FIGURE 2. The composite scheme of the Upper Ordovician in the Leningrad region, including strata eroded before the Devonian (biozones after Suyarkova & Koren' 2009; age dates after Gradstein et al. 2020)
Department of science and research, Kuban State University, Stavropol'skaya Str., 149, Krasnodar, 350040, Russia. & Kazan Federal University, Kremlevskaya Str., 18, Kazan, 420008, Russia.
Petr V. Fedorov
Saint Petersburg State University, Universitetskaya nab. 7-9, St. Petersburg, 199034, Russia.