Magnetic susceptibility measurements play a key role in Quaternary studies. Magnetic proxies, such as low field and frequency-dependent magnetic susceptibility, are widely applied in the reconstruction of terrestrial paleoclimate, e.g., in the study of loess-paleosol successions. In general, the interpretation of loess magnetic susceptibility signals is based on two commonly accepted models: the pedogenic magnetic enhancement and wind-vigour models. However, there are an increasing number of cases where such models cannot be used. These cases show unusual relationships between the two common loess magnetic susceptibility proxies: low field and frequency-dependent magnetic susceptibility. Such relationships have been attributed to various phenomena including the dissolution of fine-grain minerals and the formation of ultrafine magnetic rims on the surface of coarser grains by weathering. Despite the growing number of these exceptional cases of magnetic enhancement, our knowledge about the occurrence and potential causes of the unusual behaviour of magnetic susceptibility parameters is still limited. This, in turn, hinders the wider application of magnetic susceptibility parameters in loess. To fill this knowledge gap, magnetic susceptibility data of various profiles from the European Loess Belt were collected and compared to reveal various enhancement trends in loess. Along with the analysis of magnetic susceptibility parameters, combined scanning electron microscopy (SEM) and rock magnetic analyses were applied to samples from the Paks loess sequence in Hungary to describe some of the irregular cases, notably the cause of increasing frequency-dependent susceptibility in non-altered sediments. Analysis of loess, paleosol and common mineral samples separated from loess (e.g., muscovite) revealed that various features may be responsible for these increasing frequency-dependent susceptibility values: i) surface weathering (maghemitization) of coarser detrital grains, ii) nanofragmentation by physical weathering and iii) the appearance of significant amounts of ultrafine magnetic inclusions in micas. These special modes of magnetic enhancement of loess do not undermine the importance of the basic theories suggested above, but rather provide three mechanisms that account for some of the increasing number of unusual cases. To aid in the wider and more accurate use of magnetic susceptibility parameters in loess, we review the current magnetic enhancement models with special emphasis on the identification of unusual trends in magnetic enhancement and understanding their drivers.

磁化率测量在第四纪研究中起着关键作用。诸如近场和随频率变化的磁化率之类的磁代理被广泛应用于陆地古气候的重建中，例如，在黄土古土壤演替研究中。通常，黄土磁化率信号的解释是基于两个公认的模型：成岩磁增强和风能模型。但是，越来越多的情况无法使用这种模型。这些案例显示了两种常见的黄土磁化率代理之间的异常关系：低磁场和频率相关的磁化率。这种关系归因于各种现象，包括细粒矿物的溶解和风化作用在较粗晶粒表面上形成超细磁性边沿。尽管磁增强的这些例外情况的数量在增加，但是我们对磁化率参数异常行为的发生和潜在原因的了解仍然有限。反过来，这阻碍了磁化率参数在黄土中的广泛应用。为了填补这一知识空白，收集并比较了欧洲黄土带各种剖面的磁化率数据，以揭示黄土的各种增强趋势。在分析磁化率参数的同时，结合扫描电子显微镜（SEM）和岩磁分析对匈牙利Paks黄土层序的样品进行了描述，以描述一些不规则的情况，特别是未改变沉积物中频率依赖性磁化率增加的原因。从黄土（例如白云母）中分离出的黄土，古土壤和普通矿物样品的分析表明，各种特征可能与这些随频率变化的磁化率值有关：i）粗碎屑颗粒的表面风化（磁化），ii）物理碎裂的纳米碎片风化和iii）云母中出现大量的超细磁性夹杂物。这些特殊的黄土磁增强模式不会破坏上述基础理论的重要性，而是提供三种机制来解决越来越多的异常情况。为了帮助在黄土中更广泛，更准确地使用磁化率参数，我们回顾了当前的磁增强模型，其中特别强调了磁增强中异常趋势的识别和对其驱动力的理解。