The early Oligocene is one of the key periods regarding the origin of modern environments and ecosystems on Earth. During this period, major Antarctic ice sheets started to accumulate, global atmospheric CO 2 decreased, and the ocean temperature dropped dramatically from the late Eocene to the early Oligocene (Pälike et al., 2006; Zachos et al., 2001, 2008). Eurasia has undergone significant environmental changes and large tectonic movements. The Paratethys became isolated from the Tethys and marine conditions retreated from Central Asia (Steininger & Wessely, 2000). The uplift of the Qinghai-Tibetan Plateau was linked with aridification in Central Asia (Dupont-Nivet et al., 2008) and contributed to global cooling at the Eocene-Oligocene transition. These tectonic events and associated climate change affected ecosystems in Central Asia.

The investigation of the fossil floras from the Turgai plateau (central Kazakhstan) contributes to a better understanding of the origin of the temperate Turgai type flora which spread to Kazakhstan and adjacent areas during the Oligocene–Miocene transition. In this paper, we present the results of a carpological and palynological study of the Kumyrtas flora collected from a flora-bearing horizon of the regional coal-bearing Zhilanchik suite, dated to the Aquitanian period. Pollen analysis identified 33 taxa, with are dominated by angiosperms (about 73%) and reflect zonal vegetation. The high percentages of Betula (27%) and Pterocarya (7.5%) that were found in this flora allows comparisons with other Aquitanian floras of Kazakhstan. Based on descriptions of fossil fruits and seeds, we determined that 19 taxa were dominant; these taxa had meosphytic herbaceous components, suggesting mostly edaphic local conditions. The incongruence between the carpological and the pollen records suggests a significant taphonomical effect. Quantitative reconstruction of the palaeoclimate based on pollen records supports---and slightly extends---previous findings based on fossil leaf data, but contradicts findings deduced from the carpological record. Plant Functional Type (PFT) classification was used to characterize the vegetation patterns. Pollen records show that about 45% of diversity relates to the arboreal broadleaved deciduous components and ca. 35% to conifers. Fossil fruit and seed data indicate riverine vegetation with a high diversity of aquatic components and shrub stratum.

No abstract