Science.gov

Sample records for craton sao francisco

  1. Combined magnetic fabrics and microstructures: evidence of an early magmatic event in the Paleoproterozoic Teofilandia granitoids (Sao Francisco craton, Brazil)

    NASA Astrophysics Data System (ADS)

    Nascimento, H. S.; Bouchez, J. L.; Nedelec, A.; Sabate, P.

    2003-04-01

    The study area concerns the southern part of the Paleoproterozoic (2.2--2.0 Ga) Itapicuru Greenstone Belt (Serrinha Block), eastern border of the Sao Francisco craton (Brazil). This is a problematic area, occupied by the Teofilandia granitoids (granites, granodiorites, tonalites, gneisses), where the overall N-S map structures rotate to E-W toward the south of the Serrinha Block. A set of 160 sampling stations covering ˜220 km^2 have been subjected to a detailed structural study combining magnetic fabrics AND microstructural characters. Three types of microstructures, corresponding to three successive events, helped to sort the different magnetic fabrics. (1) Purely magmatic microstructures, sometimes slightly overprinted by the following events, characterize preserved sectors that carry N-S trending magnetic lineations. Around these relictual sectors (2) the granitoids display typical high-T orthogneissic microstructures, attesting for their pervasive deformation in the solid-state parallel to E-W (±30^o), as observed in the field and attested by the E-W trending magnetic lineations. Finally (3) low-T/high-stress, sub-mylonitic microstructures under greenschist facies conditions, affect the area with various intensities, and are associated with E-W trending magnetic lineations. We conclude that the Teofilandia granitoids reveal their N-S-directed emplacement at ˜2.1 Ga, probably coeval with the N-S stretch of the whole Rio Itapicuru belt, within the relictual cores of kilometer-thick lenses that were preserved from the following events. The pervasive high-T structures, with foliations dipping to the south and E-W stretching directions, are ascribed to a lateral ramp of the shear event that accompanied the convergence of the Serrinha block with the Salvador Curaca mobile belt. The final, low-T/high stress event is likely coeval with the hydrothermal episode responsible for the gold mineralizations of the Teofilandia area at 2.08 Ga.

  2. Agriculture, Rio Sao Francisco, Brazil, South America

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The large field patterns in this view of the Rio Sao Francisco basin, Brazil, South America, (11.5S, 43.5W) indicate a commercial agriculture venture; family subsistence farms are much smaller and laid out in different patterns. Land clearing in Brazil has increased at an alarming rate in recent years and preliminary estimates suggest a 25 to 30% increase in deforestation since 1984. The long term impact on the ecological processes are still unknown.

  3. Radar image of Rio Sao Francisco, Brazil

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This radar image acquired by SRTM shows an area south of the Sao Francisco River in Brazil. The area is predominantly scrub forest. Areas such as these are difficult to map by traditional methods because of frequent cloud cover and local inaccessibility. Image brightness differences in this image are caused by differences in vegetation type and density. Tributaries of the Sao Francisco are visible in the upper right. The Sao Francisco River is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, forestation and human influences on ecosystems.

    This radar image was obtained by the Shuttle Radar Topography Mission as part of its mission to map the Earth's topography. The image was acquired by just one of SRTM's two antennas, and consequently does not show topographic data but only the strength of the radar signal reflected from the ground. This signal, known as radar backscatter, provides insight into the nature of the surface, including its roughness, vegetation cover, and urbanization.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.

  4. Shaded Relief of Rio Sao Francisco, Brazil

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This topographic image acquired by SRTM shows an area south of the Sao Francisco River in Brazil. The scrub forest terrain shows relief of about 400 meters (1300 feet). Areas such as these are difficult to map by traditional methods because of frequent cloud cover and local inaccessibility. This region has little topographic relief, but even subtle changes in topography have far-reaching effects on regional ecosystems. The image covers an area of 57 km x 79 km and represents one quarter of the 225 km SRTM swath. Colors range from dark blue at water level to white and brown at hill tops. The terrain features that are clearly visible in this image include tributaries of the Sao Francisco, the dark-blue branch-like features visible from top right to bottom left, and on the left edge of the image, and hills rising up from the valley floor. The San Francisco River is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, forestation and human influences on ecosystems.

    This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter

  5. The Brasiliano São Francisco craton revisited (central Brazil)

    NASA Astrophysics Data System (ADS)

    Trompette, R.; Uhlein, A.; da Silva, M. E.; Karmann, I.

    1992-08-01

    The Brasiliano (˜600 Ma) belt of Paramirim divides the São Francisco craton (as defined by Almeida, 1967, 1969) into two parts: to the west is the São Francisco craton proper; to the east is the Salvador craton, forming an extension of the Congo craton. The basement of the Paramirim belt, of Archean and Early Proterozoic age, is intruded by subalkaline granitoids dated around 1700 Ma. The cover, known as the Espinhaço Supergroup, consists of felsic magmatic rocks, overlain by clastic sediments depoited in a continental rift during the time interval ˜1700-1100 Ma. The Espinhaço Supergroup was deformed during the Brasiliano orogeny, at about 600 Ma. It is characterized by shallow-dipping, submeridional, large-scale ductile shear zones with western vergence and mineral and/or extension lineation indicating tectonic transport from east to west. These ductile shear zones extend south into the outer units of the Brasiliano Araçuaí mobile belt and the Lower Proterozoic of the Quadrilatero Ferrifero. There are no structural data supporting the hypothesis of a Middle Proterozoic deformation of the Paramirim belt that should have been obliterated during the Brasiliano orogeny. However, a possible pre-Brasiliano deformation does not affect the question of the division of the Brasiliano-São Francisco craton.

  6. Agricultural and Ranching area, Rio Sao Francisco, Brazil

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This agricultural and Ranching area, Rio Sao Francisco, Brazil (13.0S, 43.5W) has been under study for several years. See scene STS-31-92-045 for comparison. This area has many small single family subsistence farms, large square and rectangular commercial farms and pastures for livestock grazing. Over the several years of observation, the number and size of farms has increased and center-pivot, swing-arm irrigation systems have been installed.

  7. Geotectonic setting and metallogeny of the northern São Francisco craton, Bahia, Brazil

    NASA Astrophysics Data System (ADS)

    Teixeira, João Batista Guimarães; da Silva, Maria da Glória; Misi, Aroldo; Cruz, Simone Cerqueira Pereira; da Silva Sá, José Haroldo

    2010-11-01

    This paper aims at establishing a tectonic and temporal framework to characterize the metallogenic processes that contributed to the origin of the mineral provinces in the northern São Francisco Craton. Many Archean mineralizations (eg. massive sulfide zinc, lead, zinc and copper, besides magnesite-talc, iron-titanium-vanadium, iron, chromite and manganese) were generated before the assembly of the Craton. Deposits of chromite, nickel, gold and emerald were produced during the Paleoproterozoic orogenic cycle, when the Craton was amalgamated into the Atlantica paleocontinent. An extension event is recorded in the Neoproterozoic, during the breakup of Rodinia, associated with deposits of phosphorite and uranium. Kimberlite diamond and gold mineralization were generated during the Brasiliano orogenic cycle, coeval with the amalgamation of West Gondwana. A long-lasting and rather uniform crustal stress is recorded in the area during the Cambrian period. Resetting of the isotopic and magnetic systems that affected the Neoproterozoic sediments of the Irecê Basin at about 520 Ma was attributed to the regional-scale fluid migration and mineralization in the aftermath of the Brasiliano orogenic cycle.

  8. Magnetotelluric deep soundings, gravity and geoid in the south São Francisco craton: Geophysical indicators of cratonic lithosphere rejuvenation and crustal underplating

    NASA Astrophysics Data System (ADS)

    Pinto, Luis Gustavo Rodrigues; de Pádua, Marcelo Banik; Ussami, Naomi; Vitorello, Ícaro; Padilha, Antonio Lopes; Braitenberg, Carla

    2010-09-01

    In the south São Francisco craton a circular and 8-m amplitude geoid anomaly coincides with the outcropping terrain of an Archean-Paleoproterozoic basement. Broadband magnetotelluric (MT) data inversions of two radial profiles within the positive geoid and Bouguer gravity anomaly yield geo-electrical crustal sections, whereby the lower crust is locally more conductive (10 to 100 Ωm) in spatial coincidence with a denser lower crust modeled by the gravity data. This anomalous lower crust may have resulted from magmatic underplating, associated with Mesoarchean and Proterozoic episodes of tholeiitic dike intrusion. Long-period MT soundings reveal a low electrical resistivity mantle (20 to 200 Ωm) from depths beyond 120 km. Forward geoid modeling, using the scope of the low electrical resistivity region within the mantle as a constraint, entails a density increase (40 to 50 kg/m 3) possibly due to Fe enrichment of mantle minerals. However, this factor alone does not explain the observed resistivity. A supplemented presence of small amounts of percolated carbonatite melting (~ 0.005 vol.%), dissolved water and enhanced oxygen fugacity within the peridotitic mantle are viable agents that could explain the less resistive upper mantle. We propose that metasomatic processes confined in the sub-continental lithospheric mantle foster the conditions for a low degree melting with variable CO 2, H 2O and Fe content. Even though the precise age of this metasomatism is unknown it might be older than the Early Cretaceous based on the evidence that a high-degree of melting in a lithospheric mantle impregnated with carbonatites originated the tholeiitic dike intrusions dispersed from the southeastern border of the São Francisco craton, during the onset of the lithosphere extension and break-up of the western Gondwana. The proxies are the NE Paraná and Espinhaço (130 Ma, Ar/Ar ages) tholeiitic dikes, which contain (~ 3%) carbonatites in their composition. The occurrence of a

  9. Lutzomyia longipalpis s.l. in Brazil and the impact of the Sao Francisco River in the speciation of this sand fly vector.

    PubMed

    Coutinho-Abreu, Iliano V; Sonoda, Ivan V; Fonseca, Jose A; Melo, Marcia A; Balbino, Valdir Q; Ramalho-Ortigão, Marcelo

    2008-01-01

    In our recently published article "Lutzomyia longipalpis s.l. in Brazil and the impact of the Sao Francisco River in the speciation of this sand fly vector" by Iliano V. Coutinho-Abreu et al. a sentence located in paragraph 8 in the Discussion section had its meaning altered due to the improper insertion of three words. PMID:18834535

  10. Dynamic study of the upper Sao Francisco River and the Tres Marias reservoir using MSS/LANDSAT images. [Brazil

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Sausen, T. M.

    1981-01-01

    The use of LANDSAT multispectral ban scanner imagery to verify the relationship between the behavior of the Tres Marias reservoir and the dynamics of the Sao Francisco River supply basin is described. The dispersion of suspended sediments and their concentration in the surface layers of the water are considered. A five year survey of the region during both dry and rainy seasons was performed. The drainage network was analyzed based on the patterns of dessication, water rises and soil use in the supply basin. Surface layers of the reservoir were tabulated as a function of the levels of gray in the imagery. In situ observations of water depth and reflectance were performed. Ground truth and LANDSAT data were correlated to determine the factors affecting the dynamics of the supply basin.

  11. Superposed folding and associated fracturing influence hypogene karst development in Neoproterozoic carbonates, São Francisco Craton, Brazil

    NASA Astrophysics Data System (ADS)

    Ennes-Silva, Renata A.; Bezerra, Francisco H. R.; Nogueira, Francisco C. C.; Balsamo, Fabrizio; Klimchouk, Alexander; Cazarin, Caroline L.; Auler, Augusto S.

    2016-01-01

    Porosity and permeability along fractured zones in carbonates could be significantly enhanced by ascending fluid flow, resulting in hypogene karst development. This work presents a detailed structural analysis of the longest cave system in South America to investigate the relationship between patterns of karst conduits and regional deformation. Our study area encompasses the Toca da Boa Vista (TBV) and Toca da Barriguda (TBR) caves, which are ca. 107 km and 34 km long, respectively. This cave system occurs in Neoproterozoic carbonates of the Salitre Formation in the northern part of the São Francisco Craton, Brazil. The fold belts that are around and at the craton edges were deformed in a compressive setting during the Brasiliano orogeny between 750 and 540 Ma. Based on the integrated analysis of the folds and brittle deformation in the caves and in outcrops of the surrounding region, we show the following: (1) The caves occur in a tectonic transpressive corridor along a regional thrust belt; (2) major cave passages, at the middle storey of the system, considering both length and frequency, developed laterally along mainly (a) NE-SW to E-W and (b) N to S oriented anticline hinges; (3) conduits were formed by dissolutional enlargement of subvertical joints, which present a high concentration along anticline hinges due to folding of competent grainstone layers; (4) the first folding event F1 was previously documented in the region and corresponds with NW-SE- to N-S-trending compression, whereas the second event F2, documented for the first time in the present study, is related to E-W compression; and (5) both folding events occurred during the Brasiliano orogeny. We conclude that fluid flow and related dissolution pathways have a close relationship with regional deformation events, thus enhancing our ability to predict karst patterns in layered carbonates.

  12. Characterization of Sao Francisco basin, Brazil: joint inversion of multiple geophysical data

    NASA Astrophysics Data System (ADS)

    Solon, F. F.; Fontes, S. L.

    2013-05-01

    The need to improve the characterization of the near surface and to generate consistent images of multiple geophysical data has led us to adopt a cross-gradient joint inversion methodology. We applied this method to characterize the basement fracture-zones and heterogeneous reservoir rocks underneath thick overburden at São Francisco basin in Brazil. The basin is mainly filled by Neoproterozoic clastic and carbonates rocks of the Bambui group formed in the Upper Proterozoic (Vendian) which makes the São Francisco basin interesting for hydrocarbon prospecting. Exploring the combined use of different geophysical methods will enhance the structural resemblance in the images that each one provides. The strategy explored in this work is to use a two-dimensional structured-coupled joint inversion from Gallardo and Meju (2003) applying to four data sets: land seismic reflection, magnetotelluric (MT), gravity and magnetic data sets along a 100 km profile across a region called Remanso do Fogo. For the joint inversion approach, we need to determine appropriate processing parameters to better estimate the individual contribution from each geophysical data type. A first experiment using three data sets (gravity, magnetic and MT) is shown in fig. 1. The evolution of the joint inversion showed that the solution is controlled by the development of common features in all models. The results of joint inversion using three and four models clearly mapped the compartmentation of the basement in this sector of São Francisco Basin. Also it is possible to identify the units of Bambui group, resulting in a constrained geological interpretation.; Fig. 1: Sections obtained in interaction 6 after joint inversion of gravity, magnetic and MT data.

  13. Lutzomyia longipalpis s.l. in Brazil and the impact of the Sao Francisco River in the speciation of this sand fly vector.

    PubMed

    Coutinho-Abreu, Iliano V; Sonoda, Ivan V; Fonseca, Jose A; Melo, Marcia A; Balbino, Valdir Q; Ramalho-Ortigão, Marcelo

    2008-01-01

    Lutzomyia longipalpis s.l. (Diptera: Psychodidae) is the principal vector of Leishmania infantum chagasi in the Americas, and constitutes a complex of species. Various studies have suggested an incipient speciation process based on behavioral isolation driven by the chemotype of male sexual pheromones. It is well known that natural barriers, such as mountains and rivers can directly influence population divergence in several organisms, including insects. In this work we investigated the potential role played by the Sao Francisco River in eastern Brazil in defining the current distribution of Lu. longipalpis s.l. Our studies were based on analyses of polymorphisms of the cytochrome b gene (cyt b) sequences from Lu. longipalpis s.l. available in public databases, and from additional field-caught individuals. Altogether, 9 distinct populations and 89 haplotypes were represented in the analyses. Lu. longipalpis s.l. populations were grouped according to their distribution in regards to the 10 degrees S parallel: north of 10 degrees S (<10 degrees S); and south of 10 degrees S (>10 degrees S). Our results suggest that although no polymorphisms were fixed, moderate genetic divergences were observed between the groups analyzed (i.e., FST = 0.184; and Nm = 2.22), and were mostly driven by genetic drift. The population divergence time estimated between the sand fly groups was about 0.45 million years (MY), coinciding with the time of the change in the course of the Sao Francisco River, during the Mindel glaciation. Overall, the polymorphisms on the cyt b haplotypes and the current speciation process detected in Lu. longipalpis s.l. with regards to the distribution of male sexual pheromones suggest a role of the Sao Francisco River as a significant geographical barrier in this process. PMID:18549496

  14. Neoarchean and Paleoproterozoic granitoids marginal to the Jeceaba-Bom Sucesso lineament (SE border of the southern São Francisco craton): Genesis and tectonic evolution

    NASA Astrophysics Data System (ADS)

    Campos, José Carlos Sales; Carneiro, Maurício Antônio

    2008-12-01

    The sialic crust of the southern São Francisco craton along the Jeceaba-Bom Sucesso lineament, central-southern part of Minas Gerais (Brazil), encompasses, among other rock types, Neoarchean and Paleoproterozoic granitoids. These granitoids, according to their petrographic, lithogeochemical and geochronologic characteristics, were grouped into two Neoarchean suites (Samambaia-Bom Sucesso and Salto Paraopeba-Babilônia) and three Paleoproterozoic suites (Cassiterita-Tabuões, Ritápolis and São Tiago). Varied processes and tectonic environments were involved in the genesis of these suites. In particular, the lithogeochemistry of the (Archean and Paleoproterozoic) TTG-type granitoids indicates an origin by partial melting of hydrated basaltic crust in a subduction environment. In the Neoarchean, between 2780 and 2703 Ma, a dominant TTG granitoid genesis related to an active continental margin was followed by another granite genesis related to crustal anatexis processes at 2612-2550 Ma. In the Paleoproterozoic, the generation of TTG and granites s.s. occurred at three distinct times: 2162, 2127 and 1887 Ma. This fact, plus the rock-type diversity produced by this granite genesis, indicates that the continental margin of the southern portion of the São Francisco craton was affected by more than one consumption episode of oceanic crust, involving different island arc segments, and the late Neoarchean consolidate continent. A Paleoproterozoic tectonic evolution in three stages is proposed in this work.

  15. Disclosing the Paleoarchean to Ediacaran history of the São Francisco craton basement: The Porteirinha domain (northern Araçuaí orogen, Brazil)

    NASA Astrophysics Data System (ADS)

    Silva, Luiz Carlos da; Pedrosa-Soares, Antonio Carlos; Armstrong, Richard; Pinto, Claiton Piva; Magalhães, Joana Tiago Reis; Pinheiro, Marco Aurélio Piacentini; Santos, Gabriella Galliac

    2016-07-01

    This geochronological and isotopic study focuses on one of the Archean-Paleoproterozoic basement domains of the São Francisco craton reworked in the Araçuaí orogen, the Porteirinha domain, Brazil. It also includes a thorough compilation of the U-Pb geochronological data related to the adjacent Archean and Rhyacian terranes from the São Francisco craton and Araçuaí orogen. The main target of this study is the TTG gneisses of the Porteirinha complex (Sample 1). The gneiss dated at 3371 ± 6 Ma unraveled a polycyclic evolution characterized by two metamorphic overprinting episodes, dated at 3146 ± 24 Ma (M1) and ca. 600 Ma (M2). The former (M1) is so far the most reliable evidence of the oldest metamorphic episode ever dated in Brazil. The latter (M2), in turn, is endemic in most of the exposed eastern cratonic margin within the Araçuaí orogen. Whole-rock Sm-Nd analysis from the gneiss provided a slightly negative εNd(t3370) = - 0.78 value, and a depleted mantle model (TDM) age of 3.5 Ga, indicating derivation mainly from the melting of a ca. 3.5 Ga tholeiitic source. Sample 2, a K-rich leuco-orthogneiss from the Rio Itacambiriçu Complex, was dated at 2657 ± 25 Ma and also presents a ca. 600 Ma M2 overprinting M2 age. The other two analyses were obtained from Rhyacian granitoids. Sample 3 is syn-collisional, peraluminous leucogranite from the Tingui granitic complex, showing a crystallization age of 2140 ± 14 Ma and strong post-crystallization Pb*-loss, also ascribed to the Ediacaran overprinting. Accordingly, it is interpreted as a correlative of the late Rhyacian (ca. 2150-2050 Ma) collisional stage of the Mantiqueira orogenic system/belt (ca. 2220-2000 Ma), overprinted by the Ediacaran collage. Sample 4 is a Rhyacian post-orogenic (post-collisional), mixed-source, peralkaline, A1-type suite, with a crystallization age of 2050 ± 10 Ma, presenting an important post-crystallization Pb*-loss related to Ediacaran collision. The focused region records some

  16. Fission track analysis of apatites from São Francisco craton and Mesozoic alcaline-carbonatite complexes from central and southeastern Brazil

    NASA Astrophysics Data System (ADS)

    Amaral, G.; Born, H.; Hadler, J. C. N.; Iunes, P. J.; Kawashita, K.; Machado, D. L.; Oliveira, E. P.; Paulo, S. R.; Tello, C. A. S.

    1997-07-01

    Thermal histories on seven Brazilian apatites were obtained by fission track analysis using Monte Carlo simulations. The apatites were collected from two distinct geotectonic provinces. One group, originated from São Francisco craton, represents a typical cratonic domain with Proterozoic and Eopaleozoic rocks and yielded Permo-Triassic ages (counted since the instant when temperature was low enough so that the damage produced by fission tracks in apatite started to be preserved). The common thermal history accepted by all samples of this group is a linear cooling from ~90 to ~25 °C for the last 240 Ma, in agreement with present day thermal gradient and denudation rates. The other group, from Mesozoic alkaline-carbonatite complexes, in central and southeastern Brazil, yielded Cretaceous ages, close to those of the intrusions. For the samples of central Brazil, fission track analysis suggests a slow cooling from ~95 ° to ~85 °C between 90 and 60 Ma ago, followed by a faster cooling from ~85 ° to ~27 °C for the last 60 Ma. Otherwise, two trends exist for the samples of southeastern Brazil. The primary one is an increase in temperature from ~75 ° to ~95 °C, which occurred between 140 and 60 Ma ago. In this period, there is also another trend: a cooling from ~100 ° to ~80 °C. However, both trends are followed by a common thermal history during the last 60 Ma: a cooling from approximately ~80 ° to ~25 °C.

  17. Studies of the Hydrological Cycle for the Sao Francisco Basin using a combination of modeling and satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Rebello, V.; Martins, T.; Rotunno Filho, O. C.; Araujo, A. A.; Lakshmi, V.

    2015-12-01

    The EPHSTC land surface hydrological model is used here in a case study for the São Francisco River Basin (area 630.000 km²) located in Northeast Brazil. The model solves the surface fluxes using ISBA prognostic equations and a gravitational drainage, a vertical diffusion process. A mechanism for subgrid-scale surface runoff generation was added. Another feature implemented in this model is the lateral redistribution of the soil water. This work will be a first attempt of evaluating EPHSTC results in a Brazil catchment for a long time period - 2001 to 2014. The GLDAS model input surface parameters would be used. Validation will be performed by the model values of soil moisture with corresponding GDLAS soil moisture (0-10,10-40,40-60 cm) and latent and heat fluxes. The two time series will be compared by calculation of the coefficient of determination and root mean square error.

  18. Evolution of the Paleoproterozoic crust in the southern portion of the San Francisco Craton - Cinturão Mineiro- Brazil

    NASA Astrophysics Data System (ADS)

    Barbosa, N. S.; Teixeira, W.; Avila, C.

    2013-12-01

    The Mineiro belt was formed by continuous amalgamation of magmatic arcs, largely juvenile whereas crustal contamination is also present. Its evolution lasted about 450 Ma, from the Siderian to the Orosirian period (2450-2000 Ma), as part of the Minas accretionary orogeny that evolved along an Archean/Early Proterozoic foreland. Paleoproterozoic granitic bodies outcrops throughout the Mineiro belt and are related to the tectonic evolution of the Minas accretionary orogen, which was interpreted as an accretion of Resende Costa (2.33 Ga), Serrinha (2.22 Ga), Ritápolis (2.15 Ga) and Alto do Maranhão (2.10 Ga) magmatic arcs, where the vast difference in ages points to a Paleoproterozoic polycyclic evolution for this sector of the craton. The metagranitoids are heterogeneous, have variable sizes, and some of them may reach batholitic proportions, as it is the case of the pluton Ritápolis. Spatially, these granitoids are limited to the north by units represented by Archean gneissic migmatitic complex, by the Rio das Velhas Supergroup (3.2-2.7 Ga) and by the Paleoproterozoic Minas Supergroup (2.6-2.4 Ga). Southward it is limited by the Meso-Neoproterozoic metasedimentary sequences whose minimum ages of deposition correspond, respectively, to 1.53 Ga, 1.38 Ga and between 1.14 Ga and 950 Ma (Ribeiro et al., 2013; Bethlehem et al., 2012). Geochronological studies recently developed in this portion of the Paleoproterozoic Craton show that its evolution begins in the Siderian and extends until the Riacian (Ávila et al., 2010; Seixas et al., 2012), where small crustal fragments correspond to remnants of the first arcs generated in the Siderian Mineiro belt (e.g.: Cassiterita orthogneiss). The rocks representative of these arcs consists mainly of orthogneisses with tonalitic to granitic compositions. The Cassiterita tonalitic orthogneiss outcrops north of the Lenheiro shear zone. The rocks of this body are slighty foliated; this foliation is characterized by the preferred

  19. U-Pb ages and geochemistry of mafic dyke swarms from the Uauá Block, São Francisco Craton, Brazil: LIPs remnants relevant for Late Archaean break-up of a supercraton

    NASA Astrophysics Data System (ADS)

    Oliveira, E. P.; Silveira, E. M.; Söderlund, U.; Ernst, R. E.

    2013-08-01

    The São Francisco Craton (SFC) is an Archaean craton that hosts a significant number of mafic intrusions. Previous attempts to date the igneous emplacement of these rocks are limited to a few dates of poor precision. Here, two dyke swarms from the Uauá Block in the northeastern portion of the craton were dated using U-Pb on baddeleyite (ID-TIMS) and zircon (SIMS). The older dyke swarm trends mainly N-S to NW-SE (but also NE) and comprises norite dykes, whereas the younger dykes are tholeiite and trend NE-SW. The ages of 2726.2 ± 3.2 and 2623.8 ± 7.0 Ma date dykes of noritic and tholeiitic compositions, respectively. The older age matches the ages of several Archaean-Large Igneous Provinces (tholeiitic-komatiite greenstone belts and continental flood basalts) worldwide and represents part of a feeder system, but the younger age is similar to Andean style continental margin magmatism in the São Francisco and Zimbabwe cratons. The two dyke swarms are tholeiitic in composition but the noritic dykes are more enriched in both compatible and incompatible elements and have higher (La/Yb)N ratios than the tholeiite dykes. The norite dykes are interpreted as low degrees of melting from enriched refractory mantle sources, whereas the tholeiite dykes represent high degrees of partial melting of more depleted mantle sources; the two mafic dyke swarms may be related to each other by progressive extension of the continental lithosphere. It is suggested that the Uauá Block with its dyke swarms is a small piece of Archaean crust dispersed after the break-up of a major Archaean supercraton.

  20. The 2012-2013 Montes Claros earthquake series in the São Francisco Craton, Brazil: new evidence for non-uniform intraplate stresses in mid-plate South America

    NASA Astrophysics Data System (ADS)

    Agurto-Detzel, Hans; Assumpção, Marcelo; Ciardelli, Caio; Albuquerque, Diogo Farrapo; Barros, Lucas V.; França, George S. L.

    2015-01-01

    On 2012 May 19, an mb = 4 earthquake shook the town of Montes Claros, Brazil in the middle of the São Francisco Craton. Because of the scarce seismicity in the area, an event like this could provide valuable information to characterize the governing seismotectonics and stress field for the region. Here, we present the results of more than 1 yr of local seismic monitoring after the main shock. We found that the seismicity originated at approximately 1-km depth in an NNW-oriented blind reverse fault, dipping to the E. The magnitude of the main shock was 4mb, with aftershocks reaching up to 3.6mb. Focal mechanisms from first motion polarities and waveform moment tensor inversions indicate a reverse faulting in agreement with the orientation of the aftershock locations. In addition, we derived a new 1-D local velocity model using a simultaneous inversion of hypocentres and velocity layers. The results indicate P-wave velocities of 4.5 km s-1 for the upper layer of carbonate rocks and 5.23 and 5.69 km s-1 for the lower fractured and compact crystalline basement layers, respectively. Higher Vp/Vs ratios were obtained for the upper two layers compared to the lowermost layer, possibly indicating presence of rock fracturing and percolated water. The calculated stress drop for the main event is 0.33 MPa, which is a relatively low value for an intraplate earthquake but still within the observed range. The inversion of the main shock focal mechanism and previously published focal mechanisms suggests a compressional stress regime in the central part of the São Francisco Craton, which is different from the strike-slip regime in the southern part, although both have an EW-oriented σ1. On the other hand, focal mechanisms of events located to the west of the craton indicate an NW-SE oriented σ1 for central Brazil. This variability highlights the importance of local sources of stresses (e.g. flexural stresses) in mid-plate South America, unlike other mid-plate areas of the world

  1. Orosirian (ca. 1.96 Ga) mafic crust of the northwestern São Francisco Craton margin: Petrography, geochemistry and geochronology of amphibolites from the Rio Preto fold belt basement, NE Brazil

    NASA Astrophysics Data System (ADS)

    Caxito, Fabrício de Andrade; Uhlein, Alexandre; Dantas, Elton Luiz; Stevenson, Ross; Pedrosa-Soares, Antônio Carlos

    2015-04-01

    The bulk of the Atlantic shield basement in the eastern South American platform is made of Rhyacian calc-alkaline magmatic rocks (˜2.2-2.15 Ga) affected by granulite-facies metamorphism at around 2.06 Ga, as part of a Paleoproterozoic orogenic system which joined Archean crustal fragments together. Orosirian (2050-1800 Ma) rocks, on the other hand, are scarce in all four major provinces of eastern South America (the Borborema, São Francisco, Tocantins and Mantiqueira provinces). Recently, however, sparse occurrences of Orosirian-aged rocks have been described, particularly in the northern São Francisco Craton margin and adjoining fold belts that compose the Borborema Province further north. In this paper, we present new geochemical, geochronological and isotopic data of amphibolites which compose the basement of the Rio Preto fold belt, in the northwestern São Francisco Craton margin. Geochemical data suggest tholeiitic gabbro protoliths intruded in a subduction-related setting, as suggested by tectonic discrimination diagrams and differentiation trends. U-Pb analyses of magmatic zircon crystals yielded a 1958.3 ± 16 Ma Concordia age. Slightly negative to positive ɛNd(1.96) = (-0.3 to +1.0) and ɛHf(1.96) from -0.76 to -4.55 suggest variable mixing of a depleted mantle source and older continental crust. We interpret the amphibolite body as a remnant of a subduction-related crustal fragment developed in the Orosirian, around 1.96 Ga ago, possibly in a continental back-arc setting. This crustal fragment was further reworked as part of the basement of the Rio Preto fold belt during the Brasiliano Orogeny (˜600-550 Ma). The Cristalândia do Piauí Complex gneisses further north might represent fragments of a coeval continental magmatic arc. These rocks could be the first well documented representatives of an Orosirian tectono-magmatic event which has been, up to now, broadly ignored within this portion of West Gondwana, and thus present major implications for

  2. Asymmetry and polarity of the South Atlantic conjugated margins related to the presence of cratons: a numerical study

    NASA Astrophysics Data System (ADS)

    Andrés-Martínez, Miguel; Pérez-Gussinyé, Marta; de Monserrat Navarro, Albert; Morgan, Jason P.

    2015-04-01

    Tectonic asymmetry of conjugated passive margins, where one margin is much narrower than the conjugate one, is commonly observed at many passive margins world-wide. Conjugate margin asymmetry has been suggested to be a consequence of lateral changes in rheology, composition, temperature gradient or geometries of the crust and lithosphere. Here we use the South Atlantic margins (from Camamu/Gabon to North Santos/South Kwanza) as a natural laboratory to understand conjugate margin asymmetry. Along this margin sector the polarity of the asymmetry changes. To the North, the Brazilian margin developed in the strong Sao Francisco craton, and this constitutes the narrow side of the conjugate pair. To the South, the Brazilian margin developed in the Ribeira fold belt, and the margin is wide. The opposite is true for the African side. We have thus numerically analysed how the relative distance between the initial location of extension and the craton influences the symmetry/asymmetry and polarity of the conjugate margin system. Our numerical model is 2D visco-elasto-plastic and has a free surface, strain weakening and shear heating. The initial set-up includes a cratonic domain, a mobile belt and a transition area between both. We have run tests with different rheologies, thickness of the lithosphere, and weak seeds at different distances from the craton. Results show asymmetric conjugated margins, where the narrower margin is generally the closest to the craton. Our models also allow us to study how the polarity is controlled by the distance between the initial weakness and the craton, and help to understand how the presence of cratonic domains affects the final architecture of the conjugated margins.

  3. The Intracratonic Caraibas-Itacarambi Earthquake of December 9, 2007 (4.9 mb), Minas Gerais, Brazil: predominance of compressional stresses in the middle of the San Francisco craton.

    NASA Astrophysics Data System (ADS)

    Chimpliganond, C. N.; Franca, G. S.; Barros, L. V.; Assumpcao, M.; Carvalho, J.

    2008-05-01

    An earthquake with magnitude 4.9 mb, in the central part of the San Francisco craton, shook the village of Caraibas, Minas Gerais state, on December 9, 2007 at 00:03 (local time). The epicentral area is near the city of Itacarambi. This event was the first to cause a fatal victim in Brazil (a little girl 6 years old). The maximum intensity reached VII Modified Mercalli and the isoseismal of VI MM intensity comprise an area of about 100 square kilometers. Since May 25, 2007, when a 3.5 mb magnitude event was widely felt by the population, this region has been shaken by small earthquakes. A field campaign was taken during October 23-28 to implement a local seismographic network composed by 6 tri-axial broadband stations that is operating until now. A seismic gap was observed some days before the main shock of December 9. Two imminent foreshocks preceded the main shock by some minutes, and 162 aftershocks followed the main event during the first day. The earthquakes with clear onset times for P and S waves were located with Hypo71 using a local velocity model with a Vp/Vs ratio of 1.72, obtained with a composite Wadati diagram. The events show a trend in the NE-SW direction, with very shallow depths, less than about 2 kilometers. The aftershocks were distributed over an area about 3 kilometers long in the NE-SW direction. A composite focal mechanism, determined using P-wave polarities with the clearest waveforms at local stations, shows a reverse faulting mechanism. This solution, consistent with P-wave polarity data for the main shock recorded at regional and teleseismic stations, shows a near horizontal P-axis trending E- W, similar to an earthquake swarm occurred 50 km to the north in 1990. Stress inversion using five different focal mechanisms in this part of the San Francisco craton indicates compressional stresses with EW maximum compression (S1) and a NS intermediate compression (S2).

  4. Juvenile accretion (2360-2330 Ma) in the São Francisco Craton, and implications for the Columbia supercontinent: evidence from U-Pb zircon ages, Sr-Nd-Hf and geochemical constraints

    NASA Astrophysics Data System (ADS)

    Teixeira, W.; Ávila, C.

    2012-12-01

    The Mineiro and the Itabuna-Salvador-Curaçá belts are segments of an Early Proterozoic orogen, in the São Francisco/West Congo-North Gabon craton. The latter segment includes island-arc rocks with preserved portions of the accretionary prism and back-arc basins, developed between 2.4 and 2.0 Ga. The Mineiro belt evolved marginally to the Minas passive margin basin (<2.55 to 2.35 Ga). It contains mainly granitoid rocks with ages between 2.25-2.20 Ga and 2.12-2.08 Ga, along with coeval back arc sequences. The overall framework includes regional metamorphism and related faults and shear zones across both belts. Similar tectonic features are portrayed by the West Central African belt (of Eburnean age) by considering the early contiguous African counterpart. We present an integrated geochronologic and geochemical study for the Resende Costa orthogneiss (Mineiro belt): the gneissic rocks are slightly metaluminous to peraluminous, subalkaline, show varied SiO2 (69 to 73wt.%) contents, and low K2O and high- Na2O +CaO ones. Chemically, they are compatible with high Al2O3 trondhjemites. They also show weak positive Eu/Eu* anomalies, low Rb (24 to 70ppm), Ba (500 to 1000ppm), Th (2.1 to 8.5ppm) contents, very high Sr/Y ratios (75 to 158) and variable LREE and low HREE patterns (Yb < 1.23 ppm). The Resende Costa pluton yields two U-Pb (LA-ICPMS) zircon crystallization ages (2358±10 Ma and 2356±12 Ma), while the zircon rims yield 2133±32 Ma, interpreted as the age of metamorphism. The Sm/Nd TDM whole rock model ages are between 2.35-2.50 Ga, whereas the ɛNd(t) values range from +1.2 to +3.0, ɛSr(t) from +10 to -6, and ɛHf(t) in zircon between -3 to +6. The nearby Ramos gneissic pluton gives U-Pb zircon age of 2331±17 Ma, TDM age of 2.4 Ga, ɛNd(t) +2.2, ɛHf(t) (-9/+9) and ɛSr(t) +40 values. The overall signature implies to short crustal residence for the protholiths with minor contamination during the petrogenesis. Published data reveal that the nearby Lagoa Dourada

  5. Were the African and South American cratons part of Rodinia?

    NASA Astrophysics Data System (ADS)

    Kröner, A.; Cordani, U. G.; D'Agrella-Filho, M. S.; Brito-Neves, B. B.

    2003-04-01

    the supercontinent Gondwana. The location of the main Neoproterozoic intra-oceanic magmatic arcs suggests that a large oceanic domain separated the core of Rodinia, namely Laurentia, Amazonia, Baltica and West Africa, from several continental masses and fragments now in the southern hemisphere, such as the Sao Francisco-Congo, Kalahari and Rio de La Plata cratons, as well as the Borborema/Trans-Saharan, Central Goiás Massif and Paraná blocks. A similar situation is envisaged for the Arabian-Nubian ocean and its extension to the south, separating the same cratonic masses from Eastern Gondwana. Many extensional tectonic events detected in the southern hemisphere continental masses and granitoids associated with this process are comprised within the 800-1000 age interval. This is incompatible with current views on the disintegration of Rodinia at around 750 Ma.

  6. Precambrian Cratons and Fold-Belts in Brazil: Overview

    NASA Astrophysics Data System (ADS)

    Fuck, R.

    2008-05-01

    The main Precambrian terrains recognized in Brazil comprise the Amazonian, São Francisco and Rio de la Plata cratons, surrounded by Neoproterozoic Brasiliano fold belts, making up the Borborema, Mantiqueira and Tocantins provinces. The Amazonian craton comprises an Archean core, surrounded by Paleoproterozoic terrains (Maroni-Itacaiunas, Ventuari-Tapajós, Rio Negro-Juruena), which southwestwards give way to the Mesoproterozoic Rondoniano-San Ignacio and Sunsas belts, the latter thought to be related to the Grenville belt of North America. The São Francisco craton comprises several Archean blocks (Gavião, Serrinha, Jequié) amalgamated by the Paleoproterozoic high-grade Itabuna-Salvador-Curaçá orogen. The Rio de la Plata craton, largely covered by Phanerozoic strata, is made of Paleoproterozoic basement gneiss and several Paleoproterozoic greenstone belts. Other cratonic blocks are hidden below large Phanerozoic basins, like the Paranapanema and Parnaíba blocks below the Paraná and Parnaíba basins, respectively. Several smaller Archean/Paleoproterozoic blocks appear within the Brasiliano provinces: some were strongly reworked during the Neoproterozoic orogenic events (São José do Campestre, Pernambuco-Alagoas, Goiás, Guanhães, Juiz de Fora, Curitiba), others were only marginally affected (São Luiz, Rio Apa, Luís Alves). The Brasiliano provinces are the result of Neoproterozoic to early Paleozoic orogenic events within the framework of West Gondwana amalgamation. The Mantiqueira Province extends from eastern Brazil to southern Uruguay and includes the Araçuaí, Ribeira and Dom Feliciano fold belts, bordering the São Francisco, Paranapanema and Rio de la Plata cratons and surrounding the Luís Alves craton. The Tocantins province in central Brazil includes the Araguaia, Paraguay and Brasília fold belts, the former bordering the Amazonian craton, the second bordering both the southern Amazonian craton and the Rio Apa block, and the last established on

  7. The Namuskluft and Dreigratberg sections in southern Namibia (Kalahari Craton, Gariep Belt): a geological history of Neoproterozoic rifting and recycling of cratonic crust during the dispersal of Rodinia until the amalgamation of Gondwana

    NASA Astrophysics Data System (ADS)

    Hofmann, Mandy; Linnemann, Ulf; Hoffmann, Karl-Heinz; Gerdes, Axel; Eckelmann, Katja; Gärtner, Andreas

    2014-07-01

    This paper presents combined U/Pb, Th/U and Hf isotope analyses on detrital and magmatic zircon grains together with whole-rock geochemical analyses of two basement and eight sedimentary rock samples from the Namuskluft and the Dreigratberg in southern Namibia (Gariep Belt). The sedimentary sections evolved during the Cryogenian on the SW part of the Kalahari Craton and where therefore deposited in an active rift setting during the break-up of Rodinia. Due to insufficient palaeomagnetic data, the position of the Kalahari Craton within Rodinia is still under discussion. There are possibilities to locate Kalahari along the western side of Australia/Mawsonland (Pisarevski et al. in Proterozoic East Gondwana: supercontinent assembly and break-up, Geological Society, London, 2003; Evans in Ancient Orogens and modern analogues. Geological Society, London, 2009; and others) or together with the Congo-Sao Francisco and Rio de la Plata Cratons (Li et al. in Prec Res 45: 203-2014, 2008; Frimmel et al. in Int J Earth Sci (Geol Rundsch) 100: 323-354, 2011; and others). It is sill unclear which craton rifted away from the Kalahari Craton during the Cryogenian. Although Middle to Upper Cryogenian magmatic activity is known for the SE Kalahari Craton (our working area) (Richtersveld Suite, Rosh Pinah Fm), all the presented samples show no U/Pb zircon ages younger than ca. 1.0 Ga and non-older than 2.06 Ga. The obtained U/Pb ages fit very well to the exposed basement of the Kalahari Craton (1.0-1.4 Ga Namaqua Province, 1.7-2.0 Ga Vioolsdrif Granite Suite and Orange River Group) and allow no correlation with a foreign craton such as the Rio de la Plata or Australia/Mawsonland. Lu-Hf isotopic signatures of detrital zircon point to the recycling of mainly Palaeoproterozoic and to a smaller amount of Archean crust in the source areas. ɛHf( t) signatures range between -24 and +14.8, which relate to TDM model ages between 1.05 and 3.1 Ga. Only few detrital zircon grains derived from

  8. University of Sao Paulo

    SciTech Connect

    Acquadro, J.C.; Added, N.; Ferraretto, M.

    1995-08-01

    Argonne has agreed to assist the University of Sao Paulo (USP) in the construction of a small superconducting heavy-ion linac to serve as an energy booster for projectiles from their 8-MV tandem. This booster will be similar in many respects to the ANL booster linac built in the late 1970s. The ANL contribution to this project will be (1) to build (at USP expense) 14 split-ring niobium resonators and some of the associated rf electronics, (2) to provide technical information, and (3) to train USP staff members in several phases of superconducting-linac technology. Two Brazilian engineers worked at Argonne for one year, gaining experience in cryogenics and in superconducting-resonator technology. Another engineer worked on the new control system at ATLAS for two years, the first year supported by Sao Paulo and the second with direct ANL support. Sao Paulo personnel returned to ANL in 1993 for assembly and testing of the first batch of completed resonators. The fabrication of the resonators will be completed by early 1995 when the Sao Paulo personnel will come back for final assembly and testing. Fabrication of electronics modules at ANL is still in progress.

  9. Origin of cratonic basins

    NASA Astrophysics Data System (ADS)

    Dev. Klein, George; Hsui, Albert T.

    1987-12-01

    Tectonic subsidence curves show that the Illinois, Michigan, and Williston basins formed by initial fault-controlled mechanical subsidence during rifting and by subsequent thermal subsidence. Thermal subsidence began around 525 Ma in the Illinois Basin, 520 460 Ma in the Michigan Basin, and 530 500 Ma in the Williston Basin. In the Illinois Basin, a second subsidence episode (middle Mississippian through Early Permian) was caused by flexural foreland subsidence in response to the Alleghanian-Hercynian orogeny. Resurgent Permian rifting in the Illinois Basin is inferred because of intrusion of well-dated Permian alnoites; such intrusive rocks are normally associated with rifting processes. The process of formation of these cratonic basins remains controversial. Past workers have suggested mantle phase changes at the base of the crust, mechanical subsidence in response to isostatically uncompensated excess mass following igneous intrusions, intrusion of mantle plumes into the crust, or regional thermal metamorphic events as causes of basin initiation. Cratonic basins of North America, Europe, Africa, and South America share common ages of formation (around 550 to 500 Ma), histories of sediment accumulation, temporal volume changes of sediment fills, and common dates of interregional unconformities. Their common date of formation suggests initiation of cratonic basins in response to breakup of a late Precambrian super-continent. This supercontinent acted as a heat lens that caused partial melting of the lower crust and upper mantle followed by emplacement of anorogenic granites during extensional tectonics in response to supercontinent breakup. Intrusion of anorogenic granites and other partially melted intrusive rocks weakened continental lithosphere, thus providing a zone of localized regional stretching and permitting formation of cratonic basins almost simultaneously over sites of intrusion of these anorogenic granites and other partially melted intrusive rocks.

  10. Xingo: Capturing the potential of the Sao Francisco River

    SciTech Connect

    Oliveira, E.F. de Jr.; Vasconcelos, A.A. de; Mariz, L.A.

    1997-03-01

    Design and construction of a 3000 MW hydroelectric project in Brazil is outlined. Construction of the Xingo plant began in 1987; the final unit of the first phase is scheduled to enter service in the third quarter of 1997. Problems encountered during construction included financing and high flood flows; the steps taken to overcome these problems are described. Technical details of the plant are also summarized in the article.

  11. Upper mantle anisotropy in SE and Central Brazil from SKS splitting: Evidence of asthenospheric flow around a cratonic keel

    NASA Astrophysics Data System (ADS)

    Assumpção, Marcelo; Heintz, Maggy; Vauchez, Alain; Silva, Marcos Egydio

    2006-10-01

    We present results of upper mantle anisotropy derived from measurements of core refracted shear wave splitting (mainly SKS phases) recorded at 48 stations covering the major tectonic provinces in Central and SE Brazil, such as the Tocantins Province (Paraguay-Araguaia and Brasília belts between the Amazon and São Francisco cratons), the Paraná intracratonic basin, the southern part of the São Francisco craton, and the Mantiqueira province (with the coastal Ribeira belt). Although the fast polarization directions vary across the region, consistent orientations are observed over hundreds of kilometers. The fast polarization directions tend to be close to the absolute plate motion given by the hot-spot reference model HS3-NUVEL1A. However, correlations with geological structures are also observed in the southern Brasilia belt and in the Ribeira belt, respectively located SW and S of the São Francisco craton. On the other hand, in the northern Tocantins province, the fast shear-wave direction (˜ N60°S) is oblique to the SW-NE trend of the geological units and faults, and no anisotropy contribution from lithospheric sources can be clearly identified. Overall, the fast polarization directions show a fan-shaped pattern strongly suggesting asthenosperic flow around a thick and stiff keel in the southern part of the São Francisco craton, consistent with the high-velocity anomaly revealed by recent surface-wave tomography. The observed NW-SE directions in the southern part of the Brasília belt may also be interpreted as resulting from asthenospheric flow channeled between the São Francisco craton and a cratonic block beneath the Paraná basin. The largest splitting delays observed in the southern Brasília belt and in the Ribeira belt (up to 2.4 s) suggest contributions from both lithospheric and asthenospheric sources in those two areas. Our preferred model for the anisotropy causing the observed pattern of SKS splitting consists of flow-induced deformation in the

  12. Widespread refertilization of cratonic and circum-cratonic lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Tang, Yan-Jie; Zhang, Hong-Fu; Ying, Ji-Feng; Su, Ben-Xun

    2013-03-01

    Studies of mantle xenoliths have confirmed that Archean subcontinental lithospheric mantle (SCLM) is highly depleted in basaltic components (such as Al, Ca and Na) due to high-degree extraction of mafic and ultramafic melts and thus is refractory and buoyant, which made it chronically stable as tectonically independent units. However, increasing studies show that ancient SCLM can be refertilized by episodic rejuvenation events like infiltration of upwelling fertile material. The North China Craton is one of the most typical cases for relatively complete destruction of its Archean keel since the eruption of Paleozoic kimberlites, as is evidenced by a dramatic change in the compositions of mantle xenoliths sampled by Paleozoic to Cenozoic magmas, reflecting significant lithospheric thinning and the change in the character of the SCLM. The compositional change has been interpreted as the result of refertilization of Archean SCLM via multiple-stage peridotite-melt reactions, suggested by linear correlations between MgO and indices of fertility, covariations of Al2O3 with CaO, La/Yb, 87Sr/86Sr, 143Nd/144Nd, 187Os/188Os and Re-depletion ages (TRD), high Re abundances, scatter in Re-Os isotopic plot, variable in situ TRD ages of sulfides, and correlation between TRD ages and olivine Fo of peridotite xenoliths in Paleozoic kimberlites and Cenozoic basalts on the craton. By integrating major and trace element, Sr, Nd and Os isotopic compositions of peridotite xenoliths and orogenic massif peridotites from the continents of Europe, Asia, America, Africa and Australia, together with previous studies of petrology and geochemistry of global peridotites, we suggest that (1) refertilization of cratonic and circum-cratonic lithospheric mantle is widespread; (2) Archean SCLM worldwide has experienced a multi-stage history of melt depletion and refertilization since segregation from the convecting mantle; (3) cratonic SCLM may be more susceptible to compositional change caused by

  13. Application of multi-dimensional discrimination diagrams and probability calculations to Paleoproterozoic acid rocks from Brazilian cratons and provinces to infer tectonic settings

    NASA Astrophysics Data System (ADS)

    Verma, Sanjeet K.; Oliveira, Elson P.

    2013-08-01

    In present work, we applied two sets of new multi-dimensional geochemical diagrams (Verma et al., 2013) obtained from linear discriminant analysis (LDA) of natural logarithm-transformed ratios of major elements and immobile major and trace elements in acid magmas to decipher plate tectonic settings and corresponding probability estimates for Paleoproterozoic rocks from Amazonian craton, São Francisco craton, São Luís craton, and Borborema province of Brazil. The robustness of LDA minimizes the effects of petrogenetic processes and maximizes the separation among the different tectonic groups. The probability based boundaries further provide a better objective statistical method in comparison to the commonly used subjective method of determining the boundaries by eye judgment. The use of readjusted major element data to 100% on an anhydrous basis from SINCLAS computer program, also helps to minimize the effects of post-emplacement compositional changes and analytical errors on these tectonic discrimination diagrams. Fifteen case studies of acid suites highlighted the application of these diagrams and probability calculations. The first case study on Jamon and Musa granites, Carajás area (Central Amazonian Province, Amazonian craton) shows a collision setting (previously thought anorogenic). A collision setting was clearly inferred for Bom Jardim granite, Xingú area (Central Amazonian Province, Amazonian craton) The third case study on Older São Jorge, Younger São Jorge and Maloquinha granites Tapajós area (Ventuari-Tapajós Province, Amazonian craton) indicated a within-plate setting (previously transitional between volcanic arc and within-plate). We also recognized a within-plate setting for the next three case studies on Aripuanã and Teles Pires granites (SW Amazonian craton), and Pitinga area granites (Mapuera Suite, NW Amazonian craton), which were all previously suggested to have been emplaced in post-collision to within-plate settings. The seventh case

  14. Metasomatism and the Weakening of Cratons: A Mechanism to Rift Cratons

    NASA Astrophysics Data System (ADS)

    Wenker, Stefanie; Beaumont, Christopher

    2016-04-01

    The preservation of cratons is a demonstration of their strength and resistance to deformation. However, several cratons are rifting now (e.g. Tanzania and North China Craton) or have rifted in the past (e.g. North Atlantic Craton). To explain this paradox, we suggest that widespread metasomatism of the originally cold depleted dehydrated craton mantle lithosphere root can act as a potential weakening mechanism. This process, particularly melt metasomatism, increases root density through a melt-peridotite reaction, and reduces root viscosity by increasing the temperature and rehydrating the cratonic mantle lithosphere. Using 2D numerical models, we model silicate-melt metasomatism and rehydration of cold cratonic mantle lithosphere that is positioned beside standard Phanerozoic lithosphere. The models are designed to investigate when a craton is sufficiently weakened to undergo rifting and is no longer protected by the initially weaker adjacent standard Phanerozoic lithosphere. Melt is added to specified layers in the cratonic mantle lithosphere at a uniform volumetric rate determined by the duration of metasomatism (3 Myr, 10 Myr or 30 Myr), until a total of ~30% by volume of melt has been added. During melt addition heat and mass are properly conserved and the density and volume increase by the respective amounts required by the reaction with the peridotite. No extensional boundary conditions are applied to the models during the metasomatism process. As expected, significant refertilization leads to removal and thinning of progressively more gravitationally unstable cratonic mantle lithosphere. We show that the duration of metasomatism dictates the final temperature in the cratonic upper mantle lithosphere. Consequently, when extensional boundary conditions are applied in our rifting tests in most cases the Phanerozoic lithosphere rifts. The craton rifts only in the models with the hottest cratonic upper mantle lithosphere. Our results indicate rifting of cratons

  15. Origin and evolution of the Amazonian craton

    NASA Technical Reports Server (NTRS)

    Gibbs, A. K.; Wirth, K. R.

    1986-01-01

    The Amazonian craton appears to be formed and modifed by processes much like those of the better-known Precambrian cratons, but the major events did not always follow conventional sequences nor did they occur synchronously with those of other cratons. Much of the craton's Archean style continental crust formation, recorded in granite-greenstone and high-grade terranes, occurred in the Early Proterozoic: a period of relative quiescence in many other Precambrian regions. The common Archean to Proterozoic transition in geological style did not occur here, but an analogous change from abundant marine volcanism to dominantly continental sedimentary and eruptive styles occurred later. Amazonian geology is summarized, explaining the evolution of the craton.

  16. Speculations on the formation of cratons and cratonic basins

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan; Priestley, Keith

    2016-02-01

    Surface wave tomography using Rayleigh waves has shown that Tibet and the surrounding mountain ranges that are now being shortened are underlain by thick lithosphere, of similar thickness to that beneath cratons. Both their elevation and lithospheric thickness can result from pure shear shortening of normal thickness continental lithosphere by about a factor of two. The resulting thermal evolution of the crust and lithosphere is dominated by radioactive decay in the crust. It raises the temperature of the lower part of the crust and of the upper part of the lithosphere to above their solidus temperatures, generating granites and small volumes of mafic alkaline rocks from beneath the Moho, as well as generating high temperature metamorphic assemblages in the crust. Thermal models of this process show that it can match the P, T estimates determined from metamorphic xenoliths from Tibet and the Pamirs, and can also match the compositions of the alkaline rocks. The seismological properties of the upper part of the lithosphere beneath northern Tibet suggest that it has already been heated by the blanketing effect and radioactivity of the thick crust on top. If the crustal thickness is reduced by erosion alone to its normal value at low elevations, without any tectonic extension, over a time scale that is short compared to the thermal time constant of thick lithosphere, of ∼250 Ma, thermal subsidence will produce a basin underlain by thick lithosphere. Though this simple model accounts for the relevant observations, there is not yet sufficient information available to be able to model in detail the resulting thermal evolution of the sediments deposited in such cratonic basins.

  17. Innovation in san francisco.

    PubMed

    Travis, J

    1992-08-01

    In San Francisco 2 weeks ago, AAAS and Science sponsored a new meeting, Science Innovation '92. The unusual gathering focused not on research results but on new techniques and instruments, particularly for biomedical science. As seen in the stories below, some of the most eye-catching innovations emerged at the intersection of physics and biology. PMID:17736460

  18. 1. Historic American Buildings Survey San Francisco Examiner Library EAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Historic American Buildings Survey San Francisco Examiner Library EAST ELEVATION - Presidio of San Francisco, Old Station Hospital, Funston Avenue & Lincoln Boulevard, San Francisco, San Francisco County, CA

  19. Craton destruction by subduction, collision or plume impingement? Comparisons of some representative cratons in the world

    NASA Astrophysics Data System (ADS)

    Wang, Zhensheng; Kusky, Timothy; Li, Xiaoyong; Wang, Xu; Fu, Jianmin; Yuan, Yuefeng; Zhu, Peimin

    2015-04-01

    The fact that cratonic lithosphere can be destructed has been demonstrated by numerous studies. However, the driving force of craton destruction and its mechanism are still unclear1,2. Subduction, collision and mantle plumes, the most important driving forces for most geological events, may also be responsible for craton destruction. However, their relationship in the destruction process including which of them is the major driving force and how they interact with each other is not understood sufficiently1,2. In this article, the North China Craton, North Atlantic Craton, Tanzania Craton, Wyoming Craton, Kaapvaal Craton, Yangtze Craton, Yilgarn Craton and Superior Craton are used as examples to study their difference and similarities during subduction, collision, or mantle plume impingement. The work is mainly based on comparison of their tectonic history, geophysical data, as well as xenolith chronology. It is suggested that large-scale craton destruction can be influenced by the interaction of subduction, collision and mantle plumes, acting to different degrees in different examples. Mantle plume related thermal action enhances the chemical stratification or layering of subcontinental lithospheric mantle (SCLM), which can form a weak-coupling mid lithosphere discontinuity (MLD) 3,4,5 and a lower denser SCLM below the MLD. Convergence (subduction and collision), especially when associated with slab rollback 6, leads to the regional thinning of the cratonic margin, which is subsequently linked by extension (mantle plume or slab rollback) related discontinuities. Continuous extension-related discontinuities extend upward to the MLD depth and cut off the shearing resistance from adjacent blocks. Next, the lower part of the chemically stratified SCLM in the cratonic interior is decoupled along the weakly coupled MLD and founders into the deep asthenosphere 7. Then the destruction of the rest of the lithosphere can be affected by upwelling related decompression melting

  20. Ambient Noise Imaging of Craton Modification: Examples from the Kaapvaal craton

    NASA Astrophysics Data System (ADS)

    Porter, R. C.; Shirey, S. B.; Fouch, M. J.; James, D. E.

    2013-12-01

    Mapping of crustal and upper-mantle seismic velocities can give important insight into the geologic evolution of cratonic regions. In order to better understand the formation and evolution of the Kaapvaal craton and surrounding regions, we use ambient noise tomography to produce a new crustal and upper-mantle 3D shear-velocity model for southeastern Africa using data collected during the (1995-1999) Kaapvaal Seismic Experiment. Ambient noise tomography enables imaging of shear-velocity variations at smaller scales (10s of km) and shallower depths (< 10 km) than previously determined using natural-source body- and surface-wave techniques within the region. The goal of this work is to image geological features of the Kaapvaal-Zimbabwe craton such as kimberlite pipe density, flood basalt feeder dike systems, granite-greenstone belts, layered mafic intrusions and craton assembly/collision patterns at mid- lower crustal levels where information is typically lacking. Our results provide important constraints on the evolution of the Kaapvaal craton, including the collision with the Zimbabwe craton and the formation of the Bushveld Complex and Witwatersrand basin, and the impact of these events on lithospheric structure. Preliminary images exhibit key first-order features of the craton. At depth ranges of 4-12 km, reduced shear velocities correlate with the Bushveld-Malopo Farms complexes. At a depth interval of 10-18 km, lower velocities are associated with the Witwatersrand sedimentary basin, and higher velocities may be attributed to unroofed mid-crustal rocks of high metamorphic grade formed during the Kaapvaal-Zimbabwe craton collision. At depths of 36-46 km, velocity patterns reflect Moho topography, with thinner crust associated with the undisturbed regions of the Kaapvaal and Zimbabwe cratons and thicker crust associated with the Limpopo Belt and Namaqua-Natal Mobile Belt. At greater depths, higher upper-mantle velocities are observed in the southern Kaapvaal

  1. Cratonic lithosphere: an electrifying view (Invited)

    NASA Astrophysics Data System (ADS)

    Jones, A. G.

    2013-12-01

    Deep-probing electromagnetic studies reveal the vertical and lateral electrical conductivity structure of cratonic lithosphere. At lithospheric temperatures and for silicate mantle minerals, semi-conduction is from small polaron hopping and, in the presence of water, proton conduction, both of which is thermally-driven and can be described by an Arrhenius equation. There is little compositional sensitivity, save for the far higher water contents prevalent in pyroxenes (typically 200-400 wt ppm) compared to olivine (typically 10-100 wt ppm), with the latter exhibiting a depth dependence and the former none. Seismological methods are sensitive to temperature and composition, and virtually insensitive to low amounts of water. Taken together, the two are highly complementary. Seismological and magnetotelluric studies across Southern Africa can be employed together to constraint temperature and water content, where there is a significant difference at 100 km depth between the Kaapvaal Craton compared to the Angola (Congo) Craton compared to the Zimbabwe Craton. The Congo Craton is driest but hottest, the Kaapvaal Craton exhibits laterally-varying water content and is coldest, and the Zimbabwe Craton is the wettest and intermediate in temperature. Such thermal and water content variation results in lateral rheological variation, with the wettest and warmest being more deformable. For the Canadian Shield, there is again significant lateral variation at 100 km, with the Superior Province being mostly dry, and the Slave Craton and Rae/Hearne Provinces being far wetter. By 200 km however, all of the Canadian Shield is dry, consistent with the xenolith-based observations from the Kaapvaal Craton of far higher water contents in olivine at 100 km (50-100 wt ppm) decreasing with depth to around 10 wt ppm at 200 km. The lithosphere beneath the Kimberley area of the Kaapvaal Craton has been forward modeled in a manner that is self-consistent not only with the seismological and

  2. LAB and other lithospheric discontinuities below Cratons

    NASA Astrophysics Data System (ADS)

    Sodoudi, Forough

    2013-04-01

    Cratons are extremely stable continental areas of the Earth's crust, which have been formed and remained largely unchanged since Precambrian. However, their formation and how they survived destruction over billions of years remains a subject of debate. Seismic properties of the cratonic lithosphere reflect its composition and physical state and obtain basic constraints on processes of the formation and evolution of continents. Insight on these issues may be gained by determining the depth and the nature of the Lithosphere-Asthenosphere Boundary (LAB), which is a necessary element of the plate tectonic theory. However, It has proved quite "elusive" beneath the oldest continental areas. What is missing to date is a consensus on the feature that would correspond to the LAB and whether such a feature exists everywhere beneath cratons. The relatively recently developed S receiver function technique employing S-to-P conversions appears promising for detecting the LAB with a sufficiently high resolution and density. A growing number of regional observations obtained from S receiver function studies has detected discontinuities characterized by a significant negative velocity contrast in the upper mantle. However, challenges still remain in detecting the S-to-P conversions from the LAB beneath the Precambrian cratons. Some recent SRF studies observed a deep (> 160 km) negative velocity contrast beneath cratons and interpreted it as the LAB. For example, a deep LAB at about 250 km was reported beneath the Kalahari craton by different authors. Similar results were also obtained beneath some parts of the Canadian shield, East European Craton, Australia, the Arabian Shield and Tanzania craton. In contrast, other SRF studies found no evidence for negative discontinuities at these depths in the North American craton, in Kalahari craton or in Australia. Instead they revealed a very sharp negative velocity gradient at much shallower depth (60-150 km), leading some authors to infer

  3. Water in the Cratonic Mantle Lithosphere

    NASA Technical Reports Server (NTRS)

    Peslier, A. H.

    2016-01-01

    The fact that Archean and Proterozoic cratons are underlain by the thickest (>200 km) lithosphere on Earth has always puzzled scientists because the dynamic convection of the surrounding asthenosphere would be expected to delaminate and erode these mantle lithospheric "keels" over time. Although density and temperature of the cratonic lithosphere certainly play a role in its strength and longevity, the role of water has only been recently addressed with data on actual mantle samples. Water in mantle lithologies (primarily peridotites and pyroxenites) is mainly stored in nominally anhydrous minerals (olivine, pyroxene, garnet) where it is incorporated as hydrogen bonded to structural oxygen in lattice defects. The property of hydrolytic weakening of olivine [4] has generated the hypothesis that olivine, the main mineral of the upper mantle, may be dehydrated in cratonic mantle lithospheres, contributing to its strength. This presentation will review the distribution of water concentrations in four cratonic lithospheres. The distribution of water contents in olivine from peridotite xenoliths found in kimberlites is different in each craton (Figure 1). The range of water contents of olivine, pyroxene and garnet at each xenolith location appears linked to local metasomatic events, some of which occurred later then the Archean and Proterozoic when these peridotites initially formed via melting. Although the low olivine water contents (<10 ppm wt H2O) at > 6 GPa at the base of the Kaapvaal cratonic lithosphere may contribute to its strength, and prevent its delamination, the wide range of those from Siberian xenoliths is not compatible with providing a high enough viscosity contrast with the asthenophere. The water content in olivine inclusions from Siberian diamonds, on the other hand, have systematically low water contents (<20 ppm wt H2O). The xenoliths may represent a biased sample of the cratonic lithosphere with an over-­abundance of metasomatized peridotites with

  4. HD-SAO-DM cross index

    NASA Technical Reports Server (NTRS)

    Nagy, T. A.; Mead, J.

    1978-01-01

    A table of correspondence SAO-HD-DM-GC was prepared by Morin (1973). The machine-readable version of this cross identification was obtained from the Centre de Donnees Stellaires (Strasbourg, France). The table was sorted at the Goddard Space Flight Center by HD number and all blank HD number records were removed to produce the HD-SAO-DM table presented. There were 258997 entries in the original table; there are 180411 entries after removing the blank HD records. The Boss General Catalogue (GC) numbers were retained on the machine-readable version after the sort.

  5. Kimberlites of the Man craton, West Africa

    NASA Astrophysics Data System (ADS)

    Skinner, E. M. W.; Apter, D. B.; Morelli, C.; Smithson, N. K.

    2004-09-01

    The Man craton in West Africa is an Archaean craton formerly joined to the Guyana craton (South America) that was rifted apart in the Mesozoic. Kimberlites of the Man craton include three Jurassic-aged clusters in Guinea, two Jurassic-aged clusters in Sierra Leone, and in Liberia two clusters of unknown age and one Neoproterozoic cluster recently dated at ˜800 Ma. All of the kimberlites irrespective of age occur as small pipes and prolific dykes. Some of the Banankoro cluster pipes in Guinea, the Koidu pipes in Sierra Leone and small pipes in the Weasua cluster in Liberia contain hypabyssal-facies kimberlite and remnants of the so-called transitional-facies and diatreme-facies kimberlite. Most of the Man craton kimberlites are mineralogically classified as phlogopite kimberlites, although potassium contents are relatively low. They are chemically similar to mica-poor Group 1A Southern African examples. The Jurassic kimberlites are considered to represent one province of kimberlites that track from older bodies in Guinea (Droujba 153 Ma) to progressively younger kimberlites in Sierra Leone (Koidu, 146 Ma and Tongo, 140 Ma). The scarcity of diatreme-facies kimberlites relative to hypabyssal-facies kimberlites and the presence of the so-called transitional-facies indicate that the pipes have been eroded down to the interface between the root and diatreme zones. From this observation, it is concluded that extensive erosion (1-2 km) has occurred since the Jurassic. In addition to erosion, the presence of abundant early crystallizing phlogopite is considered to have had an effect on the relatively small sizes of the Man craton kimberlites.

  6. The record of the Amazon craton in two supercontinents: Paleomagnetic and geological constraints for Mesoproterozoic to Paleozoic times

    NASA Astrophysics Data System (ADS)

    Tohver, E.

    2008-05-01

    The Amazon craton plays a fundamental role in the evolution of two supercontinents, the late Mesoproterozoic Rodinia, the break-up of which led to thethe late Neoproterozoic-early Paleozoic formation of Gondwana. A recent review of the paleomagnetic database for South America and Africa highlights the different role of the principal elements of western Gondwana elements Amazonia, conjoined with West Africa, versus the more centrally- located pieces of Gondwana; -Congo-São Francisco, Kalahari, the Rio de Plata, and the accreted terranes of the Arabia-Nubia shield. Whereas the Amazon-West Africa conjoined craton appears to have been alongside Laurentia within the framework of Rodinia, the other "central Gondwana" cratons were not part of Rodinia. New paleomagnetic data from the SW Amazon craton demonstrate the transpressive evolution of the Grenvillian collision, which resulted in thousands of kilometers of along-strike between the Amazon and Laurentia cratons. Portions of Amazonian crust stranded within the North American craton, notably the Blue Ridge province of the southern Appalachians, is evidence for this long-lived motion. An extensive review of recent thermochronological data from the North American Grenville Province and new data from the SW Amazon belts of "Grenvillian" age reveals the effects of differential post-orogenic exhumation. Restoration of this exhumation gives us a crustal-scale cross-section of the synorogenic structure, marked by thrust-related imbrication on the North American side, and large-scale, strike-slip faults on the Amazon side. It is this asymmetric structure that accounts for the differences in tectonic style between the two cratons. The timing of the break-up of Rodinia is still mostly unconstrained by geochronological data from rift-related sediments from the Amazon side. The Paraguai belt that marks the SE margin of the Amazon craton is a curved, fold-and-thrust belt that affected the late Neoproterozoic-Cambrian sediments that

  7. Lithospheric Mantle Deformation beneath the Indian Cratons.

    PubMed

    Pandey; Agrawal

    1999-11-01

    The nature of deformation of the deep continental roots beneath the Archean-Early Proterozoic terrains opens the question whether these ancient terrains have had stable roots since the Precambrian or whether recent plate motions have deformed them. In view of this, we make an attempt to study the thermal structure beneath the cratonic regions of the Indian shield, which vary in lithospheric thickness from 65 km in the Singhbhum craton to 148 km in the Archean Dharwars. The average depth of 104 km to the top of the underlying asthenosphere is consistent with other termination methods and is in fact less than half the 200-400-km depth found in other stable areas of the earth. Similarly, the average reduced heat flow of about 35 mW/m2 and Moho temperature of about 550 degrees C (range: 400 degrees -730 degrees C) for the Indian cratons are also much higher than their counterparts elsewhere. Our study indicates a large-scale deformation of the cratonic mantle lithosphere beneath the Indian shield since the Mesoproterozoic caused by various geodynamic causes, challenging the idea of stability of deep continental roots. PMID:10517883

  8. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.

    ERIC Educational Resources Information Center

    Wilkinson, Bruce H.

    1982-01-01

    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  9. Phanerozoic surface history of the Slave craton

    NASA Astrophysics Data System (ADS)

    Ault, Alexis K.; Flowers, Rebecca M.; Bowring, Samuel A.

    2013-09-01

    apatite (U-Th)/He (AHe) thermochronometry data and key geologic constraints from Slave craton kimberlites are used to develop a model for the Phanerozoic burial, unroofing, and hypsometric history of the northwestern Canadian shield. AHe dates range from 210 ± 13 to 382 ± 79 Ma, are older in the eastern Slave craton and decrease westward, and resolve the spatial extent, thickness, and history of now-denuded sedimentary units. Results indicate Paleozoic heating to temperatures ≥85-90°C, suggesting regional burial beneath ≥2.8 km of strata while the region was at sea level, followed by the westward migration of unroofing across the craton. This Paleozoic-Mesozoic history does not correlate with sea level change, instead requiring Paleozoic subsidence of the craton followed by surface uplift. The AHe data restrict Cretaceous burial to ≤1.6 km, followed by unroofing, Eocene terrestrial sediment deposition, and removal of Phanerozoic sedimentary cover across the region by present day. The craton underwent ≥300 m of post-100 Ma elevation gain, based on ~100 Ma marine sedimentary xenoliths entrained in ~75-45 Ma kimberlites at modern elevations of 550-600 m. The transition from Paleozoic-Mesozoic subsidence to surface uplift may signal a change from predominantly northern (Franklinian-Innuitian) to western (Canadian Cordillera) plate boundary controls on continental interior processes, with the latter driving the east-to-west wave of unroofing. Canadian Cordillera evolution also affected the Cretaceous-early Tertiary history. Dynamic topography due to changing mantle flow regimes and proximity to sediment sources influenced the Phanerozoic surface evolution of the northwestern Canadian shield.

