三陸沖海底コアを用いた第四紀後期の北西太平洋縁辺域における古海況 -珪藻化石群集からのアプローチ- Late Quaternary Paleoceanography in the Northwestern Pacific Margin Reconstructed with a Submarine Core Recovered Off Sanriku : An Approach Using Diatom Fossil Assemblage

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三陸沖より採取された堆積物コア中の珪藻化石群集の主成分分析にもとづき,三陸沖および北西太平洋縁辺域における第四紀後期の古環境変遷を検討した.<br>酸素同位体比ステージ3では,珪藻殻数が増加するとともに海氷指標種が卓越する.これは,生産性の高い季節海氷の縁辺域が少なくとも三陸沖まで南進したことを示唆する.つまり親潮は,氷期に海氷のようなオホーツク起源の環境要素の供給を過剰にうけており,現在のような間氷期とは質的に著しく異なっていた可能性がある.

A Q-mode principal components analysis (PCA) based on downcore variation of diatom fossil assemblage was carried out in order to reveal the late Quaternary paleoceanography of the NW Pacific margin with the qualified submarine core KH 94-3, LM-8, recovered off the Sanriku coast, NE Japan.<br>It is recognized that increase of diatom valve concentration (DVC: valves/g) occurred in oxygen isotopic Stage 3 (interstadial during the last glacial) and Stage 1 (Holocene). However, diatom assemblages show drastic change between the two periods. As the result of PCA, we delineated four principal components explaining 93.6% of total variance. Principal compoent 1 is composed mainly of <i>Thalassionema nitzschioides</i> (Grunow) H. et M., which dominates in the coldest Stages 4 and 2 with diatom valves being poorly preserved and DVC being the lowest. Principal component 2 with some ice-related diatoms predominates in Stage 3, whereas principal component 3, which is characterized by <i>Neodenticula seminae</i> (Simonsen et Kanaya) Akiba et Yanagisawa and <i>Odontella aurita</i> (Lyngbye) Agardh, displays high values in Stage 1.<br>Here, we suggest that intensified discharge of sea ice originated in the Sea of Okhotsk in Stage 3. This interpretation subsequently enables us to explain the high DVC during the period as being due to high productivity at the sea ice edge. We can also infer that the qualitative difference in the Oyashio between the glacial and the interglacial is due to change in the supplying mode of the Okhotsk-originating factor such as sea ice, and consequently that there is a different mechanism of high primary productivity in the area off Sanriku during each period.

収録刊行物

  • 第四紀研究  

    第四紀研究 38(2), 125-144, 1999-04-01 

    Japan Association for Quaternary Research

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各種コード

  • NII論文ID(NAID)
    10002511176
  • 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
    4694347
  • 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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