著者

河西 学

出版者

国立歴史民俗博物館

雑誌

国立歴史民俗博物館研究報告 (ISSN:02867400)

巻号頁・発行日

vol.172, pp.209-229, 2012-03

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本研究では,栃木県内の4遺跡から出土した縄文早期井草式・夏島式土器を対象として薄片による岩石学的胎土分析を行い,関東地方河川砂との比較により土器の原料産地推定を試み,当時の土器作りと土器の移動について,従来の草創期土器の分析事例と比較検討した。その結果,宇都宮市内の宇都宮清陵高校地内遺跡・山崎北遺跡の井草式では,変質火山岩類を主体とし安山岩・デイサイト~流紋岩を伴う岩石鉱物組成の土器が含まれ,これらの組成が栃木県中央部の河川砂の組成と類似性が認められることから,地元原料を用いた土器作りが推定された。真岡市市ノ塚遺跡の全試料と山崎北遺跡の一部の井草式では,花崗岩類主体の岩石鉱物組成を示す土器から構成され,花崗岩類分布地域に原料産地が推定され,土器あるいは原料として運び込まれた可能性が考えられた。花崗岩類の原料産地候補地は,筑波岩体周辺が有力であるが,山崎北遺跡の場合足尾山地などの小岩体についても可能性が残る。小山市間々田六本木遺跡の夏島式は,変質火山岩類が多く花崗岩類・珪質岩などを伴う組成を示し,原料産地が栃木県中央部地域に推定された。地元原料を用いた土器作りは,宇都宮清陵高校地内遺跡・山崎北遺跡・間々田六本木遺跡などで認められる一方,市ノ塚遺跡では認められない。井草式・夏島式の花崗岩類主体の胎土は,千葉県内でも確認されることから広域に移動していた可能性が推定されるが,各遺跡内の胎土組成の多様性が乏しく遠方に原料産地が推定される胎土がほとんどないことから,他の胎土の土器の移動頻度は低調で,移動距離も小さいと推定された。In this study, for the pottery of the Igusa and Natsushima types unearthed from four remains in Tochigi Prefecture, petrographic analysis of the paste was conducted on its thin sections. In comparison with river sand in the Kanto region, the presumed fields of raw materials of the pottery were identified, and the manufacturing and transfer of pottery at that time were studied in comparison with the conventional analysis examples for the pottery of the beginning of the Jomon period.As a result, it was found that the pottery of the Igusa type from the Utsunomiya Seiryo High School site and the Yamazaki-kita site in Utsunomiya city includes the pottery having the mineralogical composition of mainly altered volcanic rocks, with andesite, decite and rhyolit. The composition is similar to that of the river sand in the central area of Tochigi Prefecture, and therefore, it was presumed that the pottery was made using the local materials. All the samples from the Ichinozuka site in Moka city and some of the Igusa type from the Yamazaki-kita site are composed of pottery having the rock mineralogical composition of mainly granite. Therefore, it was presumed that the material fields were located in the granite distribution regions, and there is a possibility that the pottery or materials were carried into the sites. The most possible granite fields are the Tsukuba pluton and its surroundings. For the Yamazaki-kita site, small plutons in the Ashio Mountains are also other possible fields. The pottery of the Natsushima type from the Mamada Roppongi site in Oyama city contains many altered volcanic rocks with granite and siliceous rocks, and it is presumed that the material field is the central area of Tochigi Prefecture. Pottery using the local materials was found at the Utsunomiya Seiryo High School site, the Yamazaki-kita site and the Mamada Roppongi site, but not at the Ichinozuka site. Since the paste of the Igusa and Natsushima types which contain mainly granite is found in Chiba Prefecture as well, there is a possibility that it was transferred over a wide area. The composition of the paste in each site has no variety, and there is less paste that is presumed to originate in remote fields. As a result, it is presumed that the frequency of transfer of pottery made of other paste is low and the transfer distance is small.