Reconstructing Post–Middle Miocene Asian Hydroclimate and Eolian Source-to-Sink Pathways Using Plant-Wax n-Alkane δD

Interactions between the midlatitude westerlies and the East Asian monsoon exert first-order control on hydroclimate and sediment transport across Central and East Asia, yet their long-term coupling and migration remain debated. Here we reconstruct post–Middle Miocene atmospheric dynamics and eolian source-to-sink pathways using plant-wax n-alkane hydrogen isotope ratios (δD_wax) from IODP/ODP Sites U1430, 886, and 1208, spanning marginal to open-ocean depositional settings. These records are integrated with published Nd–Sr provenance constraints and regional environmental reconstructions and evaluated against simulations from the HadCM3L general circulation model.

We identify five distinct phases since ~13 Ma: (1) 13–9.6 Ma, characterized by relatively warm, stable conditions and dominant sediment input from northern Tibet and the Gobi region; (2) 9.6–6.0 Ma, marked by Late Miocene cooling, increasing Gobi contributions, and strengthening of the East Asian winter monsoon; (3) 6.0–3.6 Ma, an interval of early Pliocene warming associated with enhanced arid-interior influence and weakened monsoonal circulation; (4) 3.6–0.7 Ma, defined by a pronounced decline in δD_wax, intensified Northern Hemisphere glaciation, southward migration of the westerly jet, strong winter monsoon conditions, and major erosion from the Qaidam Basin; and (5) 0.7–0 Ma, reflecting renewed dominance of arid-interior sources and reduced monsoonal influence. The results demonstrate phased migration and dynamic coupling of the westerlies and East Asian monsoon over the past ~13 Myr, driven by evolving regional topography and high-latitude glacial forcing, and highlight the utility of plant-wax n-alkanes for reconstructing long-term Asian hydroclimate and sediment source-to-sink evolution.