Hedvika Weinerová

Microproblematica, calcareous algae, and microbialites at the Frasnian-Famennian boundary interval in the Šumbera section (Moravian Karst, Czech Republic) and their significance in the context of the Kellwasser Crisis

The Kellwasser Crisis represents one of the most severe extinction events in the Phanerozoic. The Šumbera section (Moravo-Silesian Basin, Moravian Karst) spans the Upper rhenana to Palmatolepis minuta minuta (or younger) conodont zones and corresponds to the upper part of a carbonate ramp with material derived from shallower areas. A rich association of calcareous algae, cyanobacteria, and microproblematica, comprising renalcids (Izhella), Girvanella, Rectangulina cf. tortuosa, Rothpletzella, “solenoporaceans”, “Keega”-like microfossils, udoteacean alga Paralitanaia, volvocean and radiospherid calcispheres, palaeoberesellids, Umbellina bella, and Wetheredella, is similar in diversity to associations known from China, Australia, Canada, and Belgium. The Šumbera section represents a unique locality where changes in shallow-water biota at the Frasnian-Famennian boundary are well calibrated by detailed conodont biostratigraphy. We track in detail the evolution of shallow-water biota and the features that are often discussed in the context of “anachronistic” facies, such as flourishing microbial structures, enhanced early marine cementation, and flat-pebble conglomerates. Some features which could be indicative of environmental stress such as flat-pebble conglomerates developed during the Frasnian part of the Kellwasser Crisis (Upper rhenana to linguiformis Zones), whereas a renalcid boom started at the Frasnian-Famennian boundary.