Abstract
SUMMARY Chemical extraction techniques are being introduced into environmental magnetism studies to aid in the interpretation of magnetic climate proxies. Previous studies have shown that the acid-ammonium-oxalate/ferrous-iron (AAO‐Fe 2+ ) extraction technique can be used to selectively dissolve very fine-grained magnetite and maghemite from synthetic samples. Here, we present the results of a study of this extraction technique to serve as a tool for selective dissolution of pedogenic magnetic minerals from a loess‐palaeosol transect. Before and after extraction, the samples were subjected to classic mineral‐magnetic methods (measurement of low-field susceptibility and hysteresis parameters), as well as first-order reversal-curve analysis. In addition, acquisition curves of the isothermal remnant magnetization (IRM) were fitted with logarithmic distributions. These analyses showed the magnetic dominance of lowcoercivity magnetic minerals. By subtracting the IRM remaining after extraction from that before extraction, the magnetic fraction that was dissolved could be characterized as well, supplying extra information concerning the performance of the extraction technique. The AAO‐Fe 2+ method successfully dissolved the superparamagnetic and part of the singledomain material from the palaeosol samples in one extraction step, repeating the extraction resulted in hardly any further changes to the magnetic content of the samples. The magnetic characteristics of the loess samples remained stable throughout the extraction experiment. The combination of the AAO‐Fe 2+ extraction with mineral‐magnetic analysis has successfully identified the pedogenic contribution in our samples. Therefore, variations in the lithogenic fraction potentially present in pedogenically enhanced intervals can be assessed, improving the merit of mineral‐magnetic climate proxy parameters.
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