OBSIDIAN HYDRATION DATING FROM HYDROGEN PROFILE USING SIMS: APPLICATION TO IKARIAN SPECIMENS IOANNIS LIRITZIS, NIKOLAOS LASKARIS INTRODUCTION The early seafaring prior to the Neolithic (ca. 7 th millennium BC) constitutes a controversial issue in Aegean archaeology and generally in the Mediterranean (SAMPSON et al. 2010; LASKARIS et al. 2011 and references therein). However, current evidence from systematic research in different parts of the Aegean started gradually changing this picture and opened up new dynamics for understanding the character of exploitation and the importance of early coastal and island environments; see the example of Crete (KOPAKA and MATZANAS 2009; STRASSER et al. 2010), the new site of Ouriakos on the island of Lemnos (dated according to preliminary evidence to the end of the Pleistocene and possibly to the beginning of the Holocene ca. 12,000 BP; N. Eustratiou, pers. comm. 2010), and the new Middle Palaeolithic site in Agios Eustratios Island (A. Sampson, pers. comm.). Our contribution sheds new light on the Late Pleistocene/Early Holocene (ca. 12 th millennium BP) exploitation of obsidian sources on the island of Melos in the Cyclades. The main source of information for these early visits on the island of Melos comes from Franchthi cave in the Argolid. Provenance studies of the material from this site indicated its Melian origin but obsidian hydration dating was not applied to the artefacts recovered. Regarding the presence of obsidian at Youra, Kythnos, Franchthi, Ikaria, and Attica several routes could be considered as possible: a direct ones and via a chaines operatoire model that include distances of ca. 120 km and crossings of ca. 15-20 km between islands (SAMPSON 2008; BROODBANK 2006, p. 209). The presence of obsidian in mainland and island sites indicates that these exploitations included successful return journeys (BROODBANK 2006, p. 209). The new obsidian hydration dates presented below (Table 3) are part of the combined work published elsewhere in LASKARIS et al. (2011), and employ the novel SIMS technique and SIMS-SS method (Fig. 19), that offers a new reliable source of absolute dating. Since the archaeological evidence of the presence of obsidian in levels that antedate the food production stage could have been the result of trade or the intrusion of younger age obsidian artefacts from the overlying Neolithic layers (see the discussion Liritzis, I & Laskaris, N (2012) Obsidian hydration dating from hydrogen profile using SIMS: applications to Ikarian specimens. Folia Quaternaria, Vol.80, 45-54.