Abstract: The rocks of the Ilin–Tass anticlinorium overlie the folded structures of the Moma Range and extend from the headwaters of the Kolyma River in the northwesterly direction to the Indigirka River basin. The first data on U–Pb dating of detrital zircons from volcanogenic–terrigenous rocks of the Bastakh series are presented. It is found that the provenance area for the rocks of the Bastakh series was located along the entire periphery from the area of accumulation of volcanogenic–sedimentary formations. It is shown that the age of the three formations of the Bastakh series lower in the section, which was previously considered to be the Tithonian, covers the Neocomian and is accepted as the Tithonian–Barremian.