書誌事項
- タイトル別名
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- K–Ar Geochronology of the Andesite Lavas of the Lower Pleistocene Enrei Formation on the Southwestern Slope of the Suwa Basin, Central Japan
- スワ ボンチ ミナミニシガワ シャメン ノ カブ コウシントウエンレイルイソウ アンザンガン ヨウガン ノ K-Ar ネンダイ
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<p> The Suwa Basin is believed to be a typical pull-apart basin formed by the 12 km left-lateral motion on the Itoigawa–Shizuoka Tectonic Line active fault system. The starting age of the basin subsidence is considered to be after the violent volcanisms that formed the Lower Pleistocene Enrei Formation (Fm) distributed in and around the basin. However, the history of the basin development is still controversial mainly because of the insufficient geochronological data on the Enrei Fm in the SW Suwa Basin. The results of K–Ar dating are presented for two samples of andesite lavas of the Enrei Fm exposed on the northeastward-dipping slope of the SW Suwa Basin. One gives an age of 2.03 ± 0.19 Ma and the other an age of 1.51 ± 0.16 Ma. The former age corresponds closely to the oldest age of the Enrei Fm to the NE Suwa Basin, and suggests that the coeval and widespread initial volcanism at both sides of the basin occurred during the early Early Pleistocene (Gelasian) before the basin subsidence. The latter age closely corresponds to the peak periods of volcanic activity of the Enrei Fm. These lines of evidence suggest that the basin started to subside after 1.5 Ma, and that the position of basal unconformity, stratigraphy and geologic structures of the Enrei Fm in the SW Suwa Basin need to be re-examined.</p>
収録刊行物
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- 地学雑誌
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地学雑誌 130 (5), 615-632, 2021-10-25
公益社団法人 東京地学協会
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詳細情報 詳細情報について
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- CRID
- 1390290088581925376
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- NII論文ID
- 130008117222
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- NII書誌ID
- AN00322536
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- ISSN
- 18840884
- 0022135X
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- NDL書誌ID
- 031797474
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- 本文言語コード
- ja
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- データソース種別
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- JaLC
- NDL
- Crossref
- CiNii Articles
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- 抄録ライセンスフラグ
- 使用不可