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Middle ro early late Viséan onset of late orogenic sedimentation in the Intra-Sudetic Basin, West Sudetes: miospore evidence and tectonic

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Turnau E. , Żelaźniewicz A. , Franke W.

Geologia Sudetica

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2002

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tom Vol. 34

9-16

EN

The Early Carboniferous fluvial and deltaic sequence of the Intra-Sudetic Basin remained undated until recently, except for a Late Viséan ammonoid fauna in its upper part. Current miospore data indicate that the oldest part of the sequence is not older than the mid Viséan Knoxisporites triradiatus-Knoxisporites stephanephorus biozone of the west European miospore division. This palynological age determination is consistent with the recently obtained Ar-Ar cooling ages of white micas from sheared metamorphic rocks at the NW margin of the basin. This suggests that the rapid late orogenic denudation of the northern and western flanks of the Intra-Sudetic Basin must have started at or shortly after c. 335 Ma.

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U-Pb zircon age of the Krásné Loučky tuffite : the dating of Visean flysch in the Moravo-Silesian Paleozoic Basin (Rhenohercynian Zone, Czech Republic)

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Jirásek J. , Wlosok J. , Sivek M. , Matýsek D. , Schmitz M. , Sýkorová I. , Vašíèek Z.

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tom Vol. 58, No. 4

659–-672

EN

The only previous U-Pb zircon date for the the Early Carboniferous flysch sequence of the Moravo-Silesian Paleozoic Basin was published in 1987 from tuffogenic material from Kobylí Quarry at Krásné Loučky near the town of Krnov (Silesia, Czech Republic). The measured age of 319 Ma did not agree with its stratigraphic position, and was used as the basis for a hypothesized block of Late Carboniferous paralic molasse incorporated during a later tectonic event. During a survey of the still active quarry in 2010, volcaniclastic horizons were identified and sampled. Direct correspondence of the tuff units to those sampled in 1987 cannot be proved but is likely. High precision chemical abrasion - thermal ionization mass spectrometry (CA-TIMS) U-Pb dating of zircon from this new material has yielded an age of 340.05 ± 0.22 Ma, which correlates to the previously inferred stratigraphic age of the locality and the current calibration of the Early Carboniferous geologic time scale. The newly established age corresponds to the Visean stage and dates the boundary between the Horní Benešov and Moravice formations that can be correlated with other foredeep basins of the Culm in the European Variscides. A population of detrital Cambro-Ordovician zircons and a single 2.0 Ga old zircon crystal from the same volcaniclastic layer dated by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) are consistent with the known age of source material in the Variscan orogenic front.

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Lower Carboniferous bentonites in the Bardo Structural Unit (central Sudetes): geological context, petrology and palaeotectonic setting

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Kryza R. , Muszer J. , August C. , Haydukiewicz J. , Jurasie M.

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tom Vol. 40

19-31

EN

The Lower Carboniferous Paprotnia beds of the Bardo Structural Unit in the central Sudetes, composed predominantly of mudstones with Upper Viséan fossils, include several bentonite layers. The bentonites, composed mainly of kaolinite, illite/smectite and smectite, with minor amounts of quartz, calcite and iron hydroxides, also contain abundant zircons, the features of which indicate their volcanic derivation. The main population of the zircons yielded a SHRIMP U-Pb age of ~ 334 Ma corresponding with, and numerically constraining, the biostratigraphic data. The field evidence, biostrati- graphic and geochronological results, together with mineralogical data from the bentonites, indicate continental margin-type sedimentation and contemporaneous volcanic (andesitic-rhyolitic) activity in the neighbouring region during the ongoing Variscan orogeny in central Europe in Late Viséan times.

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Lower Carboniferous (Mississippian) stratigraphy of northwestern Poland : conodont, miospore and ostracod zones compared

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Matyja H. , Turnau E. , Żbikowska B.

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tom Vol. 70, No. 3-4

193-217

EN

Detailed stratigraphy of the Tournaisian and Viséan in western Pomerania has been established on conodonts, miospores and ostracods recovered from 25 boreholes. Miospore associations from the Tournaisian and Viséan are assigned to nine biostratigraphic units (zones and subzones) erected earlier. Three successive benthic ostracod assemblages and two sub-assemblages are distinguished for the Tournaisian. The miospore zones/subzones and the ostracod assemblages/subassemblages are correlated with the Tournaisian sandbergi, Lower crenulata, isosticha-Upper crenulata, and typicus conodont zones. Stratigraphic gap has been demonstrated at the Devonian/Carboniferous boundary, using the results of both conodont and miospore studies. The Tournaisian/ Viséan boundary has been established approximately on the first appearance of the miospore species Lycospora pusilla Somers.

PL

Przedstawiono szczegółową stratygrafię turneju i wizenu Pomorza Zachodniego w oparciu o konodonty, miospory i małżoraczki. Materiał do badań biostratygraficznych pochodził z 25 otworów wiertniczych. Zespoły miospor z badanych utworów zaliczono do dziewięciu wcześniej wyróżnionych jednostek biostratygraficznych (zon i podzon). Dla turneju wyróżniono trzy kolejne zespoły i dwa podzespoły małżoraczków bentonicznych. Zony/podzony miosporowe i zespoły/podzespoły małżoraczkowe skorelowano z turnejskimi zonami konodontowymi sandbergi, dolna crenulata, isosticha-górna crenulata i typicus. Obecność luki stratygraficznej na granicy dewon/karbon udokumentowano na podstawie konodontów i miospor. Granica turnej/wizen została ustalona jedynie w przybliżeniu, na podstawie pierwszego pojawienia się gatunku miosporowego Lycospora pusilla Somers.