Pedogenic processes can explain the trends in magnetic susceptibility and soil magneticmineralogy of the Ljubljana Basin chronosequence. The chronosequence formed in predominantlycarbonate sandy gravel outwash terrace...Pedogenic processes can explain the trends in magnetic susceptibility and soil magneticmineralogy of the Ljubljana Basin chronosequence. The chronosequence formed in predominantlycarbonate sandy gravel outwash terraces ranging from 5 to 1800 ka. Magnetic susceptibilityenhancement can be attributed to the formation of secondary superparamagnetic （SP） and singledomain （SD） ferrimagnetic minerals in eluvial horizons. Magnetic minerals that form in illuvialhorizons are predominantly antiferromagnetic. Downward migration of pedogenic iron compoundswith clay （formation of ferri-argillans） causes thickening of the enhanced zone with soil age.In contrast to other published soil chronosequence studies, magnetic susceptibility values donot increase with soil-age （duration of pedogenesis）. Nevertheless, frequency dependence ofmagnetic susceptibility （FD%） and indices such as maximum eluvial magnetic susceptibility （MS）divided by minimum illuvial MS (Max. E / Min. IX<sub>lf</sub> and maximum eluvial MS minus minimumilluvial MS (Max. E -Min. IX<sub>lf</sub>) increase with the logarithm of soil age suggesting that the magneticmineral transformations continue with time, but that their rate decreases. These indices are usefulfor comparisons, and may be useful for age correlations. Hypothesis that magnetic susceptibilityenhancement and precipitation have a positive correlation seems to be valid until the precipitationexceeds the critical value of 100-150 cm/year. The critical value in different settings may dependon the temperature regime and on the yearly distribution of precipitation.展开更多
Most researchers agree that pedogenesis plays a significant role in determining thevertical distribution of magnetic susceptibility in soils and in the loess/paleosol sequences found inthe People’s Republic of China....Most researchers agree that pedogenesis plays a significant role in determining thevertical distribution of magnetic susceptibility in soils and in the loess/paleosol sequences found inthe People’s Republic of China. Magnetic susceptibility distribution from Jiaodao on the Chinesecentral loess plateau matches other published magnetic susceptibility curves. Using the CBDmethod and a mixing model, the lithogenic and pedogenic components of magnetic susceptibilityfrom Jiaodao were quantified. The estimated lithogenic component showed a long-term decreasewith depth and had short-term periodic fluctuations in tune with the occurrence of paleosol andloess strata. The results of the mixing model suggest that interpretations based only on fluctuationsin total magnetic susceptibility will be in error and that a single estimate of average lithogenicsusceptibility is not an accurate basis for adjustment of the total susceptibility.展开更多
文摘Pedogenic processes can explain the trends in magnetic susceptibility and soil magneticmineralogy of the Ljubljana Basin chronosequence. The chronosequence formed in predominantlycarbonate sandy gravel outwash terraces ranging from 5 to 1800 ka. Magnetic susceptibilityenhancement can be attributed to the formation of secondary superparamagnetic （SP） and singledomain （SD） ferrimagnetic minerals in eluvial horizons. Magnetic minerals that form in illuvialhorizons are predominantly antiferromagnetic. Downward migration of pedogenic iron compoundswith clay （formation of ferri-argillans） causes thickening of the enhanced zone with soil age.In contrast to other published soil chronosequence studies, magnetic susceptibility values donot increase with soil-age （duration of pedogenesis）. Nevertheless, frequency dependence ofmagnetic susceptibility （FD%） and indices such as maximum eluvial magnetic susceptibility （MS）divided by minimum illuvial MS (Max. E / Min. IX<sub>lf</sub> and maximum eluvial MS minus minimumilluvial MS (Max. E -Min. IX<sub>lf</sub>) increase with the logarithm of soil age suggesting that the magneticmineral transformations continue with time, but that their rate decreases. These indices are usefulfor comparisons, and may be useful for age correlations. Hypothesis that magnetic susceptibilityenhancement and precipitation have a positive correlation seems to be valid until the precipitationexceeds the critical value of 100-150 cm/year. The critical value in different settings may dependon the temperature regime and on the yearly distribution of precipitation.
文摘Most researchers agree that pedogenesis plays a significant role in determining thevertical distribution of magnetic susceptibility in soils and in the loess/paleosol sequences found inthe People’s Republic of China. Magnetic susceptibility distribution from Jiaodao on the Chinesecentral loess plateau matches other published magnetic susceptibility curves. Using the CBDmethod and a mixing model, the lithogenic and pedogenic components of magnetic susceptibilityfrom Jiaodao were quantified. The estimated lithogenic component showed a long-term decreasewith depth and had short-term periodic fluctuations in tune with the occurrence of paleosol andloess strata. The results of the mixing model suggest that interpretations based only on fluctuationsin total magnetic susceptibility will be in error and that a single estimate of average lithogenicsusceptibility is not an accurate basis for adjustment of the total susceptibility.
