New Data on the Middle Devonian Biostratigraphy of the Salair, Southwestern Siberia

The biostratigraphic data on the ammonoid, brachiopod, conodont, and ostracod assemblages of the Mamontovo and Zarechnoe horizons of the Salair were revised and analyzed. The stratigraphic succession of the Middle Devonian deposits of the Salair is clarified, and the new Zarechnoe Horizon, including the Akarachkino, Safonovo, and Kerlegesh beds, is proposed. The upper Eifelian ammonoid assemblage of the Agoniatites Zone, established in the upper part of the Akarachkino Beds, is the biostratigraphic level for global correlations. The upper Eifelian and lower Givetian brachiopod assemblage ( Indospirifer padaukpinensis (= I. pseudowilliamsi )) characterizes the Safonovo Beds. Two middle Givetian brachiopod zones were recognized in the Kerlegesh Beds: Rhynchospirifer hians (=Ilmenia subhians) and Subrensselandia? salairica (=“Chascothyris” salairica). The conodont assemblage of the Akarachkino Beds characterizes the upper Eifelian. The middle Givetian conodont assemblage, including Icriodus difficilis Ziegler et Klapper, Polygnathus linguiformis klapperi Clausen, Leuteritz et Ziegler, Po. parawebbi Chatterton beta morphotype, Po. ovatinodosus Ziegler et Klapper, and Po. pseudofoliatus Wittekind, was found in the upper part of the Safonovo Beds. No conodont assemblage was found in the Kerlegesh Beds.