Accurate dating for volcanic glass shards of middle Pleistocene widespread tephra determined by ITP-FT method and DC-FT method

ITP-FT法和DC-FT法对中更新世广泛分布的火山灰火山玻璃碎片的精确定年

• 批准号: 21740365
• 负责人: AOKI Kaori
• 金额: $ 3.16万
• 依托单位: Rissho University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Young Scientists (B)
• 财政年份: 2009
• 资助国家: 日本
• 起止时间: 2009 至 2012
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21740365/
• 关键词: テフロクロノロジー; 第四紀学; 年代測定; 火山灰編年; 第四紀; 火山ガラス; フィッショントラック; ITP-FT; DC-FT

In this study, I innovated Isothermal Plateau Fission Track（ITP-FT）method and Diameter Correction Fission Track（DC-FT）method to date the volcanic glass shards of early to middle Quaternary tephra. First of all, it was necessarily to check the precision of counting system on the basis of standard dating samples. The reflecting light of microscope is effective to identify the edge of each fission track and improve the precision to measure the track diameter. Then, in order to compare age determined by ITP-FT and DC-FT to age determined by another dating method, 138 tephra beds in marine sedimentary cores, which collected by SO202-INOPEX cruise in 2009, were employed. Geochemistry of such marine tephra was determined by the electron microprobe analyzer. In this point, the eruptive age determined by ITP-FT and DC-FT dating methods seems to match with tephrostratigraphy, radiometric age, biostratigraphy, and oxygen isotopic stratigraphy in northwest Pacific. Hence, ITP-FT and DC-FT ding methods is useful to date early to middle Quaternary glass materials.

本研究创新性地采用等温平台裂变径迹法（ITP-FT）和直径校正裂变径迹法（DC-FT）对第四纪早、中期火山碎屑岩的火山玻璃碎片进行了定年。首先，有必要在标准测年样品的基础上对计数系统的精度进行检验。显微镜的反射光可以有效地识别出裂变径迹的边缘，提高径迹直径测量的精度。然后，为了将ITP-FT和DC-FT测定的年龄与另一种定年方法测定的年龄进行比较，使用了2009年SO202-INOPEX巡航收集的138个海洋沉积岩芯中的火山灰层。用电子探针分析仪测定了这类海相火山灰的地球化学特征。在这一点上，ITP-FT和DC-FT测年方法确定的火山喷发年龄与西北太平洋火山灰地层学、放射性年龄、生物地层学和氧同位素地层学相吻合。因此，ITP-FT和DC-FT方法可用于早中第四纪玻璃材料的定年。