ASSELIAN–SAKMARIAN BRACHIOPOD CORRELATION OF THE BULKUR AND UST-LENA STRUCTURAL-FACIES ZONES OF THE LOWER REACHES OF THE LENA RIVER

As a result of the monographic study of the Early Permian brachiopods from the Kubalakh and Chekurovka sections, a zonal correlation of the Asselian–Sakmarian deposits, respectively, of the Ust-Lena and Bulkur structural facies zones (SFZ) was performed. The Jakutoproductus verkhoyanicus (including layers with Jakutoproductus lenensis in the upper part of zone), Jakutoproductus insignis, Jakutoproductus terechovi, and Jakutoproductus rugosus zones are established in both SFZ (up-section). In the Kubalakh section, the Jakutoproductus verkhoyanicus Zone is present in full and conformably superposes the Upper Carboniferous Jakutoproductus protoverkhoyanicus Zone, while in the Chekurovka section, the lower part of the J. verkhoyanicus Zone unconformable overlies Upper Cambrian formations, and the lower part of this zone is probably absent in the section. In the direction from the Kubalakh section to the Chekurovka one, a significant reduction in the thickness of all established biostratigraphic units is observed, and their total thickness decreases by more than two times.