Magnetic susceptibility of Holocene loess-black loam sequence from Jiaodao, Shaanxi before and after citrate-bicarbonate-dithionite extraction

Magnetic susceptibility, anhysteretic susceptibility, frequency-dependent a nd temperature-dependent magnetic susceptibilities are measured before and after citrate-bicarbonate -dithionite (CBD) treatment on the Holocene loess -black loam sequence from Jiaodao, Shaanxi province. In this paper, we empl oy the correlativity between anhysteretic and magnetic susceptibilities to determine the domain state of magnetic minerals of the studied profile. The differences between pre- and post-CBD susceptibilities imply that not only the ultrafine superparamagnetic, but also some larger single-domain grains can be produced due to pedogenesis. Thermomagnetic analyses of the typical Holocene loess and black-loam specimens and magnetic susceptibility measur ements before and after CBD treatment show that CBD has no absolute selecti vity of dissolving the pedogenic magnetite grains, although it can efficien tly dissolve the pedogenic maghemite grains. The results also show that CBD technique strongly supports the pedogenic model of susceptibility enhancem ent. In addition, a combination study of soil chemistry and rock magnetism supplies a new evidence for the eolian origin of Chinese loess.