The medial offshore record of explosive volcanism along the central to eastern Aegean Volcanic Arc, part 2: Tephra ages and volumes, eruption magnitudes and marine sedimentation rate variations

We use the tephrostratigraphic framework along the Aegean Volcanic Arc established in part 1 of this contribution to determine hemipelagic sedimentation rates, calculate new tephra ages, and constrain the minimum magnitudes of (sub)plinian eruptions of thelast 200 kyrs. Hemipelagic sedimentation rates range from ~0.5 cm/kyr up to ~40 cm/kyr and vary laterally as well as over time. Interpolation between dated tephras yields an eruption age of ~37 ka for the Firiplaka tephra, showing that explosive volcanism on Milos is ~24 kyrs younger than previously thought. The four marine Nisyros tephras (N1 to N4) identified in part 1 (including the Upper (N1) and Lower (N4) Pumice) have ages of ~57 ka, ~63 ka, ~69 ka, and ~76 ka, respectively. Eruption ages for the Yali-1 and Yali-2 tephras are ~55ka and ~34 ka, respectively. The Yali-2 tephra comprises two geochemically and laterally distinct marine facies. The southern facies is identical to the Yali-2 fall deposit on land but the western facies has slightly less evolved glass compositions.

Overall, erupted plinian and co-ignimbrite fall tephra volumes range from < 1 to 56 km³ (excluding possible caldera fillings and ignimbite volumes), and 80% of the eruptions had magnitude 5.5 < M ≤ 7.2 (M = log(m)-7; m = erupted magma mass in kg). Twenty percent of the tephras represent 3.2 < M < 5.5 eruptions. The long-term average tephra magma mass flux through highly explosive eruptions of Santorini is estimated at ~40 kg/s. The analogous data for the Kos-Yali-Nisyros volcanic complex is less-well constrained but similar to Santorini.