A study in the dynamics of the geoelectrical medium from electrotelluric field data

The manner in which the dynamics of geoelectric earth inhomogeneities can be studied using receiving lines oriented in different directions at a single site is considered. It is shown that the presence of a local geoelectric inhomogeneity allows monitoring the state of electric conductivity in the earth by observation of the telluric tensor. We quote results from long-continued monitoring of the electrotelluric tensor in Kamchatka. The tensor’s behavior showed an appreciable anomaly, which may have been related to great (magnitude 8.2 and 8.3) earthquakes in the Kuril-Kamchatka region.     

Geochemistry and origin of the Proterozoic ultrapotassic rocks of the Churchill Province,Canada

Summary Early Proterozoic ultrapotassic dikes, lava flows, and pyroclastic rocks of the Christopher Island Formation (CIF) erupted throughout an area 600 × 300 km within the Churchill Province of the Canadian Shield at 1.84 Ga. The rocks range from mafic lamprophyres (mg # 60; SiO₂ 47–54%, mean K₂O/Na₂O > 4) with phenocrysts of phlogopite + diopside + apatite ± olivine ± magnetite, to phenocryst-poor felsic rocks and sanidine porphyries (SiO₂55–69%). All samples have high incompatible element contents and display large depletions of high field strength elements relative to K, Rb, Sr, Ba, and Th. The CIF has geochemical and petrographic characteristics of both minettes and lamproites, but overall most closely resembles young Mediterranean lamproites. Felsic rocks of the CIF were produced by crystal fractionation and crustal contamination of mafic ultrapotassic magma, and include both high-silica lamproites strongly enriched in Zr, U, and Th, and weakly potassic to sodic rocks of trachytic composition. Flows and feeder dikes have relatively homogeneous _{Nd, 1840 Ma} (–6 to –11) but highly variable ES., 1840 Ma (–40 to + 100); samples classified as lamproites have higher average _Sr. Dike samples have highly variable present-day Pb isotope compositions, ranging from moderately to strongly nonradiogenic. Geochemical and isotopic data are consistent with contributions from depleted Archean lithospheric mantle, and OIB-type convecting mantle, both metasomatized by subduction-related processes during the Early Proterozoic. The lithospheric mantle probably contained Archean enriched domains as well. Proterozoic enrichment may have accompanied shallow underplating of subducted oceanic lithosphere beneath the Churchill Province during amalgamation of the Laurentian supercontinent. There are strong analogies in isotopic composition, and interpreted source region history, between the CIF and lamproites and minettes of the Wyoming Province and western Greenland, which suggest the existence of a Laurentian ultrapotassic superprovince.

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Geochemie und Entstehung der Proterozoischen ultrapotassischen Gesteine der Churchill Provinz, Kanada

Zusammenfassung Altproterozoische, ultrapotassische Gänge, Lavaströme und pyroklastische Gesteine der Christopher Island Formation (CIF), eruptierten in einem Gebiet von 600 × 300 km in der Churchill Provinz des Kanadischen Schildes vor 1.84 Ga. Die Zusammensetzung dieser Gesteine variiert von mafischen Lamprophyren (mg > 60; SiO₂ = 47–54%, durchschnittliches K₂O/Na₂O > 4) mit Phänokristallent von Phlogopit + Diopsid + Apatit + Olivin + Magnetit, bis zu phänokristallarmen felsischen Gesteinen und Sanidinporphyren (SiO₂ = 55–69%). Alle Proben zeigen hohe Gehalte an inkompatiblen Elementen und zeigen beträchtliche Verarmung an high field strength Elementen relativ zu K, Rb, Sr, Ba und Th. Die CIF hat geochemische und petrographische Eigenschaften sowohl von Minetten wie von Lamproiten, aber im allgemeinen ähnelt sie am stärksten jungen mediterranen Lamproiten. Felsische Gesteine der CIF wurden durch Fraktionierung und Krustenkontamination aus mafischen ultrapotassischen Magmen gebildet. Letztere umfassen sowohl siliziumreiche Lamproite, die deutlich an Zr, U und Th angereichert sind und schwach potassische bis sodische Gesteine von trachytischer Zusammensetzung. Lavenergüsse und zufuhrgänge zeigent ein relativ homogenes _{Nd, 1840 Ma} (–6 bis –11) aber ein sehr variables _{Sr, 1840 Ma} (-40 bis + 100); Proben die als Lamproite klassifiziert wurden, zeigent höhere durchschnittliche _Sr-Werte. Proben von Gängen haben sehr variable Bleiisotopen-Zusammensetzungen, die von mäßig bis stark nichtradiogen variieren. Geochemische und Isotopendaten weisen auf Beiträge aus verarmtem archaischen lithosphärischen Mantel und aus konvektierendem OIB-Typ Mantel hin, die beide während des Alproterozoikums durch Subduktions-Vorgänge metasomatisiert wurden. Der lithosphärische Mantel enthielt wahrscheinlich auch angereicherte archaische Domänen. Proterozoische Anreicherungsvorgänge dürften seichtes Underplating subduzierter ozeanischer Lithosphäre unter der Churchill Provinz während der Amalgamation des laurentischen Superkontinentes begleitet haben. Es gibt starke Analogien in der Isotopenzusammensetzung und in der interpretierten Geschichte der Ursprungsregion, zwischen den CIF und Lamproiten und Minetten der Wyoming Provinz, und des westlichen Grönland. Diese weisen auf die Existenz einer laurentischen ultrapotassischen Superprovinz hin.

