Florida’s surface is young, but its foundations are not. In 1994 Paul Mueller and colleagues dated single zircon grains from deep subsurface samples—lower Paleozoic sandstone of the Suwannee basin in Alachua County and the Osceola granite in Osceola County—by SHRIMP ion microprobe[1]. Forty grains gave ages from 515 to 2,860 million years[1].
Two populations dominated, at about 515–637 million years and about 1,967–2,282 million years. These match the Pan-African and Birimian or Eburnian mountain-building cycles of Africa and the Brasiliano and Trans-Amazonian cycles of South America[1]. The authors concluded that this detritus “clearly places the basement of Florida in Gondwanaland proximal to the West African and/or Trans-Amazonian–San Luis cratons in the early Paleozoic”[1].
A later study by Mueller and colleagues examined the Suwannee suture, along which this Gondwanan block, the Suwannee terrane, was transferred to North America during the assembly of Pangaea[2]. It has remained part of North America since.
ASA Digital Art’s theory: this shared heritage with the South American and African crust where carbonado occurs is part of why we look to South Florida. The published work says nothing about carbonado.