  10. Jean Parker School, San Francisco.

    ERIC Educational Resources Information Center

    Larson, Soren

    1999-01-01

    Describes the post-earthquake renovation of a San Francisco urban elementary school that preserved its historical detail within a modern replacement. Design features are detailed; photos and a floorplan are included. (GR)

  11. Seismic reflection profiling of Neoarchean cratons

    NASA Astrophysics Data System (ADS)

    van der Velden, Arie Jan

    Deep seismic reflection data from the Superior and Slave cratons in Canada and the Yilgarn craton in Australia are processed with similar processing flows and display parameters to facilitate comparative analysis. The profiles are characterized by subhorizontal to shallowly dipping reflection fabrics in the crust and upper mantle. These reflection fabrics are interpreted as ˜2.8-2.6 Ga ductile structural fabrics associated with peak orogenesis that led to cratonization. A re-evaluation of the seismic data has led to alternative interpretations compared to those published previously. In western Ontario, at Red Lake, divergent reflection patterns are interpreted as products of mainly collisional tectonics rather than extensional tectonics, and at Pickle Lake, mantle reflections connect to a mapped suture and strikeslip fault system. In western Quebec, steep structures are interpreted on the north flank of the Opatica domain. In the Kalgoorlie area of western Australia, subhorizontal upper crustal reflections are interpreted as pre-deformational layers within anticlines. A new tectonic model is presented for the western Slave Province in which divergent reflections at Yellowknife are interpreted to be associated with convergence between the Snare arc and the central Slave basement complex. Reflections that project from the reflection Moho into the upper mantle are observed on all profiles and are interpreted as relict subduction zones and/or major terrane-bounding structures. Listric mid-crustal reflections resembling roofing shingles are interpreted as products of underthrusting and subcretion. Strike-slip faults are manifested as near-vertical zones of reflection truncations. Greenstone belts are often poorly reflective. These reflection patterns are consistent with tectonic models in which greenstone belts form adjacent to protocratons and are thickened by protocontinent-dipping subduction, tectonic underplating, formation of nappes, and thrust-and-fold structures

  12. The electrical structure of the Slave craton

    NASA Astrophysics Data System (ADS)

    Jones, Alan G.; Lezaeta, Pamela; Ferguson, Ian J.; Chave, Alan D.; Evans, Rob L.; Garcia, Xavier; Spratt, Jessica

    2003-12-01

    The Slave craton in northwestern Canada, a relatively small Archean craton (600×400 km), is ideal as a natural laboratory for investigating the formation and evolution of Mesoarchean and Neoarchean sub-continental lithospheric mantle (SCLM). Excellent outcrop and the discovery of economic diamondiferous kimberlite pipes in the centre of the craton during the early 1990s have led to an unparalleled amount of geoscientific information becoming available. Over the last 5 years deep-probing electromagnetic surveys were conducted on the Slave, using the natural-source magnetotelluric (MT) technique, as part of a variety of programs to study the craton and determine its regional-scale electrical structure. Two of the four types of surveys involved novel MT data acquisition; one through frozen lakes along ice roads during winter, and the second using ocean-bottom MT instrumentation deployed from float planes. The primary initial objective of the MT surveys was to determine the geometry of the topography of the lithosphere-asthenosphere boundary (LAB) across the Slave craton. However, the MT responses revealed, completely serendipitously, a remarkable anomaly in electrical conductivity in the SCLM of the central Slave craton. This Central Slave Mantle Conductor (CSMC) anomaly is modelled as a localized region of low resistivity (10-15 Ω m) beginning at depths of ˜80-120 km and striking NE-SW. Where precisely located, it is spatially coincident with the Eocene-aged kimberlite field in the central part of the craton (the so-called "Corridor of Hope"), and also with a geochemically defined ultra-depleted harzburgitic layer interpreted as oceanic or arc-related lithosphere emplaced during early tectonism. The CSMC lies wholly within the NE-SW striking central zone defined by Grütter et al. [Grütter, H.S., Apter, D.B., Kong, J., 1999. Crust-mantle coupling; evidence from mantle-derived xenocrystic garnets. Contributed paper at: The 7th International Kimberlite Conference

  13. Lithospheric layering in the North American craton.

    PubMed

    Yuan, Huaiyu; Romanowicz, Barbara

    2010-08-26

    How cratons-extremely stable continental areas of the Earth's crust-formed and remained largely unchanged for more than 2,500 million years is much debated. Recent studies of seismic-wave receiver function data have detected a structural boundary under continental cratons at depths too shallow to be consistent with the lithosphere-asthenosphere boundary, as inferred from seismic tomography and other geophysical studies. Here we show that changes in the direction of azimuthal anisotropy with depth reveal the presence of two distinct lithospheric layers throughout the stable part of the North American continent. The top layer is thick ( approximately 150 km) under the Archaean core and tapers out on the surrounding Palaeozoic borders. Its thickness variations follow those of a highly depleted layer inferred from thermo-barometric analysis of xenoliths. The lithosphere-asthenosphere boundary is relatively flat (ranging from 180 to 240 km in depth), in agreement with the presence of a thermal conductive root that subsequently formed around the depleted chemical layer. Our findings tie together seismological, geochemical and geodynamical studies of the cratonic lithosphere in North America. They also suggest that the horizon detected in receiver function studies probably corresponds to the sharp mid-lithospheric boundary rather than to the more gradual lithosphere-asthenosphere boundary. PMID:20740006

  14. Host-parasite relationships of monogeneans in gills of Astyanax altiparanae and Rhamdia quelen of the São Francisco Verdadeiro River, Brazil.

    PubMed

    Ferrari-Hoeinghaus, A P; Takemoto, R M; Oliveira, L C; Makrakis, M C; Baumgartner, G

    2006-12-01

    This study investigates the ecology of monogenean gill parasites of Aslyanax altiparanae Garutti & Britski, 2000 and Rhamdia quelen (Quoy & Gaimard, 1824) in a stretch of the Sao Francisco Verdadeiro River, Parana, Brazil. Statistical and ecological indices were used to examine observed levels of parasitism in relation to host and environmental characteristics. A. altiparance and R. quelen had infestation intensities of 2.8 and 23.1 parasites per fish, respectively. The only significant environmental influence was observed at the upstream station for R. quelen. For both host species, parasitized and non-parasitized individuals presented similar weight-ength relationships. Parasitized individuals had dispersed K,, values indicating abnormal conditions. The low levels of parasitism observed in this study suggest that the environment is relatively undisturbed. Additional studies should compare these two species and their respective parasites following completion of the hydroelectric headquarters planned for construction in this stretch of the Sao Francisco Verdoadeiro River. PMID:17285853

  15. 78 FR 34895 - Safety Zone; San Francisco Independence Day Fireworks Display, San Francisco Bay, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-11

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Independence Day Fireworks Display, San.... SUMMARY: The Coast Guard will enforce the safety zones for the San Francisco Independence Day Fireworks... INFORMATION: The Coast Guard will enforce the San Francisco Independence Day Fireworks Display safety...

  16. 77 FR 15260 - Safety Zone; San Francisco Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Fireworks Display, San Francisco, CA AGENCY... safety zone for the San Francisco Giants Fireworks Display in the Captain of the Port, San Francisco area... and property of the maritime public from the hazards associated with the fireworks display. During...

  17. 76 FR 38305 - Safety Zone; San Francisco Chronicle Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-30

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Chronicle Fireworks Display, San Francisco... will enforce the safety zones for the annual San Francisco Chronicle Fireworks Display (Independence Day Celebration for the City of San Francisco Fireworks). This action is necessary to control...

  18. 75 FR 39166 - Safety Zone; San Francisco Giants Baseball Game Promotion, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-08

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Francisco Giants Baseball Game... Bay off San Francisco, CA in support of the San Francisco Giants Baseball Game Promotion. This safety... Giants will sponsor the San Francisco Giants Baseball Game Promotion on July 16, 2010, on the...

  19. Tracing origins of cratonic eclogites by magnesium isotopes

    NASA Astrophysics Data System (ADS)

    Wang, S.; Teng, F. Z.; Rudnick, R. L.; Li, S. G.

    2014-12-01

    Cratonic eclogites are samples of lithospheric mantle preserved beneath ancient continental cratons. Hence, the origin of cratonic eclogites is closely related to the formation and evolution of cratonic mantle. Here we report Mg isotopic compositions for 27 cratonic eclogites and 52 garnet and clinopyroxene mineral separates from Koidu, Bellsbank and Kaalvallei kimberlite pipes in South and West Africa. Whole-rock Mg isotopic compositions vary widely, with δ26Mg ranging from -1.60 to +0.17, significantly different from the value (δ26Mg = -0.25 ± 0.07) of peridotite xenoliths. Garnet and clinopyroxene in these cratonic eclogites record equilibrium inter-mineral Mg isotope partitioning at mantle temperatures, with Δ26MgCpx-Grt (= δ26MgCpx - δ26MgGrt) in the range of 0.43 - 0.85 ‰. The constructed bulk δ26Mg values based on mineral compositions are identical to the measured whole-rock values, indicating limited influence of kimberlite infiltration on Mg isotopic compositions of cratonic eclogites. As significant Mg isotope fractionation can only occur during low-temperature surface processes, the large Mg isotopic variations of cratonic eclogites suggest the incorporation of subducted materials in their protoliths. Therefore, our Mg isotopic data suggest the cratonic eclogites are the remnants of subducted oceanic crust within the lithospheric mantle. Collectively, Mg isotopes are potentially excellent tracers of the formation and evolution of sub-continental lithospheric mantle.

  20. San Francisco Bay Sediment Concentration

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This March 3, 2000 image of the San Francisco Bay region shows a 60 by 75 kilometer Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image in band 1 (near infrared, 0.52-0.60 microns). The color coded suspended sediment image was created from band 1 by blacking out the land, and assigning colors to the relative brightnesses in the water. High values were colored white, then red, yellow, green, and blue. Brighter values in band 1 indicate higher sediment load in the water. The highest values are in Suisun and San Pablo Bays, into which the Sacramento River empties, and along the coast of the San Francisco Peninsula. The Pacific Ocean and San Francisco Bay water are relatively clear. Image courtesy ASTER Science Team

  1. Crustal composition of the Western Australian craton and implications for craton formation tectonics

    NASA Astrophysics Data System (ADS)

    Yuan, H.

    2014-12-01

    The Western Australian craton is composed of two Archean blocks, the early-to-mid Archean Pilbara craton and the late Archean Yilgarn craton, and surrounding Proterozoic orogens. Early seismic studies found that these Archean blocks are characterized as a signature type of simple crust and sharp crust-mantle transition, while the orogenic terranes have rather complex crustal structure and much diffused Moho, posing a question whether a possible change in the crustal forming processes occurred between Archean and Proterozoic. Applying receiver functions to available seismic stations, we estimate the bulk crustal thickness and Vp/Vs ratio across the Western Australian craton. The use of the 3D AuSREM velocity models greatly improves the robustness in the bulk crustal property estimates, especially the Vp/Vs ratio that is essential in deriving the crustal composition as well as inferring the tectonic history of individual tectonic units. Our crustal thickness estimates agree well with early studies. The Pilbara crust is uniformly thin (30 km) with a sharp Moho (20% receiver function relative amplitude), and is inferred as extremely felsic in crustal composition (Vp/Vs ratio 1.70, among the lowest in the craton crust globally). The Yilgarn crust is relatively thick (>35km), and is more toward intermediate (Vp/Vs ratio > 1.73). Lateral variations of the Vp/Vs ratios in Yilgarn correlate well with the sub-terranes, reinforcing the early proposal that individual sub-units had gained their unique seismic originality BEFORE the craton amalgamation. Differences between the Pilbara and Yilgarn crust suggest that the vertical and accretional tectonics may have played different roles in forming the cratons. Along the Proterozoic orogens, thicker crust and weaker and possibly dipping Moho interfaces are observed, agreeing with that the regions have been repeatedly reworked. A 20-km thick lower crustal layer with >1.86 Vp/Vs ratio is observed in the Musgrave orogen, reflecting a

  2. VizieR Online Data Catalog: SAO Star Catalog J2000 (SAO Staff 1966; USNO, ADC 1990)

    NASA Astrophysics Data System (ADS)

    SAO Staff

    1995-10-01

    This machine-readable SAO catalog from the Astronomical Data Center is based on an original binary version of the Smithsonian Astrophysical Observatory Star Catalog (SAO, SAO Staff 1966). Subsequent improvements by T. A. Nagy (1979) included the addition of equatorial coordinates in radians and cross-identifications from the Table of Correspondences SAO/HD/DM/GC (Morin 1973). As a prelude to creation of the 1984 version of the SAO, a new version of the SAO-HD-GC-DM Cross Index was prepared (Roman, Warren, and Schofield 1983). The 1984 version of the SAO contained the corrected and extended cross identifications, all errata published up to January 1984 and known to the ADC, numerous errors forwarded to the ADC by colleagues, and errors discovered at the ADC during the course of this work. Clayton A. Smith of the U. S. Naval Observatory provided J2000.0 positions and proper motions for the SAO stars. Published and unpublished errors discovered in the previous version (1984) have been corrected (up to May 1991). The catalog contains SAO number; the right ascension and declination with a B1950.0 equinox and epoch; annual proper motion and its standard deviation, photographic and visual magnitudes; spectral type; references to sources; the Durchmusterung (DM) identifier if the star is listed in the Bonner DM (BD), Cordoba DM (CD), or Cape Photographic DM (CP); component identification; The Henry Draper (Extension) (HD or HDE) number; and J2000 positions and proper motions. Multiple-star component identifications have been added to stars where more than one SAO entry has the same DM number. The Henry Draper Extension (HDE) numbers have been added for stars found in both volumes of the extension. Data for duplicate SAO entries (those referring to the same star) have been flagged. J2000 positions in usual units and in radians have been added. (1 data file).

  3. Seeking Justice in San Francisco

    ERIC Educational Resources Information Center

    Pascopella, Angela

    2010-01-01

    This article discusses the life of Carlos A. Garcia, superintendent at the San Francisco Unified School District. Garcia was born in Chicago, but his parents shortly thereafter moved back to their homeland of Mexico for a few years. When Garcia was almost 5, his family moved to Los Angeles, where his parents worked in factories and Garcia was…

  4. The deep water cycle and origin of cratonic flood basalts: two examples from the Siberian craton

    NASA Astrophysics Data System (ADS)

    Ivanov, A. V.

    2014-12-01

    Cratonic flood basalt volcanism is the most puzzling phenomenon compared to all other types of intraplate volcanism. Cratons are thick and cold; the two parameters which suppress melting of either sublithospheric or lithospheric mantle in dry conditions. Fusible eclogites at hot plume geotherm start to melt in sublithospheric depth (~ 230 km), but geochemical arguments require that, in addition to eclogitic component, significant volume of flood basalts are from peridotitic mantle. Dry peridotitic mantle cannot be melted unless the lithospheric thickness reduced to about 60 km. That is why modern plume models incorporate lithospheric delamination and/or initially thinned lithosphere to explain cratonic flood basalts. However, if lithosphere remained thick, which was the case for the Siberian craton by the time of formation of its Devonian (Vilyui) and Permo-Triassic (Siberian) flood basalt provinces, then plume model is unable to explain the flood basalt volcanism. If mantle is wet, the peridotitic solidus lowered such as it can start to melt at sublithospheric depth (for example, 2 wt. % H2O-bearing peridotite starts to melt at ~320 km depth even at a normal mantle geotherm). In this presentation I will show that fluxing of mantle via the deep water cycle process may explain the Siberian craton flood basalts and many other continental flood basalts. According to the deep water cycle model, water is carried to the mantle transition zone by fast subducting slabs (may be in form of solid ice VII), then water is released from the slabs due to warming to the ambient mantle temperature, then localized hydration creates buoyant wet diapirs (or melt-bearing diapirs), the diapirs raise up to the sublithosheric depth were melt accumulates for the following tectonically triggered flood basalt eruptions.

  5. Mesoproterozoic rapakivi granites of the Rondonia Tin Province, southwestern border of the Amazonian craton, Brazil-I. Reconnaissance U-Pb geochronology and regional implications

    USGS Publications Warehouse

    Bettencourt, Jorge S.; Tosdal, R.M.; Leite, W.B., Jr.; Payolla, B.L.

    1999-01-01

    Rapakivi granites and associated mafic and ultramafic rocks in the Rondonia Tin Province, southwestern Amazonian craton, Brazil were emplaced during six discrete episodes of magmatism between ca 1600 and 970 Ma. The seven rapakivi granite suites emplaced at this time were the Serra da Providencia Intrusive Suite (U-Pb ages between 1606 and 1532 Ma); Santo Antonio Intrusive Suite (U-Pb age 1406 Ma); Teotonio Intrusive Suite (U-Pb age 1387 Ma); Alto Candeias Intrusive Suite (U-Pb ages between 1346 and 1338 Ma); Sao Lourenco-Caripunas Intrusive Suite (U-Pb ages between 1314 and 1309 Ma); Santa Clara Intrusive Suite (U-Pb ages between 1082 and 1074 Ma); and Younger Granites of Rondonia (U-Pb ages between 998 and 974 Ma). The Serra da Providencia Intrusive Suite intruded the Paleoproterozoic (1.80 to 1.70 Ga) Rio Negro-Juruena crust whereas the other suites were emplaced into the 1.50 to 1.30 Ga Rondonia-San Ignacio crust. Their intrusion was contemporaneous with orogenic activity in other parts of the southwestern Amazonian craton, except for the oldest, Serra da Providencia Intrusive Suite. Orogenic events coeval with emplacement of the Serra da Providencia Intrusive Suite are not clearly recognized in the region. The Santo Antonio, Teotonio, Alto Candeias and Sao Lourenco-Caripunas Intrusive Suites are interpreted to represent extensional anorogenic magmatism associated with the terminal stages of the Rondonian-San Ignacio orogeny. At least the Sao Lourenco-Caripunas rapakivi granites and coeval intra-continental rift sedimentary rocks may, in contrast, represent the products of extensional tectonics and rifting preceding the Sunsas/Aguapei orogeny (1.25 to 1.0 Ga). The two youngest rapakivi suites, the Santa Clara Intrusive Suite and Younger Granites of Rondonia, seemingly represent inboard magmatism in the Rondonian-San Ignacio Province during a younger episode of reworking in the Rio Negro-Juruena Province during the waning stages of the collisional 1.1 to 1.0 Ga

  6. Modeling of craton stability using a viscoelastic rheology

    NASA Astrophysics Data System (ADS)

    Beuchert, Marcus; Podladchikov, Yuri; Simon, Nina; Rüpke, Lars

    2010-05-01

    Archean cratons belong to the most remarkable features of our planet, since they represent continental crust that has avoided reworking for several billions of years. Even more, it has become evident from both geophysical and petrological studies that cratons exhibit deep lithospheric keels which equally remained stable ever since the formation of the cratons in the Archean. Dating of inclusions in diamonds from kimberlite pipes give Archean ages, showing that the Archean lithosphere must have been cold soon after its formation in the Archean, in order to allow for the existence of diamonds, and must have stayed in that state ever since. Yet, whereas the stability of Archean cratonic lithosphere for billions of years is a fact, some numerical models failed to reproduce this observed long-term stability (see review by King, 2005). We devised a viscoelastic mantle convection model for exploring cratonic stability. Our modeling results indicate that the application of sufficiently high temperature-dependent viscosity ratio can provide for the observed cratonic stability for billions of years. From our numerical simulations, we derived a relation between Rayleigh number, viscosity ratio, size of the model craton and time to instability of the cratonic root. The comparison between simulations with viscous and viscoelastic rheology indicates no significant influence of elasticity on craton stability. Yet, stress distributions within the model craton differ significantly between viscous and viscoelastic rheologies. This has important implications for future models that include stress-dependent processes like plasticity, power law creep and shear heating. If those processes are to be modeled accurately in mantle convection models that include the lithosphere, a viscoelastic rheology would have to be applied.

  7. Flat slab subduction, trench suction, and craton destruction: Comparison of the North China, Wyoming, and Brazilian cratons

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy M.; Windley, Brian F.; Wang, Lu; Wang, Zhensheng; Li, Xiaoyong; Zhu, Peimin

    2014-09-01

    The mechanisms of growth and destruction of continental lithosphere have been long debated. We define and test a unifying plate tectonic driving mechanism that explains the numerous petrological, geophysical, and geological features that characterize the destruction of cratonic lithospheric roots. Data from three Archean cratons demonstrate that loss of their roots is related to rollback of subducted flat slabs, some along the mantle transition zone, beneath the cratons. During flat slab subduction dehydration reactions add water to the overlying mantle wedge. As the subducting slabs roll back, they suck in mantle material to infill the void space created by the slab roll back, and this fertile mantle becomes hydrated. The roll-back causes concomitant lithospheric thinning of the overlying craton so the flux of newly hydrated mantle material inevitably rises causing adiabatic melting, generating new magmas that gradually destroy the roots of the overlying craton through melt-peridotite reactions. Calculated fluxes of new mantle material beneath cratons that have lost their roots range from 2.7 trillion to 70 million cubic kilometers, which is sufficient to generate enough melt to completely replace the affected parts of the destroyed cratons. Cratonic lithosphere may be destroyed in massive quantities through this mechanism, warranting a re-evaluation of continental growth rates with time.

  8. Disentangling Middle Paleozoic sea level and tectonic events in cratonic margins and cratonic basins of North America

    NASA Astrophysics Data System (ADS)

    Bond, Gerard C.; Kominz, Michelle A.

    1991-04-01

    The cratonic margins and basins of North America contain evidence of distinct changes in relative sea level, one of the most intriguing of which occurred in middle Paleozoic time. The change in relative sea level began in Frasnian time (Late Devonian) and continued through Visean time (Middle Mississippian) in the Cordilleran miogeocline, in the Southern Oklahoma Aulacogen, in the Appalachian miogeocline and in the Michigan, Illinois, and Williston basins. The synchroneity and wide geographic distribution of this event are striking and would seem to argue for an eustatic mechanism. An estimate of the middle Paleozoic sea level rise relative to the stable craton in Iowa suggests that while a large sea level rise occurred, it is smaller than the magnitude of subsidence in the cratonic basins and margins. Flexural foreland basin models do not appear to account for the all of the events in the cratonic margins, and thermal subsidence mechanisms do not seem appropriate for the subsidence in the cratonic basins. The middle Paleozoic stratigraphic record from the North American craton and its margins, therefore, poses a basic problem of identifying a mechanism for producing a large-amplitude rise in sea level relative to the stable craton at the same time as a synchronous onset of tectonic subsidence in widespread basinal and marginal settings of diverse tectonic origin. One plausible mechanism for the tectonic subsidence in the basins and margins is a pulse of intraplate compressive stress. The origin of the large sea level rise relative to the stable craton could reflect an unusually large eustatic sea level change, but we cannot eliminate the possibility of a small component of subsidence or change in dynamic topography of the North American craton. The synchroneity of the sea level rise relative to the craton with the subsidence of basins and margins may be fortuitous, but it is also predicted by recent mantle convection models for the early stages of accretion of

  9. 10. Office of the Post Engineer, Presidio of San Francisco. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Office of the Post Engineer, Presidio of San Francisco. Location of Water Lines, Presidio of San Francisco. Sheet 30. November 1943. SHOWING EASTERN PORTION OF CRISSY FIELD AND AREA A. - Presidio of San Francisco, Storehouse & Administration, Crissy Field North cantonment, Allen Street, San Francisco, San Francisco County, CA

  10. 9. Office of the Post Engineer, Presidio of San Francisco. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Office of the Post Engineer, Presidio of San Francisco. Location of Water Lines, Presidio of San Francisco. Sheet 29. June 1944. SHOWING EASTERN PORTION OF CRISSY FIELD. - Presidio of San Francisco, Storehouse & Administration, Crissy Field North cantonment, Allen Street, San Francisco, San Francisco County, CA

  11. 36. Post Engineer Office, Presidio of San Francisco. Plot Plan, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    36. Post Engineer Office, Presidio of San Francisco. Plot Plan, Letterman Army Hospital, San Francisco, Calif. 1958. SHOWING LOCATION OF BUILDINGS 1006 AND 1049 IN LETTERMAN HOSPITAL COMPLEX IN 1958. - Presidio of San Francisco, Letterman General Hospital, Building No. 27, Letterman Hospital Complex, Edie Road, San Francisco, San Francisco County, CA

  12. ASTER Flyby of San Francisco

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Advanced Spaceborne Thermal Emission and Reflection radiometer, ASTER, is an international project: the instrument was supplied by Japan's Ministry of International Trade and Industry. A joint US/Japan science team developed algorithms for science data products, and is validating instrument performance. With its 14 spectral bands, extremely high spatial resolution, and 15 meter along-track stereo capability, ASTER is the zoom lens of the Terra satellite. The primary mission goals are to characterize the Earth's surface; and to monitor dynamic events and processes that influence habitability at human scales. ASTER's monitoring and mapping capabilities are illustrated by this series of images of the San Francisco area. The visible and near infrared image reveals suspended sediment in the bays, vegetation health, and details of the urban environment. Flying over San Francisco (3.2MB) (high-res (18.3MB)), we see the downtown, and shadows of the large buildings. Past the Golden Gate Bridge and Alcatraz Island, we cross San Pablo Bay and enter Suisun Bay. Turning south, we fly over the Berkeley and Oakland Hills. Large salt evaporation ponds come into view at the south end of San Francisco Bay. We turn northward, and approach San Francisco Airport. Rather than landing and ending our flight, we see this is as only the beginning of a 6 year mission to better understand the habitability of the world on which we live. For more information: ASTER images through Visible Earth ASTER Web Site Image courtesy of MITI, ERSDAC, JAROS, and the U.S./Japan ASTER Science Team

  13. Northern California near San Francisco

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A part of northern California centered near San Francisco Bay (38.0N, 122.0W) photographed at 3 p.m. January 1, 1974, from the Skylab space station in Earth orbit. This near vertical view encompasses the coastline from Monteray Bay (right) to about 50 miles north of Point Reyes (left) and includes, from bottom to top, San Francisco Bay (center), Sacramento Valley (left center), San Joaquin Valley (right center), and the snow-covered Sierra Nevada. Afternoon shadows sharply delineate a valley which parallels San Francisco Bay, crosses Point Reyes, and lies between the Bay and the Pacific coastline. This valley marks the location of the San Andreas Fault. Forces acting on the crust are causing the land west (bottom) of the fault line to move north relative to land on the east side. Agricultural areas in the Sacramento and San Joaquin Valleys are indicated by the tan areas which are easily discerned in contrast to the green-gray background.

  14. Cratons: Why Are The Little Ones So Tough?

    NASA Astrophysics Data System (ADS)

    Keller, G. R.

    2013-12-01

    Cratons are ancient (>1 Ga) survivors of multiple tectonic events and diverse tectonic regimes. The question that arises is why are they so tough? If one looks around the world at relatively small cratons, the answer at least partly lies in their crustal structure. This is not to say that their lithospheric mantle is not also part of the answer, but mapping the LAB is still a challenge. Some examples of relatively small cratons in North America that are relatively well studied are the Wyoming and SASK cratons. A good example in Africa is the Tanzanian craton, and a good example in China is the North China craton. The Wyoming craton initially formed at ~2.5 Ga and formed has very thick (~50 km) crust that includes a high velocity layer (Vp ~7.5 km/s) at its base. Recent xenolith studies indicate that at least some of this high velocity layer was underplated at ~1.8 Ga. The recently discovered Sask craton in Canada was caught up in the Trans-Hudson orogen and is completely covered by younger rocks. It also has a thick crust. The Tanzanian craton has been strong enough to cause the East African rift system to split into two arms that wrap around it. It has relatively thick crust (and lithospheric keel?). The Colorado plateau in the western U. S. and the Ordos block in north China are very similar in many respects and have resisted deformation in the their interiors while they are bounded on three sides by rifts. A common theme among these examples is relatively thick crust, and in most cases, a unusually fast lower crust.

  15. The Building of the Archean Superior Craton: Thermal Perspective

    NASA Astrophysics Data System (ADS)

    Jaupart, C. P.; Mareschal, J. C.

    2014-12-01

    The building of a craton involves the extraction of continental crust from the Earth's mantle and the lateral accretion of juvenile volcanic terranes. Ascertaining which conditions allow a newborn continental assemblage to survive requires information on its mechanical strength, which depends on the amount and vertical distribution of radioactive elements in the crust. There is thus a connection between crust formation mechanisms and a successful amalgamation process. To address outstanding questions concerning Archean cratons, the Superior province in Canada is the perfect region because it contains a well preserved geological record of accretion that provides compelling evidence for plate tectonic processes at 2.7 Ga. At almost the same time, the rate of continental growth decreased significantly, which may result from either slower crust formation or enhanced destruction through erosion and subduction. These issues are linked to the strength of the newborn continent. The extensive heat flow data set now available in the Superior Province reveals a clear demarcation between a chemically depleted and differentiated craton core and weakly differentiated enriched juvenile accreted terranes. The Superior craton was thus made of a strong core surrounded by weak terranes. This dichotomy implies that the accretion process could not involve complex imbrication of the accreted belts into the craton core. Subsequently, the craton may have been protected from convective disruption or delamination by its weak margins. Differences between the craton core and accreted terranes may be due to different crustal extraction processes, such as melting in a mantle plume or magmatism in a subduction zone. If subduction started at about 3 Ga, as advocated by several authors, the assembly and survival of large cratons may well be a consequence of this key shift in mantle activity. Alternatively, the chemical depletion of the craton core may be due to a prolonged history of internal

  16. Seismic experiment reveals rifting of craton in Tanzania

    NASA Astrophysics Data System (ADS)

    Nyblade, Andrew A.; Langston, Charles A.; Last, Robert J.; Birt, Christopher; Owens, Thomas J.

    A research project in Tanzania, East Africa, is being conducted to examine seismic velocities within the crust and upper mantle in an area where cratonic lithosphere is experiencing extensional tectonism. The results will be used to evaluate models of cratonic structure. Waveforms from several hundred teleseismic earthquakes and over 10,000 regional and local earthquakes recorded in 1994 and 1995 by the Tanzania Broadband Seismic Experiment are not only yielding new insights into deep continental structure, but are also helping to determine the tectonic stability of cratons by identifying the locus of rifting within northeastern Tanzania.

  17. Limiting depth of magnetization in cratonic lithosphere

    NASA Technical Reports Server (NTRS)

    Toft, Paul B.; Haggerty, Stephen E.

    1988-01-01

    Values of magnetic susceptibility and natural remanent magnetization (NRM) of clino-pyroxene-garnet-plagioclase granulite facies lower crustal xenoliths from a kimberlite in west Africa are correlated to bulk geochemistry and specific gravity. Thermomagnetic and alternating-field demagnetization analyses identify magnetite (Mt) and native iron as the dominant magnetic phases (totaling not more than 0.1 vol pct of the rocks) along with subsidiary sulfides. Oxidation states of the granulites are not greater than MW, observed Mt occurs as rims on coarse (about 1 micron) Fe particles, and inferred single domain-pseudosingle domain Mt may be a result of oxidation of fine-grained Fe. The deepest limit of lithospheric ferromagnetism is 95 km, but a limit of 70 km is most reasonable for the West African Craton and for modeling Magsat anomalies over exposed Precambrian shields.

  18. Proterozoic granitoids of the Amazonian craton

    NASA Astrophysics Data System (ADS)

    dalĺAgnol, R.; Costi, H. T.; Lamarão, C. N.; Teixeira, N. P.; Bettencourt, J. S.; Fraga, L. M.

    2003-04-01

    Proterozoic granitoids are widespread in all provinces of the Amazonian craton. In the Maroni-Itacaiunas Province, granitoids associated with the Trans-Amazonian event include: subduction related, 2.16 to 2.14 Ga, calc-alkaline tonalites and trondhjemites; 2.10 to 2.08 Ga, syncolisional potassic granites; 2.05 Ga, charnockites. In the Tapajós Province, ˜2.01 Ga, tonalites are followed by ˜2.0 Ga volcanic sequences and ˜1.98 to 1.96 Ga calc-alkaline granitoids. A reappraisal of magmatic activity occurred at ˜1.88 Ga when calc-alkaline granitoids, as well as subalkaline, A-type granites, associated with felsic volcanic sequences were formed. A similar picture is observed in the northern Roraima region, where post-collisional 2.0 to 1.96 Ga calc-alkaline granitoids and associated volcanic sequences are followed by 1.92 Ga A-type granites. The remarkable 1.88 Ga magmatic event has a continental scale and is related to an extensional tectonism. It affected also the Archean Carajás Province, where, at this time, within-plate, shallow-level, A-type granites were emplaced. Coeval intermediate to felsic volcanic sequences are widespread in the Central Amazonian Province. In the Pitinga region, these sequences are intruded by ˜1.82 Ga, tin-mineralized granites. In the Central Guiana Belt and in the northwestern domains of the Guiana shield ˜1.55 Ga rapakivi complexes, locally with associated anorthosites and mangerites, are common. In the Rio Negro Province, 1.8 to 1.60 calc-alkaline (?) granitoids and gneisses are dominant. They are followed by 1.55 to 1.52 Ga, oxidized, titanite-bearing A-type granites and S-type, two-mica granites. The evolution of the southwestern part of the Amazonian craton is characterized by the occurrence of successive tectonic events extending from ˜1.75 Ga to ˜1.0 Ga. The oldest granitoids are dominantly calc-alkaline tonalites, trondhjemites and granodiorites. However, the Rondonia region is marked by the occurrence of 1.6 to 1.0 Ga old

  19. 77 FR 28771 - Safety Zone; San Francisco Giants Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-16

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Giants Fireworks Display, San Francisco, CA... enforce the safety zone for the San Francisco Giants Fireworks Display in the Captain of the Port, San... life and property of the maritime public from the hazards associated with the fireworks display....

  20. 78 FR 20792 - Safety Zone; San Francisco Giants Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-08

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Giants Fireworks Display, San Francisco, CA... enforce the safety zone for the San Francisco Giants Fireworks Display in the Captain of the Port, San... life and property of the maritime public from the hazards associated with the fireworks display....

  1. 75 FR 35651 - Safety Zone; San Francisco Chronicle Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-23

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Chronicle Fireworks Display, San Francisco... will enforce the Independence Day Celebration for the City of San Francisco Fireworks safety zone from 11 a.m. through 10 p.m. on July 4, 2010. The fireworks will be fired simultaneously from two...

  2. 78 FR 18238 - Safety Zone; SFPD Training Safety Zone; San Francisco Bay, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    ... of Homeland Security FR Federal Register SFPD San Francisco Police Department NPRM Notice of Proposed... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; SFPD Training Safety Zone; San Francisco... Guard is establishing a temporary safety zone in the navigable waters of the San Francisco Bay...

  3. 77 FR 57494 - Safety Zone; Fleet Week Fireworks, San Francisco Bay, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-18

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; Fleet Week Fireworks, San Francisco Bay, San Francisco... will enforce the safety zone for the Fleet Week Fireworks in the Captain of the Port, San Francisco...'' W (NAD83) for the Fleet Week Fireworks in 33 CFR 165.1191, Table 1, item number 25. This safety...

  4. 77 FR 37603 - Safety Zone; San Francisco Independence Day Fireworks Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-22

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; San Francisco Independence Day Fireworks Display, San... Guard will enforce the safety zones for the San Francisco Independence Day Fireworks Display in the... INFORMATION: The Coast Guard will enforce the San Francisco Independence Day Fireworks Display safety...

  5. 29. Photocopy of photograph (from San Francisco Chronicle Library, San ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. Photocopy of photograph (from San Francisco Chronicle Library, San Francisco, California, c. 1930 (?) EXTERIOR, GENERAL VIEW OF CONVENTO, FRONT VIEW, AFTER RESTORATION - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA

  6. Late Precambrian aulacogens of the North China craton

    NASA Technical Reports Server (NTRS)

    Qian, X.

    1985-01-01

    According to tectonic styles, the Precambrian evolution history of the North China craton may be subdivided into four stages: (1) Archean consolidation in 3.5 to 2.5 Ga, (2) Early Proterozoic rifting in 2.5 to 1.8 Ga, (3) Late Precambrian aulacogen in 1.8 to 0.8 Ga and (4) Platform regime after 0.8 Ga. In the Late Precambrian aulacogen stage of the North China craton there were two main aulacogens, Yanliao and Zhongtiao (Y and Z), developed in Middle Proterozoic time with an age 1.8 to 1.0 Ga. Their NE trend caused them to meet together in the central part of the craton and build up one great Y-Z aulacogen throughout the craton.

  7. Geological evolution of the Antongil Craton, NE Madagascar

    USGS Publications Warehouse

    Schofield, D.I.; Thomas, Ronald J.; Goodenough, K.M.; De Waele, B.; Pitfield, P.E.J.; Key, R.M.; Bauer, W.; Walsh, G.J.; Lidke, D.J.; Ralison, A.V.; Rabarimanana, M.; Rafahatelo, J.-M.; Randriamananjara, T.

    2010-01-01

    The Antongil Craton, along with the Masora and Antananarivo cratons, make up the fundamental Archaean building blocks of the island of Madagascar. They were juxtaposed during the late-Neoproterozoic to early Palaeozoic assembly of Gondwana. In this paper we give a synthesis of the geology of the Antongil Craton and present previously published and new geochemical and U-Pb zircon analyses to provide an event history for its evolution.The oldest rocks in the Antongil Craton form a nucleus of tonalitic gneiss, characteristic of Palaeo-Mesoarchaean cratons globally, including phases dated between 3320 ?? 14. Ma to 3231 ?? 6. Ma and 3187 ?? 2. Ma to 3154 ?? 5. Ma. A series of mafic dykes was intruded into the Mesoarchaean tonalites and a sedimentary succession was deposited on the craton prior to pervasive deformation and migmatisation of the region. The age of deposition of the metasediments has been constrained from a volcanic horizon to around 3178 ?? 2. Ma and subject to migmatisation at around 2597 ?? 49. Ma. A subsequent magmatic episode generated voluminous, weakly foliated granitic rocks, that also included additions from both reworked older crustal material and younger source components. An earlier granodiorite-dominated assemblage, dated between 2570 ?? 18. Ma and 2542 ?? 5. Ma, is largely exposed in xenoliths and more continuously in the northern part of the craton, while a later monzogranite-dominated phase, dated between 2531 ?? 13. Ma and 2513 ?? 0.4. Ma is more widely developed. Together these record the stabilisation of the craton, attested to by the intrusion of a younger dyke swarm, the age of which is constrained by a sample of metagabbro dated at 2147 ?? 6. Ma, providing the first evidence for Palaeoproterozoic rocks from the Antongil Craton.The youngest events recorded in the isotopic record of the Antongil Craton are reflected in metamorphism, neocrystallisation and Pb-loss at 792 ?? 130. Ma to 763 ?? 13. Ma and 553 ?? 68. Ma. These events are

  8. The Thermal Structure and Strength of Cratons and their Margins

    NASA Astrophysics Data System (ADS)

    Jaupart, C. P.; Mareschal, J. C.

    2015-12-01

    The large cratons of today are made of younger terranes that wrap around older cores. Deformation due to accretion did not proceed in homogeneous fashion and was concentrated in the younger belts. This is illustrated clearly in the Archean Superior Province, Canada. In this area, one observes little imbrication of accreted crust and craton core, in contrast to the laterally extensive thrusting that has affected the younger terranes to the South. The boundary between the craton core and accreted belts is a nearly vertical interface delineated by steeply dipping electrical and seismic anomalies extending to the base of the lithosphere. These steeply dipping structures have been interpreted as relicts of the subduction that drove accretion. By contrast, the sub-crustal subduction remnant that is imaged beneath younger terranes to the south shows up as a moderately dipping (≈30°) structure. These observations suggest a stiff craton surrounded by weaker belts. This strength contrast may have affected later events, such as the Keweenawan rifing, which propagated northward through the accreted terranes but stopped short of impinging the craton core. In the Superior Province, crustal heat production is much higher in the accreted terranes than in the craton core, implying higher temperatures and lower mechanical strength. Such a remarkable dichotomy also exists in South Africa, where the Limpopo and Namaqua belts are characterized by higher heat flux and crustal heat production than the adjacent Archean Kaapvaal and Zimbabwe cratons. The generality of this cannot be assessed on the basis of heat flow and heat production data which are scarce in most other cratons. These cratons, however, are characterized by post-orogenic high temperature metamorphism which is best explained by high crustal heat production. This is true, for example, for the Jimperding metamorphic belt at the edge of the Yilgarn craton, Western Australia. Thus, cratons appear to be surrounded, and

  9. Patterns and origin of igneous activity around the Tanzanian craton

    NASA Astrophysics Data System (ADS)

    Foley, S. F.; Link, K.; Tiberindwa, J. V.; Barifaijo, E.

    2012-01-01

    Tertiary and later igneous activity is common on and around the Tanzanian craton, with primitive magma compositions ranging from kimberlites and varieties of picrites through nephelinites, basanites and alkali basalts. This review focuses on elucidating the conditions of origin of the melts, addressing the question of the state and involvement of the Tanzanian cratonic lithosphere in magma genesis. The Tanzanian craton is anomalous with a surface elevation of >1100 m reflecting buoyancy supported by a subcratonic plume whose effects are seen in the volcanics of both western and eastern rift branches. Magmatism on the craton and at its edge has high K/Na and primitive melts show fractionation dominated by olivine. Slightly further from the craton pyroxene fractionation dominates and K/Na ratios in the magmas are lower. Off-craton melts are nephelinites, basanites and alkali basalts with low K/Na. Potassium enrichment in the melts correlates with the occurrence of phlogopite in mantle-derived xenoliths, and also with carbonate in the magmas. This is attributed to melting at >140 km depths of mixed source regions containing phlogopite pyroxenite and peridotite, whereby the carbonate is derived from oxidation of diamonds concentrated near the base of the cratonic lithosphere. Mixed source regions are required by arrays of radiogenic isotopes such as Os and Sr in the volcanic rocks. The temporal progression of lamproites to phlogopite + carbonate-rich rocks to melilitites, nephelinites and alkali basalts seen during the erosion of the North Atlantic craton are seen around the Tanzanian craton as the coeval occurrence kimberlites, kamafugites and related rocks, nephelinites and alkali basalts showing spatial instead of temporal variation. This is due to the different stages of development of rifting around the craton: in northwestern Uganda and northern Tanzania, K-rich volcanism occurs at the craton edge, whereas nephelinites, basanites and alkali basalts occur where

  10. Construction and destruction of some North American cratons

    NASA Astrophysics Data System (ADS)

    Snyder, D. B.; Humphreys, G.

    2015-12-01

    Construction histories of Archean cratons remain poorly understood; their destruction is even less clear because of, by definition, its rarity. By assembling geophysical and geochemical data in 3-D lithosphere models, a clearer understanding of the geometry of major structures within the Rae, Slave and Wyoming cratons of central North America is now possible. Little evidence exists of subducted slabs similar to modern oceanic lithosphere in these construction histories whereas underthrusting and wedging of proto-continental lithosphere is inferred from multiple dipping discontinuities. Archean continental building blocks may resemble the modern lithosphere of Ontong-Java-Hikurangi oceanic plateau. Radiometric dating of xenoliths provides estimates of rock types and ages at depth beneath sparse kimberlite occurrences. These ages can be correlated to surface rocks. The 3.6-2.6 Ga Rae, Slave and Wyoming cratons comprise smaller continental terranes that 'cratonized' during a granitic bloom at 2.61-2.55 ga. Cratonization probably represents the final differentiation of early crust into a relatively homogeneous, uniformly thin (35-42 km), tonalite-trondhjemite-granodiorite crust with pyroxenite layers near the Moho atop depleted lithospheric mantle. Peak thermo-tectonic events at 1.86-1.7 Ga broadly metasomatized, mineralized and recrystallized mantle and lower crustal rocks, apparently making mantle peridotite more 'fertile' and conductive by introducing or concentrating sulfides or graphite throughout the lithosphere at 80-120 km depths. This metasomatism may have also weakened the lithosphere or made it more susceptible to tectonic or chemical erosion. The arrival of the subducted Shatsky Rise conjugate at the Wyoming craton at 65-75 Ma appears to have eroded and displaced the thus weakened base of the craton below 140-160 km. This replaced old refertilized continental mantle with new depleted oceanic mantle. Is this the same craton?

  11. 3D numerical model of the plume-lithosphere interactions near cratonic blocks: Implications for the Tanzanian craton

    NASA Astrophysics Data System (ADS)

    Koptev, Alexander; Burov, Evgueni; Calais, Eric; Leroy, Sylvie; Gerya, Taras

    2014-05-01

    We explore the evolution of plume-activated rifting in a heterogeneous continental lithosphere containing embedded cratonic blocks, with a particular focus on the impact of horizontal position of a plume with respect to the craton. We also study the influence of a preexisting far-field stress/strain field on the «active» rifting style by implementing a slow far-field extension during the plume-lithosphere interaction. In the experiments, a «cratonic» block (cold, thick depleted mantle) is embedded into a «normal» lithosphere roughly mimicking the configuration of the Tanzanian craton and of its surroundings. We next varied the far-field extension rates, the thickness of the craton as well as the thermo-rheological profile and the position of the plume with respect to the center of the craton (placed either strictly under the center of the «Tanzanian» craton or slightly shifted in the NE direction). Despite significant disparities in style and timing of rifting process observed in models with different parameters, the common feature for all cases with central plume position refers to the development of largely symmetric diverging rift branches embracing the craton. The models with shifted initial plume position demonstrate a fundamentally different behavior because in this case the cratonic block deflects plume material to one side of the craton, leading to a strongly asymmetric spreading of plume-head material under the bottom of the lithosphere. This asymmetry results in development of two different rift branches: the first one is more pronounced and develops right above the plume head at the north-east of the craton, with a lot of magmatic material arriving to the surface. The second branch appears almost simultaneously but is less pronounced, amagmatic, and propagates northward over the western part of the craton. This evolution resembles the one inferred for east (warm and magmatic) and west (cold and amagmatic) rift braches in the East African rift

  12. South San Francisco Bay, California

    USGS Publications Warehouse

    Dartnell, Peter; Gibbons, Helen

    2007-01-01

    View eastward. Elevations in mapped area color coded: purple (approx 15 m below sea level) to red-orange (approx 90 m above sea level). South San Francisco Bay is very shallow, with a mean water depth of 2.7 m (8.9 ft). Trapezoidal depression near San Mateo Bridge is where sediment has been extracted for use in cement production and as bay fill. Land from USGS digital orthophotographs (DOQs) overlaid on USGS digital elevation models (DEMs). Distance across bottom of image approx 11 km (7 mi); vertical exaggeration 1.5X.

  13. San Francisco floating STOLport study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The operational, economic, environmental, social and engineering feasibility of utilizing deactivated maritime vessels as a waterfront quiet short takeoff and landing facility to be located near the central business district of San Francisco was investigated. Criteria were developed to evaluate each site, and minimum standards were established for each criterion. Predicted conditions at the two sites were compared to the requirements for each of the 11 criteria as a means of evaluating site performance. Criteria include land use, community structure, economic impact, access, visual character, noise, air pollution, natural environment, weather, air traffic, and terminal design.

  14. Trouble Brewing in San Francisco. Policy Brief

    ERIC Educational Resources Information Center

    Buck, Stuart

    2010-01-01

    The city of San Francisco will face enormous budgetary pressures from the growing deficits in public pensions, both at a state and local level. In this policy brief, the author estimates that San Francisco faces an aggregate $22.4 billion liability for pensions and retiree health benefits that are underfunded--including $14.1 billion for the city…

  15. Jack London and the San Francisco earthquake

    USGS Publications Warehouse

    Sachs, J.S.

    1982-01-01

    After it was over, it seemed to many, and especially to eyewitnesses like Jack London, that the earthquake and fire had devastated San Francisco. However people were confident that, like the phoeniz, San Francisco would rise from the ashes and regain her palce as the "Imperial City of the West." 

  16. Proterozoic history of the Borborema province (NE Brazil): Correlations with neighboring cratons and Pan-African belts and implications for the evolution of western Gondwana

    NASA Astrophysics Data System (ADS)

    Neves, SéRgio Pacheco

    2003-08-01

    Geological and geochronological correlations between Borborema province (NE Brazil) and neighboring cratons and Brasiliano/Pan-African belts indicate that the Amazonian, West African, and São Francisco/Congo cratons and the basement of the Araguaia, Borborema, Nigerian, and Cameroon provinces were part of the Atlantica supercontinent. This continent was established at the end of the Transamazonian/Eburnean cycle (˜2.0 Ga) and, apart from ubiquitous taphrogenesis in the 1.8-1.7 Ga interval, remained largely unaffected for the following 1 Ga. Around 1 Ga an important magmatic event in Borborema province correlates with rifting episodes and anorogenic magmatism in the São Francisco, Congo, and Amazonian cratons. These events are interpreted as failed attempts to break up Atlantica, which at this time may have been part of the larger Rodinia supercontinent. Renewed extensional conditions in Borborema province during the middle and late Neoproterozoic are attributed to far-field stresses transmitted to the interior of Atlantica by outwardly dipping subduction zones that encircled its northern (present day coordinates) portion. The rarity of petrotectonic assemblages typical of subduction zone environments indicates that extension did not evolve enough to form large oceans basins and thus that the Borborema province essentially includes reworked intracontinental domains. Regional deformation and metamorphism, starting at 650-640 Ma, and shear zone development, beginning at 590-595 Ma, were continuously developed through time and were synchronous throughout most of the Borborema, Araguaia, Cameroon, and Nigerian provinces. Postorogenic conditions were reached 540-530 Myr ago, while active deformation was still occurring in other belts that accreted around Atlantica to form western Gondwana.

  17. Water in the Cratonic Mantle: Insights from FTIR Data on Lac De Gras Xenoliths (Slave Craton, Canada)

    NASA Technical Reports Server (NTRS)

    Peslier, Anne H.; Brandon, Alan D.; Schaffer, Lillian Aurora; O'Reilly, Suzanne Yvette; Griffin, William L.; Morris, Richard V.; Graff, Trevor G.; Agresti, David G.

    2014-01-01

    The mantle lithosphere beneath the cratonic part of continents is the deepest (> 200 km) and oldest (>2-3 Ga) on Earth, remaining a conundrum as to how these cratonic roots could have resisted delamination by asthenospheric convection over time. Water, or trace H incorporated in mineral defects, could be a key player in the evolution of continental lithosphere because it influences melting and rheology of the mantle. Mantle xenoliths from the Lac de Gras kimberlite in the Slave craton were analyzed by FTIR. The cratonic mantle beneath Lac de Gras is stratified with shallow (<145 km) oxidized ultradepleted peridotites and pyroxenites with evidence for carbonatitic metasomatism, underlain by reduced and less depleted peridotites metasomatized by kimberlite melts. Peridotites analyzed so far have H O contents in ppm weight of 7-100 in their olivines, 58 to 255 in their orthopyroxenes (opx), 11 to 84 in their garnet, and 139 in one clinopyroxene. A pyroxenite contains 58 ppm H2O in opx and 5 ppm H2O in its olivine and garnet. Olivine and garnet from the deep peridotites have a range of water contents extending to higher values than those from the shallow ones. The FTIR spectra of olivines from the shallow samples have more prominent Group II OH bands compared to the olivines from the deep samples, consistent with a more oxidized mantle environment. The range of olivine water content is similar to that observed in Kaapvaal craton peridotites at the same depths (129-184 km) but does not extend to as high values as those from Udachnaya (Siberian craton). The Slave, Kaapvaal and Siberian cratons will be compared in terms of water content distribution, controls and role in cratonic root longevity.

  18. Majorite Garnet and Lithosphere Evolution: Kaapvaal Craton

    NASA Astrophysics Data System (ADS)

    Griffin, W. L.; Tessalina, S.; O'Reilly, S. Y.

    2013-12-01

    The uppermost 50-70 km of the subcontinental lithospheric mantle (SCLM) beneath the Kaapvaal Craton (S. Africa) consists largely of highly-depleted chromite harzburgites. These rocks are understudied, mainly because of their uniformity and their lack of indicator minerals such as garnet and clinopyroxene (cpx). Kimberlite-borne xenoliths of these rocks contain rare volumes of cpx-spinel (modal 76/24) symplectite, with smooth grain boundaries; many studies have suggested that these might represent low-pressure breakdown products of garnet (majorite + olivine → cpx + spinel). Our reconstruction of a suite of these grains, using element mapping and EMP analysis of constituent minerals, gives a majoritic garnet with mean composition 21.8% CaO, 15.8% Cr2O3, 9.22% Al2O3, Si=3.118, mg#=0.93. The majorite contents suggest formation at depths of 250-280 km. Ni contents imply temperatures ≥1500 °C, but have large uncertainties related to the subtraction of olivine (ca 20%) during the reconstruction calculation. LAM-ICPMS analyses show strongly sinuous REE patterns with CN Dy/Lu <0.1 and Ce/Dy >100. Most analyses have negative Eu anomalies, consistent with chromite compositions that indicate strongly reducing conditions (ΔfO2(FMQ) = -4 to -5). Melt modeling suggests that the harzburgites are products of 30-40% melting of asthenospheric mantle at 250 km depth, leaving residues of ol+opx+chromite. The presence of the majorites and their overall LREE enrichment are ascribed to the introduction of carbonatitic metasomatic fluids, similar to those recorded by diamond-inclusions (subcalcic garnets), shortly after the depletion. We suggest that the melting, the metasomatism and the ultimate breakdown of the majorite track a process of mantle upwelling, with melt-extraction at depth providing the buoyancy that allowed the residual harzburgites to rise to shallow levels and stabilize the SCLM. Os-isotope analyses of sulfides associated with the majorites give TRD = 2.5-3.4 Ga

  19. The Paleoproterozoic APWP of the Kalahari Craton

    NASA Astrophysics Data System (ADS)

    Gose, W. A.; Hanson, R. E.

    2006-05-01

    An apparent polar wander path for the Precambrian of the Kalahari craton, south Africa, still remains an elusive goal. This is not due to the lack of paleomagnetic data but rather the paucity or lack of age control. The need for radiometric ages became particularly clear when we were collecting dolerite dikes of the 1.1 Ga Umkondo suite in an attempt to delineate its areal extent. Seven dikes west of Pietersburg, South Africa, mapped as Umkondo dolerites, yielded a direction of magnetization distinctively different from the Umkondo direction. 300 km to the northeast in the Soutpansberg area, 5 dolerite sills and 3 basalt flows carry a direction antipodal to these dikes at the 1percent significance level. The combined data set has a pole position of 17.4°N, 17.2°E, with an error of A95=8.2°. One of the sampled dikes and two nearby dikes have U-Pb baddeleyite crystallization ages of 1871±1.2 Ma, 1873±0.8 Ma, and 1878±0.5 Ma (Hanson et al. 2004). These data provide an important pole position for defining the Paleoproterozoic segment of the Kalahari APWP. Our results do not support recent suggestions that the geomagnetic field was asymmetrical during the Precambrian. Hanson, R. E. et al., 2004, South African J. Geol., 107,233-254.

  20. Remagnetized cratonic Cambrian strata from southern Nevada

    NASA Astrophysics Data System (ADS)

    Gillett, Stephen L.

    1982-08-01

    Stratigraphic sections of Cambrian strata in southeastern Nevada are akin to thin, cratonic facies exposed in the Grand Canyon; their structural setting is much more complicated, however, from Mesozoic and Cenozoic tectonism. Paleomagnetic samples from two sections through these strata appear to have been completely remagnetized. Coarse-grained, lightcolored sandstone from the Tapeats Sandstone yields scattered magnetizations, residing in hematite, that appear to reflect protracted diagenetic acquisition of remanence. A hematitic sandstone in the Bright Angel Shale yields relatively consistent `Paleozoic' directions of magnetization, but petrographic study shows that the hematite results from diagenetic oxidation, and stratigraphic arguments suggest that the oxidation was not penecontemporaneous. Gray limestones of the Jangle and Muav Limestones yield a magnetization, residing in magnetite, that may reflect late Tertiary remagnetization, being imposed during uplift related to the onset of Basin and Range deformation. In any case, this magnetization differs greatly in direction from a hematite magnetization reported from slightly younger Muav Limestone in the Grand Canyon. Both the sampling sites also appear to have been tectonically rotated, but whether this rotation is true or a geometric artifact of the tilt correction cannot be determined from the present data. These results suggest that paleomagnetic data from rocks as old as Cambrian must be scrutinized very carefully before their magnetizations can be accepted as penecontemporaneous, and such scrutiny must include geologic data.

  1. A Precambrian cratonic block in the west-central Chihuahua - The Sierra del Nido cratonic block

    SciTech Connect

    Goodell, P.C. . Dept. of Geological)

    1993-02-01

    Precambrian rocks in west-central Chihuahua have been recognized by Denison (1969) and Mauger et al. (1983), on the basis of radiometric dating. The rocks are rhyolite clasts, and an allucthonous block, respectively, however their source direction and vergence can be measured. They point back to and are on the edge of a large, uniform, negative Bouguer gravity anomaly, having values greater than 200 milligals. The isotopic geochemical character of several Tertiary felsic fields within this anomalous are has been determined, and initial strontium isotopic ratios are all greater than 0.7055. Outside the anomalous area these ratios are lower, and Basin and Range extension tectonism is more evident. It is proposed that a Precambrian cratonic block, the Sierra del Nido, is present in the crust in west-central Chihuahua. It is reasonable to propose that it was decreted from North America during a Precambrian extensional (1.1. By ) event, from somewhere along the Arizona Transition Zone-Texas Linament region. The Sierra del Nido Block is separated form the ATZ-TL by a region of disrupted craton and extended crust, the Basin and Range Province. Implications of the pressure of the Sierra del Nido Block on other regional tectonic events will be discussed.

  2. SAO HMC photodetector/event timer engineering model test report

    SciTech Connect

    1994-10-05

    The test unit is a custom photodetector/event timer, PET, built for the Smithsonian Astrophysical Observatory, SAO, by Los Alamos which records elapsed time in 10 ps steps. The 1 Kg, 12 cm diameter PET unit uses 10 watts of electrical power and was tested to SAO`s specified flight conditions. The event timer has two inputs -- a reference clock oscillator input and a stop signal. Like a stop watch with split timing capability, the event timer records the instant a stop signal arrives. At that sample instant, the number of elapsed clock cycles are stored and the sample instant position between two reference clock edges is interpolated and stored. Then that stored data can be shifted serially to an external computer. The photodetector part of the PET responds to an optical input and provides the electrical output signal to the event timer specifying the sample instant. This test report discusses the event timer test results. Test equipment is shown for most of the operational tests. The relay rack contains test pursers and clocks. The environmental chamber controls temperature. The computer reads and records the serial data from the PET. Reported testing topics include: Pulse shapes to be used as test inputs, test results obtained using the electrical source`s input, optical test results which are the best simulation of specified operational conditions, heat sink operation in vacuum. Vibration tests performed to SAO`s specification.

  3. 42. Post Engineer Office, Presidio of San Francisco, Letterman Army ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. Post Engineer Office, Presidio of San Francisco, Letterman Army Hospital, X-Ray Department and Second Floor Plan, X-Ray Department Plan, Building 1006. no date. BUILDING 1006. - Presidio of San Francisco, Letterman General Hospital, Building No. 27, Letterman Hospital Complex, Edie Road, San Francisco, San Francisco County, CA

  4. 21. Post Engineer Office, Presidio of San Francisco, Letterman Army ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. Post Engineer Office, Presidio of San Francisco, Letterman Army Hospital. EKG Cardiology Clinic, Building 1049. December 1955. BUILDING 1049. - Presidio of San Francisco, Letterman General Hospital, Building No. 12, Letterman Hospital Complex, Edie Road, San Francisco, San Francisco County, CA

  5. 22. Post Engineer Office, Presidio of San Francisco, Building # ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. Post Engineer Office, Presidio of San Francisco, Building # 1049 Letterman General Hospital. Alterations to EKG Cardiology Clinic. November 1963. BUILDING 1049. - Presidio of San Francisco, Letterman General Hospital, Building No. 12, Letterman Hospital Complex, Edie Road, San Francisco, San Francisco County, CA

  6. Heat flux and topography constraints on thermochemical structure below North China Craton regions and implications for evolution of cratonic lithosphere

    NASA Astrophysics Data System (ADS)

    Wang, Yongming; Huang, Jinshui; Zhong, Shijie; Chen, Jiaming

    2016-04-01

    The eastern North China Craton (NCC) has undergone extensive reactivation during the Mesozoic and Cenozoic, while the western NCC has remained stable throughout its geological history. Geophysical and geochemical observations, including heat flux, surface topography, crustal and lithospheric thicknesses, and volcanism, show significant contrast between the eastern and western NCC. These observations provide constraints on thermochemical structure and reactivation process of the eastern NCC, thus helping understand the dynamic evolution of cratonic lithosphere. In this study, we determined the residual topography for the NCC region by removing crustal contribution to the topography. We found that the residual topography of the eastern NCC region is generally 0.3-0.9 km higher than the western NCC. We computed a large number of two-dimension thermochemical convection models for gravitational instability of cratonic lithosphere and quantified surface heat flux and topography contrasts between stable and destabilized parts of cratonic lithosphere. These models consider different chemical buoyancy (i.e., buoyancy number B) and viscosity for the cratonic lithosphere. Our models suggest that to explain the difference in heat flux (25-30 mW/m2) and residual topography (0.3-0.9 km) between the eastern and western NCC regions, the buoyancy number B is required to be ~0.3-0.4. This range of B implies that as much as 50% of the original cratonic lithospheric material remains in the present-day eastern NCC lithosphere and its underlying shallow mantle and that the new lithosphere in the eastern NCC may be a mixture of the relics of old craton materials and the normal mantle.

  7. Space Radar Image of San Francisco, California

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This image of San Francisco, California shows how the radar distinguishes between densely populated urban areas and nearby areas that are relatively unsettled. Downtown San Francisco is at the center and the city of Oakland is at the right across the San Francisco Bay. Some city areas, such as the South of Market, called the SOMA district in San Francisco, appear bright red due to the alignment of streets and buildings to the incoming radar beam. Various bridges in the area are also visible including the Golden Gate Bridge (left center) at the opening of San Francisco Bay, the Bay Bridge (right center) connecting San Francisco and Oakland, and the San Mateo Bridge (bottom center). All the dark areas on the image are relatively smooth water: the Pacific Ocean to the left, San Francisco Bay in the center, and various reservoirs. Two major faults bounding the San Francisco-Oakland urban areas are visible on this image. The San Andreas fault, on the San Francisco peninsula, is seen in the lower left of the image. The fault trace is the straight feature filled with linear reservoirs which appear dark. The Hayward fault is the straight feature on the right side of the image between the urban areas and the hillier terrain to the east. The image is about 42 kilometers by 58 kilometers (26 miles by 36 miles) with north toward the upper right. This area is centered at 37.83 degrees north latitude, 122.38 degrees east longitude. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture (SIR-C/X-SAR) imaging radar when it flew aboard the space shuttle Endeavour on October 3, 1994. SIR-C/X-SAR, a joint mission of the German, Italian and the United States space agencies, is part of NASA's Mission to Planet Earth.

  8. 2. SAN FRANCISCO STREET PROFILES: Photocopy of engraving, c. 1880, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. SAN FRANCISCO STREET PROFILES: Photocopy of engraving, c. 1880, showing street profiles of two San Francisco cable railroads. Figure 10 illustrates the mainline of the Sutter Street Railroad on Sutter Street, while Figure 11 shows the route of the Presidio & Ferries Railroad along Union Street. Note the lack of significant grades along the Sutter Street route. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  9. 1. SAN FRANCISCO STREET PROFILES: Photocopy of engraving, c. 1880, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. SAN FRANCISCO STREET PROFILES: Photocopy of engraving, c. 1880, showing street profiles of three San Francisco cable lines. Figure 7, at bottom of engraving, is the profile of Hallidie's Clay Street Hill Railroad. Figures 8 and 9 show the grades for the California Street Cable Railroad and the Geary Street Park & Ocean Railroad respectively. Note the lack of significant grades along Geary Street. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  10. 11. Office of the Post Engineer, Presidio of San Francisco. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Office of the Post Engineer, Presidio of San Francisco. Location of Water Lines, Presidio of San Francisco. Sheet 31. November 1943. SHOWING EASTERN PORTION OF AREA A; BUILDINGS 274, 275, AND 277; AND POST ENGINEER'S SHOP AND YARDS INCLUDING BUILDINGS 280, 282-285, AND 288. - Presidio of San Francisco, Storehouse & Administration, Crissy Field North cantonment, Allen Street, San Francisco, San Francisco County, CA

  11. The 3-dimensional construction of the Rae craton, central Canada

    NASA Astrophysics Data System (ADS)

    Snyder, David B.; Craven, James A.; Pilkington, Mark; Hillier, Michael J.

    2015-10-01

    Reconstruction of the 3-dimensional tectonic assembly of early continents, first as Archean cratons and then Proterozoic shields, remains poorly understood. In this paper, all readily available geophysical and geochemical data are assembled in a 3-D model with the most accurate bedrock geology in order to understand better the geometry of major structures within the Rae craton of central Canada. Analysis of geophysical observations of gravity and seismic wave speed variations revealed several lithospheric-scale discontinuities in physical properties. Where these discontinuities project upward to correlate with mapped upper crustal geological structures, the discontinuities can be interpreted as shear zones. Radiometric dating of xenoliths provides estimates of rock types and ages at depth beneath sparse kimberlite occurrences. These ages can also be correlated to surface rocks. The 3.6-2.6 Ga Rae craton comprises at least three smaller continental terranes, which "cratonized" during a granitic bloom. Cratonization probably represents final differentiation of early crust into a relatively homogeneous, uniformly thin (35-42 km), tonalite-trondhjemite-granodiorite crust with pyroxenite layers near the Moho. The peak thermotectonic event at 1.86-1.7 Ga was associated with the Hudsonian orogeny that assembled several cratons and lesser continental blocks into the Canadian Shield using a number of southeast-dipping megathrusts. This orogeny metasomatized, mineralized, and recrystallized mantle and lower crustal rocks, apparently making them more conductive by introducing or concentrating sulfides or graphite. Little evidence exists of thin slabs similar to modern oceanic lithosphere in this Precambrian construction history whereas underthrusting and wedging of continental lithosphere is inferred from multiple dipping discontinuities.

  12. A Community Stormwater Investigation, San Francisco, CA

    NASA Astrophysics Data System (ADS)

    Chio, J.; Garcia, E.; Hernandez, M.; Devine, M.; Isip, N.; Jiang, J.; Li, A.; Li, D.; Lopez, J.; Mark, J.; McGuire, S.; Navarro, K.; Negrete, R.; Orellana, S.; Yun, C.; Bissell, M.; Neiss, J.

    2008-12-01

    The San Francisco Bay watershed covers 40% of the State of California. Nonpoint source pollutants from cars, lawns, houses, parks and people residing within the watershed contribute contamination into San Francisco Bay. To measure the contribution from our neighborhoods we collected runoff from storm-drains at 10 different sites around San Francisco and tested them for heavy metals, Total Organic Carbons (TOC), and Methylene Blue Active Substances (MBAS) during a six-month period. Each sample site location is situated within one block of each participant's home. The goal of this study was to determine the contaminants contributed as nonpoint source pollution into San Francisco Bay. Our results show that a variety of contaminants are entering the Bay's ecosystem via sources in our residential settings. While this contribution may be thought of as unsubstantial, our results show that our neighborhoods are significant sources of watershed pollution.

  13. Suicide Among Chinese in San Francisco

    ERIC Educational Resources Information Center

    Bourne, Peter G.

    1973-01-01

    Reports on a study which investigated suicide among Chinese in San Francisco, its relationship to age and sex distribution, place of birth, marital status, occupation, and methods and causes of suicide. (SF)

  14. Computerized Bus Routing in San Francisco.

    ERIC Educational Resources Information Center

    Caswell, Peter J.; Jungherr, J. Anton

    1979-01-01

    A computerized routing and scheduling system for the San Francisco Public Schools includes the batch processing of bus route assignments and schedules for all schools and the online terminal processing of daily changes. (Author/MLF)

  15. Craton stability and longevity: The roles of composition-dependent rheology and buoyancy

    NASA Astrophysics Data System (ADS)

    Wang, Hongliang; van Hunen, Jeroen; Pearson, D. Graham; Allen, Mark B.

    2014-04-01

    Survival of thick cratonic roots in a vigorously convecting mantle system for billions of years has long been studied by the geodynamical community. High strength of the cratonic root is generally considered to be the most important factor, but the role of lithospheric mantle depletion and dehydration in this strengthening is still debated. Geodynamical models often argue for a significant strength or buoyancy contrast between cratonic and non-cratonic mantle lithosphere, induced by mantle depletion and dehydration. But recent laboratory experiments argue for only a modest effect of dehydration strengthening. Can we reconcile laboratory experiments and geodynamical models? We perform and discuss new numerical models to investigate craton stability and longevity with different composition-dependent rheology and buoyancy. Our results show that highly viscous and possibly buoyant cratonic root is essential to stabilise a geometry in which thick cratonic lithosphere and thinner non-cratonic lithosphere coexist for billions of years. Using non-Newtonian rheology, a modest strengthening factor of Δη=3 can protect compositionally buoyant cratonic roots from erosion by mantle convection for over billions of years. A larger strengthening factor (Δη=10) can maintain long term craton stability even with little or no intrinsic buoyancy. Such composition-dependent rheology is comparable to the laboratory experiments. This implies that a strict isopycnic state of cratonic lithosphere may not be necessary for the preservation of a cratonic root, provided a sufficient level of compositional strengthening is present.

  16. Archean crustal evolution of the northern North China Craton

    NASA Technical Reports Server (NTRS)

    Qian, Xianglin; Chen, Yaping; Liu, Jinzhong

    1988-01-01

    The Archean granultie facies rocks of the North China (Sino-Korean) Craton mostly occur inside the northern boundary forming a unique and spectacular granulite belt trending roughly E-W from eastern Hebei, North China in the east to Mt. Daqinchan, western Inner Mongolia in the west, ranging about 1,000 km long. Over the years in the middle portion of this Archean high-grade metamorphic belt a stratigraphic unconformity between the khondalite rock assemblage and the medium in composition granulite assemblage in Datong-Xinghe area is determined. The geological structural properties of the North China Craton are discussed.

  17. The Role of Water in the Stability of Cratonic Keels

    NASA Technical Reports Server (NTRS)

    Peslier, Anne H.; Woodland, Alan B.; Bell, David R.; Lazarov, Marina

    2011-01-01

    Cratons are typically underlain by large, deep, and old lithospheric keels (to greater than 200 km depth, greater than 2.5 Ga old) projecting into the asthenosphere (e.g., Jordan, 1978; Richardson et al., 1984). This has mystified Earth scientists as the dynamic and relatively hot asthenosphere should have eroded away these keels over time (e.g., Sleep, 2003; O'Neill et al., 2008; Karato, 2010). Three key factors have been invoked to explain cratonic root survival: 1) Low density makes the cratonic mantle buoyant (e.g., Poudjom Djomani et al., 2001). 2) Low temperatures (e.g., Pollack, 1986; Boyd, 1987), and 3) low water contents (e.g., Pollack, 1986), would make cratonic roots mechanically strong. Here we address the mechanism of the longevity of continental mantle lithosphere by focusing on the water parameter. Although nominally anhydrous , olivine, pyroxene and garnet can accommodate trace amounts of water in the form of H bonded to structural O in mineral defects (e.g., Bell and Rossman, 1992). Olivine softens by orders of magnitude if water (1-1000 ppm H2O) is added to its structure (e.g., Mackwell et al., 1985). Our recent work has placed constraints on the distribution of water measured in peridotite minerals in the cratonic root beneath the Kaapvaal in southern Africa (Peslier et al., 2010). At P greater than 5 GPa, the water contents of pyroxene remain relatively constant while those of olivine systematically decrease from 50 to less than 10 ppm H2O at 6.4 GPa. We hypothesized that at P greater than 6.4 GPa, i.e. at the bottom of the cratonic lithosphere, olivines are essentially dry (greater than 10 ppm H2O). As olivine likely controls the rheology of the mantle, we calculated that the dry olivines could be responsible for a contrast in viscosity between cratonic lithosphere and surrounding asthenosphere large enough to explain the resistance of cratonic root to asthenospheric delamination.

  18. Smithsonian Astrophysical Observatory (SAO) star catalog (Sao staff 1966, edition ADC 1989): Documentation for the machine-readable version

    NASA Technical Reports Server (NTRS)

    Roman, Nancy G.; Warren, Wayne H., Jr.

    1989-01-01

    An updated, corrected, and extended machine readable version of the catalog is described. Published and unpublished errors discovered in the previous version were corrected, and multiple star and supplemental BD identifications were added to stars where more than one SAO entry has the same Durchmusterung number. Henry Draper Extension (HDE) numbers were added for stars found in both volumes of the extension. Data for duplicate SAO entries (those referring to the same star) were flagged. J2000 positions in usual units and in radians were added.

  19. Toxic phytoplankton in San Francisco Bay

    USGS Publications Warehouse

    Rodgers, Kristine M.; Garrison, David L.; Cloern, James E.

    1996-01-01

    The Regional Monitoring Program (RMP) was conceived and designed to document the changing distribution and effects of trace substances in San Francisco Bay, with focus on toxic contaminants that have become enriched by human inputs. However, coastal ecosystems like San Francisco Bay also have potential sources of naturally-produced toxic substances that can disrupt food webs and, under extreme circumstances, become threats to public health. The most prevalent source of natural toxins is from blooms of algal species that can synthesize metabolites that are toxic to invertebrates or vertebrates. Although San Francisco Bay is nutrient-rich, it has so far apparently been immune from the epidemic of harmful algal blooms in the world’s nutrient-enriched coastal waters. This absence of acute harmful blooms does not imply that San Francisco Bay has unique features that preclude toxic blooms. No sampling program has been implemented to document the occurrence of toxin-producing algae in San Francisco Bay, so it is difficult to judge the likelihood of such events in the future. This issue is directly relevant to the goals of RMP because harmful species of phytoplankton have the potential to disrupt ecosystem processes that support animal populations, cause severe illness or death in humans, and confound the outcomes of toxicity bioassays such as those included in the RMP. Our purpose here is to utilize existing data on the phytoplankton community of San Francisco Bay to provide a provisional statement about the occurrence, distribution, and potential threats of harmful algae in this Estuary.

  20. The story of a craton from heart to margins: illuminating cratonic lithosphere with Rayleigh wave phase velocities in Eastern Canada

    NASA Astrophysics Data System (ADS)

    Petrescu, L.; Darbyshire, F. A.; Gilligan, A.; Bastow, I. D.; Totten, E. J.

    2015-12-01

    Cratons are Precambrian continental nuclei that are geologically distinct from modern continental regions and are typically underlain by seismically fast lithospheric roots (keels) to at least 200 km depth. Both plate and non-plate tectonic origin theories such as stacking of subducted slabs or multiple mantle plume underplating have been proposed to explain keel growth.Eastern Canada is an ideal continental region to investigate cratonization processes and the onset of plate tectonics. It comprises part of the largest Archean craton in the world, the Superior Province, flanked by a ~1.1 Ga Himalayan-scale orogenic belt, the Grenville Province, and the 500-300 Ma old Appalachian orogenic province, following the same general SW-NE axial trend. The region is also cross-cut by the Great Meteor Hotspot track, providing an excellent opportunity to study the interaction of hotspot tectonism with progressively younger lithospheric domains.We investigate the lithospheric structure of Precambrian Eastern Canada using teleseismic earthquake data recorded at permanent and temporary networks. We measure interstation dispersion curves of Rayleigh wave phase velocities between ~15 and 220 s, and compare the results to standard continental and cratonic reference models. We combine the dispersion curves via a tomographic inversion which solves for isotropic phase velocity heterogeneity and azimuthal anisotropy across the region at a range of periods. The phase velocity maps indicate variations in lithospheric properties from the heart of the Superior craton to the SE Canadian coast.The new regional-scale models will help to understand the processes that generated, stabilized and reworked the cratonic roots through their billion-year tectonic history. We investigate how surface tectonic boundaries relate to deeper lithospheric structural changes, and consider the effects of the multiple Wilson cycles that affected Laurentia.