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With 7 Figures     

Effectiveness of vegetative filter strips in abating fecal coliform based on modified soil and water assessment tool

Pathogenic bacteria are a serious public health concern. Exposure to these microorganisms can result in illnesses or even death. Therefore, it is important to control pathogenic bacteria sources, transport mechanisms and fate. Best management practices proved to be very effective in the control of non-point source pollution. In this study, the soil and water assessment tool (SWAT) was modified and used to simulate the fecal coliform in Chao River of Miyun Reservoir watershed, China. The model was then used to explore the effectiveness of vegetative filter strips (VFS) in reducing fecal coliform abundance throughout the watershed. The water temperature equation within the SWAT was modified to align the model more closely with the characteristics of the study area and generate a more accurate simulation. The DAFS_ratio (20, 50, 80, 120 and 150) and DF_con (0.25, 0.4, 0.6 and 0.75) parameters were considered for VFS to see their effects on removal efficiency. The results show that calibration and validation results for fecal coliform and flow can be accepted. Different values for DAFS_ratio and DF_con have great influence on VFS. Increasing values resulted in a decrease in the removal efficiency of VFS.     

The upper Bajocian of the Crimean Mountains: Paleogeography and sedimentation conditions from palynological data

Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes.     

Enzymatic and cellular responses in relation to body burden of PAHs in bivalve molluscs: A case study with chronic levels of North Sea and Barents Sea dispersed oil

Mytilus edulis and Chlamys islandica were exposed to nominal dispersed crude oil concentrations in the range 0.015–0.25 mg/l for one month. Five biomarkers (enzymatic and cellular responses) were analysed together with bioaccumulation of PAHs at the end of exposure. In both species, PAH tissue residues reflected the exposure concentration measured in the water and lipophylicity determined the bioaccumulation levels. Oil caused biomarker responses in both species but more significant alterations in exposed C. islandica were observed. The relationships between exposure levels and enzymatic responses were apparently complex. The integrated biomarker response related against the exposure levels was U-shaped in both species and no correlation with total PAH body burden was found. For the monitoring of chronic offshore discharges, dose- and time-related events should be evaluated in the selection of biomarkers to apply. From this study, cellular damages appear more fitted than enzymatic responses, transient and more complex to interpret.     

