Iu Plain - Ouhei

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[Ancient times]
Kami Province (Engishiki) belonging to the San'in Road. Initial regional unification progressed mainly in eastern Izumo, where the chiefs of the Oo Plain rose to prominence, rather than in western Izumo, where many chiefs lived in the lower reaches of the Hii River (Hikawa) and the Kando River. In other words, a distinctive ancient tomb culture developed in the eastern part of Izumo, with a dense distribution of square tombs and keyhole-shaped tombs from the late 4th century to the 5th century, and the Kunibiki myth, which appears only in the Izumo no Kuni Fudoki, was also nurtured here.

*Some of the terminology that refers to "Iu Plain" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

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【古代】
　山陰道に属する上国(《延喜式》)。当初の地域的統一は，簸（ひ）ノ川(斐伊（ひい）川)･神門(戸)（かんど）川下流域に諸首長が併立した出雲西部よりも，意宇（おう）平野の首長が卓越的に台頭した出雲東部を中心にすすんだ。すなわち，東部には4世紀末から5世紀の方墳や前方後方墳が濃密な分布を示す特色ある古墳文化が発達し，《出雲国風土記》にだけみえる国引き神話もここではぐくまれた。…

※「意宇平野」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報