Fig. 1.

The Great Unconformity. (A) Global preserved sedimentary rock volume increases by more than a factor of 5 across the Phanerozoic–Proterozoic boundary in both the estimate of Ronov et al. (4) and a global scaling of North American units from the Macrostrat database by the area ratio of global land area to North American land area (a factor of 6.1) according to Husson and Peters (8), excluding recent alluvium. (B) The Cambrian Ignacio quartzite overlies the Mesoproterozoic ($\sim$1.35 Ga) Eolus granite at a sharp peneplanar nonconformity in the Needle Mountains, CO.