琵琶湖高島沖ボーリングコアの火山灰層序

概要

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In 1986, Takashima-oki core boring was carried out in the central part of Lake Biwa, as shown in Fig. 1. The core samples are about 141 meters in total length and composed mainly of dark greenish grey silty clay sediments ranging in age from the middle Pleistocene to Holocene. Approximately 45 distinct volcanic ash layers and 31 volcanic ash-horizons which do not form megascopically distinct layers are found in the core sediments. Stratigraphy, lithology and petrography of the volcanic ashes are investigated, and the following results are obtained. 1) Tephrostratigraphy and properties of each volcanic ashes are made clear, and summarized in Figs. 2, 3 and Table 1. 2) On the basis of the stratigraphic positions and properties of volcanic ashes, the Takashima-oki and the 200m boring core samples from the bottom of Lake Biwa are correlated with each other as shown in Fig. 4, Sixteen corresponding volcanic ashes are found in these cores. 3) Five well-known widespread volcanic ash layers are discovered in these core sediments from Lake Biwa such as Kikai-Akahoya, Ulreung-Oki, Aira-Tn, Aso-4 and Kikai-Tozurahara volcanic ashes.
地学団体研究会の論文
1991-03-25