Abstract
Thermoluminescence (TL) age determination was carried out for 18 samples from four pyroclastic flow deposits(Mutsugi, Kureishibaru, Furue and Yugawachi) of Unzen volcano, SW Japan. The TL growth curve method was used for quartz phenocrysts to determine the ages. Major inaccuracy of TL dating is caused in annual dose evaluation, especially in determination of beta rays contributions. Therefore, the beta ray correction was done by measurement of quartz phenocryst diameter on thin sections.
The TL ages for Mutsugi, Kureishibaru, Furue and Yugawachi pyroclastic flow deposits indicated 4.9±0.4 ka, 23±1 ka, 23±1 ka and 77±6 ka, respectively, which are average of 3 to 6 samples collected from same outcrop each. These ages consistent with 14C ages and stratigraphy identified by tephra.
