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    Wyświetlanie 1-3 z 3
    Tytuł:
    Peculiar calcite speleothems filling fissures in calcareous sandstones and their palaeohydrological and palaeoclimatic significance: an example from the Polish Carpathians
    Autorzy:
    Gradziński, M.
    Duliński, M.
    Hercman, H.
    Górny, A.
    Przybyszowski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060492.pdf
    Data publikacji:
    2012
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    flysch Carpathians
    Pleistocene
    Holocene
    speleothems
    stable isotopes
    ascending water
    Opis:
    Peculiar calcite speleothems developed in fissures in the Cergowa Sandstones were found in the Klęczany Quarry (Polish Western Carpathians). They represent flowstone and stalactites, rafts and various sparry crusts. Such speleothems, especially phreatic ones, are uncommon in the Outer Carpathians that are composed mainly of siliciclastic rocks of flysch type, with only limited calcium carbonate content. The speleothems analysed grew in vadose and phreatic conditions as well as at the air-water interface. Phreatic speleothems and thin rafts comprise calcite crystals of eccentric morphology. Based on their stable isotope composition the majority of the speleothems form two clusters. The first is characterized by d18O values between –9.8 and –8.5‰ and of d13C values between –5.7 and –0.6‰ whereas the second cluster of samples yields d18O values between –9.4 and –7.3‰ and d13C values from –11.5 to –9.7‰. Speleothems grew between 230+14–13 ka and Holocene time. Phreatic speleothems, including massive rafts, precipitated from ascending water of deep circulation whereas vadose and water table speleothems crystallized from local infiltration water charged with soil CO2. Mixing of both waters in the shallow phreatic zone is plausible.
    Źródło:
    Geological Quarterly; 2012, 56, 4; 711--732
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Depth of the water column in relation to carbon isotope ratios in methane in fresh water sediments
    Autorzy:
    Jędrysek, M. O.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058951.pdf
    Data publikacji:
    2005
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    stable carbon isotopes
    methane
    fresh water sediments
    diagenesis
    environmental record
    Opis:
    Methane was collected from the surficial sedimentary layer (0 to about 20 cm) in 45 fresh water lakes in Poland. Sampling was also carried out at various depths of the over lying water column (0.15 to 12 m) between noon and early after noon, on a seasonal basis, between 1992 and 1996. A positive correlation between the depth of the lake water, the δ13 C (CH4) value (from ca. -l.4 to -2.3% per l m depth) and the wider δ13 C (CH4) variation over the thermocline are probably due to: the time of sinking of organic particles resulting in more in tense acetate fermentation in shallower portions of the lake; the temperature variation; differences in the precursors of methane, the diffusion effect, and an increase of bioavailable DIC (dissolved inorganic carbon) at greater depths. Non-seasonal variation of isotope ratios in methane and the depth-isotope ratio correlation show that the lake system is in dynamic equilibrium on a scale of hours and days. Therefore, earlier models of methanogenesis relating and the atmospheric methane isotopic budget, proposed by other authors and based on sampling of methane from sediments, need to be revised. More over, δ13 C (CH4) values higher during seasonal over turn (mixing of benthic and surface waters) than during stagnation, have been observed. This is probably due to the fact that during over turn periods some organic compounds (methane precursors) and methane in the surficial part of sediments, are oxidized with a resalting kinetic isotope effect. It is proposed that oxidation of methane and other organic compounds during seasonal over turn may be responsible for post-depositional lamination observed as pale (autumn over turn) and dark (summer organic-rich unoxic stagnation) millimetres-thick layers in fresh water lake sediments.
    Źródło:
    Geological Quarterly; 2005, 49, 2; 151-164
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparative oxygen and carbon isotopic records of Miocene and recent lacustrine unionid bivalves from Poland
    Autorzy:
    Błażejowski, B.
    Racki, G.
    Gieszcz, P.
    Małkowski, K.
    Kin, A.
    Krzywiecka, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060015.pdf
    Data publikacji:
    2013
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    sclerochronology
    stable isotopes
    fresh water
    Miocene and recent Unionidae
    Bełchatów
    Gil Wielki Lake.
    Opis:
    The δ13C and δ18O isotope data from both fossil (Miocene) and modern freshwater bivalve shells of family Unionidae from Poland (species Margaritifera flabellatiformis and Unio tumidus, respectively) show a similar, truncated sinusoidal pattern.. The isotopic profiles of the whole shell are visibly marked by three growth stages, linked with a progressive loss of environmental record because of declining intra-annual biocarbonate accretion rate. The juvenile and gerontic phases exhibit generally more positive and stable (plateau) isotopic pattern than the mid-age stage. An increasing δ13C trend is typical for the final life stage, likely influenced by nutrient overloading, reversing the tendency towards δ13C depletion throughout the individual’s life induced by metabolic processes. Due to the progressive loss of environmental signals through ontogeny, these initial and final isotopic profile segments probably correspond to, respectively, an instant signature of the first season growth, and a multiyear value set of summer maxima during geriatric stage. Vague seasonal cyclic record is the striking feature of the mid-age δ18O and δ13C profile slices. In case of low-amplitude δ18O curve, this is probably promoted by a sensitivity of the lake ecosystem to many dynamic intra-annual factors affecting water budget balance. This consistent signature mode seems to be typical for lake-dwelling unionid shells at least since Miocene from different climatic zones, as confirmed by coeval lacustrine low-latitude mussels from Amazonia. Thus, this isotope record is relevant to obtain information on the habitat and life cycle of the fossil freshwater bivalves, as well as could help understand modern environmental change.
    Źródło:
    Geological Quarterly; 2013, 57, 1; 113--122
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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