The morphometrical analysis of Sloanea elliptica (Andreánszky) Z. Kvaček & Hably from the Oligocene of the Buda and Bükk Mountains and its palaeogeographic implications

Significant tectonic movements characterized the Oligocene of the Inner Carpathian Region. After a northeastward escape ensued in a relatively short period, the Buda and Bükk units moved 200-300 km to the north, to their present position. The Tard Clay deposited in the once integral Palaeogene basin comprises a rich macroflora both in the Bükk and Buda Mountains. Earlier palaeofloristical studies concluded that the two areas are quite similar and most species occur in both. However, it is conspicuous that leaf remains belonging to one and the same taxon display a smaller size in the Bükk than in the Buda Mountains. Morphometric analysis was adopted to make more exact this empirical fact since conclusions drawn by the analysis may provide essential pieces of information concerning the climate and environment of the former Palaeogene basin. Leaves of Sloanea elliptica were chosen for the analysis since, taxonomically, the species is well based, supported by both cuticular evidence and fruit remains. At the same time, the species was exclusively recorded from the Palaeogene of the Inner Carpathian Region, however, from both the Bükk and Buda units and from Slovenian deposits that retained the original position of the Palaeogene basin. The morphometric analysis has proved unequivocally that leaves from the Bükk Mountains are smaller and mainly narrower than those from the Buda Mountains. These features possibly indicate drier climatic conditions in the Bükk unit.