In 2009, it was decided to make the Quaternary with its base at approximately 2.6 million years ago. Corresponding to this revision, Geological Survey of Japan, AIST has published VOLCANOES OF JAPAN (third edition), including Gelasian volcanoes (Nakano
et al., 2013). Naramata caldera, which is located in the northeastern part of the Gunma Prefecture, NE Japan, is one of such volcanoes. This caldera is made up of rhyolitic pyroclastics and overlying lacustrine sediments filling a depression 2 km in diameter. Fission-track age of zircons from rhyolitic pyroclastics was determined as 2.1±0.2 Ma.
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