Two‐Stage Climate and Vegetation Change at the East Asian Monsoonal Margin Across the Miocene Climatic Optimum

Abstract The change in vegetation at the margins of the East Asian summer monsoon (EASM) during the Miocene Climatic Optimum (MCO) remains poorly understood. Here, we present a high‐resolution terrestrial sequence, paleomagnetically dated to 18.2–13.5 Ma, from the Tongxin Basin of midwestern China. Our multi‐indicator analysis, encompassing pollen, δ 13 C TOC , δ 18 O carb ‐δ 13 C carb, and magnetic susceptibility, reveals that the regional vegetation and climate had two distinct stages during the MCO, manifesting as stable arid steppe from 17.0 to 16.0 Ma, and woodland steppe with six forested environments from 16.0 to 14.0 Ma. Together with other adjacent records, this supports the EASM as the main control on terrestrial vegetation. Further comparisons of marine‐terrestrial data and time series analysis suggest that in the late MCO, the oceanic carbon reservoir (OCR) experienced strong perturbations (mainly C max events) accompanied by multiple oscillations. The instability signals likely impacted and were amplified as rapid shifts in forest‐steppe environments at the monsoon margins via EASM. Our study highlights the regulation of inland ecologically vulnerable areas by low‐latitude forcing in a greenhouse world.