Loess–palaeosol sequences are important terrestrial archives for studying Quaternary climate change. A major assumption for palaeoenvironmental reconstruction based on loess organic matter (OM) is that it represents the signal of syn-sedimentary incorporated plant biomass, i.e. predominantly grass vegetation. However, recent studies on rhizoliths (roots encrusted by secondary carbonate) formed in loess reveal the possibility of post-sedimentary penetration of loess–palaeosol sequences by deeply rooting plants. This likely led to incorporation of younger root-derived OM into surrounding loess, potentially causing an overprinting of the initial plant-derived signal of loess OM.