Sakmarian Stage

The section and point for the base-Sakmarian has been changed to the Usolka section in Russia and a proposal was to have been voted on in 2012, but there have been some delays. The Kondurovsky section failed to reproduce the requisite conodont results and problems about the evolution of Sweetognathus merrilli were discussed during ICOS2009. Fortunately, the Usolka section had been fully worked up as a potential parastratotype and we have excellent carbon isotope (Zeng et al., 2012, Gondwana Research), U-Pb isotopic ages and abundant conodonts to define the boundary. Detailed conodont samples from the approximate GSSP interval were collected by V. Davydov and were processed in Calgary. The isotopic ages have been published by Mark Schmitz and Vladimir Davydov (2012) in GSA Bulletin. This material will form the basis of a report that will be prepared in 2013 and then followed by a vote.