Late Cenozoic Stratigraphy and Paleoenvironmental Change of the Coastal Area along the Sea of Japan

研究了北海道西北、北海道西南、青森、秋田山形、新泻、新州、北陆、三仁等8省的晚新生代地层学。建立了包括生物地层学、层序地层学和年代地层学在内的各省份岩石地层分类，完成了北海田至三仁的第三系地层对比。根据这项研究，每个省的新第三纪古地理地图都是在大约50万到100万年之间绘制的。在此基础上，绘制了日本海边境线内近纪古地理图6张。从化石（硅藻、有孔虫、放射虫、软体动物）、沉积和构造面等方面研究了日本古海近第三纪海洋环境。下面列举了一些重要的结果和问题。对日本东北地区中新世中期至中期沉积盆地浊积面进行了深入的研究。提出了粗颗粒沉积和海底扇形成的模型。讨论了硅质沉积物的焦点变化、沉积环境和沉积比例。泥岩中的有机质（干酪根）可用于沉积环境的重建。考察了有孔虫、软体动物和海洋脊椎动物等化石的地理和地层分布，并讨论了它们的变化。根据研究结果，提出了日本海东部边缘地区的重要海洋事件。中中新世早期，热带环境下大海侵开始，热带动植物未见踪影；中新世中期岛弧隆起开始，温带组合出现，日本海扩张加深，形成近代日本海的深海环境；中新世晚期，在日本东北部和边缘海域出现陆地区域，温带太平洋王国建立；上新世中期，出现严重的结晶运动，冷温带海洋生物南移。明确了古环境变化与组合的关系。少

Late Cenozoic stratigraphy was examined in eight provinces along the borderland of the sea of Japan, namely northwest Hokkaido, southwest Hokkaido, Aomori, Akita-Yamagata, Niigata, Shinshu, Hokuriku and San-in provinces. Lithostratigraphic classification inclusive of biostratigraphy, tephrastratigaraphy and chronostratigraphy, was established in each province and Heagene carrelatiorl from Hokkaida to San-in were completed.According to it, more than five sheets of Neogene paleogeographical maps of each province wore drawn at intervals of about half million to a million year. Moreover, in accordance with them six sheets of Neagene paleageographical map in the borderland of the sea of Japan were drawn.Neagene marine environment in the palea-sea of Japan was studied from the viewpoint of fossil (diatom, foraminifera, radiolaria, molluscs), sedimentary and tectonic faces. Some of important results and problems are cited as follows.The study an turbidits faces of sedimentary basin during mid … More dle Middle Miocene in northeast Japan was advanced. Some models an sedimentation of coarse materials and formation of submarine fan were proposed. Focus change of siliceous sediments, its sedimentary environment and the sedimentary ratio were discussed. Organic matters (kerogen) in mudstone is available for reconstruction of sedimentary environment. Geographical and stratigraphical distributions of fossils, such as foraminifera, malluscs and marine vertebrate assemblages were examined and their changes were discussed.From the results, important marine events in the east marginal area of the sea of Japan are mentioned. During early Middle Miocene time, commencement of large transgression under tropical environment, nothing of tropical fauna and flora; During Middle Miocene commencement of upheaval of island arc, appearance of temperate assemblage, expansion and deeping of the sea of Japan, formation of deep sea environment like the recent sea of Japan; during Late Miocene time, appearance of land area, in cardillera of northeast Japan and marginal sea, establishment of temperate Pacific realm: During Mid-Pliocene time, occurrence of serious crtistal movement and southing of cool-temperate marine organisms. The relationship between the change of paleoenvironment and assemblages was made clear. Less