Schists within Grand Canyon's Precambrian crystalline basement were possibly created supernaturally on Creation Days 1–2. They were then uplifted by the upheaval on Creation Day 3. At the onset of the Flood they were beveled before Flood sediment layers were deposited unconformably over them. Fifty samples were collected from two schist units. Radiohalos in these samples were identified and counted. Thirty-six of the 37 Vishnu Schist samples contain 210Po radiohalos, 33 also contain 238U radiohalos and four contain 218Po and 214Po radiohalos. The thirteen Ramu Schist samples contain fewer 210Po and 238U radiohalos. The different apparent metamorphic conditions in the lithotectonic blocks were irrelevant. The two factors that control radiohalos numbers are the abundance of biotite flakes available to host radiohalos and the abundance of tiny zircon inclusions in them. Two models proposed previously to resolve the Po radiohalos enigma are creation by fiat of the host schists with the Po radiohalos during Creation Days 1–2, or rapid transport of the Po atoms by hydrothermal fluids while grossly accelerated radioactive decay was occurring during the Flood. Any radiohalos in these supernaturally created schists likely were annealed by the Creation Day 3 upheaval and the onset of the Flood. Thus, the origin of these radiohalos is consistent only with the hydrothermal fluid transport model for their formation during the Flood.