**5. Conclusion**

The results of lithologic and paleobotanical investigations of Lower and Middle Jurassic sedi‐ ments of the Irkutsk Basin allowed to draw the following conclusions.

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

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‐ ally, Toarcian).

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 (Aalenian).
