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Wyszukujesz frazę "ore-bearing clay" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
The significance of mudstone fabric combined with palaeoecological evidence in determining sedimentary processes - an example from Middle Jurassic of southern Poland
Autorzy:
Leonowicz, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/2059717.pdf
Data publikacji:
2013
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
black mudstones
parallel lamination
storm deposits
ichnofabric
bottom oxygenation
Ore-Bearing Częstochowa Clay Formation
Opis:
Analysis of the fabric of laminated black mudstones of the Ore-Bearing Częstochowa Clay Formation (Bathonian, southern Poland) is used for reconstruction of sedimentary processes and conditions. Small-scale sedimentary features indicate that ore-bearing clays were deposited below storm-wave base in a shallow epicontinental sea, but structures reflecting quiet settling from suspension are not common. Most of recognized lamina types record the activity of bottom currents generated by storms. The benthic faunal association indicates that suboxic conditions prevailed on the seafloor, restricting infaunal activity to cryptobioturbation. Recurrent short-lived reoxygenetion events, linked probably to storms, resulted in the development of dysoxic conditions, recorded by a more diverse trace fossil association (consisting of Chondrites, Trichichnus, pyritized burrows, Palaeophycus and Protovirgularia) and colonization of the seafloor by epifaunal bivalves (Bositra). Truly anoxic conditions might have been briefly established, leading to mass mortality of Bositra.
Źródło:
Geological Quarterly; 2013, 57, 2; 243--260
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Storm-influenced deposition and cyclicity in a shallow-marine mudstone succession - example from the Middle Jurassic ore-bearing clays of the Polish Jura (southern Poland)
Autorzy:
Leonowicz, P. M.
Powiązania:
https://bibliotekanauki.pl/articles/2060303.pdf
Data publikacji:
2015
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
bioturbated mudstones
storm deposits
transgressive-regressive cycles
Ore-Bearing Częstochowa Clay Formation
Silesian-Cracow region
Opis:
Sedimentological analysis of bioturbated mudstones from the Middle Jurassic ore-bearing Częstochowa Clay Formation has revealed common relics of sedimentary structures, such as thin silt/sand laminae, bedding-plane accumulations of shell debris, small and medium silt-sand lenses, as well as silt-, sand- and shell-debris-rich levels, accompanied by erosion surfaces and minor scours. These features document periodical high-energy conditions of mud deposition, including storm stirring, event sedimentation and the activity of storm-generated bottom currents, which were responsible for seafloor erosion and sediment supply from shallower parts of the basin. The sea bottom was prevalently below the storm wave base, but it rose above it during exceptionally strong storms and in the Early Bathonian zigzag chron when the basin experienced considerable shallowing. The shallowest and highest energy conditions occurred in the late macrescens subchron, when the bottom was close to, or above the fair-weather wave base. The estimated depth of the sea did not exceed several tens of metres, but in some periods it could be even less than 20 m. Based on the vertical variation of the sand, silt and clay contents, seven transgressive-regressive cycles have been distinguished in the approximately 75-m thick succession spanning the Upper Bajocian - Upper Bathonian. Cycles TR1, TR2+3, TR5 and TR6+7 correlate with those distinguished in the coeval succession from central Poland, although the stratigraphic position of cycle boundaries is slightly shifted. These cycles record relative sea-level changes that affected the entire Polish Basin. Regressions R2 and R6 were smaller-scale-events, generated in response to a local tectonic activity and autocyclic shoreline progradation.
Źródło:
Geological Quarterly; 2015, 59, 2; 325--344
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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