55.4 m (bed 26/3) in the Usolka section
Usolka section, Southern Ural Mts, Russia. 53.9247°N, 56.7287°E.
Conodont FAD Mesogondolella monstra
Chernykh VV, Chuvashov BI, Shen S, Henderson CM, Yuan D, Stephenson MH. The Global Stratotype Section and Point (GSSP) for the base- Sakmarian Stage (Cisuralian, Lower Permian). Episodes 2020;43:961-979. https://doi.org/10.18814/epiiugs/2020/020059 [PDF]