Title

G. S. Iskyul

The storm sedimentation features in bioclastic packstone-grainstone beds of Kunda stage (Middle Ordovician), Leningrad Region

The paper describes texture-taphonomic features of the pack-grainstones marking regressive interval of the Orthoceratite Limestones. At the first time the number of features typical for “event” deposits – erosion surfaces, relicts of graded and sorted sediments and redeposited shell fossils are described. The most informative for the sedimentological analyses are the large remains of shell faunas (nautiloids, gastropods) that within their shells preserve carbonate relicts of the “first cycle” sediments denudated outside. Peculiarities of the studied deposits allow to propose the storm sedimentation environment with the predominance of turbulence. Traces of redeposition of shell fossils were also noticed in more deep water and muddy microfacies.
Key words: Leningrad Region, Ordovician, Kunda stage, tempestites, shells-intraclasts, phosphatized erosion surface.