Abstract
Extensive folding, rather than a predominance of horizontal Cretaceous strata as heretofore mapped between Pirapora (Minas Gerais) and Formosa (Goiaz), southwest of the Sao Francisco river basin, Brazil, is revealed by the drainage pattern, aerial photographs, and field observations. The formations involved are analogous to those of the Sao Francisco-Bambui and Gerais series, and thus are probably Ordovician and Silurian. They have been folded, presumably in the Taconian or Caledonian orogeny, peneplaned, armored with a protective lateritic crust, uplifted, and intensely dissected, with the result that an Appalachian type of topography was developed.

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