Conceptual model of Proterozoic icehouse-greenhouse marine As cycling.
(a) Snowball Earth scenario characterized by global ice sheets and low sea levels. (b) Greenhouse Earth characterized by ice retreat, sea level rise and massive As flux into the ocean. (c) Model of temporal sedimentary As inventory from Fig. 4, superimposed on oxygen dynamics through Earth History1. Stages I–VI are defined according to Fig. 4.