Relationship between soil magnetic susceptibility enhancement and precipitation in Cretaceous paleosols

Magnetic susceptibility (MS) is widely used for paleoclimate reconstruction. In one of the previous studies, data from 12 locations of modern middle- and low-latitude soils revealed that MS increases with increasing precipitation from approximately 200 to 1000–1200 mm yr⁻¹ and then decreases with further precipitation. However, as a result of diverse sediment sources from different locations, the MS value can deviate, affecting its relationship with the climate. Sediments of a section experience dry-wet contrast due to the migration of climate zones as a function of geological time, and form different soil types with various colors. If the sediments of a section have the same source material, different soil types in that section would enable us to explore the relationship between MS enhancement and precipitation using paleosols and to verify the previous results. Herein, we investigated Cretaceous variegated sediments in the Zhonggou and Xiagou Formations located in the Hexi Corridor of China. The rare earth and trace element analyses reveal that these sediments have the same source area. Environmental magnetism and geochemical methods reveal that the sedimentary environment of the yellowish-brown, red, and grayish-white sediments ranges from dry to wet. Precipitation reconstruction for the paleosols with a climate transfer function shows that MS increases with increasing precipitation up to approximately 800 ± 182 mm yr⁻¹ and decreases with higher precipitation amounts. The changing pattern of MS is consistent with the previous results, but the inflection point in the MS vs. precipitation curve appears at slightly lower precipitation value. Thus, paleosol sequences are suited for the analysis of paleoprecipitation trends with the help of MS.