Reconstruction of high-resolution paleogeography in the Plio-Pleistocene

通过对更新世-更新世大规模火山喷发形成的广泛沉积盆地的对比，研究了日本晚第三纪沉积盆地的地层学和年代学。这些地质资料揭示了日本几个主要平原的古地理和地貌发育。本研究取得的主要成果有以下几点。在距今4 Ma(100万年前)至1 Ma之间，我们发现了至少12层分布广泛的上更新世盖层，其中包括九州中期1.3 Ma的Shikito-Ylowl Tephra。这些盖层标志着几十万年间隔的显著时间指标，并极大地促进了上更新世沉积的精度和分辨率的提高。我们研究发现的酒井火山灰(4.1 Ma)是日本已知的最古老的广泛分布的火山灰，由非常细小的火山玻璃组成，具有碱性的岩石化学成分。这项研究促进了广泛存在的…之间的关联取自关东平原地下的钻孔岩心样品和博索半岛和多摩丘陵的火山灰层中，有较多的SH层。利用这些Tephra数据揭示了0.6 Ma关东西平面的古地理和Fukaya-Ayasegawa断裂带的活动。经Tephra研究改善的关东平原地下地质结构表明，K Into活动断裂的活动是对日本海开张阶段形成于15 Ma的老基底裂缝的复活。本研究收集了北海道各地的非洲菊数据。我们揭示了托亚火山在更新世的活跃史。利用年代学方法详细揭示了宫崎县平原上更新世以来的地层和地貌发育情况。利用精确的盖菲拉对比，揭示了更新世阿萨马火山活动与阿萨马火山泥石流外流过程以及该地区地貌发育的关系。将改进后的Tephra对比和年代学方法应用于埃塞俄比亚的古人类学研究。较少

Stratigraphy and chronology of the late Neogene sedimentary basins in Japan were investigated through the correlation of widespread teparas derived from the huge volcanic eruption in the Plio-Pleistocene. The paleo-geography and landform development of several major plains in Japan were revealed by these geological data. Main results obtained by this study are as follows.1. We found at least 12 layers of widespread Plio-Pleistocene tephras between 4 Ma (million years ago) to 1 Ma including Shikito-Yallowl tephra from at 1.3 Ma from mid-Kyushu. These tephras mark the prominent time index of several hundred thousand years interval and greatly contributed to the advancement of accuracy and resolution of Plio-Pleistocene sediments.2. The Sakai volcanic ash (4.1Ma) which found in our research is the oldest widespread tephra known in Japan and consists of very fine volcanic glass with alkalic petrochemical composition.3. This study promoted the correlation of widespread tephras between the a … More sh layers in the boring core samples obtained from the underground of the Kanto Plain and the ash layers in Boso Peninsula and Tama Hills. The paleo-geography of the western Kanto Plan at 0.6Ma and activity of the Fukaya-Ayasegawa fault zone were revealed by using these tephra data.4. Underground geological structure of the Kanto Plain improved by tephra researches revealed that the movements of active faults in K into are rejuvenation of the old basement fractures formed at 15Ma in the opening stage of Japan Sea.5. Tephra data in various part of Hokkaido were compiled in this study. We revealed the active history of Toya volcano in the Pleistocene.6. The stratigraphy and landform development of the Miyazaki Plain in the Plio-Pleistocene were revealed in detail by this study using tephrochronology.7. The relationship between the activity of Asama volcano in the Pleistocene and the outflow process of mudflow from Asama volcano an I the landform development of the region were revealed by this study using precise tephra correlation.8. The tephra correlation and chronological techniques improved by our study were applied to the paleo-anthropologic research in Ethiopia. Less