宮城県仙台市北東部に分布する中新統の統合年代層序  [in Japanese] Integrated chronostratigraphy of the Miocene sedimentary sequence in the northeastern area of Sendai City, Miyagi Prefecture, Northeast Honshu, Japan  [in Japanese]

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Author(s)

    • 鈴木 拓馬 Suzuki Takuma
    • 島根大学大学院総合理工学研究科 Interdisciplinary Graduate School of Science and Engineering, Shimane University
    • 林 広樹 Hayashi Hiroki
    • 島根大学大学院総合理工学研究科 Interdisciplinary Graduate School of Science and Engineering, Shimane University
    • 柳沢 幸夫 Yanagisawa Yukio
    • 産業技術総合研究所 地質調査総合センター 地質情報研究部門 AIST, Geological Survey of Japan, Research Institute of Geology and Geoinformation
    • 藤原 治 Fujiwara Osamu
    • 産業技術総合研究所 地質調査総合センター 地質情報基盤センター AIST, Geological Survey of Japan, Geoinformation Service Center

Abstract

<p><b> </b>宮城県仙台市北東部には海成中部~上部中新統志田(しだ)層群が広く分布し,下位より,入菅谷(いりすがや)層,番ヶ森山(ばんがもりやま)層,青麻(あおそ)層,七北田(ななきた)層に区分される.このうち青麻層は海流堆積物を主体とし,軟体動物や海生哺乳類等の化石を多産することから,東北日本の古環境・古地理の変遷や古生物地理などの研究上重要である.本研究では,青麻層の模式地を含む仙台平野中部で浮遊性有孔虫及び珪藻化石層序を再検討し,あわせて凝灰岩のフィッション・トラック(FT)年代測定を行った.入菅谷層からはNPD5B帯に相当する珪藻化石が,青麻層からはN.16帯~ N.17A亜帯最下部に対比される浮遊性有孔虫化石及びNPD5D帯に対比される珪藻化石が,七北田層からはNPD6A帯及びNPD6B帯に相当する珪藻化石が産出した.また,青麻層最上部の凝灰岩からは9.3 ±0.4 Ma,七北田層下部の凝灰岩からは7.6 ±0.7 MaのFT年代が得られた.これらの結果は相互に矛盾せず,また,周辺地域の中新統層序とも整合する.</p>

<p>The middle to upper Miocene Shida Group is widely distributed in the northeastern Sendai area, Miyagi Prefecture, Northeast Japan. This group is divided into the Irisugaya, Bangamoriyama, Aoso and Nanakita Formations in ascending order. Among them, the Aoso Formation is mainly composed of ocean current-dominated sedimentary facies and yields abundant molluscan and marine vertebrate fossils. Therefore, this formation has been focused for paleoenvironmental, paleogeographic and paleontological studies of Northeast Japan. In this study, we established integrated biostratigraphy using planktonic foraminifera and diatom for the Shida Group in the northeastern Sendai Plain, which includes the type locality of the Aoso Formation. We also report fission track (FT) ages of two pyroclastic layers of Aoso and Nanakita Formations. Consequently, the Irisugaya Formation is correlated with the diatom zone NPD5B. The Aoso Formation is assigned to the diatom zone NPD5D and planktonic foraminiferal zone N.16–N.17A. The Nanakita Formation is correlative with zones NPD6A and NPD6B. FT ages of the uppermost part of the Aoso Formation and the lower part of the Nanakita Formation were determined at 9.3 ± 0.4 Ma and 7.6 ± 0.7 Ma, respectively. These results are concordant with each other and support previous chronostratigraphic data of adjacent areas.</p>

Journal

  • BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN

    BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN 70(1-2), 17-41, 2019

    National Institute of Advanced Industrial Science and Technology, Geological Survey of Japan

Codes

  • NII Article ID (NAID)
    130007631552
  • NII NACSIS-CAT ID (NCID)
    AA11587519
  • Text Lang
    JPN
  • ISSN
    1346-4272
  • NDL Article ID
    029727397
  • NDL Call No.
    Z15-177
  • Data Source
    NDL  J-STAGE 
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