土岐砂礫層堆積地域に立地する湧水湿地の成因と形成時期

概要

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Some field surveys of marshes around Tajimi, Japan, were carried out to determine the origin of the spring-water marshes distributed in the Tono area of Gifu prefecture. Microtopography, geological features, soil, and groundwater around the marshes were investigated. It became clear that the marshes are on different geomorphic surfaces, such as upper and lower side-hollows, terraces, channelways, and bottomlands. Terraces were formed around the boundary between the Toki gravel formation and the basement stratum, and they were made by the collapse of the gravel bed. The marshes located on terrace surfaces are the most upper part marshes in the valley. Other marshes were formed on the down-stream side of the terraces. This area received the block movement after the Tertiary Period, and was divided into many parts. The basement stratum was located to the various altitudes, and the marshes were formed above various sea levels. The marshes' formation started after MIS (Marine isotope stage) 3, in terms of the age of terrace formations around the Toki River.
2013-04-25