Search

The Milos, Christiana‐Santorini‐Kolumbo (CSK) and Kos‐Yali‐Nisyros (KYN) volcanic complexes of the Aegean Volcanic Arc have repeatedly produced highly explosive eruptions from at least ∼360 ka into historic times and still show recent unrest. We present the marine tephra record from an array of 50, up to 7.4 m long, sediment cores along the arc collected in 2017 during RV Poseidon cruise POS513, which complements earlier work on distal to ultra‐distal eastern Mediterranean sediment cores. A unique set of glass‐shard trace element (LA‐ICPMS) compositions complements our major element (EMP) data on 220 primary ash layers and 40 terrestrial samples to support geochemical fingerprinting for correlations with 19 known tephras from all three volcanic complexes and with the 39 ka Campanian Ignimbrite from the Campi Flegrei, Italy. The correlations include 11 eruptions from CSK (Kameni, Kolumbo 1650, Minoan, Cape Riva, Cape Tripiti, Upper Scoriae 1 and 2, Middle Pumice, Cape Thera, Lower Pumice, Cape Therma 3). We identify a previously unknown widespread tephra from a plinian eruption on Milos (Firiplaka Tephra). Near the KYN we correlate marine tephras with the Kos Plateau Tuff, the Yali 1 and Yali 2 tephras, and the Upper and Lower Pumice on Nisyros. Between these two major tephras, we found two tephras from Nisyros not yet observed on land. The four Nisyros tephras form a systematic trend toward more evolved magma compositions. In the companion paper we use the tephrostratigraphic framework established here to constrain new eruption ages and magnitudes as a contribution to volcanic hazard assessment. Plain Language Summary: The Aegean Volcanic Arc comprises the Milos, Christiana‐Santorini‐Kolumbo and Kos‐Yali‐Nisyros volcanic complexes that present particularly high threats for humans and economy due to abundant highly explosive eruptions in the past. The systematic catalog of how eruption products are dispersed on the seafloor (marine tephras) with time provides information on the number and recurrence of eruptions, on their size, and intensities and is thus essential to quantitatively assess future volcanic hazards and risks. During RV Poseidon cruise POS513 in the Eastern Aegean Sea we recovered 50 sediment cores up to 7.4 m long. More than 220 tephra deposits (e.g., volcanic glass shards) from these eruptions were identified. Glass shard compositions from all layers were used for subsequent geochemical fingerprinting to correlate them with 19 known onshore Aegean eruptions as well as with the 39 ka Campanian Ignimbrite eruption from the Campi Flegrei, Italy. Correlations with 11 eruptions from Christiana‐Santorini‐Kolumbo are established. We identify a previously unknown widespread tephra from an eruption on Milos (Firiplaka Tephra). At the eastern region of the arc, we correlate 7 marine tephras with the Kos‐Yali‐Nisyros volcanic complex. Key Points: Marine tephrostratigraphy for the Aegean ArcChemical fingerprinting to correlate on and offshore tephras [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: Sediment cores from the seafloor of the eastern Aegean Sea contain numerous ash layers from (sub)plinian eruptions from the Aegean Volcanic Arc that were correlated in Part 1. These correlations facilitate determination of sedimentation rates of ∼0.5–∼40 cm/kyr within the hemipelagic sediment bracketing the dated tephras. Sedimentation rates show temporal and lateral variations in the context of climate changes, and regional tectonics. Exceptionally high hemipelagic sedimentation rates within the last 4 kyrs, are linked to the 3.6 ka Minoan and the 1650 AD Kolumbo eruptions that emplaced abundant erodible tephra. Using the sedimentation rates we additionally determine the ages of hitherto undated tephras. We deduce an age of ∼37 ka for a Milos eruption, as well as ∼57 ka to ∼76 ka for marine Nisyros and ∼34 and ∼55 ka for Yali tephras, for which previous dating attempts yielded controversial ages. The ash distribution in the marine realm of up to 105 km2 represents a major fraction of the erupted tephra volumes that range from <1 to 56 km3, placing 60% of the investigated eruptions into magnitude category M6, 20% into M7, and 20% into M3 to M5 classes. Over the past ∼200,000 years, Santorini discharged magmas at an average rate of ∼40 kg/s. Key Points: Tephrochronology for the Aegean Arc eruptionsSedimentation rate variability in the Aegean SeaEruptive volumes and masses for the major Aegean Arc eruptions [ABSTRACT FROM AUTHOR]