Climate-driven microstructural differentiation between loess and paleosol in the Central-Eastern loess Plateau of China

Abstract

Loess-paleosol sequences constitute critical terrestrial archives for reconstructing Quaternary paleoclimatic dynamics. This study integrates paleomagnetic stratigraphy, physicochemical analyses, and high-resolution microstructural characterization to elucidate climate-driven structural differentiation in a typical loess-paleosol sequence from the central-eastern Loess Plateau, China. Three diagnostic distinctions emerge: (1) Particle morphology: loess exhibits loose aeolian stacking with angular particles accompanied by parallel cleavages with pairable contours and the same mineral composition on both sides, contrasting with paleosol’s tight stacking with relatively rounded grains showing chemical weathering features, e.g., dissolution-derived rounded pits; (2) Matrix composition: Loess matrix (<30 vol%) consists primarily of illite-chlorite assemblages forming point contacts, contrasting with paleosol’s enriched matrix (>40 vol%) dominated by secondary calcite and illite–smectite and kaolinite clays that create pervasive cementation; (3) Pore architecture: loess preserves well-aligned macropores with smooth walls, while paleosol develops poorly-aligned irregular micropores infilled with pedogenic materials. These structural divergences reflect fundamentally different formation processes: loessification under cold-arid conditions versus pedogenesis during warm-humid conditions. The systematic microstructure-climate relationships advance mechanistic understanding of East Asian monsoon evolution, demonstrating how loess pedostratigraphy encodes Pleistocene-Holocene environmental transitions through measurable structural responses to atmospheric forcing.