductile asthenosphere layers, is the seismic discontinuity with the negative velocity contrast of the Earth's interior [Fischer et al., 2010]. The LAB has been also termed the Gutenberg (G) discontinuity that defines the top of the low velocity zone in the upper mantle [Gutenberg, 1959; Revenaugh and Jordan, 1991]. The seismic velocity, viscosity, resistivity and other physical parameters change rapidly with the depths across the boundary [Eaton et al., 2009]. Seismic detections on the LAB in subduction zone regions are of great help to understand the interactions between the lithosphere and asthenosphere layers and the geodynamic processes related with the slab subductions. In this study, the vertical broadband waveforms are collected from three deep earthquake events occurring from 2000 to 2014 with the focal depths of 400 600 km beneath the Izu-Bonin area. The waveform data is processed with the linear slant stack method [Zang and Zhou, 2002] to obtain the vespagrams in the relative travel-time to slowness domain and the stacked waveforms. The sP precursors reflected on the LAB (sLABP), which have the negative polarities with the amplitude ratios of 0.17 0.21 relative to the sP phases, are successfully extracted. Based on the one-dimensional modified velocity model (IASP91-IB), we obtain the distributions for six reflected points of the sLABP phases near the source region. Our results reveal that the LAB depths range between 58 and 65 km beneath the Izu-Bonin Arc, with the average depth of 62 km and the small topography of 7 km. Compared with the results of the tectonic stable areas in Philippine Sea [Kawakatsu et al., 2009; Kumar and Kawakatsu, 2011], the oceanic lithosphere beneath the Izu-Bonin Arc shows the obvious thinning phenomena. We infer that the lithospheric thinning is closely related with the partial melting, which is caused by the volatiles continuously released

Lithospheric strength variations in Mainland China : Tectonic implications

NARCIS (Netherlands)

Deng, Yangfan; Tesauro, M.

2016-01-01

We present a new thermal and strength model for the lithosphere of Mainland China. To this purpose, we integrate a thermal model for the crust, using a 3-D steady state heat conduction equation, with estimates for the upper mantle thermal structure, obtained by inverting a S wave tomography model.

Resveratrol, phenolic antioxidants, and saccharides in South American red wines

Directory of Open Access Journals (Sweden)

Osorio-Macías DE

2018-01-01

Full Text Available Daniel E Osorio-Macías,1,2 Pamela Vásquez,3 Cristhian Carrasco,3 Bjorn Bergenstahl,1 J Mauricio Peñarrieta2 1Department of Food Technology, Faculty of Engineering LTH, Lund University, Lund, Sweden; 2School of Chemistry, Faculty of Pure and Natural Sciences, 3Institute of Research and Development of Chemical Processes, Department of Chemical Engineering, Faculty of Engineering, Universidad Mayor de San Andrés (UMSA, La Paz, Bolivia Abstract: Wine is an important beverage with a long tradition, and its moderate consumption may be considered beneficial for human health. Although there are many studies regarding phenolic compounds in wines, there is a lack of information about antioxidants and phenolic content in South American wines. In this study, 35 South American red wines from four different countries, vintages 2004–2013, purchased at retail stores in La Paz, Bolivia, were studied. Resveratrol content, total antioxidant capacity (TAC by the 2,2′-azino-bis(3-ethylbenzotiazoline-6-sulfonic acid (ABTS and ferric-reducing antioxidant power (FRAP methods, total phenolic content (TPH, total flavonoids (TF, and main saccharides were assessed using the well-established spectrophotometric and high-performance liquid chromatography methods. The results ranged from 4 to 24 mmol/L for TAC determined by ABTS method and 14 to 43 mmol/L for TAC determined by FRAP method, 1600 to 3500 mg gallic acid equivalents/L for TPH, and 2 to 6 mmol catechin equivalents /L for TF. The resveratrol content ranged from 0.1 to 8 mg/L. Saccharides, glucose, and fructose content ranged from 0.4 to 10 g/L, 1.4 to 8.6 g/L, and 0.2 to 12 g/L, respectively. There was a high correlation among the different methods. The results showed that some wines growing at high altitude (>1500 meters above the sea level have higher amounts of TAC and phenolic content, including resveratrol, while non-varietal wines showed the lowest values. It was also observed that the saccharose

"No Unfavorable Comments from Any Quarter": Teaching Black History to White Students in the American South, 1928-1943

Science.gov (United States)

Woyshner, Christine

2012-01-01

Background/Context: The history curriculum is often used to help reach the goal of racial tolerance and understanding by teaching about the nation's diversity. Many educators believe that teaching about diverse peoples in schools will bring about greater equity in society. This historical study looks at the segregated American South from 1928 to…

Global maps of the magnetic thickness and magnetization of the Earth’s lithosphere

OpenAIRE

Foteini Vervelidou; Erwan Thébault

2015-01-01

We have constructed global maps of the large-scale magnetic thickness and magnetization of Earth’s lithosphere. Deriving such large-scale maps based on lithospheric magnetic field measurements faces the challenge of the masking effect of the core field. In this study, the maps were obtained through analyses in the spectral domain by means of a new regional spatial power spectrum based on the Revised Spherical Cap Harmonic Analysis (R-SCHA) formalism. A series of regional spectral analyses wer...

Lithospheric Structure of the Yamato Basin Inferred from Trans-dimensional Inversion of Receiver Functions

Science.gov (United States)

Akuhara, T.; Nakahigashi, K.; Shinohara, M.; Yamada, T.; Yamashita, Y.; Shiobara, H.; Mochizuki, K.

2017-12-01

The Yamato Basin, located at the southeast of the Japan Sea, has been formed by the back-arc opening of the Japan Sea. Wide-angle reflection surveys have revealed that the basin has anomalously thickened crust compared with a normal oceanic crust [e.g., Nakahigashi et al., 2013] while deeper lithospheric structure has not known so far. Revealing the lithospheric structure of the Yamato Basin will lead to better understanding of the formation process of the Japan Sea and thus the Japanese island. In this study, as a first step toward understanding the lithospheric structure, we aim to detect the lithosphere-asthenosphere boundary (LAB) using receiver functions (RFs). We use teleseismic P waveforms recorded by broad-band ocean-bottom seismometers (BBOBS) deployed at the Yamato Basin. We calculated radial-component RFs using the data with the removal of water reverberations from the vertical-component records [Akuhara et al., 2016]. The resultant RFs are more complicated than those calculated at an on-land station, most likely due to sediment-related reverberations. This complexity does not allow either direct detection of a Ps conversion from the LAB or forward modeling by a simple structure composed of a handful number of layers. To overcome this difficulty, we conducted trans-dimensional Markov Chain Monte Carlo inversion of RFs, where we do not need to assume the number of layers in advance [e.g., Bodin et al., 2012; Sambridge et al., 2014]. Our preliminary results show abrupt velocity reduction at 70 km depth, far greater depth than the expected LAB depth from the age of the lithosphere ( 20 Ma, although still debated). If this low-velocity jump truly reflects the LAB, the anomalously thickened lithosphere will provide a new constraint on the complex formation history of the Japan Sea. Further study, however, is required to deny the possibility that the obtained velocity jump is an artificial brought by the overfitting of noisy data.

Genetic diversity of neotropical Myotis (chiroptera: vespertilionidae with an emphasis on South American species.

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Roxanne J Larsen

Full Text Available BACKGROUND: Cryptic morphological variation in the Chiropteran genus Myotis limits the understanding of species boundaries and species richness within the genus. Several authors have suggested that it is likely there are unrecognized species-level lineages of Myotis in the Neotropics. This study provides an assessment of the diversity in New World Myotis by analyzing cytochrome-b gene variation from an expansive sample ranging throughout North, Central, and South America. We provide baseline genetic data for researchers investigating phylogeographic and phylogenetic patterns of Myotis in these regions, with an emphasis on South America. METHODOLOGY AND PRINCIPAL FINDINGS: Cytochrome-b sequences were generated and phylogenetically analyzed from 215 specimens, providing DNA sequence data for the most species of New World Myotis to date. Based on genetic data in our sample, and on comparisons with available DNA sequence data from GenBank, we estimate the number of species-level genetic lineages in South America alone to be at least 18, rather than the 15 species currently recognized. CONCLUSIONS: Our findings provide evidence that the perception of lower species richness in South American Myotis is largely due to a combination of cryptic morphological variation and insufficient sampling coverage in genetic-based systematic studies. A more accurate assessment of the level of diversity and species richness in New World Myotis is not only helpful for delimiting species boundaries, but also for understanding evolutionary processes within this globally distributed bat genus.

The Eocene South American metatherian Zeusdelphys complicatus is not a protodidelphidid but a hatcheriform: Paleobiogeographic implications

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Leonardo M. Carneiro

2017-09-01

Full Text Available Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of “condylarths”; a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to “Alphadontidae”. The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes.

Invasion of South American suckermouth armoured catfishes Pterygoplichthys spp. (Loricariidae) in Kerala, India - a case study

OpenAIRE

A. Bijukumar; R. Smrithy; U. Sureshkumar; S. George

2015-01-01

This paper documents the occurrence of the exotic South American suckermouth armoured catfishes (Loricariidae) of the genus Pterygoplichthys spp. in the drainages of Thiruvananthapuram City, Kerala.  The morphological taxonomy revealed that the specimens are closely related to Pterygoplichthys disjunctivus (Weber, 1991) and P. pardalis (Castelnau, 1855), in addition to intermediary forms of unknown identity.  DNA barcoding using the mitochondrial DNA cytochrome c oxidase 1 (CO1) also failed t...

76 FR 18419 - Movement of Hass Avocados From Areas Where Mediterranean Fruit Fly or South American Fruit Fly Exist

Science.gov (United States)

2011-04-04

... where the infested avocados were grown will immediately be suspended from the export program until an... Avocados From Areas Where Mediterranean Fruit Fly or South American Fruit Fly Exist AGENCY: Animal and... certain restrictions regarding the movement of fresh Hass variety avocados. Specifically, we are proposing...

75 FR 41237 - Public Land Order No. 7746; Withdrawal of Public Lands, South Fork of the American River; California

Science.gov (United States)

2010-07-15

... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLCAC08000-L1430000-ET0000; CACA 41334] Public Land Order No. 7746; Withdrawal of Public Lands, South Fork of the American River; California AGENCY: Bureau of Land Management, Interior. ACTION: Public Land Order. SUMMARY: This order withdraws 2...

Current meter and bathythermograph data from moored current meter and xbt casts in the North American Coastline-South as part of the Outer Continental Shelf - South Atlantic (OCS-South Atlantic) project from 1982-02-16 to 1985-07-01 (NODC Accession 8600124)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Current direction and bathythermograph (xbt) data were collected using moored current meter casts and other instruments in the North American Coastline-South from...

Origin of Starting Earthquakes under Complete Coupling of the Lithosphere Plates and a Base

Science.gov (United States)

Babeshko, V. A.; Evdokimova, O. V.; Babeshko, O. M.; Zaretskaya, M. V.; Gorshkova, E. M.; Mukhin, A. S.; Gladskoi, I. B.

2018-02-01

The boundary problem of rigid coupling of lithospheric plates modeled by Kirchhoff plates with a base represented by a three-dimensional deformable layered medium is considered. The possibility of occurrence of a starting earthquake in such a block structure is investigated. For this purpose, two states of this medium in the static mode are considered. In the first case, the semi-infinite lithospheric plates in the form of half-planes are at a distance so that the distance between the end faces is different from zero. In the second case, the lithospheric plates come together to zero spacing between them. Calculations have shown that in this case more complex movements of the Earth's surface are possible. Among such movements are the cases described in our previous publications [1, 2].

Depositional history of sedimentary linear alkylbenzenes (LABs) in a large South American industrial coastal area (Santos Estuary, Southeastern Brazil)

International Nuclear Information System (INIS)

Martins, Cesar C.; Bicego, Marcia C.; Mahiques, Michel M.; Figueira, Rubens C.L.; Tessler, Moyses G.; Montone, Rosalinda C.

2010-01-01

This paper reports the reconstruction of the contamination history of a large South American industrial coastal area (Santos Estuary, Brazil) using linear alkylbenzenes (LABs). Three sediment cores were dated by 137 Cs. Concentrations in surficial layers were comparable to the midrange concentrations reported for coastal sediments worldwide. LAB concentrations increased towards the surface, indicating increased waste discharges into the estuary in recent decades. The highest concentration values occurred in the early 1970s, a time of intense industrial activity and marked population growth. The decreased LAB concentration, in the late 1970s was assumed to be the result of the world oil crisis. Treatment of industrial effluents, which began in 1984, was represented by decreased LAB levels. Microbial degradation of LABs may be more intense in the industrial area sediments. The results show that industrial and domestic waste discharges are a historical problem in the area. - The contamination history of a large South American industrial coastal area indicated by molecular indicator of sewage input.

Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

Science.gov (United States)

Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

2012-01-01

A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

Crustal seismicity and the earthquake catalog maximum moment magnitude (Mcmax) in stable continental regions (SCRs): Correlation with the seismic velocity of the lithosphere

Science.gov (United States)

Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

2012-12-01

A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens.

Directory of Open Access Journals (Sweden)

Larissa Rosa de Oliveira

Full Text Available The South American sea lion (Otaria flavescens is widely distributed along the southern Atlantic and Pacific coasts of South America with a history of significant commercial exploitation. We aimed to evaluate the population genetic structure and the evolutionary history of South American sea lion along its distribution by analyses of mitochondrial DNA (mtDNA and 10 nuclear microsatellites loci. We analyzed 147 sequences of mtDNA control region and genotyped 111 individuals of South American sea lion for 10 microsatellite loci, representing six populations (Peru, Northern Chile, Southern Chile, Uruguay (Brazil, Argentina and Falkland (Malvinas Islands and covering the entire distribution of the species. The mtDNA phylogeny shows that haplotypes from the two oceans comprise two very divergent clades as observed in previous studies, suggesting a long period (>1 million years of low inter-oceanic female gene flow. Bayesian analysis of bi-parental genetic diversity supports significant (but less pronounced than mitochondrial genetic structure between Pacific and Atlantic populations, although also suggested some inter-oceanic gene flow mediated by males. Higher male migration rates were found in the intra-oceanic population comparisons, supporting very high female philopatry in the species. Demographic analyses showed that populations from both oceans went through a large population expansion ~10,000 years ago, suggesting a very similar influence of historical environmental factors, such as the last glacial cycle, on both regions. Our results support the proposition that the Pacific and Atlantic populations of the South American sea lion should be considered distinct evolutionarily significant units, with at least two managements units in each ocean.

Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens)

Science.gov (United States)

Gehara, Marcelo C. M.; Fraga, Lúcia D.; Lopes, Fernando; Túnez, Juan Ignacio; Cassini, Marcelo H.; Majluf, Patricia; Cárdenas-Alayza, Susana; Pavés, Héctor J.; Crespo, Enrique Alberto; García, Nestor; Loizaga de Castro, Rocío; Hoelzel, A. Rus; Sepúlveda, Maritza; Olavarría, Carlos; Valiati, Victor Hugo; Quiñones, Renato; Pérez-Alvarez, Maria Jose; Ott, Paulo Henrique

2017-01-01

The South American sea lion (Otaria flavescens) is widely distributed along the southern Atlantic and Pacific coasts of South America with a history of significant commercial exploitation. We aimed to evaluate the population genetic structure and the evolutionary history of South American sea lion along its distribution by analyses of mitochondrial DNA (mtDNA) and 10 nuclear microsatellites loci. We analyzed 147 sequences of mtDNA control region and genotyped 111 individuals of South American sea lion for 10 microsatellite loci, representing six populations (Peru, Northern Chile, Southern Chile, Uruguay (Brazil), Argentina and Falkland (Malvinas) Islands) and covering the entire distribution of the species. The mtDNA phylogeny shows that haplotypes from the two oceans comprise two very divergent clades as observed in previous studies, suggesting a long period (>1 million years) of low inter-oceanic female gene flow. Bayesian analysis of bi-parental genetic diversity supports significant (but less pronounced than mitochondrial) genetic structure between Pacific and Atlantic populations, although also suggested some inter-oceanic gene flow mediated by males. Higher male migration rates were found in the intra-oceanic population comparisons, supporting very high female philopatry in the species. Demographic analyses showed that populations from both oceans went through a large population expansion ~10,000 years ago, suggesting a very similar influence of historical environmental factors, such as the last glacial cycle, on both regions. Our results support the proposition that the Pacific and Atlantic populations of the South American sea lion should be considered distinct evolutionarily significant units, with at least two managements units in each ocean. PMID:28654647

Knowledge and screening of head and neck cancer among American Indians in South Dakota.

Science.gov (United States)

Dwojak, Sunshine; Deschler, Daniel; Sargent, Michele; Emerick, Kevin; Guadagnolo, B Ashleigh; Petereit, Daniel

2015-06-01

We established the level of awareness of risk factors and early symptoms of head and neck cancer among American Indians in South Dakota and determined whether head and neck cancer screening detected clinical findings in this population. We used the European About Face survey. We added questions about human papillomavirus, a risk factor for head and neck cancer, and demographics. Surveys were administered at 2 public events in 2011. Participants could partake in a head and neck cancer screening at the time of survey administration. Of the 205 American Indians who completed the survey, 114 participated in the screening. Mean head and neck cancer knowledge scores were 26 out of 44. Level of education was the only factor that predicted higher head and neck cancer knowledge (b = 0.90; P = .01). Nine (8%) people had positive head and neck cancer screening examination results. All abnormal clinical findings were in current or past smokers (P = .06). There are gaps in American Indian knowledge of head and neck cancer risk factors and symptoms. Community-based head and neck cancer screening in this population is feasible and may be a way to identify early abnormal clinical findings in smokers.

[South American camelids in Switzerland. II. Reference values for blood parameters].

