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  • Cambridge University Press  (853)
  • PANGAEA
  • 1980-1984  (895)
Collection
Keywords
Years
Year
  • 1
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Cyamex Scientific Team; Francheteau, Jean; Needham, H D; Choukroune, P; Juteau, Thierry; Séguret, Marie J M; Ballard, R D; Fox, P J; Normark, William R; Carranza, A; Cordoba, D; Guerrero, Gerardo; Rangin, Claude (1981): First manned submersible dives on the East Pacific Rise at 21�N (project RITA): General results. Marine Geophysical Research, 4(4), 345-379, https://doi.org/10.1007/BF00286034
    Publication Date: 2023-08-28
    Description: A submersible study has been conducted in February - March 1978 at the axis of the East Pacific Rise near 21°N. The expedition CYAMEX, the first submersible program to be conducted on the East Pacific Rise, is part of the French-American-Mexican project RITA (Rivera - Tamayo), a 3-year study devoted to detailed geological and geophysical investigations of the East Pacific Rise Crest. On the basis of the 15 dives made by CYANA in the axial area of the Rise, a morphological and tectonic zonation can be established for this moderately-fast spreading center. A narrow, 0.6 to 1.2 km wide zone of extrusion (zone 1), dominated by young lava flows, is flanked by a highly fissured and faulted zone of extension (zone 2) with a width of 1 to 2 km. Further out, zone 3 is dominated by outward tilted blocks bounded by inward-facing fault scarps. Active or recent faults extend up to 12 km from the axis of extrusion of the East Pacific Rise. This represents the first determination from direct field evidence of the width of active tectonism associated with an accreting plate boundary. Massive sulfide deposits, made principally of zinc, copper and iron, were found close to the axis of the Rise. Other signs of the intense hydrothermal activity included the discovery of benthic fauna of giant size similar to that found at the axis of the Galapagos Rift. We emphasize the cyclic character of the volcanicity. The main characteristics of the geology of this segment of the East Pacific Rise can be explained by the thermal structure at depth below this moderately-fast spreading center. The geological observations are compatible with the existence of a shallow magma reservoir centered at the axis of the Rise with a half-width of the order of 10 km.
    Keywords: CY78-16DF; CY78-17V; CY78-18V; CYAMEX; Cyana (Submersible); Deposit type; DEPTH, sediment/rock; Description; East Pacific Rise; Event label; Identification; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; OBSE; Observation; Position; Quantity of deposit; Sediment sample; Sediment type; SES; Substrate type; Visual description
    Type: Dataset
    Format: text/tab-separated-values, 21 data points
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  • 2
    facet.materialart.
    Unknown
    PANGAEA
    In:  Supplement to: Juteau, Thierry; Eissen, Jean-Philippe; Francheteau, Jean; Needham, David; Choukroune, P; Rangin, Claude; Séguret, Marie J M; Ballard, R D; Fox, P J; Normark, William R; Carranza, A; Cordoba, D; Guerrero, J (1980): Homogeneous basalts from the East Pacific Rise at 21° N: seady state magma reservoirs at moderately fast spreading centers. Oceanologica Acta, 3(4), 487-503, https://archimer.ifremer.fr/doc/00323/43430/
    Publication Date: 2023-08-28
    Description: Forty basaltic rocks collected by submersible during the Cyamex expedition (1978) on the East PacifIc Rise at 21°N, a moderately fast spreading segment (6 cm/year opening rate) of the mid-ocean ridge, consist of angular pillow fragments and glass buds, sheet-flow slabs and samples of columnar pillars standing in collapsed fossillava pools. Most of the rocks are from the crestal are a of the Rise. The collection shows a striking petrographic homogeneity wh en compared with the range of basalts found on other segments of midocean ridges: olivine-phyric, or highly plagioclase-phyric rocks, so common in the slowspreading Famous are a in the Atlantic, are absent. All samples are typical lowpotassium oceanic tholeiites with a limited fractionation trend. Pillow-lavas, thin and thick sheet-flows cannot be distinguished by their major element compositions, as in the Galapagos rift which has the same spreading rate as the EPR at 21°N. Further, ferrobasalts have been described from the Galapagos rift, but do not appear in the Cyamex rocks. In the Cyamex area, olivine and plagioclase are the main silicate phases, and clinopyroxene is absent. In the pillows and sheet-flow samples, four generations of olivine and plagioclase crystals are distinguished. Samples from the fossillava pools are aphyric. The corresponding magma batches are presumed to have migrated rapidly through the magma chamber, and to have been extruded in large volumes, possibly during episodes ofhigh instantaneous opening rate. Fe-Ni and Fe-Cu-rich sulphide phases are common in an lava types as massive globules scatterred through the glass, or as microglobules decorating the walls of empty vesicles. Palagonite and Fe-Mn oxide thicknesses across the strike of the Rise indicate relative ages compatible with successive extrusions at the Rise axis.
