Effect of Anthropogenic Eutrophication on Zooplankton Distribution in Kondopoga Bay of Lake Onega

Changes in the quantitative and qualitative characteristics of zooplankton in Kondopoga Bay, Lake Onega, under long-term anthropogenic influence are discussed, and the effect of water pollution on changes in the zooplankton community is considered.     

Use of microtremor measurement for assessing site effects in Northern Belgium – interpretation of the observed intensity during the MS = 5.0 June 11 1938 earthquake

To provide quantitative information on site effects in the northern part of Belgium, forty-seven H/V microtremor measurements were performed with 5 second seismometers over an area of about 15.000 km². Most of the results show a northward regular increase of the fundamental period in agreement with the augmentation of the Mesozoic and Cainozoic soft sedimentsthickness from a few meters 40 km south of Brussels to 900 m at the Netherlands-Belgium border. The measured resonance frequency values wereconsistent with theoretical computations performed at different sites onthe basis of existing information and shallow seismic experiments. At oneparticular site (Uccle) where borehole data were available, microtremor measurements using an array of four seismological stations with differentapertures allowed to obtain the low frequency part of the Rayleigh wave dispersion curve, extending the range covered by the analysis of surfacewaves artificially generated. The Vs profile derived from the surface waveinversion corroborates the 1 Hz natural frequency of the site. Comparison of these results with the macroseismic information concerning the M_S = 5.0 1938 earthquake which occurred 50 km west of Brussels,confirmed the hypothesis that the geological structure of the Brabant massifis likely to control damage distribution during such an earthquake. Comparisonbetween the intensity map of the 1938 earthquake and the resonance period ofsediments obtained by our microtremor study shows a clear relation betweenthe two parameters. During the 1938 earthquake, site effects played a prominent role due to the dimension of the source whose corner frequency wasabout 1 Hz.     

Carbon-Oxidizing and Sulfate-Reducing Bacteria in Mozhaisk Reservoir Soils

The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied.     

Geophysical exploration for interlayer slip breccia gold deposits: example from Pengjiakuang gold deposit, Shandong Province, China

Interlayer slipping breccia‐type gold deposit – a new type of gold deposit, defined recently in the northern margin of the Jiaolai Basin, Shandong Province, China – occurs in interlayer slip faults distributed along the basin margin. It has the features of large orebody thickness (ranging from 14 m to 46 m, with an average thickness of 30 m), shallow embedding (0–50 m thickness of cover), low tenor of gold ore (ranging from 3 g/t to 5 g/t), easy mining and ore dressing. This type of gold deposit has promising metallogenic forecasting and potential for economic exploitation. A ground gamma‐ray survey in the Pengjiakuang gold‐ore district indicates that the potassium/thorium ratio is closely related to the mineralization intensity, i.e. the larger the potassium/thorium ratio, the higher the mineralization. The gold mineralized alteration zone was defined by a potassium/thorium ratio of 0.35. A seismic survey confirms the location of the top and bottom boundaries and images various features within the Pengjiakuang gold mineralization belt. The gold‐bearing shovel slipped belt dips to the south at an angle of 50–55° at the surface and 15–20° at depth. The seismic profile is interpreted in terms of a structural band on the seismic section characterized by a three‐layered model. The upper layer is represented by weakly discontinuous reflections that represent the overlying conglomerates. A zone of stronger reflections representing the interlayer slip fault (gold‐bearing mineralized zone) is imaged within the middle of the section, while the strongest reflections are in the lower part of the section and represent metamorphic rocks at depth. At the same time, the seismic reflection survey confirms the existence of a granite body at depth, indicating that ore‐forming fluids may be related to the granite. A CSAMT survey showed that the gold‐bearing mineralized zone is a conductive layer and contains a low‐resistivity anomaly ranging from 2 Ωm to 200 Ωm.     

