A date for volcanic eruption inferred from a siltstone xenolith

Abstract

We present a TL age determination of a heated siltstone xenolith found at Kueishantao, a volcanic island 10 km off the northeastern shoreline of Taiwan. Before this study, no reliable numeric age determination had been obtained for the volcanic rocks. Its age has long been desired due to its active tectonic environment. Previous studies of the other radiometric dating methods indicate a very young age for the eruption of this volcano, possibly later than 10 ka. However, reliable age is not allowed because it is younger than the lower dating limit. Our result shows a TL age of 7±0.7 ka for the lower part of the volcanic sequence, indicating that other volcanic eruptions occurred later than 7 ka. This finding suggests that the volcanic island, Kueishantao, has not ceased its igneous activity and is still active geologically.