The two main provinces of Pleistocene tephra eruption in the Mediterranean Sea are the eastern half of the Hellenic arc, represented by calc-alkalic and weakly alkalic material, and the Neapolitan area, represented by high-K2O material.

Of twenty distinctive ash layers that have been identified in Pleistocene deep-sea cores of the eastern Mediterranean, one is calc-alkalic ash that originated in the Minoan eruption of Santorini at about 3500 B.P., and another is trachytic ash that originated in the Citara-Serrara eruption on Ischia Island at about 25,000 B.P. Rb, Zr, and Y content has been analyzed in the upper and the lower ash from both the land and deep-sea cores and in three tephra deposits from the east Hellenic volcanoes of Nisyros, Yali, and Kos.

In addition to the K2O/SiO2 ratio, values of the trace elements Rb, Zr, and Y versus SiO2 in the ash layers can be used in correlating the ash layers and in tracing the source of ash. All relative K2O, Rb, Zr, and Y contents can be used to trace the source of ash to one of the two main provinces of tephra eruption. Zr and Y are most useful for identifying individual volcanoes as sources.

Good agreement of chemical analyses of correlatable samples of the two ash layers from land and deep-sea cores argues against major alteration of the glass shards or a measurable cation exchange between glass shards and sea water on the time scale of 25,000 yr.

First Page Preview

First page PDF preview
You do not currently have access to this article.