Science.gov (United States)

Hengrave Burri, I; Tschudi, P; Martig, J; Liesegang, A; Meylan, M

2005-08-01

In order to establish reference values for blood parameters of South American camelids in Switzerland, 273 blood samples were collected from 141 llamas and 132 alpacas. These animals were classified in three categories (young animals blood cell count, white blood cell count, electrolytes, metabolites and enzymes). Significant differences between llamas and alpacas were evident for 26 parameters. This study also showed that differences between young animals, females and males must be taken into consideration. A comparison of blood values with the results of fecal analysis for parasite eggs showed that an infestation with Dicrocoelium dendriticum was associated with elevated activity of two liver enzymes (GLDH and gamma-GT) in the serum. In contrast, no differences were found in the results of blood analyses between animals shedding eggs of gastrointestinal strongyles or not.

Observatory geoelectric fields induced in a two-layer lithosphere during magnetic storms

Science.gov (United States)

Love, Jeffrey J.; Swidinsky, Andrei

2015-01-01

We report on the development and validation of an algorithm for estimating geoelectric fields induced in the lithosphere beneath an observatory during a magnetic storm. To accommodate induction in three-dimensional lithospheric electrical conductivity, we analyze a simple nine-parameter model: two horizontal layers, each with uniform electrical conductivity properties given by independent distortion tensors. With Laplace transformation of the induction equations into the complex frequency domain, we obtain a transfer function describing induction of observatory geoelectric fields having frequency-dependent polarization. Upon inverse transformation back to the time domain, the convolution of the corresponding impulse-response function with a geomagnetic time series yields an estimated geoelectric time series. We obtain an optimized set of conductivity parameters using 1-s resolution geomagnetic and geoelectric field data collected at the Kakioka, Japan, observatory for five different intense magnetic storms, including the October 2003 Halloween storm; our estimated geoelectric field accounts for 93% of that measured during the Halloween storm. This work demonstrates the need for detailed modeling of the Earth’s lithospheric conductivity structure and the utility of co-located geomagnetic and geoelectric monitoring.

3D Numerical Examination of Continental Mantle Lithosphere Response to Lower Crust Eclogitization and Nearby Slab Subduction

Science.gov (United States)

Janbakhsh, P.; Pysklywec, R.

2017-12-01

2D numerical modeling techniques have made great contribution to understanding geodynamic processes involved in crustal and lithospheric scale deformations for the past 20 years. The aim of this presentation is to expand the scope covered by previous researchers to 3 dimensions to address out-of-plane intrusion and extrusion of mantle material in and out of model space, and toroidal mantle wedge flows. In addition, 3D velocity boundary conditions can create more realistic models to replicate real case scenarios. 3D numerical experiments that will be presented are designed to investigate the density and viscosity effects of lower crustal eclogitization on the decoupling process of continental mantle lithosphere from the crust and its delamination. In addition, these models examine near-field effects of a subducting ocean lithosphere and a lithospheric scale fault zone on the evolution of the processes. The model solutions and predictions will also be compared against the Anatolian geology where subduction of Aegean and Arabian slabs, and the northern boundary with the North Anatolian Fault Zone are considered as two main contributing factors to anomalous crustal uplift, missing mantle lithosphere, and anomalous surface heat flux.

Hematozoa of forest birds in American Samoa - Evidence for a diverse, indigenous parasite fauna from the South Pacific

Science.gov (United States)

Atkinson, C.T.; Utzurrum, R.C.; Seamon, J.O.; Savage, Amy F.; Lapointe, D.A.

2006-01-01

Introduced avian diseases pose a significant threat to forest birds on isolated island archipelagos, especially where most passerines are endemic and many groups of blood-sucking arthropods are either absent or only recently introduced. We conducted a blood parasite survey of forest birds from the main islands of American Samoa to obtain baseline information about the identity, distribution and prevalence of hematozoan parasites in this island group. We examined Giemsa-stained blood smears from 857 individual birds representing 20 species on Tutuila, Ofu, Olosega, and Ta'u islands. Four hematozoan parasites were identified - Plasmodium circumflexum (1%, 12/857), Trypanosoma avium (4%, 32/857), microfilaria (9%, 76/857), and an Atoxoplasma sp. (parasite infections. Given the central location of American Samoa in the South Pacific, it is likely that avian malaria and other hematozoan parasites are indigenous and widespread at least as far as the central South Pacific. Their natural occurrence may provide some immunological protection to indigenous birds in the event that other closely related parasites are accidentally introduced to the region.

Deformation of the Pannonian lithosphere and related tectonic topography: a depth-to-surface analysis

OpenAIRE

Dombrádi, E.

2012-01-01

Fingerprints of deep-seated, lithospheric deformation are often recognised on the surface, contributing to topographic evolution, drainage organisation and mass transport. Interactions between deep and surface processes were investigated in the Carpathian-Pannonian region. The lithosphere beneath the Pannonian basin has formerly been extended, significantly stretched and heated up and thus became extremely weak from a rheological point of view. From Pliocene times onward the ‘crème brulee’ ty...

3-D lithospheric structure and regional/residual Bouguer anomalies in the Arabia-Eurasia collision (Iran)

Science.gov (United States)

Jiménez-Munt, I.; Fernãndez, M.; Saura, E.; Vergés, J.; Garcia-Castellanos, D.

2012-09-01

The aim of this work is to propose a first-order estimate of the crustal and lithospheric mantle geometry of the Arabia-Eurasia collision zone and to separate the measured Bouguer anomaly into its regional and local components. The crustal and lithospheric mantle structure is calculated from the geoid height and elevation data combined with thermal analysis. Our results show that Moho depth varies from ˜42 km at the Mesopotamian-Persian Gulf foreland basin to ˜60 km below the High Zagros. The lithosphere is thicker beneath the foreland basin (˜200 km) and thinner underneath the High Zagros and Central Iran (˜140 km). Most of this lithospheric mantle thinning is accommodated under the Zagros mountain belt coinciding with the suture between two different mantle domains on the Sanandaj-Sirjan Zone. The regional gravity field is obtained by calculating the gravimetric response of the 3-D crustal and lithospheric mantle structure obtained by combining elevation and geoid data. The calculated regional Bouguer anomaly differs noticeably from those obtained by filtering or just isostatic methods. The residual gravity anomaly, obtained by subtraction of the regional components to the measured field, is analyzed in terms of the dominating upper crustal structures. Deep basins and areas with salt deposits are characterized by negative values (˜-20 mGal), whereas the positive values are related to igneous and ophiolite complexes and shallow basement depths (˜20 mGal).

Uncinaria hamiltoni (Nematoda: Ancylostomatidae) in South American Sea Lions, Otaria flavescens, From Northern Patagonia, Argentina

OpenAIRE

Berón-Vera, B.; Crespo, Enrique Alberto; Raga Esteve, Juan Antonio; Pedraza, S. N.

2004-01-01

Thirty-one South American sea lion pups (Otaria flavescens) found dead in Punta León, Argentina, during the summer of 2002, were examined for hookworms (Uncinaria hamiltoni). Parasite parameters were analyzed in 2 locations of the rookery, i.e., a traditional, well-structured breeding area and an expanding area with juveniles and a lax social structure. Prevalence of hookworms was 50% in both localities, and no difference was observed in prevalence between pup sexes (P > 0.05). Hookworms were...

Whole-genome characterization of Uruguayan strains of avian infectious bronchitis virus reveals extensive recombination between the two major South American lineages.

Science.gov (United States)

Marandino, Ana; Tomás, Gonzalo; Panzera, Yanina; Greif, Gonzalo; Parodi-Talice, Adriana; Hernández, Martín; Techera, Claudia; Hernández, Diego; Pérez, Ruben

2017-10-01

Infectious bronchitis virus (Gammacoronavirus, Coronaviridae) is a genetically variable RNA virus that causes one of the most persistent respiratory diseases in poultry. The virus is classified in genotypes and lineages with different epidemiological relevance. Two lineages of the GI genotype (11 and 16) have been widely circulating for decades in South America. GI-11 is an exclusive South American lineage while the GI-16 lineage is distributed in Asia, Europe and South America. Here, we obtained the whole genome of two Uruguayan strains of the GI-11 and GI-16 lineages using Illumina high-throughput sequencing. The strains here sequenced are the first obtained in South America for the infectious bronchitis virus and provide new insights into the origin, spreading and evolution of viral variants. The complete genome of the GI-11 and GI-16 strains have 27,621 and 27,638 nucleotides, respectively, and possess the same genomic organization. Phylogenetic incongruence analysis reveals that both strains have a mosaic genome that arose by recombination between Euro Asiatic strains of the GI-16 lineage and ancestral South American GI-11 viruses. The recombination occurred in South America and produced two viral variants that have retained the full-length S1 sequences of the parental lineages but are extremely similar in the rest of their genomes. These recombinant virus have been extraordinary successful, persisting in the continent for several years with a notorious wide geographic distribution. Our findings reveal a singular viral dynamics and emphasize the importance of complete genomic characterization to understand the emergence and evolutionary history of viral variants. Copyright © 2017 Elsevier B.V. All rights reserved.

Antarctica: Arena for South American Cooperation or Conflict.

Science.gov (United States)

Child, Jack

A number of converging circumstances suggest that Antarctica may be a major object of geopolitical attention in South America in the decade to come. The Malvinas/Falklands crisis focused geopolitical attention on the South Atlantic and the chain of Southern (Austral) Islands which link the southern tip of South America to the Antarctic Peninsula.…

Thermochronology of the Sulu ultrahigh-pressure metamorphic terrane: Implications for continental collision and lithospheric thinning

Science.gov (United States)

Liu, Li-Ping; Li, Zheng-Xiang; Danišík, Martin; Li, Sanzhong; Evans, Noreen; Jourdan, Fred; Tao, Ni

2017-08-01

The thermal history of the Dabie-Sulu orogenic belt provides important constraints on the collision process between the South China and North China blocks during the Mesozoic, and possible lithospheric thinning event(s) in the eastern North China Block. This study reports on the thermal evolution of the Sulu ultrahigh-pressure metamorphic (UHP) terrane using zircon U-Pb geochronology and multiple thermochronology methods such as mica and hornblende 40Ar/39Ar, zircon and apatite fission track, and zircon and apatite (U-Th)/He dating. 40Ar/39Ar and zircon (U-Th)/He data show that the UHP terrane experienced accelerated cooling during 180-160 Ma. This cooling event could be interpreted to have resulted from extensional unroofing of an earlier southward thrusting nappe, or, more likely, an episode of northward thrusting of the UHP rocks as a hanging wall. A subsequent episode of exhumation took place between ca. 125 Ma and 90 Ma as recorded by zircon (U-Th)/He data. This event was more pronounced in the northwest section of the UHP terrane, whereas in the southeast section, the zircon (U-Th)/He system retained Jurassic cooling ages of ca. 180-160 Ma. The mid-Cretaceous episode of exhumation is interpreted to have resulted from crustal extension due to the removal of thickened, enriched mantle. A younger episode of exhumation was recorded by apatite fission track and apatite (U-Th)/He ages at ca. 65-40 Ma. Both latter events were linked to episodic thinning of lithosphere along the Sulu UHP terrane in an extensional environment, likely caused by the roll-back of the Western Pacific subduction system.

Tectonically asymmetric Earth: From net rotation to polarized westward drift of the lithosphere

Directory of Open Access Journals (Sweden)

Carlo Doglioni

2015-05-01

Full Text Available The possibility of a net rotation of the lithosphere with respect to the mantle is generally overlooked since it depends on the adopted mantle reference frames, which are arbitrary. We review the geological and geophysical signatures of plate boundaries, and show that they are markedly asymmetric worldwide. Then we compare available reference frames of plate motions relative to the mantle and discuss which is at best able to fit global tectonic data. Different assumptions about the depths of hotspot sources (below or within the asthenosphere, which decouples the lithosphere from the deep mantle predict different rates of net rotation of the lithosphere relative to the mantle. The widely used no-net-rotation (NNR reference frame, and low (1°/Ma net rotation (shallow hotspots source, all plates, albeit at different velocity, move westerly along a curved trajectory, with a tectonic equator tilted about 30° relative to the geographic equator. This is consistent with the observed global tectonic asymmetries.

The Dual Role a Buddhist Monk Played in the American South: The Balance between Heritage and Citizenship in the Refugee Community

OpenAIRE

Daniel Rhodes

2016-01-01

Buddhist Monks in Vietnam struggle with cultural preservation differently from a monk in the U.S. where the forces of acculturation for new arrivals, often refugees, are extraordinarily overwhelming. The author provides a case study examining how Buddhist leaders engage in cultural preservation and community building in the American South. Fusing ideas of Engaged Buddhism and community building, the author will demonstrate how a Buddhist monk is able to navigate the broader American culture a...

The role of SST on the South American atmospheric circulation during January, February and March 2001

Science.gov (United States)

Drumond, Anita Rodrigues De Moraes; Ambrizzi, Tércio

2005-06-01

Precipitation deficits were observed over southeastern, northeastern and Central Brazil during the 2001 Austral Summer. They contributed to the worsening of the energy crisis that was occurring in the country. A low-level anomalous anticyclonic circulation observed over eastern Brazil enhanced the deviation of moisture transport that usually occurs from the Amazon Basin to southeastern Brazil and inhibited the occurrence of South Atlantic Convergence Zone events in that period. However, an anomalous low-level northerly moisture flux was observed over the La Plata Basin, and positive precipitation anomalies occurred over Bolivia, Paraguay, northeastern Argentina and southern Brazil. Using the ensemble technique, a numerical study was carried out to investigate the role of different sea surface temperature (SST) forcings observed over this anomalous South American atmospheric circulation. Reynolds SST monthly means were used as boundary conditions to study the influence of South Atlantic, South Indian, South Pacific and Equatorial Pacific oceans. The simulations were run from September 2000 to April 2001 using the Community Climate Model version 3.6 General Circulation Model. Ten integrations using different initial conditions were done to each experiment. Numerical experiments suggested that the combined influence of South Pacific and Equatorial Pacific oceans could be responsible for the drought observed over Central Brazil. These experiments simulated the low-level anticyclonic anomaly observed over eastern Brazil. However, both experiments have poorly reproduced the intensity of the anomalous low-level northerly moisture flux observed over the La Plata Basin. Therefore, the intensity of the simulated precipitation anomalies over the subtropical regions was much weaker than observed.

Earthquake Source Depths in the Zagros Mountains: A "Jelly Sandwich" or "Creme Brulee" Lithosphere?

Science.gov (United States)

Adams, A. N.; Nyblade, A.; Brazier, R.; Rodgers, A.; Al-Amri, A.

2006-12-01

The Zagros Mountain Belt of southwestern Iran is one of the most seismically active mountain belts in the world. Previous studies of the depth distribution of earthquakes in this region have shown conflicting results. Early seismic studies of teleseismically recorded events found that earthquakes in the Zagros Mountains nucleated within both the upper crust and upper mantle, indicating that the lithosphere underlying the Zagros Mountains has a strong upper crust and a strong lithospheric mantle, separated by a weak lower crust. Such a model of lithospheric structure is called the "Jelly Sandwich" model. More recent teleseismic studies, however, found that earthquakes in the Zagros Mountains occur only within the upper crust, thus indicating that the strength of the Zagros Mountains' lithosphere is primarily isolated to the upper crust. This model of lithospheric structure is called the "crème brûlée" model. Analysis of regionally recorded earthquakes nucleating within the Zagros Mountains is presented here. Data primarily come from the Saudi Arabian National Digital Seismic Network, although data sources include many regional open and closed networks. The use of regionally recorded earthquakes facilitates the analysis of a larger dataset than has been used in previous teleseismic studies. Regional waveforms have been inverted for source parameters using a range of potential source depths to determine the best fitting source parameters and depths. Results indicate that earthquakes nucleate in two distinct zones. One seismogenic zone lies at shallow, upper crustal depths. The second seismogenic zone lies near the Moho. Due to uncertainty in the source and Moho depths, further study is needed to determine whether these deeper events are nucleating within the lower crust or the upper mantle.

Elysium region, mars: Tests of lithospheric loading models for the formation of tectonic features

International Nuclear Information System (INIS)

Hall, J.L.; Solomon, S.C.; Head, J.W.

1986-01-01

The second largest volcanic province on Mars lies in the Elysium region. Like the larger Tharsis province, Elysium is marked by a topographic rise and a broad free air gravity anomaly and also exhibits a complex assortment of tectonic and volcanic features. We test the hypothesis that the tectonic features in the Elysium region are the product of stresses produced by loading of the Martian lithosphere. We consider loading at three different scales: local loading by individual volcanoes, regional loading of the lithosphere from above or below, and quasi-global loading by Tharsis. A comparison of flexural stresses with lithospheric strength and with the inferred maximum depth of faulting confirms that concentric graben around Elysium Mons can be explained as resulting from local flexure of an elastic lithosphere about 50 km thick in response to the volcano load. Volcanic loading on a regional scale, however, leads to predicted stresses inconsistent with all observed tectonic features, suggesting that loading by widespread emplacement of thick plains deposits was not an important factor in the tectonic evolution of the Elysium region. A number of linear extensional features oriented generally NW-SE may have been the result of flexural uplift of the lithosphere on the scale of the Elysium rise. The global stress field associated with the support of the Tharsis rise appears to have influenced the development of many of the tectonic features in the Elysium region, including Cerberus Rupes and the systems of ridges in eastern and western Elysium. The comparisons of stress models for Elysium with the preserved tectonic features support a succession of stress fields operating at different times in the region

Part 1: aspects of lithospheric evolution on Venus. Part 2: thermal and collisional histories of chondrite parent bodies. Ph.D. Thesis

International Nuclear Information System (INIS)

Grimm, R.E.

