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  • Articles  (131)
  • paleolimnology  (131)
  • Geosciences  (131)
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Organic Geochemistry 20 (1993), S. 867-900 
    ISSN: 0146-6380
    Keywords: C/N ratios ; biomarkers ; carbon isotopes ; diagenesis ; humic substances ; lake sediments ; lignin ; paleolimnology ; pigments
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Geosciences
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 2 (1989), S. 263-283 
    ISSN: 1573-0417
    Keywords: paleolimnology ; lake ; lake sediment ; Quaternary ; limnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract I describe Quaternary paleolimnology on the basis of a review of abstracts published for meetings of: (1) American Society of Limnology and Oceanography (ASLO), 10 meetings since 1980; (2) International Association of Theoretical and Applied Limnology (SIL), 4 since 1977, (3) International Symposia on Paleolimnology (ISP), 4 since 1967, and (4) International Union for Quaternary Research (INQUA), 5 since 1969. A total of 9538 abstracts were scanned to find 678 with paleolimnological content. A data base constructed from the 678 contains frequencies of coverage of techniques, parameters, themes, interpretive aspects, and character and geography of study sites. These data indicate that Quaternary paleolimnology has been a diverse science dealing with many of the same aspects of lakes as neolimnology but with a longer time perspective. Most frequently studied paleolimnological characteristics were trophic state, water chemistry (particularly salinity, pH, alkalinity (ANC), micronutrients and oxygen), water levels, lake morphology, and mixis and other hydrology. Lake biological parameters that received greatest attention were diatoms, pigments, Cladocera, Mallomonadaceae, non-siliceous algae, Ostracoda, and Mollusca. Most often considered to influence these characteristics and parameters were climate; catchment vegetation, soil, geology, land use and erosion; water chemistry; aerial and non aerial pollutants; sedimentation; and tectonism. Most frequent chronologic sequences were (1) late-glacial to present, and (2) modern (ca. 0.3 ka to present). Lakes in moist temperate and boreal regions were most heavily studied. Of the four series, INQUA covered the longest time scales (to late Tertiary), but emphasized the last 100 ka. INQUA stressed outside-lake geomorphology (as it relates to lake) and lake morphology, physical forcing functions (e.g., climate and tectonism), hydrologic factors including water levels, paleosalinities, and reconstruction of paleoclimates. In contrast, SIL and ASLO rarely covered pre-15 ka. Most SIL and ASLO abstracts dealt with only the most recent ∼ 0.3 ka. Of strong interest to SIL and ASLO were the effects of catchment vegetation and soils, land uses, and pollutants (e.g., acid deposition) on past lake chemistry, biology, and trophic conditions. To infer these conditions from sediment contents, frequent use was made of modern analogues and, starting in the 1970's of microfossil (mostly diatoms) transfer functions based on calibration data sets. In several respects, ISP subject coverage and approaches were intermediate between those of INQUA and SIL/ASLO. Major improvements in paleolimnology have occurred since the 1960's, particularly in the areas of chronology and use of multivariate statistical techniques for paleoenvironmental inference based on microfossils. I conclude this paper with several suggestions for further advancement of the science.
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  • 3
    ISSN: 1573-0417
    Keywords: acid rain ; biostratigraphy ; diatoms ; paleolimnology ; lake acidification ; Sierra Nevada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We have completed a paleolimnological analysis of sediment cores from four lakes in the Sierra Nevada Range of California (USA). The diatom-inferred pH profile from Harriet Lake in Yosemite National Park (present pH=6.52) indicates no significant trends over the last 250 years. Inferred pH from Emerald Lake in Sequoia National Park (present pH=6.10) indicates a very small increase (〈0.1 pH unit) over the past 60 years and perhaps another small increase (ca. 0.15 pH unit) since 1976. Eastern Brook Lake in Inyo National Forest (present pH=7.06) shows evidence of both long-term alkalinification (ca. 0.3 pH unit over the last 200 years) and pH fluctuations since 1970. Lake 45 in King's Canyon National Park (present pH=5.16) appears to have acidified slightly (ca. 0.2 pH unit) over the last 60 years. Factors causing the observed trends are uncertain, but a role for acidic deposition cannot be ruled out.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 20 (1998), S. 353-368 
    ISSN: 1573-0417
    Keywords: Argentina ; Holocene ; paleolimnology ; diatom assemblages ; paleoclimatology ; paleoenvironments ; brackish water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We present a climatic reconstruction of Holocene lacustrine episodes in the Salinas del Bebedero basin (Argentina), based on geological and diatom information. Morphological, sedimentological and diatom evidence between 11600 ± 140 yr BP and 325 ± 95 yr BP, allowed us to interpret the paleoenvironments of the basin. Episodes of high energy (sandy levels) are linked to large inflow of meltwater through the Desaguadero River, related to development of glaciers on the Andes. This inflow is characterized by peaks of relative abundance of the brackish water diatom Cyclotella choctawatcheeana Prasad. The values of C. choctawatcheeana decrease in deposits of low energy (clay levels), where it co-dominates with oligohalobous Fragilaria and Epithemia spp. To the last two peaks of large inflow of meltwater, radiocarbon dates corrected to sidereal ages, are AD 1280/1420 and AD 1443/1656. These ages agree with two cold episodes clearly recorded in dendrological studies from the Patagonian Andes and were correlated to the Little Ice Age. Thus, older Holocene episodes of large inflow of water to the basin were correlated with the Neoglacial Advances defined by Mercer (1976) for the Andes.
