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Although the Río de la Plata craton is exposed over a relatively large area in Uruguay, eastern Argentina, and southernmost Brazil, its geological evolution is poorly known because of great geological complexity and paucity of data. We report here U–Pb ages of detrital zircons from samples of five Neoproterozoic sandstone units deposited on the Río de la Plata Craton (RPC) in Uruguay and Argentina. The zircon ages provide definitive evidence of a great range of ages of rocks composing the craton—ages that would not have been known without the geochronology of detrital zircons. In turn, these new ages allow for a much fuller understanding of the nature and history of the craton. Quartz arenites of the Piedras de Afilar Formation show typical Transamazonian ages with peaks at 2.00–2.07, 1.87 and 1.78Ga. However, the most important zircon population in the sample analyzed is Mesoproterozoic with maxima …