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  • 1
    Electronic Resource
    Electronic Resource
    Frequency-dependent susceptibility measurements of environmental materials (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The theory, measurement and interpretation of frequency-dependent susceptibility (χFD) are examined. A new model is proposed which explains χFD in terms of the behaviour of all superparamagnetic grains (SP) with diameters between 0 and ∼0.03 μm. The model predicts maximum χFD percentage values of 14–17 per cent for spherical SP ferrimagnetic grains in the grain-size range 0.01–0.025 μm, and a maximum value of 10–12 per cent for grain assemblages spanning a wider range of grain sizes (0–0.03 μm). Synthetic and experimental data support the model predictions in terms of both maximum χFD percentage values and the relationship between χFD percentage and mass specific χFD, which exhibits an envelope of data points partly related to grain-size distributions within the SP range. When the χFD percentage is at a maximum, the mass specific χFD term can be used to estimate the concentration of SP grains in a sample. Lower values of χFD percentage in soils are caused by the presence of narrow distributions of ultrafine SP grains, frequency-independent stable single and multi-domain ferrimagnetic grains. Some soils with low susceptibilities may have low χFD percentages because of an appreciable content of paramagnetic and canted antiferromagnetic minerals. A simple mixing model predicts proportions of SP grains in mixed grain assemblages, but model validation requiring further characterization of grain interaction and grain-size distributions is needed before it can be applied to environmental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06366.x
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic susceptibility of soil: an evaluation of conflicting theories using a national data set (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 127 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Magnetic susceptibility values for topsoils across England arc combined with data for soil type, geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism. Strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains. Magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils, and crop burning is discounted as a major factor. A small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates. The results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes. The fundamental driving force in the mechanism is Fe supply, which may be linked to climate. Observed causative associations between climate and the magnetic susceptibility of loess-palaeosol sequences are supported by the findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb04051.x
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic differentiation of atmospheric dusts (1985)
    [s.l.] : Nature Publishing Group
    Nature 317 (1985), S. 516-518 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Chester et al.8 were able to distinguish between and characterize dust source types in the Mediterranean region by plotting aluminium concentration against the magnetic susceptibility/aluminium concentration quotient. Soil-derived dusts of North African origin fell at one extreme, with high ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/317516a0
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  • 4
    Electronic Resource
    Electronic Resource
    A late Holocene record of land-use history, soil erosion, lake trophy and lake-level fluctuations at Bjäresjösjön (south Sweden) (1991)
    Springer
    Journal of paleolimnology 6 (1991), S. 51-81 
    Details
    ISSN: 1573-0417
    Keywords: South Sweden ; Late Holocene ; catchment history ; soil erosion ; lake trophy ; lake-level fluctuations ; palaeolimnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Land-use history, soil erosion, lake trophy and lake-level fluctuations during the last 3000 years were reconstructed through a multidisciplinary palaeolimnological study (pollen, plant macrofossils, diatoms, physical and chemical analysis, magnetic measurements and radiometric methods) of a small eutrophic lake in southern Sweden (Bjäresjösjön, Scania). There are striking responses in diatom, chemical, sediment yield and magnetic records to land-use changes documented by pollen analysis or historical sources, and to lake-level changes identified from sedimentary changes. Our multidisciplinary approach assists interpretation of the processes controlling long-term changes and separation of the effects of different factors (land-use changes, lake-level fluctuations) on individual biostratigraphical records. Climate has controlled processes in the lake indirectly, through lake-level fluctuations, from the Late Bronze Age to the Viking Age (700 BC-AD 800). Since the Viking Age, land-use controlled most of the changes observed in the lake's development and soil erosion processes. Major changes in lake development occurred during the last 200 years, due to a drastic increase in soil erosion and water eutrophication during a period of agricultural modernization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201299
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  • 5
    Electronic Resource
    Electronic Resource
    Catchment disturbance inferred from paleolimnological studies of three contrasted sub-humid environments in Morocco (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 293-322 
    Details
    ISSN: 1573-0417
    Keywords: catchment disturbance ; sediment cores ; magnetic minerals ; geochemistry ; pollen ; diatoms ; Morocco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Paleolimnological techniques for assessing recent drainage basin disturbance are evaluated in three Moroccan lakes with catchments contrasted in terms of land-use and vegetation. Rates of sediment accumulation in the two lakes with agricultural catchments were relatively high (〉1.6 cm yr-1) in the most recent past. Dilution effects prevented core dating by the 210Pb method alone and post-1953 chronologies were constructed by combining 210Pb and 137Cs data. The recent sediment accumulation rate at the currently least disturbed site, where natural Cedrus forest is still abundant, was relatively low (〈0.4 cm yr-1) but has increased since the mid-19th century. Magnetic, geochemical, pollen, and diatom studies of all three lake sediment cores linked with modern field survey data show that soil erosion in the most vegetationally disturbed catchment (Dayat-er-Roumi) has been high throughout the recent past and that intensity peaks are probably associated with wetland drainage operations beginning in the 1940's. At the partially forested site (Dayat Affougah), pre-1950's woodland clearance and other land-use changes are the likely cause of past major soil erosion episodes. The site currently dominated by natural Cedrus forest (Lac Azigza) shows only minor disturbance during the past c. 150 years although a major soil erosion episode occrred in the 17th century. Paleolimnological analysis has clearly demonstrated that major landscape change has occurred at all three sites. However, only at the two sites with catchment cultivation do previously accelerated soil erosion and lake sediment accumulation rates persist to the present. Information essential for formulation of appropriate management plans is presented and the importance of paleolimnology in assessing man-induced lake-catchment disturbance is stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00184003
