[SVC38-P13] Eruption age determination of the latest two lava flows and characteristics of volcaniclastic materials from the recent activity of Yokodake Volcano, Japan
Keywords:Yokodake Volcano, Latest lava, Eruption age determination, TL dating, Volcaniclastic materials from the recent activity
TL dating was performed by using poly-minerals (ca 10~50 µm) sample extracted from Y8 and Y9 lava. TL age of Y8 sample was 3.3 ± 1.2 ka. Y9 lava sample didn’t emit TL intensity. As for Y9 lava, we tried to estimate the age using VRM. However, the estimated ages were widely scattered. We conclude eruption age of the Y8 lava is ca. 3.3 ka, which is consistent with our previous paleomagnetic age of 3.35~3.85ka. On the other hand, five eruption ages of Y9 lava (0.60 ka, 1.80 ka, 1.90~1.95 ka, 2.20∼2.25 ka, 2.4~2.45 ka) are still remained.
We recognized light gray volcanic ash deposit just above Y9 lava which composed of sand to silt size and contained carbonaceous material. It may be comparable to NYk-1 tephra (Okuno, 1995). Four volcaniclastic layers were found at summit region and the lower layer is a possibility of being correlated with NYk-2 tephra (2.35~2.15 cal ka BP; Okuno and Kobayashi, 2010). Two volcaniclastic layers above NYk-2 tephra seem to be derived from Yokodake volcano, suggesting at least two volcanic eruptions were occurred after NYk-2 tephra eruption.