215 resultados para Minimum phase
Resumo:
This study deals with the mineralogical variability of siliceous and zeolitic sediments, porcellanites, and cherts at small intervals in the continuously cored sequence of Deep Sea Drilling Project Site 462. Skeletal opal is preserved down to a maximum burial depth of 390 meters (middle Eocene). Below this level, the tests are totally dissolved or replaced and filled by opal-CT, quartz, clinoptilolite, and calcite. Etching of opaline tests does not increase continously with deeper burial. Opal solution accompanied by a conspicuous formation of authigenic clinoptilolite has a local maximum in Core 16 (150 m). A causal relationship with the lower Miocene hiatus at this level is highly probable. Oligocene to Cenomanian sediments represent an intermediate stage of silica diagenesis: the opal-CT/quartz ratios of the silicified rocks are frequently greater than 1, and quartz filling pores or replacing foraminifer tests is more widespread than quartz which converted from an opal-CT precursor. As at other sites, there is a marked discontinuity of the transitions from biogenic opal via opal-CT to quartz with increasing depth of burial. Layers with unaltered opal-A alternate with porcellanite beds; the intensity of the opal-CT-to-quartz transformation changes very rapidly from horizon to horizon and obviously is not correlated with lithologic parameters. The silica for authigenic clinoptilolite was derived from biogenic opal and decaying volcanic components.
Resumo:
Equilibrium melting and controlled cooling experiments were undertaken to constrain the crystallization and cooling histories of tholeiitic basalts recovered by the Ocean Drilling Program drilling of Site 989 on the Southeast Greenland continental margin. Isothermal experiments conducted at 1 atm. and at the fayalite-magnetite-quartz buffer using lava sample Section 163-989B-10R-7 yielded the equilibrium appearance sequence with decreasing temperature: olivine at 1184 ± 2ºC; plagioclase at 1177ºC ± 5ºC; augite at 1167 ± 5ºC; and pigeonite at 1113 ± 12ºC. In controlled cooling experiments using the same starting composition and cooling rates between 10ºC/hr and 2000ºC/hr, we find a significant temperature delay in the crystallization of olivine, plagioclase, and augite (relative to the equilibrium appearance temperature); pigeonite does not form under any dynamic crystallization conditions. Olivine exhibits the largest suppression in appearance temperature (e.g., 30º for 10ºC/hr and >190º at 100ºC/hr), while plagioclase shows the smallest (~10ºC at 10ºC/hr; 30ºC at 100ºC/hr, and ~80ºC at 1000ºC/hr). These results are in marked contrast to those obtained on lunar basalts, which generally show a large suppression of plagioclase crystallization and modest suppression of olivine crystallization with an increased cooling rate. The results we report agree well with the petrography of lavas recovered from Site 989. Furthermore, the textural analysis of run products, representing a large range of cooling rates and quench temperatures (1150ºC to 1000ºC), provide a framework for evaluating cooling conditions necessary for glass formation, rates of plagioclase growth, and kinetic factors governing plagioclase growth morphology. Specifically, we use these insights to interpret the textural and mineralogical features of the unusual compound flow recovered at Site 989. We concluded from the analysis that this flow most likely records multiple breakouts from a distal tube at an abrupt break in slope, possibly a fault scarp, resulting in the formation of a lava fan delta. This interpretation implies that normal faulting of the oldest lava sequences (lower and, possibly, middle series) preceded eruption of Site 989 lavas.
Total nitrogen from solid phase in the Jena Experiment (Main Experiment up to 30cm depth, year 2008)
Resumo:
This data set contains measurements of total nitrogen from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Soil sampling and analysis: Stratified soil sampling was performed in April 2008 to a depth of 30 cm. Three independent samples per plot were taken using a split tube sampler with an inner diameter of 4.8 cm (Eijkelkamp Agrisearch Equipment, Giesbeek, the Netherlands). Soil samples were segmented to a depth resolution of 5 cm in the field, giving six depth subsamples per core, and made into composite samples per depth. Sampling locations were less than 30 cm apart from sampling locations in other years. Samples were dried at 40°C. All soil samples were passed through a sieve with a mesh size of 2 mm. Because of much higher proportions of roots in the soil, the samples were further sieved to 1 mm according to common root removal methods. No additional mineral particles were removed by this procedure. Total nitrogen concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany).
