Exhumation of Grand Canyon’s basement along the Great Escarpment of Laurentia

The Grand Canyon encompasses two billion years of Earth history, but more than half this record is absent across a regionally extensive erosional surface known as the Great Unconformity. This enigmatic surface has been linked to multi-phase regional tectonics accompanying supercontinent assembly and breakup and to Cryogenian glacial erosion. Although rift-related uplift during the breakup of Rodinia has long been implicated in erosion associated with the Great Unconformity, we argue that exhumation in the Grand Canyon region was focused along a continent-scale rift-flank escarpment. This “Great Escarpment of Laurentia,” initiated ca. 800−750 Ma, occupied a position analogous to major escarpments generated during Mesozoic Gondwana breakup and experienced similar magnitudes of exhumation. Our landscape evolution models simulating rift-driven topography suggest that rocks within several hundred kilometers of this feature endured substantial erosion, reaching 8 km near the escarpment and decreasing to ≤2 km at lateral distances of ∼200 km from its peak. Such differential erosion, evidenced in prior thermochronology models, necessitates exhumation of mid-crustal basement lithologies including along reactivated crustal fault blocks. This model helps explain the variable magnitude of erosion associated with the Great Unconformity in the southwestern United States.