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Ash fall layers and vitroclastic-carrying sediments distributed throughout the entire Permian stratigraphic range of the Parana Basin (Brazil and Uruguay) occur in the Tubarao Supergroup (Rio Bonito Formation) and the Passa Dois Group (Irati, Estrada Nova/Teresina, Corumbatai, and Rio do Rasto Formations), which constitute the Gondwana 1 Supersequence. U-Pb zircon ages, acquired by SHRIMP and isotope-dissolution thermal ionization mass spectrometer (ID-TIMS) from tuffs within the Mangrullo and Yaguari Formations of Uruguay, are compatible with a correlation with the Irati and parts of the Teresina and Rio do Rasto Formations, respectively, of Brazil. U-Pb zircon ages suggest maximum depositional ages for the samples: (1) Rio Bonito Formation: ages ranging from 295.8±3.1 to 304.0±5.6 Ma (Asselian, lowermost Permian), consistent with the age range of the Protohaploxypinus goraiensis subzone; (2) Irati Formation: ages ranging from 279.9±4.8 to 280.0±3.0 Ma (Artinskian, Middle Permian), consistent with the occurrence of species of the Lueckisporites virkkiae zone; (3) Rio do Rasto Formation: ages ranging from 266.7±5.4 to 274.6±6.3 Ma (Wordian to Roadian, Middle Permian). All the SHRIMP U-Pb zircon ages are consistent with their superimposition order in the stratigraphy, the latest revisions to the Permian timescale (International Commission of Stratigraphy, 2018 version), and the most recent appraisals of biostratigraphic data. The ID-TIMS U-Pb zircon ages from the Corumbatai Formation suggest that U-Pb ages may be >10% younger than interpreted biostratigraphic ages.

The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana.  In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordon del Plata range, within the Frontal Cordillera of Mendoza, Argentina.  The site is representative of the magmatism and deformation through different Andean cycles.  Results of the study indicate three lithological facies of increasing acidity upwards.  Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence.  Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above.  The fault zone of La Polcura – La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members.  These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic.  In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion.  Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone.  In contrast, the felsic rocks range from high-potassium rhyolites to shoshonites, typically depleted in Eu.  This indicate partial melting of a lithospheric mantle in an average to thin crust. 

Permian volcanic deposits are widespread throughout southwestern Gondwana and record voluminous silicic continental arc volcanism (e.g., Choiyoi Province) that may have contributed to Permian global warming and environmental degradation. Many Permian volcanic deposits of southwestern Gondwana (southern South America, southern Africa, West Antarctica and eastern Australia), however, remain to be accurately correlated to magmatic source regions along the active paleo-Pacific margin of Gondwana, and this lack of correlation limits our understanding of the timing and distribution of voluminous volcanism. Here we present detrital zircon U-Pb and Hf isotope data for Permian volcaniclastic sedimentary rocks from the Ellsworth Mountains, Pensacola Mountains, and the Ohio Range of central Antarctica in southwestern Gondwana used to determine their volcanic source along the paleo-Pacific margin of Gondwana. Rocks in central Antarctica record Permian (ca. 268 Ma) volcanism with a mean zircon εHfi of -0.04 ± 4.8 (2 standard deviation). Comparison of these zircon age and Hf data with compilations for adjacent regions along the Gondwana margin suggest derivation of the Antarctic zircons from a major episode of Permian explosive arc volcanism that is broadly synchronous with, and geochemically similar to, the voluminous Choiyoi Province in South America. This correlation also relates the source of synchronous volcaniclastic deposits in the Karoo Basin, South Africa, to the same major Permian volcanic episode associated with the Choiyoi Province. In aggregate, geochemical data from Permian zircon in central Antarctica support an along-arc variation in geochemistry, with isotopically enriched high-flux magmatism associated with thicker crust and lithospheric mantle in South America, and isotopically depleted magmatism and thinner crust and lithospheric mantle in Australia. The timing of inferred Choiyoi-related explosive arc volcanism recorded in the Antarctic sector, South African sector, and South American sector is contemporaneous with a documented increase in global arc flux, an increase in atmospheric CO2, a decrease in δ13C of benthic marine fossils, and mass extinction events. We suggest that the Choiyoi Province and correlated arc volcanism along the Gondwana margin contributed to increased global arc flux in the Permian leading to elevated background levels of atmospheric CO2 conducive to producing an environmental crisis during mafic large igneous province emplacement, and may serve as an example of continental arc outgassing exerting a first order control on climate.