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Origin of red pelagic carbonates as an interplay of global climate and local basin factors: Insight from the Lower Devonian of the Prague Basin, Czech Republic
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SYSNO ASEP 0483848 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Origin of red pelagic carbonates as an interplay of global climate and local basin factors: Insight from the Lower Devonian of the Prague Basin, Czech Republic Author(s) Bábek, O. (CZ)
Faměra, Martin (UACH-T) SAI, ORCID, RID
Hladil, Jindřich (GLU-S) RID, SAI
Kapusta, J. (CZ)
Weinerová, Hedvika (GLU-S) SAI, ORCID
Šimíček, D. (CZ)
Slavík, Ladislav (GLU-S) RID, SAI, ORCID
Ďurišová, Jana (GLU-S) RID, SAISource Title Sedimentary geology. - : Elsevier - ISSN 0037-0738
Roč. 364, FEB (2018), s. 71-88Number of pages 18 s. Language eng - English Country NL - Netherlands Keywords Bottom redox conditions ; Geochemistry ; Palaeoceanography ; Spectral reflectance ; Pragian stage ; Red pelagic carbonates ; Trophic levels Subject RIV DD - Geochemistry OECD category Geology Subject RIV - cooperation Institute of Geology - Geology ; Mineralogy R&D Projects GA14-18183S GA ČR - Czech Science Foundation (CSF) Institutional support UACH-T - RVO:61388980 ; GLU-S - RVO:67985831 UT WOS 000425205700006 EID SCOPUS 85038441136 DOI 10.1016/j.sedgeo.2017.12.007 Annotation Red pelagic sediments are relatively common in the Phanerozoic. They are often interpreted as products of sea-bottom oxidation during greenhouse climate showing a conspicuous alternation with black shales and thus carrying important palaeoceanographic information. The Lower Devonian (Pragian) carbonate strata of the Prague Basin, Czech Republic (Praha Formation) contain a marked band of red pelagic carbonate, up to ~ 15 m thick, which can be correlated for several tens of km. We investigated seven sections (17 to 255 m thick) of the Prague Basin using the methods of facies analysis, outcrop gamma-ray logging, diffuse reflectance spectroscopy, optical microscopy, element geochemistry, magneto-mineralogy and electron microprobe analysis. The aim was to find the mineral carriers of the red colour, investigate the stratigraphic context of the red carbonates and evaluate the local and global prerequisites for their formation. The red pigmentation represents enrichment by hematite with respect to goethite. Approximately 31% of the total reflectance falling in the red colour band represents a threshold for red coloration. The red pigmentation is carried by submicronic hematite dispersed in argillaceous pelagic calcilutite and/or inside skeletal allochems. Gamma-ray log correlation indicates that the red carbonate band developed in stratigraphic levels with low sedimentation rates, typically from 1 to 7.1 mm/kyr, which are comparable to the Mesozoic Rosso Ammonitico facies. The red beds and the whole Praha Formation (Pragian to early Emsian) are characterized by low TOC values (< 0.05%) and low U/Th, Mo/Al, V/Al, Zn/Al, Cu/Al and P/Al ratios indicating oligotrophic, highly oxic sea-bottom conditions. This period was characterized by global cooling, a drop in silicate weathering rates and in atmospheric pCO2 levels. The lower Devonian successions of the Prague Basin indicate that switching between two greenhouse climatic modes, colder oligotropic and warmer mesotrophic, may have been responsible for the alternation of red and grey carbonate strata, respectively. Workplace Institute of Inorganic Chemistry Contact Jana Kroneislová, krone@iic.cas.cz, Tel.: 311 236 931 Year of Publishing 2019
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