Evaluation of impacts by sea-level rise on the alluvial deltas

本文对新泻平原西部约泻130 m岩心冲积沉积物进行了沉积相、生物相分析，并对54个样品进行了年龄测定。在此基础上，重建了末次冰期后新泻平原因海平面上升而形成的裂谷埋藏过程和沉积过程。近1万年来，该地区的降陷率约为3毫米/年。咸水入侵随淡水季和高水季水量波动、咸水水质和淡水水质的变化；测定了新泻阿野河河口水团沉积物和底泥沉积物的沉积学和化学特征。在淡季，咸水达到离河口12公里处。回声探测系统显示盐斜为弱混合型盐/淡水边界的盐水楔。为研究更多细粒沉积物的运动沉降提供了重要的基础资料。研究了越南南部湄公河三角洲德荣省巴登海岸长沙洲和沙滩在旱季和雨季的地貌和沉积特征。在侵蚀海岸和沉积海岸，枯水季和湿水季，随着滨流和海浪方向和速度的变化，滨沙坝和滩表面的地貌和沉积结构发生了变化。本文总结了2000 ~ 2005年在湄公河支流曹建河（Co Chien Rivet）进行的咸水入侵测量结果，并发表了论文。利用扫描声呐对2007年中崎大地震发生时新泻市中崎县出津崎海域海底表面出现的大量古木的发生模式进行了研究。结合海底木材的赋存模式，对绳纹木材的14C年龄和种类进行了综合分析，并对绳纹木材的形成和搬运过程进行了探讨。研究结果为详细考虑地层提供了基础数据。冲积三角洲和平原的演变过程

Sedimentological facies and biofacies have been analyzed and ages of 54 samples have been dated for alluvial sediments of 130 m core bored at Yoroigata, located in the western part of Niigata Plain On the basis of the results, burial process of the incised valley and sedimentary process of the Niigata plain by sea-level rise after the last glacial age have been reconstructed. Depression rate of the present area is about 3 mm/year during last 10,000 years.Changes of salt water intrusion as fluctuation of water discharge in low flow and high flow seasons, water quality of salt and fresh water; and sedimentological and chemical features of sediments in water masses and bottom sediments have been measured at the river mouth of Agano Rives Niigata. In the low flow season, salt water reached at 12 km from river mouth. Halocline by echo-sounding system revealed salt water wedge of weak-mixed type of salt/fresh water boundary. The important basic data has been get for movement and settle of fi … More ne-grained sediments.Prosperity and decline of longshore bars and sand beaches have been investigated geomorphologically and sedimentologically during dry and wet seasons at the Badon coast, Tra Vinh Province, Mekong River delta, south Vietnam. Geomorphology and sedimentary structure of surface of longshore bars and beaches have been changed as changes of direction and speed of longshore and wave currents during dry and wet seasons at the erosional and depositional coasts.The result of salt water intrusion measured along Co Chien Rivet one tributary of the Mekong River from 2000 to 2005 were summarized and published as papers.Occurrence mode of a lot of old woods appeared on the sea bottom surface off Izumozaki, Chuetsu district, Niigata, at the time of 2007 Chuetsu-Oki Earthquake has been investigated by scanning sonar. The analysis of 14C ages and species of woods were synthesized with occurrence mode on the sea bottom of the woods, and a formation and transportation processes of a lot of Jomon woods were discussed.The result of present study supplied the basic data for the detail consideration of formation. process of alluvial delta and plain Less