  1. Physico-chemical constraints on cratonic lithosphere discontinuities

    NASA Astrophysics Data System (ADS)

    Aulbach, Sonja; Rondenay, Stéphane; Huismans, Ritske

    2014-05-01

    The origins of the mid-lithospheric discontinuity (MLD) and lithosphere-asthenosphere boundary (LAB) have received much attention over the recent years. Peculiarities of cratonic lithosphere construction - compositional and rheological stratification due to thickening in collisional settings or by plume subcretion, multiple metasomatic overprints due to longevity - offer a variety of possibilities for the generation of discontinuities. Interconnected small degrees of conductive partial melt (carbonate-rich melts, such as carbonatites and kimberlites, or highly alkaline melts) at the cratonic LAB, which produce seismic discontinuities, may be generated in the presence of volatiles. These depress the peridotite solidus sufficiently to intersect the mantle adiabat at depths near the cratonic LAB at ~160-220 km, i.e. above the depth of metal saturation where carbonatite becomes unstable. The absence of agreement between the different seismic and magnetotelluric estimates for the depth of the LAB beneath Kaapvaal may be due to impingement of a plume, leading to a pervasively, but heterogeneously metasomatised ('asthenospherised') hot and deep root. Such a root and hot sublithosphere may yield conflicting seismic-thermal-geochemical depths for the LAB. The question arises whether the chemical boundary layer should be defined as above or below the asthenospherised part of the SCLM, which has preserved isotopic, compositional (non-primitive olivine forsterite content) and physical evidence (e.g. from teleseismic tomography and receiver functions) for a cratonic heritage and which therefore is still distinguishable from the asthenospheric mantle. If cratonic lithosphere overlies anomalously hot mantle for extended periods of time, the LAB may be significantly thinned, aided by penetration of relatively high-degree Fe-rich partial melts, as has occurred beneath the Tanzanian craton. Xenoliths from the deep Slave craton show little evidence for 'asthenospherisation'. Its root

  2. Promoting the Earth Charter in Sao Paulo's Municipal Education System

    ERIC Educational Resources Information Center

    Inojosa, Rose Marie

    2010-01-01

    This article presents the process of widespread teacher training based on the Earth Charter in the municipal area of Sao Paulo, Brazil, South America. This effort diffused knowledge of the Earth Charter through 800 educators and by means of them, to one million children. This process was developed by the team from UMAPAZ--Open University of the…

  3. Biological effects of air pollution in Sao Paulo and Cubatao

    SciTech Connect

    Boehm, G.M.S.; Saldiva, P.H.; Pasqualucci, C.A.; Massad, E.; Martins M de, E.; Zin, W.A.; Cardoso, W.V.; Criado, P.M.; Komatsuzaki, M.; Sakae, R.S. )

    1989-08-01

    Rats were used as biological indicators of air quality in two heavily polluted Brazilian towns: Sao Paulo and Cubatao. They were exposed for 6 months to ambient air in areas where the pollution was known to be severe. The following parameters were studied and compared to those of control animals: respiratory mechanics, mucociliary transport, morphometry of respiratory epithelium and distal air spaces, and general morphological alterations. The results showed lesions of the distal and upper airways in rats exposed in Cubatao, whereas the animals from Sao Paulo showed only alterations of the upper airways but of greater intensity than those observed in the Cubatao group. There are both qualitative and quantitative differences in the pollutants of these places: in Sao Paulo automobile exhaust gases dominate and in Cubatao the pollution is due mainly to particulates of industrial sources. The correlation of the pathological findings with the pollutants is discussed and it is concluded that biological indicators are useful to monitor air pollutions which reached dangerous levels in Sao Paulo and Cubatao.

  4. 76 FR 14051 - Notice of Inventory Completion: San Francisco State University, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-15

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR National Park Service Notice of Inventory Completion: San Francisco State University, San Francisco, CA AGENCY: National Park Service, Interior. ACTION: Notice. Notice is here given in accordance with the Native American Graves Protection...

  5. New heat flow determination in northern Tarim Craton, northwest China

    NASA Astrophysics Data System (ADS)

    Liu, Shaowen; Lei, Xiao; Wang, Liangshu

    2015-02-01

    Tarim Craton is a Precambrian block situated in northwest China, just north of the Tibetan Plateau, where a large sedimentary basin with abundant hydrocarbon potential has developed. Accurate heat flow data for Tarim is vital for understanding the lithospheric evolution and hydrocarbon generation in this area; however, there were unavailable until now, due to a lack of high quality steady-state temperature logging data. Here, we report 10 new heat flow values derived from steady-state temperature logging and measured thermal conductivity data. New heat flow values range from 40.1 to 49.4 mW m-2, with a mean of 43.1 ± 3.0 mW m-2. In addition, radiogenic heat production from the sediments accounts for 20 per cent of the observed surface heat flow, whilst the mantle heat flow is estimated to be as low as 6-15 mW m-2; this indicates a dominant contribution from crustal heat, to the observed heat flow. The average heat flow and crustal temperature in the Tarim Craton are markedly lower than those in the Tibetan Plateau, whilst the calculated rheological strength of the lithosphere, beneath Tarim, is sufficiently large to resist the elevation-induced gravitational potential energy difference between Tarim and Tibet. This inherited thermal and rheological contrast, between the craton and Plateau, can be traced back to before the India-Asia collision; this accounts for the differential active deformation pattern in the Tarim Craton and adjacent areas.

  6. Recycling lower continental crust in the North China craton.

    PubMed

    Gao, Shan; Rudnick, Roberta L; Yuan, Hong-Ling; Liu, Xiao-Ming; Liu, Yong-Sheng; Xu, Wen-Liang; Ling, Wen-Li; Ayers, John; Wang, Xuan-Che; Wang, Qing-Hai

    2004-12-16

    Foundering of mafic lower continental crust into underlying convecting mantle has been proposed as one means to explain the unusually evolved chemical composition of Earth's continental crust, yet direct evidence of this process has been scarce. Here we report that Late Jurassic high-magnesium andesites, dacites and adakites (siliceous lavas with high strontium and low heavy-rare-earth element and yttrium contents) from the North China craton have chemical and petrographic features consistent with their origin as partial melts of eclogite that subsequently interacted with mantle peridotite. Similar features observed in adakites and some Archaean sodium-rich granitoids of the tonalite-trondhjemite-granodiorite series have been interpreted to result from interaction of slab melts with the mantle wedge. Unlike their arc-related counterparts, however, the Chinese magmas carry inherited Archaean zircons and have neodymium and strontium isotopic compositions overlapping those of eclogite xenoliths derived from the lower crust of the North China craton. Such features cannot be produced by crustal assimilation of slab melts, given the high Mg#, nickel and chromium contents of the lavas. We infer that the Chinese lavas derive from ancient mafic lower crust that foundered into the convecting mantle and subsequently melted and interacted with peridotite. We suggest that lower crustal foundering occurred within the North China craton during the Late Jurassic, and thus provides constraints on the timing of lithosphere removal beneath the North China craton. PMID:15602559

  7. Longevity and rheology of cratons: key constraints from surface topography

    NASA Astrophysics Data System (ADS)

    Francois, T.; Burov, E. B.; Meyer, B.; Agard, P.

    2011-12-01

    Archean cratons are stable remnants of Earth's early continental lithosphere. Their structure, composition and survival over geological time spans make them ones of the most unique and enigmatic features of the Earth's surface. It has become evident from both geophysical and petrological studies that cratons exhibit deep lithospheric roots, which remained stable ever since their formation in the early Archean. The question of how some of the cratons survived destruction over timescales of billions of years remains a subject of vigorous debate. In order to understand what controls the long-term stability of the cratons, we investigated the impact of the thermo-rheological structure of the lithosphere on the evolution of both surface topography and cratonic roots using fully coupled thermo-mechanical numerical models (600*3000 km, free upper surface topography, layered lithospheric structure). Our model has a particular focus on the Canadian Shield, where considerable structural and thermal data are available from both geological and geophysical studies. In particular, we compare the implications of the "Cratonic" "Jelly-Sandwich" rheology (JS; strong dry olivine mantle, strong crust, cold geotherm with Moho temperature of 400°C, thermal lithosphere thickness of 250 km) with those of the "Crème Brûlée" rheology (CB; strong crust, weak wet olivine mantle, Moho temperature of 600°C, thermal lithosphere thickness of 150 km) (Figure 1). Our experiments show that, in the case of a laterally homogeneous lithosphere and in the absence of tectonic shortening or extension (blocked borders), both JS and CB rheologies may account for the stability of the shield and its surface topography. In this case continental lithosphere remains stable over large time spans, even for the weakest wet olivine mantle (but for "cold" thermal gradients). Nevertheless, for a laterally heterogeneous crust, as is the case for the Canadian Shield and most cratons, dry olivine mantle JS rheology

  8. Temperature-dependent transient creep and dynamics of cratonic lithosphere

    NASA Astrophysics Data System (ADS)

    Birger, Boris I.

    2013-11-01

    Large-scale mantle convection forms the upper boundary layer (lithosphere) where the vertical temperature drop is about 1300 K. Theoretical rheology and laboratory experiments with rock samples show that transient creep occurs while creep strains are sufficiently small. The transient creep is described by the temperature-dependent Andrade rheological model. Since plate tectonics allows only small deformations in lithospheric plates, creep of the lithosphere plates is transient whereas steady-state creep, described by non-Newtonian power-law rheological model, takes place in the underlying mantle. The solution of stability problem shows that the lithosphere is stable but small-scale convective oscillations are attenuated very weakly in regions of thickened lithosphere beneath continental cratons (subcratonic roots) where the thickness of the lithosphere is about 200 km. These oscillations create small-scale convective cells (the horizontal dimensions of the cells are of the order of the subcratonic lithosphere thickness). Direction of motion within the cells periodically changes (the period of convective oscillations is of the order of 3 × 108 yr). In this study, the oscillations of cratonic lithosphere caused by initial relief perturbation are considered. This relief perturbation is assumed to be created by overthrusting in orogenic belts surrounding cratons. The perturbation of the Earth's surface relief leads to a fast isothermal process of isostatic recovery. In the presence of vertical temperature gradient, vertical displacements, associated with the recovery process in the lithosphere interior, instantly produce the initial temperature perturbations exciting thermoconvective oscillations in the cratonic lithosphere. These small-amplitude convective oscillations cause oscillatory crustal movements which form sedimentary basins on cratons.

  9. Establishment and characterization of a new highly metastatic human osteosarcoma cell line derived from Saos2

    PubMed Central

    Du, Lin; Fan, Qiming; Tu, Bing; Yan, Wei; Tang, Tingting

    2014-01-01

    Osteosarcoma is the most common primary malignancy of bone in adolescents and young adults. There is a shortage of tumorigenic and highly metastatic human osteosarcoma cell lines that can be used for metastasis study. Here we establish and characterize a highly metastatic human osteosarcoma cell line that is derived from Saos2 cell line based on bioluminescence. The occasional pulmonary metastatic cells developed from Saos2 were isolated, harvested, characterized and named Saos2-l. The parental Saos2 and Saos2-l cells were further characterized both in vitro and in vivo. Results showed that Saos2-l cells demonstrated increased cell adhesion, migration and invasion compared to the parental Saos2 cells. Conversely, Saos2-l cells grew at a slightly slower rate than that of the parental cells. When injected into nude mice, Saos2-l cells had a greater increase in developing pulmonary metastases compared to the parental Saos2 cells. Further transcriptional profiling analysis revealed that some gene expression were up-regulated or down-regulated in the highly metastatic Saos2-l cells, indicating possible influencing factors of metastasis. Thus, we have established and characterized a highly metastatic human osteosarcoma cell line that should serve as a valuable tool for future investigations on the pathogenesis, metastasis and potential treatments of human osteosarcoma. PMID:25031706

  10. Flat Slab Subduction, Trench Suction, and Craton Destruction: Comparison of the North China, Wyoming, and Brazilian Cratons

    NASA Astrophysics Data System (ADS)

    Kusky, Timothy; Windley, Brian; Wang, Lu; Wang, Zhensheng; Li, Xiaoyong; Zhu, Peimin

    2015-04-01

    We define and test a unifying plate tectonic driving mechanism that explains the characteristics of the destruction of cratonic lithospheric roots. We document and model the relationships between flat slab subduction, trench suction, and craton destruction, using examples from the North China and Wyoming cratons, each of which locally lost approximately 100 km of their lithospheric roots in the Cretaceous and which show spatio-temporal relationships with episodes of flat slab subduction in the mantle transition zone associated with deep mantle hydration, coupled with slab rollback and concomitant influx of fertile mantle material to accommodate the space created by slab rollback. A similar process has more recently operated along the western side of the Brazilian craton where it is thrust beneath the thickened crust of the Andes in an area of trench rollback. The importance of the mutual interaction between these processes for destruction of cratonic roots may be greater than currently perceived. Together with the other processes of subduction erosion and arc subduction, larger amounts of continental lithosphere may have been subducted or otherwise returned to the sub-lithospheric mantle than previously appreciated. When oceanic lithosphere subducts, it hydrates the upper mantle beneath an arc from well-known dehydration reactions. However, some hydrous phases (e.g., Phase A, Phase E, and -γt and β-phase olivine) are stable to much greater depths and dehydrate even when a slab is in the mantle transition zone. It is estimated that 40% of the water subducted in hydrated oceanic crust, mantle, sediments, and subducted continental material reaches the mantle transition zone between 410 and 660 km. For instance lawsonite may contain up to 11% water, and is stable up to 11 GPa or about 300 km and serpentinites can contain up to 13% water and are stable up to 7 GPa, and after conversion to denser hydrous phases such as β-phase olivine they can be stable up to 50 GPa

  11. Accretion and reworking beneath the North China Craton

    NASA Astrophysics Data System (ADS)

    Zheng, J. P.; Griffin, W. L.; Ma, Q.; O'Reilly, S. Y.; Xiong, Q.; Tang, H. Y.; Zhao, J. H.; Yu, C. M.; Su, Y. P.

    2012-09-01

    How has the Earth's continental lithosphere evolved? Most of our knowledge is derived from surface exposures, but xenoliths carried in volcanic rocks can be an important source of information. The North China Craton (NCC) is one of the oldest in the world and Phanerozoic volcanic rocks with abundant xenoliths are widespread, making it an ideal area to study the formation and evolution of continents. New analyses of U-Pb ages and Hf isotopes in zircon were obtained for lower crustal xenoliths from four localities including the Paleozoic Yingxian lamproites, and the basalts of Pingquan (Paleocene), Hebi and Nushan (Neogene). Published ages and compositions of lower crustal and upper mantle xenoliths from the NCC are synthesized to constrain the accretion and reworking processes that have affected the deep lithosphere beneath the craton. The peridotite bodies within the Dabie-Sulu ultrahigh-pressure (UHP) belt, along the southern edge of the NCC, are compared with the xenolith peridotites to constrain early Mesozoic dynamics. The oldest components of the NCC may be ~ 4.0 Ga old. The craton experienced complex accretion and reworking processes in its deep lithosphere, accompanied by the formation (or aggregation) and differentiation of the ancient continental nucleus. The small size of the NCC, compared with many other cratons worldwide, made it more susceptible to the effects of marginal subduction and collision with surrounding blocks. The subcontinental lithosphere mantle (SCLM) was generally coupled with the lower crust through the Paleozoic, while decoupling occurred in late Mesozoic-Cenozoic time, except locally (such as the Neoarchen lower crust and SCLM in Hebi), suggesting strong interactions between the asthenosphere and the lithosphere (both upper mantle and lower crust) in Phanerozoic time. In the lower crust, the ancient components of the craton were re-worked in Paleoarchean (3.80-3.65 Ga) time. The craton also experienced two important accretionary

  12. On the Origin of Cratonic Sag Basins: Did They Sag?

    NASA Astrophysics Data System (ADS)

    Morgan, Jason P.

    2015-04-01

    Cratonic sag basins are regions of long-lived, extremely slow (~20-30 m/Myr) shallow water and terrestrial sediment accumulation that have no striking signs of tectonic activity (cf. Allen and Armitage, 2012). In their evolution, hundreds of Myr-long periods of slow sediment accumulation are separated by unconformities. The mechanisms for their formation resist geodynamic characterization by other common hypotheses for basin subsidence because of their extremely slow subsidence and lack of evident tectonic activity. I propose their dynamics are better understood within the geodynamic context of continental cratons that ride over a ~250km-deep sub-asthenospheric mantle with lateral temperature variations between a few wide and persistent 1000s-km broad ~1400C 'superplume' upwelling mantle structures (e.g. currently beneath S. African Atlantic and French Polynesia) and prevalent surrounding ~1150C average temperature sub-asthenospheric mantle. When continents pass over typical mantle plumes, buoyant plume material tends to drain beneath the continent along junctions between cratons where the lithosphere is relatively thin, keeping the lithosphere over regions where plume material drains hotter than the average temperature of ~250km-deep mantle. (e.g., the Cameroon Line.) Regions where melting of plume material occurs during decompression associated with either plume ascent or lateral drainage beneath continents are associated with the addition of a buoyant rind of more depleted mantle to the continent. In addition, regions where plume material can pond in a relatively thin sub-lithospheric 'anti-basin' beneath a continent, or that stay stationary for long times over super plumes will heat to a lithospheric basal temperature of ~1400C instead of ~1150C, with ~700m of associated uplift. (e.g., Southern Africa). In this scenario (cf. Yamamoto, Morgan, and Morgan in "Plumes, Plates, and Paradigms"), it is the relative plume-passage-induced uplift of arches between

  13. 30. Photocopy of photograph (from National Park Service, San Francisco, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. Photocopy of photograph (from National Park Service, San Francisco, California, 1930 (?) EXTERIOR, EAST SIDE OF MISSIONA AFTER RESTORATION, C. 1930 (?) - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA

  14. 27. Photocopy of photograph (from National Park Service, San Francisco, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. Photocopy of photograph (from National Park Service, San Francisco, California, Date unknown) EXTERIOR, SOUTH FRONT, DETAIL OF ENTRANCE AFTER RESTORATION, C. 1930 (?) - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA

  15. 13. Photocopy of photograph (from Golden Gate Museum, San Francisco, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. Photocopy of photograph (from Golden Gate Museum, San Francisco, California, 1850's) EXTERIOR, VIEW OF CONVENTO BEFORE RESTORATION, 1850'S - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA

  16. 40. Historic American Buildings Survey San Francisco Chronicle Collection San ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    40. Historic American Buildings Survey San Francisco Chronicle Collection San Francisco, California March 24, 1924 VIEW OF HIGH ALTAR - Mission San Carlos Borromeo, Rio Road & Lausen Drive, Carmel-by-the-Sea, Monterey County, CA

  17. 2. Historic American Buildings Survey San Francisco Chronicle Library San ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Historic American Buildings Survey San Francisco Chronicle Library San Francisco, California Year Built: 1834 Photo Taken: About 1925 VIEW FROM EAST - General Sherman Quarters, 464 Calle Principal, Monterey, Monterey County, CA

  18. The Fazenda Largo off-craton kimberlites of Piauí State, Brazil

    NASA Astrophysics Data System (ADS)

    Kaminsky, Felix V.; Sablukov, Sergei M.; Sablukova, Ludmila I.; Zakharchenko, Olga D.

    2009-10-01

    In the late 1990s, the Fazenda Largo kimberlite cluster was discovered in the Piauí State of Brazil. As with earlier known kimberlites in this area - Redondão, Santa Filomena-Bom Jesus (Gilbues) and Picos - this cluster is located within the Palaeozoic Parnaiba Sedimentary Basin that separates the São Francisco and the Amazonian Precambrian cratons. Locations of kimberlites are controlled by the 'Transbrasiliano Lineament'. The Fazenda Largo kimberlites are intensely weathered, almost completely altered rocks with a fine-grained clastic structure, and contain variable amounts of terrigene admixture (quartz sand). These rocks represent near-surface volcano-sedimentary deposits of the crater parts of kimberlite pipes. By petrographic, mineralogical and chemical features, the Fazenda Largo kimberlites are similar to average kimberlite. The composition of the deep-seated material in the Fazenda Largo kimberlites is quite diverse: among mantle microxenoliths are amphibolitised pyrope peridotites, garnetised spinel peridotites, ilmenite peridotites, chromian spinel + chromian diopside + pyrope intergrowths, and large xenoliths of pyrope dunite. High-pressure minerals are predominantly of the ultramafic suite, Cr-association minerals (purplish-red and violet pyrope, chromian spinel, chromian diopside, Cr-pargasite and orthopyroxene). The Ti-association minerals of the ultramafic suite (picroilmenite and orange pyrope), as well as rare grains of orange pyrope-almandine of the eclogite association, are subordinate. Kimberlites from all four pipes contain rare grains of G10 pyrope of the diamond association, but chromian spinel of the diamond association was not encountered. By their tectonic position, by geochemical characteristics, and by the composition of kimberlite indicator minerals, the Fazenda Largo kimberlites, like the others of such type, are unlikely to be economic.

  19. Contrasting crustal evolution processes in the Dharwar craton

    NASA Astrophysics Data System (ADS)

    Lancaster, Penelope J.; Dey, Sukanta; Storey, Craig D.; Mitra, Anirban; Bhunia, Rakesh K.

    2015-04-01

    Archaean cratons provide a critical window into early Earth dynamics, preserving a record of crustal evolution processes that include the start of 'modern' plate tectonics and the development of supercontinents. However, these same processes can also destroy or rework substantial volumes of crust, and the oldest extant Archaean terrane is only ~3.9 Ga. Where Archaean rocks are exposed, bulk techniques such as Pb and Nd isotopes can provide considerable information about continental formation, but these may have been altered by later metamorphic events. Another method is to examine sedimentary units, which can preserve fragments of the crust that are no longer exposed at the Earth's surface. Resistant detrital minerals such as zircon have particular use in these studies, as they incorporate a range of isotopic and geochemical tracers and can survive multiple crystallisation and/or sedimentary events. In this manner, a more complete record of a craton's evolution may be obtained, with the benefit of contributions from contrasting isotopic systems. The Dharwar craton of southern India is one such Archaean block, comprising >2.7 Ga trondjhemite-tonalite-granodiorite (TTG) gneisses, volcano-sedimentary belts (>3.0 and 2.9-2.6 Ga) and 2.7-2.5 Ga calc-alkaline to potassic granitoids. These rocks preserve evidence for several cycles of supracrustal formation, deformation, metamorphism and granitic activity during the Precambrian. New in situ U-Pb-Hf analyses of detrital zircons from across the craton indicate significant juvenile crustal extraction events at ~3.3 and 2.7 Ga, and continuous extraction from 3.7-3.3 Ga. Reworking in the older western block at ~3.0 Ga marks the onset of cratonisation, most likely due to 'modern' plate tectonic processes, while reworking in both the western and younger eastern block at 2.55-2.50 Ga indicates accretion of the two terranes and final cratonisation much later than in most other Archaean terranes (~2.7 Ga). Different patterns of

  20. Paleomagnetism of the Wyoming Craton: A Pre-Laurentian Puzzle

    NASA Astrophysics Data System (ADS)

    Kilian, T.; Chamberlain, K.; Mitchell, R. N.; Evans, D. A.; Bleeker, W.; Lecheminant, A. N.

    2010-12-01

    The Archean Wyoming craton is mostly buried beneath Phanerozoic sediments in the Rocky Mountains of the west central United States. Exposures of the craton are entirely in thrust-bounded Laramide uplifts and contain numerous swarms of Neoarchean-Proterozoic mafic dikes. U-Pb ages from these dikes include ~2685 Ma from a dike in the Owl Creek Mountains (Frost et al., 2006) as well as another in the Bald Mountain region of the Bighorn Mountains (this study), ~2170 Ma from the Wind River Mountain quartz diorite (Harlan et al., 2003), ~2110 Ma from a dike in the Granite Mountains (Bowers and Chamberlain, 2006), ~2010 Ma from a Kennedy dike in the Laramie Range (Cox et al., 2000), and ~780 Ma for dikes in the Beartooth and Teton Mountains (Harlan et al., 1997). These possible age ranges of magmatic events will allow a detailed comparison with other cratons, especially Superior and Slave. Prior to the assembly of Laurentia, Wyoming may have been connected with Slave in supercraton Sclavia (Bleeker, 2003; Frost et al., 2007), or alternatively, Wyoming may have been attached to the present southern margin of Superior in the supercraton Superia, as judged by similarities of the thrice-glaciated Huronian and Snowy Pass sedimentary successions (Roscoe and Card, 1993). Paleomagnetic results will be presented from over 150 dikes in the Wyoming craton. All dikes were from the basement uplifts of the Beartooth Mountains, Bighorn Mountains, Owl Creek Mountains, Granite Mountains, Ferris Mountains and Laramie Range. Dikes range in widths from 1 to >100 meters, and trends vary across all orientations. Stable remanence is observed in majority of sites with at least 8 different directions from the various uplifts. Structural corrections are applied when necessary to restore shallowly dipping Cambrian strata to horizontal. The paleomagnetic study is being integrated with precise U-Pb geochronology of dikes that bear stable remanence directions. Results will eventually allow a

  1. San Francisco and Bay Area, CA, USA

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This cloud free color infrared view of San Francisco and Bay Area, CA (38.0N, 122.5W) is unusual because the city is normally concealed from view by clouds and fog. Gray tones represent urban areas and the red toned areas are vegetated. Within the city, parks easily stand out from the well-developed parts of the city as enclaves of color. The trace of the San Andreas fault shows as a straight valley running across the San Francisco peninsula.

  2. The San Francisco volcanic field, Arizona

    USGS Publications Warehouse

    Priest, S.S.; Duffield, W.A.; Malis-Clark, Karen; Hendley, J. W., II; Stauffer, P.H.

    2001-01-01

    Northern Arizona's San Francisco Volcanic Field, much of which lies within Coconino and Kaibab National Forests, is an area of young volcanoes along the southern margin of the Colorado Plateau. During its 6-million-year history, this field has produced more than 600 volcanoes. Their activity has created a topographically varied landscape with forests that extend from the Pi?on-Juniper up to the Bristlecone Pine life zones. The most prominent landmark is San Francisco Mountain, a stratovolcano that rises to 12,633 feet and serves as a scenic backdrop to the city of Flagstaff.

  3. On craton thinning/destruction: Insight from 2D thermal-mechanical numerical modeling

    NASA Astrophysics Data System (ADS)

    Liao, J.

    2014-12-01

    Although most cratons maintain stable, some exceptions are present, such as the North China craton, North Atlantic craton, and Wyoming craton, which have experienced dramatic lithospheric deformation/thinning. Mechanisms triggering cratonic thinning remains enigmatic [Lee et al., 2011]. Using a 2D thermo-mechanical coupled numerical model [Gerya and Yuen, 2007], we investigate two possible mechanisms: (1) stratification of cratonic lithospheric mantle, and (2) rheological weakening due to hydration.Lithospheric mantle stratification is a common feature in cratonic areas which has been demonstrated by geophysical and geochemical studies [Thybo and Perchuc, 1997; Griffin et al., 2004; Romanowicz, 2009; Rychert and Shearer, 2009; Yuan and Romanowicz, 2010]. The influence of lithospheric mantle stratification during craton evolution remains poorly understood. A rheologically weak layer representing hydrated and/or metasomatized composition is implemented in the lithospheric mantle. Our results show that the weak mantle layer changes the dynamics of lithospheric extension by enhancing the deformation of the overlying mantle and crust and inhibiting deformation of the underlying mantle [Liao et al., 2013; Liao and Gerya, 2014]. Modeling results are compared with North China and North Atlantic cratons. Our work indicates that although the presence of a weak layer may not be sufficient to initiate craton deformation, it enhances deformation by lowering the required extensional plate boundary force. Rheological weakening due to hydration is a possible mechanism triggering/enhancing craton deformation, especially for cratons jaxtaposing with a subduction, since water can release from a subducting slab. We investigate the influence of wet mantle flow laws [Hirth and Kohlstedt, 2003], in which a water parameter (i.e. constant water content) is involved. Our results show that wet dislocation alone does not accelerate cratonic deformation significantly. However, if wet diffusion

  4. Early Cambrian magmatism in the northeastern Siberian Craton (Olenek Uplift)

    NASA Astrophysics Data System (ADS)

    Kiselev, A. I.; Kochnev, B. B.; Yarmolyuk, V. V.; Egorov, K. N.

    2015-12-01

    The Vendian-Lower Cambrian tectonomagmatic activation took place in the northeastern Siberian Craton, within the Olenek Uplift and in the Kharaulakh segment of the Verkhoyansk fold-and-thrust belt (the lower reaches of the Lena River). The Early Paleozoic volcanic activity in the Olenek Uplift is expressed in the form of basitic diatremes, small basaltic covers, and doleritic dikes and sills intruding and covering the Upper Vendian carbonate deposits. The material specificity of the Lower Cambrian basites and their mantle sources, jointly with the Vendian-Cambrian sedimentation history, gives reason to consider the Lower Cambrian riftogenesis and the associated magmatism as a consequence of the plume-lithosphere interaction in the northeastern Siberian Craton.

  5. Isopycnicity, Thermal State and Secular Evolution of Cratonic Mantle Keels

    NASA Astrophysics Data System (ADS)

    Eaton, D. W.; Bastow, I. D.; Kendall, J. M.; Perry, C.

    2010-12-01

    The lithosphere-asthenosphere boundary (LAB) beneath ancient continental nuclei (cratons) is thought to be anomalously deep (> 200 km) due to the presence of cold, compositionally distinct mantle keels that are readily identifiable as high-velocity features in global tomographic models. The empirical concept of isopycnicity, which posits that a pervasive state of near-neutral buoyancy is created by offsetting thermal and compositional effects on density, is often invoked to explain the long-term stability of cratonic mantle keels and general absence of an accompanying long-wavelength gravity signature. Although the concept is appealing, the mechanisms by which an isopycnic state can be sustained are not clear. For example, on a billion-year (Gyr) timescale, secular cooling of a mantle keel could induce a gradual departure from isopycnicity. This possibility is examined by thermal modeling of a cold cratonic keel starting from an approximately isopycnic state near thermal equilibrium. Our models assume that the temperature of the LAB intersects the mantle adiabat, and consider secular cooling (40 K per Gyr) as well as gradual loss of radiogenic heating in the lithosphere. Several scenarios corresponding to ‘average’ Archean and Proterozoic mantle compositions are considered and used to predict seismic and gravitational observables. Our results confirm that, under similar thermal conditions, less-depleted mantle keels of ‘Proterozoic’ composition are less buoyant than Archean keels, but are indistinguishable based on seismic wave velocity. In general, cratonic keels are predicted to founder isostatically at about 1 km / Gyr, which should impose an easily observed epeirogenic signal in the core regions of continents.

  6. San Francisco's New Zoo's Connections for Conservation.

    ERIC Educational Resources Information Center

    Routman, Emily

    2001-01-01

    Provides information on a redevelopment project at the San Francisco Zoo known as the New Zoo. The explicit goal of the project is to inspire a sense of caring and appreciation for wildlife that is the foundation of a conservation ethic. (DDR)

  7. San Francisco, California: Solar in Action (Brochure)

    SciTech Connect

    Not Available

    2011-10-01

    This brochure provides an overview of the challenges and successes of San Francisco, CA, a 2007 Solar America City awardee, on the path toward becoming a solar-powered community. Accomplishments, case studies, key lessons learned, and local resource information are given.

  8. Simulations of the 1906 San Francisco Earthquake

    SciTech Connect

    Rodgers, A; Petersson, A; Tkalcic, H

    2005-12-16

    Simulations of the Great 1906 San Francisco earthquake are being performed as part of the event's centenary. LLNL is participating in a large effort to study this event and possible consequences if the event were to happen today. This document is meant to describe our efforts to others participating in the project.

  9. Educational and Demographic Profile: San Francisco County

    ERIC Educational Resources Information Center

    California Postsecondary Education Commission, 2004

    2004-01-01

    This profile uniquely presents educational and socioeconomic information for San Francisco County, nearby counties, and the state. It highlights the relationship between various factors that affect the economic well-being of individuals and communities. This information provides a framework for enhanced communication and collaboration between the…

  10. Potamocorbula amurensis discovered in San Francisco Bay

    USGS Publications Warehouse

    Schemel, Laurence E.

    1989-01-01

    The small Asian clam, Potamocorbula amurensis, is now a major component of benthic communities in most areas of northern San Francisco Bay and some areas of South Bay. Because of its wide tolerance of salinity and other environmental variables and its high abundance in many areas, benthic ecologists believe this recent invasion may represent a major and permanent change in the bay system.

  11. The Third International San Francisco Book Fair.

    ERIC Educational Resources Information Center

    Kalmon, Winn; And Others

    Friends of Books and Comics presents its catalog of the Third International San Francisco Book Fair, a marketplace of alternative books, comics, and magazines. Nearly 200 alternative and small presses are listed alphabetically with address, telephone number, names of principal people involved, and a brief description of type and subject of…

  12. Seismic structure and dynamics of cratons: Stability and modification, continental collision and subduction

    NASA Astrophysics Data System (ADS)

    Lebedev, Sergei; Meier, Thomas; Schaeffer, Andrew J.; Agius, Matthew R.; Adam, Joanne M.-C.

    2014-05-01

    The Archean crust of stable cratons within today's continents is typically underlain by cold, thick mantle lithosphere. These mechanically strong, compositionally buoyant mantle roots (overall, roughly neutrally buoyant due to the density increase caused by low temperatures) have ensured the survival of cratons since their formation. Global and regional seismic tomography detects cratons readily by the anomalously high seismic velocities within their mantle lithosphere. The increasing resolution of seismic imaging now enables detailed mapping of the locations, boundaries and properties of cratons and offers new insight into their dynamics and evolution. Here, we summarise inferences on cratonic structure and dynamics based on recent multimode-waveform tomography on the global and continental (Europe, N America) scales and from regional, surface-wave array imaging. Where crustal cratonic boundaries can be mapped at the surface, they are, normally, closely matched by the boundaries of the high-velocity (thick and cold) mantle lithosphere beneath. Where the ancient crust is covered by sediments, with crustal block boundaries thus unclear, cratons can be mapped accurately by the seismic imaging of their high-velocity lithosphere. (Important exceptions include cratons that lost their ancient mantle roots in the Phanerozoic, e.g., eastern Sino-Korean Craton). On average, the upper mantle beneath cratons shows shear-wave speeds higher than elsewhere down to depths smaller than 300 km; large shear-speed anomalies are seen down to around 200 km depth only. Layered azimuthal anisotropy within cratonic lithosphere indicates frozen fabric that is probably a record of complex, vertically stratified deformation during the formation and stabilisation of cratons. Lateral variations in seismic velocities within cratonic roots present evidence for their modification and evolution after their formation. Beneath cratons in northern Europe, the locations of kimberlites coincide with

  13. Salt Ponds, South San Francisco Bay

    NASA Technical Reports Server (NTRS)

    2002-01-01

    higher resolution 1000 pixel-wide image The red and green colors of the salt ponds in South San Francisco Bay are brilliant visual markers for astronauts. The STS-111 crew photographed the bay south of the San Mateo bridge in June, 2002. This photograph is timely because a large number of the salt ponds (more than 16,500 acres) that are owned by Cargill, Inc. will be sold in September for wetlands restoration-a restoration project second in size only to the Florida Everglades project. Rough boundaries of the areas to be restored are outlined on the image. Over the past century, more than 80% of San Francisco Bay's wetlands have been filled and developed or diked off for salt mining. San Francisco Bay has supported salt mining since 1854. Cargill has operated most of the bay's commercial salt ponds since 1978, and had already sold thousands of acres to the State of California and the Don Edwards National Wildlife Refuge. This new transaction will increase San Francisco Bay's existing tidal wetlands by 50%. The new wetlands, to be managed by the California Department of Fish and Game and the U.S. Fish and Wildlife Service, will join the Don Edwards National Wildlife Refuge, and provide valuable habitat for birds, fish and other wildlife. The wetlands will contribute to better water quality and flood control in the bay, and open up more coastline for public enjoyment. Additional information: Cargill Salt Ponds (PDF) Turning Salt Into Environmental Gold Salt Ponds on Way to Becoming Wetlands Historic Agreement Reached to Purchase San Francisco Bay Salt Ponds Astronaut photograph STS111-376-3 was provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth

  14. Small-scale upper mantle extension beneath a destroyed craton

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Zheng, T.; Chen, L.; Ai, Y.; He, Y.; Xu, X.

    2014-12-01

    The North China Craton (NCC), as an unusual craton with part of its thick lithosphere destructed, records the geodynamic processes associated with the convergence of Eurasia and the Pacific and Philippine plates lasting from the Mesozoic to the Cenozoic. How the cratonic lithosphere deformed in response to the extensional tectonics caused by the oceanic plate subduction, however, remains debated. In order to investigate the mantle deformation of the NCC, we present new shear wave splitting measurements and updated tomographic models beneath a 900-km long profile across the north NCC. Compared to our other observations in the NCC, this profile is shorter but also crosses a region that experienced strong lithospheric destruction, therefore provides a good opportunity to improve our understanding of upper mantle deformation during the craton destruction. The upper mantle deformation is studied using SKS data from 60 broadband stations with average spacing of 15 km. For the data from events occurring at distances of 85º-115º, fast polarization directions and delay times (fδt) are retrieved by a routine method, while for the events at distances < 85º, waveform modeling are applied to obtain (fδt) after separating the effects of S and SKS. The measured splitting parameters show small-scale variations from east to west: the major fast directions, trending NE-SW or NW-SE in contrast, distribute intermittently along the profile. We plot the splitting parameters overlapping on the geological map and the tomography image for a depth range of 120-300 km. Comparison shows good consistency of the splitting pattern and structural features both at shallow and deep depths: NW-SE trending fast directions are observed at stations located within the basins or extensional zones like metamorphic core complexes, with the fast direction parallel to the extensional or stretching directions; the fast directions and the shear-wave velocity anomalies within the upper mantle

  15. Modeling the QBO and SAO Driven by Gravity Waves

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Chan, K. L.; Porter, H. S.

    1999-01-01

    Hines' Doppler spread parameterization (DSP) for small scale gravity waves (GW) is applied in a global scale numerical spectral model (NSM) to describe the semi-annual and quasi-biennial oscillations (SAO and QBO) as well as the long term interannual variations that are driven by wave mean flow interactions. This model has been successful in simulating the salient features observed near the equator at altitudes above 20 km, including the QBO extension into the upper mesosphere inferred from UARS measurements. The model has now been extended to describe also the mean zonal and meridional circulations of the upper troposphere and lower stratosphere that affect the equatorial QBO and its global scale extension. This is accomplished in part through tuning of the GW parameterization, and preliminary results lead to the following conclusions: (1) To reproduce the upwelling at equatorial latitudes associated with the Brewer/Dobson circulation that in part is modulated in the model by the vertical component of the Coriolis force, the eddy diffusivity in the lower stratosphere had to be enhanced and the related GW spectrum modified to bring it in closer agreement with the form recommended for the DSP. (2) To compensate for the required increase in the diffusivity, the observed QBO requires a larger GW source that is closer to the middle of the range recommended for the DSP. (3) Through global scale momentum redistribution, the above developments are conducive to extending the QBO and SAO oscillations to higher latitudes. Multi-year interannual oscillations are generated through wave filtering by the solar driven annual oscillation in the zonal circulation. (4) In a 3D version of the model, wave momentum is absorbed and dissipated by tides and planetary waves. Thus, a somewhat larger GW source is required to generate realistic amplitudes for the QBO and SAO.

  16. Ferric iron budget of Kaapvaal cratonic mantle peridotite

    NASA Astrophysics Data System (ADS)

    Woodland, A.

    2012-04-01

    Oxidation fugacity plays an important role in many geochemical processes, such as partial melting and melt-rock interaction. How mantle peridotite responds during such processes is dependent on the amount of Fe2O3 present, since it occurs in much smaller quantities than Fe2+ and affects buffering capacity. This is particularly the case since redox reactions have been directly implicated in the rejuvenation and eventual breakup of cratons (e.g. Foley 2008, 2011). In addition, oxygen fugacity also influences the incorporation of OH in nominally anhydrous minerals, which can affect the mechanical integrity of cratonic blocks (Peslier et al. 2010). These issues are important for understanding the evolution of the upper mantle beneath the Kaapvaal craton. Canil and coworkers (1994, 1996) reported bulk ferric iron contents for 11 peridotites (10 garnet-bearing and 1 spinel-bearing) from the Kaapvaal. The purpose of this study is to build on their pioneering work to better assess the ferric iron budget of Kaapvaal cratonic mantle and to improve our understanding of how ferric iron is distributed within the peridotitic assemblage. Our data set includes more than 30 additional samples, predominantly garnet peridoites, from 7 localities in South Africa and Lesotho. Bulk Fe2O3 contents were determined by combining measured Fe3+ contents of individual minerals (by Mössbauer spectroscopy) with their respective modal proportion in each sample. Fe3+ contents of garnet and clinopyroxene reported in Woodland & Koch (2003), Lazarov et al. (2009) and Woodland (2009) were combined with new data for orthopyroxene (opx) and modal mineralogy to make this assessment. Opx has Fe3+/Fetot of 0.04-0.1 and Fe3+ contents are comparable between Opx and coexisting Cpx. Calculated whole rock Fe2O3 contents range from 0.02 to 0.29 wt % with contents systematically decreasing with increasing degrees of depletion (as indicated by increasing MgO and decreasing Al2O3 content). For a given MgO content

  17. Discussing the air pollution of Sao Paulo City -- Brazil

    SciTech Connect

    Assuncao, J.V. de; Filho, J.B.G.

    1999-07-01

    The city of Sao Paulo has a population of about 10 million people (1998 estimate) and a vehicle fleet of about 4.5 millions. A great increase in the ratio of persons per car occurred in the last 28 years, starting from 11.4 persons per car in 1970 and reaching 2.2 persons per car in 1998, a ratio similar to those in developed countries. The population of the city represents about 6% of the Brazilian population, 30% of the State population, and 61% of Metropolitan population. In the 60's and in the beginning of the 70's the air quality in Sao Paulo Metropolitan Region and in Sao Paulo City was more influenced by industrial sources. Nowadays emissions in the metropolitan region come mainly from vehicles (94.8% of CO, 94.9% of NO{sub x}, 94.3% of HC and 54.1% of SO{sub x}, in 1997) and 40% contribution in relation to inhaling particulate (PM10) and in the city of Sao Paulo the contribution of vehicle emissions is the same or greater. Light-duty vehicles are powered by gasohol, a mixture of 78% gasoline and 22%, ethanol, and by plain ethanol. Heavy-duty vehicles are diesel oil fueled. A great concern exists in relation to health effects of small sized particulate and photochemical oxidants and its precursors. Besides the implementation of a strong air pollution control for stationary sources of particulate and sulfur dioxide, since the 70's and the existence of a federal law that established a program of emission control for new vehicles in 1986, only the sulfur dioxide control program was successful since the air quality levels of other common pollutants are still above the air quality standards for some part of the year. Other attempts were made in the last years, like the prohibition of free circulation of 20% of cars each day during the weekdays (rodizio of cars). Even with that the air quality levels don't meet the standards the all year, and other measures must be taken to solve the problem.

  18. Geothermal resources of Sao Miguel Island, Azores, Portugal

    SciTech Connect

    Duffield, W.A.; Muffler, L.J.P.

    1984-01-01

    Geothermal studies were carried out on the island of Sao Miguel, Azores to characterize the nature of the resource, to estimate its magnitude, and to identify target areas toward which exploration and developmental drilling might be directed. The main geothermal resource areas are Furnas, Agua de Pau, and Sete Cidades, three Quaternary silicic volcanic centers characterized by summit calderas beneath which magmatic heat sources provide thermal energy to overlying hydrothermal convection systems. For each of the systems, the studies have defined the size of the system, the subsurface temperature, the thermodynamic state of fluid in the system, the chemical composition of the fluid, and permeable parts of the system. 8 figs. (ACR)

  19. Craton stability and continental lithosphere dynamics during plume-plate interaction

    NASA Astrophysics Data System (ADS)

    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

  20. Smad7 mediates inhibition of Saos2 osteosarcoma cell differentiation by NF{kappa}B

    SciTech Connect

    Eliseev, Roman A. . E-mail: Roman_Eliseev@urmc.rochester.edu; Schwarz, Edward M.; Zuscik, Michael J.; O'Keefe, Regis J.; Drissi, Hicham; Rosier, Randy N.

    2006-01-01

    The transcription factor NF{kappa}B is constitutively activated in various tumor cells where it promotes proliferation and represses apoptosis. The bone morphogenetic proteins (BMPs) delay cell proliferation and promote differentiation and apoptosis of bone cells through activation of Smad downstream effectors and via Smad-independent mechanisms. Thus, NF{kappa}B and BMP pathways play opposing roles in regulating osteoblastic cell fate. Here, we show that in osteosarcoma Saos2 osteoblasts, NF{kappa}B regulates the activity of the BMP/Smad signaling. Inhibition of NF{kappa}B by overexpression of mI{kappa}B leads to the induction of osteoblast differentiation. Saos2 cells overexpressing mI{kappa}B (Saos2-mI{kappa}B) exhibit higher expression of osteoblast phenotypic genes such as alkaline phosphatase, Runx2 and osteocalcin and are more responsive to BMP2 in comparison to wild-type cells (Saos2-wt) or empty vector infected controls (Saos2-EV). Furthermore, BMP-2 signaling and Smad phosphorylation are significantly increased in Saos2-mI{kappa}B cells in comparison to Saos2-EV cells. Inhibition of NF{kappa}B signaling in Saos2-mI{kappa}B cells is associated with decreased expression of the BMP signaling inhibitor Smad7. While gain of Smad7 function in Saos2-mI{kappa}B cells results in inhibition of BMP signaling, anti-sense knockdown of Smad7 in Saos2-EV cells leads to upregulation of BMP signaling. We therefore conclude that in osteosarcoma Saos2 cells, NF{kappa}B represses BMP/Smad signaling and BMP2-induced differentiation through Smad7.

  1. Radar image San Francisco Bay Area, California

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The San Francisco Bay Area in California and its surroundings are shown in this radar image from the Shuttle Radar Topography Mission (SRTM). On this image, smooth areas, such as the bay, lakes, roads and airport runways appear dark, while areas with buildings and trees appear bright. Downtown San Francisco is at the center and the city of Oakland is at the right across the San Francisco Bay. Some city areas, such as the South of Market district in San Francisco, appear bright due to the alignment of streets and buildings with respect to the incoming radar beam. Three of the bridges spanning the Bay are seen in this image. The Bay Bridge is in the center and extends from the city of San Francisco to Yerba Buena and Treasure Islands, and from there to Oakland. The Golden Gate Bridge is to the left and extends from San Francisco to Sausalito. The Richmond-San Rafael Bridge is in the upper right and extends from San Rafael to Richmond. Angel Island is the large island east of the Golden Gate Bridge, and lies north of the much smaller Alcatraz Island. The Alameda Naval Air Station is seen just below the Bay Bridge at the center of the image. Two major faults bounding the San Francisco-Oakland urban areas are visible on this image. The San Andreas fault, on the San Francisco peninsula, is seen on the left side of the image. The fault trace is the straight feature filled with linear reservoirs, which appear dark. The Hayward fault is the straight feature on the right side of the image between the urban areas and the hillier terrain to the east.

    This radar image was acquired by just one of SRTM's two antennas and, consequently, does not show topographic data, but only the strength of the radar signal reflected from the ground. This signal, known as radar backscatter, provides insight into the nature of the surface, including its roughness, vegetation cover and urbanization. The overall faint striping pattern in the images is a data processing artifact due to the

  2. Teleseismic receiver functions modeling of the eastern Indian craton

    NASA Astrophysics Data System (ADS)

    Mandal, Prantik; Biswas, Koushik

    2016-09-01

    We estimate receiver functions (RFs) through the time-domain deconvolution using three-component broadband data of 100 teleseismic events (30° ⩽ ∧ ⩽ 90°) from 15 seismographs in the eastern Indian craton. Estimated radial RFs show a positive phase at 4.6-5.8 s delay time corresponding to the crustal thicknesses of 37-46 km. Through the differential evolution (DE) waveform inversion modeling of radial receiver functions, we delineate the crustal structure at 15 broadband stations. On an average, the Archean Singhbhum Odisha Craton (SOC) is characterized by a thick crust of 43 ± 3 km in comparison to a relatively thin crust of 41 ± 1 km underlying the Proterozoic Chotanagpur Granite Gneissic terrain (CGGT). While, a thin crust of 38 ± 1 km characterizes the younger Eastern Ghats Mobile Belt (EGMB). The main results of our modeling reveal a 46 km thick Archean crust underlying the Singhbhum granite (SG) of 3.6 Ga, which is characterized by a 3 km crustal thickening probably resulted from the Archean subduction process. Our modeling also detects a 2-3 km crustal thinning with the thinnest crust of 37 km below the region near South Singhbhum Shear Zone, which could be attributed to the 1.6 Ga plume activity associated with Dalma volcanic. Our modeling also led to the delineation of a crustal thinning of 2-3 km underlying the region in EGMB, which was influenced by a much younger (∼117 Ma) Rajmahal magmatism associated with the Gondwana break-up episode. However, our study could not detect any age-dependent variation of crustal thicknesses in the eastern Indian craton. The main result of our modeling suggests a two-phase crustal evolution process for the SOC viz. older E-W crustal thickening due to E-W plate compression and later crustal thinning episodes associated with the Dalma volcanism in the north and the Rajmahal volcanism in the South.

  3. Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton

    SciTech Connect

    van Houten, F.B.

    1980-06-01

    Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing distribution, facies, and thickness of relevant sequences are adequate for the three northern basins only. High detrital influx near the end of Jurassic time and in mid-Cretaceous time produced regressive nubian facies composed largely of low-sinuosity stream and fahdelta deposits. In the west and southwest the Ghadames, Murzuk, and Kufra basins were filled with a few hundred meters of detritus after long-continued earlier Mesozoic aggradation. In northern Egypt the regressive sequence succeeded earlier Mesozoic marine sedimentation; in the Sirte and Southern basins correlative deposits accumulated on Precambrian and Variscan terranes after earlier Mesozoic uplift and erosion. Waning of detrital influx into southern Tunisia and adjacent Libya in the west and into Israel in the east initiated an Albian to early Cenomanian transgression of Tethys. By late Cenomanian time it had flooded the entire cratonic margin, and spread southward into the Murzuk and Southern basins, as well as onto the Arabo-Nubian shield. Latest Jurassic-earliest Cretaceous, mid-Cretaceous, and Late Cretaceous transgressions across northeastern Africa recorded in these sequences may reflect worldwide eustatic sea-level rises. In contrast, renewed large supply of detritus during each regression and a comparable subsidence history of intracratonic and marginal basins imply regional tectonic control. 6 figures.

  4. San Francisco and Bay Area, CA, USA

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Although clouds obscure part of the city of San Francisco and the mouth of the Bay (37.5N, 122.0W), many cultural and natural features in the immediate vicinity are obvious. The Bay Bridge which was damaged in the 1989 earthquake, Candlestick Park, San Mateo and Dumbarton Bridges as well as the various colored settling ponds rimming the south end of the Bay, the San Andreas and Calaveras faults and many of the major highways can be seen.

  5. Remobilization in the cratonic lithosphere recorded in polycrystalline diamond

    PubMed

    Jacob; Viljoen; Grassineau; Jagoutz

    2000-08-18

    Polycrystalline diamonds (framesites) from the Venetia kimberlite in South Africa contain silicate minerals whose isotopic and trace element characteristics document remobilization of older carbon and silicate components to form the framesites shortly before kimberlite eruption. Chemical variations within the garnets correlate with carbon isotopes in the diamonds, indicating contemporaneous formation. Trace element, radiogenic, and stable isotope variations can be explained by the interaction of eclogites with a carbonatitic melt, derived by remobilization of material that had been stored for a considerable time in the lithosphere. These results indicate more recent formation of diamonds from older materials within the cratonic lithosphere. PMID:10947983

  6. An archean impact layer from the Pilbara and Kaapvaal cratons.

    PubMed

    Byerly, Gary R; Lowe, Donald R; Wooden, Joseph L; Xie, Xiaogang

    2002-08-23

    The Barberton greenstone belt of South Africa and the eastern Pilbara block of Western Australia provide information about Earth's surface environments between 3.2 and 3.5 billion years ago, including evidence for four large bolide impacts that likely created large craters, deformed the target rocks, and altered the environment. We have obtained identical single-zircon uranium-lead ages of 3470 +/- 2 million years ago for the oldest impact events from each craton. These deposits represent a single global fallout layer that is associated with sedimentation by an impact-generated tsunami and in Western Australia is represented by a major erosional unconformity. PMID:12193781

  7. An overview of San Francisco Bay PORTS

    USGS Publications Warehouse

    Cheng, Ralph T.; McKinnie, David; English, Chad; Smith, Richard E.

    1998-01-01

    The Physical Oceanographic Real-Time System (PORTS) provides observations of tides, tidal currents, and meteorological conditions in real-time. The San Francisco Bay PORTS (SFPORTS) is a decision support system to facilitate safe and efficient maritime commerce. In addition to real-time observations, SFPORTS includes a nowcast numerical model forming a San Francisco Bay marine nowcast system. SFPORTS data and nowcast numerical model results are made available to users through the World Wide Web (WWW). A brief overview of SFPORTS is presented, from the data flow originated at instrument sensors to final results delivered to end users on the WWW. A user-friendly interface for SFPORTS has been designed and implemented. Appropriate field data analysis, nowcast procedures, design and generation of graphics for WWW display of field data and nowcast results are presented and discussed. Furthermore, SFPORTS is designed to support hazardous materials spill prevention and response, and to serve as resources to scientists studying the health of San Francisco Bay ecosystem. The success (or failure) of the SFPORTS to serve the intended user community is determined by the effectiveness of the user interface.

  8. Downward Atmospheric Longwave Radiation in the City of Sao Paulo

    SciTech Connect

    Barbaro, Eduardo W.; Oliveira, Amauri P.; Soares, Jacyra; Ferreira, Mauricio J.; Boznar, Marija Z.; Mlakar, Primoz; Escobedo, Joao F.

    2009-03-11

    This work evaluates objectively the consistency and quality of a 9 year dataset based on 5 minute average values of downward longwave atmospheric (LW) emission, shortwave radiation, temperature and relative humidity. All these parameters were observed simultaneously and continuously from 1997 to 2006 in the IAG micrometeorological platform, located at the top of the IAG-USP building. The pyrgeometer dome emission effect was removed using neural network technique reducing the downward long wave atmospheric emission error to 3.5%. The comparison, between the monthly average values of LW emission observed in Sao Paulo and satellite estimates from SRB-NASA project, indicated a very good agreement. Furthermore, this work investigates the performance of 10 empirical expressions to estimate the LW emission at the surface. The comparison between the models indicates that Brunt's one presents the better results, with smallest ''MBE,''''RMSE'' and biggest ''d'' index of agreement, therefore Brunt is the most indicated model to estimate LW emission under clear sky conditions in the city of Sao Paulo.

  9. Geophysical constraints on the link between cratonization and orogeny: Evidence from the Tibetan Plateau and the North China Craton

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongjie; Teng, Jiwen; Romanelli, Fabio; Braitenberg, Carla; Ding, Zhifeng; Zhang, Xuemei; Fang, Lihua; Zhang, Sufang; Wu, Jianping; Deng, Yangfan; Ma, Ting; Sun, Ruomei; Panza, Giuliano F.

    2014-03-01

    Understanding the geodynamic process of orogeny and cratonization, and their transition is among the key topics of research in evaluating the link between plate tectonics and continental dynamics. The Tibetan Plateau and the North China Craton (NCC), two key areas in mainland China, offer excellent laboratories to understand continental tectonics over a broad span of Earth history. Particularly, the deep structure of the lithosphere as imaged from geophysical data on the Tibetan Plateau and the NCC provide important clues in understanding orogeny and cratonization. The Tibetan Plateau is the largest and highest plateau on Earth in terms of mean altitude, and is an important region for understanding the mechanisms of continent-continent collision and Cenozoic plateau uplift. The NCC is an Archean craton that underwent lithospheric disruption during the Mesozoic. Here we reconstruct the main features of the structure of the crust and upper mantle from surface wave tomography and gravity modeling in Tibet and its neighboring regions, in order to understand the modality of the convergence and collision process between the Indian and Eurasian plates, and the influence of this process on the uplift of the plateau. In the NCC, geological, geochemical, geophysical and tectonic investigations demonstrate that lithospheric destruction mainly occurred in the Eastern Block. The crustal structure of the NCC is reconstructed from ambient noise surface wave tomography and the different possible disruption mechanisms are evaluated. The Vs (shear-wave velocity) tomography results, and the density (ρ) structure of the crust and upper mantle (to about 350 km depth) demonstrate the lateral variation of the thickness of the metasomatic lid between the south and north of the Bangong-Nujiang suture (BNS) and the west and east of Tibet, which suggest that the leading edge of the subducting Indian slab reaches the BNS. The subduction angle of Indian Plate indicates a transition from steep

  10. Space Radar Image of San Francisco, California

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is a radar image of San Francisco, California, taken on October 3,1994. The image is about 40 kilometers by 55 kilometers (25 miles by 34 miles) with north toward the upper right. Downtown San Francisco is visible in the center of the image with the city of Oakland east (to the right) across San Francisco Bay. Also visible in the image is the Golden Gate Bridge (left center) and the Bay Bridge connecting San Francisco and Oakland. North of the Bay Bridge is Treasure Island. Alcatraz Island appears as a small dot northwest of Treasure Island. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on orbit 56. The image is centered at 37 degrees north latitude, 122degrees west longitude. This single-frequency SIR-C image was obtained by the L-band (24 cm) radar channel, horizontally transmitted and received. Portions of the Pacific Ocean visible in this image appear very dark as do other smooth surfaces such as airport runways. Suburban areas, with the low-density housing and tree-lined streets that are typical of San Francisco, appear as lighter gray. Areas with high-rise buildings, such as those seen in the downtown areas, appear in very bright white, showing a higher density of housing and streets which run parallel to the radar flight track. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: the L-band (24 cm), C-band (6 cm) and X-band (3cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes

  11. ASTER Images San Francisco Bay Area

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image of the San Francisco Bay region was acquired on March 3, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters about 50 to 300 feet ), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

    Image: This image covers an area 60 kilometers (37 miles) wide and 75 kilometers (47 miles) long in three bands of the reflected visible and infrared wavelength region. The combination of bands portrays vegetation in red, and urban areas in gray. Sediment in the Suisun Bay, San Pablo Bay, San Francisco Bay, and the Pacific Ocean shows up as lighter shades of blue. Along the west coast of the San Francisco Peninsula, strong surf can be seen as a white fringe along the shoreline. A powerful rip tide is visible extending westward from Daly City into the Pacific Ocean. In the lower right corner, the wetlands of the South San Francisco Bay National Wildlife Refuge appear as large dark blue and brown polygons. The high spatial resolution of ASTER allows fine detail to be observed in the scene. The main bridges of the area (San Mateo, San Francisco-Oakland Bay, Golden Gate, Richmond-San Rafael, Benicia-Martinez, and Carquinez) are easily picked out, connecting the different communities in the Bay area. Shadows of the towers along the Bay Bridge can be seen over the adjacent bay water. With enlargement the entire road network can be easily mapped; individual buildings are visible, including the shadows of the high-rises in downtown San Francisco.

    Inset: This enlargement of the San Francisco Airport highlights the high spatial resolution of ASTER. With further enlargement and careful examination, airplanes can be seen at the terminals.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth

  12. English Articulation between the San Francisco Unified School District and the City College of San Francisco. Youth Data Archive Issue Brief

    ERIC Educational Resources Information Center

    Gurantz, Oded

    2012-01-01

    San Francisco's Bridge to Success (BtS) initiative brings together the City and County of San Francisco, the San Francisco Unified School District (SFUSD), the City College of San Francisco (CCSF), and key community organizations to promote postsecondary success for underrepresented students. Various working groups, each comprised of staff from…

  13. Mesozoic Thermal Evolution of the Kaapvaal Craton Mantle Root.

    NASA Astrophysics Data System (ADS)

    Bell, D. R.

    2002-12-01

    Recent thermobarometry1 and accessory-mineral thermochronology2 studies on mantle and lower crustal xenoliths proposed a thermal pulse that affected the southern African mantle lithosphere during the Mesozoic and may relate to supercontinent breakup and associated mantle upwelling. Effects are concentrated on the margins of the Archean craton and in the surrounding Proterozoic terrains, but are not obvious within the core of the craton. In order to examine more closely the evidence for a thermal effect within the craton itself, we performed thermobarometry studies of a large suite of peridotite xenoliths from the 114 Ma Newlands orangeite (group II kimberlite). A variety of mineral thermobarometers were applied to analyses of coexisting minerals separated from fifty xenoliths. The resultant P-T arrays lie sub-parallel to those defined by xenoliths from the 84 Ma Kimberley group I kimberlites, some 50 km to the SE, but at temperatures from 60 to 120 C lower (depending on thermobarometer) at a given depth. This result, which is consistent with seismic images of a 250 - 300 km thick mantle root, confirms previous reports3,4 of unusually low temperatures, and inferences from garnet xenocryst studies5 that proposed a change from <37 to 40 mW/m2 model geotherms over this 30 Ma time interval. The corresponding depth difference for Kimberley and Newlands isotherms ranges from 12 - 20 km and exceeds expectations for mid-Cretaceous uplift5. It thus appears that the mantle root of the Kaapvaal craton has been heated, at least in the local regions sampled by Group I kimberlites, and that both the inflected and un-inflected limbs of Mesozoic group-I kimberlite-hosted geotherms on the Kaapvaal Craton may represent a perturbed thermal state of limited lateral extent. Petrologic studies on Kimberley xenoliths have documented the common presence of metasomatic diopside, phlogopite, and amphibole that are not common in the Newlands peridotites. Modal, trace element and isotope data

  14. 78 FR 57482 - Safety Zone; America's Cup Aerobatic Box, San Francisco Bay, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... San Francisco, CA in support of 2013 America's Cup air shows. These safety zones are established to provide a clear area on the water for pilots to initiate maneuvers and also provide for the safety of... rule is effective as to persons with actual notice starting September 6, 2013. This rule is...

  15. 78 FR 34123 - Notice of Inventory Completion: San Francisco State University NAGPRA Program, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-06

    ... from site CA-PLA-9 in Placer County, CA. This notice is published as part of the National Park Service... site CA-PLA-9 in Placer County, CA, by San Francisco State University personnel in conjunction with... point. The age of site CA-PLA-9 is unknown, but the site is located within the historically...

  16. 77 FR 70891 - Safety Zone; Bay Bridge Construction, San Francisco Bay, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-28

    ...The Coast Guard is establishing a temporary safety zone in the navigable waters of the San Francisco Bay near Yerba Buena Island, CA in support of the Bay Bridge Construction Safety Zone from November 1, 2012 through July 31, 2013. This safety zone is being established to protect mariners transiting the area from the dangers associated with over-head construction operations. Unauthorized......

  17. Uranus occults SAO158687. [stellar occultation and planetary parametric observation

    NASA Technical Reports Server (NTRS)

    Elliot, J. L.; Veverka, J.; Millis, R. L.

    1977-01-01

    Experience gained in obtaining atmospheric parameters, oblatenesses, and diameters of Jupiter and Mars from recent stellar occultations by these planets is used to predict what can be learned from the March 1977 occultation of the star SAO158687 by Uranus. The spectra of this star and Uranus are compared to indicate the relative instrument intensities of the two objects, the four passbands where the relative intensities are most nearly equal are listed, and expected photon fluxes from the star are computed on the assumption that it has UBVRI colors appropriate for a K5 main-sequence object. It is shown that low photon noise errors can be achieved by choosing appropriate passbands for observation, and the rms error expected for the Uranus temperature profiles obtained from the occultation light curves is calculated. It is suggested that observers of this occultation should record their data digitally for optimum time resolution.

  18. The Sao Paulo Microtron: Equipment and Planned Experiments

    SciTech Connect

    Martins, M. N.; Maidana, N. L.; Vanin, V. R.

    2007-10-26

    The Linear Accelerator Laboratory (LAL) of the Instituto de Fisica da Universidade de Sao Paulo (IFUSP) is building a two-stage racetrack microtron, which will generate continuous wave electron beams with energies up to 38 MeV. This paper describes the characteristics of the accelerator, and reports on the experimental equipment that will be available in order to pursue the photonuclear physics research program. Operation will begin with the first stage (5 MeV), and concentrate on NRF (Nuclear Resonance Fluorescence) measurements and radiation physics studies. Planned experiments for the second stage explore the cw character of the beam on coincidence experiments. A photon tagger has been already tested with radioactive sources and is ready to be installed. Gamma and neutron detector arrays are being developed for the detailed study of photoneutron reactions. Plans include the study of NRF and pygmy resonances, near the neutron binding energy.

  19. Early experience of the SAO Satellite-Tracking Program

    NASA Astrophysics Data System (ADS)

    Pearlman, M. R.

    When Fred L. Whipple of Harvard University assumed the directorship of the Smithsonian Astrophysical Observatory (SAO) in mid-1955, he proposed to the National Academy of Sciences and the National Science Foundation that the observatory be given responsibility for optical tracking of satellites during the IGY of 1957-1958. Several countries had expressed their intentions to launch satellites during the 18-month period to support research in ionospheric and upper atmospheric physics, including the effects of solar flares and solar radiation, and in geodesy and geophysics. On the basis of his experience at the Harvard College observatory with the Super-Schmidt cameras for meteor photography, Whipple was confident that optical tracking could provide a powerful means of monitoring satellite positions. The proposal was accepted in late 1955, and it was assumed that the total observing program would last only 18 months and would involve only a few satellites.

  20. Validation of the Updated SAO OMI Formaldehyde Retrieval

    NASA Astrophysics Data System (ADS)

    Gonzalez Abad, G.; Liu, X.; Liu, C.; Nowlan, C. R.; Chance, K.; Fried, A.; Janz, S. J.; Kanaya, Y.; Puentedura, O.

    2014-12-01

    The new SAO OMI formaldehyde retrieval, version v3.0.2 publicly released in June 2014, introduces major changes with respect to the previous version of the product. These changes include optimization of fitting window and fitting parameters, update of reference cross sections, reference sector normalization to the Pacific Ocean and a new air mass factor calculation. In this context it is necessary to assess the accuracy of the new product and perform a validation exercise. We compare the new data with other satellite retrievals from OMI, GOME-2 and SCIAMACHY performed by the Belgian Institute for Space Aeronomy, with in situ airborne measurements recorded using a Difference Frequency Generation Absorption Spectrometer (DFGAS) instrument, with aircraft passive remote sensing retrievals from the ACAM and GeoTASO instruments recorded during the DISCOVER-AQ field campaigns in Maryland and Texas and with ground-based DOAS measurements.

  1. Performance evaluation of the SAO VLG-11 atomic hydrogen masers

    NASA Technical Reports Server (NTRS)

    Levine, M. W.; Vessot, R. F.; Mattison, E. M.

    1978-01-01

    A new generation of frequency standards, the VLG-11 hydrogen maser, has been designed and built at the Smithsonian Astrophysical Observatory (SAO). A comprehensive series of environmental and short-term stability tests on three VLG-11 masers has been completed and evaluated. The test results reported here show substantial improvements over previous hydrogen masers in measured sensitivity to variations in ambient temperature, barometric pressure, and magnetic fields. The maser frequency stability, as represented by the two-sample (Allan) variance, has been measured for averaging times ranging from 1 to 100,00 seconds. The variance is lower than 1 x 10 to the -15th for averaging intervals between 1400 and 20,000 seconds. For times shorter than 4000 seconds, the measured stability data agree remarkably well with theoretical values calculated from thermal noise mechanisms and the 'noise within the linewidth' regime is clearly discernable in the data.

  2. Properties of QBO and SAO Generated by Gravity Waves

    NASA Technical Reports Server (NTRS)

    Mayr, H. G.; Mengel, J. G.; Reddy, C. A.; Chan, K. L.; Porter, H. S.

    1999-01-01

    We present an extension for the 2D (zonal mean) version of our Numerical Spectral Mode (NSM) that incorporates Hines' Doppler spread parameterization (DSP) for small scale gravity waves (GW). This model is applied to describe the seasonal variations and the semi-annual and quasi-biennial oscillations (SAO and QBO). Our earlier model reproduced the salient features of the mean zonal circulation in the middle atmosphere, including the QBO extension into the upper mesosphere inferred from UARS measurements. In the present model we incorporate also tropospheric heating to reproduce the upwelling at equatorial latitudes associated with the Brewer-Dobson circulation that affects significantly the dynamics of the stratosphere as Dunkerton had pointed out. Upward vertical winds increase the period of the QBO observed from the ground. To compensate for that, one needs to increase the eddy diffusivity and the GW momentum flux, bringing the latter closer to values recommended in the DSP. The QBO period in the model is 30 months (mo), which is conducive to synchronize this oscillation with the seasonal cycle of solar forcing. Multi-year interannual oscillations are generated through wave filtering by the solar driven annual oscillation in the zonal circulation. Quadratic non-linearities generate interseasonal variations to produce a complicated pattern of variability associated with the QBO. The computed temperature amplitudes for the SAO and QBO are in substantial agreement with observations at equatorial and extratropical latitudes. At high latitudes, however, the observed QBO amplitudes are significantly larger, which may be a signature of propagating planetary waves not included in the present model. The assumption of hydrostatic equilibrium not being imposed, we find that the effects from the vertical Coriolis force associated with the equatorial oscillations are large for the vertical winds and significant for the temperature variations even outside the tropics but are

  3. San Francisco and Bay Area, CA, USA

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Although clouds obscure part of the city of San Francisco and the mouth of the Bay (37.5N, 122.0W), many cultural and natural features in the immediate vicinity are obvious. The Bay Bridge which was damaged in the 1989 earthquake, Candlestick Park, San Mateo and Dumbarton Bridges as well as the various colored settling ponds rimming the south end of the Bay, the San Andreas and Calaveras faults and many of the major highways can be seen. Color infrared photography is very useful for haze penetration and greater definition of the imagery as well as vegetation detection, depicted as shades of red.

  4. Destruction of the North China Craton: Lithosphere folding-induced removal of lithospheric mantle?

    NASA Astrophysics Data System (ADS)

    Zhang, Kai-Jun

    2012-01-01

    High heat flow, high surface topography, and widespread volcanism indicate that the lithospheric mantle of typical cratonic character of the North China Craton has been seriously destroyed in its eastern half. However, the mechanism of this process remains open to intense debate. Here lithosphere folding-induced lithospheric mantle removal is proposed as a new mechanism for the destruction of the craton. Four main NNE-SSW-striking lithospheric-scale anticlines and synclines are recognized within North China east of the Helan fold-and-thrust belt. The lithosphere folding occurred possibly during the Late Triassic through Jurassic when the Yangzi Craton collided with the North China Craton. It was accompanied or followed by lithospheric dripping, and could have possibly induced the lithosphere foundering of the North China Craton. The lithosphere folding would have modified the lithosphere morphology, creating significant undulation in the lithospheric base and thus causing variations of the patterns of the small-scale convection. It also could have provoked the formation of new shear zones liable to impregnation of magma, producing linear incisions at the cratonic base and resulting in foundering of lithospheric mantle blocks. Furthermore, it generated thickening of the lithosphere or the lower crust and initiated the destabilization and subsequent removal of the lithospheric mantle.

  5. 3-D Structure of the Slave and Rae Cratons Provides Clues to Their Construction

    NASA Astrophysics Data System (ADS)

    Snyder, D. B.

    2013-12-01

    Deep geologic structures within cratons that make up continental cores were long neglected. Recently acquired geophysical data from large observational arrays and geochemical data resulting from exploration for diamond has now made possible co-registration of large-scale (400-km depth), truly 3-dimensional data sets. P-waves, surface waves and magnetotelluric observations provide 3-D wavespeed and conductivity models. Multi-azimuthal receiver functions map seismic discontinuity surfaces in 3-D. Xenolith suites erupted in kimberlites provide rock samples at key lithospheric depths, albeit at sparsely distributed locations. These multi-disciplinary models are becoming available for several key cratons worldwide; here the deep structure of the Slave and Rae cratons of the Canadian Shield is described. Lithospheric layers with tapered, wedge-shaped margins are common. Slave craton layers are sub-horizontal and indicate construction of the craton core at 2.7 Ga by underthrusting and flat stacking of lithosphere. The central Rae craton has predominantly dipping discontinuities that indicate construction at 1.9 Ga by thrusting similar to that observed in crustal ';thick-skinned' fold-and-thrust belts. 3-D mapping of conductivity and metasomatism, the latter via mineral recrystallization and resetting of isotopic ages, overprints primary structures in both cratons. Distribution of more conductivitve mantle suggests that assumed causative pervasive metasomatism occurs at 100-200 km depths with ';chimneys' reaching to shallower depths, typically in locations where kimberlites or mineralization has occurred.

  6. Cratonic root beneath North America shifted by basal drag from the convecting mantle

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; Mooney, Walter D.; Petrunin, Alexey G.

