新潟・長野県に広域に分布する後期更新世の炭層準の発見  [in Japanese] Late Pleistocene fossil charcoal horizons discovered in Niigata and Nagano Prefectures, Central Japan  [in Japanese]

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Author(s)

    • 吉川 周作 YOSHIKAWA Shusaku
    • 大阪市立大学大学院理学研究科生物地球系専攻 Department of Biology and Geosciences, Graduate school of Science, Osaka City University
    • 井上 淳 INOUE Jun
    • 大阪市立大学大学院理学研究科生物地球系専攻 Department of Biology and Geosciences, Graduate school of Science, Osaka City University

Abstract

後期更新世の米原・貝坂ローム層に含まれる炭化片の実体顕微鏡観察,電子顕微鏡観察および化学分析によって,これらは,高い表面反射率,細胞壁構造の均質化,H/C比の推定炭化温度(430℃~460℃)から,高温状態で炭化した炭であることを明らかにした.そして,ローム層より産出する炭は新潟・長野県に広く連続的に分布することを発見した.これらの炭は米原ローム層及びその相当層のM3とM4の間(約11~12万年前),M6上部から直上(約9~10万年前),米原ローム最上部(約7万年前)の3層準から産出した.このうち,M3とM4の間の津南-1炭層準は50km以上,M6上部から直上の津南-2炭層準は30km以上,米原ローム層最上部の津南-3炭層準は20km以上に渡って追跡可能で,大規模な森林火災を示すことを明らかにした.今後,過去の森林火災を示す炭層準は,広く連続的に追跡でき,時間面を示すことから鍵層準として,層序学的研究に重要な役割を果たすことを指摘した.

The Late Pleistocene Maibara and Kaisaka Loam Formations, consisting of weathered eolian deposits, are widely distributed in Niigata and Nagano Prefectures, Central Japan. Plants preserved fossil-charcoal are identified from these formations. The fossils consist of small angular fragments (mostly 1 to 50 mm diameters), a dull black lustre, brittle fracture and homogenised cell wall. H/C thermometer indicates that the fossil charcoal fragments were charred in the range 430-460°C. Stratigraphically, the fossil charcoal, indicating the occurrence of wildfire, have been recognized at three stratigraphic levels, called Tsunan-1, Tsunan-2 and Tsunan-3 fossil charcoal horizons, in these formations. Tsunan-1 fossil charcoal exists at the horizon between the M 4 and M 3 tephra bed (ca.110-120 ka), and is widely distributed in Niigata and Nagano areas, for a distance of more than 50 km. Tsunan-2 fossil charcoal occurs at a horizon of immediately above the M 6 tephra bed (ca.90-100 ka), and is sporadically distributed in Niigata and Nagano areas, along the Shinano River for a distance of about 30 km. Tsunan-3 fossil charcoal occurs at a horizon of immediately below the K 0 tephra bed (ca. 70 ka), and is distributed in Niigata and Nagano areas, for a distance of more than 20 km. We conclude that these fossil charcoal horizons are useful for understanding the wildfire history during late Quaternary and are important as stratigraphic marker horizons.

Journal

  • The Journal of the Geological Society of Japan

    The Journal of the Geological Society of Japan 109(1), 63-70, 2003-01-15

    The Geological Society of Japan

References:  34

Codes

  • NII Article ID (NAID)
    110003009757
  • NII NACSIS-CAT ID (NCID)
    AN00141768
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    00167630
  • NDL Article ID
    6452722
  • NDL Source Classification
    ZM49(科学技術--地球科学--地質)
  • NDL Call No.
    Z15-174
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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