Ar‐Ar ages, and petrographical and geochemical characteristics of pyroclastics and an overlying lava from Teshima Island, southwest Japan are presented. Although previous geological and age data suggested Teshima pyroclastics were products of magmatism > 3 my prior to lava flows of Setouchi volcanic rocks generated in association with southward migration of the southwest Japan arc sliver during opening of the Sea of Japan backarc basin at ~ 15 Ma, the present results led to the conclusion that a sequence of Setouchi volcanism, induced by slab melting and subsequent melt‐mantle reactions, produced both pyroclastics and lava at 14.6–14.8 Ma. This age is oldest among those reported so far and may represent the timing of onset of characteristic Setouchi magmatism immediately posterior to and hence as a result of the mega‐tectonic event including rotation of the southwest Japan arc sliver.

中文翻译：

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Teshima火山碎屑岩：板坯在14.8 Ma熔化引起的特征性濑户内岩浆作用的发生

本文介绍了日本西南部Teshima岛的Ar-Ar年龄，火山碎屑岩和上覆熔岩的岩石学和地球化学特征。尽管先前的地质和年龄数据表明，Teshima火山碎屑岩是岩浆作用的产物，其强度大于濑户内火山岩熔岩流动之前3 s，这与日本西南部弧海盆地在约15 Ma的开放期间与日本西南部弧状银条的向南移动有关。目前的结果得出的结论是，板坯融化和随后的熔幔反应引起的濑户内火山序列在14.6-14.8 Ma产生了火山碎屑和熔岩。