Ueno Basin

A basin in the mid-west of Mie Prefecture. It is also called the Iga Basin. It is a rift basin with a basin floor elevation of about 130 meters. The Nunobiki Mountains in the east and the Takami Mountains in the south are high barriers of 700 to 800 meters that separate it from the Ise Plain, while the Kasagi Mountains in the west are slightly lower, and the Minakuchi Hills in the northeast are even more gentle, separating it from the Omi Basin. From the end of the Tertiary Period to the Pleistocene (Pleistocene Epoch), most of the basin was located at the bottom of a lake called Kobiwako. It is particularly old in the southern part, and the Iga Formation, the lowest part of the Kobiwako Group, is widely distributed from the vicinity of Nabari City to the hills to the north. The basin is divided by small faults into the Ueno Basin in the narrow sense near the former Ueno City (now the center of Iga City), as well as the Nabari Basin, Oyamada Basin, Ayama Basin, and others, all of which belong to the Kizugawa River basin. There are two cities, Iga and Nabari, and the JR Kansai Main Line, Kintetsu Railway Osaka Line, and Meihan National Highway cross the basin, and the Iga Railway Iga Line runs through it.

[Tatsuo Ito]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

三重県中西部にある盆地。伊賀盆地(いがぼんち)ともいう。地溝性構造盆地で盆地底高度は約130メートル。東の布引(ぬのびき)山地、南の高見(たかみ)山地が700～800メートルの高峻(こうしゅん)な障壁となって伊勢(いせ)平野とくぎるが、西はやや低い笠置(かさぎ)山地、北東部はさらに緩やかな水口(みなくち)丘陵を隔てて近江(おうみ)盆地に続く。第三紀末から更新世（洪積世）にかけて盆地の大部分が古琵琶(びわ)湖とよばれる湖の湖底にあった。とくに南部ほど古く、名張(なばり)市付近から北の丘陵に古琵琶湖層群最下部の伊賀累層が広く分布する。盆地内は小断層によって、旧上野市付近（現、伊賀市の中心部）の狭義の上野盆地のほか名張盆地、大山田盆地、阿山(あやま)盆地などにくぎられるが、すべて木津川(きづがわ)流域に属する。伊賀、名張の2市があり、JR関西本線、近畿日本鉄道大阪線、名阪国道が盆地を横断し、伊賀鉄道伊賀線が縦断している。

［伊藤達雄］

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