北海道の古第三系堆積盆の変遷 Evolution of the Paleogene Sedimentary Basins in Hokkaido

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The Paleogene of Hokkaido is dominated in coal-bearing formations. Four stages are discriminated in evolution of the Paleogene sedimentary basins, above all, coal basins. A subsiding deep trough extended in the axial part of Hokkaido and southeastern Sakhalin between the East Asian continent and the Okhotsk microcontinent, and was filled with a 5 km-thick, clastic turbidite facies in the Paleocene. At the stage I in the latest Paleocene to earliest Eocene, the Haboro coal basin formed as a fore-arc basin in north-central Hokkaido on the west side of the trough. By contrast, the Nemuro shelfal clastic basin existed on the east side of the trough and encircled the southwest margin of the microcontinent. A drastic paleogeographic change occurred in the Early Eocene. The axial part of Hokkaido, which had been occupied by the deep trough, turned to upheaving associated with the Hidaka metamorphism, probably due to collision of the Okhotsk microcontinent against the East Asian continent. As a result, the trough and the sedimentary basins on its both sides were converted into a land. At the stage II in the middle Middle Eocene, the Ishikari-Uryu coal basin formed as an inter-arc basin in south-central Hokkaido where the Late Cretaceous continental fore-arc basin preexisted. The coal basin was first restricted to the Ishikari coalfield in the south, and later it enlarged to the Uryu coalfield in the north by the northward Wakanabe-Shiraki transgression. At the stage III in the late Middle Eocene, the Ishikari-Uryu coal basin extended to the west due to the subsidence of the Kabato-Rebun Cretaceous volcanic terrane. Basal fanglomerates, a few hundreds meters thick, overlapped the Cretaceous basement rocks in the west part of the coal basin. At the same stage, the Kushiro coal basin of the Kushiro coalfield formed incisely within the Nemuro shelfal basin in southeast Hokkaido, although it extended to the west and overlapped the Cretaceous basement rocks of the Tokoro terrane with conspicuous fanglomerates. At the stage IV in the Late Eocene to Early Oligocene, all coal basins of the previous stages subsided to the site of the deposition of shallow-marine to upper bathyal muddy sediments. In central Hokkaido, the Late Eocene marine basin of the Poronai Formation and its equivalents extended northwards from the Ishikari-Uryu coal basin to the Haboro coal basin of the stage I, and further to the north, to Sakhalin. However, the Early Oligocene mudrocks of the Momijiyama Formation was recognized only in the southern part of the Ishikari coalfield, and showed a restricted embayment environment. In east Hokkaido, the Early Oligocene continental sediments of the Wakamatsuzawa Formation overlapped the Cretaceous basement rocks of the Tokoro terrane on the northwest of the Late Eocene to Early Oligocene marine basin of the Onbetsu Group.<BR>The Paleogene of Hokkaido has a total thickness of two to five kilometers. The Paleogene strata of central Hokkaido are commonly extensively folded and overthrusted. The thick and folded Paleogene in central Hokkaido is undoubtedly traceable to Sakhalin, and possibly to the west side of central and northern Kamchatska.<BR>The third-ordered eustatic curves of Haq <I>et al</I>. (1987) indicate that, as a whole, Late Eocene is low stand while Early Oligocene is high stand. In Hokkaido, however, marine basins are most widespread in the Late Eocene, whereas they are restricted in the Early Oligocene. Local tectonic movements are therefore essential for the evolution of the Paleogene sedimentary basins in Hokkaido.

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  • 地學雜誌

    地學雜誌 105(2), 178-197, 1996-04-25

    Tokyo Geographical Society

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各種コード

  • NII論文ID(NAID)
    10003774627
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    0022135X
  • NDL 記事登録ID
    3953609
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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