Altaid Plateau forced Late Triassic Earth’s freezing state

Late Triassic was critical in paving the age of dinosaurs and emergence of modern ecosystems. The end-Triassic mass extinction ( ~201 Ma) was triggered by warming, linked to massive volcanism, yet evidence suggests freezing conditions prevailed before this event. Here, we reconstruct the palaeoelevation of southern Altaids (Central Asian Orogenic Belt) during Late Triassic (ca. 204.6‒201.9 Ma) using hydrogen isotopes of n-alkanes and a novel ultraviolet-B proxy of pollen. The results show that the Junggar Basin and surrounding mountains reached palaeoelevations of 3,028‒4,050 m. This high-altitude setting subjected alpine flora to severe stress, evidenced by malformed pollen grains and elevated ultraviolet-absorbing compounds in sporopollenin. These findings indicate a Tibetan-style “Altaid Plateau” was formed by the amalgamations of the Tarim, European, and Siberian cratons, which catalysed mountain glaciation and alpine ecosystems. In summary, the uplift of the Altaid Plateau reset the Earth’s climate and regional ecosystem, connecting global cooling with monsoon intensification. The uplift of the Altaid Plateau during the Late Triassic drove major climatic shifts that triggered glaciation, stronger monsoons, and ultimately the collapse of regional alpine and terrestrial ecosystems, according to tectonic, sedimentological, and biogeochemical analyses.