The Medial Offshore Record of Explosive Volcanism Along the Central to Eastern Aegean Volcanic Arc: 2. Tephra Ages and Volumes, Eruption Magnitudes and Marine Sedimentation Rate Variations

Abstract

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 the last 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 ∼55 ka 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 ignimbrite 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.