Sea-Borne Pumice Deposits of Archaeological Interest on Aegean and Eastern Mediterranean Beaches

Particular areas are: Greece: on Crete (Kissamos, Ayia Marina, Rethimnon, Amnisos, Mallia, Gournia) and on Anaphi, Limnos, Paros and Samothraki; Cyprus: Ayia Irini (Morphou Bay); Israel: Tel Haratz and Dor.

Chemical and mineralogical analyses of numerous samples from each deposit reveal the presence of pumices from various eruptions of the Thera volcano (especially that of the Bronze Age). In addition, there are one or two examples of Yali pumices and a considerable quantity of rhyodacitic biotite-bearing pumice, which does not originate from the Santorini volcano and is found in all the above-mentioned deposits, even in Israel.

On the basis of stratigraphic considerations, this biotite-bearing pumice was probably laid down several decades later than the Late Minoan eruption of the Thera volcano.

INTRODUCTION

During the 1984 summer Antonio Praturlon and the author made the first discovery of rounded pumice inbedded in a palaeo-beach along the coast of the gulf of Kissamos (western Crete) (Fig. 2).

A systematic survey was carried out along the northern coast of Crete in search for sea-borne ancient pumices.

Different kinds of rounded pumices have been found in Ayia Marina, Rethimnon, Amnisos, Nirou Khani, Mallia and Kato Zakros. Other rounded pumices have been recognized on Anaphi, Paros, Limnos and Samothraki in the northern Aegean. In addition, other rounded pumices have been collected in Israel in two localities: Tel Haratz (near Ashdod) and Dor (on the ruins of the old Caesarea). The more we search, the more we find.

The presence of rounded sea-borne pumices on Aegean beaches is not surprising in itself. It is well known that there are several volcanoes in this area: besides the most famous and most studied Thera (Santorini), there are Milos in the Cyclades and Nisyros, together with Yali in the Dodecanese.

That sea-borne pumices could reach the coast of Israel is understandable, according to the maps of surface current patterns published by Pichler and Friedrich (1980) and McCoy (1980) (Fig. 1).

On the contrary, the presence of sea-borne pumices on Samothraki and Limnos (i.e. in the uppermost northern part of the Aegean) is difficult to explain. In fact, according to the above-mentioned current maps, sea-currents are south-bound in this area. The presence of submarine volcanic edifices in the northern Aegean cannot be ruled out. For the sake of impartiality, we have to consider the possibility that these two maps are wrong or vague. Further surprise arose when we analysed all the collected pumices. Among pumices from various Theran eruptions (but mostly from the Late Minoan or Bronze Age one), a constant presence of a rhyodacitic biotite-bearing type could be noticed. Biotite-bearing pumices of rhyodacitic composition from the Ayia Irini excavation on Cyprus were first studied by Fornaseri et. al. (1976). They did not succeed in recognizing the origin of this anomalous pumice. In this case, as well as in others, biotite-bearing rounded pumices and Theran Late Minoan ones were found mixed together on a palaeo-beach and on Roman ruins.

A huge block of biotite-bearing pumice has been found in a Middle (?) Minoan tomb at Gournia (Crete). This sample has been analysed by Pichler and Schiering (1984): they ruled out the possibility that this kind of pumice originated from Thera, Lipari, Milos, Nisyros or Yali, but they did not link this finding with that on Cyprus.

Dimitri Jaranov (1939) indicated the presence of sea-borne rounded pumices in palaeo-beaches of the island of Samothraki, and assumed a Theran origin.

Max Pfannenstiel (1952) communicated the presence of rounded sea-borne pumices in Palestinian terraces. He suggested a Liparian origin.

Spyridon Marinatos (1932) found huge quantities of rounded pumices on the ruins of a Minoan Villa at Amnisos. Without analysis, he linked all of them to the (then not famous) Theran eruption (1939).

Yannis Tzedakis, during the excavations of the Minoan settlement of Kastelli in Khania (Crete) (Tzedakis 1976) discovered a pumice bed at a level which he attributed to LM IA.

Rapp, Strathmor and Henrickson (1973) identified sea-borne pumices from Thera in an archaeological excavation in the Peloponnese.

Francaviglia (1986), by means of comparative analyses of various Aegean pumices, has been able to come to the conclusion that the Kastelli pumices originate from the Late Bronze Age eruption of the Santorini volcano.

