Natural and Cultural Histories of San'in Region

研究的主要对象是海平面变化和泻湖的地理、文化和社会环境的综合研究，特别是中海湖和真地湖。在钻探、岩心取样和回声测深调查的基础上，重建了详细的地理发展，并讨论了10,000 y.b.p.以来的海平面变化。从全新世海平面变化的角度重新审视了中海湖和真司湖周围的许多低地考古遗址。我们祖先的活动已被新认识为多方面利用湖泊作为渔场、渔港和运输基地。周边低地为人类活动特别是水稻种植提供了便利条件。这些使得古出云的繁荣成为可能。研究了全球变暖导致的海平面上升对沿海泻湖地区的影响，如盐度增加、盐水侵入淡水含水层等。通过对中海湖沉积物岩心的地球化学研究，确定了中海湖全新世气候适宜期的沉积环境。研究结果将为预测未来全球变暖的潟湖环境提供基础信息。建立了一个研究沿海泻湖和河口盐斜行为的长期观测系统。该系统已在中umi湖成功实施，并将在不久的将来有助于控制无氧盐水的运动。该系统还在日本最著名的潮汐河之一岛根县Gonokawa河成功实施。本文从环境科学的角度对1963年启动的中海填海工程进行了讨论，并提出了合理利用和生态平衡的方案。

The main objects of the research are sea-level changes and synthetic studies on geographical, cultural, and social environments of lagoons, especially in Lakes Nakaumi and Shinji. The detailed geographic developments were reconstructed on the basis of drilling, core sampling and echo-sounding surveys and sea-level changes since 10,000 y.B.P.were discussed. Many lowland archaeological sites around Lakes Nakaumi and Shinji were reexamined from the view point of the Holocene sea level changes. The activities of our ancestors have been newly recognized as multi-sided using of the lakes as fishery ground, fishery ports and transportation bases. The surrounding lowland areas had provided convenient conditions for human activities especially for rice cultivation. These had made possible the prosperity of Paleo-Izumo. The effects of sea-level rise due to global warming on coastal lagoon areas such as salinity increase, salt water intrusion into freshwater aquifers, were examined. The depositional environment during the Holocene climatic optimum have been established from geochemical study of the sediment cores of Lake Nakaumi. The results will offer basic information for projections of lagoonal environments in future glob warming.A long-term observation system for the study of Halocline behavior in coastal lagoons and estuaries has been developed. This system was successfully carried out in Lake Nakaumi and would contribute to control the movement of oxygen-free saline water in near future, The system was also successfully carried out at River Gonokawa in Shimane Prefecture, one of the most famous tidal rivers in Japan.The Lake Nakaumi Reclamation Project, which was started in 1963, and have been suspected, are discussed from the view point of environmental sciences, and a program for wise use and balanced ecosystem has been proposed.