| details |
Late Eocene |
Early Oligocene |
USSR(Kazakh SSR) |
Boytsova,E.P. et al. Plant remains from Late Cretaceous and Paleogene deposits of Western Kazakhstan and their stratigraphic significance. |
1960 |
| details |
Tertiary |
|
Canada(British Columbia) |
Hills,L.V. et al. Azolla primaeva and its phylogenetic significance. |
1967 |
| details |
Late Eocene |
|
USSR(Kazakh SSR) |
Akhmeteev,M.A. et al. Upper Eocene Oligocene spore and pollen, plant macrofossils and phytoplankton in stratotypes of Tchegan and Astsheairyk Formations (North Usturt, Kazakhstan). |
1992 |