東シベリア, 北極海周辺に分布する永久凍土"エドマ"の形成環境と形成期 Paleoenvironment and Period of The "Edoma" Formation in High Arctic Eastern Siberia

この論文にアクセスする

この論文をさがす

著者

抄録

There exists large scale ground ice, which locally called "Edoma", in plains along the Arctic coasts of eastern Siberia and the New Siberian Islands. The Edoma is mainly composed of massive ground ice with pillar-shaped frozen soil. The massive ice is considered as syngenetic ice-wedge origin, which develops alternative accumulations of ice-wedge and sedimentation on ground surface. The soil pillars are arranged in regular intervals of several meters in the massive ice, and contain a lot of ice lenses and several peat layers.<BR>A geological and geochemical survey was carried out in the Bykovsky Peninsula near the Lena Delta (Loc. 1), Bolshoi Lyakhovsky Island, the southern part of the New Siberian Islands (Loc. 2) and Oiyagosky Yar facing the Arctic Sea in middle of eastern Siberia (Loc. 3). Results of grain size analysis and determinations of radiocarbon datings of the Edoma in these surveyed sites were summarized as follows : <BR>1) Sediments of the Edoma in Loc. 1 are composed of dark gray silt to fine sand with a lot of organic matters. Compositional ratio of grain size varies vertically, and is characterized by bimodality in the grain size distribution. This suggests that the sediments were formed under two different transportation agents. Sediments of the Edoma both at Loc. 2 and Loc. 3 characterized by dark gray to brown silt, and also contains abundant organic matter. Grain-size distribution of these sediments is similar to the finer population in Loc. 1. Judging from the characteristics of grain size distribution, these sediments are considered as aeolian deposits.<BR>2) Radiocarbon ages at Loc. 1 scatter within a range from about 30, 000 to 20, 000 yr BP in upper part and about 11, 000 yr BP in uppermost. The ages at Loc. 2 are resulted in about 30, 000 to 40, 000 yr BP in case of the most parts and about 7, 000 yr BP at uppermost part in permafrost just under the active layer. At Loc. 3, most of the ages of the Edoma are determined over 40, 000 yr BP and that of uppermost is determined as about 22, 000 yr BP.<BR>Based on the results of radiocarbon dating mentioned above, it is suggested that the Edoma in eastern Siberia might have formed during Karginkiy Interstadial to Sartan Stadial in the Last Glacial stage, and especially main parts of the Edoma developed during Karginkiy Interstadial, in which period climate was more unstable than Sartan Stadial. Grain size distribution of sediments also suggest that the Edoma have accumulated under the sedimental condition at water flood plain or marsh, which were favorable locations to growth of syngenetic ice wedge as well as loess accumulation. Supply of sediments in Loc. 1 may have been stable because the main transport of sediments have been performed by fluvial activities of the Lena River and the wind action. On the other hand, since the sediments in Loc. 2 and Loc. 3 is probably derived from aeolian loess, the amounts of supplied sediments might have been less than Loc. 1. Therefore, flux of sedimentation, forming the Edoma in Loc. 1 maintained longer than those at Loc. 2 and Loc. 3.

収録刊行物

  • 地學雜誌

    地學雜誌 105(1), 15-30, 1996-02-25

    Tokyo Geographical Society

参考文献:  30件中 1-30件 を表示

被引用文献:  2件中 1-2件 を表示

各種コード

  • NII論文ID(NAID)
    10003774346
  • 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
    3934802
  • 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 
ページトップへ