Provenance of Neogene deposits of Barreiras Formation in the southeastern Brazilian continental margin.

The Barreiras Formation records continental-to-shallow–water marine sequences deposited during the Paleogene–Neogene periods in the Brazilian continental margin. In northern Rio de Janeiro and southern Espírito Santo states, the Barreiras Formation preserve alluvial depositional system. The sediments were derived from a source located in the hinterland of the southeastern Brazilian continental margin, where rocks formed or reworked notably during the Gondwana supercontinent assembly are exposed. Detrital zircon U–Pb ages are mostly late Neoproterozoic, dominantly close to 608 Ma. Source rocks of this age occurred within the Ribeira and Araçuaí belts and were formed during their main magmatic activity. U–Pb zircon age distribution is similar to the southern and central Ribeira belt. Zircon fission-track ages occur in four main groups, between 429 and 358 Ma, 351 and 274 Ma, 270 and 171 Ma, and 167 and 127 Ma. Complex variation in the detrital zircon fission-track ages is related to the continental crust thermal evolution in the source areas. Older ages also occur between 534 and 433 Ma (Cambrian-to-Silurian periods) and are chrono-correlated to post-orogenic processes after the Gondwana supercontinent agglutination. Zircon fission-track ages between 429 and 274 Ma (Silurian to Permian periods) are related to the formation of the Pangea supercontinent, whereas the predominant zircon fission-track age group, between 270 and 171 Ma (Permian to Jurassic periods), is chrono-correlated to both orogeneses in the Gondwana supercontinent west margin and the Pangea supercontinent breakup. Zircon fission-track ages from 167 to 127 Ma are in the same period as the opening of the North and South Atlantic oceans. Data indicate that the thermal evolution of the source region either during the Gondwana supercontinent and South America Platform stages is complex. [ABSTRACT FROM AUTHOR]