Mechanism of magnetic enhancement and depletion of the loess from northern piedmont of Dabie Mountains, east-central China

IF 5.4 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena Pub Date : 2025-06-20 DOI:10.1016/j.catena.2025.109251

Yan Han , Guoyong Zhao , Bin Lyu , Xiuming Liu

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Abstract

Loess from the northern piedmont of the Dabie Mountains is exceptional, with classical loess to the north (i.e. the Chinese Loess Plateau), the Quaternary red soils to the south, and the Xiashu loess to the east. However, the mechanisms underlying the magnetic variation (enhancement and depletion) are not sufficiently understood. In this study, a multi-methodological approach (magnetic, geochemical, colorimetric, granulometric, and citrate-bicarbonate-dithionite (CBD)) was applied to improve our understanding of these issues. The following findings are highlighted. (1) The magnetic properties were remarkably different between the three light yellowish-brown silts and other units in the Hudian section. Specifically, minor fine ferrimagnetic minerals and more goethite were found in all three units. (2) The magnetic enhancement had a pedogenic origin, as suggested by the magnetic and CBD measurements. Specifically, ∼90 % of the magnetic mineralogy is affected by magnetic enhancement and ∼ 10 % is of detrital origin. (3) The fact that the three units underwent strong soil development was inconsistent with the magnetic records. Based on our records, combined with evidence from previous studies, our findings show that fine maghemite produced by strong pedogenic development were transformed into weakly magnetic goethite under humid environmental conditions. Dissolution of ferrimagnetic minerals can also contribute to magnetic depletion; however, the effect is limited. In summary, the magnetic enhancement of the loess from the northern piedmont of the Dabie Mountains was first induced by the development of pedogenesis, and then decreased by the conversion of fine pedogenic maghemite into weakly magnetic goethite and by dissolution due to wet pedogenic conditions. This provides critical regional evidence for studying the spatial evolution of the magnetic characteristics of loess in the north-south transect of China.

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中东部大别山北麓黄土的强磁和衰竭机制

大别山北麓的黄土较为特殊，北为典型黄土（即中国黄土高原），南为第四纪红壤，东为下蜀黄土。然而，磁场变化的机制（增强和损耗）还没有得到充分的了解。在这项研究中，采用了多种方法（磁性，地球化学，比色法，颗粒法和柠檬酸盐-碳酸氢盐-二硫代盐（CBD））来提高我们对这些问题的理解。重点介绍了以下发现。(1) 3个浅黄褐色粉砂的磁性能与湖甸剖面其他单元有显著差异。具体来说，在这三个单元中都发现了少量的细铁磁性矿物和更多的针铁矿。(2)磁增强与CBD测量结果一致，表明磁增强具有成土作用。具体来说，约90%的磁性矿物学受到磁增强的影响，约10%为碎屑来源。(3) 3个单元土壤发育强烈，与磁学记录不一致。根据我们的记录，结合前人的研究证据，我们的发现表明，在潮湿的环境条件下，强成土发育产生的细粒磁赤铁矿转变为弱磁性针铁矿。铁磁性矿物的溶解也会导致磁性耗竭；然而，效果是有限的。综上所述，大别山北麓黄土的磁性增强首先是由成土作用的发育引起的，然后是细粒成土磁赤铁矿向弱磁性针铁矿的转化和湿性成土条件下的溶蚀作用。这为研究中国南北样带黄土磁性特征的空间演化提供了重要的区域证据。

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来源期刊

Catena 环境科学-地球科学综合

CiteScore

10.50

自引率

9.70%

发文量

816

审稿时长

54 days

期刊介绍： Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.