Japan Geoscience Union Meeting 2022

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-GL Geology

[S-GL23] Geochronology and Isotope Geology

Wed. May 25, 2022 9:00 AM - 10:30 AM 102 (International Conference Hall, Makuhari Messe)

convener:Takahiro Tagami(Graduate School of Science, Kyoto University), convener:Yuji Sano(Center for Advanced Marine Core Research, Kochi University ), Chairperson:Takahiro Tagami(Graduate School of Science, Kyoto University), Yuji Sano(Center for Advanced Marine Core Research, Kochi University)

9:30 AM - 9:45 AM

[SGL23-02] The radiometric age value and the geological event

*Ichiro Kaneoka1 (1.Earthquake Research Institute, University of Tokyo)

Keywords:radiometric age value, geological event, dating method, closure temperature

A radiometric age is obtained by using the variation of radioisotope and/or isotope ratios including a radiogenic isotope and the effect of crystals due to radioactive decay with time based on the assumption that radioactive decay occurs independently from the physical and chemical conditions of environments. The age vaue is required to satisfy such conditions as a closed system concerning related isotopes and the effect of crystals caused by the radioactive decay is not damaged by the secondary effects. Such conditions are different among each radiometric method. In each radiometric method, there are much endeavours to increase the reliability of obtained values.
On the other hand, the obtained age value is commonly treated as representing an age of geological event without detailed consideration.
However, in recent years, analytical precision of analytical instruments has much improved and quite a small analytical error is often assigned. Hence it is necessary to consider carefully how an age value correlates with a geological event. In this talk, I will discuss this point by showing several cases and demonstrate the importance to consider the required conditions of each dating method and correponding phenomena of the geological event.