Trilobites and Biostratigraphy of the Cambrian Section of the Khantaysk-Sukhotungusskaya-1 Well, Northwest of the Siberian Platform

Almost the complete Cambrian sequence was uncovered in the Khantaysk-Sukhotungusskaya-1 well. Five formations have been established in the well: Chopkо, Ust-Brus, Shumnaya, Krasnoporozhskaya, and Sukharikhа. Their deposits belong to the lower Tukalandian, Mokuteian, and Omnian Region Stages of the Upper Cambrian (corresponding to the lower part of the Aksaian Stage and the Saksian Stage) and to the Glyptagnostus stolidotus Zone, Layers with Tomagnostella sulcifera, Layers with Lejopyge, Layers with Anomocarioides, and Layers with Linguagnostus of the Middle Cambrian, as well as Layers with Pagetiellus porrectus of the Lower Cambrian. The G. stolidotus Zone established in the well is a paleontological subdivision directly underlying the stratotype of the Omnian Region Stage, which is located in the natural section of the Chopko River. Five new Middle Cambrian trilobite species have been described: Ammagnostus minutus sp. nov., Parasolenopleura siberica sp. nov., Onchonotellus arealis sp. nov., Pseudanomocarina falcata sp. nov., and Toxotiformis tchopkiensis sp. nov.