This case study provides insight into magnetic susceptibility (MS), iron and bulk-sample geochemistry patterns in an Upper Mississippian siliciclastic–carbonate cyclothemic section Polotnyanyi Zavod (Moscow Basin, Russia), with many subaerial disconformities and Stigmaria impressions. The goal of this paper is to test whether the MS and geochemical signals in this section are linked to any specific geological processes. The section is dominated by limestones but contains several siliciclastic units and numerous subaerial disconformities. This lithological heterogeneity is vividly expressed on MS and bulk geochemical logs. MS shows the strongest positive correlation to bulk iron and also strong correlations to Al2O3, MgO, K2O and TiO2, pointing to close association of iron with siliciclastic fines rich in detrital mica and clays. The correlation of iron and MS to siliciclastic fines or subaerial exposure horizons is not straightforward. The highest ferruginization with most intense MS excursions occurs in basal sooty silts and shales of three main siliciclastic units of the studied section. In addition, many other thin pedogenized shales are ferruginized and show a relative high magnetism, but some ferruginized shales are not palaeosols.

The effect of a tea plantation on soil basic properties, chemical and mineralogical compositions, and magnetic properties of Alfisols from eastern China was studied. Under the tea plantation, acidification took place within a soil depth of 70 cm, with the maximum difference in pH in the upper 17 cm (ΔpH = 2.80). Both the tea plantation and unused soil profiles were predominated by free Fe and Al oxides, i.e. citrate/bicarbonate/dithionite extractable Fe (Fe(d)) and Al (Al(d)). Tea plantation soil was characterized by higher Al(d) and Fe(d) and lower Fe oxalate, Fe(2)O(3) and Al(2)O(3); CaO was depleted, whereas SiO(2) accumulated. Acidification induced by the tea plantation led to destruction of vermiculite followed by dissolution of the hydroxy-Al interlayers within its structure. The data clearly demonstrated that significant soil weathering occurred with acidification caused by tea cultivation. This acidification also resulted in decreased content of ferrimagnetic minerals due to the dissolution of minerals and movement of Fe in the profile.

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