Chronological study on widespread tephra and volcanic stratigraphy of the past 100,000 years

Abstract

Widespread tephra layers provide time maker for geological records, including the eruptive history. This paper reviews the recent progress in chronological studies on widespread tephra and volcanic eruptions over the past 100,000 years in and around the Japanese Islands. Tephrochronology is highly useful for assessing the reliability of various age determination methods. Outcrops and core samples recording stratigraphic relationships are very important. Radiocarbon ages obtained by accelerator mass spectrometer have been calibrated to calendar ages throughout the past 50,000 years by using the Lake Suigetsu dataset to establish the IntCal13 calibration curve. However, because varve chronology always includes some counting errors, it remains difficult to implement with one-year accuracy. Recently, the discovery of AD 775 ¹⁴C spike revealed the eruption age of B-Tm tephra to be AD 946. By using ¹⁴C spike and oxygen isotope dendrochronology, it will be possible to extend the application range of annual tree rings to establish a calibration curve. For volcanic eruptions older than 50,000 years, K-Ar, luminescence and fission-track age determinations have been reported. Unspiked K-Ar, ⁴⁰Ar/³⁹Ar, single-aliquot regeneration-dose red thermoluminescence, and isothermal red thermoluminescence dating can also provide useful ages. Varve chronology, dendrochronology, marine isotope stage, and magnetostratigraphy can link results to environmental changes.