Microstructural evolution and characteristics of loess-paleosol sequences: a case study from the Liujiapo (LJP) profile, Southern loess Plateau, China

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  • The loess-paleosol sequence of the Loess Plateau, with its distinct microstructural characteristics, provides critical insights into paleoclimate and soil formation. This study investigates a 52.7-meter-thick loess-paleosol profile (L0-S9 layers) in the southern Loess Plateau of China using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The analyses focus on the microstructural characteristics and their depth-dependent variations. Marked differences were identified between loess and paleosols regarding particle morphology, contact relationships, pore structure, and cementation, as analyzed through particle size distribution, quantitative pore characteristics, and mineral composition. The results show that loess predominantly comprises clay particles and clay-silt aggregates, featuring scaffolding pores and weak cementation. In contrast, paleosols consist primarily of clay-silt aggregates characterized by mosaic and cemented pores with notable cementation. As burial depth increases, structural differences between loess and paleosol progressively diminish, particularly in the middle and lower layers, where increased viscosity and cementation strength lead to a denser microstructure. Moreover, these microstructural changes are intricately linked to climatic fluctuations. A comparative reference to the Duanjiapo (DJP) profile, based on published datasets of silt content, magnetic susceptibility, and delta C-1(3), highlights that the microstructural evolution in the Liujiapo (LJP) section corresponds to wet-cold and dry-cold climatic cycles in the southern Loess Plateau. During glacial periods, the intense winter monsoon promoted the accumulation of silt particles and loess deposition, while the warm, humid interglacial phases facilitated weathering and leaching, forming paleosols. This study deepens understanding of loess-paleosol microstructural dynamics and their ties to paleoclimate, offering a foundation for future research on loess formation and its role in climate studies.