Studies on widespread tephras associated with Quaternary volcanism, sealevel fluctuations and climatic history in Japan

1在本研究项目中，在日本及其周边地区报告了11个晚第四纪的主要火山灰。所有这些特征和识别的岩相和地层方法。它们在火山学和第四纪研究中具有重要意义。广泛分布的玻璃质细颗粒灰起源于巨大的破火山口火山都被解释为coignimbrite灰福尔斯。用电子探针分析了火山玻璃碎片的化学成分，证明它是表征和鉴定日本岛屿周围海底火山灰的有力工具。3根据<^（230）Th> / <^（238）U>方法，估算了本州中部四个标志火山灰的年龄。- <^（238）U>放射性不平衡在火山岩的镁铁质矿物中观察到。4确定北方日本和九州南部的标志火山岩有利于对比和识别末次间冰期的海洋阶地，导致对年代框架的修订和对这些区域构造性质的认识。5南极和海底氧同位素值的垂直变化本文报道了对西北太平洋两个灰岩年代测定柱样的有孔虫试验，建立了日本周边深海沉积物年代学标准序列。

1 In this research project eleven major volcanic ashes of the Late Quaternary age are reported in and around Japan. All of them are characterized and identified by petographic and stratigraphical methods. They are of great significance in volcanology as well as Quaternary research. The widespread vitric fine-grained ashes which originated from gigantic caldera volcanoes are all interpreted as coignimbrite ash falls. This type of tephra should be the dominant class of widespread tephra.2 Chemical composition of volcanic glass shards analysed by EPMA proved to be a powerful tool in characterization and identification of submarine volcanic ashes around the Japanese islands.3 The ages of four marker tephras occurring in central Honshu are estimated by the <^(230)Th> / <^(238)U> method based on the <^(230)Th> - <^(238)U> radioactive disequilibrium observed in the mafic minerals of the tephras.4 Determinations of marker tephras in northern Japan and southern Kyushu are favorable for correlation and identification of marine terraces of the last interglacial age, resulting in revision of the chronological framework and recognition of the tectonic nature of these regions.5 Vertical changes in oxygen isotope values of the planktonic and benthic foraminiferal tests of the two tephrochronologically dated cores from the northwestern Pacific are reported, resulting in establishment of the standard sequence of deepsea sediment chronology around Japan.