    2015-10-01

    Stable continental cratons are the oldest geologic features on the planet. They have survived 3.8 to 2.5 billion years of Earth’s evolution. The key to the preservation of cratons lies in their strong and thick lithospheric roots, which are neutrally or positively buoyant with respect to surrounding mantle. Most of these Archaean-aged cratonic roots are thought to have remained stable since their formation and to be too viscous to be affected by mantle convection. Here we use a combination of gravity, topography, crustal structure and seismic tomography data to show that the deepest part of the craton root beneath the North American Superior Province has shifted about 850 km to the west-southwest relative to the centre of the craton. We use numerical model simulations to show that this shift could have been caused by basal drag induced by mantle flow, implying that mantle flow can alter craton structure. Our observations contradict the conventional view of cratons as static, non-evolving geologic features. We conclude that there could be significant interaction between deep continental roots and the convecting mantle.

  7. Three-Dimensional Forward Modeling of Magnetotelluric Data Over Cratonic Lithosphere and Attendent Geological Structures: Case Study of the Zimbabwe Craton

    NASA Astrophysics Data System (ADS)

    Miensopust, M. P.; Jones, A. G.; Farquharson, C. G.; MT Team

    2007-12-01

    The Southern African MagnetoTelluric Experiment (SAMTEX) is covering a huge area - containing parts of South Africa, Namibia and nearly the whole of Botswana - with acquisition of magnetotelluric (MT) data. The project's aim is to gain more information on the lithospheric geometries of the geological structures of this region which contains some of the oldest lithospheric pieces on Earth - the cratons (e.g. Kaapvaal and Zimbabwe cratons). Since the standard modeling of MT data is only in two-dimensions and the recently developed three-dimensional inversion programs require a lot of computation time and high speed computers with large memories, 3D forward modeling is a good compromise on the way to full 3D interpretation of MT data. Forward modeling of subsurface structures similar to the cratonic areas of study will give some indication of how the MT responses should look like and if they change significantly when the cratons have a different shape or extent or resistivity. The determined synthetic data then can be compared with the real data collected in the SAMTEX project. The area for the case study is the western edge of the Zimbabwe craton in eastern Botswana. The craton is surrounded by the Damara Mobile Belt and the Magondi Mobile Belt to the north and west and the Limpopo belt to the south. The giant northern Botswana dyke swarm is cross cutting the craton in about WNW to ESE direction. Based on this geological information, a 3D model was created to calculate synthetic MT responses using the forward modeling routine implemented in the 3D inversion program MT3Dinv (developed by the Geophysical Inversion Facility, University of British Columbia). We will show the results of this modeling exercise and compare them with the observations.

  8. Driving of the SAO by gravity waves as observed from satellite

    NASA Astrophysics Data System (ADS)

    Ern, M.; Preusse, P.; Riese, M.

    2015-04-01

    It is known that atmospheric dynamics in the tropical stratosphere have an influence on higher altitudes and latitudes as well as on surface weather and climate. In the tropics, the dynamics are governed by an interplay of the quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) of the zonal wind. The QBO is dominant in the lower and middle stratosphere, and the SAO in the upper stratosphere/lower mesosphere. For both QBO and SAO the driving by atmospheric waves plays an important role. In particular, the role of gravity waves is still not well understood. In our study we use observations of the High Resolution Dynamics Limb Sounder (HIRDLS) satellite instrument to derive gravity wave momentum fluxes and gravity wave drag in order to investigate the interaction of gravity waves with the SAO. These observations are compared with the ERA-Interim reanalysis. Usually, QBO westward winds are much stronger than QBO eastward winds. Therefore, mainly gravity waves with westward-directed phase speeds are filtered out through critical-level filtering already below the stratopause region. Accordingly, HIRDLS observations show that gravity waves contribute to the SAO momentum budget mainly during eastward wind shear, and not much during westward wind shear. These findings confirm theoretical expectations and are qualitatively in good agreement with ERA-Interim and other modeling studies. In ERA-Interim most of the westward SAO driving is due to planetary waves, likely of extratropical origin. Still, we find in both observations and ERA-Interim that sometimes westward-propagating gravity waves may contribute to the westward driving of the SAO. Four characteristic cases of atmospheric background conditions are identified. The forcings of the SAO in these cases are discussed in detail, supported by gravity wave spectra observed by HIRDLS. In particular, we find that the gravity wave forcing of the SAO cannot be explained by critical-level filtering alone; gravity

  9. 33 CFR 80.1142 - San Francisco Harbor, CA.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false San Francisco Harbor, CA. 80.1142 Section 80.1142 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1142 San Francisco Harbor, CA. A straight...

  10. [The demographic characteristics of slaves in Sao Paulo, 1777-1829].

    PubMed

    Luna, F V

    1992-01-01

    "The introduction and development of sugar and coffee production in Sao Paulo [Brazil] led to deep changes in its populational structure. The large number of slaves who entered the province, mainly adult men, destroyed the population's relative balance, both in terms of sex and age structures. The study, based on manuscripts known as ¿Macos de Populacao' which belong to the Arquivo do Estado de Sao Paulo, covers twenty-five different communities in Sao Paulo, in the years 1777, 1804 and 1829. The demographic characteristics of the slaves and their relation with economic variables were analysed.... Special attention was given to the slaves' marriage and their reproductive capacity." (EXCERPT) PMID:12321100

  11. Diamond genesis, seismic structure, and evolution of the Kaapvaal-Zimbabwe craton.

    PubMed

    Shirey, Steven B; Harris, Jeffrey W; Richardson, Stephen H; Fouch, Matthew J; James, David E; Cartigny, Pierre; Deines, Peter; Viljoen, Fanus

    2002-09-01

    The lithospheric mantle beneath the Kaapvaal-Zimbabwe craton of southern Africa shows variations in seismic P-wave velocity at depths within the diamond stability field that correlate with differences in the composition of diamonds and their syngenetic inclusions. Middle Archean mantle depletion events initiated craton keel formation and early harzburgitic diamond formation. Late Archean accretionary events involving an oceanic lithosphere component stabilized the craton and contributed a younger Archean generation of eclogitic diamonds. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the Archean diamond suite. PMID:12215642

  12. Coeval large-scale magmatism in the Kalahari and Laurentian cratons during Rodinia assembly.

    PubMed

    Hanson, Richard E; Crowley, James L; Bowring, Samuel A; Ramezani, Jahandar; Gose, Wulf A; Dalziel, Ian W D; Pancake, James A; Seidel, Emily K; Blenkinsop, Thomas G; Mukwakwami, Joshua

    2004-05-21

    We show that intraplate magmatism occurred 1106 to 1112 million years ago over an area of two million square kilometers within the Kalahari craton of southern Africa, during the same magnetic polarity chron as voluminous magmatism within the cratonic core of North America. These contemporaneous magmatic events occurred while the Rodinia supercontinent was being assembled and are inferred to be parts of a single large igneous province emplaced across the two cratons. Widespread intraplate magmatism during Rodinia assembly shows that mantle upwellings required to generate such provinces may occur independently of the supercontinent cycle. PMID:15105458

  13. A Sharp Edge of the Cratonic Lithosphere of North America

    NASA Astrophysics Data System (ADS)

    Harper, T. B.; Skryzalin, P. A.; Menke, W. H.; Levin, V. L.; Darbyshire, F. A.

    2015-12-01

    Using teleseismic travel time delays, we develop a tomographic model of the lithosphere beneath northeastern North America, from the shore of James Bay in Quebec to the Atlantic coast of New England and to a depth of 300 km. Three major terranes lie within this cratonic margin: the 2.7 Ga Superior province, the 1 Ga Grenville orogenic belt and the 0.3-0.4 Ga Appalachian terranes, which are bounded by the Grenville Front (GF) and Appalachian Front (AF), respectively. Additionally, the 0.8 Ga Avalon terrain was accreted to coastal New England by strike-skip faulting during the Appalachian orogeny. Our tomographic model uses earthquake seismograms recorded by permanent US and Canadian stations, the Transportable Array and the temporary QMIII deployment. All data were corrected for instrument response and record sections were examined visually to identify gross errors in response and timing. Differential arrival times of P and PKP waves were determined by cross-correlation and have a maximum amplitude of about ±1 second. In our model, lithospheric boundaries do not correlate well with geological boundaries, nor do they strike parallel to them. The seismically-fast (by 5% relative to AK135) cratonic lithosphere of North America is much thicker than that of the younger terranes, extending to 200 km or more depth but with a sharp east-dipping eastern edge located (at Moho depths) 100-250 km northwest of the GF. The lithosphere beneath the Grenville and Appalachian terranes, which were affected by subduction during the Grenville and Appalachian orogenies, is slower (by 4%). A sliver of seismically-fast lithosphere, extending to ~150 km depth, occurs along the Atlantic coast and is interpreted as the Avalonian lithosphere.

  14. 77 FR 15799 - Notice of Intent To Repatriate a Cultural Item: San Francisco State University, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-16

    ... National Park Service Notice of Intent To Repatriate a Cultural Item: San Francisco State University, San... University, in consultation with the appropriate Indian tribes, has ] determined that the cultural item meets... affiliated with the cultural item may contact the San Francisco State University NAGPRA Program....

  15. 33 CFR 165.T11-534 - Safety zone; Bay Bridge construction, San Francisco Bay, San Francisco, CA.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Safety zone; Bay Bridge construction, San Francisco Bay, San Francisco, CA. 165.T11-534 Section 165.T11-534 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PORTS AND WATERWAYS SAFETY REGULATED NAVIGATION AREAS AND LIMITED ACCESS...

  16. New aerosol particles formation in the Sao Paulo Metropolitan Area

    NASA Astrophysics Data System (ADS)

    Vela, Angel; Andrade, Maria de Fatima; Ynoue, Rita

    2016-04-01

    The Sao Paulo Metropolitan Area (SPMA), in the southeast region of Brazil, is considered a megalopolis comprised of Sao Paulo city and more 38 municipalities. The air pollutant emissions in the SPMA are related to the burning of the fuels: etanol, gasohol (gasoline with 25% ethanol) and diesel. According to CETESB (2013), the road vehicles contributed up to about 97, 87, and 80% of CO, VOCs and NOx emissions in 2012, respectively, being most of NOx associated to diesel combustion and most of CO and VOCs from gasohol and ethanol combustion. Studies conducted on ambient air pollution in the SPMA have shown that black carbon (BC) explains 21% of mass concentration of PM2.5 compared with 40% of organic carbon (OC), 20% of sulfates, and 12% of soil dust (Andrade et al., 2012). Most of the observed ambient PM2.5 mass concentration usually originates from precursors gases such as sulphur dioxide (SO2), ammonia (NH3), nitrogen oxides (NOx) and VOCs as well as through the physico-chemical processes such as the oxidation of low volatile hydrocarbons transferring to the condensed phase (McMurry et al., 2004). The Weather Research and Forecasting with Chemistry model (WRF-Chem; Grell et al. 2005), configured with three nested grid cells: 75, 15, and 3 km, is used as photochemical modeling to describe the physico-chemical processes leading to evolution of particles number and mass size distribution from a vehicular emission model developed by the IAG-USP laboratory of Atmospheric Processes and based on statistical information of vehicular activity. The spatial and temporal distributions of emissions in the finest grid cell are based on road density products compiled by the OpenStreetMap project and measurements performed inside tunnels in the SPMA, respectively. WRF-Chem simulation with coupled primary aerosol (dust and sea-salt) and biogenic emission modules and aerosol radiative effects turned on is conducted as the baseline simulation (Case_0) to evaluate the model

  17. The SAO/NASA Astrophysics Data System: A Gateway to the Planetary Sciences Literature

    NASA Astrophysics Data System (ADS)

    Henneken, E. A.; Accomazzi, A.; Grant, C. S.; Kurtz, M. J.; Thompson, D.; Bohlen, E.; Murray, S. S.

    2009-03-01

    The SAO/NASA Astrophysics Data System (ADS) provides various free services for finding, accessing, and managing bibliographic data, including a basic search form, the myADS notification service, and private libraries, plus access to scanned published articles.

  18. Concept and Use of Psychoactive Drugs Among University Students in the Sao Paulo Area

    ERIC Educational Resources Information Center

    Zanini, Antonio C.; And Others

    1977-01-01

    This paper presents the results of a medical-social questionnaire made by members of the Scientific Commission of the First International Congress of Drug Addiction Among University Students, Sao Paulo, Brazil, 1974. (Author)

  19. Plume-induced dynamic instabilities near cratonic blocks: Implications for P-T-t paths and metallogeny

    NASA Astrophysics Data System (ADS)

    Guillou-Frottier, L.; Burov, E.; Cloetingh, S.; Le Goff, E.; Deschamps, Y.; Huet, B.; Bouchot, V.

    2012-06-01

    Plume head-lithosphere interactions around cratonic blocks result in thermo-mechanical disturbances that lead to heating and burial phases of crustal rocks. We present results from numerical models of plume head-cratonic blocks interactions where a free upper surface condition and realistic rheologies are accounted for. These models include distinct cratonic blocks embedded within a continental lithosphere and separated by several hundreds of kilometers. Surface topography, thermal field and effective viscosity values are tracked for 20 Myr of interactions. The modeled dynamic interaction of a plume head around cratonic blocks results in two main types of instabilities, each of them resulting in a distinct P-T-t path. The "slab-like" instability, focused on cratonic edges when plume head is away from the craton center, shows a near-isothermal burial phase, while the "drip-like" instability occurring above plume head material results in a near-isobaric heating phase. Consequently, both clockwise and counterclockwise P-T-t paths can be expected around cratons, as actually observed around the Tanzanian craton and other cratonic areas. Metallogenic data from gemstone-bearing rocks in south-east Africa and data from ultrahigh temperature and ultrahigh pressure metamorphism are compatible with our model. It appears that vertical mantle dynamics around cratons may also explain thermobarometric signatures that are often attributed to horizontal tectonics.

  20. On the relations between cratonic lithosphere thickness, plate motions, and basal drag

    USGS Publications Warehouse

    Artemieva, I.M.; Mooney, W.D.

    2002-01-01

    An overview of seismic, thermal, and petrological evidence on the structure of Precambrian lithosphere suggests that its local maximum thickness is highly variable (140-350 km), with a bimodal distribution for Archean cratons (200-220 km and 300-350 km). We discuss the origin of such large differences in lithospheric thickness, and propose that the lithospheric base can have large depth variations over short distances. The topography of Bryce Canyon (western USA) is proposed as an inverted analog of the base of the lithosphere. The horizontal and vertical dimensions of Archean cratons are strongly correlated: larger cratons have thicker lithosphere. Analysis of the bimodal distribution of lithospheric thickness in Archean cratons shows that the "critical" surface area for cratons to have thick (>300 km) keels is >6-8 ?? 106 km2 . Extrapolation of the linear trend between Archean lithospheric thickness and cratonic area to zero area yields a thickness of 180 km. This implies that the reworking of Archean crust should be accompanied by thinning and reworking of the entire lithospheric column to a thickness of 180 km in accord with thickness estimates for Proterozoic lithosphere. Likewise, extrapolation of the same trend to the size equal to the total area of all Archean cratons implies that the lithospheric thickness of a hypothesized early Archean supercontinent could have been 350-450 km decreasing to 280-400 km for Gondwanaland. We evaluate the basal drag model as a possible mechanism that may thin the cratonic lithosphere. Inverse correlations are found between lithospheric thickness and (a) fractional subduction length and (b) the effective ridge length. In agreement with theoretical predictions, lithospheric thickness of Archean keels is proportional to the square root of the ratio of the craton length (along the direction of plate motion) to the plate velocity. Large cratons with thick keels and low plate velocities are less eroded by basal drag than small

  1. Vehicular emissions of organic particulate matter in Sao Paulo, Brazil

    NASA Astrophysics Data System (ADS)

    Oyama, B. S.; Andrade, M. F.; Herckes, P.; Dusek, U.; Röckmann, T.; Holzinger, R.

    2015-12-01

    Vehicular emissions have a strong impact on air pollution in big cities. Many factors affect these emissions: type of vehicle, type of fuel, cruising velocity, and brake use. This study focused on emissions of organic compounds by Light (LDV) and Heavy (HDV) duty vehicle exhaust. The study was performed in the city of Sao Paulo, Brazil, where vehicles run on different fuels: gasoline with 25 % ethanol (called gasohol), hydrated ethanol, and diesel (with 5 % of biodiesel). The vehicular emissions are an important source of pollutants and the principal contribution to fine particulate matter (smaller than 2.5 μm, PM2.5) in Sao Paulo. The experiments were performed in two tunnels: Janio Quadros (TJQ) where 99 % of the vehicles are LDV, and Rodoanel Mario Covas (TRA) where up to 30 % of the fleet was HDV. The PM2.5 samples were collected on quartz filters in May and July 2011 at TJQ and TRA, respectively, using two samplers operating in parallel. The samples were analyzed by Thermal-Desorption Proton-Transfer-Reaction Mass-Spectrometry (TD-PTR-MS), and by Thermal-Optical Transmittance (TOT). The organic aerosol (OA) desorbed at TD-PTR-MS represented around 30 % of the OA estimated by the TOT method, mainly due to the different desorption temperatures, with a maximum of 870 and 350 °C for TOT and TD-PTR-MS, respectively. Average emission factors (EF) organic aerosol (OA) and organic carbon (OC) were calculated for HDV and LDV fleet. We found that HDV emitted more OA and OC than LDV, and that OC emissions represented 36 and 43 % of total PM2.5 emissions from LDV and HDV, respectively. More than 700 ions were identified by TD-PTR-MS and the EF profiles obtained from HDV and LDV exhibited distinct features. Nitrogen-containing compounds measured in the desorbed material up to 350 °C contributed around 20 % to the EF values for both types of vehicles, possibly associated with incomplete fuel burning. Additionally, 70 % of the organic compounds measured from the aerosol

  2. Observations of gravity waves from satellite and implications for the wave driving of the SAO

    NASA Astrophysics Data System (ADS)

    Ern, Manfred; Preusse, Peter; Riese, Martin

    2015-04-01

    The dynamics at low latitudes in the stratosphere and lower mesosphere is governed by an interplay of the quasi-biennial oscillation (QBO) and the semiannual oscillation (SAO) of the zonal wind. It is known that tropical dynamics has significant influence on the atmosphere over a large range of altitudes and latitudes. For example, QBO and SAO effects are seen in the MLT region, and there is a significant influence of the QBO on surface weather and climate in the Northern Hemisphere during winter. Still, global models have large difficulties in simulating a realistic QBO and SAO. One main uncertainty is the wave driving of these oscillations, in particular the driving by gravity waves (GWs). We derive GW temperature variances, GW momentum fluxes and potential GW drag from over three years of High Resolution Dynamics Limb Sounder (HIRDLS) satellite data in the stratopause region. These observations are compared with the SAO driving due to planetary waves, as well as the zonal wind tendencies, both determined from the ECMWF ERA-Interim (ERAI) reanalysis. HIRDLS satellite observations and ERAI support the general assumption that, due to selective filtering of the GW spectrum by the QBO in the stratosphere, GWs mainly contribute to the SAO momentum budget during SAO eastward wind shear. However, during SAO westward wind shear the GW contribution is usually smaller, and the wave driving is dominated by planetary waves, probably of extratropical origin. Still, we find indications in both satellite observations and ERAI that sometimes GW drag is important also during SAO westward wind shear.

  3. Microbial biogeography of San Francisco Bay sediments

    NASA Astrophysics Data System (ADS)

    Lee, J. A.; Francis, C. A.

    2014-12-01

    The largest estuary on the west coast of North America, San Francisco Bay is an ecosystem of enormous biodiversity, and also enormous human impact. The benthos has experienced dredging, occupation by invasive species, and over a century of sediment input as a result of hydraulic mining. Although the Bay's great cultural and ecological importance has inspired numerous surveys of the benthic macrofauna, to date there has been almost no investigation of the microbial communities on the Bay floor. An understanding of those microbial communities would contribute significantly to our understanding of both the biogeochemical processes (which are driven by the microbiota) and the physical processes (which contribute to microbial distributions) in the Bay. Here, we present the first broad survey of bacterial and archaeal taxa in the sediments of the San Francisco Bay. We conducted 16S rRNA community sequencing of bacteria and archaea in sediment samples taken bimonthly for one year, from five sites spanning the salinity gradient between Suisun and Central Bay, in order to capture the effect of both spatial and temporal environmental variation on microbial diversity. From the same samples we also conducted deep sequencing of a nitrogen-cycling functional gene, nirS, allowing an assessment of evolutionary diversity at a much finer taxonomic scale within an important and widespread functional group of bacteria. We paired these sequencing projects with extensive geochemical metadata as well as information about macrofaunal distribution. Our data reveal a diversity of distinct biogeographical patterns among different taxa: clades ubiquitous across sites; clades that respond to measurable environmental drivers; and clades that show geographical site-specificity. These community datasets allow us to test the hypothesis that salinity is a major driver of both overall microbial community structure and community structure of the denitrifying bacteria specifically; and to assess

  4. U-Pb baddeleyite and zircon ages of 2040 Ma, 1650 Ma and 885 Ma on dolerites in the West African Craton (Anti-Atlas inliers): Possible links to break-up of Precambrian supercontinents

    NASA Astrophysics Data System (ADS)

    Kouyaté, Djiky; Söderlund, Ulf; Youbi, Nasrrddine; Ernst, Richard; Hafid, Ahmid; Ikenne, Moha; Soulaimani, Abderrahmane; Bertrand, Hervé; El Janati, M'hamed; R'kha Chaham, Khalid

    2013-08-01

    Precambrian inliers of the Anti-Atlas belt in the southern part of Morocco contain numerous dolerite dyke and sill swarms which were previously poorly dated. Four dykes and two sills dated by the U-Pb TIMS method on baddeleyite and zircon provide the first steps toward a magmatic ‘barcode' for the West African Craton (WAC) and constraints on the timing of breakup of the WAC from Precambrian supercontinents. A 2040 ± 2 Ma (U-Pb zircon) age for a WNW dyke in the Zenaga inlier, matches the published age of a dyke in the Tagragra of Tata inlier, and also those of Eburnean granites observed in several inliers, which are collectively interpreted to represent ca. 2040 Ma bimodal magmatism due to a mantle plume. Based on the presence of matching 2040 Ma ages, the WAC may have been connected to the North Atlantic Craton at the initial stage of fragmentation of a late Archean continent. U-Pb baddeleyite ages of 1656 ± 9 Ma and ca. 1655 Ma from sills in the Zenaga inlier and 1654 ± 16 Ma from a NE-trending dyke in the Agadir Melloul inlier are similar to intraplate magmatic ages in eastern and northern Baltica, and support the SAMBA reconstruction (part of the Nuna supercontinent) of the WAC adjacent to Baltica. Approximate U-Pb ages of 885 Ma for two dykes in the Iguerda-Taïfast and Zenaga inliers date a NE trending swarm (named herein the Iguerda-Taïfast swarm) which is connected to the initial breakup of the supercontinent Rodinia, and a specific link with the São Francisco/Congo and North China craton is considered.

  5. Developing Early Warning Indicators for the San Francisco Unified School District. Youth Data Archive Issue Brief

    ERIC Educational Resources Information Center

    John W. Gardner Center for Youth and Their Communities, 2011

    2011-01-01

    San Francisco's Bridge to Success (BtS) initiative brings together the City and County of San Francisco, the San Francisco Unified School District (SFUSD), the City College of San Francisco (CCSF), and key community organizations to promote postsecondary success for underrepresented students. Partners agree that the first step in achieving this…

  6. The meaning of midlithospheric discontinuities: A case study in the northern U.S. craton

    NASA Astrophysics Data System (ADS)

    Hopper, Emily; Fischer, Karen M.

    2015-12-01

    Converted wave imaging has revealed significant negative velocity gradients, often termed midlithospheric discontinuities, within the thick, high-velocity mantle beneath cratons. In this study, we investigate the origins and implications of these structures with high-resolution imaging of mantle discontinuities beneath the Archean Wyoming, Superior and Medicine Hat, and Proterozoic Yavapai and Trans-Hudson terranes. Sp phases from 872 temporary and permanent broadband stations, including the EarthScope Transportable Array, were migrated into three-dimensional common conversion point stacks. Four classes of discontinuities were observed. (1) A widespread, near-flat negative velocity gradient occurs largely at 70-90 km depth beneath both Archean and Proterozoic cratons. This structure is consistent with the top of a frozen-in layer of volatile-rich melt. (2) Dipping negative velocity gradients are observed between 85 and 200 km depth. The clearest examples occur at the suture zones between accreted Paleoproterozoic Yavapai arc terranes and the Wyoming and Superior cratons. These interfaces could represent remnant subducting slabs, and together with eclogite in xenoliths, indicate that subduction-related processes likely contributed to cratonic mantle growth. (3) Sporadic positive velocity gradients exist near the base of the lithospheric mantle, perhaps due to laterally variable compositional layering. (4) In contrast to off-craton regions, clear Sp phases are typically not seen at lithosphere-asthenosphere boundary depths beneath Archean and Proterozoic terranes, consistent with a purely thermal contrast between cratonic mantle lithosphere and asthenosphere.

  7. Two modes of extension in the North China Craton: Insights from numerical modeling

    NASA Astrophysics Data System (ADS)

    Lin, F.; Liu, M.

    2013-12-01

    The North China Craton was formed around 1.8 Ga by collision and amalgamation of the Eastern and Western blocks. It remained tectonically stable since then until Mesozoic, when its eastern part experienced wide-distributed extension and volcanism. This distributed extension waned down in the early Cenozoic, and was replaced by localized extension (rifting) in the western part of the North China Craton. We have developed a series of viscoplastic finite element models to investigate the lithospheric conditions associated with these changing modes of extension in the North China Craton. Our results show that the wide-distributed extension in North China requires a thin and hot lithosphere, which is probably the result of delamination or thermal erosion of the lithospheric root under the eastern part of the North China Craton. The localized rifting during the late Cenozoic in the western part of the North China Craton indicates a relatively cold and thick lithosphere. Furthermore, preexisting lithospheric weakening was needed to explain the formation of the Late Cenozoic rift zones. These preexisting weakening zones may be inherited from the Paleoprotozoic collision that formed the North China Craton.

  8. Anisotropy structure beneath the eastern edge of the North China Craton

    NASA Astrophysics Data System (ADS)

    Lin, R.; Wang, Y.; Wang, W.; Wen, L.; Chen, X.

    2013-12-01

    The North China Craton is one of the most ancient craton which is considered as a perfect area to observe the craton basement destruction, replacement and reconstruction. But the mechanism and kinetics background of the lithospheric thinning of the North China Craton are still under debate. The upper mantle velocity and anisotropy structures, temperature and chemical composition are important for us to understand the destruction process of the North China Craton. Most of previous studies used shear wave splitting or surface wave analysis to study anisotropy structure, which have a poor vertical resolution in upper mantle. Waveform modeling of upper mantle triplication phases can provide a high vertical resolution. We develop a method based on the generalized reflection and transmission method (GRTM) to calculate synthetic seismograms for wave propagating in stratified VTI media, so we can waveform model triplication phases to study the upper mantle anisotropy structures. In this study, we waveform model the tangential and radial seismic triplication data recorded in Chinese digital seismic stations at a epicentral distance of 10-30 degree for several events occurring in southeast of Russia to constrain the fine upper mantle velocity and anisotropy structures beneath the eastern edge of the North China Craton . We also use mineral physic simulation to explore thermal and compositional models that would explain the inferred seismic structures.

  9. Implementing Technology for Science Classrooms in Sao Tome and Principe

    NASA Astrophysics Data System (ADS)

    Jardim, Maria Dolores Rodrigues

    This qualitative bounded case study was designed to understand how technology integration in schools could be addressed in a first-wave country. The integration of educational technology in Sao Tome and Principe (STP), a first-wave agricultural civilization, can narrow the divide between STP and third-wave information age societies. The conceptual framework was based on theories of change, learning, and context. Toffler's wave theory described how societies changed while Fullan's change theory examined how the people might change. Roger's diffusion of innovations addressed how processes change. Bandura, Vygotsky, and Siemen provided the framework for the learning within the model of change. Finally, the context theories of Tessmer and Richey's instructional design, Lave and Wenger's situated learning, and Sticht's functional context theory were applied. Twenty five individuals from 5 schools, including teachers, school directors, key educational stakeholders, and the minister of education were involved in a pilot project to integrate technology into the science curriculum. The data were collected via interviews, reflective summaries, and confidential narratives. The resulting data were analyzed to find emerging patterns. The results of this analysis showed that a first-wave civilization can adopt a third-wave civilization's features in terms of technology integration, when there is the support of opinion leaders and most of the necessary contextual requirements are in place. The study contributes to social change by providing access to knowledge through technology integration, which empowers both teachers and students.

  10. Forecasting the Next Great San Francisco Earthquake

    NASA Astrophysics Data System (ADS)

    Rundle, P.; Rundle, J. B.; Turcotte, D. L.; Donnellan, A.; Yakovlev, G.; Tiampo, K. F.

    2005-12-01

    The great San Francisco earthquake of 18 April 1906 and its subsequent fires killed more than 3,000 persons, and destroyed much of the city leaving 225,000 out of 400,000 inhabitants homeless. The 1906 earthquake occurred on a km segment of the San Andreas fault that runs from the San Juan Bautista north to Cape Mendocino and is estimated to have had a moment magnitude m ,l 7.9. Observations of surface displacements across the fault were in the range m. As we approach the 100 year anniversary of this event, a critical concern is the hazard posed by another such earthquake. In this talk we examine the assumptions presently used to compute the probability of occurrence of these earthquakes. We also present the results of a numerical simulation of interacting faults on the San Andreas system. Called Virtual California, this simulation can be used to compute the times, locations and magnitudes of simulated earthquakes on the San Andreas fault in the vicinity of San Francisco. Of particular importance are new results for the statistical distribution of interval times between great earthquakes, results that are difficult or impossible to obtain from a purely field-based approach. We find that our results are fit well under most circumstances by the Weibull statistical distribution, and we compute waiting times to future earthquakes based upon our simulation results. A contrasting approach to the same problem has been adopted by the Working Group on California Earthquake Probabilities, who use observational data combined with statistical assumptions to compute probabilities of future earthquakes.

  11. Paleoproterozoic postcollisional magmatic belt of the southern Siberian craton

    NASA Astrophysics Data System (ADS)

    Salnikova, E. B.; Larin, A. M.; Kotov, A. B.; Levitsky, V. I.; Reznitsky, L. Z.; Kovach, V. P.; Yakovleva, S. Z.

    2003-04-01

    Paleoproterozoic time is characterized by large-scale collisional and postcollisional magmatic activity evidenced in the most of ancient cratons. This global event is related to the Arctic supercontinent assemblage (Rogers, 1996). The formation of postcollisional magmatic belt at 1.9-1.8 Ga within the south-west flanking of the Siberian craton is a remarkable example of these processes happened during overall lithospheric convergence. This belt is extends for about 3000 km from the southern Enisey ridge at the west to the central Aldan shield at the east. Within the central Aldan shield the latest collisional event occurred 1925+/-5 Ma (Kotov et al, 2003) and post-collisional subalkaline S- and I-type granites emplaced at 1916+/-10 Ma (Bibikova et al., 1989), 1901+/-1 Ma (Frost et al., 1998) and 1899+/-6 Ma (Kotov et al, 2003). However at the southern Olekma terrain (western Aldan shield) the syncollisional granites have formed at 1906+/-4 Ma and postcollisional Kodar granitoids were generated at 1876-1873 Ma (Larin et al., 2000). The is a tendency outlined in timing of postcollision processes to the west (in modern coordinates). Ages of postcollisional Kevakta granitoid plutons (1846+/-8 Ma) and volcanics of North-Baikal volcano-plutonic belt (1869+/-6 Ma 1856+/-3 Ma), Baikal folded area, support this tendency. Emplacement of the Primorsky complex postcollisional rapakivi-type granitoids (southern Baikal lake) occurred at 1859+/-16 Ma (Donskaya et al., 2002). New results of U-Pb single zircon and baddeleyite dating demonstrate that formation of late-synkinematic syenite, charnockite and pegmatitic veins (1856±12 Ma, 1853±20 Ma) and calciphyre (1868±2 Ma) within the eastern part of the Sharyzhalgay block (southern Baikal lake) occurred virtually within the same episode. Postcollisional intrusive charnockite of the Shumikha complex from the western Sharyzhalgay block dated at 1861±1 Ma (Donskaya et al., 2001) and 1871±17 Ma (Levitsky et al., 2002). Subalcaline

  12. Metasomatic control of water contents in the Kaapvaal cratonic mantle

    NASA Astrophysics Data System (ADS)

    Peslier, A. H.; Woodland, A. B.; Bell, D. R.; Lazarov, M.; Lapen, T. J.

    2012-11-01

    Water and trace element contents were measured by FTIR and laser ablation-ICPMS on minerals from peridotite xenoliths in kimberlites of the Kaapvaal craton from Finsch, Kimberley, Jagersfontein (South Africa), Letseng-La-Terae, and Liqhobong (Lesotho) mines. The peridotites record a wide range of pressure, temperature, oxygen fugacity, and metasomatic events. Correlations between water content or OH vibration bands with major, minor and trace elements in pyroxene and garnet precludes disturbance during xenolith entrainment by the host kimberlite magma and indicate preservation of mantle water contents. Clinopyroxene water contents (150-400 ppm H2O, by weight) correlate with those of orthopyroxene (40-250 ppm). Olivines (Peslier et al., 2008, 2010) and garnets have 0-86 and 0-20 ppm H2O, respectively. Relations in individual xenolith suites between the amount of water and that of incompatible elements Ti, Na, Fe3+ and rare earths in minerals suggests that metasomatism by oxidizing melts controls the water content of olivine, pyroxene and garnet. At pressures ⩽5.5 GPa, hydrous, alkaline, siliceous fluids or melts metasomatized Liqhobong and Kimberley peridotites, producing high water contents in their olivine, pyroxenes and garnet. At higher pressures, the percolation of ultramafic melts reacting with peridotite resulted in co-variation of Ca, Ti and water at the edge of garnets at Jagersfontein, and the overall crystallization of garnet with lower water contents than those in the original peridotites. The upward migration of these ultramafic melts through the lithospheric mantle also increased the water content of olivines with decreasing pressure at Finsch Mine. H2O/Ce ratios of melts in equilibrium with Kaapvaal peridotites range from 100 to 20,000 and the larger values may indicate metasomatism in subduction zone settings. Metasomatic events in Kaapvaal peridotites are thought to have occurred from the Archean to the Mesozoic. However, circumstantial evidence

  13. Heterogeneously hydrated mantle beneath the late Archean Yilgarn Craton

    NASA Astrophysics Data System (ADS)

    Ivanic, T. J.; Nebel, O.; Jourdan, F.; Faure, K.; Kirkland, C. L.; Belousova, E. A.

    2015-12-01

    Archean mafic-ultramafic melts, crystallized as layered intrusions in the upper crust and extruded as komatiitic flows, are primary probes of upper mantle chemistry. However, the message from their primary chemical composition can be compromised by different modes of contamination. Contaminants are typically cryptic in terms of their geochemical and isotopic signals but may be related to metasomatised mantle sources, ambient crustal assimilation or subduction-related inputs. In this work we present critical evidence for both dry and wet Archean mantle sources for two juxtaposed layered intrusions in the Australian Yilgarn Craton. The ca. 2813 Ma Windimurra and ca. 2800 Ma Narndee Igneous Complexes in Western Australia are two adjacent layered intrusions and would be expected to derive via similar mantle sections. A key difference in their chemistry is the presence of crystal-bound water in the Narndee Igneous Complex, represented primarily by abundant hornblende. Such a primary hydrous phase is notably absent in the Windimurra Igneous Complex. New 40Ar/39Ar plateau ages for fresh Narndee hornblende (weighted mean: 2805 ± 14 Ma, MSWD = 1.8, probability = 0.18) agrees with the published U-Pb age of 2800 ± 6 Ma for the complex and is consistent with a magmatic origin for this phase. Zircon Hf and whole-rock Hf and Nd isotopes for the Narndee Igneous Complex indicate only minor crustal contamination, in agreement with H and O isotope values in amphibole and O isotope values in rare zircon crystals, plagioclase and pyroxene within both complexes. These findings illustrate a fast temporal transition, in proximal bodies, from anhydrous to hydrous mantle sources with very minor crustal contamination. These large layered mafic-ultramafic intrusions are igneous bodies with a primitive chemical bulk composition that requires large degrees of mantle melting. This has been attributed by many workers to mantle plume activity, yet not without dispute, as subduction-related flux

  14. Closed-loop control of SaO2 in the neonate.

    PubMed

    Morozoff, P E; Evans, R W

    1992-01-01

    A microprocessor-based device has been designed to control oxygen saturation (SaO2) in neonates by adjusting the inspired air-oxygen mixture (FiO2) delivered by a mechanical blender. The user sets a target SaO2, which the controller attempts to maintain. Alarms are actuated if the neonate's SaO2 is outside predefined limits. SaO2 levels are extracted from a commercial pulse oximeter and analyzed by an eight-bit microprocessing unit (MPU). Delivered percentages of FiO2 are adjusted by a motorized air-oxygen blender. The controller has a menu-driven user interface and can graphically present four-hour trends of the SaO2, FiO2, or blender setting. Sixteen hours of collected data can be stored and later downloaded to a personal computer. A real-time multitasking operating system forms the nucleus of the controller's software. Major tasks that share MPU time are control, filtering, user display, data collection, data archiving, alarm monitoring, and user input. Analog SaO2 levels are read and converted to digital values, which are then filtered to extract noise. A differential control algorithm is used to determine the required FiO2 blender setting. The blender is then adjusted to the new setting, after which the controller waits to repeat the process of sampling SaO2 and adjusting FiO2. System response time and blender increments are adjustable to allow a user to tune the controller to the patient's needs. Alarm conditions of concern within the device are SaO2 and FiO2 sensor disconnection, blender disconnection, and SaO2 limiting errors. In preliminary trials, for a target of 92.0% SaO2, a prototype controller maintained an average of 91.6% with a standard deviation of 5.0% over a one-hour period.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1562825

  15. Lithospheric Structure of the North American Craton Imaged Using Waveform Inversion of Global and Usarray Data

    NASA Astrophysics Data System (ADS)

    Schaeffer, A. J.; Lebedev, S.

    2014-12-01

    The North American Craton, now forming the stable core of North America, has a long, eventful tectonic history. The assembly of the craton, collisions and accretion at its current boundaries, major rifting episodes within it, and the loss of ancient lithosphere beneath parts of it are type examples of these key components of cratonic dynamics and evolution. Seismic tomography offers rich evidence on the structure and evolution of the cratonic lithosphere. With the deployment of the USArray during the last decade, much of the North American continent has been densely sampled with broadband seismic data. The resolution of regional-scale imaging, however, remains uneven, with important questions regarding deep structure, lateral extent and evolution difficult to answer. Here we present a new high-resolution model of the upper mantle beneath North America constrained by waveform fits of over 700,000 vertical-component broadband seismograms. Automated multimode waveform inversion was used to extract structural information from surface and S waveforms, yielding resolving power from the crust down to the transition zone, and improved resolution for a variety of features in North America. The internal structure of the Craton is resolved in detail. The lithosphere surrounding the 1 Ga failed Mid-Continental Rift shows reduced wavespeeds compared to the surrounding craton, likely indicating thermo-chemical alteration of the sub-continental lithospheric mantle. The sharp northern boundaries of the cratonic lithosphere closely follow the coastlines, with North America's and Greenland's lithospheric roots clearly separated. Strong lateral velocity gradients at depth observed in western Canada indicate the transition from cratonic lithosphere to Cordillera closely follows the surface trace of the Deformation Front. On the eastern margin of the continent, where multiple episodes of continental rifting are superimposed, the craton boundary coincides with the western extent of the

  16. Mantle Discontinuities and the Origins of the U.S. Cratonic Lithosphere

    NASA Astrophysics Data System (ADS)

    Fischer, K. M.; Hopper, E.

    2014-12-01

    The goals of this work are to probe how mantle lithosphere discontinuity structure varies beneath the cratonic terranes of the northern U.S. and to relate this structure to the processes that created and modified the cratonic mantle. Our region samples the Archean Wyoming, Medicine Hat and Superior cratons, and the Proterozoic terranes that lie between them. We imaged the mantle using Sp phases recorded by permanent and temporary seismic networks, including EarthScope's Transportable Array. Sp receiver functions for individual waveforms were obtained by extended time multi-taper deconvolution, and migrated into a 3D volume using common conversion point stacking, a spline representation of phase Fresnel zones, and 3D models for crust and mantle structure. The stack was bootstrapped. In the cratonic mantle, we observe multiple mid-lithospheric discontinuities (MLDs) that are characterized by three types of structures: a relatively continuous negative discontinuity (velocity decrease with depth) that lies in the 65-100 km depth range; deeper negative MLDs (80-145 km) that are more discontinuous and intermittent; and occasional positive MLDs at the greatest depths (>125 km). In contrast to the tectonically active western U.S., beneath cratonic regions we typically do not observe a strong negative discontinuty at the base of the tomographically-defined lithosphere, indicating that the transition to asthenospheric properties is gradual. The MLDs indicate strong layering in the cratonic mantle lithosphere. In multiple cases, one negative discontinuity dips below another, consistent with a slab of lithosphere imbricated beneath pre-existing cratonic mantle. One of the clearest examples is a north-dipping phase at depths of 80-130 km beneath the Cheyenne Belt, the suture between the Wyoming Craton and the accreted Proterozoic terranes to its south. In Sept. 2013, an unusual earthquake occurred within the high velocity mantle of the Wyoming craton at ~76 km, a depth that

  17. Activism in Concrete: Student Union, San Francisco State University

    ERIC Educational Resources Information Center

    Progressive Architecture, 1978

    1978-01-01

    The San Francisco State University Student Union is a futurist design of two steel space-frame pyramids. Each contains a stairway leading to four partial floors that diminish in size as the pyramid tapers. (Author/MLF)

  18. 2. Historic American Buildings Survey, National Park Service, San Francisco ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Historic American Buildings Survey, National Park Service, San Francisco Re-photo: May 1940 - Miners' Union Hall, West side B Street, between Union & Sutton Streets, Virginia City, Storey County, NV

  19. 27 CFR 9.157 - San Francisco Bay.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Mountain, California, scale 1:24,000, dated 1956, Photorevised 1980; (25) Half Moon Bay, California, scale... Francisco South, Montara Mountain, Half Moon Bay, San Gregorio, Pigeon Point, Franklin Point, Año Nuevo...

  20. 27 CFR 9.157 - San Francisco Bay.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Mountain, California, scale 1:24,000, dated 1956, Photorevised 1980; (25) Half Moon Bay, California, scale... Francisco South, Montara Mountain, Half Moon Bay, San Gregorio, Pigeon Point, Franklin Point, Año Nuevo...

  1. 27 CFR 9.157 - San Francisco Bay.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Mountain, California, scale 1:24,000, dated 1956, Photorevised 1980; (25) Half Moon Bay, California, scale... Francisco South, Montara Mountain, Half Moon Bay, San Gregorio, Pigeon Point, Franklin Point, Año Nuevo...

  2. 27 CFR 9.157 - San Francisco Bay.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Mountain, California, scale 1:24,000, dated 1956, Photorevised 1980; (25) Half Moon Bay, California, scale... Francisco South, Montara Mountain, Half Moon Bay, San Gregorio, Pigeon Point, Franklin Point, Año Nuevo...

  3. 2. Historic American Buildings Survey National Park Service San Francisco, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Historic American Buildings Survey National Park Service San Francisco, California Year Built: 1835 Photo Taken: 1939 GENERAL VIEW - Pacific House, 200-222 Calle Principal, Monterey, Monterey County, CA

  4. Paleozoic cratonal/miogeoclinal stratigraphy in the western Mojave Desert

    SciTech Connect

    Martin, M.W.; Walker, J.D. )

    1991-02-01

    Detailed mapping of metasedimentary rocks by many workers in the western Mojave Desert, California, has revealed Paleozoic lithologies of cratonal/miogeoclinal affinity. These exposures are metamorphosed, highly strained, and dismembered, and sit as roof pendants to Mesozoic and Tertiary intrusive rocks. In most outcrops no diagnosis fossils are preserved. Age correlation of these units is based, therefore, solely on similarities to lithologic packages outside the region. Despite the complex tectonic history this area has suffered since the late Paleozoic paleogeographic elements trend southwest into the region from where they are last clearly defined near the California-Nevada border. Dolomitic and calcitic marbles, quartzites, and biotite schists make up a major part of the stratigraphy in many areas. The stratigraphy and lithology of these units strongly suggest that they are correlative with late Precambrian-Cambrian units in the Death Valley region. Possible Ordovician and Devonian marbles also are present within some sections; at least one locality contains stromatoporoids of probable Devonian age. Calcite marbles tentatively correlated with lithologically similar Permian units in the Death Valley area are also represented and appear to be depositionally overlain by Mesozoic( ) shallow-marine and are-derived clastic rocks. Although the western Mojave Desert region has experienced compressional, transcurrent, and extensional deformation since late Paleozoic, our current understanding and restoration of this deformation history does not significantly alter the general southwest Paleozoic paleogeographic trends known to exist farther east.

  5. Spatial distribution of eclogite in the Slave cratonic mantle: The role of subduction

    NASA Astrophysics Data System (ADS)

    Kopylova, Maya G.; Beausoleil, Yvette; Goncharov, Alexey; Burgess, Jennifer; Strand, Pamela

    2016-03-01

    We reconstructed the spatial distribution of eclogites in the cratonic mantle based on thermobarometry for ~ 240 xenoliths in 4 kimberlite pipes from different parts of the Slave craton (Canada). The accuracy of depth estimates is ensured by the use of a recently calibrated thermometer, projection of temperatures onto well-constrained local peridotitic geotherms, petrological screening for unrealistic temperature estimates, and internal consistency of all data. The depth estimates are based on new data on mineral chemistry and petrography of 148 eclogite xenoliths from the Jericho and Muskox kimberlites of the northern Slave craton and previously reported analyses of 95 eclogites from Diavik and Ekati kimberlites (Central Slave). The majority of Northern Slave eclogites of the crustal, subduction origin occurs at 110-170 km, shallower than in the majority of the Central Slave crustal eclogites (120-210 km). The identical geochronological history of these eclogite populations and the absence of steep suture boundaries between the central and northern Slave craton suggest the lateral continuity of the mantle layer relatively rich in eclogites. We explain the distribution of eclogites by partial preservation of an imbricated and plastically dispersed oceanic slab formed by easterly dipping Proterozoic subduction. The depths of eclogite localization do not correlate with geophysically mapped discontinuities. The base of the depleted lithosphere of the Slave craton constrained by thermobarometry of peridotite xenoliths coincides with the base of the thickened lithospheric slab, which supports contribution of the recycled oceanic lithosphere to formation of the cratonic root. Its architecture may have been protected by circum-cratonic subduction and shielding of the shallow Archean lithosphere from the destructive asthenospheric metasomatism.

  6. 76 FR 19519 - Intent To Prepare an Environmental Impact Statement for the Downtown San Francisco Ferry Terminal...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-07

    ... Francisco Ferry Terminal Expansion Project in the City and County of San Francisco, CA AGENCY: Federal... Downtown San Francisco Ferry Terminal at the Port of San Francisco Ferry Building. The proposed project... document. Purpose and Need for the Project The purpose of the Downtown San Francisco Ferry...

  7. Benthic fluxes in San Francisco Bay

    USGS Publications Warehouse

    Hammond, Douglas E.; Fuller, C.; Harmon, D.; Hartman, Blayne; Korosec, M.; Miller, L.G.; Rea, R.; Warren, S.; Berelson, W.; Hager, S.W.

    1985-01-01

    Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (??1??) of 30% or more over distances of a few meters to tens of meters, presumably due to spatial heterogeneity in the benthic community. Fluxes of radon were greater at the shoal station than at the channel station because of greater macrofaunal irrigation at the former, but showed little seasonal variability at either station. At both stations fluxes of oxygen, carbon dioxide, ammonia, and silica were largest following the spring bloom. Fluxes measured during different seasons ranged over factors of 2-3, 3, 4-5, and 3-10 (respectively), due to variations in phytoplankton productivity and temperature. Fluxes of oxygen and carbon dioxide were greater at the shoal station than at the channel station because the net phytoplankton productivity is greater there and the organic matter produced must be rapidly incorporated in the sediment column. Fluxes of silica were greater at the shoal station, probably because of the greater irrigation rates there. N + N (nitrate + nitrite) fluxes were variable in magnitude and in sign. Phosphate fluxes were too small to measure accurately. Alkalinity fluxes were similar at the two stations and are attributed primarily to carbonate dissolution at the shoal station and to sulfate reduction at the channel station. The estimated average fluxes into South Bay, based on results from these two stations over the course of a year, are (in mmol m-2 d-1): O2 = -27 ?? 6; TCO2 = 23 ?? 6; Alkalinity = 9 ?? 2; N + N = -0.3 ?? 0.5; NH3 = 1.4 ?? 0.2; PO4 = 0.1 ?? 0.4; Si = 5.6 ?? 1.1. These fluxes are comparable in magnitude to those in other temperate estuaries with similar productivity, although the seasonal

  8. High Water Contents in the Siberian Cratonic Mantle: An FTIR Study of Udachnaya Peridotite Xenoliths

    NASA Technical Reports Server (NTRS)

    Doucet, Luc S.; Peslier, Anne H.; Ionov, Dimitri A.; Brandon, Alan D.; Golovin, Alexander V.; Ashchepkov, Igor V.

    2013-01-01

    Water is believed to be a key factor controlling the long-term stability of cratonic lithosphere, but mechanisms responsible for the water content distribution in the mantle remain poorly constrained. Water contents were obtained by FTIR in olivine, pyroxene and garnet for 20 well-characterized peridotite xenoliths from the Udachnaya kimberlite (central Siberian craton) and equilibrated at 2-7 GPa. Water contents in minerals do not appear to be related to interaction with the host kimberlite. Diffusion modeling indicates that the core of olivines preserved their original water contents. The Udachnaya peridotites show a broad range of water contents in olivine (6.5 +/- 1.1 to 323 +- 65 ppm H2O (2 sigma)), and garnet (0 - 23 +/- 6 ppm H2O). The water contents of olivine and garnet are positively correlated with modal clinopyroxene, garnet and FeO in olivine. Water-rich garnets are also rich in middle rare earth elements. This is interpreted as the result of interaction between residual peridotites and water rich-melts, consistent with modal and cryptic metasomatism evidenced in the Siberian cratonic mantle. The most water-rich Udachnaya minerals contain 2 to 3 times more water than those from the Kaapvaal craton, the only craton with an intact mantle root for which water data is available. The highest water contents in olivine and orthopyroxene in this study (>= 300 ppm) are found at the bottom of the lithosphere (> 6.5 GPa). This is in contrast with the Kaapvaal craton where the olivines of peridotites equilibrated at > 6.4 GPa have < 1 ppm H2O. The latter "dry" olivine may make the base of the Kaapvaal cratonic root strong and thus protects it from erosion by the convective mantle The calculated viscosity for water-rich Udachnaya peridotites at > 6 GPa is lower or similar (8.4× 10(exp 16) to 8.0× 10(exp 18) Pa./s) to that of the asthenosphere (<= 3.7x10(exp 18) Pa./s ). Such lithologies would not be able to resist delamination by the convecting asthenosphere

  9. The Preservation of Meso- Archean Refractory Lithospheric Mantle Underneath the Eastern Margin of the Tanzania Craton

    NASA Astrophysics Data System (ADS)

    Shu, Q.; Liu, J.; Pearson, G. D.; Gibson, S. A.

    2014-12-01

    Numerous studies on the petrology and geochemistry of peridotite xenoliths from the Tanzanian Craton and its rifted margins have investigated the origin, chemical change and thermal state of the cratonic roots from its core area (Nzega and Mwadui), its Northern (Marsabit) and Eastern margin Labait and Lashaine area (e.g. Dawson, 1964; Henjes-Kunst and Altherr, 1991; Lee & Rudnick, 1999; Chesley et al., 1999; Gibson et al., 2013). These studies suggest that the Tanzanian cratonic mantle formed via high degrees of melt extraction in the Archean (oldest Re-depletion age TRD = 3.4 Ga, Burton et al., 2000) and sev­eral episodes of refertilization. In order to gain further temporal and chemical understanding on the effects of tectonic processes on cratonic roots, we carried out a Re-Os isotopic study on peridotites (n = 11) from Lashaine, which will be followed by Lu-Hf, Sm-Nd and Sr isotope investigations of the constituent minerals of the same samples. The preliminary whole-rock Os isotope data from Lashaine peridotites show a large range of 187Os/188Os (0.1061 - 0.1261), with TRD ages from Meso-Archean to very young (3.1 Ga to 0.3 Ga). There is a negative correlation between TRD and bulk alumina contents. One sample with the lowest Al2O3 yields the oldest age of 3.1 Ga. Five samples range from 2.5 to 2.8 Ga, three give ages close to 2 Ga, and one sample with a high Al2O3 has a TRD at 0.3 Ga. The positive Al2O3-187Os/188Os correlation trend passes above the PM composition may reflect ancient metasomatism by high Re/Os melts or recent metasomatism by very radiogenic Os plume-derived melts. These processes could be related to the evolution of the peripheral Proterozoic mobile belts, or Cenozoic rifting on the Eastern margin. Collectively, our new Os isotope data demonstrate that Meso-Archean (at least 3.1 Ga old) mantle portions are still retained underneath the rifted Eastern margin of the Craton. This is in line with previous results indicating that Archean cratonic

  10. Mantle insulation beneath the West African craton during the Precambrian-Cambrian transition

    NASA Astrophysics Data System (ADS)

    Doblas, Miguel; López-Ruiz, José; Cebriá, José-María; Youbi, Nasrrddine; Degroote, Eugenio

    2002-09-01

    At the time of the Precambrian-Cambrian transition, the West African craton underwent widespread magmatism, hydrothermal activity, and thermal rejuvenation. This tectonothermal event gave rise to an anorogenic “ring of fire” along the rim of this craton, following the Pan-African Brasiliano belt that was reactivated by extension and transtension. The thermal phenomena were due to the progressive peripheral release of mantle heat that had built up beneath this craton because of strong insulating conditions. The West African craton at the Precambrian-Cambrian transition can thus be envisioned in terms of a gigantic pressure-cooker with a thick blanketing lithospheric lid. These insulation processes triggered an unusually hot mantle that was channeled by edge-driven convection toward the peri West African craton extensional corridors and released through magmatic pressure-relief valves. Massive ice melting and outgassing of volcanic CO2 gave rise to a planet-scale sea-level rise, a greenhouse effect, and the end of the icehouse snowball Earth. These processes played an important role in the Phanerozoic explosion of life on Earth.

  11. Trans Women Doing Sex in San Francisco.

    PubMed

    Williams, Colin J; Weinberg, Martin S; Rosenberger, Joshua G

    2016-10-01

    This research investigates the sexuality of trans women (individuals who were assigned male status at birth who currently identify as women), by focusing on the "bodily techniques" (Crossley, 2006) they use in "doing" sexuality. The "doing sexuality" framework not only is modeled after the "doing gender" approach of West and Zimmerman (1987), but also utilizes the idea of "sexual embodiment" to emphasize the agency of trans women as they conceptualize and organize their sexuality in a socially recognized way. This is often difficult as they confront discrimination from medical and legal professionals as well as intimate partners who may find it difficult to adapt to the trans woman's atypical body and conception of gender. However, with a study group of 25 trans women from San Francisco, we found the study participants to be adept at overcoming such hurdles and developing techniques to "do" their sexuality. At the same time, we found trans women's agency constrained by the erotic habitus (Green, 2008) of the wider society. The interplay between innovation and cultural tradition provides an opportunity to fashion a more general model of "doing" sexuality. PMID:27091188

  12. Supercontinents, True Polar Wander, and Paleogeography of the Slave Craton

    NASA Astrophysics Data System (ADS)

    Mitchell, Ross Nelson

    evidence in support of a long-lived, Ediacaran-aged hotspot. The consistency of paleocurrent directions derived from the Great Slave Supergroup argues against significant regional vertical-axis rotations and for large and rapid TPW to explain discordant paleomagnetic directions observed within section. The last frontier for paleomagnetic constraints on supercontinents, TPW, and the antiquity of plate tectonics is earliest Proterozoic time. Laurentia, one of Earth's oldest continents that formed at the core supercontinent Nuna, contains several cratons that have adequate paleomagnetic and geochronologic data with which to test for evidence of early TPW and relative plate motion, the hallmark of tectonics. Although past comparisons have been made between the Slave and Superior cratons at each "bookend" of Laurentia, new paleomagnetic data supported by baked contact tests allow for conclusive early Proterozoic reconstructions. Similar to periods following Proterozoic supercontinents Nuna and Rodinia, early Proterozoic time is characterized by large TPW oscillations and large-scale plate reorganizations prior to amalgamation, possibly indicating the presence of `Kenorland', an Archean supercontinent.

  13. Layered structure of the lithospheric mantle changes dynamics of craton extension

    NASA Astrophysics Data System (ADS)

    Liao, J.; Gerya, T.; Wang, Q.

    2013-11-01

    Although presence of weak layers due to hydration and/or metasomatism in the lithospheric mantle of cratons has been detected by both geophysical and geochemical studies, its influence on craton evolution remains elusive. Using a 2‒D thermomechanical viscoelastoplastic numerical model, we studied the craton extension of a heterogeneous lithospheric mantle with a rheologically weak layer. Our results demonstrate that the effect of the weak mantle layer is twofold: (1) enhances deformation of the overlying lithosphere and (2) inhibits deformation of the underlying lithospheric mantle. Depending on the weak‒layer depth, the Moho temperature and extension rate, three extension patterns are found (1) localized mantle necking with exposed weak layer, (2) widespread mantle necking with exposed weak layer, and (3) widespread mantle necking without exposed weak layer. The presence of the weak mantle layer reduces long‒term acting boundary forces required to sustain extensional deformation of the lithosphere.

  14. East asian gold: Deciphering the anomaly of phanerozoic gold in precambrian cratons

    USGS Publications Warehouse

    Goldfarb, R.J.; Hart, C.; Davis, G.; Groves, D.

    2007-01-01

    Early Cretaceous orogenic gold deposits in eastern Asia are globally unique in that large Phanerozoic lode gold deposits occur in Archean-Paleoproterozoic cratons. In the northern Pacific region, ca. 125 Ma orogenic gold deposits in the North China, Yangzte, and Siberian craton margins, as well as in young terranes in California, may ultimately relate to the giant Cretaceous mantle plume in the southern Pacific basin and the relatively rapid tectonic consequences along both continental margins from resulting Pacific plate reconfigurations. In eastern Asia, such consequences include reactivation of and fluid flow along major fault systems, with fluid focusing into simultaneously forming, isolated core complexes of uncertain genesis. Deposition of gold ores in previously devolatilized high-grade Precambrian metamorphic rocks requires an exotic source of ore fluid, most likely subducted Mesozoic oceanic crust and/or overlying sediment. An implication is that Phanerozoic metamorphic core complexes in other destabilized craton margins could host large gold resources. ?? 2007 by Economic Geology.

  15. African hot spot volcanism: small-scale convection in the upper mantle beneath cratons.

    PubMed

    King, S D; Ritsema, J

    2000-11-10

    Numerical models demonstrate that small-scale convection develops in the upper mantle beneath the transition of thick cratonic lithosphere and thin oceanic lithosphere. These models explain the location and geochemical characteristics of intraplate volcanos on the African and South American plates. They also explain the presence of relatively high seismic shear wave velocities (cold downwellings) in the mantle transition zone beneath the western margin of African cratons and the eastern margin of South American cratons. Small-scale, edge-driven convection is an alternative to plumes for explaining intraplate African and South American hot spot volcanism, and small-scale convection is consistent with mantle downwellings beneath the African and South American lithosphere. PMID:11073447

  16. PdS Receiver Function Evidence for Mafic Underplating in the Superior Craton: A Discussion About Cratonic Stabilization

    NASA Astrophysics Data System (ADS)

    Thurner, S.; Niu, F.; Margolis, R. E.; Levander, A.; Lee, C. T.

    2014-12-01

    The Trans-Hudson orogen (THO) in the north central United States represents a major suturing event between the Wyoming and Superior Archean provinces. It is bounded to the south by the NE-SW striking Yavapai province, which was accreted along the southeastern margin of North America between 1.71 and 1.68 Ga and was one of a series of major collisional events responsible for the assembly of Laurentia. In this study, PdS teleseismic receiver functions were used to investigate the deep crustal structure associated with these collisions. Using data from over 800 broadband seismic stations distributed throughout the Great Plains/Midcontinent region, we calculated .5 Hz receiver functions using 245 M > 6.0 teleseismic events. The receiver functions were then CCP (common conversion point) stacked to create a 3D image volume. Profiles through this image volume show evidence of crustal scale thrusting of the Wyoming province in the west over the Superior province in the east and structural underplating associated with the Yavapai-Superior boundary. We also performed a density analysis of the region using the 2p1s and 0p1s receiver function phases from 233 stations. These data indicate a relatively low Moho density contrast throughout the THO and northern Yavapai region associated with a region of thickened crust (> 50 km), which we interpret to be evidence of a dense lower crustal layer that may be the result mafic underplating. Additionally, we investigate the role that this dense layer may have on the stabilization of the Superior craton and others relative to compositionally and thermally derived density variations in the mantle lithosphere.

  17. Passive margin asymmetry and its polarity in the presence of a craton

    NASA Astrophysics Data System (ADS)

    Andres-Martinez, Miguel; Perez-Gussinye, Marta; Neto-Araujo, Mario; Morgan, Jason

    2016-04-01

    When continental lithosphere is extended to break-up it forms two conjugate passive margins. In many instances these margins are asymmetric: while one is wide and extensively faulted, the conjugate thins more abruptly and exhibits little faulting. Recent observational studies have suggested that this asymmetry results from the formation of an oceanward-younging sequential normal fault array on the future wide margin. Numerical models have shown that fault sequentiality arises as a result of asymmetric uplift of the hot mantle towards the hanging wall of the active fault, which weakens this area and promotes the formation of a new oceanward fault. In numerical models the polarity of the asymmetry is random. It results from spontaneous preferential localization of strain in a given fault, a process reinforced by strain weakening effects. Slight changes in the experiments initial grid result in an opposite polarity of the asymmetry. However, along a long stretch of the South Atlantic margins, from the Camamu-Gabon to the North Santos-South Kwanza conjugates, the polarity is not random and is very well correlated with the distance of the rift to nearby cratons. Here, we use numerical experiments to show that the presence of a thick cratonic root inhibits asthenospheric flow from underneath the craton towards the adjacent fold belt, while flow from underneath the fold belt towards the craton is favoured. This enhances and promotes sequential faulting towards the craton and results in a wide faulted margin located in the fold belt and a narrow conjugate margin in the craton side, thereby determining the polarity of the asymmetry, as observed in nature.

  18. Shear Wave Structure in the Crust and Upper Mantle Beneath the Wyoming Craton

    NASA Astrophysics Data System (ADS)

    Dave, R.; Li, A.

    2013-12-01

    The Wyoming craton was pervasively deformed during the Laramide and has been encroached by the Yellowstone hotspot. It is therefore an ideal place to study the survival and evolution of cratonic lithosphere. We have analyzed Rayleigh wave data recorded by the USArray and applied the two-plane-wave tomography method to determine average and 2-D phase velocities in the Wyoming craton area. These phase velocities were inverted to construct 3-D shear wave structure of the crust and upper mantle. Vertical component seismograms from 82 events at 103 stations were filtered at 18 center frequencies with a narrow bandwidth of 10 mHz. The average phase velocity varies from 3.48 km/s at 20 s to 4.36 km/s at 166 s. Compared to the average global phase velocities, these values are lower at longer periods, indicating a generally slower upper mantle. 2-D variation of phase velocity shows significantly low velocities at the hotspot and relatively high velocities in the north of the stable craton. The same pattern of velocity variation is also imaged in the 3-D shear wave model. The lowest velocity tilted to north and east to the current hotspot location with depth, reflecting shearing of the hotspot material due to the relative motion of the North American plate. In addition, a low velocity anomaly is imaged at central-eastern portion of the craton at depths greater than 150 km, correlated with a thin crust. Relative high velocity anomaly is found in between this slow anomaly and the hotspot. This slow-fast-slow velocity variation in the upper mantle could be associated with small-scale mantle convection of upwelling-downwelling-upwelling trigged by the hotspot, which could thermally erode the cratonic lithosphere.

  19. The driving of the SAO by gravity waves derived from satellite data

    NASA Astrophysics Data System (ADS)

    Ern, Manfred; Preusse, Peter; Riese, Martin

    2014-05-01

    The dynamics in the tropical stratosphere and lower mesosphere is strongly influenced by an interplay of the quasi-biennial oscillation (QBO) and the semiannual oscillation (SAO) of the zonal wind. The tropical dynamics has significant influence on atmospheric dynamics over a large range of altitudes and latitudes. For example, QBO and SAO effects are seen in the MLT region, and there is a significant influence of the QBO on the surface weather and climate in the Northern Hemisphere during winter. Still, global models have large difficulties in reproducing a realistic QBO and SAO. One of the main reasons are uncertainties in the wave driving of these oscillations, in particular the driving by gravity waves (GWs) that are too small-scale to be resolved by the global models. Direct estimates of the GW driving of the QBO and SAO from global observations are still missing. We derive GW temperature variances, GW momentum fluxes and GW drag from over three years of High Resolution Dynamics Limb Sounder (HIRDLS) satellite data. These observations are compared with the zonal wind tendencies and the drag that is still missing in the tropical momentum budget of the ECMWF ERA Interim (ERAI) reanalysis after considering zonal wind tendency, Coriolis force, advection terms and drag of resolved global-scale waves. In the stratopause region ERAI is no longer well-constrained by data assimilation. Nevertheless, the missing drag and its relative variations can be used as a proxy for GW drag. Qualitatively, we find good agreement between satellite observations and ERAI, however the missing drag in ERAI is likely too high by about a factor of two. Both HIRDLS satellite observations and ERAI support the general assumption that, due to the pre-filtering of the GW spectrum by the QBO in the stratosphere, GWs mainly contribute to the SAO momentum budget during SAO eastward wind shear. During SAO westward wind shear the GW contribution is usually smaller, and the wave driving is dominated

  20. African, southern Indian and South American cratons were not part of the Rodinia supercontinent: evidence from field relationships and geochronology

    NASA Astrophysics Data System (ADS)

    Kröner, Alfred; Cordani, Umberto

    2003-11-01

    constitute marginal parts of cratonic domains or represent crustal blocks (terranes or microcontinents?) of unknown derivation. This is also the case for most terranes included in the Borborema/Trans-Saharan belt of northeastern Brazil and west-central Africa, as well as those of the Central Goı´ás Massif in central Brazil and the Mantiqueira province of eastern and southeastern Brazil. Furthermore, there is evidence for extensive granitoid magmatism in the period ~840 to <600 Ma whose predominant calc-alkaline chemistry suggests subduction-related active margin processes during the assembly of the supercontinent Gondwana. The location of the main Neoproterozoic magmatic arcs suggests that a large oceanic domain separated the core of Rodinia, namely Laurentia plus Amazonia, Baltica and West Africa, from several continental masses and fragments now in the southern hemisphere, such as the São Francisco/Congo, Kalahari and Rio de La Plata cratons, as well as the Borborema/Trans-Saharan, Central Goiás Massif and Paraná blocks. Moreover, many extensional tectonic events detected in the southern hemisphere continental masses, but also many radiometric ages of granitois that are already associated with the process of amalgamation of Gondwana, are comprised within the 800-1000 age interval. This seems incompatible with current views on the time of disintegration of Rodinia, assumed to have occurred at around 750 Ma.

  1. ASTER Images San Francisco Bay Area

    NASA Technical Reports Server (NTRS)

    2000-01-01

    These images of the San Francisco Bay region were acquired on March 3, 2000 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. Each covers an area 60 kilometers (37 miles) wide and 75 kilometers (47 miles) long. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image the Earth for the next 6 years to map and monitor the changing surface of our planet.

    Upper Left: The color infrared composite uses bands in the visible and reflected infrared. Vegetation is red, urban areas are gray; sediment in the bays shows up as lighter shades of blue. Thanks to the 15 meter (50-foot) spatial resolution, shadows of the towers along the Bay Bridge can be seen.

    Upper right: A composite of bands in the short wave infrared displays differences in soils and rocks in the mountainous areas. Even though these regions appear entirely vegetated in the visible, enough surface shows through openings in the vegetation to allow the ground to be imaged.

    Lower left: This composite of multispectral thermal bands shows differences in urban materials in varying colors. Separation of materials is due to differences in thermal emission properties, analogous to colors in the visible.

    Lower right: This is a color coded temperature image of water temperature, derived from the thermal bands. Warm waters are in white and yellow, colder waters are blue. Suisun Bay in the upper right is fed directly from the cold Sacramento River. As the water flows through San Pablo and San Francisco Bays on the way to the Pacific, the waters warm up.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is

  2. Community Heavy Metal Exposure, San Francisco, California

    NASA Astrophysics Data System (ADS)

    Chavez, A.; Devine, M.; Ho, T.; Zapata, I.; Bissell, M.; Neiss, J.

    2008-12-01

    Heavy metals are natural elements that generally occur in minute concentrations in the earth's crust. While some of these elements, in small quantities, are vital to life, most are harmful in larger doses. Various industrial and agricultural processes can result in dangerously high concentrations of heavy metals in our environment. Consequently, humans can be exposed to unsafe levels of these elements via the air we breathe, the water and food we consume, and the many products we use. During a two week study we collected numerous samples of sediments, water, food, and household items from around the San Francisco Bay Area that represent industrial, agricultural, and urban/residential settings. We analyzed these samples for Mercury (Hg), Lead (Pb), and Arsenic (As). Our goal was to examine the extent of our exposure to heavy metals in our daily lives. We discovered that many of the common foods and materials in our lives have become contaminated with unhealthy concentrations of these metals. Of our food samples, many exceeded the EPA's Maximum Contaminant Levels (MCL) set for each metal. Meats (fish, chicken, and beef) had higher amounts of each metal than did non-meat items. Heavy metals were also prevalent in varying concentrations in the environment. While many of our samples exceeded the EPA's Sediment Screening Level (SSL) for As, only two other samples surpassed the SSL set for Pb, and zero of our samples exceeded the SSL for Hg. Because of the serious health effects that can result from over-exposure to heavy metals, the information obtained in this study should be used to influence our future dietary and recreational habits.

  3. Sex worker health: San Francisco style

    PubMed Central

    Cohan, D; Lutnick, A; Davidson, P; Cloniger, C; Herlyn, A; Breyer, J; Cobaugh, C; Wilson, D; Klausner, J

    2006-01-01

    Objectives To describe the characteristics of sex workers accessing care at a peer based clinic in San Francisco and to evaluate predictors of sexually transmitted infections (STI). Methods We conducted an observational study of sex workers at St James Infirmary. Individuals underwent an initial questionnaire, and we offered screening for STI at each clinic visit. We performed univariate, bivariate, and multivariable analyses to assess for predictors of STI in this population. Results We saw 783 sex workers identifying as female (53.6%), male (23.9%), male to female transgender (16.1%), and other (6.5%). 70% had never disclosed their sex work to a medical provider. Participants represented a wide range of ethnicities, educational backgrounds, and types of sex work. The most common substance used was tobacco (45.8%). Nearly 40% reported current illicit drug use. Over half reported domestic violence, and 36.0% reported sex work related violence. Those screened had gonorrhoea (12.4%), chlamydia (6.8%), syphilis (1.8%), or herpes simplex virus 2 (34.3%). Predictors of STI included African‐American race (odds ratio (OR) 3.3), male gender (OR 1.9), and sex work related violence (OR 1.9). In contrast, participants who had only ever engaged in collective sex work were less likely to have an STI (OR 0.4). Conclusions The majority of sex workers have never discussed their work with a medical provider. Domestic violence is extremely prevalent as is work related violence. Working with other sex workers appears to be protective of STIs. STI prevention interventions should target African‐American and male sex workers. Addressing violence in the workplace and encouraging sex workers to work collectively may be effective prevention strategies. PMID:16854996

  4. Seismic evidence for stratification in composition and anisotropic fabric within the thick lithosphere of Kalahari Craton

    NASA Astrophysics Data System (ADS)

    Sodoudi, F.; Yuan, X.; Kind, R.; Lebedev, S.; Tilmann, F. J.

    2013-12-01

    S receiver functions obtained from the data of 97 seismic stations present evidence for the existence of a layered and thick lithosphere beneath the Kalahari Craton. We identified three negative discontinuities within the lithosphere of the Archean cratons and Proterozoic mobile belts of southern Africa. We also employed a novel combination of SRFs and surface-wave analysis to constrain the anisotropic properties of the lithosphere and its internal layering. Our results show that frozen-in anisotropy and compositional changes can generate sharp Mid-Lithospheric Discontinuities (MLD) at depths of 85 and 150-200 km, respectively. We found that a 50 km thick anisotropic layer containing 3% S wave anisotropy and with a fast-velocity axis different from that in the layer beneath can account for the first MLD at about 85 km depth. This depth is largely consistent with that of 8° discontinuity suggested as a global characteristic of cratonic lithosphere. Significant correlation between the depths of an apparent boundary separating the depleted and metasomatic refertilized lithosphere, as inferred from chemical tomography, and those of our second MLD (at 150-200 km depth) led us to characterize this negative discontinuity as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. We detected this MLD at a depth of about 150 km beneath the Zimbabwe Craton and Limpopo belt with a steep deepening to about 200 km underneath the Kaapvaal Craton and its passive margin. The deepening of this boundary is spatially correlated with the surficial expression of the ancient Thabazimbi-Murchison Lineament (TML). This may imply that the translithospheric TML isolates the lithospheric block of the relatively younger Limpopo terrane from that of the ancient Kaapvaal terrane. Finally, the largest velocity contrast (3.6-4.7%) is observed at a boundary located at depths of 260-280 km beneath the Archean domains and the older

  5. Dynamic study of the upper Sao Francisco river and Tres Marias reservoir using MSS/LANDSAT images. M.S. Thesis; [BRazil

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Sausen, T. M.

