Glycerol Dialkyl Glycerol Tetraethers (GDGTs)-Based Paleotemperature Reconstruction Along a North-South Transect of the Chinese Loess Plateau Since the Late Pleistocene

Glycerol Dialkyl Glycerol Tetraethers (GDGTs)—archaeal/bacterial membrane lipids—enable reliable loess paleotemperature reconstruction, having supported 800-ka records for the Chinese Loess Plateau (CLP). However, their semi-arid utility (capturing latitudinal temperature dynamics, linking to soil organic matter (SOM) processes) is underexplored, hampered by temperature overestimation and 6-methyl branched GDGT (brGDGT) interference.We analyzed GDGTs in three north-south CLP profiles (Weinan, Luochuan, Jingbian) with complete Late Pleistocene strata (S0-L1-S1-L2). We dated Jingbian via AMS¹⁴C/OSL, using existing chronologies for well-documented Weinan/Luochuan.To reconstruct Late Pleistocene paleo-mean annual temperatures (MAAT), we employed a regionally calibrated arid-semiarid model (Chinese SSM: MAAT = 7.5 + 16.1×MBT - 1.2×CBT; R²=0.86, RMSE=1.8℃), which outperformed global models.Results confirmed a persistent north-south gradient: Last Interglacial MAAT reached 18.32℃ (Weinan), 15.40℃ (Luochuan), 13.89℃ (Jingbian); Holocene MAAT hit 17.77℃ (Weinan), 15.90℃ (Luochuan). All exceed current regional MAAT, framing present conditions as a relatively low benchmark. Notably, GDGT curves aligned with magnetic susceptibility/phytolith records but revealed a 4–6 ka lag (soil pedogenesis trailing atmospheric warming), illuminating climate-SOM feedbacks.Uncertainties persist: GDGT signals may be confounded by paleoprecipitation, C3/C4 shifts, or soil moisture (shaping microbial GDGT synthesis). Source ambiguity (microbial vs. vegetation inputs) and 6-methyl brGDGT interference also remain unresolved. Future work should integrate GDGTs with SOM, leaf waxes, isotopes; expand transects; refine pedoclimatic models (accounting for brGDGT subgroups)—strengthening GDGTs as a bridge between SOM dynamics and semi-arid loess paleotemperatures.