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  • 5
    ISSN: 1573-0417
    Keywords: ostracodes ; environmental change ; Holocene ; northern Great Plains ; Saskatchewan ; paleolimnology ; Canada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Holocene paleoenvironments of Harris Lake, southwestern Saskatchewan, are reconstructed from the ostracode stratigraphy of a 10.4 m sediment core. Twenty three taxa, representing nine genera, were identified and counted from 113 samples. At each depth, a theoretical faunal assemblage was derived from the raw counts. The mean and variance of chemical, climatic and physical variables were inferred from modern analogues of the fossil assemblages, using existing autecological data from 6720 sites, mostly in western Canada. These data suggest four paleoenvironments: an early-Holocene (9240–6400 years BP) variable climate supporting aspen parkland vegetation; the warm dry hypsithermal (6400–4500 years BP); a short transitional period of ameliorating climate and expanding subboreal forest (4500–3600 years BP); and the present environment since 3600 years BP. A change in regional climate with the draining of Glacial Lake Agassiz (ca. 8500 years BP) and landsliding in the watershed (ca. 4000 years BP) caused relatively rapid environmental change. The ostracode record generally corroborates the interpretations of other proxy data previously published for Harris Lake. Most of the discrepancy involves the timing and severity of maximum Holocene warmth and aridity. Peak aridity interpreted from the pollen data is earlier than in the other proxy records. Both the diatoms and ostracodes indicate highest paleosalinity between ca. 6500 and 5000 years BP, but maximum salinity in the diatom record occurs between ca. 6000–5700 years BP, whereas the ostracode-inferred salinity is relatively low at this time and peaks later at ca. 5000 years. Neither of these reconstructions suggests the short episodes of hypersalinity interpreted from the mineralogy.
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  • 6
    ISSN: 1573-0417
    Keywords: lake sediments ; near infrared (NIR) spectroscopy ; sediment characteristics ; loss-on-ignition ; paleolimnology ; northern Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Near-infrared (NIR) spectral data were obtained from 165 surface sediment samples from a northern Swedish humic, mesotrophic lake (0.5 km2). The NIR spectra, together with data on water depth and loss-on-ignition (LOI), allow an evaluation of the source of spatial variance in sediment characteristics. The results show that water depth and organic matter (LOI) account for 20 and 16%, respectively, of the variance in the NIR-absorbance data. More importantly, the spatial variance in the spectral data suggest that NIR analysis of lake sediments mainly reflect sediment properties that cannot simply be explained by depth or amount of organic matter. The influence of inlets and land-use (e.g. clear-cutting) on sediment characteristics was more pronounced in the spectral data than would be expected from the LOI data. This is explained by differences in the chemical composition of the organic matter, as revealed by NIR spectroscopy, rather than in the amount of organic matter or depth-related sedimentation properties (e.g. particle size or density). This initial attempt to characterise sediment properties using NIR suggests that NIR analysis might become a valuable complementary tool to traditional sediment characterisation.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 21 (1999), S. 235-255 
    ISSN: 1573-0417
    Keywords: saline lake ; groundwater inputs ; geochemical modelling ; closed-basin lake ; paleolimnology ; Great Plains ; paleohydrology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediment cores from Chappice Lake, a hypersaline, groundwater-fed lake in southeastern Alberta, have been used in previous studies to reconstruct Holocene climate using lake levels as a source for proxy climate data. This assumes that the lake is fed by a shallow groundwater system sensitive to changes in climate. In this study we use the dynamics and chemistry of groundwater entering the lake to test this hypothesis. Groundwater inputs calculated from historical records using a simple water budget were highest during periods when the precipitation deficit was high. Over specific time intervals, the expected relationship between lake volumes and climate were not always found. Feedback loops between lake levels and groundwater input, and time lags within the system are the mechanisms proposed to explain these discrepancies. Field measurements suggest discharge of a local surficial groundwater system. Slug tests reveal a high conductivity