Southern Eurasian magmatic shutdown triggered Eocene global cooling

Accumulating multidisciplinary evidence reveals that plate tectonic processes have played a pivotal role in Cenozoic paleoclimate changes, with Neo-Tethyan magmatic spurts matching well with the Early Eocene Climatic Optimum (EECO; ca. 53-50 Ma). However, the tectonic driving mechanism of the subsequent (ca. 49-34 Ma) global long-term cooling after the EECO still remains contentious. Here, we compile available magmatic records from southern Eurasia, together with a global dataset of magmatic rocks/zircons and a recent well-constrained uplift history of the Tibetan Plateau, to uncover the tectonic processes regulating Eocene paleoclimate changes. The combined data, along with geologic observations, highlight a widespread reduction in magmatic activities and volcanic/metamorphic CO₂ outgassing throughout southern Eurasia in the middle to late Eocene, which probably resulted from the termination of Neo-Tethyan subduction and consequent coupling and flat subduction of the Indo-Australian plate after Neo-Tethyan slab break-off. Particularly, we find that the gradual decrease in atmospheric CO₂ concentration and temperature dropping after EECO was synchronous with southern Eurasian magmatic wanning, but was inconsistent with the uplift history of the Tibetan Plateau. Such a strong synchronicity led us to propose southern Eurasian magmatic shutdown as the main tectonic driver of Eocene global cooling.