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  • 1
    ISSN: 1573-5117
    Keywords: 210Pb and 226Ra measurements ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lead-210 and radium-226 measurements by direct gamma assay can now provide a record of changing concentrations in lake sediments sufficiently reliable and precise to form a suitable basis for age/depth and dry-sedimentation-rate calculations. There are additional benefits in terms of non destructive sample preparation and simultaneous assay for other environmentally significant gamma-emitting radioisotopes (e.g. 137Cs and 241Am). Results from L. Fleet, S. W. Scotland illustrate the value of this approach especially in lakes with disturbed catchments where variable input of supported 210Pb has occurred.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2932
    Keywords: pigments ; diatoms ; cladocera ; ostracods ; chironomids ; chrysophytes ; sediments ; Late Pleistocene ; Holocene ; crater lake ; Italy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reports the results of biological analyses (pigments, diatoms, chrysophyte cysts, cladocerans, chironomids and ostracods) of a ca. 14 m-long sediment core recovered from Lake Albano (Central Italy) in the course of the EU-funded project PALICLAS (PALaeoenvironmental analysis of Italian Crater Lake and Adriatic Sediments). A reconstruction of the environmental evolution and ecosystem response of Lake Albano during the last ca. 30 kyr was possible. Additional information on lake level oscillation is obtained from benthic and planktonic palaeocommunities. Several oscillations in the productivity and the level of the lake were detected in the oldest sediment layers (from ca. 30 kyr BP to ca. 17 kyr BP), followed by a long (ca. 5 kyr BP) period of low productivity in which cold, holomictic conditions prevailed. A period of high biological activity and, probably, meromictic conditions during the early-mid Holocene was detected. A clear impact of human activities in the catchment was found at ca. 4 kyr BP in the form of increased erosion, associated with a decline in the abundance of biological remains. Further signs of human impact on the lake ecosystem are recorded during the Roman period. Although large-scale environmental changes (e.g. regional climate changes) caused many of the observed biological changes, human activities were important during the mid-late Holocene.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1437-3262
    Keywords: Key words Climate change ; Diatoms ; Turbidites ; Palaeolimnology ; Lake Baikal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The presence of inhomogeneous sedimentation is acknowledged as being an important problem in palaeolimnological studies. Sediment records can be disturbed by erosional and redepositional events, which redeposit microfossils within a basin and may then lead to misinterpretations of fossil diatom assemblages. This study uses a combination of sedimentological tools, magnetic susceptibility measurements and high-resolution diatom analysis to show that a sediment core, BAIK80, taken in 345 m water depth from a shoulder region in the North Basin of Lake Baikal, is free of disturbances. Our results confirm that the sediment record is consistent and continuous for the uppermost sediment. Consequently, the fossil diatom data can be used to establish a continuous record of past climate variability over approximately the past 1300 years. Distinct changes occur in downcore abundances of endemic taxa Aulacoseira baicalensis and Cyclotella minuta, and principal components analysis (PCA) indicates a gradual transformation of taxa over the past 1300 years. These changes are likely to be related to climate, although definite links still have to be established.
    Type of Medium: Electronic Resource
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