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Secondary remanent magnetization of pelagic clay in the South Pacific: Application of thermal demagnetization
Author(s) -
Yamazaki Toshitsugu
Publication year - 1986
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl013i013p01438
Subject(s) - remanence , geology , natural remanent magnetization , demagnetizing field , paleomagnetism , pelagic sediment , magnetization , magnetostratigraphy , pelagic zone , geophysics , rock magnetism , geochemistry , oceanography , sedimentary rock , magnetic field , physics , quantum mechanics
Previous paleomagnetic studies have revealed that pre‐Quaternary pelagic clay with neither siliceous nor calcareous fossils has unstable remanent magnetization, and that alternating field (AF) demagnetization is not effective to remove the secondary magnetization. This study applied thermal demagnetization on pelagic clay from the South Pacific, and recovered characteristic directions. The observed paleolatitudes agree with those from plate tectonic analysis, which proves that the thermal demagnetization worked well. The magnetic overprint is estimated to be viscous remanent magnetization (VRM) from VRM acquisition experiment. A hypothesis is proposed that the magnitude of the VRM of pelagic clay has been controlled by the grain size of magnetic minerals of eolian origin, which has been subjected to the intensity of the global atmospheric circulation. This can explain the Late‐Pliocene unstable‐to‐stable transition of the remanence, which has been observed widely in the Pacific.