OSTRACODS AND BIOSTRATIGRAPHY OF THE LOWER-MIDDLE JURASSIC DEPOSITS OF YAMAL (NORTH OF WEST SIBERIA)

Ostracods are an effective tool for dissecting and correlating Mesozoic sedimentary strata in closed areas. However, the degree of geologic certainty of ostracods from the marine Lower-Middle Jurassic deposits of West Siberia is very weak. The paper presents the results of monographic and biostratigraphic studies of the Jurassic ostracod complexes of the Yamal Peninsula. 5 stratigraphically important species are described, and images are given for 6 forms. The biostratigraphic division of the Lower and Middle Jurassic of West Siberia by ostracods is substantiated. In the Pliensbachian – Bajocian, a sequence of 6 biostratons was traced by ostracods in the rank of layers with characteristic species: layers with Ogmoconcha longula; with Camptocythere (C.) mandelstami; with Camptocythere (C.) foveolata (established by the author); with Camptocythere (C.) nordvikensis; with Camptocythere (A.) spinulosa; with Camptocythere (A.) arangastachiensis. The West Siberian ostracod biostratons are compared with divisions of the zonal scale for the ostracods of East Siberia, which was developed on natural outcrops of the Jurassic and is сorrelated to the scales for ammonites and other groups of macro- and microfauna.