LATE GLACIAL FRESHENING OF THE LEVANTINE BASIN: ISOTOPIC EVIDENCE FROM ISKENDERUN BAY

Recently the Black Sea, the Marmara Sea, and the Levantine Basin have been studied in search of evidence for Noah’s Flood (Ryan et al., 1997). They proposed that once rising postglacial sea level reached the northern sill of the Bosporus it catastrophically flooded late Glacial basin (-140 m below present). However, Aksu et al. (2002) proposed that persistent Holocene outflow from the Black Sea into the Eastern Mediterranean contradicts that hypothesis. The main goal of our study is to verify a possible influence of the Black Sea outflow on the post-Glacial Eastern Mediterranean exemplified by Iskenderun Bay (eastern Levantine Basin), using isotopic analysis of planktic (G. ruber) and benthic (buliminids, Ammonia tepida and Porosononion martkobi) foraminifera from 5 cores containing sediments from the last 14 ka. This study is a part of the international Avicenne project funded by the European Union (1993-1996). Our data revealed that d¹⁸O values of planktonic foraminifera from Iskenderun Bay (-2.03 to -0.17‰) are more negative (lighter) than those from the Levantine Basin (-1.42 to 0.6‰; Sperling et al., 2003) and totally different (0.1 to 1.9‰; Aksu et al., 2002) than those of the Marmara Sea. Benthic foraminifera have significantly more positive d¹⁸O values (0.2 to 1.1‰) compared to planktonic foraminifera indicating a vertical water mass structure in the Iskenderun Bay during the last 14 ka. The d¹⁸O values of benthic foraminifera from the Marmara Sea (Aksu et al. 2002) are remarkably more positive (up to 9‰) than those in Iskenderun Bay and to isotopic records from the Levantine Basin and the Marmara Sea. The different isotopic values of foraminifera from the eastern part of the Levantine Basin (including Iskenderun Bay), the Sea of Marmara and the Black Sea suggest that efficient connections and water exchanges were missing among these basins in the last 14 ka and that the Black Sea outflow (if any) had no significant effects upon the Levantine Basin. Another contributor of southern Mediterranean origin, such as the Nile River (Rossignol-Strick et al., 1982; ODP Leg 160, Scientific Results) could be responsible for the freshening of the Levantine Basin, contradicting the Aksu hypothesis. In Iskenderun Bay, an additional freshwater source could have been provided by the Ceyhan River (Spezafferi et al., 2000).