**Author details**

E. Leb. Species *C. hymenophylloides* (Brongn.) Sew., *C. simplex* (L. et H.) Harris, *C. vsevolodii* E. Leb. Occur everywhere. Genus *Phoenicopsis*, presented by 10 species, is the most diverse among Leptostobales. Species *Ph. taschkessiensis* Krasser and *Ph. mogutchevae* Kiritch. et Trav. are the first to occur among them. The most abundant are species *Ph. samylinae* Kiritch. et Moskvin., *Ph. sibirica* Kiritch. et Trav., and *Ph. varia* Kiritch. et Trav. The age of sediments including Azharminskii fossil plant assemblage is determined in the range of Bajocian stage. Analysis of flora taxonomic composition from the sections of the Topka river revealed in it the lack of all new species of genera *Coniopteris* and *Phoenicopsis* typical of Azharminskii assemblage (**Table 1**). Thus, according to the available data, there is no

96 Seismic and Sequence Stratigraphy and Integrated Stratigraphy - New Insights and Contributions

The results of lithologic and paleobotanical investigations of Lower and Middle Jurassic sedi‐

Two uneven‐aged fossil plant assemblages: Cheremkhovo for the Middle and Upper Cheremkhovskaya Subformations and Prisayan for the Prisayanskaya and Kudinskaya

Species *Equisetites lateralis* (Phill.) Phill., *E. asiaticus* Pryn., *Cladophlebis haiburnensis* (L. et H.) Sew., *Sphenobaiera czekanowskiana* (Heer) Flor., *S. vigentis* Kiritch. et Bat., *Czekanowskia baikalica* Kiritch. et Samyl., and *Cz. rigida* Heer were dominated in sections of Middle and Upper Cheremkhovskaya Subformations. Level of development of Cheremkhovo assemblage is com‐ parable with flora of Nizhnenovogodnii (Western Siberia) and Kamzasskii (Kuznetsk Basin) assemblages. Therefore, the age of Middle and Upper Cheremkhovskaya Subformations including Cheremkhovo assemblage is determined by the end of Early Jurassic (convention‐

Species *Coniopteris maakiana* (Heer) Pryn. emend. Kiritch. et Trav., *C. murrayana* (Brongn.) Brongn., *C. spectabilis* Brick., *Cladophlebis nebbensis* (Brongn.) Nath., *Raphaelia diamensis* Sew., *R. tapkensis* (Heer) Pryn. emend Kost., *Phoenicopsis angustifolia* Heer, *Ph. cognata* Kiritch., and *Ph. irkutensis* Dolud. et Rasskaz. are typical of Prisayan assemblage. The identified species composition of the Prisayan assemblage allowed to compare it with Verkhnepeshkovskii (Western Siberia), Rybinskii (Kansk Basin), and Etapskii (Kuznetsk Basin) fossil plant assemblages and to establish the formation age at the beginning of the Middle Jurassic

The study was financially supported by the Russian Foundation for Basic Research (16‐35‐60005).

ments of the Irkutsk Basin allowed to draw the following conclusions.

Bajocian flora within the Irkusk Basin.

**5. Conclusion**

ally, Toarcian).

(Aalenian).

**Acknowledgements**

Formations were identified.

Andrey Olegovich Frolov, Nikolay Ivanovich Akulov\* and Irina Mikhailovna Mashchuk

\*Address all correspondence to: akulov@crust.irk.ru

Institute of the Earth's Crust Siberian branch of Russian academy of science, Irkutsk, Russia
