Triassic–Jurassic Boundary Deposits in the Area of Cape Tsvetkov (Eastern Taimyr): Biostratigraphic and Lithological Features

The Triassic–Jurassic section of Cape Tsvetkov is a reference section for large-scale mapping of local units in the Tsvetkov geological area of Eastern Taimyr. Along with the lithological subdivision of deposits, the stage subdivision of the Triassic and Jurassic is important for mapping local units. On the basis of the materials obtained by the authors during the study of outcrops in the Cape Tsvetkov area in 1987 and 2014, the lithological and paleontological characteristics of the Triassic–Jurassic boundary deposits are presented. On the basis of these characteristics, local stratigraphic units were revised. For the first time in this area, the Bulunkan and Laptev Sea formations were established in the part of the section, which was recently attributed to the terminal part of the Nemtsov Formation, as well as to the Tumul and Zimnyaya formations. On the basis of bivalves and brachiopods, the Rhaetian age of the Bulunkan Formation and the Hettangian age of the lower part of the Laptev Sea Formation were determined. On the basis of new data, it was proposed to combine the Triassic–Jurassic boundary in this section with the base of the Laptev Sea Formation. Images of Rhaetian and Hettangian bivalves and brachiopods are provided.