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The Vittatina costabilis Zone revisited: New characterization and implications on the Pennsylvanian-Permian icehouse-to-greenhouse turnover in the Paraná Basin, Western Gondwana

2020; Elsevier BV; Volume: 106; Linguagem: Inglês

10.1016/j.jsames.2020.102968

1873-0647

Paulo A. Souza, Daiana Rockenbach Boardman, Eduardo Premaor, Cristina M. Félix, Rafael Reis Bender, Edvaldo José Oliveira,

Geological and Geochemical Analysis

The accuracy of the radiometric ages for the Pennsylvanian-Permian section of the Paraná Basin has been progressively increased in the past two decades, allowing a better chronostratigraphic calibration to the related biozones. Most of these new ages are from levels containing spore-pollen associations assigned to the Vittatina costabilis Zone (VcZ), which is revised in detail herein. Unlike previous biostratigraphic proposals, we verified that VcZ is positioned between the Gzhelian and the Artinskian, documenting the Pennsylvanian-Permian transition. A new palynological characterization is proposed for this palynozone, including (i) changes in the definition of its lower and upper limits and (ii) the invalidation of its subzones. Although spores and monosaccate pollen grains are dominant in the VcZ, gymnospermic taeniate bisaccate and polyplicate pollen grains become progressively more abundant up section, representing new plant groups mainly linked to gymnosperms and allied groups. The VcZ documents the first appearance of certain Gondwana taxa of stratigraphic value, such as Converrucosisporites confluens and several species of Vittatina. The stratigraphical distribution of the VcZ is redefined based on previous and unpublished data. In general, the zone is well developed along the basin, but it is better represented between Santa Catarina and São Paulo States. No palynostratigraphic changes were consistently observed throughout the palynozone, which is recognized into two lithostratigraphical units of distinct paleoclimatic nature: the upper Itararé Group and the Rio Bonito Formation. Considering that earliest appearance of the Glossopteris in Paraná Basin is recorded within the upper Itararé Group from levels bearing palynological associations assigned to the VcZ, a Pennsylvanian age is evidenced for this plant group, which only became dominant across the Gondwana areas in Permian times.