北関東,小貝川低地における立川期礫層の年代とその意義

概要

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The Kokaigawa Lowland around Shimodate, northern end of Ibaragi Prefecture, is filled up with the Tachikawa Gravels transported by the Paleo-Kinu River. Those are more than 15 meters in thickness and divided into three units; Upper Sand & Gravel, 13, 000-19, 000y.B.P, Middle Gravel, 20, 000-26, 000, and Lower Gravel, 34, 000-, as shown in Tables 1 and 2.Prior to 26, 000y.B.P, the Paleo-Kinu River was flowing from the Kokaigawa Lowland through the Kyowa Upland to the Sakura River Lowland (IKEDA, et al., 1977; SUZUKI, 1980: SUZUKI et al., 1981). About 26, 000y.B.P, middle-stream of the Paleo-Kinu River was captured by the Present-Kokaigawa Lowland, and Middle Gravel and Upper Sand & Gravel were deposited during 26, 000 to 20, 000y.B.P. After their deposi-tion, probably in Holocene time middle-course of the Paleo-Kinu River was changed again to the Present-Kinu River.
日本第四紀学会の論文