Acta Palaeobotanica 41(2): 141–146, 2001

Structure of the Turgayan flora in the Oligocene and Miocene and its palaeoclimatic features

Summary: Five phases should be distinguished in the evolution and development of the Turgayan flora in Kazakhstan and the south of Western Siberia, namely: 1. The end of the Late Eocene. Involvement of the temperate nucleus in a subtropical flora of a Drevlyanian type, representing the Poltavian flora sensu Krishtofovich. 2. The beginning of the Early Oligocene. Transformation of the subtropical Drevlyanian flora into the warm temperate Turgayan flora. 3. The end of the Early Oligocene. The origin of the warm temperate Turgayan flora, retaining a noticeable portion of a subtropical relictual elements (in separate local floras it comprises one tenth to one third of the total). The Turgayan flora of the third phase is typical predominantly of central and western parts of Kazakhstan. The systematic composition of the flora at this phase is rather unusual due to an appreciable fraction of the subtropical inherited from the previous flora of Drevlyanian type. 4. The Late Oligocene – Early Miocene (the Aquitanian). The flora characteristic of this phase is practically devoid of a Subtropical element and is extensively distributed far beyond the Kazakhstan limits. In Kazakhstan this is a phase of a typical Turgayan flora. A small portion of Eocene relict plants retained in the flora was sufficiently adapted to new climatic conditions. This flora occurs in the Central and Western Kazakhstan, it is also well developed in eastern part of Kazakhstan and the south of Western Siberia and in the Southern Urals. Most general notions on the ecological type of the Turgayan flora that can be found in the palaeobotanical literature are based on this particular phase in the history of the Tertiary floras from Kazakhstan and Western Siberia. 5. The end of the Early Miocene (the Burdigalian). The proper Turgayan flora starts to decline in Kazakhstan and its numerous derivatives begin to form in other regions. In my opinion, palaeofloras of Mamontova Gora (Mamontova Mountain) are referred, for example, to such derivatives, their most probable age is Middle Miocene.

Keywords: Drevlyanian, Turgayan flora, thermophilic element, initial Turgayan (mesophilous) element, palaeoflora, Oligocene, Miocene