Reconstructing seawater δ18O and [formula omitted]O values with solid Earth system evolution

Abstract

There has been extensive debate about how to link sedimentary oxygen isotope records to changes in solid Earth and surface processes. We present a new model of coupled ocean-crust-mantle evolution to investigate the geological processes that are responsible for the evolution of seawater δ18O values. In our model, the rates of low- and high-temperature crustal alteration are constrained by mantle cooling and crustal evolution. This way, we were able to outline the possible path of solid Earth evolution that matches the observed seawater δ18O records. Our results suggest that marine δ18O values may have been as low as −10‰ to −5‰ in the late Archean. The corresponding Δ′17O value may have been 0.015‰±0.01‰ in the late Archean and then decreased with time. The evolution of seawater δ18O is shown to be sufficiently sensitive to the history of continental formation, and our modeling suggests the presence of a considerable amount of continental crust in the early Archean.