Department of Geological and Mining Engineering and Sciences
Oceans cover 70% of Earth's surface, setting it apart from the other terrestrial planets in the solar system, but the mechanisms driving oceanic chemical evolution through time remain an important unresolved problem. Imbalance in the strontium cycle, introduced, for example, by increases in continental weathering associated with mountain building, has been inferred from shifts in marine carbonate 87Sr/86Sr ratios. There are, however, uncertainties about the spatial and temporal patterns of crustal evolution in Earth's past, particularly for the period leading up to the Cambrian explosion of life. Here we show that U-Pb age and trace element data from a global compilation of detrital zircons are consistent with marine carbonate 87Sr/86Sr ratios, suggesting changes in radiogenic continental input into Earth's oceans over time. Increases in riverine Sr input were related to the break-up and dispersal of continents, with increased weathering and erosion of a higher proportion of radiogenic rocks and high-elevation continental crust. Tectonic processes exert a strong influence on the chemical evolution of the planet's oceans over geologic time scales and may have been a key driver for concomitant increases in atmosphere-ocean oxygenation and global climate cooling.
Continental Magmatism and Uplift as the Primary Driver for First-Order Oceanic 87Sr/86Sr Variability with Implications for Global Climate and Atmospheric Oxygenation.
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