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  • 6
    Electronic Resource
    Electronic Resource
    Sedimentary indicators of lake-level changes in the humid temperate zone: a critical review (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 1-14 
    Details
    ISSN: 1573-0417
    Keywords: lake-levels ; sedimentation ; temperate climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Evidence for lake-level changes derived from stratigraphic sequences in cores from littoral zones is reviewed in the context of lake sedimentation processes. These are illustrated with published case-studies which have used multiple-core data. Possible approaches for choosing optimum sites are examined. Sedimentation controls which may change over time are also considered; these include, wind strength and frequency, wind exposure, water depth and underwater slopes, sediment type and littoral vegetation. A final section discusses how lake-level studies can be optimised so that results can be used with confidence in paleoclimatic and paleohydrological reconstructions. Sedimentary data showing shifts in littoral vegetation along shallow underwater gradients in sheltered margins, and transitions between sediment compositions linked to specific hydrological conditions give the strongest lines of evidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007916210820
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  • 7
    Electronic Resource
    Electronic Resource
    Lake-catchments and environmental chemistry: a comparative study of contemporary and historical catchment processes in midland England (1987)
    Springer
    GeoJournal 14 (1987), S. 285-297 
    Details
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract Post-war agricultural “industrialisation” has resulted in the intensification of land use, amalgamation of production units and, in many cases, has led to environmental degradation. This degradation is in part reflected in increased pollution from fertilisers, pesticides and isecticides and in part is seen in higher sediment yields derived from agricultural ecosystems. This study attempts to examine the relative significance of agricultural intensification through a comparison of two lake catchments in Midland England. Assessment of agricultural impact is achieved by utilising one lake-catchment system as an afforested control. Contemporary studies of water chemistry and hydrology are used to complement the reconstruction and interpretation of historical sediment yields and chemical loadings to the limnic environment derived by analysis of lake sediment chemistry. It is suggested that such studies might, if carefully calibrated, provide direct quantitative information with regard to environmental degradation through changing erosion and agricultural pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208202
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  • 8
    Electronic Resource
    Electronic Resource
    Lake sediment records of erosional processes (1991)
    Springer
    Hydrobiologia 214 (1991), S. 99-106 
    Details
    ISSN: 1573-5117
    Keywords: lake-catchment systems ; erosional processes ; sediment sources ; erosion models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Accumulations of sediment at the beds of lakes, estuaries and reservoirs provide partial records of materials transported from the surrounding water catchment areas. Physical, chemical, biological and magnetic analyses, with data for accumulation rates, have been used in a range of environmental settings to infer the rate, form, cause and source of erosion. This paper is a brief review of these studies from a hydrological perspective, setting sediment studies within a lake-catchment system. The need for long term erosional records is discussed in terms of the type of erosional data which may be obtained. Alternative approaches to studying short and long term erosion are assessed with regard to their cost-effectiveness and their levels of precision and accuracy. Finally, some suggestions are made about how these erosion records may be used to model hydrological, pedological and geomorphological processes, thus linking together long term, short term and contemporary timescales of process operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050938
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  • 9
    Electronic Resource
    Electronic Resource
    A multidisciplinary study of the lake Bjäresjösjön (S Sweden): land-use history, soil erosion, lake trophy and lake-level fluctuations during the last 3000 years (1991)
    Springer
    Hydrobiologia 214 (1991), S. 107-114 
    Details
    ISSN: 1573-5117
    Keywords: Holocene ; South Sweden ; cultural landscape ; land-use history ; soil erosion ; lake trophy ; lake-level fluctuations ; pollen ; diatoms ; chemical analysis ; palaeomagnetic measurements ; sediment yields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The lake Bjäresjösjön, Southern Scania, Southern Sweden, was studied in the context of the project ‘The cultural landscape of the past 6000 years in Southern Sweden’. Pollen, plant macrofossils, diatoms, physical and chemical analysis, magnetic measurements and radiometric methods (210Pb, 14C) have been used to study palaeoecological changes, i.e. climate, land use, lake trophy and soil erosion during the past 3000 years. This multidisciplinary study shows striking responses of diatom communities, physical and chemical characteristics, sediment yields and magnetic parameters to land-use changes and lake-level fluctuations. Moreover, the latter are closely related to the settlement history at the site, inferred from archaeological records and historical sources. Before 650 AD, the limnological development was affected mainly by lake-level fluctuations, but partly also by human impact (extensive forest clearings and dominant pastoral farming). With the expansion of arable farming (around 650 AD), human impact on the landscape was the major factor influencing soil erosion processes in the catchment and limnological changes in the lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050939
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  • 10
    Electronic Resource
    Electronic Resource
    Changing patterns of sediment accumulation in a small lake in Scania, southern Sweden (1983)
    Springer
    Hydrobiologia 103 (1983), S. 59-64 
    Details
    ISSN: 1573-5117
    Keywords: paleolimnology ; sedimentation pattern ; magnetic susceptibility ; Scanian lakes ; palaeomagnetism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Magnetic susceptibility measurements have been used to correlate synchronous depths in ca. 50 l m. cores of recent sediment from a small lake (area ca. 55 ha) in Scania, southern Sweden. The three-dimensional picture of sediment accumulation which emerges provides a basis for studying sediment deposition patterns through time. Using a palaeomagnetic chronology, the results show that the pattern and rate of accumulation have dramatically altered during the past 350 years, thus making semiquantitative studies of downcore sediment properties in a single core problematical. Possible reasons for these phenomena are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028428
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