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Wyszukujesz frazę "carbonate concretions" wg kryterium: Wszystkie pola

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    Wyświetlanie 1-2 z 2
    Tytuł:
    Palaeoenvironmental significance of iron carbonate concretions from the Bathonian (Middle Jurassic) ore-bearing clays at Gnaszyn, Kraków-Silesia Homocline, Poland
    Autorzy:
    Witkowska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/138739.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    baton
    bioturbacja
    jura
    konkrecja syderytu
    monoklina śląsko-krakowska
    paleośrodowisko
    Polska
    redoks
    wczesna diageneza
    Bathonian
    bioturbation
    Cracow-Silesia Homocline
    early diagenesis
    Jurassic
    palaeoenvironment
    Phosphate-siderite concretions
    Polska
    Redox boundary
    Siderite concretions
    Opis:
    Iron carbonate concretion horizons are characteristic features of the Bathonian (Middle Jurassic) claystone-mudstone succession at Gnaszyn. They occur in single horizons, which generally represent the same genetic type. The siderite concretions are the main type of iron carbonate concretions at Gnaszyn; a second type is represented by phosphate-siderite concretions. On the basis of the fieldwork, and their petrographical and mineralogical characteristics, the genesis of the concretions and their palaeoenvironmental significance is discussed. The results of this study (based on the localization, mode of occurrence, mineralogy of iron carbonate concretions and also the textural relationship between the concretions and host sediment layers) suggest an early diagenetic origin of the concretions. The preferential occurrence of the concretion horizons in single layers in the ambient sediments was associated with particular conditions of their deposition and early diagenesis, favored by a slower sedimentation rate and more intense bioturbation, and related primarily to the greater availability of reactive iron ions. From the viewpoint of physicochemical conditions the horizons with iron carbonate concretions in the study area reflect the redox boundary between oxic/bioturbated and anoxic/non-bioturbated zones. The conditions favoring the formation of such horizons was possibly due to longer periods of diminished sedimentation rate when the redox boundary remained in the same position within the sediment.
    Źródło:
    Acta Geologica Polonica; 2012, 62, 3; 307-324
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Origin and significance of early-diagenetic calcite concretions and barite from Silurian black shales in the East European Craton, Poland
    Autorzy:
    Bojanowski, Maciej J.
    Kędzior, Artur
    Porębski, Szczepan J.
    Radzikowska, Magdalena
    Powiązania:
    https://bibliotekanauki.pl/articles/138638.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    carbonate concretions
    stable isotopes
    cathodoluminoscopy
    sedimentation rate
    marine productivity
    biogenic gas production
    bacterial sulfate reduction
    shale gas
    konkrecje węglanowe
    izotopy stabilne
    katodoluminoskopia
    szybkość sedymentacji
    produktywność morska
    gaz biogenny
    redukcja bakteryjna siarczanu
    gaz łupkowy
    Opis:
    The Silurian Pelplin Formation is a part of a thick, mud-prone distal fill of the Caledonian foredeep, which stretches along the western margin of the East European Craton. The Pelplin Formation consists of organic carbon-rich mudstones that have recently been the target of intensive investigations, as they represent a potential source of shale gas. The Pelplin mudstones host numerous calcite concretions containing authigenic pyrite and barite. Mineralogical and petrographic examination (XRD, optical microscopy, cathodoluminoscopy, SEM-EDS) and stable isotope analyses (δ13Corg, δ13C and δ18O of carbonates, δ34S and δ18O of barite) were carried out in order to understand the diagenetic conditions that led to precipitation of this carbonate-sulfide-sulfate paragenesis and to see if the concretions can enhance the understanding of sedimentary settings in the Baltic and Lublin basins during the Silurian. Barite formed during early diagenesis before and during the concretionary growth due to a deceleration of sedimentation during increased primary productivity. The main stages of concretionary growth took place in yet uncompacted sediments shortly after their deposition in the sulfate reduction zone. This precompactional cementation led to preferential preservation of original sedimentary structures, faunal assemblages and earlydiagenetic barite, which have been mostly lost in the surrounding mudstones during burial. These components allowed for the reconstruction of important paleoenvironmental conditions in the Baltic and Lublin basins, such as depth, proximity to the detrital orogenic source and marine primary productivity. Investigation of the concretions also enabled estimation of the magnitude of mechanical compaction of the mudstones and calculation of original sedimentation rates. Moreover, it showed that biogenic methane was produced at an earlydiagenetic stage, whereas thermogenic hydrocarbons migrated through the Pelplin Formation during deep burial.
    Źródło:
    Acta Geologica Polonica; 2019, 69, 3; 403-430
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-2 z 2

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