Triassic-Jurassic Boundary in the Anabar Bay Section (Northern Yakutia)

The section of Cape Airkat on the western shore of the Anabar Bay has been a reference section for the study of the Triassic and Jurassic in the Anabar region, but its subdivision is still a subject of controversy. A detailed lithological and paleontological characteristic of the section is given. Based on the existing data on the genesis of the Triassic-Jurassic boundary deposits, the boundaries of local stratigraphic units were revised, and for the first time the Bulunkan Formation was identified in the interval of the section, which was previously considered the basal part of the “Zimnyaya Formation”. A new Laptevomorskaya Formation was identified in place of the Zimnyaya Formation, which was previously found to be widespread in western Siberia. Its lower boundary is drawn at the base of a marking horizon of clays of coastal-marine genesis. The Hettangian age of the lower part of the Laptevomorskaya Formation was determined on the basis of bivalves. The Triassic-Jurassic boundary is proposed to be conditionally combined with the base of the Laptevomorskaya Formation. Key species of Rhaetian and Lower Hettangian bivalves and brachiopods are figured.