The fluvial Peruc Member (Middle to Upper Cenomanian) of the Bohemian Cretaceous Basin near the town of Benešov nad Ploučnicí (North Bohemia)

 

Jaroslav Valečka

Geoscience Research Reports 48, 2015 (GRR for 2014), pages 31–36
Map sheets: Děčín (02-23)

Full text (PDF, 1.6 MB)

Published online: 12 October 2015

Export to RIS

 

Abstract

The deep drilling SK-1t situated near the town of Benešov nad Ploučnicí (North Bohemia, see fig. 1) verified the sedimentary sequence of the Bohemian Cretaceous Basin, 870.15 m thick. Typical fluvial deposits of the Peruc Member defined by Čech et al. (1980) occur at the sequence base. The Peruc Member (Upper to Middle Cenomanian in age) is 22.95 m thick, overlies the Permo-Carboniferous sediments and volcanics, and is covered with marine sandstones of the Korycany Member (Fig. 2). The sedimentological analysis of the Peruc Member was based on the modified method of Miall (1985, 1996). Six facies were distinguished in the Peruc Member section (Fig. 2): 1) mud-supported conglomerates (the only layer on the section base), 2) clast-supported conglomerates, 3) coarse-grained sandstones, 4) silty-clayey, fine-grained sandstones, 5) dark mudstones with sandy laminae and lenses, and 6) dark homogeneous mudstones. In the facies designated as 4, 5 and 6, coalified plants, wood remains and roots are frequent as well as the fusite fragments which are present also in facies 3. Cross-bedded sets occur in facies 2 and 3. The facies are separated by sharp, often erosional surfaces or by gradual transitions. The facies are mostly arranged into upward-fining cyclothems (see Fig. 2). The interpretation of the facies is as follows: facies 1 – plastic debris-flow (avalanche deposit), facies 2 – channel-floor deposits (longitudinal or transverse bars), facies 3 – longitudinal or transverse bars far from the channel floor or point bar deposits, facies 4 – point bar, crevasse splay and flood-plain deposits, facies 5 and 6 – flood-plain deposits. Facies 6 represents also a sedimentation from suspension in the lakes, pools and former channels on the flood plain. One thin layer of facies 6 inserted into very coarse sediments in the lower part of the section was possibly deposited in an ephemeral pool between emerged bars. The wide difference between the lower and upper parts of the Peruc Member section is apparent (see Fig. 2 and Tab. 1). The lower part of the Peruc Member is interpreted to be deposited in a narrow, high-relief valley with a braided stream, the upper part is interpreted as sediments of a meandering river in a low-relief valley. The abrupt change of the braided river to a meandering one is explained in terms of a rapid base-level rise caused by some of the Cenomanian marine transgressions.
 

References

Bridge, J. S. (1985): Paleochannel patterns inferred from alluvial deposits. A critical evaluation - J. sed. Petrology 55, 4, 579-589.

Bridge, J. S. (1993): Description and interpretation of fluvial deposits: a critical perspective. - Sedimentology 40, 801-810.

Bridge, J. S. - Lunt, I. A. (2005): Depositional models of braided rivers. Dostupné na : www.geo.arizona.edu/geo5.

Čech, S. - Klein, V. - Kříž, J. - Valečka, J. (1980): Revision of the Upper Cretaceous stratigraphy of the Bohemian Cretaceous Basin. - Věst. Ústř. Úst. geol. 55, 5, 277-296.¬¬

Čech, S. - Valečka, J. (1991): Významné transgrese a regrese v české křídové pánvi. - MS Čes. geol. služba. Praha.

Duff, P. Mc. I. D. - Hallam, A. - Walton, E. K (1967): Cyclic sedimentation. Developments in Sedimentology 10. - Elsevier, Amsterdam, London, New York.

Miall, A. D. (1985): Architectural-Elements Analysis: A New Method of Facies Applied to Fluvial Deposits. - Earth Sci. Rev. 22, 261-308.

Miall, A. D. (1996): The Geology of Fluvial Deposits, Sedimentary facies, Basin Analysis, and Petroleum Geology. - Springer-Verlag.

Michael, D. B. - Torbjörn, E. T. (2000): Fluvial responses to climate and sea-level change: e review and look forward. - Sedimentology 47, 2-48.

Opluštil, S. - Martínek, K. - Tasáryová, Z. (2005): Facies and architectural analysis of fluvial deposits of the Nýřany Member and the Týnec Formation (Westphalian D - Barruelian) in the Kladno-Rakovník and Pilsen basins. - Bull. Geosci. 80, 46-56.

Plint, A. G. - Browne, G. H. (1994): Tectonic event stratigraphy in fluvial-lacustrine, strike-slip setting: the Boss Point Formation (Westphalian A), Cumberland Basin, Maritime Canada. - J. Sed. Res. 64, 341-364.

Schumm, S. A. (1993): River response to baselevel change: implications for sequence stratigraphy. - J. Geol. 101, 279-294.

Uličný, D. - Špičáková, L. - Grygar, R. - Svobodová, M. - Čech, S. - Laurin, J. (2009): Palaeodrainage systems at the basal unconformity of the Bohemian Cretaceous Basin: roles of inherited fault systems and basement lithology during the onset of basin filling.- Bull. Geosci. 84, 577-610.

Valečka, J. (1974): Litofaciální a paleogeografický vývoj svrchní křídy v severních Čechách. Kandidát. disert. práce. - MS Přírodověd. fak. Univ. Karl. v Praze. Praha.

Valečka, J. (1975): Litologie, cyklická stavba a geneze bazálních svrchnokřídových sedimentů západně od Děčína. - Čas. Mineral. Geol. 20, 409-416.

Voigt, T. (1998): Entwicklung und Architektur einer fluviatilen Talfüllung - die Niederschöna Formation im Sächsischen Kreidebecken. - Abh. Staatl. Mus. Mineral. Geol. Dresden 43/44, 121-139.

Waksmundzka, M. I. (2012): Braided-river and hyperconcentrated-flow deposits from the Carboniferous of the Lublin Basin (SE Poland) - a sedimentological study of core data. - Geologos 18, 3, 135-161.