Tianchi volcano, is a huge stratavolcano located on the border of NE China and North Korea The Millennium eruption of Tianchi volcnao, erupted at somewhat AD 1000, is one of the world biggest eruptions in the last 2000 years. Historical documents reveal that the last eruption may occurred in about 300 years ago(AD1668 and AD1702). Activity of this volcano is monitored by all modern methods. Potential eruptions of this world most dangerous volcano attract attentions from both the public and the scientific. However, better understanding of the historical eruptions of Tianchi volcano will help us to learn more about the future activity. Here we report our recent studies on major historical eruptions of Tianchi volcano.
And from: "Identification and correlation of visible tephras in the Lake Suigetsu SG06 sedimentary archive, Japan: chronostratigraphic markers for synchronising of east Asian/west Pacific palaeoclimatic records across the last 150 ka"
Which I was able to sign up for free and download.
In the 2nd paper: Tianchi/Baitoushan Millennium eruption of Tianchi Volcano B-Tm 50 E 0.921 e0.941 e 950 NW 1,8 The 0.921-0.941 is a range of calibrated C14 dates for this layer. These are taken from: "Utilising the large number of radiocarbon measurements (n > 600) from terrestrial plant macrofossils in the Lake Suigetsu SG06 record, we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka."
And since those dates are matched to the varves this gives a known historic eruption with a layer in the right place in lake Suigetsu.