By the early 1980s, a monographic description of the main groups of organic remains from the Chergak series of Tuva had been largely completed and published: stromatoporates, tabulates, rugosas, bryozoans, crinoids.

Carbonate rocks of the Silurian of Tuva are of exclusively organogenic origin. In Central Tuva they form a significant part of the Silurian strata, are the most diverse in structure and origin.

The Tuva transgressive-regressive sedimentary complex combines the Shemushdag, Chergak and Khondergean series, connected by gradual transitions ...

Upper Ordovician and Lower Silurian sediments are widespread in the Altai-Sayan folded region. They have been studied to varying degrees, paleontologically characterized differently, and have different relationships with each other.

All researchers note the wide distribution of Ordovician sediments in the area of the Western Sayan, although the volume and structure of sediments attributed to the Ordovician are understood in different ways. In spite of sufficient geological study of the territory, the number of locations of remains of reliable Ordovician fauna is still measured here in units. One of these localities is the Karyn-Sug river. Karyn-Sug (according to I. B. Filippova) is located in the central part of the Western Sayan, the other two - the Manchurek River, the upper Manchurek River, and the upper Manchurek River. Manchurek River and the headwaters of the Ak-Sug River are located on its south-western edge, within Tuva. Locations of Ordovician fauna are also described on the northern and northeastern margins of Tuva - in the area of its interface with the Western Sayan ...