Effect of low-temperature treatments on pseudo-Thellier paleointensity determination -: art. no. 2198

[1] In paleointensity determination on multidomain ( MD) magnetite, demagnetization is always easier than restoring remanence in companion acquisition steps. As a result, paleointensity results follow a convex- down curve on the Arai plot. In an attempt to overcome this problem, the effect of systematic low-temperature demagnetization (LTD) on pseudo-Thellier results was examined. LTD was applied not only to the initial anhysteretic remanent magnetization ( ARM, simulating natural remanent magnetization or NRM) but also after each partial anhysteretic remanent magnetization (pARM) acquisition step. Three practical benefits of systematic LTD were discovered. ( 1) LTD-treated pseudo-Thellier results always yielded more accurate intensity values regardless of grain size and sample lithology. ( 2) LTD improved the behavior of MD magnetite in paleointensity determination, although not as much as for single-domain and pseudosingle-domain grains. ( 3) An unanticipated bonus was a more even distribution of data points on the Arai plot, resulting from the fact that LTD causes a shift of points toward the upper end of the Arai curves. Constructing a three-dimensional map of the distributions c and c LTD was successful in quantitatively explaining behavior on the Arai plots.