Dating of Quaternary with ESR, TL and OSL methods : intercomparison

电子自旋共振（ESR）、热释光（TL）和光释光（OSL）等方法基于相同的原理，在第四纪地质年代测定中有着广泛的应用，其应用范围超过了放射性碳法。然而，这些仍然被认为是可行的方法。在本项目中，这三种方法被应用于不同已知年龄的相同火山碎屑样品，以便获得的年龄可以相互比较，也可以与已知年龄进行比较。从Zenigame-Menagawa、Shibahara、Shirakawa-Ten'ei、Shirakawa-Saigo、Nantai-Shichihonzakura、Ikedako、Irito Aira-Tanzawa（Irito火山灰岩）、Aira-Shiko、Aira-Iwato、Kikai-Kuzuhara、Ata-Torihama、Kuju-1、Kuju-Handa和AT火山岩中提取了石英颗粒。用ESR和等温热释光方法获得了自然累积剂量。在本研究中发现，OSL是不适合测量日本tefras，因为再累积率太大，以获得可靠的累积剂量。用低本底γ能谱测量样品中U、Th和K的浓度，得到天然剂量率，等温TL年龄与已知年龄一致，ESR年龄在100 ka以前的范围内不太一致，但在较老年龄的样品中有时年龄很分散。问题可能是添加剂剂量法，其中伽马射线剂量被施加到样品上，以观察信号强度的增加，信号强度被外推到零纵坐标，以获得自然累积剂量。对信号再生进行了初步实验，发现该协议的统计误差变得更小。

ESR(electron spin resonance), TL(thermoluminescence), and OSL(optically stimulated luminescence) dating methods, based on the same principle, have wide applications of age determination in quaternary in the range beyond that of radiocarbon method. However, these have still been considered to be viable methods. In the present project, these three methods were applied to the same tephra samples of various known ages so that the obtained ages can be compared with each other, also with the know ages. Tepharas are also appropriate samples in the present project in the aspect that they are important key layers in many geological contexts.Quartz grains were extracted from Zenigame-Menagawa, Shibahara, Shirakawa-Ten'ei, Shirakawa-Saigo, Nantai-Shichihonzakura, Ikedako, Irito Aira-Tanzawa (Irito Ignimbrite), Aira-Shiko, Aira-Iwato, Kikai-Kuzuhara, Ata-Torihama, Kuju-1, Kuju-Handa, and AT tephras. Natural accumulated doses were obtained by ESR and isothermal TL methods. It was found in the present study that OSL is not appropriate for measurement of Japanese tephras because the rate of recupelation is too large to obtain reliable accumulated doses. Natural dose rates were obtained from the concentrations of U, Th and K concentrations in the samples which were measured by the low background gamma ray spectroscopy.Isothermal TL ages were consistent well with the known ages while ESR ages are not so much inconsistent in the range younger than 100ka, but sometimes the ages were so much scattered in the samples of older ages. The problem should probably be the additive dose method where the gamma ray dose were applied to the samples to see the increase of the signal intensities which are extrapolated to the zero ordinate to obtain natural accumulated doses. Preliminary experiments on signal regeneration were performed to find the statistical errors become much smaller with this protocol.