Main Ordovician–Silurian events in the South Ural and event stratigraphy regional tasks

The main regional abiotic events of the Ordovician and Silurian of the Southern Urals are manifested in the restructuring of sedimentation in the paleobasin. Eustatic fluctuations and tectonic motions primarily cause changes in the lithological composition of strata. Geochemical events influence the isotopic composition of elements. Biotic events affect biodiversity in micro- and macrofauna complexes. The largest of the five Phanerozoic extinctions was the global extinction event at the Ordovician–Silurian boundary (LOME). The Ordovician biotic diversification event (GOBE) is divided into three phases. The Darrivillian level of manifestation of this event is noted in the Southern Urals. The location of the global biotic events GOBE, LOME, and the geochemical event HICE in the sections of the Southern Urals is substantiated. Based on the analysis of the connection between biotic and abiotic events in the Ordovician-Silurian deposits of the Southern Urals, the significant role of conodonts, graptolites, chitinosoans and their correlation potential were revealed. Insufficient knowledge of the sections makes it possible to correlate regional events with certain assumptions. In order to carry out global event correlations, in addition to the comprehensive biostratigraphic characteristics of the Ordovician and Silurian deposits of the Southern Urals, geochemical studies of a number of sections are necessary. The most promising sections for identifying event levels are the sections of the western slope of the Zilair synclinorium: Nabiullino, Maksyutovo, Gremyachiy, Kaga-V.Avzyan, Sermenevo.