The Argentine Precordillera is a continental fragment rifted from the Ouachita embayment of the southern margin of Laurentia (North America) during Cambrian time [about 515 million years ago (Ma)] and accreted to the western margin of Gondwana (South America) during Ordovician time (about 455 Ma). Similarities of Cambrian stratigraphic successions and faunas, Grenville basement rocks, and dimensions link the Argentine Precordillera to the Ouachita embayment. Evidence of rifting during Cambrian time and of a wide ocean basin during Ordovician time indicates that the Precordillera traveled as an independent microcontinent to collide with Gondwana.