Mesoproterozoic volcanosedimentary units and tectonic events occurring in the Ri´o de la Plata Craton (RPC) are reviewed. A belt consisting of volcanosedimentary successions exhibiting greenschist-facies metamorphism
is exposed in the eastern RPC (Nico Pe´rez Terrane) in Uruguay. The Parque UTE Group consists of basic volcanics and gabbros at the base (1,492 ± 4 Ma, U–Pb on zircon), carbonates in its middle part and interbedded carbonates, shales and acid volcanics (1,429 ± 21 Ma, U–Pb on zircon) at the top. The Mina Verdu´n Group is made up of rhyolites and acid pyroclastics at its base and
top, and Conophyton-bearing limestones and massive dolostones in the middle. A U–Pb LA-ICP MS zircon age of 1,433 ± 6 Ma is reported here for lapilli-tuffs at the base of the Mina Verdu´n Group (Cerro de las Vi´boras Formation).
This age shows that the Mina Verdu´n Group immediately postdates the Parque UTE Group, a fact supported by carbon isotope chemostratigraphy. Both units were deformed and metamorphosed between 1.25 and 1.20 Ga, as shown
by K–Ar and Ar–Ar ages. This tectonic event affected most of the RPC and led to the accretion of the Nico Pe´rez Terrane to the remainder of the RPC along the Sarandi´ del Yi´ megashear. We report a U–Pb LA-ICP MS zircon age
(upper intercept) of 3,096 ± 45 Ma for metatonalites of the La China Complex (Nico Pe´rez Terrane), which yield a lower intercept age of 1,252 Ma. A proto-Andean, Mesoproterozoic belt is envisaged to account for abundant
Mesoproterozoic detrital zircon ages occurring in Ediacaran sandstones of the RPC. If the RPC is fringed at both sides by Mesoproterozoic, Grenville-aged belts it is likely that it occupied a rather central position in Rodinia. A possible
location between Laurentia and the Kalahari Craton, and to the south of Amazonia, is suggested.