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    Wyświetlanie 1-3 z 3
    Tytuł:
    Ordovician–Silurian boundary in the Bardo Syncline, Holy Cross Mountains, Poland—new data on fossil assemblages and sedimentary succession
    Autorzy:
    Masiak, M.
    Podhalańska, T.
    Stempień-Sałek, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058822.pdf
    Data publikacji:
    2003
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Holy Cross Mountains
    Bardo Syncline
    Ordovician-Silurian boundary
    lithology
    graptolites
    acritarchs
    Opis:
    A gradual transition from sandy through silty to clayey strata occurs near the Ordovician–Silurian (O/S) boundary in the southern part of Holy Cross Mountains, in the Bardo Syncline. Three graptolite biozones are distinguished for the O/S boundary interval deposits: ?persculptus, ascensus-acuminatus and vesiculosus. The first, rare graptolites appear below “graptolitic shales” in the ?persculptus Biozone. The diversity of the assemblage increases in the next two biozones. An analysis of acritarch frequency shows a decrease of acritarch frequency at the O/S boundary and then a gradual increase in the lower part of the ascensus-acuminatus biozone with a maximum in the vesiculosus Biozone. The taxonomic diversity of the acritarch assemblage shows a similar trend although the maximum of acritarch frequency observed in the vesiculosus Biozone do not coincide the maximum of acritarch taxonomic diversity.
    Źródło:
    Geological Quarterly; 2003, 47, 4; 311--330
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Ordovician-Silurian boundary beds between Saaremaa and Gotland, Baltic Sea, based on high resolution seismic data
    Autorzy:
    Tuuling, I.
    Flodén, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059526.pdf
    Data publikacji:
    2007
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Baltic Bas
    Ordovician-Silurian boundary
    seismostratigraphy
    carbonate buildups
    erosional features
    stratigraphic gaps
    Opis:
    New seismic profiles have been used to revise earlier interpretations of the Ordovician-Silurian bound ary beds be tween Saaremaa and Gotland. Atrans-Baltic reflector with erosional fea ures (S2) above the erosional Ordo vician-Silurian boundary reflector (S1) correlates with the bound ary between the Raikküla and Adavere stages. The sporadic reflector or2 below the S1 reflector off shore from Gotland represents the erosional boundary between the Pirgu and Porkuni stages. Three stratigraphic gaps occur in the Ordovician-Silurian boundary beds off shore from Gotland. The amount of eroded rocks between the Pirgu and Porkuni stages, the Ordovician and Silurian systems and the Raikküla and Adavere stages can change rapidly. Consequently, the thick ness and stratigraphy of the Ordovician-Silurian boundary beds around Gotland can change considerably across short distances. The O4-5-S1 unit off shore from Gotland, including carbonate build ups and erosional incisions infilled with Porkuni strata, belongs facially to the transi ional belt between the Estonian Shelf and the Livonian Tongue. The thick ness changes in the S1-S2 unit (Juuru and Raikküla stages) indicate an extensive subma rine erosional channel, streching from north of Estonia across the Baltic Sea and central Gotland, which developed in the Baltic Basin along a shelf to deep-basin transect dur ng Llandovery time.
    Źródło:
    Geological Quarterly; 2007, 51, 3; 217-229
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microphytoplankton from middle palaeolatitudes of the Southern Hemisphere : a record from climate change strata of Baltica’s O/S boundary
    Autorzy:
    Masiak, Monika
    Stempień-Sałek, Marzenna
    Podhalańska, Teresa
    Powiązania:
    https://bibliotekanauki.pl/articles/2058561.pdf
    Data publikacji:
    2020
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Polska
    Ordovician boundary
    Silurian boundary
    palynology
    acritarch frequency
    bathymetry
    climate
    Opis:
    In the present study, data on the diversity of acritarch and prasinophyte microphytoplankton were collected from Ordovician-Silurian transitional strata at three different geological localities in Poland: southern part of the Holy Cross Mountains (Małopolska Block, southern Poland), East European Platform (Baltica), and Koszalin-Chojnice Zone (NW Poland). The material represents the mucronata (trilobite) to vesiculosus (graptolite) biozones. The Ordovician microphytoplankton assemblages are characterized by low frequency and low diversity: up to 110 specimens and 12 genera per slide, in contrast to Silurian ones that are more frequent and more diverse - >3000 specimens and 16 genera per slide (diversity at the species level is also higher). Throughout the Ordovician part of the succession, typical Ordovician genera occur, such as Acanthodiacrodium, Ordovicidium, Orthosphaeridium and large Baltisphaeridium, together with isolated occurrences of typical Silurian genera, especially in the upper part of the Hirnantian (e.g., Diexallophasis). The Silurian assemblages are typified by high frequency of prasinophytes followed by typical Siluran acritarchs: Tylotopalla, Ammonidium, Domasia and Oppilatala. The palynological material from Poland is compared with material known from other localities: the Rapla and Valga boreholes (Estonia) and Anticosti Island (Canada), as well as others placed in different palaeocontinents and different bathymetric zones. Palynological assemblages obtained from Polish material confirm that bathymetry played the key role in taxonomic diversification of the microphytoplankton assemblage. This supports the existing models of distribution: dominance of prasinophytes (leiospheres) and cryptospores is characteristic for shallow-water environments. In deeper water, dominance of acanthomorphs is observed. In the deepest-water zones - mixed assemblages occur. For the Holy Cross Mountains, microphytoplankton frequency is compared with a TOC curve in the same interval.
    Źródło:
    Geological Quarterly; 2020, 64, 1; 86--103
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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