CO2 buildup drove global warming, the Marinoan deglaciation, and the genesis of the Ediacaran cap carbonates

•The lack of THg/TOC peak in Ediacaran cap carbonates suggests background volcanic activity drove the Marinoan deglaciation.•Mercury isotopes suggest a binary mixing of seawater- and terrestrial-derived Hg in early Ediacaran Ocean.•The Marinoan deglaciation triggered enhanced terrestrial inputs of alkalis and large-scale dissolution of atmospheric CO2 into seawater.