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1
Content available Regressive-transgressive cyclothem with facies record of the re-flooding window in the Late Silurian carbonate succession (Podolia, Ukraine)
Łuczyński P., Kozłowski W., Skompski S.
Acta Geologica Polonica
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2015
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Vol. 65, no. 3
297--318
EN
The term “re-flooding window” was recently proposed as a time-interval connected with the transgressive stage of present day peri-reefal development. In the analysis presented here, a fossil record of a re-flooding window has been recognized. Nine Late Silurian carbonate sections exposed on the banks of the Dnister River in Podolia (Ukraine) have been correlated base on bed-by-bed microfacies analysis and spectral gamma ray (SGR) measurements. Correlated were sections representing settings ranging from the inner part of a shallow-water carbonate platform to its slope, through an organic buildup. The reconstructed depositional scenario has been divided into six development stages, with the first three representing a regressive interval and the latter three a transgressive interval of the basin’s history. The re-flooding window has been identified at the beginning of a transgressive part of the succession. Surprisingly, it is characterized by an extremely fast growth of a shallow, tide-dominated platform and by deposition of calciturbiditic layers in a more basinal area. The interpreted succession is a small-scale model illustrating the reaction of carbonate depositional sub-environments to sea level changes and determining the facies position of the stromatoporoid buildups within the facies pattern on a Silurian shelf. The use of SGR analyses in shallow water, partly high-energy, carbonate facies, both for correlation purposes and for identifying depositional systems, is a relatively new method, and thus can serve as a reference for other studies of similar facies assortment.
2
Content available remote New Late Silurian to Middle Devonian acanthodians of the Timan-Pechora region
Valiukevicius J.
Acta Geologica Polonica
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2003
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Vol. 53, nr 3
209-245
EN
New Pridoli to Eifelian acanthodian scales from various structural units of the Timan-Pechora region are described. Among 15 new species and 1 new genus, there are: 10 new species of nostolepids, common members of most of the biostratigraphic associations, the monospecific genus Monospina gen. nov., a single new species of Cheiracanthoides (all Climatiida), Diplacanthus pechorensis sp. nov. (Diplacanthida), and two new species of Gomphonchus (Ischnacanthida). Besides morphologic descriptions the taxa are also characterised histologically. Acanthodian taxa with scale crowns and bases composed of cellular bone, or very similar tissue, proposed as a primitive feature in their evolution, are reported for the first time.
3
Content available remote Integrated correlation of Late Silurian (Pridoli s.l.) - Devonian chitinozoans and miospores in the Solimoes Basin, northern Brazil
Grahn Y., Łoboziak S., Melo J.
Acta Geologica Polonica
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2003
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Vol. 53, nr 4
283-300
EN
Chitinozoans from the Late Silurian (Pridoli s.l.) and Devonian, and miospores from the Middle and Late Devonian, have been investigated from the Solimoes Basin in northern Brazil. Of the 37 chitinozoan species encountered, 16 are retained in open nomenclature, because of an insufficient number of well-preserved specomens, and Ramochitina jutaiense is newly described. Three or four miospore zones have been recognized: the LE - LN and VH zones of late to latest Famennian age, and a poorly characterized interval not older than the AP zone of latest Emsian - early Eifelian age. A regional chitinozoan biozonation, consisting of six zones, is proposed for the investigated interval. These zones are, from the oldest to the youngest: concurrent range zone of Ancyrochitina ancyrea and Ancyrochitina aff. A libyensis (Pridoli s.l.); interval range zone of Angochitina filosa (early Lochkovian); concurrent range zone of Urochitina loboi and Ramochitina jutaiense sp.nov. (late Lochkovian); concurrent range zone of Ancyrochitina arirambaense and Alpenachitina eisenacki (Eifelian s.l. - early Givetian); interval range zone of Angochitina mourai (Frasnian - middle Famennian); and total range zone of Fungochitina ultima (late Famennian).
4
Content available remote Lagoonal to normal marine Late Silurian - Early Devonian ostracode assemblages of the Eurasian Arctic
Abusik A., Evdokimova I.
Acta Geologica Polonica
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1999
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Vol. 49, no. 2
133-143
EN
In the Eurasian Arctic the ostracode faunas indicate mostly normal marine environments during the Late Silurian. The Lower Devonian deposits are characterized by ostracode assemblages, which indicate the presence of marine outer shelf to lagoonal environments during the Early Devonian. The dynamics of their taxonomic diversity and some examples of the marine and lagoonal assemblages are shown. Correlation of facially mono- and heterogenous deposits is based on ostracode data
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