    Keywords: CY-78-07-12D; CY-78-10-17D; CY-78-10-18D; CY-78-11-26D; CY-78-12-35D; CY-78-13-42D; CY-78-13-43D; CY-78-13-44D; CY-78-15-55D; CY-78-15-56D; CY-78-16-57D; CY-78-16-58D; CY-78-17-60D; CY-78-17-61D; CY-78-18-63D; CY-78-18-65D; CY-78-18-66D; CY-78-19-69D; CY-78-20-76D; CYAMEX; Cyana (Submersible); Deposit type; DEPTH, sediment/rock; Description; East Pacific Rise; Elevation of event; Event label; Identification; Latitude of event; Longitude of event; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; Percentage; Position; ROBA; Robotic arm; Sediment type; Substrate type; Visual description
    Type: Dataset
    Format: text/tab-separated-values, 108 data points
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  • 3
    Publication Date: 2024-01-19
    Keywords: AGE; SPECMAP; Spectral Mapping Project (Mapping Species Variability in Global Climate); δ18O
    Type: Dataset
    Format: text/tab-separated-values, 392 data points
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  • 4
    Publication Date: 1983-04-01
    Description: SUMMARYA multifactorial experiment sown to winter wheat cv. Hustler in autumn 1978 tested the effects of combinations of the following eight factors, each at two levels: drill type, sowing date, amount of nitrogen, division of nitrogen, irrigation, autumn pesticide (aldicarb), summer aphicide (pirimicarb), and fungicide (carbendazim, maneb and tridemorph).The mean grain yield of all plots was 9·7 t/ha and the best eight-plot treatment mean was 11·3 t/ha. The factors that had the greatest effect on yield were aphicide and fungicide, mainly from the control of Metopolophium dirhodum and Septoria spp. respectively. Both factors increased grain size and their effects were more than additive and greater with 250 than with 160 kg N/ha. Aphicide and fungicide also temporarily decreased the numbers of microbes on the developing ears. Autumn pesticide gave good control of aphids in the winter and some control in the summer: it also decreased nematode populations and slightly increased yields.Precision sowing compared with random distribution of seeds along the row had little effect on growth or yield. Sowing on 21 September compared with 13 October greatly increased growth early in the season but had less effect after anthesis; it was the only factor that increased yield when aphicide and fungicide were applied. There was negligible infection by barley yellow dwarf virus in crops sown on either date. The amount and division of N fertilizer affected N uptake early in the season and had small effects on the production and survival of tillers. Three N applications instead of one slightly increased grain yields but did not affect total N uptake by grains plus straw, which averaged 190 kg N/ha. The larger amount of N always increased N uptake but decreased yield in the absence of aphicide and fungicide. Irrigation slightly decreased yield despite prolonging the duration of green leaf area.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 5
    Publication Date: 1981-01-01
    Description: SummaryLate Triassic Radiolaria have been recovered from a bedded chert collected early in 1977 in the South Orkney islands. This is the first reliable palaeontological evidence for the age of the so-called basement complex that forms most of the exposed rock of a microcontinent on the southern limb of the Scotia Ridge. The fossils place a lower limit on the age of deformation of at least part of the complex as post-Karnian or Norian. The basement is overlain by undeformed Jurassic to Cretaceous conglomerates, which suggests this event took place during the early Mesozoic Gondwanian orogeny.The new data are consistent with the interpretation that the basement complex of the South Orkney Islands represents part of a subduction complex and was accreted to the Pacific margin of Gondwanaland during the late Triassic or early Jurassic time.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 6
    Publication Date: 1983-01-01
    Description: There is at present a need to develop a better technique for measuring the rate of icing on structures such as, for example, overhead transmission lines. For aircraft and helicopter icing, the most widely used method of measurement is the rotating cylinder. However, for measuring the icing of structures, this method is difficult to apply and also less accurate due to lower wind velocities. Different approaches are now being developed using fixed cylinders.Icing tests were conducted with fixed and rotating cylinders in a wind tunnel. The rate of icing was obtained through measurements of volume, accretion cross-section and time of deposition. Tests were made using five different liquid water contents and droplet diameter spectra, and four cylinder diameters, keeping the wind velocity and temperature constant. The rate of icing is presented as a function of the diameters of the fixed and rotating cylinders for each of the liquid water contents tested. Results indicate that at lower wind velocities the accretion rate is overestimated for the smaller rotating cylinders. This difference is probably due to the variation of the collection efficiency with diameter. From these results it is suggested that the rate of ice accretion on structures should be based on at least two fixed cylinders of different small sizes in order to take into account the effect of the collection efficiency.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 7
