Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks

The potential of carbon isotope excursions as a stratigraphic correlation tool has been proved by several earlier studies, but partly indistinct biostratigraphic definition hinders their usage. Six positive carbon isotope excursions have been established in the Baltic Silurian (values of the first four in the East Baltic): the early Aeronian excursion (peak δ13C values reach +3.7‰); the early Telychian excursion (+2.7‰); the early Sheinwoodian excursion (+5.2‰); the middle to late Homerian double-peaked excursion (+4.6‰); the late Gorstian excursion (+1.1‰, in Gotland) and the middle Ludfordian excursion—the most prominent shift in the Phanerozoic (maximum values reach in the East Baltic +8.2‰, in Scania +11.2‰).The biostratigraphic dating of three Wenlock and Ludlow excursions (the early Sheinwoodian, mid to late Homerian and mid-Ludfordian) is discussed and refined in the paper and despite minor problems, these could successfully serve as a tool for geological correlation and as chronostratigraphic markers. Using the mid-Ludfordian shift as a marker, it is suggested that the upper part of the Hamra-Sundre interval on Gotland correlate with the lower part of the Kuressaare Stage in Estonia.