Boundary between the Porkuni and Juuru regional stages in the Neitla section, Estonia

Conodonts and chitinozoans were studied from the Neitla section, which exposes the boundary between the Porkuni and Juuru regional stages. This level, although not proved biostratigraphically, has been traditionally considered to correspond to the Ordovician–Silurian boundary. However, stable carbon isotope data indicate that the system boundary lies higher in the succession, in the lower part of the Juuru Regional Stage. Rare conodonts and chitinozoans discovered in the section do not provide any criteria for locating the boundary. Although conodonts are represented by taxa characteristic of the Silurian, all of them are known to have already appeared elsewhere in the Upper Ordovician.