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Rockmagnetic Characterization of the Setana and Chiraigawa Formations in SW Hokkaido (Soebetsu River, Kuromatsunai)

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Title: Rockmagnetic Characterization of the Setana and Chiraigawa Formations in SW Hokkaido (Soebetsu River, Kuromatsunai)
Authors: Gautam, Pitambar Browse this author →KAKEN DB
Takashima, Reishi Browse this author
Dick, Matthew H. Browse this author →KAKEN DB
Kanamatsu, Toshiya Browse this author
Rijal, Moti L. Browse this author
Nishi, Hiroshi Browse this author
Mawatari, Shunsuke F. Browse this author
Keywords: Magnetic susceptibility
Rock magnetism
Curie temperature
Setana Formation
Issue Date: 2008
Publisher: 21st Century COE for Neo-Science of Natural History, Hokkaido University
Citation: Edited by Hisatake Okada, Shunsuke F. Mawatari, Noriyuki Suzuki, Pitambar Gautam. ISBN: 978-4-9903990-0-9
Journal Title: Origin and Evolution of Natural Diversity : Proceedings of the International Symposium, The Origin and Evolution of Natural Diversity, held from 1-5 October 2007 in Sapporo, Japan
Start Page: 101
End Page: 107
Abstract: Rockmagnetic investigations were conducted on sediments constituting the upper part of the Setana Formation and the Chiraigawa Formation, of Plio-Pleistocene age, exposed along the Soebetsu River in the vicinity of Kuromatsunai town, Hokkaido. Average mass-specific low-field magnetic susceptibility (χ) had the lowest value (15.2 x 10^[-8] m^3kg^[-1]) at one site in the Kuromatsunai Formation, but higher values represented by wide ranges of (26.1-132.2) x 10^[-8] m^3kg^[-1] and (135.6-870.1) x 10^[-8] m^3kg^[-1] characterized the Chiraigawa and Setana Formations, respectively. Magnetomineralogical analyses by isothermal remanence (IRM) acquisition, Curie temperature determinations, and electron microscopy aided with energy dispersive X-ray analysis suggest the presence of several types of magnetic minerals: (i) one of a soft coercivity phase, probably a Ti-poor magnetite, with a Curie temperature of ca. 535-555℃, occurring throughout the section; (ii) one of intermediate coercivity, relatively rich in Ti (ca. 10% by weight), with a Curie temperature of ca. 460-475℃, restricted to two relatively thin layers of the Chiraigawa Formation, each several tens of cm thick; and (iii) a hard-coercivity hematite-like and/or a very-hard-coercivity goethite-like phase contributing up to 0.5-5% of the saturation IRM acquired at 2.5 T. Combined use of susceptibility and several ratios or differences derived from IRM acquisition data, bi-plots of IRM vs. χ, and magnetomineralogical inferences were used to discriminate rockmagnetic zones within the Soebetsu River Section. Similar rockmagnetic analyses have proven to be effecive for mapping as well as for lithostratigraphical correlations of geological sections. Combined use of these rockmagnetic zones with other environment/climate proxy data may prove effective in paleoenvironmental reconstruction.
Description: International Symposium, "The Origin and Evolution of Natural Diversity". 1–5 October 2007. Sapporo, Japan.
Conference Name: International Symposium, "The Origin and Evolution of Natural Diversity"
Conference Place: Sapporo
Type: proceedings
Appears in Collections:Origin and Evolution of Natural Diversity > Proceedings

Submitter: Gautam Pitambar

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