The Deep Earth Origin of the Great Unconformity

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 . 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 Precambrian uplift and long­term 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 large area of Laurentia and limited deformation at its margins explain why the Great Unconformity is best preserved and documented there. We show that a single cycle of Precambrian dynamic uplift followed by Phanerozoic dynamic subsidence is the ideal geodynamic scenario for the formation and preservation of the Great Unconformity at continental scale. Our models predict cycles of dynamic topography that are broadly reflected in the preserved sediment volume across continents ^1,13 .