BIOSTRATIGRAPHY OF THE UPPER VENDIAN-LOWE R CAMBRIAN IN THE SUKHARIKHA RIVER SECTION (SIBERIAN PLATFORM)

One of the key sections of the Lower Cambrian of the Siberian Platform , the Sukharikha River section, Igarka region, has been described with in the interval Upper Vendian-Lower Cambrian, including the Sukharikha , Krasny Porog, and Shumny Formations. For the first time the Sukharik ha Formation was completely paleontologically characterized by trace f ossils of soft-bodied organisms and calcareous algae. It has been show n once more that the Vendian-Lower Cambrian boundary is correctly draw n 1.5-2.0 meters below the roof of the Sukharikha Formation, at the ba se of the Tommotian Stage, consisting of three archaeocyathid zones co mparable with type locality zone at the Aldan and Lena Rivers. To corr elate the Krasny Porog Formation, weakly characterized by archaeocyati ds and trilobites in the part referred to the Atdabanian Stage, the au thors have recognized accessory stratigraphic subdivisions - beds with small shelly fossils (SSF). The rocks of the Krasny Porog and Shumny Formations developed under increasing transgression in the basin leadi ng to the disappearance of algae-archaeocyatid organogenic buildings a nd formation of black shales.