Journal Article

U-Pb zircon dating of ash fall deposits from the Paleozoic Parana Basin of Brazil and Uruguay; a reevaluation of the stratigraphic correlations

Basei, M. A. S, Santos, P. R, Santa Ana, H, Veroslavsky, G, Rocha-Campos, A. C, Nutman, A. P, Canile, F. M, Rosa, O. C. R, Passarelli, C. R, Fernandes, M. T

2019

Overview

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.

• Publisher: University of Chicago Press,University of Chicago, acting through its Press
• Subject: absolute age / Appraisals / ash falls / Ashes / Basins / biostratigraphy / Brazil / cathodoluminescence / Choiyoi Group / chronostratigraphy / correlation / Corumbatai Formation / dates / Dating / deposition / electron microscopy data / Estrada Nova Formation / evaluation / Formations / Geochronology / Geochronometry / Geological time / Gondwana / ion probe data / Ionization / Irati Formation / Isotopes / Itarare Subgroup / Lead / Lueckisporites virkkiae / Magma / Mangrullo Formation / mass spectra / nesosilicates / orthosilicates / outcrops / Paleozoic / Parana Basin / Passa Dois Group / Permian / Protohaploxypinus goraiensis / Radiometric dating / Rio Bonito Formation / Rio do Rasto Formation / Sediments / SEM data / SHRIMP data / silicates / South America / spatial distribution / spectra / Stratigraphy / Superposition (mathematics) / thermal ionization mass spectra / thin sections / Tubarao Group / U/Pb / Upper Permian / Uruguay / Yaguari Formation / Zircon / zircon group