Brachiopods from the Lower Permian of the Khospokhchon Section in the Southern Verkhoyanie (Northeast Russia)

Abstract

A biostratigraphic division of the Lower Permian into brachiopod zones of Jakutoproductus verkhoyanicus, Jakutoproductus insignis, Jakutoproductus terechovi, and Jakutoproductus rugosus is observed within the Northern and  Western Verkhoyanie. According to the literature, only the complex of the lower biostratigraphic unit (Verkhoyanicus Zone) was previously confidently established in the Southern Verkhoyanie. Meanwhile, representatives of the two middle zones were not observed, and the presence of the index species of the Rugosus zone was only indicated in the southern part of the region (Yudoma River Basin). A monographic study of the brachiopod collection from the Upper Olchan Subformation of the stratotype of the Olchan Formation (Khospohchon section) allowed us to rethink the biostratigraphic division of the Asselian-Sakmarian deposits in the Southern Verkhoyanie. The brachiopods of the Upper Olchan Subformation of the Khospohchon Creek (Menkule River Basin) belong to three successive biostratigraphic zones: Verkhoyanicus, Insignis, and Terechovi. Information on the presence of representatives of the species Jakutoproductus rugosus Ganelin in the Southern Verkhoyanie leads to the assumption that all four biostratigraphic zones of the Asselian-Sakmarian deposits of Verkhoyanie are present in this region. Three upper zones (Insignis, Terechovi, and Rugosus) demonstrated a direct correlation with the Ogonerian Regional Stage of the Omolon massif by their common zonal species. The new results indicate the need for a comprehensive study of the key sections of the Olchan Formation to substantiate the Carboniferous-Permian and Asselian-Sakmarian boundaries in Verkhoyanie using both biostratigraphic and chemostratigraphic methods.