1988-10-01

The geological evolution of distinctly different kinds of solar system objects is addressed. Venus has been observed over the past decade by orbital radars on both American and Soviet spacecraft. These surface measurements provide clues to the structure and evolution of the lithosphere. The parent bodies of chondritic meteorites, thought to resemble asteroids, represent the other end of the size spectrum of terrestrial objects. Their early thermal and collisional histories may be constrained by the chemical and textural record preserved in meteorite samples. Impact craters on Venus have been observed by the Soviet Venera 15/16 spacecraft. A formalism is presented by which the size-frequency distribution of impact craters may be used to estimate upper bounds on the mean global rates of volcanic resurfacing and lithospheric recycling on that planet over the past several hundred million years. The impact crater density reported from Venera observations, indicates a mean volcanic flux no greater than 2 cu km/y. For the lowest estimated mean crater retention age of the surface of Venus imaged by Venera 15/16, the rate of lithospheric recycling on Venus does not exceed 1.5 sq km/y. Ordinary chondrite meteorites show textural and chemical patterns indicative of varying intensities of thermal metamorphism. The conventional onion-shell model, envisions highly metamorphosed material in the core and less intensely heated rocks near the surface, but none has been observed. A metamorphosed-planetesimal model is devised to explain this discrepancy. Thermal and collisional constraints are examined, and the model is found to be applicable only to highly insulating Al-26-rich planetesimals. An alternative model is presented

Precipitation changes in the South American Altiplano since 1300 AD reconstructed by tree-rings

Directory of Open Access Journals (Sweden)

M. S. Morales

2012-03-01

Full Text Available Throughout the second half of the 20th century, the Central Andes has experienced significant climatic and environmental changes characterized by a persistent warming trend, an increase in elevation of the 0 °C isotherm, and sustained glacier shrinkage. These changes have occurred in conjunction with a steadily growing demand for water resources. Given the short span of instrumental hydroclimatic records in this region, longer time span records are needed to understand the nature of climate variability and to improve the predictability of precipitation, a key factor modulating the socio-economic development in the South American Altiplano and adjacent arid lowlands. In this study we present the first quasi-millennial, tree-ring based precipitation reconstruction for the South American Altiplano. This annual (November–October precipitation reconstruction is based on the Polylepis tarapacana tree-ring width series and represents the closest dendroclimatological record to the Equator in South America. This high-resolution reconstruction covers the past 707 yr and provides a unique record characterizing the occurrence of extreme events and consistent oscillations in precipitation. It also allows an assessment of the spatial and temporal stabilities of the teleconnections between rainfall in the Altiplano and hemispheric forcings such as El Niño-Southern Oscillation. Since the 1930s to present, a persistent negative trend in precipitation has been recorded in the reconstruction, with the three driest years since 1300 AD occurring in the last 70 yr. Throughout the 707 yr, the reconstruction contains a clear ENSO-like pattern at interannual to multidecadal time scales, which determines inter-hemispheric linkages between our reconstruction and other precipitation sensitive records modulated by ENSO in North America. Our reconstruction points out that century-scale dry periods are a recurrent feature in the Altiplano climate, and that the

[Pathology of South American Camelids: a retrospective study of necropsies at the Institute of Veterinary Pathology, University of Leipzig, Germany].

Science.gov (United States)

Theuß, T; Goerigk, D; Rasenberger, S; Starke, A; Schoon, H-A

2014-01-01

The number of South American Camelids (New World Camelids) housed in Germany has increased in the recent years. While these species were formerly kept solely in zoological gardens, ever more private and commercial livestock is being established. Compared to indigenous livestock animals, they bear some distinctive differences, particularly in terms of digestive tract anatomy and physiology. Therefore, it is of considerable interest for veterinarians working with South American Camelids to obtain knowledge about the distinguishing features of these animals and the typical diseases affecting them in Germany. For this purpose, the necropsy reports, including the anamnestic data, and their diagnostic usefulness, from 1995 to 2012 were studied retrospectively. Du- ring this period, a total of 233 New World Camelids were examined (195 alpacas and 38 llamas). Anamnestic data of diagnostic usefulness regarding the cause of disease were only submitted in a limited number of cases, because most of the animals died without specific symptoms. The following were the most frequent pathological findings: enteritis (n = 91), gastritis (n = 76), cachexia (n = 73), pneumonia (n = 30), stomatitis (n = 27), azotaemia (n = 22) and anaemia (n = 9). An endoparasitosis occurred in 107 cases and was considered the predominant cause of enteritis. As with indigenous ruminants, llamas and alpacas primarily suffered from diseases of the digestive and respiratory tracts. Other organ systems were affected to a lesser extent. Even in cases with severe alterations in the affected organs, South American Camelids do not show or show too late diagnostically indicative clinical symptoms. Therefore, a detailed clinical examination of these animals is important.

Evidence for multiphase folding of the central Indian Ocean lithosphere

Digital Repository Service at National Institute of Oceanography (India)

Krishna, K.S.; Bull, J.M.; Scrutton, R.A.

Long-wavelength (100-300 km) folding in the central Indian Ocean associated with the diffuse plate boundary separating the Indian, Australian, and Capricorn plates is Earth's most convincing example of organized large-scale lithospheric deformation...

European Lithospheric Mantle; geochemical, petrological and geophysical processes

Science.gov (United States)

Ntaflos, Th.; Puziewicz, J.; Downes, H.; Matusiak-Małek, M.

2017-04-01

The second European Mantle Workshop occurred at the end of August 2015, in Wroclaw, Poland, attended by leading scientists in the study the lithospheric mantle from around the world. It built upon the results of the first European Mantle Workshop (held in 2007, in Ferrara, Italy) published in the Geological Society of London Special Publication 293 (Coltorti & Gregoire, 2008).

High-temperature peridotites - lithospheric or asthenospheric?

International Nuclear Information System (INIS)

Hops, J.J.; Gurney, J.J.

1990-01-01

High-temperature peridotites by definition yield equilibration temperatures greater than 1100 degrees C. On the basis of temperature and pressure calculations, these high-temperature peridotites are amongst the deepest samples entrained by kimberlites on route to the surface. Conflicting models proposing either a lithospheric or asthenospheric origin for the high-temperature peridotites have been suggested. A detailed study of these xenoliths from a single locality, the Jagersfontein kimberlite in the Orange Free State, has been completed as a means of resolving this controversy. 10 refs., 2 figs

Lithospheric-scale analogue modelling of collision zones with a pre-existing weak zone, in "Deformation Mechanisms, Rheology and Tectonics: from Minerals to the Lithosphere"

NARCIS (Netherlands)

Willingshofer, E.; Sokoutis, D.; Burg, J.P.

2005-01-01

Lithospheric-scale analogue experiments have been conducted to investigate the influence of strength heterogeneities on the distribution and mode of crustal-scale deformation, on the resulting geometry of the deformed area, and on its topographic expression. Strength heterogeneities were

Near-vertical seismic reflection image using a novel acquisition technique across the Vrancea Zone and Foscani Basin, south-eastern Carpathians (Romania).

NARCIS (Netherlands)

Panea, I; Stephenson, R.A.; Knapp, C.; Mocanu, V.I.; Drijkoningen, G.; Matenco, L.C.; Knapp, J.; Prodehl, K.

2005-01-01

The DACIA PLAN (Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics) deep seismic sounding survey was performed in August-September 2001 in south-eastern Romania, at the same time as the regional deep refraction seismic survey VRANCEA 2001. The main goal of the

Petrogenesis of Cretaceous shoshonitic rocks in the northern Wuyi Mountains, South China: A result of the roll-back of a flat-slab?

Science.gov (United States)

Li, Wu-Xian; Li, Xian-Hua; Wang, Xuan-Ce; Yang, Dong-Sheng

2017-09-01

Potassic magmatism is commonly linked to post-/late-orogenic environments, such as foundering or convection thinning of continental lithosphere. Their petrogenesis is crucial for constraining the chemical and physical properties of the remnant sub-continental lithospheric mantle. Here we report new SHRIMP zircon U-Pb ages, whole rock geochemical results and Sr-Nd and zircon Hf isotope data from four potassic plutons (the Da'an, Yingcheng, Zixi and Honggong plutons) in the northern Wuyi Mountains, South China. SHRIMP U-Pb zircon analyses indicate that these potassic rocks formed at 139-126 Ma. They are characterized by high SiO2 (56-73%) and K2O (3.8-6.7%), with a K2O/Na2O ratio of 2.18-2.04, plotting within the field of high-SiO2 shoshonites. Their ISr and εNd(t) values vary from 0.7077 to 0.7162 and - 5.66 to - 10.52, respectively. The initial zircon εHf(t) values range from 2.3 to - 13.1, corresponding to TDM modal ages between 707 and 1330 Ma. These geochemical and isotope characteristics indicate that these shoshonites derived from a subduction-modified ancient subcontinental lithospheric mantle, and then underwent significantly fractional crystallization of K-feldspar, plagioclase, and accessory minerals, such as apatite and Fe-Ti oxides during magma ascent. We interpret that asthenospheric mantle upwelling (caused by eastward roll-back of a flat-slab?) triggered partial melting of the metasomatized lithospheric mantle to result in the Early Cretaceous shoshonitic magmatism in the northern Wuyi Mountains. An integration of our new results with compiled data from the interior of the South China Block reveals that the arc-like geochemical signature is confined to the Wuyi Mountains region, but becomes little or even invisible toward inland in South China. This implies that the far-field effects of the early Mesozoic subduction only reached the Wuyi Mountains, ca. 500 km away from the trench, consistent with flat or shallow subduction models.

Strategies to Improve Teacher Retention in American Overseas Schools in the Near East South Asia Region: A Qualitative Analysis

Science.gov (United States)

Mancuso, Steven V.; Roberts, Laura; White, George P.; Yoshida, Roland K.; Weston, David

2011-01-01

Using a qualitative analysis and drawing from sociological theory, this study examined reasons for teacher turnover and retention from a representative sample of 248 teachers in American overseas schools in the Near East South Asia region. Results suggested that the most important reasons to stay or move pertained to supportive leadership,…

Microbial oxidation of lithospheric organic carbon in rapidly eroding tropical mountain soils.

Science.gov (United States)

Hemingway, Jordon D; Hilton, Robert G; Hovius, Niels; Eglinton, Timothy I; Haghipour, Negar; Wacker, Lukas; Chen, Meng-Chiang; Galy, Valier V

2018-04-13

Lithospheric organic carbon ("petrogenic"; OC petro ) is oxidized during exhumation and subsequent erosion of mountain ranges. This process is a considerable source of carbon dioxide (CO 2 ) to the atmosphere over geologic time scales, but the mechanisms that govern oxidation rates in mountain landscapes are poorly constrained. We demonstrate that, on average, 67 ± 11% of the OC petro initially present in bedrock exhumed from the tropical, rapidly eroding Central Range of Taiwan is oxidized in soils, leading to CO 2 emissions of 6.1 to 18.6 metric tons of carbon per square kilometer per year. The molecular and isotopic evolution of bulk OC and lipid biomarkers during soil formation reveals that OC petro remineralization is microbially mediated. Rapid oxidation in mountain soils drives CO 2 emission fluxes that increase with erosion rate, thereby counteracting CO 2 drawdown by silicate weathering and biospheric OC burial. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Attenuation of S-waves in the lithosphere of the Sea of Crete according to OBS observations

Science.gov (United States)

Kovachev, S. A.; Kuzin, I. P.; Shoda, O. Yu.; Soloviev, S. L.

1991-11-01

Five OBS were installed in the Sea of Crete in 1987. During a period of nine days 430 local earthquakes were recorded. Hypocentres were determined for 85 microearthquakes. A correlation between magnitude ML and duration of seismic events on the records of the ocean bottom seismographs (OBS) was found from data of 14 shocks recorded simultaneously by OBS and some land-based Greek stations. A magnitude-frequency relationship for earthquakes recorded by OBS was obtained in the magnitude range ML = 2-4. Amplitude curves describing the attenuation of body waves in the lithosphere of the Sea of Crete were compiled. Assessment of quality factor Qs was made by comparison of empirical and theoretical amplitude curves. The values of Qs for the lithosphere of the Sea of Crete were calculated and found equal to 200-300. Low values of Qs and consequently strong attenuation of S-waves in the lithosphere of the Sea of Crete could be explained by extension of the lithosphere accompanied by its partial contamination with melted magma.

A review of the paleomagnetic data from Cretaceous to lower Tertiary rocks from Vietnam, Indochina and South China, and their implications for Cenozoic tectonism in Vietnam and adjacent areas

Science.gov (United States)

Cung, Thu'ọ'ng Chí; Geissman, John W.

2013-09-01

Available paleomagnetic data from rock formations of Cretaceous age from Vietnam, Indochina and South China are compiled and reviewed in the context of their tectonic importance in a common reference frame with respect to Eurasia's coeval paleopoles. Key factors that play an important role in determining the reliability of a paleomagnetic result for utilization in tectonic studies have been taken into consideration and include the absence of evidence of remagnetization, which is a feature common to many rocks in this region. Overall, the Cretaceous paleomagnetic data from the South China Block show that the present geographic position of the South China Block has been relatively stable with respect to Eurasia since the mid-Cretaceous and that the paleomagnetically detected motion of a coherent lithospheric block must be based on the representative data obtained from different specific localities across the block in order to separate more localized, smaller scale deformation from true lithosphere scale motion (translation and/or rotation) of a tectonic block. Cretaceous to early Tertiary paleomagnetic data from the Indochina-Shan Thai Block reveal complex patterns of intra-plate deformation in response to the India-Eurasia collision. Paleomagnetically detected motions from the margins of tectonic blocks are interpreted to mainly reflect displacement of upper crustal blocks due to folding and faulting processes. Rigid, lithosphere scale block rotation is not necessarily supported by the paleomagnetic data. The paleomagnetic results from areas east and south of the Red River fault system suggest that this major transcurrent fault system has had a complicated slip history through much of the Cenozoic and that it does not demarcate completely non-rotated and significantly rotated parts of the crust in this area. However, most paleomagnetic results from areas east and south of the Red River fault system at the latitude of Yunnan Province are consistent with a very modest

Hierarchical modeling of genome-wide Short Tandem Repeat (STR) markers infers native American prehistory.

Science.gov (United States)

Lewis, Cecil M

2010-02-01

This study examines a genome-wide dataset of 678 Short Tandem Repeat loci characterized in 444 individuals representing 29 Native American populations as well as the Tundra Netsi and Yakut populations from Siberia. Using these data, the study tests four current hypotheses regarding the hierarchical distribution of neutral genetic variation in native South American populations: (1) the western region of South America harbors more variation than the eastern region of South America, (2) Central American and western South American populations cluster exclusively, (3) populations speaking the Chibchan-Paezan and Equatorial-Tucanoan language stock emerge as a group within an otherwise South American clade, (4) Chibchan-Paezan populations in Central America emerge together at the tips of the Chibchan-Paezan cluster. This study finds that hierarchical models with the best fit place Central American populations, and populations speaking the Chibchan-Paezan language stock, at a basal position or separated from the South American group, which is more consistent with a serial founder effect into South America than that previously described. Western (Andean) South America is found to harbor similar levels of variation as eastern (Equatorial-Tucanoan and Ge-Pano-Carib) South America, which is inconsistent with an initial west coast migration into South America. Moreover, in all relevant models, the estimates of genetic diversity within geographic regions suggest a major bottleneck or founder effect occurring within the North American subcontinent, before the peopling of Central and South America. 2009 Wiley-Liss, Inc.

Comprehensive analysis of Curie-point depths and lithospheric effective elastic thickness at Arctic Region

Science.gov (United States)

Lu, Y.; Li, C. F.

2017-12-01

Arctic Ocean remains at the forefront of geological exploration. Here we investigate its deep geological structures and geodynamics on the basis of gravity, magnetic and bathymetric data. We estimate Curie-point depth and lithospheric effective elastic thickness to understand deep geothermal structures and Arctic lithospheric evolution. A fractal exponent of 3.0 for the 3D magnetization model is used in the Curie-point depth inversion. The result shows that Curie-point depths are between 5 and 50 km. Curie depths are mostly small near the active mid-ocean ridges, corresponding well to high heat flow and active shallow volcanism. Large curie depths are distributed mainly at continental marginal seas around the Arctic Ocean. We present a map of effective elastic thickness (Te) of the lithosphere using a multitaper coherence technique, and Te are between 5 and 110 km. Te primarily depends on geothermal gradient and composition, as well as structures in the lithosphere. We find that Te and Curie-point depths are often correlated. Large Te are distributed mainly at continental region and small Te are distributed at oceanic region. The Alpha-Mendeleyev Ridge (AMR) and The Svalbard Archipelago (SA) are symmetrical with the mid-ocean ridge. AMR and SA were formed before an early stage of Eurasian basin spreading, and they are considered as conjugate large igneous provinces, which show small Te and Curie-point depths. Novaya Zemlya region has large Curie-point depths and small Te. We consider that fault and fracture near the Novaya Zemlya orogenic belt cause small Te. A series of transform faults connect Arctic mid-ocean ridge with North Atlantic mid-ocean ridge. We can see large Te near transform faults, but small Curie-point depths. We consider that although temperature near transform faults is high, but mechanically the lithosphere near transform faults are strengthened.

Normalized difference vegetation index for the South American continent used as a climatic variability indicator

International Nuclear Information System (INIS)

Liu, W.T.; Massambani, O.; Festa, M.

1992-01-01

The NOAA AVHRR GAC data set was used to produce Normalized Difference Vegetation Index (NDVI) maps for the South American Continent covering the period from August 1, 1981 to June 30, 1987. A 15-day maximum value composite procedure was used to partially eliminate the cloud contamination and atmospheric attenuation. Monthly evolution of NDVI for a dry and a wet year within the period studied was used to estimate the area covered by NDVI value less than 0.223, This value was used as an indicator of the drought area and the delineation of the Low rainfall areas in the continent. It was observed a well defined regional dependence of the drought area variability for the Northeast, Southwest and Northwest continent and also for the Amazon region. It is shown a relative estimation of the area coverage with NDVI less than 0.223 for the years 1982/83 and 1984/85. The dynamics of the drought area evolution in the continent is discussed. It is also presented a diagnosis of regional variability of the continental distribution of drought area from 1981 to 1987 for the months of May and September. This information is also used to discuss its relationship with the EL-Nino-Southern Oscillation (ENSO) and the South American Precipitation patterns during this period. It is suggested that the use of NDVI image to identify the dynamics of the drought induced by low rainfall may provide us valuable information to study the large scale climatic variation

Review of the South American characiform fish genus Chilodus, with description of a new species, C. gracilis (Pisces, Characiformes, Chilodontidae)

NARCIS (Netherlands)

Isbrücker, I.J.H.; Nijssen, H.

