“…intermedia Subzone, and NJT17 calcareous nannofossil zone), as well as important palaeoecological trends: nannofossil calcification event (e.g., Bornemann et al, 2003), demise of Saccocoma microfacies (e.g., Grabowski et al, 2019) and change of calpionellid lorica structure (Reháková, Michalik, 1993). Correlation with Neuquen Basin (Argentina) seems easier in the Upper Tithonian than in the Lower Berriasian, due to robust magnetostratigraphic data and good consensus concerning ammonite stratigraphy (e.g., Aguiree-Urreta et al, 2019;Kietzmann et al, 2021). When comparing Siberian and Russian proxies (e.g., Bragin et al, 2013;Schnabl et al, 2015;Rogov et al, 2015) the interval might correspond either to the Middle/Upper Volgian boundary or to the Okensis/Tajmyrensis (Subditus/Nodiger) ammonite zonal boundary in the Upper Volgian.…”