The conventional rules, derived from empirical and theoretical considerations, for the interpretation of anisotropy of magnetic susceptibility (AMS) in terms of microstructure and deformation are subject to numerous exceptions as a result of particular rock magnetic effects. Unusual relationships between structural and magnetic axes (so‐called inverse or intermediate magnetic fabrics) can occur because of the presence of certain magnetic minerals, either single domain magnetite or various paramagnetic minerals. When more than one mineral is responsible for magnetic susceptibility, various problems appear, in particular the impossibility of using anisotropy to make quantitative inferences on the intensity of the preferred orientation and consequently on strain. In ferromagnetic grains, AMS may also be influenced by the magnetic memory of the grains (including natural remanence). The effect of alternating field or thermal demagnetization on AMS is briefly discussed. Various rock magnetic techniques, specific to AMS interpretation, have to be developed for a better assessment of the geological significance of AMS data. These techniques mainly rely on measurements of susceptibility versus magnetic field and temperature, together with anisotropy of remanence.

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Hysteresis measurements, Lowrie-Fuller tests, Cisowski tests, and low-temperature demagnetization experiments on samples of the Knox Dolomite, Trenton Limestone, and Onondaga

For 40 years magnetic anisotropy has provided successful geological interpretations of magnetic ellipsoid orientations; in contrast the interpretation of anisotropy magnitudes is far more convoluted. This is due to complexities at various levels within rocks, including different physical magnetic responses of different minerals, grain-scale magnetic anisotropy, the anisotropy of interacting ensembles, the mineralogical constitution of rocks and the processes and mechanisms that align minerals in nature. The chief factors determining the magnetic fabrics of tectonized rocks include: mineral-physics properties, crystal symmetry, mineral-abundances, tectonic symmetry and crystal orientation-distribution, strain or stress, kinematic history and certain tectono-metamorphic processes (e.g. diffusion, crystal plasticity, dynamic recrystallization, particulate flow, neomineralization). AMS ultimately provides an integrated record of some combination of these factors. Subfabrics due to distinct processes or events may be expressed in different mineral and/or grain-size fractions, and are superposed in the conventionally observed AMS. Their discrimination may be achieved by various laboratory techniques such as magnetization and torque measurements in weak and strong applied fields, anisotropy of ARM and IRM, gyroremanence, Rayleigh magnetization, chemical leaching. However, under limited circumstances, statistical approaches such as differential analysis, tensor standardization, symmetry of confidence regions for the principal axes may partly isolate different subfabric orientations.

S U M M A R YWe suggest that inclination errors in detrital remanent magnetization (DRM) may be recognized and corrected by measurement of the anisotropy of anhysteretic remanent magnetization (ARM). ARM anisotropy reflects directional variations in the remanence capacity of relatively fine-grained magnetic particles in rocks or sediments, generally the same particles that carry the stable component of DRM.Relative vertical and horizontal DRM magnitudes are controlled by this directional remanence capacity, as well as by the alignment efficiency of the particle magnetic moments, which in turn is governed by the relative intensities of the vertical and horizontal components of the ambient magnetic field. Thus the respective vertical and horizontal components of palaeointensity , and therefore palaeofield inclination, may be obtained by normalizing the measured DRM components by parallel ARM intensities.Synthetic sediments containing silica, kaolin, and sized magnetite powders have previously been found to acquire experimental DRM with an inclination error that is a direct function of kaolin concentration. Further experiments have now shown that ARM anisotropy in the synthetic sediments is also a direct function of kaolin content, and thus a correlation exists between DRM inclination errors and ARM anisotropy. Multiplying the measured DRM vector by the inverse of the ARM anisotropy matrix yields an improved estimate of the actual laboratory depositional field in all cases. For samples with acicular 0.5 p m magnetite, this procedure reduces a mean inclination error of over 5" to less than 0.5". Samples with subequant magnetite of slightly larger grain size (0.75 pm) exhibit similar ARM anisotropy (-10 per cent), but somewhat larger inclination errors (-10'). We interpret this in terms of stronger horizontal alignment but weaker particle anisotropies for the larger, more equant magnetites.

S U M M A R YTemperature dependence of magnetic susceptibility (χ − T ) has been widely used to determine changes in mineralogy of natural samples during heat treatment. We carried out integrated rock magnetic experiments to interpret the χ − T curves of the Chinese loess/palaeosols in argon. We used both raw materials and heated samples. In addition, we also investigated the magnetic properties of magnetic extracts and residues to quantify contributions from each fraction to the bulk magnetic properties. For the heating curves, the susceptibility loss (∼30 per cent) between ∼300-400 • C is caused by the inversion from pedogenic fine-grained maghemite to haematite, suggesting that the susceptibility loss can be used as a new concentration index of the pedogenic fine-grained superparamagnetic (SP) particles in the Chinese loess/palaeosols. Unlike the warming curves, the cooling curves are dominated by newly formed fine-grained magnetites with a dominant size of ∼35 nm. The onset for the new production of these finegrained magnetic particles occurs at ∼400 • C. It is interesting that the room-temperature magnetic susceptibility (χ ph ) of the samples heated after a 700 • C run is independent of the degree of pedogenesis and saturates at approximately 33-35 × 10 −7 m 3 kg −1 , indicating that the susceptibility enhancement is controlled only by the reduction of Fe-bearing aeolian minerals during heating. It appears that the 700 • C thermal treatment in argon could be in some sense an analogue to the pedogenic processes. Thus, we predict that ∼33-35 × 10 −7 m 3 kg −1 is the maximum susceptibility that pedogenesis can generate for the last interglacial palaeosol unit (S1). In practice, χ ph would be useful to quantify the aeolian inputs to the Chinese Loess plateau.

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