The author of this paper has had the possibility of re-sampling and/or re-analysing pumices from Gournia (kindly given by Professor Hans Pichler) as well as pumices from Cyprus (kindly given by Professor Mario Fornaseri) and pumices from Israel (thanks to the invaluable help of Dr Akiva Flexer, Dr Nathan Bakler and Dr Avi Lifschitz). He went to Samothraki in order to sample those pumices from Cape Akrotiri mentioned by D. Jaranov.

Rounded pumices from palaeo-beaches of the islands of Paros and Limnos have been collected by Arch. Luciano Cessari.

From the XRF-analyses, carried out by the author, on all the above-mentioned pumices we learn that:

1. The rhyodacitic pumices are easily distinguishable from Santorinian pumices of the Upper Pumice Level or Bimsstein, oberer, or Bo (Neumann van Padang, 1936): see Al₂O₃-SiO₂ and K₂O-SiO₂ diagrams (Fig. 3 and 4).
2. It is possible to distinguish between pumices from the various Theran pyroclastic eruptions (Francaviglia, volume two of this Congress); two kinds of pumices are recognizable on the ruins of the Villa Marinatos excavated at Amnisos in 1928. Unfortunately, we will never know whether the pumices he found in the Villa well (Fig. 5) are of Santorinian Bronze Age origin or from elsewhere.
3. Biotite-bearing puinices are present on the palaeo-beaches of Zakros, and Nirou Khani - i.e. in the vicinity of the Minoan sites which have been excavated by Nikolaos Platon (1952, 1969). Unless we have access to the stores of the Archaeological Museums of Iraklion and Sitia, in which those pumice are held, we will never know whether the volcanic event which produced the pumices in question was Thera or an unknown one, which erupted the biotite-bearing pumices; all the pumices collected on Samothraki belong (with a few exceptions of Santorini origin) to the unidentified biotite-bearing type.
4. At Paros, Limnos, Anaphi, Mallia and Zakros pumices of the unidentified type co-exist with pumices from the famous Theran Late Minoan eruption. This circumstance allows us to deduce that they are almost coeval. The age of this famous eruption is a matter of great controversy: this eruption is now dated to 1645 BC - the oldest dating ever made (Hammer et al. 1987).
5. At Tel Haratz, the pumices mentioned by Bakler et al. (1985) belong to the biotite-bearing unidentified type. According to the dates given by these authors, the pumices of Tel Haratz could be of Middle Minoan age. Even in the case of Dor (Caesarea), pumices of the unidentified type are found mixed together with Theran Late Minoan pumices as well as with other pumices of unknown origin.
6. Furthermore, in the case of Amnisos, two kinds of pumices - the one biotite-bearing and the other Theran Late Minoan - are mixed together on the hill behind the Villa, at 10 to 15 m a.s.l. This could be the first true evidence for tsunami effects. In fact, the pumices discovered by Marinos (1963) and Marinos and Melidonis (1971) at some 250 m a.s.l. on Anaphi and thought to have been thrown up by a Theran Late Minoan tsunami, are definitively of ballistic and eolian transport. Anyway, they belong to the Santorinian Lower Pumices level (Neumann van Padang's Bimsstein, unterer, or Bu, 1936) - i.e. 100,000 years old.

CONCLUSIONS

It is important to see how pumices of this still mysterious eruption are more widespread than those of the Theran Late Minoan eruption.

From a mineralogical point of view, the source of these mysterious pumices could be related to the formation of the plateau-tuff of Kos (Dodecanese; Keller 1966). Nevertheless, the pumice analyses carried out by Keller differ slightly from those of the author, although their mineralogical composition is very similar. Keller himself (pers. comm.) rules out any possibility that the unknown biotite-bearing pumice has anything to do with Kos plateau-tuffs.

Furthermore, one cannot rule out the possibility that these unidentified pumices may have been erupted by a volcano which later entirely collapsed into the sea. Most likely, the unknown volcano is one of the less-studied in the region between Greece and Turkey.

Finally, if such a huge amount of pumice can be found in the whole eastern Mediterranean, tephra actually produced during that volcanic event should be detectable on the marine bottom. A re-analysis of the 'Upper Tephra Layer' cores sampled by the R/V Trident (McCoy 1980) is strongly urged.

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