DISTRIBUTION OF FORAMINIFERA OF THE GAUDRYINOPSIS GENUS IN THE JURASSIC-PALEOGENE OF WESTERN SIBERIA

The species of Gaudryinopsis Podobina, 1975 Genus assigned previously to other genera have been met at different levels of the Jurassic-Cretaceous-Palaeogene. The tests of species of the Gaudryinopsis Genus have a quartz-siliceous wall and a rounded cross-section. The representatives of the similar Gaudryina Orbigny, 1840 Genus are characterized by a different chemical composition of the wall (the calcareous agglutinate with the same cement) and by the angular cross-section of the test. The species of the Gaudryinopsis Genus have been considered from diverse stratigraphic levels, and their development has been marked within the maximum transgressions in Western Siberia. That is why the species of the genus are often taken as zonal species. The Gaudryinopsis (Gaudryina) filiformis (Berthelin) Species is known established previously by G. Berthelin (1880) from the Albian of France. This species has first been discovered by us from the Middle Albian deposits of the Polyarnaya-1 borehole section (depth 1748.34 m) in the Turukhansk district of the north-east Western Siberia. Its Turonian descendants Gaudryinopsis angustus Podobina are relatively abundant in many borehole sections in the central district of this region, and their quantitative predominance is connected with the Early Turonian enlarged transgression. In the Santonian deposits of Western Siberia the Gaudryinopsis vulgaris (Kyprianova) Species is known. However, its finds are sparser in comparison with the Turonian species, and it is accordingly not accepted as a zonal species. In the Middle Eocene the most extensive transgression is observed, and the Gaudryinopsis subbotinae Podobina Species has been confined to it and taken as zonal. The deposits of this zone correspond to the second middle Eocene rock complex from the Lomonosov Ridge section. This is evidenced by the lithology of these rocks composed of the bio-siliceous material, as the Lyulinvorskaya Suite is (the middle subsuite, the Gaudryinopsis subbotinae Zone). In the Lomonosov Ridge section, the underlying deposits of the lower Lyulinvorskaya Subsuite and the Talitskaya Suite correspond to the similar dark-grey clays of the Palaeocene-lower Eocene of the third rock complex. The data on the lithology and stratigraphy have been taken from the paper of Akhmetyev, et al. (2010). The confinement of diverse species of the Gaudryinopsis Genus to deposits corresponding to the maximum transgressions enhances their stratigraphic and correlational significance for the refinement of the age of the most controversial stratums. So the wide lateral distribution and the narrow vertical occurrence of the Gaudryinopsis subbotinae Podobina Species in Western Siberia and of its middle Eocene vicariant Gaudryinopsis superturkestanika (Bykova) in Central Asia (Bykova, 1959) evidence the middle Eocene age of the Gaudryinopsis subbotinae Zone as well as that of the middle Lyulinvorskaya Subsuite (Lyulinvorskaya Suite) to which this assemblage is confined.