Bathymetric and geochemical investigation of Kawah Ijen Crater Lake, East Java, Indonesia

A bathymetric survey of Kawah Ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922, 1925 and 1938, and to calculate the present lake volume. Even though the lake experienced several hydrothermal eruptions, the maximum depth became shallower (182 m) than before (200 m), resulting in a reduced lake volume (3.0×10⁷ m³).Fifty-two major and minor constituents including rare earth elements and polythionates (PT) of the lake waters at various depths were determined by ICP-AES, ICP-MS and HPLC, respectively. These ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of Kawah Ijen volcano. Most ions are homogeneously distributed throughout the lake, although PT showed a considerable vertical variation. Rare earth elements (REE) in the Kawah Ijen water as well as those from other hyper-acidic crater lakes show distribution patterns likely due to the three rock dissolution (preferential, congruent and residual) types, and their logarithmic concentrations linearly depend upon the pH values of the lake waters.Using the PT degradation kinetics data, production rates of PT, injection rates of SO₂ and H₂S into the lake were estimated to be 114, 86 and 30 tons/day, respectively. Also travel time of the spring water at the Banyupahit Riverhead from Kawah Ijen was estimated to be 600–1000 days through the consideration of decreasing rates of PT. Molten sulfur stocks containing Sn, Cu, Bi sulfides and Pb-barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom. This was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of Pb-chlorocomplex formation.     

Magmatic effects of the lunar late heavy bombardment

Large volumes of mare basalts are present on the surface of the moon, located preferentially in large impact basins. Mechanisms relating impact basins and mare basalt eruptions have previously been suggested: lunar impacts removed low-density material that may have inhibited eruption, and created cracks for fluid flow [Icarus 139 (1999) 246], and lunar basins have long been described as catchments for magma (e.g., [Rev. Geophys. Space Phys. 18 (1980) 107] and references therein). We present a new model for melt creation under near side lunar basins that is triggered by the impacts themselves. Magma can be produced in two stages. First, crater excavation depressurizes underlying material such that it may melt in-situ. Second, the cratered lithosphere rises isostatically, warping isotherms at the lithosphere-asthenosphere boundary which may initiate convection, in which adiabatic melting can occur. The first stage produces by far the largest volume of melt, but convective melting can continue for up to 350 Ma. We propose that giant impacts account for a large portion of the volume and longevity of mare basalt volcanism, as well as for several compositional groups, including high alumina, high titanium, KREEP-rich, and picritic magmas.     

Pedogenic factors affecting magnetic susceptibility of the last interglacial palaeosol S1 in the Chinese Loess Plateau

The magnetic susceptibility has been used as a quantitative or semi‐quantitative proxy for reconstructing the summer monsoon intensity in the Chinese Loess Plateau based on extensive studies on climatic or/and environmental mechanisms producing the magnetic susceptibility signatures. However, the precise nature of the link between past climates and the susceptibility signatures has remained uncertain primarily due to lack of our understanding in the ?nalizing and preserving processes of the signatures. This paper attempts to examine the reliability or acceptability of this summer monsoon proxy from non‐magnetic perspectives of soil‐forming processes. We chose nine sections along two transects: one across the western part of the Chinese Loess Plateau and another across the eastern part. Several conclusions can be drawn from our analytical data. First, clay translocation within the S1 palaeosol pro?les, as indicated by ?eld‐observed clay coatings on ped faces in Bt and Bk horizons and demonstrated by laboratory‐analysed clay contents, must have moved some of the magnetic minerals downward so that the susceptibility re?ects only the post‐translocation distribution of the magnetic‐susceptibility‐producing minerals. Second, the best‐developed palaeosol S1S3 at most of the sections studied is not expressed by the magnetic susceptibility because this palaeosol developed in underlying coarse loess (L2) and coarse textures tend to lower the susceptibility. Third, carbonate concentration is normally negatively correlated with the magnetic susceptibility or simply suppresses the magnetic susceptibility peak when the susceptibility enhancement exceeds the carbonate dilution effect. To conclude, extreme caution must be observed when using magnetic susceptibility signatures to retrieve high‐resolution records of the last interglacial palaeoclimate in the Chinese Loess Plateau. Copyright © 2004 John Wiley & Sons, Ltd.     

The effect of an interface boundary layer on the resonance properties of a buried structure

This paper presents a model for the analysis of the diffraction of plane waves at a cavity in an infinite homogeneous linear elastic medium supported by a segmented lining. An elastic boundary layer is introduced between the cavity lining and the infinite medium. The boundary layer is simulated by ‘elastic boundary conditions’ in which the stress is proportional to the relative displacement of the lining and of the surrounding medium boundary. A closed‐form analytical solution of the problem was obtained using the Fourier–Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance. Using amplitude–frequency response analysis it was shown that the boundary layer produces additional ‘pseudo‐resonance’ frequencies that depend on the layer properties. These frequencies are almost identical to the eigenvalues obtained from the simple analysis of a segmented elastically supported lining. Copyright © 2003 John Wiley & Sons, Ltd.