According to the scheme of structural-formation zoning of the Southern Tien Shan, the Zeravshan region belongs to the Zeravshan-Alai zone, where the sections of the Lower and Middle Paleozoic are characterized by predominantly carbonate composition. The Upper Silurian sediments of the Zeravshan Range are represented by the characteristic lithologically uniform Arg Formation composed of dolomites and dolomitic limestones with benthic fauna. The lower subformity of the Arg Formation corresponds to the Upper Wenlock-Ludlow Formation; the upper subformity corresponds to the Post-Ludlow (Prjidol) ...