Late Oligocene leaf and pollen flora of Southwestern Siberia: taxonomy, biogeography and palaeoenvironments

ABSTRACT

Late Oligocene leaf assemblages from four sites in Southwestern Siberia (Kurgan, Tyumen, Omsk oblasts) are described. Twenty-three leaf taxa and 3 reproductive structures represent local vegetation of a lake (Salvinia, Typha, Phragmites, Nelumbo, Hemitrapa, Liquidambar, Pterocarya, Alnus, Populus, Salix, Nyssa). Additionally, 57 spore and pollen taxa were recorded from one site (Shish River). Gymnosperms dominate the assemblage with ~30% Pinaceae and ~25% taxodiaceous (papillate) Cupressaceae pollen. Ferns and peat mosses (Sphagnaceae) comprised ~6%. Angiosperms were dominated by Fagaceae, Betulaceae, Juglandaceae and Ulmus and comprised a few exotic elements (Liquidambar, Eucommia, Nyssa, Symplocos); scarce herbaceous plants reflect lakeshore vegetation. The flora of the Turgay type comprised old elements (Nelumbo protospeciosa, Liquidambar europaea, taxodiaceous/papillate Cupressaceae, Quercus sect. Protobalanus) and taxa present in Siberia/Kazakhstan during the Paleogene with later arrivals in Europe (Ulmus pyramidalis, Quercus pseudocastanea, Alnus julianiformis, Byttneriophyllum tiliifolium). A few taxa were endemic in the late Oligocene of western Siberia (Trapa praeconocarpa, Platycrater iljinskajae sp. nov.). Combined macrofossil and palynological evidence places the Shish River site flora into the late Oligocene Zhuravka (Turtas) Formation. Floras of similar composition from western Eurasia are commonly middle Miocene or younger in age highlighting the dynamic spatiotemporal evolution of temperate Eurasian floras during the Cenozoic.

KEYWORDS:

• Biostratigraphy
• palaeobotany
• palaeopalynology
• biogeography
• Cenozoic
• Eurasia
• Quercus section Protobalanus

Acknowledgments

We thank the curators of the palaeontological collections at the “Regional Tyumen Museum Complex named after Ivan Slovtsov” for making this collection available and Aleksandra Olokhova for preparing photographs of plant fossil specimens. TD acknowledges financial support through the Swedish Research Council (VR, project no. 2015-03986).

This study was funded by the Ministry of Science and Higher education of the Russian Federation and was performed as a part of project FEWZ-2020-0007 “Fundamentals of the natural environment history of the south of Western Siberia and Turgay in the Cenozoic: sequence sedimentology, abiotic geological events and the evolution of the Paleobiosphere“. The investigations were carried out using the equipment of the Center for Collective Use “Bioinert Systems of the Cryosphere”, Tyumen Scientific Center, SB RAS. Valuable comments by Christa Charlotte Hoffman and an anonymous reviewer helped improving the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the Vetenskapsrådet [grant 2015-03986 to TD].