system (K = 10-5 m/s) surrounding the lake. Hydraulic heads measured in standpipe, multilevel and minipiezometers installed around Chappice Lake show that the lake is situated in a closed hydraulic head contour. Hydraulic heads and water table elevations show strong annual fluctuations corresponding to seasonal changes in recharge. Horizontal hydraulic gradients measured in areas of groundwater springs indicate a strong horizontal component of flow towards the lake. Vertical hydraulic gradients are low and indicate the upward flow of water consistent with the discharge of a shallow, surfical groundwater system. Groundwater sampled from deposits surrounding Chappice Lake and springs feeding the lake have compositions similar to both shallow surficial aquifers and bedrock aquifers suggesting that the lake may be receiving inputs from both sources. However, evaporation simulations using PHRQPITZ, show that the evaporation of water typical of bedrock aquifers result in a mineral assemblage and brine composition different from that found at Chappice Lake. This suggests that discharge of a regional groundwater system can be eliminated as a dominant source over the lake's history. Evaporation simulations suggest that evaporation of groundwater from shallow surficial deposits can best explain the present mineral assemblage and brine chemistry and were likely the dominant source of water to the lake. Bedrock and shallow surficial groundwater sources have different chemistries and isotopic compositions. In hydrogeological settings such as Chappice Lake where more than one source may contribute to the lake, the relative importance of the different sources may change with changes in climate. If the source water composition to the lake changes, identifying changes in climate or hydrology based on changes in the composition of the lake preserved in sediment core will be made more difficult. This may complicate paleoclimate and paleohydrological reconstructions that rely on mineralogical and isotopic data.
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  • 8
    ISSN: 1573-0417
    Keywords: diatoms ; paleolimnology ; palynology ; Holocene ; climate change ; Lake Baikal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 10 (1994), S. 265-273 
    ISSN: 1573-0417
    Keywords: climate ; paleolimnology ; diatom ; data cooperative ; paleoclimatology ; ostracode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
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  • 10
    ISSN: 1573-0417
    Keywords: paleolimnology ; Great Basin ; carbonate minerals ; isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Lake Bonneville marl provides a stratigraphic record of lake history preserved in its carbonate minerals and stable isotopes. We have analyzed the marl in shallow cores taken at three localities in the Bonneville basin. Chronology for the cores is provided by dated volcanic ashes, ostracode biostratigraphy, and a distinctive lithologic unit believed to have been deposited during and immediately after the Bonneville Flood. A core taken at Monument Point at the north shore of Great Salt Lake encompasses virtually the entire Bonneville lake cycle, including the 26.5 ka ‘Thiokol’ basaltic ash at the base and deposits representing the overflowing stage at the Provo shoreline at the top of the core. Two cores from the Old River Bed area near the threshold between the Sevier basin and the Great Salt Lake basin (the main body of Lake Bonneville) represent deposition from the end of the Stansbury oscillation (≈ 20 ka) to post-Provo time (≈ 13 ka), and one core from near Sunstone Knoll in the Sevier basin provides a nearly complete record of the period when Lake Bonneville flooded the Sevier basin (≈20–13 ka). In all cores, percent calcium carbonate, the aragonite to calcite ratio, and percent sand were measured at approximately 2-cm intervals, and δ18O and δ13C were determined in one core from the Old River Bed area. The transgressive period from about 20 ka to 15 ka is represented in all cores, but the general trends and the details of the records are different, probably as a result of water chemistry and water balance differences between the main body and the Sevier basin because they were fed by different rivers and had different hypsometries. The Old River Bed marl sections are intermediate in position and composition between the Monument Point and Sunstone Knoll sections. Variations in marl composition at the Old River Bed, which are correlated with lake-level changes, were probably caused by changes in the relative proportions of water from the two basins, which were caused by shifts in water balance in the lake.
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