Detection of the widespread tephra beds since Miocene in Japanese Islands and the investigation of the modes of their distribution and deposition

1.通过日本海一侧、太平洋一侧和中部山区（如新泻地区、秋田地区、房总半岛、卡克川地区、长野地区等）对日本列岛中新世以来广泛分布的火山灰层进行了探测，结果在这些地区之间对比了10多个大面积火山灰层。特别是对Znp-Ohta火山碎屑层（4.0Ma）和Omine-SK 110火山碎屑层（1.6Ma）的广泛探测，为地质和生态重建提供了有用的基准面。2、在分散和沉积模式的研究方面，特别是对水下沉积物重力流沉积及其搬运和沉积机制的认识。结果表明，上越火山灰和SK 050火山灰具有典型的浊流特征，而SK 110火山灰则以近似活塞流的形式向下流动。此外，Omine-SK 110火山喷发可能是在长野西部地区的陆地上喷发，进入新泻地区的水下环境，并进一步沿着距离陆地火山源450 km的海底槽沿着流向秋田地区。这些调查结果在2006年8月的第17届国际塞迪心理学大会上报告。

1. Detection of the wideaspread tephra beds since Miocene in Japanese Islands was achieved through the Japan Sea side, the Pacific Ocean Side and cenrtal moun taineous regions, such as Niigata region, Akita region, Boso Peninsula, Kakegawa region, Nagano region and so on. In results, more than 10 widearea tephras were correlated among these regions. Especially, the Znp-Ohta Tephra Bed(4.0Ma) and the Omine-SK110 Tephra Bed(1.6Ma) were detected widely, making useful datum plan es in geological and geoecological reconstruction.2, As for the investigation of the modes of dispersion and sedimentation were achieved especially on the recognition of subaqueous sediment gravity flow depos its and their mechanism of transportation and sedimentation. In results, several types of gravity flows were clarified: the Joetsu Ash and the SK050 Tephra show typical turbidite character, while the SK110 Tephra was supposed to flow down as nearly plug flow condition. In addition, the Omine-SK110 Tephra was possibly suspcted that it erupted on-land in the western Nagano region, and entered in suba queous environment in the Niigata region, and further flowed down to the Akita region along the submarine trough 450km far from the on-land volcanic source The results of these investigations was reported at the 17th International Sedi mentological Congress on August, 2006.