Fission Track Dating of the Obsidians from Pyroclastic Flow Deposits

Abstract

Fission track ages of obsidians in the Aso pyroclastic flow deposits (Aso-1, 2, 3, 4) have been measured in order to bring some light on the history of the activity of the Aso volcano. As the diameter of the fission track has been considerably shortened by annealing, a correction of the age was made in the present study, using the results of the annealing examination. The fission track ages of obsidians from the Aso pyroclastic flow deposits are as follows: Fission track ages (×10⁵y.) Aso-4 0.29±0.14 Aso-3 1.03±0.42 Aso-2 1.54±0.60 Aso-1 2.60±0.76 V3.58±0.72