Modeling the history of Lake of the Woods since 11,000 cal yr B.P. using GIS

Because of differential isostatic rebound, many lakes in Canada have continued to change their extent and depth since retreat of the Laurentide Ice Sheet. Using GIS techniques, the changing configuration and bathymetry of Lake of the Woods in Ontario, Manitoba, and Minnesota were reconstructed for 12 points in time, beginning at 11,000 cal yr B.P. (9.6 ¹⁴C ka B.P.), and were also projected 500 years into the future, based on the assumption that Lake of the Woods continued to have a positive hydrological budget throughout the Holocene. This modeling was done by first compiling a bathymetric database and merging that with subaerial data from the Shuttle Radar Topography Mission (SRTM). This DEM file was then adjusted by: (1) isobase data derived from Lake Agassiz beaches prior to 9000 cal yr B.P. (8.1 ¹⁴C ka B.P.) and (2) modeled isostatic rebound trend analysis after 9000 cal yr B.P. Just after the end of the Lake Agassiz phase of Lake of the Woods, only the northernmost part of the basin contained water. Differential rebound has resulted in increasing water depth. In the first 3000 years of independence from Lake Agassiz, the lake transgressed >50 km to the south, expanding its area from 858 to 2857 km², and more than doubling in volume. Continued differential rebound after 6000 cal yr B.P. (5.2 ¹⁴C ka B.P.) has further expanded the lake, although today it is deepening by only a few cm per century at the southern end. In addition, climate change in the Holocene probably played a role in lake level fluctuations. Based on our calculation of a modern hydrological budget for Lake of the Woods, reducing runoff and precipitation by 65% and increasing evaporation from the lake by 40% would end overflow and cause the level of the lake to fall below the outlets at Kenora. Because this climate change is comparable to that recorded during the mid-Holocene warming across the region, it is likely that the area covered by the lake at this time would have been less than that determined from differential isostatic rebound alone.     

Speleothems as high-resolution paleoenvironment archives: Records from northeastern China

The isotopic compositions of oxygen and carbon and trace concentrations of magnesium and strontium in speleothems formed in limestone caves respond to climate changes outside the caves. Measurements of these properties on a stalagmite from Shihua Cave near Beijing, China, allowed reconstruction of the regional changes in precipitation, temperature and nature of vegetation. Over the last ∼ 500 years, there were fourteen precipitation cycles with a periodicity of 30–40 years, which may well reflect fluctuations in the strength of the East Asian summer monsoons reaching northeastern China. Relative to the mean temperature of this time interval, the period 1620–1900 AD was cold and periods 1520–1620 and 1900–1994 were warm. Over the last ∼ 3000-years, about eight wet/cool-dry/warm climatic cycles of 300–400 years duration occurred, the latest wet/cool half cycle corresponding to the Little Ice Age. The δ¹³C record registers the anthropogenic activities of fossil fuel CO₂ combustion in recent decades and regional deforestation between 13 and 16 centuries when Beijing was bustling with palatial constructions and being developed into the world’s most populated city.     

Spectral characteristics of Rossby waves in the Northwestern Pacific based on satellite altimetry

Using satellite altimetry measurement data for 1993–2013, we study the spectral characteristics of Rossby waves in the Northwestern Pacific (25°–50° N, 140°–180° E). For each latitude degree, we draw integral plots of spectral power density calculated with a two-dimensional Fourier transform (2D-FFT). We compare the dispersion equations of Rossby waves calculated from the WKB-approximation and an approximation of a two-layer ocean model with the empirical velocities determined by the slope of isopleths by the Radon method; also, we compare the dispersion equations with the spectral distributions of level variations. It is shown that the main energy of Rossby waves in the Northwestern Pacific corresponds to the first baroclinic mode. At almost all latitudes, there is good agreement between the empirical phase velocities calculated by isopleths by the Radon method and the theoretical values; also, the spectral peaks correspond to graphs of the dispersion equations for the first baroclinic mode Rossby waves, except for the Kuroshio region, where some peaks correspond to the second mode.     

The effects of gravitational radiation on circular binary systems with spins

In any theory of gravitation that predicts the existence of gravitational waves, it is shown that, in the absence of mass exchange and mass loss and subjected to a condition, a circular binary system with spherically-symmetrical components cannot evolve in such a way that the spin angular velocity is always a linear function of the orbital velocity. Probably this relation between the angular velocities cannot be realized in any time interval. In particular, the system cannot remain in a synchronized state. Of eight special cases of evolution of this binary system, three cases, where the separation increases, are shown to be kinematically impossible while a restriction on the variation of a parameter governing the evaluation of the system can be made in another. In one of the kinematically allowed special cases the separation increases.