The Silurian Sedgwickii Event: Carbon isotope excursion, graptolite mass extinction, sedimentary rekord

The late Aeronian Sedgwickii Event belongs is one of the most dramatic global extinctions among planktic graptolites and roughly coincides with one of the most significant carbon isotope excursions so far recorded through the Silurian System. Carbon isotopic data, combined with stratigraphic distribution of oxic beds or gaps in sedimentation, account for sea-level drawdown, tentatively attributed to glacial interval recorded in the Amazon Basin. In the Barrandian area, the mass extinction has been recorded in the latest convolutus-early sedgwickii Biozone along with mottled oxic beds in a generally black-shale succession. In some Barrandian sections, however, this interval is missing due to an offshore gap in sedimentation. A section, temporarily exposed in the Radotin tunnel, provided a unique opportunity for a detailed multidisciplinary study of the whole Sedgwickii Event interval. The Radotin section data will be supplemented with that from other partial sections and correlated with El Pintado section of SW Spain. Detailed analysis of the graptolite mass extinction and recovery, palynomorph abundance and diversity fluctuation, Corg isotope excursion, and facies changes aims to elucidate scenarios, relative timing and causal links of these chemical, biotic and sedimentary proxies of the early Silurian climatic and sea-level fluctuations.