The Late Miocene floras from Crete; vegetational and palaeoclimatic trends

On the island of Crete, three Late Miocene outcrops have been discovered so far consisting of significant terrestrial plant macro-remains that have provided a considerable amount of floristic data and constituted the material for a series of palaeobotanical studies in the recent past. The oldest outcrop is located at the southern part of central Crete, near Pitsidia village in the Messara basin, where radiometric data from superjacent layers yielded an age of around 10.5 million years ago, into Early Tortonian. The recovered plant assemblage is still under investigation by the authors and todate its taxonomic composition includes more than 25 different taxa. The second outcrop is located near Makrilia village in the eastern part of the Island in Ierapetra basin. The palaeoflora consists of 62 identified taxa and the age of the sediments is defined by integrated biostratigraphy of dinocysts and nannoplankton as Late Tortonian, approximately 7.7 to 8.6 million years. The youngest plant assemblage originates from different small outcrops exposed near Vrysses village in the homonymus sedimentary basin in the western part of the Island. It includes 19 identified taxa and is assumed to be of Latest Tortonian – Early Messinian age, based on biostratigraphic considerations (ca. 6.0 to 7.5 million years). For the Makrilia outcrop, pollen and spores data exist as well, while a few more palynological reports are available from other contemporaneous sediments from the Island.
   As these palaeofloras cover a time span of about 5 million years of the Cretan vegetation history, comparing the floristic data, valuable information about the possible changes in floristic composition, the vegetation succession and the evolution of climatic conditions during this period of the ancient Cretan region can be revealed. However, the interpretation of the plant assemblages and the extraction of definite conclusions are rather risky due to the inadequate number of floras, their particularly different depositional environment and undoubtedly the taphonomical bias.
   The discovered plant macro-remains comprise mainly of foliage (impressions, seldom carbonized compressions) and less frequently of fruits, seeds, shoots, flowers and inflorescences. The preservation quality varies significantly from bad to almost excellent but generally is characterized as fairly fine.
   Floristically, the three palaeofloras share only a few common species, like Quercus mediterranea Unger, Acer pseudomenspessulanum Unger, Buxus pliocenica Saporta et Marion and Daphnogene polymorpha (A. Braun) Ettingshausen. However, the assemblages from Makrilia and Pitsidia are obviously closer, as they share many taxa like the wetland plants Myrica lignitum (Unger) Saporta, Taxodium Rich., Equisetum L., Populus L., Salix L. and some, more or less, mesic arboreal elements including Fagus type attenuata, Quercus kubinyii (Kovats ex Ettingshausen) Czeczott, Podocarpium podocarpum (A. Braun) Herendeen. Contrary to Pitsidia, the Makrilia flora illustrates a remarkable higher diversity. Especially, the mixed mesophytic forests comprise a great number of various deciduous accessory elements like Zelkova zelkovaefolia (Unger) Kotlaba, Ulmus L., Carpinus L., Fraxinus L. and Tilia L. Likewise, the families Lauraceae and Magnoliaceae are well diversified in Makrilia flora, accompanied by other thermophilic taxa like Engelhardieae, Tetraclinis salicornioides (Unger) Kvacek and Asterocalyx styriacus Ettingshausen. At the same time, in Makrilia the sclerophyllous woody plants are more frequent and diverse.
   Conversely, the flora of Vrysses demonstrates a more sub-humid character with many xeromorphic elements that indicate the occurrence of well-developed sclerophyllous plant associations. The mesophytic woodland palaeocoenoses are clearly less diverse and probably poorly developed. Tall deciduous trees like beech and oaks are apparently lacking. Instead, only a few deciduous shrubs like “Parrotia” pristina (Ettingshausen) Stur and Ziziphus ziziphoides (Unger) Weyland seldomly occur. Typical swampy plants are completely absent here.
   Climatically, the examined plant assemblages demonstrate a warm temperate character for the Late Miocene of Crete. Without any doubt, all of them include a prominent proportion of sclerophyllous woody plants which increases gradually from the Early Tortonian to the Messinian and these elements eventually established a very strong representation at the Messinian stage. This fact probably indicates a gradual transition to drier conditions and an increased seasonality of precipitation during the Late Miocene in the Cretan area. This conclusion is strongly supported as well by all the related palynological records from the island.