Radiocarbon dating of residual organic matter in travertine formed along the Yumoto Fault in Oga Peninsula, northeast Japan: Implications for long-term hot spring activity under the influence of earthquakes

Radiocarbon dating was performed on trace amounts of organic matter included in travertines formed along the Yumoto fault in Oga Peninsula, NE Japan. The reliability of the dating method was confirmed by the consistency of ages obtained with the stratigraphy of the travertine mound and the ratio of carbon stable isotopes. The radiocarbon chronology of the travertines shows that (1) the hot springs at Oga have been active for approximately 29,000 years, with average depositional rates ranging from 0.24 to 1.75 mm/yr, and (2) the principal hot spring activity has migrated southward with time. Variations in the accumulation rates and the progressive migration of the main focus of the hot spring activity imply irregular spring behaviour. This behaviour has not been influenced by paleoclimate, but may have been controlled by the earthquakes that occur frequently in the region around Oga Peninsula.