Multiproxy study of the Frasnian/Famennian boundary interval in the Moravian Karst (Czech Republic)

The late Frasnian Kellwasser Crises are connected with one of the most severe mass extinctions in the Phanerozoic. The Lower Kellwasser Event was previously assigned to the lower or middle part of the Upper Palmatolepis... [ view full abstract ]

The late Frasnian Kellwasser Crises are connected with one of the most severe mass extinctions in the Phanerozoic. The Lower Kellwasser Event was previously assigned to the lower or middle part of the Upper Palmatolepis rhenana Zone whereas the Upper Kellwasser Event was placed in the uppermost part of the Palmatolepis linguiformis Zone.
The Frasnian to Famennian successions of the Moravian Karst facies were deposited in the Moravosilesian Basin which is considered as a part of southeastern margin of Laurussia. The Frasnian reefs were progressively disintegrated at the Frasnian/Famennian boundary which resulted in the deposition of massive limestone breccias or calcarenites/calcilutites with common intraclasts. These sequences representing carbonate ramp environment were studied at three sections. The Šumbera and Hády sections contain common limestone breccias in the Upper Frasnian and Lower Famennian. The Lesní lom section includes limestone breccias especially in the lower part and mainly wackestones in the upper part around the Frasnian/Famennian boundary. In all these sections, the Upper Kellwasser horizon is not clearly developed as intercalations of black shales or limestones. The Lower Kellwasser horizon is also not typically developed or not exposed. Wackestones/packstones to floatstones/rudstones contain variable amount of intraclasts, peloids and bioclasts, mostly brachiopods, corals, stromatoporoids, molluscs, ostracods, foraminifers, algae and microproblematics. Microbialites represented mostly by thrombolites are common and were also recorded in intraclasts from various beds across the sections. Stromatactis structures, Frutexites encrustations and microproblematics represented mostly by Allonema and Rothpletzella are locally present.
The conodonts indicate the total span of the Upper Palmatolepis rhenana to Middle Palmatolepis triangularis Zones. The oldest Famennian interval was recognized by the common presence of Palmatolepis subperlobata or by the presence of Palmatolepis triangularis in the Šumbera and Hády sections. Palmatolepis linguiformis Zone was recorded only in two samples from Šumbera and Lesní lom sections because of rare occurence of the guide species.
In all sections, foraminiferal Eonodosaria evlanensis Zone was distinguished in the latest Frasnian and Eonodosaria evlanensis-Quasiendothyra communis Interzone in the basal Famennian. Only in the Lesní lom section the lower part of the Eonodosaria evlanensis Zone characterized by the presence of Multiseptida corralina was traced, in Hády and Šumbera sections only the upper part of the zone is present.
Gamma ray spectrometry enabled only tentative correlation between the sections and does not allow to clearly recognize the Kellwasser Events. The results of magnetic susceptibility and XRF analyses will be also discussed. Funding: GA14-18183S.