1988-01-01

Examination of 291 specimens of Chilodus, a genus of South American fresh water fishes, yielded the presence of three species, viz.: C. punctatus, C. zunevei, and C. gracilis. Of the first species the lectotype is designated. The type material of C. zunevei is lost; new material enabled a

Comparing gravity-based to seismic-derived lithosphere densities : A case study of the British Isles and surrounding areas

NARCIS (Netherlands)

Root, B.C.; Ebbing, J; van der Wal, W.; England, R.W.; Vermeersen, L.L.A.

2017-01-01

Lithospheric density structure can be constructed from seismic tomography, gravity modelling, or using both data sets. The different approaches have their own uncertainties and limitations. This study aims to characterize and quantify some of the uncertainties in gravity modelling of lithosphere

Widespread pollution of the South American atmosphere predates the industrial revolution by 240 years

Science.gov (United States)

Uglietti, Chiara; Gabrielli, Paolo; Cooke, Colin; Vallelonga, Paul; Thompson, Lonnie

2015-04-01

In the Southern Hemisphere, evidence for preindustrial atmospheric pollution is restricted to a few geological archives of low temporal resolution that record trace element deposition originating from past mining and metallurgical operations in South America. Therefore the timing and the spatial impact of these activities on the past atmosphere remain poorly constrained. Here we present an annually resolved ice-core record (793-1989 AD) from the high altitude drilling site of Quelccaya (Peru) that archives preindustrial and industrial variations in trace elements. During the pre-colonial period (i.e., pre-1532 AD), the deposition of trace elements was mainly dominated by the fallout of aeolian dust and of ash from occasional volcanic eruptions indicating that metallurgic production during the Inca Empire (1438-1532 AD) had a negligible impact on the South American atmosphere. In contrast, a widespread anthropogenic signal is evident after 1540 AD, which corresponds with the beginning of colonial mining and metallurgy in Peru and Bolivia, 240 years prior to the Industrial Revolution. This shift was due to a major technological transition for silver extraction in South America (1572 AD), from lead-based smelting to mercury amalgamation, which precipitated a massive increase in mining activities. However, deposition of toxic trace metals during the Colonial era was still several factors lower than 20th century pollution that was unprecedented over the entirety of human history.

Widespread pollution of the South American atmosphere predates the industrial revolution by 240 y.

Science.gov (United States)

Uglietti, Chiara; Gabrielli, Paolo; Cooke, Colin A; Vallelonga, Paul; Thompson, Lonnie G

2015-02-24

In the Southern Hemisphere, evidence for preindustrial atmospheric pollution is restricted to a few geological archives of low temporal resolution that record trace element deposition originating from past mining and metallurgical operations in South America. Therefore, the timing and the spatial impact of these activities on the past atmosphere remain poorly constrained. Here we present an annually resolved ice core record (A.D. 793-1989) from the high-altitude drilling site of Quelccaya (Peru) that archives preindustrial and industrial variations in trace elements. During the precolonial period (i.e., pre-A.D. 1532), the deposition of trace elements was mainly dominated by the fallout of aeolian dust and of ash from occasional volcanic eruptions, indicating that metallurgic production during the Inca Empire (A.D. 1438-1532) had a negligible impact on the South American atmosphere. In contrast, a widespread anthropogenic signal is evident after around A.D. 1540, which corresponds with the beginning of colonial mining and metallurgy in Peru and Bolivia, ∼240 y before the Industrial Revolution. This shift was due to a major technological transition for silver extraction in South America (A.D. 1572), from lead-based smelting to mercury amalgamation, which precipitated a massive increase in mining activities. However, deposition of toxic trace metals during the Colonial era was still several factors lower than 20th century pollution that was unprecedented over the entirety of human history.

Food Insecurity, Not Stress is Associated with Three Measures of Obesity in Low-Income, Mexican-American Women in South Texas.

Science.gov (United States)

Salinas, Jennifer J; Shropshire, William; Nino, Ana; Parra-Medina, Deborah

2016-01-01

To determine the relationship between obesity, food insecurity and perceived stress in very low income Mexican American women. Cross-sectional baseline data analysis of a randomized clinical trial. Texas-Mexico border region of South Texas. Very Low Income Mexican American Women. The relationship between obesity and food insecurity in a sample of very low income Hispanic women living in South Texas depends on the measure of obesity and the dimension of food insecurity. The only measure of food insecurity associated with all measures of obesity was often not having enough money to afford to eat balanced meals. Waist circumference was associated with the most dimensions of food insecurity, while BMI had the least associations. Finally, perceived stress was not significantly associated with BMI, waist circumference or percent body fat when adjusted for other covariates. We have found a strong and significant relationship between food insecurity related to having enough resources to eat a balanced diet and BMI, waist circumference, and percent body fat in low-income Mexican American women. While behavioural change is an important strategy for reducing obesity, consideration may need to be made as to how food access with high nutritional value, may be in and of itself a contributing factor in obesity in low income populations.

Phylodynamic analysis of avian infectious bronchitis virus in South America.

Science.gov (United States)

Marandino, Ana; Pereda, Ariel; Tomás, Gonzalo; Hernández, Martín; Iraola, Gregorio; Craig, María Isabel; Hernández, Diego; Banda, Alejandro; Villegas, Pedro; Panzera, Yanina; Pérez, Ruben

2015-06-01

Infectious bronchitis virus (IBV) is a coronavirus of chickens that causes great economic losses to the global poultry industry. The present study focuses on South American IBVs and their genetic relationships with global strains. We obtained full-length sequences of the S1 coding region and N gene of IBV field isolates from Uruguay and Argentina, and performed Phylodynamic analysis to characterize the strains and estimate the time of the most recent common ancestor. We identified two major South American genotypes, which were here denoted South America I (SAI) and Asia/South America II (A/SAII). The SAI genotype is an exclusive South American lineage that emerged in the 1960s. The A/SAII genotype may have emerged in Asia in approximately 1995 before being introduced into South America. Both SAI and A/SAII genotype strains clearly differ from the Massachusetts strains that are included in the vaccine formulations being used in most South American countries. © 2015 The Authors.

A lithospheric magnetic field model derived from the Swarm satellite magnetic field measurements

Science.gov (United States)

Hulot, G.; Thebault, E.; Vigneron, P.

2015-12-01

The Swarm constellation of satellites was launched in November 2013 and has since then delivered high quality scalar and vector magnetic field measurements. A consortium of several research institutions was selected by the European Space Agency (ESA) to provide a number of scientific products which will be made available to the scientific community. Within this framework, specific tools were tailor-made to better extract the magnetic signal emanating from Earth's the lithospheric. These tools rely on the scalar gradient measured by the lower pair of Swarm satellites and rely on a regional modeling scheme that is more sensitive to small spatial scales and weak signals than the standard spherical harmonic modeling. In this presentation, we report on various activities related to data analysis and processing. We assess the efficiency of this dedicated chain for modeling the lithospheric magnetic field using more than one year of measurements, and finally discuss refinements that are continuously implemented in order to further improve the robustness and the spatial resolution of the lithospheric field model.

Preservation of an Archaean whole rock Re-Os isochron for the Venetia lithospheric mantle: Evidence for rapid crustal recycling and lithosphere stabilisation at 3.3 Ga

Science.gov (United States)

van der Meer, Quinten H. A.; Klaver, Martijn; Reisberg, Laurie; Riches, Amy J. V.; Davies, Gareth R.

2017-11-01

Re-Os and platinum group element analyses are reported for peridotite xenoliths from the 533 Ma Venetia kimberlite cluster situated in the Limpopo Mobile Belt, the Neoarchaean collision zone between the Kaapvaal and Zimbabwe Cratons. The Venetian xenoliths provide a rare opportunity to examine the state of the cratonic lithosphere prior to major regional metasomatic disturbance of Re-Os systematics throughout the Phanerozoic. The 32 studied xenoliths record Si-enrichment that is characteristic of the Kaapvaal lithospheric mantle and can be subdivided into five groups based on Re-Os analyses. The most pristine group I samples (n = 13) display an approximately isochronous relationship and fall on a 3.28 ± 0.17 Ga (95 % conf. int.) reference line that is based on their mean TMA age. This age overlaps with the formation age of the Limpopo crust at 3.35-3.28 Ga. The group I samples derive from ∼50 to ∼170 km depth, suggesting coeval melt depletion of the majority of the Venetia lithospheric mantle column. Group II and III samples have elevated Re/Os due to Re addition during kimberlite magmatism. Group II has otherwise undergone a similar evolution as the group I samples with overlapping 187Os/188Os at eruption age: 187Os/188OsEA, while group III samples have low Os concentrations, unradiogenic 187Os/188OsEA and were effectively Re-free prior to kimberlite magmatism. The other sample groups (IV and V) have disturbed Re-Os systematics and provide no reliable age information. A strong positive correlation is recorded between Os and Re concentrations for group I samples, which is extended to groups II and III after correction for kimberlite addition. This positive correlation precludes a single stage melt depletion history and indicates coupled remobilisation of Re and Os. The combination of Re-Os mobility, preservation of the isochronous relationship, correlation of 187Os/188Os with degree of melt depletion and lack of radiogenic Os addition puts tight constraints on

Three-Dimensional Rheological Structure of North China Craton Determined by Integration of Multiple observations: Controlling Role for Lithospheric Rifting

Science.gov (United States)

Xiong, X.; Shan, B.; Li, Y.

2017-12-01

The North China Craton (NCC) has undergone significant lithospheric rejuvenation in late Mesozoic and Cenozoic, one feature of which is the widespread extension and rifting. The extension is distinct between the two parts of NCC: widespread rifting in the eastern NCC and localized narrow rifting in the west. The mechanism being responsible for this difference is uncertain and highly debated. Since lithospheric deformation can be regarded as the response of lithosphere to various dynamic actions, the rheological properties of lithosphere must have a fundamental influence on its tectonics and deformation behavior. In this study, we investigated the 3D thermal and rheological structure of NCC by developing a model integrating several geophysical observables (such as surface heatflow, regional elevation, gravity and geoid anomalies, and seismic tomography models). The results exhibit obvious lateral variation in rheological structure between the eastern and western NCC. The overall lithospheric strength is higher in the western NCC than in the east. Despite of such difference in rheology, both parts of NCC are characterized by mantle dominated strength regime, which facilitates the development of narrow rifting. Using ancient heatflow derived from mantle xenoliths studies, and taking the subduction-related dehydration reactions during Mesozoic into account, we constructed the thermal and rheological structure of NCC in Ordovician, early Cretaceous and early Cenozoic. Combining the evidence from numerical simulations, we proposed an evolution path of the rifting in NCC. The lithosphere of NCC in Ordovician was characterized by a normal craton features: low geotherm, high strength and mantle dominated regime. During Jurassic and Cretaceous, the mantle lithosphere in the eastern NCC was hydrated by fluid released by the suduction of the Pacific plate, resulting in weakening of the lithosphere and a transition from mantle dominated to crust dominated regime, which

Lithospheric scale conductivity anomalies at the Proterozoic-Phanerozoic transition of Australia- Insights from AusLAMP MT data

Science.gov (United States)

Robertson, K. E.; Thiel, S.; Heinson, G. S.

2017-12-01

The intraplate deformation of the north-south trending Neoproterozoic Ikara-Flinders Ranges in South Australia, Australia, draws interest due to its high heat flow, elevated seismicity and the presence of diamondiferous kimberlites and mineral deposits. To the west lies the highly prospective Archean-Paleoproterozoic Gawler Craton, boasting the world's largest IOCG-U deposit, Olympic Dam. The Paleo-Mesoproterozoic Curnamona Province lies to the east, thought to have once been connected to the Gawler Craton and host to the world-class Broken Hill Ag-Pb-Zn deposit. A total of 162 long-period (10 s - 10,000 s) magnetotelluric (MT) stations from the Australia-wide AusLAMP (Australian Lithospheric Architecture Magnetotelluric Project) dataset were used to image the electrical resistivity beneath the Ikara-Flinders Ranges and adjacent Curnamona Province. The most recent acquisition extends this survey region northward to an area predominantly covered with Paleo-Mesozoic sedimentary basins including the most significant on-shore oil and gas region in Australia, the Cooper Basin. The resultant model from 3D inversions using ModEM software shows a relatively resistive Ikara-Flinders Ranges, with two parallel arcuate conductors (the WNAC and ENAC) at 20 to 80 km depth in the Nackara Arc. These conductors correlate well with locations of diamondiferous kimberlites which suggests that the conductors may have derived from the ascent of carbon-rich kimberlite-hosting magma and volatiles up large lithospheric scale structures. The conductors appear to have no correlation with regions of intraplate seismicity within the Ikara-Flinders Ranges which may mean that enhanced pore fluid pressure is not the main cause for the seismicity as was recently proposed. A large conductor covering most of the Curnamona Province (the CC) extends over depths of 10-40 km. The Curnamona Province's most recent tectonothermal activity is from Delamerian reworking during the Cambrian at its margins but

Mycobacterium pinnipedii: Transmission from South American sea lion (Otaria byronia) to Bactrian camel (Camelus bactrianus bactrianus) and Malayan tapirs (Tapirus indicus)

NARCIS (Netherlands)

Moser, I.; Prodinger, W.M.; Hotzel, H.; Greenwald, R.; Lyashchenko, K.P.; Bakker, D.; Gomis, D.; Seidler, T.; Ellenberger, C.; Hetzel, U.; Wuennemann, K.; Moisson, P.

2008-01-01

Tuberculosis infections caused by Mycobacterium (M.) pinnipedii in a South American sea lion, Bactrian camel, and Malayan tapirs kept in two zoological gardens spanning a time period of 5 years are reported. The zoos were linked by the transfer of one tapir. Conventional bacteriological and

Regional Crustal Deformation and Lithosphere Thickness Observed with Geodetic Techniques

Science.gov (United States)

Vermeer, M.; Poutanen, M.; Kollo, K.; Koivula, H.; Ahola, J.

2009-04-01

The solid Earth, including the lithosphere, interacts in many ways with other components of the Earth system, oceans, atmosphere and climate. Geodesy is a key provider of data needed for global and environmental research. Geodesy provides methods and accurate measurements of contemporary deformation, sea level and gravity change. The importance of the decades-long stability and availability of reference frames must be stressed for such studies. In the future, the need to accurately monitor 3-D crustal motions will grow, both together with increasingly precise GNSS (Global Navigation Satellite System) positioning, demands for better follow-up of global change, and local needs for crustal motions, especially in coastal areas. These demands cannot yet be satisfied. The project described here is a part of a larger entity: Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas, DynaQlim, an International Lithosphere Project (ILP) -sponsored initiative. The aims of DynaQlim are to understand the relations between upper mantle dynamics, mantle composition, physical properties, temperature and rheology, to study the postglacial uplift and ice thickness models, sea level change and isostatic response, Quaternary climate variations and Weichselian (Laurentian and other) glaciations during the late Quaternary. We aim at studying various aspects of lithospheric motion within the Finnish and Fennoscandian area, but within a global perspective, by the newest geodetic techniques in a multidisciplinary setting. The studies involve observations of three-dimensional motions and gravity change in a multidisciplinary context on a range of spatial scales: the whole of Fennoscandia, Finland, a regional test area of Satakunta, and the local test site Olkiluoto. Objectives of the research include improving our insight into the 3-D motion of a thick lithosphere, and into the gravity effect of the uplift, using novel approaches; improving the kinematic 3-D models in the

Glacial refugia and the prediction of future habitat coverage of the South American lichen species Ochrolechia austroamericana

OpenAIRE

Martin Kukwa; Marta Kolanowska

2016-01-01

The biogeographic history of lichenized fungi remains unrevealed because those organisms rarely fossilize due to their delicate, often tiny and quickly rotting thalli. Also the ecology and factors limiting occurrence of numerous taxa, especially those restricted in their distribution to tropical areas are poorly recognized. The aim of this study was to determine localization of glacial refugia of South American Ochrolechia austroamericana and to estimate the future changes in the coverage of ...

Lithospheric-scale structures from the perspective of analogue continental collision.

NARCIS (Netherlands)

Sokoutis, D.; Burg, J.P.; Bonini, M.; Corti, G.; Cloetingh, S.A.P.L.

2005-01-01

Analogue models were employed to investigate continental collision addressing the roles of (1) a suture zone separating different crustal blocks, (2) mid-crustal weak layers and (3) mantle strengths. These models confirmed that low-amplitude lithospheric and crustal buckling is the primary response

Geochemical Consequences of Lithospheric Delamination in the Eastern Mediterranean: Evidence From Young Turkish Basalts

Science.gov (United States)

Furman, T.; Kurkcuoglu, B.; Plummer, C.

