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Wyświetlanie 1-2 z 2
Tytuł:
Framboidy pirytowe jako wskaźniki paleośrodowiska
Pyrite framboids as paleoenvironmental indicators
Autorzy:
Zatoń, M.
Rakociński, M.
Marynowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/2074589.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
framboidy pirytowe
redoks
warunki środowiskowe oksyczne
warunki środowiskowe dysoksyczne
warunki środowiskowe euksyniczne
jura
dewon
Polska
pyrite framboids
redox
euxinia
anoxia
dysoxia
Jurassic
Devonian
Polska
Opis:
The problemof application of pyrite framboids in reconstructions of the redox conditions is presented. The characteristics of pyrite framboids, their origin and principles of application in paleoenvironmental interpretations are given. The pyrite framboid diameter distribution as indicators of redox conditions was presented on the examples of the Middle Jurassic (Upper Bajocian-Lower Bathonian) ore-bearing clays of the Polish Jura, and Upper Devonian (Middle and Upper Famennian) dark grey and black shales from Kowala (Holy Cross Mountains). It has been shown, that during the sedimentation of the ore-bearing clays, the pyrite framboids formed in the sediment, below the oxic water column; however, some episodic oscillation around the dysoxic conditions cannot be entirely excluded. During the sedimentation of the Middle Famennian dark grey shales, the redox conditions at the sea-floor oscillated around dysoxia. In both examples, the framboids are characterized by wide range of their diameters and the presence of large, >10 "my"m, framboids. On the contrary, the Upper Famennian black shales, representing the Hangenberg event, were deposited below the euxinic conditions in the water column. It is indicated by a high frequency of small-size framboids, far below 6 "my"m in diameter, and the lack of the large ones. The overlying shales, on the other hand, show the transition to more oxic conditions. The redox conditions interpreted above are in agreement with the independent biomarker analyses and paleontological observations.
Źródło:
Przegląd Geologiczny; 2008, 56, 2; 158-164
0033-2151
Pojawia się w:
Przegląd Geologiczny
Dostawca treści:
Biblioteka Nauki
Artykuł
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
    Wyświetlanie 1-2 z 2

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