Southern Asian arc magmatism drove Eocene global climate

Substantial evidence supports plate tectonics as a primary driver of Cenozoic paleoclimate evolution, with southern Asian (or Neo-Tethyan) magmatic pulses closely coinciding with the Early Eocene Climatic Optimum (EECO; ⁓53–49 Ma). However, the driving mechanism for the subsequent (⁓49–34 Ma) long-term global cooling remains contentious. Here, we synthesized available magmatic and detrital records across southern Asia, integrating a global radiometric dataset and a newly reconstructed, robust uplift history for the Tibetan Plateau (TP). Our synthesis, in conjunction with previous investigations, reveals a widespread magmatic lull, including a waning phase (⁓49–45 Ma) followed by a shutdown phase (⁓45–32 Ma), throughout southern Asia that probably resulted from coupled flat subduction of the Indo-Australian plate. We demonstrate that early Eocene magmatic flare-ups in southern Asia correlate with the atmospheric CO₂ buildup during ⁓60–50 Ma, ultimately triggering the EECO, whereas the subsequent magmatic lull strikingly coincides temporally with the secular decline in atmospheric CO₂ and global cooling. This long-term (⁓60–32 Ma) close correlation is not captured by models invoking TP uplift or enhanced tropical chemical weathering as primary driver of global cooling. These strong systematic covariations, as further supported by CO₂ flux calculations of the Linzizong volcanics and geochemical modeling of Neo-Tethyan CO₂ outgassing flux, compel us to propose that southern Asian arc magmatism (i.e., flare-ups and lull) may be the first-order control on Eocene global climate fluctuations, with the widespread magmatic lull and topographic weathering serving as the principal tectonic driver of post-EECO atmospheric CO₂ drawdown and resultant global cooling.