AMS radiocarbon dating of the Sakurajima tephra group, Southern Kyushu, Japan

Abstract

Sakurajima volcano is located on the southern rim of Aira caldera, southern Kyushu, Japan. To establish the chronology of the Sakurajima tephra group, we perform AMS 14C dating mainly of soil samples closely relating to tephra layers. We point out that non-disturbed tephra layers can indicate good depositional conditions of the soil layers (continuity of soil accumulation, non-existence of bio-turbation), and can be a barrier to prevent movements of soil organic matter along the profile. The CN ratio can be a promising indicator of the soil decomposition.The first eruption of Sakurajima volcano occurred at 23 ka, shortly after the ignimbrite eruption of Aira caldera (24.5 ka). The first stage, “Old Kita-dake”, ended by 20 ka. After an 8 500 yr break, the “Young Kita-dake” stage started at 11.5 ka with the Satsuma eruption. This stage continued until 3.5 ka with repeated eruptions of an 800 ∼ 2000 yr recurrence interval. For historical eruptions in the “Minami-dake” stage, the calibrated year ranges are consistent with calendar dates based on historical documents.