1. The Northern Joso upland is a diluvial terrace consisting of two surfaces nominated Juri-face and Genpoji-face, the specific height of which in comparison with the alluvial plain are more or less 10 meters and 15-20 meters, respectively.
2. Paleozoic and Granitic rocks found in the eastern margin of this area compose the base rock under the terrace gravels. This forms a foundation of the Kanto Tectonic Basin, inclining to the south-east with considerable undulations. Between these terrace gravels and the base rocks intervene the sediments covering the whole base made up of a large scale of alternation, gravelly and muddy layers which is liore than 100 meters thick, and considered to be identified with the Narita group. Furthermore, the fine grained rocks thought to be formed in pliocene or miocene epoch is formed under the afore mentioned sediments covering a part of the northern margin of this area.
3. Due mainly to these geological environments, the deep ground-water is for more dominant in the west and southwest than any other directions, supplying groundwater to the law land of the eastern district of Kinu giver around Simodate City, thus forms an eminant flowing well zone there.
As for the groundwater of terraces themselves, the lower Jari face is superior to the Genpoji face, concerning the shallow one, while deep ground water isn't dependent on such a terrace configuration but dominated by the geological structure of the Kanto basin. In this respect, it is thought to be able to expect a considerable amount of artesian groundwater in the gravelly layers (Yamato, Shimozuma and Kyowa formations) belonging so-called “the Narita group”, although slightly inferior to thoso around Shimodate City.
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