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Earth, Planets and Space

, Volume 52, Issue 5, pp 337–345 | Cite as

Magnetic minerals and magnetic properties of the Siwalik Group sediments of the Karnali river section in Nepal

  • Pitambar Gautam
  • Azumi Hosoi
  • Kamal Raj Regmi
  • Dharma Raj Khadka
  • Yoshiki Fujiwara
Open Access
Article

Abstract

Sandstones and siltstones collected from the Siwalik molasse sequence (~ 16 to 5 Ma) of the Karnali river section have been studied for their magnetic properties. Behavior of the specimens during demagnetization (of the NRM and IRM) and magnetic susceptibility vs. temperature data suggest that goethite, maghemite/magnetite, and hematite are the main magnetic minerals in the section. Goethite, carrying a recent component, is the dominant magnetic mineral in the fine-grained lithologies from the lower part. Maghemite and magnetite, which also carry a secondary remanence, occur in the sandstones from the upper part. Hematite, mainly of detrital origin, is present in the whole sequence. The magnetic fabric is defined by mainly oblate AMS ellipsoids and a low degree of anisotropy (P′ < 1.20). The magnetic lineations (declinations: 75°–130° or 245°–310°; peak orientation: 290°/2.8°) are subparallel to the fold axes/bedding strikes/thrust fronts (WNW-ESE). The initial sedimentary-compactional fabric has been overprinted by a secondary tectonic fabric, which was probably induced by mild deformation active in the compressive tectonic setting.

Keywords

Goethite Magnetic Mineral Natural Remanent Magnetization Isothermal Remanent Magnetization Isothermal Remanent Magnetization Saturation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2000

Authors and Affiliations

  • Pitambar Gautam
    • 1
    • 2
  • Azumi Hosoi
    • 1
  • Kamal Raj Regmi
    • 1
    • 2
  • Dharma Raj Khadka
    • 2
  • Yoshiki Fujiwara
    • 1
  1. 1.Division of Earth and Planetary Sciences, Graduate School of ScienceHokkaido UniversitySapporoJapan
  2. 2.Central Department of GeologyTribhuvan UniversityKathmanduNepal

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