Occurrence, stratigraphy and geochemistry of Late Quaternary tephra layers in the Aegean Sea and the Marmara Sea

Several discrete tephra layers occur in 2.5–10.3 m-long cores from the Aegean Sea, whereas a single tephra is identified in 3.5–9.7 m-long cores from the Marmara Sea. Major and trace-element data on these tephras delineate eight distinct groups. The geochemical data and multivariate statistics allow the correlation of the tephra layers with six previously described marine tephras from the eastern Mediterranean Sea; potential terrestrial sources are suggested for the others. The chronostratigraphy of the tephra layers was established using several radiocarbon dates and the oxygen isotope stratigraphy from two long piston cores. Four widespread tephra layers occur within the upper Quaternary sediments of the Aegean Sea. The two youngest widespread tephra layers were derived from the Santorini volcano of south-central Aegean Sea: Z2 (the Minoan eruption, ca. 3.6 ka) and Y2 (the Cape Riva eruption, ca. 21.7 ka). The Y2 tephra is also identified in three piston cores from the Marmara Sea. The two older widespread tephra layers originated from the eruptions which emplaced the Campanian Ignimbrite of the Italian Volcanic Provinces (i.e., the Y5 tephra, ca. 39.3 ka) and from the Nisyros volcano of the southeastern Aegean Sea. The consistent occurrence of the Nisyros tephra below the Y5 tephra confirms similar findings in a lake core on the Island of Lesbos. Linear extrapolations using the oxygen isotope stratigraphy suggest an age of 42–44 ka for the Nisyros eruption. Three additional tephra layers with a limited regional distribution are identified in the Aegean Sea cores. Two of these tephras originated from the Yali volcano of the southeastern Aegean Sea and from the Aeolian Islands (i.e., X1 tephra). A series of six mugearite tephra beds in the South Skiros Basin is interpreted as a set of redeposited turbidites.