Resumo:
This data set contains measurements of total nitrogen from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Soil sampling and analysis: Stratified soil sampling to a depth of 1m was performed before sowing in April 2002. Three independent samples per plot were taken of all plots in block 2 using a motor-driven soil column cylinder (Cobra, Eijkelkamp, 8.3 cm in diameter). Soil samples were dried at 40°C and segmented to a depth resolution of 5 cm giving 20 depth subsamples per core. All samples were analyzed independently. All soil samples were passed through a sieve with a mesh size of 2 mm. Rarely present visible plant remains were removed using tweezers. Total nitrogen concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany).
Total nitrogen from solid phase in the Jena Experiment (Main Experiment up to 30cm depth, year 2004)
Resumo:
This data set contains measurements of total nitrogen from the main experiment plots of a large grassland biodiversity experiment (the Jena Experiment; see further details below). In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. Soil sampling and analysis: Stratified soil sampling was performed in April 2004 to a depth of 30 cm. Three independent samples per plot were taken using a split tube sampler with an inner diameter of 4.8 cm (Eijkelkamp Agrisearch Equipment, Giesbeek, the Netherlands). Soil samples were segmented to a depth resolution of 5 cm in the field, giving six depth subsamples per core, and made into composite samples per depth. Sampling locations were less than 30 cm apart from sampling locations in other years. Samples were dried at 40°C. All soil samples were passed through a sieve with a mesh size of 2 mm. Because of much higher proportions of roots in the soil, the samples were further sieved to 1 mm according to common root removal methods. No additional mineral particles were removed by this procedure. Total nitrogen concentration was analyzed on ball-milled subsamples (time 4 min, frequency 30 s-1) by an elemental analyzer at 1150°C (Elementaranalysator vario Max CN; Elementar Analysensysteme GmbH, Hanau, Germany).
Resumo:
The sampling area was extended to the Western-South area off the Black Sea coast from Kaliakra cape toward the Bosforous. Samples were collected along four transects. The whole dataset is composed of 17 samples (from 10 stations) with data of mesozooplankton species composition abundance and biomass. Sampling for zooplankton was performed from bottom up to the surface at depths depending on water column stratification and the thermocline depth. These data are organized in the "Control of eutrophication, hazardous substances and related measures for rehabilitating the Black Sea ecosystem: Phase 2: Leg I: PIMS 3065". Data Report is not published. Zooplankton samples were collected with vertical closing Juday net,diameter - 36cm, mesh size 150 µm. Tows were performed from surface down to bottom meters depths in discrete layers. Samples were preserved by a 4% formaldehyde sea water buffered solution. Sampling volume was estimated by multiplying the mouth area with the wire length. Mesozooplankton abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Kremena Stefanova using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972). Taxon-specific abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Copepods and Cladoceras were identified and enumerated; the other mesozooplankters were identified and enumerated at higher taxonomic level (commonly named as mesozooplankton groups). Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Kremena Stefanova using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972).
Resumo:
Sediments associated with freshwater ferromanganese concretions in Lake Charlotte, Nova Scotia, contained microscopic precipitates of manganese and iron. These precipitates were dispersed throughout the sediment and were as rich in nickel, cobalt, and copper as deep sea concretions. In addition, the development of the precipitates appeared to be associated with the microbial oxidation of manganese. Results from the deployment of poisoned and unpoisoned dialysis probes or peepers demonstrated that microbial manganese oxidation and nickel binding were closely associated, causing a fivefold enhancement of abiotic processes such as adsorption.