Continental Magmatic Arcs as Drivers of Neoproterozoic and Phanerozoic Icehouse-Greenhouse Transitions

English Abstract:

Tectonic outgassing from volcanic and metamorphic degassing contributes the major CO₂ flux to the atmosphere, whereas silicate weathering and organic matter burial draws down CO₂ on multimillion-year timescales. Variation in silicate weathering is generally consider the dominant controller of atmospheric pCO₂ and shifts in global climate regimes. Recent studies, however, postulate that continental arc magmatic systems in particular may play the major role in pCO₂ variation. Here we present a compilation of ~120,000 new and published single grain detrital zircon U-Pb age-dates acquired from globally dispersed siliciclastic sedimentary rocks with depositional ages that span the last ~720 million years. Globally, age distributions are skewed towards relatively young detrital zircon populations during periods of greenhouse climates, e.g., the Cambrian, Jurassic, and Cretaceous, whereas age distributions during the Cryogenian and Permian icehouse climates are broader with relatively low concentrations of young grains. These shifts in the relative abundance of young zircon grains indicate that continental volcanic arcs were spatially extensive during greenhouse climates and spatially reduced during icehouse climates. Based on this relationship, we propose that major shifts in atmospheric pCO₂ have been principally controlled by the continental arc volcanic flux, which drove major icehouse-greenhouse transitions from the Cryogenian to the modern.