2007-12-01

Magmatism associated with continental collision is increasingly attributed to major disturbance of or within the lithosphere. Geochemical and isotopic data on post-collisional primitive mafic lavas from across the Anatolian plate enable us to assess the effects of lithospheric delamination (slab rollback and breakoff) as indicated by geophysical studies. The Anatolian province displays geodynamically complex manifestations of the closure of neo-Tethys and the collision between Africa and Europe that commenced circa 30 Ma. The current south- southwestward motion of Anatolia, a.k.a. "Turkish escape", is accommodated by slab rollback along the Hellenic trench and orogenic collapse along both the eastern and western margins of the microplate. Volcanism occurs primarily along the fault zones that border and cross-cut Anatolia, and major element characteristics of the lavas vary with both space and time. In Western Anatolia, early Miocene collisional calc- alkaline magmatism was followed by Quaternary alkaline volcanism (Alici et al. 1998, 2002; Aldanmaz et al. 2000, 2006) related to orogenic collapse, presumably resulting from slab rollback. Orogenic collapse in Eastern Anatolia is facilitated by slab breakoff as determined by geophysical studies (Zor et al. 2003; Angus et al. 2006; Lei & Zhao 2007). This transition was accompanied a change from mid-Miocene calc-alkaline to Quaternary alkaline volcanism (e.g., Yilmaz 1990; Pearce et al. 1990). Central Anatolia displays calc-alkaline and tholeiitic volcanism, including alkali olivine basalts; plate tectonic reconstructions (Lyberis et al. 1992) indicate that the African slab did not reach Central Anatolia. Sr-Nd isotope values from each volcanic province define linear arrays that converge upon a common unradiogenic value typical of global depleted mantle. We suggest that mafic volcanism throughout Anatolia is supported by a common asthenospheric component, modified by identifiable, location-specific additions. In areas

Generation of continental rifts, basins, and swells by lithosphere instabilities

Science.gov (United States)

Fourel, Loïc.; Milelli, Laura; Jaupart, Claude; Limare, Angela

2013-06-01

Continents may be affected simultaneously by rifting, uplift, volcanic activity, and basin formation in several different locations, suggesting a common driving mechanism that is intrinsic to continents. We describe a new type of convective instability at the base of the lithosphere that leads to a remarkable spatial pattern at the scale of an entire continent. We carried out fluid mechanics laboratory experiments on buoyant blocks of finite size that became unstable due to cooling from above. Dynamical behavior depends on three dimensionless numbers, a Rayleigh number for the unstable block, a buoyancy number that scales the intrinsic density contrast to the thermal one, and the aspect ratio of the block. Within the block, instability develops in two different ways in an outer annulus and in an interior region. In the outer annulus, upwellings and downwellings take the form of periodically spaced radial spokes. The interior region hosts the more familiar convective pattern of polygonal cells. In geological conditions, such instabilities should manifest themselves as linear rifts striking at a right angle to the continent-ocean boundary and an array of domal uplifts, volcanic swells, and basins in the continental interior. Simple scaling laws for the dimensions and spacings of the convective structures are derived. For the subcontinental lithospheric mantle, these dimensions take values in the 500-1000 km range, close to geological examples. The large intrinsic buoyancy of Archean lithospheric roots prevents this type of instability, which explains why the widespread volcanic activity that currently affects Western Africa is confined to post-Archean domains.

Crustal evolution of South American Platform based on Sm-Nd isotope geochemistry

International Nuclear Information System (INIS)

Sato, Kei

1998-01-01

Sm-Nd isotopic systematics is relevant to the topics of origin and evolution the of continental crust, where model ages refer to the time when crustal material was differentiated from the upper mantle. Alternative interpretations are due to a lack of adequate information on crustal processes and the variable composition of the mantle sources. The Sm-Nd methods are presented, and applied on rock materials from the South American Platform. The main conclusions indicate juvenile accretion with higher growth rates (peaks), around 3.7-3.5 Ga (∼ 0.5% in volume), 3.1 - 2.9 Ga (∼16%), 2.7 - 2.6 (∼ 9%), 2.2 - 1.9 (35%) and 1.3-1.0 (7%). The continental growth curve indicates that about 35 % of the crust was formed by 2.5 Ga, 88% by 1.8 Ga and 99% by 1.0 Ga, and the remaining ∼ 1 % was added in the Phanerozoic. Rapid crustal growth occurred between 2.2 and 1.9 Ga. The main period of continental crust formation occurred during the Paleoproterozoic, corresponding to 54 % in volume. Sm-Nd model ages, when compared with the crystallisation ages of granitoid rocks, furnish a rough estimate of juvenile vs. reworked material. Within the South American Platform about 45% of juvenile continental crust is still preserved within tectonic provinces of different ages. The remainder represents continental crust reworked in younger tectono-thermal events. In particular crustal reworking was predominating over juvenile accretion during Meso-Neoproterozoic. The Transbrasiliano Lineament is a megasuture, active in the Neoproterozoic, which separates a large northwestern mass, including the Amazonian and Sao Luis Cratons, from a southeastern mass, formed by a collage of cratonic fragments, of which the Sao Francisco and Rio de La Plata are the largest. The crustal evolutions of these two large continental masses are considered individually, and can be resumed following form: I - Old Archean rocks (>3.4 Ga) are found only within the south-eastern part (Gaviao Block, Contendas

The electrical conductivity of the upper mantle and lithosphere from the magnetic signal due to ocean tidal flow

DEFF Research Database (Denmark)

Schnepf, Neesha Regmi; Kuvshinov, Alexey; Grayver, Alexander

galvanically with Earth’s lithosphere (i.e. by direct coupling of the source currents in the ocean with the underlying substrate), enabling conductivity estimations at shallower depths. Here we present the results of determining a 1-D conductivity-depth profile of oceanic lithosphere and upper mantle using...

Influence of the lithosphere-asthenosphere boundary on the stress field northwest of the Alps

Science.gov (United States)

Maury, J.; Cornet, F. H.; Cara, M.

2014-11-01

In 1356, a magnitude 6-7 earthquake occurred near Basel, in Switzerland. But recent compilations of GPS measurements reveal that measured horizontal deformation rates in northwestern continental Europe are smaller than error bars on the measurements, proving present tectonic activity, if any, is very small in this area. We propose to reconcile these apparently antinomic observations with a mechanical model of the lithosphere that takes into account the geometry of the lithosphere-asthenosphere boundary, assuming that the only loading mechanism is gravity. The lithosphere is considered to be an elastoplastic material satisfying a Von Mises plasticity criterion. The model, which is 400 km long, 360 km wide and 230 km thick, is centred near Belfort in eastern France, with its width oriented parallel to the N145°E direction. It also takes into account the real topography of both the ground surface and that of the Moho discontinuity. Not only does the model reproduce observed principal stress directions orientations, it also identifies a plastic zone that fits roughly the most seismically active domain of the region. Interestingly, a somewhat similar stress map may be produced by considering an elastic lithosphere and an ad-hoc horizontal `tectonic' stress field. However, for the latter model, examination of the plasticity criterion suggests that plastic deformation should have taken place. It is concluded that the present-day stress field in this region is likely controlled by gravity and rheology, rather than by active Alpine tectonics.

Extension of thickened and hot lithospheres: Inferences from laboratory modeling

NARCIS (Netherlands)

Tirel, C.; Brun, J.P.; Sokoutis, D.

2006-01-01

The extension of a previously thickened lithosphere is studied through a series of analogue experiments. The models deformed in free and boundary-controlled gravity spreading conditions that simulate the development of wide rift-type and core complex-type structures. In models, the development of

American marsupials chromosomes: why study them?

Directory of Open Access Journals (Sweden)

Marta Svartman

2009-01-01

Full Text Available Marsupials, one of the three main groups of mammals, are only found in Australia and in the American continent. Studies performed in Australian marsupials have demonstrated the great potential provided by the group for the understanding of basic genetic mechanisms and chromosome evolution in mammals. Genetic studies in American marsupials are relatively scarce and cytogenetic data of most species are restricted to karyotype descriptions, usually without banding patterns. Nevertheless, the first marsupial genome sequenced was that of Monodelphis domestica, a South American species. The knowledge about mammalian genome evolution and function that resulted from studies on M. domestica is in sharp contrast with the lack of genetic data on most American marsupial species. Here, we present an overview of the chromosome studies performed in marsupials with emphasis on the South American species.

Optimizing Surveillance for South American Origin Influenza A Viruses Along the United States Gulf Coast Through Genomic Characterization of Isolates from Blue-winged Teal (Anas discors).

Science.gov (United States)

Ramey, A M; Walther, P; Link, P; Poulson, R L; Wilcox, B R; Newsome, G; Spackman, E; Brown, J D; Stallknecht, D E

2016-04-01

Relative to research focused on inter-continental viral exchange between Eurasia and North America, less attention has been directed towards understanding the redistribution of influenza A viruses (IAVs) by wild birds between North America and South America. In this study, we genomically characterized 45 viruses isolated from blue-winged teal (Anas discors) along the Texas and Louisiana Gulf Coast during March of 2012 and 2013, coincident with northward migration of this species from Neotropical wintering areas to breeding grounds in the United States and Canada. No evidence of South American lineage genes was detected in IAVs isolated from blue-winged teal supporting restricted viral gene flow between the United States and southern South America. However, it is plausible that blue-winged teal redistribute IAVs between North American breeding grounds and wintering areas throughout the Neotropics, including northern South America, and that viral gene flow is limited by geographical barriers further south (e.g., the Amazon Basin). Surveillance for the introduction of IAVs from Central America and northern South America into the United States may be further optimized through genomic characterization of viruses resulting from coordinated, concurrent sampling efforts targeting blue-winged teal and sympatric species throughout the Neotropics and along the United States Gulf Coast. © Published 2014. This article is a US Government work and is in the public domain in the USA.

Semen preservation and artificial insemination in domesticated South American camelids.

Science.gov (United States)

Bravo, P Walter; Alarcon, V; Baca, L; Cuba, Y; Ordoñez, C; Salinas, J; Tito, F

2013-01-10

Semen preservation and artificial insemination in South American camelids are reviewed giving emphasis to work done in Peru and by the authors. Reports on semen evaluation and the preservation process indicate that semen of alpacas and llamas can be manipulated by making it liquid first. Collagenase appears to be the best enzyme to eliminate viscosity. Tris buffer solution maintains a higher motility than egg-yolk citrate, phosphate buffered saline (PBS), Triladyl, and Merck-I extenders. Cooling of semen took 1h after collected, and equilibrated with 7% glycerol presented a better motility and spermatozoa survival at 1, 7, 15 and 30days after being slowly frozen in 0.25mL plastic straws. Trials of artificial insemination with freshly diluted semen and frozen-thawed semen are encouraging and needs to be tested extensively under field conditions. Recently, fertility rates varied from 3 to 67%. Semen preservation and most important, artificial insemination appear to be a reality, and could be used to improve the genetic quality of alpacas and llamas. Copyright © 2012 Elsevier B.V. All rights reserved.

An Equivalent Source Method for Modelling the Lithospheric Magnetic Field Using Satellite and Airborne Magnetic Data

DEFF Research Database (Denmark)

Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris

. Advantages of the equivalent source method include its local nature and the ease of transforming to spherical harmonics when needed. The method can also be applied in local, high resolution, investigations of the lithospheric magnetic field, for example where suitable aeromagnetic data is available......We present a technique for modelling the lithospheric magnetic field based on estimation of equivalent potential field sources. As a first demonstration we present an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010. Three component vector field...... for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid with an increasing grid resolution towards the airborne survey area. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model...

Using crustal thickness, subsidence and P-T-t history on the Iberia-Newfoundland & Alpine Tethys margins to constrain lithosphere deformation modes during continental breakup

Science.gov (United States)

Jeanniot, L.; Kusznir, N. J.; Manatschal, G.; Mohn, G.; Beltrando, M.

2013-12-01

Observations at magma-poor rifted margins such as Iberia-Newfoundland show a complex lithosphere deformation history and OCT architecture, resulting in hyper-extended continental crust and lithosphere, exhumed mantle and scattered embryonic oceanic crust before continental breakup and seafloor spreading. Initiation of seafloor spreading requires both the rupture of the continental crust and lithospheric mantle, and the onset of decompressional melting. Their relative timing controls when mantle exhumation may occur; the presence or absence of exhumed mantle provides useful information on the timing of these events and constraints on lithosphere deformation modes. A single kinematic lithosphere deformation mode leading to continental breakup and sea-floor spreading cannot explain observations. We have determined the sequence of lithosphere deformation events, using forward modelling of crustal thickness, subsidence and P-T-t history calibrated against observations on the present-day Iberia-Newfoundland and the fossil analogue Alpine Tethys margins. Lithosphere deformation modes, represented by flow fields, are generated by a 2D finite element viscous flow model (FeMargin), and used to advect lithosphere and asthenosphere temperature and material. FeMargin is kinematically driven by divergent deformation in the topmost upper lithosphere inducing passive upwelling beneath that layer; the upper lithosphere is assumed to deform by extensional faulting and magmatic intrusions, consistent with observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996). Buoyancy enhanced upwelling is also included in the kinematic model as predicted by Braun et al (2000). We predict melt generation by decompressional melting using the parameterization and methodology of Katz et al., 2003. We use a series of numerical experiments, tested and calibrated against crustal thicknesses and subsidence observations, to determine the distribution of lithosphere

Social Identity Integration, Parental Response, and Psychological Outcomes among Lesbian, Gay, Bisexual, and Queer South Asian Americans

OpenAIRE

Kishore, Saanjh Aakash

2015-01-01

The goal of this study is to understand how social identities are integrated across domains of identity. Focusing on a population in which cultural norms dictate sexuality behaviors as a condition of ethnic membership, the study examines how South Asian LGBQ Americans integrate their ethnic and sexual orientation identities, and also examines the role of this dual social identity integration in the relationship between the distal stress of parental responses to LGBQ identity, the proximal str...

Deep magmatism alters and erodes lithosphere and facilitates decoupling of Rwenzori crustal block

Science.gov (United States)

Wallner, Herbert; Schmeling, Harro

2013-04-01

The title is the answer to the initiating question "Why are the Rwenzori Mountains so high?" posed at the EGU 2008. Our motivation origins in the extreme topography of the Rwenzori Mountains. The strong, cold proterozoic crustal horst is situated between rift segments of the western branch of the East African Rift System. Ideas of rift induced delamination (RID) and melt induced weakening (MIW) have been tested with one- and two-phase flow physics. Numerical model parameter variations and new observations lead to a favoured model with simple and plausible definitions. Results coincide in the scope of their comparability with different observations or vice versa reduce ambiguity and uncertainties in model input. Principle laws of the thermo-mechanical physics are the equations of conservation of mass, momentum, energy and composition for a two-phase (matrix-melt) system with nonlinear rheology. A simple solid solution model determines melting and solidification under consideration of depletion and enrichment. The Finite Difference Method with markers is applied to visco-plastic flow using the streamfunction in an Eulerian formulation in 2D. The Compaction Boussinesq and the high Prandtl number Approximation are employed. Lateral kinematic boundary conditions provide long-wavelength asthenospheric upwelling and extensional stress conditions. Partial melts are generated in the asthenosphere, extracted above a critical fraction, and emplaced into a given intrusion level. Temperature anomalies positioned beneath the future rifts, the sole specialization to the Rwenzori situation, localize melts which are very effective in weakening the lithosphere. Convection patterns tend to generate dripping instabilities at the lithospheric base; multiple slabs detach and distort uprising asthenosphere; plumes migrate, join and split. In spite of appearing chaotic flow behaviour a characteristic recurrence time of high velocity events (drips, plumes) emerges. Chimneys of increased

Review of South American mines

International Nuclear Information System (INIS)

Anon.

1984-01-01

A general overview is presented of the mining activity and plans for South America. The countries which are presented are Columbia, Argentina, Brazil, Venezuela, Chile, Peru, and Bolivia. The products of the mines include coal, bauxite, gold, iron, uranium, copper and numerous other minor materials. A discussion of current production, support and processing facilities, and mining strategies is also given

Using open sidewalls for modelling self-consistent lithosphere subduction dynamics

NARCIS (Netherlands)

Chertova, M.V.; Geenen, T.; van den Berg, A.; Spakman, W.

2012-01-01

Subduction modelling in regional model domains, in 2-D or 3-D, is commonly performed using closed (impermeable) vertical boundaries. Here we investigate the merits of using open boundaries for 2-D modelling of lithosphere subduction. Our experiments are focused on using open and closed (free

Lithospheric Structure and Active Deformation in the Salton Trough from Coseismic and Postseismic Models of the 2010 Mw 7.2 El Mayor-Cucapah Earthquake

Science.gov (United States)

Fielding, E. J.; Huang, M. H.; Dickinson, H.; Freed, A. M.; Burgmann, R.; Gonzalez-Ortega, J. A.; Andronicos, C.

2016-12-01

The 4 April 2010 Mw 7.2 El Mayor-Cucapah (EMC) Earthquake ruptured about 120 km along several NW-striking faults to the west of the Cerro Prieto Fault in the Salton Trough of Baja California, Mexico. We analyzed interferometric synthetic aperture radar (SAR), SAR and optical pixel offsets, and continuous and campaign GPS data to optimize an EMC coseismic rupture model with 9 fault segments, which fits the complex structure of the faults. Coseismic slip inversion with a layered elastic model shows that largely right-lateral slip is confined to upper 10 km with strong variations along strike. Near-field GPS measures slip on a north-striking normal fault that ruptured at the beginning of the earthquake, previously inferred from seismic waveforms. EMC Earthquake postseismic deformation shows the Earth's response to the large coseismic stress changes. InSAR shows rapid shallow afterslip at the north and south ends of the main ruptures. Continuous GPS from the Plate Boundary Observatory operated by UNAVCO measures the first six years of postseismic deformation, extremely rapid near the rupture. Afterslip on faults beneath the coseismic rupture cannot explain far-field displacements that are best explained by viscoelastic relaxation of the lower crust and upper mantle. We built a viscoelastic 3D finite element model of the lithosphere and asthenosphere based on available data for the region with the EMC coseismic faults embedded inside. Coseismic slip was imposed on the model, allowed to relax for 5 years, and then compared to the observed surface deformation. Systematic exploration of the viscoelastic parameters shows that horizontal and vertical heterogeneity is required to fit the postseismic deformation. Our preferred viscoelastic model has weaker viscosity layers beneath the Salton Trough than adjacent blocks that are consistent with the inferred differences in the geotherms. Defining mechanical lithosphere as rocks that have viscosities greater than 10^19 Pa s (able

South American camelid illegal traffic detection by means of molecular markers.

