Microboring organisms — an overlooked Early-Mid Palaeozoic marine ecosystem: Case study from the Prague Basin (Czech Republic)

Abstract

Nearly 800 of Ordovician to Middle Devonian petrographic slides from the Prague Basin (Barrandian area, Czech Republic) have been inspected for the presence of microboring structures in bioclasts. Traces of microbioerosion are rare in the Ordovician to Lower Devonian of the studied area and are produced almost exclusively by bacteria and fungi on bioclast surfaces. However, a gradual increase in the abundance of microboring structures and their shift into bioclast interior is observed during the Silurian to the Early Devonian interval. This coincides with a generally ascending quantity of tunnels possibly produced by phototrophic microboring organisms (Cyanobacteria and Algae). Subsequently, the abundance of microendolithic structures notably increased from the Emsian onwards. They are not randomly distributed in relation to their palaeoenvironments, with most abundant occurrences in low-energy hemipelagic red carbonates. Although this may partially reflect the global marine evolutionary trends, the changes in microbioeroder ecosystems were more likely driven by local factors such as the drift of the Prague Basin from temperate to tropical climate zone, increased oxygen content near the sea floor or to a larger extent, the preserved shallow littoral facies.