Chronology of Tephra Layers in Southern Kyushu, SW Japan, for the Last 30, 000 Years

Abstract

Many tephra layers erupted from volcanoes in southern Kyushu, SW Japan. This paper reviews chronological studies of tephra layers during the past 30, 000 years in this area. The methods for determination of eruption ages are classified into four categories: (a) comparison with historical documents, (b) position on the calibration curve, (c) projection of ¹⁴C dates to the calibration curve, and (d) estimation from stratigraphic position. Eruption ages of two widespread tephra, the Kikai-Akahoya (K-Ah) and the Aira-Tn (AT) are estimated to be 7.3cal ka BP and 29cal ka BP based on their positions on the calibration curve. Eruptions preceding and following the large-scale ignimbrite eruptions occurred within 1, 000 to 3, 000 years. Eruption ages of the Sakurajima-Satsuma (Sz-S/P14), Ikedako (Ik) and Kirishima-Mi-ike (Kr-M) tephras, widely distributed in southern Kyushu, are approximately 13cal ka BP, 6.4cal ka BP, 4.6cal ka BP, respectively. Thus, it seems that the Ik tephra erupted after an interval of about 1, 000 years from the K-Ah eruption. In order to estimate precisely this time interval, we have to determine the position of the Ik tephra on the calibration curve.