地質学雑誌
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
検索
詳細検索
OR
閲覧
検索
127 巻, 11 号
選択された号の論文の5件中1～5を表示しています
すべての抄録を表示する
    • |<
    • <
    • 1
    • >
    • >|
論説
レター
  • 北海道北部天塩中川地域から産出した白亜紀中期セノマニアン期の珪藻化石群集
    嶋田 智恵子, 齋藤 めぐみ, 山﨑 誠, 田中 裕一郎, 疋田 吉識
    2021 年 127 巻 11 号 p. 667-672
    発行日: 2021/11/15
    公開日: 2022/01/01
    DOIhttps://doi.org/10.5575/geosoc.2021.0026
    ジャーナル フリー
    抄録を表示する抄録を非表示にする

    Diatoms are one of the most important eukaryotic primary producers in the lower ecosystem; understanding their evolutionary history is therefore also important. Throughout most of the Cenozoic hydrosphere, diatoms have flourished. However, as a result of progressive diagenesis and dissolution of the opaline silica that forms their frustules, their early evolution during the Cretaceous is unclear, so the fossil record is incomplete. Largely because of this poor fossil record, little is known about the mid-Cretaceous interval (Cenomanian to Turonian). This study presents a new fossil record of Cenomanian opaline diatoms in carbonate concretions hosting ammonites from Hokkaido in the northwestern Pacific Ocean. Primitive floral assemblages composed of dominantly cylindrical or discoid forms are associated with a few hemiaulid diatoms, one of the predominant taxa since the Campanian age. The Cenomanian diatoms are similar to late Early Cretaceous (Albian) flora reported mainly from the Southern Hemisphere, but given their association with a few taxa typical of the Late Cretaceous, they are somewhat transitional.

    抄録全体を表示
    PDF形式でダウンロード (1783K)
  • 愛知県東部中新統北設亜層群の分布域南東部における岩相層序の再検討：梅平砂岩部層の提唱
    藪田 桜子, 竹内 誠
    2021 年 127 巻 11 号 p. 673-679
    発行日: 2021/11/15
    公開日: 2022/02/01
    DOIhttps://doi.org/10.5575/geosoc.2021.0027
    ジャーナル フリー
    抄録を表示する抄録を非表示にする

    The Hokusetsu Subgroup in the eastern Shidara basin, eastern Aichi Prefecture, central Japan, is the lower part of the Miocene Shidara Group. In ascending stratigraphic order, the subgroup consists of the Kawakado, Shimoda, Tsubosawa, and Kuroze formations, which formed during a continuous transgression. Re-examination of the lithostratigraphy of the Hokusetsu Subgroup in the eastern Shidara basin has revealed a thick sandstone formation in the upper part of the Shimoda Formation, which otherwise consists mainly of mudstone. The sandstone beds, which had previously been considered part of the Kawakado Formation, clearly extend to the north where they interfinger with the mudstone of the Shimoda Formation. The existence of these newly identified sandstone beds in the Shimoda Formation, named the Umedaira Sandstone Member, suggests that the Hokusetsu Subgroup formed not only by simple transgression, but also by the influence of tectonic movements. The Umedaira Sandstone Member may be the key to clarifying Miocene tectonics in the Shidara Basin.

    抄録全体を表示
    PDF形式でダウンロード (2399K)
ノート
  • 汎用マイコンとWindows PCによる旧式EPMA（JXA-8600SX）の駆動
    植田 勇人, 高澤 栄一
    2021 年 127 巻 11 号 p. 681-686
    発行日: 2021/11/15
    公開日: 2022/01/01
    DOIhttps://doi.org/10.5575/geosoc.2021.0028
    ジャーナル フリー
    抄録を表示する抄録を非表示にする

    Here we report on the operation of the JEOL JXA-8600SX wavelength-dispersive electron probe microanalyzer (EPMA) after replacing the outdated and damaged native computers with popular and up-to-date microcomputers (Arduino) and a desktop Windows PC. Stepper motors actuating the sample stage and spectrometers are driven by computerized numerical control (CNC) kits commercialized for hand-made 3D printers, open-source firmware GRBL installed on Arduino, and a common text-based command “G-code” sent from a PC. X-ray pulse signals from the single-channel pulse-height analyzer (SCA) and analog signals from the probe ammeter are also acquired by Arduino. Sending commands from the PC to Arduino and receiving signals from Arduino to the PC are routinized by a homemade program coded by Visual Basic.NET. Quantitative analyses of anhydrous silicates and oxides, applying the Bence-Albee correction, provide reasonable oxide concentrations that are generally within 99-101 wt.% in total and compatible with stoichiometry within a 1%-2% relative deviation. This alternative control system not only extends the use of EPMA hardware regardless of generational changes in computer technology, but also introduces optional analytical techniques not available in the built-in system.

    抄録全体を表示
    PDF形式でダウンロード (2849K)
口絵
    • |<
    • <
    • 1
    • >
    • >|
feedback
 Top