    Publication Date: 1983-01-01
    Description: There is at present a need to develop a better technique for measuring the rate of icing on structures such as, for example, overhead transmission lines. For aircraft and helicopter icing, the most widely used method of measurement is the rotating cylinder. However, for measuring the icing of structures, this method is difficult to apply and also less accurate due to lower wind velocities. Different approaches are now being developed using fixed cylinders. Icing tests were conducted with fixed and rotating cylinders in a wind tunnel. The rate of icing was obtained through measurements of volume, accretion cross-section and time of deposition. Tests were made using five different liquid water contents and droplet diameter spectra, and four cylinder diameters, keeping the wind velocity and temperature constant. The rate of icing is presented as a function of the diameters of the fixed and rotating cylinders for each of the liquid water contents tested. Results indicate that at lower wind velocities the accretion rate is overestimated for the smaller rotating cylinders. This difference is probably due to the variation of the collection efficiency with diameter. From these results it is suggested that the rate of ice accretion on structures should be based on at least two fixed cylinders of different small sizes in order to take into account the effect of the collection efficiency.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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  • 8
    Publication Date: 1980-01-01
    Description: 14C and 13C enrichment values are reported for a series of surface soil profiles which represent the progressive transition from mor to mull humus induced by birch (Betula pendula) colonization.Variations in Δ and δ13C, which range between 85 to 154‰ modern and −28.1 to −25.3‰ (PDB), respectively, reflect changes in the rate and mode of organic decomposition. The most marked alterations in soil character occur over the first few decades following the introduction of birch, with clear isotopic evidence for the deeper penetration and accelerated mineralization of organic material.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 9
    Publication Date: 1983-01-01
    Description: Data on the depth distribution of the major atmospheric gases and the abundance of gaseous 12CO2, 13CO2, and 14CO2 in the subsoil unsaturated zone have been obtained from several sites in the western Great Plains of the United States. Sample profiles range from land surface to depths of 50m. Although each site must be considered on an individual basis, several general statements can be made regarding the profiles. 1) Diffusion of these gaseous molecules through the unsaturated zone is an important transport mechanism. 2) As predicted by diffusion theory, depth profiles of the various isotopic species of CO2 differ substantially from one another, depending on individual sources and sinks such as root respiration and oxidation of organic carbon at depth. 3) In general, post-bomb (〉 100% modern) 14C activities are not observed in the deep unsaturated zone, in contrast to diffusion model predictions. 4) In spite of generally decreasing 14C activities with depth, absolute partial pressures of 14CO2 in the subsoil unsaturated zone are 1–2 orders of magnitude higher than the partial pressure of 14CO2 in the atmosphere.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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  • 10
    Publication Date: 1983-01-01
    Description: The Harwell system for measuring milligram size samples using Brookhaven miniature gas counters is fully operative. It comprises 12 counters of different sizes which operate simultaneously within a single NaI crystal (300mm diameter × 300mm long) acting as an anti-coincidence guard counter. Brief details are given of the construction and commissioning of the system, including counter assembly, shield design, electronics, data capture, data analysis, and chemical processing and filling procedures. The performance of the system and an overall view of the fields of application for which the counters have important applications are discussed.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
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