Tournaisian (Mississippian) anoxic events in the Moravian Karst, Czechia
| Autoři | |
|---|---|
| Rok publikování | 2025 |
| Druh | Další prezentace na konferencích |
| Fakulta / Pracoviště MU | |
| Citace | |
| Popis | The Mississippian (early Carboniferous) was a time of profound climactic changes, widespread anoxia, continental collisions, and extinction events. Several anoxic events and glaciations occurred during the Tournaisian age and had a global impact on life and geochemical cycles (e.g. Siegmund et al., 2002; Qie et al., 2019). We studied a section in the Mokrá quarry in the Moravian Karst (Czechia), which exposes Tournaisian limestone strata of the Líšeň Formation. The Mokrá-west MZ1 section is a newly uncovered section preserving a uniquely tectonically undisturbed succession with a presence of black limestone interval. Methods of conodont biostratigraphy, sedimentology, petrophysics (gamma-ray spectrometry), and carbonate carbon isotope chemostratigraphy have been used to provide a correlation of the black limestone interval with the Carboniferous global events. A detailed conodont biostratigraphy was established using sixteen samples. The Mokrá-west MZ1 section spans a stratigraphic interval from the lower Tournaisian Siphonodella quadruplicata conodont Zone to the upper Tournaisian Scaliognathus anchoralis anchoralis Zone. Gamma-ray spectrometry was employed to investigate compositional changes in limestone and provided data for the interpretation of hypoxic to anoxic conditions during the deposition of the black limestone. The paleoenvironmental and carbon cycle disruptions were assessed using stable carbon isotope analysis showing a positive ?13Ccarb excursion in the upper part of the black limestone interval. The integration of data from conodont and lithological analysis, gamma-ray spectrometry, and stable carbon isotope geochemistry supports the correlation of the examined strata with global anoxic events, specifically the Lower Alum Shale Event (Siphonodella crenulata conodont Zone; preliminary correlation due to the scarcity of conodonts) and an overlying anoxic event linked to the glacial mid-Tournaisian ?13Ccarb excursion, reaching up to 3.7 ‰ ?13Ccarb within the Lower Gnathodus typicus conodont Zone. This period was followed by a transition back to warmer, oxygenated conditions in the upper Tournaisian. |