Traces of the global Ludford Lau event in a section of the Silurian Sizim horizon on the western slope of the Subpolar Urals

Research subject. To present new results obtained when studying clayey-carbonate deposits of the Sizim Regional Stage of the Upper Ludlow in the Silurian reference section on the western slope of the Subpolar Urals. Materials and methods. Representative collections of sedimentary rock samples with fossil fauna collected by the authors from Upper Silurian deposits in different years during fieldwork on the western slope of the Subpolar Urals, the Chernov and Chernyshev Uplifts, as well as new C-isotope data, were used. Results. For the first time, a biostratigraphically dated interval with positive δ 13 C values marking the Middle Ludford Lau isotope event in the Upper Ludlow section of the Subpolar Urals has been distinguished. The isotope curve has a stepped structure and records a distinct positive trend. The previously determined positive isotope excursion of the Early Pridolian Klev Event at the base of the Belush’ya Regional Stage of the Pridoli marks the boundary of the Ludlow and Pridoli in the same section of the Subpolar Urals. Conclusions. The conducted integral study of successive changes in facies, biota composition, and behavior of stable carbon isotopes in the Sizim Regional Stage section on the western slope of the Subpolar Urals made it possible to identify the manifestations of the global biotic and isotopic Middle Ludford Lau Event.