Mid-Cambrian Agnostoid Trilobites From the Chaya Formation of the Ust’-Mayskaya-366 Well (Southeast of the Siberian Platform)

Abstract

The paper presents the characteristic of the Middle Cambrian agnostoid trilobites in the small interval of Chaya Formation (1313,55-1290,3 m) of Ust-Mayskaya 366 well. The 10 genera, 12 species (including aff.) and 6 forms in open nomenclature are described. Biostratigraphic subdivision of the studied interval of Chaya Formation and its comparison with the Stratigraphic Scale of Russia are given. The composition of the fossils indicates the Tomagnostus fissus-Paradoxides hicksi Lone and Anopolenus henrici Lone of Middle Cambrian Mayan Regional Stage.