    1981-01-01

    The relationship between the dispersion and concentration of sediment in the superficial layers of the Tres Marias reservoir and the dynamics of the drainage basins of its tributaries was verified using LANDSAT MSS imagery. The drainage network, dissection patterns, and land use of each watershed were considered in an analysis of multispectral images, corresponding to bands 4,5, and 7, of dry and rainy seasons in 1973, 1975, 1977, and 1978. The superficial layer water layers of the reservoir were also divided according to the grey level pattern of each image. Two field trips were made to collect Secchi depths and in situ water reflectance. It is concluded that it is possible to determine the main factors that act in the dynamics of the drainage basins of a reservoir by simultaneous control of the physical variables and the antropic action of each basin.

  6. An Integrated Crustal Analysis of Craton-Terrane Transition

    NASA Astrophysics Data System (ADS)

    Contenti, S. M.; Gu, Y. J.; Shen, L.

    2012-12-01

    velocities along the Thorsby/Rimbey domains. The proximity of these two domains to the STZ may shed new light on the spatial variability of subduction during the Proterozoic era. The combination of crustal depth, velocity, Vp/Vs ratios and anisotropy enables a careful re-examination of the existing tectonic model regarding the domain formation and reworking near the western edge of the North American Craton.

  7. 41. Historic American Buildings Survey San Francisco CallBulletin Library San ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    41. Historic American Buildings Survey San Francisco Call-Bulletin Library San Francisco, California INTERIOR VIEW OF CHURCH BEFORE RESTORATION - 1934 - Mission San Carlos Borromeo, Rio Road & Lausen Drive, Carmel-by-the-Sea, Monterey County, CA

  8. 76 FR 45421 - Drawbridge Operation Regulation; China Basin, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-29

    ... necessary to allow the public to cross the bridge to participate in the scheduled San Francisco Marathon, a..., 2011, to allow participants in the San Francisco Marathon to cross the bridge during the event....

  9. San Francisco Bay, California as seen from STS-59

    NASA Technical Reports Server (NTRS)

    1994-01-01

    San Francisco Bay as seen from STS-59. View is oriented with the sea up. The delta of the combined Sacramento and San Joaquin Rivers occupies the foreground with San Francisco Bay in the middle distance, then the Pacific Ocean. Variations in water color caused both by sediment load and by wind streaking strike the eye. Man-made features dominate this scene. The Lafayette/Concord complex is left of the bay head, Vallejo is to the right, the Berkeley/Oakland complex rims the shoreline of the main bay, and San Francisco fills the peninsula beyond. Salt-evaporation ponds contain differently-colored algae depending on salinity. The low altitude (less than 120 nautical miles) and unusually-clear air combine to provide unusually-strong green colors in this Spring scene.

  10. What is causing the phytoplankton increase in San Francisco Bay?

    USGS Publications Warehouse

    Cloern, J.E.; Jassby, A.D.; Schraga, T.S.; Dallas, K.L.

    2006-01-01

    The largest living component of San Francisco Bay is the phytoplankton, a suspension of microscopic cells that convert sunlight energy into new living biomass through the same process of photosynthesis used by land plants. This primary production is the ultimate source of food for clams, zooplankton, crabs, sardines, halibut, sturgeon, diving ducks, pelicans, and harbor seals. From measurements made in 1980, we estimated that phytoplankton primary production in San Francisco Bay was about 200,000 tons of organic carbon per year (Jassby et al. 1993). This is equivalent to producing the biomass of 5500 adult humpback whales, or the calories to feed 1.8 million people. These numbers may seem large, but primary production in San Francisco Bay is low compared to many other nutrient-enriched estuaries.

  11. H2O in olivine and garnet inclusions still trapped in diamonds from the Siberian craton: Implications for the water content of cratonic lithosphere peridotites

    NASA Astrophysics Data System (ADS)

    Novella, Davide; Bolfan-Casanova, Nathalie; Nestola, Fabrizio; Harris, Jeffrey W.

    2015-08-01

    We investigated the H2O content of olivine and garnet inclusions still trapped in seven uncut and unpolished kimberlitic diamonds from Udachnaya (Siberain craton). Fourier Transform Infrared (FTIR) spectroscopy analyses of the inclusions show spectra similar to those observed for the same minerals in mantle xenoliths. The olivine inclusions are found to contain 0.5 to 5 ppm wt. H2O while the garnets do not show any clear absorption bands and therefore are considered to be dry. These data contrast with H2O contents reported for olivines and garnets in xenoliths, 300 and 20 ppm wt. H2O respectively, as well as olivine xenocrysts (up to ~ 400 ppm wt. H2O), from the same kimberlite. We interpret the high H2O concentrations in xenolithic minerals or xenocrysts to be the result of interactions with either the kimberlitic magmas or metasomatic fluids/melts, and believe that the inclusions in diamonds investigated here preserve their mantle signature which is not altered during ascent to the surface. Based on the data collected in this study we conclude that the deep roots of the Siberian craton were essentially dry when the diamond formed and that this was possibly the reason for making this portion of the lithosphere stable with respect to the convective mantle. Finally, using H2O partition coefficient data, we estimate that the diamond-forming melts in this cratonic lithosphere contain below 0.1 wt.% H2O.

  12. Developing Alternative Placement Criteria for English Courses at City College of San Francisco. Issue Brief

    ERIC Educational Resources Information Center

    Castrechini, Sebastian

    2013-01-01

    Recognizing the need to improve postsecondary access and success for underrepresented populations, the San Francisco Unified School District (SFUSD), City College of San Francisco (CCSF), the City and County of San Francisco, and key community organizations formed the Bridge to Success initiative in 2009. The John W. Gardner Center for Youth and…

  13. 75 FR 65985 - Safety Zone: Epic Roasthouse Private Party Firework Display, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-27

    ... Guard is establishing a temporary safety zone in the navigable waters of San Francisco Bay 1,000 yards... place on November 5, 2010, on the navigable waters of San Francisco Bay, 1,000 yards off Epic Roasthouse...) Location. This temporary safety zone is established for the waters of San Francisco Bay 1,000 yards...

  14. The Social Distribution of Reports of Health-Related Concerns among Adolescents in Sao Paulo, Brazil

    ERIC Educational Resources Information Center

    de Moura, S. L.

    2004-01-01

    This study investigated the health-related concerns of adolescents living on streets as compared to poor and privileged adolescents living with their families in Sao Paulo, Brazil. The different groups of respondents were similar in terms of individuals' fear of disease and lack of concern about health in old age. AIDS and cancer were feared by…

  15. Unravelling the Drivers of the Recent Drought over Sao Paulo (Brazil) using HadCM3

    NASA Astrophysics Data System (ADS)

    Pattnayak, K. C.; Tindall, J. C.; Brienen, R.; Baker, J.; Spracklen, D. V.; Gloor, E. U.

    2015-12-01

    Since ca. 2010, Sao Paulo has struggled with a multi-year drought. Reservoir levels of Sao Paulo, south-America's largest city, are at a record low level, and as a result the city has implemented water-controlling measures. Usually, the rainy season runs from October through March, bringing important rain for this city. However, over the last 5 years, Sao Paulo has experienced multiple years of below average rainfall. In this study, we try to explain the climatic drivers and mechanisms behind the observed drought over Sao Paulo using a combination of observations and model simulations. We analyse observed precipitation, air temperature and sea surface temperature (SST) datasets over the recent past to characterise the climate anomalies and visualize the extent of the drought. We then use the Hadley Centre Climate model (HadCM3) with prescribed observed SST anomalies to probe the possible causes behind the drought. This analysis will show us possible climatic drivers behind the drought in the most densely populated region of South America.

  16. Landscape risk factors for attacks of vampire bats on cattle in Sao Paulo, Brazil.

    PubMed

    Gomes, Murilo Novaes; Monteiro, Antonio Miguel Vieira; Lewis, Nicola; Gonçalves, Celso Alberto; Filho, Vladimir de Souza Nogueira

    2010-02-01

    Vampire-bat (Desmodus rotundus) attacks on cattle are a major concern for cattle-raising area. Blood loss and paralytic rabies due to bat bites can impose severe losses on the livestock. We took four municipalities inside the Sao Joao da Boa Vista veterinary district (Sao Paulo, Brazil) as a study area and tested a set of landscape features for spatial correlation with distance to areas in which vampire-bat attacks on cattle were documented. Bat- and cattle-related data from the Sao Paulo State Rabies Control Program were used. Landscape data (first-order rivers and their tributaries, main roads, railways and urban areas) were obtained from official cartographic agencies; forest, sugarcane and pasture data were acquired from remote-sensing mappings. The study area was taken as a grid split into 178 cells. Each 4kmx4km cell was filled with bat, cattle and landscape data. Our analysis detected that grid cells that were closer to areas of bat attacks on cattle had higher cattle density and a greater percentage of the land committed to sugarcane cropping, and were close to forest fragments. These results shed light on the need for rethink the Rabies Control Program strategies for defining the surveillance of vampire-bat populations and rabies control in the state of Sao Paulo, Brazil. PMID:20004487

  17. The new structure of the gas industry in the State of Sao Paulo

    SciTech Connect

    Neto, J.A.J.

    1998-07-01

    The rapidly increasing availability of natural gas is leading to a significant increase in the importance of the gas industry in Brazil. This new era is already causing major changes in the existing gas distribution companies. Gas distribution concessions are a natural monopoly and the growth in demand for this energy source will require that these growing concessions are regulated. The south/south-east of Brazil is the center of the country's industrial base and the State of Sao Paulo is where most of the manufacturing activity is located. In addition, natural gas from Bolivia is scheduled to arrive in the State of Sao Paulo at the end of 1998. These two facts combined will mean major changes in the operations of manufacturing industry and in the gas supply business. Comparing the experience faced by other countries where a competitive environment in the gas industry has been introduced with privatization programs and the dismantlement of monopolies, this paper attempts to look into the future of the natural gas industry in the State of Sao Paulo in respect to the possible regulation that might be applicable, focusing on the new regulatory framework proposed to the gas industry sector and the perspectives for the introduction of the competition in gas industry in the State of Sao Paulo.

  18. "Conscientizacao" through Graffiti Literacies in the Streets of a Sao Paulo Neighborhood: An Ecosocial Semiotic Perspective

    ERIC Educational Resources Information Center

    Iddings, Ana Christina DaSilva; McCafferty, Steven G.; da Silva, Maria Lucia Teixeira

    2011-01-01

    In this study, we applied an ecosocial semiotic theoretical framework to the analysis of graffiti literacies in the Vila Madalena neighborhood of Sao Paulo, Brazil, to inquire about the nature and processes of "conscientizacao" (critical awareness) for adult street dwellers who had no or little ability to read and write (as traditionally defined).…

  19. The diameter of 88 Thisbe from its occultation of SAO 187124

    NASA Technical Reports Server (NTRS)

    Millis, R. L.; Wasserman, L. H.; Franz, O. G.; White, N. M.; Bowell, E.; Klemola, A.; Elliott, R. C.; Smethells, W. G.; Price, P. M.; Mckay, C. P.

    1982-01-01

    The 7 October, 1981 occultation of SAO 187124 by 88 Thisbe was observed at twelve sites. The occultation observations, together with information about the asteroid's light curve, gives a mean diameter for Thisbe of 232 + or - 10 km. This value is 10 percent larger than the previously published radiometric diameter of Thisbe.

  20. FAP Group Supervision: Reporting Educational Experiences at the University of Sao Paulo, Brazil

    ERIC Educational Resources Information Center

    Wielenska, Regina Christina; Oshiro, Claudia Kami Bastos

    2012-01-01

    The present article describes and analyzes educational experiences related to the teaching of FAP for psychology graduate students and psychiatry residents at the University of Sao Paulo. The first experience involved psychology graduate students and includes an example of the shaping process occurring within the supervisor-supervisee…

  1. Spatial distribution of ~ 1950-1800 Ma metamorphic events in the North China Craton: Implications for tectonic subdivision of the craton

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Wang, Xinping; Windley, Brian F.; Guo, Jinghui; Zhai, Mingguo; Li, Yun

    2014-08-01

    Great progress has been made in the last twenty years in understanding the unification of the North China Craton. According to a prevailing model it developed by amalgamation of four sub-blocks by three spatially and temporally separate orogenic belts: the first at ~ 1950 Ma formed the Western Block, the second at ~ 1900 Ma created the Eastern Block, and the third at ~ 1850 Ma unified the Eastern and Western Blocks. However, new data show that the 1950 Ma orogen was affected by granulite facies reequilibration at 1800 Ma, and parts of the 1850 Ma orogen have evidence of metamorphism at 1950-1900 Ma. New zircon U-Pb ages enable the Paleoproterozoic metamorphic events to be statistically sub-divided into four: at ~ 1955 Ma (M1),~1920 Ma (M2), ~ 1885 Ma (M3) and ~ 1850 Ma (M4). The M1-2 events always appear together, mainly in two belt areas including the Helanshan-Qianlishan, northern Ordos, Yinshan, Liangcheng, Huai'an, Lushan, Jiaobei and Liaodong regions; whereas the M3-4 events are distributed over larger areas and were superimposed on the M1-2 activities. This age distribution is inconsistent with previous models of three separate orogens. It should also be noted that the igneous rocks contemporary with the regional (ultra-)high-temperature/high-pressure granulite facies metamorphisms (M1-2) were previously described as arc-related series, i.e., the gabbro-norites, I-/S-type granites and trimodal volcanics. Based on the spatial distribution of the Paleoproterozoic metamorphic events (M1-4), and of the coeval igneous rocks, we speculate that the assembly of the NCC was created by one orogen, which formed between the Eastern and Western Cratons in two tectonic stages: two marginal arcs, the Korean and Xuwujia, developed against both eastern sides of the two sub-cratons, and were both accreted and deformed at 1965-1900 Ma (M1-2). Subsequently the amalgamation of the two sub-cratons resulted in metamorphism on the western side of the Eastern Craton, and in

  2. Integrated Seismic Arrays for Imaging the North China Craton: the ¡°Destruction of the North China Craton¡± Project

    NASA Astrophysics Data System (ADS)

    Chen, Y. J.; Chen, L.; Zheng, T.; Zhou, S.

    2007-12-01

    It has been known, mostly according to the petrological and geochemical studies particularly the xenolith's data, that the North China craton (NCC), which is part of the Archaean Sino-Korean craton, had been reactivated since Mesozoic, and experienced widespread extension and volcanism through much of the Cenozoic. Currently the NCC is characterized by a thin lithosphere (as thin as 80 km according to published studies) and strong internal deformation, where over half of the eastern China's earthquakes occurred while the two major plate boundaries about China are thousands kilometers away. Although it is seismically quite active this region encompasses the China's capital and several mega cities which together hosts a large population and are very important to China's growing economy. Supported by the Chinese earth science community, the Chinese NSF recently started a major research program, the ¡°Destruction of the North China craton¡± (DNCC). About 150 million RMB (~ 20 million US dollars) will be allocated for this 5-year multi-disciplinary research program which is open for competition for all the earth scientists in China. Here we report one major seismic observation project of ¡°Integrated Seismic Arrays of DNCC¡± just funded during the first phase funding of DNCC. This observation-driven project integrates two groups at the Institute of Geology and Geophysics, Chinese Academy of Sciences and Peking University, and both institutions have their own broadband seismometers and have recently conducted pilot portable seismic array studies in North China. Up to seven linear broadband seismic arrays, each consists of 60-100 stations, are planned within the NCC. The principle objectives are to quantify the range and degree of the craton destruction in spatial domain with major focus on the east-west variation from the previously proposed intact craton in the west to the rejuvenated region in the east and the transition zone in the middle. With the expected

  3. Lithospheric architecture of the Slave craton, northwest Canada, as determined from an interdisciplinary 3-D model

    NASA Astrophysics Data System (ADS)

    Snyder, D. B.; Hillier, M. J.; Kjarsgaard, B. A.; de Kemp, E. A.; Craven, J. A.

    2014-05-01

    geologic structures characteristic of mantle lithosphere within cratons found in continent interiors are interpreted using geo-registered diverse data sets from the Slave craton of northwest Canada. We developed and applied a new method for mapping seismic discontinuities in three dimensions using multiyear observations at sparse, individual broadband receivers. New, fully 3-D conductivity models used all available magnetotelluric data. Discontinuity surfaces and conductivity models were geo-registered with previously published P-wave and surface-wave velocity models to confirm first-order structures such as a midlithosphere discontinuity. Our 3-D model to 400 km depth was calibrated by "drill hole" observations derived from xenolith suites extracted from kimberlites. A number of new structural discontinuities emerge from direct comparison of coregistered data sets and models. Importantly, we distinguish primary mantle layers from secondary features related to younger metasomatism. Subhorizontal Slave craton layers with tapered, wedge-shaped margins indicate construction of the craton core at 2.7 Ga by underthrusting and flat stacking of lithosphere. Mapping of conductivity and metasomatism in 3-D, the latter inferred via mineral recrystallization and resetting of isotopic ages in xenoliths, indicates overprinting of the primary layered structures. The observed distribution of relatively conductive mantle at 100-200 km depths is consistent with pervasive metasomatism; vertical "chimneys" reaching to crustal depths in locations where kimberlites erupted or where Au mineralization is known.

  4. Sao Paulo Lightning Mapping Array (SP-LMA): Deployment, Operation and Initial Data Analysis

    NASA Technical Reports Server (NTRS)

    Blakeslee, R.; Bailey, J. C.; Carey, L. D.; Rudlosky, S.; Goodman, S. J.; Albrecht, R.; Morales, C. A.; Anseimo, E. M.; Pinto, O.

    2012-01-01

    An 8-10 station Lightning Mapping Array (LMA) network is being deployed in the vicinity of Sao Paulo to create the SP-LMA for total lightning measurements in association with the international CHUVA [Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)] field campaign. Besides supporting CHUVA science/mission objectives and the Sao Luiz do Paraitinga intensive operation period (IOP) in November-December 2011, the SP-LMA will support the generation of unique proxy data for the Geostationary Lightning Mapper (GLM) and Advanced Baseline Imager (ABI), both sensors on the NOAA Geostationary Operational Environmental Satellite-R (GOES-R), presently under development and scheduled for a 2015 launch. The proxy data will be used to develop and validate operational algorithms so that they will be ready for use on "day1" following the launch of GOES-R. A preliminary survey of potential sites in the vicinity of Sao Paulo was conducted in December 2009 and January 2010, followed up by a detailed survey in July 2010, with initial network deployment scheduled for October 2010. However, due to a delay in the Sao Luiz do Paraitinga IOP, the SP-LMA will now be installed in July 2011 and operated for one year. Spacing between stations is on the order of 15-30 km, with the network "diameter" being on the order of 30-40 km, which provides good 3-D lightning mapping 150 km from the network center. Optionally, 1-3 additional stations may be deployed in the vicinity of Sao Jos dos Campos.

  5. The Río de la Plata craton and the assembly of SW Gondwana

    NASA Astrophysics Data System (ADS)

    Rapela, C. W.; Pankhurst, R. J.; Casquet, C.; Fanning, C. M.; Baldo, E. G.; González-Casado, J. M.; Galindo, C.; Dahlquist, J.

    2007-07-01

    The extent and nature of the Archaean-Palaeoproterozoic craton of Río de la Plata of southern South America, a major but poorly understood crustal component in Neoproterozoic plate reconstructions, as well as the depositional, metamorphic and magmatic history of the surrounding orogenic belts, are reviewed and reassessed, in part through the analysis of material recovered from deep boreholes in western Argentina that penetrated Palaeozoic cover into basement. U-Pb SHRIMP zircon ages for these samples of 2162 ± 6 Ma (diorite), 2189 ± 14 Ma (amphibolitic schist) and 2088 ± 6 Ma (granite) encompass the range of ages determined for the major Palaeoproterozoic orogenic events in the exposed parts of the craton close to the Atlantic coasts of Uruguay and Argentina. Taken together with the geochemical and Nd-isotope characteristics of these samples and an olivine gabbro from a further borehole that failed to yield zircon, these results strongly suggest that the Río de la Plata craton is extremely uniform in its dominant chrono-tectonic and lithological make-up, and that it extends westwards as far as the 535-520 Ma Pampean orogenic belt, against which it probably has a fault contact. U-Pb SHRIMP zircon detrital age patterns are presented for representative metasedimentary samples from the craton cover in the Tandilia belt of eastern Argentina, and from the Pampean (Cambrian) and Famatinian (Ordovician) belts to the west of the craton. Whereas the oldest cover rocks in Tandilia clearly show material derived from the underlying craton, such detritus only appears in the younger (Ordovician) units to the west. Sedimentary protoliths in the Pampean belt were dominated by Neoproterozoic (broadly ˜ 600 Ma) and late Mesoproterozoic (broadly ˜ 1100 Ma) provenance, and derivation from the Río de la Plata craton is highly unlikely. Regional considerations, including previously published zircon data, palaeocurrent and structural data, suggest that these rocks must have had an

  6. Neoproterozoic-Early Paleozoic rifting of the craton margin in eastern Kentucky: Evidence from subsidence analysis

    SciTech Connect

    Goodman, P.T. . Dept. of Geological Sciences); Walker, D. )

    1992-01-01

    Analysis of subsidence along the craton margin in eastern Kentucky indicates a Neoproterozoic to Early through Middle Cambrian rifting event developing on a subsiding passive margin of the Laurentian craton to the Iapetus Ocean. Subsidence associated with rifting is confined to the Rome Trough; an internally broken half-graben within the Laurentian craton; the trough trends sub-parallel to the Appalachian orogenic belt. In cross section the through as an abrupt faulted margin on the carton side and a tapering, gentle extension toward the orogenic belt. The stratigraphic sequence within the Rome Trough and toward the orogen consists of Neoproterozoic or early Cambrian basal sands overlying Grenville basement, and succeeded by silts, shales and discontinuous carbonates of the Rome Fm. that are overlain by shales and carbonates of the Conesauga Fm. Stratigraphic relationships suggest that an out-of-sequence, inboard rift developed along the Laurentian margin adjacent to a drift-phase continental shelf represented by strata of the Blue Ridge and Valley and Ridge. Analysis of the subsidence history of this region reveals trends which support the notion that the subsidence history of this area cannot be accounted for by typical passive-margin development. The subsidence history of the area within the Rome Trough presents a pattern of high thermal subsidence and produces beta values greater than in areas nearer the craton margin. These data indicate that an inboard locus of anomalous crustal extension occurred in the area of the Rome Trough while the remainder of the cratonal margin underwent drift-phase subsidence, and that the timing and magnitude of this event is related to the development of the Iapetan margin.

  7. Multiscale finite-frequency Rayleigh wave tomography of the Kaapvaal craton

    NASA Astrophysics Data System (ADS)

    Chevrot, S.; Zhao, L.

    2007-04-01

    We have measured phase delays of fundamental-mode Rayleigh waves for 12 events recorded by the Southern Africa Seismic Experiment at frequencies between 0.005 and 0.035 Hz. A novel multiscale finite-frequency tomographic method based on wavelet decomposition of 3-D sensitivity kernels for the phase of Rayleigh waves is used to map the shear velocities in the upper mantle beneath southern Africa. The kernels are computed by summing coupled normal modes over a very fine grid surrounding the seismic array. To estimate and minimize the biases in the model resulting from structures outside the tomographic grid, a jackknife inversion method is implemented. The contribution of heterogeneities outside the target volume is significant, but produces artefacts in the tomographic model that are easily identified and discarded before interpretation. With structures on length scales as short as 100 km retrieved beneath the array, the deep structure of the Kaapvaal craton is revealed with unprecedented detail. Outside the array, the corresponding resolution is 200 km. High velocity cratonic roots are confined to the Archean craton, and extend to depths of at least 250 km. Confirming earlier surface structural studies, we recognize two distinct units in the Kaapvaal craton. The eastern Witwatersrand block and the western Kimberley block are separated by a major near-vertical translithospheric boundary which coincides with the Colesberg Lineament. Lower than average velocities south and east of the Kaapvaal craton reveal extensive metasomatism and heating of the lithosphere, probably related to the Karoo magmatic event and to the opening of the South Atlantic Ocean.

  8. Craton Development and Stabilization: Insights from SE Canada using P and S Wave Tomography

    NASA Astrophysics Data System (ADS)

    Boyce, A.; Bastow, I. D.; Darbyshire, F. A.; Gilligan, A.; Ellwood, A.; Levin, V. L.; Menke, W. H.

    2015-12-01

    Cratons, the ancient cores of the continents, are the longest-lived parts of Earth's surface that have survived thermal and mechanical erosion during multiple Wilson cycles. They are visible in tomographic images due to their thick (>200km), seismically fast keels or roots. The Laurentian keel beneath North America is intriguing since its root is thought to extend beneath both the Archean Superior craton and the Proterozoic Grenville province thus implying that keel formation may not have been restricted to Archean times. In order to address this issue we present a P and S wave relative arrival-time tomographic study using data from seismograph networks in SE Canada and the NE US, stretching from the southern tip of Hudson Bay within the Superior craton to the coastal Phanerozoic Appalachian terranes. The tomographic images display three broad zones of increasing mantle wavespeed from globally "slow" in the Appalachian terranes, to a "fast" Grenville Province and "extremely fast" Superior craton. We observe a linear low-velocity feature resulting from modification of the Laurentian keel by the passage of the Great Meteor hotspot. This feature is progressively offset southwestward with depth, potentially due to viscous coupling with mantle flow. No major plate-scale underthrusting during the Grenville Orogeny is apparent, which contradicts the inferred results from crustal seismic reflection and refraction studies. Our results therefore may have fundamental implications for the nature of the Grenville orogenic collision and cratonic stabilization of North America. The results also support the developing consensus that keels form in two stages: a chemically depleted core of Archean age followed by a thermally developed, less-depleted lithosphere during Proterozoic times, highlighted by an abrupt wavespeed contrast in the tomographic images.

  9. Late Holocene Marsh Expansion in Southern San Francisco Bay, California

    EPA Science Inventory

    Currently, the largest tidal wetlands restoration project on the US Pacific Coast is being planned and implemented in southern San Francisco Bay; however, knowledge of baseline conditions of salt marsh extent in the region prior to European settlement is limited. Here, analysis o...

  10. Ethnicity and Phonetic Variation in a San Francisco Neighborhood

    ERIC Educational Resources Information Center

    Hall-Lew, Lauren

    2009-01-01

    This dissertation advances research in sociolinguistics by analyzing phonetic variation in a majority Asian American community in San Francisco, California. As one of the first community studies focusing on Asian Americans in an urban US context, this work speaks to ongoing discussions about speaker ethnicity, phonetic variation, and regional…

  11. The Health, Mobility & Safety Lab at San Francisco State University.

    ERIC Educational Resources Information Center

    Yee, Darlene; Melichar, Joseph F.

    The purpose of this research project at San Francisco State University was to develop and evaluate integrated assessment and intervention strategies to locate the "at risk" older driver and remediate deficits in knowledge or skills about driving and traffic safety. The identification of the "at risk" older driver should suggest appropriate, cost…

  12. VIEW OF PELTON WATER WHEEL COMPANY (SAN FRANCISCO) TURBINE: SPEED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF PELTON WATER WHEEL COMPANY (SAN FRANCISCO) TURBINE: SPEED 225 RPM, 17,500 HP. PHOTO BY JET LOWE, HAER, 1995. (Note: the dark hole in the concrete column to the left is from a tear in the negative.) - Elwha River Hydroelectric System, Glines Hydroelectric Dam & Plant, Port Angeles, Clallam County, WA

  13. Asian American Students: A Look at San Francisco State.

    ERIC Educational Resources Information Center

    Okutsu, James K.

    The attitudes of American Asian students at San Francisco State University toward their education were studied. Responses were obtained from 585 students who were enrolled in Asian American Studies classes in spring 1986. Sixty percent of the sample were of Chinese ancestry, 20% were Filipino, and 20% were other Asian (including Japanese, Korean,…

  14. Relocated American Indians in the San Francisco Bay Area.

    ERIC Educational Resources Information Center

    Ablon, Joan

    1964-01-01

    American Indians who come to the San Francisco Bay Area choose to associate primarily with other Indians of their own or differing tribes in both informal and formal social interaction. Urbanization of Indians occurs on a large scale because of government relocation programs; however, the background in small rural folk communities creates a…

  15. San Francisco Bay Area Environmental Education Needs Study.

    ERIC Educational Resources Information Center

    Fish, Duane

    To identify environmental technician positions in the public and private sectors of the San Francisco Bay Area as well as to determine the skills and knowledge necessary for employment in the field, questionnaires were distributed to companies, agencies, individuals of the private sector in the area, and 33 institutions offering an Occupational…

  16. Solar for Your Present Home. San Francisco Bay Area Edition.

    ERIC Educational Resources Information Center

    Barnaby, Charles S.; And Others

    This publication provides information about present uses of solar energy for space, water, and swimming pool heating that are practical for the San Francisco Bay area. It attempts to provide interested persons with the information needed to make decisions regarding installations of solar heating systems. The point of view taken is that any…

  17. A Water Quality Study: Heron's Head Park, San Francisco, California

    NASA Astrophysics Data System (ADS)

    Li, A.; Wu, K.; Neiss, J.

    2007-12-01

    Heron's Head Park, formerly known as Pier 98, is a 24-acre restored wetland, owned and operated by the Port of San Francisco and situated at the base of the Hunter's Point Power Plant. Heron's Head is a unique environment that is built on landfill and is now a thriving marsh maintained primarily by youth and community volunteers. Adjacent to the park stands a PG&E power plant (closed May 2006), a county waste transfer station, and a combined sewer overflow (CSO) pipe. The park is bordered by San Francisco Bay on the north, east and south sides of the park. We examined the levels of ammonia, nitrite, nitrate, phosphate and fecal coliform at nine sites around the park. Utilizing historical data from other San Francisco Bay sites and other similar estuarine settings in California, we assessed the health of the Bay waters surrounding the park. We found the levels of ammonia, nitrate, nitrite and phosphates to be within the parameters of historical San Francisco Bay data and similar to settings such as Elkhorn Slough, Tomales Bay and Tijuana Estuary. In our study we did find a potential hazard to human health. Fecal coliform concentrations in waters that border the park range from 340 MPN/100 mL - 24,000 MPN/100 mL. This level significantly exceeds Environmental Protection Agency recommendations of 300 MPN/100 mL for human contact with water.

  18. The San Francisco Joint Institutional Transportation Systems Management Program.

    ERIC Educational Resources Information Center

    Fink, Ira; LaPointe, Robert

    1981-01-01

    Transportation systems management (TSM) programs are discussed, particularly the 1977 program of the University of California, San Francisco, which led to traffic reduction and improved vehicle flow. The city's implementation plan for a similar TSM program for 14 educational institutions and hospitals is described. (MLW)

  19. Cultural Factors Related to Smoking in San Francisco's Irish Bars

    ERIC Educational Resources Information Center

    Satterlund, Travis D.; Antin, Tamar M. J.; Lee, Juliet P.; Moore, Roland S.

    2009-01-01

    California's Smoke-Free Workplace Act was extended to include bars in 1998. While the majority of bars in the state have become smoke free, in many bars patrons and staff continue to smoke despite the law. The authors present findings from a study which assessed cultural factors related to continued smoking in bars in the city of San Francisco. In…

  20. 33 CFR 161.50 - Vessel Traffic Service San Francisco.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... the San Joaquin River, as far north as the port of Sacramento on the Sacramento River. ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Vessel Traffic Service San... Movement Reporting System Areas and Reporting Points § 161.50 Vessel Traffic Service San Francisco. The...

  1. 33 CFR 161.50 - Vessel Traffic Service San Francisco.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... the San Joaquin River, as far north as the port of Sacramento on the Sacramento River. ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Vessel Traffic Service San... Movement Reporting System Areas and Reporting Points § 161.50 Vessel Traffic Service San Francisco. The...

  2. 33 CFR 161.50 - Vessel Traffic Service San Francisco.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Vessel Traffic Service San Francisco. 161.50 Section 161.50 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PORTS AND WATERWAYS SAFETY VESSEL TRAFFIC MANAGEMENT Vessel Traffic Service and Vessel Movement Reporting System Areas and...

  3. 33 CFR 161.50 - Vessel Traffic Service San Francisco.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... the San Joaquin River, as far north as the port of Sacramento on the Sacramento River. ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Vessel Traffic Service San... Movement Reporting System Areas and Reporting Points § 161.50 Vessel Traffic Service San Francisco. The...

  4. 33 CFR 161.50 - Vessel Traffic Service San Francisco.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... the San Joaquin River, as far north as the port of Sacramento on the Sacramento River. ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Vessel Traffic Service San... Movement Reporting System Areas and Reporting Points § 161.50 Vessel Traffic Service San Francisco. The...

  5. 1906 Letter to the San Francisco Health Department

    ERIC Educational Resources Information Center

    Schmachtenberg, Kristin

    2006-01-01

    On Wednesday, April 18, 1906, an earthquake, measuring 7.8 on the Richter magnitude scale and lasting 48 seconds, erupted along the San Andreas fault with a flash point originating in the San Francisco Bay area. The force of the earthquake tore apart buildings and roads, causing water and gas mains to twist and break. The resulting effects of the…

  6. Polychlorinated biphenyls (PCBs) in San Francisco Bay.

    PubMed

    Davis, J A; Hetzel, F; Oram, J J; McKee, L J

    2007-09-01

    San Francisco Bay is facing a legacy of polychlorinated biphenyls (PCBs) spread widely across the land surface of the watershed, mixed deep into the sediment of the Bay, and contaminating the Bay food web to a degree that poses health risks to humans and wildlife. In response to this persistent problem, water quality managers are establishing a PCB total maximum daily load (TMDL) and implementation plan to accelerate the recovery of the Bay from decades of PCB contamination. This article provides a review of progress made over the past 15 years in managing PCBs and understanding their sources, pathways, fate, and effects in the Bay, and highlights remaining information needs that should be addressed in the next 10 years. The phaseout of PCBs during the 1970s and the 1979 federal ban on sale and production led to gradual declines from the 1970s to the present. However, 25 years after the ban, PCB concentrations in some Bay sport fish today are still more than ten times higher than the threshold of concern for human health. Without further management action it appears that the general recovery of the Bay from PCB contamination will take many more decades. PCB concentrations in sport fish were, along with mercury, a primary cause of a consumption advisory for the Bay and the consequent classification of the Bay as an impaired water body. Several sources of information indicate that PCB concentrations in the Bay may also be high enough to adversely affect wildlife, including rare and endangered species. The greater than 90% reduction in food web contamination needed to meet the targets for protection of human health would likely also generally eliminate risks to wildlife. PCB contamination in the Bay is primarily associated with industrial areas along the shoreline and in local watersheds. Strong spatial gradients in PCB concentrations persist decades after the release of these chemicals to Bay Area waterways. Through the TMDL process, attention is being more sharply

  7. Documentation for the machine-readable version of the SAO-HD-GC-DM cross index version 1983

    NASA Technical Reports Server (NTRS)

    Roman, N. G.; Warren, W. H., Jr.; Schofield, N., Jr.

    1983-01-01

    An updated and extended machine readable version of the Smithsonian Astrophysical Observatory star catalog (SAO) is described. A correction of all errors which were found since preparation of the original catalog which resulted from misidentifications and omissions of components in multiple star systems and missing Durchmusterung numbers (the common identifier) in the SAO Catalog are included and component identifications from the Index of Visual Double Stars (IDS) are appended to all multiple SAO entries with the same DM numbers, and lower case letter identifiers for supplemental BD stars are added. A total of 11,398 individual corrections and data additions is incorporated into the present version of the cross index.

  8. Documentation for the machine-readable version of the Smithsonian Astrophysical Observatory Star catalogue (SAO) version 1984

    NASA Technical Reports Server (NTRS)

    Roman, N. G.; Warren, W. H., Jr.

    1984-01-01

    An updated, corrected and extended machine readable version of the Smithsonian Astrophysical Observatory star catalog (SAO) is described. Published and unpublished errors discovered in the previous version have been corrected, and multiple star and supplemental BD identifications added to stars where more than one SAO entry has the same Durchmusterung number. Henry Draper Extension (HDE) numbers have been added for stars found in both volumes of the extension. Data for duplicate SAO entries (those referring to the same star) have been blanked out, but the records themselves have been retained and flagged so that sequencing and record count are identical to the published catalog.

  9. 77 FR 15798 - Notice of Intent To Repatriate Cultural Items: San Francisco State University, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-16

    ...The San Francisco State University, in consultation with the appropriate Indian tribes, has determined that the cultural items meet the definition of sacred objects and repatriation to the Indian tribes stated below may occur if no additional claimants come forward. Representatives of any Indian tribe that believes itself to be culturally affiliated with the cultural items may contact the San......

  10. Plankton studies in San Francisco Bay, VIII, Chlorophyll distributions and hydrographic properties of South San Francisco Bay, 1983

    USGS Publications Warehouse

    Alpine, Andrea E.; Wienke, Sally M.; Cloern, James E.; Cole, Brian E.; Wong, Raymond L. J.

    1985-01-01

    This report summarizes the distribution of phytoplankton Momass and selected hydrographic properties measured in South San Francisco Bay during 1983- There were a total of 45 cruises over the year with the most frequent sampling occurring during the spring. Parameters measured were: chlorophyll a, phaeopigments, in-vivo fluorescence, turbidity, salinity, and temperature.

  11. Plankton studies in San Francisco Bay; IX, Chlorophyll distributions and hydrographic properties of South San Francisco Bay, 1984-86

    USGS Publications Warehouse

    Alpine, Andrea A.; Wienke, Sally M.; Cloern, James E.; Cole, Brian E.

    1988-01-01

    This report summarizes the distribution of phytoplankton biomass and selected hydrographic properties in South San Francisco Bay during 1984- 1986. There were a total of 67 cruises during the three-year period with the most frequent sampling occurring during the spring. Parameters measured were chlorophyll a, phaeopigments, in-vivo fluorescence, turbidity, salinity, and temperature.

  12. A preliminary assessment of metal bioaccumulation in the blue crab, Callinectes danae S., from the Sao Vicente Channel, Sao Paulo State, Brazil.

    PubMed

    Bordon, Isabella C A C; Sarkis, Jorge E S; Tomás, Acácio R G; Souza, Marcelo R; Scalco, Allan; Lima, Mariana; Hortellani, Marcos A

    2012-04-01

    The concentrations of metals in tissues of Callinectes danae were evaluated, aiming to determine the bioaccumulation process of this species. Gills presented the highest mean concentrations for most metals, except for Hg (Sao Vicente Channel is included) would be important to confirm if this pattern of bioaccumulation can be extended to the population of C. danae of this estuary. PMID:22349281

  13. Shear velocity and anisotropy distributions beneath southern Africa's cratons: Lithospheric structure, deformation, LAB and other discontinuities

    NASA Astrophysics Data System (ADS)

    Adam, Joanne; Lebedev, Sergei

    2013-04-01

    Seismic-velocity structure and anisotropy of cratonic lithosphere offer important clues on the enigmatic formation and stabilization of cratons. Broad-band surface waves are highly sensitive to both the isotropic-average shear speeds from the upper crust down to the asthenosphere (characterising the composition and thermal state of the lithosphere) and to radial and azimuthal shear-wave anisotropy (indicative of ancient and recent deformation and flow). Recently, receiver function studies have yielded exciting but puzzling new evidence, revealing multiple discontinuities at different depths within the lithosphere-asthenosphere depth range beneath cratons. While some of the receiver-function signals probably indicate the lithosphere-asthenosphere boundary (LAB), others must be due to sharp radial changes in the mantle-rock composition or anisotropy. We have recently used teleseismic interferometry to measure thousands of inter-station, Rayleigh- and Love-wave, phase-velocity curves across southern Africa (Adam and Lebedev 2012). Here, we invert the very-broadband dispersion data for the profiles of the shear speed and azimuthal and radial anisotropy beneath different parts of the Kaapvaal Craton and the Limpopo Belt. Systematic model space mapping is used to evaluate parameter trade-offs and to ensure the robustness of the anisotropy profiles. Our results, firstly, reconcile the long-debated previous models based on different interpretations of SKS-splitting measurements in southern Africa (one end-member model placing anisotropy primarily into the lithosphere and attributing it to Archean deformation and the other placing it into the asthenosphere, with recently developed fabric). We show that the depth distribution of anisotropy comprises elements of both models: anisotropy in the asthenosphere shows fast-propagation directions parallel to the plate motion; anisotropy in the Limpopo and northern Kaapvaal lithosphere shows fast directions parallel to the Archean

  14. Density heterogeneity of lithospheric mantle beneath the Siberian craton: testing geophysical models by petrological data

    NASA Astrophysics Data System (ADS)

    Cherepanova, Yulia; Artemieva, Irina

    2015-04-01

    Using free-board modeling, we examine a vertically-averaged mantle density beneath the Archean-Proterozoic Siberian Craton in the layer from the Moho down to base of the chemical boundary layer (CBL). Two models are tested: in Model 1 the base of the CBL coincides with the LAB, whereas in Model 2 the base of the CBL is at a 180 km depth. The uncertainty of density model is < 0.02 t/m3 or < 0.6% with respect to primitive mantle. The results, calculated at in situ and at room temperature (SPT) conditions, indicate a heterogeneous density structure of the Siberian lithospheric mantle with a strong correlation between mantle density variations and the tectonic setting. Three types of cratonic mantle are recognized from mantle density anomalies. 'Pristine' cratonic regions not sampled by kimberlites have the strongest depletion with density deficit of 1.8-3.0% (and SPT density of 3.29-3.33 t/m3 as compared to 3.39 t/m3 of primitive mantle). Cratonic mantle affected by magmatism (including the kimberlite provinces) has a typical density deficit of 1.0-1.5%, indicative of a metasomatic melt-enrichment. Intracratonic sedimentary basins have a high density mantle (3.38-3.40 t/m3 at SPT) which suggests, at least partial, eclogitization. Moderate density anomalies beneath the Tunguska Basin imply that the source of the Siberian LIP lies outside of the Craton. In situ mantle density is used to test the isopycnic condition of the Siberian Craton. Both CBL thickness models indicate significant lateral variations in the isopycnic state, correlated with mantle depletion and best achieved for the Anabar Shield region and other intracratonic domains with a strongly depleted mantle. A comparison of synthetic Mg# for the bulk lithospheric mantle calculated from density with Mg# from petrological studies of peridotite xenoliths from the Siberian kimberlites suggests that melt migration may produce local patches of metasomatic material in the overall depleted mantle.

  15. Tale of three cratons: Tectonostratigraphic anatomy of the Damara orogen in northwestern Namibia and the assembly of Gondwana

    NASA Astrophysics Data System (ADS)

    Prave, Anthony R.

    1996-12-01

    The Neoproterozoic Damara orogen in Namibia records the Gondwanan assembly of the Congo Kalahari Rio de la Plata cratons. Sedimentological and stratigraphic analyses of the Otavi (mostly carbonate) and Mulden (siliciclastic molasse) Groups exposed along the southwestern margin of the Congo craton indicate that foreland-basin orogenesis began during middle Otavi (ca. 600 750 Ma); this time frame is earlier than that for the Nama foreland (ca. 550 Ma) on the Kalahari craton. Evidence for this interpretation includes (1) an intra-Otavi angular unconformity; (2) concomitant development of increasing accommodation space, basin segmentation, and backstepping depositional systems composed mostly of deep-basin and slope hemipelagic and sediment gravity-flow deposits; and (3) a near reversal in paleocurrents (initially northward off the Congo craton, then switching to southeastward from a west-northwestern orogen). Thus, Congo Rio de la Plata suturing predated Congo-Kalahari suturing during the assembly of Gondwana.

  16. Phenotypic instability of Saos-2 cells in long-term culture

    SciTech Connect

    Hausser, Heinz-Juergen . E-mail: heinz-juergen.hausser@medizin.uni-ulm.de; Brenner, Rolf E.

    2005-07-22

    The human osteosarcoma cell line Saos-2 is widely used as a model system for human osteoblastic cells, though its phenotypic stability has not been ascertained. We therefore propagated these cells over 100 passages and compared relevant phenotypic properties. In general, higher passage cells exhibited higher proliferation rates and lower specific alkaline phosphatase activities, though mineralization was significantly more pronounced in cultures of late passage cells. Whereas expression of most genes investigated did not vary profoundly, some genes exhibited remarkable differences. Decorin, for instance, that has been discussed as a regulator of proliferation and mineralization, is strongly expressed only in early passage cells, and two receptors for pleiotrophin and midkine exhibited an almost mutually exclusive expression pattern in early and late passage cells, respectively. Our observations indicate that special care is required when results obtained with Saos-2 cells with different culture history are to be compared.

  17. Geologic mapping of the Bauru Group in Sao Paulo state by LANDSAT images. [Brazil

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Godoy, A. M.

    1983-01-01

    The occurrence of the Bauru Group in Sao Paulo State was studied, with emphasis on the western plateau. Regional geological mapping was carried out on a 1:250.000 scale with the help of MSS/LANDSAT images. The visual interpretation of images consisted basically of identifying different spectral characteristics of the geological units using channels 5 and 7. Complementary studies were made for treatment of data with an Interative Image (I-100) analyser in order to facilitate the extraction of information, particularly for areas where visual interpretation proved to be difficult. Regional characteristics provided by MSS/LANDSAT images, coupled with lithostratigraphic studies carried out in the areas of occurrence of Bauru Group sediments, enabled the homogenization of criteria for the subdivision of this group. A spatial distribution of the mapped units was obtained for the entire State of Sao Paulo and results were correlated with proposed stratigraphic divisions.

  18. Radiocarbon dates for lava flows and pyroclastic deposits on Sao Miguel, Azores

    USGS Publications Warehouse

    Moore, R.B.; Rubin, M.

    1991-01-01

    We report 63 new radiocarbon analyses of samples from Sao Miguel, the largest island in the Azores archipelago. The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall and lacustrine deposits and lava flows. One calcite date is reported. These dates establish ages for 48 previously undated lava flows and pyroclastic deposits, and revise three ages previously reported. These data are critical to deciphering the Holocene and late Pleistocene eruptive history of Sao Miguel and evaluating its potential volcanic hazards. Average dormant intervals during the past 3000 years are about 400 years for Sete Cidades volcano, 145 years for volcanic Zone 2, 1150 years for Agua de Pau volcano and 320 years for Furnas volcano. No known eruptions have occurred in volcanic Zone 4 during the past 3000 years. -from Authors

  19. Osteogenic potential of biosilica on human osteoblast-like (SaOS-2) cells.

    PubMed

    Wiens, Matthias; Wang, Xiaohong; Schlossmacher, Ute; Lieberwirth, Ingo; Glasser, Gunnar; Ushijima, Hiroshi; Schröder, Heinz C; Müller, Werner E G

    2010-12-01

    Biosilica is a natural polymer, synthesized by the poriferan enzyme silicatein from monomeric silicate substrates. Biosilica stimulates mineralizing activity and gene expression of SaOS-2 cells. To study its effect on the formation of hydroxyapatite (HA), SaOS-2 cells were grown on different silicatein/biosilica-modified substrates (bone slices, Ca-P-coated coverslips, glass coverslips). Growth on these substrates induced the formation of HA nodules, organized in longitudinal arrays or spherical spots. Nodules of sizes above 1 μm were composed of irregularly arranged HA prism-like nanorods, formed by aggregates of three to eight SaOS-2 cells. Moreover, growth on silicatein/biosilica-modified substrates elicited increased [(3)H]dT incorporation into DNA, indicative of enhanced cell proliferation. Consequently, an in vitro-based bioassay was established to determine the ratio between [(3)H]dT incorporation and HA formation. This ratio was significantly higher for cells that grew on silicatein/biosilica-modified substrates than for cells on Ca-P-coated coverslips or plain glass slips. Hence, we propose that this ratio of in vitro-determined parameters reflects the osteogenic effect of different substrates on bone-forming cells. Finally, qRT-PCR analyses demonstrated that growth of SaOS-2 cells on a silicatein/biosilica matrix upregulated BMP2 (bone morphogenetic protein 2, inducer of bone formation) expression. In contrast, TRAP (tartrate-resistant acid phosphatase, modulator of bone resorption) expression remained unaffected. We conclude that biosilica shows pronounced osteogenicity in vitro, qualifying this material for studies of bone replacement also in vivo. PMID:20725824

  20. VizieR Online Data Catalog: SAO-HD-GC-DM Cross Index (ADC 1983) (Roman+ 1983)

    NASA Astrophysics Data System (ADS)

    Roman, N. G.; Warren, W. H., Jr.; Schofield, N. J., Jr.

    1996-05-01

    The catalog is an updated, corrected, and extended version of a table of correspondences originally prepared by Morin (1973). The individual data corrections, additions, and changes included in the new version number 11398, with 8600 data records having at least one change. In addition to the correction of all errors found since preparation of the original catalog, most of which resulted from misidentifications and omissions of components in multiple-star systems and missing Durchmusterung numbers (the common identifier) in the SAO Catalog, component identifications from the Index Catalogue of Visual Double Stars (IDS) have been appended to all multiple SAO stars having the same DM numbers, and lowercase identifications for supplemental (footnoted) BD stars have been added. Stars deleted (duplicate entries) in the SAO Catalog have been appended with a "D" and their data removed, although the records have been kept (with SAO number only) in order not to change the number of SAO stars. The data include SAO number, HD number, HD multiplicity code, GC number, DM identification code (BD, CD, CP), and number. There are fewer objects than records because of the deleted entries appended with a "D" as described above (35 stars deleted). (1 data file).

  1. Semi-annual oscillation (SAO) of the nighttime ionospheric D region as detected through ground-based VLF receivers

    NASA Astrophysics Data System (ADS)

    Silber, Israel; Price, Colin; Rodger, Craig J.

    2016-03-01

    Earth's middle and upper atmosphere exhibits several dominant large-scale oscillations in many measured parameters. One of these oscillations is the semi-annual oscillation (SAO). The SAO can be detected in the ionospheric total electron content (TEC), the ionospheric transition height, the wind regime in the mesosphere-lower thermosphere (MLT), and in the MLT temperatures. In addition, as we report for the first time in this study, the SAO is among the most dominant oscillations in nighttime very low frequency (VLF) narrowband (NB) subionospheric measurements. As VLF signals are reflected off the ionospheric D region (at altitudes of ˜ 65 and ˜ 85 km, during the day and night, respectively), this implies that the upper part of the D region is experiencing this oscillation as well, through changes in the dominating electron or ion densities, or by changes in the electron collision frequency, recombination rates, and attachment rates, all of which could be driven by oscillatory MLT temperature changes. We conclude that the main source of the SAO in the nighttime D region is NOx molecule transport from the lower levels of the thermosphere, resulting in enhanced ionization and the creation of free electrons in the nighttime D region, thus modulating the SAO signature in VLF NB measurements. While the cause for the observed SAO is still a subject of debate, this oscillation should be taken into account when modeling the D region in general and VLF wave propagation in particular.

  2. 33 CFR 165.1187 - Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay, California. 165.1187 Section 165.1187 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PORTS AND WATERWAYS SAFETY REGULATED NAVIGATION AREAS...

  3. 33 CFR 165.1187 - Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay, California. 165.1187 Section 165.1187... SAFETY REGULATED NAVIGATION AREAS AND LIMITED ACCESS AREAS Specific Regulated Navigation Areas and Limited Access Areas Eleventh Coast Guard District § 165.1187 Security Zones; Golden Gate Bridge and...

  4. 33 CFR 165.1187 - Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay, California. 165.1187 Section 165.1187... SAFETY REGULATED NAVIGATION AREAS AND LIMITED ACCESS AREAS Specific Regulated Navigation Areas and Limited Access Areas Eleventh Coast Guard District § 165.1187 Security Zones; Golden Gate Bridge and...

  5. 33 CFR 165.1187 - Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay, California. 165.1187 Section 165.1187... SAFETY REGULATED NAVIGATION AREAS AND LIMITED ACCESS AREAS Specific Regulated Navigation Areas and Limited Access Areas Eleventh Coast Guard District § 165.1187 Security Zones; Golden Gate Bridge and...

  6. 33 CFR 165.1187 - Security Zones; Golden Gate Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Bridge and the San Francisco-Oakland Bay Bridge, San Francisco Bay, California. 165.1187 Section 165.1187... SAFETY REGULATED NAVIGATION AREAS AND LIMITED ACCESS AREAS Specific Regulated Navigation Areas and Limited Access Areas Eleventh Coast Guard District § 165.1187 Security Zones; Golden Gate Bridge and...

  7. 33 CFR 3.55-20 - Sector San Francisco: San Francisco Bay Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Sector San Francisco: San Francisco Bay Marine Inspection Zone and Captain of the Port Zone. 3.55-20 Section 3.55-20 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY GENERAL COAST GUARD AREAS, DISTRICTS, SECTORS, MARINE INSPECTION ZONES, AND CAPTAIN...

  8. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction

    NASA Astrophysics Data System (ADS)

    Pilet, Sebastien; Guex, Jean; Muntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Schaltegger, Urs

    2016-04-01

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here, we present a synthesis of stratigraphic constraints on the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries combined with geochronological data in order to establish the sequence of events that initiate two of the major mass extinctions recorded in Earth's history. This synthesis demonstrates that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. The initial regressive events recorded at T-J and Pl-To boundaries seem difficult to reconcile either with large initial CO2 degassing associated with plume activity or by volatile-release (CO2, CH4, Cl2) from deep sedimentary reservoirs during contact metamorphism associated to dykes and sills intrusion because massive CO2 degassing is expected to produce super greenhouse conditions. We evaluate, here, an alternative suggesting that the initial cooling could be due to gas release during the initial thermal erosion of the cratonic lithosphere due to emplacement of the CAMP and Karoo-Ferrar volcanic provinces. Petrological constraints on primary magmas indicate that the mantle is hotter and melts more extensively to produce LIP lavas than for current oceanic islands basalts. However, available data suggest that the Karoo and CAMP areas were underlain by thick lithosphere (>200 km) prior to continental break up. The presence of thick lithosphere excludes significant melting of the asthenospheric mantle without initial stage of thermal erosion of the cratonic lithosphere. This initial step of thermal erosion / thermal heating of the cratonic lithosphere is critical to understand the volatile budget associated with LIPs while

  9. Formation of cratonic mantle keels by arc accretion: Evidence from S receiver functions

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; Eaton, David W.

    2010-09-01

    Delineating mantle interfaces can provide important clues for understanding the formation of continents. We use S-wave receiver functions to investigate lithospheric structure along a transect extending from Vancouver Island to Baffin Island. Observed Sp converted waves allow for interpretation of boundaries in the depth range expected for tectonic plates. Receiver functions show a distinct negative amplitude feature, interpreted as the lithosphere-asthenosphere boundary, at shallow depths beneath British Columbia (˜85km), deepening abruptly at the eastern edge of the Cordillera to ˜260km beneath the Canadian Shield. Dipping mid-lithospheric discontinuities extend beneath several giant ca. 1.8 Ga epicontinental magmatic arcs, consistent with formation of cratonic lithosphere by arc accretion. This model provides a plausible explanation for global mid-lithospheric discontinuities within cratons and aids in understanding their formation.

  10. Early Archean sialic crust of the Siberian craton: Its composition and origin of magmatic protoliths

    NASA Astrophysics Data System (ADS)

    Vovna, G. M.; Mishkin, M. A.; Sakhno, V. G.; Zarubina, N. V.

    2009-12-01

    This study demonstrates that the base of the Archean deep-seated granulite complexes within the Siberian craton consists of a metabasite-enderbite association. The major and trace element distribution patterns revealed that the protoliths of this association are represented by calc-alkaline andesites and dacites, containing several minor sequences of komatiitic-tholeiitic volcanic rocks. The origin of the primary volcanic rocks of the metabasite-enderbite association is inferred on the basis of a model of mantle plume magmatism, which postulates that both andesitic and dacitic melts were derived from the primary basitic crust at the expense of heat generated by ascending mantle plumes. The formation of the protoliths of the Archen metabasite-enderbite association of the Siberian craton began at 3.4 Ga and continued until the late Archean.

  11. First find of biogenic activity in the Palaeoproterozoic of the Singhbhum craton (E India)

    NASA Astrophysics Data System (ADS)

    Loon, A. J. van; Mazumder, R.

    2013-09-01

    The Palaeoproterozoic succession of the Singhbhum craton in E. India was hitherto considered as almost entirely siliciclastic and partly volcanogenic. Here we describe, from the fine-grained, tidally influenced shale facies of the Palaeoproterozoic Chaibasa Formation (2.1-1.6 Ga), a fine, originally more or less horizontal, wavy to strongly undulating (later locally deformed) lamination. Investigation of these laminae shows that they must be ascribed to the accumulation of fine particles on microbial mats that covered a sandy substrate. The structures must therefore be considered as stromatolites, features that are accepted as proof of the presence of micro-organisms, in this case most probably cyanobacteria. The interpretation of biogenic activity is supported by microscopic analysis. It is the first description of traces left by biogenic activity that took place in the Palaeoproterozoic of the Singhbhum craton.

  12. Mantle density beneath the Siberian craton based on free board constrains

    NASA Astrophysics Data System (ADS)

    Cherepanova, Yulia; Artemieva, Irina

    2014-05-01

    We present the mantle density model of the Archean-Proterozoic Siberian Craton (SC). The density model is constrained by free-board (buoyancy) modeling (Lachenbruch and Morgan, 1990). The approach assumes isostatic compensation of the region, and is justified by the near-zero free-air gravity for most of the region, except for the flanking orogenic belts with high topography. Despite a relatively uniform topography of the SC (ca. 400 m for most of the region and reaching 700 m in the shields), the craton has a strongly heterogeneous crustal structure with large regional variations in Moho and average crustal Vp (Cherepanova et al., 2013) which reflects its complex tectonic evolution. Formed by amalgamation of several Archean terranes, the craton has been significantly affected by Proterozoic collisional and extensional events, the late- Proterozoic rifting at its margins, the Devonian rifting of the Vilyui rift, several pulses of kimberlite magmatism, and the Permo-Triassic trap basalt magmatism. The strong lateral and vertical heterogeneity of the lithospheric mantle has been documented so far in the studied of the mantle xenoliths from kimberlite pipes and in a limited number of geophysical studies. Here we extend geophysical analysis of mantle compositional heterogeneity by evaluating mantle density structure and interpreting its regional variations in terms of mantle mg#. We link regional large-amplitude variations in mantle depletion to the tectonic evolution of the craton and compare these results with geophysical models and petrologic data. We speculate on the origin of compositional heterogeneity of the lithospheric mantle, which is in overall agreement with results of a joint analysis of seismic and thermal data (Artemieva, 2009) and mantle xenolith studies which provide information on metasomatic enrichment of the depleted lithospheric mantle by the tectonic events. The results indicate the heterogeneous structure of mantle density, with the average

  13. Hospitalization flow in the public and private systems in the state of Sao Paulo, Brazil

    PubMed Central

    Rocha, Juan Stuardo Yazlle; Monteiro, Rosane Aparecida; Moreira, Marizélia Leão

    2015-01-01

    OBJECTIVE To describe the migration flows of demand for public and private hospital care among the health regions of the state of Sao Paulo, Brazil. METHODS Study based on a database of hospitalizations in the public and private systems of the state of Sao Paulo, Southeastern Brazil, in 2006. We analyzed data from 17 health regions of the state, considering people hospitalized in their own health region and those who migrated outwards (emigration) or came from other regions (immigration). The index of migration effectiveness of patients from both systems was estimated. The coverage (hospitalization coefficient) was analyzed in relation to the number of inpatient beds per population and the indexes of migration effectiveness. RESULTS The index of migration effectiveness applied to the hospital care demand flow allowed characterizing health regions with flow balance, with high emigration of public and private patients, and with high attraction of public and private patients. CONCLUSIONS There are differences in hospital care access and opportunities among health regions in the state of Sao Paulo, Brazil. PMID:26465661

  14. Atlantic tropical forest mapping in the northern coastal zone of Sao Paulo State, Brazil

    SciTech Connect

    Simi, R. Jr.; Almeida, S.A.S.; Manso, A.P.

    1997-06-01

    The northern coastal zone of Sao Paulo State includes the cities of Ubatuba, Caraguatatuba, Sao Sebastiao and Ilha Bela. Large development projects, such as road and highway constructions and joint real estate exploration of susceptible coastal ecosystems have threatened the harmony and ecological stability of these ecosystems. Recently, the Atlantic tropical rain forest has been the most destructed ecosystem in the coastal zone in response to real estate investments in urban areas along the main roads. In the northern coastal zone of Sao Paulo State, 80% of the counties are included in the State Park of Serra do Mar. As tourism is a strong growing economical activity, as well as coastal production, it should be of interest to create a plan for sustainable development. The objective of this study is to map and characterize land use cover changes with emphasis on the Atlantic tropical rain forest degradation using Landsat TM images. Preliminary results for land use cover changes indicate that the Atlantic tropical rain forest was reduced by 6.1 % during the period of July 1992 and October 1995.

  15. Preliminary Goddard geopotential using optical tracking data and a comparison with SAO models

    NASA Technical Reports Server (NTRS)

    Lerch, F. J.; Wagner, C. A.; Putney, B. H.; Nickerson, K. G.

    1971-01-01

    A preliminary Goddard Space Flight Center (GSFC) geopotential and center of mass station coordinate solution was obtained from satellite orbital data using numerical integration theory. This geodetic solution is a prelude to a more general solution which will combine the 1971 International Satellite Geodesy Experiment (ISAGEX) laser data with the present data being employed. The present GSFC geopotential solution consists of the spherical harmonic coefficients through degree and order eight with higher order satellite resonant coefficients. The solution represents a first iteration result from 17 satellites with approximately 150 weekly orbital arcs containing some 40,000 optical observations. The GSFC preliminary result is compared with final results from the Smithsonian Astrophysical Observatory (SAO) solutions including the 1969 SAO Standard Earth II solution. One aspect of interest for the comparison is that SAO uses an analytic theory for the orbital solution whereas GSFC uses a numerical integration theory. The comparison of geopotential results shows that good agreement exists in general but that there are some areas of minor differences.

  16. Seasonal behavior of tropospheric ozone in the Sao Paulo (Brazil) metropolitan area

    NASA Astrophysics Data System (ADS)

    Massambani, Oswaldo; Andrade, Fatima

    This paper presents a study of the seasonal behavior of tropospheric ozone and its precursors in the Sao Paulo Metropolitan Area as observed during 1987. The 03, NO, NO 2, NMHC, and meteorological data were collected at an air quality station in downtown Sao Paulo by the State Environmental Protection Agency (CETESB). The air pollutant measurements were related to both daily total insolation and the number of hours of insolation measured at the Sao Paulo University Climatological Station. Correlations between both radiation parameters and total daily integrated ozone amounts were performed. The total number of sunshine hours was highly correlated to mean hourly ozone concentration values during each month of 1987. The seasonal behavior of NO, NO 2, and NMHC was also studied. Two diurnal peaks in average NO concentration were observed, i.e. one in early morning and one in early evening; both were due to emissions from urban mobile sources. The magnitude of these peaks doubled in value during the winter months. Its diurnal concentration variation was inverse to that of the 03; similar behavior was found for NO 2 and for NMHC. The data presented herein show the influence of solar radiation and of ozone precursors on photochemical smog formation in this tropical region.

  17. Early proterozoic evolution of the saskatchewan craton and its allochthonous coyer, trans-hudson Orogen

    USGS Publications Warehouse

    Chiarenzelli, J.; Aspler, L.; Villeneuve, M.; Lewry, J.

    1998-01-01

    The composition, chronology, and structural relations of the Saskatchewan Craton and enveloping mylonitic rocks exposed in basement windows of the Glennie Domain, Trans-Hudson Orogen, have been determined by geochemical, geochronologic, and structural studies accompanying detailed field mapping. Basement windows lie along the hinge zone of a regional crustal culmination and consist mostly of 2.4-2.5 Ga felsic plutonic rocks enveloped by the Nistowiak Thrust. The Nistowiak Thrust is a folded, 1-2 km thick, upper amphibolite facie??s mylonite zone formed during emplacement of the Flin Flon-Glennie Complex across the Saskatchewan Craton. It is likely correlative to the Pelican Thrust, which envelops basement windows in the Hanson Lake Block -100 km to the east. An internal high strain zone within the overlying nappe pile, the Guncoat Thrust, is composed primarily of mylonitized porphyroclastic pelitic and psammitic migmatites. U-Pb geochronological results suggest calc-alkaline plutonism from 1889-1837 Ma, thrust stacking, peak metamorphism and associated anatexis between 1837 and 1809 Ma, isotopic closure of titanite at 1790-1772 Ma, and intrusion of late granitic rocks at 1770-1762 Ma. This is in agreement with ages from the Hanson Lake Block, and La Ronge, Kisseynew, and Flin-Flon domains in Saskatchewan and Manitoba, and from the Ungava-Baffin portion of Trans-Hudson Orogen, suggesting broadly synchronous thermotectonic processes along a strike length of 2000 km. We speculate that the Saskatchewan Craton, rather than representing an exotic continental fragment, rifted from the Superior and/or Hearne Provinces at ca. 2.1 Ga and that the Trans-Hudson Orogen is an internal orogen. In this scenario the Maniwekan Ocean, developed between the Rae-Hearne and Superior cratons, opened and closed about similar pole(s) of plate motion. ?? 1998 by The University of Chicago. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Pre- and Post-Cratonization History of the Northern Wyoming Province

    NASA Astrophysics Data System (ADS)

    Mogk, D.; Mueller, P.; Wooden, J.; Foster, D.

    2004-05-01

    Cratonization of the northern Wyoming Province (NWP) occurred ~2.8-2.9 Ga with the cessation of convergent margin magmatism and the development of passive margin sedimentary sequences. Cratonization was preceded by an extended period of crustal growth via episodic, convergent margin magmatism; major events are dated at 2.8-2.9 and 3.2-3.5 Ga. Earlier events are recorded by numerous detrital zircon and Nd model ages, which indicate felsic magmatism was ongoing by at least 4.0 Ga. TTG magmatism at 2.8-2.9 was the culminating event and is clearly imprinted in the isotopic systems of mantle xenoliths. Cratonization was followed by tectonic and magmatic quiescence from ~2.8-1.9 Ga. Subsequent tectonism is marked by a 2-stage Paleoproterozoic incorporation of the NWP into Laurentia. Stage 1 (~1.8-1.9 Ga) involved the juxtaposition of the NWP with the Archean Superior and Hearne cratons and the production of minor calc-alkaline magmatism (e.g., Little Belt Mountains of the Great Falls Tectonic Zone). Stage-2 (~1.7-1.8 Ga) involved the accretion of Paleoproterozoic terranes (2.4-1.8 Ga) to the amalgamated Wyoming-Laurentian continent, resulting in granulite facies metamorphism, but little magmatism, in the NWP (e.g., Tobacco Root Mountains). Paleoproterozoic tectonism in the NWP is distinctive because of: 1) a paucity of contemporaneous magmatism and 2) a lack of tectonic activity away from the active margins. These observations suggest that the NWP developed a long-lived and structurally robust tectosphere contemporaneously with the stabilization of a felsic crust 2.8-2.9 Ga. This tectosphere appears to have had a substantial impact on the subsequent geologic evolution of the northern Rocky Mountain crust, including the development of the Belt basin, the Yellowstone- Snake River Plain system, and a range of Laramide and Sevier-style structures.

  20. Olivine water contents in the continental lithosphere and the longevity of cratons.

    PubMed

    Peslier, Anne H; Woodland, Alan B; Bell, David R; Lazarov, Marina

    2010-09-01

    Cratons, the ancient cores of continents, contain the oldest crust and mantle on the Earth (>2 Gyr old). They extend laterally for hundreds of kilometres, and are underlain to depths of 180-250 km by mantle roots that are chemically and physically distinct from the surrounding mantle. Forming the thickest lithosphere on our planet, they act as rigid keels isolated from the flowing asthenosphere; however, it has remained an open question how these large portions of the mantle can stay isolated for so long from mantle convection. Key physical properties thought to contribute to this longevity include chemical buoyancy due to high degrees of melt-depletion and the stiffness imparted by the low temperatures of a conductive thermal gradient. Geodynamic calculations, however, suggest that these characteristics are not sufficient to prevent the lithospheric mantle from being entrained during mantle convection over billions of years. Differences in water content are a potential source of additional viscosity contrast between cratonic roots and ambient mantle owing to the well-established hydrolytic weakening effect in olivine, the most abundant mineral of the upper mantle. However, the water contents of cratonic mantle roots have to date been poorly constrained. Here we show that olivine in peridotite xenoliths from the lithosphere-asthenosphere boundary region of the Kaapvaal craton mantle root are water-poor and provide sufficient viscosity contrast with underlying asthenosphere to satisfy the stability criteria required by geodynamic calculations. Our results provide a solution to a puzzling mystery of plate tectonics, namely why the oldest continents, in contrast to short-lived oceanic plates, have resisted recycling into the interior of our tectonically dynamic planet. PMID:20811455

  1. Lower Crustal Seismicity, Volatiles, and Evolving Strain Fields During the Initial Stages of Cratonic Rifting

    NASA Astrophysics Data System (ADS)

    Lambert, C.; Muirhead, J.; Ebinger, C. J.; Tiberi, C.; Roecker, S. W.; Ferdinand-Wambura, R.; Kianji, G.; Mulibo, G. D.

    2014-12-01

    The volcanically active East African rift system in southern Kenya and northern Tanzania transects thick cratonic lithosphere, and comprises several basins characterized by deep crustal seismicity. The US-French-Tanzania-Kenya CRAFTI project aims to understand the role of magma and volatile movement during the initiation and evolution of rifting in cratonic lithosphere. Our 38-station broadband network spans all or parts of fault-bounded rift segments, enabling comparison of lithospheric structure, fault kinematics, and seismogenic layer thickness with age and proximity to the deeply rooted Archaen craton. Seismicity levels are high in all basins, but we find profound differences in seismogenic layer thickness along the length of the rift. Seismicity in the Manyara basin occurs almost exclusively within the lower crust, and in spatial clusters that have been active since 1990. In contrast, seismicity in the ~ 5 My older Magadi basin is localized in the upper crust, and the long border fault bounding the west side of the basin is seismically inactive. Between these two basins lies the Natron rift segment, which shows seismicity between ~ 20 and ~2 km depth, and high concentrations at Oldoinyo Lengai and Gelai volcanoes. Older volcanoes on the uplifted western flank (e.g., Ngorongoro) experience swarms of activity, suggesting that active magmatism and degassing are widespread. Focal mechanisms of the frequent earthquakes recorded across the array are spatially variable, and indicate a stress field strongly influenced by (1) Holocene volcanoes, (2) mechanical interactions between adjacent rift basins, and (3) a far-field ESE-WNW extensional stress regime. We explore the spatial correlation between zones of intense degassing along fault systems and seismicity, and examine the influence of high gas pressures on lower and upper crustal seismicity in this youthful cratonic rift zone.

  2. Modes, tempo, and spatial variability of Cenozoic cratonic denudation: The West African example

    NASA Astrophysics Data System (ADS)

    Beauvais, Anicet; Chardon, Dominique

    2013-05-01

    long-term erosion of tropical shields is crucial to constraining the role of lateritic regolith covers as prominent sinks and sources of CO2 and sediments in the context of long-term Cenozoic climate change. It is also a key to understanding long-term landform evolution processes operating over most of the continental surface and their control onto the sediment routing system. We study the surface evolution of West Africa over three erosion periods (~ 45-24, ~ 24-11 and ~ 11-0 Ma) recorded by relicts of three subcontinental-scale lateritic paleolandsurfaces whose age is bracketed by 39Ar/40Ar dating of lateritic K-Mn oxides. Denudation depths and rates compiled from 380 field stations show that despite heterogeneities confined to early-inherited reliefs, the subregion underwent low and homogeneous denudation (~ 2-20 m Ma-1) over most of its surface whatever the considered time interval. This homogeneity is further documented by a worldwide compilation of cratonic denudation rates, over long-term, intermediate and modern Cenozoic time scales (100-107 yr). These results allow defining a steady state cratonic denudation regime that is weathering-limited, i.e., controlled by the thickness of the (lateritic) regolith available for stripping. Steady state cratonic denudation regimes are enabled by maintained compartmentalization of the base levels between river knick points controlled by relief inheritance. Under such regimes, lowering of base levels and their fossilization are primarily imposed by long-term eustatic sea level fall and climate rather than by epeirogeny. The expression of steady state cratonic denudation regimes in clastic sedimentary fluxes remains to be investigated.

  3. Cold cratonic roots and thermal blankets: How continents affect mantle convection

    USGS Publications Warehouse

    Trubitsyn, V.P.; Mooney, W.D.; Abbott, D.H.

    2003-01-01

    Two-dimensional convection models with moving continents show that continents profoundly affect the pattern of mantle convection. If the continents are wider than the wavelength of the convection cells (???3000 km, the thickness of the mantle), they cause neighboring deep mantle thermal upwellings to coalesce into a single focused upwelling. This focused upwelling zone will have a potential temperature anomaly of about 200??C, much higher than the 100??C temperature anomaly of upwelling zones generated beneath typical oceanic lithosphere. Extensive high-temperature melts (including flood basalts and late potassic granites) will be produced, and the excess temperature anomaly will induce continental uplift (as revealed in sea level changes) and the eventual breakup of the supercontinent. The mantle thermal anomaly will persist for several hundred million years after such a breakup. In contrast, small continental blocks (<1000 km diameter) do not induce focused mantle upwelling zones. Instead, small continental blocks are dragged to mantle downwelling zones, where they spend most of their time, and will migrate laterally with the downwelling. As a result of sitting over relatively cold mantle (downwellings), small continental blocks are favored to keep their cratonic roots. This may explain the long-term survival of small cratonic blocks (e.g., the Yilgarn and Pilbara cratons of western Australia, and the West African craton). The optimum size for long-term stability of a continental block is <3000 km. These results show that continents profoundly affect the pattern of mantle convection. These effects are illustrated in terms of the timing and history of supercontinent breakup, the production of high-temperature melts, and sea level changes. Such two-dimensional calculations can be further refined and tested by three-dimensional numerical simulations of mantle convection with moving continental and oceanic plates.

