Impact of the Taihang Mountains Uplift on the Formation of Asian Monsoon Climate during the Miocene: Constraints from Sedimentary Environment in the Jiyuan Basin

Previous studies have suggested that during the Miocene, Asia transitioned from a planetary wind system to a monsoon system (Guo et al., 2008). This shift is considered to be primarily related to the uplift of the Tibetan Plateau. Between the Late Oligocene and Early Miocene, the Taihang Mountains underwent a critical phase of rapid uplift. This tectonic event closely coincides with the major transition in Asia's climate from dominance by the planetary wind system to dominance by the monsoon system. During this period, the region inland of Asia, with the Taihang Mountains-Qinling Mountains as a boundary, developed a continental arid climate.

This study, based on detailed research of climatic proxy indicators and paleomagnetic data from Cenozoic strata in the Jiyuan Basin, eastern Taihang Mountains, proposes that during the Middle to Late Oligocene (approximately 24–28 Ma), the climate of the Jiyuan Basin shifted from warm and humid conditions in the early stage to cool-temperate and dry conditions in the late stage. A distinct humidification process occurred between 24 and 21 Ma, which is associated with the global Early Miocene climatic warming and increased humidity. The uplift of the Taihang Mountains enhanced the orographic lifting effect encountered by the East Asian summer monsoon as it penetrated inland, potentially leading to increased precipitation on its eastern windward slopes. Concurrently, the rain shadow effect on its western leeward slopes was also intensified, thereby amplifying the east-west spatial differentiation of aridity and humidity across North China. This process is regarded as one of the important mechanisms that drove the reorganization of Asia's climate in the early Miocene and helped shape the prototype of modern monsoon precipitation patterns.