Boundary between Permian series in diverse sedimentary facies of north European Russia: Constraints of event stratigraphy

摘要

Lithologic-facies and ecologic-taphonomic methods are jointly used to study the Lower-Upper Permian boundary deposits of a complex structure, which are represented by laterally variable marine, coastal, deltaic, lagoonal, and terrestrial facies. The created landscape model elucidates spatial relations between different sedimentary facies and respective sea-level fluctuations in the Kungurian shallow basin. The established brachiopod zonation is carefully correlated with ammonoid biostratigraphy. It is shown that mid-Kungurian and Solikamsk stratigraphic events are of a high correlation potential in the Boreal realm. The Kungurian age is substantiated for marine facies of the northeastern Pai-Khoi Ridge and Subpolar Urals, which are correlative with the Solikamsk Horizon. New results and data on interconnection between the lower Kazanian marine and Sheshma red-bed facies imply inexpediency of including the Ufimian Stage into the General stratigraphic scale. The Kazanian Stage base corresponding to the Lower-Middle Permian boundary in the International scale is most appropriate candidate for the General scale level that should separate the Lower Permian from the upper or middle series in the two- or three-unit subdivision of the system, respectively.