Late Cambrian-Early Ordovician Condensed Oceanic Siliceous Deposits in the Iradyr Zone, Northern Kazakhstan

摘要

The data on conodonts and the geological structure of the siliceous sections in the Ishkeolmes and Iradyr Formations within the Iradyr Zone of the Northern Kazakhstan are reported. The layer-by-layer collection of conodonts provided the possibility to establish a wide (from the Upper Cambrian to the mid-Floian of the Lower Ordovician) age range of both formations and their relatively small thickness. The age intervals of the Ishkeolmes and Iradyr Formations are almost identical, and thus it is senseless to distinguish two formations with similar composition and age.