The deep Earth origin of the Great Unconformity

Abstract The Great Unconformity marks a globally extensive erosive surface linked to climatic shifts 1 and environmental transitions 2 that preceded the Cambrian explosion of life. The processes proposed to explain the formation of the Great Unconformity include glacial erosion during the Snowball Earth 1,3,4 , rifting and plume activity 5–7 , sea-level fall 8 and mantle-driven dynamic topography 6,9–11 . However, the dynamics of these processes have not been tested. Here we show that continental-scale uplift and subsidence associated with long-wavelength dynamic topography 12 due to mantle convection drove the formation and preservation of the Great Unconformity. Our models predict prolonged continental-scale Neoproterozoic uplift and long-term Phanerozoic subsidence for Laurentia, Baltica and North China. This vertical motion scenario is ideal for the formation and preservation of the Great Unconformity, which is a first-order surface expression of deep Earth processes. The predicted prolonged continental uplift throughout Cryogenian times would have resulted in marked erosion due to the action of glaciers 13 . The large area of Laurentia and limited deformation at its margins explain why the Great Unconformity is best preserved and documented there. Our models predict cycles of dynamic topography that are broadly reflected in preserved sediment volume across continents 1,14 , and open new avenues for understanding the environments of Cambrian animal diversification.