Science.gov (United States)

Di Rocco, F; Posik, D M; Ripoli, M V; Díaz, S; Maté, M L; Giovambattista, G; Vidal-Rioja, L

2011-11-01

South American camelids comprise the wild species guanaco and vicuña and their respective domestic relatives llama and alpaca. The aim of the present study was to determine by DNA analysis to which of these species belong a herd of camelids confiscated from a llama breeder but alleged to be alpacas by the prosecution, and to evaluate the usefulness of mitochondrial and autosomal DNA markers to solve judicial cases involving camelid taxa. Cytochrome b and cytochrome oxidase I mitochondrial genes and 7 STR were analyzed in 25 confiscated samples. Mitochondrial results were inconclusive because 18 of the sequestered samples presented haplotypes that corresponded to the guanaco haplogroup and the remaining seven belonged to a vicuña linage. Microsatellite data of casework samples and llama reference samples revealed different genetic profiles by the presence of private alleles at two microsatellites suggesting that the confiscated animals could be alpaca, or at least alpaca hybrids instead of pure llama. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

The population genetics of Quechuas, the largest native South American group: autosomal sequences, SNPs, and microsatellites evidence high level of diversity.

Science.gov (United States)

Scliar, Marilia O; Soares-Souza, Giordano B; Chevitarese, Juliana; Lemos, Livia; Magalhães, Wagner C S; Fagundes, Nelson J; Bonatto, Sandro L; Yeager, Meredith; Chanock, Stephen J; Tarazona-Santos, Eduardo

2012-03-01

Elucidating the pattern of genetic diversity for non-European populations is necessary to make the benefits of human genetics research available to individuals from these groups. In the era of large human genomic initiatives, Native American populations have been neglected, in particular, the Quechua, the largest South Amerindian group settled along the Andes. We characterized the genetic diversity of a Quechua population in a global setting, using autosomal noncoding sequences (nine unlinked loci for a total of 16 kb), 351 unlinked SNPs and 678 microsatellites and tested predictions of the model of the evolution of Native Americans proposed by (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496). European admixture is Quechua or Melanesian populations, which is concordant with the African origin of modern humans and the fact that South America was the last part of the world to be peopled. The diversity in the Quechua population is comparable with that of Eurasian populations, and the allele frequency spectrum based on resequencing data does not reflect a reduction in the proportion of rare alleles. Thus, the Quechua population is a large reservoir of common and rare genetic variants of South Amerindians. These results are consistent with and complement our evolutionary model of South Amerindians (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496), proposed based on Y-chromosome data, which predicts high genomic diversity due to the high level of gene flow between Andean populations and their long-term effective population size. Copyright © 2012 Wiley Periodicals, Inc.

An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

DEFF Research Database (Denmark)

Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris

2014-01-01

We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when...... are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm...... in the CHAOS-4 and MF7 models using more conventional spherical harmonic based approaches. Advantages of the equivalent source method include its local nature, allowing e.g. for regional grid refinement, and the ease of transforming to spherical harmonics when needed. Future applications will make use of Swarm...

Gravity Maps of Antarctic Lithospheric Structure from Remote-Sensing and Seismic Data

Science.gov (United States)

Tenzer, Robert; Chen, Wenjin; Baranov, Alexey; Bagherbandi, Mohammad

2018-02-01

Remote-sensing data from altimetry and gravity satellite missions combined with seismic information have been used to investigate the Earth's interior, particularly focusing on the lithospheric structure. In this study, we use the subglacial bedrock relief BEDMAP2, the global gravitational model GOCO05S, and the ETOPO1 topographic/bathymetric data, together with a newly developed (continental-scale) seismic crustal model for Antarctica to compile the free-air, Bouguer, and mantle gravity maps over this continent and surrounding oceanic areas. We then use these gravity maps to interpret the Antarctic crustal and uppermost mantle structure. We demonstrate that most of the gravity features seen in gravity maps could be explained by known lithospheric structures. The Bouguer gravity map reveals a contrast between the oceanic and continental crust which marks the extension of the Antarctic continental margins. The isostatic signature in this gravity map confirms deep and compact orogenic roots under the Gamburtsev Subglacial Mountains and more complex orogenic structures under Dronning Maud Land in East Antarctica. Whereas the Bouguer gravity map exhibits features which are closely spatially correlated with the crustal thickness, the mantle gravity map reveals mainly the gravitational signature of the uppermost mantle, which is superposed over a weaker (long-wavelength) signature of density heterogeneities distributed deeper in the mantle. In contrast to a relatively complex and segmented uppermost mantle structure of West Antarctica, the mantle gravity map confirmed a more uniform structure of the East Antarctic Craton. The most pronounced features in this gravity map are divergent tectonic margins along mid-oceanic ridges and continental rifts. Gravity lows at these locations indicate that a broad region of the West Antarctic Rift System continuously extends between the Atlantic-Indian and Pacific-Antarctic mid-oceanic ridges and it is possibly formed by two major

Diet-to-female and female-to-pup isotopic discrimination in South American sea lions.

Science.gov (United States)

Drago, Massimiliano; Franco-Trecu, Valentina; Cardona, Luis; Inchausti, Pablo

2015-08-30

The use of accurate, species-specific diet-tissue discrimination factors is a critical requirement when applying stable isotope mixing models to predict consumer diet composition. Thus, diet-to-female and female-to-pup isotopic discrimination factors in several tissues for both captive and wild South American sea lions were estimated to provide appropriate values for quantifying feeding preferences at different timescales in the wild populations of this species. Stable carbon and nitrogen isotope ratios in the blood components of two female-pup pairs and females' prey muscle from captive individuals were determined by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) to calculate the respective isotopic discrimination factors. The same analysis was carried out in both blood components, and skin and hair tissues for eight female-pup pairs from wild individuals. Mean diet-to-female Δ(13) C and Δ(15) N values were higher than the female-to-pup ones. Pup tissues were more (15) N-enriched than their mothers but (13) C-depleted in serum and plasma tissues. In most of the tissue comparisons, we found differences in both Δ(15) N and Δ(13) C values, supporting tissue-specific discrimination. We found no differences between captive and wild female-to-pup discrimination factors either in Δ(13) C or Δ(15) N values of blood components. Only the stable isotope ratios in pup blood are good proxies of the individual lactating females. Thus, we suggest that blood components are more appropriate to quantify the feeding habits of wild individuals of this species. Furthermore, because female-to-pup discrimination factors for blood components did not differ between captive and wild individuals, we suggest that results for captive experiments can be extrapolated to wild South American sea lion populations. Copyright © 2015 John Wiley & Sons, Ltd.

The identity of three South American “smiliine” treehoppers (Hemiptera: Membracidae) and related taxonomic changes, including description of a new genus in Thuridini

Science.gov (United States)

Based on examination of holotype or interpretation of original descriptions, four taxonomic changes are proposed for South American species erroneously placed in the tribe Smiliini: Flynnia, n. gen. (Thuridini) and F. fascipennis (Funkhouser), n. comb. from Bolivia; Antianthe atromarginata (Goding),...

A comparative in silico linear B-cell epitope prediction and characterization for South American and African Trypanosoma vivax strains.

Science.gov (United States)

Guedes, Rafael Lucas Muniz; Rodrigues, Carla Monadeli Filgueira; Coatnoan, Nicolas; Cosson, Alain; Cadioli, Fabiano Antonio; Garcia, Herakles Antonio; Gerber, Alexandra Lehmkuhl; Machado, Rosangela Zacarias; Minoprio, Paola Marcella Camargo; Teixeira, Marta Maria Geraldes; de Vasconcelos, Ana Tereza Ribeiro

2018-02-27

Trypanosoma vivax is a parasite widespread across Africa and South America. Immunological methods using recombinant antigens have been developed aiming at specific and sensitive detection of infections caused by T. vivax. Here, we sequenced for the first time the transcriptome of a virulent T. vivax strain (Lins), isolated from an outbreak of severe disease in South America (Brazil) and performed a computational integrated analysis of genome, transcriptome and in silico predictions to identify and characterize putative linear B-cell epitopes from African and South American T. vivax. A total of 2278, 3936 and 4062 linear B-cell epitopes were respectively characterized for the transcriptomes of T. vivax LIEM-176 (Venezuela), T. vivax IL1392 (Nigeria) and T. vivax Lins (Brazil) and 4684 for the genome of T. vivax Y486 (Nigeria). The results presented are a valuable theoretical source that may pave the way for highly sensitive and specific diagnostic tools. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Prospects for the development of the South American methanol industry

International Nuclear Information System (INIS)

Motilal, R.

1995-01-01

The industry entered 1994 with positive market conditions and became increasingly robust as consumers mobilized for the anticipated needs of the second phase of the Clean Air Act. These conditions were reinforced by structural changes taking place in the industry the prime result being the emergence of a single marketer as the dominant force in world trade. In 1995 however, the drawdown of stockpiles of MTBE and methanol accumulated earlier, created conditions of excess as the industry continued to run at nearly full capacity and as opt outs from the reformulated gasoline program dampened the rate of MTBE consumption. The historical forces that attend market cycles on its way up by exerting stickiness upward also contrived to accelerate prices on their way down. Market pricing in the methanol industry, as in other commodities is set largely by the incremental molecules entering the market place. Accordingly, the terms and conditions of the transactions covering traded volumes represent a major influence on market pricing. The major portion of traded volumes are sourced from offshore locations where the domestic market is small in comparison to the production capacities. The South American region is one such strategic offshore location on which increasing emphasis must be placed, if any realistic prognosis of the future direction of the industry is to be made. It is in this context, that this paper attempts to review the underlying factors which led to the rapid growth of the major methanol producing countries in South America and to emphasize the potential for continued development of this region and its strategic importance to the global methanol industry both as a major source of production and as a significant force in the world methanol trade

Petrogenesis of postcollisional magmatism at Scheelite Dome, Yukon, Canada: Evidence for a lithospheric mantle source for magmas associated with intrusion-related gold systems

Science.gov (United States)

Mair, John L.; Farmer, G. Lang; Groves, David I.; Hart, Craig J.R.; Goldfarb, Richard J.

2011-01-01

are attributes of the ancient North American cratonic margin that appear to be essential prerequisites to this style of postcollisional magmatism and associated gold-rich fluid exsolution. This type of magmatic hydrothermal activity occurs in a very specific tectonic setting that typically sets intrusion-related gold deposits apart from orogenic gold deposits, which are synorogenic in timing and have no consistent direct relationship to such diverse and contemporaneous lithospheric mantle-derived magmas, although they too are commonly sited adjacent to lithospheric boundaries.

Comparison of Childrearing Practices of Anglos, Cuban-Americans, and Latin Americans. Occasional Papers Series, Dialogues #5.

Science.gov (United States)

Escovar, Luis; Escovar, Peggy L.

In this report perceived childrearing practices among three cultural groups (American Anglos, Cuban Americans, and Latin Americans) were compared. Subjects were 445 college students (168 males and females from universities in Colombia and Venezuela, and 154 from a university in South Florida). A multivariate analysis of covariance was used to…

Simultaneous estimation of lithospheric uplift rates and absolute sea level change in southwest Scandinavia from inversion of sea level data

DEFF Research Database (Denmark)

Nielsen, Lars; Hansen, Jens Morten; Hede, Mikkel Ulfeldt

2014-01-01

the relative sea level data. Similar independent data do not exist for ancient times. The purpose of this study is to test two simple inversion approaches for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates for ancient times in areas where a dense coverage of relative...... sea level data exists and well-constrained average lithospheric movement values are known from, for example glacial isostatic adjustment (GIA) models. The inversion approaches are tested and used for simultaneous estimation of lithospheric uplift rates and absolute sea level change rates in southwest...... Scandinavia from modern relative sea level data series that cover the period from 1900 to 2000. In both approaches, a priori information is required to solve the inverse problem. A priori information about the average vertical lithospheric movement in the area of interest is critical for the quality...

Lithospheric Contributions to Arc Magmatism: Isotope Variations Along Strike in Volcanoes of Honshu, Japan

Science.gov (United States)

Kersting; Arculus; Gust

1996-06-07

Major chemical exchange between the crust and mantle occurs in subduction zone environments, profoundly affecting the chemical evolution of Earth. The relative contributions of the subducting slab, mantle wedge, and arc lithosphere to the generation of island arc magmas, and ultimately new continental crust, are controversial. Isotopic data for lavas from a transect of volcanoes in a single arc segment of northern Honshu, Japan, have distinct variations coincident with changes in crustal lithology. These data imply that the relatively thin crustal lithosphere is an active geochemical filter for all traversing magmas and is responsible for significant modification of primary mantle melts.

The adrenergic retulation of the cardiovascular system in the South American rattlesnake, Crotalus durissus

DEFF Research Database (Denmark)

Galli, G.L.J.; Jensen, Nini Skovgaard; Abe, A.S.

2007-01-01

The present study investigates adrenergic regulation of the systemic and pulmonary circulations of the anaesthetised South American rattlesnake, Crotalus durissus. Haemodynamic measurements were made following bolus injections of adrenaline and adrenergic antagonists administered through a systemic...... arterial catheter. Adrenaline caused a marked systemic vasoconstriction that was abolished by phentolamine, indicating this response was mediated through α-adrenergic receptors. Injection of phentolamine gave rise to a pronounced vasodilatation (systemic conductance (Gsys) more than doubled), while...... injection of propranolol caused a systemic vasoconstriction, pointing to a potent α-adrenergic, and a weaker β-adrenergic tone in the systemic vasculature of Crotalus. Overall, the pulmonary vasculature was far less responsive to adrenergic stimulation than the systemic circulation. Adrenaline caused...

Magnetotelluric Imaging of Lower Crustal Melt and Lithospheric Hydration in the Rocky Mountain Front Transition Zone, Colorado, USA

Science.gov (United States)

Feucht, D. W.; Sheehan, A. F.; Bedrosian, P. A.

2017-12-01

We present an electrical resistivity model of the crust and upper mantle from two-dimensional (2-D) anisotropic inversion of magnetotelluric data collected along a 450 km transect of the Rio Grande rift, southern Rocky Mountains, and High Plains in Colorado, USA. Our model provides a window into the modern-day lithosphere beneath the Rocky Mountain Front to depths in excess of 150 km. Two key features of the 2-D resistivity model are (1) a broad zone ( 200 km wide) of enhanced electrical conductivity (minerals, with maximum hydration occurring beneath the Rocky Mountain Front. This lithospheric "hydration front" has implications for the tectonic evolution of the continental interior and the mechanisms by which water infiltrates the lithosphere.

Genomic Insights into the Ancestry and Demographic History of South America

Science.gov (United States)

Homburger, Julian R.; Moreno-Estrada, Andrés; Gignoux, Christopher R.; Nelson, Dominic; Sanchez, Elena; Ortiz-Tello, Patricia; Pons-Estel, Bernardo A.; Acevedo-Vasquez, Eduardo; Miranda, Pedro; Langefeld, Carl D.; Gravel, Simon; Alarcón-Riquelme, Marta E.; Bustamante, Carlos D.

2015-01-01

South America has a complex demographic history shaped by multiple migration and admixture events in pre- and post-colonial times. Settled over 14,000 years ago by Native Americans, South America has experienced migrations of European and African individuals, similar to other regions in the Americas. However, the timing and magnitude of these events resulted in markedly different patterns of admixture throughout Latin America. We use genome-wide SNP data for 437 admixed individuals from 5 countries (Colombia, Ecuador, Peru, Chile, and Argentina) to explore the population structure and demographic history of South American Latinos. We combined these data with population reference panels from Africa, Asia, Europe and the Americas to perform global ancestry analysis and infer the subcontinental origin of the European and Native American ancestry components of the admixed individuals. By applying ancestry-specific PCA analyses we find that most of the European ancestry in South American Latinos is from the Iberian Peninsula; however, many individuals trace their ancestry back to Italy, especially within Argentina. We find a strong gradient in the Native American ancestry component of South American Latinos associated with country of origin and the geography of local indigenous populations. For example, Native American genomic segments in Peruvians show greater affinities with Andean indigenous peoples like Quechua and Aymara, whereas Native American haplotypes from Colombians tend to cluster with Amazonian and coastal tribes from northern South America. Using ancestry tract length analysis we modeled post-colonial South American migration history as the youngest in Latin America during European colonization (9–14 generations ago), with an additional strong pulse of European migration occurring between 3 and 9 generations ago. These genetic footprints can impact our understanding of population-level differences in biomedical traits and, thus, inform future medical

Genomic Insights into the Ancestry and Demographic History of South America.

Directory of Open Access Journals (Sweden)

Julian R Homburger

2015-12-01

Full Text Available South America has a complex demographic history shaped by multiple migration and admixture events in pre- and post-colonial times. Settled over 14,000 years ago by Native Americans, South America has experienced migrations of European and African individuals, similar to other regions in the Americas. However, the timing and magnitude of these events resulted in markedly different patterns of admixture throughout Latin America. We use genome-wide SNP data for 437 admixed individuals from 5 countries (Colombia, Ecuador, Peru, Chile, and Argentina to explore the population structure and demographic history of South American Latinos. We combined these data with population reference panels from Africa, Asia, Europe and the Americas to perform global ancestry analysis and infer the subcontinental origin of the European and Native American ancestry components of the admixed individuals. By applying ancestry-specific PCA analyses we find that most of the European ancestry in South American Latinos is from the Iberian Peninsula; however, many individuals trace their ancestry back to Italy, especially within Argentina. We find a strong gradient in the Native American ancestry component of South American Latinos associated with country of origin and the geography of local indigenous populations. For example, Native American genomic segments in Peruvians show greater affinities with Andean indigenous peoples like Quechua and Aymara, whereas Native American haplotypes from Colombians tend to cluster with Amazonian and coastal tribes from northern South America. Using ancestry tract length analysis we modeled post-colonial South American migration history as the youngest in Latin America during European colonization (9-14 generations ago, with an additional strong pulse of European migration occurring between 3 and 9 generations ago. These genetic footprints can impact our understanding of population-level differences in biomedical traits and, thus, inform

Genomic Insights into the Ancestry and Demographic History of South America.

