Deep sea tephra from Nisyros Island, eastern Aegean Sea, Greece

Abstract

Abstract Isopach maps have been constructed onland for the proximal deposits of the caldera-forming pyroclastic eruptions from the Quaternary volcano Nisyros and are augmented by a newly recognized Nisyros ash layer in the SE Aegean. The Lower Pumice eruption had a NE-SW dispersal direction with onland isopachs from 1–7m thickness and a vent position on the eastern side of the ancestral cone. A 3mm thick layer of Lower Pumice ash is found 75km away to the SW of the island at a depth of 133cm. This layer yields a Lower Pumice age estimate of 35ka. The Upper Pumice had a NNE dispersal direction with onland isopachs from 1–7m thickness and a vent position on the northern side of the island. No Upper Pumice ash has been found in the core record. Preliminary volume estimates derived from the isopach maps and the lack of regionally correlatable Nisyros ash deposits in the Aegean core record suggest that the caldera formation on the island was incremental and tephrostratigraphic markers suggest it occurred between c. 35 and 31 ka ago.