  4. Crustal and Lithospheric Structure across the Boundary of the East European Craton from Receiver Functions

    NASA Astrophysics Data System (ADS)

    Knapmeyer-Endrun, B.; Krueger, F.

    2014-12-01

    The Trans-European Suture Zone (TESZ), which extends from the North Sea to the Black Sea, marks a fundamental lithospheric boundary in Europe. It separates the East European Craton to the north-east, which has been stable for at least 1.45 Ga, from the younger lithosphere of Phanerozoic Europe to the south-west. In this study we use a large dataset of more than 40,000 teleseismic P- and S-receiver functions from almost 500 seismological stations to image crustal and lithospheric structure across central and eastern Europe between the Benelux and the Baltic countries. An important data source is the PASSEQ project, which deployed close to 200 temporary stations between Germany and Lithuania for two years with the aim to obtain detailed, 3D information on the upper mantle structure across the TESZ. Combining P and S observations, we find a stepwise transition in crustal thickness, spread over 200 km laterally, from on average of 30 km in Phanerozoic Europe to more than 45 km beneath the East European Craton. Individual Paleoproterozoic terranes in Lithuania can also be distinguished based on crustal thickness. Crustal layering is not resolved with the receiver functions, but a high Poisson's ratio of 0.27 is obtained for the craton, compared to 0.25 for Phanerozoic Europe, which is consistent with a thick mafic lower crust. Moho depth results show an excellent correlation with the interpretation of a seismic line in the area, lending confidence to the interpretation of deeper structures. The lithosphere-asthenosphere boundary (LAB), as mapped by S-receiver functions, is located at an average depth of 90 km beneath Phanerozoic Europe. Towards the east, the LAB is dipping to about 125 km depth beneath the Elbe Line. Below the craton, a mid-lithospheric discontinuity is found at about 80 km depth, whereas weak indications of the LAB are found at an average depth of 260 km.

  5. Environmental contaminants in canvasbacks wintering on San Francisco Bay, California

    USGS Publications Warehouse

    Miles, A.K.; Ohlendorf, H.M.

    1993-01-01

    The concentrations of 11 trace elements, 21 organochlorines, 13 polycyclic aromatic hydrocarbons, and 13 aliphatic hydrocarbons were determined in canvasbacks (Aythya valisineria) wintering on San Francisco Bay, California during 1988. With the exception of Se, concentrations of potentially toxic elements were low. Similarly, concentrations of most organic compounds were near or below detection limits. Aliphatic hydrocarbons, PCBs, and DDE were common, but at levels lower than those known to be harmful to waterfowl. Innocuous trace elements (Cu, Fe, and Zn), which are often associated with anthropogenic contamination, occurred at high levels. Concentrations of toxic elements were several times lower and those of benign elements were similar or greater than concentrations reported for surf scoters (Melanitta perspicillata) or greater scaup (Aythya marila) from San Francisco Bay.

  6. Sand waves at the mouth of San Francisco Bay, California

    USGS Publications Warehouse

    Gibbons, Helen; Barnard, Patrick L.

    2007-01-01

    The U.S. Geological Survey; California State University, Monterey Bay; U.S. Army Corps of Engineers; National Oceanic and Atmospheric Administration; and Center for Integrative Coastal Observation, Research and Education partnered to map central San Francisco Bay and its entrance under the Golden Gate Bridge using multibeam echosounders. View eastward, through the Golden Gate into central San Francisco Bay. Depth of sea floor color coded: red (less than 10 m deep) to purple (more than 100 m deep). Land from USGS digital orthophotographs (DOQs) overlaid on USGS digital elevation models (DEMs). Sand waves in this view average 6 m in height and 80 m from crest to crest. Golden Gate Bridge is about 2 km long. Vertical exaggeration is approximately 4x for sea floor, 2x for land.

  7. How Did the North China Craton Move from Nuna to Rodinia

    NASA Astrophysics Data System (ADS)

    Zhang, S.

    2015-12-01

    Several models that include the paleogeographic positions of the North China Craton (NCC) in Precambrian supercontinents Nuna and Rodinia were tested in this study using Proterozoic global paleomagnetic database. During ca. 1.8 - 1.4 Ga, the NCC can be placed far from Laurentia and Baltica. In Nuna, the present southern margin of the NCC faced an open ocean, whilst its present northern margin was likely connected to Indian and Australian cratons. In Rodinia, however, during ca. 1.1 - 0.85 Ga, the paleomagnetic data indicate a proximate connection between the NCC and the arctic side of Laurentia. These two models, if both are right, suggest that the NCC may have moved a long distance since the departure from Nuna to the joining of Rodinia. Moreover, paleomagnetic data and our reconstructions require many cratons to drift away from their connections in Nuna after ca. 1.35 Ga. These reconstructions strongly challenges the currently influential speculation of limited breakup of Nuna, which is mainly based on the observation of low abundance of passive margins that were formed during the boring billion years (ca. 1.75 - 0.75 Ga).

  8. P wave radial anisotropy tomography of the upper mantle beneath the North China Craton

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Wu, Huohua; Zhao, Dapeng

    2014-06-01

    present the first P wave radial anisotropy tomography of the crust and upper mantle beneath the North China Craton (NCC), determined using a large number of high-quality arrival-time data of local earthquakes and teleseismic events. Our results show a prominent high-velocity (high-V) anomaly down to ˜250 km depth beneath the Ordos block, a high-V anomaly in the mantle transition zone beneath the eastern NCC, and a low-velocity (low-V) anomaly down to ˜300 km depth beneath the Trans-North China Orogen (TNCO). The Ordos block exhibits significant negative radial anisotropy (i.e., vertical Vp > horizontal Vp), suggesting that its cratonic lithosphere has kept the frozen-in anisotropy formed by vertical growth via high-degree melting mantle plume in the early Earth. Prominent low-V anomalies with positive radial anisotropy (i.e., horizontal Vp > vertical Vp) exist beneath the Qilian and Qaidam blocks down to ˜400 km depth, suggesting that the horizontal material flow resulting from the Tibetan Plateau is blocked by the Ordos thick lithosphere. Beneath the eastern NCC, high-V anomalies with negative radial anisotropy exist in the upper mantle, possibly reflecting sinking remains of the Archean cratonic lithosphere. A high-V anomaly with positive radial anisotropy is revealed in the mantle transition zone under the eastern NCC, which reflects the stagnant Pacific slab.

  9. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction

    PubMed Central

    Guex, Jean; Pilet, Sebastien; Müntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Sell, Bryan; Schaltegger, Urs

    2016-01-01

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here we present a synthesis of ammonite biostratigraphy, isotopic data and high precision U-Pb zircon dates from the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries demonstrating that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. We explain these transitions as a result of changing gas species emitted during the progressive thermal erosion of cratonic lithosphere by plume activity or internal heating of the lithosphere. Our petrological model for LIP magmatism argues that initial gas emission was dominated by sulfur liberated from sulfide-bearing cratonic lithosphere before CO2 became the dominant gas. This model offers an explanation of why LIPs erupted through oceanic lithosphere are not associated with climatic and biotic crises comparable to LIPs emitted through cratonic lithosphere. PMID:27009463

  10. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction

    NASA Astrophysics Data System (ADS)

    Guex, Jean; Pilet, Sebastien; Müntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Sell, Bryan; Schaltegger, Urs

    2016-03-01

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here we present a synthesis of ammonite biostratigraphy, isotopic data and high precision U-Pb zircon dates from the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries demonstrating that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. We explain these transitions as a result of changing gas species emitted during the progressive thermal erosion of cratonic lithosphere by plume activity or internal heating of the lithosphere. Our petrological model for LIP magmatism argues that initial gas emission was dominated by sulfur liberated from sulfide-bearing cratonic lithosphere before CO2 became the dominant gas. This model offers an explanation of why LIPs erupted through oceanic lithosphere are not associated with climatic and biotic crises comparable to LIPs emitted through cratonic lithosphere.

  11. Moho offsets beneath the Western Ghat and the contact of Archean crusts of Dharwar Craton, India

    NASA Astrophysics Data System (ADS)

    Saikia, Utpal; Rai, S. S.; Meena, Rishikesh; Prasad, B. N. V.; Borah, Kajaljyoti

    2016-03-01

    We present the Moho depth variation along a 600 km long profile from the west to the east coast of South India covering the passive continental margin, and the Western Ghat escarpment created during India-Madagascar separation at ~ 85 Ma; Archean western and eastern Dharwar Craton, and Proterozoic basin. The image is generated through three different approaches: H - vP/vS stacking, common conversion point (CCP) migration and inversion of teleseismic receiver functions at 38 locations. The Moho depth along the profile varies smoothly between 34 and 41 km, except beneath the Western Ghat and at the contact of east and west Dharwar Craton, where it is offset by up to ~ 8 km. The study suggests (i) the possible differential uplift of the Western Ghat, as a consequence of India-Madagascar separation and the prominent role of deep crustal structure in the location of the escarpment, compared to the surface process and (ii) presence of long-lived steeply dipping fault separating the two distinct Archean crustal blocks indicative of mechanically strong continental lithosphere beneath the Dharwar Craton.

  12. Lithospheric Structure of the Northeastern North China Craton Imaged by S Receiver Functions

    NASA Astrophysics Data System (ADS)

    Wang, Xingchen; Ding, Zhifeng; Zhu, Lupei

    2016-08-01

    Lithosphere thickness variation is important for understanding the significant tectonic reactivation of the North China Craton (NCC) in the Mesozoic and Cenozoic time. Here, we determined the lithospheric structure in the northeastern NCC using S receiver functions from 305 teleseismic events recorded by 223 seismic stations. The Moho and lithosphere-asthenosphere boundary (LAB) are imaged clearly beneath the region. The Moho depth decreases from ~45 km beneath the western NCC to ~25 km beneath the eastern NCC. We found that the lithospheric thickness varies from 60 to 80 km beneath the Trans-North China Orogen (TNCO) and eastern NCC with no significant change of the LAB depth. The lithosphere thickness beneath the northwestern Ordos plateau is 100-130 km. In addition, there is a mid-lithosphere discontinuity at a depth of 80 km beneath the plateau that is connected to the base of thinned lithosphere in TNCO and eastern NCC. We suggest that the mid-lithosphere discontinuity represents a mechanically weak zone in the original cratonic lithosphere of the NCC. The material in the lower lithosphere of the craton, when warmed and hydrated by water released from the subducting slab of Western Pacific, became weak due to decrease in viscosity and/or partial melting and was subsequently removed through small-scale mantle convections.

  13. Regional geophysics and the basement of cratonic basins: a comparative study with the Michigan basin

    SciTech Connect

    Hinze, W.J.; Lidiak, E.G.

    1986-08-01

    The basement of the Michigan basin consists of four major provinces - the complex metasedimentary, metavolcanic, and igneous rocks of the Penokean orogenic assemblage in the north, the felsic anorogenic igneous rocks to the south, the highly metamorphosed schists, gneisses, and related igneous intrusions of the Grenville province in the east, and a middle Proterozoic rift zone, which transects the basin from the north to the southeast margin. Sparse basement drill holes and characteristic geophysical patterns support this interpretation. The direct geologic information on the basement of other cratonic basins is not as well known. However, regional geophysical surveys and sparse, poorly distributed basement drill holes provide information on the complex character and structural relationships of the basement of other basins. Like the Michigan basin, many cratonic basins (e.g., Illinois, Williston, and Paris basins) are underlain by dense and commonly more magnetic rocks than adjacent areas. As in the Michigan basin, these rocks are interpreted to have a profound effect on the origin and tectonic development of the basins. Geologic and geophysical evidence indicates that many of these dense basement rocks originated in rifts that formed hundreds of millions of years prior to basin development. A comparison of the basement in cratonic basins provides important constraints on the origin and tectonic development of the Michigan basin.

  14. Thermal erosion of cratonic lithosphere as a potential trigger for mass-extinction.

    PubMed

    Guex, Jean; Pilet, Sebastien; Müntener, Othmar; Bartolini, Annachiara; Spangenberg, Jorge; Schoene, Blair; Sell, Bryan; Schaltegger, Urs

    2016-01-01

    The temporal coincidence between large igneous provinces (LIPs) and mass extinctions has led many to pose a causal relationship between the two. However, there is still no consensus on a mechanistic model that explains how magmatism leads to the turnover of terrestrial and marine plants, invertebrates and vertebrates. Here we present a synthesis of ammonite biostratigraphy, isotopic data and high precision U-Pb zircon dates from the Triassic-Jurassic (T-J) and Pliensbachian-Toarcian (Pl-To) boundaries demonstrating that these biotic crises are both associated with rapid change from an initial cool period to greenhouse conditions. We explain these transitions as a result of changing gas species emitted during the progressive thermal erosion of cratonic lithosphere by plume activity or internal heating of the lithosphere. Our petrological model for LIP magmatism argues that initial gas emission was dominated by sulfur liberated from sulfide-bearing cratonic lithosphere before CO2 became the dominant gas. This model offers an explanation of why LIPs erupted through oceanic lithosphere are not associated with climatic and biotic crises comparable to LIPs emitted through cratonic lithosphere. PMID:27009463

  15. Reactivation and mantle dynamics of North China Craton: insight from P-wave anisotropy tomography

    NASA Astrophysics Data System (ADS)

    Tian, You; Zhao, Dapeng

    2013-12-01

    We determined the first 3-D P-wave anisotropic tomography beneath the North China Craton (NCC) using a large number of high-quality arrival-time data from local earthquakes and teleseismic events, which reveals depth-dependent azimuthal anisotropy in the crust and upper mantle down to 600 km depth. In the NCC western block, the fast velocity direction (FVD) varies from east-west in the southern part to northeast-southwest in the northern part, which may reflect either the interaction between the Yangtze block and NCC or fossil lithospheric fabrics in the craton. Under the NCC eastern block, a uniform northwest-southeast FVD is revealed in the lower part of the upper mantle (300-410 km depths) and the mantle transition zone (410-660 km depths), which may reflect horizontal and upwelling flows in the big mantle wedge (BMW) above the stagnant Pacific slab in the mantle transition zone. The NCC central block exhibits a northeast-southwest FVD, consistent with the surface tectonic orientation there, suggesting that the cold and thick (>300 km) cratonic root of the NCC western block may obstruct the northwest-southeast trending mantle flow induced by the Pacific Plate subduction, resulting in a northeast-southwest trending mantle flow under the central block. Our present results indicate that the corner flow in the BMW associated with the deep subduction of the Pacific Plate is the main cause of NCC reactivation and mantle dynamics under East China.

  16. Lithospheric Structure of the Northeastern North China Craton Imaged by S Receiver Functions

    NASA Astrophysics Data System (ADS)

    Wang, Xingchen; Ding, Zhifeng; Zhu, Lupei

    2016-04-01

    Lithosphere thickness variation is important for understanding the significant tectonic reactivation of the North China Craton (NCC) in the Mesozoic and Cenozoic time. Here, we determined the lithospheric structure in the northeastern NCC using S receiver functions from 305 teleseismic events recorded by 223 seismic stations. The Moho and lithosphere-asthenosphere boundary (LAB) are imaged clearly beneath the region. The Moho depth decreases from ~45 km beneath the western NCC to ~25 km beneath the eastern NCC. We found that the lithospheric thickness varies from 60 to 80 km beneath the Trans-North China Orogen (TNCO) and eastern NCC with no significant change of the LAB depth. The lithosphere thickness beneath the northwestern Ordos plateau is 100-130 km. In addition, there is a mid-lithosphere discontinuity at a depth of 80 km beneath the plateau that is connected to the base of thinned lithosphere in TNCO and eastern NCC. We suggest that the mid-lithosphere discontinuity represents a mechanically weak zone in the original cratonic lithosphere of the NCC. The material in the lower lithosphere of the craton, when warmed and hydrated by water released from the subducting slab of Western Pacific, became weak due to decrease in viscosity and/or partial melting and was subsequently removed through small-scale mantle convections.

  17. Groundwater quality in the San Francisco Bay groundwater basins, California

    USGS Publications Warehouse

    Parsons, Mary C.; Kulongoski, Justin T.; Belitz, Kenneth

    2013-01-01

    Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Selected groundwater basins of the San Francisco Bay area constitute one of the study units being evaluated.

  18. Aggregate Settling Velocities in San Francisco Estuary Margins

    NASA Astrophysics Data System (ADS)

    Allen, R. M.; Stacey, M. T.; Variano, E. A.

    2015-12-01

    One way that humans impact aquatic ecosystems is by adding nutrients and contaminants, which can propagate up the food web and cause blooms and die-offs, respectively. Often, these chemicals are attached to fine sediments, and thus where sediments go, so do these anthropogenic influences. Vertical motion of sediments is important for sinking and burial, and also for indirect effects on horizontal transport. The dynamics of sinking sediment (often in aggregates) are complex, thus we need field data to test and validate existing models. San Francisco Bay is well studied and is often used as a test case for new measurement and model techniques (Barnard et al. 2013). Settling velocities for aggregates vary between 4*10-5 to 1.6*10-2 m/s along the estuary backbone (Manning and Schoellhamer 2013). Model results from South San Francisco Bay shoals suggest two populations of settling particles, one fast (ws of 9 to 5.8*10-4 m/s) and one slow (ws of < 1*10-7 to 1.4*10-5 m/s) (Brand et al. 2015). While the open waters of San Francisco Bay and other estuaries are well studied and modeled, sediment and contaminants often originate from the margin regions, and the margins remain poorly characterized. We conducted a 24 hour field experiment in a channel slough of South San Francisco Bay, and measured settling velocity, turbulence and flow, and suspended sediment concentration. At this margin location, we found average settling velocities of 4-5*10-5 m/s, and saw settling velocities decrease with decreasing suspended sediment concentration. These results are consistent with, though at the low end of, those seen along the estuary center, and they suggest that the two population model that has been successful along the shoals may also apply in the margins.

  19. Contaminant levels in fish tissue from San Francisco Bay

    SciTech Connect

    Fairey, R.; Taberski, K.

    1995-12-31

    Edible fish species were collected from thirteen locations throughout San Francisco Bay, during the spring of 1994, for determination of contaminants levels in muscle tissue. Species collected included white croaker, surfperch, leopard and brown smoothhound sharks, striped bass, white sturgeon and halibut Sixty six composite tissue samples were analyzed for the presence of PAHs, PCBs, pesticides, trace elements and dioxin/furans. The US EPA approach to assessing chemical contaminant data for fish tissue consumption was used for identifying the primary chemicals of concern. Six chemicals or chemical groups were found to exceed screening levels established using the US EPA approach. PCBs (as total Aroclors) exceeded the screening level of 3 ppb in all sixty six tissue samples, with the highest concentrations (638 ppb) found near San Francisco`s industrial areas. Mercury was elevated (> 0.14 ppm) in forty of the sixty-six samples with the highest levels (1.26 ppm) occurring in shark muscle tissues. Concentrations of the organochlorine pesticides dieldrin, total chlordanes and total DDTs exceeded screening levels in a number of samples. Dioxin/furans (as TEQs) were elevated (above 0.15 ppt) in 16 of the 19 samples analyzed. Fish with high lipid content (croaker and surfperch) in their muscle tissue generally exhibited higher contaminant levels while fish with low lipid levels (halibut and shark) exhibited lower organic contaminant levels. Tissue samples taken from North Bay stations most often exhibited high levels of chemical contamination. The California Office of Health Hazard Assessment is currently evaluating the results of this study and has issued an interim Health Advisory concerning the human consumption of fish tissue from San Francisco Bay.

  20. Ice, quakes, and a wobble shake San Francisco

    SciTech Connect

    Kerr, R.A.

    1995-01-06

    The fall meeting of the American Geophysical Union (AGU) in San Francisco last month was bumped to the Moscone Center while the Civic Auditorium, its venue in past years, was being reinforced against earthquakes. And that may have been fitting, given the meeting`s focus on sudden events in Earth history; the first moments of fault rupture, repeated outbursts of icebergs during the last ice age, and a shift in the seasons in the middle of this century.

  1. The earthquake educational institute at San Francisco State University

    USGS Publications Warehouse

    Sullivan, R.; Pestrong, R.; Strongin, H.

    1980-01-01

    The Earthquake Educational Institute was established in 1978 at San Francisco State University under a grant from the U.S National Science Foundation. The goal of the Institute is to develop earthquake-related curricula for use in elementary and secondary schools in the hope that, by educating students about earthquakes, they will be better prepared for the disruptions associated with a major quake. To date, about 140 elementary and secondary school teachers and administrators have enrolled in the program. 

  2. Microbial diversity in restored wetlands of San Francisco Bay

    SciTech Connect

    Theroux, Susanna; Hartman, Wyatt; He, Shaomei; Tringe, Susannah

    2013-12-09

    Wetland ecosystems may serve as either a source or a sink for atmospheric carbon and greenhouse gases. This delicate carbon balance is influenced by the activity of belowground microbial communities that return carbon dioxide and methane to the atmosphere. Wetland restoration efforts in the San Francisco Bay-Delta region may help to reverse land subsidence and possibly increase carbon storage in soils. However, the effects of wetland restoration on microbial communities, which mediate soil metabolic activity and carbon cycling, are poorly studied. In an effort to better understand the underlying factors which shape the balance of carbon flux in wetland soils, we targeted the microbial communities in a suite of restored and historic wetlands in the San Francisco Bay-Delta region. Using DNA and RNA sequencing, coupled with greenhouse gas monitoring, we profiled the diversity and metabolic potential of the wetland soil microbial communities along biogeochemical and wetland age gradients. Our results show relationships among geochemical gradients, availability of electron acceptors, and microbial community composition. Our study provides the first genomic glimpse into microbial populations in natural and restored wetlands of the San Francisco Bay-Delta region and provides a valuable benchmark for future studies.

  3. The phytoplankton component of seston in San Francisco Bay

    USGS Publications Warehouse

    Wienke, S.M.; Cloern, J.E.

    1987-01-01

    Phytoplankton biomass (as carbon) was estimated from chlorophyll a concentrations (Chla) and a mean value for the ratio of phytoplankton carbon to chlorophyll a in San Francisco Bay. The ratio was determined as the slope of a Model II regression of POC' against (Chla), where POC' is total particulate organic carbon minus sediment-associated non-phytoplankton carbon. Samples from 30 fixed sites in the channel and lateral shoals of San Francisco Bay were collected once or twice a month from April to November 1980, and at irregular intervals in South Bay during 1984 and 1985. For all data the calculated mean value of phytoplankton C:Chla was 51 (95% confidence interval = 47-54). No significant differences were found in the C:Chla ratio between shallow and deep sites (where light availability differs) or between northern and southern San Francisco Bay (where phytoplankton community composition differs). Using the mean C:Chla ratio of 51, we calculated that phytoplankton biomass constitutes about one third of seston carbon under most circumstances, but this fraction ranges from about 95% during phytoplankton blooms to less than 20% during spring periods of low phytoplankton biomass and high suspended sediment concentration. ?? 1987.

  4. Magnetostratigraphic Study of Chengde Basin, Yanshan Area and its Restriction on the Peaking Age of North China Craton Destruction

    NASA Astrophysics Data System (ADS)

    Cai, S.; He, H.; Zhu, R.

    2011-12-01

    The timing of North China Craton destruction has been contineous paid attention to. There have already been plenty of research from Geology, Geophysics and Geochemistry. However, the exact destruction age of North China Craton is still controversial. In this paper, we try to put forward geomagnetic evidence of the peaking destruction age of North China Craton. Yanshan orogen is located at the north edge of North China Craton and affected significantly by its destruction. Chengde Basin is located at the middle section of Yanshan orogen, which makes it an ideal area for studying the basin record of North China Craton destruction. Oriented core samples are collected from Yuanjiazhuang section of Chengde Basin for magnetostratigraphic and rock-magnetic study. Fresh massive volcanic samples are also collected for radiometric dating. The rock-magnetic results show that magnetic minerals of volcanics are complex, including magnetite, maghemite and hematite while sedimentary magnetic minerals are mainly magnetite, possibly including small amount of maghemite and hematite. An age of 128~129Ma is obtained from the radiometric dating result. Magnetostratigraphic result shows three polarity sections: the lower normal section(N2), the reversal section(R1) and the upper normal section(N1). Comparing with the Geologic Time Scale 2004 and combining the radiometric result, it is believed that the N2 section is related to M3n, R1 related to M1r and N1 related to M1n. Therefore, the start age of lacustrine sediment at Yuanjiazhuang section is ~128Ma. According to the magnetostratigraphic study and radiometric dating of Chengde Basin in Yanshan area, the peak destruction age of North China Craton is confirmed to be no later than 128Ma. It is believed that North China Craton destruction is the primary element leading to Mesozoic basin at the Yanshan area changed from Late Triassic-Late Jurassic flexural basin to rift basin. One of the shallow responses accompanying with the peak age of

  5. Melt-Peridotite Reaction Mechanism of North China Craton Destruction: Experimental Constrains

    NASA Astrophysics Data System (ADS)

    Wang, C.; Jin, Z.; Gao, S.; Zhang, J.; Zheng, S.

    2009-12-01

    Although the geoscientsts in the world have reached an agreement about the Mesozoic thinning of North China Craton, the dynamics of this process is still under debate, especially the thinning mechanism. There are two popular thinning mechanisms were proposed for the North China Craton, one is the delamination model and the other is thermo-mechanical erosion model. The delamination model has aroused great interests since Gao et al. use it to explain the formation of Xilonggou high Mg# andesite from Liaoxi region of Liaoning Province. These Lavas, which possessed an adakitic signature with high Mg#, were believed to origin by the interaction between silica rich and yttrium delepted melt, which are formed by partile melting of low crust eclogite, and asthenospheric peridotite. The discovery of zoned mantle olivine and pyroxene xenocrysts, especially zoned mantle peridotitic xenoliths in Mesozoic basaltic rocks from eastern North China, indicates that peridotite-melt reaction was widespread in Mesozoic lithospheric mantle beneath the southeastern North China craton. Such interaction could be an important mechanism for the compositional transformation and rapid enrichment of the lithospheric mantle. We conducted a series of experiments at a pressure of 2.0 GPa and temperatures of 1250-1400 °C using Bixiling eclogite and Damaping peridotite as starting materials to study the mechanism of melt-peridotite reaction. Our results show that olivine and orthopyroxene were dissolved in the reacting melts between eclogite and peridotite, resulting in clinopyroxene precipitation along the interface of melts and lherzolite. The experimental run products, possessing a lherzolite-pyroxenite-garnet pyroxenite sequence, are identical to the composite mantle xenoliths in the Neogene Hannuoba basalt of the North China craton. The later is considered as strong evidence of the maffic lower continental crust recycling into the mantle during the Mesozoic Era. The reacting melts have a high

  6. Seismic Tomography of the Arctic: Continental Cratons, Ancient Orogens, Oceanic Lithosphere and Convecting Mantle Beneath (Invited)

    NASA Astrophysics Data System (ADS)

    Lebedev, S.; Schaeffer, A. J.

    2013-12-01

    Lateral variations in seismic velocities in the upper mantle, mapped by seismic tomography, reflect primarily the variations in the temperature of the rock at depth. Seismic tomography thus reveals lateral changes in the temperature and thickness of the lithosphere; it maps deep boundaries between tectonic blocks with different properties and with different age of the lithosphere. Our new global, shear-wave tomographic model of the upper mantle and the crust is constrained by an unprecedentedly large number of broadband waveform fits (nearly one million seismograms, with both surface and S waves included) and provides improved resolution of the lithosphere across the whole of the Arctic region, compared to other available models. The most prominent high-velocity anomalies, seen down to 150-200 km depths, indicate the cold, thick, stable mantle lithosphere beneath Precambrian cratons. The northern boundaries of the Canadian Shield's and Greenland's cratonic lithosphere closely follow the coastlines, with the Greenland and North American cratons clearly separated from each other. In Eurasia, in contrast, cratonic lithosphere extends hundreds of kilometres north of the coast of the continent, beneath the Barents and eastern Kara Seas. The boundaries of the Archean cratons mapped by tomography indicate the likely offshore extensions of major Phanerozoic sutures in northern Eurasia. The old oceanic lithosphere of the Canada Basin is much colder and thicker than the younger lithosphere beneath the adjacent Amundsen Basin, north of the Gakkel Ridge. Beneath the slow-spreading Gakkel Ridge, we detect the expected low-velocity anomaly associated with partial melting in the uppermost mantle; the anomaly is weaker, however, than beneath faster-spreading ridges globally. South of the ridge, the Nansen Basin shows higher seismic velocities in the upper mantle beneath it, compared to the Amundsen Basin. At 150-250 km depth, most of the oceanic portions of the central Arctic (the

  7. Aeromagnetic interpretation in the south-central Zimbabwe Craton: (reappraisal of) crustal structure and tectonic implications

    NASA Astrophysics Data System (ADS)

    Ranganai, Rubeni T.; Whaler, Kathryn A.; Ebinger, Cynthia J.

    2015-12-01

    Regional aeromagnetic data from the south-central Zimbabwe Craton have been digitally processed and enhanced for geological and structural mapping and tectonic interpretation integrated with gravity data, to constrain previous interpretations based on tentative geologic maps and provide new information to link these structural features to known tectonic events. The derived maps show excellent correlation between magnetic anomalies and the known geology, and extend lithological and structural mapping to the shallow/near subsurface. In particular, they reveal the presence of discrete crustal domains and several previously unrecognised dykes, faults, and ultramafic intrusions, as well as extensions to others. Five regional structural directions (ENE, NNE, NNW, NW, and WNW) are identified and associated with trends of geological units and cross-cutting structures. The magnetic lineament patterns cut across the >2.7 Ga greenstone belts, which are shown by gravity data to be restricted to the uppermost 10 km of the crust. Therefore, the greenstone belts were an integral part of the lithosphere before much of the upper crustal (brittle) deformation occurred. Significantly, the observed magnetic trends have representatives craton-wide, implying that our interpretation and inferences can be applied to the rest of the craton with confidence. Geological-tectonic correlation suggests that the interpreted regional trends are mainly 2.5 Ga (Great Dyke age) and younger, and relate to tectonic events including the reactivation of the Limpopo Belt at 2.0 Ga and the major regional igneous/dyking events at 1.8-2.0 Ga (Mashonaland), 1.1 Ga (Umkondo), and 180 Ma (Karoo). Thus, their origin is here inferred to be inter- and intra-cratonic collisions and block movements involving the Zimbabwe and Kaapvaal Cratons and the Limpopo Belt, and later lithospheric heating and extension associated with the break-up of Gondwana. The movements produced structures, or reactivated older fractures

  8. The provenance of sub-cratonic mantle beneath the Limpopo Mobile Belt (South Africa)

    NASA Astrophysics Data System (ADS)

    van der Meer, Quinten H. A.; Klaver, Martijn; Waight, Tod E.; Davies, Gareth R.

    2013-06-01

    Petrological, whole rock major element and mineral chemical analysis of mantle xenoliths from the Venetia kimberlite pipes (533 Ma) in South Africa reveals an apparently stratified cratonic mantle beneath the Central Zone of the Limpopo Mobile Belt (LMB) that separates the Kaapvaal and Zimbabwe Cratons. Combined pressure-temperature (P-T) data and petrographic observations indicate that the mantle consists of an upper layer of Low-T coarse-equant garnet + spinel lherzolite (~ 50 to ~ 130 km depth). This layer is underlain by a region of mixed garnet harzburgites and garnet lherzolites that are variably deformed (~ 130 to ~ 235 km depth). An equilibrated geotherm did not exist at the time of kimberlite eruption (533 Ma) and a localised heating event involving the introduction of asthenospheric material to the High-T lithosphere below 130 km is inferred. Low-T garnet-spinel lherzolites are highly melt depleted (40% on average). In contrast, the High-T lithosphere (mostly at diamond stable conditions) consists of a mixed zone of variably sheared and melt depleted (30% on average) garnet harzburgite and mildly melt depleted (20% on average) garnet lherzolite. The chemistry of the High-T xenoliths contrasts with that of minerals included in diamond originating from the same depth. Inclusions suggest diamond crystallisation in a more melt depleted lithosphere than represented by either Low- or High-T xenoliths. High-T xenoliths are proposed to represent formerly melt depleted lithosphere, refertilised by asthenosphere-derived melts during the diapiric rise of a proto-kimberlitic melt pocket. This process is coupled to the positive temperature perturbation observed in the High-T xenoliths and may represent a common process in the lower lithosphere related to localised but intense tectono-magmatic events immediately preceding kimberlite eruption. The presence of clinopyroxene, garnet and abundant orthopyroxene in the Low-T lherzolite implies a history of melt depletion

  9. The building and stabilization of an Archean Craton in the Superior Province, Canada, from a heat flow perspective

    NASA Astrophysics Data System (ADS)

    Jaupart, C.; Mareschal, J.-C.; Bouquerel, H.; Phaneuf, C.

    2014-12-01

    How continental lithosphere responds to tectonic stresses and mantle convective processes is determined in large part by its mechanical strength and temperature distribution, which depend on crustal heat production. In order to establish reliable crustal and thermal models for the Superior Craton, Canadian Shield, new measurements of heat flux and heat production in 28 deep boreholes at 16 sites are combined with a larger set of older data. The Superior Province was assembled by the docking of volcanic/plutonic and metasedimentary terranes and continental fragments to the southern margin of an older core around 2.7 Ga. The average heat flux is much lower in the craton core than in the accreted terranes, 31 versus 43 mW m-2. The major accreted volcanic/plutonic belts share the same heat production characteristics, testifying to the remarkable uniformity of crust-building mechanisms. The marked difference between the crusts of the core and the accreted belts supports the operation of two different crust-forming processes. The crust of the craton core has an enriched upper layer, in contrast to that of the younger belts which lack marked internal differentiation. At the end of amalgamation, the lithosphere of the craton core was colder and mechanically stronger than the lithosphere beneath newly accreted material. Surrounding the craton core with weaker belts may have ensured its stability against tectonic and mantle convection perturbations. This large strength contrast accounts for the lack of lithospheric imbrication at the edge of the craton core as well as for the different characteristics of seismic anisotropy in the lithospheres of the craton core and the younger terranes.

  10. Plankton studies in San Francisco Bay; II, Phytoplankton abundance and species composition, July 1977-December 1979

    USGS Publications Warehouse

    Wong, Raymond L. J.; Cloern, James E.

    1981-01-01

    Data are presented on the phytoplankton species composition and abundance in San Francisco Bay from July 1977 through December 1979. Phytoplankton identification and enumerations were made at selected stations. Sample collections were made at selected stations in the main channel of the Bay from Rio Vista on the Sacramento River to Calaveras Point in South San Francisco Bay, and at shoal stations in the central portion of South San Francisco Bay, San Pablo Bay, and Suisun Bay. Also reported, from October 1978 through December 1979, are the calculated phytoplankton carbon and percent nondiatom carbon, and the species list. This study is one component of an ongoing interdisciplinary study of San Francisco Bay. (USGS)

  11. Upper mantle structure beneath southern African cratons from seismic finite-frequency P- and S-body wave tomography

    NASA Astrophysics Data System (ADS)

    Youssof, M.; Thybo, H.; Artemieva, I. M.; Levander, A.

    2015-06-01

    We present a 3D high-resolution seismic model of the southern African cratonic region from teleseismic tomographic inversion of the P- and S-body wave dataset recorded by the Southern African Seismic Experiment (SASE). Utilizing 3D sensitivity kernels, we invert traveltime residuals of teleseismic body waves to calculate velocity anomalies in the upper mantle down to a 700 km depth with respect to the ak135 reference model. Various resolution tests allow evaluation of the extent of smearing effects and help defining the optimum inversion parameters (i.e., damping and smoothness) for regularizing the inversion calculations. The fast lithospheric keels of the Kaapvaal and Zimbabwe cratons reach depths of 300-350 km and 200-250 km, respectively. The paleo-orogenic Limpopo Belt is represented by negative velocity perturbations down to a depth of ˜ 250 km, implying the presence of chemically fertile material with anomalously low wave speeds. The Bushveld Complex has low velocity down to ˜ 150 km, which is attributed to chemical modification of the cratonic mantle. In the present model, the finite-frequency sensitivity kernels allow to resolve relatively small-scale anomalies, such as the Colesberg Magnetic Lineament in the suture zone between the eastern and western blocks of the Kaapvaal Craton, and a small northern block of the Kaapvaal Craton, located between the Limpopo Belt and the Bushveld Complex.

  12. Laurentia and Salvador-Congo: Keystone cratons in Late Proterozoic break-up of Rodinia and assembly of Gondwana supercontinents

    SciTech Connect

    Unrug, R. . Dept. of Geological Sciences)

    1992-01-01

    The break-up of Rodinia, the supercontinent assembled in the Middle Proterozoic chelogenic cycle (1.65--1.0 Ga), and the simultaneous assembly of the Gondwana Supercontinent were the major tectonic events of the Neoproterozoic. Laurentia occupied a central keystone position in the configuration of Rodinia. Its break-up resulted in rearrangement of Rodinia fragments: some were incorporated in the accreting Gondwana, while Laurentia, Baltica and Siberia drifted independently. Reconstructions of the position of Laurentia in the Rodinia Supercontinent are based on two criteria. The first is the continuity of Middle Proterozoic mobile belts suturing the older cratons and the match of piercing points of the mobile belts at the post- Middle Proterozoic margins of the older cratons. The second is the similarity of sedimentary sequences along Late Proterozoic passive margins formed during break-up of Rodinia. The first criterion allows for several interpretations. The second may be invalid, as conjugate margins developing over an oblique detachment will accumulate dissimilar sedimentary sequences. In reconstructions of the Gondwana Supercontinent the recently redefined Salvador-Congo craton occupied the central keystone position, between the East Gondwana continent and a number of smaller cratons of West Gondwana. It is entirely surrounded by collisional mobile belts, all containing important transcurrent shear zone systems. The margins of the Salvador-Congo craton were facing three major Late Proterozoic oceans.

  13. Late Mesozoic and Cenozoic thermotectonic evolution along a transect from the north China craton through the Qinling orogen into the Yangtze craton, central China

    NASA Astrophysics Data System (ADS)

    Hu, Shengbiao; Raza, Asaf; Min, Kyoungwon; Kohn, Barry P.; Reiners, Peter W.; Ketcham, Richard A.; Wang, Jiyang; Gleadow, Andrew J. W.

    2006-12-01

    Cretaceous and Cenozoic reactivation of the Triassic Qinling-Dabie orogen between the north China and Yangtze cratons resulted from the combined effects of Pacific subduction-back-arc extension in east China and collisions in west China. We report new apatite fission track and apatite and zircon (U-Th)/He data from east Qinling along a >400-km-long N-S transect from Huashan through the Qinling orogen to Huangling. The ages show a general pattern of younging northward. Three major cooling phases are defined by modeling the multiple thermochronologic data sets. The first phase occurred locally in the North and South Qinling during the late Triassic to early Jurassic, following heating associated with the Triassic Yangtze subduction and exhumation of the Wudang metamorphic core complex on the cratonal edge. A second phase represents regional exhumation between 100 and 60 Ma, coeval with rifting marked by the Late Cretaceous-Eocene (K2-E) red bed deposition in eastern China and possibly indicating a link with Pacific subduction-back-arc extension in eastern China; however, it may also have been superimposed by eastward tectonic escape resulting from the Lhasa-West Burma-Qiangtang-Indochina collision. The third cooling phase was initiated at ˜45 Ma exclusively in the north Qinling and in the footwall of the graben-bounding normal fault of the Weihe graben in the Lesser Qinling. We suggest the third phase was related to reactivation of the Qinling fault system as a result of eastward tectonic escape imposed by the India-Asia collision at ˜50 Ma.

  14. LARGE-SCALE ASYMMETRIES IN THE TRANSITIONAL DISKS OF SAO 206462 AND SR 21

    SciTech Connect

    Pérez, Laura M.; Chandler, Claire J.; Isella, Andrea; Carpenter, John M.

    2014-03-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations in the dust continuum (690 GHz, 0.45 mm) and {sup 12}CO J = 6-5 spectral line emission of the transitional disks surrounding the stars SAO 206462 and SR 21. These ALMA observations resolve the dust-depleted disk cavities and extended gaseous disks, revealing large-scale asymmetries in the dust emission of both disks. We modeled these disk structures with a ring and an azimuthal Gaussian, where the azimuthal Gaussian is motivated by the steady-state vortex solution from Lyra and Lin. Compared to recent observations of HD 142527, Oph IRS 48, and LkHα 330, these are low-contrast (≲ 2) asymmetries. Nevertheless, a ring alone is not a good fit, and the addition of a vortex prescription describes these data much better. The asymmetric component encompasses 15% and 28% of the total disk emission in SAO 206462 and SR 21, respectively, which corresponds to a lower limit of 2 M {sub Jup} of material within the asymmetry for both disks. Although the contrast in the dust asymmetry is low, we find that the turbulent velocity inside it must be large (∼20% of the sound speed) in order to drive these azimuthally wide and radially narrow vortex-like structures. We obtain residuals from the ring and vortex fitting that are still significant, tracing non-axisymmetric emission in both disks. We compared these submillimeter observations with recently published H-band scattered light observations. For SR 21 the scattered light emission is distributed quite differently from the submillimeter continuum emission, while for SAO 206462 the submillimeter residuals are suggestive of spiral-like structure similar to the near-IR emission.

  15. Airport Choice in Sao Paulo Metropolitan Area: An Application of the Conditional Logit Model

    NASA Technical Reports Server (NTRS)

    Moreno, Marcelo Baena; Muller, Carlos

    2003-01-01

    Using the conditional LOGIT model, this paper addresses the airport choice in the Sao Paulo Metropolitan Area. In this region, Guarulhos International Airport (GRU) and Congonhas Airport (CGH) compete for passengers flying to several domestic destinations. The airport choice is believed to be a result of the tradeoff passengers perform considering airport access characteristics, airline level of service characteristics and passenger experience with the analyzed airports. It was found that access time to the airports better explain the airport choice than access distance, whereas direct flight frequencies gives better explanation to the airport choice than the indirect (connections and stops) and total (direct plus indirect) flight frequencies. Out of 15 tested variables, passenger experience with the analyzed airports was the variable that best explained the airport choice in the region. Model specifications considering 1, 2 or 3 variables were tested. The model specification most adjusted to the observed data considered access time, direct flight frequencies in the travel period (morning or afternoon peak) and passenger experience with the analyzed airports. The influence of these variables was therefore analyzed across market segments according to departure airport and flight duration criteria. The choice of GRU (located neighboring Sao Paulo city) is not well explained by the rationality of access time economy and the increase of the supply of direct flight frequencies, while the choice of CGH (located inside Sao Paulo city) is. Access time was found to be more important to passengers flying shorter distances while direct flight frequencies in the travel period were more significant to those flying longer distances. Keywords: Airport choice, Multiple airport region, Conditional LOGIT model, Access time, Flight frequencies, Passenger experience with the analyzed airports, Transportation planning

  16. Finding Aedes aegypti in a natural breeding site in an urban zone, Sao Paulo, Southeastern Brazil

    PubMed Central

    Lima-Camara, Tamara Nunes; Urbinatti, Paulo Roberto; Chiaravalloti-Neto, Francisco

    2016-01-01

    ABSTRACT This is the description of how nine Aedes aegypti larvae were found in a natural breeding site in the Pinheiros neighborhood, city of Sao Paulo, SP, Southeastern Brazil. The record was conducted in December 2014, during an entomological surveillance program of dengue virus vectors, with an active search of potential breeding sites, either artificial or natural. Finding Ae. aegypti larvae in a tree hole shows this species’ ability to use both artificial and natural environments as breeding sites and habitats, which points towards the importance of maintaining continuous surveillance on this mosquito in all kinds of water-holding containers. PMID:26982959

  17. Smithsonian Astrophysical Observatory Ozone Mapping and Profiler Suite (SAO OMPS) formaldehyde retrieval

    NASA Astrophysics Data System (ADS)

    González Abad, Gonzalo; Vasilkov, Alexander; Seftor, Colin; Liu, Xiong; Chance, Kelly

    2016-07-01

    This paper presents our new formaldehyde (H2CO) retrievals, obtained from spectra recorded by the nadir instrument of the Ozone Mapping and Profiler Suite (OMPS) flown on board NASA's Suomi National Polar-orbiting Partnership (SUOMI-NPP) satellite. Our algorithm is similar to the one currently in place for the production of NASA's Ozone Monitoring Instrument (OMI) operational H2CO product. We are now able to produce a set of long-term data from two different instruments that share a similar concept and a similar retrieval approach. The ongoing overlap period between OMI and OMPS offers a perfect opportunity to study the consistency between both data sets. The different spatial and spectral resolution of the instruments is a source of discrepancy in the retrievals despite the similarity of the physic assumptions of the algorithm. We have concluded that the reduced spectral resolution of OMPS in comparison with OMI is not a significant obstacle in obtaining good-quality retrievals. Indeed, the improved signal-to-noise ratio of OMPS with respect to OMI helps to reduce the noise of the retrievals performed using OMPS spectra. However, the size of OMPS spatial pixels imposes a limitation in the capability to distinguish particular features of H2CO that are discernible with OMI. With root mean square (RMS) residuals ˜ 5 × 10-4 for individual pixels we estimate the detection limit to be about 7.5 × 1015 molecules cm-2. Total vertical column density (VCD) errors for individual pixels range between 40 % for pixels with high concentrations to 100 % or more for pixels with concentrations at or below the detection limit. We compare different OMI products (SAO OMI v3.0.2 and BIRA OMI v14) with our OMPS product using 1 year of data, between September 2012 and September 2013. The seasonality of the retrieved slant columns is captured similarly by all products but there are discrepancies in the values of the VCDs. The mean biases among the two OMI products and our OMPS product

  18. Visceral leishmaniasis in the state of Sao Paulo, Brazil: spatial and space-time analysis

    PubMed Central

    Cardim, Marisa Furtado Mozini; Guirado, Marluci Monteiro; Dibo, Margareth Regina; Chiaravalloti, Francisco

    2016-01-01

    ABSTRACT OBJECTIVE To perform both space and space-time evaluations of visceral leishmaniasis in humans in the state of Sao Paulo, Brazil. METHODS The population considered in the study comprised autochthonous cases of visceral leishmaniasis and deaths resulting from it in Sao Paulo, between 1999 and 2013. The analysis considered the western region of the state as its studied area. Thematic maps were created to show visceral leishmaniasis dissemination in humans in the municipality. Spatial analysis tools Kernel and Kernel ratio were used to respectively obtain the distribution of cases and deaths and the distribution of incidence and mortality. Scan statistics were used in order to identify spatial and space-time clusters of cases and deaths. RESULTS The visceral leishmaniasis cases in humans, during the studied period, were observed to occur in the western portion of Sao Paulo, and their territorial extension mainly followed the eastbound course of the Marechal Rondon highway. The incidences were characterized as two sequences of concentric ellipses of decreasing intensities. The first and more intense one was found to have its epicenter in the municipality of Castilho (where the Marechal Rondon highway crosses the border of the state of Mato Grosso do Sul) and the second one in Bauru. Mortality was found to have a similar behavior to incidence. The spatial and space-time clusters of cases were observed to coincide with the two areas of highest incidence. Both the space-time clusters identified, even without coinciding in time, were started three years after the human cases were detected and had the same duration, that is, six years. CONCLUSIONS The expansion of visceral leishmaniasis in Sao Paulo has been taking place in an eastbound direction, focusing on the role of highways, especially Marechal Rondon, in this process. The space-time analysis detected the disease occurred in cycles, in different spaces and time periods. These meetings, if considered, may

  19. Elevation of a cane-growing area of the state of Sao Paulo using LANDSAT data

    NASA Technical Reports Server (NTRS)

    Dejesusparada, N. (Principal Investigator); Mendonca, F. J.; Lee, D. C. L.; Tardin, A. T.; Shimabukuro, Y. E.; Chen, S. C.; Lucht, L. A. M.; Moreira, M. A.; Delima, A. M.; Maia, F. C. S.

    1981-01-01

    Images at a scale of 1:250.000 were visually interpreted for identification and area estimates of sugar cane plantations in Sao Paulo. The basic criteria for crop identification were the spectral characteristics of channels 5 and 7 and their temporal variations observed from different LANDSAT passes. Using this technique, it was possible to map the sugar cane areas as well as the sugar cane already harvested. An area of 801,950 hectares was estimated within the study area. The confidence interval of correct classification ranged from 87.11% to 94.71%.

  20. San Francisco Bay Sand Mining Resource Evaluation and Impact Analysis

    NASA Astrophysics Data System (ADS)

    Fenical, S.; Tirindelli, M.; Sicular, D.; Gragg, J.; Huitt, C.

    2012-12-01

    This paper presents results of the evaluation of potential future sand resources within certain Central San Francisco Bay (Central Bay) sand mining lease areas, as well as the potential impacts of further mining these areas for a ten-year period. The study consisted of morphological analysis using field measurements and hydrodynamic modeling, and covered a wide spectrum of physical processes including tidal and river circulation, salinity, sediment transport, and morphology. The study was conducted within the framework of an Environmental Impact Report (EIR) prepared by the California State Lands Commission (CSLC) as part of the discretionary approval process for issuing new mining leases. The results of the morphological analysis indicate a measurable depletion of sand resources in the Central Bay lease areas during the period 1997-2008, and that for the purposes of the proposed ten-year mining lease renewal, sand mining resources in Central Bay are largely limited to material already in place. The morphological analysis results also indicate that the proposed additional ten years of sand mining in the Central Bay lease areas are not likely to cause a significant impact on sediment transport and budgets in areas outside the vicinity of the lease areas, such as the San Francisco Bar, Ocean Beach, etc. Numerical modeling results, including particle tracking exercises, do indicate a net seaward transport of sand, and that a linkage exists between the mining areas and offshore areas (San Francisco Bar, Ocean Beach, etc). However, the modeling results demonstrate that the linkage is weak, and that any measurable changes in hydrodynamics, salinity and sediment transport/morphology caused by the mining activities are likely to be confined to the vicinity of the mining areas.

  1. Superplume Under the Siberian Craton: Evidence from Metasomatic Signatures in Kimberlitic Xenoliths

    NASA Astrophysics Data System (ADS)

    Pokhilenko, N.; Taylor, L. A.; Agashev, A. M.; Pokhilenko, L.; Baziotis, I. P.; Carmody, L.; Smith, G. B.

    2012-12-01

    A superplume is proposed to have existed under the Siberian Craton from the mid-Paleozoic to the late Mesozoic. The most dramatic result of this was the eruption of 17 million km3 of the Siberian trap magma at 250 ±2 Ma. However, the effects of this plume were recorded earlier in Devonian (~360 Ma) kimberlitic peridotites, as minor "basaltic" metasomatic overprinting. Indeed, peridotites from later kimberlites (~145 Ma) show evidence for similar, yet extensive, metasomatism, thereby bracketing the major plume climax with possible effects both prior and after this extensive activity. Indeed, a comparative analysis of petrological, mineralogical, and geochemical results from these early and late, Devonian versus Jurassic, peridotites have shown that the thickness of lithosphere of North-Eastern part of Siberian Platform was around 230 km at Middle Paleozoic time and decreased to 140-150 km by Late Mesozoic time. The Devonian Udachnaya kimberlite (central craton), one of the largest diamondiferous pipes in the world, provides a suite of garnet peridotites (>90%), many of which possess a 'sheared' texture. These peridotites possess evidence for a late-stage cryptic metasomatism, particularly in the garnets, exemplified by a notable increase in CaO, with a near constant Cr2O3 content, as the garnet compositions move from the harzburgitic field into that of lherzolites. Conversely, the xenolith suite from the Mesozoic Obnazhennaya kimberlite (north-east craton) is comprised of more pyroxenite xenoliths, with rare peridotite lithologies. The metasomatic over-print on these xenoliths has produced a more fertile chemistry, with the garnets becoming less Cr-rich, following a lherzolitic trend. These two trends in the garnets suggest that a long-lasting metasomatic ultra-event, the same metasomatic processes (and possibly similar sources), operated during both time periods. Changes from harzburgitic in the older Udachnaya peridotite rims to lherzolitic core-rim compositions

  2. A review of benthic faunal surveys in San Francisco Bay

    USGS Publications Warehouse

    Nichols, Frederic H.

    1973-01-01

    During the past 60 years, considerable effort has been expended in studies of the relations of the biotic community and physicochemical characteristics of San Francisco Bay water. In very recent years these studies have emphasized the relations between the 'state of health' of bottom-living invertebrates (the benthos) and the levels of pollutants in the bay. Benthic organisms, generally sessile, are unable to escape deleterious environmental changes, and they reflect these changes in alterations of normal species composition of assemblages and species abundance. Data that expands understanding of these relations in urbanized areas such as San Francisco Bay are critical. Because of the implications of such data in control of water quality, the U.S. Geological Survey undertook a review of the results and major conclusions of San Francisco Bay benthic surveys. The size and species composition of faunal assemblages are largely controlled by the salinity of the water, the texture of the bottom sediments, and locally by wastes discharged into the bay. Efforts to describe the structure and function of benthic communities of the bay and to quantify the effects of waste discharge on them have been hampered by inconsistent and often faulty sampling methodology and species identification. Studies made show a lack of information on the normal life processes of the organisms concerned. The diversity index (a mathematical expression of the number of kinds of organisms present at a location), commonly used to describe the 'health' of the benthic community, has been employed without regard for the need for standardizing methodology and species identifications or for understanding natural biological processes that affect such mathematical indices. There are few reliable quantitative data on the distribution of benthic organisms in San Francisco Bay with which future assessments of the 'health' of the benthic community might be compared. Methods for study of the benthos must be

  3. Swash zone characteristics at Ocean Beach, San Francisco, CA

    USGS Publications Warehouse

    Erikson, L.H.; Hanes, D.M.; Barnard, P.L.; Gibbs, A.E.

    2007-01-01

    Runup data collected during the summer of 2005 at Ocean Beach, San Francisco, CA are analyzed and considered to be typical summer swash characteristics at this site. Analysis shows that the beach was dissipative with Iribarren numbers between 0.05 and 0.4 and that infragravity energy dominated. Foreshore slopes were mild between 0.01 and 0.05 with swash periods on the order of a minute. Predicted runup heights obtained with six previously developed analytical runup formulae were compared to measured extreme runup statistics. Formulations dependent on offshore wave height, foreshore slope and deep water wavelength gave reasonable results.

  4. Syringe Disposal Among Injection Drug Users in San Francisco

    PubMed Central

    Martinez, Alexis N.; Carpenter, Lisa; Geckeler, Dara; Colfax, Grant; Kral, Alex H.

    2011-01-01

    To assess the prevalence of improperly discarded syringes and to examine syringe disposal practices of injection drug users (IDUs) in San Francisco, we visually inspected 1000 random city blocks and conducted a survey of 602 IDUs. We found 20 syringes on the streets we inspected. IDUs reported disposing of 13% of syringes improperly. In multivariate analysis, obtaining syringes from syringe exchange programs was found to be protective against improper disposal, and injecting in public places was predictive of improper disposal. Few syringes posed a public health threat. PMID:20466956

  5. A week of SRI 2003 in San Francisco

    SciTech Connect

    Robinson, Art

    2003-09-29

    The Eighth International Conference on Synchrotron Radiation (SRI 2003) ended its August 25-28 run at the Yerba Buena Center for the Arts in San Francisco with almost as many in attendance as at the beginning. The steady attendance was surely a tribute to the quality of the program and the excitement it generated among the more than 700 registrants who gathered for four days of plenary talks, parallel sessions, and posters, as well as facility tours of the ALS and SSRL on August 29.

  6. Characterizing the scientific potential of satellite sensors. [San Francisco, California

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Analytical and programming support is to be provided to characterize the potential of the LANDSAT thematic mapper (TM) digital imagery for scientific investigations in the Earth sciences and in terrestrial physics. In addition, technical support to define lower atmospheric and terrestrial surface experiments for the space station and technical support to the Research Optical Sensor (ROS) study scientist for advanced studies in remote sensing are to be provided. Eleven radiometric calibration and correction programs are described. Coherent noise and bright target saturation correction are discussed along with image processing on the LAS/VAX and Hp-300/IDIMS. An image of San Francisco, California from TM band 2 is presented.

  7. California State Waters Map Series: offshore of San Francisco, California

    USGS Publications Warehouse

    Cochrane, Guy R.; Johnson, Samuel Y.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Golden, Nadine E.; Hartwell, Stephen R.; Endris, Charles A.; Manson, Michael W.; Sliter, Ray W.; Kvitek, Rikk G.; Watt, Janet Tilden; Ross, Stephanie L.; Bruns, Terry R.

    2015-01-01

    Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

  8. Cambrian-Ordovician craton margin section, southern Great Basin: A sequence stratigraphic perspective

    SciTech Connect

    Cooper, J.D. ); Edwards, J.C. )

    1991-02-01

    The Upper Cambrian through Upper Ordovician cratonal to miogeoclinal transition section in southern Nevada and eastern California accumulated on a gentle homoclinal ramp and includes a variety of peritidal and subtidal carbonate facies. This section consists of a westward-thickening wedge assigned to the Nopah and Mountain Springs formations and can be related to one type 1 and least four type 2 sequences. The basal part of the section is the Dunderberg Shale Member of the Nopah Formation, which is composed of meter-scale cyclical shale-carbonate bundles. Carbonate interbeds signify a variety of peritidal to deep subtidal paleoenvironments that comprise shelf margin and transgressive systems tracts. The progradation of a thrombolitic bank complex in the overlying upper Nopah may reflect emergence on the craton, evidenced by the Sauk II-Sauk III cratonic disconformity. The overlying A' member of the Mountain Springs Formation rests in sharp and, in places, slightly discordant contact with the top of the Nopah. This contact is interpreted as a marine flooding surface and type 2 sequence boundary. Member A consists of Lower Ordovician transgressive and highstand systems tracts comprised of oolitic shoal and back-shoal to intertidal carbonates. The type 1 unconformity that separates member A from overlying B' member is the top of the first-order Sauk Sequence. The B' member is a thin stratal interval of late Middle to Late Ordovician age and consists of dark, burrow-mottled skeletal wackestone and mudstone that is part of a transgressive systems tract. It is bounded above by another type 1 unconformity and therefore represents the first-order Tippecanoe sequence of Sloss.

  9. An upper mantle model for a western rim of the East European Craton

    NASA Astrophysics Data System (ADS)

    Dec, M.; Malinowski, M.; Nita, B.; Perchuc, E.

    2012-04-01

    The upper mantle structure is a subject of many seismological analysis but existent global models are often too general to depict regional variations. Our seismic model is a trial to construct a new reference model for the regional upper mantle structure in the western rim of the East European Craton. It is based on the P-wave traveltime analysis from seismograms recorded on Suwalki (SUW) seismic station belonging to the Polish Seismological Network. SUW station is situated in NE part of Poland on the East European Craton. The data from 249 natural seismic events were divided into four groups referring to the epicenters in the Western Mediterranean Sea region, Greece and Turkey region, Caucasus region and Mid-Atlantic Ridge region. Our analysis is based on the P-wave traveltimes observed up to 3000 km distance, which is sufficient to investigate upper mantle structure down to about 500 km. For each region, we established a single model which was fitted to all sections. 1D model was calculated for all regions except Jan Mayen region, for which we had to estimate 2D model because waves propagate through both oceanic and continental structure. However, the continental part of the Jan Mayen region model is similar to 1D model established for other regions. We also include data from TOR and SVEKALAPKO experiments to check the presence of the 300-km discontinuity. Our model of the upper mantle in the western rim of the East European Craton documents low velocity zone (LVZ), 300-km discontinuity and zone with the reduction of P-wave velocity above 410-km discontinuity. We attribute the existence of the 300-km discontinuity to the paleotectonic interaction between Laurentia, Baltica and Avalonia during the closure of the Tornquist Sea.

  10. Sediment budget of cratons: insights from West Africa over the Cenozoic

    NASA Astrophysics Data System (ADS)

    Jean-Louis, G.; Chardon, D.; Rouby, D.; Beauvais, A.

    2015-12-01

    The sediment load of rivers constitutes the material that builds the stratigraphic successions found from continental margins to the deep ocean. Measure of this flux is relevant to understanding continental controls on denudation, riverine transport and basin filling. An increasing number of sediment yield measures is available but whether these modern values can be extrapolated at geological timescales for large watersheds is still questioned. One reason is the lack of long-term data. Here, we present a sediment budget for Sub-Saharan West Africa over the Cenozoic to compare with the modern rates. The denudation of this cratonic area is constrained using three regional lateritic paleo-landsurfaces that formed during periods of enhanced weathering since the Paleocene-Eocene greenhouse peak. The 3D interpolation of these surfaces allowed building three successive denudation maps for the 45-24, 24-11 and 11-0 Ma intervals together with reconstructions of the paleo-drainage. The regional distribution of erosion suggests the influence of lithospheric deformation, concentrated around a southern marginal upwarp and eastern hotspot swells. The export of large-scale drainages was calculated by converting denudated volumes into sediment fluxes using the porosity and density of lateritic regolith. Exported volumes calculated for the Niger watershed fall within the same range as the Cenozoic clastic accumulations of the Niger delta. Comparisons also show that modern fluxes can be an order of magnitude above the long-term fluxes for moderately large watersheds but that modern and long-term yields are similar for the largest watersheds (e.g. Niger, Volta, Senegal). These results suggest that the export of very large cratonic watersheds is independent of the measurement timescale and that their modern yields can be extrapolated at long-timescale. Finally, it allows assessing the relative contribution of cratons, i.e. non-active orogenic areas, to the global sediment budgets at

  11. "13 BB star" - broadband seismic array at the edge of East European Craton in Poland

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin; Grad, Marek; Wilde-Piórko, Monika; Suchcicki, Jerzy; Arant, Tadeusz

    2014-05-01

    "13 BB star" is a dense array of 13 Reftek 151-120 broadband seismometers located in unpopulated forests in northern Poland - just on the edge of East European Craton. The shape of array was designed as a "star" with one central station and 12 station located on two circles (radius of about 30 and 60 km) around it. This geometry allows us to study seismic waves (in particular surface waves) incoming from all azimuths. Our "13 BB star" array stations are self powered (solar panels and batteries), equipped with local storage system and on-line transmission of seismic and auxiliary data using 2G and 3G cellular network. We also developed on-line application for monitoring array status (transmission, connections, power, temperature, etc.) and on-line data visualization. Main advantages of our array are: 1) 120s broadband seismometers recording with 100Hz sampling, 2) density of array - distances between neighboring stations does not exceed 30 km, 3) station placement in underground wells, 4) stations located in forests far (usually 2-3 km) from industries, roads, villages and other human activity. "13 BB star" started operating in July 2013 and since that time recorded several local, regional, and teleseismic events proving good array functionality. The scientific aim of the "13 BB star" project is development of a quantitative model of the lithosphere-asthenosphere-structure in the marginal zone of the East European Craton in northern Poland. New acquired data will be analyzed using integrated seismic methods, which will yield images of lithosphere-asthenosphere system hitherto unknown for this area. The knowledge of detailed structure of the cratonic lithosphere-asthenosphere system is crucial for the better understanding of the regional, as well as global mantle dynamics and evolution of the Earth's interior. This work was supported by NCN-grant DEC 2011/02/A/ST10/00284.

  12. Seismic structure of the crust and lithospheric mantle of the southern African cratonic region

    NASA Astrophysics Data System (ADS)

    Youssof, M.; Thybo, H.; Artemieva, I. M.; Levander, A.

    2013-12-01

    We present a new seismic model for the structure of the crust and lithospheric mantle in southern Africa constrained by a joint study of seismic receiver functions and finite-frequency tomography, using the high-quality data from the South Africa Seismic Experiment (SASE). A) The crust has a highly heterogeneous structure with short wavelength variations in (i) thickness, (ii) composition (reflected in Vp/Vs-ratio calculated for all SASE stations), and (iii) Moho sharpness (which is quantified and mapped for the entire region) (Youssof et al., Tectonophysics, in review). By mapping these three parameters, we distinguish ~20 crustal blocks that do not everywhere coincide with surface tectonic features. Our RFs also demonstrate strong azimuthal anisotropy in the crust, with a typical crustal contribution to the total S-wave splitting of at least 30%. Spatial correlation of the S-wave polarization directions of crustal and mantle anisotropy indicates (i) the presence of three distinct Archean lithospheric terranes and (ii) coupling between the crust and lithospheric mantle in most of the study area, with a strong decoupling in western Kaapvaal where the crustal anisotropy is strongest. The similarity of anisotropy directions in the crust and mantle beneath much of the Kaapvaal craton indicates that (a) the seismic anisotropy originates at the time of cratonization and (b) the observed correspondence between the present direction of absolute plate motion (APM) and lithosphere anisotropy is coincidental. B) A new 3D high-resolution seismic model of the lithospheric mantle has been determined from finite frequency tomographic inversions of teleseismic P- and S- body wave data. The two velocity models are very similar in structure, but differ in the relative P- and S-wave velocity anomalies. We find that: 1) the fast lithospheric keels extends very deep, perhaps to depths of 300-350 km and 250 km beneath the Kaapvaal and Zimbabwe cratons, respectively, and 2) the Archean

  13. The ambient noise and earthquake surface wave tomography of the North China Craton

    NASA Astrophysics Data System (ADS)

    Pan, J.; Obrebski, M. J.; Wu, Q.; Li, Y.

    2010-12-01

    The North China Craton (NCC) is unique for its unusual Phanerozoic tectonic activity. The NCC was internally tectonically stable until Jurassic when its southern margin collided with the Yangzte Craton. Subsequently, the eastern and central part of the NCC underwent distinctive evolutions during the Late Mesozoic and Cenozoic. In contrast to the Erdos block located in the western part of NCC and that seems to have preserved the typical features of a stable craton, the eastern NCC has experienced significant lithospheric thinning as evidenced by widespread magmatism activity and normal faulting, among other manifestations. The eastern part of the NCC is also one of the most seismically active intracontinental regions in the world. Here we focus on the region that comprises the North China Basin and the Yanshan-Taihang Mountains, two major tectonic units located to the east and in the center of the NCC, respectively. We combine ambient noise data and ballistic surface wave data recorded by the dense temporary seismic array deployed in the North China to obtain phase velocity maps at periods ranging from 5s to 60s. 1587 and 3667 ray paths were obtained from earthquake surface waves and ambient noise correlations, respectively. The phase velocity distribution was reconstructed with grid size 0.25x0.25 degrees and 0.5x0.5 degrees from ambient noise tomography and earthquake surface wave tomography. For periods shorter than 15s, the phase velocity variations are well correlated with the principal geological units in the NCC, with low-speed anomalies corresponding to the major sedimentary basins and high-speed anomalies coinciding with the main mountain ranges. Within the period range from 20s to 30s, the phase velocity variations seem to be related to the local variations of the crustal thickness. For the periods above 30s, the strength of the phase velocity variations decreases with increasing periods, which may imply that the uppermost mantle is much more homogeneous

  14. Bouguer images of the North American craton and its structural evolution

    NASA Technical Reports Server (NTRS)

    Arvidson, R. E.; Bowring, S.; Eddy, M.; Guinness, E.; Leff, C.; Bindschadler, D.

    1984-01-01

    Digital image processing techniques have been used to generate Bouguer images of the North American craton that diplay more of the granularity inherent in the data as compared with existing contour maps. A dominant NW-SE linear trend of highs and lows can be seen extending from South Dakota, through Nebraska, and into Missouri. The structural trend cuts across the major Precambrian boundary in Missouri, separating younger granites and rhyolites from older sheared granites and gneisses. This trend is probably related to features created during an early and perhaps initial episode of crustal assembly by collisional processes. The younger granitic materials are probably a thin cover over an older crust.

  15. 33 CFR 167.405 - Off San Francisco: Main ship channel.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Off San Francisco: Main ship channel. 167.405 Section 167.405 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Separation Schemes and Precautionary Areas Pacific West Coast § 167.405 Off San Francisco: Main ship...

  16. 33 CFR 167.405 - Off San Francisco: Main ship channel.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Off San Francisco: Main ship channel. 167.405 Section 167.405 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Separation Schemes and Precautionary Areas Pacific West Coast § 167.405 Off San Francisco: Main ship...

  17. 33 CFR 167.405 - Off San Francisco: Main ship channel.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Off San Francisco: Main ship channel. 167.405 Section 167.405 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Separation Schemes and Precautionary Areas Pacific West Coast § 167.405 Off San Francisco: Main ship...

  18. 33 CFR 167.405 - Off San Francisco: Main ship channel.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Off San Francisco: Main ship channel. 167.405 Section 167.405 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Separation Schemes and Precautionary Areas Pacific West Coast § 167.405 Off San Francisco: Main ship...

  19. SITE MANAGEMENT AND MONITORING PLAN IMPLEMENTATION MANUAL - SAN FRANCISCO DEEP OCEAN DISPOSAL SITE (SF-DODS)

    EPA Science Inventory

    EPA published in 1994 a Final Rule formally designating the San Francisco Deep Ocean Disposal Site (SF-DODS) for the disposal of suitable dredged material removed from the San Francisco Bay region and other nearby harbors or dredging sites. This Final Rule contained an extensive ...

  20. 76 FR 65120 - Drawbridge Operation Regulation; Islais Creek, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-20

    ... of the Third Street Drawbridge across Islais Creek, mile 0.4, at San Francisco, CA. The deviation is..., mile 0.4, over Islais Creek, at San Francisco, CA. The drawbridge navigation span provides a vertical clearance of 4 feet above Mean High Water in the closed-to-navigation position. As required by 33 CFR...

  1. 77 FR 1407 - Drawbridge Operation Regulation; Islais Creek, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-10

    ... of the Third Street Drawbridge across Islais Creek, mile 0.4, at San Francisco, CA. The deviation is..., mile 0.4, over Islais Creek, at San Francisco, CA. The drawbridge navigation span provides a vertical clearance of 4 feet above Mean High Water in the closed-to-navigation position. As required by 33 CFR...

  2. 77 FR 4501 - Special Local Regulation and Safety Zone; America's Cup Sailing Events, San Francisco, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-30

    ...The Coast Guard proposes to adopt a temporary special local regulation and temporary safety zone for those portions of the ``America's Cup World Series,'' the ``Louis Vuitton Cup'' challenger selection series, and the ``America's Cup Finals Match'' sailing regattas that may be conducted in the waters of San Francisco Bay adjacent to the City of San Francisco waterfront in the vicinity of the......

  3. The Public School System of San Francisco, California. Bulletin, 1917, No. 46

    ERIC Educational Resources Information Center

    Bureau of Education, Department of the Interior, 1917

    1917-01-01

    During the month of December, 1914, representatives of the San Francisco Chamber of Commerce conferred with the Commissioner of Education in Washington concerning the possibility of a survey of the San Francisco public school system under the direction of the Bureau of Education. At that time the Commissioner of Education drafted a statement of…

  4. After-School Pursuits: An Examination of Outcomes in the San Francisco Beacon Initiative

    ERIC Educational Resources Information Center

    Walker, Karen E.; Arbreton, Amy J.A.

    2004-01-01

    The San Francisco Beacon Initiative (SFBI) has been in effect in the San Francisco Unified School District since 1996. A collaboration of public and private funders, SFBI operates comprehensive after-school programs in six middle schools, one elementary school and one high school. Public/Private Ventures' (P/PV's) evaluation found that SFBI…

  5. 78 FR 54487 - YP Western Directory LLC, San Francisco Division, Publishing Operations Group, YP Subsidiary...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-04

    ... Francisco, California. The notice was published in the Federal Register on February 25, 2013 (78 FR 12796... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF LABOR Employment and Training Administration YP Western Directory LLC, San Francisco Division,...

  6. Melt infiltration of the lower lithosphere beneath the Tanzania craton and the Albertine rift inferred from S receiver functions

    NASA Astrophysics Data System (ADS)

    WöLbern, Ingo; Rümpker, Georg; Link, Klemens; Sodoudi, Forough

    2012-08-01

    The transition between the lithosphere and the asthenosphere is subject to numerous contemporary studies as its nature is still poorly understood. The thickest lithosphere is associated with old cratons and platforms and it has been shown that seismic investigations may fail to image the lithosphere-asthenosphere boundary in these areas. Instead, several recent studies have proposed a mid-lithospheric discontinuity of unknown origin existing under several cratons. In this study we investigate the Tanzania craton in East Africa which is enclosed by the eastern and western branches of the East African Rift System. We present evidence from S receiver functions for two consecutive discontinuities at depths of 50-100 km and 140-200 km, which correspond to significant S wave velocity reductions under the Tanzania craton and the Albert and Edward rift segments. By comparison with synthetic waveforms we show that the lower discontinuity coincides with the LAB exhibiting velocity reductions of 6-9%. The shallower interface reveals a velocity drop that varies from 12% beneath the craton to 24% below the Albert-Edward rift. It is interpreted as an infiltration front marking the upper boundary of altered lithosphere due to ascending asthenospheric melts. This is corroborated by computing S velocity variations based on xenolith samples which exhibit a dense system of crystallized veins acting as pathways of the infiltrating melt. Mineral assemblages in these veins are rich in phlogopite and pyroxenite which can explain the reduced shear wave velocities. Melt infiltration represents a suitable mechanism to form a mid-lithospheric discontinuity within cratonic lithosphere that is underlain by anomalously hot mantle.

  7. 207Pb-206Pb zircon ages of eastern and western Dharwar craton, southern India : Evidence for contemporaneous Archaean crust

    NASA Astrophysics Data System (ADS)

    Maibam, B.; Goswami, J. N.; Srinivasan, R.