Science.gov (United States)

Homburger, Julian R; Moreno-Estrada, Andrés; Gignoux, Christopher R; Nelson, Dominic; Sanchez, Elena; Ortiz-Tello, Patricia; Pons-Estel, Bernardo A; Acevedo-Vasquez, Eduardo; Miranda, Pedro; Langefeld, Carl D; Gravel, Simon; Alarcón-Riquelme, Marta E; Bustamante, Carlos D

2015-12-01

South America has a complex demographic history shaped by multiple migration and admixture events in pre- and post-colonial times. Settled over 14,000 years ago by Native Americans, South America has experienced migrations of European and African individuals, similar to other regions in the Americas. However, the timing and magnitude of these events resulted in markedly different patterns of admixture throughout Latin America. We use genome-wide SNP data for 437 admixed individuals from 5 countries (Colombia, Ecuador, Peru, Chile, and Argentina) to explore the population structure and demographic history of South American Latinos. We combined these data with population reference panels from Africa, Asia, Europe and the Americas to perform global ancestry analysis and infer the subcontinental origin of the European and Native American ancestry components of the admixed individuals. By applying ancestry-specific PCA analyses we find that most of the European ancestry in South American Latinos is from the Iberian Peninsula; however, many individuals trace their ancestry back to Italy, especially within Argentina. We find a strong gradient in the Native American ancestry component of South American Latinos associated with country of origin and the geography of local indigenous populations. For example, Native American genomic segments in Peruvians show greater affinities with Andean indigenous peoples like Quechua and Aymara, whereas Native American haplotypes from Colombians tend to cluster with Amazonian and coastal tribes from northern South America. Using ancestry tract length analysis we modeled post-colonial South American migration history as the youngest in Latin America during European colonization (9-14 generations ago), with an additional strong pulse of European migration occurring between 3 and 9 generations ago. These genetic footprints can impact our understanding of population-level differences in biomedical traits and, thus, inform future medical

Attitudes toward Family Obligations among American Adolescents with Asian, Latin American, and European Backgrounds.

Science.gov (United States)

Fuligni, Andrew J.; Tseng, Vivian; Lam, May

1999-01-01

Examined attitudes toward family obligations in American tenth and twelfth graders from Filipino, Chinese, Mexican, Central and South American, and European backgrounds. Found that even within a society emphasizing adolescent autonomy and independence, youths from families with collectivistic traditions retain their parents' familial values and…

Experimental transmission of Sarcocystis speeri Dubey and Lindsay, 1999 from the South American opossum (Didelphis albiventris) to the North American opossum (Didelphis virginiana).

Science.gov (United States)

Dubey, J P; Speer, C A; Bowman, D D; Horton, K M; Venturini, C; Venturini, L

2000-06-01

Sarcocystis speeri Dubey and Lindsay, 1999 from the South American opossum Didelphis albiventris was successfully transmitted to the North American opossum Didelphis virginiana. Sporocysts from a naturally infected D. albiventris from Argentina were fed to 2 gamma-interferon knockout (KO) mice. The mice were killed 64 and 71 days after sporocyst feeding (DAF). Muscles containing sarcocysts from the KO mouse killed 71 DAF were fed to a captive D. virginiana; this opossum shed sporocysts 11 days after ingesting sarcocysts. Sporocysts from D. virginiana were fed to 9 KO mice and 4 budgerigars (Melopsittacus undulatus). Schizonts, sarcocysts, or both of S. speeri were found in tissues of all 7 KO mice killed 29-85 DAF; 2 mice died 39 and 48 DAF were not necropsied. Sarcocystis stages were not found in tissues of the 4 budgerigars fed S. speeri sporocysts and killed 35 DAE These results indicate that S. speeri is distinct from Sarcocystis falcatula and Sarcocystis neurona, and that S. speeri is present in both D. albiventris and D. virginiana.

Recurrent evolution of melanism in South American felids.

Science.gov (United States)

Schneider, Alexsandra; Henegar, Corneliu; Day, Kenneth; Absher, Devin; Napolitano, Constanza; Silveira, Leandro; David, Victor A; O'Brien, Stephen J; Menotti-Raymond, Marilyn; Barsh, Gregory S; Eizirik, Eduardo

2015-02-01

Morphological variation in natural populations is a genomic test bed for studying the interface between molecular evolution and population genetics, but some of the most interesting questions involve non-model organisms that lack well annotated reference genomes. Many felid species exhibit polymorphism for melanism but the relative roles played by genetic drift, natural selection, and interspecies hybridization remain uncertain. We identify mutations of Agouti signaling protein (ASIP) or the Melanocortin 1 receptor (MC1R) as independent causes of melanism in three closely related South American species: the pampas cat (Leopardus colocolo), the kodkod (Leopardus guigna), and Geoffroy's cat (Leopardus geoffroyi). To assess population level variation in the regions surrounding the causative mutations we apply genomic resources from the domestic cat to carry out clone-based capture and targeted resequencing of 299 kb and 251 kb segments that contain ASIP and MC1R, respectively, from 54 individuals (13-21 per species), achieving enrichment of ~500-2500-fold and ~150x coverage. Our analysis points to unique evolutionary histories for each of the three species, with a strong selective sweep in the pampas cat, a distinctive but short melanism-specific haplotype in the Geoffroy's cat, and reduced nucleotide diversity for both ancestral and melanism-bearing chromosomes in the kodkod. These results reveal an important role for natural selection in a trait of longstanding interest to ecologists, geneticists, and the lay community, and provide a platform for comparative studies of morphological variation in other natural populations.

7Be content in rainfall and soil deposition in South American coastal ecosystems

International Nuclear Information System (INIS)

Cardoso, R.; Ayub, J. Juri; Anjos, Roberto Meigikos dos; Cid, Alberto Silva; Velasco, H.

2011-01-01

Full text: Research about input, circulation and accumulation of natural and anthropogenic radionuclides in terrestrial ecosystems allows examining sources, establishing time scales and elucidating environmental processes. Thinking this way, researchers at UFF and UNSL have applied short-lived particle-reactive tracers to understand the behaviour of species evolution, functioning and restorations of natural and semi-natural ecosystems as well as to investigate the patterns and frequency of disturbances due to modern global changes. This can be accomplished through a detailed understanding on the hydrology and water circulation pattern, soil characteristics, erosion, resuspension, reduction/oxidation, speciation, precipitation and accumulation, diagenetic processes and microbial activities. 7 Be is a natural radionuclide (Eγ = 477.6 keV, t 1 / 2 = 53.3 d), which originates in the upper atmosphere as a result of bombardment by cosmic rays. The global distribution of this radionuclide provides a valuable means for testing and validating global circulation models on short time-scales. Its removal from the atmosphere by wet or dry deposition provides a useful tool for developing and validation of models about transport processes from the troposphere to the land surface. Knowledge of site-specific atmospheric fluxes is also crucial to evaluate the impact of atmospherically delivered pollutants on terrestrial ecosystems. The distribution of South American lands on different latitudes and its diversified topography can influence the development and action of many atmospheric systems contributing to generate non-homogeneous climatic conditions in this region. Increasing anthropogenic loads can further modify the precipitation rates and hence the climate of this region. Therefore it is important to study intra-system and inter-system interactions in different South American terrestrial ecosystems. Since 2006, UNSL has been investigating the 7 Be contents in rainfall and

Bridging the gap between the deep Earth and lithospheric gravity field

Science.gov (United States)

Root, B. C.; Ebbing, J.; Martinec, Z.; van der Wal, W.

2017-12-01

Global gravity field data obtained by dedicated satellite missions can be used to study the density distribution of the lithosphere. The gravitational signal from the deep Earth is usually removed by high-pass filtering of the data. However, this will also remove any long-wavelength signal of the lithosphere. Furthermore, it is still unclear what value for the truncation limit is best suited. An alternative is to forward model the deep situated mass anomalies and subtract the gravitational signal from the observed data. This requires knowledge of the mantle mass anomalies, dynamic topography, and CMB topography. Global tomography provides the VS distribution in the mantle, which is related to the density distribution in the mantle. There are difficulties in constructing a density model from this data. Tomography relies on regularisation which smoothens the mantle anomalies. Also, the VS anomalies need to be converted to density anomalies with uncertain conversion factors. We study the observed reduction in magnitude of the density anomalies due to the regularisation of the global tomography models. The reduced magnitude of the anomalies cannot be recovered by increasing the conversion factor from VS-to-density transformation. The reduction of the tomographic results seems to resemble the effect of a spatial Gaussian filter. By determining the spectral difference between tomographic and gravimetric models a reverse filter can be constructed to reproduce correct density variations in the complete mantle. The long-wavelengths of the global tomography models are less affected by the regularisation and can fix the value of the conversion factor. However, the low degree gravity signals are also dominated by the D" region. Therefore, different approaches are used to determine the effect of this region on the gravity field. The density anomalies in the mantle, as well as the effect of CMB undulations, are forward modelled into their gravitational potential field, such that

High-energy physics, the South American way

CERN Multimedia

Katarina Anthony

2011-01-01

The 6th CERN–Latin American School of High-Energy Physics (CLASHEP) was held in Brazil from 23 March to 5 April. With its record-breaking attendance and strong international spirit, CLASHEP is yet another sign of the continent's growing particle physics community.   Participants in the 6th CERN–Latin American School of High-Energy Physics outside the Hotel Porto do Mar, Natal (Brazil), where the School was held. CLASHEP was established in 2001 as a way of engaging young Latin American scientists in the field of particle physics - particularly in the experimental aspects of research. It has played an important role in encouraging Latin American institutes to collaborate with CERN and showing how non-Member-State physicists can work as equals with Member-State nationals. “CLASHEP reflects some of CERN’s guiding policies: enlarging its membership and involving new nations in its programmes,” says Nick Ellis, director of the CERN Schools of High-Ene...

Glyphosate sustainability in South American cropping systems.

Science.gov (United States)

Christoffoleti, Pedro J; Galli, Antonio J B; Carvalho, Saul J P; Moreira, Murilo S; Nicolai, Marcelo; Foloni, Luiz L; Martins, Bianca A B; Ribeiro, Daniela N

2008-04-01

South America represents about 12% of the global land area, and Brazil roughly corresponds to 47% of that. The major sustainable agricultural system in South America is based on a no-tillage cropping system, which is a worldwide adopted agricultural conservation system. Societal benefits of conservation systems in agriculture include greater use of conservation tillage, which reduces soil erosion and associated loading of pesticides, nutrients and sediments into the environment. However, overreliance on glyphosate and simpler cropping systems has resulted in the selection of tolerant weed species through weed shifts (WSs) and evolution of herbicide-resistant weed (HRW) biotypes to glyphosate. It is a challenge in South America to design herbicide- and non-herbicide-based strategies that effectively delay and/or manage evolution of HRWs and WSs to weeds tolerant to glyphosate in cropping systems based on recurrent glyphosate application, such as those used with glyphosate-resistant soybeans. The objectives of this paper are (i) to provide an overview of some factors that influence WSs and HRWs to glyphosate in South America, especially in Brazil, Argentina and Paraguay soybean cropped areas; (ii) to discuss the viability of using crop rotation and/or cover crops that might be integrated with forage crops in an economically and environmentally sustainable system; and (iii) to summarize the results of a survey of the perceptions of Brazilian farmers to problems with WSs and HRWs to glyphosate, and the level of adoption of good agricultural practices in order to prevent or manage it. Copyright (c) 2008 Society of Chemical Industry.

Lithospheric Structure, Crustal Kinematics, and Earthquakes in North China: An Integrated Study

Science.gov (United States)

Liu, M.; Yang, Y.; Sandvol, E.; Chen, Y.; Wang, L.; Zhou, S.; Shen, Z.; Wang, Q.

2007-12-01

The North China block (NCB) is geologically part of the Archaean Sino-Korean craton. But unusual for a craton, it was thermally rejuvenated since late Mesozoic, and experienced widespread extension and volcanism through much of the Cenozoic. Today, the NCB is characterized by strong internal deformation and seismicity, including the 1976 Tangshan earthquake that killed ~250,000 people. We have started a multidisciplinary study to image the lithospheric and upper mantle structure using seismological methods, to delineate crustal kinematics and deformation via studies of neotectonics and space geodesy, and to investigate the driving forces, the stress states and evolution, and seismicity using geodynamic modeling. Both seismic imaging and GPS results indicate that the Ordos plateau, which is the western part of the NCB and a relic of the Sino-Korean craton, has been encroached around its southern margins by mantle flow and thus is experiencing active cratonic destruction. Some of the mantle flow may be driven by the Indo-Asian collision, although the cause of the broad mantle upwelling responsible for the Mesozoic thinning of the NCB lithosphere remains uncertain. At present, crustal deformation in the NCB is largely driven by gravitational spreading of the expanding Tibetan Plateau. Internal deformation within the NCB is further facilitated by the particular tectonic boundary conditions around the NCB, and the large lateral contrasts of lithospheric strength and rheology. Based on the crustal kinematics and lithospheric structure, we have developed a preliminary geodynamic model for stress states and strain energy in the crust of the NCB. The predicted long-term strain energy distribution is comparable with the spatial pattern of seismic energy release in the past 2000 years. We are exploring the cause of the spatiotemporal occurrence of large earthquakes in the NCB, especially the apparent migration of seismicity from the Weihe-Shanxi grabens around the Ordos to

Lithospheric Structure of Northeastern Tibet Plateau from P and S Receiver Functions

Science.gov (United States)

Zhang, C.; Guo, Z.; Chen, Y. J.

2017-12-01

We obtain the lithospheric structure of the Northeast Tibet (NE Tibet) along an N-S trending profile using P- and S-wave receiver function recorded by ChinArray-Himalaya II project. Both P- and S-receiver function migration images show highly consistent lithospheric features. The Moho depth is estimated to be 50 km beneath the Songpan-ganzi (SPGZ) and Qaidam-Kunlun-West Qinling (QD) blocks with little or no fluctuation. However, at the northern boundary of QD, the crust abruptly uplifts to 40 km depth within a distance of 50 km. Meanwhile, at the southernmost of QD, the Moho is found at the depth of 60 km, which forms a double Moho conversion beneath the western Qinling fault (WQF). At the Qilian block, the first order feature of the PRF image is the northward crustal thinning from 60 km to 45 km. The strong Moho fluctuations beneath the Qilian block reflects the on-going mountain building processes. Further to the north, the Moho depth begins to deepen to 55 km and then gradually thins to 40 km at the Alxa block. We observe significant Moho variations at the Central Asian Orogenic belt (CAOB). Furthermore, Moho jumps and offsets are shown beneath major thrust and strike-slip faults zones, such as the a >5 km Moho uplift across the North Qilian Fault (NQF), implying that these faults cut through the crust and partly accommodate the continuous deformation/crustal shorting that is propagated from the India-Eurasia collision. Strong negative signals found in both P and S receiver functions at around 100-150 km depth can be interpreted as the lithosphere-asthenosphere boundary (LAB). The LAB deepens from 100 km at the northern to a maximum of 150 km at the southern end of the CAOB. A relatively flat LAB with the depth of 150 km is shown beneath the Alax block, and then it gradually thins to 100 km from the QD to SPGZ. Beneath the SPGZ, our results indicate a thin and flat lithosphere ( 100 km).

Recycling of Oceanic Lithosphere: Water, fO2 and Fe-isotope Constraints

Science.gov (United States)

Bizmis, M.; Peslier, A. H.; McCammon, C. A.; Keshav, S.; Williams, H. M.

2014-01-01

Spinel peridotite and garnet pyroxenite xenoliths from Hawaii provide important clues about the composition of the oceanic lithosphere, and can be used to assess its contribution to mantle heterogeneity upon recycling. The peridotites have lower bulk H2O (approximately 70-114 ppm) than the MORB source, qualitatively consistent with melt depletion. The garnet pyroxenites (high pressure cumulates) have higher H2O (200-460 ppm, up to 550 ppm accounting for phlogopite) and low H2O/Ce ratios (less than 100). The peridotites have relatively light Fe-isotopes (delta Fe -57 = -0.34 to 0.13) that decrease with increasing depletion, while the pyroxenites are significantly heavier (delta Fe-57 up to 0.3). The observed xenolith, as well as MORB and OIB total Fe-isotope variability is larger that can be explained by existing melting models. The high H2O and low H2O/Ce ratios of pyroxenites are similar to estimates of EM-type OIB sources, while their heavy delta Fe-57 are similar to some Society and Cook-Austral basalts. Therefore, recycling of mineralogically enriched oceanic lithosphere (i.e. pyroxenites) may contribute to OIB sources and mantle heterogeneity. The Fe(3+)/Sigma? systematics of these xenoliths also suggest that there might be lateral redox gradients within the lithosphere, between juxtaposed oxidized spinel peridotites (deltaFMQ = -0.7 to 1.6, at 15 kb) and more reduced pyroxenites (deltaFMQ = -2 to -0.4, at 20-25kb). Such mineralogically and compositionally imposed fO2 gradients may generate local redox melting due to changes in fluid speciation (e.g. reduced fluids from pyroxenite encountering more oxidized peridotite). Formation of such incipient, small degree melts could further contribute to metasomatic features seen in peridotites, mantle heterogeneity, as well as the low velocity and high electrical conductivity structures near the base of the lithosphere and upper mantle.

Perceived social stress, pregnancy-related anxiety, depression and subjective social status among pregnant Mexican and Mexican American women in south Texas.

