New data on Ordovician stable isotope record and conodont biostratigraphy from the Viki reference drill core, Saaremaa Island, western Estonia

The Viki drill core is one of the reference sections for the Estonian bedrock succession, characterizing strata of Mid Ordovician through early Silurian age in the eastern part of the Baltoscandian basin. In this article, we present the hitherto missing Ordovician stable carbon isotope curve and Middle Ordovician conodont biostratigraphy from the Viki core to complement the previous lithological, geochemical, geophysical and biostratigraphic studies. For the first time, the Hirnantian sulfur isotope excursion is reported from the eastern Baltic region, showing high amplitude and tight coupling with carbon cycling.