New Palaeobotanical Data for the Evolutionary History of Plants in the Aegean Area, with Special Reference to the Palaeoflora of Thera

The investigations have produced new palaeobotanical data and new conclusions about the stratigraphy and the palaeogeography of the areas, permitting better correlations between the different outcrops. The main contribution has been the elucidation of the phytogeographical distribution of some plants from the Upper Oligocene to recent times - for example, the palms which are found in the Quaternary volcanic tuffs of Thera. The Quaternary palaeoflora of Thera is characterized as unique in the Hellenic area, with special interest in its composition, determining the relative age of the volcanic tuff of the Middle Sequence in which fossil plants are found.

INTRODUCTION

The last ten years have been dominated by palaeobotanical-palaeontological-stratigraphical researches in cainophytic sediments of Greece with rich floras - Thrace, West Macedonia, Lemnos, Chios, Lesbos, Thera and Crete. The systematic and stratigraphic determination of the fossil floras, together with correlations with other floras of the Mediterranean and south-east Europe yielded important data for the phytogeographical distribution of plants, but also outstanding stratigraphical-palaeoclimatological-palaeoecological results. This publication shows especially the phytogeographical-stratigraphical distribution of palms in Greece.

The Quaternary flora from Santorini is of great importance for the evolutionary history of Greek fossil plants. The youngest leaf floras are marked by the occurrence of well-preserved palm remains of Chamaerops humilis and Phoenix theophrasti, which are both important for the distribution of recent taxa.

HISTORY

The first remarks about the fossil flora from Santorini were made by Lacroix (1896), and later on many scientists worked on it (Schuster 1936; Friedrich 1980; Friedrich and Velitzelos 1986). This flora is therefore well studied and the author believes that a systematic excavation would bring important finds, as in 1987, when a seed of Chamaerops humilis was found during the course of a geological excursion of the University of Athens (prepared by courtesy of colleague H.J. Gregor). This is especially important because it is proof of the ripe fruits of this taxa on Santorini 50,000 years ago - a very good indicator of a highly subtropical climate together with other plant remains: Tamarix, Pistacia lentiscus, Olea europea, Phoenix theophrasti etc. (and many plant remains whose identification is problematic).

Most palaeobotanical findings come from browncoal deposits or limnic-fluviatile sediments, but here volcanogenic sediments show a composition of the flora of a great and dry area, similar to other localities with tuffitic components like Lesbos and Evia. If the flora is not burnt by hot lavas, it is possible to study ecological factors which are different from those in browncoal areas.

Kopp (1966) cites palm remains from the Thracian Oligocene, attested by silicified woods found a short time ago.

Fliche (1898) mentions Palmoxylon sp. from the petrified forest of Lesbos.

THE PETRIFIED FOREST OF LESBOS

The fossil forest from Lesbos is a unique geological monument of great scientific significance, spread over a wide area and offering the possibility of a study of the entire vegetation, including silicified trees and leaves.

In the course of a scientific research programme, the author is engaged upon palaeobotanical studies on Lesbos and has found trunks that certainly belong to palms.

Earlier authors have had their problems with palms, including stratigraphy etc. (see Gessner 1933; Gregor 1980; Bûzèk 1977; Hantke 1984; Kolakovski 1964; Schaarschmidt and Wilde 1986; Yelitzelos and Schneider 1979; Friedrich and Velitzelos 1986).

Depending on their data, palms are missing in younger sediments of the Neogene in northern areas such as West Germany.

In contrast, our research in Greece shows that palms are distributed from the Oligocene up to the present by macroremains (Antissa area on Lemnos with leaves of Phoenix).

Depending on the recent level of our studies, the flora of this local point was subtropical in the Upper Oligocene. Further remains of palms come from tuffitic layers near Mundres Lemnos, concerning leaves and silicified woods.

From the Upper Miocene browncoal deposit of Vegora/Florina, Velitzelos and Schneider (1979) describe Chamaerops humilis - the youngest occurrence of this type together with Phoenix theophrasti in the middle of the pumice south of Phira, Santorini.

THE HISTORY OF PALMS

The family of palms is several times attested by palynological records. We can make the following remarks on the occurrence of the above-mentioned species.

In respect of the autochthonous palm forest of 'Vai', Sitia (Crete) with Phoenix theophrasti: this is an older element; the need for a discussion of Chamaerops humilis in Greece remains. It has long been known, that the recent distribution of this type is confined to the western Mediterranean (Gessner 1933; Greuter 1967), but ancient authors mention Chamaerops humilis also in the eastern Mediterranean (see also Hantke 1983; Velitzelos and Schneider 1979; Friedrich 1978; Friedrich and Velitzelos 1986).

The recent distribution of Chamaerops humilis is restricted to Spain, Sicily, Morocco and Algeria. If one compares the eastern and western Mediterranean climatological conditions (especially in Crete. Kerkyra, Zakynthos, Naxos etc.) where Chamaerops humilis grows wild (Hantke 1983; Velitzelos and Schneider 1979), one notices that both palms (Chamaerops humilis and Phoenix theophrasti) should also live wild in the Mediterranean, because of favourable climatological conditions like 48.000 years ago. The recent climatic data for Santorini are: mean temperature: January: 11.0; July: 25.1; year: 17.4; precipitation 370.6 mm.

The palaeobotanical findings of Greece thus show that Chamaerops humilis is 'wild' in Greece; this is a botanical question for further research.

Yaltirik and Boydak (1989) mentioned two natural resources with Phoenix theophrasti from Turkey, that means that the distribution of palms extends to the Eastern countries.

The findings of Thera are rare witnesses of a historical evolution of plants in ancient Greece and Europe.

The work in the 'bims' of the caldera of Thera destroys the plant macrofossils of a unique occurrence in Europe and despite this outstanding geological monument (as the caldera was called by geoscientists) the entire history of the volcanogenic time-span of the Mediterranean, seen on the caldera walls, soon dies and vanishes.

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