There are vast and dry areas of deserts in the interior of Australia,but none of loess section has been reported until 2003,Mackenzie's Waterholes Creek(MWC)profile in New South Wales was first studied as loess.In this paper,various measurements of magnetic parameters from MWC were carried out,comparison was made with those of Luochuan profile,which lies in the Central Chinese Loess Plateau(CLP).The types of magnetic minerals are similar to the CLP: magnetite,maghemite,limonite and hematite.However,the magnetic properties of Australian aeolian sediment show quite different.Frequency-dependent magnetic susceptibility (χfd ％ )is rather high,while values of magnetic susceptibility is low.The relative content of hard(paramagnetic)-magnetic components is much higher than CLP,whereas the content of maghemite and hematite is obviously much less.Furthermore this proportion increases along with the depth.Maghemite is more sensitive than magnetite under pedogenic condition of experiencing humid and stagnant watered environment.Maghemite increases along with enhancement of magnetic susceptibility in Luochuan section; however,decreases with that in MWC profile.This very likely indicate that the pedogenic process in MWC took place under environment that maghemite/magnetite are unstable.The modern annual precipitation is 924.2mm in MWC area,which is about 300mm higher than that in Luochuan.That extra moisture may lead MWC exceeding stable range for maghemite/magnetite.Those minerals therefore gradually converted to more stable goethite under the condition,causing magnetic susceptibility to decrease.Fe and Mn nodules are commonly observed in the lower part of section,implying pedogenic chemical weathering happened that Fe was dissolved and migrated downward and enriched in certain position,indicating that wind-blown maghemite/magnetite under such moisture condition were transformed to iron hydroxides,such as goethite/limonite,or paramagnetic minerals,resulting in magnetic susceptibility reduced.Although the susceptibility from the most of section shows a general positive relation to the particle size,it seems fit well to the 'wind vigor’ Alaskan mode.However,Fe chemical weathering and moved downward happened in MWC suggest that the precondition for 'wind vigor’ mode cannot be satisfied,the susceptibility variation can only find a solution from pedogenesis.
|Number of pages||12|
|Publication status||Published - 2011|
- Australian loess
- loess magnetic susceptibility
- magnetic properties
- global change