New finds of ferns from Middle Jurassic deposits of Ob-Tazovsky facies area of Western Siberia

The article describes the Middle Jurassic ferns from the core of wells in the central part of Western Siberia (the Ob-Tazovsky facies area). The studied plants have the Bajocian-Bath age and belong to the deposits of the Tyumen suite (Azharminskiy and Malyshevskiy complexes of plants of the Tomsk phytohorizon). The macroflora of Western Siberia is important for phyto-stratigraphic segmentation and for palaeo-geographic reconstruction. The Malyshevsky complex of plants of Ob-Tazovsky facies area contains ferns: Coniopteris vialovae, C. depensis, Raphaelia diamensis, R. stricta. The Ob-Tazovsky facies area is located in the central part of Western Siberia and is a place of distribution of deposits of transitional deposits, a part of the Tyumen suite of the Middle Jurassic age. New finds of the Middle Jurassic ferns are selected from cuts of wells of Frolovsky, Tymsky, Nyurolsky and Varyegansky structural facies regions of the Ob-Tazovsky facies area. Each print of a fern is unique by nature, it plays an important role in phyto-stratigraphic segmentation of deposits of transitional deposits in the studied area, and also broadens the horizons of our ideas of structure and evolution of the Jurassic vegetation of all Western Siberia. For deposits of the Tyumen suite prints of ferns, ginkgo, czekanovskia, and equisetales are characteristic. Among ferns Coniopteris, Cladophlebis, and, to a lesser extent, Raphaelia are widespread. Prints of macroflora are important for phyto-stratigraphic segmentation of Western Siberia. The complex of plants of the Ob-Tazovsky facies area studied by us (Coniopteris vialovae, C. burejensis, C. kalinoviensis, C. depensis, Raphaelia diamensis and R. stricta) should be assigned to Bath deposits (the Malyshevsky complex of plants of the Tomsk phytohorizon). Raphaelia finds in the Ob-Tazovsky facies area allow to increase areas of its distribution during the Middle Jurassic era further to the southeast of Western Siberia. New finds of prints of Coniopteris and Raphaelia help not only with bio-stratigraphic segmentation, but also are indicators of tropical conditions with high and uniform humidity, which were established during the Middle Jurassic era in the central part of Western Siberia.

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