Science.gov (United States)

Fleuriet, K Jill; Sunil, T S

2014-05-01

The purpose of this study was to determine differences in subjective social status, perceived social stress, depressive symptoms, and pregnancy-related anxiety between pregnant Mexican American and Mexican immigrant women. Three hundred pregnant Mexican immigrant and Mexican American women in South Texas were surveyed for pregnancy-related anxiety, perceived social stress, depressive symptoms, and subjective social status. Pregnant Mexican immigrant women had higher levels of pregnancy-related anxiety and lower levels of depression and perceived social stress than pregnant Mexican American women. Change in these variables among Mexican immigrant women was relatively linear as time of residence in the United States increased. Mexican immigrant and Mexican American women had significantly different correlations between subjective social status, self-esteem and perceived social stress. Results indicate that subjective social status is an important psychosocial variable among pregnant Hispanic women. Results contribute to ongoing efforts to provide culturally responsive prenatal psychosocial support services.

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

Digital Repository Service at National Institute of Oceanography (India)

Rao, G.S.; Radhakrishna, M.; Sreejith, K.M.; Krishna, K.S.; Bull, J.M.

The oceanic lithosphere in the Bay of Bengal (BOB) formed 80-120 Ma following the breakup of eastern Gondwanaland. Since its formation, it has been affected by the emplacement of two long N-S trending linear aseismic ridges (85°E and Ninetyeast...

Evaluation of depressive symptoms in mid-aged women: report of a multicenter South American study.

Science.gov (United States)

Salazar-Pousada, Danny; Monterrosa-Castro, Alvaro; Ojeda, Eliana; Sánchez, Sandra C; Morales-Luna, Ingrid F; Pérez-López, Faustino R; Chedraui, Peter

2017-11-01

To evaluate depressive symptoms and related factors among mid-aged women using the 10-item Center for Epidemiologic Studies Depression Scale (CESD-10). This was a cross-sectional multicenter study in which women aged 40 to 65 from various South American countries were surveyed with the CESD-10 and a general questionnaire containing personal and partner data. In all, 864 women were interviewed from Colombia (Afro-Colombian, n = 215), Ecuador (Mestizo, n = 202), Perú (Quechua at high altitude, n = 231), and Paraguay (Mestizo, n = 216). Mean age of the whole sample was 49.1 ± 6.0 years. Although the rate of postmenopausal status was similar among studied sites, differences were observed in relation to age, parity, hormone therapy use, hot flush rate, sedentary lifestyle, chronic medical conditions, habits, and partner aspects. Median total CESD-10 score for all sites was 7.0, with a 36.0% (n = 311) having scores equal to 10 or more (suggestive of depressed mood). Higher scores were observed for Afro-Colombian and Quechua women, and also for postmenopausal and perimenopausal ones. Multivariate linear regression analysis found that depressed mood (higher CESD-10 total scores) was significantly associated with ethnicity (Afro-Colombian), hot flush severity, hormone therapy use, sedentary lifestyle, postmenopause, perceived unhealthy status, and lower education. Higher monthly coital frequency and having a healthy partner without premature ejaculation was related to lower scores, hence less depressed mood. In this mid-aged female South American sample, depressive symptoms correlated to menopausal status and related aspects, ethnicity, and personal and partner issues. All these features require further research.

Recent progress in modelling 3D lithospheric deformation

Science.gov (United States)

Kaus, B. J. P.; Popov, A.; May, D. A.

2012-04-01

Modelling 3D lithospheric deformation remains a challenging task, predominantly because the variations in rock types, as well as nonlinearities due to for example plastic deformation result in sharp and very large jumps in effective viscosity contrast. As a result, there are only a limited number of 3D codes available, most of which are using direct solvers which are computationally and memory-wise very demanding. As a result, the resolutions for typical model runs are quite modest, despite the use of hundreds of processors (and using much larger computers is unlikely to bring much improvement in this situation). For this reason we recently developed a new 3D deformation code,called LaMEM: Lithosphere and Mantle Evolution Model. LaMEM is written on top of PETSc, and as a result it runs on massive parallel machines and we have a large number of iterative solvers available (including geometric and algebraic multigrid methods). As it remains unclear which solver combinations work best under which conditions, we have implemented most currently suggested methods (such as schur complement reduction or Fully coupled iterations). In addition, we can use either a finite element discretization (with Q1P0, stabilized Q1Q1 or Q2P-1 elements) or a staggered finite difference discretization for the same input geometry, which is based on a marker and cell technique). This gives us he flexibility to test various solver methodologies on the same model setup, in terms of accuracy, speed, memory usage etc. Here, we will report on some features of LaMEM, on recent code additions, as well as on some lessons we learned which are important for modelling 3D lithospheric deformation. Specifically we will discuss: 1) How we combine a particle-and-cell method to make it work with both a finite difference and a (lagrangian, eulerian or ALE) finite element formulation, with only minor code modifications code 2) How finite difference and finite element discretizations compare in terms of

Comparative study of the atmospheric chemical composition of three South American cities

Science.gov (United States)

Vasconcellos, Pérola C.; Souza, Davi Z.; Ávila, Simone G.; Araújo, Maria P.; Naoto, Edson; Nascimento, Kátia H.; Cavalcante, Fernando S.; Dos Santos, Marina; Smichowski, Patricia; Behrentz, Eduardo

2011-10-01

PM10 samples were collected in 2008 at three sites in South America in the framework of an international project (South American Emissions Megacities, and Climate; SAEMC). The concentration of metals, metalloids, ion and organic compounds of most PM10 samples collected at three sites (Buenos Aires (BAI), Bogotá (BOG) and São Paulo (SPA)) is below the air quality standard of the respective countries. At the sites n-alkanes and carbon preference index distribution indicated the influence of petroleum residues derived from vehicular emissions. Most PAH detected are attributed to light-duty gasoline vehicles and to stationary sources. At all sites benzo[a]pyrene equivalent values mean a significant cancer risk. Sulfate, nitrate, ammonium, calcium and sodium are the most abundant water-soluble ions at the three sites. Ammonium sulfate is likely the form presented for these species formed by photochemical reactions of precursors emitted mainly by vehicles. At BAI and SPA, formate/acetate ratios indicated the contribution of photochemical reactions; on the contrary, at BOG site, acetate is predominant, indicating strong contribution of vehicular emissions. São Paulo samples showed the highest concentrations of elements among all the sites. None of the toxic or potentially toxic elements exceed the guideline values of the World Health Organization. At BAI site earth crust seems to be the major source of Fe and Mn; at SPA, anthropogenic source is responsible for Pb and Zn presences. Traffic related element is well correlated at the three sites.

Glacial refugia and the prediction of future habitat coverage of the South American lichen species Ochrolechia austroamericana.

Science.gov (United States)

Kukwa, Martin; Kolanowska, Marta

2016-12-08

The biogeographic history of lichenized fungi remains unrevealed because those organisms rarely fossilize due to their delicate, often tiny and quickly rotting thalli. Also the ecology and factors limiting occurrence of numerous taxa, especially those restricted in their distribution to tropical areas are poorly recognized. The aim of this study was to determine localization of glacial refugia of South American Ochrolechia austroamericana and to estimate the future changes in the coverage of its habitats using ecological niche modeling tools. The general glacial potential range of the studied species was wider than it is nowadays and its niches coverage decreased by almost 25% since last glacial maximum. The refugial areas were covered by cool and dry grasslands and scrubs and suitable niches in South America were located near the glacier limit. According to our analyses the further climate changes will not significantly influence the distribution of the suitable niches of O. austroamericana.

Seasonal precipitation patterns along pathways of South American low-level jets and aerial rivers

Science.gov (United States)

Poveda, Germán.; Jaramillo, Liliana; Vallejo, Luisa F.

2014-01-01

We study the seasonal dynamics of the eastern Pacific (CHOCO) and Caribbean low-level jets (LLJ), and aerial rivers (AR) acting on tropical and subtropical South America. Using the ERA-Interim reanalysis (1979-2012), we show that the convergence of both LLJs over the eastern Pacific-western Colombia contributes to the explanation of the region's world-record rainfall. Diverse variables involved in the transport and storage of moisture permit the identification of an AR over northern South America involving a midtropospheric easterly jet that connects the Atlantic and Pacific Oceans across the Andes, with stronger activity in April to August. Other major seasonal AR pathways constitute part of a large gyre originating over the tropical North Atlantic, veering to the southeast over the eastern Andes and reaching regions of northern Argentina and southeastern Brazil. We illustrate the distribution of average seasonal precipitation along the LLJs and AR pathways with data from the Tropical Rainfall Measuring Mission (1998-2011), combined with considerations of CAPE, topography, and land cover. In addition, the theory of the biotic pump of atmospheric moisture (BiPAM) is tested at seasonal time scales, and found to hold in 8 out of 12 ARs, and 22 out of 32 forest-covered tracks (64% in distance) along the ARs. Deviations from BiPAM's predictions of rainfall distribution are explained by the effects of topography, orography, and land cover types different from forests. Our results lend a strong observational support to the BiPAM theory at seasonal time scales over South American forested flat lands.

Anomalous variations of lithosphere magnetic field before several earthquakes

Science.gov (United States)

Ni, Z.; Chen, B.

2015-12-01

Based on the geomagnetic vector data measured each year since 2011 at more than 500 sites with a mean spatial interval of ~70km.we observed anomalous variations of lithospheric magnetic field before and after over 15 earthquakes having magnitude > 5. We find that the field in near proximity (about 50km) to the epicenter of large earthquakes shows high spatial and temporal gradients before the earthquake. Due to the low frequency of repeat measurements it is unclear when these variations occurred and how do them evolve. We point out anomalous magnetic filed using some circles with radius of 50km usually in June of each year, and then we would check whether quake will locat in our circles during one year after that time (June to next June). Now we caught 10 earthquakes of 15 main shocks having magnitude > 5, most of them located at less than10km away from our circles and some of them were in our circles. Most results show that the variations of lithosphere magnetic filed at the epicenter are different with surrending backgroud usually. When we figure out horizontal variations (vector) of lithosphere magnetic field and epicenter during one year after each June, we found half of them show that the earthquakes will locat at "the inlands in a flowing river", that means earthquakes may occur at "quiet"regions while the backgroud show character as"flow" as liquid. When we compared with GPS results, it appears that these variations of lithospere magnetic field may also correlate with displacement of earth's surface. However we do not compared with GPS results for each earthquake, we are not clear whether these anomalous variations of lithospere magnetic field may also correlate with anomalous displacement of earth's surface. Future work will include developing an automated method for identifying this type of anomalous field behavior and trying to short repeat measurement period to 6 month to try to find when these variations occur.

The lithosphere-asthenosphere boundary observed with USArray receiver functions

Directory of Open Access Journals (Sweden)

P. Kumar

2012-05-01

Full Text Available The dense deployment of seismic stations so far in the western half of the United States within the USArray project provides the opportunity to study in greater detail the structure of the lithosphere-asthenosphere system. We use the S receiver function technique for this purpose, which has higher resolution than surface wave tomography, is sensitive to seismic discontinuities, and is free from multiples, unlike P receiver functions. Only two major discontinuities are observed in the entire area down to about 300 km depth. These are the crust-mantle boundary (Moho and a negative boundary, which we correlate with the lithosphere-asthenosphere boundary (LAB, since a low velocity zone is the classical definition of the seismic observation of the asthenosphere by Gutenberg (1926. Our S receiver function LAB is at a depth of 70–80 km in large parts of westernmost North America. East of the Rocky Mountains, its depth is generally between 90 and 110 km. Regions with LAB depths down to about 140 km occur in a stretch from northern Texas, over the Colorado Plateau to the Columbia basalts. These observations agree well with tomography results in the westernmost USA and on the east coast. However, in the central cratonic part of the USA, the tomography LAB is near 200 km depth. At this depth no discontinuity is seen in the S receiver functions. The negative signal near 100 km depth in the central part of the USA is interpreted by Yuan and Romanowicz (2010 and Lekic and Romanowicz (2011 as a recently discovered mid-lithospheric discontinuity (MLD. A solution for the discrepancy between receiver function imaging and surface wave tomography is not yet obvious and requires more high resolution studies at other cratons before a general solution may be found. Our results agree well with petrophysical models of increased water content in the asthenosphere, which predict a sharp and shallow LAB also in continents (Mierdel et al., 2007.

3D Thermo-Mechanical Models of Plume-Lithosphere Interactions: Implications for the Kenya rift

Science.gov (United States)

Scheck-Wenderoth, M.; Koptev, A.; Sippel, J.

2017-12-01

We present three-dimensional (3D) thermo-mechanical models aiming to explore the interaction of an active mantle plume with heterogeneous pre-stressed lithosphere in the Kenya rift region. As shown by the recent data-driven 3D gravity and thermal modeling (Sippel et al., 2017), the integrated strength of the lithosphere for the region of Kenya and northern Tanzania appears to be strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localization and propagation of rifting. In order to test this hypothesis, we have performed a series of ultra-high resolution 3D numerical experiments that include a coupled mantle/lithosphere system in a dynamically and rheologically consistent framework. In contrast to our previous studies assuming a simple and quasi-symmetrical initial condition (Koptev et al., 2015, 2016, 2017), the complex 3D distribution of rock physical properties inferred from geological and geophysical observations (Sippel et al., 2017) has been incorporated into the model setup that comprises a stratified three-layer continental lithosphere composed of an upper and lower crust and lithospheric mantle overlaying the upper mantle. Following the evidence of the presence of a broad low-velocity seismic anomaly under the central parts of the East African Rift system (e.g. Nyblade et al, 2000; Chang et al., 2015), a 200-km radius mantle plume has been seeded at the bottom of a 635 km-depth model box representing a thermal anomaly of 300°C temperature excess. In all model runs, results show that the spatial distribution of surface deformation is indeed strongly controlled by crustal structure: within the southern part of the model box, a localized narrow zone stretched in NS direction (i.e. perpendicularly to applied far-field extension) is aligned along a structural boundary within the lower crust, whereas in the northern part of the model domain, deformation is more diffused and its eastern limit coincides with

Revision of the Bee Genus Chlerogella (Hymenoptera, Halictidae, Part II: South American Species and Generic Diagnosis

Directory of Open Access Journals (Sweden)

Michael Engel

2010-05-01

Full Text Available The South American species of the rare bee genus Chlerogella Michener (Halictinae: Augochlorini are revised, completing the study of the genus. Chlerogella diversity is significantly expanded beyond the five previously described South American species of Cherlogella azurea (Enderlein, comb. n., C. nasus (Enderlein, C. mourella Engel, C. octogesima (Brooks & Engel, comb. n., and C. buyssoni (Vachal. Twenty-two new species are described – C. agaylei sp. n., C. arhyncha sp. n., C. borysthenis sp. n., C. breviceps sp. n., C. cochabambensis sp. n., C. cooperella sp. n., C. cyranoi sp. n., C. dolichorhina sp. n., C. elysia sp. n., C. eumorpha sp. n., C. euprepia sp. n., C. hauseri sp. n., C. hypermeces sp. n., C. materdonnae sp. n., C. oresbios sp. n., C. picketti sp. n., C. rostrata sp. n., C. silvula sp. n., C. terpsichore sp. n., C. tychoi sp. n., C. vachali sp. n., C. xuthopleura sp. n. – and the distribution of the genus is expanded beyond Perú and Ecuador to include Bolivia, Colombia, and Venezuela. The female of C. azurea is described for the first time while the placement of Halictus buyssoni Vachal in Chlerogella is considered tentative, following the usage of previous authors, as the holotype and sole specimen is untraceable. The genus is newly diagnosed based on a greater understanding of variation in malar length across the species and a dichotomous key is provided. New floral records for species of Chlerogella include Psychotria pongoana Standl. (Rubiaceae and a putative record on Phragmopedium longifolium (Warsz. & Rchb.f. Rolfe (Orchidaceae.

Continents as lithological icebergs: The importance of buoyant lithospheric roots

Science.gov (United States)

Abbott, D.H.; Drury, R.; Mooney, W.D.

1997-01-01

An understanding of the formation of new continental crust provides an important guide to locating the oldest terrestrial rocks and minerals. We evaluated the crustal thicknesses of the thinnest stable continental crust and of an unsubductable oceanic plateau and used the resulting data to estimate the amount of mantle melting which produces permanent continental crust. The lithospheric mantle is sufficiently depleted to produce permanent buoyancy (i.e., the crust is unsubductable) at crustal thicknesses greater than 25-27 km. These unsubductable oceanic plateaus and hotspot island chains are important sources of new continental crust. The newest continental crust (e.g., the Ontong Java plateau) has a basaltic composition, not a granitic one. The observed structure and geochemistry of continents are the result of convergent margin magmatism and metamorphism which modify the nascent basaltic crust into a lowermost basaltic layer overlain by a more silicic upper crust. The definition of a continent should imply only that the lithosphere is unsubductable over ??? 0.25 Ga time periods. Therefore, the search for the oldest crustal rocks should include rocks from lower to mid-crustal levels.

South Korea

International Nuclear Information System (INIS)

Hayes, P.

1990-01-01

South Korea aspires to become a major nuclear supplier in the world nuclear market. There is no doubt that South Korea has great potential to fulfill these aspirations. South Korea is well positioned in terms of competitiveness, market relationships, institutional capability, ability to deliver, and commitment to nonproliferation values. As a mercantilist state, South Korea hopes to capitalize on its close relationships with transnational nuclear corporations in this endeavor. It hopes to participate in two- or three-way joint ventures---especially with the American firms that have traditionally predominated in the South Korean domestic nuclear business---to market their nuclear wares abroad. This paper is divided into four parts. The first section describes South Korea's intent to become a nuclear supplier in the 1990s. It delineates the networks of prior transactions and relationships that South Korea may use to penetrate export markets. The second section reviews South Korea's nuclear export potential, particularly its technological acquisitions from the domestic nuclear program. These capabilities will determine the rate at which South Korea can enter specific nuclear markets. The third section describes the institutional framework in South Korea for the review and approval of nuclear exports