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Studies to attain high accuracy in radiocarbon dating with AMS of sedimentary samples older than 30,000y.B.P.

研究利用 AMS 对距今 30,000 年以上的沉积样品进行放射性碳测年，获得高精度。

基本信息

批准号：
03640656
负责人：
NAKAMURA Toshio
金额：
$ 1.09万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

Radiocarbon (^<14>C) dating with accelerator mass spectrometry (AMS) has enabled us to measure ages of geological samples as old as 40 to 60 ky.B.P. with a reasonable accuracy. This study has been organized to test the reliability of ^<14>C dates of 40 to 60 ky.B.P. The samples are collected in geological and geographical fields, mainly selected from well-defined horizons, i.e., those horizons identified by tephrochronology.With this investigation, the followings have been clarified, concerning the age dating of old samples with a Tandetron accelerator mass spectrometer:(1)^<14>C dates are consistent with sedimentary horizons, for ages from 40 to 60 ky.B.P.(2)For ^<14>C dates beyond 60ky.B.P., a saturation of ^<14>C dates comes up, and ^<14>C dates are no more consistent with sedimentary sequences. The appearance of the plateau in ^<14>C dates is expected from the observation that dead graphite, which is too old to contain ^<14>C, showed apparent ^<14>C dates of 60 to 70 ky.B.P (average value: 65,080 y.B.P.).^<14>C dates are compared with those dates measured by some other dating methods in this investigation. The ^<14>C dates of charcoal collected from Tokyo pumice flow deposits are compared with a fission-track date of obsidian collected from Tokyo pumice deposits, and the ^<14>C dates of charcoal from the Ontake volcanic deposits with a K-Ar age of lava covering the deposits. The comparisons showed a good agreement. Details of the experiments are given elsewhere. Consistency tests among different dating methods are one of the important themes to be performed intensively.

用加速器质谱法（AMS）测定放射性碳（^<14>C）年代，使我们能够测量年龄在40至60千万年的地质样品的年龄。以合理的准确性。本研究的目的是测试40 ~ 60kyb.p.的^<14>C日期的可靠性。样品是在地质和地理领域采集的，主要选自定义明确的层位，即通过地层年代学确定的层位。通过这次调查，关于用Tandetron加速器质谱计测定老样品的年龄，澄清了以下几点：(1)^<14>C的年龄与沉积层位一致，年龄在40 ~ 60 ky.B.P之间。(2)对于^<14>C日期超过60kyb.p.。结果表明，^<14>C测年与沉积层序不一致。在^<14>C年代，高原的出现是由观测到的，因为死石墨太老而不含有^<14>C，显示明显的^<14>C年代为60至70 ky.B.P（平均值：65,080 y.B.P）。^<14>C的年代与本研究中其他测年方法测得的年代进行了比较。将东京浮石流沉积炭的^<14>C测年与东京浮石沉积的黑曜石的裂变径迹测年以及御竹火山沉积炭的^<14>C测年进行了比较，并对其进行了K-Ar年龄的熔岩覆盖。比较结果很一致。实验的细节在别处给出。不同测年方法之间的一致性检验是研究的重点之一。