40 Ar ∕ 39 Ar constraints on the eruption history of the Christiana Volcano of the Christiana-Santorini-Kolumbo volcanic field, Greece

Abstract. The Christiana Islands group consists of three at present uninhabited islands 20 km SW of Santorini, Aegean Sea, Greece, that are the subaerial remnants of the Christiana volcano. The age of the Christiana Islands has been unclear and has been previously assumed to have started around the same time as the emergence of Santorini (600 ka). Other studies, based on seismic reflection studies have correlated volcanic deposits of the Christiana archipelago to Pliocene sedimentary layers. This study reports new groundmass 40Ar/39Ar ages of ten volcanic samples from Christiana Island. Subaerial Christiana volcanic rocks of the Upper Lava formation cluster tightly between 2.5–2.7 Ma with relatively small uncertainties (0.02–0.14 Ma). One sample dated much younger: 133 ka; this is most likely derived from the Middle Pumice Plinian eruption of Santorini. The 2.5–2.7 Ma age for Christiana volcano shows that all volcanic fields of the South Aegean Volcanic Arc (SAVA) were active around 3 Ma ago and started when oceanic crust arrived at 100 km depth below the SAVA volcanic fields after long periods of continental lithosphere subduction. The Christiana volcano was constructed when the local stress field showed NNE-SSW extension. During the transition from NNE-SSW to NW-SE extension the Christiana volcano became extinct and a period of >1.0 Ma with volcanic quiescence and/or low volcanic output followed until the start of submarine volcano Poseidon and present-day volcanic centres Santorini and Kolumbo.