Science and earth science

Acta Geologica Polonica


Acta Geologica Polonica | 2017 | vol. 67 | No 2 |

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This paper presents for the first time X-ray computed microtomography (μCT) analysis as a technique for Silurian graptolite detection in rocks. The samples come from the Jantar Bituminous Claystones Member of the Opalino core, Baltic Basin, northern Poland. Images were obtained with spatial resolution of 25 μm, which enabled the authors to create a 3-D visualization and to calculate the ratio of fissure and graptolite volume to the total sample volume. A set of μCT slices was used to create a 3-D reconstruction of graptolite geometry. These μCT slices were processed to obtain a clearly visible image and the volume ratio. A copper X-ray source filter was used during exposure to reduce radiograph artifacts. Visualization of graptolite tubaria (rhabdosomes) enabled Demirastrites simulans to be identified. Numerical models of graptolites reveal promising applications for paleontological research and thus for the recognition and characterization of reservoir rocks.
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Authors and Affiliations

Łukasz Kaczmarek
Anna Kozłowska
Michał Maksimczuk
Tomasz Wejrzanowski
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The Gėluva regional stage stratigraphically corresponds to the late Wenlock. This time interval witnessed significant graptolite extinctions and turnovers of conodont faunas, as well as a large positive Mulde carbon isotopic excursion. Thus, the development of a detailed stratigraphy is a necessary step in understanding the complex patterns of regional and global variations in the sediments accumulating during the time interval studied. Therefore, in this contribution we present a cyclostratigraphic analysis of gamma ray (GR) logs from four wells, which are located in the deep water facies belt of the Lithuanian part of the Silurian Baltic Basin of the Gėluva regional stage. The analysis was performed using REDFIT spectral estimation, continuous wavelet transform and signal filtering techniques. As a result two 4th order and five 5th order cycles were distinguished and named in all sections. The correlation of cycles between sections was calibrated with the graptolite biozones. The comparative analysis revealed that intra-basinal cyclostratigraphic correlation could achieve resolution of the order of several tens of thousands of years.
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Authors and Affiliations

Sigitas Radzevičius
Brigita Tumakovaitė
Andrej Spiridonov

Editorial office

Ireneusz Walaszczyk, Faculty of Geology, University of Warsaw, Poland

Editorial Advisory Board Andrzej Radwański, University of Warsaw, Poland Zdzisław Bełka, Adam Mickiewicz University Poland Max Laurence Coleman, The University of Reading, U.K. Jerzy Fedorowski, Adam Mickiewicz University Poland Ryszard Gradziński, Polish Academy of Sciences, Poland Peter J. Harries, University of South Florida, USA John W.M. Jagt, Natuurhistorisch Museum Maastricht, The Netherlands William James Kennedy, Oxford Natural History Museum, U.K. Jan Kutek, University of Warsaw, Poland Anatoly MikhailovicNikishin, Moscow State Univesity, Russia Nestor Oszczypko, Jagiellonian University, Poland Michał Szulczewski, University of Warsaw, Poland Karl-Armin Tröger, Technische Universiät, Freiberg, Germany Sue Turner, Queensland Musem, Australia Alfred Uchman, Jagiellonian University, Poland Jerzy Znosko, Stage Geological Survey, Poland Andrzej Żelaźniewicz, Polish Academy of Sciences, Poland


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