Climate-driven Compositional Modifications of Arc Volcanoes along the East Equatorial Pacific Margin — the Magmatic Response to a Cooling Planet

Magmatic arcs modulate global climate over geological timescales through outgassing and rock weathering, but recognizing the fingerprints of climate change in arc magmas remains challenging. Here we combine geologic, tectonic, and geochemical data of seafloor sediments and arc volcanoes from the East Equatorial Pacific (EEP) to build a biogeodynamic framework by which we can relate the compositions of arc volcanoes to those of sub -ducted sediments, and by extension, to regional and global environmental changes. Using this framework, we show that the well-documented increases in biologically mediated authigenic Ba and U contents of seafloor sediments at the onset of the so-called "carbonate crash" (12-9 Ma) were triggered by an escalation in biological productivity and an augmented efficiency of respiratory carbon storage. We suggest that the temporal modifi-cation of the oceanic carbon cycle was not solely enabled by the uplift of the Panama Isthmus, but also regulated by the synchronous formation of three wind-powered seasonal upwellings systems -Tehuantepec, Papagayo, and Panama- that developed in the context of steepening meridional temperature gradients, intensified at-mospheric circulation and global climate cooling since the Middle Miocene. Sediments deposited in the context of these newly established upwelling systems became anomalously enriched in authigenic U and Ba not only in comparison to older sediments, but also with respect to geographically adjacent areas of the EEP where vigorous upwellings are absent. These peculiar environmental conditions thus produce a heterogeneous ocean floor that upon subduction and eventual interaction with the mantle wedge creates arc volcanoes with compositional fluctuations that mimic those of the ocean sediments. These findings indicate that the oceanographic and biogeochemical effects of climate change can be engraved on the silicate Earth.