変動地形からみた津軽半島の地形発達史 Late Quaternary Terraces and Their Deformations on Tsugaru Peninsula, Northeastern Japan

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津軽半島に分布する段丘をIm面・IIf面・IIIm面・IIIf面・IVf面・Vm面に区分し,そのうちのIIIm面を最終間氷期最盛期に形成された海成段丘に対比した.IIIm面の旧汀線高度は,津軽半島北部(高度13~41m)と東部(高度14~30m)で波長約30kmの波状変形に加えて,北部では短波長(約3km)の波状変動を示す.津軽山地東西両縁の活断層(活動度B~C級)は,段丘上に平野側へ傾き下がる撓曲崖(変位量10~30m)やその背後の逆向き低断層崖(変位量2~10m)を形成し,半島が東西圧縮場にあることを示す.段丘の変動様式は,基盤となる新第三系の分布と関係し,おもに鮮新世の固結度の小さい堆積岩が分布するところで変位が大きい.第四紀後期には,半島東部でより山地・平野境界部の地殻変動が活発である.

Late Quaternary terraces on Tsugaru Peninsula, northernmost Honshu, are divided into five levels (Terrace I-V), and each terrace is of marine (m) and fluvial (f) origin. Terrace IIIm, which is distributed most widely and is overlain by the Toya ash (100-130ka), was formed during the last interglacial maximum of ca.124ka (oxygen isotope sub-stage 5e). The height of the former shoreline of Terrace IIIm reaches 40m above sea level (average uplift rate is ca.0.3m/ka), and its height distribution shows a warping with short wave-length (ca.3km) on the north and a warping with about 30km wave-length on the east. Two active fault systems, running north-south, bound the plains area from the central mountains and dislocate Terrace Im, IIf on the west and IIIm on the east. The fault system on the west is composed of a main synthetic fault, represented by a west-facing flexural scarp and an antithetic fault which has a range-facing scarplet. The degree of fault activity is class B-C (slip rate; 0.08-0.15m/ka) for the synthetic fault and C (<0.1m/ka) for the antithetic fault. The slip rate of flexural scarp on the east is larger (0.14-0.30m/ka) than on the west. These faults are estimated to be reverse faults which have been produced under a stress field with E-W compression. Late Quaternary terraces have been deformed significantly in the eastern part and the northern central part of the peninsula where Pliocene sediments are thickly deposited.

収録刊行物

  • 第四紀研究  

    第四紀研究 34(2), 75-89, 1995-05-31 

    Japan Association for Quaternary Research

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各種コード

  • NII論文ID(NAID)
    10002632506
  • NII書誌ID(NCID)
    AN0034136X
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    04182642
  • NDL 記事登録ID
    3624229
  • NDL 刊行物分類
    ME61(地質・地史)
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質)
  • NDL 請求記号
    Z15-67
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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