    2009-04-01

    Dharwar craton is one of the major Archaean crustal blocks in the Indian subcontinent. The craton is comprised of two blocks, western and eastern. The western domain is underlain by orthogneisses and granodiorites (ca. 2.9-3.3 Ga) collectively termed as Peninsular Gneiss [e.g., 1] interspersed with older tracts of metasedimentary and metamorphosed igneous suites (Sargur Group and Dharwar Group; [2]). The eastern part of the craton is dominated by Late Archaean (2.50-2.75 Ga) granitoids and their gneissic equivalents. They are interspersed with schist belts (also of Sargur Group and Dharwar Group), which are lithologically similar to the Dharwar Supergroup in the western block, but are in different metamorphic dress. Here we report 207Pb-206Pb age of zircons separated from the metasedimentary and gneissic samples from the two blocks to constrain the evolution of the Dharwar craton during the early Archaean. Detrital zircons of the metasedimentary rocks from both the blocks show a wide range of overlapping ages between ~2.9 to >3.5 Ga. Zircon ages of the orthogneisses from the two blocks showed that most of the analysed grains of the eastern Dharwar block are found to be of the age as old as the western Dharwar gneisses. Imprints of younger events could be discerned from the presence of overgrowths in zircons from the studied samples throughout the craton. Our data suggest that crust forming cycles in the two blocks of the Dharwar craton occurred contemporaneously during the Archaean. References [1] Beckinsale, R.D., Drury, S.A., Holt, R.W. (1980) Nature 283, 469-470. [2] Swami Nath J., Ramakrishnan M., Viswanatha M.N. (1976) Rec. Geol. Surv. Ind., 107, 149-175.

  8. 33 CFR 100.1105 - San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false San Francisco Bay Navy Fleetweek... WATERS § 100.1105 San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration. (a) Effective Periods. This section is effective during the U.S. Navy/City of San Francisco Fleetweek Parade...

  9. 33 CFR 100.1105 - San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false San Francisco Bay Navy Fleetweek... WATERS § 100.1105 San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration. (a) Effective Periods. This section is effective during the U.S. Navy/City of San Francisco Fleetweek Parade...

  10. 33 CFR 100.1105 - San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false San Francisco Bay Navy Fleetweek... WATERS § 100.1105 San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration. (a) Effective Periods. This section is effective during the U.S. Navy/City of San Francisco Fleetweek Parade...

  11. 33 CFR 100.1105 - San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false San Francisco Bay Navy Fleetweek... WATERS § 100.1105 San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration. (a) Effective Periods. This section is effective during the U.S. Navy/City of San Francisco Fleetweek Parade...

  12. 33 CFR 100.1105 - San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false San Francisco Bay Navy Fleetweek... WATERS § 100.1105 San Francisco Bay Navy Fleetweek Parade of Ships and Blue Angels Demonstration. (a) Effective Periods. This section is effective during the U.S. Navy/City of San Francisco Fleetweek Parade...

  13. 75 FR 81854 - Safety Zone; New Year's Celebration for the City of San Francisco, Fireworks Display, San...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-29

    ... Celebration for the City of San Francisco Fireworks Display. The temporary safety zone will extend 100 feet... will extend 1,000 feet from the nearest point of the barge during the fireworks display. This safety... feet from the San Francisco Ferry Building in San Francisco, CA. The fireworks display is...

  14. VizieR Online Data Catalog: Hamburg/SAO Survey for ELGs. III. (Hopp+, 2000)

    NASA Astrophysics Data System (ADS)

    Hopp, U.; Engels, D.; Green, R. F.; Ugryumov, A. V.; Izotov, Y. I.; Hagen, H.-J.; Kniazev, A. Y.; Lipovetsky, V. A.; Pustilnik, S. A.; Brosch, N.; Masegosa, J.; Martin, J.-M.; Marquez, I.

    2000-03-01

    We present the third list with results of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO - Special Astrophysical Observatory, Russia). This survey is based on the digitized objective-prism photoplate database of the Hamburg Quasar Survey (HQS). Here, we present new spectroscopic results of candidates which were obtained in 1998 with the 2.1m KPNO and the 2.2m Calar Alto telescopes. All candidates are selected in the declination band +35{deg} to +40{deg}. The follow-up spectroscopy with the 2m class telescopes confirmed 85 emission-line objects out of 113 observed candidates and allowed their quantitative spectral classification. For 80 of them, the redshifts are determined for the first time. For 5 previously known Emission-Line Galaxies (ELGs), line ratios are presented for the first time. We could classify 55 out of the 85 emission-line objects as BCG/HII galaxies or probable BCGs (Blue Compact Galaxies) , 4 - as QSOs, 6 - as Seyfert galaxies, 1 - as super-association in a subluminous spiral galaxy, and 11 are low-excitation objects - either starburst nuclei (SBN), or dwarf amorphous nuclei starburst galaxies (DANS). We could not classify 8 ELGs. Further, for 8 more galaxies we did not detect any significant emission lines. (5 data files).

  15. An Einstein Observatory SAO-based catalog of B-type stars

    NASA Technical Reports Server (NTRS)

    Grillo, F.; Sciortino, S.; Micela, G.; Vaiana, G. S.; Harnden, F. R., Jr.

    1992-01-01

    About 4000 X-ray images obtained with the Einstein Observatory are used to measure the 0.16-4.0 keV emission from 1545 B-type SAO stars falling in the about 10 percent of the sky surveyed with the IPC. Seventy-four detected X-ray sources with B-type stars are identified, and it is estimated that no more than 15 can be misidentified. Upper limits to the X-ray emission of the remaining stars are presented. In addition to summarizing the X-ray measurements and giving other relevant optical data, the present extensive catalog discusses the reduction process and analyzes selection effects associated with both SAO catalog completeness and IPC target selection procedures. It is concluded that X-ray emission, at the level of Lx not less than 10 exp 30 ergs/s, is quite common in B stars of early spectral types (B0-B3), regardless of luminosity class, but that emission, at the same level, becomes less common, or nonexistent, in later B-type stars.

  16. Planetary Signatures in the SAO 206462 (HD 135344B) Disk: A Spiral Arm Passing through Vortex?

    NASA Astrophysics Data System (ADS)

    Bae, Jaehan; Zhu, Zhaohuan; Hartmann, Lee

    2016-03-01

    The disk surrounding SAO 206462, an 8 Myr old Herbig Ae star, has recently been reported to exhibit spiral arms, an asymmetric dust continuum, and a dust-depleted inner cavity. By carrying out two-dimensional, two-fluid hydrodynamic calculations, we find that a planetary-mass companion located at the outer disk could be responsible for these observed structures. In this model, the planet excites primary and secondary arms interior to its orbit. It also carves a gap and generates a local pressure bump at the inner gap edge where a vortex forms through Rossby wave instability. The vortex traps radially drifting dust particles, forming a dust-depleted cavity in the inner disk. We propose that the vortex is responsible for the brightest southwestern peak seen in infrared scattered light and sub-millimeter dust continuum emission. In particular, it is possible that the scattered light is boosted as one of the spiral arms passes through the high density vortex region, although the vortex alone may be able to explain the peak. We suggest that a planetary companion with a mass of 10-15 {M}J is orbiting SAO 206462 at 100-120 au. Monitoring of the brightest peak over the next few years will help reveal its origin because the spiral arms and vortex will show distinguishable displacement.

  17. Updated Smithsonian Astrophysical Observatory Ozone Monitoring Instrument (SAO OMI) formaldehyde retrieval

    NASA Astrophysics Data System (ADS)

    González Abad, G.; Liu, X.; Chance, K.; Wang, H.; Kurosu, T. P.; Suleiman, R.

    2015-01-01

    We present and discuss the Smithsonian Astrophysical Observatory (SAO) formaldehyde (H2CO) retrieval algorithm for the Ozone Monitoring Instrument (OMI) which is the operational retrieval for NASA OMI H2CO. The version of the algorithm described here includes relevant changes with respect to the operational one, including differences in the reference spectra for H2CO, the fit of O2-O2 collisional complex, updates in the high-resolution solar reference spectrum, the use of a model reference sector over the remote Pacific Ocean to normalize the retrievals, an updated air mass factor (AMF) calculation scheme, and the inclusion of scattering weights and vertical H2CO profile in the level 2 products. The setup of the retrieval is discussed in detail. We compare the results of the updated retrieval with the results from the previous SAO H2CO retrieval. The improvement in the slant column fit increases the temporal stability of the retrieval and slightly reduces the noise. The change in the AMF calculation has increased the AMFs by 20%, mainly due to the consideration of the radiative cloud fraction. Typical values for retrieved vertical columns are between 4 × 1015 and 4 × 1016 molecules cm-2, with typical fitting uncertainties ranging between 45 and 100%. In high-concentration regions the errors are usually reduced to 30%. The detection limit is estimated at 1 × 1016 molecules cm-2.

  18. Application of echinoid sperm and embryo bioassays for the pollution assessment of Sao Sebastiao Channel, Brazil

    SciTech Connect

    Zamboni, A.J.; Nipper, M.G.

    1995-12-31

    The Sao Sebastiao Channel, located on the Southeastern Brazilian coast, encompasses the largest oil terminal in the country and is also a highly touristic area. Frequent oil spills are responsible for chronic contamination problems and sewage disposal in the waters of the channel is also common practice. the water and sediment quality in different sites along Sao Sebastiao Channel was evaluated quarterly throughout a year, by toxicity testing with sperm cells and embryos of the sea urchin Lytechinus variegatus. Water samples were collected from two depths (1 m below surface and 1 m above the bottom). Sediments, collected by a grab sampler, had their pore water extracted by centrifuging. It was then analyzed for toxicity. The results showed that the pore water from most sites impaired sperm viability and embryo development of the test organisms. Sediments were further characterized for particle size distribution, TOC, heavy metals and petroleum hydrocarbons content. They contained baseline concentrations of Cu, Pb, Zn, Ni and Fe, but the hydrocarbons levels were above the average for nearby coastal areas. The overlying water from the deeper layer was of better quality than the surface, but very fast changes were observed along time and space. This seems to be intimately associated with the predominant hydrodynamic and meteorological phenomena in that region. The results showed that these toxicity test methods can be applied in association with other forms of analysis, for the establishment of quality criteria for Brazilian coastal environments.

  19. Prevalence and populations of Listeria monocytogenes in meat products retailed in Sao Paulo, Brazil.

    PubMed

    Ristori, Christiane Asturiano; Rowlands, Ruth Estela Gravato; Martins, Cecília Geraldes; Barbosa, Maria Luisa; Yoshida, Júlia T U; Franco, Bernadette D G de Melo

    2014-12-01

    This study evaluated the prevalence of the populations and serotypes of Listeria monocytogenes in 552 refrigerated samples of ground beef, chicken leg, hot dog, and pork sausage collected in supermarkets in the city of Sao Paulo, SP, Brazil, between May 2008 and July 2009. The supermarkets were selected after stratification by geographical region and by random draw. Tests for presence and enumeration of L. monocytogenes were based on ISO 11290-1:1996/Amd.1:2004 and ISO 11290-2:1998 methods, respectively. Listeria spp. were detected in 469 (85.0%) of the studied meat products. The most frequently isolated species was L. innocua (64.1%), followed by L. monocytogenes (48.7%), L. welshimeri (13.4%), L. seeligeri (7.1%), L. ivanovii (0.2%), and L. grayi subspecies murrayi (0.2%). L. monocytogenes was detected in 269 (48.7%) samples, with highest prevalence in ground beef (59.4%) followed by chicken legs (58.0%), pork sausages (39.8%), and hot dogs (37.7%). The populations were <10(2) colony-forming units/g in the majority of samples (62.5%). Prevalence of serotypes varied according to the type of meat product. These data are relevant for estimating the risks of listeriosis associated with consumption of meat products in Sao Paulo, and for establishing science-based intervention strategies aimed at reducing these risks, especially for pregnant women and immunocompromised individuals. PMID:25407460

  20. High resolution spectroscopy of the high latitude rapidly evolving post-AGB star SAO 85766 (= IRAS 18062+2410)

    NASA Astrophysics Data System (ADS)

    Parthasarathy, M.; García-Lario, P.; Sivarani, T.; Manchado, A.; Sanz Fernández de Córdoba, L.

    2000-05-01

    SAO 85766 (b = +20o) is an IRAS source with far-infrared colours similar to planetary nebulae. According to the HDE catalogue, its spectrum in 1940 was that of an A5 star. The UV fluxes and colours derived from data obtained by the TD1 satellite in 1972 also indicate that SAO 85766 was an A-type supergiant at that epoch. However, high resolution spectra of SAO 85766 obtained in 1993 in the wavelength interval 4350Ä to 8820Ä shows that now it is similar to that of an early B type post-AGB supergiant. In addition to the absorptions lines typical of a B1I type star, the spectrum of SAO 85766 is found to show numerous permitted and forbidden emission lines of several elements, typically observed in the spectra of young high density low excitation planetary nebulae. From an analysis of the absorption lines we have estimated Teff=22000+/-500 K, log g=3.0+/-0.5, xi t=15+/-2km s-1 and [M/H]=-0.6. Carbon is found to be strongly underabundant ([C/Fe] = -1.0), similarly to what has been observed in other high galactic latitude hot post-AGB stars. The underabundance of carbon and metals, high galactic latitude, high radial velocity (46 km s-1), the presence of planetary nebula type detached cold circumstellar dust shell and also the presence of low excitation nebular emission lines in the spectrum indicate that SAO 85766 is a low mass star in the post-AGB stage of evolution. The above mentioned characteristics and the variations observed in the spectrum of SAO 85766 suggest that it has rapidly evolved during the past 50 years and it is now in the early stages of the planetary nebula phase. The central star may just have become hot enough to photoionize the circumstellar envelope ejected during the previous AGB phase. >From an analysis of the nebular emission lines we find Te=10000+/- 500K and Ne=2.5 104 cm-3. The nebula also shows an abundance pattern similar to that of the central star. The rapid post-AGB evolution of SAO 85766 appears to be similar to that observed in the

  1. The Prince, the Captain and "The State": An Examination of the Mesquita Family Ownership of "O Estado de Sao Paulo" to 1969.

    ERIC Educational Resources Information Center

    Etsinger, Jean

    Julio Mesquita joined the staff of "O Estado de Sao Paulo" in 1885 and became a director in 1891, when he also began his first term as a deputy of the Sao Paulo state assembly. Until his death in 1927, Mesquita guided the newspaper's growth in all respects--editorial, political, technological, and economic. Julio de Mesquita Filho assumed…

  2. Two Moments of School Architecture in Sao Paulo: Ramos de Azevedo and His Republican Pioneering Schools/Helio Duarte and the "Educational Agreement"

    ERIC Educational Resources Information Center

    Lima, Ana Gabriela Godinho

    2005-01-01

    There are two peculiar moments in the history of the "struggle for national education", which, specifically in the city of Sao Paulo, capital of the State of Sao Paulo, one of the major and richest cities in Brazil, produced very interesting results in school architecture. The first moment happened in the period called the "First Republic"…

  3. Zircon from East Antarctica: evidence for Archean intracrustal recycling in the Kaapvaal-Grunehogna Craton from O and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Marschall, H. R.; Hawkesworth, C. J.; Storey, C.; Leat, P. T.; Dhuime, B.

    2010-12-01

    The Grunehogna Craton (GC, East Antarctica) is interpreted as part of the Archean Kaapvaal Craton of southern Africa prior to Gondwana breakup. The basement of the GC is only exposed within a small area comprising the dominantly leucocratic Annandagstoppane (ADT) granite. The granite (and hence the craton) has been dated previously only by Rb-Sr and Pb-Pb mica and whole-rock methods. Here, the crystallisation age of the granite was determined to 3,067 ± 8 Ma by U-Pb dating of zircon. This age is coeval with granitoids and volcanics in the Swaziland and Witwatersrand blocks of the Kaapvaal Craton. Inherited grains in the ADT granite were discovered with ages of up to 3,433 ±7 Ma, and are the first evidence of Palaeoarchean basement in Dronning-Maud Land. The age spectrum of the inherited grains reflects well-known tectono-magmatic events in the Kaapvaal Craton and form important pieces of evidence for the connection of the GC to the Kaapvaal Craton for at least three billion years and probably longer. Whole-rock chemistry and zircon O isotopes demonstrate a supracrustal sedimentary source for the granite, and Hf model ages show that at least two or three different crustal sources were contributing to the magma with model ages of ~3.50, ~3.75 and possibly ~3.90 Ga, respectively. 3.1 Ga granites covering ~60 % of the outcrop area of the Kaapvaal-Grunehogna Craton played a major role in the mechanical stabilisation of the continental crust during the establishment of the craton in the Mesoarchean. Combined zircon Hf-O isotope data and the lack of juvenile additions to the crust in the Mesoarchean strongly suggest that crustal melting and granite formation was caused by the deep burial of clastic sediments and subsequent incubational heating of the crust. Intracrustal recycling of this type may be an important process during cratonisation and the long-term stabilisation of continental crust.

  4. Redox state of deep off-craton lithospheric mantle: new data from garnet and spinel peridotites from Vitim, southern Siberia

    NASA Astrophysics Data System (ADS)

    Goncharov, A. G.; Ionov, D. A.

    2012-11-01

    Oxygen fugacity ( fO2) affects melting, metasomatism, speciation of C-O-H fluids and carbon-rich phases in the upper mantle. fO2 of deep off-craton mantle is poorly known because garnet-peridotite xenoliths are rare in alkali basalts. We examine the redox and thermal state of the lithospheric mantle between the Siberian and North China cratons using new Fe3+/ΣFe ratios in garnet and spinel obtained by Mössbauer spectroscopy, major element data and P- T estimates for 22 peridotite xenoliths as well as published data for 15 xenoliths from Vitim, Russia. Shallow spinel-facies mantle is more oxidized than deep garnet peridotites (average, -0.1 vs. -2.5 Δlog fO2(FMQ)). For intermediate garnet-spinel peridotites, fO2 estimates from spinel-based oxybarometers are 1.5-3.2 Δlog fO2(FMQ) lower than those from garnet-based oxybarometers. These rocks may be out of phase and chemical inter-mineral equilibrium because the spinel-garnet reaction and concomitant changes in mineral chemistry do not keep up with P- T changes (e.g., lithospheric heating by recent volcanism) due to slow diffusion of trivalent cations and because gar-, gar-spl and spl-facies rocks may coexist on centimeter-meter scale. The spinel-based fO2 estimates may not be correct while garnet-based fO2 values provide conditions before the heating. The T (780-1,100 °C) and fO2 ranges of the Vitim xenoliths overlap those of coarse garnet and spinel cratonic peridotites. However, because of a higher geothermal gradient, the deepest Vitim garnet peridotites are more reduced (by 0.5-2.0 Δlog fO2(FMQ)) than cratonic garnet peridotites at similar depths, and the "water maximum" conditions (>80 % H2O) in the off-craton mantle exist in a more shallow and narrow depth range (60-85 km) than in cratonic roots (100-170 km). The base of the off-craton lithospheric mantle (≥90 km) at 2.5 GPa and 1,150 °C has fO2 of -3.0 ∆log fO2(FMQ), with dominant CH4 and H2O and minor H2 in the fluid. Melting near the base of off-craton

  5. Littoral processes: US Coast Guard Station, Fort Point, San Francisco

    SciTech Connect

    Ecker, R.M.; Whelan, G.

    1983-10-01

    The US Coast Guard Station, Fort Point is located three-quarters of a nautical mile southeast of the Golden Gate Strait, the entrance to San Francisco Bay. The existing storm wave conditions at Fort Point Station pier make it extremely dangerous for the SAR crews to get on and off the Motor Life Boats at times requiring the vessels to be moored at the San Francisco Yacht Harbor about 1.5 miles east of the Fort Point Station. To mitigate these harsh working conditions the US Coast Guard is considering the feasibility of constructing suitable all-weather moorings for the three Motor Life Boats at the Fort Point Station to enable unimpeded SAR operations, to provide safe working conditions for Coast Guard small boat crews, and to improve small boat maintenance conditions at Fort Point Station. The purpose of this report is to identify, analyze and evaluate physical environmental factors that could affect all-weather moorings siting, configuration and entrance location, as well as potential post construction alterations to littoral conditions and processes. This report includes a description of the site, description of pertinent littoral processes, evaluation of how these processes could affect construction of all-weather moorings, and discussion of design considerations, as well as mitigation measures to minimize potential adverse effects to the physical environment. 19 references, 27 figures, 26 tables.

  6. Deep Borehole Instrumentation Along San Francisco Bay Bridges - 2000

    SciTech Connect

    Hutchings, L.; Kasameyer, P.; Turpin, C.; Long, L.; Hollfelder, J.; McEvilly, T.; Clymer, R.; Uhrhammer, R.

    2000-03-01

    This is a progress report on the Bay Bridges downhole network. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges in San Francisco Bay, California. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty-one sensor packages at fifteen sites. The downhole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 731 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes. Preliminary results on phasing across the Bay Bridge, up and down hole wave amplification at Yerba Buena Island, and sensor orientation analysis are presented. Events recorded and located during 1999 are presented. Also, a senior thesis on the deep structure of the San Francisco Bay beneath the Bay Bridge is presented as an addendum.

  7. Projected Bioclimatic Change for the San Francisco Bay Area

    NASA Astrophysics Data System (ADS)

    Torregrosa, A.; Taylor, M.; Flint, L. E.; Flint, A. L.; Weiss, S. B.

    2011-12-01

    Past and future climate data for the San Francisco Bay Area were classified using the Rivas-Martinez (R-M) system to group long-term annual climate averages into categories with biotic significance based on thermotypic and ombrotypic regimes. Bioclimate maps were generated at 270 meter resolution for ten San Francisco Bay Area counties for six 30-year periods from 1911 to 2100 which include the historical 1) 1911-1940, 2) 1941-1970, 3) 1971-2000, and future 4) 2011-2040, 5) 2041-2070, and 6) 2071-2100. Historic averages were generated from PRISM climate data. Future climate projections were generated from two IPCC-based future scenarios (A2 and B1) and two coupled atmosphere-ocean general circulation models (NOAA Geophysical Fluid Dynamics Laboratory and the Parallel Climate Model). Strong congruence was found among the boundaries for historic bioclimates and current vegetation types. However, future scenarios had varying patterns of losses and gains in bioclimate classes and these tracked mesoclimate gradients. Comparisons between projected bioclimatic categories and modeled future climatic water deficit show strong correspondence except in zones of deep alluvial deposits. Maps show areas of bioclimatic stability, e.g. areas that did not change under any future projection, versus areas with significant bioclimatic shifts in all future scenarios. These analyses and maps will be useful for assessing natural resource vulnerability to climate change and natural resource conservation-based climate adaptation decisions.

  8. 2005 hydrographic survey of south San Francisco Bay, California

    USGS Publications Warehouse

    Foxgrover, Amy C.; Jaffe, Bruce E.; Hovis, Gerald T.; Martin, Craig A.; Hubbard, James R.; Samant, Manoj R.; Sullivan, Steve M.

    2007-01-01

    An acoustic hydrographic survey of South San Francisco Bay (South Bay) was conducted in 2005. Over 20 million soundings were collected within an area of approximately 250 sq km (97 sq mi) of the bay extending south of Coyote Point on the west shore, to the San Leandro marina on the east, including Coyote Creek and Ravenswood, Alviso, Artesian, and Mud Sloughs. This is the first survey of this scale that has been conducted in South Bay since the National Oceanic and Atmospheric Administration National Ocean Service (NOS) last surveyed the region in the early 1980s. Data from this survey will provide insight to changes in bay floor topography from the 1980s to 2005 and will also serve as essential baseline data for tracking changes that will occur as restoration of the South San Francisco Bay salt ponds progress. This report provides documentation on how the survey was conducted, an assessment of accuracy of the data, and distributes the sounding data with Federal Geographic Data Committee (FGDC) compliant metadata. Reports from NOS and Sea Surveyor, Inc., containing additional survey details are attached as appendices.

  9. Source apportionment of carbonaceous aerosol in Sao Paulo using 13C and 14C measurements

    NASA Astrophysics Data System (ADS)

    Oyama, Beatriz; Andrade, Maria de Fatima; Holzinger, Rupert; Röckmann, Thomas; Meijer, Harro A. J.; Dusek, Ulrike

    2016-04-01

    The Metropolitan Area of Sao Paulo is affected by high aerosol concentrations, which contain a large fraction of organic material. Up to date, not much is known about the composition and origin of the organic aerosol in this city. We present the first source apportionment of the carbonaceous aerosol fraction in Sao Paulo, using stable (13C) and radioactive carbon isotopes (14C). 14C provides a clear-cut distinction between fossil sources, which contain no 14C, and contemporary sources such as biofuels, biomass burning, or biogenic sources, which contain a typical contemporary 14C/12C ratio. 13C can be used to distinguish C3 plants, such as maize and sugarcane, from C4 plants. This can help to identify a possible impact of sugarcane field burning in the rural areas of Sao Paulo State on the aerosol carbon in the city. In the first part of the study, we compare two tunnel studies: Tunnel 1 is frequented only by light duty vehicles, which run mainly on mixtures of gasoline with ethanol (gasohol, 25% ethanol and 85% gasoline) or hydrated ethanol (5% water and 95% ethanol). Tunnel 2 contains a significant fraction of heavy-duty diesel vehicles, and therefore the fraction of biofuels in the average fleet is lower. Comparison of 14C in organic and elemental carbon (OC and EC) shows that in both tunnels there is no significant contribution of biofuels to EC. Combusting ethanol-gasoline fuels in a vehicle engine does apparently not result in significant EC formation from ethanol. Biofuels contribute around 45% to OC in Tunnel 1 an only 20% in Tunnel 2, reflecting a strong impact of diesel vehicles in Tunnel 2. In the second part of the study we conduct a source apportionment of ambient aerosol carbon collected in a field study during winter (July-August) 2012. Ambient EC has two main sources, vehicular emissions and biomass burning. We estimate a contribution of vehicular sources to EC of roughly 90% during weekdays and 80% during weekends, using the 14C values measured in

  10. azimuthal anisotropy underneath western North China Craton from surface wave tomography

    NASA Astrophysics Data System (ADS)

    Li, D.; Liu, Y.; Zhou, S.

    2013-12-01

    Azimuthal anisotropic velocity structure beneath the western North China Craton (NCC) has been extracted using Rayleigh wave data from 69 broad-band seismographs of China Earthquake Networks Center and 23 of Peking University. We get the surface wave structure for period of 20s to 125s of Rayleigh wave. Surface wave velocity in a slight anisotropic media can be expressed as following: v_1=v_0+asinθ+bcosθ Where v_0 is the isotropic velocity and θ is the back azimuth. The primary results indicate that the Ordos Craton, which has been stable since Archean is obviously high-velocity-anomaly for over 200 km depth. While the Central part of NCC, including the Shanxi Rift, has obvious low-velocity-anomaly going down to 200 km. We interpret this enormous velocity changes as an evidence for the apart geologic processes of the eastern and western parts of NCC. The reactivation since Mesozoic of NCC may have caused upwelling of upper mantle right beneath Shanxi Rift.

  11. Archaean ultra-depleted komatiites formed by hydrous melting of cratonic mantle.

    PubMed

    Wilson, A H; Shirey, S B; Carlson, R W

    2003-06-19

    Komatiites are ultramafic volcanic rocks containing more than 18 per cent MgO (ref. 1) that erupted mainly in the Archaean era (more than 2.5 gigayears ago). Although such compositions occur in later periods of Earth history (for example, the Cretaceous komatiites of Gorgona Island), the more recent examples tend to have lower MgO content than their Archaean equivalents. Komatiites are also characterized by their low incompatible-element content, which is most consistent with their generation by high degrees of partial melting (30-50 per cent). Current models for komatiite genesis include the melting of rock at great depth in plumes of hot, diapirically rising mantle or the melting of relatively shallow mantle rocks at less extreme, but still high, temperatures caused by fluxing with water. Here we report a suite of ultramafic lava flows from the Commondale greenstone belt, in the southern part of the Kaapvaal Craton, which represents a previously unrecognized type of komatiite with exceptionally high forsterite content of its igneous olivines, low TiO(2)/Al(2)O(3) ratio, high silica content, extreme depletion in rare-earth elements and low Re/Os ratio. We suggest a model for their formation in which a garnet-enriched residue left by earlier cratonic volcanism was melted by hydration from a subducting slab. PMID:12815428

  12. The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton

    NASA Astrophysics Data System (ADS)

    Hou, Guiting; Wang, Yanxin; Hari, K. R.

    2010-09-01

    The transmission of the tectonic regime from the Paleo-Asian Ocean to the Pacific Ocean during Mesozoic era was reconstructed using the modeling of Late Triassic (T 3) and Late Jurassic (J 3) stress fields employing two dimensional linear finite element models (2-D FEM). The model at T 3 proposes that Qinling-Dabie-Sulu orogens coevally collided and the model J 3 proposes that Subei block continued to collide with the North China block along the Sulu orogen while the collision of the Qinling-Dabie orogen was terminated. The stress fields at T 3 and J 3 during the two episodes were calculated based on mechanical conditions under different deviatoric stresses acting along the boundaries of the North China craton by elastic finite modeling. The transmission between two episodes of stress fields resulted from Qinling-Dabie-Sulu collision between North China and South China in the Late Triassic period, and from continued collision between the Subei block and North China by the NW-trending movement of Izanagi plate during Late Jurassic. The results from modeling of the Mesozoic stress fields of the North China suggest that late Jurassic was the key transmission period of the tectonic regime of the North China block when large scale thrusting triggered the subsequent destruction of the North China craton.

  13. Neogene cratonic erosion fluxes and landform evolution processes from regional regolith mapping (Burkina Faso, West Africa)

    NASA Astrophysics Data System (ADS)

    Grimaud, Jean-Louis; Chardon, Dominique; Metelka, Václav; Beauvais, Anicet; Bamba, Ousmane

    2015-07-01

    The regionally correlated and dated regolith-paleolandform sequence of Sub-Saharan West Africa offers a unique opportunity to constrain continental-scale regolith dynamics as the key part of the sediment routing system. In this study, a regolith mapping protocol is developed and applied at the scale of Southwestern Burkina Faso. Mapping combines field survey and remote sensing data to reconstruct the topography of the last pediplain that formed over West Africa in the Early and Mid-Miocene (24-11 Ma). The nature and preservation pattern of the pediplain are controlled by the spatial variation of bedrock lithology and are partitioned among large drainage basins. Quantification of pediplain dissection and drainage growth allows definition of a cratonic background denudation rate of 2 m/My and a minimum characteristic timescale of 20 Ma for shield resurfacing. These results may be used to simulate minimum export fluxes of drainage basins of constrained size over geological timescales. Background cratonic denudation results in a clastic export flux of ~ 4 t/km2/year, which is limited by low denudation efficiency of slope processes and correlatively high regolith storage capacity of tropical shields. These salient characteristics of shields' surface dynamics would tend to smooth the riverine export fluxes of shields through geological time.

  14. The character of the Moho and lower crust within Archean cratons and the tectonic implications

    NASA Astrophysics Data System (ADS)

    Abbott, Dallas H.; Mooney, Walter D.; VanTongeren, Jill A.

    2013-12-01

    Undisturbed mid Archean crust (stabilized by 3.0-2.9 Ga) has several characteristics that distinguish it from post Archean crust. Undisturbed mid-Archean crust has a low proportion of internal seismic boundaries (as evidenced by converted phases in seismic receiver functions), lacks high seismic velocities in the lower crust and has a sharp, flat Moho. Most of the seismic data on mid-Archean crust comes from the undisturbed portions of the Kaapvaal and Zimbabwe (Tokwe segment) cratons. Around 67-74% of younger Archean crust (stabilized by 2.8-2.5 Ga) has a sharp, flat Moho. Much of the crust with a sharp, flat Moho also lacks strong internal seismic boundaries, but there is not a one to one correspondence. In cases where its age is known, basaltic lower crust in Archean terranes is often but not always the result of post Archean underplating. Undisturbed mid-Archean cratons are also characterized by lower crustal thicknesses (Archean median range = 32-39 km vs. post-Archean average = 41 km) and lower crustal seismic velocities. These observations are shown to be distinct from those observed in any modern-day tectonic environment. The data presented here are most consistent with a model in which Archean crust undergoes delamination of dense lithologies at the garnet-in isograd resulting in a flat, sharp Moho reflector and a thinner and more felsic-intermediate crust. We discuss the implications of this model for several outstanding paradoxes of Archean geology.

  15. Thermal evolution of cratonic mantle keels: implications for buoyancy and rheology of continental lithosphere (Invited)

    NASA Astrophysics Data System (ADS)

    Eaton, D. W.; Perry, C.

    2013-12-01

    On a billion-year timescale, post-formation cooling or heating of cratonic mantle keels predicts secular changes in lithospheric buoyancy, isopycnicity and rheology that may be expressed as an epeirogenic signal in the core regions of continents. To examine the consequences of these secular changes, we use a finite-difference approach to simulate the thermal evolution of cratonic lithosphere, starting from endmember initial states that represent hot (plume) or cool (slab) formation scenarios. Our models are axisymmetric and assume that the temperature of the lithosphere-asthenosphere boundary (LAB) intersects the mantle adiabat. We consider secular cooling (40 K per Gyr) of the mantle as well as gradual loss of radiogenic heating in the lithosphere. Various scenarios are considered, including ';average' Archean and Proterozoic mantle compositions, as well as layering of the lithosphere with several distributions of heat-producing elements. The thermal and compositional models are used to compute seismic wavespeed, density structure, and spatially-varying mantle viscosity, which are compared with observational constraints from metamorphic P-T-t paths, diamond stability and subsidence of intractronic basins in Africa and North America.

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

    PubMed Central

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

    2014-01-01

    Lithium elemental and isotopic compositions of olivines in peridotite xenoliths from Hebi in the North China Craton provide direct evidence for the highly variable δ7Li in Archean lithospheric mantle. The δ7Li 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 δ7Li 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 δ7Li characteristics of the Hebi olivines could not have been produced by recent diffusive-driven isotopic fractionation of Li and therefore the δ7Li in the cores of these olivines record the isotopic signature of the subcontinental lithospheric mantle. Our data demonstrate that abnormal δ7Li 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. PMID:24589693

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

    PubMed

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

    2014-01-01

    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. PMID:24589693

  18. On-, off-cratonic, orogenic and oceanic mantle roots: lithosphere unite

    NASA Astrophysics Data System (ADS)

    Wittig, Nadine; Pearson, D. Graham

    2010-05-01

    Associated with Earth's crust is the underlying lithospheric mantle, which is often categorized according its surface availability for sampling. For example, we frequently describe sub-continental lithospheric peridotite xenoliths as on- or off-cratonic to highlight the approximate lithosphere stabilization age as being Archean or post-Archean and contrast them against the lithospheric peridotites recovered from present-day oceanic basins. Orogenic peridotites and ophiolites are obducted in subduction zones and mark paleo-suture zones in amalgamated continents. Regardless of its present-day occurrence, lithospheric mantle is buoyant as a result of substantial extraction or mafic to ultramafic silicate melts. This depletion and buoyancy results in a thermal and mechanical boundary layer (lithosphere-asthenosphere boundary layer, LAB) and isolates Earth's lithosphere from the convecting mantle. The mineralogical and geochemical similarities of some of the oldest cratonic sub-continental lithosphere and highly-depleted young oceanic peridotites require common geochemical mechanisms that are capable of introducing well-correlated major element variability - until metasomatic enrichment masks the depletion signature. Efficient extraction of basaltic melts from the convecting mantle occurs at mid-ocean ridges and removes clinopyroxene and to some extent garnet leaving the olivine-rich buoyant residual lithospheric mantle. We will examine the oceanic heritage of garnet and spinel-facies sub-continental lithospheric mantle in general, but focus on xenoliths (n = 62) sampled across the North Atlantic Craton (~700km, NAC), West Greenland at c. 600 and 200 Ma. These Greenlandic samples are strongly serpentinized, harzburgitic to dunitic peridotites and generally comprise less than 15% orthopyroxene and very little clinopyroxene (<< 5%). If garnet is present it occurs in variable amounts (12 to 0.3%). Major element systematics of these peridotites are highly refractory with Al

  19. Implications of a simple mantle transition zone beneath cratonic North America

    NASA Astrophysics Data System (ADS)

    Thompson, D. A.; Helffrich, G.; Bastow, I. D.; Kendall, J.-M.; Wookey, J.; Eaton, D. W.; Snyder, D. B.

    2011-12-01

    Many areas of old continental interiors have thick roots that extend to depths of 250 km or more, in contrast to the oceans and younger continents, whose lithospheric thickness is less than 100 km. These cratonic roots might perturb temperatures in their surrounding mantle, though the net result could be either cooling or heating; both of which may lead to small-scale convective flow around the root. We show here, using new data from a study of the seismic structure of the Canadian Shield, that the relative positions of the 410 km and 660 km seismic discontinuities are unperturbed beneath one of the deepest and broadest cratonic roots on the Earth. Differential arrival times and internal discontinuity structure are remarkably uniform and simple, varying by little more than ± 0.5 s over the root's 3500 km lateral extent. This implies that the root has no significant thermal effect on the underlying mantle (< 50 K), and any small-scale convection or cold mantle downwelling associated with the large free-air gravity anomaly beneath the shield must be confined to the upper mantle. Our observations are also consistent with phase changes solely in the olivine system ((Mg,Fe) 2SiO 4), with the caveat that our method is dominantly sensitive to S-wave velocity jumps alone.

  20. Origin of garnet peridotites in the lithospheric mantle beneath the Siberian craton

    NASA Astrophysics Data System (ADS)

    Doucet, L. S.; Ionov, D. A.; Brey, G. P.; Golovin, A. V.; Ashchepkov, I. V.

    2012-04-01

    Garnet peridotites represent the largest part of the lithospheric mantle beneath Archean crust, yet the origin of garnet in these rocks continues to be debated. The cratonic mantle is believed to be produced by extensive melt extraction indicated by common low Al and Ca (<1%) and high Mg#WR (≥0.92) of cratonic peridotites [1]. However, even though many garnet peridotites are low in Al and Ca, they usually have lower Mg#WR (<0.92) than spinel harzburgites, which together with common high modal cpx and garnet (>5%) appear to be inconsistent with a residual origin by high degrees of partial melting [2]. To better constraint the origin of garnet in cratonic mantle we report modal, major and trace element compositions for >30 garnet peridotites from the Udachnaya kimberlite in central Siberia (as well as preliminary Nd-isotope data for selected samples). These rocks, unlike many other kimberlite-hosted peridotites worldwide, are unusually fresh, with very low LOI (≤1%) and unaltered minerals [3]. The garnet peridotites in this study are coarse (mostly low-T) to sheared (high-T) harzburgites with Mg#WR of 0.90-0.92 and ≤1% Al2O3 and CaO as well as two lherzolites. Their cpx (2-6%) and garnet (1-9%) have complex REE patterns affected by both melt extraction and various enrichment events. Modal and major oxide compositions of spinel harzburgites from Udachnaya indicate an origin by >35% of partial melting in a broad depth range (2-7 GPa) based on experimental results [4]. By comparison, only 5 out 30 garnet harzburgites in this study plot close to the melting trends defined by spinel harzburgites. The majority of garnet harzburgites in this study (especially high-T) show a range of enrichments in Fe, Si, Ti, HREE etc. relative to pristine melting residues. Moreover, the Nd isotope data for the garnet peridotites (calculated from garnet and cpx analyses) yield an isochron age of 0.8-0.7 Ga, which is much younger than whole-rock Re-Os formation ages (2 Ga [5]). The

  1. Provenances of the Mesozoic sediments in the Ordos Basin and implications for collision between the North China Craton (NCC) and the South China Craton (SCC)

    NASA Astrophysics Data System (ADS)

    Chuang, Bao; Yuelong, Chen; Dapeng, Li; Shanhui, Wang

    2014-12-01

    To constrain the provenance of the Ordos Basin and the evolution history of the Qinling Orogen Belt from the Triassic to the Jurassic, 10 samples from the Dongsheng area and 28 samples from the Yan'an area were analyzed for U-Pb ages and Lu-Hf and Sm-Nd isotopic compositions. The results indicate that Middle Jurassic sediments in the Dongsheng area were derived from the Khondalite Belt, Langshan Mountain and the Yinshan Terrane. Mesozoic sediments in the Yan'an area consist of two parts. One part is derived from the North China Craton (NCC), which has U-Pb age groups of ∼1.8 Ga and ∼2.5 Ga, and Hf model ages of ∼2.8 Ga. The other part is derived from the Qilian-Qinling Orogenic Belt, which has U-Pb age groups of 600-1500 Ma and 100-500 Ma, and Nd and Hf isotopic model ages of less than 2.2 Ga. Combining the U-Pb ages with the Hf and Nd isotopic model ages, Mesozoic detrital zircons with U-Pb age groups of ∼1.8 Ga and ∼2.5 Ga in the Yan'an area are found to also be derived from the Khondalite Belt, Langshan Mountain and the Yinshan Terrane, not from the Trans-China Orogen Belt. From the late-Late Triassic sediments of the Yan'an area, the low average values of the Hf (2.03 Ga) and Nd (2.03 Ga) model ages and the characteristic age population of 600-1500 Ma reveal that the main collision or continental subduction between the NCC and the South China Craton (SCC) occurred in the late-Late Triassic. After the main collision or continental subduction, the proportion of sediments from the Qinling-Qilian Orogenic Belt began to decrease (recorded in the early Jurassic samples), which may be in response to the gradual slowing of the uplift speed of the Qinling Orogenic Belt. In the early-middle Jurassic, the sediments have a main U-Pb age population of 100-500 Ma, low detrital zircon Hf model ages (average value is 1.17 Ga) and low whole rock Nd model ages (average value is 1.13 Ga), which suggests that the Qilian-Qinling Orogenic Belt may have a fast uplift

  2. Coastal Adaptation: The Case of Ocean Beach, San Francisco

    NASA Astrophysics Data System (ADS)

    Cheong, S.

    2012-12-01

    Coastal erosion, storms, sea-level rise, and tsunamis all lead to inundation that puts people and communities at risk. Adapting to these coastal hazards has gained increasing attention with climate change. Instead of promoting one particular strategy such as seawalls or defending against one type of hazard, scholars and practitioners encourage a combination of existing methods and strategies to promote synergistic effects. The recently published Intergovernmental Panel on Climate Change (IPCC) Special Report on climate extremes reflects this trend in the integration of disaster risk management and climate change adaptation. This paper focuses on the roles, compatibilities, and synergies of three coastal adaptation options - engineering, vegetation, and policy - in the case of Ocean Beach in San Francisco. Traditionally engineering approach and ecosystem conservation often have stood in opposition as hard shoreline structures destroy coastal habitats, worsen coastal erosion, divert ocean currents, and prevent the natural migration of shores. A natural migration of shores without structure translates into the abandonment of properties in the coastal zone, and is at odds with property rights and development. For example, policies of relocation, retreat, and insurance may not be popular given the concerns of infrastructure and coastal access. As such, engineering, natural defense, and policy can be more conflictual than complementary. Nonetheless, all these responses are used in combination in many locations. Complementarities and compatibilities, therefore, must be assessed when considering the necessity of engineering responses, natural defense capabilities, and policy options. In this light, the question is how to resolve the problem of mixed responses and short- and long-term interests and values, identify compatibilities, and generate synergies. In the case of Ocean Beach, recent erosions that endangered San Francisco's wastewater treatment system acted as major

  3. Perspective View with Landsat Overlay, San Francisco Bay Area, Calif.

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The defining landmarks of San Francisco, its bay and the San Andreas Fault are clearly seen in this computer-generated perspective viewed from the south. Running from the bottom of the scene diagonally up to the left, the trough of the San Andreas Fault is occupied by Crystal Springs Reservoir and San Andreas Lake. Interstate 280 winds along the side of the fault. San Francisco International Airport is the angular feature projecting into the bay just below San Bruno Mountain, the elongated ridge cutting across the peninsula. The hills of San Francisco can be seen beyond San Bruno Mountain and beyond the city, the Golden Gate.

    This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

    Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D

  4. SAO and Kelvin Waves in the EuroGRIPS GCMS and the UK Meteorological Offices Analyses

    NASA Technical Reports Server (NTRS)

    Amodei, M.; Pawson, S.; Scaife, A. A.; Lahoz, W.; Langematz, U.; Li, Ding Min; Simon, P.

    2000-01-01

    This work is an intercomparison of four tropospheric-stratospheric climate models, the Unified Model (UM) of the U.K. Meteorological Office (UKMO), the model of the Free University in Berlin (FUB). the ARPEGE-climat model of the National Center for Meteorological Research (CNRM), and the Extended UGAMP GCM (EUGCM) of the Center for Global Atmospheric Modelling (CGAM), against the UKMO analyses. This comparison has been made in the framework of the "GSM-Reality Intercomparison Project for SPARC" (GRIPS). SPARC (Stratospheric Processes and their Role in Climate) aims are to investigate the effects of the middle atmosphere on climate and the GRIPS purpose is to organized a comprehensive assessment of current Middle Atmosphere-Climate Models (MACMs). The models integrations were made without identical contraints e.g. boundary conditions, incoming solar radiation). All models are able to represent the dominant features of the extratropical circulation. In this paper, the structure of the tropical winds and the strengths of the Kelvin waves are examined. Explanations for the differences exhibited. between the models. as well as between models and analyses, are also proposed. In the analyses a rich spectrum of waves (eastward and westward) is present and contributes to drive the SAO (SemiAnnual Oscillation) and the QBO (Quasi-Biennal Oscillation). The amplitude of the Kelvin waves is close to the one observed in UARS (Upper Atmosphere Research Satellite) data. In agreement with observations, the Kelvin waves generated in the models propagate into the middle atmosphere as wave packets which underlines convective forcing origin. In most models, slow Kelvin waves propagate too high and are hence overestimated in the upper stratosphere and in the mesosphere, except for the UM which is more diffusive. These waves are not sufficient to force realistic westerlies of the QBO or SAO westerly phases. If the SAO is represented by all models only two of them are able to generate

  5. Smithsonian Astrophysical Observatory Ozone Mapping and Profiler Suite (SAO OMPS) formaldehyde retrieval

    NASA Astrophysics Data System (ADS)

    González Abad, G.; Vasilkov, A.; Seftor, C.; Liu, X.; Chance, K.

    2015-09-01

    This paper presents our new formaldehyde (H2CO) retrievals, obtained from spectra recorded by the nadir instrument of the Ozone Mapping and Profiler Suite (OMPS) flown on-board NASA's Suomi National Polar-orbiting Partnership (SUOMI-NPP) satellite. Our algorithm is similar to the one currently in place for the production of NASA's Ozone Monitoring Instrument (OMI) operational H2CO product. We are now able to produce a consistent set of long term data from two different instruments that share a similar concept. The ongoing overlap period between OMI and OMPS offers a perfect opportunity to study the consistency between both data sets. The different spatial and spectral resolution of the instruments is a source of discrepancy in the retrievals despite the similarity of the physic assumptions of the algorithm. We have concluded that the reduced spectral resolution of OMPS in comparison with OMI is not a significant obstacle in obtaining good quality retrievals. Indeed, the improved signal to noise ratio (SNR) of OMPS with respect to OMI helps to reduce the noise of the retrievals performed using OMPS spectra. However, the size of OMPS spatial pixels imposes a limitation in the capability to distinguish particular features of H2CO that are discernible with OMI. With root mean square (RMS) residuals ~ 5 × 10-4 for individual pixels we estimate the detection limit to be about 7.5 × 1015 molecules cm-2. Total vertical column densities (VCD) errors for individual pixels range between 40 % for pixels with high concentrations to 100 % or more for pixels with concentrations at or below the detection limit. We compare different OMI products with our OMPS product using one year of data, between September 2012 and September 2013. The seasonality of the retrieved slant columns is captured similarly by all products but there are discrepancies in the values of the VCDs. The mean biases among the two OMI products and our OMPS product are 21 % between OMI SAO and OMPS SAO and 38

  6. The Water Crisis in Sao Paulo City: Drought and its Climate Connections

    NASA Astrophysics Data System (ADS)

    Ribeiro Lima, C. H.; Lall, U.

    2014-12-01

    In 2014, Sao Paulo city had its largest water shortage in history. By the end of the first half of 2014, the Cantareira system of water reservoirs, which is responsible for supplying fresh water for about 9 million people in the city, dried to less than 10% of its active storage, leading to a critical situation and the need to pump water from its dead storage and allocate water from other smaller systems of reservoirs in order to meet the demand of the city and avoid a mandatory water rationing. Understanding and identifying the leading factors for such a water crisis is critical for the security of the city. Here, we investigate historical data of water levels and inflows into the Cantareira system and of the rainfall series over the contributing basin in order to estimate the contribution of climate factors to the variability of the water storage levels at the Cantareira system and shed some light on the main causes of the current water shortage. Preliminary results based on natural inflow data from 1930 to 2014 and water storage levels from 2004 through 2014 reveal that, about 60% of the low frequency (beyond seasonal cycle) variance in the storage level trends is explained by trends in the inflows. A remarkably monotonic decreasing trend of about 1.5% per month in the storage levels is observed since 2010 and is closely associated with a similar decreasing trend in the inflows into the system for the period. In fact, the annual average inflow for 2012 (25.6 m3/s) and 2013 (25.7 m3/s) was 65% of the long term average and still below the 2004-2012 average withdrawal to supply Sao Paulo (26.64 m3/s). By the end of the 2013 rainy season the system had accumulated 63% of its total capacity, but the persistence of low inflows and high temperatures during 2013 did not allowed any increase in the water levels. In 2014 austral summer the system experienced the worst hydrological drought since 1930 based on the available streamflow records. The average inflow for the

  7. Quantifying impacts on air quality of vehicular emissions in Sao Paulo and Rio de Janeiro

    NASA Astrophysics Data System (ADS)

    Artaxo, Paulo; Ferreira de Brito, Joel; Godoy, José Marcus; Luiza Godoy, Maria; Junior, Djacinto

    2016-04-01

    Vehicular emissions in megacities such as Sao Paulo and Rio de Janeiro are increasingly becoming a global issue. The São Paulo Metropolitan Area (SPMA), located in Southeast of Brazil, is a megacity with a population of 18 million people, with 7 million cars and large-scale industrial emissions. Rio de Janeiro is also a large city with different meteorology than São Paulo. All cars in Brazil runs gasohol, with 23% ethanol in gasoline, and for the last 10 years, flex cars that can run on gasohol, ethanol or any mixture dominate the market. Overall ethanol accounts for about 30-40% of fuel burned in both cities. To improve the understanding of vehicular emission impacts on aerosol composition and life cycle in these two large megacities a source apportionment study, combining online and offline measurements, was performed. Aerosols were collected for one year to capture seasonal variability at 4 sites in each city, with inorganic and organic aerosol component being sampled. Organic and elemental carbon were measured using a Sunset Laboratory Dual Optics (transmission and reflectance) Carbon Analyzer and about 22 trace elements has been measured using polarized X-Ray Fluorescence (XRF). Aerosol mass and black carbon were also measured, as well as trace gases to help in aerosol source apportionment. In Sao Paulo, the average PM2.5 mass concentration obtained varied from 9.6 to 12.2 μg m-3 for the several sites, and similar concentrations were measured in Rio de Janeiro. At all sites, organic matter (OM) has dominated fine mode aerosol concentration with 42 to 60% of the aerosol mass. EC accounted for 21 to 31% of fine mode aerosol mass concentration. Sulfate accounted for 21 to 26% of PM2.5 for the sites. Aerosol source apportionment was done with receptor analysis and integration with online data such as PTR-MS, Aethalometers, Nephelometers and ACSM helped to apportion vehicular emissions. For the 8 sites operated in Sao Paulo and Rio de Janeiro, vehicular

  8. Tumstatin induces apoptosis and stimulates phosphorylation of p65NF-κB in human osteoblastic osteosarcoma Saos-2 cells.

    PubMed

    Wang, Yang; Yin, Ruo-Feng; Teng, Jia-Song

    2016-06-01

    The present study was aimed to investigate the effect of tumstatin on inhibition of proliferation and induction of apoptosis in Saos-2 human osteosarcoma cells and to understand the mechanism involved. Inhibition of cell proliferation was analyzed by MTT assay and induction of apoptosis through nuclear fragmentation assay. Viability of Saos-2 cells was reduced to 19% on treatment with 25 µM concentration of tumstatin after 48 h. Presence of characteristic apoptotic nuclei, rounded cell shape and shrunken size were caused by tumstatin treatment at 25 µM concentration. The level of mRNA corresponding to PTEN, FasR and FasL was increased significantly in tumstatin treated Saos-2 cells compared to untreated control. Investigation of the mechanism revealed NF-κB activation by phosphorylation on serine 536. The activated NF-κB was translocated into the nucleus from the cytoplasm on treatment with tumstatin. Degradation of the IκBα by tumstatin was found to be much slower compared to that induced by treatment with TNF-α. Thus, tumstatin inhibits proliferation and induces apoptosis in Saos-2 cells through activation of NF-κB and its translocation to the nucleus. Therefore, tumstatin can play an important role in the treatment of osteosarcoma. PMID:27109498

  9. SURVEY OF VOLATILE ORGANIC COMPOUNDS ASSOCIATED WITH AUTOMOTIVE EMISSIONS IN THE URBAN AIRSHED OF SAO PAULO, BRAZIL

    EPA Science Inventory

    The Metropolitan Region of Sao Paulo (MRSP), Brazil, is one of the largest metropolitan areas in the world (population 17 million, approx.) and relies heavily on alcohol-based fuels for automobiles. It is estimated that about 40% of the total volume of fuel is ethanol with som...

  10. Environmental benefits of replacing fuel oil by natural gas in the metropolitan region of Sao Paulo, Brazil

    SciTech Connect

    Kondo, S.; Assuncao, J.V. de

    1998-12-31

    The Metropolitan Region of Sao Paulo (Brazil) has a population 16.322 million people (1995 estimate) living in an area of 8,051 km2 with most of them concentrated in the city of Sao Paulo with 9.8 million people and 4.6 million cars. Although with an air quality better than some other Latin American megacities such as Mexico and Santiago do Chile, the air quality still exceeds the national air quality standards. In 2/17/1993 Brazilian Petroleum Company (PETROBRAS) and the Bolivian Petroleum Company (Yacimientos Petroliferos Fiscales Bolivianos -- YPFB) signed an agreement to bring natural gas from Bolivia to the south and southeast of Brazil. The end of the construction of the gas pipeline will be in 1999, and it will deliver 4 million Nm3/day of natural gas to COMGAS Sao Paulo State Gas Company. This amount will increase to 8.1 million Nm3/day by the year 2006, that will be sufficient to supply the Sao Paulo Metropolitan Region market need at that time. In this study an estimate of the influence in the air quality was performed supposing the substitution of fuel oil by natural gas in industry and also in diesel buses. The results showed that there will be benefits in relation to sulfur dioxide, PM10, greenhouse gases and trace elements, and negligible effects in relation to NO{sub x}, NMTOC and carbon monoxide.

  11. Education, Training and Employment in Small-Scale Enterprises: Three Industries in Sao Paulo, Brazil. IIEP Research Report No. 63.

    ERIC Educational Resources Information Center

    Leite, Elenice M.; Caillods, Francoise

    Despite the prophecies forecasting their probable disappearance or annihilation, small-scale enterprises have persisted in the Brazilian industrial structure since 1950. To account for the survival of small firms in Brazil, specifically in the state of Sao Paulo, a study examined 100 small firms in three industrial sectors: clothing, mechanical…

  12. Body fat distribution in stunted compared with normal-height children from the shantytowns of Sao Paulo, Brazil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objective: The objective of this study was to determine whether central fat distribution varies between children who were growth retarded as young children, compared to normal height children from the same impoverished communities of Sao Paulo, Brazil. Research methods and procedures: A prospectiv...

  13. Thermal history and origin of the Tanzanian Craton from Pb isotope thermochronology of feldspars from lower crustal xenoliths

    NASA Astrophysics Data System (ADS)

    Bellucci, Jeremy J.; McDonough, William F.; Rudnick, Roberta L.

    2011-01-01

    Common and radiogenic Pb isotopic compositions of plagioclase and anti-perthitic feldspars from granulite-facies lower crustal xenoliths from the Labait Volcano on the eastern margin of the Tanzanian Craton have been measured via laser ablation MC-ICP-MS. Common Pb in plagioclase and a single stage Pb evolution model indicate that the lower crust of the Tanzanian Craton was extracted from mantle having a 238U/ 204Pb of 8.1 ± 0.3 and a 232Th/ 238U of 4.3 ± 0.1 at 2.71 ± 0.09 Ga (all uncertainties are 2σ). Since 2.4 Ga, some orthoclase domains within anti-perthites have evolved with a maximum 238U/ 204Pb of 6 and 232Th/ 238U of 4.3. The spread in Pb isotopic composition in the anti-perthitic feldspars yields single crystal Pb-Pb isochrons of ˜ 2.4 Ga, within uncertainty of U-Pb zircon ages from the same sample suite. The Pb isotopic heterogeneities imply that these granulites resided at temperatures < 600 °C in the lower crust of the Tanzanian Craton from ca. 2.4 Ga to the present. In concert with the chemistry of surface samples, mantle xenoliths, and lower crustal xenoliths, our data imply that the cratonic lithosphere in Tanzania formed ca. ˜ 2.7 Ga, in a convergent margin setting, and has remained undisturbed since 2.7 Ga.

  14. A Sm-Nd and Pb isotope study of Archaean greenstone belts in the southern Kaapvaal Craton, South Africa

    NASA Technical Reports Server (NTRS)

    Wilson, A. H.; Carlson, R. W.

    1989-01-01

    An Sm-Nd and Pb study on a wide variety of lithologies in Archaean greenstone belt fragments in the southern Kaapvaal Craton reveals a complex petrogenetic history. The fragments are important because they represent a 350 km transect through the craton south of Barberton to its southern margin. The Commondale greenstone belt yields a precise Sm-Nd age of 3334 + or - 18 Ma on an exceptionally well preserved peridotite suite of komatiitic affinity. The wide range of Sm/Nd from 0.6 to 1.0 is attributed to the unusual occurrence of orthopyroxene in the spinifex-bearing rocks. A considerably younger age of about 3.2 Ga is suggested for the Nondweni greenstone belt close to the southern margin of the craton on the basis of separate Sm-Nd isochrons on individual lithologies ranging from komatiite, through komatiitic basalt and basalt to felsic volcanic rocks. On the basis of the present study the greenstone belts appear to have been emplaced at progressively younger ages toward the southern margin of the craton.

  15. Validation of OMI Total Ozone Retrievals from the SAO Ozone Profile Algorithm and Three Operational Algorithms 3 with Brewer Measurements

    NASA Astrophysics Data System (ADS)

    Bak, Juseon; Kim, Jae H.; Liu, Xiong; Chance, Kelly

    2015-04-01

    The optimal estimation (OE) based ozone profile algorithm developed at Smithsonian 3 Astrophysical Observatory (SAO) is assessed as to its accuracy to extract total ozone amount from 4 Ozone Monitoring Instrument (OMI) measurements through the validation using Brewer ground 5 based measurements between January 2005 and December 2008. We compare it against the quality of 6 three OMI operational ozone products, derived from NASA TOMS, KNMI DOAS, and KNMI OE 7 algorithms, respectively. The validation demonstrates that the SAO ozone profile algorithm generally 8 has the best total ozone retrieval performance compared to the three OMI operational ozone products. 9 The individual station comparisons show an agreement between SAO and Brewer within ± 1% except 10 at polar stations (~ -2 %), with a high correlation coefficient of ~ 0.99 at most stations. The KNMI OE 11 algorithm systematically overestimates the true total ozone value at all stations with a bias from 2 % 12 at low/mid latitude stations to 5 % at high latitude stations. On the other hand, TOMS/DOAS 13 algorithm underestimates total ozone by ~ -1.7 % on average. The standard deviations of differences 14 are ~ 1.8 % for SAO and TOMS while DOAS and KNMI show the standard deviation values of 2.2 15 and 2.5 %, respectively. The remarkable stability of SAO OE algorithm is found with no significant 16 dependency on algorithmic variables such as viewing geometries, cloud parameters, and time. In 17 comparison, the severe dependency on both solar and viewing zenith angles is found in KNMI OE 18 algorithm, which is characterized with a negative (positive) correlation with smaller (larger) solar 19 zenith angles and the strong cross-track dependent biases ranging from 4% at nadir and 1% at off-20 nadir positions. The dependence of DOAS and TOMS algorithms on the algorithmic variables is 21 marginal compared to KNMI OE algorithm, but distinct compared to SAO OE algorithm. Relative 22 differences between SAO/DOAS and

  16. Moho depth and crustal structure of the Siberian Craton and the West Siberian Basin: An appraisal of existing seismic data

    NASA Astrophysics Data System (ADS)

    Cherepanova, Yulia; Artemieva, Irina M.; Thybo, Hans

    2013-04-01

    We present a digital model of the crustal structure of the Archean-Proterozoic Siberian craton and the Paleozoic-Mesozoic West Siberian basin, based on seismic profiles published since 1960 in international and Russian journals, books, theses and reports. Data quality was assessed and quantitatively assigned to each profile based on acquisition and interpretation method and completeness of the model. The database represents major improvement in coverage and resolution with a nominal sample interval of 50 km before interpolation onto a uniform grid. It includes depth to Moho, thickness and average P-wave velocity of five crustal layers (sediments, and upper, middle, lower, and lowermost crust) and Pn velocity. Results are presented in maps and cross-sections, which demonstrate strong crustal heterogeneity. Crustal structure shows weak correlation with tectono-thermal age and strong correlation with tectonic setting. Sedimentary thickness varies from 0-3 km in stable craton to 10-20 km in extended regions. Typical Moho depths are 44-46 km in stable Archean crust, 40-42 km in Proterozoic craton and Neoproterozoic/Paleozoic orogens, 35-38 km in extended cratonic crust, and 38-40 km in the West Siberian basin. Average crustal velocity is ~6.2-6.4 km/s, ranging from <5.8 km/s in deep sedimentary basins to ~6.6 km/s around the up-to 54 km thick Anabar shield crust. The cratonic crust generally consists of three layers and has no high-velocity lowermost crust (Vp~7.4 km/s), which is observed only in magmatic areas. Upper mantle Pn velocities are generally ~8.2 km/s in the craton and West Siberian Basin, lower in Baikalian and Caledonian areas, higher in the Tunguska and Viluy basins, and abnormally high (8.6-8.9 km/s) around kimberlite fields. We provide an extensive summary of the tectonic and geodynamic evolution of the region and discuss the origin of crustal heterogeneity and processes of crustal evolution in Precambrian cratons and major Phanerozoic basins and rift

  17. Is Nubia plate rigid? A geodetic study of the relative motion of different cratonic areas within Africa.

    NASA Astrophysics Data System (ADS)

    Njoroge, M. W.; Malservisi, R.; Hugentobler, U.; Mokhtari, M.; Voytenko, D.

    2014-12-01

    Plate rigidity is one of the main paradigms of plate tectonics and a fundamental assumption in the definition of a global reference frame as ITRF. Although still far for optimal, the increased GPS instrumentation of the African region can allow us to understand how rigid one of the major plate can be. The presence of diffused band of seismicity, the Cameroon volcanic line, Pan African Kalahari orogenic belt and East Africa Rift suggest the possibility of relative motion among the different regions within the Nubia. The study focuses on the rigidity of Nubia plate. We divide the plate into three regions: Western (West Africa craton plus Nigeria), Central (approximately the region of the Congo craton) and Southern (Kalahari craton plus South Africa) and we utilize Euler Vector formulation to study internal rigidity and eventual relative motion. Developing five different reference frames with different combinations of the 3 regions, we try to understand the presence of the relative motion between the 3 cratons thus the stability of the Nubia plate as a whole. All available GPS stations from the regions are used separately or combined in creation of the reference frames. We utilize continuous stations with at least 2.5 years of data between 1994 and 2014. Given the small relative velocity, it is important to eliminate eventual biases in the analysis and to have a good estimation in the uncertainties of the observed velocities. For this reason we perform our analysis using both Bernese and Gipsy-oasis codes to generate time series for each station. Velocities and relative uncertainties are analyzed using the Allan variance of rate technique, taking in account for colored noise. An analysis of the color of the noise as function of latitude and climatic region is also performed to each time series. Preliminary results indicate a slight counter clockwise motion of West Africa craton with respect to South Africa Kalahari, and South Africa Kalahari-Congo Cratons. In addition

  18. Selenium and heavy metals in San Francisco Bay diving ducks

    USGS Publications Warehouse

    Ohlendorf, H.M.; Lowe, R.W.; Kelly, P.R.; Harvey, T.E.

    1986-01-01

    We analyzed for selenium (Se) and heavy metals in greater scaups (Aythya marila) and surf scoters (Melanitta perspicillata) collected from southern San Francisco Bay in March and April 1982. There were no differences (P > 0.05) between species for liver concentrations of silver (Ag), mercury (Hg), or lead (Pb). Copper (Cu) (P 0.05) between the 2 species. The geometric mean cadmium (Cd) concentration in scoter kidneys (24.6 ppm, dry wt) was higher than in scaups (15.5 ppm) (0.1 > P > 0.05). Liver concentrations of Hg and Se were correlated (P < 0.01). The toxicological significance of some elements in these species is not known. However, Se levels in scoters (34.4 ppm, dry wt) were similar to those in livers of dabbling ducks (Anas spp.) in the nearby San Joaquin Valley where reproduction was impaired severely.

  19. Large scale simulations of the great 1906 San Francisco earthquake

    NASA Astrophysics Data System (ADS)

    Nilsson, S.; Petersson, A.; Rodgers, A.; Sjogreen, B.; McCandless, K.

    2006-12-01

    As part of a multi-institutional simulation effort, we present large scale computations of the ground motion during the great 1906 San Francisco earthquake using a new finite difference code called WPP. The material data base for northern California provided by USGS together with the rupture model by Song et al. is demonstrated to lead to a reasonable match with historical data. In our simulations, the computational domain covered 550 km by 250 km of northern California down to 40 km depth, so a 125 m grid size corresponds to about 2.2 Billion grid points. To accommodate these large grids, the simulations were run on 512-1024 processors on one of the supercomputers at Lawrence Livermore National Lab. A wavelet compression algorithm enabled storage of time-dependent volumetric data. Nevertheless, the first 45 seconds of the earthquake still generated 1.2 TByte of disk space and the 3-D post processing was done in parallel.

  20. Rocks and geology in the San Francisco Bay region

    USGS Publications Warehouse

    Stoffer, Philip W.

    2002-01-01

    The landscape of the San Francisco Bay region is host to a greater variety of rocks than most other regions in the United States. This introductory guide provides illustrated descriptions of 46 common and important varieties of igneous, sedimentary, and metamorphic rock found in the region. Rock types are described in context of their identification qualities, how they form, and where they occur in the region. The guide also provides discussion about of regional geology, plate tectonics, the rock cycle, the significance of the selected rock types in relation to both earth history and the impact of mineral resources on the development in the region. Maps and text also provide information where rocks, fossils, and geologic features can be visited on public lands or in association with public displays in regional museums, park visitor centers, and other public facilities.

  1. Characterizing the scientific potential of satellite sensors. [San Francisco, California

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Eleven thematic mapper (TM) radiometric calibration programs were tested and evaluated in support of the task to characterize the potential of LANDSAT TM digital imagery for scientific investigations in the Earth sciences and terrestrial physics. Three software errors related to integer overflow, divide by zero, and nonexist file group were found and solved. Raw, calibrated, and corrected image groups that were created and stored on the Barker2 disk are enumerated. Black and white pixel print files were created for various subscenes of a San Francisco scene (ID 40392-18152). The development of linear regression software is discussed. The output of the software and its function are described. Future work in TM radiometric calibration, image processing, and software development is outlined.

  2. Water Quality Analysis of Yosemite Creek Watershed, San Francisco, California

    NASA Astrophysics Data System (ADS)

    Davis, J. R.; Snow, M. K.; Aquino, A.; Huang, C.; Thai, A.; Yuen, C.

    2003-12-01

    Surface water quality in urban settings can become contaminated by anthropogenic inputs. Yosemite Creek watershed is situated on the east side of San Francisco near Bayview Hunters Point and provides an ideal location for water quality investigations in urban environments. Accordingly, students from Philip and Sala Burton High School monitored water quality at three locations for their physicochemical and biological characteristics. Water was tested for pH, dissolved oxygen, conductivity, total dissolved solids, salinity, and oxidation reduction potential. In addition, a Hach DR 850 digital colorimeter was utilized to measure chlorine, fluorine, nitrogen, phosphorous, and sulfate. The biological component was assessed via monitoring benthic macro invertebrates. Specifically, the presence of caddisfly (Trichoptera) were used to indicate low levels of contaminants and good water quality. Our results indicate that water quality and macro invertebrate populations varied spatially within the watershed. Further investigation is needed to pinpoint the precise location of contaminant inputs.

  3. Deep bore hole instrumentation along San Francisco Bay Bridges

    SciTech Connect

    Bakun, W.; Bowman, J.; Clymer, R.; Foxall, W.; Hipley, P.; Hollfelder, J.; Hutchings, L.; Jarpe, S.; Kasameyer, P.; McEvilly, T.; Mualchin, L.; Palmer, M.

    1998-10-01

    The Bay Bridges down hole network consists of sensors in bore holes that are drilled 100 ft. into bedrock around and in the San Francisco Bay. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty- one sensor packages at fifteen sites. Extensive financial support is being contributed by Caltrans, UCB, LBL, LLNL-LDRD, U.C. Campus/Laboratory Collaboration (CLC) program, and USGS. The down hole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 73 1 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes.

  4. Deep Borehole Instrumentation Along San Francisco Bay Bridges - 2001

    SciTech Connect

    Hutchings, L.; Kasameyer, P.; Long, L.; McEvilly, T.; Clymer, R.; Urhhammer, R.; Baise, L.

    2001-05-01

    This is a progress report on the Bay Bridges downhole network. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges in San Francisco Bay, California. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty-one sensor packages at fifteen sites. The downhole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 731 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes. This report list earthquakes and stations where recordings were obtained during the period February 29, 2000 to November 11, 2000. Also, preliminary results on noise analysis for up and down hole recordings at Yerba Buena Island is presented.

  5. Perspective View with Landsat Overlay, San Francisco Bay Area, Calif.

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The cities of San Francisco and the East Bay are highlighted in this computer-generated perspective viewed from west of the Golden Gate. San Francisco occupies the peninsula jutting into the picture from the right. Golden Gate Park is the long rectangle near its left end and the Presidiois the green area at its tip, from which Golden Gate Bridge crosses to Marin. Treasure Island is the bright spot above San Francisco and Alcatraz Island is the small smudge below and to the left. Across the bay from San Francisco lie Berkeley (left) and Oakland (right). Mount Diablo, a landmark visible for many miles, rises in the distance at the upper right.

    This three-dimensional perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced false-color Landsat 5 satellite image. Colors are from Landsat bands 3, 2, and 1 as red, green and blue, respectively. Topographic expression is exaggerated two times.

    Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

    The Landsat Thematic Mapper image used here came from an on-line mosaic of Landsat images for the continental United States (http://mapus.jpl.nasa.gov), a part of NASA's Digital Earth effort.

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

  6. Microplastic contamination in the San Francisco Bay, California, USA.

    PubMed

    Sutton, Rebecca; Mason, Sherri A; Stanek, Shavonne K; Willis-Norton, Ellen; Wren, Ian F; Box, Carolynn

    2016-08-15

    Despite widespread detection of microplastic pollution in marine environments, data describing microplastic abundance in urban estuaries and microplastic discharge via treated municipal wastewater are limited. This study presents information on abundance, distribution, and composition of microplastic at nine sites in San Francisco Bay, California, USA. Also presented are characterizations of microplastic in final effluent from eight wastewater treatment plants, employing varying treatment technologies, that discharge to the Bay. With an average microplastic abundance of 700,000particles/km(2), Bay surface water appears to have higher microplastic levels than other urban waterbodies sampled in North America. Moreover, treated wastewater from facilities that discharge into the Bay contains considerable microplastic contamination. Facilities employing tertiary filtration did not show lower levels of contamination than those using secondary treatment. As textile-derived fibers were more abundant in wastewater, higher levels of fragments in surface water suggest additional pathways of microplastic pollution, such as stormwater runoff. PMID:27289280

  7. Enteric pathogenic protozoa in homosexual men from San Francisco.

    PubMed

    Ortega, H B; Borchardt, K A; Hamilton, R; Ortega, P; Mahood, J

    1984-01-01

    The prevalence of enteric protozoa was studied in a survey conducted among 150 male homosexual patients in San Francisco. All patients were from a private practice in internal medicine. Each was asked to complete a questionnaire and to submit multiple stool specimens for examination. Of this group, 47% were positive for one or more potentially pathogenic intestinal protozoa; Entamoeba histolytica was found in 36%, Entamoeba hartmanni in 35%, Giardia lamblia in 5%, and Dientamoeba fragilis in 1.3%. Symptoms were unreliable as a diagnostic index of intestinal protozoan infection. Colonization rates could not be correlated with any specific sexual technique. The large number of homosexuals at risk, combined with the potential for difficulties in diagnosis and contact-tracing, indicate the possibility that enteric pathogenic protozoa will cause future health problems in this population. PMID:6087479

  8. 2004 Fall Meeting Expands to San Francisco Marriott !

    NASA Astrophysics Data System (ADS)

    Wesson, Rob; Burch, Jim; Plescia, Jeff

    2004-10-01

    After only one year, the AGU Fall Meeting has grown beyond the capacity of Moscone West. Sessions at the upcoming Fall Metting (13-17 December) will be held in both the Moscone West faicility, site of last year's meeting and the San Francisco Marriott Hotel. The Marriott is a 5-minute walk across the street, a distance not farther than the walk from Moscone North to Moscone South, the facilities in which the meeting was held for several years prior to 2003. The Program Committe has tried to schedule sessions to minimize the inconvenience of the 5-minute walk between the two locations. Most Union sessions, including the Union tutorials and the Frontiers of Geophysics lecture, along with many other sessions, will be held at theMarriott. In addition, most Section and Focus groups social events and other activities will be held at the Marriott.

