The South Aegean forearc ridge, the Hellenic Arc, known also as the Peloponnese-Cretan ridge, separates the 3000 to 5000 m deep Hellenic "trench" to the southwest from the 1000 to 2000 m deep Cretan Sea basin to the northeast (Fig. 1). The large-scale internal structure of the Hellenic forearc ridge developed during the late Eocene-early Miocene in response to the collision of the Apulia microcontinent (attached to the African plate). At present only parts of the Apulia are exposed as most of it was subducted and/or accreted against the active European continental margin (the Pelagonian "terrane") (Thomson and others, 1998). The sedimentary cover of Apulia is mostly represented by the rocks of the Phyllite-Quartzites unit (PQU) and the Tripolitza unit (recrystallized limestone), which are exposed over wide areas on the Peloponnese-Cretan ridge. In this study we apply U-Pb dating of detrital zircons from the PQU and inherited zircons from arc volcanic rocks to constrain the depositional age and sources of the PQU.