  9. Birds and environmental contaminants in San Francisco and Chesapeake Bays

    USGS Publications Warehouse

    Ohlendorf, H.M.; Fleming, W.J.

    1988-01-01

    The direct and indirect effects of human activities, including environmental contamination, upon bird populations in San Francisco Bay and Chesapeake Bay are imperfectly understood, and few data are available. that allow a comparison of the contamination levels in birds from these two areas. Certain trace elements and organochlorine compounds have been found at sufficiently high concentrations in bird tissues or their foods to expect adverse effects in these birds, based upon results of field and laboratory studies conducted with other avian species. The decline and recovery of populations of many avian species have been recorded, including some associated with organochlorine contamination. The present paper summarizes available information on the occurrence and potential effects of contaminants upon birds in these two regions.

  10. Supraphysiological Levels of Quercetin Glycosides are Required to Alter Mineralization in Saos2 Cells

    PubMed Central

    Nash, Leslie A.; Peters, Sandra J.; Sullivan, Philip J.; Ward, Wendy E.

    2016-01-01

    Flavonoid intake is positively correlated to bone mineral density (BMD) in women. Flavonoids such as quercetin exhibit strong anti-oxidant and anti-inflammatory activity that may be beneficial for bone health. Quercetin, previously shown to positively influence osteoblasts, is metabolized into glycosides including rutin and hyperoside. We compared the effects of these glycosides on mineralization in human osteoblast (Saos2) cells. Administration of rutin (≥25 µM) and hyperoside (≥5 µM) resulted in higher mineral content, determined using the alizarin red assay. This was accompanied by higher alkaline phosphatase activity with no cell toxicity. The expression of osteopontin, sclerostin, TNFα and IL6, known stimuli for decreasing osteoblast activity, were reduced with the addition of rutin or hyperoside. In summary, rutin and hyperoside require supraphysiological levels, when administered individually, to positively influence osteoblast activity. This information may be useful in developing nutraceuticals to support bone health. PMID:27136576

  11. SEISMIC STUDY OF THE AGUA DE PAU GEOTHERMAL PROSPECT, SAO MIGUEL, AZORES.

    USGS Publications Warehouse

    Dawson, Phillip B.; Rodrigues da Silva, Antonio; Iyer, H.M.; Evans, John R.

    1985-01-01

    A 16 station array was operated over the 200 km**2 central portion of Sao Miguel utilizing 8 permanent Instituto Nacional de Meterologia e Geofisica stations and 8 USGS portable stations. Forty four local events with well constrained solutions and 15 regional events were located. In addition, hundreds of unlocatable seismic events were recorded. The most interesting seismic activity occurred in a swarm on September 6 and 7, 1983 when over 200 events were recorded in a 16 hour period. The seismic activity around Agua de Pau was centered on the east and northeast slopes of the volcano. The data suggest a boiling hydrothermal system beneath the Agua de Pau volcano, consistent with a variety of other data.

  12. Lidar/photometry studies at Sao Paulo in the 2003-2005 period, Brazil

    NASA Astrophysics Data System (ADS)

    Landulfo, Eduardo; Sawamura, Patricia; Uehara, Sandro T.; Nakaema, Walter M.; Torres, Ani S.; Lopes, Fábio J. S.; Matos, Caio A.; de Jesus, Wellington C.

    2007-09-01

    A lidar system has been operational at Sao Paulo, Brazil (23° S, 46° W) since 2001 and colocated is a sunphotometer belonging to AERONET . During this last years aerosol properties has been extracted from both systems and seasonal trends have been observed specially when long range transport takes place bringing plumes with biomass burning aerosol which can distinctively be extracted from a heavy loaded atmosphere as SÃ#o Paulo. These events trigger poor air quality conditions which can be easily correlated. The parameters for studying these patterns are Aerosol Optical Depth, Angström Exponent and Lidar Ratio. We show here some case studies belonging to years 2003, 2004 and 2005.

  13. Urban land use of the Sao Paulo metropolitan area by automatic analysis of LANDSAT data

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Niero, M.; Foresti, C.

    1983-01-01

    The separability of urban land use classes in the metropolitan area of Sao Paulo was studied by means of automatic analysis of MSS/LANDSAT digital data. The data were analyzed using the media K and MAXVER classification algorithms. The land use classes obtained were: CBD/vertical growth area, residential area, mixed area, industrial area, embankment area type 1, embankment area type 2, dense vegetation area and sparse vegetation area. The spectral analysis of representative samples of urban land use classes was done using the "Single Cell" analysis option. The classes CBD/vertical growth area, residential area and embankment area type 2 showed better spectral separability when compared to the other classes.

  14. SAO/NASA joint investigation of astronomical viewing quality at Mount Hopkins Observatory: 1969-1971

    NASA Technical Reports Server (NTRS)

    Pearlman, M. R.; Bufton, J. L.; Hogan, D.; Kurtenbach, D.; Goodwin, K.

    1974-01-01

    Quantitative measurements of the astronomical seeing conditions have been made with a stellar-image monitor system at the Mt. Hopkins Observatory in Arizona. The results of this joint SAO-NASA experiment indicate that for a 15-cm-diameter telescope, image motion is typically 1 arcsec or less and that intensity fluctuations due to scintillation have a coefficient of irradiance variance of less than 0.12 on the average. Correlations between seeing quality and local meteorological conditions were investigated. Local temperature fluctuations and temperature gradients were found to be indicators of image-motion conditions, while high-altitude-wind conditions were shown to be somewhat correlated with scintillation-spectrum bandwidth. The theoretical basis for the relationship of atmospheric turbulence to optical effects is discussed in some detail, along with a description of the equipment used in the experiment. General site-testing comments and applications of the seeing-test results are also included.

  15. Thirty Years, One Million Spectra: Public Access to the SAO Spectral Archives

    NASA Astrophysics Data System (ADS)

    Mink, J.; Moran, S.

    2015-09-01

    Over the last 30 years, the SAO Telescope Data Center has reduced and archived over 1,000,000 spectra, consisting of 287,000 spectra from five high dispersion Echelle spectrographs and 717,000 spectra from four low dispersion spectrographs, across three telescopes. 151,000 spectra from six instruments are currently online and publicly available, covering many interesting objects in the northern sky, including most of the galaxies in the Updated Zwicky Catalog which are reachable through NED or Simbad. A majority of the high dispersion spectra will soon be made public, as will more data from the MMT multi-fiber spectrographs. Many objects in the archive have multiple spectra over time, which make them a valuable resource for archival time-domain studies. We are now developing a system to make all of the public spectra more easily searchable and viewable through the Virtual Observatory.

  16. Supraphysiological Levels of Quercetin Glycosides are Required to Alter Mineralization in Saos2 Cells.

    PubMed

    Nash, Leslie A; Peters, Sandra J; Sullivan, Philip J; Ward, Wendy E

    2016-01-01

    Flavonoid intake is positively correlated to bone mineral density (BMD) in women. Flavonoids such as quercetin exhibit strong anti-oxidant and anti-inflammatory activity that may be beneficial for bone health. Quercetin, previously shown to positively influence osteoblasts, is metabolized into glycosides including rutin and hyperoside. We compared the effects of these glycosides on mineralization in human osteoblast (Saos2) cells. Administration of rutin (≥25 µM) and hyperoside (≥5 µM) resulted in higher mineral content, determined using the alizarin red assay. This was accompanied by higher alkaline phosphatase activity with no cell toxicity. The expression of osteopontin, sclerostin, TNFα and IL6, known stimuli for decreasing osteoblast activity, were reduced with the addition of rutin or hyperoside. In summary, rutin and hyperoside require supraphysiological levels, when administered individually, to positively influence osteoblast activity. This information may be useful in developing nutraceuticals to support bone health. PMID:27136576

  17. APPLICATION OF AUDIO-MAGNETOTELLURIC SURVEYS ON SAO MIGUEL ISLAND, AZORES PORTUGAL.

    USGS Publications Warehouse

    Hoover, Donald; Rodrigues Da Silva, A.; Pierce, Herbert A.; Amaral, Roberto

    1984-01-01

    Geothermal exploration and development has been under way on Sao Miguel Island, Azores since 1975. This work had been restricted to the Fogo volcano, one of three dormant silicic volcanic centers on the island. The USGS in 1982 and 1983 conducted reconnaissance natural-source audio-magnetotelluric (AMT) surveys of all three silicic centers to evaluate the potential for geothermal systems at each and to demonstrate the utility of the method in areas of difficult terrain. Results on Fogo showed a low resistivity trend extending from the present production area upslope to the caldera boundary. The upper part of this trend is the upwelling zone of a thermal plume which supplies the production area. Further exploration and drilling are now planned for this area.

  18. Physical and chemical properties of San Francisco Bay, California, 1980

    USGS Publications Warehouse

    Ota, Allan Y.; Schemel, L.E.; Hager, S.W.

    1989-01-01

    The U.S. Geological Survey conducted hydrologic investigations in both the deep water channels and the shallow-water regions of the San Francisco Bay estuarine system during 1980. Cruises were conducted regularly, usually at two-week intervals. Physical and chemical properties presented in this report include temperature , salinity, suspended particulate matter, turbidity, extinction coefficient, partial pressure of CO2, partial pressure of oxygen , dissolved organic carbon, particulate organic carbon, discrete chlorophyll a, fluorescence of photosynthetic pigments, dissolved silica, dissolved phosphate, nitrate plus nitrite, nitrite, ammonium, dissolved inorganic nitrogen, dissolved nitrogen, dissolved phosphorus, total nitrogen, and total phosphorus. Analytical methods are described. The body of data contained in this report characterizes hydrologic conditions in San Francisco Bay during a year with an average rate of freshwater inflow to the estuary. Concentrations of dissolved silica (discrete-sample) ranged from 3.8 to 310 micro-M in the northern reach of the bay, whereas the range in the southern reach was limited to 63 to 150 micro-M. Concentrations of phosphate (discrete-sample) ranged from 1.3 to 4.4 micro-M in the northern reach, which was narrow in comparison with that of 2.2 to 19.0 micro-M in the southern reach. Concentrations of nitrate plus nitrite (discrete-sample) ranged from near zero to 53 micro-M in the northern reach, and from 2.3 to 64 micro-M in the southern reach. Concentrations of nitrite (discrete-sample) were low in both reaches, exhibiting a range from nearly zero to approximately 2.3 micro-M. Concentrations of ammonium (discrete-sample) ranged from near zero to 14.2 micro-M in the northern reach, and from near zero to 8.3 micro-M in the southern reach. (USGS)

  19. Variation of the Beach Profile, Ocean Beach, San Francisco, California

    NASA Astrophysics Data System (ADS)

    Hansen, J. E.; Ho, T.; Li, A.; Perez, A.; Wong, Y.; Bissell, M.

    2006-12-01

    Ocean Beach is a 7-km-long stretch of beach that is the western boundary of the city of San Francisco with the Pacific Ocean. This beach is exposed to large winter waves produced in the North Pacific and smaller summer waves from both the North and South Pacific. Recent decades have seen an increased rate of erosion at the south end of the beach that has led to the partial collapse of a parking lot, and continued erosion threatens both public and private infrastructure. To gain an understanding of the variation in beach profiles we established six cross-shore profiles approximately 1 km apart. Each profile represents a part of the beach that experiences different wave conditions, caused by refraction across the San Francisco Bar, and thus has a different morphologic response to offshore sea conditions. The six sub-aerial profiles were measured using a total station one week apart in August 2006. All profiles increased in elevation and five of the six profiles showed the early formation or continued growth of berms. The same profiles will be re-analyzed in the autumn to determine further change, and compared to data collected by a 2004 SF-ROCKS group that also studied Ocean Beach. We will relate beach profile change to wave conditions measured at an offshore buoy to determine what wave conditions cause profile accretion or erosion. The results of this study will shed light on the processes occurring at Ocean Beach and will help us to understand why the south end of the beach is eroding.

  20. Biological effects of anthropogenic contaminants in the San Francisco Estuary

    USGS Publications Warehouse

    Thompson, B.; Adelsbach, T.; Brown, C.; Hunt, J.; Kuwabara, J.; Neale, J.; Ohlendorf, H.; Schwarzbach, S.; Spies, R.; Taberski, K.

    2007-01-01

    Concentrations of many anthropogenic contaminants in the San Francisco Estuary exist at levels that have been associated with biological effects elsewhere, so there is a potential for them to cause biological effects in the Estuary. The purpose of this paper is to summarize information about biological effects on the Estuary's plankton, benthos, fish, birds, and mammals, gathered since the early 1990s, focusing on key accomplishments. These studies have been conducted at all levels of biological organization (sub-cellular through communities), but have included only a small fraction of the organisms and contaminants of concern in the region. The studies summarized provide a body of evidence that some contaminants are causing biological impacts in some biological resources in the Estuary. However, no general patterns of effects were apparent in space and time, and no single contaminant was consistently related to effects among the biota considered. These conclusions reflect the difficulty in demonstrating biological effects due specifically to contamination because there is a wide range of sensitivity to contaminants among the Estuary's many organisms. Additionally, the spatial and temporal distribution of contamination in the Estuary is highly variable, and levels of contamination covary with other environmental factors, such as freshwater inflow or sediment-type. Federal and State regulatory agencies desire to develop biological criteria to protect the Estuary's biological resources. Future studies of biological effects in San Francisco Estuary should focus on the development of meaningful indicators of biological effects, and on key organism and contaminants of concern in long-term, multifaceted studies that include laboratory and field experiments to determine cause and effect to adequately inform management and regulatory decisions. ?? 2006 Elsevier Inc. All rights reserved.

  1. Keck Observations of HD 169142 and SAO 26804: Results from a Survey of Vega-like sources

    NASA Astrophysics Data System (ADS)

    Fisher, R. S.; Telesco, C. M.; Pina, R. K.; Knacke, R. F.

    2001-05-01

    We present new mid-IR (10 and 18 μm ) observations of two Vega-like sources, HD 169142 and HD 233517 (SAO 26804). Using OSCIR on Keck II, we have detected extended emission around HD 169142 in what appears to be a nearly face-on disk. The mid-IR-emitting region of the disk has a diameter of ~175 AU, comparable to HD 141569 and the Vega-like archetype β Pictoris. The position of HD 169142 in the H-R diagram implies that it is close to, but not yet on, the ZAMS. Comparison with PMS evolutionary tracks indicates that it is 3 - 10 Myr old, in transition between the Herbig Ae/Be and Vega-like classes. Assuming that the mid-IR-emitting dust particles are Mie spheres implies that their diameter is < 3 μm . We also present new 10 and 18 μm images of HD 233517 (SAO 26804) that show this source is unresolved at the highest resolution currently attainable in the mid-IR. Our imaging with OSCIR on Keck II places full-width at half maximum (FWHM) limits on the source size of 0\\farcs31 at 10.8 μm and 0\\farcs inconsistent with previously published values. The fact that SAO 26804 is unresolved in the mid-IR has implications for the evolutionary status. We propose that the unresolved nature of SAO 26804 is strong circumstantial evidence that the source is not a main sequence (luminosity class V dwarf) Vega-like source, but a lithium-rich giant (luminosity class III). The giant classification for SAO 26804 is supported by its position in the H-R diagram. This research was supported in part by NSF and NASA grants to the University of Florida and Pennsylvania State University at Erie.

  2. Exploiting radiation damage control on apatite (U Th)/He dates in cratonic regions

    NASA Astrophysics Data System (ADS)

    Flowers, Rebecca M.

    2009-01-01

    Apatites from four pairs of samples of Precambrian basement from the western Canadian shield were analyzed by (U-Th)/He thermochronometry to test for the influence of radiation damage on apatite (U-Th)/He dates in this cratonic region. Recent studies have demonstrated that the accumulation of radiation damage increases the apatite He retentivity, so that apatites with a span of effective U concentrations, eU, that experienced the same thermal history may be characterized by a range of closure temperatures. In this investigation, each sample pair consisted of a mafic dike cross-cutting felsic gneisses from a single outcrop or nearby outcrops that contained apatites with a span of eU. The apatites yielded (U-Th)/He dates from 846 to 123 Ma, and were positively correlated with eU within each sample pair. These results can be explained using a model that tracks the evolution of He mobility in response to the accumulation of radiation damage. When coupled with regional geological constraints, the data appear to require partial to complete He loss due to burial and reheating in Phanerozoic time. New apatite fission- track dates and length data were obtained for five of these samples. The apatite fission- track dates are Proterozoic regardless of apatite eU. Thermal history simulations indicate that the apatite fission-track data are compatible with the (U-Th)/He results, although the thermal histories are not identical in detail and the fission-track results alone do not require Phanerozoic heating. Together the data are consistent with burial of this region by ≥ 1 km of Phanerozoic strata that were subsequently denuded, thus pointing toward significant Phanerozoic deposition in the North American cratonic interior hundreds of kilometers east of where previously documented. The results suggest that exploiting radiation damage control on apatite (U-Th)/He dates through investigation of surface sample apatites with a span of closure temperatures can impose tighter

  3. Source of Mesozoic intermediate-felsic igneous rocks in the North China craton: Granulite xenolith evidence

    NASA Astrophysics Data System (ADS)

    Jiang, Neng; Carlson, Richard W.; Guo, Jinhui

    2011-07-01

    Four intermediate to felsic igneous rocks from the Zhangjiakou region, along the northern margin of the North China craton, have magmatic zircon U-Pb ages from 122 to 144 Ma. Two of these samples have inherited zircon U-Pb ages of ~ 2.5 Ga, similar to the zircon ages of rocks from the surrounding granulite terrain. Zircons from two intermediate composition granulite xenoliths (JN0811 and JN0919) in the nearby Cenozoic Hannuoba basalts yield two groups of ages. The rims have concordant Mesozoic ages mostly between 120 and 145 Ma, coeval with the Mesozoic intermediate-felsic magmatism in the region, while the cores have discordant U-Pb ages with upper-intercepts of ~ 2.5 Ga, overlapping the zircon ages of granulite terrain rocks, and lower-intercept ages of ~ 130 Ma, approximating the ages of the Mesozoic intermediate-felsic magmatism. The Sr-Nd isotopic compositions of the Mesozoic intermediate-felsic igneous rocks are completely different from those expected for basaltic melts from either the lithospheric mantle or the asthenospheric mantle, precluding a derivation by extensive fractional crystallization of mantle-derived magmas. The lack of correlation between (86Sr/87Sr)i, εNd(t) and SiO2 for the Mesozoic igneous rocks, the very narrow range of zircon εHf(t) for individual intermediate-felsic igneous rocks, and simple binary mixing calculations argue against them being formed by mixing between mantle-derived magma and preexisting crust that has extremely evolved Sr-Nd isotopic compositions like granulite xenoliths JN0811 and JN0919. Hf isotopic compositions of the Mesozoic zircons and whole-rock geochemistry show that the granulite xenoliths with extremely evolved Sr-Nd isotopic compositions have not undergone partial melting during the Mesozoic and thus do not contribute to the Mesozoic intermediate-felsic magmas. Further comparisons show that the source rocks for the Mesozoic intermediate-felsic magmas likely were late Archean lower crustal rocks similar in

  4. Paleogene post-collisional lamprophyres in western Yunnan, western Yangtze Craton: Mantle source and tectonic implications

    NASA Astrophysics Data System (ADS)

    Lu, Yong-Jun; Campbell McCuaig, T.; Li, Zheng-Xiang; Jourdan, Fred; Hart, Craig J. R.; Hou, Zeng-Qian; Tang, Suo-Han

    2015-09-01

    A suite of lamprophyres, spatially associated with mafic lavas and potassic felsic intrusive rocks, was emplaced between 36.5 ± 0.2 and 33.7 ± 0.5 Ma (based on phlogopite 40Ar/39Ar dating) on the eastern side of the Ailao Shan-Red River shear zone in the western Yangtze Craton. These shoshonitic and ultrapotassic intrusive rocks post-date the ~ 60-55 Ma collisional event between the Indian and the Asian continents. They are characterized by: (1) enrichment in large-ion lithophile elements and light rare-earth elements with (La/Sm)n = 3.15-7.15; (2) strong positive Pb spikes; (3) depletion in high-field-strength elements (e.g. Nb/La = 0.08-0.98); (4) high initial 87Sr/86Sr (0.706-0.709) with negative εNd(t) values of - 10.5 to - 0.9; (5) old Nd model ages of 1542-945 Ma; and (6) radiogenic (207Pb/204Pb)i of 15.57-15.70 and (208Pb/204Pb)i (38.70-39.06). These features suggest that the mantle source was metasomatized by Proterozoic subduction beneath the Yangtze Craton. The lamprophyres have similar trace element patterns, and Sr-Nd-Pb isotope compositions, as coeval mafic lava, indicating a common source of metasomatized veined continental lithospheric mantle (CLM). Lower degree partial melting of metasomatic veins likely generated the lamprophyres, whereas the coeval mafic lava was likely derived from melting of phlogopite harzburgite. The lamprophyres and mafic lava have similar Sr-Nd isotope systematics as CLM-derived Neoproterozoic mafic rocks and Late Permian Emeishan low-Ti basalt in the region, indicating that they share the same Proterozoic source. We envisage that mantle plumes thermally eroded the Proterozoic metasomatized CLM beneath the western part of the Yangtze Craton during 825-750 Ma and 260-250 Ma, although residual metasomatized domains remained before being tapped by delamination after the India-Asia continental collision during the Paleogene period.

  5. Cover sequences at the northern margin of the Antongil Craton, NE Madagascar

    USGS Publications Warehouse

    Bauer, W.; Walsh, G.J.; De Waele, B.; Thomas, Ronald J.; Horstwood, M.S.A.; Bracciali, L.; Schofield, D.I.; Wollenberg, U.; Lidke, D.J.; Rasaona, I.T.; Rabarimanana, M.H.

    2011-01-01

    The island of Madagascar is a collage of Precambrian, generally high-grade metamorphic basement domains, that are locally overlain by unmetamorphosed sedimentary rocks and poorly understood low-grade metasediments. In the Antalaha area of NE Madagascar, two distinct cover sequences rest on high-grade metamorphic and igneous basement rocks of the Archaean Antongil craton and the Neoproterozoic Bemarivo belt. The older of these two cover sequences, the Andrarona Group, consists of low-grade metasedimentary rocks. The younger sequence, the newly defined Ampohafana Formation, consists of unmetamorphosed sedimentary rocks. The Andrarona Group rests on Neoarchaean granites and monzogranites of the Antongil craton and consists of a basal metagreywacke, thick quartzites and an upper sequence of sericite-chlorite meta-mudstones, meta-sandstones and a volcaniclastic meta-sandstone. The depositional age of the volcaniclastic meta-sandstone is constrained in age by U–Pb laser-ablation ICP-MS analyses of euhedral zircons to 1875 ± 8 Ma (2σ). Detrital zircons of Archaean and Palaeoproterozoic age represent an input from the Antongil craton and a newly defined Palaeoproterozoic igneous unit, the Masindray tonalite, which underlies the Andrarona Group, and yielded a U–Pb zircon age of 2355 ± 11 Ma (2σ), thus constraining the maximum age of deposition of the basal part of the Andrarona Group. The Andrarona Group shows a low-grade metamorphic overprint in the area near Antalaha; illite crystallinity values scatter around 0.17°Δ2Θ CuKα, which is within the epizone. The Ampohafana Formation consists of undeformed, polymict conglomerate, cross-bedded sandstone, and red mudstone. An illite crystallinity value of >0.25°Δ2Θ CuKα obtained from the rocks is typical of the diagenetic zone. Occurrences of rhyodacite pebbles in the Ampohafana Formation and the intrusion of a basaltic dyke suggest a deposition in a WSW-ENE-trending graben system during the opening of the Indian

  6. At the Cratonic Crossroads: A geochronologic and geochemical perspective on the Little Rocky Mountains, Montana

    NASA Astrophysics Data System (ADS)

    Gifford, J. N.; Mueller, P. A.; Foster, D. A.; Mogk, D. W.

    2012-12-01

    The Medicine Hat Block (MHB) is a poorly constrained structural element in the Paleoproterozoic amalgamation of Laurentia. It lies between the Wyoming and Hearne cratons along the northern margin of the Great Falls Tectonic Zone. The block was caught between the Hearne and Wyoming cratons during the Paleoproterozoic closure of an ocean and subsequent continental collision. The majority of the MHB is concealed by younger material, and it is recognized primarily by its seismic signature and its influence on the geochemistry of younger igneous rocks. The MHB appears to be composed of Archean (2.6-3.1 Ga) and Proterozoic (1.75 Ga) continental crust based on limited data from drill holes and xenoliths. The Little Rocky Mountains (LRM) are the only potential exposure of Precambrian basement rocks in the northeastern GFTZ, and represent unique surface exposure of the MHB. The LRM is cored by a dome-shaped Tertiary syenite intrusion, with Precambrian metamorphic units exposed along the margins of the dome. Limited previous geochronology from the LRM includes K/Ar ages of 1.7-1.75 Ga and a Rb/Sr age of c. 2.55 Ga from a quartzofeldspathic paragneisses. These data leave the affinity of the LRM uncertain, either representing reworked Archean crust and/or Paleoproterozoic material generated during the subduction of oceanic lithosphere and formation of the GFTZ. New U/Pb ages of zircons from the Precambrian meta-igneous rocks in the LRM range from 2.2 - 3.3 Ga, with prominent peaks between 2.6 - 2.8 Ga. Outliers clustering around 1.7 - 1.8 Ga are rare and likely reflect Paleoproterozoic reworking of older material. These ages are consistent with a MHB affinity for the LRM. Pb-isotope data define a 3.1 Ga model age, which suggests some influence of older Wyoming Craton or MHB crust. The dominance of 2.6-2.8 Ga U/Pb ages suggests that the Paleoproterozoic igneous arc was constructed on pre-existing MHB crust. Models for reconciling the high angle junction between the GFTZ and

  7. The Impact of Antipsychotic Polytherapy Costs in the Public Health Care in Sao Paulo, Brazil

    PubMed Central

    Razzouk, Denise; Kayo, Monica; Sousa, Aglaé; Gregorio, Guilherme; Cogo-Moreira, Hugo; Cardoso, Andrea Alves; Mari, Jair de Jesus

    2015-01-01

    Introduction Guidelines for the treatment of psychoses recommend antipsychotic monotherapy. However, the rate of antipsychotic polytherapy has increased over the last decade, reaching up to 60% in some settings. Studies evaluating the costs and impact of antipsychotic polytherapy in the health system are scarce. Objective To estimate the costs of antipsychotic polytherapy and its impact on public health costs in a sample of subjects with psychotic disorders living in residential facilities in the city of Sao Paulo, Brazil. Method A cross-sectional study that used a bottom-up approach for collecting costs data in a public health provider´s perspective. Subjects with psychosis living in 20 fully-staffed residential facilities in the city of Sao Paulo were assessed for clinical and psychosocial profile, severity of symptoms, quality of life, use of health services and pharmacological treatment. The impact of polytherapy on total direct costs was evaluated. Results 147 subjects were included, 134 used antipsychotics regularly and 38% were in use of antipsychotic polytherapy. There were no significant differences in clinical and psychosocial characteristics between polytherapy and monotherapy groups. Four variables explained 30% of direct costs: the number of antipsychotics, location of the residential facility, time living in the facility and use of olanzapine. The costs of antipsychotics corresponded to 94.4% of the total psychotropic costs and to 49.5% of all health services use when excluding accommodation costs. Olanzapine costs corresponded to 51% of all psychotropic costs. Conclusion Antipsychotic polytherapy is a huge economic burden to public health service, despite the lack of evidence supporting this practice. Great variations on antipsychotic costs explicit the need of establishing protocols for rational antipsychotic prescriptions and consequently optimising resource allocation. Cost-effectiveness studies are necessary to estimate the best value for money

  8. Cost and benefits of a distribution automation system for the northeast area of Sao Paulo

    SciTech Connect

    Jardini, J.A.; Carvalho, J.C.M.

    1995-12-31

    An evaluation of the costs and the benefits of distribution automation was done for an area in the northeastern part of Sao Paulo State, Brazil. The results showed that the savings pay for the automation cost. The major gain relies on the substation supervision and staff reduction. CESP is one of the three utilities responsible for the distribution of electricity in Sao Paulo, a state crossed by the Capricornium Tropic in the southeast of Brazil. CESP generates power (9,3 GW), has transmission (20,000 km), bulk power supply to other utilities, and distributes power to six regions covering 120,000 km2 , where 1,300,000 customers are located. The main regional office is in a town called RIO CLARO, which economy is based on agro industries and manufacturers. RIO CLARO area represents 8% of CESP`s area, has 26% of customers, and is responsible for 37% of the income. In Brazil, the experience with DA is limited, and consists basically on prototypes installed in a few pilot areas, being one in CESP`s area. This prototype includes digital automation of three substations and feeders in GUARUJA, a seaside town. The system has been in operation since 1984 and has proved to be satisfactory. DA has not been given an adequate attention before, because: salaries in Brazil are low if compared to the developed countries; Brazilian computer market was protected up to 1992 meaning that only a few Brazilian manufacturers could offer automation products; foreign products were not available; there was shortage of investment even in the main equipments due to the course of the Brazilian economy. Recently, there has been access to foreign technology, there is a competitive market and offer of good products and maintenance services.

  9. Investigating environmental determinants of diet, physical activity, and overweight among adults in Sao Paulo, Brazil.

    PubMed

    Jaime, Patricia Constante; Duran, Ana Clara; Sarti, Flávia Mori; Lock, Karen

    2011-06-01

    There is worldwide recognition that the burden of noncommunicable diseases (NCDs) and obesity-related health problems is rapidly increasing in low- and middle-income countries. Environmental determinants of obesity are likely to differ between countries, particularly in those undergoing rapid socioeconomic and nutrition transitions such as Brazil. This study aims to describe some built environment and local food environment variables and to explore their association with the overweight rate and diet and physical activity area-level aggregated indicators of adults living in the city of Sao Paulo, the largest city in Brazil. This formative study includes an ecological analysis of environmental factors associated with overweight across 31 submunicipalities of the city of Sao Paulo using statistical and spatial analyses. Average prevalence of overweight was 41.69% (95% confidence interval 38.74, 44.64), ranging from 27.14% to 60.75% across the submunicipalities. There was a wide geographical variation of both individual diet and physical activity, and indicators of food and built environments, favoring wealthier areas. After controlling for area socioeconomic status, there was a positive correlation between regular fruits and vegetables (FV) intake and density of FV specialized food markets (r = 0.497; p < 0.001), but no relationship between fast-food restaurant density and overweight prevalence was found. A negative association between overweight prevalence and density of parks and public sport facilities was seen (r = -0.527; p < 0.05). Understanding the relationship between local neighborhood environments and increasing rates of poor diet, physical activity, and obesity is essential in countries undergoing rapid economic and urban development, such as Brazil, in order to provide insights for policies to reduce increasing rates of NCDs and food access and health inequalities. PMID:21327549

  10. IS THE POST-AGB STAR SAO 40039 MILDLY HYDROGEN-DEFICIENT?

    SciTech Connect

    Rao, S. Sumangala; Pandey, Gajendra; Giridhar, Sunetra; Lambert, David L. E-mail: pandey@iiap.res.in E-mail: dll@astro.as.utexas.edu

    2011-08-10

    We have conducted an LTE abundance analysis for SAO 40039, a warm post-AGB star whose spectrum is known to show surprisingly strong He I lines for its effective temperature and has been suspected of being H-deficient and He-rich. High-resolution optical spectra are analyzed using a family of model atmospheres with different He/H ratios. Atmospheric parameters are estimated from the ionization equilibrium set by neutral and singly ionized species of Fe and Mg, the excitation of Fe I and Fe II lines, and the wings of the Paschen lines. On the assumption that the He I lines are of photospheric and not chromospheric origin, a He/H ratio of approximately unity is found by imposing the condition that the adopted He/H ratio of the model atmosphere must equal the ratio derived from the observed He I triplet lines at 5876, 4471, and 4713 A, and singlet lines at 4922 and 5015 A. Using the model with the best-fitting atmospheric parameters for this He/H ratio, SAO 40039 is confirmed to exhibit mild dust-gas depletion, i.e., the star has an atmosphere deficient in elements of high condensation temperature. The star appears to be moderately metal-deficient with [Fe/H] = -0.4 dex. But the star's intrinsic metallicity as estimated from Na, S, and Zn, elements of a low condensation temperature, is [Fe/H]{sub o} {approx_equal} -0.2 ([Fe/H]{sub o} refers to the star's intrinsic metallicity). The star is enriched in N and perhaps O as well, changes reflecting the star's AGB past and the event that led to He enrichment.

  11. Mineralization of bone-related SaOS-2 cells under physiological hypoxic conditions.

    PubMed

    Müller, Werner E G; Schröder, Heinz C; Tolba, Emad; Diehl-Seifert, Bärbel; Wang, Xiaohong

    2016-01-01

    Inorganic polyphosphate (polyP) is a physiological energy-rich polymer with multiple phosphoric anhydride bonds. In cells such as bone-forming osteoblasts, glycolysis is the main pathway generating metabolic energy in the form of ATP. In the present study, we show that, under hypoxic culture conditions, the growth/viability of osteoblast-like SaOS-2 cells is not impaired. The addition of polyP to those cells, administered as amorphous calcium polyP nanoparticles (aCa-polyP-NP; approximate size 100 nm), significantly increased the proliferation of the cells. In the presence of polyP, the cells produce significant levels of lactate, the end product of anaerobic glycolysis. Under those conditions, an eight-fold increase in the steady-state level of the membrane-associated carbonic anhydrase IX is found, as well as a six-fold induction of the hypoxia-inducible factor 1. Consequently, biomineral formation onto the SaOS-2 cells decreases under low oxygen tension. If the polyP nanoparticles are added to the cells, the degree of mineralization is enhanced. These changes had been measured also in human mesenchymal stem cells. The assumption that the bicarbonate, generated by the carbonic anhydrase in the presence of polyP under low oxygen, is deposited as a constituent of the bioseeds formed during initial hydroxyapatite formation is corroborated by the identification of carbon besides of calcium, oxygen and phosphorus in the initial biomineral deposit onto the cells using the sensitive technology of high-resolution energy dispersive spectrometry mapping. Based on these data, we conclude that polyP is required for the supply of metabolic energy during bone mineral formation under physiological, hypoxic conditions, acting as a 'metabolic fuel' for the cells to grow. PMID:26453899

  12. The Consequences of Uniform High Temperatures in the Cordillera and Other Subduction Backarc Mountain Belts Compared to Cratons

    NASA Astrophysics Data System (ADS)

    Hyndman, R. D.

    2012-12-01

    Many if not most continental areas have experienced a period of being in the subduction zone backarc. The thermal regime of the Cordillera and other current and recent subduction backarcs is concluded to be remarkably uniformly hot, 800-900C at Moho, in contrast to cratons, 400-500C at Moho. Constraints come from: heat flow-heat generation models; mantle tomography velocities; xenolith pressure (depth)-temperatures, Te (effective elastic lithosphere thickness); seismic and electrical thickness of lithosphere; maximum depth of seismicity; depth of Curie temperature; and thermal elevation. The consequences of these high temperatures are reviewed: (1) In the Cordillera there is a surprisingly constant 1,600 m elevation contribution due to thermal isostasy compared to the cratons. The thermal expansion contribution results in the Cordillera having a high elevation in spite of having an average thin crust (~35 km), compared to the cratons (~40 km). (2) Weak mobile belts like the Cordillera are a consequence of their high temperatures. Plate boundary forces and elevation potential are sufficient for ongoing lithosphere deformation. Cratons are cold and strong. (3) In the Cordillera and most other back arcs, the lower crust is very weak and commonly acts as a detachment over long distances. Lower crust horizontal reflectors may mark the detachment. Also, foreland basal thrusting often detaches into the backarc lower crust. (4) In backarcs, high metamorphic temperature gradients (e.g., Barrovian metamorphism) predate collision orogeny; there is no "heat of orogeny" required. (5) Cordillera earthquakes occur only in the brittle upper crust, 10-15 km. When subduction terminates, backarcs cool with a time constant of about 300 m.y. and approach a cold craton thermal regime by ~1 Ga. As an example, the former Appalachian backarc has now substantially cooled.

  13. Sone megafan: A non-Himalayan megafan of craton origin on the southern margin of the middle Ganga Basin, India

    NASA Astrophysics Data System (ADS)

    Sahu, Sudarsan; Saha, Dipankar; Dayal, Shankar

    2015-12-01

    Researchers in the last few decades have focused on the fluvial megafans at the base of Himalayan foothills in the Ganga Basin. No major effort has so far been made to delineate any such large depositional environment at the base of the northern Indian peninsular craton at the distal parts of the basin. In this work, for the first time, we document a megafan, unusually created by the cratonic Sone River in the marginal plains south of the Ganga. The geomorphology of the megafan surface, distribution of palaeochannels, sedimentology, and areal extent of the megafan are described. The study also reconstructs the tectonic and palaeoclimatic conditions, which might have helped in sediment supply from the cratonic catchment areas of the Sone. We suggest tectonic control over the Sone River channel dynamics and development of the megafan. The oval- and fan-shaped, craton-derived sediment body covers an area of around 12,000 km2 in the marginal plains and about 9000 km2 in the central alluvium north of the Ganga River. The megafan is around 190 km long and ~ 240 km wide. The mean slope of the megafan surface is ~ 0.03°. An onlap of Himalayan sediments has occurred over the megafan at its toe parts caused by southward encroachment of the Ganga during the Holocene. The megafan sediments comprise brownish yellow fine to coarse sand and gravels with an admixture of carbonaceous nodules (kankars). The thickness of the megafan sediment, which directly overlies the Precambrian basement, varies from only a few meters in the south near the peninsular craton to ~ 1000 m at the north in the central alluvial plain. The granular zones form prolific aquifer systems in an otherwise poor hydrogeological setting of the marginal plains.

  14. The Precambrian of Transangaria, Yenisei Ridge (Siberia): Neoproterozoic microcontinent, Grenville-age orogen, or reworked margin of the Siberian craton?

    NASA Astrophysics Data System (ADS)

    Kuzmichev, Alexander B.; Sklyarov, Eugene V.

    2016-01-01

    The Yenisei Ridge was traditionally perceived as an uplifted segment of the western Siberian craton affected by Neoproterozoic collision events. However, the suggestions for Archaean or Palaeoproterozoic ('Siberian') basement in Transangaria have not been confirmed by reliable geochronological data. A new view regards most of the Ridge, namely, its Transangarian segment, to be an exotic Neoproterozoic terrane that collided with Siberia in the late Neoproterozoic. This paper presents new U-Pb SHRIMP zircon ages demonstrating that Archaean rocks (2611 ± 12 Ma) actually exist in this territory. We also provide a review of published U-Pb zircon ages for igneous and metamorphic rocks of Transangaria together with our new age data. This geochronological dataset clarifies the geology of the Yenisei Ridge and leads to new conclusions, as follows. (1) It is likely that Transangaria was originally underlain by an Archaean-Palaeoproterozoic basement, similar to that of the Siberian craton. (2) Geochronological data do not confirm the idea of widespread "Greenvillian age" granitoides in Transangaria. (3) The Neoproterozoic evolution of the Yenisei Ridge segment of the Siberian craton margin includes the following events. (i) Collision of an unidentified terrane with the western margin (in recent coordinates) of the Siberian craton during 900-855 Ma. The colliding terrane is no longer present in the current structure. (ii) Dextral shearing during 830-800 Ma may have been caused by counter-clockwise rotation of the Siberian craton. (iii) Extensional conditions prevailed during 800-700 Ma. The Isakovka oceanic basin formed at this time interval. (iv) Thrusting of the Isakovka island arc and accretionary prism onto the Siberian margin occurred during the late Neoproterozoic (650-630 Ma) and caused high-pressure metamorphism.

  15. Thermo-chemical structure of the lithospheric mantle underneath the Siberian craton inferred from long-range seismic profiles

    NASA Astrophysics Data System (ADS)

    Kuskov, O. L.; Kronrod, V. A.; Prokofyev, A. A.; Pavlenkova, N. I.

    2014-03-01

    Based on a self-consistent thermodynamic-geophysical approach and xenolith-based constraints, we map the 2-D seismic, thermal and density structure of the mantle beneath the Siberian craton along the long-range profiles (Craton, Kimberlite, Rift and Meteorite) carried out in Russia with peaceful nuclear explosions. Structural peculiarities of the cratonic mantle are manifested by changes in seismic velocities, the degree and nature of layering and the relief of seismic boundaries. The results predict appreciable lateral temperature variations within the root to a depth of about 200 km, which are the main cause of seismic velocity variations. We find that the cratonic mantle is 300-400 °C colder than the tectonically younger surrounding mantle in this depth range. At greater depths, lateral changes in temperatures have little effect implying that thermal heterogeneity rapidly decreases. The present-day geotherms pass close to the 32.5-35 mW m- 2 conductive models and suggest low mantle heat flow. Within the model resolution, the thickness of the thermal boundary layer, TBL (defined as the depth of the 1300 °C adiabat) beneath Siberia does not depend significantly on the composition and can be estimated as 300 ± 30 km; temperature at the base of the TBL is close to the 1450 ± 100 °C isotherm. Changes in the composition from depleted to fertile material reveal a negligible effect on seismic velocities, which are practically unresolved by seismic methods, but remain the most important factor for the density increase of the cratonic root. Density variations in the lower part of the root due to the chemical composition are greater than those caused by temperature. We find that both compositional and thermal anomalies are required to explain the Siberian mantle by a keel model consisting of depleted garnet peridotite at depths of 100 to 180 km and more fertile material at greater depths.

  16. A major Archean, gold- and crust-forming event in the Kaapvaal craton, South Africa.

    PubMed

    Kirk, Jason; Ruiz, Joaquin; Chesley, John; Walshe, John; England, Gavin

    2002-09-13

    The 2.89- to 2.76-gigayear-old conglomerates of the Central Rand Group of South Africa host an immense concentration of gold. The gold and rounded pyrites from the conglomerates yield a rhenium-osmium isochron age of 3.03 +/- 0.02 gigayears and an initial 187Os/188Os ratio of 0.1079 +/- 0.0001. This age is older than that of the conglomerates. Thus, the gold is detrital and was not deposited by later hydrothermal fluids. This Middle Archean gold mineralization event corresponds to a period of rapid crustal growth in which much of the Kaapvaal craton was formed and is evidence for a significant noble metal flux from the mantle. PMID:12228713

  17. The Montesbelos mass-flow (southern Amazonian craton, Brazil): a Paleoproterozoic volcanic debris avalanche deposit?

    NASA Astrophysics Data System (ADS)

    Roverato, M.

    2016-07-01

    The present contribution documents the extremely well-preserved Paleoproterozoic architecture of the Montesbelos breccia (named here for the first time), which is interpreted as a rare example of a subaerial paleoproterozoic (>1.85 Ga) granular-dominated mass-flow deposit, few of which are recorded in the literature. Montesbelos deposit is part of the andesitic Sobreiro Formation located in the São Felix do Xingu region, southern Amazonian craton, northern Brazil. The large volume, high variability of textural features, presence of broken clasts, angular low sphericity fragments, mono- to heterolithic character, and the size of the outcrops point to a volcanic debris avalanche flow. Fluviatile sandy material and debris flows are associated with the deposit as a result of post-depositional reworking processes.

  18. Petrophysical constraints on the seismic properties of the Kaapvaal craton mantle root

    NASA Astrophysics Data System (ADS)

    Baptiste, V.; Tommasi, A.

    2014-01-01

    We calculated the seismic properties of 47 mantle xenoliths from 9 kimberlitic pipes in the Kaapvaal craton based on their modal composition, the crystal-preferred orientations (CPO) of olivine, ortho- and clinopyroxene, and garnet, the Fe content of olivine, and the pressures and temperatures at which the rocks were equilibrated. These data allow constraining the variation of seismic anisotropy and velocities within the cratonic mantle. The fastest P and S2 wave propagation directions and the polarization of fast split shear waves (S1) are always subparallel to olivine [100] axes of maximum concentration, which marks the lineation (fossil flow direction). Seismic anisotropy is higher for high olivine contents and stronger CPO. Maximum P wave azimuthal anisotropy (AVp) ranges between 2.5 and 10.2% and the maximum S wave polarization anisotropy (AVs), between 2.7 and 8%. Changes in olivine CPO symmetry result in minor variations in the seismic anisotropy patterns, mainly in the apparent isotropy directions for shear wave splitting. Seismic properties averaged over 20 km-thick depth sections are, therefore, very homogeneous. Based on these data, we predict the anisotropy that would be measured by SKS, Rayleigh (SV) and Love (SH) waves for five endmember orientations of the foliation and lineation. Comparison to seismic anisotropy data from the Kaapvaal shows that the coherent fast directions, but low delay times imaged by SKS studies, and the low azimuthal anisotropy with with the horizontally polarized S waves (SH) faster than the vertically polarized S wave (SV) measured using surface waves are best explained by homogeneously dipping (45°) foliations and lineations in the cratonic mantle lithosphere. Laterally or vertically varying foliation and lineation orientations with a dominantly NW-SE trend might also explain the low measured anisotropies, but this model should also result in backazimuthal variability of the SKS splitting data, not reported in the

  19. Petrophysical constraints on the seismic properties of the Kaapvaal craton mantle root

    NASA Astrophysics Data System (ADS)

    Virginie, Baptiste; Andrea, Tommasi

    2014-05-01

    We calculated the seismic properties of 47 mantle xenoliths from 9 kimberlitic pipes in the Kaapvaal craton based on their modal composition, the crystal preferred orientations (CPO) of olivine, ortho- and clinopyroxene, and garnet, the Fe content of olivine, and the pressures and temperatures at which the rocks were equilibrated. These data allow constraining the variation of seismic anisotropy and velocities within the cratonic mantle. The fastest P and S2 waves propagation direction and the polarization of fast split shear wave (S1) are always subparallel to olivine [100] axes maximum concentration, which marks the lineation (fossil flow direction). Seismic anisotropy is higher for high olivine contents and stronger CPO. Maximum P-wave azimuthal anisotropy (AVp) ranges between 2.5 and 10.2% and the maximum S-wave polarization anisotropy (AVs), between 2.7 and 8%. Changes in olivine CPO symmetry result in minor variations in the seismic anisotropy patterns, mainly in the apparent isotropy directions for shear wave splitting. Seismic properties averaged over 20 km thick depth sections are, therefore, very homogeneous. Based on these data, we predict the anisotropy that would be measured by SKS, Rayleigh (SV) and Love (SH) waves for 5 end-member orientations of the foliation and lineation. Comparison to seismic anisotropy data in the Kaapvaal shows that the coherent fast directions, but low delay times imaged by SKS studies and the low azimuthal anisotropy with SH faster than SV measured using surface waves are best explained by a homogeneously dipping (45°) foliation and lineation in the cratonic mantle lithosphere. Laterally or vertically varying foliation and lineation orientations with a dominantly NW-SE trend might also explain the low measured anisotropies, but this model should also result in backazimuthal variability of the SKS splitting data, not reported in the seismological data. The strong compositional heterogeneity of the Kaapvaal peridotite

  20. East-China Geochemistry Database (ECGD):A New Networking Database for North China Craton

    NASA Astrophysics Data System (ADS)

    Wang, X.; Ma, W.

    2010-12-01

    North China Craton is one of the best natural laboratories that research some Earth Dynamic questions[1]. Scientists made much progress in research on this area, and got vast geochemistry data, which are essential for answering many fundamental questions about the age, composition, structure, and evolution of the East China area. But the geochemical data have long been accessible only through the scientific literature and theses where they have been widely dispersed, making it difficult for the broad Geosciences community to find, access and efficiently use the full range of available data[2]. How to effectively store, manage, share and reuse the existing geochemical data in the North China Craton area? East-China Geochemistry Database(ECGD) is a networking geochemical scientific database system that has been designed based on WebGIS and relational database for the structured storage and retrieval of geochemical data and geological map information. It is integrated the functions of data retrieval, spatial visualization and online analysis. ECGD focus on three areas: 1.Storage and retrieval of geochemical data and geological map information. Research on the characters of geochemical data, including its composing and connecting of each other, we designed a relational database, which based on geochemical relational data model, to store a variety of geological sample information such as sampling locality, age, sample characteristics, reference, major elements, rare earth elements, trace elements and isotope system et al. And a web-based user-friendly interface is provided for constructing queries. 2.Data view. ECGD is committed to online data visualization by different ways, especially to view data in digital map with dynamic way. Because ECGD was integrated WebGIS technology, the query results can be mapped on digital map, which can be zoomed, translation and dot selection. Besides of view and output query results data by html, txt or xls formats, researchers also can

  1. Low water contents in diamond mineral inclusions: Proto-genetic origin in a dry cratonic lithosphere

    NASA Astrophysics Data System (ADS)

    Taylor, Lawrence A.; Logvinova, Alla M.; Howarth, Geoffrey H.; Liu, Yang; Peslier, Anne H.; Rossman, George R.; Guan, Yunbin; Chen, Yang; Sobolev, Nikolay V.

    2016-01-01

    The mantle is the major reservoir of Earth's water, hosted within Nominally Anhydrous Minerals (NAMs) (e.g., Bell and Rossman, 1992; Peslier et al., 2010; Peslier, 2010; Nestola and Smyth, 2015), in the form of hydrogen bonded to the silicate's structural oxygen. From whence cometh this water? Is the water in these minerals representative of the Earth's primitive upper mantle or did it come from melting events linked to crustal formation or to more recent metasomatic/re-fertilization events? During diamond formation, NAMs are encapsulated at hundreds of kilometers depth within the mantle, thereby possibly shielding and preserving their pristine water contents from re-equilibrating with fluids and melts percolating through the lithospheric mantle. Here we show that the NAMs included in diamonds from six locales on the Siberian Craton contain measurable and variable H2O concentrations from 2 to 34 parts per million by weight (ppmw) in olivine, 7 to 276 ppmw in clinopyroxene, and 11-17 ppmw in garnets. Our results suggest that if the inclusions were in equilibrium with the diamond-forming fluid, the water fugacity would have been unrealistically low. Instead, we consider the H2O contents of the inclusions, shielded by diamonds, as pristine representatives of the residual mantle prior to encapsulation, and indicative of a protogenetic origin for the inclusions. Hydrogen diffusion in the diamond does not appear to have modified these values significantly. The H2O contents of NAMs in mantle xenoliths may represent some later metasomatic event(s), and are not always representative of most of the continental lithospheric mantle. Results from the present study also support the conclusions of Peslier et al. (2010) and Novella et al. (2015) that the dry nature of the SCLM of a craton may provide stabilization of its thickened continental roots.

  2. (142)Nd evidence for an enriched Hadean reservoir in cratonic roots.

    PubMed

    Upadhyay, Dewashish; Scherer, Erik E; Mezger, Klaus

    2009-06-25

    The isotope (146)Sm undergoes alpha-decay to (142)Nd, with a half-life of 103 million years. Measurable variations in the (142)Nd/(144)Nd values of rocks resulting from Sm-Nd fractionation could therefore only have been produced within about 400 million years of the Solar System's formation (that is, when (146)Sm was extant). The (142)Nd/(144)Nd compositions of terrestrial rocks are accordingly a sensitive monitor of the main silicate differentiation events that took place in the early Earth. High (142)Nd/(144)Nd values measured in some Archaean rocks from Greenland hint at the existence of an early incompatible-element-depleted mantle. Here we present measurements of low (142)Nd/(144)Nd values in 1.48-gigayear-(Gyr)-old lithospheric mantle-derived alkaline rocks from the Khariar nepheline syenite complex in southeastern India. These data suggest that a reservoir that was relatively enriched in incompatible elements formed at least 4.2 Gyr ago and traces of its isotopic signature persisted within the lithospheric root of the Bastar craton until at least 1.48 Gyr ago. These low (142)Nd/(144)Nd compositions may represent a diluted signature of a Hadean (4 to 4.57 Gyr ago) enriched reservoir that is characterized by even lower values. That no evidence of the early depleted mantle has been observed in rocks younger than 3.6 Gyr (refs 3, 4, 7) implies that such domains had effectively mixed back into the convecting mantle by then. In contrast, some early enriched components apparently escaped this fate. Thus, the mantle sampled by magmatism since 3.6 Gyr ago may be biased towards a depleted composition that would be balanced by relatively more enriched reservoirs that are 'hidden' in Hadean crust, the D'' layer of the lowermost mantle or, as we propose here, also within the roots of old cratons. PMID:19553997

  3. Nature and timing of multiple metasomatic events in the sub-cratonic lithosphere beneath Labait, Tanzania

    NASA Astrophysics Data System (ADS)

    Koornneef, Janne M.; Davies, Gareth R.; Döpp, Sonja P.; Vukmanovic, Zoja; Nikogosian, Igor K.; Mason, Paul R. D.

    2009-11-01

    Petrography, mineral major- and trace element analyses and Rb-Sr and Sm-Nd systematics of xenoliths from Labait volcano, north-central Tanzania, document multiple metasomatic events after initial depletion of the Archaean sub-lithospheric mantle. Four distinct metasomatic phases occurred during the 2.8-3.2 Ga history of the mantle section of the Tanzanian craton. 1) Garnet and Cr-diopside in two depleted lherzolites record LREE enrichment in an early cryptic metasomatic event (~ 2 Ga) resulting in unradiogenic ɛ Nd (- 6.6) and relatively radiogenic Sr signature ( 87Sr/ 86Sr = 0.7049); 2) Four texturally equilibrated peridotites contain phlogopite and Cr-diopside inferred to be introduced by a hydrous melt/fluid that produced LREE enrichment related to the subduction and collision during the 650 Ma Pan-African Orogeny; 3) Fe-enrichment is observed in many garnet-free wehrlites and dunites having low Mg# olivines. Timing of this enrichment event remains poorly defined; and 4) One spinel lherzolite records orthopyroxene replacing clinopyroxene due to recent infiltration of a rift-related H 2O poor, K-alkaline silicate melt. This ongoing metasomatic reaction caused by rift-related magmatism would result in the conversion of lherzolite to orthopyroxene-rich harzburgite. The reaction possibly represents the mechanism involved in the formation of orthopyroxene-rich sub-continental lithospheric mantle below the Kaapvaal and Siberian cratons. Generally, the rift-related metasomatism beneath Tanzania has caused formation of interstitial clinopyroxene, melt veins and melt pockets and new rims of phlogopite, all of which are in chemical disequilibrium with the original xenolith mineralogy.

  4. Is the Paleoproterozoic Jiao-Liao-Ji Belt (North China Craton) a rift?

    NASA Astrophysics Data System (ADS)

    Li, Zhuang; Chen, Bin; Wei, Chunjing

    2016-04-01

    As a typical example of the Paleoproterozoic crust in the Eastern Block of the North China Craton, the Paleoproterozoic Jiao-Liao-Ji Belt consists principally of the Liaohe Group (and its equivalents), Liaoji granites and mafic intrusions. Previous studies indicate that the evolution of the Jiao-Liao-Ji Belt has been mainly attributed to the opening and closing of an intracontinental rift along the eastern continental margin of the North China Craton. Here we synthesize the Paleoproterozoic magmatism, sedimentation, metamorphism and metallogeny against the rift model and propose a process of arc-continent collision between the northern Longgang and the southern Nangrim Blocks. This conclusion is consistent with the observations, including that (a) the 2.0- to 2.2-Ga magmatism shows a typical subalkaline series, rather than a bimodal distribution, since the mafic rocks mostly have arc affinities and the acidic-intermediate rocks belong to the calc-alkaline series; (b) the main source of the 1.9- to 2.0-Ga sedimentary rocks is the Paleoproterozoic arc materials, indicating a fore-arc or back-arc basin setting; (c) a couple of big borate deposits occur in the boron-rich volcanic rocks that were formed in convergent continental margins; (d) the North and South Liaohe Groups show different rock associations and metamorphic histories (P-T paths); and (e) the Nangrim and Longgang Blocks vary in lithological units, geochronology and metamorphic features. Thus, an arc-continent collision tectonic scenario for the Paleoproterozoic Jiao-Liao-Ji Belt is involved: (a) a southward subduction in the period 2.0-2.2 Ga; (b) sedimentation during the period 1.9-2.0 Ga; (c) arc-continent collision at ca. 1.9 Ga; and (d) post-collisional extension at 1.82-1.87 Ga, marking the end of the Paleoproterozoic tectonothermal event.

  5. Wisconsin gravity minimum: Solution of a geologic and geophysical puzzle and implications for cratonic evolution

    SciTech Connect

    Allen, D.J.; Hinze, W.J. )

    1992-06-01

    An intense Bouguer gravity anomaly minimum extending across much of Wisconsin cannot be explained by the surface Phanerozoic sedimentary strata, the basement Precambrian geology, or the topography of the region. The most intense ({minus}100 mgal) part of the minimum coincides with the 1.47 Ga anorogenic granitic Wolf River batholith of northeastern Wisconsin. In southern Wisconsin, however, the densities of the Precambrian basement rocks, which are older than the batholith, provide no clue to the origin of the anomaly. The gradients of the minimum indicate that the source of the anomaly is in the upper crust. Furthermore, nearby deep seismic reflection data indicate that lower crustal structures do not significantly contribute to the gravity minimum. Thus, the minimum is appropriately interpreted as originating from the low-density Wolf River batholith that crops out only in northeastern Wisconsin but is buried beneath a veneer of older rocks in the southern and central parts of the state. Gravity modeling suggests that the batholith is at least 10 km thick and encompasses an area of {approximately}50,000 km{sup 2}. This interpretation provides an important clue to the origin of similar negative gravity anomalies of the Phanerozoic strata-covered craton. Also, the presence of this massive granitic body appears to have influenced the evolution of the craton - e.g., by controlling the location of the 1.1 Ga Midcontinent rift system and the Paleozoic Wisconsin arch. The fact that the Wolf River batholith is mostly buried suggests that central Wisconsin has been tectonically stable for the past 1.47 b.y. and that the Precambrian basement has been minimally eroded.

  6. Lithosphere formation in the central Slave Craton (Canada): plume subcretion or lithosphere accretion?

    NASA Astrophysics Data System (ADS)

    Karlsen, Stein Rune; Solheim, Inger; Beck, Pieter S. A.; Høgda, Kjell Arild; Wielgolaski, Frans Emil; Tømmervik, Hans

    2007-10-01

    Major-element compositions of minerals in peridotite xenoliths from the Lac de Gras kimberlites provide constraints on the mode of lithosphere formation beneath the central Slave Craton, Canada. Magnesia contents of reconstructed whole rocks correlate positively with NiO and negatively with CaO contents, consistent with variable partial melt extraction. Alumina and Cr2O3 contents are broadly positively correlated, suggestive of melt depletion in the absence of a Cr Al phase. Garnet modes are high at a given Al2O3 content (a proxy for melt depletion), falling about a 7 GPa melt depletion model. These observations, combined with high olivine Mg# and major-element relationships of FeO-poor peridotites (<7.5 wt%) indicative of melt loss at pressures >3 GPa (residual FeO content being a sensitive indicator of melt extraction pressure), and similar high pressures of last equilibration (˜4.2 to 5.8 GPa), provide multiple lines of evidence that the mantle beneath the central Slave Craton has originated as a residue from high-pressure melting, possibly during plume subcretion. Apparent low melt depletion pressures for high-FeO peridotites (>7.5 wt%) could suggest formation in an oceanic setting, followed by subduction to their depth of entrainment. However, these rocks, which are characterised by low SiO2 contents (<43 wt%), are more likely to be the result of post-melting FeO-addition, leading to spuriously low estimates of melt extraction pressures. They may have reacted with a silica-undersaturated melt that dissolved orthopyroxene, or experienced olivine injection by crystallising melts. A secular FeO-enrichment of parts of the deep mantle lithosphere is supported by lower average Mg# in xenolithic olivine (91.7) compared to olivine inclusions in diamond (92.6).

  7. Cryogenian rift-related magmatism and sedimentation: South-western Congo Craton, Namibia

    NASA Astrophysics Data System (ADS)

    McGee, Ben; Halverson, Galen P.; Collins, Alan S.

    2012-11-01

    We present LA-ICPMS U-Pb zircon ages and field data from the rift-related, Cryogenian-aged Toekems Sub-basin in the south-western Welwitschia Inlier on the southern margin of the Congo Craton in the Damara Belt (Northern Margin Zone), Namibia. The Toekems Sub-basin comprises a wedge up to 730 m-thick of dominantly clastic sediments between Palaeoproterozoic basement and the Cryogenian Abenab Subgroup. The base of the succession is a distinct coarsening upward breccia that contains entirely basement clasts. The overlying strata consist of mixed polymictic conglomerates, debris flow diamictites, tuffs, volcaniclastic sandstone, siltstone, and minor carbonates. A pegmatite cross-cutting the basal breccia has yielded a mean weighted average 206Pb/238U age of 763 ± 5 Ma. This age statistically overlaps the nearby 756 ± 2 Ma Oas Syenite and 760 ± 1 Ma ash bed in the Ombombo Subgroup to the north and is somewhat older than the ca. 746 Ma Naauwpoort Volcanics, which underlie the glacigenic Chuos Formation in the Summas Mountains to the south. This indicates that initial sedimentation in the Toekems Sub-basin began prior to 763 Ma. However, the presence of laminae-deforming lonestones, iron-formation and the stratigraphic position relative to the overlying Rasthof cap carbonate suggest that most of the succession is glacially-influenced, and hence correlates with the Chuos Formation. These results imply a significant disconformity beneath the Naauwpoort Volcanics and suggest multi-phase rifting during the breakup of south-western Congo Craton from Rodinia.

  8. The Escuela Moderna Movement of Francisco Ferrer: "Por la Verdad y la Justicia."

    ERIC Educational Resources Information Center

    Fidler, Geoffrey C.

    1985-01-01

    The educational theory and practice of the Escuela Modern (Modern School) movement of the Spanish educator Francisco Ferrer, born in 1850, are discussed. Two fundamental tendencies of the movement are child-centered education and education in didactic terms. (RM)

  9. Breakthrough for Bilingual Education: Lau v. Nichols and the San Francisco School System

    ERIC Educational Resources Information Center

    Waugh, Dexter; Koon, Bruce

    1974-01-01

    An examination of the issues and implications of the Lau case in which the San Francisco school district was instructed to provide meaningful bilingual-bicultural educational programs for non-English speaking students. (EH)

  10. Coastal processes study at Ocean Beach, San Francisco, CA: summary of data collection 2004-2006

    USGS Publications Warehouse

    Barnard, Patrick L.; Eshleman, Jodi; Erikson, Li H.; Hanes, Daniel M.

    2007-01-01

    Ocean Beach in San Francisco, California, contains a persistent erosional section in the shadow of the San Francisco ebb tidal delta and south of Sloat Boulevard that threatens valuable public infrastructure as well as the safe recreational use of the beach. Coastal managers have been discussing potential mediation measures for over a decade, with little scientific research available to aid in decision making. The United States Geological Survey (USGS) initiated the Ocean Beach Coastal Processes Study in April 2004 to provide the scientific knowledge necessary for coastal managers to make informed management decisions. This study integrates a wide range of field data collection and numerical modeling techniques to document nearshore sediment transport processes at the mouth of San Francisco Bay, with emphasis on how these processes relate to erosion at Ocean Beach. The Ocean Beach Coastal Processes Study is the first comprehensive study of coastal processes at the mouth of San Francisco Bay.

  11. 30. Photocopy of October 1926 photograph in San Francisco CallBulletin ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. Photocopy of October 1926 photograph in San Francisco Call-Bulletin Library. ARTICLES SAVED FROM THE FIRE OF OCTOBER 23, 1926 - Mission Santa Clara de Asis, Franklin & Grant Streets, Santa Clara, Santa Clara County, CA

  12. 1. Photocopy of photograph (from San Francisco Examiner Library, GazetteMariposa ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Photocopy of photograph (from San Francisco Examiner Library, Gazette-Mariposa Folder) Photographer unknown, 1904 GENERAL EXTERIOR VIEW WITH SCENIC BACKGROUND - Sentinel Hotel, Yosemite Village, Mariposa County, CA

  13. Specific conductance, water temperature, and water level data, San Francisco Bay, California, water year 1998

    USGS Publications Warehouse

    Buchanan, Paul A.

    1999-01-01

    Specific conductance and water temperature data are continuously recorded at four sites in San Francisco Bay, California: San Pablo Strait at Point San Pablo, Central San Francisco Bay at Presidio Military Reservation, Pier 24 at Bay Bridge, and South San Francisco Bay at San Mateo Bridge near Foster City (Figure 1). Water level data are recorded only at San Pablo Strait at Point San Pablo. These data were recorded by the Department of Water Resources (DWR) before 1988, by the US Geological Survey (USGS) National Research Program from 1988 to 1989, and by the USGS-DWR cooperative program since 1990. This article presents time-series plots of data from the four sites in San Francisco Bay during water year 1998 (1 October 1997 through 30 September 1998).

  14. Water level, specific conductance, and water temperature data, San Francisco Bay, California, for Water Year 2000

    USGS Publications Warehouse

    Buchanan, P.A.

    2002-01-01

    Time series of water-level, specific-conductance, and watertemperature data were collected at seven sites in San Francisco Bay during water year 2000 (October 1, 1999 through September 30, 2000). Water-level data were recorded only at Point San Pablo. Specific-conductance and water-temperature data were recorded at 15-minute intervals at the following locations (Figure 1): • Carquinez Strait at Carquinez Bridge • Napa River at Mare Island Causeway near Vallejo • San Pablo Bay at Petaluma River Channel Marker 9 • San Pablo Strait at Point San Pablo • Central San Francisco Bay at Presidio Military Reservation • Central San Francisco Bay at Pier 24 • South San Francisco Bay at San Mateo Bridge near Foster City.

  15. BACTERIOPLANKTON DYNAMICS IN NORTHERN SAN FRANCISCO BAY: ROLE OF PARTICLE ASSOCIATION AND SEASONAL FRESHWATER FLOW

    EPA Science Inventory

    Bacterioplankton abundance and metabolic characteristics were observed in northern San Francisco Bay, California, during spring and summer 1996 at three sites: Central Bay, Suisun Bay, and the Sacramento River. These sites spanned a salinity gradient from marine to freshwater, an...

  16. Plankton studies in San Francisco Bay; IV, Phytoplankton abundance and species composition, January 1980 - February 1981

    USGS Publications Warehouse

    Wong, R.L.; Cloern, J.E.

    1982-01-01

    Data are presented on the phytoplankton species composition and abundance in San Francisco Bay from January 1980 through February 1981. Phytoplankton were identified and enumerated in surface samples collected approximately every two weeks at selected stations in the main channel of the Bay, and at shoal stations in the central portion of South San Francisco Bay, San Pablo Bay, and Suisun Bay. Also reported are separate species lists for microphytoplankton (< 60 micrometers) and macrophytoplankton (> 60 micrometers). (Author 's abstract)

  17. High-resolution marine seismic reflection data from the San Francisco Bay area

    USGS Publications Warehouse

    Childs, Jonathan R.; Hart, Patrick; Bruns, Terry R.; Marlow, Michael S.; Sliter, Ray

    2000-01-01

    Between 1993 and 1997, the U.S. Geological Survey acquired high-resolution, marine seismic-reflection profile data across submerged portions of known and inferred upper crustal fault zones throughout the greater San Francisco Bay area. Surveys were conducted oversouth San Francisco Bay in the vicinity of the San Bruno shoal (roughly between the San Francisco and Oakland airports), over the offshore extension of the San Andreas fault system west of the Golden Gate, over the Hayward fault to Rodgers Creek fault step-over in San Pablo Bay, and over the Kirby Hills fault where it crosses the western Sacramento Delta. Reconnaissance profiles were acquired elsewhere throughout the San Francisco and San Pablo Bays. These data were acquired by the U.S. Geological Survey, Western Coastal and Marine Geology Team, under the auspices of the Central California/San Francisco Bay Earthquake Hazards Project. Analysis and interpretation of some of these profiles has been published by Marlow and others (1996, 1999). Further analysis and interpretation of these data are available in a USGS. Professional Paper Crustal Structure of the Coastal and Marine San Francisco Bay Region, T. Parsons, editor, http://geopubs.wr.usgs.gov/prof-paper/pp1658/ [link added 2012 mfd].

  18. Alkaline Phosphatase Activity in San Francisco and Monterey Bays

    NASA Astrophysics Data System (ADS)

    Nicholson, D. P.

    2002-12-01

    Phosphorus (P) is an essential nutrient utilized by all living organisms, and has been recognized as a limiting nutrient in some oceanic systems (Cotner et al., 1997; Karl et al., 1995; Michaels et al., 1996; Wu et al., 2000). However, relatively little is known about the extent of P limitation in natural environments, how P limitation varies spatially and temporally, and what determines how and when P becomes limiting (Benitez-Nelson, 2000). A more direct estimate of the degree of P limitation in a variety of oceanic systems is needed to better understand P cycling and dynamics within the ocean and how these have and will change in response to global climate and environmental perturbation. Accordingly, the objective this study is to assess the P-status of marine planktonic communities in Monterey and San Francisco Bays using the activity of alkaline phosphatase in the water column. Alkaline phosphatase (AP) is the most widely used enzyme that marine organisms use to hydrolize organic P compounds to biologically available orthophosphate. Accordingly it is expected that in areas where P is a limiting nutrient organisms will produce and release more AP to seawater so they can utilize the dissolved and particulate organic P compounds. Indeed it has been suggested that the AP activity is a reliable indicator of P-availability to planktonic communities (Ammerman and Azam, 1985; Cotner and Wetzel, 1991; Hong et al., 1998). High enzyme activities indicate low dissolved inorganic phosphate (DIP) availability while low levels suggest that DIP supply satisfies the community P-demand. This study examines AP activity in San Francisco and Monterey Bays over a 12 month period, from November, 2001 through November, 2002 using two enzyme assays. The study encompasses data from a three-station transect in Monterey Bay, at depths ranging from 0-60 meters. The stations range from coastal waters to open ocean depths of several thousand meters. In San Francisco Bay, surface water from

  19. Crustal Structure across The North China Craton from long-range seismic wide angle reflection/refraction profile

    NASA Astrophysics Data System (ADS)

    Tian, Xiaofeng; Wang, Fuyun; Jia, Shixu; Duan, Yonghong

    2014-05-01

    The North China Craton (NCC) is the oldest craton in China, which formed around 2.5Ga and had a 200 km thick lithosphere during the Paleozoic. The cratonic lithosphere of NCC has experienced strong thinning since the Mesozoic. In the past 30 years, a lot of excellent research about NCC have provided some different tectonic models, however, carton destruction is a sophisticated process. Though there have been many deep seismic sounding profiles in North China, but none of them is long enough to sample the complete section of thinned and preserved Craton. Recent long range seismic wide angle reflection/refraction experiment have provided the best opportunities to obtain better knowledge of seismic structure and properties of lithosphere. A 1500 km long wide angle reflection/refraction profile was completed in 2009. Our long range profile extends from west end of Ordos Plateau, across Shanxi Plateau, Taihang Mountains, to Luxi Uplift. We present a hybrid tomographic and layered velocity model of the crust and uppermost mantle along the profile crossed whole the north China craton. The model shows the crustal thickness of the region is very variable. The Moho topography varies more than 10km in the Central part of the north China craton. In particular, the crust appears the thinnest in the North China Plain, where the crust consists of very thick upper-mid crust and very thin lower crust, and the lower crust is with a lower velocity (~6.8km/s). The Moho dip with thinner lower crust beneath the Shanxi plateau may support the Central NCC has been affected at some time since its formation in the Archean. Furthermore, the TFZ is manifested in the deep structure. Our model provide the seismic evidences supporting that the TFZ extend deep into the uppermost mantle. It is the hypothesis that TFZ is a major channel for asthenosphere upwelling accompanying the tectonic extension and lithospheric reactivation in the Mesozoic-Cenozoic time. The different structural features may

  20. Factors Controlling Tidal Flat Morphology in South San Francisco Bay

    NASA Astrophysics Data System (ADS)

    Bearman, J. A.; Foxgrover, A.; Friedrichs, C.; Jaffe, B.

    2006-12-01

    Since the 1850's, the San Francisco Bay has been subjected to a wide array of human-induced change. From the time of the first US Coast and Geodetic Survey bathymetric surveys in 1858, the saltmarshes and mudflats of South San Francisco Bay (SSFB) have decreased in area by 80% and 40%, respectively. Much of the saltmarsh loss was due to salt pond leveeing, while mudflat loss can be related to lack of sediment input, wind-wave erosion, and sea level rise. Plans for marsh restoration include breaching of salt pond levees with the goal of restoring the 15,100 acres of acquired ponds to tidal marsh the largest such restoration in the western US. The effect this would have upon the adjacent mudflats is unclear. In this analysis, the tidal flats of SSFB are broken into geographically similar regions and multiple cross-sections are drawn from mean high water to below mean lower low water at close intervals, allowing for a mean tidal flat bathymetric profile to be determined for each segment and for each time period 1858, 1898, 1931, 1956, 1983, 2005. Eigenfunction analysis is used to separate the spatial and temporal changes in profile shape into the dominant components of variability, allowing evaluation of the behavior of mudflats relative to spatially and temporally-varying forcings. The components of bathymetric variability derived from objective statistical analysis are compared to theoretical models for tidal flat profiles as a function of waves, tides and sediment supply. Theoretical models predict that wave-dominated or sediment-starved flats tend to have concave-upwards bathymetric profiles, whereas tide-dominated or accretionary flats tend to have convex-upwards bathymetric profiles. Initial results from an analysis of the 1980's bathymetry data suggest the South Bay mudflats can be broken into three morphologically distinct sections: 1) concave-up, erosional mudflats in the Eastern zone, which is most subject to wind waves; 2) convex-up, accretionary flats in